Preamble
Monday, September 21st, 2009
What follows is the original preamble (more or less the same as those from M2M, etc). A
few notes on DEMS:
1) Dr. Michaels is approachable, will answer your questions, and will in many other
ways stand in for your mom just like she did in Anatomy. This does not mean
she’s a pushover, so be warned.
2) Biochem is a small part of DEMS and a comparatively enormous part of Step
One. If you can nail biochem here, in this course, you will save yourself an
enormous headache trying to cram it in April.
3) To this end, I recommend Lippincott’s Illustrated Biochemistry (and I can’t stand
studying from textbooks). Really good book for that part of this course and for the
USMLE.
4) Everything in Endocrine is a feedback loop. If you approach it from that
perspective rather than as a bunch of individual factors influencing each other you
will drive yourself much less crazy.
5) The DEMS material is so-so, interest-wise—above M2M and Life Cycle but
below Neuro and CVPR. Don’t expect to be wowed by clinical application here.
However, the LOs generally match up to what they want you to know pretty well.
Also, this is high-yield stuff for USMLE: stuff most people don’t bother studying
because, well, it’s the guts, and who cares about the guts? Easy points.
6) Many people start their abstinence from class to study for the boards about this
time of year. Don’t be surprised if the lecture halls start looking a little empty. On
a personal note, I think that’s nuts.
–jcr
PS- if you find these useful and can go without a latte for a couple of days, I’d like you to
give another $5 to charity.
Hey, everybody. These are my compiled learning objectives for DEMS when I took it
in the fall of 2008. I hope you find them useful. A few notes:
1. These aren't to be taken as everything-you-need-to-know material, or
anything close to it. They can be, however, extremely useful, if only to
look at the material a second time in a different format.
2. Learning objectives change. Granted, in our vaunted institution, they
often don't change a lot. But it's worth figuring out where these
overlap with what you're studying and where they don't to avoid any
unnecessary learning (God forbid).
3. They can be incorrect. I hope this is infrequent, but I'm sure there are
things in here that aren't accurate. I've tried to curate them
reasonably well; I hope one of your classmates will do likewise. If you
find an error, kindly let him or her know.
4. They are nothing more or less than my personal take on what we
happened to be learning on a given day. Sometimes they're very
detailed, sometimes they're uncomprehending, frequently they're
irreverent. I occasionally call babies vampires and things like that
(dude, they are). Internet lesson: free trumps tasteful. In any case
you are free to disagree with me.
5. To anyone who's wondering: I honored this block and all the rest in
my first two years. That's not supposed to impress you, but it is
supposed to give you some kind of confidence that I have a reasonably
good handle on what's going on.
6. To the many of you who are thinking, "How can I repay this wonderful,
wonderful man?" I would reply that I never turn down free beer if I
can help it. The problem with that is that I suspect I will never meet
most of your class, and beer-buying in absentia is a cold and heartless
thing. So if you find these useful and would like to do something for
me, I would prefer it if you donated $5 to the charity of your choice; if
you're stumped, I suggest browsing www.charitynavigator.com for
some good options. Kindly do not donate money to armed
insurrectionist groups.
i.
Addendum on donating to charity: always always ALWAYS have
an email account that you set aside purely to sign up for or
donate to things (thus ducking all the spam associated
therewith). I think I have 1,200 emails in mine, mostly from a
donation I made to the SPCA a couple of years ago. Gmail and
Hotmail work well. I also recommend using a false street
address to avoid direct-mail campaigns.
ii.
"That seems like a lot of trouble to go through to donate five
bucks"-- yeah, well, welcome to the world, sonny Jim. Doing
things for other people frequently is a pain in the ass. Doesn't
make it less worth doing.
Digestive System Overview
Monday, October 13, 2008
7:51 AM
Digestive System Overview, 10/13/08:
[Note that I have given up trying to fight the new LO numbering system on
Blackboard and henceforth these things will have numbers instead of nice clean
bullet points (bullet points, precious). Direct complaints, bomb threats, etc to
Thomas.French@uchsc.edu.]
1. Discuss the role of the intrinsic (enteric) nervous system in gut motility. What is
the advantage of having extrinsic nervous system input?
 The enteric autonomic nervous system (not parasympathetic or
sympathetic) is comprised of postganglionic sympathetic- and
parasympathetic-like fibers (in/from Meissner's and Auerbach's plexi,
see below) that participate in what seems to be a kind of GI reflex arc:
they release parasympathetic signals based on local input without
going through the CNS.
 So I asked Dr. Michaels about all this nervous system coordination.
Here's what I got out of her response.


There's three layers of nervous activity going on.
One isn't technically part of the nervous system at all. That's
the intrinsic pacemaker activity in the smooth muscle cells of
the GI tract. Effectively these function somewhat similarly to
cardiac pacemaker cells: the impulse is conveyed through gap
junctions to provide some extent of rhythmic depolarization
across the smooth muscle in the digestive system.
 The next is the enteric nervous system (which, recall, isn't
technically part of the CNS-- it's kind of a very local reflex arc).
This responds to local conditions (ie. a stretch in local smooth
muscle from a nearby bolus of food) by triggering a cascade of
local nervous system activity (contracting the lumen upstream
of the food, widening the lumen downstream, etc). You can
sever all CNS input and still produce peristalsis due to this
mechanism.
 The final one is the CNS-directed sympathetic and
parasympathetic input, which is important for coordinating the
response of the system as a whole.
 How these fit together: it seems like the pacemaker cells allow
the cell-polarity underpinning that allows the enteric and CNS
signals to take place rhythmically rather than all at once (you'd
like movement in the gut to be pulselike rather than tetanic)-the cells are only depolarized enough to be susceptible to
further nervous-system-signaled depolarization at particular,
regular intervals. Then the enteric system controls local flow
during those intervals and the CNS controls overall flow and
coordination.
 My clumsy attempt at metaphor: my impression is that the
pacemaker muscles are like the electricity grid of a city street.
Without them, nothing happens. The enteric nerves are the
individual stop lights that direct traffic along a given street-they'll turn green when someone's waiting. The CNS nerves are
the circuitry that makes sure that if one light turns green, the
next light down isn't turning red, ensuring that traffic down the
entire street flows smoothly.
2. Describe the structural properties of smooth muscle in the gut that contribute to
its performance as a single functional unit. What factors influence the behavior of
smooth muscle in the gut?
 Stretching of the GI tract by a food bolus sets off a cascade of events
in peristalsis:
 Upstream of the bolus, the circular muscular layer constricts
and longitudinal muscle layer relaxes (preventing retrograde
movement); downstream, the opposite happens (circular
relaxes, longitudinal contracts) to promote anterograde
movement. Different neurotransmitters are used to make each
of these happen.
 Note that at certain periods of time, particularly in the small
bowel and colon, you actually use the same contractions
upstream and downstream, the theory being that you really
just want to smush the food against the side of the intestine
(thus increasing contact with absorptive factors on the
intestinal walls) without moving it along. This is called
segmentation and is a separate concept from peristalsis.

Recall that smooth muscle can maintain a contraction for long periods
of time without using up a lot of ATP.
 The smooth muscle found in the GI tract is called "single unit" or
unitary smooth muscle; distinct populations of smooth muscle cells act
in concert as a single unit (thus the clever name). This is in contrast
with (for example) the smooth muscle controlling the iris, which are
called "multi-unit" and contain populations of muscles that act
independently.
 How the single-unit smooth muscle cells work together:
 Adherence junctions (structural connections)
 Nervous system innervation of multiple areas by a single
nerve (ensure widespread response to one stimulus)
 Gap junctions between cells that carry the pacemaker
current, as mentioned above.
 But note that, obviously, working as a unit doesn't mean that
you want everything to be doing the same thing as once
(otherwise the next portion of the GI can't open up when the
portion containing the food bolus contracts). If you'll permit
another metaphor, it's the difference between a concerto and a
bunch of different people playing whatever they want at their
own tempo. One is classical music, the other is postmodern art
(the creative trash bin of artistic history). Classical music is
peristalsis; postmodern art is spasm.
 Factors influencing smooth muscle behavior: mainly, the enteric (localresponse) and CNS (global-response) innervation.
3. Identify the four layers of the GI tract wall and the basic structural components of
each. How does the digestive system protect itself from auto-digestion and
pathogenic bacterial invasion?
 From lumen outward:
 (1) Mucosa: three layers:
 (a) Epithelial cells. These are specialized according to
the region of the GI tract they're in (water absorption,
acid secretion, etc).
 [Stratified squamous (protective) epithelium
covers skeletal muscle layers at either end of GI
tract (esophagus and rectum). In between
there's generally simple columnar epithelial
cells.]
 [Apical region of the epithelium: everything
above (towards the lumen from) the tight
junction plane. Basal region: everything below
that plane.]
 (b) Lamina propria: loose connective tissue containing
blood vessels, lymphatics, immune cells, nerves, etc.
 (c) Muscularis mucosa: very well-vascularized muscular
layer, used in local movement/folding (think rugae!
..which should be on a t-shirt).
 Recall that in the small intestine, "fingers" of epithelial
cells filled with lamina propria poke up into the lumen to
increase absorptive surface area (the intestinal villi).
 Throughout the stomach/intestines, also see
invaginations: gastric pits and glands in the stomach,
crypts of Lieberkuhn in intestines. These seem to be



important in protection from auto-digestion and/or
bacteria, though recall also that the gut associated
lymphatic tissue is located in the mucosa.
(2) Submucosa
 Denser connective tissue; contains most of the larger
blood vessels.
 In the esophagus and duodenum, the submucosa also
contains glands (in the esophagus and duodenum) that
can be used to localize a histology section (submucosal
glands are only found in those two locations).
 Towards the basal side of the submucosal layer, there
are ganglia called Meissner's plexi (part of the enteric
system, see above).
(3) Muscularis externa/Muscularis propria (same thing)
 Two muscular layers (from inner to outer):
 (a) Circular muscle that constricts the lumen
 (b) Longitudinal muscle that widens the lumen
 In stomach there's an additional, innermost, obliquely
directed layer to aid churning of contents.
 There are enteric ganglia between the circular and
longitudinal muscle layer of the muscularis externa
called Auerbach's plexi.
(4) Adventitia or serosa
 Resists over-expansion of GI tube.
 If it's just connective tissue: called adventitia.
 If it's surrounded by a mesentery (mesothelium): called
serosa.
Upper GI Histology
Monday, October 13, 2008
10:59 AM
Upper GI Histology, 10/13/08:
1. Be able to identify and describe the normal histology of the esophagus including
the epithelial transition at the junction with the stomach.
 There's skeletal muscle in the top half of the esophageal muscularis
externa (sphincter/voluntary control); the rest is smooth muscle
(involuntary).
 Epithelium in the esophagus: stratified squamous.
 Recall that one of the distinguishing features of the esophagus (and
duodenum) is submucosal glands: these produce lubrication in the
esophagus.
 Note that the muscularis mucosa is particularly thick in the esophagus.
 At gastroesophageal junction: see a sharp transition from stratified
squamous to simple columnar epithelium (no gradual transition).
2. Identify and describe the normal histological features of the stomach.
 3 regions:
 Cardiac region at the intake produces mainly mucus to lubricate
the food bolus.

Pyloric region at the exit produces mucus to neutralize the
chyme before it gets to the duodenum. It also produces
gastrin to stimulate HCl secretion from the parietal cells in the
presence of increased pH.
 Body and fundus region (histologically indistinguishable from
each other): what we're mainly interested in here.
 Initially, relaxes (stretches) to allow food entry.
 Upon stretching, a vagal reflex is activated to trigger
rhythmic mixing and churning.
 Histologically, contain shallow pits (as opposed to the
cardiac and pyloric layers, which have deep pits) that
terminate in a narrow isthmus with gland-cell-containing
recesses spreading out beneath. More on these and their
histology in the next LO, but above the isthmus they're
called gastric pits; below that, they're called gastric
glands.
 Recall that there's a special muscular layer in the muscularis externa
of the esophagus called the oblique layer that drives the churning and
mixing.
 Rugae: folds of mucosal and submucosal layers when the stomach is
empty to allow expansion when you eat four pizzas. Also allow greater
surface area to allow for more mucus and acid secretion.
3. Identify and describe the major cell types in the stomach epithelium. What are the
major cell types in the epithelium (as discussed in lecture and lecture notes), how do
they protect themselves from the stomach acid, and what do they produce? What is
the overall effect of the product on the digestive process and what are the clinical
implications of increased or decreased activity of these cells?
 In the pit region (above the isthmus) there's only one cell type:
surface mucus cells. These produce the mucus that lines the stomach
surface and contain lots of mucus granules near the apical surface.
 Note that surface mucus cells have really, really tight junctions
to forbid intracellular proton movement into the deeper layer.
Note further that H. pylori destabilizes these tight junctions.
 The other thing they do is to produce and release bicarbonate
into the mucosal layer. This neutralizes protons that come into
contact with the mucus layer (pH in the apical space: around 2;
pH on the surface of the epithelial cells: 7).
 Even so, cells in the surface epithelium turn over very rapidly
(lifetime of about 3-5 days).
 In the neck region (just below the isthmus) there are several different
types of cells: stem cells, which produce new cells, neck mucus cells,
which produce a slightly more acidic mucus than the surface mucus,
and parietal cells, which produce acid.
 Neck mucus cells: look like champagne glasses with a bunch of
mucus vesicles (olives?).
 Parietal cells: look like fried eggs; eosinophilic due to their very
very high mitochondrial content.
 3 things that activate acid production: hormones (eg.
gastrin), acetylcholine from the PNS, and histamine. All
of these activate G protein-coupled receptors on the
apical surface of parietal cells.
 Recall that carbonic anhydrase facilitates this reaction:
H2O + CO2 <--> H2CO3 <--> H+ + HCO3-. The

bicarbonate (HCO3-) is exchanged for a chloride atom at
the basal side of the cell and thence diffuses into the
blood.
 There's a H+/K+ ATPase pump in the apical surface of
the parietal cell; this extrudes the protons out into the
lumen. Chloride follows.
 Note that when parietal cells are activated, deep folds
(canaliculi) appear in their apical surfaces to increase
the surface area of secretion.
 Notice that intrinsic factor is also produced by parietal
cells. Recall that IF safeguards vitamin B12 (cobalamin)
until it gets to the terminal ileum; dysfunction of parietal
cells (as due to erosion in the stomach) can cause B12
deficiency.
In the base region (below the neck, at the bottom of each glandular
recess), you see chief cells, which produce pepsinogen (these are
more basophilic with a washed-out appearance), and enteroendocrine
cells, which secrete various hormones (of which the most notable is
gastrin, from G cells) into the bloodstream.
 Pepsinogen is cleaved to its active form (pepsin) at pH 1-3.
 Recall that the name of an enzyme that's secreted in an
inactive form and cleaved to become activated under
certain conditions is zymogen.
 Chief cells also produce lipase and, in newborns, a milk clotting
enzyme, rennin.
 Recall that gastrin promotes release of HCl (from parietal cells)
and pepsinogen (from chief cells; it'll be activated by the HCllowered pH).
Lower GI Histology and Accessory Organs
Tuesday, October 14, 2008
7:51 AM
Lower GI Histology and Accessory Organs, 10/14/08:
1. Discuss the functional significance of increased surface area in the small
intestines.
 Maximizes absorption.
 3 mechanisms for this: permanent, spiral folds (the plicae circulares,
increase surface area 2x), villi projections covering the plicae
(increase surface area 10x), and microvilli projections covering the
villi (increase surface area 30-40x).
 Note the distinction between the rugae in the stomach and the plicae
in the small intestine: the rugae are there so that the stomach can
expand, while the plicae are there to increase surface area contact
with the contents.
 Note also that the plicae circulares are particularly pronounced in the
jejeunum, since this is where most of the absorption actually takes
place (the duodenum is more concerned with breaking down and
neutralizing the incoming stomach contents).

Note further that each villus has its own blood and lymph supply. This
is important (since that's where the absorbed nutrients go into the
circulation).
2. Discuss the structure of the intestinal villus in terms of its role in nutrient
absorption.
 As mentioned, it sticks out into the lumen to increase its contact with
nutrients.
 Cell types in the villi:
 (1) Goblet cells (shaped like goblets with a basal nucleus and
apical granules): produce mucus.
 (2) Enterocytes (very distinctive microvilli on apical surface
called the brush border, with delicate lipoproteins coming off
them called the glycocalyx): responsible for the absorption of
nutrients (see following lectures).
 Enterocytes contain, on their brush border, an enzyme
called enterokinase; this cleaves (and activates) trypsin,
a pancreatic peptidase and major activator/cleaver of
other pancreatic pepsidases.
 The brush border also contains lots of other enzymes for
processing fats, carbohydrates, etc. More on this in a
few lectures.
 The point of having all these enzymes here
seems to be to do the final processing of ingested
materials as close to the actual site of absorption
as possible, to deny the intestinal bacteria access
to pre-processed, ready-to-eat peptides and
monosaccharides.
 The glycocalyx and mucosal layer help prevent bacteria
from sticking to the brush border.
 Note that intrinsic factor absorption in the terminal ileum requires
special IF receptors in its epithelial membrane.
 Note also that fat absorption (in chylomicrons) takes place through
large fenestrations (lacteals) in the lymphatic channels in the villi
(chylomicrons are too large to get directly into the capillaries); these
eventually get dumped back into the venous circulation through the
thoracic duct. Again, more on this later.
3. Identify and describe the structure, location and function of Brunner’s Glands.
 Brunner's Glands: submucosal glands (recall that submucosal glands
are found only in the esophagus and duodenum); release a mucosal
alkaline secretion that liquefies and neutralizes the chyme from the
stomach. Their ducts release into the crypts of Lieberkuhn and from
there out into the lumen.
 These glands are particularly numerous in the upper part of
duodenum.
 [Note a handy little table on the bottom of page 8 of these notes describing
regional differences between duodenum, jejeunum, and ileum.]
4. Identify and describe the structure of the crypts of Lieberkuhn. What do cells in
the crypt produce and what is their overall effect on the digestive process and on the
process of epithelial cell turnover?
 Crypts of Lieberkuhn: invaginations from the mucosal layer into the
laminal layer.
 Cell types in the crypts of Lieberkuhn:

Stem cells in the crypts make the cells in the epithelium of the
crypt and also the villi (they migrate up out of the crypt, up to
the tip of the villus, and desquamate off).
 Endocrine cells that secrete cholecystokinin (stimulates
pancreatic enzyme secretion and bile release from gall bladder)
and secretin (stimulates pancreatic fluid and bicarbonate
release).
 Paneth cells (eosinophilic cells): produce lysozyme
(antibacterial) and defensins (positively-charged, amphipathic
small peptides that insert in and destabilize the cell membranes
of bacteria).
 A side note on this: some commensal bacteria promote
Paneth cell development-- they're resistant to the
defensins but they make sure the defensins are secreted
(sort of like burglars who break in and then install
burglar bars, who basically just want to watch your TV
and maybe drink one or two of your beers).
5. Compare and contrast a cross section of a villus with a cross section of a crypt of
Lieberkuhn.
 Villus: Whitish-looking cells (goblet cells) surrounded by fairly uniform
enterocytes in the epithelium; may be able to see the brush border.
Lots of nerves and blood vessels in the middle of the villus.
 Crypt: Highly eosinophilic (defensin) Paneth cells are characteristic;
look for the empty lumen in the middle.
 [Note that in the ileum, you start to see much less plicae folding and more
Peyer's patches:]
o Peyer's patches: contain M cells that take samples of material in the
lumen and transport them to antigen-presenting cells, which in turn
present them to local B cells, which consequently turn into plasma
cells and make IgA, which is then transported into the luminal
surface.
6. Identify and describe the structure of the colon. Compare and contrast the cell
population in a crypt of the small intestine to one of the large intestine.
 Colon: water/mineral absorption; no digestion; lots of commensal
bacteria.
 Note it has an incomplete longitudinal muscular layer (three bands,
the taenia coli). Because of this relatively weak muscularis externa,
the large intestine is more vulnerable to being pushed out from within
(diverticulosis).
 Note there are no villi in the large intestines, only crypts.
 Cell types in large intestinal crypts:
 Goblet cells, as in the villi (but not the crypts) of the small
intestine.
 Stem cells
 Absorptive cells (not enterocytes, since they have no enzymatic
activity).
 A cross-section of a large-intestine crypt cell would show lots
and lots of goblet cells and no Paneth cells (both distinguishing
it from small intestinal crypts).
 Once it gets to the rectum, you transition back from simple columnar
to stratified squamous epithelium.
7. Identify and describe the normal histology of the pancreas and discuss how
enzymes released in their inactive form become activated.

As mentioned, the pancreas produces lots of zymogens that are
activated by trypsin-mediated cleavage, as well as a bicarbonate
solution that liquefies and neutralizes the chyme.
 Histologically, see lots of acini: terminal cul-de-sacs of gland cells
which produce enzymes. Note there are centroacinar cells that secrete
bicarbonate solution into the enzyme solution up at the beginning of
the duct.
 Enzyme-producing cells: Eosinophilic apical surface, basophilic basal
surface. All cells make all pancreatic enzymes.
 Centroacinar cells (bicarbonate-producing cells): lots of granules on
the apical surface.
8. Identify and describe the normal histology of the gallbladder. Compare and
contrast the histology of the gallbladder and the small intestines.
 Gall bladder functions: storage and concentration of bile (bile salts,
bilirubin, cholesterol).
 Grossly, bumpy, rough surface, similar to stomach.
 Histologically, similar to layers of the gut (other than no muscularis
mucosa layer). Cells are simple columnar; epithelium has lots of
microvilli. These cells take up sodium and pump it into the basolateral
region (water follows).
9. Be able to identify and describe the normal histological features of a salivary
gland. Compare and contrast the structure of acini in the salivary gland with those of
the exocrine pancreas.
 As in the pancreas, you see gland cells organized into clusters of acini
(gland cells, contained in a cul-de-sac, that secrete mucus into a duct;
the duct cells in turn secrete serous products that modify the secretion
of the gland cells).
o Mucus-producing cells: washed-out appearance, flattened
nucleus at basal side.
o Serous-producing cells: bigger, more centrally-located nuclei.
o Notice submandibular glands release a mixed serous and
mucosal product (serous cells surrounding mucosal cells).
Sublingual glands are mucus-secreting, while parotid glands are
serous-secreting.
o Specialized smooth muscle cells wrap around acinae
(myoepithelial cells), only in salivary gland cells: contract to
help expel gland contents into the mouth.
 Distinctions between pancreas and salivary glands: the acini of the
salivary glands secrete all the expelled solution, while the acini of the
pancreas secrete the enzyme part of the solution and the centroacinar
cells in the duct add bicarbonate to it.
GI Motility and Regulation
Tuesday, October 14, 2008
9:00 AM
GI Motility and Regulation, 10/14/08:
1. Be able to describe how the neurotransmitter acetylcholine causes contraction of
the smooth muscle cells in the GI tract.

[Ca++ + calmodulin activates myosin light chain kinase, which
phosphorylates myosin and allows actin-myosin cross-bridge cycling
activity.]
 ACh: causes action potentials to fire at each peak of the basic
electrical rhythm (see next LO). Binds to Gq muscarinic receptors and
causes an increase in intracellular calcium.
2. Describe the characteristics of the basic electrical rhythm (BER) of the small
intestine and its relation to smooth muscle contractile activity.
 As described in "Digestive System Overview," the GI tract has
pacemaker cells that create cardiac-like depolarizations of about 15
mV every 5 seconds or so. Most of the time, those depolarizations
don't result in an action potential, but they do provide the "kindling"
for ACh to provoke action potentials at the peak of each
depolarizations. This rhythmic, basal depolarization is called the basic
electrical rhythm.
3. State the stimulus that initiates the swallowing sequence. Identify the point at
which the swallowing sequence becomes automatic (independent of voluntary
control).
 Food enters the pharynx, pushed by the tongue; the soft palate
elevates and the upper constrictor muscle contracts. After this point
everything is automatic.
 Note that respiration is centrally suspended for a couple of seconds
during the swallowing phase.
4. Describe the storage, digestion, and motility roles of the stomach.
 Not sure on this. It stores, it digests, it's motile.
5. Describe the mechanisms which regulate gastric secretion (i.e. the effects of acid,
fat, and solutions of high osmolarity in the duodenum, etc.).
 Acidity and high osmolarity (from the stomach's chyme mixture) in the
duodenum causes increased contraction of the pyloric sphincter (the
duodenum is already full).
 The presence of fat in the duodenum causes release of cholecystokinin
by enteric endocrine cells and, again, a decrease of gastric motility.
 More gastro-centric mechanisms in the next lecture.
6. Describe the origin of the progression of peristaltic waves across the body and
antrum of the stomach. Include their role in mixing and propulsion of gastric
contents.
 The peristaltic waves begin in the mid-stomach after the stomach has
stretched to accommodate the food bolus.
 The funny thing about the stomach is that the peristaltic waves get
faster and stronger and begin to outrun the food bolus. They reach the
pyloric sphincter, and are reflected back towards the body of the
stomach, pushing the bolus back towards the fundus-- churning. This
allows more exposure of the bolus to gastric fluids and also
mechanically breaks it down into smaller particles.
 Note that the stronger the gastric contractions, the more chyme is
forced out through the pyloric sphincter.
7. Contrast the patterns of intestinal motility seen during the absorptive phase
(segmentation) with that of the post-absorptive phase between meals (the migrating
motility complex (MMC)).
 Segmentation: "mixing without net propulsion." That is, everything
contracts around the bolus, squeezing it around in both directions and
pressing it into the surrounding GI tract; then everything relaxes, and
the bolus returns to its original position in the GI tract. The point here
is to absorb more nutrients by increasing the exposure of the bolus to
the absorptive surface of the GI tract, but not to move it along until all
available nutrients have been harvested.
 (note: past the stomach, you don't really have a bolus any
more; it's just chyme or post-chyme. But for ease of discussion
I'm going to still call it a bolus. I'm a born rebel, me.)
 Migratory/peristaltic: once all the nutrients have, in fact, been
harvested, migrating myoelectric motor complexes (MMCs) use
peristaltic (as opposed to segmentation) contractions to move along
the nutrient-exhausted bolus. This process begins about once every 90
minutes (notes also seem to say every two hours) or so-- a long wave
of peristalsis begins in the stomach, travels all the way down to the
end of the ileum, and then begins again in the stomach. In each GI
region it takes about 10-15 minutes to go through (about 40 cm of the
GI tract is involved at any given time)-- hence the long time taken to
travel to the terminal ileum. Note that MMCs shouldn't originate during
or immediately following meals.
8. Contrast the colonic motor activity during a “mass movement” with that during
haustral shuttling and the consequence of each type of colonic motility.
 Haustra: pouches of large intestine that result from the fact that the
three taenia coli (longitudinal bands in the muscularis externa) are
shorter than the rest of the colon, causing bunching.
 At least that's what Wiki implies. The notes seem to indicate
that the segmentation contractions are what form the haustra.
 Dr. Michaels on this seeming discrepancy: "Both are correct on
some level, James. The taenia are shorter than the colon so
they do contribute to the haustra 'pouches'....and you see this
even in the anatomy lab cadavers (i.e. when there is no
segmentation...).....so anatomically, that’s probably the best
answer. I think Dr. G means that when you have segmentation
in the colon, haustra become more prominent and during mass
movement, the haustra become far less prominent (it’s a
noticeable difference during imaging!)."
 The segmentation process is particularly pronounced in the large
intestine. These segmentation processes, during which contents can
shift back and forth between one haustra and another, are called
haustral shuttling. By contrast, the mass movements are peculiar to
the large intestine and involve a intense, prolonged peristaltic
contraction.
 Notes say that "the most prominent patterns of motility" are
segmentation, while the mass movements are responsible for "forward
propulsions." Take it for what it's worth.
9. Describe the sequence of events occurring during reflexive defecation,
differentiating those movements under voluntary control and those under intrinsic
control.
 The mass movements just described push fecal material into the
rectum, stretching it and initiating the defecation reflex (relaxes the
internal sphincter). This can be controlled by voluntary contraction of
the external sphincter.
 Note that this generally occurs right after a meal (need to clear out the
old stuff to make room for the new).
GI Secretion and Digestion
Tuesday, October 14, 2008
9:58 AM
GI Secretion and Digestion, 10/14/08:
1. Describe the mechanism of gastric acid generation and secretion, including the
role of K+, Cl /HCO3, carbonic anhydrase and H+-K+ ATPase.
 As mentioned in "Upper GI Histology," carbonic anhydrase facilitates
the conversion of CO2 (from the blood) and H2O to HCO3- and H+. The
H-K ATPase pumps H+ out and K+ in from the apical surface. HCO3- is
expelled from the basal side of the cell in exchange for Cl - uptake; the
Cl- follows the H+ out the apical surface.
 Note that H2O follows H+ and Cl-, leading to a efflux of water into the
lumen of the stomach.
 Note also that the blood leaving the parietal cell is basic (high pH) due
to the basal efflux of HCO3-.
 Note further that luminal K+ depletion can occur near the apical H/K
ATPase pumps. Thus you have potassium channels in the apical
surface to allow K+ to maintain a sufficient level to allow the pump to
function. Note that this is kind of like spilling your drink (K+ release)
on someone you like, in order to clean it up (K+ uptake), because
that's the only way you know how to start a conversation with them
(H+ intake). Yeah, the parietal cells are kind of desperate.
 Note, finally, that the secretion of H+ is more of a spurt than a trickle,
to clear the surrounding mucosa. The muscularis mucosa contracts
around the crypts to do this.
2. Describe how the three acid secretagogues induce acid secretion by parietal cells.
 "Secretagogues" (which is now the leading contender for the name of
my firstborn):
 (1) ACh
 Binds to Gq muscarinic receptors and causes an increase
in intracellular Ca++. This causes increased activity of
protein kinase C.
 (2) Gastrin
 Causes an increase of intracellular Ca++ (mechanism
not clear). Likewise, increased PKC activity.
 Recall gastrin also stimulates chief cells to release
pepsinogen.
 (3) Histamine
 Binds to a different G protein-coupled receptor (the Gs
histamine H2 receptor) to increase adenylyl cyclase,
increasing cAMP levels-- this causes increased protein
kinase A activity.
 The point of all this is that the increased PKA/PKC activity
phosphorylates the H/K ATPase pumps, increasing their activity
to increase proton efflux (and, by Le Chatelier, increasing the
rate of water/CO2 breakdown).
 Note that the abovementioned pathways are all called the direct
pathway of acid secretion stimulation. The indirect pathway, then, is
when ACh and gastrin stimulate "enterochromaffin-like" (ECL) cells to
secrete histamine (which in turn acts directly). This seems to be the
major route for gastrin to affect H+ secretion.
3. Describe the modulation of gastric acid secretion throughout the day and night.
 The rate of acid secretion follows a circadian rhythm, regardless of
food intake.
 It's highest in the evening and lowest in the morning.
 Smelling, looking at, or tasting food initiates a vagal nerve reflex
(cephalic phase), which releases ACh and gastrin (and thus
histamine), and inhibit somatostatin release (somatostatins block
cAMP formation).
 Entry of food into the stomach (gastric phase) distends the gastric
mucosa, which stimulates another vagal reflex with much the same
consequences. Partially digested proteins also stimulate gastrinreleasing cells in the stomach and also in the duodenum (gastric and
intestinal phases, respectively)
 Not sure if it's important, but the percent of total acid secretion from
each of the cephalic, gastric, and intestinal phases is 30%, 60%, and
10% respectively.
4. Describe the protective barrier of the gastric surface.
 What you're looking to protect yourself against: pepsin (proteolytic
enzyme) and acid.
 Recall that mucus infused with bicarbonate coats the entirety of the
stomach mucosa. Recall also that there's something like a 6.4 pH
gradient (ie. 10^6.4 = about a 2.5-million fold concentration
difference) between the lumen of the stomach (pH 1) and the blood
beneath the cell (pH 7.4) due to this bicarb in the mucosa.
 So much for the acid. As for pepsin, it doesn't function above pH about
5 or so-- thus by the time the pepsin gets to the surface of the cell,
the ambient pH is high enough that it doesn't autodigest the stomach
epithelium.
 Note, however, that this mucus-bicarb layer would prevent HCl from
getting out into the lumen if the HCl was passively secreted. As
mentioned, what happens is that the HCl is not just secreted but
squirted out into the lumen (contraction of the muscularis mucosa by
the parietal cells)-- this gets it clear of the mucus/bicarb solution and
out into the lumen.
5. Discuss possible targets of the current generation of ulcer drugs.
 Essentially you're looking to stop acid secretion. You can do this by
blocking the H/K ATPase pumps (proton pump inhibitors) or by
blocking the activators of the H/K pumps (antimuscarinics,
anticholinergics).
 [Functions of the stomach: motor, secretory, endocrine.]
 [Secretory products of the stomach: HCl, pepsinogen, mucin, HCO 3-, intrinsic
factor, and water.]
GI Digestion and Absorption
Tuesday, October 14, 2008
10:34 AM
GI Digestion and Absorption, 10/14/08:
1. Describe the role, if any, of HCl in the gastric digestion of carbohydrates, proteins
and fats.
 Proteolytic enzymes like pepsin are activated (from pepsinogen) by
low pH (HCl). Low pH also denatures proteins and exposes their
cleavage sites to pepsin. HCl contributes to the breakdown of all food
to some degree, but the great majority of the breakdown of
carbohydrates and fats occurs due to salivary and duodenal/pancreatic
enzymes.
 Note that intrinsic factor is the only indispensable secretion of the
stomach (can do pretty well without HCl or pepsin).
2. List the chemical classes of the carbohydrates entering the duodenum from the
stomach, and identify mechanisms mediating further digestion and absorption across
the apical and basolateral membranes of the intestinal epithelia. Include pancreatic
secretions and brush-border enzymes.
 [A couple introductory notes will make the section on carb digestion
much easier.]
o Most dietary carbohydrates are composed of plant starch of
amylopectin, a poly-glucose saccharide in which adjacent
glucose molecules can be linked by either or both of alpha-1,6
bonds and alpha-1,4 bonds.
o Alpha-limit dextrin is amylopectin in which most of the 1,4
bonds have been broken (so there's two or three 1,4-linked
glucose molecules that are tagged through a 1,6 link to two or
three other 1,4-linked glucose molecules).
o Maltose is two 1,4-linked glucose molecules. Maltotriose is
three 1,4-linked glucose molecules.
 Classes of carbohydrate coming in:
 Plant starch, or amylopectin (the main carbohydrate in most
human diets): contains both alpha-1,4 and alpha-1,6 glucose
linkage bonds.
 Cellulose: contains beta-1,4 linkages, thus it passes through
the GI tract undigested, as dietary fiber.
 Enzymes and stuff in the lumen of the duodenum:
 Alpha-amylase (breaks alpha-1,4 bonds) from the salivary
glands and also the pancreas
1. Since alpha-1,6 glucose linkages are not digested by
amylase, amylase never produces free glucose (it tends
to produce alpha-dextrin).
 HCl and pepsin from the stomach
 About 30 zymogens from the pancreas including trypsinogen
 Bile salts and bile acids from the liver
 HCO3- from all over
 Enzymes on the brush-border:
 Sucrase-isomaltase (breaks alpha-1,6 glucose bonds to get
maltose and/or maltotriose)
 Maltase-glucoamylase (breaks down maltotriose and maltose to
glucose)
 Lactase (breaks down lactose to glucose and galactose)
 Sucrase (breaks down sucrose to glucose and fructose)
 So around the brush border, you're getting things boiled down to
individual glucose, fructose, and galactose molecules
(monosaccharides).

The monosaccharides are then absorbed by the enterocytes in the
following manner:
 Na+-glucose cotransporter functions along the sodium gradient
created by Na/K ATPase pumps on the basal membrane. Cotransporter = SGLT1.
 Same thing with galactose (cotransport with sodium down its
gradient).
 Fructose can enter independently of the sodium intake
(transporter = GLUT5); thus if an infant has no working SGLT1
transporters, can avoid malnutrition by a fructose diet.
 All three monosaccharides are transported out the basal side of the
cell by the same transporter (GLUT2) and go into the capillary system.
3. Predict the small intestine and colonic consequence of a deficiency in the enzyme
lactase, and identify age groups who commonly exhibit this deficiency.
 Can't digest milk sugar (lactose). Unabsorbed lactose draws water
back into the intestinal lumen by osmosis, causing diarrhea. Colonic
bacteria also metabolize the lactose, creating byproducts of methane,
CO2, etc-- pain, bloating, etc. This mainly shows up in older
populations.
 [Note SGLT1 deficiency also causes osmotic diarrhea.]
4. State the mechanism for activating pepsinogen, and describe the digestion
products of pepsin activity.
 As mentioned, pepsinogen is cleaved and activated by low pH due to
HCl secretion.
 It's an endopeptidase (see below) that cleaves next to aromatic amino
acid residues-- so its digestion products are smaller peptides, like any
peptidase.
 It's not essential for normal protein digestion.
5. List the chemical classes of the proteins entering the duodenum from the
stomach, and identify mechanisms mediating further digestion and absorption across
the apical and basolateral membranes of the intestinal epithelia. Include pancreatic
secretions and brush-border enzymes.
 Chemical classes of the proteins: I wouldn't know where to begin.
They're proteins.
 Digestion begins in the stomach with pepsin.
 Digestion: In the duodenum, recall that the brush border consists
largely of enterocytes, which secrete enteropeptidase-- which converts
trypsinogen to trypsin. Trypsin, in turn, activates all the other secreted
zymogens (including other trypsinogens), which are all proteolytic.
 Note, however, that there are two distinct classes of peptidases
(ie. proteolytic enzymes): endopeptidases and exopeptidases.
Endopeptidases, as the name implies, cleave amino acid
linkages within proteins (between two non-terminal residues).
Exopeptidases cleave off the last amino acid residue from either
the C- or N-terminus of the protein.
 Endopeptidases (all are secreted by the pancreas in zymogen
form):
 Pepsin (cleaves next to aromatic amino acids)
 Trypsin (cleaves arginine-lysine linkages)
 Chymotrypsin (cleaves next to aromatic amino acids)
 Elastase (cleaves next to small, hydrophobic amino
acids)
 Exopeptidases:
Carboxypeptidases A and B target the C terminus and
are secreted by the pancreas.
 Aminopeptidases target the N-terminus and are
contained in the brush border.
 How this works:
 The secreted peptidases in the lumen of the duodenum digest
ingested proteins to small oligopeptides.
 At the brush border, aminopeptidases (and a few others)
further digest the oligopeptides into single amino acids or the
di- and tripeptides are absorbed intact.
 Eventually, the pancreatic enzymes digest themselves and each
other (so that they don't act on the walls of the intestine all the
way down).
 Absorption:
 PePT1 transporter co-transports di- and tripeptides into the cell
along with H+ down the H+ gradient (the H+ concentration
inside the cell is kept low by an adjacent apical Na/H
transporter). From there they're digested to single amino acids
in the cytoplasm.
 Single-amino-acid transporters can generally be grouped by
whether they transport neutral, basic, acidic, or proline/glycine
amino acids. They're all co-transporters with Na+.
 Cytoplasmic single amino acids follow their concentration
gradients out the basal side of the cell and are absorbed by the
capillaries.
6. Contrast the secondary active transport of amino acids with that of di- and tripeptides, including the ion used as the energy source.
 Amino acids: co-transport with Na+. Di- and tripeptides: co-transport
with H+.
7. List the chemical classes of the lipids entering the duodenum from the stomach,
and identify mechanisms mediating further digestion and absorption across the
apical and basolateral membranes of the intestinal epithelia. Include the roles of
pancreatic lipase, colipase, and micelles.
 Classes: the most important dietary lipid is triglycerides (glycerol with
three ester bonds to fatty acids). These are way, way too big and
lipidey to get into the intestinal cells. Here's how we work around it.
 First, triglyceride droplets (separated out by mastication and stomachchurning) are emulsified by bile salts and lecithin to form
microparticles (~1 micron in diameter).
 Next, lipase anchors to the surface of the fatty microparticles (with the
help of colipase) and digests them into monoglycerides and fatty acids.
These are small enough to actually take into the cell, but they're still
too hydrophobic to travel in the fluid of the lumen.
 So next, the monoglycerides and fatty acids are solubilized in bile salts
to form micelles (like soap foam: hydrophilic outside, hydrophobic
inside). The micelles can be transported to the brush border. When
they get there, the lipids diffuse out and through the brush border
membrane (lipid-emptied bile salt micelles return to the lumen to pick
up more lipids).
 Inside the enterocytes, the triglycerides - which have just been
laboriously broken down into monoglycerides and fatty acids - are now
reassembled into triglycerides again. Then they're packaged into
lipoproteins called chylomicrons (remember these from CVPR?) and

migrate out into the lacteals and thence into the lymphatic system
(see "Lower GI Histology and Accessory Organs"), and from there gets
dumped back into the venous circulation, whence to the liver.
 Again, if fat can't be absorbed from the lumen of the intestine, it pulls
water back with it, causing fatty diarrhea (which sounds like a ton of
fun, let me tell you). Fatty stool is called steatorrhea and is a
hallmark of fat malabsorption. Naturally, if you've got steatorrhea,
your absorption of the ADEK fat-soluble vitamins is going to be pretty
poor.
8. Describe the composition and formation of chylomicrons, their movement across
the enterocyte basolateral membrane, and the route of entry into the cardiovascular
system.
 See above and CVPR notes ("Lipids, Lipoproteins, and Atherosclerosis I
+ II;" specifically, apoB48 units are packaged into chylomicron
backbones).
9. Define steatorrhea, and predict the effects of steatorrhea on the absorption of fatsoluble vitamins.
 See above.
10. Describe the absorption of water-soluble vitamins, including the role of intrinsic
factor in the absorption of vitamin B12.
 Water-soluble vitamins are absorbed either by co-transport with Na+
or passive diffusion. This all takes place in the upper small intestine.
 Note the exception of cobalamin, which is bound to IF in the stomach
and reabsorbed by a special transport receptor in the terminal ileum.
11. Describe the pathways, if any, by which Na ions and water are absorbed in the
small intestine and colon.
 In the small intestine, the Na+ is absorbed down its concentration
gradient (driven by Na/K ATPase pumps in the basal membrane) and
the water follows. There's also an apical Na/H exchanger (mentioned
above in the section on amino acid absorption).
 In the colon, there are also apical sodium channels that are down- or
up-regulated in response to plasma aldosterone increases and
decreases, respectively. Note that increased Na absorption through
this route means more K secretion into the lumen.
Diseases of the Upper GI: Pathology of the Esophagus
Wednesday, October 15, 2008
8:02 AM
Diseases of the Upper GI: Pathology of the Esophagus, 10/15/08:
[For those like myself who had no idea what "H+E stain" meant: it stands for
hematoxylin and eosin stain.]
1. Define Mallory-Weiss tear and explain its relevance in alcoholic patients.
 Mallory-Weiss tear: repeated retching causes an increase in
esophageal pressure, resulting in a small tear of variable depth down
by the gastroesophageal junction.

Alcoholics, obviously, retch a fair amount. M-W tears can also cause
esophageal varices (which result with some frequency from alcoholic
liver cirrhosis) to tear open.
 [Note the distinction in depth between Mallory-Weiss tears and
Boerhaave Syndrome (full-depth perforation of esophagus).]
2. Define achalasia.
 Achalasia: Motility disorder, mainly due to degenerative neural
changes-- upper sphincter of the esophagus can't relax after
swallowing.
 Note that Dr. Peterson discusses achalasia in terms of the
lower, not upper, sphincter.
 Achalasia can result from Chagas disease (parasitic disease
around Amazon basin), which I actually saw quite a bit of this
summer. If you ever head down to Bolivia it's all over the place
and is a leading cause of heart failure (dilated cardiomyopathy).
3. List the two most common classes of esophagitis and three etiologies within each
class.
 Non-infectious esophagitis:
 Chemical injury (acid, lye, detergent)-- scar, form strictures.
 Pill esophagitis: alendronate (Fosamax), quinidine, potassium
chloride, etc, can get stuck in the esophagus and release their
contents there, causing ulcerations. Tends to occur where the
aortic arch compresses the esophagus or in the lower
esophageal sphincter. Patients not taking enough fluid with pills
can be a cause.
 Reflux:
 GERD is the most common type of esophagitis.
 Note that obesity can cause poor functioning of the
lower esophageal sphincter, as can caffeine, CNS
depressants, tobacco, nasogastric tubes, etc.
 Radiation injury (particularly in radiation therapy to the chest)
 Thermal injury
 Some anti-cancer drugs
 Infectious esophagitis: (more common, as you would expect, in
immunocompromised or elderly)
 There's no evidence of bacterial involvement in esophageal
ulcers (as opposed to gastric ulcers, where they're the main
players).
 Fungal: frequently due to Candida infection (classic for AIDS),
Aspergillus, histoplasmosis, or blastomycosis (all mainly in
immunocompromised patients).
 Viral:
 Mainly due to a herpes simplex virus (which infects
squamous epithelium) or a cytomegalovirus (which
infects endothelial cells in blood vessels and glandular
epithelium). Sometimes direct HIV infection.
4. List the four histologic features of "non-specific" esophagitis as well as the
microscopic findings that indicate specific diagnoses (reflux, also called GERD, or
viral or fungal disease).
 Histologic features of non-specific esophagitis: mixed inflammatory
infiltrate; inflammation-reactive epithelium.
 Histology of GERD:

basal epithelial cells undergo hyperplasia, aka reflux-associated
squamous hyperplasia (RASH).
 Also see mixed inflammatory infiltrate with PMNs and,
especially, eosinophils.
 Also get elongation of the fibrovascular papillae of the lamina
propria.
 Note that GERD can cause metaplasia to a columnar epithelium.
More on this later.
 Histology of fungal esophagitis: Candida shows up as
yeast/pseudohyphae forms; use PAS-D (Periodic Acid-Schiff diastase
stain) and GMS (a silver stain) to detect.
 Histology of viral esophagitis:
 Herpes infection causes multinucleation of infected cells-- look
also for an eosinophilic nuclear inclusion. Sample the edges of
the ulcer (living part), not the middle (dead part).
 CMV infection causes increase in cell size (cytomegaly). Also
look for both eosinophilic nuclear inclusions and basophilic
cytoplasmic inclusions.
 [HIV infection causes multiple small thrush-like lesions early;
later it can cause necrosis of squamous cells, leading to ulcers
and fistulas.]
5. Define Barrett esophagus and describe the most dangerous form. State how this
form is recognized microscopically.
 Barrett esophagus: metaplastic changes of squamous epithelium to
columnar. 2 types:
 Cardiac-type epithelium: distal 2-3 cm of esophagus looks like
columnar cells without goblet cells (as in the cardiac region of
the stomach). Note this may not actually be Barrett esophagus
(could just be the normal boundary of the stomach with the
esophagus).
 Small-intestinal epithelium: distal 2-3 cm of the esophagus
looks like columnar cells with goblet cells. This second form is
more predisposed to dysplasia and is hence more dangerous.
 Microscopically, you look for columnar epithelium with
goblet cells.
 Risk of progression to adenocarcinoma seems to
increase the farther up it projects from the
gastroesophageal junction.
 Grossly, looks like a salmon-pink patch of esophagus down by the
junction on endoscopy. But note that it's a diagnosis that can only be
made histologically.
 10% of patients with GERD acquire Barrett esophagus; 10% of those
develop adenocarcinoma of the esophagus.
6. List the five classifications (with respect to premalignant changes) that should be
used to describe Barrett esophagus. Describe in general terms how these classes of
changes are related to each other.
 [Nuclear abnormalities: most important prognostically is stratification;
look for variation in size and shape, increased nuclear:cytoplasmic
ratio, loss of goblet cells, etc.]
 (1) Negative for dysplasia: inflammatory-reactive changes only.
 (2) Indeterminate for dysplasia: hard to tell if it's dysplasia or
inflammation reaction.

(3) Low-grade dysplasia: retention of goblet cells, still has mucin;
some nuclear crowding.
 (4) High-grade dysplasia: less goblet cells, some mucin but much less.
Increased stratification, nuclear changes.
 (5) Carcinoma (in situ, not yet breaking through the basement
membrane, or invasive, in which it's already broken through the
basement membrane): FUBARed cells. You know.
7. List the two common types of esophageal carcinoma and state the commonly
associated or predisposing conditions for each type. Describe how the incidence of
these tumors has been changing over recent decades.
 Squamous cell carcinoma: dysplasia arising from tobacco or alcohol
use. More likely to be in the middle esophagus.
 Increased risk: Plummer-Vinson syndrome (congenital
esophageal webs) and hyperkeratosis in acral skin.
 Adenocarcinoma: Dysplasia arising from Barrett's esophagus. More
likely to be in the lower esophagus.
 Esophageal adenocarcinoma is the cancer with the most rapidly
increasing incidence in the US (GERD from obesity = one proposed
reason).
 Survival rates for both types at 5 years is poor, around 30%; most
patients present with metastatic, highly invasive disease states.
 Clinically, look for progressive dysphagia.
Diseases of the Upper GI: Pathology of the Stomach and
Small Bowel
Wednesday, October 15, 2008
8:55 AM
Diseases of the Upper GI: Pathology of the Stomach and Small Bowel,
10/15/08:
1. State the difference between erosion and ulcer in microscopic terms.
 Erosion: destroys the superficial mucosa (epithelium, lamina propria)
but not the muscularis mucosa or deeper layers.
 Ulcer: all mucosa (including muscularis mucosa) has been destroyed;
injury extends into the layers beneath.
2. Define acute gastritis and describe its microscopic appearance. List two main
classes of etiologically associated factors.
 Acute gastritis: As might be surmised from the name, rapid-onset
gastritis. Histologically, look for mucosal edema, intramucosal
hemorrhage, and some degree of erosion.
 Etiologically, think chemical (NSAIDs, EtOH, tobacco, chemotherapy,
bile reflux) or stress (due to infection, trauma, surgery, or shock)-things that destroy the protective mucus coating in the stomach.
 Note that NSAID-induced injury is more complicated than these
notes would suggest, on account of prostaglandins do quite a
number of things in the stomach. More on this later, but I think
you can classify NSAID injury into both an acute and a chronic
phase.
3. State the relationship between acute gastritis and chemical gastropathy, and the
principal difference in their microscopic appearances.

Chemical gastropathy: as mentioned, a subtype of acute gastritis
caused by various chemicals.
 Principal difference: in chemical gastropathy, the pits in the gastric
epithelium become hyperplastic (possibly to increase protective mucus
secretion?).
4. Define chronic gastritis and list the two most important forms. State the
underlying etiology of these two forms.
 Chronic gastritis isn't just a chronic form of acute gastritis-- there's a
different underlying pathology.
 Both acute and chronic gastritis destroy the mucus-producing cells in
the gastric pits. The difference is that in acute gastritis, the cells can
recover or be replaced, while in chronic gastritis, the cells never
regenerate (and thus progression to ulceration and perforation is more
common).
 Histologically in chronic gastritis, look for an infiltration of the lamina
propria with plasma cells and lymphocytes, with or without
neutrophils. Also look for atrophy of the mucus glands and pits (in the
antrum/pylorus), and parietal cells (in the body/fundus).
 Note the contrast: in chemical acute gastritis, you look for
epithelial hyperplasia in order to secrete more mucus; in
chronic gastritis, you look for epithelial atrophy instead.
 Type A chronic gastritis: autoimmune etiology.
 Loss of parietal cells due to autoantibodies
 Less common (10%)
 Watch out for B12 malabsorption (no IF)
 Increased rate of adenocarcinoma/carcinoma of neuroendocrine
cells
 Mainly targets body and fundus of stomach.
 Type B chronic gastritis: mainly infectious; "active" gastritis (PMN
infiltration) or follicular with lymphocyte germinal centers.
 Main etiology is Helicobacter pylori, which burrows into the
gastric mucosa.
 More common (90%)
 H. pylori produces ammonia, raising the pH in the stomach.
 Look for peptic ulcers; also MALT lymphoma (can be resolved
with antibiotics).
 Mainly targets antrum and pylorus of stomach.
 [Dr. Peterson: all atrophic (chronic) gastritis is due to H. pylori,
autoantibody- and infectious mechanisms alike. Where this leaves
Crohn's disease gastritis is sort of up in the air.]
 [Note that most gastritis is asymptomatic most of the time.]
5. Describe the histological appearance of active gastritis, atrophy and intestinal
metaplasia.
 "Active" gastritis: neutrophils in the epithelium.
 Atrophy: loss of parietal cells (type A) or mucus glands/pits (type B)
 Intestinal metaplasia: makes the stomach epithelium look either like
the small intestine (complete) or colon (incomplete).
6. List six special types of gastritis that can be recognized histologically.
 Sarcoidosis, Crohn's disease, amyloidosis, eosinophilic, lymphocytic,
graft-vs-host.
7. List four mechanisms that protect the gastric mucosa from ulceration.
 (1) Mucus (surface mucus cells in pits)
 (2) Bicarbonate (also surface mucus cells in pits)


(3) Tight junctions between epithelial cells
(4) Mucosal blood flow (under prostaglandin control, thus the influence
of NSAIDS) to wash away acid that makes it through the tight
junctions
 [(5) The notes also mention the rapid turnover rate of these cells.]
8. List four clinical factors that predispose to ulcer formation.
 (1) Helicobacter infection (about 90%)
 (2) NSAID use (about 10%, although lots of comorbidity with H. pylori
infection)
 (3) Tobacco/EtOH
 (4) Alcoholic cirrhosis
 (5) Corticosteroid use.
9. Compare and contrast the epidemiologic trends, predisposing factors, and
histologic features of the two common variants of gastric carcinoma.
 3% of all cancer mortality.
 Associated with EtOH, tobacco, and certain diets (common in Japan).
 Two histological types of gastric carcinoma:
 Diffuse type: poorly differentiated ("signet ring") cells; usually
found in younger patients; some familial forms (associated with
cadherin mutations).
 Intestinal type: atrophy with intestinal metaplasia.
Adenocarcinoma cells look like colonic adenocarcinoma.
 Intestinal type has gotten less common; diffuse type has stayed about
constant.
10. Compare and contrast the clinical and histologic features that allow
differentiation of the three hypertrophic gastropathy syndromes.
 Hypertrophic gastropathies: easily mistaken for carcinoma; see
prominent rugal folds and thickening of the gastric wall.
 Zollinger-Ellison syndrome:
 High serum gastrin levels (neuroendocrine tumor) leads
to hyperplastic parietal cells, creating high HCl
concentration in lumen.
 Note there seems to be some disagreement about where
these gastrinomas are actually located; the one thing
that seems reasonably sure is that they're not in the
stomach itself. They're in either the pancreas or
duodenum, from which they release gastrin into the
circulation; the circulating gastrin then goes back to the
stomach and causes increased acid secretion.
 High risk of peptic ulcers, but in distal duodenum only.
 Hypertrophic-hypersecretory gastropathy:
 Idiopathic (no high gastrin), but still get hyperplastic
parietal cells, creating high HCl concentrations in the
lumen.
 High risk of peptic ulcer.
 Menetrier disease:
 Hyperplasia of mucus-producing cells in pits of stomach;
no increase in parietal cells or HCl levels.
 No risk of peptic ulcer.
11. List the two common histologic patterns of small bowel mucosa in patients with
symptomatic malabsorption and give at least three examples associated with
each pattern.

Villous blunting: short, stunted villi. Mainly caused by autoimmune
disorders (eg. celiac disease) reacting to either gluten or the
transporters that bind to gluten. Malabsorption and diarrhea stops with
a gluten-free diet. Can also be caused by viral infections in kids,
"tropical sprue" (the other leading contender for name of my
firstborn), "non-tropical sprue," or T-cell lymphomas. For celiac
disease, look for T cell infiltration in villi.
 Villous distention: long, spindly villi. Caused by:
 Dilated lymphatics (lymphangiectasia): either a congenital
disorder (primary) or acquired by lymphatic obstruction
(tumors, sarcoidosis, fibrosis).
 Macrophage accumulation in villi:
 Whipple disease: macrophage infection with an
intracellular bacterium (Tropheryma whippelli). Also
seen in joints and CNS. Can be addressed by antibiotics.
 In immunocompromised: Mycobacterium aviumintracellulare infection (MAI). Use PAS (Periodic acidSchiff) and acid-fast stains to distinguish from Whipple's.
12. Describe the two common immune reactions that underlie gluten enteropathy.
State what features of gluten peptides influence immunogenicity and deduce which
grains would be appropriate to recommend to patients with this condition.
 As mentioned, reactions against either gluten or the gluten
transporters in the villi.
 Intensity of immune reaction correlates with basic-amino-acid content:
wheat is highest, then rye, barley, and oats. Recommend oats, I
guess. This is weird.
13. Describe an appropriate histochemical evaluation to differentiate Whipple's
disease from Mycobacterium avium-intercellulare infection.
 As mentioned, PAS and acid-fast to distinguish.
 Note that a quick Internet search seems to indicate that both MAI and
Whipple's stain positive for PAS, but only MAI will be positive for the
acid-fast stain. Maybe you use them both, PAS to make sure you're in
the right ballpark and acid-fast to distinguish.
14. List two histologic variants of gastrointestinal stromal tumors and describe the
features that allow differentiation of benign and malignant forms.
 GIST (gastrointestinal stromal tumors): generally arise from overexpression of a tyrosine kinase (CD117). Note this, like CML, is also
treated with Gleevec.
 Types: can have either predominantly spindle cells or predominantly
epithelioid cells. Epithelioid are slightly worse prognostic markers.
 Benign vs malignant depends on the size and number of tumors and
the mitotic/dysplastic features on histology.
Diseases of the Upper GI: Stomach and Duodenum, Part I
Wednesday, October 15, 2008
9:59 AM
Diseases of the Upper GI: Stomach and Duodenum, Part I
[Good to look at slides for this-- lots and lots of material not covered by these LOs.]

Note that dysphagia for solids is usually an obstruction. Dysphagia for liquids
is usually a motility disorder.
1. Given a patient with esophageal symptoms and esophageal manometry, be able
to diagnose systemic sclerosis, achalasia, and gastroesophageal reflux (GER).
 Manometry: catheter placed into the esophagus; measures pressure at
various points.
 Systemic sclerosis (like scleroderma)-- fibrosis leads to destruction of
smooth muscle: no peristaltic pressure in esophagus; weak or absent
lower esophageal sphincter pressure (which can lead to GERD).
 Achalasia (incomplete relaxation of the lower esophageal sphincter due
to degeneration of inhibitory vagal neurons in the esophageal wall).
Often see low levels of peristaltic pressure and inability to relax LES
(high pressure at base).
 GERD: note that it's not just acid; pepsin, bile, and pancreatic
enzymes reflux as well. The lower esophageal sphincter pressure
either is uniformly weak or relaxes at inappropriate times (transient
lower sphincter relaxations or TLSRs).
 Note that we don't really have drugs that target TLSRs
themselves-- instead we target the contents of the stomach to
make the reflux less harmful.
2. List the four major structural complications of GER.
 (1) Esophagitis
 (2) Stricture (scarring-- much less common now due to ready access
to anti-acid-secretion meds)
 (3) Barrett's esophagus
 (4) Mucosal rings (ie. Schatski's rings or B rings: weblike obstructions
in esophagus)
 [Maybe less common but important:]
 Dental erosions
 Asthma and alveolar injury from aspiration of reflux contents
 Laryngitis and vocal cord injury
3. Compare and contrast the two types of esophageal cancer.
 Squamous-cell vs. adenocarcinoma: for pathology, see 2 lectures
back.
 Squamous: especially common in Asian/African ancestry. Other
risk factors: cigarettes, EtOH, salty/spiced foods, low vitamin
A/C, Mg, Se, Zn. In relative decline but still prevalent.
 Adenocarcinoma: especially common in fat white dudes with
GERD. Increased incidence lately, probably due to increase in
obesity/GERD.
 In general, both types have high mortality and are much more
common in men.
 [MMCs begin in 'pacemaker' cells in stomach (not to be confused with the
basic electric tone pacemaker activity) every 90 minutes or so in the unfed
state.]
 [Note duodenal reflexes that slow down gastric emptying: decrease in pH,
increase in osmolality, increase in fat and caloric content; also viral enteritis.
Note that by slowing gastric emptying, these can produce vomiting if the
stomach becomes overly distended.]
4. List the three major stimuli and two major inhibitors of parietal cell acid secretion
and their role in normal gastric physiology.
 Stimuli:




(1) Gastrin (from enteroendocrine cells in pits)
(2) Histamine (mainly from ECF cells)
(3) Acetylcholine (from vagus)
Recall that gastrin and ACh stimulate histamine production by
ECL cells. This seems to be their main mechanism of acid
secretion stimulation; histamine is the major direct stimulator
of parietal cells.
 Note that parietal cells, when activated by these stimuli, open
up canaliculi to increase their surface area available for
excretion.
 Physiological inhibitors:
 Somatostatins (somatostatin production is inhibited by ACh).
 Prostaglandins also prevent acid secretion. This is why NSAIDs
can be bad for gastric business.
 Note that prostaglandins also increase mucosal blood
flow and mucus/bicarbonate secretion (three other
reasons why NSAIDs are trouble for the stomach). More
on this in the next lecture.
 Note also that protons have a negative feedback effect on
gastrin secretion-- when there's lots of acid, the gastrin
secretion rate goes down, and when there's not much acid, the
gastrin secretion rate goes up. This is the basis for the
development of gastric tolerance to antihistamines (see "Upper
GI Pharmacology").
 [Note advanced age, of itself, has no effect on acid secretion rates.]
5. Describe how cobalamin is absorbed.
 Recall that intrinsic factor is secreted by the parietal cells in the necks
of gastric pits.
 Cobalamin is isolated from ingested food by acid and pepsin in the
stomach.
 In the saliva there's something called R factor- this binds to
cobalamin once it's isolated in the stomach.
 R factor is split off from the B12 by pancreatic enzymes in the
duodenum; at this point, the IF binds to it and allows it to be taken up
in the terminal ileum.
 To repeat: R factor is secreted in saliva but doesn't bind B12 till the
stomach; IF is secreted in the stomach but doesn't bind B12 til the
duodenum. The entire normal pathway requires adequate supply of
B12, normal salivation, normal parietal cells, normal pancreatic
enzyme release, and normal IF receptors.
 Note that inadequate dietary B12 is extremely uncommon.
 Failure to absorb cobalamin can also result from small bowel bacterial
overgrowth or ileal disease.
 Note that, evidently, proton pump inhibitors can cause diminished B12
absorption due to diminished B12 isolation (secondary to decreased
acid secretion), though perhaps not enough to make a clinical longterm difference.
 Recall Schilling test from Blood and Lymph ("Under-Production
Anemias").
 [Note that gastritis, as a diagnosis, can only be made histologically.]
o Classes of gastritis as told by Dr. Peterson: infectious, lymphocytic,
eosinophilic, systemic-disease-associated.
o Note, again, that most gastritis is asymptomatic.
Diseases of the Upper GI: Stomach and Duodenum, Part II
Thursday, October 16, 2008
7:47 AM
Diseases of the Upper GI: Stomach and Duodenum, Part II, 10/16/08:
[In case you're confused about definitions: peptic ulcers are just ulcers in an acidic
area of the GI tract. The word presumably has a relationship with "pepsin;" both
etymologies are from Latin pepticus, from Greek peptikos "able to digest," from
peptos "cooked, digested," which is the verbal adjective of peptein "to cook." Gotta
love online etymology dictionaries.]
[Evidently "Pepsi," of second-tier cola fame, has the same root-- it was originally
marketed as a digestive aid. No kidding.]
1. Describe the pathophysiology of the two most common causes of ulcer disease.
 (Inflammatory) Gastritis: generally due to H. pylori (Gram-negative
rod) infection.
 One of the most common human bacterial infections; never
completely eradicated without antibiotics. Sets off a robust
immune response which, along with the ammonia produced by
the bacterium, destroys the surrounding gastric cells.
 Mainly contracted during childhood; the degree of crowding
during childhood correlates with the likelihood of contracting H.
pylori. Socioeconomic status likewise.
 Transmission is person to person; fecal-oral, oral-oral, gastrooral routes.
 Tests:
 With a biopsy:
 Culture (though it's difficult to culture due to a
long growth time)
 Histology (most stains work)
 Rapid urease test (H. pylori has urease action)
 Non-biopsy-based tests:
 Urea breath test (radiolabeled carbon), urea
blood test
 Blood antibody test (probably the most reliable,
cheapest test)
 Stool antigen test
 Localizations of symptoms:
 Antrum and pyloric gastritis (APG): in the antrum and
pylorus, no kidding. High levels of acid; possibility of
developing duodenal ulcers.
 Chronic active superficial gastritis (CASG): all over the
stomach; mild (asymptomatic) form. Most common (p.
11, 10-15-08 11-12 AM). Note that I think he said in
class that APG is most common.




Multifocal atrophic gastritis: all over, severe form; look
for atrophy of the body and fundus. Carries the highest
risk for gastric ulceration.
Note that H. pylori infection can also cause proximal
duodenal ulcers.
Signs:
 See increased serum gastrin with H. pylori infection.
Recall that you can also get MALT lymphoma.
 Acid secretion: varies inversely with the degree of
stomach body involvement. APG = low body
involvement = high acid levels; MAG = high body
involvement = low acid levels. I would guess that
CASG's acid levels are relatively normal.
 Treatment:
 Triple therapy: PPI plus two antibiotics (generally
metronidazole or amoxicillin and clarithromycin) for 1014 days.
 'Rescue' therapy for non-responders: quadruple
therapy: PPI, bismuth, and two antibiotics.
 Who to treat:
 Patients with peptic ulcer disease
 Patients with gastric lymphoma
 Patients with a family history of gastric carcinoma
 Anyone who has H. pylori infection and wants treatment
(Non-inflammatory) Gastropathies: generally caused by NSAIDs,
EtOH, and stress-related mucosal damage.
 NSAID use:
 Prostaglandins increase mucosal blood flow, decrease
acid secretion, and increase mucus and bicarbonate
secretion-- so NSAIDs do the opposite.
 Acutely, you see hyperemia, small local hemorrhages,
and erosions due to direct depletion of local
prostaglandins. These don't seem to have a lot of clinical
effect.
 Chronically, you deplete systemic stores of prostaglandin
and begin to be at risk for ulceration.
 Diagnosis:
 Symptoms: heartburn, nausea, dyspepsia,
vomiting, abdominal pain.
 Mucosal lesions
 Perforated ulcers or GI bleed (can be ulcers in
stomach or duodenum)
 Recall that COX-2 specific NSAIDs don't cause ulcers.
Celecoxib (the only one still widely used) actually has
some COX-1 activity as well and so still poses some risk
(though not as the doses generally prescribed).
 EtOH use:
 Dr. Peterson is adamant about the idea that ethanol,
while it causes erosion and erythema, does not cause
inflammation-- it causes gastropathy, but not gastritis.
This means it shouldn't bleed much, perforate, or cause
pain. (that said, it still presumably exacerbates existing
inflammatory conditions.)

(yes, what this seems to be saying is that EtOH shouldn't cause
bleeding, perforation, or pain, because it's non-inflammatory.
Why NSAIDs then cause all of the above while still being noninflammatory is one of those questions. What I think he's trying
to say is that EtOH, like NSAIDs, has an acute effect that
doesn't seem to be terribly clinically important. Unlike NSAIDs,
there is scant chronic effect of EtOH use in the stomach.)
 Stress-related mucosal damage (SRMD):
 Now relatively infrequent due to improved ICU care, but
related to systemic physiological stress, possibly causing
mucosal ischemia or increased acid secretion.
 [Peptic ulcer disease:]
 Dr. Peterson: unless you have Zollinger-Ellison syndrome, acid
doesn't cause peptic ulcers unless your mucosal defense is
already compromised. What compromises it: H. pylori, NSAIDs,
tobacco, some other junk. On the other hand, if you've already
got a mucosal defect, then increased acid is going to contribute
to an ulcer.
 The key thing I think he wants us to know here is that the sine
qua non of peptic ulcer disease is mucosal problems and not an
over-abundance of acid secretion.
 Note that duodenal ulcers tend to be due to Zollinger-Ellison
(more distal), H. pylori infection (proximal in the bulb), or
NSAID use (proximal in the bulb).
 [A theme here: duodenal ulcers tend to be due to increased levels of acid (ZE, NSAIDs, pyloric H. pylori infections). Gastric ulcers tend to be due to
atrophy of the stomach body itself (multifocal H. pylori, also NSAIDs).]
2. Given the clinical presentation of any patient with ulcer disease, be able to
recognize when bleeding, perforation, obstruction and penetration are present.
 Bleeding (30% lifetime risk in ulcer patients, particularly with aspirin
use): most clinical ulcers are bleeding ulcers at this point. Look for
anemia, melena, shortness of breath, pallor, or pale conjunctiva, or
just scope them and look for ulcers and blood.
 Perforation (almost always with NSAIDs): rigid belly from peritonitis.
Most should go to surgery.
 Penetration: perforates into a surrounding organ rather than into the
peritoneum; eg. into the pancreas, causing pain radiating to the back.
 Obstruction: scar formation causes gastric outlet obstruction (scar
squeezes shut the pylorus). Not very common anymore due to a much
lower prevalence of H. pylori and an abundance of antacids. That said,
look for nausea, vomiting, and early satiety.
3. Compare and contrast the five most common gastric neoplasms.
 (1) Gastric adenocarcinoma:
 Worldwide, it's the second most common cancer/cause of death
from cancer.
 H. pylori is necessary but not sufficient to cause gastric
adenocarcinoma-- the other factors are unknown. It's unlikely
that antibiotic therapy to get rid of H. pylori will cause
regression of neoplasms.
 (2) Gastric polyps:
 Hyperplastic polyps: in the colon, these are premalignant
lesions; in the stomach, however, they have no malignant
potential. Generally secondary to hypergastrinemia.




Adenomatous polyps are premalignant (remember Dr. Low's
lecture on colon cancer and familial adenomatous polyposis in
D+D? Thought not. He's lecturing again on it next week in case
you somehow fell asleep the first time).
 Fundic gland polyps: related to chronic PPI use? Uncertain
significance.
 (Generally we take all polyps out.)
(3) Stromal tumors: leiomyoma/sarcoma, lipoma/sarcoma, or GISTs
(gastrointestinal stromal tumors):
 GISTs: most common mesenchymal tumor of the stomach:
progression to malignancy is relatively common (10-30%), but
can be treated with Gleevec (tyrosine kinase inhibitor).
(4) Neuroendocrine tumors:
 Gastrinomas, insulinomas, VIPomas (vasoactive intestinal
peptide; these occur at the rate of about 1 per 10 million
according to Wiki).
 Carcinoids: arise from ECL cells; found in fundus/body.
Sporadic type are more dangerous than clumped type; latter
seem to be related to hypochlorhydria (low acid secretion), and
resection of the antrum often resolves them). Possibly the
second most common neoplasm in the duodenum after
adenocarcinoma.
(5) Gastric lymphoma:
 Arises in MALT as a result of H. pylori infection. Eradication of
H. pylori induces regression of the lymphoma.
Upper GI Pharmacology
Thursday, October 16, 2008
8:54 AM
Upper GI Pharmacology, 10/16/08:


[Factors that lead to increased acid production: increased H-K ATPase pump
activity, H2 receptor activity, and M3 receptor activity; or decreased
prostaglandin receptor activity.]
[Factors that lead to increased mucosal production: increased prostaglandin
receptor activity or somatostatin receptor activity. Decreased by H. pylori and
NSAIDs.]
1. ANTACIDS: Describe the general properties, primary ingredients [CaCO3,
Mg(OH)2, Al(OH)3, NaHCO3], and general mechanisms of action, and guidelines for
use.
 Extremely cheap and fast-acting.
 Primary ingredients: CaCO3, Mg(OH)2, Al(OH)3, NaHCO3.
 Pharmacokinetics: not systemically absorbed.
 MoA: Chemical antagonism (neutralization, no receptor action).
 Uses: acute gastritis. Not for chronic high-dose use (see below).
 Adverse effects: Calcium and aluminum are constipating; magnesium
is diarrheic (maalox and mylanta combine aluminum and magnesium
to balance effects). In patients with renal dysfunction, you can start to
see hypercalcemia. Sodium bicarbonate increases sodium uptake (and
hence H2O), which can be problematic.
2. ANTISECRETORY AGENTS (plus sucralfate): Describe the site and mechanism of
action and the relative efficacy of:
 Antimuscarinic agents:
 Note these aren't actually mentioned in his notes or his drug
list for upper GI symptoms; not used much for this.
 MoA: block muscarinic receptors. Problem is that the muscarinic
tone in the stomach is much lower than the tone in the mouth,
etc (see next point).
 Adverse effects: at the levels necessary to be efficacious, see
antimuscarinic side effects: dizziness, mydriasis, dry mouth,
tachycardia, constipation, urinary retention.
 H2 receptor blockers [ranitidine / cimetidine / famotidine /
nizatidine]:
 Often given at night to decrease nocturnal acid secretion.
Cheap as hell.
 Suffix: -tidine (note distinct from "loratadine")
 Pharmacokinetics: rapid onset; renally excreted.
 MoA: Reversible, competitive antagonist of H2 receptors.
 Uses: GERD, peptic ulcer disease (second-line to PPIs due to
lower efficacy)
 Adverse drug reactions: few. Decrease the dose in renal
dysfunction. Note that cimetidine, specifically, decreases
CYP450 function.
 Proton pump inhibitors [omeprazole, esomeprazole, pantoprazole]:
 Available over the counter. Can be fairly expensive, even
generics.
 Suffix: -prazole.
 Pharmacokinetics: Enteric coated (it's acid-labile)-- absorbed
into bloodstream from duodenum first, then returns to the
stomach and act. May take 2-5 days to reach steady-state (not
good for acute onset). Increased half-life for S-omeprazole
(Nexium).
 MoA: Irreversibly binds, when activated by protons, to the H/K
ATPase. Note no tolerance develops.
 Uses: GERD, peptic ulcer disease, NSAID-induced ulcers,
Zollison-Ellinger
 Efficacy: no particular difference between varieties.
 Adverse drug reactions: few. Minor inhibition of CYP450
system.
 Prostaglandin analogs [misoprostol]:
 Suffix: -prostol.
 Pharmacokinetics: short half-life (30 minutes), acute onset.
Rarely used since you have to dose 4 times a day.
 MoA: Acts like endogenous prostaglandins: decreases acid
secretion, increases mucus/HCO3- production.
 Uses: NSAID-induced ulcers.
 Adverse drug reactions: Diarrhea, cramping.
 Sucralfate:
 Pharmacokinetics: non-systemic, activated by low stomach pH.
 MoA: coats ulcer; decreases pepsin activity.
 Uses: peptic ulcer disease, but currently limited use.
 Adverse drug reactions: bloating, flatulence.
3. Describe the possible side effects and drug interactions of H2 receptor blockers.
 Recall that they're mainly renally excreted, which means the dose
needs to go down in kidney-impaired patients.
 Also recall that cimetidine decreases CYP450 function.
 If you really slug the stuff you can see CNS/mental status dysfunction.
 Note tolerance develops to H2 antagonists-- decreased H+ increases
gastrin secretion, which increases histamine secretion, which
outcompetes the blockers.
4. Explain the rationale for antibiotic therapy of peptic ulcers.
 (1) Eliminate H. pylori.
 (2) Prevent recurrence of ulcers.
5. Describe the actions of proton pump inhibitors and prostaglandins in protecting
the gastrointestinal tissues.
 PPIs: block H/K ATPase pumps. Reduces scarring and exacerbation of
ulcers.
 Prostaglandins: increase mucosal blood flow; decrease acid secretion;
increase mucosal and bicarbonate secretion.
6. PROKINETIC AGENTS: Describe the site and mechanism of action and list the side
effects of: cisapride, metoclopramide.
 Haven't gotten to these yet.
7. ANTIEMETIC AGENTS: Describe the site and mechanism of action and the relative
efficacy and list the side effects of: antihistamines (dimenhydrinate)
metoclopramide, ondansetron, and phenothiazines (prochlorperazine).
 Haven't gotten to these yet either.
Pediatric Gastrointestinal Diseases
Friday, October 17, 2008
11:02 AM
Pediatric Gastrointestinal Diseases, 10/17/08:
1. Describe the major features (as featured in this handout) of:
 Tracheo-esophageal fistula:
 Connection between the distal esophagus and the trachea;
generally co-occurs with esophageal atresia.
 Depending on the extent of esophageal atresia, this can present
with polyhydramnios in utero (can't swallow amniotic fluid) or
postnatally with dysphagia/pneumonia.
 ["H-type atresia": counterintuitively, has no esophageal
atresia, but has an open fistula between the esophagus
and the trachea (like the middle arm of a capital "H").
Often presents postnatally with pneumonia.]
 1/3,000 live births.
 Associated with a high incidence of other congenital defects,
especially cardiac.
 Infantile hypertrophic pyloric stenosis:
 Hypertrophy/hyperplasia of gastric smooth muscle in the
pylorus-- obstructs passage to duodenum.






Typical clinical presentation is projectile vomiting at about 3
weeks postnatally; also look for upper abdominal mass. Note
that the vomitus isn't biliary (from stomach, not small bowel).
 Male predominance; 1/200 live births.
Meckel's diverticulum:
 Small blind pouch protrudes from the terminal ileum, containing
mucosa from another part of the GI tract (often gastric
mucosa-- can thus get gastric ulcers in the ileum). The pouch is
a remnant of the connection between the intestine and the yolk
sac through the umbilicus (the vitelline duct).
 This can cause small bowel obstruction or umbilical herniation.
 Most common congenital small bowel malformation (2-4% of
population); typically asymptomatic.
Omphalocele:
 During development, the fetal intestines don't return from the
coelom to the abdominal cavity properly (recall they come out
about week 6, then rotate and go back in around week 10).
 See a defect in the abdominal wall at the umbilicus, through
which a sac filled with bowel protrudes. Sac is composed of
peritoneum and amniotic membrane.
 Associated with other congenital defects (30-50%).
 1/2000 live births; associated with advanced maternal age (as I
recall, > 35).
 [Note contrast with gastroschisis, in which the abdominal wall
itself doesn't develop properly; in this case the bowel herniates
out between the muscle groups. No amniotic membrane
covering. Not associated with other malformations.]
Malrotation:
 As might be guessed, during development, here the intestines
don't rotate properly when they're returning into the abdominal
cavity. They also tend not to fixate correctly.
 This can complicate omphalocele or gastroschisis.
 Most cases are asymptomatic; can present with midgut (small
and most of large intestine) bowel obstruction.
 1/500 live births.
 [Normal rotation of bowel:]
 Small intestine rotates 270 degrees counterclockwise
around the SMA.
 Large intestine rotates 270 degrees clockwise around
the SMA.
 Note that certain malrotations can cause the appendix to locate
in a variety of other places (cited as upper right quadrant)-- so
appendicitis can show up in eclectic locations.
Duplications/Cysts:
 Cystic or tubular structures that duplicate normal GI structures;
these may or may not communicate with the functional GI
tract. Can occur anywhere along GI tract; most commonly near
small intestine.
 They can cause bowel obstruction, but are generally
innocuous/asymptomatic.
Intestinal Stenosis or Atresia:
 Stenosis: narrowing. Atresia: blind ending.

Most common site is the duodenum; up to 40% of these occur
in Down's Syndrome (tri-21) kids.
 Present with polyhydramnios in utero (generally when it's
complete atresia), or bilious vomiting postnatally.
 1/3000 live births.
 Imperforate anus/Rectal agenesis:
 Imperforate: thin membrane covering the anus. Rectal
agenesis: no development of the rectum at all. The former is
easily dealt with; the latter is more serious.
 Associated with fistulas (rectovaginal or rectovesical).
 Associated with other congenital abnormalities.
 1/5000 live births.
2. List and describe the major features of Hirschsprung Disease.
 Hirschsprung, aka "congenital megacolon:" massive dilation of the
intestinal lumen.
 Caused by lack of ganglionation of various lengths of intestine; this
causes them to constrict somewhat and be unable to participate in
peristalsis, causing ingested matter to build up behind the stricture
and expand the preceding length of bowel.
 In newborns, look for a failure to pass meconium (viscous, sticky fetal
stool) shortly after birth. In adults, can present with perforated bowel
from overexpansion.
 Treatment is surgical; outcomes are generally good unless the section
is pretty long.
 Pathogenesis: commonly (50%), mutations in RET receptor/ligand
genes that drive the migration of neural crest cells to form the enteric
nervous system.
 More common in males (4:1).
3. List and describe the major features of Neonatal Necrotizing Enterocolitis.
 Develops in the first week or so postnatally; look for abdominal
distention and bloody stools.
 Strongly associated with prematurity, particularly extreme
prematurity.
 Caused by intestinal hypoxemia (recall that premies' lungs are usually
kind of crap, especially real early on) and resultant ischemia and
inflammation, causing commensal bacterial invasion below the
mucosal layer. This can lead to peritonitis and gas gangrene in the
intestine.
Diseases of the Lower GI: Pathology
Monday, October 20, 2008
7:58 AM
Diseases of the Lower GI: Pathology, 10/20/08:
1. Describe the histologic features associated with bacterial enterocolitis and the
clinical symptoms (e.g. type of diarrhea), and state a common non-bacterial entity
that also shows this histologic pattern.
 Clinical symptoms of enterocolitis: depends to some extent on the
bacterium involved:

Toxin-producing bacteria (Vibrio cholerae, Clostridium
perfringens/botulinum, noninvasive E. coli, Clostridium difficile,
Campylobacter, etc) cause explosive diarrhea with a rapid
onset after exposure. Recall that pseudomembranous colitis is
caused by C. difficile toxin, among other things (see below).
 Invasive bacteria (invade the bowel wall: Shigella,
Salmonella, Yersinia) cause marked abdominal pain and
exudative, usually bloody diarrhea (invasive bacteria tend to
cause a more extensive mucosal necrosis).
 Histologically:
 See PMN infiltration ("active," acute inflammation).
 Clostridium difficile: "explosion" of fibrinopurulent exudate
(putting the "pseudomembrane" in "pseudomembranous
colitis"). Also associated with antibiotic use (due to C. difficile
resistance and overgrowth) and a number of other organisms
(Salmonella, etc).
 Ischemic colitis also shows pseudomembrane formation (breakdown of
mucosa and tight junctions allows commensal bacteria below the
mucosal layer).
 Note this can be due either to primary vascular compromise
(stenosis of arteries or thrombosis) or secondary to a section of
strangulated bowel.
 Particularly vulnerable to ischemia: watershed areas of colon
near splenic flexure and rectosigmoidal junction.
2. List four microscopic parasites that can be identified in stool samples or in biopsy
material from infested patients.
 Infect immunocompetent individuals: Giardia and Entamoeba
histolytica (amebiasis).
 Infect immunocompromised individuals: Cryptosporidium and
Microsporidium.
 (quick recall: if it's got spores in it, it's probably an
immunocompromised deal.)
 Ova and Parasite test (O+P) on stool is the best way to identify GI
parasites; can be done somewhat less effectively in biopsies.
3. Explain how the life cycle of Entamoeba histolytica determines the gross and
microscopic appearance of associated lesions. Discuss the clinical symptoms and
possible complications of this disease.
 Amebiasis: associated with travelers outside US; acquired through
oral-fecal route. Up to 90% of patients asymptomatic, but can get
necrotizing colitis and liver cysts, particularly in immunocompromised
patients.
 Life cycle:
 Cyst is ingested by human.
 Organism breaks out of cyst near ileocecal junction and forms
trophozoite.
 Trophozoites can get into blood and go to liver (forming large
cystic spaces), can invade the colon (usually near the ileocecal
junction), or can passively colonize the colon (asymptomatic).
 Invasion: Since it happens in the terminal ileum, the
symptoms can be confused with Crohn's Disease.
 They form cysts in the colon which are expelled with stool.
4. Explain the role of biopsy in diagnosis of colon disease causing diarrhea.

Stool samples are more reliably diagnostic than biopsy in determining
the causative organism, whether bacterial or parasitic.
 He also mentioned that a clinical history is often important, since
histologically ischemic and bacterial enterocolitis can look identical.
5. Describe the anatomic process underlying diverticulosis. List the clinical factors
that predispose to this illness. Describe the clinical staging of diverticulitis.
 Diverticulum: a herniation in which all three layers of the normal wall
are present. The appendix can therefore be described as a
normophysiological diverticulum.
 By contrast, what we describe as diverticula don't actually
qualify; they're stretched so much that there's no muscularis
propria. Therefore "diverticulosis" actually only causes
"pseudodiverticula." No, it doesn't really matter.
 Etiology: straining at stool causes increase in pressure, resulting in
herniation at points of structural weakness.
 Predisposing factors of diverticulosis:
 Mainly age. If you see it in a patient under 40, that's unusual
and suggest an underlying collagen defect. Poor diet also has
an impact.
 Staging of diverticulitis (inflammation resulting from diverticulosis):
 Stage 1: abscess confined to the pericolic region
 Stage II: distant abscess (in pelvic organs or retroperitoneum)
 Stage III: generalized peritonitis without communication with
bowel lumen
 Stage IV: fecal peritonitis with open perforation
 Note can cause fistula formation (interbowel openings due to
inflammatory ulceration) or bowel obstruction.
 Note these are called the "Hinchey classification" if you want
more info online.
 Note the distinction between diverticulosis and diverticulitis: the latter
is an active inflammation with PMN infiltration that results from the
former, frequently caused by fecal obstruction.
 Random info:
 Diverticulosis is found mainly on the left side of the colon.
 Note that diverticulosis tends to occur in pairs: this follows the
pairs of arteries that pass into the colonic wall.
6. Compare and contrast Crohn's disease and ulcerative colitis. What four (or more)
pieces of information are useful in differentiating these diseases, and what is their
relative importance?
 Idiopathic inflammatory bowel disease: broken down into Crohn's
Disease and ulcerative colitis. No evidence of causative organisms.
Probably an autoimmune condition, reacting to bowel contents.
 Crohn's Disease:
 Can involve anywhere from the mouth to the anus, but
mainly in:
 Terminal ileum
 Proximal colon
 Anus (1/3 of patients, heavily emphasized)
 Characteristics of Crohn's:
 Skip lesions (lesions with large intervening areas
of normal bowel).
 Full-thickness inflammation and scarring (which
can lead to fistulas and fissures/perforation).






Non-necrotizing granulomas show up in the
lamina propria. Note that not all Crohn's patients
have them.
 Lymphoid aggregates, particularly transmural
ones.
 You can also see blunting of the villi in the ileum.
 "Creeping fat:" fat becomes adherent to bowel,
as opposed to hanging freely, due to fullthickness inflammation spreading into the fat. It
sort of works circumferentially around the
perimeter of the colon and can extend into the
small bowel.
 Grossly, also see a cobblestoned mucosal pattern
in the lower GI tract (preserved mucosa
interspersed with deep ulcerations).
 On barium swallow: "string sign": the lumen is so
constricted that the lumen of the bowel shows up
as a thin string.
 Incidence: 7 per 100,000.
Ulcerative colitis:
 Spreading involvement from the rectum (he made a
point of saying the rectum is always involved with
ulcerative colitis): rectum to sigmoid colon to
descending colon to splenic flexure to transverse colon
to ascending colon.
 Tends to be a more continuous involvement than
Crohn's Disease, but also more superficial (ulcers are
rarely full-thickness; inflammation limited to mucosa
and superficial submucosa).
 Note that ulcerative colitis leaves behind normal areas
between ulcerative areas ("pseudopolyps," wind up
looking like a shag carpet), whereas in Crohn's you see
less complete ulceration coverage but they go very
deep.
 About 7 times more common than Crohn's Disease;
incidence is 50/100,000.
[Point here, I think, is that UC ulcers are less deep but more
continuous, while Crohn's are deeper but more sporadic. Also
the anal-Crohn's, rectal-UC distinction.]
Common histological features with both; hard to make
histological diagnosis.
 See inflammation and PMN infiltration inside the crypts
and lamina propria (cryptitis).
 See crypt abscesses-- distended, can burst and release
PMNs into the stroma.
Note both idiopathic IBDs are characterized by relapsingremitting courses; this means current biopsies should be
compared with former biopsies to sketch the arc of the disease
progression.
Note also that both diseases are associated with an increased
risk of cancer; thus biopsies also need to be scanned for
dysplasia.
A point that seems to have been made repeatedly since
then is that ulcerative colitis shows a higher risk of
cancer development than Crohn's.
 Note that in both diseases you see a decreased number of crypts and
'blunting' of them, as opposed to acute self-limiting conditions. This is
due to chronic, fibrotic change and can also be seen after long courses
of infectious or diverticular disease.
7. Describe the two common histologic patterns associated with the clinical entity of
microscopic colitis. What features do they share and which feature differentiates
them?
 Microscopic colitis: chronic thin, watery diarrhea, with normalappearing mucosa on endoscopic inspection.
 Histologically, can see either lymphocytic invasion of the superficial
epithelium by itself (lymphocytic enterocolitis), or can see it with a
thick band of subepithelial collagen beneath that epithelium
(collagenous colitis).
 Note that the former type is 1:1 men to women and idiopathic, while
the latter (collagenous) type is 10 times more common in women and
is associated with NSAID use.
8. Describe the histologic features of melanosis coli. What causes it?
 Melanosis coli: macrophages in the lamina propria acquire a brown
pigment; sometimes, this hue can be seen endoscopically.
 Caused by overuse of cascara laxatives.

Pathophysiology of the Lower GI, Parts I + II
Monday, October 20, 2008
10:00 AM
Pathophysiology of the Small Intestine and Colon, Parts I + II, 10/20/08:
[Note his LOs have been changed for this lecture.]

[Localization of absorption, good for boards:]
o Iron absorption: mainly in duodenum, some in jejeunum.
o Folate absorption: in jejeunum.
o B12 absorption: in specialized cells of terminal ileum.
o Vitamins ADEK: absorbed along with fat, mainly in the proximal
jejeunum.
 Problems with malabsorption of each:
 A: xerophthalmia (dry eyes)
 D: bone mineralization defects, osteomalacia
 E: progressive neuronal dysfunction
 K: clotting dysfunction
1. List the four major organ systems required for fat absorption and describe their
roles and interactions.
 Liver (necessary for bile salt formation and storage, as well as fat
storage and mobilization)
 Stomach (grinds up food and secretes lipase from the chief cells)
 Small intestine (breaks down macronutrients and absorbs
micronutrients)
 Pancreas (secrete lipase and other lytic enzymes)

Severe pancreatitis, generally caused by alcoholism, can cause
fat malabsorption; this is the most common cause of impaired
lipolysis.
 [Recall that bile salts that form micelles stick around in the lumen of the
duodenum; after fat's been absorbed in the proximal 2/3 of the jejeunum, the
bile salts get reabsorbed in the terminal ileum (thus in Crohn's, ulcerative
colitis, etc, you get not only B12 deficiency but also can't reabsorb your bile
salts and thus get watery diarrhea) and are stored again in the liver.]
2. Describe the clinical presentation of patients with fat malabsorption.
 Weight loss, diarrhea, steatorrhea ("ring on the toilet bowel," floating
stools in the toilet caused by air trapped in steatorrheic stools,) foulsmelling stools, vitamin deficiencies.
3. Name the four type of diarrhea based on stool characteristics.
 Types: watery, fatty, inflammatory, exudative, or "functional" (we
have no idea).
o Watery diarrhea:
 Osmotic diarrhea: lactose intolerance, sorbitol from
chewing gum, high-fructose diets, osmotic laxatives,
etc. Caused by the presence of poorly absorbed
intestinal osmoles; this brings water into the intestinal
lumen.
 To make sure: measure stool sodium +
potassium, multiply by 2, and subtract from 290;
if the difference is over 50, that's osmotic
diarrhea.
 Non-osmotic ("secretory") watery diarrhea: bacterial
toxins, neuroendocrine tumors (rare), bile salt
malabsorption, stimulant laxatives, disordered motility
or regulation (diabetic neuropathy, Crohn's/UC, postvagotomy).
 Note also that means that if you're taking bile
acid resins for hypercholesterolemia, you'll likely
wind up with watery diarrhea.
o Fatty diarrhea:
 Caused by fat malabsorption due to Whipple's (recall it's
a lymphatic disease and fat is mainly absorbed through
the lacteals), celiac, bacterial overgrowth, etc. Can also
have a problem with lipolysis (eg. from pancreatitis).
 Note that you use a "Sudan stain" to stain the fat
globules in stool to diagnose.
o Inflammatory/Exudative:
 As due to IBD, toxin-producing or invasive bacterial
infection, parasite infection, or ischemic colitis.
 Look for white cells in the stool. These are absent in
certain infections (cholera, toxin-producing E. coli and S.
aureus, Giardia), but present in others (Shigella,
Campylobacter, invasive E. coli)-- not enormously
sensitive but presumably fairly specific.
4. Given a patient with symptoms relating to the colon, recognize obstruction,
pseudo-obstruction and constipation.
 [this one got a little confusing.]
 Constipation: decreased frequency or ease of defecation, generally
caused by either colonic inertia or outlet obstruction. Test by ingesting
X-ray-detectable solid material. If it's diffused throughout the colon
after a time, that's inertia (nothing's much moving). If they're all
clustered down by the rectum, that's outlet obstruction.
 Obstruction: can be either benign or malignant. Get an X-ray or CT;
usually see air and blockage in a distended colon.
 The distinction between constipative outlet obstruction and
obstruction per se seems to be that outlet obstruction is, you
know, at the outlet and nowhere else. Obstruction per se is in
the colon itself.
 Pseudoobstruction: looks like obstruction on X-ray or CT (distended
colon, full of air), but no blockage is found.
 [Note that fecal incontinence is often caused by trauma to the anal canal or
diabetes/other neuropathies. Just in case you were wondering.]
5. Given a patient with symptoms of colitis, be able to determine whether ischemic
colitis, ulcerative colitis or Crohn’s disease is most likely.
 Ischemic colitis: classically it's older people with CV disease, but it also
occurs in young athletes, particularly runners (not enough fluid
intake).
 Ulcerative colitis: look for mucosal involvement in the colon (always
rectal involvement). Never involved in the small bowel. Fairly obvious
on colonoscopy.
 Note that you can get megacolon and/or perforation with
ulcerative colitis. We're not sure why.
 Also look for bloody diarrhea and urgency (latter due to rectal
involvement).
 Crohn's disease: look for transmural involvement in the colon and
ileum (often anal involvement as well)-- can be purely colonic, in
which case it's often tough to distinguish from ulcerative colitis.
 Crohn's tends to have a lot more pain associated with it. Also
look for the string sign on barium swallow.
 As might be expected from the string sign, obstruction is a big
problem with Crohn's, particularly in the small intestine. Also,
as mentioned, fistula formation from one GI segment to
another due to transmural involvement. Note that you can also
get fistulas out into the skin, usually out through surgical scars
or through the umbilicus.
 Perianal fistulas and/or abscesses (anal involvement) is more
common with Crohn's. Also recall that granulomas and
lymphoid aggregates only show up in Crohn's.
 [Note that Crohn's always recurs after surgery, possibly because of the
process of the surgery itself.]
6. Given a patient with inflammatory bowel disease, recognize the extra-colonic
manifestations.
 Ulcerative colitis: fever, malaise, non-inflammatory necrosis in the skin
of extremities, fatty liver, uveitis, etc. Complete list is on his slide 17.
 Crohn's: peripheral arthritis, gallstones, renal stones.
 Generally peripheral arthritis shows up in large joints, not distal
small ones.
 Presentation says arthritis is common to both of them (internet
search backs this up), notes only mention it for Crohn's.
 [Note the distinction between IBD - Crohn's or UC - and IBS (irritable bowel
syndrome), which is a functional diagnosis of abdominal pain and bloating,
generally in young, otherwise healthy people without blood in the stool, fever,
or a high white count. GI docs can get cranky about this.]
[No longer an LO: List the five major tests used in the evaluation of patients with fat
malabsorption. For each test, describe: the indications, the physiology of the test
and the results of the test in six specific disease categories.]
 Note bacterial overgrowth can cause fat (and B12 and ADEK)
malabsorption. Note that with overgrowth, you'll have normal folate
levels (due to bacterial production).
 Celiac sprue or celiac disease: villous blunting, inflammatory cells in
lamina propria.
 Serologic tests: anti-endomysial antibodies, anti-tissue
transglutaminases, anti-gliadin IgA and IgG.
 Best diagnostic tool: biopsy.
 Tropical sprue: looks histologically identical to celiac disease, but
caused by bacterial toxins/colonization, generally after travel (need
history).
 Classic presentation: megaloblastic anemia from B12
deficiency.
 Whipple's disease: Gram-positive T. whippelii infection.
 Clinical presentation: fever, joint pain, neurological symptoms.
 Diagnosis made by small intestine biopsy (look at PAS stain for
macrophages).
 Mesenteric ischemia: caused acutely by emboli, chronically by 2 of 3
major vessels occluded (2 of celiac, superior mesentery, or inferior
mesentery), often by atherosclerosis.
 Clinical: post-prandial abdominal pain, weight loss (due to
sitophobia: fear of eating).
 Look for other signs of CV involvement or get an angiogram.
 Tends to happen at the recto-sigmoid or splenic flexure areas
(watersheds).
 Small intestinal tumors: very rare that you get primary tumors in this
region. Can present with symptoms of obstruction. Check with barium
swallow.
Treatments for Lower GI Disorders
Tuesday, October 21, 2008
8:00 AM
Treatments for Lower GI Disorders, 10/21/08:
[From "Upper GI Pharmacology," continued:]
6. PROKINETIC AGENTS: Describe the site and mechanism of action and list the side
effects of: cisapride, metoclopramide.
 Cisapride: 5-HT4 agonist to activate cholinergic motor neurons.
 Note 5-HT3 agonists do the same thing.
 Side effects: at high levels, act like class III antiarrhythmics
(block potassium channels), lengthening the QT interval and
predisposing to torsades de pointes.

Metoclopramide: D2 receptor antagonist to inhibit D2's inhibition of
cholinergic motor neurons.
 Side effects in CNS: D2 blockade causes increased directpathway tone (involuntary movement/tremor).
 MoA: Both of these facilitate ACh release and cause smooth muscle
contraction in the GI tract.
 [Other things you can use for this: erythromycin (increases ACh
release), neostigmine (decreases ACh breakdown), bethanochol (ACh
receptor agonist).]
7. ANTIEMETIC AGENTS: Describe the site and mechanism of action and the relative
efficacy and list the side effects of: antihistamines (dimenhydrinate)
metoclopramide, ondansetron, and phenothiazines (prochlorperazine).
 Background: there's a vomiting center in the medulla.
 The chemoreceptor trigger zone (CTZ), outside the blood brain barrier,
frequently mediates plasma drug effects on the vomiting center.
 Receptors on CTZ: M1 receptors, D2 receptors, 5-HT3
receptors.
 Ondansetron blocks the 5-HT3 receptors on the CTZ. Mainly
used to prevent vomiting coming out from general anesthesia
(stage II). Also blocks the opioid receptors (see below).
 It can be expensive but it's well tolerated.
 Phenothiazines and metoclopramide block the D2 receptors on
the CTZ.
 At higher doses, can get tortacollis and other
antidopaminergic effects; treat with antimuscarinics
(benztropine).
 Note opioids have their own receptors in the BBB, but can also affect
the D2 receptors on the CTZ.
 Note that there are muscarinic and histamine receptors in the
cerebellum (not in the CTZ) that affect the vomiting center as well.
 First-generation antihistamines like dimenhydrinate block both
M and H1 receptors here.
 [Scopolamine (muscarinic antagonist) blocks the M receptors
here.]
---1. LAXATIVES: Describe the mechanism of action of each class, drawbacks to use,
guidelines for use [psyllium seed, dioctyl sodium sulfosuccinate, mineral oil, MgSO4,
bisacodyl].
 Bulk-forming (psyllium seed): put bulk in colon, indirectly stimulate
peristalsis. May take 1-3 days but safe for chronic use.
 Osmotic (MgSO4): increase osmolality of GI lumen, drawing water out.
This swells and distends the colon, indirectly promoting motility. Safe
for chronic use. Note can also be used as a purgative before surgery.
 Wetting agents (mineral oil): lubricate the colon (which is just nothing
I ever thought I'd be writing). Dioctyl sodium sulfosuccinate (aka
docasate) acts as a surfactant to make foamy bubbles in and around
the stool (this keeps getting better and better).
 Stimulants/irritants (bisacodyl, senna): directly increase motility and
ion secretion. Most effective (15-60 minutes with a suppository). Tend
to be overused. At regular doses, can be used chronically. Often
prescribed with opioids.
2. ANTI-DIARRHEALS: Describe the mechanism of action and explain the rationale
for and guidelines for use [opiates / anticholinergics, kaolin / pectin, polycarbophil].
 Opioid: loperamide (Imodium). Slows GI intestinal motility, secretion,
and absorption by direct agonist action on mu and delta opioid
receptors in the GI tract. Most effective drug of those listed here. Note
that this has some anti-secretory activity against cholera toxin; can
also be used in traveler's diarrhea, but discontinue if no improvement
after 48 hours.
 Kaopectate: adsorbents to reduce fluidity. Note they can also absorb
nutrients and drugs. Note also that they have scant effect on the
actual fluid volume excreted.
 Polycarbophil: treats both constipation (pulls in water to itself,
prevents fecal desiccation) and diarrhea (pulls in water to itself,
absorbs some excess from lumen). Again, doesn't do much to prevent
the fluid loss.
 [Remember you're worried about electrolyte loss, not just fluid,
particularly in kids.]
3. DRUGS FOR IBS: Describe the site and mechanism of action and the relative
efficacy and list the side effects of: tegaserod and alosetron.
 Treatments for IBS:
 IBS is kind of funny (not ha-ha funny, uh-oh funny) in that it
can come in either diarrheic or constipated flavors.
 For pain: use tricyclic antidepressants (NE/5-HT action, but
note that the antimuscarinic effects will worsen constipation)
and SSRIs.
 For constipation, if present: use 5-HT4 agonist (tegaserod, like
cisapride).
 For diarrhea, if present: use 5-HT3 antagonist (alosetron).
 Note both of the latter are restricted use in women due to
dangerous side effects (ischemic colitis, cardiac problems); they
don't seem to work as well in men.
 They're both used mainly for refractory symptoms.
Exocrine Pancreas and Salivary Gland Physiology
Tuesday, October 21, 2008
8:56 AM
Exocrine Pancreas and Salivary Gland Physiology, 10/21/08:
[Contents of saliva: mucins, amylase and lingual lipase, sodium bicarbonate, IgA,
lactoferrin.]
1. Contrast the plasma and saliva concentrations of Na+, Cl-, and HCO3- at low
secretion rates and at high secretion rates and the principal cell types involved in
each secretion rate.
 At the time the saliva is excreted by the acinus (primary secretion),
it's isotonic to plasma/physiological saline solution:
 Na+ = 140 mM
 K+ = 4 mM
 HCO3- = 25 mM
 Cl- = 100 mM




As the primary secretions travel through the intercalated ducts that
connect it to the mouth, the duct cells modify the secretion. The longer
the secretions are in the ducts (ie. the lower the secretion rate is), the
more they're modified.
 Salivary duct cells: remove Na+ and Cl-, add in K+ and HCO3-.
Note that salivary duct cell membrane are water-impermeable
(the secretions can be and are diluted, making them
hypotonic). This is different from pancreatic duct cells; see
below.
Low secretion rates in the salivary glands: the secretions sit in the
salivary ducts long enough for the ducts to modify them extensively.
The bicarb levels are very high; the chloride levels are very low. The
sodium levels are low. The solution is very hypotonic.
 Na+ = 60 mM
 K+ = 15 mM
 HCO3- = 60 mM
 Cl- = 60 mM
High secretion rates in the salivary glands: the secretions aren't in the
salivary ducts long enough to be extensively modified by the duct. The
bicarb levels are slightly high; the chloride levels are slightly low. The
sodium levels are mildly depressed. The solution is slightly
hypotonic.
 Na+ = 120 mM
 K+ = 10 mM
 HCO3- = 30 mM
 Cl- = 80 mM
[Common secretion mechanisms in both salivary and pancreatic acinar cells:]
 There's your standard Na-K ATPase pumps in the basolaterial
membrane (2 K in, 3 Na out).
 These establish the sodium gradient that's used to power cotransporters to take in Na+ and K+. Chloride follows the influx of
positive ions into the cell and flows out the apical side through
numerous passive channels in the apical membrane.
 Sodium and water follow the chloride paracellularly through the notso-tight junctions between the acinar cells.
 Note you have muscarinic (M3) receptors in the blood; upon activation,
intracellular calcium rises, which increases the rate of insertion of Cl channels in the apical membrane (which in turn increases the rate of
sodium and water secretion).
 The specifics change depending on where you're at (eg. pancreatic
acinar cells are stimulated by cholecystokinin). But that's the common
idea.
 Enzymes in both types of acinar cell are stored in vesicles (amylase,
mucin, IgA for salivary, zymogens etc. for pancreatic); the signal for
exocytosis of these vesicles is the M3 muscarinic receptor for both, as
well as CCK and secretin for the pancreatic cells. Effectively you get
increased Ca++ or cAMP content that changes the cytoskeletal
configuration to release vesicle.
2. Describe three types of stimuli that increase salivary secretion.
 Sympathetic and parasympathetic input both increase salivary
secretion (parasympathetic input moreso). I have no idea what else
she's talking about. If you do, post it. Note that First Aid only
describes the two.
3. Describe the components of the saliva important in oral hygiene.
 At pH less than 7, the calcium in the teeth begins to become leached
out; the HCO3- is therefore important to preserve the pH above that
level.
 For more on dental caries, see "Oral Healthcare Issues In
Clinical Practice."
 IgA is obviously antibiotic.
 Lactoferrin chelates iron and prevents its use by bacteria.
4. List the major ionic and peptide/protein components secreted by the pancreas.
Contrast the plasma and pancreatic concentrations of Na+, Cl-, and HCO3- at low
secretion rates and at high secretion rates and the principal cell types involved in
each secretion rate.
 Again, the primary fluid excreted by the pancreas (right after
secretion) is isotonic to saline. And again, this fluid is modified by the
duct cells that lead out from the acinus.
 Main difference between pancreatic and salivary ducts: the duct cells
in the pancreas do not form an impermeable barrier to water (recall
that the salivary duct cells do).
 Pancreatic secretions:
 Ok. A couple things to consider here.
 One: you have two secretory components, one in the acinus
and one in the ducts. The one in the acinus secretes isotonic
saline solution with lots of digestive enzymes. The one in the
ducts secretes lots of bicarb and swaps it out for chloride.
 If you have predominantly the first type of secretion, the
pancreatic juices are going to be bicarb-low. If you have
predominantly the second type of secretion, the juices
are going to be bicarb-high.
 At "high flow rates" the second secretion is going to
dominate. At "low flow rates" the first secretion is going
to dominate.
 Two: there are evidently some other duct cells that do the
reverse of the first type (swap out bicarb for chloride). At low
flow rates, the bicarb gradually decreases as the secretions
have more time to sit around in the duct.
 Sheep picture in the pancreas: high-flow-rates-equals-highbicarb. Low-flow-rates-equals-low-bicarb. Baa.
 Details on pancreatic duct cells (bicarb-secreting):
 There's a HCO3- (out)/Cl- (in) exchanger in the apical
membrane to get the process rolling.
 Chloride then leaks out CFTR channels in the apical membrane
to be able to activate the exchanger again and pump out more
HCO3-.
 Note that CFTR channels are the ones that are
nonfunctional in cystic fibrosis; this erases the
substrate for the HCO3-/Cl- exchanger, which doesn't
pump HCO3- into the lumen any more. This screws up
the whole shebang and you don't have adequate water
secretion into the pancreas.
 In CF, the zymogens get stuck in the ducts (not enough
water to move them along); they can't act on their
targets in the duodenum, and the patient gets
malabsorption.
 Once again, you have the 3 Na/2 K ATPase pumps in the basal
membrane.
 The Na gradient that these establish drive the following:
 Co-transporter for Na+ and HCO3- (NBC transporter) in
the basal membrane (bring in HCO3- to be pumped out
by the apical exchanger).
 (Note you also get CO2 diffusion from the
bloodstream-- this combines with H2O to form
bicarb and protons. The protons are pumped out
by:)
 Na+/H+ exchangers to bring in Na+ and pump out H+ (to
facilitate the carbonic-anhydrase-mediated synthesis of
bicarb and protons from water and CO2).
 Finally, you have a HCO3-/Na+ co-transporter (NBCn1) in
the basal surface.
 Low secretion rates in the pancreas: Secretion is isotonic. Bicarb
levels are low, chloride levels are high. Sodium levels are relatively
normal to saline.
 High secretion rates in the pancreas: Secretion is isotonic. Bicarb
levels are high, chloride levels are low. Sodium levels are relatively
normal to saline.
 [Reviewing the distinctions between high and low flow rates and relative
bicarb concentrations in saliva and pancreatic fluid is probably a good idea.]
5. Describe the mechanism by which pancreatic zymogens are activated in the small
intestine.
 Trypsin is cleaved and activated by enterokinases (which should
actually be called enteropeptidases, as they have peptide cleavage
action); it in turn cleaves and activates all the other zymogens (as well
as any leftover trypsinogen not cleaved by enterokinase).
 Note that if even a small amount of these zymogens are activated in
the pancreas, it can set off a chain reaction in which the active
enzymes activate other enzymes, which activate others, etc; they all
chew the hell out of the pancreas (acute pancreatitis). I'm not sure
exactly how this works (what gets it started?) but it seems to be a
major player in causing cell injury in acute pancreatitis.
6. Describe the mechanisms by which chyme from the stomach is neutralized in the
duodenum.
 Mainly it's the HCO3- in pancreatic secretions. Note the neutral/alkaline
pH in the duodenum is necessary for the pancreatic zymogens to
function.
Pathology of the Gall Bladder and Exocrine Pancreas
Wednesday, October 22, 2008
7:53 AM
Pathology of the Gall Bladder and Exocrine Pancreas, 10/22/08:
1. List the clinical factors that increase risk for cholelithiasis. What are the major
types of gallstones and what are the clinical implications of each type? What
procedures can help establish the diagnosis of cholelithiasis, and under what
conditions will one procedure not be informative?
 Cholelithiasis: gall bladder stones. Form when the concentration of
material (cholesterol or bilirubin) exceeds the solubilizing capacity of
the bile. Etiology:
 (1) Supersaturation of cholesterol
 (2) Hypomotility of bile
 (3) Crystallization around calcium salts or proteins (nucleation)
 [Note "cholesterolosis:" excess cholesterol is absorbed into the wall of
the gall bladder and phagocytized by macrophages instead of forming
stones. Sort of an atherosclerosis of the gall bladder?]
 Factors: age (older is worse), gender (female is worse), weight (more
is worse), cholesterol levels (more is worse), family history (any is
worse). Also increased incidence among Native Americans.
 Types of gallstones:
 Cholesterol stones (most common; not many are radio-opaque)
 Pigment stones (composed of calcium salts of unconjugated
bilirubin-- as due to hemolytic anemias or alcoholic cirrhosis.
Most are radio-opaque).
 (note: don't confuse these with kidney stones, which are a
whole different beast. Not that, you know, I ever asked my
preceptor about struvite gall bladder stones or anything. 'Cause
that would be stupid.)
 Procedures:
 X-rays-- these only pick up stones with a lot of calcium salt
(radio-opaque-- very dense) and don't detect others well
(radiolucent-- not as dense).
 Abdominal ultrasound (picks up all stones)
 Oral cholecystogram (essentially an iodine swallow that gets
excreted into the bile, followed by an X-ray; picks up all stones)
2. List at least three important complications of cholelithiasis.
 Stones can obstruct the cystic duct (usually associated with
cholecystitis, leading to an infection and/or perforation of the gall
bladder) or the common bile duct (choledocholithiasis, often leading to
an infection of the biliary tree called cholangitis).
 Stones can block the pancreatic duct and trigger acute pancreatitis.
 Stones can erode through the wall of the gall bladder and form a
fistula with the small bowel. Uncommon.
3. Compare and contrast the macroscopic (visible appearance) and microscopic
features of acute and chronic cholecystitis.
 Acute cholecystitis (usually caused by a stone obstructing the cystic
duct):
 Upper quadrant pain, fever, nausea, vomiting.
 When there's common bile duct involvement, look for an
increase in serum alkaline phosphatase.
 Grossly: swelling and edema in the wall of the gall bladder,
sometimes hemorrhage.
 Histologically:
 Infiltration of PMNs and lymphocytes.
 Damage to the mucosa from the breakdown products of
bile .
 Can also get pus and necrosis (cholangitis), usually due
to a secondary bacterial infection.
Can see thickening of the muscularis propria.
[Recall that there is no muscularis mucosa in the gall
bladder.]
 Note that the cystic artery is an end artery, so any compromise
in it (as per swelling due to obstruction) can cause gall bladder
ischemia and coagulative necrosis.
 Chronic cholecystitis (usually caused by a string of subclinical acute
episodes):
 Nearly all patients have cholelithiasis.
 Grossly: marked thickening and fibrosis of the wall of the gall
bladder due to repeated bouts of inflammation.
 Histologically:
 There's lots of connective tissue from fibrosis, as well as
an infiltrate of lymphocytes and plasma cells. No PMNs
(it's not acute).
 May be a thickening of muscularis propria.
 Can also see mucosal outpouches ("Rokitansky-Aschoff
sinuses") coming deep into the wall from the lumen.
 [Boards note: bile acids are formed from cholesterol in the liver; they're
linked to taurine or glycine to form bile salts, which are more capable of
foaming up to form micelles. The excretion of about 5% of secreted bile salts
in the stool is the body's main/only mechanism for eliminating cholesterol.]
o (this makes the bile acid binding resins from CVPR make a little more
sense- you're stripping the body of its bile salts, which means it has to
mobilize its stored cholesterol to make more, which helps with
hypercholesterolemia.)
 [Note that "bile" isn't just bile salts; contains water, bicarb, bile salts,
phospholipids, protein (lecithin, etc), cholesterol, and bilirubin.]
4. Describe the histopathologic features of gallbladder cancer.
 Gall bladder cancer: Adenocarcinoma, associated with gallstones and
parasitic infection. Highly infiltrative growth pattern; frequently goes
into the liver or nearby lymph nodes. Often picked up late; very poor
prognosis.
 Like pancreatic cancer (see below), it can produce a lot of
scar/connective tissue.
 It can also fill up the lumen of the gall bladder.
5. Compare and contrast the histopathologic and clinical features of acute and
chronic pancreatitis.
 Acute pancreatitis:
 Associated with alcoholism and gallstones (lodged in pancreatic
duct), as well as cystic fibrosis and a host of other less common
problems.
 Clinically (from Wiki), see pain radiating to the back,
nausea/vomiting, sometimes fever and chills, possibly
hypovolemic shock from hemorrhage, and steatorrhea. Not
uncommonly fatal.
 Acute pancreatitis is where you see fat necrosis. Acute injury
to pancreatic cells causes them to release lipases; the lipases
break down surrounding fat and membranes to liberate free
fatty acid; FFAs form insoluble calcium soaps, making those
fatty lumps you see at autopsy.
 Histopathologically, see PMN infiltrate laced throughout thin
layers of fat.



Chronic pancreatitis:
 Associated with repeated bouts of acute pancreatitis due to
alcoholism or cystic fibrosis.
 Clinically, malabsorption and malnutrition develop due to
pancreatic insufficiency; often a considerable amount of pain
accompanies it.
 See atrophy and scarring of the duct and destruction of the
acinar tissue.
 Histopathologically, see broad swaths of scar tissue and
lymphocyte infiltrate. Note the islets are intact (chronic
pancreatitis doesn't generally produce diabetes).
6. Describe a pancreatic pseudocyst and know the clinical settings where a
pseudocyst sometimes occurs
 Pseudocyst: a cyst-like pouch within the pancreas, usually filled with
necrotic debris and blood. Not a true "cyst" since it does not contain an
epithelium.
 These can become infected and lead to peritonitis. Dr. Peterson's oftrepeated refrain: drain any pus.
 Often occur secondary to trauma.
7. Know the two common types of pancreatic neoplasms. Compare and contrast the
clinical syndromes and microscopic appearance of each type of lesion.
 Pancreatic adenocarcinoma: weak associations with smoking, chronic
pancreatitis, and obesity. Associated with BRCA mutations and family
history.
 Clinically, usually present at a late stage, with widespread
disease (weight loss and metastasis). Can also present with
back pain (cancer invades nerves) or painless jaundice
(blockage of the common bile duct).
 Trousseau Syndrome: In about 10% of pancreatic cancer
patients, see a hypercoagulable state (due to increased mucins
in the bloodstream? Common to all mucinous
adenocarcinomas.).
 Microscopically, the adenocarcinomas make a lot of connective
tissue and malignant glands that expand out to fill the pancreas
and invade the small bowel.
 Islet cell tumors:
 Associated with Multiple Endocrine Neoplasia, type I (MEN1,
Wermer's syndrome).
 Usually beta-cell tumors; usually benign. May produce a lot of
insulin; thus patients often present with hypoglycemia.
 If gastrin-producing tumors, can see Zollinger-Ellison syndrome
(high gastrin levels in serum, parietal hyperplasia, ulcers in
duodenum); they are more often malignant.
 Microscopically, cells look like carcinoid tumors (glandular
organization) with spherical, glassy nuclei.
Pathophysiology of the Gall Bladder and Exocrine Pancreas
Wednesday, October 22, 2008
9:02 AM
Pathophysiology of the Gall Bladder and Exocrine Pancreas, 10/22/08:
1. Understand the primary manifestations of acute pancreatitis.
 Acute and severe abdominal pain, nausea, and vomiting. See elevated
pancreatic enzymes (amylase and lipase) in the serum. Note that
acute pancreatitis is self-limiting.
 Two types of acute pancreatitis: necrotizing and interstitial (interstitial
is more common and less severe). Use a CT to differentiate, at least
according to the notes (Dr. Peterson is skeptical about utility).
 Note you can get systemic manifestations: ARDS, renal failure. Also
see hypocalcemia (since Ca++ is bound in lipid soaps), hyperglycemia,
and acidosis.
2. Understand the primary manifestations of chronic pancreatitis.
 Chronic inflammation and abdominal pain, often with malabsorption
and steatorrhea. Often see weight loss, malabsorption (so look for
bleeding disorders due to lack of vitamin K), and diarrhea.
3. Understand the pathophysiology of gallstone formation.
 Most pathological stones are cholesterol stones (and most of those
aren't radio-opaque).
 Occur due to:
 (1) Cholesterol hypersecretion (eg. obesity, genetic, rapid
weight loss, age: too much cholesterol)
 (2) Bile acid hyposecretion (eg. in ileal diseases like Crohn's:
too little bile)
 (3) Both.
 Recall: stasis plus a supersaturating concentration of cholesterol in the
bile plus "nucleation" (the seed around which the stone crystallizes)
forms stones.
 Note: generally don't take out asymptomatic gallstones.
4. Understand the pathophysiology of acute cholecystitis.
 Caused by cystic duct obstruction from a gallstone.
 If there's cholangitis (infection of the biliary tree secondary to bile duct
obstruction, check the blood's white count), always drain the pus to
avoid or ameliorate secondary bacterial infections.
 Liver function tests are generally elevated; total bilirubin is usually
normal. Can have elevated alkaline phosphatase if the stone's in the
common bile duct).
 Look for a positive Murphy's sign.
Colorectal Cancer
Thursday, October 23, 2008
7:53 AM
Colorectal Cancer, 10/22/08:
1. Recognize the magnitude of the CRC (colorectal cancer) problem.
 It's big. Says here that it's the second most common cause of cancer
death in both men and women. We've been taught elsewhere, and
Internet searching seems to support, that it's actually third, behind
lung and breast/prostate, in any given individual.

Dr. Ahnen on this: it's the second most common cause of
cancer death in COMBINED men and women. Evidently the
stats are meant for hermaphrodites.
 CRC is in relative decline among women, but the rates are pretty
steady (and higher) among men.
2. Understand the mechanisms of pathophysiologic consequences of CRC.
 Strong risk factors: age, country of birth, genetics (familial
adenomatous polyposis, hereditary non-polyposis colon cancer), longstanding ulcerative colitis.
 Note that there's a strong correlation between family history
and colon cancer risk-- get it more often, get it younger.
 "Country of origin" influence seems to have a lot to do with
diet-- immigrants from one country to another have children
whose cancer risk is the same as the indigenous population.
 About two-thirds of all colon cancers occur in the descending colon.
 Adenomas (not adenocarcinomas) in the colon rarely cause any
functional complications except bleeding-- thus one of the main
screens for benign tumors is blood in the stool.
 Note that adenomas are sort of "cancer in waiting" (like
carcincoma in situ is like "lazy cancer")-- they are dysplastic,
just not to the point where they're verging on invasion or
metastasis.
 Adenocarcinomas have a variety of other presentations (eg. can
perforate the bowel or grow into surrounding structures), but they also
very commonly bleed.
 Note that unexplained weight loss seems to be only infrequently
associated with colorectal cancer.
 Right-sided colorectal cancers: bleeding is occult and not easily visible
since the stool is liquid at this point in the colon.
 This means they generally aren't caught until they've grown to
a larger size.
 Note also that since the stool is liquid, the tumor isn't going to
perceptibly obstruct flow until it's extremely large.
 Left-sided colorectal cancers: more obvious bleeding: blood on the
surface of brown stool (stool is more solid by the time it's descending).
 These are more likely to cause a change in bowel habits
(constipation, obstruction) and can sometimes be felt on rectal
exam; therefore they're caught more frequently at an early
stage.
 More on left vs. right at the bottom of the next lecture's LOs.
 Look for tubular vs. villous patterns of dysplasia: tubular is sort of
standard glandular approach, villous pushes out in 'fingers' into the
lumen. (again, next lecture has more.)
3. Understand how pathophysiology has modulated the clinical approachprevention/treatment of CRC.
 Fecal occult blood tests: large adenomas and adenocarcinomas bleed
intermittently. Goljan says blood in the stool in a person over 50 is
colorectal cancer (or adenoma) unless proven otherwise.
 Can also look for the cells that adenocarcinomas shed in the
lumen-- stool DNA testing is beginning to be used.
 The dominant screening form in the US is regular colonoscopies-visualize, remove adenomas and polyps.
 It's also possible to use CT colonography instead of colonoscopy.
4. Understand that the molecular basis of CRC is not uniform and that this impacts
the pathophysiology of the disease.
 It's not uniform.
 3 molecular driving forces for developing colorectal cancer (more on all
of these in the next lecture):
 Microsatellite-stable:
 Chromosomal instability pathway
 Most sporadic cancers and FAP cancers (about
80% of all CRCs). Most mutations in oncogenes
or tumor suppressor genes fall into this category.
 Defective DNA pathway
 Failure of DNA mismatch repair: when due to a
germ line problem, accounts for HNPCC cases.
 Microsatellite-stable cancers look like fairly typical
adenocarcinomas.
 Microsatellite-unstable:
 Epigenetic mutation pathway
 Due to post-translational modifications of DNA.
 What we're talking about here is altered DNA
methylation (recall that DNA methylation is a
normal inactivation mechanism), primarily of CpG
islands (CG repeats). A hypermethylation of
these islands results in underexpression of
certain genes (CpG islands are often located in
promoter regions). Hypomethylation of other
regions can result in their overexpression.
General principle: when you screw with
repressor-promoter patterns, you tend to get
cancer. This seems to be responsible for about
15% of all colorectal cancers.
 Note that just because it's not directly genetic
doesn't mean the tendency to create
inappropriate methylation patterns can't be
hereditary.
 Microsatellite unstable cancers tend to show serrated
edges and have high levels of mucin production, as
opposed to typical adenocarcinomas (low levels of mucin
production).
 They also don't respond as well to adjuvant
chemotherapy. Despite this, they tend to have a better
prognosis than microsatellite-stable cancers.
 Note also that they're more frequently located in the
ascending, rather than the descending, colon.
Polyps and Colon Carcinoma
Thursday, October 23, 2008
9:01 AM
Polyps and Colon Carcinoma, 10/22/08:
1. Describe and compare the three major types of GI polyps.




[Note a piece of basic vernacular: polyps can either be sessile (lying
flat along the mucosal surface) or pedunculated (attached to the
mucosa by a thin stalk).]
Hyperplastic polyps:
 Very common in middle aged or older adults, particularly in the
left (descending) colon.
 Grossly: small, smooth, yellow, raised spots.
 Histologically: crypt cells are normal, and columnar cells are
normal with normal mucin production. Proliferative activity is
limited to the basal mucosa, as per normal tissue. The only
thing odd about them is that the lumen of the crypt is dilated
and looks serrated or cross-like.
 Note that there is more or less no risk of progression of cancer
from most hyperplastic polyps, except in rare isolated cases or
in some rare familial conditions that cause giant hyperplastic
polyposis (can progress to adenomas).
Neoplastic (adenomatous) polyps:
 Most common clinically significant polyp.
 Three varieties, in order of frequency: tubular, tubulovillous,
and villous.
 Common histological theme: hyperplastic columnar,
mucin-producing epithelium on a fibrous, vascularized
stalk.
 Tubular adenomas look like trees: a poofy ball on
top of a thin stalk. Ok, more like trees drawn by
artistically challenged 3-year-olds (or me in
present day).
 Villous adenomas are more embedded in the
surface of the mucosal wall and send out folds or
fingers into the lumen.
 Tubulovillous adenomas are sort of the bastard
children of both types.
 Most of these polyps are benign; malignancy takes years
to develop. The bigger the polyp, the larger the risk of
developing malignancy.
 Look for dysplastic changes and glands present in
the stalk as signs of cancer development and
invasion.
 Villous (less than 1%) are at highest risk for progression
(they're right there next to the submucosa).
 Theme here: the overwhelming majority of colon cancers
progressed from a pre-existing polyp. Resect the polyps, save
the world.
Hamartomatous polyps:
 Very slight risk of progression, but generally benign.
 Recall that a hamartoma is essentially a tissue construction
project with misplaced blueprints-- it's composed all of normal
tissue elements, but they're all disorganized and growing
haphazardly. There's no dysplasia to speak of.
 When they arise in the mesenchymal tissue of the
submucosa, they can push the mucosa out into the
lumen of the colon. Note that this submucosal growth
can include fat, connective tissue, or nervous/vascular
tissue (vascular tissue bleeds easily).
 When they arise in the mucosa itself, they can be either
juvenile or Peutz-Jeghers polyps. The former is a
significant etiology for GI bleeding in children; the latter
has submucosa and smooth muscle proliferation in
addition to mucosal proliferation, and carries an
increased risk of malignancy in the pancreas and other
locations (Peutz-Jegher syndrome; see below).
2. Understand the key genetic changes that underlie progression from a benign
adenomatous polyp to frank carcinoma in "sporadic" cases of cancer.
 Adenomatous polyps progress to cancer due to an expansion of a stem
cell that has inactivating mutations in both APC genes (chromosome
5q).
 [Take-home for boards: APC = main tumor suppressor gene in colon
cancer.]
3. Discuss which genetic syndromes carry an increased risk to develop GI carcinomas
at a young age.
 Familial adenomatous polyposis (FAP): inherited inactivation mutation
in one APC gene Results in thousands of colonic polyps; typically
progresses to colon cancer inside 10-15 years.
 Note different mutations in the APC gene (it's a big gene with
systemic effects) can cause fibromatosis or malignant brain
tumors.
 Hereditary non-polyposis colon cancer (HNPCC, also called Lynch
syndrome): mutations in the DNA mismatch repair pathway. Doesn't
show the overabundance of polyps that FAP does, but the polyps that
are there tend to progress to cancer.
 MYH polyposis: mutations in the DNA base excision pathway for taking
out mispaired guanine bases.
 Some hereditary epigenetic modification syndromes, as mentioned in
the last lecture.
4. Discuss and describe hamartomatous polyps and which genetic syndrome carries a
propensity to develop hamartomatous polyps in the GI tract.
 Mainly described above.
 Serine/threonine kinase 11 (STK11) mutations can cause PeutzJeghers syndrome (P-J hamartomas, plus increased risk of pancreatic,
breast, lung, ovary, uterus cancers).
5. Describe the major histologic features of colon cancer, including the common
patterns of growth seen in right-sided versus left sided lesions and how this affects
the way these cancers present clinically.
 Histologically, colon cancer usually looks like medium- to welldifferentiated adenocarcinoma (possible exception for microsatelliteunstable cancers).
 Cancers on the right:
 Tend to present late (as mentioned in the last lecture, the stool
is fluid at that point and the colon has significant expansile
ability, so obstruction isn't obvious).
 Tend to be exophytic (masses growing out into the lumen).
 Cancers on the left:
 Tend to present earlier (again as mentioned, it's easier to pick
up obstruction when the stool is more solid).
 Tend to be circumferential (sort of colonic stenosis).

Tend to metastasize to the liver, sometimes also to the lungs.
Oral Healthcare Issues In Clinical Practice
Friday, October 24, 2008
10:33 AM
Oral Healthcare Issues In Clinical Practice, 10/24/08:
[Starred with "**" are the points he heavily suggested would be testable material.]
1. Describe normal child and adult oral anatomy.
 **"Neglected sites:" lateral tongue, under tongue, behind lips, floor of
mouth.
 **Periodontal ligament: binds tooth root to alveolar bone. This is what
you want to watch out for during various oral infections to prevent
tooth loss.
 By age 3, child should have a full set of 20 teeth. By age 18-20, adults
should have 32 teeth (8 + wisdoms).
2. Understand how oral and systemic health are inter-related (caries, periodontal
disease, cancer).
 It works both ways: oral affects systemic, systemic affects oral.
 Caries: pain, poor eating/nutrition, impaired speech development, etc.
 **Note cavities are caused by an infectious, transmissible disease:
 Streptococcus mutans: breaks down sucrose to lactic acid.
Mouth + Strep. mutans + sucrose = acids --> caries.
 Technically, Wiki notes that S. mutans can break down
fructose, lactose, and glucose to acid as well, but says
that only in sucrose metabolism is one other byproduct
produced: a sticky residue that adheres the acid to the
tooth surface, which seems to be necessary for tooth
decay. Thus sucrose metabolism by these bacteria is
necessary to actually cause caries.
 That said, lots of (say) glucose in the diet (or in the
blood-- see below under diabetics) probably doesn't
help.
 Acid causes demineralization of teeth-- long periods between
sucrose ingestion or regular teeth brushing helps clean off
sucrose/acid and allow teeth to remineralize again.
 First sign of caries: white spots on teeth (demineralization).
Apply fluoride.
 Caries can go into the soft tissues and cause facial cellulitis.
 Oral cancer: increased risk with EtOH and smoking.
 If there's chronic inflammation in the oral cavity, the resultant
inflammatory mediators (TNF-alpha, IL-1) can circulate systemically
and get up to distant mischief.
 Chronic periodontitis: when the inflammation gets between the gum
and the tooth, it starts attacking the periodontal ligament.
 Diabetes: poor glycemic control = higher risk of periodontitis.
 Obesity: promotes inflammatory mediator release = higher risk of
periodontitis.

Dry mouth, caused by a variety of drugs, can lead to higher rates of
periodontitis, as do chemo drugs or anything else that suppresses the
immune system.
 Periodontitis-derived inflammatory response is associated with
coronary artery disease.
 Periodontitis is also associated with higher rates of preecclampsia.
 **Most common chronic disease of childhood: dental caries.
3. Encourage medical and dental collaboration.
 Or the dentists will come for you in the night.
Functional Histology of the Liver
Monday, October 27, 2008
7:42 AM
Functional Histology of the Liver, 10/27/08:
[Functions of liver:]
 Bile production (emulsify fats); stores iron, glucose, and vitamins;
synthesizes albumin and other plasma proteins; does metabolite
exchange in blood; detoxifies blood in smooth endoplasmic reticulum
(note SER hypertrophy on ingestion of toxins) and traps NH3 and
other wastes for excretion.
1. Be able to discuss (in a very general sense) the digestion/absorption of lipids and
the role of bile in the emulsification of fats. Why do we need bile?
 Ok. Dr. Michaels explains this a little differently from Dr. Grichtchenko.
Here, the bile salts form micelles immediately (before pancreatic
lipase/colipase administration); the lipases and colipases get into the
micelles and break the triglycerides up into smaller molecules that the
cells can absorb. Then the bile salt micelles transport the smaller
molecules to the cell membrane.
 Note that triglycerides get into the caval system without going through
the hepatic portal circulation (go through the lymphatics).
 Note also that while the cholesterol and bilirubin in bile are largely
excreted in the stool, the bile salts are reabsorbed in the terminal
ileum.
 We need bile, in any case, because we can't absorb fat without it, and
also because it's our only way of excreting cholesterol.
2. Review the blood supply to the liver. Explain the statements: 1) the liver has a
double blood supply and 2) the liver is an exocrine and an endocrine gland. What is
the major exocrine role of the liver? Endocrine role (general)?
 Right hepatic artery supplies right lobe. Left hepatic artery supplies
left, caudate, and quadrate lobes.
 No anastamosis between left and right hepatic arteries (independent
blood supplies).
 Exocrine role: bile (stored in gall bladder, released upon ingestion of
fats; contains bile salts, bilirubin, cholesterol, water, ions, and IgA)-secreted by the liver but doesn't go into the blood.
 How this storage thing works: when you're not eating fatty
foods, a sphincter (specifically the Sphincter of Oddi) down by
the Ampulla of Vater contracts to prevent bile from flowing into
the duodenum; it backflows up into the gall bladder.

Endocrine role: albumin, clotting factors, lipoproteins and
glycoproteins, etc. Essentially, everything made in the liver that goes
into the blood.
3. Discuss the morphological boundaries and the functional significance of a hepatic
(classic) lobule, a portal lobule and an acinar lobule. Be able to describe how blood,
bile and lymph flows in a lobule.
 Not to speak ill of Our Medical Forefathers, but this terminology sucks
balls. Bear with me, I'm going to try and figure it out. Shout-out to Dr.
Michaels for shoring me up with this.
 Structural organization of the liver: parallel chains of linked
hepatocytes make up a hexagonal 'block' of liver tissue. This 'block' is
called a lobule and is the smallest functional unit of the liver. It is
surrounded by six hepatic triads running parallel to it at each 'point' of
the hexagon.
 The hepatic artery (containing well-oxygenated blood with few
nutrients) and the portal vein (containing poorly-oxygenated
blood rich in nutrients) drain blood towards the center of each
lobule through sinusoids (tracts running to the center flanked
by hepatocytes). At the center of each lobule there's a central
vein that eventually drains to the caval system.
 The bile ducts are being drained out into by small bile canaliculi
that run between adjacent hepatocytes.
 Okay. Having described the structural organization, there are now
three ways of conceiving of this organization, depending on what
you're interested in tracking. Unfortunately, someone decided to name
the conceptual organizations by the same name as the structural
organizations, ie. "lobules." Here we go:
 Classic lobules: A "classic lobule" seems to be equivalent to a
structural "lobule;" you're looking at one lobule structure, all of
the blood flow into it, and all of the bile flow out of it. It's used
mainly when you want to think about big-picture blood flow and
drainage.
 Portal lobules: Here, you're looking at bile secretion. The
"portal lobule" looks at all the bile canaliculi that drain into a
bile duct in a given hepatic triad. This corresponds roughly to a
triangularly-shaped area between three central veins, with the
bile duct in question in the middle.
 Acinar lobules: Used for looking at areas of relative perfusion.
Dr. Michaels says this is the most clinically relevant way of
thinking about it. They're diamond-shaped territories between
two central veins (the long axis of the diamond) and two
adjacent hepatic triads (the short axis of the diamond). There
are three zones in each structural lobule corresponding to the
extent of oxygen and nutrient perfusion from those triads:
 Zone I: closest to blood supply (on the outside of the
lobules, farthest from the central vein). This is where
hepatitis virus damage tends to cluster (first tissue
exposed).
 Zone II: intermediate distance from blood supply.
 Zone III: farthest from blood supply (nearest to the
central vein).
 Note that not only are these zone III cells most
vulnerable to ischemia, they also tend to be most
vulnerable to blood-borne toxins (less capacity to
detoxify). Main 2 toxins: EtOH and acetaminophen (and
its metabolites).
 This is a relatively significant concept for boards and
whatnot.
 If you're looking at a lobule histologically, the large vessels seen are
almost always the portal venules. Just FYI.
4. Be able to discuss the functional and structural specializations of hepatocytes,
sinusoidal endothelial cells, Kupffer cells, stellate cells, the space of Disse and bile
canaliculi.
 Hepatocytes: big, polygonal cells, situated between sinusoids on either
side. Can be multinucleated, possibly because the liver's stem cell
capacity is fairly astounding.
 Polarity of hepatocytes is weird.
 Apical surface of a hepatocyte is the surface that faces
the bile canaliculi that lie between adjacent hepatocytes.
 Basolateral surface is the surface that faces blood in
sinusoids on both sides. Lots of microvilli on these
surfaces.
 Note that a given hepatocyte has two basolateral
surfaces-- maximizing its contact with the blood
in the surrounding sinusoids. See note, below,
about the liver being kind of a massive capillary
bed.
 Essentially the hepatocytes modify incoming blood from
sinusoids - take oxygen and nutrients from it, do
toxin/metabolite exchange with it - and then allow the blood to
keep going down the sinusoids to the central vein. Kind of like
capillary beds.
 Sinusoids: have a discontinuous endothelium with big gaps in
it.
 If you consider the liver - minus the biliary function - as
one big capillary bed doing oxygen exchange and
detox/endocrine functions, these are the actual
capillaries carrying the blood through the gas- and
metabolite-exchange portion of the bed.
 Space of Disse: Space between the endothelium of the
sinusoids and the basement membrane on the basal side of the
hepatocytes. Unrelated to the fabled city of Hell in Dante. If you
don't know it, go get some culture. Can't study the liver without
culture.
 Kupffer cells: macrophages that live within the walls of the
sinusoid endothelium.
 Stellate cells: fat and fat-soluble vitamin storage cells of liver.
Live between the hepatocyte and the sinusoid endothelium (in
the space of Disse). With damage to those cells, they start
acting like fibroblasts and produce fibrosis and scarring.
 Bile canaliculi: as mentioned, formed by the plasma membrane
of two adjacent hepatocytes. These drain out into canals of
Hering and from there out into the bile ductules.
Pediatric Liver Disease
Monday, October 27, 2008
8:56 AM
Pediatric Liver Disease, 10/27/08:
[Note that as per notice from Megan Tripp-Addison and Laura Friedlander, our right
honorable course reps, the LOs for this lecture were changed.]
1. Review common anatomic abnormalities of the hepatobiliary system
 Total hepatic agenesis (incompatible with life)
 Hepatic lobe agenesis (usually asymptomatic)
 Situs inversus totalis (mirror image of normal anatomic arrangement)
 Asplenia/polysplenia (midline, symmetrical liver lobes)
 Omphalocele and diaphramatic hernia can shift hepatic location and
mess with its vascular supply.
 Choledochal cyst: ductal dilation and biliary stasis in and above the
common bile duct.
 Most present before 10 years with jaundice and upper quadrant
pain, can see a RUQ mass as well.
 Can get infection, gallstones, pancreatitis if obstruction of
pancreatic duct, etc.
2. Discuss the differential diagnosis of neonatal cholestasis, with focus on biliary
atresia
 DDx:
 Physiological jaundice (harmless; largely due to immature
bilirubin conjugation system)
 Infection
 Medication
 TPN (total parenteral nutrition, as given to prematurely born
infants)
 Obstruction/biliary atresia
 Metabolic disease
 Hereditary hyperbilirubinemia
 Idiopathic neonatal hepatitis
 Biliary atresia:
 1 in 8,000; obstruction of extrahepatic biliary tree.
 More common form: acquired perinatally; biliary tree
undergoes fibrosis and closure after birth. Shows normal at
birth, but develops cholestasis; progressive hyperbilirubinemia
(can't excrete it). No compelling evidence for any one etiology,
but viral heads the list of maybes.
 Rarer form: embryonic/fetal. Shows immediate jaundice after
birth due to abnormal development of biliary tree in utero.
3. Review common metabolic storage diseases that involve the liver
 Most common are the disorders of iron (hemochromatosis) and copper
(Wilson's disease) storage. Tend to present in adult life. More in "NonViral Liver Disease."
 Also see glycogen and lysosomal storage disorders. Not extensively
discussed here.
4. Discuss hepatic involvement in common genetic diseases including alpha-1antitrypsin deficiency and cystic fibrosis

Alpha-1 antitrypsin disease: AR disorder characterized by a misfolded
protein (which is involved in neutralizing endopeptidases secreted by,
among other things, neutrophils.) Results in excessive damage from
inflammatory reactions. In this setting, we're concerned about
accumulation of the (toxic) misfolded protein in the liver, not the
response to inflammation (that's significant in the lungs, where it's
what gives you pan-acinar, early-onset emphysema). Can result in
cirrhosis.
 Cystic fibrosis: the liver really isn't the first thing you worry about in
CF, but as patients live longer it starts to be more of a problem.
Pathology: focal cirrhosis causing loci of fibrosis. Grossly it looks like
massive bulbules growing out of the liver (kind of the opposite of
adult-onset polycystic kidney disease).
5. Review the most common hepatic neoplasms in the pediatric population, with
focus on hepatoblastoma
 Benign: hamartomas, teratomas, hepatocellular adenomas,
hyperplasias.
 Malignant: hepatoblastomas (mainly under 5 years) hepatocellular
carcinomas (mainly over 5 years, mainly adults)
 Hepatoblastoma:
 27% of pediatric liver tumors, about half of all malignant
pediatric liver tumors.
 2:1 male:female incidence
 No association with underlying disease.
 Tends to present with anorexia, weight loss, nausea/vomiting,
pain, RUQ abdominal mass.
 See elevation of serum alpha-fetoprotein (also elevated in
hepatocellular carcinomas).
 Genetics: activation of Wnt/beta-catenin pathway; link with FAP
(similar mechanism) and Beckwith-Wiedemann Syndrome
(overgrowth disorder with abdominal wall defects).
 Histology: can be epithelial, mesenchymal, or mixed. Tend to
be very large and not resectable until it's shrunken with
chemotherapy.
 Overall survival is 65-70%.
Some other stuff he covered that's not in the new LOs:
 Idiopathic neonatal hepatitis: diagnosis of exclusion but fairly common
(25-40%). Some familial patterns but mostly sporadic. Sporadic form
has a better prognosis. Most cases spontaneously resolve but can also
see chronic liver damage or death.
 See multinucleated giant cells in liver (common liver disease
finding).
 Hereditary hyperbilirubinemias: unconjugated vs. conjugated.
 Unconjugated hyperbilirubinemia: generally a lack of
conjugation enzymes. Note that unconjugated bilirubin is
neurotoxic to neonates (incomplete BBB).
 Crigler-Najjar Syndrome: decreased (AD) or no (AR)
function in glucuronidation enzyme.
 Gilbert's syndrome: slightly reduced function of the
same enzyme; only really clinically significant during
periods of systemic stress. This is extremely common
(5-10% of population).


Conjugated hyperbilirubinemia: defects in transporter proteins
such that the conjugated product can't be excreted properly.
 Dubin-Johnson syndrome: defect in excretion of
conjugated product due to a mutation in MRP; generally
significant during systemic stress.
 Rotor Syndrome: defects in hepatocellular
uptake/excretion of bile pigments.
Reye syndrome: currently rare; used to be a main cause of
encephalopathy in children. Caused by use of aspirin in viral febrile
illnesses. Mitochondrial injury in liver leads to microvesicular (smaller
than the nucleus) fatty degeneration of organs, particularly the liver.
(note microvesicular fat storage tends to be indicative of metabolic
storage diseases; macrovesicular fat storage tends to be indicative of
dietary etiology.)
Viral and Non-Viral Liver Disease
Monday, October 27, 2008
9:43 AM
Viral and Non-Viral Liver Disease, 8/27/08:
[Lots of material here. If you're really pressed for time, check out his "review slides"
at the end of each powerpoint presentation for things he seemed to think were
particularly important.]
1. Describe the pattern of histological findings that is referred to as “acute hepatitis”.
List the two principal recognized etiologies for this disorder in order of their
likelihood. State the most common factor associated with each etiology.
 Acute hepatitis: liver damage within 6 months of symptoms (chronic is
after 6 months). Generally due to drugs or hepatitis A/B virus. Most
common cause of drug-induced acute hepatitis: acetaminophen. Hep A
transmitted fecal-oral; hep B transmitted through blood/body fluids.
 Histologically: apoptotic bodies (shrunken, apoptosing
hepatocytes); also diffuse, mixed inflammation.
 Hyperacute subtype: fulminant hepatic failure (liver damage
within 4 weeks of onset); most of these cases are due to
acetaminophen overdose. See "bridging necrosis" between
adjacent central veins.
2. List the five most important hepatotropic viruses and indicate their mode of
transmission and clinical behavior. What histological pattern is associated with each?
Which viruses are most likely to cause chronic hepatitis, acute hepatic failure and
cirrhosis?
 Last point first:
 Acute hepatitis only: A and E (both in the word acute)
 Chronic hepatitis only: C (for chronic)
 Both acute and chronic: B and D (D needs B, see below; no
clever mnemonic)
 Cirrhosis follows chronic disease. Note cirrhosis and the chronic
fibrosis it suggests can lead to hepatocarcinoma.
 Hepatitis A: most common in US.

Single-stranded RNA, non-enveloped virus. Does not cause
chronic hepatitis; acute only.
 Acquired through fecal-oral route.
 Has an incubation of about 4 weeks; acute disease occurs 1-2
months after exposure.
 Histologically: see above (acute hepatitis).
 Hepatitis B: next most common in US.
 Circular DNA virus (can integrate into host genome). Can cause
chronic, acute, and/or fulminant hepatitis.
 Acquired through blood and/or other body fluids (is an STD).
Can be acquired by fetus in utero from infected mother.
 In chronic infection, the blood markers (antigens) remain
detectable for years. Watch out for cirrhosis and hepatocellular
carcinoma development.
 Histologically: see "ground glass" hepatocytes (crystalline viral
particles) in which the organelles have been pushed to the rim
of the cytoplasm in acute hepatitis B episodes, but not in
chronic. Also see "sanded" or finely stippled nuclei (inclusion
and expansion of viral DNA).
 Hepatitis C:
 Single-stranded RNA virus. High genetic variability, facilitating
escape from antibodies.
 I assume you all know this already, but there's vaccines for Hep
A/B and none for C.
 Almost never causes acute hepatitis.
 Repeated bouts of viral mutation and escape from immune
control, and the corresponding inflammatory responses, are
characteristic and cause chronic fibrotic injury.
 Acquired through blood/body fluids; mainly drug use and sexual
exposure. Can also be transferred to fetus from mother.
 Histologically, look for lymphoid infiltrates in portal tracts, fatty
liver, and lesions in the bile ducts. Also chronic inflammation
and fibrosis, as expected.
 Hepatitis D: circular RNA. Infection is completely dependent on cohepatitis B infection, and potentiates it-- increases inflammation,
fibrosis, and rate of progression.
 Hepatitis E: similar to hepatitis A, but water-borne and more
aggressive; causes acute and not chronic hepatitis. Note it's a major
risk of fulminant liver failure in pregnant women.
 [Note hepatitis G is not associated with disease, inhibits HIV
replication, and may be protective against other forms of hepatitis.]
 [Not in the LOs but he did put some emphasis on it: end-stage liver disease:
coagulopathy, hypoalbuminemia, hyperbilirubinemia, encephalopathy,
hepatorenal syndromes (kidney ischemia and failure secondary to liver
failure), skin changes, portal hypertension.]
o Portal hypertension: ascites (fluid in peritoneal cavity), engorgement
of portal-systemic shunts (esophageal varices, paraumbilical veins),
and splenomegaly.
o Biopsy descriptions: Grade = degree of inflammation. Stage = degree
of fibrosis.
3. Name several non-viral causes of chronic liver disease that show a "chronic
hepatitis pattern" similar to viral hepatitides. How are these diseases differentiated
from viral disease histologically and serologically?

Autoimmune hepatitis:
 Can present with jaundice and fever.
 Usually shows up in women 15-40 years of age.
 Diagnose by serum autoantibodies and plasma cell infiltrates on
biopsy. Treat with steroids.
 Metabolic liver diseases (see below).
 [Note: for the rest of the lecture, he largely goes off two tables at the end of
his notes. Knowing them might be useful.]
4. Based on Table 1, describe the pattern of histologic findings associated with the
diagnosis of alcoholic liver disease/ steatohepatitis. Name the histologic findings (if
any) that indicate the etiology of the disease. List the clinical features associated
with nonalcoholic steatohepatitis.
 Steatohepatitis (most is alcohol-induced):
 Histologically, frequently indistinguishable from many other
things (steatosis, inflammation, fibrosis, damage to
hepatocytes, etc).
 PMNs dominate infiltrate in acute alcohol-induced
steatohepatitis.
 In alcoholic steatohepatitis, look for "ropy" pink deposits
(Mallory hyaline) and fibrosis extending out into the sinusoids.
 [Steatosis: the triglycerides in hepatocytes are not only not
broken down by beta-oxidation, but not exported as VLDL
either. Alcohol inhibits both pathways.]
 Factors associated with non-alcoholic steatohepatitis: obesity,
diabetes mellitus, hypertriglyceridemia, amiodarone use, and
chemotherapy.
 Note distinction: "fatty liver" is steatosis alone, where
steatohepatitis also includes damage to the hepatocytes.
5. Based on Table 1, describe the pattern of histologic findings associated with
chronic biliary injury. List the two most important diseases that show this pattern.
Name the histologic findings (if any) that differentiate these two entities. State the
non-tissue based diagnostic modalities that may influence the interpretation of the
biopsy.
 Basic problem: obstruction of the biliary tree causes a buildup of bile
salts and copper; these seem to destroy nearby hepatocytes.
 Two diseases associated with it: primary biliary cirrhosis (autoimmune
destruction of bile ducts) and sclerosing cholangitis (fibrosis-mediated,
circumferential stricture of bile ducts).
 Primary biliary cirrhosis:
 95% of patients have anti-mitochondrial antibodies, most have
other autoimmune diseases.
 Note no risk of cancer and insidious onset (itching before
jaundice).
 Histologically, see "florid duct lesions:" bile ducts surrounded by
granulomatous inflammation.
 Like most autoimmune conditions, more common in women.
 Sclerosing cholangitis:
 Two thirds of SC patients also have inflammatory bowel
disease.
 Clinically, see progressive fatigue, itching, and jaundice.
 Histologically: see "onion skin fibrosis" buildup around bile
ducts, gradually causing strictures in bile ducts.

Radiology is important: get an endoscopy or MRI study to
confirm strictures.
 See increased risk of cancer.
 More common in men.
 Note this can be caused (secondary SC) by pretty much
anything that causes chronic obstruction in the biliary tree.
6. Based on Table 1, define chronic hepatitis. List the histochemical stains that are
used for diagnosis of the two most important diseases of iron or copper accumulation
in the liver. Describe the genetic basis of these disorders and the relationship to the
usefulness of genetic testing. What associated clinical findings accompany each of
these diseases?
 Hemochromatosis (iron buildup):
 Hereditary form: AR-inherited, fairly common in white people.
Doesn't mention much about genetic testing, but I would
imagine it can be useful for picking up the severe mutations.
 Present in middle age; classically show up with liver disease,
diabetes, and heart failure, due to accumulation of iron in liver,
pancreas, and pacemaking heart tissue respectively.
 Acquired form: from repeated bouts of transfusions or
hemolysis.
 Histologically, can see brown pigment (iron) inside hepatocytes.
Note difference from brown pigment inside macrophages due to
overuse of cascara laxatives (melanosis coli).
 Note accumulation of iron in the liver begins closest to portal
vein (Zone I).
 Wilson's Disease (copper buildup):
 AR-inherited mutation in copper excretion protein; rare. Hard to
do genetic testing (many mutations).
 Tends to present in childhood with neurologic symptoms
(copper in lenticulate nucleus, leads to Parkinsonian syndrome),
Kayser-Fleischer rings (copper-colored rings around the iris).
Sometimes "bronze diabetes"-- copper in pancreas and skin.
 Can get steatohepatitis and fibrosis.
 Copper staining shows this up.
7. Based on Table 1, name a genetic cause of chronic liver injury that is associated
with lung disease. Describe the genetic diagnosis of individuals at risk for this
disorder. What histologic finding is commonly seen in patients with this disease?
What is the histochemical stain that shows this finding most clearly?
 Alpha-1 Antitrypsin Deficiency:
 AR- inheritance; most severe form is PiZZ form (< 10% normal
alpha-1 AT levels).
 Note alpha-1 AT is made in the liver (liver transplant cures the
deficiency).
 Mutant form of alpha-1 AT gets stuck in the liver, causing injury
and cirrhosis in about 1 in 10 PiZZ patients.
 PAS-diastase stain picks up alpha-1 AT-heavy hepatocytes
(cytoplasmic inclusions). Affects mainly Zone I hepatocytes.
8. List three benign tumors and three malignant tumors that arise in the liver (i.e.
not metastatic disease). Describe the histologic findings that would allow their
differentiation. What clinical or history features are useful in suggesting particular
diagnoses?
 Benign:


Focal nodular hyperplasia: actually a vascular malformation.
Acquired. Causes local hepatocyte hyperplasia. Histologically,
look for thick-walled vessels with non-trabecular proliferation of
hepatocytes around them. Excised.
 Hepatocellular adenoma: steroid-induced disease, usually
associated with oral contraceptives in women or anabolic
steroid use in men. Histologically, no portal triads, central
veins, or sinusoids; just solid hepatocytes packed cheek to
jowl. Excised.
 Hemangioma: most common benign tumor of the liver. An
incidental finding.
 Biliary adenoma/cyst: about what you'd expect. Watch out
for biliary cysts as a sign of autosomal dominant polycystic
kidney disease.
Malignant:
 Hepatocellular carcinoma: most common liver cancer;
number one cause of cancer death worldwide. Usually arises at
advanced age from cirrhotic liver, but can also present at a
younger age associated with hepatitis B. Note incidence is
increasing in the US. Histologically, normal trabecular
framework is destroyed (may be glandular patterns). Can
infiltrate into either the blood or the lymphatics.
 Fibrolamellar variant of HCC: better-prognosis,
younger-presenting HCC with large amounts of collagen
banding.
 Cholangiocarcinoma: adenocarcinoma of the biliary tree;
typically not associated with cirrhosis. Histologically, disordered
glandular formation with dysplasia.
 Angiosarcoma: rare, mainly occurs in elderly patients with
exposure to discontinued radiation contrast dye.
Liver Function Tests
Tuesday, October 28, 2008
7:43 AM
Liver Function Tests, 10/28/08:
[From his notes: "Serum liver chemistry tests are often referred to as liver function
tests (LFTs). This is a misnomer in that most of these tests do not actually assess
liver function." He prefers "liver chemistry tests." That said-- everyone is going to
call them LFTs.]
1. Understand common liver chemistry tests and their clinical implications when
abnormal:
 AST/ALT: reflect hepatocellular damage.
 ALT is only expressed in the liver; AST is also expressed in the
heart, muscle, and blood. ALT is cytosolic, while AST is also in
mitochondria.
 Alkaline phosphatase: reflects cholestasis, infiltrative disease, or biliary
obstruction

Present pretty much everywhere; generated in response to
obstruction (thus also infiltrative disease, cancer, etc).
 Also elevated in bone disease and pregnancy.
 Can get tests that are more specific for liver-generated alkphos (GGT test, 5'-nucleotidase test).
 Bilirubin: reflects cholestasis, impaired conjugation, or biliary
obstruction
 (see #3 below)
 Can also look at albumin levels (production is in the liver) and
prothrombin time (to test production of liver-produced clotting
factors).
 Note elevated prothrombin time can be due to vitamin K
deficiency or malabsorption as well; administer sub-q vitamin K
to look for normalization.
2. Characterize patterns of liver chemistry test abnormalities:
 Two general patterns of liver dysfunction:
 Hepatocellular: predominantly AST/ALT elevation
 Cholestatic: predominantly alk-phos elevation
3. Understand bilirubin metabolism and causes of jaundice:
 Normal heme degradation product; insoluble in water until it's
conjugated.
 Unconjugated = indirect bilirubin; conjugated = direct bilirubin.
 Mnemonic he mentioned: unconjugated and indirect both have
a prefix.
 Basically once you take the iron out of heme and pop one or two
things off it, you have bilirubin. It gets picked up out of the blood in
the liver sinusoids by the hepatocytes, conjugated by UDP glucuronyl
transferase (UDP-GT) in their SER, then secreted by active transport
into the bile canaliculi.
 High levels of unconjugated bilirubin indicate that the problem is
occurring before the bilirubin gets to the liver-- ie. hemolytic anemia.
 High levels of conjugated bilirubin indicate that the problem is
occurring somewhere in the biliary tree or liver-- ie. a biliary
obstruction.
 Gilbert's disease: inherited problem with UDP-GT gene. Can't
conjugate bilirubin well, so unconjugated bilirubin builds up in a
stressed, fasting or febrile state, or any other situation in which there's
increased heme breakdown. Very common but also very mild.
 Crigler-Najaar Syndrome: no UDP-GT enzyme at all, presents at birth
with severe jaundice. Technically there are two variants of this, one
with slight enzyme activity.
 Dubin-Johnson Syndrome: defect not in UDP-GT, but in active
transport of conjugated bilirubin into the bile canaliculus; benign
condition, no therapy required.
4. Review abnormal liver chemistry test algorithms:
 Elevated AST/ALT (<5x nml):
 AST:ALT ratio < 1 = normal; AST:ALT ratio > 1 is usually
cirrhosis; AST:ALT ratio > 2 is suggestive of alcoholic liver
disease.
 Differential is pretty big and includes both hepatic and nonhepatic disorders.
 Algorithm:
 Take history and physical.
Check medications, discontinue if necessary.
Look at alk. phos, bilirubin, INR, albumin, iron studies,
viral serologies.
 If everything is negative and the patient is
asymptomatic, try lifestyle modifications, check again in
3-6 months.
 If everything is negative and the patient is symptomatic,
get more specific tests: ultrasound, autoimmune
serology tests, alpha-1 antitrypsin tests.
 Elevated alk phos:
 Differential is even bigger, and is notable for having more nonhepatic sources (more extrahepatic sources of alkaline
phosphatase).
 Algorithm:
 Take history and physical.
 Check other liver chemistries:
 If the AST/ALT is normal, get a GGT test.
 If the GGT is normal, it's not from a
hepatobiliary source.
 If the GGT is abnormal, get a right upper
quadrant ultrasound to look for biliary
duct dilation.
 If the AST/ALT is abnormal, get a RUQ
ultrasound.
 If the ultrasound is positive for dilation, get either
an endoscopy or an MRI to check it out.
 If it's not, get an AMA (anti-mitochondrial
antibody) test.
 If it's positive, it's primary biliary cirrhosis
(see "Non-Viral Liver Disease").
 If not, get biopsy or endoscopy/MRI.
 Jaundice:
 Algorithm:
 Take history and physical.
 Get liver chemistries:
 If it's the unconjugated bilirubin that's high, but
the AST/ALT and alk-phos are normal, it's
probably Gilbert's syndrome, but look for
hemolysis.
 If it's the conjugated bilirubin that's high, and the
AST/ALT and alk-phos are abnormal, get a RUQ
ultrasound to look for biliary duct dilation.
 If it's present, get an endoscopy/MRI.
 If not, get various more specific tests
(AMA, etc).
5. Review abnormal liver chemistry tests cases.
 As per Powerpoint.


Ethics: Liver Transplantation
Wednesday, October 29, 2008
8:00 AM
Ethics: Liver Transplantation, 10/29/08:
1. Discuss the decision to undergo LDLT (Living Donor Liver Transplantation) with
both donor and recipient.
 ...
2. Define the indications for liver transplantation, and LDLT in particular.
 MELD score: survival statistic that predicts 3-month survival; based on
creatinine, bilirubin, and INR. The lower, the better. Higher MELD
score takes priority for transplants.
3. Discuss the ethical issues surrounding transplantation, especially in patients with
substance abuse issues or with a marginal outcome.
 ...
Chronic Liver Disease
Thursday, October 30, 2008
7:50 AM
Chronic Liver Disease, 10/30/08:
1. Be able to identify physical exam and laboratory and radiological findings
suggestive of cirrhosis.
 Histologically: regenerative nodules surrounded by fibrous tissue.
 Clinically: can be compensated (no complications) or uncompensated
(complications). Complications in question: variceal hemorrhage,
ascites, encephalopathy, jaundice.
 Presentation: look for abovementioned complications, as well as:
 Physical exam: jaundice, spider angiomatas, white
nails/clubbing, edema, scleral icterus, enlarged liver, purpura,
palmar erythema, umbilical hernia, gynecomastia, etc.
 Labs: chronically elevated AST and ALT and/or elevated
alkaline phosphatase. Also low albumin, prolonged PT time,
high bilirubin, and low platelet counts.
 Imaging: nodular liver, caudate hypertrophy (caudate drains
directly into the IVC, and therefore can have better drainage),
ascites, splenomegaly (blood backs up into the spleen),
enlarged venous collaterals (caput medusae, esophageals),
hepatocellular carcinoma.
 Note cirrhosis is a common endpoint for lots of different disorders-most of the serious pathologies we've talked about wind up here. Note
also that hepatitis C and alcohol abuse account for about half of all
liver transplantation in the States.
 Side note on cirrhosis and carcinoma: generally, HCC arises
from pre-existing cirrhosis. But notice that chronic hepatitis B,
before it progresses to cirrhosis, can cause HCC in the absence
of cirrhotic changes.
 A liver biopsy is not necessary to make the diagnosis if you see chronic
liver disease and cirrhotic complications, a CT scan showing cirrhotic
findings, or characteristic physical findings.
2. Understand mechanisms of portal hypertension and role in formation of varices
and development of ascites and hepatorenal syndrome.








Initially: increase in intrahepatic vascular resistance. In cirrhosis, this
takes place in the sinusoids (as opposed to, say, Budd-Chiari
syndrome, in which the vascular clot forms in the outgoing hepatic
vein).
 In cirrhosis, the increased resistance is due to both structural
factors (increased fibrosis and nodular development) and
hemodynamic factors (reduction in nitric oxide production in
the endothelium).
Next, the increase in intrahepatic vascular resistance means that more
blood gets pushed back into the splanchnic circulation. The increased
pressure in the splanchnics causes increased NO production in the
splanchnic endothelium, which causes a dilation of its lumen, which
increases the volume of blood the splanchnics take in, which increases
the amount of blood trying to get into the liver, which further
increases the portal hypertension.
Portal hypertension boiled down: P = Q x R. Increased resistance
(fibrosis, lack of NO in portal system) plus increased flow (from
splanchnics) equals a very high pressure (portal hypertension).
[Measuring portal hypertension: you measure it by sticking a balloon
up in the hepatic venous system, inflating it, and measuring the
pressure drop when you decrease it. Normal portal pressure is less
than 6 and the pressure drop is around 3-4; in cirrhosis you can get a
pressure drop of 15+. The measurements are different in other causes
of portal hypertension (pre-hepatic portal occlusion, for example, will
have more or less normal measurements)-- there's a summary slide in
his Powerpoint if you're interested.]
Varices: recall that, by LaPlace's Law, the wall tension in a vessel
goes up with the diameter of the vessel. By shunting lots of blood into
the paraumbilical and esophageal veins, you dilate the hell out of
them, increasing wall tension and risk of rupture.
Transjugular intrahepatic portal shunt (TIPS): go in through the
jugular vein, create a large shunt from the portal to the hepatic vein.
 Notice that by putting in a shunt, you're bypassing the
physiological effects of the liver on blood-- can develop hepatic
encephalopathy, etc.
Ascites: Cirrhosis is by far the most common cause of ascites.
 Develops from an increase in nitric oxide production in the
splanchnic circulation, as mentioned above-- the resultant
relaxed endothelium allows fluid to escape out into the
surrounding space.
 Vicious cycle:
 This creates a low arterial volume state.
 That kicks off the RAA system, sympathetic system, etc
to compensate (which means you wind up with sodium
and water retention).
 This leads to further stretch in the splanchnics, leading
to more NO production.
 The increased splanchnic NO leads to more ascites.
 Note that refractory ascites can lead to hepatorenal syndrome
(see below).
 Dr. Burton is really keen on diagnostic paracentesis on newonset ascites patients.
Hepatorenal syndrome: can show up in advanced cirrhosis:

A disease of increased renal vascular resistance, connected to
the abovementioned ascites cycle.
 Increased volume in the splanchnic circulation leads to increase
NO production and vasodilation/ascites with resultant low
arterial volumes. This activates sympathetic mechanisms that
promote renal vasoconstriction.
 The increased renal vasoconstriction drops the GFR fairly
drastically.
 Note that there are no significant histological changes in the
kidney.
 The kidney is capable of working but it's not in the right
environment to do so. After transplanting out the kidney into
someone else or transplanting a new liver into the cirrhotic
patient, the kidney will work fine.
 This can be rapid (type 1) or progressive (type 2).
 Note lots of things can make this worse: NSAIDs, infections or
vasodilators, diarrhea or hemorrhage, diuretics, etc.
 Note also that ascites is universal in hepatorenal syndrome; if
they don't have ascites, they almost certainly don't have HRS.
They also tend to have water retention out of proportion to
their sodium retention (thus hyponatremia).
 [Nice little summary slide of cirrhosis and how it leads to ascites, HRS,
and hyponatremia in his Powerpoint.]
3. Understand the role of the serum-to-ascites albumin gradient in evaluating the
etiology of ascites.
 (indisputably on the test, as per Dr. B.)
 SAAG: Serum albumin minus ascites albumin, obtained at the same
time.
 Correlates well with sinusoidal pressure; a SAAG of greater than 1.1 is
consistent with portal hypertension.
 Look for total protein in the ascitic fluid to check the cause of the
ascites:
 Low protein (< 2. 5) = sinusoidal hypertension
 High protein (> 2.5) = cardiac ascites or veno-occlusive
disease.
 A SAAG less than 1.1 is often diagnostic of malignancy or tuberculosis
instead of portal hypertension.
 [Note that ascites is a risk factor for developing spontaneous bacterial
peritonitis-- bacteria get out into the peritoneum with the fluid. SBP, in turn,
puts patients at increased risk for HRS.]
4. Identify precipitating factors for development of hepatic encephalopathy.
 Recall that the leading etiological contender of hepatic encephalopathy
is ammonia (also recall that astrocytes are the only CNS cells that
metabolize ammonia).
 On increasing the ammonia load, as in cirrhosis, astrocytes go a little
nutty and start overexpressing BDZ receptors, activating neurosteroids
that kick up GABA-ergic tone.
 In brief, it looks like varying levels of increased GABA-ergic tone: mild
confusion, limited attention span, and messed up sleep all the way to
somnolence, disorientation, aphasia, and coma. Check out table 6 in
his notes for further details on progression of HE.
 Largely a clinical diagnosis; liver disease + confusion is usually hepatic
encephalopathy.

Precipitating factors:
 Largely has to do with bacteria metabolism of protein to
ammonia:
 High ingested protein load
 GI bleeding (high protein levels in colon)
 Constipation (bacteria has lots of time to digest)
 Also infection and over-diuresis.
 As mentioned, placement of a TIPS can also precipitate HE.
Energy Balance and Physical Activity
Tuesday, November 04, 2008
7:48 AM
Energy Balance and Physical Activity, 11/4/08:
[Don't forget we have a dietary self-monitoring exercise due on November 26th.]
1. Estimate the accuracy of energy balance in “normal” people.
 Roughly a 0.3% imbalance between energy intake and energy
expenditure, in the direction of intake. You'll probably gain, on
average, about a pound every year. That would mean that I'll weigh
about 250 pounds when I'm 75. That's depressing. I'm going to have
some chocolate. Freakin' self-reinforcing cycle.
2. List the components of the energy balance equation including components of
energy expenditure.
 Resting Metabolic Rate (RMR): energy cost involved in maintaining
heartbeat, brain/liver/kidney activity, body temperature, Na/K pumps,
etc. Comprises 75% energy expenditure in resting people. Classically
this is called "basal metabolic rate."
 Thermic Effect of Food (TEF): energy cost involved in digesting and
distributing ingested nutrients. Comprises 8% energy expenditure in
most people.
 Energy Expenditure of Physical Activity (EEPA): fairly selfexplanatory. Comprises up to 30-40% of energy expenditure in highly
active or exercising people, less in sedentary individuals.
 Note part of this can be used in unconscious movement
(shifting posture, etc)-- it's not all from walking around and
jogging (or climbing mountains, you unnatural, unnatural
people).
 The unconscious movement energy expenditure is called NEAT- non-exercise activity thermogenesis. Don't you love cutesy
acronyms? 'Cause they make me want to rip the heads off
bunnies.
 Note that part of all energy expenditures is made up of heat 'waste'-the second law of thermodynamics being what it is. Note also that that
'waste' is what makes us warm-blooded creatures and is essential for
life-- without waste we can't live. Comfort yourself with that fact next
time you're curled on the floor in a drunken heap.
3. Describe the relationship between energy expenditure and body weight.
 Two possible points he's referencing with this.

(1) With greater body mass, the total energy expenditure
generally goes up, partly because of increased resting
metabolic rate and partly because they expend more energy to
do the same mechanical work than a leaner person (moving
more mass)-- thus EEPA goes up for the same degree of
movement. TEF seems to be about the same.
 (2) Changes in TEF and RMR don't seem to correlate much with
changes in body weight. Activity energy expenditure, on the
other hand, is strongly correlated with them-- exercise-related
or not.
 Specifically, active energy expenditure is correlated with
an increase in fat-free body mass. Exercise induces
oxidation of fat.
4. List the methods available to measure energy intake and energy expenditure.
Describe the reliability and accuracy of these measures.
 Intake: Not a lot of good ways to measure this (most people underreport food intake by 20-40%). If a person isn't gaining or losing
weight, then their energy intake must, by definition, be equal to their
total energy expenditure (which can be directly measured, see below).
 Expenditure:
 RMR can be measured by indirect calorimetry (measures
respiratory gas composition and flow to estimate VO2 and
VCO2, providing an estimate of the rate of energy consumption
of a fasting person at rest).
 Can also estimate RMR from age, sex, height, weight,
and (if known) lean body mass or fat-free mass.
 TEF can be measured sort of the same way that RMR is
measured: take a RMR of a fasting patient, then take the same
measure (indirect calorimetry) in the same patient following a
test meal, then measure the difference.
 EEPA is measured by subtracting RMR and TEF from the total
energy expenditure (TEE).
 TEE is measured by the "doubly labeled water" method (use
double-labeled H2O and track CO2 production over a period of
time to measure overall metabolism).
5. Estimate the pool sizes of stored fuels (fat, carbohydrate and protein) within the
body.
 Fat stores comprise the largest fuel store (120,000 kcal or 13
kilograms in most people).
 Carbohydrate stores are next (3,000 kcal, 750 grams), mainly in
glycogen in muscle and liver.
 Protein isn't generally used as a store except in starvation situations,
in which muscle protein will be broken down to make glucose.
6. List the hierarchy of fuels for oxidation and discuss how this affects weight gain.
 Since there's no fuel storage for protein, dietary protein is
preferentially oxidized over carbohydrates and fat.
 Similarly, between carbohydrates and fat, carbohydrates will be
preferentially oxidized, since there's a lower capacity to store them.
 Theme here: the body prefers to store what it stores well (fat >
carbohydrates > proteins). It prefers to oxidize (ie. utilize for energy)
what it can't store well (proteins > carbohydrates > fat).
 What this means: if your food intake is balanced and, in total, is more
than your total energy expenditure, you're going to get fat-- you'll
preferentially utilize the overabundant proteins and carbs for energy
and store the fat in adipose tissue.
Overview of Biochemical Pathways
Tuesday, November 04, 2008
8:41 AM
Overview of Biochemical Pathways, 11/4/08:
1. Identify the structures of glucose, fatty acids and amino acids.
 (pictures help with these.)

Glucose: C6H12O6; aldehyde group on top of a five-carbon chain,
each carbon of which has a hydroxyl group attached to it. Recall that
this can be thought of either as a linear (6-carbon) or an etherized 5carbon ring structure with a carbon hanging off it:
as compared to

Fatty acids: a hydrocarbon chain with a carboxylic acid group at one
end and a methyl group at the other.



(triglyceride, or more properly triacylglycerol: three fatty
acids esterified to glycerol, C3(OH)3H5.)
Amino acids: central carbon with a hydrogen attached to it; the
remaining three groups are a carboxylic acid group (COOH) at one end
(the C terminal end) and a primary amine group (NH2)at the other
(the N terminal end), with a side chain in the middle (specific side
chains vary by amino acid):

2. Explain the general functions of the biochemical pathways.
 Break down stored material for energy (catabolism) when in negative
energy balance state. Store material (anabolism) when in positive
energy balance state. Note that the form something's ingested in
doesn't necessarily correlate to the form it's stored as (eg. glucose can
wind up as fat, protein can wind up as glucose, etc); see next point.
3. List the 8 main biochemical pathways involved in carbohydrate, fat and amino acid
metabolism.
 Carbohydrate metabolism:
 Glycolysis: occurs when glucose is present in the blood in
excess, as following a carbohydrate-rich meal. Occurs in
cytoplasm. Breaks down glucose to pyruvate with 2 ATP
formed.
 Tricarboxylic Acid Cycle (aka TCA cycle or Krebs cycle):
occurs in the presence of oxygen to further break down
pyruvate to CO2. Occurs in mitochondria. Forms lots more ATP
(specifics to follow, but you're producing NADH and FADH2 to
reduce O2 to H2O).
 Note they're including the electron transport chain and
oxidative phosphorylation in this step.
 Note also that the TCA cycle serves other purposes than
the breakdown of pyruvate. More on this, again, later.
 Note further that in the absence of oxygen, pyruvate
does not enter the TCA cycle but is converted to lactate.
 Gluconeogenesis: occurs when the body is in negative energy
balance, in order to provide glucose-only tissue (mainly brain
and RBCs) with sufficient energy. Occurs only in the liver and
kidneys. Converts a variety of carbon skeletons (eg. lactate and
amino acids) to glucose. Starts in the mitochondria but ends up
in the cytoplasm.
 Glycogenesis (formation of glycogen): occurs when glucose is
present in excess; forms glucose polymers that can be quickly
broken down to release free glucose. Occurs in the cytoplasm.
Can be reversed to break down glycogen into glucose again
(glycogenolysis).
 Hexose Monophosphate Shunt (aka Pentose Phosphate
Shunt): again, occurs when glucose is present in excess.
Drives the generation of NADPH (not NADH), which drives de
novo lipogenesis from glucose-derived acetyl CoA (see below).
Occurs in the cytoplasm.
 Fat metabolism:

De novo lipogenesis (triacylglycerol synthesis): occurs in a
glucose-rich, positive energy state. Glucose can be broken
down to pyruvate and enter the TCA cycle to form acetyl CoA.
Instead of being fully oxidized, acetyl CoA can be used to form
fatty acid chains which are esterified to glycerol to form
triacylglycerol, then stored in adipose tissue.
 Beta oxidation (triacylglycerol degradation): occurs in a
negative energy state. Triacylglycerols are broken down into
fatty acids and glycerol and released into circulation, where
they're taken up by non-glucose-exclusive tissue (eg. liver and
muscle) and broken down in the mitochondria, two carbons at a
time. These two-carbon units are linked to CoA to form acetyl
CoA, which can enter the TCA cycle to generate energy in that
tissue.
 Note that beta oxidation is used to provide energy for
non-glucose-exclusive tissue so that glycogen stores can
be used for the tissues that depend on them.
 Note also that beta oxidation can produce ketone bodies
under certain situations (generally when glucose is
extremely scarce, as in diabetic ketoacidosis).
 Protein metabolism:
 Urea cycle: not much detail on it in these notes. Effectively, if
you're breaking down amino acids, you have to get rid of the
ammonium (which is toxic) derived from the amine group. The
urea cycle (occurs in the liver) converts ammonium to urea,
which is a fairly nontoxic carrier of nitrogen and which can
circulate until it gets excreted by the kidneys. This is where you
get your BUN measurement.
 Note abovementioned entry of amino acids into the
gluconeogenesis pathway.
4. Describe the general layout of the main metabolic pathways for carbohydrate, fat
and amino acids.
 Carbohydrates:
 Glucose is transported into a cell; it's phosphorylated to glucose
6-phosphate, which makes it impossible for it to leave the cell
again (it now has a charge).
 At this point, it can be stored as glycogen or it can be broken
down.
 If it's being broken down, it undergoes glycolysis.
 After glycolysis, if oxygen is present, pyruvate can enter the
mitochondria and go into the TCA cycle as acetyl CoA. If not,
the pyruvate is converted to lactate in the cytoplasm instead,
or used in de novo lipogenesis.
 The glycolysis pathway can also be reversed in gluconeogenesis
to make glucose out of pyruvate.
 Fats:
 Acetyl CoA molecules can be chained together to form fat
(triacylglycerol synthesis).
 Conversely, existing fatty acids can also be broken down to
form acetyl CoA. The glycerol from triacylglycerols can also be
used as the base skeleton for gluconeogenesis.
 Proteins:


Amino acids can enter the TCA cycle at various points
(depending on the amino acid); from there they can either be
fully oxidized to CO2 or can undergo gluconeogenesis to form
glucose.
Note that amino acids contain nitrogen, which needs to be
gotten rid of if you're breaking them down to make ATP or
glucose. This occurs through the urea cycle (more on this
later).
Introduction to Carbohydrate Metabolism
Tuesday, November 04, 2008
9:48 AM
Introduction to Carbohydrate Metabolism, 11/4/08:
1. Describe the features that make a particular step in a linked enzyme pathway a
"key step."
 (1) Change of location-- entering or leaving the cell or mitochondrion.
 (2) Investiture of energy-- generally in phosphorylating a substrate.
 Note that, as per enzyme kinetics, generally an activation
energy has to be invested in even an exothermic reaction in
order for the energy to be released. So, in glycolysis, 4 ATP are
produced, but 2 ATP are consumed to push the reaction to that
point. On a molecular basis, there's no such thing as a free
lunch. There is, however, good return on investment.
 (3) Rate limiting steps-- in terms of enzyme kinetics, the slowest step
in a pathway, due to low levels of substrate, low reaction rate, low
enzyme affinity, etc. This creates a "bottleneck" that determines how
fast the overall reaction can go (the overall reaction can't go faster
than its slowest component).
 Note that the boards love rate-limiting steps. Note also that the
body tends to target rate-limiting steps as ways to modulate
how fast the reaction is going. See discussion of
phosphofructokinase 1 in the next lecture for an example of
regulation of the rate limiting step in glycolysis.
2. Describe the primary functions of glycolysis, gluconeogenesis, and glycogen
synthesis and breakdown.
 Glycolysis: (1) generates energy and (2) gets you to the TCA cycle,
from which point you can use the pyruvate carbon skeleton for lots of
things. Key steps of glycolysis:
 Glucose, as mentioned, enters the cell and is phosphorylated
(key step) to glucose 6-phosphate by hexokinase and/or
glucokinase (see next lecture). This process takes 1 ATP.
 After being rearranged to fructose (non-key step), it's further
phosphorylated to fructose 1,6-bisphosphate by
phosphofructokinase. This process takes 1 ATP.
 A while later, it's eventually converted from phosphoenol
pyruvate to pyruvate by pyruvate kinase. This process
produces 2 ATP.




(note there's a step I'm not mentioning where 2 more ATP are
produced, brining the total to +2. See next lecture for more
detail.)
Gluconeogenesis: makes glucose from other structures, generally
amino acid and lactate structures.
 Oxaloacetate is produced in the TCA cycle, and can be fed from
there into phosphoenolpyruvate and go backward up the
glycolysis pathway.
 Note that this formation of phosphoenolpyruvate (by
phosphoenolpyruvate carboxykinase) is the rate-limiting
step in this pathway.
 Other key steps of gluconeogenesis: similar to glycolysis, but
reversed (dephosphorylation of fructose 1,6-bisphosphate by
fructose 1,6-bisphosphatase and dephosphorylation of
glucose 6-phosphate by glucose 6-phosphatase).
 Recall that glucose needs to be dephosphorylated to be
able to escape the cell and get out into the circulation
(whence to brain, etc). Note that liver and kidney are
the only tissues that contain glucose 6-phosphatase-thus circulating glucose can only be produced (via
gluconeogenesis) from liver and kidney.
 Note there tends to be an inverse relationship between
glycolysis and gluconeogenesis-- as you might expect (no point
in making it and then immediately breaking it down again).
Way more than you ever wanted to know about this in the next
lecture.
Glycogen synthesis (glycogenesis): stores excess glucose.
 Instead of glucose 6-phosphate being re-phosphorylated as
fructose 1,6-bisphosphate, it's rearranged to glucose 1phosphate instead by phosphoglucomutase.
 Glucose 1-phosphate is converted to UDP-glucose (UDP = uracil
diphosphate).
 These UDP-glucose molecules are linked both by 1-4 bonds
(more or less linear chains) and 1-6 bonds (branch points) to
form glycogen. The branching allows more efficient metabolism.
 Key enzymes (not in notes): to add 1-4 linkages: glycogen
synthase. To add 1-6 linkages: branching enzyme.
Glycogen breakdown (glycogenolysis): liberates glucose during fasting
or exercise conditions.
 Need separate enzymes to break the 1-4 and 1-6 bonds.
Defects in either of these enzymes, predictably, cause trouble
in the form of glycogen storage disorders.
 Glycogen phosphorylase cleaves 1-4 bonds. Debranching
enzymes cleave 1-6 bonds.
 After all that's been cleaved, the glucose 1-phosphate is reconverted to glucose 6-phosphate by the enzyme
phosphoglucomutase (same one as converted it from 6-P to 1D in the first place).
 The free glucose 6-phosphate, recall, still has to be
dephosphorylated if you want it to get out of the cell and into
circulation. The only cells that can do this are in the liver and
kidneys.
[Note a word on terminology: breakdown of glucose = glycolysis. Synthesis of
glucose = gluconeogenesis. Synthesis of glycogen = glycogenesis. Breakdown of
glycogen = glycogenolysis. It's kind of a mess.]
3. Describe the primary functions of the TCA cycle and the electron transport system.
 Good analogy from the notes: the TCA cycle is "like a roundabout at
an intersection"-- a variety of carbon skeletons can enter at a variety
of points and leave at various points depending on the energy state of
the organism and the need for different TCA products.
 The classical, and presumably most often-used, pathway through the
TCA cycle/ET system (+ oxidative phosphorylation) involves complete
oxidation of acetyl CoA (which can be derived from glucose,
triacylglycerols, or proteins). Note that this function of the TCA cycle
takes NAD and FAD and reduces them to NADH and FADH2.
 Note also the oxidative TCA cycle is sort of a big, circular
enzyme (doesn't get used up)-- it's just a pathway to take an
acetyl group and oxidize the living hell out of it, then come
back to its starting point. The CoA is recycled too.
 There are lots of other entry points (and exit points)-- acetyl CoA can
be used for fatty acid synthesis, oxaloacetate can be used to start
gluconeogenesis, certain fatty acid breakdown products can come into
the cycle as succinyl CoA, etc.
4. Describe in a general sense the flux through these pathways in liver and skeletal
muscle in the fasted and fed states.
 4 mechanisms for regulating balance:
 Amount of substrate (lots of glucose, very little glucose)
 Quantities of different key enzymes
 Covalent modification of enzymes (eg. PO4ation) can change
their activity.
 Allosteric regulation: feedback mechanisms to non-covalently
alter the activity of a key enzyme (generally, in A + B --> C, C
modifies the enzyme controlling the reaction to reduce its
activity).
 Hormone notes:
 "I just ate" hormone: insulin.
 "I'm starving" hormones: (1) catecholamines, (2) glucagon,
(3) cortisol, (4) growth hormone.
 The flux of hormones between one end and the other largely
determines which carbohydrate pathways are up-regulated and
which are down-regulated.
 Insulin: activate glycolysis and glycogenesis pathways, inhibit
gluconeogenesis and glycogenolysis.
 Starving hormones: activate gluconeogenesis and
glycogenolysis, inhibit glycolysis and gluconeogenesis.
 How this generally works: hormone hits cells, activates secondmessengers, alter enzymes (often through kinase-mediated
phosphorylation reactions). Again, see discussion of PFK2 in
next lecture for an example.
Glycolysis and the Pentose Phosphate Shunt
Tuesday, November 04, 2008
10:37 AM
Glycolysis and the Pentose Phosphate Shunt, 11/4/08:
1. Know the final products of aerobic and anaerobic glycolysis.
 Technically the final product is pyruvate.
 Final final products of aerobic glycolysis: acetyl CoA, NAD+ (enter TCA
cycle).
 Final final products of anaerobic glycolysis: lactate, NADH.
2. List the reactions that are important in regulating the activity through glycolysis.
 [General notes: 3 things are going on in glycolysis. One, the 6-carbon
glucose skeleton is being cleaved down to two 3-carbon halves. Two,
ATP is being both consumed and generated; this process can be
divided into an energy investment phase (utilizing 2 ATP) and a energy
generation phase (producing 4 ATP). Three, 2 molecules of NADH are
being formed from 2 molecules of NAD +; the NAD+ has to be
regenerated, and is so through the generation of acetyl CoA (in the
presence of O2) or lactate (without O2).]
Glycolysis:









(1) Glucose is phosphorylated by glucokinase or hexokinase to glucose
6-phosphate. Uses 1 molecule of ATP. Irreversible reaction. See
below notes on hexokinase vs. glucokinase.
(2) Glucose 6-phosphate is isomerized to fructose 6-phosphate.
(3) Fructose 6-phosphate is phosphorylated by phosphofructokinase 1
(PFK1) to fructose 1,6-bisphosphate. Uses 1 molecule of ATP.
Irreversible reaction.
 Note that this is the rate-limiting step for glycolysis. See below
for more details on PFK1.
(4) Fructose 1,6-bisphosphate is cleaved to two 3-carbon molecules of
glyceraldehyde-3-phosphate.
(5) Glyceraldehyde-3-phosphate is phosphorylated and oxidized (loses
2 H+) to 1,3-bisphosphoglycerate. The two protons reduce 2 NAD+ to
2 NADH. First energy-conserving reaction. Does not use ATP (uses
inorganic phosphate). Creates 2 NAD+ --> 2 NADH. Catalyzed by
glyceraldehyde-3-phosphate dehydrogenase.
(6) 1,3-bisphosphoglycerate donates one of its phosphate groups to
ADP, forming ATP and 3-phosphoglycerate. Produces 2 molecules of
ATP (one for each 1,3-bisphosphoglycerate). Catalyzed by
phosphoglycerate kinase.
(7) The phosphate group is shuffled to form 2-phosphoglycerate.
(8) 2-phosphoglycerate is dehydrated to form H2O and
phosphoenolpyruvate.
(9) Phosphoenolpyruvate + 2 ADP --> pyruvate + 2 ATP. Catalyzed
by pyruvate kinase. Produces 2 molecules of ATP (one for each
phosphoenolpyruvate). Irreversible reaction.
 Note that pyruvate kinase activity can be promoted by fructose
1,6-bisphosphate (feed-forward allosteric promotion).
 It can also be covalently modified by phosphorylation initiated
by protein kinase A; this inactivates pyruvate kinase.
 Note that a deficiency in pyruvate kinase is the second most
common enzyme-deficiency hemolytic anemia (second to
glucose 6-phosphate dehydrogenase).





(10) Pyruvate has a couple of fates, as noted above; in the presence
of oxygen it's transformed into acetyl CoA and enters the TCA cycle,
while in anaerobic conditions it's transformed into lactate.
 Why this is: you need NAD+ to keep glycolysis going. You
reduce NAD+ to NADH during the middle part of glycolysis;
thus you need to be able to oxidize it again before you can
undergo glycolysis again.
 If you have oxygen, the TCA cycle will regenerate NAD+ from
NADH.
 If you don't, transforming pyruvate into lactate will do the
same thing.
[Note that these numbers don't match what's in the notes; they're
from what she wrote on the board. It's all the same stuff, anyway.]
[Dr. Bessesen's take on three important enzymes/steps to remember
in glycolysis:]
 (1) Phosphorylation of glucose to glucose 6-phosphate by
hexokinase or glucokinase.
 (2) Phosphorylation of fructose 6-phosphate by
phosphofructokinase 1, and associated details regarding PFK2
regulation.
 (3) Dephosphorylation of phosphoenolpyruvate to pyruvate by
pyruvate kinase, and associated details regarding regulation by
fructose 1,6-bisphosphate and PKA.
Hexokinase: present in all cells in the body. Non-specific for glucose- reacts with glucose, fructose, galactose, whatever. Has a fairly low
Km (activated at very low sugar concentration), but a fairly low Vmax
(slow maximal reaction speed).
Glucokinase: present only in the liver and beta cells in the pancreatic
islets. Specific for glucose. Has a fairly high Km (activated only at high
glucose concentrations), but a fairly high Vmax (fast maximal reaction
speed).
 What that means: at low glucose concentrations, hexokinase
works faster than glucokinase. At high glucose concentrations,
glucokinase works faster than hexokinase. The activity rate of
glucokinase is what's changing (low when levels are low, fast
when levels are high); the rate of hexokinase activity stays
pretty much stable no matter what the glucose concentration
is.
 Why:
 When the glucose levels in the blood are high, the liver
cells are frantically pulling in glucose (with glucokinase)
to store it as glycogen. When the glucose levels in the
blood are low, the liver cells don't really want to pull in
and store glucose; they want the glucose to remain free
to be used by other, more glucose-dependent tissues.
 How this works: glucokinase is sequestered in
the nucleus until high levels of glucose are
detected in the blood.
 By contrast, the other tissues in the body pretty much
always want to pick up the same amount of glucose and
use it to keep functioning, no matter what the overall
glucose levels are. Thus hexokinase just sort of keeps on

chugging at the same ol' rate and doesn't pay much
attention to blood glucose levels.
 On reading this again: when I say "pull in," I mean
"phosphorylate to trap inside the cell." Glucose enters
the cell through GluT transporters (of which exhaustively
more shall be covered later in the week).
Notes on PFK1:
 There's another, related enzyme: PFK2. This, instead of
converting fructose 6-phosphate to 1,6-bisphosphate, converts
it to 2,6-bisphosphate.
 Why you care: 2,6-bisphosphate is the main regulator of PFK1
activity. As such, you can mess with PFK2 to control the rate of
glycolysis.
 Unbelievably irritating but extremely testable details:
 PFK2 is Dr. Jekyll. Dr. Jekyll is a kindly old
fellow who likes glycolysis. Bear with me.
 PFK2 has a secret identity as fructose 2,6bisphosphatase (FBPase). FBPase is Mr. Hyde, a
monstrous brute who hates glycolysis. Bear with
me.
 Recall that PFK2 catalyzes the addition of a
phosphate group to fructose 6-phosphate to form
fructose 2,6-bisphosphate.
 Well, FBPase does the exact opposite: it
catalyzes the removal of a phosphate group from
fructose 2,6-bisphosphate to form fructose 6phosphate.
 As alluded to above, the amount of fructose 2,6bisphosphate is directly related to the degree of
glycolysis, and inversely related to the degree of
gluconeogenesis, that's going on in the cell. So
PFK2 (Dr. Jekyll) promotes glycolysis and inhibits
gluconeogenesis, while his evil dark half, FBPase
(Mr. Hyde) inhibits glycolysis and promotes
gluconeogenesis.
 Note the distinction between fructose 1,6bisphosphatase (an enzyme that cleaves
phosphate off 1,6-bisphosphate to form
fructose 6-phosphate, a step in the
gluconeogenesis pathway) and fructose
2,6-bisphosphatase (the Mr. Hyde that
cleaves phosphate off fructose 2,6bisphosphate to form fructose 6phosphate, removing the key promoter of
the glycolysis pathway). One's part of the
gluconeogenic pathway; the other is part
of the enzymatic machinery that regulates
that pathway (and the glycolysis pathway
as well).
 These two enzymes, PFK2 and FBPase, form a
kind of Siamese twin enzyme, only one side of
which is active at a time.

There's a switch on the Siamese twin that flips it
from one to the other. The switch is
phosphorylation.
 When they're phosphorylated, the FBPase is
active (promoting gluconeogenesis). When
they're dephosphorylated, the PFK2 is active
(promoting glycolysis).
 What controls the switch: largely, cAMP levels in
the cell; cAMP activates protein kinase A, which
phosphorylates PFK1/FBPase.
 cAMP levels, in turn, are regulated by hormones
like insulin and glucagon.
 Insulin decreases cAMP levels (thus promoting
glycolysis).
 Glucagon increases cAMP levels by activating our
old pal adenylyl cyclase (thus promoting
gluconeogenesis).
 In a couple lectures I'm going to make a
remark about insulin/glucagon as they
relate to patterns of phosphorylation. I
think it's pretty helpful and it makes me a
sort of God among men. I also mostly
pulled it out of Lippincott. Anyway keep
your eyes out.
 Note that, in addition to the PFK/FBPase pathways, PFK1
activity can also be allosterically inhibited by ATP and citrate
(both of which are products of the TCA cycle) in a negative
feedback loop.
3. Know the role of pentose phosphate pathway in glucose metabolism.
 When glucose is present in excess, the pentose phosphate shunt
generates NADPH (not the same as NADH), which is necessary to
power the de novo lipogenesis pathway (fatty acids, steroids, etc).
NADPH is also necessary for detoxification pathways and a few other
things (see note below).
Pentose phosphate pathway: (occurs in the cytoplasm)


Oxidative phase:
 Glucose 6-phosphate loses a hydrogen atom as it's
converted to 6-phosphogluconate (by glucose 6phosphate dehydrogenase, see below).
 6-phosphogluconate loses both a hydrogen and CO2 as
it's converted to ribulose 5-phosphate.
 (how you can remember the change in the
carbon skeleton: it's called the 'pentose' shunt
because you're going from a six-carbon sugar to
a five-carbon sugar.)
 The hydrogens that come off from each of these two
reactions are used to generate NADPH from NADP+.
Non-oxidative phase:
 (ribulose 5-phosphate is rearranged to ribose 5phosphate.)
3 molecules of ribose 5-phosphate (15 carbons) are
broken up into 2- and 3-carbon fragments and
rearranged to form 2 molecules of fructose 6-phosphate
(12 carbons) and 1 molecule of glyceraldehyde 3phosphate (3 carbons). All of these molecules go back
into the glycolysis pathway.
 Note that ribose 5-phosphate can alternatively go
into nucleic acid synthesis pathways, as you
might expect.
 The enzymes that do the rearranging are transketolase
(carries 2-carbon fragments) and transaldolase
(carries 3-carbon fragments). Note there's an error in
the notes on p. 36 on this point (she describes both as
transketolases).
More on glucose 6-phosphate dehydrogenase:
 As mentioned, you need G6PD to make NADPH from NADP+.
NADPH is necessary to reduce glutathione and make it function
as an antioxidant. In red blood cells, which depend heavily on
glutathione antioxidants to defend against structural injury, a
deficiency in G6PD results in low NADPH and thus low GSH
(reduced glutathione), consequently resulting in membrane
damage and hemolytic anemia.
 You also need NADPH to make hydrogen peroxide in your
neutrophils. A long, long time ago, we learned about chronic
granulomatous disease, in which neutrophils can't make an
effective oxidative burst. This has to do with a problem with the
gene for an enzyme called NADPH oxidase. Obviously if you
ain't got NADPH you ain't got oxidative burst either.


**
TCA Cycle/Ox-Phos/Gluconeogenesis
Wednesday, November 05, 2008
8:01 AM
TCA Cycle/Ox-Phos/Gluconeogenesis, 11/5/08:
1. Know the metabolic fates of pyruvate.
 Glycolytic pyruvate (ie., pyruvate derived from glycolysis) fates:
 In the absence of oxygen: as mentioned, in order to regenerate
NAD+ from NADH, pyruvate is converted to lactate by lactate
dehydrogenase.
 In the presence of oxygen: pyruvate loses a hydrogen ion and a
carboxy group (as CO2) in being converted to acetyl CoA,
catalyzed by pyruvate dehydrogenase. The hydrogen atom is
used to make more NADH from NAD+.
 Note that the conversion into acetyl CoA happens in the
mitochondrial matrix (in the presence of oxygen,
pyruvate is transported into the mitochondria).
 This requires an enormous complex of enzymes and
cofactors-- it's a very important reaction, as you might
imagine. This is significant because these cofactors
include components of vitamins B1, B2, B3, and B5:
 Thiamine pyrophosphate (TPP) requires thiamine
(B1).
 FAD requires riboflavin (B2).
 NAD requires niacin (B3).
 CoA requires pantothenate (B5).
 Also need lipoic acid (which, incidentally, is
inhibited by arsenic).
 This complex of enzymes and cofactors (the
phosphodehydrogenase or PDH complex) is regulated as
a unit by phosphorylation, which deactivates the
complex.
 Lots of acetyl CoA or ATP or NADH promotes
phosphorylation of the complex by a PDH kinase- makes sense, if you have lots of the products
already, you don't want to make more.
 Lots of pyruvate promotes dephosphorylation by
inhibiting that PDH kinase-- again, makes sense,
if you have lots of the substrate, you want to
push it through the pathway.
 High calcium levels also dephosphorylate
(activate) the PDH complex to promote acetyl
CoA formation (makes sense if you're in a
contracting muscle and need energy).
 (For that really insightful note about insulin and
glucagon that's coming later, keep in mind that
insulin causes dephosphorylation (activation) of
pyruvate dehydrogenase and that glucagon
causes phosphorylation (inactivation) of it.)
 Keep track of carbon number: pyruvate is a 3-carbon
skeleton, but here it's losing CO2 and is hence converted
to a 2-carbon acetyl skeleton.
 It can go from here into the TCA cycle to make ATP and
regenerate NADH, or it can go into de novo lipogenesis
pathways if sufficient NADPH is present.
 Non-glycolytic pyruvate fates:
 In fed state: pyruvate is converted to alanine and used for
protein synthesis, or it can be converted to acetyl CoA, as
above, and enter the de novo lipogenesis pathway to create
fatty acids.
 In fasting state: pyruvate is carboxylated to oxaloacetate by
pyruvate carboxylase and goes to phosphoenol in the
gluconeogenesis pathway.
2. List reactions that give rise to energy in the form of NADH.
 See below (discussion of TCA specifics) for elaboration on these four
points.
 As mentioned, pyruvate to acetyl CoA through the pyruvate
dehydrogenase complex.
 Isocitrate's decarboxylation to alpha-ketoglutarate by isocitrate
dehydrogenase.
 Alpha-ketoglutarate's decarboxylation to succinyl CoA by alphaketoglutarate dehydrogenase.


Malate's oxidation to oxaloacetate by malate dehydrogenase.
[Note that FADH2 is produced from FAD from succinate -> fumarate
by succinate dehydrogenase.]
3. Understand the concept of electron flow and its coupling to ATP synthesis.
 Here's the thing. The actual thing that's getting broken down to H2O
and CO2 in the TCA cycle is an acetyl molecule (in the form of acetyl
CoA). In the process you produce one molecule of GTP (a "substratelevel phosphorylation"), but the main energy production you're getting
from the TCA cycle is in the form of stored hydrogen atoms (ie.,
electrons) on NADH and FADH2, which are later converted into ATP.
 The protons on NADH and FADH2 are sent through the electron
transport chain and oxidative phosphorylation, and that's where the
ATP money is. Each molecule of NADH can generate about 2.5
molecules of ATP; each molecule of FADH2 can generate about 1.5
molecules of ATP. I don't feel like doing the math but you can see the
TCA cycle makes a metric buttload more ATP than the 2 molecules you
get out of glycolysis.
 Recall that you've already regenerated the NADH you used in
glycolysis in the process of transforming pyruvate into acetyl CoA-- so
all the NADH and FADH2 produced in the TCA cycle can be used to
make ATP.
 How this works, more or less:
 In the inner mitochondrial membrane, the hydrogen atoms are
delivered down three steps to form water from oxygen. Each
of these steps pumps a proton across the membrane (out of the
matrix and into the intermembrane space) against a gradient.
This is the electron transport chain.
 Next, the built-up hydrogen gradient is allowed to equilibrate
across the membrane through a specialized transporter called
Complex V-- which is an ATP synthase enzyme. By releasing
the hydrogen gradient, ATP is generated.
4. Understand the metabolic role of the TCA cycle.
 The thing to remember about the TCA cycle is that the basic
substrates of the cycle don't change. You add in the acetyl CoA and it
gets broken down, but as long as you've got more acetyl CoA to throw
in, the TCA wheel is going to keep on turnin'.
TCA cycle:




(1) Acetyl CoA is combined with oxaloacetate to form citrate by
citrate synthase. Irreversible.
 The citrate synthase reaction is the rate-limiting step of the
TCA cycle. As such, this is the step that tends to be regulated
by the cell (high energy balance inhibits, low energy balance
promotes).
(2) Citrate is rearranged to isocitrate by aconitase.
(3) Isocitrate is decarboxylated to alpha-ketoglutarate by isocitrate
dehydrogenase. This produces CO2 and NADH.
(4) Alpha-ketoglutarate is decarboxylated to succinyl CoA by alphaketoglutarase dehydrogenase. The enzyme complex is extremely
similar to the pyruvate dehydrogenase complex. This produces CO2
and NADH.

(5) CoA is removed from succinyl CoA to form succinate by
thiokinase. This produces GTP from GDP (later converted to ATP).
 (6) Succinate is oxidized to fumarate by succinate dehydrogenase.
This produces FADH2.
 (7) Fumarate is hydrated to malate by fumarase.
 (8) Malate is oxidized to oxaloacetate by malate dehydrogenase.
This produces NADH.
 Oxaloacetate combines with acetyl CoA again to begin a new iteration
of the cycle.
 Dr. Bessesen's comments: focus on pyruvate forming acetyl CoA,
acetyl CoA forming citrate, and the formation of oxaloacetate (since it
can go into gluconeogenic pathways, see below).
5. Understand metabolic role of gluconeogenesis and list the major gluconeogenic
precursors.
 In between meals, as an adjunct to glycogenolysis, you can also create
glucose from cleaved carbohydrate and non-carbohydrate precursors.
 Recall that there are only two tissues that can synthesize glucose: the
liver (main) and the kidney. Recall also that the RBCs, the brain, and
the sperm (among other tissues)
 Main gluconeogenic precursors:
 Lactate
 Recall that RBCs don't have mitochondria; thus they're
constantly breaking down glucose to lactate.
 This lactate is released into the plasma and goes to
liver, where it's converted back to pyruvate through
lactate dehydrogenase (same enzyme that catalyzes
pyruvate -> lactate).
 The liver can then put it through gluconeogenesis, make
glucose 6-phosphate, pluck off the phosphate, and send
the glucose back out into the plasma to be picked up
again by the red blood cells for energy.
 This is called the Cori cycle (RBC -> lactate, to liver ->
glucose, and back again), for what it's worth.
 Glycerol (from breakdown of triacylglycerols)
 Note that the fatty acids themselves can't be used for
gluconeogenesis.
 Amino acids
 Generally these enter the TCA cycle as alphaketoglutarate or oxaloacetate and leave as oxaloacetate
to get turned into PEP (see below).
 A note about gluconeogenesis: you can't use acetyl CoA to make more
glucose. This is why, as a rule, you can't break down fatty acids to
promote gluconeogenesis-- the fatty acids are oxidized to acetyl CoA
in the TCA cycle and there's no pathway to turn them into either
pyruvate or oxaloacetate. There are one or two exceptions. We'll talk
about them later.
6. Identify the bypass reactions in gluconeogenesis and the enzymes responsible for
these reactions.
 Key enzymes:
 (1) Pyruvate carboxylase [requires biotin]
 (2) Phosphoenolpyruvate carboxykinase
 (3) Fructose 1,6-bisphosphatase
 (4) Glucose 6-phosphatase (only present in liver and kidney)






Okay. Most of gluconeogenesis involved a simple reversal of glycolytic
steps. When you're making glucose, you need to get around the
enzymes involved in the irreversible steps of glycolysis (don't want to
break it down as it's being made).
This process involves "bypass reactions"-- getting around the
irreversible glycolytic reactions by substituting another, more
energetically favorable reaction in the opposite direction.
Bypass of the breakdown of phosphoenolpyruvate to pyruvate:
 Pyruvate is carboxylated with CO2 to form oxaloacetate; the
oxaloacetate is then decarboxylated again and phosphorylated
to form phosphoenolpyruvate. Each of these reactions takes 1
ATP and you need to do them each twice to generate enough
carbon to make glucose; thus your energy expenditure at this
point is 4 ATP.
 The first enzyme is pyruvate carboxylase, the second
is PEP-carboxykinase.
 Dr. Bessesen: really important enzyme here is
this second enzyme (PEP-CK), which is the ratelimiting step in gluconeogenesis.
 Specifics: pyruvate is carboxylated to oxaloacetate; it's
transformed to malate to get out of the mitochondria
into the cytoplasm; once in the cytoplasm it's converted
back to oxaloacetate; from there it's decarboxylated
again into PEP.
 The first step (pyruvate to oxaloacetate) uses biotin (vitamin
B7) as a coenzyme-- in the absence of biotin, you can't convert
pyruvate to oxaloacetate, and pyruvate tends to build up and
be converted into lactic acid (resulting in lactic acidosis).
 Take-home on substrates here: this step (2x pyruvate to 2x
PEP) requires 4 ATP and uses no net CO2.
Climbing the glycolysis tree backwards, you also need to
phosphorylate 3-phosphoglycerate to 1,3-bisphosphoglycerate twice
(reversal of normal glycolysis pathway), which doesn't need a special
enzyme but does take 2 more ATP.
Bypass of the phosphorylation of fructose 6-phosphate to fructose 1,6bisphosphate:
 Fructose 1,6-bisphosphate is dephosphorylated by fructose
1,6-bisphosphatase to form fructose 6-phosphate.
 This is regulated by that PFK2/FBPase pathway we were talking
about so painfully yesterday. High levels of fructose 2,6bisphosphate inhibit this step in gluconeogenesis; low levels
promote it and inhibit the reverse (phosphorylation of fructose
6-phosphate).
 Note this recoups 1 ATP.
Bypass of the phosphorylation of glucose to glucose 6-phosphate:
 Glucose 6-phosphate is dephosphorylated by glucose 6phosphatase. Recall that only liver and kidney actually have
this enzyme (the rest of the tissues can't release glucose into
the circulation).
 Note that this also recoups 1 ATP.
 Note that absence of glucose 6-phosphatase results in von
Gierke's disease-- the most common type of glycogen storage
disease (type I). We'll talk about it later, but it results in severe
hypoglycemia (no glucose can get out into the blood).
 Net energy consumption of gluconeogenesis: 4 ATP per
molecule of glucose. You also make 2 NAD+. Note that you spend
more ATP making glucose than you get from breaking it down-- again,
that Second Law is a bitch.
7. Understand coordinate regulation of glycolysis/gluconeogenesis.
 Some of this has to do with regulation of PFK1 and its reaction, as
discussed in the last lecture.
 There's no way I'm going through the PFK2/FBPase discussion
again. But keep in mind that insulin indirectly increases PFK1
activity (more glycolysis!) and glucagon indirectly decreases it
(more gluconeogenesis!).
 Other things that activate PFK1: AMP (need more ATP, do
glycolysis). Other things that deactivate PFK1: citrate, ATP
(have a lot of ATP and breakdown products, do gluconeogenesis
instead).
 Also, understand that pyruvate can go into acetyl coA (to be oxidized
in the TCA cycle, following the glycolytic energy-liberating pathway) or
it can be converted to oxaloacetate (to go to PEP and go up the
gluconeogenic ladder)-- so whether you have a lot of pyruvate
dehydrogenase activity (to make acetyl CoA) or have a lot of pyruvate
carboxylase activity (to make oxaloacetate) can determine which
direction it goes in.
 Finally, pyruvate kinase (which converts PEP to pyruvate) is inhibited
by PKA (which goes up with glucagon stimulation and goes down with
insulin stimulation). Presumably that frees the PEP up to go into
gluconeogenesis. Note there's still a clever note on insulin and
glucagon coming.
Endocrine Pancreas: Insulin and Glucagon
Wednesday, November 05, 2008
10:02 AM
Endocrine Pancreas: Insulin and Glucagon, 11/5/08:
[Note he didn't actually cover all the ground discussed by his LOs (it would have
taken another hour). I've starred (*) the LOs he didn't get to.]
1. Describe the cell types in the Islets of Langerhans and the hormones secreted by
them.
 In the center of the islets of Langerhans you have beta cells; around
the edges of the islets you alpha cells, D-cells or delta cells, and PP
cells.
 Beta cells: produce insulin.
 Alpha cells: produce glucagon.
 D-cells: produce somatostatin.
 PP cells: produce pancreatic polypeptide.
 The blood supply in the islets first comes into the middle of the islet
(beta cells) and then proceeds to the outside cells (everything else).

The hormones that are secreted go into the portal vein and from there
into the liver.
 Note that a lot of insulin is deactivated in the liver.
2. Describe the structure of Insulin and the various stimuli that lead to its release.
 Insulin: two chains, a shorter alpha and a longer beta, linked by
disulfide bonds.
 Synthesized as preproinsulin, in which the alpha and beta chains are
connected by a C-peptide and there's an amine group on the end.
 In the endoplasmic reticulum in the beta cell, the amine group is
cleaved (now it's proinsulin).
 In the secretory vesicles it's stored in inside the beta cell, the C
peptide is cleaved (now it's insulin and C peptide).
 Note that the C peptide and insulin are released at the same
time (important diagnostically since C peptide has a longer halflife in the plasma).
3. Describe cellular mechanisms leading to the secretion of Insulin in response to an
increase in serum glucose.
 Important side notes:
 Initiators (cause insulin release from beta cells):
 Glucose
 Amino acids
 Potentiators (enhance insulin release from beta cells in the
presence of glucose):
 Glucagon-like peptides
 Vasoactive peptide (VIP)
 Inhibitors (prevent insulin release from beta cells in the
presence of glucose):
 Epinephrine
 Somatostatin
 A couple of possible transporters of glucose into cells:
 Glut2 (insulin-independent transporter)
 Glut4 (insulin-dependent transporter, only works when
insulin's around)
 The release is very rapid. Here's how it works:
 Glucose is transported into the beta cell by Glut2 (insulinindependent transporter)
 The glucose undergoes glycolysis and oxidation, generating
ATP.
 The increased levels of ATP inhibits K channels in the
membrane, depolarizing the beta cell membrane.
 Note this is why amino acids also induce insulin
secretion-- they enter the TCA cycle and produce ATP to
have the same effect.
 The changing membrane voltage opens voltage-dependent
calcium channels, which increases intracellular calcium levels.
 Increased calcium levels prompts release of insulin and C
peptide-containing vesicles.
4. Describe the actions of Insulin in the Muscle, Liver and Adipose tissue.
 Dr. VJ: "The fundamental job of insulin is to store energy."
 The cells in all these tissues have an insulin receptor with a tyrosine
kinase domain (about which much more in the next lecture): the signal
is then transmitted through second messengers to insulin-responsive
systems.

Liver:
 Note that glucose enters hepatocytes through a Glut2 receptor
(insulin independent).
 Insulin activates glycogen synthase to drive glycogen
production.
 Increases phosphofructokinase 1 activity (to increase
glycolysis) and pyruvate dehydrogenase activity (to convert
pyruvate to acetyl CoA). It then promotes fatty acid formation
from the increased stores of acetyl CoA.
 (take-home: increased glycogen and fatty acid formation in
liver.)
 Muscle:
 Note that glucose enters myocytes through a Glut4 transporter
(insulin dependent)-- when insulin enters the cell, the Glut4
receptors are inserted in the membrane and increase glucose
uptake by the myocyte. This in turn promotes glycogen
formation.
 There's lots more about this mechanism in the next lecture.
 (take-home: insert glucose channels in myocytes to drive
glycogen synthesis)
 Adipose:
 Similarly to myocytes, there are Glut4 receptors stored in the
adipocyte which are inserted in the membrane upon stimulation
with insulin.
 Increased glucose levels are converted to glycerol to serve as
the backbone for triacylglycerols.
 Insulin also catalyzes the insertion of lipoprotein lipase into the
cell membrane to increase uptake of free fatty acids from
circulating VLDL or chylomicron molecules.
 Finally, insulin inhibits hormone-sensitive lipase (an enzyme
that promotes triacylglycerol breakdown in adipose tissue).
 (take home: insert glucose channels in adipocytes to drive
triglyceride synthesis, insert enzyme in membrane to increase
uptake of FFA from circulating lipoproteins, inhibit ability to
break down triacylglycerol.)
5. Describe the actions of glucagon.
 [Alpha cells respond to a decrease in blood glucose by releasing
glucagon. Note that they have Glut4 receptors-- so you can't have
simultaneous increased insulin and glucagon release going on at once
(insulin prompts glucose inflow, which shuts off glucagon release).]
 Note exception to this: high-protein meals cause release of
both. Maybe it would be better to say that blood sugar levels
alone can't cause stimulation of both at once.
 Glucagon in the liver (most important target organ):
 Mobilizes glycogen to glucose
 Activates glucose 6-phosphatase to release glucose into the
blood
 Inhibits pyruvate dehydrogenase and promotes pyruvate
carboxylase to promote gluconeogenesis
 Increases the rate of beta-oxidation of fatty acids (can build up
acetyl CoA and ketone bodies)
 [You may be wondering, "I thought he just said insulin caused a
buildup of acetyl CoA. What gives?" Turns out that, yes, they both do
that, but whereas insulin promotes the cellular pathways that lead to
fatty acid synthesis, glucagon inhibits those pathways, so that the
glucagon-mediated acetyl CoA is used for oxidation instead.]
*6. Describe the role of other counter-regulatory hormones (Catecholamines,
Glucocorticoids, Growth Hormone, Thyroid Hormone).
 Catecholamines:
 Mimic glucagon actions in the liver.
 Inhibit insulin secretion by binding to inhibitory
adrenergic receptors on beta cells.
 Increase the resistance to insulin in muscle.
 Stimulate hormone-sensitive lipase (increase lipolysis).
 Glucocorticoids:
 Inhibit intracellular effects of insulin (induces insulin
resistance).
 Potentiate glucagon and epinephrine.
 Promotes muscle breakdown for use of AAs as food.
 Stimulates lipolysis and ketogenesis.
 Growth hormone:
 Decreases insulin sensitivity.
 Promotes lipolysis and protein synthesis.
 Thyroid hormone:
 Decreases basal metabolic rate over several weeks in response
to starvation.
7. Describe the responses of Insulin and counter-regulatory hormones to changes in
nutrient intake.
 After a carbohydrate meal: increased glucose levels lead to increased
insulin secretion. Decreased glucagon.
 After a protein meal: increased amino acid levels lead both to
increased insulin and increase glucagon secretion - the glucagon is
there to make sure the liver doesn't stop making glucose altogether.
 After a fat meal: when was the last time you had a fat meal? Slight
increase in insulin.
 Fasting: see "Integrated Metabolism: Fed/Fasting States."
*8. Describe the coupling and uncoupling of plasma glucose and Insulin
concentrations.
 Note thresholds: plasma glucose < 70 mg/dL starts to deprive the
brain of nutrients, but plasma glucose > 150 mg/dL has negative
effects on vasculature and connective tissue.
 Normally, glucose and insulin levels are closely coupled together, as
you might think-- more glucose, more insulin secretion, which lowers
the glucose, which in turn lowers the insulin secretion to match.
 However, obesity can uncouple the two, mainly due to increased free
fatty acids in the blood. FFAs screw up the uptake of glucose through
insulin-dependent channels (Glut4)-- consequently, at the same
secreted level of insulin, the plasma glucose stays higher. This results
in the beta cells pumping out more insulin to achieve the same glucose
level results.
 Note that I suspect that the mechanism linking obesity to
insulin resistance is far from being this clear.
 Prolonged, increased levels of epinephrine can also uncouple the two,
due both to its lipolytic effect (FFA mechanism) and also its direct
inhibition of beta cells.
*9. Define insulin resistance.

As far as I can tell from his notes, he seems to just mean that it takes
a higher level of insulin to decrease the blood glucose level a certain
amount.
*10. List the steps that are altered in states of insulin resistance.
 I'm not sure what he means here. Maybe the obesity/epinephrine
discussion, above?
 There's lots more on this in the next lecture.
Insulin Signaling and Insulin Resistance
Wednesday, November 05, 2008
11:02 AM
Insulin Signaling and Insulin Resistance, 11/5/08:

[Ok. She went and junked the LOs she had posted up previously (which is
probably for the best, since her handout is so dense it has its own event
horizon). Here are the new and revised ones:]

(1) Understand that insulin has more than one signaling pathway.
o After insulin binds to its receptor, there are two main resultant
pathways; one is metabolic; the other mitogenic (stimulates growth
pathways).
 The metabolic pathway is the main subject of discussion here.
As discussed in the previous lecture, it pushes glycogen
synthesis and glucose transport, inhibits protein breakdown and
gluconeogenesis, and drives lipid storage. These effects are
unevenly distributed throughout tissues (gluconeogenesis takes
place in the liver, etc), also as described in the last lecture.
(2) Describe the 5 main steps of insulin-mediated glucose transport [in
skeletal muscle]:
o (recall from the last lecture that muscle has Glut4 receptors
sequestered in vesicles-- the question for insulin is how to make them
come to the surface.)
o 3 critical nodes here: insulin binding to its receptor and forming an
IRS complex; activation of PI3K (phosphoinositol 3-kinase), and
activation of Akt.
 (these are what you want to pay special attention to for test
purposes.)
 Insulin binding to tyrosine kinase receptor:
 Insulin binds to alpha subunits, causing the beta
subunits to auto-phosphorylate their tyrosine residues;
this activates the receptor.
 The beta subunits attract and bind to a variety of
insulin-receptor substrates (we'll call them IRS1). These
attract and mess with a bunch of other things, including
PI3K.
 PI3K:
 One of the things that is attracted and bound to the
insulin receptor complex is PI3K (note it has two
subunits, p85a-alpha and p110-alpha).




Akt:

PI3K phosphorylates phosphoinositol 4,5-bisphosphate
(aka PIP2) to form inositol 3,4,5-triphosphate (aka
PIP3).
Why on earth we care: the extra phosphate group on
PIP3 causes it to attract and phosphorylate other
proteins, including Akt.
Akt is the effector molecule for insulin. When it's
phosphorylated in a couple places, it activates both
mitogenic and metabolic effects: increased growth
signaling, increased protein synthesis, decreased
gluconeogenesis, increased glucose transport, and
increased glycogen synthesis.
 How, generally, it does this: it phosphorylates and
deactivates various enzymes, either promoters or
inhibitors of various pathways.
o 2 less important steps after that: (steps 4 and 5)
 Akt phosphorylates and inactivates an enzyme called AS160;
this leads to an increase in GTP production in the cell.
 The increased GTP binds to Glut4-containing vesicles, which
activates their movement onto the membrane.
 The insertion of Glut4 transporters into the membrane causes
an inflow of glucose into the cell.
 Define insulin resistance and discuss signaling defects in obesity-associated
IR.
o Ok. Basically, insulin resistance is a chronic over-activation of the
negative pathways that counter insulin secretion. So let's discuss those
pathways:
o Three ways to turn off insulin signaling (negative pathways):
 Phosphatases:
 (1) As just mentioned, phosphorylation of tyrosine
residues turn on insulin signaling inside the cell. So you
can remove the phosphate groups on the insulin
receptor tyrosine residues to turn off the signal. This is
interrupting the pathway at the first critical node.
 (2) You can also remove the phosphate group on PIP3 to
counter the activity of PI3K (which, recall, puts a
phosphate group onto PIP2). This is interrupting the
pathway at the second critical node.
 Serine kinases:
 These can phosphorylate serine residues on the insulin
receptor or the IRS1 complex. This blocks tyrosine
phosphorylation (first critical node step).
 This also causes IRS1 to dissociate from the insulin
receptor and IP3K to dissociate from IRS1.
 Finally, it stimulates ubiquitin-mediated degradation of
IRS1.
 p85-alpha (a subunit of PI3K):
 Self-regulates-- increase in nutrients or insulin causes
p85-alpha to turn itself (PI3K) off.
[Important thing to remember: glucose can't enter the cells by simple diffusion; it
needs to be transported by Glut transporters.]
Glycogen Metabolism: Synthesis and Degradation
Thursday, November 06, 2008
7:59 AM
Glycogen Metabolism: Synthesis and Degradation, 11/6/08:
1. Be able to recognize the structure of glycogen.
 This one's easy. You have a bunch of glucose molecules linked in one
long chain (alpha-1,4 bonds) and linked in branches off that chain
(alpha-1,6 bonds).
[Glycogen is sort of your rapid-reaction source of glucose (as opposed to
gluconeogenesis, which takes a while)-- it responds to sudden need.]
[Recall that, except in the liver and the kidneys, there's no glucose 6-phosphate-- so
the glucose can't get out into the blood. It's therefore used within the tissue it's
being produced in.]
[Major sources of glycogen storage: liver (whence to the blood) and muscle.]
2. Describe the reactions catalyzed by glycogen phosphorylase and glycogen
synthase.
Glycogen synthesis:





3 key enzymes: phosphoglucomutase, glycogen synthase, and
branching enzyme (arguably also glycogenin).
Ok. Phosphoglucomutase shifts glucose 6-phosphate to glucose 1phosphate.
The phosphate on glucose 1-phosphate is swapped out for a highenergy UDP attachment (UDP-glucose).
Glycogen synthase takes UDP-glucose and tacks it onto a glucose
chain. Note two things: the UDP is taken off (glycogen synthesis takes
energy), and glycogen synthase only adds 1-4 bonds.
 Note that glycogen synthase can't start de novo-- it needs to
add onto a primer. There's an enzyme called glycogenin that
gets things rolling by initiating the glycogen chain.
After about 11 glucose molecules are added, branching enzyme takes
6-8 of them off as a group and tacks them onto the rest of the chain
through a 1-6 bond. This chain can then be further elongated by
glycogen synthase.
Glycogen degradation:



3 key enzymes: glycogen phosphorylase, debranching enzyme,
and phosphoglucomutase.
Glycogen phosphorylase breaks 1-4 bonds in glycogen: it pulls a
glucose molecule off the glycogen chain (which is phosphorylated in
the process to glucose 1-phosphate). This starts from each free end
and works in towards the middle until it reaches a couple of glucose
molecules away from a branch point.
Debranching enzyme, as you might expect, breaks 1-6 bonds in
glycogen once a branch point is exposed by glycogen phosphorylases.
 Note there's a couple of reactions involved with this. One is a
transferase function-- it takes the glucose chain that's left
around the branch point (the couple of 1,4-linked glucose
molecules attached to the glucose that's 1,6-bound) and
transfers it to the main (hitherto mostly undigested) glycogen
chain.
 Then it hydrolyzes the 1-6 bond and liberates the last glucose
molecule hanging off there. Notice that this one molecule is
liberated as glucose, not glucose 1-phosphate.
 If this doesn't make any sense, it's easier to grok as a picture.
Dr. Flores has a good image in her lecture from this hour, and
Lippincott's figure 11.8 is ok as well (pay attention to the
pathway on the right).
 Phosphoglucomutase shifts glucose 1-phosphate to glucose 6phosphate, whence it can be used in traditional glycolytic pathways.
3. Understand the coordinate regulation of glycogenesis/glycogenolysis.
 This has to do with the relative activation or inhibition of glycogen
phosphorylase and glycogen synthase.
 In the muscle:
 High levels of calcium (indicating lots of contraction) or AMP
(indicating low energy states) promote glycogen phosphorylase
activity. High levels of glucose 6-phosphate or ATP inhibit
glycogen phosphorylase. High levels of glucose 6-phosphate
also activate glycogen synthase.
 In the liver:
 High levels of glucose, glucose 6-phosphate, or ATP inactivate
glycogen phosphorylase. High levels of glucose 6-phosphate
activate glycogen synthase as well.
 [This seems like a lot of random detail, but it makes sense if you take
it back to "what states require more energy to be liberated, and what
states require less?"]
 There are some complex but testable reactions having to do with
glycogen phosphorylase:
 Glycogen phosphorylase is only active when it itself is
phosphorylated (technically it's called the "a" form when active
and "b" when inactive).
 The enzyme that controls phosphorylation of glycogen
phosphorylase is called glycogen phosphorylase kinase.
 Glycogen phosphorylase kinase is, in turn, active either
when it's phosphorylated or when it's bound to calcium.
 This is how calcium in muscle triggers glycogen phosphorylase
(activate GPK).
 Low levels of ATP (ie. high levels of AMP) trigger increased PKA
activity-- PKA phosphorylates GPK, which activates glycogen
phosphorylase.
 The same sort of thing is going on with glycogen synthase but it's only
activated when it's not phosphorylated.
 Recap (pay attention for testable stuff): glycogen phosphorylase is
active when it's phosphorylated. Glycogen synthase is active when it's
not.
 Long-awaited really insightful note:
 You know, one way to look at insulin/glucagon effects is to
think of insulin as a phosphorylase and glucagon as a kinase.
Glucagon phosphorylates stuff (glycogen synthase, glycogen
phosphorylase, PFK2/FBPase, PDH complex, pyruvate kinase),


while insulin dephosphorylates stuff (all the same enzymes).
Once you know that, and once you know what a given reaction
does in terms of energy storage, you can kind of figure out
what effect insulin or glucagon is going to have on a given
enzyme in that reaction.
Ie: say we don't know, or have unaccountably forgotten, that
glycogen synthase is inactivated by phosphorylation and
glycogen phosphorylase is activated by it. What we do know is
that glycogen synthase is energy-storing and glycogen
phosphorylase is energy-liberating. Thus we could assume that
insulin's effect (dephosphorylation) is going to promote
glycogen synthesis and inhibit glycogen breakdown-- so if
pesky test or board questions come up about whether
phosphorylated glycogen synthase is activated or inactivated,
just ask yourself, "is this more likely to be active with insulin or
glucagon?"
No, it doesn't apply to everything, most notably the intracellular
insulin receptor pathway itself. But it's not bad.
Integrated Metabolism: Fed/Fasting States
Thursday, November 06, 2008
9:01 AM
Integrated Metabolism: Fed/Fasting States, 11/6/08:
1. Discuss the effect of insulin or glucagon on glycogen synthase, glycogen
phosphorylase and glycogen phosphorylase kinase.
 We went through this last time. Insulin: promotes glycogen synthase,
inhibits glycogen phosphorylase, inhibits glycogen phosphorylase
kinase. Glucagon: the reverse.
2. Understand the role of insulin and glucagon on mobilization of carbohydrate
stores.
 We mentioned that insulin inhibits this mobilization; glucagon
promotes it.
3. Describe the changes in insulin, glucagon and glucose following a meal.
 Right after a meal: blood glucose goes up. This means insulin levels go
up. High levels of insulin, as mentioned previously, inhibit the release
of glucagon.
 This is a reasonably good thing to keep in mind, if you'll pardon the
expression: glucagon is insulin's bitch. When insulin is high, glucagon
is low; when insulin is low, glucagon is high. It doesn't work the other
way around. Insulin follows glucose; glucagon follows insulin.
 There are a few exceptions (ie. after a protein meal both of
them go up) but generally this seems to be true.
4. Be able to distinguish between glucose metabolism in the liver, the muscle and
brain under fed and fasting conditions.
 See Lippincott p. 335, figure 24.18 for a good map of most of this.
 Well-fed state: everything uses glucose for fuel.
 Liver:
 Rapid uptake of glucose from blood into hepatocyte
(Glut2 receptors) and conversion to glucose 6-






phosphate by glucokinase (high concentration of
glucose, thus high rate of phosphorylation).
Since insulin levels are high, glycogen synthase is
promoted.
Lots of acetyl CoA generated; some used for TCA cycle
and energy, some used for de novo lipogenesis
(promoted by the pentose pathway shunt and NADPH).
The fatty acids generated by de novo lipogenesis are
packaged into VLDL and sent out into the bloodstream
(more on this later).
Brain:
 Pretty simple: glucose is broken down in the TCA cycle
for energy.
 Muscle:
 Uptake of glucose from blood (Glut4 receptors,
combined with high insulin levels), conversion by
hexokinase. Glycogen production is upregulated; any
uptaken amino acid is used to synthesize protein.
Fasting state (3-36 hours after last meal):
 Liver:
 Early on, increased glucagon levels promote glycogen
phosphorylase kinase, promoting glycogen
phosphorylase, leading to increased glycogen
mobilization.
 When glycogen stores are beginning to be drained,
gluconeogenesis pathways kick in, shunting pyruvate to
oxaloacetate and inhibiting its breakdown to acetyl CoA.
 Fatty acids are uptaken and/or mobilized by the liver
and oxidized down to acetyl CoA; the liver uses the
fatty-acid-derived fuel instead of glucose for its own
energy needs (it liberates the created glucose for
glucose-dependent tissues).
 The glucose made by gluconeogenesis is released into
the blood, mainly for the RBCs and the brain.
 Muscle:
 Like the liver, the muscle prefers to use fatty acids as an
energy source in fasting states (preserving the glucose
in the blood for RBCs and the brain).
 Muscle begins to break down its proteins to liberate AAs
into the bloodstream so that the liver can pick them up
and use them in gluconeogenesis.
 Brain:
 Glucose is still broken down in the TCA cycle; the brain
gradually begins to adapt towards a ketone body-based
metabolism as well.
[Starvation state (3-5 days after last meal):]
 Adipose tissue releases free fatty acids and glycerol into the
bloodstream.
 Brain:
 Brain begins to use ketone bodies as a fuel source-- thus
reducing the need for gluconeogenesis.
 Note that the RBCs can't use ketone bodies-- it's glucose
or nothing.


Muscle:
 Muscle is still using the free fatty acids in the blood,
occasionally using ketone bodies as well.
Liver:
 Liver is breaking down glycerol to make glucose for the
RBCs.
 For itself it's also using the free fatty acids in the blood
for energy.
Dietary Carbohydrates
Thursday, November 06, 2008
10:06 AM
Dietary Carbohydrates, 11/6/08:
1. Describe how to calculate the number of grams of carbohydrate consumed per day
by an individual in energy balance.
 Ok. So if energy intake equals energy expenditure (as in energy
balance), then you can measure energy expenditure (doubly labeled
water, remember?) to get energy intake.
 Then if you take the proportion of caloric energy intake attributable to
a given type of macronutrient, you can multiply the total energy intake
by the percent attributable to carbohydrates to get the total ingested
kilocalories of carbohydrates.
 Then if you assume that each gram of carbohydrates has 4 kcal, you
can divide the number of ingested carb kilocalories by 4 to get the
ingested number of carb grams.
 Example:
 Guy's taking in 2100 kilocalories per day. Say 50% is carbs-- so
that's 1050 kilocalories from carbs.
 Divide 1050 by 4 to get 262.5 grams of carbs per day.
 Note average total energy expenditure is about 30 kcal per kg per day.
2. List the chemical characteristics of sugars, oligosaccharides and polysaccharides.
 Monomeric sugars: glucose, fructose, galactose. There are also
indigestible sugars (sugar alcohols). Directly taken up by SGLT1/Glut5
receptors.
 Disaccharides: sucrose (glucose-fructose), lactose (glucose-galactose).
Broken down by brush-border enzymes, then absorbed.
 (Oligosaccharides: comprised of 6-10 linked monosaccharides.)
 Polysaccharides (starches):
 Digestible by endogenous enzymes: amylopectin (lots of 1-6
bonds), amylose (no 1-6 bonds). Slowly broken down (amylose
more slowly than amylopectin), then further broken down by
brush border enzymes, then absorbed.
 Indigestible by endogenous enzymes (some can still be
digested by intestinal bacteria): cellulose, pectins,
hemicellulose.
3. Compare and contrast the properties of resistant starch and fiber.
 Resistant starches (eg. cornstarch): poorly and slowly digested.

Fiber: not digested at all. Insoluble fiber doesn't absorb a lot of water,
soluble fiber absorbs water (and hence creates more bulk in the GI
tract).
4. Describe the concepts of glycemic index and glycemic load.
 Glycemic index: how much blood glucose levels rise after you eat a
given type of food, per unit weight of the food.
 Note that fructose, although it doesn't raise glucose levels and
hence has a low glycemic index, causes insulin resistance in
rats (results are inconclusive in humans).
 Note also that high fat foods also have low glycemic indices but
are not necessarily great for you either.
 Generally GI tends to be lower in complex starches (eg.
amylose or amylopectin, takes longer to break down) than
simple sugars (eg. sucrose, very rapidly broken down and
absorbed).
 Glycemic load: glycemic index multiplied by the amount of the food
due to carbohydrates that was actually eaten.
 Note high glycemic load and low fiber intake correlates strongly with a
higher incidence of diabetes.
5. List the types of studies that can be used to inform nutritional recommendations.
 Animal or in vitro studies: good control, but have to assume the
results are applicable to humans. Also you're experimenting on
animals, which - lest we forget - is not actually a great thing to do.
 Epidemiological studies: self-reported diet, look for health problems.
Problem is (a) people lie, and (b) correlation is not causation.
 Small trials: control diets, look for changes in blood or molecular
markers (insulin sensitivity, LDL levels, etc). Problem is (a)
generalizability and (b) markers like LDL don't always go along with
actual health events (heart attack, diabetes).
 Long-term interventional studies: take a bunch of people, feed one of
them a certain diet, look for clearly-defined health end points. Pretty
good for this sort of thing. Watch out for confounding factors (health
benefits due to increased exercise or better diet?) and the degree of
control of the diet.
 [Note that restricted fat and high carbohydrate diets, with high fiber and
increased physical activity, seems to have a fairly large protective effect
against developing diabetes. But note also that high-fat, low-carbohydrate
diets with increased physical activity also seems to be protective. Maybe it's
just about total energy balance.]
Living With Diabetes
Thursday, November 06, 2008
11:00 AM
Living With Diabetes, 11/6/08:
[Some notes on diabetes:]
 Microvascular disease defines diabetes:
 Kidney: Proteinuria and renal failure
 Eye: Retinopathy and blindness
 Nerves: Pain, numbness, poor wound healing


Macrovascular disease is a much more common cause of death but does not
define diabetes:
 Coronary artery disease
 Stroke
 Peripheral vascular disease
Note glucose levels:
 Fasting glucose >= 126 mg/dL
 Glucose after 75g oral glucose load >= 200 mg/dL
 Glucose on a random glucose test >= 200 mg/dL
 Note that a fasting glucose between 100 (normal) and 126 (diabetic)
indicates a prediabetic patient. They don't generally have
microvascular disease but are at higher risk for macrovascular disease.
1. List the signs and symptoms that a person might experience with new onset
diabetes.
 (1) Polyuria (osmotic diuresis)
 (2) Polydipsia (thirsty all the time, secondary to both increased
urination and increased plasma osmolarity)
 (3) Blurry vision (lens swelling due to osmotic shift)
 (4) Weight loss (breakdown of proteins' amino acids to fuel
gluconeogenesis)
2. Describe the clinical features of the 4 types of diabetes.
 Type I:
 Younger
 Negative family history (weak genetic component)
 Auto-immune etiology (vs. beta cells)
 Insulin-deficient
 Correlated with lean individuals
 Develop ketoacidosis from oxidation of fatty acids for fuel
 Type II:
 Older
 Positive family history (strong genetic component)
 Insulin resistance (note insulin deficiency develops later in
course)
 Correlated with overweight individuals
 Unknown etiology
 Generally don't get ketoacidosis
 Gestational Diabetes:
 Pregnant women (no kidding)
 Develops during pregnancy, resolves spontaneously; however,
both mother and child are at risk for developing type II
diabetes later on in life.
 Note that people at risk for type II diabetes are more likely to
develop gestational diabetes.
 Pancreatic Diabetes:
 Caused by surgical removal of the pancreas or pancreatic injury
due to pancreatitis.
 Similar to type I diabetes, but look for the following:
 No pancreatic enzymes (steatorrhea, malabsorption)
 Marked weight loss
 Lack of glucagon in addition to a lack of insulin-predisposed to hypoglycemia as well as hyperglycemia.
Look for comorbidity with alcoholism and liver injury
(thus impaired gluconeogenic pathways).
3. List the tools available to a person with diabetes that allow them to assess their
own blood sugar level.
 Home glucose monitor
 Current insulin meds are 24-hour; you also take short-acting insulin
before meals. See "Treatment of Type I Diabetes."
 Insulin pump: allows variable-rate but near-continuous infusion of
rapid-acting insulin-- sort of a pancreatic mimic. This helps customize
'background' insulin release during the day and night to get around "3
AM" activation of counter-regulatory hormones (glucagon,
epipnephrine, cortisol, growth hormone) to prevent nocturnal
hypoglycemia.
 The insulin pump is subcutaneous-- it's not going into the portal
system (unlike pancreatic secretions).
 Essentially you stick a tiny catheter under the skin and leave it
in; it's changed every three days. Note it can also have a builtin glucose monitor to continually alert patients to effects of
various foods.
 Note that insulin pumps are much less obvious than sticking a
needle in your thigh. Note also that these pumps keep records
of the fluctuating glucose levels so the doc can check to see
how the patient's doing.
4. List factors that will tend to make a person with diabetes have an increase in their
blood sugar levels.
 Not much discussed, aside from the obvious (food intake).
5. List factors that will tend to lower blood glucose levels in a person with diabetes.
 Not much discussed, aside from the obvious (insulin intake). Also
exercise. Also, as mentioned, the "3 AM" rise in counter-regulatory
hormones.

Pathophysiology of Type I Diabetes
Friday, November 07, 2008
8:00 AM
Pathophysiology of Type I Diabetes, 11/7/08:
1. Discuss the sequence of events that occurs from normal to overt diabetes in
someone who develops type 1 diabetes (T1D).
 Autoimmune-inciting event happens (see #5, below).
 Then there's a silent period in which there are still enough beta cells
around to make a functional level of insulin.
 When the functional beta cell count gets down to about 10%,
symptoms of diabetes start showing up.
 [Insulin deficiency causes:]
 Decreased glucose transport through Glut4 (insulin-mediated)
channels
 Increased glucose production (glycogen mobilization,
gluconeogenesis)
 Increased activity of hormone sensitive lipase (mobilizing FFA
and producing of ketone bodies).

2. List the
3. List the
4. List the
5. List the
If treatment is started promptly, the symptoms are alleviated and the
remaining beta cells can make a comeback for a while (the
"honeymoon period" of treatment).
 After a certain point, all the beta cells are completely gone, and the
diabetes becomes more difficult to manage.
antibody tests that might become positive as a person develops T1D.
 Autoantibodies: islet cell autoantibody (ICA), anti-insulin, GAD65, IA2;
also anti-zinc transporter ZnT8.
 Good clinical note: you need more than one autoantibody to develop
type I diabetes. That said, having one is usually a good indication of
developing others.
 T cell response markers are in the works as well.
environmental factors that might be related to the development of T1D.
 High correlation with geographical areas (Finland, Sardinia, USA, etc;
low in China and Africa).
 Incidence is increasing over the past 50 years.
 Could be related to viral infections, diet, or obesity; immunizations
have been definitively shown not to cause diabetes.
 Diet: early exposure to solid cereal (at the recommended time, 6
months) seems to correlate with lower risk for diabetes. Perhaps some
link with type I diabetes and GI immune system? Increased intake of
omega-3 fatty acids correlate with lower risk, as well.
 Viral infections: evidence is mixed.
 Obesity: hypothesis is that obesity causes beta-cell stress and exposes
previously unexposed beta-cell antigens to the immune system.
genetic factors that predispose to or protect from T1D.
 Note that the great majority of patients with type I diabetes have no
relatives with it.
 Mainly this involves certain genotypes of HLA class II proteins:
 DR3/4 (two-gene combination) heavily predisposes to type I
diabetes.
 DQA1*0102, DQB1*0602 (one gene) seems to protect from
type I diabetes.
 Why HLA II? Evidently particular types of HLA II can bind to insulin
when they're presenting antigens-- thus they can inadvertently set off
a reaction against insulin.
 Note that once you develop diabetes, outcomes and time course aren't
correlated with HLA genotype.
 In addition to HLA II types, T1D can also be involved with the number
of repeats within the 5' region of the insulin gene-- a higher number of
repeats is associated with increased expression in the thymus, which
would lead to more negative selection against insulin-reactive T cells
and decrease risk of type I diabetes. Less repeats, then, cause an
increased risk.
parts of the immune system that are involved in the development of T1D.
 Islet cell antigens get presented to T cells, which ramp up an immune
response. The notes are somewhat unclear on this point, but seem to
emphasize the main role of the T cell in this process (despite the
involvement of B cells and autoantibodies).
 Note that this is process countered by T-regulatory cells (which, recall,
are kind of a brake on the whole process). Part of type I diabetes
entails a gradual failure of T-regulatory cells to brake the process--

which is why you can have a positive antibody test but not necessarily
have overt diabetes.
Note also that people with a predisposition towards type I diabetes
seem to need some kind of "inciting event" to make the actual
autoimmune attack happen. Most genetically high-risk people don't
develop type I diabetes because their bodies never encounter
whatever it is that causes recognition of beta cells as antigen.
Pathophysiology of Type II Diabetes
Friday, November 07, 2008
9:02 AM
Pathophysiology of Type II Diabetes, 11/7/08:
1. List the clinical features that suggest type 2 diabetes.
 Usually age > 40 years
 90% obesity
 Family history
 Insulin resistant (more than half eventually require insulin treatment)
 Note, germane to PBL, that T2D predisposes to polycystic ovarian
disease.
2. Discuss how changes in body weight predispose to type 2 diabetes.
 Obesity predisposes to T2D. The T2D prevalence is following the
obesity prevalence in the country quite closely. Why is still an open
question.
3. List the criteria used to define diabetes, impaired glucose tolerance and impaired
fasting glucose.
 Diabetes: one of:
 Fasting plasma glucose of 126 or higher (most common test)
 Random plasma glucose of 200 or higher, plus symptoms
(polyuria, nocturia, polydipsia, polyphagia, weight loss)
 2 hour post oral glucose tolerance test glucose of 200 or higher
(less frequently used and should be confirmed)
 Impaired fasting glucose (prediabetic): fasting plasma glucose
between 100 and 125.
 Impaired glucose tolerance: 2 hour post oral glucose tolerance test of
140-199.
4. Discuss the 2 key factors in the pathophysiology of type 2 diabetes.
 Increased insulin resistance (decreased glucose uptake in
peripheral tissues).
 Etiology seems to have something to do with increased
negative-pathway activity (discussed in "Insulin Signaling and
Insulin Resistance"); also decreased synthesis and increased
degradation of insulin receptors.
 Note also that GI bacterial activity may influence this (which
would relate back to diet composition).
 Failure of beta cell function (problem with insulin secretion).
 Generally, the more insulin-resistant you are, the more your
beta cells work to put out more insulin to compensate.
 At some point, the beta cells can't put out any more insulin,
and in fact start to die off-- thus not only are you not
compensating for insulin resistance but you're actively
decompensating, leading to onset of clinical features.
5. Describe interventions that have been shown to prevent type 2 diabetes in those
at risk.
 Frequent screening is always a good idea.
 Watch out for what prospective mothers are eating-- the little
vampires can pick up problems if it's an all-Twinkie diet.
 Predisposing: FMH, HTN, dyslipidemia, central obesity, gestational
diabetes, ethnicity, birth weight (really big or really little).
 Lifestyle changes are the big intervention here. Exercise, weight loss,
stop smoking. It's more effective than metformin alone.
6. Describe the role of genetics in the development of type 2 diabetes.
 Familial clustering is much more common in type 2 diabetes than type
I: about a 1 in 3 risk for siblings or parents.
 Prevalence is also increased in African-Americans, Hispanics, and
American Indians.
 Note that unlike type I diabetes, there's no correlation with HLA types- it's a very heterogenic disorder involving lots of different genes
(current research is looking at genes involved in mitochondrial
oxidation processes).
Treatment of Type I Diabetes - Insulin
Friday, November 07, 2008
9:53 AM
Treatment of Type I Diabetes - Insulin, 11/7/08:
1. Describe the normal pattern of insulin secretion that occurs in the absence of
diabetes.
 Normal: About 30 units of insulin secreted per day into the portal vein.
Note that there's a basal level of insulin secretion that occurs even in
the absence of food intake.
 First phase of insulin secretion: peaks quickly about five minutes after
food intake; involves release of preformed granules of insulin and
peptide C.
 Second phase: more prolonged but occurs later after food intake;
involves synthesis and release of new insulin.
 Glucose levels reach their nadir about 90-120 minutes after eating.
2. Compare the five different types of insulin and their durations of action.
 [These tend to be 100 units/mL solutions, about 10 mL or 1000 units
per vial.]
 Normal insulin (short-acting, recombinant human, "clear" solution):
 Onset of action 30-60 minutes
 Peak insulin levels at 2 hours
 Last 6-8 hours (watch out for overlap with the next injection)
 Has some zinc in it to improve shelf life
 SQ or IV injection (only insulin that's approved for both)
 NPH insulin (Intermediate-acting, "cloudy" solution):
 Onset of action 2-4 hours
 Peak insulin levels at 6-7 hours
 Last 10-20 hours
 SQ Injection only
Rapid-acting insulin analogs ("clear" solution):
 Contain mutations in the alpha chain that cause the insulin to
form monomers and decrease time of onset.
 Onset of action 5-15 minutes
 Peak insulin levels at 1-1.5 hours
 Last 3-5 hours
 SQ injection or in insulin pump
 Can be mixed with NPH insulin.
 Long-acting insulin analogs (2 types, detemir and glargine):
 Glargine (longer duration) contains AA substitutions to make
the molecule more acidic; it precipitates in the SQ tissue and
slowly dissolves out into the blood. Detemir (shorter duration)
binds to albumin and is slowly released from it.
 Onset of action: 1 or 1.5 hours
 Peak insulin levels: none (no peak time)
 Last 17 or 24 hours
 Can't be mixed with other insulins.
 Inhaled insulin:
 Pulled off market for lack of sales.
 Absorption was quite variable with respiratory infections or
chronic respiratory disease.
 There's a nice graph in her Powerpoint that show the peaks and
durations of the various types.
 Intermediate (NPH) plus rapid-onset insulin are often used combined
in a syringe before a meal-- rapid-acting for the meal, intermediate for
basal insulin level maintenance. See below for more on regimens.
 Problem is, the mixed solution isn't stable (has to be mixed
right before meal). Modified intermediate-acting insulins that
are more stable when premixed can be used instead.
 Note that NPH is much less expensive than the long-acting insulin
analogs.
3. Outline 2 common treatment regimens for type 1 diabetes and explain the
rationales for their use.
 (1) Glargine once a day to provide basal 24-hour coverage, rapidacting insulin injected before each meal.
 Alternative: Detamir at dinner, rapid-acting insulin injected at
breakfast and dinner, NPH in the morning to cover lunch (at
school, working, etc).
 (2) (if affording the long-acting insulins is a problem) Rapid-acting
insulin injected before each meal, larger doses of NPH in morning and
at dinner.
 Can also use small doses of NPH and rapid-acting insulin
together before each meal to maintain a more constant basal
rate.
 The point of maintaining basal insulin seems to be to suppress
inappropriate gluconeogenesis and free fatty acid release between
meals.
4. Describe 2 clinical scenarios that would prompt the use of insulin therapy in type 2
diabetes.
 When lifestyle modifications and non-insulin therapy isn't working to
adequately reduce blood glucose levels.



People with liver/kidney disease or CHF: can't use non-insulin
therapies.
Use insulin when: (know for test)
 (1) Signs of insulin deficiency on presentation: weight loss,
fasting blood glucose > 250, random blood glucose > 300,
HbA1C > 10%.
 (2) Hospital admission for diabetic emergency (DKA,
hyperglycemic hyperosmotic state).
 Note that in these situations, insulin should be continued after
the immediate crisis is over.
Treatment of Type II Diabetes
Friday, November 07, 2008
10:50 AM
Treatment of Type II Diabetes, 11/7/08:
1. Discuss the sites of action for glucose-lowering therapies.
 Mainly beta cells (increase insulin secretion), liver (potentiate
suppression of gluconeogenesis), and muscle/adipose (potentiate
insulin action); see below.
2. List four classes of medications that can be used in the treatment of diabetes and
explain their mechanisms of action.
 Sulfonylureas: insulin secretagogues
 Most commonly: glipizde, glyburide, glimepiride.
 Recall that beta cells act to secrete insulin by having their cell
membranes depolarized to trigger voltage-gated calcium
channels, which allow the release of insulin-containing vesicles.
 Sulfonylureas block potassium channels in beta cells,
depolarizing them to achieve the same end. Note these are the
same K channels that are closed with an increase in
intracellular ATP elevation during physiological insulin secretion
stimulation by high glucose levels. Effectively you're fooling the
body into thinking it has high blood glucose levels.
 Pros: inexpensive, infrequent dosing, can be combined with
other drugs.
 Cons: side effects (weight gain, hypoglycemia), doesn't work
well as beta-cell function declines.
 Metabolized by the liver, excreted by the kidneys.
 Metformin:
 Acts mainly in the liver to potentiate insulin's suppression of
gluconeogenesis; no stimulation of insulin secretion, no
increase in circulating insulin levels.
 Pros: doesn't cause hypoglycemia, very cheap, no weight gain,
can be combined with other drugs.
 Cons: GI side effects (nausea, diarrhea), small risk of lactic
acidosis (can't be used in CHF/renal insufficiency/liver disease).
 Thiazolidinediones:
 Enhance insulin sensitivity at the level of muscle and adipose
tissue. Bind to PPR-gamma receptors to effect physiological
sensitization to insulin (increased glucose uptake, etc).

Pros: Doesn't increase insulin resistance, helps in beta-cell
dysfunction phase of type II diabetes, infrequent dosing.
 Cons: very expensive. Can cause fluid retention, making
congestive heart failure worse.
 Incretin enhancers:
 Based on the fact that oral glucose causes a much higher
insulin secretion than the same amount of IV glucose, due to
factors called "incretins."
 This incretin effect is decreased in T2D patients. Incretin
enhancers, then, attempt to rectify the difference.
 Incretins: GIP, GLP1 (no, I don't care what it stands for).
 GLP1: stimulates insulin secretion, suppresses glucagon
secretion (both suppress hepatic gluconeogenesis); also
slows gastric emptying and inhibits food intake.
 Note GLP1 is broken down by DPP4 (still don't care
about the name).
 So the drugs are either GLP1 receptor agonists, or DPP4
inhibitors.
 Pros of GLP1 agonists: glucose-dependent effects on
insulin/glucagon secretion (no hypoglycemia), weight loss
induction.
 Cons of GLP1 agonists: 2x/day SQ injection, nausea, extremely
expensive.
 Pros of DPP inhibitors: glucose-dependent effects, as above,
but no weight loss effect. Once per day, oral administration.
 Cons: extremely expensive, nasopharyngitis, headache,
Stevens-Johnson syndrome (dangerous epidermis-dermis
separation).
 Amylin analogs:
 Amylin: secreted from beta cells; suppresses glucagon, slows
gastric emptying, decreases food intake.
 Amylin analogs can be used in much the same way as GLP1
agonists.
 Pros: glucagon suppression, appetite reduction, weight loss.
 Cons: SQ injection prior to every meal, must be given in
addition to insulin (but can't be mixed with it), GI side effects,
extremely expensive.
3. Outline the blood glucose goals for individuals with diabetes.
 HbA1c: < 6% if possible, < 7% if not.
 Fasting glucose: 70-130 mg/dL (note the handout is incorrect here)
 2-hour postprandial glucose: < 180 mg/dL
4. Describe routine monitoring and preventive care that should be provided to
individuals with diabetes.
 Monitor HbA1c
 Regularly review home-checking of blood sugar trends
(hypo/hyperglycemia)
 Education (causes of symptoms, blood glucose variability, effects/side
effects of meds)
Diabetic Complications
Monday, November 10, 2008
7:52 AM
Diabetic Complications, 11/10/08:
[Diabetes: from a 1998 report: #1 on the list of direct costs to the health care
system. #2 on this list of direct and indirect costs to the health care system. Save
the diabetics, save the world. No, really.]
1. Overview of acute complications of diabetes including DKA and Hypoglycemia.
 They include DKA and hypoglycemia. Note she didn't talk about this.
 Recall that DKA comes about because the body thinks it's
starving all the time (no intracellular glucose). This causes it to
start breaking down fatty acids for fuel. The fatty acids, under
conditions of very low levels of insulin, are converted to ketone
bodies (which is why you don't usually see DKA in most type II
diabetics-- their levels of insulin are overly high). Most ketone
bodies produced are acidic. Missing your insulin shots is the
most common cause. Treat with insulin but watch out for
cerebral edema in peds (can treat with mannitol) and
hypokalemia in everyone (H-K exchanger stops pumping
potassium out into the serum once you correct the acidosis).
 Hypoglycemia: What you watch out for is an altered mental
state.
 So glucagon is the body's first-line defense against
hypoglycemia. Eventually the responsiveness to
glucagon is lost and epinephrine is used instead. Signs
of over-stimulation (sympathetic stimulation) can be
looked for to detect hypoglycemia. Note that it's possible
to lose responsiveness to epinephrine as well with
prolonged or repeated hypoglycemic states (thus altered
mental state in hypoglycemia comes on with no warning
at all); this can be corrected by avoiding hypoglycemic
states for several weeks.
2. Provide an overview of the mechanisms underlying the excess macro-vascular
complications in diabetes and therapeutic interventions.
 Macrovascular: acute MI, stroke, peripheral vascular disease.
 Leading cause of death and disability, most common cause of
hospitalization. Incidence is much higher, prognosis is poorer.
CV disease is "more common, more severe, more deadly" in
DM.
 Note even in type I DM, heart disease is the most common
cause of death.
 Pathophysiology:
 Insulin resistance leads to:
 Increased triglycerides and LDL
 Decreased HDL
 Increased blood pressure
 Increased thrombosis due to promotion of prothombin
activators
 All these lead to increased atherosclerotic risk (tight endothelial
junctions loosen, NO production ceases, lipids invade wall,
inflammatory signals set off).

See "Lipids, Lipoproteins, and Atherosclerosis" from CVPR for
further details.
 People with diabetes should be treated as if they have coronary
vascular disease.
 Note hypertension in diabetes make all of the above worse.
 Blood pressure goals in diabetes: aim for 120/80, accept
130/80.
 3 treatment goals: cholesterol, blood pressure, thrombolytics
(aspirin).
3. Understand the mechanisms by which hyperglycemia causes the development of
micro-vascular diabetic complications.
 Way too much glucose causes a shunting into pathways that are
probably supposed to be acute relief, not long-term and chronic
(polyol, hexosamine, PKC, AGE pathways).
 Polyol pathway: glucose gets reduced to sorbitol, which gets
oxidized to fructose. Both of them cause oxidative stress.
Sorbitol evidently gets stuck in cells and causes problems.
 Cataracts: due to sorbitol getting stuck in the lens.
 AGE pathway: glucose molecules get stuck in a non-degradable
fashion to the basement membrane, causing decreased
endothelial function and NO production. They can go into the
cell and cause BM thickening, etc. Can attach to LDL molecules
and increase their pro-inflammatory effects.
 PKC (protein kinase C): causes BM thickening; promotes
adhesion molecules in endothelium (ICAMs) that promote
leukocyte extravasation.
4. Review the micro-vascular complications of diabetes.
 Retinopathy (diabetes is the leading cause of blindness in the US):
 Pericytes (nerve cells in retina that regulate blood flow to the
retinal capillaries): both hyper- and hypoglycemia are toxic to
pericytes. Get dysregulation, exudates, and hypoxia in the
retina. The blood vessels in the back of the eye hypertrophy in
response, causing blurry vision (they're growing out into the
vitreous humor). These proliferative vessels are also
susceptible to bursting.
 Look for inflammatory exudates (white) and microhemorrhage
(red).
 Nephropathy (diabetes in the leading cause of renal failure and
dialysis):
 BM thickening, mesangial expansions, glomerular fibrosis.
 Note the GFR stays normal for a long time-- so the marker you
want to look for is protein, particularly albumin.
 Microalbuminemia (need a special test, can't see on a dipstick)
is the best way to detect diabetic nephropathy at a preventable
stage.
 Once they get past a certain point of albuminemia, the
nephropathy is inevitable; however, glycemic control and ACE
inhibitors can slow progression.
 Neuropathies:
 Distal symmetrical polyneuropathy is most common.
"Stocking-glove neuropathy;" taller patients tend to be affected
before shorter patients (the price we pay for being able to
reach the top shelf).
Lose strength and feeling in feet and hands.
In the feet, in particular, you get ulcers that the patient
can't feel.
 Diabetes is the #1 cause of nontraumatic foot
amputations.
 Autonomic neuropathy: tend to bother patients most:
 Erectile dysfunction
 Gastroparesis (slowed gastric emptying, making it really
hard to control blood sugar)
 Cardiac (predicts cardiovascular disease)
 Also note that autonomic dysfunction can cause you to
not be able to feel the effects of hypoglycemia or
hyperglycemia-- thus masking symptoms and making it
hard to dose.
 "Weird" neuropathies:
 Mononeuritis multiplex: Single nerve injury, often
saphenous or femoral. Generally recovers with time. Can
also happen to cranial nerves; these also seem to
recover.
5. List treatment approaches that have been shown to be useful in preventing
complications from diabetes.
 Retinopathy is preventable if it's caught early, by laser treatment.
Glycemic control also prevents progression of retinopathy.
 Aggressive blood sugar control is always a good idea.


Overview of Lipid Biochemistry
Monday, November 10, 2008
10:05 AM
Overview of Lipid Biochemistry, 11/10/08:
1. Identify the structures of fatty acids, phospholipids, cholesterol and cholesterol
esters.


Note that the "Steroid," above, is the structure of cholesterol.
Cholesterol esters: hydroxyl group down at lower left corner of the
molecule above is replaced with an ester bond to a fatty acid.
 Note that most phospholipids, like triacylglycerols, also begin with a
glycerol backbone. Unlike triacylglycerols, however, they usually have
a phosphorylated, charged group taking up one of the glycerol carbons
instead of a fatty acid.
 Why this is important: the point of most phospholipids is to
make up cell membrane bilayers. As such they need one end to
be hydrophobic (face the aqueous environment either outside
or inside the cell) and the other end to be hydrophobic (face
the inside of the lipid bilayer).
 Sphingolipids: a slightly different class of phospholipids. We'll discuss
them later (in "Complex Lipids").
2. Describe the chemical properties of each of these lipids.
 Polarity (note the polarity determines the main location they're found):
 Free fatty acids (attached to plasma proteins) (most polar)
 Phospholipids (in membrane)
 Cholesterol (in membrane)
 Cholesterol esters and triglycerides (sequestered) (least polar)
3. Describe the sources of lipids, the uses of these lipids, and the relative amounts of
stored lipids in adipose tissue, skeletal muscle and liver.
 Can't say he goes into it in his notes. I'm going to go out on a limb
and say there's more fat in adipose tissue than the liver and more in
the liver than the muscle.
 Note that you use lipids for cell membranes and signaling molecules
and all kinds of keen stuff, and not just fuel.
4. Describe in general the “outline” of the following pathways: lipogenesis, betaoxidation, ketogenesis, the lipoprotein pathways, cholesterol synthesis, and
phospholipid synthesis.
 Lipogenesis:






In the mitochondria, acetyl CoA turns into citrate, which leaves
the mitochondria and is promptly reconverted into acetyl CoA in
the cytoplasm. Cytoplasmic acetyl CoA is transformed into
malonyl CoA by acetyl CoA carboxylase. Fatty acid
synthase then hooks malonyl CoA molecules together into
fatty acid chains to form palmitate.
Beta-oxidation:
 Mainly takes place in muscle and liver (recall fatty acids are the
main source of energy for those two tissues in a prolonged
fasting state).
 Hormone-sensitive lipase catalyzes the breakdown of
triglyceride stores in adipocytes to fatty acids and glycerol.
These are released into the blood. The fatty acids are taken up
by liver cells and have a CoA tagged onto them, becoming fatty
acyl CoA. This is converted to acyl-carnitine by carnitine
acyltransferase, then taken into the mitochondria. There
they're converted back to fatty acyl CoA and broken down by a
four-enzyme process two carbons at a time, generating acetyl
CoA. This acetyl CoA (in the mitochondria) can enter the TCA
cycle, or when levels of insulin are very low or counterregulatory hormone levels are very high it can go into
ketogenesis, or it can also be made into cholesterol.
Ketogenesis:
 As mentioned, acetyl CoA can go into an alternative pathway if
insulin levels are extremely low (or counter-regulatory
hormones are very high, as epinephrine during exercise).
 Acetyl CoA becomes a ketone body by passing through an
HMG CoA intermediate in a reaction catalyzed by
hydroxymethylglutaryl CoA synthase, better known as
HMG CoA synthase (NOT the same as HMG COA reductase,
the target of statins). This is the main regulated step of ketone
body synthesis.
 Main ketone bodies: 3-hydroxy-butyrate, acetoacetate.
 Recall that ketone bodies are the main fuel for the brain during
prolonged fasting or starvation states.
Cholesterol synthesis:
 Also assembled from acetyl CoA. The rate-limiting step is
catalyzed by HMG CoA reductase (note error in notes, where
this is labeled as "synthase" on p. 19). Intermediates:
mevalonic acid is a precursor to geranyl pyrophosphate and
farnesyl pyrophosphate, which in turn are precursors to
cholesterol.
Phospholipid synthesis:
 Hard to say from his notes, they're pretty vague. Suffice to say
you assemble a fatty acid chain, stick it onto a backbone of
some description, and modify it further to form whatever it is
you're forming.
 He makes note of arachidonic acid being a derivative of this
pathway (recall that prostaglandins and leukotrienes are
derived from it, the former through cyclooxygenase 1 and 2).
 Way more detail on this in "Complex Lipids."
Lipoprotein pathways:

Lipoproteins are particles (made up of apolipoproteins and
lipids) that transport lipids through the blood. Their targeting is
largely determined by the apolipoproteins that are stuck onto
their surface:
 Chylomicron pathway: transport of recently ingested fat
from the GI tract to the liver and other tissues.
 VLDL pathway: transport of stored fat from the liver to
other tissues.
 HDL pathway: reverse cholesterol transport (from other
tissues to liver).
Biosynthesis of Fatty Acids
Monday, November 10, 2008
10:53 AM
Biosynthesis of Fatty Acids, 11/10/08:
Note he's already filled out all his LOs in his first handout. What follows is just my
notes on the matter- for more complete details check out what he's got there.
1. Know the difference between a saturated and unsaturated fatty acid.
 Saturated fatty acids: contain no double bonds.
 Unsaturated fatty acids: contain double bonds.
 Note distinction between cis and trans double bonds-- cis bonds
make a bend in the fatty acid (steric interference), trans don't.
 Generally more double bonds in fatty acids cause a lowering of
the melting point of that fatty acid.
 Note also that a decreasing number of carbons in the
hydrocarbon chain of a fatty acid also decreases the melting
point.
 Another way of talking about degrees of saturation is how many
hydrogen atoms a fatty acid has (more double bonds, less hydrogen
atoms, less saturation).
[Note the precursor of arachadonic acid, linoleic acid, and the precursor of certain
omega-3 fatty acids, linolenic acid, can't be synthesized; they have to be ingested,
and are thus called essential fatty acids. For a bit more on why this is, see the end
of the lecture notes.]
 ["omega" is the end of the fatty acid away from the acid end (at the
end of the hydrocarbon). "Omega-3" refers to having a double bond
three carbons away from that end.]
[Good nuggets of info re fatty acid synthesis:]
 Takes place in the liver, in the cytosol.
 All carbon atoms in fatty acids come from mitochondrial acetyl CoA.
 This acetyl CoA is shuttled out of the mitochondria through a citrate
intermediate.
 Carboxylation of acetyl CoA (to form malonyl CoA) is the rate-limiting
step in lipogenesis.
2. Describe how and why fatty acid synthesis is favored when energy sources are in
excess.
 Increased acetyl CoA, NADPH, and pyruvate levels in a cell leads to
lipogenesis.

How: high pyruvate and acetyl CoA cause citrate to exit the
mitochondria and enter the cytosol. Citrate triggers the ratelimiting step in de novo lipogenesis (activation of acetyl CoA
carboxylase). NADPH is necessary for the lipogenesis (as
below).
 Why: more or less what you'd expect; increased substrates
lead to increased rate of reaction (Le Chatelier rocks!).
3. Describe the three phases of fatty acid synthesis and know the substrates for fatty
acid synthesis.
 (1) Transport of mitochondrial acetyl CoA into the cytosol:
 As mentioned, in the TCA cycle, mitochondrial acetyl CoA +
oxaloacetate --> citrate. Instead of rearranging citrate to
isocitrate (the next step in the TCA cycle), it can be transported
out into the cytosol, where it's re-cleaved into acetyl CoA and
oxaloacetate again.
 (2) Conversion of acetyl CoA to malonyl CoA:
 Cytosolic acetyl CoA is carboxylated to malonyl CoA by acetyl
CoA carboxylase (uses biotin as coenzyme).
 Handy tip for boards: carboxylation reactions tend to
use biotin, which carries a spare CO2 group. The other
important one is pyruvate carboxylase (forms OAA in
gluconeogenesis).
 (3) Malonyl CoA is added to a growing fatty acid chain by fatty acid
synthase to make palmitate.
 So that's reasonably important: de novo lipogenesis always
ends in palmitate (16-carbon, saturated fatty acid).
 After its synthesis, it can undergo elongation, desaturation, etc
to make other fatty acids.
 There's a four-step cyclic reaction catalyzed by fatty acid
synthase, each cycle of which adds two carbons onto the fatty
acid chain. This is where NADPH is necessary.
 It looks a little like the ribosome complex, actually. You
have one site on fatty acid synthase that holds the
elongating chain, and another that holds the incoming
malonyl CoA molecules, clips off the added malonyl
carbon and the CoA, and shoves the acetyl group onto
the chain.
 4 steps: essentially you condense (link the two groups)
to form a ketone, then reduce the carbonyl to a
hydroxide group, then convert it into a carbon-carbon
double bond instead, then reduce the double bond to a
single bond. More details in the notes if you want them.
According to Lippincott, 4 NADPH are necessary for each
cycle.
 Note that these 4 steps are reversed in betaoxidation, so it's probably worth paying at least
passing attention to them.
 Note that since palmitate is a sixteen-carbon chain, you need 8
malonyl CoA units (each of which contributes 2 carbons to the
growing structure) to construct it.
4. Describe the mechanisms of action of four regulators of fatty acid synthesis.

(1) Citrate: determines the amount of acetyl CoA available in the
cytosol for fatty acid synthesis; helps produce NADPH; activates acetyl
CoA carboxylase (by polymerization).
 (2) Palmitoyl CoA: acts as an inhibitor (negative feedback) of acetyl
CoA carboxylase (by depolymerization).
 (3) Malonyl CoA: inhibits carnitine acyltransferase (the RLS for the
beta-oxidation pathway). This seems to have a fair amount of
emphasis placed on it.
 (4) Insulin/Glucagon:
 Insulin: indirectly promotes fatty acid synthesis by increasing
glucose breakdown and increasing pyruvate levels.
 Glucagon: directly phosphorylates (remember, glucagon
phosphorylates things) acetyl CoA carboxylase, inactivating it.
 [Most important point for regulation of lipogenesis: acetyl CoA
carboxylase. Can be polymerized (activated), depolymerized
(deactivated), or phosphorylated (deactivated).]
5. Describe the special pathways and enzymes required for the synthesis of longer
chain and unsaturated fatty acids from the short chain, saturated products of fatty
acid synthase.
 Elongation: occurs in the mitochondria and ER. In mitochondria:
involves reversing the beta-oxidation pathway (requires NADPH).
Catalyzed by fatty acid elongases.
 Desaturation: takes place in the ER. Catalyzed by cytochome b5,
NADH-cyt b5 reductase, and desaturase.
 Note that mammalian cells can't unsaturate fatty acids at
particular carbons positions (9, 12)-- thus unsaturated fatty
acids with those unsaturation points need to be ingested (eg.
linoleic, linolenic) and are therefore called "essential" fatty
acids.
Fatty Acid Oxidation
Tuesday, November 11, 2008
7:57 AM
Fatty Acid Oxidation, 11/11/08:
[Why it's called beta-oxidation: recall that the carboxy carbon at the acidic end of a
fatty acid (the one that attaches to CoA) is called the alpha carbon and the one at
the other end is called the beta carbon. Beta-oxidation cleaves off two carbons (ie.,
after the beta carbon) at the alpha end of the fatty acid to form acetyl CoA and a
shorter fatty acid with a new alpha position.]
1. Explain why fatty acids are a major/preferred fuel source for liver, heart and
muscle (but not the brain) at all times, and the major energy source for all tissues
under starvation conditions.
 Recall that the body is very concerned with keeping the tissues that
can only metabolize glucose supplied. In high-glucose conditions, it's
not a problem. Fatty acids, as we've been taught it, are mainly used in
fasting or starvation conditions by the muscle and liver in order to
preserve the glucose in the blood for RBCs and the brain. What he's
getting after with "the major energy source for all tissues," I think, is
that during starvation conditions, fatty acid breakdown provides direct
energy for the liver and muscle through beta-oxidation and indirect
energy to the brain due to the fact that it's broken down to ketone
bodies (which, recall, the brain can use during starvation).
2. List the steps of the cycle that converts fatty acids to acetyl CoA.
 Fatty acid to acetyl CoA: effectively a reverse of the four steps of fatty
acid synthase described last lecture. Notice, though, that whereas it
takes only a single enzyme in the cytosol to synthesize fatty acids
(fatty acid synthase), it takes four component enzymes in the
mitochondria to break them down.
 (1) You make the single carbon-carbon bond into a double bond
(dehydrogenate).
 (2) You hydrate the double bond into a hydroxyl group (on the gamma
carbon).
 (3) You dehydrogenate the hydroxyl group into a carbonyl (thus
making a ketone).
 (4) You cleave the ketone to result in an acetyl CoA group and a
shorter fatty acid (which you immediately attach CoA to).
 Note you get 1 NADH and 1 FADH2 from each round of beta-oxidation,
above and beyond the acetyl CoA that can enter the TCA cycle.
 Enzymes used:
 (1) Acyl CoA dehydrogenase: located in the mitochondrial
matrix;
 Note that there are a variety of kinds of this enzyme;
some break down medium-chain, some short, some
long, etc. Note infants need the medium-chain kind to
break down fatty acids in mothers' milk (which is rich in
medium-chain fatty acids).
 (2) Enoyl CoA Hydratase
 (3) Beta-Hydroxy-CoA Dehydrogenase
 (4) Thiolase (cleavage; important since it can be reversed to
form four-carbon acetoacetyl CoA ketones from two acetyl CoA
molecules in ketone body synthesis)
3. Recognize critical intermediates in the beta-oxidation pathway and describe the
properties of the enzymes and co-factors involved in this pathway.
 Enzymes: See above.
 General schema: Fatty acid is released from triacylglycerols in adipose
tissue by hormone-sensitive lipase; the fatty acid gets a CoA attached
to it in the cell; the fatty acyl CoA is transported into the mitochondria
by carnitine acyltransferase (temporarily converts the fatty acyl
CoA into carnitine CoA) in a process known as the carnitine shuttle.
It's then oxidized, two carbons at a time, to form mitochondrial acetyl
CoA.
 The carnitine step is quite important, both here and for boards;
it's the rate-limiting step. Without it there is no beta-oxidation
of long-chain fatty acids.
 Recall that malonyl CoA inhibits carnitine
acyltransferase.
 [Note that short- and medium-chain fatty acids don't
need carnitine acyltransferase to enter the mitochondria
(Lippincott p. 192); they can still be beta-oxidized in the
absence of carnitine acyltransferase or the presence of
large amounts of malonyl CoA.]
 Note that there's an obvious problem here: what if you have a fatty
acid with an odd number of carbons? The answer is that you leave the
last 3 carbons all together (propionoyl CoA). This molecule has a
couple of interesting ramifications:
 Propionoyl CoA gets carboxylated to methylmalonyl CoA.
 Methylmalonyl CoA gets rearranged to succinyl CoA.
 **Boards-important** This reaction requires vitamin
B12. Recall from Blood and Lymph that one of the only
tests that accurately distinguishes folate deficiency from
B12 deficiency is methylmalonyl levels; they should be
high in B12 deficiency, because this step (conversion to
succinyl CoA) can't go forward.
 Succinyl CoA can either be used in the TCA cycle for oxidation,
or it can be used in gluconeogenesis.
 **Also boards-important** This is the other exception
to the fact that triacylglycerols (fat) can't be used to
make glucose (the first was the glycerol backbone). If
the fatty acid chain is odd-numbered, the last, threecarbon breakdown product can be converted to succinyl
CoA (and from there converted to oxaloacetate) and
enter the gluconeogenic pathway.
 Note another obvious problem: what if you've got double bonds in the
fatty acids? Not a lot of emphasis placed on it here, but the point is
that there's an isomerase and a reductase to shuffle them around.
Recall that beta-oxidation involves forming double bonds anyway, so
you can incorporate them into the cleavage process.
 Note you can also have alpha oxidation: not nearly as important, but
its absence can cause disease, so basically the deal is that certain fatty
acids (mainly phytanic acid, from plant sources) need to have one
carbon taken off the alpha end. After it's done, the rest is oxidized
through the beta pathway. The associated deficiency disease is called
Refsum's Disease (see below).
 Note finally you can also have fatty acids that are so long they can't be
broken down by normal mechanisms (very-long-chain fatty acids);
these go into peroxisomes to be pared back to where they can get
hooked up to carnitine acyltransferase and taken to the mitochondria
for beta-oxidation.
 Diseases associated with oxidation enzyme deficiencies:
 Medium-chain acyl CoA dehydrogenase deficiency: may result
in sudden infant death syndrome due to inability to break down
fatty acids in mothers' milk.
 Refsum disease: defect in alpha oxidation of branched fatty
acids, which (since they can't be broken down) accumulate in
the liver and kidney.
 Zellweger's syndrome: usually fatal before age 2; defect in
peroxisomal function (thus a problem with metabolizing verylong-chain fatty acids).
4. Explain how fatty acid breakdown and synthesis are coordinately regulated, and
connected to carbohydrate metabolism.
 This step, thankfully, we've already seen most of.

Beta-oxidation is mostly regulated at the level of carnitine
acyltransferase I.
 Recall, again, that malonyl CoA inhibits carnitine
acyltransferase.
 Again, you have the glucagon-phosphorylation, insulindephosphorylation dance with acetyl CoA carboxylase and hormonesensitive lipase.
 Glucagon phosphorylates hormone-sensitive lipase and acetyl
CoA carboxylase (activating lipase, deactivating acetyl CoA
carboxylase).
 Insulin dephosphorylates the same enzymes (inactivating
lipase, activating acetyl CoA carboxylase).
5. Outline the enzymatic steps of ketone body synthesis and breakdown.
 3 ketone bodies:
 Acetoacetate
 Beta-hydroxybutyrate
 Acetone (less produced, but responsible for the "fruity" odor
on breaths of people with diabetic ketoacidosis)
 Recall that ketone bodies are generally only produced under conditions
of very low insulin or very high counter-regulatory hormone levels.
High levels of acetyl CoA/NADH and low pyruvate levels (which
indicates low glucose levels, if you think about it) also help ketone
body synthesis.
 Generally occurs in prolonged starvation, an excessively lowcarbohydrate diet, or uncorrected type I diabetes.
 As mentioned, ketone bodies (other than acetone) are acidic.
Look for an increased anion gap metabolic acidosis.
 Big picture: the acetyl CoA molecules from fatty acid synthesis (which,
recall, can't be used to make glucose) are combined into (mainly)
four-carbon ketones by reversing the last step of beta-oxidation.
 Enzymes:
 Thiolase (same as in beta-oxidation) combines two molecules
of acetyl CoA to form acetoacetyl CoA (a ketone).
 HMG CoA synthase: condenses another molecule of acetyl
CoA into the compound to form HMG CoA.
 HMG CoA lyase: takes an acetyl-CoA group off to leave
acetoacetate.
 [Acetoacetate can interconvert with beta-hydroxybutyrate and
acetone, mainly the former.]
 For those of you who are rereading the above and going "why do you
add an acetyl CoA and then take it off again?", I have no idea.
[Note he's got a good summary slide in the last bits of this lecture's Powerpoint
containing comparisons between fatty acid oxidation and synthesis: location
(mitochondria vs. cytosol), enzymes (4 different enzymes vs. just fatty acid
synthase), redox cofactors (FADH2 and NADH vs. NADPH), site (muscle and liver vs.
just liver), activator (free fatty acids vs. citrate), inhibitor (malonyl CoA vs. fatty acyl
CoA), carrier between cytosol and mitochondria (carnitine vs. citrate). Check it out.
Lippincott has a similar table on p. 194 (16.19).]
Dietary Fats
Tuesday, November 11, 2008
9:02 AM
Dietary Fats, 11/11/08:
1. Describe the fat content of the average American diet in % carbohydrate, grams
of carbohydrate and calories per day.
 For our hypothetical 70-kilo, weight-balanced American, we're going to
say 30 kcal/kg per day total energy expenditure = 2100 kcal per
day energy intake.
 Recall that there are 9 kcal/gram of energy in fat, as opposed to 4
kcal/gram of energy in carbs and proteins. FYI, alcohol is 7
kcal/gram.
 Average American diet is about, say, 35% fat (half of which is
saturated). About 15% of it is protein, mainly from animals, and about
50% is carbohydrates, largely from simple sugars.
 Simplifying the fat portion of the diet to 33%, 1/3 of 2100 kcal is 700
kcal. Divided by 9 (9 kcal per gram of fat) gives about 77.8 grams of
fat per day.
2. Describe the physical property that allows a person to distinguish saturated and
trans-fats from un-saturated fats.
 Melting point-- but more to the point, crystallization. High melting
point fats (saturated and trans-unsaturated fats) are solid at room
temperature. Low melting point fats (cis-unsaturated) aren't.
Something to think about: the reason solid fats are solid at RT is that
they're able to be really tightly packed together (largely linear). They
can also be tightly packed together in your arteries. Enjoy your burger.
3. List the foods that contain high levels of saturated fat, monounsaturated fat,
omega-3 fat, omega-6 fat, polyunsaturated fat, and trans-fat.
 [Worth pointing out: omega 3 double bonds are between the 3 and 4
carbons (not the 2 and the 3) from the omega end of the fatty acid.
Similarly, omega 6 double bonds are between the 6 and the 7
carbons.]
 (note that these aren't all-or-nothing categories: the "saturated fats"
category is fats whose fatty acid chains are mainly saturated.)
 Saturated fats: butter, lard, manteca (which last I checked is Spanish
for lard), and red-meat fat.
 Monounsaturated fats: olive oil, canola oil.
 Polyunsaturated fats: fish oil, soybean oil, corn oil, cottonseed oil.
 Omega-3 fats: flaxseed oil, salmon oil.
 Note that omega-3s are regularly prescribed for cardiovascular
conditions in parts of Europe.
 Omega-6 fats: corn oil, vegetable oil. Note that these are often
considered deleterious, but evidence is mixed.
 Trans-fats: big one in the US is partially hydrogenated soybean or
vegetable oil.
4. Describe the mechanisms that underlie the relationships between a high fat diet
and adverse health consequences including atherosclerosis and obesity.
 Atherosclerosis: polyunsaturated fat is better than monounsaturated
fat, saturated fat is much worse than both-- shown in primates and
mice. Lots of evidence that polyunsaturated and monounsaturated fats
are better than saturated in humans as well (raise HDL cholesterol,
lower triglycerides and total cholesterol.

Note also that high-saturated fat diets have been linked to insulin
resistance in mice (the cis-unsaturated fats protect against it),
partially because it causes obesity and partially because it's saturated
fat (don't see as much resistance with fish oils, etc).
5. List the components of a healthy diet as relates to dietary fat.
 Restrict saturated and trans fat to less than 10% of total intake (and,
really, try and cut out all the trans fat, it's bad for you). Total fat
content varies but current guidelines go between 25% and 35%. Fish
should be consumed twice a week (go to H-Mart on 2751 S. Parker
Road for great fresh fish at low prices). Cholesterol intake should not
go above 300 mg/day.
 The gold standard, which here seems sort of arbitrary, is a lower-fat,
modest caloric restriction.
 Overall: restrict total energy intake. Dr. Bessesen: your total intake is
probably the most important factor here. The type of nutrient
composition that allows adherence to the restricted intake is,
therefore, often more important than the specifics of the nutrients.
[Note, as a sideline, that alcohol metabolism produces NADH; it interferes with
gluconeogenesis and promotes ketone body formation (see Lippincott, p. 317)]
Complex Lipids
Wednesday, November 12, 2008
7:44 AM
Complex Lipids, 11/12/08:
[This lecture is a patented PhD "you tried to do WHAT in a hour?" mess. Best
attempt at organization follows.]
[Note that although "phospholipid" as a category seems to include both
glycerophospholipids and sphingolipids, it's sometimes used here interchangeably
with "glycerophospholipid," probably because they're much more common. Keep this
in mind as you read the LOs below.]
1. Recognize the categories of phospholipids, including the ether linked lipids, and
the sphingolipids.
 So the big question in dividing up phospholipids is: what's the
backbone made of?
 If it's glycerol: it's a glycerophospholipid. These were
mentioned before; they have a phosphate group at the end
carbon of the glycerol, off which a "head group" is generally
attached.
 If it's sphingosine: it's a sphingolipid. Sphingosine is a big,
complex molecule that looks a little like an unsaturated fatty
acid with an amino group stuck on (which is, in fact, how
they're made). Note that the fatty acid linked to sphingosine in
sphingolipids is attached by an amide, not an ester, bond.
Their "head group" is also attached to the bottom carbon of
their backbone, but doesn't always have a phosphate group
involved.

Note that glycerophospholipids can have two fatty acids
attached to them; sphingolipids only have room for one
(although there's another fatty acid built into their backbone
structure).
 Most of the time the fatty acids in phospholipids are linked to the
backbone by an ester bond (O=C-O). In certain cases, as in plateletactivating factor, they're linked by an ether bond instead.
 Reiterate: sphingolipids' fatty acids = amide links;
phospholipids' fatty acids = ester or ether links.
2. Describe the special properties and functions of these classes of lipids.
 How these are categorized: all of these have more or less the same
backbone and fatty acids, so the thing that differentiates one
phospholipid from another is the "head group" (the group attached on
the other side of the phosphate).
 Phosphatidylcholines:
 Glycerophospholipid with a choline (hydrocarbon chain with an
amino group at one end and an alcohol at the other) head
group. Together with phosphatidylethanolamine, the most
abundant phospholipids in eukaryotic cell membranes.
 Used in RBC membranes.
 Found in myelin.
 Major constituent of lung surfactant.
 Phosphatidylglycerol:
 Has a glycerol (C3(OH)3) head group.
 Used in mitochondrial membranes.
 Precursor of cardiolipin, which can be cross-reacted to by
certain antibodies.
 Also important in lung surfactant.
 Phosphatidylinositol:
 Has an inositol head group (cyclohexane-like structure).
 Reservoir of arachidonic acid.
 Used in signal transduction and anchoring membrane proteins.
 Note that phosphatidylinositol can be multiply phosphorylated
to form PIP3 (phosphoinositol triphosphate), which - recall - is
important in lots of signaling, including the insulin receptor
pathway.
 Sphingomyelin:
 As mentioned, used extensively in myelin.
 Also makes up a great deal of the membranes of gray matter
in the brain.
 Also makes up a large component of RBC plasma membranes.
 Glycolipids:
 This seems to be the category that includes most of the
sphingolipids mentioned below.
 Have a mono/oligosaccharide head group.
 Located in nerve tissue and plasma membranes.
 Include the blood group antigens (ABO).
3. Outline the two pathways for phospholipids synthesis.
 General idea of phospholipid synthesis:
 (1) Make a glycerol backbone and activate it with a phosphate
group.
 (2) Attach fatty acid through either ester or amide linkages.

(3) Add a head group to the phosphate group through a
phosphodiester linkage.
 (4) Alter/exchange head group.
 The good stuff comes in step 3, since steps 1 and 2 are pretty similar
for most phospholipids.
 Generally you derive glycerol 3-phosphate from either glucolytic
intermediates (in all cells) or triacylglyceride breakdown (in the liver);
after that, you transfer fatty acids onto the two remaining carbon
residues on glycerol.
 The resultant molecule (glycerol with two fatty acids and a phosphate
group) is called phosphatidic acid and is the precursor molecule for
the more complex phospholipids that follow.
 This seems to be the rub: you have a head group (choline, inositol,
etc) and a phosphatidic acid (diacylglycerol 3-phosphate, as just
mentioned) molecule. You want to put them together. You can activate
either the head group (as in PC and PE synthesis) or the remaining
carbon on the diacylglycerol (as in PI and PG/cardiolipin synthesis) by
adding a CDP group (like UDP activation of glucose 1-phophate in
glycerol synthesis). Whichever group isn't activated has an alcohol
moiety on it. The two come together, the CDP group takes off, and
love shall rule the stars. There's a diagram on p. 10 of his learning
objective notes if you want the (fairly sparse) details.
 Note that more or less all cells except mature RBCs can synthesize
glycerophospholipids.
4. Describe the special case for synthesis/salvage of phosphatidyl choline.
 Humans are fairly poor at synthesizing phosphatidylcholine; they
require three methyl transfers to make it from
phosphatidylethanolamine. Without methyltransferases they're kind of
hosed in the phosphatidylcholine department, which is unfortunate
since it's one of the main constituents of plasma membranes.
 Note that the "base exchange pathway" (which seemed totally
frivolous to me but extremely interesting to him) mediates the
swap of ethanolamine with serine to make phosphatidylserine-therefore you can also synthesize phosphatidylcholine from
phosphatidylserine with a phosphatidylethanolamine
intermediate if you want. Diagram for phosphatidylcholine
synthesis is in Lippincott, p. 204 if you're interested.
 Note also that dietary choline can be phosphorylated, activated by
CDP, and stuck back onto diacylglycerol instead of having to go
through the tortuous synthesis pathway de novo.
5. Outline sphingolipid biosynthesis and list the properties of the different classes of
sphingolipids.
 Sphingolipids that come in through the diet are generally degraded;
thus endogenous sphingolipids are generally synthesized de novo.
 How this happens: a serine amino acid and palmitoyl (fatty acid) CoA
condense to form the sphingosine backbone. A fatty acid is attached,
then a head group. The head group, as with glycerophospholipids,
determines what flavor of sphingolipid it is.
 From his lecture: "Be able to recognize a sphingolipid." Essentially look
for the backbone molecules, then look for the head group on the
bottom carbon.
 Types:

Ceramide: mediator of stress response. Head group = OH
(technically the head group is a hydrogen atom, but since it's
stuck onto an open oxygen atom, effectively it's a hydroxyl
group). Serves as the precursor for most other
sphingolipids (can swap out the -OH for other junk).
 Sphingomyelin: already mentioned; has a phosphate-choline
linkage for a head group. In RBCs and the myelin sheath.
 Cerebrosides: have simple sugars (glucose/galactose) as a
head group.
 Sulfatides: have a sulfate ester linkage as a head group.
 Globosides: have more complex sugar linkages. These are
involved in the ABO cell surface signaling system.
 Gangliosides: have the most complex sugars. Note these are
the receptors that cholera and diphtheria toxins attach to.
6. Explain how defects in metabolism of the sphingolipids result in devastating
genetic diseases.
 Sphingolipids are degraded in the lysosomes.
 Defects in the breakdown of the various classes of sphingolipids result
in the various lysosomal storage diseases-- the degradation always
starts with the head group components, so each type of sphingolipids
has its characteristic enzyme that begins its degradation process.
Deficiencies in these enzymes result in specific diseases-- Lippincott p.
212 has a graph of the relevant points.
 Failure to break down gangliosides: Tay-Sachs.
 Failure to break down glucocerebrosides: Gaucher disease.
 Failure to break down globosides: Fabry disease.
 Failure to break down sphingomyelin: Niemann-Pick disease.
 Etc.
[Bessesen's take: recognize basic structure of phospholipid backbones, then head
groups. Don't worry too much about pathways; don't worry too much about specific
lysosomal storage diseases yet (we'll study it next week). Know the functions of
various phospholipids. Also know key intermediates: phosphatidic acid in
glycerophospholipids, ceramide in sphingolipids.]
Cholesterol Synthesis and Utilization
Wednesday, November 12, 2008
8:57 AM
Cholesterol Synthesis and Utilization, 11/12/08:
[Note cholesterol is necessary for bile acid and steroid synthesis.]
1. Outline the steps in the synthesis of cholesterol from acetyl CoA.
 This occurs in the cytoplasm.
 (1) Mevalonate synthesis from 3 acetyl CoA (similar to ketone body
formation, goes through HMG CoA but requires HMG CoA reductase,
which is the rate-limiting step).
 (2) Conversion of mevalonate to two activated isoprenes. Recall that
"activated" tends to refer to the attachment of charged groups; here
it's talking about phosphates.

(3) Condensation of six activated isoprenes to squalene. This is where
those geranyl pyrophosphate and farnesyl pyrophosphate
intermediates show up (partially condensed isoprenes).
 (4) Ring closure of squalene.
 Probably the most important thing to remember here is that the
mevalonate synthesis from HMG CoA is the rate-limiting part of all this
and subject to considerable regulation (see below).
 [Cholesterol is generally made in the liver, but can also be made in the
adrenal cortex, the ovaries, and the testes in order to be converted to
hormones.]
2. Compare and contrast ketone body synthesis to cholesterol synthesis.
 Ketone body synthesis: takes place in mitochondria. Cholesterol
synthesis: takes place in cytosol.
 In ketone body synthesis, HMG CoA synthase is the rate-limiting step.
In cholesterol synthesis, HMG CoA reductase is the rate-limiting step.
 In ketone body synthesis, HMG CoA is transformed into ketone bodies.
In cholesterol synthesis, HMG CoA is transformed into mevalonate.
3. Describe the regulation of cholesterol synthesis (HMG CoA reductase, LDL
receptor, SREBP).
 Expression of the HMG CoA reductase gene is controlled by a particular
transcription factor (SREBP). Low levels of cholesterol activate more
transcription of that gene; high levels turn it off.
 High levels of cholesterol destabilize HMG CoA reductase mRNA
transcript stability; they also degrade the HMG CoA reductase protein
itself.
 As mentioned, statins block the HMG CoA reductase receptor.
 HMG CoA reductase can also be directly phosphorylated to inactivate it
(again, glucagon phosphorylates and therefore inactivates it; insulin
does more or less the inverse).
 It's a little unclear in his notes, but it also seems that LDL cholesterol
receptors (promoting cellular uptake of cholesterol from circulating
LDL) are inactivated by high intracellular cholesterol levels.
4. Trace the pathways from cholesterol to the different classes of sterols including
the bile acids and the steroid hormones.
 Cholesterol + cholesterol 7-alpha-hydroxylase --> bile acid (cholic
acid), which can be modified further to form other bile acids.. I think.
 Bile acids are linked to either glycine or taurine to form bile
salts before they're released from the liver into the biliary tree.
 Cholesterol forms pregnenolone, the precursor for all other steroids
(can be converted into progesterone, which is the basis for
synthesizing cortisol, testosterone, aldosterone, and estradiol). Note
that this requires CYP450 enzymes.
 Lippincott: figures 18.9 and 18.10 for bile acid/salt synthesis, 18.24
for steroids.
 Note that activated isoprene intermediates can be used to anchor
proteins to plasma membranes.
 Note you form vitamin D from cholesterol in the skin.
5. Identify the key enzyme in bile acid metabolism and describe the role of bile acids
and cholesterol in gall stone formation.
 Recall that cholesterol is a component of bile (which is more or less
the only mechanism we have for excreting cholesterol), along with bile
acids/salts. In order to keep this solution fluid, the cholesterol to bile
acid ratio needs to be below a certain level (otherwise the cholesterol


will precipitate out). In normal bile, the ratio hovers fairly close to that
level; with a relatively small additional amount of cholesterol in the
bile, it will precipitate and begin to form gallstones.
Key enzyme in bile acid metabolism: cholesterol 7-alphahydroxylase. This is the rate-limiting step of the synthesis of bile
acids from cholesterol.
Obviously one way of having less bile acid and more cholesterol is to
screw up the enzyme that makes bile acid from cholesterol.
Eating Disorders
Wednesday, November 12, 2008
10:11 AM
Eating Disorders, 11/12/08:
[Another eager lecturer who goes off his meds when he's matching lecture to plan.
What follows is what he talked about and what's in his notes, but its link to the LOs
is tenuous.]
1. Identify the clinical features, evaluation, and treatment of patients with eating
disorders.
 Anorexia nervosa:
 Clinical features: low body weight, intense fear of gaining
weight, distorted body image, extreme focus on shape and
weight, denial of seriousness of illness, amenorrhea, age of
onset generally in the teens.
 Physical exam features:
 Bradycardia, hypotension, cold intolerance (starvation
symptoms)
 Amenorrhea
 Osteoporosis
 Lanugo (extremely fine hair on body)
 Carotenemia (orange or yellow-colored skin)
 Can get "refeeding syndrome" when food is given:
this involves a too-sudden shift from fat-based to carbbased metabolism, causing hypophosphoremia and
liver problems.
 Bulimia nervosa:
 Clinical features: recurrent binge-eating, then laxative abuse,
vomiting, excessive exercise, and/or fasting. Tend to feel out of
control. Again, an extreme focus on body shape and image.
 Physical exam features:
 Loss of dental enamel
 Russel's sign (scarring on the knuckles or the back of
the hand due to contact with the incisors during
induction of vomiting)
 Parotid enlargement, or "chipmunk cheeks" due to
swelling after repeated vomiting.
 Subconjunctival hemorrhages (vomiting increases
intraocular pressure)
 Esophagitis and Mallory-Weiss tears
Arrhythmias
Can get toxicity from agents used to induce vomiting
(such as ipecac, which can produce dilated
cardiomyopathy and renal failure).
 Note that there's significant overlap between the two-- about half of
diagnosed anorexics will go into bulimia inside a couple of years.
2. Discuss the etiologic hypotheses, clinical features, epidemiology, course, comorbid disorders, complications (including re-feeding syndrome), and treatment for
anorexia nervosa.
 Largely mentioned above. Note anorexia nervosa has the highest
mortality of any psychiatric disorder.
 Etiology: genetic, environmental, temperamental (see below). Early
onset puberty, perfectionist environment or personality, tend to have
low self-esteem and are wary of new things (as opposed to bulimics,
who tend to be impulsive and pursue new things).
3. Discuss the role of the primary care physician in the prevention and early
identification of eating disorders.
 This is about what you'd expect. Look out for it, be understanding,
don't be a jerk.
 His axe to grind: not disorders of choice; can't blame family, patient,
or society. Here, evidently it's a genetic thing.
 My take: this is a classic example of someone who feels he has
to reverse current thinking and in the process overstates his
case in the opposite direction. Taking the individual, the family,
and society out of it is absurd. I think his actual point is that
there is a "substantial" genetic component to eating disorders,
which seems reasonably well supported.
4. Discuss the medical complications and indications for hospitalization in patients
with eating disorders.
 Again, largely discussed above. His notes have little to say about
hospitalization other than you can do intensive outpatient visits (3
nights per week for 4 hours), partial hospitalization programs (every
day for 11 hours) or complete inpatient hospitalization.


Lipoprotein Physiology
Thursday, November 13, 2008
7:57 AM
Lipoprotein Physiology, 11/13/08:
[This is kind of long and involved, but the basic principles are fairly straightforward.
Dr. Bessesen's notes are good reading and may be a better place to look than mine.]
1. List the relative polarities of cholesterol ester, triglyceride, unesterified cholesterol
and phospholipids
 Triglycerides and cholesterol esters: most nonpolar
 Cholesterol: middle of the road
 Phospholipids (and free fatty acids): most polar
2. Describe the characteristics of the 5 classes of lipoproteins.
 Lipo: contains fat. Protein: contains apolipoproteins.

Recall that the lipoproteins have a certain density of
cholesterol/cholesterol ester, on top of which is a variable amount of
triglycerides.
 Recall also, in all this discussion about density, that the more
triglycerides a particle has, the less dense it is.
 (1) Chylomicrons: made in GI tract and filled with intaken dietary
fats; go to liver and other tissues to offload the triglycerides. Large,
have way more triglycerides than cholesterol (10:1 ratio). After a
meal, the triglyceride levels in your blood go up due to these guys.
 Chylomicron apolipoproteins: apo B48, apo C-2, apo E.
 (2) Very Low Density Lipoproteins: made by liver and filled with
triglycerides to be taken to the peripheral tissues. Still pretty big, have
more triglycerides than cholesterol (5:1 ratio). These are primarily
made between meals, although some is also made after meals.
 VLDL apolipoproteins: apo B100, apo C-2, apo E.
 (3) Intermediate Density Lipoproteins or Remnant particles: the
byproducts of chylomicrons after they've offloaded a lot of their
triglycerides. Since they've gotten rid of so much triglyceride, they
have about equal amounts of triglyceride and cholesterol (1:1 ratio).
They are atherogenic. Note that "intermediate" here sort of refers to
"intermediate between very low and low," not "intermediate between
low and high."
 IDL apolipoproteins: apo E, apo B48 (sort of varies-- see next
point)
 [Note about IDLs: according to Dr. Bessesen, chylomicrons are
metabolized down to remnant particles, while VLDLs are metabolized
down to LDL (see next point) instead. Although remnant particles and
VLDLs on their way to becoming LDLs both have an 'intermediate'
density, they're tagged differently - VLDLs have apo B100 and no apo
E, chylomicrons have apo B48 and apo E - in an attempt by the body
to keep tabs on where circulating fat is coming from by what kinds of
apolipoprotein markers are on it.]
 [Note about the note: according to Dr. Bessesen, this is not,
technically, 100% true-- VLDL does actually seem to have apo
E (First Aid backs this up). But it's good enough for the test as
far as how each particle is absorbed by the liver (see notes
below on reuptake ligand function of apolipoproteins).]
 (4) Low Density Lipoproteins: byproducts produced by the
offloading of triglycerides from VLDL. They've offloaded tons of
triglycerides, and consequently they have a low amount of triglyceride
relative to cholesterol (maybe 1:4 ratio). Quite atherogenic.
 LDL lipoproteins: apo B100.
 (5) High Density Lipoproteins: Almost all cholesterol, but they're
not related to chylomicrons/VLDL like IDL and LDL are. These are
particles that are made to collect cholesterol from other tissues and
return it to the liver. They also exchange lipids and apolipoproteins
with other lipoproteins. They are atheroprotective.
 HDL apolipoproteins: apo A1.
 Note that the relative size of these particles is directly related to the
amount of triglycerides stored in them.
3. Describe the fate of these lipoproteins in the Chylomicron, VLDL and HDL
pathways.
 Chylomicrons:





After triacylglycerols have been resynthesized in the
enterocytes, they're packaged into an apo B48 protein shell and
released into the lacteals (recall that most ingested fat goes
into the lymphatic system first) and then the bloodstream.
In the circulation, they pick up apo C-2 and apo E
apolipoproteins from HDL particles.
When they get to their target tissues, lipoprotein lipase (LPL)
attaches to the apo C-2 protein and starts to suck out
triglycerides (LPL-apo C-2 is like a straw with which the tissue
sucks out the fatty goodness).
After they've been largely evacuated, chylomicrons continue to
circulate as remnant particles (see below).
VLDL:
 Triacylglycerides are packaged into apo B100 and released into
the circulation. Like chylomicrons, they pick up apo C-2 and
apo E from HDL.
 When they get to their tissues, again, apo C-2 binds to LPL to
offload triglycerides.
 Again, after being mostly emptied of triglycerides, VLDL
continues as either a remnant particle or a LDL particle.
[Note that the liver has receptors to pick up LDL and remnant particles back out of
the circulation-- for LDL it uses the apo B100 protein as a ligand, for remnant
particles it uses apo E as a ligand. This allows the liver to recycle cholesterol. In the
statin pathway, for example, since we're inhibiting the de novo synthesis of
cholesterol in the liver, the hepatocytes upregulate their expression of apo B100
receptors, to pull more LDL particles from the blood to replenish their cholesterol
pool (to make bile, etc)-- thus decreasing circulating LDL cholesterol.]
 HDL:
 "Reverse cholesterol transport:" synthesized by the liver and GI
tract from apo A1 proteins. When it's synthesized, it doesn't
have any lipids in it-- it picks those up from other tissues.
 It circulates and picks up cholesterol from tissues through the
"ABC-A1 cassette" (which I don't know what is but sounds
80's).
 Without ABC-A1, you get Tangier's Disease: you get
abnormally high levels of cholesterol accumulation in
tissues (classically, you look down their throat and see
orange tonsils).
 Something that's reasonably important: HDL converts
cholesterol to cholesterol esters, locking it into the HDL for
transport to the liver. Enzyme that does this: lecithin
cholesterol acyl-transferase (LCAT).
 Note HDL can also transport cholesterol esters to VLDLs in
exchange for triglycerides if there's too much triglyceride in the
blood (catalyzed by cholesterol ester transfer protein, CETP).
This is one reason why we care about hypertriglyceridemia:
HDL doesn't function as well to pick up cholesterol (it's
offloading cholesterol in exchange for triglcyerides) under those
conditions. Also HDL levels tend to be lower in these patients
because HDL is getting filled and used up and returned to the
liver faster.
4. List the functions of apo-lipoproteins and give examples of each.

(1) Structural backbone: they're just proteins that solubilize lipids. Apo
B100 is just the full-length version of apo B48. They're structural
proteins that bind to lipids. Apo A1 is another example.
 (2) Enzymatic cofactors: apo C-2 co-catalyzes transfer of triglycerides
into cells along with LPL.
 (3) Receptor ligands: apo E and apo B100 bind to reuptake receptors
on hepatocytes.
5. Describe the functions of CETP, ABCa1 and LCAT.
 CETP: catalyzes transfer of cholesterol esters to VLDL from HDL in
exchange for triglycerides. This is, generally, bad.
 ABC-A1: catalyzes transfer of cholesterol to HDL from tissues. This is,
generally, good.
 LCAT: catalyzes esterification of cholesterol inside HDL. This is,
generally, neutral-borderline-good.
 Note all three of these are involved in the HDL pathway but have
varying degrees of virtue.
Dyslipidemias
Thursday, November 13, 2008
9:02 AM
Dyslipidemias, 11/13/08:
1. Describe the Friedwald equation for estimating LDL cholesterol levels and the
limitations of this equation.
 Total (fasting) cholesterol = HDL + LDL + VLDL.
 Friedwald: LDL cholesterol = total cholesterol - HDL (triglycerides/5).
 If triglycerides are greater than 400, this doesn't work (generally
indicates either hypertriglyceridemia or, more likely, that they snuck a
Twinkie).
[Correlations of heart disease with types of blood-borne lipids:]
o LDL: pretty good correlation, less is better (epidemiology, biological
plausibility, clinical trials).
o Triglycerides: some correlation, less is better (epidemiology, not a lot
of biological plausibility, mixed evidence in clinical trials).
o HDL: some correlation, more is better (epidemiology, some biological
plausibility, mixed evidence in clinical trials).
2. List the cardiovascular risk factors used in the NCEP ATPIII risk stratification
scheme and describe the point cutoffs.
 Risk factors:
 Age (men 45 years and up, women 55 years and up)
 Family history: CHD in male first-degree relative before age
55, or in female first-degree relative before age 65.
 Cigarette smoking (current)
 HTN : blood pressure > 140/90 or on antihypertensive meds
 Low HDL (< 40 mg/dL)
 Note that high HDL (> 60) is a 'negative' risk factor
(removes a risk factor)
3. List the LDL cholesterol targets for each risk category.
 With 0-1 risk factors: LDL target is less than 160 mg/dL.

With 2+ risk factors: assess risk of CHD in next 10 years:
 Less than 10% risk in 10 years: LDL target is less than 130
mg/dL.
 10-20% risk in 10 years: LDL target is less than 130 or 100
mg/dL.
 Greater than 20% risk in 10 years: LDL target is less than 100
or 70 mg/dL.
 (Second number is the "therapeutic option.")
 (Given their track record with "optimal," I'd be careful
with the exact wording of "therapeutic" here.)
4. List the "non-HDL" cholesterol targets for each risk category and describe why
they are important.
 LDL is your primary target. But triglycerides are kind of important too.
I know, it's not exactly a strong stance. We seem to be kind of
confused about this.
 If high triglycerides (> 200) persist after treating LDL, you can set a
"non-HDL" goal of 30 mg/dL higher than the LDL goal.
 Watch out for diabetic women with high triglyceride levels
(dramatically increases CHD risk).
5. List the secondary causes of dyslipidemia and how they are screened for in clinical
practice.
 In clinic, don't forget to look for underlying causes of dyslipidemia:
kidney and liver dysfunction, diabetes, hypothyroidism, obesity,
genetic deficiencies, etc. There's a slide (slide 6) with the complete
list.
 How they're screened for: TSH, creatinine, LFTs, fasting glucose,
complete H+P.
 [Genetic deficiencies:]
 Familial hypercholesterolemia: deficiency in LDL receptors
on hepatocytes. Homozygotes are worse than heterozygotes.
Get atherosclerosis very early.
 "Familial combined hyperlipidemia:" high triglycerides, high
LDL, or both. Much more common. Which type of lipid seems to
vary both between related individuals and in the same
individual over time. Associated with increased apo B protein
production and coronary artery disease.
 Broad beta disease: high triglycerides, high LDL. Lots of
remnant/IDLs. Due to apo E deficiency.
 Hypertriglyceridemia: apo C-2 deficiency or LPL deficiency.
Can't offload triglycerides into tissues.
 Tangier's disease: mentioned in the last lecture (mutation of
ABC-A1, can't pick up cholesterol from tissues by HDL).
6. Describe the physical findings associated with Familial Hypercholesterolemia,
severe hypertriglyceridemia, broad beta disease, and Tangiers disease.
 Hypercholesterolemia:
 Arcus senilis: lipid deposits in the cornea.
 Xantholasmas: lipid deposits in the skin of the eyelid.
 Hypertriglyceridemia:
 Eruptive xanthomas: small, yellow-red pimple-like rash on
arms and legs, generally pop up after a fat-heavy meal or after
heavy drinking.
 Familial hypercholesterolemia:



Tendinous xanthomas: buildup of fat in tendons. Pathognomic
for familial hypercholesterolemia.
Broad-beta disease:
 Palmar xanthoma: xanthomas on palms, no kidding.
Pathognomic for broad-beta disease (abnormal apo E).
Tangier's:
 Orange tonsils: pathognomic for Tangier's Disease (or drinking
lots of Tang).
Treatment of Dyslipidemias
Thursday, November 13, 2008
9:59 AM
Treatment of Dyslipidemias, 11/13/08:
[Drug summary:]
 For lowering LDL:
 Statins
 Ezetimibe
 Resins
 Sterol/sterol esters
 Niacin (nicotinic acid)
 For lowering triglycerides:
 Fibrates (two flavors: gemfibrozil, fenofibrate)
 Fish oils
 Niacin
 Statins
 For elevating HDL:
 Fibrates
 Niacin
 Statins
1. Know the general clinical evidence behind each lipid lowering therapy.
 Statin evidence:
 Good for primary prevention of CAD in high-risk patients,
particularly with diabetes
 Good for secondary prevention in the general population
 Probably good for primary prevention in moderate and low risk
patients, may also be good for peripheral vascular disease.
 Plant sterols/stanols: not much clinical evidence but seem to be very
safe and mildly effective.
 Ezetimibe: definitely lowers LDL, both by itself and with statins, but it's
been shown that there's no difference between statins alone and
statins + ezetimibe in terms of atherosclerotic plaque. It is particularly
indicated with a rare cholesterol-like absorptive disease.
 Bile acid resins: probably beneficial vs CAD in moderate risk patients.
 Fibrates: definitely effective vs CAD.
 Fish oils: unclear benefit vs. CAD.
 Niacin: unknown benefit vs CAD; maybe some decrease in MIs; longterm benefits?
2. Understand the mechanism of action of the statins, ezetimibe, resins, and
sterol/stanol esters.
 Statin MoA: inhibit HMG-CoA reductase; this causes upregulation of
LDL reuptake receptors on the hepatocytes, reducing circulating LDL.
 Note that you get most of the LDL-lowering action with the first
dose; doubling the dose gives diminishing returns.
 Ezetimibe MoA: inhibits uptake of cholesterol from the gut lumen.
 Resins: bind to bile acids in the intestine and prevent their reuptake.
 Sterol/stanol esters: prevent micelle formation in the intestine.
 [FYI: Fibrates work mainly through PPAR alpha induction and altered
gene expression (including increased apo A1 transcription); also seem
to promote increased LPL activity.]
3. Describe the primary drug class to treat elevated LDL-cholesterol and elevated
triglycerides. Know the options for secondary drugs for these conditions.
 First-line for elevated LDL: statins.
 Second-line for elevated LDL: resins, ezetimibe.
 First-line for elevated triglycerides: fibrates. Change diet first if the
triglycerides are really high (> 1000).
 Second-line for elevated triglycerides: niacin.
 Note the goal in very high triglyceride level patients is to prevent acute
pancreatitis.
Note that in this case you seem to want to lower triglycerides before lowering
LDL.
4. Know the adverse effects and contra-indications of the statins, fibrates, and
nicotinic acid.
 Statin adverse effects: generally well-tolerated, but include
hepatotoxicity (rare, dose-dependent, monitor ALT) and myopathy
(non-dose-dependent; boards likes myopathy). Myopathy increases
with fibrates or niacin (which also cause myopathy).
 Side effects get worse with drug interactions, hepatic or renal
dysfunction, serious infection, hypothyroidism.
 All statins are contraindicated in pregnant women.
 Fibrate adverse effects: rash, elevated LFTs, myopathy (fenofibrate);
myopathy, GI distress, and cholelithiasis (gemfibrozil).
 Gemfibrozil is contraindicated in renal and liver disease,
fenofibrate is contraindicated only in liver disease.
 Other problem with fibrates is that they can raise LDL.
 Niacin adverse effects: many: flushing, rash, peptic ulcers and GI
distress, hepatotoxicity, myopathy, gout (increased uric acid). Usually
lessen with time; prescribe with aspirin or NSAID to lessen flushing.
The number and severity of the side effects are the primary reason we
don't use it more (though it seems to do all the things we want: raise
HDL, lower triglycerides and LDL). In diabetics it can screw with
glucose control and worsen acanthosis nigricans.
 Contraindications: liver disease, gout, peptic ulcer disease,
some with diabetes mellitus, as mentioned.
[I suddenly want to hear "Nights in White Statin" on the radio-- maybe a ballad of a
month spent in an Alabama BBQ roadhouse.]
Nutritional Counseling
Monday, November 17, 2008
7:24 AM
Nutritional Counseling, 11/17/08:
[Note that there's a few days here I stopped attending lecture until I ran into purine
metabolism like a brick wall; these notes are therefore from the handouts and the
Powerpoints.]
[I should also note that I don't take this topic with any degree of reverence
whatsoever. Yes, it's important. No, I don't have to catch my breath and cry a little
inside.]
[Look, you want this boiled down? Be a decent goob. Listen more than you talk. Be
reasonable. Care about your patients and make sure that comes through to them.
Understand that their frame of mind is more important than your ego. Once you get
that, you can do all the things below without coming off like a total jackass
manipulative prick. Before that, for the love of God, don't bother.]
1. List the “stages of change” and typical responses that a patient might make in a
clinical interview that help you establish their stage.
 Ah, back to Communications:
 Precontemplative ("I have no problem. Who am I? How did I
get here?")
 Contemplative ("Yeah, I have a problem, but I can't change
it.")
 Planning ("I was thinking of solving my problem with X.")
 Action ("I'm doing X to solve my problem.")
 Maintenance ("I've been doing X to solve my problem for Y
years.")
 Relapse ("I tried X and it didn't work. Plus ca change, plus c'est
la meme chose. Oh, the humanity.")
 Identification ("I have become one with X. Here, have a
pamphlet.")
2. List the most important topic of discussion for a counseling session with a patient
at each stage of change.
 Precontemplative: show a compelling need: "Allow me - while fully
respecting our shared and common humanity - to point out that your
heart might be a teensy bit better if you stopped drinking the lard
straight from the can."
 Contemplative: assist in selecting an approach: "While fully respecting
our shared and common humanity, should you decide of your own free
volition to try and cut your BMI to below 50, I would be honored to
help select a bariatric surgeon."
 Planning: encourage and troubleshoot: "I think, in light of my respect
for our shared and common humanity, that you're doing a fantastic job
thinking about this. However, I think perhaps it would be even more
effective if your plan didn't involve cutting the lard with partially
hydrogenated soybean oil and engine grease."

Action: encourage and point towards the future: "I just got a text
message from our shared and common humanity. It says great job,
and soon you won't have to buy two seats on airlines anymore."
 Relapse: encourage and point to past success: "Remember when you
could see your feet? You really liked that! Common and shared
humanity."
 Identification: roll around in bliss: "This is the dawning of the Age of
Aquarius! Get away from me with that pamphlet."
3. Describe the use of the “10 point scale” in motivational interviewing.
 The 10 point scale is, effectively, a trick. What you want to do, when
the patient inevitably says they're somewhere in the middle, is say,
"well, you're not a 1, so clearly you see there's a problem with your
diet." Then you say, "but you're also not a 9 or a 10, so how can I get
you there?" Then the sky rains puppies with wings.
 Other tricks: get people to take small steps to build up their
confidence. Again, do this with the 10-point scale ("on a scale of 1 to
10, how confident are you that you can move from one side of the
Barcalounger to the other tomorrow?").
 The important thing, evidently, is to get them to the 7 or higher range,
because apparently that's when statistics show people may actually do
something about it.
4. Describe the meaning of “alternative futures”, “rolling with resistance”, “pros and
cons” and “highlighting discrepancies.”
 Alternative futures: attempting to get patients to construct several
possible futures, one with the change you want and one without, and
get them to come face to face with the consequences of their actions
("I see a future in which I accidentally roll over onto my dog and he's
not found in my skin folds for weeks").
 Rolling with resistance: when someone threatens to bash your head in
if you mention their Cheetos addiction again, don't push it.
 Highlighting discrepancies: expose your patients' cognitive dissonances
to them ("I think we should all look like Brad Pitt and Angelina Jolie"
and "Could you pass the second can of lard?"). Crush their feeble
minds!
 Pros and cons: most people (not, of course, godlike physicians such as
ourselves) see the pros in doing what they're already doing and the
cons in not doing what they're not already doing. So you can point out
the cons of their current behavior and the pros of an alternative in
addition to those. It's described in the notes as a 2x2 table, like a
lifestyle modification game of four-square.
5. Describe 2 important steps in “Values based counseling.”
 1. Explore with your patients what their core values are.
 2. Tie health related behaviors to those core values.
 [3. Feel bad about yourself late at night because you're a manipulative
sod.]
 [4. Rob banks.]
Overview of Protein Biochemistry
Monday, November 17, 2008
7:54 AM
Overview of Protein Biochemistry, 11/17/08:
1. List a number of different ways to categorize amino acids.
 (1) They're often grouped based on the chemical properties of their
side chains:
 Acidic vs. basic
 Polar vs. non-polar
 (2) They can also be grouped based on our ability to synthesize them:
 Essential: we can't synthesize them at all and have to ingest
them.
 Non-essential: we can synthesize enough to fully supply our
need.
 Conditionally essential: we can synthesize them, but the
amount we synthesize sometimes isn't enough to supply our
need for them-- so if we're burning them fast, we can't
replenish our supply unless we ingest them.
 (3) Also on structural properties and various contained molecules or
atoms:
 Sulfur (or, to cite our second lecturer today, "sulfer")containing
 Nitrogen
 Branched-chain
 Aromatics
 (4) They can be grouped according to which carbon skeletons they're
broken down into:
 Glucogenic: can be used as substrates for gluconeogenesis.
 Ketogenic: broken down to acetyl CoA (can't be used for
gluconeogenesis)
 [Note you also have amino acids that are post-translationally modified.
We'll get to that in the next lecture.]
2. Describe how proteins are broken down to amino acids in the gut and in tissues.
 Recall that there are two classes of peptidases, endopeptidases and
exopeptidases. The former cleave inside the amino acid chain,
generally between particular types of residues, while the latter cleave
on the ends of the chain.
 Recall the peptidases we've discussed so far:
 Pepsin (endopeptidase from stomach)
 Trypsin (endopeptidase from pancreas, in duodenum)
 Chymotrypsin, elastase, etc (other endopeptidases from
pancreas)
 Carboxypeptidase (exopeptidase, from pancreas)
 Aminopeptidase (exopeptidase, in brush border of small
intestine)
 So much for the gut. Inside cells there are a couple of different routes
for protein breakdown that we haven't looked much at since Molecules
to Medicine:
 Ubiquination (attach ubiquitin molecules to a protein, target it
for degradation in the proteosome)
 Lysosomal degradation
 [More on these in the next lecture.]
3. Describe the flow of nitrogen from an amino acid to urea.
 [Overview:]


It would be a exaggeration to say that protein metabolism more
or less consists of "show me the nitrogen," but not by much.
Tracking the nitrogen - like following which cup has the peanut
under it - is going to take up much of our time in the following
few days.
 So, since nitrogen atoms don't generally hang out by
themselves, what we're going to care about is amine groups.
 Lest we've forgotten: amine group: -NH2.
 Amine groups are often shuttled about with, unsurprisingly,
aminotransferases. In amino catabolism (breakdown), the
point of this is to get the amine group off the amino acid so
that the remaining skeleton can be used for gluconeogenesis or
energy. In amino anabolism (synthesis), the point of this is to
stick the amine group onto a carbon skeleton so you can make
amino acids to make proteins.
 So where does the amine group go once you've taken it off?
The eventual target of amino acid catabolism is urea, which is
our bodies' way of getting ammonia (unattached amino group,
NH3, toxic) into a padded cell until we can urinate it out. What
urea looks like: (NH2)2-C=O. Sort of like carbon dioxide if you
took off an oxygen atom and stuck on these crazy amine wings.
[Answer to LO:]
 An amine group is taken off the amino acid by an
aminotransferase and put onto alpha-ketoglutarate (same one
from the TCA cycle). This produces glutamate (carrying the
amine group) and an alpha keto acid (the original amino acid
sans amine).
 The amine group can then be taken off glutamate (regenerating
the alpha-ketoglutarate) as free ammonia and put into the
urea cycle.
 The ammonia is converted to carbamoyl phosphate. This is
the rate-limiting step in the urea cycle and is catalyzed by
carbamoyl phosphate synthase I.
 Recall that urea has two, not one, amine groups. Where does
the other one come from? It comes from aspartate, a NH3containing amino acid that also enters the urea cycle. Aspartate
is a four-carbon structure that shows up in the cycle long
enough to ditch its amine group and then leaves as fumarate
(see below).
 Now you have two amine groups circulating in the urea cycle,
and as luck would have it they're on the same carbon. At this
point, that carbon is hydrolyzed off to ditch urea and
regenerate your starting products.
 Note that this process starts in the mitochondria and goes out
into the cytosol. Probably the important things to remember are
that ammonia comes into the cycle in the mitochondria,
aspartate comes in in the cytosol, and both urea and fumarate
leave in the cytosol.
 [Couple things:]
 You remember how the TCA cycle was basically an
exercise in getting rid of two carbons (per acetyl CoA)
and generating energy? The urea cycle is basically an
exercise in picking up two amine groups, tying them to a
carbon atom, and throwing them out.
 Note, however, that whereas only one thing goes into
the TCA cycle (acetyl CoA), two things go into the urea
cycle (carbamoyl and aspartate). Note also that whereas
in the TCA cycle the only byproducts of the cycle were
more or less small intermediates (NADH, FADH2, CO2),
the urea cycle actually generates a larger molecule
(fumarate).
 Fumarate is converted to malate (TCA cycle, again)
which can do a number of things. It can stay in the
cytosol and become converted into oxaloacetate to go
into gluconeogenesis (next step: PEP-carboxykinase). It
can also go into the mitochondria to become a substrate
in the TCA cycle.
4. List some of the special issues associated with sulfer containing, gluconeogenic,
ketogenic, branched chain and aromatic amino acids.
 Again with the "sulfer." Maybe it's some kind of code word.
 Sulfur-containing amino acids: cysteine and methionine. Why
they're important:
 (1) Cysteine (but not methionine) forms disulfide bridges to
stabilize tertiary protein structure.
 (2) Methionine is important because the single most important
methyl donor in the body is S-adenosylmethionine (SAM;
methionine with an adenosyl group stuck on). More on this two
lectures down ("Sulfur Amino Acid Metabolism"), but how it
works involves B12, folate, THF, and homocysteine.
 (3) Cysteine is important because it's what makes glutathione
work as an antioxidant. Remember how we discussed one of
the consequences of not having enough NADPH as an inability
to regenerate glutathione, leading to hemolytic anemia?
 Gluconeogenic/ketogenic amino acids: as mentioned, some skeletons
form acetyl CoA (can't be used to make glucose) and some are more
extensive and can be used for glucose. Specifics are in the next
lecture.
 Branched-chain amino acids (leucine, isoleucine, valine): an inability to
break down these compounds leads to a condition called maple syrup
urine disease (really).
 Aromatic amino acids (tryptophan, tyrosine, phenylalanine): the ring
structures on these are used as precursors to make niacin,
adrenergic neurotransmitters, thyroid hormone, and
tetrahydrobiopterin (required for lots of stuff, see following
lectures).
Amino Acid Metabolism
Monday, November 17, 2008
8:40 AM
Amino Acid Metabolism, 11/17/08:
[Ok. As you probably know all the LOs for some of the following lectures were all
changed Friday at noon. The new LOs will be at the top of these notes; the old LOs
will be at the bottom.]
1. Describe the unique feature of hydroxylysine and hydroxyproline and the cofactor
that is important in their synthesis.
 Unique feature: hydroxylation and presence in collagen to promote
tighter binding.
 Cofactor important: vitamin C.
2. List the names of the proteases that are present in the GI tract and describe the
mechanisms by which they are activated.
 Important here:
 Pepsin: activated by low pH in the stomach.
 Enterokinase: not sure if it's activated or not, but it's secreted
by enterocytes.
 Trypsin: activated by enterokinase and other activated trypsin.
 Chymotrypsin: activated by trypsin.
 Elastase: activated by trypsin.
3. Briefly describe the 2 pathways for intracellular protein degradation.
 Proteosome: proteins are ubiquinated and pulled into the proteosome
to be cut apart. Requires ATP.
 Lysosome: mainly extracellular proteins are phagocytosed, then
transported to the lysosome and degraded by the proteases therein.
4. Describe the following aspects of transamination reactions
 The general nature of the precursors and products
 Precursors: one amino acid and one alpha-keto acid. Products:
the amino acid becomes an alpha-keto acid and the alpha-keto
acid becomes an amino acid.
 The specific precursors and products for alanine aminotransferase and
aspartate aminotransferase
 ALT: alpha-ketoglutarate plus alanine --> glutamate plus
pyruvate
 AST: alpha-ketoglutarate plus aspartate --> glutamate plus
OAA
 The cofactor that is involved in these reactions
 PLP, a derivative of vitamin B6
 What regulates the directionality of a transamination reaction.
 Mainly, the concentrations of products and reactants.
----old LOs---1. Know the names, three-letter abbreviations and chemical types of the amino acids
in proteins. (Note: You are not required to know the structure of any molecules).
 Here we go:
 Glucogenic:
Alanine (Ala)
Arginine (Arg)
Asparagine (Asn)
Aspartate (Asp)
Cysteine (Cys)
Glutamate (Glu)
Glutamine (Gln)
Glycine (Gly)
Histidine (His)
Proline (Pro)
Serine (Ser)
Methionine (Met)
Threonine (Thr)
Valine (Val)
 Ketogenic:
Leucine (Leu)
Lysine (Lys)
 Both:
Tyrosine (Tyr)
Isoleucine (Iso)
Phenylalanine (Phe)
Tryptophan (Trp)
 Thoughts and suggestions:
 The only three-letter abbreviations that are hard to remember
are the -ate vs -ine ones. The ones with '-ine' always have a
"n" in the three-letter code.
 Remember that most of them are glucogenic.
 Remember that the only ones that aren't are the ones that
begin with "L."
 Remember that the ones that can do both are mainly the
aromatics (tryptophan, tyrosine, and phenylalanine).
2. List the amino acids that are not derived from dietary protein, but rather are
synthesized by post-translational modification of proteins.
 Well, there are evidently about 300 of them. The most important ones
in this discussion are regular ol' proline and lysine residues that have a
hydroxyl group on them: hydroxyproline (Hyp) and hydroxylysine
(Hyl).
 Why they're important:
 Remember that collagen has lots of proline and a fair number of
lysine residues.
 Remember also that it has a characteristic 'triple helix'
conformation that's really tight and strong.
 How it gets tight and strong: after it's synthesized, the proline
and lysine residues are hydroxylated (forming Hyp and Hyl).
 Hydroxyproline allows hydrogen bond formation
between the chains.
 The lysine residues on one chain covalently bond with
the hydroxylysine residues on another.
 This would be a good point for a test question: "<blank>
forms covalent chains between collagen strands in the
triple helix" or "<blank> forms hydrogen bonds between
collagen strands in the triple helix."
 Enzymes that catalyze hydroxylation of proline and lysine: prolyl
hydroxylase and lysyl hydroxylase respectively.
 Important clinical thing here: both of these enzymes require
vitamin C (ascorbate) as a coenzyme.
 A lack of vitamin C leads to a lack of tight collagen, which leads
to scurvy (bleeding gums, easy bruising, anemia) due to
defects in the collagenous vascular endothelium.

2 other post-translationally modified AAs:
 Gamma-carboxyglutamate (or Gla), which is part of
prothrombin: note that the carboxylation reaction depends on
vitamin K.
 Ornithine: as we've seen, is a part of the urea cycle.
3. Know the substrate specificities of pepsin, trypsin, chymotrypsin,
carboxypeptidase A and carboxypeptidase B. Describe how the body is able to obtain
essential amino acids during fasting.
 Wow. This is astoundingly unimportant in the grand scheme of things.
Knowing the trypsin residues might be helpful in a lab if you do a lot of
protein work.
 Pepsin: cleaves aromatics (Tyr, Trp, Phe) on the N-terminal side.
Activated by low pH levels in stomach. An aspartic protease (contains
an aspartate residue).
 Trypsin: cleaves basics (Arg, Lys) on the C-terminal side. Activated by
enterokinase. A serine protease.
 Chymotrypsin: cleaves aromatics and some hydrophobics (Tyr, Trp,
Phe, Leu, Met) on the C-terminal side. Activated by trypsin. A serine
protease.
 Carboxypeptidase A: cleaves C-terminal amino acids (any).
 Carboxypeptidase B: cleaves C-terminal basic amino acids.
 Fasting: Not sure. I would assume you break down existing protein to
get them.
4. Be able to discuss the process of transamination and protein degradation. What
are the control points for protein catabolism.
 Transamination:
 Before we get into this: an alpha-keto acid is, for the purposes
of the current discussion, an amino acid that's had the amine
group taken off (it's replaced by a ketone group and it still has
its carboxylic acid group, which is why it's called a keto acid).
Note pyruvate and oxaloacetate are both alpha-keto acids, not
to mention alpha-ketoglutarate.
 Aminotransferases, aka transaminases, transfer amine groups
off an amino acid onto an alpha-keto acid, creating another
amino acid (from the original alpha-keto acid) and another
alpha-keto acid (from the original amino acid).
 This is generally an easily reversible reaction, as you
might expect; the Keq is about equal to 1.
 There are lots of aminotransferases; each one is
generally specific for one or two amino acids.
 Point of this, germane to our discussion: you want to produce
glutamate (which, recall, will have its NH3 clipped off) and
aspartate to make the nitrogen-containing products that enter
the urea cycle.
 Most important transaminases: (we've seen these before)
 Alanine aminotransferase (ALT)
 Makes alanine (AA) and alpha-ketoglutarate
(alpha-KA) into pyruvate (new alpha-KA) and
glutamate (new AA).
 Aspartate aminotransferase (AST)
 Makes aspartate (AA) and alpha-ketoglutarate
(alpha-KA) into oxaloacetate (new alpha-KA) and
glutamate (new AA).
Remember that both of these are reversible.
Recall that increased ALT and AST levels often indicate
liver damage.
 Glutamate is therefore particularly important not only because
it donates the NH3 group for the urea cycle, but can be made
into aspartate to provide the other NH3 for the cycle (reverse
the AST reaction above to do this)-- glutamate is sort of the
original amine donor, times two, for the urea cycle.
 Say you've got some alanine, some alpha-ketoglutarate,
and some oxaloacetate kicking around (and in most cells
you'll probably have the last two, since they're part of
the TCA cycle). You make glutamate and pyruvate with
ALT, then take some of the glutamate and pick off the
ammonia while you combine the rest of the glutamate
with OAA to make aspartate and alpha-ketoglutarate.
You've just provided all the input you need to make the
urea cycle go round a turn (and you've regenerated
some of your alpha-ketoglutarate and made some
pyruvate while you're doing it).
 Necessary for transamination reactions: vitamin B6 derivative
called PLP (pyridoxal phosphate).
 Essentially it's bound to lysine residues on the
transaminase and holds the NH3 group during the
transfer.
Degradation:
 Recall there are two ways to go about this: ubiquination and
lysosomal degradation.
 Ubiquination: ubiquitin molecules are attached to the protein's
lysine residues. Once the protein has enough ubiquitins
attached, it's ferried to the proteosome for degradation.
 Note that the ubiquination/proteosomal mechanism
takes ATP.
 Lysosomes: recall from way back in M2M that when molecules
were phagocytosed (engulfed by the cell), the resultant vesicles
were eventually transferred to the lysosome. Extracellular
proteins that are engulfed are, therefore, generally degraded in
the lysosome.
 The lysosome is a membrane-bound organelle with a low
pH (4.5) and lots of digestive enzymes. Some of these
enzymes are proteases. He feels it necessary to specify
that they're aspartic proteases.




Control points for protein catabolism:
 (1) Different concentrations of substrate and product control
the direction of the aminotransferase reactions (remember that
they swing both ways).
 (2) To activate carbamoyl phosphate synthetase I (which,
recall, is the rate-limiting enzyme for the urea cycle), you need
N-acetylglutamate.
 (3) The plucking of NH3 off glutamate (by glutamate
dehydrogenase) also depends on relative concentrations of
substrate and products.


(4) Glutamate dehydrogenase's removal of NH3 from glutamate
is inhibited by high levels of ATP and GTP (high energy state)
and activated by high levels of ADP and GDP (low energy
state).
 Makes sense: in a high-energy state, don't break down
protein.
He seems to go over these a lot. Might be worth knowing.
Sulfur Amino Acid Metabolism
Monday, November 17, 2008
9:58 AM
Sulfur Amino Acid Metabolism, 11/17/08:
1. List the 2 important sulfur containing amino acids and why they are important.
 Cysteine: form disulfide bridges to promote protein structure, also a
key part of glutathione (see below).
 Methionine: used in methyl transfer reactions through SAM.
2. Describe the main function of SAM. List the targets of this process.
 Methylation reactions:
 Methylation of NE to EPI
 Methylation of cytosine residues in DNA
 Also important in cancer, host defense, depression, pregnant
women, etc.
3. List the key steps in the conversion of methionine to homocysteine and back to
methionine and the key co-factors involved in this process.
 Methionine is activated by the addition of adenosine (forming Sadenosyl methionine).
 Requires SAM synthetase.
 SAM donates a methyl group to the target, forming S-adenosyl
homocysteine.
 Requires methyltransferases.
 S-adenosyl homocysteine loses its adenosine group, forming
homocysteine.
 Requires adenosyl homocysteine hydrolase.
 Homocysteine is remethylated to form methionine.
 This last step requires methionine synthase and, more
important for the current discussion, N5-methyl-THF and
vitamin B12 (the methyl group is transferred from THF to B12
to homocysteine).
4. Discuss the role of glutathione as a reducing agent and “SH buffer”. List three
important functions of GSH.
 Glutathione: reduced form = GSH, oxidized dimer form = GSSG (see
below for structural notes).
 The "SH" is a thiol group (sulfur and hydrogen); it can give up its
hydrogen to form a disulfide bond with another molecule of GSH that's
given up its H as well. That hydrogen can go act as a reducing
(antioxidant) compound.
 Three functions:
 Redox buffer (keep proteins in the reduced state)
 Cofactor for several enzymes: glutathione transferase, GST

Antioxidant activity against hydrogen peroxide (reduces it to
water) and other reactive oxygen species.
 [Also important: in RBCs, it keeps iron in Fe2+ as opposed to
Fe3+, preventing methemoglobinemia, and protects the
membrane integrity.]
 [Also: GSSG (the oxidized, hydrogen-less dimer form) can
accept hydrogens from -SH groups in proteins to encourage
them to form disulfide bonds with each other and, hence, fold
properly; this also regenerates GSH.]
5. Name the compound from which tetrahydrofolate is derived and what is unique
about tetrahydrofolate as compared to SAM.
 Tetrahydrofolate is derived from, no kidding, folate (vitamin B9).
 THF can carry other types of single-carbon groups aside from just
methyl groups-- can carry methylene, formyl, formimino, etc groups.
 This is important in nucleic acid synthesis.
 [Note methotrexate, a cancer drug, targets the enzyme responsible for
generating THF from folate, dihydrofolate reductase.]
----old LOs:---


[Recall that methionine and cysteine are the two amino acids that contain
sulfur.]
[Note that cysteine didn't make the list of essential amino acids, while
methionine did. That's because cysteine can be made from methionine, but
not vice versa.]
[Note also that when cysteine is cross-linked to another cysteine by a
disulfide bond, it's called cystine. Who came up with that one?]
1. Discuss the role of SAM as a high energy compound. What is the meaning of the
term “active sulfate”.
 Recall that ATP has a "high-energy phosphate" attached to it, which is
attached at the expense of energy and which it can slough off in return
for some of that energy back again. It's a storage unit for energy.
 SAM (S-adenosylmethionine) is analogous; it's a storage unit for
methyl. Generally, if you recall from organic chemistry, methyl groups
aren't the easiest things in the world to move around. The one in SAM
is easy to move because it's attached to a sulfur atom that's attached
to an adenosine group; the sulfur atom is therefore "activated" (it's
carrying a positive charge and wants to ditch one of its bonds,
preferably the methyl-carrying one).
 Why you care: you can't methylate DNA or make epinephrine, among
other things, without SAM. So if you want to express every silenced
gene in your body and pick up abnormal metabolism, birth defects,
depression, and cancer, you go right ahead. I'll stay here with SAM.
 How you make SAM: you tack an adenosine group onto methionine.
 The SAM cycle:
 Start off with methionine.
 Add adenosine to activate the sulfur atom and make SAM.
 Donate the methyl group to make S-adenosylhomocysteine.
 Take off the adenosine group to make homocysteine.
 Remethylate homocysteine to make methionine again. Repeat.
Where the methyl group comes from to remethylate the
homocysteine: N5- methyl-tetrahydrofolate (see 2
LOs down).)
 What you need to do it: vitamin B12 and methionine
synthase.
 Again, because it's important: you need THF and B12 to
regeneration methionine from homocysteine.
[As an aside here: note that various B vitamins tend to serve roles as carriers for
particular groups. Biotin, as we discussed last week, tends to carry CO2. B12 carries
methyl groups. B6 carries NH3. I'm not sure yet but I'd guess that niacin and
riboflavin (part of NADH and FADH2 respectively) carry hydrogen atoms. Something
to keep an eye out for.]
 If you don't want to use homocysteine to regenerate methionine, you
can add a serine molecule to homocysteine to make cystathione and
from there you can split off succinyl CoA to make cysteine.
 From the notes: too much homocysteine is bad.
 Ways to get too much homocysteine:
 (1) Deficiency in the enzyme that fuses serine with
homocysteine (cystathionine beta synthase) (accumulation is
called homocystinuria). Cysteine becomes an essential amino
acid, since you can't make it. Leads to vascular disease, mental
retardation, osteoporosis. Treat with B6 to prompt more
cystathionine beta-synthase activity.
 (2) Defect in the cysteine reuptake transporter in the kidney
(also transports lysine and arginine), resulting in cysteine
stones (condition is called cystinuria).
 Note you treat cysteine stones by alkalizing the urine,
usually with acetazolamide (blocks carbonic anhydrase,
inhibits HCO3- reuptake from the tubule lumen).
 Note, vis-a-vis boards, that alkalizing the urine
makes struvite stones worse. So make sure what
kind it is.
 (3) Low levels of folate, B6, and B12: you can't regenerate
methionine from homocysteine and you can't make cysteine
from it either. Leads to vascular disease (condition is called
hyperhomocysteinemia). Cysteine becomes an essential amino
acid; treat with the missing vitamins.
2. Discuss the role of glutathione as a reducing agent and “SH buffer”. What are
three important functions of GSH?
 Glutathione: a three-amino-acid peptide: glutamate-cysteineglycine. Why it's called GSH in its reduced form: it's glutathione (G)
with a thiol group on it (-SH).
 GSH, when oxidized, can form dimers through a disulfide bond
between cysteine residues. This is called GSSG (glutathione, G, with a
sulfur atom, S, attached to another sulfur atom, S, that's attached to
another glutathione, G).
 Notice that the thiol group in each GSH is losing a hydrogen atom in
this process. That's where the antioxidant properties come into it.
 How that hydrogen atom is used:
 (1st important function) Reduce (add H to) free radicals and
H2O2 to neutralize them.
 (2nd important function) Maintain proteins in a reduced form.
 (GSH is a cofactor for various reactions.)







3. Be able to









GSSG is also useful in proper protein folding in the endoplasmic
reticulum-- you want all those thiol (-SH) groups in proteins to lose
their hydrogens and form disulfide bonds to fold right. GSSG is a great
acceptor of those hydrogens to make it happen.
Glutathione is found all over the place, in high concentrations-- it's
very soluble and very useful to cells.
How you make GSH: add cysteine to glutamate, then add glycine. Not
rocket science. Takes ATP.
Important enzymes related to glutathione:
 Glutathione reductase: reduces 1 molecule of GSSG to 2
molecules of GSH. Requires NADPH as a cofactor (which is why
G6-PD deficiency is bad for GSH).
 Glutathione peroxidase: oxidizes 2 molecules of GSH to 1
molecule of GSSG to neutralize hydrogen peroxide to water.
Deficiency leads to increased breast cancer risk.
 Glutathione S-transferase: conjugates GSH to other agents
in order to detoxify them. This is upregulated in tumors and is
the basis for some forms of their drug resistance.
(3rd important function) GSH is, as alluded to several times, extremely
important to red blood cells, for several reasons. One, as mentioned,
has to do with membrane stability and free radicals. Another has to do
with methemoglobin (when the iron in the heme is oxidized to the
Fe3+ state); GSH + Fe3+ --> GSSG + Fe2+. Recall that
methemoglobin can't bind oxygen, so keeping heme in the right
oxidation state is pretty important.
In passing, recall that GSH isn't the only antioxidant out there. See
also superoxide dismutase and catalase for a couple other good ones.
understand and discuss 1-carbon transfer at all oxidation levels.
When they say "1-carbon transfer," what they usually mean is "methyl
transfer;" carbons don't travel alone (they bring their three-hydrogen
entourage). Occasionally the carbon has some other funky group on it.
So we already discussed methyl transfer from S-adenosylmethionine.
The other biggie in methyl donation is tetrahydrofolate (THF).
As the name implies, it's a derivative of folate (vitamin B9); note that
it can transfer not only methyl but a couple other weird methyl-related
groups (CH=NH, CH=O).
It's essential for making amino acids and nucleic acids (see 3 lectures
down); thus it's a common target for chemo drugs where you want to
target rapidly dividing cells that are making a lot of DNA.
How you make THF: take folate, reduce it to dihydrofolate, reduce it
again to tetrahydrofolate. Tetrahydrofolate is just folate with two of
the nitrogen-carbon double bonds replaced with four hydrogen atoms,
one on each carbon or nitrogen.
Enzyme that does this: Dihydrofolate reductase (it does both
reduction reactions).
Chemo therapy that targets this enzyme: methotrexate (blocks
DHFR, can't make THF, can't make nucleic acids).
How THF acts as a methyl donor: there are lots of nitrogen atoms in
ring structures in THF. You tack a methyl group onto the fifth one (N5)
to make N5-methyl-THF, then take the methyl off again when you're
regenerating methionine from homocysteine (recall that B12 is
necessary for this). I don't know why it's easy to take off and put on a
methyl group to THF, but maybe it's got something to do with the
shared electrons in the ring structure.
 Note again that THF is important in one-carbon transfers in
nucleotide synthesis-- so if you screw with it to mess up
nucleotide synthesis, you can also get hyperhomocysteinemia.
Urea Cycle
Tuesday, November 18, 2008
7:31 AM
Urea Cycle, 11/18/08:
1. Describe how a nitrogen atom gets from an amino acid to urea. List the 2 entry
points for nitrogen into the urea cycle. Describe why glutamate and glutamate
dehydrogenase are important in this process.
 From the amino acid, it's shuffled around (as an amine group) by
aminotransferases to different alpha-keto acids until it winds up joining
with alpha-ketoglutarate to form glutamate.
 From mitochondrial glutamate, it's peeled off (still as an amine group)
by glutamate dehydrogenase to be linked up with CO2 to form
carbamoyl phosphate (catalyzed by carbamoyl phosphate
synthetase I. Yes, the I is actually important.).
 Carbamoyl phosphate fuses with mitochondrial ornithine to form
citrulline.
 Citrulline is transported out of the mitochondria and fuses with
cytosolic aspartate to produce arginosuccinate.
 Fumarate leaves arginosuccinate (and the cycle-- has several fates,
see below for details), leaving behind cytosolic arginine.
 Arginine is split by arginase (only found in liver) to urea and
ornithine.
 The urea leaves the cycle; the ornithine goes back into the
mitochondria to begin another iteration.
2. Name the key/rate limiting step in the entry of nitrogen into the urea cycle and its
allosteric activator.
 That would be carbamoyl phosphate synthetase I. Note it requires
2 ATP.
 It requires N-acetyl glutamate as a cofactor for activation.
 [Note also that glutamate dehydrogenase is regulated by both the
concentrations of products and reactants and also the relative levels of
ATP/ADP in the cell (high ATP inhibits, high ADP enhances).]
3. Describe how nitrogen gets from peripheral tissues to the liver to ultimately enter
the urea cycle. Name the enzymes that are important in this process.
 It does so mainly by being carried around by glutamine (which is
effectively glutamate with an extra amine group).
 In the peripheral tissues: alpha-ketoglutarate reacts with alanine to
form glutamate (ALT reaction). The glutamate has another amino
group added by glutamate synthetase to form glutamine.
 The glutamine travels through the blood to the liver (or kidney, but
that's a different pathway).

In the liver, glutaminase splits off the extra amine group and leaves
just plain ol' glutamate. The amine group can enter the urea cycle.
 Note, of course, that glutamate can then either donate the other
amino group on it to the urea cycle (catalyzed by glutamate
dehydrogenase) or can go through a reverse AST-catalyzed reaction
with OAA to generate aspartate, providing the other necessary
substrate for the urea cycle.
4. Describe the difference between a ketogenic amino acid, a glucogenic amino acid,
and an amino acid that is both.
 Ketogenic amino acids: can only be broken down into products that
can't go into gluconeogenic pathways (acetyl CoA, etc). Include lysine
and leucine.
 Both: can either be broken down into non-gluconeogenic products or
gluconeogenic products. Includes the aromatics (tyrosine, tryptophan,
phenylalanine) and isoleucine.
 Glucogenic: can only be broken down into gluconeogenic products
(pyruvate, or just about anything else in the TCA cycle other than
acetyl CoA). Include all the other AAs.
----old LOs---1. Be able to discuss the steps in the urea cycle. What is the urinary end product of
N metabolism?
 As described before, the urea cycle's point is to capture nitrogen (or
ammonia, if you prefer) and store it in a nontoxic form until it can be
excreted.
 Urinary end product: for reasons that will be mentioned in a bit, the
liver is the only organ that produces significant amounts of urea. But
ammonia can also be excreted through the kidneys in the urine. It
does this through the breakdown of glutamine (see below for more
details, but the long and short of it is that it's excreted directly as
ammonia, NH3); the urea generated by the liver is also excreted into
the urine.
Urea Cycle:
 (0) [recall that NH3 is broken off, often from glutamate with
glutamate dehydrogenase.]
 (1) Mitochondrial ammonia (NH3) fuses with CO2 and a
phosphate group to get carbamoyl phosphate, catalyzed by
carbamoyl phosphate synthetase I.
 This is the rate-limiting step of urea synthesis and uses
2 ATP.
 Note that this step also requires N-acetyl glutamate to
proceed.
 Deficiencies or mutations in this step result in increased
ammonia levels in blood.
 Note that his notes have both ammonia (NH3) and
ammonium (NH4+) as the substrate here. I don't think it
much matters.
 (2) Carbamoyl phosphate fuses with mitochondrial ornithine to
form mitochondrial citrulline.

(3) Citrulline leaves the mitochondria and goes into the cytosol,
where's it's fused with aspartate (carrying the other ammonia
group) to form arginosuccinate.
 (4) Arginosuccinate is cleaved, forming fumarate (which
leaves the cycle) and arginine (which stays in the cycle).
 (5) Arginine splits into urea and ornithine, catalyzed by
arginase. The urea leaves the cycle; the orthinine enters the
mitochondria to begin the cycle again with fresh carbamoyl
phosphate.
 Note that arginase is, more or less, only found in the
liver. That is: the liver is the only organ that can make
significant amounts of urea.
 Note that the carbon that is lost to urea comes from CO2.
2. Discuss the significance of Arg to nerve and muscle function and to gene
expression.
 Arginine is where we get nitric oxide (NO), that we've heard so much
about. The same reaction that produces NO also produces citrulline
for the urea cycle. He describes NO as a neurotransmitter.
 Arginine is also the source of ornithine (urea cycle) and creatine
phosphate (which is the backup fuel for muscles).
 Why it's important to gene expression evidently has to do with NO
regulating gene function, as well as the fact that histones are argininerich.
3. Discuss the significance of Gln to renal ion exchange and to the normal functioning
of the brain.
 Ammonia is toxic (which is why we have the urea cycle to begin with).
So while it's bouncing around the peripheral tissues, we would prefer
to bind it into a form that's not toxic until we can get it to either the
kidneys or the liver to dispose of it. That form is glutamine.
 A quick note on structure: glutamine is effectively glutamate with
another amine group stuck on. Therefore, once it gets to the liver, the
NH3 can be plucked off (by glutaminase) and go into the urea cycle;
glutamate itself can also be broken down by glutamate dehydrogenase
to liberate the other amine group, which can also go into the urea
cycle.
 In the kidney, more or less the same thing happens: the NH3 is taken
off glutamine (again, by glutaminase) to form glutamate; glutamate is
acted on by glutamate dehydrogenase to liberate the other NH3. The
difference is that in the kidney they're simply excreted into the urine
instead of going into the urea cycle.
 Ion exchange: recall from CVPR that the excretion of ammonia is
important in the synthesis of bicarbonate-- the ammonia binds
excreted H+ to form ammonium, allowing the kidneys to keep breaking
down CO2 to H+ and HCO3- and reabsorbing the HCO3-.
 Brain: Actually there's nothing in his slides about this (or renal ion
exchange, for that matter), but recall that hepatic encephalopathy is
thought to result from the accumulation of ammonia in the brain.
Binding NH3 as glutamine prevents this from occurring, I would
imagine.
 Recall that glutamate dehydrogenase is another key point of regulation
in nitrogen metabolism.
4. List the amino acids that are ketogenic, both ketogenic and glucogenic, or only
glucogenic. What are ketogenic or glucogenic amino acids metabolized to?


These are listed in "Amino Acid Metabolism."
Ketogenic amino acids are metabolized to either acetyl CoA (Ile, Leu,
Trp) or acetoacetate, which is broken down to acetyl CoA (Leu, Lys,
Phe, Trp, Tyr).
 Glucogenic amino acids are metabolized to a variety of steps in the
TCA cycle-- alpha-KG, succinyl CoA, fumarate, oxaloacetate, pyruvate.
 Note that in the transamination and urea cycle reactions, both
oxaloacetate and fumarate are produced (OAA from aspartate in the
AST transamination reaction, fumarate as a byproduct of the urea
cycle).
 He seems to find it significant that asparagine is broken down to
aspartate (liberates ammonia), which can be broken down to
oxaloacetate by AST. Evidently the enzyme that catalyzes this reaction
(asparaginase) is used as an anti-leukemia drug.
5. Understand the functional role of cofactors derived from several B vitamins in
carbon chain metabolism.
 Again, not in his notes here, but we've discussed:
 B6 and PLP: necessary for transamination reactions
 B9 (folate): necessary for THF formation and hence
regeneration of methionine from homocysteine.
 B12: necessary for homocysteine -> methionine reaction itself.
 (Biotin, B7, is necessary for various carboxylation reactions in
carbohydrate and lipogenic metabolism.)
6. Be able to discuss how a-keto acids from transamination are oxidatively
decarboxylated to acids that lack one C. The a-keto acids from Val, Leu and Ile are
metabolized by one enzyme complex, the lack of which results in what disease.
 What he seems to be talking about here is the branched-chain amino
acids.
 All of them, being amino acids, carry amine groups.
 Once the amine groups are pulled off by transaminases, what's left is
branched-chain alpha-keto acids.
 These alpha-keto acids are dehydrogenated by the branched chain
alpha-keto acid dehydrogenase complex (BCKDH), which pulls off
a carbon as CO2. The resulting forms can evidently go into the TCA
cycle (how isn't entirely clear to me).
 A deficiency in BCKDH results in maple syrup urine disease (high
concentrations of branched chain amino acids in the urine, which
evidently smell rather fruity).
7. Amino acid decarboxylases, acting on PP Schiff bases, provide amines for a
number of important functions. Discuss four such functions.
 No longer a LO.
Phe, Tyr, Trp, and Heme Metabolism
Tuesday, November 18, 2008
8:29 AM
Phe, Tyr, Trp, and Heme Metabolism, 11/18/08:
[Recall that phenylalanine, tyrosine, and tryptophan are your aromatic amino acids.]
[Phenylalanine and tryptophan are essential amino acids; tyrosine isn't.]
1. List the molecules that are derived from tryptophan and the cofactor that is
involved in these pathways.
 Tryptophan is made into 5-HT, melatonin, and niacin.
 Requires tryptophan hydroxylase as an enzyme, but more importantly
for current discussion also requires tetrahydrobiopterin as a
cofactor.
2. List the enzyme responsible for, the cofactor involved and regulation of the step
converting phenylalanine to tyrosine.
 Enzyme: phenylalanine hydroxylase
 Cofactor involved: still tetrahydrobiopterin.
 Regulation: Not sure. Obviously if you have a lot of tyrosine around
(as in various types of tyrosemia) it won't go forward as fast. More
medically relevant, without phenylalanine hydroxylalanine it won't go
forward at all and you'll get phenylketonuria (about which more later
and below) due to the buildup of Phe and its derivatives (if it can't be
made into tyrosine, it'll be made into other things-- phenylpyruvate,
phenylacetate, etc).
3. Describe the synthesis of dopamine, norepinephrine and epinephrine from
tyrosine. List the first regulated step in this pathway and the cofactor involved in this
step? What disease results from a deficiency or a malfunction of dopamine?
 (Regulated step) Tyrosine is hydroxylated to DOPA by tyrosine
hydroxylase; requires as a co-factor tetrahydrobiopterin again.
 DOPA is decarboxylated to dopamine.
 Dopamine is hydroxylated to norepinephrine. Note for later: this
takes vitamin C as a cofactor.
 Norepinephrine is methylated (by SAM, recall) to epinephrine.
 Without dopamine, as you recall, you get Parkinson's.
4. Discuss the role of MAO in catecholamine degradation and the utility of MAO
inhibitors in the treatment of disorders of the catecholamine synthetic pathway.
 MAO: degrade catecholamines by removing their amine groups.
 Recall that MAOs can help prevent Parkinson's symptoms (though the
first line remains L-DOPA) by decreasing the rate of catecholamine
degradation.
 Note, however, that they'll also decrease the rate of degradation of
everything else (NE, EPI, serotonin)-- so can have some
neurotransmitter issues.
5. What is the important product of tryptophan metabolism, the relevant enzyme and
the needed cofactor.
 As mentioned: 5-HT; requires tryptophan hydroxylase as an enzyme
and tetrahydrobiopterin as a cofactor.
6. Name the key committed/rate controlling step in porphyrin synthesis. Describe the
general problem present in the porphyrias and the specific clinical presentation of
porphyria cutanea tarda and acute hepatic porphyria.
 Porphyrin (ring): basis for heme (needs a Fe atom in the middle)
 Rate limiting step in porphyrin synthesis: formation of aminolevulinate
(ALA, not alanine) from glycine and succinyl CoA.
 Porphyrias: inherited defects in heme synthesis.
 Porphyria cutanea tarda (from Wiki): blistering of skin in areas
exposed to sunlight, usually caused by a deficiency of an enzyme
involved in heme synthesis.
 Acute hepatic porphyria (also from Wiki, under "acute intermittent
porphyria"): extreme pain in the gut and possibly extremities,
constipation, muscle weakness. Precipitated by a number of factors.
----old LOs---1. Discuss Phe hydroxylation. What disease results from non-functional Phe
hydroxylase?
 Hydroxylation of phenylalanine (by phenylalanine hydroxylase)
converts it to tyrosine (which is why tyrosine isn't essential).
Tetrahydrobiopterin is required an a cofactor. This is important
because phenylalanine can't be broken down into TCA cycle
substituents without going through tyrosine first.
 If you can't convert Phe to Tyr, you get a buildup of Phe called
phenylketonuria (PKU), which can lead to irreversible brain injury
and seizures if not controlled (recall that it's controlled by diet).
 Essentially what happens is that you try an alternative pathway to get
rid of the excess phenylalanine. How you try to do it: transfer off the
amino group to get an alpha-keto acid (phenylpyruvate), then reduce
phenylpyruvate to get either phenylacetate or phenyllactate.
 All of these are excreted in the urine (phenylalanine, phenylpyruvate,
phenylacetate, phenyllactate). Phenylacetate has the characteristic
"musty" smell of sweat and urine in PKU.
 Note PKU is a fairly common inherited disease (deficiency of
phenylalanine hydroxylase): 1 in 10,000 are affected. It's autosomal
recessive.
2. Discuss synthesis of dopamine, norepinephrine and epinephrine from Tyr. What is
the first regulated step in this pathway? What diseases result from a deficiency or a
malfunction of dopamine?
 First regulated step: tyrosine is hydroxylated (by tyrosine
hydroxylase) to DOPA.
 This reaction is the rate-limiting step and also requires
tetrahydrobiopterin.
 DOPA is decarboxylated to dopamine.
 Dopamine is hydroxylated to norepinephrine.
 Norepinephrine is methylated on its amine group to form epinephrine.
 General notes: "catechol" is a benzene ring with two hydroxyl groups
on it. "Catecholamine" is a little misleading since there's a couple
carbons between the catechol group and the amine group, but it's
more or less there in the name.
 A deficiency in dopamine causes Parkinson's Disease; the first-line
treatment, if you recall, is administration of L-DOPA.
3. Discuss the role of MAO in catecholamine degradation. What effect do MAO
inhibitors have on the body?
 MAOs remove the amine groups from catecholamines.
 [COMTs, by contrast, stick a methyl group on one of the hydroxyl
groups of the benzene rings.]
 [Note two pharmacological ways of prolonging catecholamine drug
action: take off the hydroxyl groups from the benzene (eliminate
COMT activity) and methylate the carbon next to the amine group
(makes it harder for MAOs to take the adjacent amine).]
 MAO inhibitors can work to preserve dopamine levels in Parkinson's,
but they can cause all manner of problems, mainly because they also
prevent the breakdown of ingested amines. Say you eat a bunch of
tyrosine all at once; this gets converted into lots and lots of
catecholamine, which would normally be broken down to reasonable
levels by MAOs but is now just free to sit around and give you a
hypertensive crisis.
4. Discuss the mechanism by which thyroxine (T4) is synthesized from Tyr in the
thyroid gland. Where is the precursor to the active thyroid hormone T3?
 Tyr is iodinated several times and kind of dimerized to itself (...sort of)
to form T4.
 T4 is the inactive precursor of T3, which is the active form of thyroid
hormone. T4 has one of its iodine residues plucked off to form T3.
 They both travel around in a kind of thyroid Batmobile called thyroxin
binding globulin.
5. Discuss the synthesis of 5-HT.
 Recall that serotonin is derived from tryptophan; so are melatonin and
niacin.
 5-HT is made by hydroxylating tryptophan (uses tryptophan
hydroxylase).
 Tetrahydrobiopterin, again, is required for this reaction.
 [5-HT is decarboxylated to make serotonin, if you're interested.]
[Note that tetrahydrobiopterin is necessary for all of the aromatic hydroxylation
reactions: Phe to Tyr, Tyr to DOPA, Trp to 5-HT. A deficiency in working
tetrahydrobiopterin levels is, therefore, bad, and will lead to phenylketonuria, among
other things.]
6. Catecholamine synapses are under strict control at both the pre- and postsynaptic
levels. Discuss the clinical use of serotonin reuptake inhibitors (SSRI).
 No longer a LO.
[He does, however, discuss heme briefly-- more or less he just said that inherited
defects in heme synthesis are called porphyrias, that a major functional group of
heme is pyrole, that ALA (not alanine but aminolevulinic acid) is a key intermediate,
that heme is degraded to bilirubin, and that unconjugated bilirubin in infants can be
converted to the more harmless biliverdin by light.]
[See Lippincott p. 278-282]
Purine, Pyrimidine, and Nucleotide Metabolism, Parts I and II
Tuesday, November 18, 2008
9:53 AM
Purine, Pyrimidine, and Nucleotide Metabolism, Parts I and II, 11/18/08:
[Dr. Kieft was kind enough to glance at these and verify that I'd covered the key
concepts. How complete that makes this document is, however, up for debate.]
1. Identify the sources of the atoms in purine and pyrimidine bases.
 Purines:
 Aspartate donates a nitrogen atom; formate (from THF), two
carbon atoms; CO2, another carbon atom; glutamine, two
nitrogen atoms; glycine, two carbons and a nitrogen.
 Note none of aspartate, glutamine, or glycine are essential
amino acids-- they can all be synthesized in the body from
something else.
 Pyrimidines:

Most of the ring comes from aspartate; you also get a nitrogen
from ammonia and a carbonyl group from CO2. Note THF isn't
used except in thymine synthesis.
 Again, aspartate's not an essential amino acid.
2. List two key differences between the syntheses of purine and pyrimidine
nucleotides.
 (1) The purine base ring is made directly on the ribose, whereas the
pyrimidine base ring is synthesized apart from, and only later attached
to, the ribose.
 (2) The first nucleotide product in purines is inosine monophosphate
(IMP); the first nucleotide product in pyrimidines is uridine
monophosphate (UMP).
 IMP is converted to G and A as a monophosphate (IMP -> GMP
or AMP); UMP is converted to C as a triphosphate (UTP ->
CTP). Note that TMP synthesis is a little screwier (see below)-it only gets made as a deoxyribonucleotide.
3. Trace the paths by which each of the nucleotides is produced.
 Purine synthesis:
 Recall that ribose 5-phosphate is important in nucleic acid
synthesis (it was one of the products produced in the pentose
phosphate shunt pathway).
 Ribose 5-phosphate is made into PRPP (5-phosphoribosyl-1pyrophosphate), which is important for most of what follows.
The enzyme that catalyzes this reaction is PRPP synthase, a
key regulated step.
 PRPP has an amine group put on, and two phosphate groups
removed, by glutamine PRPP amidotransferase, another
key regulated step.
 Then a bunch of reactions occur. Note that some of them
require THF.
 Eventually you wind up with inosine monophosphate (IMP),
which is the precursor for the final purine products.
 GMP (guanosine monophosphate) and AMP (adenosine
monophosphate) are formed by adding some other junk onto
the IMP base ring. Different junk for each base.
 Important junk in the AMP-forming pathway: an enzyme
called adenylosuccinate lyase forms AMP from
adenylosuccinate. A deficiency in this enzyme causes a
form of autism.
 Once you have GMP and AMP, they get phosphorylated to GDP
and ADP (-diphosphates).
 For RNA, no sweat, we just phosphorylate twice more to get
GTP and ATP.
 For DNA: recall that the "D" in DNA has a "deoxy-" in it. That
means we have to go pull a hydroxyl group off of the ribose
group. We do this through an enzyme called ribonucleotide
reductase.
 How ribonucleotide reductase works: Dr. Kieft compared
this to a TV with an on/off switch and four channels (one
for each type of ribonucleotide that it reduces). It's a
strange enzyme: it can catalyze any one of four
reactions (channels), each of which is the
dehydroxylation of a nucleotide diphosphate. It
effectively senses the balance between the
concentrations of NDPs (nucleotide diphosphates) and
dNDPs, and dehydroxylates or stops dehydroxylating
different NDPs to maintain an ideal concentration
balance. Complex little bugger.
 The on/off switch: it's turned on by ATP and turned off
by dATP.
 After the dADP or dGDP is made, it's phosphorylated a third
time to dATP or dGTP, which can be used to make DNA.
 Feedback: AMP, GMP, and IMP all allosterically inhibit the two
early regulated steps in purine synthesis (PRPP synthase and
glutamine PRPP amidotransferase). AMP and GMP also inhibit
their respective syntheses from IMP.
 Pyrimidine synthesis:
 Different animal from purines. The rate-limiting step is
carbamoyl phosphate synthetase II (not the same one
involved in the urea cycle), which makes carbamoyl from CO2
and an amine group.
 Then a bunch of reactions occur.
 What you end up with is uridine monophosphate (UMP), which
is going to be the basis for C and T residues.
 This is a little funky. Instead of just modifying the ring to either
the C or the T structure and then
phosphorylating/dehydroxylating from there (as in purine
synthesis), the synthesis of pyrimidines from UMP is, shall we
say, tortuous.
 Cytosine is made by fully phosphorylating UMP to UTP,
then converting to CTP (cytosine triphosphate), then
taking a phosphate off (making CDP), then
dehydroxylating to dCDP, then rephosphorylating to
dCTP.
 Thymine is made by partially phosphorylating UMP to
UDP, then dehydroxylating it to dUDP, then
dephosporylating it back to dUMP, then converting to
dTMP, then phosphorylating twice to dTTP.
 Note that thymine synthesis from UMP requires
THF.
 Absurd? Probably. Take it up with evolution. Or the
intelligent designer, I suppose (who may have been
smoking the good stuff that day).
 Note that it's a lot easier to make the bases required for
RNA-- you don't muck around with the dehydroxylation,
you just phosphorylate the monophosphates a couple
times and you're done. Note that, as above, CTP is
made directly from UTP. Thymine you don't use at all in
RNA (use UTP instead).
4. Name the primary regulatory steps and feedback loops within the de novo purine
and pyrimidine synthesis and degradation pathways.
 Purine synthesis:
 Primary regulated step (actually occurs second in pathway):
glutamine PRPP amidotransferase (puts an amine group
onto PRPP)

Secondary regulated step (actually occurs first in pathway):
phosphoribosyl pyrophosphate (PRPP) synthase (makes
PRPP out of ribose 5-phosphate).
 As mentioned, AMP, IMP, and GMP are involved in feedback
loops (see above).
 Purine degradation:
 [Essentially purine degradation involves pulling off the ribose,
then breaking down the free base to uric acid. Note the base
ring is never opened up in purine degradation (uric acid is still
closed).]
 The reaction catalyzed by adenosine deaminase is an important
step, although I'm not sure how regulated it is. Without
adenosine deaminase you can't degrade adenosine; this results
in severe combined immunodeficiency (SCID), see below.
 Pyrimidine synthesis:
 As mentioned, the first step (carbamoyl phosphate formation)
is the key regulated step.
 Feedback loops: ..?
 Pyrimidine degradation:
 A little different from purine degradation; this involves pulling
off the base, as before, but then opening up the ring and
breaking it down to succinyl CoA, malonyl CoA, and/or acetyl
CoA.
 Regulated steps: ..?
5. Identify the enzyme that reduces ribose to deoxyribose, describe the strategy this
enzyme uses for catalysis, and name its substrates.
 That would be ribonucleotide dehydrogenase.
 Its function has already been mentioned. Of note, it only acts on ADP,
GDP, UDP, and CDP (it does not act on TDP because TDP doesn't
exist-- dTDP is synthesized from an already-dehydroxylated dUDP as
mentioned above).
 Repeat: ribonucleotide reductase only acts on ADP, GDP, UDP, and
CDP.
6. List the enzyme deficiencies that give rise to these diseases and describe the
biochemical effect of the deficiency: Gout, SCID, and LHS.
 SCID: deficiency in adenosine deaminase (in degradation pathway of
AMP).
 Why you get immunodeficiency: recall that ribonucleotide
reductase is activated by high levels of ATP and deactivated by
high levels of dATP. If you can't break down adenosine (as in
ADA deficiency), some of it winds up being dehydroxylated and
phosphorylated to dATP, which inhibits the dehydroxylation of
all ribonucleotides. This means you can't make DNA very well,
which generally targets the rapidly turning-over cells like
lymphocytes (which also, per Lippincott, normally have the
highest concentration of ADA in the body).. thus SCID.
 Gout: can be caused by any number of things, really. Recall that gout
is the result of a buildup and precipitation of uric acid crystals; uric
acid is the end breakdown product of purine degradation. Increased
intake of purines or purine precursors (ie. organ meat), and/or a
problem with excreting them, causes gout. It's treated, chronically,
with allopurinol, which inhibits the final step transforming xanthine to
uric acid (xanthine doesn't precipitate in the same unpleasant ways
that uric acid does).
 Lesch-Nyhan Syndrome: involved in the salvage pathway (not
mentioned above) of IMP and GMP; essentially the pathway is involved
in using premade purine base fragments to avoid having to
resynthesize the whole thing. An enzyme called HGPRTase catalyzes
the conversion of either hypoxanthine or guanine to IMP and GMP,
respectively. Without this enzyme you get lots of uric acid (the base
fragment is broken down to uric acid since it can't be used in salvage),
leading to gout-like symptoms, and mental impairment leading to
bizarre behavior (self-mutilation, etc).
 Imagine SCID and L-N syndrome as defects in similar enzymes
but going in different directions. SCID is a problem in breaking
apart adenosine (thus you get no breakdown product but a
whole ton of dATP that inhibits synthesis). L-N is a problem
recycling guanine (thus you get no GTP but a whole ton of
breakdown product).
7. Describe how 5-fluorouracil and similar drugs inhibit nucleotide synthesis.
 5-flurouracil: an analog of thymine; it binds to the enzyme that is
supposed to make dTMP from dUMP and permanently inactivates it.
 Methotrexate: inactivates dihydrofolate reductase; this means you
can't regenerate THF from DHF, which inactivates a key step in both
the purine (IMP) synthesis pathway and also the dUMP -> dTMP
pathway.
Metabolic Defects: PKU, Homocystinuria, and Urea Cycle
Defects
Tuesday, November 18, 2008
2:32 PM
Metabolic Defects: PKU, Homocysteinuria, and Urea Cycle Defects,
11/19/08:
1. Describe the clinical presentation, diagnostic approach, and treatment strategies
for classic PKU.
 [Problem: either a defect in phenylalanine hydroxylase (can't convert
to tyrosine) or a defect in tetrahydrobiopterin (cofactor for the
reaction).]
 Clinical presentation (generally in infancy):
 Irritability
 Hyperreflexia
 Dry skin
 Seizures
 Acquired (postnatal) microcephaly
 Hypopigmentation (lack of tyrosine leading to a lack of
melanin)
 Mousy odor
 Severe, irreversible mental retardation if untreated
 Diagnostic approach:
 Get a blood spot after 12 hours; use to test Phe and Phe/Tyr
levels.

If that's high, their serum is drawn and tested for Phe levels
directly.
 Might also check tetrahydrobiopterin levels (BH4 deficiency can
also cause PKU).
 It's autosomal recessive, so might check siblings while you're at
it.
 Treatment:
 Largely dietary, avoiding foods that contain high levels of Phe.
 Must have small amounts of Phe for normal growth and
development.
 Want to keep Phe levels between 2-6 mg/dL (120-360
micromoles per L)
 Can try administering tetrahydrobiopterin (aka BH4) after 6
months to try and help reduce the need for a restricted diet.
Problem is, it doesn't cross the BBB.
 Can also use large neutral amino acid therapy to compete with
Phe for BBB transport into the brain if adults can't comply with
dietary therapy.
 Get regular blood Phe levels (once a day if not uncontrolled,
once a week to month if controlled) checked.
 [Note that if a woman has mild, even asymptomatic PKU, she needs to
be on diet restriction if she gets pregnant. Even slightly elevated levels
of Phe are teratogenic and produce babies with a similar phenotype to
fetal alcohol syndrome.]
2. Name the general pathway involved and describe the clinical features of
Alkaptonuria.
 Alkaptonuria: a problem with the tyrosine breakdown pathway.
 Look for: black urine, black pigmentation of cartilage and collagen, and
arthritis starting in the patient's 40's.
3. Describe the clinical presentation and treatment approach for classic
homocystinuria.
 [Problem: lack of the enzyme that makes homocysteine into
cystathione.]
 Clinical presentation of homocysteinuria: seizures, mental retardation,
pro-thrombotic state, tall/thin, dislocated (depressed) lenses,
osteoporosis, psych features.
 Can mimic Marfan's syndrome.
 Treatment:
 Limit dietary methionine and supplement with cysteine (it's now
essential since you can't make it from homocysteine).
 Can administer vitamin B6 in a similar fashion to BH4 above
(it's a cofactor for the homocysteine to cystathione reaction);
about half of patients respond to some extent.
 Folate and B12 are used to provide a large pool of available THF
to help remethylate homocysteine to methionine (which is more
useful and less toxic).
 In older patients, use aspirin to alleviate the prothrombotic
state.
4. Describe in general terms the nature of the defect in maple syrup urine disease
and the clinical features.
 Generally: it's a defect in the enzyme that begins the breakdown of
branched-chain amino acids (specifically BCKDH). This results in a
buildup of branched-chain AAs.

The buildup can cause encephalopathy (eg. effects in the basal
ganglia) due to high levels of leucine, coma, and death.
 [Defects in subsequent steps of branched-chain AA metabolism can
cause buildup of organic acids, resulting in metabolic acidosis and
hyperammonemia plus neurological symptoms.]
5. Describe the clinical presentation and key diagnostic tests for urea cycle defects.
Name the most common urea cycle defect.
 Clinical presentation: vomiting, altered mental status, and seizures.
Ammonia also stimulates the respiratory centers in the brain and can
cause respiratory alkalosis. Note that urea cycle disorders can be
caused by a whole lot of things (eg. liver failure or enzyme deficiency)
and hence can present at any age.
 Diagnostic tests: in addition to standard newborn screening tests, also
look for:
 Plasma ammonia
 Plasma amino acids
 Urine orotic acid
 Most common: ornithine transcarbamylase deficiency. Note that
this isn't screened for by basic newborn screening. Causes increased
orotic acid in urine.
6. The following are basic concepts of biochemical genetics/inborn errors of
metabolism: [maybe just read over and understand?]
1. A block in a biochemical pathway may lead to clinical symptoms
because of an excess of an accumulated product, a deficiency of a
substance downstream of the block, the accumulation of side products,
or a combination of the above.
2. An enzyme deficiency may be due to a defect in the enzyme itself, or
to a defect in the synthesis, transport, or recycling of a vitamin
cofactor.
3. In so-called "small molecule" diseases a defect in one organ, e.g. the
liver, may have deleterious consequences for other organ systems,
because of the transport of substances to other parts of the body, e.g.
the brain.
4. Diagnosis of many inborn errors of metabolism is based on the
detection of characteristic substances in the blood or urine. Newborn
screening of blood spots allows pre-symptomatic detection of some
inborn errors of metabolism, allowing early treatment and reduction of
morbidity and mortality.
5. Treatment often includes dietary therapy to limit flux through the
pathway, and pharmacologic doses of the enzyme co-factor. It is
important to remember that some amount of the "offending" amino
acid must be supplied in order to allow normal growth and
development.
----old LOs---[Notes:]


Different amino acid deficiencies have very distinct clinical pictures-therefore it's important to know what deficiency associates with what
disorder, to be able to treat it accurately when you see it.
 Note that newborn screening, while it's good at picking up PKU,
does not detect all disorders-- so keep an eye out in the clinic
for something that was missed.
PKU:
 Etiologies:
 Deficiency of phenylalanine hydroxylase-- can't break
down Phe to Tyr. Note it's a AR-inherited disorder, about
1 in 10,000 births.
 Recall that Phe hydroxylase requires a cofactor:
tetrahydrobiopterin (BH4). If you have a defect in BH4,
you'll get PKU as well. Notice that BH4 deficiency will
also result in a failure of hydroxylation of tyrosine and
tryptophan, as mentioned before, and problems with
synthesizing neurotransmitters, etc.
 Presentation in infancy:
 Irritability, hyperreflexia, seizures, acquired (postnatal)
microcephaly, hypopigmentation (lack of tyrosine
leading to melanin).
 Spectrum of severity:
 Classic PKU: peak plasma [Phe] > 1200 micromoles per
liter or 20 mg/dL. Will lead to mental retardation if diet
is unaltered. Complete absence of Phe hydroxylase.
 Mild PKU: incomplete enzyme deficiency: [Phe] levels
between 600 and 1200 (or 10-20 mg/dL). Required
dietary therapy, but greater tolerance for Phe.
 Benign hyperphenylalaninemia: [Phe] levels less than
600 (or less than 10 mg/dL). Doesn't generally require
dietary therapy except in women of childbearing age
(Phe levels over 6 mg/dL are teratogenic).
 Women with elevated Phe, from mild to severe,
who don't control it while they're pregnant get in
in utero microcephaly, cardiac defects, etc-- it
looks like fetal alcohol syndrome.
 Take-home: if males have a mild syndrome, don't
generally need to follow up past childhood; if
females do, need to follow up in clinic to make
sure they control their levels during pregnancy.
 Get a blood stick at birth (put on an agar plate with some
bacteria that need high levels of Phe to grow, see if they do);
monitor Phe and Tyr levels.
 Goals here: want dietary therapy within the first several weeks
of life; also look at BH4 levels to make sure it's Phe
hydroxylase deficiency instead of BH4 deficiency. Want to
maintain [Phe] between 120-360 micromoles per liter (or 2 and
6 mg/dL). Always check siblings.
 Treatment: mainly, dietary restriction. Can try giving BH4 later
in childhood, or in pregnancy, to help improve Phe
hydroxylation and keep Phe levels down. We're not entirely
sure how BH4 works, but if they're on a stable diet and their
Phe levels go down 30% with application of BH4, that's a yes.

Responsiveness to BH4 doesn't correspond to genotype as far
as we can tell.
 Can also given other large, neutral amino acids (like
Phe) to compete with Phe for large, neutral amino acid
transporters across the BBB (decreasing some of the
toxic neurological effects).
Management: check Phe levels daily until it's within goal range,
then once a week or month. Note that dietary restriction is
tough for most patients-- the food is expensive and not greattasting.

Tyrosinemia:
 Tyrosine goes through a particular pathway to be broken down.
Blocks at different points in the degradation pathway
(tyrosinemia types I, II, or III) produce different symptoms.
Type I can cause liver and kidney problems, for example, while
type II can show up with eye problems and thickening of the
soles and palms.

Homocysteinuria:
 Etiology:
 "Classic" homocysteinuria is caused by a defect in the
enzyme (cystathione beta synthase) that fuses
homocysteine and serine to cystathionine on the way to
forming cysteine.
 Other etiologies: B12 defects or defects in methionine
synthase.
 Presentation:
 Seizures, mental retardation, pre-thrombotic state,
tall/thin, dislocated (depressed) lenses, osteoporosis,
psych features.
 Can mimic Marfan's syndrome.
 Detection:
 Look for elevated methionine. However, this is not a
very sensitive test, particularly for patients who respond
to B6 administration (see below).
 Also look for dislocated lenses.
 Treatment:
 Limitation of dietary methionine
 Supplementation of cysteine
 About half of patients respond to vitamin B6 (a cofactor;
similar to BH4's relationship with PKU, as above).
 Folate and B12 supplementation to help THF pathway to
remethylate homocysteine.
 Aspirin in older patients to alleviate prothrombotic state.

Branched-chain amino acid (Val, Ile, Leu) metabolism disorders:
 Maple syrup urine disease: as mentioned, due to a defect in
an enzyme in the second catabolic step (branched-chain ketodehydrogenase or BCKDH) of branched-chain amino acids. Can
cause leucine encephalopathy (eg. effects in the basal ganglia),
coma, and death.



Defects in subsequent steps of branched-chain AAs can cause
buildup of organic acids, resulting in metabolic acidosis and
hyperammonemia plus neurological symptoms.
Screened for at newborn screening but should be considered
with any child with developmental delays or neurological
problems.
Urea cycle disorders:
 Classically, hyperammonemia presents in the newborn period
with altered mental status, vomiting, and seizures. Remember
that ammonia is neurologically toxic and does irreversible
damage-- so it's better to catch this early.
 Note that hyperammonemia can be caused by a large number
of things (the complete list is in her slides), not just primary
urea cycle defects. We've discussed liver failure, for example.
 The most common urea cycle defect - ornithine
transcarbamylase - isn't detected with newborn screening.
 Due to this multiplicity of etiologies, urea cycle disorders
can occur at any age, not just childhood.
 Note ammonia isn't part of the standard chem screen.
 Ornithine transcarbamylase facilitates the incorporation
of carbamoyl phosphate into ornithine to make citrulline.
 A deficiency in OT results in high levels of
ornithine and low levels of citrulline (most
newborn screening tests look for high levels of
citrulline instead).
 It can result in a buildup of orotic acid (what the
excess carbamoyl phosphate is made into) as
well as ammonemia-- orotic acid is what's tested
for.
 Recall this is the most common urea cycle
disorder.
 It's X-linked-- generally males are affected more
than females (and may die during newborn
period), but carrier females can still manifest
symptoms.
 Can use liver transplant to treat severe, recurrent
cases.
 Arginase, recall, facilitates the elimination of urea out of
arginine.
 Classic presentation of arginase deficiency: spasticity,
seizures, milder hyperammonemia.
 Lots more (on slide-- eg. defects in N-acetyl glutamate that's
required to promote glutamate dehydrogenase).
 General presentation of urea cycle disorders:
 In newborn period, severe disorders (seizures, vomiting,
decreased alertness).
 Ammonia stimulates the respiratory center, causing
respiratory alkalosis.
 Hyperammonemia: [NH3] > 400 micromoles/liter are
associated with developmental delay. The duration
causes problems, too. Infection or increased dietary
protein can be triggers for an acute attack.

Treatment:
 Limit dietary protein (all of which contain nitrogen), give
ammonia scavenging medications (like sodium
benzoate). Possibly arginine administration depending
on the defect.
1. Understand the following basic concepts of biochemical genetics/inborn errors of
metabolism:
 A block in a biochemical pathway may lead to clinical symptoms
because of an excess of an accumulated product, a deficiency of a
substance downstream of the block, the accumulation of side products,
or a combination of the above.
 An enzyme deficiency may be due to a defect in the enzyme itself, or
to a defect in the synthesis, transport, or recycling of a vitamin
cofactor.
 In so-called "small molecule" diseases a defect in one organ, e.g. the
liver, may have deleterious consequences for other organ systems,
because of the transport of substances to other parts of the body, e.g.
the brain.
 Diagnosis of many inborn errors of metabolism is based on the
detection of characteristic substances in the blood or urine. Newborn
screening of blood spots allows pre-symptomatic detection of some
inborn errors of metabolism, allowing early treatment and reduction of
morbidity and mortality.
 Treatment often includes dietary therapy to limit flux through the
pathway, and pharmacologic doses of the enzyme co-factor. It is
important to remember that some amount of the "offending" amino
acid must be supplied in order to allow normal growth and
development.
2. Urea Cycle Defects:
 Describe how ammonia is eliminated by the urea cycle.
 (we know this)
 Describe the clinical symptoms of a neonatal onset urea cycle disorder.
 (seizures, vomiting, decreased alertness)
 Describe the biochemical testing used to diagnose urea cycle
disorders.
 (DNA tests, organic acid levels including orotic acid, ammonia
levels)
 Describe the inheritance pattern of the most common urea cycle
disorder and the importance of taking a family history when
considering this disorder.
 (Ornithine transcarbamylase: X-linked recessive, but can still
affect carrier females. Family history is important.)
Glycogen, Carb, Fat, and Energy Disorders
Wednesday, November 19, 2008
10:02 AM
Glycogen, Carb, Fat, and Energy Disorders, 11/19/08:
1. Glycogen/carbohydrate disorders:
[In general with glycogen storage disorders, look for hypoglycemia, impaired
gluconeogenesis (with accompanying lactic acidosis), muscle weakness and
rhabdomyolysis, and hemolytic anemia. All symptoms will get worse when
fasting.]


Describe the clinical presentation, treatment and long term
complications of glucose 6 phosphatase deficiency.
 (Type I, or von Gierke's disease)
 Signs and symptoms: severe hypoglycemia, hepatomegaly,
nephromegaly, lactic acidosis, hypertriglyceridemia and
hypercholesterolemia, hyperuricemia, and a short stature and
doll-like face. Note that this is the most severe glycogen
storage disease (as you might expect from a condition where
you can't liberate glucose into the bloodstream).
 Symptoms come on rapidly with fasting-- on average
about 4 hours. Keep in mind that your average newborn
feeds every 2-3 hours so this may not be picked up right
away.
 Glucose is converted to pyruvate and lactate (producing
lactic acidosis) and fat (producing hypertriglyceridemia
and hypercholesterolemia). You also get increased
breakdown of AMP and ADP to uric acid (thus
hyperuricemia).
 Note that the deficiency can be either in the transporter
of glucose 6-phosphate in the ER (type b) or the enzyme
that removes the phosphate (type a). Type b will also
cause chronic granulomatous disease due to inhibited
neutrophil oxidase activity.
 Inherited in an autosomal recessive pattern.
 Detect with an enzyme assay from the liver or (more
commonly) genetic analysis for the known mutation.
 Treatment:
 Frequent feeding (every 3 hours while awake), IV
glucose, nasogastric drip feeding, uncooked cornstarch
ingestion (takes a long time for digestion and
absorption). Should avoid galactose, fructose, and fats.
 Late complications (avoid with tight control of hypoglycemia
and lactate):
 Renal scarring (focal segmental glomerulosclerosis),
kidney calcium stones.
 Hepatic adenomas
 Osteoporosis
 Gout
 Platelet dysfunction:
 Pulmonary hypertension
 Polycystic ovary syndrome
 Short stature
Describe the clinical presentation of debranching enzyme deficiency
 (Type III)
 Symptoms:
 Clinically, looks a little like a mild type I, but see next
point.


Late:

Glycogen has an abnormal structure-- this structure
causes damage to the liver (elevated AST/ALT
enzymes).
Cardiomyopathy/myopathy, neuropathy, cirrhosis and
hepatic carcinoma.
 Describe the clinical presentation, treatment and long term
complications of muscle glycogen phosphorylase deficiency.
 (Type V)
 Signs and symptoms:
 Elevated creatine kinase
 Muscle cramps and pain with anaerobic exercise, leading
to avoidance of exercise, leading to loss of muscle tone
and bulk (atrophy and weakness).
 Hemolytic anemia, may be mild and chronic.
 With exercise, see only a small rise in lactate (small
increase in circulating glucose) but a large rise in NH3
(breakdown of nucleic acids for fuel).
 Treatment: aerobic or low-grade exercise training, taking carbs
pre-exercise.
 Late: as mentioned, atrophy and weakness.
 Describe the clinical presentation and treatment of Galactosemia.
 Galactosemia: deficiency of UDP-galactosyltransferase
(breakdown of phosphorylated galactose). The precursors
(galactose and activated galactose) build up in the liver and are
toxic.
 Signs and symptoms:
 Hemolysis
 Rapid onset of toxic hepatopathy
 Renal tubular dysfunction
 Cataracts (buildup of toxic byproduct)
 Sepsis (E. coli) in second week of life
 They get sick in the first few days of life, generally on
ingesting mother's milk (contains lactose).
 Treatment: avoidance of lactose/galactose.
 [Late: progressive developmental delays, speech delay, ataxia,
ovarian failure.]
 [Note that the body needs a certain level of galactose to make
certain glycoproteins.]
 [for boards: Pompe disease (type II) causes severe cardiomyopathy
resulting from glycogen storage in the lysosome.]
2. Fat Oxidation Disorders:
 Describe the clinical presentation of and diagnostic approach for fatty
acid oxidation disorders in general.
 Look for problems after prolonged fasting or infection. Example
given: 6-month infant gets his first ear infection, throws up his
dinner, and goes to sleep-- in the morning he's very sick.
 Also look for myopathy, cardiomyopathy, arrhythmias and/or a
Reye's-like syndrome (fatty liver, hyperammonemia, etc).
 Note you can get sudden death with this so it's a big thing.
 Diagnosis:
 Look for an absence or low level of ketones along with
hypoglycemia.
Also look for low acylcarnitine levels.
Also get a urine sample and look for high levels of
organic acids.
 Can also do acylcarnitine analysis or genetic mutation
testing.
 Describe the clinical features that are unique to long chain fatty acid
oxidation disorders.
 Unique:
 Retinitis pigmentosa
 Peripheral neuropathy
 Cholestasis
 Lactic acidosis
 Acute fatty liver of pregnancy (AFLP)
 Describe the clinical presentation, diagnostic approach and treatment
strategies for medium chain acyl Co-A dehydrogenase (MCAD)
deficiency
 [This only targets fatty acids with 8-12 carbons in the chain.]
 Symptoms: Often none. With long fasting or severe infection,
or both, starts showing up as Reye-like syndrome, arrhythmias,
sudden death.
 Diagnostic approach:
 90% of clinical cases are caused by a particular
mutation (A985G). Can look for that.
 Also can use acylcarnitine analysis (mass spec, I think?)
during newborn screening for this.
 Treatment: avoid prolonged fasts, use uncooked cornstarch to
get through the night; for acute episodes, you can use Lcarnitine administration.
 Describe the signs and symptoms of the 3 forms of MADD and the
treatment of this condition
 MADD: multiple acyl-CoA dehydrogenase deficiency.
 Neonatal form: myopathy, cardiomyopathy with arrhythmias,
renal cysts, bad odor, brain malformations.
 Infantile form: Reye-like syndrome, liver dysfunction,
acidosis, hypoglycemia, bone marrow depression.
 Late-onset form: lipid myopathy.
 Treatment: very low-fat diet, avoidance of fasting, carnitine
and ketone body administration.
 List the abnormalities that can occur when there are defects in ketone
body generation and utilization
 Generation:
 Generally a problem with either HMG CoA synthase or
HMG CoA lyase.
 With HMG CoA synthase: hypoketotic hypoglycemia,
enlarged liver, no rise in ketones on fasting.
 With HMG CoA lyase: look for HMG CoA in the urine.
 Utilization:
 Can see severe metabolic acidosis from hyperketosis.
Can also see ketones in the fed state.
 [General first-line tests: urine organic acids, carnitine levels,
acylcarnitine analysis.]
3. Energy Disorders:




List the organs that can be affected, the metabolite abnormalities and
histological changes in muscle that are seen with a genetic
mitochondrial disorder.
 Organs that can be affected: any.
 Metabolite abnormalities:
 Elevated lactate and pyruvate (particularly lactate,
moreso after exercise)
 Increased alanine
 Increased Krebs cycle metabolites
 Decreased carnitine in muscle
 Histological changes:
 Ragged red fibers in muscle fiber biopsy beneath the
sarcolemma.
 Possibly crystalline inclusions on electron microscopy.
[Old stuff on mitochondria disorders:]
 Recall that mitochondria have their own, circular, DNA, the vast
majority of which encode proteins needed for the electron transport
chain and oxidative phosphorylation.
 Recall also that both nuclear DNA and mitochondrial proteins do
service in mitochondrial function; sort of a delicate dance
between them. Like anything delicate it's easy to break.
 Here's the fun thing: different mitochondria can have different
mitochondrial genomes. In the same cell you can have literally
thousands of mitochondrial genomes. This means that the
abnormal mitochondrial genotype in distributed throughout a
given percentage of the mitochondria in a cell. Past a certain
critical threshold (varies based on organ type), you're going to
get pathology.
 Note this means that affected mitochondria can be unevenly
divided in cell divisions, which means you can be largely
asymptomatic but have a kid who has severe disease. This
concept is called the "bottleneck syndrome," for reasons that
aren't clear to me.
 Note also that your (somatic) mitochondria accumulate genetic
defects as they go on.
 Recall that your mitochondria are inherited solely from the
mother.
 Histologically, you often see mitochondrial proliferation in the
muscles, which under the normal stains show up as "ragged red fibers"
near the sarcolemma. He mentioned these as significant.
 Describe the clinical features of Leigh disease and the genetic causes
 Affects the most energy-consuming nuclei in the brain:
 Basal ganglia
 Periaqueductal gray
 Dentate nucleus (cerebellum)
 See loss of neurons, microvessel proliferation
 Clinically: developmental delay, relapsing-remitting course;
ataxia, athetosis, dystonia, spasticity, nystagmus, optic
atrophy, ophthalmoplegia, and respiratory abnormalities.

Causes: pyruvate dehydrogenase deficiency, pyruvate
carboxylase deficiency, complexes I-V in the electron transport
chain; all different kinds of causes and inheritances.
Lysosomal Storage Disorders
Thursday, November 20, 2008
7:34 AM
Lysosomal Storage Disorders, 11/20/08:
1. Describe the basic pathophysiology of lysosomal storage disorders.
 You basically can't break a certain type of molecule down in your
lysosomes due to an enzyme defect. Most commonly the molecule is
something like a sphingolipid, but it can be just about anything (lots of
things are degraded in lysosomes). Note that LSDs can also be due to
defects in lysosome construction or transport, but they're more rare.
 This doesn't mean the molecule is toxic; it's more like you can't throw
away a given disposable thing in your house (take bottle caps as an
example). The bottle caps won't hurt you, but eventually you're not
going to be able to move much (or, past a certain point, eat or
breathe) because those damn things are everywhere.
 The lysosomes swell over time due to the fact that they're chock-full of
stuff, and interfere with normal cell function.
 Lysosomes are found in more or less all cells, so this is a big problem.
 Note these are all progressive diseases. Most, if not all, cause
irreversible damage.
2. Describe the common clinical presentations of lysosomal storage disorders.
 Most important (underlined):
 Coarse skin
 Macrocephaly
 Regression of motor and cognitive skills
 Clouding of the cornea
 "Cherry-red spot" on the retina (in Tay-Sachs and others)
 Macroglossia (enlarged tongue)
 Hepatosplenomegaly
 Joint stiffness
 Dysostosis multiplex (skeletal broadening, particularly in
vertebrae and fingers)
 Growth retardation
 Not underlined:
 Mental disturbance, seizures, hirsutism, sleep problems,
cardiomyopathy, hearing loss, etc, etc (full list in the slides).
3. Describe the general approach to diagnosis and treatment of lysosomal storage
disorders.
 Diagnosis:
 Clinical suspicion
 Biochemical screening tests (blood/urine tests)
 Confirmation by enzyme assay (white blood cell or cell culture)
 Confirmation by genetic analysis to detect mutations
 Confirmation by tissue biopsy
 Sometimes MRI of brain
Treatment:
 Bone marrow transplant or hematopoietic stem cell transplant
(must be done early) is a traditional approach and sometimes
works.
 More recently, we've been trying enzyme replacement therapy:
works for Gaucher's and a few others. Can reverse some of the
peripheral damage (but the enzymes can't cross BBB, so no
effect in brain). Can also be combined with the transplant
option. Extremely expensive (> $15,000 per month).
 Substrate reduction therapy: bind and excrete most of the
substance being stored with glycolipid inhibitors (some can
cross BBB) to reduce accumulation in tissues.
 Supportive/preventative care (treat symptomatically).
4. Describe the clinical symptoms, cause, and treatment of a selected group
(sphingolipidoses) of lysosomal storage disorders, including Gaucher, Tay-Sachs,
Fabry and Nieman-Pick Disease A/B.
 Gaucher's Disease:
 3 types:
 Type 1: Bone disease, no CNS disease
 Type 2: CNS disease, no bone disease
 Type 3: Both CNS and bone disease
 Clinical signs/symptoms of type I:
 Variable age of onset
 Normal life expectancy for the most part
 Look for Gaucher cells (large, foamy macrophages) in
bone marrow
 Hepatosplenomegaly
 Pathological bone fractures
 Bleeding disorders (nosebleeds)
 Bone pain (look for femoral head necrosis)
 GI, respiratory, cardiovascular, and skin symptoms as
well.
 On X-ray: look for Erlenmeyer flask deformities in
long bones.
 Clinical signs/symptoms of type II:
 More severe (survival beyond 2 years is rare)
 Symptoms are mainly in the CNS, but also ocular,
musculoskeletal, GI, and respiratory.
 Clinical signs/symptoms of type III:
 Often more severe and more rapidly progressive.
 CNS symptoms plus femoral head necrosis and ocular
problems.
 Treatment: mainly enzyme replacement therapy for type I; it's
less effective for II and doesn't work in III (can try bone
marrow transplant instead). In type I can also use substrate
inhibition therapy.


Tay-Sachs:
 3 types:
 Infantile form (onset 3-6 months): complete deficiency
of enzyme
Juvenile form (onset 2-10 years): partial deficiency of
enzyme
 Adult form (onset after 20): smaller partial deficiency of
enzyme
Clinical signs/symptoms:
 Cherry-red spot on retina (early blindness)
 Neurological symptoms: progressive mental and motor
deterioration, seizures.
 Increased 'startling' response (increased auditory
reception in a given frequency)
 Note that bones and peripheral organs aren't involved.
 No hepatosplenomegaly.
 In acute (infantile) form, death is frequent before 4
years.
(More severe form is called Sandhoff's: no betahexosaminidase A or B; see hepatosplenomegaly.)
Treatment:
 Supportive/preventive. Enzyme replacement and bone
marrow transplant don't work. Substrate reduction is in
trial.





Fabry disease:
 Clinical signs/symptoms:
 X-linked recessive, so mainly in males, but carrier
females can be partially affected too.
 Corneal opacity
 Intermittent pain in fingers and feet
 Fever
 Heat/cold intolerance
 Progressive renal insufficiency
 Diagnosis: symptoms, enzyme testing
 Treatment: enzyme replacement therapy. Very effective.

Nieman-Pick Disease A and B:
 Type A: more severe, CNS involvement
 Type B: less severe
 Clinical signs/symptoms:
 Significant hepatosplenomegaly
 Fatty deposits in the skin
 Cherry red spots in retina
 Mental retardation
 Growth delays
 Diagnosis: clinical and enzyme assay.
 Treatment: enzyme replacement therapy. Bone marrow
transplant doesn't work.
[Other notes from the last part, not on new LOs:]
 Gaucher's:
o Enzyme defect is acid-beta-glucosylceramidase
o Gene: autosomal recessive inheritance, GA gene 1q21
o 1/40,000 births
o High incidence in Ashkenazi Jewish population
 Tay-Sach's:


 Enzyme defect is beta-hexosaminidase A
 1/201,000 births
 Higher incidence in Ashkenazi Jewish population
Fabry's:
 Enzyme defect in alpha-galactosidase
 1/117,000 live births
 Inherited in an X-linked recessive fashion (one of only two X-linked
LSDs, with Hunter's), so all males affected. Carrier females can be
affected to some extent.
Nieman-Pick:
 Enzyme defect in acid sphingomyelinase
 Autosomal recessive
 1/248,000 live births
 Higher in Ashkenazi Jews
Introduction to Nutrition in Medicine / Nutrition and Public
Health
Thursday, November 20, 2008
8:58 AM
Introduction to Nutrition in Medicine / Nutrition and Public Health,
11/20/08:
[Given the last several days, I'm glad to have a slightly fuzzier topic.. but really you
should just read her notes, it's 6 pages and not heavy going and I could easily have
missed something here she considers important.]
1. Describe situations that place a patient at risk for nutritional problems.
 Her slide:
 Very young
 Very old
 Underweight
 Nutritional losses (eg. chronic diarrhea or vomiting)
 "Hypermetabolic" (eg. sepsis, trauma, major burns, etc)
 Alcoholic
 Impoverished
 Altered mental capacity
 Chronic illness (diabetes, IBD, hyperlipidemia, hypertension,
etc)
2. Identify and describe the components of nutrition assessment.
 History of illness, food intake
 Anthropometrics: length or height, weight, head circumference in
infants, waist circumference, etc.
 Physical exam and clinical symptoms
 Labs
3. Describe 3 methods of obtaining diet intake information: questions to be asked,
content to be seeking.
 Qualititative: either more open ("tell me about your diet") or more
focused ("how's your weight/activity levels been changing?" and look
for variety and/or excess). Latter approach is abbreviated WAVE
(weight, activity, variety, excess).

Semi-quantitative:
 Type A: 24-hr recall or "a typical day"
 Type B: written diet program over multiple days
 Never ever declare someone nutritionally deficient based on diet
history alone.
 What you're looking for:
 Is this person getting enough variety in their diet?
 Are they eating too much or not enough?
 How does what they're eating dovetail with what the patient's
problems are?
4. Define nutrient requirement and allowance and the RDA's.
 RDA: requirement is enough to satisfy the nutritional needs of 95% of
the population (2 SD's above the mean). Used to establish goal intake
for healthy individuals.
 EAR (estimated average requirement): requirement is enough to
satisfy the nutritional needs of 50% of the population. Used to
establish goal intake for a group.
5. Describe key messages of the US Dietary Guidelines (DG) and the rationale behind
each.
 Consume nutrient-dense foods/beverages from a wide variety of food
groups.
 Consume less sugar, salt, trans/saturated fats, cholesterol, and
alcohol.
 Get your adequate nutrients by a balanced eating pattern:
 Recall that the DASH diet (fruit, veggies, low-fat dairy, whole
grain, poultry, fish, nuts, with small amounts of red meat,
sweets, and total/saturated fat) was significantly effective at
reducing heart disease.
 Thing is you can't isolate any one element-- you need to eat a
range of healthy stuff.
 Balance your caloric intake with caloric expenditure. Small decreases
in caloric intake and small increases in physical activity prevent
gradual weight gain over time.
 Do physical activity.
 To reduce risk of chronic disease: more than 30 minutes of
moderate physical activity, most days of the week.
 To prevent gradual weight gain: more than 60 minutes of
moderate+ physical activity most days of the week.
 To sustain weight loss: 60-90 minutes of moderate physical
activity most days of the week.
 Eat fruits and veggies, get a good variety and go for bright colors.
 Eat < 10% fat calories from saturated fats.
 Eat < 300 mg/day of cholesterol.
 Don't eat trans fats.
 Eat whole grain, fiber-rich carbohydrates.
 Don't eat a lot of sugar.
 Don't drink too much (more than 1 drink per day for gals, 2 for guys, 5
for med students)
6. Describe how current typical dietary patterns and food choices in U.S. differ from
DG.
 No one eats fruits. Note fruit intake is directly correlated to triglyceride
levels.

We eat pretty crappy veggies: iceberg lettuce and (mainly) French
fries.
 No one eats a lot of whole grains.
 Fat intake is more or less within range for total fat, but we eat too
much saturated fat. Cholesterol is actually more or less okay on
average.
 We screw up with added sweetener, particularly high fructose corn
syrup.
 We eat way too much salt. It tastes good!
7. Describe how the new USDA food guide (MyPyramid) complements the messages
in the DG.
 You've got different colors in the pyramid. They indicate different kinds
of food and how much you should be eating.
 I can't think they would ask us this. Nevertheless:
 Orange is carbs. Green is veggies. Red is fruits. Blue is
dairy. Yellow is oil and fat. Purple is meat and beans.
 There's steps on the side to indicate physical activity.
 The bottom of the pyramid has stuff with lots of sugar, the stuff at the
bottom has a little. In order to eat the stuff at the top you have to
climb the steps on the side. Ya.
 Evidently it promotes "one size doesn't fit all." Not sure how.
8. Discuss 3 benefits of a diet rich in whole grains, vegetables, and fruits for
promoting health.
 Decrease risk of heart disease, cancer, type 2 diabetes, hypertension,
and stroke.
Fat Soluble Vitamins
Thursday, November 20, 2008
11:06 AM
Fat Soluble Vitamins, 11/20/08:

[General notes on fat-soluble vitamins:]
o Accumulated in stores in the body.
o Need intact fat digestion/absorption system for intake; also need
carrier system to transport them in the blood.
o Can be toxic with excessive intake.
o "Number one best buy" for fixing the world's problems per dollar:
micronutrient supplementation, particularly vitamin A and zinc.
Note she has a helpful "symptom to deficiency" chart at the end of her notes.
1. For each of the vitamins discussed in class, describe the biochemical functions and
major physiologic metabolic roles, major dietary sources, and characteristic
deficiency findings.
 Vitamin A:
 Promotes gene response through retinoic acid receptors.
 Functions:
 Essential for phototransduction in retinal rods
 Maintains conjunctival membranes and cornea
 Differentiation and proliferation of epithelial cells






Dietary sources:
 Preformed only in animal fats:
 Liver
 Butterfat
 Egg yolks
 Note can get toxicity from preformed A.
 As precursor beta-carotene:
 Deep green and deep yellow vegetables
 Note beta-carotene isn't toxic.
Deficiency findings:
 Night blindness
 Dry eyes (xerophthalmia): vitamin A deficiency is the
leading cause of blindness in the world.
 Look for "Bitot's spot" (white, foamy change in
conjunctiva).
 It's getting really serious when it goes into the
cornea.
 Increased susceptibility to infection, esp. diarrhea and
measles.
Could reduce child mortality 23-34% in developing world with
vitamin A supplements.
Stored in liver, in stellate cells.
Toxicity: can increase intracranial pressure and associated
symptoms, plus bone pain and hepatomegaly (extensive
damage to the liver).
Vitamin D:
 Functions:
 Maintains intra/extracellular calcium balance
 Stimulates absorption, renal reabsorption, and bone
mobilization of Ca++ and phosphorus
 Important for immune function of monocytes and
leukocytes, decreases incidence of autoimmune
disorders.
 Functions more like a hormone than a vitamin.
 Dietary sources:
 Main source isn't from diet but from synthesis.
Dehydrocholesterol is stored in skin; it's converted to
vitamin D3 (cholecalciferol) by UV radiation. Skin
pigmentation and sunblock reduces this conversion.
 Specifically, D3 is activated to 25-OH D by the
liver and 1,25-OH D by the kidney. 1,25 is the
fully active form.
 In diet: fish liver oils, fatty fish, egg yolks; fortified milk
and formulas.
 Deficiency findings:
 Ricketts: cartilage and calcifications don't mature. Look
for "rachitic rosary" (knobs) on ribs, bowed legs,
widened wrists, bone pain, fractures.
 See low calcium, low phosphorus, high alkaline
phosphorus, low activated vitamin D level, high PTH
 Can show seizures.
At risk: dark-skinned or minimal-sunlight-exposure
patients, solely breastfed infants, liver or kidney
disease, or obesity.
Toxicity: hypercalcemia, soft tissue calcification, vomiting,
seizures. Note that UV exposure isn't going to cause toxicity-this is due to supplementation.



Vitamin E:
 Functions:
 Antioxidant/free radical scavenger; stabilizes cell
membranes.
 Dietary sources:
 Polyunsaturated vegetable oils
 Wheat germ
 Deficiency findings:
 Neurological degeneration (loss of proprioception and
vibratory sense, loss of DTRs), hemolytic anemia
 At risk: fat malabsorption syndromes, some premature
infants
 Low toxicity, though large doses can inhibit blood clotting
factors.

Vitamin K:
 Functions:
 Carboxylates/forms coagulation proteins II, VII, IX, and
X.
 Also necessary for Protein C and S synthesis.
 Also necessary for bone synthesis.
 Dietary sources:
 Leafy green vegetables, fruits, seeds.
 It's also synthesized by intestinal bacteria.
 Deficiency findings:
 Prolonged coag times (INR)
 Hemorrhagic disease of the newborn
 Purpura
 GI/CNS bleeds
 At risk: newborns, late-born infants, especially
breastfed, fat malabsorption syndromes, chronic
antibiotic use.
 All newborns should receive a single intramuscular dose of
vitamin K.
2. Be able to
high.





identify circumstances in which risk of vitamin deficiency or toxicity is
Inadequate food intake or intake of only one type of food
Increased nutrient requirements
Increased metabolic demands
Maldigestion (cystic fibrosis) or malabsorption (celiac disease)
Drug-nutrient and treatment-nutrient interactions
Water-Soluble Vitamins
Thursday, November 20, 2008
11:09 AM
Water-Soluble Vitamins, 11/21/08:

[General notes on water-soluble vitamins:]
o Note water-soluble vitamins aren't stored in the body except for B12;
absorption from the GI tract is high.
o Note B6 can be toxic in excess, but the rest are more or less nontoxic.
o Water-soluble vitamins are usually excreted in urine.
o Note water-soluble vitamins are generally transmitted through breast
milk to kids.
1. For each of the vitamins discussed in class, describe the biochemical functions and
major physiologic metabolic roles, major dietary sources, and characteristic
deficiency findings.
 Thiamine (B1):
 Functions:
 Thiamine is an essential cofactor for lots of reactions-glycolysis, TCA, AA metabolism, etc. It's used in
particular for decarboxylation and transketolation
reactions.
 May help nerve conduction as well.
 Dietary sources:
 Found all over; abundant only in whole or enriched
grains, lean pork, and legumes (beans/peas/etc).
 Deficiency findings:
 Classically, thiamine deficiency leads to beriberi:
 Dry beriberi: peripheral neuropathy,
sensory/motor impairment. Preferentially affects
distal limbs, esp. legs. Weakness, atrophy.
 Wet beriberi: edema, dilated cardiomyopathy,
and CHF, additionally can have symptoms of dry
beriberi.
 Cerebral beriberi or Wernicke-Korsakoff's: as
discussed in Neuro, ataxia, nystagmus, amnesia,
confabulations. Note that this can cause
irreversible damage (only a quarter of patients
recover fully with thiamine administration).
 Alcoholics are at risk of deficiency, as are the elderly,
anorexics, and bariatric surgery patients (perhaps due to
sudden weight loss?).
 Note that sudden refeeding after prolonged deficiency
can acutely worsen the condition by depleting the small
amount of thiamine left-- which is why you give
thiamine with IV glucose in the ED.
 Riboflavin (B2):
 Functions:
 An essential part of FAD/FADH2 and FMN, both
important in oxidation-reduction reactions in the TCA
cycle and electron transport.
Also involved in amino acid and fatty acid metabolism.
Also involved in vitamin K, folate, B6, and niacin
metabolism.
 Dietary sources:
 Mainly dairy products.
 Also meat, poultry, liver, and wheat germ
 Deficiency findings:
 Cracking of lips (cheilosis)
 Sores at corners of mouth (angular stomatitis)
 Increased vascularization of the conjunctiva and some
night blindness
 Note all of these can be caused by multiple B vitamin
deficiencies.
 At risk: people who don't ingest any milk, or patients
with malabsorption, diarrhea, or excess UV light
exposure.
Niacin (B3):
 Functions:
 An essential part of NAD and NADP; thus important for
pretty much every energy metabolism pathway.
 Dietary sources:
 Preformed niacin: meats, poultry, fish, peanut butter,
legumes
 Tryptophan (precursor): milk and eggs
 Deficiency findings:
 Pellagra:
 4 D's:
 Diarrhea
 Dermatitis (symmetric, scaling rash with
light and dark areas, aggravated in areas
exposed to the sun)
 "Casal's necklace:" dermatitis in
ring pattern around neck due to
sun exposure.
 Note that rash in Kwashiorkor's is
similar ("pellagroid").
 Dementia
 Death (niacin deficiency is fatal)
 See it in alcoholics, people who consume diets that
mainly consist in corn or extremely restricted diets, and
in breastfed infants of deficient mothers.
 Also at risk: people who have carcinoid tumors (secrete
lots of serotonin; this diverts the tryptophan away from
niacin production into serotonin production, causing
niacin deficiency).
Vitamin C (ascorbic acid):
 Functions:
 Antioxidant/reducing agent (prevention of
methemoglobinemia)
 Note that vitamins C and E are sort of
interchangeable, at least as far as their
antioxidant properties go-- an abundance of one





can partially make up for a deficiency of the
other.
 Essential for proper collagen formation (hydroxylation of
proline and lysine, as mentioned before)
 Essential for carnitine acyltransferase formation
 Essential for norepinephrine and serotonin synthesis
 Note that it is involved in chemotaxis and has
antihistamine effects-- may decrease duration of cold
symptoms by a day or so.
 Dietary sources:
 Fruits and veggies; not in grains, meat, or dairy.
 Note that when cooked/dried, most vitamin C is
lost.
 Absorption is a saturable process, but only at extremely
high intakes. If you want to take a lot of vitamin C, use
a slow-release capsule or take a lot of smaller doses.
Note that above about 500 mg/day, you just urinate out
the difference. Note that you only need about 10
mg/day to prevent scurvy.
 A typical pool of vitamin C (1500 mg) will ward off
scurvy for about a month to a month and a half.
 Note that C is better absorbed from foods than from
supplements.
 Deficiency findings:
 Scurvy:
 Defective collagen in basement membrane:
bleeding gums, easy bruises, and petechiae
(non-blanching rash, particularly around hair
follicles).
 Hyperkeratosis of hair follicles, depression,
weakness, anemia, joint/bone/muscle pain.
 At risk: infants fed cow's milk without supplementation,
burn/wound victims (more need for collagen synthesis),
diets without fruits and vegetables.
 True story: at my first college out west, the year
after I left there was a guy who actually got
scurvy. Presumably a computer science major.
 In principle, you can get renal oxaloacetate stones if you chug a
bottle of tablets a day. Can also get "rebound" scurvy if you are
taking a high dose and suddenly go off.
Folate (B9):
 Functions:
 Essential for THF formation and thus 1-carbon transfers- which is necessary for lots of things, but of note the
synthesis of nucleic acid and the regeneration of
methionine from homocysteine.
 Dietary sources:
 Deep green leafy vegetables, whole grains, orange juice,
broccoli.
 Prolonged cooking destroys the folate.
 Deficiency findings:
 Neural tube defects in pregnant women (note RDA
requirement for pregnancy goes up).
Macrocytic anemia, hypersegmented neutrophils
Glossitis, increased plasma homocysteine (can cause
coagulation, etc, problems)
 At risk: chronic hemolytic anemia or blood loss patients,
infants fed goat's milk without supplementation,
premature infants
Cobalamin (B12):
 Functions:
 Used in THF hydrogenation/reactions and metabolism of
odd chain-length fatty acids (catalyze methylmalonyl
CoA to succinyl CoA).
 Essential for nucleic acid synthesis.
 Dietary sources:
 Animal products only (watch out for deficiency in strict
vegans)
 Recall that the absorption is complex. Note that her
description of it doesn't match what Dr. Peterson said
earlier. I think the important points are: need IF, IF is
secreted by stomach, it's absorbed in the terminal
ileum.
 So watch out for Crohn's, gastric bypass or
atrophy, ileal or gastric resection, etc.
 Note that B12 is the one water-soluble vitamin that's
stored well in the body.
 Deficiency findings:
 Macrocytic anemia, hypersegmented PMNs
 Neurological symptoms (often irreversible):
numbness/tingling, gait problems, depression.
 "Pernicious anemia" is the non-secretion of IF by the
parietal cells.
Pyroxidine (B6):
 Functions:
 Necessary for amino acid metabolism (transaminases)
 Dietary sources:
 Animal products, vegetables, whole grains
 Deficiency findings:
 Anemia, seizures, glossitis, maybe depression
 At risk: patients taking isoniazid
 Note that B6 is the only water-soluble vitamin that can reach
toxic levels pretty easily (500 mg/day): get a bunch of
neurological effects (ataxia, fine touch/vibration sensory loss).
Note that folate, cobalamin, and B6 are necessary for methionine
regeneration from homocysteine-- deficiencies in these vitamins can
cause hyperhomocysteinemia, which can lead to atherosclerosis,
thrombus formation, etc.
Remark the table from her notes, p 4, for an excellent and testable
summary matching symptoms to deficiencies (I'd put it here but it
doesn't copy well).
identify circumstances in which risk of vitamin deficiency or toxicity is






2. Be able to
high.
 See last lecture's LOs.
Trace Minerals
Friday, November 21, 2008
9:05 AM
Trace Minerals, 11/21/08:
(called "trace" because you need less than 100 mg/day)
For iron and zinc only:
1. Describe physiologic functions, dietary sources, and factors that affect
bioavailability.
 Iron:
 Functions:
 Oxygen transport in hemoglobin (RBCs) and
myoglobin (muscle)
 Electron transfer enzymes (cytochromes)
 Enzymes for activation of oxygen and respiratory burst
in PMNs
 Enzymes for dopamine synthesis and CNS myelination.
 Dietary sources:
 Iron contained in heme: cellular animal protein
(meats, poultry, liver); not milk (either human or
animal).
 Iron not contained in heme: legumes, nuts, whole
grains, leafy greens
 Bioavailability:
 Much better from animal sources (heme) than from nonanimal sources.
 Insoluble complexes in plant matter inhibit absorption
(eg. phytate, oxalate, fiber, etc)-- phytate is the storage
form of phosphorus in plants, but we can't break it
down. It binds zinc, iron, and calcium in the intestine
and can cause mineral deficiency.
 By contrast, iron is better absorbed when it's around
vitamin C.
 Note that there's no way of quickly getting rid of iron-once it's absorbed, it's more or less retained. So
regulation of iron takes place largely at the enterocyte
(absorption) level.
 Iron deficiency increases iron uptake.
 Inflammation causes hepcidin release, which
decreases absorption.
 Zinc:
 Functions:
 Regulation of gene expression through zinc finger
proteins
 Membrane structure and stability
 Various metalloenzymes
Extremely important for tissue proliferation
(development, immune system, wound healing, tissue
integrity).
 Necessary for sense of taste, sexual maturation,
immune function, normal growth.
 Dietary sources:
 All over, but mainly in animal products (beef > poultry >
fish > milk).
 Bioavailability:
 Lower absorption from plant foods; again, absorption is
inhibited by phytate.
 Note that absorption is not increased with deficiency (as
opposed to iron).
2. Describe key aspects of homeostasis, and compare/contrast differences in
homeostasis among these traces minerals.
 Iron:
 As mentioned, regulated at the absorption level only.
 Iron in transferrin: transport form.
 Iron in ferritin: storage form (hemosiderin: aggregated
ferritin).
 Iron storage is about 300-1000 mg for women, 500-1500 for
men; overload disorders start happening above 40-50,000 mg.
 Zinc:
 Unlike iron, both excretion and absorption are regulated (it
goes out into the GI tract in pancreatic or biliary secretions).
3. Describe etiology and consequences of deficiency, and comment on prevalence of
deficiency.
 Iron:
 Iron deficiency is the most common nutritional deficiency in the
world.
 At-risk: premature infants or infants > 6 months, adolescent
women, pregnant women, people with chronic disease or
helminthic infestations.
 If you see iron deficiency in a man or a post-menopausal
woman, work them up for bleeds.
 Clinically:
 Microcytic, hypochromic anemia, fatigue, impaired
cognitive function (irreversible) and impaired growth.
 Look for low Hb/hematocrit, along with low ferritin
(though this can be higher during inflammation so check
CRP).
 To find this before it gets to anemia: check TIBC (total iron
binding capacity) and transferrin % saturation: a high TIBC and
low transferrin saturation indicates a deficiency.
 Zinc:
 Extremely widespread cause of stunted growth in the
developing world; along with vitamin A, an extremely costeffective way of decreasing infant mortality.
 At risk: infants and young children (high growth rate/need for
zinc), particularly breastfed infants (human milk is low in Zinc
compared to need); also pregnant women, anyone on a
monotonous or plant-based diet, anyone with chronic diarrhea,
anyone with wounds or burns.


Clinically:
 Mild deficiency: growth/developing delays, impaired
immune function.
 Moderate to severe deficiency: severe dermatitis,
immune dysfunction, anorexia, diarrhea.
 Note a condition called Acrodermatitis enteropathica: inherited
defect in zinc transporters in the enterocytes. It's fatal if
untreated, but will respond to high levels of zinc
supplementation. Presents with severe dermatitis, diarrhea,
growth failure.
4. Describe and compare toxicity potential.
 Iron:
 As mentioned, above 40-50,000 mg you start getting
hemochromatosis symptoms (liver toxicity, heart damage, etc).
 Be very careful about giving IV iron infusions (bypasses
regulation at enterocyte).
 Excess iron can interfere with zinc and copper absorption. Don't
generally supplement unless it's needed.
 Note a condition called hereditary hemochromatosis: inability to
regulate iron uptake with hepcidin, get increased iron stores
over time.
 Acute Fe overdose: shock, liver failure, hemorrhagic GI
symptoms. You can kill a kid with about 1-2 grams of iron (not
recommended).
 Zinc:
 Not much toxicity; possibly lowers HDL and impairs iron/copper
absorption, with diarrhea and nausea.
Malnutrition
Friday, November 21, 2008
10:02 AM
Malnutrition, 11/21/08:
[Again, might be high-yield to read through her notes: they're pretty concise (3
pages) and I may have missed something.]
1. Define malnutrition; describe its environmental and biological causes & clinical
consequences.
 PEM (protein energy malnutrition):
 20% world's children (at 5 years) underweight, 32% stunted
(much more common and much more problematic), 3.5%
wasted.
 50% of child deaths are related to malnutrition.
 Caused by about what you'd expect. For the record, the US
could produce enough grain by itself to feed everyone on the
planet. Of course, we'd need to stop eating such obscene
amounts of meat. Oh, well, who cares about starving children
when we've got hamburgers?
 Wasting: low weight relative to length; stunting: low height for age.

She makes a big deal of the difference. Note you can be malnourished
while still being within normal weight limits and/or not looking skinny.
2. Compare and contrast energy and substrate metabolism in short term and long
term starvation.
 Short term: increased gluconeogenesis, breakdown of protein and
glycogen.
 Long term: increased used of fatty acids and ketone bodies.
3. Describe the pathophysiology and adaptive responses to PEM, and to compare and
contrast features of marasmus and kwashiorkor.
 Marasmus: term for severe wasting due to energy or across-theboard inadequacy of intake. Tends to be slower onset and better
adaptation. Marasmus usually refers to individuals who are on the
verge of decompensation.
 Endocrine changes (increased stress hormones, decreased
thyroid hormone and especially insulin), impaired GI
absorption.
 Loss of physiological ability to react to stress.
 Decreased metabolic rate (hypotension. bradycardia,
hypothermia).
 Kwashiorkor: term for edematous, non-wasting protein intake
inadequacy. Tends to be rapid-onset and poorly adapted to. Involves
oxidative and metabolic stress.
 Note distinction between someone who's starving and someone who's
cachexic:
 Starvation: organism adapts to conserve lean body mass,
increase fat metabolism. Reversed by feeding.
 Cachexia: associated with inflammatory or neoplastic
conditions; not reversed by feeding; associated with anorexia.
4. Identify likely physical exam findings associated with the two major types of
undernutrition.
 Marasmus:
 Generally responsive, alert children that are extremely
skinny/bony (loss of muscle and fat).
 Kwashiorkor:
 Edema (belly, limbs, face) secondary to hypoalbuminemia
 Not much loss of muscle or fat
 Flaky skin and rash
 Hair texture and pigmentation changes ("flag sign")
 Hepatomegaly
 "Miserable"
 Note mortality is much higher with Kwashiorkor.
5. Describe general appropriate treatment approaches to PEM.
 Most important: go slowly, preferably enteric feeding.
 Initially, give maintenance doses of food, not catch-up doses.
 Kwashiorkor: want to see resolution of the edema before full feeding.
6. Describe metabolic derangements associated with “refeeding syndrome.”
 Potassium, phosphorus, magnesium serum levels all decrease:
 Potassium: feeding leads to increased insulin secretion, leading
to a shift of potassium into cells (hypokalemia), causing altered
nerve/muscle function and potentially arrhythmias.
 Phosphorus: feeding leads to increased insulin secretion,
leading to a shift of phosphorus into cells ("increased
phosphorylated intermediates"?).

Magnesium: sudden increased metabolic rate increases the
requirement for magnesium.
Pediatric Obesity: Health Implications
Monday, November 24, 2008
7:36 AM
Pediatric Obesity: Health Implications, 11/24/08:
1. State the definitions and classification of childhood weight status, including use of
BMI-for-age charts.
 Overweight: BMI in the 85th-95th percentile for age and gender
 Obese: BMI > 95th percentile for age and gender
 Morbidly/'extremely' obese: BMI in the 99th or higher percentile for
age and gender
 Note obesity, by the above definition, is associated with increased
prevalence of comorbidities.
 Note BMI is a screening tool only -- it's not the same as a body
composition test. That said, it does correlate reasonably well in most
people with total body fat.
2. Describe the current demographics of childhood overweight & obesity, including
national rates, ethnic and age distributions.
 17% of children 2-19 years old in the US are obese.
 25-30% of children in the overweight range.
 Rates differ by age (currently 12-19 is a little heavier than 6-11) and
ethnicity (white kids are generally skinnier - by comparison - than
black or Hispanic kids, though it bounces around).
 No significant difference by gender.
 If you're obese from about age 7 or so on into adulthood, on average
you'll wind up with an adult BMI of 41-- which is morbid obesity with
its associated health consequences.
3. Describe the major co-morbidities associated with childhood obesity
 Pulmonary: obstructive sleep apnea (most common, often overlooked)
 Cardiovascular: hyperlipidemia, dyslipidemia, hypertension
 Metabolic Syndrome: increased triglycerides, increased insulin,
decreased HDL, hypertensions.
 Mental health: depression, low self-esteem
 Endocrine: type 2 diabetes (now about 30% of new pediatric diabetes
cases), menstrual irregularities
 GI: fatty liver disease
 Orthopedic: back, knee, ankle pain
 As mentioned, the prevalence of these in overweight or, especially,
obese children goes way up.
4. Describe key components of assessment including diet, physical activity, family
history (hx), review of systems, physical exam, positive and negative labs.
 Plot BMI at least every year for all children over 2 years old.
 Get FMH.
 Diet: about what you'd expect. Less sugar, particularly in drinks;
increased fruits and veggies; meal patterns; don't eat out as much;
reduce portion sizes; etc.

Sweetened drinks: reducing intake by 82% drops BMI
significantly.
 Physical exam: she makes the point of saying you can't tell BMI from
visual analysis. (That said, I think that treating people based on a
number that everyone admits is an only moderately accurate
screening tool, and against the evidence of your eyes, isn't such a
fantastic idea either.)
 Look for comorbidities with physical exam and ROS.
 Labs: possibly fasting lipids, LFTs, fasting glucose
5. Briefly describe treatment principles.
 Again, this more or less makes sense:
 Involve family, do joint decision-making, target a few specific
behaviors, etc.
 Physical activity is good.
Adult Obesity and the Metabolic Syndrome
Monday, November 24, 2008
9:06 AM
Adult Obesity and the Metabolic Syndrome, 11/24/08:
1. Define obesity using BMI and waist circumference.
 First-line assessment: BMI:
 BMI: weight in kilos, divided by height in meters squared.
 Same calculation for men and women, although BMI tends to
correlate with different body % fat for the two genders
(correlates to the same kind of health hazards, though).
 Overweight in adults: BMI 25 or higher.
 Obese in adults: BMI 30 or higher.
 BMI of over 40 is extreme obesity and correlates with very
high health risks.
 Note BMI is less accurate in the elderly, certain ethnic groups,
or people with lots of muscle mass.
 Second-line assessment: waist circumference:
 High medical risk: > 40 inches for men, > 35 inches for
women.
 Why: abdominal adiposity correlates most strongly to health
risks.
 Below BMI 35, risk due to high waist circumference is additive
with the BMI-associated risk.
 If BMI > 35, usually not necessary to measure waist (no
additional risk).
 Also look at weight change over time.
 66% of adults in the US are currently either overweight or obese.
 Note that I, by BMI, am overweight. I think that's retarded. So
I take all this end-of-the-world ballyhoo with a grain of salt.
Classic scenario of over-selling a valid point.
 Editorial: Doctors who deal with obesity have a really annoying
true-believer approach to lecture. After two hours of this I
actually want to go out and inhale a six-pack of Yoo-hoo just to
2.
3.
4.
5.
give the finger to smug self-righteous turds. News flash: so will
your patients. Don't be dicks.
 Further editorial: Look, I get that BMIs 25-30 are associated
with greater health risks. You know what else is? Living in a
city, driving in a car, and stepping outside. At some point you
have to decide where to stop pushing. If you push standards
with cutoffs based solely on increased health risks, your
patients are more likely to give up on it and you're more likely
to get disillusioned with all your 'noncompliant' patients. Don't
be dicks even when you have statistical backup.
List the health problems that are associated with obesity.
 Type 2 diabetes and increasing glucose resistance
 Dyslipidemia
 Coronary artery disease
 Sleep apnea
 Fatty liver disease
 Treatment: (she mentioned this was important to know)
 Diet and exercise therapy should be considered at BMIs of 2527 if a comorbidity is present, or without a comorbidity at BMIs
over 27.
 Medications should be considered at BMIs of 27-30 with a
comorbidity, or without a comorbidity at BMIs over 30.
 Surgery considered at BMIs of 35-40 with a comorbidity, or
even without a comorbidity at BMIs over 40.
 Note increasing BMI is related to both genetics and environment.
Define Metabolic Syndrome using the current AHA/NCEP definition.
 Essentially it's a clinical picture that arises from obesity and
corresponding insulin resistance and screams "this person is going to
develop heart disease."
 Need 3 out of the following 5 risk factors:
 (1) Waist circumference > 40 in men, > 35 in women
 (2) Hypertension
 (3) High triglycerides (>150)
 (4) Low HDL
 (5) Impaired fasting glucose (> 100)
Discuss the controversy over the use of the term "metabolic syndrome".
 Not mentioned.
List the steps in the clinical evaluation of the obese patient.
 Measure degree of adiposity
 Assess other existing risk factors
 Screen for complications of obesity
 Rule out other medical causes of obesity
 Assess readiness for treatment
Obesity Treatment: Diet and Physical Activity
Monday, November 24, 2008
9:53 AM
Obesity Treatment: Diet and Physical Activity, 11/24/08:
1. List the important components of a weight loss diet program.

Negative energy balance: reduce food intake, increase exercise.
Reducing food intake by 500-1000 kcal/day is easier for taking weight
off, exercise is important for keeping it off.
2. List three specific approaches that can be used in the office to help obese patients
change their diet.
 Decrease portion sizes (75% of normal)
 Meal replacements (bar, shake, Lean Cuisine)
 Commercial programs
 Self-monitoring: fat gram or calorie 'budget'
3. Define the amount of physical activity that is likely needed to prevent weight gain
and to produce a reduced weight in a previously obese person.
 Prevent weight gain: 30 minutes of vigorous activity per day, 60
minutes of moderate activity per day. She cites 60-90 minutes per
day in lecture; 30 minutes is evidently just for heart health (which..
er.. is the reason I thought we wanted people to reduce weight?).
 Reduce weight: 1-2 hours of vigorous activity per day (bicycling), 3-5
hours of moderate (walking).
 (this is why you usually use diet restriction, not exercise alone,
to reduce weight)
 To repeat: physical activity is critical to maintenance of reduced
weight. While it'll work for reducing the weight to begin with (and
maybe preserve lean mass at the expense of fat), most of us don't
have the time, so dietary restriction is a better option.
 There are a completely different set of recommendations in the slides
for both adults and kids. I'm not sure which she wants us to know.
4. Describe the use of a pedometer in clinical practice.
 Walking is, generally, pretty easy and not hard to fit into your daily
routine. By giving patients pedometers you can give them a hard
number to adjust for weight loss goals ("take 12 million steps before
Tuesday").
 Specifically she suggests raising people 500 steps/day per week up til
about 11-12,000 steps per day. That's about 2 hours a day.
5. List the things that individuals in the National Weight Control Registry do to help
maintain a reduced state.
 Increased carbohydrates, decreasing fat (keep in mind this is to
maintain weight, not reduce it actively)
 Frequent self-monitoring (record intake, check body weight)
 Eating breakfast
 Lots of physical activity (an hour a day or so)
 Limiting TV watching
Community Approaches to Obesity Prevention
Monday, November 24, 2008
10:58 AM
Community Approaches to Obesity Prevention, 11/24/08:
[Just read his slides. This is like being bitten to death by butterflies.]
[Again, go read "Nudge" by Sunstein and Thaler and read the section on health for a
much more entertaining and well-referenced discussion of this.]
1. Describe the epidemiology of obesity including time trends and groups that are
particularly affected.
 Going up for everybody at about the same rate. It's still higher in
lower-income groups, for whom interventions on an individual basis
are often less feasible.
2. Suggest evidence-based approaches to prevent diabetes/obesity at the individual
and population levels based on the results of the DPP.
 Obesity:
 Individual diet and lifestyle modifications are ok, a little better
with meds.
 When you add in group-style behavioral modifications, it gets
better.
 Diabetes:
 Individual diet and lifestyle modifications outperform meds
alone. Note that a 4% sustained weight loss due to lifestyle
modifications reduces type 2 diabetes risk by around 60%.
3. Recognize public health factors which have contributed to the increase in the
prevalence and incidence of these two diseases over the past 20 years including food
costs, food portion size and time spent in sedentary activities.
 He more or less just mentioned them.
 "Obesity appears to spread through social ties."
4. List the strategies that could be used at the environmental, population and
community level to combat obesity and diabetes.
 Environmental changes that affect behavior without choice: healthy
defaults (change the food supply, increase distance to parking/dropoff, etc).
 Environmental changes that support behavior changes: improve
environment, make walkable communities, healthy-food vending
machines (see this season of "The Office" for Dwight Schrute's take on
this), incentives at work, make healthy foods cheaper.
 How you'd like to start: take off about 100 kcal/day to prevent further
weight gain.
5. Discuss the relative efficacy and cost effectiveness of individual based prevention
strategies versus community based strategies for these conditions.
 OH GOD I'M DYING OF BOREDOM AND HE JUST KEEPS TALKING
 Oh, sorry. I mean, it's more cost-effective to work at this on a societal
level.
6. Describe and discuss work that is being done in public health by local researchers
to try to overcome some of these barriers.
 Suggested: slightly less fat, smaller portions, more fiber, less sugary
beverages, lower energy density foods.
 Menu labeling with caloric content
 One common 'good for you' smart-choices label on foods with
particular nutritional cutoffs.
7. Describe possible directions and future frontiers in individual and population
prevention.
 Yeah.
Obesity Treatment: Drugs, Surgical Options and Popular
Diets
Tuesday, November 25, 2008
7:59 AM
Obesity Treatment: Drugs, Surgical Options, and Popular Diets, 11/25/08:
1. List the medications that are currently available for the treatment of obesity,
describe their efficacy, mechanisms of action, and list their side effects.
 Sibutramine:
 Efficacy: gets weight off (5-10% body weight), keeps it off as
long as you're taking the drug. Also reduces triglycerides,
raises HDL cholesterol, and reduces weight circumference.
Works better in combination with diets-- a lot better, actually
(can get up to 20% weight reduction).
 Mechanism of action: NE/serotonin reuptake inhibitor (SNRI);
inhibits appetite.
 Side effects: dry mouth, constipation, insomnia, dizziness, HTN,
tachycardia
 The one you worry about is HTN-- rare but need to
watch for it. Shouldn't prescribe for uncontrolled HTN,
can use in controlled HTN.
 Orlistat:
 Efficacy: 5-8% weight loss. Approved for long-term use.
Reduces fasting glucose and HbA1c as well-- good for lowering
risk of type 2 diabetes.
 Mechanism of action: pancreatic lipase inhibitor: can't break
down dietary fats.
 Side effects: oily stools and urgency. The OTC version (Alli)
reduces effective levels of warfarin and cyclosporin.
 Phentermine:
 Efficacy: 5-8% weight loss. Note it's currently FDA-approved for
only 3 months use at a time. Most widely prescribed and
cheapest.
 Mechanism of action: increases norepinephrine content in brain.
Similar to amphetamines, but non-addictive.
 Side effects: HTN, headache, nervousness.
2. List the medications that are used for other health problems that contribute to
weight gain and describe an approach to minimizing this problem.
 Some anti-diabetic meds: sulfonylureas, insulin, TZDs
 Mood stabilizers and antipsychotics
 Oral contraceptives, Depo shots
 Glucocorticoids
 What to do: about what you'd expect (diet, change meds, lower dose,
figure out if the weight gain is worth the benefits of the drug).
3. List the benefits and risks of gastric bypass surgery and laparoscopic banding.
 Benefits:
 Long-term weight loss with both (30% with bypass, 20-25%
with banding)
 Good reduction in overall mortality (MI and cancer) and
diabetes (one outstanding study = 83% resolution of diabetes
and no new diabetes development).

Reduces hypertension, sleep apnea, reflex, urinary
incontinence.
 Short-term risk:
 Death:
 Bypass: 0-2% death within 30 days (another 1% or so
within 2 years).
 Banding: much lower death rate. Generally banding is
done more.
 Sometimes it doesn't produce weight loss.
 Pulmonary embolus
 Sepsis
 Wound problems
 Strictures
 Long-term risk:
 Diarrhea, vomiting, "dietary indiscretion"
 Vomiting without diarrhea (probably stricture)
 Ulcer
 Depression
 Protein/calorie malabsorption
 Folate/B12 deficiency
 Iron deficiency
4. Describe the patient who is best suited to both pharmacological and surgical
treatments for obesity.
 Pharmacological: BMI > 27 with co-morbidities or > 30 without comorbidities.
 Surgical: BMI > 35 with co-morbidities (diabetes, sleep apnea, reflex,
HTN, joint disease) or > 40 without co-morbidities. Also people in
whom other therapies have failed. Don't want anyone with serious
cardiac, pulmonary, or psychiatric disease.
Hormones and Receptors
Monday, December 01, 2008
7:58 AM
Hormones and Receptors, 12/1/08:
[The relationship of notes to lecture to LOs is tenuous. I've tried to fit what he talked
about into the general rubric of one or the other LOs, but sometimes it clearly goes
way beyond what the LO is actually asking. Better safe than sorry. There's some
assorted notes at the bottom where what he talked about just didn't fit a thing. I'll
do the same thing for the next two lectures.]
[Note that these LOs are somewhat outdated and, as such, he may feel no reserve
about asking questions unrelated to them. Beware.]
1. Distinguish the structure of peptide, steroid and thyroid hormones.
 Hormones can be classified based on what their basic structure comes
from: (1) tyrosine, (2) cholesterol, or (3) peptides and proteins.


Tyrosine-based hormones: catecholamines and T4 (thyroxin)
Cholesterol-based hormones: cortisol, testosterone, estrogens,
aldosterone, vitamin D, progesterone
 Peptide-based: vasopressin, angiotensin, most hypothalamic
hormones
 Protein-based: insulin, glucagon, most anterior pituitary
hormones
 Note that the dividing line between peptides and proteins is
pretty thin.
 [Note that hormones can also be classified based on what their basic
function is: (1) water/mineral balance, (2) energy balance, (3) growth
regulation, or (4) reproductive function.]
 Water/mineral: ADH, aldosterone, vitamin D
 Energy balance: growth hormone, insulin, glucagon, cortisol
 Growth regulation: growth hormone, testosterone, estrogen
 Reproductive function: estrogen, testosterone, progesterone
 [Note that a single hormone can have multiple physiological
roles.]
2. Contrast the structures and cellular locations of the peptide and the
steroid/thyroid hormones types of receptors.
 Peptide receptors are, generally, on the surface of their target cells
(they need to be, since peptides can't permeate plasma membranes).
 3 classes of surface hormone receptors:
 Cytokine receptor family: bind prolactin and growth
hormone.
 Receptor triggers a tyrosine kinase receptor
(JAK), which phosphorylates both the cytokine
receptor and other downstream signal
transducers called STATs.
 FYI: JAK stands for "Janus Kinase." Janus
was the two-faced Roman god of gates
and doorways, reflecting that this kinase
phosphorylates in retro- and anterograde
directions.
 EGF receptor family: bind insulin, IGF-1.
 Receptor is itself a tyrosine kinase; ligands
trigger autophosphorylation and downstream
signaling molecules (eg. IRS).
 G protein-coupled receptor family:
 Receptor is a seven-times membrane-spanning
protein; recall there are three types:
 Gs: ligand binding causes increased
adenylate cyclase levels, increasing
[cAMP] and consequently causing
increased protein kinase A activity
(causing both short- and long-term gene
expression changes).
 Gi: ligand binding causes decreased
adenylate cyclase levels, decreasing
[cAMP] and decreasing PKA activity.
 Gq: ligand binding causes increased levels
of phospholipase C, causing increased
levels of PIP3, DAG, and IP3. Calcium is
released from intracellular stores to raise
cytosolic calcium levels.
 Steroid receptors are, generally, intracellular, either in the cytosol or
the nucleus. The receptor-steroid complex, in turn, activates
transcription of particular genes. Note the distinction from peptide
hormones, which never enter their target cell.
 Thing they bind to in the nucleus: HREs (hormone responsive
elements).
3. Identify the mechanisms of signaling of peptide hormones.
 Tyrosine, protein, and peptide hormones (exception is thyroxin, which
- though a tyrosine derivative - behaves more like a steroid. More on
this later.):
 Generally all water-soluble.
 Packaged into intracellular vesicles after synthesis, which are
exocytosed upon influx of calcium.
 Once they're exocytosed, they can travel freely throughout the
bloodstream to their targets.
 Note that the plasma contains a significant amount of
proteases and peptidases-- thus the protein- and
peptide-based hormones have a short half-life once
released.
 [Not so much in notes but in BRS Phys: note that there's a
good bit of homology amongst the anterior pituitary
hormones:]
 PRL and GH are extremely similar.
 FSH, LH, and TSH share an identical (alpha) subunit;
they differ in their beta subunits.
4. Compare the mechanisms of action of steroid and thyroid hormones.
 Actually, according to Dr. Vijay, this LO is supposed to read, "Compare
the MOA of steroid and thyroid hormones to the MOA of peptide
hormones."
 Note that, as alluded to, thyroid hormone behaves like a steroid
(evidently due to its ether linkage). We'll talk more about why later,
but for now, just remember that they act similarly.
 Peptide hormone MoA: bind to surface membrane receptors, as
mentioned (diffuse freely in the plasma).
 Cholesterol-based hormones (ie. steroids):
 Lipophilic; no vesicles necessary. Once synthesized, they're
released from the cell.
 Transport through the plasma, however, requires carrier
proteins. Most steroids are bound to specific proteins (albumin
or globulins) to do this.
 Since they're bound to (and protected by) protein,
steroids have a long half-life.
 Maybe 95% of a given type of steroid in the blood is
bound to protein; only about 5% is free.
 However, note that the regulation of release of a given
steroid is based not on how much of the steroid is bound
to plasma proteins but how much is free and unbound in
the plasma.
 To reiterate, since he did: the level of free steroid
determines synthesis and release of more steroid (it's
the 'biologically active' form). The bound steroid is
simply a reservoir.
[General notes:]
 Measurement of plasma levels of hormones:
 Bioassays: measure hormone activity by adding patient's serum
to an exogenous system (eg. a cell line) and measuring the
response. Measures degree of function of the hormone in the
plasma. However, note that multiple hormones can have the
same function-- so measuring function alone may confound
several different hormones. It's also expensive.
 Radio-immunoassays or ELISA: use antibodies to bind a specific
hormone. Measures quantity of the hormone in the plasma. RIA
uses labeled antibodies; ELISA uses fixed antibodies. Same
basic idea.
 Recall that autocrine compounds function on the cell that secreted
them, while paracrine compounds function on cells nearby the cell that
secreted them. Both are distinct from endocrine hormones, which are
spread hematogenously and have effects on distant tissues. Note that
the portal system from the hypothalamus to the anterior pituitary is
'distant enough' that it still counts as endocrinal instead of paracrinal.
Hypothalamic Control of the Pituitary Gland
Monday, December 01, 2008
9:00 AM
Hypothalamic Control of the Pituitary Gland, 12/1/08:
1. Identify the hypothalamic hormones that regulate anterior pituitary function.
 Note the hypothalamus and the anterior pituitary - unlike the posterior
pituitary - have no direct nervous connection. This is due to the fact
that the posterior pituitary is a nervous-system structure (it grows out
of the diencephalon), while the anterior pituitary isn't-- it grows out of
the pharyngeal epithelium (from a structure called Rathke's pouch).
 So the hypothalamus has to rely on a small portal venous system that
links it with the APit for communication: the "hypothalamohypophyseal portal system" (hypophysis is another name for the
pituitary).
 The hypothalamus thus releases its hormones into this portal system,
from which they act on the anterior pituitary, where they trigger the
release (or suppression) of the next, pituitary-based round of hormone
release.
 Hypothalamic hormones are generally peptide hormones:
 Thyrotropin releasing hormone (TRH)
 Causes TSH secretion from APit (acts on thyrotrophic
cells)
 Growth hormone releasing hormone (GHRH)
 Promotes growth hormone (GH) release (acts on
somatotrophic cells)
 Somatostatin
Inhibits growth hormone release (acts on somatotrophic
cells)
 Note that both GNRH and somatostatin act, in different
directions, on the same cell types (somatotrophs).
 Gonadotropin releasing hormone (GNRH)
 Causes LH and FSH release (acts on gonadotrophic
cells)
 Corticotrophin releasing hormone (CRH)
 Causes ACTH release (acts on corticotrophic cells)
 You also have prolactin-inhibiting hormone (PIH):
 Inhibits prolactin release (acts on lactotrophic cells)
 Note that PIH is an equivalent term to dopamine (the
exception to the APit=peptide rule, as it's a
catecholamine/tyrosine derivative).
 Note all pituitary hormones listed above are secreted from the anterior
lobe of the APit (the PPit just stores and releases compounds formed in
the hypothalamus). Note also that the APit hormones are mostly
protein/peptide.
2. Describe the general principles of hormone release from hypothalamic neurons.
 The appropriate region of the hypothalamus receives a depolarization
signal. Voltage-gated calcium channels in neuron membranes in that
part of the hypothalamus cause an influx of calcium, causing
membrane fusion of stored hormone vesicles and release into the local
portal circulation.
3. Identify the receptors and signal transduction mechanisms for hypothalamic
hormones.
 In general, release of APit hormones is dependent on calcium, but
there are a couple of different pathways to elevate it (or depress it, in
the case of inhibitory hormones).
 All hypothalamic hormones bind to G protein-coupled receptors:
 TRH, GHRH, CRH: bind Gs receptors (increase cAMP)
 Note TRH also has some Gq activity.
 Somatostatin and PIH: bind Gi receptors (decrease cAMP)
 GNRH: binds Gq receptor (increase DAG and PIP3, increase PKC
activity)
 [Note distinction between this info and BRS:]
 BRS Phys: GnRH, TRH, GHRH are all Gq (IP3). CRH is
Gs. The other two aren't listed.
5. Diagram the general mechanisms of feedback control for hypothalamic hormone
release.
 Regulation of hormones:
 Most hormones are tightly maintained at a particular
concentration, or set point. This is generally regulated by
feedback loops:
 Negative feedback: consider the following sequence:
hypothalamus releases thyrotropin releasing hormone,
which acts on the pituitary, which releases thyroid
stimulating hormone, which acts on the thyroid, which
releases thyroxin (T4). T4, in turn, inhibits TRH release
from the hypothalamus and TSH release from the APit.
 Another example is glucose and glucagon: high
blood levels of glucose trigger insulin release,
which lowers blood glucose levels. Low blood





glucose levels trigger glucagon release, which
raise blood glucose.
 Positive feedback: rare in the body; where it's used,
usually results in an explosive event which 'resets' the
system. Example cited is oxytocin during labor (dilates
cervix, stimulated by dilation of cervix): builds on itself
until the baby's finally kicked out, at which point it shuts
off.
Note that there's a normal, circadian fluctuation of most
hormones during 24-hour periods.
Note also that the release of APit and hypothalamic hormones
is generally pulsatile-- short, rapid bursts of hormones are
released, rather than a slow steady stream, to produce a rise in
hormone concentration.
Downregulation: if a particular cell is being stimulated too
much by surface hormones (there's an abnormally high level of
secretion, for example), the receptors can be endocytosed
(taken into the cell) to decrease the potential effect of a
hormone on that cell.
Upregulation: if a particular cell isn't being stimulated enough
by surface hormones (there's an abnormally low level of
secretion, for example), "spare" receptors kept inside the cell
can be inserted into the membrane to increase the cell's
response to the existing level of hormone.
[Note his LO #4, "Outline the interrelationships among various hypothalamic centers,
and their inputs from other areas of the brain, and their outputs to the pituitary
gland," was supposed to be deleted.]
Pituitary Physiology: GH and PRL
Monday, December 01, 2008
9:59 AM
Pituitary Physiology: GH and PRL, 12/1/08:
[I've rearranged these a bit-- he talked about PRL first, and some of what he said
about it applies to GH, so for ease of reading they're swapped up.]
[Recall that prolactin and GH both, as protein/peptide hormones, have a short
duration of action - on the order of 30 minutes' half-life - due to the
protease/peptidase enzymes in the plasma.]
[Note that GH and PRL have relatively similar structures and that there's some crossreactivity between their receptors.]
[Note also a slightly confusing (to my brain, at least) nomenclature: primary
endocrine disorders are located at the ultimate target organ (eg. a GH receptor
dysfunction); secondary endocrine disorders are located at the pituitary level (eg. a
GHRH receptor dysfunction); tertiary endocrine disorders are located at the
hypothalamic level (eg. a problem with secreting GHRH). It starts at the end and
works backwards.]
4. List the actions of prolactin and identify the mechanism of action of prolactin.
Prolactin: polypeptide (ie, to my ears, protein-- a protein is just a big
peptide, and both PRL and GH are about 23-kDa peptides complete
with disulfide bonds) hormone released from the APit's lactrotrophic
cells. Recall that it acts on the cytokine family of surface receptors.
 Prolactin's 3 main functions in the cells of the mammary gland:
 (1) Increases mammogenesis (which is the name of
my next band)
 (2) Increases lactogenesis (fills breast's glands with
milk)
 (3) Increases galactopoiesis (aka lactation: release of
milk from mammary glands)
 Prolactin is mainly under inhibitory control via PIH
(dopamine). Dopamine/PIH binds to a D2 (Gi) receptor on the
lactotrophs and inhibits prolactin release.
 Note that thyrotropin releasing hormone increases prolactin
release.
 Note also that estrogen and progesterone also affect the
system: they increase prolactin's effect on mammogenesis, but
inhibit its effect on lactogenesis and galactopoiesis (which is
perhaps why ladies can see an increase in bust size, but don't
lactate, when pregnant or on birth control).
o Increased levels of prolactin are often caused by lactotrophic tumors
(prolactinomas), but can also be caused by preventing the action of
dopamine/PIH (recall that prolactin is tonically inhibited). Recall also
that classic antipsychotics (eg. chlorpromazine) are D2 antagonists-this releases prolactin from inhibition, prompting lactation.
Compression of the pituitary stalk by surrounding tumors or structures
can also reduce the tonic inhibition of PRL.
 Results of increased prolactin: increased milk secretion
(galactorrhea), loss of libido, and amenorrhea. Note the first
two occur in men as well as women.
 Why the second two happen: excess levels of prolactin inhibit
GNRH release from the hypothalamus. This winds up being
clinically significant.
o Decreased levels, or function, of prolactin is usually caused by
decreased general function of the hypothalamus (and thus is usually
accompanied by signs of other endocrine dysfunctions).
 Sheehan's Syndrome: necrosis of the anterior pituitary,
generally immediately postpartum in women who's undergone
serious hemorrhage during delivery.
 Look for an absence of lactation in would-be
breastfeeding mothers.
1. Describe the effects of growth hormone on organs and systems.
 Growth hormone: peptide produced by the somatotrophs in the APit.
 [Note that some of it may be bound to carrier molecules in the blood
that are made up of its receptor fragments.]
 [Note that human growth hormone is the only GH effective in humans;
cadaver-isolated GH was noted to cause Creuzfeldt-Jacob disease in
the 80's, so we now only use recombinant GH.]
 Note that decreased plasma glucose, and increased plasma AA levels,
both promote growth hormone production in the APit. This, too, is
clinically significant.
o

Metabolic function of GH: controls serum level of glucose/AA/lipids
(sources of energy/growth).
 Glucose control: increases gluconeogenesis in the liver; also
decreases insulin effectiveness in certain tissues
(adipocytes and muscle). The effect is to increase blood glucose
and decrease uptake of that glucose by tissues. Note that this
also means GH is a diabetogenic hormone.
 Lipid control: as mentioned, prevents lipid synthesis and
storage in adipocytes; however, it also actively promotes
lipolysis there by promoting hormone-sensitive lipase. This
decreases subcutaneous fat (which is why girls eventually
deigned to go out with me after I hit my growth spurt).
 AA control: increases rate of amino acid uptake in muscle to
promote muscle protein anabolism (buildup).
 General concept: there's a balance between insulin (storage of
energy) and GH (utilization of energy for growth). However,
they're both required for growth of tissues (see next point).
 Growth function of GH: not directly mediated by GH, but indirectly
through its promotion of insulin-like growth factor (IGF) production in
the liver.
 Alternative name for IGF: somatomedin.
 Note that you need both GH and insulin to produce IGF (only
want to divert energy to growth if you have the energy to
spare). Hypoglycemia from insulin injection, for example, would
promote both GH and IGF, but hypoglycemia from prolonged
starvation will only promote GH (no insulin around).
 Mainly, IGF acts by binding to EGF family receptors (recall that
these are tyrosine kinase receptors).
 Effects of IGF-1: see below.
 [Increased production of GH: usually occurs due to somatotroph tumors.]
o Before puberty, this causes gigantism (increased linear growth, with
cardiac hypertrophy, diabetes, and inhibited GNRH, resulting in delay
of puberty-- which results in additional growth). Lifespan is short
(20s).
o After puberty, this causes acromegaly (hands, feet, and jaw size
increase; tend towards diabetes and cardiomyopathy, but the effects
are milder). Lifespan is reduced but longer than prepubertal onset
(50s).
 [Decreased production of GH: generally a decrease in overall APit function.]
o Before puberty, results in dwarfism: decreased GH and IGF leads to
short stature, craniofacial abnormalities, excess subcutaneous fat, and
poorly developed muscles.
 Note that there's a variety called Laron's dwarfism in which GH
levels are normal but IGF levels are low-- it's a receptor defect.
 [Note also that achondroplasia is a genetic defect in long
bone growth without the facial features and subcutaneous fat;
it's unrelated to GH levels.]
2. Explain the mechanism of action of growth hormone through binding to its
receptor.
 Recall that the GH receptor is a cytokine family receptor (acts through
JAK/STAT pathway)-- when bound, it dimerizes and activates the JAK
tyrosine kinase.
3. Categorize the functions of IGF-1 and its mechanism of action.

As mentioned, the mechanism of action is through EGF/tyrosine kinase
receptor activation and subsequent promotion of particular genes.
 Functions:
 (1) Increases long bone growth (only works until epiphyses seal
off after puberty).
 (2) Increases cell number and size (mitogenic), particularly in
muscle.
 (3) Stimulates uptake of glucose and inhibits lipolysis in
adipocytes. Note that this effect antagonizes GH and supports
insulin action.
[5. Localize the sites of release and action of anti-diuretic hormone.]
 (notice that this LO wasn't actually supposed to be in here. But it's
important for the next lecture, so I've left it in.)
 Stimulated by increases in plasma osmolarity or large decreases in
plasma volume (eg. a large-volume hemorrhage).
 Released from posterior pituitary upon hypothalamic stimulation from
various pressure/osmolarity receptors.
 [Action: inserts aquaporins into the collecting duct of the kidney
(concentrates urine, retains water); also acts directly on the smooth
muscle of the vasculature to cause vasoconstriction.]
Hypothalamic and Pituitary Pharmacology
Monday, December 01, 2008
10:50 AM
Hypothalamic and Pituitary Pharmacology, 12/1/08:
[Note that there's another growth-hormone releasing hormone that acts at different
receptors from GHRH: ghrelin. Seems to be associated with the GI tract. Note also
that hypoglycemia (or insulin administration) increases GH secretion.]
[Note also that notes, lectures, and LO interweave only casually. I've tried to keep it
mainly to asked-for details here.]
1. Contrast the role of releasing (sermorelin) and replacement (recombinant GH)
therapy drugs in the management of hyposecretion of GH.
 Sermorelin: synthetic GHRH (promotes release of GH).
 Recombinant GH: has direct GH action, obviously. Note that although
GH has a short half-life, you can use a depot form.
 Therefore, sermorelin can't be used when the APit is the source of the
problem (no effect of GHRH).
 Generally you use GH rather than sermorelin (GHRH) to treat low
levels of GH (maybe because you're assuming a problem with the APit
rather than the hypothalamus).
 Note that long-term overuse of GH (as for the short-term anti-aging
effects) can lead to cancer and kidney/CV disease.
2. Explain the role of release inhibiting drugs (octreotide and bromocriptine) in the
management of hyper-secretion of GH and prolactin.
 Octreotide: similar to somatostatin; preferentially decreases GH (less
effect on insulin, glucagon, and TSH release than somatostatin).
 Bromocriptine: dopamine receptor agonist (it's a drug for Parkinson's).
Can work to inhibit GH, but only if GH is being secreted from
lactotrophs instead of somatotrophs (if it's secreted from
somatotrophs, dopamine will stimulate GH secretion).
Correspondingly, bromocriptine can also be used to prevent excess
prolactin secretion from lactotrophs.
3. Compare the structure, pharmacokinetics and actions of vasopressin and analogs
such as desmopressin.
 Vasopressin (aka ADH, arginine vasopressin, or AVP):
 Structure: peptide (specific structure on p. 22)
 Actions: as mentioned in last lecture's notes, retains water and
directly constricts arteries. Note that ADH is a stress hormone
(released during stress conditions): it causes glycogenolysis, a
pro-thrombotic state, and ACTH release. Note also that urea is
reuptaken along with water in the kidneys.
 Pharmacokinetics: V1 receptors (Gq) are responsible for
vasoconstriction and the stress response. V2 receptors (Gs) are
responsible for kidney effects (retention of water)-- they
increase cAMP and PKA levels in renal collecting duct cells.
 (Note that Dr. Woodmansee cites V3 receptors as
involved with the stress response and V1 receptors as
only involved in the vasoconstriction response.)
 Not much discussion of half-life; Web search says 10-20
minutes.
 Desmopressin (aka DDAVP):
 Structure: again, a peptide (specific structure on p. 22)-- note
next point.
 Pharmacokinetics: selective for the V2 receptor (kidney effects
only); has a D-enantiomer of arginine (lasts longer, isn't broken
down as quickly).
 Actions: again, affects only the V2, Gs receptors (in kidney).
4. Identify the effects of vasopressin on receptor subtypes and signal transduction
systems in vascular smooth muscle and the kidney.
 As mentioned: V1 = Gq = stress response and vasoconstriction; V2 =
Gs = renal reuptake of water and urea.
5. Compare drugs that affect vasopressin release or action and their relationship to
the therapy of diabetes insipidus (DI) and SIADH (chlorpropamide, demeclocycline,
desmopressin and vasopressin).
 Recall that a deficiency of ADH, or an inability to respond properly to
it, is called diabetes insipidus (central if no ADH, nephrogenic if no
response to it in the kidneys). Central diabetes can be due to head
trauma, tumor, cerebral aneurysms, CNS ischemia, genetics, etc;
nephrogenic is usually either familial or drug-induced.
 Useful for DI:
 Chlorpropamide: potentiates renal effect of vasopressin,
useful in central DI.
 Desmopressin/vasopressin: useful for central diabetes
insipidus.
 They're also used for von Willebrand Disease (increase
vWF levels); ADH is used for nocturnal enuresis as well.
 For familial nephrogenic DI, indomethacin seems to reduce the
inhibition of vasopressin by prostaglandins. Thiazides seem to
help too, for unknown reasons (5 theories on p. 23).

For drug-induced (caused by lithium) nephrogenic DI,
discontinuing lithium or administering amiloride (blocks sodium
channels in collecting ducts, blocking the reuptake of lithium).
 Recall that SIADH, or syndrome of inappropriate ADH secretion, is
where you have too much ADH being put out by the PPit. Caused by
CNS injury, surgery, drugs, and certain cancers (especially lung
cancer). Causes dilutional hyponatremia (can be fatal).
 Useful for SIADH:
 Demeclocycline: blocks increase in cAMP caused by ADH in
kidneys.
6. List drugs that can cause diabetes insipidus (nephrogenic and neurogenic) and
SIADH.
 Nephrogenic: lithium, demeclocycline; Wiki cites amphotericin B as
well.
 SIADH: ecstasy (MDMA); ADH regulation gets screwed up at the same
time body temperature is increased-- people tend to drink lots of
water and get hyponatremia.
Hypothalamus, Pituitary, Pineal and Adrenal Histology
Tuesday, December 02, 2008
7:40 AM
Hypothalamus, Pituitary, Pineal and Adrenal Histology, 12/2/08:
1. Describe the embryological development and basic structure of the hypothalamus
and pituitary gland.
 Pituitary:
 Ok. Not to be crass, but the thing looks like a nutsack. One ball
is bigger and is in front (that's the anterior pituitary); the other
is smaller and in the back (the posterior pituitary). Both of
them hang by a scrotal kind of thing (the 'stalk').
 Anterior pituitary is derived from Rathke's pouch (ectoderm
from pharynx).
 3 parts of the anterior pituitary:
 Pars distalis: contains the working bits, pretty
much-- the cells that secrete hormones and the
capillaries that they secrete them into.
 Pars tuberalis: forms a sheath around the
pituitary stalk.
 Pars intermedia: forms a thin border between the
anterior (pars distalis) and posterior (pars
nervosa) pituitary.
 The pars intermedia seems to be more or
less useless.
 Posterior pituitary is derived from the
hypothalamus/diencephalon.
 3 parts of the posterior pituitary:
 Pars nervosa: again, contains the working bits;
these secrete ADH and vasopressin. The specific
axons that release them are called
magnocellular neurons; these form large
bundles called Herring's bodies that make up
most of the posterior pituitary.
 Note that the pars nervosa is nearly
anuclear-- it's almost all axon and
vesicles.
 Note that this means that many traditional
stains are going to be much lighter in the
pars nervosa than the pars distalis
because of the lack of nuclear material.
 Median eminence and infundibulum: most of the
"stalk" of the pituitary; contain the hypothalamohypophyseal portal system, as well as the axons
passing from hypothalamus to the pars nervosa.
 Note that the median eminence is the
boundary between the hypothalamus and
the anterior pituitary-- thus the
hypothalamic hormones released into the
H-H portal system are sent here to be
released (more on the blood supply in the
next LO).
2. Illustrate the blood supply to the hypothalamus and the pituitary gland, including
the hypothalamo-hypophyseal portal system.
 The median eminence, the infundibulum, and pars tuberalis (the stalk,
more or less) get blood through the superior hypophyseal arteries.
 The pars nervosa gets blood through the inferior hypophyseal
arteries. (makes sense; the posterior pituitary 'ball' is below the
stalk.)
 The pars distalis receives no direct arterial supply; it's dependent
instead on the hypothalamo-hypophyseal portal system.
 This system receives its incoming blood from the superior
hypophyseal arteries in the primary capillary plexus (which go
through the median eminence and pick up the secreted
hormones from the hypothalamus); the outgoing venous blood
leaves the pars distalis through the hypophyseal veins to go
into the secondary capillary plexus.
3. Match the individual cell types in the anterior pituitary with the hormones they
release.
 Chromophobes (uptake no stain)
 These are the cells that don't secrete anything (the sleeper
cells. Get it? Because they don't secrete anything and they're..
oh, never mind.).
 Acidophils (uptake acidic stains)
 These are somatotrophs (secrete GH) and lactotrophs (secrete
PRL).
 Basophils (uptake basic stains)
 These are gonadotrophs (secrete FSH and LH), corticotrophs
(secrete ACTH), and thyrotrophs (secrete TSH).
4. Describe the structure and function of the pineal gland.
 Structure:
 The pineal gland seems to be largely made up of specialized
nerves called pinealocytes: these produce and secrete
melatonin (which, recall, is a derivative of tryptophan).
 There's also some glial cells in there.

The pineal gland accumulates mineral crystals over time
(CaCO3 and PO4); this is picked up on CT scans as "brain sand"
(really) and is used as a reference point.
 Function:
 Seems to be important in establishing circadian rhythm.
 Has a direct input from the visual system (makes sense-- want
to adjust circadian rhythm to light cycles).
 Light inhibits melatonin secretion, absence of light
promotes it.
 Goljan rather melodramatically calls melatonin the
"hormone of darkness."
 Note this can also be useful in circannual routines-- the ratio of
day to night can give information about what season of year it
is, which can be useful for a variety of reasons from mating to
figuring out whether your Uggs are in fashion (or figuring out if
your potential mate's Uggs are in fashion, I suppose).
5. Diagram the structure of the adrenal gland and identify the various hormones
released by the adrenal gland.
 Again, it's an organ of mixed embryological origin.
 3 major parts:
 Capsule on the outside (not much further discussed here)
 Adrenal cortex (under the capsule)
 Derived from mesenchymal cells; classical endocrine
cells.
 Secrete steroid hormones.
 3 distinct sections, from outer to inner:
 Zona glomerulosa: synthesizes and releases
mineralocorticoids
 Zona fasciculata: synthesizes and releases
glucocorticoids
 Zona reticularis: synthesizes and releases sex
hormones
 First Aid's mnemonic: GFR; "salt, sugar, sex."
 I have tried in vain to link either of these to Guns
N' Roses or the Red Hot Chili Peppers album
"Blood Sugar Sex Magik." Email me with
suggestions.
 Recall that steroid hormones take a while to make, take
a while to cause their effects, and take a while to get out
of your system.
 Recall also:
 Mineralocorticoids: mainly aldosterone. These
regulate salt and water balance.
 Glucocorticoids: mainly cortisol. These regulate
glucose and energy balance.
 Sex hormones: these are sort of the 'backup' sex
hormone generation centers (primary ones are in
the ovaries/testes).
 Adrenal medulla (the innermost part of the adrenal gland)
 Derived from neural crest cells. These are sort of the
sympathetic ganglion cells of the adrenal gland.
 As such, they secrete norepinephrine and epinephrine.
 [Blood supply of the adrenal gland:]


Arteries go through capsule and form a subcapsular plexus; big
medullary arteries go straight down (don't stop in the cortex) to
provide fresh blood to the medullary; capillaries go down
through the cortex before going into the medulla.
Note this means the medullary cells get a dual blood supply of
both fresh and post-cortical blood (so their blood contains any
secreted cortical hormones).
Testing Hypothalamic and Pituitary Function
Tuesday, December 02, 2008
9:02 AM
Testing Hypothalamic and Pituitary Function, 12/2/08:
[Bunch of random notes:]
 Hypopituitarism:
 A lack of a functional anterior pituitary. Can be partial or complete.
 Can be from mass lesions, surgery, radiation, infiltrative diseases,
genetic factors, etc.
 [Again, recall the nomenclature is backwards, to my eyes: primary
disorders are at the end target organs, secondary disorders are in the
pituitary, and tertiary are in the hypothalamus.]
 Note that she uses "central" to refer to secondary or tertiary
disorders (ie. in the pituitary or hypothalamus-- anywhere but
at the target organs).
 Treatment: correct hormonal deficiency (-ies). This is fairly
straightforward in principle.
 Note that, in hypothyroidism, you can't always use TSH to
guide T4 level adjustment (TSH levels tend to be normal even
with APit thyrotrope dysfunction). She seems to put a lot of
emphasis on this.
 Note all hypopituitarism patients should wear medical alert
bracelets.
 Types of hypopituitarism:
 Central hypogonadism:
 Clinical: Amenorrhea, erectile dysfunction, decreased
libido.
 Exam: soft testes in men, loss of body hair.
 Labs: low testosterone, or low/normal FSH/LH.
 Central hypothyroidism:
 Clinical: fatigue, weight gain, constipation, dry skin/hair.
 Exam: delayed deep tendon reflexes and bradycardia
 Labs: low free T4 with low or normal TSH.
 Central adrenal insufficiency:
 Clinical: fatigue, dizziness, nausea/vomiting.
 Exam: lowish blood pressure; no hyperpigmentation
(which only shows up with as a primary problem in the
adrenal gland itself).
 Labs: do ACTH stimulating test; will not stimulate > 20.
 Growth hormone deficiency:
 Clinical: central obesity, fatigue, "poor quality of life."



Exam: not much specific.
Labs: do GH stimulating test with GHRH (but this is no
longer available in the US?); results in low levels of IGF1 (adjusted for age and gender). Can also make people
hypoglycemic to check (low plasma glucose increases
GH secretion) but there's some obvious problems with
this.
Pituitary apoplexy: sudden "worst headache of my life," ophthalmoplegia, and
cranial nerve palsy developing as a result of a sudden hemorrhage into the
pituitary gland-- often as a result of a tumor overgrowing its blood supply and
necrosing (along with its vessels). Usually occurs in patients without a
previously diagnosed tumor.
 Looks similar to subarachnoid hemorrhage and, to some extent,
bacterial meningitis.
 Manage with high-level steroids (they often can't make them for
themselves) and intensive care; can use surgical decompression if the
symptoms are rapidly progressive or if the symptoms are particularly
severe.
1. Identify the major anterior pituitary hormones and describe their main functions.
 Corticotropin, or adrenocorticotropic hormone (ACTH): stimulates the
adrenal cortex to produce cortisol.
 Prolactin (PRL): stimulates the breast tissue to grow and lactate
(discussed in "Pituitary Physiology: GH and PRL").
 Growth hormone (GH): stimulates a bunch of stuff, including IGF
(discussed in "Pituitary Physiology: GH and PRL"); main function is to
increase plasma glucose and stimulate muscle and bone growth.
 Thyroid stimulating hormone (TSH): stimulates the thyroid to secrete
thyroxin (T4).
 Luteinizing hormone/follicle stimulating hormone (LH/FSH): stimulate
the gonads to produce sex hormones (more in "General Overview of
the Reproductive Axis"), stimulates gamete development and release.
2. List the tests performed to measure normal anterior pituitary hormone secretion,
recognizing the importance of measuring target organ hormone levels.
 Generally you try to stimulate the gland to test for hypofunction and
suppress the gland to test for hyperfunction-- if the test doesn't work,
then it's indicative of the related disorder.
 Hypofunction:
 Looking for hypothyroidism, GH deficiency, hypogonadism, or
adrenal insufficiency.
 Physical exam:
 Hypothyroidism: dry skin, delayed DTRs
 Hypogonadism: loss of body hair, amenorrhea, testicular
softness
 Primary adrenal insufficiency: low blood pressure.
 If Addison's: hyperpigmentation as well.
 GH deficiency: central adiposity.
 Hyperfunction:
 Looking for hyperthyroidism, GH excess, or Cushing's
syndrome.
 Physical exam:
Hyperthyroidism: soft skin, tremor, increased DTRs,
tachycardia
 Hypergonadism: minimal symptoms
 Cortisol excess: Cushing's syndrome
 GH excess: gigantism or acromegaly depending on age
Always do a ophthalmologic and neuro exam to look for visual acuity,
increased intracranial pressure, and cranial nerve palsies.
Tests:
 Most of these, really, are just levels of the appropriate
hormones.
 The thing to remember is what things suppress or promote
what other things:
 GH is suppressed by glucose (as in oral glucose
tolerance tests).
 PRL is suppressed by DA and promoted by TRH and
estrogens.
 GnRH is suppressed by PRL.
 ..and then you can apply that knowledge to the test results and
make some sense out of them. As in:
 GH: Levels that stay elevated over 2 ng/mL after oral
glucose load are indicative of non-suppressible GH (ie.,
generally, GH-secreting tumors).
Yeah, this LO kind of wandered all over and was repetitious. Not my
idea.
the clinical presentations of different types of pituitary adenomas.
Recall that the pituitary gland is right next to the optic chiasm.
Pituitary adenomas can hence present with visual syndromes (eg.
tunnel vision, bitemporal hemianopia).
Headaches, cerebral nerve palsies, and visual complaints are masslesion signs of pituitary adenomas.
Types:
 [Note nearly all pituitary adenomas do not progress to
carcinomas.]
 Prolactinoma:
 Again, recall things that promote (estrogen, TRH) or
inhibit (DA) PRL release.
 Presents with galactorrhea (lactation), hypogonadism,
hirsutism, gynecomastia, and mass lesion effects.
 Hypogonadism: causes amenorrhea, infertility,
erectile dysfunction, and arrested growth. Caused
by the increased PRL level's inhibition of GnRH
release from the hypothalamus.
 Also can see increased bone loss.
 Can be a fair number of other things:
 Pregnancy
 Drugs: dopamine depletion (recall DA inhibits PRL
release)
 Primary hypothyroidism (recall TRH stimulates
PRL release)
 Etc (neurogenic, cirrhosis, ectopic production
from ovarian tumors, idiopathic)
 Treatment: dopamine agonists (bromocriptine,
cabergoline). These actually work extremely well, but




3. Recognize





watch out for cardiac valve abnormalities at very high
doses. Can use surgery to debulk or radiation for very
small tumors.
Acromegaly (as from a somatotrophinoma):
 Recall this is what happens in adults with an
overabundance of GH.
 Shows up with big hands, feet, and tongue, often with
early cardiac problems (cardiomegaly and CHF, often
in their 30's or 40's) that are the precipitating factor for
clinical visits (the disease process is fairly far along).
 Also see diabetes, sleep apnea, colon polyps/cancer,
arthritis, etc.
 Look for elevated GH levels, failure to suppress GH
during oral glucose tolerance test, and pituitary MRIs.
 Treatment: surgery (treatment of choice for smaller
tumors), octreotide, GH antagonists,
Cushing's disease:
 Caused by an ACTH-producing tumor (as opposed to
Cushing's syndrome, which is any cause of increased
cortisol levels).
 Presents as rapid weight gain, central adiposity, moon
facies, fat pads on upper back ("buffalo hump"), purple
striae on the abdomen, hirsutism, menstrual
irregularities, HTN and CAD, muscle weakness,
osteoporosis, mood disturbances.
 Note tumors are frequently very small.
 [Cushing's syndrome: frequently caused by
administration of exogenous steroids. Other than that,
it's mostly ACTH-producing adenoma (Cushing's
disease).]
 How to test for Cushing's disease:
 (1) Check cortisol levels in the urine. Can also
administer dexamethasone (should feedbackinhibit cortisol levels)-- if the cortisol levels go
down appropriately and the urine levels are
normal, it's not Cushing's (syndrome or disease).
Can also check late-night salivary cortisol levels,
but it's not considered an equivalent test yet.
 (2) If the cortisol levels don't go down or if
there's a high level of cortisol in the urine, test
ACTH levels: if the pituitary is normal, but there's
lots of cortisol (as in an adrenal tumor), the
ACTH should be low (feedback). If there's an
ACTH-secreting tumor (as in Cushing's disease),
the ACTH should be high.
 (3) If the ACTH is high, need to make sure the
tumor is pituitary as opposed to ectopic. You do
this by petrosal venous sampling of ACTH levels
before and after administering recombinant CRH
and comparing petrosal to peripheral ACTH
levels.

Obviously there's a lot of this; it reflects the fact
that ACTH-secreting tumors are the most difficult
pituitary adenomas to detect and localize.
 Note you want to document hypercortisolemia
before doing further tests. Not sure why this got
emphasis.
 Can repeat urine test 3 times if there's a high
index of suspicion.
 Treatment: surgical, but treat symptoms as well
(diabetes, coagulopathy, osteoporosis, etc).
 Null cell tumor:
 Fairly common (1/3 of all pituitary tumors).
 No significant endocrine secretion, but cause mass lesion
effects (consequently they often aren't caught until
late).
 Treatment of choice is surgery.
 Thyrotropinoma:
 Rare.
 Tend to present with "bug eyes." Note that this is
technically distinct from the exophthalmos seen in
Graves' Disease-- that's an actual protuberance of the
eye, whereas this is "lid lag" (exposure of whites around
eyes).
 Note that TSH can be normal.
 Treatment: surgery, octreotide (not FDA approved but
works).
 Gonadotropinoma:
 Evidently these will be discussed later.
 Generally these are non-metastatic, but they push out and around
surrounding structures. Once they grow to a certain size, they're hard
to take out completely-- lots of small structures nearby.
 Common theme: many enzymes are normal or near-normal on labs
even with pituitary adenomas. Hypogonadism, in particular (as that
caused by elevated prolactin levels), tends to show "inappropriately
normal" LH and FSH levels.
4. Describe the function of the posterior pituitary and identify the clinical
presentation of the most common posterior pituitary disorders.
 Clinically, primarily associated with disorders of ADH.
 Overproduction of ADH: SIADH.
 Underproduction of AVP: diabetes insipidus (recall that the central type
arises from the pituitary, while the nephrogenic type arises from
resistance in the kidney).
 Recall that ADH is secreted mainly in response to hyperosmolarity or
hypovolemia (thus inhibited by hypoosmolarity or hypervolemia).
 Polyuria:
 Urine output > 3 L/day
 Etiologies:
 Diabetes mellitus
 Primary polydipsia (psychogenic)
 Diabetes insipidus (central/nephrogenic)
 Diabetic insipidus:
 Signs/symptoms: Generally polydipsia, increased thirst,
polyuria, possibly hypernatremia if they're water-deprived;

possibly neurologic symptoms. Can be acute onset. Make sure
the urine is hypotonic.
 Can be either congenital or acquired (eg. from traumatic brain
injury or craniopharyngiomas).
 Testing: history, quantification of urine output, water
deprivation test (look for increased plasma osmolality but no
increase in urine osmolality-- give ADH at that point to see if it
corrects, to test for central vs. nephrogenic source).
SIADH (not discussed extensively in class, but from the notes):
 Signs/symptoms: hyponatremia with good volume; low Posm
with high Uosm.
 Treat with water restriction (note distinction from DI, which you
diagnose with water restriction).
 Again: if someone's got abnormal electrolyte status, don't
correct too fast-- get central pontine myelinolysis if you're
correcting hyponatremia (as in SIADH), get cerebral edema if
you're correcting hypernatremia (as, potentially, in DI). Either
one's a good setup for a (successful) lawsuit.
Hypothalamic and Pituitary Tumors and Other Lesions
Tuesday, December 02, 2008
11:27 AM
Hypothalamic and Pituitary Tumors and Other Lesions, 12/2/08:
[Lots of emphasis, here and elsewhere, on the fact that prolactin is the only APit
hormone to be under tonic suppression (by DA).]
[This was Dr. DeMasters' whirlwind tour of tumors: more or less everything she said
was significant. This is probably high-yield.]
1. Contrast the normal histology and the pathology of a pituitary adenoma.
 Normal histology:
 Anterior pituitary: lots of nuclear matter; posterior pituitary:
just nervous matter (storage of PPit hormones) (note that the
cell bodies of the magnocellular neurons are located in the
hypothalamus).
 Note that, within the anterior pituitary, the acidophiles are
segregated from the basophiles are segregated from the
chromophobes.
 In the APit you see an acinar organization (looks a little
reticular).
 Adenoma: see loss of the normal acinar/reticular pattern.
2. List the different types of anterior pituitary tumors and their prevalence.
 Carcinomas are virtually unknown; APit tumors usually grow locally
and do not metastasize. They mainly cause problems by pressing on
surrounding structures and secreting their hormones.
 Acidophile tumors are usually GH-secreting adenomas
(somatotropinomas)
 Basophile tumors are usually ACTH-secreting adenomas
(corticotrophinomas)

Note the following:
 Excess GH is a tumor until proven otherwise;
 Excess PRL can be other things, but excluding other causes, it's
a tumor;
 Hyperthyroidism isn't a pituitary tumor until proven that it is
(it's much more often a problem in the thyroid).
 She emphasized, as did our last lecturer, that the first line treatment
for prolactinomas is medical (bromocriptine or other DA agonists). This
decreases the cytoplasmic area of the prolactinoma and increases
fibrosis inside it.
 ACTH-producing tumors: generally very small but very high rate of
excretion, hard to pin down and identify. The most difficult tumor
to identify, locate, and treat.
 As mentioned in the last lecture, to make sure it's a pituitary
tumor that's secreting ACTH, the petrosal veins are
catheterized.
 Treatment is more or less always indicated for ACTH- and GHproducing tumors.
 Treatment is usually surgical except for PRL-secreting tumors, as
mentioned.
 [Craniopharyngioma: calcified tumors that arise from the pituitary
stalk (above the sella turcica); tend to occur in children; generate
"machine-oil" fluid.]
 [Can be mistaken for germinomas, a rare type of tumor with lots of
mitotic activity and big nucleoli.]
 [Rathke cleft cyst: can be mistaken for pituitary adenomas.]
 Prevalence:
 Prolactinomas
 GH-secreting adenomas
 Null cell adenomas
 ACTH-secreting adenomas
3. Name other types of hypothalamic and pituitary lesions that can lead to pituitary
dysfunction, and identify their pathological features.
 Anything that presses on the pituitary stalk can interrupt the negativetone flow of DA from the hypothalamus to the APit, resulting in
prolactinemia.
 The ones she mentions in the notes:
 Craniopharyngiomas, Rathke cleft cysts, germinomas (as
above), and meningiomas. The only one she talked about at
length was craniopharyngiomas.
 There's a few more discussed in "Radiology of the Hypothalamus and
Pituitary" (hamartomas of the hypothalamus, pilocytic astrocytomas,
etc).
4. Describe clinical findings related to the disruption of structures surrounding the
sella turcica by a large pituitary tumor.
 This is particularly a problem with GH-secreting and non-secretory
tumors.
 Traction on the dura can lead to headache.
 As mentioned, pressure on the optic chiasm leads to visual
dysfunction.
 Can press on other APit structures and cause their dysfunction.
 Cranial nerve palsies: CNs II, III, and VI are often compressed.

Tumors can grow out into and compress the cavernous sinus
structures.
5. Recognize the clinical signs and symptoms of a growth hormone-secreting
pituitary tumor.
 Acromegaly or (pre-pubertal) gigantism: gone over in last several
lectures.
6. Identify the clinical signs and symptoms of a prolactin-secreting pituitary tumor,
contrasting the modes of presentation in men and women.
 In premenopausal women: amenorrhea, galactorrhea.
 In men: loss of libido, visual loss, headache. (we've been told that
galactorrhea can happen here too.)
General Overview of the Reproductive Axis
Wednesday, December 03, 2008
7:37 AM
General Overview of the Reproductive Axis, 12/3/08:
I have, in my notes, a suggestion that my description of the two-cell hypothesis in
the male as described here may be incorrect. A cursory glance reveals that third year
has driven out what scant knowledge of the system I once possessed, and thus I am
in no position to judge the merits of the case. Proceed with caution.
[General notes:]
 Distinctions between male and female sex hormone secretions:
 Patterns of secretion: male is tonic, female is cyclic.
 Types of hormones: testosterone for males, progesterone and
estradiol for females.
 Names (and mechanisms) of the secreting cells are distinct.
 The levels of secretion change dramatically with age.
 There are a number of extragonadal sources of sex hormone synthesis
and modification: skin, [prostate,] adipose tissue, placenta, and the
adrenal gland.
 Note that the APit produces two hormones in response to a single
GnRH stimulus (FSH and LH).
1. Recognize the cholesterol molecule and correctly number the carbon atoms in the
steroid nucleus.
 Ok. Basically it's got four rings, three six-carbon and one five-carbon.
The five-carbon ring has a hydrocarbon sticking onto the end of it. The
other end is where the numbering starts, on the six-carbon ring with a
hydroxyl group on it. Irritatingly, the numbering doesn't start with the
carbon attached to the hydroxyl group but the carbon two carbons
clockwise to it.
 There's 27 carbons all together (the end ones are on the hydrocarbon
tail).
 I really can't list all the numbers out. It's in Lippincott p. 220, top left.
 If you count total carbons you should be able to get a reasonable idea
of what structure you're looking at. 27 = cholesterol, 21 = progestin,
19 = androgen, 18 = estrogen. More on this below.
2. List the molecules synthesized from cholesterol throughout the body, including
examples from each of the three major classes of steroid hormones and the three
major classes of sex steroids.
 Cholesterol is used to make:
 Bile acids
 Steroid hormones
 Cell membrane components
 Hollandaise sauce
 Three major class of steroid hormones:
 Glucocorticoids (eg. cortisol)
 Mineralocorticoids (eg. aldosterone)
 Sex hormones (eg. see next point)
 Three major classes of sex hormones (categorized by number of
carbons):
 Progestins (21 carbons)
 Androgens (19 carbons)
 Estrogens (18 carbons)
3. Describe key features in the biosynthesis of the sex steroids and describe the
rate-limiting step.
 Of note: all of the sex hormones have less than 27 carbons (ie., some
get cleaved off in the transition from cholesterol). The key features,
then, mainly involve reduction of the hydrocarbon tail (and a couple of
random hydroxylations on other points). The only other specific
significant step I can think of is that making estrogens involves making
a six-carbon ring aromatic (using an enzyme with a very limited
distribution called aromatase).
 The rate-limiting step in sex hormone synthesis is to cleave 6 carbons
off that tail. The enzyme for this step is called 20,22 desmolase
(Lippincott just calls it desmolase).
 Pregnenolone - the resultant 21-carbon - is the precursor to all the
other sex steroids.
 Progestins and androgens are derived from pregnenolone.
 Estrogens are derived from androgens (specifically androstenedione
and testosterone).
 Note important concept here: things only get smaller. Progestins (21
C) can be made into smaller molecules (19-C androgens and 18-C
estrogens), but estrogens can't be made into anything else. As far as
sex hormone synthesis is concerned, you can cleave carbons but you
can't put them back on.
4. List the endogenous sex steroids and classify them into the three major classes of
sex steroids on the basis of the number of carbon atoms they contain.
 Progestins (21 carbons): pregnenolone, progesterone, and 17-alphahydroxy-progesterone (17-OH-P).
 Androgens (19 carbons): testosterone, dehydroepiandrosterone
(DHEA), DHEA-sulfate (DHEA-S), dihydrotestosterone (DHT), and
androstenedione.
 In men:
 Testosterone and androstenedione come from the
gonads.
 The DHEA androgens come from the adrenal glands.
 Her mnemonic: DHEA = adrenal. In the interest
of intelligence I would like to point out that it
could easily be DHEA = gonad.
[She didn't mention it in lecture, but DHT (a much more
potent form of testosterone) is made from testosterone
mainly in the skin and prostate.]
 In women:
 The DHEA androgens come largely (95%) from the
adrenal glands. The rest comes from the ovaries.
 Testosterone comes half from the gonad and half from
the adrenal glands.
 Androstenedione comes largely (95%) from the ovaries.
The rest comes from the adrenal glands.
 Yes, you actually need to know all the numbers. No, I
don't know why.
 Estrogens (18 carbons): estrone (E1), estradiol (E2), and estriol (E3).
These have one, two, and three OH groups respectively.
 The major circulating form of estrogen is estradiol (in both men
and women).
 Estradiol is derived from testosterone.
 Estrone comes from fat: adipose tissue converts
adrostenedione to estrone. This is evidently why obese women
have less menopausal symptoms (the estrogen level is kind of
buffered).
 Estriol is only made in the placenta (not found in men).
5. Name the hormones involved in the hypothalamic - pituitary - gonadal axis and
label them on a diagram of that axis.
 Hypothalamus (preoptic area and arcuate nucleus) secretes GnRH.
 Recall that GnRH is released in a pulsatile fashion. This winds
up being important (below).
 APit, in response, secretes FSH and LH. FSH: helps ovary secrete an
egg. LH: helps uterus receive and nurture the fertilized egg. Under
stimulation from FSH and LH, the ovaries produce estradiol and
progesterone, while the testicles produce testosterone. Lots more on
this below.
 Estradiol and progesterone in women, and testosterone in men,
feedback-inhibit the secretion of GnRH, LH, and FSH.
 Note that this means that in menopause (no more secreted
estradiol and progesterone), LH and FSH are very high (lack of
negative feedback), while in pregnancy (sky-high levels of
estradiol and progesterone), LF and FSH are very low.
6. List the primary areas of the hypothalamus responsible for the production of GnRH
and describe key features of hypothalamic GnRH secretion.
 Preoptic area and arcuate nucleus.
 GnRH is secreted into the portal system.
 As mentioned and as will be mentioned further, it's released in a
pulsatile fashion (continuous administration of GnRH evidently
suppresses rather than activates the APit).
 In men the pulse rate is fairly constant. In women it varies a lot.
7. Describe the structure, functions and mechanisms of action of the hormones
involved in the hypothalamic - pituitary - gonadal axis in both men and women.
 (Note structure, other than the number of carbons, went largely
undiscussed, as did the MoA. They're steroid hormones, so they bind
to intracellular cytosolic/nuclear receptors to affect gene transcription,
and they're lipophilic, so they're mainly carried by plasma proteins.)
 Androgens: 2 functions:




(1) Anabolic: promote growth of bone and muscle.
(2) Androgenic:
 Promote secondary sex characteristics (hair growth,
voice changes)
 Promote development, growth and differentiation of
external genitalia
 Promote development of gametes in the male
 Promote libido
 Promote sebum production (--> acne)
Estradiol/Progesterone:
 Before we get into this, recall that GnRH is released in a
pulsatile fashion. The number of pulses per day is fairly steady
for men but changes from day to day for women. This means
the release of the subsequent hormones fluctuates a lot, in
strange and wonderful ways that occasionally entail me
sleeping on the couch.
 In a given 28-day cycle, where day 1 is the beginning of
menses, ovulation begins at day 14. The half before ovulation is
called the follicular phase; the half after ovulation is called the
luteal phase.
 Estradiol has two peaks, one in each phase.
 Progesterone has one peak, in the luteal phase.
 This is, again, significant for the exam. See Bob's email
with the diagram from B & B for a good illustration (the
one in the handout is all grayscale).
 FSH and LH both peak at the same time, towards the end of the
follicular phase.
 In women, most of the time, estradiol is a negative feedback
inhibitor of the HPG axis. However, once estradiol levels have
stayed elevated above a certain level for five days, it turns into
a positive stimulator.
 What this means: the first peak of estradiol in the follicular
phase, which goes on for some time, winds up being briefly
stimulatory, which is responsible for the raise in FSH and LH,
which drives ovulation.
 Note that this doesn't hold during pregnancy (in which
estradiol levels are way, way above normal)-- then
they're back to being inhibitory again (thus you don't
menstruate when pregnant).
 In practice you seem to inhibit estradiol to promote
fertility and promote estradiol to inhibit it (basic
feedback stuff) and not pay much attention to this caninhibit, can-stimulate business.
 Ok. Now on to functions.
 Estradiol and progesterone are more or less there to
support pregnancy:
 They change the endometrial surface-- it thickens
to receive an egg in the second half of the cycle,
then sheds during menstruation.
 They help to prepare breast tissue for lactation.
 Progesterone (not estradiol) is a smooth muscle
relaxant (to allow the uterus to expand).
8. Describe the 2-cell theory of sex steroid production and name the gonadal cell
responsible for the production of sex steroids in men and women.
 Cells in question:
 In male testicles: Leydig cells and Sertoli cells.
 In female ovaries: Theca cells and granulosa cells.
 It takes both types of cell to produce the final mix of circulating sex
hormones, due to the presence or absence of the necessary enzymes
within each type.
 More details than you would ever, ever want to know but which will be
on the test:
 In Leydig cells, with an influx of LH, cholesterol is uptaken and
converted into testosterone, which is released into the blood.
 Some of that testosterone is taken up into Sertoli cells, which
contain the developing gametes.
 Estradiol is produced in Sertoli cells in response to FSH but
can't be produced in Leydig cells due to the absence of
aromatase in the latter.
 The testosterone from the Leydig cells are taken up into Sertolli
cells, and secreted out into the seminiferous tubule along with
the gametes and the estradiol.
 Leydig = LH-responsive.
 Sertoli = FSH-responsive. And they make estradiol, though that
could just as easily have been testosterone. I suppose you
could remember that all the consonants in "Sertoli" are also in
"estradiol," in approximately the same order.
 In women:
 Theca cells are responsive to LH and make cholesterol into
testosterone, which is released into the blood (as in Leydig
cells).
 In the granulosa cells, the egg is developing in a follicle which
will eventually burst (releasing the egg). The granulosa cells
have receptors for FSH to promote uptake of cholesterol.
 After cholesterol's taken up, it's converted to
progesterone. But the enzyme to reduce it further isn't
in the granulosa cells, it's in the theca cells. So the
progesterone is taken up into the theca cell and
converted into androstenedione. The androstenedione is
released from the thecal cell, goes back to the granulosa
cell, and is converted into estradiol.
 Is this stupid complicated? Yes.
 Mnemonics given: E-F-G (estradiol, produced in eventual
response to FSH, in the granulosa cells), P-T-L (progesterone,
processed in the thecal cell, in response to LH).
 The second part of this mnemonic is iffy, as
progesterone is made in both cells.
 Note that the placenta can do all of this rolled into one.
9. List the major extra-gonadal sources of various sex steroids.
 Skin/prostate (dihydrotestosterone, a hyper-potent version of
testosterone), fat (estrone), adrenal cortex (DHEA androgens, and
testosterone/androstenedione in women) and the placenta (estriol).
10. Compare and contrast features of the normal hypothalamic-pituitary-gonadal
axis in men and women.

I think what she's getting at is the variable rate of pulsatile GnRH
release in women vs. the relative constant rate in men (8-14 pulses
per 24 hours).
11. Label a diagram of the ovarian/menstrual cycle and describe how disruptions of
the hypothalamic-pituitary-ovarian axis can lead to irregular periods in women.
 Low levels of estrogen can be insufficient to prompt the release of FSH
and LH during the follicular phase. This can be due to extreme stress
or illness.
 I actually think we're going to talk more about this later.
12. Frame discussions of the physiology, pathophysiology, and pharmacology of the
reproductive system in terms of the hypothalamic-pituitary-gonadal axis.
 I will absolutely do that.
Radiology of the Hypothalamus and Pituitary Gland
Wednesday, December 03, 2008
10:04 AM
Radiology of the Hypothalamus and Pituitary Gland, 12/3/08:
1. Understand available imaging modalities.
 Mainly this is just MRI. If someone has a contraindication to MRIs (eg.
pacemaker) you can use CT; if you're looking for calcified tumors (like
craniopharyngiomas), you can add CT to MRI (CT seems to be good for
picking up calcifications).
2. Identify structures on imaging.
 Yeah. Go to it.
 Mainly this has to do with adenomas: look for a bulge on the pituitary,
particularly if it's non-enhancing (the rest of the pituitary enhances
pretty good).
 This isn't to be confused with the bright spot on the posterior pituitary
(there for who knows what reason).
3. Know the normal appearance of the pituitary and sella.
 Basically the thing sits in the middle of the brain about the way you'd
expect. It's a bulge on top of the sella turcica. It's got a stalk.
 The region of the hypothalamus right next to the pituitary stalk is the
tuber cinerium.
4. Identify common disease states.
 Congenital abnormalities: ectopic neurohypophysis (PPit never
descends from the hypothalamus), or cysts/craniopharyngiomas from
remnants of Rathke's pouch.
 Neoplasms:
 In the stalk: germinomas, pineocytomas, a few other things.
 In the gland: (most common) adenomas (macro: > 1 cm;
micro: < 1 cm).
 In the tuber cinerium: hamartomas (causes hypopituitarism
and seizures) or astrocytomas.
 In the optic chiasm: pilocytic astrocytomas (assoc. with NF-1)
 In the nearby meninges: meningiomas
 Lymphomas and melanocytic tumors are more rare.
 Inflammations:

Commonly, hematomas (hemorrhage of adenoma)-- can lead
to pituitary apoplexy or be a sign of Sheehan's syndrome.
 Meningitis can also cause issues.
 Can be lymphocytic hypophysitis (inflammation of the
pituitary).
5. Describe several rare disease states.
 Hm.. lymphomas and melanocytic tumors?
 It's extremely rare to see a pituitary carcinoma.
Adrenal Gland Physiology
Thursday, December 04, 2008
8:00 AM
Adrenal Gland Physiology, 12/4/08:
1. Identify the key steps in steroid hormone biosynthesis.
 3 classes of steroid hormones (salt, sugar, sex) are each derived from
one of 3 precursors in the following basic pathway:
 (1) Cholesterol is converted to pregnenolone (by either
desmolase, as we were already taught, or also by CYP450
enzymes as per these notes).
 (2) Pregnenolone is acted upon by 17-hydroxylase to form 17OH pregnenolone.
 (3) 17-OH pregnenolone is then converted to
dehydroepiandrosterone (DHEA).
 Mineralocorticoids are derived from pregnenolone.
 Recall that they (salt) are synthesized by the zona glomerulosa.
 Glucocorticoids are derived from 17-OH pregnenolone.
 Recall that they (sugar) are synthesized by the zona
fasciculata.
 Sex steroids are derived from dehydroepiandrosterone.
 Recall that they (sex) are synthesized by the zona reticularis.
 Where the differentiation in synthesis comes from: different levels of
the enzymes required for various stages of cholesterol metabolism in
the pathway above are present in each zona of the adrenal cortex.
2. Describe the transport of glucocorticoids in the plasma.
 Cortisol (the representative glucocorticoids) is lipophilic: most of it is
carried in the plasma by cortisol binding globulins.
 [Once it reaches its target, it binds to cytosolic receptors. The
receptors are normally bound to heat shock protein-70 (Hsp70); once
bound with cortisol, Hsp70 dissociates, the hormone-receptor complex
dimerizes with another hormone-receptor complex, and the dimer
goes into the nucleus to bind to hormone-responsive elements (HREs)
to effect gene expression.
3. Categorize the actions of cortisol on various systems.
 Cortisol: "the fundamental stress hormone in the body." (the other
stress response from the adrenal gland is epinephrine.)
 EPI is very fast-acting, very short-acting; cortisol responds both to
acute and long-term stress by effecting slow but long-acting changes.
 Note that long-term secretion of cortisol can have deleterious effects.
 Metabolic roles of cortisol:

Glucose:
 Induces gluconeogenesis, particularly in the liver.
 Protein:
 Induces breakdown of proteins in muscle to produce AA
for gluconeogenic fuel; leads to weakness over time.
 Lipids: It's lipolytic in the periphery but lipogenic in the central
region:
 Induces breakdown of lipids into free fatty acids in
extremities.
 Induces lipid synthesis from free fatty acids in trunk
(moon facies, buffalo hump).
 Bone:
 Antagonizes the actions of vitamin D in the gut: inhibits
absorption of calcium and phosphate; this leads to
osteoporosis over time as calcium is mobilized from
bone.
 Cardiovascular:
 Increases sensitivity of beta adrenergic receptors; also
potentiates epinephrine release.
 Note that this effect of cortisol isn't direct, but
potentiates the sympathetic nervous system (it's
"permissive" on catecholamines).
 Increases RBC production.
 (Cortisol deficiency = anemia; overproduction =
polycythemia.)
 Connective tissue:
 Decreases the proliferation of fibroblasts (which is why
long-term exposure to cortisol causes skin thinning,
easy bruising, and poor wound healing).
 Kidneys:
 Decreases ADH function (facilitates excretion of water
load).
 Immune system:
 Anti-inflammatory agent due to its suppression of
arachidonic acid synthesis from phospholipase A2 (also,
from Wiki, suppresses histamine effect).
 Without AA and histamines, there isn't a lot of
vasodilation (and thus PMN extravasation) in
response to injury-- the negative effects on
fibroblasts additionally means that wounds can't
be effectively sealed off. Cortisol is thus generally
not given for external wounds.
 Immunosuppressive agent due to its inhibition of T cell
proliferation (from Wiki, evidently due to blocking IL-1
response in T cells).
 Brain function:
 Modulates various signaling cascades; exact role
unknown.
4. Diagram the regulation of ACTH production and release.
 ACTH is produced from the APit in response to CRH stimulation from
the hypothalamus through the portal system.

ACTH is originally produced as a proprotein (proopiomelanocortin or
POMC) and is activated by cleavage (all the comments I'm not
making).
 POMC actually produces a number of different substances: not just
ACTH but MSH (melanocyte stimulating hormones) and endorphin.
 (in passing, this is why if you have primary adrenal
insufficiency, you get hyperpigmentation: too much ACTH
hanging around leads to too much MSH.)
 Note that cortisol, and only cortisol, has a negative feedback effect on
ACTH and CRH, even though ACTH stimulates all three types of
corticosteroids (see next point).
5. Define the actions of ACTH.
 (1) Induces cell proliferation in all layers of the adrenal cortex.
 (2) Increases levels of steroid-synthetic enzymes in all layers of the
adrenal cortex.
 Again, emphasis: despite the fact that ACTH induces increased
production and function of all layers of the adrenal cortex
(sugar, salt, sex), cortisol is the only resultant hormone that
feedback-inhibits ACTH secretion.
 Note a small discrepancy: while in class he implied that ACTH's
effect on aldosterone was respectable, if not the major effector
(that'd be the renin axis), in his notes he says that ACTH only
has a minimal effect on aldosterone.
6. Define the various changes in cortical hormones during adrenal gland dysfunction.
 This is broken down into cortisol hypofunction and cortisol
hyperfunction.
 Cortisol hypofunction etiologies:
 Dysfunction of the adrenal glands themselves: as discussed
here, largely due to Addison's disease (autoimmune
destruction of the adrenals). In this case, the cortisol and
aldosterone levels are low, but the ACTH levels are high (no
feedback inhibition).
 Dysfunction of the pituitary: in this case, the cortisol and the
ACTH levels are low, but the aldosterone levels are normal
(primary regulation of aldosterone is kidney-based: the RAA
axis).
 Cortisol hyperfunction (Cushing's syndrome) etiologies:
 Dysfunction of the adrenal glands (eg. adrenal tumors):
increased cortisol, probably increased aldosterone, decreased
ACTH.
 Dysfunction of the pituitary (eg. Cushing's disease): increased
cortisol, normal aldosterone, increased ACTH.
 Over-administration of exogenous glucocorticoids (iatrogenic):
low endogenous cortisol, normal aldosterone, decreased ACTH.
 Congenital adrenal hyperplasia:
 Genetic defect in certain adrenal corticosteroid synthetic
pathways:
 Defects in the 21-hydroxylase or 11 beta-hydroxylase
enzymes lead to a decrease in cortisol production.
 The decreased cortisol leads to an absence of negative
feedback on ACTH (recall that only cortisol negatively
feeds back onto ACTH); the increased level of ACTH
(which, recall, stimulates all zonas of the adrenal
cortex), plus the backup of steroid precursors, leads to
adrenal hyperplasia and an overproduction of sex
hormones.
 Symptoms: in females, masculinization.
 Signs: increased precursor products to the defective
enzymes (11-deoxycortisol, 17-ketosteroids).
 Note that these can still have some slight effect
on the cortisol receptors.
7. Diagram the release and mechanism of signaling of the medullary catecholamines.
 Adrenal chromaffin cells in the adrenal medulla produce
epinephrine.
 They do this under stimulation from the sympathetic nervous system:
 EPI is stored in secretory granules in the cytoplasm.
 On ACh stimulation from the greater splanchnic nerve, the
membrane depolarizes (it has nicotinic ACh receptors that allow
Na+ influx on stimulation), opening voltage-gated calcium
channels.
 The influx of calcium causes the EPI vesicles to fuse with the
membrane, releasing EPI into the bloodstream.
 Pathway (this should be review by this point): tyrosine is hydroxylated
to form DOPA; DOPA is decarboxylated to form dopamine; dopamine is
hydroxylated to norepinephrine; norepinephrine is methylated to
epinephrine.
 Note this means some small amount of these other compounds
(particularly NE) are produced and secreted as well.
 Where this happens: tyrosine is converted to DOPA and then to
DA in the cytoplasm; DA is uptaken into vesicles and converted
into NE, which then leaves the vesicles to go back into the
cytoplasm and be converted to EPI, which is then stored in
vesicles again.
 The appropriate enzymes are fairly easy to remember once you
know the pathway: tyrosine + tyrosine hydroxylase --> DOPA;
DOPA + DOPA decarboxylase --> dopamine; dopamine +
dopamine hydroxylase --> NE. The NE to EPI enzyme is the
exception (NE + phenylethanolamine N-methyl transferase
(PNMT) --> EPI).
 Putting these two things together, note that certain enzymes
must be stored in the cytoplasm (eg. PNMT and tyrosine
hydroxylase) and certain others (eg. dopamine hydroxylase)
must be stored in the vesicles.
8. Categorize the metabolic actions of the medullary catecholamines.
 Recall that adrenergic receptors come in two main flavors, alpha and
beta. All of them affect G protein-coupled systems:
 Beta-adrenergic receptors act through Gs pathways (increases cAMP
and PKA).
 Alpha-adrenergic receptors are a little distinct:
 Alpha-1 adrenergic receptors act through Gq pathways (PLC,
DAG, IP3, PKC).
 Alpha-2 adrenergic receptors act through Gi pathways (oppose
beta receptor actions).
 Metabolic roles of epinephrine (and NE):
 Glucose:
 Increases gluconeogenesis, mainly from the liver.
 Increases glycolysis, mainly in the liver.
Lipids:
 Increases lipolysis in adipocytes to produce free fatty
acids (activates hormone-sensitive lipase).
 Insulin secretion and action:
 Note that all the above effects are glucagon-like (they
counter insulin).
 Insulin secretion is also regulated: it's more or less
suppressed with the sympathetic response. It's a little
more complicated than that (EPI actually slightly
promotes insulin secretion. NE decreases it)-- but the
EPI response is more or less always drowned out by the
NE response.
 Dr. Vijay: "It [the sympathetic NE/EPI response] is
transiently uncoupling glucose from insulin to prevent
hypoglycemia during times of stress."
briefly, the integrated response of the human body to stress.
"Stress" is perceived by the brain ("oh, crap! Stress!")
Activation of CRH (produces ACTH and thus cortisol).
Direct activation of the sympathetic nervous system (produces NE and
EPI).
The released cortisol acts on the medulla to increase production of EPI
(promotes synthesis of PNMT).
Hypothalamus also releases ADH from the PPit; ADH acts on the APit
to increase ACTH release as well.
 (note this is probably why, as noted above, ACTH depresses,
rather than increases, ADH release-- otherwise you have a
positive feedback loop.)

9. Delineate,





Adrenal Pharmacology
Thursday, December 04, 2008
10:01 AM
Adrenal Pharmacology, 12/4/08:
[Lecture wandered. Best guess follows.]
[There are two main uses for exogenous adrenal steroids: replacement steroids (as
in Addison's) or as anti-inflammatory drugs. Note that when they're used for antiinflammatory purposes, the doses given are usually supraphysiological and entail a
lot of side effects related to an exaggerated degree of their normal physiological
effects.]
[Cortisol is involved with both activation and repression of gene expression.
Activation of gene transcription is generally associated with effects on glucose,
fibroblasts, etc; repression of gene transcription is generally associated with antiinflammatory processes. Note that the repression of transcription involves interfering
with transcription factors; specifically, an inhibition of NF-kB (recall Cohen: "the
mother of all inflammatory processes.").]
[Note that there seems to be no way yet to dissociate anti-inflammation effects
(generally desired) from the other glucocorticoid effects (generally undesired).]
[Note also that all endogenous steroids have some degree of functionality both as a
glucocorticoid and a mineralocorticoid. There are synthetics that do not share this
feature.]
1. Compare the structure-activity relationship of synthetic glucocorticoids
(hydrocortisone, prednisone, dexamethasone, beclomethasone, triamcinolone),
especially those modifications that affect pharmacodynamic activity or route of
administration.
 At the 11 position:
 Hydroxylation (-OH, as in cortisol or hydrocortisone) = intrinsic
glucocorticoid activity.
 Carbonylation (=O, as in cortisone) = inactive until acted upon
by a particular liver enzyme (11-beta-hydroxysteroid
dehydrogenase type I). Note this enzyme isn't found in the skin
(thus you can't use cortisone effectively on skin).
 Note the enzyme converts the carbonyl to a hydroxyl
group in order to activate the compound.
 At the 1 position:
 A double bond between 1 and 2 increases glucocorticoid effect
4-5x (makes prednisolone).
 At the 6 position:
 The further addition of a methyl group increases glucocorticoid
effect to 5-6x (makes methyl prednisolone).
 At the 9 position:
 A fluorine atom creates fludrocortisone: has increased
glucocorticoid activity and also mineralocorticoid activity. Used
in primary adrenal insufficiency.
 If you have both fluorine at carbon 9 and a double bond between 1
and 2, plus a methyl group down on the 16th carbon, you have
dexamethasone (18x the glucocorticoid effect, no mineralocorticoid
activity).
 Prednisone: just prednisolone (cortisol + a 1-2 double bond) with the
11-hydroxyl group converted to a carbonyl (thus inactive until acted
on by the liver).
 Triamcinolone (acetonide): fairly non-polar; can be given as an IM
depot form for long, sustained release or as topical administration.
 Triamcinolone (hexacetonide): injected directly into joints for
inflammation.
 Beclamethasone: can use in inhalers (high-dose delivery direct to
tissues, low systemic effects). Fairly nonpolar.
 Note an abrupt switch from systemic to inhaled glucocorticoids
can cause adrenal insufficiency (see "rapid withdrawal," below).
2. Identify the differences in corticosteroid disposition (protein binding,
biotransformation and enzyme induction) that may necessitate changes in dosage
regimens.
 The more lipophilic the steroid, the more it's going to go into fat and
have a longer duration of action.
 Note that there's an enzyme in the kidney (11-beta-hydroxysteroid
dehydrogenase II) that's more or less the converse of 11-BHDSD I
enzyme in the liver-- it converts the active -OH form to the inactive
=O form. Affinity for this kidney enzyme decreases half-life.
 Synthetics generally bind to circulating cortisol binding globulin much
less well than cortisol does.
 Increased affinity for the receptor extends the half-life.
3. List the adverse effects and contraindications related to corticosteroid use as antiinflammatory and immunosuppressive agents.
 Contraindications: I'm not sure. If your patient is acutely ill, it can be a
bad idea to administer corticosteroids (impair the immune response).
 Two categories of side effects:
 Rapid withdrawal can produce acute adrenal insufficiency.
Here's why:
 Exogenous cortisol feedback-inhibits CRH and ACTH
production.
 If you've been on it for a while, the adrenal glands can
atrophy (they're not getting any ACTH and not
producing any steroids).
 If you then suddenly take the exogenous steroids away,
you can't maintain a normal level of cortisol from your
atrophied adrenal glands.
 Therefore: taper steroids if you're giving them beyond
about 2 weeks.
 Glucocorticoid effects (Cushing's syndrome):
 Diabetogenic
 Osteoporosis (secondary hyperparathyroidism)
 Myopathy
 Amenorrhea
 Hypertension (most glucocorticoids have some
mineralocorticoid activity and lead to sodium retention
and CV volume expansion)
 Purple striae
 Decreased growth in children
 Increased susceptibility to infections
 Psychoses, depression/suicide
 Central obesity/moon facies/buffalo hump
4. Explain the rationale for alternate day therapy and the necessity for slow
withdrawal following chronic therapy with glucocorticoids.
 Necessity for slow tapering withdrawing: discussed above.
 Alternate day therapy: give every other day; the idea is to prevent
atrophy of the adrenal glands. You time the administration of cortisol
during the times of the day when ACTH is low anyway.
5. Compare the actions of the following drugs:
 Aminoglutethimide: inhibits cleavage of side chain (inhibits conversion
of cholesterol to pregnenolone); also inhibits aromatase (which
catalyzed conversion of androgens to estrogens).
 Ketoconazole: inhibit CYP450 enzymes that mediate steroid synthesis.
 Metyrapone: inhibits 11-beta-hydroxylase (like congenital adrenal
hyperplasia deficiency)-- inhibits cortisol synthesis. Note that this is
the only compound listed here that is specific to glucocorticoids.
 Mifepristone: progesterone receptor antagonist; at high doses, also
blocks glucocorticoid receptors.
 Mitotane: compound toxic to adrenal mitochondria.
6. List the analogs used in mineralocorticoid replacement therapy.


You don't use aldosterone (degraded way too quickly by liver).
Fludrocortisone is generally the replacement drug in primary adrenal
insufficiency.
7. Explain the rationale for spironolactone in treating primary hyperaldosteronism.
 Spironolactone is an aldosterone receptor antagonist: it can help treat
the excess aldosterone secreted by adrenal tumors. Note it can also
block some sex hormones.
Cultural Sensitivity Surrounding Patient Care
Thursday, December 04, 2008
10:59 AM
Cultural Sensitivity Surrounding Patient Care, 12/4/08:
[As per Dr. Michaels: we will, in fact, be tested on this.]
[See statistics on first page of notes.]
[I really have no idea how to fill these out. I'd glance at this and read the
notes/slides thoroughly, but I'm stumped.]
1. Recognize the clinical presentation of adolescent patients with Diabetes Mellitus.
 ..?
 [Discuss:]
 Type of insulin, dose, what the basal rate of a pump is.
 Ask what the average blood sugar readings are (diabetic
teenagers tend to have higher readings than adults-- often in
the 300's).
 Framing the question is important ("your blood sugars
are in the 300's or 400's, right?").
 Ask how many low blood sugars since last visit.
 Ask about episodes of DKA or other illnesses
 Ask about diet and exercise.
 Emphasis here is placed on how you ask questions to
adolescents: "do you drink 5 or 6 cans of soda a day?" as
opposed to "do you drink soda?"
2. Identify the elements of the chronic care model appropriate to Diabetes Care.
 Increase patient motivation for self-care (put a face on the disease, be
upfront about risks of lack of care-- possibly have an example of
someone who doesn't take care of their diabetes).
 Make education/care guidelines available.
 Improve the delivery system design: make sure missed appointments
are minimized (plan patient visits well in advance, stay in contact,
aggressively pursue missed appointments).
 The problems are largely psychosocial and less medical with
adolescents-- putting them in an environment in which other people
have diabetes and letting them get more comfortable and more
"normal" with their diabetes care is often a good idea.
 Increase awareness and support in community and family.
3. Elaborate the issues of applying the chronic care model with patients varying in
age or educational background.



..?
"Learn your [diabetic] medicine, be aware of culture [both medical and
patient's], ask and listen, validate differences, empower your
patients."
That last one: make sure the patient knows that it's their call-- "I get
paid whether or not you take your insulin."
Hospital-Based Nutrition
Friday, December 05, 2008
7:50 AM
Hospital-Based Nutrition, 12/5/08:
1. Describe an approach to deciding when to begin feeding a hospitalized patient who
cannot feed themselves.
 When patients will probably start to develop serious nutritional
deficiencies (feed around these times):
 Previously well-nourished patients who can't eat but are
minimally ill: 10-14 days.
 Previously well-nourished patients who are seriously, acutely ill,
or previously undernourished patients who are minimally ill: 57 days.
 Previously undernourished patients who are seriously, acutely
ill: 3-5 days.
 [Note that we feed infants after about 2 days-- they have way
increased metabolic needs.]
 [why you don't just stick a feeding tube in everyone immediately:
tube/IV feeding has significant risks (aspiration, infection). Want to
wait if you can.]
 [that said: sometimes you really do need to stick a tube in someone
immediately. And you want to watch out for GI atrophy when someone
isn't feeding.]
2. Describe an approach to estimating the number of calories per day that a sick
patient in the hospital will need.
 Ranges from 22-25 kcal/kg/day in a reasonably healthy patient to 3032 kcal/kg/day in a very sick patient. So you need to multiply the
appropriate number in this range by the patient's weight in kilos.
 "Dan's Sick-O-Meter:" from 22-32 kcal/kg/day, depending on how sick
they are (more sick = higher Sick-O-Meter).
3. Describe an approach to writing an order for nutritional support in a hospitalized
patient.
 Assessment, largely clinical, for need for feeding:
 Hx of alcoholism/homelessness, elderly, bad chronic disease,
prior weight loss, BMI < 19, thenar wasting, etc.
 Can also use albumin and lymphocyte counts, but have low
sensitivity.
 If you can feed enterally, do it. Less infection risk, better absorption,
and maintains GI integrity. Can feed regular small amounts (mLs) just
to do that last one.
 Need to figure out how many calories, protein, etc are in the enteral
feeding goop at a given hospital.
 Note that, in general, calorie content is 1 kcal/mL.
Note also that most people in the hospital are getting IV glucose (5%
dextrose); so you may need to reduce the carbohydrate content of the
enteral feed.
 Want to start feeding slowly (maybe 10-20 mL/hr).
 Central issues: can the person swallow safely? How well can the GI
tract deal with nutrients?
 Types of diets:
 Clear liquids: carbohydrates and broth
 All liquids: + juice, etc.
 Canned supplements: Ensure, etc.
 Mechanical soft: ground meat, oatmeal, tapioca
 Low-sodium diet
 Diabetic diet (want consistent amounts of carbohydrates)
4. Describe an approach for determining if a person who is getting long term
nutritional support is being fed adequately.
 Overfeeding: watch for hyperglycemia after a few days of overfeeding
(glycogen stores have been saturated); it will probably be resistant to
correction by insulin (notes: "the cupboard is full"). May take a few
days to resolve (glycogen stores need to be broken back down).
 Underfeeding: watch for increased excretion of nitrogen in the urine
(measure of protein breakdown) relative to the amount of
nitrogen/protein coming in.
 (how to do this:) multiply grams of nitrogen in the urine by
6.25-- this will give you a measure of how many grams of
protein were broken down. Then compare that to how many
grams of proteins are being taken in. If the first number's more
than the second number, it's probable the patient is being
underfed.
 Make sure patients are getting enough vitamins, essential fatty acids,
and AAs-- note that sometimes AAs are essential in illness even if
they're usually nonessential (eg. glutamine, arginine).
5. List some of the special issues associated with feeding a hospitalized patient with
pulmonary, liver or kidney disease.
 Respiratory failure (usually on a ventilator):
 Overfeeding is bad-- it causes increased CO2 production (end
product of metabolism) and increased O2 consumption; this
increases the need for ventilation and can delay getting the
patient off the ventilator.
 Liver failure:
 Problems with hepatic encephalopathy and ascites.
 HE arises (probably) from amino acid breakdown; ascites is
worsened by high salt and water intake.
 Thus probably want to restrict protein, water, and salt intake.
 Kidney failure:
 Problems with excreting urea (product of protein breakdown).
 Thus probably want to restrict protein intake.
 Note that if you're restricting protein intake, don't be dumb. People
need protein. Just don't give too much.

International Nutrition
Friday, December 05, 2008
8:55 AM
International Nutrition, 12/5/08:
1. Name 3 of the 8 Millennium Development Goals (MDG)
 MDGs (to be achieved by 2015):
 Eradicate extreme poverty and hunger
 Achieve universal primary education
 Promote gender equality and empower women
 Reduce child mortality
 Improve maternal health
 Combat HIV/AIDS, malaria, and other diseases
 Ensure environmental sustainability
 Develop a global partnership for development
2. Describe a framework for the contextual factors that contribute to malnutrition
 The idea is to understand malnutrition not as simply inadequate food
intake but all the causes that contribute to it. Why this is important:
you can't kill a hydra just by destroying its heads
(http://www.perseus.tufts.edu/Herakles/hydra.html).
 Basic or fundamental causes:
 Lack of capital
 Social, economic, and political context
 Underlying causes (or sort of 'intermediate'):
 Poverty
 Food insecurity
 Unhealthy household environment
 Inadequate health care
 Immediate causes:
 Inadequate intake
 Disease
3. State and describe 3 major nutrition problems in developing countries
 (this really could be either of two sets of information:)
 (1A) General nutrition requirements (total calories, carbs, fat,
protein):
 Poor growth (predominantly stunting) is the biggest mortality
risk factor in children.
 Maternal nutrition deficiencies: stunted-growth girls grow up
into stunted-growth women who have trouble with pregnancy.
 (1B) Micronutrient requirements
 Predominantly vitamin A, zinc (+iodine, calcium), iron.
 No zinc: cognitive defects, stunted growth. Note that the WHO
recommends 20 mg of zinc at the onset of diarrhea.
 (1C) Infectious disease (mainly diarrhea)
 (2A) Target maternal health and birth outcomes:
 Iron and folate supplementation, iodine fortification, limit
indoor pollution and tobacco use, decrease incidence of
postpartum hemorrhage, treat HIV/AIDS.
 (2B) Target newborn babies:
 Promotion of breastfeeding.
 (2C) Target infants and children:

4. State and
populations;








Promotion of Zn supplementation (diarrhea, growth), iodine
fortification of salt, handwashing/hygiene.
describe 4 approaches to improving nutritional status in vulnerable
describe pros and cons of each approach
(the pros are generally fairly obvious. Here I've just listed the cons.)
Food giveaways: problems with depressing the markets in the target
countries.
Daily micronutrient supplements: need to think about doses
(particularly with iron), interactions, safety; also which ones to use,
and how to distribute it and make it sustainable.
Home fortifications with micronutrients ("Sprinkles" being distributed
by the WHO): efficacy, bioavailability (+ phytate = less absorption),
dose, etc.
Staple food fortifications: what vehicle? Is the dose safe for
everybody?
Plant breeding to enhance bioavailability, reduce phytate: doesn't have
a lot of effect.
Plant breeding to enhance nutrient content: cost, sustainability.
Dietary diversification (small animal husbandry, increased fertilizer
distribution for home gardens, etc): cost, sustainability.
Neuroendocrine Regulation of Appetite
Friday, December 05, 2008
11:00 AM
Neuroendocrine Regulation of Appetite, 12/5/08:
[An unenviable mix of too much detail and too many tangents. Best guess follows.]
1. Describe the respective roles of the arcuate nucleus, paraventricular nucleus,
ventromedial nucleus, and lateral hypothalamus in regulation of appetite, meal size,
and long-term maintenance of body weight.
 Lateral hypothalamus: 'hunger center' (stimulation --> eating when
full)
 Uses melanin concentrating hormone and orexins as
neurotransmitters-- these peptides seem to be responsible for
food-eating behavior.
 Ventromedial nucleus: 'satiety center' (stimulation --> no eating when
hungry)
 Arcuate nucleus: can promote either hunger or satiety. Its neurons
project to the paraventricular nucleus and lateral hypothalamus; some
of them release appetite-stimulating neurotransmitters, some release
appetite suppressing NTs.
 The two types of NTs (found in distinct populations in the
arcuate nucleus) synapse onto neurons that produce the
appropriate effects (appetite stimulation or suppression).
 Note one of the appetite-suppressant NTs is melanocyte
stimulating hormone (MSH), part of the ACTH proprotein.
(stress response --> appetite suppression so's you don't stop
for a burger while running from the lions).

Note that injections of these various NTs cause the appetite
effects they're associated with.
 Melanocortin receptors: promote satiety.
 MSH acts on melanocortin receptors (promotes satiety) and has
effects in the spinal cord.
 NPY acts to promote appetite.
 This is a big mess. Go look at the diagram on p. 5 of her notes to try
and sort it out.
 Note that, like temperature, body weight has a sort of 'set point' in the
hypothalamus; after force-feeding or deprivation, body weight tends to
return to that point.
 Paraventricular nucleus: project to brainstem and spinal cord
(sympathetic neurons); also contains neurons that secrete TRH-alterations in thyroid hormone levels influence appetite, since they
determine the rate of metabolic energy expenditure.
 [The median eminence (next to the arcuate nucleus) lacks a bloodbrain barrier-- thus substances in the brain can have effects through
the median eminence on arcuate/paraventricular nuclei and thus on
appetite.]
 (Note norepinephrine and serotonin release onto the arcuate nucleus
also cause satiety.)
 Short-term regulation: mainly GI mechanisms and blood glucose levels
(see below).
 Long-term regulation of body weight:
 Main mechanisms used are leptin (hormone produced by
adipose cells, affects arcuate nucleus and VMN) and insulin
(circulates at a proportional level to body fat mass, transported
into the hypothalamus to affect hunger/satiety). Note that
insulin also changes the blood glucose levels, which affect
hypothalamic appetite signaling as described above.
2. Describe the mechanisms used by the hypothalamus to induce eating.
 ANS
 Endocrine mechanisms
 Control over somatic muscles
3. Define glucostat and describe the mechanisms used for glucose sensing in the
hypothalamus.
 As far as I can tell, the only mention of "glucostat" in her notes is in
reference to the "glucostat hypothesis," which (implicitly) states that
glucose levels affect appetite regulation.
 Hypoglycemia: induces feedings; inhibits satiety.
 Specifically, in the ventromedian nucleus, an increased glucose is
stimulatory; in the lateral hypothalamus, a decreased glucose is
stimulatory.
 How that works:
 In the VMN, increased glucose increases intracellular ATP,
closing potassium channels (kind of like the glucose-sensitive
insulin release in beta cells) and depolarizing the cells.
 In the LH, decreased glucose decreases intracellular ATP,
decreasing the activity of the ATP-dependent Na/K pump,
leading to a decrease in intracellular potassium and
depolarizing the cells.
4. Predict the impact on body weight of "knocking out" the POMC gene (and
therefore, alpha-MSH), of "knocking out" the NPY gene, and of mutations in the
melanocortin receptor.
 Knocking out the POMC gene (and thus MSH) would result in
inappropriate hunger (recall MSH mediates satiety) and presumable
weight gain.
 Knocking out the NPY gene would result in inappropriate satiety (recall
NPY mediates hunger) and presumable weight loss.
 Mutations in the melanocortin receptor would result in inappropriate
hunger (recall MSH binds to the melanocortin receptors) and
presumable weight gain.
5. Describe the role of peripheral hormones derived from the GI tract (ghrelin,
cholecystokinin, gastrin releasing peptide, glucagon-like peptide), pancreas (insulin,
glucagon), and adipose tissue (leptin) in regulating meal size and body weight.
 Ghrelin induces hunger (acts directly on hypothalamus to active NPY).
 CCK, GRP, and GLP all act on an area called the area postrema (next
to the nucleus of the solitary tract) to bring about satiety. Gastric
stretch also communicates through the solitary tract (through the
vagus).
 Note that the solitary tract sends efferents to the arcuate nucleus,
VMN, and PVN (also to the thalamus, amygdala, and 'visceral cortex').
 Leptin: as noted, acts on the hypothalamus to promote satiety.
6. Discuss the role of brain reward pathways in development of obesity.
 "Animals will consume sweet and salty foods past the need for
repletion of energy."
 Taste information is passed to the reward pathways in the brain
(amygdala, nucleus accumbens, PFC)-- the dopamine pathways
therein seem to be implicated in building addictive behavior to food.
 Evidently there are connections back and forth between the nucleus
accumbens and the lateral hypothalamus.
 Food addiction, particularly to sweet things, tends to obesity. Next in
the news: sunlight predisposes to tanning.
Adrenal Disorders
Monday, December 08, 2008
7:39 AM
Adrenal Disorders, 12/8/08:
[LOs interpreted: "understand all 15 pages of my handout." FYI.]
1. To understand the features of tumors arising in the adrenal gland medulla:
pheochromocytoma.
 Rare tumor: 2-8/million/year.
 Signs/symptoms: possibly hypertension; more classically, headache,
palpitations, and diaphoresis. This triad has > 90% specificity for
pheochromocytomas.
 Etiology:
 RET receptor on the adrenal medulla cell (binds GDNF, causes
growth of cell and catecholamine secretion) contains a mutation
that causes it to be perpetually active.







This mutation can be sporadic or familial. Familial types are
associated with clinical syndromes (the RET receptor is
scattered throughout the body): specifically, multiple endocrine
neoplasia 2 syndromes (MEN-2A and MEN-2B).
 Hereditary pheochromocytomas are also associated with
the VHL gene and the NF-1 gene.
Note that adrenal chromaffin cells secrete both EPI and NE, in varying
proportions.
 Recall that EPI causes vasodilation (through beta-2 receptors),
while NE causes vasoconstriction (through alpha-1 receptors).
 An EPI-dominant tumor is unlikely to cause hypertension, while
with a NE-dominant tumor it's more likely.
 So if you put a pheochromocytoma patient on beta-blockers,
what you're doing is removing the vasodilatory effects that are
opposing the excess NE's vasoconstriction-- you can cause a
hypertensive crisis.
Pheochromocytoma symptoms can be episodic and have a wide
differential diagnosis; history is very useful in narrowing it down. It's
relatively common to misdiagnose pheochromocytomas as anxiety.
Note that pheochromocytomas do not cause flushing.
"Endocrine principle:" always make a biochemical diagnosis before
imaging. The reason is that there are frequently nonfunctional or
incidental tumors found on imaging that don't correlate to the clinical
symptoms. So make sure there really is an excess of a given
biochemical before getting the MRI.
Biochemical tests for pheochromocytomas:
 Predominantly, you look for catecholamines (dopamine, EPI,
NE) and their metabolites (HVA, VMA). The tumor can secrete
varying levels of lots of different related enzymes, so want to
cast a fairly wide net.
 Generally you don't measure them in plasma, since sticking a
needle in a person frequently causes high levels of
catecholamines (though you can measure metabolites); instead
you use 24-hour urine collections.
 Over this 24 hours, the patient needs to avoid a wide
variety of drugs that could affect the results (see notes
p. 4 for complete list).
 This is most useful when symptoms occur during that
24-hour period.
10% rule of pheochromocytomas: 10% bilateral, 10% extra-adrenal
(though usually still in the abdomen), 10% malignant. If you can't find
something on the adrenals, try the rest of the abdomen.
Treatment:
 Adrenergic blockade (watch out for beta-blockers alone; can
use alpha + beta or alpha-beta blockers like labetalol).
 Only curative treatment is surgery-- problem is that with
manipulation, the pheochromocytoma is going to emit crazy
amounts of catecholamines. So make sure the patient is on
adrenergic blockade first.
2. To understand the disorders caused by excess function of the adrenal cortex:
Cushing's syndrome and Hyperaldosteronism.
 Primary hyperaldosteronism: aka Conn's syndrome.


Note this is the second most common cause of HTN and the
most common cause of non-primary HTN.
 Screening: look at aldosterone levels in comparison to plasma
renin:
 If the aldosterone levels are high and the renin levels
are low, suspect Conn's syndrome.
 If the aldosterone high and the renin is also high, that's
not Conn's, that's a normal physiological response to
something (problem isn't in the adrenals, it's somewhere
else).
 If the aldosterone is low and the renin is low as well,
suspect congenital adrenal hyperplasia (11-beta-OHase
deficiency) or Cushing's syndrome.
 Specifically:
 Aldosterone should be > 15 ng/dL
 Aldosterone/plasma renin ratio should be > 20
 To confirm diagnosis, try to suppress aldosterone levels by
giving IV saline for a few hours. If aldosterone stays up, that's
probably primary hyperaldosteronism; if not, it's probably not.
 Clinical presentation:
 Hypertension (must be there)
 Hypokalemia-- aldosterone wastes K (not always there)
 Young age
 Resistant to multiple HTN medications
 Severe HTN (> 160/100)
 (note, in passing, that severe HTN resistant to multiple
medications can also be kidney disease.)
 Imaging: get an adrenal CT. If that's negative, try adrenal vein
sampling (can be a dysfunction within the adrenal gland
without hyperplasia).
 More rare causes: glucocorticoid-remediable
hyperaldosteronism, aldosterone-producing carcinoma.
 Glucocorticoid-remediable hyperaldosteronism is caused
by a mutation where the zonas glomerulosa and
fasciculata layers are kind of fused, and the ACTH
receptor is placed directly upstream of the promoter of
aldosterone synthase.
 This causes you to have increased levels of aldosterone
every time you secrete ACTH (which is fairly frequently).
 You can treat it with glucocorticoids, which suppress
ACTH.
 Treatment: generally surgery; can also treat with
spironolactone (or glucocorticoids if you're fortunate enough to
have the GRH variety).
Cushing's syndrome:
 Any chronic glucocorticoid excess (iatrogenic or not). Iatrogenic
is by far the most common cause (exogenous glucocorticoid
administration).
 Other than that, ACTH-secreting tumors are the most common
cause (Cushing's disease). Cortisol-secreting adrenal tumors
are relatively infrequent (< 20% of endogenous).



[Long discussion on side effects of glucocorticoid excess. We've
covered it several times already, though this is a reasonably
good summation (p. 9-10).]
Testing: also already gone over, but worth repeating. Recall
cortisol levels are pulsatile, so you can't just take a random
blood sample. Get a 24-hour free cortisol measurement in the
urine and/or do an overnight dexamethasone suppression test.
If those show Cushing's results (high cortisol/no suppression),
get plasma ACTH levels to see if it's ACTH-dependent (ie, from
an ACTH-secreting tumor). If that's low (generally lower than
normal), there's likely an adrenal source-- ACTH is being
suppressed by the over-abundant cortisol production. (note in
small groups the approach was different.)
Treatment: generally surgery. Can also use various anti-adrenal
drugs like ketoconazole. Note adrenal carcinoma has an
extremely poor prognosis; can use mitotane to chemically
destroy the adrenal glands.
3. To understand the features that characterize adrenal cortex hypofunction:
Addison's disease.
 In the US, the leading cause of primary adrenal insufficiency is
autoimmune, and that means Addison's disease.
 (Worldwide, the leading cause is tuberculosis.)
 (There are a plethora of minor causes: fungal, HIV, metastases, etc.)
 (Note that the primary cause of secondary, or central, adrenal
insufficiency is abrupt withdrawal of glucocorticoid administration or
curing Cushing's syndrome.)
 Effects of cortisol deficiency:
 Decreased appetite, hypotension, decreased cardiac output,
decreased ability to respond to stress, hypovolemia.
 Chronic signs/symptoms of Addison's:
 Hyperpigmentation, fatigue, anorexia, weight loss, nausea,
abdominal pain, diarrhea. Note most of these are very
nonspecific except for hyperpigmentation (but that's not always
present).
 Hyperpigmentation in the palmar creases, the nail beds,
the pubic or axillary regions, the gumline, etc, should
give you pause and suspicion.
 As mentioned before, the cause of this
hyperpigmentation is that ACTH is secreted as part of a
larger proprotein (POMC), part of which contains a
melanocyte-stimulating hormone.
 Acute signs/symptoms of Addison's (life-threatening crisis, as in times
of extreme physiological stress): Severe hypotension, fever,
obtundation. Addison's patients should wear medical alert bracelets so
that paramedics can give them steroids.
 Diagnosis:
 Labs are frequently unhelpful. Classically you see hyponatremia
and hyperkalemia (inverse of Conn's). Look for hypoglycemia in
the fasting state.
 Use a stimulatory test: administer synthetic ACTH, look for an
absence of associated rise in cortisol.




Alternative method: look for loss of diurnal secretion pattern.
Normally you see a nadir in the evening and a peak at about 8
AM; check midnight levels of ACTH (should be low) and see if
they're high.
Treatment:
 Generally replace with oral steroids; depending on how much
mineralocorticoid support they need, can use prednisone (has
low mineralocorticoid activity), hydrocortisone (has some
mineralocorticoid activity), and/or fludrocortisone (has high
mineralocorticoid activity).
 Acutely, give fluids and IV stress-dose (high-dose)
hydrocortisone.
Polyglandular Autoimmune Syndrome:
 Associated autoimmune disorders with Addison's:
 Hypothyroidism (very common)
 Hypoparathyroidism
 Diabetes type I
 Pernicious anemia
 Graves' Disease
 Premature ovarian failure
"Main point: the symptoms of hypoaldosteronism are so vague, you
need to have a high clinical index of suspicion in order to diagnose it."
Look for other autoimmune diseases, etc.
Adrenal Imaging
Monday, December 08, 2008
9:57 AM
Adrenal Imaging, 12/8/08:
No LOs were posted. Here's some notes from the lecture. Note that I have no idea
what she's talking about for the most part.
[They did, eventually, post LOs, but they were pretty vague (1. Understand available
imaging modalities; 2. Identify structures on imaging; 3. Know the normal
appearance of the adrenal gland; 4. Identify common disease states; 5. Describe
several rare disease states). I don't know that I can add much here. Might go look at
the Powerpoint.]
Three general imaging modalities: CT, MRI, PET. Note diagnostic characterization is
roughly the same between CT and MRI.
Benign/malignant adrenal lesions are differentiated based on the degree of
intracellular fat, as picked up by CT or MRI (PET really only looks at metabolic
activity).
 This is largely differentiated by "HU" ('threshold level' or attenuation
value) - a value of 10 HU or less is sort of the magic number, at which
the sensitivity is 71% and the specificity is 98% for benign lesions.
Higher than that and you need more tests to figure out if it's
malignant.
Benign lesions:
 Adenoma, myelolipoma, cyst.
 Take three scans: no contrast, with contrast, and then a delayed
contrast.
 Myelolipomas are diagnosed by macroscopic fat (low take-up of
contrast).
 Adenomas have < 10 HUs and/or a high "wash-out percentage" (>
60%).
 Cysts just have < 10 HUs (without "wash-out"?)
Non-benign lesions:
 Metastases, pheochromocytomas, primary carcinomas.
 These don't demonstrate as much "wash-out percentage" (< 60%)
and are often HU > 20 or 30.
 Low "wash-out" = retention of contrast (= not a lot of fat.. I think?) =
more malignant
Incidental, generally asymptomatic findings on imaging: adrenal adenomas,
renal/hepatic/pancreatic cysts, hepatic hemangioma, thyroid nodules.
Thyroid and Parathyroid Histology
Tuesday, December 09, 2008
7:47 AM
Thyroid and Parathyroid Histology, 12/9/08:
1. Illustrate the basic structure of the thyroid and parathyroid glands.
 Thyroid glands: majority of the gland isn't made up of cells, but
rather extracellular gell-like structures full of protein. These are called
colloids and are the storage depot for thyroglobulin (pro-thyroid
hormone).
 Each of these colloids are surrounded by a single layer of columnar
epithelium-- the unit of colloid plus epithelium is called a follicle and
the epithelial cells are also named follicular cells.
 In addition to the follicles, there is a more or less unstaining type of
cell wedged in between the follicles-- the C cell ("C" for "clear," or
alternatively for "calcitonin"), which secretes, you guessed it,
calcitonin.
 Thyroid hormone:
 Starts with tyrosine (has a hydroxylated aromatic ring as a side
chain).
 If you hook up two tyrosine residues through an aromatic ether
linkage, and throw a few iodine residues onto it, you've more or
less got thyroid hormone.
 Note that the dimer can have three (T3) or four (T4) iodine
residues.
 The thyroid makes considerably (15-20x) more T4 than T3;
however, T3 is much more biologically active than T4. Note that

T4 can be activated (converted to T3) in various peripheral
tissues.
 Synthesis:
 The follicular cells uptake iodide through an ATPdependent mechanism (basolateral side) and release it
into the colloid (out the apical side).
 The follicular cells also synthesize thyroglobulin-- a big
protein with lots of tyrosine residues. This, also, is
secreted into the colloid.
 The final thing that the follicular cells secrete into the
colloid is thyroperoxidase: this both mediates the
attachment of 1 or 2 iodines to tyrosine residues on
thyroglobulin (making monoiodotyrosine or MIT and
diiodotyrosine or DIT) and also couples two nearby
iodinated tyrosine residues together.
 If one of the two tyrosine residues is MIT and the
other is DIT, the resultant dimer will have three
iodine residues (T3).
 If both of them are DIT, the resultant dimer will
have four iodine residues (T4).
 It doesn't seem to happen that you link two
MITs.
 So thyroglobulin is hanging out in the colloid, with all its linked
and iodinated tyrosine residues. When a signal comes by to
release some thyroid hormone, the follicular cells endocytose
(uptake through endosomes) thyroglobulin and take it to their
lysosomes.
 Once the thyroglobulin arrives at the lysosomes (which are
numerous in follicular cells), it's degraded by proteases-- this
releases the cross-linked tyrosine residues to form free T3 and
T4. These, then, are released into the bloodstream.
 The TSH signal is what stimulates the uptake of thyroglobulin
into the follicular cell.
 Without TSH signaling, you accumulate lots and lots of
thyroglobulin in the colloid; this expands the colloid and
can cause goiter (thyroid nodules).
 With too much TSH signaling (as in low dietary iodine,
see next point), the TSH stimulation causes cellular
hypertrophy; this can also cause goiter.
 Low dietary iodine can cause increased TSH secretion:
can't iodinate tyrosine, so not much thyroid hormone, so
not much feedback inhibition on TSH.
 Note T3 and T4 are necessary for proper development of
the nervous system-- iodine deficiency in utero and in
childhood causes mental retardation and stunted growth
(thyroid hormone is essential for GH synthesis).
Calcitonin: decreases calcium levels in blood (generally to deposit it in
the bone matrix). Note it's not really under regulation by the pituitary- mainly just by Ca++ levels in the blood.
 Specifically, calcitonin inhibits osteoclasts and activates
osteoblasts.

Parathyroid glands: 4 of them (occasionally 6 instead); are
generally embedded in the posterior capsule of the thyroid gland.
Contain chief or principal cells, which secrete parathyroid hormone.
 Parathyroid hormone: peptide that opposes the activity of
calcitonin. It increases calcium levels in the blood, but through
a few different mechanisms:
 In the bone, it activates osteoclasts and inactivates
osteoblasts.
 Acts in the kidney to increase the reabsorption of
calcium.
 Acts in the intestinal tract to increase the uptake of
calcium.
 Note that parathyroid hormones are absolutely essential for
calcium regulation, as opposed to calcitonin, which only "finetunes" the plasma calcium levels.
2. Identify the basic blood supply to the thyroid and parathyroid glands.
 Not actually in this lecture. The following lecture specifies that the
superior and inferior thyroid arteries supply the thyroid.
 Wiki says the superior parathyroids get blood from the inferior thyroid
artery, while the inferior parathyroids get blood from the superior
thyroid artery.
 Note the thyroid gland receives the greatest blood supply of all
endocrine organs.
3. Describe the embryological origin and development of the thyroid and parathyroid
glands.
 The follicular cells of the thyroid are derived from pharyngeal
endoderm. The C cells (aka parafollicular cells) are derived from the
fourth branchial pouch.
 The parathyroids seem to arise from the third and fourth branchial
pouches.
4. Match the hormones produced with the cell types that produce them.
 Thyroid hormone: follicular cells
 Calcitonin: C cells
 Parathyroid hormone: chief/principal cells
Regulation of Thyroid Hormone Synthesis
Tuesday, December 09, 2008
8:53 AM
Regulation of Thyroid Hormone Synthesis, 12/9/08:
1. Describe the uptake of iodine from plasma by the thyroid gland.
 Iodide, as mentioned, is a trace mineral in the diet.
 The follicular cells uptake iodide through an ATP-dependent
arrangement on their basolateral side (from the blood).
 You need an ATP-dependent mechanism because the iodide is pumping
against both a concentration gradient (30x more I in the cell) and an
electrical gradient (cell's ICF is already more negative than the ECF
surrounding it).

How it works: sodium and iodide are co-transported into the cell, then
sodium is pumped out of the cell in exchange for potassium by the
basolateral Na-K ATPase.
 This is also called the "iodide trap."
 The iodide (I-) is taken toward the apical (/colloidal) side of the cell,
where it's acted upon by thyroperoxidase to convert it into a free
radical, or active, iodine (I·).
2. Explain the synthesis and release of thyroglobulin into the lumen of the thyroid
follicle.
 The follicular cells synthesize lots of thyroglobulin, as mentioned-- this
is the source of thyroid hormone tyrosine. It's transported out into the
colloid.
 [Note that colloid is really just highly concentrated and cross-linked
thyroglobulin.]
3. Identify the steps in thyroid hormone synthesis and its release into the blood.
 In the colloid, the tyrosine residues on the thyroglobulin are iodinated
by thyroperoxidase (either once or twice).
 Thyroperoxidase then catalyzes the ether linkage of two adjacent
tyrosine residues.
 As mentioned in the last lecture, this can produce either 3x (MIT +
DIT) or 4x-iodinated (DIT + DIT) dimers, still attached to the larger
molecule.
 Again, upon stimulation with TSH, the follicular cells reuptake
thyroglobulin from the colloid and degrade it to release T3 and T4
(much more T4 than T3). Note that the other byproducts of this
degradation are amino acids and unlinked MIT and DIT residues.
 T3 and T4 are then released into the bloodstream by T3/4-specific
transporters.
 Note the positions of the iodine residues on T4: 3, 5, 3', 5'. On T3: 3,
5, 3'.
 This is important because there's another, inactive form of T3 (reverse
T3), which has a different iodination pattern (3, 3', 5').
 Recall that there's an aromatic ether linkage in thyroid hormone. This
makes it not very soluble-- alone among the major tyrosine derivative
hormones. This is why it behaves largely as a steroid hormone
(lipophilic).
4. Describe the transport of thyroid hormones in the plasma.
 As mentioned, T3/4 aren't very soluble. Only a very small fraction of
T3/4 are freely dissolved in the plasma; the great majority is bound to
thyroid hormone binding globulin (THBG, not to be confused with
thyroglobulin in the gland itself).
 Like other steroid hormones, it's the free levels of thyroid hormone
that determines the biological activity of thyroid hormone.
 Note that THBG likes to bind T4 (99.97%) better than T3 (99.6%).
5. Categorize the actions of thyroid hormone.
 T3 and T4 enter the cell by active transport.
 In the cytosol, T4 is deiodinated (converted to T3).
 T3 binds to its receptors (usually nuclear, bound to the DNA itself).
 Resultant actions:
 Primary function is to control the balance of anabolism and
catabolism, through the local metabolic pathways in the cell.
 It promotes both sides of that balance-- but by reducing thyroid
hormone, you shift the set point to favor anabolism
(synthesis/storage); by increasing thyroid hormone, you shift
the set point to favor catabolism (breakdown/heat generation).
Another way of saying this is that increased thyroid hormone
promotes a higher basal metabolic rate.
 Hypothyroidism: energy utilization and heat production are
impaired (cold intolerance).
 Hyperthyroidism: heat is overproduced (heat intolerance),
energy storage is impaired.
 (Prolonged starvation: drops TSH dramatically, decreasing
basal metabolic rate to conserve energy.)
 Thyroid hormone is essential for development; excess levels of thyroid
hormone accelerate maturation.
 Many hormones' function and synthesis are dependent on thyroid
hormone levels, growth hormone in particular (TH is permissive for
GH).
 Hypothyroidism is reasonably common (1/5,000 live births in the US)- check thyroid hormone levels at birth to effect early intervention.
 Uncorrected hypothyroidism during development leads to cretinism-severe mental and growth retardation.
6. Diagram the normal regulation of thyroid hormone levels by the hypothalamicpituitary axis.
 Hypothalamus produces TRH, which acts on the thyrotrophs of the APit
to produce TSH. TSH acts on the thyroid to stimulate cleavage and
release of T3 and T4.
 T3 (evidently only the active form, not T4) has an inhibitory feedback
effect on TRH and TSH.
 How TSH works in a nutshell:
 TSH is a peptide hormone; its receptor is a Gs receptor which,
when bound, increases the level of cAMP and PKA activity in the
follicular cells.
 This causes increased follicular cell proliferation; it also
increases the levels and activities of thyroperoxidase,
thyroglobulin production, and the iodide uptake system.
 Note that the iodide transporter can be competed for by other small
anions-- certain vegetables, like cabbage, contain thiocyanate, which
competes for iodide's uptake transporters. End message: if you don't
want to eat your cabbage, tell your parents it'll stunt your growth and
make you stupid.
[Some discussion of hypo- and hyperfunction of the thyroid gland:]
 Hypothyroidism (low T3/T4 levels) can result from:
 A destruction or blockade of the thyroid gland (as autoimmune
in Hashimoto's thyroiditis; will be discussed next hour)-- leads
to high levels of TSH secretion (released from feedback
inhibition).
 Note low levels of iodide in the diet (or too much
cabbage) can look like this (low T3, high TSH) as well.
 Hypopituitarism-- low TSH secretion, low stimulation of thyroid.
 Hyperthyroidism (high T3/T4 levels) can result from:
 Thyroid tumors (produce high amount of T3)-- high T3, low
TSH (feedback inhibition on the APit).
 Pituitary TSH-producing tumors-- high T3, high TSH.

Graves' Disease-- an autoimmune condition in which you have
IgG antibodies that actually stimulate the TSH receptors in the
thyroid gland-- high T3, low TSH.
Autoimmune Thyroid Disease and Interpretation of Thyroid
Tests
Tuesday, December 09, 2008
10:01 AM
Autoimmune Thyroid Disease and Interpretation of Thyroid Tests, 12/9/08:
Normal replacement dose of T4: 100 ug/day.
Normal replacement dose of T3: 26 ug/day (6 secreted, 20 converted from T4).
Deiodinases: have selenium in them; selectively deiodinate at either the 5' or 5
position.
 Peripheral deiodination:
 Activating (normal) deiodination: takes place intracellularly,
near the nucleus-- converts T4 to T3 (takes off 5' iodine): type
2 deiodinase.
 Inactivating deiodination: converts T4 to reverse (inactive) T3
(takes off 5 iodine): type 3 deiodinase.
 The question of how much T4 is inactivated to reverse T3
rather than activated to T3 is under metabolic control-- stress
and glucocorticoids head the list of causes of inactivation,
though there's a substantial list of drugs as well (see
Powerpoint for details).
T3 has a shorter half-life and less affinity for binding to THBG-- its free concentration
in the plasma is roughly equal to the free concentration of T4 in the plasma (more T4
in total, but greater proportion of T3 is free).
Most common cause of increased T3/T4 levels in blood: increased thyroid hormone
binding globulin. Estrogen promotes THBG synthesis-- exogenous administration
(as birth control pills) or pregnancy causes increases of total T3/T4 levels. Note free
thyroid hormone (T3/T4) are independent of the rise in total T3/T4 due to increased
THBG. Elevated free T3/T4 levels, on the other hand, are actually indicative of
hyperthyroidism. Note also that THBG levels don't generally go down (so low total
T3/T4 levels are more correlated with low free T3/T4 levels).
Thyroid hormone inhibits somatostatin and promotes growth hormone production.
The level of circulating TSH is roughly proportional to the metabolic rate, because
free T3 levels control both metabolic rate and TSH levels.
1. Identify the major symptoms and signs of hyperthyroidism.
 Nervousness, weight loss (only 50% of patients), decreased appetite,
increased appetite, fatigue, tremor, heat intolerance (most common).
2. List the disorders leading to hyperthyroidism.
 [2 broad types: overproduction by the thyroid (usually under the
control of TSH) and low synthesis but high release of T4/T3.]







3. Recognize




Distinguish: use radioactive iodine test; if a lot of uptake into
the thyroid ("hot" nodule), that's an overproduction problem; if
low uptake into the thyroid, that's an
underproduction/overexcretion state ("cold" nodule).
Graves' Disease: as mentioned, autoantibodies bind to and stimulate
the TSH receptor without any feedback inhibition. Leads to a highiodine-uptake state with suppressed TSH production. Have a number
of complications due to autoimmune problems:
 See exophthlamos (bulging eyes or proptosis) due to
periorbital inflammation.
 Also see pretibial myxedema: brawny, red, non-pitting
edema on the front of the leg, also due to inflammation.
Treated with topical corticosteroids.
 Also vitiligo (depigmentation) and premature grey hair (before
age 30).
Increased consumption of thyroid supplements ("factitious
hyperthyroidism"):
 Causes TSH to go to 0; no labeled iodide uptake.
Toxic (ie. "hot") nodules (produce TSH-independent thyroid hormone):
 Causes TSH to go to 0; however, the autonomous cells in the
nodule are synthesizing thyroid hormone, so labeled iodide
uptake is high.
 Caused by a mutation in the TSH receptor of a single cell which
causes the receptor to be constitutively active-- the mutant cell
divides like crazy and pumps out T4/T3 like there's no
tomorrow.
Subacute thyroiditis:
 High fever and painful, swollen thyroid.
 Damage to the thyroid tissue causes acute secretion of thyroid
hormone.
 Causes TSH suppression; radiolabeled iodide uptake is low
(underproduction, oversecretion).
 Note "silent" thyroiditis can also occur-- same numbers but no
pain (can occur postpartum).
TSH-secreting pituitary tumors:
 High TSH, high T3/T4; radioactive iodide uptake high.
 Note that a really big brain tumor can cause some proptosis
just as a result of the increase in intracranial pressure.
Thyroid hormone resistance (mutation in beta thyroid hormone
receptor):
 The same receptor inhibits the feedback mechanism-- so see
high TSH and thyroid hormones with high iodide uptake.
the major symptoms and signs of hypothyroidism.
Mental slowness, weight gain, increased/decreased appetite, fatigue,
muscle cramps, cold intolerance. Relatively pathognomic, if seen, is
delayed relaxation of deep tendon reflexes.
 Notice that appetite changes or fatigue are common to both
hypo- and hyperthyroidism.
Note a hypothyroid connection to CHF (thyroid hormones have a big
impact on cardiac contractility).
Generally you see extremely high TSH levels.
Prevalence is generally higher in males than females, though in the
elderly (in hypothyroidism only) it levels out.
4. Name the conditions leading to hypothyroidism.
 Most commonly, Hashimoto's thyroiditis (5-10% of the population).
Elevated TSH levels.
 Also pituitary insufficiency (no TSH elevation).
 Can be a problem with the hypothalamus as well.
 Or low iodine diet.
5. Interpret the different tests used to evaluate thyroid function.
 "Ridgway rule:" if you want to know about thyroid functionalism, all
you need is the TSH test. If the serum TSH level is normal (euthyroid),
the patient does not have a thyroid function abnormality (though they
can still have a thyroid goiter or cancer). Only a few small exceptions
to the rule.
 If the TSH is abnormal, measure both total and free T4 to get a better
handle on what the underlying problem is.
 Overt hyperthyroidism: TSH = 0, FT4 = high.
 Sub-clinical hyperthyroidism: TSH = low, FT4 = normal.
 Overt hypothyroidism: low TT4 and FT4.
 Sub-clinical hypothyroidism: normal TT4 and FT4.
 Also labeled iodide test, as mentioned: increased uptake indicates a
"hot," overproducing nodule; decreased uptake indicates a "cold,"
oversecreting nodule.
Thyroid Nodules: Clinical, Pathologic, and Pathophysiological
Correlates
Tuesday, December 09, 2008
10:59 AM
Thyroid Nodules: Clinical, Pathologic, and Pathophysiological Correlates,
12/9/08:
(originally titled "Thyroid Tumors and Fine Needle Aspiration")
[Random genetics notes:]
 [insert basic cancer principles, multi-hit hypothesis, etc]
 One pathway in particular is important in thyroid cancers: RET
receptors and a ras tyrosine kinase system. In thyroid cancers, you
see rearrangement of RET (constituitively activated), mutations in ras
(now needs no upstream signaling), and mutations in the tumor
suppression gene (BRAF) that inactivates it. The last one is more
associated with severe, aggressive cancers. Note that you can look for
particular genetic mutations in the thyroid aspirate to detect various
problems in this system. Mutations in the p53 system further cause
problems.
 Can also get a pax6-PPAR-gamma gene rearrangement to lead to
malignancy.
1. Recognize the pathological disorders that can lead to the appearance of a solitary
or multiple thyroid nodules.
 Note palpable thyroid nodules are extremely common (5-10% of the
general population). Note ultrasound-detectable thyroid nodules are
even more common (30-60%).

5-10% rule of the thyroid (not to be confused with the 10% rule of
pheochromocytomas):
 5-10% of people have a palpable nodule.
 The risk of cancer is about 5-10% for a given nodule.
 About 5-10% of the people with cancer have significant
morbidity/mortality.
 Etiologies of dysplasia:
 Benign: follicular adenomas (overwhelming majority)
 Can arise from follicular cells or Hurthle cells
(dedifferentiated follicular cells).
 Generally a solitary nodule (as opposed to malignant,
which are often multifocal).
 Look for the invasion of capsule or blood vessels.
 Malignant:
 Papillary (80-85%) (from follicular cells) (multifocal,
spread by lymphatics, excellent prognosis)
 Papillary carcinomas are cystic: the tumors
outrun their vascular supply.
 Form papillae within the cystic structure (thus the
name).
 Cells: "cleared-out nuclei" or "Orphan Annie
nuclei"-- thick rims, no contents.
 Produce psammoma bodies (round collections of
calcium).
 Note that papillary carcinoma has a 98% 20-year
survival rate-- extremely good.
 Follicular/Hurthle (10-15%) (spread through vascular
system)
 Anaplastic (undifferentiated, very aggressive-- many
types of cell patterns found within the tumor)
 Note that anaplastic carcinomas have a 50% 6month survival rate-- extremely bad.
 Medullary (familial, associated with MEN 2A)
 Medullary tumors: arise from C cells (all other
tumors discussed her arise from follicular cells).
Can produce amyloid; can calcify (but no
psammoma bodies).
 Lymphomas: generally occurs in the setting of autoimmune
thyroiditis.
 Note you can get metastases from other tissues in the thyroid
as well.
2. Describe the tests that are helpful to evaluate a thyroid nodule.
 Fine needle aspiration / cytological section.
 Note FNA can't detect invasion of capsule or blood vessels (marker of
carcinomas).
 Cytological sections can detect both.
 Often do an ultrasound (look for blood flow and calcification); can also
get a TSH (look at function) and do a fine-needle aspiration biopsy
("mainstay" of diagnosis).
 Which of ultrasound vs. TSH should be first seems to be an
issue of some debate. TSH has votes from two lecturers vs. one
and a half for ultrasound.

FNA has a very good sensitivity/specificity for most nodules;
but if it's a 'suspicious' nodule it's harder to figure out. For
these, use the radioactive iodine uptake test (if cold, send to
surgery).
 Radioactive iodine: to evaluate nodule functionality.
 "Hot" nodules (take up iodine) are almost never
malignant. However, few nodules are hot (which is why
you don't use this as a routine screening test).
 "Cold" nodules (don't take up iodine) have a potential
for malignancy.
3. Differentiate the cytological features seen in samples of fine needle aspiration
biopsies.
 Okay. Sometimes this is easy (see big ugly changes). Most of the time,
though, it depends on how much colloid you're seeing.
 Normal thyroid tissue (as in an over-TSH-stimulated goiter): you'll see
a mix of small and large colloid-containing follicles.
 Dysplastic thyroid tissue contains "microfollicles": tiny little spaces of
colloid squeezed between lots and lots of follicular cells. These can be
common to both follicular adenomas (benign) and follicular carcinomas
(malignant).
 Note adenomas and carcinomas can look very similar on FNA, though
they don't have to.
 Some colloid + well-differentiated groups of follicular cells: generally
adenomas.
 Ugly changes:
 Papillary carcinomas: highly cellular, scant or absent colloid,
clear nuclei, form papillae. See psammoma bodies.
 Anaplastic carcinomas: dedifferentiated or giant cells.
 Medullary carcinoma: lots of calcification and amyloid.
4. Outline the general principles of treatment of benign and malignant thyroid
tumors.
 Clinical Evaluation:
 History of nodule growth (faster is worse)/pain, also
cough/voice change. Risk factors: head and neck irradiation as
a child, or family history of thyroid cancer (worried about MEN
2A or papillary carcinoma).
 Physical exam: look at size, consistency (harder is worse),
fixation (more fixed is worse- local invasion), lymphadenopathy
(painful local lymph nodes).
 High clinical suspicion correlates pretty well to malignancy.
 (see Tests section, above)
 Generally, you resect "cold" nodules that look like they could be
malignant. Generally, you use I131 to take out "hot" nodules that are
causing issues.
Congenital Hypothyroidism and Iodine Deficiency
Wednesday, December 10, 2008
7:49 AM
Congenital Hypothyroidism and Iodine Deficiency, 12/10/08:
1. Describe the method used to screen newborns in the state of Colorado for
congenital hypothyroidism (CHT).
 Mainly this is due to incomplete or absent development of the thyroid.
Transient forms can be due to maternal autoantibodies (as in
Hashimoto's) and/or drugs that pass through the placental barrier
from the mother.
 Note "sick euthyroid" condition-- in conditions of illness, the
thyroid cuts back on its thyroid hormone production (also
favors conversion of T4 into reverse T3 rather than T3). Recall
that cortisol (stress hormone) is largely responsible for this.
 Not a lot of gross changes for congenital hypothyroidism-- it can look
like a whole lot of things (jaundice is probably the most common
symptom, but it's still only about 55% of congenital hypothyroid
babies, and jaundice can be a lot of other things).
 Along the same lines, size at birth is independent of thyroid hormone
levels-- growth in utero is dependent on insulin and IGF-1, not GH or
TH (more on this under "Growth Disorders").
 By the time it becomes clinically manifest, you're already looking at a
significant degree of mental retardation. So: want to screen, and treat
within the first 3 weeks of life. There is no safe period of
hypothyroidism during development.
 In utero, mother's T4 can make up for the deficiency in the fetus. So
screen at birth, and then screen again at 2 weeks (after the mother's
T4 has been used).
 Screen specifics: Measure total T4; if the total T4 is low, measure
TSH. Recall that in most cases of hypothyroidism, you're looking at low
T4 and high TSH. Alternatively, the T4 can be low and the TSH can
also be low (as in hypopituitarism).
2. Identify the normal changes in thyroid stimulating hormone (TSH) in the first
week of life and how they affect the interpretation of the first newborn screen.
 TSH is made in a burst after the cord is cut to adapt to a colder
environment; this can mask hypothyroidism. This is one of the reasons
you take a second screen at 2 weeks (elevated TSH should have
passed).
 So if the first screen shows low-normal T4 and highish TSH (20-60),
could be normal (TSH surge after birth).
 Note you can also have a deficiency in thyroid hormone binding
globulin -- have normal free T4 levels even though the total T4 levels
are low (the TSH is usually normal).
3. Recognize the two benefits of the second newborn screen performed at 2 weeks of
age.
 (1) Make sure an initial high TSH is not an artifact of the postpartum
surge.
 (2) About 20% of all congenital hypothyroidism is picked up on the
second screen, even when the first test is normal.
 These can be cases of "compensated" hypothyroidism-- normal
T4 levels with elevated TSH. This is generally treated before it
becomes uncompensated.
4. Develop a schedule for monitoring the treatment of a child with CHT.
 Measure free T4 and TSH at well baby/child checks.
 What you want to watch at first is the free T4 level, not the TSH level-normalize T4 quickly to minimize chances of impaired IQ, and the TSH
5.
6.
7.
8.
will come down by itself. Once TSH becomes normal, then you can use
it as an indication for dose increase.
Identify populations most at risk for iodine deficiency disorders.
 Generally in developing countries, particularly ones that are inland.
Look at urinary iodine (< 100 micrograms per liter is diagnostic).
 Notice about 2 billion people worldwide are probably iodine deficient,
including about 285 million school-age children.
Discuss food sources of iodine and methods for supplementing intake.
 Sources: saltwater fish, shellfish, sea salt (pretty much anything from
the sea).
 Fortification of salt with iodine is the big supplementation method.
Describe the population effects of severe iodine deficiency.
 Goiters and low energy in adults, cretinism in children.
Discuss preventative approaches and treatment approaches for iodine deficiency.
 Mainly supplementation-- but once the IQ is lost it doesn't come back.
Thyroid Pharmacology
Wednesday, December 10, 2008
8:40 AM
Thyroid Pharmacology, 12/10/08:
1. Describe the process and regulation of the biosyntheses and release of thyroid
hormones with special emphasis on sites for pharmacotherapeutic intervention in
hyperthyroidism.
 This is mainly discussed elsewhere.
 Glucocorticoids interrupt the activation of T4 to T3 (thus more T4 gets
shunted into inactive reverse T3). As per the quiz, so evidently do
beta-blockers.
 Note lithium inhibits the effect of TSH on the thyroid gland.
 PTU and methimazole inhibit thyroperoxidase (inhibiting synthesis of
T4 and T3)-- this is a long-term strategy (haven't done anything about
the extant stores in the colloid). More about them below.
 Recall that estrogens increase the synthesis of thyroid hormone
binding globulin.
2. Explain the treatment of hypothyroidism.
 Primarily, replacement therapy. If myxedema coma (found in severe
hypothyroidism, as opposed to pretibial myxedema, a completely
different entity found in Graves' Disease) is present, it's managed
more acutely (life-threatening illness).
 Note T4 has a reasonably long half-life (7 days) as opposed to T3 (1
day). This affects monitoring-- it takes about 4-5 half-lives to reach a
new steady-state (4-5 weeks) and another couple of weeks to see the
effects on protein transcription (6-8 weeks).
3. Compare and contrast the advantages and disadvantages of various preparations
for thyroid hormone replacement.
 Primary replacement drug: levothyroxin, aka LT4 (it's a T4 analog).
 Has an extremely narrow therapeutic index but is up there in
the top 10 prescribed drugs (along with warfarin and insulin,
two others with narrow TIs).
 PK review:
MD/tau = Cpss x CL: maintenance dose / dosing interval
= the plasma concentration at steady state times the
clearance.
 Fluctuations in plasma concentration (ratio of peak to
trough levels) in a given interval = 2x, where x = the
number of half-lives in the interval.
 Note that with estrogen administration, you have increased
THBG-- this will affect the dosing of LT4. So if the patient is
pregnant and on thyroid meds, you need to start paying close
attention to the dose (need to give more-- more of the LT4 is
going into the THBG). (If the patient is pregnant but is
euthyroid, TSH and the thyroid gland will compensate for the
increased THBG).
 Liothyronine: pure T3; isn't much used (too much fluctuation in
plasma concentrations to dose every day, also see cardiac effects)
except in some myxedema coma patients.
 Liotrix: combination of synthetic T4 and T3.
 Thyroid USP: combination of T4 and T3 from pig thyroid. Potential
antigenicity. Also the balance of T3 with T4 is higher in pig than
human.
 In most clinical situations, LT4 is your guy.
4. Describe the pharmacokinetics, mechanism of action, and toxicities of antithyroid
agents.
 Propithiouracil (PTU): blocks thyroperoxidase. Is a "goitrogen":
lower levels of free T3 give rise to higher levels of TSH, which is
mitogenic for thyroid follicular cells. At higher doses, note that PTU can
also block the conversion of T4 to T3.
 Methimazole: also blocks thyroperoxidase (and is also a goitrogen).
Less protein-bound than PTU; generally preferred for efficacy, better
dosing.
 Both of these cross the placental barrier, PTU a little less than
methimazole (more of it's bound to plasma proteins)-- PTU is
preferred in pregnancy.
 Nasty, rare side effect of both of these: agranulocytosis.
 Can use iodide to block release of T3 and T4 (see below).
 Radioactive iodine: orally administered; can cause thyroiditis with
release of lots of preformed thyroid hormone. Note that you often wind
up producing hypothyroidism to replace the hyperthyroidism (but
hypothyroidism is more easily managed).
5. Explain the treatment of hyperthyroidism and thyroid storm.
 Hyperthyroidism:
 Interfere with thyroid hormone function: PTU, methimazole.
 Modify tissue response: beta-blockers, glucocorticoids (the
latter interfere with the conversion of T4 to T3).
 Note that thyroid hormone increases the
metabolism of glucocorticoids, so hyperthyroidism
can cause hypocortisolemia.
 Note also that thyroid hormone increases bone
turnover.
 Both of these should be considered in the setting of
iatrogenic hyperthyroidism.
 Destroy the gland, with either radioactive iodine (preferred) or
surgery.


Thyroid storm: acute exacerbation of hyperthyroidism.
 Acutely, this revs up the sympathetic nervous system-- this
causes tachycardia, palpitations, and potentially atrial
fibrillation, and thus can be life-threatening.
 (1) You can treat the SNS effects with beta-blockers.
 (2) You can use high iodide levels to inhibit the release of T4
and T3.
 (3) Can block thyroperoxidase with PTU.
 (4) Can use glucocorticoids to reduce T4 to T3 conversion.
6. Compare and contrast antithyroid drugs vs. thyroidectomy vs. radioactive iodine
in the treatment of hyperthyroidism.
 Radioactive iodine is the preferred method in most cases; surgery is
good only if the gland is large.
 Antithyroid drugs can work okay if the patient is young or if the gland's
dysfunction is pretty mild. Note that there's a high relapse rate.
Radiology of the Thyroid Gland
Wednesday, December 10, 2008
10:02 AM
Radiology of the Thyroid Gland, 12/10/08:
1. Understand available imaging modalities.
 Anatomic imaging: ultrasound, CT, MRI.
 Plain X-ray: not much help unless the thyroid is big enough to
deviate the trachea.
 Ultrasound: best modality for thyroid (she repeated this about
5 times); no radiation, real-time imaging, Doppler used to
evaluate vascularity. Also can use it to evaluate nearby lymph
node metastasis or to guide fine needle aspiration. Note that it
can't distinguish between benign and malignant nodules.
 CT: not much good for evaluating the thyroid gland itself (size
alone), but can be used to pick up metastases in lymph nodes,
etc. Also good for looking at structures surrounding thyroid.
 MRI: can be good for looking at looking infiltration in the
thyroid area (ultrasound isn't good at picking that up). Again,
not as good as ultrasound for direct evaluation of the thyroid.
 Functional imaging: iodine (I123 or I131) scan.
 I123 evaluates function of thyroid-- normal is a diffuse,
homogenous uptake, while "hot" nodules have higher,
concentrated uptake. "Cold" nodules have little or no uptake;
further evaluate with ultrasound +- FNA to test for cancer.
 Recall the 5-10 rule: 5-10% of "cold" nodules are
malignant.
 I131 looks for local and distant metastases; in high doses, it's
also used for thyroid ablation (destruction by radioactive I).
 Metastases generally show up in the lymph nodes and
lungs.
2. Identify structures on imaging.
 It's relatively normal to have a small pyramidal lobe arising from the
isthmus, going up.
3. Know the normal appearance of the thyroid gland on imaging.
 The handout has some pictures (probably better in color, as in the
Powerpoint).
4. Identify common disease states.
 Not much discussion. This is something that should probably be clear
from other lectures.
Growth Disorders
Thursday, December 11, 2008
7:37 AM
Growth Disorders, 12/11/08:
1. Recognize the difference in growth rate in children of different ages.
 Different things are important for growth at different ages:
 Stage 1 (conception to 4-6 months postpartum): endogenous
growth hormone and thyroid hormone aren't really that
important for physical growth of the fetus. What is important is
insulin and IGF-1. (note thyroid is still essential for mental
development.)
 Note that this means that kids with congenital GH
and/or TH deficiency are generally thoroughly normalsized at birth.
 Stage 2 (4-6 months postpartum to adolescence): growth
hormone, thyroid hormone, and insulin/IGF-1 are all important
for growth.
 Stage 3 (adolescence to adulthood): all of the above are
important for growth, as well as GnRH and sex hormones.
 What's important for all three: internal environment (nutrition, disease
state, etc).
 Note, as per the notes, that familial stature is the most common cause
of variation in height.
2. List the most common causes of growth failure in children.
 Malnutrition
 Systemic disease
 Metabolic abnormalities (diabetes, achondroplasia, etc)
3. Produce a strategy for the evaluation of poorly-growing children.
 First think about chronic illness or nutritional deprivation-- this
causes excess cortisol to be secreted, which (a) promotes muscle
protein breakdown, and (b) blocks IGF-1 secretion by promoting
resistance to growth hormone. The result is wasting and stunting.
 "Height-age" and "weight-age:" the age at which the child would be at
the 50th percentile of height and weight, respectively.
 "Target heights:" for boys, average of father's height and (mother's
height in inches + 5). For girls, average of mother's height and
(father's height in inches - 5).
 "Bone age:" take a X-ray of left hand and wrist-- look at skeletal
maturation, compare to landmarks.
 Note that this seems to be particularly affected in thyroid
deficiency-- thyroid hormone seems to affect more bone
maturation than bone growth.

This means that thyroid hormone replacement after deficiency
can cause maturation at a rate faster than growth.
 Labs: comprehensive metabolic panel, CBC, sed rate, urinalysis.
4. Develop a means of assessing growth hormone secretion based on its physiology
and its responses to pharmacologic stimuli.
 (Actually in the next lecture notes..?)
 As we've mentioned, if increased GH can't be suppressed by an oral
glucose tolerance test, it's probably a GH-secreting tumor.
 Secretory pattern: most GH is secreted at night; random samples of
blood in the clinic is rarely sufficient to get a good handle on GH
secretion.
 Generally, as with most deficiency tests, you use stimulation tests:
 Can use clonidine to stimulate GHRH secretion, then take GH
levels every 30 minutes or so for a few hours. Can also use LDOPA or arginine (both of which stimulate GH secretion).
 Perhaps more commonly, you can use glucagon. Glucagon
raises blood sugar, causing insulin secretion; in response to
insulin secretion, the body secretes cortisol and growth
hormone to ensure no hypoglycemia. So can measure GH about
2 hours after glucagon administration.
[Endocrine causes:]
 Growth hormone deficiencies: most children with low GH have normal
MRIs. Can also have CNS tumors, etc. Radiation (as for bone marrow
transplantation) can destroy the parts of the hypothalamus responsible
for TRH, GHRH, or GnRH secretion. Turner's syndrome is also a cause
(can be treated with GH).
 Acquired thyroid hormone deficiency:
 Ectopic thyroid gland: gets stuck at root of tongue
 Autoimmune: Hashimoto's thyroiditis
 Get free T4 and TSH tests
 Gonadal steroid hormone deficiency:
 Turner's syndrome (deficient sex hormones)-- can be
somewhat corrected with GH administration.
 Recall that frequent doses of glucocorticoids reduce GH and TH
efficacy.
Ethics of Growth Hormone Use
Thursday, December 11, 2008
8:51 AM
Ethics of Growth Hormone Use, 12/11/08:
1. Recognize the sources of therapeutic human growth hormone (GH) from 1958
compared to the present.
 Pre-1958: used bovine growth hormone. Doesn't work enormously
well.
 1960-1985: cadaver-derived human GH (ground-up pituitary).
Stopped by FDA after Creuzfeldt-Jacob transmission.
 1985 to present: recombinant human GH (grown from E. coli).
2. Identify the "FDA-approved" uses of human GH from 1958 to the present.

1958-1985: derived from cadavers (took 50 cadavers per child per
year).
 1985 to present: recombinant from bacteria. Abundant, if expensive.
3. List categories of children who might not be candidates for GH therapy.
 [Approved for therapy for: severe GH deficiency in children and adults,
chronic renal disease, AIDS wasting, Turner and Prader-Willi
syndromes, etc--list on p. 54]
 Controversial one (approved by FDA): idiopathic short stature (child is
short for general population, but not family).
 May not be candidates: severe mental retardation, most genetic
abnormalities, high-dose pharmacological steroid therapy.
4. Develop a plan to treat children with isolated GH deficiency.
 Can treat until "normal potential" is reached (< 2 standard deviations
from normal or mid-parental stature).
 Can just treat til final height is reached.
 Can stop GH for 6 months during development and re-assess growth
velocity (growth hormone deficiency can self-resolve at some point in
childhood).
Histology
Friday, December 12, 2008
8:32 AM
(this really had little bearing on his talk. Study the quiz.)
1. Characterize the basic arrangement of cells relative to blood vessels in these
glands, as they are involved in secretion of products into the bloodstream.
2. Describe the basic blood flow through the organs.
3. Define any innervation and the role it plays in release of hormones.
4. Explain the basic functions of the hormones these glands produce.
5. Summarize the mechanisms of hormone formation in different glands, and basic
mechanisms of control of hormone release.
Control of Mineral Metabolism, PTH, Vitamin D, and Calcium
Distribution
Monday, December 15, 2008
8:02 AM
Control of Mineral Metabolism, PTH, Vitamin D, and Calcium Distribution,
12/15/08:
1. Describe the physiological roles for calcium and phosphate.
 Calcium:
 Structural: major constituent of bone's mineral matrix.
 Biochemical: excitation-contraction, clotting, secretion of
vesicles, membrane excitability, etc.
 Eg.: decreased serum calcium levels (< 7 mg/dL) lead
to hyperexcitability of muscle and seizures in the CNS.
Also eg.: calcium is probably the most important
second-messenger substance in the body.
 Free intracellular calcium levels: 50-100 nM (extremely low
compared to extracellular calcium, 8-10 mg/dL or 2.5 mM).
Maintained very tightly.
 Phosphate:
 Structural: other major constituent of bone matrix.
 Biochemical: integral to DNA backbone, second messenger,
main energy currency in body (ATP/GTP).
2. Illustrate the various compartments involved in calcium and phosphate
hemostasis and identify the mechanisms for distribution of calcium and phosphate
between plasma and the bone.
 Calcium:
 Blood:
 Serum pool, as mentioned, is about 8-10 mg/dL.
 In the blood, calcium is largely present either bound to
albumin or as bicarbonate/phosphate salts.
 GI tract:
 Calcium is absorbed very poorly from the gut.
 Normal intake is about 1 g per day.
 You absorb about 500 mg. Then you lose 325 mg back
into the lumen.
 So from 1 g of intaken calcium you actually keep about
175 mg.
 825 mg of that 1 g, then, is lost in the feces.
 Bone:
 Normally the calcium levels going into the bone are
equal to the levels coming out of it; it's in equilibrium.
 There's a fairly regular amount of calcium (280 mg, or
210 in his notes) being slowly broken out of and then
returned to the bone matrix every day. This is called
osteoclastic osteolysis.
 There's also a very rapid movement of calcium (10 mg)
going in and out of the mineral matrix every day. This is
called osteocytic osteolysis.
 Calcium levels in the canaliculi within the bone
are lower than the calcium levels in the blood.
Calcium therefore flows into canaliculi from the
serum (through surface osteoblasts) and is taken
up by osteocytes within the bone.
 The osteocytes then return the calcium to the
serum by means of a rapid pump. This is the
rapid-fire calcium circulation (10 mg/day).
 Although this doesn't affect phosphate levels, the
10 mg/day transfer affects the equilibrium 'set
point' of both calcium and phosphorus in the
bone.
 He really emphasized this rapid transfer.
 Kidney:
 About 10 g of calcium is filtered every day; about 9.8 g
of it is reabsorbed, for a net loss of 175 mg of calcium
per day in the urine.
 Phosphate:


Blood:
 Serum pool is 3-4 mg/dL.
 GI tract:
 Normal intake is about 1400 mg per day.
 Absorption is somewhat better than calcium- absorb
1100 mg, of which only 200 mg leaks back into the gut
lumen.
 Bone:
 Again, there's an equilibrium of deposition and
breakdown here; in phosphate it's about 210 mg per
day.
 Note that this is done entirely by osteoclasts in the bone
matrix.
 Osteocytic osteolysis does not transfer phosphate (only
calcium).
 Kidney:
 Filtered: 7 g per day. Reabsorbed: 6.1 g per day.
Excreted in urine: 900 mg per day.
 [Note that the main site of calcium excretion is in the GI tract, while
the main site of phosphate excretion is in the kidneys.]
3. Describe the regulation of PTH release.
 (peptide hormone, stored in vesicles, released by calcium-dependent
exocytosis)
 Trigger for PTH secretion: drop in serum calcium.
 There's a G protein-coupled receptor on the chief cells in the
parathyroid, right next to a calcium-binding receptor. Under
normocalcemic conditions, the calcium-binding receptor is bound and
the G protein-coupled receptor remain inactive.
 When the calcium levels drop, the calcium-binding receptors stops
being fully bound and activates the G protein-coupled receptor (a Gqtype receptor)-- which releases intracellular calcium from the ER and
causes exocytosis of stored PTH-containing vesicles.
4. List the actions of PTH.
 PTH binds to G protein-coupled receptors on target cells (Gs-- it
increases cAMP and protein kinase A activity).
 Main function: raise serum calcium.
 Mechanisms:
 In the kidney, PTH causes increased Ca++ reabsorption in the
distal tubule, decreased phosphate reabsorption, and increased
synthesis of activated vitamin D (1,25-OH-D).
 The balance between the calcium and phosphate levels
is important-- if you have a lot of calcium and a lot of
phosphate at the same time, you can get precipitation of
calcium phosphate crystals in the tissues (bad news).
Perhaps more to the point, the less phosphate there is
around, the less calcium is bound to it (and the more
free calcium there is). So when PTH increases retention
of Ca++, it decreases retention of PO4-.
 [In the GI tract, the increased levels of activated vitamin D
increases the absorption of Ca++.]
 In the bone, PTH directly affects the rapid-exchange process
(osteocytic osteolysis) towards mobilization of calcium from the
bone-- it alters the equilibrium such that calcium breakdown
from bone is favored over deposition into bone.
 "Indirectly," it also affects the slow-exchange process
(osteoclastic osteolysis) to do the same thing. Note that
this process, unlike the rapid-exchange process, also
involves phosphate (osteoclasts produce both calcium
and phosphate from the breakdown of the matrix).
 What the "indirectly" means: PTH directly stimulates
osteoblasts, which then go on to stimulate osteoclasts
which do the bone resorption. They seem to do this
through the RANK/RANK-L pathway (more on this later).
 So: direct increase of calcium resorption through
osteocytes, indirect increase of calcium and phosphate
resorption through osteoclasts.
5. Diagram the steps of Vitamin D synthesis and their regulation.
 Vitamin D: a steroid hormone derived from cholesterol. Produced in
the skin and also absorbed from the GI tract.
 Vitamin D from either of these sources is inactive-- needs to be
activated by consecutive steps.
 In the liver, it's hydroxylated to 25-OH vitamin D.
 This is further hydroxylated in the kidneys to either 1,25-OH vitamin D
or 24,25-OH vitamin D.
 The 1,25-form is the activated form of vitamin D; the 24,25-form is
the inactive form-- sort of like T4 being converted to either active T3
or reverse T3 in cells.
 PTH increases 25-hydroxylation in the liver; it also favors the
formation of 1,25-D and inhibits the formation of 24,25-D in the liver.
 [Note low phosphate levels favor 1,25-formation as well.]
 [Note 1,25-OH D inhibits its own synthesis.]
6. List the actions of Vitamin D.
 Main function is in the GI tract: it increases the efficiency of calcium
uptake.
 Recall that normally calcium uptake is extremely inefficient; with
activated vitamin D, it gets much more efficient.
 How that works: activated vitamin D causes increased synthesis of a
protein called calbindin in the enterocytes, which drives Ca++ uptake
from the GI lumen.
 Note it also increases phosphate absorption from the gut as well
(which is presumably why low phosphate levels increase synthesis of
the active form).
[Note estrogen modulates slow-calcium exchange in favor of deposition into bone
(which is why after menopause there's a tendency towards osteoporosis).]
[Under stress, the absorption of calcium becomes less efficient due to cortisol's
inhibition of vitamin D's GI actions.]
Hypercalcemia and Hypocalcemia
Monday, December 15, 2008
9:03 AM
Hypercalcemia and Hypocalcemia, 12/15/08:
[Note that calcium-raising mechanisms (PTH, 1,25-OH vitamin D, calcitonin) are
initiated below a serum calcium of 9.0 mg/dL; calcium-lowering mechanisms are
initiated above a serum calcium of 10.0 mg/dL.]
[General notes:]
 D3, or cholecalciferol, is made in the skin.
 D3 is made from 7-dehydrocholesterol (you have less 7DHcholesterol as you age).
 D2, or ergocalciferol, is ingested (can ingest D3 from fish also).
 25-OH vitamin D is the major storage form of vitamin D-- 25hydroxylase isn't much regulated.
 Note that 25-OH vitamin D is present in nanogram/mL
quantities.
 Note that 1,25-OH vitamin D is present in picogram/mL
quantities (1000x less).
 Note that 24,25-vitamin D (inactive form) is promoted by high levels
of calcium or phosphate.
 Calcitonin is a relatively weak mechanism: it lowers serum calcium by
inhibiting bone resorption.
 There's a reasonably good summary slide in the middle of page 80.
 Calcium sensor receptor: as mentioned, hangs out next to the G
protein-coupled receptor on chief cells in the parathyroid gland; also
hangs out in the C cells in the thyroid gland (for calcitonin secretion)
and in the renal tubular cells (to regulate calcium excretion).
 Really quite good clinical tip: if calcium and phosphate move in the
same direction, look for a 1,25-OH vitamin D disorder (vitamin D
causes increased absorption of both); if calcium and phosphate move
in opposite directions, look for a PTH disorder (PTH causes increases
calcium at the expense of phosphate).
1. Contrast the mechanisms underlying the main causes of hypercalcemia: primary
hyperparathyroidism and hypercalcemia of malignancy.
 Most common causes of hypercalcemia: hyperparathyroidism and
malignancy. These account for ~ 90% of all cases. Other causes:
sarcoidosis (granulomas secrete activated vitamin D), vitamin A or D
excess, thiazides (impair calcium secretion), immobilization,
hyperthyroidism, acute renal failure, etc.
 First test: measure PTH. This will usually distinguish between primary
hyperparathyroidism and malignancy.
 Primary hyperparathyroidism:
 Mainly due to solitary adenomas in one parathyroid gland
(85%).
 Sometimes it's general parathyroid hyperplasia (all 4 glands are
enlarged-- this is nearly always a congenital condition. (15%)
 Note that secondary hyperparathyroidism (as due to
kidney failure) can cause a diffuse hyperplasia as well-but that didn't get as much discussion time.
 Rarely it's a carcinoma (< 1 %).
 Presentation:
 Most commonly asymptomatic; more than half of
people with this disorder are found on routine screening.
Symptoms: osteoporosis, kidney stones,
nausea/vomiting/pancreatitis, psychiatric symptoms:
"Bones, Stones, Groans, and Moans."
 Can also see arthritis, muscle weakness, HTN, and
anemia.
 Can see "brown tumors" made up of osteoclasts-- not
cancerous but lots of osteolytic activity. Note that the osteolysis
will generally correct itself if caught in time.
 If not caught in time, with long-standing parathyroid
bone disease you get widespread bone cysts and brown
tumors, a condition called osteitis fibrosa cystica (see
faded but still extremely unpleasant hand X-ray at the
top of p. 82 for example).
 Can get pseudogout from overcalcification of cartilage.
 Diagnosis:
 Increased serum calcium, decreased serum phosphate;
but the diagnosis is made on the basis of an elevated
(or inappropriately normal for high calcium levels) PTH.
 Associations with primary hyperparathyroidism:
 Generally solitary (90% no associations).
 10% of the time it's familial (4-gland hyperplasia).
 When it's familial, it can be associated with MEN
type I or IIA.
 Side note: MEN I is associated with mutations in
menin gene, MEN II is associated with mutation
in RET gene.
 [Treatment:]
 Mainly surgery:
 Can just take out the one if it's an adenoma.
 If it's hyperplasia: take out 3 and a half glands.
Usually actually take out all 4, section one, and
stick it into the forearm (easier access to go back
in later).
 Can also use calcimimetic drugs to drive down PTH
secretion-- not FDA approved but used. Also use
bisphosphonates to inhibit osteoclasts.
 Note that about 80% of people with primary
hyperparathyroidism don't need surgery-- if they don't
have a markedly increased serum or urine calcium,
kidney stones, etc, then they can just be observed.
Malignancy:
 Occurs when cancer secretes factors that increase bone
resorption or calcium excretion. Most commonly, it's a PTH-like
peptide. Can also secrete activated vitamin D (like in
sarcoidosis).
 PTH-related peptide (PTH-RP): main physiological function is
to regulate transfer of calcium across the placenta and also into
breast milk.
 PTH-RP binds to the PTH receptor.
 Diagnosis:
 High serum calcium but low PTH-- endogenous
production is repressed by high calcium levels. If you
look for PTH-RP, it's often high.



Treatment:
 Promote urinary calcium excretion by saline infusion
 Inhibit osteoclasts by bisphosphonates
 Can also use calcitonin or osteoclast-specific chemo
drugs, or use dialysis to remove the excess calcium
2. Describe the effects of prolonged untreated hyperparathyroidism on the bones and
kidneys.
 Bones: osteitis fibrosa cystica as above.
 Kidney: mainly stones from high calcium concentrations.
3. Understand the difference in pathophysiology and treatment of primary
hyperparathyroidism when caused by adenoma versus hyperplasia.
 As mentioned above: hyperplasia involves all 4 glands and is generally
familial, while adenomas usually involve 1 gland and is sporadic. In
hyperplasia, 3 1/2 glands are removed (the remaining 1/2 is usually
moved to the forearm or strap muscles in the neck); for adenomas,
usually only need the one gland removed.
4. List five causes of hypocalcemia and the mechanisms of each of these disorders.
 He has 8.
 (1) Vitamin D deficiency (generally due to a combination of poor oral
intake and inadequate sun exposure. Note D is absorbed in the
terminal ileum, so think Crohn's.)
 [A long discussion of vitamin D deficiency ensued:]
 Note a variety of other mechanisms for deficiency on p. 87.
 Note that you can see "pseudofractures" (demineralization) on
X-ray due to vitamin D deficiency.
 Two types of congenital rickets-- one with a problem in the 1OHase in the kidney (type 1), one with a problem with the
vitamin D receptor itself (type 2). Both respond to application
of vitamin D and activated vitamin D.
 (2) Hypoparathyroidism (often autoimmune or iatrogenic)
 (3) Hypomagnesemia (magnesium is essential for parathyroid and PTH
function)
 (4) Pseudohypoparathyroidism (PTH receptors don't work well)
 (can show up with short 4th and 5th metacarpals)
 (5) Renal failure (inability to make 1,25-OH vitamin D)
 (6) Liver failure (inability to make 25-OH vitamin D)
 (7) Acute pancreatitis (not entirely sure why)
 (8) Hypoproteinemia (ie. Kwashiorkor's-- 50% of serum calcium is
bound to protein)
5. Describe the clinical and laboratory features of hypoparathyroidism.
 Clinical:
 Parasthesias: numbness and tingling, esp. around the lips.
 Muscle cramps and weakness
 Chvostek's sign (tapping on facial nerve causes tic at the corner
of the mouth)
 Trousseau's sign ("carpopedal spasm" on inflating blood
pressure cuff)
 [Note polyendocrine syndrome involving multiple autoimmune
diseases can cause hypoparathyroidism-- look for
mucocutaneous candidiasis due to a T cell defect.]
 Laboratory:
 Low serum calcium
 High serum phosphate


Low serum PTH
(note distinction from pseudohypoparathyroidism, in which
serum PTH is markedly increased-- it's just not working.)
 Treatment:
 Give activated (1,25-OH) vitamin D (calcitriol); can also give
thiazides to lower urinary excretion of calcium. Treatment is the
same for pseudohypoparathyroidism.
6. Describe the calcium receptor and the abnormalities caused by its dysfunction.
 Seven-membrane-spanning receptor on parathyroid cells, C cells, or
renal tubular cells, as mentioned.
 Inactivating mutations in the calcium receptor protein: generally cause
familial hypocalciuric hypercalcemia. Generally about 50%
function in the remaining receptors.
 Diagnosed by high serum calcium but very low urine calcium-fractional excretion of calcium is less than 0.01. See a mildly elevated
PTH.
 No treatment is necessary; avoid surgery.
Osteoporosis and Other Metabolic Bone Disorders
Monday, December 15, 2008
10:28 AM
Osteoporosis and Other Metabolic Bone Disorders, 12/15/08:
[Mechanics of bone remodeling:]
 Every 7 years, the skeleton is completely replaced.
 Osteocytes (embedded within bone): signal bone remodeling according
to mechanical stresses.
 Osteoclasts break bone matrix down; they then signal osteoblasts,
which follow while secreting a special type of collagen with a high
affinity for hydroxyapatite (the collagen, plus some other stuff that's
secreted with it, is called osteoid). The osteoid is mineralized by
hydroxyapatite/calcium/phosphate to form bone matrix.
 Signaling cascade: the RANK-L (Receptor Activator of NF-kB, Ligand)
system.
 Osteoblasts secrete RANK-L. These bind to RANK receptors on
osteoclasts.
 RANK-L: increases bone resorption (activates osteoclasts)-drug target.
 There's a "decoy receptor" called osteoprogeterin that binds
RANK-L before it can bind to osteoclasts-- OPG decreases bone
resorption.
[General notes:]
 Like GnRH, the effects of constant PTH administration are different
from the effects of intermittent, pulsatile PTH administration.
 Bone density increases (increased bone formation) with
pulsatile (couple of hours' exposure) PTH administration.
 Bone density decreases (increased bone breakdown) with
constant PTH administration.
 Daily injections of PTH can be used in treatment.
1. Identify the modes of presentation of osteoporosis.
 Osteoporosis predisposes to increased risk of fragility fractures
(responds to trauma less than or equal to falling from a standing
height).
 Most often these are vertebral fractures (often aren't painful); often
also hip and wrist fractures.
 Vertebral fractures often present as loss of height and dorsal
kyphosis.
 Generally fragility fractures are osteoporosis until proven otherwise.
 Pre-fracture, can use bone density scans: the "T score" looks at how
many standard deviations under average 20-year-old bone mass a
person's bone density is.
 Normal: T > -1.
 Osteopenia (2-6-fold relative risk): T = -1 to -2.5.
 Osteoporosis (> 6-fold relative risk): T < -2.5.
 Note that low bone density is not necessarily osteoporosis-- get H+P,
do routine lab tests plus 25-OH vitamin D levels and GFR, testosterone
levels in men, and 24-hour urine collection (look at calcium,
creatinine). Can test for celiac disease, which can cause hypocalcemia.
Can also check TSH.
2. Contrast the prevalence and causes of osteoporosis in men and women of
different ages.
 Prevalence goes up across the board with age above 55. After
menopause women are particularly susceptible (no more estrogen
protection).
 He really doesn't say much about this in his notes.
3. Recognize the impact of osteoporotic fractures on health and the economy.
 Total fragility fractures per year in US: 1.5 million.
 It sucks and it's expensive.
4. Diagram normal and abnormal bone formation and resorption.
 Normal: they're balanced.
 Abnormal: they ain't.
5. Define osteoporosis and identify its risk factors.
 Osteoporosis: either clinically defined (previous fragility fractures +
exclusion of other causes) or defined by lab values (< -2.5 T score +
exclusion of other causes).
 Previous fractures, low bone mass, falls, and increasing age (mainly
above 55) are all risk factors for fragility fractures. Previous fractures
is a big one. Note age is an independent predictor of fracture
(independent of bone density).
 Menopause: net resorption increases, net deposition decreases.
 Non-modifiable risk factors: age, gender, race, slender build, early
menopause, family history.
 Modifiable risk factors: low calcium or vitamin D intake, estrogen
deficiency, lack of exercise, cigarette smoking, excess EtOH/caffeine
(bad news), some medications.
 Note you need gastric acid secretion to absorb calcium well-- so if
someone's on PPIs, might put them on some calcium carbonate too.
6. Define osteomalacia and list its causes.
 Osteomalacia: impaired osteoid mineralization in adults (same disorder
in children is rickets-- different outcomes).

Inadequate calcium-phosphate product (< 24 -- means a low calcium,
phosphate, or both) doesn't allow sufficient mineralization of the
osteoid laid down by osteoblasts.
 Caused by things that produce low calcium or phosphate:
 Acquired vitamin D deficiency: poor oral intake, inadequate
sunlight, malabsorption.
 Acquired 1,25-OH vitamin D deficiency (renal
disease/hypoparathyroidism)
 Congenital 1-OHase deficiency (can fix with vitamin D)
 Congenital vitamin D receptor deficiency (can fix with vitamin
D)
 Acquired hypophosphatemia: poor oral intake, renal phosphate
wasting
 Congenital hypophosphatemic rickets (most common cause of
rickets): can't fix with vitamin D, have to give phosphorus.
 [Clinical features:]
 Osteomalacia: manifests as pain in long bones, deformities
(bone bowing), and fractures.
 Rickets: manifests as pain in the long bones, severe deformities
(bone bowing, esp. around the knees), proximal muscle
weakness, and short stature.
7. Recognize the clinical presentation and course of Paget's disease.
 Idiopathic condition in which there's unregulated, excessive bone
resorption and reformation. Sort of a disease of disordered, irregular
absorption/deposition.
 Etiology: some genetic (mutations in the "sequestosome" activate
osteoclasts), some infectious (chronic paramyxovirus-- measles
vaccine lowers rate of Paget's).]
 Clinical presentation: pain in the bone, deformities, fractures,
osteoarthritis, acetabular protrusion (femur protruding up into the
hip), hypervascularity (recall osteoclasts stimulate vessel formation),
osteogenic sarcoma.
 Most commonly, it's involving the pelvis, skull, vertebrae, femur, and
tibia. Note that it doesn't spread from bone to bone-- extent of the
disease on diagnosis is the same extent it will always be. Its severity
and scope within that extent, however, can change over time.
 Can also cause neurologic symptoms: deafness (in ossicles or
compression of VIII), or compression of other cranial nerves (by bone)
or spinal cord (by vascularity).
 Also causes vascular disease.
 As mentioned, causes disordered bone formation following the
breakdown by osteoclasts.
 The X-rays are brutal. The osteoclasts are progressively chewing up
bone-- the osteoblasts are making deformed, weak, exaggeratedly
thick bone in their wake.
 Histologically, you see lots of osteoclasts with lots of nuclei.
 [Treat with anti-resorptives (bisphosphonates, calcitonin), as well as
analgesics and corrective surgery.]
8. Contrast the pathological features of bones affected by osteoporosis, osteomalacia
and Paget's disease.
 Paget's:
 Osteolytic lesions: "blade of grass" sign in long bones, can
watch a progressive "resorption front" in flat bones.



Sclerotic lesions (result of disordered bone deposition) near
lytic areas
 Expansion of bone size with thick, disordered trabeculae.
Osteomalacia:
 Bone bowing
Osteoporosis:
 Bone fractures
Dietary Calcium
Tuesday, December 16, 2008
7:53 AM
Dietary Calcium and Other Nutritional Influences on Bone Health,
12/16/08:
1. Describe the role of calcium in bone health and identify at least 2 stages of life
when inadequate dietary calcium may lead to increased risk of metabolic bone
disease.
 A "major mineral:" requires intake > 100 mg/day, contribute > 0.01%
of body weight.
 (others: Mg, P, Na, Cl, K, S)
 Most abundant mineral in body, nearly all of it in bone. The 1% or so
that's extracellular is generally for metabolic functions (signaling, etc,
as mentioned previously).
 Note that lifetime calcium intake is correlated with bone
density.
 Premature infants: 3rd trimester is a period of rapid bone mineral
accretion, so prematurely born infants are at risk of osteopenia with
inadequate calcium.
 Adolescence: pubertal changes cause bone deposition of calcium
(about 50% of total adult bone calcium).
 Menopause: high calcium requirements, high bone loss; there's
frequently low intake.
2. Identify dietary and lifestyle factors that may adversely impact bone health.
 Body's ability to respond to low calcium intake is limited-- there's no
up-regulation of absorption to compensate for a low intake.
 Nutritional:
 Vitamin D deficiency lowers your ability to absorb calcium.
 High protein intake -> increase in urinary calcium but it's also
protective of calcium stores.
 Sodium intake is associated with an increase in urinary calcium
(no protective effects)
 Vegetarian diet decreases urinary calcium (although watch for
certain compounds, see below).
 Caffeine increases urinary calcium.
 Recall that magnesium is essential for PTH activity.
 Non-nutritional:
 Weight bearing exercise and muscle mass increases bone
density.
 Hypogonadism, particularly low estrogen, decreases bone
density.

Genetics (the biggest factor, by far, for determining peak bone
density)
 Age (strongest "empiric predictor" of bone density)
 Tobacco use decreases bone density.
 Alcohols use decreases bone density.
 Corticosteroids and other medications decrease bone density.
3. Discuss strategies to optimize bone density, including "whole diet" approaches
such as DASH diet.
 Adequate intake of calcium: 1-1.3 g/day. Note typical intakes are
much lower (300-500 mg).
 Make sure adolescents take enough calcium in between sulking and
mooning over girls. The early pubertal period is especially important
for this. Calcium, not mooning over girls. Actually both.
 Note that calcium absorption is potentiated by lactose (increases
solubility) and dietary protein.
 Watch out for oxalate in spinach and phytate in legumes, soy, corn,
and wheat-- they decrease absorption of dietary calcium.
 Lifestyle stuff (exercise, etc) as mentioned.
 DASH: reduction in sodium associated with reduced Ca++
excretion/bone turnover.
4. Identify food sources of calcium; discuss role of supplements for bone health.
 Dairy, canned salmon, tofu (watch for phytate), cooked greens,
broccoli.
 Supplements: calcium carbonate (eg. Tums): has most elemental
calcium; best absorbed without meals, "has least lead" (which is
frankly disturbing). Can also use calcium citrate (better absorbed
between meals).
5. Describe quick assessment of patient's calcium intake.
 2 or more daily servings of calcium in childhood is good, particularly
with high protein.
 Other than that and the general guidelines for intake (1 g for normal
adults, 1200-1300 mg for adolescents/post-menopausal women, etc),
not much mentioned about this.
Pharmacology of Parathyroid and Metabolic Bone Disorders
Tuesday, December 16, 2008
9:02 AM
Pharmacology of Parathyroid and Metabolic Bone Disorders, 12/16/08:
1. Describe how PTH, Vitamin D, and calcitonin coordinate to regulate Ca++ levels
and describe the effects of each at the GI tract, bone, and kidney.
 This was mainly gone over in Dr. Vijay's lecture ("Control of Mineral
Metabolism").
 There's a negative feedback mechanism for calcitriol (1,25-OH vitamin
D): it inhibits PTH release. Calcitriol analogs (no effects on kidney or
GI) can be used in secondary hyperparathyroidism to reduce PTH
secretion.
 Note calcitonin doesn't do all that much physiologically, but at
pharmacological doses it can be used in osteoporosis and Paget's to
oppose bone resorption.

Note that the first 34 amino acids of PTH (it has 84) are the ones with
biological activity. The synthetic analogs of PTH only have those first
34 AAs.
2. List the sites of Vitamin D metabolism and activation (D3, 25-OH D3, 1,25-(OH)2
D3) and use of the various analogs in deficiency states.
 Recall that 1,25-OH D = calcitriol.
 Vitamin D synthesis (again): 7-dehydrocholesterol in skin + UV
radiation is converted to D3 (cholecalciferol); this is 25-OH'd in the
liver to calcifediol, then 1-OH'd in the kidney to calcitriol.
 Vitamin D2 (ergocalciferol) is plant-derived (comes from ergosterol, a
main constituent of fungal cell membranes, rather than cholesterol).
Recall that D3 can also be taken in through the diet (from animal
sources).
 As an alternative to calcitriol, can use dihydrotachysterol (vitamin D
analog that's activated in the liver and is then fully active), it's a little
cheaper. But generally you use calcitriol if there's a problem with
kidneys.
 PTH and activated D promote osteoclast precursor formation (have
RANK receptors); they also seem to activate osteoblasts to produce
RANK-L (ligands) to activate those osteoclast precusors into fully
functioning osteoclasts.
 As mentioned, we use monoclonal antibodies against RANK-L
(denosumab) or synthetic osteoprotegerins (more the former).
3. Describe the treatment of and pharmacotherapeutic options for:
 Hypercalcemia:
 Use saline diuresis (decrease sodium reabsorption, decrease
calcium reabsorption as well).
 Loop diuretic like furosemide (wastes calcium).
 Bisphosphonate (eg. alendronate) infusion.
 Hypocalcemia:
 Activated vitamin D (calcitriol) to promote calcium absorption
from the gut.
 Note that both calcitriol and PTH increase calcium
reabsorption in the kidney, but calcitriol increases
phosphate reabsorption while PTH increases phosphate
excretion.
 Calcium supplementation (citrate or carbonate).
 Can use thiazide diuretics (retains calcium).
 Acutely/emergently: IV calcium gluconate; correct low
magnesium.
 Osteoporosis:
 Bisphosphonates (1st line)
 SERM like raloxifene (2nd line-- doesn't stimulate breast
tissue like estrogen, so no increase in breast cancer risk, but
does increase thromboembolic disorder risk like estrogen)
 Calcitonin (3rd line-- administered intranasally)
 All of these will reduce bone resorption.
 In severe cases, can use PTH analogs-- it's the only agent we
have with anabolic effects on bone (as opposed to just
inhibiting bone catabolism).
4. Compare and contrast the effect on Ca++ levels for: Calcitonin, estrogens,
glucocorticoids, thiazide diuretics, alendronate, teriparatide.

Calcitriol: blocks PTH release, decreases excretion of Ca ++ and PO4- in
kidneys and increases their uptake-- increases Ca++ levels.
 Estrogens: Selective estrogen receptor modulator (SERM):
Raloxifene. Estrogens inhibit osteoclast activity and promotes
osteoblast activity; they also promote osteoprotegerin production.
Decrease Ca++ levels.
 Glucocorticoids: cause osteoporosis by inhibiting osteoblast activity
and increase RANK-L/decrease osteoprotegerin. Also inhibit D
activation and activity in the gut. Increase Ca++levels.
 Thiazides: retain calcium-- thus increase Ca++ levels (as opposed to
loop diuretics-- recall First Aid mnemonic, "Loops Lose Calcium,"
though also recall that it's talking about losing it from the blood, not
the kidney tubules).
 Alendronate: interferes with osteoclast formation/maturation. Can
cause pill esophagitis; is dosed weekly/monthly, etc. Generally safe
and effective. 1st line vs. osteoporosis. Decreases Ca++ levels.
 Teriparatide: active fragment of PTH hormone (AAs 1-34). Intermittant
administration increases bone formation (constant administration
decreases it)-- thus intermittant use decreases Ca++ levels, while
constant use increases them.
5. Describe the mechanism of action, pharmacokinetics, clinical uses, and adverse
effects of the bolded drugs listed below.
 (not mentioned in class but, loosely, from notes:)
 Bisphosphonates: block calcium resorption from bone by inhibiting
osteoclast and promoting osteoblast activity.
 Calcium carbonate/citrate: discussed elsewhere.
 Calcium gluconate: acute IV administration.
 Calcitonin: opposes osteoclast activity, promotes osteoblast activity.
 Dihydrotachysterol: partially activated; only needs an activation step
by the liver to become fully activated. According to the notes, it has a
faster onset and greater effect on bone mobilization than vitamin D.
 Note raloxifene can worsen hot flashes/cramps, and, like estrogen,
causes a pro-thrombotic state.
 [Note therapeutic uses of vitamin D: in hypoparathyroidism, chronic renal
failure, and certain congenital forms of rickets.]
Radiology of the Parathyroid Gland/Bone
Tuesday, December 16, 2008
10:06 AM
Radiology of the Parathyroid Gland/Bone, 12/16/08:
1. Understand available imaging modalities.
 Plain film: look at wedge compression fractures, lucent bones.
 DEXA scan: used for osteoporosis evaluation.
 CT: evaluate bone detail; distinguish metabolic disease from tumor
infiltration.
 MRI: similar to CT
 Nuclear scans: look for adenomas; can also pick up metabolic bone
disease, but not much used.
 US: can be used to evaluate PT gland for masses.
2. Identify structures on imaging.
 ..
3. Know the normal appearance of the parathyroid glands and bones.
 ..
4. Identify common disease states.
 Rickets: irregular epiphysis on film
 Hyperparathyroidism: clavicular/distal finger resorption. Can also see
'salt and pepper' osteopenic distribution in the skull. Can see brown
tumors (expansion of osteoclasts and fibrous tissues). In secondary
hyperparathyroidism, can also see some bony sclerosis (like Paget's).
 Parathyroid adenomas: ultrasound Doppler shows vascularity (not a
cyst). Parathyroid scan uses isotopes (Tc-99)-- goes to salivary
glands, heart, thyroids, and parathyroids. If you see an immediate hot
spot in the neck, can be parathyroid adenoma. Note that parathyroid
adenomas are I123-silent (parathyroids don't take up iodide).
 With ectopic (malignant) PTH-RP production, can see dense
calcification of the basal ganglia on CT.
 Paget's: lytic/sclerotic mixture of lesions.
Complementary and Alternative Medicine
Wednesday, December 17, 2008
7:39 AM
Complementary and Alternative Medicine, 12/17/08:
1. State the differences in regulation of medications labeled as supplement, overthe-counter, and prescription.
 Supplement: vitamin, mineral, herb, amino acid, enzymes, organ
tissues, metabolites. Called "foods," not drugs-- different regulation.
 FDA has the burden of proof to prove that it's unsafe-- no need
for proof of efficacy, no quality control requirements. Can't
claim to cure a disease but can suggest effect on a symptom
("can help with men's urinary tract health").
 Only 1 product withdrawn (Ephedra); Kava kava is still saleable
but no one buys it.
 No guarantee of bioavailability, no regulation of quantity
(variability of strength of products), etc.
 Vitamins: vitamins (subset of supplements).
 Herbs: supplements of plant origin (subset of supplements).
 Prescription:
 Need to do Phase I-IV trials, post-marketing surveillance,
additional restrictions on over-the-counter marketing.
Essentially the burden of making sure everything is safe is on
the company producing the drug.
2. Discuss how these differences affect the safety of herbal medications.
 See above.
 Often herbal supplements are cut with fillers; sometimes the fillers are
over-the-counter drugs like aspirin or NSAIDS (or heavy metals,
steroids, antibiotics).
 Few studies done on drug-drug interactions with other medications.


Can't patent a natural product-- thus no impetus to do safety studies.
Note 2006 act requires reporting of serious adverse reactions; 2007
act requires stronger controls on manufacturing by 2010. Still no
problem with safety or efficacy.
 "Look for label:" quality approved by consumerlab.com; USP
verification of dietary supplements.
3. List toxicities of the more commonly used herbs.
 See next point.
4. Discuss the uses, mechanisms of action, and side effects of some commonly used
herbs.
 Coffee: PDE inhibitor; increases side effects of ephedra, can cause
infertility or miscarriage.
 Garlic: inhibitor of HMG CoA-reductase. Scanty proof of effect on
cholesterol or BP. Can cause bleeding (inhibits platelet aggregation).
 Saw palmetto: inhibitor of 5-alpha reductase (formation of
testosterone) for benign prostatic hypertrophy; some proof of effect,
but not much. Not a lot of significant side effects.
 Ginkgo biloba: free radical scavenger, increases NO half-life, some
inactivation of platelets, for dementia. Generally safe, some rare
problems with bleeding, headaches, etc.
 Soy: similar to estrogen/SERM (stimulate or antagonize estrogen
receptor); ok for hot flashes, maybe ok for some bone loss/lipid
lowering. No definite side effects (the worry would be increased breast
cancer).
 Ginseng: steroid-like activity; no proof of efficacy. Estrogen-like side
effects, hypertension, bleeding, hyperglycemia. Frequently cut with
fillers. Multiple drug interactions. Stick with coffee.
 St. John's Wort: MAOI, SSRI, may stimulate GABA/DA. Effective for
mild to moderate depression. Side effects: sun sensitivity, can induces
mania or serotonin syndrome, induces cytochrome P450 3A4 (which
affects lots of narrow-TI drugs), part of it binds irreversibly to DNA.
 Glucosamine: substrate for GAGs, etc, in joints. Seems to have some
persistent effect. Not a lot of side effects.
 Probiotics: good evidence for improving various GI problems (eg.
prevention of antibiotic-associated diarrhea). No side effects known
except in cases of severe immunocompromise.
 Vitamin D: as previously mentioned.
 Coenzyme Q10: other name = 'ubiquinone,' found in all cells, essential
for ATP production. Some efficacy in preventing doxorubicin cardiac
toxicity, assisting heart function, maybe some benefit in breast cancer
or statin-induced myopathy? No known side effects.
 Fish oil: anti-inflammatory, supplements arachidonic acid production;
generally safe, though can inhibit coagulation.
5. Demonstrate ability to find information on specific supplements using online
resources.
 Yeah.
6. Advise patients on the safest way to use herbs.
 USP verification label and consumerlab.com seem to be emphasized
here.