Face the Fats:
The Biochemistry of Lipids
by
Nancy A. Rice
Western Kentucky University
1
Vytorin
Pete was glad to finally be home. He’d been gone since 8 o’clock this
morning - first to classes all day and then straight to his job at Dillard’s.
Now it was 8 pm. He walked into his apartment and threw his backpack
on the floor. Whew! He was tired and hungry! He found some hot
pockets in the freezer and threw two in the microwave before he
slumped on the couch and turned on the TV.
Another one of those annoying drug company commercials! This one
was about some drug called VytorinTM.
As the microwave beeped that his dinner was ready, Pete watched the
commercial and laughed at all of the people who resembled what they
ate. He wondered….do I look like a Hot Pocket?
http://www.youtube.com/watch?v=kBfWybm0218 or search on Youtube for “Vytorin Ad”
2
As Pete wolfed down his
dinner, he was curious. How
much cholesterol was in a
hot pocket anyway?
He grabbed the box from the
trash can and read the
nutrition label on the back.
3
CQ#1: How much
cholesterol was in Pete’s
dinner?
A.
B.
C.
D.
25 milligrams
50 milligrams
6 grams
13 grams
4
Too young to have high
cholesterol
• Whoa! After reading the package, Pete realized that only
one hot pocket is considered a serving so he had eaten 620
calories for dinner! Not to mention 50 mg of cholesterol.
Although he had no idea if this was high or not, he figured it
couldn’t be too good or there wouldn’t be a need for a “Lean
Pocket”!
• He decided to research cholesterol levels on the internet.
He was not even sure what cholesterol was to begin with.
He also wondered: what should a normal person’s
cholesterol level be? Did he have high cholesterol? Nah, he
reasoned. How could I? I’m too young.
5
Nutritional analysis of 3 common
fast food meals
Wendy’s
• 1.4 lb single with
cheese
– 530 calories
– 27 g of total
fat
• Medium french
fries
– 420 calories
– 20 g of total
fat
47 g total fat
Subway
• 6” turkey breast
sandwich (no
mayo or
cheese)
– 280 calories
– 3.5 g total
fat
• 2oz bag of
Doritos
– 280 calories
– 14 g total fat
Steak n Shake
• Frisco Melt
– 1173 calories
– 93 g of total fat
17.5 g total fat
124 g total fat
• French fries
– 211 calories
– 10g total fat
• Vanilla shake
– 654 calories
– 21 g total fat
6
CQ#2: What percent of your average
daily food intake is fresh fruits and/or
vegetables?
A. 0%
B. 10%
C. 25 %
D. 50% or greater
7
CQ#3: What percentage of your
average daily food intake is lipids?
A. 0%
B. 10%
C. 25 %
D. 50% or greater
8
Pete searched the internet…
• After a quick Google search, Pete found
the following information:
“The American Heart Association and the United States
Department of Agriculture recommend that you limit your
fat intake to no more than 30% of your daily calories. Of
that 30%, 10% or less of the fat calories should come
from saturated fat. One gram of fat = 9 calories.”
• Fat? Saturated fat? Are these different
than cholesterol?
• Pete kept searching….
9
CQ#4: Pete normally consumes ~ 2000 calories
per day. What % of his total daily caloric intake is
coming from the two Hot Pockets? What % of his
total daily calories is coming from the fat in his
two Hot Pockets?
A. ~ 30%; 5%
B. ~ 30 %; 11%
C. ~ 50 %; 20%
D. ~ 60 %; 11%
Is Pete meeting AHA recommended
guidelines for fat consumption?
(…limit your fat intake to no more than 30% of
your daily calories…)
10
Cholesterol is a Lipid
• Lipids are the group of biological macromolecules
that have a major hydrocarbon component and
are mostly nonpolar and hydrophobic.
• Functionally, lipids are important in cell
membrane structure and in energy production.
• There are three main families of lipids:
– Steroids
– Fats
– Phospholipids
11
Steroids
• Typically have a
core structure of
four fused
carbon rings
• Cholesterol is
an example.
• Many hormones
and vitamins are
steroids.
Cholesterol
12
Fats and Fatty Acids
• A fat, also known as a
triacylglycerol or
triglyceride, is a glycerol
linked to three fatty
acids.
• Condensation reactions
between glycerol
hydroxyl groups and fatty
acid carboxyl groups
form ester linkages
joining the two subunits.
• Fatty acids can be either
saturated or unsaturated.
13
Saturated and Unsaturated
Fatty Acids
• Fats that have no double bonds
in the hydrocarbon chain are
“saturated” with hydrogens and
are very linear, e.g. animal fats.
• Fats that have a double bond
are called unsaturated and
have “kinks” in the hydrocarbon
chain, e.g. plant oils.
• Unsaturated fats can be either
monounsaturated as shown or
polyunsaturated (more than one
double bond).
• Unsaturated fats are generally
healthier than saturated fats.
14
CQ#5: Which of the following is the best
explanation for why vegetable oils are liquid at
room temperature?
A. Vegetable oils are saturated fatty acids that do not pack
together efficiently and therefore have a low melting
point.
B. Vegetable oils are saturated fatty acids that pack
together very efficiently and therefore have a low
melting point.
C. Vegetable oils are unsaturated fatty acids that do not
pack together efficiently and therefore have a low
melting point.
D. Vegetable oils are unsaturated fatty acids that pack
together very efficiently and therefore have a low
melting point.
15
Phospholipids
• Phospholipids consist of
a 3-carbon glycerol linked
to a negatively charged
phosphate group, and two
fatty acids.
• Phospholipids are a major
component of cell
membranes due to their
amphipathic nature.
• Amphipathic molecules
have a nonpolar region
(hydrophobic) and a polar
region (hydrophilic).
16
CQ#6: Which of these best describes
the term phospholipid?
A. A polar lipid molecule that fully interacts with
water.
B. A nonpolar lipid molecule that is made
amphipathic by the addition of a phosphate.
C. A nonpolar lipid molecule that is made polar by
the addition of a phosphate.
D. A polar lipid molecule that fully repels water.
17
Pete was beginning to understand a little
bit about cholesterol and fats. But he still
didn’t understand: why were they so
unhealthy? And if they are unhealthy, why
do we even need cholesterol and fat?
In small groups, develop an answer. What
would you tell Pete?
18
Pete learned that your body needs some
cholesterol. In addition to being a component of
cell membranes, cholesterol is also used to make
hormones, vitamin D, and substances that help
you digest foods.
Your liver makes all the cholesterol your body
needs. And excess cholesterol and fat in our
bodies is dangerous. It often means you are
overweight, and it can damage your vascular
system. The amount of cholesterol a person
produces varies depending upon their genetic
makeup.
19
• Since cholesterol is
hydrophobic (water fearing)
and blood is hydrophilic
(water loving), the two do not
mix.
• Cholesterol is carried
through the bloodstream in
protein packages called
lipoproteins, made up of
lipid on the inside and
protein on the outside.
• Two kinds of lipoproteins
carry cholesterol throughout
your body.
- High density lipoproteins (HDL)
- Low density lipoproteins (LDL)
20
LDL and HDL continued….
• LDL cholesterol is sometimes called bad cholesterol.
– High LDL cholesterol leads to a buildup of
cholesterol in arteries. The higher the LDL level in
your blood, the greater chance you have of getting
heart disease.
• HDL cholesterol is sometimes called good cholesterol.
– HDL carries cholesterol from other parts of your body
back to your liver. The liver removes the cholesterol
from your body. The higher your HDL cholesterol
level, the lower your chance of getting heart disease.
21
Hyperlipidemia can lead to disease
• When there is too much
cholesterol /LDL in your body
(because of diet and the rate at
which the cholesterol is
processed) it is deposited in
arteries, including those of the
heart, which can lead to
narrowing of the arteries and
heart disease.
• Studies of people with heart
disease have shown that
lowering cholesterol/LDL
reduces the risk for dying from
heart disease, having a heart
attack, or needing heart bypass
surgery or angioplasty.
22
Pete was beginning to get the idea. Low
cholesterol/LDL levels in your blood help
keep you healthy by preventing heart
attacks and strokes. Therefore, maybe
eating foods that are low in cholesterol may
ultimately be able to lower your risk for
these diseases.
But what would a normal blood cholesterol
level be?
23
Lipoprotein Profile
• Cholesterol levels are measured in milligrams (mg) of cholesterol per
deciliter (dL) of blood.
• Desirable or optimal levels for adults with or without existing heart
disease are:
– Total cholesterol: Less than 200 mg/dL.
– Low Density Lipoprotein (LDL) cholesterol: Less than 100 mg/dL.
– High Density Lipoprotein (HDL): 40 mg/dL or higher.
– Triglycerides: Less than 150 mg/dL.
• The National Cholesterol Education Program recommends that healthy
adults over 20 years of age have their cholesterol levels checked once
every 5 years.
24
Pete heads to the campus
health center…
• Pete decided he better check out his own
lipid profile.
• He went to the campus health center after
fasting all night and had his blood drawn.
• A few days later the doctor called with his
results.
25
CQ#7: Review Pete’s lipid profile results
below. What should Pete know?
A. Pete has acceptable
cholesterol levels.
B. Pete has borderline high
cholesterol and high LDL
levels; however the fact
that his HDL is elevated
is a benefit to him.
C. Pete has high cholesterol
and HDL levels yet the
fact that his LDL is
elevated is a benefit to
him.
Total cholesterol: 233.4 mg/dl
HDL: 55 mg/dl
LDL: 122 mg/dl
Triglycerides:125 mg/dl
26
• Pete was surprised. He was young, relatively active (he
walked to class everyday at least), was only a little
overweight, and he thought he ate pretty well. But
apparently his body did not think so.
• His doctor suggested three things to help lower his blood
cholesterol:
– Reduce the amount of saturated fat and cholesterol in
his diet.
– Lose some weight. Losing weight can help lower your
LDL and total cholesterol levels, as well as raise your
HDL and lower your triglyceride levels.
– Be physically active for at least 30 minutes most, if not
all, days.
27
So if KFC already cooks their chicken in
vegetable oil, what’s the problem?
• “Ok, doc. No more burgers and fries. But I don’t
get it. I’ve been reading a lot on the internet and I
know that oil, like corn oil, is not saturated. It’s
unsaturated. So why are things cooked in
margarine also bad? Isn’t margarine made from
corn oil?”
• “Yes, you’re right, Pete,” his doctor said. “There is
another type of bad fat out there. It’s called a
trans fat. Lots of trans fats exist in products like
margarine.”
28
CQ#8: Trans fats _____
A. Are essential.
B. Are antioxidants.
C. Have trans double bonds.
D. Are present in all foods.
E. Are in transition from unsaturated to
saturated fats.
29
CQ#9: Trans fats are formed when:
A. Liquid fat is chemically changed to solid fat.
B. Solid fat is chemically changed to liquid fat.
C. Liquid fat is refrigerated.
D. Solid fat is melted.
30
Trans Fats – The Double Whammy
• Trans fats come from adding
hydrogen to vegetable oil
(unsaturated fats) through a
process called hydrogenation.
• “Partially hydrogenated” oils may
contain higher levels of trans fats.
• Trans fats are more solid than oils.
• Trans fats increase the shelf life of
foods.
• Unlike other fats, trans fats both
raise your "bad" (LDL) cholesterol
and lower your "good" (HDL)
cholesterol.
31
CQ#10: Which of these does not
contain trans fats?
A. Fast-food french fries
B. Grilled hamburger
C. Store-bought cookies
D. Frozen chicken nuggets
32
CQ#11: What does trans-fat-free
mean on food labels?
A. Less than 1.5g per serving
B. Less than 1g per serving
C. Less than 0.5g per serving
D. 0g per serving
33
FDA recommendations for labeling
trans fats
• In January 2006, all food labels were required to
list saturated fat and cholesterol amounts AND
trans fat content.
• Foods with 0.5 g or less / serving are considered
“trans fat free.”
– From the FDA: If the ingredient list includes the words
“shortening,” “partially hydrogenated vegetable oil” or
“hydrogenated vegetable oil,” the food contains trans
fat. Because ingredients are listed in descending order
of predominance, smaller amounts are present when
the ingredient is close to the end of the list.
34
Ban the Trans Fats!
• Many cities and several states have
lobbied to ban trans fats from restaurants
– Tiburon, CA, was first.
– New York City was second.
• For more information see
– http://www.bantransfats.com/
35
Resolution
Wow! Pete never knew that food could be so
complicated. But now it all makes sense. He didn’t
think he ate a lot of high cholesterol foods, but he
did eat a lot of processed snacks and fast food –
cookies, french fries – foods with high trans fat
content. Pete decided it was time to really start
paying more attention to what he ate, especially
with regard to fats and cholesterol, and to
exercise. It’s never to early to “Face the Fats.”
36
Postscript
• Are all partially hydrogenated products bad?
• NO! Recent changes in the food industry with regard to
processing of oils results in partially hydrogenated products
with minimal trans fat content.
• A recent publication in Ann Nutr Metab 2009; 54
(Suppl.1):15-24 states that:
“…margarines and cooking products, and to a lesser extent dressings, have
been adapted to contain less trans fatty acids (TFA), less saturated fatty
acids (SFA) and more essential (polyunsaturated, PUFA) fatty acids…By
blending vegetable oils rich in the essential PUFAs a-linolenic acid (w-3) or
linoleic acid (w-6), margarines and dressings with both essential fatty acids
present in significant quantities can be realized. In addition, full
hydrogenation and fat rearrangement have enabled the production of costeffective margarines virtually devoid of TFA and low in SFA. Dietary surveys
indicate that vegetable oils, soft margarines and dressings are indeed often
important sources of essential fatty acids in people's diets, whilst providing
negligible amounts of TFA and contributing modestly to SFA intakes. “
37
Statin Drugs (optional slide)
• Statin drugs inhibit the enzyme
HMG-CoA reductase
• This is an enzyme in the
synthesis pathway of
cholesterol
• Statins also increase
cholesterol uptake from the
bloodstream by resulting in
more LDL receptor expression
• Vytorin is actually a
combination drug made of
simvastatin and ezetimibe,
(Zetia) which prevents
cholesterol absorption from the
digestive tract.
38
Image Credits
Slides 3, 4 and 9 – right
Description: Image of the nutritional data from a cheeseburger Hot Pockets.
Slide 7 – lower right
Description: Fruits and vegetables
Source: Wikimedia commons
Link: http://upload.wikimedia.org/wikipedia/commons/b/bd/Shukaku_no_aki_autumn_fruit_vegetables.JPG
Permission: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License,
Version 1.2 or any later version published by the Free Software Foundation
Slide 8 – lower right
Description: Oils
Source: National Institutes of Health
Link: http://www.nlm.nih.gov/medlineplus/images/oliveoil.jpg
Permission: Open source free access; work of U.S. Federal government under the terms of Title 17, Chapter 1, Section 105, of the U.S. Code.
Slide 12 – right
Description: Molecular structure of cortisol and Vitamin D
Source: Wikimedia Commons
Link: http://commons.wikimedia.org/wiki/File:Steroid_hormones,_cortisol_and_Vitamin_D3.jpg
Permission: This image of a simple structural formula is ineligible for copyright and therefore in the public domain, because it consists entirely of
information that is common property and contains no original authorship.
Slide 12 – right (lower)
Description: Cell membrane structure
Source; Wikimedia Commons
Link: http://commons.wikimedia.org/wiki/File:Cell_membrane_detailed_diagram_en.svg
Permission: This image has been released into the public domain by its author, LadyofHats.
39
Slide 13 – right
Description: Molecular structure of a triglyceride backbone
Source: Wikimedia Commons
Link: http://commons.wikimedia.org/wiki/File:Triglyceride-2D-skeletal.png
Permission: This image has been released into the public domain by its author
Slide 14 – right top
Description: Space filling model of myristic acid
Source: Wikimedia commons
Link: http://commons.wikimedia.org/wiki/File:Myristic-acid-3D-vdW.png
Permission: image has been released into the public domain by its author
Slide 14 – right middle
Description: Molecular structure of myristic acid
Source: Wikimedia commons
Link: http://commons.wikimedia.org/wiki/File:Myristic_acid.svg
Permission: This image is ineligible for copyright and therefore in the public domain, because it consists entirely of information that is common property and
contains no original authorship
Slide 14 – right middle
Description: Space filling model of oleic acid
Source: Wikimedia commons
Link: http://commons.wikimedia.org/wiki/File:Oleic-acid-3D-vdW.png
Permission: This image has been released into the public domain by its author
Slide 14 – right bottom
Description: Molecular structure of oleic acid
Source: Wikimedia Commons
Link: http://commons.wikimedia.org/wiki/File:Oleic-acid-skeletal.svg
Permission: This image has been released into the public domain by its author
Slide 16 – right (left hand side)
Description: Molecular structure of phosphatidylcholine
Source: Wikimedia commons
Link: http://commons.wikimedia.org/wiki/File:Phosphatidylcholine.png
Permission: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any
later version published by the Free Software Foundation
40
Slide 16 – right (right hand side)
Description: Structure of phospholipids in solution
Source: Wikimedia commons
Link: http://commons.wikimedia.org/wiki/File:Phospholipids_aqueous_solution_structures.svg
Permission: This image has been released into the public domain by its author, LadyofHats.
Slide 20 – right
Description: lipoprotein structure
Source: "lipoprotein." The Oxford Dictionary of Sports Science . Oxford University Press, 1998, 2006, 2007. Answers.com 21 Jul. 2009.
http://www.answers.com/topic/lipoprotein
Link: http://content.answers.com/main/content/img/oxford/Oxford_Sports/0199210896.lipoprotein.1.jpg
Permission:
Slide 22 – right
Description: Artherosclerosis
Source: National Heart Lung Blood Institute of the NIH
Link: http://www.nhlbi.nih.gov/health/dci/Diseases/Hbc/HBC_WhatIs.html
Permission: Open source free access; work of U.S. Federal government under the terms of Title 17, Chapter 1, Section 105, of the U.S. Code.
Slide 30 – right
Description: Krispy Kreme donuts
Source: Wikimedia
Link: http://upload.wikimedia.org/wikipedia/commons/b/b6/Krispy_Kreme_donut_assortment.JPG
Permission; Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any
later version published by the Free Software Foundation
Slide 38 – right
Description: HMG-CoA reductase pathway (cholesterol)
Source: Wikimedia
Link http://commons.wikimedia.org/wiki/File:HMG-CoA_reductase_pathway.png
Permission: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any
later version published by the Free Software Foundation
41