Diabetes Mellitus
Type 1 Diabetes and Its Current Treatments
Michelle Adams
CHEM 5389
April 3, 2007
Presentation Outline
Diabetes
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What is Diabetes?
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How do people get diabetes?
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What are the signs and symptoms?
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Importance of Control – Complications of Diabetes
Control
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Being In Control
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Methods for Control
Insulin
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History of Insulin
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Insulin Structure
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Insulin Synthesis
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Insulin Secretion
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Insulin Receptor
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Insulin Synthetically Produced
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Insulin Analogues
Developments
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Recent developments in the field
What is Diabetes?
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Diabetes Mellitus – the presence of elevated glucose levels in the blood due to absolute or relative
insufficiencies of insulin
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171 million people suffer from diabetes
Type 1
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Autoimmune destruction of the b cells in the pancreas which are used to product insulin
1. Insulin administration
Type 2
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Combination of defective insulin secretion and increased insulin resistance
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Generally seen in overweight patients (85%)
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Thought that obesity contributes to insulin resistance due to secretion of hormones called
adipokines that impairs glucose tolerance
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Used to be seen in older patients, now disease is becoming more prevalent in children as obesity
grows among children
1. Life style change
2. Oral medications
i. Improve insulin production
ii. Regulate abnormal release of glucose by the liver
iii. Decrease insulin resistance
3. Insulin administration
Gestational diabetes
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Insulin resistance caused by hormones during pregnancy
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Usually improves or disappears after giving birth
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Seen in 5% of pregnant women
1. Diet control
How do people get diabetes?
Type 1
• Genetic element/mutation, susceptibility to triggers:
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Viral infections
Stress
Environmental exposure - exposure to certain chemicals or drugs
White blood cells, T lymphocytes, produce immune factors called cytokines which attack
and destroy b cells of pancreas
Can take 7yrs. or longer to develop to absolute, by the time know something is wrong
80% - 90% of b cells are destroyed
10% chance of inheriting if first degree relative has diabetes
Most likely to inherit from father
Increase incidences would take at least 400 years if genetic factors were the only cause
Viruses
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Infection introduces a viral protein that resembles a b cell protein
T-cells and antibodies tricked by this resemblance into attacking b protein and virus
• Cases rising in certain areas of U.S. – particularly Northeastern region
• Cow’s milk – certain protein which may trigger attack on b cells
• Breast milk – hormones which protect body from attack on b cells
Type 2
• Inheritance pattern, first degree relatives with type 2 have much higher risk for
developing
• Perhaps inheriting a tendency towards obesity since 85% obese
Gestational
• Genetically predisposed, have greater chance for developing type 2 later in life
What are the Signs and
Symptoms?
Polyuria (frequent urination)
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Glucose concentration in blood is high
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Reabsorbtion of glucose in the proximal renal tubuli is incomplete,
glucose remains in urine
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Osmotic pressure of urine increases
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Inhibits reabsorbtion of water by kidney, resulting in increase urine
production
Dehydration
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Lost water volume in kidney replaced from water held in body,
increased thirst and increased fluid intake - polydipsia
Polyphagia
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Increased appetite, no glucose delivered to muscles, tissues,
body sends signal to brain to eat something to renourish
Weight loss and weakness
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glucose cannot participate in crib cycle to be used as energy, use
of fat as alternative energy source
Vision changes
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changes shapes of lens in eye
Importance of Control –
Complications of Diabetes
Diabetic Ketoacidosis
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Fat break down accelerates and increase the production of fatty acids
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Fatty acids converted into ketone bodies
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Ketones are toxic at high levels
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Symptoms - rapid, deep breathing, polyuria, nausea, vomiting, abdominal pain, altered states of
mind such as hostility, mania, confusion, lethargy, and hypotension, coma, death
Hypoglycemia
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Low blood sugar, too much insulin or not enough glucose to cover insulin treatment
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Symptoms - sympathetic activation of the autonomic nervous system: immobilized panic, dread,
agitated, sweaty, seizures
Amputations
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Heal slowly
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Fail to heal
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Infection
Vascular diseases
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Damage to blood vessels
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Damage to arteries
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Diabetic retinopathy – growth of poor quality
new blood vessels in retina, retinal damage, blindness
Diabetic nephropathy – damage to kidney,
chronic renal failure – dialysis
Coronary artery disease, stroke, peripheral vascular,
diabetic myonecrosis (‘muscle wasting’)
Diabetic foot – neuropathy and arterial disease
Being In Control
Non-diabetic
Generally between 80mg/dL-120mg/dL
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Fasting glucose level: <110mg/dL
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2 hours after a 75g carb meal: <140mg/dL
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110mg/dL-125mg/dL: impaired fasting glucose
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By definition 2 fasting glucose above 126 mg/dL – positive for diabetes
Diabetic Goals
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90mg/dL-130mg/dL before meals
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110mg/dL-150mg/dL bedtime
HbA1c (glycosylated hemoglobin) – measures the level of glucose irreversibly bound to hemoglobin,
90 day measure of average blood sugar – can be misleading
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<6.0% for non diabetics = 114mg/dL
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<7.0% for diabetics = 147mg/dL
Feelings of High
Feelings of Low
Blood Sugars
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Control best obtained with pre-meal testing,
2 hour post meal testing, and bed time = 7x per day
Lows more frequent in controlled diabetics,
can’t feel them as well
Long term diabetics, may not feel lows as well
Lows can occur more in less educated diabetics
Exercise – increases insulin sensitivity
Blood Sugars
Frequent Urination
Shakes
Increased Thirst
Dizzy
Lethargy
Feeling of confusion,
disorientation
Irritability
Sweaty
Anxiety
Headache
Methods for Control
• Daily Injections
– Bolus insulin
– Basal insulin
– Two to five shots a day
• Insulin Pump Therapy
– Constant insulin delivery
– One insulin type become the bolus
insulin and the basal insulin
– Catheter changed every three days
History of Insulin
• 1920 – Insulin is first discovered by Fredrick Banting and
Charles Best
• November 1922 - Eli Lilly and Company is first to
produce large amounts of insulin
• 1923 - MacLeod and Banting receive Nobel Prize in
Physiology and Medicine for insulin discovery
• 1964 - Dorothy Crowfoot Hodgkin receives Nobel Prize
in Chemistry for determination of spatial conformation of
molecule
• 1980 - Frederick Sanger, British molecular biologist,
receives Nobel Prize in Chemistry for amino acid
structure determination
What is Insulin?
3D Structure of Insulin
Insulin Synthesis
• Produced within the pancreas by b
cells, islets of langerhans –
identified by Paul Langerhans in
1869
Islets of Langerhans – 1 million islets
a cells – secrete glucagons
b cells – produce insulin, most abundant
d cells – secrete somatostatin
• It is very difficult for small proteins to
fold into stable structures so larger
precursors are synthesized first
Stored as b granule
• When b cell is appropriately
stimulated, insulin is secreted from
the cell by exocytosis and diffuses
into islet capillary blood
Insulin Secretion
• Glucose transported into b cell by a glucose
transporter
• Results in membrane depolarization and an
influx of extracellular calcium
• Fusion of insulin storage vesicle in plasma
occurs
• Hexamer released from cell as crystal and
dissolves to monomer
Reasons for monomer transformation:
– Change in pH
– Loss of ligands due to dilution, dissociation of allosteric ligands
– Endogenous chelator removes the His B10 Zn2+ ions
Insulin Receptor
• 2 a subunits linked by disulfide bonds to 2 b
subunits
• Insulin binds to a subunits
• Causes autophosphorylation of b subunits within
plasma
• Activates catalytic activity of receptor
• Phosphorylates a number of intracellular
proteins
• Website:
http://www.vivo.colostate.edu/hbooks/pathphys/e
ndocrine/pancreas/insulin_phys.html
How is Insulin Synthetically
Produced by Recombinant DNA?
1. Isolate Gene (pig)
2. Prepare target DNA (cut plasmid ring open with
special proteins)
3. Insert DNA into plasmid (circular piece of DNA)
4. Insert Plasmid back into cell
5. Plasmid multiplies
6. Target cells gathered and purified
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Cells used are e-coli and yeast
Normal Insulin Secretion and
Insulin Analogues
Insulin Stability
Insulin decomposition
• Hydrolysis and intermolecular
transformation leading to
covalent insulin dimers
Hexamer Structure
• Hexamer – helps with storage
in pancreas
• Zn2+ and Ca2+ binding likely
becomes significant only at a
tetrameric stage of assembly
• Insulin hexamer much more
stable to chemical and/or
physical degradation than the
insulin monomer
Regular Insulin
• No alteration in structure of human insulin
• Insulin present in hexameric and
monomeric form
• Fast absorption of the insulin is due to the
monomeric form already present
• Does not peak until 1 to 2 hours later
because hexameric form must be
converted to monomeric form
• Lasts about 4 to 6 hours in body
Fast-acting Insulin
• Lispro (Humalog): B28 and
B29 amino acids reversed
• Aspart (Novolog): B28
replaced with Asp
• Glulisine (Apidra): B3 replaced
with Lys, B29 replaced by Glu
• Inhibiting the molecule's
natural tendency to form
hexamers by self-association,
means better, faster
absorption, more rapid onset
and peak, and shorter duration
NPH
• Neutral Protamine Hagedorn
• Protamine and Zinc added
to the insulin structure
• These additions resulted in more of the
hexameric form present in the mixture than the
monomeric form
• Thus, more hexamers had to be transformed to
monomers for insulin absorption
• The duration, onset, and peak of the insulin
prolonged
Glucagon
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Linear peptide, 29 amino acids
Synthesized as proglucagon
Brain can only use glucose, not alternative energy sources like fatty acids
• Insulin stimulates liver to store glucose in the form of glycogen
In liver:
1. Stimulates break down of glycogen stored in liver
2. Activates hepatic gluconeogenisis: non-hexose substrate (amino acids)
are converted to glucose
Injection of this hormone is given to patients when seizures
from low blood sugars occur
Seizures most likely to occur during the middle
of the night, most specifically when using
Regular insulin and NPH insulin
Insulin Glargine - Lantus
• Addition of positively charged
amino acids
• Isoelectric point of human
insulin is at pH = 5.4
• Isoelectric point of insulin
glargine is at pH = 6.8
• Soluble in acidic environment,
formulated to a pH of 4
• Forms microprecipitate after
injection because of neutral pH
environment
• Crystals slowly dissolve – slow
release of insulin dimers and
monomer to tissue and blood
stream
• Very little peak
Insulin Detemir - Levemir
• Addition of fatty acid
moiety on lysine in
position B29 and removal
of threonine from position
B30
• Fatty acid is a 14-carbon
fatty acid side chain,
Myristic acid
• Binds reversibly to
albumin, contributing to
long duration action
(20hrs)
• Very little peak
Recent Developments
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Constant glucose monitoring – sensor
records blood glucose every 10 seconds and
sends an average of the glucose
measurements every 5 minutes to the pump
for 3 days
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Symlin – analog of human amylin, a hormone
that contributes to glucose control during
postprandial periods
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Calibration by glucometer still required
Slows gastric emptying
Supresses glucagon secretion
Implanted Insulin Pump (not yet fully
developed)
Transplants
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Pancreas and kidney dual transplants have
been successful, must take
immunosuppressant for rest of life
Islet cell injections – several injections must
take place, not viable for the whole population
because costly and not enough supply, most
take immunosuppressant for rest of life
Conclusions
• Diabetes is a rapidly increasing disease
• Controlling diabetes is extremely important for good
health
• Control for type 1 diabetes must be obtained by insulin
administration
• The hexamer form of the insulin molecule is a very
important aspect in designing insulin analogues
• Several insulin analogues can be used in conjuction for
treatment
• Recent developments offer better control but much
research is still needed to help control diabetes and
possibly find a cure for it
References
B. Cheatham, C. Kahn, Endocrine Reviews, 1995, 16, 117-142
W. Duckworth, R. Bennet, F. Hamel, Endocrine Reviews, 1998, 19, 608-624
S. Taylor, A. Cama, D. Accili, F. Barbetti, M. Quon, M. De La Luz Sierra, Y.
Suzuki, E. Koller, R. Levy-Toledano, E. Wertheimer, V. Moncada, H.
Kadowaki, T. Kadowaki, Endocrine Reviews, 1992, 13, 566-595
Z. Vajo, J. Fawcett, W. Duckworth, Endocrine Reviews, 2001, 22, 706-717
J. Brange, Diabetologia, 1997, 40, S48-S53
U. Derewenda, Z. Derewenda, E. Dodson, G. Dodson, X. Bing, J. Markussen,
Journal of Molecular Biology, 1991, 220, 425-433
M. Dunn, BioMetals 2005, 18, 295-303
J. Goldman-Levine, K. Lee, The Annals of Pharmacotherapy, 2005, 39, 502507
A. Barnett, Diabetic Medicine, 2003, 20, 873-885
T. Levien, D. Baker, J. White Jr., R. Campbell, The Annals of
Pharmacotheraphy, 2002, 36, 1019-1027
http://en.wikipedia.org/wiki/Diabetes
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/index.html