Amylin AND GLUCOSE HEMOSTASIS

1. Amylin
and Glucose Hemostasis
1

2. Outlines
• Introduction
• Functions
• Metabolism
• Amyloid formation
• Therapeutic applications
2

3. Amylin
or Islet Amyloid Polypeptide (IAPP)
 A neuroendocrine hormone
 37-amino acid peptide first reported in 1987
 Co-localized and co-secreted with insulin from pancreatic b-cells
 actions as a hormone, growth factor, and modifier of behavior
 Deficient in diabetes
Amylin InsulinHuman amylin
3

4. • calcitonin family, CGRP, adrenomedullin
• A disulfide bridge between amino acid residues 2 and 7
• Amidated COOH terminus
4

5. Discovery
IAPP was discovered through its ability to
aggregate into pancreatic islet amyloid
deposits,
in association with type 2 diabetes in humans
and monkeys and cats
5

6. 1.Asahormone
2.Modificationofbehavior
increasing satiety,thirst
3.Growthfactor
Function
6

7. An overview of the major actions of amylin
activate specific receptors in the brainstem
1. suppression of glucagon release
2.reduction in food intake
3. gastric emptying
7

8. Synthesis
• Expressed by one single-copy gene on the short
arm of chromosome 12
• Prepro-IAPP : 89-aa residue containing a 22-aa
signal peptide preproprotein and two short
flanking peptides,
• The signal peptide is cleaved off in the ER
• Proislet amyloid polypeptide (proIAPP, proamylin,
proislet protein) a 67 amino acid
• conversion of proIAPP to IAPP takes place in
the secretory vesicles
8

9. ProIAPP and proinsulin are both processed by he two ndoproteases
hormone
1. Protei convertase 2 (PC2) and prohormone convertase 1/3
(PC1/3)
2. carboxypeptidase E (CPE)
IAPP and insulin genes contain similar
promoter elements, and the transcription
factor PDX1 regulates the effects
of glucose on both genes
9

10. FEBS Lett 247: 154–158, 1989
11

11. Secretion
amylin and insulin were co‐localized in, and
were co‐secreted
factors modulating insulin secretion also
appeared to cause an obligatory modulation of
amylin secretion
glucose , arginine, carbachol, fatty acids
somatostatin
12

12. Amylin And Insulin Were Co‐secreted
ranges from 3–5 pM in the fasting state to
postprandial concentrations of 15–25 pM
13

13. 14

14. • Like the C peptide, IAPP is eliminated in the kidney
• Insulin-degrading enzyme (IDE,Insulysin and insulinase)
• A second protease capable of degrading amyloid is neprolysin
Metabolism
15

15. Amylin degradation is
inhibited by excess
insulin or amylin.
A.
B.
16

16. • approximately 40% amino acid
sequence identity with calcitonin
• Calcitonin gene related peptide (CGRP)
 G protein–coupled receptors
(GPCRs)
• Receptor Activity-Modifying Proteins
(RAMPs)
• They are not receptors in
themselves, but when they
dimerize with the calcitonin
receptors, they interact and alter the
affinity for ligands
Receptors
17
(Hei et al 2015)

17. Receptor activity-modifying proteins (RAMPs) are a class of protein that
interact with and modulate the activities of several Class B G Protein-Coupled
Receptors including the receptors for calcitonin(CT), glucagon,and vasoactive
intestinal peptide (VIP).
There are three distinct types of RAMPs, designated RAMP1, RAMP2,
and RAMP3, each encoded by a separate gene
18

18. lung, stomach fundus, spleen, and brain
19

19. A.WhatIsAmyloid?
• a specific protein aggregation state in which molecules in β -
sheet conformation are bound to each other predominantly
by hydrogen bonds but also by other bonds
• This state of aggregation creates thin (10 nm), stable fibrils in
which the β-strands are oriented perpendicular to the fibril
axis.
ISLET AMYLOID POLYPEPTIDE
AND AMYLOID
Human IAPP is one of the most
amyloidogenic
peptides known.
20

20. AmyloidFormation
21
( Karen et al 2013)

21. 22

22. Amylin ReducesTheAd PathologyAnd Improves Cognitive Impairment In
TheAnimal Models ForAD
amylin type peptides enhance the
removal of neurotoxic Aβ out of the
brain.
23
(Qui et al, 2014)

23. Amylin increases expression of the synaptic marker synapsin I and the
kinase cyclin-dependent kinase-5 in the hippocampus, as well as
decreased oxidative stress and inflammatory markers in the
hippocampus
24

24. Glucose Homeostasis
• Amylin is released during the feeding/fed state in response to
nutrient entry into the gastrointestinal tract
• appetite
• glucagon
• Gastric empting
25

25. InsulinDeficiencyandGlucagonHypersecretionin
Diabetes
26

26. PostprandialGlucagon
NotCorrectedby ExogenousInsulin
27

27. Deregulationofamylinin
diabetesmellitus
There is an absence of secretion of b-cell
hormones in type 1 diabetes,
whereas
β-cell deregulation in type 2 diabetes
(depending on its severity) can range from
mild to severe.
28

28. Gastric Emptying and Diabetes.
Gastric emptying as a therapeutic target
29

29. Pramlintide
• An analog of amylin that overcomes the tendency of human
amylin to:
• Aggregate, form insoluble particles
• Adhere to surfaces
• Pharmacokinetic and pharmacodynamic properties similar to
human amylin
Human amylin Pramlintide (analog of amylin)
Amide
S S
A
Y
T
N
S
G
V N
T
T T
T
N
A
A
A
L
I
K
S
S
C
C
Q
R
L N
N
NF
G
F
L
V
H
Amide
P
P
P
Y
T
N
S
G
V N
T
T T
T
N
A
A
A
L
I
K
S
S
C
C
Q
R
L N
N
NF
G
F
L
V
H
30
(Fineman et al 2002)

30. PramlintideMimickedThree Important
Actions of AmylinThat ImpactGlucose
Appearance






Amylin* Pramlintide
Slows gastric emptying
Promotes satiety and reduces caloric intake
Inhibits inappropriately high postprandial
glucagon secretion
31

31. Pramlintide Reduces Postprandial Glucagon
T1DM
Time (h)
Placebo
Pramlintide
Placebo or 25 µg/h pramlintide infusion
-20
0
10
20
30
-10
Insulin
0 2 3 4 51
T2DM, Late Stage
Time (h)
PlasmaGlucagon(pg/mL)
Insulin
60
40
30
50
Placebo or 100 µg/h pramlintide infusion
0 1 2 3 4 5
PlasmaGlucagon(pg/mL)
32
feedingfeeding

32. %Emptiedperhr
afterbreakfast
Placebo 30 ug
Pramlintide
60 ug
Pramlintide
PramlintideSlowedGastric
Emptying-T1DM
Insulin + Placebo
Insulin + Pramlintide
Gastric Emptying Is
Accelerated in T1DM
33

33. PramlintideReducedCaloric Intake
in Type2 Diabetes
0
250
500
750
1000
1250
Protein
CHO
Fat
CHO
Fat
Protein
-202 kcal
(-23%)
P <0.01
Ad-Libitum
Caloric Intake
(kcal)
Placebo
Pramlintide
34

34. Pramlintide Improved Postprandial
Glucose
100
150
200
250
300
0 60 120 180 240
Time Relative to Meal and Pramlintide (min)
Mean (SE)
Plasma Glucose
(mg/dL)
100
150
200
250
300
0 60 120 180 240
Mean (SE)
Plasma Glucose
(mg/dL)
Lispro Insulin
Pramlintide 60 ug + Lispro Insulin
Regular Insulin
Pramlintide 60 ug + Regular Insulin
TYPE 1 DIABETES
35

35. Pramlintide Clinical Effects
-0.8
-0.6
-0.4
-0.2
0
-4
-2
0
2
4
6
8
-2
-1
0
1
***
***
***
**
*
***
***
***
Week 4 Week 13 Week 26Week 4 Week 13 Week 26Week 4 Week 13 Week 26
Insulin Use (%)A1C (%) Weight (kg)
Placebo + Insulin
30 or 60 ug Pramlintide TID or QID + Insulin
TYPE 1 DIABETES COMBINED PIVOTALS
36

36. PramlintideReducedFastingand
PostprandialGlucose
120
140
160
180
pre-bf post-bf pre-lu post-lu pre-di post-di bedtime
Glucose(mg/dL)
Baseline
6 Months
*
*
TYPE 1 DIABETES
37

37. PramlintideSafety and Tolerability in
Type1 Diabetes
• Nausea:
• Mostly mild-to-moderate nausea. Occurred more
frequently during initiation and then decreased with time
but can increase risk of hypoglycemia.
• Nausea reduced by dose titration
• Could increase risk of insulin-induced severe hypoglycemia
due to reduced food intake
• Insulin-Induced Severe Hypoglycemia:
– More common in type 1 diabetes; risk reduced by appropriate
patient selection, careful patient instruction and insulin dose
adjustments as stated in the Boxed Warning
38

38. AmylinHelps Regulate PostprandialGycemiaBy
MultipleMechanisms
• Enhances feeling of fullness at meals
• Slows inappropriately accelerated gastric
emptying
• Decreases hepatic glucose output
via suppression of postprandial pancreatic
glucagon secretion
39
Young A. Adv Pharmacol. 2005;52:67-77.
39

39. 40

40. 1. Hay, D.L., et al., Amylin: Pharmacology, Physiology, and Clinical Potential.
Pharmacol Rev, 2015. 67(3): p. 564-600.
2. Westermark, P., A. Andersson, and G.T. Westermark, Islet amyloid polypeptide,
islet amyloid, and diabetes mellitus. Physiological reviews, 2011. 91(3): p. 795-826.
3. Westermark, P., et al., A novel peptide in the calcitonin gene related peptide
family as an amyloid fibril protein in the endocrine pancreas. Biochemical and
biophysical research communications, 1986. 140(3): p. 827-831.
4. Woods, S.C., et al., Pancreatic signals controlling food intake; insulin, glucagon
and amylin. Philosophical Transactions of the Royal Society of London B: Biological
Sciences, 2006. 361(1471): p. 1219-1235.
5. Marzban, L., et al., Erratum. Small Interfering RNA-Mediated Suppression of
Proislet Amyloid Polypeptide Expression Inhibits Islet Amyloid Formation and Enhances
Survival of Human Islets in Culture. Diabetes 2008;57:3045-3055. Diabetes, 2016. 65(3):
p. 818.
6. Lee, S.M., D.L. Hay, and A.A. Pioszak, Calcitonin and Amylin Receptor Peptide
Interaction Mechanisms: Insights into Peptide-binding Modes and Allosteric Modulation
of the Calcitonin Receptor by Receptor Activity-modifying Proteins. J Biol Chem, 2016.
References
41

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42

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