1. GLP-1
Beyond blood sugar lowering effect
The effect of cardiovascular system
大里仁愛醫院新陳代謝科 林文玉醫師
月眉福容 June 30, 2012

2. Introduction

3. IN-CRET-IN
INtestine seCRETion INsulin
Definition: gut derived factors that increase glucose stimulated
insulin secretion
Two hormones: (1) glucagon-like peptide-1 (GLP-1)
(2) glucose-dependent insulinotropic polypeptide (GIP)
Source :Creutzfeldt Diabetologia 28: 5645 1985

4. Discovery and identification of regulatory peptides in gastrointestional tract. Peptides may act
as hormones, neurotransmitters, and growth factors. Sometimes 1 peptide acts in 2 or all of
the 3 roles.
Physiological Reviews vol. 78, No 4, October 1998

5. Gut Hormones
Gut hormones signals the brain (hypothalamus) to
achieve efficient nutrient digestion and absorption:
gut-brain interaction ( your brain in your gut )

6. Melanocortin System and Regulation of Body Weight
And Energy Expenditure
NTS

7. Central Melanocortin System and AgRP/NPY
• This system is involved in body weight regulation through its role in appetite and
energy expenditure via leptin, grhelin and Agouti related protein. It receives
inputs from hormone, nutrients and afferent neural inputs, and is unique in its
composition of fibers which express both agonists and antagonists of melanocortin
receptors.
• The melanocortin receptors, MC3-R and MC4-R, are directly positive linked to
metabolism and negative to body weight control. These receptors are activated by
the peptide hormone α-MSH (melanocyte-stimulating hormone) and antagonized by
the agouti-related protein.
• Agouti-related protein also called Agouti-related peptide (AgRP) is a
neuropeptide produced in the brain by the AgRP/NPY neuron. It is only synthesised
in NPY containing cell bodies located in the ventromedial part of the arcuate nucleus
in the hypothalamus. AgRP is co-expressed with Neuropeptide Y and works by
increasing appetite and decreasing metabolism and energy expenditure ( increased
weight ). It is one of the most potent and long-lasting of appetite stimulators

8. Regulation of gastric emptying
DIABETES CARE, VOLUME 31, NUMBER 12, DECEMBER 2008

9. Regulation of Gastric Emptying
• Normally, the rate of gastric emptying is tightly regulated as a result of
neural and hormonal feedback triggered by the interaction of nutrients within
the small intestine known as the ileal break mechanism or “extrinsic
pathway” of control. This feedback is caloric load dependent, relates to the
length of small intestine exposed to nutrient, and regulates the overall rate
of emptying to about 2–3 kcal/min.
• The intrinsic pathway is dependent upon the action of hyper- or
hypoglycemia on gastric emptying. The increase in hIAPP and decrease in
ghrelin both slow the gastric emptying rate by producing a parasympathetic
signal. Ghrelin secretion enhances antropyloric coordination, a signal
transmitted via the vagus nerve, which accelerates gastric emptying.

10. Rates of Remission of Diabetes
Adjustable Roux-en-Y Biliopancreatic
Gastric Banding Gastric Bypass Diversion
48% (Slow) 84% (Immediate) >95% (Immediate)

11. Foregut or Hindgut ?
• The “foregut hypothesis” raised by Rubino et al suggests that
nutrient interactions in the duodenum are diabetogenic and, hence,
bypassing the duodenum would reverse this defect. Their
conclusions come from experiments in rodents that underwent
jejunoileal bypass and subsequent refeeding through the bypassed
intestine.
• The “hindgut hypothesis” raised by Cummings et al suggests that
accelerated transit of concentrated nutrients (particularly glucose) to
the distal intestine results in increased production of insulinotropic
and appetite-controlling substances, which account for the reversal
of hyperglycemia and obesity.

12. Improvement of Glycemia after Metabolic
Surgery is Independent of Body Weight Loss

13. In 1930 La Barre described a greater effect of oral rather
parenteral glucose in increasing insulin secretion.
In 1932, the name incretin was coined.

14. In 1986 Nauck demonstrated that a glucose infusion graded to
achieve plasma glucose levels identical to those with oral load led
to a insulin response that was only one quarter as great.
J Clin Endocrinol Metab. 1986;63:492-498.

15. Incretin effect on insulin secretion
80 Control subjects (n=8) 80 People with Type 2 diabetes (n=14)
60 60
Insulin (mU/l)
Insulin (mU/l)
40 Incretin 40
effect
20 20
0 0
0 60 120 180 0 60 120 180
Time (min) Time (min)
Oral glucose load
Intravenous glucose infusion
Nauck et al. Diabetologia. 1986

16. Gastrointestinally mediated glucose disposal ( GIGD ): 20-80%, normal > 70%
If 25g iv glucose is required to copy a 75g oral glucose load ( glucose excursion ), The
GIGD amounts to 100x (75-25)/75 = 66%
Diabetes care, Volume 34, Supplement 2, May 2011

17. What is GLP-1?
Increased insulin response Key observations
80 • A 31 amino acid peptide
• Cleaved from proglucagon in
60 L-cells in the GI-tract (and neurons in
IR-insulin (mU/l)
hindbrain/hypothalamus)
Incretin
effect
• Secreted in response to meal ingestion
40 (direct luminal and indirect neuronal
stimulation)
* *
20 * * * • Member of incretin family (GIP, GLP-1 and
* *
others)
0
• GLP-1 has following effects:
–10 –5 60 120 180 • Glucose-dependently stimulates insulin secretion
and decreases glucagon secretion
Time (min)
Insulin response to oral glucose load (50 g/400 • Delays gastric emptying
ml, ●) and during isoglycaemic i.v. glucose infusion • Decreases food intake and induces satiety
(●)
• Stimulates -cell function and preserves or
increases -cell mass in animal models
Nauck et al. Diabetologia 1986;29: 46–52, *p ≤ 0.05.

18. Glucose-lowering effect of GLP-1
Endocrine Review, April 2012, 33(2):187-215

19. Why not GIP ?

20. Because of its short half-life, native GLP-1 has
limited clinical value
DPP-IV
i.v. bolus GLP-1 (15 nmol/l)
His Ala Glu Gly Thr Phe Thr Ser Asp 1000 Healthy individuals
Intact GLP-1 (pmol/l)
Val Type 2 diabetes
7 9
Ser
500
Lys Ala Ala Gln Gly Glu Leu Tyr Ser
Glu
Phe 37
0
Ile Ala Trp Leu Val Lys Gly Arg Gly
–5 5 15 25 35 45
Time (min)
Enzymatic cleavage t½ = 1.5–2.1 minutes
High clearance (i.v. bolus 2.5–25.0 nmol/l)
(4–9 l/min)
Adapted from Vilsbøll et al. J Clin Endocrinol Metab 2003;88: 220–224.

21. GLP-1 enhancement
GLP-1 secretion is impaired in Type 2 diabetes
Natural GLP-1 has extremely short half-life
Add GLP-1 analogues Block DPP-4, the
with longer half-life: enzyme that degrades
• exenatide GLP-1:
• liraglutide • Sitagliptin
• Vildagliptin
• Linagliptin
Injectables
Oral agents
Drucker. Curr Pharm Des. 2001; Drucker. Mol Endocrinol. 2003

22. Pharmacokinetic Properties of DPP-4 Inhibitors
Sitagliptin Vildagliptin Saxagliptin Alogliptin Linagliptin
(Merck)1 (Novartis)2 (BMS/AZ)3 (Takeda)5 (BI)6–9
Absorption tmax 2 h (4 h for active
1–4 h 1.7 h 1–2 h 1.34–1.53 h
(median) metabolite)
Bioavailability ~87% 85% >75 %4 N/A 29.5%
Half-life (t1/2) at 2.5 h (parent) 12.4–21.4 h 113–131 h
clinically relevant 12.4 h ~2–3 h
3.1 h (metabolite) (25–800 mg) (1–10 mg)
dose
Prominent
concentration-
dependent protein
Distribution 38% protein bound 9.3% protein bound Low protein binding N/A
binding:
<1 nM: ~99%
>100 nM: 70%–80%
69% metabolized Hepatic
Metabolism ~16% metabolized mainly renal (active metabolite) <8% metabolized ~10% metabolized
(inactive metabolite) CYP3A4/5
Feces 81.5%
Renal 75% Renal (74.1% unchanged);
Renal 87% Renal 85%
Elimination (24% as parent; 36% as (60%–71%
(79% unchanged) (23% unchanged) Renal 5.4%
active metabolite) unchanged)
(3.9% unchanged)
DPP-4=dipeptidyl peptidase-4.
1. EU-SPC for JANUVIA, 2010. 2. EU-SPC for Galvus, 2010. 3. EU-SPC for Onglyza, 2010. 4. EPAR for Onglyza.
http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Public_assessment_report/human/001039/WC500044319.pdf. Accessed May 4, 2011. 5. Christopher R
22
et al. Clin Ther. 2008;30:513–527. 6. Heise T et al. Diabetes Obes Metab. 2009;11:786–794. 7. Reitlich S et al. Clin Pharmacokinet. 2010;49:829–840. 8. Fuchs H et al. J
Pharm Pharmacol. 2009;61:55–62. 9. Blech S et al. Drug Metab Dispos.2010;38:667–678.

23. The majority of Linagliptin is excreted
unchanged via bile and gut
Absorption Metabolism
Tablet intake: 5mg
QD, independent of food
Absolute bioavailability:
~30%, with or without food ~90%
~10% transferred
(inactive) unchanged
~95% bound to plasma proteins metabolite
(in essence DPP-4)
Excretion1: ~ 95% of orally administered ~ 5% of orally administered
linagliptin is excreted via the linagliptin is excreted via the
bile and gut kidneys
1 At steady state
Source: US prescribing information

24. Linagliptin is the first only DPP-4 inhibitor that does
not require dose adjustment
Linagliptin Sitagliptin Vildagliptin Saxagliptin
(Trajenta®) (Januvia®) (Galvus®) (Onglyza®)
No renal
100 mg
issues
50 mg BID
5 mg
At risk 5 mg
of renal
impairment
Mild
renal
impairment
50 mg 25 mg
2.5 mg
Moderate
50 mg QD
renal
impairment
Severe
renal
impairment

25. Influence of hepatic impairment on
pharmacokinetics & exposure of Linagliptin
Patients with mild moderate and severe hepatic impairment
(according to the Child-Pugh classification A-C)
Child-Pugh Grade Points
A Well-compensated disease 5-6
1.5
Fold Increase in exposurerelative to
B Significant functional compromise 7-9
Fold increase in exposure relative
C Decompensated disease 10-15
normal hepatic function
to normal hepaticfunction
1
0.5
0
Healthy Mild (Grade A) Moderate (Grade B) Severe (Grade C)
Hepatic impairment (Child-Pugh classification)
n=8 n=7 n=9 n=8
No dosage adjustment for linagliptin is necessary for patients
with mild, moderate or severe hepatic impairment
Source: Data on file

26. Effect on Cardiovascular
System

27. GLP-1R expression in mouse
cardiac and vascular tissue
Polycloal Anti-GLP-1R Ab Pre-absorption Mesenteric arerty
Anti-SM (red )
Anti-GLP-1 (green )
Nuclear stain ( blue )
In media SM
Endocardium
Circulation. 2008;117:2340-2350

28. Effects of GLP-1 in p’ts with AMI and LV
dysfunction after successful reperfusion
• Glucose-insulin-potassium (GIK) infusions benefit patient with AMI, with
enhancement of myocardial glucose uptake and oxidation and the efficacy
of generating ATP.
• Dutch investigators reported beneficial effects of GIK therapy in patients
with AMI s/p PCI, the benefits were limited to those in Killip class I. Patients
with CHF (Killip class III–IV) exhibited an adverse trend with GIK therapy.
• Glucagon-like peptide-1 (GLP-1 [7–36] amide, with insulinotrophic and
insulinmimetic effect, minimizing risks of hypoglycemia and the need for
glucose infusion.
• If a continuous 72 hr infusion of GLP-1( post PCI ) improves global and
regional ventricular function?
Lazaros A. Nikolaidis, Circulation 2004 109:962-965

29. Effects of GLP-1 in patients with AMI and LV
dysfunction after successful reperfusion
Circulation 2004 109:962-965

30. The benefits of GLP-1 were independent of AMI
location or history of Diabetes
Circulation 2004 109:962-965

31. GLP-1R Agonist liraglutide: cardioprotective
pathways, treated before ischemic episode
• Whether liraglutide exerts cardioprotective actions in a preclinical murine
model of experimental ischemia after coronary artery occlusion.
• If treatment with liraglutide before induction of ischemia leads to activation
of prosurvival kinases and cytoprotective genes in the heart and limits
infarct size, expansion, and cardiac rupture in the normal and diabetic
heart?
• Moreover, liraglutide increases cAMP and reduces apoptosis in a GLP-1R–
dependent manner in murine cardiomyocytes cultured in vitro.
Mohammad Hossein Noyan-Ashraf, Diabetes 58: 975-983, 2009

32. GLP-1R Agonist Improves Outcomes After
Experimental Myocardial Infarction in Mice
( n=20 )
Non-diabetic ) ( n=35 )
( n=60)
( n=60)
( Lir75 + WL, n= 25 )
Diabetic blood sugar lowering
Mohammad Hossein Noyan-Ashraf, Diabetes 58: 975-983, 2009

33. Cardiac Rupture Post-MI
Mohammad Hossein Noyan-Ashraf, Diabetes 58: 975-983, 2009

34. After weight correction,
No percent difference between.
Diabetes vol. 58, April 2009

35. Liraglutide increases cAMP and reduces apoptosis in a GLP-1R–dependent manner
In murine cardiomyocytes in vitro.
Forskolin is commonly used to raise levels of cAMP in the study and
research of Cell physiology.
Indian Coleus: Forskoin ( adenylate cyclase activator )
Diabetes vol. 58, April 2009

36. Lira 200 for 7 d, Killed before MI ( wild type ) 4 days after MI
Diabetes vol. 58, April 2009

37. • Liraglutide administration induces changes in the expression of
cardioprotective proteins in normal non-AS murine heart, by
phosphorylation of Akt and GSK3β and increased expression of Nrf2,
PPAR- β/ δ and HO-1.
• Reduced levels of MMP-9 and cleaved caspase 3 in the infarct region at
day 4 post-MI.

38. Extracellular signal-regulated kinases
Endocrine Review, April 2012, 33(2): 187-215

39. Direct Effects of GLP-1 on Myocardial
Contractivity and Glucose Uptake
in Normal and Postischemic Rat Heart
• GLP-1 increased heart rate and blood pressure in intact rodents
through sympathostimulatory effect ( Barragan 1994, 1996;
Yamamoto, 2002 ).
• But depressed myocardial contractivity in isolated rat ventricular
myocytes ( Vila petroff, 2001 ).
• GLP-1 enhanced recovery of LV function after transient coronary
occlusion. Whether it is from GLP-1 direct effects and/or from
increased myocardial glucose uptake ( like insulin effect ).
Tingcun Zhao, JPET 317:1106-1113, 2006

40. GLP-1 or insulin on LV dev. P, LV dP/dt, heart rate
and coronary flow ( normal heart rat )
JPET 317:1106-1113, 2006

41. The effect of GLP-1 or insulin on myocardial
glucose uptake and myocardial lactate
production (normal heart rat )
JPET 317:1106-1113, 2006

42. GLP-1 increased myocardial glucose uptake
through a non-Akt-1-dependent mechanism,
distinct from insulin
JPET 317:1106-1113, 2006

43. The effect of GLP-1 or insulin on coronary flow, LV dev.
P, LV dP/dt and LVEDP during 30 min of low flow
ischemia ( 5% baseline ) and 30 min of reperfusion
JPET 317:1106-1113, 2006

44. After 30 min of low flow ischemia,
the change of myocardial glucose uptake
and lactate production
JPET 317:1106-1113, 2006

45. Myocardial signal transduction with
increased myocardial glucose uptake
in postischemic myocardium
JPET 317:1106-1113, 2006

46. • GLP-1 and insulin has comparable effects on myocardial glucose
uptake, but via different cellular mechanism. Insulin-mediated
glucose uptake was associated with Akt-1 phosphorylation and
GLUT-4 translocation. In contrast, GLP-1 did not increased Akt-1
and GLUT-4, but did result in increased GLUT-1 expression in
sacrolemma.
• The benefits of GLP-1 and insulin to improve postischemic
contractile dysfunction are related simply to enhanced glucose
uptake.

47. Extracellular signal-regulated kinases
Endocrine Review, April 2012, 33(2): 187-215

48. GLP-1R expression in mouse cardiac and vascular tissue
Pre-absorption Anti-SM (red )
Polycloal Anti-GLP-1R Ab
Anti-GLP-1 (green )
Nuclear stain ( blue )
In media SM
Endocardium
Loading control: GADPH, beta-actin

49. Cardioprotective and Vasodilatory Actions of GLP-1
Receptor Are Mediated Through Both GLP-1
Receptor-Dependent and –Independent Pathways
Circulation. 2008;117:2340-2350

50. Functional recovery after I/R injury in WT and
Glp 1r-/- hearts with GLP-1 (9-36).
Circulation. 2008;117:2340-2350

51. GLP-1 ( 9-36 ) Vasodilatory effect might be
through NO release
Only GLP-1 (7-36)
Rae GLP-9-26
Circulation. 2008;117:2340-2350

52. 1. Both GLP-1 and GLP-1(9-36) produced increased coronary flow in
constant-pressure perfused isolated hearts and vasodilatation of
resistance-level mesenteric arteries from WT and Glp1r -/- mice.
Furthermore, this vasodilatory effect correlated with presumably
NO-dependent cGMP release. But exendin-4 did not in that
exendin-4 cannot bind to novel receptor of GLP-1 (9-36 )--- GLP-1
independent pathway.

53. What about endothelium?

54. GLP-1 Prevents Reactive Oxygen species-Induced
Endothelial Cell Senescence
Arteriolscle Thromb Vasc Biology 2010; 30: 1407-1414

55. The PI3K/Akt Survival pathway Is Not required for
the GLP-1Protective Effect in HCAEC
Arteriolscle Thromb Vasc Biology 2010; 30: 1407-1414

56. GLP-1 Protective effect Is cAMP/PKA Dependent
H89: inhibitor of Forkolin Arteriolscle Thromb Vasc Biology 2010; 30: 1407-1414

57. Liraglutide attenuates induction of PAI-1
and vascular adhesion molecules
Journal of endocrinology ( 2009 ) 201, 59-66

58. Liraglutide attenuates induction of PAI-1
and vascular adhesion molecules
Journal of endocrinology ( 2009 ) 201, 59-66

59. Real-time Q-PCR of the effects of Liraglutide
treatment on Nur77 mRNA expression
Journal of endocrinology ( 2009 ) 201, 59-66

60. • GLP-1 administration attenuates endothelial
cell dysfunction in diabetic patients and inhibits
TNF α -mediated PAI-1 induction in human
vascular endothelial cells.

61. Endocrine Review, April 2012, 33(2): 187-215

62. Conclusion

63. Ongoing Trials

64. CAROLINA will evaluate CV safety of Linagliptin in
patients with T2DM at high CV risk
Inclusion if at least one of the following is fulfilled
1. Previous vascular complications
2. Evidence of end organ damage such as e.g. albuminuria
3. Age > 70 years
4. Two or more specified traditional CV risk factors
With or without metformin background therapy (including
patients with contraindication to Metformin use in renal
impairment)
Linagliptin 5mg vs. Glimepiride 1-4mg1
n= 6,000; approx. 6-7 year follow up
Primary endpoint: Time to the first occurrence of the primary composite endpoint:
1. CV death (including fatal stroke and fatal MI) 3. Non-fatal stroke
2. Non-fatal MI 4. Hospitalization for unstable
angina pectoris
1 16 weeks titration phase of glimepiride up to 4mg/day
Rosenstock J., et al. ADA 2011 Poster 1103-P
Clinicaltrial.gov NCT01243424

65. Thanks for your attention!!