1. The pathophysiology of type 2 diabetes Jean GIRARD Institut Cochin Paris

2. Genetic factors Insulin-resistance Acquired factors Hyperinsulinemia ß-cell deficiency Compensation Normal glucose tolerance Gluco-lipotoxicity Acquired factors Type 2 diabetes Insulin-resistance Glucose production Insulin secretion Genetic factors

3. Causes of hyperglycemia in type 2 diabetes Muscle Glucose Liver Pancreas Insulin Glucagon

4. 5 0 10 50 0 100 hours 0 123 90 80 70 60 100 The euglycemic clamp Plasma glucose (md/dl) Exogenous glucose (mg/min/kg) Plasma insulin (mU/ml)

5. Insulin resistance in type 2 diabetes Hepatic glucose production Peripheral glucose utilisation Plasma insulin (µU/ml) T2D Control 0 50 100 0 200

6. Glucose uptake (mg/min/kg) Glycogen synthesis Glycolysis Oxidation 3 2 0 1 Control Type 2 diabetes Insulin-stimulated glucose uptake and glycogen synthesis are reduced in Type 2 diabetes

7. Non-oxidative glucose metabolisme in skeletal muscle Glucose Glucose-6-P GlycogenPyruvate Glucose transport Hexokinase II Glycogen synthaseGlycolysis

8. Effect of insulin on glucose transport in skeletal muscle of type 2 diabetes 3-O-methylglucose transport (mmol/h/ml cell water) 2.5 2.0 1.5 1.0 0.5 0 Type 2 diabetes Control 01001000200400 Insulin (  U/ml)

9. Control Type 2 diabetes 10 5 15 0 020406080100120Minutes Glycogen synthesis in skeletal muscles during a hyperglycemic hyperinsulinemic clamp Glycogen concentration in gastrocnemius (mmol/kg) 20

10. Skeletal muscles are responsible for the decreased whole body insulin-stimulated glucose uptake Glucose transport is the rate-limiting step of insulin-stimulated glucose metabolism in skeletal muscle Insulin-stimulated skeletal muscle glycogen metabolism is reduced in type 2 diabetes Conclusions

11. Insulin Binding AutophosphorylationTyrosine kinase activity    Tyr ATP    Tyr-P    IRS IRS-Tyr-P Metabolic effects Extracellular Intracellular  Tyr-P P-Tyr

12. Glucose transport Glycogen synthesis Inhibition of glucose production IRS-1 P-Tyr Tyr-P Insuline Tyr-P p85 PDK-1 p110 Protéine kinase C Protéine kinase B PI 3 kinase Metabolic effects Tyr-P

13. IRS-1 tyrosine phosphorylation in human skeletal muscle ControlType 2 diabetes Clamp Basal 8 4 0 % of basal values

14. IRS-1 associated PI 3 kinase in human skeletal muscle ControlType 2 diabetes Clamp Basal 500 250 0 % of basal values

15. Defects in insulin-signaling pathways in Type 2 diabetes The insulin receptor number is reduced by 20%, but this is compensated by hyperinsulinemia The tyrosine phosphorylation of IRS-1 and the activation of PI 3 kinase are decreased in Type 2 diabetes Increased activity of tyrosine phosphatases ? Serine phosphorylation of IRSs ?

16. Factors responsible for the decrease in insulin signaling in Type 2 diabetes Defect Insulin receptor number Tyrosine kinase activity Glucose transport Factors responsible Increased plasma insulin Serine Phosphorylation of IRS Hyperglycemia, decreased Glut4 translocation

17. Insulin Hyperglycemia IRS-1 Tyr-P Ser-P Tyr-P Glucose transport Protein Kinase C Decreased association with PI 3 Kinase

18. The hexosamine pathway Glycolysis Glucose Glucose-6-P Fructose-6-P Glutamine:fructose-6-P amidotransferase Glucosamine-6-P Pyruvate N-acetyl-glucosamine-6-P UDP-N-acetyl-glucosamine Glutamine Glutamate

19. Glucose Pyruvate N-acétyl-Glucosamine-6-P UDP-N-Acétyl-glucosamine G-6-P Glycoprotéines Glucosamine-6-P F-6-P GFA Glucose Glycogène G-1-P Possible role of metabolites of the hexosamine pathway in insulin resistance due to chronic hyperglycemia GFA = Glutamine:fructose-6-P amidotransferase

20. 101001000 G-6-P (  M) 100 50 0 Glycogen synthase activity % of total Insulin Insulin + glucosamine The O-GlcNac glycosylation of glycogen synthase results in reduced activation in response to insulin

21. Insulin resistance in type 2 diabetes Adipose tissue lipolysis Plasma insulin (µU/ml) T2D Control 0100 0 30

22. Type 2 diabetics have high plasma FFA all along the day Plasma FFA (  mol/l) Type 2 diabetes Control Hours 8101214161820 800 0 200 400 600

23. Fatty acid-induced insulin resistance : Randle’s hypothesis 1963 FFA Fatty acyl-CoA Acetyl-CoA NADH Mitochondria Citrate Glucose G-6-P Pyruvate Glucose PFK HK PDH

24. Potential steps controlling muscle glucose metabolism in response to FFA Glucose G-6-P Glycogen Glucose transportHexokinaseGlycogen synthase Metabolite levels during the clamp Control FFA Arbitrary units 100 0 50 ControlFFA

25. Fatty acid-induced insulin resistance : Shulman 1999 FFA Fatty acyl-CoA Protein kinase C  IRS-SerP PI 3 Kinase Glucose transport Insulin

26. Adipose tissue of type 2 diabetics Insulin resistance Résistine TNF  IL-6Adiponectine Visfatine Insulin sensitivity

27. Insulin TNF  IRS-1 Tyr-P Ser-P Tyr-P Biological effects Sphingomyelinase Ceramides Protein Kinase C PTPase Decreased association with PI 3 Kinase

28. TNF , IL-6 IRS-Ser P PI 3 Kinase Glucose transport Metabolic effects Insulin Cytokine-induced insulinoresistance IKKß JNK = Jun kinase JNK SOCS IKKß = Inhibitor of kappa B kinase ß SOCS =Suppressor of cytokine signaling

29. IRS-Ser P PI 3 Kinase Effets métaboliques de l’insuline Insuline L’insulinorésistance induite par les cytokines IKKß IKKß = Inhibitor of kappa B kinase ß SalicilateTNF , IL-6

31. Gluconeogenesis is responsible for increased hepatic Glucose production in type 2 diabetes Hepatic glucose production (mg/min/kg) 4 3 2 1 0 Control Type 2 diabetes Gluconeogenesis Glycogenolysis

32. Factors responsible for increased hepatic glucose production in Type 2 diabetes 1- Liver insulin resistance 2- Increased plasma glucagon levels 3- Increased plasma FFA levels

33. Insulin resistance in type 2 diabetes Hepatic glucose production (mg/min/kg) Plasma insulin (µU/ml) T2D Control 0100 4 0 50 2

34. Plasma glucagon (pg/ml) Type 2 diabetes Control 200 0 50 100 150 Hours 8101214161820 Type 2 diabetics have high plasma glucagon despite hyperglycemia

35. Increased mass of A cells Increased ratio A cells/B cells Hyperglucagonemia despite hyperglycemia Increased secretion in response to amino-acids Secretion of glucagon is less inhibited in response to glucose The impairement of glucagon secretion precedes the appearance of type 2 diabetes Glucagon in type 2 diabetes

36. Insulin resistance of A cells ? No: The impairement of A cells is not corrected by appropriate insulin-therapy Chronic hyperglycemia desensitizes A cell ? Possible : glucagon secretion is corrected by normalization of glycemia in response to phlorizine Mechanisms responsible for glucose « blindness » of A cells ? Factors responsible for hyperglucagonemia in Type 2 diabetes

37. Consequences of chronic hyperglucagonemia on hepatic glucose production in type 2 diabetes Increased transcription of genes coding for gluconeogenic enzymes : for exemple PEPCK Glucose production mainly due to gluconeogenesis Gluconeogenesis is less sensitive than glycogenolysis to the inhibition by insulin : Insulin resistance The absence of inhibition of glucagon secretion in the postprandial state induced glucose intolerance due to the non-suppression of hepatic glucose production

38. 01020304050 0 1 2 3 4 5 6 Glucogeogenesis Glycogenolysis Portal insulin (mU/ml) Glycogenolysis Gluconeogenesis (mg/min/kg) Basal Glycogenolysis is very sensitive whereas gluconeogenesis is insensitive to an increase in portal insulin

39. Glucose intolerance after oral glucose administration In type 2 diabetes

40. Glucose utilization (mg/min/kg) 0 2 4 6 -60 060120180240360 Control Minutes 8 Type 2 diabetes Hepatic glucose production (µmol/min/kg) 0 1.0 2.0 3.0 4.0 -60060120180240360 Minutes Type 2 diabetes Control Glucose Glucose intolerance after oral glucose administration is due to non-suppression of hepatic glucose production

41. Plasma insulin (µU/ml) 0 25 50 75 100 -60 060120180240360 Control Type 2 diabetes Minutes Plasma glucagon (pg/ml) 0 50 100 150 200 -60060120180240360 Minutes Type 2 diabetes Control Glucose Glucose intolerance after oral glucose administration is due to non-suppression of plasma glucagon and to the absence of early insulin secretion

42. 0 100 200 300 -60060120180240360 GLP-1 Type 2 diabetes Plasma glucose Minutes 400 (mg/dl) Glucose What could be expected from an inhibition of glucagon secretion in type 2 diabetes ? 0 1.0 2.0 3.0 4.0 -60060120180240360 GLP-1 Hepatic glucose production (µmol/min/Kg) Minutes Glucose GLP-1 Type 2 diabetes

43. 0 100 200 300 -60060120180240360 Répaglinide Type 2 diabetes Plasma glucose Minutes 400 (mg/dl) Glucose Répaglinide What could be expected from restoring the first phase of insulin secretion, in type 2 diabetes ? Hepatic glucose production (µmol/min/kg) 0 1.0 2.0 3.0 4.0 -60060120180240360 Minutes Type 2 diabetes Répaglinide Glucose Répaglinide

44. Type 2 diabetics have high plasma FFA Plasma FFA (  mol/l) Type 2 diabetes Control Hours 8101214161820 800 0 200 400 600

45. Visceral fat and insulin resistance % visceral fat Insulin Sensitivity mmol/min/kg) 100 20 50 40 30

46. Hepatic fatty acid oxidation provides co-factors essential for gluconeogenesis Fatty acid oxidation PyruvateOAAPEP3-PGA1,3-DPGGAPGlucose ATPGTPNADHATP Acetyl-CoAATPNADH

47. Role of Free Fatty Acids in Hyperglycemia Muscle Liver Adipose tissue FFA Hyperglycemia Gluconeogenesis Glucose utilization

48. Glucose-induced insulin secretion is decreased in chronically hyperglycemic Type 2 diabetic patients Mean plasma insulin during the OGTT (  U/ml) 80100120140160180 Fasting plasma insulin (mU/ml) 100 80 60 40 20 0 Fasting plasma glucose levels (mg/dl)

49. Compensation of insulin-resistance by pancreatic ß-cells Increased insulin secretion Increased ß-cell mass Replication of pre-existing ß-cells, neogenesis of ß-cells Alteration of proliferation or survival of ß-cells

50. Functional defect –Pulsatility –First phase –Glucose-induced insulin secretion Pancreatic ß cells from type 2 diabetic patients Decrease in ß-cell mass –Genetic factors (HNF1, HNF4, Kir6.2, TCF7L2, Mitochondrial genes) –Environmental factors (Gluco-lipotoxicity, physical inactivity)

51. Fatty acid metabolism in pancreatic ß-cells Fatty acids Acyl-CoA Fatty acids Acyl-CoA Glucose Normal ß-cell ß-cell from T2D TG Mitochondria Glucose

52. Cytotoxic effects of fatty acids in ß-cell from type 2 diabetic patients Fatty acids Acyl-CoA TG Apoptosis Glucose Normal ß-cellß-cell from T2D Mitochondria Fatty acids Acyl-CoA NO, Ceramides, ROS

53. Liver Hyperglycemia Pancreas Adipose tissue FFA Muscle Insulin Fatty acid oxidation Gluconeogenesis Fatty acid oxidation Glucose uptake

55. Thiazolidinediones and Sulfonylurea prevent cytotoxic effects of fatty acids on pancreatic ß-cells of type 2 diabetic patients ß-cell from treated T2D TG Apoptosis Glucose ß-cell from T2D Mitochondria Fatty acids Acyl-CoA NO, Ceramides, ROS TG Apoptosis Glucose Mito Fatty acids Acyl-CoA NO, Ceramides, ROS SFU TZD