1. Moderator: Dr. DINESH PURIPresenter: Dr. KAPIL DEV

2. OBJECTIVES1. To understand the pathophysiology of acute complications of DM dueto: Diabetic Ketoacidosis Hyperosmolar state2. To understand the pathophysiology of chronic complications of DMdue to hyperglycemia (micro vascular and macrovascular complications)3. To gain an understanding of the mechanisms that leadto glucose induced vascular damage. 3. INTRODUCTION Diabetes mellitus -Group of metabolic disorders that share acommon feature of HYPERGLYCEMIA Prevalence of diabetes in India- 50.8 million(2010) Expected to rise to 87 million in 2030 4. Diabetes Type 1 DM: absolute deficiency of insulin cause by beta celldestruction Type 2 DM: combination of peripheral resistance to insulinaction and inadequate secretory response Results from defects in Insulin secretion, action or mostcommonly both 5. Pathogenesis of Type 1 DM Lack of insulin is caused by an immunologically mediated destructionof the beta cells Genetic susceptibility: multiple loci are associated, most commonlyMHC class II The autoimmune insult is chronic by the time the patients firstpresents, 80-90% b cell destruction has already occurred 6. Pathogenesis of Type 2 DM Environmental factors play a large role (lifestyle, dietary habits etc.) 2 Metabolic defects Decreased ability of peripheral tissues to respond to insulin b-cell dysfunction that is manifested as impaired insulin secretion 7. COMPLICATIONS OF DIABETESAcute complications Diabetic ketoacidosis HHSChronic complications Microcvascular/ Macrovascular Microvascular Nephro/Retino/Neuropathy Macrovascular CAD, PVD, CVDOthers 8. Hyperglycemia Overall net reduction in effective circulation insulin with a net increasein counter regulatory hormones (epinephrine, cortisol, glucagon) Hyperglycemia is due to: Impaired peripheral utilization in tissue (post prandial) Increased gluconeogenesis (fasting state) Insulin deficiency is more prominent in DKA over HHS HHS ketoacidosis is not seen Glucose levels are much higher in HHS than in DKA 9. Diabetic nephropathyDiabetic nephropathy is characterized clinically as a triad of hypertension,proteinuria, and, ultimately, renal impairment 10. Retinopathy Retinopathy has the highest correlation with severity and duration ofdiabetes Hyperglycemia is the primary cause of diabetic retinopathy but thespecific pathophysiologic mechanisms are not well understood. Death of microvascular contractile cells (pericytes) and the loss of intracellularcontacts which leads to microaneurysms and leakage. Growth factors have been implicated in the development of the next phase -proliferative retinopathy. Vascular Endothelium Growth Factor (VGEF) 11. Classification of Diabetic Retinopathy Pre proliferative increased vascular permeability venous dilation Microaneurysms intraretinal hemorrhage Fluid leakage Retinal ischemia. Proliferative Neovascularization Vitreous hemorrhage Fibrous proliferation (scarring). 12. Diabetic Neuropathy Sensorimotor neuropathy (acute/chronic) Ulceration (painless), Charcot arthropathy, Callosities. Autonomic neuropathy Mononeuropathy cranial nerve palsies (mc- IV,VI,VII)SpontaneousEntrapmentExternal pressure palsiesProximal motor neuropathy 13. MECHANISMS Hyperglycemia and susceptibility Endothelial cells and mesangial cellsMECHANISMS *Increased flux through Polyol pathway *Intracellular synthesis of AGEprecursors *Activation of PKC pathway *Increased hexosamine pathway activity 14. POLYOL PATHWAYNature 414:813820,2001. 15. Aldose reductase pathway Certain cells are unable to regulate glucose uptake inhyperglycemic states (ex. Endothelial cells) In a hyperglycemic state glucose is metabolized intracellularlyby an enzyme aldose reductase into sorbitol and eventually intofructose Intracellular NADPH is used as a cofactor in the pathway but isalso used to regenerate glutathione Glutathione is an antioxidant which prevent which decreases cellularsusceptibility to oxidative stress 16. INCREASED AGE PRECURSORS Non enzymatic reaction btwn sugars & amine residues From reactive carbonyl grp like 3 deoxyglucosone, glyoxal,methylglyoxalMECHANISM: Modification of intracellular proteins (regulation of gene transcription) Modify extracellular matrix protein (changes signaling between thematrix and cell and causes cellular dysfunction) Modify circulating proteins (albumin. Bind to AGE receptors andactivate , causing production of inflammatory cytokines & growthfactors, in turn causes vascular pathology) 17. AGE PRECURSORS 18. AGE GENERATION - CONTD RECEPTORS: RAGE AGE receptor:AGE-R1, AGE-R2, and AGE-R3/galactin-3 ezrin, radixin, and moesin (ERM) familyRAGE: Ig superfamily of receptors. Activation of secondary messenger PK- C. Target for rage signalling is NF-B transcription of intercellular adhesionmolecule-1, E- selectin, endothelin 1, tissue factor, VEGF, cytokines 19. Advanced glycation products invascular pathology. 20. Advanced glycation products innephropathy 21. Advanced glycation products aremetabolized to small peptides 22. ACTIVATION OF PK-C 23. ACTIVATION OF PK-C Hyperglycemia synthesis of a DAG A cofactor for protein kinase-C , , Effects gene expression eNOSendothelinTGF PAI- 1George King, showing that inhibition of PKC prevented early changes inthe diabetic retina and kidney 24. INCREASED FLUX THROUGH HEXOSAMINEPATHWAY 25. INCREASED FLUX THROUGH HEXOSAMINEPATHWAY GFAT (glutamine:fructose-6 phosphate amidotransferase) Fructose-6 phosphate to glucosamine-6 phosphate and finally toUDP N-acetyl glucosamine. N-acetyl glucosamine gets attached to serine and threonine residuesof transcription factors changes in gene expression phosphorylation, and overmodification by this glucosamine oftenresults in pathologic changes in gene expression increased modification of Sp1 TGF 1, PAI 1 26. SUPEROXIDE PRODUCTION BY ETC 27. SUPEROXIDE PRODUCTION BY ETC In diabetic cells more glucose oxidized in the TCA cycle moreNADH and FADH2 voltage gradient across mitochondrialmembrane increases Electron transfer inside complex III is blocked coenzyme Qdonates electrons to molecular oxygen, generating superoxide Mn SOD degrades O2- to H2O2 subsequently H2O and O2 28. SUPEROXIDE PRODUCTION BY ETC Hyperglycemia production of ROS If mitochondria ETC is removed, the effect of hyperglycemia on ROSproduction is lost UCP effect mitochondrial electron transport chain is the source ofthe hyperglycemia-induced superoxide 29. SUPEROXIDE ACTIVATES 4 MECHANISMSNature 414:813820, 2001 30. UNIFIED PATHWAY Hyperglycemia in cells, decrease activity of enzyme GAPDH Intermediates upstream to GAPDH - glyceraldehyde-3-phosphate *activates AGE pathway*activates the PKC pathway 31. UNIFIED PATHWAY F6P increases flux through hexosamine pathwayUDP-GlcNAc Inhibition of GAPDH increases intracellular levels glucose fluxthrough the polyol pathway Hyperglycemia induced superoxide inhibits GAPDH activity bymodifying the enzyme with poly ADP-ribose 32. PARP ACTIVATION 33. PARP ACTIVATION PARP : nucleus, inactive increased ROS in the mitochondria, induce DNA strand breaks activating PARP PARP splits the NAD into : nicotinic acid and ADP-ribose PARP makes polymers of ADP-ribose accumulate on GAPDH andother nuclear proteins leads to reduced activity 34. MACROVASCULARCOMPLICATIONS 35. MACROVASCULAR COMPLICATIONS Hyperglycemia is not the major determinant of macrovasculardisease(UKPDS) Insulin resistance FFA flux from adipocytes into arterialendothelial cells FFA oxidation generate NADH andFADH2overproduction of ROS Activates AGEs, PKC, the hexosamine pathway and NFB pathway 36. REFERENCES Williams Textbook of Endocrinology 12th Edition Brownlee M: Banting Lecture 2004,The Pathobiology of Diabeticcomplications.Diabetes 54:1615-27 Gohs, Copper M E, The Role of Advanced Glycation End Products in Progressionand Complications of Diabetes. J Clin Endocrinol Metab, 93(4):11431152 Yamagashi S, Matsui T, Advanced glycation end products, oxidative stress anddiabetic nephropathy. Oxidative Medicine and Cellular Longevity 3:2, 101-108 37. Diagnostic criteria for diabetic ketoacidosis (DKA)and hyperosmolar hyperglycemic state (HHS)