Diabetes mellitus Definition of diabetes mellitus (DM) • DM is a group of metabolic disorders characterized by hyperglycemia resulting from a lack of insulin effect • due to either defect in insulin secretion or insulin action • chronic hyperglycemia leads to long-term cell, tissue & organ damage = diabetic complications • retina • kidney • nerves Regulation of glycemia • humoral • principal • insulin • glucagon • auxiliary • glucocorticoids • adrenalin • growth hormone • neural • sympaticus • hyperglycemia • parasympaticus • hypoglycemia plasma (glycaemia 3–6 mmol/l) FOOD PRODUCTION of GLUCOSE by LIVER CNS A OTHER TISSUES MUSCLE, ADIPOSE TISSUE glykogenolysis inzulin-dependent utilisation non-inzulindependent utilisation glukoneogeneze - pyruvát - laktát - aminokyseliny - glycerol INSULIN GLUCAGON Main contra-regulation: insulin/glucagon Diagnosis of DM • diabetes • classical symptoms + random plasma glycemia 11.1 mmol/l (venous plasma) • random = any time of the day • symptoms include polyuria and polydipsia • FPG (fasting plasma glucose) 7.0 mmol/l • fasting means at least 8 h from the last meal • 2-h PG (postprandial glucose) 11.1 mmol/l during oGTT • oGTT: according to the WHO consists of FPG examination followed by a standard load of 75g of glucose (diluted in water) and examination of glycemia in 60th and 120th minute • impaired glucose tolerance (IGT) • excluded <7.8 mmol/l • 2-h PG 7.8 - <11.1 mmol/l during oGTT • impaired fasting glucose (IFG) • diabetes excluded by FPG 5.6 mmol/l • FPG 5.6 – <7 mmol/l Interpretation of glycemia 11,1 11,1 7,0 5,6 7,8 7,8 3 4 5 6 7 8 9 10 11 12 FPG 60 min 120 min glycemia(mmol/L) diabetes IGT IFG normal The way glucose enters the cell??? glukózaNa+ glukóza Insulin • exocytosis from B-cells of islets of Langerhans into portal circulation • 50% degraded during first pass through liver • parallel cleavage of the C-peptide • total daily production in healthy subject ~20-40 U • 1/2 basal (postabsortive) secretion • pulsatile (5 - 15 min intervals) • 1/2 stimulated (postprandial) • early phase (ready insulin) • Glc/KATP-dependent • late phase (synthesis de novo) • other secretagogues • stimulation of secretion • <<> after i.v. Glc • hypoglycemia – if the patient still conscious then better to give Glc per os • “forward” regulatory mechanism – anticipation of increase of Glc • 2 major incretin hormones • GIP (glucose-dependent insulinotropic peptide or gastric inhibitory peptide) • GLP-1 (glucagon-like peptide-1) • treatment of T2DM [= delayed effect of Glc on Ins stimulation] by incretin analogues • GLP-1 analogue - exenatide (GLP-receptor agonist) • DPP-4 inhibitors (dipeptyl peptidase 4 proteolytic degradation of incretins) - gliptins • improvement of Glc-stimulated Ins secretion after meal • supression of postprandial glucagon release • delayed gastric emptying • protection of β-cells from apoptosis NEFA and insulin secretion • NEFA can enter cells (incl. B-cells) • directly by diffusion across the membrane (short-chain FA)  metabolism (oxidation)  ATP …. insulin secretion • via receptor (GPR40)  see the figure • however, long term exposure to NEFA, esp. long-chain saturated (e.g. palmitate), suppress secretion of insulin and damages B-cells Insulin receptor Insulin receptor signal cascade • insulin receptor • tyrosinkinase type (2  and 2  subunits) • (1) cascade of phosphorylations (down-stream kinases) • balanced activation or inhibition of hormones • activation of anabolic pathways (i.e. glycegenogenesis, lipogenesis) • inhibition of catabolic pathways (e.g. lipolysis, glycogenolysis) and gluconeogenesis • (2) translocation of GLUT4 Classification of tissues according to insulin action: • insulin-sensitive • skeletal and heart muscle • adipose tissue • in both glucose uptake facilitated by GLUT4, which becomes integrated into cell membrane after insulin receptor activation • liver • metabolic actions • insulin- insensitive • all others incl. muscle, adipose and liver • glucose uptake is realized by facilitated diffusion by GLUT1, 2, 3, 5, … permanently localized in the cell membrane • transport of glucose depends solely on • concentration gradient • type and density of GLUTs Pathophysiology of diabetes mellitus • heterogeneous syndrome characterized by hyperglycemia due to deficiency of insulin action as a result of • absolute insulin deficiency • destruction of the -cells of the islets of Langerhans • relative deficiency of insulin secretion and/or action • abnormal molecule of insulin (mutation of insulin gene) • defective conversion of preproinsulin to insulin • circulating antibodies against insulin or its receptor • insulin resistance in peripheral tissues + secondary failure of -cells of the islets of Langerhans • receptor defect • post-receptor defect • prevalence of DM in general population 5%, over the age of 65 already 25% Prevalence (%) of diabetes (population 20-79 years) 2010 – 4.3 bil. (from a total of 7 bil.) 285 mil. diabetics 0.75 mil. diabetics in Czech rep. 2030 – 5.6 bil. (from a total of 8.5 bil.) 30% 438 mil. diabetics 54% 1.2 mil. diabetics in Czech Rep. 60% [IDF Diabetes Atlas, 4th ed. International Diabetes Federation, 2009 ] Classification of DM 1. Diabetes mellitus type 1 (T1DM) ~5% 2. Diabetes mellitus type 2 (T2DM) ~90% 3. Other specific types: a. genetic defects of B-cell - monogenic DM (MODY1 - 6) - mutation of mitochondrial DNA b. genetic defects leading to insulin resistance - type A insulin resistance, leprechaunismus, Rabson-Mendenhal syndrome, lipoatrophic DM c. diseases of exocrine pancreas - pancreatitis, tumor, cystic fibrosis, hemochromatosis d. endokrinopathies - Cushing syndrome, acromegaly, pheochromocytoma, hyperthyreosis e. iatrogenic DM (i.e. drugs and toxins) f. other genetic syndromes associated with DM - Down, Klinefelter, Turner syndromes, … 4. Gestational diabetes mellitus T1DM (formerly IDDM) • selective autoimmune destruction of  cells of IofL in genetically predisposed individuals • genetic susceptibility • chromosome 6 – MHC class III • DR3-DQ2 and DR4-DQ8 • chromosome 11 - insulin gene • promotor polymorphism (variable length) • in both cases genetic background leads to insufficient deletion of autoreactive T-lymphocytes in thymus and therefore suboptimal central immune (auto)tolerance • cytotoxic autoimmunity mediated by T-lymphocytes • there are also antibodies against  cell structures (ICA, GAD, IAA), but they are rather markers of autoimmunity than causal agents • common association of T1DM with other autoimmune diseases • celiac disease, thyreopathy, • Addison syndrome T1DM • autoimmunity has to be triggered by various factors • infection • viruses • rubella, measles, coxsackie B, CMV, EBV, enteroviruses, retro-viruses • mechanism is unclear • cytolytic ( sequestration of antigens • formation of neoantigens • molecular mimicry or superantigens • environmental factors (according to the epidemiologic evidence) • diet – early exposition proteins of cow’s milk • bovine insulin • vitamin D – reason for northern-southern geographical gradient? • toxins (diet, water, bacteria) • gluten??? • manifestation typically in childhood • absolute dependence on exogenous supplementation by insulin Natural history of T1DM Insulin resistance … T2DM • insulin sensitivity (= given effect of dose of insulin on individual‘s glycaemia) is a continuous trait with distinct interindividual variability, it can be assessed by: • hyperinsulinemic euglycemic clamp • calculated indexes (based on relationship between glycaemia and insulin during fasting or oGTT) • e.g. HOMA, QUICKI, … • insulin sensitivity changes (= insulin resistance) in many situations • physiologically in pregnancy • pathologically in obesity, inflammation etc. • should increasing insulin resistance always lead to compensatory increase of insulin secretion than glycaemia would stay stable • however capacity to compensatory increase secretion of insulin by beta-cells is apparently limited • main pathophysiologic feature of T2DM is an imbalance between insulin secretion and its effect • in the time of clinical manifestation there are both insulin resistance and impairment of insulin secretion T2DM (formerly NIDDM) • what is “chicken” and what is “egg”?? • insulin resistance • genetic predisposition (polygenic) – thrifty phenotype • acquired factors • competition of Gls with NEFA!!! (diet) • effect of adipokines from adipose tissue (obesity) •  mobilization of GLUT4 in physical inactivity • down-regulation of ins. receptor due to hyperinsulinemia • impairment of secretion • inherited factors • fewer B-cells (~20-40%) • defect of 1. phase of Ins secretion (~80% reduction) • acquired factors • – gluco- and lipotoxicity for B-cells • 90% of subjects are obese – metabolic syndrome!!! Natural history of T2DM Insulin- and “sport”-dependent translocation of GLUT4 • 2 intracellular “pools” of GLUT4 • insulin-dependent (see cascade of Ins-receptor) • Ca2+ / NO / AMPK?-dependent • this mechanism is responsible for improvement of insulin sensitivity in physically active subjects Secondary failure of  cells • hyperglycemia induces: • oxidative stress • endoplasmic reticulum (ER) stress • high concentration of NEFA causes lipotoxicity • short term increase of NEFA stimulates secretion of insulin • long term exposure to NEFA, esp. long-chain saturated (e.g. palmitate), suppress secretion of insulin and damages B-cells •  ceramide  apoptosis ER stress  Unfolded protein response • The unfolded protein response (UPR) is activated in response to an accumulation of unfolded or misfolded proteins in the lumen of ER • incl. insulin in -cells • UPR has two primary aims: • initially to restore normal function of the cell by halting protein translation and activate the signaling pathways that lead to increasing the production of molecular chaperones involved in protein folding • if these objectives are not achieved within a certain time lapse or the disruption is prolonged, the UPR aims to apoptosis Overt T2DM • manifest T2DM is characterized by (variable degree of): • fasting hyperglycemia (due to gluconeogenesis) • insulin resistance in liver • postprandial hyperglycemia (due to decreased peripheral glucose uptake • insulin resistance in muscle and adipose tissue • mixed dyslipidemia • increased plasma NEFA (due to unsuppressed lipolysis) • insulin resistance in adipose tissue • pro-atherogenic dyslipidemia (due to stimulated VLDL production in liver) • substrate effect Main characteristics of T1DM and T2DM T1DM T2DM onset childhood adults genetic disposition yes (oligogenic) yes (polygenic) clinical manifestation often acute mild or none autoimmunity yes No insulin resistance no yes dependence on insulin yes No obesity no yes Other types of DM • LADA (Latent Autoimmune Diabetes in Adults ) = slow-onset T1DM • diagnosis in > 30yrs of age, clinically similar to T2DM (slow onset) • initially on diet and pills, no ketoacidosis • later insulin dependent (during months – 1 year) • positive antibodies (= autoimmunity), low or no C-peptide • negative family history of T2DM • MODY (Maturity-onset diabetes of the young) – cca 5% T2DM • monogenic diabetes with familiar clustering and well defined (Mendelian) inheritance (usually AD), early manifestation (childhood or adolescence) and without obesity • 6 types (MODY1-6) • pathophysiology: genetically conditioned dysfunction of -cells but long-term measurable C-peptide without the signs of autoimmunity • MODY due to glucokinase mutations (MODY2) • glucokinase = “glucose sensor” (impaired insulin secretion) • milder form without the complication risk • MODY due to transcription factor mutations (other 5 types) • severe defects of -cells progressively leading to diabetes with complications • impairment of glucose-stimulated insulin secretion and proliferation and differentiation of -cells MODY lokus gen produkt prim. defekt závažn o s t k o m p l i k a c e 1 2 0 q HNF4A hepatocyte nuclear factor-4 pankreas vysoká časté 2 7 p GCK glukokináza pancreas/játra mírná vzácně 3 1 2 q TCF1 (HNF1A) hepatocyte nuclear factor-1 pancreas/ledviny vysoká časté 4 1 3 q IPF1 insulin promoter factor-1 pancreas vysoká ? 5 17q TCF2 (HNF4B) hepatocyte nuclear factor-1 pancreas/ledviny vysoká renální 6 2q32 NEUROD1 NEUROD1 pankreas vysoká ? Diabetic “triumvirate” ??? Acute manifestation and long-term consequences (complications) of diabetes Effect of rising plasma glucose ??? OSMOLARITA = 2 Na+ + urea + glukóza 275 - 295 = 2 x 140 + 2.5 + 5 > 300 = 2 x 140 + 2.5 + 35 Clinical presentation of DM • due to the mild increase of blood osmolarity, osmotic diuresis and dehydratation • classical • polyuria, thirst, polydipsia • tiredness • temporary impairment of vision • others • recurrent infections • perio-/parodontitis • extreme hyperglycemia (>40 mmol/l, osmolarity >350 mosmol/l) • ketoacidosis/coma •  ketone bodies, metabolic acidosis an d hyperglycemia • non-ketoticidotic hyperglycemic coma • hyperglycemia, dehydration and pre-renal uremia • lactic acidosis/coma • either complication of therapy (biguanides / type of peroral antidiabetics) • associated with hypoxic states (sepsis, shock, heart failure, …) Diabetic ketoacidosis Late complications of DM • microvascular • diabetic retinopathy • diabetic nephropathy • diabetic neuropathy • sensoric • motoric • autonomous • macrovascular • accelerated atherosclerosis (CAD, peripheral and cerebrovascular vascular disease) • combined • diabetic foot (ulcerations, amputations and Charcot´s joint) • others • periodontitis • cataract • glaucoma Chronic hyperglycemia Pathogenesis of complications Advanced glycation end products (AGEs) • cross-linking of extracellular proteins • modification of intracellular proteins and DNA • ubiquitin/proteasom • binding to patternrecognition receptors and activation of signaling pathways Maillard reaction in food – AGEs in diet • AGEs are similar to products of Maillard reaction (MRP) formed during thermal processing of food • sugar + protein • Louis Camille Maillard (1878 - 1936) • original description of reactions during cooking (“browning”) leading to formation of MRPs (=AGEs) •MRP influence taste and visual characteristics, smell, shelve life • biologic properties of MRP •positive – antioxidants •melanoidins, polyphenols •negative – carcinogens •acrylamid