ANMCO 2008 Minimaster Cuore e Diabete SINDROME CORONARICA ACUTAIperglicemia, diabete e aterotrombosi: basi fisiopatologiche GianpaoloReboldi DipartimentodiMedicinaInternaUniversitàdegliStudidi Perugia
Acute Cardiovascular Effectsof Hyperglycemia • Reduced glycolysis and glucose oxidation • Impaired insulin secretion and insulin stimulated glucose uptake • Increased lipolysis and free fatty acid levels • Endothelial dysfunction • Increased cytokine activation • Increased oxidative stress (Increased myocardial apoptosis) • Platelet hyperreactivity • Impaired microcirculatory function (“no-reflow” phenomenon) • Impaired ischemic preconditioning Adapted from Zarich & Nesto. Circulation. 2007;115:e436-e439
Cardiac Energy Metabolism Energy metabolism in the heart has three components: • Substrate utilization (in red) • Oxidative phosphorylation (in blue) • Energy transfer and utilization (in green) Adapted from Neubauer S. N Engl J Med 2007;356:1140-51.
The production of energy rich phosphates (ATP) in myocardial cells NGT 60% NGT 40% NGT = Normal Glucose Tolerance PDH = Pyruvate Dehydrogenase Adapted from Bartnik et al Journal of Internal Medicine 2007; 262; 145–156
Glucose metabolism during ischemia Nonischemic Ischemic Immunofluorescence of GLUT-4 in sections from nonischemic (low power in A, high power in B) and ischemic (low power in C, high power in D) regions of left ventricle by confocal microscopy • Myocardial ischemia results in an increased rate of glycogenolysis and glucose uptake via translocation of GLUT-4 receptors to the sarcolemma • Glucose oxidation requires less oxygen than free fatty acid oxidation per molecule of ATP produced • Nonischemic region: • GLUT-4 demonstrated a predominantlyintracellular pattern • Ischemic region: • more prominent cell surface GLUT-4 labelingwas evident, with associated decreases in the intracellularfluorescence Zarich & Nesto. Circulation. 2007;115:e436-e439 Young LH et al Circulation. 1997;95:415-422
Glucose metabolism during ischemia Nonischemic Ischemic Immunofluorescence of GLUT-1 in sections from nonischemic (low power in A, high power in B) and ischemic (low power in C, high power in D) regions of left ventricle by confocal microscopy • Nonischemic region: • GLUT-1 was present primarily on the sarcolemma, some intracellular fluorescence could also be detected withincardiac myocytes • Ischemic region: • difficult to determine any increase in GLUT-1 surface fluorescence in the ischemic region Young LH et al Circulation. 1997;95:415-422
Hyperglycemia and ACS In the setting of hyperglycemia, with relative insulinopenia (or with defective insulin action), the ischemic myocardium is forced to use free fatty acids instead of glucose as an energy source because myocardial glucose uptake is acutely impaired. Thus, a metabolic crisis may ensue as the hypoxic myocardium becomes less energy efficient in the setting of hyperglycemia Zarich & Nesto. Circulation. 2007;115:e436-e439
The production of energy rich phosphates (ATP) in myocardial cells NGT 60% Hyperglycemia 90% NGT 40% Hyperglycemia 10% NGT = Normal Glucose Tolerance PDH = Pyruvate Dehydrogenase Adapted from Bartnik et al Journal of Internal Medicine 2007; 262; 145–156
Myocardialglucose and lipid toxicity Excess uptake of FFAs suppresses glucose uptake and glucose derived ATP formation and promotes cellular apoptosis via synthesis of ceramide Adapted from Bartnik et al Journal of Internal Medicine 2007; 262; 145–156
Lipotoxicity: high FFA availability low oxidative capacity Schrauwen et al Diabetes 2004; 53:1412–1417
Candidate Mechanism for Poor Outcome in Critically Ill: Free Fatty Acids (FFA) Increased levels result in endothelial dysfunction Increased FFA associated with increased oxidative stress Increased cardiac sympathetic over-activity Increased FFA shown to increase PAI-I Manzella D, et al. Diabetologia. 2002;45:1737-1738. Nilsson L, et al. Arterioscler Thromb Vasc Biol. 1998;18:1679-1685.
Metabolic consequences of hyperglycaemiaand free fatty acid overload Bartnik et al Journal of Internal Medicine 262; 145–156
Glucotoxicity, lipotoxicity, and inflammation underliereciprocal relationships between insulin resistance and endothelial dysfunction. • Hyperglycemia impairs both metabolic and vascular actions of insulin by multiple biochemical and cellular mechanisms • These include: • Elevated oxidative stress • Increased flux through polyol and hexosamine biosynthetic pathways • Protein Glycation • Activation of diacylglycerol and PKC. Adapted from Muniyappa et al Endocrine Reviews 28: 463–491, 2007
Glucotoxicity and Insulin Secretion Low-dose High-dose Profiles of glucose and insulin secretion rates (ISR) in 3 individual subjects during low-dose oscillatory glucose infusion (A, C, E) and during high-dose glucose infusion (B, D, F). In subject 1 (A and B) spectral power (SP) for glucose and ISR decreased from 15.7 and 6.4 to 5.7 and 5.7, respectively, during the high-dose glucose infusion; in subject 5 (C and D), SP for glucose and ISR decreased from 11.2 and 12.4 to 8.0 and 3.4, respectively; in subject 6 (E and F) SP for glucose and ISR decreased from 13.8 and 10.7 to 10.2 and 1.7, respectively. Meyer J et al Am J Physiol Endocrinol Metab 282: E917-E922, 2002
Major actions of counterregulatory hormonesand cytokines in mediating stress hyperglycemia Hormone Mechanism Glucagon Increased gluconeogenesis Increased hepatic glycogenolysis Epinephrine Muscle insulin resistance (postreceptor) Increased gluconeogenesis Increased glycogenolysis Increased lipolysis increased FFA Direct suppression of insulin secretion Norepinephrine Increased lipolysis Increased gluconeogenesis Direct suppression of insulin secretion Glucocorticoids Skeletal muscle insulin resistance Increased lipolysis Increased gluconeogenesis ( substrate) Growth hormone Skeletal muscle insulin resistance Increased lipolysis Increased gluconeogenesis TNFa Muscle insulin resistance (postreceptor) Hepatic insulin resistance McCowen et al Nutr Clin Pract 2004; 19; 235
Why is glucose elevated in the critically ill patient? Activation of the sympathetic nervous system and hypothalamic-pituitary axis stress induced hyperglycemia (“stress diabetes”, “diabetes of injury”) Epinephrine: glycogen synthesis glycogenolysis gluconeogenesis Inhibits insulin secretion Norepinephrine Inhibits insulin secretion
Cytokines TNF-αIL-6 Hyperglycemia FFA - phosphorylation - Iκß (inhibitor κß) + - INSULIN liver CRP - + NF-Kb APPs eNOS SAA + Translocation to the nucleus iNOS NO NO Adhesion molecules Proinflammatory genes transcription transcription ICAM-1 MMPs VCAM-1 TNF-α IL-8, MCP-1 IL-6 E-selectin Monocyte/Macrohage Endothelial Cell NF-Kb is a transcriptional factor regulating the activity of at least 125 genes, most of which are pro-inflammatory
Putting this all together… • Insulin and glucose co-modulate inflammation • Hyperinsulinemia with euglycemia is anti-inflammatory • Hyperinsulinemia with hyperglycemia is pro-inflammatory • Inability to control glucose in CREATE/ECLA and DIGAMI 2 likely explains the negative results using GIK in these two studies… besides many other study related factors
Acute, Short-Term Hyperglycemia Enhances Shear Stress-Induced Platelet Activation in Patients With T2DM Shear stress-induced platelet activation before and after the euglycemic and hyperglycemic clamps. (A) Filter closure time (s). (B) Platelets retained between 20 and 40 s (% of total). #p = 0.0012 vs. hyper-pre § p = 0.002 vs. hyper-pre Hyperglycemic clamp Euglycemic clamp Gresele et al, J Am Coll Cardiol 2003;41:1013–20)
Acute, Short-Term Hyperglycemia Enhances Shear Stress-Induced Platelet Activation in Patients With T2DM Platelet activation in bleeding-time blood before and after the euglycemic and hyperglycemic clamps. P-selectin expression on platelets. Data are reported as the percent increase in positive platelets between samples * p < 0.04, § p < 0.02 **p < 0.004 Hyperglycemic clamp Euglycemic clamp Gresele et al, J Am Coll Cardiol 2003;41:1013–20)
Acute, Short-Term Hyperglycemia Enhances Shear Stress-Induced Platelet Activation in Patients With T2DM Short-term hyperglycemia induces a significant rise in plasma vWF (whereas after 4 h of euglycemia, no changes in vWF were observed) vWF:activity showed an inverse correlation with shear stress-induced platelet activation (filter closure time) and a positive correlation with P-selectin expression on platelets in bleeding-time blood (AUC) Gresele et al, J Am Coll Cardiol 2003;41:1013–20)
Fibrin structures formed from fibrinogen purified from controls (left) and a subject with poor glycaemic control Poor glycaemic control Control Subject Glycation of fibrinogen leads to the formation of a clot which has more densely packed thinner fibres that are resistant to fibrinolysis. The glycated structure binds less tPA and plasminogen, generates less plasmin and has enhanced antiplasmin binding Dunn E, Diabetologia 2005; 48: 1198-206. & Diabetologia 2006; 49: 1071-80.
Dynamic progression of lysis fronts observed by confocal microscopy Progression of the lysis front after: 0 10 20 min Control Subject Diabetic Fibrin clots were formed from purified fibrinogen (1 mg/ml), FXIII (22 μg/ml), α- thrombin (1 U/ml) and CaCl2 (5 mmol/l). Lysis was induced by application of 10 μl of a solution of t-PA (5 μg/ml) and Glu-plasminogen (210 μg/ml) Dunn E, Diabetologia 2005; 48: 1198-206. & Diabetologia 2006; 49: 1071-80.
“Glucometrics” and Mortality Risk Kosiborod et al Circulation. 2008;117:1018-1027
Iperglicemia in Corso di Sindrome Coronarica Acuta Marcatore di deficit insulinico (Incrementata Lipolisi, danno Miocardico da FFA, etc) • Fattore aggravante la prognosi della SCA • “Crisi metabolica” (sbilancio tra disponibilità ed utilizzazione dei substrati energetici) • Gluco- e lipotossicità • Stress Ossidativo • Aggregazione piastrinica e fibrinolisi Danno Strutturale e Funzionale Marcatore di Insulino-resistenza Marcatore di attivazione ormonale ed adrenergica in particolare, in grado di amplificare il danno miocardico Marcatore di alterazioni non note del metabolismo del glucosio che hanno già contribuito al danno cardiovascolare
AMP-Activated Protein Kinase Conducts the Ischemic Stress Response Orchestra • AMP-activated protein kinase (AMPK), a molecular stress response pathway that is activated by increases in the intracellular concentration of AMP. • AMP is not to be confused with cAMP, a molecular signal produced during stress by catecholamine-induced β-adrenergic stimulation Alterations in myocardial energy production during ischemia lead to an imbalance in ATP generation and utilization. Thus, ischemia leads to the formation of AMP, which signals that the cell is developing metabolic compromise. Young LH Circulation. 2008;117:832-840
AMP-Activated Protein Kinase Conducts the Ischemic Stress Response Orchestra Effects of activated AMPK during ischemia and reperfusion Activated AMPK in the ischemic heart has diverse effects on metabolic pathways, ion channels, protein synthesis, and cellular function that modulate the response to ischemia and reperfusion. The red lines represent pathways that are stimulated by AMPK, and the blue lines indicate those that are inhibited. ER indicates endoplasmic reticulum.. Young LH Circulation. 2008;117:832-840
AMP-Activated Protein Kinase Conducts the Ischemic Stress Response Orchestra Activated AMPK also directs the enzyme LPL to the capillary endothelium, where it mediates the uptake of fatty acids from triglyceride-containing lipoproteins Activated AMPK stimulates the movement of membrane transporters to the cardiomyocyte cell surface, where they are physiologically active, facilitating the entry of glucose and fatty acids into the cell for subsequent metabolism Within the cardiomyocyte, activated AMPK stimulates cellular energy generation by glycolysis during ischemia and fatty acid oxidation during reperfusion. Metabolic actions of activated AMPK Young LH Circulation. 2008;117:832-840