ALTERED PPARx SIGNALING IN THE ISCHEMIC DIABETIC HEART

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This SCCOR project will focus on abnormalities of myocardial lipid metabolism in the diabetic patient. Chronically increased rates of fatty acid utilization in the diabetic heart predispose to cardiotoxic effects related to increased oxygen consumption and accumulation of intracellular fipids ("lipotoxicity"). In the setting of myocardial ischemia, high rates of mitochondrial fatty acid oxidation (FAO) may lead to increased myocyte injury and death. Recently, we have found that the nuclear receptor, peroxisome proliferator-activated receptor alpha or PPARalpha, drives increased fatty utilization in the diabetic heart. This project will test the hypothesis that metabolic derangements due to chronic activation of the cardiac PPARalpha pathway are a major determinant of heart failure and death in diabetics following acute coronary isehemia insult. We have developed mouse models to reproduce the lipid metabolic derangements of the diabetic heart. Transgenic mice with cardiac-specific overexpression of PPARalpha (MHC-PPAR) exhibits a metabolic phenotype remarkedly similar to the diabetic heart. A second model involves cardiac-specific overexpression of lipoprotein lipase to increase delivery of fatty acids to the heart. We will study the response of the mouse models to ischemic insult. First, the mouse models will be used to evaluate the metabolic and functional response to myocardial infarction and ischemia/reperfusion. Second, we will evaluate the contributory role of cardiac lipotoxicity in the diabetic cardiomyopathic phenotype by evaluating the influence of dietary fat content and the effects of increased or decreased delivery of lipoprotein-derived fatty acid using LPL transgenics and "knockouts", respectively. Third, we will evaluate the influence of pharmacologic agents targeted at the PPAR pathway and its target genes. Lastly, we will perform fimctional studies of the effects of common single nucleotide polymorphisms (SNPs) within genes of the PPARalpha complex to compliment the results of population studies planned in Projects 4 and 5. The long-term goal of this project, in collaboration with Projects 2-5, is to identify novel lipid biochemical, metabolic imaging, and genetic determinants predictive of outcome in an individual diabetic patient at risk for acute cornary ischemic insult.