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(M20) DISSECTING METABOLIC REGULATION IN THE HEART USING CONDITIONAL GENE TARGETING. Abel, E. Dale1, 1 Human Molecular Biology and Genetics and Endocrinology, Salt Lake City, UT ABSTRACT- Our lab is focussed on understanding the molecular pathogenesis of a complex disorder—diabetic cardiomyopathy, which is characterized by decreased glucose oxidation and glycolytic rates, decreased glucose transporter expression, and increased fatty acid oxidation rates. In a mouse model of type 2 diabetes we have observed reduced rates of glucose oxidation and impaired insulin signaling in hearts obtained from insulin resistant (pre-diabetic) animals. Thus we hypothesized that cardiac insulin resistance selectively impairs glucose oxidation, and that the other metabolic changes associated with diabetes occur in response to decreased expression of glucose transporters that develops after the onset of hyperglycemia. To directly test these hypotheses we generated transgenic mice with cardiac-restricted deletion of the insulin receptor gene and the GLUT4 glucose transporter gene respectively, using cre-loxP gene targeting. Cre recombinase expression was driven by the KEY WORDS: Conditional Gene Targeting, Cre-Recombinase, Knockout and Transgenic Mice, Diabetes and Cardiac Metabolism |
-myosin heavy chain gene promoter, which is active in the late embryonic and early neonatal left ventricle. Early post-natal insulin receptor deficiency recapitulated certain features of the diabetic cardiomyopathy such as decreased cardiac function persistent expression of the fetal 
myosin heavy chain gene and reduced rates of glucose oxidation. In contrast, deletion of GLUT4 resulted in decreased glycolysis decreased glucose oxidation and increased rates of fatty acid oxidation. These observations support our hypothesis that the initial reduction in glucose oxidation in the diabetic heart results from resistance to, or lack of insulin action in the heart, and the subsequent changes in glycolysis and fatty acid oxidation are direct consequences of reduced GLUT4 expression. The presentation will emphasize the utility of cre-loxP gene targeting in achieving cell specific deletions of genes in vivo. Additional refinements to this approach that will allow for temporal activation of cre recombinase in the adult heart will be presented.