Accelerated atherosclerosis resulting in coronary heart disease and stroke is the major cause of mortality in patients with types 1 and 2 diabetes. In addition, patients with diabetes are affected by a cardiomyopathy that diminishes the ability of their hearts to pump blood and can lead to heart failure. An emerging body of evidence suggests that the metabolic abnormalities associated with diabetes, most notably those due to high blood glucose levels, contribute to these problems; however, the mechanisms involved are controversial. The 4 projects in this program are based on preliminary data that have led us to propose the following hypotheses. (1) In diabetes, high levels of certain plasma free fatty acids (FFA), as well as hyperglycemia, cause the endothelial cell damage that initiates atherogenesis. (2) They do so by causing an imbalance between fatty acid availability and oxidation that leads to changes in cell signaling (e.g., DAG-PKC, """"""""oxidative stress"""""""", ceramides) and gene expression. These changes, in turn, enhance apoptosis, impair insulin signaling and increase the expression of adhesion molecules and other factors that mediate vascular inflammation. (3) The adverse effects of hyperglycemia and FFA can be prevented by activating AMP-activated protein kinase (AMPK), an enzyme first characterized in vascular endothelium by investigators in this program. (4) Similar events, with some variations, occur in cardiomyocytes and may be relevant to the pathogenesis and prevention of diabetic cardiomyopathy. The four projects in this program will utilize metabolic, pharmacological and molecular biological approaches to evaluate how sustained hyperglycemia and excess FFA interact to cause cardiovascular damage and AMPK activation prevents it. Initial studies will be carried out in cultured cells (Projects 1-4) to work out mechanisms. We will then test our hypotheses in intact rodents in which diabetes accelerates atherosclerosis (Project 3) or causes cardiomyopathy (Project 4). A program project grant is requested because of the multidisciplinary nature of the research and the need for methods and experimental models that are beyond those available in a single laboratory. The proposed investigations should yield novel insights into the metabolic basis for the cardiovascular complications of diabetes and suggest new approaches for their prevention. Finally, we have recently obtained data suggesting that the combination of FFA and hyperglycemia accelerates apoptosis in retinal pericytes and that, here too, AMPK activation prevents this. Thus, the information we obtain should also be relevant to the pathogenesis and therapy of diabetic retinopathy.
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