MECHANISMS OF DYSLIPIDEMIA IN CARDIAC MUSCLE PRIOR TO ONSET OF ATHEROSCLEROSIS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Obesity has reached epidemic dimensions in the United States and correlates with the increased incident of cardiovascular disease. In obesity, the levels of cholesterol, free fatty acids, and tumor necrosis factor alpha (TNF-alpha) are elevated, and contribute to the increased risk of dyslipidemic cardiomyopathy. We hypothesize that cholesterol, palmitate, and TNF-alpha will induce cardiac contractile dysfunction via changes in the lipid composition of the membrane, and activation of intracellular signaling cascades that lead to diminished contractile performance. We will compare cholesterol fed and high fat fed mice with young dyslipidemic (ob/ob) mice, to distinguish cholesterol and lipid toxicity-mediated effects from effects mediated by atherosclerosis, and complications due to the onset of insulin resistance in the dyslipidemic in vivo mouse models. High cholesterol content in membranes causes them to become leaky, and in addition decreases the activity of major ion pumps. This leads to disturbed ion homeostasis with intracellular accumulation of sodium and calcium, and contributes to contractile dysfunction. We hypothesize that the energetic state of the myocyte is affected by increased ATP utilization to maintain ion homeostasis. Important questions are to what extent and in what time course leaky membranes cause disturbances in the ion homeostasis and energy metabolism of cardiac myocytes, and whether this causes a mismatch in cardiac energy supply and demand. The prevention of disturbances in membrane lipid homeostasis is a potential therapeutic approach to prevent or delay the cardiovascular complications associated with obesity.