Pathogenic contribution of lipid homeostasis to chagasic Cardiomyopathy

Rbhs-New Jersey Medical School, Newark NJ

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Abstract

DESCRIPTION (provided by applicant): Chagasic Cardiomyopathy (CCM) caused by the intracellular protozoan Trypanosoma cruzi is a major cause of mortality and morbidity in the endemic regions of Latin America with an estimated 15 million infected with or are carriers of the disease. Globalization has increased the risk of Chagas disease in developed countries including North America, Europe and Australia. We demonstrated that elevated cholesterol increased the rate of T. cruzi invasion and that this parasite utilizes LDLr to invade host cells. Parasite invasion was associated with a significant increase in the levels of LDL in organs such as heart and adipose tissue. Our studies reveal that : (i) T. cruzi targets adipose tissue (AT) during acute infection which acts as an energy source and reservoir for this parasite, (ii) In AT acute infection results in a significant decrease in fatty acid and an increase in cholesterol, and importantly a significant level of lipolysis (fat loss) and fat cell necrosis, (iii) Lipolysis resuts in increased serum lipid levels and parasitemia (serum parasite level) during acute stage of infection both of which significantly decrease by the end of acute infection, (iv) By the end of acute stage of infection, cardiac lipid levels and parasite load are significantly increased, (v) Elevated expression of SREBPs and cholesterol levels in the myocardium associate with the indeterminate stage of infection, (vi) Cardiac cholesterol levels are still elevated during chronic infection, and (vii) ER and mitochondrial oxidative stress is associated with acute infection and persists to chronic stage in murine chagas model. Lipodystrophy and elevated cardiac cholesterol is observed in CCM patients. This suggests that interlinked AT-cardiac lipid metabolism play a major role in the development of CCM. However, the exact mechanisms through which T. cruzi alter AT-cardiac lipid metabolism at different stages of infection is not known. Based on these observations we hypothesize that chronic CCM is developed through two distinct perturbations in lipid metabolism; (1) acute infection-induced increase in lipolysis and lipid influx to myocardium, and (2) Indeterminate (intermediate) stage infection-associated induction of de novo lipogenesis in myocardium. In short, we propose that adipose tissue lipolysis regulates cardiac lipid deposition, and the altered cardiac lipid homeostasis results in CCM. The overall goal of this proposal is to investigate the mechanistic link between AT and cardiac lipid metabolism in the progression of CCM during different stages of T. cruzi infection. In order to fully appreciate the role of adipocytes and Lipoproteins in the pathogenesis of human CCM we are using transgenic FAT-ATTAC and double transgenic CETP-ApoB mice respectively. Understanding the factors responsible for chronic CCM will aid in the development of new approaches to prevent progression of Chagasic heart disease for which currently no vaccine or effective drug available.