The long-term goal is to elucidate the mechanisms of energy deprivation in the development of cardiomyopathy and heart failure. Cardiomyopathy associated with diabetes has been well documented, however, the mechanism of its development remains unknown. The objective of this study is to determine the contribution of energy deprivation in the development of contractile dysfunction during increased workload in isolated heats of streptozotocin-induced diabetic rats.
The specific aims are to: (1) define the contractile dysfunction that develops during increased workload, (2) determine the changes in high-energy phosphate metabolism during increased workload, (3) examine the mechanisms of development of energy deficits, and (4) examine the mechanism of energy deprivation which contributes to contractile dysfunction. Isolated work-performing hearts of diabetic and age-matched control rats will be subjected to increased workload and its effects on the increase in the rate of development of left ventricular pressure and relaxation of the pressure will be examined. The changes in high-energy phosphate metabolism, free energy release from ATP breakdown and creatine kinase (CK) reaction velocity in isolated hearts during increased workload will be determined employing 31P-NMR spectroscopy and 31P saturation transfer techniques. The inhibition of Ca2+ uptake into mitochondria and its consequences on intramitochondrial free Ca2+ concentration ([Ca2+]m), activation of Ca2+ -sensitive matrix dehydrogenases, and rates of NADH, ATP and PCr synthesis will be determined in mitochondria in vitro and in situ in isolated myocytes of control and diabetic hearts. [Ca2+]m in isolated mitochondria and single cardiomyocytes will be determined by measuring intramitochondrial indo-1 fluorescence. The rate of NADH synthesis in isolated single cardiomyocytes will be determined by measuring rate of increase in NAD(P)H fluorescence. The consequences of inhibition of CK activity on the sarcoplasmic reticulum (SR) Ca2+ -pump will be determined in vitro in isolated SR and in situ in single cardiomyocytes. The results of this study will determine the contributions as well as elucidate the mechanism of energy deprivation in the development of diabetic cardiomyopathy. In the long run, the results will be important in the development of effective therapeutic interventions by avoiding or preventing energy deprivation in cardiomyopathic and failing hearts.
