Impact of 1 wk of diabetes on the regulation of myocardial carbohydrate and fatty acid oxidation

The aim of this study was to investigate the effect of increasing exogenous palmitate concentration on carbohydrate and palmitate oxidation in hearts from control and 1-wk diabetic rats. Hearts were perfused with glucose, [3- C-13]lactate, and [U-C-13]palmitate. Substrate oxidation rates were determi ned by combining C-13-NMR glutamate isotopomer analysis of tissue extracts with measurements of oxygen consumption. Carbohydrate oxidation was markedl y depressed after diabetes in the presence of low (0.1 mM) but not high (1. 0 mM) palmitate concentration. Increasing exogenous palmitate concentration 10-fold resulted in a 7-fold increase in the contribution of palmitate to energy production in controls but only a 30% increase in the diabetic group . Consequently, at 0.1 mM palmitate, the rate of fatty acid oxidation was h igher in the diabetic group than in controls; however, at 1.0 mM fatty acid oxidation, it was significantly depressed. Therefore, after 1 wk of diabet es, the major differences in carbohydrate and fatty acid metabolism occur p rimarily at low rather than high exogenous palmitate concentration.