Physical Training Reverses Defect in Mitochondrial Energy Production in Heart of Chronically Diabetic Rats

This study examined the impact of physical training on cardiac mitochondrial respiration of rats with chronic diabetes mellitus. Diabetes was induced by an intravenous injection of STZ (50 mg/kg) and only rats with a blood glucose level between 14 and 22 mM 1 wk later were kept in the protocol. Exercise training was conducted on a treadmill with a progressive 10-wk program. Animals were killed at the end of the training program, and mitochondria were isolated from ventricular tissue by differential centrifugation. Both state 3 respiration and oxidative phosphorylation rates were depressed significantly in the mitochondria of diabetic rats. These alterations were reversed completely to normal by physical training, without any significant changes in plasma glucose or insulin levels. The activity of ANT was not affected by diabetes or training. These results indicate that the depressed OPR present in isolated heart mitochondria from chronically diabetic rats is reversed to normal by physical training, apparently by mechanisms independent of blood glucose control. This correction in mitochondrial energy production may explain the improvement in cardiac function previously reported in trained diabetic rats.