PHYSICAL-TRAINING REVERSES DEFECT IN MITOCHONDRIAL ENERGY-PRODUCTION IN HEART OF CHRONICALLY DIABETIC RATS

This study examined the impact of physical training on cardiac mitocho ndrial respiration of rats with chronic diabetes mellitus. Diabetes wa s 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 i n the protocol. Exercise training was conducted on a treadmill with a progressive 10-wk program. Animals were killed at the end of the train ing program, and mitochondria were isolated from ventricular tissue by differential centrifugation. Both state 3 respiration and oxidative p hosphorylation 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 gluco se 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 reverse d to normal by physical training, apparently by mechanisms independent of blood glucose control. This correction in mitochondrial energy pro duction may explain the improvement in cardiac function previously rep orted in trained diabetic rats.