EXERCISE TRAINING IMPROVES CARDIAC-PERFORMANCE IN DIABETIC RATS

Diabetes mellitus is often associated with a cardiomyopathy characteri zed by alterations in cardiac metabolism and declines in cardiac perfo rmance. We sought to determine whether exercise training would attenua te the depressed cardiac performance seen in diabetic animals. Female rats were divided into four groups: sedentary control, trained control , sedentary diabetics, and trained diabetics. After 1 week of training , we induced diabetes by intravenous injection of streptozotocin (65 m g/kg). We trained animals on a treadmill using a progressive protocol that plateaued at 27 m/min for 1 hr/day, 5 days/week for a total of 8 weeks. We measured cardiac output at a variety of left atrial filling pressures with an isolated working heart apparatus; glucose was the so le metabolic substrate for the heart. Training increased succinate deh ydrogenase activity in the soleus muscle of exercised rats, but did no t change heart and body weights or plasma glucose and thyroid hormone levels. The diabetic groups exhibited depressed cardiac outputs at hig h workloads compared to nondiabetics. Training increased the cardiac o utput of both sedentary and diabetic animals at high, but not low, pre loads. We suggest that exercise can attenuate the severity of diabetic cardiomyopathy.