Exercise training improves cardiac function in diabetes independent of plasma glucose control

Abstract

Exercise training benefits skeletal muscle glucose homeostasis in diabetes. However the benefit of exercise training on the diabetic cardiac muscle function is not clear. In this study we tested the hypothesis that exercise training benefits cardiac function in diabetes. We used a rat model made diabetic by streptozotocin treatment. The following three groups were studied: a) sedentary non-diabetic control, b) sedentary diabetic and c) exercised diabetic. The rats in the exercised diabetic group were trained on a treadmill for 11 weeks. At the end of training period, cardiac function was evaluated with EKG gated MRI. Left ventricular volumetric analyses revealed diminished stroke volume and ejection fraction in the sedentary diabetic animals. These abnormalities were prevented by exercise training. Exercise training also improved the left ventricular output in diabetic rats. Interestingly the exercise induced functional benefits on diabetic hearts occurred without any benefits on plasma glucose control. The glycated hemoglobin levels were not significantly different between sedentary diabetic and exercise trained diabetic animals. The improvement of diabetic heart function independent of systemic glucose homeostasis suggests the possibility of an endogenous focal mechanism of the cardiac tissue as the mediator of exercise induced functional benefits in diabetes. This possibility was strengthened further by numerical evidence for improved myocardial kinetics in exercise trained diabetic rats obtained from time derivatives of the left ventricular volumetric function. These results underscore the importance of exercise in preventing cardiac dysfunction in diabetes.