Effect of Hyperglycemia and Hyperlipidemia on Cardiac Muscle Glycogen Usage during Exercise in Rats

Lee, Suck Kang; Kim, Eun Jung; Kim, Yong Woon

Abstract

Rats were studied during 45 minutes treadmill exercise to determine the effects of hyperglycemia and hyperlipidemia on the utilization of cardiac muscle glycogen, and the utilization of diaphragm muscle glycogen was also studied for comparing to cardiac muscle. The hyperglycemia was produced by ingestion of 25% glucose solution(1ml/100gm, BW) and the hyperlipidemia by 10% intralipose ingestion(1ml/100gm, BW) with intraperitoneal injection of heparin(500 IU) 15 minutes before treadmill exercise. The mean blood glucose concentrations(mg/dL) in control and hyperglycemic rats were 110 and 145, respectively, and the mean plasma free fatty acid concentrations(micronEq/L) in control, control exercise(control-E) and hyperlipidemia exercise(HL-E) rats were 247, 260 and 444, respectively. In the hyperglycemic trial, the cardiac muscle glycogen concentration was not significantly decreased by the exercise but the concentration in control rats was decreased to 73.9%(p<0.05). The glycogen concentration of diaphragm was significantly decreased in both groups by the exercise, but the hyperglycemia decreased the glycogen utilization by approximately 10% compared to the control. The cardiac muscle glycogen concentration was not decreased by the exercise in control and hyperlipidemic rats but the utilization of glycogen in hyperlipidemic rats is lower than that of the control. These data illustrate the sparing effect of hyperglycemia on cardiac muscle glycogen usage during exercise, but the effect of hyperlipidemia was not conclusive. In the skeletal muscle, the usage of glycogen by exercise was spared by both hyperglycemia and hyperlipidemia.