Effect of High Fat Diet on Glycogen Supercompensation in Rat Skeletal Muscle

The purpose of this study was to examine the effect of high fat diet on glycogen supercompensation in rat skeletal muscle. Male Wistar rats, 5 weeks old, were assigned to either a high fat (60% calories as fat and 18% calories as carbohydrate) diet or a low fat (14% calories as fat and 56% calories as carbohydrate) diet. They ate their diets ad libitum for 5 weeks. After overnight fast, the rats were exercised using a swimming protocol with a weight equal to 2 % of their body weight for 2 hours to deplete muscle glycogen. The rats were given the low fat diet plus 5% sucrose in their drinking water ad libitum during the recovery period. There were no significant differences in serum glucose and insulin levels before and after exercise between the high fat and the low fat diet. The concentration of glycogen in vastus lateralis muscle averaged 9.2±4.6μ mol/g in the high fat group and 13.6±8.9μmol/g in the low fat group before exercise. Although there were remarkable increases in glycogen concentration 4h after exercise in both diet groups, there was no significant difference in glycogen concentrations between the high fat fed and the low fat fed rats (28.8±6.6 and 23.7±6.5μmol/g, respectively). There was no significant difference in glycogen synthase %I activity 4h after exercise between the high fat and the low fat group. There was no significant difference in GLUT-4 glucose transporter protein in epitrochlearis muscles. These results suggest that long term feeding of high fat diet may not influence GLUT4 content and glycogen synthase activity in skeletal muscle and then the magnitude of glycogen supercompensation in rat skeletal muscle