Effect of Different Types of Carbohydrate Supplementation on Glycogen Supercompensation in Rat Skeletal Muscle

Abstract

0154 Nakatani et al. (J Appl Physiol. 1997) reported that exercise training that induces an increase in muscle GLUT-4 content results in a large increase in the muscle glycogen supercompensation level after a glycogen-depleting bout of exercise in rats. In their study, rats were given not only Purina chow but also 5 % sucrose in their drinking water ad libitum after glycogen depleting swimming exercise. The rationale for supplementation of sucrose was to ensure an adequate carbohydrate intake. However, to our knowledge, there have been few studies that examined the influence of the different types of carbohydrate consumed on glycogen supercompensation. PURPOSE: To examine effect of different types of carbohydrate on glycogen accumulation in rat skeletal muscle and liver after endurance exercise. METHODS: Four- to five-week-old male Sprague-Dawley rats with an initial body weight ranging from 90 to 110 g were used for this study. All rats were trained by using a 7-daylong swimming exercise program, during which rats swam 6 h/day in two 3-h bouts separated by 45 min of rest. On the last training day, swimming training was finished before 9:00 PM, and food was restricted to 8 g/rat after 10:00 PM the night before the glycogen depletion exercise bout. Between 3:00 PM and 4:00 PM on the next day of the last training, the rats performed 240 min of swimming exercise with a weight equivalent to 3 % of their body weight to deplete muscle and liver glycogen. After glycogen-depleting exercise, rats were given a ad libitum rodent chow diet plus either 5 % sucrose (S), 5 % glucose (G), 5 % fructose (F) or water (C) for 6 h or 24 h. Immediately after two repletion periods, rat epitrochlearis muscle and liver were dissected out. Glycogen concentrations in epitrochlearis muscle and liver were determined by enzymatic methods after acid hydrolysis. At the same point, plasma glucose concentration was also measured. RESULTS: Glycogen concentration in epitrochlearis muscle of G group rats after 6-h and 24-h repletion periods was significantly higher compared with that observed in F and C groups (p<0.01; 6 h, p<0.01; 24 h, respectively). There was no significant difference in the muscle glycogen among S, F and C groups or between S and G groups. No significant difference in liver glycogen and plasma glucose concentration was observed among the four groups after both recovery periods. CONCLUSIONS: The present investigation may suggest that glucose supplementation efficiently promotes glycogen supercompensation in rat skeletal muscle.