Effect of Insulin on Glycogen Supercompensation and Exercise-Induced GLUT4 Gene Expression in Different Muscle Fibers

胰島素對肌纖維肝醣超補與運動誘發之GLUT4基因表現之影響

郭家驊(Chia-Hua Kuo)

《北體學報》 6期 (1997/11) Pp. 75-98

https://doi.org/10.6167/TPEC/1997.6.5

並列摘要

Early studies have shown that insulin is not required for initial recovery of muscle glycogen, but it does appear to be essential for glycogen supercompensation post exercise. The purpose of this study was to determine the role of insulin on GLUT4 protein expression and its relationship to glycogen supercompensation after exercise. Male Sprague Dawley rats were injected with streptozocin (STZ) 72 hours before exercise, which successfully eliminated the insulin response to carbohydrate supplementation. Immediately after prolonged exercise in normal rats, GLUT4 protein increased 30% above control in red gastrocnemius muscle (RG) and 21% above control in white gastrocnemius muscle (WG). However, these increases did not occur in the STZ-treated rats. Five hours after the post-exercise carbohydrate supplementation in normal rats, GLUT4 protein was increased 52% above control in red gastrocnemius muscle (RG) and 47% above control in white gastrocnemius muscle (WG) and muscle glycogen supercompensation resulted. Again, the STZ-treated rats failed to increase GLUT4 protein levels, and showed no glycogen supercompensation. GLUT4 mRNA immediately increased (61%) after the glycogen depleting exercise in normal rats and declined during the 5-hour recovery period. In STZ treated rats, GLUT4 mRNA levels remained unaltered immediately following exercise and were slightly elevated above STZ-treated sedentary control 5 hours later. These results suggest that insulin is essential for exercise-induced GLUT4 protein expression, which may account for the insulin-dependency of the post-exercise glycogen supercompensation in skeletal muscle.