Effect Of Post-exercise Carbohydrate Supplementation On Glucose Uptake-associated Gene Expression In Human Skeletal Muscle

Abstract

PURPOSE: We previously found that the exercise-induced elevation in GLUT4 mRNA of rat muscle can be rapidly downregulated when glucose is given immediately following exercise. The purpose of this study was to determine the effect of post-exercise carbohydrate diet on GLUT4 and hexokinase (HK) II mRNA levels in human skeletal muscle. METHODS: Eight untrained male subjects (age 20.7 ±3.1 yr) exercised for 60 min on a cycle ergometer at 70–75% maximal oxygen consumption. The post-exercise dietary treatment was performed in a cross-over design. Immediately after exercise, a diet with 70% carbohydrate content (1g per kg body weight; 356 ±19.8 kcal) was given to half of the subjects (eaten in 10 min) followed by a 3-h recovery, while the control subjects remained unfed for 3 h. Biopsies were performed on the deep portion of the vastus lateralis muscle of all subjects immediately after exercise and 3 h after the carbohydrate ingestion. Blood glucose and serum insulin concentrations were measured every 30 min for 3 h. RESULTS: At the end of the 3 h recovery, blood glucose and serum insulin levels were not different from control levels, indicating that the oral carbohydrate was mostly disposed in the body within 3 h. In addition, GLUT4 and HK II mRNA levels were significantly lowered in the exercised human skeletal muscle in subjects receiving the carbohydrate diet. CONCLUSIONS: The present study demonstrates that GLUT4 and HK II mRNA in exercised human skeletal muscle was significantly lowered by a high carbohydrate diet.