Glucose transporter subtype 4 (GLUT4) is an important factor for glucose uptake in human skeletal muscle. The mRNA and protein level of GLUT4 can be regulated with exercise or carbohydrate supplementation in rat and human skeletal muscles. This study investigated the effect of different glycemic index (GI) carbohydrate supplementations after a bout of exercise on GLUT4 protein expression in human skeletal muscle. Twenty-four subjects (age 21.30±1.46 yrs, height 173.10±5.33cm, weight 70.21±7.34 kg, VO2 peak 43.65±10.58ml/kg/min) were asked to take a single bout of cycle ergometer at 75% peak oxygen consumption for 60 minutes. The subjects were randomly assigned to one of the three treatment groups after exercise: fasting, high GI carbohydrate (HGI) supplement or low GI carbohydrate (LGI) supplement. Biopsies were performed on the deep portion of the vastus lateralis muscle of all the subjects immediately after exercise and 3 hours after the carbohydrate ingestion. The protein expressions of GLUT4 were shown quantitatively with the Western Blotting technique. The blood samples were collected immediately after the exercise and every 30 minutes thereafter, up to 3 hours. The blood samples were collected for glucose and insulin analyses. Insulin AUC was significantly higher in the HGI group than in the LGI group (p<.05). The GLUT4 protein content in the HGI group significantly increased above the LGI group and the fasting trail (p<.05). The results of this study found that the HGI carbohydrate supplement after exercise can enhance GLUT4 protein expression and increase insulin secretion during the recovery period.
Glucose transporter subtype 4 (GLUT4) is an important factor for glucose uptake in human skeletal muscle. The mRNA and protein level of GLUT4 can be regulated with exercise or carbohydrate supplementation in rat and human skeletal muscles. This study investigated the effect of different glycemic index (GI) carbohydrate supplementations after a bout of exercise on GLUT4 protein expression in human skeletal muscle. Twenty-four subjects (age 21.30±1.46 yrs, height 173.10±5.33cm, weight 70.21±7.34 kg, VO2 peak 43.65±10.58ml/kg/min) were asked to take a single bout of cycle ergometer at 75% peak oxygen consumption for 60 minutes. The subjects were randomly assigned to one of the three treatment groups after exercise: fasting, high GI carbohydrate (HGI) supplement or low GI carbohydrate (LGI) supplement. Biopsies were performed on the deep portion of the vastus lateralis muscle of all the subjects immediately after exercise and 3 hours after the carbohydrate ingestion. The protein expressions of GLUT4 were shown quantitatively with the Western Blotting technique. The blood samples were collected immediately after the exercise and every 30 minutes thereafter, up to 3 hours. The blood samples were collected for glucose and insulin analyses. Insulin AUC was significantly higher in the HGI group than in the LGI group (p<.05). The GLUT4 protein content in the HGI group significantly increased above the LGI group and the fasting trail (p<.05). The results of this study found that the HGI carbohydrate supplement after exercise can enhance GLUT4 protein expression and increase insulin secretion during the recovery period.