| Summary: | 碩士 === 中臺科技大學 === 醫學生物科技研究所 === 97 === Most athletes used ergogenic supplements including protein, creatine and caffeine to enhance performance. According to human studies, performance was enhanced through the increased level of skeletal muscle glycogen. (-)-Hydroxycitric acid (HCA) is an herbal supplement which is a potent competitive inhibitor of ATP-citrate lyase. HCA has been used as anti-obesity treatment via decreased fat resynthesis and increased fat oxidation. However, little is known regarding whether coingestion of HCA with carbohydrate meal following exercise causes the increased level of skeletal muscle glycogen via increasing in fat oxidative capacity and sparing in carbohydrate oxidation in human skeletal muscle. The purpose of this study was to investigate coingestion of HCA with carbohydrate meal following exercise, and to verify the gene expression of glucose transporter type 4 (GLUT4) and fatty acid translocase/cluster of differentiation 36 (FAT/CD36). Eight healthy active male volunteers (22.00 ± 0.27 years of age) were the subjects for two experiments carried out at an interval of 7 days, designed in a two-way crossover manner. Subjects were subjected to a 60-min cycling exercise at 70% VO2peak. After exercise, subjects consumed either a high carbohydrate meal (2g/kg body weight) (control group) or coingestion of HCA (500 mg/day) with carbohydrate supplementation (HCA group). Samples were taken for analyses during the 3-h recovery period: muscle samples taken at 0 and 3 h, postprandial blood samples every 30-min. The analyses performed included 1) concentrations of GLUT4
and FAT/CD36 mRNA and protein and glycogen in the muscle samples, 2) concentrations of glucose, insulin and free fatty acid in the blood samples. The results indicated that, in the 3-h recovery period, the HCA group exhibited a significantly lower insulin secretion level (p＜0.05), but no differences were observed for the concentrations of glucose (p＞0.05) as compared with those in the control group. In addition, it was found that 1) the level of glycogen synthesis in HCA group was 22.1% higher than that in the control group (p＜0.05), 2) FAT/CD36 mRNA in the HCA group increased by 57.7%, but no differences were found for the level of FAT/CD36 protein, 3) the level of GLUT4 mRNA decreased significantly in HCA and control groups (decreased by 21.8% and 31.6%, respectively), and 4) the GLUT4 protein decreased by 21.7％ in the HCA group, but not in the control group. These results suggest that coingestion of HCA with post-exercise carbohydrate supplementation enhances fatty acid oxidation, thus reduces carbohydrate catabolism, which in turn favors glycogen re-synthesis. In conclusion, coingestion of HCA with carbohydrate supplementation during post-exercise recovery can be an effective way to enhance muscle glycogen re-synthesis.
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