Study on the mechanisms responsible for improvements of glucose and amino acid metabolism by exercise

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It is well known that exercise has a beneficial effect in keeping and/or promoting health. However, the mechanisms responsible for the effects of exercise are limitedly elucidated. In this study, we examined effects of ageing and exercise training on gene expression and protein contents of the enzymes in the insulin signaling cascade. The results obtained using rats suggest that insulin resistance caused by ageing was suppressed by exercise training through sustaining the high levels of proteins of insulin receptor substrate-1 (IRS- 1) and phosphatidylinositol 3-kinase (PI3-kinase), and gene expression of IRS-1 in skeletal muscle.Glucose is a major source of energy for all of the mammalian cells. The glucose metabolism in the cells is regulated by two enzymes: glucose transporter-IV (Glut-IV) catalyzing glucose uptake into the cells and pyruvate dehydrogenase complex (PDC) which located at the position connecting between glycolysis and citric acid cycle. The Glut-IV content and PDC activities decrease in association with decreasing the insulin sensitivity. Since it has been reported that exercise training increases insulin sensitivity and promotes glucose metabolism, we examined effects of exercise training on these parameters in rat skeletal muscle. The results in the present study suggest that exercise training increases glucose metabolism by increasing Glut-IV content and PDC activity in the skeletal muscle.Branched-chain amino acid metabolism is regulated by the rate-limiting enzyme branched-chain α-keto acid dehydrogenase complex (BCKDC). We examined exercise training on activity and gene expression of hepatic BCKDC in diabetic rats, and found that exercise training suppressed the increases in activity and gene expression of hepatic BCKDC in the rats, suggesting suppression of branched-chain amino acid catabolism increased by diabetes.