Regulation of branched-chain α-keto acid dehydrogenase complex in rat liver and skeletal muscle by exercise and nutrition

Summary

Branched-chain α-keto acid dehydrogenase complex catalyzes oxidative decarboxylation of branched-chain α-keto acids. This reaction is the rate-limiting step in the catabolism of branched-chain amino acids. The enzyme complex is subject to covalent modification; a phosphorylation / dephosphorylation cycle regulates the enzyme activity. It has been reported that dietary protein has a great effect on the activity state of the enzyme complex in rat liver. We describe here effects of exercise and high-fat diet intake on the activity state of the hepatic enzyme complex. The activity state of the enzyme complex in rat skeletal muscle is very low under rested conditions and was significantly elevated by a bout of exercise or muscle contractions elicited by electrical stimulation. Inhibition of branched-chain α-keto acid dehydrogenase kinase by branched-chain α-keto acids, which are increased in the muscle cell by exercise, is suggested to be the mechanism responsible for the enzyme activation induced by exercise. Physical training enhanced activation of the enzyme complex in skeletal muscle by starvation and leucine administration, suggesting that the kinase is sensitized by training. Only long-term training increased the amount of the enzyme complex in the muscle, which was associated with mitochondrial biogenesis.