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Supplement: 3rd Amino Acid Workshop

Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise¹

Yoshiharu Shimomura^*,2, Taro Murakami^*, Naoya Nakai, Masaru Nagasaki^* and Robert A. Harris^**

^* Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan; Department of Biochemistry, Mie University School of Medicine, Tsu, Mie 514-8507, Japan; and ^** Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202-5122, USA

² To whom correspondence should be addressed. E-mail: shimomura.yoshiharu{at}nitech.ac.jp.

Branched-chain amino acids (BCAAs) are essential amino acids that can be oxidized in skeletal muscle. It is known that BCAA oxidation is promoted by exercise. The mechanism responsible for this phenomenon is attributed to activation of the branched-chain -keto acid dehydrogenase (BCKDH) complex, which catalyzes the second-step reaction of the BCAA catabolic pathway and is the rate-limiting enzyme in the pathway. This enzyme complex is regulated by a phosphorylation-dephosphorylation cycle. The BCKDH kinase is responsible for inactivation of the complex by phosphorylation, and the activity of the kinase is inversely correlated with the activity state of the BCKDH complex, which suggests that the kinase is the primary regulator of the complex. We found recently that administration of ligands for peroxisome proliferator-activated receptor- (PPAR) in rats caused activation of the hepatic BCKDH complex in association with a decrease in the kinase activity, which suggests that promotion of fatty acid oxidation upregulates the BCAA catabolism. Long-chain fatty acids are ligands for PPAR, and the fatty acid oxidation is promoted by several physiological conditions including exercise. These findings suggest that fatty acids may be one of the regulators of BCAA catabolism and that the BCAA requirement is increased by exercise. Furthermore, BCAA supplementation before and after exercise has beneficial effects for decreasing exercise-induced muscle damage and promoting muscle-protein synthesis; this suggests the possibility that BCAAs are a useful supplement in relation to exercise and sports.

KEY WORDS: • exercise • branched-chain amino acids • branched-chain -keto acid dehydrogenase complex • peroxisome proliferator-activated receptor- • rat

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