ISSN Mini-Symposium on Branched Chain Amino Acids and Athletic Performance

  1. Nutraceutical effects of branched-chain amino acids (BCAA) on skeletal muscle: Specific features of the regulation of BCAA catabolism during exercise. Yoshiharu Shimomura, Ph.D., Professor, Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya, Japan
    Abstract: Branched-chain amino acids (leucine, isoleucine, and valine) are indispensable amino acids for humans. These amino acids are essential to protein synthesis and (especially leucine) stimulate protein synthesis. It has been shown that the BCAA catabolism is enhanced by exercise, suggesting the BCAA requirement is increased by exercise. I will show specific features of the regulation of BCAA catabolism and a piece of evidence for the nutraceutical effects of BCAA on skeletal muscle.
  2. Leucine as a Critical Regulator of Skeletal Muscle Metabolism Regulation of Muscle Protein Synthesis after Exercise. Donald K. Layman, Ph.D., Professor, Department of Food Science & Nutrition, University of Illinois, Urbana-Champaign, IL.
    Abstract: High performance physical activity and post-exercise recovery require significant changes in amino acid and protein metabolism in skeletal muscle. Central to these changes is increased metabolism of the branched-chain amino acid (BCAA) leucine. During exercise, muscle protein synthesis decreases while net protein degradation and BCAA oxidation increases. The decrease in protein synthesis is associated with inhibition of a translational initiation complex (eIF4), which is controlled by intracellular insulin signaling and leucine concentrations. BCAA oxidation increases through activation of the branched-chain keto acid dehydrogenase (BCKAD). Activity and capacity of the BCKAD are determined by exercise training and dietary protein intake. In total, these changes limit muscle use of energy for synthesis of new proteins and enhance release of alanine in support of hepatic gluconeogenesis and glycemic control. After exercise, recovery of muscle protein synthesis requires dietary protein or BCAA to increase tissue levels of leucine, which releases the inhibition of the eIF4 complex through activation of the protein kinase mTOR. Leucine’s effect on mTOR is synergistic with insulin via the PI3-kinase signaling pathway. Together, insulin and leucine allow skeletal muscle to coordinate metabolism with physiological state and dietary intake.
  3. The interaction of exercise and amino acids in regulating muscle protein synthesis. Robert R. Wolfe, Ph.D., Professor, Department of Surgery, University of Texas Medical Branch, and Metabolism Unit, Shriners Hospital for Children, Galveston TX.
    Abstract: We have used stable isotopically-labeled amino acid tracers, arterial-venous catheteri¬zat¬ion, muscle biopsies and a three-pool model to quantify muscle protein synthesis and break¬down in normal human volunteers before and after exercise. Whereas resistance exercise alone reduced the negative protein balance across the leg, it remained negative (i.e., net muscle protein break¬down) in the fasted state. Ingestion of amino acids, either before or after exercise, stimulated mus¬cle protein synthesis and resulted in a positive muscle protein balance. Ingestion of protein had the same effect, but an optimal blend of amino acids was more potent on a gram/gram basis. Prior exercise amplifies the anabolic response to the ingestion of amino acids.
  4. Nutritional effects of ingesting amino acids for athletes. Masaru Ohtani, Ph.D., Professor, Department of Environmental Studies, Sports Sciences for Health & Activity, Tokyo University, Kashiwa-City, Chiba, Japan
    Abstract: We examined the nutritional effects of ingesting defined amino acid mixtures in athletes by analyzing changes in a variety of hematological parameters. Results will be discussed for two groups, long-distance runners and elite rugby players regarding both short-term, dose-response studies and chronic studies.
  5. Branched-chain amino acids and central fatigue. Eva Blomstrand Ph.D., Associate Professor, University College of Physical Education and Sports and Department of Physiology and Pharmacology, Karolinska Institute, Box 5626, 114 86 Stockholm, Sweden
    Abstract: Increased synthesis of the neurotransmitter serotonin (5-HT) during physical exercise may be one factor causing central fatigue. The rate limiting step in the synthesis of 5-HT is the transport of tryptophan over the blood-brain barrier. During exercise the entry of tryptophan into the brain is favored by an increase in the level of free tryptophan (unbound to albumin) and the decrease in BCAA due to an uptake by muscle, i.e. the ratio free tryptophan/BCAA increases. Intake of BCAA prevents this increase and the effect of BCAA on mental fatigue, cognitive performance and physical performance will be discussed.
  6. Learned Preference for a Mixture of Branched-chain L-Amino Acids (BCAA) and Homeostatic Control of the Brain Serotonin Release in Exercising Rats Kunio Torii, PhD, Manager, Physiology and Nutrition Group, Institute of Life Sciences, Ajinomoto Co., Kawasaki, Japan
    Abstract: We studied a proposed mechanism by which BCAA ingestion might counteract central fatigue, namely that it prevents the exercise-induced increase in brain 5-HT release. Unrestrained rats bearing a microdialysis probe in their hypothalamus had free access to running wheels and a BCAA-based or a control solution. Rats ingesting the BCAA-containing solution had an increased ratio of BCAAs/tryptophan and lower 5-HT release in the hypothalamus than rats consuming the control solution. These findings thus support the notion that BCAA ingestion counteracts exercise-induced increases in brain 5-HT release, and thus may moderate central fatigue.