AJP - Endocrinology and Metabolism, Vol 267, Issue 6 E1010-E1022, Copyright © 1994 by American Physiological Society

ARTICLES

Branched-chain amino acids augment ammonia metabolism while attenuating protein breakdown during exercise

D. A. MacLean, T. E. Graham and B. Saltin
School of Human Biology, University of Guelph, Ontario, Canada.

In this study, five men exercised the knee extensor muscles of one leg for 60 min (71 +/- 2% maximal work capacity) with and without (control) an oral supplement (77 mg/kg) of branched-chain amino acids (BCAA). BCAA supplementation resulted in a doubling (P < 0.05) of the arterial BCAA levels before exercise (339 +/- 15 vs. 822 +/- 86 microM). During the 60 min of exercise, the total release of BCAA was 68 +/- 93 vs. 816 +/- 198 mumol/kg (P < 0.05) for the BCAA and control trials, respectively. The intramuscular BCAA concentrations were higher (P < 0.05) for the BCAA trial and remained higher (P < 0.05) throughout exercise. In both trials, substantial quantities of NH3 were released, and when NH3 production equivalent to IMP accumulation was subtracted the net NH3 production was 1,112 +/- 279 and 1,670 +/- 245 mumol/kg (P < 0.05) for the control and BCAA trials, respectively. In contrast, the release of the essential amino acids (EAA) was much lower for the BCAA than the control trial (P < 0.05). When the BCAA were subtracted from the EAA (EAA-BCAA), the total release of EAA minus BCAA was lower (P < 0.05) for the BCAA (531 +/- 70 mumol/kg) than the control (924 +/- 148 mumol/kg) trial. These data suggest that BCAA supplementation results in significantly greater muscle NH3 production during exercise. Furthermore, the increased intramuscular and arterial BCAA levels before and during exercise result in a suppression of endogenous muscle protein breakdown during exercise.

This article has been cited by other articles:

				V. Kumar, P. Atherton, K. Smith, and M. J. Rennie Human muscle protein synthesis and breakdown during and after exercise J Appl Physiol, June 1, 2009; 106(6): 2026 - 2039. [Abstract] [Full Text] [PDF]

				X. Guan, B. J. Bequette, G. Calder, P. K. Ku, K. N. Ames, and N. L. Trottier Amino Acid Availability Affects Amino Acid Flux and Protein Metabolism in the Porcine Mammary Gland J. Nutr., June 1, 2002; 132(6): 1224 - 1234. [Abstract] [Full Text] [PDF]

				E. Blomstrand and B. Saltin BCAA intake affects protein metabolism in muscle after but not during exercise in humans Am J Physiol Endocrinol Metab, August 1, 2001; 281(2): E365 - E374. [Abstract] [Full Text] [PDF]

				M. J. Gibala, M. Lozej, M. A. Tarnopolsky, C. McLean, and T. E. Graham Low glycogen and branched-chain amino acid ingestion do not impair anaplerosis during exercise in humans J Appl Physiol, November 1, 1999; 87(5): 1662 - 1667. [Abstract] [Full Text] [PDF]

				W. J. Kraemer, J. S. Volek, J. A. Bush, M. Putukian, and W. J. Sebastianelli Hormonal responses to consecutive days of heavy-resistance exercise with or without nutritional supplementation J Appl Physiol, October 1, 1998; 85(4): 1544 - 1555. [Abstract] [Full Text] [PDF]

				P. Galassetti, F. K. Gibbons, K. S. Hamilton, D. B. Lacy, A. D. Cherrington, and D. H. Wasserman Enhanced muscle glucose uptake facilitates nitrogen efflux from exercised muscle J Appl Physiol, June 1, 1998; 84(6): 1952 - 1959. [Abstract] [Full Text] [PDF]