1: Life Sci. 2006 Apr 22; [Epub ahead of print] Related Articles, Links
Effect of chronic supplementation with branched-chain amino acids on the performance and hepatic and muscle glycogen content in trained rats.
de Araujo JA Jr, Falavigna G, Rogero MM, Pires IS, Pedrosa RG, Castro IA, Donato J Jr, Tirapegui J.
Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, Brazil.
The objective of this study was to evaluate the effects of a diet supplemented with branched-chain amino acids (BCAA; 3.57% and 4.76%) on the performance and glycogen metabolism of trained rats. Thirty-six adult male Wistar rats received the control diet (AIN-93M) (n=12) and two diets supplemented with BCAA (S1: AIN-93M+3.57% BCAA, n=12, and S2: AIN-93M+4.76% BCAA, n=12) for 6 weeks. The training protocol consisted of bouts of swimming exercise (60 min day(-1)) for 6 weeks at intensities close to the lactate threshold. On the last day of the experiment, all groups were trained for 1 h (1H) or were submitted to the exhaustion test (EX). The time to exhaustion did not differ between groups. The groups submitted to the exhaustion test presented a reduction in plasma glucose and an increase in plasma ammonia and blood lactate concentrations compared to the 1H condition. In the 1H condition, hepatic glycogen concentration was significantly higher in group S2 compared to the control diet and S1 groups (132% and 44%, respectively). Group S2 in the 1H condition presented a higher muscle glycogen concentration (45%) compared to the control diet group. In the EX condition, a significantly higher hepatic glycogen concentration was observed for group S2 compared to the control diet and S1 groups (262% and 222%, respectively). Chronic supplementation with BCAA promoted a higher hepatic and muscle glycogen concentration in trained animals, with this effect being dose dependent.
PMID: 16698042 [PubMed - as supplied by publisher]
J Nutr. 2006 Feb;136(2):544S-547S. Related Articles, Links
A role for branched-chain amino acids in reducing central fatigue.
Astrand Laboratory, University College of Physical Education and Sports and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. email@example.com
Several factors have been identified to cause peripheral fatigue during exercise, whereas the mechanisms behind central fatigue are less well known. Changes in the brain 5-hydroxytryptamine (5-HT) level is one factor that has been suggested to cause fatigue. The rate-limiting step in the synthesis of 5-HT is the transport of tryptophan across the blood-brain barrier. This transport is influenced by the fraction of tryptophan available for transport into the brain and the concentration of the other large neutral amino acids, including the BCAAs (leucine, isoleucine, and valine), which are transported via the same carrier system. Studies in human subjects have shown that the plasma ratio of free tryptophan (unbound to albumin)/BCAAs increases and that tryptophan is taken up by the brain during endurance exercise, suggesting that this may increase the synthesis of 5-HT in the brain. Ingestion of BCAAs increases their concentration in plasma. This may reduce the uptake of tryptophan by the brain and also 5-HT synthesis and thereby delay fatigue. Accordingly, when BCAAs were supplied to human subjects during a standardized cycle ergometer exercise their ratings of perceived exertion and mental fatigue were reduced, and, during a competitive 30-km cross-country race, their performance on different cognitive tests was improved after the race. In some situations the intake of BCAAs also improves physical performance. The results also suggest that ingestion of carbohydrates during exercise delays a possible effect of BCAAs on fatigue since the brain's uptake of tryptophan is reduced.
J Nutr. 2006 Feb;136(2):538S-543S. Related Articles, Links
Amino acid mixture improves training efficiency in athletes.
Ohtani M, Sugita M, Maruyama K.
Department of Environmental Studies, Graduate School of Frontier Sciences, the University of Tokyo, Chiba, Japan. Ohtani@k.u-tokyo.ac.jp
This review discusses some of the beneficial effects of a dietary amino acid supplement on muscle function, fatigue, and recovery in exercising athletes. The supplement, a mixture of amino acids that included the branched-chain amino acids, arginine and glutamine, was studied chronically at several daily dose levels for extended periods of time (10, 30, and 90 d). Outcome variables included physical measures of muscle strength, fatigue and damage, and blood indices of muscle damage and oxygen-carrying capacity. One beneficial effect of the amino acid supplement was a quicker recovery from the muscle fatigue that followed eccentric exercise training. A dose-response study of the amino acid mixture at 2.2, 4.4, and 6.6 g/d for 1 mo showed that at the highest dose, indices of blood oxygen-carrying capacity were increased and those of muscle damage were decreased at the end of the trial. When the amino acid mixture was given for 90 d to elite rugby players during training at a dose of 7.2 g/d, a blood-component analysis indicated improvements in the oxygen-carrying capacity of the blood. Together, the studies suggest that the amino acid supplement contributed to an improvement in training efficiency through positive effects on muscle integrity and hematopoiesis.
1: J Nutr. 2006 Feb;136(2):533S-537S. Related Articles, Links
Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise.
Norton LE, Layman DK.
Division of Nutritional Sciences, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
High-performance physical activity and postexercise recovery lead to significant changes in amino acid and protein metabolism in skeletal muscle. Central to these changes is an increase in the metabolism of the BCAA leucine. During exercise, muscle protein synthesis decreases together with a net increase in protein degradation and stimulation of BCAA oxidation. The decrease in protein synthesis is associated with inhibition of translation initiation factors 4E and 4G and ribosomal protein S6 under regulatory controls of intracellular insulin signaling and leucine concentrations. BCAA oxidation increases through activation of the branched-chain alpha-keto acid dehydrogenase (BCKDH). BCKDH activity increases with exercise, reducing plasma and intracellular leucine concentrations. After exercise, recovery of muscle protein synthesis requires dietary protein or BCAA to increase tissue levels of leucine in order to release the inhibition of the initiation factor 4 complex through activation of the protein kinase mammalian target of rapamycin (mTOR). Leucine's effect on mTOR is synergistic with insulin via the phosphoinositol 3-kinase signaling pathway. Together, insulin and leucine allow skeletal muscle to coordinate protein synthesis with physiological state and dietary intake.
1: J Nutr. 2006 Jan;136(1 Suppl):274S-6S. Related Articles, Links
Branched-chain amino acids and central fatigue.
Newsholme EA, Blomstrand E.
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. firstname.lastname@example.org
An account of the tryptophan (Trp)-5-hydroxytryptamine (5-HT)-central fatigue theory is provided and an explanation of how oral administration of BCAAs can decrease fatigue on the basis of this theory is given. The rate-limiting step in the synthesis of 5-HT is the transport of Trp across the blood-brain barrier. This transport is influenced by the fraction of Trp available for transport into the brain and the concentration of the other large neutral amino acids, including the BCAAs, which are transported via the same carrier system. During endurance exercise, there is an uptake of Trp by the brain, suggesting that this may increase the synthesis and release of 5-HT in the brain. Oral intake of BCAAs may reduce this uptake and also brain 5-HT synthesis and release, thereby delaying fatigue. Other hypotheses for the effect of BCAAs on central fatigue are included.
PMID: 16365097 [PubMed - indexed for MEDLINE]