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THE EFFECT OF BCAA SUPPLEMENTATION UPON THE IMMUNE RESPONSE OF TRIATHLETES. |
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Reinaldo Abunasser BASSIT Mara Assis MALVERDI |
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Bassit, R.A.2,4; Sawada, L.A.3; Bacurau, R.F.P.1,4; Navarro, F.2,4 & Costa Rosa, L.F.B.P.2,4 1Department of Physiology and Biophysics and 2Department of Histology and Embryology, Institute of Biomedical Sciences, University of Sao Paulo, Brazil. 3Department of Biodynamic of the Movement of the Human Body, School of Sport and Physical Education, University of Sao Paulo, Brazil. 4Laboratory of Human Nutrition for Athletes - CEPEUSP, University of São Paulo, Brazil Short tittle: BCAA supplementation and immune response Key words: triathlon, immune system, glutamine, immunossupression, cytokines, lymphocyte proliferation Correspondence to:
Discussion Participation in triathlon is continuously growing. This sport, which began in the mid-seventies, includes three sequentially performed endurance events: swimming, cycling and running. The distance of each segment varies substantially, so that the total time of competition ranges from 30 min to several hours (25). The physiological effects of a triathlon have been extensively studied (5, 7, 8, 12, 14, 19, 24, 26, 35, 41). It is interesting to note that the physiological and energetic demands, of such a sequence of exercise are unique and require the triathletes to develop a blend of characteristics seen in endurance swimming, cycling and running (33). As a consequence of these elevated demands triathletes presented some side-effects such as glomerular damage (41) and the presence of oxidised DNA bases in urine (12) as well as cellular dehydration and a decrease in serum amino acids, reflecting a catabolic state (19). The imbalance in plasma amino acids concentration could be related to the increased risk of upper respiratory tract infections that follows intense long-duration exercise (13, 23, 29), by inducing, in the host, a suppression of natural killer and lymphokine activated cells activity and lymphocyte proliferation (36, 37). Glutamine decrease seems to be the main factor causing immunessuppresion, since this amino acid is essential for lymphocyte and macrophage metabolism (2, 27, 30) and its concentration is reduced in the plasma of athletes after long-term, strenuous exercise (17, 28). Rhodes and colleagues (30) showed that after a long term intense exercise (a triathlon consisting of 2.5km swimming, 81km cycling and 19km running) there was a reduction in NK and LAK cell activities paralleled by a decrease in serum glutamine concentrations. In this study we have evaluated the effect of branched chain amino acid supplementation (BG) upon peripheral blood lymphocyte proliferation, serum glutamine concentration and the production of IL-1, IL-2, TNF-a and INF-g , as well as in the incidence of infections by a questionnaire. As previously reported (30) the athletes presented reduced serum glutamine concentration (22.8%) after the triathlon, what is very similar to the observed by Parry-Billings and colleagues (28) after a marathon (a reduction of 16%) and by Rhode and colleagues (30), after another triathlon - 2.5km swimming, 81km cycling and 19km running (reduction of 32%). The supplementation of the athletes with BCAA restored serum glutamine concentration to values similar to those found before the competition. In fact, it is known that supplementation with BCAA is able to increase the circulating levels of these amino acids and their metabolisation to glutamine in the skeletal muscle (21) leading to a greater muscle NH3 production (21). NH3, in such model, is derived from the transamination with 2-oxoglutarate which forms glutamate and branched-chain oxo acids, a reaction catalysed by BCAA aminotransferase. Glutamate can then be oxidatively deaminated by glutamate dehydrogenase, releasing the NH3 and reforming 2-oxoglutarate (22). The NH3 produced in such pathway, during exercise, is released in the form of glutamine (21) . This mechanism is reinforced by the fact that the rate limiting step in BCAAs catabolism involves the non-reversible decarboxylation of the BCOAs by branched-chain oxo acid dehydrogenase, which is activated during exercise (11, 16, 38) and is responsive to an increase in the intracellular concentration of BCOAs (21). It is interesting to note that in the athletes of the PG, who showed a reduction in serum glutamine concentration after the triathlon, an increased proliferative response of peripheral blood lymphocytes, harvested before and after the exercise session, cultivated without mitogens was also observed. These cells, however, showed a reduced response to ConA and LPS, mitogens for T and B cells, respectively, when compared to those obtained from BG athletes, who presented a normal serum glutamine concentration after the triathlon. An important aspect of immune response concerns the production of cytokines by immune cells. This group of intercellular signalling proteins regulates local and systemic immune and inflammatory responses, as well as other biologic processes. Their effect often overlap considerably and one cytokine may induce the secretion of others, producing a cascade of biological effects. We have evaluated the effect of BCAA supplementation upon cultivated blood mononuclear cells capacity to produce IL-1 and -2, TNF and INF. IL-1 is expressed during infections, particularly with Gram-negative bacteria, and activates B and T cells besides stimulating haemopoiesis (3). IL-1 and TNF share most of their activities, except for the toxic effect of TNF against tumour cells (9). INF is synthesised by T and NK cells in response to mitogens, antigens and IL-2 and enhances macrophage tumoricidal, anti-microbial and antigen presenting activities as well as presents anti-viral properties (34). IL-2 is produced by activated T lymphocytes and is essential for clonal T cell proliferation and for NK cytolytic activity. It also induces the production of IFN, TNF, IL-3, -4, -5 and -6 by activated lymphocytes. BCAA supplementation increased IL-1, IL-2, TNF and INF production in cells cultivated for 48h in the presence of LPS or PHA. Cells obtained from the PG showed a reduction in cytokine production after the competition, except for IL-2, whose synthesis was not changed after exercise. BCAA supplementation increased the production of all cytokines before the competition, but only that of IL-1 and IL-2 after the test (20% and 41%, respectively). The production of IFN and TNF by the BG athletes was the same before and after the triathlon. Considering the importance of these cytokines in the establishment and control of immune response, the supplementation of the athletes with BCAA seems to be important to keep this signalling and effector mechanism working properly, leading to a reduced incidence of infections in those athletes. The data show that BCAA supplementation can reverse the reduction in serum glutamine concentration observed after prolonged intense exercise such as an Olympic triathlon. This change in plasma glutamine concentration is paralleled by an increased incidence of infections that results in augmented proliferative response of lymphocytes cultivated in the absence of mitogens. The prevention of the lowering of plasma glutamine concentration allows an increased response of lymphocytes to ConA and LPS, as well as an increased production of IL-1 and 2, TNF and IFN, possibly linked to the lower incidence of infection, reported by the supplemented athletes. Acknowledgements - We gratefully acknowledge Twinlabâ for kindly provide the amino acids for this project. The work was supported by FAPESP 98/07141-7. REFERENCES
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Reinaldo Abunasser BASSIT |
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CRN - 6845 Formação Profissional
Atividades Profissionais
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Mara Assis MALVERDI |
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CRN - 6844 Formação Profissional
Atividades Profissionais Área de Educação Física
Área de Nutrição
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