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 immunosuppression, because 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). Rohde and colleagues (30) showed that after long-term intense exercise (a triathlon consisting of 2.5 km swimming, 81 km cycling, and 19 km 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 BCAA supplementation (BG) upon peripheral blood lymphocyte proliferation, serum glutamine concentration, and the production of IL-1, IL-2, TNF-α, and INF-γ, as well as by a questionnaire, in the incidence of infections.
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 with those obtained from BG athletes, who presented a normal serum glutamine concentration after the triathlon.
BCAA supplementation increased IL-1, IL-2, TNF and INF production in cells cultivated for 48 h 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 signaling and effector mechanism working properly, leading to a reduced incidence of infections in those athletes.
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