Effects of Diets Supplemented with Branched-Chain Amino Acids on the Performance and Fatigue Mechanisms of Rats Submitted to Prolonged Physical Exercise

This study aimed to determine the effects of diets chronically supplemented with branched-chain amino acids (BCAA) on the fatigue mechanisms of trained rats. Thirty-six adult Wistar rats were trained for six weeks. The training protocol consisted of bouts of swimming exercise (one hour a day, five times a week, for six weeks). The animals received a control diet (C) (n = 12), a diet supplemented with 3.57% BCAA (S1) (n = 12), or a diet supplemented with 4.76% BCAA (S2) (n = 12). On the last day of the training protocol, half the animals in each group were sacrificed after one hour of swimming (1H), and the other half after a swimming exhaustion test (EX). Swimming time until exhaustion was increased by 37% in group S1 and reduced by 43% in group S2 compared to group C. Results indicate that the S1 diet had a beneficial effect on performance by sparing glycogen in the soleus muscle (p < 0.05) and by inducing a lower concentration of plasma ammonia, whereas the S2 diet had a negative effect on performance due to hyperammonemia (p < 0.05). The hypothalamic concentration of serotonin was not significantly different between the 1H and EX conditions. In conclusion, chronic BCAA supplementation led to increased performance in rats subjected to a swimming test to exhaustion. However, this is a dose-dependent effect, since chronic ingestion of elevated quantities of BCAA led to a reduction in performance.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Efeitos de dietas suplementadas com aminoácidos de cadeia ramificada sobre mecanismos de fadiga em ratos submetidos a exercício moderado

Os processos de fadiga durante o exercício prolongado podem envolver mecanismos relacionados ao músculo (fadiga periférica) e/ou ao sistema nervoso central (fadiga central). O desenvolvimento de estratégias nutricionais, como a suplementação com aminoácidos de cadeia ramificada (ACR), pode representar uma alternativa para melhorar o rendimento durante o exercício. Diante disso, o presente estudo avaliou os efeitos de dietas suplementadas com ACR, de forma crônica, sobre mecanismos de fadiga em ratos submetidos à natação. Foram utilizados 54 ratos Wistar (peso inicial: 240 g) divididos em grupos sedentários e treinados, que receberam dieta controle (C), suplementada com 3,57% (S1) ou 4,76% de ACR (S2) durante 6 semanas. O treinamento em natação realizado nesse período foi: 1 hora ao dia, 5 vezes por semana, com sobrecarga equivalente a 5% do peso corporal atada à cauda. No último dia do protocolo os animais treinados foram sacrificados após 1 hora de natação e após o teste de exaustão, e os sedentários foram sacrificados em repouso. Os resultados obtidos demonstraram que o tempo de natação até exaustão aumentou em 37% para o grupo S1, e diminuiu em 43% para o grupo S2, em relação ao grupo C. Observou-se que o exercício prolongado ocasionou redução da glicemia, da insulinemia e das concentrações de glicogênio hepático e muscular. Notou-se, ainda, aumento das concentrações de amônia plasmática, corticosterona sérica, lactato sangüíneo e serotonina do hipotálamo. Referente ao efeito das suplementações nos grupos submetidos ao teste de exaustão, a dieta S1 aumentou a concentração de glicogênio muscular (sóleo) e diminuiu a amônia plasmática, enquanto a S2 causou aumento da concentração da amônia plasmática. Portanto, a dieta S1 promoveu um efeito benéfico no desempenho físico, provavelmente por poupar glicogênio no músculo sóleo e pela menor concentração de amônia plasmática. Diferentemente, a dieta S2 proporcionou um efeito negativo no desempenho, possivelmente devido a hiperamonemia.The fatigue processes during prolonged exercise can envolve mechanisms related to muscle (peripheral fatigue) and/or central nervous system (central fatigue). Development of dietary manipulation represents an alternative to improve exercise performance. This study has assessed the effects of chronic diet supplementations with branched-chain amino acids (BCAA) on fatigue mechanisms in rats submitted to swim. Wistar rats (n=54), weighing 240 g, were divided in sedentary and trained groups, under control diet (C), supplemented diet with 3,57% (S1) or 4,76% (S2) of BCAA, for 6 weeks. The swimming protocol was 1 hour per day, 5 days per week, with 5% of body- weight attached to the animal tail. The last experimental day was realized killing the trained animals by two conditions: after 1 hour of swimming or after swimming until exhaustion. Sedentary groups were killed at rest. The results obtained showed the time to exhaustion 37% longer for S1 group, and 43% lower for S2 group, compared to control group. The concentrations of plasma glucose, serum insulin, muscular and hepatic glycogen was decreased by prolonged exercise. However, the concentrations of plasma ammonia, serum cortisol, blood lactate and hypothalamus serotonin was increased. The BCAA diets induced on animals submitted to exhaustion the following effects: diet S1) higher concentration of muscular glycogen (soleus) and lower concentration of plasma ammonia; diet S2) increment of plasma ammonia concentration. Thus, diet S1 promoted better performance through sparing muscular glycogen (soleus) and lower concentration of plasma ammonia. Differently, diet S2 suggest a negative effect on performance, possibly by hyperammonemia