Effect of glutamine supplementation on exercise-induced changes in lymphocyte function

The purpose of this study was toinvestigate the possible role of glutamine in exercise-inducedimpairment of lymphocyte function. Ten male athletesparticipated in a randomized, placebo-controlled, double-blindcrossover study. Each athlete performed bicycle exercise for 2 hat 75% of maximum O₂ consumption on 2 separate days.Glutamine or placebo supplements were given orally during and up to2 h postexercise. The trial induced postexercise neutrocytosisthat lasted at least 2 h. The total lymphocyte count increased bythe end of exercise due to increase of bothCD3⁺TCR⁺ andCD3⁺TCR⁺ T cells as well asCD3CD16⁺CD56⁺ naturalkiller (NK) cells. Concentrations of CD8⁺ andCD4⁺ T cells lacking CD28 and CD95 on their surfaceincreased more than those of cells expressing these receptors. Withinthe CD4⁺ cells, only CD45RA memory cells, butnot CD45RA⁺ naive cells, increased in response to exercise.Most lymphocyte subpopulations decreased 2 h after exercise.Glutamine supplementation abolished the postexercise decline in plasmaglutamine concentration but had no effect on lymphocyte trafficking, NKand lymphokine-activated killer cell activities, T cell proliferation,catecholamines, growth hormone, insulin, or glucose. Neutrocytosis wasless pronounced in the glutamine-supplemented group, but it is unlikelythat this finding is of any clinical significance. This study does notsupport the idea that glutamine plays a mechanistic role inexercise-induced immune changes.