Acute glutamine ingestion modulates lymphocytic responses to exhaustive exercise in the heat

The purpose of this study was to determine if acute intake of glutamine modulates homeostatic, hematologic, immune, and inflammatory responses to exhaustive exercise in the heat. Thirteen healthy, untrained young men participated in this randomized, double-blind, placebo-controlled, crossover study. They served as their own control and completed 2 trials of treadmill exercise at 40% maximal oxygen uptake to exhaustion in a hot environment (temperature, 38.0 ± 1.0 °C; relative humidity, 60.0% ± 5.0%; oxygen, 20.8%) following placebo (PLA) and glutamine (GLN) consumption. Heart rate, gastrointestinal temperature, forehead temperature, the rating of perceived exertion, and body weight were measured. Blood samples were collected before and after exercise. After exhaustive exercise in the heat (PLA vs. GLN: 42.0 ± 9.5 vs. 39.6 ± 7.8 min, p > 0.05), significant changes in homeostatic, hematologic, and immune parameters (elevated natural killer (NK) cells and neutrophils, and reduced CD4+/CD8+ ratio and CD19+ lymphocytes) were found in the control group owing to the time effect (p < 0.05). Moreover, a condition × time interaction effect was observed for the absolute count of CD3+ (F = 4.26, p < 0.05) and CD3+CD8+ T lymphocytes (F = 4.27, p < 0.05), which were elevated following acute glutamine intervention. While a potential interaction effect was also observed for the absolute count of CD3+CD4+ T lymphocytes (F = 3.21, p = 0.08), no condition or interaction effects were found for any other outcome measures. The results of this study suggest that acute glutamine ingestion evokes CD3+ and CD3+CD8+ T lymphocytosis but does not modulate neutrophil and NK cell leukocytosis and immune disturbances after exhaustive exercise in the heat.