Glutamine supplementation affects Th1 and Th2 cell populations in endurance horses

Abstract

This study was set out to test the effect of glutamine supplementation on Th1 and Th2 cell populations in endurance horses. The sample was comprised 33 horses competing in four FEI races and successfully completing the final vet check. Horses competed in different distance categories, as follows: 80 km (13 horses, 6 supplemented and 3 controls), 120 km (14 horses; 9 supplemented and 5 controls) and 160 km (6 horses; 3 supplemented and 7 controls). Supplementation consisted of 60 mg/kg bodyweight of oral L-glutamine given for 30 days prior to and 15 days after the race. Blood samples were collected into vacuum tubes with and without EDTA at the following time points: short before race start time, prior to tack fitting (T0); right after and within 3 h of the final vet check (T1 and T2 respectively). Further blood samples were collected at the farm of origin 3, 7 and 14 days after the race (T3, T4 and T5 respectively). Glutamine supplementation affected T-lymphocyte population balance, as shown by increased CD4+/CD8+ ratio, and increased Th1 and Th2 cytokine production. Glutamine also modulated post-exercise cortisol increased in supplemented horses in this sample. These findings suggest glutamine supplementation attenuates exercise-induced immunosuppression.