l-Cysteine supplementation protects the erythrocyte glucose-6-phosphate dehydrogenase activity from reduction induced by forced training

Background: l-Cysteine (l-cys) is implicated in the reduction of free radical production. Aim: To investigate the effect of training and l-cys supplementation on the erythrocyte glucose-6-phosphate dehydrogenase (G6PD) activity. Methods: Blood was obtained from 10 basketball players pre-game (group A), post-game (group B) and after 1 week on l-cys (0.5 g/24 h orally) supplementation pre- (group C) and post-training (group D). Total antioxidant status (TAS) and G6PD activity were evaluated with commercial kits. Results: TAS increased in the groups with l-cys addition (group C and group D). Post-exercise, TAS and G6PD activity were remarkably higher (1.48 ± 0.12 mmol/L, 8.9 ± 1.7 U/g Hb, respectively) in group D than those in group B (0.92 ± 0.10 mmol/L, 4.8 ± 1.6 U/g Hb, p < 0.01). G6PD activity positively correlated with TAS (r = 0.70, p < 0.001 pre- and r = 0.61, p < 0.001 post-training) in all the studied groups. Conclusions: G6PD activity is lowered by training probably due to free radical action. l-cys supplementation may protect G6PD activity from reduction by increasing total antioxidant capacity and glutathione production. G6PD activity should be evaluated in the blood of athletes of Mediterranean origin and female G6PD-deficient heterozygotes.