Antioxidant supplementation, muscle damage, oxidative stress, and leukocyte apoptosis

PURPOSE: The purpose of this study was to investigate the effect of antioxidant supplementation on biomarkers of muscle damage, oxidative stress, and leukocyte apoptosis following repeated downhill runs. METHODS: Twenty-two moderately trained (VO2max: 45-65 mL/kg/min) males 18-35 years participated in the study. They were randomly assigned to a supplement (S) or placebo (P) group (n=11/group). Supplementation (capsules) consisted of 1000 mg vitamin C (ascorbic acid) and 400 IU vitamin E (dl-alpha-tocopherol acetate) for S or maltodextrin for P ingested daily for 2 weeks before the first (1D) and second (2D) downhill runs and for 2 additional days post-exercise. Trials were separated by 3 weeks. Each trial consisted of a 40 min downhill (-10% grade) run at a speed eliciting 65-70% VO2max. Blood samples were collected before exercise and immediately after, 24 h, and 48 h postexercise and analyzed for total leukocyte count, serum creatine kinase (CK) activity, oxygen radical absorbance capacity (ORAC), leukocyte apoptosis (apoptotic index: AI), and anti-/pro- apoptotic protein (Bcl-2 and Bax) concentration. Delayed onset of muscle soreness (DOMS) of the front thigh, shin, buttocks, back thigh, and calf was recorded at immediately after, 24, 48, and 72 h postexercise. RESULTS: Overall, DOMS of the front thigh was lower in S than P (P\u3c0.05). CK at 48 h following 1D remained elevated above pre-exercise in P but not S (P\u3c0.01). DOMS of the front thigh and shin was higher (P\u3c0.05) at 24 and 48 h than 72 h following 1D in P. Bcl-2 was lower than before exercise at 24 h following 1D in P but not S (P \u3c 0.05). CK and DOMS were attenuated (P\u3c0.01) and ORAC was higher (P\u3c0.05) following 2D. Bcl-2 was upregulated (P\u3c0.05) and leukocyte apoptosis was attenuated (P\u3c0.01) following 2D. At 24 h postexercise in S, CK was lower (P\u3c0.01) and ORAC was higher (P\u3c0.05) following 2D than 1D. At 24 h following 2D, AI of neutrophils was higher than before exercise and immediately after exercise in P not S (P\u3c0.01). CONCLUSION: Antioxidant supplementation attenuated the increase in CK activity and DOMS in the front thigh and shin after 1D, and also blunted the decrease in anti-apoptotic protein at 24 h following 1D indicating oxidative stress is involved in eccentric exercise-induced muscle damage and the early stage of leukocyte apoptosis. The repeated bout effect was evidenced in this study by the increase in ORAC prior to 2D and the attenuation in muscle damage, DOMS, and leukocyte apoptosis following 2D. Antioxidant supplementation enhanced the protective effect triggered by the first bout of eccentric exercise as indicated by the attenuation of biomarkers of muscle damage, neutrophil apoptosis and a boost in antioxidant capacity observed 24 h following 2D