Effects of α-lipoic Acid on mtDNA Damage after Isolated Muscle Contractions

Although pharmacological antioxidants have previously been investigated for a prophylactic effect against exercise oxidative stress, it is not known if α-lipoic acid supplementation can protect against DNA damage after high-intensity isolated quadriceps exercise. This randomized controlled investigation was designed to test the hypothesis that 14 d of α-lipoic acid supplementation can attenuate exercise-induced oxidative stress. Methods: Twelve (n = 12) apparently healthy male participants (age = 28 ± 10 yr, stature = 177 ± 12 cm and body mass = 81 ± 15 kg) were randomly assigned to receive either a daily supplement of 1000mg of α-lipoic acid (2 x 500-mg tablets) for 14 d (n = 6) or receive no supplement (n = 6) in a double-blinded experimental approach. Blood and muscle biopsy tissue samples were taken at rest and after the completion of 100 isolated and continuous maximal knee extension (minimum force = 200 N, speed of contraction = 60°.s⁻¹). Results: Exercise increased mitochondrial 8-hydroxy-2-deoxyguanosine (8-OHdG) concentration in both groups (P G 0.05 vs rest) with a concomitant decrease in total antioxidant capacity (P G 0.05 vs rest). There was a marked increase in blood total antioxidant capacity after oral α-lipoic acid supplementation (P < 0.05 vs nonsupplemented), whereas DNA damage (Comet assay and 8-OHdG), lipid peroxidation, and hydrogen peroxide increased after exercise in the non-supplemented group only (P < 0.05 vs supplemented). Exercise increased protein oxidation in both groups (P < 0.05 vs rest). Conclusions: These findings suggest that short-term α-lipoic acid supplementation can selectively protect DNA (but not in muscle mitochondria) and lipids against exercise-induced oxidative stress.