Effects of prophylactic supplementation of N-acetyl-cysteine and epigallocatechin gallate on markers of oxidative stress, inflammation and apoptosis after eccentric contraction-induced injury in untrained males.
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Kerksick, Chad M.
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The purpose of this study was the examine the effects of 14 days of prophylactic supplementation of N-acetyl-cysteine (NAC) and epigallocatechin gallate (EGCG) on changes in peak torque production, muscle soreness, muscle damage, oxidative stress, inflammation and apoptosis after a single damaging bout of eccentric muscle contractions. Thirty healthy, recreationally active males (20.0±1.8 years, 160±7.1cm, 167.4±37.3 kg) were randomized in a double-blind fashion to ingest daily either 1800 mg of NAC, 1,200 mg of EGCG, or 1,500 mg of glucomannan placebo (PLC) in a prophylactic fashion for 14 days. After supplementation, subjects completed one eccentric exercise bout (100 repetitions @ 30o•s-1) of the dominant knee extensors. Participants completed strength and soreness assessments while providing fasting blood samples and vastus lateralis muscle biopsies (no 72 h biopsy) before and after supplementation, as well as 6h, 24h, 48h and 72h post-exercise to assess changes in muscle damage, oxidative stress, inflammation, and apoptosis. Separate 3 x 6 repeated measures ANOVA with a probability level of 0.05 was used for the statistical analysis with LSD post-hoc comparisons for all significant interactions. Significant reductions in peak torque as well as increases in soreness and creatine kinase at 6 h post-ex were found in all groups. No changes (p > 0.05) were observed for the indicators of oxidative stress, serum superoxide dismutase, serum 8-isoprostane and muscle glutathione reductase, as well as the indicators of stress and inflammation, serum cortisol and tumor necrosis factor-alpha. For the apoptosis markers, significant increases (p < 0.05) in muscle levels of bax, bcl-2, caspase-3 enzyme activity and decreases in total DNA content were observed in all groups with no significant differences among groups, whereas no changes (p>0.05) were reported for cytochrome C. At all time points, PLC demonstrated greater caspase-3 enzyme activity and lower levels of total DNA content in comparison to either supplementation group. An eccentric bout of muscle contractions appears to significantly increases muscle damage and apoptosis with no changes in oxidative stress and inflammation. More research is needed to determine the impact supplementation with EGCG and NAC may have on changes related to apoptosis and eccentric exercise.