Changes in skeletal muscle proteolytic gene expression after prophylactic supplementation of EGCG and NAC and eccentric damage.
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PURPOSE: The impact of prophylactic supplementation of N-acetyl-cysteine (NAC) and epigallocatechin gallate (EGCG) on intramuscular expression of proteolytic genes after unaccustomed eccentric muscle contractions was investigated. METHODS: Thirty apparently healthy males (mean SD: 20.0 1.8 years, 175 7.1cm, 76.1 16.9 kg) ingested daily either 1,800 mg of NAC or 1,800 mg of EGCG (98% total polyphenols, 80% total catechins, and 50% EGCG), or 1,000 mg of a glucomannan placebo (PLA) in a double blind, prophylactic fashion for 14 days. Subjects then completed an unaccustomed eccentric exercise bout (100 repetitions at 30 s(-1)) using the dominant knee extensors. Skeletal muscle biopsies were collected from the vastus lateralis at baseline and both 6 and 24h after exercise. The expression of proteolytic genes [i.e., muscle ring-finger 1 (MuRF1), atrogin-1, -type 20S subunit C2 (HC2), -type 20S subunit C3 (HC3), ubiquitin protein ligase 3B (UBE3B), -calpain, and m-calpain] was quantified using real-time RT-PCR. Separate 3 3 (group time) repeated measures ANOVAs were used to analyze changes in gene expression over time between groups. RESULTS: No significant group time interactions were detected between groups for the expression of any of the atrogenes or calpains (p>0.05). Significant main effects for time identified increases in MuRF1 (6h: 5.3 10.8 fold; p=0.046), UBE3B (6h: 5.3 7.7 fold; p=0.006; 24h: 3.3 4.5 fold; p=0.005), and m-calpain expression (6h: 2.7 4.4 fold; p=0.045) in all participants following exercise. Increases approached significance in HC2 (6h: 1.9 2.4 fold; p=0.079; 24h: 1.6 1.9 fold; p=0.084) and m-calpain expression (24h: 1.8 2.3 fold; p=0.084) following exercise. CONCLUSIONS: Prophylactic supplementation of NAC and EGCG did not impact acute changes in skeletal muscle proteolytic gene expression following eccentric exercise. Eccentric muscle contractions elevated MuRF1 and UBE3B, while m-calpain and HC2 mRNA tended to increase.
