Tart cherry supplement enhances skeletal muscle glutathione peroxidase expression and functional recovery after muscle damage

Introduction: Montmorency cherry concentrate (MCC) supplementation enhances functional recovery from exercise, potentially due to antioxidant and anti-inflammatory effects. However, to date, supporting empirical evidence for these mechanistic hypotheses is reliant on indirect blood biomarkers. This study is the first to investigate functional recovery from exercise alongside molecular changes within the exercised muscle following MCC supplementation. Methods: Ten participants completed two maximal unilateral eccentric knee extension trials following MCC or placebo supplementation for 7 days prior to and 48 hours following exercise. Knee extension maximum voluntary isometric contractions (MVC), maximal isokinetic contractions, single leg jumps, and soreness measures were assessed before, immediately, 24 and 48 h after exercise. Venous blood and vastus lateralis muscle samples were collected at each time point. Plasma concentrations of IL-6, TNF-⍺, C-reactive protein, creatine kinase, and phenolic acids were quantified. Intramuscular mRNA expression of SOD 1 and 3, GPX1, 3, 4 and 7, Catalase, and Nrf2 and relative intramuscular protein expression of SOD1, Catalase and GPX3 were quantified. Results: MCC supplementation enhanced recovery of normalized MVC 1s average compared to placebo (Post- Exercise PLA: 59.5±18.0% vs MCC: 76.5±13.9%; 24 h PLA: 69.8±15.9% vs MCC: 80.5±15.3%; supplementation effect p=0.024). MCC supplementation increased plasma hydroxybenzoic, hippuric and vanillic acid concentrations (supplementation effect p = 0.028, p = 0.002, p= 0.003); SOD3, GPX3, GPX4, GPX7 (supplement effect p < 0.05) and GPX1 (interaction effect p = 0.017) gene expression; and GPX3 protein expression (supplementation effect p = 0.004) versus placebo. There were no significant differences between conditions for other outcome measures. Conclusion: MCC supplementation conserved isometric muscle strength and upregulated antioxidant gene and protein expression in parallel with increased phenolic acid concentrations