Influence of Fermented Red Clover Extract on Skeletal Muscle in Early Postmenopausal Women: A Double-Blinded Cross-Over Study

To investigate effects of supplementation with a fermented red clover (RC) extract on signaling proteins related to muscle protein synthesis and breakdown at rest and in response to a resistance exercise bout. Ten postmenopausal women completed a double-blinded cross-over trial with two different intervention periods performed in random order: (A) RC extract twice daily for 14 days, and (B) placebo drink twice daily for 14 days. The intervention periods were separated by a two-week washout period. After each intervention period a muscle tissue sample was obtained before and three hours after a one-legged resistance exercise bout. Muscle strength was assessed before and after each intervention period. Protein expression of FOXO1 and FOXO3a, two key transcription factors involved in protein degradation, were significantly lower and HSP27, a protein involved in cell protection and prevention of protein aggregation was significantly higher following RC extract compared to placebo. No significant treatment × time interaction was observed for muscle protein expression in response to exercise. However, p-mTOR, p-p70S6k and HSP90 protein content were significantly increased in response to exercise in both groups. This study demonstrates that RC extract supplementation downregulates molecular markers of muscle protein degradation compared to placebo in postmenopausal women.