Abstract
This study aimed to investigate the role and underlying molecular mechanism of quercetin in regulating skeletal muscle fiber type transition. We found that dietary quercetin supplementation in mice significantly increased oxidative fiber-related gene expression, slow-twitch fiber percentage and succinic dehydrogenase (SDH) activity. By contrast, quercetin decreased lactate dehydrogenase (LDH) activity, fast MyHC protein expression, fast-twitch fiber percentage, and MyHC IIb mRNA expression. Furthermore, quercetin significantly increased serum adiponectin (AdipoQ) concentration, and the expression levels of AdipoQ and AdipoR1. However, inhibition of adiponectin signaling by AdipoR1 siRNA significantly attenuated the effects of quercetin on muscle fiber type-related gene expression, the percentages of slow MyHC-positive and fast MyHC-positive fibers, and metabolic enzyme activity in C2C12 myotubes. Together, our data indicated that quercetin could promote skeletal fiber switching from glycolytic type II to oxidative type I through AdipoQ signaling.