Ferulic acid regulates muscle fiber type formation through the Sirt1/AMPK signaling pathway

Ferulic acid (FA) is a polyphenolic compound of plant cell walls. Several recent studies demonstrated that polyphenolic compounds could regulate muscle fiber type formation. In this study, we investigated the effect of FA on muscle fiber type formation and also explored its molecular mechanism in mouse C2C12 myotubes. Real-time quantitative PCR showed that FA significantly increased the mRNA abundances of myosin heavy chain (MyHC) I, MyHC IIa, sirtuin1 (Sirt1), peroxisome proliferator-activated receptor gamma coactivator-1-alpha (PGC-1 alpha) and myocyte enhancer factor 2C (MEF2C), but decreased the mRNA abundance of MyHC IIb. FA increased succinate dehydrogenase (SDH) activity and decreased lactate dehydrogenase (LDH) activity. Western blot analysis showed that FA significantly increased the protein level of slow-MyHC, but significantly decreased the protein level of fast-MyHC, which were attenuated by AMP-activated protein kinase (AMPK) inhibitor Compound C, AMPKa2 siRNA or Sirt1 inhibitor EX527. We also showed that EX527 attenuated FA-induced increase in the phosphorylation levels of AMPK and liver kinase B1 (LKB1), indicating that AMPK serves as a downstream target of Sirt1. Our present study provides the first in vitro evidence that FA regulates muscle fiber type formation via the Sirt1/AMPK signal pathway.