Effects And Mechanism Of ?-lipoic Acid On C2C12 Cell Protein Turnover

Skeletal muscle protein turnover is regulated by endocrine hormones, nutrients, and inflammation. ?-Lipoic acid(ALA) plays an important role in energy homeostasis. Therefore, the aim of this study was to investigate the effects of ALA on protein synthesis in skeletal muscles and revealed the underlying mechanism.In order to reseach the effect of ALA on skeletal muscle protein synthesis, this experiment got clue from the previous studies. Protein synthesis in C2C12 myotubes was measured by using the total protein/genomic DNA ratio and the SUn SET method; genes expression level related to muscle protein synthesis and inflammation in C2C12 myotubes was detected by using fluorescence quantitative PCR and Western Blot; the expression levels of MHC?b was detected by using immunocytochemistry in C2C12 myotubes. In vivo, Kunming mice(3 weeks old) with similar average body weight(20 g) were randomly divided into two groups. Alpha-lipoic acid(50 mg/kg) was intraperitoneally administered for 3 h, to research the effect of ALA on skeletal muscle protein synthesis. As a result:(1) ALA(25 ?M) significantly increased the protein synthesis and phosphorylation of Akt, m TOR, and S6 in C2C12 myotubes with attenuated phosphorylation of AMPK, Ikk?/?, and e IF2?(P<0.05).(2) 25 ?M ALA significantly increased the phosphorylation of Fox O1, Akt, m TOR, S6, and MHC?expression and decreased the phosphorylation of e IF2? and AMPK in mice gastrocnemius(P<0.05), but 4E-BP1 was not altered in the ALA-treated mice gastrocnemius(P>0.05).In order to reseach the regulation mechanism of ALA on skeletal muscle protein synthesis, in this study we explored the mechanism from in vitro. Protein synthesis in C2C12 myotubes was measured by using the total protein/genomic DNA ratio and the SUn SET method; genes expression level related to muscle protein synthesis and inflammation in C2C12 myotubes was detected by using fluorescence quantitative PCR and Western Blot; protein binding mutually was detected using co-immunoprecipitation method. As a result:(1) Both the PI3K(LY294002) and m TOR(Rapamycin) inhibitors abolished the effects of ALA on protein synthesis in C2C12 myotubes(P<0.05). However, AICAR(AMPK agonist) failed to block the activation of m TOR and S6 by ALA(P>0.05).(2) ALA increased TLR2 and My D88 m RNA expression in C2C12 myotubes(P<0.05). TLR2 knockdown by si RNA almost eliminated the effects of ALA on protein synthesis and the Akt/m TOR pathway in C2C12 myotubes(P<0.05). Immunoprecipitation data showed that ALA enhanced the p85 subunit of PI3 K binding to My D88(P<0.05).These evidence indicate that ALA induces protein synthesis in C2C12 myotubes. The possible mechanism may be realized by activating TLR2 to promote the combination of My D88 and PI3 K, and enhance the Akt/m TOR signaling pathway conduction, ultimately promote protein synthesis.