The Effect Of EPA And DHA On Muscle Protein Degradation Of C2C12 Myotubes After Lipopolysaccharide Challenge

As a major metabolic center,skeletal muscle is a major reserve of protein and provides energy for a variety of organs,such as heart,liver and brain.The balance between protein synthesis and degradation governs the muscle mass and function,and its regulation mechanism is very complex.It has been found that the immune stress-induced inflammatory response can lead to protein breakdown,but the regulatory mechanism is unclear.Thus,this study was designed to investigate the effects of the inflammatory induced by lipopolysaccharide(LPS)on the protein degradation in C2C12 myotubes.Meanwhile,Eicosapentaenoic acid(EPA)and Docosahexaenoic acid(DHA)belong to n-3 polyunsaturated fatty acids(PUFA)have been found to inhibit inflammation.Therefore,in this study,we also investigate the potential role of EPA and DHA in the skeletal muscle protetin breakdown.In order to establish an inflammatory cell mode,the C2C12 myotubes were treated with graded concentrations of LPS(10,100 and 1000 ng/m L),and then the m RNA expression of TNF-α and IL-6 were determined by RT-PCR method.Then the C2C12 myotubes were treated with 1000 ng/m L LPS for 0 min,30 min,1 h,3 h,6 h,12 h and 24 h,the m RNA expression of MAFbx and Mu RF1 were also determined by RT-PCR.The results showed that the expressions of Mu RF1,IL-1βand TLR4 were significantly up-regulated at 12 h and 24 h after LPS treatment(P<0.05).And the activation of Akt/Foxo,m TOR and p38 MAPK signaling pathway was detected by western blot at 12 h after LPS treatment.Data revealed that after LPS treatment 12 h the phosphorylation of Akt and Foxo1 in C2C12 myotubes was significantly suppressed(P<0.05).Finally,the effect of EPA and DHA on protein breakdown by inflammation was verified.At the same time the activation of NF-κB signaling pathway was detected by immunofluorescence technique.EPA and DHA decreased m RNA abundance of TNF-α,IL-1β and IL-6(P<0.05)in C2C12 myotubes.In addition,EPA and DHA significantly inhibited the expression of NFκB in the nucleus.However,EPA and DHA showed no down-regulated the m RNA expression of Mu RF1 after LPS treatment.Then the activation of Akt was detected by western blot,the data revealed that after EPA and DHA treatment the phosphorylation of Akt in C2C12 myotubes was no significant difference compared with the LPS treatment.Muscle atrophy is defined as a decrease in muscle mass and it occurs when protein degradation exceeds protein synthesis.Potential triggers of muscle wasting are long-term malnutrition,severe burns,aging as well as various serious chronic diseases.So the muscle wasting cand lead to poor quality of life and significantly increase the risk of dying.In order to provide preventive measures and theoty for alleviating muscle protein degradation,this study was conducted to reveal the regulatory mechanism of inflammation on muscle protein degradation...