Research On Exercise Regulating ERK1/2 And MTOR Pathway Via AR In Skeletal Muscle

Objective:By blocking AR, to investigate the effects of exercise on ERK1/2 and mTOR pathway in skeletal muscle, and by blocking ERK1/2 and mTOR pathway, to discuss the relationship between ERK1/2 pathway and mTOR pathway under the condition of exercise.Methods:In the first and second experiment,7w-old male SD rats were randomly divided into sedentary control group, AR inhibitor group, exercise group, exercise+AR inhibitor group and sham group. AR inhibitor group were implanted subcutaneously with a flutamide release pellet, and exercise group exercised 10d on treadmill (20 m/min,10% slope,60 min/d). Extensor Digitorum Longus (EDL) were isolated at 6 h after final exercise, and its wet weight, cross section area, MHC content and the mRNA, phosphoiylation and protein expression of AR, mTOR pathway and ERK1/2 pathway. In the third experiment,7w-old male SD rats were randomly divided into sedentary control group, DMSO group, mTOR inhibitor group, ERK1/2 inhibitor group, mTOR+ERKl/2 inhibitor group, exercise group, exercise+mTOR inhibitor group, exercise+ERK1/2 inhibitor group, exercise+mTOR+ERK1/2 inhibitor group. mTOR inhibitor group were injected intraperitoneally 1.5mg/kg/d of Rapamycin at 2h before the beginning of exercise, and ERK1/2 inhibitor group were injected intraperitoneally 5mg/kg/d of PD98059 at 30min before the beginning of exercise. EDL were isolated at 6 h after final exercise, and its wet weight, MHC content and the phosphorylation and protein expression of AR, mTOR pathway and ERK1/2 pathway.Results: ① Compared with sedentary control group, the wet weight and cross section area of EDL, MHC content, AR mRNA, p-ARSer210, the mRNA expression of mTOR, P70S6K and 4EBP1, the phosphorylation of mTOR and 4EBP1 in AR inhibitor group were significantly decreased (p<0.01-0.05), and the mRNA expression and phosphorylation of MEK1/2、ERK1/2、P90RSK had no significant change. MHC content, AR mRNA, p-ARSer210, the mRNA expression and phosphorylation of MEK1/2、ERK1/2、P90RSK, and the mRNA, protein and phosphorylated expression mTOR、P70S6K、4EBP1 in exercise group was significantly increased comparing with sedentary control group (p<0.01-0.05). The wet weight and cross section area of EDL, MHC content, AR mRNA, p-ARSer210, the mRNA expression and phosphorylation of MEK1/2、ERK1/2、P90RSK, and the mRNA, protein and phosphorylated expression mTOR、P70.4EBP1 in exercise+AR inhibitor group were significantly decreased comparing with exercise group (p<0.01-0.05). ② Compared with sedentary control group, the phosphorylation of MEK1/2, ERK1/2, mTOR, P70S6K and 4EBP1 in ERK1/2 inhibitor group were significantly decreased (p<0.01-0.05). In mTOR inhibitor group, the phosphorylation of mTOR, P70S6K and 4EBP1 were significantly decreased (p<0.01-0.05), while the phosphorylated expression of MEK1/2 were significantly increased (p<0.01). The phosphorylation of MEK1/2, ERK1/2 and P90RSK and the protein and phosphorylated expression of mTOR, P70s6K and 4EBP1 in mTOR+ERK1/2 inhibitor group were significantly decreased (p<0.01-0.05). Compared with exercise group, the phosphorylation of ERKl/2 and P90RSK and the protein and phosphorylated expression of mTOR, P70S6K and 4EBP1 in exercise+ERK1/2 inhibitor group were significantly decreased (p<0.01-0.05). In exercise+mTOR inhibitor group, the protein and phosphorylated expression of mTOR, P70S6K and 4EBP1 were significantly decreased (p<0.01-0.05), while the phosphorylation of ERK1/2, ERK1/2 and P90RSK had no significant change. The phosphorylation of ERK1/2, ERK1/2 and P90RSKand the protein and phosphorylated expression of mTOR, P70S6K and 4EBP1 were significantly decreased in exercise+mTOR+ERK1/2 inhibitor group (p<0.01).Conclusions:① Exercise can regulate ERK1/2 and mTOR pathway via AR to promote protein synthesis.② Our experiment confirmed that under the condition of exercise, ERK1/2 pathway may be located in the upstream of the mTOR pathway, and had up-regulated effects to mTOR pathway.