Effect Of Cyclic Mechanic Stretch Combined With Vitamin D On The Proliferation And Oxidative Phosphorylation In C₂C₁₂ Myoblasts

Objective:Vitamin D,as a kind of steroid derivative,is mainly used to regulate the balance of calcium and phosphorus in the body and affect the metabolism of bone.Recent studies have found that vitamin D is also involved in skeletal muscle metabolism and plays an important role in muscle growth and repair.It has not been reported that mechanical stretch combined with vitamin D supplementation can improve mybolast cell proliferation and metabolism in vitro cultured.In view of this,the purpose of our study was to explore the effects of vitamin D intervention on myocyte proliferation and metabolism levels in muscle cells stimulated by mechanical stretch,and to explore possible mechanisms.Methods:C₂C₁₂ myoblast cell lines were divided into four groups: quiet control group,vitamin D group,mechanical stretch group,mechanical stretch and vitamin D group.Vitamin D group and mechanical stretch combined with vitamin D group used vitamin D concentration of 50nmol/L and 10% fetal bovine serum cell culture medium.The quiet control group and the mechanical stretch group used 10% fetal bovine serum culture medium.By using the Flexcell cell stretch system,the C₂C₁₂ cells were subjected to 10% tensile strength,and the frequency was 0.5hz,which lasted for 3 consecutive days and lasted for 3 consecutive days.The quiet control group and the vitamin D group did not intervene.Tension on the third day after the intervention to collect cells,to test the cell proliferation,and cell oxygen consumption,using Western Blot method to detect rp S6,AKT-m TOR signaling protein expression and citrate synthase protein expression.Results: 1.The effect of cyclic mechanic stretch combined with vitamin D on the proliferation of C₂C₁₂ cells.Cell proliferation test results show that compared with the quiet control group,mechanical stretch group had significantly increased（P < 0.05）,and compared with the three other groups,mechanical stretch combined with vitamin D group was very significant increased（P < 0.01）.2.The effect of cyclic mechanic stretch combined with vitamin D on signal protein expression in C₂C₁₂ cells.The results of Western Blotting showed that the ratio of P-AKT/AKT,P-rp S6 /rp S6 was significantly increased,compared with quite control group,the mechanical stretch combined with vitamin D group was significantly increased（P<0.05）,while there was no significant change in P-m TOR /m TOR ratio（P>0.05）.3.Cyclic mechanic stretch combined with vitamin D on oxidative phosphorylation of C₂C₁₂ cells.（1）The results of oxygen consumption showed,compared with the three other groups,mechanical stretch combined with vitamin D group was significantly increased（P < 0.05）;（2）Western Blot measured citrate synthase（CS）,there was no significant difference in four groups.（P>0.05）Conclusions:1.Cyclic mechanical stretch and vitamin D can promote the proliferation of C₂C₁₂ myoblast cell,the possible mechanisms is mechanical stretch combined with vitamin D increased the expression of AKT、rp S6 signal protein,promoted protein synthesis.2.Cyclic mechanical stretch and vitamin D can enhance the oxygen consumption of skeletal muscle cells,which can enhance the level of oxidative phosphorylation of cells.