Vitamin D Supplementation Enhances Overload-induced Skeletal Muscle Hypertrophy In Aged Rats And Its Possible Mechanism

Objective With aging, muscle atrophy and muscle strength decline become an important factor affecting the quality of elderly`s life. A number of studies reported that muscle loss and vitamin D deficiency during aging process was positively correlated. so whether vitamin D supplements can delay aging or improve muscle loss ? Our aim was to explore the influence of vitamin D on process of skeletal muscle hypertrophy in ageing rats and its mechanisms.Methods Animal experiment:20 male aging rats(24 months),Cut off left leg`s distal gastrocnemius tendons(ovld side),the other side of the sham surgery(sham side).After a week recovery,the rats were randomly divided into control group and experimental group.Experimental group supplement 1000 iu/kg of vitamin D by fill the stomach, the control supplement with equal amount of soybean oil.One week after the intervention,Take abdominal aortic blood under aseptic conditions. Weigh soleus and plantaris. Stored in low temperature refrigerator. Detection of serum 25(OH) D levels and the content of skeletal muscle system of VDR by enzyme-linked immune. Detect the expression of mTOR, rp S6 protein and phosphorylation level by Western blotting.Cell experiment : C2C12 myoblasts at 37℃in a 5%CO2-humidified atmosphere were grown in proliferation medium( 90%DMEM/10%FBS/1% double resistant).After 3days,Differentiation Medium(98%DMEM/2%HS/1%double resistant) induced to differentiate. After 7 days, use of mechanical force and 100 nm vitamin D intervention for 3 days.Finally cracking cell extraction of total protein,- 80 ℃ refrigerator frozen under test.Western blotting technique to detect pi3 k, and AKt, mTOR, p70s6 k, rp S6,ERK1/2, e EF2, TNF- a protein expression and phosphorylation level.Results Animal experiment :(1) The mass of overload side plantaris significantly increased(p < 0.05) to control side(sham).(2)Enzyme-linked immune shows Vitamin D improve the rat serum 25 OH D level(p < 0.05).(3) In vitamin D supplement group the ovld side cell`s VDR is significantly higher than sham side(p < 0.05), but in placebo group no significant difference, so vitamin D supplement increase the expression of VDR in ovld side.(4) The Western blotting show Ovld model promoted the ratio of p-mTOR/mTOR and p- rp S6 / rp S6 increases, but only in the vitamin D supplement group had significant difference(p < 0.05). Compared with placebo group vitamin D significantly promoted ovld side ratio of p- mTOR/mTOR and p- rp S6 / rp S6 increases,while had no significant effect of sham.Cell experiment:(1) C2C12 cells after horse serum starvation differentiation processing antioxidant capacity decreased significantly(p < 0.05), the cells appeared aging characteristics.(2) In cell experiment, vitamin D supplementation group compared with control group of TNF- a protein expression level decreased obviously.(3) The result of Cells experiment show that Compared with the control force and vitamin D supplement C2C12 cells under enhanced the expression of PI3 K, AKt, mTOR, p70s6 k, rps6, e EF2,ERK1/2protein phosphorylation levels increased significantly.Conclusion Vitamin D promotes the elderly overload induced skeletal muscle hypertrophy. Possible mechanisms is that vitamin D improved the levels of inflammatory factors of aging muscle cells, as well as the promotion of VDR expression in skeletal muscle of aged rats and the expression of protein synthesis related signal proteins.