The Effects Of Exercise On The Bone Mineral Density And The Osteoimmunological Factors Of The Mice

Background:Skeleton is considered as a support and protection organ of the body. And the health level of it is an important guarantee for the daily life.Skeleton always keep a variational state,which can make bone renewal and reconstruction.Its internal cause is the interaction between osteoclast and osteoblast,which make bone updating;and its external reason is the combined action of many factors,such as exercise and life style and so on. Additionally,immune system is always involved in the regulation of bone metabolism as well:the immune factors can regulate RANKL/RANK signal pathway to affect bone metabolism directly and indirectly.Besides, the factors in bone metabolism can affect immune system as well, such as OPG.Therefore,the interaction between skeleton system and immune system is also called "Osteoimmunological system’It is known that exercise play an important role in the development of bone.And regular exercise can not only enhance the bone mineral density to improve the peak bone mass, but also prevent osteoporosis and reduce the fracture rate.Especially,exercise has an obvious effect during the growth period.However,whether exercise can influence bone metabolism through the way that exercise can regulate osteoimmunological system or not.At present,there is a few research on exercise and osteoimmunological system at home and abroad,so it is still unknown.Objective:In this study,we have trained the 4-week-old mice by treadmil,downhill treadmill and swim for 8weeks.And after the intervention,we will start from the lymphocytes,osteoimmunological factors to explore the relationship among exercise,osteoimmunological factors and RANKL/TRAF 6 signal pathway,and aimed to provided a new thought for the mechanism research that exercise promote bone health.Methods:We have divided the C57BL/6 mouse into treadmill group(T),downhill treadmill group(DT), swim group (S) and control group (C) at random. There are 6 in each group. And the mouse have been fed water and food by randomly, and the light cycle is 12 hours as well. The animal have been trained at 6 p.m. T group and DT group run 40 min at the speed of 0.8km/h, the DT group has a-9°grape, and the T group is 0°; the S group always swim 40 min,and will been drived by the brush to guarantee the mouse keep swimming all the time,and after the exercise it will been dried by air blower, then put back to the cage. After 8-week exercise intervention, the mice will been broken the neck to death, and separate the limbs to detecting the indicators.The dual energy X-ray absorptiometry was used to test the BMD;the qRT-PCR was used to test the mRNA expression of RANKL,TRAF-6 and IL-l,and so on;and the paraffin section immunohistochemical was used to test the number of CD4+T cells.Results:(1)The results of BMD testing by dual energy X-ray absorptiometry show that:after 8 weeks exercise intervention,the BMD have been increased,and compared with C group,S and T group have significant difference(P<0.05),and DT group have extremely significant difference (P<0.01);among the S. T and DT group, there exist no significant difference.(2) The results of RANKL and TRAF 6 detection by qRT-PCR indicated that: compared with C group,the expression of RANKL has no obvious change in S,T and DT group,and compared with S group,T group has a significant down-regulation(P<0.05); and compared with C group the expression of TRAF 6 showed a significant decrease in T group(P<0.05).The results of osteoimmunological factors indicated that compared with C group,IL-6 has a significant decrease in S and DTgroup(P<0.05),and has no obvious change in T group,and compared with S group,T group has a significant down-regulation(P<0.05). Compared with C group,TNF-a has a significant decrease in S,T,DT group(P<0.01),and among S,T,DT group,there has no obvious change.Compared with C group,IL-Iβ has a significant up regulation in S and T group(P<0.05), Compared with S and T group,DT group has a significant decrease of IL-Iβ(P<0.05).Compared with C group,IFN-y has an extremely significant increase in S,T and DT group(P<0.01),and compared with S group,IFN-y has an extremely significant decrease(P<0.01),and in T and DT group,it has no difference.(3) The result of T lymphocyte in bone marrow detecting by paraffin immunohistochemical showed that:compared with C group,T cell number is inclined to increase in S group^ T group and DT group;while there exist no significant among the exercise groups.Conclusions:(1) Exercise intervention has a positive effect on BMD increasing.(2) Exercise can up-regulate the number of T lymphocytes,which can enhance the function of immune system.(3) Exercise can down regulate the mRNA expression of TNF-a,and up regulate the expression of IFN-y mRNA.,and swim and treadmill can decrease IL-6,these results can decrease the expression of RANKL,TRAF 6,which can inhibit the bone resorption.