Impact Of The Downhill-Run During Growing Period On The Ovariectomized Mice’ Bone Density And Osteoclast Differentiation

ObjectiveWe explore the effects of down-hill running during the growing period on the bone density and bone metabolism, and the changes after menopause. So we can provide the scientific basis in cellular and molecular level for sporting preventing osteoporosis.MethodWe divided randomly the4-week female C57BL/6mice into5groups:control group(n=16), down-hill group(n=16), control+sham group(n=16), control+ovx group(n=16), down-hill+ovx(n=16). The bone denisty, blood biochemical parameters, osteoclast factor expression and osteoclast differentiation of the control and down-hill groups are measured after8weeks. Then we operate the left mice on the ovarium or the fat around the ovarium. The bone density, blood biochemical parameters, osteoclast factor expression and osteoclast differentiation of the left groups are measured after another6-week.ResultsAfter8-week down-hill running:The down-hill group had a higher BMD than the control group. The serum calcium level of the down-hill group was significantly lower than the control group, but the serum ALP level was significantly higher than the control group. There was no significant difference in serum phosphorus between the groups. The serum TRAP of the down-hill group was significantly lower than the control group.The down-hill group had a higher relative expression of OPG mRNA than the control group, but a lower of RANK, RNAKL and M-CSF. The speed and amount of OC differentiation of the down-hill group was significantly higher than the control group.Six weeks after the surgery:The downhill+ovx and sham groups had significantly higher BMD than the control ovx group, but there was no significant difference between the downhill+ovx group and the sham group. The serum calcium levels of three groups had no significant difference.The serum phosphorus of sham and downhill+ovx groups were significantly higher than the control ovx group, and the sham was higher than the downhill+ovx group. The serum ALP level of the sham group was significantly higher than the two ovx groups. The serum TRAP of the control ovx group was higher than the sham and downhill+ovx groups. The OPG mRNA relative expression level of the sham group was significantly higher than the two ovx groups, and the downhill+ovx group was significantly higher than the control ovx group. The RANK, RANKL and M-CSF mRNA expressions of the control ovx group were significantly higher than the downhill+ovx group and the control sham group. The sham group had a significantly higher RANK and M-CSF mRNA expression than the downhill+ovx group. There was no significant difference between the sham group and the downhill+ovx group in RANKL mRNA expression. The sham group had a significantly lower speed and amount in OC differentiation speed than the two ovx groups, and the downhill+ovx group was lower than the control ovx group.Conclusions1. The down-hill running during the growing period can effectively increase the BMD and the PBM, and can slow down the loss of the bone mass after ovariectomy.2. The down-hill running during the growing period can increase the activity of the ALP. increase the use of serum calcium. It can also restrain the activity of OC after ovariectomy, and reduce the release of phosphorus.3. The down-hill running during the growing period can reduce the speed and amount of the OC differentiation, and the effect could last to the ovariectomy period.4. The down-hill running during the growing period can enhance the activity of the OC, increase the relative expression of OPG mRNA. It could also effectively inhibit OB cells’ differentiation, and reduce the relative expressions of RANK. RANKL and M-CSF factors. The similar effects can continue to ovariectomy.