Does Exercise Have an Additional Effect To Strontium Ranelate On Bone Status?

Abstract

Physical exercise is known to exert beneficial effects on bone status. Strontium Ranelate (SR) has been shown to have anti-osteoporotic properties. PURPOSE: We conducted a study testing impact activity, using strontium ranelate alone, or impact activity (E) + strontium ranelate in female rats either ovariectomized (OVX) or not (SHAM). METHOD: 96 female Wistar rats, 5 weeks old at baseline were used. Animals in the E groups were subjected to 10 impacts per day from 45 cm, 5 days a week over 8 weeks. Strontium ranelate group animals received 625 mg/kg of SR per gavage in 0.5 % carboxymethylcellulose (vehicle) daily for 8 weeks. Sham (SHAM) group animals were used as a control. Bone mineral density (BMD) and content (BMC) (whole body and left femur) were measured by DXA at weeks 0, 4 and 8. Morphological properties of trabecular and cortical bone from femur, tibia and L2 to L4 vertebrae were analyzed by μCT (Skyscan, 1072). Osteocyte apoptosis was studied by cleaved caspase-3 immunostaining and expressed as a percentage of total cells. RESULTS: μCT (Skyscan) analysis showed a deleterious effect of OVX, and a beneficial effect of Strontium Ranelate and of impact activity on Bone Volume (BV)/TV, Trabecular Number (Tb.N), Trabecular Thickness (Tb.Th), Trabecular Separation (Tb.Sp) and SMI. Strontium Ranelate and impact activity demonstrated a significant additive effect for these parameters. This was confirmed at all sites (femur, tibia and L2-L4 vertebrae). Cortical thickness was increased in Strontium ranelate groups; cortical porosity (Ct.Po) and Pore Number (Po.N) were improved at femur and tibia in the strontium ranelate groups, and significantly more in the impact activity + strontium ranelate groups. OVX groups had a significant excess of osteocyte apoptosis versus SHAM. Impact activity did not significantly reduce osteocyte apoptosis in SHAM and OVX groups while strontium ranelate significantly reduced osteocyte apoptosis in all groups. There was no significantly cumulative effect of impact activity when combined with strontium ranelate on this parameter. CONCLUSION: This data constitutes the first description of an additive effect of strontium ranelate + impact activity on bone status, and of a beneficial effect of Strontium ranelate on osteocyte apoptosis.