Effects of swimming on bone loss and mechanisms in ovariectomized osteoporotic rats

Objectives To investigate the effects of swimming on bone loss and the OPG/RANKL/RANK pathway in ovariectomized (OVX) osteoporotic rats. Methods Twenty female SD rats were randomly divided into a sham-operated group, a ovariectomized osteoporosis group, a short-duration exercise group, and a long-duration exercise group. Bone volume fraction (BV/TV), trabecular thickness (Tb.Th), bone mineral density (BMD), trabecular separation (Tb.Sp), and trabecular number (Tb.N) of bone tissue were measured by Micro-CT. The expression of human C-terminal peptide collagen type I (CTX-Ⅰ), tartrate-resistant acid phosphatase 5b (TRAP-5b), bone-specific alkaline phosphatase (BALP) and serum bone glycoprotein (BGP) were measured by ELISA. The mRNA and protein expression of OPG, RANKL, and RANK in bone tissue were detected by qRT-PCR and Western bolt, respectively. Results After swimming treatment, compared with the ovariectomized osteoporosis group, BV/TV, BMD, Tb.Th, and Tb.N increased, while Tb.Sp decreased; CTX-Ⅰ, TRAP-5b, BGP, and BALP levels decreased. OPG mRNA and protein expression increased, while RANKL and RANK decreased. Conclusions Swimming training alleviated ovariectomy-induced bone loss and was accompanied by a shift of the OPG/RANKL/RANK axis toward an anti-resorptive profile, suggesting that modulation of this pathway may contribute to the bone-protective effects of swimming. Further functional studies are warranted to test causality.