Protective effects of Dipsacus asper polysaccharide on osteoporosis in vivo by regulating RANKL/RANK/OPG/VEGF and PI3K/Akt/eNOS pathway

A homogenous polysaccharide (DAP), with a molecular weight of 2.61 × 104 Da, was isolated from the roots of Dipsacus asper Wall. Gas chromatography (GC) indicated that DAP was composed of galactose and mannose with a molar ratio of 1:1. The purpose of this study was to evaluate the effect of DAP on the progress of bone loss in the ovariectomized (OVX) rat model of osteoporosis. Administration of DAP (50 and 200 mg/kg/body wt. day) for 12 weeks significantly prevented OVX-induced bone loss, biomechanical reduction, the body weight gain, the loss of the uterus weight, as well as increased U-Ca/Cr, U-P/Cr, ALP, TRAP, OC and DPD/Cr levels in rats, which was further supported by the histopathological examinations. Furthermore, we found that the mechanism by which DAP elicited anti-osteoporotic effects was mediated by up-regulation of VEGF and OPG, but down-regulation of RANK and RANKL in both protein and mRNA expression in OVX rats, as well as the activation of PI3K/Akt/eNOS signaling pathway, indicating that DAP can be clinically used as a potential alternative medicine for the prevention and treatment of postmenopausal osteoporosis.