Ginsenosides Rg3 attenuates glucocorticoid-induced osteoporosis through regulating BMP-2/BMPR1A/Runx2 signaling pathway

• Bone loss in the proximal femurs induced by dexamethasone is attenuated by ginsenosides Rg3.
• Ginsenosides Rg3 improved bone metabolism in dexamethasone-induced osteoporosis.
• BMP-2 signaling pathway is involved in the osteoporosis prevention effects of ginsenosides Rg3.

Glucocorticoid-induced osteoporosis (GIOP) is the primary cause of secondary osteoporosis and the existing therapeutic strategies are limited. The aim of this study is to evaluate the effects of ginsenosides (GS) Rg3 on dexamethasone (DEX)-induced osteoporosis in vivo and in vitro. GIOP rat was established by DEX injection for 5 weeks and treated by GS Rg3 10 or 20 mg/kg. Body weight and bone mineral density (BMD) of rats were measured at the beginning and the end of the experiment. Histological changes of femurs were observed using HE staining. The in vitro model was established on primary osteoblasts induced by DEX. CCK-8 assay was used to test the cell viability. Bone metabolism markers in serum or primary osteoblasts were detected using biochemical kits. Real time PCR and western blot were used to measure nuclear factor-kappa B ligand (RANKL), osteoprotegerin (OPG), bone morphogenic protein-2 (BMP-2), BMP receptor 1A (BMPR1A) and Runx2 expression. The results demonstrated that GS Rg3 prevented DEX-induced body weight and BMD reduction, enhanced secretion of bone formation markers and decreased bone resorption markers. In addition, GS Rg3 was found to prevent the suppression of BMP-2/BMPR1A/Runx2 signals induced by DEX both in GIOP rats and primary osteoblasts. Inhibition of BMP-2 by noggin completely blocked the bone-alkaline phosphatase-secretion-promoted effect of GS Rg3 in vitro. These data suggest that GS Rg3 attenuates GIOP through regulating BMP-2 signaling pathway. This study provides a potential drug candidate for GIOP therapy.