ginsenoside-rg3 and Osteoporosis

Ginsenoside Rg3, a ginsenoside isolated from Panax ginseng, can regulate autophagy via AMP-activated protein kinase/mammalian target of rapamycin (AMPK/mTOR) signaling pathway. AMPK/mTOR signaling and autophagy have been reported to be involved in osteogenesis. Here, the effect of Rg3 on ovariectomy (OVX)-induced osteoporosis is explored. In vivo, rats were treated with 20 mg/kg Rg3 after OVX and the body weight (BW) was monitored. Bone mineral density (BMD), hematoxylin-eosin staining of femur tissues, osteogenesis, autophagy, and AMPK/mTOR signaling were analyzed. In vitro, MC3T3-E1 cells were treated with 0, 1, 5, 10, 20, and 100 μmol/L Rg3. 10 and 20 μmol/L Rg3, which had no significant effect on cell viability and significantly affected AMPK/mTOR signaling, were chosen for further analysis. Then osteogenic differentiation was induced with Rg3 or/and AMPK inhibitor (Compound C). AMPK/mTOR signaling, autophagy, osteogenic differentiation, and mineralization by Alizarin Red staining were analyzed. The expression or activity of AMPK/mTOR signaling-related proteins, autophagy markers, and osteogenesis markers was measured by western blotting or commercial kits, and cell viability by cell counting kit-8 assay kits. Rg3 significantly alleviated OVX-induced BW increases, BMD declines and histological changes of femur tissues, promoted osteogenesis, autophagy, and AMPK signaling, but inhibited mTOR signaling in vivo. Moreover, Rg3 significantly enhanced AMPK signaling, autophagy, osteogenic differentiation, and mineralization, but suppressed mTOR signaling in vitro. However, Compound C significantly reversed Rg3-induced alterations in vitro, indicating that Rg3 regulated autophagy, osteogenic differentiation, and mineralization via AMPK/mTOR signaling. Hence, it was speculated that Rg3 might attenuate OVX-induced osteoporosis via AMPK/mTOR signaling pathway.

Topics: AMP-Activated Protein Kinases; Animals; Bone Density Conservation Agents; Cell Line; Cell Survival; Female; Femur; Ginsenosides; Mice; Osteogenesis; Osteoporosis; Ovariectomy; Rats, Sprague-Dawley; Signal Transduction; TOR Serine-Threonine Kinases

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.

Topics: Animals; Anti-Inflammatory Agents; Bone Density Conservation Agents; Bone Morphogenetic Protein 2; Bone Morphogenetic Protein Receptors, Type I; Cell Survival; Cells, Cultured; Core Binding Factor Alpha 1 Subunit; Dexamethasone; Female; Femur; Ginsenosides; Osteoblasts; Osteoporosis; Rats, Sprague-Dawley; Signal Transduction