The anti-osteoporotic effect of Yijung-tang in an ovariectomized rat model mediated by inhibition of osteoclast differentiation

Ethnopharmacological relevance: Yijung-tang (YJ), a traditional Asian medicine, is used to treat various diseases. However, its anti-osteoporotic effect and mechanism of action remain unclear. The aim of the present study was to evaluate the anti-osteoporotic effect of YJ in ovariectomized (OVX) rats. Materials and methods: Sprague-Dawley rats were divided into five groups as follows: sham-operated, ovariectomized (OVX), OVX rats treated with 100 g/kg/day 17-estradiol, and OVX rats treated with 0.3 and 1.0 g/kg/day YJ for 12 weeks. Trabecular bone mineral density (BMD) and bone microarchitecture were evaluated by microcomputed tomography. The effects of YJ on osteoblast and osteoclast formation were also investigated in an in vitro model using primary murine bone marrow-derived macrophages and murine calvarial preosteoblasts. mRNA expression of osteoclast differentiation-related genes was measured by real-time quantitative reverse transcription-polymerase chain reaction. Activation of the mitogen-activated protein kinases and nuclear factor-kappa B (NF-kappa B) were determined by Western blot. Results: The decrease of BMD and destruction of bone microarchitecture were significantly reduced in the OVX-induced osteoporosis rat model after 12 weeks of YJ treatment. The anti-osteoporotic effect of YJ on bone loss was due to inhibition of osteoclast differentiation through down-regulation of the NF-kappa B pathway. In addition, YJ suppressed the induction of nuclear factor of activated T-cells, cytoplasmic 1 and c-Fos following receptor activator of nuclear factor kappa-B ligand stimulation. Conclusions: These results suggest that YJ possess potent anti-osteoporotic activity in OVX rats and may be a useful remedy for the treatment of postmenopausal osteoporosis. (C) 2012 Elsevier Ireland Ltd. All rights reserved.