Osteoprotective Effects of Boi-ogi-to a Kampo Medicine in Ovariectomized Mice

Currently available treatments for osteoporosis suppress bone resorption and formation, which can lead to complications such as atypical femoral fracture. Although the Kampo medicine Boi-ogi-to (BOT), a traditional prescription, has been used clinically to treat arthritis and obesity, no study has examined its efficacy in estrogen deficiency induced postmenopausal osteoporosis. Consequently, the present study was designed to examine whether BOT exerts beneficial effects on bone in an ovariectomized (OVX) mice model of postmenopausal osteoporosis compared with bazedoxifene (BAZ). Six-week-old female mice underwent ovariectomy, and were randomized into the sham control, OVX control, OVX + BOT (600 mg/kg/day), and OVX+BAZ (0.5 mg/kg/day) groups after 2 weeks. After 30 weeks of treatment, histomorphometric analysis of the tibia and gene expression analyses of the femur were performed, and serum biochemical markers were examined. The results suggested that treatment with BOT or BAZ increased trabecular bone volume and thickness and improved bone structural parameters of the tibia in OVX mice. OVX mice treated with BAZ resulted exhibited a significant decrease in bone resorption and bone formation. Whereas OVX mice treated with BOT exhibited inhibited bone resorption, with no marked effect on bone formation. Changes in serum biochemical markers, osteocalcin and tartrate-resistant acid phosphatase-5b provided similar evidence. Thus, the present study demonstrated that BOT suppresses bone resorption induced by estrogen deficiency and improved trabecular bone microstructure in OVX mice.