Effect of daidzein together with raloxifene in osteoblast-like cells

Objectives: Osteoporosis is caused by decrease in bone mass resulting from estrogen deficiency. Hormone replacement therapy has been widely used for preventing and treating osteoporosis. However, the side effect including breast cancer is known to be accompanied. Daidzein (Dz) is a phytoestrogen derived from soy isoflavone, and raloxifene (Ral), which is a selective estrogen receptor modulator (SERM), is now accepted as anti-resorptive agents. We hypothesized that taking SERM with dietary intake of isoflavones could have a mutually potentiating effect in postmenopausal women with osteoporosis. The purpose of this study is to investigate the effect of Dz together with Ral, which act as a different antiresorptive agents, in osteoblasts. Methods: Osteoblastic KUSA-1 cells were grown in culture medium with Dz and/or Ral. The differentiation and mineralization of osteoblasts were determined using alkaline phosphatase (ALP) activity and von kossa staining. Osteocalcin production in culture supernatant was evaluated by ELISA. Results: The ALP activity was expressed significantly in the presence of Dz (10^-6M) and Ral (10^-7M) at 14 d. Osteocalcin production was slightly increased with both agents at 14d and 21d. At 21 days von kossa staining was increased in the presense of Dz with or without Ral. Conclusion: These results suggested that the effect of Dz was stable in osteoblasts in the presence of Ral.