Stimulatory effect of daidzein in osteoblastic MC3T3-E1 cells

Daidzein is a natural isoflavone found in Leguminosae. The effect of daidzein on osteoblastic MC3T3-E1 cells was investigated. Cells were cultured in a serum-free medium for 48 hr in the presence of daidzein (10(-7)-10(-5) M). Daidzein (10(-6) and 10(-5) M) caused a significant elevation of protein content, alkaline phosphatase activity, and DNA content in cells; those increases were about 1.4-, 1.5-, and 2.0-fold, respectively. The ability of daidzein (10(-5) M) to increase protein content, alkaline phosphatase activity, and DNA content in cells was prevented completely by the presence of cycloheximide (10(-6) M), an inhibitor of protein synthesis, indicating that the isoflavone has a stimulatory effect on cellular protein synthesis. The anabolic effect of daidzein (10(-6) or 10(-5) M) in cells was not distinguishable from that of genistein (10(-6) or 10(-5) M). Meanwhile, cell protein showed an additive effect of 17beta-estradiol and daidzein, but their effects on alkaline phosphatase were not additive. Moreover, the effect of daidzein (10(-5) M) in elevating cellular protein content and alkaline phosphatase activity was inhibited completely by the presence of tamoxifen (10(-6) M), suggesting that the effect of the isoflavone is mediated partly through estrogen action. This study demonstrates that daidzein has an anabolic effect in osteoblastic MC3T3-E1 cells.