8,8″-Biapigeninyl stimulates osteoblast functions and inhibits osteoclast and adipocyte functions: Osteoprotective action of 8,8″-biapigeninyl in ovariectomized mice

8,8″-Biapigeninyl (BA), a condensation product of two apigenin molecules, is found abundantly in the nuts of Cupressus sempervirens. We investigated the effects of BA on murine bone cells in vitro and in ovariectomized (OVx) mice. BA at 10−10 M and 10−8 M, inhibited osteoclastogenesis of bone marrow cells (BMCs) and displayed concentration dependence. BA at 10−8 M and 10−6 M inhibited differentiation of 3T3-L1 and BMCs to mature adipocytes. BA (10−10 M) stimulated osteoblast proliferation, differentiation and mineralization. In stimulating osteoblast function, BA was found to be 104-fold more potent than apigenin. The effect of BA in osteoblasts appeared to be mediated via estrogen receptors (ER) as antiestrogen, ICI-182780 abolished BA-stimulated osteoblast differentiation. In OVx mice BA treatment (at 1.0-, 5.0- and 10.0 mg kg−1 day−1 doses) given orally for 30 days dose-dependently inhibited mRNA levels of osteoclastic genes including tartrate-resistant acid phosphatase, receptor activator of nuclear factor (RANK), tumor necrosis factor alpha, interleukin-6 and the ratio of RANK ligand/osteoprotegerin ratio in bones compared with OVx mice treated with vehicle. In addition, BA treatment to OVx mice dose-dependently stimulated production of osteoprogenitor cells in the bone marrow and increased mRNA levels of osteogenic genes core binding factor alpha-1, type I collagen and bone morphogenic protein-2 in bones compared with OVx + vehicle group. Microcomputed tomography revealed that BA treatment to OVx mice improved parameters of trabecular and cortical architecture. BA exhibited no uterine estrogenicity. From these data, we conclude that BA exerts osteoprotective effect in OVx mice by multiple beneficial effects on bone cells.