Abstract

Osteoclasts are responsible for bone metabolic diseases including osteoporosis, rheumatoid arthritis, multiple myeloma and peritonitis. Recently, the anti-osteoporotic activities of natural product extracts have become the subject of research interest. Rice bran (RB) extracts exhibits anti-inflammatory activity and ameliorates anti-oxidative stress. However, the effects of RB extracts on osteoclastogenesis-related diseases such as osteoporosis have not been investigated. Here, we investigated the effects of RB extracts and of its fractions on RANKL-induced osteoclast differentiation. Interestingly, the butanol extracts of RB (RB-BuOH) dose-dependently inhibited osteoclast differentiation by down-regulating the RANKL-induced activations of mitogen-activated protein (MAP) kinases. Moreover, the mRNA expression of osteoclast-mediating molecules such as c-Fos, NFATc1, DC-STAMP and cathepsin K were dose-dependently attenuated by RB-BuOH during osteoclast differentiation. Furthermore, RB-BuOH depressed the protein levels of NFATc1 and its promoter activity. The findings of this study show that RB-BuOH and its components might prevent osteoclast-related bone loss.

Key words: Rice bran, osteoclast differentiation, NFATc1, mitogen-activated protein (MAP) kinase.