title: Cooperative effects of soy isoflavones and carotenoids on osteoclast formation.
abstract: Osteoclasts play a major role in bone resorption. Several functional food components, such as soy isoflavones and carotenoids, are reported to inhibit osteoclast formation. However, the cooperative effect of functional foods or their constituents on bone metabolism has not been clarified. This study aimed to investigate the cooperative effect of soy isoflavones and carotenoids on osteoclast formation in vitro using cultures of RAW264 and bone marrow cells in the presence of receptor activator of nuclear factor κ-B ligand. In RAW264 cells, treatment with soy isoflavones (genistein or equol) or carotenoids (β-carotene) suppressed osteoclast formation. At 10 µM, genistein and equol inhibited RAW264 cell proliferation but did not affect cell viability. When 10 µM genistein or equol was combined with 0.1 µM β-carotene, we observed an additive suppressive effect on osteoclast differentiation. Similar results were observed with bone marrow cell cultures. We found that 10 µM of zeaxanthin or lutein suppressed osteoclast formation singly, and further enhanced the suppressive effects of daidzein or genistein when administered in combination. These results suggest that the combination of soy isoflavones and carotenoids have an enhanced suppressive effect on osteoclast formation. This knowledge might be important in planning diet for bone health.
authors.affiliation: Department of Food Function and Labeling, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Tadaishi
authors.affiliation: Department of Food Function and Labeling, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636, Japan.
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Nishide
authors.affiliation: Department of Food Function and Labeling, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tousen
authors.affiliation: Institute of Food, Nutrition and Human Health, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand.
authors.forename: Marlena C
authors.initials: MC
authors.lastname: Kruger
authors.affiliation: Department of Food Function and Labeling, National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8636, Japan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Ishimi
keywords: bone; carotenoids; osteoclast formation; soy isoflavones