Effects of Aleurone Layer Extract From Black Rice (Oryza sativa L.) on Bone Mineral Density and Bone-Related Biomarkers of Ovariectomized Rats (FS14-05-19)

OBJECTIVES: Black rice contains functional compounds, including anthocyanins. In a previous study, black rice increased bone mineral density and strength in ovariectomized rats, although its biological effects on bone-related markers have not been evaluated. The aleurone layer of black rice (BRA) contains most of anthocyanins of black rice. This study examined the effects of BRA extract on bone mineral density and bone-related markers of ovariectomized rats. METHODS: We compared the anthocyanin amount between BRA and whole grain of black rice and evaluated whether BRA extract can effectively improve bone health in ovariectomized rats at 30 mg/kg body weight (BRA30) and 90 mg/kg body weight (BRA90). These amounts are approximately one seventh and one half of the level (200 mg/kg body weight) used in the previous experiments. We compared its effects on bone-related biomarkers with those of isoflavones, which have been used to improve bone health in postmenopausal women. RESULTS: The cyanidin 3-glucoside and peonidin-3-glucoside contents in BRA were 7.18 mg/g and 1.79 mg/g, respectively, which are 5.5-fold and 4.2-fold higher than those in the whole grain of black rice. Supplementation with BRA extract significantly decreased body weight compared with the control group of ovariectomized rats not treated with BRA extract. Mineral density of tibia was significantly higher in the BRA90 group than in the control group. The breaking force of tibia and femur and the concentrations of serum and bone calcium were higher in BRA30 and BRA90 than in the control. However, urinary pyridinoline level, serum alkaline phosphatase activity, and parathyroid hormone concentration decreased in the BRA groups compared to the control group. CONCLUSIONS: The results suggest that BRA has more anthocyanin than whole grain black rice and can improve bone health by modulating bone metabolism and reducing postmenopausal osteoporosis. Furthermore, the BRA extract showed similar or even higher effect on bone-related biomarkers than isoflavones and hence can be used as a good food source to manage bone health of most postmenopausal women. FUNDING SOURCES: PJ01327901, National Institute of Agricultural Sciences.