Royal jelly affects collagen crosslinking in bone of ovariectomized rats

Royal jelly (RJ) is an essential food for queen bees, and it reportedly has estrogen-like activity. The objective of this study was to evaluate the effect of RJ intake on bone quality with a focus on the posttranslational modifications of type I collagen. RJ was fed to ovariectomized (OVX) rats for 12 weeks. RJ intake did not affect OVX-induced reduction in bone volume at the femur epiphysis; however, the reduction of collagen crosslinks (pyridinoline and deoxypyridinoline), which represent an aspect of bone quality, were significantly mitigated. In cultured MC3T3-E1osteoblasts, RJ treatment did not affect cell proliferation, cell differentiation, matrix formation, or mineralization. However, RJ treatment did stimulate expression of plods, which encode lysyl hydroxylase isoforms that control the collagen crosslinking pathway, and it also affected collagen crosslinking. These results indicate that oral intake of RJ could improve bone quality by modulating the posttranslational modification of type I collagen.