Basic and Translational Research Center for Hard Tissue Disease, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8588, Japan.
Int J Mol Sci. 2020 Oct 12;21(20):7513. doi: 10.3390/ijms21207513.
Osteocalcin (Ocn), which is specifically produced by osteoblasts, and is the most abundant non-collagenous protein in bone, was demonstrated to inhibit bone formation and function as a hormone, which regulates glucose metabolism in the pancreas, testosterone synthesis in the testis, and muscle mass, based on the phenotype of Ocn mice by Karsenty's group. Recently, Ocn mice were newly generated by two groups independently. Bone strength is determined by bone quantity and quality. The new Ocn mice revealed that Ocn is not involved in the regulation of bone formation and bone quantity, but that Ocn regulates bone quality by aligning biological apatite (BAp) parallel to the collagen fibrils. Moreover, glucose metabolism, testosterone synthesis and spermatogenesis, and muscle mass were normal in the new Ocn mice. Thus, the function of Ocn is the adjustment of growth orientation of BAp parallel to the collagen fibrils, which is important for bone strength to the loading direction of the long bone. However, Ocn does not play a role as a hormone in the pancreas, testis, and muscle. Clinically, serum Ocn is a marker for bone formation, and exercise increases bone formation and improves glucose metabolism, making a connection between Ocn and glucose metabolism.
骨钙素（Ocn）是成骨细胞特异性产生的，是骨骼中最丰富的非胶原蛋白，Karsenty 小组通过 Ocn 小鼠的表型证实，其作为一种激素，可调节胰腺中的葡萄糖代谢、睾丸中的睾酮合成和肌肉量，进而影响骨形成和功能。最近，两个独立的研究小组新生成了 Ocn 小鼠。骨强度取决于骨量和骨质量。新的 Ocn 小鼠表明，Ocn 不参与骨形成和骨量的调节，但通过使生物磷灰石（BAp）与胶原纤维平行排列，调节骨质量。此外，新的 Ocn 小鼠的葡萄糖代谢、睾酮合成和精子发生以及肌肉量均正常。因此，Ocn 的功能是调整 BAp 平行于胶原纤维的生长方向，这对长骨的加载方向的骨强度很重要。然而，Ocn 在胰腺、睾丸和肌肉中并不作为激素发挥作用。临床上，血清 Ocn 是骨形成的标志物，运动增加骨形成并改善葡萄糖代谢，将 Ocn 与葡萄糖代谢联系起来。
