ビタミンＤと骨・ミネラル代謝

Update on recent progress in vitamin D research. Vitamin D and bone, mineral metabolism.

　ビタミンＤはカルシウムやリンなどのミネラルの生体内動態に影響し，さらに骨の細胞機能を変化させながら，骨・ミネラル代謝を調節する。骨・ミネラル代謝におけるビタミンＤの標的器官は，食事からのミネラル成分を吸収する消化管（小腸），吸収したミネラルの尿への排泄を調節する腎臓尿細管，血中ミネラルを感知する副甲状腺，ミネラル貯蔵庫の骨である。本稿では，これまでに明らかにされたそれぞれの器官でのビタミンＤの作用に触れながら，骨量を適正に維持し，カルシウムやリン等の骨の主要ミネラル成分の生体内恒常性を整える仕組みを概説する。

　Vitamin D endocrine system is required for bone and mineral homeostasis through the active form of vitamin D［1α,25（OH）2D3］transported to the target organs, where the vitamin D receptor（VDR）is present. The biological significance of 1α,25（OH）2D3-VDR signalling is regarded not only in classical target of vitamin D involved in calcium and phosphate homeostasis, such as intestine, bone, kidney and parathyroid glands, but also in many other non-classical target cells of vitamin D including skin keratinocytes, pancreatic β cells, cardiomyocytes, T-lymphocytes, bone marrow macrophages, among others. Although 1α,25（OH）2D3-VDR signalling in classical target organs of vitamin D has been extensively studied, its precise function in these target organs still needs further investigation.