骨格筋のビタミンDの役割：形態、機能、代謝

骨格筋のビタミンDの役割：形態、機能、代謝に関するレビュー論文を紹介します。

Girgis CM, Clifton-Bligh RJ, Hamrick MW, Holick MF, Gunton JE. The roles of vitamin d in skeletal muscle: form, function, and metabolism. Endocr Rev. 2013 Feb;34(1):33-83. doi: 10.1210/er.2012-1012.

50頁もあるのでまだ抄録と図程度しか読めていませんが、この論文1本でビタミンDと筋肉・サルコペニアの基本的な知識は十分習得できるのではと感じます。ビタミンD欠乏でミオパチー、筋肉痛を生じることがありビタミンD投与で改善することや、筋力・身体機能と一定の関連があることは確かなようです。

ただビタミンDの骨格筋細胞内のシグナルやメカニズムはまだよくわかっていませんし、ビタミンDリセプターが十分に分化した成人の骨格筋に存在するかどうかやその生理学的重要性もわかっていないようです。ビタミンDが欠乏していてサルコペニアのときには投与すべきですが、課題が多いですね。

Abstract

Beyond its established role in bone and mineral homeostasis, there is emerging evidence that vitamin D exerts a range of effects in skeletal muscle. Reports of profound muscle weakness and changes in the muscle morphology of adults with vitamin D deficiency have long been described. These reports have been supplemented by numerous trials assessing the impact of vitamin D on muscle strength and mass and falls in predominantly elderly and deficient populations. At a basic level, animal models have confirmed that vitamin D deficiency and congenital aberrations in the vitamin D endocrine system may result in muscle weakness. To explain these effects, some molecular mechanisms by which vitamin D impacts on muscle cell differentiation, intracellular calcium handling, and genomic activity have been elucidated. There are also suggestions that vitamin D alters muscle metabolism, specifically its sensitivity to insulin, which is a pertinent feature in the pathophysiology of insulin resistance and type 2 diabetes. We will review the range of human clinical, animal, and cell studies that address the impact of vitamin D in skeletal muscle, and discuss the controversial issues. This is a vibrant field of research and one that continues to extend the frontiers of knowledge of vitamin D's broad functional repertoire.