Vitamin D has a key role in stimulating calcium absorption from the gut and promoting skeletal health, as well as many other important physiological functions. Vitamin D is produced in the skin. It is subsequently metabolized to its hormonally active form, 1,25-dihydroxyvitamin D (1,25(OH)2D), by the 1-hydroxylase and catabolized by the 24-hydroxylase. In this Review, we pay special attention to the effect of mutations in these enzymes and their clinical manifestations. We then discuss the role of vitamin D binding protein in transporting vitamin D and its metabolites from their source to their targets, the free hormone hypothesis for cell entry and HSP70 for intracellular transport. This is followed by discussion of the vitamin D receptor (VDR) that mediates the cellular actions of 1,25(OH)2D. Cell-specific recruitment of co-regulatory complexes by liganded VDR leads to changes in gene expression that result in distinct physiological actions by 1,25(OH)2D, which are disrupted by mutations in the VDR. We then discuss the epidermis and hair follicle, to provide a non-skeletal example of a tissue that expresses VDR that not only makes vitamin D but also can metabolize it to its hormonally active form. This enables vitamin D to regulate epidermal differentiation and hair follicle cycling and, in so doing, to promote barrier function, wound healing and hair growth, while limiting cancer development.

中文翻译：

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维生素D代谢和作用的新方面-解决皮肤作为来源和目标的问题。

维生素D在刺激肠内钙吸收，促进骨骼健康以及许多其他重要的生理功能方面具有关键作用。维生素D在皮肤中产生。随后，它被1-羟化酶代谢为激素活性形式的1,25-二羟基维生素D（1,25（OH）2D），并被24-羟化酶分解代谢。在这篇综述中，我们特别注意这些酶突变的作用及其临床表现。然后，我们讨论了维生素D结合蛋白在将维生素D及其代谢物从其来源运输到靶标，用于细胞进入的游离激素假说以及用于细胞内运输的HSP70中的作用。接下来是讨论介导1,25（OH）2D的细胞活动的维生素D受体（VDR）。配体VDR的细胞特异性募集的共调节复合物导致基因表达的变化，导致1,25（OH）2D产生独特的生理作用，而VDR中的突变会破坏这种行为。然后，我们讨论表皮和毛囊，以提供表达VDR的组织的非骨骼示例，该组织不仅可以制造维生素D，而且还可以将其代谢为激素活性形式。这使维生素D能够调节表皮分化和毛囊循环，从而促进屏障功能，伤口愈合和头发生长，同时限制癌症的发展。提供表达VDR的组织的非骨骼示例，该组织不仅可以制造维生素D，还可以将其代谢为激素活性形式。这使维生素D能够调节表皮分化和毛囊循环，从而促进屏障功能，伤口愈合和头发生长，同时限制癌症的发展。提供表达VDR的组织的非骨骼示例，该组织不仅可以制造维生素D，还可以将其代谢为激素活性形式。这使维生素D能够调节表皮分化和毛囊循环，从而促进屏障功能，伤口愈合和头发生长，同时限制癌症的发展。