[Bone and Nutrition. The vitamin D functions in osteoblasts and osteocytes]

The active form of vitamin D, 1α,25-dihydroxyvitamin D(3) (1α,25 (OH) (2)D(3)), plays a key role in mineral and bone homeostasis. 1α,25 (OH) (2)D(3), through binding to the vitamin D receptor (VDR), a member of the nuclear receptor superfamily, regulates the expression of many genes in osteoblasts and osteocytes. The VDR functions in a largely 1α,25 (OH) (2)D(3)-controlled manner by interacting directly with vitamin D response elements located within regulatory regions that are linked to cell-specific target genes. However, the mechanism of VDR action on these bone cell types remains largely unknown. While the direct actions of 1α,25 (OH) (2)D(3) on bone cells are complex and include both cell autonomous and paracrine mechanisms. In this review, we discuss how the VDR affects the transcriptional response of these cells and contribute to bone homeostasis.