Vitamin D and Vitamin D-Binding Protein in Health and Disease

Abstract

Vitamin D is a fat-soluble secosteroid that exists in two forms: vitamin D₂ and vitamin D₃ [...].

Figure 1

Vitamin D exerts its biological effects through the vitamin D receptor (VDR). 1,25(OH)₂D₃ can quickly diffuse through cell membranes and bind to VDR. VDR forms heterodimers with the retinoid X receptor (RXR) after binding to the ligand, moving into the nucleus where it binds to vitamin D response elements (VDREs) to regulate gene transcription. The VDR also controls the transcription of genes by interacting with other nuclear receptors. The functions of vitamin D include growth and bone mineralization, immune function regulation, insulin secretion regulation, cell proliferation control, cell differentiation stimulation, apoptosis induction, phosphor–calcium homeostasis regulation, and muscle calcium transport regulation.

Figure 2

An overview of vitamin-D-binding protein’s various physiological roles, including the binding of vitamin D metabolites, the binding of fatty acids, the transport of endotoxins, neutrophil chemotaxis, the influence on T cell response, actin scavenging, and the influence of vitamin-D-binding protein-macrophage activating factor (DBP-MAF) on bone metabolism and cancer.