[Bone remodeling through a phosphate metabolism.]

Phosphorus is the second abundant mineral stored in bones, and disturbance of phosphate metabolisms results in various disease developments such as hypophosphatemic rickets. Blood phosphorus levels are regulated by dietary intake or its absorption from intestine, proximal tubular reabsorption, and number of factors plays roles for maintaining phosphate homeostasis. Vitamin D stimulates intestinal phosphorus absorption, and phosphorus promotes FGF23 secretion from osteocytes. FGF23 inhibits Cyp27b1, an enzyme to produce an active vitamin D3, 1,25(OH)2D3, through FGF receptor/Klotho complex. In this review, I will discuss about the roles of Enpp1 in regulating the FGF23-Klotho-vitamin D axis and bones.