Inhibition of intestinal sodium-dependent inorganic phosphate transport by fibroblast growth factor 23.

The mechanisms by which fibroblast growth factor 23 (FGF23) alters inorganic phosphate (Pi) homeostasis is not entirely clear. In the present study, we examined the effect of FGF23 on intestinal sodium-dependent Pi transport in mice. Injection of FGF23(R179Q) markedly reduced serum Pi and 1,25(OH)2D3 levels in normal mice. Those animals show the reduction of intestinal sodium-dependent Pi transport activity and the amount of type IIb sodium-dependent Pi cotransporter (type IIb NaPi) protein in the brush border membrane vesicles. In vitamin D receptor null mice (VDR-/-), FGF23(R179Q) had no effect on intestinal sodium-dependent Pi transport activity and type IIb NaPi protein levels. The present study suggests that FGF23(R179Q) reduces intestinal sodium-dependent Pi transport activity and type IIb NaPi protein levels by a mechanism that is dependent on VDR.