Changes in circulating levels of fibroblast growth factor 23 induced by short-term dietary magnesium deficiency in rats.

Fibroblast growth factor 23 (FGF23) is a potent regulator of phosphorus (P) and vitamin D metabolism. Long-term dietary magnesium (Mg) deficiency increases circulating levels of FGF23, whereas the effects of short-term dietary Mg deficiency are unclear. Thus, the present study investigated whether short-term dietary Mg deficiency affects circulating levels of FGF23. We also assessed changes in renal mRNA expression of vitamin D metabolizing enzymes and type II sodium-phosphate (Na/Pi) cotransporters, since these are regulated by FGF23. Rats were fed a control diet (control group) or an Mg-deficient diet (Mg-deficient group) for 2, 4 or 7 days. Serum Mg levels were significantly lower in the Mg-deficient group than in the control group at all time points. Serum FGF23 levels were significantly higher in the Mg-deficient group than in the control group at day 7. The 25-hydroxyvitamin D-24-hydroxylase (24(OH)ase) mRNA levels were significantly higher in the Mg-deficient group than in the control group at day 7 . No significant differences in types IIa and IIc Na/Pi cotransporter mRNA levels were observed between the control and Mg-deficient groups. These results suggest that dietary Mg deficiency causes a rapid increase in circulating levels of FGF23 and renal 24(OH)ase mRNA levels.