FGF-23 is a potent regulator of vitamin D metabolism and phosphate homeostasis

J Bone Miner Res. 2004 Mar;19(3):429-35. doi: 10.1359/JBMR.0301264. Epub 2003 Dec 29.

Abstract

We analyzed the effects of an FGF-23 injection in vivo. FGF-23 caused a reduction in serum 1,25-dihydroxyvitamin D by altering the expressions of key enzymes for the vitamin D metabolism followed by hypophosphatemia. This study indicates that FGF-23 is a potent regulator of the vitamin D and phosphate metabolism.

Introduction: The pathophysiological contribution of FGF-23 in hypophosphatemic diseases was supported by animal studies in which the long-term administration of recombinant fibroblast growth factor-23 reproduced hypophosphatemic rickets with a low serum 1,25-dihydroxyvitamin D [1,25(OH)2D] level. However, there is no clear understanding of how FGF-23 causes these changes.

Materials and methods: To elucidate the molecular mechanisms of the FGF-23 function, we investigated the short-term effects of a single administration of recombinant FGF-23 in normal and parathyroidectmized animals.

Results: An injection of recombinant FGF-23 caused a reduction in serum phosphate and 1,25(OH)2D levels. A decrease in serum phosphate was first observed 9 h after the injection and was accompanied with a reduction in renal mRNA and protein levels for the type IIa sodium-phosphate cotransporter (NaPi-2a). There was no increase in the parathyroid hormone (PTH) level throughout the experiment, and hypophosphatemia was reproduced by FGF-23 in parathyroidectomized rats. Before this hypophosphatemic effect, the serum 1,25(OH)2D level had already descended at 3 h and reached the nadir 9 h after the administration. FGF-23 reduced renal mRNA for 25-hydroxyvitamin D-1alpha-hydroxylase and increased that for 25-hydroxyvitamin D-24-hydroxylase starting at 1 h. In addition, an injection of calcitriol into normal mice increased the serum FGF-23 level within 4 h.

Conclusions: FGF-23 regulates NaPi-2a independently of PTH and the serum 1,25(OH)2D level by controlling renal expressions of key enzymes of the vitamin D metabolism. In conclusion, FGF-23 is a potent regulator of phosphate and vitamin D homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Fibroblast Growth Factors / administration & dosage
  • Fibroblast Growth Factors / pharmacology*
  • Homeostasis / physiology
  • Hypophosphatemia / physiopathology
  • Male
  • Mice
  • Phosphates / metabolism*
  • Rats
  • Recombinant Proteins / administration & dosage
  • Time Factors
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood
  • Vitamin D / metabolism*
  • Vitamin D / urine

Substances

  • Phosphates
  • Recombinant Proteins
  • Vitamin D
  • Fibroblast Growth Factors
  • 1,25-dihydroxyvitamin D
  • fibroblast growth factor 23