title: Circulating FGF-23 is regulated by 1alpha,25-dihydroxyvitamin D3 and phosphorus in vivo.
abstract: Fibroblast growth factor-23 (FGF-23), a novel phosphate-regulating factor, was elevated in hypophosphatemic patients with X-linked hypophosphatemic rickets/osteomalacia and also in patients with chronic kidney disease. These observations suggested the pathophysiological importance of FGF-23 on phosphate homeostasis. However, regulation of FGF-23 production is still unclear. We investigated effects of both dietary phosphorus and 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) on circulating FGF-23 in vivo Administration of. 1alpha,25(OH)(2)D(3) dose-dependently increased serum FGF-23 in thyroparathyroidectomized rats without correlating with serum inorganic phosphorus or serum parathyroid hormone. On the other hand, vitamin D receptor null mice had very low serum FGF-23 and did not respond to the 1alpha,25(OH)(2)D(3) administration. These observations suggested 1alpha,25(OH)(2)D(3) directly or indirectly regulates circulating FGF-23. Serum FGF-23 had a strong correlation with serum inorganic phosphorus controlled by dietary phosphorus in 5/6 nephrectomized rats. High phosphate diet elicited a 5-fold increase in serum FGF-23 compared with sham-operated rats, whereas serum FGF-23 did not correlate with serum calcium or serum creatinine in 5/6 nephrectomized rats. Administration of 1alpha,25-dihydroxyvitamin D(3) also elicited a severalfold increase in serum FGF-23 in the uremic rats. Taken together, this shows that both serum phosphorus and 1alpha,25(OH)(2)D(3) regulate circulating FGF-23 independent of each other. Therefore, we proposed there was a feedback loop existing among serum phosphorus, 1alpha,25(OH)(2)D(3), and FGF-23, in which the novel phosphate-regulating bone-kidney axis integrated with the parathyroid hormone-vitamin D(3) axis in regulating phosphate homeostasis.
authors.affiliation: Pharmaceutical Research Department II, Chugai Pharmaceutical Co., Ltd., Gotemba, Shizuoka 412-8513, Japan. saitohts@chugai-pharm.co.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Saito
authors.forename: Akira
authors.initials: A
authors.lastname: Maeda
authors.forename: Shu-Ichi
authors.initials: S
authors.lastname: Ohtomo
authors.forename: Michinori
authors.initials: M
authors.lastname: Hirata
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Kusano
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Kato
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ogata
authors.forename: Hiroko
authors.initials: H
authors.lastname: Segawa
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Miyamoto
authors.forename: Naoshi
authors.initials: N
authors.lastname: Fukushima
mesh_terms: D000821:Animal Feed; D000818:Animals; D002117:Calcitriol / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D003404:Creatinine / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D025461:Feedback, Physiological; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010710:Phosphates / Q000378:metabolism; D010758:Phosphorus / Q000097:blood / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013961:Thyroid Gland / Q000378:metabolism
chemical_list: C000717427:FGF23 protein, human; C000717428:Fgf23 protein, mouse; D010710:Phosphates; D010758:Phosphorus; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D003404:Creatinine; D002117:Calcitriol; D002118:Calcium