title: Bone formation regulates circulating concentrations of fibroblast growth factor 23.
abstract: We examined the role of bone remodeling in the regulation of circulating concentrations of FGF23 using mouse models manifesting differing degrees of coupled and uncoupled bone turnover. Administration of the antiresorptive agent osteoprotegerin produced a profound reduction in bone resorption and formation in male and oophorectomized female mice, accompanied by an increase in serum levels of fibroblast growth factor 23 (FGF23) and a reduction in circulating 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. In contrast, exogenous PTH(1-34) administration increased bone turnover and reduced circulating FGF23. In 1,25(OH)(2)D-deficient, 25-hydroxyvitamin D 1alpha-hydroxylase null mice on a high-calcium diet, endogenous PTH was elevated, bone formation but not resorption was increased, and serum FGF23 was virtually undetectable; on a rescue diet, serum calcium was normalized, PTH levels were reduced, bone formation was reduced, and serum FGF23 levels increased. After PTH treatment of wild-type mice, gene expression of dentin matrix protein 1 (DMP1) in bone was increased, whereas gene expression of FGF23 was reduced. In vitro studies in the osteoblastic cell line UMR-106 showed that externally added DMP1 could inhibit FGF23 gene expression and production stimulated by 1,25(OH)(2)D(3). The results show that osteoblastic bone formation is a potent modulator of FGF23 production and release into the circulation, suggest that the biological consequences on mineral homeostasis of circulating FGF23 may also be dependent on the prevailing rate of bone turnover, and provide evidence that DMP1 may be a direct negative regulator of FGF23 production in osteoblastic cells.
authors.affiliation: Calcium Research Laboratory, Royal Victoria Hospital, 687 Pine Avenue, Room H4.67, Montreal, Quebec, Canada H3A 1A1.
authors.forename: Rana
authors.initials: R
authors.lastname: Samadfam
authors.forename: Christian
authors.initials: C
authors.lastname: Richard
authors.forename: Loan
authors.initials: L
authors.lastname: Nguyen-Yamamoto
authors.forename: Isabel
authors.initials: I
authors.lastname: Bolivar
authors.forename: David
authors.initials: D
authors.lastname: Goltzman
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism; D002460:Cell Line; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010006:Osteoblasts / Q000378:metabolism; D010012:Osteogenesis; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: C513308:Dmp1 protein, mouse; D016326:Extracellular Matrix Proteins; C000717428:Fgf23 protein, mouse; D014807:Vitamin D; D005346:Fibroblast Growth Factors; C097949:1,25-dihydroxyvitamin D; D000089703:Fibroblast Growth Factor-23