title: Leptin stimulates fibroblast growth factor 23 expression in bone and suppresses renal 1alpha,25-dihydroxyvitamin D3 synthesis in leptin-deficient mice.
abstract: Leptin is the LEP (ob) gene product secreted by adipocytes. We previously reported that leptin decreases renal expression of the 25-hydroxyvitamin D(3) 1alpha-hydroxylase (CYP27B1) gene through the leptin receptor (ObRb) by indirectly acting on the proximal tubules. This study focused on bone-derived fibroblast growth factor 23 (FGF-23) as a mediator of the influence of leptin on renal 1alpha-hydroxylase mRNA expression in leptin-deficient ob/ob mice. Exposure to leptin (200 ng/mL) for 24 hours stimulated FGF-23 expression by primary cultured rat osteoblasts. Administration of leptin (4 mg/kg i.p. at 12-hour intervals for 2 days) to ob/ob mice markedly increased the serum FGF-23 concentration while significantly reducing the serum levels of calcium, phosphate, and 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. Administration of FGF-23 (5 microg i.p. at 12-hour intervals for 2 days) to ob/ob mice suppressed renal 1alpha-hydroxylase mRNA expression. The main site of FGF-23 mRNA expression was the bone, and leptin markedly increased the FGF-23 mRNA level in ob/ob mice. In addition, leptin significantly reduced 1alpha-hydroxylase and sodium-phosphate cotransporters (NaP(i)-IIa and NaP(i)-IIc) mRNA levels but did not affect Klotho mRNA expression in the kidneys of ob/ob mice. Furthermore, the serum FGF-23 level and renal expression of 1alpha-hydroxylase mRNA were not influenced by administration of leptin to leptin receptor-deficient (db/db) mice. These results indicate that leptin directly stimulates FGF-23 synthesis by bone cells in ob/ob mice, suggesting that inhibition of renal 1,25(OH)(2)D(3) synthesis in these mice is at least partly due to elevated bone production of FGF-23.
authors.affiliation: Section of Biochemistry, Department of Oral Function and Molecular Biology, Ohu University School of Dentistry, Koriyama 963-8611, Japan.
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Tsuji
authors.forename: Toyonobu
authors.initials: T
authors.lastname: Maeda
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kawane
authors.forename: Ayako
authors.initials: A
authors.lastname: Matsunuma
authors.forename: Noboru
authors.initials: N
authors.lastname: Horiuchi
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism*; D002117:Calcitriol / Q000096:biosynthesis*; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D020738:Leptin / Q000008:administration & dosage / Q000172:deficiency* / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D054411:Receptors, Leptin / Q000172:deficiency / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C000717427:FGF23 protein, human; C000717428:Fgf23 protein, mouse; D020738:Leptin; D012333:RNA, Messenger; D054411:Receptors, Leptin; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002117:Calcitriol