title: Short-term dietary phosphate restriction up-regulates ileal fibroblast growth factor 15 gene expression in mice.
abstract: Members of the fibroblast growth factor (FGF) 19 subfamily, including FGF23, FGF15/19, and FGF21, have a role as endocrine factors which influence the metabolism of inorganic phosphate (Pi) and vitamin D, bile acid, and energy. It has been reported that dietary Pi regulates circulating FGF23. In this study, the short-term effects of dietary Pi restriction on the expression of FGF19 subfamily members in mice were analyzed. An initial analysis confirmed plasma FGF23 levels positively correlated with the amount of dietary Pi. On the other hand, ileal Fgf15 gene expression, but not hepatic Fgf21 gene expression, was up-regulated by dietary Pi restriction. In addition, we observed the increase of plasma 1,25-dihydroxyvitamin D [1,25(OH)2D] levels by dietary Pi restriction, and the up-regulation of ileal Fgf15 mRNA expression by 1,25(OH)2D3 and vitamin D receptor (VDR). Importantly, dietary Pi restriction-induced Fgf15 gene expression was prevented in VDR-knockout mice. Furthermore, diurnal variations of plasma triglyceride concentrations and hepatic mRNA expression of the bile acid synthesis enzyme Cyp7a1 as one of Fgf15 negative target genes was influenced by dietary Pi restriction. These results suggest that dietary Pi restriction up-regulates ileal Fgf15 gene expression through 1,25(OH)2D3 and VDR, and may affect hepatic bile acid homeostasis.
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Otoki
authors.initials: O
authors.lastname: Nakahashi
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan ; Department of Health and Nutrition, Faculty of Human Life, Jin-ai University, 3-1-1 Ohde-cho, Echizen-shi, Fukui 915-8586, Japan ; Division of Nephrology, Department of General Medicine, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Yamamoto
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Sarasa
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Mina
authors.initials: M
authors.lastname: Kozai
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Takei
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Masuda
authors.affiliation: Department of Molecular Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kaneko
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Taketani
authors.affiliation: Division of Nephrology, Department of General Medicine, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iwano
authors.affiliation: Department of Molecular Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Miyamoto
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Takeda
keywords: 1,25-dihydroxyvitamin D; fibroblast growth factor 15; gene regulation analysis; inorganic phosphate; mice