Ablation of vitamin D signaling rescues bone, mineral, and glucose homeostasis in Fgf-23 deficient mice.
To explore further the role of the vitamin D axis for fibroblast growth factor-23 (FGF23) signaling, we mated Fgf-23 deficient (Fgf-23(-/-)) mice and vitamin D receptor (VDR) mutant mice with a non-functioning VDR. To prevent secondary hyperparathyroidism in VDR and compound mutant mice, all mice were kept on a rescue diet enriched with calcium, phosphorus, and lactose. Consistent with previous findings, Fgf-23(-/-) animals showed hypercalcemia, hyperphosphatemia, growth retardation, ectopic calcifications, severe osteoidosis, skin atrophy, and renal dysfunction. In addition, here we describe that Fgf-23(-/-) mice are hypoglycemic, and have profoundly increased peripheral insulin sensitivity and improved subcutaneous glucose tolerance, but normal renal expression of the aging suppressor gene Klotho. Although VDR and double mutants on the rescue diet still had moderately elevated parathyroid hormone serum levels and lower bone mineral density compared to wild-type mice, double mutant mice were normocalcemic and normophosphatemic, and had normal body weight, normal renal function, and no ectopic calcifications. Ablation of vitamin D signaling in compound mutants also normalized subcutaneous glucose tolerance tests and insulin secretory response. In conclusion, our results indicate that the alterations in mineral and carbohydrate metabolism present in Fgf-23(-/-) mice require an intact vitamin D signaling pathway.
Hesse
Martina
M
Institute of Pathophysiology, Department of Natural Sciences, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria.
Fröhlich
Leopold F
LF
Zeitz
Ute
U
Lanske
Beate
B
Erben
Reinhold G
RG
D000704:Analysis of Variance; D000818:Animals; D015152:Blotting, Northern; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003433:Crosses, Genetic; D017931:DNA Primers; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000172:deficiency* / Q000235:genetics; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D005966:Glucuronidase / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology*; D007328:Insulin / Q000378:metabolism; D000090265:Klotho Proteins; D051379:Mice; D018345:Mice, Knockout; D010281:Parathyroid Hormone / Q000097:blood; D018167:Receptors, Calcitriol / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014807:Vitamin D / Q000378:metabolism*
D017931:DNA Primers; C000717428:Fgf23 protein, mouse; D007328:Insulin; D010281:Parathyroid Hormone; D018167:Receptors, Calcitriol; D014807:Vitamin D; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D005966:Glucuronidase; D000090265:Klotho Proteins; D005947:Glucose; D002118:Calcium