FGF23 Fails to Inhibit Uremic Parathyroid Glands

• Published in: Journal of the American Society of Nephrology Vol. 21; no. 7; pp. 1125 - 1135
• Main Authors: CANALEJO, Rocío, CANALEJO, Antonio, MARTINEZ-MORENO, Julio Manuel, RODRIGUEZ-ORTIZ, M. Encarnacion, ESTEPA, Jose C, MENDOZA, Francisco Javier, MUNOZ-CASTANEDA, Juan Rafael, SHALHOUB, Victoria, ALMADEN, Yolanda, RODRIGUEZ, Mariano
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society of Nephrology 01-07-2010
• Subjects: Animals; Basic Research; Biological and medical sciences; Cell Proliferation - drug effects; Disease Models, Animal; Fibroblast Growth Factors - pharmacology; Glucuronidase - metabolism; Hyperplasia - metabolism; Hyperplasia - pathology; Klotho Proteins; Male; Medical sciences; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - metabolism; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Parathyroid Glands - drug effects; Parathyroid Glands - metabolism; Parathyroid Glands - pathology; Parathyroid Hormone - metabolism; Rats; Rats, Wistar; Receptor, Fibroblast Growth Factor, Type 1 - metabolism; Receptors, Calcitriol - metabolism; Receptors, Calcium-Sensing - metabolism; Renal failure; Tissue Culture Techniques; Uremia - metabolism; Uremia - pathology; Kidney disease; Nephrology; Urinary system disease; Renal failure; Parathyroid glands; Inhibitor; Urology
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/asn.2009040427

Fibroblast growth factor 23 (FGF23) modulates mineral metabolism by promoting phosphaturia and decreasing the production of 1,25-dihydroxyvitamin D(3). FGF23 decreases parathyroid hormone (PTH) mRNA and secretion, but despite a marked elevation in FGF23 in uremia, PTH production increases. Here, we investigated the effect of FGF23 on parathyroid function in normal and uremic hyperplastic parathyroid glands in rats. In normal parathyroid glands, FGF23 decreased PTH production, increased expression of both the parathyroid calcium-sensing receptor and the vitamin D receptor, and reduced cell proliferation. Furthermore, FGF23 induced phosphorylation of extracellular signal-regulated kinase 1/2, which mediates the action of FGF23. In contrast, in hyperplastic parathyroid glands, FGF23 did not reduce PTH production, did not affect expression of the calcium-sensing receptor or vitamin D receptor, and did not affect cell proliferation. In addition, FGF23 failed to activate the extracellular signal-regulated kinase 1/2-mitogen-activated protein kinase pathway in hyperplastic parathyroid glands. We observed very low expression of the FGF23 receptor 1 and the co-receptor Klotho in uremic hyperplastic parathyroid glands, which may explain the lack of response to FGF23 in this tissue. In conclusion, in hyperparathyroidism secondary to renal failure, the parathyroid cells resist the inhibitory effects of FGF23, perhaps as a result of the low expression of FGF23 receptor 1 and Klotho in this condition.