Localization of fibroblast growth factor 23 protein in the rat hypothalamus

Abstract

Fibroblast growth factor 23 (FGF23) is an endocrine growth factor and known to play a pivotal role in phosphate homeostasis. Interestingly, several studies point towards a function of FGF23 in the hypothalamus. FGF23 classically activates the FGF receptor 1 in the presence of the co‐receptor αKlotho, of both gene expression in the brain was previously established. However, studies on gene and protein expression of FGF23 in the brain are scarce and have been inconsistent. Therefore, our aim was to localise FGF23 gene and protein expression in the rat brain with focus on the hypothalamus. Also, we investigated the protein expression of αKlotho. Adult rat brains were used to localise and visualise FGF23 and αKlotho protein in the hypothalamus by immunofluorescence labelling. Furthermore, western blots were used for assessing hypothalamic FGF23 protein expression. FGF23 gene expression was investigated by qPCR in punches of the arcuate nucleus, lateral hypothalamus, paraventricular nucleus, choroid plexus, ventrolateral thalamic nucleus and the ventromedial hypothalamus. Immunoreactivity for FGF23 and αKlotho protein was found in the hypothalamus, third ventricle lining and the choroid plexus. Western blot analysis of the hypothalamus confirmed the presence of FGF23. Gene expression of FGF23 was not detected, suggesting that the observed FGF23 protein is not brain‐derived. Several FGF receptors are known to be present in the brain. Therefore, we conclude that the machinery for FGF23 signal transduction is present in several brain areas, indeed suggesting a role for FGF23 in the brain.

The Effect of Intracerebroventricular Fibroblast Growth Factor 23 on gene expression in the Rats’ Hypothalamus

“…Using a specific monoclonal FGF23 antibody, we observed FGF23 protein in the hypothalamus and more specifically in the arcuate nucleus, as well as in the third ventricle lining and choroid plexus of rats. 15 However, no FGF23 gene expression was observed, suggesting the detected protein in the brain is from peripheral origin and is thus probably bone-derived. In humans, FGF23 protein has been found in CSF.…”

Non-Classical Effects of FGF23: Molecular and Clinical Features

“…FGF23 consists of 251 amino acids and is mainly expressed in bone, specifically in osteoblasts and osteocytes [3], although it can also be detected in various organs such as the liver [4], brain [5], heart [6], thyroid [7], intestine [8], and skeletal muscle [9].…”