Regulation of Gpr173 expression, a putative phoenixin receptor, by saturated fatty acid palmitate and endocrine-disrupting chemical bisphenol A through a p38-mediated mechanism in immortalized hypothalamic neurons.

GPR173 is a highly conserved G protein coupled receptor associated with the hypothalamic-pituitary-gonadal reproductive axis. It is expressed in the brain and ovaries, however considerable knowledge about its function remains unknown. One putative ligand for this receptor is phoenixin (PNX), a newly identified reproductive peptide involved in hypothalamic coordination of the estrous cycle. In order to characterize GPR173, it is vital to determine how Gpr173 is regulated in the hypothalamus. Since the hypothalamus senses compounds from the blood, such as nutrients and chemicals, we examined the effect of palmitate, a saturated fatty acid, and bisphenol A (BPA), an endocrine disrupting chemical, on Gpr173 gene expression. Immortalized hypothalamic neurons were treated with palmitate or BPA for 2-24 h and Gpr173 mRNA levels were assessed with RT-qPCR. Palmitate and BPA both reduced Gpr173 mRNA levels, in part through the mitogen-activated protein kinase (MAPK), p38. Pre-treatment with palmitate for 24 h blocked the PNX-induction of phosphorylated cAMP response element-binding protein (CREB) levels. In conclusion, nutrition levels and environmental chemicals may influence reproductive function through modulation of Gpr173 expression, which may prove to be a future therapeutic target in reproductive health.