Gonadotropin-releasing hormone, kisspeptin, and gonadal steroids directly modulate nucleobindin-2/nesfatin-1 in murine hypothalamic gonadotropin-releasing hormone neurons and gonadotropes.

Abstract

Neuroendocrine regulation of metabolism and reproduction are tightly interlinked. Nesfatin-1 is an 82 amino acid metabolic peptide derived from nucleobindin-2 (NUCB2). NUCB2 mRNA and protein significantly increase in the hypothalamus of rats during puberty-to-adult transition. Administration of nesfatin-1 modulates circulating LH and testosterone in male rats. However, whether nesfatin-1 acts directly on neurons and gonadotropes remain unknown. In addition, whether reproductive hormones of the hypothalamo-pituitary gonadal axis modulate NUCB2/nesfatin-1 is unclear. To address these, we employed murine hypothalamic (GT1-7) and pituitary (LβT2) cells in vitro. Nucb2 expression, and NUCB2/nesfatin-1 immunoreactivity were observed in both GT1-7 and LβT2 cells, and in the hypothalamus of mice. Nesfatin-1 co-localized GnRH in GT1-7 cells, and in the hypothalamic perikarya of mice. Cells were treated with kisspeptin, GnRH, and estradiol and testosterone, as well as nesfatin-1 for 2, 6 or 24 hours. Synthetic nesfatin-1 increased Kiss1r and Gnrh expression in GT1-7 cells and Lhβ in LβT2. Nesfatin-1 increased GnRH and LHβ protein expression in GT1-7 and LβT2 at 6-hour post incubation respectively. Both NUCB2 mRNA and protein were increased in GT1-7 cells treated with kisspeptin. Testosterone increased NUCB2 mRNA and protein expression in GT1-7 and LβT2. 17β-estradiol increased NUCB2 mRNA and protein expression in LβT2. Nesfatin-1 acts directly on hypothalamic neurons and gonadotropes to elicit a generally positive influence on the endocrine milieu regulating reproduction in mice. Reproductive hormones, in turn, modulate brain and pituitary NUCB2/nesfatin-1. In conclusion, we provide additional information to designate nesfatin-1 as a novel, additional factor that helps reproductive success.