Involvement of NPY Y2 receptor subtype in the control of the spontaneous NO/GnRH release at the rat median eminence

1H NMR plasma metabolomic profiling of ovarian quiescence in energy balanced postpartum dairy cows

Background: As the milk production of dairy cows increases, the reproductive capacity gradually declines. Ovarian quiescence has become one of the concerns of the dairy industry.

Objective: To explore the different plasma metabolite levels between estrus and anestrus in energy balanced (EB) dairy cows.

Methods: Ten estrous and 10 anestrus EB Holstein cows in early lactation were selected for the study. ¹H nuclear magnetic resonance technology was used to detect plasma metabolites and screen different plasma metabolites between anestrous and estrous cows at 60–90 days postpartum using multivariate statistical analysis.

Results: Within an elective waiting period of 60−90 days postpartum mean plasma concentration of total estrogens was significantly higher in estrus cows as compared to anestrus cows (71.2 ± 26.0 and 42.4 ± 16.7 pg/mL, respectively). Seven plasma metabolites (isoleucine, leucine, valine, alanine, arginine, choline and phosphatecholine) demonstrated significant decreases in estrous dairy cows relative to anestrous subjects. The main pathway was leucine, isoleucine and valine biosynthesis.

Conclusion: Anestrus in dairy cows is accompanied by alterations in amino acid, glucose and lipid metabolism based on ¹H NMR analysis.

Expression of Neuropeptide Y and Its Relationship with Molecular and Morphological Changes in Human Pituitary Adenomas

The purpose of this study was to explore the role of neuropeptide Y (NPY) on molecular and histological changes in human pituitary adenomas. The localization of NPY and its expression at the protein, messenger RNA (mRNA), and receptor levels were investigated here in different subcategories of pituitary adenomas. Immunohistochemical staining was performed in all cases to assess expression of NPY. Reverse transcription-polymerase chain reaction (RT-PCR) was used to study the mRNA expression of NPY. NPY subcellular localization was observed using immunoelectron microscopy in cytoplasm, rough endoplasmic reticulum, and cell matrix in four of the six cases of pituitary adenoma. NPY protein expression was observed in 59.6% of 57 cases of pituitary adenoma and in 2 cases of pituitary hyperplasia. mRNA expression of NPY was observed in all 57 cases of pituitary adenoma and in 2 cases of pituitary hyperplasia. Significantly different levels of expression were observed across different subcategories of pituitary adenoma. mRNA expression of Y1R and Y2R was observed across all subcategories of pituitary adenomas, and a positive correlation was observed between NPY and Y2R. In conclusion, evidence is provided here for the expression of NPY and its receptors, Y1R and Y2R, in human pituitary adenoma, and the levels of expression were found to differ across different subcategories. Differences in expression of Y2R in human pituitary adenomas were found to have remarkable statistical significance.

Neuropeptide Y induces gonadotropin-releasing hormone gene expression directly and through conditioned medium from mHypoE-38 NPY neurons

Neuropeptide Y (NPY) regulates reproductive function at the level of the hypothalamus through control of GnRH secretion. However, the direct control of GnRH gene expression by NPY has not yet been studied. GT1-7 neurons were treated with 100 nM of NPY over a 36 h time course. GnRH mRNA levels were significantly increased by NPY up to 12 h. We determined that GT1-7 neurons expressed Y1, Y2, and Y4 NPY receptors, but not Y5. Functional analysis of NPY receptor activation indicated that the Y1/Y4/Y5 receptor agonist [Leu31, Pro34] significantly induced cAMP accumulation in the GT1-7 neurons. Western blot studies demonstrated changes in the phosphorylation status of AKT, ERK1/2, CREB and ATF-1 after NPY exposure. Pharmacological inhibitors of the MAPK and PKA signal transduction pathways attenuated the NPY-mediated increase in GnRH transcription. This NPY-mediated increase in GnRH mRNA was also inhibited with the Y1-receptor specific antagonist BIBP-3226. The mHypoE-38 neurons secrete detectable levels of NPY and can be used as an endogenous source of NPY. Conditioned medium from mHypoE-38 neurons induced an increase in GnRH mRNA, which was inhibited by the Y1 receptor antagonist BIBP-3226. Together, these studies strengthen the evidence for the importance of NPY in the regulation of reproductive function.

Progesterone-receptive dopaminergic and neuropeptide Y neurons project from the arcuate nucleus to gonadotropin-releasing hormone-rich regions of the ovine preoptic area

Progesterone inhibits gonadotropin-releasing hormone (GnRH) secretion in sheep through an interneuronal system located in the mediobasal hypothalamus. This study focused on known inhibitors of GnRH secretion in sheep, dopamine and neuropeptide Y (NPY). As the distributions of tyrosine hydroxylase (TH)- and NPY-immunoreactive neurons overlap with progesterone receptors (PR) in the arcuate nucleus, we hypothesized that, if these neurons mediate, at least partially, the inhibitory feedback signal of progesterone, then they should co-express PRs. Fluorogold (FG), a retrograde tracer, was injected into the preoptic area of ovariectomized ewes pretreated with estrogen and progesterone. When the FG injection site encompassed at least 80 GnRH neurons, sections from the arcuate nucleus were processed using dual immunocytochemistry for PR and either TH or NPY. We found that 30% of PR-immunoreactive, 12% of TH-containing and 21% of NPY-synthesizing neurons project toward this GnRH-rich region. Of the PR/TH dual-labeled cells, which represent 21% of PR and 31% of TH cells, respectively, 22% displayed FG labeling. Of the PR/NPY neurons, which account for 19% of PR and 67% of NPY neurons, respectively, 26% were FG fluorescent. This study suggests that subsets of arcuate nucleus dopaminergic and NPY neurons may transduce, at least in part, the progesterone-mediated inhibition of GnRH secretion.