17β-Estradiol Increases Arcuate KNDy Neuronal Sensitivity to Ghrelin Inhibition of the M-Current in Female Mice

Abstract

Obesity and anorexia result in dysregulation of the hypothalamic-pituitary-gonadal axis, negatively impacting reproduction. Ghrelin, secreted from the stomach, potentially mediates negative energy states and neuroendocrine control of reproduction by acting through the growth hormone secretagogue receptor (GHSR). GHSR is expressed in hypothalamic arcuate (ARC) Kisspeptin/Neurokinin B (Tac2)/Dynorphin (KNDy) neurons. Ghrelin is known to inhibit the M-current produced by KCNQ channels in other ARC neurons. In addition, we have shown 17β-estradiol (E2) increases Ghsr expression in KNDy neurons 6-fold and increases the M-current in NPY neurons. We hypothesize that E2 increases GHSR expression in KNDy neurons to increase ghrelin sensitivity during negative energy states. Furthermore, we suspect ghrelin targets the M-current in KNDy neurons to control reproduction and energy homeostasis. We utilized ovariectomized Tac2-EGFP adult female mice, pretreated with estradiol ben-zoate (EB) or oil vehicle and performed whole-cell-patchclamp recordings to elicit the M-current in KNDy neurons using standard activation protocols in voltage-clamp. Using the selective KCNQ channel blocker XE-991 (40 µM) to target the M-current, oil-and EB-treated mice showed a decrease in the maximum peak current by 75.7 ± 13.8 pA (n = 10) and 68.0 ± 14.7 pA (n = 11), respectively. To determine the actions of ghrelin on the M-current, ghrelin was perfused (100 nM) in oil-and EB-treated mice resulting in the suppression of the maximum peak current by 58.5 ± 15.8 pA (n = 9) and 59.2 ± 11.9 pA (n = 9), respectively. KNDy neurons appeared more sensitive to ghrelin when pretreated with EB, revealing that ARC KNDy neurons are more sensitive to ghrelin during states of high E2.

Effects of electroacupuncture on the expression of hypothalamic neuropeptide Y and ghrelin in pubertal rats with polycystic ovary syndrome

“…Although the specific mechanism is unclear, we speculate that NPY and GHRL in hypothalamus may participate in development of pubertal PCOS through kisspeptin / GnRH system in view of both our previous study [ 8 ] and study of Shen et al [ 29 ] showed that the increased expression and release of kisspeptin and GnRH in hypothalamus are the key pathogenesis of pubertal PCOS. The following provides evidence for our conjecture: a, Immunofluorescence double-labeling experiment showed that GnRH neurons and kisspeptin neurons in ARC were the direct targets of NPY and GHRL in hypothalamus respectively, consistent with research of Conde et al [ 30 ] and Dhillon et al [ 31 ]; b, Kisspeptin, as the nodal regulatory centre of reproductive function, binds into kisspeptin receptor (G-protein coupled receptor-54, GPR-54) on GnRH neurons or NPY neurons and promotes GnRH and NPY secretion from hypothalamus [ 32 – 35 ]; c, Previous studies have shown that NPY is necessary for the pulsatility of GnRH release [ 36 ], promoting the secretion of GnRH [ 11 ]. However, GHRL is inhibitory to GnRH/LH release [ 12 ].…”

Effects of electroacupuncture on the expression of hypothalamic neuropeptide Y and ghrelin in pubertal rats with polycystic ovary syndrome

“…Although the specific mechanism is unclear, we speculate that NPY and GHRL in hypothalamus may participate in development of pubertal PCOS through kisspeptin / GnRH system in view of our previous study showed that the increased expression and release of kisspeptin and GnRH in hypothalamus are the key pathogenesis of pubertal PCOS [7]. The following provides evidence for our conjecture: a, Immunofluorescence doublelabeling experiment showed that GnRH neurons and kisspeptin neurons in ARC were the direct targets of NPY and GHRL in hypothalamus respectively, consistent with research of Conde et al [24] and Dhillon et al [25]; b, Kisspeptin, as the nodal regulatory centre of reproductive function, binds into kisspeptin receptor (G-protein coupled receptor-54, GPR-54) on GnRH neurons or NPY neurons and promotes GnRH and NPY secretion from hypothalamus [26][27][28][29]; c, Previous studies have shown that NPY is necessary for the pulsatility of GnRH release [30], promoting the secretion of GnRH [10]. However, GHRL is inhibitory to GnRH/LH release [11].…”

CRISPR knockdown of Kcnq3 attenuates the M-current and increases excitability of NPY/AgRP neurons to alter energy balance

“…However, the much lower abundance of Kcnq5 suggested that increased expression was unlikely to be the sole reason for the E2-enhanced M-current [ 27 ]. Other E2-driven mechanisms must regulate the M-current such as altered coupling between ghrelin receptors and KCNQ channels in ARH kisspeptin neurons [ 82 ]. However, the strategy we outlined can easily be adapted to study other KCNQ subunits to more fully explicate the M-current in future experiments.…”