Kisspeptin Stimulates Growth Hormone Release by Utilizing Neuropeptide Y Pathways and Is Dependent on the Presence of Ghrelin in the Ewe

• Published in: Endocrinology (Philadelphia) Vol. 158; no. 10; pp. 3526 - 3539
• Main Authors: Foradori, Chad D, Whitlock, Brian K, Daniel, Jay A, Zimmerman, Arthur D, Jones, Melaney A, Read, Casey C, Steele, Barbara P, Smith, Jeremy T, Clarke, Iain J, Elsasser, Theodore H, Keisler, Duane H, Sartin, James L
• Format: Journal Article
• Language: English
• Published: Washington, DC Endocrine Society 01.10.2017; Oxford University Press
• Subjects: Activation; Animals; Arcuate nucleus; Arcuate Nucleus of Hypothalamus - drug effects; Arcuate Nucleus of Hypothalamus - metabolism; Arginine - analogs & derivatives; Arginine - pharmacology; Atropine - pharmacology; c-Fos protein; Endocrinology; Energy balance; Fasting - metabolism; Female; Fluorescent Antibody Technique; Food availability; Ghrelin; Ghrelin - metabolism; Gonadotropin-releasing hormone; Gonadotropins; Growth Hormone - drug effects; Growth Hormone - secretion; Growth Hormone-Releasing Hormone; Growth hormones; Hormone release; Hypothalamic-pituitary-gonadal axis; Hypothalamus; Kiss1 protein; Kisspeptins - pharmacology; Muscarinic Antagonists - pharmacology; Neuropeptide Y; Neuropeptide Y - metabolism; Neuropeptides; Nuclei (cytology); Oligopeptides - pharmacology; Ovis aries; Periventricular nucleus; Pituitary; Pituitary (anterior); Pituitary-gonadal axis; Proto-Oncogene Proteins c-fos - drug effects; Proto-Oncogene Proteins c-fos - metabolism; Receptors, Ghrelin - antagonists & inhibitors; Receptors, Neuropeptide Y - antagonists & inhibitors; Secretion; Sheep; Sheep, Domestic; Somatostatin; Somatostatin-Secreting Cells - drug effects; Somatostatin-Secreting Cells - secretion
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2017-00303

Abstract Although kisspeptin is the primary stimulator of gonadotropin-releasing hormone secretion and therefore the hypothalamic–pituitary–gonadal axis, recent findings suggest kisspeptin can also regulate additional neuroendocrine processes including release of growth hormone (GH). Here we show that central delivery of kisspeptin causes a robust rise in plasma GH in fasted but not fed sheep. Kisspeptin-induced GH secretion was similar in animals fasted for 24 hours and those fasted for 72 hours, suggesting that the factors involved in kisspeptin-induced GH secretion are responsive to loss of food availability and not the result of severe negative energy balance. Pretreatment with the neuropeptide Y (NPY) Y1 receptor antagonist, BIBO 3304, blocked the effects of kisspeptin-induced GH release, implicating NPY as an intermediary. Kisspeptin treatment induced c-Fos in NPY and GH-releasing hormone (GHRH) cells of the arcuate nucleus. The same kisspeptin treatment resulted in a reduction in c-Fos in somatostatin (SS) cells in the periventricular nucleus. Finally, blockade of systemic ghrelin release or antagonism of the ghrelin receptor eliminated or reduced the ability of kisspeptin to induce GH release, suggesting the presence of ghrelin is required for kisspeptin-induced GH release in fasted animals. Our findings support the hypothesis that during short-term fasting, systemic ghrelin concentrations and NPY expression in the arcuate nucleus rise. This permits kisspeptin activation of NPY cells. In turn, NPY stimulates GHRH cells and inhibits SS cells, resulting in GH release. We propose a mechanism by which kisspeptin conveys reproductive and hormone status onto the somatotropic axis, resulting in alterations in GH release. Kisspeptin induces GH release in short-term fasted but not fed sheep through NPY and GHRH cellular activation and requires the presence of the gut-derived hormone ghrelin.