Adipocytokines and pituitary function
Maria M. Malagon1, Francisca Rodríguez-Pacheco1, Antonio J. Martínez-Fuentes1, Rafael Vázquez-Martínez1, Manuel Tena-Sempere1, Carlos Diéguez2 & Justo P. Castaño1
It is widely accepted that, in addition to serving as a repository for energy reserves, adipose tissue is an active endocrine organ that secretes a variety of signalling molecules, the adipokines, which play important roles in the regulation of metabolism, energy balance, feeding behaviour, vascular homeostasis and immunity. In particular, leptin, resistin and adiponectin have been implicated in energy and glucose homeostasis. Additional neuroendocrine functions have also been recognized for leptin as it regulates the secretion of pituitary GH and LH. In order to elucidate whether adiponectin, as leptin, may be involved in the regulation of pituitary cell function, we investigated the effect of this adipokine on somatotrophs and gonadotrophs and analyzed its interaction with major stimulatory regulators of these cells (ghrelin, GHRH, GnRH), as well as with their corresponding receptors (GHS-R, GHRH-R, and GnRH-R, respectively). Results show that adiponectin inhibits GH and LH secretion as well as both ghrelin-induced GH release and GnRH-stimulated LH secretion in rat pituitary cell cultures, wherein the adipokine also increases GHRH-R and GHS-R mRNA content while decreasing that of GnRH-R. Additionally, we have demonstrated that the pituitary expresses both adiponectin and the adiponectin receptors, AdipoR1 and AdipoR2, under the regulation of the adipokine. Taken together, these data indicate that adiponectin, either locally produced or from other sources, may play a neuroendocrine role in the control of both somatotrophs and gonadotrophs. These results will be further discussed on the context of adiponectin expression in pituitary tumoral cells and its interaction with other adipokines present in the pituitary.
Financial-support: CVI-139-J.Andalucia, BFU2004-03883-MEC/FEDER, and CIBER Obesity&Nutrition-ISCIII. Spain.