Ghrelin hormone in vertebrates is involved in the regulation of different important functions, such as feed intake, energy metabolism, intestinal motility or digestive enzymes activity, but also has an effect promoting growth through stimulation of growth hormone (GH) expression in pituitary. However, the functions of ghrelin and its tissue distribution seem to be species-specific and may differ substantially among vertebrates. The aim of this work was to identify and study the responses of ghrelin to different nutritional conditions in an important Mediterranean fish species, gilthead sea bream (Sparus aurata). To achieve this goal, first the phylogeny of S. aurata ghrelin among vertebrates was analyzed, and then a tissue screening by qPCR was performed. Afterwards, the effects of fasting (FA) and refeeding (RF) on ghrelin, GH and IGF-I plasma levels were analyzed, as well as the gene expression of ghrelin and the GH/IGF-I axis-related genes analyzed in key tissues. The results revealed that S. aurata ghrelin sequence is well conserved among fish species, and it is mainly expressed in stomach, pyloric caeca and intestine. In juveniles after 21 days of FA the GH plasma levels were significantly increased, to progressively decrease after 7 days of RF, whereas the hepatic mRNA of GH receptors followed an opposite pattern. Similarly, both IGF-I plasma and mRNA levels in liver decreased with FA and recovered with RF. Regarding ghrelin, its gene expression in stomach increased just at the moment of RF coinciding with the changes observed in the GH-IGF axis; thus, suggesting the involvement of this hormone in the regulation of growth in this species.

Trabajo presentado en el 11º Congreso de la Asociación Ibérica de Endocrinología Comparada (AIEC), celebrado en Vigo (España), del 13 al 15 de julio de 2017

Supported by MINECO (AGL2015-70679-R) and XRAq

Peer reviewed