Gilthead sea bream ghrelin characterization and transcriptional regulation during fasting and refeeding

Abstract

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 the 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 real-time quantitative PCR (qPCR) was performed. Afterwards, the effects of fasting and refeeding on ghrelin gene expression in key tissues and also its plasmatic levels were determined. The results revealed that S. aurata ghrelin is well conserved among fish species, and it is mainly expressed in stomach, pyloric caeca and intestine. Furthermore, in the experiment with juveniles, ghrelin’s gene expression was up-regulated in response to fasting and downregulated with refeeding, suggesting that this hormone may have an important role regulating the physiological functions related to nutritional state, such as feed intake and growth among others.