The effect of starvation and re-feeding on vasotocinergic and isotocinergic pathways in immature gilthead sea bream (Sparus aurata)

Abstract

This study describes the responses of the vasotocinergic and isotocinergic systems to food deprivation and re-feeding processes in immature gilthead sea bream (Sparus aurata). The animals were subjected to the following experimental treatments: (1) normal feeding (control), (2) food deprivation for 21 days; and (3) re-feeding for 7 days, beginning 14 days after starvation. The animals were sampled at 0, 7, 14 and 21 days from the beginning of the trial. The pituitary and plasma arginine vasotocin (AVT) and isotocin (IT) levels and the hypothalamic pro-vasotocin and pro-isotocin mRNA expression levels were measured. In addition, the mRNA levels of three receptors, avtr v1, avtr v2 and itr, were analyzed in target organs associated with (1) the integration and control of different physiological pathways related to stress and food intake (i.e., the hypothalamus), (2) hormonal release into the bloodstream (i.e., the pituitary), and (3) metabolism and its control (i.e., the liver). The metabolic parameters in the liver were also determined. The hepatosomatic index decreased, and hepatic metabolites were mobilized beginning in the early stages of starvation. Moreover, an over-compensation of these parameters occurred when the fish were re-fed after starvation. In terms of the vasotocinergic and isotocinergic systems, feed restriction induced a clear time-dependent regulation among metabolic organization, stress regulation and orexigenic processes in the mature hormone concentration and pro-peptide and receptor mRNA expression. Our results reveal the important role of the AVT/IT endocrine systems in the orchestration of fish physiology during starvation and re-feeding and indicate their involvement in both central and peripheral organs.

Unraveling vasotocinergic, isotocinergic and stress pathways after food deprivation and high stocking density in the gilthead sea bream

“…Endocrine regulation of stress pathways involves several players (Wendelaar Bonga, 2011;Gorissen and Flik, 2016). In fact, our Research Group has assessed the role of different endocrine systems in the gilthead sea bream after different challenges (Arends et al, 1999(Arends et al, , 2000Martos-Sitcha et al, 2013, 2014aSkrzynska et al, 2017;Ruiz-Jarabo et al, 2017,…”

“…A C C E P T E D M A N U S C R I P T among others). Concerning vasotocinergic and isotocinergic pathways, previous results suggested a role of Avt and It hormones in the stress response (Mancera et al, 2008;Cádiz et al, 2015;Skrzynska et al, 2017) together with a stimulatory metabolic role (Sangiao-Alvarellos et al, 2006). However, the complex action of the Avt/It endocrine cascade after FD and HSD conditions in S. aurata in particular, and in teleost fish in general, remains unclear due to the scarce information available.…”

“…These eight tanks constituted the four experimental groups (in duplicate): 1) fed at low stocking density (control, LSD-F; 5 kg•m -3 ); 2) fed at high stocking density (HSD-F, 40 kg•m -3 ); 3) fooddeprived at LSD (LSD-FD); and 4) food-deprived at HSD (HSD-FD). These experimental conditions have previously been tested by our Research Group and clearly demonstrated an activation of the stress axis in S. aurata (Arends et al, 1999(Arends et al, , 2000Sangiao-Alvarellos et al, 2005, Mancera et al, 2008Skrzynska et al, 2017). Fish from LSD-F and HSD-F groups were fed once a day with commercial dry pellets at a ratio of 1 % of body mass, whereas animals from food-deprived groups (LSD-FD and HSD-FD) were not fed during the 21 days of the experimental time.…”

“…In the last years, our Research Group has focused his research activities on the study of the vasotocinergic and isotocinergic pathways and their interaction with the stress axis in the gilthead sea bream (Sparus aurata) (Kleszczyńska et al, 2006;Sangiao-Alvarellos et al, 2006;Mancera et al, 2008Mancera et al, , 2017Martos-Sitcha et al, 2013, 2014aCádiz et al, 2015;Skrzynska et al, 2017). S. aurata is a highly cultured fish in all the Mediterranean area, and is considered as a model species not only for the aquaculture industry but also at physiological level, given the great knowledge reported in terms of growth, nutrition or energy metabolism, among others (Pavlidis and Mylonas, 2011).…”

Myrcia sylvatica essential oil in the diet of gilthead sea bream (Sparus aurata L.) attenuates the stress response induced by high stocking density

“…Furthermore, some studies demonstrated the lack of a direct relationship between primary and secondary responses (Iversen et al., ; Park et al., ), and under long‐term stressful conditions, other hormones could exert both stress and metabolic regulation. Arginine vasotocin (Avt), a neurohypophysial hormone in non‐mammalian vertebrates that presents a pleiotropic function in both stress and metabolic pathways of teleosts, may be another important player mediating metabolic and stress adaptation (Martos‐Sitcha, Wunderink, Gozdowska, Mancera, & Martínez‐Rodríguez, ; Sangiao‐Alvarellos et al., ; Skrzynska, Martos‐Sitcha, Martínez‐Rodríguez, & Mancera, ; Skrzynska et al., ), as the hypothalamic neurons responsible for the synthesis and release of Avt also innervate the adenohypophyseal cells from the HPI axis (Moons, Cambre, Batten, & Vandesande, ). In addition to increasing lactate levels in the control group, HD also reduced hepatic glycogen storage in all diets tested, indicating the activation of glycogenolytic processes to increase the supply of glucose due to energy expenditure resulting from HD condition.…”