The Interplay between Central and Peripheral Systems in Feed Intake Regulation in European Seabass (Dicentrarchus labrax) Juveniles

Abstract

The present study aimed to evaluate the effects of feeding or feed deprivation on the orexigenic and anorexigenic responses at the central (whole brain) and peripheral (anterior and posterior intestine, stomach, and liver) system levels in European seabass. For this purpose, a group of fish (208 g) was fed a single meal daily for 8 days (fed group) and another group was feed-deprived for 8 days (unfed group). Compared to the fed group, in the whole brain, feed deprivation did not induce changes in npy, agrp1, and cart2 expression, but increased agrp2 and pomc1 expression. In the anterior intestine, feed deprivation increased cck expression, while in the posterior intestine, the npy expression increased and pyyb decreased. In the stomach, the ghr expression decreased regardless of the feeding status. The hepatic lep expression increased in the unfed fish. The present results suggest a feed intake regulation mechanism in European seabass similar to that observed in other teleosts.

Keywords: anorexigenic; fasting; feeding; orexigenic.

Figure 1

Diagram showing the interaction of peptides and hormones at the central level (brain) and peripheral levels (intestine, liver, and stomach) involved in the regulation of food intake in fish and how they can be affected by feeding deprivation and feeding. agrp: Agouti-related peptide; cart: cocaine- and amphetamine-regulated transcript; cck: cholecystokinin; npy: neuropeptide Y; pomc: proopiomelanocortin; pyy: peptide YY; ghr: ghrelin.

Figure 2

Plasma glucose (a), total cholesterol (b), triglyceride (c), and phospholipid (d) levels of European seabass juveniles after 8 days pf feed deprivation (unfed) or continuous feeding (fed). Values are presented as means (n = 6) and standard error (SE). Small letters denote significant differences in sampling times regardless of feeding conditions and capital letters denote significant differences in sampling times between feeding conditions.

Figure 3

Orexigenic (a) and anorexigenic (b) expressions in the central system of European seabass juveniles after 8 days of feed deprivation (unfed) or continuous feeding (fed). Data were normalized with two housekeeping genes, ribosomal 18S (18S) and α-elongation factor (ef1), according to [56]. Values are presented as means and standard error (SE). Small letters denote significant differences in sampling time under the same feeding conditions and capital letters denote significant differences in sampling times regardless of the feeding conditions. py: neuropeptide Y; agrp: Agouti-related protein; cart: cocaine-and amphetamine-regulated transcript; pomc: proopiomelanocortin.

Figure 4

mRNA relative expression of main hormones and peptides in the peripheral systems anterior intestine (a), posterior intestine (b), liver and stomach (c) of European seabass days after feed deprivation (unfed) or continuous feeding (fed). Data were normalized with two housekeeping genes, ribosomal 18S (18S) and α-elongation factor (ef1), according to [56]. Values are presented as means and standard error (SE). Small letters denote significant differences in sampling time under the same feeding conditions and capital letters denote significant differences in sampling times regardless of feeding conditions. npy: neuropeptide Y; pyyb: peptide YYb; cck: cholecystokinin; lep: leptin; ghr: ghrelin.

Figure 4

mRNA relative expression of main hormones and peptides in the peripheral systems anterior intestine (a), posterior intestine (b), liver and stomach (c) of European seabass days after feed deprivation (unfed) or continuous feeding (fed). Data were normalized with two housekeeping genes, ribosomal 18S (18S) and α-elongation factor (ef1), according to [56]. Values are presented as means and standard error (SE). Small letters denote significant differences in sampling time under the same feeding conditions and capital letters denote significant differences in sampling times regardless of feeding conditions. npy: neuropeptide Y; pyyb: peptide YYb; cck: cholecystokinin; lep: leptin; ghr: ghrelin.