Characterization, tissue distribution and regulation by fasting of the agouti family of peptides in the sea bass (Dicentrarchus labrax)

The melanocortin system is one of the most complex hormonal systems in vertebrates. Atypically, the signaling of melanocortin receptors is regulated by the binding of endogenous antagonists, named agouti-signaling protein (ASIP) and agouti-related protein (AGRP). Teleost specific genome duplication (TSGD) rendered new gene copies in teleost fish and up to four different genes of the agouti family of peptides have been characterized. In this paper, molecular cloning was used to characterize mRNA of the agouti family of peptides in sea bass. Four different genes were identified: AGRP1, ASIP1, AGRP2 and ASIP2. The AGRP1 gene is mainly expressed in the brain whereas ASIP1 is mainly expressed in the ventral skin. Both ASIP2 and AGRP2 are expressed in the brain and the pineal gland but also in some peripheral tissues. Immunocytochemical studies demonstrated that AGRP1 is exclusively expressed within the lateral tuberal nucleus, the homologue of the mammalian arcuate nucleus in fish. Long-term fasting (8-29. days) increased the hypothalamic expression of AGRP1 but depressed AGRP2 expression (15-29. days). In contrast, the hypothalamic expression of ASIP2 was upregulated during short-term fasting suggesting that this peptide could be involved in the short term regulation of food intake in the sea bass. © 2014 Elsevier Inc.This work was supported by Grants AGL2010-22247-C03-01 and CSD 2007-00002 from the Spanish Science and Education Ministry (MEC) to J.M.C.-R. Additional funding was obtained from the “Generalitat Valenciana” (PROMETEO 2010/006). M.J.A. and R.C. are recipients of a “Juan de la Cierva” research contract (2009) and an FPI fellowship, respectively, from the Spanish Science and Innovation Ministry.Peer Reviewe