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

Novel hypophysiotropic AgRP2 neurons and pineal cells revealed by BAC transgenesis in zebrafish

“…Zebrafish agrp2 mRNA is expressed in the pineal gland282930 and was suggested, on the basis of morpholino-mediated knock-down experiments, to regulate background pigment adaptation for camouflage30. Pineal gland expression of agrp2 was reported in sea bass ( Dicentrarchus labrax )20, and we have also detected its expression in the pineal gland of Nile tilapia ( Oreochromis niloticus ) and rainbow trout ( Oncorhynchus mykiss ; unpublished data). This suggests a conserved pineal gland expression of agrp2 among teleosts.…”

“…This finding suggests that AgRP2 neurons are hypophysiotropic and may affect pituitary hormonal secretion. Expression of agrp2 mRNA was previously detected by PCR in the brains of sea bass20, Atlantic salmon ( Salmo salar )18 and pufferfish ( Takifugu rubripes )17, suggesting that the preoptic AgRP2 system may not be specific to zebrafish. Thus, the present anatomical findings, together with previous studies in zebrafish, suggest this is an example of subfunctionalization, in which agrp1 has retained its function as a central regulator of food consumption2762, while agrp2 has taken over the putative neuroendocrine role of agrp in the pituitary.…”

“…Teleost fish, such as the zebrafish, possess two agrp genes, agrp1 and agrp2 1718192021, possibly as a result of a whole-genome duplication event2223242526. Tissue distribution analysis of agrp1 and agrp2 transcripts in several teleost fish species, mainly by RT-PCR, has indicated that both genes are expressed in the brain, as well as in variety of peripheral tissues1317181920. In the zebrafish, agrp1 is expressed exclusively in the hypothalamus, and, like mammalian Agrp , was shown to be involved in feeding behavior1227.…”

The Neuroendocrine Regulation of Food Intake in Fish: A Review of Current Knowledge

“…In fish, AgRP has been identified in several species, including teleosts (e.g., goldfish Carassius auratus Cerdá-Reverter and Peter, 2003 and zebrafish Danio rerio Song et al, 2003, Atlantic salmon Salmo salar Murashita et al, 2009a, and seabass Dicentrarchus labrax Agulleiro et al, 2014, pufferfish Takifugu rubripes Klovins et al, 2004; Kurokawa et al, 2006), who have two genes products (AgRP1 and AgRP2; Cérda-Reverter et al, 2011) and Holocephali (Chimaeriforme, elephant fish Callorhinchus milii Västermark and Schioth, 2011). …”

“…However, this is contradicted by another study in carp showing that brain AgRP mRNA expression decreases after fasting and increases after re-feeding (Wan et al, 2012). In seabass (Perciforme), long-term fasting increases hypothalamic expression of AgRP1 but decreases that of AgRP2 (Agulleiro et al, 2014), suggesting an isoform-specific orexigenic action.…”