Cloning and tissue distribution of appetite-regulating peptides in pirapitinga (Piaractus brachypomus)

Pirapitinga (or red-bellied pacu, Piaractus brachypomus, Characiforme, Serrasalmidae) is an economically important South American fish for which the endocrine mechanism of the regulation of feeding has never been examined. To better understand these mechanisms, cDNAs encoding the appetite-regulating peptides orexin, cocaine- and amphetamine-regulated transcript (CART), apelin, cholecystokinin (CCK), peptide YY (PYY), leptin and ghrelin were isolated in pirapitinga and their mRNA distributions examined in peripheral tissues and brain. When compared to other fish, the sequences obtained for all peptides were most similar to those of other Characiforme fish (i.e. Mexican cavefish) and Siluriformes (catfish) as well as Cypriniformes (i.e. goldfish, zebrafish). All peptides were widely expressed within the brain. With the exception of CART, which was only expressed in brain, the mRNAs of all peptides were present in several peripheral tissues, including gastrointestinal tract, kidneys and gills. The widespread and peptide-specific distributions suggest that each peptide might have distinct physiological actions in the brain and on peripheral tissues, in particular on the gastrointestinal tract, which include feeding regulation. This preliminary study opens new avenues for further functional studies on the endocrine regulation of feeding in Serrasalmidae fish, including pirapitinga.