Exposição à salinidade induz alteração na expressão de genes relacionados à regulação do apetite e danos oxidativos na tilápia-do-Nilo (Oreochromis niloticus)

Abstract

Tilapia is one of the most important species in aquaculture and a primary source of protein in many developing countries. In recent years, studies have been carried out to efficiently develop the production of this species in brackish water. In fish, environmental variations such as fluctuations in salinity can induce changes in feeding behavior and growth. Currently, little is known about the influence of high salinities on genetic variations related to endocrine factors that regulate appetite in fish, more specifically in the species Oreochromis niloticus. In the context of fish farming, a better understanding of these variations can lead to the improvement of the species and increasing the quality of production of farmed fish. Therefore, the objective of this study was to identify the marker genes of appetite regulation in tilapia exposed to different salinities. In addition, the study aimed to sequence and characterize the genes cart, cck and pyy and quantify their expression in the brain and intestine of fish through the quantitative reverse transcription polymerase chain reaction. The animals were exposed to 6 and 12ppt of salt for 21 days. Oxidative parameters such as lipid peroxidation, reactive oxygen species (ROS), DNA damage, and blood cell membrane fluidity were quantified by flow cytometry. The results indicated an increase in the expression of genes cart, pyy and cck and a decrease in the expression of npy in the brain of fish exposed to higher salt concentration, while cck had its expression up- regulated and npy was down-regulated in the intestine. These results together with other adaptive responses may have caused the significant decrease in final body weight, specific growth, and observed weight gain. In addition, we show oxidative damage in blood cells, since lipid peroxidation, ROS, DNA damage had its high levels in fish exposed to 12ppt. Thus, this study generated important data for the development of biotechnologies that help to improve the production of farmed fish.