Post-feeding Molecular Responses of Cobia (Rachycentron canadum): RNA-Sequencing as a Tool to Evaluate Postprandial Effects in Hepatic Lipid Metabolism.

Abstract

We used transcriptome sequencing to investigate the hepatic postprandial responses of Rachycentron canadum (cobia), an important commercial fish species. In total, 150 cobia juveniles (50 per tank, triplicate) were fed ad libitum with a commercial diet for 7days, fasted for 24h, and fed for 10min. The liver was sampled 10min prior to feeding and 30min, 1, 2, 4, 8, 12, and 24h after the feeding event. Each sample was evaluated in terms of liver fatty acid profile and gene expression. Differential gene expressions were evaluated, focusing on fatty acid synthesis and oxidation pathways. In general, the liver fatty acid profile reflected diet composition. Docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) levels increased at 8 to 12h but decreased at 24h after the feeding event. A high number of differentially expressed genes (DEGs) were observed comparing fish that fasted for 8h with those fasted for 30min and 24h, while a reduced number of DEGs was observed comparing individuals who fasted for 30min compared with those who fasted for 24h. Similarly, the main differences in the expression of genes related to the fatty acid biosynthesis and oxidation pathways were noticed in individuals who fasted for 8h compared with those who fasted for 30min and 24h. The results suggested that the adequate time to sample the individuals ranged between 8 and 12h after the meal since, apparently, after 24h, differential gene expression was not necessarily influenced by food intake.