Identification, characterization and nutritional regulation of fatty acid‐binding protein ( fabp ) genes by vegetable oils in European seabass ( Dicentrarchus labrax ) reared in low water temperatures

Abstract

Dietary n-3 highly unsaturated fatty acids (HUFAs), which are low in vegetable oils (VO), are natural ligands of fatty acid-binding protein (fabp) genes, which function in molecular n-3 HUFAs metabolism in fish. Low water temperature (LWT) also affects fish fatty acid (FA) metabolism. Therefore, in this study, we investigated mRNA expression levels of fabp genes in European seabass (Dicentrarchus labrax) reared in LWTs. For this purpose, we cloned and characterized open reading frames of 10 fabp genes. Changes in the expression of fabp genes to VO-based diets for 60 days and fish oil (FO)-based diet for 30 days were determined. The present study's results suggest the following: (1) D. labrax fabp genes are orthologues of vertebrate fabp/FABP genes. (2) fabp1b.1/fabp1b.2 and fabp7a/fabp7b are retained in the D. labrax genome most likely because of the subfunctionalization. (3) The variation in tissue-specific expression of fabp10a/fabp10b and fabp11a/fabp11b paralogues also provides evidence of subfunctionalization; however, nutrigenomic results did not support this observation. Therefore, more detailed promoter analyses are needed to better understand their retentions in the D. labrax genome. (4) Feeding D. labrax with a FO-based diet following feeding with VO-based diets is insufficient for molecular FA metabolism recovery. This study is the first report on the characterization and nutritional regulation of fabp genes by dietary FAs in D. labrax reared in LWTs and suggests that transcriptional control of fabp genes by agonists would be helpful to maintain lipid homeostasis, protect fish health and increase fish welfare for sustainable aquaculture production.