Cloning and characterization of fatty acid-binding proteins (fabps) from Japanese seabass (Lateolabrax japonicus) liver, and their gene expressions in response to dietary arachidonic acid (ARA)

In the present study, putative cDNA of five fabp isoforms, i.e., fabp1, fabp2, fabp3, fabp4, and fabp7, was cloned and characterized from the liver of Japanese seabass (Lateolabrax japonicus), and their expression in response to diets with different arachidonic acid (ARA) levels (0.05%, 0.22%, 0.37%, 0.60%, 1.38% and 2.32% of dry matter) was investigated following a feeding trial. The Japanese seabass fabps showed high identity to their orthologs in other fish species and mammals. However, a specific fabp of Japanese seabass showed much lower identity to other Japanese seabass fabps. fabp1 has high expressions in liver and intestine, whereas fabp2 is mainly expressed in the gastrointestinal tract. The highest expression level of fabp3, fabp4, and fabp7 was observed in muscle, eye, and liver respectively. Different tissue expression patterns of fabp2, fabp4, and fabp7 between Japanese seabass and other teleost may indicate specific evolutionary Fabp functions in Japanese seabass. Moderate levels of dietary ARA (0.37-0.60%) enhanced the gene expressions of fabp1 in liver and intestine, fabp2 in intestine, and fabp3 in intestine, whereas excess dietary ARA levels (1.38-2.323%) were ineffective. The highest level of dietary ARA (2.32%) increased only the expression of fabp3 in muscle compared to the control diet. Gene expressions of fabp3 and fabp7 in liver, and fabp4 in liver, intestine, and muscle were not significantly influenced by dietary ARA. To our knowledge, this is the first study investigating the regulation of fabp expressions by dietary ARA.