Identification, tissue expression, and response to various fatty acid inductions of the fabp gene family in grass carp (Ctenopharyngodon idella)

The grass carp (Ctenopharyngodon idella) holds significant economic value worldwide. However, intensive farming practices often result in lipid metabolic disorder of fish. It is essential to explore the influence of pivotal genes in the process of fat accumulation, particularly from the perspective of fat transport. Fatty acid binding proteins (FABPs) are crucial for selectively binding and transporting free fatty acids (FAs) within cells. Nevertheless, the types of fabp genes in the grass carp genome and their responses to various FAs remain unclear. In the current study, exhaustive bioinformatic analysis identified nine fabp genes in the grass carp genome: fabp1a, fabp1b.1, fabp2, fabp3, fabp6, fabp7a, fabp10a, fabp11a, and fabp11b. Although these genes showed widespread expression across various tissues, each gene displayed distinct preferences for specific primary expression tissues. Notably, fabp1a exhibited prominent expression in muscle, fabp1b.1 in abdominal fat, fabp2 and fabp6 in the intestine, fabp7a in the brain, fabp10a in the hepatopancreas, and fabp11a showed maximal expression in the eye. Findings from primary grass carp hepatocytes revealed that the addition of palmitic acid (PA), high concentrations oleic acid (OA) and docosahexaenoic acid (DHA) (400 µM), significantly increased intracellular lipid accumulation. Intriguingly, the addition of PA resulted in increased expression of fabp2 and fabp11a, while DHA significantly enhanced the expression of fabp7a (P < 0.01). Given that the accumulated FAs are primarily saturated fatty acids, these results suggest that regulating fabps, especially fabp2 and fabp11a, could be a strategy to control fat deposition in grass carp.