Mengqing Liang

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.

Moderate levels of dietary arachidonic acid reduced lipid accumulation and tended to inhibit cell cycle progression in the liver of Japanese seabass Lateolabrax japonicus

To investigate the physiological roles of dietary arachidonic acid (ARA) in fish, a feeding trial with Japanese seabass was conducted, followed by a hepatic transcriptome assay. Six experimental diets differing basically in ARA level (0.05%, 0.22%, 0.37%, 0.60%, 1.38% and 2.32% of dry matter) were used in the feeding trial. Liver samples from fish fed diets with 0.05% and 0.37% ARA were subjected to transcriptomic assay, generating a total of 139 differently expressed unigenes, which were primarily enriched in lipid metabolism and cell cycle-related signaling pathways. Then, qRT-PCR validation on lipid metabolism and cell cycle-related genes as well as corresponding enzyme-linked immunosorbent assay of selected proteins were conducted with liver samples from all six groups. Moderated ARA levels reduced lipogenesis and stimulated β-oxidation concurrently, but high ARA levels seemed to affect lipid metabolism in complicated ways. Both gene expression and protein concentration of cell cycle-related proteins were decreased by moderate levels of dietary ARA. The lipid content and fatty acid composition in fish confirmed the transcription and protein concentration results related to lipid metabolism. In conclusion, moderate levels of dietary ARA (0.37% and 0.60%) reduced lipid accumulation and tended to inhibit cell cycle progression in the liver of Japanese seabass.