Functional divergence of <i>fabp</i> genes in common carp and the effects of high‐fat diets supplemented with linalool on growth, fatty acid composition and <i>fabp</i> gene expressions

The fatty acid-binding protein (fabp) genes involved in β-oxidation were identified and characterized in the common carp (Cyprinus carpio) genome. Fish were then fed high-fat diets supplemented with various amounts of linalool, a natural peroxisome proliferator-activated receptor α ligand, for 9 weeks. We determined that C. rapio genome contains 19 fabp genes. The mRNA expression of 4R-whole genome duplication copies of fabp genes was differently regulated by the diets, except for fabp3a.1/fabp3a.2 and fabp7a.1/fabp7a.2. These findings indicate that the transcriptional regulatory mechanisms governing nutritional regulation by linalool-supplemented diets for these specific genes do not show significant differences. Linalool-supplemented diets markedly changed fatty acid composition in the liver and muscle. They also played a positive role in mitigating adverse health effects associated with high-fat diets in common carp. Conversely, the highest lipid amount in the liver was found in fish fed high-fat diet 3, which also had the lowest feed conversion ratio. We concluded that the effects of linalool as a feed additive in common carp are limited. However, detailed studies with various linalool concentrations in different weights of common carp and other farmed fish species should be conducted to reach a more definitive result.