Lipid metabolism in juvenile of Yellowtail, Seriola dorsalis fed diets containing different lipid levels

Abstract

This study aimed to evaluate how lipids are being catabolized or retained when offered under restriction to optimum levels by determining the genes involved in the lipid metabolism of Seriola dorsalis (yellowtail) juveniles. An eight-week nutritional trial was carried out using four isoproteic diets with various levels of lipids. Four diets were then formulated to contain 60, 90, 130, and 150 g crude fat kg−1 diet. One hundred and twenty juvenile S. dorsalis (19.15 g ± 0.67 g, mean ± SE) were located in 12 tanks of 500 L each in triplicate groups. After eight weeks of feeding experiment, while no differences were revealed in growth, significant differences were obtained in lipid deposition and lipid gene expression. While FA profile and pparα expression results corroborate that ARA, EPA, and DHA are preserved, mainly in the liver, in the muscle tissue, EPA increased significantly, while ARA and DHA remained also preserved. The results suggested that the SFAs palmitic and stearic are mainly catabolized, and then the MUFAs with oleic acid and linoleic acid. However, the lipid metabolism is reflected by the gene expression, where we found several differences. The increase in pparα shows the activation from saturated fatty acids when the palmitoleic acid is increased to be used in the β-oxidation into the mitochondria. The cptl1, which mediates long-chain fatty acid uptake into the mitochondrion, decreases at higher crude fat (CF) levels. In comparison, the acadvl dedicated to catalyzing the LC-PUFAs into the mitochondrial β-oxidation is only expressed when the LC-PUFAs are in excess. It is concluded that apart from ratification that 13% CF is the ideal amount for S. dorsalis, it is suggested that SFAs primarily get oxidized and then the MUFAs, and linoleic acid, whereas the LC-PUFAs are only oxidized when offered in excess.