Dietary luteolin alleviates the slow-growing and hepatic fat deposition in large yellow croaker (Larimichthys crocea) caused by replacement of fish oil with soybean oil in feed

The complete replacement of dietary fish oil with soybean oil disrupts fat metabolism in large yellow croaker ( Larimichthys crocea ), leading to a severe compromise in growth performance. Accordingly, this study assessed whether luteolin, a hepatoprotective compound, could mitigate the adverse effects of completely replacing fish oil (FO) with soybean oil (SO) in the diet of large yellow croaker. A 10-week feeding trial was implemented with an experimental design consisting of five treatments: a positive control (100 % FO), a negative control (100 % SO), and three experimental treatments formulated with 100 % SO and graded inclusion level of luteolin at 0.02 %, 0.04 %, and 0.08 %. The results showed that luteolin significantly alleviated the initial weight from 28 g (SO) to 40 g (luteolin0.04 %). Compared to the SO, adding luteolin had a series of metabolically important effects: i) increased crude protein content from 13.28 % (SO) to 13.91 % (luteolin0.02 %) and reduced the crude fat content from 6.93 % (SO) to 6.47 % (luteolin0.02 %) in the whole body; ii) reduced triglycerides and cholesterol levels in the liver and blood; iii) modified liver fatty acid profiles, with a reduction of n-6 PUFA and increase in n-3 PUFA, especially n-3 LC-PUFA; iv) upregulation of fat synthesis genes (srebp1, fas and dgat1), downregulation of fat transport genes (cd36 and fabp3), and downregulation of lipolysis genes (ppar α and cpt1); v) reduction of malondialdehyde and the inhibition of antioxidant enzyme activity (CAT and SOD) caused by dietary SO; and vi) inhibition of induced over-expression of phosphatases (AKP and ACP) and transaminases (ALT and AST). • Application of luteolin in marine fish such as the large yellow croaker, along with its optimal dosage. • Preliminary investigation about flavonoid-based additives regulate lipid metabolism, as an evidence for further application. • Examine the effects of luteolin on fish growth and health when vegetable oil replaces fish oil for reducing costs.