Dietary with proper ratio of alpha‐linolenic acid to linoleic acid enhanced the unsaturated fatty acids deposition of Chinese perch ( Siniperca Chuatsi )

The study explored the effect of increasing α-linolenic acid (LNA; 18:3n-3)-to-linoleic acid (LA; 18:2n6) ratios on the growth, fatty acid (FA) composition/deposition, hepatic expression of various genes responsible for fatty acid metabolism, fatty acid binding proteins (fabp1) from the level of DNA methylation and liver/intestinal histology in Chinese perch, Siniperca chuatsi. A total of 5 isonitrogenous and isolipidic diets were formulated at LNA/LA ratios of 0.15, 0.38, 0.94, 1.43 and 2.94, hereafter referred to as D1, D2, D3, D4 and D5, respectively, and fed to the fish that could accept artificial diets successfully for 90 days. Results showed that the D3 diet led to significantly higher growth than all other treatments. Additionally, the D3 diet led to significantly longer intestinal villi, greater number of hepatic lipid droplets and higher hepatic triglyceride (TG) content. With increasing LNA/LA ratios, the LNA content increased and LA decreased in both the liver and muscle. Dietary LNA/LA ratios markedly affected the relative expression level of some genes of FA metabolism in hepatic, including fatty acid synthase (fas), fatty acid binding proteins (fabp1), fatty acid desaturase 2 (fads2) and fatty acid elongase 5 (elovl5). The D3 diet enhanced hepatic FA metabolism in hepatic markedly and thus promoted the arachidonic acids (ARA) deposition. In addition, it can promote the deposition of eicosapentaenoic acids (EPA) in muscle. It was shown that dietary with the ratio of LNA to LA being 0.94 can enhance the FA metabolism in hepatic markedly and thus promoted the polyunsaturated fatty acid (PUFA) deposition. And we found that there was high DNA methylation in six CpG sites of fabp11 for D1 group and D3 group, but D3 group had no marked difference with control group (D1). Finally, through the broken-line regression analysis, it was found that the optimal dietary LNA/LA ratio of Chinese perch was 0.81.