Influence of Dietary Lipids and Environmental Salinity on the n-3 Long-Chain Polyunsaturated Fatty Acids Biosynthesis Capacity of the Marine Teleost Solea senegalensis

Abstract

Fish vary in their ability to biosynthesise long-chain polyunsaturated fatty acids (LC-PUFA) depending upon the complement and function of key enzymes commonly known as fatty acyl desaturases and elongases. It has been reported in Solea senegalensis the existence of a Δ4 desaturase, enabling the biosynthesis of docosahexaenoic acid (DHA) from eicosapentaenoic acid (EPA), which can be modulated by the diet. The present study aims to evaluate the combined effects of the partial replacement of fish oil (FO) with vegetable oils and reduced environmental salinity in the fatty acid composition of relevant body compartments (muscle, hepatocytes and enterocytes), the enzymatic activity over α-linolenic acid (ALA) to form n-3 LC-PUFA through the incubation of isolated hepatocytes and enterocytes with [1-14C] 18:3 n-3, and the regulation of the S. senegalensis fads2 and elovl5 in the liver and intestine. The presence of radiolabelled products, including 18:4n-3, 20:4n-3 and EPA, provided compelling evidence that a complete pathway enabling the biosynthesis of EPA from ALA, establishing S. senegalensis, has at least one Fads2 with ∆6 activity. Dietary composition prevailed over salinity in regulating the expression of fads2, while salinity did so over dietary composition for elovl5. FO replacement enhanced the proportion of DHA in S. senegalensis muscle and the combination with 20 ppt salinity increased the amount of n-3 LC-PUFA in hepatocytes.

The Impact of Rearing Salinity on Flesh Texture, Taste, and Fatty Acid Composition in Largemouth Bass Micropterus salmoides

“…In the present research, the contents of most fatty acids detected in muscle tissue were affected significantly by water salinity ( Table 2 ), among which the contents of MUFA and n-6 PUFA in the S 3 and S 9 groups were significantly lower than S 0 group ( p < 0.05), while the contents of n-3 LC-PUFA, including C20: 5n-3 (EPA) and C22: 6n-3 (DHA), and the ratio of n-3 PUFA to n-6 PUFA were significantly higher in S 3 and S 9 groups than S 0 group ( p < 0.05). In fact, salinity promotes deposition of EPA, and DHA has been well-verified in several fish species [ 5 , 39 , 40 ]. Therefore, it seems a practical approach to rearing fish in water with proper salinity to enhance EPA and DHA deposition from the perspective of human nutrition.…”