Chitosan-Mediated Expression of Caenorhabditis elegans fat-1 and fat-2 in Sparus aurata: Short-Term Effects on the Hepatic Fatty Acid Profile, Intermediary Metabolism, and Proinflammatory Factors

A single dose of chitosan-tripolyphosphate (TPP) nanoparticles carrying expression plasmids for fish codon-optimized Caenorhabditis elegans fat-1 and fat-2 was intraperitoneally administered to gilthead seabream (Sparus aurata) to stimulate the biosynthesis of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) and evaluate subsequent short-term effects on liver intermediary metabolism and immunity. Seventy-two hours post-injection, the upregulation of fat-1 elevated eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and total n-3 fatty acids in the liver, while fat-2 enhanced DHA and n-3 fatty acids. Co-expression of fat-1 and fat-2 increased EPA, DHA, PUFA, and the total n-6 and n-3 LC-PUFA, while reducing plasma triglycerides. The expression of fat-1 and fat-2 suppressed hepatic lipogenesis by downregulating srebf1 and pparg, and consequently key genes in fatty acid synthesis (acaca, acacb, fasn, scd1, and fads2). In contrast, the co-expression of fat-1 and fat-2 upregulated hnf4a, chrebp, and pfkl, a rate-limiting enzyme in glycolysis. Furthermore, fat-1 and fat-2 reduced hepatic proinflammatory markers such as tnfa and nfkb1. In addition to enhancing EPA and DHA biosynthesis, promoting glycolysis, and suppressing lipogenesis, our findings suggest that the short-term expression of C. elegans fat-1 and fat-2 in the liver may also reduce inflammation and, therefore, could impact the health and growth performance of cultured fish.