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