Lipidomic analysis of phospholipids and transcript expression of lipid metabolism genes in the liver and muscle of Atlantic salmon fed microbial oil and canola oil.

The increasing global demand for aquaculture products requires sustainable fish feed strategies. This study investigated how replacing fish oil with microbial oil (MO) and canola oil (CO) combinations affects lipid metabolism and gene expression in Atlantic salmon (Salmo salar), correlating these changes with phospholipid profiles. Four isonitrogenous, isoenergetic diets were tested: 20% fish oil (FO); 10% fish oil +10% CO (FO/CO); 15% CO + 5% MO (CO/MO); and 10% CO + 10% MO (MO-10). After 16 weeks, liver and skeletal muscle tissues were sampled for lipidomics and gene expression analysis. Multivariate analysis revealed distinct dietary group separations. The CO/MO diet induced the highest hepatic expression of de novo lipogenesis gene fatty acid synthase b while suppressing fatty acid oxidation marker acyl-CoA oxidase 1, indicating lipid storage promotion. Inflammatory marker arachidonate 12-lipoxygenase was associated with groups with reduced ω3 LC-PUFA (FO/CO, CO/MO). Muscle tissue showed subtler but diet-specific gene expression patterns, with de novo lipogenesis genes (stearoyl-CoA desaturase b, ATP citrate lyase 2) associated with decreased ω3 LC-PUFA (i.e., EPA and DHA) and correlating with monounsaturated fatty acids. The MO-10 group mirrored FO-fed fish, demonstrating successful fish oil replacement at 10% inclusion. Lipidomic pathway analysis revealed diet-induced phospholipid remodelling, for example, enhanced PE-to-PC conversion in the FO/CO and CO/MO groups, suggesting membrane-fluidity and inflammatory modulation. These results demonstrate tissue-specific metabolic adaptations to alternative lipid sources, with 10% CO + 10% MO effectively substituting for fish oil while maintaining metabolic profiles in the trial timeline. The findings advance our understanding of lipid metabolism regulation in salmon and support sustainable feed development for aquaculture and enhanced nutritional quality of aquaculture products.