Supplementary material from "Interaction between ω6 and ω3 fatty acids of different chain lengths regulates Atlantic salmon hepatic gene expression and muscle fatty acid profiles"

Atlantic salmon smolts (approx. 20-month old) were fed experimental diets with different combinations of omega-6:omega-3 fatty acids (FAs) (high-ω6, high-ω3, or balanced) and EPA + DHA levels (0.3, 1.0 or 1.4%) for 12 weeks. Muscle FA (% total FA) reflected dietary C₁₈-polyunsaturated FA; however, muscle EPA % and content (mg g⁻¹) were not different in salmon-fed high-ω3 or balanced diets. Muscle DHA % was similar among treatments, while DHA content increased in fish-fed 1.4% EPA + DHA, compared with those fed 0.3–1.0% EPA + DHA combined with high-ω6 FA. Muscle 20 : 3ω6 (DGLA) content was highest in those fed high-ω6 with 0.3% EPA + DHA. Hepatic quantitative polymerase chain reaction showed that the monounsaturated FA synthesis-related gene, scdb, was upregulated in fish-fed 1.0% EPA + DHA with high-ω6 compared to those fed 0.3% EPA + DHA. In high-ω3 fed salmon, liver elovl2 transcript levels were higher with 0.3% EPA + DHA than with 1.0% EPA + DHA. In high-ω6 fed fish, elovl2 did not vary with EPA + DHA levels, but it was positively correlated with muscle ARA, 22 : 4ω3 and DGLA. These results suggest dietary 18 : 3ω3 elongation contributed to maintaining muscle EPA + DHA levels despite a two- to threefold change in dietary proportions, while 18 : 2ω6 with 0.3% EPA + DHA increased muscle DGLA more than ARA. Positive correlations between hepatic elovl2 and fabp10a with muscle ω6:ω3 and EPA + DHA + ARA, respectively, were confirmed by reanalysing data from a previous salmon trial with lower variations in dietary EPA + DHA and ω6:ω3 ratios.This article is part of the XX ‘The next horizons for lipids as ‘trophic biomarkers’: evidence and significance of consumer modification of dietary fatty acids’.