Influence of Dietary Oil Content and Conjugated Linoleic Acid (CLA) on Lipid Metabolism Enzyme Activities and Gene Expression in Tissues of Atlantic Salmon (Salmo salar L.)

摘要

The overall objective is to test the hypothesis that conjugated linoleic acid(CLA) has beneficial effects in Atlantic salmon through affecting lipid andfatty acid metabolism. The specific aims of the present study were to determinethe effects of CLA on some key pathways of fatty acid metabolism including fattyacid oxidation and highly unsaturated fatty acid (HUFA) synthesis. Salmon smoltswere fed diets containing two levels of fish oil (low, ~18% and high, ~34%)containing three levels of CLA (a 1:1 mixture of 9-cis,trans-11 and trans-10,cis-12 at 0, 1 and 2% of diet) for 3 months. The effects of dietary CLA onHUFA synthesis and β-oxidation were measured and the expression of key genes inthe fatty acid oxidation and HUFA synthesis pathways, and potentially importanttranscription factors, peroxisome proliferators activated receptors (PPARs),determined in selected tissues. Liver HUFA synthesis and desaturase geneexpression was increased by dietary CLA and decreased by high dietary oilcontent. Carnitine palmitoyltransferase-I (CPT-I) activity and gene expressionwere generally increased by CLA in muscle tissues although dietary oil contenthad relatively little effect. In general CPT-I activity or gene expression wasnot correlated with β-oxidation. Dietary CLA tended to increase PPARα and β geneexpression in both liver and muscle tissues, and PPARγ in liver. In summary,gene expression and activity of the fatty acid pathways were altered in responseto dietary CLA and/or oil content, with data suggesting that PPARs are alsoregulated in response to CLA. Correlations were observed between dietary CLA,liver HUFA synthesis and desaturase gene expression, and liver PPARα expression,and also between dietary CLA, CPT-I expression and activity, and PPARαexpression in muscle tissues. In conclusion, this study suggests that dietaryCLA has effects on fatty acid metabolism in Atlantic salmon and on PPARtranscription factors. However, further work is required to assess the potentialof CLA as a dietary supplement, and the role of PPARs in the regulation of lipidmetabolism i