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 as a result of affecting lipid and FA metabolism. The specific aims of the present study were to determine the effects of CLA on some key pathways of FA metabolism, including FA oxidation and highly unsaturated FA (HUFA) synthesis. Salmon smolts were fed diets containing two levels of fish oil (low, similar to 17%, and high, similar to 34%) containing three levels of CLA (a 1:1 mixture of cis-9,trans-11 and trans-10,cis-12 at 0, 1, and 2% of diet) for 3 mon. The effects of dietary CLA on HUFA synthesis and P-oxidation were measured, and the expression of key genes in the FA oxidation and HUFA synthesis pathways, and the potentially important transcription factors peroxisome proliferators activated receptors (PPAR), were determined in selected tissues. Liver HUFA synthesis and desaturase gene expression was increased by dietary CLA and decreased by high dietary oil content. Carnitine pal mitoyltransferase-I (CPT-1) activity and gene expression were generally increased by CLA in muscle tissues although they were relatively unaffected by dietary oil content. In general CPT-I activity or gene expression was not correlated with beta-oxidation. Dietary CLA tended to increase PPAR alpha and beta gene expression in both liver and muscle tissues, and PPAR gamma in liver. In summary, gene expression and activity of the FA pathways were altered in response to dietary CLA and/or oil content, with data suggesting that PPAR are also regulated in response to CLA. Correlations were observed between dietary CLA, liver HUFA synthesis and desaturase gene expression, and liver PPAR alpha expression, and also between dietary CLA, CPT-I expression and activity, and PPAR alpha expression in muscle tissues. In conclusion, this study suggests that dietary CLA has effects on FA metabolism in Atlantic salmon and on PPAR transcription factors. However, further work is required to assess the potential of CLA as a dietary supplement, and the role of PPAR in the regulation of lipid metabolism in fish.