Influence of dietary fatty acids on muscle fatty acid composition and expression levels of Δ6 desaturase-like and Elovl5-like elongase in common carp (Cyprinus carpio var. Jian)

The effects of dietary fatty acids on muscle fatty acid composition and liver expression levels of Δ6 desaturase-like and Elovl5-like elongase were investigated in common carp (Cyprinus carpio var. Jian). Two Δ6 desaturase-like cDNAs (Fad6-a and Fad6-b) and two Elovl5-like elongase (Elovl5-a and Elovl5-b) cDNAs were cloned. Juvenile carp were fed three semi-purified diets (D1-3) for 6 weeks with different lipid sources: D1, fish oil with high highly unsaturated fatty acids (HUFAs); D2, corn oil with high linoleic acid (LA), but no HUFAs; and D3, linseed oil with high α-linolenic acid (LNA), but no HUFAs. Comparing muscle fatty acids among fish fed D1-3, the content of LA and arachidonic acid (AA) in common carp fed D2 and the content of LNA, EPA and DHA in common carp fed D3 were higher than initial levels (P < 0.05), respectively. The liver transcript levels of Fad6-a and Elovl5-a in fish fed D2 and D3 were higher than initial levels (P < 0.05), but Fad6-b and Elovl5-b levels were seldom affected by the diets. The dietary fatty acids affect the muscle fatty acid composition and the liver Fad6-a and Elovl5-a gene expression levels in common carp, and further studies should be undertaken.