Dietary sunflower, linseed and fish oils affect phospholipid fatty acid composition, development of cardiac lesions, phospholipase activity and eicosanoid production in Atlantic salmon ( Salmo salar)

Abstract

Atlantic salmon (Salmo salar) post-smolts were fed practical-type diets in which the lipid was supplied either as fish oil (FO), sunflower oil (SFO) or linseed oil (LO) for 12 weeks. In general, the heart phospholipids from SFO-fed fish had increased 18:2n-6, 20:2n-6, 20:3n-6 and 20:4n-6 but decreased 20:5n-3 compared to both other dietary treatments. This was reflected in a decreased n-3/n-6 polyunsaturated fatty acid (PUFA) ratio and an increased 20:4n-6/20:5n-3 or eicosanoid precursor ratio in SFO-fed fish. While heart phospholipids of fish fed LO had increased levels of 18:2n-6, 20:2n-6 and 20:3n-6 compared to fish fed FO, 20:4n-6 levels were reduced, although only significantly in phosphatidylcholine (PC). Dietary-induced changes in phospholipid fatty acid compositions of blood leucocytes were similar to those in heart, although fish fed LO had increased 20:5n-3 compared to fish fed FO. Thromboxane B 2 (TXB 2) produced by stimulated blood cells was reduced in fish fed LO compared to those fed SFO. Prostaglandin E 2 (PGE 2) production was reduced in LO-fed fish compared to both other dietary treatments. Fish fed LO had reduced PC in heart membranes compared to the other two dietary treatments, resulting in a ratio of PC:PE (phosphatidylethanolamine) less than unity. Fish fed SFO developed a marked cardiac histopathology which, while present in FO-fed fish albeit in a less severe form, was virtually absent in fish fed LO. Fish fed SFO had increased heart phospholipase A activity compared to those given either FO or LO.