Different changes of n-6 fatty acids in lipoproteins from hyperlipemic subjects after diets supplemented with n-3 fatty acids.

After diets supplemented with canned mackerel or herring, in a cross-over design, containing different amounts of long-chain n-3 fatty acids (eicosapentaenoic acid, C20:5n-3-EPA, and docosahexaenoic acid, C22(6)n-3-DHA) an increase of both EPA and DHA was confirmed in triglycerides (TG), cholesterol esters (CE) and phospholipids (PL) of very low density (VLDL) and low density lipoproteins (LDL) as well as in high density lipoproteins (HDL) from hyperlipidemic subjects. An unexpected finding was the simultaneous increase of arachidonic acid (C20:4n-6-AA) in TG and CE and its constant portion in PL of lipoproteins, whereas linoleic acid (C18:2n-6-LA) appeared lower in CE and in PL of VLDL + LDL and HDL. In general, the changes were minor after a diet supplemented with canned herring providing a lower dose of n-3 fatty acids. The results indicate dose-related changes not only of n-3 fatty acids, but also of n-6 fatty acids in serum lipids after fish diets. This different behavior of LA and AA in serum lipids might be a new aspect in the interrelations and the dietary modulation of both families of polyunsaturated fatty acids (PUFA). The accumulation of AA in neutral lipids could be linked with an elevation of prostaglandin I2, which was found apart from an increased formation of prostaglandin I3 after diets supplemented with n-3 fatty acids. The concomitant increase of prostaglandins I2 and I3 spotlights widely ignored interrelations within the eicosanoid pathway, which become evident after diets enriched with long-chain n-3 fatty acids.