Lack of effects of trans fatty acids on eicosanoid biosynthesis with adequate intakes of linoleic acid.

The minimum requirement of linoleic acid to prevent effects of dietary C18 trans fatty acids on eicosanoid biosynthesis in rats was assessed. In a first experiment, six groups of animals were fed diets with a high content of trans fatty acids [20% of energy (en%)], and increasing amounts of linoleic acid (0.4 to 7.1 en%). In a second experiment, four groups of rats were fed diets designed to compare trans fatty acids with saturated and cis-monounsaturated fatty acids of the same chain length at the 2 en% linoleic acid level. After 9-14 weeks the biosynthesis of prostacyclin by pieces of aorta and the biosynthesis of hydroxy-heptadecatrienoic acid and 12-hydroxy-eicosatetraenoic acid by platelets were measured. The fatty acid compositions of aorta phospholipid and platelet lipid were also determined. Both the prostacyclin-production by aorta pieces and the production of hydroxy-heptadecatrienoic acid and 12-hydroxy-eicosatetraenoic acid by platelets appeared to be a linear function of the arachidonic acid level in aorta phospholipid and platelet lipid, irrespective of the trans fatty acid content in the diet. This indicates that trans fatty acids do not directly influence enzymes involved in eicosanoid biosynthesis. In a direct comparison with cis-monounsaturated or saturated fatty acids with 2 en% linoleic acid in the diet, only a moderate reduction in arachidonic acid level in aorta phospholipids in the group fed trans fatty acids was observed. The geometry of the double bond did not influence the arachidonic acid level in platelet lipid, although the diet rich in saturated fatty acids increased arachidonic acid levels significantly compared with all other diets.(ABSTRACT TRUNCATED AT 250 WORDS)