Effect of dietary fats on arachidonic acid and eicosapentaenoic acid biosynthesis and conversion to C 22 fatty acids in isolated rat liver cells

Abstract

The desaturation, chain elongation and esterification of [1- 14C]eicosapentaenoic acid, [1 14C]arachidonic acid, [1- 14C]eicosatrienoic acid, [1- 14C]linolenic acid and [1- 14C]linoleic acid were studied in isolated liver cells. Rats fed diets with either 15% hydrogenated coconut oil or 15% partially hydrogenated marine oil, both deficient in essential fatty acids, 15% soybean oil or standard pellet diet with 6% fat, were used. The Δ 4-desaturation of 22:5( n−3) and 22:4( n−6) as well as the Δ 6-desaturase activity was distinctly higher in cells from animals fed coconut or marine oil than with soybean oil or standard pellet. The rate of Δ 5-desaturation of 20:3( n−6) and 20:4( n−3) was nearly the same in cells from rats fed coconut, marine and soybean oils and higher than with standard pellet. The chain elongation of 20:5( n−3) to 22:5( n−3) was distinctly more pronounced than the elongation of 20:4( n−6) with all four diets. 20:5( n−3) was mainly esterified in the phospholipids with marine and coconut oils, and mainly in triacylglycerol with standard pellet and soybean oils. The proportion of [1- 14C]20:4( n−6) in the phospholipids to that in triacylglycerol decreased in the order marine oil > coconut oil > standard pellet > soybean oil. The different endogenous arachidonic acid content in the phospholipids induced by the different diets increased in the same order. 20:5( n−3) was rapidly esterified in triacylglycerol and phospholipids, then liberated especially from the triacylglycerol fraction, chain elongated to 22:5( n−3) and reesterified.