Influence of dietary arachidonic acid on metabolism in vivo of 8cis,11cis,14-eicosatrienoic acid in humans

Emken, E.A.; Adlof, R.O.; Duval, S.M.; Nelson, G.J.

Lipids 32(4): 441-448


ISSN/ISBN: 0024-4201
PMID: 9113634
Accession: 002871223

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This study investigated the influence of dietary arachidonic acid (20:4n-6) on DELTA-5 desaturation and incorporation of deuterium-labeled 8cis, 11cis, 14-eicosatrienoic acid (20:3n-6) into human plasma lipids. Adult male subjects (n = 4) were fed diets containing either 1.7 g/d (H120:4 diet) or 0.21 g/d (LO20:4 diet) of arachidonic acid for 50 d and then dosed with a mixture containing ethyl esters of 20:3n-6(d4) and 18:1 n-9(d2). A series of blood samples was sequentially drawn over a 72-h period, and methyl esters of plasma total lipid, triacylglycerol, phospholipids, and cholesteryl ester were analyzed by gas chromatography-mass spectrometry. Based on the concentration of 20:3n-6(d4) in total plasma lipid, the estimated conversion of 20:3n-6(d4) to 20:4n-6(d4) was 17.7 +- 0.79% (H120:4 diet) and 2.13 +- 1.44% (LO20:4 diet). The concentrations of 20:4n-6(d4) in total plasma lipids from subjects fed the H120:4 and LO20:4 diets were 2.10 +- 0.6 and 0.29 +- 0.2 mu-mole/mL plasma/mmole of 20:3n-6(d4) fed/kg of body weight. These data indicate that conversion of 20:3n-6(d4) to 20:4n-6(d4) was stimulated 7-8-fold by the H120:4 diet. Phospholipid acyltransferase was 2.5-fold more selective for 20:3n-6(d4) than 18:1n-9(d2), and lecithin:cholesterol acyltransferase was 2-fold more selective for 18:1 n-9(d2) than 20:3n-6(d4). These differences in selectivity were not significantly influenced by diet. Absorption of ethyl 20:3n-6(d4) was about 33% less than ethyl 18:1 n-9(d2). The sum of the n-6 retroconversion products from 20:3n-6(d4) in total plasma lipids was about 2% of the total deuterated fatty acids. Neither absorption nor retroconversion appears to be influenced by diet.