Submitted to: Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 4, 1997
Publication Date: N/A
Interpretive Summary: Arachidonic acid is compound that is present in animal but not vegetable fats. Dihomogammalinolenic acid (DHL) is a compound that the body produces from linoleic acid which is found in many edible vegetable oils. The body synthesizes a number of powerful biologically active compounds from arachidonic acid. If the biological effects of these compounds are not controlled by substances that arise from DHL, they can have negative effects on a variety of chronic diseases such as heart disease, arthritis, asthma, and hypertension. For this reason, a better understanding of the influence of dietary arachidonic acid has on nutrition and health is needed. Results of human studies indicate that the body does not compensate for increased dietary intake of arachidonic acid by lowering the amount the body produces. Also, dietary arachidonic acid did not effect other measures of fatty acid metabolism. These findings contribute to the basic knowledge needed to develop recommendations for dietary fat intake.
Technical Abstract: This study investigated the influence of dietary arachidonic acid (20:4n-6) on delta-5 desaturation and incorporation of deuterium-labeled 8c,11c,14-eicosatrienoic acid (20:3n-6) into human plasma lipids. Adult male subjects (n=4) were fed diets containing either 1.8 g\day (HI20:4 diet) or 0.3 g\day (LO20:4 diet) of arachidonic acid for 50 days and then dosed with a mixture containing ethyl esters of 20:3n-6[d4] and 18:1n-9[d2]. Plasma total lipid (TL), triglyceride (TG), phospholipids (PL), and cholesterol ester (CE) were analyzed by GC-MS. Conversion of 20:3n-6[d4] to 20:4n-6[d4] was 17.7 + 0.79% (HI20:4 diet) and 2.13 +/- 1.44% (LO20:4 diet). And indicate that conversion of 20:3n-6[d4] to 20:4n-6[d4] was stimulated 7-8 fold by the HI20:4 diet. Phospholipid acyltransferase was 2.5 fold more selective for 20:3n-6[d4] than 18:1n-9[d2] and lecthin:cholesteryl acyltransferase was 2 fold more selective than for 18:1n-9[d2] than 20:3n-6[d4]. These differences in selectivity were not significantly influence by diet. Absorption of the 20:3n-6[d4] ethyl ester was about 22% less than for the 18:1n-9[d2] ethyl ester. 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 or retroconversion appear to be influenced by diet.