Effect of dietary arachidonic acid on metabolism of deuterated linoleic acid by adult male subjects.
The influence of dietary supplementation with 20:4n-6 on uptake and turnover of deuterium-labeled linoleic acid (18:2n-6[d2]) in human plasma lipids and the synthesis of desaturated and elongated n-6 fatty acids from 18:2n-6[d21 were investigated in six adult male subjects. The subjects were fed either a high-arachidonic acid (HIAA) diet containing 1.7 g/d or a low-AA (LOAA) diet containing 0.21 g/d of AA for 50 d. Each subject was then dosed with about 3.5 g of 18:2n-6[d2] as the triglyceride (TG) at 8:00 A.M., 12:00, and 5:00 P.M. The total 18:2n-6[d21] fed to each subject was about 10.4 g and is approximately equal to one-half of the daily intake of 18:2n-6 in a typical U.S. male diet. Nine blood samples were drawn over a 96-h period. Methyl esters of plasma total lipid (TL), TG, phospholipid, and cholesterol ester were analyzed by gas chromatography-mass spectroscopy. Dietary 20:4n-6 supplementation did not affect uptake of 18:2n-6[d2] in plasma lipid classes over the 4-d study period nor the estimated half-life of 24-36 h for 18:2n-6[d2]. The percentages of major deuterium-labeled desaturation and elongation products in plasma TL, as a percentage of total deuterated fatty acids, were 1.35 and 1.34% 18:3n-6[d2]; 0.53 and 0.50% 20:2n-6[d2]; 1.80 and 0.92% 20:3n-6[d2] and 3.13 and 1.51% 20:4n-6[d2] for the LOAA and HIAA diet groups, respectively. Trace amounts (<0.1%) of the 22:4n-6[d2] and 22:5n-6[d2] metabolites were present. Plasma TL concentration data for both 20:3n-6[d2] and 20:4n-6[d2] were 48% lower (P < 0.05) in samples from the HIAA diet group than in samples from the LOAA diet group. For a normal adult male consuming a typical U.S. diet, the estimated accumulation in plasma TL of 20:4n-6 synthesized from 20 g/d (68 mmole) of 18:2n-6 is 677 mg/d (2.13 mmole). Dietary supplementation with 1.5 g/d of 20:4n-6 reduced accumulation of 20:4n-6 synthesized from 20 g/d of 18:2n-6 to about 326 mg/d (1.03 mmole).
Emken
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EA
USDA, ARS, NCAUR, Food Quality and Safety Research, Peoria, Illinois 61604, USA. eaemken@yahoo.com
Adlof
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Duval
S M
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Nelson
G J
GJ
D000284:Administration, Oral; D000328:Adult; D016718:Arachidonic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D002784:Cholesterol / Q000097:blood; D002788:Cholesterol Esters / Q000097:blood; D003903:Deuterium; D004041:Dietary Fats; D006801:Humans; D019787:Linoleic Acid / Q000378:metabolism*; D008055:Lipids / Q000097:blood*; D008297:Male; D010743:Phospholipids / Q000097:blood; D014280:Triglycerides / Q000097:blood
D002788:Cholesterol Esters; D004041:Dietary Fats; D008055:Lipids; D010743:Phospholipids; D014280:Triglycerides; D016718:Arachidonic Acid; D002784:Cholesterol; D019787:Linoleic Acid; D003903:Deuterium