Metabolism in vivo of deuterium-labelled linolenic and linoleic acids in humans
1990
Emken, E.A. | Adlof, R.O. | Rakoff, H. | Rohwedder, W.K. | Gulley, R.M.
Four healthy, young men were given a low-fat (24% total energy) diet containing 1.6 or 6.6% by energy (7 or 28% total fat) linoleic acid. The polyunsaturate:saturate ratio was 0.13 or 0.8. After 12 days, a mixture of triacylglycerols (TAG) containing deuterium-labelled fatty acids was blended with caseinate 30 g, sucrose 15 g, D-glucose 30 g and water 180 ml, and given as a single saline dose by mouth. Blood was taken 9 times for estimation of plasma chylomicron lipids and phosphatidylcholine. Maximum incorporation of the deuterium-labelled fatty acids in the chylomicron TAG samples occurred 4 to 6 h after the mixtures of deuterium-labelled TAG were given. The ranges of percentage absorption of the deuterium-labelled fats were 64 to 85% for linolenic; 79 to 82%, linoleic; 27 to 94%, octadecanoic; 76 to 79%, hexadecanoic. Area selectivity values indicated that 18:2, ω6 was the preferred substrate for both lecithin:cholesterol acyltransferase and phosphatidylcholine acyltransferase. There was a high isotope enrichment for the ω3 fatty acids relative to the ω6 fatty acids. The results raise several questions about the metabolism of ω3 and ω6 fatty acids in man and point out the need to learn much more before a rationale can be developed to explain the physiological effects produced by ω3 fatty acids.
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