In vivo distribution and turnover of trans- and cis-10-octadecenoic acid isomers in human plasma lipids.

Abstract Triacylglycerols containing deuterium-labeled trans -10- and cis -10-octadecenoic acid (10 t -18:1, 10 c -18: l ) plus the triacylglycerol of deuterated cis -9-octadecenoic acid (9 c -18: l ) were fed as a mixture to two young, adult male subjects. Analysis by mass spectroscopy of the labeled fats in blood samples collected periodically for 48 h allowed the uptake, distribution and turnover of both 10-octadecenoic acid isomers to be directly compared to 9 c -18:1. A feature of this study is that actual weight data for the labeled fats were obtained. These data allowed plasma triacylglycerol turnover rates of 3.47–5.13 mg/min per kg to be estimated. Plasma and chylomicron triacylglycerol data also provided evidence that absorption of the deuterated fats mobilized 10–12 g of a triacylglycerol pool present in the intestinal cells. Other results are summarized as follows: (1) the 10 t -, 10 c - and 9 c -18:1 fatty acids were equally well absorbed, (2) both Δ10–18:1 isomers were oxidized more rapidly than 9 c -18: l , (3) conversion of the Δ10–18:1 isomers into their corresponding 16:1 isomers was about 3-times faster than for 9 c -18: l , (4) the Δ10–18:1 isomers were preferentially incorporated at the 1-acyl and excluded from the 2-acyl position of phosphatidylcholine, (5) esterification of cholesterol with the Δ10–18:1 fatty acids was 2.5–4.3-times slower than for 9 c -18:1 and (6) desaturation and elongation rates for the Δ10–18:1 acids were very low.