Absorption and distribution of deuterium-labeled trans- and cis-11-octadecenoic acid in human plasma and lipoprotein lipids.

Triglycerides of deuterium-labeledtrans-11-,trans-11-cis-11- andcis-9-octadecenoic acid (11t-18∶1-2H, 11c-18∶1-2H) were simultaneously fed to two young adult male subjects. Plasma lipids from blood samples collected periodically for 48 hr were analyzed by gas chromatography-mass spectroscopy. The results indicate (i) the Δ11-18∶1-2H acids and 9c-18∶1-2H were equally well absorbed; (ii) relative turnover rates were higher for the Δ11-18-1-2H acids in plasma triglycerides; (iii) incorporation of the Δ11-18∶1-2H acids into plasma phosphatidylcholine was similar to 9c-18∶1-2H, but distribution at the 1-and 2-acyl positions was substantially different; (iv) esterification of cholesterol with 11t-18∶1 was extremely low; (v) chain shortening of the Δ11-18∶1-2H acids was 2–3 times greater than for 9c-18∶1-2H; (vi) no evidence for desaturation or elongation of the 18∶1-2H acids was detected; and (vii) a 40% isotopic dilution of the 18∶1-2H acids in the chylomicron triglyceride fraction indicated the presence of a substantial intestinal triglyceride pool. Based on our present knowledge, these metabolic results for Δ11-18∶1 acids present in hydrogenated oils and animal fats indicate that the Δ11 isomers are no more likely than 9c-18∶1 to contribute to dietary fat-related health problems.