title: Metabolism in humans of cis-12,trans-15-octadecadienoic acid relative to palmitic, stearic, oleic and linoleic acids.
abstract: Mixtures of triglycerides containing deuterium-labeled hexadecanoic acid (16:0), octadecanoic acid (18:0), cis-9-octadecenoic acid (9c-18:1), cis-9,cis-12-octadecadienoic acid (9c, 12c-18:2) and cis-12,trans-15-octadecadienoic acid (12c,15t-18:2) were fed to two young-adult males. Plasma lipid classes were isolated from samples collected periodically over 48 hr. Incorporation and turnover of the deuterium-labeled fats in plasma lipids were followed by gas chromatography-mass spectrometry (GC-MS) analysis of the methyl ester derivatives. Absorption of the deuterated fats was followed by GC-MS analysis of chylomicron triglycerides isolated by ultracentrifugation. Results were the following: (i) endogenous fat contributed about 40% of the total fat incorporated into chylomicron triglycerides; (ii) elongation, desaturation and chain-shortened products from the deuterated fats were not detected; (iii) the polyunsaturated isomer 12c,15t-18:2 was metabolically more similar to saturated and 9c-18:1 fatty acids than to 9c,12c-18:2; (iv) relative incorporation of 9c,12c-18:2 into phospholipids did not increase proportionally with an increase of 9c,12c-18:2 in the mixture of deuterated fats fed; (v) absorption of 16:0, 18:0, 9c-18:1, 9c,12c-18:2 and 12c,15t-18:2 were similar; and (vi) data for the 1- and 2-acyl positions of phosphatidylcholine and for cholesteryl ester fractions reflected the known high specificity of phosphatidylcholine acyltransferase and lecithin:cholesteryl acyltransferase for 9c,12c-18:2. These results illustrate that incorporation of dietary fatty acids into human plasma lipid classes is selectively controlled and that incorporation of dietary 9c,12c-18:2 is limited. These results suggest that nutritional benefits of diets high in 9c,12c-18:2 may be of little value to normal subjects and that the 12c,15t-18:2 isomer in hydrogenated fat is not a nutritional liability at the present dietary level.
authors.forename: E A
authors.initials: EA
authors.lastname: Emken
authors.forename: W K
authors.initials: WK
authors.lastname: Rohwedder
authors.forename: R O
authors.initials: RO
authors.lastname: Adlof
authors.forename: H
authors.initials: H
authors.lastname: Rakoff
authors.forename: R M
authors.initials: RM
authors.lastname: Gulley
mesh_terms: D000328:Adult; D002788:Cholesterol Esters / Q000097:blood; D002914:Chylomicrons / Q000097:blood; D003903:Deuterium; D004041:Dietary Fats / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism*; D008297:Male; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D010743:Phospholipids / Q000097:blood; D011865:Radioisotope Dilution Technique; D013229:Stearic Acids / Q000378:metabolism*; D014280:Triglycerides / Q000097:blood / Q000378:metabolism*
chemical_list: D002788:Cholesterol Esters; D002914:Chylomicrons; D004041:Dietary Fats; D005231:Fatty Acids, Unsaturated; D008041:Linoleic Acids; D009829:Oleic Acids; D010169:Palmitic Acids; D010743:Phospholipids; D013229:Stearic Acids; D014280:Triglycerides; C027369:octadecadienoic acid; D019301:Oleic Acid; D019308:Palmitic Acid; C031183:stearic acid; D019787:Linoleic Acid; D003903:Deuterium