出版社：American Society for Biochemistry and Molecular Biology
摘要：An important question for mammalian nutrition is the relativeefficiency of C18 versus C20 essential fatty acids (EFAs) forsupporting the tissue composition of n-3 and n-6 pathway endproducts. One specific question is whether C22 EFAs are madeavailable to tissues more effectively by dietary -linolenicacid (18:3n-3) and linoleic acid (18:2n-6) or by dietary eicosapentaenoicacid (20:5n-3) and dihomo--linolenic acid (20:3n-6). To addressthis question in a direct manner, four stable isotope compoundswere given simultaneously in a novel paradigm. A single oraldose of a mixture of 2H5-18:3n-3, 13C-U-20:5n-3, 13C-U-18:2n-6,and 2H5-20:3n-6 was administered to rats given a defined diet.There was a preferential in vivo conversion of arachidonic acid(20:4n-6) to docosatetraenoic acid (22:4n-6) and of 22:4n-6to n-6 docosapentaenoic acid (22:5n-6) when the substrates originatedfrom the C18 precursors. However, when the end products docosahexaenoicacid (22:6n-3) or 22:5n-6 were expressed as the total amountin the plasma compartment divided by the dosage, this parameterwas 11-fold greater for 20:5n-3 than for 18:3n-3 and 14-foldgreater for 20:3n-6 than for 18:2n-6.
Thus, on a per dosage basis, the total amounts of n-3 and n-6end products accreted in plasma were considerably greater forC20 EFA precursors relative to C18.Abbreviations: 18:2n-6, linoleic acid; 18:3n-3, -linolenic acid; 20:4n-6, arachidonic acid; 20:3n-6, dihomo--linolenic acid; 22:6n-3, docosahexaenoic acid; 22:5n-6, n-6 docosapentaenoic acid; 20:5n-3, eicosapentaenoic acid; AUC, area under the curve; CE, cholesteryl ester; Cmax, maximal concentration of labeled fatty acids in plasma; Dmax, maximal percentage of dose; EFA, essential fatty acid; Emax, maximal enrichment of labeled fatty acids at maximal concentration; MESSI, multiple simultaneous stable isotope; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PL, phospholipid; TG, triglyceride; Tmax, sampling time at maximal concentration
Supplementary key words stable isotope tracer • -linolenic acid • eicosapentaenoic acid • docosahexaenoic acid • linoleic acid • dihomo--linolenic acid • arachidonic acid • gas chromatography-mass spectrometry • multiple simultaneous stable isotopes
-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) or by dietary eicosapentaenoic acid (20:5n-3) and dihomo-
-linolenic acid (20:3n-6). To address this question in a direct manner, four stable isotope compounds were given simultaneously in a novel paradigm. A single oral dose of a mixture of 2H5-18:3n-3, 13C-U-20:5n-3, 13C-U-18:2n-6, and 2H5-20:3n-6 was administered to rats given a defined diet. There was a preferential in vivo conversion of arachidonic acid (20:4n-6) to docosatetraenoic acid (22:4n-6) and of 22:4n-6 to n-6 docosapentaenoic acid (22:5n-6) when the substrates originated from the C18 precursors. However, when the end products docosahexaenoic acid (22:6n-3) or 22:5n-6 were expressed as the total amount in the plasma compartment divided by the dosage, this parameter was 11-fold greater for 20:5n-3 than for 18:3n-3 and 14-fold greater for 20:3n-6 than for 18:2n-6.
Thus, on a per dosage basis, the total amounts of n-3 and n-6 end products accreted in plasma were considerably greater for C20 EFA precursors relative to C18.
Abbreviations: 18:2n-6, linoleic acid; 18:3n-3, 
