Geometry of conjugated double bonds of CLA isomers in a commercial mixture and in their hepatic 20∶4 metabolites

Abstract

Rats were fed a fat-free diet for 2 wk. After this period, while maintaining the animals on the same diet, the rats were given intragastrically 180 mg per day of a mixture of conjugated linoleic acids (CLA) as triacylglycerols. Gas chromatography mass spectrometry (GC-MS) analyses of this mixture, as well as hydrazine reduction and GC-MS and GC-Fourier transform infrared analyses of the resulting monoenes, revealed the presence of two major isomers, the 9c,11t- and the 10t,12c-18:2 accompanied by smaller amounts of the 8t, 10c and the 11c, 13t-18:2 isomers. Minor quantities of cis,cis and trans,trans conjugated isomers also were detected. The total fatty acid methyl esters from the liver lipids were fractionated by reversed-phase high-performance liquid chromatography, and the fraction containing the 20:4 isomers was further fractionated by silver nitrate thin-layer chromatography. A band containing two 20:4 conjugated isomers was submitted to hydrazine reduction and the resulting monoenes analyzed by GC-MS as dimethyl-oxazoline derivatives. The two conjugated isomers were tentatively identified as 5c,8c, 11c, 13t-20:4 and 5c,8c,12t,14c-20:4. These could be formed by desaturation and elongation of the 9c,11t- and 10t,12c-18:2 present in the commercial CLA mixture.

The effect of conjugated linoleic acid isomers on fatty acid profiles of liver and adipose tissues and their conversion to isomers of 16∶2 and 18∶3 conjugated fatty acids in rats

“…4), where the two 20:4 conjugated isomers were the major metabolites of the 9cis,11trans-and 10trans,12cis-18:2 (50). In the present study, the animals received an equilibrated diet.…”

“…They were randomly divided into four experimental groups of five animals which were fed a semisynthetic diet containing 6% (by weight) of lipids. The composition of the diet, in terms of dry weight (g/1000 g), was as follows: casein, 180; corn starch, 460; sucrose, 220; cellulose, 20; mineral mixture, 50 p-aminobenzoic acid, 50 mg; inositol, 100 mg; sucrose, 5.5 g); oil, 50; free fatty acids, 10. Dietary lipids were made up of 5% of a mixture of high-oleic sunflower and linseed oils (98:2, w/w) and 1% of conjugated CLA as free fatty acid (FFA: experimental groups) or 1% of oleic acid (control group).…”

Trans-10,cis-12-CLA-Caused Lipodystrophy Is Associated with Profound Changes of Fatty Acid Profiles of Liver, White Adipose Tissue and Erythrocytes in Mice: Possible Link to Tissue-Specific Alterations of Fatty Acid Desaturation

“…This mechanism has been shown in intestinal bacteria [41] . It is also likely that t 10, c 12-CLA is quickly elongated and desaturated into conjugated tri-or tetraenes or is partially ␤ -oxidized in peroxisomes or microsomes [42][43][44] . Moreover, the production of C20: 4-derivatives might lead to the generation of lipid peroxidation products.…”

Separation of conjugated linoleic acid isomers and parinaric fatty acid isomers by capillary electrophoresis

“…For biological studies it is therefore important to have available analytical methods for accurate determination of the isomeric composition of CLA mixtures. In this regard, silver-ion high-performance liquid chromatography [11] and gas-liquid chromatography have emerged as important tools [12,13]. The present paper explores the potential of capillary electrophoresis for the separation of various octadecadienoate isomers.…”