Incorporation profiles of isomers of conjugated linoleic acids (CLA) into raft and non‐raft lipids of CHO cells.

Abstract

The aim of this study was to determine whether part of the biological effects of CLA is due to their incorporation into membrane lipids, and consequent modification of membrane raft function. The incorporation of four CLA isomers, trans 10‐cis 12 (A), trans 9‐trans 11 (B), cis 9‐trans 11 (C), and cis 9‐cis 11 (D), and of linoleic acid (LA) into raft lipids, and their positional distribution in phospholipids was studied. In all cases, more than 60% of the cellular CLA was present in the raft fraction. Part of the CLA was converted to the 18:3 and 20:2 derivatives by the cells. Of the total CLA incorporated, 60% was present in phosphatidylcholine (PC), and 30% in phosphatidylethanolamine (PE). Unlike LA, which was present almost exclusively in the sn‐2 position of phospholipids, 30–40% of A, C, and D, and up to 70% of B were found in the sn‐1 position of PC. About 65% of the total CLA in PE was present in sn‐1 position for all the isomers. In all cases endogenous 18:1 was the predominant fatty acid replaced by CLA, but saturated fatty acids were also replaced by B. Furthermore, A, C, and D inhibited the Δ9 desaturase activity, as evident from the decreased ratios of monunsaturates/saturates. CLA‐B, however, increased this ratio, indicating no inhibition of the enzyme by it. These results show that CLA incorporate preferably into raft lipids, with a large percentage in sn‐1 position of phospholipids, which may affect the membrane functions.