Effects of conjugated linoleic acid isomers on the hepatic microsomal desaturation activities in vitro.

The influence of individual conjugated linoleic acid (CLA) isomers on the delta6 desaturation of linoleic and alpha-linolenic acids and on the delta9 desaturation of stearic acid was investigated in vitro, using rat liver microsomes. The delta6 desaturation of 18:2n-6 was decreased from 23 to 38% when the ratio of 9cis,11trans-18:2 to 18:2n-6 increased from 0.5 to 2. The compound 10trans,12cis-18:2 exhibited a similar effect only at the highest concentration. The delta6 desaturation of alpha-linolenic acid was slightly affected by the presence of CLA isomers. The sole isomer to induce an inhibitory effect on the delta9 desaturation of stearic acid was 10trans,12cis-18:2.