Effects of trans-10,cis-12 conjugated linoleic acid and cognates on apolipoprotein B secretion in HepG2 cells

Conjugated linoleic acid (CLA) has been shown to decrease apolipoprotein B (apoB) secretion in HepG2 cells. The purpose of this study was to determine the activity of individual CLA isomers-and to test cognates that are structurally related to CLA-with regard to apoB secretion. Trans-10,cis-12 CLA decreased apoB secretion whereas cis-9,trans-11, cis-9,cis-11, trans-9,trans-11, and the chloride, alcohol, or amide forms of CLA had no effect on apoB secretion. Trans-9,cis-12 octadecadienoic acid had no effect whereas cis-9,cis-12 octadecadienoic acid (linoleic acid) enhanced apoB secretion. Among 18-carbon monounsaturated fatty acids tested, only trans-10 octadecenoic acid decreased apoB secretion. Trans-11, trans-12, trans-13, cis-9,cis-11, and cis-13 octadecenoic acids increased apoB secretion whereas trans-9 and cis-12 octadecenoic acids were without effect. None of the 20-carbon compounds tested or cis-12 octadecen-10-ynoic acid had an effect on apoB secretion. Conjugated nonadecadienoic acid decreased apoB secretion whereas cis-10,cis-13 nonadecadienoic acid did not. The reduction of apoB secretion by CLA mixture is caused by the unique structural features of trans-10,cis-12 CLA. A trans double bond at the 10th position appears to be a key structure involved in the inhibition of apoB secretion.