Conjugated diene and trans fatty acids in tissue lipids of rats fed an hepatocarcinogenic choline-devoid diet

Groups of male Fischer-344 rats were fed two pairs of semi-purified choline-devoid and choline-supplemented diets, one set containing 5% corn oil and 10% partially hydrogenated fat, and the other only corn oil (15%). Analyses were performed on lipids extracted from whole liver, liver nuclei and adipose tissue of the rats. The analyses consisted of quantitation of conjugated dienes by UV spectrophotometry, separation of fatty acids with conjugated dienes by HPLC and quantitation of trans fatty acids by IR spectrophotometry. Conjugated dienes and conjugated diene and trans fatty acids were observed in adipose tissue total lipids, at concentrations that reflected those in the diets fed. The same was true of trans fatty acids in liver lipids. However, no conjugated dienes, or fatty acids with conjugated dienes, were detected in liver lipids of rats fed the diets formulated with only corn oil. In contrast, conjugated dienes were detected in total and neutral lipids, but not in phospholipids, of whole liver and liver nuclei of rats fed the diets formulated with partially hydrogenated fat. The neutral lipids contained fatty acids with conjugated dienes that eluted with the retention time of conjugated diene fatty acids, present in the dietary partially hydrogenated fat. It is concluded that a choline-devoid diet, which is hepatocarcinogenic in the rat, does not induce a peroxidation of liver cell membrane lipids, and that not only trans fatty acids, but also fatty acids with conjugated dienes present in a partially hydrogenated fat, are absorbed and assimilated in rat tissue lipids.