Monounsaturated trans fatty acids, elaidic acid and trans-vaccenic acid, metabolism and incorporation in phospholipid molecular species in hepatocytes

The incorporation of [C-14]elaidic acid (trans18:1(n-9)) in phosphatidylcho line and phosphatidylethanolamine molecular species in isolated rat liver c ells has been studied, and the results compared with the incorporation, pre viously published (B. Woldseth et al. Biochim Biophys Acta 1993;1167:296-30 2), of [C-14]palmitic acid (16:0) and [C-14]stearic acid (18:0) and with th at of [C-14]oleic acid (cis18 : 1(n-9)). The pattern of incorporation in ph ospholipid molecular species is similar to that of [C-14]stearic acid and d ifferent from that of [C-14]palmitic acid. In phosphatidylcholine [C-14]tra ns18:1-18:2 and [C-14]trans18:1-20:4 were the most abundant species, and in phosphatidylethanolamine [C-14]trans18:1-20:4 was the predominant species. With increasing concentration of [C-14]elaidic acid increasing amounts of [C-14]trans18: 1-[C-14]trans18: 1 were found. The total incorporation in ph ospholipids was less than that of [C-14]stearic acid, but more than that of [C-14]palmitic acid. The distribution in percent of [C-14]elaidic acid in phospholipid classes was 8.8% in phosphatidylinositol, 1.8% in phosphatidyl serine, 59.1% in phosphatidylcholine and 30.3% in phosphatidylethanolamine with 0.1 mmol l(-1) substrate concentration. More [C-14]elaidic acid than [ C-14]palmitic acid or [C-14]stearic acid was oxidized. The incorporation in phospholipids of [C-14]elaidic acid was very different from that of[C-14]o leic acid. The main species with [C-14]oleic acid were 16:0-[C-14]cis18:1 i n phosphatidylcholine, and [C-14]cis18:1-20:4 in phosphatidylethanolamine. In some experiments [C-14]18:2(n-6) was incubated together with unlabelled elaidic or unlabelled trans-vaccenic acid (trans18:1(n-7)). In these experi ments, more trans18:1-18:2 was formed from elaidic acid than from trans-vac cenic acid, especially in phosphatidylethanolamine.