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

Abstract

The incorporation of [¹⁴C]elaidic acid (trans18 : 1(n-9)) in phosphatidylcholine and phosphatidylethanolamine molecular species in isolated rat liver cells has been studied, and the results compared with the incorporation, previously published (B. Woldseth et al. Biochim Biophys Acta 1993;1167:296-302), of [¹⁴C]palmitic acid (16 : 0) and [¹⁴C]stearic acid (18 : 0) and with that of [¹⁴C]oleic acid (cis18 : 1(n-9)). The pattern of incorporation in phospholipid molecular species is similar to that of [¹⁴C]stearic acid and different from that of [¹⁴C]palmitic acid. In phosphatidylcholine [¹⁴C]trans18 : 1-18 : 2 and [¹⁴C]trans18 : 1-20 : 4 were the most abundant species, and in phosphatidylethanolamine [¹⁴C]trans18 : 1-20 : 4 was the predominant species. With increasing concentration of [¹⁴C]elaidic acid increasing amounts of [¹⁴C]trans18 : 1-[¹⁴C]trans18 : 1 were found. The total incorporation in phospholipids was less than that of [¹⁴C]stearic acid, but more than that of [¹⁴C]palmitic acid. The distribution in percent of [¹⁴C]elaidic acid in phospholipid classes was 8.8% in phosphatidylinositol, 1.8% in phosphatidylserine, 59.1% in phosphatidylcholine and 30.3% in phosphatidylethanolamine with 0.1 & mmol l^-1 substrate concentration. More [¹⁴C]elaidic acid than [¹⁴C]palmitic acid or [¹⁴C]stearic acid was oxidized. The incorporation in phospholipids of [¹⁴C]elaidic acid was very different from that of [¹⁴C]oleic acid. The main species with [¹⁴C]oleic acid were 16 : 0-[¹⁴C]cis18 : 1 in phosphatidylcholine, and [¹⁴C]cis18 : 1-20 : 4 in phosphatidylethanolamine. In some experiments [¹⁴C]18 : 2(n-6) was incubated together with unlabelled elaidic or unlabelled trans-vaccenic acid (trans18 : 1(n-7)). In these experiments, more trans18 : 1-18 : 2 was formed from elaidic acid than from trans-vaccenic acid, especially in phosphatidylethanolamine.