Incorporation of dietary n−3 fatty acids into molecular species of phosphatidyl choline and cholesteryl ester in normal human plasma

To understand the differences in the antiatherogenic actions of eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6), we determined their incorporation into molecular species of phosphatidylcholine (PC) and cholesteryl ester (CE) after feeding 12 g marine lipid concentrate/d to six normolipidemic males for 28 d. The time course of incorporation of EPA into plasma PC and CE showed a precursor-product relationship. In contrast, the DHA concentration of CE was markedly lower than that in PC, and the EPA-DHA ratio was 2–6-fold higher in CE than in PC at all time intervals. Three PC species—16:0–20:5, 16:0–22:6, and 18:0–20:5—increased, whereas 18:1–18:2, 18:0–18:2, and 16:0–20:3 decreased. In vitro formation of CE species in plasma by lecithin-cholesterol acyltransferase (LCAT) showed an increased formation of 20:5 CE but not 22:6 CE, indicating that DHA is a poor substrate for LCAT. These results demonstrate a differential incorporation of EPA and DHA into plasma lipids, which may be related to the differences in their biological effects.