Blood compartmental metabolism of docosahexaenoic acid (DHA) in humans after ingestion of a single dose of [C-13]DHA in phosphatidylcholine

The amount and distribution of [C-13]docosahexaenoic acid (DHA) in plasma, platelet, and erythrocyte lipid classes were followed as a function of time (1 to 72 h) in young adults after ingestion of a single dose of [C-13]DHA esterified in a phosphatidylcholine (PC), in using gas chromatography combu stion-isotope ratio mass spectrometry. [C-13]DHA first appeared in plasma n on-esterified fatty acids (NEFA) and triglycerides (TG), with a maximal app earance at 6 h and a further decline, then being delayed 3-fold compared to [C-13]DHA ingested in triglycerides, Lysophosphatidylcholine (LPC) was als o enriched in [C-13]DHA, due mainly to earlier hepatic secretion, and plate aued at 6 h, whereas phosphatidylethanolamine (PE) and phosphatidylcholine (PC) containing [C-13]DHA plateaued at 9 h, The labeling of erythrocyte and platelet phospholipids exhibited different kinetics, probably involving di fferent metabolic pathways for [C-13]DHA incorporation in cell membranes, C omputation of the relative contribution of LPC and NF,FA for delivery of [C -13]DHA to blood cells showed that the supply to platelets occurred through NEFA, In contrast, [C-13]DHA was carried by both LPC and NEFA to erythrocy tes, which differs from what was previously been observed after intake of t riglycerides labeled with [C-13]DHA where LPC was the only source of [C-13] DHA for erythrocrytes.jlr We conclude that the lipid form of ingested DHA. affects markedly its kinetics and partly its metabolic fate.