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

Abstract

The amount and distribution of [13C]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 [13C]DHA esterified in a phosphatidylcholine (PC), in using gas chromatography combustion–isotope ratio mass spectrometry. [13C]DHA first appeared in plasma non-esterified fatty acids (NEFA) and triglycerides (TG), with a maximal appearance at 6 h and a further decline, then being delayed 3-fold compared to [13C]DHA ingested in triglycerides. Lysophosphatidylcholine (LPC) was also enriched in [13C]DHA, due mainly to earlier hepatic secretion, and plateaued at 6 h, whereas phosphatidylethanolamine (PE) and phosphatidylcholine (PC) containing [13C]DHA plateaued at 9 h. The labeling of erythrocyte and platelet phospholipids exhibited different kinetics, probably involving different metabolic pathways for [13C]DHA incorporation in cell membranes. Computation of the relative contribution of LPC and NEFA for delivery of [13C]DHA to blood cells showed that the supply to platelets occurred through NEFA. In contrast, [13C]DHA was carried by both LPC and NEFA to erythrocytes, which differs from what was previously been observed after intake of triglycerides labeled with [13C]DHA where LPC was the only source of [13C]DHA for erythrocytes. We conclude that the lipid form of ingested DHA affects markedly its kinetics and partly its metabolic fate.—Lemaitre-Delaunay, D., C. Pachiaudi, M. Laville, J. Pousin, M. Armstrong, and M. Lagarde. Blood compartmental metabolism of docosahexaenoic acid (DHA) in humans after ingestion of a single dose of [13C]DHA in phosphatidylcholine. J. Lipid Res. 1999. 40: 1867–1874.

Keywords

• docosahexaenoic acid
• stable isotope
• plasma
• platelets
• erythrocytes