Maternal-fetal in vivo transfer of [13C]docosahexaenoic and other fatty acids across the human placenta 12 h after maternal oral intake.

BACKGROUND Fetal growth and development require n-3 (omega-3) long-chain polyunsaturated fatty acids, but mechanisms for their placental transfer are not well understood. OBJECTIVE We assessed distribution and human placental transfer of (13)C-labeled fatty acids (FAs) 12 h after oral application. DESIGN Eleven pregnant women received 0.5 mg [(13)C]palmitic acid ((13)C-PA; 16:0), 0.5 mg [(13)C]oleic acid ((13)C-OA; 18:1n-9), 0.5 mg [(13)C]linoleic acid ((13)C-LA; 18:2n-6), and 0.1 mg [(13)C]docosahexaenoic acid ((13)C-DHA; 22:6n-3) per kilogram of body weight orally 12 h before elective cesarean section. Maternal blood samples were collected before tracer intake (-12 h) and at -3, -2, -1, 0, and +1 h relative to the time of cesarean section. At birth, venous cord blood and placental tissue were collected, and FA concentrations in individual lipid fractions and their tracer content (atom percent excess values) were determined. RESULTS Relatively stable tracer enrichment was achieved in maternal lipid fractions 12 h after tracer administration. In maternal plasma, most (13)C-PA and (13)C-OA were found in triglycerides, whereas (13)C-LA and (13)C-DHA were found mainly in plasma phospholipids and triglycerides. In placental tissue, (13)C-FAs were mainly found in phospholipids, which comprise 80% of placental tissue lipids. Placenta-maternal plasma ratios and fetal-maternal plasma ratios for (13)C-DHA were significantly higher than those for any other FA. CONCLUSIONS Twelve hours after oral application of (13)C-labeled FAs, relatively stable tracer enrichment was achieved. We found a significantly higher ratio of (13)C-DHA concentrations in cord plasma than in maternal plasma, which was higher than that for the other studied FAs. (13)C-DHA is predominantly esterified into phospholipids and triglycerides in maternal plasma, which may facilitate its placental uptake and transfer.