α-Tocopherol Stereoisomer Profiles in Matched Human Maternal and Umbilical Cord Plasma.

Background: α-Tocopherol (αT) is essential for fetal development. One study has shown that the human placenta preferentially transfers the natural stereoisomer, -αT. But prenatal supplements generally contain synthetic αT (S-αT).

Objectives: We aimed to determine if umbilical cord plasma is enriched for -αT in racially diverse neonates from both uncomplicated and complicated pregnancies and if cord -αT enrichment is impacted by maternal αT stereoisomer profile.

Methods: We measured αT and αT stereoisomers in plasma from a randomly selected subset of 66 predominantly black and Hispanic maternal-fetal pairs from the Camden Study involving control (= 28) and complicated pregnancies (= 38). We collected maternal plasma at study entry (week 16 gestation; w16) and week 28 gestation (w28) and cord plasma at birth.

Results: -αT was the predominant stereoisomer in all maternal and cord plasma samples, but S-αT stereoisomers were found in most samples and comprised a high percentage of αT in some maternal-neonate pairs. Cord plasma had a higher percentage -αT (< 0.05) and lower percentage S-αT (< 0.0001) than w28 plasma. Pregnancy status did not impact maternal or cord plasma concentrations of αT, -αT, or S-αT; except plasma from complicated pregnancies was higher in S-αT at w28 than at w16 (< 0.05). Maternal w28 αT did not correlate with cord αT. However, both maternal w28 αT and S-αT positively correlated with both cord S-αT ( = 0.340, = 0.0049;  = 0.538, < 0.00001) and percentage S-αT ( = 0.399, = 0.001;  = 0.786, < 0.00001) but negatively correlated with cord percentage -αT ( = -0.399, = 0.0009; = -0.786, < 0.00001).

Conclusions: The proportion of -αT was higher in cord compared with maternal plasma in both uncomplicated and complicated pregnancies. Our data suggest that maternal S-αT raises cord S-αT and decreases the proportion of -αT in the neonatal circulation. Because the bioactivities of -αT and S-αT differ, this warrants future research to determine the importance of our observations to neonatal αT status.