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

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

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

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 (n = 28) and complicated pregnancies (n = 38). We collected maternal plasma at study entry (week 16 gestation; w16) and week 28 gestation (w28) and cord plasma at birth.

RRR-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 RRR-αT (P < 0.05) and lower percentage S-αT (P < 0.0001) than w28 plasma. Pregnancy status did not impact maternal or cord plasma concentrations of αT, RRR-αT, or S-αT; except plasma from complicated pregnancies was higher in S-αT at w28 than at w16 (P < 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 (r = 0.340, P = 0.0049; r = 0.538, P < 0.00001) and percentage S-αT (r = 0.399, P = 0.001; r = 0.786, P < 0.00001) but negatively correlated with cord percentage RRR-αT (r = -0.399, P = 0.0009; r = -0.786, P < 0.00001).

The proportion of RRR-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 RRR-αT in the neonatal circulation. Because the bioactivities of RRR-αT and S-αT differ, this warrants future research to determine the importance of our observations to neonatal αT status.