Vitamin B 12 and Placental Expression of Transcobalamin in Pregnant Adolescents

Background Transcobalamin is a key placental protein involved in transport of vitamin B 12 to the fetus. However, few data currently exist on the ability of the placenta to modify vitamin B 12 transporter expression, particularly among high‐risk populations such as pregnant adolescents. Objective This study was conducted to determine the impact of maternal and neonatal vitamin B 12 status on placental transcobalamin (TC) expression in a cohort of healthy pregnant adolescents in the United States. Design Serum total vitamin B 12 concentrations were measured from maternal blood samples at mid‐gestation (26.4 ± 2.8 weeks) and delivery (39.8 ± 1.4 weeks) and infant cord blood samples at birth. Placentas were collected at delivery and TC mRNA expression (ΔΔCt) and TC protein abundance (TC:α‐actin) were determined. Linear and binomial regression models were used to examine the associations of maternal (mid‐gestation, delivery) and infant cord blood vitamin B 12 status with placental TC mRNA expression and TC protein abundance (n=63). Results Maternal serum vitamin B 12 concentrations at mid‐gestation were not associated with placental TC mRNA expression or TC protein abundance (p>0.05). Higher maternal serum vitamin B 12 concentrations at delivery were associated with higher placental TC mRNA expression (p=0.03), but not TC protein abundance (p>0.05). Higher placental TC protein abundance was also associated with higher infant cord blood vitamin B 12 concentrations (p=0.003). Conclusions Higher placental TC protein abundance was associated with higher neonatal vitamin B 12 status, indicating an important role in vitamin B 12 transport to the fetus. Support or Funding Information The United States Department of Agriculture (USDA): USDA 2005‐35200‐15218 and USDA 2010‐34324‐20769; and the Division of Nutritional Sciences, Cornell University