Fetal serum folate concentrations and placental folate transport in obese women

OBJECTIVE: We hypothesized that fetal folate serum concentrations are lower and placental folate transport is impaired in pregnancies of obese women. STUDY DESIGN: Umbilical vein serum and placental tissue were collected from normal weight and obese pregnant women at term. Cellular localization (immunohistochemistry) of folate receptor-alpha (FR-alpha), proton coupled folate transporter (PCFT), and reduced folate carrier (RFC) was established. Protein expression (Western blot) and transporter activity (isotope labeled methyltetrahydrofolate) were determined in syncytiotrophoblast microvillus membranes (MVM). RESULTS: Fetal folate concentrations were similar in obese women as compared with normal weight women. Protein expression of FR-alpha in microvillus membranes was increased (+173%), in RFC was decreased (-41%), and in PCFT was unchanged. However, activity of FR-alpha, PCFT, and RFC was unaltered in obesity. CONCLUSION: Fetal serum folate concentrations and placental folate transport activity are not altered in obesity at term, which suggests that limited availability of folate does not contribute to abnormal gene methylation and developmental programming.