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. 2011 Jul;205(1):83.e17-25.
doi: 10.1016/j.ajog.2011.02.053. Epub 2011 Feb 23.

Fetal serum folate concentrations and placental folate transport in obese women

Margaret F Carter  1 , Theresa L Powell, Cun Li, Leslie Myatt, Donald Dudley, Peter Nathanielsz, Thomas Jansson
Affiliations

Fetal serum folate concentrations and placental folate transport in obese women

Margaret F Carter et al. Am J Obstet Gynecol. 2011 Jul.

Abstract

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-α (FR-α), 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-α in microvillus membranes was increased (+173%), in RFC was decreased (-41%), and in PCFT was unchanged. However, activity of FR-α, 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.

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Figures

Figure 1
Figure 1. Maternal and fetal serum folate concentrations
For maternal samples n=15 (Normal BMI) and n=13 (Obese) and for fetal samples n= 9 (Normal BMI) and n=8 (Obese). Data are presented as mean ± SEM, t-test.
Figure 2
Figure 2. Cellular localization of placental folate transporters using immunohistochemistry
A-1, FR-α negative control; A-2, FR-α zinc fixative; A-3, FR-α formalin fixative, stained with methyl-green. B-1, PCFT negative control; B-2, PCFT zinc fixative; B-3, PCFT formalin fixative, stained with methyl-green. C-1, RFC negative control; C-2, RFC zinc fixative; C-3, RFC formalin fixative, stained with methyl-green.
Figure 3
Figure 3. MVM protein expression of folate transporters using Western blot
H, Homogenates; MVM, Microvillous Plasma Membranes, FR-α, Folate Receptor-α; PCFT, Proton Coupled Folate Carrier; RFC, Reduced Folate Carrier.
Figure 4
Figure 4. Quantification of Homogenates and MVM protein expression of folate transporters
n=7-9. A, Homogenates. B, MVM. * p ≤ 0.05, t-test.
Figure 5
Figure 5. Time dependence of MTHF binding/uptake in MVM
A, MTHF (methyltetrahydrofolate) uptake measured at a pH of 7.4. B, MTHF uptake measured at a pH of 6.0. Each point represents the mean of four determinations.
Figure 6
Figure 6. MVM MTHF binding/uptake
MTHF, Methyltetrahydrofolate; MVM, Microvillus Plasma Membranes; BMI, Body Mass Index. A, MTHF binding/uptake measured at a pH of 7.4. B, MTHF binding/uptake measured at a pH of 6.0. Data is presented as mean ± SEM, t-test.
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