Temporal expression of genes involved in folate metabolism and transport during placental development, preeclampsia and neural tube defects.

Folate is an essential micronutrient during pregnancy. The differential expression of genes related to folate transport and metabolism during the advancing gestation and pregnancy complications is not well established. Hence, we studied the gene expression of folate metabolism and transport proteins in the placenta with advancing gestation, preeclampsia and neural tube defects (NTD). The expression of folate transporters and enzymes involved in folate metabolism in the placenta with advancing gestation and pregnancy-related disorders were studied by 2-step RT-PCR. Folate levels were estimated by microbiological assay using Lactobacillus casei. Significant changes in levels of placental folate metabolizing enzymes were found in both physiological and pathological pregnancies during advancing gestation. Expression of methyltetrahydrofolate reductase (MTHFR) (p < 0.001) and cystathionine-β-synthase (CBS) (p < 0.001) was decreased while that of methionine synthase (MS) (p < 0.001) was increased with advancing gestation. A much-reduced expression of MTHFR (p < 0.01) and an abnormally high expression of methionine synthase reductase (p < 0.001) were observed in the NTD group. In NTDs, there was an adaptive up-regulation of folate transporters mainly reduced folate carrier (p < 0.001) and folate receptor alpha (p < 0.001). MTHFR expression showed a strong positive correlation (r = 0.96, p < 0.01) with folate levels in placenta. Pregnant women with preeclampsia had low expression of MS (p < 0.01) in association with low folate levels. Placental folate metabolizing enzymes exhibited a differential pattern during advancing gestation. Deficient folate status in association with alteration in expression of enzymes involved in folate metabolism might be associated with pregnancy complications such as preeclampsia and NTDs.