Vitamin B6 (PLP) and Neural Tube Defects: Is There an Association?
Neural tube defects (NTD) originate from an incomplete closure of the neural tube and are one of the most common and severe congenital malformations. The aetiology of NTD is multifactorial, indicating a combination of environmental and genetic factors. One of the most important environmental factors is the maternal vitamin status. Periconceptional folic acid supplementation can prevent about 60% of the NTD cases (1, 2). The exact preventive mechanism of folate on the occurrence and recurrence of NTD is unknown. Folate in the form of 5-methyltetrahydrofolate (5-meTHF) is required for the remethylation of homocysteine to methionine by the enzyme methionine synthase (MS). Therefore, a deficiency in folate may result in elevated plasma homocysteine concentrations. Although mothers of NTD children are not deficient in folate, their folate levels are in the lower range of the control levels and their plasma homocysteine concentrations are elevated (3, 4, 5). The 677C>T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is the first genetic risk factor for NTD and is partly responsible for these changes in homocysteine concentrations (6). Another vitamin involved in the methylation of homocysteine is vitamin B12, which functions as a cofactor of methionine synthase (MS). Some studies showed an association between decreased plasma vitamin B12 levels or decreased plasma holo-transcobalamin (holo-tc) levels and NTD (7, 8).
KeywordsHPLC Glycine Cysteine Serine Folate
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