Effects Of Folic Acid Supplementation During Pregnancy On The Neurodevelopment By DNA Methylation In Infants And Toddlers:A Birth Cohort Study

Objective:Folic acid(FA)is an important vitamin for neurodevelopment and cofactor for carbon metabolism,which is involved in DNA and RNA synthesis and DNA methylation.The purpose of this study is to reveal the effect of folic acid supplementation on the neurodevelopment of offspring aged 1,3 and 24 months,and to explore the mechanism of DNA methylation.Methods:This study was carried out in Tianjin from July 2015 to December 2018.Our team cooperated with a district level maternal and child health care center and six community health service centers in Tianjin.Maternal pregnancy test,production and postpartum test records were collected by querying database.Maternal folic acid supplementation during pregnancy was retrospectively collected at the first post-natal examination and offspring aged 1,3 and 24 months were followed up.The neuropsychological development checklist of 0-6 year old children was used to evaluate the neurodevelopment of offspring by doctors of child health care.According to the dosage of maternal folic acid supplement during pregnancy,it can be divided into three groups: Non-users group,FA-400?g/d,MMN(FA-400?g/d)and MMN(FA-800?g/d).According to the duration of supplementation,it can be divided into three groups: Nonusers group,Users ? 3 mo,Users 3-6 mo,and Users > 6 mo.The venous blood of pregnant women at 16-18 weeks of gestation was collected to detect DNA methylation and the level of one carbon metabolite.Serum Homocysteine(Hcy)was detected by automatic biochemical analyzer,Plasma Sadenosyl-homocysteine(SAH)and S-adenosyl-methionine(SAM)were detected by high performance liquid chromatography,5-methylcytosine(5m C)was detected by ELISA,DNA methylation level of folate metabolizing gene was detected by Methyl Target.A mixed effect model was used to investigate the relationship between the level of FA supplementation,one carbon metabolite and DNA methylation during pregnancy and the neurodevelopment of offspring.Using IBM SPSS Amos to build a structural equation model,namely path analysis,to explore the relationship between the influencing factors of pregnancy and the neurodevelopment of offspring.The test level of all analysis results was?=0.05.P<0.05 was statistically significant.Results:The results showed that the proportion of low education level,low family monthly income(? 5000 yuan),and premature birth(< 37 weeks)in the non-users group were higher than those in the other groups.Compared with non-users group,FA-400?g/d supplementation group,MMN(FA-400?g/d)and MMN(FA-800?g/d)supplementation group had positive effects on the development quotient(DQ)of offspring at 1 and 24 months of age;there was no difference between the supplementation groups.The effects of folic acid supplementation period on the neurodevelopment of offspring were compared with that of non-users group.The Users ? 3 mo,Users 3-6 mo and Users > 6 mo groups had positive effects on DQ of offspring at 1 and 24 months of age,and there was no difference among the supplementation duration.Different dosage and duration of folic acid supplementation had no effect on DQ of 3-month-old offspring.Hcy,SAH,SAM,SAM/SAH and 5m C%,which reflect the level of DNA methylation,were detected.Path analysis showed the plasma SAM/SAH value of folic acid supplementation group was higher in the second trimester,and SAM/SAH had a positive effect on DQ of offspring.There was no significant difference in the methylation level of methylenetetrahydrofolate reductase(MTHFR),methionine synthase reductase(MTRR),methionine synthetase(MTR)gene among different folic acid supplementation groups(P > 0.05).We observed statistical differences in the methylation haplotype frequency of different gene fragments and the methylation level of different Cp G sites in the three groups(P < 0.05),which may be related to folic acid supplementation.Conclusions:This study revealed folic acid supplementation during pregnancy improve the neurodevelopment of offspring at 1 and 24 months old,but no difference beween DQ of offspring was found in different groups of dosage and duration of folic acid supplementation.Path analysis showed that folic acid supplementation during pregnancy indirectly promoted DQ of offspring by increasing plasma SAM/SAH value in the second trimester.Because SAM/SAH can reflect the potential of methylation,this study suggests that folic acid supplementation during pregnancy may affect the neurodevelopment of offspring through DNA methylation.