The Role Of Reduced Folate Level In Growth Retardation Of Offspring In Early Life Induced By Vitamin D Deficiency During Pregnancy

Maternal vitamin D status during pregnancy is closely related to fetal growth and development,but the effect of maternal vitamin D status during different stages of pregnancy on growth retardation of offspring in early life and its mechanism are not fully elucidated.Therefore,based on the prospective birth cohort study,the effects of maternal vitamin D status at different stages of pregnancy on the growth retardation of offspring in early life were analyzed.The effects of maternal vitamin D status on maternal blood folate,cord blood folate and placental folate transport were analyzed,and the role of cord blood folate in fetal intrauterine growth restriction induced by maternal vitamin D deficiency was explored.This study includes two parts.1.The association between vitamin D status and growth retardation of offspring in early life during different stages of pregnancy.Based on the national birth queue platform of China,1193 single mothers,who were prenatal examination and delivery in Wuxi maternal and child health care hospital,and babies were enrolled in the period from March 2017 to December 2018.Maternal peripheral blood and information were collected during different stages of pregnancy period?early pregnancy,mid pregnancy and late pregnancy?.Matched maternal and cord blood and information of newborn at birth were collected during delivery.The growth development indexes such as weight,length,head circumference and tooth eruption quantity were monitored regularly during infancy?1-month,3-months,6-months,8-months,12-months,18-months and24-months-old?.The serum vitamin D[25?OH?D]levels of maternal blood and cord blood were measured by electrochemiluminescence immunoassay.According to the serum level of[25?OH?D],<50?50-75??75?nmol/L?were respectively defined as vitamin D deficiency?insufficient and sufficient group.The status and influencing factors of vitamin D in maternal and cord blood serum at different stages of pregnancy were analyzed.The relationship between the serum 25?OH?D levels of maternal blood and cord blood in different stages of pregnancy and birth weight,birth length and birth head circumference were analyzed.The risk of vitamin D deficiency in maternal and cord blood at different stages of pregnancy with premature birth,low birth weight and small than gestational age were analyzed.The effect of vitamin D deficiency in maternal blood and cord blood at different stages of pregnancy on the growth index?weight,length and head circumference?of fetus in utero and infancy were analyzed.The effects of vitamin D deficiency in maternal blood and cord blood on the growth rate and acceleration of infants growth were analyzed.The results showed that the serum 25?OH?D concentrations in the first,second and third trimester of pregnancy were 42.50,44.80,48.88 and 55.55?nmol/L?,respectively.The ratios of vitamin D deficiency in maternal blood during different pregnancy and cord blood were 75.0%,63.5%,62.3%and 47.8%,respectively.Compared with the group without vitamin D supplementation during pregnancy,the concentration of 25?OH?D in maternal early,late pregnancy and cord blood in the supplement group increased 4.58,6.30 and 6.78 nmol/L,respectively.Compared with spring,the 25?OH?D concentration in maternal blood of early,middle and late pregnancy in autumn increased 3.52,9.78 and 10.67 nmol/L,respectively.Loess curve equation fitting analysis showed that,there was a linear correlation between maternal blood and cord blood in early and late pregnancy serum 25?OH?D concentration and birth weight,birth length and birth head circumference.Multiple linear regression analysis showed that,compared with serum vitamin D sufficient group in maternal early and late pregnancy and cord blood,the birth weight decreased 0.18,0.21 and 0.19 kg,the birth length decreased 0.48,0.82 and 0.62 cm,and the birth head circumference decreased 0.55,0.69 and 0.45 cm,respectively in vitamin D deficiency group.Logistic regression analysis showed that,compared with the non-deficiency group??50 nmol/L?,the risk of preterm delivery increased 3.42and 6.39 times in late pregnant women and cord blood vitamin D deficiency group?<50 nmol/L?,respectively.The risk of low birth weight increased 2.85,6.04 and3.46 times respectively in the early,late pregnant and cord blood vitamin D deficiency groups.The risk of small than gestational age increased 2.12 and 2.36times respectively in vitamin D deficiency in early and late pregnancy group.Repeated measurement analysis of variance showed that the decline of growth retardation of the fetus and the delay of growth retardation infancy in male offspring were affected by the deficiency of vitamin D in maternal blood and cord blood in the early and late pregnancy.The analysis of latent variable quadratic growth curve model showed that low 25?OH?D concentration in maternal serum at different stages of pregnancy decreased the growth rate of weight,length and head circumference,but increased the acceleration of catch-up in male offspring in infancy.2.The effect of maternal vitamin D deficiency during delivery on folate level and placental folate transport.The parturient and fetus in the birth cohort were selected as the research objects.The matched maternal and cord blood,as well as the neonatal birth information were collected during the delivery period.The folate levels in serum from maternal blood and cord blood were detected by electrochemiluminescence immunoassay.The relationship between vitamin D level in maternal serum and maternal and the folate levels in cord blood was analyzed.The effect of vitamin D level in maternal blood serum on the folate levels in maternal blood and cord blood,as well as the folate placental transport efficiency?ratio of cord blood/maternal blood folate?were analyzed.The effect of maternal vitamin D status on the transporter of placental folate was further analyzed by three experiments.Experiment 1,the effect of maternal vitamin D deficiency on the expression levels of m RNA and protein in placental folate transport pump were analyzed by adopting the mouse model of vitamin D deficiency during pregnancy.Experiment 2,the effect of calcitriol?active vitamin D₃?on the m RNA expression level of folate transporter pump in human placental trophoblast?HTR8/SVneo?was analyzed by cell experiment in vitro.Experiment 3,the effect of maternal vitamin D deficiency at delivery on the m RNA expression level of folate transporter pump in human placenta was analyzed.The mediating effect of folate in cord blood between maternal vitamin D deficiency during pregnancy and intrauterine growth retardation of offspring was analyzed.Cohort study results showed that the average concentration of folate in maternal blood and cord blood were 19.28 and 31.77?nmol/L?,respectively.Correlation analysis showed that the vitamin D level in maternal blood was positively correlated with the folate level in maternal blood?r=0.476,P<0.01?and cord blood?r=0.338,P<0.05?.One-way ANOVA test showed that vitamin D deficiency in maternal blood decreased folate levels in maternal and cord blood,but did not affect placental folate transport efficiency.In vivo animal studies showed that there was no difference in the expression levels of m RNA and protein of placental folate transport pumps?pcft and rfc-1?between different groups.Vitro cell experiments showed that there was no significant difference in the m RNA expression level of folate transporter?PCFT and RFC-1?among different time points?12,24,36 hour?and doses?10,100,500 nm?groups.There was also no significant difference in the m RNA expression level of placental folate transporter?PCFT and RFC-1?in different groups of maternal serum vitamin D status.The mediating effect model analysis showed that the folate level in cord blood is fully responsible for the association between maternal vitamin D deficiency and intrauterine growth retardation of offspring.According to the results above,the following conclusions can be drawn in this study:1.Vitamin D deficiency in maternal blood during early and late pregnancy and cord blood not only reduced fetal growth and increased the risk of low birth weight,but also interfere the growth speed and catch-up acceleration of male offspring growth retardation in infancy.2.Maternal serum vitamin D level at delivery was positively correlated with the folate levels in maternal and cord blood.Maternal vitamin D deficiency at delivery did not affect the placental transport of folate in maternal blood,but decreased the folate levels in maternal and cord blood.The low levels of folate in maternal and cord blood may be the mechanism of fetal intrauterine growth retardation induced by maternal vitamin D deficiency in pregnancy.