A Case-Control Study On Effect Of Environmental Risk Factors And Polymorphism Of Metabolic Enzyme Gene On Preterm Birth

Background:Whether in developing or developed counties,preterm birth is still one of the important reasons that cause perinatal infants' morbidity and mortality,also leads to children complications and sequelaes,such as growth retardation,visual impairment, hearing impairment,chronic lung disease,cerebral palsy and movement dysfunction etc.,as well as cause hypertension,coronary heart disease,Ⅱdiabetes etc.after they grow up.Thus preterm birth has a profound impact on individual's physical and mental health and causes huge financial burden on social and family.In recent 20 years,prevention measures used by the various adverse pregnancy outcomes are not very effective.The incidence of preterm birth has not declined but in some countries there is an upward trend.The incidences of preterm birth are different with different areas,ethnic and nationality.The data show that the incidence rate of preterm birth is 5%-15%,while the incidences of preterm of the United States and Canada in recent years are upward trend.China's incidence rate of preterm birth is still a lack of unified national research datum,and about 10 percent.Therefore,it is still an significant subject to further explore causes of preterm birth and reduce its incidence.The problem of preterm birth has aroused extensive attention of scholars at home and abroad and epidemiological studies on risk factors for preterm birth have also been carried out,but mainly concentrated in one or several factors,such as clinical factors,nutrition,psychological and socio-economic aspects.However,with the constant deterioration of the people's living environment and the complexity of environmental factors,people should study in a larger range of environmental risk factors impact on preterm birth.In addition to environmental factors and the impact of socio-economic conditions, genetic factors may also be an important factor on preterm birth.The studies found that preterm birth of black people are significantly families gathered;a mother who has a history of preterm birth increased the probability of having preterm infants again, which suggested that the occurence of preterm birth is affected by genetic factors. Now,the researches on genetic factors related to preterm birth are less and more less on environmental pollution and genetic susceptibility of preterm birth.From the perspective of multifactor,this study explored the effects of environmental risk factors,which highlights the life of the current environmental exposure,the metabolism enzyme of genetic susceptibility factors and internal exposure content of chemical pollutants in the environment on preterm birth,to provide a scientific references for preventing and reducing the occurrence of adverse pregnancy outcomes and infant mortality.Objectives:1.To explore the environmental risk factors of preterm birth in Taiyuan City;2.To explore the relationship between internal exposure content of chemical pollutants and preterm birth;3.To explore the impact of the neonatal infants and their mothers toxic metabolic enzymes gene polymorphism on preterm birth,while understanding the interaction of gene-gene and gene-environment in preterm birth.Methods:1.To survey the environmental risk factors on preterm birth by epidemiological investigation. Using a 1:2 match case-control method to choose preterm birth cases and the control,a epidemiological investigation were carried out about environmental risk factors of preterm birth.At the same time using Logistic regression model to screen environmental risk factors.2.To detect the content of chemical pollutants in biological samples by method of chemical analysis.Using enzyme hydrolysis -High Performance Liquid Chromatography(HPLC) to detect the content of 1-OH-Py in mothers' urine in cases and the control groups; Using automatic biochemical analyzer to detect urine creatinine;Using Inductively Coupled Plasma Mass Spectrometry(ICP-MS) to detect the heavy metals and trace element in mothers' vein blood and neonate umbilical cord blood in cases and the control groups.3.To detect metabolic enzyme gene polymorphism by the method of molecular epidemiology.Using Multiplex PCR to detect GSTM1,GSTT1 gene polymorphism;Using RFLP-PCR to detect MspI polymorphism on CYP1A1 gene and RsaI polymorphism on CYP2E1 gene.Using logistic regression model to analyses genetic polymorphism and screen genetic risk factors.Results:The partⅠ:A 1:2 matched case-control study on environmental risk factors for preterm birth1.The results of singie-factor logistic regression model analysis.1.1 General situation of neonates' parents:Possible risk factors of Preterm birth:The mother's occupation that is farmer (OR=4.176,95%CI 1.920-9.082) or the mother who is unemployed(OR=1.447,95% CI 1.006-2.081) or the father's occupation that is farmer(OR=10.851,95%CI 3.674-32.058);The father's height(OR=1.137,95%CI 1.016-1.708);Less weight gain during pregnancy(OR=1.771,95%CI for 1.282-2.445).High education level of mother and father is a protective factor for preterm birth, which OR are 0.731(95%CI 0.621-0.860) and 0.692(95%CI 0.591-0.811) separately.The mother's height,weight,BMI and father's weight,BMI has no obvious relationship with preterm birth.1.2 High household income is a protective factor for preterm birth(OR=0.750, 95%CI 0.649-0.867);Times of less prenatal examination is a risk factor of preterm birth(OR=3.362,95%CI 2.238-5.051).1.3 The relationship between living environment exposure of pregnant women and preterm birth.The risk factors are:Permanent living places in factories and mines and in rural areas,OR are 2.447(95%CI 1.587-3.773) and 4.368(95%CI 1.166-16.365) separately,volume of fumes from cooking(OR=1.656,95%CI 1.275-2.150);the use of coal fuel in home(OR=3.447,95%CI 1.956-6.074),the ways of getting warm in home(OR=2.664,95%CI 1.764-4.022,the use of well water or simple tap water (OR=1.608,95%CI 1.173-2.205),decoration during pregnancy(OR=2.213,95%CI 1.035-4.734).Use of exhaust equipment is a preterm birth protective factor(OR=0.519,95% CI 0.364-0.740).There is not obvious relationship between use of microwave ovens, induction cooker,mobile phones,keeping of pets during pregnancy,dyeing hair during pregnancy and preterm birth.1.4 Passive smoking of pregnant mothers(OR=1.237,95%CI 1.030-1.485)and smoking fathers(OR=1.170,95%CI 1.016-1.135) are possible risk factors for preterm birth.1.5 Eating habits and nutrition during pregnancy.Regular consumption of meat food during pregnancy(OR=0.729,95%CI 0.561-0.949),taking folic acid before and during pregnancy(OR=0.681,95%CI 0.521-0.892) are protective factors of preterm birth;Regular consumption of supplementary vitamins,fruits,vegetables,eggs and milk during pregnancy is not associated with preterm birth obviously.1.6 Fetus education(OR=0.667,95%CI 0.499-0.891) is a protective factor of preterm birth.The relationship between pregnant women's psychological factors and family history of birth with preterm birth still remain to be further explored.2.The results of multi-factors Logistic regression model analysis.After adjusted other bias factors,using of unclean fuels(OR=2.083,95%CI 1.126-3.855),less times of prenatal examination(OR=2.581,95%CI 1.710-3.897) may be the main risk factors for preterm birth;High family incomes(OR=0.831, 95%CI 0.701-0.986) and no the history of prematurity(OR=0.107,95%CI 0.013-0.911) are protective factors of preterm birth.The partⅡ:The relationship between the content of internal exposure of the environmental chemical pollutants and preterm birth1.The relationship between the content of 1-OH-Py in mothers' urine and preterm birth.The content of 1-OH-Py in mothers urine samples in preterm group is(median) 1.0521μmol/mol creatinine,while in control group is(median) 0.7792μmol/mol creatinine;After logarithm conversion and using matched t-test,it is not enough to draw a conclusion that there is a statistic difference between the value of 1-OH-Py in mothers urine in cases and in matching the control group samples(t=1.982,P=0.051), and it remains to be further expanding sample sizes for research.2.Element content in mothers' vein blood in the cases and the control groups.There is no statistically significant difference between mothers vein blood Pb content in the cases and that in the control groups(Z=-0.144,P=0.886).There is a statistically significant difference between mothers vein blood chromium content in the cases and that in the control groups,chromium content in control group is higher than that in the case group(Z=-2.462,P=0.014);There is a statistically significant difference between mothers vein blood Cu content in the Cases and that in the control group(Z=-2.247,P=0.025),Cu content in control group is higher than that in the case group.3.Neonate umbilical cord blood elements in cases and the control groups.There is no statistically significant difference between newborn infants umbilical cord blood Pb content in the Cases and that in the control groups(Z=-0.309,P= 0.757);There is no statistically significant difference between neonate umbilical cord blood chromium content in the Cases and that in the control groups,(Z=-1.634,P= 0.102);There is a statistically significant difference between neonate umbilical cord blood Cu content in the cases and that in the control groups(Z=-2.993,P=0.003), Cu content in control group is higher than that in the case group.The partⅢ:the relationship between the metabolic enzyme gene polymorphism of the mothers and the neonates and preterm birth1.The results of single-factor logistic regression model analysis of relationship between the mother's metabolic enzyme genetic polymorphism and preterm birth.GSTT1 null genotypes are related to preterm birth.The individuals carrying GSTT1 null genotypes have higher risk on preterm birth,OR=1.704(95%CI 1.059-2. 740);CYP1A1 mutation genotypes are related to preterm birth,the individuals carrying CYP1A1 mutation genotypes(heterozygous and homozygous mutation) have higher risk on preterm birth,OR=2.259(95%CI 1.229-4.152),OR=2.384(95%CI 1.083-5.250);GSTM1 and CYP2E1 genotypes are not associated with preterm birth (P＞0.05).2.The combined effects of different genotypes in mothers' GSTM1,GSTT1, CYP2E1 and CYP1A1.GSTM1 and CYP1A1 combined genotypes are associated with preterm birth(P＜0.05).The preterm birth risks of the individuals who carrying GSTT1 non-null genotypes and CYP1A1 heterozygous genotypes at the same time are higher than that of those who carrying GSTT1 non-null genotypes and CYP1A1 wild-genotypes.GSTT1 and CYP1A1 combined genotypes are related to preterm birth(P＜0.05). The preterm birth risks of the individuals who carrying GSTT1 non-null genotypes and CYP1A1 heterozygous or mutant genotypes at the same time and the individuals who carrying GSTT1 null genotypes and CYP1A1 wild or heterozygous or mutant genotypes at the same time are significantly increased,comparing with that of individuals who carrying GSTT1 non-null genotypes and CYP1A1 wild-genotypes at the same time.3.Mothers' different genetic multi-factors conditional logistic regression analysis.After adjusted for other confounding factors,GSTT1 gene and CYP1A1 gene polymorphism are shown relationship with preterm birth(P＜0.05),OR values are 1.700(95%CI 1.042-2.772),2.250(95%CI 1.215-4.169),2.391(95%CI 1.066-5.367), separately.4.The results of single factor conditional logistic analysis on relationship between neonatal infant metabolic enzyme gene polymorphism and the preterm birth.Neonatal infant GSTT1 null genotypes are related to preterm birth(P＜0.05).The preterm birth risks of the individuals who carrying GSTT1 null genotypes are high, OR=1.818(95%CI 1.081-3.059);CYP1A1 mutant genotypes are may be related to preterm birth,it is not enough to draw a conclusion that neonatal infant CYP1A1 mutant genotypes is related to preterm birth(P=0.0658),and it remains to be further expanding sample sizes for research,according to a=0.05;GSTM1 and CYP2E1 genotypes are not shown relationship with preterm birth(P＞0.05).5.The relationship between combined effect of neonatal infant GSTM1,GSTT1, CYP2E1 and CYP1A1 genotypes and preterm birth.Neonatal infant GSTM1 and CYP1A1 joint genotypes are related to preterm birth(P＜0.05).The preterm birth risks of the individuals who carrying GSTT1 non-null genotypes and CYP1A1 mutant genotypes and the individuals who carrying GSTM1 null genotypes and CYP1A1 heterozygous genotypes at the same time are significantly increased,comparing with that of individuals who carrying GSTM1 null genotypes and CYP1A1 wild-genotypes at the same time.Neonatal infant GSTT1 and CYP1A1 joint genotypes are related to preterm birth(P＜0.05).The preterm birth risks of the individuals who carrying GSTT1 null genotypes and CYP1A1 or mutant genotypes at the same time are significantly increased,comparing with that of individuals who carrying GSTT1 non-null genotypes and CYP1A1 wild-genotypes at the same time.6.The results of different neonatal infant genes multifactor conditional logistic regression analysis.After adjusted the other genes effect,neonatal infant GSTT1 gene polymorphism is related to preterm birth,OR=1.755(95%CI 1.040-2.962);CYP1A1 mutant homozygous genotypes are may be related to preterm birth,it is not enough to draw a conclusion that neonatal infant CYP1A1 mutant genotypes is related to preterm birth(P=0.0566),and it remains to be further expanding sample sizes for research,according to a=0.05.7.Multifactor analysis of relationship between environmental risk factors and maternal metabolic enzyme gene polymorphism and preterm birth.After adjusted other confounding factors,environmental risk factors related to preterm birth are the fuel used by family(OR-4.758,95CI 1.859-12.178),the use of exhaust equipment(OR=0.368,95%CI 0.147-0.920);the genetic factors related to premature is the CYP1A1 gene,which carrying mutant heterozygous CYP1A1 genotype compared with CYP1A1 genotype homozygous wild has higher risk, OR=2.433,95%CI for 1.170-5.058.8.Interaction analysis on the environmental risk factors and mothers' metabolic enzyme genes polymorphism in preterm birth.Domestic fuel and mother CYP1A1 gene polymorphism exists interaction,at home in the use of non-clean fuels,and the mother carrying CYP1A1 MspI one or two mutant alleles,mutant heterozygous or mutation homozygous genotype,could increase in the risk of premature(carrying mutant heterozygous genotypes:OR= 14.467,95%CI 3.618-57.852;carrying homozygous mutation genotypes:OR=26.708, 95%CI 2.804-254.430).Using the product model,to the further test the interaction of two factors,found that there was a significant difference on the interaction of two factors(P＜0.01).Conclusion:Through this research results can be considered:the occurence of preterm birth was affected by environmental factors and genetic factors.1.The main environmental factors related to preterm birth:After adjusted the other confounding factors,the use of unclean fuel,less times of prenatal examination may be the main risk factors for preterm birth;high-income of families and the mothers without preterm birth history is the protective factors. 2.The parents occupations and education degrees,Cooking Oil-Smoke,heating ways,house decoration during pregnancy,passive smoking,smoking of father, whether taking folic acid before pregnancy,fetus education during pregnancy,eating meat during pregnancy,less weight gain before pregnancy may be all association with preterm birth.3.The content of 1-OH-Py in maternal urinary in preterm birth groups were slightly higher than that in control groups,according to a=0.05 level,it was can not draw a conclusion temporary.But the contents of maternal urinary 1-OH-Py were slightly higher in Taiyuan City,which indicating that Taiyuan's maternal were exposure to higher polycyclic aromatic hydrocarbons;That may be related to serious air pollution in Taiyuan,which prompted concern about air pollution's impact on the outcome of pregnancy.4.There are not statistically significant differences of the mothers vein blood lead and the neonates umbilical cord blood lead between the cases and the controls.But that the whole blood lead levels are high may be related to environmental pollution.In addition,the mothers and neonates blood copper content in case groups are lower than that in the control groups,which prompted concern about the lack of maternal trace elements,which is meaningful for the prevention of possible adverse pregnancy outcomes.5.After adjusted for other gene confounding factors,the mothers' and neonates' GSTT1 gene polymorphism are related to preterm birth;The preterm birth risks of the individuals who carrying GSTT1 null genotype are higher than that of individuals carrying non-null genotypes;and the mothers' CYP1A1 gene polymorphism are related to preterm birth;the preterm birth risks of the individuals who carrying CYP1A1 mutant genotypes(mutant heterozygous genotypes and homozygous mutation genotypes)are higher than that of the individual carrying wild genotypes; The results prompt our concern on maternal individual differences and prevent the incidence of premature delivery.6.The mothers' GSTT1 and CYP1A1 combined genotypes are associated with preterm birth;Neonatal infant GSTT1 and CYP1A1 combined genotypes are associated with preterm birth.The preterm birth risks of the individuals who carrying GSTT1 null genotype and CYP1A1 genotype or mutant genotype at the same time are higher than that of those who carrying GSTT1 non-null genotypes and CYP1A1 wild-genotypes.7.After adjusted other confounding factors,the use of coal fuel in family is risk factor for preterm birth,the use of the exhausting cooking oil-smoke equipment is preterm birth protective factor;mothers carrying CYP1A1 mutant heterozygous genotypes are risk factors for preterm birth.8.An interaction was observed in gene-environment co-effect in the premature, Domestic fuel and mother CYP1A1 gene polymorphism exists interaction,at home in the use of non-clean fuels,and the mother carrying CYP1A1 MspI one or two mutant alleles,mutant heterozygous or mutation homozygous genotype,could increase in the risk of premature.