Analysis Of The Predictors Of Adverse Perinatal Outcomes In ICP And Study On The Relationship Between ABC Family Gene And The Pathogenesis Of ICP

Background and ObjectiveIntrahepatic cholestasis of pregnancy(ICP)is a liver disorder in pregnant women that is characterized by pruritus and elevated levels of aminotransferase and total bile acids(TBA).It is the most common pregnancy-related liver disorder,affecting 0.1–1.5% of singleton pregnancies in Australia,Asia,Europe and North America,and 5-15% of pregnancies in South America.ICP is accompanied with increased risk of adverse perinatal outcomes(APOs)such as preterm birth <37 weeks(19-60%of ICP cases),meconium passage(17.9%),intrapartum non-reassuring fetal heart tracing(22-41%),respiratory distress syndrome(29%)and stillbirth(0.75-7%).Current diagnostic criteria for ICP: TBA≥10umol/L.Clinical data showed that patients with ICP associated with elevated alkaline phosphatase(ALP),but the research literature reported less about the relationship between increased ALP and ICP,and the quantitative analysis of predictors of adverse perinatal outcomes in ICP was less.This study will make quantitative analysis about biochemical indexes of ICP and adverse perinatal outcomes,exploring the predictors of adverse perinatal outcomes in ICP and deciding the time to termination of pregnancy.The pathogenesis and etiology of ICP have not been clear until now.At present,relevant studies have shown that ICP is related to heredity,estrogen metabolism,environment,immunity and molecular metabolism.In terms of genetics,numerous studies have been conducted on the following genes: ABCB11,ABCC2,ABCB1,ABCB4,ABCG5,ABCG8,ABCG2,AE2,MATE1,AQPs,FIC1,ATP8B1,MDR3,FXR,ATPB8B1,MRP2,MRP3,PXR,MDR3,OATP1A2,OATP1B1,OATP1B3,PFIC3,NR1H4,FGF19 et al.Polymorphism and variation of these genes were correlated with the etiology of ICP.Some scholars believe that ABC family genes are closely related to the pathogenesis of ICP.Therefore,in recent years,relevant literature has reported the association between ABC family genes and ICP.Among them,ABCB11,ABCB4 and ABCC2 have been found to be controversial in several articles.Some scholars believe that ABCB4 and ABCB11 were strongly associated with ICP,while ABCC2 was not.Another group of researchers concluded that ABCC2 was associated with ICP,with ABCB4 occurring mostly in TBA> 40umol/L and ABCB11 mutation occurring in only 1% of the population,while few relevant studies were reported in China.Based on the controversy above,we studied the correlation between the variation and polymorphism of ABCB4,ABCC2 and ABCB11 genes and ICP.Methods(1)Analysis of clinical data of 570 ICP cases: Data of pregnant women with 570 cases admitted to our hospital from June to December 2018 were obtained from an electronic database.The records include name,age,gravidity,parity,delivery pregnancy week,biochemical indicators at admission including aspartate aminotransferase(AST),alanine aminotransferase(ALT),total bilirubin(TBIL),maximum TBA during pregnancy,symptoms,delivery mode,the amount of postpartum bleeding,Apgar score,birth weight,meconium stained amniotic fluid,complications of pregnant women and newborn.To understand the proportion of age distribution,chief complaints,biochemical indicators,adverse perinatal outcomes and complications.(2)Correlation analysis between biochemical indexes of ICP and adverse perinatal outcomes in 419 ICP: Excluding diseases of the hepatobiliary system and other factors that may cause adverse perinatal outcomes,419 cases with ICP were included in the study.419 cases of ICP were classified as mild(10 umol/L≤ total bile acids(TBA)< 40 umol/L,n=276)or severe ICP(TBA≥ 40 umol/L,n=143).Clinical characteristics,perinatal outcomes,and biochemical markers were compared.Receiver operating characteristic curve analysis was used to determine the optimal alkaline phosphatase(ALP)cutoff values for predicting ICP and APOs,while univariate and logistic regression were used to determine predictors of APOs.(3)The correlation between ABCB4,ABCB11 and ABCC2 gene variation and polymorphism and the pathogenesis of ICP: Fifty-seven cases with ICP diagnosed and delivered in our hospital in 2019 were selected ICP group,and 37 cases of pregnant women who were hospitalized in our hospital at the same time and without complications were selected them as the control group.There was no statistical difference between ICP group and the control group in terms of age,region and dietary habits,and there were no complications such as viral hepatitis and fatty liver,hepatobiliary diseases,et al that might cause liver function damage among these people.Methods:3ml of peripheral blood was extracted from each study subject.Primers of ABCB4,ABCB11 and ABCC2 were designed,and then the three genes ABCB4,ABCB11 and ABCC2 were captured in the extracted peripheral blood by multiple PCR amplification method,and the three genes ABCB4,ABCB11 and ABCC2 were sequenced.The Armitage trend test was used to identify sites that were statistically different between the ICP group and the control group.Results(1)Among the 570 ICP patients,the ratio of chief complaints were as follows:273 cases had skin itching(48%),106 cases had elevated bile acid(19%),61 cases had elevated liver enzymes(11%),14 cases had fetal distress(2%),143 cases had no symptoms(25%).(2)TBA,ALP,total bilirubin(TBIL),and direct bilirubin(DBIL)levels were significantly higher in the severe ICP group than in the mild ICP group.The rates of delivery before 34 gestational weeks,pruritus,meconiumstained amniotic fluid and neonate intensive care unit admission were significantly higher in the severe ICP group than in the mild ICP group.After adjusting for potential confounders,TBA>40 umol/L and DBIL>10 umol/L were independent risk factors for delivery at <34 weeks,while ALP>269.55U/l,TBA>40 umol/L and DBIL>10 umol/L were independent risk factors for meconium-stained amniotic fluid.TBA>40 umol/L,ALP>273.75 U/L and DBIL>10 umol/L were associated with composite APOs.The optimal ALP cutoff value for predicting ICP was 146.5 U/L.(3)There were three sites with statistical differences between ICP group and the control group: rs2389612(C>T),rs2287616(A>G),and rs3815675(A>G)of ABCB11 gene locus.Among them,the OR values of the mutant gene loci of these three ABCB11 loci were all <1,indicating that they were not risk factors of ICP.Gene ABCB11 rs2389612 C>T,homozygous mutant-type TT,OR value> 1,were risk factors for ICP,but P> 0.05 showed no significant difference.There were 4 SNPs in ABCB4(rs1014283C> A,rs2109505 T> A,rs1202283 G> A,rs2302387 G> A).Although there was no significant difference between ICP group and the control group,the mutant allele may be a risk factor for ICP disease(OR>1).All patients with ABCB4rs1014283 C >A gene site mutation also had ABCB4 rs 2109505 T > A gene site mutation.The mean value of TBA in ICP patients with ABCB4 mutation fluctuated between 44.7-51.02umol/L.Conclusions(1)ICP has a high incidence(7.4%),mainly manifested as itchy skin.Even if 25% of the 570 ICP cases had no itchy symptoms,ICP also occurred.It is necessary to pay attention to the biochemical indicators of ICP,so as to achieve early diagnosis of ICP,timely treatment,timely termination of pregnancy and improvement of prognosis.(2)Among the 419 ICP patients,serum ALP,TBA and DBIL were positively correlated with adverse perinatal outcomes of ICP.Among them,ALP may be associated with ICP related adverse perinatal outcomes(including meconium stained amniotic fluid,delivery weeks < 34 weeks,and adverse neonatal outcomes).(3)ABCB4 and ABCB11 may be related to the incidence of ICP.Most patients with ABCB4 mutation are patients with severe ICP.ABCB4rs1014283C> A and ABCB4 rs 2109505 T> A may have synergistic effect on the occurrence of ICP.