Metabonomics And Lipidomics Of Fetal Amniotic Fluid And Urine Of Pregnant Women With Down’s Syndrome

Objective: At present,there is no effective cure for Down’s syndrome.Prenatal screening and diagnosis are the best method nowadays to identify fetuses with Down’s syndrome and reduce the birth of Down’s syndrome fetus.Metabolomics,which has been widely used in medical science for disease marker screening,drug targeted therapy and personalized medicine has provided a new approach for prenatal screening.Although it has been found that the difference of metabolites in pregnant women is closely related to fetal development,there are few studies on the metabolites and pathways in amniotic fluid and urine of pregnant women with Down’s syndrome.Therefore,from the perspective of metabolomics and lipid metabolomics,we used liquid chromatography-mass spectrometry(LC-MS)to screen the different metabolites between pregnant women who carry Down’s syndrome fetuses and healthy controls using their amniotic fluid and urine.Methods: Amniotic fluid and urine samples of 20 pregnant women with Down’s syndrome fetuses and 20 healthy controls were collected.Firstly,principal component analysis(PCA),partial least squares method discriminant analysis(PLS-DA)and response model were used to test the variable importance in the projection of the first principal component of PLS-DA model,combined with the fold change(FC)and Student’s t-test to screen the metabolite differences.Secondly,hierarchical cluster analysis(HCA)was used to show the correlation and expression of different metabolites.Finally,KEGG and Compound Discoverer 3.0 software were used to identify the metabolic pathway.Lipid metabolomics using samples from the same participants were analyzed.The metabolite with significant differences were identified with the classification standard of international lipid classification and Nomenclature Committee.Results: PCA and PLS-DA data analysis of metabolomics data showed that there were significant differences between patients who carry Down’s syndrome fetus and healthy controls in both positive and negative ion modes.Combined with nonparametric test,7 differential metabolites in amniotic fluid samples were further screened and identified;a total of 2differential metabolites were identified in urine samples.In the positive ion mode,compared with healthy controls,the differential metabolites were enriched in 20 metabolic pathways,including GABAergic synapses,amyotrophic lateral sclerosis pathway,adrenergic signal transduction in cardiomyocytes,and metabolism of D-glutamine and D-glutamic acid metabolic pathway.In the negative ion mode,compared with the healthy case control,the differential metabolites were enriched in 20 metabolic pathways,in which aldosterone synthesis and secretion pathway were significantly enriched.Phenylalanine metabolism pathway was significantly enriched in urine compared with healthy controls.The results of lipidomes showed that there were significant differences between Down’s syndrome patients and healthy controls.Further nonparametric test showed that 23 kinds of differential lipids were further screened and identified in amniotic fluid samples,of which 10 kinds of differential lipid molecules were up regulated and 13 kinds were down regulated;8kinds of differential lipid molecules were identified in urine samples,of which 2 kinds were upregulated and 6 kinds were down regulated.According to the classification standard of the International Committee for classification and nomenclature of lipids,the differential lipids are classified,which can be divided into 8 lipid subtypes and 3 lipids.Conclusion: Metabolomics and lipidomes were used to screen different metabolites between pregnant women who carry Down’s syndrome fetuses and healthy controls using their amniotic fluid and urine.Compared with the healthy group,a total of 7 differential metabolites were screened out,of which 6 differential metabolites were significantly enriched in 5metabolic pathways,and the other one,2-hexenylcarnitine,was significantly up-regulated in amniotic fluid and urine samples,it has the potential to be a metabolic marker of Down’s syndrome.In lipidomics,a total of 31 different lipid molecules were screened and classified into8 major lipid subclasses and 3 major lipids.In addition,significant enrichment of GABAergic synapses,amyotrophic lateral sclerosis pathway,adrenergic signal transduction of cardiomyocytes,D-glutamine and D-glutamate metabolism,aldosterone synthesis and secretion,glyceride metabolism,both sphingolipid metabolism and glycerophospholipid metabolism pathways are related to Down syndrome.