Dynamic Metabolomics Alteration In The Urine Of Healthy Pregnant Women During Normal Pregnancy And Its Relationship With The Metals Exposure

During normal pregnancy, in order to meet the needs of fetal growth and development, the maternal body faces a significant challenge in the sugar, protein and lipid metabolism. In the early stage of pregnancy, the anabolism is dominant to meet the demand of the energy in late pregnancy and lactation. During this period, the fasting blood glucose and fasting insulin levels are not significantly changed, while the maternal insulin sensitivity decreases significantly. As the pregnancy progressing, fasting blood glucose showes a progressive decrease, and glucose synthesis in the liver is significantly increased. In late pregnancy, the catabolism is dominant, and showes a significant increase in insulin resistance and decrease in insulin sensitivity, resulting in significantly elevated glucose level and free fatty acid concentration. In addition, during this period, amino acid and protein metabolism is very active. Urea cycle and branched chain amino acid metabolism are also significantly suppressed. These phenomenons are thought to be a necessary and indispensable physiological change during normal pregnancy. Under this context, it is valuable to study the dynamic metabolomics change induced by normal pregnancy. Previous study mainly applied a cross-sectional study design by recruiting different subjects at each time point,thus, interference introduced by interindividual variation was inevitable. However, the metabolic trajectory of longitudinal cohorts of healthy pregnant women from urine samples obtained in a non-traumatic manner are still lacking.In this study, a UPLC-QTOFMS-based untargeted metabolomics approach was employed to investigate dynamic variations in the urine metabolites in a cohort of 232 healthy pregnant women during the course of pregnancy. And the overall level of urine metals exposure were also measured by ICP-MS. To further investigate the relationship between the metals exposure and metabolomics alteration, a panel data model was introduced into this study to characterize the correlation between the metal exposure and the metabolic change.Part I:Normal pregnancy related metabolic alteration in a longitudinal cohort of healthy women by UPLC-QTOFMS based metabolomics studyObjectives:The purpose of this part is to investigate the dynamic metabolomics alteration in maternal urine during normal pregnancy.Methods:We conducted a UPLC-QTOFMS based untargeted metabolomics approach to investigate the dynamic metabolomics signature in a longitudinal cohort including 232 healthy pregnant women in their first, second and third trimesters.Results:The profile of metabolites in different trimester was significantly changed with the progress of pregnancy.236 metabolites in second trimester and 235 metabolites in third trimester both passed the rules of VIP> 1 and SDSD test were identified. In the second trimester,121 metabolites were significantly increased,115 metabolites were significantly decreased; in the third trimester,85 metabolites were significantly increased,150 metabolites were significantly decreased. And the pathway analysis found 16 metabolites were involved in amino acid metabolism including tryptophan metabolism, arginine and proline metabolism, tyrosine metabolism, glutathione metabolism and 16 metabolites were involved in glucose metabolism including insulin resistance, glucuronidation, gluconeogenesis, three carboxylic acid cycle, N-glycosylation, cellulose digestion and absorption.Conclusion:The maternal metabolic status in different stages of normal pregnancy was significantly different. This study provided novel insight into understanding the mechanisms of normal pregnancy induced metabolic stress and pregnancy related biomarkers screening, which in turn could provide an ideal start for a large-scale epidemiological study of women who subsequently develop diseases, e.g., gestational depression, gestational diabetes mellitus and preeclampsia.Part ?:Dynamic alteration in the exposure level of multi-metals in the urine of the healthy pregnant women during normal pregnancyObjectives:The purpose of this part is to investigate the dynamic alteration in internal exposure level of multi-metals in maternal urine of healthy pregnant women during normal pregnancy.Methods:We investigated the concentration of 16 metals and metaloids of Al, V, Mn, Fe, Co, Cu, Zn, As, Se, Rb, Sr, Cd, Cs, Ba, T1 and Pb in the urine of 232 healthy pregnant women in their first trimester, second trimester and third trimester by using ICP-MS. Wilcoxon rank test was used to compare the changes in metal concentration of different metals in different trimesters. Pearson's correlation coefficients (r) of each metal pair in intra-trimester were analyzed and significance threshold o f|r|?0.6 and p< 0.05 were applied to select the most correlated metal pairs, and then the correlation relationship of these pairs were used to compute a correlation network.Results:It was found that one metal of cobalt increased time-dependently; vanadium, manganese, copper, barium, lead increased significantly in the second trimester and maintained this high level in the third trimester; aluminum, iron, zinc, arsenic, strontium, thallium increased significantly in the third trimester during the course of normal pregnancy. And the correlation network analysis presented that several metals such as selenium, cesium and thallium and so on had extensive correlation with other metals, which indicated there were significant synergistic effect among these metals during normal pregnancy.Conclusion:Metal exposure levels in single time-point can not accurately reflect the complete metal exposure information during the course of normal pregnancy and the multitime, dynamic metals exposure data should be used to comprehensively evaluate the metals exposure level during the normal pregnancy.Part III:Relationship between metal exposure and typical metabolites during normal pregnancy by Panel model based data analysisObjectives:The purpose of this part is to investigate the relationship between urine metals exposure and intermediates involved in amino acid metabolism during normal pregnancy.Methods:According to the results of urine metabolomics and metals profile generated from the first two parts, the panel regression analysis was established by using intermediates involved in amino acid metabolism as dependent variables and the metals exposure data as the independent variables.Results:Among the sixteen metals, seven metals were found significantly related to the metabolites of amino acids metabolism. Cd exposure significantly affected the urine level of 2-oxoarginine, Creatinine, Indole, N2-succinyl-l-glutamic acid 5-semialdehyde, N-methyltryptamine and N-succinyl-1,1-2,6-diaminopimelate. Co exposure significantly affected the urine level of 2-oxoarginine,3-indoleacetonitrile, Creatinine, Indole, Indole-5,6-quinone, N2-succinyl-l-glutamic acid 5-semialdehyde, N-methyltryptamine and N-succinyl-1,1-2,6-diaminopimelate. Cs exposure significantly affected the urine level of N2-succinyl-l-glutamic acid 5-semialdehyde. Cu exposure significantly affected the urine level of Creatinine, N2-succinyl-l-glutamic acid 5-semialdehyde and N-succinyl-1,1-2,6-diaminopimelate. Mn exposure significantly affected the urine level of Creatinine and N2-succinyl-l-glutamic acid 5-semialdehyde. T1 exposure significantly affected the urine level of 2-oxoarginine, Indole, N2-succinyl-l-glutamic acid 5-semialdehyde and N-methyltryptamine. V exposure significantly affected the urine level of 2-oxoarginine, Indole-5,6-quinone, N2-succinyl-l-glutamic acid 5-semialdehyde and N-succinyl-1,1-2,6-diaminopimelate.Conclusion:During normal pregnancy, the exposure of the metals of Cd, Co, Cs, Cu, Mn, T1 and V significantly affects the amino acid metabolism in maternal body, and different metals have different effects on the metabolism of amino acid.