The Mediating Role Of Gut Microbiota In The Influence Of PM_2.5 Exposure On Gestational Diabetes Mellitus

ObjectiveTo analyze the relationship among PM_2.5,gut microbiota and gestational diabetes mellitus（GDM）,and to explore whether PM_2.5 exposure affects the risk of GDM by changing gut microbiota,so as to provide epidemiological basis for the prevention and treatment of GDM.MethodsPart Ⅰ:The participants were recruited from the Pregnancy Metabolic Disease and Adverse Pregnancy Outcome（PMDAPO）study,which is an ongoing large prospective observational cohort study of pregnant women in Guangzhou Women and Children’s Medical Center.A total of 1268 pregnant enrolled in the PMDAPO study from September 2018 to December 2020 were selected as the study subjects.Air pollution exposure level in 3 months before pregnancy,first trimester（1-12 gestational weeks）,13-24 gestational weeks and 3 months before pregnancy to 12 gestational weeks were collected.The maternal examination data and the results of oral glucose tolerance test（OGTT）during 24-28 gestational weeks were collected.Logistic regression model was used to analyzed the association between exposure to PM_2.5 during different window periods and risk for GDM.Multiple linear regression model was used to analyzed the association between PM_2.5 exposure and blood glucose levels.Part Ⅱ:A total of 647 pregnant women enrolled in the cohort from September 2018to December 2020 in the first part of this article were selected as the study subjects.Fecal samples were collected from all the subjects at 13-24 gestational weeks.16S r RNA gene sequencing technology was performed to detect the gut microbiota in 112pregnant women with GDM and 535 normal pregnant women.LEf Se analysis was performed to screen the differential microbiota taxa between pregnant women with GDM and normal pregnant women.Spearman correlation analysis was conducted to search the gut microbiota related to glucose level in pregnant women.Part Ⅲ:647 pregnant women in second part of this article were used as the study subjects.Air pollutants exposure data and gut microbiota data were combined to analyze the correlation between PM_2.5 exposure and gut microbiota.Mediation analysis was performed to analyze the mediation effect of gut microbiota on the associations of PM_2.5 exposure with risk of GDM and blood glucose level.ResultsPart Ⅰ:Correlation between PM_2.5 exposure and GDM1.A total of 1268 pregnant women were enrolled in this study,including 236pregnant women with GDM and 1032 normal pregnant women.The incidence of GDM was 18.61%.2.The results of general data analysis showed that the age,pre-pregnancy weight and pre-pregnancy BMI of pregnant women with GDM were all higher than those of normal pregnant women.Both the proportion of pregnancies greater than or equal to one and the proportion of deliveries greater than or equal to one in GDM pregnant women were higher than those in normal healthy pregnant women.The OGTT fasting blood glucose,1-hour blood glucose and 2-hour blood glucose of pregnant women with GDM were higher than those of normal pregnant women.All the differences were statistically significant（P<0.05）.3.The results of pregnancy outcomes data analysis showed that the incidence of cesarean section（35.59%vs 27.52%）and macrosomia（5.08%vs 2.42%）in pregnant women with GDM was significantly higher than that in normal pregnant women（P<0.05）.The proportion of male offspring（61.44%vs 52.71%）in pregnant women with GDM was significantly higher than that in normal pregnant women（P<0.05）.4.The results of logistic regression model showed that there was no significant correlation between PM_2.5 and the risk of GDM in the single pollutant model（P>0.05）.After controlling SO₂ and NO₂ in multi-pollutant model,the risk of GDM increased by50%（RR:1.50,95%CI:1.10-2.04）for each 10μg/m³increase in PM_2.5 exposure during first trimester;and the risk of GDM increased by 51%（RR:1.51,95%CI:1.04-2.20）for each 10μg/m³increase in PM_2.5 exposure from 3 months before pregnancy to 12gestational weeks.5.The results of multiple linear regression model showed that the fasting blood glucose increased by 0.04（95%CI:0.01-0.08）mmol/L,for each 10μg/m³increase in PM_2.5 exposure during first trimester.After controlling SO₂ and NO₂ in multi-pollutant model,the fasting blood glucose,1-hour blood glucose and 2-hour blood glucose were respectively increased by 0.07（95%CI:0.01-0.08）,0.23（95%CI:0.04-0.41）and 0.17（95%CI:0.01-0.33）mmol/L,for each 10μg/m³increase in PM_2.5 exposure during first trimester;and the fasting blood glucose increased by 0.06（95%CI:0.02-0.11）mmol/L for each 10μg/m³increase in PM_2.5 exposure from 3 months before pregnancy to 12gestational weeks.Part Ⅱ:Correlation between gut microbiota and GDM1.There was no significant difference in bothαdiversity andβdiversity between pregnant women with GDM and normal pregnant women（P<0.05）.2.In Linear discriminant effect size（LEf Se）analysis,10 differential microbiota taxa were found between pregnant women with GDM and normal pregnant women.Bacteroides uniformis,Phascolarctobacterium and Phascolarctobacterium unclassified species were enriched in pregnant women with GDM;Lactobacillus,Lacillaceae,Peptostreptococcaceae unclassified genus,Peptostreptococcaceae unclassified species,Clostridium Celatum,Peptostreptococcaceae and Clostridiaceae were enriched in normal pregnant women（P<0.05）.3.Fasting blood glucose of OGTT was significantly positively correlated with Roseburia（r=0.08）,Bacteroidetes（r=0.08）and Bacteroidetes uniformis（r=0.11）;and was significantly negatively correlated with Lachnospiraceae Ruminococcus（r=-0.09）,Streptococcus（r=-0.11）,Dorea（r=-0.09）and Clostridium（r=-0.08）（P<0.05）.2 h blood glucose was significantly negatively correlated with Lactobacillus（r=-0.10）and Lactobacillus（r=-0.09）（P<0.05）.Part Ⅲ:Mediation effect of gut microbiota on the associations between PM_2.5 and glucose homeostasis in pregnant women1.No significant correlation was found between PM_2.5 andαdiversity indices（P>0.05）.2.PM_2.5 was significantly positively correlated with Bacteroidetes（r=0.11）,Bacteroidetes uniformis（r=0.08）,Phascolarctobacterium（r=0.10）and Phascolarctobacterium unclassified species（r=0.10）;and was significantly negatively correlated with Lachnospiraceae Ruminococcus（r=-0.15）,Streptococcus（r=-0.15）and Dorea（r=-0.11）（P<0.05）.3.The results of mediation analysis showed that there was no significant mediation effect of microbiota on the association between PM_2.5 and th risk of GDM（P>0.05）.Whereas both Lachnospiraceae Ruminococcus（8.55%）and Dorea（5.14%）had significant mediation effects on the influence of PM_2.5 on fasting blood glucose level（P<0.05）.Conclusions1.PM_2.5 exposure from 3 months before pregnancy to 12 gestational weeks can affect the risk of GDM.With the increase of PM_2.5 exposure level,the risk of GDM and the blood glucose level of pregnant women significantly increase,and the first trimester may be a sensitive period.2.There is an imbalance of gut microbiota in pregnant women with GDM at 13-24 gestational weeks,and there is a significant correlation between gut microbiota and blood glucose level in pregnant women.3.This study did not find that gut microbiota had significant mediation effect on the association between PM_2.5 and the risk of GDM,but found that PM_2.5 exposure might affect fasting blood glucose level in pregnant women by altering Lachnospiraceae Ruminococcus and Dorea.