Longitudinal changes during pregnancy in gut microbiota and methylmercury biomarkers, and reversal of microbe-exposure correlations

Abstract

Objective: Gut microorganisms contribute to the metabolism of environmental toxicants, including methylmercury (MeHg). Our main objective was to investigate whether associations between biomarkers for prenatal MeHg exposure and maternal gut microbiota differed between early and late gestation.Methods: Maternal blood and stool samples were collected during early (8.3-17 weeks, n=28) and late (27-36 weeks, n=24) gestation. Total mercury and MeHg concentrations were quantified in biomarkers, and inorganic mercury was estimated by subtraction. The diversity and structure of the gut microbiota were investigated using 16S rRNA gene profiling (n=52). Biomarkers were dichotomized, and diversity patterns were compared between high/low mercury concentrations. Spearman's correlation was used to assess bivariate associations between MeHg biomarkers (stool, blood, and meconium), and 23 gut microbial taxa (genus or family level, >1% average relative abundance).Results: Within-person and between-person diversity patterns in gut microbiota differed between early/late gestation. The overall composition of the microbiome differed between high/low MeHg concentrations (in blood and stool) during early gestation, but not late gestation. Ten (of 23) taxa were significantly correlated with MeHg biomarkers (increasing or decreasing); however,

Association between gut microbiota composition and glycoalbumin level during pregnancy in Japanese women: Pilot study from Chiba Study of Mother and Child Health

“…Several previous reports showed that the microbiota composition changes during pregnancy. In the present study, unlike that in a previous study, Proteobacteria and Actinobacteria did not change during pregnancy, but the proportion of the TM7 phylum did change.…”

“…In the present study, unlike that in a previous study, Proteobacteria and Actinobacteria did not change during pregnancy, but the proportion of the TM7 phylum did change. Previous studies reported that the gut microbiota in different populations are distinct from one another, and that long‐term dietary habits affect human gut microbiota. The differences between previous studies and the present study might be due to different ethnicities and dietary habits of the study populations.…”

“… reported no dramatic changes in gut microbiota during pregnancy. Other studies have shown differences in the microbial diversity or abundance of some phyla. It is unclear how gut microbiota are affected by pregnancy and whether the changes are associated with metabolic status in pregnant women.…”

Influence of toxic metal exposure on the gut microbiota (Review)

“…The mechanisms involved in the complex bio-physicochemical process of Hg methylation and demethylation remain to be fully understood. However, MeHg metabolism is the core research in experiments focused on methylation/demethylation processes in GM, that is considered to be involved in the biochemical interplay responsible for its demethylation to inorganic mercury (64).…”

Maternal Microbiome and Metabolic Health Program Microbiome Development and Health of the Offspring

“…However, this pro-inflammatory status is also implicated in metabolic alterations during pregnancy, which contribute to ensuring a healthy pregnancy. The microbial changes in the gut mainly manifest as an increase in Actinobacteria and Proteobacteria phylum, alongside a reduction in microbial diversity and butyrate-producing bacteria [32]. Some studies have identified shifts in the gut microbiota during pregnancy [33,34], while others have failed to identify any microbial changes during gestation [35].…”