Methylmercury Lab

Highlights

• Pregnant mothers donated blood and stool samples during early/late gestation.
• Total mercury and methylmercury (MeHg) were determined in both biomarkers.
• Gut microbiota community structure was determined using 16 S rRNA gene profiling.
• Within- and between-person diversity patterns differed between early/late gestation.
• Associations between gut microbiota and MeHg biomarkers differed longitudinally.

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 16 S 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 blood and stool MeHg concentrations during early gestation, but not late gestation. Ten (of 23) taxa were significantly correlated with MeHg biomarkers (increasing or decreasing); however, associations differed, depending on whether the sample was collected during early or late gestation. A total of 43% of associations (69/161) reversed the direction of correlation between early/late gestation.

Conclusions

The time point at which a maternal fecal sample is collected may yield different associations between gut microorganisms and MeHg biomarkers, which may be due in part to remodeling of maternal microbiota during pregnancy. Our results suggest the effectiveness of dietary interventions to reduce prenatal MeHg exposure may differ between early and late gestation.