Association between Exposure to Metals during Pregnancy, Childhood Gut Microbiome, and Risk of Intestinal Inflammation in Late Childhood

Abstract

Alterations to the gut microbiome and exposure to metals during pregnancy have been suggested to impact inflammatory bowel disease. Nonetheless, how prenatal exposure to metals eventually results in long-term effects on the gut microbiome, leading to subclinical intestinal inflammation, particularly during late childhood, has not been studied. It is also unknown whether such an interactive effect drives a specific subgroup of children toward elevated susceptibility to intestinal inflammation. We used an amalgamation of machine-learning techniques with a regression-based framework to explore if children with distinct sets of gut microbes and certain patterns of exposure to metals during pregnancy (metal-microbial clique signature) had a higher likelihood of intestinal inflammation, measured based on fecal calprotectin (FC) in late childhood. We obtained samples from a well-characterized longitudinal birth cohort from Mexico City (n = 108), Mexico. In the second and third trimesters of pregnancy, 11 metals were measured in whole blood. Gut microbial abundances and FC were measured in stool samples from children 9-11 years of age. Elevated FC was defined as having FC above 100 μg/g of stool. We identified subgroups of children in whom microbial and metal-microbial clique signatures were associated with elevated FC (false discovery rate (FDR) < 0.05). In particular, we found two metal-microbial clique signatures significantly associated with elevated FC: (1) low cesium (Cs) and copper (Cu) in the third trimester and low relative abundance of Eubacterium ventriosum (OR [95%CI]: 10.27 [3.57,29.52], FDR < 0.001) and (2) low Cu in the third trimester and high relative abundances of Roseburia inulinivorans and Ruminococcus torques (OR [95%CI]: 7.21 [1.81,28.77], FDR < 0.05). This exploratory study demonstrates that children with specific gut microbes and specific exposure patterns to metals during pregnancy may have higher fecal calprotectin levels in late childhood, denoting an elevated risk of intestinal inflammation.

Figure 1

Prenatal metal exposures, gut microbial relative abundances, and elevated fecal calprotectin level. (A) Prenatal metal exposures and odds of high fecal calprotectin (≥100 μg/g) presented through forest plots. (B) Microbial relative abundance and adjusted odds of high fecal calprotectin. Part (A) shows the individual associations (adjusted odds ratios (OR) and 95% CI) between prenatal metal exposures at second and third trimesters and high fecal calprotectin (≥100 μg/g). The metal concentrations were transformed into quartiles for robustness. Part (B) demonstrates the OR for associations between microbial relative abundance and elevated fecal calprotectin. The p-values and the ORs are plotted through a volcano plot. The red horizontal line denotes the log(p-value) at 0.05, the nominal p-value. In contrast, the black horizontal line denotes the log(p-value) at 0.002, the multicomparison error adjusted p-value.

Figure 2

Distribution (density plot) of fecal calprotectin (continuous and binary) over subgroups of children with (or without) metal–microbial clique signatures. (A and B) The density plots of log-transformed calprotectin levels for subgroups of children with and without metal–microbial clique signatures. (C and D) Similar distributions through stacked bar plots for binary calprotectin levels.

Figure 3

Metal–microbial clique signatures, odds of high fecal calprotectin, and the Spearman correlation between components of metal and microbial cliques. (A) The associations with metal and microbial clique signatures. The top rows (red, green) denote second- and third-order metal clique signatures, the middle rows (blue) denote microbial clique signatures, and the bottom rows (purple) denote the metal–microbe clique signatures. The sample proportion of children for each clique is denoted within brackets. The names of the clique signatures are noted on the Y-axis of (A). (B) The Spearman correlation between variables that constitute the clique signatures. 2T, second trimester; 3T, third trimester.