Urinary Paraben Concentrations and Associations with the Periconceptional Urinary Metabolome: Untargeted and Targeted Metabolomics Analyses of Participants from the Early Pregnancy Study

Abstract

Background: Parabens, found in everyday items from personal care products to foods, are chemicals with endocrine-disrupting activity, which has been shown to influence reproductive function.

Objectives: This study investigated whether urinary concentrations of methylparaben, propylparaben, or butylparaben were associated with the urinary metabolome during the periconceptional period, a critical window for female reproductive function. Changes to the periconceptional urinary metabolome could provide insights into the mechanisms by which parabens could impact fertility.

Methods: Urinary paraben concentrations were measured in paired pre- and postconception urine samples from 42 participants in the Early Pregnancy Study, a prospective cohort of 221 women attempting to conceive. We performed untargeted and targeted metabolomics analyses using ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry. We used principal component analysis, orthogonal partial least-squares discriminant analysis, and permutation testing, coupled with univariate statistical analyses, to find metabolites associated with paraben concentration at the two time points. Potential confounders were identified with a directed acyclic graph and used to adjust results with multivariable linear regression. Metabolites were identified using fragmentation data.

Results: Seven metabolites were associated with paraben concentration (variable importance to projection score $>1$, false discovery rate-corrected $q\text{-value}<0.1$). We identified four diet-related metabolites to the Metabolomics Standards Initiative (MSI) certainty of identification level 2, including metabolites from smoke flavoring, grapes, and olive oil. One metabolite was identified to the class level only (MSI level 3). Two metabolites were unidentified (MSI level 4). After adjustment, three metabolites remained associated with methylparaben and propylparaben, two of which were diet-related. No metabolomic markers of endocrine disruption were associated with paraben concentrations.

Discussion: This study identified novel relationships between urinary paraben concentrations and diet-related metabolites but not with metabolites on endocrine-disrupting pathways, as hypothesized. It demonstrates the feasibility of integrating untargeted metabolomics data with environmental exposure information and epidemiological adjustment for confounders. The findings underscore a potentially important connection between diet and paraben exposure, with applications to nutritional epidemiology and dietary exposure assessment. https://doi.org/10.1289/EHP12125.

Figure 1.

Directed acyclic graph showing potential confounders in the relationship between urinary paraben concentration and the urinary metabolome and bias paths remaining after adjustment. Thin green lines connecting covariates indicate that associations on those paths are blocked, and potential confounding is accounted for in regression models. Any remaining paths from urinary paraben concentration to the urinary metabolome—regardless of arrow direction—indicate possible sources of bias and are represented by thick red lines with numbers corresponding to bias paths. Bias path 1 is via personal care product use, and bias path 2 is via physical activity and personal care product use. Boxed variables are measured for study participants and included in regression models, whereas unboxed variables are neither measured for study participants nor included in regression models.

Figure 2.

Percent change in metabolite intensity associated with a doubling of urinary paraben concentration (ng/mL, specific gravity–adjusted) after adjustment for confounding using multivariable linear regression in 42 participants in the Early Pregnancy Study. Error bars represent 95% confidence intervals. Metabolite numbers (1–7) correspond to the metabolites described in Table 4, and model letters (a–d) correspond to adjusted models summarized in Table 5, with full model results found in Table S4. Covariates used for adjustment can be visualized in Figure 1 and are also listed in Table 2. Data for this figure are from Table 5.