High-dimensional mediation analysis to elucidate the role of metabolites in the association between PFAS exposure and reduced SARS-CoV-2 IgG in pregnancy.

Objective: We previously found that per- and polyfluoroalkyl substances (PFAS) mixture exposure is inversely associated with SARS-CoV-2 IgG (IgG) antibody levels in pregnant individuals. Here, we aim to identify metabolites mediating this relationship to elucidate the underlying biological pathways.

Methods: We included 59 pregnant participants from a US-based pregnancy cohort. Untargeted metabolomic profiling was performed using Liquid Chromatography-High Resolution Sass spectrometry (LC-HRMS), and weighted Quantile Sum (WQS) regression was applied to assess the PFAS and metabolites mixture effects on IgG. Metabolite indices positively or negatively associated with IgG levels were constructed separately and their mediation effects were examined independently and jointly.

Results: The PFAS-index was negatively associated with IgG levels (beta=-0.273, p=0.002), with PFHpS and PFHxS as major contributors. Two metabolite-indices were constructed, one positively (beta=1.260, p<0.001) and one negatively (beta=-0.997, p<0.001) associated with IgG. Key contributors for these indices included protoporphyrin, 5-hydroxytryptophan, n-acetylproline, and tyrosine. Analysis of single mediator showed that 48.9% (95%CI: 21.9%,125.0%) and 50.1% (95% CI: 8.1%, 90.1%) of the PFAS index-IgG total effect were mediated by the negative and positive metabolite-indices, respectively. Joint analysis of the metabolite-indices indicated a cumulative mediation effect of 73.6% (95%CI: 44.9%, 116.4%). Enriched pathways associated with these metabolites indices were phenylalanine, tyrosine, and tryptophan biosynthesis and arginine metabolism.

Conclusions: We observed significant mediation effects of plasma metabolites on the PFAS-IgG relationship, suggesting that PFAS disrupts the balance of plasma metabolites that contributes to reduced plasma IgG production.