Background Animal studies have shown that exposure to organophosphate esters (OPEs) disturbs the composition of gut microbiome in rodents and zebrafish. However, current associated evidence in humans is limited. Considering the importance of gut microbiome in neonatal development, we need to investigate the impact of OPEs exposure on the early development stage of neonatal microbiome.

Objective To investigate the associations between umbilical OPEs exposure and the diversity and composition of gut microbiome in newborns.

Methods Based on the Shanghai Maternal-Child Pairs Cohort (MCPC), 391 mother-infant pairs with comprehensive follow-up information and bio-samples were enrolled in this study. Concentrations of OPEs in neonatal cord blood were quantified using ultra performance liquid chromatography-tandem mass spectrometry. Meconium samples were collected after delivery and measured through 16S rRNA sequencing on the Illumina Miseq platform. Multiple linear regression models were used to assess the effects of OPEs exposure on the alpha diversity of meconium microbiome. Principal coordinate analysis and permutational multivariate analysis of variance based on unweighted UniFrac distance were used to compare the beta diversity differences between high and low exposure groups of OPEs. Linear discriminant analysis effect size (LEfSe) was utilized to analyze the differential gut microbiome taxa between high and low OPEs exposure groups. The functional pathways involved in the meconium microbiome were predicted based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and multivariate analysis by linear models (MaAsLin2) were conducted to explore the effects of OPEs exposure on gut microbiome pathways.

Results Seven OPEs were detectable in the neonatal cord blood samples, of which four were detected higher than 50% including tributyl phosphate (TBP), tris (2-butoxyethyl) phosphate (TBEP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tris (2-chloro-1 (chloromethyl) ethyl) phosphate (TDCPP), and the median concentrations of these four congeners were as follows: 0.52 μg·L⁻¹ for TBP, 2.41 μg·L⁻¹ for TBEP, 0.13 μg·L⁻¹ for EHDPP, and 2.23 μg·L⁻¹ for TDCPP. A significant association was observed between umbilical TBEP and TDCPP exposure and alpha diversity indices in neonatal meconium microbiome. Beta diversity significantly differed across varied high and low OPEs exposure groups. The results of LEfSe analysis indicated a significant correlation between umbilical OPEs exposure and 27 genera, including Streptococcus, Corynebacterium, Neisseria, Haemophilus, and Parabacteroides. The MaAsLin2 analysis identified associations between OPEs exposure and upregulation of pathways related to linoleic acid metabolism, steroid biosynthesis, Toll and Imd signaling pathway, retinol metabolism, NOD like receptor signaling pathway, and fatty acid biosynthesis .

Conclusion Umbilical OPEs exposure is associated increased alpha diversity indices, increased relative abundances of Neisseria, Streptococcus, Parabacteroides, and Corynebacterium in the gut microbiome, as well as predicted metabolic pathway alterations in linoleic acid metabolism, fatty acid biosynthesis, etc. These findings indicate that umbilical OPEs exposure may disrupt meconium microbiome equilibrium.