Combined analysis of microplastic quantification and blood metabolomics for spotted seal mothers and their calves

The present study set out with the objective of systematically revealing the impact of microplastics transplacent on the metabolic physiology of spotted seal offspring. To this end, microplastics were quantitatively detected in placental tissues from the same batch of spotted seal mothers and their fetuses. Furthermore, peripheral serum samples from mothers and pups were analysed and compared using non-targeted metabolomics techniques. The results demonstrated that PVC was the most prevalent polymer detected in placental tissue, with an average concentration of 4.718 μg/g on the maternal side, while the concentration decreased to 1.105 μg/g on the fetal side, yet still dominated among all detected polymers. Furthermore, PE and PS exhibited a clear "transfer from maternal to fetal side" characteristic; the average concentration of PE on the maternal side was 2.527 μg/g, while it decreased to 0.104 μg/g on the fetal side. This finding suggests that, despite the placental barrier's capacity to intercept certain polymers (including PVC, PS, and PE), microplastic particles can nevertheless traverse this barrier and gain entry into the fetus. At the metabolomics level, the study identified 499 differentially expressed metabolites in the serum of mothers and offspring. The analysis revealed that the offspring group exhibited a significant enrichment of metabolites, predominantly comprising small peptides, nucleotides, phospholipids, and metabolites of exogenous compounds. Multivariate statistical analysis demonstrated a clear separation of the metabolomic profiles of offspring and mothers along principal component 1 (PCA1, variance contribution rate 49.1%), and the PLS-DA model (R²Y=0.999, Q²=0.855) confirmed the systematic differences in the metabolomic profiles between mothers and offspring. Pathway enrichment analysis demonstrated significant enrichment in the nucleotide and purine metabolic pathways in offspring, with a high concentration in lysine biosynthesis and degradation pathways. This finding is highly consistent with the physiological state of offspring during rapid growth, active cell division, and tissue construction.