Impacts of polystyrene microplastic on the gut barrier, microbiota and metabolism of mice

Microplastics (MPs), which are new environmental pollutants with a diameter of <5 mm, have received wide attention in recent years. However, there are still very limited data regarding the risks of MPs to animals, especially higher mammals. In this study, we exposed male mice to 5 μm pristine and fluorescent polystyrene MP for six weeks. The results showed that the polystyrene MP was observed in the guts of mice and could reduce the intestinal mucus secretion and cause damage the intestinal barrier function. In addition, high-throughput sequencing of the V3-V4 region of the 16S rRNA gene was used to explore the change of the gut microbiota composition in the cecal content. At the phylum level, the content of Actinobacteria decreased significantly in the polystyrene MP-treated group. The PD whole-tree indexes of the alpha diversity and principal component analysis (PCA) of the beta diversity indicated that the diversity of gut microbiota was altered after polystyrene MP exposure. At the genus level, a total of 15 types of bacteria changed significantly after exposure to polystyrene MP. Furthermore, the predicted KEGG (Kyoto Encyclopedia of Genes and Genomes) metabolic pathway differences indicated that the main metabolic pathways of the functional genes in the microbial community were significantly influenced by the polystyrene MP. In addition, indexes of amino acid metabolism and bile acid metabolism in the serum were analyzed after polystyrene MP exposure. These results indicated that polystyrene MP caused metabolic disorders. In conclusion, the polystyrene MP induced gut microbiota dysbiosis, intestinal barrier dysfunction and metabolic disorders in mice. This study provided more data on the toxicity of MPs in a terrestrial organism to aid in the assessment of the health risks of polystyrene MP to animals.