Effects of microplastics and nanoplastics on rodent gut microbiota diversity: A systematic review and meta-analysis

The increasing presence of microplastics (MPs) and nanoplastics (NPs) in food and water has raised concerns about their potential effects on gut microbiota. This study provides a comprehensive synthesis through a systematic review and meta-analysis evaluating the impact of micro and nanoplastics (MNPs) on gut microbiota diversity in rodent experimental models. Following PRISMA guidelines, eligible studies were identified from PubMed, Scopus, and Web of Science, and risk of bias was assessed using the SYRCLE tool. A quantitative meta-analysis was conducted on three commonly reported α-diversity indices (Chao1, Shannon, Simpson), while β-diversity and taxonomic changes were qualitatively synthesized. MNPs exposure showed no statistically significant effect on α-diversity (g = 0.17,p = 0.259), with substantial heterogeneity across studies. Subgroup analyses confirmed the absence of significant effects across particle size, animal model, polymer type, dose, and exposure duration. β-diversity was consistently and significantly altered in the vast majority of studies, indicating consistent microbial community restructuring. Taxonomic shifts were variable at the phylum level, particularly for Firmicutes and Bacteroidota, while decreases in Lactobacillaceae/Lactobacillus and increases in Ruminococcaceae, Lachnospiraceae, and Desulfobacterota were frequently observed. These findings indicate that MNPs primarily reshape microbial composition. The high heterogeneity highlights the need for standardized, environmentally relevant experimental designs to better assess microbiome-related alterations associated with MNPs exposure and their potential implications for host health.