Microplastics are emerging pollutants that have garnered significant attention, with evidence suggesting their association with the pathogenesis of type 2 diabetes mellitus. In order to assess the impact of polystyrene microplastic exposure on alterations in the gut microbiota and the subsequent implications for glucose dysregulation under different dietary conditions in mice, we investigated the effects and disparities in the blood glucose levels induced by polystyrene microplastic exposure in mice fed a high-fat diet versus those fed a normal diet. Using 16S rRNA sequencing and bioinformatics analyses, we explored the dynamic changes and discrepancies in the gut microbiota stability induced by polystyrene microplastic exposure under varied dietary conditions, and we screened for gut genera associated with the potential of polystyrene microplastics to disrupt glucose homeostasis. Our findings indicate that a high-fat diet resulted in abnormal mouse body weight, energy intake, blood glucose levels and related metabolic parameters. Additionally, polystyrene microplastic exposure exacerbated the glucose metabolism disorders induced by a high-fat diet. Furthermore, the composition and diversity of the mouse gut microbiota were significantly altered following microplastic exposure, with 11 gut genera exhibiting a differential presence between mice fed a high-fat diet combined with microplastic exposure compared to those fed a normal diet with microplastic exposure. Moreover, Ucg-009 played an intermediary role in the association between a high-fat diet and the fasting blood glucose. Hence, our study demonstrates that polystyrene microplastic exposure exacerbates high-fat diet-induced glucose metabolism disorders, whereas its impact on the blood glucose under normal dietary conditions is not significant, highlighting the differential influence attributable to distinct alterations in characteristic gut genera.

Background: Despite escalating global pollution from microplastics (MPs) and the concurrent surge in high-fat food consumption, the health impacts of MP exposure on individuals under different dietary patterns remain poorly understood. Methods: This study investigated the differential effects of environmentally relevant concentrations of polystyrene microplastics (5 μm, 8 mg/kg) on gut barrier function in mice fed either a normal chow diet (CD) or a high-fat diet (HFD). Results: Key findings revealed that, in HFD-fed mice, MP exposure significantly reduced (p < 0.05) the transcriptional levels of genes encoding the tight junction proteins (ZO-1, Occludin, and Claudin-1), as well as the mucin protein Muc-2, accompanied by decreased protein expression levels of these markers in both colonic and ileal tissues. In contrast, no significant differences were observed in CD-fed mice exposed to MPs. Analysis of the gut microbiota and measurement of short-chain fatty acid (SCFA) metabolites showed that MPs induced significant alterations in the composition and diversity indices of the gut microbiota, along with a marked decrease (p < 0.05) in the levels of the characteristic metabolite butyrate in HFD-fed mice. Conversely, butyrate levels remained unchanged in CD-fed mice following MP exposure. Quantitative PCR (qPCR) and immunofluorescence staining of colonic tissues demonstrated that MP exposure significantly downregulated (p < 0.05) both the transcription and protein expression of peroxisome proliferator-activated receptor γ (PPARγ) in HFD-fed mice. Again, no significant changes were detected in CD-fed mice. Conclusions: These results collectively indicate that the impact of microplastics on the intestinal barrier differs significantly between mice fed normal and high-fat diets. The gut microbiota and its metabolites, particularly butyrate, may play a critical role, possibly through modulating PPARγ signaling. This study contributes valuable insights into understanding the toxicity profiles of microplastics and establishing crucial links between dietary patterns and the health effects of emerging pollutants.