Oral exposure to polyethylene microplastics of adult male mice fed a normal or western-style diet: impact on gut and gut-liver axis homeostasis

Plastics in the environment are fragmented into small particles known as microplastics (MPs). In humans, MPs have been detected in stools, attesting to their transit along the gastrointestinal tract. Few studies have assessed their potential effects on the digestive tract in at-risk populations. Based on this background, we aimed at studying the consequences of oral exposure to polyethylene (PE) MPs under nutritional stress. Adult male mice were daily exposed to PE MPs on a Western (WD) vs. normal (ND) diet for 90 days, to reveal any exacerbating/synergistic effects between MP and nutritional stresses. The following assays were performed in mice exposed to ND or WD with or without MPs: follow-up of body weight, food and water intake; oral glucose tolerance test; measurement of in vivo intestinal permeability (using FITC-labeled dextran), colonic lipocalin-2 level, and distal colon mucus thickness (Alcian Blue staining); fecal microbiota composition (16S rDNA gene metabarcoding); gene expression in small intestine and colon (inflammation, tight junctions, antimicrobial peptides, mucus biosynthesis and secretion), gene expression and histology in liver (size and size distribution of lipid droplets using Red Oil staining). The effects of WD on gut homeostasis impairment were demonstrated, including defects in epithelium and mucus barriers as well as shifts in fecal bacterial communities. Liver homeostasis was also disrupted. Concerning the impact of MP exposure with ND or WD, results on the gut barrier function and gut-liver axis revealed signatures common or specific to each exposure condition. To support this toxicological assessment, and as a biophysics-based innovation in the field, near-infrared spectroscopy (NIRS), coupled to chemometrics, was used to monitor, in all exposed groups, changes in the intestine (contents, tissues) and the liver. This work enables a better assessment of the hazards of oral exposure to MPs in an at-risk WD-fed population (altered intestinal barrier, dysbiotic gut microbiota). Also see: https://micro2024.sciencesconf.org/558619/document