Polystyrene microplastics alter the intestinal microbiota function and the hepatic metabolism status in marine medaka (Oryzias melastigma)

To assess the potential effects of microplastics (MPs) on gut microbiome, a simple investigation of gut microbial structure is not sufficient, and the function and association of gut microbial structure with host health should also be taken into account. Here, the effects of two particle sizes (2 and 200 μm) of polystyrene MPs (PS-MPs) on the gut microbiota of medaka were evaluated following oral administration at 0.3 and 3.0 μg/mg for 28 days. No change in body length and gut histopathology damage were observed. However, the exposure to PS-MPs significantly decreased fish body weight and disrupted the liver anti-oxidative status. The PS-MPs caused a shift in the gut microbial structure of medaka accompanied by changes in community function, including significant environmental stress, increased carbon degradation/fixation activities, and partially modified nitrogen/phosphorus/sulfur metabolic abilities. Furthermore, the PS-MPs exposure disturbed the glycolipid/tyrosine/energy metabolism and the endocrine balance. A potential correlation between the gut microecology and host response to PS-MPs exposure was also observed. These results indicated that the PS-MPs may contribute to gut-liver axis disruption, which could be the underlying toxicological mechanisms of PS-MPs exposure. This work has improved our knowledge about the relationship between gut microbiota dysbiosis and host metabolic disorders following MPs exposure.