Low-dose polystyrene microplastics exposure increases susceptibility to obesity-induced MASLD via disrupting intestinal barrier integrity and gut microbiota homeostasis

The global incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) has surged in recent years, potentially impacted by both high-energy food intake (e.g., high-fat diet, HFD) and environmental pollutants like microplastics (MPs). However, the combined impacts of MPs exposure and HFD feeding, particularly under long-time exposure, low concentrations MPs conditions, on the MASLD progression remain to be fully elucidated. In this study, C57BL/6 J male mice were fed either a normal chow diet or HFD with or without low-dose MPs (polystyrene) exposure (25–30 μg/kg body weight /day) for 14 weeks. The adverse health effects associated with MASLD development were evaluated, including intestinal permeability, gut microbiota composition, hepatic lipid metabolism, and the mediating role of the gut-liver axis. Additionally, HFD with or without low-dose MPs exposure was withdrawn to further verify this process. Our data demonstrated that low-dose MPs exposure or HFD feeding significantly increased the gut permeability, oxidative stress, pro-inflammatory response and apoptosis, while concurrently contributing to gut dysbiosis (e.g., reduced levels of Akkermansia) and MASLD development. Furthermore, low-dose MPs exposure exacerbated these effects in combination with HFD feeding, exhibiting a ‘double hit’ effect. Notably, the impacts of low-dose MPs exposure combined with HFD feeding on MASLD were difficult to reverse after two weeks withdrawing, likely due to the limited recovery potential of intestinal barrier integrity and gut microbiota homeostasis. These finding underscore the importance of avoiding MPs exposure in the pathogenesis of MASLD, particularly under a metabolic disorder conditions, and provide valuable insights for the developing therapeutic strategies to combat MASLD caused by MPs exposure.