Dietary exposure to polystyrene microplastics impairs muscle growth via gut microbiota dysbiosis and hepatic oxidative stress along the gut-liver-muscle axis in Qihe gibel carp (Carassius gibelio var. Qihe).

Microplastics (MPs) are emerging contaminants of significant environmental concern; however, their cross-tissue physiological impacts and growth-inhibitory mechanisms in economically important freshwater fish remain insufficiently characterized. This study investigated the systemic effects of dietary exposure to 500 μm polystyrene microplastics (PS-MPs) on the gut-liver-muscle axis in Qihe gibel carp (Carassius gibelio var. Qihe). Fish were exposed to environmentally relevant concentrations (0, 5, 50, and 100 μg/g feed) for 28 days. PS-MPs exposure significantly suppressed growth performance in a dose-dependent manner, evidenced by reductions in body weight (BW), weight gain rate (WGR), and specific growth rate (SGR). Histopathological analysis revealed tissue-specific injuries: intestinal villus atrophy and epithelial barrier disruption; hepatocellular vacuolar degeneration and nuclear displacement; and muscular endomysial disruption with myofiber atrophy. Biochemical assays indicated hepatic oxidative stress (elevated malondialdehyde, suppressed antioxidant enzymes) and intestinal metabolic dysfunction (decreased amylase and trypsin, increased lipase). 16S rRNA sequencing demonstrated significant gut microbiota dysbiosis, characterized by reduced beneficial Bacillota and enrichment of opportunistic pathogenic Verrucomicrobiota and Actinomycetota. Transcriptomic analysis revealed upregulation of apoptosis and autophagy pathways in the liver and intestine. Concurrently, widespread downregulation of genes involved in the cell cycle, DNA replication, and motor proteins was observed in muscle. These findings establish a mechanistic framework linking gut-liver-muscle axis disruption to microplastic toxicity, providing critical insights into the ecological risks of microplastic pollution in freshwater aquaculture systems.