Emerging microplastic and nanoplastic threats: Decoding winter survival mechanisms in hybrid groupers through hepatic metabolic disruption

This study explores the impact of microplastics (MPs) and nanoplastics (NPs) on hepatic lipid metabolism in pearl gentian grouper ( Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) during overwintering and elucidates the underlying mechanisms. Fish were exposed to polystyrene (PS) MPs and NPs of varying sizes (5 μm, 500 nm, and 50 nm) for a 15-day exposure period. Histopathological analysis, oxidative stress assessment, and gene expression profiling related to lipid metabolism revealed significant toxic effects on the liver. Results showed that NPs preferentially accumulated in the liver, causing hepatocyte swelling, inflammation, and lipid metabolism disorders. Smaller particle sizes intensified oxidative stress, reduced triglyceride (TG) content, and elevated low-density lipoprotein cholesterol (LDL-C) and total cholesterol (T-CHO) levels. Transcriptomic analysis indicated that MPs and NPs altered the expression of lipid metabolism genes, particularly those in glyceride metabolism and lipolysis pathways, with significant upregulation of PNPLA2 and LIPG ( p < 0.05) under cold stress. This led to excessive energy reserve depletion and hepatic lipid metabolism dysfunction. This study establishes a “environmental stress-gene-metabolism” response model and provides novel insights into the molecular mechanisms by which NPs disrupt lipid homeostasis in aquatic organisms, offering a theoretical basis for understanding the toxicological effects of emerging contaminants. • Liver was the main target organ for NPs action. • Size effect adjusted oxidative stress in liver. • MPs and NPs promoted lipid depletion in the liver at low temperatures. • MPs and NPs interfered with lipid metabolism in liver.