Polystyrene microplastics induce hepatic lipid metabolism and energy disorder by upregulating the NR4A1-AMPK signaling pathway

Microplastics (MPs) are widespread throughout global ecosystems, and their impact on living organisms has garnered increasing attention in recent years. Research has demonstrated that exposure to different sizes (0.08-100 μm) polystyrene microplastics (PS-MPs) can disrupt hepatic lipid and energy metabolism while promoting oxidative stress. Despite these findings, the precise molecular mechanisms underlying PS-MP-induced toxicity are not fully understood. NR4A1 is known to regulate apoptosis and lipid metabolism, but few studies have explored its role in modulating hepatic lipid metabolism following PS-MP exposure. In this study, animal experiments showed that PS-MPs reduced triglyceride levels and significantly increased reactive oxygen species (ROS) in liver tissue. Transcriptional profiles of mouse liver tissues were processed and analyzed using Ingenuity Pathway Analysis (IPA) software and Gene Set Enrichment Analysis (GSEA) to identify relevant pathways and molecular signatures. The results revealed a significant upregulation in NR4A1 gene expression after exposure to PS-MPs. PS-MP accumulation in the liver activated NR4A1 and the AMPK-autophagy pathway, reducing lipid biosynthesis. In vitro study, NR4A1 knockdown in hepatocytes exposed to PS-MPs reduced the expression of AMPK and lipid metabolism-related proteins. In summary, this study indicated that PS-MPs disrupt lipid metabolism in the liver by affecting the NR4A1, leading to liver damage. Prolonged exposure to these microplastics could raise concerns about long-term liver health and the regulation of overall metabolic functions.