Metabolomics reveals lipid metabolic disruption in frogs exposed to tire wear particle leachates.

Tire wear particle (TWP) contribute considerably to microplastic contamination in aquatic environments and are increasingly recognized as emerging contaminants of ecological concern. However, their effects on lipid metabolism in amphibians remain unclear. In this study, adult male black-spotted frogs (Pelophylax nigromaculatus) were exposed for 21 days to TWP leachates at concentrations of 0, 0.0005, 0.005, 0.05, and 0.5 mg/mL. The results showed that TWP leachate exposure significantly induced hepatic lipid droplet accumulation. Additionally, significant increases were observed in the hepatosomatic index and hepatic lipid parameters, including triglycerides, total cholesterol, and low-density lipoprotein cholesterol. Untargeted LC-MS-based metabolomics further revealed significant changes in hepatic metabolites after TWP exposure. Pathway analysis showed significant disruption of energy metabolism (TCA cycle and oxidative phosphorylation) and lipid metabolism (glycerophospholipid and sphingolipid pathways). These results suggest that TWP leachates may induce hepatic lipid accumulation associated with disturbances in mitochondrial energy metabolism. Our findings provide new insights into the hepatotoxic effects of TWP in amphibians.