Untargeted metabolomic analysis reveals a time-course hepatic metabolism disorder induced by short-term 6PPD exposure in rats

The tire antioxidant 6PPD has garnered extensive attention due to its widespread presence in the environment and the harmful effects of its transformation products on aquatic organisms. 6PPD has been detected in airborne dust, and it can enter mammals through inhalation exposure. While the toxic effects of 6PPD exposure have been reported in mammals, its effects on hepatic metabolism still remain poorly understood. Here, we collected the serum and liver samples at 1, 6, and 72 h following a single oral exposure of 100 mg/kg body weight (bw) 6PPD, respectively. We also investigated changes in serum and hepatic physiological indicators and metabolites, correspondingly. Results indicated that single time oral exposure a high dose of 6PPD did not significantly affect the physiological indexes of rats within a short time frame. However, untargeted metabolomics analysis of the metabolites in the liver at 1, 6, and 72 h revealed that the number of differential expression metabolites gradually increased over time and the most affected substances were lipids and lipid-like molecules. Interestingly, the KEGG pathway enrichment analysis indicated that 6PPD disrupted the riboflavin metabolism, leading to a significant decrease in FMN levels at all time points. In addition, the hepatic glucose metabolism was significantly affected at 6 and 72 h after oral administration. Taken together, short-term exposure to 6PPD disturbed lipid and riboflavin metabolism and gradually affected glucose metabolism in the liver of rats. These findings revealed the impacts of 6PPD on the hepatic metabolism in animals, and also offered some important insights into its toxicology and health risk.