Systems Biology Investigation to Discover Metabolic Biomarkers of Acetaminophen-Induced Hepatic Injury Using Integrated Transcriptomics and Metabolomics

Background: Drug-induced hepatotoxicity is one of the major reasons for drug recall and hence it is of major concern to the FDA and consumers. Overdose of acetaminophen (APAP) can cause acute hepatic injury. The current clinical biomarkers of liver injury are insufficient in predicting the extent of injury; thus novel biomarkers are needed to integrate with the current biomarkers for better risk assessment during drug development and clinical use. Methods: Sprague-Dawley rats were orally gavaged with a single dose of 0.5% methylcellulose (control), 100 mg APAP/kg body weight or 1250 mg APAP/kg body weight. Urine, terminal blood samples and tissues were collected at 6, 24, 72, and 168 h for clinical chemistry and histopathology analyses. Based on the clinical chemistry data and histopathology, liver injury occurred in treated animals during the first 24 h, while recovery occurred during 72 to 168 h. A systems biology investigation of APAP-induced hepatic injury was conducted to elucidate novel metabolic biomarkers using an integrated transcriptomic and metabolomic approach. Both open metabolic profiling and broad metabolic profiling were utilized to examine metabolic changes in blood and open profiling was used to evaluate changes in the urinary metabolite profiles. Results: In total, 270 metabolites were evaluated in blood and/or urine. Metabolites involved in energy, urea and bile acid pathways were found to have strong correlations to hepatic necrosis scores and elevated alanine aminotransferase levels. The pathways associated with these metabolites were altered at the first 72 h but had generally recovered at 168 h. Changes in hepatic gene expression of the bile acid pathway supported the interpretation from the metabolomics data. Conclusion: The combination of the transcriptomics and metabolic profiling technologies discovered novel injury biomarkers (arginine, 2-oxoarginine, medium chain dicarboxylic acids, α-ketoglutarate and bile acids), which are involved in energy, bile acid, and arginine metabolism pathway.