title: Serum metabolomics reveals irreversible inhibition of fatty acid beta-oxidation through the suppression of PPARalpha activation as a contributing mechanism of acetaminophen-induced hepatotoxicity.
abstract: Metabolic bioactivation, glutathione depletion, and covalent binding are the early hallmark events after acetaminophen (APAP) overdose. However, the subsequent metabolic consequences contributing to APAP-induced hepatic necrosis and apoptosis have not been fully elucidated. In this study, serum metabolomes of control and APAP-treated wild-type and Cyp2e1-null mice were examined by liquid chromatography-mass spectrometry (LC-MS) and multivariate data analysis. A dose-response study showed that the accumulation of long-chain acylcarnitines in serum contributes to the separation of wild-type mice undergoing APAP-induced hepatotoxicity from other mouse groups in a multivariate model. This observation, in conjunction with the increase of triglycerides and free fatty acids in the serum of APAP-treated wild-type mice, suggested that APAP treatment can disrupt fatty acid beta-oxidation. A time-course study further indicated that both wild-type and Cyp2e1-null mice had their serum acylcarnitine levels markedly elevated within the early hours of APAP treatment. While remaining high in wild-type mice, serum acylcarnitine levels gradually returned to normal in Cyp2e1-null mice at the end of the 24 h treatment. Distinct from serum aminotransferase activity and hepatic glutathione levels, the pattern of serum acylcarnitine accumulation suggested that acylcarnitines can function as complementary biomarkers for monitoring the APAP-induced hepatotoxicity. An essential role for peroxisome proliferator-activated receptor alpha (PPARalpha) in the regulation of serum acylcarnitine levels was established by comparing the metabolomic responses of wild-type and Ppara-null mice to a fasting challenge. The upregulation of PPARalpha activity following APAP treatment was transient in wild-type mice but was much more prolonged in Cyp2e1-null mice. Overall, serum metabolomics of APAP-induced hepatotoxicity revealed that the CYP2E1-mediated metabolic activation and oxidative stress following APAP treatment can cause irreversible inhibition of fatty acid oxidation, potentially through suppression of PPARalpha-regulated pathways.
authors.affiliation: Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Chi
authors.initials: C
authors.lastname: Chen
authors.forename: Kristopher W
authors.initials: KW
authors.lastname: Krausz
authors.forename: Yatrik M
authors.initials: YM
authors.lastname: Shah
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Idle
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Gonzalez
mesh_terms: D000082:Acetaminophen / Q000633:toxicity*; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood; D056486:Chemical and Drug Induced Liver Injury; D002853:Chromatography, Liquid; D019392:Cytochrome P-450 CYP2E1 / Q000172:deficiency / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D008107:Liver Diseases / Q000378:metabolism / Q000473:pathology; D013058:Mass Spectrometry; D055432:Metabolomics; D051379:Mice; D018345:Mice, Knockout; D047493:PPAR alpha / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors
chemical_list: D005227:Fatty Acids; D047493:PPAR alpha; C116917:acylcarnitine; D000082:Acetaminophen; D019392:Cytochrome P-450 CYP2E1; D005978:Glutathione; D002331:Carnitine