Comprehensive analysis of alterations in lipid and bile acid metabolism by carbon tetrachloride using integrated transcriptomics and metabolomics

Abstract

Understanding mechanisms of liver injury can enable better preclinical testing and clinical management of patients. Carbon tetrachloride (CCl4), used extensively as a model hepatotoxicant, induces lipid perturbation and increases in plasma bile acids (BAs). An integrated transcriptomics and metabolomics approach was employed to investigate CCl4-induced alterations in lipid and BA metabolism. Sprague-Dawley rats were treated orally with corn oil, 50 (low dose, LD) or 2,000 mg CCl4/kg/d (high dose, HD). Animals were sacrificed at 6, 24 or 72 h. Terminal blood was collected for clinical chemistry and metabolomics analyses. Livers were harvested for histopathology, metabolomics and transcriptomics analyses. Both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased in the treated groups with the greatest increases observed in the HD group at 24 and 72 h. Blood cholesterol and triglycerides (TGs) were significantly decreased in the HD group at both 24 and 72 h, and hepatocyte vacuolization was observed at these timepoints. Consistent with the clinical chemistry and histopathological data, metabolomics results showed that levels of total fatty acids increased in the liver but decreased in the blood in the HD group at the 24 and 72 h timepoints. This suggested that lipids accumulate in the liver. Primary BAs increased in both liver and blood, while secondary and conjugated BAs decreased in the liver and increased in the blood, which indicated that the BA conjugation pathway and that BA uptake by the liver were inhibited by CCl4. Results from this study provide a better understanding of the mechanisms of CCl4-induced hepatotoxicity.