Drug Metabolism Pathways in Hepatic Disorders

Abstract

Hepatic disorders -- encompassing non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), viral hepatitis B and C, and cirrhosis -- collectively disrupt the enzymatic machinery governing phase I and phase II drug metabolism, precipitating clinically significant alterations in drug clearance, bioavailability, and toxicity risk. This study systematically quantified the expression and activity of twelve cytochrome P450 enzymes (CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, CYP3A5) and five phase II conjugating enzymes (UGT1A1, UGT1A4, SULT1A1, NAT2, GSTM1) across 180 liver biopsy specimens spanning five hepatic disorder categories and matched healthy controls (n = 30 per group). Enzyme expression was quantified by targeted LC-MS/MS proteomics, and functional activity by substrate probe cocktail assay in freshly prepared liver microsomes. CYP3A4 protein expression was reduced by 78% in cirrhotic tissue relative to healthy controls (p < 0.001), with proportional reductions in midazolam 1-hydroxylation activity (81% reduction; IC50 shift from 2.4 to 14.7 µM). CYP2E1 was paradoxically upregulated 2.8-fold in ALD (p < 0.001), driving hepatotoxic acetaminophen N-deacetylation and reactive oxygen species generation. UGT1A1 activity was uniformly suppressed across all disorder categories (38-67% reduction), with the most severe impairment in decompensated cirrhosis. These findings provide a quantitative enzyme activity atlas for hepatic disorder-stratified drug dosing guidance and identify CYP2E1 upregulation in ALD as a priority target for hepatoprotective pharmacological intervention