Bariatric surgery-induced weight loss reduces hepatic lipid peroxidation levels and affects hepatic cytochrome P-450 protein content

Objective: To evaluate the effects of surgical weight loss on hepatic lipid peroxidation levels and cytochrome P-450 protein expression in patients with nonalcoholic fatty liver disease (NAFLD). Summary background data: NAFLD and nonalcoholic steatohepatitis (NASH) affect hepatic cytochrome P-450 (CYP) protein expression and activity, and CYP2E1 may play a role in the pathogenesis of NAFLD and NASH through induction of oxidative stress and lipid peroxidation. NAFLD and NASH are associated with increased systemic lipid peroxidation levels and elevated hepatic CYP2E1 activity, but hepatic CYP3A4/5 activity is decreased. Methods: Liver biopsies from 20 patients with NAFLD who underwent bariatric surgery were obtained intraoperatively and at 15 ± 7 months following surgery. Hepatic malondialdehyde (MDA) levels (a marker of lipid peroxidation), CYP2E1 and CYP3A4/5 protein expression, and steatosis, as a percent of total area, were measured by immunohistochemistry followed by digital image quantitation. Results: Following weight loss, as reflected by reduced BMI (54 ± 9 vs. 37 ± 9 kg/m; P < 0.001), features of the metabolic syndrome, grade and stage of liver disease, and liver histology were all significantly improved (P < 0.01). Hepatic MDA staining (35 ± 18% vs. 23 ± 14%; P = 0.02), CYP2E1 protein content (68 ± 9% vs. 56 ± 11%; P < 0.001), and steatosis (17 ± 7% vs. 2 ± 3%; P < 0.001) were significantly reduced following weight loss. CYP3A4/5 protein content was unchanged (57 ± 13% vs. 55 ± 13%; P = 0.433). The reduction in lipid peroxidation was independently associated with changes in CYP2E1 protein expression after bariatric surgery (r = 0.477; P = 0.033). Conclusion: Elevations in hepatic lipid peroxidation and CYP2E1 expression that are seen in NAFLD improve significantly with weight loss induced by bariatric surgery.