Dysregulated expression of fatty acid oxidation enzymes and iron‐regulatory genes in livers of Nrf2‐null mice

Abstract

Hepatic excessive iron may play a role in the pathogenesis of non-alcoholic steatohepatitis (NASH). Nrf2 is a master regulator of antioxidative responses. However, the role of Nrf2 in lipid and iron homeostasis remains unclear. Accordingly, it was examined how Nrf2 regulates lipid-related and iron-regulatory genes after feeding a high-fat diet (HFD) with iron. Wild-type and Nrf2-null mice were fed the following diets: (i) control diet (4% soybean oil) for 12 weeks, (ii) control diet for 8 weeks followed by control diet containing 0.5% carbonyl iron for 4 weeks, (iii) HFD (4% soybean oil and 16% lard) for 12 weeks, (iv) HFD for 8 weeks followed by HFD containing 0.5% carbonyl iron for 4 weeks. Blood and livers were removed after 12 weeks. Nrf2-null control mice exhibited a tendency towards higher hepatic triglycerides compared to wild-type control mice. Hepatic malondialdehyde was higher and hepatic iron levels tended to be higher in Nrf2-null mice than wild-type counterparts while on a HFD. The HFD with iron synergistically induced mRNA expression of Pparα targets, including Acox and Cpt1 in wild-type mice, yet the induction was diminished in Nrf2-null mice. Hepatic hepcidin and ferroportin 1 mRNA expression were increased in wild-type mice after feeding a HFD with iron, but were unchanged in any group of Nrf2-null mice. Nrf2 deletion dysregulates hepatic mRNA expression of β-oxidation enzymes and iron-related genes, possibly causing a trend for increased hepatic triglyceride and iron concentrations. Nrf2 may have roles in the progression of NASH.