Mechanism of valproic acid-induced hepatic steatosis via enhancing NRF2-FATP2-mediated fatty acid uptake.

Abstract

Rationale: Valproic acid (VPA), a first-line antiepileptic drug, can induce life-threatening hepatic steatosis with prolonged use; however, the underlying mechanisms remain inadequately elucidated. Nuclear factor E2-related factor 2 (NRF2) is a hepatoprotective factor that maintains redox homeostasis; however, increased levels have been observed in VPA-induced hepatic steatosis. Therefore, the present study aimed to investigate the function of NRF2 in VPA-triggered hepatic steatosis. Methods: NRF2 overexpression mice, NRF2 knockout mice, and fatty acid transport protein 2 (FATP2) knockout mice were constructed using adeno-associated virus, homologous recombination, and CRISPR/Cas9 technology, respectively. The mice were then treated with or without oral VPA to induce hepatic steatosis. Results: NRF2 nuclear expression was positively correlated with triglyceride levels in VPA-induced hepatic steatosis. NRF2 overexpression exacerbated VPA-triggered inflammation and steatosis, whereas NRF2 knockout alleviated the effects. Chromatin immunoprecipitation and dual-luciferase reporter gene assay confirmed that FATP2 is a target gene of NRF2. NRF2 exacerbated VPA-induced hepatic steatosis dependent on FATP2. VPA bound to Cys288 and Arg415 of Kelch-like ECH-associated protein 1 (KEAP1), leading to its autophagic degradation and subsequent nuclear translocation of NRF2. Conclusions: Our results revealed a mechanism that VPA binds to specific KEAP1 sites, promoting its degradation and disrupting the KEAP1-NRF2 complex, thereby facilitating NRF2 nuclear translocation. Subsequently, NRF2 activates FATP2 transcription, enhancing fatty acid uptake and contributing to hepatic steatosis. Our findings suggest that inhibiting the NRF2-FATP2 axis could improve VPA-induced hepatic steatosis, offering promising insights into managing drug-induced fatty liver disease.