Betaine-driven Keap1 methylation promotes p62-mediated autophagy and Nrf2 stabilization to alleviate glutathione-dependent redox dyshomeostasis in liver injury.

Abstract

Nuclear factor erythroid 2-related factor 2 (Nrf2) coordinates detoxification and antioxidant programs that protect the liver from chemical and metabolic stress. Nrf2 is restrained by Kelch-like ECH-associated protein 1 (Keap1), which can be removed through p62-mediated selective autophagy; however, nutritional cues that engage this pathway remain incompletely understood. This study provides evidence that betaine (trimethylglycine; BET) can regulate the Keap1-Nrf2 axis through modulation of Keap1. In biochemical and cellular assays, betaine was associated with methylation of Keap1 at Cys513 and Cys518 within the Kelch domain, which was linked to enhanced p62-dependent autophagic degradation of Keap1 and Nrf2 stabilization. In AML12 hepatocytes and in mice, betaine enhanced Nrf2 activity, induced canonical Nrf2 target genes, and increased cellular glutathione (GSH), consistent with improved GSH-dependent redox capacity. In an acetaminophen (AAP) overdose model, betaine attenuated hepatic injury, consistent with improved redox capacity under acute toxic stress. In an MCD diet-induced steatotic liver disease model, betaine was associated with reduced steatohepatitis-like histopathology, inflammatory signaling, and lipogenic markers. Finally, RNA-seq analysis of a large human metabolic dysfunction-associated steatotic liver disease (MASLD) cohort revealed Nrf2-related transcriptomic signatures associated with disease severity, providing correlative support for the disease relevance of this pathway. Collectively, these findings suggest that Keap1 cysteine methylation may represent a regulatory node linking betaine to p62-mediated autophagy, Nrf2 stabilization, and GSH homeostasis, while further studies are required to establish the causal and translational relevance of this mechanism in human liver disease.