Daidzein treatment exerts antioxidant effect via SIRT3–FOXO3a axis activation

Abstract Metabolic dysfunction-associated progression of steatotic liver disease is closely associated with lipotoxicity-induced oxidative stress and inflammation. This study investigated whether daidzein, a major soy isoflavone, protects hepatocytes against free fatty acid-induced oxidative damage via endogenous antioxidant signaling. In HepG2 cells, daidzein treatment suppressed free fatty acid-induced reactive oxygen species (ROS) production, mitochondrial DNA fragmentation, and pro-inflammatory cytokine expression. Daidzein induced the expression of antioxidant enzymes, including MnSOD and catalase, at the transcriptional level and enhanced FOXO3a transcriptional activity. FOXO3a knockdown attenuated daidzein-induced antioxidant enzyme expression and ROS reduction. Daidzein promoted FOXO3a nuclear localization and deacetylation. Furthermore, daidzein increased SIRT3 expression levels, and SIRT3 knockdown suppressed daidzein-mediated FOXO3a activation and antioxidant effects. These findings demonstrate that daidzein attenuates lipotoxic oxidative damage by activating the SIRT3–FOXO3a axis in hepatocytes.