Sodium butyrate protects against oxidative stress in HepG2 cells through modulating Nrf2 pathway and mitochondrial function

Sodium butyrate (NaBu) is a by-product of microbial fermentation of dietary fiber in the gastrointestinal tract and has been shown to increase the activity of antioxidant enzymes, such as catalase or heme oxidase-1, in vivo. However, the mechanism of this effect is still unclear. This study investigated the antioxidant effect of NaBu on HepG2 cells under H2O2-induced oxidative stress. NaBu (0.3 mM) attenuated cell death and accumulation of reactive oxygen species and improved multiple antioxidant parameters in H2O2-injured HepG2 cells. NaBu inhibited glycogen synthase kinase-3 beta (GSK-3 beta) by increasing the p-GSK-3 beta (Ser9) level and promoted nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), which increased the expression of downstream antioxidant enzymes. Together with promotion of peroxisome proliferator-activated receptor gamma coactivator 1-alpha and mitochondrial DNA copy number, NaBu modulated energy metabolism and mitochondrial function, decreasing glycolysis, increasing beta-oxidation, and enhancing the tricarboxylic acid cycle and oxidative phosphorylation. NaBu increased mitochondrial manganese-superoxide dismutase and glutathione peroxidase activity. In conclusion, NaBu protected HepG2 cells against oxidative stress by modulating Nrf2 pathway activity and mitochondrial function.