SIRT1-dependent mitochondrial biogenesis supports therapeutic effects of 4-butyl-polyhydroxybenzophenone compounds against NAFLD

The mitochondria have been identified as key targets in nonalcoholic fatty liver disease (NAFLD), one of the most prevalent chronic liver damage diseases globally. Meanwhile, the biological information analysis in this study revealed that SIRT1, PPARG, PPARA, and PPARGC1A (mitochondrial biogenesis-related proteins) were NAFLD therapeutic targets. Therefore, the design and synthesis of targeted drugs that promote mitochondrial biogenesis and improve mitochondrial function are particularly important for NAFLD treatment. Recently, we introduced butyls, hydroxyls, and halogens to benzophenone and synthesized a series of NAFLD-related 4-butylpolyhydroxybenzophenone compounds, aiming at investigating the hepatoprotective activity from the aspect of mitochondrial biogenesis. The structure-activity relationship demonstrated that hydroxyl and ketone groups were active groups interacting with mitochondrial biogenesis proteins (SIRT1 and PGC1α), and the activity was stronger when the o-hydroxyl group was present on the benzene ring. In contrast, the activity was little affected by the presence of the p-hydroxyl group, m-hydroxyl group, butyl group type, or halogen. In addition, in vitro studies confirmed that these compounds could directly bind to SIRT1 and PGC1α, markedly promote their interaction, significantly increase the expression of proteins and genes related to mitochondrial biogenesis (SIRT1, PGC1α, NRF1, TFAM, COX1, and ND6) and subsequently ameliorate mitochondria dysfunction, which was evidenced by the decreased ROS, upregulated ATP production, increased MMP, and enhanced mitochondrial number. According to the outcomes of our in vitro and in vivo experiments, 4-butyl-polyhydroxybenzophenone compounds could also effectively reduce the formation of lipid droplets and liver injury index (ALT, AST, LDH, AKP, γ-GT, and GDH) and improve the level of antioxidant enzymes (GSH and SOD). Particularly, the treatment of these compounds after a high-fat diet could significantly reduce body weight, decrease liver coefficient, attenuate liver damage, and ameliorate lipid accumulation in rat liver, demonstrating their therapeutic effects on NAFLD. Mechanistically, 4-butyl-polyhydroxybenzophenone compounds promoted mitochondrial biogenesis and eventually prevented NAFLD liver injury by activating the PGC1α signaling pathway in a SIRT1-dependent manner, which was strongly supported by SIRT1 inhibitor EX527.