Mechanistic study of chenodeoxycholic acid targeting pyruvate kinase to regulate hepatic lipid metabolism

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease globally. Chenodeoxycholic acid (CDCA), a key component of bile acids, improves hepatic lipid metabolism. The present study aimed to investigate whether CDCA regulates hepatic lipid metabolism by interacting with pyruvate kinase (PK), and to elucidate the underlying molecular mechanism. High-fat cell and murine models were generated. The levels of total cholesterol (TC), triglycerides (TG), superoxide dismutase (SOD) and malondialdehyde (MDA) in cells and animal livers were measured. BODIPY and Oil Red staining were employed to detect the lipid droplet content. Reverse transcription-quantitative PCR was used to assess the expression of the lipid-related genes. Immunoprecipitation and molecular docking were used to examine the interaction between CDCA and PK, as well as their interaction sites. The effects of their binding on PK activity and pyruvate synthesis were investigated. Both in vitro and in vivo experiments demonstrated that compared with the high-fat group, the TG, TC and MDA levels in the CDCA-treated group were markedly reduced. In addition, lipid droplet count was markedly decreased and SOD activity was increased. The mRNA expression levels of lipid synthesis genes (such as fatty acid synthase and sterol regulatory element-binding transcription factor 1) were notably decreased, whereas those of lipid metabolism genes (CTP synthase 1 and peroxisome proliferator-activated receptor α) exhibited the opposite trend. CDCA specifically bound to the PK-M2 subtype, which promoted PK activity and pyruvate production. Pretreatment with a PK inhibitor completely reversed lipid synthesis inhibition and β-oxidation enhancement induced by CDCA. CDCA notably ameliorated hepatic lipid deposition, and its underlying mechanism was revealed to be closely associated with the direct binding of CDCA to PK and subsequent enhancement of PK activity.