Bupleurum chinense ameliorates metabolic-associated fatty liver disease by modulating Sirtuin 6

Bupleurum chinense (Bc) is a traditional Chinese medicine commonly used to treat metabolic-associated fatty liver disease (MAFLD), demonstrating hepatoprotective, anti-inflammatory, and antioxidant effects. Sirtuin 6 (SIRT6) regulates fatty acid metabolism and oxidative stress, playing a crucial role in MAFLD treatment.

To investigate Bc's mechanisms in ameliorating MAFLD and analyze the primary active components contributing to its therapeutic effects.

C57BL/6J mice developed MAFLD through 12-week high-fat diet (HFD) feeding, followed by 4-week interventions with Bc decoction (1.3, 0.65, 0.325 g/kg/d) or pioglitazone (0.1 g/kg/d). Lipid metabolism, oxidative stress, inflammation, and insulin resistance were measured. RNA-seq identified the key Bc targets, which were validated in liver-specific knockout mice. Bioactive constituents were initially screened using the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database, followed by molecular docking, dynamics simulations, and microscale thermophoresis (MST) to validate target affinity and binding stability. An in vitro MAFLD model was established using primary mouse hepatocytes (MPHs) challenged with oleic and palmitic acid (OAPA).

Bc significantly ameliorated lipid accumulation and HFD-induced oxidative stress. Pioglitazone and Bc (1.3 g/kg/d) administration demonstrated marked reductions in circulating TG, ALT, and AST concentrations in a dose-responsive manner. Furthermore, Bc ameliorated hepatic oxidative stress, as evidenced by elevated GSH and SOD levels alongside reduced H₂O₂ content. Transcriptomic profiling and mechanistic validation identified SIRT6 as the central mediator. Bc upregulated SIRT6 expression and enhanced its deacetylase activity, resulting in reduced acetylation of histone H3K9 and H3K56 compared to HFD controls. This promoted PPARα/NRF2 nuclear translocation, upregulating fatty acid β-oxidation genes (such as Cpt1a) and antioxidant genes (such as Ho-1). Crucially, hepatocyte-specific Sirt6 knockout abolished Bc's therapeutic effects. Moreover, molecular docking, molecular dynamics, and MST results indicated that Saikosaponin C (SSc), the major component of Bc, has a strong affinity for SIRT6. Cell experiments confirmed that SSc (25 μM) significantly improved lipid deposition and redox imbalance in MAFLD models, exhibiting SIRT6-dependent efficacy.

Bc alleviates MAFLD by activating SIRT6 through its core component SSc. This activation, via SIRT6-mediated histone deacetylation, enhances PPARα/NRF2-driven metabolic-redox homeostasis, establishing the Bc-SSc-SIRT6 axis as a therapeutic target.