Honokiol Ameliorates Hepatic Lipid Accumulation by Deacetylating PPARG via SIRT3

Dysregulated lipid metabolism is a core pathogenic driver of type 2 diabetes. Honokiol (HKL), the major bioactive constituent of Magnolia officinalis, possesses anti-diabetic and lipid-regulatory properties. However, the underlying molecular mechanism remains elusive. This study investigates how HKL ameliorates high-glucose/high-fat (HGHF)-induced hepatic lipid accumulation, with a focus on the role of SIRT3-mediated deacetylation of peroxisome proliferator-activated receptor γ (PPARG). The core targets of HKL were identified through network pharmacology and molecular docking. Human hepatic MIHA cells were treated with glucose (Glu, 40 mM) and palmitic acid (0.2~0.3 mM PA) to establish a lipid accumulation model, followed by treatment with HKL (5–10 μM) with or without a confirmed selective SIRT3 inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP). Lipid accumulation was assessed by Oil Red O staining and by measuring triglyceride (TG) and total cholesterol (TC) levels. Protein expression and the SIRT3-PPARG interaction were analyzed by Western blot and co-immunoprecipitation (Co-IP). SIRT3 and PPARG were identified as core targets of HKL, exhibiting strong binding with calculated energies of −6.834 and −6.579 kcal/mol, respectively. In MIHA cells, HGHF (40 mM Glu + 0.2–0.3 mM PA) induced lipid accumulation, including increased lipid droplets, and elevated TG (2.5–3.2-fold) and TC (2.2–2.8-fold) contents in a dose-dependent manner, accompanied by downregulated SIRT3/PPARG expression and heightened global protein acetylation. The non-cytotoxic HGHF-M condition (40 mM Glu + 0.2 mM PA) was selected for further experiments. HKL (5–10 μM) dose-dependently reduced lipid accumulation by ~38–60%, decreased TG and TC levels by up to ~13% and ~30%, and restored SIRT3/PPARG expression. The protective effects of HKL were reversed by inhibition of SIRT3 with 3-TYP. Co-IP confirmed the interaction between SIRT3 and PPARG, and SIRT3 overexpression significantly decreased the acetylation level of PPARG. This study suggests that HKL ameliorates hepatic lipid accumulation via SIRT3-mediated deacetylation of PPARG, providing an experimental basis for considering HKL as a potential therapeutic agent against metabolic disorders.