Integrative transcriptomics and lipidomics unravels the amelioration effects of Radix Bupleuri on non-alcoholic fatty liver disease

Radix Bupleuri (Bupleurum chinense DC.) is the most commonly used traditional Chinese medicine (TCM) for the treatment of liver diseases. While the effects of Radix Bupleuri (BR) on lipid-lowering and liver protection have been established, its role in the development of non-alcoholic fatty liver disease (NAFLD) induced by a high-fat diet remains unclear. The objective of this study was to evaluate the alleviation effects of the active fraction of BR on NAFLD in vivo and to explore the underlying mechanisms through an analysis of liver transcriptome and lipidomics. The NAFLD model was established in SD rats by administering a high-fat diet (HFD) for 8 weeks. Subsequently, the NAFLD model rats were continuously gavaged with different polarity fractions of BR (25 g/kg/d) and melatonin (MT) (30 mg/kg/d) for an additional 6 weeks to assess therapeutic effects. The potential mechanism of the low polarity fraction of BR (LBR) in treating NAFLD was investigated through hepatic transcriptome analysis, non-targeted lipidomics, RT-qPCR, protein-protein interaction (PPI) network construction, molecular docking, and Western blotting, aiming to elucidate the underlying mechanisms by which LBR may ameliorate NAFLD. These results demonstrated that LBR significantly alleviated the effects of HFD-induced NAFLD, as evidenced by reductions in body weight (BW), liver weight (LW), and epididymal fat weight (EFW) compared to model rats and other polarity fractions of BR. Furthermore, LBR notably down-regulated serum and liver levels of total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C), while up-regulating high-density lipoprotein cholesterol (HDL-C) in serum. Mechanistically, liver transcriptome analysis indicated that fatty acid metabolism may be a crucial pathway for the improvement of NAFLD following LBR treatment. Lipidomics data suggested that LBR can modulate the metabolic profile in NAFLD rats. Enrichment analysis revealed that glycerophospholipid and glycerolipid metabolism might be key pathways involved in the development of NAFLD. RT-qPCR analysis demonstrated that LBR could regulate the expression of lipid-related genes in these critical pathways. Additionally, Spearman correlation analysis showed a strong relationship between lipid metabolic biomarkers, pathological indices, and lipid-related genes. Moreover, protein-protein interaction (PPI) network and molecular docking analyses identified seven key targets with six ingred