Objective To investigate the therapeutic effect and mechanism of total triterpenoid from Cyclocarya paliurus (CPT) on high-fat diet (HFD)-induced metabolic-associated fatty liver disease (MAFLD) mice. Methods C57BL/6J mice were randomly divided into control group, model group, CPT (100 mg/kg) group, metformin (MET, 100 mg/kg) group and CPT + MET group. Except for the control group receiving regular feeding, all other groups were fed HFD for 12 weeks to establish MAFLD models. After successful establishment of MAFLD model, drugs were given eight weeks. During the experiment, the activity levels of mice were observed, their body weight and food intake were measured regularly. One week before the end of medication, the oxygen consumption (VO₂), carbon dioxide production (VCO₂) and energy consumption of mice were measured using indirect calorimetry. After the end of administration, glucose tolerance test and insulin resistance test were conducted to detect glucose tolerance. Liver weight was measured, and liver index was calculated. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), γ-glutamyl transpeptidase (γ-GT), triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), fasting blood glucose (FBG), fasting insulin (FINS) in serum were detected, and insulin resistance index (HOMA-IR) was calculated. The levels of TC and TG in hepatic tissues and feces, as well as the levels of total bile acids (TBA) in serum, hepatic tissues and feces were measured. Hematoxylin-eosin and oil red O staining were used to observe the pathological changes in hepatic tissues of mice. Five hepatic tissue and five colon content samples from each group were randomly selected for bile acid (BAs) metabolomics analysis. The mRNA expressions of cholesterol 7α-hydoxylase 1 (Cyp7a1), Cyp7b1, Cyp27a1, Cyp8b1, bile acid coenzyme A synthetase (Bacs), bile acid coenzyme a: amino acid N-acyltransferase (Baat), bile salt export pump (Bsep), recombinant Na⁺ taurocholate cotransporting polypeptide (Ntcp), farnesoid X receptor (FXR), small heterodimeric partner (SHP), fibroblast growth factor receptor 4 (FGFR4), sterol regulatory element-binding protein-1c (SREBP-1c), stearyl coenzyme A desaturation enzyme 1 (SCD1), fatty acid synthetase (FASN), peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyl transferase 1 (CPT1), lipoprotein lipase (LPL), microsomal triglyceride transfer protein (MTTP) in hepatic tissues and FXR, fibroblast growth factor 15 (FGF15), apical sodium-dependent bile acid transporter (Abst), intestinal bile acid-binding protein (Ibabp), organic solute transporter-α (Ost-α), Ost-β in ileum tissues were determined by qRT-PCR. Western blotting was used to detect the protein expressions of CYP7a1, Cyp7b1, Cyp27a1, Cyp8b1, FXR, SHP, FGFR4, SREBP-1c, SCD1, FASN, PPARα, CPT1, LPL, MTTP in hepatic tissues and FXR, FGF15, Abst in ileum tissues. Results Compared with model group, CPT and its association with MET significantly reduced the body weight, improved glucose tolerance, elevated insulin sensitivity, lowered liver weight and liver index, raised VO₂, VCO₂, VO₂/VCO₂, and daytime and nighttime energy consumptions and total energy consumption in mice (P < 0.01). CPT and its association with MET reduced ALT, AST, ALP, γ-GT, TC, TG, LDL-C, FINS, FBG, TBA levels in serum and TC and TG levels in hepatic tissue as well as HOMA-IR, elevated levels of HDL-C in serum and TC, TG, TBA in feces, reduced liver histopathological scores and lipid deposition (P < 0.01). CPT and its association with MET elevated hepatic tissue TBA level, lowered the contents of unconjugated BAs, primary BAs, secondary BAs and the ratio of primary BAs/secondary BAs in hepatic tissues, as well as the levels of unconjugated BAs and secondary BAs in colon contents, elevated the content of conjugated BAs and the ratio of conjugated BAs/unconjugated BAs in hepatic tissue, as well as the levels of conjugated BAs, primary BAs and the ratios of conjugated BAs/unconjugated BAs, primary BAs/secondary BAs in colon contents (P < 0.01). In addition, CPT and its association with MET elevated Cyp7a1, Cyp7b1, Cyp27a1, Bacs, Baat, FXR, SHP, Bsep, Ntcp, PPARα, CPT1, LPL, MTTP mRNA expressions and Cyp7a1, Cyp7b1, Cyp27a1, FXR, SHP, PPARα, CPT1, LPL, MTTP protein expressions in hepatic tissues, reduced the mRNA and protein expressions of Cyp8b1, FGFR4, SREBP-1c, SCD1, FASN in hepatic tissues, depressed FXR, FGF15, Asbt, Ibabp, Ost-α, Ost-β mRNA expressions and FXR, FGF15, Asbt protein expressions in ileum tissues (P < 0.01). The combination of CPT and MET showed better efficacy than CPT alone (P < 0.05, 0.01). Conclusion CPT may activate the hepatic FXR/SHP pathway by inhibiting intestinal FXR/FGF15 signaling, facilitating the synthesis of BAs in the hepatic intestinal circulation, repressing their ileal reabsorption, and boosting the excretion of BAs with feces. The activated hepatic FXR/SHP pathway restrains lipid synthesis by suppressing SREBP-1c/SCD1/FASN signaling axis, while activated hepatic FXR promotes lipid oxidation and lipid decomposition through activating the PPARα/CPT1 and LPL/MTTP signaling axes to treat MAFLD.

total triterpenoid from Cyclocarya paliurus  /  metabolic-associated fatty liver disease  /  bile acid  /  lipid metabolism  /  farnesoid X receptor