Gypenosides Induce Preadipocyte Browning via FXR/Rubicon Pathway-Mediated Inhibition of Autophagy

To determine whether gypenosides (GPs) induce preadipocyte browning via famesoid X receptor (FXR)/Rubicon-mediated autophagy inhibition and ameliorate obesity-related metabolic disorders in mice.

In vitro, differentiated 3T3-L1 preadipocytes were treated with 1-6 µ g/mL GPs. Browning markers [uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1 α), PR domain containing 16 (Prdm16)], autophagy markers [microtubule-associated protein 1 light chain 3 form II/form I (LC3II/LC3I), Beclin-1, recombinant autophagy related protein 7 (ATG7), p62], and FXR/Rubicon expression were assessed by Western blot and qPCR. FXR knockdown was performed using shRNA lentivirus. Autophagic flux was evaluated using an mRFP-GFP-LC3 tandem reporter. In vivo, high-fat diet-induced obese mice were randomly divided into 5 groups using a random number sequence (n=6 per group): control, model, low- and high-dose GPs (300, 600 mg/kg per day by oral gavage, respectively), and sitagliptin (SIT, 30 mg/kg daily) groups. All treatments were administered daily for 12 weeks. Metabolic parameters, adipocyte histology, and protein expression in inguinal white adipose tissue were then analyzed.

GPs (3-6 µ g/mL) significantly upregulated UCP1, PGC-1α, and Prdm16 protein levels and reduced the LC3II/LC3I ratio compared with the differentiation medium control (all P<0.01). FXR and Rubicon expression were increased by GPs (P<0.01). FXR knockdown abolished these effects (P<0.01). In obese mice, GPs (600 mg/kg) reduced body weight, serum triglycerides, total cholesterol, and fasting blood glucose, decreased adipocyte size, and increased UCP1, PGC-1α, Prdm16, FXR, and Rubicon while decreasing LC3II/LC3I, Beclin-1, and ATG7 compared with the model group (P<0.05).

GPs activate FXR/Rubicon signal pathway to inhibit autophagy, inducing preadipocyte browning and offering a novel herbal-based anti-metabolic diseases strategy.