Abstract: To explore the mechanism by which hawthorn proanthocyanidins (HPC) combined with vitamin C (VC) alleviates liver oxidative stress in insulin resistance (IR) rats through the Wnt/β-catenin signaling pathway. To create an animal model of IR, 80 Wistar male rats were given a high-fat diet. The changes in body mass, fasting blood glucose and serum insulin concentration were measured before and after the establishment of the model. Colorimetry was used to test the activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline?phosphatase (ALP). A total of 50 IR rats were randomly selected and divided into model, HPC (56 μg/mL), VC (180 μg/mL), HPC (56 μg/mL) + VC (180 μg/mL) and metformin (2 μg/mL)?groups, each consisting of 10 animals. Blood glucose and insulin levels, as well as the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and the content of malondialdehyde (MDA) in liver homogenate were determined after 12 weeks of continuous administration. The mRNA expression of Wnt1, Axin, glycogen synthasc kinase-3β (GSK-3β), adenomatous polyposis coli protein (APC), β-catenin and peroxisome proliferators-activated receptors γ (PPARγ) were tested by real-time polymerase chain reaction (PCR). The expression of Wnt1, β-catenin and PPARγ proteins was tested by Western blotting. The binding capacity of Wnt1 to dishevelled (Dsh) proteins was evaluated by fluorescence resonance energy transfer (FRET) assay. IR was successfully induced in 54 (67.5%) of the 80 rats. The body mass, fasting blood glucose, serum insulin, and ALT, AST and ALP activities of the model group were significantly higher than those of the control group (P < 0.01). Compared with the model group, the three intervention groups exhibited significant differences in all the studied parameters in the liver homogenate (P < 0.01), and the effect of HPC + VC was better than that of HPC alone (P < 0.05). In the HPC + VC group, the relative mRNA expression of Wnt1 and β-catenin was decreased significantly (P < 0.01), while the relative mRNA expression of Axin, GSK-3β, APC and PPARγ were significantly increased (P < 0.01). Moreover, the expression of Wnt1 and β-catenin proteins were decreased significantly (P < 0.01), whilst the protein expression of PPARγ was increased significantly (P < 0.01). The FRET signal for the HPC + VC group was obviously weakened, indicating that the binding force between Wnt1 and Dsh was significantly weakened over time, and the formation of heterodimers was reduced significantly (P < 0.05). The results from this study showed that the combined application of HPC with VC could ameliorate liver oxidative stress in rats with insulin resistance through the Wnt/β-catenin signaling pathway.

Key words: hawthorn proanthocyanidin; vitamin C; Wnt/β-catenin pathway; insulin resistance; liver oxidative stress