Y-box binding protein 1 regulates liver lipid metabolism by regulating the Wnt/beta-catenin signaling pathway

Background: We mainly investigated how y-box binding protein 1 (YB-1) regulates liver lipid metabolism through the Wnt/13-catenin signaling pathway using multiple models. Methods: The LO2 cells were treated with palmitic acid (PA) to create an NAFLD model in vitro. Immunohistochemistry and Western blotting assays were used to detect the expression of YB-1, beta-Catenin, SREBP-1c, LXRa, FXR1 and PPAR alpha protein, and RNAs of them was detected by qRT-PCR. Oil Red O assay was applied to observe lipid droplets in LO2 cells and liver tissues. H&E staining was performed to observe the degree of liver inflammation. Proteomics in LO2 cells were conducted by Tandem mass tag proteomics assay. Co-immunoprecipitation and Western blotting assays were used to verify YB-1 complexed pGSK313. ELISA and Western blotting assays were used to detect the concentrations of TNFa and IL-6 in supernates of LO2 cells and liver tissues, respectively. Results: We found that YB-1 and 13-catenin were highly expressed in the LO2 cell NAFLD model, and that the expression of TNFa and IL-6 also increased. Lipid synthases (SREBP-1c and LXRa) expression were decreased, while 13-oxidation-related factors (FXR1 and PPAR alpha) expression were increased. The expression of SREBP-1c and LXRa were increased while FXR1 and PPAR alpha were decreased, though such responses were rescued through inhibiting 13-catenin expression. Finally, tandem mass tag proteomics, coimmunoprecipitation, and Western blotting demonstrated that YB-1 could form a protein complex with phosphorylated glycogen synthase kinase 3 beta (pGSK313) to regulate Wnt/13-catenin. In mouse NAFLD livers, immunohistochemistry and Western blotting validated the finding of YB-1 gene downregulation leading to the inhibition of Wnt/13-catenin pathway activation, ultimately inhibiting lipid synthesis and reducing the inflammatory response. Similar to the in vitro investigation, 13-catenin overexpression reversed such YB-1 downregulation-induced downstream effects. Upregulation of the YB-1 gene promoted the activation of the Wnt/13-catenin pathway, thus increasing lipid synthesis and the inflammatory response. However, downregulation of 13-catenin reversed this phenomenon caused by upregulating YB-1. Conclusions: In summary, these results demonstrate that YB-1 regulates liver lipid metabolism by regulating the Wnt/13-catenin signaling pathway.