Mechanism of IGF2BP2 regulation of PPAR-γ/GLUT4 pathway in insulin resistance induced by sodium arsenite exposure in HepG2 cells

BackgroundArsenic is an environmentally harmful substance that causes hepatic insulin resistance and liver damage, increasing the risk of type 2 diabetes mellitus. ObjectiveTo explore whether the insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) is involved in insulin resistance in HepG2 cells after arsenic exposure through the peroxisome-proliferator-activated receptor γ (PPAR-γ) / glucose transporter 4 (GLUT4) pathway. MethodsCell viability was determined using cell counting kit 8 (CCK8) and an appropriate NaAsO2 infection dose was determined. A cellular arsenic exposure model of HepG2 cells was established by four concentrations of NaAsO2 solution for 24 h (the experiment was divided into four groups: 0, 2, 4, and 8 μmol·L−1); HepG2 cells were firstly treated with pcDNA3.1-IGF2BP2 and pcDNA3.1-NC respectively for 6 h, then with 8 μmol·L−1 NaAsO2 for 24 h to establish a IGF2BP2 overexpression cell model (the experiment was divided into 4 groups: control, NaAsO2, NaAsO2+pcDNA3.1-IGF2BP2, and NaAsO2+pcDNA3.1-NC); finally the cells were subject to 100 nmol·L−1 insulin stimulation for 30 min. Glycogen and glucose in HepG2 cells were determined by glycogen and glucose assay kits; mRNA expression levels of IGF2BP2 were measured by quantitative real-time PCR; protein expression levels of IGF2BP2, PPAR-γ, and GLUT4 in HepG2 were detected by Western blot (WB); and the binding of IGF2BP2 to PPAR-γ and PPAR-γ to GLUT4 was verified by co-immunoprecipitation (CO-IP) experiment. ResultsThe results of CCK8 experiment showed a dose-effect relationship between NaAsO2 concentration and cell viability. When the concentration of NaAsO2 was ≥4 μmol·L−1 , the cell viabilities were lower than that of the control group (P <0.05). With the increasing dose of NaAsO2 infection, reduced glucose consumption and glycogen levels in HepG2 cells were found in the 2, 4, and 8 μmol·L−1 NaAsO2 treatment groups compared to the control group (P <0.05). The difference between the mRNA expression level of IGF2BP2 in the HepG2 cells treated with 4 or 8 μmol L−1 NaAsO2 and the control group was significant (P <0.05). In the IGF2BP2 overexpression cell model, compared with the control group, glucose consumption and glycogen levels were lowered in the NaAsO2 group (P <0.05), the mRNA expression level of IGF2BP2 and the protein expression levels of IGF2BP2, PPAR-γ, and GLUT4 in the cell membrane were all decreased (P <0.05). Compared with the NaAsO2 group, the glucose consumption and glycogen levels were increased in the NaAsO2+pcDNA3.1-IGF2BP2 group (P <0.05), and the mRNA expression level of IGF2BP2 and the protein expression levels of IGF2BP2, PPAR-γ, and GLUT4 in the cell membrane were all increased (P <0.05). The results of CO-IP experiments showed that IGF2BP2 interacted with PPAR-γ as well as PPAR-γ with GLUT4 protein. ConclusionIGF2BP2 is involved in arsenic exposure-induced insulin resistance in HepG2 cells by acting on the PPAR-γ/GLUT4 pathway.