Effects of rhein on insulin signaling pathway and its negative regulatory protein protein tyrosine phosphatase 1B / 医学研究生学报

ABSTRACT

Objective Recent studies have shown that rhein could improve glucose metabolism,while the specific mechanism is not yet clear，the aim of this study is to explore the effects of rhein on the insulin signaling pathway in C2C12 cells.Methods To measure the optimum substrate and optimum enzyme concentrations of rhein and the protein tyrosine phosphatase-1B(PTP1B)and calculate the half maximal inhibitory concentration of rhein on PTP1B(IC50). Differentiated and maturated C2C12 myotubes were divided into two groups, the rhein group and the control group. The rhein groups were treated with different rhein concentrations(0.1,1, 10,100 μmol/L) , the positive control group was given 10 nmol/L insulin stimulation for 0.5 hours and the blank control group was treated with equal volume solvent. Related proteins in the insulin signaling pathway were detected by Western blotting and PTP-1B activity was measured by immunoprecipitation.Results The IC50 of rhein to PTP1B was 80.5 μmol/L,and when C2C12 myotubes were treated with 100 μmol/L rhein, the activity of PTP1B decreased significantly. Compared with the blank control group, the rhein groups' phosphorylation levels in insulin receptor and insulin receptor substrates were enhanced and the levels of GLUT4 were obviously improved in C2C12 cells. Moreover, the protein levels of insulin receptor and insulin receptor substrates were not affected significantly.Conclusion Rhein could reduce the activity of PTP1B and enhance insulin signaling transduction. Therefore，we speculated that the enhancement of insulin signaling may be related to the decrease of PTP1B activity in skeletal muscle cells.