Microwave-assisted synthesis of chitosan biguanidine hydrochloride and its regulation on InsR and GLUT2 in insulin resistant HepG2 cells

Insulin receptor (InsR) and GLUTs play a very important role in pathophysiological changes in terms of diabetes and insulin resistance, and metformin can regulate their expression and activity in order to alleviate insulin resistance. By reference to the molecular structure of metformin, chitosan biguanidine hydrochloride (CSGH) was synthesized by reacting chitosan (CS) with dicyandiamide under microwave irradiation and characterized by FT-IR, C NMR spectroscopy and XRD. The substitution degree (DS) of CSGH, measured by potentiometric titration method, varied in the range of 41.8% to 68.5%. After cytotoxicity testing of CSGH, nontoxic samples were selected. Then insulin resistance (IR) model using human hepatocarcinoma HepG2 cells was established, and the effect of CSGH on glucose consumption was investigated. Moreover, the expression of InsR and the signal protein glucose transporters-2 (GLUT2) were further investigated to study the mechanism. Results showed that CSGH samples with DS 43.2% and DS 52.7% were nontoxic and could improve the vitality, markedly promoting the glucose consumption of HepG2 cells. Besides, the effect of CSGH (DS 52.7%) on promoting glucose consumption was better than metformin and not dose-dependent. It is also found that CSGH could induce the expression of InsR protein and significantly inhibit the over-expression of GLUT2 transport protein, which was probably the mechanism of the therapeutic effect of CSGH on IR HepG2 cells.