Objective: To study the effects of homocysteine (Hcy) on the insulin secretion and apoptosis of pancreatic beta cells.
Methods: Clonal mouse pancreatic beta cells of the line NIT-1 were cultured and exposed to Hcy of 50, 100, 250, 500 and 1000 micromol/L for 6, 12, 24, and 48 hours respectively, then glucose of the concentrations of 5.6 mmol/L or 16.7 mmol/L was added for 1 h, and then the insulin concentration in the culture medium was determined by radioimmunoassay, and MTT method was used to detect the survival rate of the cells. NIT-1 cells were exposed to Hcy of the concentrations of 0, 50, 100, 250, 500 and 1000 micromol/L respectively for 24 h, another NIT-1 cells were exposed to Hcy of the final concentration of 250 micromol/L for 0, 6, 12, and 48 h respectively, then flow cytometry (FC) was used to detect the apoptosis of the cells. After exposure to Hcy of the concentrations of 50, 100, 250, 500 and 1000 micromol/L for 72 h DNA agarose gel electrophoresis was performed.
Results: Hcy inhibited the basal and glucose-induced insulin secretion in a time- and dose-dependent manner. The insulin secretion amounts of the NIT-1 cells after exposure to 50 micromol/L Hcy for 24 hours and to 100 micromol/L Hcy for 12 hours were significantly lower by 17.1% and 10.8% compared with the control group (all P < 0.01). Incubated with 100 micromol/L Hcy for 12 hours and 24 hours respectively, the survival rates of the NIT-1 cells were 94.56% and 87.93% respectively (P < 0.05, P < 0.01). Incubated with 100 micromol/L Hcy for 24 hours, the apoptosis rate of the NIT-1 cells was 7.21% (P < 0.01); and incubated with 250 micromol/L Hcy for 12 hours, the apoptosis rate of the NIT-1 cells was 12.93% (P < 0.01). Both FC and agarose gel electrophoresis indicated that Hcy induced cell apoptosis time- and concentration-dependently.
Conclusion: Hcy impairs insulin secretion and induces cell apoptosis of pancreatic beta cells time- and concentration-dependently.