Effects of Exenatide on INS-1 cells and cell cycle protein in intermittent high glucose

Objective To investigate the effects of Exenatide on insulinoma cells-1(INS-1 cells) in intermittent high glucose,and study the related molecular mechanism of cell proliferation changes. Methods The cells were divided into 5 groups: normal glucose group, which the cells were cultured in the RPMI-1640 complete medium containing 5.5 mmol/L glucose; constant high glucose group, which the cells were cultured in the RPMI-1640 complete medium with 30.0 mmol/L glucose; intermittent high glucose group, which the cells were cultured in rotation per 24-hour in the RPMI-1640 complete medium containing 5.5 mmol/L or 30.0 mmol/L glucose; constant high glucose + Exenatide group, which the cells were cultured in RPMI-1640 complete medium with 30.0 mmol/L glucose and 100.0 nmmol/L Exenatide; intermittent high glucose + Exenatide group, which the cells were cultured in rotation per 24-hour in 5.5 mmol/L or 30.0 mmol/L glucose RPMI-1640 complete medium with 100.0 nmmol/L Exenatide. The cells were cultured at 37 ℃ in 5 % CO2 incubator for 7 days, Cell Counting Kit-8 was used to detect the proliferation activity, and cell cycle progression was detected by propidium iodide staining and flow cytometry. The expression of cyclin D1 and p21 were detected by Western blot. Results The cell proliferation activity of constant high glucose + Exenatide group and intermittent high glucose + Exenatide group was not significantly different as compared with that of normal glucose group,but higher than that of constant high glucose group and intermittent high glucose group(F = 3 026, P = 0.000). The G0/G1 phase cell proportion in constant high glucose + Exenatide group(49.12 % ± 3.72 %) and intermittent high glucose + Exenatide group(49.73 % ±4.04 %) was not significantly different as compared with that in normal glucose group, but lower than that in constant high glucose group(56.54 % ± 3.50 %) and intermittent high glucose group(65.54 % ± 3.63 %)(F = 20.054, P = 0.000). The cyclin D1 expression in constant high glucose + Exenatide group(0.41 ± 0.02) and intermittent high glucose + Exenatide group(0.43 ± 0.07) was not significantly different as compared with that in normal glucose group, but significantly higher than that of constant high glucose group(0.31 ± 0.02) and intermittent high glucose group(0.18 ± 0.03)(F = 29.284, P = 0.000). The p21 expression in constant high glucose + Exenatide group(0.21 ± 0.05) and intermittent high glucose + Exenatide group(0.22 ± 0.03) was not significantly different as compared with that in normal glucose group, but significantly lower than that in constant high glucose group(0.40 ± 0.03) and intermittent high glucose group(0.51 ± 0.04)(F = 40.296, P = 0.000). Conclusion It is demonstrated that in intermittent or constant high glucose, the Exenatide could increase the INS-1 cell cycle progression by up-regulating the expression of cyclin D1 and own regulating the expression of cell cycle inhibitory protein p21.