Damage mechanism of intermittent exposure to high concentrations of glucose to beta cell lines (HIT-T15 cell)]

OBJECTIVE: To test the effect of intermittent exposure to high concentrations of glucose on HIT-T15 cells. METHODS: The HIT-T15 cells (pancreatic betacell lines) were exposed to 16.7 mmol/L of glucose for two hours, at an interval of three hours. Such intermittent exposure was repeated three times a day. Otherwise, the cells were exposed to 5.5 mmol/L of glucose. The control groups included continuing exposure to 5.5 mmol/L of glucose (normal control group) and continuing exposure to 16.7 mmol/L of glucose. The impact of N-acetyl-L-cysteine (NAC) was also tested in the groups with intermittent and continuing exposure to 16. 7 mmol/L of glucose. The insulin was detected by radioimmunoassay (RIA). The mitochondrial membrane potential (MMP) was measured by laser scanning confocal microscope. The ATP levels of beta cells were examined by the luciferin-luciferase kit. The Malonaldehyde (MDA) was measured through thiobarbituric acid reaction (TBA). The intracellular reactive oxygen species (ROS) was observed by flow cytometry. RESULTS: The HIT-T15 cells exposed to intermittent and continuing high glucose secreted (3.13 +/- 1.11) microIU/mLD and (5.18 +/- 0. 95) microIU/mL] of insulin, significantly less than the control (9.33 +/- 0.62) microIU/mL, P < 0.05]. The MDA and ROS levels increased while the ATP and MMP levels decreased significantly in the cells exposed to intermittent and continuing high glucose (P < 0.05). The cells exposed to intermittent high glucose produced more ROS than the cells exposed to continuing high glucose (P < 0.05). CONCLUSION: Exposure of HIT-T15 to high glucose leads to oxidative stress of mitochondrial. Intermittent exposure causes more serious stress than continuing exposure. Such response might be a result of decreased MMP level and ATP contents.