[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 beta cell 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).


CONCLUSIONS
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.
Qiu
Ping
P
Department of Endocrinology, West China Hospital, Sichuan University, Chengdu 610041, Chnia.
Zhao
Tie-yun
TY
Li
Xiu-jun
XJ
Liu
Su-yi
SY
Li
Xiao-yu
XY
D002460:Cell Line; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects*; D008315:Malondialdehyde / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism
D007328:Insulin; D017382:Reactive Oxygen Species; D008315:Malondialdehyde; D005947:Glucose