[Impairment of pancreatic islet beta cell function induced by intermittent high glucose through oxidative and endoplasmic reticulum stress: experiment with rat pancreatic islet beta cells].

OBJECTIVE

To investigate the effect of intermittent high glucose (IHG) on the pancreatic islet beta-cell function and mechanism thereof.

METHODS

Rat pancreatic islet p-cells of the line INS-1 were cultured and randomly divided into 3 groups: IHG group exposed to fluctuating concentrations of glucose, stable high glucose (SHG) group exposed to 16. 7 mmol/L glucose, and control group exposed to normal concentration (5.5 mmol/L) glucose. 24, 48, and 72 hours later radioimmunoassay was used to detect the insulin secretion index (ISI). 72 h later, the concentration of insulin in the cells was detected with radioimmunoassay. The contents of oxidative stress markers, nitrotyrosine (NT) and 8-hydroxy-2-deoxyguanosine (8-OHdG) were detected. Real-time PCR was used to detect the mRNA expression of peroxiredoxin 1 (PDX-1), ATF-4, one of the transcription factors of the family bZIP, and insulin. Western blotting was used to detect the protein expression of ATF-4.

RESULTS

The ISI of the IHG and SHG groups decreased time-dependently, The ISI of IHG and SHG groups were 0.64 +/- 0.11 and 1.31 +/- 0. 04 respectively, both significantly lower than that of the control group (1.67 +/- 0.23, both P < 0.05). The intracellular insulin contents of the IHG and SHG groups were (10.91 +/- 0.14) and (11.08 +/- 0.03) +/- U/microg respectively, both significantly lower than that of the control group [(12.37 +/- 0.37) microU/microg, both P < 0.05]. The intracellular concentrations of 8-OHdG and NT of the SHG and IHG groups, were significantly higher than those of the control group (all P < 0.01), and those of the IHG group were significantly higher than those of the SHG group (both P < 0.05). The mRNA and protein expression levels of ATF-4 of the IHG group were all significantly higher than those of the control group (all P < 0.05) and those of the IHG group were significantly higher than those of the SHG group (both P < 0.05).

CONCLUSION

IHG and SHG induce severe impairment in pancreatic islet beta cell functions, especially IHG, which is closely associated with the aggravation of oxidative stress and endoplasmic reticulum stress triggered by intermittent high glucose.