| In recent years, the apoptosis ofβ-cells has become a major focus of diabetes research. Overwhelming body of evidence has suggested that chronic persistent hyperglycemia results inβ-cells dysfunction and ultimately apoptosis, called asβ-cell glucotoxicity. However, the previous research almost focused on the toxic effect of persistent high glucose, infact, in addition to chronic persistent hyperglycemia, another general and important phenomenon is the repeated fluctuation in blood glucose existed in diabetes patients which is more excessive than in health individuals, Recently, a few published reports demonstrated the effects of intermittent high glucose on development of diabetic complications, but the effect of intermittent high glucose onβ-cell and the potential mechanisms involved in remain unknown.There are many potential mechanisms whereby excess glucose metabolites traveling along these pathways might cause beta cell damage. However, all these pathways have in common the formation of reactive oxygen species that cause chronic oxidative stress, which in turn causes increased apoptosis. However, few reports show whether intermittent high glucose triggers the oxidative stress within pancreatic beta cell.In the present study, we therefore aimed at analyzing the role of intermittent high glucose in inducingβ-cell apoptosis and determining whether the chronic oxidative stress involved in.Objective To investigate the effect of intermittent high glucose (IHG)on the apoptosis of pancreatic isletβ-cells and mechanism thereof.Methods Rat pancreatic isletβ-cells of the line Ins—1 were cultured and randomly divided into 3 groups:control group(NG) exposed to normal concentration(5.5 mmol/ L) glucose,stable high glucose (SHG) group exposed to 33.3 mmol/L glucose, and IHG group exposed to fluctuating concentrations of glucose (alternating 5.5 mmol/L and 33.3 mmol/L glucose every 12 h).72h later, the cell viability of Ins-1 cells was explored using MTT reduction assay;Apoptosis rate were analyzed by flow cytometry using AnnexinⅤ—FITc and PI double staining, and morphology was examined by Hoechst 33258 staining. The intracellular reactive oxygen species(ROS)was observed by flow cytometry. The malonaldehyde (MDA) was measured through thiobarbituric acid reaction (TBA). Glutathione(GSH) level was determined by dithiobis-2-nitrobenzoic acid colorimetry.Results (1)the cell viability in islets exposed to SHG and IHG was approximately decreased compared with control treatment, respectively (P<0.05),and IHG group lower than SHG group.(2) Ins-1 cells showed changes of apoptosis in intermittent and stable high glucose concentrations. The apoptosis induced by intermittent high glucose concentration was more obvious than that by stable high glucose (apoptosis rate:NG (2.79±0.96)%, IHG(23.66±2.42)%, SHG(13.12±5.91)%, P<0.05).(3) The MDA and ROS levels increased while the GSH level decreased significantly in the cells exposed to intermittent and stable high glucose(P< 0.05). The cells exposed to intermittent high glucose produced more ROS and MDA than those exposed to continuing high glucose(P< O.05).Conclusion Intermittent and stable high glucose could induce the apoptosis of pancreatic isletβ-cells, especially IGH, which closely associated with the aggravation of oxidative stress triggered by intermittent high glucose.
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