The Correlation Of High Glucose On Islet Function And Islet Apoptosis

Objective To investigate the effects of high glucose on rat islet secretion and islet cells apoptosis in vitro.Methods SD rat islets were isolated and identified through DTZ stain and insulin immunohistochemical techniques. Then according to the concentration of glucose in medium and the culture days, islets were divided into six groups: NG group 1 (glucose 5.6mmol/L,incubated 1 day), NG group 2(glucose 5.6mmol/L, incubated 3 days), NG group 3 (glucose 5.6mmol/L, incubated 5 days); HG groupl(glucose 25.6mmol/L, incubated 1 day), HG group 2(glucose 25.6mmol/L, incubated 3 days), HG group 3(glucose 25.6mmol/L, incubated 5 days). After the treatment, the insulin concentrations in culture medium were detectded by radio-immunity after glucose-stimulated insulin secretion test; Apoptotic cells in islet were indentified by TUNEL method; the expressions of insulin mRNA, Caspase-3 mRNA and BAX mRNA was quantitated by reverse transcription - fluorescence quantitative -polymerase chain reaction(RT-FQ-PCR).Results (1)Compare with NG groups, Insulin secretion decrease when islets were incubated in high glucose(P<0.05); in HG group 1, Insulin secretion increase compare with HG group 2 and HG group 3; but there were no difference between NG group1,NG group2 and NG group3(P>0.05).(2) Compare with the six groups, insulin gene expression is the highest in the HG group 1(P<0.05), but Compare with NG group 2 and NG group 3 , insulin gene espress is lower in HG group 2 and HG group 3(P<0.05); PDX-1 gene expression in each HG groups were respective higher than NG groups(P<0.05), but in HG groups, group3 is lower than group1and group2. (3)The apoptotic rates of islet cells in each HG groups were markedly higher than each NG groups(P<0.05).(4) The ratio of expression of Caspase-3 and BAX in each HG groups were higher respective than NG groups(P<0.05); but in HG groups, HG group3 is higher than there was in HG group2, HG group2 is higher than in HG groupl(P<0.05); in NG groups, the expression of Caspase-3 and BAX in NG group3 were higher than NG group1 and NG group2.Conclusion (1)We establish a method of islation and purification of islets from SD rat to fumble its diversify in vitro.(2)The glucose-simulated insulin secretion were markedly decreased in high glucose circumstance, there was correlated with incubation time.(3)Short term exposure of islated rat islets to high concenteation of glucose maybe stimulate insulin and PDX-1 gene expression, but chronic exposure to high concenteation of glucose decreased insulin and PDX-1 gene expression, suggesting a normal blood sugar plays an important role in maintaining islet function for diabetic patients.(4)The apoptotic rates and the expression of Caspase-3 and BAX were increase when islets were in high concenteation of glucose, and there was correlated with incubation time, suggesting that high glucose induce islet cells apoptosis possiblely on account of oxidative stress and increasing the apoptotic genes.