ABSTRACT
Objective To compare the effects of intermittent high blood glucose and consistent hilgh blood glucose on pancreatic islet β-cell function and β-cell apoptosis in GK rats.Methods Twenty-two male GK rats were randomly divided into 2 groups consisting of consistent hish blood glucose group(HG)and intermittent high blood glucose group(FG).Eleven male Wistar rats were used as normal glucose controls(NG).The fluctuating high blood glucose animal model was induced by intraperitoneal injection of insulin and glucose at different time for six weeks.Intraperitoneal injection glucose tolerance test and insulin release test were performed.The area under curve of glucose(AUCg).the area under carve of insulin(AUCi)/AUCg and the ratio of insulin increment to blood glucose increment 15 min after glucose load(Δ115'/ΔG15')were calculated routinely.Then the pancreatic slides were stained with insulin antibody.The apoptotic β cells in islets were detected and quantified by the TUNEL technique.Results(1)The fasting plasma glucose and 15,30,60,and 120 min plasma glucose levels after glucose loading in FG group were significantly higher than those in control group(all P<0.01),and AUCg was also markedly increased[(1 012.14±82.62 vs 813.60±56.70)ng·ml~(-1)·h~(-1)·10~4,P<0.01].Insulin levels of FG group at 15,30,60,and 120 rain after glucose loading were significantly lower than those in HG group[(0.554± 0.18 vs 0.95±0.28.0.43±0.17 vs 0.85±0.21,0.47±0.11 vs 0.76±0.16,0.58±0.13 vs 1.08±0.26)ng/ml,P<0.05],along with decreased AUCi/AUCg and Δ115'/ΔG15'[(9.56±2.53 vs 21.36±4.16)×10~(-7);(3.95±3.45 vs 27.02±8.62)×10~(-7),both P<0.05].(2)Image analysis of pancreatic islet immunocytoehemistry showed that the insulin staining positive area,area ratio and total density of insulin positive cells per islet were significantly lower in FG group than those in HG group(P<0.05).(3)The percentage of β-cell apoptosis in the FG group was statistically higher than that in the HG group[(24.17±7.25 vs 16.55±5.11)%,P<0.01].Conclusion Compared with the consistent high blood glucose,intermittent high glucose could lead to further impairment of β-cell function and increased β-cell apoptosis may partially contribute to this process.