胃旁路术对糖尿病大鼠胰岛β细胞凋亡的影响及其机制研究

Effects of Gastric bypass surgery on the apoptosis of islet β-cells in type 2 nonobese diabetic （NOD） rats and its mechanism

目的 研究胃旁路手术对非肥胖2型糖尿病大鼠胰岛β细胞凋亡的影响及其机制.方法 将72只8周龄的GK大鼠随机分为手术组（O组,18只）、假手术组（S组,18只）、饮食控制组（F组,18只）和对照组（C组,18只）,术前和术后1、2、4、8周检测比较空腹、餐后血糖、胰岛素和胰高血糖素样肽-1（GLP-1）水平.术后2、4、8周取血测餐后血糖后,分批随机处死大鼠,每批每组处死6只,大鼠处死后分离胰腺并取出待用.原位末端标记法检测胰岛β细胞凋亡;免疫组化方法检测凋亡相关蛋白Bcl-2、Bax的表达.结果 O组术后第4周空腹血糖由术前的（16.2 ±0.8）mmol/L下降到（9.2±0.6）mmol/L,术后第8周血糖为（9.7±0.7）mmoL/L;术后第4周餐后血糖由术前的（31.1±1.1）mmoi/L降至（13.1±0.7）mmol/L,术后第8周为（12.3 ±0.7）mmol/L;术后第4周空腹血清胰岛素水平由术前的（28.0±1.2）mU/L升至（62.8±1.9）mU/L,术后第8周为（61.7±1.4）mU/L,术后第4、8周餐后血清胰岛素水平分别为（77.4±1.1）mU/L、（77.1±1.0）mU/L;术后第2周空腹GLP-1由术前的（10.7±1.0）pmol/L升至（13.5±0.8）pmol/L,至术后第4、8周分别为（26.1±0.9）pmol/L、（25.3±1.2）pmol/L;O组各测量值术后各时相点与术前比较差异均有统计学意义（P＜0.05）,与其他组比较差异亦有统计学意义（P＜0.05）.O组大鼠胰岛细胞凋亡率术后4周下降至（5.9 ±0.7）%,术后8周凋亡率为（6.3±1.1）%,差异有统计学意义（P＜0.05）.O组Bcl-2蛋白表达术后2、4、8周表达量分别为31.3±1.5、35.7±1.0和35.8 ±0.8,明显高于同时间点的其他3组,差异有统计学意义（P＜0.05）;Bax蛋白术后2、4、8周表达量分别为13.3±0.9、10.8 ±0.9和10.9±1.1,明显低于相同时间点的其他3组,差异有统计学意义（P＜0.05）.结论 胃旁路手术可显著降低糖尿病大鼠血糖,促进GLP-1分泌,从而调节Bcl-2通路,显著抑制胰岛β细胞凋亡,保护胰岛B细胞.

Objective To investigate the effects of Gastric bypass surgery on the apoptosis of islet β-cells in type 2 nonobese diabetic （NOD）rats and its mechanisms. Methods Seventy-two 8-week-old GK rats were randomly divided into four groups： operation group （group O, n = 18）, sham operation group （group S, n=18）, diet control group （group F, n=18） and control group （group C, n=18）. The levels of fasting, postprandial blood glucose, insulin and glucagon-like peptide-1 （GLP-1） were measured and compared among the 4 groups before the operation and at 1,2, 4 and 8 weeks following the operation. The blood samples were collected at 2,4 and 8 weeks after the operation for the measurement of postprandial blood glucose, and then the rats in batches（6 rats in each group）were decapitated to retrieve the pancreas.The apoptosis of the islet β-cells was detected by using TUNEL assay, and the expression of apoptosisrelated proteins Bcl-2, Bax was measured with immunohistochemistry. Results As for group O, the fasting blood glucose level decreased from （ 16. 2 ±0. 8） mmol/L before the operation to respectively （9. 2 ±0. 6）mmol/L and （9.7 ±0. 7 ） mmol/L at 4 and 8 weeks after the operation; postprandial blood glucose decreased from （ 31.1 ± 1.1 ） mmol/L before the operation to respectively （ 13. 1 ± 0. 7 ） mmol/L and （ 12. 3 ±0. 7） mmol/L at 4 and 8 weeks after the operation. Fasting insulin level increased from （28. 0 ±1.2） mU/L before the operation to respectively （62. 8 ± 1.9） mU/L and （61.7 ± 1.4） mU/L at 4 and 8 weeks after the operation; and at 4 and 8 weeks after the operation postprandial insulin level was （77. 4 ±1.1） mU/L and （77. 1 ± 1. 0） mU/L. At 2 weeks from the operation, the fasting GLP-1 in group O increased from （ 10. 7 ± 1.0） pmol/L to （ 13. 5 ±0. 8） pmol/L, and respectively to （26. 1 ±0. 9） pmol/L and （25. 3 ± 1.2） pmol/L at 4 and 8 weeks after the operation. The differences in the above-mentioned items before and after the operation were all significant in group O （ P 〈 0. 05 ）, and the differences in the items among group O and the other three groups （ P 〈 0. 05 ） were all significant as well. In group O, the apoptosis rate of pancreatic islet cell decreased to （5.9 ± 0. 7 ） % at 4 weeks from the operation, and （6. 3 ±1.1 ） % at 8 weeks from the operation（ P 〈 0. 05 ）. The expression of Bcl-2 protein in group O was 31.3 ±1.5, 35.7 ± 1.0 and 35. 8 ± 0. 8 at 2, 4 and 8 weeks post operation, which was significantly higher in statistics than those of the same time point in the other three groups （ P 〈 0. 05 ）. The expression of Bax protein in group O was 13.3 ±0.9, 10.8 ±0.9 and 10.9 ±1.1 at 2, 4 and 8 weeks from the operation,which was significantly lower in statistics than those of the same time point in the other three groups（P 〈0. 05）.Conclusions Gastric bypass surgery can significantly reduce the blood glucose level and promote the secretion of GLP-1, and therefore inhibit the apoptosis of the islet β cells in diabetic rats through the Bcl-2 pathway.