桑叶多糖MLPⅡ对糖尿病大鼠胰腺组织氧化应激的保护作用

The Protective Effects of Polysaccharide MLP Ⅱ from Mulberry Leaf on Oxidative Stress in Pancreas of Diabetic Rat

用从桑叶中分离提取的粗多糖MLPⅡ连续5周灌胃给药治疗Ⅱ型糖尿病模型大鼠,在电子显微镜下观察大鼠胰岛β细胞超微结构,采用免疫组化法检测核转录因子κB(nuclear transcription factorκB,NF-κB)的表达变化,并利用Western blot、半定量RT-PCR法分别检测肿瘤坏死因子α(tumor necrosis factorα,TNF-α)和胰岛素2(insulin 2,INS-2)在蛋白质表达水平和基因转录水平的变化。与糖尿病模型对照组大鼠相比,桑叶多糖MLPⅡ治疗组糖尿病模型大鼠的胰岛β细胞超微结构损伤程度明显减轻,胰岛β细胞中NF-κB的表达明显降低,胰腺组织中TNF-α蛋白的表达和基因mRNA的转录显著下调(P<0.01),而INS-2蛋白的表达和基因mRNA的转录显著上调(P<0.01)。试验结果表明,桑叶多糖MLPⅡ可明显改善Ⅱ型糖尿病模型大鼠胰腺组织氧化应激损伤,其作用机制可能与下调胰腺组织NF-κB和TNF-α的表达有关。

The type Ⅱ diabetic model rats were consecutively treated with polysaccharide MLPⅡ extracted from mulberry leaves for 5 weeks. The ultrastructure of pancreatic β-cells was observed under electron microscope. The changes of nuclear transcription factor κB（NF-κB） was detected by immunohistochemistry. Meanwhile,the changes on protein expression level and gene transcription level of tumor necrosis factor α（TNF-α） and insulin 2（INS-2） were detected by Western blotting and semi-quantitative RT-PCR. Compared with the rats of diabetic model control group,the injury to ultrastructure of pancreatic β-cells in MLPⅡtreated rats was obviously alleviated,the expression of NF-κB in pancreatic β-cells was obviously reduced,the expression of TNF-α protein and transcription of TNF-α mRNA in pancreatic tissue were significantly decreased（P0. 01）,whilst the expression of INS-2 protein and transcription of INS-2 mRNA in pancreatic tissue were significantly increased（P0. 01）. The results show that mulberry leaf polysaccharide MLPⅡcould obviously ameliorate the oxidative stress injury to pancreas of diabetic rats possibly through a mechanism related with decreasing the expressions of NF-κB and TNF-α in pancreas.