长期高浓度葡萄糖对胰岛细胞凋亡和功能相关基因表达的影响

Effects of sustained high glucose on the expressions of genes related to apoptosis and function of islet cells

目的 探明长期高浓度葡萄糖对体外胰岛细胞功能和凋亡相关基因表达的影响。方法应用放免法检测不同浓度葡萄糖培养后大鼠胰岛细胞和小鼠 βTc3细胞在葡萄糖刺激时培育上清液和细胞内的胰岛素水平 ;应用半定量多重RT PCR和Northern印迹法检测培养后IDX 1(Isletduodenalhomeobox 1) ,葡萄糖激酶 (GK ) ,葡萄糖转运子 2 (GLUT2 ) ,C/EBPβ和Bcl xmRNA的表达情况 ;应用TUNEL法检测培养后的细胞凋亡百分率。结果 ( 1)长期高浓度葡萄糖培养导致大鼠胰岛细胞和小鼠βTc3细胞对葡萄糖刺激的胰岛素分泌反应降低和细胞内胰岛素含量的减少 ;( 2 )高糖培养 14天可以使大鼠胰岛细胞IDX 1和GLUT2mRNA表达明显减少 (P <0 .0 5 ) ,C/EBPβmRNA表达明显增加 ,GKmRNA表达无明显变化 ;( 3 )高糖培养可以明显增加大鼠胰岛细胞和小鼠 βTc3细胞凋亡百分率 ;( 4 )大鼠胰岛细胞高糖培养 14天后Bcl xSmRNA水平明显增加 ,Bcl xLmRNA水平无明显变化 ,Bcl xL/Bcl xSmRNA比率明显减少 (P <0 .0 5 )。结论 ( 1)长期高糖培养可以诱导大鼠胰岛细胞和小鼠 βTc3细胞凋亡和功能缺陷 ;( 2 )IDX 1表达的变化在大鼠胰岛细胞功能缺陷中起重要作用 ;( 3 )大鼠胰岛细胞的Bcl xL/Bcl xS比率变化在高糖所致的胰岛细胞凋亡中起重要作用。

Objective To investigate the effects of sustained high glucose on the expressions of genes related to apoptosis and function of islet cell in vitro. Methods Response of glucose stimulating insulin secretion (GSIS) and intracellular insulin content of rat islet cell and mouse βTc3 cells were measured by radioimmunoassay. The cells were cultured with sustained high glucose (25.5 mmol/L) and normal glucose (5.5 mmol/L), the latter served as control. The mRNA levels of genes related to glucose metabolism such as glucose transporter (GLUT2), IDX-1 (Islet duodenal homeobox 1), glucokinase (GK) and C/EBPβ and apoptotic gene Bcl-x in these cells cultured by above condition were evaluated by semi-quantitative multiplex RT-PCR and Northern blot. Apoptotic cells were identified by TUNEL method. Results (1) GSIS and the intracellular insulin levels were decreased in rat islet cells and mouse βTc3 cells cultured with sustained high glucose. Normalization of glucose concentration from 25.5 mmol/L to 5.5 mmol/L could partially improve GSIS in mouse βTc3 cells. (2) mRNA levels of IDX-1 and GLUT2 were decreased and the levels of C/EBP β increased in rat islet cells incubated with 25.5 mmol/L glucose for 14 days, but no changes in GK mRNA levels were found in the cells incubated at different glucose concentrations. (3) The apoptotic proportions of rat islet cells and mouse βTc3 cells were significantly increased at high glucose concentration. Lowering the glucose concentration reduced the apoptosis of mouse βTc3 cells. (4) Expression of Bcl-xS mRNA was increased and the ratio of Bcl-xL/Bcl-xS was decreased in rat islet cells after 14 day incubation in 25.5 mmol/L glucose.Conclusion (1) Sustained high glucose concentration was toxic to rat islet cells and mouse βTc3 cells, as manifested by the increasing percentage of apoptotic cells and dysfunction of GSIS and decreasing synthesis of insulin; (2) Rat islet cell dysfunction caused by sustained glucose were mediated by decreased expression IDX-1 as a major gene; (3) The expression change of Bcl-xS in rat islet cells cultured with sustained high glucose suggests that the ratio of Bcl-xL/Bcl-xS seems to be an important predictor of islet cells apoptosis.