胰岛素信号转导基因表达的改变与α细胞胰岛素抵抗的实验研究

The expression of insulin signal transduction molecules and islet α cell insulin resistance

目的探讨高脂喂养及大剂量链脲佐菌素(STZ)去β细胞处理的肥胖大鼠胰岛α细胞信号转导通路分子的表达情况及其可能机理。方法 30只 SD 大鼠分为高脂饲料喂养的肥胖(HF)组和普通饲料喂养的正常对照(NC)组。喂养20周后,(1)检测空腹血胰岛素(Ins)、胰高糖素(Glc)、游离脂肪酸(FFA)、甘油三酯(TG)水平。(2)正常血糖高胰岛素钳夹试验评价外周胰岛素抵抗程度(NC 组7只,HF 组7只)。(3)NC 组和 HF 组各8只,给予大剂量链脲佐菌素(STZ)去β细胞处理,即 NC-B 组,HF-B 组。使用胰岛素控制血糖,5d 后处死动物,分离胰岛细胞。(4)采用实时定量聚合酶链反应方法比较两组大鼠α细胞 Glc、胰岛素受体底物-1(IRS-1)、胰岛素受体底物-2(IRS-2)、磷酯酰肌醇3激酶(PI3K)的 mRNA 表达的情况。结果(1)HF 组葡萄糖输注率(GIR)明显低于NC 组(5.3 mg·min^(-1)·kg^(-1)±1.2 mg·min^(-1)·kg^(-1)vs 13.6 mg·min^(-1)·kg^(-1)±1.7 mg·min^(-1)·kg^(-1),P<0.01),HF 组血 FFA、Ins 及 Glc 水平显著高于 NC 组(FFA 508(394～622)μmol/L vs 325(240～410)μmol/L,Ins 23.7(14.0～33.4)mIU/L vs 11.5(3.6～19.4)mIU/L;Glc 345(298.6～391.4)pg/ml vs 256(226.4～285.6)pg/ml;P<0.05);(2)HF-B 组比 NC-B 组α细胞 Glc mRNA 的表达高34.2%±2.1%,IRS-2及 PI3K mRNA 分别低28.5%±1.8%、21.3%±1.6%(均 P<0.01),而IRS-1仅降低7.0%±1.2%(P>0.05)。(3)相关分析显示,HF 组血 FFA 水平与 GIR 呈负相关(r=-0.675,P<0.01);且与α细胞 IRS-2 mRNA 表达也呈负相关(r=-0.458,P<0.05)。结论高脂饮食诱导的去β细胞肥胖大鼠胰岛α细胞存在胰岛信号转导分子表达降低,且与血 FFA 水平升高有关。

Objective To study the changes of insulin signal transduetion molecules in islet α cells in high-fat-diet plus β cell-deleting rat models and its underlying mechanism. Methods Thirty SD rats were randomly divided into 2 equal groups and fed with high-fat-diet （ HF group） or normal diet （ normal control group, NC group） respectively. At the end of twenty-week feeding , the fasting serum insulin （Ins）, glueagon （ Glc）, free fatty acid （ FFA）, and triglyeeride （ TG were measured. The glucose infusion rate （GIR） was measured by using euglycemic hyperinsulinemia clamp to evaluate the peripheral insulin resistance . At the same time, large dose streptozocin （ 100 mg/kg） was injected so as to establish β cell- deleting rat models, i. e., HF-B group （ n = 8） and NC-B group （ n = 8）. Five days later, the rats of the HF-B and NC-B subgroups were sacrificed, and the pancreatic islets were isolated and collected. The expression of Glc, insulin receptor substrate-1 （ IRS-1 ）, IRS-2, and phosphatidylinositol-3-kinase（PI3K） gene in the islets were detected by RT-PCR. Results （ 1 ） The serum FFA, insulin and Glc concentrations of the HF group were 508 （ 394 - 622） μmol/L, 23.7 （ 14.0 - 33.4） mIU/L, and 345 （ 298.6 - 391.4） pg/ml respectively, all significantly higher than those of the NC group [ 325 （240 - 410） μmol/L, 11.5 （ 3.6 - 19.4） mIU/L, 256 （ 226.4 - 285.6） pg/ml ; respectively, all P 〈 0.05 ]. The GIR of the HF group was 5.25 mg ·min^-1·kg^-1±1.2mg·min^-1·kg^-1, significantly lower than that of the NC group （ 13.6 mg·min^-1·kg^-1±1.7mg·min^-1·kg^-1,P〈0.01））. （2） The gene expression of Glc of the HF-B subgroup was significantly higher than that of the NC-B subgroup by 34.2% ± 2. 1%. In contrast, the expression of IRS-2, and PI3K of the HF-B subgroup was significantly lower than that of the NC-B subgroup by 28.5% ± 1.8% and 21.3% ± 1.6% respectively （ both P 〈 0.01 ）. （3） The plasma FFA concentration was asignificantly negatively correlated with GIR （ r = - 0. 675, P 〈 0.05 ） and IRS-2 gene expression in islet α cells （ r = - 0. 458, P 〈 0.05） in the HF-B group. Conclusion High-fat-diet feeding plus β cell- deleting rat model shows an impaired expression of insulin signal transduction molecules in islet α cells which may relate with the increased plasma FFA concentration.