胰岛α细胞胰岛素抵抗与炎症通路激活的关系及机制

The relationship between islet a cell insulin resistance and inflammatory pathway activation and its mechanism

目的探讨高脂饲养大鼠胰岛α细胞炎症通路分子基因的表达变化及吡格列酮干预的影响。方法 8周龄雄性 SD 大鼠随机分为3组(每组15只):正常饲养组(NC)、高脂饲养组(HF)、高脂+吡格列酮组(HP)。喂养20周后检测空腹血胰岛素(FIns)、胰高血糖素(Glc)、游离脂肪酸(FFA)、高敏 C 反应蛋白(hsCRP)水平;正常血糖高胰岛素钳夹试验评价外周胰岛素抵抗程度;离体胰岛细胞表面灌注检测高糖状态 Glc 分泌的动态变化,同时3组大鼠各随机入组8只给予大剂量链脲菌素去β细胞处理,分为正常去β细胞组(NC-B),高脂去β细胞组(HF-B),高脂+吡格列酮去β细胞组(HP-B),采用定量 PCR 方法比较3组去β细胞大鼠α细胞 NF-B、NF-B抑制蛋白α(IBα)mRNA 表达的情况。结果 (1)HF 组葡萄糖输注率(GIR)明显低于 NC 组,血 FIns、Glc、FFA及 hsCRP 水平均显著高于 NC 组;而 HP 组以上各项指标较 HF 组均明显改善。(2)胰岛细胞表面灌注,HF 组基础 Glc 的分泌高于 NC 组(P<0.01),16.7 mmol/L 葡萄糖灌注后 HF 组胰岛的 Glc 分泌未受抑制,HP 组与 NC 组比较差异无统计学意义。(3)与 NC-B 组相比,HF-B 组α细胞 NF-B mRNA的表达增高20.5%,IBα mRNA 表达降低24.3%(P 值均<0.01)。HP-B 组较 HF-B 组 NF-κB、IκBαmRNA 分别改善78.3%、58.8%。(4)HF 组血 FFA 水平与 GIR 呈负相关(r=-0.675,P<0.01);与NF-κB mRNA 表达呈正相关(r=0.775,P<0.05)。结论高脂饲养导致胰岛α细胞胰岛素抵抗,同时激活了α细胞炎症通路基因的表达且与 FFA 升高有关。吡格列酮干预能改善上述变化。

Objective To study the changes of inflammatory path molecules in the islet α cells in high-fat-diet fed plus β cell-deleted rat models and the effects of pioglitazone intervention. Methods Forty five normal male SD rats, 8 week old, were randomly divided into 3 groups, i. e. , a normal diet group （NC）, a high fat diet fed group （HF）, and a high fat diet fed and pioglitazone treated group （HP, pioglitazone 15 mg · kg^-1· d^-1 ）. At the end of twenty weeks of feeding, fasting serum insulin （ Fins）, glucagon,free fatty acid （FFA）and high sensitive C reactive protein （hsCRP） were determined. Glucose infusion rate （GIR） was measured by using euglycemic hyperinsulinemia clamp to evaluate the peripheral insulin resistance. The contents of glucagon in perfusion medium during islet cell perfusion was measured with RIA. At the same time, β cell-deleted rat models were established by injecting large dose streptozocin （100 mg/kg） in 8 rats in each of the three groups, i.e. , HF-B group,HP-B group and NC-B group. Five days later, the rats were sacrificed and the pancreatic islets were isolated and collected. The expression of NF-κB and inhibitor κBα（IκBα） gene in the islets was detected with real-time PCR. Results （1） GIR was decreased significantly in HF group as compared with NC group （P 〈 0. 01 ）. The concentrations of serum Fins, glucagon, FFA and hsCRP in HF group were higher than those in NC group. Pioglitazone intervention could reverse these effects. （2） 16. 7 mmol/L glucose could inhibit the glucagon secretion by the islet a cells of the NC group rats, but not of the HF group rats. Pioglitazone intervention could reverse these effects. （3） The gene expression of NF-κB was significantly increased by 20. 5% in the HF-B group than in the NC-B group （ P 〈 0. 01 ）. In contrast, the expression of IκBα was significantly decreased by 24. 3% （P 〈0. 01 ）. The expression of NF-κB and IκBα mRNAs in HP-B group,when compared with that of HF-B group,was improved 78. 3% and 58.8% ,respectively. Conclusions High-fat-diet feeding induces islet α cell insulin resistance and activates the mRNA expression of inflammatory path molecules in β cell-deleted rat models and it may relate with the increased plasma FFA concentration. Pioglitazone intervention can reverse these effects.