甲状腺素T3对四氧嘧啶诱导糖尿病小鼠胰腺的保护作用

Thyroid Hormone T3 Counteracts Pancreastic Dysfunction in Alloxan-Induced Diabetic Mice

目的:研究甲状腺素T3对四氧嘧啶(alloxan,ALX)诱导糖尿病小鼠胰腺损伤的预防和保护作用。方法:24只雄性昆明小鼠随机分成4组,分别给予一次性腹腔注射生理盐水、ALX、ALX和甲状腺素T3、甲状腺素T3,在注射后1、4、6、12、24 h各时间点测定小鼠血液活性氧(reactive oxygen species,ROS)水平,并在注射后28 d内定期测定小鼠血糖水平变化。28 d后,处死小鼠,取出胰腺进行形态学和生物化学指标分析:检测甲状腺素T3对小鼠胰腺超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)、谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)活力以及还原型谷胱甘肽(glutathione,GSH)和氧化型谷胱甘肽(oxidized glutathione,GSSG)含量的影响,分析甲状腺素T3对胰腺细胞抗氧化酶相关基因Nrf2、SOD、GSH-Px、CAT,细胞凋亡相关基因Caspase-3、Caspase-9、Bax、Bcl-2表达的影响。结果:经ALX诱导的小鼠血糖和血液ROS水平极显著升高(P<0.01),血液胰岛素水平极显著下降(P<0.01),血液和胰腺抗氧化酶的活力均极显著下降(P<0.01)。此外,抗氧化酶相关基因以及细胞凋亡相关基因表达水平均出现了极显著变化(P<0.01)。注射甲状腺素T3能够改善由ALX引起的小鼠血糖水平上升和胰岛素分泌不足,显著或极显著地缓解抗氧化酶活力下降及抗氧化相关基因表达下调(P<0.05或P<0.01),极显著抑制Caspase-3、Caspase-9、Bax等促凋亡基因表达的升高(P<0.01),促进抗凋亡基因Bcl-2的表达。结论:甲状腺素T3能够改善ALX诱导的糖尿病小鼠机体氧化还原状态,调节胰腺细胞凋亡相关基因的表达水平,保护胰腺组织,避免胰腺出现β细胞凋亡的情况,从而维持和保护胰腺调节血糖水平的功能。

Objective： The protective effects of thyroid hormone T3 on the dysfunction of pancreas in alloxan（ALX）-induced diabetic mice were investigated in this study. Methods： Twenty-four Kunming mice were randomly divided into four groups, including negative control group, ALX group, ALX plus T3（ALX ＋ T3） group, and T3 group, which were subjected to intraperitoneal administration of normal saline, ALX, ALX plus T3, and T3, respectively. The levels of reactive oxygen species（ROS） in blood were tested at 1, 4, 6, 12, and 24 h after injection. Blood glucose was tested every 3 days. Mice were sacrificed at 28 days after injection. Whole pancreas and plasma were utilized for morphological and biochemical analyses. The activities of superoxide dismutase（SOD）, catalase（CAT） and glutathione peroxidase（GSH-Px）, the contents of reduced and oxidative glutathione（GSH and GSSG）, the expression levels of antioxidant enzyme genes including Nrf2, SOD, GSH-Px, and CAT, and the expression levels of the apoptosis-associated genes Caspase-3, Caspase-9, Bax, Bcl-2 were examined in each group. Results： ALX induced a high level of blood glucose and ROS（P〈0.01）, low level of insulin in plasma（P〈0.01）, and lower activities of antioxidant enzymes in plasma and pancreas（P〈0.01）, as well as down-regulation of the antioxidant enzyme genes and apoptosis-related genes（P〈0.01）. T3 could ameliorate the enhancement of blood glucose and defective insulin secretion. The redox imbalance caused by ALX, including the decrease of antioxidant enzyme activities and gene expression levels, was counteracted by T3. Moreover, the up-regulated pro-apoptosis genes（Caspase-3, Caspase-9 and Bax） and down-regulated anti-apoptosis Bcl-2 gene were counteracted by T3 remarkably（P〈0.01）. Conclusion： T3 could improve the redox status of ALX-induced diabetic mice and protect pancreatic β-cells from cell death to maintain normal physiological function of pancreas.