Research for molecular mechanism of diabetes development in obese type 2 diabetes model db/db mice

本研究的目的是阐明自发性糖尿病的肥胖db/db小鼠发生糖尿病和细胞功能障碍的分子机制。我们对胰岛进行了形态和生化分析。此外，还利用激光捕获显微切割(LCM)方法进行了胰岛选择性基因表达谱分析。第一步，用db基因纯合子db/db、db基因杂合子db/m和野生型m/m小鼠比较它们的糖尿病表型和胰岛基因表达谱。Db/db组小鼠患上了糖尿病，但其他组小鼠没有。Db/db小鼠与细胞增殖相关的ERK1和细胞周期蛋白E基因表达下调，CAD基因表达上调。糖尿病db/db小鼠氧化应激相关基因表达上调，抗凋亡基因bcl2表达下调。另一方面，db/m小鼠bcl2基因表达上调，胰岛素基因表达和胰岛素含量显著高于…。在下一步中，我们试图观察饮食限制和/或抗糖尿病药物吡格列酮对糖尿病db/m小鼠胰腺B细胞功能紊乱的影响。饮食干预能有效降低体重，降低血糖/胰岛素水平。胰岛ERK1基因表达增加，凋亡基因表达减少。抗氧化应激相关基因表达上调。因此，我们认为去甲肾上腺素治疗能有效改善紊乱的胰腺β细胞功能。吡格列酮还能有效改善db/db小鼠的糖脂毒性。吡格列酮治疗后，b细胞增殖相关基因表达增加，而凋亡相关基因表达降低。此外，吡格列酮降低氧化应激相关基因的表达，增加抗氧化应激相关基因的表达。即使在非糖尿病db/m或m/m小鼠中，吡格列酮也会影响该基因的表达。这些结果有力地表明，吡格列酮通过两种机制改善β-细胞功能，一种是作为γ激动剂的直接作用，另一种是通过改善糖代谢毒性的间接作用。较少

The aim of this study is to clarify a molecular mechanism of diabetes development and cell dysfunction in obese db/db mice with spontaneous onset of diabetes. We carried out the morphological and biochemical analyses of pancreatic islets. In addition, The islet-selective gene expression profiling was done by using laser capture microdissection (LCM) method. In the first step, db gene homozygous db/db, db gene heterozygous db/m, and wild type m/m mice were used to compared their diabetic phenotypes and gene expressio profiles in the pancreatic islets. The db/db mice developed diabetes, but the other mice not. ERK1 and cyclinE genes related with cell proliferation were down-regulated, and CAD gene was up-regulated in db/db mice. The genes associated with oxidative stress were up-regulated, and anti-apoptotic bcl-2 gene was down-regulated in diabetic db/db mice. On the other hand, the bcl-2 gene was up-regulated in db/m mice, and insulin gene expression and insulin content were significan … More tly increased in db/m mice, suggesting the compensatory mechanism against diabetes development in db gene heterozygous (db/m) mice.In the next step, we tried to see the effects of diet restriction and/or anti-diabetic agent, pioglitazone on the pancreatic b cell function deranged in the diabetic db/db mice. The intervention with diet was effective to reduce the body weight, and blood glucose/insulin levels. ERK1 gene expression in the islet was increased, and apoptotic gene expressions were decreased. Anti-oxidative stress-related gene expression was up-regulated. Thus we concluded that deit treatment was effective to amekiorate the deranged pancreatic β cell function. Pioglitazone was also effective to improve glucolipotoxicity in db/db mice. The treatment with pioglitazone increased b cell proliferation-related gene expression, and decreased apoptosis-related gene expression. In addition, pioglitazone ddecreased oxidative stress-related gene expressions, and increased anti-oxidative stress-related gene expressions. Pioglitazone affected the gene expression even in non-diabetic db/m or m/m mice. These results strongly suggested that pioglitazone ameliorates the β-cell function via two mechanisms, a direct action as a PPARγ agonist and an indirect effect through improving glucolipotoxicity. Less