Molecular Pathogenesis of diabetes in rodent models

我们利用啮齿动物疾病模型研究了糖尿病的分子发病机制。(1) TSOD小鼠我们之前对TSOD小鼠的糖尿病和肥胖进行了遗传分析，鉴定出3个数量性状位点（qtl）。我们的最终目标是确定每个QTL的遗传改变。为此，我们已经产生了几个同源菌株。以2号染色体上影响TSOD小鼠体重和血浆胰岛素水平的QTL为例，构建了17个同源菌株。通过比较同源菌株与亲本TSOD小鼠的表型，可以缩小QTL区域。以2号染色体上的QTL为例，我们成功地将其定义为12.8 mb的区域，包含49个候选基因。(2)秋田小鼠我们先前发现，秋田小鼠的常染色体显性糖尿病是由胰岛素2基因突变引起的，胰岛素2基因的产物取代了参与分子内二硫键形成的半胱氨酸残基。杂合小鼠表现出严重的胰岛素缺乏，尽管来自胰岛素1和胰岛素2基因的其他三个野生型等位基因的正常胰岛素分子共表达。我们研究了突变型胰岛素原2诱导的显性阴性致病机制，发现秋田小鼠胰岛中组成性分泌碱性磷酸酶的运输显著减少。形态学分析还显示，秋田小鼠β-细胞分泌通路细胞器结构被逐渐破坏。这些发现表明，由于细胞内错误折叠的原胰岛素2的积累导致的细胞器功能障碍是秋田β细胞共存的野生型胰岛素分泌缺陷的主要原因。

We have investigated the molecular pathogenesis of diabetes using rodent disease models.(1) TSOD mouseWe previously performed genetic analysis of diabetes and obesity in TSOD mice and identified three quantitative trait loci (QTLs). Our final goal is to identify genetic alterations at each QTL. For this-purpose, we have generated several congenic strains. For example, 17 congenic strains were constructed for the QTL on chromosome 2 that influences the body weight and plasma insulin levels of TSOD mice. By comparing phenotypes between the congenic strains and parental TSOD mice, the QTL regions can be narrowed down. In case of the QTL on chromosome 2, we can successfully define it to a 12.8-Mb region that contains 49 candidate genes.(2) Akita mouseWe previously discovered that autosomal dominant diabetes in the Akita mouse is caused by mutation of, the insulin 2 gene, whose product replaces a cysteine residue that is engaged in the formation of an intramolecular disulfide bond. The heterozygous mice exhibit severe insulin deficiency despite coexpression of normal insulin molecules derived from three other wild-type alleles of the insulin 1 and 2 genes. We investigated the dominant-negative pathogenic mechanisms induced by the mutant proinsulin 2, and found that the trafficking of constitutively secreted alkaline phosphatase is significantly decreased in the islets of Akita mice. Morphologic analysis also revealed that secretory pathway organelle architecture is progressively devastated in the β-cells of Akita mice. These findings suggest that the organelle dysfunction due to the intracellular accumulation of misfolded proinsulin 2 is primarily responsible for the defect of coexisting wild-type insulin secretion in Akita β-cells.