Riggs A C, Bernal-Mizrachi E, Ohsugi M, Wasson J, Fatrai S, Welling C, Murray J, Schmidt R E, Herrera P L, Permutt M A
Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, St Louis, MO 63110-1010, USA.
Diabetologia. 2005 Nov;48(11):2313-21. doi: 10.1007/s00125-005-1947-4. Epub 2005 Oct 8.
AIMS/HYPOTHESIS: Wolfram syndrome is an autosomal recessive disorder characterised by childhood diabetes mellitus, optic atrophy and severe neurodegeneration, resulting in premature death. The aim of this study was to investigate the mechanisms responsible for the phenotype of carbohydrate intolerance and loss of pancreatic beta cells in this disorder.
To study the role of the Wolfram gene (Wfs1) in beta cells, we developed a mouse model with conditional deletion of Wfs1 in beta cells by crossing floxed Wfs1 exon 8 animals with mice expressing Cre recombinase under the control of a rat insulin promoter (RIP2-Cre). Complementary experiments using RNA interference of Wfs1 expression were performed in mouse insulinoma (MIN6) cell lines (WfsKD).
Male knockout mice (betaWfs(-/-)) began developing variable and progressive glucose intolerance and concomitant insulin deficiency, compared with littermate controls, by 12 weeks of age. Analysis of islets from betaWfs(-/-) mice revealed a reduction in beta cell mass, enhanced apoptosis, elevation of a marker of endoplasmic reticulum stress (immunoglobulin heavy chain-binding protein [BiP]), and dilated endoplasmic reticulum with decreased secretory granules by electron microscopy. WfsKD cell lines had significantly increased apoptosis and elevated expression of the genes encoding BiP and C/EBP-homologous protein (CHOP), two markers of endoplasmic reticulum stress.
CONCLUSIONS/INTERPRETATION: These results indicate that (1) lack of expression of Wfs1 in beta cells was sufficient to result in the diabetes mellitus phenotype; (2) beta cell death occurred by an accelerated process of apoptosis; and (3) lack of Wfs1 was associated with dilated endoplasmic reticulum and increased markers of endoplasmic reticulum stress, which appears to be a significant contributor to the reduction in beta cell survival.
目的/假设：沃夫勒姆综合征是一种常染色体隐性疾病，其特征为儿童期糖尿病、视神经萎缩和严重神经退行性变，可导致过早死亡。本研究的目的是探究该疾病中碳水化合物不耐受和胰腺β细胞丧失表型的相关机制。
为研究沃夫勒姆基因（Wfs1）在β细胞中的作用，我们通过将携带第8外显子条件性敲除的Wfs1动物与在大鼠胰岛素启动子（RIP2-Cre）控制下表达Cre重组酶的小鼠杂交，构建了β细胞中Wfs1条件性缺失的小鼠模型。在小鼠胰岛素瘤（MIN6）细胞系（WfsKD）中进行了使用Wfs1表达RNA干扰的补充实验。
与同窝对照小鼠相比，雄性基因敲除小鼠（βWfs(-/-)）在12周龄时开始出现程度各异且进行性加重的葡萄糖不耐受以及伴随的胰岛素缺乏。对βWfs(-/-)小鼠胰岛的分析显示，β细胞数量减少、凋亡增加、内质网应激标志物（免疫球蛋白重链结合蛋白[BiP]）升高，并且通过电子显微镜观察到内质网扩张、分泌颗粒减少。WfsKD细胞系的凋亡显著增加，编码BiP和C/EBP同源蛋白（CHOP）（内质网应激的两个标志物）的基因表达升高。
结论/解读：这些结果表明：（1）β细胞中Wfs1表达缺失足以导致糖尿病表型；（2）β细胞死亡通过加速的凋亡过程发生；（3）Wfs1缺失与内质网扩张和内质网应激标志物增加相关，这似乎是β细胞存活减少的一个重要因素。
