Abstract：
Genetic polymorphisms in nuclear respiratory factor-1 (Nrf1), a key transcriptional regulator of nuclear-encoded mitochondrial proteins, have been linked to diabetes. Homozygous deletion of Nrf1 is embryonic lethal in mice. Our goal was to generate mice with β-cell-specific reduction in NRF1 function to investigate the relationship between NRF1 and diabetes. We report the generation of mice expressing a dominant-negative allele of Nrf1 (DNNRF1) in pancreatic β-cells. Heterozygous transgenic mice had high fed blood glucose levels detected at 3 wks of age, which persisted through adulthood. Plasma insulin levels in DNNRF1 transgenic mice were reduced, while insulin sensitivity remained intact in young animals. Islet size was reduced with increased numbers of apoptotic cells, and insulin content in islets by immunohistochemistry was low. Glucose-stimulated insulin secretion in isolated islets was reduced in DNNRF1-mice, but partially rescued by KCl, suggesting that decreased mitochondrial function contributed to the insulin secretory defect. Electron micrographs demonstrated abnormal mitochondrial morphology in β-cells. Expression of NRF1 target genes Tfam, Tfb1m and Tfb2m, and islet cytochrome c oxidase and succinate dehydrogenase activities were reduced in DNNRF1-mice. Rescue of mitochondrial function with low level activation of transgenic c-Myc in β-cells was sufficient to restore β-cell mass and prevent diabetes. This study demonstrates that reduced NRF1 function can lead to loss of β-cell function and establishes a model to study the interplay between regulators of bi-genomic gene transcription in diabetes.
摘要：
核呼吸因子-1（Nrf1）的遗传多态性，核编码线粒体蛋白的关键转录调节因子，与糖尿病有关。Nrf1的纯合缺失在小鼠中是胚胎致死的。我们的目标是产生NRF1功能β细胞特异性降低的小鼠，以研究NRF1与糖尿病之间的关系。我们报道了在胰腺β细胞中表达Nrf1（DNNRF1）显性阴性等位基因的小鼠的产生。杂合转基因小鼠在3周龄时检测到高血糖水平，一直持续到成年。DNNRF1转基因小鼠的血浆胰岛素水平降低，而年轻动物的胰岛素敏感性保持完整。胰岛大小随着凋亡细胞数量的增加而减少，通过免疫组织化学，胰岛中的胰岛素含量较低。在DNNRF1小鼠中，分离的胰岛中葡萄糖刺激的胰岛素分泌减少，但部分被氯化钾救出，提示线粒体功能下降导致胰岛素分泌缺陷。电子显微照片显示β细胞中线粒体形态异常。NRF1靶基因Tfam的表达,Tfb1m和Tfb2m，DNNRF1小鼠的胰岛细胞色素c氧化酶和琥珀酸脱氢酶活性降低。通过β细胞中转基因c-Myc的低水平激活来挽救线粒体功能足以恢复β细胞质量并预防糖尿病。这项研究表明NRF1功能降低可导致β细胞功能丧失，并建立了一个模型来研究糖尿病中双基因组基因转录调节因子之间的相互作用。
