Shih David Q, Heimesaat Markus, Kuwajima Satoru, Stein Roland, Wright Christopher V E, Stoffel Markus
Laboratory of Metabolic Diseases, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Proc Natl Acad Sci U S A. 2002 Mar 19;99(6):3818-23. doi: 10.1073/pnas.062605899.
Defects in pancreatic beta-cell function contribute to the development of type 2 diabetes, a polygenic disease that is characterized by insulin resistance and compromised insulin secretion. Hepatocyte nuclear factors (HNFs) -1alpha, -3beta, -4alpha, and Pdx-1 contribute in the complex transcriptional circuits within the pancreas that are involved in beta-cell development and function. In mice, a heterozygous mutation in Pdx-1 alone, but not Hnf-1alpha(+/-), Hnf-3beta(+/-), or Hnf-4alpha(+/-), causes impaired glucose-stimulated insulin secretion in mice. To investigate the possible functional relationships between these transcription factors on beta-cell activity in vivo, we generated mice with the following combined heterozygous mutations: Pdx-1(+/-)/Hnf-1alpha(+/-), Pdx-1(+/-)/Hnf-3beta(+/-), Pdx-1(+/-)/Hnf-4alpha(+/-), Hnf-1alpha(+/-)/Hnf-4alpha(+/-), and Hnf-3beta(+/-)/Hnf-4alpha(+/-). The greatest loss in function was in combined heterozygous null alleles of Pdx-1 and Hnf-1alpha (Pdx-1(+/-)/Hnf-1alpha(+/-)), or Pdx-1 and Hnf-3beta (Pdx-1(+/-)/Hnf-3beta(+/-)). Both double mutants develop progressively impaired glucose tolerance and acquire a compromised first- and second-phase insulin secretion profile in response to glucose compared with Pdx-1(+/-) mice alone. The loss in beta-cell function in Pdx-1(+/-)/Hnf-3beta(+/-) mice was associated with decreased expression of Nkx-6.1, glucokinase (Gck), aldolase B (aldo-B), and insulin, whereas Nkx2.2, Nkx-6.1, Glut-2, Gck, aldo-B, the liver isoform of pyruvate kinase, and insulin expression was reduced in Pdx-1(+/-)/Hnf-1alpha(+/-) mice. The islet cell architecture was also abnormal in Pdx-1(+/-)/Hnf-3beta(+/-) and Pdx-1(+/-)/Hnf-1alpha(+/-) mice, with glucagon-expressing cells scattered throughout the islet, a defect that may be connected to decreased E-cadherin expression. Our data suggest that functional interactions between key islet regulatory factors play an important role in maintaining islet architecture and beta-cell function. These studies also established polygenic mouse models for investigating the mechanisms contributing to beta-cell dysfunction in diabetes.
胰腺β细胞功能缺陷会导致2型糖尿病的发生，这是一种多基因疾病，其特征为胰岛素抵抗和胰岛素分泌受损。肝细胞核因子（HNFs）-1α、-3β、-4α和Pdx-1参与胰腺内复杂的转录调控网络，这些网络与β细胞的发育和功能相关。在小鼠中，单独的Pdx-1杂合突变（而非Hnf-1α(+/-)、Hnf-3β(+/-)或Hnf-4α(+/-)）会导致小鼠葡萄糖刺激的胰岛素分泌受损。为了研究这些转录因子在体内对β细胞活性可能存在的功能关系，我们构建了具有以下复合杂合突变的小鼠：Pdx-1(+/-)/Hnf-1α(+/-)、Pdx-1(+/-)/Hnf-3β(+/-)、Pdx-1(+/-)/Hnf-4α(+/-)、Hnf-1α(+/-)/Hnf-4α(+/-)以及Hnf-3β(+/-)/Hnf-4α(+/-)。功能丧失最严重的是Pdx-1和Hnf-1α的复合杂合无效等位基因（Pdx-1(+/-)/Hnf-1α(+/-)），或Pdx-1和Hnf-3β的复合杂合无效等位基因（Pdx-1(+/-)/Hnf-3β(+/-)）。与单独的Pdx-1(+/-)小鼠相比，这两种双突变体均出现葡萄糖耐量逐渐受损，并在对葡萄糖的反应中呈现出第一相和第二相胰岛素分泌受损的情况。Pdx-1(+/-)/Hnf-3β(+/-)小鼠β细胞功能丧失与Nkx-6.1、葡萄糖激酶（Gck）、醛缩酶B（aldo-B）和胰岛素的表达降低有关，而在Pdx-1(+/-)/Hnf-1α(+/-)小鼠中，Nkx2.2、Nkx-6.1、Glut-2、Gck、aldo-B、丙酮酸激酶的肝脏同工型以及胰岛素的表达均降低了。Pdx-1(+/-)/Hnf-3β(+/-)和Pdx-1(+/-)/Hnf-1α(+/-)小鼠的胰岛细胞结构也异常，表达胰高血糖素的细胞散布于整个胰岛，这一缺陷可能与E-钙黏蛋白表达降低有关。我们的数据表明，关键胰岛调节因子之间的功能相互作用在维持胰岛结构和β细胞功能中起重要作用。这些研究还建立了多基因小鼠模型，用于研究导致糖尿病中β细胞功能障碍的机制。
