Molecular Mechanisms on Pancreatic β cell Proliferation

1. IRS-2 mRNA的分子机制及蛋白水平测定。利用小鼠体内胰岛和离体胰岛，我们发现了以下实验事实。(A) IRS-2 mRNA和蛋白水平主要受葡萄糖刺激正向调节。(B)这种葡萄糖刺激的IRS-2诱导需要葡萄糖代谢和Ca2+内流。(C)胰岛中葡萄糖刺激的IRS-2诱导需要CREB磷酸化/激活。(D)钙调素依赖性激酶，而不是PKA，在CREB磷酸化和随后的葡萄糖2诱导IRS-2中起主要作用。完整的葡萄糖- irs -2通路在应对胰岛素抵抗的适应性β细胞生长中的重要性。通过检查肥胖糖尿病小鼠的胰岛，包括ob/ob， db/db， KK- ay和KK/Ta小鼠，我们发现当这些胰岛能够对胰岛素抵抗进行增殖时，CREB磷酸化增强，IRS-2 mRNA和蛋白水平升高。这些观察结果证实了葡萄糖- irs -2通路在适应性β细胞生长中的重要性。IRS-2在应对胰岛素抵抗的适应性β细胞生长中的重要性。除了我们之前的出版物（J Cline Invest. 2004; 114； 917-27和Diabetes 2000； 49: 1880-9），我们进一步证实了IRS-2在应对胰岛素抵抗的适应性β细胞生长中的重要性。胰腺特异性葡萄糖激酶杂合敲除小鼠在高脂肪饮食中表现出β细胞生长缺陷和胰岛IRS-2蛋白减少。转基因表达的IRS-2部分改善了葡萄糖激酶杂合敲除小鼠的缺陷β细胞生长。鉴定参与适应性β细胞生长的新基因。应用DNA微阵列技术研究胰岛素抵抗小鼠胰岛基因表达谱。我们确定了300多个基因的表达水平显著改变。

1. Molecuar mechanisms of IRS-2 mRNA and protein level determination. Utilizing mouse pancreatic islets in vivo as well as isolated islets, we discovered following experimental facts. (A) IRS-2 mRNA and protein levels were positively regulated chiefly by glucose stimulation. (B) This glucose-stimulated IRS-2 induction requires glucose metabolism and Ca2+ influx. (C) CREB phosphorylation/activation was required for Glucose-stimulated IRS-2 induction in the islets. (D) Calmodulin-dependent kinases, not PKA, play a major roles in CREB phoshorylation and subsequent IRS-2 induction by glucose2. Importance of intact Glucose-IRS-2 pathway in adaptive β cell growth in response to insulin resistance. By examining the pancreas islets of obese diabetic mice, including ob/ob, db/db, KK-Ay, and KK/Ta mice, we discovered that CREB phosphorylation was enhanced and IRS-2 mRNA and protein levels were elevated when these pancreatic islets were capable of proliferating in response to insulin resistance. These observations confirmed the importance of glucose-IRS-2 pathway in adaptive β cell growth.3. Importance of IRS-2 in adaptive β cell growth in response to insulin resistance. In addition to our previous publications (J Cline Invest. 2004; 114; 917-27 and Diabetes 2000; 49: 1880-9) we further confirmed the importance of IRS-2 in adaptive adaptive β cell growth in response to insulin resistance. Pancreatic specific glucokinase heterozygous knockout mice exhibited defective β cell growth and reduced IRS-2 protein in the islets when these mice were fed with a high fat diet. A transgenic expression of IRS-2 partially ameliorated the defective β cell growth in glucokinase heterozygous knockout mice.4. Identifying new genes involved in adaptive β cell growth. Gene expression profiles of the pancreatic islets of insulin resistant mice were surveyed with DNA microarrays. We identified more than 300 genes of which their expression levels were significantly altered.