Dissection of the Mechanism of Insulin Resistance by Transgenic and knockout Mice Technology

2型糖尿病是由两种生理缺陷引起的：胰岛素抵抗和胰岛素分泌缺陷。用于建立2型糖尿病动物模型的转基因和基因敲除技术对体内新发现的与葡萄糖稳态调节有关的分子的调节产生了重大影响。(I)IRS-1和IRS-2基因敲除小鼠的胰岛素抵抗和糖尿病的发展。为了了解2型糖尿病发生的分子基础，我们产生了IRS-1和IRS-2基因敲除小鼠(Tamemoto H，等人)。《自然》372：182-186,1994；久保田等人，糖尿病，49：1880-1889,2000)。我们证明了这两只小鼠都表现出胰岛素抵抗。然而，当IRS-1基因敲除小鼠保持正常的糖耐量，β细胞能够增殖(Teruchi Y等人，J Clin Invest 99：861-866,1997)，IRS-2基因敲除小鼠患上糖尿病，β细胞不能增殖。有可能β细胞对…的能力更多的增殖反应胰岛素抵抗可能决定了人类2型糖尿病的发展过程。我们还证明了缺乏PI3-Kinase 85 kDa亚基的小鼠表现出更高的胰岛素敏感性(Teruchi，Y.等人，自然遗传学21：230-235,1999)。(Ii)肥胖诱导胰岛素抵抗的机制肥胖被定义为脂肪组织的过度堆积。我们研究了肥胖导致胰岛素抵抗的分子基础。首先，我们研究了γ激动剂噻唑烷二酮改善胰岛素抵抗的分子机制。TZD对Zucker FA/FA大鼠的胰岛素抵抗有明显改善作用。脂肪组织的组织学检查显示，较小的脂肪细胞的数量显著增加，而较大的脂肪细胞的数量减少(Okuno，A.等人，J.Clin。投资。101：1354-1361,1998)。我们进一步建立了PPARγ基因敲除小鼠(Kubota N，et al.，MOL Cell4：597-609,1999)，并证明了在高脂饮食下，杂合子可以免受肥胖和胰岛素抵抗的影响。杂合子胰岛素抵抗的改善至少部分是通过增加血清瘦素浓度来解释的。我们还证明，在人类中，低活性的PPARg多态，密码子12的丙氨酸，与密码子12的高活性多态丙氨酸相比，可以防止胰岛素抵抗和糖尿病的发生(Hara，K，等人：生物化学。生物物理。Res)。交警。271：212-216,2000少

Type 2 diabetes is caused by two physiological defects : resistance to insulin action and defects in insulin secretion. Transgenic and knockout technology used to create animal models of type 2 diabetes have had a major impact in the regulation of newly identified molecules implicated in the regulation of glucose homeostasis in vivo.(i) Development of insulin resistance and diabetes in IRS-1 and IRS-2 knockout mice. To understand the molecular basis of type 2 diabetes development, we have generated IRS- 1 and IRS-2 knockout mice (Tamemoto H, et al. Nature 372 : 182-186, 1994 ; Kubota, N., et al., Diabetes, 49 : 1880-1889, 2000). We demonstrated that both of these mice showed insulin resistance. However, while IRS-1 knockout mice remained normal glucose tolerance in which β cells are able to proliferate (Terauchi Y, et al., J Clin Invest 99 : 861-866, 1997), IRS-2 knockout mice developed diabetes in which β cells are not able to proliferate. It is possible that the ability of β cells to … More proliferate in response to insulin resistance may determine the process for human type 2 diabetes development. We also demonstrated that mice lacking PI3-kinase 85kDa subunit showed increased insulin sensitivity (Terauchi, Y.et al., Nature Genetics 21 : 230-235, 1999).(ii) Mechanisms of obesity-induced insulin resistanceObesity is defined as an excessive accumulation of adipose tissue. We investigated the molecular basis of obesityinduced insulin resistance. First, we studied the molecular mechanism of how thiazolidinedione, a PPAR γ agonist, improves insulin resistance. Administration of TZD into Zucker fa/fa rats resulted in a marked improvement of insulin resistance. Histological examination of adipose tissue revealed a marked increase in the number of smaller adipocytes with a decreased number of larger adipocytes (Okuno, A., et al., J.Clin. Invest. 101 : 1354-1361, 1998). We further generated PPAR γ knockout mice (Kubota N, et al., Mol Cell 4 : 597-609, 1999) and demonstrated that heterozygotes were protected from obesity and insulin resistance under a high-fat diet. Amelioration of insulin resistance in heterozygotes were explained, at least in part, by increased serum leptin concentration. We also demonstrated that, in human, the lower activity PPARg polymorphism, alanine at codn 12, are protected from the development of insulin resistance and diabetes compared the higher one, proline at codon 12 (Hara, K., et al : Biochem.Biophys.Res. Commun. 271 : 212-216, 2000 Less