Insulin stimulates primary β-cell proliferation via Raf-1 kinase
Insulin stimulates primary β-cell proliferation via Raf-1 kinase
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DOI：
10.1210/en.2007-1557
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发表时间：
2008-05-01
期刊：
影响因子：
4.8
通讯作者：
Johnson, James D.
中科院分区：
文献类型：
--
作者：
Beith, Jennifer L.;Alejandro, Emilyn U.;Johnson, James D.
β细胞质量的相对减少是1型糖尿病、2型糖尿病和移植胰岛移植物失败的发病机制的关键。现在清楚的是，β细胞复制在成人β细胞质量的调节中起主导作用。因此，β细胞复制的内源性调节因子的知识对于理解β细胞群的生理控制和治疗上利用该过程是至关重要的。我们已经证明，已知存在于体内的胰岛素浓度直接作用于β细胞以促进存活。胰岛素是否刺激成人β细胞增殖仍不清楚。我们使用5-溴-2-脱氧尿苷和胰岛素抗血清双标记的分散的原代小鼠胰岛细胞来验证这一假设。用200-pM胰岛素处理细胞显著增加了每天0.15%的基线增殖率。将葡萄糖从5- 15 mM升高并没有显著增加β细胞复制。β-细胞增殖受到生长抑素以及胰岛素信号传导抑制剂的抑制。有趣的是，抑制Raf-1激酶可以阻断低剂量胰岛素刺激的增殖，但不能阻断高剂量胰岛素刺激的增殖。胰岛素刺激的小鼠胰岛素瘤细胞增殖依赖于磷脂酰肌醇3-激酶/Akt和Raf-1/MAPK激酶途径。Raf-1的过表达足以在没有胰岛素的情况下增加增殖，而显性负性Raf-1在200 pM胰岛素的存在下减少增殖。总之，这些结果首次证明，在体内测量的水平下，胰岛素可以直接刺激β细胞增殖，并且Raf-1激酶参与了这一过程。这些发现对于理解在各种形式的糖尿病中发生的高胰岛素血症和胰岛素缺乏状态中β细胞质量的调节具有重要意义。
A relative decrease in beta-cell mass is key in the pathogenesis of type 1 diabetes, type 2 diabetes, and in the failure of transplanted islet grafts. It is now clear that beta-cell duplication plays a dominant role in the regulation of adult beta-cell mass. Therefore, knowledge of the endogenous regulators of beta-cell replication is critical for understanding the physiological control of beta-cell mass and for harnessing this process therapeutically. We have shown that concentrations of insulin known to exist in vivo act directly on beta-cells to promote survival. Whether insulin stimulates adult beta-cell proliferation remains unclear. We tested this hypothesis using dispersed primary mouse islet cells double labeled with 5-bromo-2-deoxyuridine and insulin antisera. Treating cells with 200-pM insulin significantly increased proliferation from a baseline rate of 0.15% per day. Elevating glucose from 5-15mM did not significantly increase beta-cell replication. beta-Cell proliferation was inhibited by somatostatin as well as inhibitors of insulin signaling. Interestingly, inhibiting Raf-1 kinase blocked proliferation stimulated by low, but not high (superphysiological), insulin doses. Insulin-stimulated mouse insulinoma cell proliferation was dependent on both phosphatidylinositol 3-kinase/Akt and Raf-1/MAPK kinase pathways. Overexpression of Raf-1 was sufficient to increase proliferation in the absence of insulin, whereas a dominant-negative Raf-1 reduced proliferation in the presence of 200-pM insulin. Together, these results demonstrate for the first time that insulin, at levels that have been measured in vivo, can directly stimulate beta-cell proliferation and that Raf-1 kinase is involved in this process. These findings have significant implications for the understanding of the regulation of beta-cell mass in both the hyperinsulinemic and insulin-deficient states that occur in the various forms of diabetes.