最近，国际学术期刊Diabetologia在线发表了中科院上海生命科学研究院营养所乐颖影研究组的最新研究成果：TNF-α acutely upregulates amylin expression in murine pancreatic beta cells。这项工作主要由博士生蔡坤等在乐颖影研究员的指导下完成。

胰淀素(amylin)，又称胰岛淀粉样多肽(islet amyloid polypeptide)，最初是从2型糖尿病病人的胰岛淀粉样沉淀中分离发现的。胰淀素主要由胰岛β细胞合成和分泌，具有控制食欲、抑制胃排空、抑制胰岛素分泌等生理功能。离体和整体实验表明，胰淀素能诱导胰岛素抵抗、促进胰岛b细胞凋亡，参与2型糖尿病的发生发展。近年来发现在急性胰腺炎、胰腺移植后发生排斥的病人、肥胖症和胰岛素抵抗症患者，血浆胰淀素水平显著升高，但其原因及机制尚不清楚。

炎性细胞因子（如TNF-α、MCP-1等）在上述疾病的胰腺组织或血循环中显著升高，它们不仅在急性胰腺炎和移植排斥中发挥重要作用，还参与胰岛素抵抗和糖尿病的发生发展。蔡坤等利用小鼠胰岛b细胞株MIN6和原代培养小鼠胰岛，研究了炎性细胞因子对胰淀素表达的影响。研究发现，TNF-α能够显著上调胰淀素基因的表达，这种调节作用呈时间和浓度依赖性。TNF-α还能促进胰淀素蛋白的合成，主要以胰淀素前体蛋白及其酶切中间产物为主。通过生化和分子生物学的多种研究手段，他们进一步探讨了TNF-α发挥调节作用的机制，发现TNF-α通过PKCζ-ERK1/2/JNK-AP1和PI3K-NF-κB相关信号通路上调胰淀素基因的表达。

炎性细胞因子TNF-α对胰淀素表达的上调作用及分子机制

此外还发现，TNF-α能显著增强人胰淀素基因启动子的活性，且这种调节作用由AP1和NF-κB介导，说明人胰淀素基因的表达和小鼠胰淀素基因一样受TNF-α调节。这些结果提示在胰腺急性炎症相关疾病中，炎性细胞因子除直接发挥作用外，还可能通过诱导胰淀素表达而促进疾病的发展，为进一步探讨胰淀素的病理作用提供了新的线索。

此项工作得到国家科技部和上海市科委经费资助。

推荐原文出处：

Diabetologia  DOI 10.1007/s00125-010-1972-9

TNF-α acutely upregulates amylin expression in murine pancreatic beta cells.

Cai K, Qi D, Wang O, Chen J, Liu X, Deng B, Qian L, Liu X, Le Y.

Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, and the Graduate School of the Chinese Academy of Sciences, Shanghai, People's Republic of China.

Abstract

AIMS/HYPOTHESIS: Amylin, a secretory protein mainly produced by pancreatic beta cells, is elevated in the circulation of patients with diseases related to acute and chronic inflammation, including acute pancreatitis, pancreas graft rejection, obesity and insulin resistance. TNF-α is involved in these disorders. We investigated the effect of TNF-α on amylin levels and the underlying mechanisms, using murine pancreatic beta cell line MIN6 and pancreatic islets.

METHODS: Amylin, proinsulin and prohormone convertase 1/3, 2 (Pc1/3, Pc2 [also known as Pcsk1/3 and Pcsk2, respectively]) mRNA levels, and amylin promoter and nuclear factor κB (NF-κB) activation were examined by real-time PCR and luciferase reporter assay, respectively. Amylin protein level and mitogen-activated protein kinase phosphorylation were detected by western blot. Activator protein 1 (AP1) activation was examined by electrophoretic mobility shift assay (EMSA).

RESULTS: TNF-α acutely induced amylin expression at the transcriptional level and increased proamylin and the intermediate form of amylin in MIN6 cells and islets. However, it had no effect on proinsulin, Pc1/3 and Pc2 expression. Studies with (1) MIN6 cells treated with inhibitors of MEK1/2, c-Jun-N-terminal kinase (JNK) or protein kinase Cζ [Formula: see text], (2) MIN6 cells expressing a c-Jun-dominant negative construct and (3) islets from Fos knockout mice demonstrated that TNF-α induced amylin expression through the [Formula: see text] signal-regulated kinase (ERK)/JNK pathways. EMSA showed that [Formula: see text], JNK and ERK1/2 were involved in TNF-α-induced AP1 activation, suggesting that TNF-α induces murine amylin expression through the [Formula: see text] and [Formula: see text] pathways. Further studies showed that TNF-α also induced murine amylin expression through the phosphatidylinositol 3 kinase-NF-κB signalling pathway and enhanced human amylin promoter activation through NF-κB and AP1.

CONCLUSIONS/INTERPRETATION: TNF-α acutely induces amylin gene expression in beta cells through multiple signalling pathways, possibly contributing to amylin elevation in acute inflammation-related pancreatic disorders.

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