Ruan Hong, Hacohen Nir, Golub Todd R, Van Parijs Luk, Lodish Harvey F
Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA.
Diabetes. 2002 May;51(5):1319-36. doi: 10.2337/diabetes.51.5.1319.
Tumor necrosis factor-alpha (TNF-alpha) is a contributing cause of the insulin resistance seen in obesity and obesity-linked type 2 diabetes, but the mechanism(s) by which TNF-alpha induces insulin resistance is not understood. By using 3T3-L1 adipocytes and oligonucleotide microarrays, we identified 142 known genes reproducibly upregulated by at least threefold after 4 h and/or 24 h of TNF-alpha treatment, and 78 known genes downregulated by at least twofold after 24 h of TNF-alpha incubation. TNF-alpha-induced genes include transcription factors implicated in preadipocyte gene expression or NF-kappaB activation, cytokines and cytokine-induced proteins, growth factors, enzymes, and signaling molecules. Importantly, a number of adipocyte-abundant genes, including GLUT4, hormone sensitive lipase, long-chain fatty acyl-CoA synthase, adipocyte complement-related protein of 30 kDa, and transcription factors CCAAT/enhancer binding protein-alpha, receptor retinoid X receptor-alpha, and peroxisome profilerator-activated receptor gamma were significantly downregulated by TNF-alpha treatment. Correspondingly, 24-h exposure of 3T3-L1 adipocytes to TNF-alpha resulted in reduced protein levels of GLUT4 and several insulin signaling proteins, including the insulin receptor, insulin receptor substrate 1 (IRS-1), and protein kinase B (AKT). Nuclear factor-kappaB (NF-kappaB) was activated within 15 min of TNF-alpha addition. 3T3-L1 adipocytes expressing IkappaBalpha-DN, a nondegradable NF-kappaB inhibitor, exhibited normal morphology, global gene expression, and insulin responses. However, absence of NF-kappaB activation abolished suppression of >98% of the genes normally suppressed by TNF-alpha and induction of 60-70% of the genes normally induced by TNF-alpha. Moreover, extensive cell death occurred in IkappaBalpha-DN-expressing adipocytes after 2 h of TNF-alpha treatment. Thus the changes in adipocyte gene expression induced by TNF-alpha could lead to insulin resistance. Further, NF-kappaB is an obligatory mediator of most of these TNF-alpha responses.
肿瘤坏死因子-α（TNF-α）是肥胖及肥胖相关的2型糖尿病中胰岛素抵抗的一个促成因素，但其诱导胰岛素抵抗的机制尚不清楚。通过使用3T3-L1脂肪细胞和寡核苷酸微阵列，我们鉴定出142个已知基因在TNF-α处理4小时和/或24小时后可重复性地上调至少三倍，以及78个已知基因在TNF-α孵育24小时后下调至少两倍。TNF-α诱导的基因包括与前脂肪细胞基因表达或NF-κB激活有关的转录因子、细胞因子和细胞因子诱导蛋白、生长因子、酶和信号分子。重要的是，一些在脂肪细胞中大量表达的基因，包括葡萄糖转运蛋白4（GLUT4）、激素敏感性脂肪酶、长链脂肪酰基辅酶A合成酶、30 kDa脂肪细胞补体相关蛋白以及转录因子CCAAT/增强子结合蛋白-α、视黄酸X受体-α和过氧化物酶体增殖物激活受体γ，经TNF-α处理后显著下调。相应地，3T3-L1脂肪细胞暴露于TNF-α 24小时导致GLUT4和几种胰岛素信号蛋白的水平降低，这些蛋白包括胰岛素受体、胰岛素受体底物1（IRS-1）和蛋白激酶B（AKT）。核因子-κB（NF-κB）在添加TNF-α后15分钟内被激活。表达IκBα-DN（一种不可降解的NF-κB抑制剂）的3T3-L1脂肪细胞表现出正常的形态、整体基因表达和胰岛素反应。然而，NF-κB激活的缺失消除了通常被TNF-α抑制的>98%的基因的抑制作用，并诱导了通常被TNF-α诱导的60-70%的基因。此外，在TNF-α处理2小时后，表达IκBα-DN的脂肪细胞中发生了广泛的细胞死亡。因此，TNF-α诱导的脂肪细胞基因表达变化可能导致胰岛素抵抗。此外，NF-κB是这些TNF-α反应中大多数反应的必需介质。
