Tumor Necrosis Factor-α Suppresses Adipocyte-Specific Genes and Activates Expression of Preadipocyte Genes in 3T3-L1 Adipocytes
Nuclear Factor-κB Activation by TNF-α Is Obligatory
- 1Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
- 2Dana-Farber Cancer Institute and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
- 3Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts
- 4Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
Abstract
Tumor necrosis factor-α (TNF-α) is a contributing cause of the insulin resistance seen in obesity and obesity-linked type 2 diabetes, but the mechanism(s) by which TNF-α 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-α treatment, and 78 known genes downregulated by at least twofold after 24 h of TNF-α incubation. TNF-α-induced genes include transcription factors implicated in preadipocyte gene expression or NF-κB 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-α, receptor retinoid X receptor-α, and peroxisome profilerator-activated receptor γ were significantly downregulated by TNF-α treatment. Correspondingly, 24-h exposure of 3T3-L1 adipocytes to TNF-α 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-κB (NF-κB) was activated within 15 min of TNF-α addition. 3T3-L1 adipocytes expressing IκBα-DN, a nondegradable NF-κB inhibitor, exhibited normal morphology, global gene expression, and insulin responses. However, absence of NF-κB activation abolished suppression of >98% of the genes normally suppressed by TNF-α and induction of 60–70% of the genes normally induced by TNF-α. Moreover, extensive cell death occurred in IκBα-DN-expressing adipocytes after 2 h of TNF-α treatment. Thus the changes in adipocyte gene expression induced by TNF-α could lead to insulin resistance. Further, NF-κB is an obligatory mediator of most of these TNF-α responses.
Footnotes
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Address correspondence and reprint requests to Professor Harvey F. Lodish, Whitehead Institute for Biomedical Research, 9 Cambridge Center, Room 601, Cambridge, MA 02142. E-mail: lodish{at}wi.mit.edu.
Received for publication 27 December 2001 and accepted in revised form 18 February 2002.
ACRP30, adipocyte complement-related protein of 30 kDa; Adm, adrenomedullin; AKT, protein kinase B; AP-1, activator protein 1; Bcl-3, B-cell leukemia/lymphoma-3; CDK, cyclin-dependent kinase; CEBP-α, CCAAT/enhancer binding protein-α; EST, expressed sequence tag; Fra-1, Fos-related antigen-1; GATA-6, GATA-binding protein 6; GFP, green fluorescent protein; HMGP-1C, high mobility group protein-1 isoform C; HSL, hormone-sensitive lipase; IKK, IκB kinase; IKKi, inducible IKK; IL-6, interleukin 6; IR, insulin receptor; IRS-1, IR substrate 1; LPSBP, lipopolysaccharide binding protein; LTR, long terminal repeat; MAPKKK, mitogen-activated protein kinase kinase kinase; MMP-3, matrix metalloproteinase 3; NF-κB, nuclear factor-κB; PAI-1, plasminogen activator inhibitor 1; pMIG, pMSCV-IRES-GFP; pIκBα-DN, pMSCV-IκBα__DN-IRES-GFP; PPAR-γ, peroxisome profilerator-activated receptor γ; RXR, receptor retinoid X receptor-α; Spi2-1, serine protease inhibitor 2-1; TNF, tumor necrosis factor-α; VCAM-1, vascular cell adhesion molecule 1.
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