title: 12/15-lipoxygenase products induce inflammation and impair insulin signaling in 3T3-L1 adipocytes.
abstract: Inflammation and insulin resistance associated with visceral obesity are important risk factors for the development of type 2 diabetes, atherosclerosis, and the metabolic syndrome. The 12/15-lipoxygenase (12/15-LO) enzyme has been linked to inflammatory changes in blood vessels that precede the development of atherosclerosis. The expression and role of 12/15-LO in adipocytes have not been evaluated. We found that 12/15-LO mRNA was dramatically upregulated in white epididymal adipocytes of high-fat fed mice. 12/15-LO was poorly expressed in 3T3-L1 fibroblasts and was upregulated during differentiation into adipocytes. Interestingly, the saturated fatty acid palmitate, a major component of high fat diets, augmented expression of 12/15-LO in vitro. When 3T3-L1 adipocytes were treated with the 12/15-LO products, 12-hydroxyeicosatetranoic acid (12(S)-HETE) and 12-hydroperoxyeicosatetraenoic acid (12(S)-HPETE), expression of proinflammatory cytokine genes, including tumor necrosis factor-alpha (TNF-alpha), monocyte chemoattractant protein 1 (MCP-1), interleukin 6 (IL-6), and IL-12p40, was upregulated whereas anti-inflammatory adiponectin gene expression was downregulated. 12/15-LO products also augmented c-Jun N-terminal kinase 1 (JNK-1) phosphorylation, a known negative regulator of insulin signaling. Consistent with impaired insulin signaling, we found that insulin-stimulated 3T3-L1 adipocytes exhibited decreased IRS-1(Tyr) phosphorylation, increased IRS-1(Ser) phosphorylation, and impaired Akt phosphorylation when treated with 12/15-LO product. Taken together, our data suggest that 12/15-LO products create a proinflammatory state and impair insulin signaling in 3T3-L1 adipocytes. Because 12/15-LO expression is upregulated in visceral adipocytes by high-fat feeding in vivo and also by addition of palmitic acid in vitro, we propose that 12/15-LO plays a role in promoting inflammation and insulin resistance associated with obesity.
authors.affiliation: Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, Virginia, USA.
authors.forename: Swarup K
authors.initials: SK
authors.lastname: Chakrabarti
authors.forename: Banumathi K
authors.initials: BK
authors.lastname: Cole
authors.forename: Yeshao
authors.initials: Y
authors.lastname: Wen
authors.forename: Susanna R
authors.initials: SR
authors.lastname: Keller
authors.forename: Jerry L
authors.initials: JL
authors.lastname: Nadler
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid / Q000378:metabolism; D041721:3T3-L1 Cells; D017667:Adipocytes / Q000201:enzymology*; D052242:Adiponectin / Q000378:metabolism; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D001093:Arachidonate 15-Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D015971:Gene Expression Regulation, Enzymologic; D007249:Inflammation / Q000201:enzymology* / Q000503:physiopathology; D018836:Inflammation Mediators / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance; D015289:Leukotrienes / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism; D009765:Obesity / Q000201:enzymology* / Q000503:physiopathology; D019308:Palmitic Acid / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D015854:Up-Regulation
chemical_list: C475064:12-15-lipoxygenase; D052242:Adiponectin; C499919:Adipoq protein, mouse; D016207:Cytokines; D018836:Inflammation Mediators; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D015289:Leukotrienes; D012333:RNA, Messenger; D019308:Palmitic Acid; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; C021201:12-HPETE; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase; D051057:Proto-Oncogene Proteins c-akt; D048055:Mitogen-Activated Protein Kinase 8