title: Conjugated linoleic acid promotes human adipocyte insulin resistance through NFkappaB-dependent cytokine production.
abstract: We previously demonstrated that trans-10, cis-12 conjugated linoleic acid (CLA) reduced the triglyceride content of human adipocytes by activating mitogen-activated protein kinase kinase/extracellular signal-related kinase (MEK/ERK) signaling via interleukins (IL) 6 and 8. However, the upstream mechanism is unknown. Here we show that CLA increased (>or=6 h) the secretion of IL-6 and IL-8 in cultures containing both differentiated adipocytes and stromal vascular (SV) cells, non-differentiated SV cells, and adipose tissue explants. CLA isomer-specific induction of IL-6 and tumor necrosis factor-alpha was associated with the activation of nuclear factor kappaB (NFkappaB) as evidenced by 1) phosphorylation of IkappaBalpha, IkappaBalpha kinase, and NFkappaB p65, 2) IkappaBalpha degradation, and 3) nuclear translocation of NFkappaB. Pretreatment with selective NFkappaB inhibitors and the MEK/ERK inhibitor U0126 blocked CLA-mediated IL-6 gene expression. Trans-10, cis-12 CLA suppression of insulin-stimulated glucose uptake at 24 h was associated with decreased total and plasma membrane glucose transporter 4 proteins. Inhibition of NFkappaB activation or depletion of NFkappaB by RNA interference using small interfering NFkappaB p65 attenuated CLA suppression of glucose transporter 4 and peroxisome proliferator-activated receptor gamma proteins and glucose uptake. Collectively, these data demonstrate for the first time that trans-10, cis-12 CLA promotes NFkappaB activation and subsequent induction of IL-6, which are at least in part responsible for trans-10, cis-12 CLA-mediated suppression of peroxisome proliferator-activated receptor gamma target gene expression and insulin sensitivity in mature human adipocytes.
authors.affiliation: Department of Nutrition, University of North Carolina at Greensboro, Greensboro, North Carolina 27402-6170, USA.
authors.forename: Soonkyu
authors.initials: S
authors.lastname: Chung
authors.forename: J Mark
authors.initials: JM
authors.lastname: Brown
authors.forename: J Nathan
authors.initials: JN
authors.lastname: Provo
authors.forename: Robin
authors.initials: R
authors.lastname: Hopkins
authors.forename: Michael K
authors.initials: MK
authors.lastname: McIntosh
mesh_terms: D021581:Active Transport, Cell Nucleus; D017667:Adipocytes / Q000166:cytology* / Q000378:metabolism; D002070:Butadienes / Q000494:pharmacology; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D003847:Deoxyglucose / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D044243:Linoleic Acids, Conjugated / Q000494:pharmacology*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D047495:PPAR gamma / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D051996:Transcription Factor RelA / Q000378:metabolism; D014162:Transfection; D014280:Triglycerides / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D002070:Butadienes; D016207:Cytokines; D004791:Enzyme Inhibitors; D005227:Fatty Acids; D051275:Glucose Transporter Type 4; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6; D016209:Interleukin-8; C526295:Irs1 protein, mouse; D044243:Linoleic Acids, Conjugated; D016328:NF-kappa B; D009570:Nitriles; D047495:PPAR gamma; D010750:Phosphoproteins; D034741:RNA, Small Interfering; C498144:Rela protein, mouse; D051996:Transcription Factor RelA; D014280:Triglycerides; D014409:Tumor Necrosis Factor-alpha; C113580:U 0126; D003847:Deoxyglucose; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020930:MAP Kinase Kinase Kinases; D005947:Glucose