Hypochlorous acid via peroxynitrite activates protein kinase Cθ and insulin resistance in adipocytes.
We recently reported that genetic deletion of myeloperoxidase (MPO) alleviates obesity-related insulin resistance in mice in vivo. How MPO impairs insulin sensitivity in adipocytes is poorly characterized. As hypochlorous acid (HOCl) is a principal oxidant product generated by MPO, we evaluated the effects of HOCl on insulin signaling in adipocytes differentiated from 3T3-L1 cells. Exposure of 3T3-L1 adipocytes to exogenous HOCl (200 μmol/l) attenuated insulin-stimulated 2-deoxyglucose uptake, GLUT4 translocation, and insulin signals, including tyrosine phosphorylation of insulin receptor substrate 1 (IRS1) and phosphorylation of Akt. Furthermore, treatment with HOCl induced phosphorylation of IRS1 at serine 307, inhibitor κB kinase (IKK), c-Jun NH2-terminal kinase (JNK), and phosphorylation of PKCθ (PKCθ). In addition, genetic and pharmacological inhibition of IKK and JNK abolished serine phosphorylation of IRS1 and impairment of insulin signaling by HOCl. Furthermore, knockdown of PKCθ using siRNA transfection suppressed phosphorylation of IKK and JNK and consequently attenuated the HOCl-impaired insulin signaling pathway. Moreover, activation of PKCθ by peroxynitrite was accompanied by increased phosphorylation of IKK, JNK, and IRS1-serine 307. In contrast, ONOO(-) inhibitors abolished HOCl-induced phosphorylation of PKCθ, IKK, JNK, and IRS1-serine 307, as well as insulin resistance. Finally, high-fat diet (HFD)-induced insulin resistance was associated with enhanced phosphorylation of PKCθ, IKK, JNK, and IRS1 at serine 307 in white adipose tissues from WT mice, all of which were not found in Mpo knockout mice fed HFDs. We conclude that HOCl impairs insulin signaling pathway by increasing ONOO(-) mediated phosphorylation of PKCθ, resulting in phosphorylation of IKK/JNK and consequent serine phosphorylation of IRS1 in adipocytes.
Section of Molecular MedicineBSEB 306A, Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
Jun
J
Zhou
Section of Molecular MedicineBSEB 306A, Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
Qilong
Q
Wang
Section of Molecular MedicineBSEB 306A, Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
Ye
Y
Ding
Section of Molecular MedicineBSEB 306A, Department of Internal Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA ming-hui-zou@ouhsc.edu.
Ming-Hui
MH
Zou
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000201:enzymology*; D000818:Animals; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006997:Hypochlorous Acid / Q000494:pharmacology*; D051550:I-kappa B Kinase / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance; D007527:Isoenzymes / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D051379:Mice; D009195:Peroxidase / Q000502:physiology; D030421:Peroxynitrous Acid / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D015398:Signal Transduction
D051275:Glucose Transporter Type 4; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D007527:Isoenzymes; C495693:Slc2a4 protein, mouse; D030421:Peroxynitrous Acid; D006997:Hypochlorous Acid; D009195:Peroxidase; D051550:I-kappa B Kinase; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D048031:JNK Mitogen-Activated Protein Kinases
IRS1; hypochlorous acid; insulin resistance; peroxynitrite