title: Angiotensin II-induced NADPH oxidase activation impairs insulin signaling in skeletal muscle cells.
abstract: The renin-angiotensin system (RAS) and reactive oxygen species (ROS) have been implicated in the development of insulin resistance and its related complications. There is also evidence that angiotensin II (Ang II)-induced generation of ROS contributes to the development of insulin resistance in skeletal muscle, although the precise mechanisms remain unknown. In the present study, we found that Ang II markedly enhanced NADPH oxidase activity and consequent ROS generation in L6 myotubes. These effects were blocked by the angiotensin II type 1 receptor blocker losartan, and by the NADPH oxidase inhibitor apocynin. Ang II also promoted the translocation of NADPH oxidase cytosolic subunits p47phox and p67phox to the plasma membrane within 15 min. Furthermore, Ang II abolished insulin-induced tyrosine phosphorylation of insulin receptor substrate 1 (IRS1), activation of protein kinase B (Akt), and glucose transporter-4 (GLUT4) translocation to the plasma membrane, which was reversed by pretreating myotubes with losartan or apocynin. Finally, small interfering RNA (siRNA)-specific gene silencing targeted specifically against p47phox (p47siRNA), in both L6 and primary myotubes, reduced the cognate protein expression, decreased NADPH oxidase activity, restored Ang II-impaired IRS1 and Akt activation as well as GLUT4 translocation by insulin. These results suggest a pivotal role for NADPH oxidase activation and ROS generation in Ang II-induced inhibition of insulin signaling in skeletal muscle cells.
authors.affiliation: Department of Internal Medicine, University of Missouri-Columbia 65212, USA.
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Wei
authors.forename: James R
authors.initials: JR
authors.lastname: Sowers
authors.forename: Ravi
authors.initials: R
authors.lastname: Nistala
authors.forename: Heping
authors.initials: H
authors.lastname: Gong
authors.forename: Grace M-E
authors.initials: GM
authors.lastname: Uptergrove
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Clark
authors.forename: E Matthew
authors.initials: EM
authors.lastname: Morris
authors.forename: Nicholas
authors.initials: N
authors.lastname: Szary
authors.forename: Camila
authors.initials: C
authors.lastname: Manrique
authors.forename: Craig S
authors.initials: CS
authors.lastname: Stump
mesh_terms: D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D020868:Gene Silencing; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D018482:Muscle, Skeletal / Q000166:cytology*; D019255:NADPH Oxidases / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; C498751:Nsfl1c protein, rat; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; C495694:Slc2a4 protein, rat; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; C079789:neutrophil cytosol factor 67K; D000804:Angiotensin II; D019255:NADPH Oxidases; D051057:Proto-Oncogene Proteins c-akt