title: Tissue inflammation and nitric oxide-mediated alterations in cardiovascular function are major determinants of endotoxin-induced insulin resistance.
abstract: BACKGROUND
  Endotoxin (i.e. LPS) administration induces a robust inflammatory response with accompanying cardiovascular dysfunction and insulin resistance. Overabundance of nitric oxide (NO) contributes to the vascular dysfunction. However, inflammation itself also induces insulin resistance in skeletal muscle. We sought to investigate whether the cardiovascular dysfunction induced by increased NO availability without inflammatory stress can promote insulin resistance. Additionally, we examined the role of inducible nitric oxide synthase (iNOS or NOS2), the source of the increase in NO availability, in modulating LPS-induced decrease in insulin-stimulated muscle glucose uptake (MGU).
  
  
  METHODS
  The impact of NO donor infusion on insulin-stimulated whole-body and muscle glucose uptake (hyperinsulinemic-euglycemic clamps), and the cardiovascular system was assessed in chronically catheterized, conscious mice wild-type (WT) mice. The impact of LPS on insulin action and the cardiovascular system were assessed in WT and global iNOS knockout (KO) mice. Tissue blood flow and cardiac function were assessed using microspheres and echocardiography, respectively. Insulin signaling activity, and gene expression of pro-inflammatory markers were also measured.
  
  
  RESULTS
  NO donor infusion decreased mean arterial blood pressure, whole-body glucose requirements, and MGU in the absence of changes in skeletal muscle blood flow. LPS lowered mean arterial blood pressure and glucose requirements in WT mice, but not in iNOS KO mice. Lastly, despite an intact inflammatory response, iNOS KO mice were protected from LPS-mediated deficits in cardiac output. LPS impaired MGU in vivo, regardless of the presence of iNOS. However, ex vivo, insulin action in muscle obtained from LPS treated iNOS KO animals was protected.
  
  
  CONCLUSIONS
  Nitric oxide excess and LPS impairs glycemic control by diminishing MGU. LPS impairs MGU by both the direct effect of inflammation on the myocyte, as well as by the indirect NO-driven cardiovascular dysfunction.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 702 Light Hall, Nashville, TN, 37232, USA. lmclhouse2@gmail.com.|College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA. lmclhouse2@gmail.com.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: House
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 702 Light Hall, Nashville, TN, 37232, USA. tmorris@missouristate.edu.|Department of Biomedical Sciences, Missouri State University, Springfield, MO, USA. tmorris@missouristate.edu.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Morris
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 702 Light Hall, Nashville, TN, 37232, USA. lundblad.tammy@gmail.com.|Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA. lundblad.tammy@gmail.com.
authors.forename: Tammy M
authors.initials: TM
authors.lastname: Barnes
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 702 Light Hall, Nashville, TN, 37232, USA. louise.lantier@vanderbilt.edu.
authors.forename: Louise
authors.initials: L
authors.lastname: Lantier
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 702 Light Hall, Nashville, TN, 37232, USA. travis.j.cyphert@vanderbilt.edu.
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Cyphert
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 702 Light Hall, Nashville, TN, 37232, USA. owen.mcguinness@vanderbilt.edu.
authors.forename: Owen P
authors.initials: OP
authors.lastname: McGuinness
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 702 Light Hall, Nashville, TN, 37232, USA. yolanda.otero@vanderbilt.edu.
authors.forename: Yolanda F
authors.initials: YF
authors.lastname: Otero
mesh_terms: D000818:Animals; D062186:Arterial Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D018932:Chemokine CCL2 / Q000235:genetics; D004452:Echocardiography; D045462:Endothelium-Dependent Relaxing Factors / Q000494:pharmacology*; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D006321:Heart / Q000187:drug effects*; D007249:Inflammation; D007333:Insulin Resistance; D015850:Interleukin-6 / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D008863:Microspheres; D032342:Muscle Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012039:Regional Blood Flow / Q000187:drug effects; D058258:Serpin E2 / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D045462:Endothelium-Dependent Relaxing Factors; D015850:Interleukin-6; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D058258:Serpin E2; C511869:Serpine2 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D005947:Glucose