title: Vascular generation of tumor necrosis factor-α reduces nitric oxide availability in small arteries from visceral fat of obese patients.
abstract: OBJECTIVE
  The aim of this study was to assess whether small arteries from visceral fat of obese patients show a reduced nitric oxide (NO)-dependent relaxation, as compared with lean control subjects, focusing on the role of the pro-inflammatory cytokine tumor necrosis factor (TNF)-α.
  
  
  BACKGROUND
  Visceral obesity is characterized by endothelial dysfunction.
  
  
  METHODS
  Small arteries from 14 obese (body mass index 48.4 ± 11 kg/m(2)) and 14 control subjects (body mass index 24.9 ± 2 kg/m(2)), dissected after a visceral fat biopsy (laparoscopy), were evaluated on a pressurized micromyograph. Endothelium-dependent relaxation was assessed by acetylcholine. The NO availability, superoxide production, and inflammation were assessed by testing acetylcholine under the nitric oxide synthase (NOS) inhibitor N(ω)-nitro-L-arginine methylester, tempol (superoxide scavenger), and infliximab (monoclonal anti-TNF-α antibody), respectively. The roles of nicotinamide adenine dinucleotide phosphate oxidase and inducible nitric oxide synthase (iNOS) were assessed by their selective inhibitors apocynin and S-methylisothiourea (SMT), respectively. Vascular superoxide generation (dihydroethidium staining) protein expression of TNF-α and NOS isoforms (Western Blot) and TNF-α localization (immunohistochemistry) were assessed.
  
  
  RESULTS
  Vessels from obese patients displayed a blunted relaxation to acetylcholine and a reduced inhibitory effect of N(ω)-nitro-L-arginine methylester. These alterations were normalized by tempol or infliximab while being partly ameliorated by apocynin and SMT. Vascular superoxide generation was increased (p < 0.01) in obese patients. This condition was abrogated by both tempol and infliximab and partly (p < 0.05 vs. control subjects) reduced by apocynin or SMT. Enhanced TNF-α and iNOS expression together with increased TNF-α localization in the vascular media were detected.
  
  
  CONCLUSIONS
  Small arteries from visceral fat of obese patients are characterized by an increased TNF-α production, which reduces NO availability by promoting superoxide generation via nicotinamide adenine dinucleotide phosphate oxidase and iNOS activation.
authors: Department of Internal Medicine, University of Pisa, Pisa, Italy. agostino.virdis@med.unipi.it
authors: Agostino
authors: A
authors: Virdis
authors: Ferruccio
authors: F
authors: Santini
authors: Rocchina
authors: R
authors: Colucci
authors: Emiliano
authors: E
authors: Duranti
authors: Guido
authors: G
authors: Salvetti
authors: Ilaria
authors: I
authors: Rugani
authors: Cristina
authors: C
authors: Segnani
authors: Marco
authors: M
authors: Anselmino
authors: Nunzia
authors: N
authors: Bernardini
authors: Corrado
authors: C
authors: Blandizzi
authors: Antonio
authors: A
authors: Salvetti
authors: Aldo
authors: A
authors: Pinchera
authors: Stefano
authors: S
authors: Taddei
mesh_terms: D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000328:Adult; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001158:Arteries / Q000378:metabolism* / Q000503:physiopathology; D015153:Blotting, Western; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000503:physiopathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D000069285:Infliximab; D007333:Insulin Resistance; D050152:Intra-Abdominal Fat / Q000098:blood supply*; D008297:Male; D019255:NADPH Oxidases / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000494:pharmacology; D009765:Obesity / Q000503:physiopathology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013113:Spin Labels; D013481:Superoxides / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D015854:Up-Regulation; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D003497:Cyclic N-Oxides; D017382:Reactive Oxygen Species; D013113:Spin Labels; D014409:Tumor Necrosis Factor-alpha; D014665:Vasodilator Agents; D013481:Superoxides; D009569:Nitric Oxide; D000069285:Infliximab; D052247:Nitric Oxide Synthase Type II; D019255:NADPH Oxidases; D000109:Acetylcholine; C001803:tempol; D019331:NG-Nitroarginine Methyl Ester