title: The effects of palmitic acid on nitric oxide production by rat skeletal muscle: mechanism via superoxide and iNOS activation.
abstract: BACKGROUND
  Increased plasma concentrations of free fatty acids (FFA) can lead to insulin resistance in skeletal muscle, impaired effects on mitochondrial function, including uncoupling of oxidative phosphorylation and decrease of endogenous antioxidant defenses. Nitric oxide (NO) is a highly diffusible gas that presents a half-life of 5-10 seconds and is involved in several physiological and pathological conditions. The effects of palmitic acid on nitric oxide (NO) production by rat skeletal muscle cells and the possible mechanism involved were investigated.
  
  
  METHODS
  Primary cultured rat skeletal muscle cells were treated with palmitic acid and NO production was assessed by nitrite measurement (Griess method) and 4,5-diaminofluorescein diacetate (DAF-2-DA) assay. Nuclear factor-kappa B (NF-ĸB) activation was evaluated by electrophoretic mobility shift assay and iNOS protein content by western blotting.
  
  
  RESULTS
  Palmitic acid treatment increased nitric oxide production. This effect was abolished by treatment with NOS inhibitors, L-nitro-arginine (LNA) and L-nitro-arginine methyl esther (L-NAME). NF-ĸB activation and iNOS content were increased due to palmitic acid treatment. The participation of superoxide on nitric oxide production was investigated by incubating the cells with DAF-2-DA in the presence or absence of palmitic acid, a superoxide generator system (X-XO), a mixture of NOS inhibitors and SOD-PEG (superoxide dismutase linked to polyethylene glycol). Palmitic acid and X-XO system increased NO production and this effect was abolished when cells were treated with NOS inhibitors and also with SOD-PEG.
  
  
  CONCLUSIONS
  In summary, palmitic acid stimulates NO production in cultured skeletal muscle cells through production of superoxide, nuclear factor-kappa B activation and increase of iNOS protein content.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil. rhlamber@yahoo.com.br
authors.forename: Rafael Herling
authors.initials: RH
authors.lastname: Lambertucci
authors.forename: Carol Góis
authors.initials: CG
authors.lastname: Leandro
authors.forename: Marco Aurélio
authors.initials: MA
authors.lastname: Vinolo
authors.forename: Renato Tadeu
authors.initials: RT
authors.lastname: Nachbar
authors.forename: Leonardo
authors.initials: L
authors.lastname: Dos Reis Silveira
authors.forename: Sandro Massao
authors.initials: SM
authors.lastname: Hirabara
authors.forename: Rui
authors.initials: R
authors.lastname: Curi
authors.forename: Tania Cristina
authors.initials: TC
authors.lastname: Pithon-Curi
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019335:Nitroarginine / Q000494:pharmacology; D019308:Palmitic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013329:Structure-Activity Relationship; D013481:Superoxides / Q000378:metabolism*
chemical_list: D013481:Superoxides; D019335:Nitroarginine; D019308:Palmitic Acid; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D019331:NG-Nitroarginine Methyl Ester