title: Macrophages inhibit insulin signalling in adipocytes: role of inducible nitric oxide synthase and nitric oxide.
abstract: OBJECTIVE
  The interaction of immune cells with adipocytes within the adipose tissues in obese persons with diabetes mellitus may play a role in insulin resistance. We examined in vitro whether nitric oxide (NO) and inducible nitric oxide synthase (iNOS) play a role in impaired insulin signalling in adipocytes exposed to activated macrophages.
  
  
  METHODS
  We used a co-culture system in which Raw264.7 macrophages were plated over differentiated, low passage 3T3-L1 cells (dif3T3) at a cell density ratio of 1:2. Inflammation was induced by a challenge with bacterial lipopolysaccharide.
  
  
  RESULTS
  Significantly (p<0.001) enhanced iNOS expression and NO synthesis was observed in activated co-cultures. In the co-cultures as compared with Raw264.7 cells alone, iNOS protein was induced up to 11-fold above background, and NO release was significantly (p<0.001) increased up to 2.8-fold. Co-culturing dif3T3 and Raw264.7 cells as compared to dif3T3 alone reduced insulin-induced Akt phosphorylation by 50% and AS160 phosphorylation by 42%. This was correlated with reduced glucose consumption when dif3T3 was exposed to 1,3-morpholinosydnonimine. Adiponectin, GLUT4 and AS160 mRNA were reduced by 4-fold, 5-fold and 2-fold, respectively, in co-cultures as compared to dif3T3 alone. On the contrary, GLUT1 mRNA levels were increased by 2-fold in co-cultures as compared to dif3T3. NG-monomethyl-L-arginine abolished NO production with modest reversal of Akt/AS160 phosphorylation.
  
  
  CONCLUSIONS
  This study demonstrated a potential association between iNOS/NO-mediated inflammation and insulin resistance.
authors.affiliation: Wayne State University School of Medicine, Detroit, Michigan, USA. Electronic address: afite@med.wayne.edu.
authors.forename: Alemu
authors.initials: A
authors.lastname: Fite
authors.affiliation: Wayne State University School of Medicine, Detroit, Michigan, USA; Hamad Medical Corporation, Doha, Qatar.
authors.forename: Abdul Badi
authors.initials: AB
authors.lastname: Abou-Samra
authors.affiliation: Hamad Medical Corporation, Doha, Qatar.
authors.forename: Berhane
authors.initials: B
authors.lastname: Seyoum
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D018920:Coculture Techniques; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism; D051272:Glucose Transporter Type 1 / Q000235:genetics / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008264:Macrophages; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D051272:Glucose Transporter Type 1; D007328:Insulin; D012333:RNA, Messenger; C495678:Slc2a1 protein, mouse; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051058:Oncogene Protein v-akt; D005947:Glucose
keywords: Akt et AS160; Akt/AS160; consommation de glucose; glucose consumption; infiltration macrophagique; inflammation; insulin resistance; insulinorésistance; macrophage infiltration