title: The effects of NOD activation on adipocyte differentiation.
abstract: OBJECTIVE
  Obesity is associated with chronic inflammation. Toll-like receptors (TLR) and NOD-like receptors (NLR) are two families of pattern recognition receptors that play important roles in immune response and inflammation in adipocytes. It has been reported that TLR4 and TLR2 activation induce proinflammatory changes that impair adipocyte differentiation. However, the effects of activation of NOD1 and NOD2, the two prominent members of NLR, on adipocyte differentiation have not been studied.
  
  
  METHODS
  3T3-L1 and human adipose-derived stem cells were tested for adipocyte differentiation in the presence or absence of NOD ligand. Adipocyte differentiation was evaluated by the adipocyte markers gene expression and Oil Red O staining for lipid accumulation.
  
  
  RESULTS
  Activation of NOD1, but not NOD2, by a synthetic ligand dose-dependently suppressed 3T3-L1 adipocyte differentiation as revealed by Oil Red O stained cell morphology, lipid accumulation, and attenuated gene expression of adipocyte markers (PPARγ, C/EBPα, SCD, FABP4, Adiponectin). Activation of NOD1, but not NOD2, induced NF-κB activation, which correlated with their abilities to suppress ligand-induced PPARγ transaction. Moreover, the suppressive effect by NOD1 activation was reversed by IκB super-repressor which blocks NF-κB activation. The suppression by NOD1 ligand C12-iEDAP on adipocyte differentiation was reversed by small RNA interference targeting NOD1, demonstrating the specificity of NOD1 activation. In contrast, activation of NOD1 and NOD2 both significantly suppressed adipocyte differentiation of human adipose-derived adult stem cells, demonstrating the species specific effects of NOD activation. In contrast to enhanced leptin mRNA by LPS and TNFα, NOD1 activation suppressed leptin mRNA in adipocytes, suggesting the differential effects of NOD1 activation in adipocytes.
  
  
  CONCLUSIONS
  Overall, our results suggest that NOD1 represents a novel target for adipose inflammation in obesity.
authors.affiliation: Department of Nutrition, University of Tennessee, Knoxville, Tennessee, USA.
authors.forename: Jaanki
authors.initials: J
authors.lastname: S Purohit
authors.forename: Pan
authors.initials: P
authors.lastname: Hu
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Burke
authors.forename: J Jason
authors.initials: JJ
authors.lastname: Collier
authors.forename: Jiangang
authors.initials: J
authors.lastname: Chen
authors.forename: Ling
authors.initials: L
authors.lastname: Zhao
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D052242:Adiponectin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D050556:Fatty Acid-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D020738:Leptin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D053474:Nod1 Signaling Adaptor Protein / Q000235:genetics* / Q000378:metabolism*; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism*; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D052242:Adiponectin; D022763:CCAAT-Enhancer-Binding Protein-alpha; C493411:Fabp4 protein, mouse; D050556:Fatty Acid-Binding Proteins; D020738:Leptin; D008070:Lipopolysaccharides; D016328:NF-kappa B; C119067:NOD1 protein, human; C429018:NOD2 protein, human; D053474:Nod1 Signaling Adaptor Protein; C507873:Nod1 protein, mouse; D053473:Nod2 Signaling Adaptor Protein; C495945:Nod2 protein, mouse; D047495:PPAR gamma; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha