title: The acute phase protein Serum Amyloid A induces lipolysis and inflammation in human adipocytes through distinct pathways.
abstract: BACKGROUND
  The acute phase response (APR) is characterized by alterations in lipid and glucose metabolism leading to an increased delivery of energy substrates. In adipocytes, there is a coordinated decrease in Free Fatty acids (FFAs) and glucose storage, in addition to an increase in FFAs mobilization. Serum Amyloid A (SAA) is an acute phase protein mainly associated with High Density Lipoproteins (HDL). We hypothesized that enrichment of HDL with SAA, during the APR, could be implicated in the metabolic changes occurring in adipocytes.
  
  
  RESULTS
  In vitro differentiated human adipocytes (hMADS) were treated with SAA enriched HDL or recombinant SAA and the metabolic phenotype of the cells analyzed. In hMADS, SAA induces an increased lipolysis through an ERK dependent pathway. At the molecular level, SAA represses PPARγ2, C/EBPα and SREBP-1c gene expression, three transcription factors involved in adipocyte differentiation or lipid synthesis. In addition, the activation of the NF-κB pathway by SAA leads to the induction of pro-inflammatory cytokines and chemokines, as in the case of immune cells. These latter findings were replicated in freshly isolated mature human adipocytes.
  
  
  CONCLUSIONS
  Besides its well-characterized role in cholesterol metabolism, SAA has direct metabolic effects on human adipocytes. These metabolic changes could be at least partly responsible for alterations of adipocyte metabolism observed during the APR as well as during pathophysiological conditions such as obesity and conditions leading to insulin resistant states.
authors.affiliation: Metabolic Pathways Center of Excellence in Drug Discovery, GlaxoSmithKline, Les Ulis, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Faty
authors.forename: Pascal
authors.initials: P
authors.lastname: Ferré
authors.forename: Stéphane
authors.initials: S
authors.lastname: Commans
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D052242:Adiponectin / Q000378:metabolism; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism*; D050356:Lipid Metabolism / Q000187:drug effects; D008066:Lipolysis / Q000187:drug effects*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D000685:Serum Amyloid A Protein / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D052242:Adiponectin; D018925:Chemokines; D016207:Cytokines; D016328:NF-kappa B; D000685:Serum Amyloid A Protein; D020928:Mitogen-Activated Protein Kinases