title: Increased heme-oxygenase 1 expression in mesenchymal stem cell-derived adipocytes decreases differentiation and lipid accumulation via upregulation of the canonical Wnt signaling cascade.
abstract: BACKGROUND
  Heme oxygenase (HO), a major cytoprotective enzyme, attenuates oxidative stress and obesity. The canonical Wnt signaling cascade plays a pivotal role in the regulation of adipogenesis. The present study examined the interplay between HO-1and the Wnt canonical pathway in the modulation of adipogenesis in mesenchymal stem cell (MSC)-derived adipocytes.
  
  
  METHODS
  To verify the role of HO-1 in generating small healthy adipocytes, cobalt protoporphyrin (CoPP), inducer of HO-1, was used during adipocyte differentiation. Lipid accumulation was measured by Oil red O staining and lipid droplet size was measured by BODIPY staining.
  
  
  RESULTS
  During adipogenesis in vitro, differentiating pre-adipocytes display transient increases in the expression of genes involved in canonical Wnt signaling cascade. Increased levels of HO-1 expression and HO activity resulted in elevated levels of β-catenin, pGSK3β, Wnt10b, Pref-1, and shh along with increased levels of adiponectin (P < 0.05). In addition, induction of HO-1 resulted in a reduction in C/EBPα, PPARγ, Peg-1/Mest, aP2, CD36 expression and lipid accumulation (P < 0.05). Suppression of HO-1 gene by siRNA decreased Wnt10b, pGSK3β and β-catenin expression, and increased lipid accumulation. The canonical Wnt responsive genes, IL-8 and SFRP1, were upregulated by CoPP and their expression was decreased by the concurrent administration of tin mesoporphyrin (SnMP), an inhibitor of HO activity. Furthermore, knockdown of Wnt10b gene expression by using siRNA showed increased lipid accumulation, and this effect was not decreased by concurrent treatment with CoPP. Also our results show that blocking the Wnt 10b antagonist, Dickkopf 1 (Dkk-1), by siRNA decreased lipid accumulation and this effect was further enhanced by concurrent administration of CoPP.
  
  
  CONCLUSIONS
  This is the first study to demonstrate that HO-1 acts upstream of canonical Wnt signaling cascade and decreases lipogenesis and adipocyte differentiation suggesting that the HO-1 mediated increase in Wnt10b can modulate the adipocyte phenotype by regulating the transcriptional factors that play a role in adipogenesis. This is evidenced by a decrease in lipid accumulation and inflammatory cytokine levels, increased adiponectin levels and elevation of the expression of genes of the canonical Wnt signaling cascade.
authors.forename: Luca
authors.initials: L
authors.lastname: Vanella
authors.forename: Komal
authors.initials: K
authors.lastname: Sodhi
authors.forename: Dong Hyun
authors.initials: DH
authors.lastname: Kim
authors.forename: Nitin
authors.initials: N
authors.lastname: Puri
authors.forename: Mani
authors.initials: M
authors.lastname: Maheshwari
authors.forename: Terry D
authors.initials: TD
authors.lastname: Hinds
authors.forename: Lars
authors.initials: L
authors.lastname: Bellner
authors.forename: Dov
authors.initials: D
authors.lastname: Goldstein
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Peterson
authors.forename: Joseph I
authors.initials: JI
authors.lastname: Shapiro
authors.forename: Nader G
authors.initials: NG
authors.lastname: Abraham
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D050156:Adipogenesis / Q000187:drug effects; D052242:Adiponectin / Q000378:metabolism; D018955:CD36 Antigens / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008055:Lipids / Q000096:biosynthesis*; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D008665:Metalloporphyrins / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011524:Protoporphyrins / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D051153:Wnt Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D060449:Wnt Signaling Pathway / Q000187:drug effects; D051176:beta Catenin / Q000378:metabolism
chemical_list: D052242:Adiponectin; D018955:CD36 Antigens; D016207:Cytokines; C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D008055:Lipids; D008665:Metalloporphyrins; D011518:Proto-Oncogene Proteins; D011524:Protoporphyrins; D034741:RNA, Small Interfering; C491119:WNT10B protein, human; D051153:Wnt Proteins; D051176:beta Catenin; C055421:tin mesoporphyrin; C007095:cobaltiprotoporphyrin; D051547:Heme Oxygenase-1