title: Heme induced oxidative stress attenuates sirtuin1 and enhances adipogenesis in mesenchymal stem cells and mouse pre-adipocytes.
abstract: Patho-physiological conditions with high oxidative stress, such as conditions associated with increased denatured heme-proteins, are associated with enhanced adipogenic response. This effect predominantly manifests as adipocyte hypertrophy characterized by dysfunctional, pro-inflammatory adipocytes exhibiting reduced expression of anti-inflammatory hormone, adiponectin. To understand how increased levels of cellular heme, a pro-oxidant molecule, modulates adipogenesis; the following study was designed to evaluate effects of heme on adipogenesis in human mesenchymal stem cells (hMSCs) and mouse pre-adipocytes (3T3L1). Experiments were conducted in the absence and in the presence of a superoxide dismutase (SOD) mimetic (tempol, 100 µM). Heme (10 µM) increased (P<0.05) adipogenesis in hMSCs and mouse pre-adipocytes, where tempol alone (100 µmol/L) attenuated adipogenesis in these cells (P<0.05). Tempol also reversed heme-induced increase in adipogenesis in both hMSCs and mouse pre-adipocytes (P<0.05). In addition, heme exposed 3T3L1 exhibited reduced (P<0.05) expression of transcriptional regulator-sirtuin 1 (Sirt1), along with, increased (P<0.05) expression of adipogenic markers peroxisome proliferators-activated receptor-gamma (PPARγ), C/EBPα, and aP2. These effects of heme were rescued (P<0.05) in cells concurrently treated with heme and tempol (P<0.05) and prevented in cells over-expressing Sirt1. Taken together, our results indicate that heme-induced oxidative stress inhibits Sirt1, thus un-inhibiting adipogenic regulators such as PPARγ and C/EBPα; which in turn induce increased adipogenesis along with adipocyte hypertrophy in pre-adipocytes. Anti-oxidant induced offsetting of these effects of heme supports the role of heme-dependent oxidative stress in mediating such events.
authors.affiliation: Department of Physiology and Pharmacology, College of Medicine, The University of Toledo, Toledo, Ohio 43614, USA.
authors.forename: Nitin
authors.initials: N
authors.lastname: Puri
authors.forename: Komal
authors.initials: K
authors.lastname: Sodhi
authors.forename: Michael
authors.initials: M
authors.lastname: Haarstad
authors.forename: Dong Hyun
authors.initials: DH
authors.lastname: Kim
authors.forename: Steven
authors.initials: S
authors.lastname: Bohinc
authors.forename: Eleonora
authors.initials: E
authors.lastname: Foglio
authors.forename: Gaia
authors.initials: G
authors.lastname: Favero
authors.forename: Nader G
authors.initials: NG
authors.lastname: Abraham
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D050156:Adipogenesis / Q000187:drug effects; D052242:Adiponectin / Q000096:biosynthesis; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000096:biosynthesis; D002460:Cell Line; D003497:Cyclic N-Oxides / Q000494:pharmacology; D050556:Fatty Acid-Binding Proteins / Q000096:biosynthesis; D006418:Heme / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D018384:Oxidative Stress; D047495:PPAR gamma / Q000096:biosynthesis; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D056564:Sirtuin 1 / Q000096:biosynthesis*; D013113:Spin Labels
chemical_list: D052242:Adiponectin; D000975:Antioxidants; D022763:CCAAT-Enhancer-Binding Protein-alpha; D003497:Cyclic N-Oxides; C493410:FABP4 protein, human; D050556:Fatty Acid-Binding Proteins; D047495:PPAR gamma; D017382:Reactive Oxygen Species; D013113:Spin Labels; D006418:Heme; D056564:Sirtuin 1; C001803:tempol