title: Mechanisms regulating adipocyte expression of resistin.
abstract: Resistin, also known as Adipocyte Secreted Factor (ADSF) and Found in Inflammatory Zone 3 (FIZZ3), is a mouse protein with potential roles in insulin resistance and adipocyte differentiation. The resistin gene is expressed almost exclusively in adipocytes. Here we show that a proximal 264-base pair fragment of the mouse resistin promoter is sufficient for expression in adipocytes. Ectopic expression of the adipogenic transcription factor CCAAT/enhancer-binding protein (C/EBPalpha) was sufficient for expression in non-adipogenic cells. C/EBPalpha binds specifically to a site that is essential for expression of the resistin promoter. Chromatin immunoprecipitation studies of the endogenous gene demonstrated adipocyte-specific association of C/EBPalpha with the proximal resistin promoter in adipocytes but not preadipocytes. C/EBPalpha binding was associated with the recruitment of coactivators p300 and CREB-binding protein and a dramatic increase in histone acetylation in the vicinity of the resistin promoter. The antidiabetic thiazolidinedione (TZD) drug rosiglitazone reduced resistin expression with an ED(50) similar to its K(d) for binding to peroxisome proliferator activated receptor gamma (PPARgamma). Other TZD- and non-TZD PPARgamma ligands also down-regulated resistin expression. However, no functional PPARgamma binding site was found within 6.2 kb of the transcriptional start site, suggesting that if PPARgamma is involved, it is either acting at a long distance from the start site, in an intron, or indirectly. Nevertheless, rosiglitazone treatment selectively decreased histone acetylation at the resistin promoter without a change in occupation by C/EBPalpha, CREB-binding protein, or p300. Thus, adipocyte specificity of resistin gene expression is because of C/EBPalpha binding, leading to the recruitment of transcriptional coactivators and histone acetylation that is characteristic of an active chromatin environment. TZD reduces resistin gene expression at least in part by reducing histone acetylation associated with the binding of C/EBPalpha in mature adipocytes.
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine and Genetics and The Penn Diabetes Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Helen B
authors.initials: HB
authors.lastname: Hartman
authors.forename: Xiao
authors.initials: X
authors.lastname: Hu
authors.forename: Keala X
authors.initials: KX
authors.lastname: Tyler
authors.forename: Chiraj K
authors.initials: CK
authors.lastname: Dalal
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Lazar
mesh_terms: D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism; D050882:CREB-Binding Protein; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D050881:E1A-Associated p300 Protein; D005343:Fibrinolytic Agents / Q000494:pharmacology; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006657:Histones / Q000378:metabolism; D006729:Hormones, Ectopic / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007438:Introns; D007700:Kinetics; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D020932:Nerve Growth Factor; D009687:Nuclear Proteins / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011506:Proteins; D052243:Resistin; D000077154:Rosiglitazone; D013844:Thiazoles / Q000494:pharmacology; D045162:Thiazolidinediones; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D022763:CCAAT-Enhancer-Binding Protein-alpha; D002843:Chromatin; D005343:Fibrinolytic Agents; D006657:Histones; D006729:Hormones, Ectopic; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D009687:Nuclear Proteins; D011506:Proteins; C499624:RETN protein, human; C486574:RETNLB protein, human; D052243:Resistin; C499623:Retn protein, mouse; C413576:Retnla protein, mouse; D013844:Thiazoles; D045162:Thiazolidinediones; D015534:Trans-Activators; D000077154:Rosiglitazone; D020932:Nerve Growth Factor; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C494364:Crebbp protein, mouse; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse