title: Thiazolidinediones (PPARgamma agonists) but not PPARalpha agonists increase IRS-2 gene expression in 3T3-L1 and human adipocytes.
abstract: Thiazolidinediones (TZD) improve insulin sensitivity in human as well as in different animal models of insulin resistance and Type 2 diabetes. However, no clear link to the insulin signaling events has been identified. Using differentiated 3T3-L1 adipocytes, we found that TZD rapidly and markedly increased IRS-2 gene expression. This effect was specific for PPARgamma agonists and was not seen with PPARalpha agonists. It was rapidly induced (within 4 h) and maintained throughout the observation period of 48 h. It was also concentration dependent (EC50 approximately 50 nM) and not inhibited by cycloheximide, suggesting a direct effect on the IRS-2 promoter. There was no evidence that TZD altered IRS-2 mRNA stability, supporting that the increased mRNA levels were due to an increased gene transcription. IRS-2 protein expression was increased approximately 30% after 48 h and approximately 50% after 96 h. No effects of TZD were seen on IRS-1, PKB/Akt, or GLUT4 gene expression. TZD also increased IRS-2 mRNA levels in cultured human adipose tissue. These data show the first direct link between TZD and a critical molecule in insulin's signaling cascade in both 3T3-L1 and human adipocytes, and indicate a novel mode of action of these compounds.
authors.affiliation: The Lundberg Laboratory for Diabetes Research, Department of Internal Medicine, Goteborg University, Sahlgrenska University Hospital, S-413 45 Goteborg, Sweden. ulf.smith@medic.gu.se
authors.forename: U
authors.initials: U
authors.lastname: Smith
authors.forename: S
authors.initials: S
authors.lastname: Gogg
authors.forename: A
authors.initials: A
authors.lastname: Johansson
authors.forename: T
authors.initials: T
authors.lastname: Olausson
authors.forename: V
authors.initials: V
authors.lastname: Rotter
authors.forename: B
authors.initials: B
authors.lastname: Svalstedt
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D046508:Culture Techniques; D051275:Glucose Transporter Type 4; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009124:Muscle Proteins; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D000077205:Pioglitazone; D020033:Protein Isoforms / Q000819:agonists; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists*; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones; D014157:Transcription Factors / Q000819:agonists*
chemical_list: D051275:Glucose Transporter Type 4; C526292:IRS1 protein, human; C526297:IRS2 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526295:Irs1 protein, mouse; C526298:Irs2 protein, mouse; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; C495692:SLC2A4 protein, human; C495693:Slc2a4 protein, mouse; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; C089946:2,4-thiazolidinedione; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000077205:Pioglitazone