title: Pioglitazone leads to an inactivation and disassembly of complex I of the mitochondrial respiratory chain.
abstract: BACKGROUND
  Thiazolidinediones are antidiabetic agents that increase insulin sensitivity but reduce glucose oxidation, state 3 respiration, and activity of complex I of the mitochondrial respiratory chain (MRC). The mechanisms of the latter effects are unclear. The aim of this study was to determine the mechanisms by which pioglitazone (PGZ), a member of the thiazolidinedione class of antidiabetic agents, decreases the activity of the MRC. In isolated mitochondria from mouse liver, we measured the effects of PGZ treatment on MRC complex activities, fully-assembled complex I and its subunits, gene expression of complex I and III subunits, and [3H]PGZ binding to mitochondrial complexes.
  
  
  RESULTS
  In vitro, PGZ decreased activity of complexes I and III of the MRC, but in vivo only complex I activity was decreased in mice treated for 12 weeks with 10 mg/kg/day of PGZ. In vitro treatment of isolated liver mitochondria with PGZ disassembled complex I, resulting in the formation of several subcomplexes. In mice treated with PGZ, fully assembled complex I was increased and two additional subcomplexes were found. Formation of supercomplexes CI+CIII2+CIVn and CI+CIII2 decreased in mouse liver mitochondria exposed to PGZ, while formation of these supercomplexes was increased in mice treated with PGZ. Two-dimensional analysis of complex I using blue native/sodium dodecyl sulfate polyacrylamide gel electrophoresis (BN/SDS-PAGE) showed that in vitro PGZ induced the formation of four subcomplexes of 600 (B), 400 (C), 350 (D), and 250 (E) kDa, respectively. Subcomplexes B and C had NADH:dehydrogenase activity, while subcomplexes C and D contained subunits of complex I membrane arm. Autoradiography and coimmunoprecipitation assays showed [3H]PGZ binding to subunits NDUFA9, NDUFB6, and NDUFA6. Treatment with PGZ increased mitochondrial gene transcription in mice liver and HepG2 cells. In these cells, PGZ decreased intracellular ATP content and enhanced gene expression of specific protein 1 and peroxisome-proliferator activated receptor (PPAR)γ coactivator 1α (PGC-1α).
  
  
  CONCLUSIONS
  PGZ binds complex I subunits, which induces disassembly of this complex, reduces its activity, depletes cellular ATP, and, in mice and HepG2 cells, upregulates nuclear DNA-encoded gene expression of complex I and III subunits.
authors.affiliation: Research Center, Laboratory of Gastroenterology and Hepatology, University Hospital 12 de Octubre, Complutense University, Madrid 28041, Spain. inmagr86@hotmail.com
authors.forename: Inmaculada
authors.initials: I
authors.lastname: García-Ruiz
authors.forename: Pablo
authors.initials: P
authors.lastname: Solís-Muñoz
authors.forename: Daniel
authors.initials: D
authors.lastname: Fernández-Moreira
authors.forename: Teresa
authors.initials: T
authors.lastname: Muñoz-Yagüe
authors.forename: José A
authors.initials: JA
authors.lastname: Solís-Herruzo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004579:Electron Transport / Q000187:drug effects; D042967:Electron Transport Complex I / Q000378:metabolism*; D014450:Electron Transport Complex III / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D008970:Molecular Weight; D009245:NADH Dehydrogenase / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D000077205:Pioglitazone; D000091402:Prohibitins; D021122:Protein Subunits / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D045162:Thiazolidinediones / Q000494:pharmacology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014316:Tritium / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D000091402:Prohibitins; D021122:Protein Subunits; D012097:Repressor Proteins; D016329:Sp1 Transcription Factor; D045162:Thiazolidinediones; D014157:Transcription Factors; D014316:Tritium; D000255:Adenosine Triphosphate; D009245:NADH Dehydrogenase; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; D000077205:Pioglitazone
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