title: Phosphatidylinositol 3-kinase (PI3K) signalling regulates insulin-like-growth factor binding protein-2 (IGFBP-2) production in human adipocytes.
abstract: OBJECTIVE
  Insulin-like-growth factor binding protein 2 (IGFBP-2) is thought to be a marker for the phosphatase and tensin homolog (PTEN) status and activity of the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. We aimed to evaluate whether or not lipoma cells of a patient with a heterozygous deletion in the PTEN gene would produce more IGFBP-2 than PTEN non deficient control cells. Moreover, we analysed the influence of pharmacological inhibitors of the PI3K/AKT/mTOR pathway on IGFBP-2 production.
  
  
  METHODS
  PTEN deficient preadipocytes and control PTEN non deficient preadipocytes were differentiated in vitro and treated with the respective inhibitors. PTEN was transiently down regulated by siRNA in human preadipocytes. IGFBP-2 mRNA and protein expression and IGFBP-2 in culture supernatant were measured.
  
  
  RESULTS
  PTEN deficient lipoma cells were found to produce IGFBP-2 during in vitro differentiation in comparable amounts to PTEN non deficient cells. In contrast, acute down regulation of PTEN in preadipocytes resulted in enhanced production of IGFBP-2. Incubation with the PI3K inhibitors LY294002 and wortmannin decreased IGFBP-2 mRNA and protein. Neither the mTOR complex 1 inhibitor rapamycin nor PD98059, an inhibitor of MEK (mitogen-activated protein kinase kinase), showed a significant effect on IGFBP-2 production.
  
  
  CONCLUSIONS
  IGFBP-2 production in PTEN deficient preadipocytes was not influenced by PTEN deficiency or by inhibition of mTORC1 and MAPK. In contrast, inhibition of PI3K decreased IGFBP-2 expression and secretion.
authors.affiliation: University Hospital for Children and Adolescents, Center for Pediatric Research Leipzig (CPL), Germany; Leipzig University Medical Center, IFB Adiposity Diseases, Leipzig, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Wilhelm
authors.affiliation: University Hospital for Children and Adolescents, Center for Pediatric Research Leipzig (CPL), Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Kässner
authors.affiliation: University Hospital for Children and Adolescents, Center for Pediatric Research Leipzig (CPL), Germany.
authors.forename: Gordian
authors.initials: G
authors.lastname: Schmid
authors.affiliation: Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostic, University Hospital Leipzig, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kratzsch
authors.affiliation: Medical Genetics Center, Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Laner
authors.affiliation: Division of Pediatric Endocrinology Diabetes, University Hospital for Children and Adolescents, Ulm, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wabitsch
authors.affiliation: University Hospital for Children and Adolescents, Center for Pediatric Research Leipzig (CPL), Germany; Leipzig University Medical Center, IFB Adiposity Diseases, Leipzig, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Körner
authors.affiliation: University Hospital for Children and Adolescents, Center for Pediatric Research Leipzig (CPL), Germany.
authors.forename: Wieland
authors.initials: W
authors.lastname: Kiess
authors.affiliation: University Hospital for Children and Adolescents, Center for Pediatric Research Leipzig (CPL), Germany. Electronic address: antje.garten@medizin.uni-leipzig.de.
authors.forename: Antje
authors.initials: A
authors.lastname: Garten
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D018971:Insulin-Like Growth Factor Binding Protein 2; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases; C546842:MTOR protein, human; C494929:PTEN protein, human
keywords: Human adipocytes; IGFBP-2; PHTS; PI3K; PTEN; Rapamycin