title: Organo-vanadium compounds are potent activators of the protein kinase B signaling pathway and protein tyrosine phosphorylation: mechanism of insulinomimesis.
abstract: Organo-vanadium compounds (OVC) have been shown to be more effective than inorganic vanadium compounds in ameliorating glucose homeostasis and insulin resistance in rodent models of diabetes mellitus. However, the precise molecular mechanism of OVC efficiency remains poorly defined. Since inorganic vanadium compounds have been found to activate several key components of the insulin signaling cascade, such as protein kinase B (PKB), the objective of the present study was to investigate if stimulation of PKB and its downstream target glycogen synthase kinase-3 (GSK-3), are responsible for the more potent insulinomimetic effects of OVC. Among several vanadium compounds tested, vanadium (IV) oxo bis (acetylacetonate) and vanadium (IV) oxo bis(maltolato) markedly induced the phosphorylation of PKB as well as GSK-3beta compared to vanadyl sulfate (VS), an inorganic vanadium salts in Chinese hamster ovary cells overexpressing the insulin receptor (IR). Furthermore, the OVC were stronger inhibitors of protein tyrosine phosphatase (PTPase) activity than VS. The higher PTPase inhibitory potential of the OVC was associated with more robust tyrosine phosphorylation of several cellular proteins, including the IRbeta subunit and insulin receptor substrate-1 (IRS-1). In addition, greater IRS-1/p85alpha interaction was elicited by the OVC than by VS. These data indicate that the higher PTPase inhibitory potential of OVC translates into greater phosphorylation of PKB and GSK-3beta, which, in turn, may contribute to a more potent effect of OVC on glucose homeostasis.
authors.affiliation: Laboratory of Cell Signaling, Research Centre, Centre Hospitalier de l'Université de Montréal (CHUM)-Hôtel-Dieu, Canada.
authors.forename: Mohamad Z
authors.initials: MZ
authors.lastname: Mehdi
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Srivastava
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003920:Diabetes Mellitus / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology / Q000627:therapeutic use; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D009942:Organometallic Compounds / Q000494:pharmacology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism; D017968:Vanadium Compounds / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D009942:Organometallic Compounds; D011518:Proto-Oncogene Proteins; D017968:Vanadium Compounds; D014443:Tyrosine; C034028:vanadyl sulfate; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D017027:Protein Tyrosine Phosphatases