title: Insulin modulates leptin-induced STAT3 activation in rat hypothalamus.
abstract: Insulin and leptin have overlapping effects in the control of energy homeostasis, but the molecular basis of this synergism is unknown. Insulin signals through a receptor tyrosine kinase that phosphorylates and activates the docking proteins IRSs (insulin receptor substrates), whereas the leptin receptor and its associated protein tyrosine kinase JAK2 (Janus kinase 2) mediate phosphorylation and activation of the transcription factor STAT3 (signal transducer and activator of transcription). Here, we present evidence for the integration of leptin and insulin signals in the hypothalamus. Insulin induced JAK2 tyrosine phosphorylation, leptin receptor phosphorylation which, in the presence of leptin, augmented the interaction between STAT3 and this receptor. Insulin also increased the leptin-induced phosphorylation of STAT3 and its activation. These results indicate that insulin modulates the leptin signal transduction pathway, and may provide a molecular basis for the coordinated effects of insulin and leptin in feeding behavior and weight control.
authors.affiliation: Departamento de Clínica Médica, Universidade Estadual de Campinas, Brazil.
authors.forename: J B
authors.initials: JB
authors.lastname: Carvalheira
authors.forename: R M
authors.initials: RM
authors.lastname: Siloto
authors.forename: I
authors.initials: I
authors.lastname: Ignacchitti
authors.forename: S L
authors.initials: SL
authors.lastname: Brenelli
authors.forename: C R
authors.initials: CR
authors.lastname: Carvalho
authors.forename: A
authors.initials: A
authors.lastname: Leite
authors.forename: L A
authors.initials: LA
authors.lastname: Velloso
authors.forename: J A
authors.initials: JA
authors.lastname: Gontijo
authors.forename: M J
authors.initials: MJ
authors.lastname: Saad
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism*; D007276:Injections, Intraventricular; D007328:Insulin / Q000008:administration & dosage*; D053614:Janus Kinase 2; D020738:Leptin / Q000008:administration & dosage*; D008297:Male; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000378:metabolism; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D007328:Insulin; D020738:Leptin; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; D015534:Trans-Activators; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; C507927:Jak2 protein, rat; D053614:Janus Kinase 2