title: Cellular insulin resistance disrupts leptin-mediated control of neuronal signaling and transcription.
abstract: Central resistance to the actions of insulin and leptin is associated with the onset of obesity and type 2 diabetes mellitus, whereas leptin and insulin signaling is essential for both glucose and energy homeostasis. Although it is known that leptin resistance can lead to attenuated insulin signaling, whether insulin resistance can lead to or exacerbate leptin resistance is unknown. To investigate the molecular events underlying crosstalk between these signaling pathways, immortalized hypothalamic neuronal models, rHypoE-19 and mHypoA-2/10, were used. Prolonged insulin exposure was used to induce cellular insulin resistance, and thereafter leptin-mediated regulation of signal transduction and gene expression was assessed. Leptin directly repressed agouti-related peptide mRNA levels but induced urocortin-2, insulin receptor substrate (IRS)-1, IRS2, and IR transcription, through leptin-mediated phosphatidylinositol 3-kinase/Akt activation. Neuronal insulin resistance, as assessed by attenuated Akt phosphorylation, blocked leptin-mediated signal transduction and agouti-related peptide, urocortin-2, IRS1, IRS2, and insulin receptor synthesis. Insulin resistance caused a substantial decrease in insulin receptor protein levels, forkhead box protein 1 phosphorylation, and an increase in suppressor of cytokine signaling 3 protein levels. Cellular insulin resistance may cause or exacerbate neuronal leptin resistance and, by extension, obesity. It is essential to unravel the effects of neuronal insulin resistance given that both peripheral, as well as the less widely studied central insulin resistance, may contribute to the development of metabolic, reproductive, and cardiovascular disorders. This study provides improved understanding of the complex cellular crosstalk between insulin-leptin signal transduction that is disrupted during neuronal insulin resistance.
authors.affiliation: Department of Physiology, University of Toronto, Medical Sciences Building 3247A, 1 Kings College Circle, Toronto, Ontario, Canada M5S 1A8.
authors.forename: Anaies
authors.initials: A
authors.lastname: Nazarians-Armavil
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Menchella
authors.forename: Denise D
authors.initials: DD
authors.lastname: Belsham
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D007031:Hypothalamus / Q000166:cytology; D007328:Insulin / Q000502:physiology; D007333:Insulin Resistance; D053614:Janus Kinase 2 / Q000378:metabolism; D020738:Leptin / Q000502:physiology*; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D002867:Chromones; D048049:Extracellular Signal-Regulated MAP Kinases; D007328:Insulin; D053614:Janus Kinase 2; D020738:Leptin; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D050796:STAT3 Transcription Factor; D000077191:Wortmannin; C494088:Stat3 protein, rat; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C507927:Jak2 protein, rat