title: Thyroid hormone promotes insulin-induced glucose uptake by enhancing Akt phosphorylation and VAMP2 translocation in 3T3-L1 adipocytes.
abstract: The purpose of this study was to test a hypothesis that T3 promotes glucose uptake via enhancing insulin-induced Akt phosphorylation and VAMP2 translocation in 3T3-L1 adipocytes. T3 significantly enhanced insulin-induced phosphorylation of Akt, cytoplasma to cell membrane translocations of vesicle-associated membrane protein 2 (VAMP2) and glucose transporter 4 (GLUT4), and glucose uptake in adipocytes. Akt inhibitor X abolished the promoting effects of T3, suggesting that Akt activation is essential for T3 to enhance these insulin-induced events in adipocytes. Knockdown of VAMP2 using siRNA abrogated the effects of T3 on insulin-induced GLUT4 translocation and glucose uptake, suggesting that VAMP2 is an important mediator of these processes. These data suggest that T3 may promote glucose uptake via enhancing insulin-induced phosphorylation of Akt and subsequent translocations of VAMP2 and GLUT4 in 3T3-L1 adipocytes. Akt phosphorylation is necessary for the promoting effects of T3 on insulin-stimulated VAMP2 translocation. Further, VAMP2 is essential for T3 to increase insulin-stimulated translocation of GLUT4 and subsequent uptake of glucose in adipocytes.
authors.affiliation: Department of Physiology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73126-0901, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
authors.forename: Zhongjie
authors.initials: Z
authors.lastname: Sun
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000493:pharmacokinetics; D007328:Insulin / Q000493:pharmacokinetics*; D051379:Mice; D010766:Phosphorylation / Q000235:genetics / Q000502:physiology; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D012694:Serine / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014284:Triiodothyronine / Q000502:physiology*; D050988:Vesicle-Associated Membrane Protein 2 / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C528734:GLUT4 enhancer factor, mouse; D007004:Hypoglycemic Agents; D007328:Insulin; D034741:RNA, Small Interfering; D014157:Transcription Factors; D050988:Vesicle-Associated Membrane Protein 2; C494808:vesicle-associated membrane protein 2, mouse; D014284:Triiodothyronine; D012694:Serine; D051057:Proto-Oncogene Proteins c-akt