title: Cyclosporine A and tacrolimus reduce the amount of GLUT4 at the cell surface in human adipocytes: increased endocytosis as a potential mechanism for the diabetogenic effects of immunosuppressive agents.
abstract: BACKGROUND
  Immunosuppressive agents are associated with profound metabolic side effects including new-onset diabetes and dyslipidemia after organ transplantation.
  
  
  OBJECTIVE
  To investigate the effects of cyclosporine A (CsA) and tacrolimus on glucose uptake and insulin signaling in human adipocytes and their impact on the regulation of cellular trafficking of the glucose transporter 4 (GLUT4).
  
  
  METHODS
  Isolated human adipocytes were incubated with therapeutic concentrations of either CsA or tacrolimus, and glucose uptake and expression of insulin signaling proteins were assessed. Furthermore, we studied effects of CsA and tacrolimus on the regulation of cellular trafficking of GLUT4 in differentiated human preadipocytes and L6 cells.
  
  
  RESULTS
  CsA and tacrolimus had a concentration-dependent inhibitory effect on basal and insulin-stimulated (14)C-glucose uptake in adipocytes. Although phosphorylation at Tyr1146 of the insulin receptor was inhibited by tacrolimus, the phosphorylation and/or protein levels of the insulin signaling proteins IRS1/2, p85-PI3K, PKB, AS160, and mTORC1, as well as GLUT4 and GLUT1, were unchanged by CsA or tacrolimus. Furthermore, CsA and tacrolimus reduced the GLUT4 amount localized at the cell surface of differentiated human preadipocytes and L6 cells in the presence of insulin. This occurred by an increased rate of GLUT4 endocytosis, with no change in the exocytosis rate.
  
  
  CONCLUSIONS
  These results suggest that therapeutic concentrations of CsA and tacrolimus can inhibit glucose uptake independent of insulin signaling by removing GLUT4 from the cell surface via an increased rate of endocytosis. This mechanism can contribute to the development of insulin resistance and diabetes associated with immunosuppressive therapy. In addition, it may provide novel pharmacological approaches for the treatment of diabetes.
authors.affiliation: Department of Medical Sciences (M.J.P., J.W.E.), Uppsala University, 751 85 Uppsala, Sweden; Center for Neuroscience and Cell Biology (M.J.P., E.C.), University of Coimbra, 3000-214 Coimbra, Portugal; Department of Molecular and Clinical Medicine (J.P., M.K.S.), the Sahlgrenska Academy at University of Gothenburg, 413 45 Gothenburg, Sweden; Department of Surgery (M.R.), Sahlgrenska University Hospital, 413 45 Gothenburg, Sweden; Centre for Marine Sciences (M.A.), Centre of Marine Sciences, Faculty of Sciences and Technology, University of Algarve, 8005-139 Faro, Portugal; and The Portuguese Diabetes Association (E.C.), 1250-203 Lisbon, Portugal.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Pereira
authors.forename: Jenny
authors.initials: J
authors.lastname: Palming
authors.forename: Magnus
authors.initials: M
authors.lastname: Rizell
authors.forename: Manuel
authors.initials: M
authors.lastname: Aureliano
authors.forename: Eugénia
authors.initials: E
authors.lastname: Carvalho
authors.forename: Maria K
authors.initials: MK
authors.lastname: Svensson
authors.forename: Jan W
authors.initials: JW
authors.lastname: Eriksson
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000273:Adipose Tissue / Q000166:cytology; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology*; D004705:Endocytosis / Q000187:drug effects*; D005089:Exocytosis / Q000187:drug effects; D005260:Female; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008875:Middle Aged; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011236:Prediabetic State / Q000139:chemically induced*; D061251:Primary Cell Culture; D015398:Signal Transduction / Q000187:drug effects; D016559:Tacrolimus / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D051275:Glucose Transporter Type 4; D007166:Immunosuppressive Agents; D007328:Insulin; D008565:Membrane Proteins; C495692:SLC2A4 protein, human; D016572:Cyclosporine; D016559:Tacrolimus