title: Agent and cell-type specificity in the induction of insulin resistance by HIV protease inhibitors.
abstract: OBJECTIVE
  To test agent and cell-type specificity in insulin resistance induced by prolonged exposure to HIV protease inhibitors (HPI), and to assess its relation to the direct, short-term inhibition of insulin-stimulated glucose uptake.
  
  
  METHODS
  Following prolonged (18 h) and short (5-10 min) exposure to HPI, insulin-stimulated glucose transport, protein kinase B (PKB) phosphorylation, and GLUT4 translocation were evaluated in 3T3-L1 adipocytes, fibroblasts, L6 myotubes, and L6 cells overexpressing a myc tag on the first exofacial loop of GLUT4 or GLUT1.
  
  
  RESULTS
  Prolonged exposure of 3T3-L1 adipocytes to nelfinavir, but not to indinavir or saquinavir, resulted in increased basal lipolysis but decreased insulin-stimulated glucose transport and PKB phosphorylation. In addition, impaired insulin-stimulated glucose uptake and PKB phosphorylation were also observed in the skeletal muscle cell line L6, and in 3T3-L1 fibroblasts. Interestingly, this coincided with increased basal glucose uptake as well as with elevated total-membrane glucose transporter GLUT1 protein content. In contrast to these unique effects of nelfinavir, the mere presence of any of the agents in the 5 min transport assay inhibited insulin-stimulated glucose-uptake activity. This appeared to be caused by direct and specific interaction of the drugs with GLUT4 fully assembled at the plasma membrane, since insulin-stimulated cell-surface exposure of an exofacial myc epitope on GLUT4 was normal.
  
  
  CONCLUSIONS
  Independent mechanisms for HPI-induced insulin resistance exist: prolonged exposure to nelfinavir interferes with insulin signaling and alters cellular metabolism of adipocytes and muscle cells, whereas a direct inhibitory effect on insulin-stimulated glucose uptake may occurs through specific interaction of HPI with GLUT4.
authors.affiliation: Department of Clinical Biochemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Ronit
authors.initials: R
authors.lastname: Ben-Romano
authors.forename: Assaf
authors.initials: A
authors.lastname: Rudich
authors.forename: Dóra
authors.initials: D
authors.lastname: Török
authors.forename: Sharon
authors.initials: S
authors.lastname: Vanounou
authors.forename: Klaris
authors.initials: K
authors.lastname: Riesenberg
authors.forename: Francisc
authors.initials: F
authors.lastname: Schlaeffer
authors.forename: Amira
authors.initials: A
authors.lastname: Klip
authors.forename: Nava
authors.initials: N
authors.lastname: Bashan
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D003847:Deoxyglucose / Q000378:metabolism; D004334:Drug Administration Schedule; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D051272:Glucose Transporter Type 1; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D006801:Humans; D019469:Indinavir / Q000494:pharmacology; D007333:Insulin Resistance; D008066:Lipolysis / Q000187:drug effects; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D019888:Nelfinavir / Q000494:pharmacology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019258:Saquinavir / Q000494:pharmacology
chemical_list: D051272:Glucose Transporter Type 1; D017320:HIV Protease Inhibitors; D009004:Monosaccharide Transport Proteins; D011518:Proto-Oncogene Proteins; C495677:SLC2A1 protein, human; D019469:Indinavir; D003847:Deoxyglucose; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019888:Nelfinavir; D019258:Saquinavir