title: Rapamycin partially prevents insulin resistance induced by chronic insulin treatment.
abstract: Chronic insulin exposure induces serine/threonine phosphorylation and degradation of IRS-1 through a rapamycin-sensitive pathway, which results in a down-regulation of insulin action. In this study, to investigate whether rapamycin (an mTOR inhibitor) could prevent insulin resistance induced by hyperinsulinemia, 3T3-L1 adipocytes were incubated chronically in the presence of insulin with or without the addition of rapamycin. Subsequently, the cells were washed and re-stimulated acutely with insulin. Chronic insulin stimulation caused a reduction of GLUT-4 and IRS-1 proteins with a correlated decrease in acute insulin-induced PKB and MAPK phosphorylations as well as a reduction in insulin-stimulated glucose transport. Rapamycin prevented the reduction of IRS-1 protein levels and insulin-induced PKB Ser-473 phosphorylation with a partial normalization of insulin-induced glucose transport. In contrast, rapamycin had no effect on the decrease in insulin-induced MAPK phosphorylation or GLUT-4 protein levels. These results suggest that chronic insulin exposure leads to a down-regulation of PKB and MAPK pathways through different mechanisms in adipocytes.
authors.affiliation: Metabolic Diseases Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064, USA.
authors.forename: Cathleen E
authors.initials: CE
authors.lastname: Berg
authors.forename: Brian E
authors.initials: BE
authors.lastname: Lavan
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Rondinone
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D007329:Insulin Antagonists / Q000494:pharmacology*; D007333:Insulin Resistance; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D020123:Sirolimus / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D007328:Insulin; D007329:Insulin Antagonists; D011518:Proto-Oncogene Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D005947:Glucose; D020123:Sirolimus