1. Rapamycin partially prevents insulin resistance induced by chronic insulin treatment
- Author
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Brian E. Lavan, Cristina M. Rondinone, and Cathleen E Berg
- Subjects
MAPK/ERK pathway ,medicine.medical_specialty ,Time Factors ,medicine.medical_treatment ,Biophysics ,mTORC1 ,Protein Serine-Threonine Kinases ,Biochemistry ,Cell Line ,Insulin Antagonists ,Phosphoserine ,Insulin resistance ,Proto-Oncogene Proteins ,Insulin receptor substrate ,Internal medicine ,Adipocytes ,medicine ,Hyperinsulinemia ,Animals ,Insulin ,Phosphorylation ,Molecular Biology ,Sirolimus ,Chemistry ,Glucose transporter ,Biological Transport ,Cell Biology ,medicine.disease ,Glucose ,Phosphothreonine ,Endocrinology ,Insulin Resistance ,Mitogen-Activated Protein Kinases ,Proto-Oncogene Proteins c-akt - 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.
- Published
- 2002