Fat Cell–Specific Ablation of Rictor in Mice Impairs Insulin-Regulated Fat Cell and Whole-Body Glucose and Lipid Metabolism
Autor: | Hwi Jin Ko, Thurl E. Harris, John C. Lawrence, Jason K. Kim, Mark A. Magnuson, Susanna R. Keller, Anil Kumar, Dae Young Jung |
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Jazyk: | angličtina |
Rok vydání: | 2010 |
Předmět: |
medicine.medical_specialty
Endocrinology Diabetes and Metabolism medicine.medical_treatment Adipose tissue Carbohydrate metabolism Protein Serine-Threonine Kinases 03 medical and health sciences Mice 0302 clinical medicine Insulin resistance Adipokines Internal medicine Internal Medicine medicine Animals Insulin Muscle Skeletal Protein kinase B 030304 developmental biology 2. Zero hunger Mice Knockout 0303 health sciences biology Lipid metabolism medicine.disease Lipid Metabolism Insulin receptor Endocrinology Glucose Rapamycin-Insensitive Companion of mTOR Protein Adipose Tissue Liver biology.protein Original Article Carrier Proteins Energy Metabolism 030217 neurology & neurosurgery GLUT4 Signal Transduction |
Zdroj: | Diabetes |
ISSN: | 1939-327X 0012-1797 |
Popis: | OBJECTIVE Rictor is an essential component of mammalian target of rapamycin (mTOR) complex (mTORC) 2, a kinase that phosphorylates and activates Akt, an insulin signaling intermediary that regulates glucose and lipid metabolism in adipose tissue, skeletal muscle, and liver. To determine the physiological role of rictor/mTORC2 in insulin signaling and action in fat cells, we developed fat cell–specific rictor knockout (FRic−/−) mice. RESEARCH DESIGN AND METHODS Insulin signaling and glucose and lipid metabolism were studied in FRic−/− fat cells. In vivo glucose metabolism was evaluated by hyperinsulinemic-euglycemic clamp. RESULTS Loss of rictor in fat cells prevents insulin-stimulated phosphorylation of Akt at S473, which, in turn, impairs the phosphorylation of downstream targets such as FoxO3a at T32 and AS160 at T642. However, glycogen synthase kinase-3β phosphorylation at S9 is not affected. The signaling defects in FRic−/− fat cells lead to impaired insulin-stimulated GLUT4 translocation to the plasma membrane and decreased glucose transport. Furthermore, rictor-null fat cells are unable to suppress lipolysis in response to insulin, leading to elevated circulating free fatty acids and glycerol. These metabolic perturbations are likely to account for defects observed at the whole-body level of FRic−/− mice, including glucose intolerance, marked hyperinsulinemia, insulin resistance in skeletal muscle and liver, and hepatic steatosis. CONCLUSIONS Rictor/mTORC2 in fat cells plays an important role in whole-body energy homeostasis by mediating signaling necessary for the regulation of glucose and lipid metabolism in fat cells. |
Databáze: | OpenAIRE |
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