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Fat Cell–Specific Ablation of Rictor in Mice Impairs Insulin-Regulated Fat Cell and Whole-Body Glucose and Lipid Metabolism

Fat Cell–Specific Ablation of Rictor in Mice Impairs Insulin-Regulated Fat Cell and Whole-Body... OBJECTIVERictor 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 METHODSInsulin signaling and glucose and lipid metabolism were studied in FRic−/− fat cells. In vivo glucose metabolism was evaluated by hyperinsulinemic-euglycemic clamp.RESULTSLoss 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.CONCLUSIONSRictor/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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Diabetes Pubmed Central

Fat Cell–Specific Ablation of Rictor in Mice Impairs Insulin-Regulated Fat Cell and Whole-Body Glucose and Lipid Metabolism

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References (63)

Publisher
Pubmed Central
Copyright
© 2010 by the American Diabetes Association.
ISSN
0012-1797
eISSN
1939-327X
DOI
10.2337/db09-1061
Publisher site
See Article on Publisher Site

Abstract

OBJECTIVERictor 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 METHODSInsulin signaling and glucose and lipid metabolism were studied in FRic−/− fat cells. In vivo glucose metabolism was evaluated by hyperinsulinemic-euglycemic clamp.RESULTSLoss 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.CONCLUSIONSRictor/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.

Journal

Diabetes – Pubmed Central

Published: Mar 23, 2010

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