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Activation of the mammalian target of rapamycin pathway acutely inhibits insulin signaling to Akt and glucose transport in 3T3-L1 and human adipocytes.
Endocrinology. 2005 Mar; 146(3):1328-37.E

Abstract

The mammalian target of rapamycin (mTOR) pathway has recently emerged as a chronic modulator of insulin-mediated glucose metabolism. In this study, we evaluated the involvement of this pathway in the acute regulation of insulin action in both 3T3-L1 and human adipocytes. Insulin rapidly (t(1/2) = 5 min) stimulated the mTOR pathway, as reflected by a 10-fold stimulation of 70-kDa ribosomal S6 kinase 1 (S6K1) activity in 3T3-L1 adipocytes. Inhibition of mTOR/S6K1 by rapamycin increased insulin-stimulated glucose transport by as much as 45% in 3T3-L1 adipocytes. Activation of mTOR/S6K1 by insulin was associated with a rapamycin-sensitive increase in Ser636/639 phosphorylation of insulin receptor substrate (IRS)-1 but, surprisingly, did not result in impaired IRS-1-associated phosphatidylinositol (PI) 3-kinase activity. However, insulin-induced activation of Akt was increased by rapamycin. Insulin also activated S6K1 and increased phosphorylation of IRS-1 on Ser636/639 in human adipocytes. As in murine cells, rapamycin treatment of human adipocytes inhibited S6K1, blunted Ser636/639 phosphorylation of IRS-1, leading to increased Akt activation and glucose uptake by insulin. Further studies in 3T3-L1 adipocytes revealed that rapamycin prevented the relocalization of IRS-1 from the low-density membranes to the cytosol in response to insulin. Furthermore, inhibition of mTOR markedly potentiated the ability of insulin to increase PI 3,4,5-triphosphate levels concomitantly with an increased phosphorylation of Akt at the plasma membrane, low-density membranes, and cytosol. However, neither GLUT4 nor GLUT1 translocation induced by insulin were increased by rapamycin treatment. Taken together, these results indicate that the mTOR pathway is an important modulator of the signals involved in the acute regulation of insulin-stimulated glucose transport in 3T3-L1 and human adipocytes.

Authors+Show Affiliations

Department of Anatomy and Physiology and Lipid Research Unit, Laval University Hospital Research Center, 2705 Laurier Boulevard, Ste-Foy, Québec, Canada G1V 4G2.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15576463

Citation

Tremblay, Frédéric, et al. "Activation of the Mammalian Target of Rapamycin Pathway Acutely Inhibits Insulin Signaling to Akt and Glucose Transport in 3T3-L1 and Human Adipocytes." Endocrinology, vol. 146, no. 3, 2005, pp. 1328-37.
Tremblay F, Gagnon A, Veilleux A, et al. Activation of the mammalian target of rapamycin pathway acutely inhibits insulin signaling to Akt and glucose transport in 3T3-L1 and human adipocytes. Endocrinology. 2005;146(3):1328-37.
Tremblay, F., Gagnon, A., Veilleux, A., Sorisky, A., & Marette, A. (2005). Activation of the mammalian target of rapamycin pathway acutely inhibits insulin signaling to Akt and glucose transport in 3T3-L1 and human adipocytes. Endocrinology, 146(3), 1328-37.
Tremblay F, et al. Activation of the Mammalian Target of Rapamycin Pathway Acutely Inhibits Insulin Signaling to Akt and Glucose Transport in 3T3-L1 and Human Adipocytes. Endocrinology. 2005;146(3):1328-37. PubMed PMID: 15576463.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Activation of the mammalian target of rapamycin pathway acutely inhibits insulin signaling to Akt and glucose transport in 3T3-L1 and human adipocytes. AU - Tremblay,Frédéric, AU - Gagnon,AnneMarie, AU - Veilleux,Alain, AU - Sorisky,Alexander, AU - Marette,André, Y1 - 2004/12/02/ PY - 2004/12/4/pubmed PY - 2005/4/5/medline PY - 2004/12/4/entrez SP - 1328 EP - 37 JF - Endocrinology JO - Endocrinology VL - 146 IS - 3 N2 - The mammalian target of rapamycin (mTOR) pathway has recently emerged as a chronic modulator of insulin-mediated glucose metabolism. In this study, we evaluated the involvement of this pathway in the acute regulation of insulin action in both 3T3-L1 and human adipocytes. Insulin rapidly (t(1/2) = 5 min) stimulated the mTOR pathway, as reflected by a 10-fold stimulation of 70-kDa ribosomal S6 kinase 1 (S6K1) activity in 3T3-L1 adipocytes. Inhibition of mTOR/S6K1 by rapamycin increased insulin-stimulated glucose transport by as much as 45% in 3T3-L1 adipocytes. Activation of mTOR/S6K1 by insulin was associated with a rapamycin-sensitive increase in Ser636/639 phosphorylation of insulin receptor substrate (IRS)-1 but, surprisingly, did not result in impaired IRS-1-associated phosphatidylinositol (PI) 3-kinase activity. However, insulin-induced activation of Akt was increased by rapamycin. Insulin also activated S6K1 and increased phosphorylation of IRS-1 on Ser636/639 in human adipocytes. As in murine cells, rapamycin treatment of human adipocytes inhibited S6K1, blunted Ser636/639 phosphorylation of IRS-1, leading to increased Akt activation and glucose uptake by insulin. Further studies in 3T3-L1 adipocytes revealed that rapamycin prevented the relocalization of IRS-1 from the low-density membranes to the cytosol in response to insulin. Furthermore, inhibition of mTOR markedly potentiated the ability of insulin to increase PI 3,4,5-triphosphate levels concomitantly with an increased phosphorylation of Akt at the plasma membrane, low-density membranes, and cytosol. However, neither GLUT4 nor GLUT1 translocation induced by insulin were increased by rapamycin treatment. Taken together, these results indicate that the mTOR pathway is an important modulator of the signals involved in the acute regulation of insulin-stimulated glucose transport in 3T3-L1 and human adipocytes. SN - 0013-7227 UR - https://www.unboundmedicine.com/medline/citation/15576463/Activation_of_the_mammalian_target_of_rapamycin_pathway_acutely_inhibits_insulin_signaling_to_Akt_and_glucose_transport_in_3T3_L1_and_human_adipocytes_ L2 - https://academic.oup.com/endo/article-lookup/doi/10.1210/en.2004-0777 DB - PRIME DP - Unbound Medicine ER -