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Glucose uptake in brown fat cells is dependent on mTOR complex 2-promoted GLUT1 translocation
Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. Monash Institute of Pharmaceutical Sciences, Australia.
Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. The Rockefeller University, USA.
Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
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2014 (English)In: Journal of Cell Biology, ISSN 0021-9525, E-ISSN 1540-8140, Vol. 207, no 3, 365Article in journal (Refereed) Published
Abstract [en]

Brown adipose tissue is the primary site for thermogenesis and can consume, in addition to free fatty acids, a very high amount of glucose from the blood, which can both acutely and chronically affect glucose homeostasis. Here, we show that mechanistic target of rapamycin (mTOR) complex 2 has a novel role in β3-adrenoceptor-stimulated glucose uptake in brown adipose tissue. We show that β3-adrenoceptors stimulate glucose uptake in brown adipose tissue via a signaling pathway that is comprised of two different parts: one part dependent on cAMP-mediated increases in GLUT1 transcription and de novo synthesis of GLUT1 and another part dependent on mTOR complex 2-stimulated translocation of newly synthesized GLUT1 to the plasma membrane, leading to increased glucose uptake. Both parts are essential for β3-adrenoceptor-stimulated glucose uptake. Importantly, the effect of β3-adrenoceptor on mTOR complex 2 is independent of the classical insulin-phosphoinositide 3-kinase-Akt pathway, highlighting a novel mechanism of mTOR complex 2 activation.

Place, publisher, year, edition, pages
2014. Vol. 207, no 3, 365
National Category
Physiology
Research subject
Physiology
Identifiers
URN: urn:nbn:se:su:diva-143136DOI: 10.1083/jcb.201403080OAI: oai:DiVA.org:su-143136DiVA: diva2:1095573
Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2017-05-16Bibliographically approved
In thesis
1. β-Adrenergic Signalling Through mTOR
Open this publication in new window or tab >>β-Adrenergic Signalling Through mTOR
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Adrenergic signalling is part of the sympathetic nervous system and is activated upon stimulation by the catecholamines epinephrine and norepinephrine. This regulates heart rate, energy mobilization, digestion and helps to divert blood flow to important organs. Insulin is released to regulate metabolism of carbohydrates, fats and proteins, mainly by taking up glucose from the blood. The insulin and the catecholamine hormone systems are normally working as opposing metabolic regulators and are therefore thought to antagonize each other.

One of the major regulators involved in insulin signalling is the mechanistic target of rapamycin (mTOR). There are two different complexes of mTOR; mTORC1 and mTORC2, and they are essential in the control of cell growth, metabolism and energy homeostasis. Since mTOR is one of the major signalling nodes for anabolic actions of insulin it was thought that catecholamines might oppose this action by inhibiting the complexes. However, lately there are studies demonstrating that this may not be the case. mTOR is for instance part of the adrenergic signalling pathway resulting in hypertrophy of cardiac and skeletal muscle cells and inhibition of smooth muscle relaxation and helps to regulate browning in white adipose tissue and thermogenesis in brown adipose tissue (BAT).

In this thesis I show that β-adrenergic signalling leading to glucose uptake occurs independently of insulin in skeletal muscle and BAT, and does not activate either Akt or mTORC1, but that the master regulator of this pathway is mTORC2. Further, my co-workers and I demonstrates that β-adrenergic stimulation in skeletal muscle and BAT utilizes different glucose transporters. In skeletal muscle, GLUT4 is translocated to the plasma membrane upon stimulation. However, in BAT, β-adrenergic stimulation results in glucose uptake through translocation of GLUT1. Importantly, in both skeletal muscle and BAT, the role of mTORC2 in β-adrenergic stimulated glucose uptake is to regulate GLUT-translocation.

Place, publisher, year, edition, pages
Stockholm: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 2017
Keyword
Glucose uptake, Brown adipose tissue, White adipose tissue, Skeletal muscle, Mechanistic target of rapamycin, Glucose transporter, Physiology
National Category
Physiology
Research subject
Physiology
Identifiers
urn:nbn:se:su:diva-142169 (URN)978-91-7649-850-7 (ISBN)978-91-7649-851-4 (ISBN)
Public defence
2017-06-14, sal E306, Arrheniuslaboratorierna, Svante Arrhenius väg 20 C, Stockholm, 14:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2017-05-22 Created: 2017-04-27 Last updated: 2017-05-16Bibliographically approved

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