| 1. |
- Chia, Ling Yeong, et al.
(författare)
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Adrenoceptor regulation of the mechanistic target of rapamycin in muscle and adipose tissue
- 2019
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Ingår i: British Journal of Pharmacology. - : Wiley. - 0007-1188 .- 1476-5381. ; 176:14, s. 2433-2448
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Forskningsöversikt (refereegranskat)abstract
- A vital role of adrenoceptors in metabolism and energy balance has been well documented in the heart, skeletal muscle, and adipose tissue. It has been only recently demonstrated, however, that activation of the mechanistic target of rapamycin (mTOR) makes a significant contribution to various metabolic and physiological responses to adrenoceptor agonists. mTOR exists as two distinct complexes named mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2) and has been shown to play a critical role in protein synthesis, cell proliferation, hypertrophy, mitochondrial function, and glucose uptake. This review will describe the physiological significance of mTORC1 and 2 as a novel paradigm of adrenoceptor signalling in the heart, skeletal muscle, and adipose tissue. Understanding the detailed signalling cascades of adrenoceptors and how they regulate physiological responses is important for identifying new therapeutic targets and identifying novel therapeutic interventions. Linked Articles This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc
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| 2. |
- Dehvari, Nodi, et al.
(författare)
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The metabolic effects of mirabegron are mediated primarily by beta(3)-adrenoceptors
- 2020
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Ingår i: Pharmacology Research & Perspectives. - : Wiley. - 2052-1707. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- The beta(3)-adrenoceptor agonist mirabegron is approved for use for overactive bladder and has been purported to be useful in the treatment of obesity-related metabolic diseases in humans, including those involving disturbances of glucose homeostasis. We investigated the effect of mirabegron on glucose homeostasis with in vitro and in vivo models, focusing on its selectivity at beta-adrenoceptors, ability to cause browning of white adipocytes, and the role of UCP1 in glucose homeostasis. In mouse brown, white, and brite adipocytes, mirabegron-mediated effects were examined on cyclic AMP, UCP1 mRNA, [H-3]-2-deoxyglucose uptake, cellular glycolysis, and O(2)consumption. Mirabegron increased cyclic AMP levels, UCP1 mRNA content, glucose uptake, and cellular glycolysis in brown adipocytes, and these effects were either absent or reduced in white adipocytes. In brite adipocytes, mirabegron increased cyclic AMP levels and UCP1 mRNA content resulting in increased UCP1-mediated oxygen consumption, glucose uptake, and cellular glycolysis. The metabolic effects of mirabegron in both brown and brite adipocytes were primarily due to actions at beta(3)-adrenoceptors as they were largely absent in adipocytes derived from beta(3)-adrenoceptor knockout mice. In vivo, mirabegron increased whole body oxygen consumption, glucose uptake into brown and inguinal white adipose tissue, and improved glucose tolerance, all effects that required the presence of the beta(3)-adrenoceptor. Furthermore, in UCP1 knockout mice, the effects of mirabegron on glucose tolerance were attenuated. Thus, mirabegron had effects on cellular metabolism in adipocytes that improved glucose handling in vivo, and were primarily due to actions at the beta(3)-adrenoceptor.
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| 3. |
- Ham, Seungmin, et al.
(författare)
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Role of G protein-coupled receptor kinases (GRKs) in β2-adrenoceptor-mediated glucose uptake
- 2024
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Ingår i: Pharmacology Research & Perspectives. - 2052-1707. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Truncation of the C-terminal tail of the beta(2)-AR, transfection of beta ARKct or over-expression of a kinase-dead GRK mutant reduces isoprenaline-stimulated glucose uptake, indicating that GRK is important for this response. We explored whether phosphorylation of the beta(2)-AR by GRK2 has a role in glucose uptake or if this response is related to the role of GRK2 as a scaffolding protein. CHO-GLUT4myc cells expressing wild-type and mutant beta(2)-ARs were generated and receptor affinity for [H-3]-CGP12177A and density of binding sites determined together with the affinity of isoprenaline and BRL37344. Following receptor activation by beta(2)-AR agonists, cAMP accumulation, GLUT4 translocation, [H-3]-2-deoxyglucose uptake, and beta(2)-AR internalization were measured. Bioluminescence resonance energy transfer was used to investigate interactions between beta(2)-AR and beta-arrestin2 or between beta(2)-AR and GRK2. Glucose uptake after siRNA knockdown or GRK inhibitors was measured in response to beta(2)-AR agonists. BRL37344 was a poor partial agonist for cAMP generation but displayed similar potency and efficacy to isoprenaline for glucose uptake and GLUT4 translocation. These responses to beta(2)-AR agonists occurred in CHO-GLUT4myc cells expressing beta(2)-ARs lacking GRK or GRK/PKA phosphorylation sites as well as in cells expressing the wild-type beta(2)-AR. However, beta(2)-ARs lacking phosphorylation sites failed to recruit beta-arrestin2 and did not internalize. GRK2 knock-down or GRK2 inhibitors decreased isoprenaline-stimulated glucose uptake in rat L6 skeletal muscle cells. Thus, GRK phosphorylation of the beta(2)-AR is not associated with isoprenaline- or BRL37344-stimulated glucose uptake. However, GRKs acting as scaffold proteins are important for glucose uptake as GRK2 knock-down or GRK2 inhibition reduces isoprenaline-stimulated glucose uptake.
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| 4. |
- Mukaida, Saori, et al.
(författare)
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Adrenoceptors promote glucose uptake into adipocytes and muscle by an insulin-independent signaling pathway involving mechanistic target of rapamycin complex 2
- 2017
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Ingår i: Pharmacological Research. - : Elsevier BV. - 1043-6618 .- 1096-1186. ; 116, s. 87-92
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Tidskriftsartikel (refereegranskat)abstract
- Uptake of glucose into skeletal muscle and adipose tissue plays a vital role in metabolism and energy balance. Insulin released from beta-islet cells of the pancreas promotes glucose uptake in these target tissues by stimulating translocation of CLUT4 transporters to the cell surface. This process is complex, involving signaling proteins including the mechanistic (or mammalian) target of rapamycin (mTOR) and Akt that intersect with multiple pathways controlling cell survival, growth and proliferation. mTOR exists in two forms, mTOR complex 1 (mTORC1), and mTOR complex 2 (mTORC2). mTORC1 has been intensively studied, acting as a key regulator of protein and lipid synthesis that integrates cellular nutrient availability and energy balance. Studies on mTORC2 have focused largely on its capacity to activate Akt by phosphorylation at Ser473, however recent findings demonstrate a novel role for mTORC2 in cellular glucose uptake. For example, agonists acting at beta(2)-adrenoceptors (ARs) in skeletal muscle or beta(3)-ARs in brown adipose tissue increase glucose uptake in vitro and in vivo via mechanisms dependent on mTORC2 but not Akt. In this review, we will focus on the signaling pathways downstream of beta-ARs that promote glucose uptake in skeletal muscle and brown adipocytes, and will highlight how the insulin and adrenergic pathways converge and interact in these cells. The identification of insulin-independent mechanisms that promote glucose uptake should facilitate novel treatment strategies for metabolic disease.
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| 5. |
- Mukaida, Saori, et al.
(författare)
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BRL37344 stimulates GLUT4 translocation and glucose uptake in skeletal muscle via beta(2)-adrenoceptors without causing classical receptor desensitization
- 2019
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Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 316:5, s. R666-R677
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Tidskriftsartikel (refereegranskat)abstract
- The type 2 diabetes epidemic makes it important to find insulinin-dependent ways to improve glucose homeostasis. This study examines the mechanisms activated by a dual beta(2)-/beta(3)-adrenoceptor agonist, BRL37344, to increase glucose uptake in skeletal muscle and its effects on glucose homeostasis in vivo. We measured the effect of BRL37344 on glucose uptake, glucose transporter 4 (GLUT4) translocation, cAMP levels, beta(2)-adrenoceptor desensitization, beta-arrestin recruitment, Akt, AMPK, and mammalian target of rapamycin (mTOR) phosphorylation using L6 skeletal muscle cells as a model. We further tested the ability of BRL37344 to modulate skeletal muscle glucose metabolism in animal models (glucose tolerance tests and in vivo and ex vivo skeletal muscle glucose uptake). In L6 cells, BRL37344 increased GLUT4 translocation and glucose uptake only by activation of beta(2)-adrenoceptors, with a similar potency and efficacy to that of the nonselective beta-adrenoceptor agonist isoprenaline, despite being a partial agonist with respect to cAMP generation. GLUT4 translocation occurred independently of Akt and AMPK phosphorylation but was dependent on mTORC2. Furthermore, in contrast to isoprenaline, BRL37344 did not promote agonist-mediated desensitization and failed to recruit beta-arrestin1/2 to the beta(2)-adrenoceptor. In conclusion, BRL37344 improved glucose tolerance and increased glucose uptake into skeletal muscle in vivo and ex vivo through a beta(2)-adrenoceptor-mediated mechanism independently of Akt. BRL37344 was a partial agonist with respect to cAMP, but a full agonist for glucose uptake, and importantly did not cause classical receptor desensitization or internalization of the receptor.
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| 6. |
- Sato, Masaaki, et al.
(författare)
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alpha(1A)-Adrenoceptors activate mTOR signalling and glucose uptake in cardiomyocytes
- 2018
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Ingår i: Biochemical Pharmacology. - : Elsevier BV. - 0006-2952 .- 1356-1839. ; 148, s. 27-40
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of G protein-coupled receptors to modulate mechanistic target of rapamycin (mTOR) activity is a newly emerging paradigm with the potential to link cell surface receptors with cell survival. Cardiomyocyte viability is linked to signalling pathways involving Akt and mTOR, as well as increased glucose uptake and utilization. Our aim was to determine whether the am-adrenoceptor (AR) couples to these protective pathways, and increased glucose uptake. We characterised alpha(1A)-AR signalling in CHO-K1 cells co-expressing the human alpha(1A)-AR and GLUT4 (CHO alpha(1A)GLUT4myc) and in neonatal rat ventricular cardiomyocytes (NRVM), and measured glucose uptake, intracellular Ga2* mobilization, and phosphorylation of mTOR, Akt, 5' adenosine monophosphate-activated kinase (AMPK) and S6 ribosomal protein (S6rp). In both systems, noradrenaline and the alpha(1A)-AR selective agonist A61603 stimulated glucose uptake by parallel pathways involving mTOR and AMPK, whereas another alpha(1A)-AR agonist oxymetazoline increased glucose uptake predominantly by mTOR. All agonists promoted phosphorylation of mTOR at Ser2448 and Ser2481, indicating activation of both mTORC1 and mTORC2, but did not increase Akt phosphorylation. In CHO alpha(1A)GLUT4myc cells, siRNA directed against rictor but not raptor suppressed alpha(1A)-AR mediated glucose uptake. We have thus identified mTORC2 as a key component in glucose uptake stimulated by alpha(1A)-AR agonists. Our findings identify a novel link between the alpha(1A)-AR, mTORC2 and glucose uptake, that have been implicated separately in cardiomyocyte survival. Our studies provide an improved framework for examining the utility of alpha(1A)-AR selective agonists as tools in the treatment of cardiac dysfunction.
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