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- Klepac, K., et al.
(author)
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The G(q) signalling pathway inhibits brown and beige adipose tissue
- 2016
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Journal article (peer-reviewed)abstract
- Brown adipose tissue (BAT) dissipates nutritional energy as heat via the uncoupling protein-1 (UCP1) and BAT activity correlates with leanness in human adults. Here we profile G protein-coupled receptors (GPCRs) in brown adipocytes to identify druggable regulators of BAT. Twenty-one per cent of the GPCRs link to the G(q) family, and inhibition of G(q) signalling enhances differentiation of human and murine brown adipocytes. In contrast, activation of G(q) signalling abrogates brown adipogenesis. We further identify the endothelin/Ednra pathway as an autocrine activator of G(q) signalling in brown adipocytes. Expression of a constitutively active G(q) protein in mice reduces UCP1 expression in BAT, whole-body energy expenditure and the number of brown-like/beige cells in white adipose tissue (WAT). Furthermore, expression of G(q) in human WAT inversely correlates with UCP1 expression. Thus, our data indicate that G(q) signalling regulates brown/beige adipocytes and inhibition of G(q) signalling may be a novel therapeutic approach to combat obesity.
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2. |
- Gnad, T., et al.
(author)
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Adenosine activates brown adipose tissue and recruits beige adipocytes via A(2A) receptors
- 2014
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 516:7531
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Journal article (peer-reviewed)abstract
- Brown adipose tissue (BAT) is specialized in energy expenditure, making it a potential target for anti-obesity therapies(1-5). Following exposure to cold, BAT is activated by the sympathetic nervous system with concomitant release of catecholamines and activation of beta-adrenergic receptors(1-5). Because BAT therapies based on cold exposureor beta-adrenergic agonists are clinically not feasible, alternative strategies must be explored. Purinergic co-transmission might be involved in sympathetic control of BAT and previous studies reported inhibitory effects of the purinergic transmitter adenosine in BAT from hamster or rat(6-8). However, the role of adenosine in human BAT is unknown. Here we show that adenosine activates human and murine brown adipocytes at low nanomolar concentrations. Adenosine is released in BAT during stimulation of sympathetic nerves as well as from brown adipocytes. The adenosine A(2A) receptor is the most abundant adenosine receptor in human and murine BAT. Pharmacological blockade or genetic loss of A(2A) receptors in mice causes adecrease in BAT-dependent thermogenesis, whereas treatment with A(2A) agonists significantly increases energy expenditure. Moreover, pharmacological stimulation of A(2A) receptors or injection of lentiviral vectors expressing the A(2A) receptor into white fat induces brown-like cells-so-called beige adipocytes. Importantly, mice fed a high-fat diet and treated with an A(2A) agonist are leaner with improved glucose tolerance. Taken together, our results demonstrate that adenosine-A(2A) signalling plays an unexpected physiological role in sympathetic BAT activation and protects mice from diet-induced obesity. Those findings reveal new possibilities for developing novel obesity therapies.
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