Cannabinoid Type 1 Receptors Are Upregulated During Acute Activation of Brown Adipose Tissue

Activating brown adipose tissue (BAT) could provide a potential approach for the treatment of obesity and metabolic disease in humans. Obesity is associated with upregulation of the endocannabinoid system, and blocking the cannabinoid type 1 receptor (CB1R) has been shown to cause weight loss and to decrease cardiometabolic risk factors. These effects may be mediated partly via increased BAT metabolism, since there is evidence that CB1R antagonism activates BAT in rodents. To investigate the significance of CB1R in BAT function, we quantified the density of CB1R in human and rodent BAT using the positron emission tomography radioligand [F-18]FMPEP-d(2) and measured BAT activation in parallel with the glucose analog [F-18]fluorodeoxyglucose. Activation by cold exposure markedly increased CB1R density and glucose uptake in the BAT of lean men. Similarly, 3-receptor agonism increased CB1R density in the BAT of rats. In contrast, overweight men with reduced BAT activity exhibited decreased CB1R in BAT, reflecting impaired endocannabinoid regulation. Image-guided biopsies confirmed CB1R mRNA expression in human BAT. Furthermore, CB1R blockade increased glucose uptake and lipolysis of brown adipocytes. Our results highlight that CB1Rs are significant for human BAT activity, and the CB1Rs provide a novel therapeutic target for BAT activation in humans

Adenosine/A2B receptor signaling ameliorates the effects of ageing and counteracts obesity

The combination of aging populations with the obesity pandemic results in an alarming rise in non-communicable diseases. Here, we show that the enigmatic adenosine A2B receptor (A2B) is abundantly expressed in skeletal muscle (SKM) as well as brown adipose tissue (BAT) and might be targeted to counteract age-related muscle atrophy (sarcopenia) as well as obesity. Mice with SKM-specific deletion of A2B exhibited sarcopenia, diminished muscle strength, and reduced energy expenditure (EE), whereas pharmacological A2B activation counteracted these processes. Adipose tissue-specific ablation of A2B exacerbated age-related processes and reduced BAT EE, whereas A2B stimulation ameliorated obesity. In humans, A2B expression correlated with EE in SKM, BAT activity, and abundance of thermogenic adipocytes in white fat. Moreover, A2B agonist treatment increased EE from human adipocytes, myocytes, and muscle explants. Mechanistically, A2B forms heterodimers required for adenosine signaling. Overall, adenosine/A2B signaling links muscle and BAT and has both anti-aging and anti-obesity potential

Lipolysis drives expression of the constitutively active receptor GPR3 to induce adipose thermogenesis

Thermogenic adipocytes possess a therapeutically appealing, energy-expending capacity, which is canonically cold-induced by ligand-dependent activation of β-adrenergic G protein-coupled receptors (GPCRs). Here, we uncover an alternate paradigm of GPCR-mediated adipose thermogenesis through the constitutively active receptor, GPR3. We show that the N terminus of GPR3 confers intrinsic signaling activity, resulting in continuous Gs-coupling and cAMP production without an exogenous ligand. Thus, transcriptional induction of Gpr3 represents the regulatory parallel to ligand-binding of conventional GPCRs. Consequently, increasing Gpr3 expression in thermogenic adipocytes is alone sufficient to drive energy expenditure and counteract metabolic disease in mice. Gpr3 transcription is cold-stimulated by a lipolytic signal, and dietary fat potentiates GPR3-dependent thermogenesis to amplify the response to caloric excess. Moreover, we find GPR3 to be an essential, adrenergic-independent regulator of human brown adipocytes. Taken together, our findings reveal a noncanonical mechanism of GPCR control and thermogenic activation through the lipolysis-induced expression of constitutively active GPR3.ISSN:0092-8674ISSN:1097-417

Direct lentivirus injection for fast and efficient gene transfer into brown and beige adipose tissue

Brown adipose tissue is a special type of fat contributing to energy expenditure in human newborns and adults. Moreover, subcutaneous white adipose tissue has a high capacity to adapt an energy-consuming, brown-like/beige phenotype. Here, we developed an easy to handle and fast to accomplish method to efficiently transfer genes into brown and beige fat pads in vivo. Lentiviral vectors are directly injected into the target fat pad of anaesthetized mice through a small incision using a modified, small needle connected to a microsyringe, which is well suited for infiltration of adipose tissues. Expression of the target gene can be detected in brown/beige fat one week after injection. The method can be applied within minutes to efficiently deliver transgenes into subcutaneous adipose tissues. Thus, this protocol allows for studying genes of interest in a timely manner in murine brown/beige fat and could potentially lead to new gene therapies for obesity. Brown adipose tissue is a special type of fat contributing to energy expenditure in human newborns and adults. Moreover, subcutaneous white adipose tissue has a high capacity to adapt an energy-consuming, brown-like/beige phenotype. Here, we developed an easy to handle and fast to accomplish method to efficiently transfer genes into brown and beige fat pads in vivo. Lentiviral vectors are directly injected into the target fat pad of anaesthetized mice through a small incision using a modified, small needle connected to a microsyringe, which is well suited for infiltration of adipose tissues. Expression of the target gene can be detected in brown/beige fat one week after injection. The method can be applied within minutes to efficiently deliver transgenes into subcutaneous adipose tissues. Thus, this protocol allows for studying genes of interest in a timely manner in murine brown/beige fat and could potentially lead to new gene therapies for obesity

Divergent effects of a designer natriuretic peptide CD-NP in the regulation of adipose tissue and metabolism

Objective Obesity is defined as an abnormal increase in white adipose tissue (WAT) and is a major risk factor for type 2 diabetes and cardiovascular disease. Brown adipose tissue (BAT) dissipates energy and correlates with leanness. Natriuretic peptides have been shown to be beneficial for brown adipocyte differentiation and browning of WAT. Methods Here, we investigated the effects of an optimized designer natriuretic peptide (CD-NP) on murine adipose tissues in vitro and in vivo. Results In murine brown and white adipocytes, CD-NP activated cGMP production, promoted adipogenesis, and increased thermogenic markers. Consequently, mice treated for 10 days with CD-NP exhibited increased â\u80\u9cbrowningâ\u80\u9d of WAT. To study CD-NP effects on diet-induced obesity (DIO), we delivered CD-NP for 12 weeks. Although CD-NP reduced inflammation in WAT, CD-NP treated DIO mice exhibited a significant increase in body mass, worsened glucose tolerance, and hepatic steatosis. Long-term CD-NP treatment resulted in an increased expression of the NP scavenging receptor (NPR-C) and decreased lipolytic activity. Conclusions NP effects differed depending on the duration of treatment raising questions about the rational of natriuretic peptide treatment in obese patients

EBI2 is a negative modulator of brown adipose tissue energy expenditure in mice and human brown adipocytes.

Pharmacological activation of brown adipose tissue (BAT) is an attractive approach for increasing energy expenditure to counteract obesity. Given the side-effects of known activators of BAT, we studied inhibitors of BAT as a novel, alternative concept to regulate energy expenditure. We focused on G-protein-coupled receptors that are one of the major targets of clinically used drugs. Here, we identify GPR183, also known as EBI2, as the most highly expressed inhibitory G-protein-coupled receptor in BAT among the receptors examined. Activation of EBI2 using its endogenous ligand 7α,25-dihydroxycholesterol significantly decreases BAT-mediated energy expenditure in mice. In contrast, mice deficient for EBI2 show increased energy dissipation in response to cold. Interestingly, only thermogenic adipose tissue depots - BAT and subcutaneous white adipose tissue -respond to 7α,25-dihydroxycholesterol treatment/EBI2 activation but not gonadal white fat, which has the lowest thermogenic capacity. EBI2 activation in brown adipocytes significantly reduces norepinephrine-induced cAMP production, whereas pharmacological inhibition or genetic ablation of EBI2 results in an increased response. Importantly, EBI2 significantly inhibits norepinephrine-induced activation of human brown adipocytes. Our data identify the 7α,25-dihydroxycholesterol/EBI2 signaling pathway as a so far unknown BAT inhibitor. Understanding the inhibitory regulation of BAT might lead to novel pharmacological approaches to increase the activity of thermogenic adipose tissue and whole body energy expenditure in humans

A2A R‐induced transcriptional deregulation in astrocytes: An in vitro study

International audienceAdenosine A2A receptors (A2A R) are modulators of various physiological processes essential for brain homeostasis and fine synaptic tuning. In certain neurodegenerative conditions, notably Alzheimer's disease (AD), A2A Rs are pathologically upregulated in neurons but also in astrocytes. In that context, the use of A2A Rs inhibitors, normalizing impaired receptor function, is seen as a potential therapeutic strategy. However, the impact of A2A R alterations, particularly in astrocytes, is not fully understood. Here, we investigated the effect of A2A R overexpression on transcriptional deregulation in primary astrocytic cultures. By performing whole transcriptome analysis, we found that A2A R overexpression promotes robust transcriptional changes, mostly affecting immune response, angiogenesis, and cell activation-related genes. Importantly, we observed that treatment with SCH58261, a selective A2A R antagonist, restored the expression levels of several inflammatory and astrocytic activation-related genes, such as Interleukin-1beta and vimentin. This supports the notion that A2A R blockade could restore some astrocytic dysfunctions associated with abnormal A2A R expression, further arguing for a potential beneficial impact of receptor antagonists in A2A R-induced transcriptional deregulation, inflammation, and astrogliosis. Overall, our findings provide novel insights into the putative impact of A2A R overexpression on transcriptional deregulation in astrocytes, thereby opening novel avenues for the use of A2A R antagonists as potential therapeutic strategy in neurodegenerative diseases

The Gq signalling pathway inhibits brown and beige adipose tissue.

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 Gq family, and inhibition of Gq signalling enhances differentiation of human and murine brown adipocytes. In contrast, activation of Gq signalling abrogates brown adipogenesis. We further identify the endothelin/Ednra pathway as an autocrine activator of Gq signalling in brown adipocytes. Expression of a constitutively active Gq 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 Gq in human WAT inversely correlates with UCP1 expression. Thus, our data indicate that Gq signalling regulates brown/beige adipocytes and inhibition of Gq signalling may be a novel therapeutic approach to combat obesity