“Activating brown adipose tissue (BAT) could provide a potential approach for the treatment of obesity and metabolic disease in humans.
Obesity is associated with up-regulation of the endocannabinoid system, and blocking the cannabinoid type 1 receptor (CB1R) has been shown to cause weight loss and decrease cardiometabolic risk factors. These effects may partly be mediated 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 (PET) radioligand [18F]FMPEP-d2 , and in parallel measured BAT activation with the glucose analogue [18F]FDG. Activation by cold exposure markedly increased CB1R density and glucose uptake in BAT of lean men. Similarly, β3-receptor agonism increased CB1R density in 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 CB1R provide a novel therapeutic target for BAT activation in humans.”
“Cannabinoid 1 receptors (CB1Rs) are expressed in peripheral tissues, including islets of Langerhans, where their function(s) is under scrutiny. Using mouse β-cell lines, human islets and CB1R-null (CB1R-/- ) mice, we have now investigated the role of CB1Rs in modulating β-cell function and glucose responsiveness. Synthetic CB1R agonists diminished GLP-1-mediated cAMP accumulation and insulin secretion as well as glucose-stimulated insulin secretion in mouse β-cell lines and human islets. In addition, silencing CB1R in mouse β cells resulted in an increased expression of pro-insulin, glucokinase (GCK) and glucose transporter 2 (GLUT2), but this increase was lost in β cells lacking insulin receptor. Furthermore, CB1R-/- mice had increased pro-insulin, GCK and GLUT2 expression in β cells. Our results suggest that CB1R signalling in pancreatic islets may be harnessed to improve β-cell glucose responsiveness and preserve their function. Thus, our findings further support that blocking peripheral CB1Rs would be beneficial to β-cell function in type 2 diabetes.”
“Endocannabinoids (ECs) are involved in immunomodulation, neuroprotection and control of inflammation in the central nervous system (CNS).
Activation of cannabinoid type 2 receptors (CB2) is known to diminish the release of pro-inflammatory factors and enhance the secretion of anti-inflammatory cytokines.
Furthermore, the endocannabinoid 2-arachidonoyl glycerol (2-AG) has been proved to induce the migration of eosinophils in a CB2 receptor-dependent manner in peripheral blood and activate neutrophils independent of CB activation in humans.
The present study revealed an upregulated endocannabinoid system in dogs with inflammatory CNS diseases, highlighting the endocannabinoid system as a potential target for treatment of inflammatory CNS diseases.”
“Endocannabinoids (eCBs) are internal lipid mediators recognized by the cannabinoid-1 and -2 receptors (CB1R and CB2R, respectively), which also mediate the different physiological effects of marijuana. The endocannabinoid system, consisting of eCBs, their receptors, and the enzymes involved in their biosynthesis and degradation, is present in a vast number of peripheral organs. In this review we describe the role of the eCB/CB1R system in modulating the metabolism in several peripheral organs. We assess how eCBs, via activating the CB1R, contribute to obesity and regulate food intake. In addition, we describe their roles in modulating liver and kidney functions, as well as bone remodeling and mass. Special importance is given to emphasizing the efficacy of the recently developed peripherally restricted CB1R antagonists, which were pre-clinically tested in the management of energy homeostasis, and in ameliorating both obesity- and diabetes-induced metabolic complications.”
“An antagonist of central cannabinoid CB1 receptors rimonabant causes weight loss in patients with obesity and metabolic syndrome, improves blood lipid parameters, increases the adiponectin level, decreases the rate of glucose and glycosylated hemoglobin in patients with diabetes mellitus type-2. However, rimonabant adverse effects include depression, anxiety, nausea, and dizziness which are apparently due to the blockade of central CB1 receptors.
In mice with a high-calorie diet, we defined that the blockade of peripheral CB1 receptors prevents obesity, steatosis of the liver, improves lipid and carbohydrate metabolism. Experimental studies suggest that peripheral CB2 receptor agonists have antiatherogenic effect. To validate the expediency of clinical research of CB2 receptor agonists in patients with atherosclerosis the comparative analysis of antiatherogenic properties of cannabinoids should be performed. In addition, experiments are needed on the combination use of cannabinoids with well-known antiatherogenic agents, such as statins.”
“Although the number of individuals suffering from stroke in the United States and worldwide will continue to grow, therapeutic intervention for treatment following stroke remains frustratingly limited.
Both the cannabinoid 1 receptor (CB1R) and the cannabinoid 2 receptor (CB2R) have been studied in relationship to stroke. Deletion of the CB2R has been shown to worsen outcome, while selective CB2R agonists have been demonstrated to be neuroprotective following stroke.
We tested the hypothesis that CB1/CB2 receptor double knockout would produce significant increases in infarct size and volume and significant worsening in clinical score, using two mouse models, one of permanent ischemia and one of ischemia/reperfusion.
The results surprisingly revealed that CB1/CB2 double knockout mice showed improved outcomes, with the most improvements in the mouse model of permanent ischemia.
Although initial studies of CB1R knockout mice demonstrated increased injury following stroke, indicating that activation of the CB1R was neuroprotective, later studies of selective antagonists of the CB1R also demonstrated a protective effect.
Surprisingly the double knockout animals had improved outcome.
Since the phenotype of the double knockout is not dramatically changed, significant changes in the contribution of other homeostatic pathways in compensation for the loss of these two important receptors may explain these apparently contradictory results.”
“This study investigated the effect of rimonabant, a cannabinoid receptor type 1 (CB1) antagonist, on calcium/calmodulin dependent protein kinase II (CaMKII) and CB1 in chronic intermittent hypoxia (CIH).
“The clinical development of the first generation of globally active cannabinoid 1 receptor (CB1R) antagonists was suspended because of their adverse neuropsychiatric effects. Selective blockade of peripheral CB1Rs has the potential to provide a viable strategy for the treatment of severe obesity while avoiding these central nervous system side effects.
In the current study, a novel compound (TXX-522) was rationally designed based on the parent nucleus of a classical CB1R-selective antagonist/inverse agonist, rimonabant (SR141716A).
TXX-522 showed good binding, CB1R-selectivity (over the CB2R), and functional antagonist activities in a range of in vitro molecular and cellular assays.
In vivo analysis of the steady state distribution of TXX-522 in the rat brain and blood tissues and the assay of its functional effects on CB1R activity collectively showed that TXX-522 showed minimal brain penetration. Moreover, the in vivo pharmacodynamic study further revealed that TXX-522 had good oral bioavailability and a potent anti-obesity effect, and ameliorated insulin resistance in high-fat diet-induced obese mice. No impact on food intake was observed in this model, confirming the limited brain penetration of this compound.
Thus, the current study indicates that TXX-522 is a novel and potent peripherally acting selective CB1R antagonist with the potential to control obesity and related metabolic disorders.”
“CB1 and GPR55 are GPCRs expressed by islet β-cells. Pharmacological compounds have been used to investigate their function, but off-target effects of ligands have been reported.
This study examined the effects of Abn-CBD (GPR55 agonist) and LH-21 (CB1 antagonist) on human and mouse islet function, and islets from GPR55-/- mice were used to determine signalling via GPR55.
Abn-CBD potentiated glucose-stimulated insulin secretion and elevated [Ca2+ ]i in human islets and islets from both GPR55+/+ and GPR55-/- mice. LH-21 also increased insulin secretion and [Ca2+ ]i in human islets and GPR55+/+ mouse islets, but concentrations of LH-21 up to 0.1 μM were ineffective in islets from GPR55-/- mice. Neither ligand affected basal insulin secretion or islet cAMP levels. Abn-CBD and LH-21 reduced cytokine-induced apoptosis in human islets and GPR55+/+ mouse islets, and these effects were suppressed following GPR55 deletion. They also increased β-cell proliferation: the effects of Abn-CBD were preserved in islets from GPR55-/- mice, while those of LH-21 were abolished. Abn-CBD and LH-21 increased AKT phosphorylation in mouse and human islets.
This study demonstrated that Abn-CBD and LH-21 improve human and mouse islet β-cell function and viability. Use of islets from GPR55-/- mice suggests that designation of Abn-CBD and LH-21 as GPR55 agonist and CB1 antagonist, should be revised.”