Tag Archives: antagonists

The endocannabinoid system in obesity and type 2 diabetes.

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“Endocannabinoids (ECs) are defined as endogenous agonists of cannabinoid receptors type 1 and 2 (CB1 and CB2). ECs, EC anabolic and catabolic enzymes and cannabinoid receptors constitute the EC signalling system. This system participates in the control of lipid and glucose metabolism at several levels, with the possible endpoint of the accumulation of energy as fat.

Following unbalanced energy intake, however, the EC system becomes dysregulated, and in most cases overactive, in several organs participating in energy homeostasis, particularly, in intra-abdominal adipose tissue. This dysregulation might contribute to excessive visceral fat accumulation and reduced adiponectin release from this tissue, and to the onset of several cardiometabolic risk factors that are associated with obesity and type 2 diabetes.

This phenomenon might form the basis of the mechanism of action of CB1 antagonists/inverse agonists, recently developed by several pharmaceutical companies as adjuvants to lifestyle modification for weight reduction, glycaemic control and dyslipidaemia in obese and type 2 diabetes patients.

It also helps to explain why some of the beneficial actions of these new therapeutics appear to be partly independent from weight loss.”

http://www.ncbi.nlm.nih.gov/pubmed/18563385

http://www.thctotalhealthcare.com/category/obesity-2/

http://www.thctotalhealthcare.com/category/diabetes/

The endocannabinoid system: a promising target for the management of type 2 diabetes.

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“Type 2 diabetes is closely related to abdominal obesity and is generally associated with other cardiometabolic risk factors, resulting in a high incidence of cardiovascular complications.

Several animal and human observations suggest that the endocannabinoid (EC) system is overactivated in presence of abdominal obesity and/or diabetes, and contributes to disturbances of energy balance and metabolism.

Not only it regulates the intake of nutrients through central mechanisms located within the hypothalamus and limbic area, but it also intervenes in transport, metabolism and deposit of the nutrients in the digestive tract, liver, adipose tissue, skeletal muscle, and possibly pancreas.

Activation of both central and peripheral CB1 receptors promotes weight gain and associated metabolic changes. Conversely, rimonabant, the first selective CB(1) receptor antagonist in clinical use, has been shown to reduce body weight, waist circumference, triglycerides, blood pressure, insulin resistance and C-reactive protein levels, and to increase HDL cholesterol and adiponectin concentrations in both non-diabetic and diabetic overweight/obese patients.

Rimonabant was generally well-tolerated, but with a slightly higher incidence of depressed mood disorders, anxiety, nausea and dizziness compared to placebo. New trials are supposed to confirm the potential role of rimonabant (and other CB1 neutral antagonists or inverse agonists) in overweight/obese patients with type 2 diabetes and high risk cardiovascular disease.”

Attenuation of morphine antinociceptive tolerance by cannabinoid CB1 and CB2 receptor antagonists.

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“Cannabinoid CB1 and CB2 receptor antagonists may be useful for their potential to increase or prolong opioid analgesia while attenuating the development of opioid tolerance.

The aim of this study was to investigate the effects of AM251 (a selective CB1 antagonist) and JTE907 (a selective CB2 antagonist) on morphine analgesia and tolerance in rats…

In conclusion, we observed that co-injection of AM251 and JTE907 with morphine attenuated expression of tolerance to morphine analgesic effects and decreased the morphine analgesia.”

http://www.ncbi.nlm.nih.gov/pubmed/25894754

Cannabinoids Inhibit T-cells via Cannabinoid Receptor 2 in an in vitro Assay for Graft Rejection, the Mixed Lymphocyte Reaction

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“Cannabinoids are known to have anti-inflammatory and immunomodulatory properties.

Cannabinoid receptor 2 (CB2) is expressed mainly on leukocytes and is the receptor implicated in mediating many of the effects of cannabinoids on immune processes.

This study tested the capacity of Δ9-tetrahydrocannabinol (Δ9-THC) and of two CB2-selective agonists to inhibit the murine Mixed Lymphocyte Reaction (MLR), an in vitro correlate of graft rejection following skin and organ transplantation. Both CB2-selective agonists and Δ9-THC significantly suppressed the MLR in a dose dependent fashion…

Together, these data support the potential of this class of compounds as useful therapies to prolong graft survival in transplant patients.

Cannabinoids were reported to have effects on immune responses as early as the 1970s, but the basis for this activity was not understood until the cannabinoid receptors were cloned

Ideally, the anatomically disparate expression of CB1 and CB2 would allow for the use of compounds selective for CB2, and thus eliminate the unwanted psychoactive effects from CB1 activation, while maintaining the anti-inflammatory and immunosuppressive properties.

CB2-selective cannabinoids have been proposed as possible candidates to block graft rejection.

The results presented in this paper show that Δ9-THC, a mixed CB1/CB2 agonist, and two CB2-selective agonists can inhibit the Mixed Lymphocyte Reaction (MLR), an in vitro correlate of organ and skin graft rejection.”

 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864984/

The role of cannabinoids and leptin in neurological diseases.

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“Cannabinoids exert a neuroprotective influence on some neurological diseases, including Alzheimer’s, Parkinson’s, Huntington’s, multiple sclerosis and epilepsy.

Synthetic cannabinoid receptor agonists/antagonists or compounds can provide symptom relief or control the progression of neurological diseases. However, the molecular mechanism and the effectiveness of these agents in controlling the progression of most of these diseases remain unclear.

Cannabinoids may exert effects via a number of mechanisms and interactions with neurotransmitters, neurotropic factors and neuropeptides.

Leptin is a peptide hormone involved in the regulation of food intake and energy balance via its actions on specific hypothalamic nuclei. Leptin receptors are widely expressed throughout the brain, especially in the hippocampus, basal ganglia, cortex and cerebellum. Leptin has also shown neuroprotective properties in a number of neurological disorders, such as Parkinson’s and Alzheimer’s.

Therefore, cannabinoid and leptin hold therapeutic potential for neurological diseases.

Further elucidation of the molecular mechanisms underlying the effects on these agents may lead to the development of new therapeutic strategies for the treatment of neurological disorders.”

A role for GPR55 in human placental venous endothelial cells.

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“Endocannabinoids and their G protein-coupled receptors have been suggested to play a key role in human pregnancy, by regulating important aspects such as implantation, decidualization, placentation and labor.

G protein-coupled receptor 55 (GPR55) was previously postulated to be another cannabinoid receptor, since specific cannabinoids were shown to act independently of the classical cannabinoid receptors CB1 or CB2.

Current knowledge about GPR55 expression and function in human placenta is very limited and motivated us to evaluate human placental GPR55 expression in relation to other human peripheral tissues and to analyze spatiotemporal GPR55 expression in human placenta.

Gene expression analysis revealed low GPR55 levels in human placenta, when compared to spleen and lung, the organs showing highest GPR55 expression.

Moreover, expression analysis showed 5.8 fold increased placental GPR55 expression at term compared to first trimester. Immunohistochemistry located GPR55 solely at the fetal endothelium of first trimester and term placentas. qPCR and immunocytochemistry consistently confirmed GPR55 expression in isolated primary placental arterial and venous endothelial cells. Incubation with L-α-lysophosphatidylinositol (LPI), the specific and functional ligand for GPR55, at a concentration of 1 µM, significantly enhanced migration of venous, but not arterial endothelial cells.

LPI-enhanced migration was inhibited by the GPR55 antagonist O-1918, suggesting a role of the LPI-GPR55 axis in placental venous endothelium function.”

Minireview: From the Bench, Toward the Clinic: Therapeutic Opportunities for Cannabinoid Receptor Modulation.

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The effects of cannabinoids have been known for centuries and over the past several decades two G-protein coupled receptors, CB1 and CB2, have been identified that are responsible for their activity.

Endogenous lipid-derived cannabinergic agents have been found, biosynthetic and catabolic machinery characterized, and synthetic agents have been designed to modulate these receptors.

Selective agents including agonists, antagonists, inverse agonists and novel allosteric modulators targeting either CB1 or CB2 have been developed to inhibit or augment their basal tone.

As a result, the role these receptors play in human physiology and their potential therapeutic applications in disease states are being elucidated.

The CB1 receptor while ubiquitous is densely expressed in the brain and CB2 is largely found on cells of immune origin.

This minireview highlights the role of CB1 in excitotoxic assaults in the brain and its potential to limit addiction liability.

In addition, it will examine the relationship between receptor activity and stimulation of insulin release from pancreatic β-cells, insulin resistance and feeding behavior leading toward obesity.

The role of CB2 in the neuropathology of amyotrophic lateral sclerosis and in the central manifestations of chronic HIV infection potentially converges at inflammatory cell activation thereby providing an opportunity for intervention.

Lastly, CB2 modulation is discussed in the context of an experimental model of post-menopausal osteoporosis.

Achieving exquisite receptor selectivity and elucidating the mechanisms underlying receptor inhibition and activation will be essential for the development of the next generation of cannabinergic-based therapeutic agents.”

Role of the endogenous cannabinoid system in nicotine addiction: novel insights.

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“Several lines of evidence have shown that the endogenous cannabinoids are implicated in several neuropsychiatric diseases. Notably, preclinical and human clinical studies have shown a pivotal role of the cannabinoid system in nicotine addiction.

The CB1 receptor inverse agonist/antagonist rimonabant (also known as SR141716) was effective to decrease nicotine-taking and nicotine-seeking in rodents, as well as the elevation of dopamine induced by nicotine in brain reward area. Rimonabant has been shown to improve the ability of smokers to quit smoking in randomized clinical trials. However, rimonabant was removed from the market due to increased risk of psychiatric side-effects observed in humans.

Recently, other components of the endogenous cannabinoid system have been explored. Here, we present the recent advances on the understanding of the role of the different components of the cannabinoid system on nicotine’s effects.

Those recent findings suggest possible alternative ways of modulating the cannabinoid system that could have implication for nicotine dependence treatment.”

http://www.ncbi.nlm.nih.gov/pubmed/25859226

http://www.thctotalhealthcare.com/category/addiction/

Chronic administration with AM251 improves albuminuria and renal tubular structure in obese rats.

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“Modulation of the endocannabinoid system as an anti-obesity therapeutic is well established, however the direct effects of CB1 antagonism on renal function and structure in a model of diet-induced obesity (DIO) are unknown. The aim of this study was to characterise the renal effects of the CB1 antagonist AM251 in a model of DIO.

Antagonism of CB1 with AM251 significantly reduced weight gain, systolic blood pressure, plasma leptin, and reduced albuminuria and plasma creatinine levels in obese rats.

Importantly, there was a significant reduction in tubular cross-section diameter in the obese rats treated with AM251. An improvement in albuminuria was likely due to the reduction in tubular size, reduced leptinemia and maintenance of megalin expression levels. In obese rats, AM251 did not alter diastolic blood pressure, sodium excretion, creatinine clearance or expression of the fibrotic proteins VEGF, TGFb1 and collagen IV in the kidney.

This study demonstrates that treatment with CB1 antagonist AM251 improves renal outcomes in obese rats.”

http://www.ncbi.nlm.nih.gov/pubmed/25804605

“Alexandros Makriyannis is a professor in the Department of Medicinal Chemistry at Northeastern University, where his research group has synthesized many new compounds with cannabinoid activity… AM-251 — an inverse agonist at the CB1 cannabinoid receptor that is structurally related to SR141716A (rimonabant), but has a higher binding affinity with a Ki value of 7.5nM.”  http://en.wikipedia.org/wiki/List_of_AM_cannabinoids

A PET study comparing receptor occupancy by five selective cannabinoid 1 receptor antagonists in non-human primates.

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“There is a medical need for safe and efficacious anti-obesity drugs with acceptable side effect profiles. To mitigate the challenge posed by translating target interaction across species and balancing beneficial vs. adverse effects, a positron emission tomography (PET) approach could help guide clinical dose optimization. Thus, as part of a compound differentiation effort, three novel selective CB1 receptor (CB1R) antagonists, developed by AstraZeneca (AZ) for the treatment of obesity, were compared with two clinically tested reference compounds, rimonabant and taranabant, with regard to receptor occupancy relative to dose and exposure. A total of 42 PET measurements were performed in 6 non-human primates using the novel CB1R antagonist radioligand [11C]SD5024. The AZ CB1R antagonists bound in a saturable manner to brain CB1R with in vivo affinities similar to that of rimonabant and taranabant, compounds with proven weight loss efficacy in clinical trials. Interestingly, it was found that exposures corresponding to those needed for optimal clinical efficacy of rimonabant and taranabant resulted in a CB1R occupancy typically around ∼20-30%, thus much lower than what would be expected for classical G-protein coupled receptor (GPCR) antagonists in other therapeutic contexts. These findings are also discussed in relation to emerging literature on the potential usefulness of ‘neutral’ vs. ‘classical’ CB1R (inverse agonist) antagonists. The study additionally highlighted the usefulness of the radioligand [11C]SD5024 as a specific tracer for CB1R in the primate brain, though an arterial input function would ideally be required in future studies to further assure accurate quantitative analysis of specific binding.”

http://www.ncbi.nlm.nih.gov/pubmed/25791528