Regulation, function, and dysregulation of endocannabinoids in models of adipose and beta-pancreatic cells and in obesity and hyperglycemia

Abnormalities in glucose metabolism in patients with schizophrenia treated with atypical antipsychotic medications

The incidence of carbohydrate intolerance and overt diabetes is increased in patients with schizophrenia treated with the newer atypical antipsychotic agents. The precise mechanism for these abnormalities remains obscure. This review examines the potential interaction between atypical antipsychotic medications and several hormones known to influence appetite regulation and carbohydrate metabolism.

Efficacy and safety of rimonabant for improvement of multiple cardiometabolic risk factors in overweight/obese patients: pooled 1-year data from the Rimonabant in Obesity (RIO) program

OBJECTIVE

To better define the efficacy and safety of rimonabant, the first selective cannabinoid type 1 (CB(1)) receptor antagonist, in a large population of overweight and obese patients using pooled efficacy data from three Phase III nondiabetes Rimonabant in Obesity and Related Metabolic Disorders (RIO) studies, selected efficacy data from the RIO-Diabetes study, and pooled safety data for all four RIO studies.

RESEARCH DESIGN AND METHODS

The RIO studies enrolled patients who were either overweight (BMI >27 kg/m(2)) with at least one comorbidity (i.e., hypertension, dyslipidemia, or, for RIO-Diabetes, type 2 diabetes) or obese. All patients received daily treatment with rimonabant (5 or 20 mg) or placebo for 1 year plus a hypocaloric diet (600 kcal/day deficit) and advice on increased physical activity. RIO-Europe (n = 1,508), RIO-North America (n = 3,045), and RIO-Lipids (n = 1,036) excluded patients with type 2 diabetes; untreated dyslipidemia was an entry requirement for RIO-Lipids. RIO-Diabetes (n = 1,047) required the presence of type 2 diabetes inadequately controlled by sulfonylurea or metformin monotherapy.

RESULTS

The pooled intention-to-treat population comprised 5,580 patients without diabetes (3,165 completed treatment) and 1,047 patients with diabetes (692 completed treatment). Most efficacy measures improved during the 4-week placebo run-in period, except that HDL cholesterol decreased as expected in the early phase of a hypocaloric diet. After 1 year of randomized treatment, changes from baseline with 20 mg rimonabant in the nondiabetic population were as follows: body weight -6.5 kg, waist circumference -6.4 cm, HDL cholesterol +16.4%, triglycerides -6.9%, fasting insulin -0.6 muU/ml, and homeostasis model assessment for insulin resistance (HOMA-IR) -0.2 (all P < 0.001 vs. placebo). In the diabetic population, 20 mg rimonabant reduced A1C levels by 0.6% (P < 0.001 vs. placebo). Regression analysis of change in HDL cholesterol, triglycerides, adiponectin (in RIO-Lipids), and A1C (in RIO-Diabetes) versus body weight at 1 year by ANCOVA suggested that 45-57% of the effect of rimonabant could not be explained by the observed weight loss. At 1 year, adverse events more frequently reported with rimonabant were gastrointestinal, neurological, and psychiatric in nature. Serious adverse events were infrequent and almost equivalent to placebo. Overall discontinuation rates were similar across treatment groups, except discontinuation from adverse events, which occurred more frequently with 20 mg rimonabant versus placebo (most commonly, depressive disorders [1.9 vs. 0.8%], nausea [1.4 vs. 0.1%], mood alterations with depressive symptoms [1.0 vs. 0.6%], and anxiety [1.0 vs. 0.3%]). A thorough review of psychiatric and neurological adverse events was performed.

CONCLUSIONS

In overweight/obese patients, 20 mg/day rimonabant produced weight loss and significant improvements in multiple cardiometabolic risk factors such as waist circumference, A1C, HDL cholesterol, and triglycerides. Rimonabant was generally well tolerated, with more frequently reported adverse events being gastrointestinal, neurological, and psychiatric in nature.

Endocannabinoid system overactivity and the metabolic syndrome: prospects for treatment

The endocannabinoid system (ECS) plays a physiologic role in modulating energy balance, feeding behavior, lipoprotein metabolism, insulin sensitivity, and glucose homeostasis, which when dysregulated can all contribute to cardiometabolic risk. Evidence has suggested that the ECS is overactive in human obesity and in animal models of genetic and diet-induced obesity. ECS stimulation centrally and peripherally drives metabolic processes that mimic the metabolic syndrome. These findings have led to the development of potential novel therapeutic targets, including the drug rimonabant, a selective CB1 receptor antagonist, which has been shown to promote weight loss, reduce inflammation, improve dyslipidemia, and improve glucose homeostasis.

Cost effectiveness of duloxetine in the treatment of diabetic peripheral neuropathic pain in the UK

OBJECTIVE

The objective of this analysis was to evaluate the cost-effectiveness of duloxetine when considered as an additional treatment option for UK-based patients suffering from diabetic peripheral neuropathic pain.

RESEARCH DESIGN AND METHODS

A decision-analytic model was used to represent the sequential management of patients with diabetic peripheral neuropathic pain. The standard UK treatment strategy was defined as first-line tricyclic antidepressants (amitriptyline), second-line anticonvulsants (gabapentin) and lastly an opioid-related treatment. The cost-effectiveness of duloxetine was evaluated as an additional first, second, third or fourth-line therapy over a 6-month treatment period for a cohort of 1000 patients. Treatment response was modelled based on changes from baseline pain severity using a standard 11-point pain scale (0-10); full response (>or= 50% change), partial response (30-49%) and no response (< 30%). The model was populated with efficacy and discontinuation data using indirect comparisons of treatment efficacy based on relative effects to a common placebo comparator.

RESULTS

The second-line use of duloxetine resulted in cost savings of pound 77,071 for every 1000 treated patients, with an additional 29 patients achieving a full pain response when compared to standard UK treatment. Additional quality-adjusted life years (QALYs) were achieved at 1.88 QALYs per 1000 patients.

CONCLUSIONS

This UK-based economic model suggests that second-line use of duloxetine is a beneficial and cost-effective treatment strategy for diabetic peripheral neuropathic pain.

Pitfalls in measuring the endocannabinoid 2-arachidonoyl glycerol in biological samples

BACKGROUND

The endocannabinoid 2-arachidonoyl glycerol (2-AG) undergoes spontaneous isomerization to biologically inactive 1-AG. This effect has not been adequately addressed in previous studies that reported 2-AG concentrations in biological samples.

METHODS

Liquid chromatography tandem-mass spectrometry (LC-MS/MS) was used for 1-AG and 2-AG analyses.

RESULTS

Identical collision-induced disintegration spectra were found for 1-AG and 2-AG. For specific detection of both compounds, which share a common mass transition, baseline chromatographic separation is mandatory, even when applying MS/MS technology with its generally high detection specificity. When using standard chromatographic conditions with the very short run times typically used in LC-MS/MS methods, co-elution of 2-AG with 1-AG, which is present in human serum, causes false 2-AG results.

CONCLUSIONS

Our data highlight that the analytical specificity of MS/MS can be limited by interference from isobaric isomers with identical disintegration patterns. The specificity of this technology must be carefully evaluated for each individual application.

The acyclic CB1R inverse agonist taranabant mediates weight loss by increasing energy expenditure and decreasing caloric intake

Cannabinoid 1 receptor (CB1R) inverse agonists are emerging as a potential obesity therapy. However, the physiological mechanisms by which these agents modulate human energy balance are incompletely elucidated. Here, we describe a comprehensive clinical research study of taranabant, a structurally novel acyclic CB1R inverse agonist. Positron emission tomography imaging using the selective CB1R tracer [(18)F]MK-9470 confirmed central nervous system receptor occupancy levels ( approximately 10%-40%) associated with energy balance/weight-loss effects in animals. In a 12-week weight-loss study, taranabant induced statistically significant weight loss compared to placebo in obese subjects over the entire range of evaluated doses (0.5, 2, 4, and 6 mg once per day) (p < 0.001). Taranabant treatment was associated with dose-related increased incidence of clinical adverse events, including mild to moderate gastrointestinal and psychiatric effects. Mechanism-of-action studies suggest that engagement of the CB1R by taranabant leads to weight loss by reducing food intake and increasing energy expenditure and fat oxidation.

Peripheral metabolic effects of endocannabinoids and cannabinoid receptor blockade

The endocannabinoid system consists of endogenous arachidonic acid derivates that activate cannabinoid receptors. The two most prominent endocannabinoids are anandamide and 2-arachidonoyl glycerol. In obesity, increased concentrations of circulating and tissue endocannabinoid levels have been described, suggesting increased activity of the endocannabinoid system. Increased availability of endocannabinoids in obesity may over-stimulate cannabinoid receptors. Blockade of cannabinoid type 1 (CB1) receptors was the only successful clinical development of an anti-obesity drug during the last decade. Whereas blockade of CB1 receptors acutely reduces food intake, the long-term effects on metabolic regulation are more likely mediated by peripheral actions in liver, skeletal muscle, adipose tissue, and the pancreas. Lipogenic effects of CB1 receptor signalling in liver and adipose tissue may contribute to regional adipose tissue expansion and insulin resistance in the fatty liver. The association of circulating 2-arachidonoyl glycerol levels with decreased insulin sensitivity strongly suggests further exploration of the role of endocannabinoid signalling for insulin sensitivity in skeletal muscle, liver, and adipose tissue. A few studies have suggested a specific role for the regulation of adiponectin secretion from adipocytes by endocannabinoids, but that has to be confirmed by more experiments. Also, the potential role of CB1 receptor blockade for the stimulation of energy expenditure needs to be studied in the future. Despite the current discussion of safety issues of cannabinoid receptor blockade, these findings open a new and exciting perspective on endocannabinoids as regulators of body weight and metabolism.

The endocannabinoid system: a promising novel mechanistic pathway in the cardiometabolic syndrome

The endocannabinoid system (ECS) is a neuroendocrine system that modulates several cardiometabolic processes. An overactive ECS is implicated as a significant contributor to the cardiometabolic syndrome and obesity, in addition to a large number of other physiologic processes. Endocannabinoid receptors have been detected centrally and peripherally, regulating appetite, food intake, metabolism, and storage. ECS blockade is thought to be a promising new pharmacologic modality of improving the unfavorable metabolic risk profile in patients with the cardiometabolic syndrome and obesity.

Anandamide regulates keratinocyte differentiation by inducing DNA methylation in a CB1 receptor-dependent manner

Anandamide (arachidonoylethanolamide, AEA) belongs to an important class of endogenous lipids including amides and esters of long chain polyunsaturated fatty acids, collectively termed "endocannabinoids." Recently we have shown that AEA inhibits differentiation of human keratinocytes, by binding to type-1 cannabinoid receptors (CB1R). To further characterize the molecular mechanisms responsible for this effect, we investigated the expression of epidermal differentiation-related genes after AEA treatment. We observed that keratin 1 and 10, transglutaminase 5 and involucrin are transcriptionally down-regulated by AEA. Most importantly, we found that AEA is able to decrease differentiating gene expression by increasing DNA methylation in human keratinocytes, through a p38, and to a lesser extent p42/44, mitogen-activated protein kinase-dependent pathway triggered by CB1R. An effect of AEA on DNA methylation because of CB1R-mediated increase of methyltransferase activity is described here for the first time, and we believe that the importance of this effect clearly extends beyond the regulation of skin differentiation. In fact, the modulation of DNA methylation by endocannabinoids may affect the expression of a number of genes that regulate many cell functions in response to these substances.

Rimonabant (SR141716) exerts anti-proliferative and immunomodulatory effects in human peripheral blood mononuclear cells

BACKGROUND AND PURPOSE

Rimonabant (SR141716) is the first selective cannabinoid receptor CB(1) antagonist described. Along with its anti-obesity action, emerging findings show potential anti-proliferative and anti-inflammatory action of SR141716 in several in vitro and in vivo models. In this study we have investigated the anti-proliferative and immunomodulatory effects of SR141716 in human peripheral blood mononuclear cells (PBMCs).

EXPERIMENTAL APPROACH

We have evaluated in vitro the effect of SR141716 in human PBMCs stimulated with different mitogens. Cell proliferation was assessed by (3)H-thymidine incorporation. Cell cycle, cell death and apoptosis were analysed by flow cytometry. Protein expression was investigated by Western blot.

KEY RESULTS

SR141716 significantly inhibited the proliferative response of PBMCs and this effect was accompanied by block of G(1)/S phase of the cell cycle without induction of apoptosis and cell death. SR141716 used in combination with 2-methyl-arachidonyl-2'-fluoro-ethylamide (Met-F-AEA), a stable analogue of the endogenous cannabinoid anandamide, showed synergism rather than antagonism of the inhibition of cell proliferation. The immunomodulatory effects of SR141716 were associated with increased expression of IkappaB, phosphorylated AKT (p-AKT) and decreased expression of NF-kappaB, p-IkappaB, p-ERK, COX-2 and iNOS.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest SR141716 is a novel immunomodulatory drug with anti-inflammatory properties.

The endocannabinoid system in the regulation of cardiometabolic risk factors

Obesity has increased at a striking rate over the last 3 decades in the Western world. This negative trend dramatically affects physical health and, ultimately, cardiovascular risks. In fact, particularly at the visceral level, obesity is strongly associated with an increased risk for life-threatening conditions, such as type 2 diabetes mellitus, hypertension, dyslipidemia, and cardiovascular disease. Although nutritional changes and physical activity are commonly thought of as the core treatments for obesity, it is necessary to further support obese patients with a pharmacologic approach for 2 reasons: to reduce the metabolic risk profile, and to avoid the regaining of weight. Among the various pharmacologic targets explored in recent years, the endocannabinoid (EC) system now constitutes the most promising proposal so far. In this review, after focusing on the central and peripheral signaling pathways that preserve energy homeostasis, we review the role of the EC system in regulating food's rewarding properties, controlling caloric intake by acting in hypothalamic pathways, and in modulating metabolic functions of several peripheral organs. In addition, we provide evidence that supports the recently proposed hypothesis that a close association exists between obesity and overactivation of the EC system.

Hypoadiponectinemia as a marker of adipocyte dysfunction -- Part I: the biology of adiponectin

Adiponectin is the most abundantly secreted adipocyte-derived peptide hormone, possessing an array of antidiabetogenic and cardiovascular protective effects. Acting through 2 distinct membrane receptors, adiponectin receptors 1 and 2 (which utilize 5'-adenosine monophosphate-activated protein kinase phosphorylation, p38 mitogen-activated protein kinase, and peroxisome proliferator-activated receptor alpha as key cell signaling elements), adiponectin increases hepatic and skeletal muscle sensitivity to insulin, enhances fatty acid oxidation, suppresses monocyte-endothelial interaction, supports endothelial cell growth, lowers blood pressure, and moderates adipose tissue growth. The secretion of adiponectin can be suppressed by adipose factors, which are turned on once fat cell mass increases, such as cytokines, adipose renin-angiotensin system, and increased oxidative stress. Inhibition of adiponectin secretion results in the loss of an array of mechanisms, which under normal conditions of fat cell homeostasis provide protection from insulin resistance, diabetes, and atherosclerosis.

Adrenocortical dysregulation as a major player in insulin resistance and onset of obesity

The aim of this review is to explore the dysregulation of adrenocortical secretions as a major contributor in the development of obesity and insulin resistance. Disturbance of adipose tissue physiology is one of the primary events in the development of pathologies associated with the metabolic syndrome, such as obesity and type 2 diabetes. Several studies indicate that alterations in metabolism of glucocorticoids (GC) and androgens, as well as aldosterone in excess, are involved in the emergence of metabolic syndrome. Cross talk among adipose tissue, the hypothalamo-pituitary complex, and adrenal gland activity plays a major role in the control of food intake, glucose metabolism, lipid storage, and energy balance. Perturbation of this cross talk induces alterations in the regulatory mechanisms of adrenocortical steroid synthesis, secretion, degradation, and/or recycling, at the level of the zonae glomerulosa (aldosterone), fasciculata (GC and GC metabolites), and reticularis (androgens and androgen precursors DHEA and DHEAS). As a whole, these adrenocortical perturbations contribute to the development of metabolic syndrome at both the paracrine and systemic level by favoring the physiological dysregulation of organs responsive to aldosterone, GC, and/or androgens, including adipose tissue.

The endogenous cannabinoid system stimulates glucose uptake in human fat cells via phosphatidylinositol 3-kinase and calcium-dependent mechanisms

BACKGROUND

The endogenous cannabinoid system participates in the regulation of energy balance, and its dysregulation may be implicated in the pathogenesis of obesity. Adipose tissue endocannabinoids may produce metabolic and endocrine effects, but very few data are available in human adipose tissue and in primary human fat cells.

EXPERIMENTAL DESIGN

We measured expression of type 1 and type 2 cannabinoid receptors (CNR), enzymes of cannabinoids synthesis and degradation in human omental, sc abdominal, and gluteal adipose tissue from lean and obese subjects. Furthermore, we assessed the effect of CNR1 stimulation on glucose uptake and intracellular transduction mechanisms in primary human adipocytes. Then we assessed the reciprocal regulation between CNR1 and peroxisome proliferator-activated receptor-gamma (PPARgamma). Finally, we tested whether leptin and adiponectin are regulated by CNR1 in human adipocytes.

RESULTS

We found that most genes of the endocannabinoid system are down-regulated in gluteal fat and up-regulated in visceral and sc abdominal adipose tissue of obese patients. Treatment of adipocytes with rosiglitazone markedly down-regulated CNR1 expression, whereas Win 55,212 up-regulated PPARgamma. Win 55,212 increased (+50%) glucose uptake, the translocation of glucose transporter 4, and intracellular calcium in fat cells. All these effects were inhibited by SR141716 and wortmannin and by removing extracellular calcium. Win 55,212 and SR141716 had no effect on expression of adiponectin and leptin.

CONCLUSIONS

These results indicate a role for the local endocannabinoids in the regulation of glucose metabolism in human adipocytes and suggest a role in channeling excess energy fuels to adipose tissue in obese humans.

Cannabinoid-1 receptor antagonists in type-2 diabetes

Type-2 diabetes is closely related to abdominal obesity and is generally associated with other cardiometabolic risk factors, resulting in a risk of major cardiovascular disease. Several animal and human observations suggest that the endocannabinoid system is over-active in the presence of abdominal obesity and/or diabetes. Both central and peripheral endocannabinoid actions, via the activation of CB1 receptors, promote weight gain and associated metabolic changes. Rimonabant, the first selective CB(1) receptor blocker in clinical use, has been shown to reduce body weight, waist circumference, triglycerides, blood pressure, insulin resistance index and C-reactive protein levels, and to increase high-density lipoprotein (HDL) cholesterol and adiponectin concentrations in both non-diabetic and diabetic overweight/obese patients. In addition, a 0.5-0.7% reduction in HbA1c levels was observed in metformin- or sulphonylurea-treated patients with type-2 diabetes and in drug-naïve diabetic patients. Almost half of the metabolic changes, including HbA1c reduction, could not be explained by weight loss, suggesting that there are direct peripheral effects. Rimonabant was generally well-tolerated, and the safety profile was similar in diabetic and non-diabetic patients, with a higher incidence of depressed mood disorders, nausea and dizziness. In conclusion, the potential role of rimonabant in overweight/obese patients with type-2 diabetes and at high risk of cardiovascular disease deserves much consideration.

Endocannabinoids and related N-acylethanolamines in the control of appetite and energy metabolism: emergence of new molecular players

PURPOSE OF REVIEW

Endocannabinoids (anandamide and 2-arachidonoylgycerol) and related N-acylethanolamines (N-oleoylethanolamine) exhibit opposite effects in the control of appetite. The purpose of this review is to highlight the similarities and differences of three major lipid-signaling molecules by focusing on their mode of action and the proteins involved in the control of food intake and energy metabolism.

RECENT FINDINGS

Anandamide and 2-arachidonoylglycerol promote food intake and are the main endogenous ligands of the cannabinoid receptors. One of them, the cannabinoid receptor 1, is responsible for the control of food intake and energy expenditure both at a central and a peripheral level, affecting numerous anorexigenic and orexigenic mediators (leptin, neuropeptide Y, ghrelin, orexin, endogenous opioids, corticotropin-releasing hormone, alpha-melanocyte stimulating hormone, cocaine and amphetamine-related transcript). In the gut, N-oleoylethanolamine plays an opposite role in food regulation, by interacting with two molecular targets different from the cannabinoid receptors: the nuclear receptor peroxisome proliferator-activated receptor alpha and a G-protein coupled receptor GPR119.

SUMMARY

Recent findings on the molecular mechanisms underlying the promotion of food intake or, in contrast, the suppression of food intake by anandamide and N-oleoylethanolamine, are summarized. Potential strategies for treating overweight, metabolic syndrome, and type II diabetes are briefly outlined.

A neutral CB1 receptor antagonist reduces weight gain in rat

Cannabinoid (CB)1 receptor inverse agonists inhibit food intake in animals and humans but also potentiate emesis. It is not clear whether these effects result from inverse agonist properties or from the blockade of endogenous cannabinoid signaling. Here, we examine the effect of a neutral CB1 antagonist, AM4113, on food intake, weight gain, and emesis. Neutral antagonist and binding properties were confirmed in HEK-293 cells transfected with human CB1 or CB2 receptors. AM4113 had no effect on forskolin-stimulated cAMP production at concentrations up to 630 nM. The Ki value of AM4113 (0.80 +/- 0.44 nM) in competitive binding assays with the CB1/2 agonist [3H]CP55,940 was 100-fold more selective for CB1 over CB2 receptors. We determined that AM4113 antagonized CB1 receptors in brain by blocking hypothermia induced by CP55,940. AM4113 (0-20 mg/kg) significantly reduced food intake and weight gain in rat. Compared with AM251, higher doses of AM4113 were needed to produce similar effects on food intake and body weight. Unlike AM251 (5 mg/kg), a highly anorectic dose of AM4113 (10 mg/kg) did not significantly potentiate vomiting induced by the emetic morphine-6-glucoronide. We show that a centrally active neutral CB1 receptor antagonist shares the appetite suppressant and weight loss effects of inverse agonists. If these compounds display similar properties in humans, they could be developed into a new class of antiobesity agents.

CB1 receptors: emerging evidence for central and peripheral mechanisms that regulate energy balance, metabolism, and cardiovascular health

Insulin resistance, dyslipidaemia and obesity are the major cardiometabolic risk factors contributing to the development of type 2 diabetes and cardiovascular disease (CVD). Owing to the increasing prevalence of obesity, type 2 diabetes, and CVD, new and effective pharmacologic therapies are urgently needed. In this regard, the endogenous cannabinoid system (ECS), a neuromodulatory system involved in the regulation of various aspects of energy balance and eating behaviour through central and peripheral mechanisms, may present the potential to meet this need. In the central nervous system (CNS), cannabinoid type 1 (CB1) receptors and their respective ligands, the endocannabinoids, have a significant role in the modulation of food intake and motivation to consume palatable food. CB1 receptors have also been found in organs involved in the regulation of metabolic homeostasis, such as liver, white adipose tissue, muscle and pancreas. Dysregulation of the ECS has been associated with the development of dyslipidaemia, glucose intolerance, and obesity, and CB1 receptor blockade may have a role in ameliorating these metabolic abnormalities. Thus, pharmacologic options targeting the ECS may provide a novel, effective approach to the prevention and management of CVD, type 2 diabetes and obesity.

The endocannabinoid network: insight into the regulation of the neuroendocrine and metabolic systems

The dramatic increase in the prevalence of obesity worldwide represents one of the most important challenges of modern medicine, owing to its myriad related complications-in particular cardiovascular disease, the leading cause of death worldwide. Originating from early studies with Cannabis sativa, the active compound of marijuana, there has been an impressive progress in the knowledge about the endocannabinoid network, leading to the identification of specific pathways that modulate feeding behavior. The effects of endocannabinoids are not limited to the central nervous system, but also include peripheral tissues. Experimental and clinic trials have demonstrated the efficacy of endocannabinoid antagonists in the management of obesity and the cardiometabolic syndrome. Better understanding of the mechanisms underlying obesity will lead to development of more active and specific agents, which surely will enlarge the role of this efficacious alternative for management of obesity.

Cannabinoids inhibit insulin secretion and cytosolic Ca2+ oscillation in islet beta-cells via CB1 receptors

Obesity is the main risk factor for the development of metabolic syndrome. Endogenous cannabinoids act on the cannabinoid type 1 (CB1) receptor, a GPCR, and stimulate appetite via central and peripheral actions, while blockade of CB1 receptor reduces body weight in humans. In this study, we aimed to explore a role of the peripheral endocannabinoid system in insulin secretion, which could be important in the metabolic effects of the cannabinoid-CB1 system. We found that mRNA for CB1 receptor, but not CB2 receptor, was expressed in mouse pancreatic islets using RT-PCR. Immunohistochemical study revealed that CB1 receptor was expressed in beta-cells. Furthermore, anandamide and a CB1 agonist, arachidonylcyclopropylamide (ACPA), inhibited glucose-induced insulin secretion from mouse pancreatic islets. Both anandamide and ACPA inhibited glucose-induced cytosolic Ca(2+) oscillation in mouse pancreatic beta-cells. These results demonstrate a novel peripheral action of cannabinoids to inhibit insulin secretion via CB1 receptors.

Role and regulation of acylethanolamides in energy balance: focus on adipocytes and beta-cells

The endocannabinoid, arachidonoylethanolamide (AEA), and the peroxisome proliferator-activated receptor (PPAR)-alpha ligand, oleylethanolamide (OEA) produce opposite effects on lipogenesis. The regulation of OEA and its anti-inflammatory congener, palmitoylethanolamide (PEA), in adipocytes and pancreatic beta-cells has not been investigated. We report here the results of studies on acylethanolamide regulation in these cells during obesity and hyperglycaemia, and provide an overview of acylethanolamide role in metabolic control. We analysed by liquid chromatography-mass spectrometry OEA and PEA levels in: 1) mouse 3T3F442A adipocytes during insulin-induced differentiation, 2) rat insulinoma RIN m5F beta-cells kept in 'low' or 'high' glucose, 3) adipose tissue and pancreas of mice with high fat diet-induced obesity (DIO), and 4) in visceral fat or blood of obese or type 2 diabetes (T2D) patients. In adipocytes, OEA levels remain unchanged during differentiation, whereas those of PEA decrease significantly, and are under the negative control of both leptin and PPAR-gamma. PEA is significantly downregulated in subcutaneous adipose tissue of DIO mice. In RIN m5F insulinoma beta-cells, OEA and PEA levels are inhibited by 'very high' glucose, this effect being enhanced by insulin, whereas in cells kept for 24 h in 'high' glucose, they are stimulated by both glucose and insulin. Elevated OEA and PEA levels are found in the blood of T2D patients. Reduced PEA levels in hypertrophic adipocytes might play a role in obesity-related pro-inflammatory states. In beta-cells and human blood, OEA and PEA are down- or up-regulated under conditions of transient or chronic hyperglycaemia, respectively.

Cannabinoids go nuclear: evidence for activation of peroxisome proliferator-activated receptors

Cannabinoids act at two classical cannabinoid receptors (CB1 and CB2), a 7TM orphan receptor and the transmitter-gated channel transient receptor potential vanilloid type-1 receptor. Recent evidence also points to cannabinoids acting at members of the nuclear receptor family, peroxisome proliferator-activated receptors (PPARs, with three subtypes alpha, beta (delta) and gamma), which regulate cell differentiation and lipid metabolism. Much evidence now suggests that endocannabinoids are natural activators of PPAR alpha. Oleoylethanolamide regulates feeding and body weight, stimulates fat utilization and has neuroprotective effects mediated through activation of PPAR alpha. Similarly, palmitoylethanolamide regulates feeding and lipid metabolism and has anti-inflammatory properties mediated by PPAR alpha. Other endocannabinoids that activate PPAR alpha include anandamide, virodhamine and noladin. Some (but not all) endocannabinoids also activate PPAR gamma; anandamide and 2-arachidonoylglycerol have anti-inflammatory properties mediated by PPAR gamma. Similarly, ajulemic acid, a structural analogue of a metabolite of Delta(9)-tetrahydrocannabinol (THC), causes anti-inflammatory effects in vivo through PPAR gamma. THC also activates PPAR gamma, leading to a time-dependent vasorelaxation in isolated arteries. Other cannabinoids which activate PPAR gamma include N-arachidonoyl-dopamine, HU210, WIN55212-2 and CP55940. In contrast, little research has been carried out on the effects of cannabinoids at PPAR delta. In this newly emerging area, a number of research questions remain unanswered; for example, why do cannabinoids activate some isoforms and not others? How much of the chronic effects of cannabinoids are through activation of nuclear receptors? And importantly, do cannabinoids confer the same neuro- and cardioprotective benefits as other PPAR alpha and PPAR gamma agonists? This review will summarize the published literature implicating cannabinoid-mediated PPAR effects and discuss the implications thereof.

Expression of Cannabinoid CB1 Receptors in Models of Diabetic Neuropathy

A clearer understanding of the mechanisms underlying the development and progression of diabetic neuropathy is likely to indicate new directions for the treatment of this complication of diabetes. In the present study we investigated the expression of cannabinoid CB(1) receptors in models of diabetic neuropathy. PC12 cells were differentiated into a neuronal phenotype with nerve growth factor (NGF) (50 ng/ml) in varying concentrations of glucose (5.5-50 mM). CB(1) receptor expression was studied at the mRNA level by reverse transcriptase-polymerase chain reaction (RT-PCR) and at the protein level via immunohistochemical and Western blot analysis. CB(1) expression was also compared in dorsal root ganglia (DRG) removed from streptozotocin-induced diabetic rats versus control animals. Total neurite length induced by NGF was reduced in cells cultured in 20 to 50 mM glucose at day 6 (P < 0.01 versus 5.5 mM; n = 6). Cell viability assays conducted in parallel on day 6 confirmed that the total cell numbers were not significantly different among the various glucose concentrations (P = 0.86; n = 12). RT-PCR, immunohistochemical, and Western blot analysis all revealed down-regulation of the CB(1) receptor in cells treated with high glucose (P < 0.05; n = 4-5 for each), and in DRG removed from diabetic rats compared with controls (P < 0.01; n = 5 for immunohistochemistry, and n = 3 for Western blot). These results suggest that high glucose concentrations are associated with decreased expression of CB(1) receptors in nerve cells. Given the neuroprotective effect of cannabinoids, a decline in CB(1) receptor expression may contribute to the neurodegenerative process observed in diabetes.

Endocannabinoid system and pathophysiology of adipogenesis: current management of obesity

The endocannabinoids are now known as novel and important regulators of energy metabolism and homeostasis. The endocrine functions of white adipose are chiefly involved in the control of whole-body metabolism, insulin sensitivity and food intake. Adipocytes produce hormones, such as leptin and adiponectin, that can improve insulin resistance or peptides, such as TNF-α, that elicit insulin resistance. Adipocytes express specific receptors, such as peroxisome proliferator-activated receptor (PPAR)-γ, which serve as adipocyte targets for insulin sensitizers such as thiazolidinediones. Recently, endocannabinoids and related compounds were identified in human fat cells. The endocannabinoid system consists primarily of two receptors, cannabinoid (CB)1 and CB2, their endogenous ligands termed endocannabinoids and the enzymes responsible for ligand biosynthesis and degradation. The endocannabinoids 2-arachidonylglycerol and anandamide or N-arachidonoylethanolamine increase food intake and promote weight gain in animals. Rimonabant, a selective CB1 blocker, reduces food intake and body weight in animals and humans.

Cannabinoids in eating disorders and obesity

Cannabinoid system is a crucial mechanism in regulating food intake and energy metabolism. It is involved in central and peripheral mechanisms regulating such behavior, interacting with many other signaling systems with a role in metabolic regulation. Cannabinoid agonists promote food intake, and soon a cannabinoid antagonist, rimonabant, will be marketed for the treatment of obesity. It not only causes weight loss, but also alleviates metabolic syndrome. We present a review of current knowledge on this subject, along with data from our own research: genetic studies on this system in eating disorders and obesity and studies locating cannabinoid receptors in areas related to food intake. Such studies suggest cannabinoid hyperactivity in obesity, and this excessive activity may have prognostic implications.

Regulation of hypothalamic endocannabinoid levels by neuropeptides and hormones involved in food intake and metabolism: insulin and melanocortins

Endocannabinoids are paracrine/autocrine lipid mediators with several biological functions. One of these, i.e. the capability to stimulate food intake via cannabinoid CB(1) receptors, has been particularly studied, thus leading to the development of the first CB(1) receptor blocker, rimonabant, as a therapeutic tool against obesity and related metabolic disorders. Hypothalamic endocannabinoids stimulate appetite by regulating the expression and release of anorexic and orexigenic neuropeptides via CB(1) receptors. In turn, the tone of the latter receptors is regulated by hormones, including leptin, glucocorticoids and possibly ghrelin and neuropeptide Y, by modulating the biosynthesis of the endocannabinoids in various areas of the hypothalamus. CB(1) receptor stimulation is also known to increase blood glucose during an oral glucose tolerance test in rats. Here we investigated in the rat if insulin, which is known to exert fundamental actions at the level of the mediobasal hypothalamus (MBH), and the melanocortin system, namely alpha-melanocyte stimulating hormone (alpha-MSH) and melanocortin receptor-4 (MCR-4), also regulate hypothalamic endocannabinoid levels, measured by isotope-dilution liquid chromatography coupled to mass spectrometry. No effect on anandamide and 2-arachidonoylglycerol levels was observed after 2h infusion of insulin in the MBH, i.e. under conditions in which the hormone reduces blood glucose, nor with intra-cerebroventricular injection of alpha-MSH, under conditions in which the neuropeptide reduces food intake. Conversely, blockade of MCR-4 receptors with HS014 produced a late (6h after systemic administration) stimulatory effect on endocannabinoid levels as opposed to a rapid and prolonged stimulation of food-intake (observable 2 and 6h after administration). These data suggest that inhibition of endocannabinoid levels does not mediate the effect of insulin on hepatic glucose production nor the food intake-inhibitory effect of alpha-MSH, although stimulation of endocannabinoid levels might underlie part of the late stimulatory effects of MCR-4 blockade on food intake.

Cardiovascular disease under the influence of excess visceral fat

Diabetes and cardiovascular disease have emerged as major threats to human health, and the risk of developing these chronic conditions is increased in individuals with abdominal obesity and the metabolic syndrome. Excess visceral abdominal tissue (VAT) accumulation appears to be a key feature of abdominal obesity contributing to the development of the metabolic syndrome. For instance, excess VAT is accompanied by elevated triglycerides, reduced high-density lipoprotein (HDL) cholesterol, elevated blood pressure, and/or elevated fasting plasma glucose. In addition, the rather normal or only marginally elevated low-density lipoprotein (LDL) cholesterol concentrations in patients with excess VAT could provide misleading information as viscerally obese patients have an increased plasma concentration of small, dense LDL particles. Prospective studies have suggested that even among patients with LDL cholesterol concentrations within normal limits, an increased concentration of small LDL particles is associated with higher risk of cardiovascular disease. With the treatment of abdominal obesity and excess VAT, an increase in patients' LDL particle size and improvements in other cardiovascular risk factors (eg, insulin levels, glucose tolerance, HDL, C-reactive protein [CRP], and adiponectin levels) can be achieved. Waist circumference can be used in clinical practice as a first approach and as a crude index to identify patients who have excess VAT, particularly when the elevated waistline is accompanied by the clinical features of the metabolic syndrome, among which an elevated fasting triglyceride concentration appears to be predictive of a reduced LDL particle size and of further metabolic abnormalities frequently referred to as the metabolic syndrome. Lifestyle changes, including more physical activity and healthier nutritional habits, are the cornerstone of therapy for high-risk abdominally obese patients with an excess of VAT. In addition, results from the RIO-Lipids study, which was conducted in high-risk obese, dyslipidemic patients, have provided evidence that CB1 receptor blockade with rimonabant can induce significant weight loss, and, more importantly, improve the cardiometabolic risk profile beyond what could be explained by the weight loss effects of the drug.

Role of cannabinoid CB2 receptors in glucose homeostasis in rats

Here we show that the activation of cannabinoid CB2 receptors improved glucose tolerance after a glucose load. Blockade of cannabinoid CB2 receptors counteracted this effect, leading to glucose intolerance. Since blockade of cannabinoid CB1 receptors mimics the actions of cannabinoid CB2 receptor agonists, we propose that the endocannabinoid system modulates glucose homeostasis through the coordinated actions of cannabinoid CB1 and CB2 receptors. We also describe the presence of both cannabinoid CB1 and CB2 receptor immunoreactivity in rat pancreatic beta- and non-beta-cells, adding the endocrine pancreas to adipose tissue and the liver as potential sites for endocannabinoid regulation of glucose homeostasis.

The endocannabinoid system: body weight and metabolic regulation

The endocannabinoid system elicits multiple physiologic functions that are not fully understood. Antagonism of cannabinoid type 1 (CB(1)) receptors has been the only successful new pharmacologic treatment approach in Phase III studies in obesity in the last 8 years. Whereas antagonism of (CB(1)) receptors acutely reduces food intake, the long-term effects on weight reduction and metabolic regulation appear to be mediated by stimulation of energy expenditure and by peripheral effects related to liver, skeletal muscle, adipose tissue, and pancreas physiology. For example, in the liver, lipogenic enzymes and fatty acid synthesis are upregulated by endocannabinoids, and in adipose tissue, antagonism of (CB(1)) receptors increases secretion of adiponectin. Some studies suggest that endocannabinoid formation is increased in obesity, perhaps because endocannabinoid degradation is decreased. Although many questions remain unanswered at present, the emerging concept of endocannabinoids as metabolic regulators helps to explain the success of rimonabant (SR141716), an antagonist of (CB(1)) receptors, currently in Phase III studies.

Effects of CB1 antagonist on the control of metabolic functions in obese type 2 diabetic patients

Clinical reports (RIO trials) have shown that chronic administration of a CB-cannabinoid receptor antagonist (rimonabant) provides improvements of disturbed metabolic parameters observed in overweight and obese patients with type 2 diabetes. The production of endocannabinoid and the expression of CB1-cannabinoid receptors are largely distributed in the different organs aside from the brain. It is now clearly established that endocannabinoids act both through orexigenic effects and peripheral metabolic effects in various tissues involved in the control of metabolism and energy expenditure (i.e. adipose tissue, liver, gastrointestinal tract, skeletal muscle and pancreas). This review will consider: i) the disturbances of glucose and lipid metabolisms in obese type 2 diabetics; ii) an overview of the pharmacological properties of rimonabant and iii) the various mechanisms involved in tissues and organs to explain the therapeutic efficacy of rimonabant. A special attention will be paid to its utilization in obese type 2 diabetics. The emerging concept of endocannabinoids acting as metabolic regulators is the more likely explanation of the success of rimonabant treatments in phase III studies.

Identification of endocannabinoids and related compounds in human fat cells

OBJECTIVE

Recently, an activation of the endocannabinoid system during obesity has been reported. More particularly, it has been demonstrated that hypothalamic levels of both endocannabinoids, 2-arachidonoylglycerol and anandamide (N-arachidonoylethanolamine), are up-regulated in genetically obese rodents. Circulating levels of both endocannabinoids were also shown to be higher in obese compared with lean women. Yet, the direct production of endocannabinoids by human adipocytes has never been demonstrated. Our aim was to evaluate the ability of human adipocytes to produce endocannabinoids.

RESEARCH METHODS AND PROCEDURES

The production of endocannabinoids by human adipocytes was investigated in a model of human white subcutaneous adipocytes in primary culture. The effects of leptin, adiponectin, and peroxisome proliferator-activated receptor (PPAR)-gamma activation on endocannabinoid production by adipocytes were explored. Endocannabinoid levels were determined by high-performance liquid chromatography (HPLC)-atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) analysis, leptin and adiponectin secretion measured by enzyme-linked immunosorbent assay (ELISA), and PPAR-gamma protein expression examined by Western blotting.

RESULTS

We show that 2-arachidonoylglycerol, anandamide, and both anandamide analogs, N-palmitoylethanolamine and N-oleylethanolamine, are produced by human white subcutaneous adipocytes in concentrations ranging from 0.042+/-0.004 to 0.531+/-0.048 pM/mg lipid extract. N-palmitoylethanolamine is the most abundant cannabimimetic compound produced by human adipocytes, and its levels are significantly down-regulated by leptin but not affected by adiponectin and PPAR-gamma agonist ciglitazone. N-palmitoylethanolamine itself does not affect either leptin or adiponectin secretion or PPAR-gamma protein expression in adipocytes.

DISCUSSION

This study has led to the identification of human adipocytes as a new source of endocannabinoids and related compounds. The biological significance of these adipocyte cannabimimetic compounds and their potential implication in obesity should deserve further investigations.

Endocannabinoids and the regulation of their levels in health and disease

PURPOSE OF REVIEW

Endocannabinoids are defined as endogenous agonists of cannabinoid receptors, that is, of the two G-protein-coupled receptors for the Cannabis psychoactive principle Delta-tetra-hydrocannabinol. Two such endogenous mediators have been most thoroughly studied so far: anandamide and 2-arachidonoylglycerol. Here we review the mechanisms for the regulation of their levels under physiological and pathological conditions, and recent findings on their role in disease.

RECENT FINDINGS

It is becoming increasingly clear that, although both anandamide and 2-arachidonoyl-glycerol are produced and degraded 'on demand', the levels of these two compounds appear to be regulated in different, and sometimes even opposing, ways, often using redundant molecular mechanisms. Alterations of endocannabinoid levels have been found in both animal models of pain, neurological and neurodegenerative states, gastrointestinal disorders and inflammatory conditions, and in blood, cerebrospinal fluid and bioptic samples from patients with various diseases.

SUMMARY

Endocannabinoid levels appear to be transiently elevated as an adaptive reaction to re-establish normal homeostasis when this is acutely and pathologically perturbed. In some chronic conditions, however, this system also contributes to the progress or symptoms of the disorder. As a consequence, new therapeutic drugs are being designed from both stimulants and blockers of endocannabinoid action.

Integrated physiology and pathophysiology of CB1-mediated effects of the endocannabinoid system

The discovery of the endocannabinoid system (ECS) has raised a large interest in the scientific community providing us with a strikingly long list of apparently independent multi organ effects. As a result, in most reviews on this issue the main function of the ECS is considered as modulatory. Unfortunately, this vision does not add much to our understanding of the specific biological function of the ECS. Thus, modulatory is what in general all biological systems are or should be. In this review we will show that the apparent inconsistent puzzle of the very different tissue specific effects of endocannabinoids (ECs) can be reconstructed in one unitary picture. This picture clearly shows that all the different CB1-mediated effects of ECs sub-serve one major physiological function: to facilitate and increase energy storage. We will also analyze the implications of this unitary vision of the ECS in different contexts. First, in the context of the systems that regulate energy balance, introducing a new systematization based on two homeostatic systems: an endostatic and an exostatic system. Second, in the context of evolution, showing how the function of the ECS has shifted from essential to survival to almost pathological in current times. Finally, in a pathophysiological context, introducing the new concept of "proactive evolution diseases", which can explain the current obesity epidemic and the role the ECS plays in it.

No evidence for an involvement of variants in the cannabinoid receptor gene (CNR1) in obesity in German children and adolescents

Studies in rodent models demonstrated that the central cannabinoid receptor (Cnr1) mediates the orexigenic effects of cannabinoids. To analyze whether genetic variation in the cannabinoid receptor gene (CNR1) is implicated in human obesity, we initially genotyped 8 single nucleotide polymorphisms (SNPs) located in the 5' region (rs9353527, rs754387, rs6454676), intron 2 (rs806379, rs1535255), exon 3 (rs2023239), intron 3 (rs806370) and the coding region (rs1049353) in up to 364 German obesity trios (extremely obese child or adolescent and both parents). The transmission disequilibrium test (TDT) was negative for these SNPs (p>0.05). However, there was a slight trend towards preferential transmission of the A-allele of rs1049353 (p=0.12). We therefore genotyped this SNP in 235 independent German obesity families (at least two obese sibs and both parents) and in parallel screened the CNR1 coding region for sequence variations in 120 German extremely obese children and adolescents who mainly contributed to the initial trend observed for rs1049353. The trend for preferential transmission of the A-allele could not be substantiated (pedigree disequilibrium test, PDT p=0.15; A-allele less frequently transmitted). In the mutation screen we detected two rare variations, one novel non-conservative mutation (c.1256C>A; A419E) and the known variant 1419+1G>C. In addition, we confirmed the presence of rs1049353. As these variants could not explain the initial TDT, we conclude that there is no evidence for an association of CNR1 alleles with obesity in our study groups.

Effects of cannabinoid receptors on skeletal muscle oxidative pathways

The endocannabinoids, a recently discovered endogenous, lipid derived, signaling system regulating energy metabolism, have effects on central and peripheral energy metabolism predominantly via the cannabinoid receptor type 1 (CB1). CB1 is expressed centrally in the hypothalamus and nucleus accumbens and peripherally in adipocytes and skeletal muscle. This study determined the effect of endocannabinoids on the expression of genes regulating energy metabolism in human skeletal muscle. Primary cultures of myotubes (lean and obese; n=3/group) were treated with the cannabinoid receptor agonist, anandamide (AEA) (0.2 and 5microM) and the CB1 specific antagonist AM251 (0.2 and 5microM) separately and in combination for 24h. The expression of mRNA for AMP-activated protein kinase (AMPK) alpha 1 (alpha1) and alpha 2 (alpha2), pyruvate dehydrogenase kinase 4 (PDK4) and peroxisome proliferator-activated receptor-gamma co-activator-1alpha (PGC-1alpha) were determined using 'Real Time' RT-PCR. AMPKalpha1 mRNA increased in lean and obese myotubes in response to AM251 (P<0.05). AEA inhibited the effect of AM251 on AMPKalpha1 mRNA levels in myotubes from lean and obese subjects (P<0.05); the dose-response curve was shifted to the left in the obese. In response to AM251, irrespective of the presence of AEA, PDK4 expression was decreased in lean and obese myotubes (P<0.05). Taken together these data suggest that endocannabinoids regulate pathways affecting skeletal muscle oxidation, effects particularly evident in myotubes from obese individuals.

Increase of cannabinoid CB1 receptor density in the hippocampus of streptozotocin-induced diabetic rats

In the hippocampus, impaired neurophysiology, compromised neurogenesis, and eventually apoptosis accompany cognitive deficits in insulinopenic (type-1) diabetes (T1D). The underlying pathological mechanisms remain to be defined. The hippocampus has a high density of the cannabinoid type 1 receptor (CB(1)R), which has been shown to control several brain functions affected by diabetes, such as synaptic plasticity, glucose utilisation, memory consolidation and cognition, and maturation and survival of hippocampal neurons. However, the role of this receptor has not been investigated yet in diabetic encephalopathy. We report now that in the streptozotocin animal model of T1D, the hippocampal densities of CB(1)R protein and of specific CB(1)R binding sites are significantly increased both in the nerve terminals and in total membranes (changes between 13% and 38%), whereas CB(1)R mRNA expression is decreased by 25%, suggesting that CB(1)Rs might play a role in diabetic encephalopathy.

The endocannabinoid system: mechanisms behind metabolic homeostasis and imbalance

Scientific interest in the endocannabinoid (EC) system developed as a result of the known effects of tetrahydrocannabinol, including an increased desire to consume food. Further investigation has led to the belief that the EC system plays a role in accumulation of intra-abdominal fat and worsening of cardiovascular disease (CVD) risk factors. The EC system has been identified as a neuromodulatory system that is normally inactive but can be overstimulated to cause and exacerbate numerous metabolic pathologies. EC agonists and receptors have been identified in the brain, liver, and peripheral adipose tissue, and the EC system is known to affect metabolism in these areas and others through neuromodulatory signals. Meal size, body weight, and numerous metabolic factors such as triglyceride and cholesterol levels, insulin resistance, and glucose intolerance can be affected via the EC system. Further research into the EC system is warranted to elucidate its role in metabolic homeostasis.

Rimonabant: more than an anti-obesity drug?

The endocannabinoid system modulates many pathophysiological functions, including the brain pathways involved in the regulation of body weight and adipose tissue function. The selective cannabinoid CB(1) receptor antagonist, rimonabant, has undergone phase III clinical testing as anti-obesity drug. Obesity is considered a mild inflammatory condition and predisposes individuals to an increased risk of developing many diseases. It has been recently suggested that a successful intervention to treat obesity is a therapy combining weight-reducing drugs with anti-inflammatory ones. In this scenario, rimonabant's anti-obesity action is accompanied by favorable changes in markers for insulin resistance, C-reactive protein, adiponectin, tumor necrosis factor alpha (TNFalpha). The results reported by Croci and Zarini in this issue highlight the anti-inflammatory and anti-hyperalgesic effect of rimonabant in obese animals, so suggesting that it could provide a more general and aggressive strategy to protect obese patients from many pathological risks.

Effect of the cannabinoid CB1 receptor antagonist rimonabant on nociceptive responses and adjuvant-induced arthritis in obese and lean rats

BACKGROUND AND PURPOSE

Obesity is a risk factor for several inflammation-based diseases including arthritis. We investigated the anti-nociceptive and anti-inflammatory effects of the cannabinoid CB1 receptor antagonist rimonabant in lean and diet-induced obese female rats with arthritis induced by complete Freund's adjuvant (CFA) injected in the right hind-paw.

EXPERIMENTAL APPROACH

The effect of oral rimonabant was assessed in rat paws on thermal hyperalgesia, mechanical allodynia, oedema, global arthritis score, nitrite/nitrate levels and ankle widths.

KEY RESULTS

After 7 but not after 14 days, the inflammatory response to CFA was significantly higher in obese than lean rats; however, the nociceptive response (thermal hyperalgesia and mechanical allodynia) was similar. Oral rimonabant (3 or 10 mg kg-1, once a day for 1 week from day 7 after CFA) only reduced the global arthritic score and joint width in obese rats, with no effect on the paw oedema. It also markedly reduced thermal hyperalgesia and mechanical allodynia in both lean and obese rats, with a greater effect in the latter.

CONCLUSION AND IMPLICATIONS

Rimonabant appears to be a potent inhibitor of sensorial hypersensitivity associated with CFA-induced arthritis in obese rats, in which the inflammatory reaction is more severe than in lean rats. It may thus have therapeutic potential in obesity-associated inflammatory diseases, particularly in the treatment of the pain associated with arthritis.

Circulating endocannabinoid levels, abdominal adiposity and related cardiometabolic risk factors in obese men

OBJECTIVE

The link between excess intra-abdominal adiposity (IAA) and metabolic complications leading to type 2 diabetes and cardiovascular disease is well recognized. Blockade of endocannabinoid action at cannabinoid CB(1) receptors was shown to reduce these complications. Here, we investigated the relationship between IAA, circulating endocannabinoid levels and markers of cardiometabolic risk in male obese subjects.

DESIGN, SUBJECTS AND MEASUREMENTS

Fasting plasma levels of the endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), were measured by liquid chromatography-mass spectrometry in a study sample of 62 untreated asymptomatic men with body mass index (BMI) from 18.7 to 35.2 kg/m(2).

RESULTS

Plasma 2-AG, but not AEA, levels correlated positively with BMI, waist girth, IAA measured by computed tomography, and fasting plasma triglyceride and insulin levels, and negatively with high-density lipoprotein cholesterol and adiponectin levels. Obese men with similar BMI values (> or =30 kg/m(2)) but who markedly differed in their amount of IAA (< vs > or = 130 cm(2), n=17) exhibited higher 2-AG levels in the presence of high IAA. No difference in 2-AG concentrations was observed between obese men with low levels of IAA vs nonobese controls.

CONCLUSIONS

These results provide evidence for a relationship in men between a key endocannabinoid, 2-AG, and cardiometabolic risk factors, including IAA.

Endocannabinoids and cardiovascular prevention: real progress?

The prevalence of obesity continues to increase and represents one of the principal causes of cardiovascular morbidity and mortality. After the discovery of a specific receptor of the psychoactive principle of marijuana, the cannabinoid receptors and their endogenous ligands, several studies have demonstrated the role of this system in the control of food intake and energy balance and its overactivity in obesity. Recent studies with the CB1 receptor antagonist rimonabant have demonstrated favorable effects such as a reduction in body weight and waist circumference and an improvement in metabolic factors (cholesterol, triglycerides, glycemia etc). Therefore, the antagonism of the endocannabinoid (EC) system, if recent data can be confirmed, could be a new treatment target for high risk overweight or obese patients. Obesity is a growing problem that has epidemic proportions worldwide and is associated with an increased risk of premature death (1–3). Individuals with a central deposition of fats have elevated cardiovascular morbidity and mortality (including stroke, heart failure and myocardial infarction) and, because of a growing prevalence not only in adults but also in adolescents, it was reclassified in AHA guidelines as a “major modifiable risk factor” for coronary heart disease (4, 5). Although first choice therapy in obesity is based on correcting lifestyle (diet and physical activity) in patients with abdominal obesity and high cardiovascular risk and diabetes, often it is necessary to use drugs which reduce the risks. The EC system represents a new target for weight control and the improvement of lipid and glycemic metabolism (6, 7).