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

Central and peripheral consequences of the chronic blockade of CB1 cannabinoid receptor with rimonabant or taranabant

The endocannabinoid system plays a crucial role in the pathophysiology of obesity. However, the clinical use of cannabinoid antagonists has been recently stopped because of its central side-effects. The aim of this study was to compare the effects of a chronic treatment with the CB(1) cannabinoid antagonist rimonabant or the CB(1) inverse agonist taranabant in diet-induced obese female rats to clarify the biological consequences of CB(1) blockade at central and peripheral levels. As expected, chronic treatment with rimonabant and taranabant reduced body weight and fat content. Interestingly, a decrease in the number of CB(1) receptors and its functional activity was observed in all the brain areas investigated after chronic taranabant treatment in both lean and obese rats. In contrast, chronic treatment with rimonabant did not modify the density of CB(1) cannabinoid receptor binding, and decreased its functional activity to a lower degree than taranabant. Six weeks after rimonabant and taranabant withdrawal, CB(1) receptor density and activity recovered to basal levels. These results reveal differential adaptive changes in CB(1) cannabinoid receptors after chronic treatment with rimonabant and taranabant that could be related to the central side-effects reported with the use of these cannabinoid antagonists.

Effects of Rimonabant, as Monotherapy and in Combination With Fenofibrate or Ezetimibe, on Plasma Adipokine Levels: A Pilot Study

Weight loss and hypolipidemic drugs can improve lipid and adipokine levels. We assessed the effects of rimonabant, alone and in combination with fenofibrate or ezetimibe, on adipokine levels in obese/overweight patients with dyslipidemia. Overweight/obese patients (n = 60, body mass index = 27-40 kg/m2) with mixed dyslipidemia were recruited. Patients received a hypocaloric diet and were randomized to rimonabant 20 mg/d (group R, n = 20), rimonabant 20 mg/d plus fenofibrate 200 mg/d (group RF, n = 20), or rimonabant 20 mg/d plus ezetimibe 10 mg/d (group RE, n = 20). After 3 months, leptin concentration was significantly reduced in all groups (—38%, P < .005; —40%, P < .005; and —44%, P < .001 in the R, RF, and RE groups, respectively). Total adiponectin remained unaltered. Visfatin concentration decreased significantly only in the RE and RF groups (—18% and —38%, respectively; P < .047). Treatment with rimonabant may improve adipokine levels in overweight/obese patients with dyslipidemia. The addition of fenofibrate or ezetimibe may reinforce this effect.

Systematic review and meta-analysis on the adverse events of rimonabant treatment: considerations for its potential use in hepatology

Background

The cannabinoid-1 receptor blockers have been proposed in the management of obesity and obesity-related liver diseases (fatty liver as NAFLD or NASH). Due to increasing number of patients to be potentially treated and the need to assess the advantage of this treatment in terms of risk/benefit, we analyze the side events reported during the treatment with rimonabant by a systematic review and meta-analysis of all randomized controlled studies.

Methods

All published randomized controlled trials using rimonabant versus placebo in adult subjects were retrieved. Relative risks (RR) with 95% confidence interval for relevant adverse events and number needed to harm was calculated.

Results

Nine trials (n = 9635) were considered. Rimonabant 20 mg was associated with an increased risk of adverse event (RR 1.35; 95%CI 1.17-1.56), increased discontinuation rate (RR 1.79; 95%CI 1.35-2.38), psychiatric (RR 2.35; 95%CI 1.66-3.34), and nervous system adverse events (RR 2.35; 95%CI 1.49-3.70). The number needed to harm for psychiatric adverse events is 30.

Conclusion

Rimonabant is associated with an increased risk of adverse events. Despite of an increasing interest for its use on fatty liver, the security profile and efficacy it is needs to be carefully assessed before its recommendation. At present the use of rimonabant on fatty liver cannot be recommended.

Efficacy and Safety of Ezetimibe Plus Orlistat or Rimonabant in Statin-Intolerant Nondiabetic Overweight/Obese Patients With Dyslipidemia

Aims: To compare the effects of ezetimibe plus orlistat or rimonabant on anthropometric and lipid parameters in nondiabetic statin-intolerant overweight/obese patients with dyslipidemia.

Methods and results: Thirty participants received a hypocaloric diet and were randomized to open-label combination of ezetimibe (10 mg/day) with orlistat (120 mg, 3 times a day with meals; ezetimibe/orlistat [EO], n = 15) or rimonabant (20 mg/day; ezetimibe/ rimonabant [ER], n = 15). Anthropometric and metabolic variables were assessed at baseline and 3 months posttreatment. Similar reductions in body weight, body mass index, and waist circumference were recorded in both groups (—8.3%, —8.6%, and —5.2% in the EO group and —7.3%, —7.2%, and —7.0% in the ER group, P < .01 vs baseline for all). Low-density lipoprotein cholesterol (LDL-C) levels decreased in both treatment groups, but this reduction tended to be more pronounced in the EO group (28.4% vs 15.3%, respectively; P < .01 vs baseline for both). Triglycerides tended to decrease more in the ER compared with the EO group (—20.4% vs —14.1%, P < .01 vs baseline for both). High-density lipoprotein cholesterol (HDL-C) levels tended to decrease in EO group, but remained unaltered with ER treatment. Apolipoprotein B levels were equally reduced in both treatment groups. Conclusion: For similar body weight reduction, the combination of ezetimibe with orlistat may be more efficient in LDL-C lowering, whereas the combination of ezetimibe with rimonabant may be more potent in terms of improving HDL-C and triglycerides.

Peripheral mechanisms in the control of appetite and related experimental therapies in obesity

The function of the stomach and the gut hormonal responses to food ingestion constitute highly integrated homeostatic responses that maintain euglycemia and normal digestion. This intrinsic feedback involves vagal and hormonal mechanisms. Important signals such as GLP-1 and PYY that arise peripherally induce satiation and also delay gastric emptying or increase insulin secretion. Novel therapies are being developed to mimic or enhance these feedback mechanisms and to control appetite as a means to treat obesity.

Delta-9-tetrahydrocannabinol enhances food reinforcement in a mouse operant conflict test

RATIONALE

Cannabinoid compounds are known to regulate feeding behavior by modulating the hedonic and/or the incentive properties of food.

OBJECTIVES

The aim of this work was to determine the involvement of the cannabinoid system in food reinforcement associated with a conflict situation generated by stress.

METHODS

Mice were trained on a fixed ratio 1 schedule of reinforcement to obtain standard, chocolate-flavored or fat-enriched pellets. Once the acquisition criteria were achieved, the reinforced lever press was paired with foot-shock exposure, and the effects of Delta(9)-tetrahydrocannabinol (THC; 1 mg/kg) were evaluated in this conflict paradigm.

RESULTS

THC did not modify the operant response in mice trained with standard pellets. In contrast, THC improved the instrumental performance of mice trained with chocolate-flavored and fat-enriched pellets. However, the cannabinoid agonist did not fully restore the baseline responses obtained previous to foot-shock delivery. THC ameliorated the performance to obtain high palatable food in this conflict test in both food-restricted and sated mice. The effects of THC on food reinforcement seem to be long-lasting since mice previously treated with this compound showed a better recovery of the instrumental behavior after foot-shock exposure.

CONCLUSIONS

These findings reveal that the cannabinoid system is involved in the regulation of goal-directed responses towards high palatable and high caloric food under stressful situations.

Rimonabant: an antagonist drug of the endocannabinoid system for the treatment of obesity

Obesity, an ever-increasing problem in the industrialized world, has long been a target of research for a cure or, at least, control of its expansion. In the search for treatment, the recently discovered endocannabinoid system has emerged as a new target for controlling obesity and its associated conditions. The endocannabinoid system plays an important role in controlling weight and energy balance in humans. This system is activated to a greater extent in obese patients, and the specific blockage of its receptors is the aim of rimonabant, one of the most recent drugs created for the treatment of obesity. This drug acts as a blockade for endocannabinoid receptors found in the brain and peripheral organs that play an important role on carbohydrate and fat metabolism. Clinical studies have confirmed that, when used in combination with a low calorie diet, rimonabant promotes loss in body weight, loss in abdominal circumference, and improvements in dyslipidemia. Rimonabant is also being tested as a potential anti-smoking treatment since endocannabinoids are related to the pleasurable effect of nicotine. Thus, rimonabant constitutes a new therapeutic approach to obesity and cardiovascular risk factors. Studies show effectiveness in weight loss; however, side effects such as psychiatric alterations have been reported, including depression and anxiety. These side effects have led the FDA (Food and Drug Administration) to not approve this drug in the United States. For a more complete evaluation on the safety of this drug, additional studies are in progress.

Effect of antiobesity medications in patients with type 2 diabetes mellitus

Obesity is considered as a major health problem, as its prevalence continuously rises worldwide. One of the common health consequences of obesity is type 2 diabetes mellitus. Therefore, antiobesity management is a prerequisite in treating diabetic patients. Lifestyle modifications combined with pharmacological agents appear to be an effective approach. Sibutramine is a serotonin-noradrenaline reuptake inhibitor, which acts centrally by promoting the feeling of satiety and decreasing caloric intake, thus resulting in weight loss. A potential association with cardiovascular side effects has been noted. Orlistat, a gastric and pancreatic lipase inhibitor, also achieves significant weight loss and improves glycaemic status, but it has gastrointestinal side effects. Rimonabant, the first endocannabinoid CB1 antagonist, is associated with weight reduction and it improves diabetic parameters; nevertheless, it is associated with psychiatric disorders; indeed, a recently conducted safety review led to the temporal suspension of its commercialization. The above-mentioned medications seem to be currently useful agents for treating obesity in patients with type 2 diabetes mellitus. Other medications used for diabetes management, such as exenatide, liraglutide and pramlintide, have also shown body weight reduction. Ongoing research is needed to scrutinize the precise impact of these agents in the daily clinical practice of management of obesity in patients with type 2 diabetes mellitus.

Cannabinoid receptor antagonists: pharmacological opportunities, clinical experience, and translational prognosis

The endogenous cannabinoid (CB) (endocannabinoid) signaling system is involved in a variety of (patho)physiological processes, primarily by virtue of natural, arachidonic acid-derived lipids (endocannabinoids) that activate G protein-coupled CB1 and CB2 receptors. A hyperactive endocannabinoid system appears to contribute to the etiology of several disease states that constitute significant global threats to human health. Consequently, mounting interest surrounds the design and profiling of receptor-targeted CB antagonists as pharmacotherapeutics that attenuate endocannabinoid transmission for salutary gain. Experimental and clinical evidence supports the therapeutic potential of CB1 receptor antagonists to treat overweight/obesity, obesity-related cardiometabolic disorders, and substance abuse. Laboratory data suggest that CB2 receptor antagonists might be effective immunomodulatory and, perhaps, anti-inflammatory drugs. One CB1 receptor antagonist/inverse agonist, rimonabant, has emerged as the first-in-class drug approved outside the United States for weight control. Select follow-on agents (taranabant, otenabant, surinabant, rosonabant, SLV-319, AVE1625, V24343) have also been studied in the clinic. However, rimonabant's market withdrawal in the European Union and suspension of rimonabant's, taranabant's, and otenabant's ongoing development programs have highlighted some adverse clinical side effects (especially nausea and psychiatric disturbances) of CB1 receptor antagonists/inverse agonists. Novel CB1 receptor ligands that are peripherally directed and/or exhibit neutral antagonism (the latter not affecting constitutive CB1 receptor signaling) may optimize the benefits of CB1 receptor antagonists while minimizing any risk. Indeed, CB1 receptor-neutral antagonists appear from preclinical data to offer efficacy comparable to or better than that of prototype CB1 receptor antagonists/inverse agonists, with less propensity to induce nausea. Continued pharmacological profiling, as the prelude to first-in-man testing of CB1 receptor antagonists with unique modes of targeting/pharmacological action, represents an exciting translational frontier in the critical path to CB receptor blockers as medicines.

Peripheral endocannabinoid dysregulation in obesity: relation to intestinal motility and energy processing induced by food deprivation and re-feeding

BACKGROUND AND PURPOSE

Endocannabinoids in tissues controlling energy homeostasis are altered in obesity, thus contributing to metabolic disorders. Here we evaluate endocannabinoid dysregulation in the small intestine of mice with diet-induced obesity (DIO) and in peripheral tissues of Zucker and lean rats following food deprivation and re-feeding.

EXPERIMENTAL APPROACH

Intestinal transit, evaluated using rhodamine-B-labelled dextran, and small intestinal endocannabinoid levels, measured by liquid chromatography mass spectrometry, were measured in mice fed normal or high-fat diets (HFDs). Endocannabinoid levels were measured also in various tissues of lean and Zucker rats fed ad libitum or following overnight food deprivation with and without subsequent re-feeding.

KEY RESULTS

After 8 weeks of HFD, baseline intestinal transit was increased in DIO mice and enhanced by cannabinoid CB(1) receptor antagonism less efficaciously than in lean mice. Small intestinal anandamide and 2-arachidonoylglycerol levels were reduced and increased respectively. In Zucker rats, endocannabinoids levels were higher in the pancreas, liver and duodenum, and lower in the subcutaneous adipose tissue. Food deprivation increased endocannabinoid levels in the duodenum and liver of both rat strains, in the pancreas of lean rats and in adipose tissues of Zucker rats.

CONCLUSIONS AND IMPLICATIONS

Reduced anandamide levels might account for increased intestinal motility in DIO mice. Regulation of endocannabinoid levels in rat peripheral tissues, induced by food deprivation and re-feeding, might participate in food intake and energy processing and was altered in Zucker rats. These data, together with previous observations, provide further evidence for dysregulation of peripheral endocannabinoids in obesity.

Cannabinoids and appetite: food craving and food pleasure

The ability of Cannabis sativa to promote eating has been documented for many centuries, with the drug reported by its users to promote strong cravings for, and an intensification of the sensory and hedonic properties of food. These effects are now known to result from the actions of cannabinoid molecules at specific cannabinoid receptor sites within the brain, and to reflect the physiological role of their natural ligands, the endocannabinoids, in the control of appetite. Recent developments in the biochemistry and pharmacology of endocannabinoid systems have generated convincing evidence from animal models for a normal role of endocannabinoids in the control of eating motivation. The availability of specific cannabinoid receptor agonists and antagonists raises the possibility of improved therapies for disorders of eating and body weight: not only in the suppression of appetite to counter our susceptibility to the over-consumption of highly pleasurable and energy-dense foods; but also in the treatment of conditions that involve reduced appetite and weight loss. Here, we outline some of the findings of the past decade that link endocannabinoid function appetite control, and the possible clinical applications of that knowledge.

Obesity, the endocannabinoid system, and bias arising from pharmaceutical sponsorship

BACKGROUND

Previous research has shown that academic physicians conflicted by funding from the pharmaceutical industry have corrupted evidence based medicine and helped enlarge the market for drugs. Physicians made pharmaceutical-friendly statements, engaged in disease mongering, and signed biased review articles ghost-authored by corporate employees. This paper tested the hypothesis that bias affects review articles regarding rimonabant, an anti-obesity drug that blocks the central cannabinoid receptor.

METHODS/PRINCIPAL FINDINGS

A MEDLINE search was performed for rimonabant review articles, limited to articles authored by USA physicians who served as consultants for the company that manufactures rimonabant. Extracted articles were examined for industry-friendly bias, identified by three methods: analysis with a validated instrument for monitoring bias in continuing medical education (CME); analysis for bias defined as statements that ran contrary to external evidence; and a tally of misrepresentations about the endocannabinoid system. Eight review articles were identified, but only three disclosed authors' financial conflicts of interest, despite easily accessible information to the contrary. The Takhar CME bias instrument demonstrated statistically significant bias in all the review articles. Biased statements that were nearly identical reappeared in the articles, including disease mongering, exaggerating rimonabant's efficacy and safety, lack of criticisms regarding rimonabant clinical trials, and speculations about surrogate markers stated as facts. Distinctive and identical misrepresentations regarding the endocannabinoid system also reappeared in articles by different authors.

CONCLUSIONS

The findings are characteristic of bias that arises from financial conflicts of interest, and suggestive of ghostwriting by a common author. Resolutions for this scenario are proposed.

Endocannabinoids, metabolic regulation, and the role of diet

Understanding the endocannabinoid system as it relates to health and disease is a relatively new area of study. The discovery and cloning of cannabinoid receptors have prompted an increase in research aimed at identifying endogenous ligands ("endocannabinoids") and how these receptors and ligands regulate a variety of physiologic and pathologic events that include bone formation, the cardiovascular system, appetite control, and energy metabolism. With regard to nutrition, researchers have begun to ask whether the known effects of diet on metabolic processes are mediated through endocannabinoids and their receptors. Although only a few studies have been conducted that directly address the role of diet, results indicate that endocannabinoids can be regulated by eating frequency and by specific dietary components, particularly fatty acids. This review provides an overview of the endocannabinoid system and its control of metabolism, with emphasis on the impact of diet.

The therapeutic modulation of atherogenic dyslipidemia and inflammatory markers in the metabolic syndrome: what is the clinical relevance?

The metabolic syndrome consists of a constellation of clinical and biochemical risk factors that cluster together and heighten the risk for atherogenesis, cardiovascular diseases, and diabetes. Established risk cardiovascular factors like hypertension, atherogenic dyslipidaemia, and glucose intolerance occur in the setting of insulin resistance and central adiposity, with genetic and environmental influences modulating the ultimate risk. Chronic insults to the endothelium take its toll in the form of silent as well as clinically evident cardiovascular events. The cellular and vascular accompaniments have shed some light into the underlying pathophysiology. Heightened, low-grade inflammatory processes as well as a continuum of vascular insults ranging from early endothelial derangements to advanced atherosclerosis have been examined. In recent years there has been an explosion of basic and clinical knowledge related to the metabolic syndrome. Although dyslipidaemia is considered a traditional risk component for the syndrome, its qualitative aspects, genetically determined subfractions, and variation in proatherogenic tendency have generated renewed interest and debate. New targets within the dyslipidaemic spectrum that have differing clinical relevance are being evaluated. The effect of heredity, lifestyle changes, pharmacotherapeutic agents, and supplements is being investigated. Further research into the impact of dyslipidemia and inflammation as both pathophysiologic risk factors and objects for targeted therapy in the metabolic syndrome should deepen our understanding and unravel answers to the underlying dynamics in this global epidemic.

Anxiolytic effects in mice of a dual blocker of fatty acid amide hydrolase and transient receptor potential vanilloid type-1 channels

The endocannabinoid-inactivating enzyme, fatty acid amide hydrolase (FAAH), and the transient receptor potential vanilloid type-1 (TRPV1) channel are new targets for the development of anxiolytic drugs. We studied the effect on anxiety-like behavior in the elevated plus maze of a dual FAAH/TRPV1 blocker, N-arachidonoyl-serotonin (AA-5-HT). In male C57BL/6J mice, acute intraperitoneal administration of AA-5-HT (0.1-2.5 mg/kg) increased both the time spent and the number of entries in the open arm, while being inactive at the highest dose tested (5 mg/kg). AA-5-HT was more potent than selective blockers of FAAH or TRPV1 (URB597 and SB366791, respectively). In male Swiss mice, AA-5-HT had to be administered chronically to observe an anxiolytic effect at an intermediate dose (2.5 mg/kg), the highest dose (5 mg/kg) being anxiogenic, and 1 mg/kg being ineffective. In both strains, the anxiolytic effects of AA-5-HT were paralleled by elevation of brain endocannabinoid levels and were reversed by per se inactive doses of the cannabinoid receptors of type-1 (CB(1)) receptor antagonist AM251, or the TRPV1 agonist, olvanil. Immunohistochemical localization of CB(1) and TRPV1 receptors was observed in mouse prefrontal cortex, nucleus accumbens, amygdala, and hippocampus. Simultaneous 'indirect' activation of CB(1) receptors following FAAH inhibition, and antagonism at TRPV1 receptors might represent a new therapeutic strategy against anxiety.

Use of cannabinoid CB1 receptor antagonists for the treatment of metabolic disorders

Abdominal obesity is associated with numerous metabolic abnormalities, including insulin resistance, impaired glucose tolerance/type-2 diabetes, and atherogenic dyslipidaemia with low high-density lipoprotein (HDL) cholesterol, high triglycerides, and increased small dense low-density lipoprotein (LDL) cholesterol. A proportion of these metabolic disorders may be attributed to increased endocannabinoid activity. The selective cannabinoid 1 (CB1) receptor antagonist rimonabant has been shown to reduce body weight, waist circumference, insulin resistance, triglycerides, dense LDL, C-reactive protein (CRP), and blood pressure, and to increase HDL and adiponectin concentrations in both non-diabetic and diabetic overweight/obese patients. Besides an improvement in glucose tolerance in non-diabetic subjects, a reduction of 0.5-0.7% in haemoglobin A1C (HbA(1c)) levels was consistently observed in various groups of patients with type-2 diabetes. Almost half the metabolic changes could not be explained by weight loss, supporting direct peripheral effects of rimonabant. Ongoing studies should demonstrate whether improved metabolic disorders with CB1 receptor antagonists (rimonabant, taranabant, etc.) would translate into fewer cardiovascular complications among high-risk individuals.

Central side-effects of therapies based on CB1 cannabinoid receptor agonists and antagonists: focus on anxiety and depression

Both agonists (e.g. Delta(9)-tetrahydrocannabinol, nabilone) and antagonists (e.g. rimonabant, taranabant) of the cannabinoid type-1 (CB(1)) receptor have been explored as therapeutic agents in diverse fields of medicine such as pain management and obesity with associated metabolic dysregulation, respectively. CB(1) receptors are widely distributed in the central nervous system and are involved in the modulation of emotion, stress and habituation responses, behaviours that are thought to be dysregulated in human psychiatric disorders. Accordingly, CB(1) receptor activation may, in some cases, precipitate episodes of psychosis and panic, while its inhibition may lead to behaviours reminiscent of depression and anxiety-related disorders. The present review discusses these side-effects, which have to be taken into account in the therapeutic exploitation of the endocannabinoid system.

Effect of rimonabant, micronised fenofibrate and their combination on cardiometabolic risk factors in overweight/obese patients: a pilot study

OBJECTIVE

To assess the effect of rimonabant, micronised fenofibrate and their combination on anthropometric and metabolic parameters in overweight/obese patients with dyslipidaemia.

METHODS

All patients (n = 30) received a hypocaloric diet ( approximately 600 kcal/day deficit) and were randomly allocated to receive open-label rimonabant (R) 20 mg/day (n = 10), micronised fenofibrate (F) 200 mg/day (n = 10) or rimonabant 20 mg/day plus fenofibrate 200 mg/day (RF) (n = 10). Anthropometric and metabolic parameters were assessed at baseline and 3 months after treatment initiation.

RESULTS

Compared with baseline similar significant reductions in body weight, body mass index and waist circumference were observed in the R (-6, -5 and -5%, respectively; p < 0.01) and RF group (-5% for all, p < 0.05), while improvements in these parameters were smaller in the F group (-2, -2.5 and -2%, respectively; p < 0.05). Triglycerides were reduced by 18% in the R group (p = NS), by 39% in the F group (p < 0.001) and by 46% in the RF group (p < 0.05). Importantly, combination treatment resulted in a 42% increase in high-density lipoprotein cholesterol (HDL-C) levels (p < 0.05), while HDL-C was not significantly altered in the two monotherapy groups. Subsequently, a more pronounced increase in apolipoprotein A-I (ApoA-I) levels (+25%) was observed in the RF group compared with changes in both monotherapy groups (p < 0.0001 vs R and p < 0.005 vs F group). Low-density lipoprotein cholesterol (LDL-C) levels were not significantly altered in any group. Apolipoprotein B (apoB) levels were reduced in all groups and this reduction was significantly more pronounced in the RF group (p < 0.05 vs baseline as well as p < 0.005 and p < 0.01 for RF vs R and F groups, respectively). ApoB/apoA-I ratio decreased by 3% with R (p = NS), by 18% with F (p < 0.05) and by 40% with RF treatment (p < 0.01). Total cholesterol to HDL-C ratio decreased by 20% with F (p < 0.0001) and by 33% with RF therapy (p < 0.005), while it was not significantly altered in R group.

CONCLUSION

The combination of rimonabant and fenofibrate may further improve metabolic parameters in overweight/obese patients with dyslipidaemia compared with each monotherapy. This improvement is particularly pronounced for HDL-C levels.

Role of endocannabinoid signaling in anxiety and depression

Cannabinoid receptors and their endogenous ligands are located throughout the limbic, or "emotional," brain, where they modulate synaptic neurotransmission. Converging preclinical and clinical data suggest a role for endogenous cannabinoid signaling in the modulation of anxiety and depression. Augmentation of endocannabinoid signaling (ECS) has anxiolytic effects, whereas blockade or genetic deletion of CB₁ receptors has anxiogenic properties. Augmentation of ECS also appears to have anti-depressant actions, and in some assays blockade and genetic deletion of CB₁ receptors produces depressive phenotypes. These data provide evidence that ECS serves in an anxiolytic, and possibly anti-depressant, role. These data suggest novel approaches to treatment of affective disorders which could include enhancement of endogenous cannabinoid signaling, and warrant cautious use of CB₁ receptor antagonists in patients with pre-existing affective disorders.

Obesity and reproduction: an educational bulletin

This Educational Bulletin describes the effect of obesity on reproduction and discusses treatment options.

Effect of tesofensine on bodyweight loss, body composition, and quality of life in obese patients: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Weight-loss drugs produce an additional mean weight loss of only 3-5 kg above that of diet and placebo over 6 months, and more effective pharmacotherapy of obesity is needed. We assessed the efficacy and safety of tesofensine-an inhibitor of the presynaptic uptake of noradrenaline, dopamine, and serotonin-in patients with obesity.

METHODS

We undertook a phase II, randomised, double-blind, placebo-controlled trial in five Danish obesity management centres. After a 2 week run-in phase, 203 obese patients (body-mass index 30-</=40 kg/m(2)) were prescribed an energy restricted diet and randomly assigned with a list of randomisation numbers to treatment with tesofensine 0.25 mg (n=52), 0.5 mg (n=50), or 1.0 mg (n=49), or placebo (n=52) once daily for 24 weeks. The primary outcome was percentage change in bodyweight. Analysis was by modified intention to treat (all randomised patients with measurement after at least one dose of study drug or placebo). The study is registered with ClinicalTrials.gov, number NCT00394667.

FINDINGS

161 (79%) participants completed the study. After 24 weeks, the mean weight loss produced by diet and placebo was 2.0% (SE 0.60). Tesofensine 0.25 mg, 0.5 mg, and 1.0 mg and diet induced a mean weight loss of 4.5% (0.87), 9.2% (0.91), and 10.6% (0.84), respectively, greater than diet and placebo (p<0.0001). The most common adverse events caused by tesofensine were dry mouth, nausea, constipation, hard stools, diarrhoea, and insomnia. After 24 weeks, tesofensine 0.25 mg and 0.5 mg showed no significant increases in systolic or diastolic blood pressure compared with placebo, whereas heart rate was increased by 7.4 beats per min in the tesofensine 0.5 mg group (p=0.0001).

INTERPRETATION

Our results suggest that tesofensine 0.5 mg might have the potential to produce a weight loss twice that of currently approved drugs. However, these findings of efficacy and safety need confirmation in phase III trials.

Brain TRPV1: a depressing TR(i)P down memory lane?

On sensory neurons, the capsaicin receptor TRPV1 (transient receptor potential, vanilloid subfamily, member 1) functions as a molecular integrator of noxious stimuli and represents a novel target for analgesic drugs. The presence of TRPV1 in the brain is now well established but, despite intensive research, its function is only beginning to be understood. New evidence implies an unexpected role for hippocampal TRPV1 in neuropsychiatric disorders. For instance, it was hypothesized that the effects of the cannabinoid-receptor antagonist rimonabant on mood might be due to its capability to antagonize TRPV1 receptors at high doses. Most studies, however, imply a positive (e.g. anxiolytic) outcome for TRPV1 antagonism. With potent small-molecule TRPV1 antagonists undergoing clinical trials, the effect of brain TRPV1 blockade might determine the future of this class of novel analgesic drugs. Clearly, more research is needed to delineate the biological role of brain TRPV1 receptors.

Endocannabinoid signaling as a synaptic circuit breaker in neurological disease

Cannabis sativa is one of the oldest herbal plants in the history of medicine. It was used in various therapeutic applications from pain to epilepsy, but its psychotropic effect has reduced its usage in recent medical practice. However, renewed interest has been fueled by major discoveries revealing that cannabis-derived compounds act through a signaling pathway in the human body. Here we review recent advances showing that endocannabinoid signaling is a key regulator of synaptic communication throughout the central nervous system. Its underlying molecular architecture is highly conserved in synapses from the spinal cord to the neocortex, and as a negative feed-back signal, it provides protection against excess presynaptic activity. The endocannabinoid signaling machinery operates on demand in a synapse-specific manner; therefore, its modulation offers new therapeutic opportunities for the selective control of deleterious neuronal activity in several neurological disorders.

The endocannabinoid system in obesity and type 2 diabetes

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.

A practical "ABCDE" approach to the metabolic syndrome

The metabolic syndrome comprises a cluster of risk factors for cardiovascular disease and type 2 diabetes mellitus that are due to abdominal obesity and insulin resistance. This increasingly important proinflammatory condition remains both underrecognized and undertreated. To aid physicians in their approach to the metabolic syndrome, we assessed and synthesized the literature on cardiovascular risk assessment and early intervention for risk reduction. We performed a comprehensive search of MEDLINE and the Cochrane database for peer-reviewed clinical studies published from January 1, 1988, to December 31, 2007, augmented by consultation with content experts. We used the search terms metabolic syndrome, abdominal obesity, waist circumference, insulin resistance, cardiovascular disease, prediabetes, diabetes, treatment, prevention, aspirin, hypertension, cholesterol, atherogenic dyslipidemia, lifestyle therapy, diet, and exercise. Criteria used for study review were controlled study design, English language, relevance to clinicians, and validity based on experimental design and appropriateness of conclusions. Although growing evidence supports early intervention in patients with the metabolic syndrome, many physicians do not recognize the risk associated with this condition and fail to initiate early treatment. A comprehensive management plan can be assembled through an "ABCDE" approach: "A" for assessment of cardiovascular risk and aspirin therapy, "B" for blood pressure control, "C" for cholesterol management, "D" for diabetes prevention and diet therapy, and "E" for exercise therapy. This ABCDE approach provides a practical and systematic framework for encouraging metabolic syndrome recognition and for implementing a comprehensive, evidence-based management plan for the reduction of cardiovascular risk.

Inhibitors of cannabinoid receptors and glucose metabolism

PURPOSE OF REVIEW

Abdominal obesity is closely related to type 2 diabetes and overactivity of the endocannabinoid system. The present review aims at evaluating the role of endocannabinoid system in glucose dysregulation and the effects of cannabinoid 1 receptor blockade on glucose metabolism in both animal models and overweight/obese humans, especially with type 2 diabetes.

RECENT FINDINGS

Cannabinoid 1 receptors have been identified not only in the brain, but also in the adipose tissue, the gut, the liver, the skeletal muscle and even the pancreas, all organs playing a key role in glucose metabolism and type 2 diabetes. Rimonabant, the first selective cannabinoid 1 receptor blocker in clinical use, has been shown to reduce body weight, waist circumference, glycated haemoglobin, triglycerides, insulin resistance index, and to increase HDL cholesterol and adiponectin concentrations in patients with type 2 diabetes, confirming data on nondiabetic overweight/obese patients. Almost half of the metabolic changes, including glycated haemoglobin reduction, could not be explained by weight loss, in agreement with direct peripheral effects.

SUMMARY

Cannabinoid 1 blockade reduces food intake and body weight and improves metabolic regulation beyond just weight loss. Because of its positive effect on glucose metabolism, rimonabant deserves consideration in the treatment of overweight/obese patients with type 2 diabetes.

Targeting the endocannabinoid system: to enhance or reduce?

As our understanding of the endocannabinoids improves, so does the awareness of their complexity. During pathological states, the levels of these mediators in tissues change, and their effects vary from those of protective endogenous compounds to those of dysregulated signals. These observations led to the discovery of compounds that either prolong the lifespan of endocannabinoids or tone down their action for the potential future treatment of pain, affective and neurodegenerative disorders, gastrointestinal inflammation, obesity and metabolic dysfunctions, cardiovascular conditions and liver diseases. When moving to the clinic, however, the pleiotropic nature of endocannabinoid functions will require careful judgement in the choice of patients and stage of the disorder for treatment.

Rimonabant in rats with a metabolic syndrome: good news after the depression

The synthetic cannabinoid CB1 receptor antagonist rimonabant (sold in the United Kingdom under the brand name Acomplia) was reported to improve the profile of cardiovascular risk factors in obese patients with the metabolic syndrome, a cluster of metabolic disorders that often precedes the onset of type II diabetes. Rimonabant is shown in the current issue of British Journal of Pharmacology to attenuate weight gain in Zucker rats, an experimental model of insulin resistance. Neutrophil and monocyte counts were lowered by rimonabant administration. Both platelet activation (by ADP) and aggregation (in response to thrombin) were inhibited. Circulating pro-inflammatory cytokine levels (monocyte chemotactic protein 1, MCP1 and Regulated upon Activation, Normal T-cell Expressed and Secreted, RANTES) were also reduced. Furthermore, fibrinogen levels returned to normal. These favourable anti-inflammatory and anti-thrombotic actions imply for rimonabant a peripheral, direct action on some cardiovascular risk factors.