Rimonabant: a cannabinoid receptor blocker for the treatment of metabolic and cardiovascular risk factors

Cannabinoid Analgesia in Postoperative Pain Management: From Molecular Mechanisms to Clinical Reality

Postoperative pain (POP) is a challenging clinical phenomenon that affects the majority of surgical patients and demands effective management to mitigate adverse outcomes such as persistent pain. The primary goal of POP management is to alleviate suffering and facilitate a seamless return to normal function for the patient. Despite compelling evidence of its drawbacks, opioid analgesia remains the basis of POP treatment. Novel therapeutic approaches rely on multimodal analgesia, integrating different pharmacological strategies to optimize efficacy while minimizing adverse effects. The recognition of the imperative role of the endocannabinoid system in pain regulation has prompted the investigation of cannabinoid compounds as a new therapeutic avenue. Cannabinoids may serve as adjuvants, enhancing the analgesic effects of other drugs and potentially replacing or at least reducing the dependence on other long-term analgesics in pain management. This narrative review succinctly summarizes pertinent information on the molecular mechanisms, clinical therapeutic benefits, and considerations associated with the plausible use of various cannabinoid compounds in treating POP. According to the available evidence, cannabinoid compounds modulate specific molecular mechanisms intimately involved in POP. However, only two of the eleven clinical trials that evaluated the efficacy of different cannabinoid interventions showed positive results.

The Role of Endocannabinoid System Blockade in the Treatment of the Metabolic Syndrome

This review considers the use of the first selective blocker of the cannabinoid receptor type 1, rimonabant, to reduce weight and improve cardiovascular disease risk factors in obese patients with metabolic syndrome or multiple cardiovascular disease risk factors. In 4 large trials-Rimonabant in Obesity (RIO)-Lipids, RIO-Europe, RIO-North America, and RIO-Diabetes-after 1 to 2 years of treatment, rimonabant (20 mg/day) led to a significantly greater weight loss and reduction in waist circumference compared with placebo. Treatment with rimonabant was also associated with other favorable changes, including better glycemic control in type 2 diabetes mellitus, improved lipid profile, reduced blood pressure, increased adiponectin levels, fall in high-sensitivity C-reactive protein concentrations, and an overall decrease in the prevalence of the metabolic syndrome. Initial experience with rimonabant shows that it is generally well tolerated with the most common side effect of mild nausea. Rimonabant may be a useful adjunct to lifestyle and behavior modification in the treatment of obese subjects with metabolic syndrome or multiple cardiometabolic risk factors.

Is nicotine a key player or spectator in the induction and progression of cardiovascular disorders?

Cigarette smoking is common in societies worldwide and a growing body of evidence suggests that chronic cigarette smoking may affect the structure and function of cardiovascular system. The chronic exposure to high levels of nicotine, a major component of cigarette smoking, has been observed to play a pathogenic role in the induction and progression of cardiovascular disorders including cardiomyopathy and peripheral vascular disease. Nicotine alters the function of vascular endothelium, initiates the adhesion cascade and stimulates the vascular inflammatory events to induce atherosclerosis and hypertension. Moreover, nicotine has been noted to induce direct coronary spasm and ischemia, which develop coronary artery disease and myocardial infarction. In addition, nicotine stimulates the excessive release of impulses from sinoatrial node that may account for the induction of cardiac arrhythmia. The present review critically discussed the possible detrimental role of chronic nicotine exposure in cardiac and vascular endothelial dysfunction. Moreover, the signaling mechanisms involved in the pathogenesis of nicotine exposure-induced cardiovascular dysfunction have been discussed. In addition, the pharmacological interventions to ameliorate chronic nicotine exposure-induced cardiovascular abnormalities have been delineated.

Smoking cessation pharmacotherapy

Cigarette smoking remains an important risk factor for premature cardiovascular disease and its many complications. There are clear benefits from treating tobacco dependence on the rate of clinical outcomes. In addition to behavioral therapies, various pharmacologic strategies have been developed to help achieve this goal. First-line therapies include nicotine replacement, bupropion and varenicline, a partial nicotine antagonist. Second-line treatments include clonidine and nortriptyline. Additional treatment strategies with less proven efficacy include monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, opioid receptor antagonists, bromocriptine, anti-anxiety drugs, nicotinic receptor antagonists (e.g. mecamylamine) and glucose tablets. Various approaches under investigation include inhibitors of the hepatic P450 enzyme (e.g. methoxsalen), cannabinoid-1 receptor antagonists (e.g. rimonabant), and nicotine vaccines.

Neuroendocrine control of food intake

Appetite is regulated by a complex system of central and peripheral signals which interact in order to modulate the individual response to nutrient ingestion. Peripheral regulation includes satiety signals and adiposity signals, while central control is accomplished by several effectors, including the neuropeptidergic, monoaminergic and endocannabinoid systems. Satiety signals, including cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), originate from the gastrointestinal (GI) tract during a meal and, through the vagus nerve, reach the nucleus tractus solitarius (NTS) in the caudal brainstem. From NTS afferents fibers project to the arcuate nucleus (ARC), where satiety signals are integrated with adiposity signals, namely leptin and insulin, and with several hypothalamic and supra-hypothalamic inputs, thus creating a complex network of neural circuits which finally elaborate the individual response to a meal. As for the neuropeptidergic system, ARC neurons secrete orexigenic substances, such as neuropeptide Y (NPY) and agouti-related peptide (AGRP), and anorexigenic peptides such as pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Other brain areas involved in the control of food intake are located downstream the ARC: among these, the paraventricular nucleus (PVN), which produces anorexigenic peptides such as thyrotropin releasing hormone (TRH), corticotrophin releasing hormone (CRH) and oxytocin, the lateral hypothalamus (LHA) and perifornical area (PFA), secreting the orexigenic substances orexin-A (OXA) and melanin concentrating hormone (MCH). A great interest in endocannabinoids, important players in the regulation of food intake, has recently developed. In conclusion, the present work reviews the most recent insights into the complex and redundant molecular mechanisms regulating food intake, focusing on the most encouraging perspectives for the treatment of obesity.

Genetic variations at the endocannabinoid type 1 receptor gene (CNR1) are associated with obesity phenotypes in men

CONTEXT

The endocannabinoid system modulates food intake and body weight in animal models. Treatment with the cannabinoid type 1 receptor blocker, rimonabant, reduces body weight in obese individuals.

OBJECTIVE

The aim of this study was to determine whether single nucleotide polymorphisms of the gene encoding cannabinoid type 1 receptor, CNR1, are associated with body fat mass and distribution in two independent samples of white European adult men.

DESIGN, SETTING, AND PARTICIPANTS

The 3813A/G and 4895A/G single nucleotide polymorphisms at the exon 4 of CNR1 were genotyped in 930 participants to the Olivetti Prospective Heart Study (OPHS) in Southern Italy and in 216 participants to the Wandsworth Heart and Stroke Study in the United Kingdom. Retrospective analysis was also performed on an OPHS subsample (n = 360) for which anthropometric data from 1987 and 1994-1995 examinations were available.

MAIN OUTCOME MEASURES

CNR1 genotypes and anthropometric measures of body fat distribution were determined.

RESULTS

In the OPHS study, the 3813G allele was associated with increased subscapular skinfold thickness (24.2 +/- 9.1 vs. 22.8 +/- 7.7 mm; P = 0.031) and waist circumference (WC) (99.1 +/- 8.8 vs. 97.7 +/- 8.8 cm; P = 0.050). No association was observed with 4895A/G variant. Haplotype analysis confirmed that the unique haplotype carrying the 3813G was associated with increased WC and subscapular skinfold thickness. Similar results were observed in the OPHS retrospective subsample and the Wandsworth Heart and Stroke Study sample. In the latter, the 3813G was associated with increased WC (96.8 +/- 11.3 vs. 91.6 +/- 10.4 cm; P = 0.006).

CONCLUSIONS

Genetic variants at CNR1 are associated with obesity-related phenotypes in men. The detection of polymorphic variants in genes involved in the process of fat accumulation may help identify specific targets for pharmacological treatment of obesity and related metabolic abnormalities.

Cannabinoids as therapeutic agents in cardiovascular disease: a tale of passions and illusions

In addition to their classical known effects, such as analgesia, impairment of cognition and learning and appetite enhancement, cannabinoids have also been related to the regulation of cardiovascular responses and implicated in cardiovascular pathology. Elevated levels of endocannabinoids have been related to the extreme hypotension associated with various forms of shock as well as to the cardiovascular abnormalities that accompany cirrhosis. In contrast, cannabinoids have also been associated with beneficial effects on the cardiovascular system, such as a protective role in atherosclerosis progression and in cerebral and myocardial ischaemia. In addition, it has also been suggested that the pharmacological manipulation of the endocannabinoid system may offer a novel approach to antihypertensive therapy. During the last decades, the tremendous increase in the understanding of the molecular basis of cannabinoid activity has encouraged many pharmaceutical companies to develop more potent synthetic cannabinoid analogues and antagonists, leading to an explosion of basic research and clinical trials. Consequently. not only the synthetic THC dronabinol (Marinol) and the synthetic THC analogue nabilone (Cesamet) have been approved in the United States, but also the standardized cannabis extract (Sativex) in Canada. At least three strategies can be foreseen in the future clinical use of cannabinoid-based drugs: (a) the use of CB(1) receptor antagonists, such as the recently approved rimonabant (b) the use of CB(2)-selective agonists, and (c) the use of inhibitors of endocannabinoid degradation. In this context, the present review examines the effects of cannabinoids and of the pharmacological manipulation of the endocannabinoid system, in cardiovascular pathophysiology.

Mechanisms of disease: HDL metabolism as a target for novel therapies

Plasma concentrations of HDL cholesterol are inversely correlated with risk of coronary heart disease, and low HDL-cholesterol levels are a risk factor even in patients aggressively treated for LDL reduction. Thus, there is great interest in targeting HDL cholesterol therapeutically. The existing approaches are limited in their ability to raise HDL-cholesterol levels, and there has, therefore, been a major focus on the development of novel therapies. The goal of new approaches is to either raise HDL-cholesterol levels or improve the function of HDL. Here, the current status of the development of novel therapies targeted toward HDL metabolism is reviewed.

Smoking Cessation Pharmacotherapy?Nicotine and Non-Nicotine Preparations

Cigarette smokers tend to die prematurely from a number of diseases. Cigarette smoking is an important modifiable risk factor for cardiovascular morbidity and mortality. Despite the clear health benefits of smoking cessation, smokers usually find it difficult to stop and behavioral therapies often prove insufficient. Pharmacologic intervention may aid the process because of the addictive nature of nicotine. Nicotine replacement therapy, which is regarded as first-line therapy, was developed to overcome the symptoms of nicotine withdrawal that many patients find distressing. Different modes of administration include inhalation and buccal or transdermal absorption. The orally administered non-nicotine drugs varenicline and bupropion are also regarded as first-line treatments, either used alone or as an adjunct to nicotine replacement therapy. Second-line treatments include clonidine and nortriptyline. Other treatment strategies that have been examined include monoamine oxidase inhibitors and selective serotonin reuptake inhibitors; efficacy has yet to be proven definitively. A novel approach to treatment using the cannabinoid-1 receptor antagonist rimonabant is also under investigation.

Effects of Combined Oleoyl-Estrone and Rimonabant on Overweight Rats

Oleoyl-estrone (OE) decreases appetite, maintains energy expediture, induces lipolysis (sparing protein), and decreases cholesterolemia and insulin resistance. Rimonabant (SR141716) is a cannabinoid-receptor inhibitor that decreases appetite and mobilizes fat. We studied whether their combination improves their slimming effects. Male overweight rats received daily gavages of 5.3 mg/kg OE, 10 mg/kg rimonabant, or both drugs during 10 days. Body weight and composition, energy balance, adipose tissue weight, and serum hormones and metabolites were measured. OE halved food intake and maintained energy expenditure at the expense of body fat. Rimonabant effects on appetite and energy balance were less marked, resulting in lower lipid mobilization. OE and rimonabant followed the OE pattern, with no additive or synergic effects. Glycemia was maintained, but OE decreased insulin, GLP-1, and cholesterol, whilst rimonabant increased cholecystokinin and cholesterol, and decreased NEFA. Both drugs decreased leptin and triacylglycerols; ghrelin was unchanged. The results hint at different mechanisms of action of both drugs: we can assume that OE effects do not involve the cannabinoid pathway. OE does not seem to act, either, after 10 days, through the secretion of ghrelin or the intestinal appetite-controlling peptides tested.

Is the metabolic syndrome a real clinical entity and should it receive drug treatment?

Metabolic syndrome represents a cluster of risk factors commonly associated with obesity and diabetes that in turn are associated with an increased risk of cardiovascular disease. The worldwide prevalence of metabolic syndrome, obesity, and diabetes is on the rise, leading to serious public health concerns surrounding the downstream consequences in the form of premature cardiovascular disease. In this review, we examine the debate surrounding the characterization and diagnosis of metabolic syndrome and discuss potential treatment options.

Rimonabant for overweight or obesity

BACKGROUND

Worldwide, the prevalence of obesity and overweight in industrialized countries and in a substantial number of developing countries is increasing at an alarming rate. Rimonabant is a selective cannabinoid-1 receptor antagonist that has been investigated for its efficacy in reducing body weight and associated risk factors in obese people. Phase III trials are now under way to test the use of rimonabant for long-term weight-loss. Given the prevalence of overweight and obesity, it is important to establish the efficacy and safety of rimonabant.

OBJECTIVES

To assess the effects of rimonabant in overweight and obese people.

SEARCH STRATEGY

MEDLINE, EMBASE, The Cochrane Library, LILACS, databases of ongoing trials and reference lists were used to identify relevant trials. The last search was conducted in June 2006.

SELECTION CRITERIA

Randomised controlled trials comparing rimonabant with placebo or other weight loss interventions in overweight or obese adults.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed all potentially relevant citations for inclusion and methodological quality. The primary outcome measures were weight loss change, morbidity and adverse effects occurrence.

MAIN RESULTS

Four studies evaluating rimonabant 20 mg versus rimonabant 5 mg versus placebo in addition to a hypocaloric diet lasting at least one year were included. Compared with placebo, rimonabant 20 mg produced a 4.9 kg greater reduction in body weight in trials with one-year results. Improvements in waist circumference, high-density lipoprotein cholesterol, triglyceride levels and systolic and diastolic blood pressure were also seen. However, the results with rimonabant 5 mg demonstrated a weight reduction which was only 1.3 kg greater when compared with placebo. No clinically relevant effects on plasma lipids and blood pressure were found. Rimonabant 20 mg caused significant more adverse effects both of general and serious nature, especially of nervous system, psychiatric or gastro-intestinal origin. Attrition rates were approximately 40% at the end of one year.

AUTHORS' CONCLUSIONS

The use of rimonabant after one year produces modest weight loss of approximately 5%. Even modest amounts of weight loss may be potentially beneficial. The observed results should be interpreted with some caution, though, since the evaluated studies presented some deficiencies in methodological quality. Studies with longer follow-ups after the end of treatment and of more rigorous quality should be done before definitive recommendations can be made regarding the role of this new medication in the management of overweight or obese patients.

Efficacy of rimonabant and other cannabinoid CB1 receptor antagonists in reducing food intake and body weight: preclinical and clinical data

The present paper focuses on the different lines of evidence indicating that cannabinoid CB(1) receptor antagonists, including the prototype rimonabant, reduce food intake and body weight in laboratory animals. Recent clinical surveys demonstrated that rimonabant significantly reduced body weight also in overweight/obese humans. Treatment with rimonabant was associated with a beneficial effect on different metabolic parameters and cardiovascular risk factors linked to overweight. The data reviewed in this paper suggest that cannabinoid CB(1) receptor antagonists may constitute a novel class of drugs potentially effective in the treatment of obesity-related disorders.

Reducing residual cardiovascular risk: the relevance of raising high-density lipoprotein cholesterol in patients on cholesterol-lowering treatment

Reducing low-density lipoprotein cholesterol (LDL-C) with statin therapy represents the cornerstone of dyslipidaemia management in patients with cardiovascular disease, as reflected in current treatment guidelines. Yet even among statin-treated patients who achieve LDL-C targets (< 2.59 mmol/L [100 mg/dL]), the residual risk of further cardiovascular events remains unacceptably high. Although clinical studies indicate that intensive LDL-C lowering may provide some additional benefit, this does not suppress the excess cardiovascular risk sufficiently. This European Expert Panel therefore recognises that there is an unmet clinical need in the management of these patients. Additional intervention to modify other clinically important risk factors should be viewed as a priority.

A reduced level of high-density lipoprotein cholesterol (HDL-C) < 1.03 mmol/L (40 mg/dL) in men and < 1.29 mmol/L (50 mg/dL) in women is an important independent predictive factor for coronary heart disease. HDL-C levels are also predictive of cardiovascular risk in statin-treated patients, irrespective of their LDL-C levels. Therefore, HDL-C represents a logical therapeutic target for reducing cardiovascular risk further in statin-treated patients, including those who achieve LDL-C targets. Given that low HDL-C is common among dyslipidaemic patients with cardiovascular disease, a therapeutic strategy aimed at effectively raising HDL-C, while at the same time lowering LDL-C to target levels, would be expected to offer clinical benefit beyond that achieved through LDL-C reduction alone. Although both nicotinic acid and fibrates raise HDL-C, nicotinic acid has greater potency. Studies show that combination therapy with prolonged-release (PR) nicotinic acid and a statin has an acceptable tolerability profile, normalises an atherogenic lipoprotein profile, and is able to induce regression of atherosclerosis and reduce coronary risk in patients with established cardiovascular disease and suboptimal HDL-C levels.

In conclusion, this European Expert Panel recommends that combination therapy with a statin and an HDL-C raising agent, such as PR nicotinic acid, should be considered in these patients, who remain at high residual risk despite achieving target LDL-C levels with statin monotherapy. Ongoing studies are essential to confirm the clinical outcome benefits of this approach.

Smoking, smoking cessation, and risk of cardiovascular disease

Cigarette smoking increases the risk of atherothrombotic clinical events such as myocardial infarction and the effect is dose dependent for persons who continue to smoke. Reductions in smoking habit and smoking cessation are important ways to improve cardiovascular risk and favorably affect primary and secondary prevention of clinical disease. Therapeutic methods to improve smoking reduction and cessation include nicotine replacement, behavioral interventions, and medications (bupropion, clonidine). Improved cessation rates are under active study and include behavioral methods, targeting smokers immediately after myocardial infarction, consideration of depression in smokers, pharmacogenomics to identify persons who may respond more favorably to specific interventions, and newer medications that affect endocannabinoid receptors.