Category Archives: Obesity

Cannabinoid receptors as therapeutic targets for obesity and metabolic diseases.

Posted on by
Reply

Abstract

“One of the most interesting pharmacological targets proposed in the past ten years for fighting obesity and related metabolic disorders is the endocannabinoid system. The role of the endocannabinoid system is crucial in regulating the rewarding properties of food, in controlling energy balance by acting at the hypothalamic circuitries involved in food intake, and in peripheral metabolism by influencing adipocytes, hepatocytes, myocytes and pancreatic endocrine cells. Obesity seems to be a condition associated with a pathological overactivation of the endocannabinoid system; therefore, restoring a normal endocannabinoid tone by antagonizing the cannabinoid receptor type 1 (CB(1)) could help arrest both the development and the maintenance of obesity.”

http://www.ncbi.nlm.nih.gov/pubmed/17027338

How many sites of action for endocannabinoids to control energy metabolism?

Posted on by
Reply

Abstract

“The promising results obtained by clinical trials using Rimonabant to tackle visceral obesity and related disorders recently promoted a remarkable impulse to carry out detailed investigations into the mechanisms of action of endocannabinoids in regulating food intake and energy metabolism. The endocannabinoid system has been known for many years to play an important role in the modulation of the neuronal pathways mediating the rewarding properties of food. However, in the last few years, with the advanced understanding of the crucial role of the hypothalamic neuronal network in the regulation of appetite, several studies have also directed attention to the orexigenic role of the endocannabinoid system, substantiating the well known appetite stimulating properties of derivatives of Cannabis sativa. Furthermore, the last 2 years have seen a number of relevant publications emphasizing the role of endocannabinoids as significant players in various peripheral metabolic processes. To date, the roles of the endocannabinoid system in influencing energy metabolism have proved to be more complex than was formerly believed. However, the diverse ability to modulate both central and peripheral processes highlights the pivotal involvement of the endocannabinoid system in the control of metabolic processes. This review describes the roles of endocannabinoids and the cannabinoid type 1 receptor (CB1) in the control of energy balance.”

http://www.ncbi.nlm.nih.gov/pubmed/16570104

Contribution of CB1 blockade to the management of high-risk abdominal obesity.

Posted on by
Reply

Abstract

“The worldwide increase in the prevalence of type 2 diabetes represents a tremendous challenge for our healthcare system, especially if we consider that this phenomenon is largely explained by the epidemic of obesity. However, despite the well-recognized increased morbidity and mortality associated with an elevated body weight, there is now more and more evidence highlighting that abdominal adipose tissue is the fat depot that conveys the greatest risk of metabolic complications. This cluster of metabolic abnormalities has been referred to as the metabolic syndrome and this condition is largely the consequence of abdominal obesity, especially when accompanied by a high accumulation of visceral adipose tissue. This cluster of metabolic complications has also been found to be predictive of a substantially increased risk of coronary heart disease beyond the presence of traditional risk factors. Moreover, a moderate weight loss in initially abdominally obese patients is associated with a selective mobilization of visceral adipose tissue, leading to improvements in the metabolic risk profile predictive of a reduced risk of coronary heart disease and of type 2 diabetes. The recent discovery of the endocannabinoid-CB1 receptor system and of its impact on the regulation of energy metabolism represents a significant advance, which will help physicians target abdominal obesity and its related metabolic complications. In this regard, studies have shown that rimonabant therapy (the first developed CB1 blocker) could be useful for the management of clustering cardiovascular disease risk factors in high-risk abdominally obese patients through its effects not only on energy balance but also on adipose tissue metabolism. For instance, the presence of CB1 receptors in adipose tissue and the recently reported effect of rimonabant on adiponectin production by adipose cells may represent a key factor responsible for the weight loss-independent effect of this CB1 blocker on cardiometabolic risk variables.”

http://www.ncbi.nlm.nih.gov/pubmed/16570106

Expression of the cannabinoid system in muscle: effects of a high-fat diet and CB1 receptor blockade

Posted on by
Reply

Abstract

“The ECS (endocannabinoid system) plays an important role in the onset of obesity and metabolic disorders, implicating central and peripheral mechanisms predominantly via CB1 (cannabinoid type 1) receptors. CB1 receptor antagonist/inverse agonist treatment improves cardiometabolic risk factors and insulin resistance. However, the relative contribution of peripheral organs to the net beneficial metabolic effects remains unclear. In the present study, we have identified the presence of the endocannabinoid signalling machinery in skeletal muscle and also investigated the impact of an HFD (high-fat diet) on lipid-metabolism-related genes and endocannabinoid-related proteins. Finally, we tested whether administration of the CB1 inverse agonist AM251 restored the alterations induced by the HFD. Rats were fed on either an STD (standard/low-fat diet) or an HFD for 10 weeks and then treated with AM251 (3 mg/kg of body weight per day) for 14 days. The accumulated caloric intake was progressively higher in rats fed on the HFD than the STD, resulting in a divergence in body weight gain. AM251 treatment reduced accumulated food/caloric intake and body weight gain, being more marked in rats fed on the HFD. CB2 (cannabinoid type 2) receptor and PPARα (peroxisome-proliferator-activated receptor α) gene expression was decreased in HFD-fed rats, whereas MAGL (monoglyceride lipase) gene expression was up-regulated. These data suggest an altered endocannabinoid signalling as a result of the HFD. AM251 treatment reduced CB2 receptor, PPARγ and AdipoR1 (adiponectin receptor 1) gene expression in STD-fed rats, but only partially normalized the CB2 receptor in HFD-fed rats. Protein levels corroborated gene expression results, but also showed a decrease in DAGL (diacylglycerol) β and DAGLα after AM251 treatment in STD- and HFD-fed rats respectively. In conclusion, the results of the present study indicate a diet-sensitive ECS in skeletal muscle, suggesting that blockade of C1 receptors could work towards restoration of the metabolic adaption imposed by diet.”

“In the present study, we focused on skeletal muscles, which are an important tissue for glucose and fat oxidation, being an important site for insulin action [27]. However, despite the fact that AEA can modify the pathways regulating fatty acid oxidation in the skeletal muscle, probably via CB1 receptors, suggesting that CB1 receptor antagonism would have an important role in oxidative metabolism and energy regulation [28,29], there is still a general lack of clarity regarding the physiological functions and molecular mechanism implicated. In fact, there are almost no studies demonstrating the presence of endocannabinoid signalling proteins and their sensitivity to HFDs (high-fat diets). Therefore, in the present study, we have (i) investigated the presence of the endocannabinoid signalling machinery in skeletal muscle, (ii) analysed the impact of an HFD on lipid and glucose metabolism and endocannabinoid-related genes, and (iii) monitored the effects of the CB1 receptor inverse agonist AM251 during an STD (standard/low-fat diet) and HFD on the endocannabinoid machinery and the genes related to lipid oxidative metabolism in skeletal muscle of rats. Among the many molecules involved in lipid metabolism of skeletal muscle, we evaluated changes in the gene and protein expression of relevant components of the ECS, such as the CB1 and CB2 receptors and some of the enzymes responsible for their synthesis.

The presence of the ECS in skeletal muscle

As a final note, the regulatory mechanisms may be different at rest and during exercise, may change as the exercise intensity increases, and this could be influential in endocannabinoid production [31,49]. It would be interesting to repeat this type of experiment combining exercise and diet in its original design. Regulation of skeletal muscle fat and glucose metabolism is clearly multifactorial, and different mechanisms may dominate in different conditions; besides, potential variations may exist between individuals in response to stimulating or blocking CB1 receptors. This could cause differences in response to treatment with CB1 receptor antagonists between different obese states. In conclusion, we have provided findings identifying important relevant players involved in the signalling pathways of CB1 receptor antagonism in skeletal muscle and determined the extent of changes in this system associated with either an HFD or CB1 receptor blockade.”

http://www.biochemj.org/bj/433/0175/bj4330175.htm

Obesity-dependent cannabinoid modulation of proliferation in adult neurogenic regions.

Posted on by
Reply

Abstract

“Endocannabinoid signalling participates in the control of neurogenesis, especially after brain insults. Obesity may explain alterations in physiology affecting neurogenesis, although it is unclear whether cannabinoid signalling may modulate neural proliferation in obese animals. Here we analyse the impact of obesity by using two approaches, a high-fat diet (HFD, 60% fat) and a standard/low-fat diet (STD, 10% fat), and the response to a subchronic treatment with the cannabinoid receptor type 1 (CB1) inverse agonist AM251 (3 mg/kg) on cell proliferation of two relevant neurogenic regions, namely the subventricular zone in the striatal wall of the lateral ventricle (SVZ) and the subgranular zone of the dentate gyrus (SGZ), and also in the hypothalamus given its role in energy metabolism. We found evidence of an interaction between diet-induced obesity and CB1 signalling in the regulation of cell proliferation. AM251 reduced caloric intake and body weight in obese rats, as well as corrected plasma levels of cholesterol and triglycerides. AM251 is shown, for the first time, to modulate cell proliferation in HFD-obese rats only. We observed an increase in the number of 5-bromo-2-deoxyuridine-labelled (BrdU+) cells in the SGZ, but a decrease in the number of BrdU+ cells in the SVZ and the hypothalamus of AM251-treated HFD rats. These BrdU+ cells expressed the neuron-specific βIII-tubulin. These results suggest that obesity may impact cell proliferation in the brain selectively, and provide support for a role of CB1 signalling regulation of neurogenesis in response to obesity.”

http://www.ncbi.nlm.nih.gov/pubmed/21395869

Obesity, the Endocannabinoid System, and Bias Arising from Pharmaceutical Sponsorship

Posted on by
Reply

“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.

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.

In summary, financial conflicts permeate the system and are by no means limited to corporations referenced in this article, such as Merck, Parke-Davis, Pfizer, Sanofi-Aventis, and Wyeth-Ayerst. On balance, pharmaceutical corporations do good work and aid in humanitarian efforts. For example Sanofi-Aventis provides artemisinin at cost to malaria-endemic countries. Nevertheless, ghost authorship and the corrupting effects of covert financial support must cease. Only three of eight rimonabant review articles disclosed corporate sponsorship; two authors specifically denied conflicts. Lack of disclosure prevents readers from judging the credibility of an author. Medical journals should require stronger author disclosure procedures, and universities should discipline academics who sign ghostwritten articles. This behavior should be regarded as unethical misconduct. More broadly, researchers with conflicts of interest should not be allowed to sit on guideline committees and regulatory boards. Corporate funding of CME programs and review articles should be abolished.

While this paper was under review, Merck halted taranabant RCTs, and Sanofi-Aventis removed rimonabant from the European market. The FDA rejected rimonabant after data submitted by Sanofi-Aventis revealed adverse effects in RIO trials that went unreported in RIO publications [86], including one death in a rimonabant-treated subject (ruled a suicide by the FDA, [86]) that did not appear in the pertinent publication [7]. Although the risk-benefit ratio of cannabinoid receptor blockade may preclude its use for chronic conditions such as obesity and drug or alcohol dependence, cannabinoid receptor blockade could serve in the treatment of acute endocannabinoid dysregulation, such as hepatic cirrhosis, hemorrhagic or endotoxic shock, cardiac reperfusion injury, and doxorubicin-induced cardiotoxicity.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2659447/

 

Rimonabant: a novel selective cannabinoid-1 receptor antagonist for treatment of obesity.

Posted on by
Reply

Abstract

“PURPOSE:

The pharmacology, pharmacokinetics, clinical efficacy, safety, drug interactions, and dosage and administration of rimonabant in the treatment of obesity and related metabolic factors are reviewed.

SUMMARY:

Discovery of the cannabinoid receptors has led to the development of rimonabant, a cannabinoid-1 (CB(1)) antagonist. Selective blockade of this receptor has been shown to lead to decreased appetite and food intake in animal models. Clinical studies have shown that rimonabant 20 mg once daily produces significant decreases in weight and waist circumference in obese human subjects and improves the lipid profile and glucose control. The frequency of metabolic syndrome also decreased significantly with rimonabant 20 mg daily. Limited data are available regarding the pharmacokinetics and pharmacodynamics of rimonabant. Preclinical data have demonstrated a long duration of action. As of yet, no drug-drug, drug-food, or drug-disease interactions have been identified with rimonabant. Adverse reactions occurred rarely, with nausea, dizziness, diarrhea, arthralgia, and back pain being the most common. Psychiatric disorders, including depression and anxiety, were the most common reasons for subjects to withdraw from rimonabant studies. Rimonabant has been shown to be safe for up to two years of treatment. Further research will clarify currently unknown areas, including pharmacokinetics, drug interactions, and the drug’s role in standard therapy.

CONCLUSION:

Rimonabant, a selective CB(1) antagonist, is a novel treatment option for obese and overweight individuals. Significant weight loss, decrease in waist circumference, and improvements in lipid profile and glucose control have been shown in clinical trials of rimonabant.”

http://www.ncbi.nlm.nih.gov/pubmed/17322160

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

Posted on by
Reply

Abstract

“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.”

http://www.ncbi.nlm.nih.gov/pubmed/19443932

[Rimonabant (Acomplia), specific inhibitor of the endocannabinoid system].

Posted on by
Reply

Abstract

“The endocannabinoid system plays a major role in the regulation of body energy by stimulation of the appetite in the hypothalamus and increase of fat accumulation in adipocytes. The blockade of the cannabinoid system (CB1) by the specific inhibitor (rimonabant) decreases food intake and adiposity in animals and in humans. Moreover rimonabant lowers tobacco addiction. Clinical studies (RIO-LIPIDS and RIO-EUROPE) have recently confirmed that rimonabant combined with a hypocaloric diet over 1 year, promoted significant decrease of body weight, waist circumference and improvement of dyslipidemia. Rimonabant was well tolerated with mild and transient side effects. The future place of rimonabant in the strategy of obesity is still to be clarified.”

http://www.ncbi.nlm.nih.gov/pubmed/16038141

The endocannabinoid system and rimonabant: a new drug with a novel mechanism of action involving cannabinoid CB1 receptor antagonism–or inverse agonism–as potential obesity treatment and other therapeutic use.

Posted on by
Reply

Abstract

“There is considerable evidence that the endocannabinoid (endogenous cannabinoid) system plays a significant role in appetitive drive and associated behaviours. It is therefore reasonable to hypothesize that the attenuation of the activity of this system would have therapeutic benefit in treating disorders that might have a component of excess appetitive drive or over-activity of the endocannabinoid system, such as obesity, ethanol and other drug abuse, and a variety of central nervous system and other disorders. Towards this end, antagonists of cannabinoid receptors have been designed through rational drug discovery efforts. Devoid of the abuse concerns that confound and impede the use of cannabinoid receptor agonists for legitimate medical purposes, investigation of the use of cannabinoid receptor antagonists as possible pharmacotherapeutic agents is currently being actively investigated. The compound furthest along this pathway is rimonabant, a selective CB(1) (cannabinoid receptor subtype 1) antagonist, or inverse agonist, approved in the European Union and under regulatory review in the United States for the treatment of obesity. This article summarizes the basic science of the endocannabinoid system and the therapeutic potential of cannabinoid receptor antagonists, with emphasis on the treatment of obesity.”

http://www.ncbi.nlm.nih.gov/pubmed/17489873