The endogenous cannabinoid system affects energy balance via central orexigenic drive and peripheral lipogenesis

Cannabinoid type 1 receptor blockade promotes mitochondrial biogenesis through endothelial nitric oxide synthase expression in white adipocytes

OBJECTIVE

Cannabinoid type 1 (CB1) receptor blockade decreases body weight and adiposity in obese subjects; however, the underlying mechanism is not yet fully understood. Nitric oxide (NO) produced by endothelial NO synthase (eNOS) induces mitochondrial biogenesis and function in adipocytes. This study was undertaken to test whether CB1 receptor blockade increases the espression of eNOS and mitochondrial biogenesis in white adipocytes.

RESEARCH DESIGN AND METHODS

We examined the effects on eNOS and mitochondrial biogenesis of selective pharmacological blockade of CB1 receptors by SR141716 (rimonabant) in mouse primary white adipocytes. We also examined eNOS expression and mitochondrial biogenesis in white adipose tissue (WAT) and isolated mature white adipocytes of CB1 receptor-deficient (CB1(-/-)) and chronically SR141716-treated mice on either a standard or high-fat diet.

RESULTS

SR141716 treatment increased eNOS expression in cultured white adipocytes. Moreover, SR141716 increased mitochondrial DNA amount, mRNA levels of genes involved in mitochondrial biogenesis, and mitochondrial mass and function through eNOS induction, as demonstrated by reversal of SR141716 effects by small interfering RNA-mediated decrease in eNOS. While high-fat diet-fed wild-type mice showed reduced eNOS expression and mitochondrial biogenesis in WAT and isolated mature white adipocytes, genetic CB1 receptor deletion or chronic treatment with SR141716 restored these parameters to the levels observed in wild-type mice on the standard diet, an effect linked to the prevention of adiposity and body weight increase.

CONCLUSIONS

CB1 receptor blockade increases mitochondrial biogenesis in white adipocytes by inducing the expression of eNOS. This is linked to the prevention of high-fat diet-induced fat accumulation, without concomitant changes in food intake.

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.

Cannabinoid CB1 receptor antagonists in therapeutic and structural perspectives

The observed antiobesity effect of rimonabant (1) in a pharmacological rodent model 10 years ago has led to a surge in the search for novel cannabinoid CB1 antagonists as a new therapeutic target for the treatment of obesity. Rimonabant showed clinical efficacy in the treatment of obesity and also improved cardiovascular and metabolic risk factors. Cannabinoid CB1 receptor antagonists have also good prospects in other therapeutic areas, including smoking and alcohol addiction as well as cognitive impairment. Solvay's research achievements in this fast-moving field are reported in relation with the current state of the art. Several medicinal chemistry strategies have been pursued. The application of the concept of conformational constraint led to the discovery of more rigid analogs of the prototypic CB1 receptor antagonist rimonabant. Replacement of the central heterocyclic pyrazole ring in rimonabant yielded imidazoles, triazoles, and thiazoles as selective CB1 receptor antagonists. Dedicated medium-throughput screening efforts delivered one 3,4-diarylpyrazoline hit. Its poor pharmacokinetic properties were successfully optimized which led to the discovery of orally active and highly CB1/CB2 receptor selective analogs in this series. Regioisomeric 1,5-diarylpyrazolines, 1,2-diarylimidazolines, and water-soluble imidazoles have been designed as novel CB1 receptor antagonist structure classes.

Modification of cardiometabolic risk through cannabinoid type-1 receptor antagonism

Large-scale epidemiological studies show that hypertension, diabetes, and dyslipidaemia are highly prevalent among obese individuals. Regrettably, preventive efforts have failed to abolish the increasing prevalence of obesity worldwide. The endocannabinoid system is implicated in the regulation of appetite, food intake, lipids, and glucose metabolism. Rimonabant is the first type-1 endocannabinoid receptor blocker that has been shown to improve the serum lipid profile, insulin and glucose levels, and blood pressure. In particular, the RIO (rimonabant in obesity) studies documented the beneficial metabolic effects of rimonabant. These favorable metabolic effects exceed by about 50% those anticipated by weight reduction, possibly due to modulation of the endocannabinoid system in peripheral tissues. The beneficial effects, however, seem to come at the cost of an increased risk of psychiatric disorders. However, given the efficacy of this treatment and the magnitude of the obesity problem, rimonabant may prove to be a valuable adjunct in targeting obesity-related cardiovascular risk factors.

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.

Endocannabinoid receptor 1 gene variations increase risk for obesity and modulate body mass index in European populations

The therapeutic effects of cannabinoid receptor blockade on obesity-associated phenotypes underline the importance of the endocannabinoid pathway on the energy balance. Using a staged-approach, we examined the contribution of the endocannabinoid receptor 1 gene (CNR1) on obesity and body mass index (BMI) in the European population. With the input of CNR1 exons and 3' and 5' regions sequencing and HapMap database, we selected and genotyped 26 tagging single-nucleotide polymorphisms (SNPs) in 1932 obese cases and 1173 non-obese controls of French European origin. Variants that showed significant associations (P < 0.05) with obesity after correction for multiple testing were further tested in two additional European cohorts including 2645 individuals. For the identification of the potential causal variant(s), we further genotyped SNPs in high linkage disequilibrium (LD) with the obesity-associated variants. Of the 25 successfully genotyped CNR1 SNPs, 12 showed nominal evidence of association with childhood obesity, class I and II and/or class III adult obesity (1.16 < OR < 1.40, 0.00003 < P < 0.04). Intronic SNPs rs806381 and rs2023239, which resisted correction for multiple testing were further associated with higher BMI in both Swiss obese subjects and Danish individuals. The genotyping of all know variants in partial LD (r(2) > 0.5) with these two SNPs in the initial case-control study, identified two better associated SNPs (rs6454674 and rs10485170). Our study of 5750 subjects shows that CNR1 variations increase the risk for obesity and modulate BMI in our European population. As CB1 is a drug target for obesity, a pharmacogenetic analysis of the endocannabinoid blockade obesity treatment may be of interest to identify best responders.

The metabolic implications of long term cannabis use in patients with psychosis

AIMS

The aim of this paper is to summarise the effects of cannabis use on appetite and energy balance, and to subsequently investigate the possible implications this may have in patients with psychosis, in whom a high prevalence of cannabis use has been reported.

METHODS

A narrative review based on the recent literature regarding cannabis use in the general population and patients with psychosis.

RESULTS

The short-term abilities of cannabis to increase appetite and body weight, through actions on the endogenous endocannabinoid system, have been well characterised throughout the literature. The long term effects of cannabis use are however unclear and only a minority of studies have been conducted in the general population with overall conflicting results. In terms of the effects of cannabis in patients with psychosis, there has only been one study to date that has investigated this and interestingly found cannabis use to be associated with increased body weight and blood glucose levels, thus providing evidence that cannabis use may be an important contributing factor to the reduced life expectancy, as is currently observed in this vulnerable patient group.

CONCLUSIONS

It is clear from the literature that patients with psychosis are at a high risk of metabolic and cardiovascular disease in comparison to the general population. However the contribution of cannabis use to this risk is as of yet undetermined and further long term studies are need to confirm current findings and evaluate hypothesised mechanisms.

The endocannabinoid system and energy metabolism

Many different regulatory actions have been attributed to endocannabinoids, and their involvement in several pathophysiological conditions is under intense scrutiny. Cannabinoid receptors [cannabinoid receptor type 1 (CB1) and CB2] participate in the physiological modulation of many central and peripheral functions. The ability of the endocannabinoid system to control appetite, food intake and energy balance has recently received considerable attention, particularly in the light of the different modes of action underlying these functions. The endocannabinoid system modulates rewarding properties of food by acting at specific mesolimbic areas in the brain. In the hypothalamus, CB1 receptors and endocannabinoids are integrated components of the networks controlling appetite and food intake. Interestingly, the endocannabinoid system was recently shown to control several metabolic functions by acting on peripheral tissues such as adipocytes, hepatocytes, the gastrointestinal tract, the skeletal muscles and the endocrine pancreas. The relevance of the system is further strengthened by the notion that visceral obesity seems to be a condition in which an overactivation of the endocannabinoid system occurs, and therefore drugs interfering with this overactivation by blocking CB1 receptors are considered as potentially valuable candidates for the treatment of obesity and related cardiometabolic risk factors.

Leptin controls adipose tissue lipogenesis via central, STAT3-independent mechanisms

Leptin (encoded by Lep) controls body weight by regulating food intake and fuel partitioning. Obesity is characterized by leptin resistance and increased endocannabinoid tone. Here we show that leptin infused into the mediobasal hypothalamus (MBH) of rats inhibits white adipose tissue (WAT) lipogenesis, which occurs independently of signal transducer and activator of transcription-3 (STAT3) signaling. Correspondingly, transgenic inactivation of STAT3 signaling by mutation of the leptin receptor (s/s mice) leads to reduced adipose mass compared to db/db mice (complete abrogation of leptin receptor signaling). Conversely, the ability of hypothalamic leptin to suppress WAT lipogenesis in rats is lost when hypothalamic phosphoinositide 3-kinase signaling is prevented or when sympathetic denervation of adipose tissue is performed. MBH leptin suppresses the endocannabinoid anandamide in WAT, and, when this suppression of endocannabinoid tone is prevented by systemic CB1 receptor activation, MBH leptin fails to suppress WAT lipogenesis. These data suggest that the increased endocannabinoid tone observed in obesity is linked to a failure of central leptin signaling to restrain peripheral endocannabinoids.

CB1 cannabinoid receptor modulates 3,4-methylenedioxymethamphetamine acute responses and reinforcement

BACKGROUND

3,4-Methylenedioxymethamphetamine (MDMA) is a popular recreational drug widely abused by young people. The endocannabinoid system is involved in the addictive processes induced by different drugs of abuse. However, the role of this system in the pharmacological effects of MDMA has not yet been clarified.

METHODS

Locomotion, body temperature, and anxiogenic-like responses were evaluated after acute MDMA administration in CB(1) cannabinoid receptor 1 knockout mice. Additionally, MDMA rewarding properties were investigated in the place conditioning and the intravenous self-administration paradigms. Extracellular levels of dopamine (DA) in the nucleus accumbens were also analyzed after a single administration of MDMA by in vivo microdialysis.

RESULTS

Acute MDMA administration increased locomotor activity, body temperature, and anxiogenic-like responses in wild-type mice, but these responses were lower or abolished in knockout animals. 3,4-Methylenedioxymethamphetamine produced similar conditioned place preference and increased dopamine extracellular levels in the nucleus accumbens in both genotypes. Nevertheless, CB(1) knockout mice failed to self-administer MDMA at any of the doses used.

CONCLUSIONS

These results indicate that CB(1) cannabinoid receptors play an important role in the acute prototypical effects of MDMA and are essential in the acquisition of an operant behavior to self-administer this drug.

Steroidogenic factor 1 regulates expression of the cannabinoid receptor 1 in the ventromedial hypothalamic nucleus

The nuclear receptor steroidogenic factor 1 (SF-1) plays essential roles in the development and function of the ventromedial hypothalamic nucleus (VMH). Considerable evidence links the VMH and SF-1 with the regulation of energy homeostasis. Here, we demonstrate that SF-1 colocalizes in VMH neurons with the cannabinoid receptor 1 (CB1R) and that a specific CB1R agonist modulates electrical activity of SF-1 neurons in hypothalamic slice preparations. We further show that SF-1 directly regulates CB1R gene expression via a SF-1-responsive element at -101 in its 5'-flanking region. Finally, we show that knockout mice with selective inactivation of SF-1 in the brain have decreased expression of CB1R in the region of the VMH and exhibit a blunted response to systemically administered CB1R agonists. These studies suggest that SF-1 directly regulates the expression of CB1R, which has been implicated in the regulation of energy homeostasis and anxiety-like behavior.

The cannabinoid CB1 receptor is expressed in pancreatic delta-cells

Antagonists of cannabinoid CB1 receptor (CB1, CNR1) promote weight loss and decrease hyperglycemia in patients with type 2 diabetes. While the endocannabinoid system may modulate islet hormone secretion, the cell-type expressing CB1 receptor in islets has not been fully resolved. In this study, we verified receptor gene expression in rodent islets and cell lines and examined the distribution of CB1 receptor in mouse, rat, and human islets by confocal immunofluorescence (IF) microscopy. IF demonstrated CB1 receptor was present in beta-cell lines, but co-localized solely with somatostatin in the islet delta-cells of Zucker rats, C57BL/6 mice, and humans; no CB1 receptor expression was observed in alpha-, beta-, or pp-cells. Similarly, a rat somatostatinoma cell line, MSL-G2-Tu6, was found to express CB1 receptor. We also found monoacylglycerol lipase (MAGL) to be expressed in delta-cells and fatty acid amide hydrolase (FAAH) to be expressed in alpha-cells. The specific expression of CB1 in delta-cells suggests that the ECS may play a role in modulating islet hormone secretion. As there are some differences between our findings and previous reports, further studies, including detailed physiological studies of the effects of the ECS on islet function, are warranted.

Endocannabinoids and liver disease. IV. Endocannabinoid involvement in obesity and hepatic steatosis

Endocannabinoids are endogenous lipid mediators that interact with the same receptors as plant-derived cannabinoids to produce similar biological effects. The well-known appetitive effect of smoking marijuana has prompted inquiries into the possible role of endocannabinoids in the control of food intake and body weight. This brief review surveys recent evidence that endocannabinoids and their receptors are involved at multiple levels in the control of energy homeostasis. Endocannabinoids are orexigenic mediators and are part of the leptin-regulated central neural circuitry that controls energy intake. In addition, they act at multiple peripheral sites including adipose tissue, liver, and skeletal muscle to promote lipogenesis and limit fat elimination. Their complex actions could be viewed as anabolic, increasing energy intake and storage and decreasing energy expenditure, as components of an evolutionarily conserved system that has insured survival under conditions of starvation. In the era of plentiful food and limited physical activity, pharmacological inhibition of endocannabinoid activity offers benefits in the treatment of obesity and its hormonal/metabolic consequences.

Peripheral endocannabinoid system activity in patients treated with sibutramine

OBJECTIVE

The endocannabinoid system (ECS) promotes weight gain and obesity-associated metabolic changes. Weight loss interventions may influence obesity-associated risk indirectly through modulation of the peripheral ECS. We investigated the effect of acute and chronic treatment with sibutramine on components of the peripheral ECS.

METHODS AND PROCEDURES

Twenty obese otherwise healthy patients received randomized, double-blind, crossover treatment with placebo and 15 mg/day sibutramine for 5 days each, followed by 12 weeks open-label sibutramine treatment. We determined circulating anandamide and 2-arachidonoylglycerol and expression levels of endocannabinoid genes in subcutaneous abdominal adipose tissue biopsies.

RESULTS

Body weight was stable during the acute treatment period and decreased by 6.0+/-0.8 kg in those patients completing 3 months of sibutramine treatment (P<0.05). Circulating endocannabinoids and the expression of ECS genes did not change with acute or chronic sibutramine treatment.

DISCUSSION

The ECS is activated in obesity. We did not find any influence of 5% body weight loss induced by sibutramine on circulating levels of endocannabinoids and adipose-tissue expression of endocannabinoid genes in obese subjects. These data confirm our previous findings on dietary weight loss and suggest that the dysregulation of the ECS may be a cause rather than a consequence of obesity.

Sustained weight loss after Roux-en-Y gastric bypass is characterized by down regulation of endocannabinoids and mitochondrial function

OBJECTIVE

To determine the physiologic importance of endocannabinoids and mitochondrial function in the long-term outcome using a rat model of Roux-en-Y gastric bypass (RYGB) surgery.

BACKGROUND

Sixteen million people are morbidly obese and RYGB surgery is the most effective treatment. Endocannabinoids are implicated in appetite stimulation and regulation of peripheral energy metabolism. We hypothesize that down-regulation of endocannabinoids and alterations in mitochondrial function and hormones favoring catabolism contribute to sustained RYGB-induced weight loss.

METHODS

Diet-induced obese Sprague-Dawley rats were randomized to sham-operated obese controls, RYGB, and sham-operated obese pair-fed rats. Body weight and food intake were recorded, and food efficiency was calculated. Endocannabinoid levels in skeletal muscle and liver, muscle mitochondrial respiratory complex I-V content, and hormones concentrations were determined 14 and 28 days postsurgery, reflecting rapid and sustained weight loss periods after RYGB, respectively.

RESULTS

Compared with pair-fed controls, RYGB rats had significant reduction in body weight and food efficiency (P < 0.001). Increased cholecystokinin, reduced insulin, leptin, adiponectin, T3, and down-regulation of mitochondrial complex I were evident on day 14 postsurgery. On day 28, leptin, insulin, and T3 remained low, whereas adiponectin and cholecystokinin were normal. Along with complex I, the endocannabinoids anandamide in muscle (P = 0.003) and 2-arachidonoylglycerol in liver were significantly down-regulated (P < 0.001).

CONCLUSIONS

The attenuated caloric intake, reduced food efficiency, and normalization of hormonal levels on day 28 post-RYGB were associated with significant down-regulation of endocannabinoids anandamide and 2-arachidonoylglycerol in muscle and liver, respectively. These results suggest a role for endocannabinoids in the mechanism of sustained weight loss and RYGB success, and may have implications for treatment of morbid obesity.

The role of adipocyte insulin resistance in the pathogenesis of obesity-related elevations in endocannabinoids

OBJECTIVE

Obesity is associated with an overactive endocannabinoid (EC) system. The mechanisms responsible for increased ECs in obese individuals are poorly understood. Therefore, we examined the role of adipocyte insulin resistance in intracellular EC metabolism.

METHODS

We used 3T3-L1 adipocytes and diet-induced obese (DIO) mice to examine the role of obesity and insulin resistance in the regulation and/or dysregulation of intracellular ECs.

RESULTS

For the first time, we provide evidence that insulin is a major regulator of EC metabolism. Insulin treatment reduced intracellular ECs (2-arachidonylglycerol [2-AG] and anandamide [AEA]) in 3T3-L1 adipocytes. This corresponded with insulin-sensitive expression changes in enzymes of EC metabolism. In insulin-resistant adipocytes, patterns of insulin-induced enzyme expression were disturbed in a manner consistent with elevated EC synthesis and reduced EC degradation. Expression profiling of adipocytes from DIO mice largely recapitulated in vitro changes, suggesting that insulin resistance affects the EC system in vivo. In mice, expression changes of EC synthesis and degradation enzymes were accompanied by increased plasma EC concentrations (2-AG and AEA) and elevated adipose tissue 2-AG.

CONCLUSIONS

Our findings suggest that insulin-resistant adipocytes fail to regulate EC metabolism and decrease intracellular EC levels in response to insulin stimulation. These novel observations offer a mechanism whereby obese insulin-resistant individuals exhibit increased concentrations of ECs.

Anandamide modulates growth and lipid metabolism in the zebrafish Danio rerio

Endocannabinoids are known to be lipidic mediators with several biological functions as the stimulation of food intake and lipid metabolism via cannabinoid receptor CB1. Many evidences, such as the presence of CB1 mRNA in fat tissue, suggest a peripheral role for endocannabinoids in regulating lipogenesis and body weight in mammals. As animal models constitute good tools to study endocannabinoid system dynamics, we analyzed the role of the endocannabinoid anandamide (AEA) in modulating lipid metabolism and growth in zebrafish larvae and adults. The data obtained indicated that AEA administered via water modulates the transcription of its own receptor CB1, besides to up-regulate gene expression of sterol regulatory element binding protein (SREBP) and of the insulin-like growth factors (IGF-1 and IGF-2). The results here obtained represent the first evidence in fish of the endocannabinoid system involvement in lipid metabolism and growth.

Dysregulation of peripheral endocannabinoid levels in hyperglycemia and obesity: Effect of high fat diets

Increasing evidence indicates that endocannabinoid (EC) signalling is dysregulated during hyperglycemia and obesity, particularly at the level of anandamide (AEA) and/or 2-arachidonoylglycerol (2-AG) concentrations in tissues involved in the control of energy intake and processing, such as the liver, white adipose tissue and pancreas. Here we review this previous evidence and provide new data on the possible dysregulation of EC levels in organs with endocrine function (adrenal glands and thyroid), involved in energy expenditure (brown adipose tissue and skeletal muscle), or affected by the consequences of metabolic disorders (heart and kidney), obtained from mice fed for 3, 8 and 14 weeks with two different high fat diets (HFDs), with different fatty acid compositions and impact on fasting glucose levels. Statistically significant elevations (in the skeletal muscle, heart and kidney) or reductions (in the thyroid) of the levels of either AEA or 2-AG, or both, were found. Depending on the diet, these changes preceded or accompanied the development of overt obesity and/or hyperglycemia. In the adrenal gland, first a reduction and then an elevation of EC levels were observed. In the brown fat, a very early elevation of both AEA and 2-AG normalized levels was observed with one of the diets, whereas delayed decreases were explained by an increase of the amount of fat tissue weight induced by the HFDs. The potential implications of these and previous findings in the general framework of the proposed roles of the EC system in the control of metabolic, endocrine and cardiovascular and renal functions are discussed.

Long-term effect of CB1 blockade with rimonabant on cardiometabolic risk factors: two year results from the RIO-Europe Study

AIMS

Rimonabant, the first selective cannabinoid type 1 receptor blocker, has been shown to produce weight loss and improvements in several cardiometabolic risk factors over 1 year. We report the 2 year efficacy and tolerability data of rimonabant.

METHODS AND RESULTS

Patients with a body mass index > or =30 or >27 kg/m(2) with treated/untreated hypertension, dyslipidaemia, or both, were randomized to double-blind treatment with placebo, rimonabant 5 or 20 mg once daily plus a calorie-restricted diet for 2 years. Weight loss from baseline to 2 years in the intention-to-treat population was significantly greater with rimonabant 20 mg (mean +/- SD: -5.5 +/- 7.7 kg; P < 0.001) and 5 mg (-2.9 +/- 6.5 kg; P = 0.002) than placebo (-1.2 +/- 6.8 kg). Rimonabant 20 mg produced significantly greater improvements than placebo in waist circumference, high-density lipoprotein cholesterol, triglycerides, fasting glucose and insulin levels, insulin resistance, and metabolic syndrome prevalence. Rimonabant 20 mg produced clinically meaningful improvements in all Impact of Weight on Quality of Life-Lite questionnaire domain scores at 2 years. Rimonabant was generally well tolerated and rates of adverse events, including depressed mood disorders and disturbances were similar to placebo during year 2. Proportions of patients with clinically significant depression (Hospital Anxiety and Depression Scale score >11) were similar in all treatment groups.

CONCLUSION

Rimonabant 20 mg over 2 years promoted clinically relevant and durable weight loss and improvements in cardiometabolic risk factors.

The endocannabinoid system in brain reward processes

Food, drugs and brain stimulation can serve as strong rewarding stimuli and are all believed to activate common brain circuits that evolved in mammals to favour fitness and survival. For decades, endogenous dopaminergic and opioid systems have been considered the most important systems in mediating brain reward processes. Recent evidence suggests that the endogenous cannabinoid (endocannabinoid) system also has an important role in signalling of rewarding events. First, CB(1) receptors are found in brain areas involved in reward processes, such as the dopaminergic mesolimbic system. Second, activation of CB(1) receptors by plant-derived, synthetic or endogenous CB(1) receptor agonists stimulates dopaminergic neurotransmission, produces rewarding effects and increases rewarding effects of abused drugs and food. Third, pharmacological or genetic blockade of CB(1) receptors prevents activation of dopaminergic neurotransmission by several addictive drugs and reduces rewarding effects of food and these drugs. Fourth, brain levels of the endocannabinoids anandamide and 2-arachidonoylglycerol are altered by activation of reward processes. However, the intrinsic activity of the endocannabinoid system does not appear to play a facilitatory role in brain stimulation reward and some evidence suggests it may even oppose it. The influence of the endocannabinoid system on brain reward processes may depend on the degree of activation of the different brain areas involved and might represent a mechanism for fine-tuning dopaminergic activity. Although involvement of the various components of the endocannabinoid system may differ depending on the type of rewarding event investigated, this system appears to play a major role in modulating reward processes.

AM251 suppresses the viability of HepG2 cells through the AMPK (AMP-activated protein kinase)-JNK (c-Jun N-terminal kinase)-ATF3 (activating transcription factor 3) pathway

AM251, a cannabinoid antagonist, has various biological activities. In this study, we found that AM251 suppressed the viability of hepatoma HepG2 cells and also increased phosphorylation of JNK (c-jun N-terminal kinase) and ATF3 (activating transcription factor 3). In addition, AM251 phosphorylated AMPK (AMP-activated protein kinase) in a time and dose-dependent manner. Inhibition of AMPK blocked AM251-induced JNK/ATF3 phosphorylation. Expression of AMPK or treatment with AICAR (5-aminoimidazole-4-carboxy-amide-1-d-ribofuranoside), an AMPK activator, activated the JNK/ATF3 pathways. Together, these results suggest that AM251 may have anti-tumor effects in hepatoma through activation of the AMPK-JNK-ATF3 signal pathway.

Pathogenic potential of adipose tissue and metabolic consequences of adipocyte hypertrophy and increased visceral adiposity

When caloric intake exceeds caloric expenditure, the positive caloric balance and storage of energy in adipose tissue often causes adipocyte hypertrophy and visceral adipose tissue accumulation. These pathogenic anatomic abnormalities may incite metabolic and immune responses that promote Type 2 diabetes mellitus, hypertension and dyslipidemia. These are the most common metabolic diseases managed by clinicians and are all major cardiovascular disease risk factors. 'Disease' is traditionally characterized as anatomic and physiologic abnormalities of an organ or organ system that contributes to adverse health consequences. Using this definition, pathogenic adipose tissue is no less a disease than diseases of other body organs. This review describes the consequences of pathogenic fat cell hypertrophy and visceral adiposity, emphasizing the mechanistic contributions of genetic and environmental predispositions, adipogenesis, fat storage, free fatty acid metabolism, adipocyte factors and inflammation. Appreciating the full pathogenic potential of adipose tissue requires an integrated perspective, recognizing the importance of 'cross-talk' and interactions between adipose tissue and other body systems. Thus, the adverse metabolic consequences that accompany fat cell hypertrophy and visceral adiposity are best viewed as a pathologic partnership between the pathogenic potential adipose tissue and the inherited or acquired limitations and/or impairments of other body organs. A better understanding of the physiological and pathological interplay of pathogenic adipose tissue with other organs and organ systems may assist in developing better strategies in treating metabolic disease and reducing cardiovascular disease risk.

Identification of cannabinoid type 1 receptor expressing cocaine amphetamine-regulated transcript neurons in the rat hypothalamus and brainstem using in situ hybridization and immunohistochemistry

Recent data have indicated that the neuropeptide cocaine amphetamine-regulated transcript (CART) may be a downstream mediator of the effect of CB1 receptor antagonist on appetite regulation. In order to identify possible interactions between CART and central CB1R expressing neurons, a detailed mapping of CART and CB1R expression and immunoreactivity in the brain was initiated. Single radioactive in situ hybridizations revealed a predominant overlap between CART and CB1R mRNA in hypothalamic and lower brainstem nuclei. Using double in situ hybridization, co-localization between CART and CB1R mRNA expressing neurons was observed to be most pronounced in the retrochiasmatic and lateral hypothalamic areas, as well as in all parts of the dorsal vagal complex. Further attempts to immunohistochemically characterize the distribution of CB1R were, however, deemed impossible as any of eight commercially available antibodies/antisera gave rise to non-specific staining patterns. Furthermore, the staining pattern obtained was not discriminate between CB1R knockout mice and wild type mice. Collectively, we demonstrate at the messenger level that CB1R expressing perikarya colocalize with CART expressing neurons in hypothalamic and brainstem areas known to be important in appetite control, whereas interactions at the protein level necessitate a demand for cautious interpretations of immunohistochemical results.

Presence of functional cannabinoid receptors in human endocrine pancreas

AIMS/HYPOTHESIS

We examined the presence of functional cannabinoid receptors 1 and 2 (CB1, CB2) in isolated human islets, phenotyped the cells producing cannabinoid receptors and analysed the actions of selective cannabinoid receptor agonists on insulin, glucagon and somatostatin secretion in vitro. We also described the localisation on islet cells of: (1) the endocannabinoid-producing enzymes N-acyl-phosphatidyl ethanolamine-hydrolysing phospholipase D and diacylglycerol lipase; and (2) the endocannabinoid-degrading enzymes fatty acid amidohydrolase and monoacyl glycerol lipase.

METHODS

Real-time PCR, western blotting and immunocytochemistry were used to analyse the presence of endocannabinoid-related proteins and genes. Static secretion experiments were used to examine the effects of activating CB1 or CB2 on insulin, glucagon and somatostatin secretion and to measure changes in 2-arachidonoylglycerol (2-AG) levels within islets. Analyses were performed in isolated human islets and in paraffin-embedded sections of human pancreas.

RESULTS

Human islets of Langerhans expressed CB1 and CB2 (also known as CNR1 and CNR2) mRNA and CB1 and CB2 proteins, and also the machinery involved in synthesis and degradation of 2-AG (the most abundant endocannabinoid, levels of which were modulated by glucose). Immunofluorescence revealed that CB1 was densely located in glucagon-secreting alpha cells and less so in insulin-secreting beta cells. CB2 was densely present in somatostatin-secreting delta cells, but absent in alpha and beta cells. In vitro experiments revealed that CB1 stimulation enhanced insulin and glucagon secretion, while CB2 agonism lowered glucose-dependent insulin secretion, showing these cannabinoid receptors to be functional.

CONCLUSIONS/INTERPRETATION

Together, these results suggest a role for endogenous endocannabinoid signalling in regulation of endocrine secretion in the human pancreas.

Endocannabinoid dysregulation in the pancreas and adipose tissue of mice fed with a high-fat diet

OBJECTIVE

In mice, endocannabinoids (ECs) modulate insulin release from pancreatic beta-cells and adipokine expression in adipocytes through cannabinoid receptors. Their pancreatic and adipose tissue levels are elevated during hyperglycemia and obesity, but the mechanisms underlying these alterations are not understood.

METHODS AND PROCEDURES

We assessed in mice fed for up to 14 weeks with a standard or high-fat diet (HFD): (i) the expression of cannabinoid receptors and EC biosynthesizing enzymes (N-acyl-phosphatidyl-ethanolamine-selective phospholipase D (NAPE-PLD) and DAGLalpha) and degrading enzymes (fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL)) in pancreatic and adipose tissue sections by immunohistochemical staining; (ii) the amounts, measured by liquid chromatography-mass spectrometry, of the ECs, 2-AG, and anandamide (AEA).

RESULTS

Although CB(1) receptors and biosynthetic enzymes were found mostly in alpha-cells, degrading enzymes were identified in beta-cells. Following HFD, staining for biosynthetic enzymes in beta-cells and lower staining for FAAH were observed together with an increase of EC pancreatic levels. While we observed no diet-induced change in the intensity of the staining of EC metabolic enzymes in the mesenteric visceral fat, a decrease in EC concentrations was accompanied by lower and higher staining of biosynthesizing enzymes and FAAH, respectively, in the subcutaneous fat. No change in cannabinoid receptor staining was observed following HFD in any of the analyzed tissues.

DISCUSSION

We provide unprecedented information on the distribution of EC metabolic enzymes in the pancreas and adipose organ, where their aberrant expression during hyperglycemia and obesity contribute to dysregulated EC levels.

Serum endocannabinoid content is altered in females with depressive disorders: a preliminary report

BACKGROUND

Preclinical research has suggested that the endocannabinoid system may be involved in the etiology and/or treatment of depression; however, there are no published studies examining circulating endocannabinoid content in patients with clinical depression.

METHODS

This study examined the endocannabinoids (anandamide; AEA) and 2-arachidonylglycerol (2-AG) in serum from ambulatory, medication-free female patients diagnosed with minor or major depression, and in controls matched for demographic characteristics.

RESULTS

Serum 2-AG content was significantly decreased in patients diagnosed with major depression, and this decrease was correlated significantly and negatively with duration of the depressive episode, such that 2-AG content was progressively lower the longer the depressive episode. While AEA was not associated with major depression PER SE, a strong negative correlation was found between serum AEA content and Hamilton ratings for cognitive and somatic anxiety, suggesting that AEA content may relate to the anxiety dimension of affective disorders. In subjects with minor depression, serum AEA was significantly elevated, with 2-AG content demonstrating a similar, but statistically insignificant trend.

DISCUSSION

These are the first clinical data to indicate that the endocannabinoid system may be disturbed in affective disease, and suggest that future research is required to determine the relevance of these changes with respect to disease manifestation and pharmacotherapy.

Endogenous opioids and cannabinoids: system interactions in the regulation of appetite, grooming and scratching

Growing evidence suggests substantial crosstalk between endogenous opioid and cannabinoid systems in the regulation of appetite. Not only is cannabinoid-induced hyperphagia abolished by opioid receptor antagonists (and vice versa), but several laboratories have reported supra-additive anorectic responses following co-administration of opioid and CB1 receptor antagonists. In the present study, videoanalysis has been used to characterise the acute effects of sub-anorectic doses of rimonabant (0.25, 0.75 mg/kg) and naloxone (0.1 mg/kg), alone and in combination, on mash intake, ingestive and non-ingestive behaviour, and post-treatment weight gain in male rats. The results confirmed that, when administered alone, none of these treatments significantly altered mash consumption, various measures of feeding behaviour, or weight gain. Although most non-ingestive behaviours were also unaffected, 0.75 mg/kg rimonabant induced compulsive scratching and grooming. However, when naloxone was given in combination with either dose of rimonabant, both food intake and time spent feeding were significantly decreased while the behavioural satiety sequence (BSS) was accelerated. On further analysis, the co-treatment reductions in food intake and feeding behaviour were found to be of an additive rather than supra-additive nature. Intriguingly, the co-administration of naloxone also virtually abolished the compulsive scratching response to the higher dose of rimonabant. Findings are discussed in relation to current views on the molecular bases of opioid-cannabinoid system interactions and the unexpected 'dual' advantage (reduction in appetite plus attenuation of side-effect) of low-dose combinations of opioid and cannabinoid CB1 receptor antagonists.

Rimonabant: the evidence for its use in the treatment of obesity and the metabolic syndrome

INTRODUCTION

Obesity and overweight affect over 1 billion people worldwide and are leading causes of morbidity and mortality. Clinical features of obesity converge with those of the metabolic syndrome and type 2 diabetes, greatly increasing the risk of long-term adverse outcomes.

AIMS

To review the evidence on rimonabant, a novel CB1 receptor antagonist, for the treatment of obese and overweight patients.

EVIDENCE REVIEW

There is clear evidence that rimonabant 20 mg/day in conjunction with a hypocaloric diet causes a mean weight loss of 4.6 kg in obese and overweight patients after 1 year's treatment, with approximately 50% of patients achieving a weight loss of ≥5%. One study demonstrated that weight loss is maintained for up to 2 years. The drug also improves lipid and glycemic cardiovascular risk factors, including high-density lipoprotein cholesterol and insulin resistance, and reduces waist circumference, thus reducing the prevalence of metabolic syndrome. Treatment of obese and overweight diabetic patients with rimonabant decreases glycosylated hemoglobin (HbA(1c)), including patients previously untreated for diabetes. The effect of rimonabant appears to be partly independent of weight loss. Rimonabant 20 mg/day is generally well tolerated, with mild to moderate transient adverse effects including nausea, diarrhea, dizziness, and anxiety. Approximately 14% of patients receiving rimonabant 20 mg/day discontinued due to adverse effects, primarily depressed mood, although overall rates of depression did not differ significantly compared with placebo.

PLACE IN THERAPY

The evidence supports the use of rimonabant 20 mg/day along with dietary modification to reduce cardiovascular risk factors in obese and overweight patients, including those with diabetes. The drug is contraindicated in patients receiving antidepressants. Long-term data on cardiovascular outcomes, morbidity, and mortality are eagerly awaited.

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.

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.

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.

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.

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.

The neonatal ventromedial hypothalamus transcriptome reveals novel markers with spatially distinct patterning

The ventromedial hypothalamus (VMH) is a distinct morphological nucleus involved in feeding, fear, thermoregulation, and sexual activity. It is essentially unknown how VMH circuits underlying these innate responses develop, in part because the VMH remains poorly defined at a cellular and molecular level. Specifically, there is a paucity of cell-type-specific genetic markers with which to identify neuronal subgroups and manipulate development and signaling in vivo. Using gene profiling, we now identify approximately 200 genes highly enriched in neonatal (postnatal day 0) mouse VMH tissue. Analyses of these VMH markers by real or virtual (Allen Brain Atlas; http://www.brain-map.org) experiments revealed distinct regional patterning within the newly formed VMH. Top neonatal markers include transcriptional regulators such as Vgll2, SF-1, Sox14, Satb2, Fezf1, Dax1, Nkx2-2, and COUP-TFII, but interestingly, the highest expressed VMH transcript, the transcriptional coregulator Vgll2, is completely absent in older animals. Collective results from zebrafish knockdown experiments and from cellular studies suggest that a subset of these VMH markers will be important for hypothalamic development and will be downstream of SF-1, a critical factor for normal VMH differentiation. We show that at least one VMH marker, the AT-rich binding protein Satb2, was responsive to the loss of leptin signaling (Lep(ob/ob)) at postnatal day 0 but not in the adult, suggesting that some VMH transcriptional programs might be influenced by fetal or early postnatal environments. Our study describing this comprehensive "VMH transcriptome" provides a novel molecular toolkit to probe further the genetic basis of innate neuroendocrine behavioral responses.

The endocannabinoid system and gut–brain signalling

The endocannabinoid system (ECS) consists of cannabinoid receptors, endogenous ligands and the biosynthetic and metabolic enzymes for their formation and degradation. Within the gastrointestinal (GI) tract, the ECS is involved in the regulation of motility, secretion, sensation, emesis, satiety and inflammation. Recent studies examining the ECS in the gut-brain axis have shed new light on this system and reveal many facets of regulation that are amenable to targeting by pharmacological interventions that may prove valuable for the treatment of GI disorders. In particular, it has been shown that endocannabinoid levels in the brain and gut vary according to states of satiety, and in conditions of diarrhea, emesis and inflammation. The expression of cannabinoid (CB)(1) receptors on vagal afferents is controlled by the states of satiety and by gut peptides such as cholecystokinin and ghrelin. Vagal control of gut motor function and emesis is regulated by endocannabinoids in the brainstem acting on CB(1), CB(2) and transient receptor potential vanilloid (TRPV)-1 receptors. The ECS is involved in the modulation of visceral sensation and likely contributes to effects of stress on GI function. This review examines recent developments in our understanding of the ECS in gut-brain signalling.

Blockade of cannabinoid CB1 receptors improves renal function, metabolic profile, and increased survival of obese Zucker rats

Obesity is a major risk factor in the development of chronic renal failure. Rimonabant, a cannabinoid CB1 receptor antagonist, improves body weight and metabolic disorders; however, its effect on mortality and chronic renal failure associated with obesity is unknown. Obese Zucker rats received either rimonabant or vehicle for 12 months and were compared to a pair-fed but untreated group of obese rats. Mortality in the obese rats was significantly reduced by rimonabant along with a sustained decrease in body weight, transient reduction in food intake, and an increase in plasma adiponectin. This was associated with significant reduction in plasma total cholesterol, low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio, triglycerides, glucose, norepinephrine, plasminogen activator inhibitor 1, and preservation of pancreatic weight and beta-cell mass index. The cannabinoid antagonist attenuated the increase in proteinuria, urinary N-acetylglucosaminidase excretion, plasma creatinine, and urea nitrogen levels while improving creatinine clearance. Renal hypertrophy along with glomerular and tubulointerstitial lesions were reduced by rimonabant. Although the drug did not modify hemodynamics, it normalized the pressor response to angiotensin II. Our study suggests that in a rat model of chronic renal failure due to obesity, rimonabant preserves renal function and increases survival.

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.

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.