Peripheral, but not central, CB1 antagonism provides food intake-independent metabolic benefits in diet-induced obese rats

Peripheral CB1 cannabinoid receptor blockade improves cardiometabolic risk in mouse models of obesity

Obesity and its metabolic consequences are a major public health concern worldwide. Obesity is associated with overactivity of the endocannabinoid system, which is involved in the regulation of appetite, lipogenesis, and insulin resistance. Cannabinoid-1 receptor (CB1R) antagonists reduce body weight and improve cardiometabolic abnormalities in experimental and human obesity, but their therapeutic potential is limited by neuropsychiatric side effects. Here we have demonstrated that a CB1R neutral antagonist largely restricted to the periphery does not affect behavioral responses mediated by CB1R in the brains of mice with genetic or diet-induced obesity, but it does cause weight-independent improvements in glucose homeostasis, fatty liver, and plasma lipid profile. These effects were due to blockade of CB1R in peripheral tissues, including the liver, as verified through the use of CB1R-deficient mice with or without transgenic expression of CB1R in the liver. These results suggest that targeting peripheral CB1R has therapeutic potential for alleviating cardiometabolic risk in obese patients.

Effects of in vitro antagonism of endocannabinoid-1 receptors on the glucose transport system in normal and insulin-resistant rat skeletal muscle

OBJECTIVE

We determined the direct effects of modulating the endocannabinoid-1 (CB1) receptor on the glucose transport system in isolated skeletal muscle from insulin-sensitive lean Zucker and insulin-resistant obese Zucker rats.

METHODS

Soleus strips were incubated in the absence or presence of insulin, without or with various concentrations of the CB1 receptor antagonist SR141716 or with the CB1 receptor agonist arachidonyl-2-chloroethylamide (ACEA).

RESULTS

CB1 receptor protein expression in visceral adipose (57%), soleus (40%) and myocardial (36%) tissue was significantly (p < 0.05) decreased in obese compared to lean animals, with a trend for a reduction (17%, p = 0.079) in the liver. In isolated soleus muscle from both lean and obese Zucker rats, CB1 receptor antagonism directly improved glucose transport activity in a dose-dependent manner. Basal glucose transport activity was maximally enhanced between 100 and 200 nM SR141716 in lean (26-28%) and obese (22-31%) soleus. The maximal increase in insulin-stimulated glucose transport for lean muscle ( approximately 30%) was achieved at 50 nM SR141716 and for obese muscle ( approximately 30%) at 100 nM SR141716. In contrast, CB1 receptor antagonism did not alter hypoxia-stimulated glucose transport activity. CB1 receptor agonism (1 mM ACEA) significantly decreased both basal (15%) and insulin-stimulated (22%) glucose transport activity in isolated lean soleus. This effect was reversed by 200 nM SR141716. In both lean and obese muscle, the functionality of key signalling proteins (insulin receptor beta-subunit, Akt, glycogen synthase kinase-3beta (GSK-3beta), AMP-dependent protein kinase (AMPK), p38 mitogen-activated protein kinase (p38 MAPK)) was not altered by either CB1 receptor agonism or antagonism.

CONCLUSION

These results indicate that the engagement of CB1 receptor can negatively modulate both basal and insulin-dependent glucose transport activity in lean and obese skeletal muscles, and that these effects are not mediated by the engagement of elements of the canonical pathways regulating this process in mammalian skeletal muscle.

A selective cannabinoid-1 receptor antagonist, PF-95453, reduces body weight and body fat to a greater extent than pair-fed controls in obese monkeys

Cannabinoid-1 (CB(1)) receptor antagonists exhibit pharmacological properties favorable to treatment of obesity, caused by both centrally mediated effects on appetite and peripherally mediated effects on energy metabolism. However, the relative contribution of these effects to the weight loss produced by CB(1) receptor antagonists remains unclear. Here, we compare food intake-related and independent effects of the CB(1)-selective antagonist 1-(7-(2-chlorophenyl)-8-(4-chlorophenyl)-2-methylpyrazolo[1,5-a][1,3,5]triazin-4-yl)-3-(methylamino) azetidine-3-carboxamide (PF-95453) in obese cynomolgus monkeys. Monkeys were divided into three study groups (n = 10 each) and treated once daily for 8 weeks with either vehicle or PF-95453 as follows: 1, fed ad libitum and dosed orally with vehicle; 2, fed ad libitum and dosed orally with PF-95453 (0.5 mg/kg weeks 1-3, 1.0 mg/kg weeks 4-8); and 3, fed an amount equal to the amount consumed by the drug-treated group and dosed orally with vehicle (pair-fed). PF-95453 treatment significantly reduced food consumption by 23%, body weight by 10%, body fat by 39%, and leptin by 34% while increasing adiponectin by 78% relative to vehicle-treated controls. Pair-fed animals did not exhibit reductions in body weight or leptin but did show significantly reduced body fat (11%) and increased adiponectin (15%) relative to vehicle-treated controls but markedly less than after PF-95453 treatment. Indeed, significant differences were noted between the drug-treated and pair-fed groups with respect to body weight reduction, body fat reduction, increased adiponectin, and leptin reduction. Similar to humans, monkeys treated with the CB(1) receptor antagonist exhibited decreased body weight and body fat, a substantial portion of which seemed to be independent of the effects on food intake.

Rational design of a novel peripherally-restricted, orally active CB(1) cannabinoid antagonist containing a 2,3-diarylpyrrole motif

A new series of 2,3-diarylpyrroles have been prepared and evaluated as CB(1) antagonists. Modulation of the topological polar surface area allowed the identification of high affinity peripherally-restricted CB(1) antagonists. Compound 11, obtained after further optimization of the metabolic profile displayed very low brain penetration, yet was able to reverse CP55940-induced gastrointestinal transit inhibition following oral administration.

The peptide hemopressin acts through CB1 cannabinoid receptors to reduce food intake in rats and mice

Hemopressin is a short, nine amino acid peptide (H-Pro-Val-Asn-Phe-Lys-Leu-Leu-Ser-His-OH) isolated from rat brain that behaves as an inverse agonist at the cannabinoid receptor CB(1), and is shown here to inhibit agonist-induced receptor internalization in a heterologous cell model. Since this peptide occurs naturally in the rodent brain, we determined its effect on appetite, an established central target of cannabinoid signaling. Hemopressin dose-dependently decreases night-time food intake in normal male rats and mice, as well as in obese ob/ob male mice, when administered centrally or systemically, without causing any obvious adverse side effects. The normal, behavioral satiety sequence is maintained in male mice fasted overnight, though refeeding is attenuated. The anorectic effect is absent in CB(1) receptor null mutant male mice, and hemopressin can block CB(1) agonist-induced hyperphagia in male rats, providing strong evidence for antagonism of the CB(1) receptor in vivo. We speculate that hemopressin may act as an endogenous functional antagonist at CB(1) receptors and modulate the activity of appetite pathways in the brain.

The novel triple monoamine reuptake inhibitor tesofensine induces sustained weight loss and improves glycemic control in the diet-induced obese rat: comparison to sibutramine and rimonabant

Tesofensine, a novel triple monoamine reuptake inhibitor, produces a significant weight loss in humans. The present study aimed at characterizing the weight-reducing effects of tesofensine in a rat model of diet-induced obesity. Sibutramine and rimonabant were used as reference comparators. Compared to baseline, long-term treatment with tesofensine (28 days, 1.0 or 2.5mg/kg, p.o.) resulted in a significant, dose-dependent and sustained weight loss of 5.7 and 9.9%, respectively. Sibutramine (7.5mg/kg, p.o.) treatment caused a sustained weight loss of 7.6%, whereas the employed dose of rimonabant (10mg/kg, p.o.) only produced a transient weight reduction. While all compounds exhibited a significant inhibitory effect on food intake which gradually wore off, the hypophagic effect of tesofensine was longer lasting than sibutramine and rimonabant. In contrast to tesofensine, the body weight of pair-fed rats returned to baseline at the end of the study, which may indicate that tesofensine stimulated energy expenditure. The differential efficacy on weight reduction was also reflected in lowered body fat depots, as tesofensine and sibutramine most efficiently reduced abdominal and subcutaneous fat mass which was paralleled by reduced plasma lipid levels. In an oral glucose tolerance test, only tesofensine significantly suppressed the plasma insulin response below the level that could be obtained by paired feeding, indicating that tesofensine further improved glycemic control. In conclusion, the robust weight loss with long-term tesofensine treatment is likely due to a combined synergistic effect of appetite suppression and increased energy expenditure.

CB(1) signaling in forebrain and sympathetic neurons is a key determinant of endocannabinoid actions on energy balance

The endocannabinoid system (ECS) plays a critical role in obesity development. The pharmacological blockade of cannabinoid receptor type 1 (CB(1)) has been shown to reduce body weight and to alleviate obesity-related metabolic disorders. An unsolved question is at which anatomical level CB(1) modulates energy balance and the mechanisms involved in its action. Here, we demonstrate that CB(1) receptors expressed in forebrain and sympathetic neurons play a key role in the pathophysiological development of diet-induced obesity. Conditional mutant mice lacking CB(1) expression in neurons known to control energy balance, but not in nonneuronal peripheral organs, displayed a lean phenotype and resistance to diet-induced obesity. This phenotype results from an increase in lipid oxidation and thermogenesis as a consequence of an enhanced sympathetic tone and a decrease in energy absorption. In conclusion, CB(1) signaling in the forebrain and sympathetic neurons is a key determinant of the ECS control of energy balance.

CB1 antagonism exerts specific molecular effects on visceral and subcutaneous fat and reverses liver steatosis in diet-induced obese mice

OBJECTIVE

The beneficial effects of the inactivation of endocannabinoid system (ECS) by administration of antagonists of the cannabinoid receptor (CB) 1 on several pathological features associated with obesity is well demonstrated, but the relative contribution of central versus peripheral mechanisms is unclear. We examined the impact of CB1 antagonism on liver and adipose tissue lipid metabolism in a mouse model of diet-induced obesity.

RESEARCH DESIGN AND METHODS

Mice were fed either with a standard diet or a high-sucrose high-fat (HSHF) diet for 19 weeks and then treated with the CB1-specific antagonist SR141716 (10 mg x kg(-1) x day(-1)) for 6 weeks.

RESULTS

Treatment with SR141716 reduced fat mass, insulin levels, and liver triglycerides primarily increased by HSHF feeding. Serum adiponectin levels were restored after being reduced in HSHF mice. Gene expression of scavenger receptor class B type I and hepatic lipase was induced by CB1 blockade and associated with an increase in HDL-cholesteryl ether uptake. Concomitantly, the expression of CB1, which was strongly increased in the liver and adipose tissue of HSHF mice, was totally normalized by the treatment. Interestingly, in visceral but not subcutaneous fat, genes involved in transport, synthesis, oxidation, and release of fatty acids were upregulated by HSHF feeding, while this effect was counteracted by CB1 antagonism.

CONCLUSIONS

A reduction in the CB1-mediated ECS activity in visceral fat is associated with a normalization of adipocyte metabolism, which may be a determining factor in the reversion of liver steatosis induced by treatment with SR141716.

Cannabinoid receptor 1 blockade ameliorates albuminuria in experimental diabetic nephropathy

OBJECTIVE

Cannabinoid receptor 1 (CB1) is localized in the central nervous system and in peripheral tissues involved in energy metabolism control. However, CB1 receptors are also expressed at low level within the glomeruli, and the aim of this study was to investigate their potential relevance in the pathogenesis of proteinuria in experimental type 1 diabetes.

RESEARCH DESIGN AND METHODS

Streptozotocin-induced diabetic mice were treated with N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,3-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251), a selective CB1-receptor antagonist, at the dosage of 1 mg x kg(-1) x day(-1) via intraperitoneal injection for 14 weeks. Urinary albumin excretion was measured by enzyme-linked immunosorbent assay. CB1 receptor expression was studied by immunohistochemistry, immunoblotting, and real-time PCR. Expression of nephrin, podocin, synaptopodin, and zonula occludens-1 (ZO-1) was assessed by immunofluorescence and real-time PCR. Fibronectin, transforming growth factor-beta1 (TGF-beta1), and connective tissue growth factor (CTGF) mRNA levels were quantitated by real-time PCR.

RESULTS

In diabetic mice, the CB1 receptor was overexpressed within the glomeruli, predominantly by glomerular podocytes. Blockade of the CB1 receptor did not affect body weight, blood glucose, and blood pressure levels in either diabetic or control mice. Albuminuria was increased in diabetic mice compared with control animals and was significantly ameliorated by treatment with AM251. Furthermore, CB1 blockade completely prevented diabetes-induced downregulation of nephrin, podocin, and ZO-1. By contrast overexpression of fibronectin, TGF-beta1, and CTGF in renal cortex of diabetic mice was unaltered by AM251 administration.

CONCLUSIONS

In experimental type 1 diabetes, the CB1 receptor is overexpressed by glomerular podocytes, and blockade of the CB1 receptor ameliorates albuminuria possibly via prevention of nephrin, podocin, and ZO-1 loss.

Regulation of lipid metabolism by energy availability: a role for the central nervous system

The central nervous system (CNS) is crucial in the regulation of energy homeostasis. Many neuroanatomical studies have shown that the white adipose tissue (WAT) is innervated by the sympathetic nervous system, which plays a critical role in adipocyte lipid metabolism. Therefore, there are currently numerous reports indicating that signals from the CNS control the amount of fat by modulating the storage or oxidation of fatty acids. Importantly, some CNS pathways regulate adipocyte metabolism independently of food intake, suggesting that some signals possess alternative mechanisms to regulate energy homeostasis. In this review, we mainly focus on how neuronal circuits within the hypothalamus, such as leptin- ghrelin-and resistin-responsive neurons, as well as melanocortins, neuropeptide Y, and the cannabinoid system exert their actions on lipid metabolism in peripheral tissues such as WAT, liver or muscle. Dissecting the complicated interactions between peripheral signals and neuronal circuits regulating lipid metabolism might open new avenues for the development of new therapies preventing and treating obesity and its associated cardiometabolic sequelae.

Reduced cannabinoid receptor 1 protein in subcutaneous adipose tissue of obese

BACKGROUND

Cannabinoid 1 receptors are identified in various tissues involved in the internal metabolism including adipose tissue and the endocannabinoid system is claimed to be overactive in the obese state. To study the potential involvement of cannabinoid receptor 1 in the endocannabinoid system over-activity in adipose tissue in the obese state, we investigated the cannabinoid receptor 1 levels in adipose tissue from different fat depots in lean and obese humans.

MATERIALS AND METHODS

The adipose tissue samples were analysed by Western blot and by RT-PCR.

RESULTS

Both the gene expression and the protein of cannabinoid receptor 1 were lower in subcutaneous abdominal adipose tissue from obese subjects as compared with lean subjects (P < 0.01 and P = 0.058). Moreover, in lean subjects, the level of cannabinoid receptor 1 was significantly higher in subcutaneous adipose tissue compared with visceral adipose tissue (P < 0.05) for both gene expression and protein. The level of cannabinoid receptor 1 was similar between the two depots in obese subjects. The expression of cannabinoid receptor 1 was higher in subcutaneous gluteal adipose tissue as compared with subcutaneous abdominal adipose tissue (P < 0.05).

CONCLUSION

We found in lean subjects, a robust lower level of cannabinoid receptor 1 in visceral adipose tissue compared with subcutaneous adipose tissue (both RNA and protein levels), but similar levels of cannabinoid receptor 1 between the two depots in obese subjects. Our present findings do not indicate that cannabinoid receptor 1 is directly involved in the endocannabinoid system over-activity in adipose tissue in obesity.

Regulation of MAP kinase-directed mitogenic and protein kinase B-mediated signaling by cannabinoid receptor type 1 in skeletal muscle cells

OBJECTIVE

The endogenous cannabinoid (or endocannabinoid) system (ECS) is part of a central neuromodulatory system thought to play a key role in the regulation of feeding behavior and energy balance. However, increasing evidence suggests that modulation of the ECS may also act to regulate peripheral mechanisms involved in these processes, including lipogenesis in adipose tissue and liver, insulin release from pancreatic beta-cells, and glucose uptake into skeletal muscle. It was recently shown that cannabinoid receptor type 1 (CB1) and type 2 (CB2), both key components of the ECS, are expressed in human and rodent skeletal muscle. However, their role in modulating insulin sensitivity in this metabolically active tissue has yet to be determined. Our aim was to establish the role, if any, of these receptors in modulating insulin sensitivity in skeletal muscle cells.

RESEARCH DESIGN AND METHODS

Cultured skeletal muscle cells were exposed to CB1 and/or CB2 pharmacological agonists/antagonists/inverse agonists, and the resulting effects on insulin-regulated phosphatidylinositol 3 kinase (PI 3-kinase)-protein kinase B (PKB) and extracellular signal-related kinases 1/2 (ERK1/2)-directed signaling were determined.

RESULTS

Here, we report that modulating the activity of the ECS in skeletal muscle regulates both insulin-dependent mitogen-activated protein (MAP) kinase (ERK1/2) and the canonical PI 3-kinase/PKB signaling pathways. We show that pharmacological activation or inhibition of CB1 receptor activity exerts a differential effect with regard to MAP kinase- and PKB-directed signaling.

CONCLUSIONS

Our study provides evidence that signaling via cannabinoid receptors can significantly modulate mitogenic and metabolic signaling in skeletal muscle with important implications for muscle growth and differentiation as well as the regulation of glucose and lipid metabolism.

Involvement of adipokines in rimonabant-mediated insulin sensitivity in ob/ob mice

Objectives

It has been recently reported that blockade of type 1 cannabinoid (CB1) receptors by specific antagonists or genetic manipulation alleviates dyslipidaemia, hyperglycaemia and insulin resistance in animal models of obesity and type 2 diabetes. However, the precise role of adipokines in the insulin-sensitising effects of the CB1 antagonist rimonabant is not clear.

Methods

ob/ob mice were treated with different doses of rimonabant and then subjected to an oral glucose tolerance test. The expression of different adipokines in white adipose tissue was analysed by quantitative real-time PCR.

Key findings

Rimonabant (30 mg/kg) significantly inhibited body weight and fat pad weight gain (P &lt; 0.05) and improved glucose tolerance. Gene expression analysis indicated that tumour necrosis factor-α, visfatin and retinol binding protein-4 were downregulated in the adipose tissue of ob/ob mice treated with rimonabant compared with controls, whereas adiponectin was significantly upregulated.

Conclusions

Rimonabant-mediated alteration of adipokines in white adipose tissues may play a role in improving insulin sensitivity in obese animals.

Food intake-independent effects of CB1 antagonism on glucose and lipid metabolism

Overactivity of the endocannabinoid system (ECS) has been linked to abdominal obesity and other risk factors for cardiovascular disease and type 2 diabetes. Conversely, administration of cannabinoid receptor type 1 (CB1) antagonists reduces adiposity in obese animals and humans. This effect is only in part secondary to the anorectic action of CB1 agonists. In order to assess the actions of CB1 antagonism on glucose homeostasis, diet-induced obese (DIO) rats received the CB1 antagonist rimonabant (10 mg/kg, intraperitoneally (IP)) or its vehicle for 4 weeks, or were pair-fed to the rimonabant-treated group for the same length of time. Rimonabant treatment transiently reduced food intake, while inducing body weight loss throughout the study. Rats receiving rimonabant had significantly less body fat and circulating leptin compared to both vehicle and pair-fed groups. Rimonabant, but not pair-feeding, also significantly decreased circulating nonesterified fatty acid (NEFA) and triacylglycerol (TG) levels, and reduced TG content in oxidative skeletal muscle. Although no effects were observed during a glucose tolerance test (GTT), rimonabant restored insulin sensitivity to that of chow-fed, lean controls during an insulin tolerance test (ITT). Conversely, a single dose of rimonabant to DIO rats had no acute effect on insulin sensitivity. These findings suggest that in diet-induced obesity, chronic CB1 antagonism causes weight loss and improves insulin sensitivity by diverting lipids from storage toward utilization. These effects are independent of the anorectic action of the drug.

Cannabinoid-1 receptor inverse agonists: current understanding of mechanism of action and unanswered questions

Rimonabant and taranabant are two extensively studied cannabinoid-1 receptor (CB1R) inverse agonists. Their effects on in vivo peripheral tissue metabolism are generally well replicated. The central nervous system site of action of taranabant or rimonabant is firmly established based on brain receptor occupancy studies. At the whole-body level, the mechanism of action of CB1R inverse agonists includes a reduction in food intake and an increase in energy expenditure. At the tissue level, fat mass reduction, liver lipid reduction and improved insulin sensitivity have been shown. These effects on tissue metabolism are readily explained by CB1R inverse agonist acting on brain CB1R and indirectly influencing the tissue metabolism through the autonomic nervous system. It has also been hypothesized that rimonabant acts directly on adipocytes, hepatocytes, pancreatic islets or skeletal muscle in addition to acting on brain CB1R, although strong support for the contribution of peripherally located CB1R to in vivo efficacy is still lacking. This review will carefully examine the published literature and provide a perspective on what new tools and studies are required to address the peripheral site of action hypothesis.

Direct control of peripheral lipid deposition by CNS GLP-1 receptor signaling is mediated by the sympathetic nervous system and blunted in diet-induced obesity

We investigated a possible role of the central glucagon-like peptide (GLP-1) receptor system as an essential brain circuit regulating adiposity through effects on nutrient partitioning and lipid metabolism independent from feeding behavior. Both lean and diet-induced obesity mice were used for our experiments. GLP-1 (7-36) amide was infused in the brain for 2 or 7 d. The expression of key enzymes involved in lipid metabolism was measured by real-time PCR or Western blot. To test the hypothesis that the sympathetic nervous system may be responsible for informing adipocytes about changes in CNS GLP-1 tone, we have performed direct recording of sympathetic nerve activity combined with experiments in genetically manipulated mice lacking beta-adrenergic receptors. Intracerebroventricular infusion of GLP-1 in mice directly and potently decreases lipid storage in white adipose tissue. These effects are independent from nutrient intake. Such CNS control of adipocyte metabolism was found to depend partially on a functional sympathetic nervous system. Furthermore, the effects of CNS GLP-1 on adipocyte metabolism were blunted in diet-induced obese mice. The CNS GLP-1 system decreases fat storage via direct modulation of adipocyte metabolism. This CNS GLP-1 control of adipocyte lipid metabolism appears to be mediated at least in part by the sympathetic nervous system and is independent of parallel changes in food intake and body weight. Importantly, the CNS GLP-1 system loses the capacity to modulate adipocyte metabolism in obese states, suggesting an obesity-induced adipocyte resistance to CNS GLP-1.

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

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

The emerging role of the endocannabinoid system in cardiovascular disease

Endocannabinoids are endogenous bioactive lipid mediators present both in the brain and various peripheral tissues, which exert their biological effects via interaction with specific G-protein-coupled cannabinoid receptors, the CB(1) and CB(2). Pathological overactivation of the endocannabinoid system (ECS) in various forms of shock and heart failure may contribute to the underlying pathology and cardiodepressive state by the activation of the cardiovascular CB(1) receptors. Furthermore, tonic activation of CB(1) receptors by endocannabinoids has also been implicated in the development of various cardiovascular risk factors in obesity/metabolic syndrome and diabetes, such as plasma lipid alterations, abdominal obesity, hepatic steatosis, inflammation, and insulin and leptin resistance. In contrast, activation of CB(2) receptors in immune cells exerts various immunomodulatory effects, and the CB(2) receptors in endothelial and inflammatory cells appear to limit the endothelial inflammatory response, chemotaxis, and inflammatory cell adhesion and activation in atherosclerosis and reperfusion injury. Here, we will overview the cardiovascular actions of endocannabinoids and the growing body of evidence implicating the dysregulation of the ECS in a variety of cardiovascular diseases. We will also discuss the therapeutic potential of the modulation of the ECS by selective agonists/antagonists in various cardiovascular disorders associated with inflammation and tissue injury, ranging from myocardial infarction and heart failure to atherosclerosis and cardiometabolic disorders.

The dysregulation of the endocannabinoid system in diabesity-a tricky problem

Endocannabinoids (ECs) are small lipid mediators that play a critical role in energy metabolism. Human studies have shown that the EC tone in peripheral tissues positively correlates with increased adiposity. Furthermore, pharmacological inhibition of EC signaling results in weight loss in humans. However, the mechanisms that cause the dysregulation of the EC system in obesity are not well-understood. Since the clinical utility of currently available EC blockers is severely limited due to their side effects like depression and suicidal ideation that are caused by central effects, it is important to delineate the role of central and peripheral effects of EC signaling in regulating glucose and lipid metabolism.

Hypothalamic lipids and the regulation of energy homeostasis

The hypothalamus is a specialised area in the brain that integrates the control of energy homeostasis, regulating both food intake and energy expenditure. The classical theory for hypothalamic feeding control is mainly based on the relationship between peripheral signals and neurotransmitters/neuromodulators in the central nervous system. Thus, hypothalamic neurons respond to peripheral signals, such as hormones and nutrients, by modifying the synthesis of neuropeptides. Despite the well-established role of these hypothalamic networks, increasing evidence indicates that the modulation of lipid metabolism in the hypothalamus plays a critical role in feeding control. In fact, the pharmacologic and genetic targeting of key enzymes from these pathways, such as AMP-activated protein kinase, acetyl-CoA carboxylase, carnitine palmitoyltransferase 1, fatty acid synthase, and malonyl-CoA decarboxylase, has a profound effect on food intake and body weight. Here, we review what is currently known about the relationship between hypothalamic lipid metabolism and whole body energy homeostasis. Defining these novel mechanisms may offer new therapeutic targets for the treatment of obesity and its associated pathologies.

Should peripheral CB(1) cannabinoid receptors be selectively targeted for therapeutic gain?

Endocannabinoids, endogenous lipid ligands of cannabinoid receptors, mediate a variety of effects similar to those of marijuana. Cannabinoid CB(1) receptors are highly abundant in the brain and mediate psychotropic effects, which limits their value as a potential therapeutic target. There is growing evidence for CB(1) receptors in peripheral tissues that modulate a variety of functions, including pain sensitivity and obesity-related hormonal and metabolic abnormalities. In this review we propose that selective targeting of peripheral CB(1) receptors has potential therapeutic value because it would help to minimize addictive, psychoactive effects in the case of CB(1) agonists used as analgesics, or depression and anxiety in the case of CB(1) antagonists used in the management of cardiometabolic risk factors associated with the metabolic syndrome.