The anti-obesity effect of rimonabant is associated with an improved serum lipid profile

Effect of the cannabinoid receptor-1 antagonist rimonabant on inflammation in mice with diet-induced obesity

We studied whether cannabinoid receptor (CB1) blockade with rimonabant has an anti-inflammatory effect in obese mice, and whether this effect depends on weight loss and/or diet consumption. High-fat diet (HFD)-induced obese mice were treated orally with rimonabant (HFD-R) or vehicle (HFD-V) for 4 weeks. Paired-feeding was conducted in two additional groups of obese mice to achieve either the same body weight (HFD-BW) or the same HFD intake (HFD DI) as HFD-R. All these groups of mice were maintained on HFD throughout, with mice on normal diet (ND) throughout as lean controls. Rimonabant treatment of obese mice induced marked diet-intake reduction and weight loss during the first week, which was followed by maintenance of low body weight but not diet-intake reduction. Lower HFD intake was required to reach the same degree of weight loss in HFD-BW. HFD-DI had similar weight loss initially, but then started to gain weight, reaching a higher body weight than HFD-R. Despite the same degree of weight loss, HFD-R had less fat mass and lower adipogenic gene expression than HFD-BW. Compared to HFD-V or HFD-DI, HFD-R had reduced inflammation in adipose tissue (AT) and/or liver indicated primarily by lower monocyte chemoattractant protein-1 (MCP-1) levels. However, MCP-1 levels were not significantly different between HFD-R and HFD-BW. In vitro incubation of rimonabant with AT explants did not change MCP-1 levels. Thus, rimonabant induced weight loss in obese mice by diet-intake-dependent and -independent fashions. Rimonabant decreased inflammation in obese mice, possibly through a primary effect on weight reduction.

Safety evaluation and treatment affect of LY2190416, a CB-1 antagonist/inverse agonist in growing beagle dogs

The objective of this study was to assess the safe use of LY2190416, a cannabinoid receptor 1 receptor antagonist/inverse agonist, for obesity management in dogs. Twenty-four clinically normal young beagle dogs were administered LY2190416 at doses of 3, 9, or 18 mg/kg or placebo, orally, once daily for 13 weeks. Food consumption and body weight were determined, and dogs were evaluated for changes in hematology, clinical chemistry, urinalysis, and serum cortisol. LY2190416 had no significant effect on hematology, clinical chemistry, urinalysis, and serum cortisol. All dogs consumed 100% of their entire daily allowance throughout the study. All dogs gained weight during the study, but treated dogs gained less than control dogs by the end of the study. During the first month, dogs exhibited a dose-dependent decrease in rate of weight gain (19.7 g/day for control dogs vs. 10.6 g/day for the 18 mg/kg dose group). LY2190416 was found to be safe at doses up to 18 mg/kg administered daily for 3 months. Results suggest that LY2190416 decreases rate of weight gain without affecting appetite or causing significant adverse health effects in normal growing dogs. Possible mechanisms for a proposed metabolic effect are discussed.

Influence of G1359A polymorphism of the cannabinoid receptor gene on anthropometric parameters and insulin resistance in women with obesity

A silent polymorphism (1359 G/A) of the cannabinoid receptor gene was reported as a common polymorphism in white populations. The aim of our study was to investigate the influence of this polymorphism (G1359A) of cannabinoid receptor gene on obesity, insulin resistance, and adipocytokines in women with obesity. A population of 290 women was analyzed. Indirect calorimetry, tetrapolar electrical bioimpedance, blood pressure measurement, serial assessment of nutritional intake with 3-day written food records, and biochemical analysis were performed. One hundred fifty-nine patients (54.8%) had the genotype G1359G (wild-type group), and 131 (45.2%) patients had G1359A (116 patients, 40.0%) or A1359A (15 patients, 5.2%) (mutant-type group). Triglycerides (122.3 ± 65.9 vs 107.2 ± 44.8 mg/dL, P < .05), insulin (15.8 ± 9.4 vs 13.6 ± 6.9 mUI/L, P < .05), and homeostasis model assessment values (3.85 ± 2.2 vs 3.33 ± 1.9, P < .05) were higher in the wild-type group than the mutant-type group. High-density lipoprotein cholesterol levels (56.8 ± 24.1 vs 58.3 ± 13.9 mg/dL, P < .05) were higher in the mutant-type group than the wild-type group. The novel finding of this study is the association of the mutant-type group G1359A and A1359A with a better cardiovascular profile (triglyceride, high-density lipoprotein cholesterol, insulin, and homeostasis model assessment levels) than the wild-type group.

Endocannabinoids in liver disease

Endocannabinoids are lipid mediators of the same cannabinoid (CB) receptors that mediate the effects of marijuana. The endocannabinoid system (ECS) consists of CB receptors, endocannabinoids, and the enzymes involved in their biosynthesis and degradation, and it is present in both brain and peripheral tissues, including the liver. The hepatic ECS is activated in various liver diseases and contributes to the underlying pathologies. In patients with cirrhosis of various etiologies, the activation of vascular and cardiac CB(1) receptors by macrophage-derived and platelet-derived endocannabinoids contributes to the vasodilated state and cardiomyopathy, which can be reversed by CB(1) blockade. In mouse models of liver fibrosis, the activation of CB(1) receptors on hepatic stellate cells is fibrogenic, and CB(1) blockade slows the progression of fibrosis. Fatty liver induced by a high-fat diet or chronic alcohol feeding depends on the activation of peripheral receptors, including hepatic CB(1) receptors, which also contribute to insulin resistance and dyslipidemias. Although the documented therapeutic potential of CB(1) blockade is limited by neuropsychiatric side effects, these may be mitigated by using novel, peripherally restricted CB(1) antagonists.

Cannabinoids and endocannabinoids in metabolic disorders with focus on diabetes

The cannabinoid receptors for Δ(9)-THC, and particularly, the CB(1) receptor, as well as its endogenous ligands, the endocannabinoids anandamide and 2-arachidonoylglycerol, are deeply involved in all aspects of the control of energy balance in mammals. While initially it was believed that this endocannabinoid signaling system would only facilitate energy intake, we now know that perhaps even more important functions of endocannabinoids and CB(1) receptors in this context are to enhance energy storage into the adipose tissue and reduce energy expenditure by influencing both lipid and glucose metabolism. Although normally well controlled by hormones and neuropeptides, both central and peripheral aspects of endocannabinoid regulation of energy balance can become dysregulated and contribute to obesity, dyslipidemia, and type 2 diabetes, thus raising the possibility that CB(1) antagonists might be used for the treatment of these metabolic disorders. On the other hand, evidence is emerging that some nonpsychotropic plant cannabinoids, such as cannabidiol, can be employed to retard β-cell damage in type 1 diabetes. These novel aspects of endocannabinoid research are reviewed in this chapter, with emphasis on the biological effects of plant cannabinoids and endocannabinoid receptor antagonists in diabetes.

New approaches to the pharmacological treatment of obesity: can they break through the efficacy barrier?

In this review we assess the range of centrally active anorectics that are either in human clinical trials, or are likely to be so in the near future. We describe their weight loss efficacy, mode of action at both pharmacological and behavioural levels, where understood, together with the range of side effects that might be expected in clinical use. We have however evaluated these compounds against the considerably more rigorous criteria that are now being used by the Federal Drugs Agency and European Medicines Agency to decide approvals and market withdrawals. Several trends are evident. Recent advances in the understanding of energy balance control have resulted in the exploitation of a number of new targets, some of which have yielded promising data in clinical trials for weight loss. A second major trend is derived from the hypothesis that improved weight loss efficacy over current therapy is most likely to emerge from treatments targeting multiple mechanisms of energy balance control. This reasoning has led to the development of a number of new treatments for obesity where multiple mechanisms are targeted, either by a single molecule, such as tesofensine, or through drug combinations such as qnexa, contrave, empatic, and pramlintide+metreleptin. Many of these approaches also utilise advances in formulation technology to widen safety margins. Finally, the practicality of peptide therapies for obesity has become better validated in recent studies and this may allow more rapid exploitation of novel targets, rather than awaiting the development of orally available small molecules. We conclude that novel, more efficacious and better tolerated treatments for obesity may become available in the near future.

Rimonabant-mediated changes in intestinal lipid metabolism and improved renal vascular dysfunction in the JCR:LA-cp rat model of prediabetic metabolic syndrome

Rimonabant (SR141716) is a specific antagonist of the cannabinoid-1 receptor. Activation of the receptor initiates multiple effects on central nervous system function, metabolism, and body weight. The hypothesis that rimonabant has protective effects against vascular disease associated with the metabolic syndrome was tested using JCR:LA-cp rats. JCR:LA-cp rats are obese if they are cp/cp, insulin resistant, and exhibit associated micro- and macrovascular disease with end-stage myocardial and renal disease. Treatment of obese rats with rimonabant (10 mg.kg(-1).day(-1), 12-24 wk of age) caused transient reduction in food intake for 2 wk, without reduction in body weight. However, by 4 wk, there was a modest, sustained reduction in weight gain. Glycemic control improved marginally compared with controls, but at the expense of increased insulin concentration. In contrast, rimonabant normalized fasting plasma triglyceride and reduced plasma plasminogen activator inhibitor-1 and acute phase protein haptoglobin in cp/cp rats. Furthermore, these changes were accompanied by reduced postprandial intestinal lymphatic secretion of apolipoprotein B48, cholesterol, and haptoglobin. While macrovascular dysfunction and ischemic myocardial lesion frequency were unaffected by rimonabant treatment, both microalbuminuria and glomerular sclerosis were substantially reduced. In summary, rimonabant has a modest effect on body weight in freely eating obese rats and markedly reduces plasma triglyceride levels and microvascular disease, in part due to changes in intestinal metabolism, including lymphatic secretion of apolipoprotein B48 and haptoglobin. We conclude that rimonabant improves renal disease and intestinal lipid oversecretion associated with an animal model of the metabolic syndrome that appears to be independent of hyperinsulinemia or macrovascular dysfunction.

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.

Transcriptional regulation of cannabinoid receptor-1 expression in the liver by retinoic acid acting via retinoic acid receptor-gamma

Alcoholism can result in fatty liver that can progress to steatohepatitis, cirrhosis, and liver cancer. Mice fed alcohol develop fatty liver through endocannabinoid activation of hepatic CB(1) cannabinoid receptors (CB(1)R), which increases lipogenesis and decreases fatty acid oxidation. Chronic alcohol feeding also up-regulates CB(1)R in hepatocytes in vivo, which could be replicated in vitro by co-culturing control hepatocytes with hepatic stellate cells (HSC) isolated from ethanol-fed mice, implicating HSC-derived mediator(s) in the regulation of hepatic CB(1)R (Jeong, W. I., Osei-Hyiaman, D., Park, O., Liu, J., Bátkai, S., Mukhopadhyay, P., Horiguchi, N., Harvey-White, J., Marsicano, G., Lutz, B., Gao, B., and Kunos, G. (2008) Cell Metab. 7, 227-235). HSC being a rich source of retinoic acid (RA), we tested whether RA and its receptors may regulate CB(1)R expression in cultured mouse hepatocytes. Incubation of hepatocytes with RA or RA receptor (RAR) agonists increased CB(1)R mRNA and protein, the most efficacious being the RARgamma agonist CD437 and the pan-RAR agonist TTNPB. The endocannabinoid 2-arachidonoylglycerol (2-AG) also increased hepatic CB(1)R expression, which was mediated indirectly via RA, because it was absent in hepatocytes from mice lacking retinaldehyde dehydrogenase 1, the enzyme catalyzing the generation of RA from retinaldehyde. The binding of RARgamma to the CB(1)R gene 5' upstream domain in hepatocytes treated with RAR agonists or 2-AG was confirmed by chromatin immunoprecipitation and electrophoretic mobility shift and antibody supershift assays. Finally, TTNPB-induced CB(1)R expression was attenuated by small interfering RNA knockdown of RARgamma in hepatocytes. We conclude that RARgamma regulates CB(1)R expression and is thus involved in the control of hepatic fat metabolism by endocannabinoids.

Leptin as a potential therapeutic target for breast cancer prevention and treatment

IMPORTANCE OF THE FIELD

Obesity is considered to be an important risk factor for postmenopausal breast cancer. Elevated estrogen levels are thought to be a growth factor associated with this relationship. However, there is increasing evidence that factors produced directly in adipose tissue, adipokines, can also affect breast cancer development. Leptin is one of the adipokines that is measured in serum/plasma in increasing amounts as body weight/body fat increases.

AREAS COVERED IN THIS REVIEW

We highlight important aspects of leptin in relationship to mammary/breast tumor development. This includes findings from human, in vitro and animal studies. Information on leptin-related compounds which may have therapeutic use is presented. Additionally strategies to alter serum leptin levels by dietary and pharmacological interventions are discussed.

WHAT THE READER WILL GAIN

The reader will gain insights into the relationship of an adipose tissue protein and its potential role in breast cancer development as well as ways to intervene in leptin's actions.

TAKE HOME MESSAGE

Continued research will determine if interfering with the action of leptin has preventive or therapeutic applications in breast cancer.

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 1 receptor blockade reduces atherosclerosis with enhances reverse cholesterol transport

AIM

A recent clinical study using coronary intravascular ultrasound showed that rimonabant, a cannabinoid 1 (CB1) receptor antagonist, significantly reduced total atheroma volume, suggesting that CB1 receptor blockade could be beneficial in anti-atherogenic therapy. The reverse cholesterol transport (RCT) system plays important roles in atherogenesis. We investigated whether CB1 receptor blockade could modulate atherogenesis in mice.

METHODS AND RESULTS

Oral administration of rimonabant (8 mg/kg/day) to apolipoprotein E-deficient mice for 3 months significantly reduced the relative area of atherosclerotic lesions in the aorta (vehicle; 12.6+/-4.0% vs. rimonabant; 9.7+/-2.3, n=12 each, p<0.05) with an increase in serum adiponectin levels (15.6+/-2.3 microg/mL vs. 12.2+/-2.1, n=12 each, p<0.001), without affecting body weight or serum cholesterol levels. Rimonabant tended to increase serum high-density lipoprotein cholesterol (HDL-C) (p=0.05). The relative area of atherosclerotic lesions in the aorta correlated inversely with serum HDL-C levels (r=-0.45, n=24, p<0.05). Rimonabant upregulated the mRNA expression levels of various components of the RCT system on THP-1 cell-derived macrophages (scavenger receptor B1: 1.15+/-0.12 fold, n=6; p<0.05, ATP-binding cassette [ABC] transporter G1: 1.23+/-0.11 fold, n=6; p<0.01), but not ABCA1 (1.13+/-0.20 fold, n=6; p=0.13).

CONCLUSION

CB1 receptor blockade reduced atherosclerosis in apoE-deficient mice through an increase in serum adiponectin levels and activation of the RCT system. CB1 receptor blockade may be therapeutically beneficial for atherogenesis by increasing the serum adiponectin level and enhancing of the RCT system.

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.

Effects of the cannabinoid CB1 antagonist rimonabant on hepatic mitochondrial function in rats fed a high-fat diet

The aim of this study was to investigate the effect of rimonabant treatment on hepatic mitochondrial function in rats fed a high-fat diet. Sprague-Dawley rats fed a high-fat diet (35% lard) for 13 wk were treated with rimonabant (10 mg·kg(-1)·day(-1)) during the last 3 wk and matched with pair-fed controls. Oxygen consumption with various substrates, mitochondrial enzyme activities on isolated liver mitochondria, and mitochondrial DNA quantity were determined. Body weight and fat mass were decreased in rats treated with rimonabant compared with pair-fed controls. Moreover, the serum adiponectin level was increased with rimonabant. Hepatic triglyceride content was increased, while serum triglycerides were decreased. An increase of mitochondrial respiration was observed in rats treated with rimonabant. The increase of mitochondrial respiration with palmitoyl-CoA compared with respiration with palmitoyl-l-carnitine stating that the entry of fatty acids into mitochondria via carnitine palmitoyltransferase I was increased in rats treated with rimonabant. Moreover, rimonabant treatment led to a reduction in the enzymatic activity of ATP synthase, whereas the quantity of mitochondrial DNA and the activity of citrate synthase remained unchanged. To summarize, rimonabant treatment leads to an improvement of hepatic mitochondrial function by increasing substrate oxidation and fatty acid entry into mitochondria for the β-oxidation pathway and by increasing proton leak. However, this increase of mitochondrial oxidation is regulated by a decrease of ATP synthase activity in order to have only ATP required for the cell function.

Metabolic responses to long-term pharmacological inhibition of CB1-receptor activity in mice in relation to dietary fat composition

BACKGROUND AND OBJECTIVES

The antiobesity effects of suppressed endocannabinoid signaling may rely, at least in part, on changes in lipid fluxes. As fatty acids exert specific effects depending on their level of saturation, we hypothesized that the dietary fatty acid composition would influence the outcome of treatment with a CB(1)-receptor antagonist (rimonabant).

METHODS

Mice were treated with rimonabant (10 mg kg(-1) body weight per day) or vehicle while equicalorically fed either a low-fat diet (LF), a high-fat (HF) diet or an HF diet in which 10% of the saturated fatty acids (SFAs) were replaced by poly-unsaturated fatty acids (PUFA) from fish oil (FO). Food intake and body weight were registered daily. Indirect calorimetry was performed and feces were collected. After 3 weeks, mice were killed for blood and tissue collection.

RESULTS

Relative to the LF diet, the HF diet caused anticipated metabolic derangements, which were partly reversed by the HF/FO diet. The HF/FO diet, however, was most obesity-promoting despite inhibiting lipogenesis as indicated by low gene expression levels of lipogenic enzymes. On all three diets, rimonabant treatment improved metabolic derangements and led to significantly lower body weight gain than their respective controls. This latter effect appeared largest in the HF/FO group, but occurred without major changes in nutrient absorption and energy expenditure.

CONCLUSION

The effects of chronic rimonabant treatment on body weight gain occurred irrespective of diet-induced changes in lipogenic activity, food intake and daily energy expenditure, and were, in fact, most pronounced in HF/FO mice. The effects of dietary PUFA replacement in an HF diet on expansion of adipose tissue might allow the favorable effects of dietary PUFA on dyslipidemia and hepatic steatosis. In light of other disadvantageous effects of weight gain, this might be a risky trade-off.

Endocrine functions of adipose tissue: focus on adiponectin

Accumulating evidence indicates that obesity and overweight are associated with, and contribute to, the development of type 2 diabetes mellitus (DM), cardiovascular disease (CVD), and chronic kidney disease (CKD). The adipocyte-derived cytokine, adiponectin, has been shown to improve insulin sensitivity, increase rates of fatty acid oxidation, decrease muscle lipid content, and reduce inflammation and vascular injury. However, adiponectin levels have been found to be reduced in persons with obesity and type 2 DM. Furthermore, adiponectin levels are inversely associated with those of tumor necrosis factor-alpha and C-reactive protein-markers of endothelial dysfunction and systemic inflammation. The 2 receptors for adiponectin-Adipo R(1) and Adipo R(2), which are expressed in muscle and liver tissue and in human fat cells-are hormonally regulated, with increased insulin levels causing a reduction in their abundance. The hyperinsulinemia observed in obesity, therefore, may be partially responsible for the reduction in the numbers of adiponectin receptors. Adiponectin aggregates range from a hexamer of low molecular weight to larger multimeric structures of high molecular weight. A smaller proteolytic fragment-the globular head domain of adiponectin, or gAd-interacts specifically with skeletal muscle. The relation of circulating adiponectin to its biologic actions is more complex than originally believed; therefore, it is the multimeric forms of the adiponectin molecule that need to be measured and evaluated in relation to associated metabolic, cardiovascular, and renal functions. Furthermore, strategies to measure the numbers of adiponectin receptors on available tissue need to be developed to fully assess the clinical role of adiponectin in type 2 DM, CVD, and CKD.

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.

Rimonabant prevents additional accumulation of visceral and subcutaneous fat during high-fat feeding in dogs

We investigated whether rimonabant, a type 1 cannabinoid receptor antagonist, reduces visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in dogs maintained on a hypercaloric high-fat diet (HHFD). To determine whether energy expenditure contributed to body weight changes, we also calculated resting metabolic rate. Twenty male dogs received either rimonabant (1.25 mg.kg(-1).day(-1), orally; n = 11) or placebo (n = 9) for 16 wk, concomitant with a HHFD. VAT, SAT, and nonfat tissue were measured by magnetic resonance imaging. Resting metabolic rate was assessed by indirect calorimetry. By week 16 of treatment, rimonabant dogs lost 2.5% of their body weight (P = 0.029), whereas in placebo dogs body weight increased by 6.2% (P < 0.001). Rimonabant reduced food intake (P = 0.027), concomitant with a reduction of SAT by 19.5% (P < 0.001). In contrast with the VAT increase with placebo (P < 0.01), VAT did not change with rimonabant. Nonfat tissue remained unchanged in both groups. Body weight loss was not associated with either resting metabolic rate (r(2) = 0.24; P = 0.154) or food intake (r(2) = 0.24; P = 0.166). In conclusion, rimonabant reduced body weight together with a reduction in abdominal fat, mainly because of SAT loss. Body weight changes were not associated with either resting metabolic rate or food intake. The findings provide evidence of a peripheral effect of rimonabant to reduce adiposity and body weight, possibly through a direct effect on adipose tissue.

The cannabinoid CB1 receptor antagonist, rimonabant, protects against acute myocardial infarction

CB1 antagonism is associated with reduced doxorubicin-induced cardiotoxicity and decreased cerebrocortical infarction. Rimonabant, a selective CB1 receptor antagonist, was, before it was withdrawn, proposed as a treatment for obesity and reported to reduce cardiovascular risk by improving glucose and lipid profiles and raising adiponectin levels. The cardioprotective actions of rimonabant in 6-week-old C57BL/6J mice fed either high-fat (HFD) or standard diets (STD) for 8 weeks were investigated. At 14 weeks, mice received rimonabant (10 mg/kg/day, i.p.) or vehicle for 1 week and were then subjected to an in vivo acute myocardial infarction. The influence of rimonabant on infarct size (IS) in CB1 knockout (CB1-/-) and wild-type (CB1+/+) mice was also examined. C57BL/6J mice that had been maintained on STD or HFD exhibited 4.3 and 21.4% reductions in body weight following 7 days rimonabant treatment. Rimonabant reduced IS in both STD (29.6 +/- 3.5% vs. 49.8 +/- 6.9% in control, P < 0.05) and HFD (26.9 +/- 1.5% vs. 48.7 +/- 7% in control, P < 0.05) mice. In CB1-/- mice rimonabant failed to reduce body weight or IS (51.0 +/- 5.3% vs. 49.7 +/- 4.7% in control, P > 0.05), although significant reductions were seen in CB1+/+ mice (IS, 48.9 +/- 4.6% control vs. 30.5 +/- 3.1% rimonabant, P < 0.05). To exclude the possibility that weight loss alone induced cardioprotection, HFD mice were switched to STD for 7 days (HFD-STD), resulting in an 11.3 +/- 1.0% decrease in body weight compared to control (+2.1 +/- 1.1% in HFD). This, however, was not associated with IS reduction (39.1 +/- 3.9% HFD-STD vs. 40.0 +/- 5.3% HFD, P > 0.05). Serum and cardiac adiponectin levels were unaltered by rimonabant treatment. HL-1 cell death was not prevented by 1 or 7 days treatment with rimonabant. We conclude that rimonabant-induced infarct limitation may involve the CB1 receptor, although not necessarily cardiac CB1 receptors, and is unrelated to weight loss or altered adiponectin synthesis.

Variants in the CNR1 and the FAAH genes and adiposity traits in the community

Pharmacologic blockade of the endocannabinoid receptor 1 leads to weight loss and an improved metabolic risk profile in overweight and obese individuals. We hypothesize that common genetic variants in the CNR1 (encoding endocannabinoid receptor 1) and FAAH genes (encoding fatty acid amide hydrolase, a key enzyme hydrolyzing endocannabinoids) are associated with adiposity traits. We genotyped 18 single-nucleotide polymorphisms (SNPs) in the CNR1 gene and 9 SNPs in the FAAH gene in 2,415 Framingham Offspring Study participants (mean age 61 +/- 10 years; 52.6% women; mean BMI 28.2 +/- 5.4 kg/m(2); 30.3% obese) and studied them for association with cross-sectional and longitudinal measures of adiposity (BMI, waist circumference, change over time in BMI and waist circumference, visceral and subcutaneous adipose tissue) using linear mixed-effect models. The selected SNPs captured 85% (r(2) = 0.8) of the common variation (minor allele frequency >5%) at the CNR1 locus and 96% (r(2) = 0.8) of the common variation at the FAAH locus (defined as the genomic segment containing the gene +20 kb upstream and +10 kb downstream). After correction for multiple testing, none of the SNPs in the CNR1 gene or in the FAAH gene displayed statistical evidence for association with BMI, waist circumference, and visceral adipose tissue or subcutaneous adipose tissue (all P > 0.18). Despite comprehensive SNP mapping across the genes and their regulatory regions in a large unselected sample, we failed to find evidence for an association of common variants in the CNR1 and FAAH genes with measures of adiposity in our community-based sample.

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.

Endocannabinoids, metabolic regulation, and the role of diet

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

AM-251 and SR144528 are acyl CoA:cholesterol acyltransferase inhibitors

Oxysterol-induced macrophage apoptosis may have a role in atherosclerosis. Macrophages lacking the type 2 cannabinoid receptor (CB2) are partially resistant to apoptosis induced by 7-ketocholesterol (7KC). AM-251 and SR144528 are selective antagonists of CB1 and CB2 receptors, respectively. We observed that both compounds reduce 7KC-induced apoptosis in Raw 264.7 macrophages. As oxysterol-induced macrophage apoptosis requires acyl-coenzymeA:cholesterol acyltransferase (ACAT) activity, we tested their affects on ACAT activity. AM-251 and SR144528 both reduced cholesteryl ester synthesis in unstimulated and acetylated LDL-stimulated Raw 264.7 macrophages, CB2(+/+) and CB2(-/-) peritoneal macrophages, as well as in vitro, in mouse liver microsomes. Consistent with inhibition of ACAT, the development of foam cell characteristics in macrophages by treatment with acetylated LDL was reduced by both compounds. This work is the first evidence that AM-251 and SR144528 are inhibitors of ACAT and as a result, might have anti-atherosclerotic activities independent of their affect on cannabinoid signaling.

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.

Rimonabant ameliorates insulin resistance via both adiponectin-dependent and adiponectin-independent pathways

Rimonabant has been shown to not only decrease the food intake and body weight but also to increase serum adiponectin levels. This increase of the serum adiponectin levels has been hypothesized to be related to the rimonabant-induced amelioration of insulin resistance linked to obesity, although experimental evidence to support this hypothesis is lacking. To test this hypothesis experimentally, we generated adiponectin knock-out (adipo(-/-))ob/ob mice. After 21 days of 30 mg/kg rimonabant, the body weight and food intake decreased to similar degrees in the ob/ob and adipo(-/-)ob/ob mice. Significant improvement of insulin resistance was observed in the ob/ob mice following rimonabant treatment, associated with significant up-regulation of the plasma adiponectin levels, in particular, of high molecular weight adiponectin. Amelioration of insulin resistance in the ob/ob mice was attributed to the decrease of glucose production and activation of AMP-activated protein kinase (AMPK) in the liver induced by rimonabant but not to increased glucose uptake by the skeletal muscle. Interestingly, the rimonabant-treated adipo(-/-)ob/ob mice also exhibited significant amelioration of insulin resistance, although the degree of improvement was significantly lower as compared with that in the ob/ob mice. The effects of rimonabant on the liver metabolism, namely decrease of glucose production and activation of AMPK, were also less pronounced in the adipo(-/-)ob/ob mice. Thus, it was concluded that rimonabant ameliorates insulin resistance via both adiponectin-dependent and adiponectin-independent pathways.

Rimonabant, a selective cannabinoid CB1 receptor antagonist, inhibits atherosclerosis in LDL receptor-deficient mice

OBJECTIVE

The objective of this study was to determine whether the potent selective cannabinoid receptor-1 antagonist rimonabant has antiatherosclerotic properties.

METHODS AND RESULTS

Rimonabant (50 mg/kg/d in the diet) significantly reduced food intake (from 3.35+/-.04 to 2.80+/-0.03 g/d), weight gain (from 14.6+/-0.7 g to -0.6+/-0.3 g), serum total cholesterol (from 8.39+/-0.54 to 5.32+/-0.18 g/L), and atherosclerotic lesion development in the aorta (from 1.7+/-0.22 to 0.21+/-0.037 mm(2)) and aortic sinus (from 101,000+/-7800 to 27,000+/-2900 microm(2)) of LDLR(-/-) mice fed a Western-type diet for 3 months. Rimonabant also reduced plasma levels of the proinflammatory cytokines MCP-1 and IL12 by 85% (P<0.05) and 76% (P<0.05), respectively. Pair-fed animals had reduced weight gain (6.2+/-0.6 g gain), but developed atherosclerotic lesions which were as large as those of untreated animals, showing that the antiatherosclerotic effect of rimonabant is not related to reduced food intake. Interestingly, rimonabant at a lower dose (30 mg/kg/d in the diet) reduced atherosclerosis development in the aortic sinus (from 121,000+/-20,000 to 62,000+/-11,000 microm(2), 49% reduction, P<0.05), without affecting serum total cholesterol (7.8+/-0.7 g/L versus 8.1+/-1.3 g/L in the control group). Rimonabant decreased lipopolysaccharide (LPS)- and IL1beta-induced proinflammatory gene expression in mouse peritoneal macrophages in vitro as well as thioglycollate-induced recruitment of macrophages in vivo (10 mg/kg, p.o. bolus).

CONCLUSIONS

These results show that rimonabant has antiatherosclerotic effects in LDLR(-/-) mice. These effects are partly unrelated to serum cholesterol modulation and could be related to an antiinflammatory effect.

Hepatic CB1 receptor is required for development of diet-induced steatosis, dyslipidemia, and insulin and leptin resistance in mice

Diet-induced obesity is associated with fatty liver, insulin resistance, leptin resistance, and changes in plasma lipid profile. Endocannabinoids have been implicated in the development of these associated phenotypes, because mice deficient for the cannabinoid receptor CB1 (CB1-/-) do not display these changes in association with diet-induced obesity. The target tissues that mediate these effects, however, remain unknown. We therefore investigated the relative role of hepatic versus extrahepatic CB1 receptors in the metabolic consequences of a high-fat diet, using liver-specific CB1 knockout (LCB1-/-) mice. LCB1(-/-) mice fed a high-fat diet developed a similar degree of obesity as that of wild-type mice, but, similar to CB1(-/-) mice, had less steatosis, hyperglycemia, dyslipidemia, and insulin and leptin resistance than did wild-type mice fed a high-fat diet. CB1 agonist-induced increase in de novo hepatic lipogenesis and decrease in the activity of carnitine palmitoyltransferase-1 and total energy expenditure were absent in both CB1(-/-) and LCB1(-/-) mice. We conclude that endocannabinoid activation of hepatic CB1 receptors contributes to the diet-induced steatosis and associated hormonal and metabolic changes, but not to the increase in adiposity, observed with high-fat diet feeding. Theses studies suggest that peripheral CB1 receptors could be selectively targeted for the treatment of fatty liver, impaired glucose homeostasis, and dyslipidemia in order to minimize the neuropsychiatric side effects of nonselective CB1 blockade during treatment of obesity-associated conditions.

Biological specificity of visceral adipose tissue and therapeutic intervention

With excess energy storage, obesity develops, leading to increased risk for type 2 diabetes and cardiovascular diseases. The distribution of body fat appears to be even more important than the total amount of fat. Abdominal and, in particular, visceral adiposity is strongly linked to insulin resistance, type 2 diabetes, hypertension, dyslipidaemia, sleep apnea, and other complications of obesity. Visceral adiposity, manifested as a high waist circumference, is now accepted as a major component of the metabolic syndrome. However, the biological mechanisms underlying the adverse impact of visceral fat accumulation remain to be established. This review will focus on the analysis of the biological specificity of adipose tissue located in the abdominal region, and will explore intervention strategies targeting the impaired function of the visceral adipocyte as potential therapies for the cardio-metabolic outcomes of patients with the metabolic syndrome.

Leptin receptor deficiency is associated with upregulation of cannabinoid 1 receptors in limbic brain regions

Leptin receptor dysfunction results in overeating and obesity. Leptin regulates hypothalamic signaling that underlies the motivation to hyperphagia, but the interaction between leptin and cannabinoid signaling is poorly understood. We evaluated the role of cannabinoid 1 receptors (CB(1)R) in overeating and the effects of food deprivation on CB(1)R in the brain. One-month-old Zucker rats were divided into unrestricted and restricted (fed 70% of unrestricted rats) diet groups and maintained until adulthood (4 months). Levels of relative binding sites of CB(1)R (CB(1)R binding levels) were assessed using [(3)H] SR141716A in vitro autoradiography. These levels were higher (except cerebellum and hypothalamus) at 4 months than at 1 month of age. One month CB(1)R binding levels for most brain regions did not differ between Ob and Lean (Le) rats (except in frontal and cingulate cortices in Le and in the hypothalamus in Ob). Four month Ob rats had higher CB(1)R binding levels than Le in most brain regions and food restriction was associated with higher CB(1)R levels in all brain regions in Ob, but not in Le rats. CB(1)R binding levels increased between adolescence and young adulthood which we believe was influenced by leptin and food availability. The high levels of CB(1)R in Ob rats suggest that leptin's inhibition of food-intake is in part mediated by downregulation of CB(1)R and that leptin interferes with CB(1)R upregulation under food-deprivation conditions. These results are consistent with prior findings showing increased levels of endogenous cannabinoids in the Ob rats corroborating the regulation of cannabinoid signaling by leptin.

Endocannabinoids and the control of energy homeostasis

Endocannabinoids (ECBs) are ubiquitous lipid mediators that act through the same G protein-coupled receptors (CB1 and CB2) that recognize plant-derived cannabinoids. As regulators of metabolism, ECBs are anabolic: they increase the intake, promote the storage, and decrease the expenditure of energy. Recent work indicates that activation of peripheral CB1 receptors by ECBs plays a key role in the hormonal/metabolic changes associated with obesity/metabolic syndrome and may be targeted for its pharmacotherapy.

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.

Targeting the endocannabinoid system: to enhance or reduce?

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

The cannabinoid receptor-1 antagonist rimonabant inhibits platelet activation and reduces pro-inflammatory chemokines and leukocytes in Zucker rats

BACKGROUND AND PURPOSE

We investigated the effect of rimonabant on inflammation and enhanced platelet reactivity in type 2 diabetic Zucker rats, an experimental model of impaired glucose tolerance and the metabolic syndrome.

EXPERIMENTAL APPROACH

Rimonabant (10 mg kg(-1) by gavage) was fed for 2 weeks to 3-month-old male obese Zucker rats as an impaired glucose tolerance model and for 10 weeks to 6-month-old male obese Zucker rats as a model of the metabolic syndrome. RANTES (Regulated upon Activation, Normal T cell Expressed, and Secreted) and MCP-1 (monocyte chemotactic protein-1) serum levels were determined by ELISA. Leukocyte populations were quantitatively assessed using a veterinary differential blood cell counter. Platelet activation was assessed by flow-cytometry, platelet aggregation, and adhesion of isolated platelets to immobilized fibrinogen.

KEY RESULTS

RANTES and MCP-1 serum levels were increased in obese vs lean Zucker rats and significantly reduced by long-term treatment with rimonabant, which slowed weight gain in rats with the metabolic syndrome. Neutrophils and monocytes were significantly increased in young and old obese vs lean Zucker rats and lowered by rimonabant. Platelet-bound fibrinogen was significantly enhanced in obese vs lean Zucker rats of both age, and was reduced by rimonabant. Platelets from obese rats were more sensitive to thrombin-induced aggregation and adhesion to fibrinogen, which were both attenuated by rimonabant therapy.

CONCLUSIONS AND IMPLICATIONS

We demonstrate positive modulation of circulating neutrophil and monocyte numbers, reduced platelet activation and lower RANTES and MCP-1 levels by rimonabant in Zucker rats. This may potentially contribute to a reduction of cardiovascular risk.

Increased energy expenditure contributes more to the body weight-reducing effect of rimonabant than reduced food intake in candy-fed wistar rats

The CB1 receptor antagonist, rimonabant, affects the endocannabinoid system and causes a sustained reduction in body weight (BW) despite the transient nature of the reduction in food intake. Therefore, in a multiple-dose study, female candy-fed Wistar rats were treated with rimonabant (10 mg/kg) and matched with pair-fed rats to distinguish between hypophagic action and hypothesized effects on energy expenditure. Within the first week of treatment, rimonabant reduced BW nearly to levels of standard rat chow-fed rats. Evaluation of energy balance (energy expenditure measured by indirect calorimetry in relation to metabolizable energy intake calculated by bomb calorimetry) revealed that increased energy expenditure based on increased fat oxidation contributed more to sustained BW reduction than reduced food intake. A mere food reduction through pair feeding did not result in comparable effects because animals reduced their energy expenditure to save energy stores. Because fat oxidation measured by indirect calorimetry increased immediately after dosing in the postprandial state, the acute effect of rimonabant on lipolysis was investigated in postprandial male rats. Rimonabant elevated free fatty acids postprandially, demonstrating an inherent pharmacological activity of rimonabant to induce lipolysis and not secondarily postabsorptively due to reduced food intake. We conclude that the weight-reducing effect of rimonabant was due to continuously elevated energy expenditure based on increased fat oxidation driven by lipolysis from fat tissue as long as fat stores were elevated. When the amount of endogenous fat stores declined, rimonabant-induced increased energy expenditure was maintained by a re-increase in food intake.

Lipid-lowering therapy in patients with type 2 diabetes: the case for early intervention

Chronic complications of type 2 diabetes, in particular, macrovascular complications, confer substantial morbidity and mortality and adversely affect a patient's quality of life. Early intensive intervention to control cardiovascular risk factors is essential in clinical management. Atherogenic dyslipidaemia characterized by elevated triglycerides, a low level of high-density lipoprotein cholesterol (HDL-C), and an increase in the preponderance of small, dense low-density lipoprotein (LDL) particles, is a key modifiable risk factor for macrovascular diabetic complications. Lowering low-density lipoprotein cholesterol (LDL-C) with a statin (or the combination of statin and ezetimibe) is the main focus for reducing cardiovascular risk in patients with diabetes. However, statins fail to address the residual cardiovascular risk associated with low HDL-C. Fibrates are effective against all components of the atherogenic dyslipidaemia associated with type 2 diabetes. Secondary analyses of the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study suggest a role for early treatment with fenofibrate in improving cardiovascular risk reduction in type 2 diabetes and provide safety data supporting the use of fenofibrate in combination with a statin. Data from the FIELD study suggest that fenofibrate may also have potential to impact on microvascular diabetic complications associated with type 2 diabetes. Data are awaited from the ongoing Action to Control Cardiovascular Risk in Diabetes (ACCORD) study to evaluate the outcome benefits of combining fenofibrate with a statin in patients with type 2 diabetes. Finally, in view of divergent study results and outstanding data, assessment of the risk of the individual with type 2 diabetes is mandatory to assist clinical decision-making when initiating lipid therapy.

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.

Psychosis following anti-obesity treatment with rimonabant

BACKGROUND

In this report, we present the case of a patient with a relapse of schizophrenia following an episode of depression and increased anxiety after antiobesity treatment with rimonabant, a cannabinoid type 1 receptor antagonist.

CASE REPORT

After 4 weeks of treatment the patient developed psychiatric symptoms, i.e. depressed mood and elevated anxiety. Four months after the discontinuation of rimonabant, the patient presented with psychotic symptoms fulfilling ICD-10 criteria of paranoid schizophrenia. Antipsychotic treatment with quetiapine was initialized. A stable recovery took further 4 weeks in which combined treatment with quetiapine and ziprasidone was given.

CONCLUSION

The course of the illness suggests that the continuous affective symptoms, which were most likely a side effect of rimonabant, may have triggered the psychosis analogous to the stress-diathesis model of schizophrenia. As a consequence, rimonabant may not be the first choice in obese patients with a history of schizophrenia due to a potentially increased risk of a relapse via an indirect mechanism.