Circulating endocannabinoid levels, abdominal adiposity and related cardiometabolic risk factors in obese men

Nutritional properties of dietary omega-3-enriched phospholipids

Dietary fatty acids regulate several physiological functions. However, to exert their properties, they have to be present in the diet in an optimal balance. Particular attention has been focused on tissue highly polyunsaturated fatty acids (HPUFAs) n-6/n-3 ratio, influenced by the type and the esterified form of dietary fatty acids. Dietary EPA and DHA when esterified to phospholipids (PLs) are more efficiently incorporated into tissue PLs and seem to possess peculiar properties through specific mechanism(s) of action, such as the capacity to affect endocannabinoid biosynthesis at much lower doses than EPA and DHA in triglyceride form, probably because of the above mentioned higher incorporation into tissue PLs. Downregulation of the endocannabinoid system seems to mediate the positive effects exerted by omega-3-enriched PLs on several parameters of metabolic syndrome. PLs are one of the major dietary forms of EPA and DHA we are exposed to with the everyday diet; therefore, it is not surprising that it guarantees an effective EPA and DHA nutritional activity. Future studies should address whether EPA and DHA in PL form are also more effective than other formulations in ameliorating other pathological conditions where n-3 HPUFAs seem to exert beneficial activities such as cancer and psychiatric disorders.

Taste sensitivity to 6-n-propylthiouracil is associated with endocannabinoid plasma levels in normal-weight individuals

OBJECTIVE

A decreased sensitivity to 6-n-propylthiouracil (PROP) has been shown to be associated with increased energy intake and therefore an increased body mass index, although other studies have not confirmed this association, suggesting the involvement of other factors. We investigated whether the endocannabinoid system, which also modulates hunger/satiety and energy balance, plays a role in modulating eating behavior influenced by a sensitivity to PROP.

METHODS

The plasma profile of the endocannabinoids 2-arachidonoylglycerol (2-AG), anandamide (AEA), and congeners of AEA, palmitoylethanolamide and oleylethanolamide (OEA), was determined in normal-weight PROP supertasters (STs) and PROP non-tasters (NTs). A cognitive eating behavior disorder was assessed by the Three-Factor Eating Questionnaire, which estimates dietary restraint, disinhibition, and perceived hunger.

RESULTS

The disinhibition score of NTs was higher than those of STs (P = 0.02). Moreover, in NTs, OEA was inversely correlated to the perceived hunger score (r = -0.7, P = 0.002), and AEA was positively correlated to the restraint score (r = 0.5, P = 0.04) and negatively to the perceived hunger score, although the latter correlation was at the limit of statistical significance (r = -0.47, P = 0.05). In addition, we found lower concentrations of AEA and 2-AG in the plasma of NT compared with ST subjects (AEA, P = 0.034; 2-AG, P = 0.003).

CONCLUSIONS

Our data suggest that a higher disinhibition behavior in NTs may be compensated in part, in normal-weight subjects, by the decrease of peripheral endocannabinoids to downregulate the hunger-energy intake circuitry.

Circulating anandamide and blood pressure in patients with obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea chronically increases blood pressure through sympathetic nervous system activation. In animals, hypertension and sympathetic activity are restrained by cannabinoid receptor activation. Therefore, we hypothesized that increased blood pressure in patients with obstructive sleep apnea is associated with increased circulating endocannabinoid concentrations.

METHODS

Arterial oxygen saturation and apnea/hypopnea episodes were recorded in 29 patients with normal glucose tolerance, 26 patients with type 2 diabetes mellitus, and 21 patients obese subjects without sleep apnea. We determined seated blood pressure, insulin, glucose, and high-sensitive C-reactive protein in the morning, and insulin sensitivity by euglycemic-hyperinsulinemic clamp the next day. Anandamide, the sum of 1-arachidonoylglycerol and 2-arachidonoylglycerol, and oleoylethanolamide were measured in plasma by liquid chromatography-tandem mass spectrometry.

RESULTS

Endocannabinoid concentrations in sleep apnea patients were increased compared to obese individuals without disordered nocturnal breathing. Correction for variables of obesity and insulin resistance almost completely abrogated this difference in endocannabinoids. Anandamide strongly correlated with blood pressure in sleep apnea patients (r = 0.60 for SBP and r = 0.58 for DBP, P < 0.001). In multivariate regression analysis, anandamide was a stronger determinant of blood pressure than sleep apnea severity, obesity, insulin resistance, and inflammation.

CONCLUSION

Obstructive sleep apnea patients show positive correlations between blood pressure and venous anandamide concentrations independent of confounding factors. Our data suggest a previously not recognized role of the endocannabinoid system for blood pressure regulation in patients with high risk for hypertension and cardiovascular disease.

Chronic treatment with krill powder reduces plasma triglyceride and anandamide levels in mildly obese men

We have previously shown that treatment of Zucker rats and mice with diet-induced obesity with dietary docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids in the form of krill oil reduces peripheral levels of endocannabinoids, ectopic fat formation and hyperglycemia. We reported that such treatment reduces plasma endocannabinoid levels also in overweight and obese human individuals, in whom high triglycerides may correlate with high circulating endocannabinoid levels. In this study, we report the effects of krill powder, which contains proteins (34%) in addition to krill oil (61.8%), on these two parameters. We submitted 11 obese men (average BMI of 32.3 kg/m², age of 42.6 years and plasma triglycerides of 192.5 ± 96.3 mg/dl) to a 24 week dietary supplementation with krill powder (4 g/day per os) and measured anthropometric and metabolic parameters, as well as blood endocannabinoid (anandamide and 2-arachidonoylglycerol) and esterified DHA and EPA levels. Six subjects were included as control subjects and not given any supplements. The treatment produced, after 12 and 24 weeks, a significant increase in DHA and EPA in total plasma, a 59 and 84% decrease in anandamide plasma levels, and a 22.5 and 20.6% decrease in triglyceride levels, respectively. There was also a significant decrease in waist/hip ratio and visceral fat/skeletal muscle mass ratio at 24 weeks, but no change in body weight. These data confirm that dietary krill powder reduces peripheral endocannabinoid overactivity in obese subjects, and might ameliorate some parameters of the metabolic syndrome.

Reduced endothelium-dependent relaxation to anandamide in mesenteric arteries from young obese Zucker rats

Impaired vascular function, manifested by an altered ability of the endothelium to release endothelium-derived relaxing factors and endothelium-derived contracting factors, is consistently reported in obesity. Considering that the endothelium plays a major role in the relaxant response to the cannabinoid agonist anandamide, the present study tested the hypothesis that vascular relaxation to anandamide is decreased in obese rats. Mechanisms contributing to decreased anandamide-induced vasodilation were determined. Resistance mesenteric arteries from young obese Zucker rats (OZRs) and their lean counterparts (LZRs) were used. Vascular reactivity was evaluated in a myograph for isometric tension recording. Protein expression and localization were analyzed by Western blotting and immunofluorescence, respectively. Vasorelaxation to anandamide, acetylcholine, and sodium nitroprusside, as well as to CB₁, CB₂, and TRPV1 agonists was decreased in endothelium-intact mesenteric arteries from OZRs. Incubation with an AMP-dependent protein kinase (AMPK) activator or a fatty acid amide hydrolase inhibitor restored anandamide-induced vascular relaxation in OZRs. CB₁ and CB₂ receptors protein expression was decreased in arteries from OZRs. Incubation of mesenteric arteries with anandamide evoked endothelial nitric oxide synthase (eNOS), AMPK and acetyl CoA carboxylase phosphorylation in LZRs, whereas it decreased phosphorylation of these proteins in OZRs. In conclusion, obesity decreases anandamide-induced relaxation in resistance arteries. Decreased cannabinoid receptors expression, increased anandamide degradation, decreased AMPK/eNOS activity as well as impairment of the response mediated by TRPV1 activation seem to contribute to reduce responses to cannabinoid agonists in obesity.

Plasma concentrations of endocannabinoids and related primary fatty acid amides in patients with post-traumatic stress disorder

Background

Endocannabinoids (ECs) and related N-acyl-ethanolamides (NAEs) play important roles in stress response regulation, anxiety and traumatic memories. In view of the evidence that circulating EC levels are elevated under acute mild stressful conditions in humans, we hypothesized that individuals with traumatic stress exposure and post-traumatic stress disorder (PTSD), an anxiety disorder characterized by the inappropriate persistence and uncontrolled retrieval of traumatic memories, show measurable alterations in plasma EC and NAE concentrations.

Methods

We determined plasma concentrations of the ECs anandamide (ANA) and 2-arachidonoylglycerol (2-AG) and the NAEs palmitoylethanolamide (PEA), oleoylethanolamide (OEA), stearoylethanolamine (SEA), and N-oleoyldopamine (OLDA) by HPLC-MS-MS in patients with PTSD (n = 10), trauma-exposed individuals without evidence of PTSD (n = 9) and in healthy control subjects (n = 29). PTSD was diagnosed according to DSM-IV criteria by administering the Clinician Administered PTSD Scale (CAPS), which also assesses traumatic events.

Results

Individuals with PTSD showed significantly higher plasma concentrations of ANA (0.48±0.11 vs. 0.36±0.14 ng/ml, p = 0.01), 2-AG (8.93±3.20 vs. 6.26±2.10 ng/ml, p<0.01), OEA (5.90±2.10 vs. 3.88±1.85 ng/ml, p<0.01), SEA (2.70±3.37 vs. 0.83±0.47, ng/ml, p<0.05) and significantly lower plasma levels of OLDA (0.12±0.05 vs. 0.45±0.59 ng/ml, p<0.05) than healthy controls. Moreover, PTSD patients had higher 2-AG plasma levels (8.93±3.20 vs. 6.01±1.32 ng/ml, p = 0.03) and also higher plasma concentrations of PEA (4.06±1.87 vs. 2.63±1.34 ng/ml, p<0.05) than trauma-exposed individuals without evidence of PTSD. CAPS scores in trauma-exposed individuals with and without PTSD (n = 19) correlated positively with PEA (r = 0.55, p = 0.02) and negatively with OLDA plasma levels (r = −0.68, p<0.01). CAPS subscores for intrusions (r = −0.65, p<0.01), avoidance (r = −0.60, p<0.01) and hyperarousal (r = −0.66, p<0.01) were all negatively related to OLDA plasma concentrations.

Conclusions

PTSD appears to be associated with changes in plasma EC/NAE concentrations. This may have pathophysiological and diagnostic consequences but will need to be reproduced in larger cohorts.

Modulating the endocannabinoid system in human health and disease--successes and failures

The discovery of the endocannabinoid system, comprising the G-protein coupled cannabinoid 1 and 2 receptors (CB1/2), their endogenous lipid ligands or endocannabinoids, and synthetic and metabolizing enzymes, has triggered an avalanche of experimental studies implicating the endocannabinoid system in a growing number of physiological/pathological functions. These studies have also suggested that modulating the activity of the endocannabinoid system holds therapeutic promise for a broad range of diseases, including neurodegenerative, cardiovascular and inflammatory disorders; obesity/metabolic syndrome; cachexia; chemotherapy-induced nausea and vomiting; and tissue injury and pain, amongst others. However, clinical trials with globally acting CB1 antagonists in obesity/metabolic syndrome, and other studies with peripherally-restricted CB1/2 agonists and inhibitors of the endocannabinoid metabolizing enzyme in pain, have introduced unexpected complexities, suggesting that a better understanding of the pathophysiological role of the endocannabinoid system is required to devise clinically successful treatment strategies.

The endocannabinoid system in energy homeostasis and the etiopathology of metabolic disorders

Endocannabinoids and cannabinoid CB1 receptors are known to play a generalized role in energy homeostasis. However, clinical trials with the first generation of CB1 blockers, now discontinued due to psychiatric side effects, were originally designed to reduce food intake and body weight rather than the metabolic risk factors associated with obesity. In this review, we discuss how, in addition to promoting energy intake, endocannabinoids control lipid and glucose metabolism in several peripheral organs, particularly the liver and adipose tissue. Direct actions in skeletal muscle and pancreas are also emerging. This knowledge may help in the design of future therapies for the metabolic syndrome.

Endocannabinoid signaling in the gut mediates preference for dietary unsaturated fats

Dietary fat exerts a potent stimulatory effect on feeding. This effect is mediated, at least in part, by a cephalic mechanism that involves recruitment of the vagus nerve and subsequent activation of endocannabinoid signaling in the gut. Here, we used a sham-feeding protocol in rats to identify fatty-acid constituents of dietary fat that might be responsible for triggering small-intestinal endocannabinoid signaling. Sham feeding rats with a corn oil emulsion increased endocannabinoid levels in jejunum, relative to animals that received either mineral oil (which contains no fatty acids) or no oil. Sham-feeding emulsions containing oleic acid (18:1) or linoleic acid (18:2) caused, on average, a nearly 2-fold accumulation of jejunal endocannabinoids, whereas emulsions containing stearic acid (18:0) or linolenic acid (18:3) had no such effect. In a 2-bottle-choice sham-feeding test, rats displayed strong preference for emulsions containing 18:2, which was blocked by pretreatment with the peripherally restricted CB1 cannabinoid receptor antagonists, AM6546 and URB447. Our results suggest that oral exposure to the monoenoic and dienoic fatty acid component of dietary fat selectively initiates endocannabinoid mobilization in the gut, and that this local signaling event is essential for fat preference.

Fat to treat fat: emerging relationship between dietary PUFA, endocannabinoids, and obesity

Obesity incidence continues to escalate as a global nutrition and health problem. Scientists and clinicians are engaged in numerous research approaches that include behavior, education, applied nutrition studies and clinical therapies to prevent, control and reverse obesity. The common goal is to identify areas of basic and clinical research to understand aspects of human biology that contribute to obesity. In these approaches recent discoveries in biology and advancing technologies are tools employed to prevent and reverse obesity. The purpose of this review article is to present the current knowledge of key components of the endocannabinoid system that contribute to eating, influence systemic energy metabolism, and dietary factors that alter the responses of ligand binding and activation of cannabinoid receptors. Herein the objectives are to (1) describe the relationship between dietary polyunsaturated fatty acids (PUFA) and obesity, (2) explain the role of this signaling system in obesity, and (3) present areas of consequential future research with dietary long chain PUFA. There are several gaps in the knowledge of the role dietary PUFA play in the tone of the endocannabinoid signaling system involving ligands and receptors. Elucidating the PUFA relationship to signaling tone may explain the presumed overstimulation of signaling believed to contribute to over eating, fat accretion and inflammation. Future research in this endeavor must be hypothesis driven utilizing appropriate models for investigations on dietary PUFA, endocannabinoids and obesity.

Pathophysiology of human visceral obesity: an update

Excess intra-abdominal adipose tissue accumulation, often termed visceral obesity, is part of a phenotype including dysfunctional subcutaneous adipose tissue expansion and ectopic triglyceride storage closely related to clustering cardiometabolic risk factors. Hypertriglyceridemia; increased free fatty acid availability; adipose tissue release of proinflammatory cytokines; liver insulin resistance and inflammation; increased liver VLDL synthesis and secretion; reduced clearance of triglyceride-rich lipoproteins; presence of small, dense LDL particles; and reduced HDL cholesterol levels are among the many metabolic alterations closely related to this condition. Age, gender, genetics, and ethnicity are broad etiological factors contributing to variation in visceral adipose tissue accumulation. Specific mechanisms responsible for proportionally increased visceral fat storage when facing positive energy balance and weight gain may involve sex hormones, local cortisol production in abdominal adipose tissues, endocannabinoids, growth hormone, and dietary fructose. Physiological characteristics of abdominal adipose tissues such as adipocyte size and number, lipolytic responsiveness, lipid storage capacity, and inflammatory cytokine production are significant correlates and even possible determinants of the increased cardiometabolic risk associated with visceral obesity. Thiazolidinediones, estrogen replacement in postmenopausal women, and testosterone replacement in androgen-deficient men have been shown to favorably modulate body fat distribution and cardiometabolic risk to various degrees. However, some of these therapies must now be considered in the context of their serious side effects. Lifestyle interventions leading to weight loss generally induce preferential mobilization of visceral fat. In clinical practice, measuring waist circumference in addition to the body mass index could be helpful for the identification and management of a subgroup of overweight or obese patients at high cardiometabolic risk.

Cannabis and Δ9-tetrahydrocannabinol (THC) for weight loss?

Obesity is one of the highest preventable causes of morbidity and mortality in the developed world [1]. It has been well known for a long time that exposure to cannabis produces an increase of appetite (a phenomenon referred to as the 'munchies'). This phenomenon led to an exploration of the role of the endocannabinoid system in the regulation of obesity and associated metabolic syndrome. This effort subsequently led to the development of a successful therapeutic approach for obesity that consisted of blocking the cannabinoid CB1 receptors using ligands such as Rimonabant in order to produce weight loss and improve metabolic profile [2]. Despite being efficacious, Rimonabant was associated with increased rates of depression and anxiety and therefore removed from the market. We recently discovered that the prevalence of obesity is paradoxically much lower in cannabis users as compared to non-users and that this difference is not accounted for by tobacco smoking status and is still present after adjusting for variables such as sex and age. Here, we propose that this effect is directly related to exposure to the Δ(9)-tetrahydrocannabinol (THC) present in cannabis smoke. We therefore propose the seemingly paradoxical hypothesis that THC or a THC/cannabidiol combination drug may produce weight loss and may be a useful therapeutic for the treatment of obesity and its complications.

The role of endocannabinoids system in fatty liver disease and therapeutic potentials

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver morbidity and mortality with no proven effective therapy as of yet. Its prevalence is increasing globally in parallel with obesity and metabolic syndrome pandemic. The endocannabinoid (EC) system has been implicated in the pathogenesis of several diseases, including fatty liver diseases. This system refers to the cannabinoid receptors type 1 (CB1) and type 2 (CB2), with both their endogenous ligands and machinery dedicated to EC synthesis and degradation. There is accumulating evidence on the role CB1 as a key mediator of insulin resistance and liver lipogenesis in both animals and humans. On the other hand, CB2 receptors have been shown to promote inflammation with anti-fibrogenic properties. The pharmacological modulation of the EC system activity for the treatment of metabolic syndrome and NAFLD are promising yet premature. The initial limited success due to deleterious central nervous system side-effects are likely to be bypassed with the use of peripherally restricted drugs.

Fatty Acid modulation of the endocannabinoid system and the effect on food intake and metabolism

Endocannabinoids and their G-protein coupled receptors (GPCR) are a current research focus in the area of obesity due to the system's role in food intake and glucose and lipid metabolism. Importantly, overweight and obese individuals often have higher circulating levels of the arachidonic acid-derived endocannabinoids anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) and an altered pattern of receptor expression. Consequently, this leads to an increase in orexigenic stimuli, changes in fatty acid synthesis, insulin sensitivity, and glucose utilisation, with preferential energy storage in adipose tissue. As endocannabinoids are products of dietary fats, modification of dietary intake may modulate their levels, with eicosapentaenoic and docosahexaenoic acid based endocannabinoids being able to displace arachidonic acid from cell membranes, reducing AEA and 2-AG production. Similarly, oleoyl ethanolamide, a product of oleic acid, induces satiety, decreases circulating fatty acid concentrations, increases the capacity for β -oxidation, and is capable of inhibiting the action of AEA and 2-AG in adipose tissue. Thus, understanding how dietary fats alter endocannabinoid system activity is a pertinent area of research due to public health messages promoting a shift towards plant-derived fats, which are rich sources of AEA and 2-AG precursor fatty acids, possibly encouraging excessive energy intake and weight gain.

The role of the endocannabinoid system in skeletal muscle and metabolic adaptations to exercise: potential implications for the treatment of obesity

The results of recent studies add the endocannabinoid system, and more specifically CB1 receptor signalling, to the complex mechanisms that negatively modulate insulin sensitivity and substrate oxidation in skeletal muscle. CB1 receptors might become overactive in the skeletal muscle during obesity due to increased levels of endocannabinoids. However, quite surprisingly, one of the most studied endocannabinoids, anandamide, when administered in a sufficient dose, was shown to improve muscle glucose uptake and activate some key molecules of insulin signalling and mitochondrial biogenesis. This is probably because anandamide is only a partial agonist at CB1 receptors and interacts with other receptors (PPARγ, TRPV1), which may trigger positive metabolic effects. This putative beneficial role of anandamide is worth considering because increased plasma anandamide levels were recently reported after intense exercise. Whether the endocannabinoid system is involved in the positive exercise effects on mitochondrial biogenesis and glucose fatty acid oxidation remains to be confirmed. Noteworthy, when exercise becomes chronic, a decrease in CB1 receptor expression in obese metabolically deregulated tissues occurs. It is then tempting to hypothesize that physical activity would represent a complementary alternative approach for the clinical management of endocannabinoid system deregulation in obesity, without the side effects occurring with CB1 receptor antagonists.

Acute stress increases circulating anandamide and other N-acylethanolamines in healthy humans

Stress plays an important role in psychiatric disorders, and preclinical evidence indicates that the central endocannabinoid system modulates endocrine and neuronal responses to stress. This study aimed to investigate the effect of acute stress on circulating concentrations of endocannabinoids (eCBs) in healthy humans. A total of 71 adults participated in two sessions in which they were exposed to either a standardized psychosocial stress procedure (Trier Social Stress Test) or a control task. Blood samples for eCB and cortisol assays and cardiovascular and subjective measures were obtained before and at regular intervals after the tasks. Serum concentrations of the eCBs, N-arachidonylethanolamine (anandamide, AEA) and 2-arachidonoylglycerol (2-AG), as well as of the N-acylethanolamides (NAEs), N-palmitoylethanolamine (PEA) and N-oleoylethanolamine (OEA), and of the O-acylglycerol, 2-oleoylglycerol (2-OG), were determined. Compared with the control condition, stress increased serum concentrations of AEA and the other NAEs immediately after the stress period. Increases in PEA were positively correlated with increases in serum cortisol after stress. Furthermore, anxiety ratings at baseline were negatively correlated with baseline concentrations of AEA. The sex and menstrual cycle status of the subject affected the NAE responses to stress. Interestingly, subjects of Asian and African-American races exhibited different patterns of stress responses compared with the Caucasian subjects. These results indicate that stress increases circulating NAEs in healthy human volunteers. This finding supports a protective role for eCBs in anxiety. Further research is needed to elucidate the function of these lipid mediators, and to determine the mechanisms that regulate their appearance in the circulation.

Short term voluntary overfeeding disrupts brain insulin control of adipose tissue lipolysis

Insulin controls fatty acid (FA) release from white adipose tissue (WAT) through direct effects on adipocytes and indirectly through hypothalamic signaling by reducing sympathetic nervous system outflow to WAT. Uncontrolled FA release from WAT promotes lipotoxicity, which is characterized by inflammation and insulin resistance that leads to and worsens type 2 diabetes. Here we tested whether early diet-induced insulin resistance impairs the ability of hypothalamic insulin to regulate WAT lipolysis and thus contributes to adipose tissue dysfunction. To this end we fed male Sprague-Dawley rats a 10% lard diet (high fat diet (HFD)) for 3 consecutive days, which is known to induce systemic insulin resistance. Rats were studied by euglycemic pancreatic clamps and concomitant infusion of either insulin or vehicle into the mediobasal hypothalamus. Short term HFD feeding led to a 37% increase in caloric intake and elevated base-line free FAs and insulin levels compared with rats fed regular chow. Overfeeding did not impair insulin signaling in WAT, but it abolished the ability of mediobasal hypothalamus insulin to suppress WAT lipolysis and hepatic glucose production as assessed by glycerol and glucose flux. HFD feeding also increased hypothalamic levels of the endocannabinoid 2-arachidonoylglycerol after only 3 days. In summary, overfeeding impairs hypothalamic insulin action, which may contribute to unrestrained lipolysis seen in human obesity and type 2 diabetes.

Selective cannabinoid-1 receptor blockade benefits fatty acid and triglyceride metabolism significantly in weight-stable nonhuman primates

The goal of this study was to determine whether administration of the CB₁ cannabinoid receptor antagonist rimonabant would alter fatty acid flux in nonhuman primates. Five adult baboons (Papio Sp) aged 12.1 ± 4.7 yr (body weight: 31.9 ± 2.1 kg) underwent repeated metabolic tests to determine fatty acid and TG flux before and after 7 wk of treatment with rimonabant (15 mg/day). Animals were fed ad libitum diets, and stable isotopes were administered via diet (d₃₁-tripalmitin) and intravenously (¹³C₄-palmitate, ¹³C₁-acetate). Plasma was collected in the fed and fasted states, and blood lipids were analyzed by GC-MS. DEXA was used to assess body composition and a hyperinsulinemic euglycemic clamp used to assess insulin-mediated glucose disposal. During the study, no changes were observed in food intake, body weight, plasma, and tissue endocannabinoid concentrations or the quantity of liver-TG fatty acids originating from de novo lipogenesis (19 ± 6 vs. 16 ± 5%, for pre- and posttreatment, respectively, P = 0.39). However, waist circumference was significantly reduced 4% in the treated animals (P < 0.04), glucose disposal increased 30% (P = 0.03), and FFA turnover increased 37% (P = 0.02). The faster FFA flux was consistent with a 43% reduction in these fatty acids used for TRL-TG synthesis (40 ± 3 vs. 23 ± 4%, P = 0.02) and a twofold increase in TRL-TG turnover (1.5 ± 0.9 vs. 3.1 ± 1.4 μmol·kg⁻¹·h⁻¹, P = 0.03). These data support the potential for a strong effect of CB₁ receptor antagonism at the level of adipose tissue, resulting in improvements in fasting turnover of fatty acids at the whole body level, central adipose storage, and significant improvements in glucose homeostasis.

Endocannabinoids measurement in human saliva as potential biomarker of obesity

Background

The discovery of the endocannabinoid system and of its role in the regulation of energy balance has significantly advanced our understanding of the physiopathological mechanisms leading to obesity and type 2 diabetes. New knowledge on the role of this system in humans has been acquired by measuring blood endocannabinoids. Here we explored endocannabinoids and related N-acylethanolamines in saliva and verified their changes in relation to body weight status and in response to a meal or to body weight loss.

Methodology/Principal Findings

Fasting plasma and salivary endocannabinoids and N-acylethanolamines were measured through liquid mass spectrometry in 12 normal weight and 12 obese, insulin-resistant subjects. Salivary endocannabinoids and N-acylethanolamines were evaluated in the same cohort before and after the consumption of a meal. Changes in salivary endocannabinoids and N-acylethanolamines after body weight loss were investigated in a second group of 12 obese subjects following a 12-weeks lifestyle intervention program. The levels of mRNAs coding for enzymes regulating the metabolism of endocannabinoids, N-acylethanolamines and of cannabinoid type 1 (CB₁) receptor, alongside endocannabinoids and N-acylethanolamines content, were assessed in human salivary glands.

The endocannabinoids 2-arachidonoylglycerol (2-AG), N-arachidonoylethanolamide (anandamide, AEA), and the N-acylethanolamines (oleoylethanolamide, OEA and palmitoylethanolamide, PEA) were quantifiable in saliva and their levels were significantly higher in obese than in normal weight subjects. Fasting salivary AEA and OEA directly correlated with BMI, waist circumference and fasting insulin. Salivary endocannabinoids and N-acylethanolamines did not change in response to a meal. CB₁ receptors, ligands and enzymes were expressed in the salivary glands. Finally, a body weight loss of 5.3% obtained after a 12-weeks lifestyle program significantly decreased salivary AEA levels.

Conclusions/Significance

Endocannabinoids and N-acylethanolamines are quantifiable in saliva and their levels correlate with obesity but not with feeding status. Body weight loss significantly decreases salivary AEA, which might represent a useful biomarker in obesity.

New vistas for treatment of obesity and diabetes? Endocannabinoid signalling and metabolism in the modulation of energy balance

Growing evidence suggests that pathological overactivation of the endocannabinoid system (ECS) is associated with dyslipidemia, obesity and diabetes. Indeed, this signalling system acting through cannabinoid receptors has been shown to function both centrally and peripherally to regulate feeding behaviour as well as energy expenditure and metabolism. Consequently, modulation of these receptors can promote significant alterations in body weight and associated metabolic profile. Importantly, blocking cannabinoid receptor type 1 function has been found to prevent obesity and metabolic dysfunction in various murine models and in humans. Here we provide a detailed account of the known physiological role of the ECS in energy balance, and explore how recent studies have delivered novel insights into the potential targeting of this system as a therapeutic means for treating obesity and related metabolic disorders.

Intense exercise increases circulating endocannabinoid and BDNF levels in humans--possible implications for reward and depression

The endocannabinoid system is known to have positive effects on depression partly through its actions on neurotrophins, such as Brain-Derived Neurotrophic Factor (BDNF). As BDNF is also considered the major candidate molecule for exercise-induced brain plasticity, we hypothesized that the endocannabinoid system represents a crucial signaling system mediating the beneficial antidepressant effects of exercise. Here we investigated, in 11 healthy trained male cyclists, the effects of an intense exercise (60 min at 55% followed by 30 min at 75% W(max)) on plasma levels of endocannabinoids (anandamide, AEA and 2-arachidonoylglycerol, 2-AG) and their possible link with serum BDNF. AEA levels increased during exercise and the 15 min recovery (P<0.001), whereas 2-AG concentrations remained stable. BDNF levels increased significantly during exercise and then decreased during the 15 min of recovery (P<0.01). Noteworthy, AEA and BDNF concentrations were positively correlated at the end of exercise and after the 15 min recovery (r>0.66, P<0.05), suggesting that AEA increment during exercise might be one of the factors involved in exercise-induced increase in peripheral BDNF levels and that AEA high levels during recovery might delay the return of BDNF to basal levels. AEA production during exercise might be triggered by cortisol since we found positive correlations between these two compounds and because corticosteroids are known to stimulate endocannabinoid biosynthesis. These findings provide evidence in humans that acute exercise represents a physiological stressor able to increase peripheral levels of AEA and that BDNF might be a mechanism by which AEA influences the neuroplastic and antidepressant effects of exercise.

The thrifty lipids: endocannabinoids and the neural control of energy conservation

The 'thrifty gene hypothesis' posits that evolution preferentially selects physiological mechanisms that optimize energy storage to increase survival under alternating conditions of abundance and scarcity of food. Recent experiments suggest that endocannabinoids - a class of lipid-derived mediators that activate cannabinoid receptors in many cells of the body - are key agents of energy conservation. The new evidence indicates that these compounds increase energy intake and decrease energy expenditure by controlling the activity of peripheral and central neural pathways involved in the sensing and hedonic processing of sweet and fatty foods, as well as in the storage of their energy content for future use.

Mechanisms of endothelial dysfunction in obesity-associated hypertension

Obesity is strongly associated with high blood pressure, dyslipidemia, and type 2 diabetes. These conditions synergistically increase the risk of cardiovascular events. A number of central and peripheral abnormalities can explain the development or maintenance of high blood pressure in obesity. Of great interest is endothelial dysfunction, considered to be a primary risk factor in the development of hypertension. Additional mechanisms also related to endothelial dysfunction have been proposed to mediate the development of hypertension in obese individuals. These include: increase in both peripheral vasoconstriction and renal tubular sodium reabsorption, increased sympathetic activity and overactivation of both the renin-angiotensin system and the endocannabinoid system and insulin resistance. The discovery of new mechanisms regulating metabolic and vascular function and a better understanding of how vascular function can be influenced by these systems would facilitate the development of new therapies for treatment of obesity-associated hypertension.

Inhibition of apolipoprotein A-I gene expression by obesity-associated endocannabinoids

Obesity is associated with increased serum endocannabinoid (EC) levels and decreased high-density lipoprotein cholesterol (HDLc). Apolipoprotein A-I (apo A-I), the primary protein component of HDL is expressed primarily in the liver and small intestine. To determine whether ECs regulate apo A-I gene expression directly, the effect of the obesity-associated ECs anandamide and 2-arachidonylglycerol on apo A-I gene expression was examined in the hepatocyte cell line HepG2 and the intestinal cell line Caco-2. Apo A-I protein secretion was suppressed nearly 50% by anandamide and 2-arachidonoylglycerol in a dose-dependent manner in both cell lines. Anandamide treatment suppressed both apo A-I mRNA and apo A-I gene promoter activity in both cell lines. Studies using apo A-I promoter deletion constructs indicated that repression of apo A-I promoter activity by anandamide requires a previously identified nuclear receptor binding site designated as site A. Furthermore, anandamide-treatment inhibited protein-DNA complex formation with the site A probe. Exogenous over expression of cannabinoid receptor 1 (CBR1) in HepG2 cells suppressed apo A-I promoter activity, while in Caco-2 cells, exogenous expression of both CBR1 and CBR2 could repress apo A-I promoter activity. The suppressive effect of anandamide on apo A-I promoter activity in Hep G2 cells could be inhibited by CBR1 antagonist AM251 but not by AM630, a selective and potent CBR2 inhibitor. These results indicate that ECs directly suppress apo A-I gene expression in both hepatocytes and intestinal cells, contributing to the decrease in serum HDLc in obese individuals.

Estimation of reference intervals of five endocannabinoids and endocannabinoid related compounds in human plasma by two dimensional-LC/MS/MS

The elucidation of the role of endocannabinoids in physiological and pathological conditions and the transferability of the importance of these mediators from basic evidence into clinical practice is still hampered by the indefiniteness of their circulating reference intervals. In this work, we developed and validated a two-dimensional LC/MS/MS method for the simultaneous measurement of plasma endocannabinoids and related compounds such as arachidonoyl-ethanolamide, palmitoyl-ethanolamide, and oleoyl-ethanolamide, belonging to the N-acyl-ethanolamide (NAE) family, and 2-arachidonoyl-glycerol and its inactive isomer 1-arachidonoyl-glycerol from the monoacyl-glycerol (MAG) family. We found that several pitfalls in the endocannabinoid measurement may occur, from blood withdrawal to plasma processing. Plasma extraction with toluene followed by on-line purification was chosen, allowing high-throughput and reliability. We estimated gender-specific reference intervals on 121 healthy normal weight subjects fulfilling rigorous anthropometric and hematic criteria. We observed no gender differences for NAEs, whereas significantly higher MAG levels were found in males compared with females. MAGs also significantly correlated with triglycerides. NAEs increased with age in females, and arachidonoyl-ethanolamide correlated with adiposity and metabolic parameters in females. This work paves the way to the establishment of definitive reference intervals for circulating endocannabinoids to help physicians move from the speculative research field into the clinical field.

Serum contents of endocannabinoids are correlated with blood pressure in depressed women

BACKGROUND

Depression is known to be a risk factor for cardiovascular diseases but the underlying mechanisms remain unclear. Since recent preclinical evidence suggests that endogenous agonists of cannabinoid receptors (endocannabinoids) are involved in both cardiovascular function and depression, we asked whether endocannabinoids correlated with either in humans.

RESULTS

Resting blood pressure and serum content of endocannabinoids in ambulatory, medication-free, female volunteers with depression (n = 28) and their age- and ethnicity-matched controls (n = 27) were measured. In females with depression, both diastolic and mean arterial blood pressures were positively correlated with serum contents of the endocannabinoids, N-arachidonylethanolamine (anandamide) and 2-arachidonoylglycerol. There was no correlation between blood pressure and endocannabinoids in control subjects. Furthermore, depressed women had significantly higher systolic blood pressure than control subjects. A larger body mass index was also found in depressed women, however, it was not significantly correlated with serum endocannabinoid contents.

CONCLUSIONS

This preliminary study raises the possibility that endocannabinoids play a role in blood pressure regulation in depressives with higher blood pressure, and suggests an interrelationship among endocannabinoids, depression and cardiovascular risk factors in women.

Effect of an acute consumption of a moderate amount of ethanol on plasma endocannabinoid levels in humans

AIMS

Animal experiments have shown that the endocannabinoid system (ECS) plays an important role in the regulation of ethanol intake. We investigated these effects in healthy volunteers who consumed a moderate amount of ethanol (red wine) and measured plasma levels of the endocannabinoids (ECs) anandamide (AEA) and 2-arachidonoylglycerol (2-AG) to test whether alcohol consumption influences the ECS in humans. Grape juice or plain non-sparkling water served as non-alcoholic control liquids.

METHODS

In total, 55 adults were enrolled in this study and assigned to one of three groups drinking either 250 ml of red wine (28.0 g of ethanol, <0.8 g of sugar and 187.5 kcal), grape juice (41.0 g of sugar, 187.5 kcal) or plain water within 10 min. Twenty minutes and 45 min thereafter, AEA, 2-AG, ethanol and glucose levels were determined from venous plasma samples.

RESULTS

AEA, 2-AG and plasma glucose levels were significantly reduced after red wine consumption. AEA had its maximal decline at 20 min (from 0.23 ± 0.12 to 0.18 ± 0.07 ng/ml, P < 0.01), whereas the nadir of 2-AG was seen after 45 min and dropped from 6.68 ± 4.13 to 5.49 ± 3.22 ng/ml (P < 0.05). Grape juice highly affected blood glucose level after 20 min, with a return to baseline after 45 min. ECs remained almost unchanged by this intervention. Water intake had no significant effect on AEA (0.21 ± 0.08 at baseline and 0.19 ± 0.06 after 45 min) but resulted in a gradual reduction in 2-AG concentrations which became significant at 45 min when compared with baseline.

CONCLUSIONS

The consumption of a moderate amount of red wine reduces plasma AEA and 2-AG concentrations, whereas the volume and caloric equivalent of the sugar containing, non-alcoholic liquid grape juice does not affect plasma ECs. Plain water has a differential effect on the ECS by reducing 2-AG concentrations without affecting AEA.

The endocannabinoid system as a key mediator during liver diseases: new insights and therapeutic openings

Chronic liver diseases represent a major health problem due to cirrhosis and its complications. During the last decade, endocannabinoids and their receptors have emerged as major regulators of several pathophysiological aspects associated with chronic liver disease progression. Hence, hepatic cannabinoid receptor 2 (CB(2)) receptors display beneficial effects on alcoholic fatty liver, hepatic inflammation, liver injury, regeneration and fibrosis. Cannabinoid receptor 1 (CB(1)) receptors have been implicated in the pathogenesis of several lesions such as alcoholic and metabolic steatosis, liver fibrogenesis, or circulatory failure associated with cirrhosis. Although the development of CB(1) antagonists has recently been suspended due to the high incidence of central side effects, preliminary preclinical data obtained with peripherally restricted CB(1) antagonists give real hopes in the development of active CB(1) molecules devoid of central adverse effects. CB(2) -selective molecules may also offer novel perspectives for the treatment of liver diseases, and their clinical development is clearly awaited. Whether combined treatment with a peripherally restricted CB(1) antagonist and a CB(2) agonist might result in an increased therapeutic potential will warrant further investigation.

Endocannabinoids and the cardiovascular response to stress

Stress activates the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS), resulting in cardiovascular responses. The endocannabinoid system (ECS), a ubiquitously expressed lipid signalling system, modulates both HPA and SNS activity. The purpose of this review is to explore the possible involvement/role of the ECS in the cardiovascular response to stress. The ECS has numerous cardiovascular effects including modulation of blood pressure, heart rate, the baroreflex, and direct vascular actions. It is also involved in a protective manner in response to stressors in cardiac preconditioning, and various stressors (for example, pain, orthostasis and social stress) increase plasma levels of endocannabinoids. Given the multitude of vascular effects of endocannabinoids, this is bound to have consequences. Beneficial effects of ECS upregulation could include cardioprotection, vasodilatation, CB(2)-mediated anti-inflammatory effects and activation of peroxisome proliferator-activated receptors. Negative effects of endocannabinoids could include mediation of the effects of glucocorticoids, CB(1)-mediated metabolic changes, and metabolism to vasoconstrictor products. It is also likely that there is a central role for the ECS in modulating cardiovascular activity via the HPA and SNS. However, much more work is required to fully integrate the role of the ECS in mediating many of the physiological responses to stress, including cardiovascular responses.

Central and peripheral cannabinoid receptors as therapeutic targets in the control of food intake and body weight

The endocannabinoid system consists of lipid-derived agonists that activate cannabinoid (CB) receptors. CB receptor agonists, namely, the phytocannabinoid Δ(9)-THC and the endocannabinoid anandamide, increase hunger sensation and food intake. These discoveries led to the clinical use of Δ(9)-THC derivatives for the treatment of cancer and HIV-related nausea and cachexia. Animal studies clarified the important role of CB1 receptors in the hypothalamus and in the limbic system in mediating orexigenic effects. In parallel, data on CB1-specific blockade either by drugs or by genetic ablation further demonstrated that CB1 inhibition protects against weight gain induced by high-fat feeding and reduces body weight in obese animals and humans. The mechanisms of weight reduction by CB1 blockade are complex: they comprise interactions with several orexigenic and anorexigenic neuropeptides and hormones, regulation of sympathetic activity, influences on mitochondrial function, and on lipogenesis. Although these mechanisms appear to be mainly mediated by the CNS, weight loss also occurs when drugs that do not reach CNS concentrations sufficient to inhibit CB1 signaling are used. The development of peripherally restricted CB1 inverse agonists and antagonists opened new routes in CB1 pharmacology because centrally acting CB1 inverse agonists, e.g., rimonabant and taranabant, exerted unacceptable side effects that precluded their further development and application as weight loss drugs. Tissue and circulating endocannabinoid concentrations are often increased in animal models of obesity and in obese humans, especially those with visceral fat accumulation. Thus, further research on CB1 inhibition is still promising to treat human obesity.

Adipose stem cell-based soft tissue regeneration

INTRODUCTION

Since their isolation and characterization nearly a decade ago, adipose-derived stem cells (ASCs) have become one of the most popular adult stem cell populations for research in soft tissue engineering and regenerative medicine applications. Compared with other stem cell sources, ASCs offer several advantages including an abundant autologous source, minor invasive harvesting (liposuction), significant proliferative capacity in culture and multi-lineage potential. Numerous preclinical studies have been pursued, with early clinical data appearing in the literature.

AREAS COVERED

Autologous fat grafting has gained tremendous momentum in clinical practice over the past several years due to its potential applications in trauma and reconstructive surgery. This review focuses on the published clinical and pre-clinical (i.e., animal) data to date using ASCs for soft tissue reconstruction, with particular attention to experimental models and methodologies. Future directions for rendering soft tissue reconstructive therapies more effective are discussed.

EXPERT OPINION

Although standardization of ASC harvesting and processing techniques, as well as long-term results of existing clinical studies, remains to be addressed, the known biological properties of ASCs suggest a potential role in enhancing fat graft retention and facilitating minimally invasive reconstructive treatments. While clinical applications are being reported, well controlled clinical studies are needed to demonstrate safety and efficacy.

Contributions of endocannabinoid signaling to psychiatric disorders in humans: genetic and biochemical evidence

The endocannabinoid signaling system is a widespread, neuromodulatory system in brain and is also widely utilized in the periphery to modulate metabolic functions and the immune system. Preclinical data demonstrate that endocannabinoid signaling is an important stress buffer and modulates emotional and cognitive functions. These data suggest the hypothesis that endocannabinoid signaling could be dysfunctional in a number of mental disorders. Genetic polymorphisms in the human genes for two important proteins of the endocannabinoid signaling system, the CB1 cannabinoid receptor (CB1R) and fatty acid amide hydrolase (FAAH), have been explored in the context of normal and pathological conditions. In the case of the gene for FAAH, the mechanistic relationships among the common genetic polymorphism, the expression of the FAAH protein, and its likely impact on endocannabinoid signaling are understood. However, multiple polymorphisms in the gene for the CB1R occur and are associated with human phenotypic differences without an understanding of the functional relationships among the gene, mRNA, protein, and protein function. The endocannabinoid ligands are found in the circulation, and several studies have identified changes in their concentrations under various conditions. These data are reviewed for the purpose of generating hypotheses and to encourage further studies in this very interesting and important area.

Peripheral effects of the endocannabinoid system in energy homeostasis: adipose tissue, liver and skeletal muscle

The endocannabinoid system (ECS) is composed of lipid signalling ligands, their G-protein coupled receptors and the enzymes involved in ligand generation and metabolism. Increasingly, the ECS is emerging as a critical agent of energy metabolism regulation through its ability to modulate caloric intake centrally as well as nutrient transport, cellular metabolism and energy storage peripherally. Visceral obesity has been associated with an upregulation of ECS activity in several systems and inhibition of the ECS, either pharmacologically or genetically, results in decreased energy intake and increased metabolic output. This review aims to summarize the recent advances that have been made regarding our understanding of the role the ECS plays in crucial peripheral systems pertaining to energy homeostasis: adipose tissues, the liver and skeletal muscle.

The activity of the endocannabinoid metabolising enzyme fatty acid amide hydrolase in subcutaneous adipocytes correlates with BMI in metabolically healthy humans

Background

The endocannabinoid system (ECS) is a ubiquitously expressed signalling system, with involvement in lipid metabolism and obesity. There are reported changes in obesity of blood concentrations of the endocannabinoids anandamide (AEA) and 2-arachidonoylglcyerol (2-AG), and of adipose tissue expression levels of the two key catabolic enzymes of the ECS, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). Surprisingly, however, the activities of these enzymes have not been assayed in conditions of increasing adiposity. The aim of the current study was to investigate whether FAAH and MGL activities in human subcutaneous adipocytes are affected by body mass index (BMI), or other markers of adiposity and metabolism.

Methods

Subcutaneous abdominal mature adipocytes, fasting blood samples and anthropometric measurements were obtained from 28 metabolically healthy subjects representing a range of BMIs. FAAH and MGL activities were assayed in mature adipocytes using radiolabelled substrates. Serum glucose, insulin and adipokines were determined using ELISAs.

Results

MGL activity showed no relationship with BMI or other adiposity indices, metabolic markers (fasting serum insulin or glucose) or serum adipokine levels (adiponectin, leptin or resistin). In contrast, FAAH activity in subcutaneous adipocytes correlated positively with BMI and waist circumference, but not with skinfold thickness, metabolic markers or serum adipokine levels.

Conclusions

In this study, novel evidence is provided that FAAH activity in subcutaneous mature adipocytes increases with BMI, whereas MGL activity does not. These findings support the hypothesis that some components of the ECS are upregulated with increasing adiposity in humans, and that AEA and 2-AG may be regulated differently.

Energy balance regulation by endocannabinoids at central and peripheral levels

Dysregulation of the endocannabinoid system (ECS) is a universal and, perhaps, causative feature of obesity. Central nervous system (CNS) circuits that regulate food intake were initially believed to be the targets for dysregulation. However, it is increasingly evident that endocannabinoids affect food intake, energy expenditure and substrate metabolism by acting on peripheral sites. Cannabinoid type 1 receptor (CB1r) antagonists can effectively treat obesity and associated metabolic alterations but, unfortunately, cause and exacerbate mood disorders. Drugs restricted to act on peripheral CB1rs might be safer and more effective, retaining the anti-obesity effects but lacking the adverse neurodepressive reactions. This review summarizes the emerging roles of the ECS in energy balance and discusses future pharmacological approaches for developing peripherally restricted CB1r antagonists.

Altered gut microbiota and endocannabinoid system tone in obese and diabetic leptin-resistant mice: impact on apelin regulation in adipose tissue

Growing evidence supports the role of gut microbiota in the development of obesity, type 2 diabetes, and low-grade inflammation. The endocrine activity of adipose tissue has been found to contribute to the regulation of glucose homeostasis and low-grade inflammation. Among the key hormones produced by this tissue, apelin has been shown to regulate glucose homeostasis. Recently, it has been proposed that gut microbiota participate in adipose tissue metabolism via the endocannabinoid system (eCB) and gut microbiota-derived compounds, namely lipopolysaccharide (LPS). We have investigated gut microbiota composition in obese and diabetic leptin-resistant mice (db/db) by combining pyrosequencing and phylogenetic microarray analysis of 16S ribosomal RNA gene sequences. We observed a significant higher abundance of Firmicutes, Proteobacteria, and Fibrobacteres phyla in db/db mice compared to lean mice. The abundance of 10 genera was significantly affected by the genotype. We identified the roles of the eCB and LPS in the regulation of apelinergic system tone (apelin and APJ mRNA expression) in genetic obese and diabetic mice. By using in vivo and in vitro models, we have demonstrated that both the eCB and low-grade inflammation differentially regulate apelin and APJ mRNA expression in adipose tissue. Finally, deep-gut microbiota profiling revealed that the gut microbial community of type 2 diabetic mice is significantly different from that of their lean counterparts. This indicates specific relationships between the gut microbiota and the regulation of the apelinergic system. However, the exact roles of specific bacteria in shaping the phenotype of db/db mice remain to be determined.

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.

Central and peripheral endocannabinoids and cognate acylethanolamides in humans: association with race, adiposity, and energy expenditure

CONTEXT

Peripheral and central endocannabinoids and cognate acylethanolamides (AEs) may play important but distinct roles in regulating energy balance.

OBJECTIVE

We hypothesized that in humans central/peripheral endocannabinoids are differently associated with adiposity and energy expenditure and differ by race.

DESIGN

We examined associations of arachindonoylethanolamide, 2-arachidonoylglycerol, palmitoylethanolamide, and oleoylethanolamide (OEA) assayed in plasma and cerebrospinal fluid (CSF) with race, adiposity, and energy expenditure.

SETTING/PARTICIPANTS

In this monitored clinical inpatient study, CSF was obtained by lumbar puncture in 27 individuals (12 Caucasian, 11 American Indian, and four African-American). Twenty-four hour and sleep energy expenditure were measured by indirect calorimetry in a respiratory chamber.

MAIN OUTCOME MEASURE

Samples were analyzed from a previous study originally designed to test a blood-brain barrier leptin transport deficit in human obesity.

RESULTS

CSF (but not peripheral) 2-arachidonoylglycerol was significantly increased in American Indians compared with Caucasians (18.48 ± 6.17 vs. 10.62 ± 4.58 pmol/ml, P < 0.01). In the whole group, peripheral AEs were positively but in CSF negatively associated with adiposity. However, in multivariate models adjusted for the other peripheral and CSF AEs, peripheral arachindonoylethanolamide was the only AE significantly associated with adiposity. Interestingly, CSF OEA concentrations were positively associated with adjusted 24 hour and sleep energy expenditure (r = 0.47, P < 0.05; r = 0.42, P < 0.05), but peripheral OEA was not.

CONCLUSIONS

These data indicate a central alteration of the endocannabinoid system in American Indians and furthermore show that AEs in both compartments play an important but distinct role in human energy balance regulation.

The gut microbiome as therapeutic target

Obesity, type-2 diabetes and low-grade inflammation are becoming worldwide epidemics. In this regard, the literature provides a novel concept that we call "MicrObesity" (Microbes and Obesity), which is devoted to deciphering the specific role of dysbiosis and its impact on host metabolism and energy storage. In the present review, we discuss novel findings that may partly explain how the microbial community participates in the development of the fat mass development, insulin resistance and low-grade inflammation that characterise obesity. In recent years, numerous mechanisms have been proposed and several proteins identified. Amongst the key players involved in the control of fat mass development, Fasting induced adipose factor, AMP-activated protein kinase, G-protein coupled receptor 41 and G-protein coupled receptor 43 have been linked to gut microbiota. In addition, the discovery that low-grade inflammation might be directly linked to the gut microbiota through metabolic endotoxaemia (elevated plasma lipopolysaccharide levels) has led to the identification of novel mechanisms involved in the control of the gut barrier. Amongst these, the impacts of glucagon-like peptide-2, the endocannabinoid system and specific bacteria (e.g., Bifidobacterium spp.) have been investigated. Moreover, the advent of probiotic and prebiotic treatments appears to be a promising "pharmaco-nutritional" approach to reversing the host metabolic alterations linked to the dysbiosis observed in obesity. Although novel powerful molecular system biology approaches have offered great insight into this "small world within", more studies are needed to unravel how specific changes in the gut microbial community might affect or counteract the development of obesity and related disorders.

Krill oil significantly decreases 2-arachidonoylglycerol plasma levels in obese subjects

We have previously shown that krill oil (KO), more efficiently than fish oil, was able to downregulate the endocannabinoid system in different tissues of obese zucker rats.

We therefore aimed at investigating whether an intake of 2 g/d of either KO or menhaden oil (MO), which provides 309 mg/d of EPA/DHA 2:1 and 390 mg/d of EPA/DHA 1:1 respectively, or olive oil (OO) for four weeks, is able to modify plasma endocannabinoids in overweight and obese subjects.

The results confirmed data in the literature describing increased levels of endocannabinoids in overweight and obese with respect to normo-weight subjects. KO, but not MO or OO, was able to significantly decrease 2-arachidonoylglycerol (2-AG), although only in obese subjects. In addition, the decrease of 2-AG was correlated to the plasma n-6/n-3 phospholipid long chain polyunsaturated fatty acid (LCPUFA) ratio. These data show for the first time in humans that relatively low doses of LCPUFA n-3 as KO can significantly decrease plasma 2-AG levels in obese subjects in relation to decrease of plasma phospholipid n-6/n-3 LCPUFA ratio. This effect is not linked to changes of metabolic syndrome parameters but is most likely due to a decrease of 2-AG biosynthesis caused by the replacement of 2-AG ultimate precursor, arachidonic acid, with n-3 PUFAs, as previously described in obese Zucker rats.

G1359A polymorphism in the cannabinoid receptor-1 gene is associated with metabolic syndrome in the Chinese Han population

BACKGROUND AND AIMS

Recent studies suggest that endocannabinoids modulate food intake and lipogenesis through cannabinoid receptor-1 (CNR1). This study aims to determine the association between G1359A polymorphism of CNR1 and metabolic syndrome (MetS) in the Chinese Han population.

METHODS

A total of 382 subjects at risk for MetS and 136 healthy subjects from Tianjin, China were genotyped for the G1359A polymorphism of CNR1 using TaqMan assay. Anthropometric measurements and serum analyses were done for body mass index (BMI), waist circumference, blood pressure, serum triglycerides (TG), serum total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, fasting plasma glucose, and plasma insulin levels.

RESULTS

GG genotype of CNR1 has a higher incidence in MetS subjects than in control subjects. Logistic regression analysis shows that the GG genotype was significantly associated with the increased risk of developing MetS (OR 2.204, 95% CI 1.277-3.803, p = 0.005). Compared with CNR1 GG genotype in MetS subjects, CNR1 GA and AA genotypes in subjects with MetS had relatively lower levels of BMI, waist circumference, homeostasis model assessment of insulin resistance (HOMA-IR) and TG.

CONCLUSIONS

Results suggest that the G1359A polymorphism of the CNR1 gene may contribute to MetS susceptibility in the Chinese Han population.

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.