Dysregulation of the peripheral and adipose tissue endocannabinoid system in human abdominal obesity

High Fat Diet Increases Circulating Endocannabinoids Accompanied by Increased Synthesis Enzymes in Adipose Tissue

The endocannabinoid system (ECS) controls energy balance by regulating both energy intake and energy expenditure. Endocannabinoid levels are elevated in obesity suggesting a potential causal relationship. This study aimed to elucidate the rate of dysregulation of the ECS, and the metabolic organs involved, in diet-induced obesity. Eight groups of age-matched male C57Bl/6J mice were randomized to receive a chow diet (control) or receive a high fat diet (HFD, 45% of calories derived from fat) ranging from 1 day up to 18 weeks before euthanasia. Plasma levels of the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (N-arachidonoylethanolamine, AEA), and related N-acylethanolamines, were quantified by UPLC-MS/MS and gene expression of components of the ECS was determined in liver, muscle, white adipose tissue (WAT) and brown adipose tissue (BAT) during the course of diet-induced obesity development. HFD feeding gradually increased 2-AG (+132% within 4 weeks, P < 0.05), accompanied by upregulated expression of its synthesizing enzymes Daglα and β in WAT and BAT. HFD also rapidly increased AEA (+81% within 1 week, P < 0.01), accompanied by increased expression of its synthesizing enzyme Nape-pld, specifically in BAT. Interestingly, Nape-pld expression in BAT correlated with plasma AEA levels (R ² = 0.171, β = 0.276, P < 0.001). We conclude that a HFD rapidly activates adipose tissue depots to increase the synthesis pathways of endocannabinoids that may aggravate the development of HFD-induced obesity.

Characterization of the endocannabinoid system in subcutaneous adipose tissue in periparturient dairy cows and its association to metabolic profiles

Adipose tissue (AT) plays a major role in metabolic adaptations in postpartum (PP) dairy cows. The endocannabinoid (eCB) system is a key regulator of metabolism and energy homeostasis; however, information about this system in ruminants is scarce. Therefore, this work aimed to assess the eCB system in subcutaneous AT, and to determine its relation to the metabolic profile in peripartum cows. Biopsies of AT were performed at 14 d prepartum, and 4 and 30 d PP from 18 multiparous peripartum cows. Cows were categorized retrospectively according to those with high body weight (BW) loss (HWL, 8.5 ± 1.7% BW loss) or low body weight loss (LWL, 2.9 ± 2.5% BW loss) during the first month PP. The HWL had higher plasma non-esterified fatty acids and a lower insulin/glucagon ratio PP than did LWL. Two-fold elevated AT levels of the main eCBs, N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), were found 4 d PP compared with prepartum in HWL, but not in LWL cows. AT levels of the eCB-like molecules oleoylethanolamide, palmitoylethanolamide, and of arachidonic acid were elevated PP compared with prepartum in all cows. The abundance of monoglyceride lipase (MGLL), the 2-AG degrading enzyme, was lower in HWL vs. LWL AT PP. The relative gene expression of the cannabinoid receptors CNR1 and CNR2 in AT tended to be higher in HWL vs. LWL PP. Proteomic analysis of AT showed an enrichment of the inflammatory pathways’ acute phase signaling and complement system in HWL vs. LWL cows PP. In summary, eCB levels in AT were elevated at the onset of lactation as part of the metabolic adaptations in PP dairy cows. Furthermore, activating the eCB system in AT is most likely associated with a metabolic response of greater BW loss, lipolysis, and AT inflammation in PP dairy cows.

Sex difference in brain CB1 receptor availability in man

The endocannabinoid system (ECS) has a widespread neuromodulatory function in the central nervous system and is involved in important aspects of brain function including brain development, cortical rhythms, plasticity, reward, and stress sensitivity. Many of these effects are mediated via the cannabinoid CB1 receptor (CB1R) subtype. Animal studies convincingly show an interaction between the ECS and sex hormones, as well as a sex difference of higher brain CB1R in males. Human in vivo studies of sex difference have yielded discrepant findings. Gender differences in CB1R availability were investigated in vivo in 11 male and 11 female healthy volunteers using a specific CB1R tracer [¹⁸F]FMPEP-d2 and positron emission tomography (PET). Regional [¹⁸F]FMPEP-d2 distribution volume was used as a proxy for CB1R availability. In addition, we explored whether CB1R availability is linked to neuropsychological functioning. Relative to females, CB1R availability was on average 41% higher in males (p = 0.002) with a regionally specific effect larger in the posterior cingulate and retrosplenial cortices (p = 0.001). Inter-subject variability in CB1R availability was similar in both groups. Voxel-based analyses revealed an inverse association between CB1R availability and visuospatial working memory task performance in both groups (p < 0.001). A CB1R sex difference with a large effect size was observed and should be considered in the design of CB1R-related studies on neuropsychiatric disorders. The behavioural correlates and clinical significance of this difference remain to be further elucidated, but our studies suggest an association between CB1R availability and working memory.

Plasma endocannabinoid levels in lean, overweight, and obese humans: relationships to intestinal permeability markers, inflammation, and incretin secretion

Intestinal production of endocannabinoid and oleoylethanolamide (OEA) is impaired in high-fat diet/obese rodents, leading to reduced satiety. Such diets also alter the intestinal microbiome in association with enhanced intestinal permeability and inflammation; however, little is known of these effects in humans. This study aimed to 1) evaluate effects of lipid on plasma anandamide (AEA), 2-arachidonyl- sn-glycerol (2-AG), and OEA in humans; and 2) examine relationships to intestinal permeability, inflammation markers, and incretin hormone secretion. Twenty lean, 18 overweight, and 19 obese participants underwent intraduodenal Intralipid infusion (2 kcal/min) with collection of endoscopic duodenal biopsies and blood. Plasma AEA, 2-AG, and OEA (HPLC/tandem mass spectrometry), tumor necrosis factor-α (TNFα), glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic peptide (GIP) (multiplex), and duodenal expression of occludin, zona-occludin-1 (ZO-1), intestinal-alkaline-phosphatase (IAP), and Toll-like receptor 4 (TLR4) (by RT-PCR) were assessed. Fasting plasma AEA was increased in obese compared with lean and overweight patients ( P < 0.05), with no effect of BMI group or ID lipid infusion on plasma 2-AG or OEA. Duodenal expression of IAP and ZO-1 was reduced in obese compared with lean ( P < 0.05), and these levels related negatively to plasma AEA ( P < 0.05). The iAUC for AEA was positively related to iAUC GIP ( r = 0.384, P = 0.005). Obese individuals have increased plasma AEA and decreased duodenal expression of ZO-1 and IAP compared with lean and overweight subjects. The relationships between plasma AEA with duodenal ZO-1, IAP, and GIP suggest that altered endocannabinoid signaling may contribute to changes in intestinal permeability, inflammation, and incretin release in human obesity.

Age-Related Changes in Glucose Metabolism, Hyperglycemia, and Cardiovascular Risk

Aging and diabetes mellitus are 2 well-known risk factors for cardiovascular disease (CVD). During the past 50 years, there has been an dramatic increase in life expectancy with a simultaneous increase in the prevalence of diabetes mellitus in the older population. This large number of older individuals with diabetes mellitus is problematic given that CVD risk associated with aging and diabetes mellitus. In this review, we summarize epidemiological data relating to diabetes mellitus and CVD, with an emphasis on the aging population. We then present data on hyperglycemia as a risk factor for CVD and review the current knowledge of age-related changes in glucose metabolism. Next, we review the role of obesity in the pathogenesis of age-related glucose dysregulation, followed by a summary of the results from major randomized controlled trials that focus on cardiovascular risk reduction through glycemic control, with a special emphasis on older adults. We then conclude with our proposed model of aging that body composition changes and insulin resistance link possible dysregulation of physiological pathways leading to obesity and diabetes mellitus-both forms of accelerated aging-and risks for CVD.

Gene Expression of Endocannabinoid System Components in Skeletal Muscle and Adipose Tissue of South Asians and White Caucasians with Overweight

OBJECTIVE

The study aimed to investigate whether markers of endocannabinoid signaling differed between men with overweight of South Asian and white Caucasian descent.

METHODS

We included South Asian (n = 10) and white Caucasian (n = 10) men with overweight and prediabetes aged 35 to 50 years. Plasma samples were analyzed for endocannabinoids, their congeners, and lipids. In white adipose tissue (WAT) and skeletal muscle biopsies, mRNA expression of genes involved in the endocannabinoid system (ECS) was assessed using quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Fasting lipid oxidation and glucose oxidation were determined with indirect calorimetry.

RESULTS

Compared to white Caucasians, South Asians had higher levels of plasma 2-linoleoyl glycerol (P < 0.01) and N-linoleoylethanolamine (P < 0.05). Interestingly, in skeletal muscle of South Asians, expression of cannabinoid receptors CB₁ and CB₂ was 10-fold lower (P < 0.001) and that of the endocannabinoid degradation enzyme fatty acid amide hydrolase 2 (FAAH2) was 5-fold lower (P < 0.001) compared to white Caucasians. Expression of genes involved in the ECS in WAT were not different between the two ethnicities. After pooling of both ethnicities, plasma 2-arachidonoylglycerol (2-AG) positively correlated with plasma triglycerides (R = 0.77, P < 0.001) and lipid oxidation (R = 0.55, P < 0.05).

CONCLUSIONS

South Asian men with overweight have higher plasma 2-linoleoyl glycerol and N-linoleoylethanolamine levels and lower expression of CB receptors and the endocannabinoid degradation enzyme FAAH2 in skeletal muscle compared to white Caucasians.

Cannabinoid Type 1 Receptors Are Upregulated During Acute Activation of Brown Adipose Tissue

Activating brown adipose tissue (BAT) could provide a potential approach for the treatment of obesity and metabolic disease in humans. Obesity is associated with upregulation of the endocannabinoid system, and blocking the cannabinoid type 1 receptor (CB1R) has been shown to cause weight loss and to decrease cardiometabolic risk factors. These effects may be mediated partly via increased BAT metabolism, since there is evidence that CB1R antagonism activates BAT in rodents. To investigate the significance of CB1R in BAT function, we quantified the density of CB1R in human and rodent BAT using the positron emission tomography radioligand [¹⁸F]FMPEP-d₂ and measured BAT activation in parallel with the glucose analog [¹⁸F]fluorodeoxyglucose. Activation by cold exposure markedly increased CB1R density and glucose uptake in the BAT of lean men. Similarly, β3-receptor agonism increased CB1R density in the BAT of rats. In contrast, overweight men with reduced BAT activity exhibited decreased CB1R in BAT, reflecting impaired endocannabinoid regulation. Image-guided biopsies confirmed CB1R mRNA expression in human BAT. Furthermore, CB1R blockade increased glucose uptake and lipolysis of brown adipocytes. Our results highlight that CB1Rs are significant for human BAT activity, and the CB1Rs provide a novel therapeutic target for BAT activation in humans.

Profiling plasma N-Acylethanolamine levels and their ratios as a biomarker of obesity and dysmetabolism

Objective

N-acylethanolamines play different roles in energy balance; anandamide (AEA) stimulates energy intake and storage, N-palmitoylethanolamide (PEA) counters inflammation, and N-oleoylethanolamide (OEA) mediates anorectic signals and lipid oxidation. Inconsistencies in the association of plasma N-acylethanolamines with human obesity and cardiometabolic risk have emerged among previous studies, possibly caused by heterogeneous cohorts and designs, and by unstandardized N-acylethanolamine measurements. We aimed to characterize changes in the plasma profile, including N-acylethanolamine levels and ratios associated with obesity, menopause in women, and ageing in men, and to define the significance of such a profile as a biomarker for metabolic imbalance.

Methods

Adult, drug-free women (n = 103 premenopausal and n = 81 menopausal) and men (n = 144) were stratified according to the body mass index (BMI) into normal weight (NW; BMI: 18.5–24.9 kg/m²), overweight (OW; BMI: 25.0–29.9 kg/m²), and obese (OB; BMI ≥30.0 kg/m²). Anthropometric and metabolic parameters were determined. Validated blood processing and analytical procedures for N-acylethanolamine measurements were used. We investigated the effect of BMI and menopause in women, and BMI and age in men, as well as the BMI-independent influence of metabolic parameters on the N-acylethanolamine profile.

Results

BMI and waist circumference directly associated with AEA in women and men, and with PEA in premenopausal women and in men, while BMI directly associated with OEA in premenopausal women and in men. BMI, in both genders, and waist circumference, in women only, inversely associated with PEA/AEA and OEA/AEA. Menopause increased N-acylethanolamine levels, whereas ageing resulted in increasing OEA relative abundance in men. AEA and OEA abundances in premenopausal, and PEA and OEA abundances in lean menopausal women, were directly associated with hypertension. Conversely, PEA and OEA abundances lowered with hypertension in elderly men. Insulin resistance was associated with changes in N-acylethanolamine ratios specific for premenopausal (reduced PEA/AEA and OEA/AEA), menopausal (reduced OEA/AEA) women and men (reduced OEA/AEA and OEA/PEA). PEA and OEA levels increased with total cholesterol, and OEA abundance specifically increased with HDL-cholesterol. Elevated triglyceride levels were associated with increased N-acylethanolamine levels only in menopausal women.

Conclusions

Obesity-related N-acylethanolamine hypertone is characterized by imbalanced N-acylethanolamine ratios. The profile given by a combination of N-acylethanolamine absolute levels and ratios enables imbalances to be identified in relationship with different metabolic parameters, with specific relevance according to gender, menopause and age, representing a useful means for monitoring metabolic health. Finally, N-acylethanolamine system appears a promising target for intervention strategies.

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Obesity is featured by plasma N-acylethanolamine excess and imbalanced ratios.

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AEA excess is a biomarker of abdominal fat irrespectively of sex and menopause/age.

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PEA and OEA protect from hypertension in gender and menopause/age specific fashion.

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AEA excess in women and OEA deficiency in men are biomarkers of insulin resistance.

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High AEA in men and low OEA in men and menopausal women reflect low HDL-cholesterol.

Regulation of Adipose Tissue Metabolism by the Endocannabinoid System

White adipose tissue (WAT) stores excess energy as triglycerides, and brown adipose tissue (BAT) is specialized in dissipating energy as heat. The endocannabinoid system (ECS) is involved in a broad range of physiological processes and is increasingly recognized as a key player in adipose tissue metabolism. High ECS tonus in the fed state is associated with a disadvantageous metabolic phenotype, and this has led to a search for pharmacological strategies to inhibit the ECS. In this review we present recent developments that cast light on the regulation of adipose tissue metabolism by the ECS, and we discuss novel treatment options including the modulation of endocannabinoid synthesis and breakdown enzymes.

Differential modulation of white adipose tissue endocannabinoid levels by n-3 fatty acids in obese mice and type 2 diabetic patients

n-3 polyunsaturated fatty acids (n-3 PUFA) might regulate metabolism by lowering endocannabinoid levels. We examined time-dependent changes in adipose tissue levels of endocannabinoids as well as in parameters of glucose homeostasis induced by n-3 PUFA in dietary-obese mice, and compared these results with the effect of n-3 PUFA intervention in type 2 diabetic (T2DM) subjects. Male C57BL/6J mice were fed for 8, 16 or 24 weeks a high-fat diet alone (cHF) or supplemented with n-3 PUFA (cHF + F). Overweight/obese, T2DM patients on metformin therapy were given for 24 weeks corn oil (Placebo; 5 g/day) or n-3 PUFA concentrate as above (Omega-3; 5 g/day). Endocannabinoids were measured by liquid chromatography-tandem mass-spectrometry. Compared to cHF-fed controls, the cHF + F mice consistently reduced 2-arachidonoylglycerol (up to ~2-fold at week 24) and anandamide (~2-fold) in adipose tissue, while the levels of endocannabinoid-related anti-inflammatory molecules N-eicosapentaenoyl ethanolamine (EPEA) and N-docosahexaenoyl ethanolamine (DHEA) increased more than ~10-fold and ~8-fold, respectively. At week 24, the cHF + F mice improved glucose tolerance and fasting blood glucose, the latter being positively correlated with adipose 2-arachidonoylglycerol levels only in obese cHF-fed controls, like fasting insulin and HOMA-IR. In the patients, n-3 PUFA failed to reduce 2-arachidonoylglycerol and anandamide levels in adipose tissue and serum, but they increased both adipose tissue and serum levels of EPEA and DHEA. In conclusion, the inability of n-3 PUFA to reduce adipose tissue and serum levels of classical endocannabinoids might contribute to a lack of beneficial effects of these lipids on glucose homeostasis in T2DM patients.

Blockade of cannabinoid 1 receptor improves glucose responsiveness in pancreatic beta cells

Cannabinoid 1 receptors (CB1Rs) are expressed in peripheral tissues, including islets of Langerhans, where their function(s) is under scrutiny. Using mouse β-cell lines, human islets and CB1R-null (CB1R-/- ) mice, we have now investigated the role of CB1Rs in modulating β-cell function and glucose responsiveness. Synthetic CB1R agonists diminished GLP-1-mediated cAMP accumulation and insulin secretion as well as glucose-stimulated insulin secretion in mouse β-cell lines and human islets. In addition, silencing CB1R in mouse β cells resulted in an increased expression of pro-insulin, glucokinase (GCK) and glucose transporter 2 (GLUT2), but this increase was lost in β cells lacking insulin receptor. Furthermore, CB1R-/- mice had increased pro-insulin, GCK and GLUT2 expression in β cells. Our results suggest that CB1R signalling in pancreatic islets may be harnessed to improve β-cell glucose responsiveness and preserve their function. Thus, our findings further support that blocking peripheral CB1Rs would be beneficial to β-cell function in type 2 diabetes.

The therapeutic potential of targeting the peripheral endocannabinoid/CB1 receptor system

Endocannabinoids (eCBs) are internal lipid mediators recognized by the cannabinoid-1 and -2 receptors (CB₁R and CB₂R, respectively), which also mediate the different physiological effects of marijuana. The endocannabinoid system, consisting of eCBs, their receptors, and the enzymes involved in their biosynthesis and degradation, is present in a vast number of peripheral organs. In this review we describe the role of the eCB/CB₁R system in modulating the metabolism in several peripheral organs. We assess how eCBs, via activating the CB₁R, contribute to obesity and regulate food intake. In addition, we describe their roles in modulating liver and kidney functions, as well as bone remodeling and mass. Special importance is given to emphasizing the efficacy of the recently developed peripherally restricted CB₁R antagonists, which were pre-clinically tested in the management of energy homeostasis, and in ameliorating both obesity- and diabetes-induced metabolic complications.

Caloric restriction lowers endocannabinoid tonus and improves cardiac function in type 2 diabetes

BACKGROUND/OBJECTIVES

Endocannabinoids (ECs) are associated with obesity and ectopic fat accumulation, both of which play a role in the development of cardiovascular disease (CVD) in type 2 diabetes (T2D). The effect of prolonged caloric restriction on ECs in relation to fat distribution and cardiac function is still unknown. Therefore, our aim was to investigate this relationship in obese T2D patients with coronary artery disease (CAD).

SUBJECTS/METHODS

In a prospective intervention study, obese T2D patients with CAD (n = 27) followed a 16 week very low calorie diet (VLCD; 450-1000 kcal/day). Cardiac function and fat accumulation were assessed with MRI and spectroscopy. Plasma levels of lipid species, including ECs, were measured using liquid chromatography-mass spectrometry.

RESULTS

VLCD decreased plasma levels of virtually all measured lipid species of the class of N-acylethanolamines including the EC anandamide (AEA; -15%, p = 0.016), without decreasing monoacylglycerols including the EC 2-arachidonoylglycerol (2-AG). Baseline plasma AEA levels strongly correlated with the volume of subcutaneous white adipose tissue (SAT; R2 = 0.44, p < 0.001). VLCD decreased the volume of SAT (-53%, p < 0.001), visceral white adipose tissue (VAT) (-52%, p < 0.001), epicardial white adipose tissue (-15%, p < 0.001) and paracardial white adipose tissue (-28%, p < 0.001). VLCD also decreased hepatic (-86%, p < 0.001) and myocardial (-33%, p < 0.001) fat content. These effects were accompanied by an increased left ventricular ejection fraction (54.8 ± 8.7-56.2 ± 7.9%, p = 0.016).

CONCLUSIONS

Caloric restriction in T2D patients with CAD decreases AEA levels, but not 2-AG levels, which is paralleled by decreased lipid accumulation in adipose tissue, liver and heart, and improved cardiovascular function. Interestingly, baseline AEA levels strongly correlated with SAT volume. We anticipate that dietary interventions are worthwhile strategies in advanced T2D, and that reduction in AEA may contribute to the improved cardiometabolic phenotype induced by weight loss.

Omega-3 fatty acids and adipose tissue biology

This review provides evidence for the importance of white and brown adipose tissue (i.e. WAT and BAT) function for the maintenance of healthy metabolic phenotype and its preservation in response to omega-3 polyunsaturated fatty acids (omega-3 PUFA), namely in the context of diseased states linked to aberrant accumulation of body fat, systemic low-grade inflammation, dyslipidemia and insulin resistance. More specifically, the review deals with (i) the concept of immunometabolism, i.e. how adipose-resident immune cells and adipocytes affect each other and define the immune-metabolic interface; and (ii) the characteristic features of "healthy adipocytes" in WAT, which are relatively small fat cells endowed with a high capacity for mitochondrial oxidative phosphorylation, triacylglycerol/fatty acid (TAG/FA) cycling and de novo lipogenesis (DNL). The intrinsic metabolic features of WAT and their flexible regulations, reflecting the presence of "healthy adipocytes", provide beneficial local and systemic effects, including (i) protection against in situ endoplasmic reticulum stress and related inflammatory response during activation of adipocyte lipolysis; (ii) prevention of ectopic fat accumulation and dyslipidemia caused by increased hepatic VLDL synthesis, as well as prevention of lipotoxic damage of insulin signaling in extra-adipose tissues; and also (iii) increased synthesis of anti-inflammatory and insulin-sensitizing lipid mediators with pro-resolving properties, including the branched fatty acid esters of hydroxy fatty acids (FAHFAs), also depending on the activity of DNL in WAT. The "healthy adipocytes" phenotype can be induced in WAT of obese mice in response to various stimuli including dietary omega-3 PUFA, especially when combined with moderate calorie restriction, and possibly also with other life style (e.g. physical activity) or pharmacological (e.g. thiazolidinediones) interventions. While omega-3 PUFA could exert beneficial systemic effects by improving immunometabolism of WAT without a concomitant induction of BAT, it is currently not clear whether the metabolic effects of the combined intervention using omega-3 PUFA and calorie restriction or thiazolidinediones depend also on the activation of BAT function and/or the induction of brite/beige adipocytes in WAT. It remains to be established why omega-3 PUFA intervention in type 2 diabetic subjects does not improve insulin sensitivity and glucose homeostasis despite inducing various anti-inflammatory mediators in WAT, including the recently discovered docosahexaenoyl esters of hydroxy linoleic acid, the lipokines from the FAHFA family, as well as several endocannabinoid-related anti-inflammatory lipids. To answer the question whether and to which extent omega-3 PUFA supplementation could promote the formation of "healthy adipocytes" in WAT of human subjects, namely in the obese insulin-resistant patients, represents a challenging task that is of great importance for the treatment of some serious non-communicable diseases.

Peripheral modulation of the endocannabinoid system in metabolic disease

Dysfunction of the endocannabinoid system (ECS) has been identified in metabolic disease. Cannabinoid receptor 1 (CB₁) is abundantly expressed in the brain but also expressed in the periphery. Cannabinoid receptor 2 (CB₂) is more abundant in the periphery, including the immune cells. In obesity, global antagonism of overexpressed CB₁ reduces bodyweight but leads to centrally mediated adverse psychological outcomes. Emerging research in isolated cultured cells or tissues has demonstrated that targeting the endocannabinoid system in the periphery alleviates the pathologies associated with metabolic disease. Further, peripheral specific cannabinoid ligands can reverse aspects of the metabolic phenotype. This Keynote review will focus on current research on the functionality of peripheral modulation of the ECS for the treatment of obesity.

Circulating Endocannabinoids: From Whence Do They Come and Where are They Going?

The goal of this review is to summarize studies in which concentrations of circulating endocannabinoids in humans have been examined in relationship to physiological measurements and pathological status. The roles of endocannabinoids in the regulation of energy intake and storage have been well studied and the data obtained consistently support the hypothesis that endocannabinoid signaling is associated with increased consumption and storage of energy. Physical exercise mobilizes endocannabinoids, which could contribute to refilling of energy stores and also to the analgesic and mood-elevating effects of exercise. Circulating concentrations of 2-arachidonoylglycerol are very significantly circadian and dysregulated when sleep is disrupted. Other conditions under which circulating endocannabinoids are altered include inflammation and pain. A second important role for endocannabinoid signaling is to restore homeostasis following stress. Circulating endocannabinoids are stress-responsive and there is evidence that their concentrations are altered in disorders associated with excessive stress, including post-traumatic stress disorder. Although determination of circulating endocannabinoids can provide important information about the state of endocannabinoid signaling and thus allow for hypotheses to be defined and tested, the large number of physiological factors that contribute to their circulating concentrations makes it difficult to use them in isolation as a biomarker for a specific disorder.

Gastric bypass in morbid obese patients is associated with reduction in adipose tissue inflammation via N-oleoylethanolamide (OEA)-mediated pathways

Paradoxically, morbid obesity was suggested to protect from cardiovascular co-morbidities as compared to overweight/obese patients. We hypothesise that this paradox could be inferred to modulation ofthe “endocannabinoid” system on systemic and subcutaneous adipose tissue (SAT) inflammation. We designed a translational project including clinical and in vitro studies at Geneva University Hospital. Morbid obese subjects (n=11) were submitted to gastric bypass surgery (GBS) and followed up for one year (post-GBS). Insulin resistance and circulating and SAT levels of endocannabinoids, adipocytokines and CC chemokines were assessed pre- and post-GBS and compared to a control group of normal and overweight subjects (CTL) (n=20). In vitro cultures with 3T3-L1 adipocytes were used to validate findings from clinical results. Morbid obese subjects had baseline lower insulin sensitivity and higher hs-CRP, leptin, CCL5 and anandamide (AEA) levels as compared to CTL. GBS induced a massive weight and fat mass loss, improved insulin sensitivity and lipid profile, decreased C-reactive protein, leptin, and CCL2 levels. In SAT, increased expression of resistin, CCL2, CCL5 and tumour necrosis factor and reduced MGLL were shown in morbid obese patients pre-GBS when compared to CTL. GBS increased all endocannabinoids and reduced adipocytokines and CC chemokines. In morbid obese SAT, inverse correlations independent of body mass index were shown between palmitoylethanolamide (PEA) and N-oleoylethanolamide (OEA) levels and inflammatory molecules. In vitro, OEA inhibited CCL2 secretion from adipocytes via ERK1/2 activation. In conclusion, GBS was associated with relevant clinical, metabolic and inflammatory improvements, increasing endocannabinoid levels in SAT. OEA directly reduced CCL2 secretion via ERK1/2 activation in adipocytes.

Perinatal maternal high-fat diet induces early obesity and sex-specific alterations of the endocannabinoid system in white and brown adipose tissue of weanling rat offspring

Perinatal maternal high-fat (HF) diet programmes offspring obesity. Obesity is associated with overactivation of the endocannabinoid system (ECS) in adult subjects, but the role of the ECS in the developmental origins of obesity is mostly unknown. The ECS consists of endocannabinoids, cannabinoid receptors (cannabinoid type-1 receptor (CB1) and cannabinoid type-2 receptor (CB2)) and metabolising enzymes. We hypothesised that perinatal maternal HF diet would alter the ECS in a sex-dependent manner in white and brown adipose tissue of rat offspring at weaning in parallel to obesity development. Female rats received standard diet (9 % energy content from fat) or HF diet (29 % energy content from fat) before mating, during pregnancy and lactation. At weaning, male and female offspring were killed for tissue harvest. Maternal HF diet induced early obesity, white adipocyte hypertrophy and increased lipid accumulation in brown adipose tissue associated with sex-specific changes of the ECS's components in weanling rats. In male pups, maternal HF diet decreased CB1 and CB2 protein in subcutaneous adipose tissue. In female pups, maternal HF diet increased visceral and decreased subcutaneous CB1. In brown adipose tissue, maternal HF diet increased CB1 regardless of pup sex. In addition, maternal HF diet differentially changed oestrogen receptor across the adipose depots in male and female pups. The ECS and oestrogen signalling play an important role in lipogenesis, adipogenesis and thermogenesis, and we observed early changes in their targets in adipose depots of the offspring. The present findings provide insights into the involvement of the ECS in the developmental origins of metabolic disease induced by inadequate maternal nutrition in early life.

Effect of whey protein supplementation on levels of endocannabinoids and some of metabolic risk factors in obese women on a weight-loss diet: a study protocol for a randomized controlled trial

Background

Besides the effects of dietary long chain PUFA on circulating endocannabinoids concentrations, the impact of other nutrients on these system is not known and, whether changes in plasma endocannabinoids levels correlated with changes in body composition and biochemical metabolic risk factors in obese individuals, however, still remains to be characterized.

Methods

We will conduct a 2 months’ open label, parallel-group, randomized controlled trial to determine the effect of whey protein supplementation on levels of endocannabinoids, glycemic and lipid profile, inflammatory factors, adipocytokines and body composition in 60 premenopausal obese women on a weight-loss diet.

Conclusion

Due to strong relationship between endocannabinoids level and insulin resistance and obesity, in this trial, we will illustrate the other benefits of weight loss diet on health and metabolic risk factors. Also for the first, the effects of simultaneous weight loss diet and whey protein supplementation on these variables will be determined.

Trial registration

Iranian Registry of Clinical Trials IRCT2017021410181N8.

Electronic supplementary material

The online version of this article (10.1186/s12937-017-0294-x) contains supplementary material, which is available to authorized users.

Adipocyte cannabinoid receptor CB1 regulates energy homeostasis and alternatively activated macrophages

Dysregulated adipocyte physiology leads to imbalanced energy storage, obesity, and associated diseases, imposing a costly burden on current health care. Cannabinoid receptor type-1 (CB1) plays a crucial role in controlling energy metabolism through central and peripheral mechanisms. In this work, adipocyte-specific inducible deletion of the CB1 gene (Ati-CB1-KO) was sufficient to protect adult mice from diet-induced obesity and associated metabolic alterations and to reverse the phenotype in already obese mice. Compared with controls, Ati-CB1-KO mice showed decreased body weight, reduced total adiposity, improved insulin sensitivity, enhanced energy expenditure, and fat depot-specific cellular remodeling toward lowered energy storage capacity and browning of white adipocytes. These changes were associated with an increase in alternatively activated macrophages concomitant with enhanced sympathetic tone in adipose tissue. Remarkably, these alterations preceded the appearance of differences in body weight, highlighting the causal relation between the loss of CB1 and the triggering of metabolic reprogramming in adipose tissues. Finally, the lean phenotype of Ati-CB1-KO mice and the increase in alternatively activated macrophages in adipose tissue were also present at thermoneutral conditions. Our data provide compelling evidence for a crosstalk among adipocytes, immune cells, and the sympathetic nervous system (SNS), wherein CB1 plays a key regulatory role.

Effects of high-fat diet and age on the blood lipidome and circulating endocannabinoids of female C57BL/6 mice

Alterations in lipid metabolism play a significant role in the pathogenesis of obesity-associated disorders, and dysregulation of the lipidome across multiple diseases has prompted research to identify novel lipids indicative of disease progression. To address the significant gap in knowledge regarding the effect of age and diet on the blood lipidome, we used shotgun lipidomics with electrospray ionization-mass spectrometry (ESI-MS). We analyzed blood lipid profiles of female C57BL/6 mice following high-fat diet (HFD) and low-fat diet (LFD) consumption for short (6weeks), long (22weeks), and prolonged (36weeks) periods. We examined endocannabinoid levels, plasma esterase activity, liver homeostasis, and indices of glucose tolerance and insulin sensitivity to compare lipid alterations with metabolic dysregulation. Multivariate analysis indicated differences in dietary blood lipid profiles with the most notable differences after 6weeks along with robust alterations due to age. HFD altered phospholipids, fatty acyls, and glycerolipids. Endocannabinoid levels were affected in an age-dependent manner, while HFD increased plasma esterase activity at all time points, with the most pronounced effect at 6weeks. HFD-consumption also altered liver mRNA levels of PPARα, PPARγ, and CD36. These findings indicate an interaction between dietary fat consumption and aging with widespread effects on the lipidome, which may provide a basis for identification of female-specific obesity- and age-related lipid biomarkers.

Translating Endocannabinoid Biology into Clinical Practice: Cannabidiol for Stroke Prevention

Introduction: The endocannabinoid system (ECS) regulates functions throughout human physiology, including neuropsychiatric, cardiovascular, autonomic, metabolic, and inflammatory states. The complex cellular interactions regulated by the ECS suggest a potential for vascular disease and stroke prevention by augmenting central nervous and immune cell endocannabinoid signaling.

Discussion: The endocannabinoid N-arachidonoylethanolamine (anandamide) plays a central role in augmenting these processes in cerebrovascular and neurometabolic disease. Furthermore, cannabidiol (CBD), a nonpsychoactive constituent of Cannabis, is an immediate therapeutic candidate both for potentiating endocannabinoid signaling and for acting at multiple pharmacological targets.

Conclusion: This speculative synthesis explores the current state of knowledge of the ECS and suggests CBD as a therapeutic candidate for stroke prevention by exerting favorable augmentation of the homeostatic effects of the ECS and, in turn, improving the metabolic syndrome, while simultaneously stalling the development of atherosclerosis.

The CB1 Receptor as the Cornerstone of Exostasis

The type-1 cannabinoid receptor (CB1) is the main effector of the endocannabinoid system (ECS), which is involved in most brain and body functions. In this Perspective, we provide evidence indicating that CB1 receptor functions are key determinants of bodily coordinated exostatic processes. First, we will introduce the concepts of endostasis and exostasis as compensation or accumulation for immediate or future energy needs and discuss how exostasis has been necessary for the survival of species during evolution. Then, we will argue how different specific biological functions of the CB1 receptor in the body converge to provide physiological exostatic processes. Finally, we will introduce the concept of proactive evolution-induced diseases (PEIDs), which helps explain the seeming paradox that an evolutionary-selected physiological function can become the cause of epidemic pathological conditions, such as obesity. We propose here a possible unifying theory of CB1 receptor functions that can be tested by future experimental studies.

Re-visiting the Endocannabinoid System and Its Therapeutic Potential in Obesity and Associated Diseases

PURPOSE OF REVIEW

The purpose of the review was to revisit the possibility of the endocannabinoid system being a therapeutic target for the treatment of obesity by focusing on the peripheral roles in regulating appetite and energy metabolism.

RECENT FINDINGS

Previous studies with the global cannabinoid receptor blocker rimonabant, which has both central and peripheral properties, showed that this drug has beneficial effects on cardiometabolic function but severe adverse psychiatric side effects. Consequently, focus has shifted to peripherally restricted cannabinoid 1 (CB1) receptor blockers as possible therapeutic agents that mitigate or eliminate the untoward effects in the central nervous system. Targeting the endocannabinoid system using novel peripheral CB1 receptor blockers with negligible penetrance across the blood-brain barrier may prove to be effective therapy for obesity and its co-morbidities. Perhaps the future of blockers targeting CB1 receptors will be tissue-specific neutral antagonists (e.g., skeletal muscle specific to treat peripheral insulin resistance, adipocyte-specific to treat fat excess, liver-specific to treat fatty liver and hepatic insulin resistance).

Developmental programming of somatic growth, behavior and endocannabinoid metabolism by variation of early postnatal nutrition in a cross-fostering mouse model

Background

Nutrient deprivation during early development has been associated with the predisposition to metabolic disorders in adulthood. Considering its interaction with metabolism, appetite and behavior, the endocannabinoid (eCB) system represents a promising target of developmental programming.

Methods

By cross-fostering and variation of litter size, early postnatal nutrition of CB6F1-hybrid mice was controlled during the lactation period (3, 6, or 10 pups/mother). After weaning and redistribution at P21, all pups received standard chow ad libitum. Gene expression analyses (liver, visceral fat, hypothalamus) were performed at P50, eCB concentrations were determined in liver and visceral fat. Locomotor activity and social behavior were analyzed by means of computer-assisted videotracking.

Results

Body growth was permanently altered, with differences for length, weight, body mass index and fat mass persisting beyond P100 (all 3>6>10,p<0.01). This was paralleled by differences in hepatic IGF-I expression (p<0.01). Distinct gene expression patterns for key enzymes of the eCB system were observed in fat (eCB-synthesis: 3>6>10 (DAGLα p<0.05; NAPE-PLD p = 0.05)) and liver (eCB-degradation: 3>6>10 (FAAH p<0.05; MGL p<0.01)). Concentrations of endocannabinoids AEA and 2-AG in liver and visceral fat were largely comparable, except for a borderline significance for higher AEA (liver, p = 0.049) in formerly overfed mice and, vice versa, tendencies (p<0.1) towards lower AEA (fat) and 2-AG (liver) in formerly underfed animals. In the arcuate nucleus, formerly underfed mice tended to express more eCB-receptor transcripts (CB1R p<0.05; CB2R p = 0.08) than their overfed fellows. Open-field social behavior testing revealed significant group differences, with formerly underfed mice turning out to be the most sociable animals (p<0.01). Locomotor activity did not differ.

Conclusion

Our data indicate a developmental plasticity of somatic growth, behavior and parameters of the eCB system, with long-lasting impact of early postnatal nutrition. Developmental programming of the eCB system in metabolically active tissues, as shown here for liver and fat, may play a role in the formation of the adult cardiometabolic risk profile following perinatal malnutrition in humans.

Daytime-Dependent Changes of Cannabinoid Receptor Type 1 and Type 2 Expression in Rat Liver

The present study was performed to investigate the diurnal expression pattern of cannabinoid receptor type 1 (CB₁) and type 2 (CB₂) in liver tissue of 12- and 51-week-old normoglycemic Wistar rats. By using real-time RT-PCR, daytime dependent changes in both age groups and, for both, hepatic Cnr1 and Cnr2 receptor mRNA levels were measured. Highest amount of mRNA was detected in the light period (ZT3, ZT6, and ZT9) while the lowest amount was measured in the dark period (ZT18 and ZT21). Diurnal transcript expression pattern was accompanied by comparable changes of protein level for CB₁, as shown by Western blotting. The current results support the conclusion that expression pattern of cannabinoid receptors are influenced by light/dark cycle and therefore seems to be under the control of a diurnal rhythm. These findings might explain the differences in the efficacy of cannabinoid receptor agonists or antagonists. In addition, investigation of liver of streptozotocin (STZ)-treated 12- and 51-week-old rats show alterations in the diurnal profile of both receptors Cnr1 and Cnr2 compared to that of normoglycemic Wistar rats. This suggests an influence of diabetic state on diurnal expression levels of cannabinoid receptors.

Endocannabinoid tone is higher in healthy lean South Asian than white Caucasian men

South Asians have a higher risk to develop obesity and related disorders compared to white Caucasians. This is likely in part due to their lower resting energy expenditure (REE) as related with less energy-combusting brown adipose tissue (BAT). Since overactivation of the endocannabinoid system is associated with obesity and low BAT activity, we hypothesized that South Asians have a higher endocannabinoid tone. Healthy lean white Caucasian (n = 10) and South Asian (n = 10) men were cold-exposed to activate BAT. Before and after cooling, REE was assessed and plasma was collected for analysis of endocannabinoids and lipids. At thermoneutrality, South Asians had higher plasma levels of 2-arachidonoylglycerol (2-AG; 11.36 vs 8.19 pmol/mL, p < 0.05), N-arachidonylethanolamine (AEA; 1.04 vs 0.89 pmol/mL, p = 0.05) and arachidonic acid (AA; 23.24 vs 18.22 nmol/mL, p < 0.001). After pooling of both ethnicities, plasma 2-AG but not AEA positively correlated with triglycerides (R² = 0.32, p < 0.05) and body fat percentage (R² = 0.18, p < 0.05). Interestingly, AA negative correlated with REE (R² = 0.46, p < 0.001) and positively with body fat percentage (R² = 0.33, p < 0.01). Cooling increased endocannabinoids. In conclusion, South Asian compared to white Caucasian men have higher endocannabinoid tone. This suggests that endocannabinoids may, at least in part, underlie the disadvantageous metabolic phenotype of South Asians later in life.

Orphan nuclear receptor ERRγ is a key regulator of human fibrinogen gene expression

Fibrinogen, 1 of 13 coagulation factors responsible for normal blood clotting, is synthesized by hepatocytes. Detailed roles of the orphan nuclear receptors regulating fibrinogen gene expression have not yet been fully elucidated. Here, we identified estrogen-related receptor gamma (ERRγ) as a novel transcriptional regulator of human fibrinogen gene expression. Overexpression of ERRγ specially increased fibrinogen expression in human hepatoma cell line. Cannabinoid receptor types 1(CB1R) agonist arachidonyl-2'-chloroethylamide (ACEA) up-regulated transcription of fibrinogen via induction of ERRγ, whereas knockdown of ERRγ attenuated fibrinogen expression. Deletion analyses of the fibrinogen γ (FGG) gene promoter and ChIP assays revealed binding sites of ERRγ on human fibrinogen γ gene promoter. Moreover, overexpression of ERRγ was sufficient to increase fibrinogen gene expression, whereas treatment with GSK5182, a selective inverse agonist of ERRγ led to its attenuation in cell culture. Finally, fibrinogen and ERRγ gene expression were elevated in liver tissue of obese patients suggesting a conservation of this mechanism. Overall, this study elucidates a molecular mechanism linking CB1R signaling, ERRγ expression and fibrinogen gene transcription. GSK5182 may have therapeutic potential to treat hyperfibrinogenemia.

Polyunsaturated fatty acids and endocannabinoids in health and disease

Polyunsaturated fatty acids (PUFAs) are lipid derivatives of omega-3 (docosahexaenoic acid, DHA, and eicosapentaenoic acid, EPA) or of omega-6 (arachidonic acid, ARA) synthesized from membrane phospholipids and used as a precursor for endocannabinoids (ECs). They mediate significant effects in the fine-tune adjustment of body homeostasis. Phyto- and synthetic cannabinoids also rule the daily life of billions worldwide, as they are involved in obesity, depression and drug addiction. Consequently, there is growing interest to reveal novel active compounds in this field. Cloning of cannabinoid receptors in the 90s and the identification of the endogenous mediators arachidonylethanolamide (anandamide, AEA) and 2-arachidonyglycerol (2-AG), led to the characterization of the endocannabinoid system (ECS), together with their metabolizing enzymes and membrane transporters. Today, the ECS is known to be involved in diverse functions such as appetite control, food intake, energy balance, neuroprotection, neurodegenerative diseases, stroke, mood disorders, emesis, modulation of pain, inflammatory responses, as well as in cancer therapy. Western diet as well as restriction of micronutrients and fatty acids, such as DHA, could be related to altered production of pro-inflammatory mediators (e.g. eicosanoids) and ECs, contributing to the progression of cardiovascular diseases, diabetes, obesity, depression or impairing conditions, such as Alzheimer' s disease. Here we review how diets based in PUFAs might be linked to ECS and to the maintenance of central and peripheral metabolism, brain plasticity, memory and learning, blood flow, and genesis of neural cells.

Investigating the link between drug-naive first episode psychoses (FEPs), weight gain abnormalities and brain structural damages: Relevance and implications for therapy

Evidence suggests that obesity and overweight may be associated with severe brain structural abnormalities and poor cognitive and functional outcomes in the general population. Despite these observations and the high prevalence of weight gain abnormalities in patients with psychosis spectrum disorders (PSDs), no studies have investigated the impact that these metabolic disturbances may have on brain structures and development in the earliest stages of PSDs. In the present review we shed light on the association between weight gain and brain structural abnormalities that may affect the course of illness in drug-naïve FEPs. Given the lack of studies directly investigating this issue, we firstly identified and critically evaluated the literature assessing weight gain abnormalities and gray or white matter (GM, WM) volumes (either globally or in specific regions of interest) in otherwise healthy obese/overweight adolescents and young adults. We then compared the results of this systematic review with those of two recent meta-analysis investigating GM and WM abnormalities in drug-naïve FEPs. Weight gain in otherwise healthy subjects was consistently associated with frontal and temporal GM atrophy and with reduced integrity of WM in the corpus callosum. Of relevance, all these brain regions are affected in drug-naïve FEPs, and their integrity is associated with clinical, cognitive and functional outcomes. The underlying mechanisms that may explain the association between weight gain, adiposity, and brain damage in both healthy subjects and drug-naïve FEPs are widely discussed. On the basis of this knowledge, we tried: a) to deduce an integrative model for the development of obesity in psychosis spectrum disorders; b) to identify the key vulnerability factors underlying the association between weight gain and psychosis; c) to provide information on new potential targets of intervention.

Overactivation of the endocannabinoid system alters the antilipolytic action of insulin in mouse adipose tissue

Evidence has accumulated that obesity-related metabolic dysregulation is associated with overactivation of the endocannabinoid system (ECS), which involves cannabinoid receptor 1 (CB1R), in peripheral tissues, including adipose tissue (AT). The functional consequences of CB1R activation on AT metabolism remain unclear. Since excess fat mobilization is considered an important primary event contributing to the onset of insulin resistance, we combined in vivo and in vitro experiments to investigate whether activation of ECS could alter the lipolytic rate. For this purpose, the appearance of plasma glycerol was measured in wild-type and CB1R^-/- mice after acute anandamide administration or inhibition of endocannabinoid degradation by JZL195. Additional experiments were conducted on rat AT explants to evaluate the direct consequences of ECS activation on glycerol release and signaling pathways. Treatments stimulated glycerol release in mice fasted for 6 h and injected with glucose but not in 24-h fasted mice or in CB1R^-/-, suggesting that the effect was dependent on plasma insulin levels and mediated by CB1R. We concomitantly observed that Akt cascade activity was decreased, indicating an alteration of the antilipolytic action of insulin. Similar results were obtained with tissue explants exposed to anandamide, thus identifying CB1R of AT as a major target. This study indicates the existence of a functional interaction between CB1R and lipolysis regulation in AT. Further investigation is needed to test if the elevation of ECS tone encountered in obesity is associated with excess fat mobilization contributing to ectopic fat deposition and related metabolic disorders.

The cannabinoid ligand LH-21 reduces anxiety and improves glucose handling in diet-induced obese pre-diabetic mice

LH-21 is a triazol derivative that has been described as a low-permeant neutral CB1 antagonist, though its pharmacology is still unclear. It has been associated with anti-obesity actions in obese rats. However, its role in preventing type 2 diabetes (T2D) onset have not been studied yet. Given CB1 receptors remain as potential pharmacological targets to fight against obesity and T2D, we wanted to explore the metabolic impact of this compound in an animal model of obesity and pre-diabetes as well as the lack of relevant actions in related central processes such as anxiety. C57BL/6J mice were rendered obese and pre-diabetic by feeding a high-fat diet for 15 weeks and then treated with LH-21 or vehicle for two weeks. Food intake, body weight and glucose handling were assessed, together with other relevant parameters. Behavioural performance was evaluated by the open field test and the elevated plus maze. LH-21 did not affect food intake nor body weight but it improved glucose handling, displaying tissue-specific beneficial actions. Unexpectedly, LH-21 induced anxiolysis and reverted obesity-induced anxiety, apparently through GPR55 receptor. These results suggest that LH-21 can be a new candidate to fight against diabetes onset. Indeed, this compound shows potential in counteracting obesity-related anxiety.

MECHANISMS IN ENDOCRINOLOGY: Endocannabinoids and metabolism: past, present and future

The endocannabinoid system (ECS), including cannabinoid type 1 and type 2 receptors (CB₁R and CB₂R), endogenous ligands called endocannabinoids and their related enzymatic machinery, is known to have a role in the regulation of energy balance. Past information generated on the ECS, mainly focused on the involvement of this system in the central nervous system regulation of food intake, while at the same time clinical studies pointed out the therapeutic efficacy of brain penetrant CB₁R antagonists like rimonabant for obesity and metabolic disorders. Rimonabant was removed from the market in 2009 and its obituary written due to its psychiatric side effects. However, in the meanwhile a number of investigations had started to highlight the roles of the peripheral ECS in the regulation of metabolism, bringing up new hope that the ECS might still represent target for treatment. Accordingly, peripherally restricted CB₁R antagonists or inverse agonists have shown to effectively reduce body weight, adiposity, insulin resistance and dyslipidemia in obese animal models. Very recent investigations have further expanded the possible toolbox for the modulation of the ECS, by demonstrating the existence of endogenous allosteric inhibitors of CB₁R, the characterization of the structure of the human CB₁R, and the likely involvement of CB₂R in metabolic disorders. Here we give an overview of these findings, discussing what the future may hold in the context of strategies targeting the ECS in metabolic disease.

Metabolite profiling identifies anandamide as a biomarker of nonalcoholic steatohepatitis

The discovery of metabolite-phenotype associations may highlight candidate biomarkers and metabolic pathways altered in disease states. We sought to identify novel metabolites associated with obesity and one of its major complications, nonalcoholic fatty liver disease (NAFLD), using a liquid chromatography-tandem mass spectrometry method. In 997 individuals in Framingham Heart Study Generation 3 (FHS Gen 3), we identified an association between anandamide (AEA) and BMI. Further examination revealed that AEA was associated with radiographic hepatic steatosis. In a histologically defined NAFLD cohort, AEA was associated with NAFLD severity, the presence of nonalcoholic steatohepatitis, and fibrosis. These data highlight AEA as a marker linking cardiometabolic disease and NAFLD severity.

Participants with Normal Weight or with Obesity Show Different Relationships of 6-n-Propylthiouracil (PROP) Taster Status with BMI and Plasma Endocannabinoids

Reduced taste sensitivity to 6-n-propylthiouracil (PROP), a genetic trait regarded as a general index for oral chemosensory perception, has been associated with a calorie-rich food preference and lower circulating endocannabinoid levels in participants with normal weight (NW), which suggests an adaptive mechanism to maintain a lean phenotype. In this study, we assessed whether participants with obesity (OB) show different patterns of plasma endocannabinoids and lipid metabolism biomarkers from those of NW, with further categorization based on their PROP sensitivity. NW and OB were classified by their PROP taster status as non-tasters (NT), medium-tasters (MT) and supertasters (ST). The blood samples were analysed for plasma endocannabinoids, nonesterified fatty acids (NEFA) and retinol, which have been associated to metabolic syndrome. In OB, we found a higher BMI and lower circulating endocannabinoids in ST vs. OB NT. However, OB ST showed lower circulating NEFA and retinol levels, which suggested a more favourable lipid metabolism and body fat distribution than those of OB NT. We confirmed lower plasma endocannabinoid levels in NW NT than in NW ST. These data suggest that PROP taste sensitivity determines metabolic changes and ultimately body mass composition differently in OB and NW.

Plasma 2-arachidonoylglycerol is a biomarker of age and menopause related insulin resistance and dyslipidemia in lean but not in obese men and women

Objective

The endocannabinoid system hypertonicity features obesity. Excess circulating 2-arachidonoylglycerol was variously associated with obesity-related metabolic impairment; however, unstandardized experimental and analytical settings have clouded its usefulness as a dysmetabolism biomarker. We aimed at assessing the influence of body mass index (BMI), menopause in women, and aging in men on 2-arachidonoylglycerol relationship with metabolic parameters.

Methods

Adult, unmedicated women (premenopausal (preMW): n = 103; menopausal (MW): n = 81) and men (n = 144) were stratified in normal weight (NW; BMI: 18.5–24.9 kg/m²), overweight (OW; BMI: 25.0–29.9 kg/m²), and obese (OB; BMI ≥ 30.0 kg/m²) classes. Anthropometric and metabolic parameters were determined. Plasma 2-arachidonoylglycerol was measured by a validated liquid chromatography-mass spectrometry assay.

Results

2-arachidonoylglycerol level was raised by menopause (P < 0.001) and by obesity in preMW (P < 0.001) and in men (P = 0.019). In the overall cohorts, 2-arachidonoylglycerol displayed BMI-independent relationships with dyslipidemia (preMW, MW and men), insulin resistance (MW and men), and hypertension (men), but not with waist circumference. Within preMW BMI classes, 2-arachidonoylglycerol correlations were found with triglycerides (P = 0.020) and total cholesterol (TC; P = 0.040) in OB women. In MW, 2-arachidonoylglycerol correlation with triglycerides was found in NW (P = 0.001) and OW (P = 0.034), but not in OB class. Moreover, we found 2-arachidonoylglycerol correlations with TC (P = 0.003), glucose (P < 0.001), and HOMA-IR (P = 0.035) specific for NW MW class. In men, 2-arachidonoylglycerol correlated with triglycerides in NW, OW (both P < 0.001), and OB (P = 0.029), with SBP (P = 0.023) and diastolic BP (DBP; P = 0.048) in OB, and with TC (P < 0.001) in OW class. In NW class 2-arachidonoylglycerol correlations were found with insulin (P = 0.003) and HOMA-IR (P = 0.001), both enhanced by aging (both P = 0.004), and with glucose (P = 0.015) and HDL (P = 0.004).

Conclusions

Plasma 2AG is a biomarker of clustering metabolic dysfunctions, especially in lean men and menopausal women, and could be of help in identifying subjects with elevated cardiometabolic risk despite a healthy anthropometric appearance.

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Plasma 2AG is a biomarker of dysmetabolism rather than obesity.

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Menopause is a major determinant of plasma 2AG levels in females.

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Increased plasma 2AG level features obese premenopausal females and obese males.

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2AG is a biomarker of dyslipidemia and insulin resistance in lean menopausal women.

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2AG is a biomarker of dyslipidemia and age-related insulin resistance in lean men.

Role of cannabinoid receptor 1 in human adipose tissue for lipolysis regulation and insulin resistance

We recently showed that the peripheral cannabinoid receptor type 1 (CNR1) gene is upregulated by the synthetic glucocorticoid dexamethasone. CNR1 is highly expressed in the central nervous system and has been a drug target for the treatment of obesity. Here we explore the role of peripheral CNR1 in states of insulin resistance in human adipose tissue. Subcutaneous adipose tissue was obtained from well-controlled type 2 diabetes subjects and controls. Subcutaneous adipose tissue gene expression levels of CNR1 and endocannabinoid synthesizing and degrading enzymes were assessed. Furthermore, paired human subcutaneous adipose tissue and omental adipose tissue from non-diabetic volunteers undergoing kidney donation or bariatric surgery, was incubated with or without dexamethasone. Subcutaneous adipose tissue obtained from volunteers through needle biopsy was incubated with or without dexamethasone and in the presence or absence of the CNR1-specific antagonist AM281. CNR1 gene and protein expression, lipolysis and glucose uptake were evaluated. Subcutaneous adipose tissue CNR1 gene expression levels were 2-fold elevated in type 2 diabetes subjects compared with control subjects. Additionally, gene expression levels of CNR1 and endocannabinoid-regulating enzymes from both groups correlated with markers of insulin resistance. Dexamethasone increased CNR1 expression dose-dependently in subcutaneous adipose tissue and omental adipose tissue by up to 25-fold. Dexamethasone pre-treatment of subcutaneous adipose tissue increased lipolysis rate and reduced glucose uptake. Co-incubation with the CNR1 antagonist AM281 prevented the stimulatory effect on lipolysis, but had no effect on glucose uptake. CNR1 is upregulated in states of type 2 diabetes and insulin resistance. Furthermore, CNR1 is involved in glucocorticoid-regulated lipolysis. Peripheral CNR1 could be an interesting drug target in type 2 diabetes and dyslipidemia.

Serum levels of endocannabinoids are independently associated with nonalcoholic fatty liver disease

OBJECTIVE

To evaluate the association between circulating levels of endocannabinoids (eCBs) and non-alcoholic fatty liver disease (NAFLD).

METHODS

The serum levels of the main eCBs, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and their endogenous precursor and breakdown product, arachidonic acid (AA), were analyzed by liquid chromatography/tandem mass spectrometry in 105 volunteers screened for NAFLD. Hepatic ultrasound, fasting blood tests, and anthropometrics were assessed. Liver fat was quantified by the hepato-renal-ultrasound index representing the ratio between the brightness level of the liver and the kidney.

RESULTS

Patients with NAFLD had higher levels (pmol/mL) of AA (2,721 ± 1,112 vs. 2,248 ± 977, P = 0.022) and 2-AG (46.5 ± 25.8 vs. 33.5 ± 13.6, P = 0.003), but not AEA. The trend for higher levels of AA and 2-AG in the presence of NAFLD was observed in both genders and within subgroups of overweight and obesity. The association of AA and 2-AG with NAFLD was maintained with adjustment for age, gender, and BMI (OR = 1.001, 1.000-1.001 95% CI, P = 0.008 and OR = 1.05, 1.01-1.09, P = 0.006, respectively) or waist circumference.

CONCLUSIONS

This study is the first to show high circulating levels of 2-AG and AA in NAFLD patients compared with controls, independent of obesity. The findings may suggest an independent role of eCBs in the pathogenesis of NAFLD.

Sleep restriction alters plasma endocannabinoids concentrations before but not after exercise in humans

Following binding to cannabinoid receptors, endocannabinoids regulate a variety of central nervous system processes including appetite and mood. Recent evidence suggests that the systemic release of these lipid metabolites can be altered by acute exercise and that their levels also vary across the 24-h sleep-wake cycle. The present study utilized a within-subject design (involving 16 normal-weight men) to determine whether daytime circulating endocannabinoid concentrations differ following three nights of partial sleep deprivation (4.25-h sleep opportunity, 2:45-7a.m. each night) vs. normal sleep (8.5-h sleep opportunity, 10:30p.m.-7a.m. each night), before and after an acute bout of ergometer cycling in the morning. In addition, subjective hunger and stress were measured. Pre-exercise plasma concentrations of 2-arachidonoylglycerol (2AG) were 80% higher 1.5h after awakening (vs. normal sleep, p<0.05) when participants were sleep-deprived. This coincided with increased hunger ratings (+25% vs. normal sleep, p<0.05). Moreover, plasma 2AG was elevated 15min post-exercise (+44%, p<0.05). Sleep duration did not however modulate this exercise-induced rise. Finally, subjective stress was generally lower on the day after three nights of short sleep vs. normal sleep, especially after exercise (p<0.05). Given that activation of the endocannabinoid system has been previously shown to acutely increase appetite and mood, our results could suggest that behavioral effects of acute sleep loss, such as increased hunger and transiently improved psychological state, may partially result from activation of this signaling pathway. In contrast, more pronounced exercise-induced elevations of endocannabinoids appear to be less affected by short sleep duration.

Metformin Is Associated With Higher Relative Abundance of Mucin-Degrading Akkermansia muciniphila and Several Short-Chain Fatty Acid-Producing Microbiota in the Gut

The global obesity epidemic, dubbed “globesity” by the World Health Organisation, is a pressing public health issue. The aetiology of obesity is multifactorial incorporating both genetic and environmental factors. Recently, epidemiological studies have observed an association between microbes and obesity. Obesity-promoting microbiome and resultant gut barrier disintegration have been implicated as key factors facilitating metabolic endotoxaemia. This is an influx of bacterial endotoxins into the systemic circulation, believed to underpin obesity pathogenesis. Adipocyte dysfunction and subsequent adipokine secretion characterised by low grade inflammation, were conventionally attributed to persistent hyperlipidaemia. They were thought of as pivotal in perpetuating obesity. It is now debated whether infection and endotoxaemia are also implicated in initiating and perpetuating low grade inflammation. The fact that obesity has a prevalence of over 600 million and serves as a risk factor for chronic diseases including cardiovascular disease and type 2 diabetes mellitus is testament to the importance of exploring the role of microbes in obesity pathobiology. It is on this basis that Massachusetts General Hospital is sponsoring the Faecal Microbiota Transplant for Obesity and Metabolism clinical trial, to study the impact of microbiome composition on weight. The association of microbes with obesity, namely, adenovirus infection and metabolic endotoxaemia, is reviewed.

Marijuana Use and Type 2 Diabetes Mellitus: a Review

Marijuana is used by millions of people, with use likely to increase in the USA because of the trend towards increased decriminalization and legalization. Obesity and diabetes mellitus (DM) rates have increased dramatically in the USA over the past 30 years, with a recent estimate of 29 million individuals with DM. Because there is a plausible link between marijuana use and diabetes due to the known effects of cannabinoids on adipose tissue and glucose/insulin metabolism, it is important to study and understand how marijuana use is related to obesity and diabetes. This paper provides background on the human endocannabinoid system and studies of the association of marijuana use with body mass index/obesity, metabolic syndrome, prediabetes, and diabetes. The studies to date have shown that marijuana use is associated with either lower odds or no difference in the odds of diabetes than non-use.

Gut Microbiota: Modulation of Host Physiology in Obesity

Many factors are involved in weight gain and metabolic disturbances associated with obesity. The gut microbiota has been of particular interest in recent years, since both human and animal studies have increased our understanding of the delicate symbiosis between the trillions of microbes that reside in the GI tract and the host. It has been suggested that disruption of this mutual tolerance may play a significant role in modulating host physiology during obesity. Environmental influences such as diet, exercise, and early life exposures can significantly impact the composition of the microbiota, and this dysbiosis can in turn lead to increased host adiposity via a number of different mechanisms. The ability of the microbiota to regulate host fat deposition, metabolism, and immune function makes it an attractive target for achieving sustained weight loss.

Association between cerebral cannabinoid 1 receptor availability and body mass index in patients with food intake disorders and healthy subjects: a [(18)F]MK-9470 PET study

Although of great public health relevance, the mechanisms underlying disordered eating behavior and body weight regulation remain insufficiently understood. Compelling preclinical evidence corroborates a critical role of the endocannabinoid system (ECS) in the central regulation of appetite and food intake. However, in vivo human evidence on ECS functioning in brain circuits involved in food intake regulation as well as its relationship with body weight is lacking, both in health and disease. Here, we measured cannabinoid 1 receptor (CB1R) availability using positron emission tomography (PET) with [(18)F]MK-9470 in 54 patients with food intake disorders (FID) covering a wide body mass index (BMI) range (anorexia nervosa, bulimia nervosa, functional dyspepsia with weight loss and obesity; BMI range=12.5-40.6 kg/m(2)) and 26 age-, gender- and average BMI-matched healthy subjects (BMI range=18.5-26.6 kg/m(2)). The association between regional CB1R availability and BMI was assessed within predefined homeostatic and reward-related regions of interest using voxel-based linear regression analyses. CB1R availability was inversely associated with BMI in homeostatic brain regions such as the hypothalamus and brainstem areas in both patients with FID and healthy subjects. However, in FID patients, CB1R availability was also negatively correlated with BMI throughout the mesolimbic reward system (midbrain, striatum, insula, amygdala and orbitofrontal cortex), which constitutes the key circuit implicated in processing appetitive motivation and hedonic value of perceived food rewards. Our results indicate that the cerebral homeostatic CB1R system is inextricably linked to BMI, with additional involvement of reward areas under conditions of disordered body weight.

Linoleic acid and the pathogenesis of obesity

The modern Western diet has been consumed in developed English speaking countries for the last 50 years, and is now gradually being adopted in Eastern and developing countries. These nutrition transitions are typified by an increased intake of high linoleic acid (LA) plant oils, due to their abundance and low price, resulting in an increase in the PUFA n-6:n-3 ratio. This increase in LA above what is estimated to be required is hypothesised to be implicated in the increased rates of obesity and other associated non-communicable diseases which occur following a transition to a modern Westernised diet. LA can be converted to the metabolically active arachidonic acid, which has roles in inducing inflammation and adipogenesis, and endocannabinoid system regulation. This review aims to address the possible implications of excessive LA and its metabolites in the pathogenesis of obesity.

Simultaneous HPLC-APCI-MS/MS quantification of endogenous cannabinoids and glucocorticoids in hair

Hair matrix could retrospectively record association of endogenous cannabinoids (e.g. 2-arachidonoyl glycerol, 2-AG and N-arachidonoyl-ethanolamine, AEA) and glucocorticoids (e.g. cortisol and cortisone) in a myriad of physiological functions. However, depending on the extraction conditions, the spontaneous isomerization of 2-AG to 1-arachidonoylglycerol (1-AG) and the possible rearrangement of O-arachidonoyl ethanolamine (OAEA) to AEA in various sample matrices could be major obstacles encountered in the detection of both 2-AG and AEA. This study aimed to develop a novel method for simultaneous quantification of 2-AG, AEA, cortisol and cortisone in hair. Methanol was used as the incubation solution and an acidic mixture of deionized water and methanol were utilized as mobile phase in order to avert possible rearrangements of both OAEA and 2-AG. The analyses were performed on a high-performance liquid chromatography tandem mass spectrometer with atmosphere pressure chemical ionization in positive mode. The method showed good linearity in the range of 3.0-250pg/mg for AEA, 15.0-1250pg/mg for 2-AG and 1-250pg/mg for cortisol and cortisone. Limit of detection was 1.5pg/mg for AEA, 6.0pg/mg for 2-AG and 0.5pg/mg for cortisol and cortisone. For all four analytes, intra and inter-day coefficients of variation were less than 20% and recovery above 90%. Population analyses in 473 hair samples established that 2-AG was significantly correlated with AEA. 2-AG was significantly and positively correlated with cortisol and cortisone. There was a significant positive correlation of AEA with cortisol, but not with cortisone. Obese participants showed a significantly higher concentration of cortisone and 2-AG. Males showed significantly higher 2-AG and cortisone levels but significantly lower AEA levels than females.

CB1 receptor blockade counters age-induced insulin resistance and metabolic dysfunction

The endocannabinoid system can modulate energy homeostasis by regulating feeding behaviour as well as peripheral energy storage and utilization. Importantly, many of its metabolic actions are mediated through the cannabinoid type 1 receptor (CB1R), whose hyperactivation is associated with obesity and impaired metabolic function. Herein, we explored the effects of administering rimonabant, a selective CB1R inverse agonist, upon key metabolic parameters in young (4 month old) and aged (17 month old) adult male C57BL/6 mice. Daily treatment with rimonabant for 14 days transiently reduced food intake in young and aged mice; however, the anorectic response was more profound in aged animals, coinciding with a substantive loss in body fat mass. Notably, reduced insulin sensitivity in aged skeletal muscle and liver concurred with increased CB1R mRNA abundance. Strikingly, rimonabant was shown to improve glucose tolerance and enhance skeletal muscle and liver insulin sensitivity in aged, but not young, adult mice. Moreover, rimonabant‐mediated insulin sensitization in aged adipose tissue coincided with amelioration of low‐grade inflammation and repressed lipogenic gene expression. Collectively, our findings indicate a key role for CB1R in aging‐related insulin resistance and metabolic dysfunction and highlight CB1R blockade as a potential strategy for combating metabolic disorders associated with aging.