Endogenous cannabinoids in the brain and peripheral tissues: regulation of their levels and control of food intake

Cannabinoid type-1 receptor signaling in dopaminergic Engrailed-1 expressing neurons modulates motivation and depressive-like behavior

The endocannabinoid system comprises highly versatile signaling functions within the nervous system. It is reported to modulate the release of several neurotransmitters, consequently affecting the activity of neuronal circuits. Investigations have highlighted its roles in numerous processes, including appetite-stimulating characteristics, particularly for palatable food. Moreover, endocannabinoids are shown to fine-tune dopamine-signaled processes governing motivated behavior. Specifically, it has been demonstrated that excitatory and inhibitory inputs controlled by the cannabinoid type 1 receptor (CB1) regulate dopaminergic neurons in the mesocorticolimbic pathway. In the present study, we show that mesencephalic dopaminergic (mesDA) neurons in the ventral tegmental area (VTA) express CB1, and we investigated the consequences of specific deletion of CB1 in cells expressing the transcription factor Engrailed-1 (En1). To this end, we validated a new genetic mouse line EN1-CB1-KO, which displays a CB1 knockout in mesDA neurons beginning from their differentiation, as a tool to elucidate the functional contribution of CB1 in mesDA neurons. We revealed that EN1-CB1-KO mice display a significantly increased immobility time and shortened latency to the first immobility in the forced swim test of adult mice. Moreover, the maximal effort exerted to obtain access to chocolate-flavored pellets was significantly reduced under a progressive ratio schedule. In contrast, these mice do not differ in motor skills, anhedonia- or anxiety-like behavior compared to wild-type littermates. Taken together, these findings suggest a depressive-like or despair behavior in an inevitable situation and a lack of motivation to seek palatable food in EN1-CB1-KO mice, leading us to propose that CB1 plays an important role in the physiological functions of mesDA neurons. In particular, our data suggest that CB1 directly modifies the mesocorticolimbic pathway implicated in depressive-like/despair behavior and motivation. In contrast, the nigrostriatal pathway controlling voluntary movement seems to be unaffected.

Aerobic Exercise and Endocannabinoids: A Narrative Review of Stress Regulation and Brain Reward Systems

Aerobic exercise is a widely adopted practice, not solely for enhancing fitness and reducing the risk of various diseases but also for its ability to uplift mood and aid in addressing depression and anxiety disorders. Within the scope of this narrative review, we seek to consolidate current insights into the endocannabinoid-mediated regulation of stress and the brain's reward mechanism resulting from engaging in aerobic exercise. A comprehensive search was conducted across Medline, SPORTDiscus, Pubmed, and Scopus, encompassing data available until November 30, 2023. This review indicates that a bout of aerobic exercise, particularly of moderate intensity, markedly augments circulating levels of endocannabinoids - N-arachidonoyl-ethanolamine (AEA) and 2-acylglycerol (2-AG), that significantly contributes to mood elevation and reducing stress in healthy individuals.  The current understanding of how aerobic exercise impacts mental health and mood improvement is still unclear. Moderate and high-intensity aerobic exercise modulates stress through a negative feedback mechanism targeting both the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic nervous system, thereby facilitating stress regulation crucial role in endocannabinoid synthesis, ultimately culminating in the orchestration of negative feedback across multiple tiers of the HPA axis, coupled with its influence over cortical and subcortical brain structures. The endocannabinoid has been observed to govern the release of neurotransmitters from diverse neuronal populations, implying a universal mechanism that fine-tunes neuronal activity and consequently modulates both emotional and stress-related responses. Endocannabinoids further assume a pivotal function within brain reward mechanisms, primarily mediated by CB1 receptors distributed across diverse cerebral centers. Notably, these endocannabinoids partake in natural reward processes, as exemplified in aerobic exercise, by synergizing with the dopaminergic reward system. The genesis of this reward pathway can be traced to the ventral tegmental area, with dopamine neurons predominantly projecting to the nucleus accumbens, thereby inciting dopamine release in response to rewarding stimuli.

Weight Regain after Metabolic Surgery: Beyond the Surgical Failure

Patients undergoing metabolic surgery have factors ranging from anatomo-surgical, endocrine metabolic, eating patterns and physical activity, mental health and psychological factors. Some of the latter can explain the possible pathophysiological neuroendocrine, metabolic, and adaptive mechanisms that cause the high prevalence of weight regain in postbariatric patients. Even metabolic surgery has proven to be effective in reducing excess weight in patients with obesity; some of them regain weight after this intervention. In this vein, several studies have been conducted to search factors and mechanisms involved in weight regain, to stablish strategies to manage this complication by combining metabolic surgery with either lifestyle changes, behavioral therapies, pharmacotherapy, endoscopic interventions, or finally, surgical revision. The aim of this revision is to describe certain aspects and mechanisms behind weight regain after metabolic surgery, along with preventive and therapeutic strategies for this complication.

Cannabinoid Receptor mRNA Expression in Central and Peripheral Tissues in a Rodent Model of Peritonitis

Introduction: Our laboratory investigates changes in the respiratory pattern during systemic inflammation in various rodent models. The endogenous cannabinoid system (ECS) regulates cytokine production and mitigates inflammation. Inflammation not only affects cannabinoid (CB) 1 and CB2 receptor gene expression (Cnr1 and Cnr2), but also increases the predictability of the ventilatory pattern. Objectives: Our primary objective was to track ventilatory pattern variability and transcription of Cnr1 and Cnr2 mRNA, and of Il1b, Il6, and tumor necrosis factor-alpha (Tnfa) mRNAs at multiple time points in central and peripheral tissues during systemic inflammation induced by peritonitis. Methods: In male Sprague Dawley rats (n=24), we caused peritonitis by implanting a fibrin clot containing either 0 or 25×106 Escherichia coli intraperitoneally. We recorded breathing with whole-animal plethysmography at baseline and 1 h before euthanasia. We euthanized the rats at 3, 6, or 12 h after inoculation and harvested the pons, medulla, lung, and heart for gene expression analysis. Results: With peritonitis, Cnr1 mRNA more than Cnr2 mRNA was correlated to Il1b, Il6, and Tnfa mRNAs in medulla, pons, and lung and changed oppositely in the pons, medulla, and lung. These changes were associated with increased predictability of ventilatory pattern. Specifically, nonlinear complexity index correlated with increased Cnr1 mRNA in the pons and medulla, and coefficient of variation for cycle duration correlated with Cnr1 and Cnr2 mRNAs in the lung. Conclusion: The mRNAs for ECS receptors varied with time during the central and peripheral inflammatory response to peritonitis. These changes occurred in the brainstem, which contains the network that generates breathing pattern and thus, may participate in ventilatory pattern changes during systemic inflammation.

Defining the Molecular Mechanisms of the Relaxant Action of Adiponectin on Murine Gastric Fundus Smooth Muscle: Potential Translational Perspectives on Eating Disorder Management

Adiponectin (ADPN), a hormone produced by adipose tissue, facilitates gastric relaxation and can be a satiety signal in the network connecting peripheral organs and the central nervous system for feeding behavior control. Here, we performed preclinical research by morpho-functional analyses on murine gastric fundus smooth muscle to add insights into the molecular mechanisms underpinning ADPN action. Moreover, we conducted a clinical study to evaluate the potential use of ADPN as a biomarker for eating disorders (ED) based on the demonstrated gastric alterations and hormone level fluctuations that are often associated with ED. The clinical study recruited patients with ED and healthy controls who underwent blood draws for ADPN dosage and psychopathology evaluation tests. The findings of this basic research support the ADPN relaxant action, as indicated by the smooth muscle cell membrane pro-relaxant effects, with mild modifications of contractile apparatus and slight inhibitory effects on gap junctions. All of these actions engaged the ADPN/nitric oxide/guanylate cyclase pathway. The clinical data failed to unravel a correlation between ADPN levels and the considered ED, thus negating the potential use of ADPN as a valid biomarker for ED management for the moment. Nevertheless, this adipokine can modulate physiological eating behavior, and its effects deserve further investigation.

Therapeutic Effects of Medicinal Cannabinoids on the Gastrointestinal System in Pediatric Patients: A Systematic Review

Changes in cannabis legalization have generated interest in medicinal cannabinoids for therapeutic uses, including those that target the gastrointestinal (GI) tract. These effects are mediated through interactions with the endocannabinoid system. Given the increasing societal awareness of the therapeutic potential of cannabinoids, it is important to ensure pediatric representation in clinical studies investigating cannabinoid use. This systematic review aims to assess the efficacy of medicinal cannabinoids in treating GI symptoms in pediatric patients. A literature search of Medline, Embase, CINAHL, Web of Science, and the Cochrane Library was performed from inception until June 23, 2020. Study design, patient characteristics, type, dose and duration of medicinal cannabinoid therapy, and GI outcomes were extracted. From 7303 records identified, 5 studies met all inclusion criteria. Included studies focused on chemotherapy-induced nausea, inflammatory bowel disease, and GI symptoms associated with severe complex motor disorders. Results varied based on the symptom being treated, the type of cannabinoid, and the patient population. Medicinal cannabinoids may have a potential role in treating specific GI symptoms in specific patient populations. The limited number and heterogenicity of included studies highlight the demand for future research to distinguish effects among different cannabinoid types and patient populations and to examine drug interactions. As interest increases, higher quality studies are needed to understand the efficacy of cannabinoids as a pediatric GI treatment and whether these benefits outweigh the associated risks (Registration Number: PROSPERO CRD42020202486).

Cannabinoids in Late Life Parkinson's Disease and Dementia: Biological Pathways and Clinical Challenges

The use of cannabinoids as therapeutic drugs has increased among aging populations recently. Age-related changes in the endogenous cannabinoid system could influence the effects of therapies that target the cannabinoid system. At the preclinical level, cannabidiol (CBD) induces anti-amyloidogenic, antioxidative, anti-apoptotic, anti-inflammatory, and neuroprotective effects. These findings suggest a potential therapeutic role of cannabinoids to neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer. Emerging evidence suggests that CBD and tetrahydrocannabinol have neuroprotective therapeutic-like effects on dementias. In clinical practice, cannabinoids are being used off-label to relieve symptoms of PD and AD. In fact, patients are using cannabis compounds for the treatment of tremor, non-motor symptoms, anxiety, and sleep assistance in PD, and managing responsive behaviors of dementia such as agitation. However, strong evidence from clinical trials is scarce for most indications. Some clinicians consider cannabinoids an alternative for older adults bearing Parkinson's disease and Alzheimer's dementia with a poor response to first-line treatments. In our concept and experience, cannabinoids should never be considered a first-line treatment but could be regarded as an adjuvant therapy in specific situations commonly seen in clinical practice. To mitigate the risk of adverse events, the traditional dogma of geriatric medicine, starting with a low dose and proceeding with a slow titration regime, should also be employed with cannabinoids. In this review, we aimed to address preclinical evidence of cannabinoids in neurodegenerative disorders such as PD and AD and discuss potential off-label use of cannabinoids in clinical practice of these disorders.

Endocannabinoid receptors are involved in enhancing food intake in rainbow trout

The mechanisms involved in hedonic regulation of food intake, including endocannabinoid system (ECs) are scarcely known in fish. We recently demonstrate in rainbow trout the presence of a rewarding response mediated by ECs in hypothalamus and telencephalon when fish fed a lipid-enriched diet, and that central administration of main agonists of ECs namely AEA or 2-AG exert a bimodal effect on feed intake in fish with low doses inducing an increase that disappears with the high dose of both endocannabinoids (EC). To assess the precise involvement of the different receptors of the ECs (CNR1, TRPV1, and GPR55) in this response we injected intracerebroventricularly AEA or 2-AG in the absence/presence of specific receptor antagonists (AM251, capsazepine, and ML193; respectively). The presence of antagonists clearly counteracts the effect of EC supporting the specificity of EC action inducing changes not only in ECs but also in GABA and glutamate metabolism ultimately leading to the increase observed in food intake response.

An Alkaloid from a Highly Invasive Seaweed Increases the Voracity and Reproductive Output of a Model Fish Species

The invasive macroalga Caulerpa cylindracea has spread widely in the Mediterranean Sea, becoming a favorite food item for native fish for reasons yet unknown. By using a combination of behavioral, morphological, and molecular approaches, herein we provide evidence that the bisindole alkaloid caulerpin, a major secondary metabolite of C. cylindracea, significantly increases food intake in the model fish Danio rerio, influencing the regulation of genes involved in the orexigenic pathway. In addition, we found that the compound improves fish reproductive performance by affecting the hypothalamus-pituitary-gonadal axis. The obtained results pave the way for the possible valorization of C. cylindracea as a sustainable source of a functional feed additive of interest to face critical challenges both in aquaculture and in human nutrition.

Regulation of Voluntary Physical Activity Behavior: A Review of Evidence Involving Dopaminergic Pathways in the Brain

Physical activity leads to well-established health benefits. Current efforts to enhance physical activity have targeted mainly socioeconomic factors. However, despite these efforts, only a small number of adults engage in regular physical activity to the point of meeting current recommendations. Evidence collected in rodent models and humans establish a strong central nervous system component that regulates physical activity behavior. In particular, dopaminergic pathways in the central nervous system are among the best-characterized biological mechanisms to date with respect to regulating reward, motivation, and habit formation, which are critical for establishing regular physical activity. Herein, we discuss evidence for a role of brain dopamine in the regulation of voluntary physical activity behavior based on selective breeding and pharmacological studies in rodents, as well as genetic studies in both rodents and humans. While these studies establish a role of dopamine and associated mechanisms in the brain in the regulation of voluntary physical activity behavior, there is clearly need for more research on the underlying biology involved in motivation for physical activity and the formation of a physical activity habit. Such knowledge at the basic science level may ultimately be translated into better strategies to enhance physical activity levels within the society.

Assessment of the Effects of Dietary Vitamin D Levels on Olanzapine-Induced Metabolic Side Effects: Focus on the Endocannabinoidome-Gut Microbiome Axis

Vitamin D deficiency is associated with poor mental health and dysmetabolism. Several metabolic abnormalities are associated with psychotic diseases, which can be compounded by atypical antipsychotics that induce weight gain and insulin resistance. These side-effects may be affected by vitamin D levels. The gut microbiota and endocannabinoidome (eCBome) are significant regulators of both metabolism and mental health, but their role in the development of atypical antipsychotic drug metabolic side-effects and their interaction with vitamin D status is unknown. We studied the effects of different combinations of vitamin D levels and atypical antipsychotic drug (olanzapine) exposure on whole-body metabolism and the eCBome-gut microbiota axis in female C57BL/6J mice under a high fat/high sucrose (HFHS) diet in an attempt to identify a link between the latter and the different metabolic outputs induced by the treatments. Olanzapine exerted a protective effect against diet-induced obesity and insulin resistance, largely independent of dietary vitamin D status. These changes were concomitant with olanzapine-mediated decreases in Trpv1 expression and increases in the levels of its agonists, including various N-acylethanolamines and 2-monoacylglycerols, which are consistent with the observed improvement in adiposity and metabolic status. Furthermore, while global gut bacteria community architecture was not altered by olanzapine, we identified changes in the relative abundances of various commensal bacterial families. Taken together, changes of eCBome and gut microbiota families under our experimental conditions might contribute to olanzapine and vitamin D-mediated inhibition of weight gain in mice on a HFHS diet.

Plasmatic endocannabinoids are decreased in subjects with ultra-high risk of psychosis

The onset of frank psychosis is usually preceded by a prodromal phase characterized by attenuated psychotic symptoms. Currently, research on schizophrenia prodromal phase (ultra-high risk for psychosis [UHR]) has focused on the risk of developing psychosis, on the transition to full blown psychosis and on its prediction. Neurobiological differences between UHR individuals who fully recover (remitters) versus those who show persistent/progressive prodromal symptoms (nonremitters) have been little explored. The endocannabinoid system constitutes a neuromodulatory system that plays a major role in brain development, synaptic plasticity, emotional behaviours and cognition. It comprises two cannabinoid receptors (CB1/CB2), two endocannabinoid ligands, arachidonylethanolamide (AEA) and 2-arachidonoylglycerol (2AG) along with their inactivation enzymes. Despite much evidence that the endocannabinoid system is imbalanced during psychosis, very little is known about it in UHR. Therefore, we aimed to quantify the plasma endocannabinoid levels in UHR and healthy controls (HC) and verify if these metabolites could differentiate between remitters and nonremitters. Circulating concentrations of AEA (p = .003) and 2AG (p < .001) were lower in UHR when compared with HC, with no difference between remitters and nonremitters. Regarding clinical evolution, it was observed that out of 91 UHRs initially considered, 16 had psychiatric complaints (3 years of follow-up). Considering those subjects, there were weak correlations between clinical parameters and plasma concentrations of endocannabinoids. Our results suggest that the endocannabinoids are imbalanced before frank psychosis and that changes can be seen in plasma of UHR individuals. These molecules proved to be potential biomarkers to identify individuals in the prodromal phase of psychosis.

A Role for Peripheral Anandamide and 2-Arachidonoylglycerol in Short-Term Food Intake and Orexigenic Hypothalamic Responses in a Species with Continuous Nutrient Delivery

The endocannabinoid system (ECS) plays a pivotal role in the complex control and regulation of food intake. Pharmacological ECS activation could improve health in energy-deficient stages by increasing food intake, at least in intermittent feeders. However, knowledge of the mechanism regulating appetite in species with continued nutrient delivery is incomplete. The objectives of this pilot study were to investigate the effect of the intraperitoneal (i.p.) administration of the endocannabinoids (ECs) anandamide (AEA) and 2-arachidonoylglycerol (2-AG) on food intake, plasma EC concentrations and hypothalamic orexigenic signaling, and to study how the circulatory EC tone changes in response to short-term food deprivation in dairy cows, a species with continuous nutrient delivery. The administration of EC resulted in higher food intake during the first hour after treatment. Plasma AEA concentrations were significantly increased 2.5 h after AEA injection, whereas plasma 2-AG concentrations remained unchanged 2.5 h after 2-AG injection. The hypothalamic immunoreactivity of cannabinoid receptor 1, agouti-related protein, and orexin-A was not affected by either treatment; however, neuropeptide Y and agouti-related protein mRNA abundances were downregulated in the arcuate nucleus of AEA-treated animals. Short-term food deprivation increased plasma 2-AG, while plasma AEA remained unchanged. In conclusion, i.p.-administered 2-AG and AEA increase food intake in the short term, but only AEA accumulates in the circulation. However, plasma 2-AG concentrations are more responsive to food deprivation than AEA.

Maternal obesity reverses the resistance to LPS-induced adverse pregnancy outcome and increases female offspring metabolic alterations in cannabinoid receptor 1 knockout mice

Maternal overnutrition negatively impacts the offspring's health leading to an increased risk of developing chronic diseases or metabolic syndrome in adulthood. What we eat affects the endocannabinoid system (eCS) activity, which in turn modulates lipogenesis and fatty acids utilization in hepatic, muscle, and adipose tissues. This study aimed to evaluate the transgenerational effect of maternal obesity on cannabinoid receptor 1 knock-out (CB1 KO) animals in combination with a postnatal obesogenic diet on the development of metabolic disturbances on their offspring. CB1 KO mice were fed a control diet (CD) or a high-fat diet (HFD; 33% more energy from fat) for 3 months. Offspring born to control and obese mothers were also fed with CD or HFD. We observed that pups born to an HFD-fed mother presented higher postnatal weight, lower hepatic fatty acid amide hydrolase activity, and increased blood cholesterol levels when compared to the offspring born to CD-fed mothers. When female mice born to HFD-fed CB1 KO mothers were exposed to an HFD, they gained more weight, presented elevated blood cholesterol levels, and more abdominal adipose tissue accumulation than control-fed adult offspring. The eCS is involved in several reproductive physiological processes. Interestingly, we showed that CB1 KO mice in gestational day 15 presented resistance to LPS-induced deleterious effects on pregnancy outcome, which was overcome when these mice were obese. Our results suggest that an HFD in CB1 receptor-deficient mice contributes to a "nutritional programming" of the offspring resulting in increased susceptibility to metabolic challenges both perinatally and during adulthood.

Analgesic and Anticancer Activity of Benzoxazole Clubbed 2-Pyrrolidinones as Novel Inhibitors of Monoacylglycerol Lipase

Ten benzoxazole clubbed 2-pyrrolidinones (11–20) as human monoacylglycerol lipase inhibitors were designed on the criteria fulfilling the structural requirements and on the basis of previously reported inhibitors. The designed, synthesized, and characterized compounds (11–20) were screened against monoacylglycerol lipase (MAGL) in order to find potential inhibitors. Compounds 19 (4-NO₂ derivative) and 20 (4-SO₂NH₂ derivative), with an IC₅₀ value of 8.4 and 7.6 nM, were found most active, respectively. Both of them showed micromolar potency (IC₅₀ value above 50 µM) against a close analogue, fatty acid amide hydrolase (FAAH), therefore considered as selective inhibitors of MAGL. Molecular docking studies of compounds 19 and 20 revealed that carbonyl of 2-pyrrolidinone moiety sited at the oxyanion hole of catalytic site of the enzyme stabilized with three hydrogen bonds (~2 Å) with Ala51, Met123, and Ser122, the amino acid residues responsible for the catalytic function of the enzyme. Remarkably, the physiochemical and pharmacokinetic properties of compounds 19 and 20, computed by QikProp, were found to be in the qualifying range as per the proposed guideline for good orally bioactive CNS drugs. In formalin-induced nociception test, compound 20 reduced the pain response in acute and late stages in a dose-dependent manner. They significantly demonstrated the reduction in pain response, having better potency than the positive control gabapentin (GBP), at 30 mg/kg dose. Compounds 19 and 20 were submitted to NCI, USA, for anticancer activity screening. Compounds 19 (NSC: 778839) and 20 (NSC: 778842) were found to have good anticancer activity on SNB-75 cell line of CNS cancer, exhibiting 35.49 and 31.88% growth inhibition (% GI), respectively.

Functional Fine-Tuning of Metabolic Pathways by the Endocannabinoid System-Implications for Health and Disease

The endocannabinoid system (ECS) employs a huge network of molecules (receptors, ligands, and enzymatic machinery molecules) whose interactions with other cellular networks have still not been fully elucidated. Endogenous cannabinoids are molecules with the primary function of control of multiple metabolic pathways. Maintenance of tissue and cellular homeostasis by functional fine-tuning of essential metabolic pathways is one of the key characteristics of the ECS. It is implicated in a variety of physiological and pathological states and an attractive pharmacological target yet to reach its full potential. This review will focus on the involvement of ECS in glucose and lipid metabolism, food intake regulation, immune homeostasis, respiratory health, inflammation, cancer and other physiological and pathological states will be substantiated using freely available data from open-access databases, experimental data and literature review. Future directions should envision capturing its diversity and exploiting pharmacological options beyond the classical ECS suspects (exogenous cannabinoids and cannabinoid receptor monomers) as signaling through cannabinoid receptor heteromers offers new possibilities for different biochemical outcomes in the cell.

Insulin and endocannabinoids in the mesolimbic system

Easy access to palatable food and an abundance of food-related cues exacerbate non-homeostatic feeding. The metabolic and economical sequelae of non-homeostatic feeding outweigh those of homeostatic feeding and contribute significantly to the global obesity pandemic. The mesolimbic dopamine system is the primary central circuit that governs the motivation to consume food. Insulin and endocannabinoids (eCBs) are two major, presumably opposing, players in regulating homeostatic and non-homeostatic feeding centrally and peripherally. Insulin is generally regarded as a postprandial satiety signal, whereas eCBs mainly function as pre-prandial orexinergic signals. In this review, we discuss the effects of insulin and eCB-mediated actions within the mesolimbic pathways. We propose that insulin and eCBs have regional- and time course-dependent roles. We discuss their mechanisms of actions in the ventral tegmental area and nucleus accumbens, as well as how their mechanisms converge to finely tune dopaminergic activity and food intake.

A proposed modulatory role of the endocannabinoid system on adipose tissue metabolism and appetite in periparturient dairy cows

To sustain the nutrient demands of rapid fetal growth, parturition, and milk synthesis, periparturient dairy cows mobilize adipose tissue fatty acid stores through lipolysis. This process induces an inflammatory response within AT that is resolved as lactation progresses; however, excessive and protracted lipolysis compounds the risk for metabolic and inflammatory diseases. The suppression of lipolytic action and inflammation, along with amplification of adipogenesis and lipogenesis, serve as prospective therapeutic targets for improving the health of periparturient dairy cows. Generally, the activation of cannabinoid receptors by endocannabinoids enhances adipogenesis and lipogenesis, suppresses lipolysis, and increases appetite in mammals. These biological effects of activating the endocannabinoid system open the possibility of harnessing the endocannabinoid system through nutritional intervention in dairy herds as a potential tool to improve dairy cows' health, although much is still to be revealed in this context. This review summarizes the current knowledge surrounding the components of the endocannabinoid system, elaborates on the metabolic effects of its activation, and explores the potential to modulate its activity in periparturient dairy cows.

Integrating Endocannabinoid Signalling In Depression

Depression is a common mental disorder and is the leading cause of suicide globally. Because of the significant diversity in mental disorders, accurate diagnosis is difficult. Hence, the investigation of novel biomarkers is a key research perspective in psychotherapy to enable an individually tailored treatment approach. The prefrontal cortex (PFC) is a vital cortical region whose circuitry has been implicated in the development of depressive disorder. The endocannabinoid system (ECS) has garnered increasing attention because of its involvement in several diverse physiological brain processes including regulation of emotional, motivational and cognitive functions. The current review article explores the function of the key elements of the ECS as a biomarker in depressive disorder. The activity of endocannabinoids is thought to be moderated by the CB1 receptors in the central nervous system (CNS). Variations in the concentration of endocannabinoids and the binding affinity of CB1 receptors and their density have been identified in the PFC of persons with depression. Such discoveries support our theory that alteration in endocannabinoid function leads to the pathophysiological features of depressive disorders. Moreover, evidence from animal and human studies has revealed that dysfunction in endocannabinoid signalling can produce depression-like behaviours; therefore, improvement of endocannabinoid signalling may represent a new therapeutic approach for the management of depressive disorders.

Specific shifts in the endocannabinoid system in hibernating brown bears

In small hibernators, global downregulation of the endocannabinoid system (ECS), which is involved in modulating neuronal signaling, feeding behavior, energy metabolism, and circannual rhythms, has been reported to possibly drive physiological adaptation to the hibernating state. In hibernating brown bears (Ursus arctos), we hypothesized that beyond an overall suppression of the ECS, seasonal shift in endocannabinoids compounds could be linked to bear’s peculiar features that include hibernation without arousal episodes and capacity to react to external disturbance. We explored circulating lipids in serum and the ECS in plasma and metabolically active tissues in free-ranging subadult Scandinavian brown bears when both active and hibernating. In winter bear serum, in addition to a 2-fold increase in total fatty acid concentration, we found significant changes in relative proportions of circulating fatty acids, such as a 2-fold increase in docosahexaenoic acid C22:6 n-3 and a decrease in arachidonic acid C20:4 n-6. In adipose and muscle tissues of hibernating bears, we found significant lower concentrations of 2-arachidonoylglycerol (2-AG), a major ligand of cannabinoid receptors 1 (CB1) and 2 (CB2). Lower mRNA level for genes encoding CB1 and CB2 were also found in winter muscle and adipose tissue, respectively. The observed reduction in ECS tone may promote fatty acid mobilization from body fat stores, and favor carbohydrate metabolism in skeletal muscle of hibernating bears. Additionally, high circulating level of the endocannabinoid-like compound N-oleoylethanolamide (OEA) in winter could favor lipolysis and fatty acid oxidation in peripheral tissues. We also speculated on a role of OEA in the conservation of an anorexigenic signal and in the maintenance of torpor during hibernation, while sustaining the capacity of bears to sense stimuli from the environment.

Endocannabinoids, endocannabinoid-like molecules and their precursors in human small intestinal lumen and plasma: does diet affect them?

PURPOSE

To determine the small intestinal concentration of endocannabinoids (ECs), N-acylethanolamines (NAEs) and their precursors N-acylphosphatidylethanolamines (NAPEs) in humans. To identify relationships between those concentrations and habitual diet composition as well as individual inflammatory status.

METHODS

An observational study was performed involving 35 participants with an ileostomy (18W/17M, aged 18-70 years, BMI 17-40 kg/m²). Overnight fasting samples of ileal fluid and plasma were collected and ECs, NAEs and NAPEs concentrations were determined by LC-HRMS. Dietary data were estimated from self-reported 4-day food diaries.

RESULTS

Regarding ECs, N-arachidonoylethanolamide (AEA) was not detected in ileal fluids while 2-arachidonoylglycerol (2-AG) was identified in samples from two participants with a maximum concentration of 129.3 µg/mL. In contrast, mean plasma concentration of AEA was 2.1 ± 0.06 ng/mL and 2-AG was 4.9 ± 1.05 ng/mL. NAEs concentrations were in the range 0.72-17.6 µg/mL in ileal fluids and 0.014-0.039 µg/mL in plasma. NAPEs concentrations were in the range 0.3-71.5 µg/mL in ileal fluids and 0.19-1.24 µg/mL in plasma being more abundant in participants with obesity than normal weight and overweight. Significant correlations between the concentrations of AEA, OEA and LEA in biological fluids with habitual energy or fat intakes were identified. Plasma PEA positively correlated with serum C-reactive protein.

CONCLUSION

We quantified ECs, NAEs and NAPEs in the intestinal lumen. Fat and energy intake may influence plasma and intestinal concentrations of these compounds. The luminal concentrations reported would allow modulation of the homeostatic control of food intake via activation of GPR119 receptors located on the gastro-intestinal mucosa.

CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE

NCT04143139; www.clinicaltrials.gov .

Cannabinoidomics - An analytical approach to understand the effect of medical Cannabis treatment on the endocannabinoid metabolome

Increasing evidence for the therapeutic potential of Cannabis in numerous pathological and physiological conditions has led to a surge of studies investigating the active compounds in different chemovars and their mechanisms of action, as well as their efficacy and safety. The biological effects of Cannabis have been attributed to phytocannabinoid modulation of the endocannabinoid system. In-vitro and in-vivo studies have shown that pure phytocannabinoids can alter the levels of endocannabinoids and other cannabimimetic lipids. However, it is not yet understood whether whole Cannabis extracts exert variable effects on the endocannabinoid metabolome, and whether these effects vary between tissues. To address these challenges, we have developed and validated a novel analytical approach, termed "cannabinoidomics," for the simultaneous extraction and analysis of both endogenous and plant cannabinoids from different biological matrices. In the methodological development liquid chromatography high resolution tandem mass spectrometry (LC/HRMS/MS) was used to identify 57 phytocannabinoids, 15 major phytocannabinoid metabolites, and 78 endocannabinoids and cannabimimetic lipids in different biological matrices, most of which have no analytical standards. In the validation process, spiked cannabinoids were quantified with acceptable selectivity, repeatability, reproducibility, sensitivity, and accuracy. The power of this analytical method is demonstrated by analysis of serum and four different sections of mouse brains challenged with three different cannabidiol (CBD)-rich extracts. The results demonstrate that variations in the minor phytocannabinoid contents of the different extracts may lead to varied effects on endocannabinoid concentrations, and on the CBD metabolite profile in the peripheral and central systems. We also show that the Cannabis challenge significantly decreases the levels of several endocannabinoids in specific brain sections compared to the control group. This effect is extract-specific and suggests the importance of minor, other-than CBD, phytocannabinoid or non-phytocannabinoid compounds.

Peptides from Natural or Rationally Designed Sources Can Be Used in Overweight, Obesity, and Type 2 Diabetes Therapies

Overweight and obesity are among the most prominent health problems in the modern world, mostly because they are either associated with or increase the risk of other diseases such as type 2 diabetes, hypertension, and/or cancer. Most professional organizations define overweight and obesity according to individual body-mass index (BMI, weight in kilograms divided by height squared in meters). Overweight is defined as individuals with BMI from 25 to 29, and obesity as individuals with BMI ≥30. Obesity is the result of genetic, behavioral, environmental, physiological, social, and cultural factors that result in energy imbalance and promote excessive fat deposition. Despite all the knowledge concerning the pathophysiology of obesity, which is considered a disease, none of the existing treatments alone or in combination can normalize blood glucose concentration and prevent debilitating complications from obesity. This review discusses some new perspectives for overweight and obesity treatments, including the use of the new orally active cannabinoid peptide Pep19, the advantage of which is the absence of undesired central nervous system effects usually experienced with other cannabinoids.

Metabolite profile comparisons between ascending and descending colon tissue in healthy adults

BACKGROUND

Obesity is a risk factor for colorectal cancer, yet metabolic distinctions between healthy right and left colon tissue, before cancer is diagnosed, remains largely unknown. This study compared right-ascending and left-descending colon tissue metabolomes to identify differences from the stool metabolome in normal weight, overweight, and obese adults.

AIM

To examine right and left colon tissue metabolites according to body mass index that may serve as mechanistic targets for interventions and biomarkers for colon cancer risk.

METHODS

Global, non-targeted metabolomics was applied to assess right-ascending and left-descending colon tissue collected from healthy adults undergoing screening colonoscopies to test the hypothesis that BMI differentially impacts colon tissue metabolite profiles. The colon tissue and stool metabolome of healthy adults (n = 24) was analyzed for metabolite signatures and metabolic pathway networks implicated in progression of colorectal cancer.

RESULTS

Ascending and descending colon contained 504 host, food, and microbiota-derived metabolites from normal weight, overweight and obese adults grouped according to body mass index. Amino acids, lipids, and nucleotides were among the chemical types that further differentiated from the stool metabolite profiles. Normal weight adults had 46 significantly different metabolites between ascending and descending colon tissue locations, whereas there were 37 metabolite differences in overweight and 28 metabolite differences for obese adults (P < 0.05). Obese adults had trimethylamine N-oxide, endocannabinoids and monoacylglycerols with different relative abundances identified between ascending and descending colon. Primary and secondary bile acids, vitamins, and fatty acids also showed marked relative abundance differences in colon tissue from overweight/obese adults.

CONCLUSION

There were metabolite profile differences between right-ascending and left-descending colon tissue in healthy adults. Colon lipids and other metabolites in obese and overweight adults were distinguished from normal weight participants and associated with gut inflammation, nutrient absorption, and products of microbiota metabolism.

The Effects of Graded Levels of Calorie Restriction: XIII. Global Metabolomics Screen Reveals Graded Changes in Circulating Amino Acids, Vitamins, and Bile Acids in the Plasma of C57BL/6 Mice

Calorie restriction (CR) remains the most robust intervention to extend life span and improve health span. Using a global mass spectrometry–based metabolomics approach, we identified metabolites that were significantly differentially expressed in the plasma of C57BL/6 mice, fed graded levels of calorie restriction (10% CR, 20% CR, 30% CR, and 40% CR) compared with mice fed ad libitum for 12 hours a day. The differential expression of metabolites increased with the severity of CR. Pathway analysis revealed that graded CR had an impact on vitamin E and vitamin B levels, branched chain amino acids, aromatic amino acids, and fatty acid pathways. The majority of amino acids correlated positively with fat-free mass and visceral fat mass, indicating a strong relationship with body composition and vitamin E metabolites correlated with stomach and colon size, which may allude to the beneficial effects of investing in gastrointestinal organs with CR. In addition, metabolites that showed a graded effect, such as the sphinganines, carnitines, and bile acids, match our previous study on liver, which suggests not only that CR remodels the metabolome in a way that promotes energy efficiency, but also that some changes are conserved across tissues.

Prediction and Experimental Confirmation of Novel Peripheral Cannabinoid-1 Receptor Antagonists

Small molecules targeting peripheral CB1 receptors have therapeutic potential in a variety of disorders including obesity-related, hormonal, and metabolic abnormalities, while avoiding the psychoactive effects in the central nervous system. We applied our in-house algorithm, iterative stochastic elimination, to produce a ligand-based model that distinguishes between CB1R antagonists and random molecules by physicochemical properties only. We screened ∼2 million commercially available molecules and found that about 500 of them are potential candidates to antagonize the CB1R. We applied a few criteria for peripheral activity and narrowed that set down to 30 molecules, out of which 15 could be purchased. Ten out of those 15 showed good affinity to the CB1R and two of them with nanomolar affinities (K_i of ∼400 nM). The eight molecules with top affinities were tested for activity: two compounds were pure antagonists, and five others were inverse agonists. These molecules are now being examined in vivo for their peripheral versus central distribution and subsequently will be tested for their effects on obesity in small animals.

Role of Cannabinoid Receptor Type 1 in Insulin Resistance and Its Biological Implications

Endogenous cannabinoids (ECs) are lipid-signaling molecules that specifically bind to cannabinoid receptor types 1 and 2 (CB1R and CB2R) and are highly expressed in central and many peripheral tissues under pathological conditions. Activation of hepatic CB1R is associated with obesity, insulin resistance, and impaired metabolic function, owing to increased energy intake and storage, impaired glucose and lipid metabolism, and enhanced oxidative stress and inflammatory responses. Additionally, blocking peripheral CB1R improves insulin sensitivity and glucose metabolism and also reduces hepatic steatosis and body weight in obese mice. Thus, targeting EC receptors, especially CB1R, may provide a potential therapeutic strategy against obesity and insulin resistance. There are many CB1R antagonists, including inverse agonists and natural compounds that target CB1R and can reduce body weight, adiposity, and hepatic steatosis, and those that improve insulin sensitivity and reverse leptin resistance. Recently, the use of CB1R antagonists was suspended due to adverse central effects, and this caused a major setback in the development of CB1R antagonists. Recent studies, however, have focused on development of antagonists lacking adverse effects. In this review, we detail the important role of CB1R in hepatic insulin resistance and the possible underlying mechanisms, and the therapeutic potential of CB1R targeting is also discussed.

A systematic review of phytocannabinoid exposure on the endocannabinoid system: Implications for psychosis

Cannabis, the most widely used illicit drug worldwide, produces psychoactive effects through its component cannabinoids, which act on the endocannabinoid system. Research on how cannabinoid exposure affects the endocannabinoid system is limited. Substantial evidence indicates cannabis use as a risk factor for psychosis, and the mechanism(s) by which this is occurring is/are currently unknown. Here, we conduct the first review of the effects of exogenous cannabinoids on the endocannabinoid system in humans with and without psychotic disorders. The most well established finding is the down-regulation of cannabinoid CB1 receptors (CB1R) after chronic and recent cannabis exposure, but it remains uncertain whether this effect is present in cannabis users with schizophrenia. We highlight where cannabis exposure affects the endocannabinoid system in a pattern that may mirror what is seen in psychosis, and how further research can push this field forward. In these times of changing cannabis legislation, research highlighting the biological effects of cannabinoids is greatly needed.

n-3 polyunsaturated N-acylethanolamines are CB2 cannabinoid receptor-preferring endocannabinoids

Anandamide, the first identified endogenous cannabinoid and TRPV1 agonist, is one of a series of endogenous N-acylethanolamines, NAEs. We have generated novel assays to quantify the levels of multiple NAEs in biological tissues and their rates of hydrolysis through fatty acid amide hydrolase. This range of NAEs was also tested in rapid response assays of CB₁, CB₂ cannabinoid and TRPV1 receptors. The data indicate that PEA, SEA and OEA are not endocannabinoids or endovanilloids, and that the higher endogenous levels of these metabolites compared to polyunsaturated analogues are a correlate of their slow rates of hydrolysis. The n-6 NAEs (AEA, docosatetraenoyl and docosapentaenoyl derivatives) activated both CB₁ and CB₂ receptors, as well as TRPV1 channels, suggesting them to be 'genuine' endocannabinoids and 'endovanilloids'. The n-3 NAEs (eicosapentaenoyl, docosapentaenoyl and docosahexaenoyl derivatives) activated CB₂ receptors and some n-3 NAEs (docosapentaenoyl and docosahexaenoyl derivatives) also activated TRPV1 channels, but failed to activate the CB₁ receptor. We hypothesise that the preferential activation of CB₂ receptors by n-3 PUFA NAEs contributes, at least in some part, to their broad anti-inflammatory profile.

LH-21 and abnormal cannabidiol improve β-cell function in isolated human and mouse islets through GPR55-dependent and -independent signalling

AIMS

To examine the effects of Abn-CBD (GPR55 agonist) and LH-21 (CB1 antagonist) on human and mouse islet function, and to determine signalling via GPR55 using islets from GPR55^-/- mice.

MATERIALS AND METHODS

Islets isolated from human organ donors and mice were incubated in the absence or presence of Abn-CBD or LH-21, and insulin secretion, [Ca²⁺ ]_i, cAMP_, apoptosis, β-cell proliferation and CREB and AKT phosphorylation were examined using standard techniques.

RESULTS

Abn-CBD potentiated glucose-stimulated insulin secretion and elevated [Ca²⁺ ]_i in human islets and islets from both GPR55^+/+ and GPR55^-/- mice. LH-21 also increased insulin secretion and [Ca²⁺ ]_i in human islets and GPR55^+/+ mouse islets, but concentrations of LH-21 up to 0.1 μM were ineffective in islets from GPR55^-/- mice. Neither ligand affected basal insulin secretion or islet cAMP levels. Abn-CBD and LH-21 reduced cytokine-induced apoptosis in human islets and GPR55^+/+ mouse islets, and these effects were suppressed after GPR55 deletion. They also increased β-cell proliferation: the effects of Abn-CBD were preserved in islets from GPR55^-/- mice, while those of LH-21 were abolished. Abn-CBD and LH-21 increased AKT phosphorylation in mouse and human islets.

CONCLUSIONS

This study showed that Abn-CBD and LH-21 improve human and mouse islet β-cell function and viability. Use of islets from GPR55^-/- mice suggests that designation of Abn-CBD and LH-21 as a GPR55 agonist and a CB1 antagonist, should be revised.

Cannabinoid Receptors, Mental Pain and Suicidal Behavior: a Systematic Review

PURPOSE OF REVIEW

The current serotonin-based biological model of suicidal behavior (SB) may be too simplistic. There is emerging evidence that other biomarkers and biological systems may be involved in SB pathophysiology. The literature on the endocannabinoid (EC) systems and SB is limited. The objective of the present article is to review all available information on the relationship between cannabinoid receptors (CB₁ and CB₂ receptors), and SB and/or psychological pain.

RECENT FINDINGS

Our review is limited by the small number and heterogeneity of studies identified: (1) an autopsy study describing elevated levels of CB₁ receptor activity in the prefrontal cortex and suicide in both depression and alcoholism and (2) studies supporting the involvement of both CB₁ and CB₂ receptors in the regulation of neuropathic pain and stress-induced analgesia. We conclude that cannabinoid receptors, particularly CB₁ receptors, may become promising targets for the development of novel therapeutic tools for the treatment of SB.

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.

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.

Central and peripheral control of food intake

The maintenance of the body weight at a stable level is a major determinant in keeping the higher animals and mammals survive. Th e body weight depends on the balance between the energy intake and energy expenditure. Increased food intake over the energy expenditure of prolonged time period results in an obesity. Th e obesity has become an important worldwide health problem, even at low levels. The obesity has an evil effect on the health and is associated with a shorter life expectancy. A complex of central and peripheral physiological signals is involved in the control of the food intake. Centrally, the food intake is controlled by the hypothalamus, the brainstem, and endocannabinoids and peripherally by the satiety and adiposity signals. Comprehension of the signals that control food intake and energy balance may open a new therapeutic approaches directed against the obesity and its associated complications, as is the insulin resistance and others. In conclusion, the present review summarizes the current knowledge about the complex system of the peripheral and central regulatory mechanisms of food intake and their potential therapeutic implications in the treatment of obesity.

Cannabinoid Receptor 1 Gene by Cannabis Use Interaction on CB1 Receptor Density

Background: Because delta-9-tetrahydrocannabinol (THC), the primary psychoactive ingredient in cannabis, binds to cannabinoid 1 (CB1) receptors, levels of CB1 protein could serve as a potential biomarker for response to THC. To date, available techniques to characterize CB1 expression and function in vivo are limited. In this study, we developed an assay to quantify CB1 in lymphocytes to determine how it relates to cannabis use in 58 daily cannabis users compared with 47 nonusers. Furthermore, we tested whether CB1 levels are associated with mutations in a single nucleotide polymorphism known to regulate CB1 functioning (i.e., rs2023239).

Methods: Total protein concentration was analyzed through the Pierce BCA Protein assay kit. CB1 protein was quantified through CNR1 enzyme-linked immunosorbent assay (ELISA) kit from MyBioSource. CB1 concentration and total protein concentration were quantified and used to calculate a ratio of CB1 to total protein.

Results: Inherent levels of peripheral lymphocyte CB1 were sufficient for quantification through ELISA without protein amplification. We found a group×genotype interaction such that users with the G allele had greater CB1 concentration than users with the A/A genotype, and a trend-level difference between genotypes in nonusers.

Conclusions: This study demonstrates a minimally invasive technique of CB1 quantification that holds promise for the use of CB1 protein concentration, along with rs2023239 genotype, as a potential biomarker for susceptibility to cannabis use. These results suggest a gene (rs2023239 G)×environment (cannabis use) effect on CB1 density.

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.

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.

Endocannabinoid modulation of homeostatic and non-homeostatic feeding circuits

The endocannabinoid system has emerged as a key player in the control of eating. Endocannabinoids, including 2-arachidonoylglycerol (2-AG) and anandamide (AEA), modulate neuronal activity via cannabinoid 1 receptors (CB1Rs) in multiple nuclei of the hypothalamus to induce or inhibit food intake depending on nutritional and hormonal status, suggesting that endocannabinoids may act in the hypothalamus to integrate different types of signals informing about the animal's energy needs. In the mesocorticolimbic system, (endo)cannabinoids modulate synaptic transmission to promote dopamine release in response to palatable food. In addition, (endo)cannabinoids act within the nucleus accumbens to increase food's hedonic impact; although this effect depends on activation of CB1Rs at excitatory, but not inhibitory inputs in the nucleus accumbens. While hyperactivation of the endocannabinoid system is typically associated with overeating and obesity, much evidence has emerged in recent years suggesting a more complicated system than first thought - endocannabinoids promote or suppress feeding depending on cell and input type, or modulation by various neuronal or hormonal signals. This review presents our latest knowledge of the endocannabinoid system in non-homeostatic and homeostatic feeding circuits. In particular, we discuss the functional role and cellular mechanism of action by endocannabinoids within the hypothalamus and mesocorticolimbic system, and how these are modulated by neuropeptide signals related to feeding. In light of recent advances and complexity in the field, we review cannabinoid-based therapeutic strategies for the treatment of obesity and how peripheral restriction of CB1R antagonists may provide a different mechanism of weight loss without the central adverse effects. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Emerging therapeutic targets in cancer induced bone disease: A focus on the peripheral type 2 cannabinoid receptor

Skeletal complications are a common cause of morbidity in patients with primary bone cancer and bone metastases. The type 2 cannabinoid (Cnr2) receptor is implicated in cancer, bone metabolism and pain perception. Emerging data have uncovered the role of Cnr2 in the regulation of tumour-bone cell interactions and suggest that agents that target Cnr2 in the skeleton have potential efficacy in the reduction of skeletal complications associated with cancer. This review aims to provide an overview of findings relating to the role of Cnr2 receptor in the regulation of skeletal tumour growth, osteolysis and bone pain, and highlights the many unanswered questions and unmet needs. This review argues that development and testing of peripherally-acting, tumour-, Cnr2-selective ligands in preclinical models of metastatic cancer will pave the way for future research that will advance our knowledge about the basic mechanism(s) by which the endocannabinoid system regulate cancer metastasis, stimulate the development of a safer cannabis-based therapy for the treatment of cancer and provide policy makers with powerful tools to assess the science and therapeutic potential of cannabinoid-based therapy. Thus, offering the prospect of identifying selective Cnr2 ligands, as novel, alternative to cannabis herbal extracts for the treatment of advanced cancer patients.

Cannabimimetic phytochemicals in the diet - an evolutionary link to food selection and metabolic stress adaptation?

The endocannabinoid system (ECS) is a major lipid signalling network that plays important pro-homeostatic (allostatic) roles not only in the nervous system but also in peripheral organs. There is increasing evidence that there is a dietary component in the modulation of the ECS. Cannabinoid receptors in hominids co-evolved with diet, and the ECS constitutes a feedback loop for food selection and energy metabolism. Here, it is postulated that the mismatch of ancient lipid genes of hunter-gatherers and pastoralists with the high-carbohydrate diet introduced by agriculture could be compensated for via dietary modulation of the ECS. In addition to the fatty acid precursors of endocannabinoids, the potential role of dietary cannabimimetic phytochemicals in agriculturist nutrition is discussed. Dietary secondary metabolites from vegetables and spices able to enhance the activity of cannabinoid-type 2 (CB₂ ) receptors may provide adaptive metabolic advantages and counteract inflammation. In contrast, chronic CB₁ receptor activation in hedonic obese individuals may enhance pathophysiological processes related to hyperlipidaemia, diabetes, hepatorenal inflammation and cardiometabolic risk. Food able to modulate the CB₁ /CB₂ receptor activation ratio may thus play a role in the nutrition transition of Western high-calorie diets. In this review, the interplay between diet and the ECS is highlighted from an evolutionary perspective. The emerging potential of cannabimimetic food as a nutraceutical strategy is critically discussed.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Evolution of the diacylglycerol lipases

Diacylglycerol lipases (DGLs) mainly catalyze "on-demand" biosynthesis of bioactive monoacylglycerols (MAGs) with different long fatty acyl chains, including 2-arachidonoylglycerol (2-AG), 2-linoleoylglycerol (2-LG), 2-oleoylglycerol (2-OG) and 2-palmitoylglycerol (2-PG). Enzymatic characterization of DGLs, their expression and distribution, and functional features has been elucidated from microorganisms to mammals in some extent. In mammals, biosynthesis, degradation and metabolism of these bioactive lipids intertwine and form a complicated biochemical pathway to affect the mammal neuromodulation of central nervous system and also other physiological processes in most peripheral organs and non-nervous tissue cells, and yet we still do not know if the neuromodulatory role of mammal DGL and MAGs is similar to invertebrates. Tracing the evolutionary history of DGLs from microorganisms to vertebrates will be an essential method to infer DGL and MAG research in organisms. In this review, we give an exhaustive explanation of the ancestral origin, divergence and evolutionary pattern through systemic searching of DGL orthologs in different species. Finally, we also summarize our recent work on the structural and functional studies of DGL in order to explore usage of DGLs in industry and the development of inhibitors for clinical intervention.

Expression of the endocannabinoid receptors in human fascial tissue

Cannabinoid receptors have been localized in the central and peripheral nervous system as well as on cells of the immune system, but recent studies on animal tissue gave evidence for the presence of cannabinoid receptors in different types of tissues. Their presence was supposed also in myofascial tissue, suggesting that the endocannabinoid system may help resolve myofascial trigger points and relieve symptoms of fibromyalgia. However, until now the expression of CB1 (cannabinoid receptor 1) and CB2 (cannabinoid receptor 2) in fasciae has not yet been established. Small samples of fascia were collected from volunteers patients during orthopedic surgery. For each sample were done a cell isolation, immunohistochemical investigation (CB1 and CB2 antibodies) and real time RT-PCR to detect the expression of CB1 and CB2. Both cannabinoid receptors are expressed in human fascia and in human fascial fibroblasts culture cells, although to a lesser extent than the control gene. We can assume that the expression of mRNA and protein of CB1 and CB2 receptors in fascial tissue are concentrated into the fibroblasts. This is the first demonstration that the fibroblasts of the muscular fasciae express CB1 and CB2. The presence of these receptors could help to provide a description of cannabinoid receptors distribution and to better explain the role of fasciae as pain generator and the efficacy of some fascial treatments. Indeed the endocannabinoid receptors of fascial fibroblasts can contribute to modulate the fascial fibrosis and inflammation.

Association between plasma endocannabinoids and appetite in hemodialysis patients: A pilot study

Uremia-associated anorexia may be related to altered levels of long chain n-6 and n-3 polyunsaturated fatty acid (PUFA) derived circulating endocannabinoids (EC) and EC-like compounds that are known to mediate appetite. Our study's hypothesis was that such molecules are associated with appetite in patients with end-stage renal disease. A cross-sectional observational study was performed in 20 chronic hemodialysis patients (9 females, 11 males) and 10 healthy female controls in whom appetite was assessed using the Simplified Nutritional Appetite Questionnaire (SNAQ) and blood drawn in the fasting (and when applicable) pre-dialysis state. Blood levels of PUFA and EC were also measured. Higher blood levels of the long chain n-6 fatty acid 20:4n6 (arachidonic acid) and lower levels of the long chain n-3 fatty acid 20:5n3 (eicosapentaenoic acid) were observed in female hemodialysis patients compared to controls. No differences were observed between male and female patients. In female study participants strong correlations between specific EC-like compounds and total SNAQ scores were noted, including with the n-6 PUFA derived linoleoyl ethanolamide (L-EA; ρ=-0.60, P<.01) and the n-3 PUFA derived docosahexaenoyl ethanolamide (DH-EA; ρ=0.63, P<.01). The L-EA:DH-EA ratio was most strongly associated with the SNAQ score (ρ=-0.74, P≤.001), and its questions associated with appetite (ρ=-0.69, P≤.01) and satiety (ρ=-0.81, P≤.001). These findings support a link between circulating EC and appetite in hemodialysis patients.

The Endocannabinoid System: Pivotal Orchestrator of Obesity and Metabolic Disease

The endocannabinoid system (ECS) functions to adjust behavior and metabolism according to environmental changes in food availability. Its actions range from the regulation of sensory responses to the development of preference for the consumption of calorically-rich food and control of its metabolic handling. ECS activity is beneficial when access to food is scarce or unpredictable. However, when food is plentiful, the ECS favors obesity and metabolic disease. We review recent advances in understanding the roles of the ECS in energy balance, and discuss newly identified mechanisms of action that, after the withdrawal of first generation cannabinoid type 1 (CB1) receptor antagonists for the treatment of obesity, have made the ECS once again an attractive target for therapy.