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

Metabolic syndrome and osteoarthritis pain: common molecular mechanisms and potential therapeutic implications

There is no clear evidence from epidemiological and animal studies of a direct link between metabolic syndrome (MetS) and cartilage degeneration in osteoarthritis (OA) once body mass index (BMI) has been considered. However, recent epidemiological studies indicate a significant role for MetS in predicting increased knee pain after adjustment for BMI. This implies there are mechanisms that underlie both MetS and OA pain. In addition to the common systemic inflammatory and pro-inflammatory components of the two disorders, there are other molecular mechanisms that may link MetS and OA pain. These include regulation of the endocannabinoid system, activation of the transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1) channel and gut dysbiosis. These three mechanisms are interlinked and are the target of therapeutic dietary or pharmacological interventions. Exploring and understanding these mechanisms may help improve outcomes for both pain and metabolic comorbidities affecting individuals with OA.

Analysis of Direct Effects of the CB1 Receptor Antagonist Rimonabant on Fatty Acid Oxidation and Glycogenolysis in Liver and Muscle Cells in vitro

Recent pharmacological findings regarding rimonabant, an anorectic and cannabinoid type 1 receptor (CB1R) antagonist, strongly suggest that some of its effects on the metabolic parameters and energy balance in rats are not related to the centrally mediated reduction in caloric intake. Instead, they may be associated with acute induction of glycogenolysis in the liver, in combination with transient increase in glucose oxidation and persistent increase in fat oxidation. It is possible that rimonabant produced direct short- or long-term stimulatory effect on these processes in primary and cultured rat cells. Rimonabant slightly stimulated β-oxidation of long-chain fatty acids in cultured rat myocytes overexpressing glucose transporter isoform 4, as well as activated phosphorylation of adenosine monophosphate-dependent protein kinase (AMPK) in primary rat hepatocytes upon long-term incubation. However, short-term action of rimonabant failed to stimulate β-oxidation in myocytes, myotubes, and hepatocytes, as well as to upregulate AMPK phosphorylation, glycogenolysis, and cAMP levels in hepatocytes. As a consequence, the acute effects of rimonabant on hepatic glycogen content (reduction) and total energy expenditure (increase) in rats fed with a standard diet cannot be explained by direct stimulation of glycogenolysis and fatty acid oxidation in muscles and liver. Rather, these effects seem to be centrally mediated.

Cannabinoids and inflammation: implications for people living with HIV

: Thanks to the success of modern antiretroviral therapy (ART), people living with HIV (PLWH) have life expectancies which approach that of persons in the general population. However, despite the ability of ART to suppress viral replication, PLWH have high levels of chronic systemic inflammation which drives the development of comorbidities such as cardiovascular disease, diabetes and non-AIDS associated malignancies. Historically, cannabis has played an important role in alleviating many symptoms experienced by persons with advanced HIV infection in the pre-ART era and continues to be used by many PLWH in the ART era, though for different reasons. Δ-Tetrahydrocannabinol (Δ-THC) and cannabidiol (CBD) are the phytocannabinoids, which have received most attention for their medicinal properties. Due to their ability to suppress lymphocyte proliferation and inflammatory cytokine production, there is interest in examining their therapeutic potential as immunomodulators. CB2 receptor activation has been shown in vitro to reduce CD4 T-cell infection by CXCR4-tropic HIV and to reduce HIV replication. Studies involving SIV-infected macaques have shown that Δ-THC can reduce morbidity and mortality and has favourable effects on gut mucosal immunity. Furthermore, ΔTHC administration was associated with reduced lymph node fibrosis and diminished levels of SIV proviral DNA in spleens of rhesus macaques compared with placebo-treated macaques. In humans, cannabis use does not induce a reduction in peripheral CD4 T-cell count or loss of HIV virological control in cross-sectional studies. Rather, cannabis use in ART-treated PLWH was associated with decreased levels of T-cell activation, inflammatory monocytes and pro-inflammatory cytokine secretion, all of which are related to HIV disease progression and comorbidities. Randomized clinical trials should provide further insights into the ability of cannabis and cannabinoid-based medicines to attenuate HIV-associated inflammation. In turn, these findings may provide a novel means to reduce morbidity and mortality in PLWH as adjunctive agents to ART.

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.

Effects of a High-Protein/Moderate-Carbohydrate Diet on Appetite, Gut Peptides, and Endocannabinoids-A Preview Study

Favorable effects of a high-protein/moderate-carbohydrate (HP/MCHO) diet after weight loss on body weight management have been shown. To extend these findings, associations between perception of hunger and satiety with endocannabinoids, and with glucagon-like peptide-1 (GLP-1) and polypeptide YY (PYY) were assessed. At approximately 34 months after weight loss, 22 female and 16 male participants (mean age 64.5 ± 5.9 years; body mass index (BMI) 28.9 ± 3.9 kg/m2) completed a 48 h respiration chamber study. Participants were fed in energy balance with a HP/MCHO diet with 25%:45%:30% or a moderate-protein/high-carbohydrate (MP/HCHO) diet with 15%:55%:30% of energy from protein:carbohydrate:fat. Endocannabinoids and related compounds, relevant postprandial hormones (GLP-1, PYY), hunger, satiety, and ad libitum food intake were assessed. HP/MCHO versus MP/HCHO reduced hunger perception. The lower decremental area under the curve (dAUC) for hunger in the HP/MCHO diet (-56.6% compared to MP, p < 0.05) was associated with the higher AUC for 2-arachidonoylglycerol (2-AG) concentrations (p < 0.05). Hunger was inversely associated with PYY in the HP/MCHO group (r = -0.7, p < 0.01). Ad libitum food intake, homeostatic model assessment for insulin resistance (HOMA-IR) and incremental AUCs for gut peptides were not different between conditions. HP/MCHO versus MP/HCHO diet-induced reduction in hunger was present after 34 months weight maintenance in the post-obese state. HP/MCHO diet-induced decrease of hunger is suggested to interact with increased 2-AG and PYY concentrations.

Cannabinoid CB1 Receptors Inhibit Gut-Brain Satiation Signaling in Diet-Induced Obesity

Gut-brain signaling controls feeding behavior and energy homeostasis; however, the underlying molecular mechanisms and impact of diet-induced obesity (DIO) on these pathways are poorly defined. We tested the hypothesis that elevated endocannabinoid activity at cannabinoid CB₁ receptor (CB₁Rs) in the gut of mice rendered DIO by chronic access to a high fat and sucrose diet for 60 days inhibits nutrient-induced release of satiation peptides and promotes overeating. Immunoreactivity for CB₁Rs was present in enteroendocrine cells in the mouse’s upper small-intestinal epithelium that produce and secrete the satiation peptide, cholecystokinin (CCK), and expression of mRNA for CB₁Rs was greater in these cells when compared to non-CCK producing cells. Oral gavage of corn oil increased levels of bioactive CCK (CCK-8) in plasma from mice fed a low fat no-sucrose diet. Pretreatment with the cannabinoid receptor agonist, WIN55,212-2, blocked this response, which was reversed by co-administration with the peripherally-restricted CB₁R neutral antagonist, AM6545. Furthermore, monoacylglycerol metabolic enzyme function was dysregulated in the upper small-intestinal epithelium from DIO mice, which was met with increased levels of a variety of monoacylglycerols including the endocannabinoid, 2-arachidonoyl-sn-glycerol. Corn oil failed to affect levels of CCK in DIO mouse plasma; however, pretreatment with AM6545 restored the ability for corn oil to stimulate increases in levels of CCK, which suggests that elevated endocannabinoid signaling at small intestinal CB₁Rs in DIO mice inhibits nutrient-induced CCK release. Moreover, the hypophagic effect of AM6545 in DIO mice was reversed by co-administration with the CCK_A receptor antagonist, devazepide. Collectively, these results provide evidence that hyperphagia associated with DIO is driven by a mechanism that includes CB₁R-mediated inhibition of gut-brain satiation signaling.

Molecular neuroscience at its "high": bibliometric analysis of the most cited papers on endocannabinoid system, cannabis and cannabinoids

BACKGROUND

Cannabis, cannabinoids and endocannabinoids are heavily investigated topics with many articles published every year. We aimed to identify the 100 most cited manuscripts among the vast literature and analyze their contents.

METHODS

Web of Science (WoS) Core Collection was searched to identify the 100 most cited relevant manuscripts, which were analyzed with reference to (1) authorship, (2) institution, (3) country, (4) document type, (5) journal, (6) publication year, (7) WoS category, and (8) citation count. Semantic content and citation data of the manuscripts were analyzed with VOSviewer.

RESULTS

The most cited manuscripts were published between 1986 and 2016, with the majority being published in the 2000s (n = 51). The number of citations for the top 100 articles ranged from 469 to 3651, with a median citation count of 635.5. The most prolific authors were Vincenzo Di Marzo (n = 11) and Daniele Piomelli (n = 11). The major contributing countries were USA (n = 49), Italy (n = 22), UK (n = 19), and France (n = 11). The most prolific institutions were University of California (n = 14), National Research Council of Italy (n = 12) and National Institutes of Health USA (n = 12). The manuscripts consisted of original articles (n = 75), reviews (n = 24) and a note (n = 1). The most dominant journal was Nature (n = 15). The major WoS categories associated were Multidisciplinary sciences (n = 31), Neurosciences (n = 20), Pharmacology / Pharmacy (n = 16), and General / Internal Medicine (n = 11).

CONCLUSIONS

The top-ranked manuscripts among the 100 were concerning analgesia, weight loss, long-term potentiation, depolarization-induced suppression of inhibition, opiates and other topics. Cannabinoid type 1 (CB1) receptor was studied by more of the top 100 papers in comparison to cannabinoid type 2 (CB2) receptor. The most frequently mentioned chemicals in these publications were 2-arachidonoylglycerol, tetrahydrocannabinol, and anandamide. Together, these manuscripts comprise the most highly cited publications in the topic, literally the molecular neuroscience at its "high".

Hypothalamic endocannabinoids inversely correlate with the development of diet-induced obesity in male and female mice

The endocannabinoid (eCB) system regulates energy homeostasis and is linked to obesity development. However, the exact dynamic and regulation of eCBs in the hypothalamus during obesity progression remain incompletely described and understood. Our study examined the time course of responses in two hypothalamic eCBs, 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamine (AEA), in male and female mice during diet-induced obesity and explored the association of eCB levels with changes in brown adipose tissue (BAT) thermogenesis and body weight. We fed mice a high-fat diet (HFD), which induced a transient increase (substantial at 7 days) in hypothalamic eCBs, followed by a progressive decrease to basal levels with a long-term HFD. This transient rise at early stages of obesity is considered a physiologic compensatory response to BAT thermogenesis, which is activated by diet surplus. The eCB dynamic was sexually dimorphic: hypothalamic eCBs levels were higher in female mice, who became obese at later time points than males. The hypothalamic eCBs time course positively correlated with thermogenesis activation, but negatively matched body weight, leptinemia, and circulating eCB levels. Increased expression of eCB-synthetizing enzymes accompanied the transient hypothalamic eCB elevation. Icv injection of eCB did not promote BAT thermogenesis; however, administration of thermogenic molecules, such as central leptin or a peripheral β3-adrenoreceptor agonist, induced a significant increase in hypothalamic eCBs, suggesting a directional link from BAT thermogenesis to hypothalamic eCBs. This study contributes to the understanding of hypothalamic regulation of obesity.

Endocannabinoid System in Hepatic Glucose Metabolism, Fatty Liver Disease, and Cirrhosis

There is growing evidence that glucose metabolism in the liver is in part under the control of the endocannabinoid system (ECS) which is also supported by its presence in this organ. The ECS consists of its cannabinoid receptors (CBRs) and enzymes that are responsible for endocannabinoid production and metabolism. ECS is known to be differentially influenced by the hepatic glucose metabolism and insulin resistance, e.g., cannabinoid receptor type 1(CB₁) antagonist can improve the glucose tolerance and insulin resistance. Interestingly, our own study shows that expression patterns of CBRs are influenced by the light/dark cycle, which is of significant physiological and clinical interest. The ECS system is highly upregulated during chronic liver disease and a growing number of studies suggest a mechanistic and therapeutic impact of ECS on the development of liver fibrosis, especially putting its receptors into focus. An opposing effect of the CBRs was exerted via the CB₁ or CB₂ receptor stimulation. An activation of CB₁ promoted fibrogenesis, while CB₂ activation improved antifibrogenic responses. However, underlying mechanisms are not yet clear. In the context of liver diseases, the ECS is considered as a possible mediator, which seems to be involved in the synthesis of fibrotic tissue, increase of intrahepatic vascular resistance and subsequently development of portal hypertension. Portal hypertension is the main event that leads to complications of the disease. The main complication is the development of variceal bleeding and ascites, which have prognostic relevance for the patients. The present review summarizes the current understanding and impact of the ECS on glucose metabolism in the liver, in association with the development of liver cirrhosis and hemodynamics in cirrhosis and its complication, to give perspectives for development of new therapeutic strategies.

Cannabis: From a Plant That Modulates Feeding Behaviors toward Developing Selective Inhibitors of the Peripheral Endocannabinoid System for the Treatment of Obesity and Metabolic Syndrome

In this review, we discuss the role of the endocannabinoid (eCB) system in regulating energy and metabolic homeostasis. Endocannabinoids, via activating the cannabinoid type-1 receptor (CB₁R), are commonly known as mediators of the thrifty phenotype hypothesis due to their activity in the central nervous system, which in turn regulates food intake and underlies the development of metabolic syndrome. Indeed, these findings led to the clinical testing of globally acting CB₁R blockers for obesity and various metabolic complications. However, their therapeutic potential was halted due to centrally mediated adverse effects. Recent observations that highlighted the key role of the peripheral eCB system in metabolic regulation led to the preclinical development of various novel compounds that block CB₁R only in peripheral organs with very limited brain penetration and without causing behavioral side effects. These unique molecules, which effectively ameliorate obesity, type II diabetes, fatty liver, insulin resistance, and chronic kidney disease in several animal models, are likely to be further developed in the clinic and may revive the therapeutic potential of blocking CB₁R once again.

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.

Tratamento farmacológico da obesidade: passado, presente e futuro

O tratamento da obesidade deve ser baseado na percepção de que a obesidade é uma enfermidade crônica, neuroquímica e recidivante. Sendo assim, a combinação de eficácia, sustentabilidade de longo prazo e perfil de segurança de excelência devem nortear a utilização dos medicamentos disponíveis assim como das novas moléculas vindouras. No momento, a liraglutida parece ser a mais completa droga para a obesidade como doença crônica, mas certamente deverá ser superada pelos novos peptídeos de múltiplo agonismo e/ou pela combinação de várias medicações ainda não disponíveis em baixas dosagens para pacientes precisa e individualmente selecionados.

Multiple endocannabinoid-mediated mechanisms in the regulation of energy homeostasis in brain and peripheral tissues

The endocannabinoid (eCB) system is widely expressed in many central and peripheral tissues, and is involved in a plethora of physiological processes. Among these, activity of the eCB system promotes energy intake and storage, which, however, under pathophysiological conditions, can favour the development of obesity and obesity-related disorders. It is proposed that eCB signalling is evolutionary beneficial for survival under periods of scarce food resources. Remarkably, eCB signalling is increased both in hunger and in overnutrition conditions, such as obesity and type-2 diabetes. This apparent paradox suggests a role of the eCB system both at initiation and at clinical endpoint of obesity. This review will focus on recent findings about the role of the eCB system controlling whole-body metabolism in mice that are genetically modified selectively in different cell types. The current data in fact support the notion that eCB signalling is not only engaged in the development but also in the maintenance of obesity, whereby specific cell types in central and peripheral tissues are key sites in regulating the entire body's energy homeostasis.

Effect of acute Δ9-tetrahydrocannabinol administration on subjective and metabolic hormone responses to food stimuli and food intake in healthy humans: a randomized, placebo-controlled study

BACKGROUND

The endocannabinoid system (ECS) is considered a key player in the neurophysiology of food reward. Animal studies suggest that the ECS stimulates the sensory perception of food, thereby increasing its incentive-motivational and/or hedonic properties and driving consumption, possibly via interactions with metabolic hormones. However, it remains unclear to what extent this can be extrapolated to humans.

OBJECTIVE

We aimed to investigate the effect of oral Δ9-tetrahydrocannabinol (THC) on subjective and metabolic hormone responses to visual food stimuli and food intake.

METHODS

Seventeen healthy subjects participated in a single-blinded, placebo-controlled, 2 × 2 crossover trial. In each of the 4 visits, subjective "liking" and "wanting" ratings of high- and low-calorie food images were acquired after oral THC or placebo administration. The effect on food intake was quantified in 2 ways: via ad libitum oral intake (half of the visits) and intragastric infusion (other half) of chocolate milkshake. Appetite-related sensations and metabolic hormones were measured at set time points throughout each visit.

RESULTS

THC increased "liking" (P = 0.031) and "wanting" ratings (P = 0.0096) of the high-calorie, but not the low-calorie images, compared with placebo. Participants consumed significantly more milkshake after THC than after placebo during oral intake (P = 0.0005), but not intragastric infusion, of milkshake. Prospective food consumption ratings during the food image paradigm were higher after THC than after placebo (P = 0.0039). THC also increased plasma motilin (P = 0.0021) and decreased octanoylated ghrelin (P = 0.023) concentrations before milkshake consumption (i.e., in both oral intake and intragastric infusion test sessions), whereas glucagon-like peptide 1 responses to milkshake intake were attenuated by THC during both oral (P = 0.0002) and intragastric (P = 0.0055) administration.

CONCLUSIONS

These findings suggest that the ECS drives food intake by interfering with anticipatory, cephalic phase, and metabolic hormone responses. This trial was registered at clinicaltrials.gov as NCT02310347.

Effect of cannabis on weight and metabolism in first-episode non-affective psychosis: Results from a three-year longitudinal study

BACKGROUND

Cannabis smoking is highly prevalent among patients with psychotic disorders. Its use has been found to be related to clinical characteristics and the prognosis of the disorder. Recent evidence indicates a protective effect of cannabis on weight gain and related metabolic alterations. However, there are no previous studies on the long-term longitudinal effects of cannabis on first-episode drug-naïve patients, which would thereby avoid the confounding effects of chronicity and previous treatment exposure. We aimed to explore the effect of cannabis smoking on weight and lipid/glycaemic metabolic measures in a sample of first-episode non-affective psychosis patients.

METHOD

Anthropometric measurements and glycaemic and lipid parameters were obtained at baseline and three years after initiation of treatment. Patients self-reported their cannabis use at both time points. To explore the longitudinal effect of cannabis, patients were divided into three groups: continuers, discontinuers and non-users.

RESULTS

Cannabis users at baseline presented a lower weight ( F=14.85, p<0.001), body mass index ( F=13.14, p<0.001), total cholesterol ( F=4.85, p=0.028) and low-density lipoprotein-cholesterol ( F=6.26, p=0.013) compared to non-users. These differences were also observed after three years: weight ( F=8.07, p=0.005), body mass index ( F=4.66, p=0.032) and low-density lipoprotein-cholesterol ( F=3.91, p=0.049). Moreover, those patients discontinuing cannabis use presented a higher increase in weight ( F=2.98, p=0.052), body mass index ( F=2.73, p=0.067) and triglyceride-high-density lipoprotein ratio ( F=2.72, p=0.067) than the 'non-users' and 'continuers'.

CONCLUSIONS

The study suggests that cannabis use may produce a protective effect against weight gain and related metabolic alterations in psychosis. However, these results need to be replicated in a larger sample size.

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.

The protective effects of Δ9 -tetrahydrocannabinol against inflammation and oxidative stress in rat liver with fructose-induced hyperinsulinemia

OBJECTIVES

A large amount of fructose is metabolized in the liver and causes hepatic functional damage. Δ⁹ -tetrahydrocannabinol (THC) is known as a therapeutic agent for clinical and experimental applications. The study aims to investigate the effects of THC treatment on inflammation, lipid profiles and oxidative stress in rat liver with hyperinsulinemia.

METHODS

Sprague-Dawley rats were divided into groups: control, fructose (10% fructose in drinking water for 12 weeks), THC (1.5 mg/kg/day for the last 4 weeks, intraperitoneally) and fructose+THC groups. Biochemical parameters were measured spectrophotometrically. ELISA method was used for insulin measurement. Apoptosis and inflammation markers were detected by the streptavidin-biotin peroxidase method.

KEY FINDINGS

The consumptions of food and fluid are inversely proportional to fructose and non-fructose groups. Insulin levels were the highest in fructose group. The reduced glutathione-S-transferase level significantly increased in fructose + THC group compared with fructose group. Total cholesterol level in the fructose + THC group was higher than the fructose group. Caspase-3 and NF-κβ immunopositive cell numbers increased in fructose + THC rats compared with fructose group. The number of IL-6 immunopositive cell decreased in fructose + THC group compared with fructose group.

CONCLUSIONS

According to the result, long-term and low-dose THC administration may reduce hyperinsulinemia and inflammation in rats to some extent.

VCE-004.8, A Multitarget Cannabinoquinone, Attenuates Adipogenesis and Prevents Diet-Induced Obesity

Over the past few years, the endocannabinoid system (ECs) has emerged as a crucial player for the regulation of food intake and energy metabolism, and its pharmacological manipulation represents a novel strategy for the management of metabolic diseases. The discovery that VCE-004.8, a dual PPARγ and CB₂ receptor agonist, also inhibits prolyl-hydroxylases (PHDs) and activates the HIF pathway provided a rationale to investigate its effect in in vitro models of adipogenesis and in a murine model of metabolic syndrome, all processes critically regulated by these targets of VCE-004.8. In accordance with its different binding mode to PPARγ compared to rosiglitazone (RGZ), VCE-004.8 neither induced adipogenic differentiation, nor affected osteoblastogenesis. Daily administration of VCE-004.8 (20 mg/kg) to HFD mice for 3-wks induced a significant reduction in body weight gain, total fat mass, adipocyte volume and plasma triglycerides levels. VCE-004.8 could also significantly ameliorate glucose tolerance, reduce leptin levels (a marker of adiposity) and increase adiponectin and incretins (GLP-1 and GIP) levels. Remarkably, VCE-004.8 increased the FGF21 mRNA expression in white and brown adipose, as well as in a BAT cell line, qualifying cannabinoaminoquinones as a class of novel therapeutic candidates for the management of obesity and its common metabolic co-morbidities.

Host- and Helminth-Derived Endocannabinoids That Have Effects on Host Immunity Are Generated during Infection

Helminths have coevolved with their hosts, resulting in the development of specialized host immune mechanisms and parasite-specific regulatory products. Identification of new pathways that regulate helminth infection could provide a better understanding of host-helminth interaction and may identify new therapeutic targets for helminth infection. Here we identify the endocannabinoid system as a new mechanism that influences host immunity to helminths. Endocannabinoids are lipid-derived signaling molecules that control important physiologic processes, such as feeding behavior and metabolism. Following murine infection with Nippostrongylus brasiliensis, an intestinal nematode with a life cycle similar to that of hookworms, we observed increased levels of endocannabinoids (2-arachidonoylglycerol [2-AG] or anandamide [AEA]) and the endocannabinoid-like molecule oleoylethanolamine (OEA) in infected lung and intestine. To investigate endocannabinoid function in helminth infection, we employed pharmacological inhibitors of cannabinoid subtype receptors 1 and 2 (CB₁R and CB₂R). Compared to findings for vehicle-treated mice, inhibition of CB₁R but not CB₂R resulted in increased N. brasiliensis worm burden and egg output, associated with significantly decreased expression of the T helper type 2 cytokine interleukin 5 (IL-5) in intestinal tissue and splenocyte cultures. Strikingly, bioinformatic analysis of genomic and transcriptome sequencing (RNA-seq) data sets identified putative genes encoding endocannabinoid biosynthetic and degradative enzymes in many parasitic nematodes. To test the novel hypothesis that helminth parasites produce their own endocannabinoids, we measured endocannabinoid levels in N. brasiliensis by mass spectrometry and quantitative PCR and found that N. brasiliensis parasites produced endocannabinoids, especially at the infectious larval stage. To our knowledge, this is the first report of helminth- and host-derived endocannabinoids that promote host immune responses and reduce parasite burden.

Anti-Obesity Therapy: from Rainbow Pills to Polyagonists

With their ever-growing prevalence, obesity and diabetes represent major health threats of our society. Based on estimations by the World Health Organization, approximately 300 million people will be obese in 2035. In 2015 alone there were more than 1.6 million fatalities attributable to hyperglycemia and diabetes. In addition, treatment of these diseases places an enormous burden on our health care system. As a result, the development of pharmacotherapies to tackle this life-threatening pandemic is of utmost importance. Since the beginning of the 19th century, a variety of drugs have been evaluated for their ability to decrease body weight and/or to improve deranged glycemic control. The list of evaluated drugs includes, among many others, sheep-derived thyroid extracts, mitochondrial uncouplers, amphetamines, serotonergics, lipase inhibitors, and a variety of hormones produced and secreted by the gastrointestinal tract or adipose tissue. Unfortunately, when used as a single hormone therapy, most of these drugs are underwhelming in their efficacy or safety, and placebo-subtracted weight loss attributed to such therapy is typically not more than 10%. In 2009, the generation of a single molecule with agonism at the receptors for glucagon and the glucagon-like peptide 1 broke new ground in obesity pharmacology. This molecule combined the beneficial anorectic and glycemic effects of glucagon-like peptide 1 with the thermogenic effect of glucagon into a single molecule with enhanced potency and sustained action. Several other unimolecular dual agonists have subsequently been developed, and, based on their preclinical success, these molecules illuminate the path to a new and more fruitful era in obesity pharmacology. In this review, we focus on the historical pharmacological approaches to treat obesity and glucose intolerance and describe how the knowledge obtained by these studies led to the discovery of unimolecular polypharmacology.

Impact of maternal western diet-induced obesity on offspring mortality and peripheral endocannabinoid system in mice

Over two-thirds of adults in the United States are obese or overweight, which is largely due to chronic overconsumption of diets high in fats and sugars (i.e., Western diet). Recent studies reveal that maternal obesity may predispose offspring to development of obesity and other metabolic diseases; however, the molecular underpinnings of these outcomes are largely unknown. The endocannabinoid system is an important signaling pathway that controls feeding behavior and energy homeostasis, and its activity becomes upregulated in the upper small intestinal epithelium of Western diet-induced obese mice, which drives overeating. In the current investigation, we examined the impact of chronic maternal consumption of Western diet on the expression and function of the endocannabinoid system in several peripheral organs important for food intake and energy homeostasis in offspring. Female C57BL/6Tac mice were fed a Western diet or low-fat/no-sucrose control chow for 10 weeks, then males were introduced for mating. Dams were maintained on their respective diets through weaning of pups, at which time pups were maintained on low-fat/no-sucrose chow for 10 weeks. Neonates born from dams fed Western diet, when compared to those born from mice fed control chow, unexpectedly displayed increases in mortality that occurred exclusively within six days following birth (greater than 50% mortality). Males comprised a larger fraction of surviving offspring from obese dams. Furthermore, surviving offspring displayed transient increases in body mass for first two days post weaning, and no marked changes in feeding patterns and endocannabinoid levels in upper small intestinal epithelium, pancreas, and plasma, or in expression of key endocannabinoid system genes in the upper small intestinal epithelium and pancreas at 10 weeks post-weaning. Collectively, these results suggest that maternal diet composition greatly influences survival of neonate C57BL/6Tac mice, and that surviving offspring from dams chronically fed a Western diet do not display marked changes in body mass, eating patterns, or expression and function of the endocannabinoid system in several peripheral organs important for feeding behavior and energy homeostasis.

Plasma fatty acid ethanolamides are associated with postprandial triglycerides, ApoCIII, and ApoE in humans consuming a high-fructose corn syrup-sweetened beverage

Epidemiological and clinical research studies have provided ample evidence demonstrating that consumption of sugar-sweetened beverages increases risk factors involved in the development of obesity, Type 2 diabetes, and cardiovascular disease (CVD). Our previous study demonstrated that when compared with aspartame (Asp), 2 wk of high-fructose corn syrup (HFCS)-sweetened beverages provided at 25% of daily energy requirement was associated with increased body weight, postprandial (pp) triglycerides (TG), and fasting and pp CVD risk factors in young adults. The fatty acid ethanolamide, anandamide (AEA), and the monoacylglycerol, 2-arachidonoyl- sn-glycerol (2-AG), are two primary endocannabinoids (ECs) that play a role in regulating food intake, increasing adipose storage, and regulating lipid metabolism. Therefore, we measured plasma concentrations of ECs and their analogs, oleoylethanolamide (OEA), docosahexaenoyl ethanolamide (DHEA), and docosahexaenoyl glycerol (DHG), in participants from our previous study who consumed HFCS- or Asp-sweetened beverages to determine associations with weight gain and CVD risk factors. Two-week exposure to either HFCS- or Asp-sweetened beverages resulted in significant differences in the changes in fasting levels of OEA and DHEA between groups after the testing period. Subjects who consumed Asp, but not HFCS, displayed a reduction in AEA, OEA, and DHEA after the testing period. In contrast, there were significant positive relationships between AEA, OEA, and DHEA vs. ppTG, ppApoCIII, and ppApoE in those consuming HFCS, but not in those consuming Asp. Our findings reveal previously unknown associations between circulating ECs and EC-related molecules with markers of lipid metabolism and CVD risk after HFCS consumption.

Endocannabinoids in Body Weight Control

Maintenance of body weight is fundamental to maintain one's health and to promote longevity. Nevertheless, it appears that the global obesity epidemic is still constantly increasing. Endocannabinoids (eCBs) are lipid messengers that are involved in overall body weight control by interfering with manifold central and peripheral regulatory circuits that orchestrate energy homeostasis. Initially, blocking of eCB signaling by first generation cannabinoid type 1 receptor (CB1) inverse agonists such as rimonabant revealed body weight-reducing effects in laboratory animals and men. Unfortunately, rimonabant also induced severe psychiatric side effects. At this point, it became clear that future cannabinoid research has to decipher more precisely the underlying central and peripheral mechanisms behind eCB-driven control of feeding behavior and whole body energy metabolism. Here, we will summarize the most recent advances in understanding how central eCBs interfere with circuits in the brain that control food intake and energy expenditure. Next, we will focus on how peripheral eCBs affect food digestion, nutrient transformation and energy expenditure by interfering with signaling cascades in the gastrointestinal tract, liver, pancreas, fat depots and endocrine glands. To finally outline the safe future potential of cannabinoids as medicines, our overall goal is to address the molecular, cellular and pharmacological logic behind central and peripheral eCB-mediated body weight control, and to figure out how these precise mechanistic insights are currently transferred into the development of next generation cannabinoid medicines displaying clearly improved safety profiles, such as significantly reduced side effects.

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.

Protective Effects of Gomisin N against Hepatic Cannabinoid Type 1 Receptor-Induced Insulin Resistance and Gluconeogenesis

Activation of the hepatic cannabinoid type 1 receptor (CB1R) induces insulin resistance and gluconeogenesis via endoplasmic reticulum (ER) stress, thereby contributing to hyperglycemia. Gomisin N (GN) is a phytochemical derived from Schisandra chinensis. In the current study, we investigated the inhibitory effects of GN on hepatic CB1R-mediated insulin resistance and gluconeogenesis in 2-arachidonoylglycerol (AG; an agonist of CB1R)-treated HepG2 cells and in high-fat diet (HFD)-induced obese mice. Treatment with 2-AG induced the expression of ER stress markers, serine/threonine phosphatase PHLPP1, Lipin1, and ceramide synthesis genes, but reduced the expression of ceramide degradation genes in HepG2 cells. However, GN reversed 2-AG-mediated effects and improved the 2-AG-mediated impairment of insulin signaling. Furthermore, GN inhibited 2-AG-induced intracellular triglyceride accumulation and glucose production in HepG2 cells by downregulation of lipogenesis and gluconeogenesis genes, respectively. In vivo, GN administration to HFD obese mice reduced the HFD-induced increase in fasting blood glucose and insulin levels, which was accompanied with downregulation of HFD-induced expression of CB1R, ER stress markers, ceramide synthesis gene, and gluconeogenesis genes in the livers of HFD obese mice. These findings demonstrate that GN protects against hepatic CB1-mediated impairment of insulin signaling and gluconeogenesis, thereby contributing to the amelioration of hyperglycemia.

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.

Allosteric modulators of cannabinoid receptor 1: developing compounds for improved specificity

The cannabinoid receptor 1 (CB1) is a G protein-coupled receptor (GPCR) that is located primarily in the central nervous system. CB1 is a therapeutic target which may impact pathways to mediate pain, neurodegenerative disorders, hunger, and drug-seeking behavior. Despite these benefits, development of orthosteric therapeutic compounds, which target the endogenous ligand-binding site of CB1, has been challenging due to detrimental side effects including psychoactivity, depression, and suicidal thoughts. However, CB1 also has an allosteric binding site(s), which is topographically distinct from the orthosteric site. Allosteric modulation of CB1 has a number of potential advantages including providing a mechanism for more precise control of downstream pathways and circumventing these side effects. In this review, we summarize the concept of allosteric modulation and focus on the structure-activity relationship studies of the well-characterized allosteric modulators, ORG27569 and PSNCBAM-1 and their derivatives, and a few other recent modulators. We review studies on the properties of these modulators on CB1 signaling in cells and their effects in vivo. While many current allosteric modulators also produce complex outcomes, they provide new advances for the design of CB1 centered therapeutics.

Involvement of cannabinoid system in the nucleus accumbens on delay-based decision making in the rat

The nucleus accumbens (NAc) plays a fundamental role in decision making and anticipation of reward. In addition, exogenous cannabinoids affect the behavior of humans and animals including disruption of short-term memory and cognitive impairments. Therefore, in this study, cannabinoid agonist and antagonist were administrated into the NAc to determine the effect of cannabinoid activation in the entire NAc on delay-based decision making. Rats were trained on a cost-benefit T-maze decision making task in which the animals were well-trained to choose between a small/immediate reward and a large/delay reward. After training, the animals were implanted with guide cannulae in the NAc. On test day, they received cannabinoid agonist (Win 55,212-2; 10, 50 and 100μM) and/or antagonist (AM251; 45μM) into the NAc. Percentage of high reward choice and latency of reward achievement were evaluated. Results showed that cannabinoid agonist administration caused a decrease in high reward choice such that rats selected small/immediate reward instead of large/delay reward. Moreover, in agonist-treated animals latency of reward achievement increased. Effects of cannabinoid activation on delay-based decision making with equivalent delays demonstrated that if the delay was equated on both arm goals, animals still had a preference for the high/delay reward, showing the results was not caused by an impairment of spatial preference or memory. These finding clarified that cannabinoid system activation in the entire NAc plays a critical role in the regulation of delay-based decision making.