New horizons on the role of cannabinoid CB1 receptors in palatable food intake, obesity and related dysmetabolism

Endocannabinoids at the synapse and beyond: implications for neuropsychiatric disease pathophysiology and treatment

Endocannabinoids (eCBs) are lipid neuromodulators that suppress neurotransmitter release, reduce postsynaptic excitability, activate astrocyte signaling, and control cellular respiration. Here, we describe canonical and emerging eCB signaling modes and aim to link adaptations in these signaling systems to pathological states. Adaptations in eCB signaling systems have been identified in a variety of biobehavioral and physiological process relevant to neuropsychiatric disease states including stress-related disorders, epilepsy, developmental disorders, obesity, and substance use disorders. These insights have enhanced our understanding of the pathophysiology of neurological and psychiatric disorders and are contributing to the ongoing development of eCB-targeting therapeutics. We suggest future studies aimed at illuminating how adaptations in canonical as well as emerging cellular and synaptic modes of eCB signaling contribute to disease pathophysiology or resilience could further advance these novel treatment approaches.

Ghrelin-Ghrelin receptor (GSHR) pathway via endocannabinoid signal affects the expression of NPY to promote the food intake of Siberian sturgeon (Acipenser baerii)

Previous data suggested that activation of endocannabinoid receptor 1 (CB1) was necessary for the orexigenic effect of Ghrelin in rodents, but the information is limited in teleosts. To investigate the feeding regulation pathway of Ghrelin and CB1 in Siberian sturgeon (Acipenser baerii), this study first identified the Ghrelin (345 bp, complete coding sequence) and Ghrelin receptor (GHSR, 500 bp, partial coding sequence) sequences, and then detected their tissue distribution patterns, which showed that Ghrelin is mainly distribution in peripheral tissues, while GSHR is mainly in different brain divisions. Besides, the qPCR before and after feeding showed that the mRNA expressions of Ghrelin and GHSR were inhibited after feeding in telencephalon, diencephalon and mesencephalon. Subsequently, the food intake and appetite factor expressions were measured by i.c.v. co-injection of Ghrelin and GSHR antagonist. The results showed that Ghrelin promoted the food intake of Siberian sturgeon, which was reversed by its receptor antagonist. Besides, i.c.v. injection of Ghrelin decreased telencephalon CART expression while increased NPY expression in the three brain regions. In addition, to further explore the relationship of Ghrelin and CB1 signal regulating feeding, the co-injection of Ghrelin and CB1 antagonists was performed. The results showed that AM6545 (CB1 peripheral restricted antagonist) failed to affect the orexigenic effect of Ghrelin and the expression pattern of NPY mRNA in the telencephalon. While in the diencephalon, the increase of food intake and NPY mRNA expression induced by Ghrelin was completely reversed by Rimonabant (CB1 global antagonist). These results indicate Ghrelin-GSHR pathway promotes the food intake of Siberian sturgeon by inducing the expression of NPY in the diencephalon, and the stimulating effect will be reversed by cannabinoid receptor antagonism. This study provides a foundation for understanding the pathways Ghrelin and CB1 signals in appetite regulation of the teleost.

(Wh)olistic (E)ndocannabinoidome-Microbiome-Axis Modulation through (N)utrition (WHEN) to Curb Obesity and Related Disorders

The discovery of the endocannabinoidome (eCBome) is evolving gradually with yet to be elucidated functional lipid mediators and receptors. The diet modulates these bioactive lipids and the gut microbiome, both working in an entwined alliance. Mounting evidence suggests that, in different ways and with a certain specialisation, lipid signalling mediators such as N-acylethanolamines (NAEs), 2-monoacylglycerols (2-MAGs), and N-acyl-amino acids (NAAs), along with endocannabinoids (eCBs), can modulate physiological mechanisms underpinning appetite, food intake, macronutrient metabolism, pain sensation, blood pressure, mood, cognition, and immunity. This knowledge has been primarily utilised in pharmacology and medicine to develop many drugs targeting the fine and specific molecular pathways orchestrating eCB and eCBome activity. Conversely, the contribution of dietary NAEs, 2-MAGs and eCBs to the biological functions of these molecules has been little studied. In this review, we discuss the importance of (Wh) olistic (E)ndocannabinoidome-Microbiome-Axis Modulation through (N) utrition (WHEN), in the management of obesity and related disorders.

Role of cannabinoids in various diseases: A review

BACKGROUND

The plant, Cannabis sativa is heavily explored and researched with many industrial and pharmaceutical applications. The medicinal and therapeutic role of cannabis Sativa has been summarized in the paper, citing its mechanism of action and influence on the human body. Diseases like metabolic disorders, infectious diseases, and psychological disorders pose negative and long-term drastic effects on the body like neurodegeneration and other chronic system failures. Several existing literature has proved its effectiveness against such diseases.

OBJECTIVES

This review aims to provide an overview of the role of cannabinoids in various diseases like metabolic disorders, infectious diseases, and psychological disorders.

METHOD

Various e-resources like Pubmed, Science Direct, and Google Scholar were thoroughly searched and read to form a well-informed and information-heavy manuscript. Here we tried to summaries the therapeutic aspect of Cannabis sativa and its bioactive compound cannabinoids in various diseases.

RESULT

This review highlights the various constituents which are present in Cannabis sativa, the Endocannabinoid system, and the role of cannabinoids in various diseases Conclusion: Recent research on Cannabis has suggested its role in neurodegenerative diseases, inflammation, sleep disorders, pediatric diseases, and their analgesic nature. Therefore, the authors majorly focus on the therapeutic aspect of Cannabis sativa in various diseases. The focus is also on the endocannabinoid system (ECS) and its role in fighting or preventing bacterial, parasitic, fungal, and viral infections.

Endogenous cannabinoids are required for MC4R-mediated control of energy homeostasis

Hypothalamic regulation of feeding and energy expenditure is a fundamental and evolutionarily conserved neurophysiological process critical for survival. Dysregulation of these processes, due to environmental or genetic causes, can lead to a variety of pathological conditions ranging from obesity to anorexia. Melanocortins and endogenous cannabinoids (eCBs) have been implicated in the regulation of feeding and energy homeostasis; however, the interaction between these signaling systems is poorly understood. Here, we show that the eCB 2-arachidonoylglycerol (2-AG) regulates the activity of melanocortin 4 receptor (MC4R) cells in the paraventricular nucleus of the hypothalamus (PVN^MC4R) via inhibition of afferent GABAergic drive. Furthermore, the tonicity of eCBs signaling is inversely proportional to energy state, and mice with impaired 2-AG synthesis within MC4R neurons weigh less, are hypophagic, exhibit increased energy expenditure, and are resistant to diet-induced obesity. These mice also exhibit MC4R agonist insensitivity, suggesting that the energy state-dependent, 2-AG-mediated suppression of GABA input modulates PVN^MC4R neuron activity to effectively respond to the MC4R natural ligands to regulate energy homeostasis. Furthermore, post-developmental disruption of PVN 2-AG synthesis results in hypophagia and death. These findings illustrate a functional interaction at the cellular level between two fundamental regulators of energy homeostasis, the melanocortin and eCB signaling pathways in the hypothalamic feeding circuitry.

New insights into bisphenols induced obesity in zebrafish (Danio rerio): Activation of cannabinoid receptor CB1

Bisphenols (BPs), as widely used plastic additives, penetrate into our daily lives. BPs are considered endocrine disruptors and could potentially induce obesity. In this study, the effects of bisphenol A (BPA) and tetrabromobisphenol A (TBBPA) on food intake and lipid metabolism in zebrafish were determined. Moreover, the impact of BPA and TBBPA on the endocannabinoid system (ECS) of zebrafish was further explored by metabolomics, transcriptomics, and molecular docking analysis. Here we show that exposure to BPA and TBBPA at concentrations commonly found in the environment (20, 100, and 500 μg/L) led to hyperphagia and obesity in adult male zebrafish. Metabolomics and histopathological analysis revealed significant lipid accumulation in the liver of zebrafish exposed to BPA and TBBPA. The expression of ECS-related genes, in conjunction with RNA-Seq results, further indicated that BPA and TBBPA increased appetite and induced obesity by activating cannabinoid receptor type 1(CB1). Furthermore, molecular docking revealed that six representative BPs including BPA and TBBPA could bind to the CB1 receptor. Collectively, these findings indicate that CB1 may be a potential target for BPs to induce obesity.

The endocannabinoidome in neuropsychiatry: Opportunities and potential risks

The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R_. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.

The Gut-Liver Axis in the Control of Energy Metabolism and Food Intake in Animals

Recent research has convincingly demonstrated a bidirectional communication axis between the gut and liver that enables the gut microbiota to strongly affect animals' feeding behavior and energy metabolism. As such, the gut-liver axis enables the host to control and shape the gut microbiota and to protect the intestinal barrier. Gut microbiota-host communication is based on several gut-derived compounds, such as short-chain fatty acids, bile acids, methylamines, amino acid-derived metabolites, and microbial-associated molecular patterns, which act as communication signals, and multiple host receptors, which sense the signals, thereby stimulating signaling and metabolic pathways in all key tissues of energy metabolism and food intake regulation. Disturbance in the microbial ecosystem balance, or microbial dysbiosis, causes profound derangements in the regulation of appetite and satiety in the hypothalamic centers of the brain and in key metabolic pathways in peripheral tissues owing to intestinal barrier disruption and subsequent induction of hepatic and hypothalamic inflammation.

Cannabidiol modulation of antinociceptive tolerance to Δ9-tetrahydrocannabinol

RATIONALE

Humans typically self-administer cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) together repeatedly (as in cannabis, cannabis extract, or Sativex®) to relieve pain. It has been suggested that one benefit of the drug combination may be decreased tolerance development.

OBJECTIVE

The present study compared the development of tolerance to the antinociceptive effects of THC given alone versus combined with CBD, in rats.

METHODS

THC dose-effect curves on tail withdrawal and paw pressure tests were obtained before and after twice-daily treatment with vehicle or CBD (10 mg/kg), plus vehicle or THC (3.6 mg/kg females; 9.3 mg/kg males) for 4 days.

RESULTS

On the first day, THC was more potent in females than males on both nociceptive tests. From pre- to post-chronic (day 1 to day 6), THC potency on the tail withdrawal test decreased more in females than males, and rats that had been treated with CBD + THC repeatedly showed greater rightward/downward shifts of the THC dose-effect curve than rats that had been treated with THC alone. Analysis of blood samples taken after day 6 testing showed that serum THC levels were higher in CBD + THC-treated females than in vehicle + THC-treated females, and THC's active metabolite 11-OH-THC and its inactive metabolite THC-COOH were lower in CBD + THC-treated rats than in vehicle + THC-treated rats of both sexes. CBD also increased serum levels of the active metabolite cannabinol in both sexes.

CONCLUSION

The decrease in THC's antinociceptive effects after repeated CBD exposure may be due to CBD-induced inhibition of THC metabolism, and/or antagonism of THC effects that emerges with repeated CBD treatment.

Endocrine disruptors in the diet of male Sparus aurata: Modulation of the endocannabinoid system at the hepatic and central level by Di-isononyl phthalate and Bisphenol A

The increasing manufacture of plastics and their mismanagement has turned plastic into a ubiquitous waste in the marine environment. Among all the substances conforming the plastic items, the effects of a dietary Bisphenol A (BPA) and Di-isononyl phthalate (DiNP) have been evaluated in adult male gilthead sea bream, focusing on their effects in the modulation of the Endocannabinoid System (ECS). In zebrafish, the ECS has been recently chosen as a new target for the activity of some Endocrine Disrupting Chemicals (EDC), since it represents a complex lipid signaling network essential for the well-being of the organisms. The results obtained in gilthead seabream showed that BPA and DiNP altered the structure and the biochemical composition of liver, increasing the presence of lipids and triglycerides and decreasing the glycogen and phospholipids. Moreover, the addition of BPA or DiNP in the gilthead sea bream diet altered the levels of endocannabinoids (EC) and EC-like mediators in the liver. These alterations were also associated to changes at the transcriptomic level of genes involved in lipid biosynthesis and ECS metabolism. At the central level, both BPA and DiNP reduced the expression of the endocannabinoid receptor type I (cnr1) and the neuropeptide Y (npy) as well as the levels of the endocannabinoid Anandamide (AEA), suggesting a downregulation of appetite. The results herein reported highlighted the negative effects of chronic dietary exposure to DiNP or BPA on ECS functions and lipid metabolism of male gilthead sea bream liver, showing a similar disruptive activity of these contaminants at metabolic level. Moreover, the novelty of the biomarkers used evidenced possible innovative endpoints for the development of novel OEDCS test guidelines.

Oximes short-acting CB1 receptor agonists

New oximes short-acting CB1 agonists were explored by the introduction of an internal oxime and polar groups at the C3 alkyl tail of Δ⁸-THC. The scope of the research was to drastically alter two important physicochemical properties hydrophobicity (log P) and topological surface area (tPSA) of the compound, which play a critical role in tissue distribution and sequestration (depot effect). Key synthesized analogs demonstrated sub-nanomolar affinity for CB1, marked reduction in hydrophobicity (ClogP∼2.5-3.5 vs 9.09 of Δ⁸-THC-DMH), and found to function as either agonists (trans-oximes) or neutral antagonists (cis-oximes) in a cAMP functional assay. All oxime analogs showed comparable affinity at the CB2 receptor, but surprisingly they were found to function as inverse agonists for CB2. In behavioral studies (i.e. analgesia, hypothermia) trans-oxime 8a exhibited a predictable fast onset (∼20 min) and short duration of pharmacological action (∼180 min), in contrast to the very prolonged duration of Δ⁸-THC-DMH (>24 h), thus limiting the potential for severe psychotropic side-effects associated with persistent activation of the CB1 receptor. We have conducted 100 ns molecular dynamic (MD) simulations of CB1 complexes with AM11542 (CB1 agonist) and both trans-8a and cis-8b isomeric oximes. These studies revealed that the C3 alkyl tail of cis-8b orientated within the CB1 binding pocket in a manner that triggered a conformational change that stabilized the CB1 receptor at its inactive-state (antagonistic functional effect). In contrast, the trans-8a isomer's conformation was coincided with that of the AM11542 CB1 agonist-bound structure, stabilizing the CB1 receptor at the active-state (agonistic functional effect). We have selected oxime trans-8a based on its potency for CB1, and favorable pharmacodynamic profile, such as fast onset and predictable duration of pharmacological action, for evaluation in pre-clinical models of anorexia nervosa.

Cannabinoids in health and disease: pharmacological potential in metabolic syndrome and neuroinflammation

The use of different natural and/or synthetic preparations of Cannabis sativa is associated with therapeutic strategies for many diseases. Indeed, thanks to the widespread diffusion of the cannabinoidergic system in the brain and in the peripheral districts, its stimulation, or inhibition, regulates many pathophysiological phenomena. In particular, central activation of the cannabinoidergic system modulates the limbic and mesolimbic response which leads to food craving. Moreover, cannabinoid agonists are able to reduce inflammatory response. In this review a brief history of cannabinoids and the protagonists of the endocannabinoidergic system, i.e. synthesis and degradation enzymes and main receptors, will be described. Furthermore, the pharmacological effects of cannabinoids will be outlined. An overview of the involvement of the endocannabinoidergic system in neuroinflammatory and metabolic pathologies will be made. Finally, particular attention will also be given to the new pharmacological entities acting on the two main receptors, cannabinoid receptor type 1 (CB1) and cannabinoid receptor type 2 (CB2), with particular focus on the neuroinflammatory and metabolic mechanisms involved.

New role of phenothiazine derivatives as peripherally acting CB1 receptor antagonizing anti-obesity agents

Developing peripherally active cannabinoid 1 (CB1) receptor antagonists is a novel therapeutic approach for the management of obesity. An unusual phenothiazine scaffold containing CB1R antagonizing hit was identified by adopting virtual screening work flow. The hit so identified was further modified by introducing polar functional groups into it to enhance the polar surface area and decrease the hydrophobicity of the resulting molecules. CB1 receptor antagonistic activity for the designed compounds was computed by the previously established pharmacophore and three dimensional quantitative structure-activity relationship models. Docking studies of these designed compounds confirmed the existence of favourable interactions within the active site of the CB1 receptor. The designed compounds were synthesized and evaluated for their CB1 receptor antagonistic activity. Parallel artificial membrane permeability assay was performed to evaluate their potential to permeate into the central nervous system wherein it was observed that the compounds did not possess the propensity to cross the blood brain barrier and would be devoid of central nervous system side effects. In pharmacological evaluation, the synthesized compounds (23, 25, 27 and 34) showed significant decrease in food intake suggesting their potential application in the management of obesity through CB1 receptor antagonist activity.

Suppressing effect of COR659 on alcohol, sucrose, and chocolate self-administration in rats: involvement of the GABAB and cannabinoid CB1 receptors

RATIONALE AND OBJECTIVES

COR659 [methyl2-(4-chlorophenylcarboxamido)-4-ethyl-5-methylthiophene-3-carboxylate] is a new, positive allosteric modulator (PAM) of the GABA_B receptor. This study evaluated whether COR659 shared with previously tested GABA_B PAMs the capacity to reduce alcohol self-administration in rats.

RESULTS

Treatment with non-sedative doses of COR659 (2.5, 5, and 10 mg/kg; i.p.) suppressed lever-responding for alcohol (15% v/v) in Sardinian alcohol-preferring (sP) rats under the fixed ratio (FR) 4 (FR4) and progressive ratio (PR) schedules of reinforcement; COR659 was more potent and effective than the reference GABA_B PAM, GS39783. Treatment with COR659, but not GS39783, suppressed (a) lever-responding for a sucrose solution (1-3% w/v) in sP rats under the FR4 and PR schedules, (b) lever-responding for a chocolate solution [5% (w/v) Nesquik®] in Wistar rats under the FR10 and PR schedules, and (c) cue-induced reinstatement of chocolate seeking in Wistar rats. Treatment with COR659 was completely ineffective on lever-responding (FR10) for regular food pellets in food-deprived Wistar rats. Pretreatment with the GABA_B receptor antagonist, SCH50911, partially blocked COR659-induced reduction of alcohol self-administration, being ineffective on reduction of chocolate self-administration. Pretreatment with the cannabinoid CB₁ receptor antagonist, AM4113, fully blocked COR659-induced reduction of chocolate self-administration, being ineffective on reduction of alcohol self-administration.

CONCLUSIONS

COR659 might exert its behavioral effects via a composite mechanism: (i) positive allosteric modulation of the GABA_B receptor, responsible for a large proportion of reduction of alcohol self-administration; (ii) an action at other receptor system(s), including the cannabinoid CB₁ receptor, through which COR659 affects seeking and consumption of highly palatable foods.

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.

The hypothalamic-pituitary-adrenal-leptin axis and metabolic health: a systems approach to resilience, robustness and control

Glucocorticoids contribute to obesity and metabolic syndrome; however, the mechanisms are unclear, and prognostic measures are unavailable. A systems level understanding of the hypothalamic-pituitary-adrenal (HPA)-leptin axis may reveal novel insights. Eighteen obese premenopausal women provided blood samples every 10 min over 24 h, which were assayed for cortisol, adrenocorticotropin releasing hormone (ACTH) and leptin. A published personalized HPA systems model was extended to incorporate leptin, yielding three parameters: (i) cortisol inhibitory feedback signalling, (ii) ACTH-adrenal signalling, and (iii) leptin-cortisol antagonism. We investigated associations between these parameters and metabolic risk profiles: fat and lean body mass (LBM; using dual-energy X-ray absorptiometry), and insulin resistance. Decreased cortisol inhibitory feedback signalling was significantly associated with greater fat (kg; p = 0.01) and insulin resistance (p = 0.03) but not LBM. Leptin significantly antagonized cortisol dynamics in eight women, who exhibited significantly lower 24 h mean leptin levels, LBM and higher ACTH-adrenal signalling nocturnally (all p < 0.05), compared with women without antagonism. Traditional neuroendocrine measures did not predict metabolic health, whereas a dynamic systems approach revealed that lower central inhibitory cortisol feedback signalling was significantly associated with greater metabolic risk. While exploratory, leptin-cortisol antagonism may reflect a 'neuroendocrine starvation' response.