Overweight and obesity associated with a missense polymorphism in fatty acid amide hydrolase (FAAH)

Sweet Taste Receptors' Genetic Variability in Advanced Potential Targets of Obesity

Background: Obesity, mainly visceral obesity, causes a low-grade of chronic inflammation (meta-inflammation), associated with comorbidities such as type 2 diabetes, cardiovascular diseases, and certain cancers. Precision Nutrition aims to understand the bidirectional crosstalk between the genome and diet to improve human health. Additionally, by leveraging individual data, Precision Nutrition seeks to predict how people will respond to specific foods or dietary patterns, with the ultimate goal of providing personalized nutritional recommendations tailored to their unique needs and lifestyle factors, including poor dietary habits (e.g., high intake of sugar or saturated fatty acids, alcohol consumption, etc.) and sedentary habits, exacerbate obesity in genetically predisposed individuals. Genetic, metabolic, and environmental factors can play a crucial role during obesity. Objective: To investigate the effects of genetic variability in sweet taste receptors and their downstream signaling pathways in the gut-brain axis on anthropometry, biochemistry, and lifestyle variables. Methods: A sample of 676 volunteers (mean age of 42.22 ± 12 years, ranging from 18 to 73 years) from the database of the GENYAL platform for nutritional trials at the IMDEA Food Institute were included in this study. We present a first-in-class genetic chip, Glucosensing, designed to interrogate 25 single-nucleotide polymorphisms (SNPs) located in genes encoding sweet taste receptors and components of downstream signaling pathways. These include elements of the gut-brain axis and its associated metabolic networks, enabling a comprehensive analysis of individual variability in sweet taste perception and metabolic responses. Results: Several significant associations were found after correction for multiple comparisons, representing potential targets for personalized interventions.

Exploring the genetic contribution in obesity: An overview of dopaminergic system genes

Obesity is a widespread global health concern that affects a significant portion of the population and is associated with reduced quality of life, morbidity, and mortality. It is considered a pandemic, with its prevalence constantly rising in Western countries. As a result, numerous studies have focused on understanding the elements that contribute to obesity. Researchers have focused on neurotransmitters in the brain to develop weight management drugs that regulate food intake. This review explores the literature on genetic influences on dopaminergic processes to determine whether genetic variation has an association with obesity in reward-responsive regions, including mesolimbic efferent and mesocortical areas. Various neurotransmitters play an essential role in regulating food intake, such as dopamine which controls through mesolimbic circuits in the brain that modulate food reward. Appetite stimulation, including primary reinforcers such as food, leads to an increase in dopamine release in the reward centers of the brain. This release is related to motivation and reinforcement, which determines the motivational weighting of the reinforcer. Changes in dopamine expression can lead to hedonic eating behaviors and contribute to the development of obesity. Genetic polymorphisms have been investigated due to their potential role in modulating the risk of obesity and eating behaviors. Therefore, it is crucial to assess the impact of genetic alterations that disrupt this pathway on the obesity phenotype.

Deleting adipose FXR exacerbates metabolic defects and induces endocannabinoid lipid, 2-oleoyl glycerol, in obesity

The nutrient sensor farnesoid X receptor (FXR) transcriptionally regulates whole-body lipid and glucose homeostasis. Several studies examined targeting FXR as a modality to treat obesity with varying conflicting results, emphasizing the need to study tissue-specific roles of FXR. We show that deletion of adipocyte Fxr results in increased adipocyte hypertrophy and suppression of several metabolic genes that is akin to some of the changes noted in high-fat diet (HFD)-fed control mice. Moreover, upon HFD challenge, these effects are worsened in adipocyte-specific Fxr knockout mice. We uncover that FXR regulates fatty acid amide hydrolase (Faah) such that its deletion lowers Faah expression. Conversely, FXR activation by its ligand, chenodeoxycholic acid, induces Faah transcription. Notably, HFD results in the reduction of adipose Faah expression in control mice and that Faah inhibition or deletion is linked to obesity. We report that the adipocyte FXR-Faah axis controls local 2-oleoyl glycerol and systemic N-acyl ethanolamine levels. Taken together, these findings show that loss of adipose FXR may contribute to the pathogenesis of obesity and subsequent metabolic defects.

Genetic Evidence of Endocannabinoid System on Perceived Stress and Restricted Food Intake: The Role of Variants rs324420 in FAAH Gene and rs1049353 in CNR1 Gene

Background: The endocannabinoid system (ECS) is active in brain regions involved in stress, food intake, and emotional regulation. The CB1 receptor and the fatty acid amide hydrolase (FAAH) enzyme regulate the ECS. Genetic variants in the FAAH gene (rs324420) and in the CNR1 gene (rs1049353) have been involved in both chronic stress and obesity. As a maladaptive strategy to evade the stress, three dysfunctional eating patterns may appear: cognitive restriction, disinhibition, and emotional eating. Aim: To evaluate the association of variants rs324420 in the FAAH gene and rs1049353 in the CNR1 gene with perceived stress, dysfunctional eating patterns, and anthropometric and body composition variables. Methods: This cross-sectional study included 189 participants from western Mexico. The Spanish version of the Three-Factor Eating Questionnaire and the Perceived Stress Scale were applied. Genotyping was performed with TaqMan® probes. Results: It was found that subjects with CA/AA genotypes in FAAH had a higher risk of presenting high scores in stress perception than CC genotype carriers (odds ratio [OR] 1.85, 95% confidence interval [CI] 1.007-3.339; p = 0.048); in addition, the CC genotype of this genetic variant was related to higher body weight and body fat, but no association was found with dysfunctional eating patterns. As for the CNR1 single-nucleotide polymorphism, this variant showed no significant association with stress perception scores, but subjects with GA/AA genotypes in CNR1 had a lower risk of presenting high scores of restriction in food intake compared with GG genotype carriers (OR 0.11, 95% CI 0.046-0.322; p < 0.001). Therefore, this study suggests a differential role of the ECS genes FAAH and CNR1 in perceived stress and dysfunctional eating patterns, respectively. Further studies in other populations are required.

Cannabidiol in Foods and Food Supplements: Evaluation of Health Risks and Health Claims

BACKGROUND

Cannabidiol (CBD) is a cannabinoid present in the hemp plant (Cannabis sativa L.). Non-medicinal CBD oils with typically 5-40% CBD are advertised for various alleged positive health effects. While such foodstuffs containing cannabinoids are covered by the Novel Food Regulation in the European Union (EU), none of these products have yet been authorized. Nevertheless, they continue to be available on the European market.

METHODS

The Permanent Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) reviewed the currently available data on adverse and potential beneficial effects of CBD in the dose range relevant for foods.

RESULTS

Increased liver enzyme activities were observed in healthy volunteers following administration of 4.3 mg CBD/kg bw/day and higher for 3-4 weeks. As lower doses were not tested, a no observed adverse effect level (NOAEL) could not be derived, and the dose of 4.3 mg/kg bw/day was identified as the lowest observed adverse effect level (LOAEL). Based on the CBD content and dose recommendations of CBD products on the market, the SKLM considered several exposure scenarios and concluded that the LOAEL for liver toxicity may be easily reached, e.g., via consumption of 30 drops of an oil containing 20% CBD, or even exceeded. A critical evaluation of the available data on potential beneficial health effects of CBD in the dose range at or below the LOAEL of 4.3 mg/kg bw/day revealed no scientific evidence that would substantiate health claims, e.g., in relation to physical performance, the cardiovascular, immune, and nervous system, anxiety, relaxation, stress, sleep, pain, or menstrual health.

CONCLUSIONS

The SKLM concluded that consumption of CBD-containing foods/food supplements may not provide substantiated health benefits and may even pose a health risk to consumers.

Genetic Tools in Rodents to Study Cannabinoid Functions

During the past 30 years, the endocannabinoid system (ECS) has emerged as a major signalling system in the mammalian brain regulating neurotransmission in numerous brain regions and in various cell populations. Endocannabinoids are able to regulate specific physiological functions and thus modify their behavioural manifestations and allostatic alterations of the ECS linked to different pathological conditions. As discussed in detail in other chapters of this book, endocannabinoids are involved in learning and memory, stress, and anxiety, feeding, energy balance, development, and ageing. Likewise, many CNS disorders (e.g. schizophrenia, epilepsy, substance use disorders, and multiple sclerosis) are associated with dysregulation of the ECS. Discerning the physiological functions of the synthetic and degrading enzymes of endocannabinoids and their receptors is a challenging task because of their distinct and complex expression patterns. Techniques of genetic engineering have been able to shed light on a number of complex ECS-related tasks during the past years. In this chapter, first, we take a critical look at the toolbox available to researchers who would like to investigate cannabinoid effects using genetic engineering techniques, then we comprehensively discuss genetically modified rodent models in various neuronal and non-neuronal cell populations, both within and outside the nervous system.

Beyond the Scale: Exploring the Endocannabinoid System's Impact on Obesity

PURPOSE OF REVIEW

This review explores the role of the endocannabinoid system (ECS) in regulating energy balance, food intake, and metabolism, with a focus on how ECS dysregulation contributes to obesity. The goal is to provide insights into the mechanisms underlying obesity and its associated metabolic disorders.

RECENT FINDINGS

Recent research indicates that the ECS significantly influences food intake, fat storage, insulin sensitivity, and inflammation, all of which are central to the development and progression of obesity. New research areas include the interaction between the ECS and gut microbiota, circadian rhythms of the ECS, and the impact of genetic and epigenetic factors on ECS function. Interest in the therapeutic potential of targeting the ECS has grown, with earlier treatments like CB1 receptor antagonists showing mixed results in efficacy and safety. Evidence from both animal and human studies highlight the impact of elevated levels of the endocannabinoids anandamide and 2-AG on food intake, insulin resistance, visceral fat accumulation, and metabolic disturbances associated with obesity. The review explores the interaction between the ECS and other physiological systems, including gut-brain communication, circadian rhythms, as well as leptin and ghrelin signaling. Additionally, genetic and epigenetic factors influencing ECS function are examined, emphasizing their contribution to obesity susceptibility. While therapeutic approaches targeting the ECS, particularly CB1 receptor antagonism, have shown potential in managing obesity, the review acknowledges the challenges posed by central nervous system side effects in earlier treatments like rimonabant. However, recent advancements in peripherally restricted CB1 antagonists offer renewed hope for safer and more effective obesity treatments. The review concludes by addressing future research directions and therapeutic strategies to combat this global health challenge.

Effect of a High Linoleic Acid Diet on Pregnant Women and Their Offspring

Nutritional intake during pregnancy can affect gestational length, fetal development, and impact postnatal growth and health in offspring. Perturbations in maternal nutrition with either an excess or deficiency in nutrients during pregnancy may have harmful effects on the offspring's development and increase the risk of developing chronic diseases later in life. In pregnancy, nutrients transfer from the mother to the fetus via the placenta. Essential fatty acids, linoleic acid (LA) and alpha linoleic acid (ALA), can only be obtained in the diet. In Western countries, the ratio of LA and ALA in the diet has increased dramatically in recent decades. Some animal and human studies have found a correlation between maternal intake of LA and birth weight; however, the association varies. In contrast, some human studies have demonstrated inconclusive findings regarding the correlation between cord blood levels of LA and birth outcomes. In addition, high dietary LA intake in animal studies in pregnancy increased the production of inflammatory markers such as prostaglandins, leukotrienes, cytokines, and tumour necrosis factor-alpha. This review aims to highlight the effect of high dietary LA intake during pregnancy on birth outcomes, obesity, maternal inflammatory markers, and the transfer of fatty acids across the placenta.

4,4-Dimethylsterols Reduces Fat Accumulation via Inhibiting Fatty Acid Amide Hydrolase In Vitro and In Vivo

4,4-Dimethylsterols constitute a unique class of phytosterols responsible for regulating endogenous cannabinoid system (ECS) functions. However, precise mechanism through which 4,4-dimethylsterols affect fat metabolism and the linkage to the ECS remain unresolved. In this study, we identified that 4,4-dimethylsterols, distinct from 4-demethseterols, act as inhibitors of fatty acid amide hydrolases (FAAHs) both in vivo and in vitro. Genetic ablation of FAAHs (faah-1) abolishes the effects of 4,4-dimethylsterols on fat accumulation and locomotion behavior in a Caenorhabditis elegans model. We confirmed that dietary intervention with 4,4-dimethylsterols in a high-fat diet (HFD) mouse model leads to a significant reduction in body weight (>11.28%) with improved lipid profiles in the liver and adipose tissues and increased fecal triacylglycerol excretion. Untargeted and targeted metabolomics further verified that 4,4-dimethylsterols influence unsaturated fatty acid biosynthesis and elevate oleoyl ethanolamine levels in the intestine. We propose a potential molecular mechanism in which 4,4-dimethylsterols engage in binding interactions with the catalytic pocket (Ser241) of FAAH-1 protein due to the shielded polarity, arising from the presence of 2 additional methyl groups (CH3). Consequently, 4,4-dimethylsterols represent an unexplored class of beneficial phytosterols that coordinate with FAAH-1 activity to reduce fat accumulation, which offers new insight into intervention strategies for treating diet-induced obesity.

Investigating the alterations of endocannabinoidome signaling in the human small intestine in the context of obesity and type 2 diabetes

Background

Human studies have linked obesity-related diseases, such as type-2 diabetes (T2D), to the modulation of endocannabinoid signaling. Cannabinoid CB1 and CB2 receptor activation by the endocannabinoids (eCBs) 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA), both derived from arachidonic acid, play a role in homeostatic regulation. Other long chain fatty acid-derived endocannabinoid-like molecules have extended the metabolic role of this signaling system through other receptors. In this study, we aimed to assess in depth the interactions between the circulating and intestinal tone of this extended eCB system, or endocannabinoidome (eCBome), and their involvement in the pathogenesis of diabetes.

Methods

Plasma and ileum samples were collected from subjects with obesity and harboring diverse degrees of insulin resistance or T2D, who underwent bariatric surgery. The levels of eCBome mediators and their congeners were then assessed by liquid chromatography coupled to tandem mass spectrometry, while gene expression was screened with qPCR arrays.

Findings

Intestinal and circulating levels of eCBome mediators were higher in subjects with T2D. We found an inverse correlation between the intestinal and circulating levels of monoacylglycerols (MAGs). Additionally, we identified genes known to be implicated in both lipid metabolism and intestinal function that are altered by the context of obesity and glucose homeostasis.

Interpretation

Although the impact of glucose metabolism on the eCBome remains poorly understood in subjects with advanced obesity state, our results suggest a strong causative link between altered glucose homeostasis and eCBome signaling in the intestine and the circulation.

Association between the FAAH C385A variant (rs324420) and obesity-related traits: a systematic review

BACKGROUND

Overweight and obesity are the consequence of a sustained positive energy balance. Twin studies show high heritability rates pointing to genetics as one of the principal risk factors. By 2022, genomic studies led to the identification of almost 300 obesity-associated variants that could help to fill the gap of the high heritability rates. The endocannabinoid system is a critical regulator of metabolism for its effects on the central nervous system and peripheral tissues. Fatty acid amide hydrolase (FAAH) is a key enzyme in the inactivation of one of the two endocannabinoids, anandamide, and of its congeners. The rs324420 variant within the FAAH gene is a nucleotide missense change at position 385 from cytosine to adenine, resulting in a non-synonymous amino acid substitution from proline to threonine in the FAAH enzyme. This change increases sensitivity to proteolytic degradation, leading to reduced FAAH levels and increased levels of anandamide, associated with obesity-related traits. However, association studies of this variant with metabolic parameters have found conflicting results. This work aims to perform a systematic review of the existing literature on the association of the rs324420 variant in the FAAH gene with obesity and its related traits.

METHODS

A literature search was conducted in PubMed, Web of Science, and Scopus. A total of 645 eligible studies were identified for the review.

RESULTS/CONCLUSIONS

After the identification, duplicate elimination, title and abstract screening, and full-text evaluation, 28 studies were included, involving 28 183 individuals. We show some evidence of associations between the presence of the variant allele and higher body mass index, waist circumference, fat mass, and waist-to-hip ratio levels and alterations in glucose and lipid homeostasis. However, this evidence should be taken with caution, as many included studies did not report a significant difference between genotypes. These discordant results could be explained mainly by the pleiotropy of the endocannabinoid system, the increase of other anandamide-like mediators metabolized by FAAH, and the influence of gene-environment interactions. More research is necessary to study the endocannabinoidomic profiles and their association with metabolic diseases.

Research progress in the management of vascular disease with cannabidiol: a review

The morbidity and mortality rates associated with vascular disease (VD) have been gradually increasing. Currently, the most common treatment for VD is surgery, with the progress in drug therapy remaining slow. Cannabidiol (CBD) is a natural extract of Cannabis sativa L. with sedative, analgesic, and nonaddictive properties. CBD binds to 56 cardiovascular-related receptors and exerts extensive regulatory effects on the cardiovascular system, making it a potential pharmacological agent for the management of VD. However, most CBD studies have focused on neurological and cardiac diseases, and research on the management of VD with CBD is still rare. In this review, we summarize the currently available data on CBD in the management of VD, addressing four aspects: the major molecular targets of CBD in VD management, pharmacokinetic properties, therapeutic effects of CBD on common VDs, and side effects. The findings indicate that CBD has anti-anxiety, anti-oxidation, and anti-inflammatory properties and can inhibit abnormal proliferation and apoptosis of vascular smooth muscle and endothelial cells; these effects suggest CBD as a therapeutic agent for atherosclerosis, stress-induced hypertension, diabetes-related vasculopathy, ischemia-reperfusion injury, and vascular damage caused by smoking and alcohol abuse. This study provides a theoretical basis for further research on CBD in the management of VD.

Role of Cannabinoid Signaling in Cardiovascular Function and Ischemic Injury

Cardiovascular disease represents a leading cause of death, morbidity, and societal economic burden. The prevalence of cannabis use has significantly increased due to legalization and an increased societal acceptance of cannabis. Therefore, it is critically important that we gain a greater understanding of the effects and risks of cannabinoid use on cardiovascular diseases as well as the potential for cannabinoid-directed drugs to be used as therapeutics for the treatment of cardiovascular disease. This review summarizes our current understanding of the role of cannabinoid receptors in the pathophysiology of atherosclerosis and myocardial ischemia and explores their use as therapeutic targets in the treatment of ischemic heart disease. Endocannabinoids are elevated in patients with atherosclerosis, and activation of cannabinoid type 1 receptors (CB1Rs) generally leads to an enhancement of plaque formation and atherosclerosis. In contrast, selective activation of cannabinoid type 2 receptors (CB2Rs) appears to exert protective effects against atherosclerosis. Endocannabinoid signaling is also activated by myocardial ischemia. CB2R signaling appears to protect the heart from ischemic injury, whereas the role of CB1R in ischemic injury is less clear. This narrative review serves to summarize current research on the role of cannabinoid signaling in cardiovascular function with the goal of identifying critical knowledge gaps and future studies to address those gaps in a way that facilitates the development of new treatments and better cardiovascular health. SIGNIFICANCE STATEMENT: Cardiovascular diseases, including atherosclerosis and myocardial infarction, are a leading cause of death. Cannabinoid drugs have well known acute effects on cardiovascular function, including tachycardia and orthostatic hypotension. The recent legalization of marijuana and cannabinoids for both medical and recreational use has dramatically increased their prevalence of use. This narrative review on the role of cannabinoid signaling in cardiovascular disease contributes to a better understanding of this topic by integrating current knowledge and identifying critical gaps.

CYP4F2 is a human-specific determinant of circulating N-acyl amino acid levels

N-acyl amino acids are a large family of circulating lipid metabolites that modulate energy expenditure and fat mass in rodents. However, little is known about the regulation and potential cardiometabolic functions of N-acyl amino acids in humans. Here, we analyze the cardiometabolic phenotype associations and genomic associations of four plasma N-acyl amino acids (N-oleoyl-leucine, N-oleoyl-phenylalanine, N-oleoyl-serine, and N-oleoyl-glycine) in 2351 individuals from the Jackson Heart Study. We find that plasma levels of specific N-acyl amino acids are associated with cardiometabolic disease endpoints independent of free amino acid plasma levels and in patterns according to the amino acid head group. By integrating whole genome sequencing data with N-acyl amino acid levels, we identify that the genetic determinants of N-acyl amino acid levels also cluster according to the amino acid head group. Furthermore, we identify the CYP4F2 locus as a genetic determinant of plasma N-oleoyl-leucine and N-oleoyl-phenylalanine levels in human plasma. In experimental studies, we demonstrate that CYP4F2-mediated hydroxylation of N-oleoyl-leucine and N-oleoyl-phenylalanine results in metabolic diversification and production of many previously unknown lipid metabolites with varying characteristics of the fatty acid tail group, including several that structurally resemble fatty acid hydroxy fatty acids. These studies provide a structural framework for understanding the regulation and disease associations of N-acyl amino acids in humans and identify that the diversity of this lipid signaling family can be significantly expanded through CYP4F-mediated ω-hydroxylation.

A genetic variant of fatty acid amide hydrolase (FAAH) exacerbates hormone-mediated orexigenic feeding in mice

Fatty acid amide hydrolase (FAAH) degrades the endocannabinoid anandamide. A polymorphism in FAAH (FAAH C385A) reduces FAAH expression, increases anandamide levels, and increases the risk of obesity. Nevertheless, some studies have found no association between FAAH C385A and obesity. We investigated whether the environmental context governs the impact of FAAH C385A on metabolic outcomes. Using a C385A knock-in mouse model, we found that FAAH A/A mice are more susceptible to glucocorticoid-induced hyperphagia, weight gain, and activation of hypothalamic AMP-activated protein kinase (AMPK). AMPK inhibition occluded the amplified hyperphagic response to glucocorticoids in FAAH A/A mice. FAAH knockdown exclusively in agouti-related protein (AgRP) neurons mimicked the exaggerated feeding response of FAAH A/A mice to glucocorticoids. FAAH A/A mice likewise presented exaggerated orexigenic responses to ghrelin, while FAAH knockdown in AgRP neurons blunted leptin anorectic responses. Together, the FAAH A/A genotype amplifies orexigenic responses and decreases anorexigenic responses, providing a putative mechanism explaining the diverging human findings.

The CB1 cannabinoid receptor regulates autophagy in the tibialis anterior skeletal muscle in mice

The endocannabinoid system (ECS) regulates energy metabolism, has been implicated in the pathogenesis of metabolic diseases and exerts its actions mainly through the type 1 cannabinoid receptor (CB1). Likewise, autophagy is involved in several cellular processes. It is required for the normal development of muscle mass and metabolism, and its deregulation is associated with diseases. It is known that the CB1 regulates signaling pathways that control autophagy, however, it is currently unknown whether the ECS could regulate autophagy in the skeletal muscle of obese mice. This study aimed to investigate the role of the CB1 in regulating autophagy in skeletal muscle. We found concomitant deregulation in the ECS and autophagy markers in high-fat diet-induced obesity. In obese CB1-KO mice, the autophagy-associated protein LC3 II does not accumulate when mTOR and AMPK phosphorylation levels do not change. Acute inhibition of the CB1 with JD-5037 decreased LC3 II protein accumulation and autophagic flux. Our results suggest that the CB1 regulates autophagy in the tibialis anterior skeletal muscle in both lean and obese mice.

CYP4F2 is a human-specific determinant of circulating N-acyl amino acid levels

N-acyl amino acids are a large family of circulating lipid metabolites that modulate energy expenditure and fat mass in rodents. However, little is known about the regulation and potential cardiometabolic functions of N-acyl amino acids in humans. Here, we analyze the cardiometabolic phenotype associations and genetic regulation of four plasma N-fatty acyl amino acids (N-oleoyl-leucine, N-oleoyl-phenylalanine, N-oleoyl-serine, and N-oleoyl-glycine) in 2,351 individuals from the Jackson Heart Study. N-oleoyl-leucine and N-oleoyl-phenylalanine were positively associated with traits related to energy balance, including body mass index, waist circumference, and subcutaneous adipose tissue. In addition, we identify the CYP4F2 locus as a human-specific genetic determinant of plasma N-oleoyl-leucine and N-oleoyl-phenylalanine levels. In vitro, CYP4F2-mediated hydroxylation of N-oleoyl-leucine and N-oleoyl-phenylalanine results in metabolic diversification and production of many previously unknown lipid metabolites with varying characteristics of the fatty acid tail group, including several that structurally resemble fatty acid hydroxy fatty acids (FAHFAs). By contrast, FAAH-regulated N-oleoyl-glycine and N-oleoyl-serine were inversely associated with traits related to glucose and lipid homeostasis. These data uncover a human-specific enzymatic node for the metabolism of a subset of N-fatty acyl amino acids and establish a framework for understanding the cardiometabolic roles of individual N-fatty acyl amino acids in humans.

Fatty Acid Amide Hydrolase: An Integrative Clinical Perspective

Introduction: Fatty acid amide hydrolase (FAAH) is one of the main terminating enzymes of the endocannabinoid system (ECS). Since being discovered in 1996, the modulation of FAAH has been viewed as a compelling alternative strategy to obtain the beneficial effect of the ECS. With a considerable amount of FAAH-related publication over time, the next step would be to comprehend the proximity of this evidence for clinical application. Objective: This review intends to highlight the rationale of FAAH modulation and provide the latest evidence from clinical studies. Methods: Publication searches were conducted to gather information focused on FAAH-related clinical evidence with an extension to the experimental research to understand the biological plausibility. The subtopics were selected to be multidisciplinary to offer more perspective on the current state of the arts. Discussion: Experimental and clinical studies have demonstrated that FAAH was highly expressed not only in the central nervous system but also in the peripheral tissues. As the key regulator of endocannabinoid signaling, it would appear that FAAH plays a role in the modulation of mood and emotional response, reward system, pain perception, energy metabolism and appetite regulation, inflammation, and other biological processes. Genetic variants may be associated with some conditions such as substance/alcohol use disorders, obesity, and eating disorder. The advancement of functional neuroimaging has enabled the evaluation of the neurochemistry of FAAH in brain tissues and this can be incorporated into clinical trials. Intriguingly, the application of FAAH inhibitors in clinical trials seems to provide less striking results in comparison with the animal models, although some potential still can be seen. Conclusion: Modulation of FAAH has an immense potential to be a new therapeutic candidate for several disorders. Further exploration, however, is still needed to ensure who is the best candidate for the treatment strategy.

Fatty acid amide hydrolase C385A polymorphism affects susceptibility to various diseases

The endocannabinoid (eCB) system is an important neuromodulatory system with its extensive network of receptors throughout the human body that has complex actions in the nervous system, immune system, and all of the body's other organs. Fatty acid amide hydrolase (FAAH) is an important membrane-bound homodimeric degrading enzyme that controls the biological activity of N-arachidonoylethanolamide (AEA) in the eCB system and other relevant bioactive lipids. It has been shown that several single nucleotide polymorphisms (SNPs) of FAAH are associated with various phenotypes and diseases including cardiovascular, endocrine, drug abuse, and neuropsychiatric disorders. A common functional and most studied polymorphism of this gene is C385A (rs324420), which results in the replacement of a conserved proline to threonine in the FAAH enzyme structure, leads to a reduction of the activity and expression of FAAH, compromises the inactivation of AEA and causes higher synaptic concentrations of AEA that can be associated with several various phenotypes. The focus of this review is on evidence-based studies on the associations of the FAAH C385A polymorphism and the various diseases or traits. Although there was variability in the results of these reports, the overall consensus is that the FAAH C385A genotype can affect susceptibility to some multifactorial disorders and can be considered a potential therapeutic target.

Anandamide and other N-acylethanolamines: A class of signaling lipids with therapeutic opportunities

N-acylethanolamines (NAEs), including N-palmitoylethanolamine (PEA), N-oleoylethanolamine (OEA), N-arachidonoylethanolamine (AEA, anandamide), N-docosahexaenoylethanolamine (DHEA, synaptamide) and their oxygenated metabolites are a lipid messenger family with numerous functions in health and disease, including inflammation, anxiety and energy metabolism. The NAEs exert their signaling role through activation of various G protein-coupled receptors (cannabinoid CB₁ and CB₂ receptors, GPR55, GPR110, GPR119), ion channels (TRPV1) and nuclear receptors (PPAR-α and PPAR-γ) in the brain and periphery. The biological role of the oxygenated NAEs, such as prostamides, hydroxylated anandamide and DHEA derivatives, are less studied. Evidence is accumulating that NAEs and their oxidative metabolites may be aberrantly regulated or are associated with disease severity in obesity, metabolic syndrome, cancer, neuroinflammation and liver cirrhosis. Here, we comprehensively review NAE biosynthesis and degradation, their metabolism by lipoxygenases, cyclooxygenases and cytochrome P450s and the biological functions of these signaling lipids. We discuss the latest findings and therapeutic potential of modulating endogenous NAE levels by inhibition of their degradation, which is currently under clinical evaluation for neuropsychiatric disorders. We also highlight NAE biosynthesis inhibition as an emerging topic with therapeutic opportunities in endocannabinoid and NAE signaling.

Impact of selenium on the intestinal microbiome-eCBome axis in the context of diet-related metabolic health in mice

Dietary micronutrients act at the intestinal level, thereby influencing microbial communities, the host endocannabinoidome, and immune and anti-oxidative response. Selenium (Se) is a trace element with several health benefits. Indeed, Se plays an important role in the regulation of enzymes with antioxidative and anti-inflammatory activity as well as indicators of the level of oxidative stress, which, together with chronic low-grade inflammation, is associated to obesity. To understand how Se variations affect diet-related metabolic health, we fed female and male mice for 28 days with Se-depleted or Se-enriched diets combined with low- and high-fat/sucrose diets. We quantified the plasma and intestinal endocannabinoidome, profiled the gut microbiota, and measured intestinal gene expression related to the immune and the antioxidant responses in the intestinal microenvironment. Overall, we show that intestinal segment-specific microbiota alterations occur following high-fat or low-fat diets enriched or depleted in Se, concomitantly with modifications of circulating endocannabinoidome mediators and changes in cytokine and antioxidant enzyme expression. Specifically, Se enrichment was associated with increased circulating plasma levels of 2-docosahexaenoyl-glycerol (2-DHG), a mediator with putative beneficial actions on metabolism and inflammation. Others eCBome mediators also responded to the diets. Concomitantly, changes in gut microbiota were observed in Se-enriched diets following a high-fat diet, including an increase in the relative abundance of Peptostreptococcaceae and Lactobacillaceae. With respect to the intestinal immune response and anti-oxidative gene expression, we observed a decrease in the expression of proinflammatory genes Il1β and Tnfα in high-fat Se-enriched diets in caecum, while in ileum an increase in the expression levels of the antioxidant gene Gpx4 was observed following Se depletion. The sex of the animal influenced the response to the diet of both the gut microbiota and endocannabinoid mediators. These results identify Se as a regulator of the gut microbiome and endocannabinoidome in conjunction with high-fat diet, and might be relevant to the development of new nutritional strategies to improve metabolic health and chronic low-grade inflammation associated to metabolic disorders.

Circulating endocannabinoid levels in pregnant women with gestational diabetes mellitus: a case-control study

BACKGROUND

The role of the Endocannabinoids (ECs) in insulin resistance, and their association with visceral obesity and metabolic profile have been studied extensively. Since the association between ECs and metabolic factors in Gestational Diabetes Mellitus (GDM) are not clear, we aimed to evaluate the levels of N-Arachidonoylethanolamide (AEA) and 2-Arachidonoylglycerol (2-AG) and their association with C-reactive protein (CRP), glycemic indices, blood pressure, and anthropometric indices in pregnant women with GDM.

METHODS

The present case-control study was conducted among 96 singleton pregnant women aged 18-40 years, including 48 healthy pregnant women (control group) and 48 women with a positive diagnosis of GDM (case group). Odds Ratios (ORs) and 95% Confidence Intervals (CIs) for GDM were checked according to endocannabinoids and anthropometric indices using Multivariable Logistic Regression.

RESULTS

AEA was significantly associated with increased risk of GDM in models 1, 2 and 3 (OR = 1.22, 95% CI: 1.06-1.41; OR = 1.54, 95% CI: 1.19-1.97; OR = 1.46, 95% CI:1.11-1.91). A positive but no significant association was found for AEA in model 4 (OR = 1.38,95% CI: 0.99-1.92). Similar to AEA, 2-AG was also positively associated with the likelihood of GDM in Models 1, 2, and 3 but the association attenuated to null in model 4 (OR = 1.25; 95% CI: 0.94- 1.65).

CONCLUSIONS

Our findings showed that levels of ECs were significantly higher in pregnant women with GDM compared to healthy ones. Also, ECs levels were associated with the likelihood of GDM, independent of BMI and weight gain.

Molecular networks underlying cannabinoid signaling in skeletal muscle plasticity

The cannabinoid system is ubiquitously present and is classically considered to engage in neural and immunity processes. Yet, the role of the cannabinoid system in the whole body and tissue metabolism via central and peripheral mechanisms is increasingly recognized. The present review provides insights in (i) how cannabinoid signaling is regulated via receptor-independent and -dependent mechanisms and (ii) how these signaling cascades (might) affect skeletal muscle plasticity and physiology. Receptor-independent mechanisms include endocannabinoid metabolism to eicosanoids and the regulation of ion channels. Alternatively, endocannabinoids can act as ligands for different classic (cannabinoid receptor 1 [CB₁ ], CB₂ ) and/or alternative (e.g., TRPV1, GPR55) cannabinoid receptors with a unique affinity, specificity, and intracellular signaling cascade (often tissue-specific). Antagonism of CB₁ might hold clues to improve oxidative (mitochondrial) metabolism, insulin sensitivity, satellite cell growth, and muscle anabolism, whereas CB₂ agonism might be a promising way to stimulate muscle metabolism and muscle cell growth. Besides, CB₂ ameliorates muscle regeneration via macrophage polarization toward an anti-inflammatory phenotype, induction of MyoD and myogenin expression and antifibrotic mechanisms. Also TRPV1 and GPR55 contribute to the regulation of muscle growth and metabolism. Future studies should reveal how the cannabinoid system can be targeted to improve muscle quantity and/or quality in conditions such as ageing, disease, disuse, and metabolic dysregulation, taking into account challenges that are inherent to modulation of the cannabinoid system, such as central and peripheral side effects.

Molecular Alterations of the Endocannabinoid System in Psychiatric Disorders

The therapeutic benefits of the current medications for patients with psychiatric disorders contrast with a great variety of adverse effects. The endocannabinoid system (ECS) components have gained high interest as potential new targets for treating psychiatry diseases because of their neuromodulator role, which is essential to understanding the regulation of many brain functions. This article reviewed the molecular alterations in ECS occurring in different psychiatric conditions. The methods used to identify alterations in the ECS were also described. We used a translational approach. The animal models reproducing some behavioral and/or neurochemical aspects of psychiatric disorders and the molecular alterations in clinical studies in post-mortem brain tissue or peripheral tissues were analyzed. This article reviewed the most relevant ECS changes in prevalent psychiatric diseases such as mood disorders, schizophrenia, autism, attentional deficit, eating disorders (ED), and addiction. The review concludes that clinical research studies are urgently needed for two different purposes: (1) To identify alterations of the ECS components potentially useful as new biomarkers relating to a specific disease or condition, and (2) to design new therapeutic targets based on the specific alterations found to improve the pharmacological treatment in psychiatry.

Comparative Transcriptome Analysis Reveals Regulatory Mechanism of Long Non-Coding RNAs during Abdominal Preadipocyte Adipogenic Differentiation in Chickens

Long non-coding RNAs (lncRNAs) are implicated in mammalian adipogenesis and obesity. However, their genome-wide distribution, expression profiles, and regulatory mechanisms during chicken adipogenesis remain rarely understood. In the present study, lncRNAs associated with adipogenesis were identified from chicken abdominal adipocytes at multiple differentiation stages using Ribo-Zero RNA-seq. A total of 15,179 lncRNAs were identified and characterized by stage-specific expression patterns. Of these, 840 differentially expressed lncRNAs were detected, and their cis- and trans-target genes were significantly enriched in multiple lipid-related pathways. Through weighted gene co-expression network analysis (WGCNA) and time-series expression profile clustering analysis, 14 key lncRNAs were identified as candidate regulatory lncRNAs in chicken adipogenic differentiation. The cis- and trans-regulatory interactions of key lncRNAs were constructed based on their differentially expressed cis- and trans-target genes, respectively. We also constructed a competing endogenous RNA (ceRNA) network based on the key lncRNAs, differentially expressed miRNAs, and differentially expressed mRNAs. MSTRG.25116.1 was identified as a potential regulator of chicken abdominal preadipocyte adipogenic differentiation by acting as a transcriptional trans-regulator of fatty acid amide hydrolase (FAAH) gene expression and/or a ceRNA that post-transcriptionally mediates FAAH gene expression by sponging gga-miR-1635.

Bisphenol A (BPA) Leading to Obesity and Cardiovascular Complications: A Compilation of Current In Vivo Study

BPA is one of the most common endocrine disruptors that is widely being manufactured daily nationwide. Although scientific evidence supports claims of negative effects of BPA on humans, there is also evidence suggesting that a low level of BPA is safe. However, numerous in vivo trials contraindicate with this claim and there is a high possibility of BPA exposure could lead to obesity. It has been speculated that this does not stop with the exposed subjects only, but may also cause transgenerational effects. Direct disruption of endocrine regulation, neuroimmune and signaling pathways, as well as gut microbiata, has been identified to be interrupted by BPA exposure, leading to overweight or obesity. In these instances, cardiovascular complications are one of the primary notable clinical signs. In regard to this claim, this review paper discusses the role of BPA on obesity in the perspective of endocrine disruptions and possible cardiovascular complications that may arise due to BPA. Thus, the aim of this review is to outline the changes in gut microbiota and neuroimmune or signaling mechanisms involved in obesity in relation to BPA. To identify potentially relevant articles, a depth search was done on the databases Nature, PubMed, Wiley Online Library, and Medline & Ovid from the past 5 years. According to Boolean operator guideline, selected keywords such as (1) BPA OR environmental chemical AND fat OR LDL OR obese AND transgenerational effects or phenocopy (2) Endocrine disruptors OR chemical AND lipodystrophy AND phenocopy (3) Lipid profile OR weight changes AND cardiovascular effect (4) BPA AND neuroimmune OR gene signaling, were used as search terms. Upon screening, 11 articles were finalized to be further reviewed and data extraction tables containing information on (1) the type of animal model (2) duration and dosage of BPA exposure (3) changes in the lipid profile or weight (4) genes, signaling mechanism, or any neuroimmune signal involved, and (5) transgenerational effects were created. In toto, the study indicates there are high chances of BPA exposure affecting lipid profile and gene associated with lipolysis, leading to obesity. Therefore, this scoping review recapitulates the possible effects of BPA that may lead to obesity with the evidence of current in vivo trials. The biomarkers, safety concerns, recommended dosage, and the impact of COVID-19 on BPA are also briefly described.

The Endocannabinoid System and Eating Behaviours: a Review of the Current State of the Evidence

PURPOSE OF THE REVIEW

The endocannabinoid system (ENS) has emerged as an important factor in food intake and may have implications for nutrition research. The objective of the current report is to summarise the available evidence on the ENS and eating behaviour from both animal and human studies.

RECENT FINDINGS

The literature reviewed demonstrates a clear link between the ENS and eating behaviours. Overall, studies indicate that 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA) via cannabinoid receptor-1 (CNR1) binding may stimulate hunger and food intake while oleylethanolamide (OEA) may inhibit hunger. Mechanisms of these associations are not yet well understood, although the evidence suggests that there may be interactions with other physiological systems to consider. Most studies have been conducted in animal models, with few human studies available. Additional research is warranted among human populations into the ENS and eating behaviour. Evaluation of relationships between variation in ENS genes and dietary outcomes is an important area for investigation.

Potential of Fatty Acid Amide Hydrolase (FAAH), Monoacylglycerol Lipase (MAGL), and Diacylglycerol Lipase (DAGL) Enzymes as Targets for Obesity Treatment: A Narrative Review

The endocannabinoid system (ECS) plays an integral role in maintaining metabolic homeostasis and may affect hunger, caloric intake, and nutrient absorption. Obesity has been associated with higher levels of the endogenous cannabinoid transmitters (endocannabinoids). Therefore, the ECS is an important target in obesity treatment. Modulating the enzymes that synthesize and degrade endocannabinoids, namely fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), and diacylglycerol lipase (DAGL), may be a promising strategy to treat obesity. This review aims to synthesize all studies investigating pharmacological or genetic manipulation of FAAH, MAGL, or DAGL enzymes in association with obesity-related measures. Pharmacological inhibition or genetic deletion of FAAH tended to promote an obesogenic state in animal models, though the relationships between human FAAH polymorphisms and obesity-related outcomes were heterogeneous, which could be due to FAAH having both pro-appetitive and anti-appetitive substrates. Genetic deletion of Mgll and Dagla as well as pharmacological inhibition of DAGL tended to reduce body weight and improve metabolic state in animal studies, though the effects of Mgll manipulation were tissue-dependent. Monitoring changes in body weight in ongoing clinical trials of FAAH inhibitors may clarify whether FAAH inhibition is a potential therapeutic strategy for treatment obesity. More preclinical work is needed to characterize the role of MAGL and DAGL modulation in obesity-related outcomes.

The Endocannabinoid System and Cannabidiol: Past, Present, and Prospective for Cardiovascular Diseases

In the past, cannabis was commonly associated with mysticism and illegality. Fortunately, in recent years perspectives and discourses have changed. More prominence has been given to the rigorous scientific effort that led to the discovery of cannabis' many physiological actions and endogenous signalling mechanisms. The endocannabinoid system is a complex and heterogeneous pro-homeostatic network comprising different receptors with several endogenous ligands, numerous metabolic enzymes and regulatory proteins. Therefore, it is not surprising that alterations and dysfunctions of the endocannabinoid system are observed in almost every category of disease. Such high degree of pathophysiological involvement suggests the endocannabinoid system is a promising therapeutic target and prompted the translation of resurgent scientific findings into clinical therapies. Shifting attitudes toward cannabis also raised other matters such as increased patient awareness, prescription requests, self-medication, recreational use, recognition of new knowledge gaps, renewed scientific activity, and seemingly exponential growth of the cannabis industry. This review, following a general overview of cannabis and the endocannabinoid system, assiduously describes its role within the context of cardiovascular diseases, paying particular attention to the Janus influence that endocannabinoid system modulators can have on the cardiovascular system.

Roles of Endocannabinoids and Endocannabinoid-like Molecules in Energy Homeostasis and Metabolic Regulation: A Nutritional Perspective

The endocannabinoid system is involved in signal transduction in mammals. It comprises principally G protein-coupled cannabinoid receptors and their endogenous agonists, called endocannabinoids, as well as the enzymes and transporters responsible for the metabolism of endocannabinoids. Two arachidonic acid-containing lipid molecules, arachidonoylethanolamide (anandamide) and 2-arachidonoylglycerol, function as endocannabinoids. N-acylethanolamines and monoacylglycerols, in which the arachidonic acid chain is replaced with a saturated or monounsaturated fatty acid, are not directly involved in the endocannabinoid system but exhibit agonistic activities for other receptors. These endocannabinoid-like molecules include palmitoylethanolamide, oleoylethanolamide (OEA), and 2-oleoylglycerol. Endocannabinoids stimulate feeding behavior and the anabolism of lipids and glucose, while OEA suppresses appetite. Both central and peripheral systems are included in these nutritional and metabolic contexts. Therefore, they have potential in the treatment and prevention of obesity. We outline the structure, metabolism, and biological activities of endocannabinoids and related molecules, and focus on their involvement in energy homeostasis and metabolic regulation. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Role of the Endocannabinoid System in the Adipose Tissue with Focus on Energy Metabolism

The endocannabinoid system is involved in a wide range of processes including the control of energy acquisition and expenditure. Endocannabinoids and their receptors are present in the central nervous system but also in peripheral tissues, notably the adipose tissues. The endocannabinoid system interacts with two main hormones regulating appetite, namely leptin and ghrelin. The inhibitory effect of the cannabinoid receptor 1 (CB₁) antagonist rimonabant on fat mass suggested that the endocannabinoid system can also have a peripheral action in addition to its effect on appetite reduction. Thus, several investigations have focused on the peripheral role of the endocannabinoid system in the regulation of metabolism. The white adipose tissue stores energy as triglycerides while the brown adipose tissue helps to dissipate energy as heat. The endocannabinoid system regulates several functions of the adipose tissues to favor energy accumulation. In this review we will describe the presence of the endocannabinoid system in the adipose tissue. We will survey the role of the endocannabinoid system in the regulation of white and brown adipose tissue metabolism and how the eCB system participates in obesity and metabolic diseases.

Effect of liraglutide on neural and peripheral markers of metabolic function during antipsychotic treatment in rats

BACKGROUND

Liraglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist that prevents metabolic side effects of the antipsychotic drugs (APDs) olanzapine and clozapine through unknown mechanisms.

AIM

This study aimed to investigate the effect of chronic APD and liraglutide co-treatment on key neural and peripheral metabolic signals, and acute liraglutide co-treatment on clozapine-induced hyperglycaemia.

METHODS

In study 1, rats were administered olanzapine (2 mg/kg), clozapine (12 mg/kg), liraglutide (0.2 mg/kg), olanzapine + liraglutide co-treatment, clozapine + liraglutide co-treatment or vehicle for six weeks. Feeding efficiency was examined weekly. Examination of brain tissue (dorsal vagal complex (DVC) and mediobasal hypothalamus (MBH)), plasma metabolic hormones and peripheral (liver and kidney) cellular metabolism and oxidative stress was conducted. In study 2, rats were administered a single dose of clozapine (12 mg/kg), liraglutide (0.4 mg/kg), clozapine + liraglutide co-treatment or vehicle. Glucose tolerance and plasma hormone levels were assessed.

RESULTS

Liraglutide co-treatment prevented the time-dependent increase in feeding efficiency caused by olanzapine, which plateaued by six weeks. There was no effect of chronic treatment on melanocortinergic, GABAergic, glutamatergic or endocannabionoid markers in the MBH or DVC. Peripheral hormones and cellular metabolic markers were unaltered by chronic APD treatment. Acute liraglutide co-treatment was unable to prevent clozapine-induced hyperglycaemia, but it did alter catecholamine levels.

CONCLUSION

The unexpected lack of change to central and peripheral markers following chronic treatment, despite the presence of weight gain, may reflect adaptive mechanisms. Further studies examining alterations across different time points are required to continue to elucidate the mechanisms underlying the benefits of liraglutide on APD-induced metabolic side effects.

What Role Does the Endocannabinoid System Play in the Pathogenesis of Obesity?

The endocannabinoid system (ECS) is an endogenous signaling system formed by specific receptors (cannabinoid type 1 and type 2 (CB₁ and CB₂)), their endogenous ligands (endocannabinoids), and enzymes involved in their synthesis and degradation. The ECS, centrally and peripherally, is involved in various physiological processes, including regulation of energy balance, promotion of metabolic process, food intake, weight gain, promotion of fat accumulation in adipocytes, and regulation of body homeostasis; thus, its overactivity may be related to obesity. In this review, we try to explain the role of the ECS and the impact of genetic factors on endocannabinoid system modulation in the pathogenesis of obesity, which is a global and civilizational problem affecting the entire world population regardless of age. We also emphasize that the search for potential new targets for health assessment, treatment, and the development of possible therapies in obesity is of great importance.

Racial and sex differences in the polymorphisms of the endocannabinoid receptor genes in obesity

BACKGROUND

Obesity is a global epidemic and prevalence of obesity is higher in African Americans (AAs) compared to Caucasians. The endocannabinoid system (EC) and polymorphism in the endocannabinoid receptor type 1 (CNR1) gene 3813A/G and 4895A/G and in the fatty acid amide hydrolase (FAAH) are associated with obesity. The objective was to explore racial and sex differences in these polymorphisms and the biochemical abnormalities seen in obesity.

METHODS

A cross-sectional study of 667 subjects (53.67% female; 49.18% AA; 69.72% were obese (body mass index [BMI] ≥30)) were screened for CNR1 3813, 4895 and FAAH 385 polymorphisms using a real-time polymerase chain reaction (PCR) system.

RESULTS

Subjects with FAAH 385 polymorphisms were more likely to be obese (75.14% vs. 67.81, P = 0.046). There were no significant sex differences for CNR1 3813 and CNR1 4895; or between obese and control group. AAs had higher prevalence of CNR1 3813 (OR, 2.80, 95% CI, 1.95-4.04) and FAAH 385 (OR, 2.48, 95% CI, 1.82-3.38). Association between African American race and the three genotypes persisted after adjustment of all the variables (P < 0.001).

CONCLUSION

FAAH 385 polymorphism is more likely seen in obese and in older subjects. AAs had higher prevalence of CNR1 3813 and FAAH 385 polymorphisms; and lower prevalence of CNR1 4895 polymorphism. These findings may explain some of the racial differences, but not the sex differences in the clinical expression of obesity.

Anti-obesity therapy with peripheral CB1 blockers: from promise to safe(?) practice

Pharmacological blockers of the cannabinoid receptor type-1 (CB1) have been considered for a long time as the holy grail of obesity pharmacotherapy. These agents were hastily released in the clinical setting, due to their clear-cut therapeutic efficacy. However, the first generation of these drugs, which were able to target both the brain and peripheral tissues, had serious neuropsychiatric effects, leading authorities to ban their clinical use. New peripherally restricted CB1 blockers, characterized by low brain penetrance, have been developed over the past 10 years. In preclinical studies, these molecules seem to overcome the neuropsychiatric negative effects previously observed with brain-penetrant CB1 inhibitors, while retaining or even outperforming their efficacy. The mechanisms of action of these peripherally restricted compounds are only beginning to emerge, and a balanced discussion of the risk/benefits ratio associated to their possible clinical use is urgently needed, in order to avoid repeating past mistakes. Here, we will critically discuss the advantages and the possible hidden threats associated with the use of peripheral CB1 blockers for the pharmacotherapy of obesity and its associated metabolic complications. We will address whether this novel pharmacological approach might 'compete' with current pharmacotherapies for obesity and diabetes, while also conceptualizing future CB1-based pharmacological trends that may significantly lower the risk/benefits ratio associated with the use of these drugs.

Cooperative enzymatic control of N-acyl amino acids by PM20D1 and FAAH

The N-acyl amino acids are a family of bioactive lipids with pleiotropic physiologic functions, including in energy homeostasis. Their endogenous levels are regulated by an extracellular mammalian N-acyl amino acid synthase/hydrolase called PM20D1 (peptidase M20 domain containing 1). Using an activity-guided biochemical approach, we report the molecular identification of fatty acid amide hydrolase (FAAH) as a second intracellular N-acyl amino acid synthase/hydrolase. In vitro, FAAH exhibits a more restricted substrate scope compared to PM20D1. In mice, genetic ablation or selective pharmacological inhibition of FAAH bidirectionally dysregulates intracellular, but not circulating, N-acyl amino acids. Dual blockade of both PM20D1 and FAAH reveals a dramatic and non-additive biochemical engagement of these two enzymatic pathways. These data establish FAAH as a second intracellular pathway for N-acyl amino acid metabolism and underscore enzymatic division of labor as an enabling strategy for the regulation of a structurally diverse bioactive lipid family.

D3 dopamine receptors and a missense mutation of fatty acid amide hydrolase linked in mouse and men: implication for addiction

The endocannabinoid and dopaminergic systems have independently been implicated in substance use disorder and obesity. We investigated a potential interaction between genetically inherited variation in fatty acid amide hydrolase (FAAH, C385A), which metabolizes the cannabis-like endocannabinoid anandamide, and dopaminergic system, measured by dopamine receptor levels and mRNA. Binding of the dopamine D3 preferring probe [C-11]-(+)-PHNO was measured with positron emission tomography (PET) in 79 human subjects genotyped for the FAAH C385A polymorphism (36/79 AC + AA). Autoradiography with [H-3]-(+)-PHNO and in situ hybridization with a D3-specific S-35 riboprobe were carried out in 30 knock-in mice with the FAAH C385A polymorphism (20/30 AC + AA). We found that the FAAH genetic variant C385A was associated with significantly higher (+)-PHNO binding in both humans and in knock-in mice, and this effect was restricted to D3 selective brain regions (limbic striatum, globus pallidus, and ventral pallidum (9-14%; p < 0.04) in humans and Islands of Calleja (28%; p = 0.036) in mice). In situ hybridization with a D3-specific S-35 riboprobe in FAAH knock-in C385A mice confirmed significantly increased D3 receptor mRNA across examined regions (7-44%; p < 0.02). The association of reduced FAAH function with higher dopamine D3 receptors in human and mouse brain provide a mechanistic link between two brain systems that have been implicated in addiction-risk. This may explain the greater vulnerability for addiction and obesity in individuals with C385A genetic variant and by extension, suggest that a D3 antagonism strategy in substance use disorders should consider FAAH C385A polymorphism.

N-acyl taurines are endogenous lipid messengers that improve glucose homeostasis

Fatty acid amide hydrolase (FAAH) degrades 2 major classes of bioactive fatty acid amides, the N-acylethanolamines (NAEs) and N-acyl taurines (NATs), in central and peripheral tissues. A functional polymorphism in the human FAAH gene is linked to obesity and mice lacking FAAH show altered metabolic states, but whether these phenotypes are caused by elevations in NAEs or NATs is unknown. To overcome the problem of concurrent elevation of NAEs and NATs caused by genetic or pharmacological disruption of FAAH in vivo, we developed an engineered mouse model harboring a single-amino acid substitution in FAAH (S268D) that selectively disrupts NAT, but not NAE, hydrolytic activity. The FAAH-S268D mice accordingly show substantial elevations in NATs without alterations in NAE content, a unique metabolic profile that correlates with heightened insulin sensitivity and GLP-1 secretion. We also show that N-oleoyl taurine (C18:1 NAT), the most abundant NAT in human plasma, decreases food intake, improves glucose tolerance, and stimulates GPR119-dependent GLP-1 and glucagon secretion in mice. Together, these data suggest that NATs act as a class of lipid messengers that improve postprandial glucose regulation and may have potential as investigational metabolites to modify metabolic disease.

Stress and glucocorticoid modulation of feeding and metabolism

This perspective highlights research presented as part of the symposium entitled, "Stress and Glucocorticoid Modulation of Feeding and Metabolism" at the 2018 Neurobiology of Stress Workshop held in Banff, AB, Canada. The symposium comprised five researchers at different career stages who each study different aspects of the interaction between the stress response and metabolic control. Their collective results reveal the complexity of this relationship in terms of behavioural and physiological outcomes. Their work emphasizes the need to consider the level of interaction (cellular, tissue, systems) as well as the timing and context in which the interaction is studied. Rather than a comprehensive review on the work presented at the Symposium, here we discuss recurring themes that emerged at the biennial workshop, which address new avenues of research that will drive the field forward.

The influence of the fatty acid amide hydrolase 385C>A single nucleotide polymorphisms on obesity susceptibility

The chronic over-activation of the endogenously produced cannabinoids in obesity has been demonstrated in several studies. A common 385C>A single nucleotide polymorphism of the fatty acid amide hydrolase, one the most important inactivating enzymes of endogenous cannabinoids, has been shown to be associated with obese phenotype. This study was designed to investigate the FAAH gene polymorphisms and to compare the obesity indices between different genotypes in Iranian overweight/obese women. A total of 180 healthy overweight/obese subjects (BMI = 25 to 40 kg/m²) and 86 normal weight individuals (BMI = 18.5 to 24.9 kg/m²) were genotyped for 385 C/A polymorphism of FAAH using amplification refractory mutation system (ARMS)-PCR. Anthropometric indices including BMI, waist circumference, neck circumference, waist to height ratio, fat mass were evaluated. A written informed consent form was given by the participants. The genotype and allele frequencies were significantly different between the overweight/obese and control groups (P = 0.04). Significant differences were observed between the CC genotype and the AA+CA genotype regarding the anthropometric indices (P < 0.05). Compared to CC group, a higher BMI, WC, WHtR, NC and fat mass was identified in allele A carriers group. After adjusting for age, marital and physical activity status, it was revealed that having the CA/AA genotype increased the probability of obesity risk almost two times (P < 0.05, 95% CI 1.19-3.67). Our findings showed that the frequency of A allele was greater in overweight/obese individuals. Also, a mutation in FAAH gene was associated with higher anthropometric indices and the CA/AA genotype increased significantly the possibility of being obese in Iranian women.

Impact of FAAH genetic variation on fronto-amygdala function during emotional processing

Recent translational studies identified a common endocannabinoid polymorphism, FAAH C385A, in the gene for the fatty acid amide hydrolase (FAAH). This polymorphism alters endocannabinoid anandamide levels, which are known to be involved in the fronto-amygdala circuitry implicated in mood regulation and anxiety-like behaviors. While it has been shown that the variant that selectively enhances fronto-amygdala connectivity at rest is associated with decreased anxiety-like behaviors, no study so far has investigated whether this finding of FAAH-related differential plasticity extends to task-related differential functional expression and regulation during negative emotional processing. Using an imaging genetics approach, this study aimed to replicate and extend prior findings by examining functional activity and task-related connectivity in fronto-amygdala regions during emotion reactivity and emotional down-regulation of negative affect. Therefore, 48 healthy young adults underwent a functional MRI resting state measurement, completed an emotion regulation paradigm and provided self-reports on anxiety and use of emotion regulation strategies. In line with previous studies, preliminary evidence suggests that A-allele carriers demonstrate stronger fronto-amygdala connectivity during rest. In addition, exploratory whole-brain analyses indicate differential functional activity of A-allele carriers during emotion reactivity and emotion regulation. There were no associations with anxiety-related self-reports and use of emotional regulation strategies. Further research using larger samples and polygenic approaches is indicated to clarify the precise role and its underlying mechanisms in emotion processing.

Genetic polymorphisms of the endocannabinoid system in obesity and diabetes

The endocannabinoid system (ECS) is involved in many physiological processes including fertility, pain and energy regulation. The aim of this systematic review was to examine the contribution of single nucleotide polymorphisms (SNPs) of the ECS to adiposity and glucose metabolism. Database searches identified 734 articles, of which 65 were included; these covered 70 SNPs in genes coding for cannabinoid receptors 1 and 2 (CB₁ , CB₂ ), fatty acid amide hydrolase (FAAH) and N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD). No studies included SNPs relating to monoacylglycerol lipase or diacylglycerol lipase. The CB₁ receptor SNP rs1049353 showed 17 associations with lower body mass index (BMI) and fat mass (five studies). It also showed three associations with lower insulin levels (one study). Conversely, the CB₁ receptor SNP rs806368 was associated with increased BMI and waist circumference (two studies). The FAAH SNP rs324420 was associated with increased obesity (three studies). A haplotype of NAPE-PLD was associated with decreased BMI (one study). A total of 60 SNPs showed no association with any measured outcome. This review suggests a complex but important role of ECS SNPs in energy and glucose metabolism.

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.

A Swath Label-Free Proteomics insight into the Faah-/- Mouse Liver

Fatty acid amide hydrolase (FAAH) is an important enzyme for lipid metabolism and an interesting pharmacological target, given its role in anandamide breakdown. The FAAH^−/− genotype is the most widely used mouse model to investigate the effects of a complete pharmacological inhibition of this enzyme. In this paper, we explore, by means of label-free SWATH proteomics, the changes in protein expression occurring in the liver of FAAH^−/− knockout (KO) mice. We identified several altered biological processes and pathways, like fatty acid synthesis and glycolysis, which explain the observed phenotype of this mouse. We also observed the alteration of other proteins, like carboxylesterases and S-methyltransferases, apparently not immediately related to FAAH, but known to have important biological roles. Our study, reporting more than 3000 quantified proteins, offers an in-depth analysis of the liver proteome of this model.

Role for fatty acid amide hydrolase (FAAH) in the leptin-mediated effects on feeding and energy balance

Endocannabinoid signaling regulates feeding and metabolic processes and has been linked to obesity development. Several hormonal signals, such as glucocorticoids and ghrelin, regulate feeding and metabolism by engaging the endocannabinoid system. Similarly, studies have suggested that leptin interacts with the endocannabinoid system, yet the mechanism and functional relevance of this interaction remain elusive. Therefore, we explored the interaction between leptin and endocannabinoid signaling with a focus on fatty acid amide hydrolase (FAAH), the primary degradative enzyme for the endocannabinoid N-arachidonoylethanolamine (anandamide; AEA). Mice deficient in leptin exhibited elevated hypothalamic AEA levels and reductions in FAAH activity while leptin administration to WT mice reduced AEA content and increased FAAH activity. Following high fat diet exposure, mice developed resistance to the effects of leptin administration on hypothalamic AEA content and FAAH activity. At a functional level, pharmacological inhibition of FAAH was sufficient to prevent leptin-mediated effects on body weight and food intake. Using a novel knock-in mouse model recapitulating a common human polymorphism (FAAH C385A; rs324420), which reduces FAAH activity, we investigated whether human genetic variance in FAAH affects leptin sensitivity. While WT (CC) mice were sensitive to leptin-induced reductions in food intake and body weight gain, low-expressing FAAH (AA) mice were unresponsive. These data demonstrate that FAAH activity is required for leptin's hypophagic effects and, at a translational level, suggest that a genetic variant in the FAAH gene contributes to differences in leptin sensitivity in human populations.

Cardiovascular effects of marijuana and synthetic cannabinoids: the good, the bad, and the ugly

Dysregulation of the endogenous lipid mediators endocannabinoids and their G-protein-coupled cannabinoid receptors 1 and 2 (CB1R and CB2R) has been implicated in a variety of cardiovascular pathologies. Activation of CB1R facilitates the development of cardiometabolic disease, whereas activation of CB2R (expressed primarily in immune cells) exerts anti-inflammatory effects. The psychoactive constituent of marijuana, Δ9-tetrahydrocannabinol (THC), is an agonist of both CB1R and CB2R, and exerts its psychoactive and adverse cardiovascular effects through the activation of CB1R in the central nervous and cardiovascular systems. The past decade has seen a nearly tenfold increase in the THC content of marijuana as well as the increased availability of highly potent synthetic cannabinoids for recreational use. These changes have been accompanied by the emergence of serious adverse cardiovascular events, including myocardial infarction, cardiomyopathy, arrhythmias, stroke, and cardiac arrest. In this Review, we summarize the role of the endocannabinoid system in cardiovascular disease, and critically discuss the cardiovascular consequences of marijuana and synthetic cannabinoid use. With the legalization of marijuana for medicinal purposes and/or recreational use in many countries, physicians should be alert to the possibility that the use of marijuana or its potent synthetic analogues might be the underlying cause of severe cardiovascular events and pathologies.