Oleoylethanolamide: A fat ally in the fight against obesity

Unveiling the "hidden quality" of the walnut pellicle: a precious source of bioactive lipids

Tree nut consumption has been widely associated with various health benefits, with walnuts, in particular, being linked with improved cardiovascular and neurological health. These benefits have been attributed to walnuts' vast array of phenolic antioxidants and abundant polyunsaturated fatty acids. However, recent studies have revealed unexpected clinical outcomes related to walnut consumption, which cannot be explained simply with the aforementioned molecular hallmarks. With the goal of discovering potential molecular sources of these unexplained clinical outcomes, an exploratory untargeted metabolomics analysis of the isolated walnut pellicle was conducted. This analysis revealed a myriad of unusual lipids, including oxylipins and endocannabinoids. These lipid classes, which are likely present in the pellicle to enhance the seeds' defenses due to their antimicrobial properties, also have known potent bioactivities as mammalian signaling molecules and homeostatic regulators. Given the potential value of this tissue for human health, with respect to its "bioactive" lipid fraction, we sought to quantify the amounts of these compounds in pellicle-enriched waste by-products of mechanized walnut processing in California. An impressive repertoire of these compounds was revealed in these matrices, and in notably significant concentrations. This discovery establishes these low-value agriculture wastes promising candidates for valorization and translation into high-value, health-promoting products; as these molecules represent a potential explanation for the unexpected clinical outcomes of walnut consumption. This "hidden quality" of the walnut pellicle may encourage further consumption of walnuts, and walnut industries may benefit from a revaluation of abundant pellicle-enriched waste streams, leading to increased sustainability and profitability through waste upcycling.

Enhancing chronic wound healing with Thai indigenous rice variety, Kaab Dum: Exploring ER stress and senescence inhibition in HaCaT keratinocyte cell line

Kaab Dum, a prominent indigenous rice variety cultivated in the Pak Phanang Basin of Nakhon Si Thammarat, Thailand, is the focus of our study. We investigate the therapeutic potential of indigenous Kaab Dum rice extract in the context of chronic wounds. Our research encompasses an examination of the nutritional compositions and chemical profiles of Kaab Dum rice extract. Additionally, we assess how the extract affects chronic wounds in TGF-β-induced HaCaT cells. Our evaluation methods include the detection of cellular oxidative stress, the examination of endoplasmic reticulum (ER) stress, wound healing assays, analysis of cell cycle arrest and the study of cellular senescence through senescence-associated β-galactosidase (SA-β-gal) staining. Our research findings demonstrate that TGF-β induces oxidative stress in HaCaT cells, which subsequently triggers ER stress, confirmed by the expression of the PERK protein. This ER stress results in cell cycle arrest in HaCaT cells, characterized by an increase in p21 protein, a cyclin-dependent kinase inhibitor (CDKI). Ultimately, this leads to cellular senescence, as confirmed by SA-β-gal staining. Importantly, our study reveals the effectiveness of Kaab Dum rice extract in promoting wound healing in the chronic wound model. The extract reduces ER stress and senescent cells. These beneficial effects are potentially linked to the antioxidant and anti-inflammatory properties of the rice extract. The findings of our study have the potential to make significant contributions to the development of enhanced products for both the prevention and treatment of chronic wounds.

Olive oil-derived endocannabinoid-like mediators inhibit palatable food-induced reward and obesity

N-oleoylglycine (OlGly), a lipid derived from the basic component of olive oil, oleic acid, and N-oleoylalanine (OlAla) are endocannabinoid-like mediators. We report that OlGly and OlAla, by activating the peroxisome proliferator-activated receptor alpha (PPARα), reduce the rewarding properties of a highly palatable food, dopamine neuron firing in the ventral tegmental area, and the obesogenic effect of a high-fat diet rich in lard (HFD-L). An isocaloric olive oil HFD (HFD-O) reduced body weight gain compared to the HFD-L, in a manner reversed by PPARα antagonism, and enhanced brain and intestinal OlGly levels and gut microbial diversity. OlGly or OlAla treatment of HFD-L mice resulted in gut microbiota taxonomic changes partly similar to those induced by HFD-O. We suggest that OlGly and OlAla control body weight by counteracting highly palatable food overconsumption, and possibly rebalancing the gut microbiota, and provide a potential new mechanism of action for the obeso-preventive effects of olive oil-rich diets.

The Role of the Endocannabinoid System in Binge Eating Disorder

Eating disorders are multifactorial disorders that involve maladaptive feeding behaviors. Binge eating disorder (BED), the most prevalent of these in both men and women, is characterized by recurrent episodes of eating large amounts of food in a short period of time, with a subjective loss of control over eating behavior. BED modulates the brain reward circuit in humans and animal models, which involves the dynamic regulation of the dopamine circuitry. The endocannabinoid system plays a major role in the regulation of food intake, both centrally and in the periphery. Pharmacological approaches together with research using genetically modified animals have strongly highlighted a predominant role of the endocannabinoid system in feeding behaviors, with the specific modulation of addictive-like eating behaviors. The purpose of the present review is to summarize our current knowledge on the neurobiology of BED in humans and animal models and to highlight the specific role of the endocannabinoid system in the development and maintenance of BED. A proposed model for a better understanding of the underlying mechanisms involving the endocannabinoid system is discussed. Future research will be necessary to develop more specific treatment strategies to reduce BED symptoms.

Profound Modification of Fatty Acid Profile and Endocannabinoid-Related Mediators in PPARα Agonist Fenofibrate-Treated Mice

Fenofibrate (FBR), an oral medication used to treat dyslipidemia, is a ligand of the peroxisome proliferator-activated receptor α (PPARα), a nuclear receptor that regulates the expression of metabolic genes able to control lipid metabolism and food intake. PPARα natural ligands include fatty acids (FA) and FA derivatives such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), known to have anti-inflammatory and anorexigenic activities, respectively. We investigated changes in the FA profile and FA derivatives by HPLC and LC-MS in male C57BL/6J mice fed a standard diet with or without 0.2% fenofibrate (0.2% FBR) for 21 days. Induction of PPARα by 0.2% FBR reduced weight gain, food intake, feed efficiency, and liver lipids and induced a profound change in FA metabolism mediated by parallel enhanced mitochondrial and peroxisomal β-oxidation. The former effects led to a steep reduction of essential FA, particularly 18:3n3, with a consequent decrease of the n3-highly unsaturated fatty acids (HUFA) score; the latter effect led to an increase of 16:1n7 and 18:1n9, suggesting enhanced hepatic de novo lipogenesis with increased levels of hepatic PEA and OEA, which may activate a positive feedback and further sustain reductions of body weight, hepatic lipids and feed efficiency.

OEA alleviates apoptosis in diabetic rats with myocardial ischemia/reperfusion injury by regulating the PI3K/Akt signaling pathway through activation of TRPV1

Reperfusion therapy after myocardial infarction may lead to myocardial injury, which can be complicated and exacerbated by diabetes. The existing therapeutic methods for myocardial ischemia-reperfusion injury (MIRI) in diabetic patients are not ideal. Oleoylethanolamide (OEA) has been found to have protective effects on diabetes and acute cerebral ischemia. This study aimed to determine whether OEA can alleviate MIRI in diabetic rats, and to explore the underlying mechanism. The model of diabetic rats with MIRI was established by blocking the left coronary artery for 30 min, followed by restoring blood flow stability for 120 min. The myocardial enzyme spectrum, area of MIRI, and expression levels of apoptosis-related proteins were detected. The results showed that OEA pretreatment could reduce myocardial infarction area, protect myocardial tissue structure, and reduce myocardial cell apoptosis in diabetic rats with MIRI. Meanwhile, the levels of creatine kinase (CK)-MB (CK-MB), lactate dehydrogenase (LDH), and malondialdehyde (MDA) were reduced, while superoxide dismutase (SOD) level was elevated. H9C2 cells were treated with high glucose and oxygen-glucose deprivation/reperfusion (OGD/R) to establish an in vitro model. Capsazepine (CPZ), an antagonist of transient receptor potential vanilloid subtype 1 (TRPV1), and LY294002, an inhibitor of PI3K, were used to treat H9C2 cells in vitro. Apoptosis level and the expression levels of apoptosis-related proteins were measured. It was found that OEA activated TRPV1 and the PI3K/Akt signaling pathway, downregulated the expression levels of apoptosis-related proteins (Bcl-2 and cleaved caspase-3), and ameliorated the apoptosis of H9C2 cells treated with high glucose and OGD/R. This study clarified that OEA, as a TRPV1 agonist, could reduce myocardial cell apoptosis by activating the PI3K/Akt signaling pathway in diabetic rats with MIRI. The findings may provide a theoretical basis for administration of OEA as a potential therapeutic agent into diabetic patients with MIRI.

Formation of N-acyl-phosphatidylethanolamines by cytosolic phospholipase A2ε in an ex vivo murine model of brain ischemia

N-Acyl-phosphatidylethanolamines (NAPEs), a minor class of membrane glycerophospholipids, accumulate along with their bioactive metabolites, N-acylethanolamines (NAEs) during ischemia. NAPEs can be formed through N-acylation of phosphatidylethanolamine by cytosolic phospholipase A₂ε (cPLA₂ε, also known as PLA2G4E) or members of the phospholipase A and acyltransferase (PLAAT) family. However, the enzyme responsible for the NAPE production in brain ischemia has not yet been clarified. Here, we investigated a possible role of cPLA₂ε using cPLA₂ε-deficient (Pla2g4e^-/-) mice. As analyzed with brain homogenates of wild-type mice, the age dependency of Ca²⁺-dependent NAPE-forming activity showed a bell-shape pattern being the highest at the first week of postnatal life, and the activity was completely abolished in Pla2g4e^-/- mice. However, liquid chromatography-tandem mass spectrometry revealed that the NAPE levels of normal brain were similar between wild-type and Pla2g4e^-/- mice. In contrast, post-mortal accumulations of NAPEs and most species of NAEs were only observed in decapitated brains of wild-type mice. These results suggested that cPLA₂ε is responsible for Ca²⁺-dependent formation of NAPEs in the brain as well as the accumulation of NAPEs and NAEs during ischemia, while other enzyme(s) appeared to be involved in the maintenance of basal NAPE levels.

Peroxisome Proliferator–Activated Receptor-α: A Pivotal Regulator of the Gastrointestinal Tract

Peroxisome proliferator–activated receptor (PPAR)-α is a ligand-activated transcription factor distributed in various tissues and cells. It regulates lipid metabolism and plays vital roles in the pathology of the cardiovascular system. However, its roles in the gastrointestinal tract (GIT) are relatively less known. In this review, after summarizing the expression profile of PPAR-α in the GIT, we analyzed its functions in the GIT, including physiological control of the lipid metabolism and pathologic mediation in the progress of inflammation. The mechanism of this regulation could be achieved via interactions with gut microbes and further impact the maintenance of body circadian rhythms and the secretion of nitric oxide. These are also targets of PPAR-α and are well-described in this review. In addition, we also highlighted the potential use of PPAR-α in treating GIT diseases and the inadequacy of clinical trials in this field.

Qualitative and Quantitative Analysis of Six Fatty Acid Amides in 11 Edible Vegetable Oils Using Liquid Chromatography-Mass Spectrometry

Fatty acid amides (FAAs) are endogenous lipid molecules that exhibit various physiological activities. FAAs are usually present at nanomolar levels in biological samples. In this study, a method for the qualitative and quantitative determination of six FAAs (linoleamide, linoleoyl ethanolamide, oleoyl ethanolamide, palmitic amide, oleamide, and octadecanamide) in edible vegetable oils was established. All six FAAs were detected in sesame, peanut, soybean (decolorized and non-decolorized), and blended oils; five in sunflower oil; four in rice oil; three in linseed and olive oils; and two in corn and canola oils. The total contents of FAAs were highest in sesame oil (104.88 ± 3.01 μg/mL), followed by peanut oil (34.96 ± 3.87 μg/mL), soybean oil (16.75 ± 1.27 μg/mL), and blended oil (13.33 ± 0.77 μg/mL), and the contents in the other edible vegetable oils were all <1.03 μg/mL. The concentrations of linoleoyl ethanolamide and oleoyl ethanolamide were highest in non-decolorized soybean oil, while the other four FAAs (linoleamide, palmitic amide, oleamide, and octadecanamide) showed the highest concentrations in sesame oil. The total contents of these FAAs in eight different oils were higher than those in biological fluids and tissue. Our study confirmed that edible vegetable oils are rich in FAAs, and provides reliable data for evaluating the nutritive value of vegetable oils.

Integrative Hedonic and Homeostatic Food Intake Regulation by the Central Nervous System: Insights from Neuroimaging

Food intake regulation in humans is a complex process controlled by the dynamic interaction of homeostatic and hedonic systems. Homeostatic regulation is controlled by appetitive signals from the gut, adipose tissue, and the vagus nerve, while conscious and unconscious reward processes orchestrate hedonic regulation. On the one hand, sight, smell, taste, and texture perception deliver potent food-related feedback to the central nervous system (CNS) and influence brain areas related to food reward. On the other hand, macronutrient composition stimulates the release of appetite signals from the gut, which are translated in the CNS into unconscious reward processes. This multi-level regulation process of food intake shapes and regulates human ingestive behavior. Identifying the interface between hormones, neurotransmitters, and brain areas is critical to advance our understanding of conditions like obesity and develop better therapeutical interventions. Neuroimaging studies allow us to take a glance into the central nervous system (CNS) while these processes take place. This review focuses on the available neuroimaging evidence to describe this interaction between the homeostatic and hedonic components in human food intake regulation.

(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.

Effects of Selective Breeding, Voluntary Exercise, and Sex on Endocannabinoid Levels in the Mouse Small-Intestinal Epithelium

The endocannabinoid (eCB) system in the gut communicates with the body and brain as part of the homeostatic mechanisms that affect energy balance. Although perhaps best known for its effects on energy intake, the eCB system also regulates voluntary locomotor behavior. Here, we examined gut eCB concentrations in relation to voluntary exercise, specifically in mice selectively bred for high voluntary wheel running behavior. We measured gut eCBs in four replicate non-selected Control (C) lines and four replicate lines of High Runner (HR) mice that had been selectively bred for 74 generations based on the average number of wheel revolutions on days 5 and 6 of a 6-day period of wheel access when young adults. On average, mice from HR lines run voluntarily on wheels ∼3-fold more than C mice on a daily basis. A recent study showed that circulating levels of primary endocannabinoids 2-arachidonoyl-sn-glycerol (2-AG) and anandamide (AEA) are altered by six days of wheel access, by acute wheel running, and differ between HR and C mice in sex-specific ways [1]. We hypothesized that eCBs in the upper small-intestinal epithelium (i.e., proximal jejunum), a region firmly implicated in eCB signaling, would differ between HR and C mice (linetype), between the sexes, between mice housed with vs. without wheels for six days, and would covary with amounts of acute running and/or home-cage activity (during the previous 30 minutes). We used the same 192 mice as in [1] , half males and half females, half HR and half C (all 8 lines), and half either given or not given access to wheels for six days. We assessed the eCBs, 2-AG and AEA, and their analogs docosahexaenoylglycerol (DHG), docosahexaenoylethanolamide (DHEA), and oleoylethanolamide (OEA). Both 2-AG and DHG showed a significant 3-way interaction of linetype, wheel access, and sex. In addition, HR mice had lower concentrations of 2-AG in the small-intestinal epithelium when compared to C mice, which may be functionally related to differences in locomotor activity or to differences in body composition and/or food consumption. Moreover, the amount of home-cage activity during the prior 30 min was a negative predictor of 2-AG and AEA concentrations in jejunum mucosa, particularly in the mice with no wheel access. Lastly, 2-AG, but not AEA, was significantly correlated with 2-AG in plasma in the same mice.

Fatty Acid Metabolism and Derived-Mediators Distinctive of PPAR-α Activation in Obese Subjects Post Bariatric Surgery

Bariatric surger (BS) is characterized by lipid metabolic changes as a response to the massive release of non-esterified fatty acids (NEFA) from adipose depots. The study aimed at evaluating changes in polyunsaturated fatty acids (PUFA) metabolism and biosynthesis of the lipid mediators N-acylethanolamines (NAE), as indices of nuclear peroxisome proliferator-activated receptor (PPAR)-α activation. The observational study was performed on 35 subjects (27 female, 8 male) with obesity, undergoing bariatric surgery. We assessed plasma FA and NAE profiles by LC-MS/MS, clinical parameters and anthropometric measures before and 1 and 6 months after bariatric surgery. One month after bariatric surgery, as body weight and clinical parameters improved significantly, we found higher plasma levels of N-oleoylethanolamine, arachidonic and a 22:6-n3/20:5-n3 ratio as evidence of PPAR-α activation. These changes corresponded to higher circulating levels of NEFA and a steep reduction of the fat mass. After 6 months 22:6-n3/20:5-n3 remained elevated and fat mass was further reduced. Our data suggest that the massive release of NEFA from adipose tissue at 1-Post, possibly by inducing PPAR-α, may enhance FA metabolism contributing to fat depot reduction and improved metabolic parameters in the early stage. However, PUFA metabolic changes favor n6 PUFA biosynthesis, requiring a nutritional strategy aimed at reducing the n6/n3 PUFA ratio.

A Duet Between Histamine and Oleoylethanolamide in the Control of Homeostatic and Cognitive Processes

In ballet, a pas de deux (in French it means "step of two") is a duet in which the two dancers perform ballet steps together. The suite of dances shares a common theme of partnership. How could we better describe the fine interplay between oleoylethanolamide (OEA) and histamine, two phylogenetically ancient molecules controlling metabolic, homeostatic and cognitive processes? Contrary to the pas de deux though, the two dancers presumably never embrace each other as a dancing pair but execute their "virtuoso solo" constantly exchanging interoceptive messages presumably via vagal afferents, the blood stream, the neuroenteric system. With one exception, which is in the control of liver ketogenesis, as in hepatocytes, OEA biosynthesis strictly depends on the activation of histaminergic H₁ receptors. In this review, we recapitulate our main findings that evidence the interplay of histamine and OEA in the control of food consumption and eating behaviour, in the consolidation of emotional memory and mood, and finally, in the synthesis of ketone bodies. We will also summarise some of the putative underlying mechanisms for each scenario.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid β-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal β-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid β-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid β-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.

The Intestinal Fatty Acid-Enteroendocrine Interplay, Emerging Roles for Olfactory Signaling and Serotonin Conjugates

Intestinal enteroendocrine cells (EECs) respond to fatty acids from dietary and microbial origin by releasing neurotransmitters and hormones with various paracrine and endocrine functions. Much has become known about the underlying signaling mechanisms, including the involvement of G-protein coupled receptors (GPCRs), like free fatty acids receptors (FFARs). This review focusses on two more recently emerging research lines: the roles of odorant receptors (ORs), and those of fatty acid conjugates in gut. Odorant receptors belong to a large family of GPCRs with functional roles that only lately have shown to reach beyond the nasal-oral cavity. In the intestinal tract, ORs are expressed on serotonin (5-HT) and glucagon-like-peptide-1 (GLP-1) producing enterochromaffin and enteroendocrine L cells, respectively. There, they appear to function as chemosensors of microbiologically produced short-, and branched-chain fatty acids. Another mechanism of fatty acid signaling in the intestine occurs via their conjugates. Among them, conjugates of unsaturated long chain fatty acids and acetate with 5-HT, N-acyl serotonins have recently emerged as mediators with immune-modulatory effects. In this review, novel findings in mechanisms and molecular players involved in intestinal fatty acid biology are highlighted and their potential relevance for EEC-mediated signaling to the pancreas, immune system, and brain is discussed.

Neuropeptidergic Control of Feeding: Focus on the Galanin Family of Peptides

Obesity/overweight are important health problems due to metabolic complications. Dysregulation of peptides exerting orexigenic/anorexigenic effects must be investigated in-depth to understand the mechanisms involved in feeding behaviour. One of the most important and studied orexigenic peptides is galanin (GAL). The aim of this review is to update the mechanisms of action and physiological roles played by the GAL family of peptides (GAL, GAL-like peptide, GAL message-associated peptide, alarin) in the control of food intake and to review the involvement of these peptides in metabolic diseases and food intake disorders in experimental animal models and humans. The interaction between GAL and NPY in feeding and energy metabolism, the relationships between GAL and other substances involved in food intake mechanisms, the potential pharmacological strategies to treat food intake disorders and obesity and the possible clinical applications will be mentioned and discussed. Some research lines are suggested to be developed in the future, such as studies focused on GAL receptor/neuropeptide Y Y₁ receptor interactions in hypothalamic and extra-hypothalamic nuclei and sexual differences regarding the expression of GAL in feeding behaviour. It is also important to study the possible GAL resistance in obese individuals to better understand the molecular mechanisms by which GAL regulates insulin/glucose metabolism. GAL does not exert a pivotal role in weight regulation and food intake, but this role is crucial in fat intake and also exerts an important action by regulating the activity of other key compounds under conditions of stress/altered diet.

Food Insecurity and Lipid Profile Abnormalities Are Associated with an Increased Risk of Nonalcoholic Fatty Liver Disease (NAFLD): A Case-Control Study

This case-control study aimed to assess the relationship between food insecurity, its related risk factors and NAFLD among 210 subjects. The demographic and socioeconomic characteristics, anthropometric indices, and food insecurity and depression status were assessed. The prevalence of food insecurity was 56.8% and 26.1% in cases and controls (p < .001), respectively. The chance of NAFLD in the food insecure, depressed, overweight, and obese subjects was 2.2 (95%CI: 1.12-3.43), 1.9 (95%CI: 1.02-3.62), 2.6 (95%CI: 1.81-3.92), and 2.9 (95%CI: 2.02-5.34) times higher than food secured, normal, and normal weight subjects, respectively. A higher waist circumference (men, OR = 2.9, p < .001; women, OR = 2.6, p < .001), a high waist-to-hip ratio (men, OR = 2.3, p < .001; women, OR = 2.7, p < .001), an increased waist-to-height ratio (OR = 2.9, p < .001), and a higher body fat percentage (men, OR = 3.0, p < .001; women, OR = 3.3, p < .001) were associated with an increased risk of NAFLD. The odds of NAFLD increased by increment in serum triglyceride (TG) levels (OR = 2.6, p < .001) and decreased by increase in serum high-density lipoprotein cholesterol (HDL-C) (OR = 0.34, p < .001). Compared to controls, patients with NAFLD were more likely to have higher TG/HDL-C ratio (OR = 3.3, p < .001). It seems food insecurity was an important risk factor for NAFLD. Additionally, some indicators of dyslipidemia significantly increased the risk of NAFLD.

Oleoylethanolamide Ameliorates Dextran Sulfate Sodium-Induced Colitis in Rats

Oleoylethanolamide (OEA) is an endogenous fatty acid ethanolamide known for its anti-inflammatory effects and its influence on gut microbiota composition; however, the effects of OEA in inflammatory bowel disease (IBD) remain unknown. During in vitro experiments, OEA downregulated the expression of tumor necrosis factor (TNF)-α and reduced phosphorylation of inhibitor of kappa (Iκ) Bα induced by lipopolysaccharide in human embryonic kidney cells. Moreover, OEA downregulated the expression of interleukin (IL)-8 and IL-1β and inhibited the phosphorylation of IκBα and p65 induced by TNF-α in human enterocytes (Caco-2). The effect of OEA in reducing the expression of IL-8 was blocked by the peroxisome proliferator-activated receptor (PPAR)-α antagonist. During in vivo experiments on rats, colitis was induced by the oral administration of 8% dextran sulfate sodium from day 0 through day 5, and OEA (20 mg/kg) was intraperitoneally injected once a day from day 0 for 6 days. OEA administration significantly ameliorated the reduction in body weight, the increase in disease activity index score, and the shortening of colon length. In rectums, OEA administration reduced the infiltration of macrophages and neutrophils and tended to reduce the histological score and the expression of inflammatory cytokines. Administration of OEA produced significant improvement in a colitis model, possibly by inhibiting the nuclear factor kappa B signaling pathway through PPAR-α receptors. OEA could be a potential new treatment for IBD.

ALIAmides Update: Palmitoylethanolamide and Its Formulations on Management of Peripheral Neuropathic Pain

Neuropathic pain results from lesions or diseases of the somatosensory nervous system and it remains largely difficult to treat. Peripheral neuropathic pain originates from injury to the peripheral nervous system (PNS) and manifests as a series of symptoms and complications, including allodynia and hyperalgesia. The aim of this review is to discuss a novel approach on neuropathic pain management, which is based on the knowledge of processes that underlie the development of peripheral neuropathic pain; in particular highlights the role of glia and mast cells in pain and neuroinflammation. ALIAmides (autacoid local injury antagonist amides) represent a group of endogenous bioactive lipids, including palmitoylethanolamide (PEA), which play a central role in numerous biological processes, including pain, inflammation, and lipid metabolism. These compounds are emerging thanks to their anti-inflammatory and anti-hyperalgesic effects, due to the down-regulation of activation of mast cells. Collectively, preclinical and clinical studies support the idea that ALIAmides merit further consideration as therapeutic approach for controlling inflammatory responses, pain, and related peripheral neuropathic pain.

The Effects of Diets Enriched in Monounsaturated Oleic Acid on the Management and Prevention of Obesity: a Systematic Review of Human Intervention Studies

Obesity is associated with an increased risk of several major noncommunicable diseases, and is an important public health concern globally. Dietary fat content is a major contributor to the increase in global obesity rates. Changes in dietary habits, such as the quality of fatty acids in the diet, are proposed to prevent obesity and its metabolic complications. In recent years, a number of studies have found that oleic acid (OA), the most common MUFA in daily nutrition, has protective effects against human disease. Importantly, there is emerging evidence indicating the beneficial effects of OA in regulating body weight. Accordingly, the objective of this systematic review was to investigate the effects of diets enriched in monounsaturated OA on the management and prevention of obesity, emphasizing possible mechanisms of action of OA in energy homeostasis. Searches were performed in PubMed/MEDLINE, ScienceDirect, Scopus, ProQuest, and Google Scholar databases for clinical trials that examined the effects of diets rich in OA on obesity. Of 821 full-text articles assessed, 28 clinical trials were included in the present study. According to the studies examined in this review, diets enriched in OA can influence fat balance, body weight, and possibly energy expenditure. Importantly, abdominal fat and central obesity can be reduced following consumption of high-OA-containing meals. Mechanistically, OA-rich diets can be involved in the regulation of food intake, body mass, and energy expenditure by stimulating AMP-activated protein kinase signaling. Other proposed mechanisms include the prevention of the nucleotide-binding oligomerization domain-like receptor 3/caspase-1 inflammasome pathway, the induction of oleoylethanolamide synthesis, and possibly the downregulation of stearoyl-CoA desaturase 1 activity. In summary, current findings lend support to advice not restricting consumption of OA-rich meals so as to maintain a healthy body weight.

Symmetrically substituted dichlorophenes inhibit N-acyl-phosphatidylethanolamine phospholipase D

N-Acyl-phosphatidylethanolamine phospholipase D (NAPE-PLD) (EC 3.1.4.4) catalyzes the final step in the biosynthesis of N-acyl-ethanolamides. Reduced NAPE-PLD expression and activity may contribute to obesity and inflammation, but a lack of effective NAPE-PLD inhibitors has been a major obstacle to elucidating the role of NAPE-PLD and N-acyl-ethanolamide biosynthesis in these processes. The endogenous bile acid lithocholic acid (LCA) inhibits NAPE-PLD activity (with an IC50 of 68 μm), but LCA is also a highly potent ligand for TGR5 (EC50 0.52 μm). Recently, the first selective small-molecule inhibitor of NAPE-PLD, ARN19874, has been reported (having an IC50 of 34 μm). To identify more potent inhibitors of NAPE-PLD, here we used a quenched fluorescent NAPE analog, PED-A1, as a substrate for recombinant mouse Nape-pld to screen a panel of bile acids and a library of experimental compounds (the Spectrum Collection). Muricholic acids and several other bile acids inhibited Nape-pld with potency similar to that of LCA. We identified 14 potent Nape-pld inhibitors in the Spectrum Collection, with the two most potent (IC50 = ∼2 μm) being symmetrically substituted dichlorophenes, i.e. hexachlorophene and bithionol. Structure-activity relationship assays using additional substituted dichlorophenes identified key moieties needed for Nape-pld inhibition. Both hexachlorophene and bithionol exhibited significant selectivity for Nape-pld compared with nontarget lipase activities such as Streptomyces chromofuscus PLD or serum lipase. Both also effectively inhibited NAPE-PLD activity in cultured HEK293 cells. We conclude that symmetrically substituted dichlorophenes potently inhibit NAPE-PLD in cultured cells and have significant selectivity for NAPE-PLD versus other tissue-associated lipases.

Oleoylethanolamide Increases Glycogen Synthesis and Inhibits Hepatic Gluconeogenesis via the LKB1/AMPK Pathway in Type 2 Diabetic Model

Oleoylethanolamide (OEA) is an endogenous peroxisome proliferator-activated receptor α (PPARα) agonist that acts on the peripheral control of energy metabolism. However, its therapeutic potential and related mechanisms in hepatic glucose metabolism under type 2 diabetes mellitus (T2DM) are not clear. Here, OEA treatment markedly improved glucose homeostasis in a PPARα-independent manner. OEA efficiently promoted glycogen synthesis and suppressed gluconeogenesis in mouse primary hepatocytes and liver tissue. OEA enhanced hepatic glycogen synthesis and inhibited gluconeogenesis via liver kinase B1 (LKB1)/5' AMP-activated protein kinase (AMPK) signaling pathways. PPARα was not involved in the roles of OEA in the LKB1/AMPK pathways. We found that OEA exerts its antidiabetic effect by increasing glycogenesis and decreasing gluconeogenesis via the LKB1/AMPK pathway. The ability of OEA to control hepatic LKB1/AMPK pathways may serve as a novel therapeutic approach for the treatment of T2DM. SIGNIFICANCE STATEMENT: Oleoylethanolamide (OEA) exerted a potent antihyperglycemic effect in a peroxisome proliferator-activated receptor α-independent manner. OEA played an antihyperglycemic role primarily via regulation of hepatic glycogen synthesis and gluconeogenesis. The main molecular mechanism of OEA in regulating liver glycometabolism is activating the liver kinase B1/5' AMP-activated protein kinase signaling pathways.

A systematic review of the effects of oleoylethanolamide, a high-affinity endogenous ligand of PPAR-α, on the management and prevention of obesity

Along with an increase in overweight and obesity among all age groups, the development of efficacious and safe anti-obesity strategies for patients, as well as health systems, is critical. Oleoylethanolamide (OEA), a high-affinity endogenous ligand of nuclear receptor peroxisome proliferator-activated receptor alpha (PPAR-α), plays important physiological and metabolic actions. OEA is derived from oleic acid, a monounsaturated fatty acid, which has beneficial effects on body composition and regional fat distribution. The role of OEA in the modulation of food consumption and weight management makes it an attractive molecule requiring further exploration in obesogenic environments. This systematic review was conducted to assess the effects of OEA on the obesity management, with emphasizing on its physiological roles and possible mechanisms of action in energy homeostasis. We searched PubMed/Medline, Google Scholar, ScienceDirect, Scopus, ProQuest, and EMBASE up until September 2019. Out of 712 records screened, 30 articles met the study criteria. The evidence reviewed here indicates that OEA, an endocannabinoid-like compound, leads to satiation or meal termination through PPAR-α activation and fatty acid translocase (FAT)/CD36. Additionally, the lipid-amide OEA stimulates fatty acid uptake, lipolysis, and beta-oxidation, and also promotes food intake control. OEA also exerts satiety-inducing effects by activating the hedonic dopamine pathways and increasing homeostatic oxytocin and brain histamine. In conclusion, OEA may be a key component of the physiological system involved in the regulation of dietary fat consumption and energy homeostasis; therefore, it is suggested as a possible therapeutic agent for the management of obesity.

Impaired brain endocannabinoid tone in the activity-based model of anorexia nervosa

OBJECTIVE

Despite the growing knowledge on the functional relationship between an altered endocannabinoid (eCB) system and development of anorexia nervosa (AN), to date no studies have investigated the central eCB tone in the activity-based anorexia (ABA) model that reproduces key aspects of human AN.

METHOD

We measured levels of two major eCBs, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), those of two eCB-related lipids, oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), and the cannabinoid type-1 receptor (CB1R) density in the brain of female ABA rats, focusing on areas involved in homeostatic and rewarding-related regulation of feeding behavior (i.e., prefrontal cortex, nucleus accumbens, caudato putamen, amygdala, hippocampus and hypothalamus). Analysis was carried out also at the end of recovery from the ABA condition.

RESULTS

At the end of the ABA induction phase, 2-AG was significantly decreased in ABA rats in different brain areas but not in the caudato putamen. No changes were detected in AEA levels in any region, whereas the levels of OEA and PEA were decreased exclusively in the hippocampus and hypothalamus. Furthermore, CB1R density was decreased in the dentate gyrus of hippocampus and in the lateral hypothalamus. After recovery, both 2-AG levels and CB1R density were partially normalized in some areas. In contrast, AEA levels became markedly reduced in all the analyzed areas.

DISCUSSION

These data demonstrate an altered brain eCB tone in ABA rats, further supporting the involvement of an impaired eCB system in AN pathophysiology that may contribute to the maintenance of some symptomatic aspects of the disease.

Intracellular Ca2+-dependent formation of N-acyl-phosphatidylethanolamines by human cytosolic phospholipase A2ε

N-Acyl-phosphatidylethanolamines (NAPEs) are known to be precursors of bioactive N-acylethanolamines (NAEs), including the endocannabinoid arachidonoylethanolamide (anandamide) and anti-inflammatory palmitoylethanolamide. In mammals, NAPEs are produced by N-acyltransferases, which transfer an acyl chain from the sn-1 position of glycerophospholipid to the amino group of phosphatidylethanolamine (PE). Recently, the ɛ isoform of cytosolic phospholipase A₂ (cPLA₂ɛ) was found to be Ca²⁺-dependent N-acyltransferase. However, it was poorly understood which types of phospholipids serve as substrates in living cells. In the present study, we established a human embryonic kidney 293 cell line, in which doxycycline potently induces human cPLA₂ɛ, and used these cells to analyze endogenous substrates and products of cPLA₂ɛ with liquid chromatography-tandem mass spectrometry. When treated with doxycycline and Ca²⁺ ionophore, the cells produced various species of diacyl- and alkenylacyl-types of NAPEs as well as NAEs in large quantities. Moreover, the levels of diacyl- and alkenylacyl-types of PEs and diacyl-phosphatidylcholines (PCs) decreased, while those of lysophosphatidylethanolamines and lysophosphatidylcholines increased. These results suggested that cPLA₂ɛ Ca²⁺-dependently produces NAPEs by utilizing endogenous diacyl- and alkenylacyl-types of PEs as acyl acceptors and diacyl-type PCs and diacyl-type PEs as acyl donors.

The effects of oleoylethanolamide, an endogenous PPAR-α agonist, on risk factors for NAFLD: A systematic review

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease. Recently, some novel compounds have been investigated for the prevention and treatment of NAFLD. Oleoylethanolamide (OEA), an endogenous PPAR-α agonist, has exhibited a plethora of pharmacological properties for the treatment of obesity and other obesity-associated metabolic complications. This systematic review was performed with a focus on the effects of OEA on the risk factors for NAFLD. PubMed, Scopus, Embase, ProQuest, and Google Scholar databases were searched up to December 2018 using relevant keywords. All articles written in English evaluating the effects of OEA on the risk factors for NAFLD were eligible for the review. The evidence reviewed in this article illustrates that OEA regulates multiple biological processes associated with NAFLD, including lipid metabolism, inflammation, oxidative stress, and energy homeostasis through different mechanisms. In summary, many beneficial effects of OEA have led to the understanding that OEA may be an effective therapeutic strategy for the management of NAFLD. Although a wide range of studies have demonstrated the most useful effects of OEA on NAFLD and the associated risk factors, further clinical trials, from both in vivo studies and in vitro experiments, are warranted to verify these outcomes.

The role of intracellular anionic phospholipids in the production of N-acyl-phosphatidylethanolamines by cytosolic phospholipase A2ɛ

N-Acyl-phosphatidylethanolamines (NAPEs) represent a class of glycerophospholipids and serve as the precursors of bioactive N-acylethanolamines, including arachidonoylethanolamide (anandamide), palmitoylethanolamide and oleoylethanolamide. NAPEs are produced in mammals by N-acyltransferases, the enzymes which transfer an acyl chain of glycerophospholipids to the amino group of phosphatidylethanolamine. Recently, the ɛ isoform of cytosolic phospholipase A2 (cPLA2ɛ, also called PLA2G4E) was identified as Ca2+-dependent N-acyltransferase. We showed that the activity is remarkably stimulated by phosphatidylserine (PS) in vitro. In the present study, we investigated whether or not endogenous PS regulates the function of cPLA2ɛ in living cells. When PS synthesis was suppressed by the knockdown of PS synthases in cPLA2ɛ-expressing cells, the cPLA2ɛ level and its N-acyltransferase activity were significantly reduced. Mutagenesis studies revealed that all of C2, lipase and polybasic domains of cPLA2ɛ were required for its proper localization as well as the enzyme activity. Liposome-based assays showed that several anionic glycerophospholipids, including PS, phosphatidic acid and phosphatidylinositol 4,5-bisphosphate, enhance the Ca2+-dependent binding of purified cPLA2ɛ to liposome membrane and stimulate its N-acyltransferase activity. Altogether, these results suggested that endogenous PS and other anionic phospholipids affect the localization and enzyme activity of cPLA2ɛ.

Oleoylethanolamide: A novel pharmaceutical agent in the management of obesity-an updated review

Obesity as a multifactorial disorder has been shown a dramatically growing trend recently. Besides genetic and environmental factors, dysregulation of the endocannabinoid system tone is involved in the pathogenesis of obesity. This study reviewed the potential efficacy of Oleoylethanolamide (OEA) as an endocannabinoid-like compound in the energy homeostasis and appetite control in people with obesity. OEA as a lipid mediator and bioactive endogenous ethanolamide fatty acid is structurally similar to the endocannabinoid system compounds; nevertheless, it is unable to induce to the cannabinoid receptors. Unlike endocannabinoids, OEA negatively acts on the food intake and suppress appetite via various mechanisms. Indeed, OEA as a ligand of PPAR-α, GPR-119, and TRPV1 receptors participates in the regulation of energy intake and energy expenditure, feeding behavior, and weight gain control. OEA delays meal initiation, reduces meal size, and increases intervals between meals. Considering side effects of some approaches used for the management of obesity such as antiobesity drugs and surgery as well as based on sufficient evidence about the protective effects of OEA in the improvement of common abnormalities in people with obese, its supplementation as a novel efficient and FDA approved pharmaceutical agent can be recommended.

Oleoylethanolamide differentially regulates glycerolipid synthesis and lipoprotein secretion in intestine and liver

Dietary fat absorption takes place in the intestine, and the liver mobilizes endogenous fat to other tissues by synthesizing lipoproteins that require apoB and microsomal triglyceride transfer protein (MTP). Dietary fat triggers the synthesis of oleoylethanolamide (OEA), a regulatory fatty acid that signals satiety to reduce food intake mainly by enhancing neural PPARα activity, in enterocytes. We explored OEA's roles in the assembly of lipoproteins in WT and Ppara ^-/- mouse enterocytes and hepatocytes, Caco-2 cells, and human liver-derived cells. In differentiated Caco-2 cells, OEA increased synthesis and secretion of triacylglycerols, apoB secretion in chylomicrons, and MTP expression in a dose-dependent manner. OEA also increased MTP activity and triacylglycerol secretion in WT and knockout primary enterocytes. In contrast to its intestinal cell effects, OEA reduced synthesis and secretion of triacylglycerols, apoB secretion, and MTP expression and activity in human hepatoma Huh-7 and HepG2 cells. Also, OEA reduced MTP expression and triacylglycerol secretion in WT, but not knockout, primary hepatocytes. These studies indicate differential effects of OEA on lipid synthesis and lipoprotein assembly: in enterocytes, OEA augments glycerolipid synthesis and lipoprotein assembly independent of PPARα. Conversely, in hepatocytes, OEA reduces MTP expression, glycerolipid synthesis, and lipoprotein secretion through PPARα-dependent mechanisms.

Oleoylethanolamide modulates glucagon-like peptide-1 receptor agonist signaling and enhances exendin-4-mediated weight loss in obese mice

Long-acting glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists (GLP-1RA), such as exendin-4 (Ex4), promote weight loss. On the basis of a newly discovered interaction between GLP-1 and oleoylethanolamide (OEA), we tested whether OEA enhances GLP-1RA-mediated anorectic signaling and weight loss. We analyzed the effect of GLP-1+OEA and Ex4+OEA on canonical GLP-1R signaling and other proteins/pathways that contribute to the hypophagic action of GLP-1RA (AMPK, Akt, mTOR, and glycolysis). We demonstrate that OEA enhances canonical GLP-1R signaling when combined with GLP-1 but not with Ex4. GLP-1 and Ex4 promote phosphorylation of mTOR pathway components, but OEA does not enhance this effect. OEA synergistically enhanced GLP-1- and Ex4-stimulated glycolysis but did not augment the hypophagic action of GLP-1 or Ex4 in lean or diet-induced obese (DIO) mice. However, the combination of Ex4+OEA promoted greater weight loss in DIO mice than Ex4 or OEA alone during a 7-day treatment. This was due in part to transient hypophagia and increased energy expenditure, phenotypes also observed in Ex4-treated DIO mice. Thus, OEA augments specific GLP-1RA-stimulated signaling but appears to work in parallel with Ex4 to promote weight loss in DIO mice. Elucidating cooperative mechanisms underlying Ex4+OEA-mediated weight loss could, therefore, be leveraged toward more effective obesity therapies.

Bioactive lipids ALIAmides differentially modulate inflammatory responses of distinct subsets of primary human T lymphocytes

Autacoid local injury antagonist amides (ALIAmides) are a family of endogenous bioactive acyl ethanolamides that include the renowned palmitoyl ethanolamide (PEA), oleoyl ethanolamide (OEA), and stearoyl ethanolamide (SEA), and that are involved in several biologic processes such as nociception, lipid metabolism, and inflammation. The role of ALIAmides in the control of inflammatory processes has recently gained much attention and prompted the use of these molecules or their analogs, and the pharmacologic manipulation of their endogenous levels, as plausible therapeutic strategies in the treatment of several chronic inflammatory conditions. Since chronic inflammation is mainly driven by cells of adaptive immunity, particularly T lymphocytes, we aimed at investigating whether such bioactive lipids could directly modulate T-cell responses. We found that OEA, PEA, and eicosatrienoyl ethanolamide (ETEA) could directly inhibit both T-cell responses by reducing their production of TNF-α and IFN-γ from CD8 T cells and TNF-α, IFN-γ and IL-17 from CD4 T cells. Furthermore, neither SEA nor docosatrienoyl ethanolamide (DTEA) could affect cytokine production from both T cell subsets. Interestingly, unlike OEA and ETEA, PEA was also able to enhance de novo generation of forkhead box P3 (FoxP3)-expressing regulatory T cells from CD4-naive T cells. Our findings show for the first time that specific ALIAmides can directly affect different T-cell subsets, and provide proof of their anti-inflammatory role in chronic inflammation, ultimately suggesting that these bioactive lipids could offer novel tools for the management of T-cell dependent chronic inflammatory diseases.-Chiurchiù, V., Leuti, A., Smoum, R., Mechoulam, R., Maccarrone, M. Bioactive lipids ALIAmides differentially modulate inflammatory responses of distinct subsets of primary human T lymphocytes.

Non-endocannabinoid N-acylethanolamines and 2-monoacylglycerols in the intestine

This review focuses on recent findings of the physiological and pharmacological role of non-endocannabinoid N-acylethanolamines (NAEs) and 2-monoacylglycerols (2-MAGs) in the intestine and their involvement in the gut-brain signalling. Dietary fat suppresses food intake, and much research concerns the known gut peptides, for example, glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK). NAEs and 2-MAGs represent another class of local gut signals most probably involved in the regulation of food intake. We discuss the putative biosynthetic pathways and targets of NAEs in the intestine as well as their anorectic role and changes in intestinal levels depending on the dietary status. NAEs can activate the transcription factor PPARα, but studies to evaluate the role of endogenous NAEs are generally lacking. Finally, we review the role of diet-derived 2-MAGs in the secretion of anorectic gut peptides via activation of GPR119. Both PPARα and GPR119 have potential as pharmacological targets for the treatment of obesity and the former for treatment of intestinal inflammation. LINKED ARTICLES: This article is part of a themed section on 8^th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.

Phosphatidylserine-stimulated production of N-acyl-phosphatidylethanolamines by Ca2+-dependent N-acyltransferase

N-acyl-phosphatidylethanolamine (NAPE) is known to be a precursor for various bioactive N-acylethanolamines including the endocannabinoid anandamide. NAPE is produced in mammals through the transfer of an acyl chain from certain glycerophospholipids to phosphatidylethanolamine (PE) by Ca²⁺-dependent or -independent N-acyltransferases. The ε isoform of mouse cytosolic phospholipase A₂ (cPLA₂ε) was recently identified as a Ca²⁺-dependent N-acyltransferase (Ca-NAT). In the present study, we first showed that two isoforms of human cPLA₂ε function as Ca-NAT. We next purified both mouse recombinant cPLA₂ε and its two human orthologues to examine their catalytic properties. The enzyme absolutely required Ca²⁺ for its activity and the activity was enhanced by phosphatidylserine (PS). PS enhanced the activity 25-fold in the presence of 1 mM CaCl₂ and lowered the EC₅₀ value of Ca²⁺ >8-fold. Using a PS probe, we showed that cPLA₂ε largely co-localizes with PS in plasma membrane and organelles involved in the endocytic pathway, further supporting the interaction of cPLA₂ε with PS in living cells. Finally, we found that the Ca²⁺-ionophore ionomycin increased [¹⁴C]NAPE levels >10-fold in [¹⁴C]ethanolamine-labeled cPLA₂ε-expressing cells while phospholipase A/acyltransferase-1, acting as a Ca²⁺-independent N-acyltransferase, was insensitive to ionomycin for full activity. In conclusion, PS potently stimulated the Ca²⁺-dependent activity and human cPLA₂ε isoforms also functioned as Ca-NAT.

Limited Access to a High Fat Diet Alters Endocannabinoid Tone in Female Rats

Emerging evidence suggest an impaired endocannabinoid activity in the pathophysiology of binge eating disorder (BED). Herein, we investigated whether endocannabinoid tone could be modified as a consequence of dietary-induced binge eating in female rats. For this purpose, brain levels of the endocannabinoids anandamide (AEA) and 2-arachidonoyl glycerol (2-AG), as well as two endocannabinoid-like lipids, oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), were assessed in different brain areas involved in the hedonic feeding (i.e., prefrontal cortex, nucleus accumbens, amygdala, hippocampus, and hypothalamus). The brain density of cannabinoid type-1 receptors (CB₁) was also evaluated. Furthermore, we determined plasma levels of leptin, ghrelin, and corticosterone hormones, which are well-known to control the levels of endocannabioids and/or CB1 receptors in the brain. To induce binge eating behavior, rats were subject to an intermittent and limited access to a high fat diet (HFD) (margarine). Three experimental groups were used, all with ad libitum access to chow: control (CTRL), with no access to margarine; low restriction (LR), with 2 h margarine access 7 days/week; high restriction (HR), with 2 h margarine access 3 days/week. Bingeing was established when margarine intake in the HR group exceeded that of the LR group. Our results show that, compared to CTRL, AEA significantly decreased in the caudate putamen, amygdala, and hippocampus of HR group. In contrast, 2-AG significantly increased in the hippocampus while OEA decreased in the hypothalamus. Similar to the HR group, AEA and OEA decreased respectively in the amygdala and hypothalamus and 2-AG increased in the hippocampus of LR group. Moreover, LR group also had AEA decreased in the prefrontal cortex and increased in the nucleus accumbens. In both groups we found the same reduction of CB₁ receptor density in the prefrontal cortex compared to CTRL. Also, LR and HR groups showed alterations in both ghrelin and corticosterone levels, while leptin remained unaltered. In conclusion, our findings show a modified endocannabinoid tone due to margarine exposure, in several brain areas that are known to influence the hedonic aspect of food. Even if not uniquely specific to binge eating, margarine-induced changes in endocannabinoid tone could contributes to the development and maintenance of this behavior.

Oleoylethanolamide: The role of a bioactive lipid amide in modulating eating behaviour

Fatty acid ethanolamides are lipid mediators that regulate a plethora of physiological functions. One such bioactive lipid mediator, oleoylethanolamide (OEA), is a potent agonist of the peroxisome proliferator-activated receptor-alpha (PPAR-α), which modulates increased expression of the fatty acid translocase CD36 that enables the regulation of feeding behaviour. Consumption of dietary fat rich in oleic acid activates taste receptors in the gut activating specific enzymes that lead to the formation of OEA. OEA further combines with PPAR-α to enable fat oxidation in the liver, resulting in enhanced energy production. Evidence suggests that sustained ingestion of a high-fat diet abolishes the anorexic signal of OEA. Additionally, malfunction of the enterocyte that transforms oleic acid produced during fat digestion into OEA might be responsible for reduced satiety and hyperphagia, resulting in overweight and obesity. Thus, OEA anorectic signalling may be an essential element of the physiology and metabolic system regulating dietary fat intake and obesity. The evidence reviewed in this article indicates that intake of oleic acid, and thereby the resulting OEA imparting anorexic properties, is dependent on CD36, PPAR-α, enterocyte fat sensory receptors, histamine, oxytocin and dopamine; leading to increased fat oxidation and enhanced energy expenditure to induce satiety and increase feeding latency; and that a disruption in any of these systems will cease/curb fat-induced satiety.

Mammalian enzymes responsible for the biosynthesis of N-acylethanolamines

Bioactive N-acylethanolamines (NAEs) are ethanolamides of long-chain fatty acids, including palmitoylethanolamide, oleoylethanolamide and anandamide. In animal tissues, NAEs are biosynthesized from membrane phospholipids. The classical "transacylation-phosphodiesterase" pathway proceeds via N-acyl-phosphatidylethanolamine (NAPE), which involves the actions of two enzymes, NAPE-generating Ca²⁺-dependent N-acyltransferase (Ca-NAT) and NAPE-hydrolyzing phospholipase D (NAPE-PLD). Recent identification of Ca-NAT as Ɛ isoform of cytosolic phospholipase A₂ enabled the further molecular biological approaches toward this enzyme. In addition, Ca²⁺-independent NAPE formation was shown to occur by N-acyltransferase activity of a group of proteins named phospholipase A/acyltransferases (PLAAT)-1-5. The analysis of NAPE-PLD-deficient mice confirmed that NAEs can be produced through multi-step pathways bypassing NAPE-PLD. The NAPE-PLD-independent pathways involved three members of the glycerophosphodiesterase (GDE) family (GDE1, GDE4 and GDE7) as well as α/β-hydrolase domain-containing protein (ABHD)4. In this review article, we will focus on recent progress made and latest insights in the enzymes involved in NAE synthesis and their further characterization.