Role of anorectic N-acylethanolamines in intestinal physiology and satiety control with respect to dietary fat

An integrated strategy for in-depth profiling of N-acylethanolamines in biological samples by UHPLC-HRMS

BACKGROUND

N-acylethanolamines (NAEs) are a class of naturally occurring bioactive lipids that play crucial roles in various physiological processes, particularly exhibiting neuroprotective and anti-inflammatory properties. However, the comprehensive profiling of endogenous NAEs in complex biological matrices is challenging due to their low abundance, structural similarity and the limited availability of commercial standards. Here, we propose an integrated strategy for comprehensive profiling of NAEs that combines chemical derivatization and a three-dimensional (3D) prediction model based on quantitative structure-retention time relationship (QSRR) using liquid chromatography coupled with high-resolution tandem mass spectrometry (LC-HRMS).

RESULTS

After acetyl chloride (ACC) derivatization, the detection sensitivity of NAEs was significantly improved. We developed a QSRR prediction model to construct an in-house database for 141 NAEs, encompassing information on RT, MS1 (m/z), and MS/MS spectra. Propargylamine-labeled fatty acids were synthesized as RT calibrants across various analytical conditions to enhance the robustness of the RT prediction model. NAEs in biological samples were then in-depth profiled using parallel reaction monitoring (PRM) acquisition. This integrated strategy identified and annotated a total of 50 NAEs across serum, hippocampus and cortex tissues from a 5xFAD mouse model of Alzheimer's disease (AD). Notably, the levels of polyunsaturated NAEs, particularly NAE 20:5 and NAE 22:6, were significantly decreased in 5xFAD mice compared to WT mice, as confirmed by accurate quantitation using ACC-d0/d3 derivatization.

SIGNIFICANCE

Our integrated strategy exhibits great potential for the in-depth profiling of NAEs in complex biological samples, facilitating the elucidation of NAE functions in diverse physiological and pathological processes.

A human gut Faecalibacterium prausnitzii fatty acid amide hydrolase

Undernutrition in Bangladeshi children is associated with disruption of postnatal gut microbiota assembly; compared with standard therapy, a microbiota-directed complementary food (MDCF) substantially improved their ponderal and linear growth. Here, we characterize a fatty acid amide hydrolase (FAAH) from a growth-associated intestinal strain of Faecalibacterium prausnitzii cultured from these children. This enzyme, expressed and purified from Escherichia coli, hydrolyzes a variety of N-acylamides, including oleoylethanolamide (OEA), neurotransmitters, and quorum sensing N-acyl homoserine lactones; it also synthesizes a range of N-acylamides, notably N-acyl amino acids. Treating germ-free mice with N-oleoylarginine and N-oleolyhistidine, major products of FAAH OEA metabolism, markedly affected expression of intestinal immune function pathways. Administering MDCF to Bangladeshi children considerably reduced fecal OEA, a satiety factor whose levels were negatively correlated with abundance and expression of their F. prausnitzii FAAH. This enzyme, structurally and catalytically distinct from mammalian FAAH, is positioned to regulate levels of a variety of bioactive molecules.

Emerging mechanisms by which endocannabinoids and their derivatives modulate bacterial populations within the gut microbiome

Bioactive lipids such as endocannabinoids serve as important modulators of host health and disease through their effects on various host functions including central metabolism, gut physiology, and immunity. Furthermore, changes to the gut microbiome caused by external factors such as diet or by disease development have been associated with altered endocannabinoid tone and disease outcomes. These observations suggest the existence of reciprocal relationships between host lipid signaling networks and bacterial populations that reside within the gut. Indeed, endocannabinoids and their congeners such as N-acylethanolamides have been recently shown to alter bacterial growth, functions, physiology, and behaviors, therefore introducing putative mechanisms by which these bioactive lipids directly modulate the gut microbiome. Moreover, these potential interactions add another layer of complexity to the regulation of host health and disease pathogenesis that may be mediated by endocannabinoids and their derivatives. This mini review will summarize recent literature that exemplifies how N-acylethanolamides and monoacylglycerols including endocannabinoids can impact bacterial populations in vitro and within the gut microbiome. We also highlight exciting preclinical studies that have engineered gut bacteria to synthesize host N-acylethanolamides or their precursors as potential strategies to treat diseases that are in part driven by aberrant lipid signaling, including obesity and inflammatory bowel diseases.

An overview of food lipids toward food lipidomics

Increasing evidence regarding lipids' beneficial effects on human health has changed the common perception of consumers and dietary officials about the role(s) of food lipids in a healthy diet. However, lipids are a wide group of molecules with specific nutritional and bioactive properties. To understand their true nutritional and functional value, robust methods are needed for accurate identification and quantification. Specific analytical strategies are crucial to target specific classes, especially the ones present in trace amounts. Finding a unique and comprehensive methodology to cover the full lipidome of each foodstuff is still a challenge. This review presents an overview of the lipids nutritionally relevant in foods and new trends in food lipid analysis for each type/class of lipids. Food lipid classes are described following the LipidMaps classification, fatty acids, endocannabinoids, waxes, C8 compounds, glycerophospholipids, glycerolipids (i.e., glycolipids, betaine lipids, and triglycerides), sphingolipids, sterols, sercosterols (vitamin D), isoprenoids (i.e., carotenoids and retinoids (vitamin A)), quinones (i.e., coenzyme Q, vitamin K, and vitamin E), terpenes, oxidized lipids, and oxylipin are highlighted. The uniqueness of each food group: oil-, protein-, and starch-rich, as well as marine foods, fruits, and vegetables (water-rich) regarding its lipid composition, is included. The effect of cooking, food processing, and storage, in addition to the importance of lipidomics in food quality and authenticity, are also discussed. A critical review of challenges and future trends of the analytical approaches and computational methods in global food lipidomics as the basis to increase consumer awareness of the significant role of lipids in food quality and food security worldwide is presented.

Administration of Linoleoylethanolamide Reduced Weight Gain, Dyslipidemia, and Inflammation Associated with High-Fat-Diet-Induced Obesity

Acylethanolamides (NAEs) are bioactive lipids derived from diet fatty acids that modulate important homeostatic functions, including appetite, fatty acid synthesis, mitochondrial respiration, inflammation, and nociception. Among the naturally circulating NAEs, the pharmacology of those derived from either arachidonic acid (Anandamide), oleic acid (OEA), and palmitic acid (PEA) have been extensively characterized in diet-induced obesity. For the present work, we extended those studies to linoleoylethanolamide (LEA), one of the most abundant NAEs found not only in plasma and body tissues but also in foods such as cereals. In our initial study, circulating concentrations of LEA were found to be elevated in overweight humans (body mass index (BMI, Kg/m2) > 25) recruited from a representative population from the south of Spain, together with AEA and the endocannabinoid 2-Arachidonoyl glycerol (2-AG). In this population, LEA concentrations correlated with the circulating levels of cholesterol and triglycerides. In order to gain insight into the pharmacology of LEA, we administered it for 14 days (10 mg/kg i.p. daily) to obese male Sprague Dawley rats receiving a cafeteria diet or a standard chow diet for 12 consecutive weeks. LEA treatment resulted in weight loss and a reduction in circulating triglycerides, cholesterol, and inflammatory markers such as Il-6 and Tnf-alpha. In addition, LEA reduced plasma transaminases and enhanced acetyl-CoA-oxidase (Acox) and Uncoupling protein-2 (Ucp2) expression in the liver of the HFD-fed animals. Although the liver steatosis induced by the HFD was not reversed by LEA, the overall data suggest that LEA contributes to the homeostatic signals set in place in response to diet-induced obesity, potentially contributing with OEA to improve lipid metabolism after high fat intake. The anti-inflammatory response associated with its administration suggests its potential for use as a nutrient supplement in non-alcoholic steatohepatitis.

The emerging role of the endocannabinoidome-gut microbiome axis in eating disorders

Among the sources of chemical signals regulating food intake, energy metabolism and body weight, few have attracted recently as much attention as the expanded endocannabinoid system, or endocannabinoidome (eCBome), and the gut microbiome, the two systems on which this review article is focussed. Therefore, it is legitimate to expect that these two systems also play a major role in the etiopathology of eating disorders (EDs), in particular of anorexia nervosa, bulimia nervosa and binge-eating disorder. The major mechanisms through which, also via interactions with other endogenous signaling systems, the eCBome, with its several lipid mediators and receptors, and the gut microbiome, via its variety of microbial kingdoms, phyla and species, and armamentarium of metabolites, intervene in these disorders, are described here, based on several published studies in either experimental models or patients. Additionally, in view of the emerging multi-faceted cross-talk mechanisms between these two complex systems, we discuss the possibility that the eCBome-gut microbiome axis is also involved in EDs.

Impact of Beauveria bassiana on antioxidant enzyme activities and metabolomic profiles of Spodoptera frugiperda

Spodoptera frugiperda is a pest that poses serious threat to the production of food and crops. Entopathogenic fungi, represented by Beauveria bassiana, has shown potential for S. frugiperda control. However, the mechanism of this biological control of pathogens is not fully understood, such as how antioxidant enzyme activities and metabolic profiles in S. frugiperda larvae are affected when infected by entomopathogenic fungi. This study assessed the antioxidant enzyme activities and shift in metabolomic profile in the S. frugiperda larvae infected with B.bassiana. The results indicate a pattern of initial increase and subsequent decrease in the activities of superoxide dismutase, catalase, and peroxidase in the B.bassiana-infected larvae. And the enzyme activities at 60 h of infection ended significantly lower than those of the uninfected larvae. A total of 93 differential metabolites were identified in the B.bassiana-infected larvae, of which 41 metabolites were up-regulated and 52 were down-regulated. These metabolites mainly included amino acids, nucleotides, lipids, carbohydrates, and their derivatives. Among the changed metabolites, cystathionine, L-tyrosine, L-dopa, arginine, alpha-ketoglutaric acid, D-sedoheptulose-7-phosphate and citric acid were significantly decreased in B. bassiana-infected larvae. This indicated that the fungal infection might impair the ability of S. frugiperda larvae to cope with oxidative stress, leading to a negative impact of organism fitness. Further analyses of key metabolic pathways reveal that B. bassiana infection might affect purine metabolism, arginine biosynthesis, butanoate metabolism, and phenylalanine metabolism of S. frugiperda larvae. The findings from this study will contribute to our understanding of oxidative stress on immune defense in insects, and offer fundamental support for the biological control of S. frugiperda.

Targeting the endocannabinoid system for the treatment of abdominal pain in irritable bowel syndrome

The management of visceral pain in patients with disorders of gut-brain interaction, notably irritable bowel syndrome, presents a considerable clinical challenge, with few available treatment options. Patients are increasingly using cannabis and cannabinoids to control abdominal pain. Cannabis acts on receptors of the endocannabinoid system, an endogenous system of lipid mediators that regulates gastrointestinal function and pain processing pathways in health and disease. The endocannabinoid system represents a logical molecular therapeutic target for the treatment of pain in irritable bowel syndrome. Here, we review the physiological and pathophysiological functions of the endocannabinoid system with a focus on the peripheral and central regulation of gastrointestinal function and visceral nociception. We address the use of cannabinoids in pain management, comparing them to other treatment modalities, including opioids and neuromodulators. Finally, we discuss emerging therapeutic candidates targeting the endocannabinoid system for the treatment of pain in irritable bowel syndrome.

Insights into the constellating drivers of satiety impacting dietary patterns and lifestyle

Food intake and body weight regulation are of special interest for meeting today's lifestyle essential requirements. Since balanced energy intake and expenditure are crucial for healthy living, high levels of energy intake are associated with obesity. Hence, regulation of energy intake occurs through short- and long-term signals as complex central and peripheral physiological signals control food intake. This work aims to explore and compile the main factors influencing satiating efficiency of foods by updating recent knowledge to point out new perspectives on the potential drivers of satiety interfering with food intake regulation. Human internal factors such as genetics, gender, age, nutritional status, gastrointestinal satiety signals, gut enzymes, gastric emptying rate, gut microbiota, individual behavioral response to foods, sleep and circadian rhythms are likely to be important in determining satiety. Besides, the external factors (environmental and behavioral) impacting satiety efficiency are highlighted. Based on mechanisms related to food consumption and dietary patterns several physical, physiological, and psychological factors affect satiety or satiation. A complex network of endocrine and neuroendocrine mechanisms controls the satiety pathways. In response to food intake and other behavioral cues, gut signals enable endocrine systems to target the brain. Intestinal and gastric signals interact with neural pathways in the central nervous system to halt eating or induce satiety. Moreover, complex food composition and structures result in considerable variation in satiety responses for different food groups. A better understanding of foods and factors impacting the efficiency of satiety could be helpful in making smart food choices and dietary recommendations for a healthy lifestyle based on updated scientific evidence.

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.

Mutual Links between the Endocannabinoidome and the Gut Microbiome, with Special Reference to Companion Animals: A Nutritional Viewpoint

There is growing evidence that perturbation of the gut microbiome, known as “dysbiosis”, is associated with the pathogenesis of human and veterinary diseases that are not restricted to the gastrointestinal tract. In this regard, recent studies have demonstrated that dysbiosis is linked to the pathogenesis of central neuroinflammatory disorders, supporting the existence of the so-called microbiome-gut-brain axis. The endocannabinoid system is a recently recognized lipid signaling system and termed endocannabinoidome monitoring a variety of body responses. Accumulating evidence demonstrates that a profound link exists between the gut microbiome and the endocannabinoidome, with mutual interactions controlling intestinal homeostasis, energy metabolism and neuroinflammatory responses during physiological conditions. In the present review, we summarize the latest data on the microbiome-endocannabinoidome mutual link in health and disease, focalizing the attention on gut dysbiosis and/or altered endocannabinoidome tone that may distort the bidirectional crosstalk between these two complex systems, thus leading to gastrointestinal and metabolic diseases (e.g., idiopathic inflammation, chronic enteropathies and obesity) as well as neuroinflammatory disorders (e.g., neuropathic pain and depression). We also briefly discuss the novel possible dietary interventions based not only on probiotics and/or prebiotics, but also, and most importantly, on endocannabinoid-like modulators (e.g., palmitoylethanolamide) for intestinal health and beyond.

(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.

Dietary oleic acid contributes to the regulation of food intake through the synthesis of intestinal oleoylethanolamide

INTRODUCTION

Among the fatty acid ethanolamides (FAEs), oleoylethanolamide (OEA), linoleoylethanolamide (LEA), and palmitoylethanolamide (PEA) are reported to be involved in feeding regulation. In particular, OEA is well characterized as a satiety signal. Following food consumption, OEA is synthesized from oleic acid (OA) via an N-acyl phosphatidylethanolamine-specific phospholipase D-dependent pathway in the gastroenterocytes, and OEA induces satiety by recruiting sensory fibers. Thus, we hypothesized that dietary OA is an important satiety-inducing molecule. However, there has been no direct demonstration of the effect of dietary OA on satiety induction without the influence of the endogenous biosynthesis of OA from stearic acid (SA) or other FAEs.

METHODS

In this study, we used two experimental diets to test our hypothesis: (i) an OA diet (OAD; 38.4 mg of OA/g and 7.2 mg of SA/g) and (ii) a low OA diet (LOAD; 3.1 mg of OA/g and 42.4 mg of SA/g).

RESULTS

Relative to mice fed the OAD, mice fed the LOAD for two weeks exhibited reduced levels of jejunal OEA but not jejunal LEA and PEA. The LOAD-fed mice showed an increase in food intake and body weight gain. Moreover, LOAD-induced increase in food intake was immediately observed after the switch from the OAD, whereas these effects were diminished by the switch back to the OAD. Furthermore, treatment with OA and OEA diminished the effects of LOAD on food intake.

CONCLUSION

Collectively, these results show that dietary OA is a key factor in the reduction of food intake and increase in satiety mediated by OEA signaling.

919 Syrup Alleviates Postpartum Depression by Modulating the Structure and Metabolism of Gut Microbes and Affecting the Function of the Hippocampal GABA/Glutamate System

Postpartum depression (PPD) is a mental disorder that affects pregnant women around the world, with serious consequences for mothers, families, and children. Its pathogenesis remains unclear, and medications for treating PPD that can be used during lactation remain to be identified. 919 syrup (919 TJ) is a Chinese herbal medicine that has been shown to be beneficial in the treatment of postpartum depression in both clinical and experimental studies. The mechanism of action of 919 TJ is unclear. 919 syrup is ingested orally, making the potential interaction between the drug and the gut microbiome impossible to ignore. We therefore hypothesized that 919 syrup could improve the symptoms of postpartum depression by affecting the structure and function of the intestinal flora, thereby altering hippocampal metabolism. We compared changes in hippocampal metabolism, fecal metabolism, and intestinal microflora of control BALB/c mice, mice with induced untreated PPD, and mice with induced PPD treated with 919 TJ, and found that 4-aminobutyric acid (GABA) in the hippocampus corresponded with PPD behaviors. Based on changes in GABA levels, multiple key gut bacterial species (Mucispirillum schaedleri, Bifidobacterium pseudolongum, Desulfovibrio piger, Alloprevotella tannerae, Bacteroides sp.2.1.33B and Prevotella sp. CAG:755) were associated with PPD. Metabolic markers that may represent the function of the intestinal microbiota in mice with PPD were identified (Met-Arg, urocanic acid, thioetheramide-PC, L-pipecolic acid, and linoleoyl ethanolamide). The relationship between these factors is not a simple one-to-one correspondence, but more likely a network of staggered functions. We therefore believe that the composition and function of the entire intestinal flora should be emphasized in research studying the gut and PPD, rather than changes in the abundance of individual bacterial species. The introduction of this concept of “GutBalance” may help clarify the relationship between gut bacteria and systemic disease.

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.

Targeting the endocannabinoid system in diabesity: Fact or fiction?

'Diabesity' refers to a rising epidemic indicated by the intricate relationship between obesity and diabetes. The global prevalence of these coexisting, insidious diseases increases social and economic health burdens at a rapid pace. Numerous reports delineate the involvement of the underlying endocannabinoid (EC) signaling system through the cannabinoid-1 (CB1) receptor in the regulation of metabolism and adiposity. Conversely, EC inverse agonists can result in severe depression and suicidal thoughts through interactions with CB1/2 receptors in the brain. This review attempts to elucidate a possible mechanism for the amelioration of diabesity. Moreover, we also highlight the available targets of the CB1 receptor, which could pave the way for safe and effective therapy.

Diet-derived fruit and vegetable metabolites show sex-specific inverse relationships to osteoporosis status

BACKGROUND

The impact of nutrition on the metabolic profile of osteoporosis (OS) is unknown.

OBJECTIVE

Identify biochemical factors driving the association of fruit and vegetable (FV) intakes with OS prevalence using an untargeted metabolomics approach.

DESIGN

Cross-sectional dietary, anthropometric and plasma metabolite data were examined from the Boston Puerto Rican Osteoporosis Study, n = 600 (46-79 yr).

METHODS

Bone mineral density was assessed by DXA. OS was defined by clinical standards. A culturally adapted FFQ assessed usual dietary intake. Principal components analysis (PCA) of 42 FV items created 6 factors. Metabolomic profiles derived from plasma samples were assessed on a commercial platform. Differences in levels of 525 plasma metabolites between disease groups (OS vs no-OS) were compared using logistic regression; and associations with FV intakes by multivariable linear regression, adjusted for covariates. Metabolites significantly associated with OS status or with total FV intake were analyzed for enrichment in various biological pathways using Mbrole 2.0, MetaboAnalyst, and Reactome, using FDR correction of P-values. Correlation coefficients were calculated as Spearman's rho rank correlations, followed by hierarchical clustering of the resulting correlation coefficients using PCA FV factors and sex-specific sets of OS-associated metabolites.

RESULTS

High FV intake was inversely related to OS prevalence (Odds Ratio = 0.73; 95% CI = 0.57, 0.94; P = 0.01). Several biological processes affiliated with the FV-associating metabolites, including caffeine metabolism, carnitines and fatty acids, and glycerophospholipids. Important processes identified with OS-associated metabolites were steroid hormone biosynthesis in women and branched-chain amino acid metabolism in men. Factors derived from PCA were correlated with the OS-associated metabolites, with high intake of dark leafy greens and berries/melons appearing protective in both sexes.

CONCLUSIONS

These data warrant investigation into whether increasing intakes of dark leafy greens, berries and melons causally affect bone turnover and BMD among middle-aged and older adults at risk for osteoporosis via sex-specific metabolic pathways, and how gene-diet interactions alter these sex-specific metabolomic-osteoporosis links. ClinicalTrials.gov Identifier: NCT01231958.

Impact of Circulating N-Acylethanolamine Levels with Clinical and Laboratory End Points in Hemodialysis Patients

BACKGROUND

Patients with ESRD on maintenance hemodialysis (MHD) are particularly susceptible to dysregulation of energy metabolism, which may manifest as protein energy wasting and cachexia. In recent years, the endocannabinoid system has been shown to play an important role in energy metabolism with potential relevance in ESRD. N-acylethanolamines are a class of fatty acid amides which include the major endocannabinoid ligand, anandamide, and the endogenous peroxisome proliferator-activated receptor-α agonists, oleoylethanolamide (OEA) and palmitoylethanolamide (PEA).

METHODS

Serum concentrations of OEA and PEA were measured in MHD patients and their correlations with various clinical/laboratory indices were examined. Secondarily, we evaluated the association of circulating PEA and OEA levels with 12-month all-cause mortality.

RESULTS

Both serum OEA and PEA levels positively correlated with high-density lipoprotein-cholesterol levels and negatively correlated with body fat and body anthropometric measures. Serum OEA levels correlated positively with serum interleukin-6 (IL-6) (rho = 0.19; p = 0.004). Serum PEA and IL-6 showed a similar but nonsignificant trend (rho = 0.12; p = 0.07). Restricted cubic spline analyses showed that increasing serum OEA and PEA both trended toward higher mortality risk, and these associations were statistically significant for PEA (PEA ≥4.7 pmol/mL; reference: PEA <4.7 pmol/mL) after adjustments in a Cox model (hazard ratio 2.99; 95% confidence interval 1.04, 8.64).

CONCLUSIONS

In MHD patients, OEA and PEA are significantly correlated with variables related to lipid metabolism and body mass. Additionally, higher serum levels of PEA are associated with mortality risk. Future studies are needed to examine the potential mechanisms responsible for these findings and their clinical implications.

Intestinal NAPE-PLD contributes to short-term regulation of food intake via gut-to-brain axis

Our objective was to explore the physiological role of the intestinal endocannabinoids in the regulation of appetite upon short-term exposure to high-fat-diet (HFD) and understand the mechanisms responsible for aberrant gut-brain signaling leading to hyperphagia in mice lacking Napepld in the intestinal epithelial cells (IECs). We generated a murine model harboring an inducible NAPE-PLD deletion in IECs (Napepld^ΔIEC). After an overnight fast, we exposed wild-type (WT) and Napepld^ΔIEC mice to different forms of lipid challenge (HFD or gavage), and we compared the modification occurring in the hypothalamus, in the vagus nerve, and at endocrine level 30 and 60 min after the stimulation. Napepld^ΔIEC mice displayed lower hypothalamic levels of N-oleoylethanolamine (OEA) in response to HFD. Lower mRNA expression of anorexigenic Pomc occurred in the hypothalamus of Napepld^ΔIEC mice after lipid challenge. This early hypothalamic alteration was not the consequence of impaired vagal signaling in Napepld^ΔIEC mice. Following lipid administration, WT and Napepld^ΔIEC mice had similar portal levels of glucagon-like peptide-1 (GLP-1) and similar rates of GLP-1 inactivation. Administration of exendin-4, a full agonist of GLP-1 receptor (GLP-1R), prevented the hyperphagia of Napepld^ΔIEC mice upon HFD. We conclude that in response to lipid, Napepld^ΔIEC mice displayed reduced OEA in brain and intestine, suggesting an impairment of the gut-brain axis in this model. We speculated that decreased levels of OEA likely contributes to reduce GLP-1R activation, explaining the observed hyperphagia in this model. Altogether, we elucidated novel physiological mechanisms regarding the gut-brain axis by which intestinal NAPE-PLD regulates appetite rapidly after lipid exposure.

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.

N-Acylphosphatidylethanolamines and N-acylethanolamines increase in saliva upon food mastication: the influence of the individual nutritional status and fat type in food

This study aimed to evaluate the influence of the individual nutritional status on the salivary concentration of N-acylethanolamines (NAEs), including linoleoylethanolamide (LEA), oleoylethanolamide (OEA), and palmitoylethanolamide (PEA), and their precursors N-acylphosphatidylethanolamines (NAPEs) upon mastication of biscuits containing different fats. Three types of biscuits were formulated with 10% extra-virgin olive oil (EVOB), 10% palm oil (PALMB) or 10% paraffin oil (0% lipids, CONB). Twenty-five healthy subjects, 12 normal weight (NW, 9 F, 30.4 ± 8.7 years) and 13 obese (OB, 8 F, 35.5 ± 10.7 years) participated in a randomized crossover study. Fasting subjects collected unstimulated saliva (US) and stimulated saliva by masticating a parafilm piece (PP), and CONB, EVOB and PALMB. NAPEs, LEA, OEA and PEA were quantified in saliva samples by liquid chromatography-high-resolution mass spectrometry. The results showed that salivary NAPE and NAE concentrations in OB were higher than in NW in both US (NAPEs: 280.0 ± 45.4 ng mL-1vs. 121.8 ± 24.4 ng mL-1, p = 0.015; NAEs: 10.8 ± 1.4 ng mL-1vs. 4.8 ± 0.8 ng mL-1, p = 0.002, respectively) and PP (NAPEs: 259.8 ± 47.1 ng mL-1vs. 121.7 ± 16.9 ng mL-1, p = 0.049; NAEs: 6.1 ± 0.8 ng mL-1vs. 3.8 ± 0.4 ng mL-1, p = 0.03, respectively). NAPE and LEA levels were similar in US and PP, while the levels of OEA and PEA were lower in PP vs. US. Compared to PP, biscuit mastication increased the salivary NAPEs, LEA, OEA and overall NAEs in NW and OB. NAPEs increased in the order of EVOB = CONB > PALMB in NW and EVOB > CONB = PALMB in OB. LEA, OEA and overall NAEs increased similarly with all the biscuits in NW and in the order of EVOB > PALMB > CONB in OB. In contrast, the PEA concentration did not vary in saliva upon biscuit mastication in NW and neither with EVOB in OB, while it lowered with CONB and PALMB in OB. In conclusion, OB showed higher salivary levels of NAPEs and NAEs than NW. Mastication itself did not vary salivary NAPEs and LEA but reduced OEA, PEA and overall NAEs. Biscuit mastication increased salivary NAPEs and all NAEs, but PEA. Altogether, the data suggested that NAPEs and NAEs were released in saliva from biscuits at levels influenced by the individual nutritional status and biscuit type. These findings may have implications in molecular mechanisms underpinning gustatory processes in humans.

Ethanolamides of essential α-linolenic and linoleic fatty acids suppress short-term food intake in rats

Food source has a significant impact on levels of fatty acids and their derivatives, fatty acid ethanolamides (FAEs), in the small intestine and brain. Among non-essential fatty acids, oleic acid and its FAE acutely reduce food intake. However, effects of the essential α-linolenic acid, linoleic acid, and their FAEs on appetite regulation remain undefined. This study tested the hypothesis that α-linolenic acid and linoleic acid mediate acute suppression of food intake through their corresponding FAEs, α-linolenoylethanolamide and linoleoylethanolamide, respectively. To allow for the differentiation of the effects of FAEs and their parent fatty acids, male Wistar rats were injected intraperitoneally with α-linolenic acid, linoleic acid, α-linolenoylethanolamide and linoleoylethanolamide after a 12-hour overnight fast. Short-term food intake, plasma and brain FAE status, and plasma concentrations of insulin and leptin were measured to determine whether these hormones mediate the anorectic effect of FAEs. Both ethanolamides, but not their parent fatty acids, acutely suppressed food intake up to one hour post-treatment and this effect was independent of insulin and leptin hormones. In conclusion, essential α-linolenic and linoleic fatty acids mediate acute suppression of food intake through their corresponding FAEs. These findings may aid in the further research of FAEs as potential therapeutic agents for the management and treatment of obesity.

Steric stabilisers govern the colloidal and chemical stability but not in vitro cellular toxicity of linoleoylethanolamide cubosomes

Linoleoylethanolamide (LEA) is an endogenous lipid with remarkable neuromodulatory properties. However, its therapeutic potential is limited by rapid clearance in vivo, targetability and solubility. This study aimed to formulate LEA into liquid crystalline nanoparticles (cubosomes) as a strategy to address the aforementioned challenges. The influence of three different steric stabilisers: Tween 80 and Pluronic F68, both of which have the potential to interact with receptors expressed at the blood-brain barrier and Pluronic F127 as a control, on colloidal stability, internal structure, chemical stability and cytotoxicity of the dispersions were investigated. We found that for effective stabilization of LEA dispersions, a higher concentration of Tween 80 was required compared to Pluronics. Freshly prepared dispersions showed mean particle size of <250 nm and low PDIs (<0.2), with an Im3m type cubic structure but with different lattice parameters. Upon storage at ambient temperature for a week, increased mean particle size and PDI, with a significant reduction in the concentration of LEA was observed in Tween 80-stabilised dispersions. Greater than 80% cell viability was observed at concentrations of up to 20 μg/mL LEA in the presence of all three stabilisers. Collectively, our results suggest that the stabiliser type influences colloidal and chemical stability but not cytotoxicity of LEA cubosomes. This study highlights the potential of endogenous bioactive lipids to be utilized as core cubosome forming lipids with the view to improving their solubility, rapid clearance and targetability to enable delivery of these bioactive molecules to the brain.

Growth effects of N-acylethanolamines on gut bacteria reflect altered bacterial abundances in inflammatory bowel disease

Inflammatory bowel diseases (IBD) are associated with alterations in gut microbial abundances and lumenal metabolite concentrations, but the effects of specific metabolites on the gut microbiota in health and disease remain largely unknown. Here, we analysed the influences of metabolites that are differentially abundant in IBD on the growth and physiology of gut bacteria that are also differentially abundant in IBD. We found that N-acylethanolamines (NAEs), a class of endogenously produced signalling lipids elevated in the stool of IBD patients and a T-cell transfer model of colitis, stimulated growth of species over-represented in IBD and inhibited that of species depleted in IBD in vitro. Using metagenomic sequencing, we recapitulated the effects of NAEs in complex microbial communities ex vivo, with Proteobacteria blooming and Bacteroidetes declining in the presence of NAEs. Metatranscriptomic analysis of the same communities identified components of the respiratory chain as important for the metabolism of NAEs, and this was verified using a mutant deficient for respiratory complex I. In this study, we identified NAEs as a class of metabolites that are elevated in IBD and have the potential to shift gut microbiota towards an IBD-like composition.

First evidence on the role of palmitoylethanolamide in energy homeostasis in fish

The objective of this study was to investigate the role of palmitoylethanolamide (PEA) in the regulation of energy homeostasis in goldfish (Carassius auratus). We examined the effects of acute or chronic intraperitoneal treatment with PEA (20 μg·g^-1 body weight) on parameters related to food intake and its regulatory mechanisms, locomotor activity, glucose and lipid metabolism, and the possible involvement of transcription factors and clock genes on metabolic changes in the liver. Acute PEA treatment induced a decrease in food intake at 6 and 8 h post-injection, comparable to that observed in mammals. This PEA anorectic effect in goldfish could be mediated through interactions with leptin and NPY, as PEA increased hepatic expression of leptin aI and reduced hypothalamic expression of npy. The PEA chronic treatment reduced weight gain, growth rate, and locomotor activity. The rise in glycolytic potential together with the increased potential of glucose to be transported into liver suggests an enhanced use of glucose in the liver after PEA treatment. In addition, part of glucose may be exported to be used in other tissues. The activity of fatty acid synthase (FAS) increased after chronic PEA treatment, suggesting an increase in the hepatic lipogenic capacity, in contrast with the mammalian model. Such lipogenic increment could be linked with the PEA-induction of REV-ERBα and BMAL1 found after the chronic treatment. As a whole, the present study shows the actions of PEA in several compartments related to energy homeostasis and feeding behavior, supporting a regulatory role for this N-acylethanolamine in fish.

Chemotherapy-induced cachexia dysregulates hypothalamic and systemic lipoamines and is attenuated by cannabigerol

BACKGROUND

Muscle wasting, anorexia, and metabolic dysregulation are common side-effects of cytotoxic chemotherapy, having a dose-limiting effect on treatment efficacy, and compromising quality of life and mortality. Extracts of Cannabis sativa, and analogues of the major phytocannabinoid Δ9-tetrahydrocannabinol, have been used to ameliorate chemotherapy-induced appetite loss and nausea for decades. However, psychoactive side-effects limit their clinical utility, and they have little efficacy against weight loss. We recently established that the non-psychoactive phytocannabinoid cannabigerol (CBG) stimulates appetite in healthy rats, without neuromotor side-effects. The present study assessed whether CBG attenuates anorexia and/or other cachectic effects induced by the broad-spectrum chemotherapy agent cisplatin.

METHODS

An acute cachectic phenotype was induced in adult male Lister-hooded rats by 6 mg/kg (i.p.) cisplatin. In total 66 rats were randomly allocated to groups receiving vehicle only, cisplatin only, or cisplatin and 60 or 120 mg/kg CBG (po, b.i.d.). Feeding behavior, bodyweight and locomotor activity were recorded for 72 hours, at which point rats were sacrificed for post-mortem analyses. Myofibre atrophy, protein synthesis and autophagy dysregulation were assessed in skeletal muscle, plasma metabolic profiles were obtained by untargeted 1H-NMR metabonomics, and levels of endocannabinoid-like lipoamines quantified in plasma and hypothalami by targeted HPLC-MS/MS lipidomics.

RESULTS

CBG (120 mg/kg) modestly increased food intake, predominantly at 36-60hrs (p<0.05), and robustly attenuated cisplatin-induced weight loss from 6.3% to 2.6% at 72hrs (p<0.01). Cisplatin-induced skeletal muscle atrophy was associated with elevated plasma corticosterone (3.7 vs 13.1ng/ml, p<0.01), observed selectively in MHC type IIx (p<0.05) and IIb (p<0.0005) fibres, and was reversed by pharmacological rescue of dysregulated Akt/S6-mediated protein synthesis and autophagy processes. Plasma metabonomic analysis revealed cisplatin administration produced a wide-ranging aberrant metabolic phenotype (Q2Ŷ=0.5380, p=0.001), involving alterations to glucose, amino acid, choline and lipid metabolism, citrate cycle, gut microbiome function, and nephrotoxicity, which were partially normalized by CBG treatment (Q2Ŷ=0.2345, p=0.01). Lipidomic analysis of hypothalami and plasma revealed extensive cisplatin-induced dysregulation of central and peripheral lipoamines (29/79 and 11/26 screened, respectively), including reversible elevations in systemic N-acyl glycine concentrations which were negatively associated with the anti-cachectic effects of CBG treatment.

CONCLUSIONS

Endocannabinoid-like lipoamines may have hitherto unrecognized roles in the metabolic side-effects associated with chemotherapy, with the N-acyl glycine subfamily in particular identified as a potential therapeutic target and/or biomarker of anabolic interventions. CBG-based treatments may represent a novel therapeutic option for chemotherapy-induced cachexia, warranting investigation in tumour-bearing cachexia models.

Diurnal Profiles of N-Acylethanolamines in Goldfish Brain and Gastrointestinal Tract: Possible Role of Feeding

N-acylethanolamines (NAEs) are a family of endogenous lipid signaling molecules that are involved in regulation of energy homeostasis in vertebrates with a putative role on circadian system. The aim of this work was to study the existence of daily fluctuations in components of NAEs system and their possible dependence on food intake. Specifically, we analyzed the content of oleoylethanolamide (OEA), palmitoylethanolamide (PEA), stearoylethanolamide (SEA), their precursors (NAPEs), as well as the expression of nape-pld (NAEs synthesis enzyme), faah (NAEs degradation enzyme), and pparα (NAEs receptor) in gastrointestinal and brain tissues of goldfish (Carassius auratus) throughout a 24-h cycle. Daily profiles of bmal1a and rev-erbα expression in gastrointestinal tissues were also quantified because these clock genes are also involved in lipid metabolism, are PPAR-targets in mammals, and could be a link between NAEs and circadian system in fish. Gastrointestinal levels of NAEs exhibited daily fluctuations, with a pronounced and rapid postprandial increase, the increment being likely caused by food intake as it is not present in fasted animals. Such periprandial differences were not found in brain, supporting that NAEs mobilization occurs in a tissue-specific manner and suggesting that these three NAEs could be acting as peripheral satiety signals. The abundance of pparα mRNA displayed a daily rhythm in the intestine and the liver, suggesting a possible rhythmicity in the NAEs functionality. The increment of pparα expression during the rest phase can be related with its role stimulating lipid catabolism to obtain energy during the fasting state of the animals. In addition, the clock genes bmal1a and rev-erbα also showed daily rhythms, with a bmal1a increment after feeding, supporting its role as a lipogenic factor. In summary, our data show the existence of all components of NAEs system in fish (OEA, PEA, SEA, precursors, synthesis and degradation enzymes, and the receptor PPARα), supporting the involvement of NAEs as peripheral satiety signals.

Satiety Factors Oleoylethanolamide, Stearoylethanolamide, and Palmitoylethanolamide in Mother's Milk Are Strongly Associated with Infant Weight at Four Months of Age-Data from the Odense Child Cohort

Regulation of appetite and food intake is partly regulated by N-acylethanolamine lipids oleoylethanolamide (OEA), stearoylethanolamide (SEA), and palmitoylethanolamide (PEA), which induce satiety through endogenous formation in the small intestine upon feeding, but also when orally or systemic administered. OEA, SEA, and PEA are present in human milk, and we hypothesized that the content of OEA, SEA, and PEA in mother’s milk differed for infants being heavy (high weight-for-age Z-score (WAZ)) or light (low WAZ) at time of milk sample collection. Ultra-high performance liquid chromatography-mass spectrometry was used to determine the concentration of OEA, SEA, and PEA in milk samples collected four months postpartum from mothers to high (n = 50) or low (n = 50) WAZ infants. Associations between OEA, SEA, and PEA concentration and infant anthropometry at four months of age as well as growth from birth were investigated using linear and logistic regression analyses, adjusted for birth weight, early infant formula supplementation, and maternal pre-pregnancy body mass index. Mean OEA, SEA, and PEA concentrations were lower in the high compared to the low WAZ group (all p < 0.02), and a higher concentration of SEA was associated with lower anthropometric measures, e.g., triceps skinfold thickness (mm) (β = −2.235, 95% CI = −4.04, −0.43, p = 0.016), and weight gain per day since birth (g) (β = −8.169, 95% CI = −15.26, −1.08, p = 0.024). This raises the possibility, that the content of satiety factors OEA, SEA, and PEA in human milk may affect infant growth.

Oleoylethanolamide treatment affects gut microbiota composition and the expression of intestinal cytokines in Peyer's patches of mice

The lipid sensor oleoylethanolamide (OEA), an endogenous high-affinity agonist of peroxisome proliferator-activated receptor-α (PPAR-α) secreted in the proximal intestine, is endowed with several distinctive homeostatic properties, such as control of appetite, anti-inflammatory activity, stimulation of lipolysis and fatty acid oxidation. When administered exogenously, OEA has beneficial effects in several cognitive paradigms; therefore, in all respects, OEA can be considered a hormone of the gut-brain axis. Here we report an unexplored modulatory effect of OEA on the intestinal microbiota and on immune response. Our study shows for the first time that sub-chronic OEA administration to mice fed a normal chow pellet diet, changes the faecal microbiota profile, shifting the Firmicutes:Bacteroidetes ratio in favour of Bacteroidetes (in particular Bacteroides genus) and decreasing Firmicutes (Lactobacillus), and reduces intestinal cytokines expression by immune cells isolated from Peyer's patches. Our results suggest that sub-chronic OEA treatment modulates gut microbiota composition towards a "lean-like phenotype", and polarises gut-specific immune responses mimicking the effect of a diet low in fat and high in polysaccharides content.

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

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

Endocannabinoid regulation of homeostatic feeding and stress-induced alterations in food intake in male rats

BACKGROUND AND PURPOSE

Stress is known to reduce food intake. Many aspects of the stress response and feeding are regulated by the endocannabinoid system, but the roles of anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) in stress-induced anorexia are unclear.

EXPERIMENTAL APPROACH

Effects of acute restraint stress on endocannabinoids were investigated in male Sprague-Dawley rats. Systemic and central pharmacological inhibition of fatty acid amide hydrolase (FAAH) or monoacylglycerol lipase (MAGL) was used to assess the effects of elevated AEA and 2-AG on homeostatic feeding and on food consumption after stress. Animals were pretreated with the FAAH inhibitor, PF-04457845, or the MAGL inhibitor, MJN110, before 2 h acute restraint stress or 2 h homecage period without food.

KEY RESULTS

Restraint stress decreased hypothalamic and circulating AEA, with no effect in the gastrointestinal tract, while 2-AG content in the jejunum (but not duodenum) was reduced. PF-04457845 (30 μg), given i.c.v., attenuated stress-induced anorexia via CB₁ receptors, but reduced homeostatic feeding in unstressed animals through an unknown mechanism. On the other hand, systemic administration of MJN110 (10 mg·kg^-1 ) reduced feeding, regardless of stress or feeding status and inhibited basal intestinal transit in unstressed rats. The ability of MAGL inhibition to reduce feeding in combination with stress was independent of CB₁ receptor signalling in the gut as the peripherally restricted CB₁ receptor antagonist, AM6545 did not block this effect.

CONCLUSIONS AND IMPLICATIONS

Our data reveal diverse roles for 2-AG and AEA in homeostatic feeding and changes in energy intake following stress.

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.

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.

Relationship Between Circulating Fatty Acids and Fatty Acid Ethanolamide Levels After a Single 2-h Dietary Fat Feeding in Male Sprague-Dawley Rats : Elevated levels of oleoylethanolamide, palmitoylethanolamide, linoleoylethanolamide, arachidonoylethanolamide and docosahexanoylethanolamide after a single 2 h dietary fat feeding in male Sprague Dawley rats

Previous studies show that long term variations in dietary fat consumption impact circulating fatty acid ethanolamide (FAE) concentrations, however, few studies have investigated short term effects of dietary fat feeding on FAE levels. The trial's objective was to explore the effect of acute feeding of varying amounts of dietary n-9 and n-3 fatty acids on plasma and organ levels of FAE. Sixty-four rats were assigned to four groups fed meals containing 40% of energy as either safflower oil (control), canola oil (CO), or DHA rich oil (DRO), each consumed as a bolus within a 2-h window. Plasma and tissue FAE levels were measured at 3, 6, 12 and 24 h following the bolus. FAE profiles over time exhibited patterns that were specific both to FAE and to dietary fat type provided. At 3 h, plasma and liver OEA levels were higher (p < 0.05) in the 95% CO:5% DRO compared with other groups. At 12 h, plasma PEA levels were lower (p < 0.05) in the 50% CO:50% DRO group compared to the 95% CO group. Plasma DEA levels showed an increase (p < 0.05) only after 24 h of feeding. All four dietary groups manifested increased DEA levels in a dose-dependent manner. Data demonstrate that a single meal feeding of diets with different ratios of fat types impacts tissue levels of FAE within a short time frame, which could further influence the physiological roles of FAE on appetite regulation and energy expenditure.

Alterations of anti-inflammatory lipids in plasma from women with chronic widespread pain - a case control study

Background

Chronic widespread pain conditions (CWP) such as the pain associated with fibromyalgia syndrome (FMS) are significant health problems with unclear aetiology. Although CWP and FMS can alter both central and peripheral pain mechanisms, there are no validated markers for such alterations. Pro- and anti-inflammatory components of the immune system such as cytokines and endogenous lipid mediators could serve as systemic markers of alterations in chronic pain. Lipid mediators associated with anti-inflammatory qualities – e.g., oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and stearoylethanolamide (SEA) – belong to N-acylethanolamines (NAEs). Previous studies have concluded that these lipid mediators may modulate pain and inflammation via the activation of peroxisome proliferator activating receptors (PPARs) and the activation of PPARs may regulate gene transcriptional factors that control the expression of distinct cytokines.

Methods

This study investigates NAEs and cytokines in 17 women with CWP and 21 healthy controls. Plasma levels of the anti-inflammatory lipids OEA, PEA, and SEA, the pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8, and the anti-inflammatory cytokine IL-10 were investigated. T-test of independent samples was used for group comparisons. Bivariate correlation analyses, and multivariate regression analysis were performed between lipids, cytokines, and pain intensity of the participants.

Results

Significantly higher levels of OEA and PEA in plasma were found in CWP. No alterations in the levels of cytokines existed and no correlations between levels of lipids and cytokines were found.

Conclusions

We conclude that altered levels of OEA and PEA might indicate the presence of systemic inflammation in CWP. In addition, we believe our findings contribute to the understanding of the biochemical mechanisms involved in chronic musculoskeletal pain.

Leptogenic effects of NAPE require activity of NAPE-hydrolyzing phospholipase D

Food intake induces synthesis of N-acylphosphatidylethanolamines (NAPEs) in the intestinal tract. While NAPEs exert leptin-like (leptogenic) effects, including reduced weight gain and food intake, the mechanisms by which NAPEs induce these leptogenic effects remain unclear. One key question is whether intestinal NAPEs act directly on cognate receptors or first require conversion to N-acylethanolamides (NAEs) by NAPE-hydrolyzing phospholipase D (NAPE-PLD). Previous studies using Nape-pld^-/- mice were equivocal because intraperitoneal injection of NAPEs led to nonspecific aversive effects. To avoid the aversive effects of injection, we delivered NAPEs and NAEs intestinally using gut bacteria synthesizing these compounds. Unlike in wild-type mice, increasing intestinal levels of NAPE using NAPE-synthesizing bacteria in Nape-pld^-/- mice failed to reduce food intake and weight gain or alter gene expression. In contrast, increasing intestinal NAE levels in Nape-pld^-/- mice using NAE-synthesizing bacteria induced all of these effects. These NAE-synthesizing bacteria also markedly increased NAE levels and decreased inflammatory gene expression in omental adipose tissue. These results demonstrate that intestinal NAPEs require conversion to NAEs by the action of NAPE-PLD to exert their various leptogenic effects, so that the reduced intestinal NAPE-PLD activity found in obese subjects may directly contribute to excess food intake and obesity.

Oleic acid-derived oleoylethanolamide: A nutritional science perspective

The fatty acid ethanolamide oleoylethanolamide (OEA) is an endogenous lipid mediator derived from the monounsaturated fatty acid, oleic acid. OEA is synthesized from membrane glycerophospholipids and is a high-affinity agonist of the nuclear transcription factor peroxisome proliferator-activated receptor α (PPAR-α). Dietary intake of oleic acid elevates circulating levels of OEA in humans by increasing substrate availability for OEA biosynthesis. Numerous clinical studies demonstrate a beneficial relationship between high-oleic acid diets and body composition, with emerging evidence to suggest OEA may mediate this response through modulation of lipid metabolism and energy intake. OEA exposure has been shown to stimulate fatty acid uptake, lipolysis, and β-oxidation, and also promote food intake control. Future research on high-oleic acid diets and body composition is warranted to confirm these outcomes and elucidate the underlying mechanisms by which oleic acid exerts its biological effects. These findings have significant practical implications, as the oleic acid-derived OEA molecule may be a promising therapeutic agent for weight management and obesity treatment.

Oral 2-oleyl glyceryl ether improves glucose tolerance in mice through the GPR119 receptor

The intestinal G protein-coupled receptor GPR119 is a novel metabolic target involving glucagon-like peptide-1 (GLP-1)-derived insulin-regulated glucose homeostasis. Endogenous and diet-derived lipids, including N-acylethanolamines and 2-monoacylglycerols (2-MAG) activate GPR119. The purpose of this work is to evaluate whether 2-oleoyl glycerol (2-OG) improves glucose tolerance through GPR119, using wild type (WT) and GPR 119 knock out (KO) mice. We here show that GPR119 is essential for 2-OG-mediated release of GLP-1 and CCK from GLUTag cells, since a GPR119 specific antagonist completely abolished the hormone release. Similarly, in isolated primary colonic crypt cultures from WT mice, GPR119 was required for 2-OG-stimulated GLP-1 release while there was no response in crypts from KO mice. In vivo, gavage with 2-oleyl glyceryl ether ((2-OG ether), a stable 2-OG analog with a potency of 5.3 µM for GPR119 with respect to cAMP formation as compared to 2.3 µM for 2-OG), significantly (P < 0.05) improved glucose clearance in WT littermates, but not in GPR119 KO mice. Finally, deletion of GPR119 in mice resulted in lower glucagon levels, whereas the levels of insulin and GIP were unchanged. In the present study we show that 2-OG stimulates GLP-1 secretion through GPR119 activation in vitro, and that fat-derived 2-MAGs are potent candidates for mediating fat-induced GLP-1 release through GPR119 in vivo. © 2016 BioFactors, 42(6):665-673, 2016.

Bile Acid Recognition by NAPE-PLD

The membrane-associated enzyme NAPE-PLD (N-acyl phosphatidylethanolamine specific-phospholipase D) generates the endogenous cannabinoid arachidonylethanolamide and other lipid signaling amides, including oleoylethanolamide and palmitoylethanolamide. These bioactive molecules play important roles in several physiological pathways including stress and pain response, appetite, and lifespan. Recently, we reported the crystal structure of human NAPE-PLD and discovered specific binding sites for the bile acid deoxycholic acid. In this study, we demonstrate that in the presence of this secondary bile acid, the stiffness of the protein measured by elastic neutron scattering increases, and NAPE-PLD is ∼7 times faster to catalyze the hydrolysis of the more unsaturated substrate N-arachidonyl-phosphatidylethanolamine, compared with N-palmitoyl-phosphatidylethanolamine. Chenodeoxycholic acid and glyco- or tauro-dihydroxy conjugates can also bind to NAPE-PLD and drive its activation. The only natural monohydroxy bile acid, lithocholic acid, shows an affinity of ∼20 μM and acts instead as a reversible inhibitor (IC₅₀ ≈ 68 μM). Overall, these findings provide important insights into the allosteric regulation of the enzyme mediated by bile acid cofactors and reveal that NAPE-PLD responds primarily to the number and position of their hydroxyl groups.

High levels of endogenous lipid mediators (N-acylethanolamines) in women with chronic widespread pain during acute tissue trauma

Although chronic widespread musculoskeletal pain is a significant health problem, the molecular mechanisms involved in developing and maintaining chronic widespread musculoskeletal pain are poorly understood. Central sensitization mechanisms maintained by stimuli from peripheral tissues such as muscle have been suggested. Lipid mediators with anti-inflammatory characteristics such as endogenous ligands of peroxisome proliferator activating receptor-α, oleoylethanolamide, and palmitoylethanolamide are suggested to regulate nociceptive transmission from peripheral locations on route towards the central nervous system. This case–control study investigates the levels of anti-inflammatory lipids in microdialysis samples collected during the first 2 h after microdialysis probe insertion and explores the association of these lipids with different pain characteristics in women with chronic widespread musculoskeletal pain (n = 17) and female healthy controls (n = 19). The levels of oleoylethanolamide, palmitoylethanolamide, and stearoylethanolamide were determined. During sampling of dialysate, pain ratings were conducted using a numeric rating scale. Pain thresholds were registered from upper and lower parts of the body. Oleoylethanolamide and stearoylethanolamide levels were significantly higher (p ≤ 0.05) in chronic widespread musculoskeletal pain at all time points. Numeric rating scale correlated with levels of stearoylethanolamide in chronic widespread musculoskeletal pain. Higher levels of lipid mediators could reflect an altered tissue reactivity in response to microdialysis probe insertion in chronic widespread musculoskeletal pain.

Lowering dietary n-6 polyunsaturated fatty acids: interaction with brain arachidonic and docosahexaenoic acids

PURPOSE OF REVIEW

Arachidonic (ARA) and docosahexaenoic (DHA) acids are the most abundant polyunsaturated fatty acids (PUFA) in the brain, where they have many biological effects, including on inflammation, cell-signaling, appetite regulation, and blood flow. The Western diet contains a high ratio of n-6: n-3 PUFA. Although interest in lowering this ratio has largely focused on increasing intake of n-3 PUFA, few studies have examined lowering dietary n-6 PUFA. This review will evaluate the effect of lowering dietary n-6 PUFA on levels and metabolism of ARA and DHA in animal models and in humans, with a primary focus on the brain.

RECENT FINDINGS

In animal models, lowering dietary ARA or linoleic acid generally lowers levels of brain ARA and raises DHA. Lowering dietary n-6 PUFA can also modulate the levels of ARA and DHA metabolizing enzymes, as well as their associated bioactive mediators. Human studies examining changes in plasma fatty acid composition following n-6 PUFA lowering demonstrate no changes in levels of ARA and DHA, though there is evidence of alterations in their respective bioactive mediators.

SUMMARY

Lowering dietary n-6 PUFA, in animal models, can alter the levels and metabolism of ARA and DHA in the brain, but it remains to be determined whether these changes are clinically meaningful.

Fatty acid amide supplementation decreases impulsivity in young adult heavy drinkers

Compromised dopamine signaling in the striatum has been associated with the expression of impulsive behaviors in addiction, obesity and alcoholism. In rodents, intragastric infusion of the fatty acid amide oleoylethanolamide increases striatal extracellular dopamine levels via vagal afferent signaling. Here we tested whether supplementation with PhosphoLean™, a dietary supplement that contains the precursor of the fatty acid amide oleoylethanolamide (N-oleyl-phosphatidylethanolamine), would reduce impulsive responding and alcohol use in heavy drinking young adults. Twenty-two individuals were assigned to a three-week supplementation regimen with PhosphoLean™ or placebo. Impulsivity was assessed with self-report questionnaires and behavioral tasks pre- and post-supplementation. Although self-report measures of impulsivity did not change, supplementation with PhosphoLean™, but not placebo, significantly reduced false alarm rate on a Go/No-Go task. In addition, an association was found between improved sensitivity on the Go/No-Go task and reduced alcohol intake. These findings provide preliminary evidence that promoting fatty acid derived gut-brain dopamine communication may have therapeutic potential for reducing impulsivity in heavy drinkers.

Anandamide drives cell cycle progression through CB1 receptors in a rat model of synchronized liver regeneration

The endocannabinoid system, through cannabinoid receptor signaling by endocannabinoids, is involved in a wide range of functions and physiopathological conditions. To date, very little is known concerning the role of the endocannabinoids in the control and regulation of cell proliferation. An anti-proliferative action of CB1 signaling blockade in neurogenesis and angiogenesis argues in favor of proliferation-promoting functions of endocannabinoids through CB1 receptors when pro-growth signals are present. Furthermore, liver regeneration, a useful in vivo model of synchronized cell proliferation, is characterized by a peak of anandamide that elicits through CB1 receptor, the expression of critical mitosis genes. The aim of this study was to focus on the timing of endocannabinoid signaling changes during the different phases of the cell cycle, exploiting the rat liver regeneration model following partial hepatectomy, the most useful to study synchronized cell cycle in vivo. Hepatic regeneration led to increased levels of anandamide and endocannabinoid-like molecules oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) in the G1 phase of the cell cycle, with a concomitant increase in CB1 mRNA levels, whose protein expression peaked later during the S phase. Blocking of CB1 receptor with a low dose of the selective antagonist/inverse agonist SR141716 (0.7 mg/kg/dose) affected cell cycle progression reducing the expression of PCNA, and through the inhibition of pERK and pSTAT3 pathways. These results support the notion that the signaling mediated by anandamide through CB1 receptor may be important for the entry and progression of cells into the cell cycle and hence for their proliferation under mitogenic signals.

Distinctive striatal dopamine signaling after dieting and gastric bypass

Highly palatable and/or calorically dense foods, such as those rich in fat, engage the striatum to govern and set complex behaviors. Striatal dopamine signaling has been implicated in hedonic feeding and the development of obesity. Dieting and bariatric surgery have markedly different outcomes on weight loss, yet how these interventions affect central homeostatic and food reward processing remains poorly understood. Here, we propose that dieting and gastric bypass produce distinct changes in peripheral factors with known roles in regulating energy homeostasis, resulting in differential modulation of nigrostriatal and mesolimbic dopaminergic reward circuits. Enhancement of intestinal fat metabolism after gastric bypass may also modify striatal dopamine signaling contributing to its unique long-term effects on feeding behavior and body weight in obese individuals.

Sensing of triacylglycerol in the gut: different mechanisms for fatty acids and 2-monoacylglycerol

Sensing of dietary triacylglycerol in the proximal small intestine results in physiological, hormonal and behavioural responses. However, the exact physiological pathways linking intestinal fat sensing to food intake and the activation of brain circuits remain to be identified. In this study we examined the role of triacylglycerol digestion for intestinal fat sensing, and compared the effects of the triacylglycerol digestion products, fatty acids and 2-monoacylglycerol, on behavioural, hormonal and dopaminergic responses in behaving mice. Using an operant task in which mice are trained to self-administer lipid emulsions directly into the stomach, we show that inhibiting triacylglycerol digestion disrupts normal behaviour of self-administration in mice, indicating that fat sensing is conditional to digestion. When administered separately, both digestion products, 2-monoacylglycerol and fatty acids, were sensed by the mice, and self-administration patterns of fatty acids were affected by the fatty acid chain length. Peripheral plasma concentrations of the gut hormones GLP-1, GIP, PYY, CCK and insulin did not offer an explanation of the differing behavioural effects produced by 2-monoacylglycerol and fatty acids. However, combined with behavioural responses, striatal dopamine effluxes induced by gut infusions of oleic acid were significantly greater than those produced by equivalent infusions of 2-oleoylglycerol. Our data demonstrate recruitment of different signalling pathways by fatty acids and 2-monoacylglycerol, and suggest that the structural properties of fat rather than total caloric value determine intestinal sensing and the assignment of reward value to lipids.

Fat sensing and metabolic syndrome

Overconsumption of dietary fat contributes to the development of obesity and metabolic syndrome. Recent evidence suggests that high dietary fat may promote these metabolic states not only by providing calories but also by inducing impaired control of energy balance. In normal metabolic states, fat interacts with various organs or receptors to generate signals for the regulation of energy balance. Many of these interactions are impaired by high-fat diets or in obesity, contributing to the development or maintenance of obesity. These impairments may arise largely from fundamental alterations in the hypothalamus where all peripheral signals are integrated to regulate energy balance. This review focuses on various mechanisms by which fat is sensed at different stages of ingestion, circulation, storage, and utilization to regulate food intake, and how these individual mechanisms are altered by high-fat diets or in obesity.