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

Plaat1l1 controls feeding induced NAPE biosynthesis and contributes to energy balance regulation in zebrafish

Dysregulation of energy balance leading to obesity is a significant risk factor for cardiometabolic diseases such as diabetes, non-alcoholic fatty liver disease and atherosclerosis. In rodents and several other vertebrates, feeding has been shown to induce a rapid rise in the intestinal levels of N-acyl-ethanolamines (NAEs) and the chronic consumption of a high fat diet abolishes this rise. Administering NAEs to rodents consuming a high fat diet reduces their adiposity, in part by reducing food intake and enhancing fat oxidation, so that feeding-induced intestinal NAE biosynthesis appears to be critical to appropriate regulation of energy balance. However, the contribution of feeding-induced intestinal NAE biosynthesis to appropriate energy balance remains poorly understood in part because there are multiple enzymes that can contribute to NAE biosynthesis and the specific enzyme(s) that are responsible for feeding-induced intestinal NAE biosynthesis have not been identified. The rate-limiting step in the intestinal biosynthesis of NAEs is formation of their immediate precursors, the N-acyl-phosphatidylethanolamines (NAPEs), by phosphatidylethanolamine N-acyltransferases (NATs). At least six NATs are found in humans and multiple homologs of these NATs are found in most vertebrate species. In recent years, the fecundity and small size of zebrafish (Danio rerio), as well as their similarities in feeding behavior and energy balance regulation with mammals, have led to their use to model key features of cardiometabolic disease. We therefore searched the Danio rerio genome to identify all NAT homologs and found two additional NAT homologs besides the previously reported plaat1, rarres3, and rarres3l, and used CRISPR/cas9 to delete these two NAT homologs (plaat1l1 and plaat1l2). While wild-type fish markedly increased their intestinal NAPE levels in response to a meal after fasting, this response was completely ablated in plaat1l1-/-fish. Furthermore, plaat1l1-/- fish fed a standard flake diet had increased weight gain and glucose intolerance compared to wild-type fish. The results support a critical role for feeding-induced NAPE and NAE biosynthesis in regulating energy balance and suggest that restoring this response in obese animals could potentially be used to treat obesity and cardiometabolic disease.

Endocannabinoid-related molecules predict the metabolic efficacy of GLP-1 receptor agonism in humans with obesity

OBJECTIVE

N-acylethanolamines (NAEs) include endocannabinoid (EC) and EC-related molecules that impact the anti-obesity and anti-diabetic efficacy of glucagon-like peptide-1 receptor agonists (GLP-1RA) in animal studies. However, the clinical relevance of these findings remains to be determined. Here, we tested whether GLP-1RA treatment affects circulating NAE levels and whether NAEs may predict the efficacy of GLP-1RA treatment in humans with obesity undergoing weight loss maintenance.

MATERIALS AND METHODS

We profiled plasma levels of NAEs in participants with obesity undergoing weight loss maintenance with (n = 23)/or without (n = 20) treatment with the GLP-1RA liraglutide. NAE levels were measured at three different time points: before the start of the study, at the end of the diet-induced weight loss, and after 52-weeks treatment. Linear regression analyses were used to investigate whether pharmacological responses could be predicted by NAEs levels.

RESULTS

Liraglutide treatment reduced plasma concentrations of the NAE and oleoyl-ethanolamide (OEA), without altering arachidonoyl-ethanolamide (AEA) levels and palmitoyl-ethanolamide (PEA) levels. High pre-treatment levels of OEA were predictive of superior compound-mediated effects on fasting insulin and triglyceride levels. High pre-treatment PEA and AEA levels were also predictive of superior Liraglutide-mediated effects on triglyceride levels.

CONCLUSIONS

Our data suggests that specific NAEs such as OEA and AEA are promising biomarkers of GLP-1RA metabolic efficacy in humans with obesity during weight loss maintenance. Plasma profiling of EC-related molecules may be a promising strategy to tailor GLP-1R-based therapies to individual needs in obesity and diabetes management.

NAPE-PLD in the ventral tegmental area regulates reward events, feeding and energy homeostasis

The N-acyl phosphatidylethanolamine-specific phospholipase D (NAPE-PLD) catalyzes the production of N-acylethanolamines (NAEs), a family of endogenous bioactive lipids, which are involved in various biological processes ranging from neuronal functions to energy homeostasis and feeding behaviors. Reward-dependent behaviors depend on dopamine (DA) transmission between the ventral tegmental area (VTA) and the nucleus accumbens (NAc), which conveys reward-values and scales reinforced behaviors. However, whether and how NAPE-PLD may contribute to the regulation of feeding and reward-dependent behaviors has not yet been investigated. This biological question is of paramount importance since NAEs are altered in obesity and metabolic disorders. Here, we show that transcriptomic meta-analysis highlights a potential role for NAPE-PLD within the VTA→NAc circuit. Using brain-specific invalidation approaches, we report that the integrity of NAPE-PLD is required for the proper homeostasis of NAEs within the midbrain VTA and it affects food-reward behaviors. Moreover, region-specific knock-down of NAPE-PLD in the VTA enhanced food-reward seeking and reinforced behaviors, which were associated with increased in vivo DA release dynamics in response to both food- and non-food-related rewards together with heightened tropism towards food consumption. Furthermore, midbrain knock-down of NAPE-PLD, which increased energy expenditure and adapted nutrient partitioning, elicited a relative protection against high-fat diet-mediated body fat gain and obesity-associated metabolic features. In conclusion, these findings reveal a new key role of VTA NAPE-PLD in shaping DA-dependent events, feeding behaviors and energy homeostasis, thus providing new insights on the regulation of body metabolism.

NAPE-PLD in the ventral tegmental area regulates reward events, feeding and energy homeostasis

The N-acyl phosphatidylethanolamine-specific phospholipase D (NAPE-PLD) catalyzes the production of N-acylethanolamines (NAEs), a family of endogenous bioactive lipids, which are involved in various biological processes ranging from neuronal functions to energy homeostasis and feeding behaviors. Reward-dependent behaviors depend on dopamine (DA) transmission between the ventral tegmental area (VTA) and the nucleus accumbens (NAc), which conveys reward-values and scales reinforced behaviors. However, whether and how NAPE-PLD may contribute to the regulation of feeding and reward-dependent behaviors has not yet been investigated. This biological question is of paramount importance since NAEs are altered in obesity and metabolic disorders. Here, we show that transcriptomic meta-analysis highlights a potential role for NAPE-PLD within the VTA®NAc circuit. Using brain-specific invalidation approaches, we report that the integrity of NAPE-PLD is required for the proper homeostasis of NAEs within the midbrain VTA and it affects food-reward behaviors. Moreover, region-specific knock-down of NAPE-PLD in the VTA enhanced food-reward seeking and reinforced behaviors, which were associated with increased in vivo DA release dynamics in response to both food and non-food-related rewards together with heightened tropism towards food consumption. Furthermore, midbrain knock-down of NAPE-PLD, which increased energy expenditure and adapted nutrient partitioning, elicited a relative protection against high-fat diet-mediated body fat gain and obesity-associated metabolic features. In conclusion, these findings reveal a new key role of VTA NAPE-PLD in shaping DA-dependent events, feeding behaviors and energy homeostasis, thus providing new insights on the regulation of body metabolism.

Study of the Effect of Intestinal Microbes on Obesity: A Bibliometric Analysis

Obesity is a serious public health problem. According to statistics, there are millions of obese people worldwide. Research studies have discovered a complex and intricate relationship between the gut microbiota and obesity. Probing and summarizing the relationship between intestinal microbes and obesity has important guiding significance for the accurate control of the research direction and expanding the choice of obesity treatment methods. We used bibliometric analysis to analyze the published literature with the intention to reveal the research hotspots and development trends on the effects of intestinal microbes on obesity from a visualization perspective, both qualitatively and quantitatively. The results showed that current research is focusing on related mechanisms of the effects of intestinal microbes on obesity and therapeutic methods for obesity. Several noteworthy hotspots within this field have garnered considerable attention and are expected to remain the focal points of future research. Of particular interest are the mechanisms by which intestinal microbes potentially regulate obesity through metabolite interactions, as well as the role of microbiomes as metabolic markers of obesity. These findings strongly suggest that gut microbes continue to be a key target in the quest for effective obesity treatments. Co-operation and communication between countries and institutions should be strengthened to promote development in this field to benefit more patients with obesity.

The phospholipase A2 superfamily as a central hub of bioactive lipids and beyond

In essence, "phospholipase A₂" (PLA₂) means a group of enzymes that release fatty acids and lysophospholipids by hydrolyzing the sn-2 position of glycerophospholipids. To date, more than 50 enzymes possessing PLA₂ or related lipid-metabolizing activities have been identified in mammals, and these are subdivided into several families in terms of their structures, catalytic mechanisms, tissue/cellular localizations, and evolutionary relationships. From a general viewpoint, the PLA₂ superfamily has mainly been implicated in signal transduction, driving the production of a wide variety of bioactive lipid mediators. However, a growing body of evidence indicates that PLA₂s also contribute to phospholipid remodeling or recycling for membrane homeostasis, fatty acid β-oxidation for energy production, and barrier lipid formation on the body surface. Accordingly, PLA₂ enzymes are considered one of the key regulators of a broad range of lipid metabolism, and perturbation of specific PLA₂-driven lipid pathways often disrupts tissue and cellular homeostasis and may be associated with a variety of diseases. This review covers current understanding of the physiological functions of the PLA₂ superfamily, focusing particularly on the two major intracellular PLA₂ families (Ca²⁺-dependent cytosolic PLA₂s and Ca²⁺-independent patatin-like PLA₂s) as well as other PLA₂ families, based on studies using gene-manipulated mice and human diseases in combination with comprehensive lipidomics.

The gut microbiota in obesity and weight management: microbes as friends or foe?

Obesity is caused by a long-term difference between energy intake and expenditure - an imbalance that is seemingly easily restored by increasing exercise and reducing caloric consumption. However, as simple as this solution appears, for many people, losing excess weight is difficult to achieve and even more difficult to maintain. The reason for this difficulty is that energy intake and expenditure, and by extension body weight, are regulated through complex hormonal, neural and metabolic mechanisms that are under the influence of many environmental factors and internal responses. Adding to this complexity, the microorganisms (microbes) that comprise the gut microbiota exert direct effects on the digestion, absorption and metabolism of food. Furthermore, the gut microbiota exerts a miscellany of protective, structural and metabolic effects both on the intestinal milieu and peripheral tissues, thus affecting body weight by modulating metabolism, appetite, bile acid metabolism, and the hormonal and immune systems. In this Review, we outline historical and recent advances in understanding how the gut microbiota is involved in regulating body weight homeostasis. We also discuss the opportunities, limitations and challenges of using gut microbiota-related approaches as a means to achieve and maintain a healthy body weight.

Identification of novel candidate genes and predicted miRNAs in atopic dermatitis patients by bioinformatic methods

Atopic dermatitis (AD) is a common, chronic inflammatory dermatosis with relapsing eruptions. Our study used bioinformatics to find novel candidate differentially expressed genes (DEGs) and predicted miRNAs between AD patients and healthy controls. The Mesh term "atopic dermatitis" was retrieved to obtain DEGs in GEO datasets. DEGs between AD patients and healthy controls were analyzed using GEO2R. Overlapping DEGs between different datasets were obtained with use of Draw Venn software. GO and KEGG enrichment analyses were conducted by the use of DAVID. STRING and miRWalk were used to individually analyze PPI networks, interactions of candidate genes and predicted miRNAs. A total of 571 skin samples, as retrieved from 9 databases were assessed. There were 225 overlapping DEGs between lesioned skin samples of AD patients and that of healthy controls. Nineteen nodes and 160 edges were found in the largest PPI cluster, consisting of 17 up-regulated and 2 down-regulated nodes. Two KEGG pathways were identified, including the cell cycle (CCNB1, CHEK1, BUB1B, MCM5) and p53 (CCNB1, CHEK1, GTSE1) pathways. There were 56 nodes and 100 edges obtained in the miRNA-target gene network, with has-miR-17-5p targeted to 4 genes and has-miR-106b-5p targeted to 3 genes. While these findings will require further verification as achieved with experiments involving in vivo and in vitro modles, these results provided some initial insights into dysfunctional inflammatory and immune responses associated with AD. Such information offers the potential to develop novel therapeutic targets for use in preventing and treating AD.

Segregated functions of two cytosolic phospholipase A2 isoforms (cPLA2α and cPLA2ε) in lipid mediator generation

Among the phospholipase A₂ (PLA₂) superfamily, group IVA cytosolic PLA₂ (cPLA₂α) is currently attracting much attention as a central regulator of arachidonic acid (AA) metabolism linked to eicosanoid biosynthesis. Following cell activation, cPLA₂α selectively releases AA, a precursor of a variety of eicosanoids, from phospholipids in perinuclear membrane compartments. cPLA₂α-null mice display various phenotypes that could be largely explained by reduced eicosanoid signaling. In contrast, group IVE cPLA₂ε, another member of the cPLA₂ family, acts as a Ca²⁺-dependent N-acyltransferase rather than a PLA₂, thereby regulating the biosynthesis of N-acylethanolamines (NAEs), a unique class of lipid mediators with an anti-inflammatory effect. In response to Ca²⁺ signaling, cPLA₂ε translocates to phosphatidylserine-rich organelle membranes in the endocytic/recycling pathway. In vivo, cPLA₂ε is induced in keratinocytes of psoriatic skin, and its genetic deletion exacerbates psoriatic inflammation due to a marked reduction of NAE-related lipids. cPLA₂ε also contributes to NAE generation in several if not all mouse tissues. Thus, the two members of the cPLA₂ family, cPLA₂α and cPLA₂ε, catalyze distinct enzymatic reactions to mobilize distinct sets of lipid mediators, thereby differently regulating pathophysiological events in health and disease. Such segregation of the cPLA₂α-eicosanoid and cPLA₂ε-NAE pathways represents a new paradigm of research on PLA₂s and lipid mediators.

Oral Adelmidrol Administration Up-Regulates Palmitoylethanolamide Production in Mice Colon and Duodenum through a PPAR-γ Independent Action

Adelmidrol is a promising palmitoylethanolamide (PEA) analog which displayed up-and-coming anti-inflammatory properties in several inflammatory conditions. Recent studies demonstrated that Adelmidrol is an in vitro enhancer of PEA endogenous production, through the so called “entourage” effect. The present study investigated the ability of Adelmidrol (1 and 10 mg/Kg per os) to increase the endogenous level of PEA in the duodenum and colon of mice after 21-day oral administration in the presence and absence of PPAR-γ inhibitor (1 mg/kg). The level of PEA was analyzed by HPLC-MS. The expression of PEA-related enzymatic machinery was evaluated by western blot and RT-PCR analysis. Our findings demonstrated that Adelmidrol significantly increased PEA levels in the duodenum and colon in a dose/time-dependent manner. We also revealed that Adelmidrol up regulated the enzymatic machinery responsible for PEA metabolism and catabolism. Interestingly, the use of the selective irreversible PPAR-γ antagonist did not affect either PEA intestinal levels or expression/transcription of PEA metabolic enzymes following Adelmidrol administration. The “entourage effect” with Adelmidrol as an enhancer of PEA was thus PPAR-γ-independent. The findings suggest that Adelmidrol can maximize a PEA therapeutic-based approach in several intestinal morbidities.

Gut microbiome and health: mechanistic insights

The gut microbiota is now considered as one of the key elements contributing to the regulation of host health. Virtually all our body sites are colonised by microbes suggesting different types of crosstalk with our organs. Because of the development of molecular tools and techniques (ie, metagenomic, metabolomic, lipidomic, metatranscriptomic), the complex interactions occurring between the host and the different microorganisms are progressively being deciphered. Nowadays, gut microbiota deviations are linked with many diseases including obesity, type 2 diabetes, hepatic steatosis, intestinal bowel diseases (IBDs) and several types of cancer. Thus, suggesting that various pathways involved in immunity, energy, lipid and glucose metabolism are affected.In this review, specific attention is given to provide a critical evaluation of the current understanding in this field. Numerous molecular mechanisms explaining how gut bacteria might be causally linked with the protection or the onset of diseases are discussed. We examine well-established metabolites (ie, short-chain fatty acids, bile acids, trimethylamine N-oxide) and extend this to more recently identified molecular actors (ie, endocannabinoids, bioactive lipids, phenolic-derived compounds, advanced glycation end products and enterosynes) and their specific receptors such as peroxisome proliferator-activated receptor alpha (PPARα) and gamma (PPARγ), aryl hydrocarbon receptor (AhR), and G protein-coupled receptors (ie, GPR41, GPR43, GPR119, Takeda G protein-coupled receptor 5).Altogether, understanding the complexity and the molecular aspects linking gut microbes to health will help to set the basis for novel therapies that are already being developed.

Gut microbiome and health: mechanistic insights

The gut microbiota is now considered as one of the key elements contributing to the regulation of host health. Virtually all our body sites are colonised by microbes suggesting different types of crosstalk with our organs. Because of the development of molecular tools and techniques (ie, metagenomic, metabolomic, lipidomic, metatranscriptomic), the complex interactions occurring between the host and the different microorganisms are progressively being deciphered. Nowadays, gut microbiota deviations are linked with many diseases including obesity, type 2 diabetes, hepatic steatosis, intestinal bowel diseases (IBDs) and several types of cancer. Thus, suggesting that various pathways involved in immunity, energy, lipid and glucose metabolism are affected.In this review, specific attention is given to provide a critical evaluation of the current understanding in this field. Numerous molecular mechanisms explaining how gut bacteria might be causally linked with the protection or the onset of diseases are discussed. We examine well-established metabolites (ie, short-chain fatty acids, bile acids, trimethylamine N-oxide) and extend this to more recently identified molecular actors (ie, endocannabinoids, bioactive lipids, phenolic-derived compounds, advanced glycation end products and enterosynes) and their specific receptors such as peroxisome proliferator-activated receptor alpha (PPARα) and gamma (PPARγ), aryl hydrocarbon receptor (AhR), and G protein-coupled receptors (ie, GPR41, GPR43, GPR119, Takeda G protein-coupled receptor 5).Altogether, understanding the complexity and the molecular aspects linking gut microbes to health will help to set the basis for novel therapies that are already being developed.

Group IVE cytosolic phospholipase A2 limits psoriatic inflammation by mobilizing the anti-inflammatory lipid N-acylethanolamine

Psoriasis is an inflammatory disorder characterized by keratinocyte hyper-proliferation and Th17-type immune responses. However, the roles of bioactive lipids and the regulation of their biosynthesis in this chronic skin disease are not fully understood. Herein, we show that group IVE cytosolic phospholipase A₂ (cPLA₂ ε/PLA2G4E) plays a counterregulatory role against psoriatic inflammation by producing the anti-inflammatory lipid N-acylethanolamine (NAE). Lipidomics analysis of mouse skin revealed that NAE species and their precursors (N-acyl-phosphatidylethanolamine and glycerophospho-N-acylethanolamine) were robustly increased in parallel with the ongoing process of imiquimod (IMQ)-induced psoriasis, accompanied by a marked upregulation of cPLA₂ ε in epidermal keratinocytes. Genetic deletion of cPLA₂ ε exacerbated IMQ-induced ear swelling and psoriatic marker expression, with a dramatic reduction of NAE-related lipids in IMQ-treated, and even normal, skin. Stimulation of cultured human keratinocytes with psoriatic cytokines concomitantly increased PLA2G4E expression and NAE production, and supplementation with NAEs significantly attenuated the cytokine-induced upregulation of the psoriatic marker S100A9. Increased expression of cPLA₂ ε was also evident in the epidermis of psoriatic patients. These findings reveal for the first time the in vivo role of cPLA₂ ε, which is highly induced in the keratinocytes of the psoriatic skin, promotes the biosynthesis of NAE-related lipids, and contributes to limiting psoriatic inflammation.