Bile Acid Recognition by NAPE-PLD

Yin-Yang control of energy balance by lipids in the hypothalamus: The endocannabinoids vs bile acids case

Obesity is a chronic and debilitating disorder that originates from alterations in energy-sensing brain circuits controlling body weight gain and food intake. The dysregulated syntheses and actions of lipid mediators in the hypothalamus induce weight gain and overfeeding, but the molecular and cellular underpinnings of these alterations remain elusive. In response to changes in the nutritional status, different lipid sensing pathways in the hypothalamus direct body energy needs in a Yin-Yang model. Endocannabinoids orchestrate the crosstalk between hypothalamic circuits and the sympathetic nervous system to promote food intake and energy accumulation during fasting, whereas bile acids act on the same top-down axis to reduce energy intake and possibly storage after the meal. In obesity, the bioavailability and downstream cellular actions of endocannabinoids and bile acids are altered in hypothalamic neurons involved in body weight and metabolic control. Thus, the onset and progression of this disease might result from an imbalance in hypothalamic sensing of multiple lipid signals, which are possibly integrated by common molecular nodes. In this viewpoint, we discuss a possible model that explains how bile acids and endocannabinoids may exert their effects on energy balance regulation via interconnected mechanisms at the level of the hypothalamic neuronal circuits. Therefore, we propose a new conceptual framework for understanding and treating central mechanisms of maladaptive lipid action in obesity.

Chemical exploration of TGR5 functional hot-spots: Synthesis and structure-activity relationships of C7- and C23-Substituted cholic acid derivatives

The activation of TGR5 bestows on bile acids the ability to modulate nongenomic signaling pathways, which are responsible of physiological actions including immunosuppressive and anti-inflammatory properties as well as the regulation of glucose metabolism and energy homeostasis. TGR5 agonists have therefore emerged in drug discovery and preclinical appraisals as promising compounds for the treatment of liver diseases and metabolic syndrome. In this study, we have been devising site-selected chemical modifications of the bile acid scaffold to provide novel chemical tools able to modulate the functions of TGR5 in different tissues. Biological results of the tested collection of semisynthetic cholic acid derivatives were used to extend the structure-activity relationships of TGR5 agonists and to clarify the molecular basis and functional role of TGR5 hot-spots in the receptor activation and selectivity. Some unexpected properties deriving from the molecular structure of bile acids have been unveiled as relevant to the receptor activation and may hence be used to design novel, selective and potent TGR5 agonists.

The 16α-hydroxylated Bile Acid, Pythocholic Acid Decreases Food Intake and Increases Oleoylethanolamide in Male Mice

Modulation of bile acid (BA) structure is a potential strategy for obesity and metabolic disease treatment. BAs act not only as signaling molecules involved in energy expenditure and glucose homeostasis, but also as regulators of food intake. The structure of BAs, particularly the position of the hydroxyl groups of BAs, impacts food intake partly by intestinal effects: (1) modulating the activity of N-acyl phosphatidylethanolamine phospholipase D, which produces the anorexigenic bioactive lipid oleoylethanolamide (OEA) or (2) regulating lipid absorption and the gastric emptying-satiation pathway. We hypothesized that 16α-hydroxylated BAs uniquely regulate food intake because of the long intermeal intervals in snake species in which these BAs are abundant. However, the effects of 16α-hydroxylated BAs in mammals are completely unknown because they are not naturally found in mammals. To test the effect of 16α-hydroxylated BAs on food intake, we isolated the 16α-hydroxylated BA pythocholic acid from ball pythons (Python regius). Pythocholic acid or deoxycholic acid (DCA) was given by oral gavage in mice. DCA is known to increase N-acyl phosphatidylethanolamine phospholipase D activity better than other mammalian BAs. We evaluated food intake, OEA levels, and gastric emptying in mice. We successfully isolated pythocholic acid from ball pythons for experimental use. Pythocholic acid treatment significantly decreased food intake in comparison to DCA treatment, and this was associated with increased jejunal OEA, but resulted in no change in gastric emptying or lipid absorption. The exogenous BA pythocholic acid is a novel regulator of food intake and the satiety signal for OEA in the mouse intestine.

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

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

Gene expression profiling reveals the genomic changes caused by MLN4924 and the sensitizing effects of NAPEPLD knockdown in pancreatic cancer

MLN4924 inhibits the proteolytic degradation of Cullin-Ring E3 ligase (CRL) substrates and exhibits antitumor activity toward various malignancies, including pancreatic cancer. MLN4924 suppresses tumor growth by altering various key regulator proteins; however, its impact on gene expression in tumors remains unknown. In this study, the genomic changes caused by MLN4924 in pancreatic cancer were examined by gene chip analysis and ingenuity pathway analysis. Eleven pathways were significantly altered (5 activated and 6 inhibited), 45 functions were significantly changed (21 activated and 24 inhibited), and the most activated upstream factor was predicted to be TNF. Of 691 differentially expressed genes, NAPEPLD knockdown showed synergism with MLN4924, as determined by real-time quantitative PCR and high content screening. NAPEPLD knockdown enhanced the effect of MLN4924 on inhibiting proliferation and inducing apoptosis in vitro. In a pancreatic cancer nude mouse model, MLN4924 inhibited tumor growth more significantly in the NAPEPLD knockdown group than in the control group. NAPEPLD expression was higher in pancreatic cancer tissues than in the normal pancreas but was not associated with prognosis. These findings indicate that MLN4924 causes extensive genomic changes in pancreatic cancer cells, and targeting NAPEPLD may increase the efficacy of MLN4924.

High-Fat, Western-Style Diet, Systemic Inflammation, and Gut Microbiota: A Narrative Review

The gut microbiota is responsible for recovering energy from food, providing hosts with vitamins, and providing a barrier function against exogenous pathogens. In addition, it is involved in maintaining the integrity of the intestinal epithelial barrier, crucial for the functional maturation of the gut immune system. The Western diet (WD)—an unhealthy diet with high consumption of fats—can be broadly characterized by overeating, frequent snacking, and a prolonged postprandial state. The term WD is commonly known and intuitively understood. However, the strict digital expression of nutrient ratios is not precisely defined. Based on the US data for 1908–1989, the calory intake available from fats increased from 32% to 45%. Besides the metabolic aspects (hyperinsulinemia, insulin resistance, dyslipidemia, sympathetic nervous system and renin-angiotensin system overstimulation, and oxidative stress), the consequences of excessive fat consumption (high-fat diet—HFD) comprise dysbiosis, gut barrier dysfunction, increased intestinal permeability, and leakage of toxic bacterial metabolites into the circulation. These can strongly contribute to the development of low-grade systemic inflammation. This narrative review highlights the most important recent advances linking HFD-driven dysbiosis and HFD-related inflammation, presents the pathomechanisms for these phenomena, and examines the possible causative relationship between pro-inflammatory status and gut microbiota changes.

Exploring the endocannabinoidome in genetically obese (ob/ob) and diabetic (db/db) mice: Links with inflammation and gut microbiota

BACKGROUND

Obesity and type 2 diabetes are two interrelated metabolic disorders characterized by insulin resistance and a mild chronic inflammatory state. We previously observed that leptin (ob/ob) and leptin receptor (db/db) knockout mice display a distinct inflammatory tone in the liver and adipose tissue. The present study aimed at investigating whether alterations in these tissues of the molecules belonging to the endocannabinoidome (eCBome), an extension of the endocannabinoid (eCB) signaling system, whose functions are important in the context of metabolic disorders and inflammation, could reflect their different inflammatory phenotypes.

RESULTS

The basal eCBome lipid and gene expression profiles, measured by targeted lipidomics and qPCR transcriptomics, respectively, in the liver and subcutaneous or visceral adipose tissues, highlighted a differentially altered eCBome tone, which may explain the impaired hepatic function and more pronounced liver inflammation remarked in the ob/ob mice, as well as the more pronounced inflammatory state observed in the subcutaneous adipose tissue of db/db mice. In particular, the levels of linoleic acid-derived endocannabinoid-like molecules, of one of their 12-lipoxygenase metabolites and of Trpv2 expression, were always altered in tissues exhibiting the highest inflammation. Correlation studies suggested the possible interactions with some gut microbiota bacterial taxa, whose respective absolute abundances were significantly different between ob/ob and the db/db mice.

CONCLUSIONS

The present findings emphasize the possibility that bioactive lipids and the respective receptors and enzymes belonging to the eCBome may sustain the tissue-dependent inflammatory state that characterizes obesity and diabetes, possibly in relation with gut microbiome alterations.

The rise and fall of anandamide: processes that control synthesis, degradation, and storage

Anandamide is an endocannabinoid derived from arachidonic acid-containing membrane lipids and has numerous biological functions. Its effects are primarily mediated by the cannabinoid receptors CB1 and CB2, and the vanilloid TRPV1 receptor. Anandamide is known to be involved in sleeping and eating patterns as well as pleasure enhancement and pain relief. This manuscript provides a review of anandamide synthesis, degradation, and storage and hence the homeostasis of the anandamide signaling system.

The Liver under the Spotlight: Bile Acids and Oxysterols as Pivotal Actors Controlling Metabolism

Among the myriad of molecules produced by the liver, both bile acids and their precursors, the oxysterols are becoming pivotal bioactive lipids which have been underestimated for a long time. Their actions are ranging from regulation of energy homeostasis (i.e., glucose and lipid metabolism) to inflammation and immunity, thereby opening the avenue to new treatments to tackle metabolic disorders associated with obesity (e.g., type 2 diabetes and hepatic steatosis) and inflammatory diseases. Here, we review the biosynthesis of these endocrine factors including their interconnection with the gut microbiota and their impact on host homeostasis as well as their attractive potential for the development of therapeutic strategies for metabolic disorders.

Structure-Activity Relationship Studies of Pyrimidine-4-Carboxamides as Inhibitors of N-Acylphosphatidylethanolamine Phospholipase D

N-Acylphosphatidylethanolamine phospholipase D (NAPE-PLD) is regarded as the main enzyme responsible for the biosynthesis of N-acylethanolamines (NAEs), a family of bioactive lipid mediators. Previously, we reported N-(cyclopropylmethyl)-6-((S)-3-hydroxypyrrolidin-1-yl)-2-((S)-3-phenylpiperidin-1-yl)pyrimidine-4-carboxamide (1, LEI-401) as the first potent and selective NAPE-PLD inhibitor that decreased NAEs in the brains of freely moving mice and modulated emotional behavior [MockNat Chem. Biol., 2020, 16, 667−67532393901]. Here, we describe the structure–activity relationship (SAR) of a library of pyrimidine-4-carboxamides as inhibitors of NAPE-PLD that led to the identification of LEI-401. A high-throughput screening hit was modified at three different substituents to optimize its potency and lipophilicity. Conformational restriction of an N-methylphenethylamine group by replacement with an (S)-3-phenylpiperidine increased the inhibitory potency 3-fold. Exchange of a morpholine substituent for an (S)-3-hydroxypyrrolidine reduced the lipophilicity and further increased activity by 10-fold, affording LEI-401 as a nanomolar potent inhibitor with drug-like properties. LEI-401 is a suitable pharmacological tool compound to investigate NAPE-PLD function in vitro and in vivo.

Bile acid composition regulates GPR119-dependent intestinal lipid sensing and food intake regulation in mice

OBJECTIVES

Lipid mediators in the GI tract regulate satiation and satiety. Bile acids (BAs) regulate the absorption and metabolism of dietary lipid in the intestine, but their effects on lipid-regulated satiation and satiety are completely unknown. Investigating this is challenging because introducing excessive BAs or eliminating BAs strongly impacts GI functions. We used a mouse model (Cyp8b1^-/- mice) with normal total BA levels, but alterations in the composition of the BA pool that impact multiple aspects of intestinal lipid metabolism. We tested two hypotheses: BAs affect food intake by (1) regulating production of the bioactive lipid oleoylethanolamide (OEA), which enhances satiety; or (2) regulating the quantity and localisation of hydrolysed fat in small intestine, which controls gastric emptying and satiation.

DESIGN

We evaluated OEA levels, gastric emptying and food intake in wild-type and Cyp8b1^-/- mice. We assessed the role of the fat receptor GPR119 in these effects using Gpr119^-/- mice.

RESULTS

Cyp8b1^-/- mice on a chow diet showed mild hypophagia. Jejunal OEA production was blunted in Cyp8b1^-/- mice, thus these data do not support a role for this pathway in the hypophagia of Cyp8b1^-/- mice. On the other hand, Cyp8b1 deficiency decreased gastric emptying, and this was dependent on dietary fat. GPR119 deficiency normalised the gastric emptying, gut hormone levels, food intake and body weight of Cyp8b1^-/- mice.

CONCLUSION

BAs regulate gastric emptying and satiation by determining fat-dependent GPR119 activity in distal intestine.

The Physiological Importance of Bile Acid Structure and Composition on Glucose Homeostasis

PURPOSE OF REVIEW

Studies have identified several effects of bile acids (BAs) in glucose homeostasis, energy expenditure, and body weight control, through receptor-dependent and independent mechanisms. BAs are produced from cholesterol and characterized by their structures, which result from enzymes in the liver and the gut microbiota. The aim of this review is to characterize the effects of BA structure and composition on diabetes.

RECENT FINDINGS

The hydroxyl groups of BAs interact with binding pockets of receptors and enzymes that affect glucose homeostasis. Human and animal studies show that BA composition is associated with insulin resistance and food intake regulation. The hydroxylation of BAs and BA composition contributes to glucose regulation. Modulation of BA composition has the potential to improve glucose metabolism.

Patent highlights December 2019-January 2020

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

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.

Hepatic NAPE-PLD Is a Key Regulator of Liver Lipid Metabolism

Diverse metabolic disorders have been associated with an alteration of N-acylethanolamine (NAE) levels. These bioactive lipids are synthesized mainly by N-acylphosphatidylethanolamine-selective phospholipase D (NAPE-PLD) and influence host metabolism. We have previously discovered that NAPE-PLD in the intestine and adipose tissue is connected to the pathophysiology of obesity. However, the physiological function of NAPE-PLD in the liver remains to be deciphered. To study the role of liver NAPE-PLD on metabolism, we generated a new mouse model of inducible Napepld hepatocyte-specific deletion (Napepld∆Hep mice). In this study, we report that Napepld∆Hep mice develop a high-fat diet-like phenotype, characterized by an increased fat mass gain, hepatic steatosis and we show that Napepld∆Hep mice are more sensitive to liver inflammation. We also demonstrate that the role of liver NAPE-PLD goes beyond the mere synthesis of NAEs, since the deletion of NAPE-PLD is associated with a marked modification of various bioactive lipids involved in host homeostasis such as oxysterols and bile acids. Collectively these data suggest that NAPE-PLD in hepatocytes is a key regulator of liver bioactive lipid synthesis and a dysregulation of this enzyme leads to metabolic complications. Therefore, deepening our understanding of the regulation of NAPE-PLD could be crucial to tackle obesity and related comorbidities.

Microbiome, bile acids, and obesity: How microbially modified metabolites shape anti-tumor immunity

Bile acids (BAs) are known facilitators of nutrient absorption but recent paradigm shifts now recognize BAs as signaling molecules regulating both innate and adaptive immunity. Bile acids are synthesized from cholesterol in the liver with subsequent microbial modification and fermentation adding complexity to pool composition. Bile acids act on several receptors such as Farnesoid X Receptor and the G protein-coupled BA receptor 1 (TGR5). Interestingly, BA receptors (BARs) are expressed on immune cells and activation either by BAs or BAR agonists modulates innate and adaptive immune cell populations skewing their polarization toward a more tolerogenic anti-inflammatory phenotype. Intriguingly, recent evidence also suggests that BAs promote anti-tumor immune response through activation and recruitment of tumoricidal immune cells such as natural killer T cells. These exciting findings have redefined BA signaling in health and disease wherein they may suppress inflammation on the one hand, yet promote anti-tumor immunity on the other hand. In this review, we provide our readers with the most recent understanding of the interaction of BAs with the host microbiome, their effect on innate and adaptive immunity in health and disease with a special focus on obesity, bariatric surgery-induced weight loss, and immune checkpoint blockade in cancer.

Bile acids in glucose metabolism and insulin signalling - mechanisms and research needs

Of all the novel glucoregulatory molecules discovered in the past 20 years, bile acids (BAs) are notable for the fact that they were hiding in plain sight. BAs were well known for their requirement in dietary lipid absorption and biliary cholesterol secretion, due to their micelle-forming properties. However, it was not until 1999 that BAs were discovered to be endogenous ligands for the nuclear receptor FXR. Since that time, BAs have been shown to act through multiple receptors (PXR, VDR, TGR5 and S1PR2), as well as to have receptor-independent mechanisms (membrane dynamics, allosteric modulation of N-acyl phosphatidylethanolamine phospholipase D). We now also have an appreciation of the range of physiological, pathophysiological and therapeutic conditions in which endogenous BAs are altered, raising the possibility that BAs contribute to the effects of these conditions on glycaemia. In this Review, we highlight the mechanisms by which BAs regulate glucose homeostasis and the settings in which endogenous BAs are altered, and provide suggestions for future research.

Metabolic Effects of Bile Acids: Potential Role in Bariatric Surgery

Bariatric surgery is the most effective and durable treatment for morbid obesity, with an unexplained yet beneficial side effect of restoring insulin sensitivity and improving glycemia, often before weight loss is observed. Among the many contributing mechanisms often cited, the altered handling of intestinal bile acids is of considerable therapeutic interest. Here, we review a growing body of literature examining the metabolic effects of bile acids ranging from their physical roles in dietary fat handling within the intestine to their functions as endocrine and paracrine hormones in potentiating responses to bariatric surgery. The roles of 2 important bile acid receptors, Takeda G-protein coupled receptor (also known as G-protein coupled bile acid receptor) and farnesoid X receptor, are highlighted as is downstream signaling through glucagon-like polypeptide 1 and its cognate receptor. Additional improvements in other phenotypes and potential contributions of commensal gut bacteria, such as Akkermansia muciniphila, which are manifest after Roux-en-Y gastric bypass and other emulations, such as gallbladder bile diversion to the ileum, are also discussed.

Secondary Bile Acids and Short Chain Fatty Acids in the Colon: A Focus on Colonic Microbiome, Cell Proliferation, Inflammation, and Cancer

Secondary bile acids (BAs) and short chain fatty acids (SCFAs), two major types of bacterial metabolites in the colon, cause opposing effects on colonic inflammation at chronically high physiological levels. Primary BAs play critical roles in cholesterol metabolism, lipid digestion, and host–microbe interaction. Although BAs are reabsorbed via enterohepatic circulation, primary BAs serve as substrates for bacterial biotransformation to secondary BAs in the colon. High-fat diets increase secondary BAs, such as deoxycholic acid (DCA) and lithocholic acid (LCA), which are risk factors for colonic inflammation and cancer. In contrast, increased dietary fiber intake is associated with anti-inflammatory and anticancer effects. These effects may be due to the increased production of the SCFAs acetate, propionate, and butyrate during dietary fiber fermentation in the colon. Elucidation of the molecular events by which secondary BAs and SCFAs regulate colonic cell proliferation and inflammation will lead to a better understanding of the anticancer potential of dietary fiber in the context of high-fat diet-related colon cancer. This article reviews the current knowledge concerning the effects of secondary BAs and SCFAs on the proliferation of colon epithelial cells, inflammation, cancer, and the associated microbiome.

Cannabidiol's Upregulation of N-acyl Ethanolamines in the Central Nervous System Requires N-acyl Phosphatidyl Ethanolamine-Specific Phospholipase D

Introduction: Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD) are bioactive cannabinoids. We recently showed that acute THC administration drives region-dependent changes in the mouse brain lipidome. This study tested the hypothesis that cell lines representing cell types present in the central nervous system (CNS), neurons (N18 cells), astrocytes (C6 glioma cells), and microglia (BV2 cells) would respond differently to THC, CBD, or their combination. This experimental strategy also allowed us to test the hypothesis that THC and CBD are metabolized differently if presented in combination and to test the hypothesis that responses to CBD are not like the fatty acid amide hydrolase (FAAH) inhibitor URB597. Finally, we tested the hypothesis that CBD's CNS effects would differ in the N-acyl phosphatidyl ethanolamine-specific phospholipase D (NAPE-PLD) knockout (KO) compared to wild-type (WT) mice. Methods: N18, C6, and BV2 cells were stimulated with 1 μM THC, 1 μM CBD, 1 μM THC:CBD, 1 μM URB597, or vehicle for 2 h and lipids extracted. Adult female WT and NAPE-PLD KO mice were injected with 3 mg/kg CBD or vehicle i.p., brains collected 2 h later, eight brain regions dissected, and lipids extracted. Extracted lipids were characterized and quantified using high-pressure liquid chromatography coupled with tandem mass spectrometry (HPLC/MS/MS). Results: Lipid levels in each cell type were differentially affected by THC, CBD, or THC:CBD with a few exceptions. In all cell lines, THC increased levels of arachidonic acid and CBD increased levels of N-acyl ethanolamines (NAEs), including N-arachidonoyl ethanolamine. More THC remained when cells were coincubated with CBD; however, levels of THC metabolites were cell-type dependent. CBD and URB597 caused very different lipid profiles in the cell-based assays with the primary similarity being increases in NAEs. CBD increased levels of NAEs in the WT hippocampus, cerebellum, thalamus, cortex, midbrain, and brainstem; however, NAEs did not increase in any brain region after CBD in NAPE-PLD KO mice. Conclusions: CBD and THC differentially modify the lipidome of the brain and CNS-type cell lines. Increases in NAEs observed after CBD treatment had previously been attributed to FAAH inhibition; however, data here suggest the alternative hypothesis that CBD is activating NAPE-PLD to increase NAE levels.

Secondary Unconjugated Bile Acids Induce Hepatic Stellate Cell Activation

Hepatic stellate cells (HSCs) are key players in liver fibrosis, cellular senescence, and hepatic carcinogenesis. Bile acids (BAs) are involved in the activation of HSCs, but the detailed mechanism of this process remains unclear. We conducted a comprehensive DNA microarray study of the human HSC line LX-2 treated with deoxycholic acid (DCA), a secondary unconjugated BA. Additionally, LX-2 cells were exposed to nine BAs and studied using immunofluorescence staining, enzyme-linked immunosorbent assay, and flow cytometry to examine the mechanisms of HSC activation. We focused on the tumor necrosis factor (TNF) pathway and revealed upregulation of genes related to nuclear factor kappa B (NF-κB) signaling and senescence-associated secretory phenotype factors. α-Smooth muscle actin (α-SMA) was highly expressed in cells treated with secondary unconjugated BAs, including DCA, and a morphological change associated with radial extension of subendothelial protrusion was observed. Interleukin-6 level in culture supernatant was significantly higher in cells treated with secondary unconjugated BAs. Flow cytometry showed that the proportion of cells highly expressing α-SMA was significantly increased in HSCs cultured with secondary unconjugated BAs. We demonstrated that secondary unconjugated BAs induced the activation of human HSCs.

Endocannabinoids in Body Weight Control

Maintenance of body weight is fundamental to maintain one's health and to promote longevity. Nevertheless, it appears that the global obesity epidemic is still constantly increasing. Endocannabinoids (eCBs) are lipid messengers that are involved in overall body weight control by interfering with manifold central and peripheral regulatory circuits that orchestrate energy homeostasis. Initially, blocking of eCB signaling by first generation cannabinoid type 1 receptor (CB1) inverse agonists such as rimonabant revealed body weight-reducing effects in laboratory animals and men. Unfortunately, rimonabant also induced severe psychiatric side effects. At this point, it became clear that future cannabinoid research has to decipher more precisely the underlying central and peripheral mechanisms behind eCB-driven control of feeding behavior and whole body energy metabolism. Here, we will summarize the most recent advances in understanding how central eCBs interfere with circuits in the brain that control food intake and energy expenditure. Next, we will focus on how peripheral eCBs affect food digestion, nutrient transformation and energy expenditure by interfering with signaling cascades in the gastrointestinal tract, liver, pancreas, fat depots and endocrine glands. To finally outline the safe future potential of cannabinoids as medicines, our overall goal is to address the molecular, cellular and pharmacological logic behind central and peripheral eCB-mediated body weight control, and to figure out how these precise mechanistic insights are currently transferred into the development of next generation cannabinoid medicines displaying clearly improved safety profiles, such as significantly reduced side effects.

Canine NAPEPLD-associated models of human myelin disorders

Canine leukoencephalomyelopathy (LEMP) is a juvenile-onset neurodegenerative disorder of the CNS white matter currently described in Rottweiler and Leonberger dogs. Genome-wide association study (GWAS) allowed us to map LEMP in a Leonberger cohort to dog chromosome 18. Subsequent whole genome re-sequencing of a Leonberger case enabled the identification of a single private homozygous non-synonymous missense variant located in the highly conserved metallo-beta-lactamase domain of the N-acyl phosphatidylethanolamine phospholipase D (NAPEPLD) gene, encoding an enzyme of the endocannabinoid system. We then sequenced this gene in LEMP-affected Rottweilers and identified a different frameshift variant, which is predicted to replace the C-terminal metallo-beta-lactamase domain of the wild type protein. Haplotype analysis of SNP array genotypes revealed that the frameshift variant was present in diverse haplotypes in Rottweilers, and also in Great Danes, indicating an old origin of this second NAPEPLD variant. The identification of different NAPEPLD variants in dog breeds affected by leukoencephalopathies with heterogeneous pathological features, implicates the NAPEPLD enzyme as important in myelin homeostasis, and suggests a novel candidate gene for myelination disorders in people.

Synthesis and characterization of the first inhibitor of N-acylphosphatidylethanolamine phospholipase D (NAPE-PLD)

N-Acylphosphatidylethanolamine phospholipase D (NAPE-PLD) is a membrane-associated zinc enzyme that catalyzes the hydrolysis of N-acylphosphatidylethanolamines (NAPEs) into fatty acid ethanolamides (FAEs). Here, we describe the identification of the first small-molecule NAPE-PLD inhibitor, the quinazoline sulfonamide derivative 2,4-dioxo-N-[4-(4-pyridyl)phenyl]-1H-quinazoline-6-sulfonamide, ARN19874.

Determination of Dynamical Heterogeneity from Dynamic Neutron Scattering of Proteins

Motional displacements of hydrogen (H) in proteins can be measured using incoherent neutron-scattering methods. These displacements can also be calculated numerically using data from molecular dynamics simulations. An enormous amount of data on the average mean-square motional displacement (MSD) of H as a function of protein temperature, hydration, and other conditions has been collected. H resides in a wide spectrum of sites in a protein. Some H are tightly bound to molecular chains, and the H motion is dictated by that of the chain. Other H are quite independent. As a result, there is a distribution of motions and MSDs of H within a protein that is denoted dynamical heterogeneity. The goal of this paper is to incorporate a distribution of MSDs into models of the H incoherent intermediate scattering function, I(Q,t), that is calculated and observed. The aim is to contribute information on the distribution as well as on the average MSD from comparison of the models with simulations and experiment. For example, we find that simulations of I(Q,t) in lysozyme are well reproduced if the distribution of MSDs is bimodal with two broad peaks rather than a single broad peak.

Mammalian enzymes responsible for the biosynthesis of N-acylethanolamines

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

Endocannabinoid Turnover

In this review, we consider the biosynthetic, hydrolytic, and oxidative metabolism of the endocannabinoids anandamide and 2-arachidonoylglycerol. We describe the enzymes associated with these events and their characterization. We identify the inhibitor profile for these enzymes and the status of therapeutic exploitation, which to date has been limited to clinical trials for fatty acid amide hydrolase inhibitors. To bring the review to a close, we consider whether point block of a single enzyme is likely to be the most successful approach for therapeutic exploitation of the endocannabinoid system.

Chemoproteomic Profiling of Bile Acid Interacting Proteins

Bile acids (BAs) are a family of endogenous metabolites synthesized from cholesterol in liver and modified by microbiota in gut. Being amphipathic molecules, the major function of BAs is to help with dietary lipid digestion. In addition, they also act as signaling molecules to regulate lipid and glucose metabolism as well as gut microbiota composition in the host. Remarkably, recent discoveries of the dedicated receptors for BAs such as FXR and TGR5 have uncovered a number of novel actions of BAs as signaling hormones which play significant roles in both physiological and pathological conditions. Disorders in BAs' metabolism are closely related to metabolic syndrome and intestinal and neurodegenerative diseases. Though BA-based therapies have been clinically implemented for decades, the regulatory mechanism of BA is still poorly understood and a comprehensive characterization of BA-interacting proteins in proteome remains elusive. We herein describe a chemoproteomic strategy that uses a number of structurally diverse, clickable, and photoreactive BA-based probes in combination with quantitative mass spectrometry to globally profile BA-interacting proteins in mammalian cells. Over 600 BA-interacting protein targets were identified, including known endogenous receptors and transporters of BA. Analysis of these novel BA-interacting proteins revealed that they are mainly enriched in functional pathways such as endoplasmic reticulum (ER) stress response and lipid metabolism, and are predicted with strong implications with Alzheimer's disease, non-alcoholic fatty liver disease, and diarrhea. Our findings will significantly improve the current understanding of BAs' regulatory roles in human physiology and diseases.