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

Cafeteria Diet Abstinence Induces Depressive Behavior and Disrupts Endocannabinoid Signaling in Dopaminergic Areas: A Preclinical Study

BACKGROUND

Alterations of dopamine (DA) transmission in the brain reward system can be associated with an addictive-like state defined as food addiction (FA), common in obese individuals. Subjects affected by FA experience negative feelings when abstinent from their preferred diet and may develop mood disorders, including depression, sustained by alterations in brain DA pathways.

OBJECTIVE

This study aims to investigate the impact of long-term abstinence from a palatable diet on depressive-like behavior in rats, exploring neurochemical alterations in monoamine and endocannabinoid signaling in DA-enriched brain regions, including ventral tegmental area, dorsolateral striatum, substantia nigra and medial prefrontal cortex.

METHODS

Rats underwent exposure and subsequent abstinence from a palatable cafeteria diet. During abstinence, animals were treated with fatty acid amide hydrolase (FAAH) inhibitor PF-3845 (10 mg/kg, intraperitoneal administration every other day). Lastly, animals were subjected to a forced swimming test, and their brains were dissected and processed for high-performance liquid chromatography measurement of monoamines and western blot analyses of markers of the endocannabinoid machinery.

RESULTS

After the withdrawal from the palatable diet, animals showed depressive-like behavior, coupled with significant variations in the concentration of brain monoamines and in the expression of endocannabinoid signalling machinery proteins in cited brain areas. Treatment with PF-3845 exerted an antidepressant- like effect and restored part of the alterations in monoaminergic and endocannabinoid systems.

CONCLUSION

Overall, our results suggest that abstinence from a cafeteria diet provokes emotional disturbances linked to neuroadaptive changes in monoamines and endocannabinoid signalling in brain areas partaking to DA transmission that could partially be restored by the enhancement of endocannabinoid signalling through FAAH inhibition.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Cellular Characteristics and Protein Signatures of Human Adipose Tissues from Donors With or Without Advanced Coronary Artery Disease

Background/Objectives: Perivascular adipose tissue (PVAT) exerts a paracrine effect on blood vessels and our objective was to understand PVAT molecular signatures related to cardiovascular disease. Methods: We studied two groups: those undergoing mitral valve repair/replacement (VR, n = 16) and coronary artery bypass graft (CABG, n = 38). VR donors did not have coronary artery disease, whereas CABG donors had advanced coronary artery disease. Clinical and tissue pathologies and proteomics from adipose tissue were assessed. Results: Donors undergoing VR had a lower body mass index (p = 0.01), HbA1C (p = 0.0023), and incidence of diabetes (p = 0.022) compared to CABG. VR donors were overall healthier, with higher cardiac function compared to CABG donors, based on ejection fraction. Although adipose histopathology between groups was not markedly different, PVAT had smaller and more adipocytes compared to subcutaneous adipose tissues. These differences were validated by whole specimen automated morphological analysis, and anisotropy analysis showed small (2.8-7.5 μm) and large (22.8-64.4 μm) scale differences between perivascular and subcutaneous adipose tissue from CABG donors, and small scale changes (2.8-7.5 μm) between perivascular and subcutaneous adipose tissue from VR donors. Distinct protein signatures in PVAT and subcutaneous adipose tissue include those involved in secretion, exosomes and vesicles, insulin resistance, and adipocyte identity. Comparing PVAT and subcutaneous adipose tissue from CABG donors, there were 82 significantly different proteins identified with log fold change ≥ 0.3 or ≤-0.3 (p < 0.05). Using this threshold, there were 36 differences when comparing PVAT and subcutaneous adipose tissue from VR donors, 58 differences when comparing PVAT from CABG or VR donors, and 55 when comparing subcutaneous adipose tissue from CABG vs. VR donors. Conclusions: Routine histopathology cannot differentiate between PVAT from donors with or without coronary artery disease, but multiscale anisotropy analysis discriminated between these populations. Our mass spectrometry analysis identified a cohort of proteins that distinguish between adipose depots, and are also associated with the presence or absence of coronary artery disease.

Screening and identification of key biomarkers associated with endometriosis using bioinformatics and next-generation sequencing data analysis

Background

Endometriosis is a common cause of endometrial-type mucosa outside the uterine cavity with symptoms such as painful periods, chronic pelvic pain, pain with intercourse and infertility. However, the early diagnosis of endometriosis is still restricted. The purpose of this investigation is to identify and validate the key biomarkers of endometriosis.

Methods

Next-generation sequencing dataset GSE243039 was obtained from the Gene Expression Omnibus database, and differentially expressed genes (DEGs) between endometriosis and normal control samples were identified. After screening of DEGs, gene ontology (GO) and REACTOME pathway enrichment analyses were performed. Furthermore, a protein–protein interaction (PPI) network was constructed and modules were analyzed using the Human Integrated Protein–Protein Interaction rEference database and Cytoscape software, and hub genes were identified. Subsequently, a network between miRNAs and hub genes, and network between TFs and hub genes were constructed using the miRNet and NetworkAnalyst tool, and possible key miRNAs and TFs were predicted. Finally, receiver operating characteristic curve analysis was used to validate the hub genes.

Results

A total of 958 DEGs, including 479 upregulated genes and 479 downregulated genes, were screened between endometriosis and normal control samples. GO and REACTOME pathway enrichment analyses of the 958 DEGs showed that they were mainly involved in multicellular organismal process, developmental process, signaling by GPCR and muscle contraction. Further analysis of the PPI network and modules identified 10 hub genes, including vcam1, snca, prkcb, adrb2, foxq1, mdfi, actbl2, prkd1, dapk1 and actc1. Possible target miRNAs, including hsa-mir-3143 and hsa-mir-2110, and target TFs, including tcf3 (transcription factor 3) and clock (clock circadian regulator), were predicted by constructing a miRNA-hub gene regulatory network and TF-hub gene regulatory network.

Conclusions

This investigation used bioinformatics techniques to explore the potential and novel biomarkers. These biomarkers might provide new ideas and methods for the early diagnosis, treatment and monitoring of endometriosis.

The endocannabinoid system in appetite regulation and treatment of obesity

The endocannabinoid system (ECS) is a complex cell-signaling system that is responsible for maintaining homeostasis by modulating various regulatory reactions in response to internal and environmental changes. The influence of ECS on appetite regulation has been a subject of much recent research, however, the full extent of its impact remains unknown. Current evidence links human obesity to ECS activation, increased endocannabinoid levels in both central and peripheral tissues, along with cannabinoid receptor type 1 (CBR1) up-regulation. These findings imply the potential pharmacological use of the ECS in the treatment of obesity. Here, we present various pathophysiological processes in obesity involving the ECS, highlighting different pharmacological options for modulating endocannabinoid activity to treat obesity. However, the potential of those pharmacological possibilities remains under investigation and requires further research.

Interplay between lipid metabolism, lipid droplets and RNA virus replication

Lipids play essential roles in the cell as components of cellular membranes, signaling molecules, and energy storage sources. Lipid droplets are cellular organelles composed of neutral lipids, such as triglycerides and cholesterol esters, and are also considered as cellular energy reserves, yet new functions have been recently associated with these structures, such as regulators of oxidative stress and cellular lipotoxicity, as well as modulators of pathogen infection through immune regulation. Lipid metabolism and lipid droplets participate in the infection process of many RNA viruses and control their replication and assembly, among others. Here, we review and discuss the contribution of lipid metabolism and lipid droplets over the replication cycle of RNA viruses, altogether pointing out potentially new pharmacological antiviral targets associated with lipid metabolism.

Different stressors uniquely affect the expression of endocannabinoid-metabolizing enzymes in the central ring ganglia of Lymnaea stagnalis

The endocannabinoid system (ECS) plays an important role in neuroprotection, neuroplasticity, energy balance, modulation of stress, and inflammatory responses, acting as a critical link between the brain and the body's peripheral regions, while also offering promising potential for novel therapeutic strategies. Unfortunately, in humans, pharmacological inhibitors of different ECS enzymes have led to mixed results in both preclinical and clinical studies. As the ECS has been highly conserved throughout the eukaryotic lineage, the use of invertebrate model organisms like the pond snail Lymnaea stagnalis may provide a flexible tool to unravel unexplored functions of the ECS at the cellular, synaptic, and behavioral levels. In this study, starting from the available genome and transcriptome of L. stagnalis, we first identified putative transcripts of all ECS enzymes containing an open reading frame. Each predicted protein possessed a high degree of sequence conservation to known orthologues of other invertebrate and vertebrate organisms. Sequences were confirmed by qualitative PCR and sequencing. Then, we investigated the transcriptional effects induced by different stress conditions (i.e., bacterial LPS injection, predator scent, food deprivation, and acute heat shock) on the expression levels of the enzymes of the ECS in Lymnaea's central ring ganglia. Our results suggest that in Lymnaea as in rodents, the ECS is involved in mediating inflammatory and anxiety-like responses, promoting energy balance, and responding to acute stressors. To our knowledge, this study offers the most comprehensive analysis so far of the ECS in an invertebrate model organism.

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

BACKGROUND

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

METHODS

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

RESULTS/CONCLUSIONS

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

A comprehensive review of genetic causes of obesity

BACKGROUND

Obesity is a multifactorial chronic disease with a high, increasing worldwide prevalence. Genetic causes account for 7% of the cases in children with extreme obesity.

DATA SOURCES

This narrative review was conducted by searching for papers published in the PubMed/MEDLINE, Embase and SciELO databases and included 161 articles. The search used the following search terms: "obesity", "obesity and genetics", "leptin", "Prader-Willi syndrome", and "melanocortins". The types of studies included were systematic reviews, clinical trials, prospective cohort studies, cross-sectional and prospective studies, narrative reviews, and case reports.

RESULTS

The leptin-melanocortin pathway is primarily responsible for the regulation of appetite and body weight. However, several important aspects of the pathophysiology of obesity remain unknown. Genetic causes of obesity can be grouped into syndromic, monogenic, and polygenic causes and should be assessed in children with extreme obesity before the age of 5 years, hyperphagia, or a family history of extreme obesity. A microarray study, an analysis of the melanocortin type 4 receptor gene mutations and leptin levels should be performed for this purpose. There are three therapeutic levels: lifestyle modifications, pharmacological treatment, and bariatric surgery.

CONCLUSIONS

Genetic study technologies are in constant development; however, we are still far from having a personalized approach to genetic causes of obesity. A significant proportion of the affected individuals are associated with genetic causes; however, there are still barriers to its approach, as it continues to be underdiagnosed. Video Abstract (MP4 1041807 KB).

FATP2 regulates non-small cell lung cancer by mediating lipid metabolism through ACSL1

Lipid metabolism is believed to play an important role in cancer. This study aimed to investigate the role and possible mechanism of fatty acid transporter protein 2 (FATP2) in non-small cell lung cancer (NSCLC). FATP2 expression and its relationship with NSCLC prognosis were analyzed using the TCGA database. The si-RNA was used to intervene FATP2 in NSCLC cells, and the effects of si-FATP2 on cell proliferation, apoptosis, lipid deposition, endoplasmic reticulum (ER) morphology, and the proteins expressions of fatty acid metabolism and ER stress were analyzed. In addition, Co-IP analyzed the interaction between FATP2 and ACSL1, and further analyzed the possible mechanism of FATP2 in regulating lipid metabolism using pcDNA-ACSL1. Results found that FATP2 was overexpressed in NSCLC and associated with poor prognosis. Si-FATP2 significantly inhibited the proliferation and lipid metabolism of A549 and HCC827 cells, and induced ER stress to promote apoptosis. Further studies confirmed the protein interaction between FATP2 and ACSL1. Si-FATP2 and pcDNA-ACSL1 co-transfection further inhibit the proliferation and lipid deposition of NSCLS cells, and promote the decomposition of fatty acids. In conclusion, FATP2 promoted the progression of NSCLC by regulating lipid metabolism through ACSL1.

Combination treatment with FAAH inhibitors/URB597 and ferroptosis inducers significantly decreases the growth and metastasis of renal cell carcinoma cells via the PI3K-AKT signaling pathway

Ferroptosis, a nonapoptotic form of programmed cell death characterized by significant iron-dependent peroxidation of phospholipids, is regulated by cellular metabolism, redox homeostasis, and various cancer-related signaling pathways. Recently, considerable progress has been made in demonstrating the critical role of lipid metabolism in regulating ferroptosis, indicating the potential of combinational strategies for treating cancer in the future. In this study, we explored the combinational effects of lipid metabolism compounds and ferroptosis inducers on renal cell carcinoma (RCC) cells. We found potent synergy of the fatty acid amide hydrolase (FAAH) inhibitor URB597 with ferroptosis inducer (1S, 3R)-RSL3 (RSL3) in inhibiting the growth and metastasis of RCC cells both in vitro and in vivo via induction of G1 cell cycle arrest and promotion of the production of lipid peroxides, malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), and cytosolic reactive oxygen species (ROS). In addition, inhibition of FAAH increased the sensitivity of RCC cells to ferroptosis. Genome-wide RNA sequencing indicated that the combination of URB597 and RSL3 has more significant effects on regulation of the expression of genes related to cell proliferation, the cell cycle, cell migration and invasion, and ferroptosis than either single agent alone. Moreover, we found that combinational treatment modulated the sensitivity of RCC cells to ferroptosis via the phosphatidylinositol 3 kinase (PI3K)-AKT signaling pathway. These data demonstrate that dual targeting of FAAH and ferroptosis could be a promising strategy for treating RCC.

Anxiety associated with palatable food withdrawal is reversed by the selective FAAH inhibitor PF-3845: A regional analysis of the contribution of endocannabinoid signaling machinery

OBJECTIVE

Consumption of energy-dense palatable "comfort" food can alleviate stress and negative emotions, while abrupt withdrawal from a palatable diet can worsen these symptoms, causing difficulties with adherence to weight-loss diets. Currently, no pharmacological treatment is effective for obesity-related anxiety, so we investigated the endocannabinoid system (ECS), and specifically the fatty acid amide hydrolase (FAAH), as an interesting emerging target in this context because of its key role in the regulation of both energy homeostasis and emotional behavior.

METHODS

Rats were subjected to exposure and subsequent abstinence from a palatable cafeteria diet. During abstinence period, rats were treated with the selective FAAH inhibitor PF-3845 (10 mg/kg; intraperitoneal administration every other day).

RESULTS

Abstinent rats displayed an anxiogenic-like behavior and changes in the proteins of ECS signaling machinery in brain areas involved both in anxiety and food intake regulation. In particular, withdrawal caused a reduction of the expression of cannabinoid receptors in the nucleus accumbens and of enzymes diacylglycerol lipase alpha and monoacylglycerol lipase (MAGL) in the amygdala. Pharmacological inhibition of FAAH exerted an anxiolytic-like effect in abstinent animals and increased both MAGL expression in amygdala and CB2 expression in prefrontal cortex.

DISCUSSION

Overall, our results suggest that emotional disturbances associated with dieting are coupled with region-specific alterations in the cerebral expression of the ECS and that the enhancement of the endocannabinoid signaling by FAAH inhibition might represent a novel pharmacological strategy for the treatment of anxiety related to abstinence from palatable food.

PUBLIC SIGNIFICANCE

The present study focused on evaluating the role of the endocannabinoid system in modulating withdrawal from naturally rewarding activities that have an impact on mood, such as feeding. The variations observed in the emotional behavior of abstinent rats was linked to neuroadaptations of the ECS in specific brain areas.

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

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

N-linoleyltyrosine ameliorates high-fat diet-induced obesity in C57BL/6 mice via cannabinoid receptor regulation

OBJECTIVES

N-linoleyltyrosine (NITyr) showed mild effects in preclinical studies. The research discussed the effect of NITyr on a high-fat diet (HFD) induced obese (DIO) mice, and preliminarily explored its mechanism.

METHODS

The DIO mice were established by feeding an HFD for 12 weeks and subsequently administrated orally with NITyr (30, 60 and 100 mg/kg) for four weeks. The indexes of serum and liver samples were determined by ELISA kit. The pathological status of adipose and liver were detected by HE staining. The factors related to energy and lipid metabolism were measured via western blot.

RESULTS

NITyr at 60 and 100 mg/kg/day suppressed the weight gain without affecting water and food intake. Accordingly, NITyr reduced adipose weight and the area of individual adipocytes and increased the number of adipocytes. Moreover, NITyr didn't affect the appetite-related indexes such as ghrelin, peptide YY and brain-derived neurotrophic factor. Besides, NITyr didn't affect other organ coefficients except for the liver. Correspondingly, NITyr reduced alanine aminotransferase and aspartate aminotransferase levels, yet didn't influence IL-1β and TNF-α levels, and the liver injury. The levels of triacylglycerol (TG), total cholesterol (TC), glucose, insulin, adiponectin and leptin in serum were assessed to evaluate the effect of NITyr on glucose and lipid metabolism. NITyr decreased the levels of TG, TC and glucose, and didn't affect insulin, adiponectin and leptin levels. Meanwhile, NITyr up-regulated p-AMPK and the cannabinoid receptor 2 (CB₂) expressions, and down-regulated PPAR, FAS and cannabinoid receptor 1 (CB₁) expressions.Overall, NITyr suppressed lipid accumulation via improving lipid and glucose metabolism involving CB₁ and CB₂ receptors.