Loss of PPAR gamma in immune cells impairs the ability of abscisic acid to improve insulin sensitivity by suppressing monocyte chemoattractant protein-1 expression and macrophage infiltration into white adipose tissue

Peroxisome Proliferator-Activated Receptor α/γ and Cannabinoid Receptor 2 Agonist Attenuated Nonalcoholic Steatohepatitis Exosome-Related Abnormalities in Mice

This study explored the mechanisms and effects of 1 month of peroxisome proliferator-activated receptor (PPAR)α/γ agonist aleglitazar (10 mg/kg per day) or cannabinoid receptor 2 (CB2R) agonist JWH015 (3 mg/kg per day), alone or combined, on visceral adipose tissue (VAT)-derived extracellular vesicle (EV) release and associated systemic/VAT inflammation, decreased VAT capillary density/fibrosis, and intestinal inflammation/hyperpermeability in nonalcoholic steatohepatitis (NASH) mice. High EV release from VAT of NASH mice was associated with severe systemic/VAT/intestinal inflammation, reduced capillary network of VAT, and intestinal hyperpermeability. Combined JWH015 with aleglitazar treatment suppressed high-fat diet-induced obesity/adiposity, inhibited VAT expansion, reduced VAT inflammation/fibrosis, normalized VAT capillary network, and attenuated intestinal mucosal injury, inflammation, and hyperpermeability in NASH + aleglitazar + JWH015 mice. The inhibition of adipose tissue (AT)-derived EV release and hypoxia-inducible factor (HIF)1α levels in AT-derived EV, normalization of CB2R, PPARα, PPARγ, PPARγ1, PPARγ2, tight junction proteins, vascular endothelial growth factor/CD31 expression, and down-regulation of HIF1α, monocyte chemoattractant protein-1, and transforming growth factor-β1 were observed in the VAT and intestine of the NASH + aleglitazar + jwh015 group. In vitro experiments revealed that PPARα/γ and CB2R activation attenuated NASH AT-derived EV-induced pathogenic changes in the J774/SVEC4-10/Caco2/3T3-L1 cell system. This study suggested that VAT-derived EVs contribute to the pathogenesis of NASH and that combined PPARα/γ and CB2R agonist treatment ameliorated the abovementioned abnormalities of NASH mice.

Role of Abscisic Acid in the Whole-Body Regulation of Glucose Uptake and Metabolism

Abscisic acid (ABA) is a hormone with a long evolutionary history, dating back to the earliest living organisms, of which modern (ABA-producing) cyanobacteria are likely descendants, which existed long before the separation of the plant and animal kingdoms, with a conserved role as signals regulating cell responses to environmental challenges. In mammals, along with the anti-inflammatory and neuroprotective function of ABA, nanomolar ABA regulates the metabolic response to glucose availability by stimulating glucose uptake in skeletal muscle and adipose tissue via an insulin-independent mechanism and increasing metabolic energy production and also dissipation in brown and white adipocytes. Chronic ABA intake of micrograms per Kg body weight improves blood glucose, lipids, and morphometric parameters (waist circumference and body mass index) in borderline subjects for prediabetes and metabolic syndrome. This review summarizes the most recent in vitro and in vivo data obtained with nanomolar ABA, the involvement of the receptors LANCL1 and LANCL2 in the hormone's action, and the importance of mammals' endowment with two distinct hormones governing the metabolic response to glucose availability. Finally, unresolved issues and future directions for the clinical use of ABA in diabetes are discussed.

The phytohormone abscisic acid enhances remyelination in mouse models of multiple sclerosis

Introduction

Over the past few decades, there has been a sudden rise in the incidence of Multiple Sclerosis (MS) in Western countries. However, current treatments often show limited efficacy in certain patients and are associated with adverse effects, which highlights the need for safer and more effective therapeutic approaches. Environmental factors, particularly dietary habits, have been observed to play a substantial role in the development of MS. In this study, we are the first to investigate the potential protective effect of the phytohormone abscisic acid (ABA) in MS. ABA, which is abundant in fruits such as figs, apricots and bilberries, is known to cross the blood-brain barrier and has demonstrated neuroprotective effects in conditions like depression and Alzheimer's disease.

Methods

In this study, we investigated whether ABA supplementation enhances remyelination in both ex vivo and in vivo mouse models.

Results

Our results indicated that ABA enhanced remyelination and that this enhanced remyelination is associated with increased lipid droplet load, reduced levels of degraded myelin, and a higher abundance of F4/80+ cells in the demyelinated brain of mice treated with ABA. In in vitro models, we further demonstrated that ABA treatment elevates lipid droplet formation by enhancing the phagocytic capacity of macrophages. Additionally, in a mouse model of microglial activation, we showed that ABA-treated mice maintain a less inflammatory microglial phenotype.

Conclusion

Our findings highlight a crucial role for macrophages and microglia in enabling ABA to enhance the remyelination process. Furthermore, ABA's ability to improve remyelination together with its ability to reduce microglial activation, make ABA a promising candidate for modulating macrophage phenotype and reducing neuroinflammation in MS.

Naturally Occurring Compounds Targeting Peroxisome Proliferator Receptors: Potential Molecular Mechanisms and Future Perspectives for Promoting Human Health

Background: Peroxisome-proliferator-activated receptors (PPARs) constitute nuclear transcription factors controlling gene expression associated with cell growth and proliferation, diverse proteins, lipids, and glucose metabolism, being related to several other pathophysiological states such as metabolic disorders, atherogenesis, carcinogenesis, etc. The present survey aims to analyze the natural compounds that can act as agonists for the PPAR-α, PPAR-β/δ, and PPAR-γ system targeting, highlighting how the amazing biochemical diversity of natural compounds can yield new insights into this “hotspot” of the scientific field. Methods: A narrative review was performed by searching the recent international literature for the last two decades in the most authoritative scientific databases, like PubMed, Scopus, Web of Science, and Embase, using appropriate keywords. Results: Several natural compounds and/or their synthetic derivatives can act as ligands of PPARs, stimulating their transcriptional activity and enabling their use as preventive and/or therapeutic agents for several disease states, such as inflammation, oxidative stress, metabolic disturbances, atherogenesis, and carcinogenesis. Although synthetic compounds are increasingly used as drugs to manage health problems, serious side effects have been observed, while their natural analogues exhibit only few minor side effects. Conclusions: Further clinical studies on natural compounds such as ligands of PPARs and the evaluation of the related molecular mechanisms are needed to implement an effective strategy concerning the pharmaco-technology, food chemistry, and nutrition to introduce them as part of clinical and dietary practice.

Abscisic acid, an evolutionary conserved hormone: Biosynthesis, therapeutic and diagnostic applications in mammals

Abscisic acid (ABA), a phytohormone traditionally recognized for its role in plant stress responses, has recently emerged as a significant player in mammalian defense mechanisms. Like plants, various mammalian cell types synthesize ABA in response to specific health challenges, although the precise pathways remain not fully elucidated. ABA is associated with the regulation of inflammation and insulin signaling, prompting extensive research into its potential as a therapeutic agent for various diseases. ABA exerts its effects through its receptors, particularly PPAR-γ and LANCL-2, which serve as signaling hubs regulating numerous pathways. Through these interactions, ABA profoundly impacts mammalian health, and new ABA targets continue to be identified. Numerous studies in animal models demonstrate ABA's benefit in managing conditions such as neurological and psychiatric disorders, cancer, and malaria infections, all of which involve significant inflammatory dysregulation. In this manuscript we review the studies covering ABA synthesis and release in cell cultures, the signaling pathways regulated by ABA, and how these impact health in preclinical models. Furthermore, we highlight recent research suggesting that measuring ABA levels in human body fluids could serve as a useful biomarker for pathological conditions, providing insights into disease progression and treatment efficacy. This comprehensive review outlines the current understanding of ABA in mammalian pathophysiology, identifying gaps in knowledge, particularly concerning ABA biosynthesis and metabolism in mammals. In addition, this study emphasizes the need for clinical trials to validate the effectiveness of ABA-based therapies and its reliability as a biomarker for various diseases.

Discovering novel targets of abscisic acid using computational approaches

Abscisic acid (ABA) is a crucial plant hormone that is naturally produced in various mammalian tissues and holds significant potential as a therapeutic molecule in humans. ABA is selected for this study due to its known roles in essential human metabolic processes, such as glucose homeostasis, immune responses, cardiovascular system, and inflammation regulation. Despite its known importance, the molecular mechanism underlying ABA's action remain largely unexplored. This study employed computational techniques to identify potential human ABA receptors. We screened 64 candidate molecules using online servers and performed molecular docking to assess binding affinity and interaction types with ABA. The stability and dynamics of the best complexes were investigated using molecular dynamics simulation over a 100 ns time period. Root mean square fluctuations (RMSF), root mean square deviation (RMSD), solvent-accessible surface area (SASA), radius of gyration (Rg), free energy landscape (FEL), and principal component analysis (PCA) were analyzed. Next, the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method was employed to calculate the binding energies of the complexes based on the simulated data. Our study successfully pinpointed four key receptors responsible for ABA signaling (androgen receptor, glucocorticoid receptor, mineralocorticoid receptor, and retinoic acid receptor beta) that have a strong affinity for binding with ABA and remained structurally stable throughout the simulations. The simulations with Hydralazine as an unrelated ligand were conducted to validate the specificity of the identified receptors for ABA. The findings of this study can contribute to further experimental validation and a better understanding of how ABA functions in humans.

Reappraisal of Adipose Tissue Inflammation in Obesity

Chronic low-grade inflammation is a central component in the pathogenesis of obesity-related expansion of adipose tissue and complications in other metabolic tissues. Five different signaling pathways are defined as dominant determinants of adipose tissue inflammation: These are increased circulating endotoxin due to dysregulation in the microbiota-gut-brain axis, systemic oxidative stress, macrophage accumulation, and adipocyte death. Finally, the nucleotide-binding and oligomerization domain (NOD) leucine-rich repeat family pyrin domain-containing 3 (NLRP3) inflammasome pathway is noted to be a key regulator of metabolic inflammation. The NLRP3 inflammasome and associated metabolic inflammation play an important role in the relationships among fatty acids and obesity. Several highly active molecules, including primarily leptin, resistin, adiponectin, visfatin, and classical cytokines, are abundantly released from adipocytes. The most important cytokines that are released by inflammatory cells infiltrating obese adipose tissue are tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), monocyte chemoattractant protein 1 (MCP-1) (CCL-2), and IL-1. All these molecules mentioned above act on immune cells, causing local and then general inflammation. Three metabolic pathways are noteworthy in the development of adipose tissue inflammation: toll-like receptor 4 (TLR4)/phosphatidylinositol-3'-kinase (PI3K)/Protein kinase B (Akt) signaling pathway, endoplasmic reticulum (ER) stress-derived unfolded protein response (UPR), and inhibitor of nuclear factor kappa-B kinase beta (IKKβ)-nuclear factor kappa B (NF-κB) pathway. In fact, adipose tissue inflammation is an adaptive response that contributes to a visceral depot barrier that effectively filters gut-derived endotoxin. Excessive fatty acid release worsens adipose tissue inflammation and contributes to insulin resistance. However, suppression of adipose inflammation in obesity with anti-inflammatory drugs is not a rational solution and paradoxically promotes insulin resistance, despite beneficial effects on weight gain. Inflammatory pathways in adipocytes are indeed indispensable for maintaining systemic insulin sensitivity. Cannabinoid type 1 receptor (CB1R) is important in obesity-induced pro-inflammatory response; however, blockade of CB1R, contrary to anti-inflammatory drugs, breaks the links between insulin resistance and adipose tissue inflammation. Obesity, however, could be decreased by improving leptin signaling, white adipose tissue browning, gut microbiota interactions, and alleviating inflammation. Furthermore, capsaicin synthesized by chilies is thought to be a new and promising therapeutic option in obesity, as it prevents metabolic endotoxemia and systemic chronic low-grade inflammation caused by high-fat diet.

New Insights into the LANCL2- Binding Mode towards the Evaluation of New LANCL Agonists

The lanthionine synthetase C-like (LANCL) proteins include LANCL2, which is expressed in the central nervous system (CNS) and in peripheral tissues. LANCL2 exhibits glutathionylation activity and is involved in the neutralization of reactive electrophiles. Several studies explored LANCL2 activation as a validated pharmacological target for diabetes and inflammatory bowel disease. In this context, LANCL2 was found to bind the natural product abscisic acid (ABA), whose pre-clinical effectiveness in different inflammatory diseases was reported in the literature. More recently, LANCL2 attracted more attention as a valuable resource in the field of neurodegenerative disorders. ABA was found to regulate neuro-inflammation and synaptic plasticity to enhance learning and memory, exhibiting promising neuroprotective effects. Up until now, a limited number of LANCL2 ligands are known; among them, BT-11 is the only compound patented and investigated for its anti-inflammatory properties. To guide the design of novel putative LANCL2 agonists, a computational study including molecular docking and long molecular dynamic (MD) simulations of both ABA and BT-11 was carried out. The results pointed out the main LANCL2 ligand chemical features towards the following virtual screening of a novel putative LANCL2 agonist (AR-42). Biochemical assays on rat H9c2 cardiomyocytes showed a similar, LANCL2-mediated stimulation by BT-11 and by AR-42 of the mitochondrial proton gradient and of the transcriptional activation of the AMPK/PGC-1α/Sirt1 axis, the master regulator of mitochondrial function, effects that are previously observed with ABA. These results may allow the development of LANCL2 agonists for the treatment of mitochondrial dysfunction, a common feature of chronic and degenerative diseases.

Abscisic acid ameliorates motor disabilities in 6-OHDA-induced mice model of Parkinson's disease

Parkinson's disease (PD) is characterized by a myriad of symptoms, encompassing both motor disabilities and cognitive impairments. Recent research has shown that abscisic acid (ABA) is a phytohormone found in various brain regions of several mammals and exhibits neuroprotective properties. To investigate the effects of ABA on cognitive and motor disorders, a mouse model of PD was utilized. The administration of 6-hydroxydopamine (6-OHDA) to the lateral ventricles was conducted, with ABA (10 and 15 μg/mouse, i. c.v.) being administered for one week after the 6-OHDA injection for 4 days. Motor and cognitive performance were evaluated through the use of open field, rotarod, wire grip, and shuttle box tests. The results indicated that cognitive function and motor disorders were significantly impaired in 6-OHDA-treated animals. However, in mice treated with 6-OHDA, ABA (15 μg/mouse) significantly reversed balance and muscle strength deficits. It should be noted that the administration of ABA did not significantly improve cognitive impairment or rearing in Parkinsonism mice. Therefore, the findings suggest that ABA plays a crucial role in protecting mice from motor disabilities caused by 6-OHDA.

Maple Syrup: Chemical Analysis and Nutritional Profile, Health Impacts, Safety and Quality Control, and Food Industry Applications

Maple syrup is a delicacy prepared by boiling the sap taken from numerous Acer species, primarily sugar maple trees. Compared to other natural sweeteners, maple syrup is believed to be preferable to refined sugar for its high concentration of phenolic compounds and mineral content. The presence of organic acids (malic acid), amino acids and relevant amounts of minerals, such as potassium, calcium, zinc and manganese, make maple syrup unique. Given the growing demand for naturally derived sweeteners over the past decade, this review paper deals with and discusses in detail the most important aspects of chemical maple syrup analyses, with a particular emphasis on the advantages and disadvantages of the different analytical approaches. A successful utilization on the application of maple syrup in the food industry, will rely on a better understanding of its safety, quality control, nutritional profile, and health impacts, including its sustainability issues.

Engineering a highly sensitive biosensor for abscisic acid in mammalian cells

Abscisic acid (ABA) is a signaling molecule conserved in plants, bacteria, fungi and animals. Recently, ABA has gained attention for its pharmacological activities and its potential as a biomarker for the severity of chronic obstructive pulmonary disease (COPD) and glioma. This prompts the development of a reliable, sensitive, rapid, and cost-effective method to quantify ABA levels in mammalian cells and tissues. The previously described ABA biosensor system based on the ABA-dependent interaction between the plant ABA receptor PYL1 and co-receptor ABI1 is not sensitive enough for the low ABA levels seen in mammals. Therefore, we optimized this system by replacing PYL1 with other high-affinity plant PYL proteins. The optimized biosensor system engineered with the PYL8 receptor enabled the quantification of ABA at low concentrations in HEK293T cells.

Phytohormone abscisic acid elicits positive effects on harmaline-induced cognitive and motor disturbances in a rat model of essential tremor

OBJECTIVE

Essential tremor (ET) as a neurological disorder is accompanied by cognitive and motor disturbances. Despite the high incidence of ET, the drug treatment of ET remains unsatisfactory. Recently, abscisic acid (ABA) has been reported to have positive neurophysiological effects in mammals. Here, the effects of ABA on harmaline-induced motor and cognitive impairments were investigated in rats.

METHODS

Male Wistar rats weighing 120-140 g were divided into control, harmaline (30 mg/kg, ip), ABA vehicle (DMSO+normal saline), and ABA (10 μg/rat, icv, 30 min before harmaline injection) groups. Exploratory, balance and motor performance, anxiety, and cognitive function were assessed using footprint, open field, wire grip, rotarod, and shuttle box tests.

RESULTS

The results indicated that ABA (10 μg/rat) can improve harmaline-induced tremor in rats. The administration of ABA significantly increased time spent on wire grip and rotarod. In addition, ABA had a promising effect against the cognitive impairments induced by harmaline.

CONCLUSION

Taken together, ABA has positive effects on locomotor and cognitive impairments induced by tremor. However, further studies are required to determine the exact mechanisms of ABA on the ET.

Abscisic acid inhibited reactive oxygen species-mediated endoplasmic reticulum stress by regulating the PPAR-γ signaling pathway in ARDS mice

Acute respiratory distress syndrome (ARDS) is a life-threatening form of a respiratory disorder, and there are few effective therapies. Abscisic acid (ABA) has been proven to be effective in influenza and asthma. Herein, we explored the protective effect of ABA on the resolution of ARDS and the underlying mechanism. Mice were challenged with lipopolysaccharide (LPS) to establish an ARDS model. We found that ABA reduced pulmonary injury, with concomitant suppression of endoplasmic reticulum (ER) stress and reduction of reactive oxygen species (ROS) production. Furthermore, after the elimination of ROS by the specific inhibitor N-acetyl-L-cysteine (NAC), ABA did not further inhibit airway inflammation or ER stress in ARDS mice. In addition, ABA inhibited ROS production through nuclear factor erythroid 2-related factor 2 (Nrf2) activation in parallel with elevated levels of peroxisome proliferator activated receptor γ (PPAR-γ). Furthermore, the addition of a PPAR-γ antagonist abrogated the suppressive action of ABA on inflammation as well as on ER stress and oxidative stress, while NAC restored the protective effect of ABA in ARDS mice treated with a PPAR-γ antagonist. Collectively, ABA protects against LPS-induced lung injury through PPAR-γ signaling, and this effect may be associated with its inhibitory effect on ROS-mediated ER stress.

Effects of Des-acyl Ghrelin on Insulin Sensitivity and Macrophage Polarization in Adipose Tissue

Background and Objectives

Obesity is the accumulation of adipose tissue caused by excess energy in the body, accompanied by long-term chronic low-grade inflammation of adipose tissue. More than 50% of interstitial cells in adipose tissue are macrophages, which produce cytokines closely related to insulin resistance. Macrophage biology is driven by two polarization phenotypes, M1 (proinflammatory) and M2 (anti-inflammatory). This study aimed to investigate the effect of gastric hormone des-acyl ghrelin (DAG) on the polarization phenotype of macrophages and elucidate the role of macrophages in adipose tissue inflammation and insulin sensitivity and its molecular mechanism.

Methods

Mice were subcutaneously administrated with DAG in osmotic minipumps. The mice were fed a normal diet or a high-fat diet (HFD). Different macrophage markers were detected by real-time revere transcription polymerase chain reaction.

Results

Exogenous administration of DAG significantly inhibited the increase of adipocyte volume caused by HFD and reduced the number of rosette-like structures in adipose tissue. HFD in the control group significantly increased M1 macrophage markers, tumor necrosis factor α (TNFα), and inducible NO synthase (iNOS). However, these increases were reduced or even reversed after DAG administration in vitro. The M2 markers, macrophage galactose type C-type Lectin-1 (MGL1), arginase 1 (Arg1), and macrophage mannose receptor 1 (MRC1) were decreased by HFD, and the downward trend was inhibited or reversed after DAG administration. Although Arg1 was elevated after HFD, the fold increase after DAG administration in vitro was much greater than that in the control group.

Conclusion

DAG inhibits adipose tissue inflammation caused by HFD, reduces infiltration of macrophages in adipose tissue, and promotes polarization of macrophages to M2, thus alleviating obesity and improving insulin sensitivity.

Chemistry, processing, and functionality of maple food products: An updated comprehensive review

Maple sap is a rich nutrient matrix collected from Acer trees to produce several food products (i.e., sap, water, extract, syrup, and sugar), of which syrup is the most famous in the food industry for its distinct taste and flavor. Maple syrup is produced from the sap of several species (Acer saccharum, Acer nigrum, and Acer rubrum) of maple. Maple syrup is chiefly produced through the concentration of sap via thermal evaporation (pan evaporation) or membrane separation. Each processing technique affects the quality and characteristics of processed maple products. The chemistry of maple products is dominated by a myriad of other phytoconstituents other than sugar, that is, phenolics, to mediate for its many health benefits. The health-promoting effects of maple products included antioxidant, antimicrobial, antimutagenic, anti-inflammatory, and antiproliferative activities. This review capitalizes on maple food products focusing on their chemistry, processing, and health benefits compared with other sugar sweeteners. The impact of processing on maple syrup composition and biological effects in relation to original maple sap are further presented. PRACTICAL APPLICATIONS: Maple food products are natural sweeteners of significant importance due to their economic, nutritional, and health benefits. Apart from the predominant ingredient sucrose, the chemical composition of maple products comprises phenolics, pyrazines, vitamins, minerals, organic acids, and phytohormones. These bioactive compounds are of potential value owing to their health-promoting benefits, including antioxidant, antiproliferative, and antimutagenic effects. Quebecol, lariciresinol, and secoisolariciresinol are suggested as distinct markers for maple products and not common in other plant-derived syrups. Several factors, including the processing parameters and the phytochemical profile, affect maple products' flavor and color. In addition, microbial contamination of maple sap can also affect maple product quality. Further research on the effect of processing techniques and environmental conditions on the phytochemicals profile and biological effects of maple food products should now follow. Application of other omics tools, that is, genomics, proteomics, and metabolomics, to understand maple syrup effects on the human body can help reveal its exact action mechanisms or points for any potential health hazards for certain ailments.

Serum Concentration of the Phytohormone Abscisic Acid Is Associated With Immune-Regulatory Mediators and Is a Potential Biomarker of Disease Severity in Chronic Obstructive Pulmonary Disease

COPD and asthma are two distinct but sometimes overlapping diseases exhibiting varying degrees and types of inflammation on different stages of the disease. Although several biomarkers are defined to estimate the inflammatory endotype and stages in these diseases, there is still a need for new markers and potential therapeutic targets. We investigated the levels of a phytohormone, abscisic acid (ABA) and its receptor, LANCL2, in COPD patients and asthmatics. In addition, PPAR-γ that is activated by ABA in a ligand-binding domain-independent manner was also included in the study. In this study, we correlated ABA with COPD-propagating factors to define the possible role of ABA, in terms of immune regulation, inflammation, and disease stages. We collected blood from 101 COPD patients, 52 asthmatics, and 57 controls. Bronchoscopy was performed on five COPD patients and 29 controls. We employed (i) liquid chromatography–tandem mass spectrometry and HPLC to determine the ABA and indoleamine 2,3-dioxygenase levels, respectively; (ii) real-time PCR to quantify the gene expression of LANCL2 and PPAR-γ; (iii) Flow cytometry to quantify adipocytokines; and (iv) immunoturbidimetry and ELISA to measure CRP and cytokines, respectively. Finally, a multinomial regression model was used to predict the probability of using ABA as a biomarker. Blood ABA levels were significantly reduced in COPD patients and asthmatics compared to age- and gender-matched normal controls. However, PPAR-γ was elevated in COPD patients. Intriguingly, ABA was positively correlated with immune-regulatory factors and was negatively correlated with inflammatory markers, in COPD. Of note, ABA was increased in advanced COPD stages. We thereby conclude that ABA might be involved in regulation of COPD pathogenesis and might be regarded as a potential biomarker for COPD stages.

Phytohormone abscisic acid boosts pentobarbital-induced sleep through activation of GABA-A, PPARβ and PPARγ receptor signaling

BACKGROUND

Sleep disorders induce anxiety and forgetfulness and change habits. The chemical hypnotic drugs currently used have serious side effects and, therefore, people are drawn towards using natural compounds such as plant-based healing agents. Abscisic acid (ABA) is produced in a variety of mammalian tissues and it is involved in many neurophysiological functions.

OBJECTIVE

To investigate the possible effect of ABA on pentobarbital-induced sleep and its possible signaling through GABA-A and PPAR (γ and β) receptors, in male Wistar rats.

METHODS

The possible effect of ABA (5 and 10 µg/rat, intracerebroventricularly) on sleep onset latency time and duration was evaluated in a V-maze model of sleep. Pentobarbital sodium (40 mg/kg, intraperitoneally) was injected to induce sleep 30 min after administration of ABA. PPARβ (GSK0660, 80 nM/rat), PPARγ (GW9662, 3 nM/rat) or GABA-A receptor (bicuculline, 6 µg/rat) antagonists were given 15 min before ABA injection. Diazepam (2 mg/kg, intraperitoneally) was used as a positive control group.

RESULTS

ABA at 5 µg significantly boosted the pentobarbital-induced subhypnotic effects and promoted induction of sleep onset in a manner comparable to diazepam treatment. Furthermore, pretreatment with bicuculline significantly abolished the ABA effects on sleep parameters, while the amplifying effects of ABA on the induction of sleep onset was not significantly affected by PPARβ or PPARγ antagonists. The sleep prolonging effect of ABA was significantly prevented by both PPAR antagonists.

CONCLUSIONS

The data showed that ABA boosts pentobarbital-induced sleep and that GABA-A, PPARβ and PPARγ receptors are, at least in part, involved in ABA signaling.

The Role of Lipid Sensing Nuclear Receptors (PPARs and LXR) and Metabolic Lipases in Obesity, Diabetes and NAFLD

Obesity and type 2 diabetes mellitus (T2DM) are metabolic disorders characterized by metabolic inflexibility with multiple pathological organ manifestations, including non-alcoholic fatty liver disease (NAFLD). Nuclear receptors are ligand-dependent transcription factors with a multifaceted role in controlling many metabolic activities, such as regulation of genes involved in lipid and glucose metabolism and modulation of inflammatory genes. The activity of nuclear receptors is key in maintaining metabolic flexibility. Their activity depends on the availability of endogenous ligands, like fatty acids or oxysterols, and their derivatives produced by the catabolic action of metabolic lipases, most of which are under the control of nuclear receptors. For example, adipose triglyceride lipase (ATGL) is activated by peroxisome proliferator-activated receptor γ (PPARγ) and conversely releases fatty acids as ligands for PPARα, therefore, demonstrating the interdependency of nuclear receptors and lipases. The diverse biological functions and importance of nuclear receptors in metabolic syndrome and NAFLD has led to substantial effort to target them therapeutically. This review summarizes recent findings on the roles of lipases and selected nuclear receptors, PPARs, and liver X receptor (LXR) in obesity, diabetes, and NAFLD.

Abscisic acid suppresses the activation of NLRP3 inflammasome and oxidative stress in murine allergic airway inflammation

Abscisic acid (ABA), a well-known natural phytohormone reportedly exerts anti-inflammatory and anti-oxidative properties in diabetes and colitis. However, the efficacy of ABA against allergic airway inflammation and the underlying mechanism remain unknown. Herein, an OVA-induced murine allergic airway inflammation model was established and treated with ABA in the presence or absence of PPAR-γ antagonist GW9662. The results showed that ABA effectively stunted the development of airway inflammation, and concordantly downregulated OVA-induced activation of NLRP3 inflammasome, suppressed oxidative stress and decreased the expression of mitochondrial fusion/fission markers including Optic Atrophy 1 (OPA1), Mitofusion 2 (Mfn2), dynamin-related protein 1 (DRP1) and Fission 1 (Fis1). Moreover, ABA treatment further increased OVA-induced expression of PPAR-γ, while GW9662 abrogated the inhibitory effect of ABA on allergic airway inflammation as well as on the activation of NLRP3 inflammasome and oxidative stress. Consistently, ABA inhibited the activation of NLRP3 inflammasome, suppressed oxidative stress and mitochondrial fusion/fission in LPS-stimulated Raw264.7 cells via PPAR-γ. Collectively, ABA ameliorates OVA-induced allergic airway inflammation in a PPAR-γ dependent manner, and such effect of ABA may be associated with its inhibitory effect on NLRP3 inflammasome and oxidative stress. Our results suggest the potential of ABA or ABA-rich food in protecting against asthma.

Abscisic acid enriched fig extract promotes insulin sensitivity by decreasing systemic inflammation and activating LANCL2 in skeletal muscle

Abscisic acid is a phytohormone found in fruits and vegetables and is endogenously produced in mammals. In humans and mice, lanthionine synthetase C-like 2 (LANCL2) has been characterized as the natural receptor for ABA. Herein, we characterize the efficacy of a fig fruit extract of ABA in promoting glycemic control. This ABA-enriched extract, at 0.125 µg ABA/kg body weight, improves glucose tolerance, insulin sensitivity and fasting blood glucose in diet-induced obesity (DIO) and db/db mouse models. In addition to decreasing systemic inflammation and providing glycemic control without increasing insulin, ABA extract modulates the metabolic activity of muscle. ABA increases expression of important glycogen synthase, glucose, fatty acid and mitochondrial metabolism genes and increases direct measures of fatty acid oxidation, glucose oxidation and metabolic flexibility in soleus muscle cells from ABA-treated mice with DIO. Glycolytic and mitochondrial ATP production were increased in ABA-treated human myotubes. Further, ABA synergized with insulin to dramatically increase the rate of glycogen synthesis. The loss of LANCL2 in skeletal muscle abrogated the effect of ABA extract in the DIO model and increased fasting blood glucose levels. This data further supports the clinical development of ABA in the treatment of pre-diabetes, type 2 diabetes and metabolic syndrome.

Natural constituents from food sources as therapeutic agents for obesity and metabolic diseases targeting adipose tissue inflammation

Adipose tissue, an endocrine and paracrine organ, plays critical roles in the regulation of whole-body metabolic homeostasis. Obesity is accompanied with a chronic low-grade inflammation status in adipose tissue, which disrupts its endocrine function and results in metabolic derangements, such as type 2 diabetes. Dietary bioactive components, such as flavonoids, polyphenols and unsaturated fatty acids from fruits and vegetables, have been widely revealed to alleviate both systemic and adipose tissue inflammation, and improve metabolic disorders. Remarkably, some dietary bioactive components mitigate the inflammatory response in adipocytes, macrophages, and other immune cells, and modulate the crosstalk between adipocytes and macrophages or other immune cells, in adipose tissue. Epidemiological and preclinical studies related to these substances have indicated beneficial effects on adipose tissue inflammation. The main purpose of this review is to provide a comprehensive and up-to-date state of knowledge on dietary components targeting adipose tissue inflammation and their underlying mechanisms. These natural products have great potential to be developed as functional food or lead compounds for treating and/or preventing metabolic disorders.

Phytohormones: Multifunctional nutraceuticals against metabolic syndrome and comorbid diseases

Metabolic syndrome is characterized by the co-occurrence of diverse symptoms initiating the development of type 2 diabetes, cardiovascular diseases, and a variety of comorbid diseases. The complex constellation of numerous comorbidities makes it difficult to develop common therapeutic approaches that ameliorate these pathological features simultaneously. The plant hormones abscisic acid, salicylic acid, auxin, and cytokinins, have shown promising anti-inflammatory and pro-metabolic effects that could mitigate several disorders relevant to metabolic syndrome. Intriguingly, besides plants, human cells and gut microbes also endogenously produce these molecules, indicating a role in the complex interplay between inflammatory responses associated with metabolic syndrome, the gut microbiome, and nutrition. Here, we introduce how bioactive phytohormones can be generated endogenously and through the gut microbiome. These molecules subsequently influence immune responses and metabolism. We also elaborate on how phytohormones can beneficially modulate metabolic syndrome comorbidities, and propose them as nutraceuticals.

Early intervention with ABA prevents neuroinflammation and memory impairment in a triple transgenic mice model of Alzheimer´s disease

Neuroinflammation and insulin resistance in the brain are intimately linked to neurodegenerative disorders, including Alzheimer's disease. Even though traditionally Alzheimer´s disease has been associated to Aβ deposits and hyperphosphorylated Tau intracellular tangles, several studies show that neuroinflammation may be the initial cause that triggers degeneration. Accordingly, a number of natural supplements that improves brain insulin sensitivity and reduce neuroinflammation have been proposed as good choices in the therapeutic prevention of cognitive decline. Further supporting this evidence, we show that phytohormone Abscisic Acid, can prevent memory impairment and neuroinflammation markers in a triple transgenic mouse model, where no peripheral inflammatory changes have occurred. Moreover, our data strongly suggests that early intervention is critical for good prognosis, and that cognitive improvement requires longer treatment than recovering neuroinflammation markers.

Phytohormone abscisic acid ameliorates cognitive impairments in streptozotocin-induced rat model of Alzheimer's disease through PPARβ/δ and PKA signaling

Aim: Alzheimer's disease (AD) is characterized by oxidative stress, neuroinflammation and progressive cognitive decline. Abscisic acid (ABA) is produced in a variety of mammalian tissues, including brain. It has anti-inflammatory and antioxidant effects and elicits a positive effect on spatial learning and memory performance. Here, the possible protective effect of ABA was evaluated in streptozotocin (STZ)-induced AD rat model which were injected intracerebroventriculary (i.c.v.) with STZ (3 mg/kg). Material and Methods: The STZ-treated animals received ABA (10 μg/rat, i.c.v.), ABA plus PPARβ/δ receptor antagonist (GSK0660, 80 nM/rat) or ABA plus selective inhibitor of PKA (KT5720, 0.5 μg/rat) for 14 d. Learning and memory were determined using Morris water maze (MWM) and passive avoidance (PA) tests. Results: The data showed that STZ produced a significant learning and memory deficit in both MWM and PA tests. ABA significantly prevented the learning and memory impairment in STZ-treated rats. However, ABA effects were blocked by GSK0660 and KT5720. Conclusion: The data indicated that ABA attenuates STZ-induced learning and memory impairment and PPAR-β/δ receptors and PKA signaling are involved, at least in part, in the ABA mechanism.

Peroxisome proliferator-activated receptor γ (PPARγ) induces the gene expression of integrin αVβ5 to promote macrophage M2 polarization

Peroxisome proliferator-activated receptor γ (PPARγ) is a member of the nuclear receptor superfamily and polarizes the macrophages into an anti-inflammatory M2 state. Integrins are transmembrane receptors that drive various cellular functions, including monocyte adhesion and foam cell formation. In this study, we first reported that the expression of integrins α_V and β₅ was up-regulated by PPARγ activation in RAW264.7 cells and human peripheral blood monocytes. Luciferase reporter and ChIP assay revealed that PPARγ directly bound to the potential PPAR-responsive elements sites in the 5'-flanking regions of both murine and human integrin α_V and β₅ genes, respectively. In addition, we showed that PPARγ augmented the ligation of integrins α_V and β₅ Knockdown of integrin α_Vβ₅ by siRNA strategy or treatment with cilengitide, a potent inhibitor of integrin α_Vβ₅, attenuated PPARγ-induced expression of Ym1 (chitinase-like protein 3), Arg1 (Arginase1), Fizz1 (resistin-like molecule RELMα), and other M2 marker genes, suggesting that the heterodimers of integrin α_Vβ₅ were involved in PPARγ-induced M2 polarization. In conclusion, these results provided novel evidence that PPARγ-mediated gene expression and the ensuing ligation of integrins α_V and β₅ are implicated in macrophage M2 polarization.

Abscisic Acid Supplementation Rescues High Fat Diet-Induced Alterations in Hippocampal Inflammation and IRSs Expression

Accumulated evidence indicates that neuroinflammation induces insulin resistance in the brain. Moreover, both processes are intimately linked to neurodegenerative disorders, including Alzheimer's disease. Potential mechanisms underlying insulin resistance include serine phosphorylation of the insulin receptor substrate (IRS) or insulin receptor (IR) misallocation. However, only a few studies have focused on IRS expression in the brain and its modulation in neuroinflammatory processes. This study used the high-fat diet (HFD) model of neuroinflammation to study the alterations of IR, an insulin-like growth factor receptor (IGF1R) and IRS expressions in the hippocampus. We observed that HFD effectively reduced mRNA and protein IRS2 expression. In contrast, a HFD induced the upregulation of the IRS1 mRNA levels, but did not alter an IR and IGF1R expression. As expected, we observed that a HFD increased hippocampal tumor necrosis factor alpha (TNFα) and amyloid precursor protein (APP) levels while reducing brain-derived neurotrophic factor (BDNF) expression and neurogenesis. Interestingly, we found that TNFα correlated positively with IRS1 and negatively with IRS2, whereas APP levels correlated positively only with IRS1 but not IRS2. These results indicate that IRS1 and IRS2 hippocampal expression can be affected differently by HFD-induced neuroinflammation. In addition, we aimed to establish whether abscisic acid (ABA) can rescue hippocampal IRS1 and IRS2 expression, as we had previously shown that ABA supplementation prevents memory impairments and improves neuroinflammation induced by a HFD. In this study, ABA restored HFD-induced hippocampal alterations, including IRS1 and IRS2 expression, TNFα, APP, and BDNF levels and neurogenesis. In conclusion, this study highlights different regulations of hippocampal IRS1 and IRS2 expression using a HFD, indicating the important differences of these scaffolding proteins, and strongly supports ABA therapeutic effects.

Perivascular Adipose Tissue as a Relevant Fat Depot for Cardiovascular Risk in Obesity

Obesity is associated with increased risk of premature death, morbidity, and mortality from several cardiovascular diseases (CVDs), including stroke, coronary heart disease (CHD), myocardial infarction, and congestive heart failure. However, this is not a straightforward relationship. Although several studies have substantiated that obesity confers an independent and additive risk of all-cause and cardiovascular death, there is significant variability in these associations, with some lean individuals developing diseases and others remaining healthy despite severe obesity, the so-called metabolically healthy obese. Part of this variability has been attributed to the heterogeneity in both the distribution of body fat and the intrinsic properties of adipose tissue depots, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, hormonal control, thermogenic ability, and vascularization. In obesity, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. The adventitial fat layer, also known as perivascular adipose tissue (PVAT), is of major importance. Similar to the visceral adipose tissue, PVAT has a pathophysiological role in CVDs. PVAT influences vascular homeostasis by releasing numerous vasoactive factors, cytokines, and adipokines, which can readily target the underlying smooth muscle cell layers, regulating the vascular tone, distribution of blood flow, as well as angiogenesis, inflammatory processes, and redox status. In this review, we summarize the current knowledge and discuss the role of PVAT within the scope of adipose tissue as a major contributing factor to obesity-associated cardiovascular risk. Relevant clinical studies documenting the relationship between PVAT dysfunction and CVD with a focus on potential mechanisms by which PVAT contributes to obesity-related CVDs are pointed out.

Abscisic acid - an anti-angiogenic phytohormone that modulates the phenotypical plasticity of endothelial cells and macrophages

Abscisic acid (ABA) has shown anti-inflammatory and immunoregulatory properties in preclinical models of diabetes and inflammation. Herein, we studied the effects of ABA on angiogenesis, a strictly controlled process that, when dysregulated, leads to severe angiogenic disorders including vascular overgrowth, exudation, cellular inflammation and organ dysfunction. By using a 3D sprouting assay, we show that ABA effectively inhibits migration, growth and expansion of endothelial tubes without affecting cell viability. Analyses of the retinal vasculature in developing normoxic and hyperoxic mice challenged by oxygen toxicity reveal that exogenously administered ABA stunts the development and regeneration of blood vessels. In these models, ABA downregulates endothelial cell (EC)-specific growth and migratory genes, interferes with tip and stalk cell specification, and hinders the function of filopodial protrusions required for precise guidance of vascular sprouts. In addition, ABA skews macrophage polarization towards the M1 phenotype characterized by anti-angiogenic marker expression. In accordance with this, ABA treatment accelerates macrophage-induced programmed regression of fetal blood vessels. These findings reveal protective functions of ABA against neovascular growth through modulation of EC and macrophage plasticity, suggesting the potential utility of ABA as a treatment in vasoproliferative diseases.

Abscisic Acid: A Novel Nutraceutical for Glycemic Control

Abscisic acid is naturally present in fruits and vegetables, and it plays an important role in managing glucose homeostasis in humans. According to the latest U.S. dietary survey, about 92% of the population might have a deficient intake of ABA due to their deficient intake of fruits and vegetables. This review summarizes the in vitro, preclinical, mechanistic, and human translational findings obtained over the past 15 years in the study of the role of ABA in glycemic control. In 2007, dietary ABA was first reported to ameliorate glucose tolerance and obesity-related inflammation in mice. The most recent findings regarding the topic of ABA and its proposed receptor lanthionine synthetase C-like 2 in glycemic control and their interplay with insulin and glucagon-like peptide-1 suggest a major role for ABA in the physiological response to a glucose load in humans. Moreover, emerging evidence suggests that the ABA response might be dysfunctional in diabetic subjects. Follow on intervention studies in healthy individuals show that low-dose dietary ABA administration exerts a beneficial effect on the glycemia and insulinemia profiles after oral glucose load. These recent findings showing benefits in humans, together with extensive efficacy data in mouse models of diabetes and inflammatory disease, suggest the need for reference ABA values and its possible exploitation of the glycemia-lowering effects of ABA for preventative purposes. Larger clinical studies on healthy, prediabetic, and diabetic subjects are needed to determine whether addressing the widespread dietary ABA deficiency improves glucose control in humans.

Abscisic Acid as Pathogen Effector and Immune Regulator

Abscisic acid (ABA) is a sesquiterpene signaling molecule produced in all kingdoms of life. To date, the best known functions of ABA are derived from its role as a major phytohormone in plant abiotic stress resistance. Different organisms have developed different biosynthesis and signal transduction pathways related to ABA. Despite this, there are also intriguing common themes where ABA often suppresses host immune responses and is utilized by pathogens as an effector molecule. ABA also seems to play an important role in compatible mutualistic interactions such as mycorrhiza and rhizosphere bacteria with plants, and possibly also the animal gut microbiome. The frequent use of ABA in inter-species communication could be a possible reason for the wide distribution and re-invention of ABA as a signaling molecule in different organisms. In humans and animal models, it has been shown that ABA treatment or nutrient-derived ABA is beneficial in inflammatory diseases like colitis and type 2 diabetes, which confer potential to ABA as an interesting nutraceutical or pharmacognostic drug. The anti-inflammatory activity, cellular metabolic reprogramming, and other beneficial physiological and psychological effects of ABA treatment in humans and animal models has sparked an interest in this molecule and its signaling pathway as a novel pharmacological target. In contrast to plants, however, very little is known about the ABA biosynthesis and signaling in other organisms. Genes, tools and knowledge about ABA from plant sciences and studies of phytopathogenic fungi might benefit biomedical studies on the physiological role of endogenously generated ABA in humans.

The effect of abscisic acid chronic treatment on neuroinflammatory markers and memory in a rat model of high-fat diet induced neuroinflammation

Background

Western diet and lifestyle are associated with overweight, obesity, and type 2 diabetes, which, in turn, are correlated with neuroinflammation processes. Exercise and a healthy diet are important in the prevention of these disorders. However, molecules inhibiting neuroinflammation might also be efficacious in the prevention and/or treatment of neurological disorders of inflammatory etiology. The abscisic acid (ABA) is a phytohormone involved in hydric-stress responses. This compound is not only found in plants but also in other organisms, including mammals. In rodents, ABA can play a beneficial role in the regulation of peripheral immune response and insulin action. Thus, we hypothesized that chronic ABA administration might exert a protective effect in a model of neuroinflammation induced by high-fat diet (HFD).

Methods

Male Wistar rats were fed with standard diet or HFD with or without ABA in the drinking water for 12 weeks. Glucose tolerance test and behavioral paradigms were performed to evaluate the peripheral and central effects of treatments. One-Way ANOVA was performed analyzed statistical differences between groups.

Results

The HFD induced insulin resistance peripherally and increased the levels of proinflammatory markers in in the brain. We observed that ABA restored glucose tolerance in HFD-fed rats, as expected. In addition, chronic ABA treatment rescued cognitive performance in these animals, while not affecting control diet fed animals. Moreover, it counteracted the changes induced by HFD in the hypothalamus; microglia activations and TNFα mRNA levels.

Conclusion

These results suggest that ABA might become a new therapeutic molecule improving the neuroinflammatory status and insulin resistance.

New insight into determining indicators of metabolic status in women: Expression of PPARγ and FABP4 in PBMCs

Adiposity and its metabolic disturbances could be regulated by adipocyte-specific peroxisome proliferator-activated receptor gamma and fatty acid-binding protein4. Although these two proteins are mainly expressed in adipose tissues, they can also be expressed in peripheral blood mononuclear cells, which could be useful for predicting body composition and blood parameters. Thus, this cross-sectional study was performed during January 2013-January 2014 with 229 women (age range, 22-52 years) who were classified as obese or nonobese. Serum glucose, insulin, lipids, and body composition were measured in the fasting state. Peripheral blood mononuclear cells were isolated to extract ribonucleic acid (RNA) and to determine gene expression by real time polymerase chain reaction (PCR). All serum parameters and components of body composition were significantly higher in obese than in nonobese women. Gene expression analysis showed that serum levels of glucose and lipids, except high-density lipoprotein (HDL), were higher in the group that expressed high fatty acid-binding protein4. Increased expression of the peroxisome proliferator-activated receptor gamma was associated with a significant reduction of blood sugar and increased HDL and other lipids and visceral fat. Therefore, it seems that the level of expression of these genes in peripheral blood mononuclear cells may indicate metabolic status.

Supplementation with Abscisic Acid Reduces Malaria Disease Severity and Parasite Transmission

Nearly half of the world's population is at risk for malaria. Increasing drug resistance has intensified the need for novel therapeutics, including treatments with intrinsic transmission-blocking properties. In this study, we demonstrate that the isoprenoid abscisic acid (ABA) modulates signaling in the mammalian host to reduce parasitemia and the formation of transmissible gametocytes and in the mosquito host to reduce parasite infection. Oral ABA supplementation in a mouse model of malaria was well tolerated and led to reduced pathology and enhanced gene expression in the liver and spleen consistent with infection recovery. Oral ABA supplementation also increased mouse plasma ABA to levels that can signal in the mosquito midgut upon blood ingestion. Accordingly, we showed that supplementation of a Plasmodium falciparum-infected blood meal with ABA increased expression of mosquito nitric oxide synthase and reduced infection prevalence in a nitric oxide-dependent manner. Identification of the mechanisms whereby ABA reduces parasite growth in mammals and mosquitoes could shed light on the balance of immunity and metabolism across eukaryotes and provide a strong foundation for clinical translation.

Abscisic-acid-induced cellular apoptosis and differentiation in glioma via the retinoid acid signaling pathway

Retinoid acid (RA) plays critical roles in regulating differentiation and apoptosis in a variety of cancer cells. Abscisic acid (ABA) and RA are direct derivatives of carotenoids and share structural similarities. Here we proposed that ABA may also play a role in cellular differentiation and apoptosis by sharing a similar signaling pathway with RA that may be involved in glioma pathogenesis. We reported for the first time that the ABA levels were twofold higher in low-grade gliomas compared with high-grade gliomas. In glioma tissues, there was a positive correlation between the ABA levels and the transcription of cellular retinoic acid-binding protein 2 (CRABP2) and a negative correlation between the ABA levels and transcription of fatty acid-binding protein 5 (FABP5). ABA treatment induced a significant increase in the expression of CRABP2 and a decrease in the expression of peroxisome proliferator-activated receptor (PPAR) in glioblastoma cells. Remarkably, both cellular apoptosis and differentiation were increased in the glioblastoma cells after ABA treatment. ABA-induced cellular apoptosis and differentiation were significantly reduced by selectively silencing RAR-α, while RAR-α overexpression exaggerated the ABA-induced effects. These results suggest that ABA may play a role in the pathogenesis of glioma by promoting cellular apoptosis and differentiation through the RA signaling pathway.

Minireview: Emerging Concepts in Islet Macrophage Biology in Type 2 Diabetes

Chronic systemic inflammation is a hallmark feature of obesity and type 2 diabetes. Both resident and recruited islet macrophages contribute to the proinflammatory milieu of the diabetic islet. However, macrophages also appear to be critical for β-cell formation during development and support β-cell replication in experimental models of pancreas regeneration. In light of these findings, perhaps macrophages in the islet need to be viewed more as a fulcrum where deleterious inflammatory activation is balanced with beneficial tissue repair processes. Undoubtedly, defining the factors that contribute to the ontogeny, heterogeneity, and functionality of macrophages in normal, diseased, and regenerating islets will be necessary to determine whether that fulcrum can be moved to preserve functional β-cell mass in persons with diabetes. The intent of this review is to introduce the reader to emerging concepts of islet macrophage biology that may challenge the perception that macrophage accumulation in islets is merely a pathological feature of type 2 diabetes.

Preliminary evidence that abscisic acid improves spatial memory in rats

Abscisic acid (ABA) is a crucial phytohormone that exists in a wide range of animals, including humans, and has multiple bioactivities. As direct derivatives of carotenoids, ABA and retinoic acid (RA) share similar molecular structures, and RA has been reported to improve spatial memory in rodents. To explore the potential effects of ABA on spatial learning and memory in rodents, 20mg/kg ABA was administered to young rats for 6weeks, and its effects on behaviour performance were evaluated through a series of behavioural tests. ABA pharmacokinetic analysis revealed that the exogenous ABA was distributed widely in the rat brain, characterised by rapid absorption and slow elimination. The behavioural tests showed that ABA increased both the duration spent in the target quadrant and the frequency it was entered in the probe test of the Morris water maze (MWM) and decreased the latency to locate the target quadrant. Moreover, ABA decreased the latency to enter the novel arm in the Y-maze test, accompanied by increases in the total entries and distance travelled in the three arms. However, there were no significant differences between the ABA-treated and control rats in the open field test and elevated plus-maze test. These results preliminarily indicate that ABA improves spatial memory in MWM and exploratory activity in Y-maze in young rats.

Peroxisome proliferator-activated receptor agonists modulate neuropathic pain: a link to chemokines?

Chronic pain presents a widespread and intractable medical problem. While numerous pharmaceuticals are used to treat chronic pain, drugs that are safe for extended use and highly effective at treating the most severe pain do not yet exist. Chronic pain resulting from nervous system injury (neuropathic pain) is common in conditions ranging from multiple sclerosis to HIV-1 infection to type II diabetes. Inflammation caused by neuropathy is believed to contribute to the generation and maintenance of neuropathic pain. Chemokines are key inflammatory mediators, several of which (MCP-1, RANTES, MIP-1α, fractalkine, SDF-1 among others) have been linked to chronic, neuropathic pain in both human conditions and animal models. The important roles chemokines play in inflammation and pain make them an attractive therapeutic target. Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors known for their roles in metabolism. Recent research has revealed that PPARs also play a role in inflammatory gene repression. PPAR agonists have wide-ranging effects including inhibition of chemokine expression and pain behavior reduction in animal models. Experimental evidence suggests a connection between the pain ameliorating effects of PPAR agonists and suppression of inflammatory gene expression, including chemokines. In early clinical research, one PPARα agonist, palmitoylethanolamide (PEA), shows promise in relieving chronic pain. If this link can be better established, PPAR agonists may represent a new drug therapy for neuropathic pain.

Role of PPARs in inflammatory processes associated with metabolic syndrome (Review)

Metabolic syndrome (MS) includes the presence of arterial hypertension, insulin resistance, dyslipidemia, cardiovascular disease (CVD) and abdominal obesity, which is associated with a chronic inflammatory response, characterized by abnormal adipokine production, and the activation of certain pro-inflammatory signaling pathways. Furthermore, the changes presented by the adipose tissue in MS favors the secretion of several molecular mediators capable of activating or suppressing a number of transcription factors, such as the peroxisome proliferator-activated receptors (PPARs), whose main functions include storage regulation and fatty acid catabolization. When they are activated by their ligands (synthetic or endogenous), they control several genes involved in intermediate metabolism, which make them, together with the PPAR gamma coactivator-1-α (PGC-1) and the silent information regulator T1 (SIRT1), good targets for treating metabolic diseases and their cardiovascular complications.

Mechanisms of chronic state of inflammation as mediators that link obese adipose tissue and metabolic syndrome

The metabolic syndrome is a cluster of cardiometabolic alterations that include the presence of arterial hypertension, insulin resistance, dyslipidemia, and abdominal obesity. Obesity is associated with a chronic inflammatory response, characterized by abnormal adipokine production, and the activation of proinflammatory signalling pathways resulting in the induction of several biological markers of inflammation. Macrophage and lymphocyte infiltration in adipose tissue may contribute to the pathogenesis of obesity-mediated metabolic disorders. Adiponectin can either act directly on macrophages to shift polarization and/or prime human monocytes into alternative M2-macrophages with anti-inflammatory properties. Meanwhile, the chronic inflammation in adipose tissue is regulated by a series of transcription factors, mainly PPARs and C/EBPs, that in conjunction regulate the expression of hundreds of proteins that participate in the metabolism and storage of lipids and, as such, the secretion by adipocytes. Therefore, the management of the metabolic syndrome requires the development of new therapeutic strategies aimed to alter the main genetic pathways involved in the regulation of adipose tissue metabolism.

Mechanisms of chronic state of inflammation as mediators that link obese adipose tissue and metabolic syndrome

The metabolic syndrome is a cluster of cardiometabolic alterations that include the presence of arterial hypertension, insulin resistance, dyslipidemia, and abdominal obesity. Obesity is associated with a chronic inflammatory response, characterized by abnormal adipokine production, and the activation of proinflammatory signalling pathways resulting in the induction of several biological markers of inflammation. Macrophage and lymphocyte infiltration in adipose tissue may contribute to the pathogenesis of obesity-mediated metabolic disorders. Adiponectin can either act directly on macrophages to shift polarization and/or prime human monocytes into alternative M2-macrophages with anti-inflammatory properties. Meanwhile, the chronic inflammation in adipose tissue is regulated by a series of transcription factors, mainly PPARs and C/EBPs, that in conjunction regulate the expression of hundreds of proteins that participate in the metabolism and storage of lipids and, as such, the secretion by adipocytes. Therefore, the management of the metabolic syndrome requires the development of new therapeutic strategies aimed to alter the main genetic pathways involved in the regulation of adipose tissue metabolism.

Preventive and prophylactic mechanisms of action of pomegranate bioactive constituents

Pomegranate fruit presents strong anti-inflammatory, antioxidant, antiobesity, and antitumoral properties, thus leading to an increased popularity as a functional food and nutraceutical source since ancient times. It can be divided into three parts: seeds, peel, and juice, all of which seem to have medicinal benefits. Several studies investigate its bioactive components as a means to associate them with a specific beneficial effect and develop future products and therapeutic applications. Many beneficial effects are related to the presence of ellagic acid, ellagitannins (including punicalagins), punicic acid and other fatty acids, flavonoids, anthocyanidins, anthocyanins, estrogenic flavonols, and flavones, which seem to be its most therapeutically beneficial components. However, the synergistic action of the pomegranate constituents appears to be superior when compared to individual constituents. Promising results have been obtained for the treatment of certain diseases including obesity, insulin resistance, intestinal inflammation, and cancer. Although moderate consumption of pomegranate does not result in adverse effects, future studies are needed to assess safety and potential interactions with drugs that may alter the bioavailability of bioactive constituents of pomegranate as well as drugs. The aim of this review is to summarize the health effects and mechanisms of action of pomegranate extracts in chronic inflammatory diseases.

Nutritional protective mechanisms against gut inflammation

Inflammatory bowel disease (IBD) is a debilitating and widespread immune-mediated illness characterized by excessive inflammatory and effector mucosal responses leading to tissue destruction at the gastrointestinal tract. Interactions among the immune system, the commensal microbiota and the host genotype are thought to underlie the pathogenesis of IBD. However, the precise etiology of IBD remains unknown. Diet-induced changes in the composition of the gut microbiome can modulate the induction of regulatory versus effector immune responses at the gut mucosa and improve health outcomes. Therefore, manipulation of gut microbiota composition and the local production of microbial-derived metabolites by using prebiotics, probiotics and dietary fibers is being explored as a promising avenue of prophylactic and therapeutic intervention against gut inflammation. Prebiotics and fiber carbohydrates are fermented by resident microflora into short chain fatty acids (SCFAs) in the colon. SCFAs then activate peroxisome proliferator-activated receptor (PPAR)γ, a nuclear transcription factor with widely demonstrated anti-inflammatory efficacy in experimental IBD. The activation of PPARγ by naturally ocurring compounds such as conjugated linoleic acid, pomegranate seed oil-derived punicic acid, eleostearic acid and abscisic acid has been explored as nutritional interventions that suppress colitis by directly modulating the host immune response. The aim of this review is to summarize the status of innovative nutritional interventions against gastrointestinal inflammation, their proposed mechanisms of action, preclinical and clinical efficacy as well as bioinformatics and computational modeling approaches that accelerate discovery in nutritional and mucosal immunology research.

Helicobacter pylori colonization ameliorates glucose homeostasis in mice through a PPAR γ-dependent mechanism

Background

There is an inverse secular trend between the incidence of obesity and gastric colonization with Helicobacter pylori, a bacterium that can affect the secretion of gastric hormones that relate to energy homeostasis. H. pylori strains that carry the cag pathogenicity island (PAI) interact more intimately with gastric epithelial cells and trigger more extensive host responses than cag⁻ strains. We hypothesized that gastric colonization with H. pylori strains differing in cag PAI status exert distinct effects on metabolic and inflammatory phenotypes.

Methodology/Principal Findings

To test this hypothesis, we examined metabolic and inflammatory markers in db/db mice and mice with diet-induced obesity experimentally infected with isogenic forms of H. pylori strain 26695: the cag PAI wild-type and its cag PAI mutant strain 99–305. H. pylori colonization decreased fasting blood glucose levels, increased levels of leptin, improved glucose tolerance, and suppressed weight gain. A response found in both wild-type and mutant H. pylori strain-infected mice included decreased white adipose tissue macrophages (ATM) and increased adipose tissue regulatory T cells (Treg) cells. Gene expression analyses demonstrated upregulation of gastric PPAR γ-responsive genes (i.e., CD36 and FABP4) in H. pylori-infected mice. The loss of PPAR γ in immune and epithelial cells in mice impaired the ability of H. pylori to favorably modulate glucose homeostasis and ATM infiltration during high fat feeding.

Conclusions/Significance

Gastric infection with some commensal strains of H. pylori ameliorates glucose homeostasis in mice through a PPAR γ-dependent mechanism and modulates macrophage and Treg cell infiltration into the abdominal white adipose tissue.

Expression of PPAR γ in intestinal epithelial cells is dispensable for the prevention of colitis by dietary abscisic acid

BACKGROUND & AIMS

Dietary abscisic acid (ABA) has shown efficacy in ameliorating experimental IBD in mice through mechanisms requiring expression of peroxisome proliferator activated-receptor γ (PPAR γ) in immune cells. The goal of this study was to determine whether PPAR γ expression in colonic epithelial cells is required for the anti-inflammatory actions of ABA.

METHODS

Conditional knockout mice expressing a transgenic recombinase in intestinal epithelial cells under the control of a villin promoter (PPAR γ flfl; Villin Cre+ or VC+) with defective expression of PPAR γ in intestinal cells (IEC) and PPAR γ-expressing wild type (PPAR γ flfl; Villin Cre- or VC-) mice in a C57BL/6 background were fed diets with and without ABA (0.1 g/kg) for 35 days and challenged with 2.5% dextran sodium sulfate (DSS) in the drinking water for 7 days. Clinical disease severity was assessed daily and colonic lesions on day 7 through macroscopic and histopathological examination. Immune cell phenotypes were examined systemically and at the mesenteric lymph nodes (MLN). Epithelial gene expression was assayed in the colon.

RESULTS

Dietary ABA-supplementation prevented colitis, reduced disease severity, improved colonic histopathology, and upregulated epithelial lanthionine synthetase C-like protein 2 (LANCL2) expression in VC+ mice. Dietary ABA significantly increased the percentages of MLN CD4+IL-10+ T cells, and blood CD4+CD25+FoxP3+ T cells and CD8+IL-10+ T cells.

CONCLUSION

Expression of PPAR γ in IECs was not required for the anti-inflammatory efficacy of ABA in IBD. LANCL2 in IECs and T cell-derived IL-10 may be implicated in the mechanism underlying ABA's immune modulatory activity in IBD.