Functional Regulation of PPARs through Post-Translational Modifications

Peroxisome Proliferator-Activated Receptor-Targeted Therapies: Challenges upon Infectious Diseases

Peroxisome proliferator-activated receptors (PPARs) α, β, and γ are nuclear receptors that orchestrate the transcriptional regulation of genes involved in a variety of biological responses, such as energy metabolism and homeostasis, regulation of inflammation, cellular development, and differentiation. The many roles played by the PPAR signaling pathways indicate that PPARs may be useful targets for various human diseases, including metabolic and inflammatory conditions and tumors. Accumulating evidence suggests that each PPAR plays prominent but different roles in viral, bacterial, and parasitic infectious disease development. In this review, we discuss recent PPAR research works that are focused on how PPARs control various infections and immune responses. In addition, we describe the current and potential therapeutic uses of PPAR agonists/antagonists in the context of infectious diseases. A more comprehensive understanding of the roles played by PPARs in terms of host-pathogen interactions will yield potential adjunctive personalized therapies employing PPAR-modulating agents.

The role of peroxisome proliferator-activated receptors in the modulation of hyperinflammation induced by SARS-CoV-2 infection: A perspective for COVID-19 therapy

Coronavirus disease 2019 (COVID-19) is a severe respiratory disease caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that affects the lower and upper respiratory tract in humans. SARS-CoV-2 infection is associated with the induction of a cascade of uncontrolled inflammatory responses in the host, ultimately leading to hyperinflammation or cytokine storm. Indeed, cytokine storm is a hallmark of SARS-CoV-2 immunopathogenesis, directly related to the severity of the disease and mortality in COVID-19 patients. Considering the lack of any definitive treatment for COVID-19, targeting key inflammatory factors to regulate the inflammatory response in COVID-19 patients could be a fundamental step to developing effective therapeutic strategies against SARS-CoV-2 infection. Currently, in addition to well-defined metabolic actions, especially lipid metabolism and glucose utilization, there is growing evidence of a central role of the ligand-dependent nuclear receptors and peroxisome proliferator-activated receptors (PPARs) including PPARα, PPARβ/δ, and PPARγ in the control of inflammatory signals in various human inflammatory diseases. This makes them attractive targets for developing therapeutic approaches to control/suppress the hyperinflammatory response in patients with severe COVID-19. In this review, we (1) investigate the anti-inflammatory mechanisms mediated by PPARs and their ligands during SARS-CoV-2 infection, and (2) on the basis of the recent literature, highlight the importance of PPAR subtypes for the development of promising therapeutic approaches against the cytokine storm in severe COVID-19 patients.

PPARγ (Peroxisome Proliferator-Activated Receptor γ) Deacetylation Suppresses Aging-Associated Atherosclerosis and Hypercholesterolemia

BACKGROUND

Atherosclerosis is a medical urgency manifesting at the onset of hypercholesterolemia and is associated with aging. Activation of PPARγ (peroxisome proliferator-activated receptor γ) counteracts metabolic dysfunction influenced by aging, and its deacetylation displays an atheroprotective property. Despite the marked increase of PPARγ acetylation during aging, it is unknown whether PPARγ acetylation is a pathogenic contributor to aging-associated atherosclerosis.

METHODS

Mice with constitutive deacetylation-mimetic PPARγ mutations on lysine residues K268 and K293 (2KR) in an LDL (low-density lipoprotein)-receptor knockout (Ldlr-/-) background (2KR:Ldlr-/-) were aged for 18 months on a standard laboratory diet to examine the cardiometabolic phenotype, which was confirmed in Western-type diet-fed 2KR:Ldlr+/- mice. Whole-liver RNA-sequencing and in vitro studies in bone marrow-derived macrophages were conducted to decipher the mechanism.

RESULTS

In contrast to severe atherosclerosis in WT:Ldlr-/- mice, aged 2KR:Ldlr-/- mice developed little to no plaque, which was underlain by a significantly improved plasma lipid profile, with particular reductions in circulating LDL. The protection from hypercholesterolemia was recapitulated in Western-type diet-fed 2KR:Ldlr+/- mice. Liver RNA-sequencing analysis revealed suppression of liver inflammation rather than changes in cholesterol metabolism. This anti-inflammatory effect of 2KR was attributed to polarized M2 activation of macrophages. Additionally, the upregulation of core circadian component Bmal1 (brain and muscle ARNT-like 1), perceived to be involved in anti-inflammatory immunity, was observed in the liver and bone marrow-derived macrophages.

CONCLUSIONS

PPARγ deacetylation in mice prevents the development of aging-associated atherosclerosis and hypercholesterolemia, in association with the anti-inflammatory phenotype of 2KR macrophages.

PPARγ Acetylation Orchestrates Adipose Plasticity and Metabolic Rhythms

Systemic glucose metabolism and insulin activity oscillate in response to diurnal rhythms and nutrient availability with the necessary involvement of adipose tissue to maintain metabolic homeostasis. However, the adipose-intrinsic regulatory mechanism remains elusive. Here, the dynamics of PPARγ acetylation in adipose tissue are shown to orchestrate metabolic oscillation in daily rhythms. Acetylation of PPARγ displays a diurnal rhythm in young healthy mice, with the peak at zeitgeber time 0 (ZT0) and the trough at ZT18. This rhythmic pattern is deranged in pathological conditions such as obesity, aging, and circadian disruption. The adipocyte-specific acetylation-mimetic mutation of PPARγ K293Q (aKQ) restrains adipose plasticity during calorie restriction and diet-induced obesity, associated with proteolysis of a core circadian component BMAL1. Consistently, the rhythmicity in glucose tolerance and insulin sensitivity is altered in aKQ and the complementary PPARγ deacetylation-mimetic K268R/K293R (2KR) mouse models. Furthermore, the PPARγ acetylation-sensitive downstream target adipsin is revealed as a novel diurnal factor that destabilizes BMAL1 and mediates metabolic rhythms. These findings collectively signify that PPARγ acetylation is a hinge connecting adipose plasticity and metabolic rhythms, the two determinants of metabolic health.

Endocannabinoid-Binding Receptors as Drug Targets

Cannabis plant has been used from ancient times with therapeutic purposes for treating human pathologies, but the identification of the cellular and molecular mechanisms underlying the therapeutic properties of the phytocannabinoids, the active compounds in this plant, occurred in the last years of the past century. In the late 1980s and early 1990s, seminal studies demonstrated the existence of cannabinoid receptors and other elements of the so-called endocannabinoid system. These G protein-coupled receptors (GPCRs) are a key element in the functions assigned to endocannabinoids and appear to serve as promising pharmacological targets. They include CB₁, CB₂, and GPR55, but also non-GPCRs can be activated by endocannabinoids, like ionotropic receptor TRPV₁ and even nuclear receptors of the PPAR family. Their activation, inhibition, or simply modulation have been associated with numerous physiological effects at both central and peripheral levels, which may have therapeutic value in different human pathologies, then providing a solid experimental explanation for both the ancient medicinal uses of Cannabis plant and the recent advances in the development of cannabinoid-based specific therapies. This chapter will review the scientific knowledge generated in the last years around the research on the different endocannabinoid-binding receptors and their signaling mechanisms. Our intention is that this knowledge may help readers to understand the relevance of these receptors in health and disease conditions, as well as it may serve as the theoretical basis for the different experimental protocols to investigate these receptors and their signaling mechanisms that will be described in the following chapters.

PPARγ and C/EBPα response to acute cold stress in brown adipose tissue

Brown adipose tissue (BAT) has the ability to burn calories as heat. Utilizing BAT thermogenesis is thus an attractive way to combat obesity. However, the transcriptional network resulting in the lipid synthesis to oxidation shift during thermogenesis is not completely understood. Here, we report the regulation of two master regulators of adipogenesis, peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα), during acute cold stress in BAT. We found PPARγ dissociates from DNA in a fifth of its binding sites and these include Cebpa enhancers, leading to decreased C/EBPα expression. This dissociation requires PPARγ binding to activating ligands and is thus modulated by diet. Meanwhile, PPARα also detaches from DNA, and co-activator PGC1α associates with ERRα as part of a transcriptional network regulating lipid metabolism. Subsequent global replacement of C/EBPα by C/EBPβ and its associated transcriptional machinery is required for upregulation of structural lipid synthesis despite general upregulation of fatty acid oxidation.

The Influence of the Differentiation of Genes Encoding Peroxisome Proliferator-Activated Receptors and Their Coactivators on Nutrient and Energy Metabolism

Genetic components may play an important role in the regulation of nutrient and energy metabolism. In the presence of specific genetic variants, metabolic dysregulation may occur, especially in relation to the processes of digestion, assimilation, and the physiological utilization of nutrients supplied to the body, as well as the regulation of various metabolic pathways and the balance of metabolic changes, which may consequently affect the effectiveness of applied reduction diets and weight loss after training. There are many well-documented studies showing that the presence of certain polymorphic variants in some genes can be associated with specific changes in nutrient and energy metabolism, and consequently, with more or less desirable effects of applied caloric reduction and/or exercise intervention. This systematic review focused on the role of genes encoding peroxisome proliferator-activated receptors (PPARs) and their coactivators in nutrient and energy metabolism. The literature review prepared showed that there is a link between the presence of specific alleles described at different polymorphic points in PPAR genes and various human body characteristics that are crucial for the efficacy of nutritional and/or exercise interventions. Genetic analysis can be a valuable element that complements the work of a dietitian or trainer, allowing for the planning of a personalized diet or training that makes the best use of the innate metabolic characteristics of the person who is the subject of their interventions.

The Potential Roles of Post-Translational Modifications of PPARγ in Treating Diabetes

The number of patients with type 2 diabetes mellitus (T2DM), which is mainly characterized by insulin resistance and insulin secretion deficiency, has been soaring in recent years. Accompanied by many other metabolic syndromes, such as cardiovascular diseases, T2DM represents a big challenge to public health and economic development. Peroxisome proliferator-activated receptor γ (PPARγ), a ligand-activated nuclear receptor that is critical in regulating glucose and lipid metabolism, has been developed as a powerful drug target for T2DM, such as thiazolidinediones (TZDs). Despite thiazolidinediones (TZDs), a class of PPARγ agonists, having been proven to be potent insulin sensitizers, their use is restricted in the treatment of diabetes for their adverse effects. Post-translational modifications (PTMs) have shed light on the selective activation of PPARγ, which shows great potential to circumvent TZDs' side effects while maintaining insulin sensitization. In this review, we will focus on the potential effects of PTMs of PPARγ on treating T2DM in terms of phosphorylation, acetylation, ubiquitination, SUMOylation, O-GlcNAcylation, and S-nitrosylation. A better understanding of PTMs of PPARγ will help to design a new generation of safer compounds targeting PPARγ to treat type 2 diabetes.

Interaction of FOXO1 and SUMOylated PPARγ1 induced by hyperlipidemia and hyperglycemia favors vascular endothelial insulin resistance and dysfunction

PPARγ1 and FOXO1 are the key transcription factors that regulate insulin sensitivity. We previously found that a small ubiquitin-related modifier of PPARγ1 at K77 (SUMOylation) favored endothelial insulin resistance (IR) induced by high fat/high glucose (HF/HG) administration. However, whether and how the crosstalk between SUMOylated PPARγ1 and FOXO1 would mediate the development of the endothelial IR and dysfunction remains unclear. Here, we emphasize how PPARγ1-K77 SUMOylation would interact with FOXO1 and participate in the development of the endothelial IR and dysfunction. Our results show that the combination of HF/HG and PPARγ1-K77 SUMOylation exhibits a synergistic deteriorative effect on the endothelial IR and dysfunction, presenting decreased NO levels and elevated ET-1 levels, weakened PI3K/Akt/eNOS signaling, and impaired endothelium-dependent vasodilation function. The further researches reveal that PPARγ1-K77 SUMOylation readily interacts with FOXO1, and FOXO1 occupies the PPAR response element (PPRE) which is supposed to be occupied by PPARγ, thus resulting in the decrease of PPARγ1 transcription activity and the mitigation of the PI3K/Akt signaling. Moreover, the mitigation of the PI3K/Akt signaling promotes in turn the accumulation of FOXO1 in the nucleus where FOXO1 interacts with the SUMOylated PPARγ1, thus exerting a positive feedback effect on IR pathogenesis. The findings uncover a novel association between PPARγ1-K77 SUMOylation and FOXO1, which contributes to our understanding of the pathogenesis of endothelial IR and dysfunction and provides novel pharmacological targets for diabetic angiopathy.

Selenium and selenoproteins in thermogenic adipocytes

Selenium (Se) is involved in energy metabolism in the liver, white adipose tissue, and skeletal muscle, and may also play a role in thermogenic adipocytes, i.e. brown and beige adipocytes. Thereby this micronutrient is a key nutritional target to aid in combating obesity and metabolic diseases. In thermogenic adipocytes, particularly in brown adipose tissue (BAT), the selenoprotein type 2 iodothyronine deiodinase (DIO2) is essential for the activation of adaptive thermogenesis. Recent evidence has suggested that additional selenoproteins may also be participating in this process, and a role for Se itself through its metabolic pathways is also envisioned. In this review, we discuss the recognized effects and the knowledge gaps in the involvement of Se metabolism and selenoproteins in the mechanisms of adaptive thermogenesis in thermogenic (brown and beige) adipocytes.

The Potential Role of PPARs in the Fetal Origins of Adult Disease

The fetal origins of adult disease (FOAD) hypothesis holds that events during early development have a profound impact on one’s risk for the development of future adult disease. Studies from humans and animals have demonstrated that many diseases can begin in childhood and are caused by a variety of early life traumas, including maternal malnutrition, maternal disease conditions, lifestyle changes, exposure to toxins/chemicals, improper medication during pregnancy, and so on. Recently, the roles of Peroxisome proliferator-activated receptors (PPARs) in FOAD have been increasingly appreciated due to their wide variety of biological actions. PPARs are members of the nuclear hormone receptor subfamily, consisting of three distinct subtypes: PPARα, β/δ, and γ, highly expressed in the reproductive tissues. By controlling the maturation of the oocyte, ovulation, implantation of the embryo, development of the placenta, and male fertility, the PPARs play a crucial role in the transition from embryo to fetus in developing mammals. Exposure to adverse events in early life exerts a profound influence on the methylation pattern of PPARs in offspring organs, which can affect development and health throughout the life course, and even across generations. In this review, we summarize the latest research on PPARs in the area of FOAD, highlight the important role of PPARs in FOAD, and provide a potential strategy for early prevention of FOAD.

RSL1D1 modulates cell senescence and proliferation via regulation of PPARγ mRNA stability

AIMS

In this study, we will examine if RSL1D1 influences PPARγ expression and explore the underlying mechanism that RSL1D1 regulates PPARγ expression. Moreover, the significance of RSL1D1-PPARγ pathway in cell senescence and proliferation will also be determined.

MAIN METHODS

Our main methods include western blotting, immunoprecipitation (IP), real-time PCR, RNA Immunoprecipitation (RIP), biotin-labeled RNA pull down assay, dual luciferase reporter gene assay, senescence-associated β-galactosidase staining, cell proliferation assay, colony formation assay, wound healing assay, blood biochemistry test and Oil red O staining.

KEY FINDINGS

By analyzing gene chip results we find that the expression of RSL1D1 and PPARγ might be correlated. Then we show that RSL1D1 is a posttranscriptional regulator of PPARγ. RSL1D1 overexpression elevates, while RSL1D1 knockdown inhibits, PPARγ mRNA and protein expression levels. Mechanistically, we find that RSL1D1 directly interacts with the 3'-untranslated region of PPARγ mRNA, and then promotes its stability and increases PPARγ protein expression level. We further demonstrate that RSL1D1 modulates cellular senescence and cell proliferation partially via PPARγ-regulated downstream target genes such as PTEN/p27, NF-κB, GLUT4, and ACL. Moreover, we find that RSL1D1 regulates PPARγ expression and function in a HuR-dependent manner. Last, we show that RSL1D1 knockout in mouse adipose tissue shortens mouse lifespan and leads to hepatic damage which may impair liver damage repair function.

SIGNIFICANCE

Collectively, our findings unveil a novel posttranscriptional regulation of PPARγ by RSL1D1 and uncover a critical role of RSL1D1-PPARγ-PPARγ downstream target genes in regulating cellular senescence and cell proliferation.

PPAR-γ Partial Agonists in Disease-Fate Decision with Special Reference to Cancer

Peroxisome proliferator-activated receptor-γ (PPAR-γ) has emerged as one of the most extensively studied transcription factors since its discovery in 1990, highlighting its importance in the etiology and treatment of numerous diseases involving various types of cancer, type 2 diabetes mellitus, autoimmune, dermatological and cardiovascular disorders. Ligands are regarded as the key determinant for the tissue-specific activation of PPAR-γ. However, the mechanism governing this process is merely a contradictory debate which is yet to be systematically researched. Either these receptors get weakly activated by endogenous or natural ligands or leads to a direct over-activation process by synthetic ligands, serving as complete full agonists. Therefore, fine-tuning on the action of PPAR-γ and more subtle modulation can be a rewarding approach which might open new avenues for the treatment of several diseases. In the recent era, researchers have sought to develop safer partial PPAR-γ agonists in order to dodge the toxicity induced by full agonists, akin to a balanced activation. With a particular reference to cancer, this review concentrates on the therapeutic role of partial agonists, especially in cancer treatment. Additionally, a timely examination of their efficacy on various other disease-fate decisions has been also discussed.

Epoxyeicosatrienoic Acids Inhibit the Activation of Murine Fibroblasts by Blocking the TGF-β1-Smad2/3 Signaling in a PPARγ-Dependent Manner

Background

Epoxyeicosatrienoic acids (EETs), the metabolite of arachidonic acid by cytochrome P450 (CYP), reportedly serve as a vital endogenous protective factor in several chronic diseases. EETs are metabolized by soluble epoxide hydrolase (sEH). We have observed that prophylactic blocking sEH alleviates bleomycin- (BLM-) induced pulmonary fibrosis (PF) in mice. However, the underlying mechanism and therapeutic effects of EETs on PF remain elusive.

Objective

In this study, we investigated the effect of CYP2J2/EETs on the activation of murine fibroblasts and their mechanisms.

Results

we found that administration of the sEH inhibitor (TPPU) 7 days after the BLM injection also reversed the morphology changes and collagen deposition in the lungs of BLM-treated mice, attenuating PF. Fibroblast activation is regarded as a critical role of PF. Therefore, we investigated the effects of EETs on the proliferation and differentiation of murine fibroblasts. Results showed that the overexpression of CYP2J2 reduced the cell proliferation and the expressions of α-SMA and PCNA induced by transforming growth factor- (TGF-) β1 in murine fibroblasts. Then, we found that EETs inhibited the proliferation and differentiation of TGF-β1-treated-NIH3T3 cells and primary murine fibroblasts. Mechanistically, we found that 14,15-EET disrupted the phosphorylation of Smad2/3 murine fibroblasts by activating PPARγ, which was completely abolished by a PPARγ inhibitor GW9662.

Conclusion

our study shows that EETs inhibit the activation of murine fibroblasts by blocking the TGF-β1-Smad2/3 signaling in a PPARγ-dependent manner. Regulating CYP2J2-EET-sEH metabolic pathway may be a potential therapeutic option in PF.

The Role of Transcription Factor PPAR-γ in the Pathogenesis of Psoriasis, Skin Cells, and Immune Cells

The peroxisome proliferator-activated receptor PPAR-γ is one of three PPAR nuclear receptors that act as ligand-activated transcription factors. In immune cells, the skin, and other organs, PPAR-γ regulates lipid, glucose, and amino acid metabolism. The receptor translates nutritional, pharmacological, and metabolic stimuli into the changes in gene expression. The activation of PPAR-γ promotes cell differentiation, reduces the proliferation rate, and modulates the immune response. In the skin, PPARs also contribute to the functioning of the skin barrier. Since we know that the route from identification to the registration of drugs is long and expensive, PPAR-γ agonists already approved for other diseases may also represent a high interest for psoriasis. In this review, we discuss the role of PPAR-γ in the activation, differentiation, and proliferation of skin and immune cells affected by psoriasis and in contributing to the pathogenesis of the disease. We also evaluate whether the agonists of PPAR-γ may become one of the therapeutic options to suppress the inflammatory response in lesional psoriatic skin and decrease the influence of comorbidities associated with psoriasis.

Cannabinoids and PPAR Ligands: The Future in Treatment of Polycystic Ovary Syndrome Women with Obesity and Reduced Fertility

Cannabinoids (CBs) are used to treat chronic pain, chemotherapy-induced nausea and vomiting, and multiple sclerosis spasticity. Recently, the medicinal use of CBs has attracted increasing interest as a new therapeutic in many diseases. Data indicate a correlation between CBs and PPARs via diverse mechanisms. Both the endocannabinoid system (ECS) and peroxisome proliferator-activated receptors (PPARs) may play a significant role in PCOS and PCOS related disorders, especially in disturbances of glucose-lipid metabolism as well as in obesity and fertility. Taking into consideration the ubiquity of PCOS in the human population, it seems indispensable to search for new potential therapeutic targets for this condition. The aim of this review is to examine the relationship between metabolic disturbances and obesity in PCOS pathology. We discuss current and future therapeutic interventions for PCOS and related disorders, with emphasis on the metabolic pathways related to PCOS pathophysiology. The link between the ECS and PPARs is a promising new target for PCOS, and we examine this relationship in depth.

Computational Analysis of Deleterious SNPs in NRAS to Assess Their Potential Correlation With Carcinogenesis

The NRAS gene is a well-known oncogene that acts as a major player in carcinogenesis. Mutations in the NRAS gene have been linked to multiple types of human tumors. Therefore, the identification of the most deleterious single nucleotide polymorphisms (SNPs) in the NRAS gene is necessary to understand the key factors of tumor pathogenesis and therapy. We aimed to retrieve NRAS missense SNPs and analyze them comprehensively using sequence and structure approaches to determine the most deleterious SNPs that could increase the risk of carcinogenesis. We also adopted structural biology methods and docking tools to investigate the behavior of the filtered SNPs. After retrieving missense SNPs and analyzing them using six in silico tools, 17 mutations were found to be the most deleterious mutations in NRAS. All SNPs except S145L were found to decrease NRAS stability, and all SNPs were found on highly conserved residues and important functional domains, except R164C. In addition, all mutations except G60E and S145L showed a higher binding affinity to GTP, implicating an increase in malignancy tendency. As a consequence, all other 14 mutations were expected to increase the risk of carcinogenesis, with 5 mutations (G13R, G13C, G13V, P34R, and V152F) expected to have the highest risk. Thermodynamic stability was ensured for these SNP models through molecular dynamics simulation based on trajectory analysis. Free binding affinity toward the natural substrate, GTP, was higher for these models as compared to the native NRAS protein. The Gly13 SNP proteins depict a differential conformational state that could favor nucleotide exchange and catalytic potentiality. A further application of experimental methods with all these 14 mutations could reveal new insights into the pathogenesis and management of different types of tumors.

Orthogonal assay for validation of Tox21 PPARγ data and applicability to in silico prediction model

High-throughput screening data from the Tox21 database is used for prioritizing hazardous chemicals and building in silico-based toxicity prediction models. One of the Tox21 dataset, peroxisome proliferator-activated receptor-gamma (PPARγ), a nuclear receptor superfamily, identified various endpoints in HEK293 cells. PPARγ mediates various toxic effects when its receptors are activated or inhibited by ligands such as thiazolidinedione and GW9662. In this study, an orthogonal assay was constructed to verify the effectiveness of the Tox21 PPARγ data, and the effect of highly reliable data on in silico model construction was investigated. The orthogonal assay was a reporter gene assay based on the PPARγ ligand binding domain in CV-1 cells. Only 39% of agonists and 55% of antagonists had similar responses in CV-1 and HEK293 cells. Thus, the effectiveness of Tox21 data on PPARγ may vary depending on the cell line. However, in silico PLS-DA analysis with only high-reliability data (i.e., the same response in both cell lines), yielded more accurate prediction of the activity of potential chemical ligands, despite the small number of samples. Thus, obtaining reliable chemical screening data for PPARγ through orthogonal analysis, even for only limited chemicals, supports the construction of highly predictive in silico models with improved screening efficiency.

Construction and Comprehensive Analysis of the ceRNA Network to Reveal Key Genes for Benign Tracheal Stenosis

Objective: To explore the possible biological functions of the differentially expressed genes in patients with benign tracheal stenosis, and to provide a valuable molecular basis for investigating the pathogenesis of benign tracheal stenosis.

Method: Whole transcriptome sequencing was performed on blood samples collected from patients with benign tracheal stenosis and normal controls. Differentially expressed mRNA, lncRNA, and circRNA were analyzed using the DESeq2 package. The protein interaction networks for differentially expressed mRNAs were constructed by STRING. The results of gene co-expression network analysis, Starbase database prediction, and differential gene expression were combined to construct a competing endogenous RNA network. The transcription factors of key genes were predicted using the Network Analyst database and a transcription factor-mRNA regulatory network was constructed. The classical pathways, intermolecular interaction networks, and upstream regulatory components of key genes were analyzed using Ingenuity Pathway Analysis (IPA). Finally, the DGIDB database was used to predict the potential therapeutic drugs to target the identified key genes.

Result: Based on mRNA, lncRNA and circRNA expression data, we found that differentially expressed mRNAs were enriched in oxygen transport, neutrophil activation, immune response, and oxygen binding. Then the pearson correlation between mRNAs of 46 key genes and lncRNAs and cricRNAs were calculated, and the correlation greater than 0.9 were selected to construct the co-expression network of “mRNA-lncRA” and “mRNA-cricRNA.” Moreover, a “lncRNA-miRNA-mRNA” network and a “circRNA-miRNA-mRNA” network were constructed. IPA analysis showed that the 46 key genes were significantly associated with inflammatory activation and acute respiratory distress syndrome. The constructed TF-mRNA regulatory network was composed of 274 nodes and 573 interacting pairs. 251 potential therapeutic drugs were identified from the DGIDB database.

Conclusion: This study analyzed the differential genes associated with benign tracheal stenosis and explored the potential regulatory mechanisms, providing a scientific reference for further studies on the pathogenesis of benign tracheal stenosis.

The Structure Basis of Phytochemicals as Metabolic Signals for Combating Obesity

The consumption of phytochemicals, bioactive compounds in fruits and vegetables, has been demonstrated to ameliorate obesity and related metabolic symptoms by regulating specific metabolic pathways. This review summarizes the progress made in our understanding of the potential of phytochemicals as metabolic signals: we discuss herein selected molecular mechanisms which are involved in the occurrence of obesity that may be regulated by phytochemicals. The focus of our review highlights the regulation of transcription factors toll like receptor 4 (TLR4), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), the peroxisome proliferator-activated receptors (PPARs), fat mass and obesity-associated protein (FTO) and regulation of microRNAs (miRNA). In this review, the effect of phytochemicals on signaling pathways involved in obesity were discussed on the basis of their chemical structure, suggesting molecular mechanisms for how phytochemicals may impact these signaling pathways. For example, compounds with an isothiocyanate group or an α, β-unsaturated carbonyl group may interact with the TLR4 signaling pathway. Regarding Nrf2, we examine compounds possessing an α, β-unsaturated carbonyl group which binds covalently with the cysteine thiols of Keap1. Additionally, phytochemical activation of PPARs, FTO and miRNAs were summarized. This information may be of value to better understand how specific phytochemicals interact with specific signaling pathways and help guide the development of new drugs to combat obesity and related metabolic diseases.

Lipid Metabolism and Cancer

Lipid metabolism is involved in the regulation of numerous cellular processes, such as cell growth, proliferation, differentiation, survival, apoptosis, inflammation, movement, membrane homeostasis, chemotherapy response, and drug resistance. Reprogramming of lipid metabolism is a typical feature of malignant tumors. In a variety of cancers, fat uptake, storage and fat production are up-regulated, which in turn promotes the rapid growth, invasion, and migration of tumors. This paper systematically summarizes the key signal transduction pathways and molecules of lipid metabolism regulating tumors, and the role of lipid metabolism in programmed cell death. In conclusion, understanding the potential molecular mechanism of lipid metabolism and the functions of different lipid molecules may facilitate elucidating the mechanisms underlying the occurrence of cancer in order to discover new potential targets for the development of effective antitumor drugs.

Lipidomics analysis of facial lipid biomarkers in females with self‐perceived skin sensitivity

Background and Aims

Self‐perception of sensitive skin (SPSS) has several consequences, including skin barrier damage, which is prevented by barrier sebum. We analyzed lipidome profiles of skin surface lipids (SSLs) in patients with SPSS and healthy controls and explored the mechanism of action of potential lipid markers on the repair of damaged barrier cells to better understand SSL abnormity in these patients.

Methods

Ultraperformance liquid chromatography–quadrupole time‐of‐flight mass spectrometry was used to investigate SSL variations in major lipid classes, subclasses, and species. Reverse‐transcription polymerase chain reaction (RT‐PCR) was used to examine changes in intracellular gene expression following cell barrier damage repair by potential lipid markers.

Results

There were significant differences in the lipidomes of individuals between groups. Individuals with SPSS showed significantly increased levels of two diacylglycerols and one very‐short‐chain free fatty acid and significantly decreased levels of three ceramides (Cers), four glycerophospholipids, and one very‐long‐chain free fatty acid. RT‐PCR revealed that after damage repair by Cer/Glucosylceramide (GlcCer), the expression of two genes in the sterol regulatory element‐binding protein and three in the peroxisome proliferator‐activated receptor pathway significantly increased. Causes of skin barrier damage in patients with SPSS are related to the amount and type of lipids.

Conclusion

Cer/GlcCer can promote lipid synthesis and secretion by upregulating lipid‐related gene expression to repair barrier damage.

MFN2 Deficiency Impairs Mitochondrial Functions and PPAR Pathway During Spermatogenesis and Meiosis in Mice

Mitochondria are highly dynamic organelles and their activity is known to be regulated by changes in morphology via fusion and fission events. However, the role of mitochondrial dynamics on cellular differentiation remains largely unknown. Here, we explored the molecular mechanism of mitochondrial fusion during spermatogenesis by generating an Mfn2 (mitofusin 2) conditional knock-out (cKO) mouse model. We found that depletion of MFN2 in male germ cells led to disrupted spermatogenesis and meiosis during which the majority of Mfn2 cKO spermatocytes did not develop to the pachytene stage. We showed that in these Mfn2 cKO spermatocytes, oxidative phosphorylation in the mitochondria was affected. In addition, RNA-Seq analysis showed that there was a significantly altered transcriptome profile in the Mfn2 deficient pachytene (or pachytene-like) spermatocytes, with a total of 262 genes up-regulated and 728 genes down-regulated, compared with wild-type (control) mice. Pathway enrichment analysis indicated that the peroxisome proliferator-activated receptor (PPAR) pathway was altered, and subsequent more detailed analysis showed that the expression of PPAR α and PPAR γ was up-regulated and down-regulated, respectively, in the MFN2 deficient pachytene (or pachytene-like) spermatocytes. We also demonstrated that there were more lipid droplets in the Mfn2 cKO cells than in the control cells. In conclusion, our study demonstrates a novel finding that MFN2 deficiency negatively affects mitochondrial functions and alters PPAR pathway together with lipid metabolism during spermatogenesis and meiosis.

Protein phosphatase 2A regulates cytotoxicity and drug resistance by dephosphorylating xenobiotic metabolism enzymes AHR and MDR1

Protein phosphatase 2A (PP2A) is a serine/threonine dephosphorylating enzyme complex that plays numerous roles in biological processes, including cell growth and metabolism. However, its specific actions in many of these critical pathways are unclear. To explore mechanisms underlying metabolic enzyme regulation in the liver, we investigated the key pathways involved in regulation of xenobiotic-metabolizing enzymes in a mouse model with hepatocyte-specific deletion of Ppp2r1a, encoding the Aα subunit of PP2A. We performed transcriptome and phosphoproteome analysis in mouse livers at the age of 3 months and identified 2695 differentially expressed genes and 549 upregulated phosphoproteins in homozygous knockout mouse livers compared with WT littermates. In particular, the expression of metabolic enzymes Cyp2e1, Cyp1a1, Cyp1a2, Mdr1a, and Abcg2 was dramatically altered in homozygous knockout mouse livers. We also demonstrated that activation of PP2A reversed the decline of metabolic enzyme expression in primary mouse hepatocytes. We found that specific PP2A holoenzymes were involved in metabolic enzyme induction through dephosphorylation of transcription factors, nuclear receptors, or the target enzymes themselves, leading to dysregulation of xenobiotic metabolism or drug-induced hepatotoxicity. Notably, we confirmed that a regulatory axis, PP2A B56α–aryl hydrocarbon receptor–Cyp1a1, was involved in benzo(a)pyrene-induced cytotoxicity through dephosphorylation of the metabolic nuclear receptor, aryl hydrocarbon receptor, at serine 36. In addition, we showed that PP2A B56δ complexes directly dephosphorylated the multidrug efflux pump MDR1 (encoded by multi-drug resistance gene 1), contributing to drug resistance against the chemotherapeutic 5-fluorouracil. Taken together, these novel findings demonstrate the involvement of PP2A in the regulation of liver metabolism.

The Role of Peroxisome Proliferator-Activated Receptor Gamma and Atherosclerosis: Post-translational Modification and Selective Modulators

Atherosclerosis is the hallmark of cardiovascular disease (CVD) which is a leading cause of death in type 2 diabetes patients, and glycemic control is not beneficial in reducing the potential risk of CVD. Clinically, it was shown that Thiazolidinediones (TZDs), a class of peroxisome proliferator-activated receptor gamma (PPARγ) agonists, are insulin sensitizers with reducing risk of CVD, while the potential adverse effects, such as weight gain, fluid retention, bone loss, and cardiovascular risk, restricts its use in diabetic treatment. PPARγ, a ligand-activated nuclear receptor, has shown to play a crucial role in anti-atherosclerosis by promoting cholesterol efflux, repressing monocytes infiltrating into the vascular intima under endothelial layer, their transformation into macrophages, and inhibiting vascular smooth muscle cells proliferation as well as migration. The selective activation of subsets of PPARγ targets, such as through PPARγ post-translational modification, is thought to improve the safety profile of PPARγ agonists. Here, this review focuses on the significance of PPARγ activity regulation (selective activation and post-translational modification) in the occurrence, development and treatment of atherosclerosis, and further clarifies the value of PPARγ as a safe therapeutic target for anti-atherosclerosis especially in diabetic treatment.

Potential Therapeutic Effects of PPAR Ligands in Glioblastoma

Glioblastoma (GB), also known as grade IV astrocytoma, represents the most aggressive form of brain tumor, characterized by extraordinary heterogeneity and high invasiveness and mortality. Thus, a great deal of interest is currently being directed to investigate a new therapeutic strategy and in recent years, the research has focused its attention on the evaluation of the anticancer effects of some drugs already in use for other diseases. This is the case of peroxisome proliferator-activated receptors (PPARs) ligands, which over the years have been revealed to possess anticancer properties. PPARs belong to the nuclear receptor superfamily and are divided into three main subtypes: PPAR-α, PPAR-β/δ, and PPAR-γ. These receptors, once activated by specific natural or synthetic ligands, translocate to the nucleus and dimerize with the retinoid X receptors (RXR), starting the signal transduction of numerous genes involved in many physiological processes. PPARs receptors are activated by specific ligands and participate principally in the preservation of homeostasis and in lipid and glucose metabolism. In fact, synthetic PPAR-α agonists, such as fibrates, are drugs currently in use for the clinical treatment of hypertriglyceridemia, while PPAR-γ agonists, including thiazolidinediones (TZDs), are known as insulin-sensitizing drugs. In this review, we will analyze the role of PPARs receptors in the progression of tumorigenesis and the action of PPARs agonists in promoting, or not, the induction of cell death in GB cells, highlighting the conflicting opinions present in the literature.

Molecular Iodine Supplement Prevents Streptozotocin-Induced Pancreatic Alterations in Mice

Pancreatitis has been implicated in the development and progression of type 2 diabetes and cancer. The pancreas uptakes molecular iodine (I₂), which has anti-inflammatory and antioxidant effects. The present work analyzes whether oral I₂ supplementation prevents the pancreatic alterations promoted by low doses of streptozotocin (STZ). CD1 mice (12 weeks old) were divided into the following groups: control; STZ (20 mg/kg/day, i.p. for five days); I₂ (0.2 mg/Kg/day in drinking water for 15 days); and combined (STZ + I₂). Inflammation (Masson’s trichrome and periodic acid–Schiff stain), hyperglycemia, decreased β-cells and increased α-cells in pancreas were observed in male and female animals with STZ. These animals also showed pancreatic increases in immune cells and inflammation markers as tumor necrosis factor-alpha, transforming growth factor-beta and inducible nitric oxide synthase with a higher amount of activated pancreatic stellate cells (PSCs). The I₂ supplement prevented the harmful effect of STZ, maintaining normal pancreatic morphometry and functions. The elevation of the nuclear factor erythroid-2 (Nrf2) and peroxisome proliferator-activated receptor type gamma (PPARγ) contents was associated with the preservation of normal glycemia and lipoperoxidation. In conclusion, a moderated supplement of I₂ prevents the deleterious effects of STZ in the pancreas, possibly through antioxidant and antifibrotic mechanisms including Nrf2 and PPARγ activation.

Comprehensive Analysis of Copy Number Variation, Nucleotide Mutation, and Transcription Level of PPAR Pathway-Related Genes in Endometrial Cancer

Endometrial cancer is a common malignant tumor in gynecology, and the prognosis of advanced patients is dismal. Recently, many studies on the peroxisome proliferator-activated receptor pathway have elucidated its crucial involvement in endometrial cancer. Copy number variation (CNA) and nucleotide mutations often occur in tumor tissues, leading to abnormal protein expression and changes in protein structure. We analyzed the exon sequencing data of endometrial cancer patients in the TCGA database and found that somatic changes in PPAR pathway-related genes (PPAR-related-gene) often occur in UCEC patients. Patients with CNA or mutation changes in the exon region of the PPAR-related-gene usually have different prognostic outcomes. Furthermore, we found that the mRNA transcription and protein translation levels of PPAR-related-gene in UCEC are significantly different from that of adjacent tissues/normal uterus. The transcription level of some PPAR-related-gene (DBI, CPT1A, CYP27A1, and ME1) is significantly linked to the prognosis of UCEC patients. We further constructed a prognostic predicting tool called PPAR Risk score, a prognostic prediction tool that is a strong independent risk factor for the overall survival rate of UCEC patients. Comparing to the typical TNM classification system, this tool has higher prediction accuracy. We created a nomogram by combining PPAR Risk score with clinical characteristics of patients in order to increase prediction accuracy and promote clinical use. In summary, our study demonstrated that PPAR-related-gene in UCEC had significant alterations in CNA, nucleotide mutations, and mRNA transcription levels. These findings can provide a fresh perspective for postoperative survival prediction and individualized therapy of UCEC patients.

In Vivo and Ex Vivo Evaluation of 1,3-Thiazolidine-2,4-Dione Derivatives as Euglycemic Agents

Thiazolidinediones (TZDs), used to treat type 2 diabetes mellitus, act as full agonists of the peroxisome proliferator-activated receptor gamma. Unfortunately, they produce adverse effects, including weight gain, hepatic toxicity, and heart failure. Our group previously reported the design, synthesis, in silico evaluation, and acute oral toxicity test of two TZD derivatives, compounds 40 (C40) and 81 (C81), characterized as category 5 and 4, respectively, under the Globally Harmonized System. The aim of this study was to determine whether C40, C81, and a new compound, C4, act as euglycemic and antioxidant agents in male Wistar rats with streptozotocin-induced diabetes. The animals were randomly divided into six groups (n = 7): the control, those with diabetes and untreated, and those with diabetes and treated with pioglitazone, C40, C81, or C4 (daily for 21 days). At the end of the experiment, tissue samples were collected to quantify the level of glucose, insulin, triglycerides, total cholesterol, and liver enzymes, as well as enzymatic and nonenzymatic antioxidant activity. C4, without a hypoglycemic effect, displayed the best antioxidant activity. Whereas C81 could only attenuate the elevated level of blood glucose, C40 generated euglycemia by the end of the treatment. All compounds produced a significant decrease in triglycerides.

Physiological Convergence and Antagonism Between GR and PPARγ in Inflammation and Metabolism

Nuclear receptors (NRs) are transcription factors that modulate gene expression in a ligand-dependent manner. The ubiquitously expressed glucocorticoid receptor (GR) and peroxisome proliferator-activated receptor gamma (PPARγ) represent steroid (type I) and non-steroid (type II) classes of NRs, respectively. The diverse transcriptional and physiological outcomes of their activation are highly tissue-specific. For example, in subsets of immune cells, such as macrophages, the signaling of GR and PPARγ converges to elicit an anti-inflammatory phenotype; in contrast, in the adipose tissue, their signaling can lead to reciprocal metabolic outcomes. This review explores the cooperative and divergent outcomes of GR and PPARγ functions in different cell types and tissues, including immune cells, adipose tissue and the liver. Understanding the coordinated control of these NR pathways should advance studies in the field and potentially pave the way for developing new therapeutic approaches to exploit the GR:PPARγ crosstalk.

OUP accepted manuscript

Tight control of gene expression networks required for adipose tissue formation and plasticity is essential for adaptation to energy needs and environmental cues. However, the mechanisms that orchestrate the global and dramatic transcriptional changes leading to adipocyte differentiation remain to be fully unraveled. We investigated the regulation of nascent transcription by the sumoylation pathway during adipocyte differentiation using SLAMseq and ChIPseq. We discovered that the sumoylation pathway has a dual function in differentiation; it supports the initial downregulation of pre-adipocyte-specific genes, while it promotes the establishment of the mature adipocyte transcriptional program. By characterizing endogenous sumoylome dynamics in differentiating adipocytes by mass spectrometry, we found that sumoylation of specific transcription factors like PPARγ/RXR and their co-factors are associated with the transcription of adipogenic genes. Finally, using RXR as a model, we found that sumoylation may regulate adipogenic transcription by supporting the chromatin occurrence of transcription factors. Our data demonstrate that the sumoylation pathway supports the rewiring of transcriptional networks required for formation of functional adipocytes. This study also provides the scientists in the field of cellular differentiation and development with an in-depth resource of the dynamics of the SUMO-chromatin landscape, SUMO-regulated transcription and endogenous sumoylation sites during adipocyte differentiation.

PPARα: An emerging target of metabolic syndrome, neurodegenerative and cardiovascular diseases

Peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor that is involved in lipid metabolism of various tissues. Different metabolites of fatty acids and agonists like fibrates activate PPARα for its transactivative or repressive function. PPARα is known to affect diverse human diseases, and we focus on advanced studies of its transcriptional regulation in these diseases. In MAFLD, PPARα shows a protective function with its upregulation of lipid oxidation and mitochondrial biogenesis and transcriptional repression of inflammatory genes, which is similar in Alzheimer's disease and cardiovascular disease. Activation of PPARα also prevents the progress of diabetes complications; however, its role in diabetes and cancers remains uncertain. Some PPARα-specific agonists, such as Wy14643 and fenofibrate, have been applied in metabolic syndrome treatment, which might own potential in wider application. Future studies may further explore the functions and interventions of PPARα in cancer, diabetes, immunological diseases, and neurodegenerative disease.

Hyperoside Ameliorates DSS-Induced Colitis through MKRN1-Mediated Regulation of PPARγ Signaling and Th17/Treg Balance

Hyperoside (HYP), a naturally occurring flavonoid compound, exerts multiple biological functions including myocardial protection, antiredox, and anti-inflammatory activities. However, the role of HYP on inflammatory bowel disease (IBD) and the underlying mechanism need to be further established. Here, we show that HYP treatment profoundly alleviated dextran sulfate sodium-induced ulcerative colitis in mice, characterized by reduced pathological scores, preserved tissue integrity, suppressed colonic inflammation, and balanced Th17/Treg response. Mechanistically, HYP was shown to restrain the expression of the E3 ubiquitin ligase, makorin ring finger protein 1 (MKRN1), which in turn promoted the ubiquitination and proteasomal degradation of peroxisome proliferator-activated receptor gamma (PPARγ), an essential regulator of Th17 and Treg differentiation. Consequently, HYP treatment enhanced PPARγ signaling and hence promoted Treg differentiation while suppressing Th17 cell development during colitis. Thus, our data indicate that HYP acts through the MKRN1/PPARγ axis to modulate the Th17/Treg axis and thereby confers protection against experimental colitis. The findings extend our understanding about HYP action and may provide a potential therapeutic target for IBD.

Integrative lipidomic and transcriptomic study unravels the therapeutic effects of saikosaponins A and D on non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become one of the most prominent causes of chronic liver diseases and malignancies. However, few therapy has been approved. Radix Bupleuri (RB) is the most frequently used herbal medicine for the treatment of liver diseases. In the current study, we aim to systemically evaluate the therapeutic effects of saikosaponin A (SSa) and saikosaponin D (SSd), the major bioactive monomers in RB, against NAFLD and to investigate the underlying mechanisms. Our results demonstrated that both SSa and SSd improved diet-induced NAFLD. Integrative lipidomic and transcriptomic analysis revealed that SSa and SSd modulated glycerolipid metabolism by regulating related genes, like Lipe and Lipg. SSd profoundly suppressed the fatty acid biosynthesis by downregulating Fasn and Acaca expression and promoted fatty acid degradation by inducing Acox1 and Cpt1a expression. Bioinformatic analysis further predicted the implication of master transcription factors, including peroxisome proliferator-activated receptor alpha (PPARα), in the protective effects of SSa and SSd. These results were further confirmed in vitro in mouse primary hepatocytes. In summary, our study uncoded the complicated mechanisms underlying the promising anti-steatosis activities of saikosaponins (SSs), and provided critical evidence inspiring the discovery of innovative therapies based on SSa and SSd for the treatment of NAFLD and related complications.

RORγt protein modifications and IL-17-mediated inflammation

RORγt, the master transcription factor for cytokine interleukin (IL)-17, is expressed explicitly in Th17 cells, γδT cells, and type 3 innate lymphoid cells in mice and humans. Since dysregulated IL-17 expression is strongly linked to several human inflammatory diseases, the RORγt-IL-17 axis has been the focus of intense research. Recently, several studies have shown that RORγt is modified by multiple post-translational mechanisms, including ubiquitination, acetylation, SUMOylation, and phosphorylation. This review discusses how post-translational modifications modulate RORγt function and its turnover to regulate IL-17-driven inflammation. Broad knowledge of these pathways is crucial for a clear understanding of the pathogenic role of RORγt+IL-17+ cells and for the development of putative therapeutic strategies to target IL-17-driven diseases such as multiple sclerosis, psoriasis, rheumatoid arthritis, systemic lupus erythematosus, and inflammatory bowel disease.

Peroxisome Proliferator-Activated Receptors (PPARs) and Oxidative Stress in Physiological Conditions and in Cancer

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor superfamily. Originally described as “orphan nuclear receptors”, they can bind both natural and synthetic ligands acting as agonists or antagonists. In humans three subtypes, PPARα, β/δ, γ, are encoded by different genes, show tissue-specific expression patterns, and contribute to the regulation of lipid and carbohydrate metabolisms, of different cell functions, including proliferation, death, differentiation, and of processes, as inflammation, angiogenesis, immune response. The PPAR ability in increasing the expression of various antioxidant genes and decreasing the synthesis of pro-inflammatory mediators, makes them be considered among the most important regulators of the cellular response to oxidative stress conditions. Based on the multiplicity of physiological effects, PPAR involvement in cancer development and progression has attracted great scientific interest with the aim to describe changes occurring in their expression in cancer cells, and to investigate the correlation with some characteristics of cancer phenotype, including increased proliferation, decreased susceptibility to apoptosis, malignancy degree and onset of resistance to anticancer drugs. This review focuses on mechanisms underlying the antioxidant and anti-inflammatory properties of PPARs in physiological conditions, and on the reported beneficial effects of PPAR activation in cancer.

A Metabolomics Investigation of the Metabolic Changes of Raji B Lymphoma Cells Undergoing Apoptosis Induced by Zinc Ions

Zinc plays a pivotal role in the function of cells and can induce apoptosis in various cancer cells, including Raji B lymphoma. However, the metabolic mechanism of Zn-induced apoptosis in Raji cells has not been explored. In this study, we performed global metabolic profiling using UPLC−Orbitrap−MS to assess the apoptosis of Raji cells induced by Zn ions released from ZnO nanorods. Multivariate analysis and database searches identified altered metabolites. Furthermore, the differences in the phosphorylation of 1380 proteins were also evaluated by Full Moon kinase array to discover the protein associated Zn−induced apoptosis. From the results, a prominent increase in glycerophosphocholine and fatty acids was observed after Zn ion treatment, but only arachidonic acid was shown to induce apoptosis. The kinase array revealed that the phosphorylation of p53, GTPase activation protein, CaMK2a, PPAR−γ, and PLA−2 was changed. From the pathway analysis, metabolic changes showed earlier onset than protein signaling, which were related to choline metabolism. LC−MS analysis was used to quantify the intracellular choline concentration, which decreased after Zn treatment, which may be related to the choline consumption required to produce choline-containing metabolites. Overall, we found that choline metabolism plays an important role in Zn-induced Raji cell apoptosis.

Thyroid hormone receptor phosphorylation regulates acute fasting-induced suppression of the hypothalamic-pituitary-thyroid axis

Fasting induces profound changes in the hypothalamic-pituitary-thyroid (HPT) axis. After binding thyroid hormone (TH), the TH receptor beta 2 isoform (THRB2) represses Trh and Tsh subunit genes and is the principle negative regulator of the HPT axis. Using mass spectrometry, we identified a major phosphorylation site in the AF-1 domain of THRB2 (serine 101, S101), which is conserved among many members of the nuclear hormone receptor superfamily. More than 50% of THRB2 is phosphorylated at S101 in cultured thyrotrophs (TαT1.1) and in the mouse pituitary. All other THR isoforms lack this site and exhibit limited overall levels of phosphorylation. To determine the importance of THRB2 S101 phosphorylation, we used the TαT1.1 cell line and S101A mutant knock-in mice (Thrb2 ^S101A ). We found that TH promoted S101 THRB2 phosphorylation and was essential for repression of the axis at physiologic TH concentrations. In mice, THRB2 phosphorylation was also increased by fasting and mimicked Trh and Tshb repression by TH. In vitro studies demonstrated that a master metabolic sensor, AMP-activated kinase (AMPK) induced phosphorylation at the same site and caused Tshb repression independent of TH. Furthermore, we identified cyclin-dependent kinase 2 (CDK2) as a direct kinase phosphorylating THRB2 S101 and propose that AMPK or TH increase S101 phosphorylation through the activity of CDK2. This study provides a physiologically relevant function for THR phosphorylation, which permits nutritional deprivation and TH to use a common mechanism for acute suppression of the HPT axis.

Bta-miR-2400 Targets SUMO1 to Affect Yak Preadipocytes Proliferation and Differentiation

Yak adipose tissue may have evolved a unique energy metabolism manner to accommodate the organism's seasonal growth rhythms. MiRNAs regulate multiple biological processes including systemic metabolism and energy homeostasis through post-transcriptional regulations. Rare reports have shown that miRNAs regulate lipid metabolism in domestic yaks. Therefore, we investigated the regulatory mechanisms of bta-miR-2400 in modulating yak preadipocytes proliferation and differentiation. We found that bta-miR-2400 was highly expressed in adipose tissue. Overexpression of bta-miR-2400 in yak preadipocytes significantly enhanced cell proliferation, increased the number of EdU fluorescence-stained cells, and promoted the expression of proliferation marker genes (CDK2, CDK4 and PCNA). Besides, overexpression of bta-miR-2400 repressed the expression of adipogenesis-related marker genes, and the content of cellular triglyceride was substantially reduced. Conversely, inhibition of bta-miR-2400 showed opposite effects compared to those of bta-miR-2400 overexpression in yak preadipocytes. Further, luciferase reporter assays revealed that SUMO1 is a target gene of bta-miR-2400, with bta-miR-2400 being able to down-regulate SUMO1 mRNA and protein expression. In conclusion, bta-miR-2400 regulates lipid metabolism and energy homeostasis in yak preadipocytes by directly targeting SUMO1 to promote cell proliferation and inhibit differentiation.

Highly Multiplexed Mass Cytometry Identifies the Immunophenotype in the Skin of Dermatomyositis

Dermatomyositis (DM) is a rare, systemic autoimmune disease that most frequently affects the skin, muscles, and lungs. The inflammatory infiltrate in the skin has not been fully characterized, and, in this study, we took a single-cell, unbiased approach using imaging mass cytometry. Substantial monocyte‒macrophage diversity was observed, with the CD14+ population correlating positively with Cutaneous Dermatomyositis Disease Area and Severity Index scores (P = 0.031). The T-cell compartment revealed CD4+ T, CD8+ T, and FOXP3+ T cells. Activated (CD69+) circulating memory T cells correlated positively with Cutaneous Dermatomyositis Disease Area and Severity Index scores (P = 0.0268). IFN-β protein was highly upregulated in the T-cell, macrophage, dendritic cell, and endothelial cell populations of DM skin. Myeloid dendritic cells expressed phosphorylated peroxisome proliferator‒activated receptor γ, phosphorylated IRF3, IL-4, and IL-31, and their quantity correlated with itch as measured in Skindex-29. Plasmacytoid dendritic cells colocalized with IFN-γ in addition to the known colocalization with IFN-β. Nuclear phosphorylated peroxisome proliferator‒activated receptor γ expression was found in the DM endothelium. Imaging mass cytometry allows us to characterize single cells in the immune cell population and identify upregulated cytokines and inflammatory pathways in DM. These findings have important implications for the development of future targeted therapies for DM.

PPARs-Orchestrated Metabolic Homeostasis in the Adipose Tissue

It has been more than three decades since peroxisome proliferator-activated receptors (PPARs) were first discovered. Many investigations have revealed the central regulators of PPARs in lipid and glucose homeostasis in response to different nutrient conditions. PPARs have attracted much attention due to their ability to improve metabolic syndromes, and they have also been proposed as classical drug targets for the treatment of hyperlipidemia and type 2 diabetes (T2D) mellitus. In parallel, adipose tissue is known to play a unique role in the pathogenesis of insulin resistance and metabolic syndromes due to its ability to “safely” store lipids and secrete cytokines that regulate whole-body metabolism. Adipose tissue relies on a complex and subtle network of transcription factors to maintain its normal physiological function, by coordinating various molecular events, among which PPARs play distinctive and indispensable roles in adipocyte differentiation, lipid metabolism, adipokine secretion, and insulin sensitivity. In this review, we discuss the characteristics of PPARs with special emphasis on the roles of the different isotypes in adipocyte biology.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid β-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal β-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid β-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid β-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.

PPAR Gamma and Viral Infections of the Brain

Peroxisome Proliferator-Activated Receptor gamma (PPARγ) is a master regulator of metabolism, adipogenesis, inflammation and cell cycle, and it has been extensively studied in the brain in relation to inflammation or neurodegeneration. Little is known however about its role in viral infections of the brain parenchyma, although they represent the most frequent cause of encephalitis and are a major threat for the developing brain. Specific to viral infections is the ability to subvert signaling pathways of the host cell to ensure virus replication and spreading, as deleterious as the consequences may be for the host. In this respect, the pleiotropic role of PPARγ makes it a critical target of infection. This review aims to provide an update on the role of PPARγ in viral infections of the brain. Recent studies have highlighted the involvement of PPARγ in brain or neural cells infected by immunodeficiency virus 1, Zika virus, or human cytomegalovirus. They have provided a better understanding on PPARγ functions in the infected brain, and revealed that it can be a double-edged sword with respect to inflammation, viral replication, or neuronogenesis. They unraveled new roles of PPARγ in health and disease and could possibly help designing new therapeutic strategies.

Development of mode of action networks related to the potential role of PPARγ in respiratory diseases

The peroxisome proliferator-activated receptor γ (PPARγ) is a key transcription factor, operating at the intercept of metabolic control and immunomodulation. It is ubiquitously expressed in multiple tissues and organs, including lungs. There is a growing body of information supporting the role of PPARγ signalling in respiratory diseases. The aim of the present study was to develop mode of action (MoA) networks reflecting the relationships between PPARγ signalling and the progression/alleviation of a spectrum of lung pathologies. Data mining was performed using the resources of the NIH PubMed and PubChem information systems. By linking available data on pathological/therapeutic effects of PPARγ modulation, knowledge-based MoA networking at different levels of biological organization (molecular, cellular, tissue, organ, and system) was performed. Multiple MoA networks were developed to relate PPARγ modulation to the progress or the alleviation of pulmonary disorders, triggered by diverse pathogenic, genetic, chemical, or mechanical factors. Pharmacological targeting of PPARγ signalling was discussed with regard to ligand- and cell type-specific effects in the context of distinct disease inductor- and disease stage-dependent patterns. The proposed MoA networking analysis allows for a better understanding of the potential role of PPARγ modulation in lung pathologies. It presents a mechanistically justified basis for further computational, experimental, and clinical monitoring studies on the dynamic control of PPARγ signalling in respiratory diseases.

Roles of Estrogens in the Healthy and Diseased Oviparous Vertebrate Liver

The liver is a vital organ that sustains multiple functions beneficial for the whole organism. It is sexually dimorphic, presenting sex-biased gene expression with implications for the phenotypic differences between males and females. Estrogens are involved in this sex dimorphism and their actions in the liver of several reptiles, fishes, amphibians, and birds are discussed. The liver participates in reproduction by producing vitellogenins (yolk proteins) and eggshell proteins under the control of estrogens that act via two types of receptors active either mainly in the cell nucleus (ESR) or the cell membrane (GPER1). Estrogens also control hepatic lipid and lipoprotein metabolisms, with a triglyceride carrier role for VLDL from the liver to the ovaries during oogenesis. Moreover, the activation of the vitellogenin genes is used as a robust biomarker for exposure to xenoestrogens. In the context of liver diseases, high plasma estrogen levels are observed in fatty liver hemorrhagic syndrome (FLHS) in chicken implicating estrogens in the disease progression. Fishes are also used to investigate liver diseases, including models generated by mutation and transgenesis. In conclusion, studies on the roles of estrogens in the non-mammalian oviparous vertebrate liver have contributed enormously to unveil hormone-dependent physiological and physiopathological processes.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

Transcriptomic Changes and the Roles of Cannabinoid Receptors and PPARγ in Developmental Toxicities Following Exposure to Δ9-Tetrahydrocannabinol and Cannabidiol

Human consumption of cannabinoid-containing products during early life or pregnancy is rising. However, information about the molecular mechanisms involved in early life stage Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) toxicities is critically lacking. Here, larval zebrafish (Danio rerio) were used to measure THC- and CBD-mediated changes on transcriptome and the roles of cannabinoid receptors (Cnr) 1 and 2 and peroxisome proliferator activator receptor γ (PPARγ) in developmental toxicities. Transcriptomic profiling of 96-h postfertilization (hpf) cnr+/+ embryos exposed (6 - 96 hpf) to 4 μM THC or 0.5 μM CBD showed differential expression of 904 and 1095 genes for THC and CBD, respectively, with 360 in common. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enriched in the THC and CBD datasets included those related to drug, retinol, and steroid metabolism and PPAR signaling. The THC exposure caused increased mortality and deformities (pericardial and yolk sac edemas, reduction in length) in cnr1-/- and cnr2-/- fish compared with cnr+/+ suggesting Cnr receptors are involved in protective pathways. Conversely, the cnr1-/- larvae were more resistant to CBD-induced malformations, mortality, and behavioral alteration implicating Cnr1 in CBD-mediated toxicity. Behavior (decreased distance travelled) was the most sensitive endpoint to THC and CBD exposure. Coexposure to the PPARγ inhibitor GW9662 and CBD in cnr+/+ and cnr2-/- strains caused more adverse outcomes compared with CBD alone, but not in the cnr1-/- fish, suggesting that PPARγ plays a role in CBD metabolism downstream of Cnr1. Collectively, PPARγ, Cnr1, and Cnr2 play important roles in the developmental toxicity of cannabinoids with Cnr1 being the most critical.

PPARdelta in Affected Atopic Dermatitis and Psoriasis: A Possible Role in Metabolic Reprograming

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors expressed in the skin. Three PPAR isotypes, α (NRC1C1), β or δ (NRC1C2) and γ (NRC1C3), have been identified. After activation through ligand binding, PPARs heterodimerize with the 9-cis-retinoic acid receptor (RXR), another nuclear hormone receptor, to bind to specific PPAR-responsive elements in regulatory regions of target genes mainly involved in organogenesis, cell proliferation, cell differentiation, inflammation and metabolism of lipids or carbohydrates. Endogenous PPAR ligands are fatty acids and fatty acid metabolites. In past years, much emphasis has been given to PPARα and γ in skin diseases. PPARβ/δ is the least studied PPAR family member in the skin despite its key role in several important pathways regulating inflammation, keratinocyte proliferation and differentiation, metabolism and the oxidative stress response. This review focuses on the role of PPARβ/δ in keratinocytes and its involvement in psoriasis and atopic dermatitis. Moreover, the relevance of targeting PPARβ/δ to alleviate skin inflammation is discussed.