Novel peroxisome proliferator-activated receptor (PPAR) gamma and PPARdelta ligands produce distinct biological effects

Exploring the Role of Peroxisome Proliferator-Activated Receptors and Endothelial Dysfunction in Metabolic Dysfunction-Associated Steatotic Liver Disease

The endothelium is a well known regulator of vascular homeostasis. Several factors can influence the balance of the bioavailability of active substances. This imbalance can lead to inflammation and, consequently, endothelial dysfunction, which is an underlying pathology in cardiovascular disease that commonly coexists with metabolic and chronic diseases such as metabolic dysfunction-associated steatotic liver disease (MASLD). In MASLD, a reduction in nitric oxide availability is observed, and as a result, hepatic stellate cells and liver sinusoidal endothelial cells are activated. Considering the extensive research dedicated to finding several targets with diagnostic and therapeutic effects, nuclear hormone receptors such as peroxisome proliferator-activated receptors have been highlighted as being highly influential in the gut-liver-adipose axis and are considered potential regulators of metabolism and inflammation in several pathologies. Currently, PPAR agonists are widely explored in clinical trials and experimental studies. Agents such as lanifibranor, elafibranor, daidzein, and Icariin have shown promise in improving the metabolic, hepatic, and cardiovascular health of patients with MASLD. This review aims to provide a comprehensive overview of the role of peroxisome proliferator-activated receptors in endothelial dysfunction and MASLD, exploring their mechanisms in disease progression and potential pharmacological targeting.

PPARs in Clinical Experimental Medicine after 35 Years of Worldwide Scientific Investigations and Medical Experiments

This year marks the 35th anniversary of Professor Walter Wahli's discovery of the PPARs (Peroxisome Proliferator-Activated Receptors) family of nuclear hormone receptors. To mark the occasion, the editors of the scientific periodical Biomolecules decided to publish a special issue in his honor. This paper summarizes what is known about PPARs and shows how trends have changed and how research on PPARs has evolved. The article also highlights the importance of PPARs and what role they play in various diseases and ailments. The paper is in a mixed form; essentially it is a review article, but it has been enriched with the results of our experiments. The selection of works was subjective, as there are more than 200,000 publications in the PubMed database alone. First, all papers done on an animal model were discarded at the outset. What remained was still far too large to describe directly. Therefore, only papers that were outstanding, groundbreaking, or simply interesting were described and briefly commented on.

The novel small molecule E0924G dually regulates bone formation and bone resorption through activating the PPARδ signaling pathway to prevent bone loss in ovariectomized rats and senile mice

Osteoporosis is particularly prevalent among postmenopausal women and the elderly. In the present study, we investigated the effect of the novel small molecule E0924G (N-(4-methoxy-pyridine-2-yl)-5-methylfuran-2-formamide) on osteoporosis. E0924G significantly increased the protein expression levels of osteoprotegerin (OPG) and runt-related transcription factor 2 (RUNX2), and thus significantly promoted osteogenesis in MC3T3-E1 cells. E0924G also significantly decreased osteoclast differentiation and inhibited bone resorption and F-actin ring formation in receptor activator of NF-κB ligand (RANKL)-induced osteoclasts from RAW264.7 macrophages. Importantly, oral administration of E0924G in both ovariectomized (OVX) rats and SAMP6 senile mice significantly increased bone mineral density and decreased bone loss compared to OVX controls or SAMR1 mice. Further mechanistic studies showed that E0924G could bind to and then activate peroxisome proliferator-activated receptor delta (PPARδ), and the pro-osteoblast effect and the inhibition of osteoclast differentiation induced by E0924G were significantly abolished when PPARδ was knocked down or inhibited. In conclusion, these data strongly suggest that E0924G has the potential to prevent OVX-induced and age-related osteoporosis by dual regulation of bone formation and bone resorption through activation of the PPARδ signaling pathway.

Amelioration of Insulin Resistance by Whey Protein in a High-Fat Diet-Induced Pediatric Obesity Male Mouse Model

This study examined whey protein's impact on insulin resistance in a high-fat diet-induced pediatric obesity mouse model. Pregnant mice were fed high-fat diets, and male pups continued this diet until 8 weeks old, then were split into high-fat, whey, and casein diet groups. At 12 weeks old, their body weight, fasting blood glucose (FBG), blood insulin level (IRI), homeostatic model assessment for insulin resistance (HOMA-IR), liver lipid metabolism gene expression, and liver metabolites were compared. The whey group showed significantly lower body weight than the casein group at 12 weeks old (p = 0.034). FBG was lower in the whey group compared to the high-fat diet group (p < 0.01) and casein group (p = 0.058); IRI and HOMA-IR were reduced in the whey group compared to the casein group (p = 0.02, p < 0.01, p < 0.01, respectively). The levels of peroxisome proliferator-activated receptor α and hormone-sensitive lipase were upregulated in the whey group compared to the casein group (p < 0.01, p = 0.03). Metabolomic analysis revealed that the levels of taurine and glycine, both known for their anti-inflammatory and antioxidant properties, were upregulated in the whey group in the liver tissue (p < 0.01, p < 0.01). The intake of whey protein was found to improve insulin resistance in a high-fat diet-induced pediatric obesity mouse model.

Prospective de novo drug design with deep interactome learning

De novo drug design aims to generate molecules from scratch that possess specific chemical and pharmacological properties. We present a computational approach utilizing interactome-based deep learning for ligand- and structure-based generation of drug-like molecules. This method capitalizes on the unique strengths of both graph neural networks and chemical language models, offering an alternative to the need for application-specific reinforcement, transfer, or few-shot learning. It enables the "zero-shot" construction of compound libraries tailored to possess specific bioactivity, synthesizability, and structural novelty. In order to proactively evaluate the deep interactome learning framework for protein structure-based drug design, potential new ligands targeting the binding site of the human peroxisome proliferator-activated receptor (PPAR) subtype gamma are generated. The top-ranking designs are chemically synthesized and computationally, biophysically, and biochemically characterized. Potent PPAR partial agonists are identified, demonstrating favorable activity and the desired selectivity profiles for both nuclear receptors and off-target interactions. Crystal structure determination of the ligand-receptor complex confirms the anticipated binding mode. This successful outcome positively advocates interactome-based de novo design for application in bioorganic and medicinal chemistry, enabling the creation of innovative bioactive molecules.

PPAR gamma agonistic activity of dillapiole: protective effects against diabetic nephropathy

Using structural similarity approach we identified dillapiole, a phenylpropanoid, the main component of Piper aduncum L. and Anethum graveolens L. essential oils as potential PPARγ agonist. Molecular docking revealed that dillapiole binds to the active site of PPARγ, similar to pioglitazone binding. In silico ADME studies showed that dillapiole has high water solubility and GI absorption. Dillapiole was also observed to be partial agonist of PPARγ receptors with EC50 of 43.95 µM. In BHK-21 cells cultured under hyperglycaemic conditions, dillapiole administration reduced oxidative stress and prevented decrease in histone H3 acetylation (k9/14) levels. In HFD + STZ induced diabetic mice, dillapiole treatment for 7 days was able to improve renal functions and decrease plasma glucose level to 138.39 ± 12.36 mg/dl along with decreasing total cholesterol (29%), triglycerides (48.8%), LDL (24.7%), and VLDL (65%) levels in serum. These results show that dillapiole is a potential PPARγ-agonist and thus needs to explore further.

Insulin resistance and Metabolic dysfunction-associated steatotic liver disease (MASLD): Pathways of action of hypoglycemic agents

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by overweight/obesity, and the presence of type 2 diabetes mellitus is the most important criterion. We propose an independent disease perspective without exclusion criteria and with less heterogeneity and greater impact because, according to the National Health and Nutrition Survey (ENSANUT), in Mexico, 25 % of adults over 60 years of age suffer from diabetes, and 96 % of those over 50 years of age have abdominal obesity. Due to the impact of insulin resistance in the pathophysiology of MASLD, which results in damage to hepatocytes, this work aims to provide an overview of the action pathways of hypoglycemic agents such as glucagon-like-1 receptor agonist and peroxisome proliferator-activated receptor-gamma agonists, whose importance lies in the fact that they are currently undergoing phase 2 studies, as well as dipeptidyl peptidase 4 inhibitors and sodium-glucose co-transporter type 2 inhibitors, which are undergoing phase 1 study trials.

Clustering Protein Binding Pockets and Identifying Potential Drug Interactions: A Novel Ligand-Based Featurization Method

Protein-ligand interactions are essential to drug discovery and drug development efforts. Desirable on-target or multitarget interactions are the first step in finding an effective therapeutic, while undesirable off-target interactions are the first step in assessing safety. In this work, we introduce a novel ligand-based featurization and mapping of human protein pockets to identify closely related protein targets and to project novel drugs into a hybrid protein-ligand feature space to identify their likely protein interactions. Using structure-based template matches from PDB, protein pockets are featured by the ligands that bind to their best co-complex template matches. The simplicity and interpretability of this approach provide a granular characterization of the human proteome at the protein-pocket level instead of the traditional protein-level characterization by family, function, or pathway. We demonstrate the power of this featurization method by clustering a subset of the human proteome and evaluating the predicted cluster associations of over 7000 compounds.

Development of bile acid activated receptors hybrid molecules for the treatment of inflammatory and metabolic disorders

The farnesoid-x-receptor (FXR) and the G protein bile acid activated receptor (GPBAR)1 are two bile acid activated receptors highly expressed in entero-hepatic, immune, adipose and cardiovascular tissues. FXR and GPBAR1 are clinically validated targets in the treatment of metabolic disorders and FXR agonists are currently trialled in patients with non-alcoholic steato-hepatitis (NASH). Results of these trials, however, have raised concerns over safety and efficacy of selective FXR ligands suggesting that the development of novel agent designed to impact on multiple targets might have utility in the treatment of complex, multigenic, disorders. Harnessing on FXR and GPBAR1 agonists, several novel hybrid molecules have been developed, including dual FXR and GPBAR1 agonists and antagonists, while exploiting the flexibility of FXR agonists toward other nuclear receptors, dual FXR and peroxisome proliferators-activated receptors (PPARs) and liver-X-receptors (LXRs) and Pregnane-X-receptor (PXR) agonists have been reported. In addition, modifications of FXR agonists has led to the discovery of dual FXR agonists and fatty acid binding protein (FABP)1 and Leukotriene B4 hydrolase (LTB4H) inhibitors. The GPBAR1 binding site has also proven flexible to accommodate hybrid molecules functioning as GPBAR1 agonist and cysteinyl leukotriene receptor (CYSLTR)1 antagonists, as well as dual GPBAR1 agonists and retinoid-related orphan receptor (ROR)γt antagonists, dual GPBAR1 agonist and LXR antagonists and dual GPBAR1 agonists endowed with inhibitory activity on dipeptidyl peptidase 4 (DPP4). In this review we have revised the current landscape of FXR and GPBAR1 based hybrid agents focusing on their utility in the treatment of metabolic associated liver disorders.

Design, Synthesis, and Anti-Inflammatory Evaluation of a Novel PPARδ Agonist with a 4-(1-Pyrrolidinyl)piperidine Structure

Peroxisome proliferator-activated receptor δ (PPARδ) is considered to be a pharmaceutical target to treat metabolic diseases including atherosclerosis, but there is no PPARδ agonist available for clinical use. We have previously reported the discovery of piperidinyl/piperazinyl benzothiazole derivatives as a new series of PPARδ agonists using docking-based virtual screening methods. In the present study, we found that introduction of a pyrrolidine group into the 4-position of their central piperidine rings enhances hPPARδ activity and subtype selectivity. This led to the discovery of 21 having strong PPARδ agonist activity (EC50 = 3.6 nM) with excellent ADME properties. Furthermore, 21 significantly suppressed atherosclerosis progression by 50-60% with reduction of the serum level of MCP-1 in LDLr-KO mice.

Body Fat-Reducing Effects of Whey Protein Diet in Male Mice

This study investigated the mechanism of reducing body fat via whey protein diet. Pregnant mice were fed whey or casein, and their offspring were fed by birth mothers. After weaning at 4 weeks, male pups received the diets administered to their birth mothers (n = 6 per group). At 12 weeks of age, body weight, fat mass, fasting blood glucose (FBG), insulin (IRI), homeostatic model assessment of insulin resistance (HOMA-IR), cholesterol (Cho), triglyceride (TG), the expression levels of lipid metabolism-related genes in liver tissues and metabolomic data of fat tissues were measured and compared between the groups. The birth weights of pups born were similar in the two groups. Compared to the pups in the casein group, at 12 weeks of age, pups in the whey group weighed less, had significantly lower fat mass, HOMA-IR and TG levels (p < 0.01, p = 0.02, p = 0.01, respectively), and significantly higher levels of the antioxidant glutathione and the anti-inflammatory 1-methylnicotinamide in fat tissues (p < 0.01, p = 0.04, respectively). No differences were observed in FBG, IRI, Cho levels (p = 0.75, p = 0.07, p = 0.63, respectively) and expression levels of lipid metabolism-related genes. Whey protein has more antioxidant and anti-inflammatory properties than casein protein, which may be its mechanism for reducing body fat.

Discovery and structure-activity relationship study of 2-piperazinyl-benzothiazole derivatives as potent and selective PPARδ agonists

Peroxisome proliferator-activated receptor δ (PPARδ) is considered to be a target for treating metabolic syndrome, whereas there is no PPARδ agonist in clinical use. Previously, we have reported the discovery of 2-(1-piperidinyl)-1,3-benzothiazole derivatives as a new series of PPARδ agonists using docking-based virtual screening techniques. In this study, we performed the further optimization study of the lead compound 1 focusing on improvement of hydrophobic interactions in the binding site to enhance agonist efficacy for PPARδ and subtype selectivity, thereby discovering a novel PPARδ agonist 5g which exhibited high in vitro agonist activity (hPPARδ, EC₅₀ = 4.1 nM) and sufficiently high selectivity ratio over PPARα and PPARγ. Moreover, 5g revealed a significant upregulation of high-density lipoprotein cholesterol level in vivo.

Scintillation Proximity Assay (SPA)-Based Radioligand Binding for PPARα, PPARγ, and PPARδ Receptors

Peroxisome proliferator-activated receptors (PPARs) have been exploited as drug targets for combating multiple diseases. Several activators with different selectivity for the PPAR α, γ, and δ subtypes have been introduced into the market or have reached advanced clinical trials. Binding assays are of utmost importance for the discovery and profiling of such PPAR ligands. Binding assays are often based on radioligands, in particular, tritiated molecules are applied. We developed synthetic procedures for tritiating various PPAR agonists and applied these radioligands for setting up a scintillation proximity assay (SPA) for PPAR α, γ, and δ. These SPAs allow to assess the binding affinities of PPAR α, γ, and δ ligands, along with their respective subtype selectivity profiles. Therefore, SPA is an important tool for hit discovery and lead optimization campaigns aimed at identifying next-generation PPAR ligands.

Peroxisome proliferator-activated receptor delta-PPAR&#x3b4; agonist (L-165041) enhances bovine embryo survival and post vitrification viability

The effect of L-165041 (PPARδ-agonist) on decreasing apoptosis and intracellular lipid content was assessed in fresh and vitrified-warmed in vitro -produced bovine embryos. It was hypothesised that the addition of L-165041 to the culture medium enhances development and cryopreservation. Oocytes were allocated to one of two treatments: control-standard culture medium, or L-165041 added to the medium on day1 with no media change. Ultrastructure, cleavage, and blastocyst rates were evaluated in fresh, and in post-vitrification cultured embryos by optical and electronic microscopy. A subset of fresh embryos were fixed for TUNEL assay and for Sudan-Black-B histochemical staining. Vitrified-warmed embryos were assessed using MALDI-MS technique. Cleavage and blastocyst rates (control 49.4±5.2, L-165041 51.8±4.3) were not influenced by L-165041. The proportion of inner cell mass cells (ICM) was higher in fresh embryos, and the rate of total and ICM apoptosis was lower in L-165041. In warmed-embryos, total and ICM apoptosis was lower in L-165041. The overall hatching rate was higher in L-165041 (66.62±2.83% vs 53.19±2.90%). There was less lipid accumulation in fresh L-165041-embryos. In conclusion, the use of L-165041 is recommended to improve the viability of in vitro -derived bovine embryos.

Targeting Nuclear Receptors in Neurodegeneration and Neuroinflammation

Nuclear receptors, also known as ligand-activated transcription factors, regulate gene expression upon ligand signals and present as attractive therapeutic targets especially in chronic diseases. Despite the therapeutic relevance of some nuclear receptors in various pathologies, their potential in neurodegeneration and neuroinflammation is insufficiently established. This perspective gathers preclinical and clinical data for a potential role of individual nuclear receptors as future targets in Alzheimer's disease, Parkinson's disease, and multiple sclerosis, and concomitantly evaluates the level of medicinal chemistry targeting these proteins. Considerable evidence suggests the high promise of ligand-activated transcription factors to counteract neurodegenerative diseases with a particularly high potential of several orphan nuclear receptors. However, potent tools are lacking for orphan receptors, and limited central nervous system exposure or insufficient selectivity also compromises the suitability of well-studied nuclear receptor ligands for functional studies. Medicinal chemistry efforts are needed to develop dedicated high-quality tool compounds for the therapeutic validation of nuclear receptors in neurodegenerative pathologies.

Cyanidin 3-O-Glucoside Induces the Apoptosis in the Osteosarcoma Cells through Upregulation of the PPARγ and P21: An <i>In Vitro</i> Study

BACKGROUND

Osteosarcoma (OS) is known as the malignant tumors in the bone. Cyanidin 3-OGlucoside (C3G) has a potential to induce the apoptotic cell death in different cancer cells; however, the mechanisms of action for C3G have not been clarified yet.

OBJECTIVE

In this study, the apoptotic effects of C3G on three different osteosarcoma cell lines including Saso-2, MG-63, and G-292 (clone A141B1) were investigated.

METHODOLOGY

The 24-hr IC50 of C3G for Saso-2, G-292, and MG-63 cells was evaluated by the MTT assay. Apoptosis induction in these cell lines after treatment with the C3G was approved by the Annexin V/PI flow cytometry. Changes at the mRNA expression level of PPARγ, P21, Bax, and Bcl-xl genes were investigated by real-time Polymerase Chain Reaction (PCR) technique, and P21 expression was further confirmed by the western blotting.

RESULTS

The MTT assay results demonstrated that the 24-hr IC50 of C3G was equal to 110μg/ml for Saso-2 and G-292 cells while it was about 140μg/ml for the MG-63 cells. The results of real-time PCR clearly showed that treatment of the cells with 24hrs IC50 of C3G caused the upregulation of PPARγ, P21, and Bax genes. Moreover, western blot analysis confirmed that P21 protein overexpressed endogenously after treatment of the cells with the C3G, and it was more upregulated in the MG-63 cells compared to the other cell lines.

CONCLUSION

According to the findings of the study, the C3G is a novel anti-osteosarcoma agent with the ability to induce the apoptosis in different osteosarcoma cells through upregulation of the PPARγ and P21 genes.

Synthesis and Evaluation of PPARδ Agonists That Promote Osteogenesis in a Human Mesenchymal Stem Cell Culture and in a Mouse Model of Human Osteoporosis

We synthesized a directed library of compounds to explore the structure-activity relationships of peroxisome proliferator-activated receptor δ (PPARδ) activation relative to mesenchymal stem cell (MSC) osteogenesis. Our scaffold used para-substituted cinnamic acids as a polar headgroup, a heteroatom and heterocycle core connecting units, and substituted phenyl groups for the lipophilic tail. Compounds were screened for their ability to increase osteogenesis in MSCs, and the most promising were examined for subunit specificity using a quantitative PPAR transactivation assay. Six compounds were selected for in vivo studies in an ovariectomized mouse model of human postmenopausal osteoporosis. Four compounds improved bone density in vivo, with two (12d and 31a) having activity comparable to that of GW0742, a well-studied PPARδ-selective agonist. 31a (2-methyl-4-[N-methyl-N-[5-methylene-4-methyl-2-[4-(trifluoromethyl)phenyl]thiazole]]aminocinnamic acid) had the highest selectivity for PPARδ compared to other subtypes, its selectivity far exceeding that of GW0742. Our results confirm that PPARδ is a new drug target for possible treatment of osteoporosis via in situ manipulation of MSCs.

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.

PPARγ and Diabetes: Beyond the Genome and Towards Personalized Medicine

PURPOSE OF REVIEW

Full and partial synthetic agonists targeting the transcription factor PPARγ are contained in FDA-approved insulin-sensitizing drugs and used for the treatment of metabolic syndrome-related dysfunctions. Here, we discuss the association between PPARG genetic variants and drug efficacy, as well as the role of alternative splicing and post-translational modifications as contributors to the complexity of PPARγ signaling and to the effects of synthetic PPARγ ligands.

RECENT FINDINGS

PPARγ regulates the transcription of several target genes governing adipocyte differentiation and glucose and lipid metabolism, as well as insulin sensitivity and inflammatory pathways. These pleiotropic functions confer great relevance to PPARγ in physiological regulation of whole-body metabolism, as well as in the etiology of metabolic disorders. Accordingly, PPARG gene mutations, nucleotide variations, and post-translational modifications have been associated with adipose tissue disorders and the related risk of insulin resistance and type 2 diabetes (T2D). Moreover, PPARγ alternative splicing isoforms-generating dominant-negative isoforms mainly expressed in human adipose tissue-have been related to impaired PPARγ activity and adipose tissue dysfunctions. Thus, multiple regulatory levels that contribute to PPARγ signaling complexity may account for the beneficial as well as adverse effects of PPARγ agonists. Further targeted analyses, taking into account all these aspects, are needed for better deciphering the role of PPARγ in human pathophysiology, especially in insulin resistance and T2D. The therapeutic potential of full and partial PPARγ synthetic agonists underlines the clinical significance of this nuclear receptor. PPARG mutations, polymorphisms, alternative splicing isoforms, and post-translational modifications may contribute to the pathogenesis of metabolic disorders, also influencing the responsiveness of pharmacological therapy. Therefore, in the context of the current evidence-based trend to personalized diabetes management, we highlight the need to decipher the intricate regulation of PPARγ signaling to pave the way to tailored therapies in patients with insulin resistance and T2D.

MicroRNA-185 inhibits the proliferation and migration of HaCaT keratinocytes by targeting peroxisome proliferator-activated receptor β

Proliferation and migration of keratinocytes are major processes of skin wound repair after injury. It has been indicated that microRNAs (miRNAs/miRs) are associated with the proliferation and migration of keratinocytes. However, the mechanism by which miR-185 affects these processes in keratinocytes remains unclear. In the present study, the expression level of miR-185 and peroxisome proliferator-activated receptor β (PPARβ) was examined by reverse transcription-quantitative PCR in HaCaT keratinocytes. Cell proliferation was evaluated using Cell Counting Kit-8 and colony formation assays. Western blot analysis was used to detect the levels of cell proliferation, migration and PI3K/AKT signaling pathway-associated proteins. In addition, the migratory capacity of the cells was determined using Transwell assay. The target gene of miR-185 was verified using dual-luciferase reporter assay. The results indicated that overexpression of miR-185 inhibited proliferation, migration and activation of the PI3K/AKT signaling pathway in HaCaT keratinocytes. PPARβ was indicated to be a target of miR-185 and its overexpression promoted the proliferation and migration of HaCaT keratinocytes, while its knockdown exhibited the adverse effects. Furthermore, PI3K inhibitor LY294002 inhibited activation of the PI3K/AKT signaling pathway and decreased the proliferation and migration of HaCaT keratinocytes. In addition, overexpressed PPARβ reversed the suppressive effects of miR-185 overexpression on proliferation, migration and activation of the PI3K/AKT signaling pathway. In conclusion, the results of the present study demonstrated that miR-185 suppressed activation of the PI3K/AKT signaling pathway via targeting PPARβ, thereby regulating proliferation and migration in HaCaT keratinocytes. The present study provided a novel theoretical basis for the use of miR-185 as a target in wound repair.

PPARγ: Potential Therapeutic Target for Ailments Beyond Diabetes and its Natural Agonism

Intense research interests have been observed in establishing PPAR gamma as a therapeutic target for diabetes. However, PPARγ is also emerging as an important therapeutic target for varied disease states other than type 2 diabetes like neurodegenerative disorders, cancer, spinal cord injury, asthma, and cardiovascular problems. Furthermore, glitazones, the synthetic thiazolidinediones, also known as insulin sensitizers, are the largely studied PPARγ agonists and the only ones approved for the treatment of type 2 diabetes. However, they are loaded with side effects like fluid retention, obesity, hepatic failure, bone fractures, and cardiac failure; which restrict their clinical application. Medicinal plants used traditionally are the sources of bioactive compounds to be used for the development of successful drugs and many structurally diverse natural molecules are already established as PPARγ agonists. These natural partial agonists when compared to full agonist synthetic thiazolidinediones led to weaker PPARγ activation with lesser side effects but are not thoroughly investigated. Their thorough characterization and elucidation of mechanistic activity might prove beneficial for counteracting diseases by modulating PPARγ activity through dietary changes. We aim to review the therapeutic significance of PPARγ for ailments other than diabetes and highlight natural molecules with potential PPARγ agonistic activity.

PPAR Beta/Delta and the Hallmarks of Cancer

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone receptor family. Three different isoforms, PPAR alpha, PPAR beta/delta and PPAR gamma have been identified. They all form heterodimers with retinoic X receptors to activate or repress downstream target genes dependent on the presence/absence of ligands and coactivators or corepressors. PPARs differ in their tissue expression profile, ligands and specific agonists and antagonists. PPARs attract attention as potential therapeutic targets for a variety of diseases. PPAR alpha and gamma agonists are in clinical use for the treatment of dyslipidemias and diabetes. For both receptors, several clinical trials as potential therapeutic targets for cancer are ongoing. In contrast, PPAR beta/delta has been suggested as a therapeutic target for metabolic syndrome. However, potential risks in the settings of cancer are less clear. A variety of studies have investigated PPAR beta/delta expression or activation/inhibition in different cancer cell models in vitro, but the relevance for cancer growth in vivo is less well documented and controversial. In this review, we summarize critically the knowledge of PPAR beta/delta functions for the different hallmarks of cancer biological capabilities, which interplay to determine cancer growth.

An overview on medicinal perspective of thiazolidine-2,4-dione: A remarkable scaffold in the treatment of type 2 diabetes

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TZDs, an important pharmacophore in the treatment of diabetes.

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Various analog-based synthetic strategies and biological significance are discussed.

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Clinical studies using TZDs along with other antidiabetic agents are also highlighted.

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SAR has been discussed to suggest the interactions between derivatives and receptor sites.

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Pyrazole, chromone, and acid-based TZDs can be considered as potential lead molecules.

Diabetes or diabetes mellitus is a complex or polygenic disorder, which is characterized by increased levels of glucose (hyperglycemia) and deficiency in insulin secretion or resistance to insulin over an elongated period in the liver and peripheral tissues. Thiazolidine-2,4-dione (TZD) is a privileged scaffold and an outstanding heterocyclic moiety in the field of drug discovery, which provides various opportunities in exploring this moiety as an antidiabetic agent. In the past few years, various novel synthetic approaches had been undertaken to synthesize different derivatives to explore them as more potent antidiabetic agents with devoid of side effects (i.e., edema, weight gain, and bladder cancer) of clinically used TZD (pioglitazone and rosiglitazone). In this review, an effort has been made to summarize the up to date research work of various synthetic strategies for TZD derivatives as well as their biological significance and clinical studies of TZDs in combination with other category as antidiabetic agents. This review also highlights the structure-activity relationships and the molecular docking studies to convey the interaction of various synthesized novel derivatives with its receptor site.

Peroxisome proliferator-activated receptor agonists and antagonists: a patent review (2014-present)

Introduction: Peroxisome proliferator-activated receptors (PPARs), PPARα, PPARδ, and PPARγ, play an important role in the regulation of various physiological processes, specifically lipid and energy metabolism and immunity. PPARα agonists (fibrates) and PPARγ agonists (thiazolidinediones) are used for the treatment of hypertriglyceridemia and type 2 diabetes, respectively. PPARδ activation enhances mitochondrial and energy metabolism but PPARδ-acting drugs are not yet available. Many synthetic ligands for PPARs have been developed to expand their therapeutic applications.Areas covered: The authors searched recent patent activity regarding PPAR ligands. Novel PPARα agonists, PPARδ agonists, PPARγ agonists, PPARα/γ dual agonists, and PPARγ antagonists have been claimed for the treatment of metabolic disease and inflammatory disease. Methods for the combination of PPAR ligands with other drugs and expanded application of PPAR agonists for bone and neurological disease have been also claimed.Expert opinion: Novel PPAR ligands and the combination of PPAR ligands with other drugs have been claimed for the treatment of mitochondrial disease, inflammatory/autoimmune disease, neurological disease, and cancer in addition to metabolic diseases including dyslipidemia and type 2 diabetes. Selective therapeutic actions of PPAR ligands should be exploited to avoid adverse effects. More basic studies are needed to elucidate the molecular mechanisms of selective actions.

The Potential of the FSP1cre-Pparb/d-/- Mouse Model for Studying Juvenile NAFLD

Non-alcoholic fatty liver disease (NAFLD) can progress from steatosis to non-alcoholic steatohepatitis (NASH) characterized by liver inflammation, possibly leading to cirrhosis and hepatocellular carcinoma (HCC). Mice with impaired macrophage activation, when fed a high-fat diet, develop severe NASH. Evidence is mounting that Kupffer cells are implicated. However, it is unknown whether the resident CD68⁺ or bone marrow-derived CD11b⁺ Kupffer cells are involved. Characterization of the FSP1cre-Pparb/d^-/- mouse liver revealed that FSP1 is expressed in CD11b⁺ Kupffer cells. Although these cells only constitute a minute fraction of the liver cell population, Pparb/d deletion in these cells led to remarkable hepatic phenotypic changes. We report that a higher lipid content was present in postnatal day 2 (P2) FSP1cre-Pparb/d^-/- livers, which diminished after weaning. Quantification of total lipids and triglycerides revealed that P2 and week 4 of age FSP1cre-Pparb/d^-/- livers have higher levels of both. qPCR analysis also showed upregulation of genes involved in fatty acid β-oxidation, and fatty acid and triglyceride synthesis pathways. This result is further supported by western blot analysis of proteins in these pathways. Hence, we propose that FSP1cre-Pparb/d^-/- mice, which accumulate lipids in their liver in early life, may represent a useful animal model to study juvenile NAFLD.

Encapsulated Mulberry Fruit Extract Alleviates Changes in an Animal Model of Menopause with Metabolic Syndrome

Currently, the therapeutic strategy against metabolic syndrome and its complications is required due to the increasing prevalence and its impact. Due to the benefits of both mulberry fruit extract and encapsulation technology, we hypothesized that encapsulated mulberry fruit extract (MME) could improve metabolic parameters and its complication risk in postmenopausal metabolic syndrome. To test this hypothesis, female Wistar rats were induced experimental menopause with metabolic syndrome by bilateral ovariectomy (OVX) and high-carbohydrate high-fat (HCHF) diet. Then, they were orally given MME at doses of 10, 50, and 250 mg/kg BW for 8 weeks and the parameters, such as percentage of body weight gain, total cholesterol, triglycerides, HDL-C, LDL-C, atherogenic index, fasting blood glucose, plasma glucose area under the curve, serum angiotensin-converting enzyme (ACE), oxidative stress status, histology, and protein expression of PPAR-γ, TNF-α, and NF-κB in adipose tissues were determined. MME improved body weight gain, adiposity index, glucose intolerance, lipid profiles, atherogenic index, ACE, oxidative stress status, and protein expression of TNF-α and NF-κB. Moreover, MME attenuated adipocyte hypertrophy and enhanced PPAR-γ expression. Taken altogether, MME decreased metabolic syndrome and its complication via the increased PPAR-γ expression. Therefore, MME is the potential candidate for improving metabolic syndrome and its related complications. However, further research in clinical trial is still necessary.

PPARδ, a Potential Therapeutic Target for Heart Disease

The nuclear receptor peroxisome proliferator-activated receptor δ (PPARδ) can transcriptionally regulate target genes. PPARδ exerts essential regulatory functions in the heart, which requires constant energy supply. PPARδ plays a key role in energy metabolism, controlling not only fatty acid (FA) and glucose oxidation, but also redox homeostasis, mitochondrial biogenesis, inflammation, and cardiomyocyte proliferation. PPARδ signaling is impaired in the heart under various pathological conditions, such as pathological cardiac hypertrophy, myocardial ischemia/reperfusion, doxorubicin cardiotoxicity and diabetic cardiomyopathy. PPARδ deficiency in the heart leads to cardiac dysfunction, myocardial lipid accumulation, cardiac hypertrophy/remodeling and heart failure. This article provides an up-today overview of this research area and discusses the role of PPARδ in the heart in light of the complex mechanisms of its transcriptional regulation and its potential as a translatable therapeutic target for the treatment of cardiac disorders.

The Anticancer Potential of Peroxisome Proliferator-Activated Receptor Antagonists

The effects on cancer-cell proliferation and differentiation mediated by peroxisome proliferator-activated receptors (PPARs) have been widely studied, and pleiotropic outcomes in different cancer models and under different experimental conditions have been obtained. Interestingly, few studies report and little preclinical evidence supports the potential antitumor activity of PPAR antagonists. This review focuses on recent findings on the antitumor in vitro and in vivo effects observed for compounds able to inhibit the three PPAR subtypes in different tumor models, providing a rationale for the use of PPAR antagonists in the treatment of tumors expressing the corresponding receptors.

Rational screening of peroxisome proliferator-activated receptor-γ agonists from natural products: potential therapeutics for heart failure

CONTEXT

Peroxisome proliferator-activated receptor-γ (PPARγ) is a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Activation of PPARγ pathway has been shown to enhance fatty acid oxidation, improve endothelial cell function, and decrease myocardial fibrosis in heart failure. Thus, the protein has been raised as an attractive target for heart failure therapy.

OBJECTIVE

This work attempted to discover new and potent PPARγ agonists from natural products using a synthetic strategy of computer virtual screening and transactivation reporter assay.

MATERIALS AND METHODS

A large library of structurally diverse, drug-like natural products was compiled, from which those with unsatisfactory pharmacokinetic profile and/or structurally redundant compounds were excluded. The binding mode of remaining candidates to PPARγ ligand-binding domain (LBD) was computationally modelled using molecular docking and their relative binding potency was ranked by an empirical scoring scheme. Consequently, eight commercially available hits with top scores were selected and their biological activity was determined using a cell-based reporter-gene assay.

RESULTS

Four natural product compounds, namely ZINC13408172, ZINC4292805, ZINC44179 and ZINC901461, were identified to have high or moderate agonistic potency against human PPARγ with EC₅₀ values of 0.084, 2.1, 0.35 and 5.6 μM, respectively, which are comparable to or even better than that of the approved PPARγ full agonists pioglitazone (EC₅₀=0.16 μM) and rosiglitazone (EC₅₀=0.034 μM). Hydrophobic interactions and van der Waals contacts are the primary chemical forces to stabilize the complex architecture of PPARγ LBD domain with these agonist ligands, while few hydrogen bonds, salt bridges and/or π-π stacking at the complex interfaces confer selectivity and specificity for the domain-agonist recognition.

DISCUSSION AND CONCLUSION

The integrated in vitro-in silico screening strategy can be successfully applied to rational discovery of biologically active compounds. The newly identified natural products with PPARγ agonistic potency are considered as promising lead scaffolds to develop novel chemical therapeutics for heart failure.

Peroxisome proliferator-activated receptors (PPARs) are potential drug targets for cancer therapy

Peroxisome-proliferator-activated receptors (PPARs) are nuclear hormone receptors including PPARα, PPARδ and PPARγ, which play an important role in regulating cancer cell proliferation, survival, apoptosis, and tumor growth. Activation of PPARs by endogenous or synthetic compounds regulates tumor progression in various tissues. Although each PPAR isotype suppresses or promotes tumor development depending on the specific tissues or ligands, the mechanism is still unclear. In this review, we summarized the regulative mechanism of PPARs on cancer progression.

5,7-dihydroxy-2-(3-hydroxy-4, 5-dimethoxy-phenyl)-chromen-4-one-a flavone from Bruguiera gymnorrhiza displaying anti-inflammatory properties

Objective:

Bruguiera gymnorrhiza (BRG) (L.) Lamk (Rhizophoraceae), a mangrove species, is widely distributed in the Pacific region, eastern Africa, Indian subcontinent, and subtropical Australia. The leaves of this plant are traditionally used for treating burns and inflammatory lesions. This study isolates the bioactive compound from the methanol extract of BRG leaves and evaluates the possible mechanisms of anti-inflammatory activity involved.

Materials and Methods:

Bioassay-guided fractionation of BRG was performed to identify the bioactive fraction (displaying inhibition of cyclooxygenase 2 [COX2] - 5-lipoxygenase (5-LOX) activities and tumor necrosis factor-alpha (TNF-α) production at the tested concentrations of 100 and 10 μg/ml). The fractionation was performed by solvent extraction and preparative high-performance liquid chromatography. The bioactive compound was characterized by ultraviolet–visible, liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The antioxidant potential was evaluated by electron spin resonance spectrum of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical at 250 μM. The effect of the compound was also studied on TNF-α converting enzyme and nuclear factor kappa B (NF-κB) activities at the concentrations 100, 10 and 1 μg/ml.

Results:

Bioassay-guided purification of BRG revealed the presence of a flavone (5,7-dihydroxy-2- [3-hydroxy-4,5-dimethoxy-phenyl]-chromen-4-one) of molecular weight 330Da. It demonstrated more than 80% inhibition against COX2, 5-LOX activities and TNF-α production at 100 μg/ml. It also displayed 40% inhibition against DPPH radical at the tested concentration along with 23.1% inhibition of NF-κB activity at 100 μg/ml.

Conclusions:

The isolated methoxy-flavone may play a predominant role in the anti-inflammatory properties displayed by BRG leaves. Such activity may involve multiple mechanisms, namely (a) modulation of oxidative stress (b) inhibition of arachidonic acid metabolism and (c) downregulation of pro-inflammatory cytokines probably through NF-κB inhibition.

Antidiabetic effect of chitosan oligosaccharide (GO2KA1) is mediated via inhibition of intestinal alpha-glucosidase and glucose transporters and PPARγ expression

We have previously reported that administration of low molecular weight chitosan oligosaccharide (GO2KA1) significantly suppressed postprandial blood glucose rise with increased plasma adiponectin and HbA1c levels in animals and humans. However, the cellular mechanisms whereby GO2KA1 exerts antihyperglycemic effects still remain to be determined. Using intestinal Caco-2 cells and 3T3-L1 cells, here we show that GO2KA1 has dual modes of antidiabetic action by (1) inhibiting intestinal α-glucosidase as well as glucose transporters SGLT1 and GLUT2 that were distinct from the acarbose effect; (2) enhancing adipocyte differentiation, PPARγ expression and its target genes, such as FABP4, adiponectin, and GLUT4, whereas the effects were abolished by co-treatment with BADGE, a PPARγ antagonist. Moreover, GO2KA1 significantly increased glucose uptake, which was reduced in the presence of BADGE. Our data show that GO2KA1 may prevent hyperglycemia by inhibiting intestinal glucose digestion and transport and also enhance glucose uptake, at least in part, by upregulating adiponectin expression through PPARγ in adipocytes. These findings may provide potential molecular modes of action for the antidiabetic effects of chitosan oligosaccharide observed in clinical and animal studies. © 2016 BioFactors, 43(1):90-99, 2017.

Peroxisome Proliferator-Activated Receptor Modulation during Metabolic Diseases and Cancers: Master and Minions

The prevalence of obesity and metabolic diseases (such as type 2 diabetes mellitus, dyslipidaemia, and cardiovascular diseases) has increased in the last decade, in both industrialized and developing countries. This also coincided with our observation of a similar increase in the prevalence of cancers. The aetiology of these diseases is very complex and involves genetic, nutritional, and environmental factors. Much evidence indicates the central role undertaken by peroxisome proliferator-activated receptors (PPARs) in the development of these disorders. Due to the fact that their ligands could become crucial in future target-therapies, PPARs have therefore become the focal point of much research. Based on this evidence, this narrative review was written with the purpose of outlining the effects of PPARs, their actions, and their prospective uses in metabolic diseases and cancers.

Thiazolidinediones and PPAR orchestra as antidiabetic agents: From past to present

Thiazolidinediones a class of drug, that provided a major breakthrough in the management of type 2 diabetes since 1990. Following the discovery of PPARs, TZDs were the first class to be reported as PPARγ modulators. This review is an attempt to summarize the chemical modifications around TZDs in past two decades to obtain a potent antidiabetic molecule. TZDs literature were initially dominated by their hypoglycemic & hypolipidemic activities, later PPARγ activity was also been incorporated. Moreover, in some cases, both benzyl and benzylidene derivatives were reported in the same manuscript for the sake of comparison. We thought of presenting the review on the basis of the variation in the linker region. Optimal linker at the time of discovery of the Ciglitazone was oxymethyl and it went on to evolve as oxyethyl (Pioglitazone) and oxyethylamino (Rosiglitazone). Few attempts were made to restrict the flexibility of the linker by introducing the cyclic structures and were summarized immediately after the respective linker class.

Peroxisome Proliferator Activated Receptor Beta (PPARβ) activity increases the immune response and shortens the early phases of skeletal muscle regeneration

Peroxisome Proliferator-Activated Receptor Beta (PPARβ) is a transcription factor playing an important role in both muscle myogenesis and remodeling, and in inflammation. However, its role in the coordination of the transient muscle inflammation and reparation process following muscle injury has not yet been fully determined. We postulated that activation of the PPARβ pathway alters the early phase of the muscle regeneration process, i.e. when immune cells infiltrate in injured muscle. Tibialis anteriors of C57BL6/J mice treated or not with the PPARβ agonist GW0742 were injected with cardiotoxin (or with physiological serum for the contralateral muscle). Muscle regeneration was monitored on days 4, 7, and 14 post-injury. We found that treatment of mice with GW0742 increased, at day 4 post-damage, the recruitment of immune cells (M1 and M2 macrophages) and upregulated the expression of the anti-inflammatory cytokine IL-10 and TGF-β mRNA. Those effects were accompanied by a significant increase at day 4 of myogenic regulatory factors (Pax7, MyoD, Myf5, Myogenin) mRNA in GW0742-treated mice. However, we showed an earlier return (7 days vs 14 days) of Myf5 and Myogenin to basal levels in GW0742- compared to DMSO-treated mice. Differential effects of GW0742 observed during the regeneration were associated with variations of PPARβ pathway activity. Collectively, our findings indicate that PPARβ pathway activity shortens the early phases of skeletal muscle regeneration by increasing the immune response.

Peroxisomes in Dermatology. Part II

Background:

Peroxisomes are small cellular organelles that were almost ignored for years because they were believed to play only a minor role in cellular functions. However, it is now known that peroxisomes play an important role in regulating cellular proliferation and differentiation as well as in the modulation of inflammatory mediators. In addition, peroxisomes have broad effects on the metabolism of lipids, hormones, and xenobiotics. Through their effects on lipid metabolism, peroxisomes also affect cellular membranes and adipocyte formation, as well as insulin sensitivity, and peroxisomes play a role in aging and tumorigenesis through their effects on oxidative stress.

Objective:

To review genetically determined peroxisomal disorders, especially those that particularly affect the skin, and some recent information on the specific genetic defects that lead to some of these disorders. In addition, we present some of the emerging knowledge of peroxisomal proliferator activator receptors (PPARs) and how ligands for these receptors modulate different peroxisomal functions. We also present information on how the discovery of PPARs, and the broad and diverse group of ligands that activate these members of the superfamily of nuclear binding transcription factors, has led to development of new drugs that modulate the function of peroxisomes.

Conclusion:

PPAR expression and ligand modulation within the skin have shown potential uses for these ligands in a number of inflammatory cutaneous disorders, including acne vulgaris, cutaneous disorders with barrier dysfunction, cutaneous effects of aging, and poor wound healing associated with altered signal transduction, as well as for side effects induced by the metabolic dysregulation of other drugs.

Multitargeted bioactive ligands for PPARs discovered in the last decade

Type 2 diabetes took insulin resistance as the main clinical manifestation. PPARs have been reported to be the therapeutic targets of metabolic disorders, such as obesity, hypertension, diabetes, and cardiovascular disease. Previously, PPARγ agonist rosiglitazone was restricted in clinic due to cardiomyocytes infarction, weight gain, and other serious side-effects, which were mainly due to the single and selective PPARγ agonism. In recent years, multitarget-directed PPAR agonists with synergistic reaction as well as fewer side-effect have been the hot topic in designing promising agents. In this review, we updated and generalized the development of PPARγ partial agonists, PPARγ antagonists, PPARα/γ dual agonists, PPARδ partial agonists, PPARδ antagonists, PPARα/δ dual agonists, PPARγ/δ dual agonists, and PPARα/γ/δ pan-agonists published in recent decade. Most of these molecules were modified from known structures or came from high-throughput screening. Among these molecules, some were expected to be promising drugs against metabolic disorders, while others seemed to provide new insight for designing novel PPAR agents.

Pleiotropic Actions of Peroxisome Proliferator-Activated Receptors (PPARs) in Dysregulated Metabolic Homeostasis, Inflammation and Cancer: Current Evidence and Future Perspectives

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) have demonstrated a lot of important effects in the regulation of glucose and lipid metabolism and in the correct functioning of adipose tissue. Recently, many studies have evaluated a possible effect of PPARs on tumor cells. The purpose of this review is to describe the effects of PPARs, their action and their future prospective;

METHODS

Narrative review aimed to synthesize cutting-edge evidence retrieved from searches of computerized databases;

RESULTS

PPARs play a key role in metabolic diseases, which include several cardiovascular diseases, insulin resistance, type 2 diabetes, metabolic syndrome, impaired immunity and the increasing risk of cancer; in particular, PPARα and PPARβ/δ mainly enable energy combustion, while PPARγ contributes to energy storage by enhancing adipogenesis;

CONCLUSION

PPAR agonists could represent interesting types of molecules that can treat not only metabolic diseases, but also inflammation and cancer. Additional research is needed for the identification of high-affinity, high-specificity agonists for the treatment of obesity, type 2 diabetes (T2DM) and other metabolic diseases. Further studies are needed also to elucidate the role of PPARs in cancer.

Hypolipidemic effects of chitosan and its derivatives in hyperlipidemic rats induced by a high-fat diet

Background

Hyperlipidemia (HLP) is the primary risk factor of cardiovascular disease (CVD). Various factors, including genetics, physical inactivity, and daily nutritional habits, affect the prevalence of HLP. Recently, it was revealed that dietary fibers, such as pectin, psyllium, and especially chitosan (CTS), may play important roles in hypolipidemic management. Thus, this study aims to determine the hypolipidemic effect and mechanism of CTS and its water-soluble derivatives, chitosan oligosaccharides (M_N≤1,000 Da (COSI) and M_N≤3,000 Da (COSIII)), in male hyperlipidemic rats induced by a high-fat diet (HFD).

Design

After the model creation, 120 Sprague-Dawley (SD) rats were equally assigned to 12 groups fed various diets as follows: the normal group with basic diet, an HFD group, an HFD group supplemented with three doses of CTS, COSI and COSIII groups, and an HFD group treated with simvastatin (7 mg/kg·d). After 6 weeks, body weight, fat/body ratio, and the relevant biomarkers of serum, liver, and feces were measured. Additionally, the histological analysis of liver and adipose tissue was performed, and the mRNA expressions of liver peroxisome proliferator-activated receptor-α (PPARα) and hepatic lipase (HL) were examined.

Results

Compared with HFD group, rats fed CTS, COSI, and COSIII showed a better ability to regulate their body weight, liver and cardiac indices, fat/body ratio, as well as serum, liver, and fecal lipids, and simultaneously to maintain the appropriate activity of liver and serum superoxide dismutase (SOD), alanine aminotransferase (ALT), aspartate aminotransferase (AST), as well as liver and fecal total bile acids (TBA). Simultaneously, there had been a higher mRNA expression of PPARα and HL in the treatment groups.

Conclusion

The obtained results suggested that these three function foods can effectively improve liver lipid metabolism by normalizing the expressions of PPARα and HL, and protect liver from the oxidized trauma by enhancing hepatic function, which could be potentially used to remedy hyperlipidemia.

PPARβ/δ and lipid metabolism in the heart

Cardiac lipid metabolism is the focus of attention due to its involvement in the development of cardiac disorders. Both a reduction and an increase in fatty acid utilization make the heart more prone to the development of lipotoxic cardiac dysfunction. The ligand-activated transcription factor peroxisome proliferator-activated receptor (PPAR)β/δ modulates different aspects of cardiac fatty acid metabolism, and targeting this nuclear receptor can improve heart diseases caused by altered fatty acid metabolism. In addition, PPARβ/δ regulates glucose metabolism, the cardiac levels of endogenous antioxidants, mitochondrial biogenesis, cardiomyocyte apoptosis, the insulin signaling pathway and lipid-induced myocardial inflammatory responses. As a result, PPARβ/δ ligands can improve cardiac function and ameliorate the pathological progression of cardiac hypertrophy, heart failure, cardiac oxidative damage, ischemia-reperfusion injury, lipotoxic cardiac dysfunction and lipid-induced cardiac inflammation. Most of these findings have been observed in preclinical studies and it remains to be established to what extent these intriguing observations can be translated into clinical practice. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.

Design and synthesis of fused soluble epoxide hydrolase/peroxisome proliferator-activated receptor modulators

Metabolic syndrome (MetS) is a widespread, complex disease cluster which consists of hypertension, atherosclerosis, dyslipidaemia and type II diabetes.

N-Benzylbenzamides: A Novel Merged Scaffold for Orally Available Dual Soluble Epoxide Hydrolase/Peroxisome Proliferator-Activated Receptor γ Modulators

Metabolic syndrome (MetS) is a multifactorial disease cluster that consists of dyslipidemia, cardiovascular disease, type 2 diabetes mellitus, and obesity. MetS patients are strongly exposed to polypharmacy; however, the number of pharmacological compounds required for MetS treatment can be reduced by the application of multitarget compounds. This study describes the design of dual-target ligands that target soluble epoxide hydrolase (sEH) and the peroxisome proliferator-activated receptor type γ (PPARγ). Simultaneous modulation of sEH and PPARγ can improve diabetic conditions and hypertension at once. N-Benzylbenzamide derivatives were determined to fit a merged sEH/PPARγ pharmacophore, and structure-activity relationship studies were performed on both targets, resulting in a submicromolar (sEH IC50 = 0.3 μM/PPARγ EC50 = 0.3 μM) modulator 14c. In vitro and in vivo evaluations revealed good ADME properties qualifying 14c as a pharmacological tool compound for long-term animal models of MetS.

A novel peroxisome proliferator response element modulates hepatic low-density lipoprotein receptor gene transcription in response to PPARδ activation

The hepatic expression of low-density lipoprotein (LDL) receptor (LDLR) gene is regulated primarily at the transcriptional level by a sterol-regulatory element (SRE) in its proximal promoter region which is the site of action of SRE-binding protein 2 (SREBP2). However whether additional cis-regulatory elements contribute to LDLR transcription has not been fully explored. We investigated the function of a putative peroxisome proliferator-activated receptor (PPAR)-response element (PPRE) sequence motif located at -768 to -752 bases upstream of the transcription start site of human LDLR gene in response to PPARδ activation. Promoter luciferase reporter analyses showed that treating HepG2 cells with PPARδ agonist L165041 markedly increased the activity of a full-length LDLR promoter construct (pLDLR-1192) without any effects on the shorter promoter reporter pLDLR-234 that contains only the core regulatory elements SRE-1 and SP1 sites. Importantly, mutation of the PPRE sequence greatly attenuated the induction of the full-length LDLR promoter activity by L165041 without affecting rosuvastatin (RSV)-mediated transactivation. EMSA and ChIP assay further confirmed the binding of PPARδ to the LDLR-PPRE site. Treating HepG2 cells with L165041 elevated the mRNA and protein expressions of LDLR without affecting the LDLR mRNA decay rate. The induction of LDLR expression by PPARδ agonist was further observed in liver tissue of mice and hamsters treated with L165041. Altogether, our studies identify a novel PPRE-mediated regulatory mechanism for LDLR transcription and suggest that combined treatment of statin with PPARδ agonists may have advantageous effects on LDLR expression.

Revisiting PPARγ as a target for the treatment of metabolic disorders

As the prevalence of obesity has increased explosively over the last several decades, associated metabolic disorders, including type 2 diabetes, dyslipidemia, hypertension, and cardiovascular diseases, have been also increased. Thus, new strategies for preventing and treating them are needed. The nuclear peroxisome proliferator-activated receptors (PPARs) are involved fundamentally in regulating energy homeostasis; thus, they have been considered attractive drug targets for addressing metabolic disorders. Among the PPARs, PPARγ is a master regulator of gene expression for metabolism, inflammation, and other pathways in many cell types, especially adipocytes. It is a physiological receptor of the potent anti-diabetic drugs of the thiazolidinediones (TZDs) class, including rosiglitazone (Avandia). However, TZDs have undesirable and severe side effects, such as weight gain, fluid retention, and cardiovascular dysfunction. Recently, many reports have suggested that PPARγ could be modulated by post-translational modifications (PTMs), and modulation of PTM has been considered as novel approaches for treating metabolic disorders with fewer side effects than the TZDs. In this review, we discuss how PTM of PPARγ may be regulated and issues to be considered in making novel anti-diabetic drugs that can modulate the PTM of PPARγ. [BMB Reports 2014; 47(11): 599-608]