Peroxisome proliferator-activated receptors in the cardiovascular system

Potentials of peroxisome proliferator-activated receptor (PPAR) α, β/δ, and γ: An in-depth and comprehensive review of their molecular mechanisms, cellular Signalling, immune responses and therapeutic implications in multiple diseases

Peroxisome proliferator-activated receptors (PPARs), ligand-activated transcription factors, have emerged as a key regulator of various biological processes, underscoring their relevance in the pathophysiology and treatment of numerous diseases. PPARs are primarily recognized for their critical role in lipid and glucose metabolism, which underpins their therapeutic applications in managing type 2 diabetes mellitus. Beyond metabolic disorders, they have gained attention for their involvement in immune modulation, making them potential targets for autoimmune-related inflammatory diseases. Furthermore, PPAR's ability to regulate proliferation, differentiation, and apoptosis has positioned them as promising candidates in oncology. Their anti-inflammatory and anti-fibrotic properties further highlight their potential in dermatological and cardiovascular conditions, where dysregulated inflammatory responses contribute to disease progression. Recent advancements have elucidated the molecular mechanisms of different PPAR isoforms, including their regulation of key signalling pathways such as NF-κB and MAPK, which are crucial in inflammation and cellular stress responses. Additionally, their interactions with co-factors and post-translational modifications further diversify their functional roles. The therapeutic potential of various PPAR agonists has been extensively explored, although challenges related to side effects and target specificity remain. This growing body of evidence underscores the significance of PPARs in understanding the molecular basis of diseases and advancing therapeutic interventions, paving way for targeted treatment approach across a wide spectrum of medical conditions. Here, we provide a comprehensive and detailed perspective of PPARs and their potential across different health conditions to advance our understanding, elucidate underlying mechanisms, and facilitate the development of potential treatment strategies.

Comparative metabolomics reveals eggshell translucency formation using LC-MS Analysis

Eggshell translucency is the common problem on eggshell that become more severe with age. They are important because it influence consumer preferences and the economic value of eggs. The reason for the eggshell translucency is currently believed to be the eggshell membrane (ESM). In this study, we screened translucency eggs and normal eggs and used metabolomics to study liver metabolism in different eggshell translucency and discuss important liver lipids and phosphatidyl metabolites. Liver samples were taken for Liquid Chromatograph Mass Spectrometer (LC-MS) during the formation of eggshell membranes in hens, that is, when eggs form eggshell membranes in the oviduct isthmus. The results showed that we identified two essential metabolic pathways through differential metabolite pathway analysis, which were glycine, serine, and threonine metabolism related to amino acids metabolism and the PPAR metabolic pathway related to lipid metabolism. Furthermore, this study helps us understand the process of translucency egg production in poultry. This laid the foundation for in-depth research on eggshell translucency. These results may and provide support for future breeding.

Transcriptional and Metabolic Changes Following Repeated Fasting and Refeeding of Adipose Stem Cells Highlight Adipose Tissue Resilience

BACKGROUND

Obesity and related metabolic disorders have reached epidemic levels, calling for diverse therapeutic strategies. Altering nutrient intake, timing and quantity by intermittent fasting seems to elicit beneficial health effects by modulating endocrine and cell signaling networks. This study explores the impact of cyclic nutrient availability in the form of every-other-day fasting (EODF) on human adipose stem cells (ASCs).

METHODS

We subjected ASCs to repeated fasting/refeeding (F/R) cycles, mimicking low glucose/high fatty acid (LGHF) conditions, and assessed phenotypic and transcriptomic changes, lipid storage capacity, insulin sensitivity, and differentiation potential.

RESULTS

Four consecutive F/R cycles induced significant changes in adipogenic gene expression, with upregulation of FABP4 and PLIN1 during fasting, and increased lipid storage in the ASCs. Upon differentiation, ASCs exposed to LGHF conditions retained a transient increase in lipid droplet size and altered fatty acid metabolism gene expression until day 9. However, these changes dissipated by day 15 of differentiation, suggesting a limited duration of fasting-induced transcriptional and adipogenic memory. Despite initial effects, ASCs showed resilience, returning to a physiological trajectory during differentiation, with respect to gene expression and lipid metabolism.

CONCLUSIONS

These findings suggest that the long-term effects of EODF on the ASC niche may be transient, emphasizing the ability of the adipose tissue to adapt and restore homeostasis.

Hypoglycemic Agents Increase Regulatory Factor X1 to Inhibit Cancer Cell Behaviour in Human Glioblastoma Cells

Glioblastoma multiforme is a deadly brain tumour in humans. We have shown that regulatory factor X1 (RFX1), a transcription factor, inhibits the proliferation, migration and invasion of human glioblastoma cells. This study was designed to identify the existing medications that could increase RFX1 in human glioblastoma cells and to determine whether these medications could inhibit the cancer cell behaviours. A bioinformatics approach was used to identify the medications that increased RFX1. The effects of these medications on human glioblastoma cell proliferation, migration and invasion were assayed under cell culture and mouse brain xenograft conditions. Pioglitazone, rosiglitazone and WY-14643 increased RFX1 based on bioinformatics prediction and Western blotting data. These hypoglycemic agents reduced the proliferation, migration and invasion of human glioblastoma cell cultures. These agents reduced metalloproteinase 2 (MMP2) activity in the culture medium. Silencing RFX1 attenuated hypoglycemic agent-induced inhibition of cancer cell behaviours and MMP2 activity. Pioglitazone reduced the xenograft tumour volume and migration distance of U87 human glioblastoma cells in the mouse brain. RFX1-siRNA attenuated these effects. Our results provide additional evidence for RFX1 as a therapeutic target for human glioblastoma and suggest that pioglitazone, rosiglitazone and WY-14643 inhibit cancer cell behaviour of human glioblastoma cells via upregulating RFX1.

Melatonin Ameliorates Atherosclerotic Plaque Vulnerability by Regulating PPARδ-Associated Smooth Muscle Cell Phenotypic Switching

Vulnerable atherosclerotic plaque rupture, the leading cause of fatal atherothrombotic events, is associated with an increased risk of mortality worldwide. Peroxisome proliferator-activated receptor delta (PPARδ) has been shown to modulate vascular smooth muscle cell (SMC) phenotypic switching, and, hence, atherosclerotic plaque stability. Melatonin reportedly plays a beneficial role in cardiovascular diseases; however, the mechanisms underlying improvements in atherosclerotic plaque vulnerability remain unknown. In this study, we assessed the role of melatonin in regulating SMC phenotypic switching and its consequential contribution to the amelioration of atherosclerotic plaque vulnerability and explored the mechanisms underlying this process. We analyzed features of atherosclerotic plaque vulnerability and markers of SMC phenotypic transition in high-cholesterol diet (HCD)-fed apolipoprotein E knockout (ApoE-/-) mice and human aortic SMCs (HASMCs). Melatonin reduced atherosclerotic plaque size and necrotic core area while enhancing collagen content, fibrous cap thickness, and smooth muscle alpha-actin positive cell coverage on the plaque cap, which are all known phenotypic characteristics of vulnerable plaques. In atherosclerotic lesions, melatonin significantly decreased the synthetic SMC phenotype and KLF4 expression and increased the expression of PPARδ, but not PPARα and PPARγ, in HCD-fed ApoE-/- mice. These results were subsequently confirmed in the melatonin-treated HASMCs. Further analysis using PPARδ silencing and immunoprecipitation assays revealed that PPARδ plays a role in the melatonin-induced SMC phenotype switching from synthetic to contractile. Collectively, we provided the first evidence that melatonin mediates its protective effect against plaque destabilization by enhancing PPARδ-mediated SMC phenotypic switching, thereby indicating the potential of melatonin in treating atherosclerosis.

Ginsenoside Rk1 improves endothelial function in diabetes through activating peroxisome proliferator-activated receptors

Ginsenoside Rk1, one kind of ginsenoside, is a minor ginsenoside found in Panax ginseng and used as traditional Chinese medicine for centuries. It exhibits anti-tumor and anti-aggregation effects. However, little research has been done on its effect on endothelial function. This study investigated whether ginsenoside Rk1 improved endothelial dysfunction in diabetes and the underlying mechanisms in vivo and in vitro. Male C57BL/6 mice were fed with a 12 week high-fat diet (60% kcal % fat), whereas treatment groups were orally administered with ginsenoside Rk1 (10 and 20 mg per kg per day) in the last 4 weeks. Aortas isolated from C57BL/6 mice were induced by high glucose (HG; 30 mM) and co-treated with or without ginsenoside Rk1 (1 and 10 μM) for 48 h ex vivo. Moreover, primary rat aortic endothelial cells (RAECs) were cultured and stimulated by HG (44 mM) to mimic hyperglycemia, with or without the co-treatment of ginsenoside Rk1 (10 μM) for 48 h. Endothelium-dependent relaxations of mouse aortas were damaged with elevated oxidative stress and downregulation of three isoforms of peroxisome proliferator-activated receptors (PPARs), PPAR-α, PPAR-β/δ, and PPAR-γ, as well as endothelial nitric oxide synthase (eNOS) phosphorylation due to HG or high-fat diet stimulation, which also existed in RAECs. However, after the treatment with ginsenoside Rk1, these impairments were all ameliorated significantly. Moreover, the vaso-protective and anti-oxidative effects of ginsenoside Rk1 were abolished by PPAR antagonists (GSK0660, GW9662 or GW6471). In conclusion, this study reveals that ginsenoside Rk1 ameliorates endothelial dysfunction and suppresses oxidative stress in diabetic vasculature through activating the PPAR/eNOS pathway.

Peroxisome proliferator-activated receptor δ improves the features of atherosclerotic plaque vulnerability by regulating smooth muscle cell phenotypic switching

BACKGROUND AND PURPOSE

Vascular smooth muscle cells (SMCs) undergo phenotypic switching during sustained inflammation, contributing to an unfavourable atherosclerotic plaque phenotype. PPARδ plays an important role in regulating SMC functions; however, its role in atherosclerotic plaque vulnerability remains unclear. Here, we explored the pathological roles of PPARδ in atherosclerotic plaque vulnerability in severe atherosclerosis and elucidated the underlying mechanisms.

EXPERIMENTAL APPROACH

Plasma levels of PPARδ were measured in patients with acute coronary syndrome (ACS) and stable angina (SA). SMC contractile and synthetic phenotypic markers, endoplasmic reticulum (ER) stress, and features of atherosclerotic plaque vulnerability were analysed for the brachiocephalic artery of apolipoprotein E-knockout (ApoE-/- ) mice, fed a high-cholesterol diet (HCD) and treated with or without the PPARδ agonist GW501516. In vitro, the role of PPARδ was elucidated using human aortic SMCs (HASMCs).

KEY RESULTS

Patients with ACS had significantly lower plasma PPARδ levels than those with SA. GW501516 reduced atherosclerotic plaque vulnerability, a synthetic SMC phenotype, ER stress markers, and NLRP3 inflammasome expression in HCD-fed ApoE-/- mice. ER stress suppressed PPARδ expression in HASMCs. PPARδ activation inhibited ER stress-induced synthetic phenotype development, ER stress-NLRP3 inflammasome axis activation and matrix metalloproteinase 2 (MMP2) expression in HASMCs. PPARδ inhibited NFκB signalling and alleviated ER stress-induced SMC phenotypic switching.

CONCLUSIONS AND IMPLICATIONS

Low plasma PPARδ levels may be associated with atherosclerotic plaque vulnerability. Our findings provide new insights into the mechanisms underlying the protective effect of PPARδ on SMC phenotypic switching and improvement the features of atherosclerotic plaque vulnerability.

Co-Delivery of Therapeutics and Bioactive Gas Using a Novel Liposomal Platform for Enhanced Treatment of Acute Arterial Injury

Atherosclerosis is a complex, multi-stage disease characterized by pathological changes across the vascular wall. Endothelial dysfunction, inflammation, hypoxia, and vascular smooth muscle cell proliferation contribute to its progression. An effective strategy capable of delivering pleiotropic treatment to the vascular wall is essential to limit neointimal formation. Echogenic liposomes (ELIP), which can encapsulate bioactive gases and therapeutic agents, have the potential to deliver enhanced penetration and treatment efficacy for atherosclerosis. In this study, liposomes loaded with nitric oxide (NO) and rosiglitazone, a peroxisome proliferator-activated receptor agonist, were prepared using hydration, sonication, freeze-thawing, and pressurization. The efficacy of this delivery system was evaluated in a rabbit model of acute arterial injury induced by balloon injury to the common carotid artery. Intra-arterial administration of rosiglitazone/NO co-encapsulated liposomes (R/NO-ELIP) immediately following injury resulted in reduced intimal thickening after 14 days. The anti-inflammatory and anti-proliferative effects of the co-delivery system were investigated. These liposomes were echogenic, enabling ultrasound imaging to assess their distribution and delivery. R/NO-ELIP delivery exhibited a greater attenuation (88 ± 15%) of intimal proliferation when compared to NO-ELIP (75 ± 13%) or R-ELIP (51 ± 6%) delivery alone. The study demonstrates the potential of echogenic liposomes as a promising platform for ultrasound imaging and therapeutic delivery.

Polyunsaturated Fatty Acids: Conversion to Lipid Mediators, Roles in Inflammatory Diseases and Dietary Sources

Polyunsaturated fatty acids (PUFAs) are important components of the diet of mammals. Their role was first established when the essential fatty acids (EFAs) linoleic acid and α-linolenic acid were discovered nearly a century ago. However, most of the biochemical and physiological actions of PUFAs rely on their conversion to 20C or 22C acids and subsequent metabolism to lipid mediators. As a generalisation, lipid mediators formed from n-6 PUFAs are pro-inflammatory while those from n-3 PUFAs are anti-inflammatory or neutral. Apart from the actions of the classic eicosanoids or docosanoids, many newly discovered compounds are described as Specialised Pro-resolving Mediators (SPMs) which have been proposed to have a role in resolving inflammatory conditions such as infections and preventing them from becoming chronic. In addition, a large group of molecules, termed isoprostanes, can be generated by free radical reactions and these too have powerful properties towards inflammation. The ultimate source of n-3 and n-6 PUFAs are photosynthetic organisms which contain Δ-12 and Δ-15 desaturases, which are almost exclusively absent from animals. Moreover, the EFAs consumed from plant food are in competition with each other for conversion to lipid mediators. Thus, the relative amounts of n-3 and n-6 PUFAs in the diet are important. Furthermore, the conversion of the EFAs to 20C and 22C PUFAs in mammals is rather poor. Thus, there has been much interest recently in the use of algae, many of which make substantial quantities of long-chain PUFAs or in manipulating oil crops to make such acids. This is especially important because fish oils, which are their main source in human diets, are becoming limited. In this review, the metabolic conversion of PUFAs into different lipid mediators is described. Then, the biological roles and molecular mechanisms of such mediators in inflammatory diseases are outlined. Finally, natural sources of PUFAs (including 20 or 22 carbon compounds) are detailed, as well as recent efforts to increase their production.

Regulation of Liver Glucose and Lipid Metabolism by Transcriptional Factors and Coactivators

The prevalence of nonalcoholic fatty liver disease (NAFLD) worldwide is on the rise and NAFLD is becoming the most common cause of chronic liver disease. In the USA, NAFLD affects over 30% of the population, with similar occurrence rates reported from Europe and Asia. This is due to the global increase in obesity and type 2 diabetes mellitus (T2DM) because patients with obesity and T2DM commonly have NAFLD, and patients with NAFLD are often obese and have T2DM with insulin resistance and dyslipidemia as well as hypertriglyceridemia. Excessive accumulation of triglycerides is a hallmark of NAFLD and NAFLD is now recognized as the liver disease component of metabolic syndrome. Liver glucose and lipid metabolisms are intertwined and carbon flux can be used to generate glucose or lipids; therefore, in this review we discuss the important transcription factors and coactivators that regulate glucose and lipid metabolism.

Effect of inflammation on cytochrome P450-mediated arachidonic acid metabolism and the consequences on cardiac hypertrophy

The incidence of heart failure (HF) is generally preceded by cardiac hypertrophy (CH), which is the enlargement of cardiac myocytes in response to stress. During CH, the metabolism of arachidonic acid (AA), which is present in the cell membrane phospholipids, is modulated. Metabolism of AA gives rise to hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) via cytochrome P450 (CYP) ω-hydroxylases and CYP epoxygenases, respectively. A plethora of studies demonstrated the involvement of CYP-mediated AA metabolites in the pathogenesis of CH. Also, inflammation is known to be a characteristic hallmark of CH. In this review, our aim is to highlight the impact of inflammation on CYP-derived AA metabolites and CH. Inflammation is shown to modulate the expression of various CYP ω-hydroxylases and CYP epoxygenases and their respective metabolites in the heart. In general, HETEs such as 20-HETE and mid-chain HETEs are pro-inflammatory, while EETs are characterized by their anti-inflammatory and cardioprotective properties. Several mechanisms are implicated in inflammation-induced CH, including the modulation of NF-κB and MAPK. This review demonstrated the inflammatory modulation of cardiac CYPs and their metabolites in the context of CH and the anti-inflammatory strategies that can be employed in the treatment of CH and HF.

Chronic Treatment With WY-14643 Induces Tumorigenesis and Triglyceride Accumulation in Mouse Livers

Peroxisome proliferator-activated receptor α (PPARα) is closely related to lipid metabolism and various liver diseases. Previous study has shown that chronic treatment with PPARα agonist WY-14643 can induce liver tumors in rodents, but the implications of this process on lipid metabolism in the liver remain unclear. Thus, this study aimed to explore the influences of chronic treatment with WY-14643 on the liver and hepatic lipid metabolism. Wild-type C57BL/6 mice were treated with WY-14643 (100 mg/kg/week, i.p.) or corn oil, and liver and serum samples were collected for testing after 42 weeks of WY-14643 treatment. The results showed that hepatomegaly, liver tumors with mild liver injury, and hepatocyte proliferation were induced in mice treated with WY-14643. The mRNA and protein expression levels of PPARα downstream targets acyl-CoA oxidase 1 and cytochrome P450 4A were significantly upregulated in the WY-14643-treated group. Lipidomic analysis revealed that chronic treatment with WY-14643 disturbed lipid homeostasis, especially triglycerides (TGs), which were significantly elevated after WY-14643 treatment. Moreover, TG homeostasis-related genes were significantly increased in the WY-14643-treated group. In conclusion, these findings demonstrated that hepatomegaly and liver tumors induced by chronic treatment with WY-14643 in mice are accompanied by hepatocyte proliferation and TG accumulation. SIGNIFICANCE STATEMENT: The present study clearly demonstrated that sustained peroxisome proliferator-activated receptor α (PPARα) activation by chronic treatment with WY-14643 induces hepatomegaly and liver tumors with triglyceride accumulation by regulating lipid homeostasis-related genes in mice. These findings may help to clarify the influences of sustained PPARα activation on liver lipid homeostasis and provide data for the clinically rational use of drugs that can activate PPARα.

PPARβ/δ priming enhances the anti-apoptotic and therapeutic properties of mesenchymal stromal cells in myocardial ischemia-reperfusion injury

BACKGROUND

Mesenchymal Stromal Cells (MSC) have been widely used for their therapeutic properties in many clinical applications including myocardial infarction. Despite promising preclinical results and evidences of safety and efficacy in phases I/ II, inconsistencies in phase III trials have been reported. In a previous study, we have shown using MSC derived from the bone marrow of PPARβ/δ (Peroxisome proliferator-activated receptors β/δ) knockout mice that the acute cardioprotective properties of MSC during the first hour of reperfusion are PPARβ/δ-dependent but not related to the anti-inflammatory effect of MSC. However, the role of the modulation of PPARβ/δ expression on MSC cardioprotective and anti-apoptotic properties has never been investigated.

OBJECTIVES

The aim of this study was to investigate the role of PPARβ/δ modulation (inhibition or activation) in MSC therapeutic properties in vitro and ex vivo in an experimental model of myocardial infarction.

METHODS AND RESULTS

Naïve MSC and MSC pharmacologically activated or inhibited for PPARβ/δ were challenged with H₂O₂. Through specific DNA fragmentation quantification and qRT-PCR experiments, we evidenced in vitro an increased resistance to oxidative stress in MSC pre-treated by the PPARβ/δ agonist GW0742 versus naïve MSC. In addition, PPARβ/δ-priming allowed to reveal the anti-apoptotic effect of MSC on cardiomyocytes and endothelial cells in vitro. When injected during reperfusion, in an ex vivo heart model of myocardial infarction, 3.75 × 10⁵ PPARβ/δ-primed MSC/heart provided the same cardioprotective efficiency than 7.5 × 10⁵ naïve MSC, identified as the optimal dose in our experimental model. This enhanced short-term cardioprotective effect was associated with an increase in both anti-apoptotic effects and the number of MSC detected in the left ventricular wall at 1 h of reperfusion. By contrast, PPARβ/δ inhibition in MSC before their administration in post-ischemic hearts during reperfusion decreased their cardioprotective effects.

CONCLUSION

Altogether these results revealed that PPARβ/δ-primed MSC exhibit an increased resistance to oxidative stress and enhanced anti-apoptotic properties on cardiac cells in vitro. PPARβ/δ-priming appears as an innovative strategy to enhance the cardioprotective effects of MSC and to decrease the therapeutic injected doses. These results could be of major interest to improve MSC efficacy for the cardioprotection of injured myocardium in AMI patients.

Receptor mechanisms underlying the CNS effects of cannabinoids: CB1 receptor and beyond

Cannabis legalization continues to progress in many US states and other countries. Δ9-tetrahydrocannabinol (Δ9-THC) is the major psychoactive constituent in cannabis underlying both its abuse potential and the majority of therapeutic applications. However, the neural mechanisms underlying cannabis action are not fully understood. In this chapter, we first review recent progress in cannabinoid receptor research, and then examine the acute CNS effects of Δ9-THC or other cannabinoids (WIN55212-2) with a focus on their receptor mechanisms. In experimental animals, Δ9-THC or WIN55212-2 produces classical pharmacological effects (analgesia, catalepsy, hypothermia, hypolocomotion), biphasic changes in affect (reward vs. aversion, anxiety vs. anxiety relief), and cognitive deficits (spatial learning and memory, short-term memory). Accumulating evidence indicates that activation of CB1Rs underlies the majority of Δ9-THC or WIN55121-2's pharmacological and behavioral effects. Unexpectedly, glutamatergic CB1Rs preferentially underlie cannabis action relative to GABAergic CB1Rs. Functional roles for CB1Rs expressed on astrocytes and mitochondria have also been uncovered. In addition, Δ9-THC or WIN55212-2 is an agonist at CB2R, GPR55 and PPARγ receptors and recent studies implicate these receptors in a number of their CNS effects. Other receptors (such as serotonin, opioid, and adenosine receptors) also modulate Δ9-THC's actions and their contributions are detailed. This chapter describes the neural mechanisms underlying cannabis action, which may lead to new discoveries in cannabis-based medication development for the treatment of cannabis use disorder and other human diseases.

Repurposing Peroxisome Proliferator-Activated Receptor Agonists in Neurological and Psychiatric Disorders

Common pathophysiological mechanisms have emerged for different neurological and neuropsychiatric conditions. In particular, mechanisms of oxidative stress, immuno-inflammation, and altered metabolic pathways converge and cause neuronal and non-neuronal maladaptative phenomena, which underlie multifaceted brain disorders. The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors modulating, among others, anti-inflammatory and neuroprotective genes in diverse tissues. Both endogenous and synthetic PPAR agonists are approved treatments for metabolic and systemic disorders, such as diabetes, fatty liver disease, and dyslipidemia(s), showing high tolerability and safety profiles. Considering that some PPAR-acting drugs permeate through the blood-brain barrier, the possibility to extend their scope from the periphery to central nervous system has gained interest in recent years. Here, we review preclinical and clinical evidence that PPARs possibly exert a neuroprotective role, thereby providing a rationale for repurposing PPAR-targeting drugs to counteract several diseases affecting the central nervous system.

PPARβ/δ Is Required for Mesenchymal Stem Cell Cardioprotective Effects Independently of Their Anti-inflammatory Properties in Myocardial Ischemia-Reperfusion Injury

Myocardial infarction ranks first for the mortality worldwide. Because the adult heart is unable to regenerate, fibrosis develops to compensate for the loss of contractile tissue after infarction, leading to cardiac remodeling and heart failure. Adult mesenchymal stem cells (MSC) regenerative properties, as well as their safety and efficacy, have been demonstrated in preclinical models. However, in clinical trials, their beneficial effects are controversial. In an experimental model of arthritis, we have previously shown that PPARβ/δ deficiency enhanced the therapeutic effect of MSC. The aim of the present study was to compare the therapeutic effects of wild-type MSC (MSC) and MSC deficient for PPARβ/δ (KO MSC) perfused in an ex vivo mouse model of ischemia-reperfusion (IR) injury. For this purpose, hearts from C57BL/6J mice were subjected ex vivo to 30 min ischemia followed by 1-h reperfusion. MSC and KO MSC were injected into the Langendorff system during reperfusion. After 1 h of reperfusion, the TTC method was used to assess infarct size. Coronary effluents collected in basal condition (before ischemia) and after ischemia at 1 h of reperfusion were analyzed for their cytokine profiles. The dose-response curve for the cardioprotection was established ex vivo using different doses of MSC (3.10⁵, 6.10⁵, and 24.10⁵ cells/heart) and the dose of 6.10⁵ MSC was found to be the optimal concentration. We showed that the cardioprotective effect of MSC was PPARβ/δ-dependent since it was lost using KO MSC. Moreover, cytokine profiling of the coronary effluents collected in the eluates after 60 min of reperfusion revealed that MSC treatment decreases CXCL1 chemokine and interleukin-6 release compared with untreated hearts. This anti-inflammatory effect of MSC was also observed when hearts were treated with PPARβ/δ-deficient MSC. In conclusion, our study revealed that the acute cardioprotective properties of MSC in an ex vivo model of IR injury, assessed by a decreased infarct size at 1 h of reperfusion, are PPARβ/δ-dependent but not related to their anti-inflammatory effects.

Anti-Diabetic Effects of Isolated Lipids from Natural Sources through Modulation of Angiogenesis

BACKGROUND

Aberrant angiogenesis plays a fateful role in the development of diabetes and diabetic complications. Lipids, as a diverse group of biomacromolecules, are able to relieve diabetes through the modulation of angiogenesis.

OBJECTIVE

Owing to the present remarkable anti-diabetic effects with no or few side effects of lipids, the aim of this study was to assess the state-of-the-art research on anti-diabetic effects of lipids via the modulation of angiogenesis.

METHODS

To study the effects of lipids in diabetes via modulation of angiogenesis, we have searched the electronic databases including Scopus, PubMed, and Cochrane.

RESULTS

The promising anti-diabetic effects of lipids were reported in several studies. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil (FO) were reported to significantly induce neovasculogenesis in high glucose (HG)-mediated endothelial progenitor cells (EPCs) neovasculogenic dysfunction in type 2 diabetic mice. Linoleic acid, mono-epoxy-tocotrienol-α (MeT3α), and ginsenoside Rg1 facilitate wound closure and vessel formation. N-Palmitoylethanolamine (PEA), α-linolenic acid (ALA), omega-3 (ω3) lipids from flaxseed (FS) oil, ω-3 polyunsaturated fatty acids (PUFA), lipoic acid, taurine, and zeaxanthin (Zx) are effective in diabetic retinopathy via suppression of angiogenesis. Lysophosphatidic acid, alkyl-glycerophosphate, crocin, arjunolic acid, α-lipoic acid, and FS oil are involved in the management of diabetes and its cardiac complications. Furthermore, in two clinical trials, R-(+)-lipoic acid (RLA) in combination with hyperbaric oxygenation therapy (HBOT) for treatment of chronic wound healing in DM patients, as well as supplementation with DHA plus antioxidants along with intravitreal ranibizumab were investigated for its effects on diabetic macular edema.

CONCLUSION

Proof-of-concept studies presented here seem to well shed light on the anti-diabetic effects of lipids via modulation of angiogenesis.

Renal NKCC2 Is Dual Regulated by the Synergy of 20-HETE and High-Fat Diet in CYP4F2 Transgenic Mice

INTRODUCTION

20-Hydroxyeicosatetraenoic acid (20-HETE) is the metabolite of cytochrome P450, which modulates blood pressure by inhibiting renal sodium transport. However, the molecular mechanisms underlying the role of 20-HETE in the development of obesity-related hypertension remain unclear, necessitating this study.

METHODS

Cytochrome P450 4F2 (CYP4F2) transgenic mice fed high-fat diet (HFD) were used as research animal models. The expression of renal ion transport molecules targeted by 20-HETE was evaluated by real-time PCR and Western blot (WB). The regulatory effect of 20-HETE and HFD on renal Na+-K+-2Cl- cotransporter, isoform 2 (NKCC2) was explored by immunoprecipitation, WB, and luciferase assay.

RESULTS

A 2-week HFD feeding dramatically decreased protein abundance but increased renal NKCC2 mRNA expression in CYP4F2 transgenic mice. The decrease in NKCC2 protein was demonstrated to be due to ubiquitination induced by the synergy between 20-HETE and HFD. The increased PPAR-γ protein in CYP4F2 transgenic mice fed HFD and the activation of rosiglitazone on the luciferase reporter construct of the NKCC2 promoter demonstrated that the increase in NKCC2 mRNA in CYP4F2 transgenic mice fed HFD was a consequence of elevated PPAR-γ protein induced by the synergy between 20-HETE and HFD.

CONCLUSIONS

Our data demonstrated that the synergy between 20-HETE and HFD could decrease NKCC2 protein via posttranslational ubiquitination, which was thought to be the main mechanism underlying the short-term effect in response to HFD and might be responsible for the adaptive modulation of renal NKCC2 to resist sodium retention. Moreover, the increased NKCC2 mRNA expression via PPAR-γ-induced transcriptional regulation was thought to be the main mechanism underlying the long-term effect in response to HFD and plays a pivotal role in the development of obesity-related hypertension.

Legumes as Functional Food for Cardiovascular Disease

Legumes are an essential food source worldwide. Their high-quality proteins, complex carbohydrates, dietary fiber, and relatively low-fat content make these an important functional food. Known to possess a multitude of health benefits, legume consumption is associated with the prevention and treatment of cardiovascular diseases (CVD). Legume crude protein isolates and purified peptides possess many cardiopreventive properties. Here, we review selected economically valued legumes, their taxonomy and distribution, biochemical composition, and their protein components and the mechanism(s) of action associated with cardiovascular health. Most of the legume protein studies had shown upregulation of low-density lipoprotein (LDL) receptor leading to increased binding and uptake, in effect significantly reducing total lipid levels in the blood serum and liver. This is followed by decreased biosynthesis of cholesterol and fatty acids. To understand the relationship of identified genes from legume studies, we performed gene network analysis, pathway, and gene ontology (GO) enrichment. Results showed that the genes were functionally interrelated while enrichment and pathway analysis revealed involvement in lipid transport, fatty acid and triglyceride metabolic processes, and regulatory processes. This review is the first attempt to collate all known mechanisms of action of legume proteins associated with cardiovascular health. This also provides a snapshot of possible targets leading to systems-level approaches to further investigate the cardiometabolic potentials of legumes.

Biomarkers and key pathways in atrial fibrillation associated with mitral valve disease identified by multi-omics study

Background

Mitral valve disease (MVD)-associated atrial fibrillation (AF) is one of the most common arrhythmias with an increased risk of thromboembolic events. This study aimed to identify the molecular mechanisms and possible biomarkers for chronic AF in MVD by using multi-omics methods.

Methods

This prospective study enrolled patients with MVD (n=100) undergoing mitral valve replacement surgery. The patients were allocated into chronic AF and sinus rhythm (SR) groups. Plasma samples were collected preoperatively. Proteomics was performed with isobaric tags for relative and absolute quantitation (iTRAQ) to identify differential proteins (DPs) between the two groups. The selected DPs were then validated in a new cohort of patients by enzyme-linked immunosorbent assay (ELISA). A gas chromatography-mass spectrometer was used in the metabolomics study to identify differential metabolites (DMs). Bioinformatics analyses were performed to analyze the results.

Results

Among the 447 plasma proteins and 322 metabolites detected, 57 proteins and 55 metabolites, including apolipoprotein A-I (ApoA-I), apolipoprotein A-II (ApoA-II), LIM domain only protein 7 (LMO7), and vitronectin (VN) were differentially expressed between AF and SR patients. Bioinformatics analyses identified enriched pathways related to AF, including peroxisome proliferator-activated receptor alpha (PPARα), the renin angiotensin aldosterone system (RAAS), galactose, biosynthesis of unsaturated fatty acids, and linoleic acid metabolism.

Conclusions

Using integrated multi-omics technologies in MVD-associated AF patients, the present study, for the first time, revealed important signaling pathways, such as PPARα, as well as possible roles of other signaling pathways, including the RAAS and galactose metabolism to understand the molecular mechanism of MVD-associated AF. It also identified a large number of DPs and DMs. Some identified proteins and metabolites, such as ApoA-I, ApoA-II, LMO7, and VN, may be further developed as biomarkers for MVD-associated AF.

Nanoemulsification of Rice Bran Wax Policosanol Enhances Its Cardio-protective Effects via Modulation of Hepatic Peroxisome Proliferator-activated Receptor gamma in Hyperlipidemic Rats

Policosanol, a mixture of long-chain alcohols found in animal and plant waxes, has several biological effects including lipid-lowering that have been extensively studied. However, its bioavailability is low. To investigate the effect of nanoemulsified rice bran wax policosanol (NPOL) on plasma homocysteine, heart and liver histology in hyperlipidemic rats, high-fat diet containing 2.5% cholesterol was used to induce hyperlipidemia in Sprague Dawley rats. The hyperlipidemic rats were treated with NPOL and rice bran wax policosanol (POL) in comparison with normal diet (ND), high-cholesterol diet (HCD) and simvastatin-treated rats. Plasma homocysteine, heart and liver histology, and hepatic mRNA expression of peroxisome proliferator-activated receptor gamma (PPARG) were evaluated. The NPOL group, similar to the simvastatin group, showed reduced plasma homocysteine, preserved heart and liver histology, and down-regulated hepatic PPARG mRNA in comparison to the control group, and was better than the POL group. The results suggest that the modest effect of NPOL on homocysteine and preservation of heart and liver histology could be through the regulation of PPARG expression on a background of increased assimilation of rice bran wax policosanol.

Enhancing fatty acid oxidation negatively regulates PPARs signaling in the heart

High fatty acid oxidation (FAO) is associated with lipotoxicity, but whether it causes lipotoxic cardiomyopathy remains controversial. Molecular mechanisms that may be responsible for FAO-induced lipotoxic cardiomyopathy are also elusive. In this study, increasing FAO by genetic deletion of acetyl-CoA carboxylase 2 (ACC2) did not induce cardiac dysfunction after 16 weeks of high fat diet (HFD) feeding. This suggests that increasing FAO, per se, does not cause metabolic cardiomyopathy in obese mice. We compared transcriptomes of control and ACC2 deficient mouse hearts under chow- or HFD-fed conditions. ACC2 deletion had a significant impact on the global transcriptome including downregulation of the peroxisome proliferator-activated receptors (PPARs) signaling and fatty acid degradation pathways. Increasing fatty acids by HFD feeding normalized expression of fatty acid degradation genes in ACC2 deficient mouse hearts to the same level as the control mice. In contrast, cardiac transcriptome analysis of the lipotoxic mouse model (db/db) showed an upregulation of PPARs signaling and fatty acid degradation pathways. Our results suggest that enhancing FAO by genetic deletion of ACC2 negatively regulates PPARs signaling through depleting endogenous PPAR ligands, which can serve as a negative feedback mechanism to prevent excess activation of PPAR signaling under non-obese condition. In obesity, excessive lipid availability negates the feedback mechanism resulting in over activation of PPAR cascade, thus contributes to the development of cardiac lipotoxicity.

Shedding Light on the Effects of Calorie Restriction and its Mimetics on Skin Biology

During the aging process of an organism, the skin gradually loses its structural and functional characteristics. The skin becomes more fragile and vulnerable to damage, which may contribute to age-related diseases and even death. Skin aging is aggravated by the fact that the skin is in direct contact with extrinsic factors, such as ultraviolet irradiation. While calorie restriction (CR) is the most effective intervention to extend the lifespan of organisms and prevent age-related disorders, its effects on cutaneous aging and disorders are poorly understood. This review discusses the effects of CR and its alternative dietary intake on skin biology, with a focus on skin aging. CR structurally and functionally affects most of the skin and has been reported to rescue both age-related and photo-induced changes. The anti-inflammatory, anti-oxidative, stem cell maintenance, and metabolic activities of CR contribute to its beneficial effects on the skin. To the best of the author’s knowledge, the effects of fasting or a specific nutrient-restricted diet on skin aging have not been evaluated; these strategies offer benefits in wound healing and inflammatory skin diseases. In addition, well-known CR mimetics, including resveratrol, metformin, rapamycin, and peroxisome proliferator-activated receptor agonists, show CR-like prevention against skin aging. An overview of the role of CR in skin biology will provide valuable insights that would eventually lead to improvements in skin health.

Catalpol ameliorates doxorubicin-induced inflammation and oxidative stress in H9C2 cells through PPAR-γ activation

Drug-induced cardiomyopathy is a severe disease that leads to refractory heart disease at late stages, with increasing detrimental effects. DOX-induced cell damage is primarily induced via cellular oxidative stress. The present study investigated the effects of catalpol on doxorubicin (DOX)-induced H9C2 cardiomyocyte inflammation and oxidative stress. The Cell Counting Kit-8 assay was performed to detect cell viability, and western blotting was performed to detect the expression of peroxisome proliferator-activated receptor (PPAR)-γ in H9C2 cells. The expression levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 were measured using ELISAs. Furthermore, the oxidative stress kit was used to detect the levels of malondialdehyde, superoxide dismutase and glutathione peroxidase. A reactive oxygen species (ROS) kit and DCF-DA staining were used to detect ROS levels. The results indicated that DOX treatment inhibited H9C2 cell expression of PPAR-γ and decreased H9C2 cell viability. Various concentrations of catalpol exhibited a less potent effect on H9C2 cell viability compared with DOX; however, catalpol increased the viability of DOX-induced H9C2 cells. Catalpol treatment also significantly decreased the expression levels of inflammatory factors (TNF-α, IL-1β and IL-6) in DOX-induced H9C2 cells, which was reversed by transfections with short hairpin RNA targeting PPAR-γ. Results from the present study indicated that catalpol ameliorated DOX-induced inflammation and oxidative stress in H9C2 cardiomyoblasts by activating PPAR-γ.

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.

To Probe Full and Partial Activation of Human Peroxisome Proliferator-Activated Receptors by Pan-Agonist Chiglitazar Using Molecular Dynamics Simulations

Chiglitazar is a promising new-generation insulin sensitizer with low reverse effects for the treatment of type II diabetes mellitus (T2DM) and has shown activity as a nonselective pan-agonist to the human peroxisome proliferator-activated receptors (PPARs) (i.e., full activation of PPARγ and a partial activation of PPARα and PPARβ/δ). Yet, it has no high-resolution complex structure with PPARs and its detailed interactions and activation mechanism remain unclear. In this study, we docked chiglitazar into three experimentally resolved crystal structures of hPPAR subtypes, PPARα, PPARβ/δ, and PPARγ, followed by 3 μs molecular dynamics simulations for each system. Our MM-GBSA binding energy calculation revealed that chiglitazar most favorably bound to hPPARγ (-144.6 kcal/mol), followed by hPPARα (-138.0 kcal/mol) and hPPARβ (-135.9 kcal/mol), and the order is consistent with the experimental data. Through the decomposition of the MM-GBSA binding energy by residue and the use of two-dimensional interaction diagrams, key residues involved in the binding of chiglitazar were identified and characterized for each complex system. Additionally, our detailed dynamics analyses support that the conformation and dynamics of helix 12 play a critical role in determining the activities of the different types of ligands (e.g., full agonist vs. partial agonist). Rather than being bent fully in the direction of the agonist versus antagonist conformation, a partial agonist can adopt a more linear conformation and have a lower degree of flexibility. Our finding may aid in further development of this new generation of medication.

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.

PPAR-γ signalling as a key mediator of human hair follicle physiology and pathology

Peroxisome proliferator-activated receptors (PPARs) are abundantly expressed in human skin, with PPAR-γ being the most intensively investigated isoform. In various ex vivo and in vivo models, PPAR-γ-mediated signalling has recently surfaced as an essential element of hair follicle (HF) development, growth and stem cell biology. Moreover, the availability of novel, topically applicable PPAR-γ modulators with a favourable toxicological profile has extended the range of potential applications in clinical dermatology. In this review, we synthesize where this field currently stands and sketch promising future research avenues, focussing on the role of PPAR-γ-mediated signalling in the biology and pathology of human scalp HFs, with special emphasis on scarring alopecias such as lichen planopilaris and frontal fibrosing alopecia as model human epithelial stem cell diseases. In particular, we discuss whether and how pharmacological modulation of PPAR-γ signalling may be employed for the management of hair growth disorders, for example, in scarring alopecia (by reducing HF inflammation as well as by promoting the survival and suppressing pathological epithelial-mesenchymal transition of keratin 15 + epithelial stem cells in the bulge) and in hirsutism/hypertrichosis (by promoting catagen development). Moreover, we explore the potential role of PPAR-γ in androgenetic alopecia, HF energy metabolism and HF ageing, and consider clinical perspectives that emanate from the limited data available on this so far. As this field of translational human hair research is still in its infancy, many open questions exist, for which we briefly delineate selected experimental approaches that promise to generate instructive answers in the near future.

Discovering highly selective and diverse PPAR-delta agonists by ligand based machine learning and structural modeling

PPAR-δ agonists are known to enhance fatty acid metabolism, preserving glucose and physical endurance and are suggested as candidates for treating metabolic diseases. None have reached the clinic yet. Our Machine Learning algorithm called "Iterative Stochastic Elimination" (ISE) was applied to construct a ligand-based multi-filter ranking model to distinguish between confirmed PPAR-δ agonists and random molecules. Virtual screening of 1.56 million molecules by this model picked ~2500 top ranking molecules. Subsequent docking to PPAR-δ structures was mainly evaluated by geometric analysis of the docking poses rather than by energy criteria, leading to a set of 306 molecules that were sent for testing in vitro. Out of those, 13 molecules were found as potential PPAR-δ agonist leads with EC50 between 4-19 nM and 14 others with EC50 below 10 µM. Most of the nanomolar agonists were found to be highly selective for PPAR-δ and are structurally different than agonists used for model building.

Effect of supplementing chromium histidinate and picolinate complexes along with biotin on insulin sensitivity and related metabolic indices in rats fed a high-fat diet

SCOPE

To investigate the effects of chromium histidinate (CrHis) and chromium picolinate (CrPic) complex along with biotin to a high-fat diet (HFD) fed to rats on the insulin sensitivity and the anti-obesity properties.

METHODS

Forty-two Sprague-Dawley male rats were divided into six groups. The rats were fed either (a): a standard diet (Control) or (b): a HFD or (c): a HFD with biotin (HFD+B) or (d): a combination of HFD and biotin along with CrPic (HFD + B + CrPic) or (e): a combination of HFD and biotin along with CrHis (HFD + B + CrHis) or (f): a combination of HFD and biotin along with CrHis and CrPic (HFD + B + CrHis + CrPic).

RESULTS

Adding biotin with chromium to HFD improved the glucose, insulin, HOMA-IR, leptin, lipid profile, with HFD+B+CrHis treatment being the most effective (p = 0.0001). Serum, liver, and brain tissue Cr concentrations increased upon Cr supplementations (p = 0.0001). Supplementing CrHis along with biotin to a HFD (HFD + B + CrHis) provided the greatest levels of GLUT-1, GLUT-3, PPAR-γ, and IRS-1, but the lowest level of NF-κB in the brain and liver tissues.

CONCLUSION

Biotin supplementation with chromium complexes, CrHis in particular, to a HFD pose to be a potential therapeutic feature for the treatment of insulin resistance.

Gemfibrozil reduces lipid accumulation in SMMC-7721 cells via the involvement of PPARα and SREBP1

Gemfibrozil (GEM) is a member of the fibrate class of lipid-lowering pharmaceuticals and has been widely used in the therapy of different forms of hyperlipidemia and hypercholesterolemia. Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is becoming an important public health concern worldwide. However, there is little knowledge about the effects of GEM on NAFLD. In the present study, oleate-treated human hepatoma SMMC-7721 cells were utilized to investigate the role of GEM in regulating hepatic lipid metabolism. The present results demonstrated that GEM attenuated excessive intracellular triglyceride content in the steatosis model. Upregulation of peroxisome proliferator-activated receptor α (PPARα) protein and sterol regulatory element-binding protein 1 (SREBP1) was detected following treatment with GEM. Additionally, reverse transcription-polymerase chain reaction analysis demonstrated that GEM increased the downstream genes related to PPARα and SREBP1, including carnitine palmitoyltransferase 2, acyl-coA oxidase 1, hydroxyacyl-CoA dehydrogenase, LIPIN1 and diacylglycerol O-acyltransferase 1. These findings demonstrated that GEM alleviated hepatic steatosis via the involvement of the PPARα and SREBP1 signaling pathways, which enhances lipid oxidation and interferes with lipid synthesis and secretion. Taken together, the data provide direct evidence that GEM may lower lipid accumulation in hepatocellular steatosis cells in vitro and that it may have a potential therapeutic use for NAFLD.

Suppression of isoproterenol-induced cardiotoxicity in rats by raspberry ketone via activation of peroxisome proliferator activated receptor-α

The peroxisome proliferator-activated receptor-α (PPAR-α) controls the lipid and glucose metabolism and also affects inflammation, cell proliferation and apoptosis during cardiovascular disease. Raspberry ketone (RK) is a red raspberry (Rubusidaeus, Family-Rosaceae) plant constituent, which activates PPAR-α. This study was conducted to assess the cardioprotective action of RK against isoproterenol (ISO)-induced cardiotoxicity. Wistar rats were randomly divided into six groups (six rats/group). Rats were orally administered with RK (50, 100 and 200 mg/kg, respectively) and fenofibrate (standard, 80 mg/kg) for 28 days and ISO was administered (85 mg/kg, subcutaneously) on 27th and 28th day. Administration of ISO in rats significantly altered hemodynamic and electrocardiogram patterns, total antioxidant capacity, PPAR-α, and apolipoprotein C-III levels. These myocardial aberrations were further confirmed during infarct size, heart weight to body weight ratio and immunohistochemical assessments (caspase-3 and nuclear factor-κB). RK pretreatment (100 and 200 mg/kg) significantly protected rats against oxidative stress, inflammation, and dyslipidemia caused by ISO as demonstrated by change in hemodynamic, biochemical and histological parameters. The results so obtained were quite comparable with fenofibrate. Moreover, RK was found to have binding affinity with PPAR-α, as confirmed by docking analysis. PPAR-α expression and concentration was also found increased in presence of RK which gave impression that RK probably showed cardioprotection via PPAR-α activation, however direct binding study of RK with PPAR-α is needed to confirm this assumption.

Molecular Actions of PPARα in Lipid Metabolism and Inflammation

Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor of clinical interest as a drug target in various metabolic disorders. PPARα also exhibits marked anti-inflammatory capacities. The first-generation PPARα agonists, the fibrates, have however been hampered by drug-drug interaction issues, statin drop-in, and ill-designed cardiovascular intervention trials. Notwithstanding, understanding the molecular mechanisms by which PPARα works will enable control of its activities as a drug target for metabolic diseases with an underlying inflammatory component. Given its role in reshaping the immune system, the full potential of this nuclear receptor subtype as a versatile drug target with high plasticity becomes increasingly clear, and a novel generation of agonists may pave the way for novel fields of applications.

Regulation of hypoxia inducible factor/prolyl hydroxylase binding domain proteins 1 by PPARα and high salt diet

BACKGROUND

Hypoxia inducible factor (HIF)/prolyl hydroxylase domain (PHD)-containing proteins are involved in renal adaptive response to high salt (HS). Peroxisome proliferator activated receptor alpha (PPARα), a transcription factor involved in fatty acid oxidation is implicated in the regulation of renal function. As both HIF-1α/PHD and PPARα contribute to the adaptive changes to altered oxygen tension, this study tested the hypothesis that PHD-induced renal adaptive response to HS is PPARα-dependent.

METHODS

PPARα wild type (WT) and knock out (KO) mice were fed a low salt (LS) (0.03% NaCl) or a HS (8% NaCl) diet for 8 days and treated with hydralazine. PPARα and heme oxygenase (HO)-1 expression were evaluated in the kidney cortex and medulla. A 24-h urinary volume (UV), sodium excretion (UNaV), and nitrite excretion (UNOx V) were also determined.

RESULTS

PHD1 expression was greater in the medulla as compared to the cortex of PPARα WT mice (p<0.05) fed with a LS (0.03% NaCl) diet. The HS diet (8% NaCl) downregulated PHD1 expression in the medulla (p<0.05) but not the cortex of WT mice whereas expression was downregulated in the cortex (p<0.05) and medulla (p<0.05) of KO mice. These changes were accompanied by HS-induced diuresis (p<0.05) and natriuresis (p<0.05) that were greater in WT mice (p<0.05). Similarly, UNOx V, index of renal nitric oxide synthase (NOS) activity or availability and heme oxygenase (HO)-1 expression was greater in WT (p<0.05) but unchanged in KO mice on HS diet. Hydralazine, a PHD inhibitor, did not affect diuresis or natriuresis in LS diet-fed WT or KO mice but both were increased (p<0.05) in HS diet-fed WT mice. Hydralazine also increased UNOx V (p<0.05) with no change in diuresis, natriuresis, or HO-1 expression in KO mice on HS diet.

CONCLUSIONS

These data suggest that HS-induced PPARα-mediated downregulation of PHD1 is a novel pathway for PHD/HIF-1α transcriptional regulation for adaptive responses to promote renal function via downstream signaling involving NOS and HO.

Identification and characterization of cis-regulatory elements 'insulator and repressor' in PPARD gene

AIM

Identification and functional characterization of cis-regulatory elements in human PPARD gene.

METHODS

We used various bioinformatic tools on the publicly available human genome and Encyclopedia of DNA Elements databases to explore potential cis-regulatory elements in PPARD gene region.

RESULTS

We predicted an insulator and an enhancer element in intron 2 of PPARD gene. Functional characterization using transient transfection, reporter assay and CTCF binding confirmed the insulator status. However, the predicted enhancer element showed repressor/silencer activity. Finally, we observed a potential interaction between these two cis-regulatory elements which is in agreement with 5C-Encyclopedia of DNA Elements data.

CONCLUSION

We report two functionally validated cis-regulatory elements in PPARD gene which will aid in understanding its regulation and role in metabolic functions.

Raspberry ketone protects against isoproterenol-induced myocardial infarction in rats

AIM

The cardioprotective role of raspberry ketone (RK) against isoproterenol (ISO)-induced myocardial infarction (MI) in rats was assessed.

MATERIALS AND METHODS

Rats were randomly divided into Group I - Vehicle control; Group II - Toxic control ISO (85mg/kg, s.c.); Group III, IV and V - RK (50, 100 and 200mg/kg, respectively) with ISO; Group VI- RK (200mg/kg) alone; Group VII - Propranolol (10mg/kg) with ISO; and Group VIII - Propranolol (10mg/kg) alone. After twenty-four hours of the last dose, animals were sacrificed and creatine kinase-MB, lactate dehydrogenase, total cholesterol, triglycerides, high-density-lipoprotein, low-density-lipoprotein, very-low-density-lipoprotein, malondialdehyde, reduced glutathione, superoxide dismutase, catalase, Na⁺, K⁺-ATPase, nitric oxide, histopathological and immunohistochemical analysis (tumor necrosis factor-α and inducible nitric oxide synthase) were performed.

KEY FINDINGS

Treatment with ISO significantly deviated the biochemical parameters from the normal levels, which were considerably restored by RK at 100 and 200mg/kg doses. 50mg/kg dose, however, did not demonstrate any significant cardioprotective action. The histopathological and immunohistochemical analysis further substantiated these findings.

SIGNIFICANCE

Our study showed a dose-dependent reduction in oxidative stress, inflammation and dyslipidemia by RK in ISO-intoxicated rats, which signifies that RK from the European red raspberry plant might be a valuable entity for the management of MI.

PPAR-γ Agonists and Their Role in Primary Cicatricial Alopecia

Peroxisome proliferator-activated receptor γ (PPAR-γ) is a ligand-activated nuclear receptor that regulates the transcription of various genes. PPAR-γ plays roles in lipid homeostasis, sebocyte maturation, and peroxisome biogenesis and has shown anti-inflammatory effects. PPAR-γ is highly expressed in human sebaceous glands. Disruption of PPAR-γ is believed to be one of the mechanisms of primary cicatricial alopecia (PCA) pathogenesis, causing pilosebaceous dysfunction leading to follicular inflammation. In this review article, we discuss the pathogenesis of PCA with a focus on PPAR-γ involvement in pathogenesis of lichen planopilaris (LPP), the most common lymphocytic form of PCA. We also discuss clinical trials utilizing PPAR-agonists in PCA treatment.

Sex differences in the immune response to experimental stroke: Implications for translational research

Ischemic stroke is a leading cause of death and disability in the United States. It is known that males and females respond differently to stroke. Depending on age, the incidence, prevalence, mortality rate, and disability outcome of stroke differ between the sexes. Females generally have strokes at older ages than males and, therefore, have a worse stroke outcome. There are also major differences in how the sexes respond to stroke at the cellular level. Immune response is a critical factor in determining the progress of neurodegeneration after stroke and is fundamentally different for males and females. Additionally, females respond to stroke therapies differently from males, yet they are often left out of the basic research that is focused on developing those therapies. With a resounding failure to translate stroke therapies from the bench to the bedside, it is clearer than ever that inclusion of both sexes in stroke studies is essential for future clinical success. This Mini-Review examines sex differences in the immune response to experimental stroke and its implications for therapy development. © 2016 Wiley Periodicals, Inc.

Noninvasive approach to mend the broken heart: Is "remote conditioning" a promising strategy for application in humans?

Currently, there are no satisfactory interventions to protect the heart against the detrimental effects of ischemia-reperfusion injury. Although ischemic preconditioning (PC) is the most powerful form of intrinsic cardioprotection, its application in humans is limited to planned interventions, due to its short duration and technical requirements. However, many organs/tissues are capable of producing "remote" PC (RPC) when subjected to brief bouts of ischemia-reperfusion. RPC was first described in the heart where brief ischemia in one territory led to protection in other area. Later on, RPC started to be used in patients with acute myocardial infarction, albeit with ambiguous results. It is hypothesized that the connection between the signal triggered in remote organ and protection induced in the heart can be mediated by humoral and neural pathways, as well as via systemic response to short sublethal ischemia. However, although RPC has a potentially important clinical role, our understanding of the mechanistic pathways linking the local stimulus to the remote organ remains incomplete. Nevertheless, RPC appears as a cost-effective and easily performed intervention. Elucidation of protective mechanisms activated in the remote organ may have therapeutic and diagnostic implications in the management of myocardial ischemia and lead to development of pharmacological RPC mimetics.

Radix Stellariae extract prevents high-fat-diet-induced obesity in C57BL/6 mice by accelerating energy metabolism

Stellaria dichotoma L. is widely distributed in Ningxia and surrounding areas in northwestern China. Its root, Radix Stellariae (RS), has been used in herbal formulae for treating asthenic-fever, infection, malaria, dyspepsia in children and several other symptoms. This study investigated whether the RS extract (RSE) alleviates metabolic disorders. The results indicated that RSE significantly inhibited body weight gain in high-fat (HF)-diet-fed C57BL/6 mice, reduced fasting glucose levels, and improved insulin tolerance. Moreover, RSE increased the body temperature of the mice and the expression of uncoupling proteins and peroxisome proliferator-activated receptors in the white adipose tissue. Thus, RSE alleviated metabolic disorders in HF-diet-fed C57BL/6 mice by potentially activating UCP and PPAR signaling.

PPARs: regulators of metabolism and as therapeutic targets in cardiovascular disease. Part I: PPAR-α

This article provides a comprehensive review about the molecular and metabolic actions of PPAR-α. It describes its structural features, ligand specificity, gene transcription mechanisms, functional characteristics and target genes. In addition, recent progress with the use of loss of function and gain of function mouse models in the discovery of diverse biological functions of PPAR-α, particularly in the vascular system and the status of the development of new single, dual, pan and partial PPAR agonists (PPAR modulators) in the clinical management of metabolic diseases are presented. This review also summarizes the clinical outcomes from a large number of clinical trials aimed at evaluating the atheroprotective actions of current clinically used PPAR-α agonists, fibrates and statin-fibrate combination therapy.

Peroxisome proliferator-activated receptors (PPARs) as therapeutic target in neurodegenerative disorders

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and they serve to be a promising therapeutic target for several neurodegenerative disorders, which includes Parkinson disease, Alzheimer's disease, Huntington disease and Amyotrophic Lateral Sclerosis. PPARs play an important role in the downregulation of mitochondrial dysfunction, proteasomal dysfunction, oxidative stress, and neuroinflammation, which are the major causes of the pathogenesis of neurodegenerative disorders. In this review, we discuss about the role of PPARs as therapeutic targets in neurodegenerative disorders. Several experimental approaches suggest potential application of PPAR agonist as well as antagonist in the treatment of neurodegenerative disorders. Several epidemiological studies found that the regular usage of PPAR activating non-steroidal anti-inflammatory drugs is effective in decreasing the progression of neurodegenerative diseases including PD and AD. We also reviewed the neuroprotective effects of PPAR agonists and associated mechanism of action in several neurodegenerative disorders both in vitro as well as in vivo animal models.

Sex differences and the role of PPAR alpha in experimental stroke

Males and females respond differently to stroke. Moreover, females often experience worse long-term stroke outcomes. Fenofibrate, a peroxisome proliferator-activated receptor alpha (PPARα) agonist has been shown to improve stroke outcome and resolve neuroinflammation in male mice. The present study compares the effect of pretreatment with fenofibrate versus vehicle control in male and female mice during experimental stroke. Mice were treated with low-dose fenofibrate 30 min before and once a day for three additional days after stroke onset. We observed a reduction in infarct volume in male mice 96 h post-stroke with low-dose fenofibrate pretreatment that was due to increase of an M2 macrophage phenotype in the brain and an increase in regulatory cells in the periphery. These outcomes were not replicated in females, likely due to the lower PPARα expression in cells and tissues in females vs males. We conclude that PPARα agonist treatment prior to stroke is neuroprotective in males but not females. These findings indicate PPARα as a probable mechanism of sex difference in stroke outcome and support the need for representation of females in stroke therapy research.

Loss of PPARα perpetuates sex differences in stroke reflected by peripheral immune mechanisms

Peroxisome proliferator-activated receptor alpha (PPARα) is a nuclear receptor transcription factor that plays a role in immune regulation. Because of its expression in cerebral tissue and immune cells, PPARα has been examined as an important regulator in immune-based neurological diseases. Many studies have indicated that pre-treatment of animals with PPARα agonists induces protection against stroke. However, our previous reports indicate that protection is only in males, not females, and can be attributed to different PPARα expression between the sexes. In the current study, we examine how loss of PPARα affects male and female mice in experimental stroke. Male and female PPARα knockout mice were subject to middle cerebral artery occlusion (MCAO) or sham surgery, and the ischemic (local) or spleen specific (peripheral) immune response was examined 96 h after reperfusion. We found that loss of PPARα perpetuated sex differences in stroke, and this was driven by the peripheral, not local, immune response. Specifically we observed an increase in peripheral pro-inflammatory and adhesion molecule gene expression in PPARα KO males after MCAO compared to females. Our data supports previous evidence that PPARα plays an important role in sex differences in the immune response to disease, including stroke.

Role of PPARα in the attenuation of bile acid-induced apoptosis by omega-3 long-chain polyunsaturated fatty acids in cultured hepatocytes

BACKGROUND

Omega-3 long-chain polyunsaturated fatty acids (ω3PUFA) have been shown to be antiinflammatory in the attenuation of hepatocellular injury. Peroxisome proliferator-activated receptor alpha (PPARα) is a nuclear receptor transcription factor that inhibits the activation of nuclear factor κB, thereby repressing inflammation, and ωPUFA are PPARα ligands. The purpose of this study was to determine if ω3PUFA attenuate bile acid-induced apoptosis via PPARα.

METHODS

Human hepatocellular carcinoma (HepG2) cells were treated with chenodeoxycholic acid (CDCA) ± ω3PUFA. Activation of PPARα was evaluated, and expression of PPARα, farnesoid X receptor, liver X receptor alpha (LXRα), and retinoid X receptor mRNA was evaluated by reverse-transcriptase PCR.

RESULTS

PPARα activation was increased in HepG2 cells treated with ω3PUFA, and decreased in the presence of CDCA when compared with untreated cells. PPARα mRNA was reduced by 67% with CDCA and restored to the level of control with ω3PUFA. LXRα mRNA increased twofold with CDCA treatment and was significantly reduced by ω3PUFA.

CONCLUSION

Expression of PPARα, as well as LXRα mRNA levels, was reduced with CDCA treatment and restored with the addition of ω3PUFA. These results suggest that PPARα and LXRα may be mediators by which ω3PUFA attenuate bile acid-induced hepatocellular injury.