Long-term effects of the PPAR gamma activator pioglitazone on cardiac inflammation in stroke-prone spontaneously hypertensive rats

Interrelationship between diabetes mellitus and heart failure: the role of peroxisome proliferator-activated receptors in left ventricle performance

Heart failure (HF) is a common cardiac syndrome, whose pathophysiology involves complex mechanisms, some of which remain unknown. Diabetes mellitus (DM) constitutes not only a glucose metabolic disorder accompanied by insulin resistance but also a risk factor for cardiovascular disease and HF. During the last years though emerging data set up, a bidirectional interrelationship between these two entities. In the case of DM impaired calcium homeostasis, free fatty acid metabolism, redox state, and advance glycation end products may accelerate cardiac dysfunction. On the other hand, when HF exists, hypoperfusion of the liver and pancreas, b-blocker and diuretic treatment, and autonomic nervous system dysfunction may cause impairment of glucose metabolism. These molecular pathways may be used as therapeutic targets for novel antidiabetic agents. Peroxisome proliferator-activated receptors (PPARs) not only improve insulin resistance and glucose and lipid metabolism but also manifest a diversity of actions directly or indirectly associated with systolic or diastolic performance of left ventricle and symptoms of HF. Interestingly, they may beneficially affect remodeling of the left ventricle, fibrosis, and diastolic performance but they may cause impaired water handing, sodium retention, and decompensation of HF which should be taken into consideration in the management of patients with DM. In this review article, we present the pathophysiological data linking HF with DM and we focus on the molecular mechanisms of PPARs agonists in left ventricle systolic and diastolic performance providing useful insights in the molecular mechanism of this class of metabolically active regiments.

Functional Food and Cardiovascular Disease Prevention and Treatment: A Review

Cardiovascular disease (CVD) is now the leading cause of death globally and is a growing health concern. Lifestyle factors, including nutrition, play an important role in the etiology and treatment of CVD. Functional foods based on their basic nutritional functions can decrease the risk of many chronic diseases and have some physiological benefits. They contain physiologically active components either from plant or animal sources, marketed with the claim of their ability to reduce heart disease risk, focusing primarily on established risk factors, which are hyperlipidemia, diabetes, metabolic syndrome, obesity/overweight, elevated lipoprotein A level, small dense low-density lipoprotein cholesterol (LDL-C), and elevated inflammatory marker levels. Functional foods are suspected to exert their cardioprotective effects mainly through blood lipid profile level and improve hypertension control, endothelial function, platelet aggregation, and antioxidant actions. Clinical and epidemiological observations indicate that vegetable and fruit fiber, nuts and seeds, sea foods, coffee, tea, and dark chocolate have cardioprotective potential in humans, as well whole-grain products containing intact grain kernels rich in fiber and trace nutrients. They are nutritionally more important because they contain phytoprotective substances that might work synergistically to reduce cardiovascular risk. This review will focus on the reciprocal interaction between functional foods and the potential link to cardiovascular health and the possible mechanisms of action.

Quantitative evaluation of PPAR-γ2 Pro12Ala polymorphism with hypertension

BACKGROUND

The peroxisome proliferator-activated receptor γ2 (PPARγ2)Pro12Ala polymorphism has been reported to be associated with hypertension. However, relevant studies have shown inconsistent results.

METHODS

To quantitatively evaluate the relationship between the PPARγ2Pro12Ala polymorphism and hypertension risk, we conducted a meta-analysis based on all available studies selected from Scopus, Web of Science, PubMed, Chinese National Knowledge Infrastructure, and Wanfang databases.

RESULTS

In all, 13 studies were finally included in this meta-analysis. In the allelic model (Ala vs. Pro), the Ala allele of PPARγ2 Pro12Ala polymorphism was associated with hypertension (Odds Ratio [OR] = 0.723, 95% confidence interval [CI] = 0.607-0.861). Sensitivity analysis and exclusion of studies with poor quality scores or controls complicated by other diseases confirmed the validity of this association. Moreover, the PPARγ2Pro12Ala polymorphism was associated with hypertension in the codominant (OR = 0.710, 95% CI = 0.626-0.806), recessive (OR = 0.561, 95% CI = 0.418-0.754), and dominant (OR = 0.693, 95% CI = 0.577-0.833) models.

CONCLUSION

The Ala allele appears to have a protective effect against hypertension and a dominant function.

Peroxisome proliferator-activated receptors as therapeutic targets for heart failure

Heart failure (HF) is a common clinical syndrome that affects more than 23 million individuals worldwide. Despite the marked advances in its management, the mortality rates in HF patients have remained unacceptably high. Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription regulators, involved in the regulation of fatty acid and glucose metabolism. PPAR agonists are currently used for the treatment of type II diabetes mellitus and hyperlipidemia; however, their role as therapeutic agents for HF remains under investigation. Preclinical studies have shown that pharmacological modulation of PPARs can upregulate the expression of fatty acid oxidation genes in cardiomyocytes. Moreover, PPAR agonists were proven able to improve ventricular contractility and reduce cardiac remodelling in animal models through their anti-inflammatory, anti-oxidant, anti-fibrotic, and anti-apoptotic activities. Whether these effects can be replicated in humans is yet to be proven. This article reviews the interactions of PPARs with the pathophysiological mechanisms of HF and how the pharmacological modulation of these receptors can be of benefit for HF patients.

A Review of the Molecular Mechanisms Underlying the Development and Progression of Cardiac Remodeling

Pathological molecular mechanisms involved in myocardial remodeling contribute to alter the existing structure of the heart, leading to cardiac dysfunction. Among the complex signaling network that characterizes myocardial remodeling, the distinct processes are myocyte loss, cardiac hypertrophy, alteration of extracellular matrix homeostasis, fibrosis, defective autophagy, metabolic abnormalities, and mitochondrial dysfunction. Several pathophysiological stimuli, such as pressure and volume overload, trigger the remodeling cascade, a process that initially confers protection to the heart as a compensatory mechanism. Yet chronic inflammation after myocardial infarction also leads to cardiac remodeling that, when prolonged, leads to heart failure progression. Here, we review the molecular pathways involved in cardiac remodeling, with particular emphasis on those associated with myocardial infarction. A better understanding of cell signaling involved in cardiac remodeling may support the development of new therapeutic strategies towards the treatment of heart failure and reduction of cardiac complications. We will also discuss data derived from gene therapy approaches for modulating key mediators of cardiac remodeling.

Effect of pioglitazone on metabolic features in endotoxemia model in obese diabetic db/db mice

BACKGROUND

Infectious diseases are more frequent in diabetic patients, leading to increased morbidity and mortality. Endotoxemia affects glucose metabolism and lipolytic capacity. The aims of the present study were to determine whether endotoxemia exacerbates metabolic features (adipose inflammation, adipogenesis, and insulin resistance [IR]) in an animal model of diabetes (i.e. db/db mice) after acute infection and the effects of pioglitazone.

METHODS

Female db/db mice treated with pioglitazone (3 and 30 mg/kg, p.o.) for 14 days were challenged with lipopolysaccharide (LPS; 200 μg/kg), followed by an oral glucose tolerance test (OGTT). Quantitative real-time polymerase chain reaction (PCR) was used to evaluate the expression of genes in white adipose tissue (WAT) involved in: (i) adipogenesis (lipoprotein lipase [Lpl], fatty acid binding protein-4 [Ap2] and adiponectin [Adipoq]); (ii) insulin signaling (peroxisome proliferator-activated receptor gamma [Pparg], suppressor of cytokine signaling 3 [Socs3], solute carrier family 2 [facilitated glucose transporter], member 4 [Slc2a4]); and (iii) inflammation (tumor necrosis factor [Tnf], interleukin-6 [Il6], monocyte chemoattractant protein-1 [Ccl2], cyclo-oxygenase-2 [prostaglandin-endoperoxide synthase 2; Ptgs2]).

RESULTS

Experimental endotoxemia downregulated mRNA expression of Pparg, Slc2a4, Adipoq, Lpl, and Ap2, which coincided with upregulation of Il6, Tnf, Ccl2, Ptgs2, and Socs3 expression. Pioglitazone dose-dependently decreased Tnf, Il6, Ccl2, Ptgs2, and Socs3 expression in WAT, in association with upregulation of Lpl, Ap2, Slc2a4, and Adipoq expression, indicating improvement in endotoxin-induced IR.

CONCLUSIONS

The findings suggest that LPS challenge exacerbates IR in db/db mice by altering the expression of genes in WAT involved in adipogenesis and inflammation, which is effectively controlled by pioglitazone treatment.

PPAR-γ is involved in the protective effect of 2,3,4',5-tetrahydroxystilbene-2-O-beta-D-glucoside against cardiac fibrosis in pressure-overloaded rats

2, 3, 4', 5-tetrahydroxystilbene-2-0-β-D glucoside (TSG) could inhibit cardiac remodeling in response to pressure overload. Peroxisome proliferator-activated receptor gamma (PPAR-γ) has been recognized as a potent, endogenous antifibrotic factor and maintaining a proper expression level in myocardium is necessary for assuring that structure and function of heart adapt to pressure overload stress. The aim of the present study was to investigate whether PPAR-γ is involved in the beneficial effect of TSG on pressure overload-induced cardiac fibrosis. TSG (120mg/kg/day) or TSG (120mg/kg/day) plus the PPAR-γ antagonist GW9662 (1mg/kg/day) was administered to rats with pressure overload induced by abdominal aortic banding. 30 days later, pressure overload-induced hypertension, cardiac dysfunction and fibrosis were significantly inhibited by TSG. TSG also significantly reduced collagen I, collagen III, fibronectin and plasminogen activator inhibitor (PAI)-1 expression, as makers of myocardial fibrosis. Theses anti-fibrotic effects of TSG in pressure overloaded hearts could be abrogated by co-treatment with GW9662. Accordingly, upregulated PPAR-γ protein expression by TSG in pressure overloaded hearts was also reversed by co-treatment with GW9662. Additionally, the inhibitory effects of TSG on angiotensin II induced cardiac fibroblasts proliferation, differentiation and expression of collagen I and III, fibronectin and PAI-1 were abrogated by PPAR-γ antagonist GW9662 and PPAR-γ silencing. Furthermore, TSG directly increased PPAR-γ gene expression at gene promoter, mRNA and protein level in angiotensin II-treated cardiac fibroblats in vitro. Our results suggested that upregualtion of endogenous PPAR-γ expression by TSG may be involved in its beneficial effect on pressure overload-induced cardiac fibrosis.

Peroxisome Proliferator-Activated Receptor-γ Is Critical to Cardiac Fibrosis

Peroxisome proliferator-activated receptor-γ (PPARγ) is a ligand-activated transcription factor belonging to the nuclear receptor superfamily, which plays a central role in regulating lipid and glucose metabolism. However, accumulating evidence demonstrates that PPARγ agonists have potential to reduce inflammation, influence the balance of immune cells, suppress oxidative stress, and improve endothelial function, which are all involved in the cellular and molecular mechanisms of cardiac fibrosis. Thus, in this review we discuss the role of PPARγ in various cardiovascular conditions associated with cardiac fibrosis, including diabetes mellitus, hypertension, myocardial infarction, heart failure, ischemia/reperfusion injury, atrial fibrillation, and several other cardiovascular disease (CVD) conditions, and summarize the developmental status of PPARγ agonists for the clinical management of CVD.

An overview of the crosstalk between inflammatory processes and metabolic dysregulation during diabetic cardiomyopathy

Metabolic disorders such as obesity, insulin resistance and type 2 diabetes mellitus are all linked to cardiovascular diseases such as cardiac hypertrophy and heart failure. Diabetic cardiomyopathy in particular, is characterized by structural and functional alterations in the heart muscle of people with diabetes that finally lead to heart failure, and which is not directly attributable to coronary artery disease or hypertension. Several mechanisms have been involved in the pathogenesis of diabetic cardiomyopathy, such as alterations in myocardial energy metabolism and calcium signaling. Metabolic disturbances during diabetic cardiomyopathy are characterized by increased lipid oxidation, intramyocardial triglyceride accumulation, and reduced glucose utilization. Overall changes result in enhanced oxidative stress, mitochondrial dysfunction and apoptosis of the cardiomyocytes. On the other hand, the progression of heart failure and cardiac hypertrophy usually entails a local rise in cytokines in cardiac cells and the activation of the proinflammatory transcription factor nuclear factor (NF)-κB. Interestingly, increasing evidences are arising in the recent years that point to a potential link between chronic low-grade inflammation in the heart and metabolic dysregulation. Therefore, in this review we summarize recent new insights into the crosstalk between inflammatory processes and metabolic dysregulation in the failing heart during diabetes, paying special attention to the role of NF-κB and peroxisome proliferator activated receptors (PPARs). In addition, we briefly describe the role of the AMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1) and other pathways regulating cardiac energy metabolism, as well as their relationship with diabetic cardiomyopathy.

Delayed cardioprotective effects of WY-14643 are associated with inhibition of MMP-2 and modulation of Bcl-2 family proteins through PPAR-α activation in rat hearts subjected to global ischaemia–reperfusion

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors regulating cardiac lipid metabolism and energy homeostasis. Although the activation of PPARs has been implicated in cardioprotection, the molecular mechanisms are largely unexplored. In this study, we aimed to investigate the effect of the PPAR-α agonist WY-14643 (WY), mimicking a delayed effect of preconditioning in rat hearts exposed to acute ischaemia–reperfusion (I/R) 24 h later, and to define whether antioxidative and antiapoptotic mechanisms are involved. Treatment with WY markedly attenuated post-ischaemic contractile dysfunction (as evidenced by the reduced infarct size), the higher left ventricular developed pressure (LVDP) recovery, and the decreased occurrence of arrhythmias. These effects were abolished in the presence of the PPAR-α antagonist MK886. Heme oxygenase-1, a key antioxidative enzyme implicated in cytoprotection, was upregulated in response to WY at baseline, but was markedly reduced after I/R, indicating reduced oxidative stress. WY treatment was also associated with decreased mRNA levels and enzymatic activity of matrix metalloproteinase-2, and increased ratios of Bcl-2:Bax proteins. These results indicate that PPAR-α activation by its selective ligand WY may confer delayed preconditioning-like protection in rat hearts subjected to I/R by modulating oxidative stress, activation of matrix metalloproteinase-2, and expression of Bcl-2 and Bax.

Pioglitazone attenuates vascular fibrosis in spontaneously hypertensive rats

Objective. We sought to investigate whether the peroxisome proliferator-activated receptor-γ (PPAR-γ) ligand pioglitazone can attenuate vascular fibrosis in spontaneously hypertensive rats (SHRs) and explore the possible molecular mechanisms. Methods. SHRs (8-week-old males) were randomly divided into 3 groups (n = 8 each) for treatment: pioglitazone (10 mg/kg/day), hydralazine (25 mg/kg/day), or saline. Normal male Wistar Kyoto (WKY) rats (n = 8) served as normal controls. Twelve weeks later, we evaluated the effect of pioglitazone on vascular fibrosis by Masson's trichrome and immunohistochemical staining of collagen III and real-time RT-PCR analysis of collagen I, III and fibronectin mRNA.Vascular expression of PPAR-γ and connective tissue growth factor (CTGF) and transforming growth factor-β (TGF-β) expression were evaluated by immunohistochemical staining, western blot analysis, and real-time RT-PCR. Results. Pioglitazone and hydralazine treatment significantly decreased systolic blood pressure in SHRs. Masson's trichrome staining for collagen III and real-time RT-PCR analysis of collagen I, III and fibronectin mRNA indicated that pioglitazone significantly inhibited extracellular matrix production in the aorta. Compared with Wistar Kyoto rats, SHRs showed significantly increased vascular CTGF expression. Pioglitazone treatment significantly increased PPAR-γ expression and inhibited CTGF expression but had no effect on TGF-β expression. Conclusions. The results indicate that pioglitazone attenuated vascular fibrosis in SHRs by inhibiting CTGF expression in a TGF-β-independent mechanism.

Transforming growth factor-β inhibits myocardial PPARγ expression in pressure overload-induced cardiac fibrosis and remodeling in mice

OBJECTIVES

Pharmacological activation of peroxisome proliferator-activated receptor gamma (PPARγ) has been shown to attenuate pressure overload-induced cardiac fibrosis, suggesting that PPARγ has an antifibrotic effect. This study tested the hypothesis that there is a functional interaction between transforming growth factor-β (TGF-β) signaling and endogenous PPARγ expression in cardiac fibroblasts and pressure overloaded heart.

METHODS AND RESULTS

We observed that, in response to pressure overload induced by transverse aortic constriction, left-ventricular PPARγ protein levels were decreased in wild-type mice, but increased in mice with an inducible overexpression of dominant negative mutation of the human TGF-β type II receptor (DnTGFβRII), in which TGF-β signaling is blocked. In isolated mouse cardiac fibroblasts, we demonstrated that TGF-β1 treatment decreased steady state PPARγ mRNA (-34%) and protein (-52%) levels, as well as PPARγ transcriptional activity (-53%). Chromatin immunoprecipitation analysis showed that TGF-β1 treatment increased binding of Smad2/3, Smad4 and histone deacetylase 1, and decreased binding of acetylated histone 3 to the PPARγ promoter in cardiac fibroblasts. Both pharmacological activation and overexpression of PPARγ significantly inhibited TGF-β1-induced extracellular matrix molecule expression in isolated cardiac fibroblasts, whereas treatment with the PPARγ agonist rosiglitazone inhibited, and treatment with the PPARγ antagonist T0070907 exacerbated chronic pressure overload-induced cardiac fibrosis and remodeling in wild-type mice in vivo.

CONCLUSION

These data provide strong evidence that TGF-β1 directly suppresses PPARγ expression in cardiac fibroblasts via a transcriptional mechanism and suggest that the down-regulation of endogenous PPARγ expression by TGF-β may be involved in pressure overload-induced cardiac fibrosis.

Cardiac peroxisome-proliferator-activated receptor expression in hypertension co-existing with diabetes

Hypertension and DM (diabetes mellitus) are common chronic disorders that often co-exist. DM and PPAR (peroxisome-proliferator-activated receptor)-γ agonists may directly impair heart function. However, the effects of DM and PPAR-γ agonists on hypertensive myocardium are not known. Hence the aim of the present study was to investigate whether DM and a PPAR-γ agonist [RGZ (rosiglitazone)] modulated the effects of hypertension on myocardial expression of PPAR isoforms. Cardiac PPAR isoforms, TNF (tumour necrosis factor)-α and IL (interleukin)-6 were evaluated by real-time PCR and Western blotting in SHRs (spontaneously hypertensive rats), diabetic SHRs, diabetic SHRs treated with RGZ (5 mg/kg of body weight) and control WKY (Wistar-Kyoto) rats. Cardiac NADPH oxidase activity was quantified using a SOD (superoxide dismutase)-sensitive cytochrome c reduction assay. When compared with hearts from control WKY rats, hearts from SHRs had decreased PPAR-α and PPAR-δ mRNA and protein levels (39 and 44% respectively for PPAR-α, and 37 and 42% respectively for PPAR-δ), but had increased PPAR-γ mRNA and protein levels (1.9- and 1.4-fold respectively). The hypertension-induced changes in mRNA and protein of cardiac PPAR isoforms were enhanced in diabetic SHRs, which were attenuated in diabetic SHRs treated with RGZ. Cardiac TNF-α and IL-6 protein levels and NADPH oxidase activities were increased in SHRs and were increased further in diabetic SHRs. RGZ treatment decreased TNF-α and IL-6 protein levels and NADPH oxidase activities in hearts from diabetic SHRs. In conclusion, these findings suggest that DM and the PPAR-γ agonist modulated the hypertensive effects on cardiac PPAR isoform expression.

Green tea polyphenols improve cardiac muscle mRNA and protein levels of signal pathways related to insulin and lipid metabolism and inflammation in insulin-resistant rats

Epidemiological studies indicate that the consumption of green tea polyphenols (GTP) may reduce the risk of coronary artery disease. To explore the underlying mechanisms of action at the molecular level, we examined the effects of GTP on the cardiac mRNA and protein levels of genes involved in insulin and lipid metabolism and inflammation. In rats fed a high-fructose diet, supplementation with GTP (200 mg/kg BW daily dissolved in distilled water) for 6 wk, reduced systemic blood glucose, plasma insulin, retinol-binding protein 4, soluble CD36, cholesterol, triglycerides, free fatty acids and LDL-C levels, as well as the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and IL-6. GTP did not affect food intake, bodyweight and heart weight. In the myocardium, GTP also increased the insulin receptor (Ir), insulin receptor substrate 1 and 2 (Irs1 and Irs2), phosphoinositide-3-kinase (Pi3k), v-akt murine thymoma viral oncogene homolog 1 (Akt1), glucose transporter 1 and 4 (Glut1 and Glut4) and glycogen synthase 1 (Gys1) expression but inhibited phosphatase and tensin homolog deleted on chromosome ten (Pten) expression and decreased glycogen synthase kinase 3beta (Gsk3beta) mRNA expression. The sterol regulatory element-binding protein-1c (Srebp1c) mRNA, microsomal triglyceride transfer protein (Mttp) mRNA and protein, Cd36 mRNA and cluster of differentiation 36 protein levels were decreased and peroxisome proliferator-activated receptor (Ppar)gamma mRNA levels were increased. GTP also decreased the inflammatory factors: Tnf, Il1b and Il6 mRNA levels, and enhanced the anti-inflammatory protein, zinc-finger protein, protein and mRNA expression. In summary, consumption of GTP ameliorated the detrimental effects of high-fructose diet on insulin signaling, lipid metabolism and inflammation in the cardiac muscle of rats.

Endogenously produced adiponectin protects cardiomyocytes from hypertrophy by a PPARgamma-dependent autocrine mechanism

In experimental animal and cell culture models, activation of peroxisome proliferator-activated receptor (PPAR) gamma in heart has been shown to have beneficial effects on cardiac function and cardiomyocyte physiology. The goal of this study was to identify the signaling pathway by which PPARgamma activation protects cardiomyocytes from the deleterious effects of hypertrophic stimuli. In primary cardiomyocyte cultures, we found that genetic or pharmacological activation of PPARgamma protected cells from cardiac hypertrophy induced by alpha-adrenergic stimulation. Examination of gene expression in these cells revealed a surprising increase in the expression of adiponectin in cardiomyocytes and secretion of the high-molecular-weight form of the hormone into media. Using RNAi to block PPARgamma-induced adiponectin production or adiponectin receptor gene expression, we found that the PPARgamma-mediated anti-hypertrophic effect required cardiomyocyte-produced adiponectin, as well as an intact adiponectin signaling pathway. Furthermore, mice expressing constitutive-active PPARgamma and cardiomyocyte specific adiponectin expression were protected from high-fat diet-induced cardiac hypertrophy and remodeling. These findings demonstrate that functional adiponectin hormone can be produced from the heart and raise the possibility that beneficial effects of PPARgamma activation in heart could be due in part to local production of adiponectin that acts on cardiomyocytes in an autocrine manner.

Whole grape intake impacts cardiac peroxisome proliferator-activated receptor and nuclear factor kappaB activity and cytokine expression in rats with diastolic dysfunction

Prolonged hypertension is the leading cause of heart failure. Failing hearts show reduced peroxisome proliferator-activating receptor (PPAR) activity and enhanced nuclear factor kappaB (NF-kappaB) activity, which together modify cardiac inflammation and fibrosis. In vitro studies suggest that phytochemicals alter PPAR and NF-kappaB activity, but the capabilities of a phytochemical-rich diet are less understood. Grapes contain an array of commonly consumed dietary phytochemicals. In Dahl salt-sensitive hypertensive rats, we showed previously that dietary provision of whole table grape powder (3% weight:weight) for 18 weeks reduced blood pressure, cardiac hypertrophy, and diastolic dysfunction. The hypothesis tested here is that, in this model, phytochemical provision from whole grape powder impacts cardiac PPAR and NF-kappaB activity and their related gene transcripts. Grape-fed rats had enhanced PPAR-alpha and PPAR-gamma DNA binding activity but reduced NF-kappaB DNA binding activity. RT-PCR revealed that grape-fed rats showed upregulated mRNA for PPAR-alpha, PPAR-gamma coactivator-1alpha, PPAR-gamma, and the cytosolic NF-kappaB inhibitor, inhibitor-kappaBalpha. By contrast, grape-fed rats showed downregulated mRNA for tumor necrosis factor-alpha and transforming growth factor-beta1. Finally, grape-fed rats showed significantly reduced cardiac tumor necrosis factor-alpha and transforming growth factor-beta protein expression, increased inhibitor-kappaBalpha expression, and reduced cardiac fibrosis. In the Dahl salt-sensitive rat, chronic intake of grapes altered cardiac transcripts related to PPAR and NF-kappaB that may be significant to the observed diet-associated cardioprotection.

The effects of thiazolidinediones on blood pressure levels – A systematic review

Insulin resistance has been proposed to be the underlying disorder of the so-called metabolic or insulin resistance syndrome, which represents the clustering in the same individual of several cardiovascular risk factors, such as type 2 diabetes mellitus, hypertension, abdominal obesity, elevated triglycerides and low high-density lipoprotein-cholesterol. As far as the connection of insulin resistance and compensatory hyperinsulinaemia with hypertension is concerned, a number of mechanisms possibly linking these disturbances have been described, such as activation of sympathetic nervous system, enhancement of renal sodium reabsorption, or impairment of endothelium-dependent vasodilatation. Thiazolidinediones (TZDs) constitute a class of oral antihyperglycaemic agents that act by decreasing insulin resistance, and apart from their action on glycaemic control, they have been also reported to exert beneficial effects on other parameters of the metabolic syndrome. In particular, during recent years a considerable number of animal and human studies have shown that the use of TZDs was associated with usually small but significant reductions of blood pressure (BP) levels. Since a possible beneficial action of these compounds on BP could be of particular value for patients with the metabolic syndrome, this review aimed to summarize and evaluate the literature data in the field, derived either from studies that just examined BP levels among other parameters or from studies that were specifically designed to determine the effect of a TZD on BP.

Phase 2 protein inducers in the diet promote healthier aging

Oxidative stress drives many aging-associated problems. Because oxidative stress can be decreased by induction of phase 2 proteins, we hypothesized that incorporating the phase 2 protein inducer 2(3)-tert-butyl-4-hydroxyanisole (tBHA) into the diet would result in healthier aging. C57BL/6 mice were placed either on control mouse chow diet or on chow containing tBHA and were examined at 6, 12, and 18 months. Dietary tBHA resulted in the antioxidant response activation, decreased both oxidative stress and pro-inflammatory gene expression in tissues examined, counteracted the decrease in the transcription factors peroxisome proliferator-activated receptor-gamma and increase in CCAAT/enhancer binding protein-alpha levels seen in liver with aging, and was associated with mice having less weight gain, despite having no differences in food consumption, and better locomotor function. We conclude that simple changes in the diet such as incorporation of phase 2 protein inducers can have a profound influence on health and, thereby, the aging process.

The many faces of PPARgamma: anti-inflammatory by any means?

The peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear receptor superfamily, a group of transcription factors that regulate expression of their target genes upon ligand binding. As endogenous ligands, oxidized fatty acids and prostanoids can bind to and activate the receptor. Natural and synthetic PPARgamma activators have been studied extensively in many inflammatory settings and in most instances they have been shown to be anti-inflammatory. In this review we give an overview of the different molecular mechanisms how PPARgamma and its agonists exert their anti-inflammatory effects both at the cellular level and the level of the organism. The action of PPARgamma in acute and chronic inflammatory diseases and disease models will be presented.

Activation of peroxisome proliferator-activated receptor gamma inhibits endothelin-1-induced cardiac hypertrophy via the calcineurin/NFAT signaling pathway

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) has been described as a negative regulator of cardiac hypertrophy. A better understanding of PPAR-gamma and cardiac hypertrophy may facilitate the development of novel therapeutic strategies to treat heart diseases related to cardiac hypertrophy by mimicking the naturally preferred mechanisms. In the present study, we investigated the interaction between PPAR-gamma and calcineurin/nuclear factor of activated T-cells (NFAT) in endothelin-1 (ET-1)-induced hypertrophy of neonatal rat cardiac myocytes. The results suggest that the treatment of cultured cardiac myocytes with a PPAR-gamma ligand, rosiglitazone, inhibited the ET-1-induced increase in protein synthesis, surface area, calcineurin enzymatic activity, and protein expression. Both the application of rosiglitazone and overexpression of the PPAR-gamma inhibited the nuclear translocation of NFATc4. Moreover, co-immunoprecipitation studies showed that rosiglitazone enhanced the association between PPAR-gamma and calcineurin/NFAT. These results suggest that ET-1-induced cardiac hypertrophy is inhibited by activation of PPAR-gamma, which is at least partly due to cross-talk between PPAR-gamma and calcineurin/NFAT.

Pomegranate flower: a unique traditional antidiabetic medicine with dual PPAR-alpha/-gamma activator properties

PPARs are transcription factors belonging to the superfamily of nuclear receptors. PPAR-alpha is involved in the regulation of fatty acid (FA) uptake and oxidation, inflammation and vascular function, while PPAR-gamma participates in FA uptake and storage, glucose homeostasis and inflammation. The PPARs are thus major regulators of lipid and glucose metabolism. Synthetic PPAR-alpha or PPAR-gamma agonists have been widely used in the treatment of dyslipidaemia, hyperglycaemia and their complications. However, they are associated with an incidence of adverse events. Given the favourable metabolic effects of both PPAR-alpha and PPAR-gamma activators, as well as their potential to modulate vascular disease, combined PPAR-alpha/-gamma activation has recently emerged as a promising concept, leading to the development of mixed PPAR-alpha/-gamma activators. However, some major side effects associated with the synthetic dual activators have been reported. It is unclear whether this is a specific effect of the particular synthetic compounds or a class effect. To date, a medication that may combine the beneficial metabolic effects of PPAR-alpha and PPAR-gamma activation with fewer undesirable side effects has not been successfully developed. Pomegranate plant parts are used traditionally for the treatment of various disorders. However, only pomegranate flower has been prescribed in Unani and Ayurvedic medicines for the treatment of diabetes. This review provides a new understanding of the dual PPAR-alpha/-gamma activator properties of pomegranate flower in the potential treatment of diabetes and its associated complications.

Candesartan improves myocardial damage in obese mice with viral myocarditis and induces cardiac adiponectin

PURPOSE

To clarify the mechanism of the effects of angiotensin II receptor type 1 antagonist, candesartan, upon cardiac adiponectin in the combination of myocarditis with obesity, we examined obese KKAy mice with acute viral myocarditis treated by candesartan and investigated cardiac adiponectin regulation.

METHODS

Mice were divided into candesartan early treatment group (Can-early) receiving orally candesartan at daily dose of 10 mg/kg 7 days starting before viral inoculation and then 7 days; candesartan late treatment group (Can-late) or vehicle (Vehicle) receiving candesartan starting simultaneously with viral inoculation and then 7 days. Encephalomyocarditis virus was used to induce the acute viral myocarditis. Differences in myocardial damages, serum adiponectin and myocardial expression of adiponectin, tumor necrosis factor-alpha (TNF-alpha), CCAAT/enhancer binding proteinalpha (C/EBPalpha) and peroxisome proliferator-activated receptor gamma (PPAR-gamma) and nuclear factor-kappaB (NF-kappaB) mRNA among three groups were determined on days 0, 4 and 7 after viral inoculation.

RESULTS

Mice in Can-early and Can-late groups showed reduced myocardial necrosis and cellular infiltration as compared with those in the Vehicle. On day 4 the circulating adiponectin levels were significantly higher in Can-early than those in Vehicle. Mice in Vehicle had significantly reduced in myocardial adiponectin mRNA after viral myocarditis. Cardiac adiponectin mRNA was significantly higher in Can-early and in Can-late than in Vehicle on days 4 and 7. Cardiac C/EBPalpha in Can-early and Can-early groups was significantly increased on day 4. Myocardial NF-kappaB and TNF-alpha mRNA in Can-early and Can-late groups were significantly reduced on day 7.

CONCLUSION

Candesartan treatment improved myocardial injury in obese mice with acute viral myocarditis and induced expression of cardiac adiponectin with the induction of C/EBPalpha as well as the reduction of cardiac NF-kappaB and TNF-alpha.

PPAR activation: a new target for the treatment of hypertension

Hypertensive patients are at increased risk for cardiovascular complications. Inhibition of different pathophysiological mechanisms involved in hypertension and hypertension-related target organ damage may revert or prevent the progression of the pathological changes observed and reduce the occurrence of cardiovascular events. One of the new targets that may prevent or regress hypertensive vascular, renal, and perhaps brain changes in hypertension is the activation of nuclear receptors that have metabolic effects but also exert antiinflammatory action, the peroxisome proliferator activator receptor (PPAR) activators alpha and gamma. This review will discuss some of the evidence, both experimental and clinical, that suggests that activation of PPAR alpha and/or gamma in hypertension may exert beneficial cardiovascular protective effects.

Ameliorative Effect of Combination of Fenofibrate and Rosiglitazone in Pressure Overload-Induced Cardiac Hypertrophy in Rats

The present study has been designed to investigate the effects of fenofibrate, a peroxisome proliferator-activated receptor (PPAR)alpha agonist, rosiglitazone, a PPARgamma agonist and the combination of both fenofibrate and rosiglitazone in partial abdominal aortic constriction (PAAC)-induced pathological cardiac hypertrophy in rats. Rats were subjected to PAAC for 4 weeks to produce pathological cardiac hypertrophy. The fenofibrate (3 mg/kg day(-1), p.o.), rosiglitazone (3 mg/kg day(-1), p.o.) and the combination of both fenofibrate (3 mg/kg day(-1), p.o.) and rosiglitazone (3 mg/kg day(-1), p.o.) were administered 3 days before PAAC and continued for 4 weeks after PAAC. The development of cardiac hypertrophy was assessed in terms of measuring ratio of left ventricular (LV) weight to body weight (LVW/BW), LV wall thickness (LVWT), LV protein content and LV collagen content. Further, the collagen accumulation in left ventricle was analyzed using picrosirius red staining. Moreover, the cross-sectional area (CSA) of cardiomyocytes was assessed using hematoxylin and eosin staining and measured using a NIH Scion image analyzer. The PAAC produced cardiac hypertrophy by increasing LVW/BW, LVWT, LV protein content, LV collagen content and mean CSA of cardiomyocytes. However, treatment with fenofibrate and rosiglitazone either alone or in combination significantly attenuated PAAC-induced increase in LVW/BW, LVWT, LV protein content, LV collagen content and mean CSA of cardiomyocytes. The combination of fenofibrate and rosiglitazone was more effective in attenuating the PAAC-induced cardiac hypertrophy than either drug alone. Thus, it may be concluded that dual activation of PPARalpha and PPARgamma may provide synergistic benefits in preventing the development of pathological cardiac hypertrophy.

PPAR Ligands: Are They Potential Agents for Cardiovascular Disorders?

Peroxisome proliferator activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. The PPAR subfamily consists of three members: PPARalpha, PPARgamma, and PPARbeta/delta. Fibrates are acting via PPARalpha, and they are used as lipid-lowering agents. PPARgamma agonists reduce insulin resistance and have been used in the treatment of type 2 diabetes. As the knowledge of the pleiotropic effects of these agents advances, further potential indications are being revealed, including a novel role in the management of cardiovascular disorders (CVD). PPARalpha/gamma dual agonists are currently under development and hold considerable promise in the management of type 2 diabetes and provide an effective therapeutic option for treating the multifactorial components of CVD. Several experimental and clinical evidences elucidated the beneficial effects of PPAR ligands in prevention and treatment of various CVD. However, PPARalpha and PPARgamma agonists have been shown to be proinflammatory and proatherogenic in a few studies. Further, PPARgamma ligands have been noted to be involved in the pathogenesis of congestive heart failure. These controversial results obtained from a few studies created further complication in understanding the role of PPARs. The function of PPARdelta and its potential as a cardiovascular therapeutic target are currently under investigation. The present review focuses on the merits and limitations of PPAR agonists with regard to their use in CVD.

Inflammation in hypertension

PURPOSE OF REVIEW

In this review we summarize the recent evidence that highlights the involvement of low-grade inflammation in the development and pathophysiology of hypertension.

RECENT FINDINGS

Essential hypertension is characterized by increased peripheral vascular resistance to blood flow, due in large part to vascular remodeling. Vascular changes in hypertension are associated with mechanical and humoral factors that modulate signaling events, resulting in abnormal function, media growth, extracellular matrix deposition and inflammation. Recent evidence suggests that inflammation is present in the vasculature in animal models of hypertension. Inflammatory markers, such as C-reactive protein, are associated with vascular lesions in humans, and are predictive of cardiovascular outcome. In animal and human studies, pro-inflammatory components of the renin-angiotensin-aldosterone system have been demonstrated in large conduit and small arteries in the kidney and heart. Peroxisome proliferator-activated receptor activators are drugs with metabolic properties that have been demonstrated to exert anti-inflammatory effects on the vasculature, and there is now evidence that these actions may be protective for blood vessels.

SUMMARY

Inflammatory processes are important participants in the pathophysiology of hypertension and cardiovascular disease. The identification of the mechanisms leading to the activation of inflammation should contribute to the development of specific therapeutic approaches to apply in hypertension and its complications.