The role of nuclear receptor PPARβ in normal and diabetic rat hearts

Cardiovascular diseases are one of the major causes of morbidity and mortality in the modern world. They are characterized by molecular, cellular and pathophysiological changes in the myocardium, a condition known as cardiac remodeling. While short-term cardiac remodeling is an adaptive response that contributes to the maintenance of cardiac function the long term remodeling leads to contractile dysfunction and eventually heart failure while it is also associated with sudden death from arrhythmias. The energy metabolism of the heart and the utilization of various substrates are modified in various pathological conditions, including cardiac hypertrophy, which is associated with an increase in the catabolism of glucose and reduction of the oxidation of fatty acids, while diabetes mellitus is characterized by increased by enhanced fatty acid metabolism and reduced glucose and lactate metabolism. Given that peroxisome proliferator activated receptors (PPARs) are key transcriptional regulators of energy metabolism and lipid homeostasis, the aim of this thesis was to investigate the role of PPARα/δ activation in cardiac hypertrophy, diabetes mellitus and ischaemia.Primary cultures of cardiomyocytes were exposed to the specific PPARα/δ agonist, GW0742, and then they were treated with a1 adrenergic agonist, phenylephrine (PE). GW0742 inhibited PE- induced increase in cell area and expression of ANP and BNP. The inhibitory effect of GW0742 on cell growth and gene expression was abolished in the presence of GSK0660, a PPARα/δ antagonist. Furthermore, gene expression levels of PPARα/δ and the target genes of the receptor involved in the oxidation of fatty acids (mCPT-1, UCP3) and glucose metabolism (PDK4, GLUT4) were determined. PE- induced down- regulation of PPARα/δ and target genes, was reversed in the presence of GW0742. These results show that activation of PPARα/δ probably compensates for the metabolic dysfunction that characterizes cardiac hypertrophy, by adjusting fatty acids oxidation and glucose metabolism.The molecular mechanisms that contribute to the development of cardiac hypertrophy include, among others, kinase signaling pathways, (MAPK, PI3K/Akt), and reactive oxygen species (ROS). GW0742 inhibited PE -induced ROS production modulating signaling and redox mechanisms that are involved in cardiac hypertrophy. The non genomic role of GW0742 was confirmed by using the antagonist GSK0660. Furthermore, a second aim was to evaluate whether the administration of GW0742, improves cardiac dysfunction in diabetes and to explore the underlying molecular mechanisms of cardioprotection. For this purpose we used the experimental model of streptozotocin (65mg/kg) induced diabetes in rats with total duration of six weeks. GW0742 was found to reduce glucose, cholesterol and triglyceride levels in blood plasma, improve impairment of cardiac contractility, decrease the diabetes-induced fibrosis and inhibits hypertrophy. Additionally, in order to assess the changes in myocardial metabolism both in streptozotocin-induced diabetes and after administration of GW0742, we determined gene expression of PPARα/δ and of the target genes involved in glucose metabolism (GLUT4) and fatty acids (MCAD and mCPT-1). The results showed that PPARα/δ, MCAD and mCPT-1 expression increased in the diabetic myocardium and remained elevated in the presence of GW0742 but at lower levels. Furthermore, GW0742 administration in diabetic animals restored the decreased expression levels of GLUT4 in the control group. These results suggest that glucose metabolism could be compensated in these animals. In parallel, we investigated whether autophagy mechanisms are involved in this experimental model of diabetes mellitus and assessed the effect of GW0742 on them. For this purpose, expression levels of autophagy marker proteins LC3II, p62 and Beclin-1 were determined. We showed that autophagy levels were reduced by diabetes, but were restored to basal levels in the presence of GW0742. Finally, it was determined the infarct size and the effect of GW0742 on ischemia-induced ventricular arrhythmias and on physiological pressure parameters (LVDP) in normal and diabetic animals. The results indicate that GW0742 and WY14643 reduce infarct size and arrhythmias in both normal and diabetic model, via activation of transcription factors PPARα/δ and PPARα, respectively. Furthermore, expression of PPARα/δ and target gene GLUT4 was determined. GLUT4 expression levels are reduced after ischemia/ reperfusion (I/R) in both normal and diabetic myocardium, which is reversed in the presence of GW0742. In contrast, administration of WY14643 in normal animals restores expression of GLUT4 after I/ R. These results suggest that PPARα ηαζ PPARα/δ regulate the expression of GLUT4 differently, although the latter is a target gene of both

Nonalcoholic Steatohepatitis (NASH) and Atherosclerosis: Explaining Their Pathophysiology, Association and the Role of Incretin-Based Drugs

Nonalcoholic steatohepatitis (NASH) is the most severe manifestation of nonalcoholic fatty liver disease (NAFLD), a common complication of type 2 diabetes, and may lead to cirrhosis and hepatocellular carcinoma. Oxidative stress and liver cell damage are the major triggers of the severe hepatic inflammation that characterizes NASH, which is highly correlated with atherosclerosis and coronary artery disease. Regarding drug therapy, research on the role of GLP-1 analogues and DPP4 inhibitors, novel classes of antidiabetic drugs, is growing. In this review, we outline the association between NASH and atherosclerosis, the underlying molecular mechanisms, and the effects of incretin-based drugs, especially GLP-1 RAs, for the therapeutic management of these conditions

Is Intrinsic Cardioprotection a Laboratory Phenomenon or a Clinically Relevant Tool to Salvage the Failing Heart?

Cardiovascular diseases, especially ischemic heart disease, as a leading cause of heart failure (HF) and mortality, will not reduce over the coming decades despite the progress in pharmacotherapy, interventional cardiology, and surgery. Although patients surviving acute myocardial infarction live longer, alteration of heart function will later lead to HF. Its rising incidence represents a danger, especially among the elderly, with data showing more unfavorable results among females than among males. Experiments revealed an infarct-sparing effect of ischemic “preconditioning” (IPC) as the most robust form of innate cardioprotection based on the heart’s adaptation to moderate stress, increasing its resistance to severe insults. However, translation to clinical practice is limited by technical requirements and limited time. Novel forms of adaptive interventions, such as “remote” IPC, have already been applied in patients, albeit with different effectiveness. Cardiac ischemic tolerance can also be increased by other noninvasive approaches, such as adaptation to hypoxia- or exercise-induced preconditioning. Although their molecular mechanisms are not yet fully understood, some noninvasive modalities appear to be promising novel strategies for fighting HF through targeting its numerous mechanisms. In this review, we will discuss the molecular mechanisms of heart injury and repair, as well as interventions that have potential to be used in the treatment of patients

Dissecting miRNA–Gene Networks to Map Clinical Utility Roads of Pharmacogenomics-Guided Therapeutic Decisions in Cardiovascular Precision Medicine

MicroRNAs (miRNAs) create systems networks and gene-expression circuits through molecular signaling and cell interactions that contribute to health imbalance and the emergence of cardiovascular disorders (CVDs). Because the clinical phenotypes of CVD patients present a diversity in their pathophysiology and heterogeneity at the molecular level, it is essential to establish genomic signatures to delineate multifactorial correlations, and to unveil the variability seen in therapeutic intervention outcomes. The clinically validated miRNA biomarkers, along with the relevant SNPs identified, have to be suitably implemented in the clinical setting in order to enhance patient stratification capacity, to contribute to a better understanding of the underlying pathophysiological mechanisms, to guide the selection of innovative therapeutic schemes, and to identify innovative drugs and delivery systems. In this article, the miRNA–gene networks and the genomic signatures resulting from the SNPs will be analyzed as a method of highlighting specific gene-signaling circuits as sources of molecular knowledge which is relevant to CVDs. In concordance with this concept, and as a case study, the design of the clinical trial GESS (NCT03150680) is referenced. The latter is presented in a manner to provide a direction for the improvement of the implementation of pharmacogenomics and precision cardiovascular medicine trials

NGIWY-Amide: A Bioinspired Ultrashort Self-Assembled Peptide Gelator for Local Drug Delivery Applications

Fibrillar structures derived from plant or animal origin have long been a source of inspiration for the design of new biomaterials. The Asn-Gly-Ile-Trp-Tyr-NH2 (NGIWY-amide) pentapeptide, isolated from the sea cucumber Apostichopus japonicus, which spontaneously self-assembles in water to form hydrogel, pertains to this category. In this study, we evaluated this ultra-short cosmetic bioinspired peptide as vector for local drug delivery applications. Combining nuclear magnetic resonance, circular dichroism, infrared spectroscopy, X-ray diffraction, and rheological studies, the synthesized pentapeptide formed a stiff hydrogel with a high β-sheet content. Molecular dynamic simulations aligned well with scanning electron and atomic-force microscopy studies, revealing a highly filamentous structure with the fibers adopting a helical-twisted morphology. Model dye localization within the supramolecular hydrogel provided insights on the preferential distribution of hydrophobic and hydrophilic compounds in the hydrogel network. That was further depicted in the diffusion kinetics of drugs differing in their aqueous solubility and molecular weight, namely, doxorubicin hydrochloride, curcumin, and octreotide acetate, highlighting its versatility as a delivery vector of both hydrophobic and hydrophilic compounds of different molecular weight. Along with the observed cytocompatibility of the hydrogel, the NGIWY-amide pentapeptide may offer new approaches for cell growth, drug delivery, and 3D bioprinting tissue-engineering applications