Metabolic and functional effects of purines in the heart

This thesis discusses metabolism and functional effects of purine nucleosides and oxypurines in the heart. The study is mainly limited to the nucleosides adenosine and inosine and the oxypurines: hypoxanthine, xanthine and urate, all adenine-nucleotide catabolites. It is confined to effects in mammals, especially rats, pigs, and humans. Within certain disciplines, various aspects of the purines have been explored extensively. Neuropharmacologists have researched the adenosine receptors. Purine analogues have been synthesized for the treatment of neoplasms and virus infections. The erythrocyte membrane has been used to evaluate the transport across membranes. The study of some metabolic diseases and renal calculus formation provided knowledge of normal purine metabolism. There are several reasons why an important part of this thesis is devoted to adenosine. The knowledge of adenosine-induced effects is the most detailed. Adenosine has stronger effects than, for example, inosine. There are indications for the involvement of adenosine in the effects of other nucleosides. Purines are important in cardiac research. Ischemia rapidly elevates purine concentrations. This elevation may serve as a diagnostic tool for the quantification of ischemia. The difference in enzyme activities between various species causes concentration differences. Both endogenous and exogenous nucleosides affect hemodynamics and metabolism. Several drugs modify purine metabolism or purine induced effects. Purinergic receptors mediate effects of the nucleosides. The effects in vivo and in isolated organs are different, as nucleosides have both direct effects on cardiac cells, and indirect through the autonomic system. The objective of this thesis is the evaluation of purine function and metabolism in the heart, in the hope that this knowledge is useful for extended basic research and for the treatment of the cardiological patient. Transport and metabolism are discussed to demonstrate what concentrations may be expected and which conditions alter purine levels. The functional effects of the nucleosides in the heart are shown and their modification by the autonomic system. Finally, effects in pathological hearts, interaction with drugs, and some clinical applications are presente

Towards a Better Understanding of Genotype-Phenotype Correlations and Therapeutic Targets for Cardiocutaneous Genes:The Importance of Functional Studies above Prediction

Genetic variants in gene-encoding proteins involved in cell-cell connecting structures, such as desmosomes and gap junctions, may cause a skin and/or cardiac phenotype, of which the combination is called cardiocutaneous syndrome. The cardiac phenotype is characterized by cardiomyopathy and/or arrhythmias, while the skin particularly displays phenotypes such as keratoderma, hair abnormalities and skin fragility. The reported variants associated with cardiocutaneous syndrome, in genes DSP, JUP, DSC2, KLHL24, GJA1, are classified by interpretation guidelines from the American College of Medical Genetics and Genomics. The genotype-phenotype correlation, however, remains poorly understood. By providing an overview of variants that are assessed for a functional protein pathology, we show that this number (n = 115) is low compared to the number of variants that are assessed by in silico algorithms (>5000). As expected, there is a mismatch between the prediction of variant pathogenicity and the prediction of the functional effect compared to the real functional evidence. Aiding to improve genotype-phenotype correlations, we separate variants into 'protein reducing' or 'altered protein' variants and provide general conclusions about the skin and heart phenotype involved. We conclude by stipulating that adequate prognoses can only be given, and targeted therapies can only be designed, upon full knowledge of the protein pathology through functional investigation

Cardiac Transthyretin-derived Amyloidosis:An Emerging Target in Heart Failure with Preserved Ejection Fraction?

Heart failure with preserved ejection fraction (HFpEF) comprises half of the heart failure population. A specific, but underdiagnosed, cause for HFpEF is transthyretin-derived (ATTR) amyloidosis. This article reviews the clinical characteristics of cardiac ATTR amyloidosis. The clinical suspicion of cardiac ATTR amyloidosis is strong if pronounced left ventricular hypertrophy is present in the absence of hypertension. Scintigraphy with a diphosphonate tracer is a diagnostic tool for the early detection of cardiac ATTR amyloidosis with high sensitivity and specificity. First treatment options for ATTR amyloidosis recently emerged, and showed a reduction in morbidity and mortality, especially if treatment was started in the early stages of disease. In light of these results, screening for ATTR amyloidosis in the general HFpEF population with left ventricular hypertrophy might be useful

Frequency of and Prognostic Significance of Cardiac Involvement at Presentation in Hereditary Transthyretin-Derived Amyloidosis and the Value of N-Terminal Pro-B-Type Natriuretic Peptide

The aim of this study is to assess the prevalence of cardiac involvement in hereditary transthyretin-derived (ATTRm) amyloidosis at the time of diagnosis and to determine the diagnostic and clinical value of N-terminal pro-B-type natriuretic peptide (NT-proBNP). The University Medical Center Groningen is the national center of expertise for amyloidosis. All consecutive patients between 1994 and 2016 with ATTRm amyloidosis were followed prospectively. Baseline was set at the time of the first positive biopsy. All patients underwent a standard cardiac and neurologic work-up. Cardiac involvement was defined by otherwise unexplained left and/or right ventricular wall hypertrophy on cardiac ultrasound and/or advanced conduction disturbances. Seventy-seven patients had ATTRm amyloidosis and were included in the study. The TTR V30M mutation was present in 30 patients (39%). In both the V30M and the non-V30M groups, the neurologic presentation dominated (77% vs 51%), whereas cardiac presentation was infrequent (7% vs 15%). Clinical work-up showed that cardiac involvement was present at baseline in 51% of all patients irrespective of genotype and was associated with increased overall mortality (hazard ratio 5.95, 95% confidence interval 2.12 to 16.7), independent from clinical confounders. At a cutoff level of 125 ng/L, NT-proBNP had a sensitivity of 92% for establishing cardiac involvement. In conclusion, irrespective of the frequent noncardiac presentation of ATTRm amyloidosis, cardiac involvement is already present at diagnosis in half of the patients and is associated with increased mortality. NT-proBNP is a useful marker to determine cardiac involvement in this disease

Functional Differences in Engineered Myocardium from Embryonic Stem Cell-Derived versus Neonatal Cardiomyocytes

Stem cell-derived cardiomyocytes represent unique tools for cell- and tissue-based regenerative therapies, drug discovery and safety, and studies of fundamental heart-failure mechanisms. However, the degree to which stem cell-derived cardiomyocytes compare to mature cardiomyocytes is often debated. We reasoned that physiological metrics of engineered cardiac tissues offer a means of comparison. We built laminar myocardium engineered from cardiomyocytes that were differentiated from mouse embryonic stem cell-derived cardiac progenitors or harvested directly from neonatal mouse ventricles, and compared their anatomy and physiology in vitro. Tissues assembled from progenitor-derived myocytes and neonate myocytes demonstrated similar cytoskeletal architectures but different gap junction organization and electromechanical properties. Progenitor-derived myocardium had significantly less contractile stress and slower longitudinal conduction velocity than neonate-derived myocardium, indicating that the developmental state of the cardiomyocytes affects the electromechanical function of the resultant engineered tissue. These data suggest a need to establish performance metrics for future stem cell applications

Peripartum Cardiomyopathy: Euro Observational Research Program

Peripartum cardiomyopathy is a rare but potentially life-threatening form of heart failure affecting women late in pregnancy or in the first months after delivery. Peripartum cardiomyopathy is difficult to diagnose and its onset and progression are variable between individuals. The pathophysiology remains poorly understood, hence treatment options are limited and possibly harmful to the foetus. Furthermore, geographical incidence varies greatly and little is known about the incidence in Western countries. To gain further understanding of the pathophysiology and incidence of peripartum cardiomyopathy, the European Society of Cardiology initiated a study group to implement a registry. This review provides an overview of current insights into peripartum cardiomyopathy, highlights the need for such a registry and provides information about this Euro Observational Research Program

Genetic Risk and Atrial Fibrillation in Patients with Heart Failure

Aims: To study the association between an atrial fibrillation (AF) genetic risk score with prevalent AF and all-cause mortality in patients with heart failure. Methods and results: An AF genetic risk score was calculated in 3759 European ancestry individuals (1783 with sinus rhythm, 1976 with AF) from the BIOlogy Study to TAilored Treatment in Chronic Heart Failure (BIOSTAT-CHF) by summing 97 single nucleotide polymorphism (SNP) alleles (ranging from 0–2) weighted by the natural logarithm of the relative SNP risk from the latest AF genome-wide association study. Further, we assessed AF risk variance explained by additive SNP variation, and performance of clinical or genetic risk factors, and the combination in classifying AF prevalence. AF was classified as AF or atrial flutter (AFL) at baseline electrocardiogram and/or a history of AF or AFL. The genetic risk score was associated with AF after multivariable adjustment. Odds ratio for AF prevalence per 1-unit increase genetic risk score was 2.12 (95% confidence interval 1.84–2.45, P = 2.15 × 10−24) in the total cohort, 2.08 (1.72–2.50, P = 1.30 × 10−14) in heart failure with reduced ejection fraction (HFrEF) and 2.02 (1.37–2.99, P = 4.37 × 10−4) in heart failure with preserved ejection fraction (HFpEF). AF-associated loci explained 22.9% of overall AF SNP heritability. Addition of the genetic risk score to clinical risk factors increased the C-index by 2.2% to 0.721. Conclusions: The AF genetic risk score was associated with increased AF prevalence in HFrEF and HFpEF. Genetic variation accounted for 22.9% of overall AF SNP heritability. Addition of genetic risk to clinical risk improved model performance in classifying AF prevalence

The phospholamban p.(Arg14del) pathogenic variant leads to cardiomyopathy with heart failure and is unreponsive to standard heart failure therapy

Phospholamban (PLN) plays a role in cardiomyocyte calcium handling as primary inhibitor of sarco/endoplasmic reticulum Ca2+-ATPase (SERCA). The p.(Arg14del) pathogenic variant in the PLN gene results in a high risk of developing dilated or arrhythmogenic cardiomyopathy with heart failure. There is no established treatment other than standard heart failure therapy or heart transplantation. In this study, we generated a novel mouse model with the PLN-R14del pathogenic variant, performed detailed phenotyping, and tested the efficacy of established heart failure therapies eplerenone or metoprolol. Heterozygous PLN-R14del mice demonstrated increased susceptibility to ex vivo induced arrhythmias, and cardiomyopathy at 18 months of age, which was not accelerated by isoproterenol infusion. Homozygous PLN-R14del mice exhibited an accelerated phenotype including cardiac dilatation, contractile dysfunction, decreased ECG potentials, high susceptibility to ex vivo induced arrhythmias, myocardial fibrosis, PLN protein aggregation, and early mortality. Neither eplerenone nor metoprolol administration improved cardiac function or survival. In conclusion, our novel PLN-R14del mouse model exhibits most features of human disease. Administration of standard heart failure therapy did not rescue the phenotype, underscoring the need for better understanding of the pathophysiology of PLN-R14del-associated cardiomyopathy. This model provides a great opportunity to study the pathophysiology, and to screen for potential therapeutic treatments

Author Correction:The phospholamban p.(Arg14del) pathogenic variant leads to cardiomyopathy with heart failure and is unresponsive to standard heart failure therapy (Scientific Reports, (2020), 10, 1, (9819), 10.1038/s41598-020-66656-9)

The title in the original version of this Article contained a typographical error of ‘unresponsive’. The error has now been corrected in the PDF and HTML versions of the Article

A Systematic Review and Network Meta-Analysis of Pharmacological Treatment of Heart Failure With Reduced Ejection Fraction

Objectives: This study sought to estimate and compare the aggregate treatment benefit of pharmacological therapy for heart failure (HF) with reduced ejection fraction. Background: The estimated treatment effects of various combinations of contemporary HF medical therapies are not well characterized. Methods: We performed a systematic network meta-analysis, using MEDLINE/EMBASE and the Cochrane Central Register of Controlled Trials for randomized controlled trials published between January 1987 and January 2020. We included angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers (BB), mineralocorticoid receptor antagonists (MRAs), digoxin, hydralazine-isosorbide dinitrate, ivabradine, angiotensin receptor–neprilysin inhibitors (ARNi), sodium glucose cotransporter-2 inhibitors (SGLT2i), vericiguat, and omecamtiv-mecarbil. The primary outcome was all-cause death. We estimated the life-years gained in 2 HF populations (BIOSTAT-CHF [BIOlogy Study to TAilored Treatment in Chronic Heart Failure] and ASIAN-HF [Asian Sudden Cardiac Death in Heart Failure Registry]). Results: We identified 75 relevant trials representing 95,444 participants. A combination of ARNi, BB, MRA, and SGLT2i was most effective in reducing all-cause death (HR: 0.39; 95% CI: 0.31-0.49); followed by ARNi, BB, MRA, and vericiguat (HR: 0.41; 95% CI: 0.32-0.53); and ARNi, BB, and MRA (HR: 0.44; 95% CI: 0.36-0.54). Results were similar for the composite outcome of cardiovascular death or first hospitalization for HF (HR: 0.36; 95% CI: 0.29-0.46 for ARNi, BB, MRA, and SGLT2i; HR: 0.44; 95% CI: 0.35-0.56 for ARNi, BB, MRA, and omecamtiv-mecarbil; and HR: 0.43; 95% CI: 0.34-0.55 for ARNi, BB, MRA, and vericiguat). The estimated additional number of life-years gained for a 70-year-old patient on ARNi, BB, MRA, and SGLT2i was 5.0 years (2.5-7.5 years) compared with no treatment in secondary analyses. Conclusions: In patients with HF with reduced ejection fraction, the estimated aggregate benefit is greatest for a combination of ARNi, BB, MRA, and SGLT2i