Heart failure research suggests that multiple biomarkers could be combined with relevant clinical information to more accurately quantify individual risk and to guide patient-specific treatment strategies. Therefore, statistical methodology is required to determine multi-marker risk scores that yield improved prognostic performance. Development of a prognostic score that combines biomarkers with clinical variables requires specification of an appropriate statistical model and is most frequently achieved using standard regression methods such as Cox regression. We demonstrate that care is needed in model specification and that maximal use of marker information requires consideration of potential non-linear effects and interactions. The derived multi-marker score can be evaluated using time-dependent ROC methods, or risk reclassification methods adapted for survival outcomes. We compare the performance of alternative model accuracy methods using simulations, both to evaluate power and to quantify the potential loss in accuracy associated with use of a sub-optimal regression model to develop the multi-marker score. We illustrate development and evaluation strategies using data from the Penn Heart Failure Study. Based on our results, we recommend that analysts carefully examine the functional form for component markers and consider plausible forms for effect modification to maximize the prognostic potential of a model-derived multi-marker score.
Cox regression; predictive accuracy; ROC curve; risk reclassification; survival analysis
Prior studies have suggested using a panel of biomarkers that measure diverse biological processes as a prognostic tool in chronic heart failure. Whether this approach improves risk prediction beyond clinical evaluation is unknown.
Methods and Results
In a multi-center cohort of 1513 chronic systolic heart failure patients, we measured a contemporary biomarker panel consisting of: high-sensitivity C-reactive protein (hsCRP), myeloperoxidase (MPO), B-type natriuretic peptide (BNP), soluble fms-like tyrosine kinase receptor-1 (sFlt-1), troponin I (TnI), soluble toll-like receptor-2 (ST2), creatinine, and uric acid. From this panel, we calculated a parsimonious multimarker score and assessed its performance in predicting risk of death, cardiac transplantation, or ventricular assist device (VAD) placement in comparison to an established clinical risk score, the Seattle Heart Failure Model (SHFM). During a median followup of 2.5 years, there were a total of 317 outcomes: 187 patients died; 99 were transplanted; and 31 had a VAD placed. In unadjusted Cox models, patients in the highest tertile of the multimarker score had a 13.7-fold increased risk of adverse outcomes compared to the lowest tertile (95%CI 8.75-21.5). These effects were independent of the SHFM (adjusted HR 6.80,95%CI 4.18-11.1). Addition of the multimarker score to the SHFM led to a significantly improved AUC of 0.803 versus 0.756 (p=0.003) and appropriately reclassified a significant number of patients who experienced the outcome into a higher risk category (NRI 25.2%,95%CI 14.2-36.2%,p<0.001).
In ambulatory chronic heart failure patients, a score derived from multiple biomarkers integrating diverse biologic pathways substantially improves prediction of adverse events beyond current metrics.
biomarkers; chronic heart failure
Recognizing that inhibitors of phosphodiesterase type 5 (PDE5) are increasingly employed in patients with pulmonary hypertension and right ventricular failure, we examined PDE5 expression in the human right ventricle (RV) and its impact on myocardial contractility.
Methods and Results
Tissue extracts from the RV of 20 patients were assayed for PDE5 expression using immunoblot and immunohistochemical (IHC) staining. Tissues were selected from groups of non-failing (NF) organ donors and transplant recipients with end-stage ischemic cardiomyopathy (ICM) or idiopathic dilated cardiomyopathy (DCM). Among DCM patients, subgroups with mild or severe RV dysfunction (RVD) and prior LV assist devices (LVAD) were analyzed separately. Our results showed that PDE5 abundance increased more than four-fold in the RVs of the ICM compared to NF group. In DCM, PDE5 up-regulation was more moderate and varied with the severity of RV dysfunction. IHC confirmed that cardiac myocytes contributed to the up-regulation in the failing hearts. In functional studies, PDE5 inhibition produced little change in developed force (DF) in RV trabeculae from NF hearts, but produced a moderate increase in RV trabeculae from failing hearts.
Our results showed the etiology- and severity-dependent up-regulation of myocyte PDE5 expression in the RV and the impact of this up-regulation on myocardial contractility. These findings suggest that RV PDE5 expression could contribute to the pathogenesis of RV failure and direct myocardial responses to PDE5 inhibition may modulate the indirect responses mediated by RV afterload reduction.
PDE5; cGMP; heart failure; myocardium; contractility
In the setting of acute decompensated heart failure, worsening renal function (WRF) and improved renal function (IRF) have been associated with similar hemodynamic derangements and poor prognosis. Our aim was to further characterize IRF and its associated mortality risk.
Methods and Results
Consecutive patients with a discharge diagnosis of congestive heart failure at the Hospital of the University of Pennsylvania were reviewed. IRF was defined as a ≥20% improvement and WRF as a ≥20% deterioration in glomerular filtration rate. Overall, 903 patients met eligibility criteria, 31.4% experiencing IRF. Baseline venous congestion/right sided cardiac dysfunction was more common (p≤0.04) and volume of diuresis (p=0.003) was greater in patients with IRF. IRF was associated with a greater incidence of pre-admission (OR=4.2, 95% CI 2.6–6.7, p<0.0001) and post-discharge (OR=1.8, 95% CI 1.2–2.7 p=0.006) WRF. IRF was associated with increased mortality (adjusted HR=1.3, 95% CI 1.1–1.7, p=0.011), a finding largely restricted to patients with post-discharge recurrence of renal dysfunction (p interaction=0.038).
IRF is associated with significantly worsened survival and may represent the resolution of venous congestion induced pre-admission WRF. Unlike WRF, the renal dysfunction in IRF patients occurs independent of the confounding effects of acute decongestion and may provide incremental information for the study of cardio-renal interactions.
Cardio-renal syndrome; Worsening renal function; Venous congestion
Using data from four community-based cohorts of African Americans (AA), we tested the association between genome-wide markers (SNPs) and cardiac phenotypes in the Candidate-gene Association REsource (CARe) study.
Methods and Results
Among 6,765 AA, we related age, sex, height and weight-adjusted residuals for nine cardiac phenotypes (assessed by echocardiogram or MRI) to 2.5 million SNPs genotyped using Genome-Wide Affymetrix Human SNP Array 6.0 (Affy6.0) and the remainder imputed. Within cohort genome-wide association analysis was conducted followed by meta-analysis across cohorts using inverse variance weights (genome-wide significance threshold=4.0 ×10−07). Supplementary pathway analysis was performed. We attempted replication in 3 smaller cohorts of African ancestry and tested look-ups in one consortium of European ancestry (EchoGEN). Across the 9 phenotypes, variants in 4 genetic loci reached genome-wide significance: rs4552931 in UBE2V2 (p=1.43 × 10−07) for left ventricular mass (LVM); rs7213314 in WIPI1 (p=1.68 × 10−07) for LV internal diastolic diameter (LVIDD); rs1571099 in PPAPDC1A (p= 2.57 × 10−08) for interventricular septal wall thickness (IVST); and rs9530176 in KLF5 (p=4.02 × 10−07) for ejection fraction (EF). Associated variants were enriched in three signaling pathways involved in cardiac remodeling. None of the 4 loci replicated in cohorts of African ancestry were confirmed in look-ups in EchoGEN.
In the largest GWAS of cardiac structure and function to date in AA, we identified 4 genetic loci related to LVM, IVST, LVIDD and EF that reached genome-wide significance. Replication results suggest that these loci may represent unique to individuals of African ancestry. Additional large-scale studies are warranted for these complex phenotypes.
echocardiography; ethnic; genome-wide association studies; Left atrium genetics; left ventricular mass genetics
Renal neurohormonal activation leading to a reduction in glomerular filtration rate (GFR) has been suggested as a mechanism for renal insufficiency (RI) in the setting of heart failure. We hypothesized that RI occurring in the presence of renal neurohormonal activation may be prognostically more important than RI in the absence of renal neurohormonal activation.
Methods and results
Subjects in the Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness (ESCAPE) trial (n = 429), Beta-Blocker Evaluation of Survival Trial (BEST) (n = 2691), and Studies Of Left Ventricular Dysfunction (SOLVD) trial (n = 6782) limited datasets were studied. The blood urea nitrogen to creatinine ratio (BUN/Creatinine) was employed as a surrogate for renal neurohormonal activation and the primary outcome was the interaction between BUN/Creatinine and RI associated mortality. Baseline RI (GFR < 60 mL/min/1.73 m²) was associated with mortality in all study populations (P < 0.001). In patients with higher BUN/Creatinine, the risk of mortality was consistently greater in patients with RI [adjusted hazard ratio (HR) ESCAPE = 2.8, 95% confidence interval (CI) 1.3–14.3, P = 0.019; BEST = 1.6, 95% CI 1.2–2.2, P = 0.002; SOLVD = 1.6, 95% CI 1.3–2.0, P = 0.001]. However, in patients with lower BUN/Creatinine, the risk of mortality was not elevated in patients with RI (adjusted HR ESCAPE = 0.94, 95% CI 0.35–2.4, P = 0.90, P interaction = 0.005; BEST = 0.97, 95% CI 0.64–1.4, P = 0.90, P interaction = 0.02; SOLVD = 1.0, 95% CI 0.8–1.3, P = 0.71, P interaction = 0.005).
The association between RI and poor survival observed in heart failure populations appears to be contingent not simply on the presence of a reduced GFR, but possibly on the mechanism by which GFR is reduced.
Cardio-renal syndrome; Heart Failure; Chronic kidney disease; Neurohormonal activation; Mortality
Systolic heart failure (HF) is a complex systemic syndrome that can result from a wide variety of clinical conditions and gene mutations. Despite phenotypic similarities, characterized by ventricular dilatation and reduced contractility, the extent of common and divergent gene expression between different forms of HF remains a matter of intense debate.
Methods and Results
Using a meta-analysis of 28 experimental (mouse, rat, dog) and human HF microarray studies, we demonstrate that gene expression changes are characterized by a coordinated and reciprocal regulation of major metabolic and signaling pathways. In response to a wide variety of stressors in animal models of HF, including ischemia, pressure overload, tachypacing, chronic isoproterenol infusion, Chagas disease, and transgenic mouse models, major metabolic pathways are invariably downregulated, while cell signaling pathways are upregulated. In contrast to this uniform transcriptional pattern observed in experimental animal models which recapitulates a fetal gene expression program, human HF microarray studies displayed a greater heterogeneity, with some studies even showing upregulation of metabolic and downregulation of signaling pathways in end-stage human hearts. These discrepant results between animal and human studies are due to a number of factors, prominently cardiac disease and variable exposure to cold cardioplegic solution in non-failing human samples which can downregulate transcripts involved in oxidative phosphorylation (OXPHOS) within the first 6h, thus mimicking gene expression patterns observed in failing samples. Additionally, beta-blockers and ACE-inhibitor use in end-stage human HF was associated with higher levels of myocardial OXPHOS transcripts, thus partially reversing the fetal gene expression pattern. In human failing samples, downregulation of metabolism was associated with hemodynamic markers of disease severity.
Irrespective of the etiology, gene expression in failing myocardium is characterized by downregulation of metabolic transcripts and concomitant upregulation of cell signaling pathways. Gene expression changes along this metabolic-signaling axis in mammalian myocardium are a consistent feature in the heterogeneous transcriptional response observed in phenotypically similar models of HF.
Heart Failure; Fetal Gene Program; Oxidative Phosphorylation
Myocardin is a muscle lineage–restricted transcriptional coactivator that has been shown to transduce extracellular signals to the nucleus required for SMC differentiation. We now report the discovery of a myocardin/BMP10 (where BMP10 indicates bone morphogenetic protein 10) signaling pathway required for cardiac growth, chamber maturation, and embryonic survival. Myocardin-null (Myocd) embryos and embryos harboring a cardiomyocyte-restricted mutation in the Myocd gene exhibited myocardial hypoplasia, defective atrial and ventricular chamber maturation, heart failure, and embryonic lethality. Cardiac hypoplasia was caused by decreased cardiomyocyte proliferation accompanied by a dramatic increase in programmed cell death. Defective chamber maturation and the block in cardiomyocyte proliferation were caused in part by a block in BMP10 signaling. Myocardin transactivated the Bmp10 gene via binding of a serum response factor–myocardin protein complex to a nonconsensus CArG element in the Bmp10 promoter. Expression of p57kip2, a BMP10-regulated cyclin-dependent kinase inhibitor, was induced in Myocd–/– hearts, while BMP10-activated cardiogenic transcription factors, including NKX2.5 and MEF2c, were repressed. Remarkably, when embryonic Myocd–/– hearts were cultured ex vivo in BMP10-conditioned medium, the defects in cardiomyocyte proliferation and p57kip2 expression were rescued. Taken together, these data identify a heretofore undescribed myocardin/BMP10 signaling pathway that regulates cardiomyocyte proliferation and apoptosis in the embryonic heart.
We sought to evaluate placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1) as clinical biomarkers in chronic heart failure (HF).
Vascular remodeling is a crucial compensatory mechanism in chronic HF. The angiogenic ligand PlGF and its target receptor fms-like tyrosine kinase 1 (Flt-1) modulate vascular growth and function, but their relevance in human HF is undefined.
We measured plasma PlGF and sFlt-1 in 1,403 patients from the Penn Heart Failure Study, a multi-center cohort of chronic systolic HF. Subjects were followed for death, cardiac transplantation, or ventricular assist device placement over a median follow-up of 2 years.
sFlt-1 was independently associated with measures of HF severity, including NYHA Class (p<0.01) and BNP (p<0.01). Patients in the 4th quartile of sFlt-1 (>379pg/ml) had a 6.17-fold increased risk of adverse outcomes (p<0.01). This association was robust, even after adjustment for the Seattle Failure Model (HR 2.54, 95%CI 1.76–2.27, p<0.01) and clinical confounders including heart failure etiology (HR 1.67, 95%CI 1.06–2.63, p=0.03). Combined assessment of sFlt-1 and BNP exhibited high predictive accuracy at 1-year (AUC 0.791, 95%CI 0.752–0.831), that was greater than either marker alone (p<0.01 and p=0.03, respectively). In contrast, PlGF was not an independent marker of disease severity or outcomes.
Our findings support a role for sFlt-1 in the biology of human heart failure. With additional study, circulating sFlt-1 may emerge as a clinically useful biomarker to assess the influence of vascular remodeling on clinical outcomes.
heart failure; soluble Flt-1; placental growth factor
The general availability of reliable and affordable genotyping technology has enabled genetic association studies to move beyond small case-control studies to large prospective studies. For prospective studies, genetic information can be integrated into the analysis via haplotypes, with focus on their association with a censored survival outcome. We develop non-iterative, regression-based methods to estimate associations between common haplotypes and a censored survival outcome in large cohort studies. Our non-iterative methods—weighted estimation and weighted haplotype combination—are both based on the Cox regression model, but differ in how the imputed haplotypes are integrated into the model. Our approaches enable haplotype imputation to be performed once as a simple data-processing step, and thus avoid implementation based on sophisticated algorithms that iterate between haplotype imputation and risk estimation. We show that non-iterative weighted estimation and weighted haplotype combination provide valid tests for genetic associations and reliable estimates of moderate associations between common haplotypes and a censored survival outcome, and are straightforward to implement in standard statistical software. We apply the methods to an analysis of HSPB7-CLCNKA haplotypes and risk of adverse outcomes in a prospective cohort study of outpatients with chronic heart failure.
Cox regression; phase ambiguity; prospective study; unphased genotypes
Matrix-metalloproteinase-9 (MMP-9) may serve as a biomarker of ventricular remodeling in selected populations, but few studies have assessed its performance in clinical practice. We tested MMP-9 as a biomarker of remodeling and predictor of outcomes in a systolic heart failure cohort derived from clinical practice, and compared its performance to brain natriuretic peptide (BNP).
Plasma MMP-9 and BNP levels were measured in 395 outpatients with systolic heart failure who participated in the Penn Heart Failure Study. We tested for 1) cross-sectional associations between biomarker levels, left ventricular end-diastolic dimension index (LVEDDI), and ejection fraction (EF), and 2) associations between baseline biomarker levels and risk of subsequent cardiac hospitalization or death over 3 years of follow-up.
MMP-9 had no significant correlation with LVEDDI (rho=0.04, P=NS) or EF (rho=−0.06, P=NS), whereas BNP showed highly significant correlations (LVEDDI: rho= 0.27, P<0.0001; EF: rho=−0.35, P<0.0001). In multivariate linear regression models, MMP-9 again showed no significant associations with LVEDDI (P=0.6) or EF (P=0.14), whereas BNP showed strong independent associations (LVEDDI: P<0.001; EF: P=0.002). Kaplan-Meier analyses showed no difference in hospital-free survival by baseline MMP-9 tertile (P=0.7), whereas higher BNP tertile predicted worse survival (P<0.0001). In multivariate Cox models, baseline MMP-9 level did not predict risk of adverse outcome (hazard ratio for log increase [HR log] 0.98, P = 0.9), whereas BNP was a significant independent predictor (HRlog 1.15, P= 0.02).
Compared to BNP, MMP-9 is a poor clinical biomarker of remodeling and outcome in patients with systolic heart failure derived from clinical practice.
matrix metalloproteinase; biomarker; heart failure; ventricular remodeling; epidemiology
Homeodomain only protein x (Hopx) is an unusual homeodomain protein that has diverse effects on cardiac growth. Manipulation of Hopx function in murine models is associated with cardiac hypertrophy, dilation and fibrosis. In the present study, we examined the expression profile of Hopx in various models of pathologic cardiac hypertrophy and failure. Hopx expression is significantly reduced in neonatal rat cardiac myocytes after α/β adrenergic receptor agonist treatment. Cardiac hypertrophy and failure induced by transaortic constriction in mice causes marked down-regulation of Hopx expression. Interestingly, HOPX expression was significantly reduced in hearts of humans with end stage heart failure when compared to non-failing control hearts, and HOPX levels remains low after LVAD support. Our findings suggest that HOPX/Hopx expression is reduced in multiple examples of human and murine cardiac hypertrophy and failure.
Hopx; hypertrophy; myocyte; heart failure; LVAD
Worsening renal function (WRF) commonly complicates the treatment of acute decompensated heart failure. Despite considerable investigation in this area, it remains unclear to what degree WRF is a reflection of treatment versus patient related factors. We hypothesized that if WRF is significantly influenced by factors intrinsic to the patient than WRF during an index hospitalization should predict WRF during subsequent hospitalization.
Consecutive admissions to the Hospital of the University of Pennsylvania with a discharge diagnosis of congestive heart failure were reviewed. Patients with >1 hospitalization were retained for analysis.
In total 181 hospitalization pairs met the inclusion criteria. Baseline patient characteristics demonstrated significant correlation between hospitalizations (p≤0.002 for all) but minimal association with WRF. In contrast, variables related to the aggressiveness of diuresis were weakly correlated between hospitalizations but significantly associated with WRF (p≤0.024 for all). Consistent with the primary hypothesis, WRF during the index hospitalization was strongly associated with WRF during subsequent hospitalization (OR=2.7, p=0.003). This association was minimally altered after controlling for traditional baseline characteristics (OR=2.5, p=0.006) and in-hospital treatment related parameters (OR=2.8, p=0.005).
A prior history of WRF is strongly associated with subsequent episodes of WRF, independent of in-hospital treatment received. These results suggest that baseline factors intrinsic to the patient’s cardiorenal pathophysiology have substantial influence on the subsequent development of WRF.
Network analysis techniques allow a more accurate reflection of underlying systems biology to be realized than traditional unidimensional molecular biology approaches. Here, using gene coexpression network analysis, we define the gene expression network topology of cardiac hypertrophy and failure and the extent of recapitulation of fetal gene expression programs in failing and hypertrophied adult myocardium.
Methods and Results
We assembled all myocardial transcript data in the Gene Expression Omnibus (n = 1617). Since hierarchical analysis revealed species had primacy over disease clustering, we focused this analysis on the most complete (murine) dataset (n = 478). Using gene coexpression network analysis, we derived functional modules, regulatory mediators and higher order topological relationships between genes and identified 50 gene co-expression modules in developing myocardium that were not present in normal adult tissue. We found that known gene expression markers of myocardial adaptation were members of upregulated modules but not hub genes. We identified ZIC2 as a novel transcription factor associated with coexpression modules common to developing and failing myocardium. Of 50 fetal gene co-expression modules, three (6%) were reproduced in hypertrophied myocardium and seven (14%) were reproduced in failing myocardium. One fetal module was common to both failing and hypertrophied myocardium.
Network modeling allows systems analysis of cardiovascular development and disease. While we did not find evidence for a global coordinated program of fetal gene expression in adult myocardial adaptation, our analysis revealed specific gene expression modules active during both development and disease and specific candidates for their regulation.
fetal; gene expression; heart failure; hypertrophy; myocardium
Pathologic stresses induce heart failure in animal models through activation of multiple cardiac transcription factors (TFs) working cooperatively. However, interactions among TFs in human heart failure are less well understood. Here we use genomic data to examine the evidence that five candidate TF families co-regulate gene expression in human heart failure.
Methods and Results
RNA isolates from failing (n=86) and non-failing (n=16) human hearts were hybridized with Affymetrix HU133A arrays. For each gene on the array, we determined conserved MEF2, NFAT, NKX, GATA, and FOX binding motifs within the −1 kb promoter region using human-murine sequence alignments and the TRANSFAC database. Across 9,076 genes expressed in the heart, TF binding motifs tended to cluster together in nonrandom patterns within promoters of specific genes (P-values ranging from 10−2 to 10−21), suggesting co-regulation. We then modeled differential expression as a function of TF combinations present in promoter regions. Several combinations predicted increased odds of differential expression in the failing heart, with highest odds ratios noted for genes containing both MEF2 and NFAT bindings motifs together in the same promoter (peak OR 3.47, P=0.005).
These findings provide genomic evidence for co-regulation of myocardial gene expression by MEF2 and NFAT in human heart failure. In doing so, they extend the paradigm of combinatorial regulation of gene expression to the human heart and identify new target genes for mechanistic study. More broadly, we demonstrate how integrating diverse sources of genomic data yields novel insights into human cardiovascular disorders.
heart failure; hypertrophy; remodeling; genes; transcription factors
Common forms of heart failure (HF) exhibit familial clustering, but specific genetic risk factors have been challenging to identify. A recent single nucleotide polymorphism (SNP) microarray study implicated a locus within an intron of FRMD4B in Caucasian HF. Here, we used next generation resequencing of pooled DNA and individual Sequenom genotyping to test for associations between FRMD4B SNPs and ischemic and/or non-ischemic cardiomyopathy in two independent populations. Exonic resequencing of Caucasians and African-Americans identified 32 FRMD4B SNPs, thirteen of which had allele frequencies greater than 1%. None of these common FRMD4B SNPs were significantly associated with ischemic, non-ischemic, or all-cause HF in either of the study populations. We individually genotyped the seminal intronic rs6787362 FRMD4B SNP in the primary study population and compared genotypes between HF cases and controls. The rs6787362 variant allele was more frequent in Caucasians with ischemic cardiomyopathy, and carriers (heterozygous or homozygous) of the variant allele had increased risk of HF (OR=1.437, CI=1.085-1.904; P=0.0118). No such association was seen for African-American HF These results confirm an association between the intronic rs6787362 FRMD4B SNP and ischemic cardiomyopathy in a European-derived population, but do not support the proposition that coding FRMD4B variants are susceptibility factors in common HF.
Current therapies for diseases of heart muscle (cardiomyopathy) and aorta (aortopathy) include inhibitors of the renin-angiotensin system, β-adrenergic antagonists, and the statin class of cholesterol-lowering agents. These therapies have limited efficacy, as adverse cardiovascular events continue to occur with some frequency in patients taking these drugs. Although cardiomyopathy and aortopathy can coexist in a number of conditions (for example, Marfan’s syndrome, acromegaly, pregnancy, and aging), pathogenetic molecular links between the two diseases remain poorly understood. We reasoned that identification of common molecular perturbations in these two tissues could point to therapies for both conditions. Here, we show that deficiency of the transcriptional regulator Kruppel-like factor 15 (Klf15) in mice leads to both heart failure and aortic aneurysm formation through a shared molecular mechanism. Klf15 concentrations are markedly reduced in failing human hearts and in human aortic aneurysm tissues. Mice deficient in Klf15 develop heart failure and aortic aneurysms in a p53-dependent and p300 acetyltransferase–dependent fashion. KLF15 activation inhibits p300-mediated acetylation of p53. Conversely, Klf15 deficiency leads to hyperacetylation of p53 in the heart and aorta, a finding that is recapitulated in human tissues. Finally, Klf15-deficient mice are rescued by p53 deletion or p300 inhibition. These findings highlight a molecular perturbation common to the pathobiology of heart failure and aortic aneurysm formation and suggest that manipulation of KLF15 function may be a productive approach to treat these morbid diseases.
Heart failure results from abnormalities in multiple biological processes that contribute to cardiac dysfunction. We tested the hypothesis that inherited variation in genes of known importance to cardiovascular biology would thus contribute to heart failure risk.
Methods and Results
We utilized the ITMAT/Broad/CARe (IBC) cardiovascular SNP-array to screen referral populations of advanced heart failure patients for variants in ~2,000 genes of predicted importance to cardiovascular biology. Our design was a two-stage case-control study. In Stage 1, genotypes in Caucasian heart failure patients (n=1,590; ejection fraction 32±16%) were compared to those in unaffected controls (n=577; ejection fraction 67±8%) recruited from the same referral centers. Associations were tested for independent replication in Stage 2 (n=308 cases, 2,314 controls). Two intronic SNPs showed replicated associations with all-cause heart failure: rs1739843 in HSPB7 (combined P=3.09×10−6) and rs6787362 in FRMD4B (P=6.09×10−6). For both SNPs the minor allele was protective. In subgroup analyses, rs1739843 associated with both ischemic and nonischemic heart failure, whereas rs6787362 associated principally with ischemic heart failure. Linkage disequilibrium surrounding rs1739843 suggested that the causal variant resides in a region containing HSPB7 and a neighboring gene, CLCNKA, whereas the causal variant near rs6787362 is probably within FRMD4B. Allele frequencies for these SNPs were substantially different in African Americans (n=635 cases, 714 controls) and showed no association with heart failure in this population.
Our findings identify regions containing HSPB7 and FRMD4B as novel susceptibility loci for advanced heart failure. More broadly, in an era of genome-wide association studies, we demonstrate how knowledge of candidate genes can be leveraged as a complementary strategy to discern the genetics of complex disorders.
cardiomyopathy; genetics; heart failure
Adipose inflammation plays a central role in obesity-related metabolic and cardiovascular complications. However, few human adipose-secreted proteins are known to mediate these processes. We hypothesized that microarray mRNA profiling of human adipose during evoked inflammation could identify novel adipocytokines.
RESEARCH DESIGN AND METHODS
Healthy human volunteers (n = 14) were treated with intravenous endotoxin (3 ng/kg lipopolysaccharide [LPS]) and underwent subcutaneous adipose biopsies before and after LPS. On Affymetrix U133Plus 2.0 arrays, adipose mRNAs modulated >1.5-fold (with P < 0.00001) were selected. SignalP 3.0 and SecretomeP 2.0 identified genes predicted to encode secreted proteins. Of these, 86 candidates were chosen for validation in adipose from an independent human endotoxemia protocol (N = 7, with 0.6 ng/kg LPS) and for exploration of cellular origin in primary human adipocytes and macrophages in vitro.
Microarray identified 776 adipose genes modulated by LPS; 298 were predicted to be secreted. Of detectable prioritized genes, 82 of 85 (96% [95% CI 90–99]) were upregulated (fold changes >1.0) during the lower-dose (LPS 0.6 ng/kg) validation study and 51 of 85 (59% [49–70]) were induced greater than 1.5-fold. Treatment of primary adipocytes with LPS and macrophage polarization to M1 proinflammatory phenotype increased expression by 1.5-fold for 58 and 73% of detectable genes, respectively.
We demonstrate that evoked inflammation of human adipose in vivo modulated expression of multiple genes likely secreted by adipocytes and monocytes. These included established adipocytokines and chemokines implicated in recruitment and activation of lymphocytes, adhesion molecules, antioxidants, and several novel genes with unknown function. Such candidates may represent biomarkers and therapeutic targets for obesity-related complications.
Neuregulin-1 (NRG-1) is a paracrine factor released by microvascular endothelial cells that has cardioprotective effects in animal models of heart failure. However, circulating NRG-1 has not been studied in human heart disease. We used a novel immunoassay to test whether circulating neuregulin-1β (NRG-1β) is associated with disease severity and clinical outcome in chronic heart failure.
Methods and Results
Serum NRG-1β was quantified in 899 outpatients in the Penn Heart Failure Study, a referral cohort representing a broad spectrum of systolic heart failure. Circulating NRG-1β was significantly elevated in patients with worse disease severity (NYHA Class IV median 6.2 versus 4.4ng/ml for Class I, p=0.002). In adjusted models, NRG-1β was independently associated with an increased risk of death or cardiac transplantation over a median follow-up of 2.4 years (adjusted HR 1.58 [95% CI 1.04–2.39, p=0.03] comparing 4th versus 1st NRG-1β quartile). Associations with outcome differed by heart failure etiology and symptom severity, with the strongest associations observed in patients with ischemic cardiomyopathy (interaction p=0.008) and NYHA Class III/IV symptoms (interaction p=0.01). These findings were all independent of BNP, and assessment of NRG-1β and BNP jointly provided better risk stratification than each biomarker individually in patients with ischemic or NYHA Class III/IV heart failure.
Circulating NRG-1β is independently associated with heart failure severity and risk of death or cardiac transplantation. These findings support a role for NRG-1/ErbB signaling in human heart failure and identify serum NRG-1β as a novel biomarker that may have clinical applications.
Neuregulin; Heart Failure; Cardiomyopathy
To identify genetic modifiers of β-blocker (BB) response and long-term survival in heart failure (HF).
Differences in BB treatment effect between Caucasians and African Americans with HF have been reported.
Prospective cohort study of 2,460 patients (711 African American; 1,749 Caucasian) enrolled between 1999 and 2007. 2039 (81.7%) were treated with BB. Each was genotyped for β1-adrenergic receptor (ADRB1) Arg389>Gly and G-protein receptor kinase 5 (GRK5) Gln41>Leu polymorphisms, which are more prevalent among African Americans than Caucasians. Primary endpoint was survival time from HF onset.
There were 765 deaths during follow up (median 46 months). BB treatment increased survival in Caucasians (Log Rank P=0.00038) but not African Americans (Log Rank P=0.327). Among patients not taking BB, ADRB1 Gly389 was associated with decreased survival in Caucasians (HR = 1.98, 95% CI = 1.1 − 3.7, P = 0.03) while GRK5 Leu41 was associated with improved survival in African Americans (HR = 0.325, CI = 0.133 − 0.796, P = 0.01). ADRB1 Gly389 GRK5 Gln41Gln African Americans derived similar survival benefit from BB therapy (HR = 0.385 95% CI = 0.182 − 0.813, P = 0.012) as ADRB1 Gly389 GRK5 Gln41Gln Caucasians (HR = 0.529, 95% CI = 0.326 − 0.858, P=0.0098).
These data demonstrate that differences caused by β-adrenergic receptor signaling pathway gene polymorphisms, rather than race, are the major factors contributing to apparent differences in BB treatment effect between Caucasians and African Americans; proper evaluation of treatment response should account for genetic variance.
SERCA2a deficiency is commonly seen in advanced heart failure (HF). This study is designed to investigate safety and biological effects of enzyme replacement using gene transfer in patients with advanced HF.
Methods and Results
A total of 9 patients with advanced HF (New York Heart Association [NYHA] Class III/IV, ejection fraction [EF] ≤30%, maximal oxygen uptake [VO2 max] <16 mL·kg·min, with maximal pharmacological and device therapy) received a single intracoronary infusion of AAV1/SER-CA2a in the open-label portion of this ongoing study. Doses administered ranged from 1.4 × 1011 to 3 × 1012 DNase resistant particles per patient. We present 6- to 12-month follow-up data for these patients. AAV1/SERCA2a demonstrated an acceptable safety profile in this advanced HF population. Of the 9 patients treated, several demonstrated improvements from baseline to month 6 across a number of parameters important in HF, including symptomatic (NYHA and Minnesota Living with Heart Failure Questionnaire, 5 patients), functional (6-minute walk test and VO2 max, 4 patients), biomarker (NT-ProBNP, 2 patients), and LV function/remodeling (EF and end-systolic volume, 5 patients). Of note, 2 patients who failed to improve had preexisting anti-AAV1 neutralizing antibodies.
Quantitative evidence of biological activity across a number of parameters important for assessing HF status could be detected in several patients without preexisting neutralizing antibodies in this open-label study, although the number of patients in each cohort is too small to conduct statistical analyses. These findings support the initiation of the Phase 2 double-blind, placebo-controlled portion of this study.
Gene therapy; heart failure; SERCA2a; cardiovascular disease
By studying genome-wide expression patterns in healthy and diseased tissues across a wide range of pathophysiological conditions, DNA microarrays have revealed unique insights into complex diseases. However, the high-dimensionality of microarray data makes interpretation of heterogeneous gene expression studies inherently difficult.
Using a large-scale analysis of more than 40 microarray studies encompassing ~2400 mammalian tissue samples, we identified a common theme across heterogeneous microarray studies evident by a robust genome-wide inverse regulation of metabolic and cell signaling pathways: We found that upregulation of cell signaling pathways was invariably accompanied by downregulation of cell metabolic transcriptional activity (and vice versa). Several findings suggest that this characteristic gene expression pattern represents a new principle of mammalian transcriptional regulation. First, this coordinated transcriptional pattern occurred in a wide variety of physiological and pathophysiological conditions and was identified across all 20 human and animal tissue types examined. Second, the differences in metabolic gene expression predicted the magnitude of differences for signaling and all other pathways, i.e. tissue samples with similar expression levels of metabolic transcripts did not show any differences in gene expression for all other pathways. Third, this transcriptional pattern predicted a profound effect on the proteome, evident by differences in structure, stability and post-translational modifications of proteins belonging to signaling and metabolic pathways, respectively.
Our data suggest that in a wide range of physiological and pathophysiological conditions, gene expression changes exhibit a recurring pattern along a transcriptional axis, characterized by an inverse regulation of major metabolic and cell signaling pathways. Given its widespread occurrence and its predicted effects on protein structure, protein stability and post-translational modifications, we propose a new principle for transcriptional regulation in mammalian biology.