Genome-wide association analysis of plasma B-type natriuretic peptide in blacks: the Jackson Heart Study

Racial and ethnic differences in circulating N-terminal pro-brain-type natriuretic peptide (NT-proBNP) in US adults

BACKGROUND

The presence and interpretation of racial and ethnic differences in circulating N-terminal pro-brain-type natriuretic peptide (NT-proBNP), a diagnostic biomarker for heart failure, are controversial.

OBJECTIVE

To examine racial and ethnic differences in NT-proBNP levels among the general US adult population.

METHODS

We performed a cross-sectional analysis of data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES). We included 4717 non-Hispanic White, 1675 non-Hispanic Black, and 2148 Mexican American adults aged 20 years or older without a history of cardiovascular disease. We examined the associations of race and ethnicity with NT-proBNP using linear and logistic regression models in the overall population and in a younger, 'healthy' subsample.

RESULTS

The mean age was 45 years. Median NT-proBNP levels were significantly lower among Black (29.3 pg/mL) and Mexican American adults (28.3.4 pg/mL) compared to White adults (49.1pg/mL, P-values<0.001). After adjusting for sociodemographic factors and cardiovascular risk factors, NT-proBNP was 34.4% lower (95%CI -39.2 to -29.3%) in Black adults and 22.8% lower (95%CI -29.4 to -15.5) in Mexican American adults compared to White adults. Our findings were consistent in a young, healthy subsample, suggesting non-cardiometabolic determinants of these differences.

CONCLUSIONS

NT-proBNP levels are significantly lower among Black and Mexican American adults compared with White adults, independent of cardiometabolic risk. Although race/ethnicity is a poor proxy for genetic differences, our findings may have clinical implications for the management of HF. However, studies in diverse populations are needed to characterize the biological basis of NT-proBNP variation.

Impact of Diabetes and Hypertension on Left Ventricular Structure and Function: The Jackson Heart Study

Background Diabetes and hypertension have been associated with adverse left ventricular (LV) remodeling. While they often occur concurrently, their individual effects are understudied. We aimed to assess the independent effects of diabetes and hypertension on LV remodeling in Black adults. Methods and Results The JHS (Jackson Heart Study) participants (n=4143 Black adults) with echocardiographic measures from baseline exam were stratified into 4 groups: neither diabetes nor hypertension (n=1643), only diabetes (n=152), only hypertension (n=1669), or both diabetes and hypertension (n=679). Echocardiographic measures of LV structure and function among these groups were evaluated by multivariable regression adjusting for covariates. Mean age of the participants was 52±1 years, and 63.7% were women. LV mass index was not different in participants with only diabetes compared with participants with neither diabetes nor hypertension (P=0.8). LV mass index was 7.9% (6.0 g/m2) higher in participants with only hypertension and 10.8% (8.1 g/m2) higher in participants with both diabetes and hypertension compared with those with neither (P<0.001). LV wall thickness (relative, posterior, and septal) and brain natriuretic peptide levels in participants with only diabetes were not significantly higher than participants with neither (P>0.05). However, participants with both diabetes and hypertension demonstrated higher LV wall thickness and brain natriuretic peptide levels than participants with neither (P<0.05). Conclusions In this cross-sectional analysis, diabetes was not associated with altered LV structure or function in Black adults unless participants also had hypertension. Our findings suggest hypertension is the main contributor to cardiac structural and functional changes in Black adults with diabetes.

Utility of Combining High-Sensitive Cardiac Troponin I and PESI Score for Risk Management in Patients with Pulmonary Embolism in the Emergency Department

BACKGROUND AND OBJECTIVES

Pulmonary embolism (PE) has a major burden of morbidity and mortality, consequently the need for a prompt risk stratification for these subjects is crucial. In order to evaluate the risk management and final disposition of patients with PE in the Emergency Department (ED), we conducted a study that was divided in two phases: Phase I retrospective study (RS), Phase II prospective study (PS).

MATERIALS AND METHODS

In Phase I, 291 patients were enrolled while in Phase II, 83 subjects were evaluated. In both study phases, the enrolled subjects were analyzed for final disposition in ED using PESI score, right ventricle (RV) imaging, and high-sensitive cardiac troponin I (hs-cTnI) data. The RS patients were divided into low risk and high risk according to the sPESI score, while PS patients were grouped in low, intermediate, and high risk classes according to PESI score. In both study phases, all the studied patients were further divided into negative (hs-cTnI-) or positive (hs-cTnI+) groups according to hs-cTnI levels within normal or above cutoff values, respectively. For all enrolled subjects, CT pulmonary angiography was analyzed to assess the RV/LV diameter and volume ratio as an indicator of RV involvement.

RESULTS

In both RS and PS phases, hs-cTnI+ group showed a higher PESI score. Nevertheless, a significant percentage of hs-cTnI+ patients resulted to be in the low-risk PESI class. Patients with a positive RV/LV ratio were more likely to have a hs-cTnI+ (p < 0.01), while among those with a negative ratio, 24 to 32% showed as hs-cTnI+. In the hs-cTnI+ group from both study phases, patients were more likely to be admitted in an ICU (RR 3.7, IC: 2.1-6.5).

CONCLUSIONS

In conclusion, in patients with PE in the ED compared PESI score alone, the combination of hs-cTnI and PESI seems to be of greater utility in improving risk stratification and final disposition decision-making.

Corin Missense Variants, Blood Pressure, and Hypertension in 11 322 Black Individuals: Insights From REGARDS and the Jackson Heart Study

Background Corin enzyme contributes to the processing of inactive natriuretic peptides to bioactive hormones. In Black individuals, Corin gene variants (rs111253292 [Q568P] and rs75770792 [T555I]) have been previously reported to have a modest association with blood pressure (BP) and hypertension. Methods and Results We evaluated the association of Corin genotype with BP traits, prevalent hypertension, and incident hypertension among self-identified 11 322 Black Americans in the REGARDS (Reasons for Geographic and Racial Differences in Stroke) study and the JHS (Jackson Heart Study) using multivariable-adjusted regression modeling. Multivariable-adjusted genotype-stratified differences in NT-proBNP (N-terminal pro-B-type natriuretic peptide) and BNP (B-type natriuretic peptide) levels were assessed. Genotype-stratified NPPA and NPPB expression differences in healthy organ donor left atrial and left ventricular heart tissue (N=15) were also examined. The rs111253292 genotype was not associated with systolic BP (β±SE, 0.42±0.58; -1.24±0.82), diastolic BP (0.51±0.33; -0.41±0.46), mean arterial pressure (0.48±0.38; -0.68±0.51), and prevalent hypertension (odds ratio [OR], 0.93 [95% CI, 0.80-1.09]; OR, 0.79 [95% CI, 0.61-1.01]) in both REGARDS and JHS, respectively. The rs75770792 genotype was not associated with systolic BP (0.48±0.58; -1.26±0.81), diastolic BP (0.52±0.33; -0.33±0.45), mean arterial pressure (0.50±0.38; -0.63±0.50), and prevalent hypertension (OR, 1.02 [95% CI, 0.84-1.23]; OR, 0.87 [95% CI, 0.67-1.13]) in both cohorts, respectively. The Corin genotype was also not associated with incident hypertension (OR, 1.35 [95% CI, 0.94-1.93]; OR, 0.95 [95% CI, 0.64-1.39]) in the study cohorts. The NT-proBNP levels in REGARDS and BNP levels in JHS were similar between the Corin genotype groups. In heart tissue, the NPPA and NPPB expression was similar between the genotype groups. Conclusions Corin gene variants observed more commonly in Black individuals are not associated with differences in NP expression, circulating NP levels, and BP or hypertension as previously reported in candidate gene studies. Understanding the genetic determinants of complex cardiovascular traits in underrepresented populations requires further evaluation.

Genetics of osteopontin in patients with chronic kidney disease: The German Chronic Kidney Disease study

Osteopontin (OPN), encoded by SPP1, is a phosphorylated glycoprotein predominantly synthesized in kidney tissue. Increased OPN mRNA and protein expression correlates with proteinuria, reduced creatinine clearance, and kidney fibrosis in animal models of kidney disease. But its genetic underpinnings are incompletely understood. We therefore conducted a genome-wide association study (GWAS) of OPN in a European chronic kidney disease (CKD) population. Using data from participants of the German Chronic Kidney Disease (GCKD) study (N = 4,897), a GWAS (minor allele frequency [MAF]≥1%) and aggregated variant testing (AVT, MAF<1%) of ELISA-quantified serum OPN, adjusted for age, sex, estimated glomerular filtration rate (eGFR), and urinary albumin-to-creatinine ratio (UACR) was conducted. In the project, GCKD participants had a mean age of 60 years (SD 12), median eGFR of 46 mL/min/1.73m2 (p25: 37, p75: 57) and median UACR of 50 mg/g (p25: 9, p75: 383). GWAS revealed 3 loci (p<5.0E-08), two of which replicated in the population-based Young Finns Study (YFS) cohort (p<1.67E-03): rs10011284, upstream of SPP1 encoding the OPN protein and related to OPN production, and rs4253311, mapping into KLKB1 encoding prekallikrein (PK), which is processed to kallikrein (KAL) implicated through the kinin-kallikrein system (KKS) in blood pressure control, inflammation, blood coagulation, cancer, and cardiovascular disease. The SPP1 gene was also identified by AVT (p = 2.5E-8), comprising 7 splice-site and missense variants. Among others, downstream analyses revealed colocalization of the OPN association signal at SPP1 with expression in pancreas tissue, and at KLKB1 with various plasma proteins in trans, and with phenotypes (bone disorder, deep venous thrombosis) in human tissue. In summary, this GWAS of OPN levels revealed two replicated associations. The KLKB1 locus connects the function of OPN with PK, suggestive of possible further post-translation processing of OPN. Further studies are needed to elucidate the complex role of OPN within human (patho)physiology.

Impact of natriuretic peptide polymorphisms on diastolic and metabolic function in a populational cohort: insights from the STANISLAS cohort

AIMS

Elevated brain natriuretic peptide (BNP) and the N-terminal fragment of its pro-hormone (NT-proBNP) have become established biomarkers for heart failure and are associated with cardiovascular morbidity and mortality. Investigating sources of inter-individual heterogeneity, particularly genetic factors, could help better identify patients at risk of future cardiovascular disease. The aim of this study was to estimate the heritability of circulating NT-proBNP levels, to perform a genome-wide association study (GWAS) and gene-candidate analysis focused on NPPB-NPPA genes on these levels, and to examine their association with cardiovascular or metabolic outcomes.

METHODS AND RESULTS

A total of 1555 individuals from the STANISLAS study were included. The heritability of circulating NT-proBNP levels was estimated at 15%, with seven single nucleotide polymorphisms (SNPs) reaching the significant threshold in the GWAS. All above SNPs were located on the same gene cluster constituted of MTHFR, CLCN6, NPPA, NPPB, and C1orf167. NPPA gene expression was also associated with NT-proBNP levels. Moreover, six other SNPs from NPPA-NPPB genes were associated with diastolic function (lateral e' on echocardiography) and metabolic features (glycated haemoglobin).

CONCLUSIONS

The heritability of natriuretic peptides appears relatively low (15%) and mainly based on the same gene cluster constituted of MTHFR, CLCN6, NPPA, NPPB, and C1orf167. Natriuretic peptide polymorphisms are associated with natriuretic peptide levels and diastolic function. These results suggest that natriuretic peptide polymorphisms may have an impact in the early stages of cardiovascular and metabolic disease.

STOP-HF Trial: Higher Endogenous BNP and Cardiovascular Protection in Subjects at Risk for Heart Failure

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Among subjects at risk for heart failure (Stage A and B), the minor C allele of the B-type natriuretic peptide (BNP) genetic variant rs198389 is associated with higher circulating levels of BNP.

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Rs198389 C allele is also associated with lower risk of hypertension, new onset of left ventricular systolic dysfunction, and major adverse cardiovascular events.

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These data support the role of BNP genetic testing and BNP-based therapy for the prevention of heart failure.

B-type natriuretic peptide (BNP) possesses blood-pressure–lowering, antifibrotic, and aldosterone-suppressing properties. In Stage A and B heart failure, the carriers of the minor C allele of the BNP genetic variant rs198389 have higher circulating levels of BNP and are at decreased risk of hypertension, new-onset left ventricular systolic dysfunction, and hospitalization for major adverse cardiovascular events. Future studies are warranted to investigate the role of BNP genetic testing and BNP-based therapy in the prevention of heart failure.

Race and genetics versus 'race' in genetics: A systematic review of the use of African ancestry in genetic studies

Social scientists have long understood race to be a social category invented to justify slavery and evolutionary biologists know the socially constructed racial categories do not align with our biological understanding of genetic variation. The completion of the Human Genome Project in 2003 confirmed humans are 99.9% identical at the DNA level and there is no genetic basis for race. A systematic review of the PubMed medical literature published since 2003 was conducted to assess the use of African ancestry to denote study populations in genetic studies categorized as clinical trials, to examine the stated rationale for its use and to assess the use of evolutionary principles to explain human genetic diversity. We searched for papers that included the terms 'African', 'African American' or 'Black' in studies of behavior (20 papers), physiological responses, the pharmacokinetics of drugs and/or disease associations (62 papers), and as a genetic category in studies, including the examination of genotypes associated with life stress, pain, stuttering and drug clearance (126 papers). Of these, we identified 74 studies in which self-reported race alone or in combination with admixture mapping was used to define the study population. However, none of these studies provided a genetic explanation for the use of the self-identified race as a genetic category and only seven proffered evolutionary explanations of their data. The concept of continuous genetic variation was not clearly articulated in any of these papers, presumably due to the paucity of evolutionary science in the college and medical school curricula.

Association between MTNR1B polymorphisms and obesity in African American: findings from the Jackson Heart Study

BACKGROUND

Melatonin is a hormone that is secreted at night by the pineal gland. It exerts its function by binding to the MT1 and MT2 receptors, which are encoded by the MTNR1A and MTNR1B genes, respectively. Previous studies reveal that MTNR1B variants are associated with insulin secretion impairments and an increased body mass index (BMI) in individuals of European and Asian ancestries. Obesity is highly prevalent in the US and disproportionately affects African Americans. Here, we hypothesized that common single nucleotide polymorphisms (SNPs) imputed in 1000 Genomes in the MTNR1B gene are associated with adiposity in African American adult men and women and that the association is modified by insomnia.

METHODS

We used an additive genetic model to describe the association between the adiposity traits (BMI and waist circumference) and selected MTNR1B variants in 3,029 Jackson Heart Study participants, with an average age of 55.13 ± 12.84 years, and 62% were women. We regressed the adiposity measures on the estimated allelic or genotypic dosage at every selected SNP and adjusted for age, sex, population stratification, and insomnia. Thirty common SNPs, spanning the MTNR1B gene, with a minor allele frequency ≥ 5%, a call rate ≥ 90%, a Hardy-Weinberg equilibrium p value > 10-6, were available for the analysis.

RESULTS

The allele T of rs76371840 was associated with adiposity (OR = 1.47 [1.13-1.82]; PFDR-adjusted = 0.0499), and the allele A of rs8192552 showed a significant association with waist circumference (β = 0.023 ± 0.007; PFDR-adjusted = 0.0077) after correcting for multiple testing. When insomnia was included in the adiposity analysis model, the following four variants became significantly associated with adiposity: rs6483208; rs4388843; rs4601728; and rs12804291.

CONCLUSIONS

Our data indicate that polymorphisms in the MTNR1B gene are associated with obesity traits in African Americans. To the best of our knowledge, this is the first study to explore the effect of insomnia on the association between the circadian MTNR1B genetic variants and metabolic traits in an African American sample population. We observed that insomnia affected the association between the MTNR1B variants and adiposity.

Plasma Protein Profile of Carotid Artery Atherosclerosis and Atherosclerotic Outcomes: Meta-Analyses and Mendelian Randomization Analyses

[Figure: see text].

The Evolving Story in the Genetic Analysis for Heart Failure

Genomic studies of cardiovascular diseases have achieved great success, not only in Mendelian genetic diseases such as hereditary arrhythmias and cardiomyopathies, but also in common diseases such as ischemic heart disease and atrial fibrillation. However, only limited success has been achieved in heart failure due to the complexity of its disease background. In this paper, we will review the genetic research for heart failure to date and discuss how we can discover new aspects of heart failure from the viewpoint of genomic perspective.

Genetic association analysis of the cardiovascular biomarker: N-terminal fragment of pro-B-type natriuretic peptide (NT-proBNP)

BACKGROUND

NT-proBNP is a biomarker of cardiovascular disease (CVD). Little is known about the heritability and genetic variants associated with NT-proBNP. Therefore, we estimated the heritability of and examined genetic associations of SNPs in the BNP gene region with circulating NT-proBNP and prevalent CVD in 4,331 participants from the Long Life Family Study (LLFS).

METHODS AND RESULTS

Genotypes of 10 SNPs from the NPPB and NPPA regions that encode BNP and A-type natriuretic peptide, respectively, were tested for association with NT-proBNP and prevalent cardiovascular disease and risk factors. We performed analyses using the Sequential Oligogenic Linkage Analysis (SOLAR) program to account for family relatedness, and adjusted all models for age, sex, and field center. The mean age of the LLFS was 69.8 years (range 24-110) with 55.4% females. NT-proBNP was significantly heritable (h2 = 0.21; P = 4x10-14), and the minor alleles of rs632793 (p<0.001) and rs41300100 (p = 0.05) were independently associated with higher serum NT-proBNP levels. Additionally, the minor allele of rs632793 was significantly and consistently associated with lower prevalent CVD, including blood pressures, independent of NT-proBNP level (all P<0.05). Results for prevalent CVD, but not NT-proBNP levels, showed significant interaction by familial generation.

CONCLUSION

In this family-based study of subjects with exceptional longevity, we identified several allelic variants in the BNP gene region associated with NT-pro-BNP levels and prevalent CVD.

Functional analysis of the brain natriuretic peptide gene for high-altitude adaptation in Tibetan pigs

High-altitude adaptation in Tibetan pigs (TP) is associated with positively-selected genes. The brain natriuretic peptide (BNP) gene is critical in the regulation of cardiovascular homeostasis and energy metabolism. The present study was conducted to identify the function of BNP for high-altitude adaptations in TP. RT-qPCR and western blotting results indicated that BNP expression could be upregulated when the pigs (especially for the Tibetan pigs) were raised to high altitude. In the 5' flanking region, three polymorphic sites, A-1964G, C-1780G, and T-940C were detected, and the genotype distribution of C-1780G was significantly different between the highland (TP) and lowland (Diannan small-eared pig; Yorkshire pig) breeds. The site of C-1780G was in active promoter regions identified using the luciferase reporter gene system, and the fragment with allele G had higher transcriptional activity than that with allele C. The TP population had a higher frequency of allele G than the two lowland breeds. Our results collectively demonstrated that the G allele of C-1780G in the BNP gene may be advantageous for high-altitude adaptation in pigs through upregulating BNP expression. Our findings provide information that helps toward a comprehensive understanding of the mechanism underlying the involvement of the BNP gene in high-altitude adaptation.

Associations of B-Type Natriuretic Peptide and Its Coding Gene Promoter Methylation With Functional Outcome of Acute Ischemic Stroke: A Mediation Analysis

Background

The prognostic role of B‐type natriuretic peptide (BNP) in stroke has been suggested, but limited studies have shown mixed results and unknown underlying mechanisms. DNA methylation, a molecular modification that alters gene expression, may represent a candidate mechanism for this purpose. We aimed to examine the associations of BNP and methylation of its coding gene (natriuretic peptide B [NPPB]) with the functional outcome in a large sample of patients with acute ischemic stroke from CATIS (China Antihypertensive Trial in Acute Ischemic Stroke).

Methods and Results

Leveraging participants from CATIS with available specimens, serum proBNP (equimolarly produced with BNP) was measured in 3216 patients (mean age, 62 years; 64% men), and peripheral blood DNA methylation of the NPPB promoter was quantified by targeted bisulfite sequencing in 806 patients (mean age, 62 years; 54% men). The functional outcome was defined as an ordered modified Rankin Scale score assessed at 14 days or hospital discharge after stroke onset. Mediation analysis was conducted to test the potential mediating effect of proBNP on the relationship between NPPB methylation and functional outcome. The results showed that a higher level of proBNP was significantly associated with a higher risk of having a poorer functional outcome (odds ratio [OR], 1.14; P=0.006). Every 5% of hypermethylation at 2 (Chr1:11919160 [OR, 0.93; P=0.022] and Chr1:11918989 [OR, 0.92; P=0.032]) of 11 CpG loci assayed was associated with 7% and 8% lower risk, respectively, of having a poor functional outcome. In addition, proBNP was negatively correlated to hypermethylation at 1 CpG (Chr1:11918989 [β=−0.029; P=0.009]) and mediated approximately 7.69% (95% CI, 2.50%–13.82%) of the association between this CpG methylation and the functional outcome.

Conclusions

Hypermethylation at the NPPB promoter is associated with the functional outcome after ischemic stroke, at least partially by suppressing BNP expression or excretion.

Associations of osteopontin and NT-proBNP with circulating miRNA levels in acute coronary syndrome

The genomic regulatory networks underlying the pathogenesis of non-ST-segment elevation acute coronary syndrome (NSTE-ACS) are incompletely understood. As intermediate traits, protein biomarkers report on underlying disease severity and prognosis in NSTE-ACS. We hypothesized that integration of dense microRNA (miRNA) profiling with biomarker measurements would highlight potential regulatory pathways that underlie the relationships between prognostic biomarkers, miRNAs, and cardiovascular phenotypes. We performed miRNA sequencing using whole blood from 186 patients from the TRILOGY-ACS trial. Seven circulating prognostic biomarkers were measured: NH₂-terminal pro-B-type natriuretic peptide (NT-proBNP), high-sensitivity C-reactive protein, osteopontin (OPN), myeloperoxidase, growth differentiation factor 15, monocyte chemoattractant protein, and neopterin. We tested miRNAs for association with each biomarker with generalized linear models and controlled the false discovery rate at 0.05. Ten miRNAs, including known cardiac-related miRNAs 25-3p and 423-3p, were associated with NT-proBNP levels (min. P = 7.5 × 10⁻⁴) and 48 miRNAs, including cardiac-related miRNAs 378a-3p, 20b-5p and 320a, -b, and -d, were associated with OPN levels (min. P = 1.6 × 10⁻⁶). NT-proBNP and OPN were also associated with time to cardiovascular death, myocardial infarction (MI), or stroke in the sample. By integrating large-scale miRNA profiling with circulating biomarkers as intermediate traits, we identified associations of known cardiac-related and novel miRNAs with two prognostic biomarkers and identified potential genomic networks regulating these biomarkers. These results, highlighting plausible biological pathways connecting miRNAs with biomarkers and outcomes, may inform future studies seeking to delineate genomic pathways underlying NSTE-ACS outcomes.

Cardiac Troponin T and Troponin I in the General Population

BACKGROUND

There is great interest in widening the use of high-sensitivity cardiac troponins for population cardiovascular disease (CVD) and heart failure screening. However, it is not clear whether cardiac troponin T (cTnT) and troponin I (cTnI) are equivalent measures of risk in this setting. We aimed to compare and contrast (1) the association of cTnT and cTnI with CVD and non-CVD outcomes, and (2) their determinants in a genome-wide association study.

METHODS

High-sensitivity cTnT and cTnI were measured in serum from 19 501 individuals in Generation Scotland Scottish Family Health Study. Median follow-up was 7.8 years (quartile 1 to quartile 3, 7.1-9.2). Associations of each troponin with a composite CVD outcome (1177 events), CVD death (n=266), non-CVD death (n=374), and heart failure (n=216) were determined by using Cox models. A genome-wide association study was conducted using a standard approach developed for the cohort.

RESULTS

Both cTnI and cTnT were strongly associated with CVD risk in unadjusted models. After adjusting for classical risk factors, the hazard ratio for a 1 SD increase in log transformed troponin was 1.24 (95% CI, 1.17-1.32) and 1.11 (1.04-1.19) for cTnI and cTnT, respectively; ratio of hazard ratios 1.12 (1.04-1.21). cTnI, but not cTnT, was associated with myocardial infarction and coronary heart disease. Both cTnI and cTnT had strong associations with CVD death and heart failure. By contrast, cTnT, but not cTnI, was associated with non-CVD death; ratio of hazard ratios 0.77 (0.67-0.88). We identified 5 loci (53 individual single-nucleotide polymorphisms) that had genome-wide significant associations with cTnI, and a different set of 4 loci (4 single-nucleotide polymorphisms) for cTnT.

CONCLUSIONS

The upstream genetic causes of low-grade elevations in cTnI and cTnT appear distinct, and their associations with outcomes also differ. Elevations in cTnI are more strongly associated with some CVD outcomes, whereas cTnT is more strongly associated with the risk of non-CVD death. These findings help inform the selection of an optimal troponin assay for future clinical care and research in this setting.

Molecular Implications of Natriuretic Peptides in the Protection from Hypertension and Target Organ Damage Development

The pathogenesis of hypertension, as a multifactorial trait, is complex. High blood pressure levels, in turn, concur with the development of cardiovascular damage. Abnormalities of several neurohormonal mechanisms controlling blood pressure homeostasis and cardiovascular remodeling can contribute to these pathological conditions. The natriuretic peptide (NP) family (including ANP (atrial natriuretic peptide), BNP (brain natriuretic peptide), and CNP (C-type natriuretic peptide)), the NP receptors (NPRA, NPRB, and NPRC), and the related protease convertases (furin, corin, and PCSK6) constitute the NP system and represent relevant protective mechanisms toward the development of hypertension and associated conditions, such as atherosclerosis, stroke, myocardial infarction, heart failure, and renal injury. Initially, several experimental studies performed in different animal models demonstrated a key role of the NP system in the development of hypertension. Importantly, these studies provided relevant insights for a better comprehension of the pathogenesis of hypertension and related cardiovascular phenotypes in humans. Thus, investigation of the role of NPs in hypertension offers an excellent example in translational medicine. In this review article, we will summarize the most compelling evidence regarding the molecular mechanisms underlying the physiological and pathological impact of NPs on blood pressure regulation and on hypertension development. We will also discuss the protective effect of NPs toward the increased susceptibility to hypertensive target organ damage.

Scientific Contributions of Population-Based Studies to Cardiovascular Epidemiology in the GWAS Era

Longitudinal, well phenotyped, population-based cohort studies offer unique research opportunities in the context of genome-wide association studies (GWAS), including GWAS for new-onset (incident) cardiovascular disease (CVD) events, the assessment of gene x lifestyle interactions, and evaluating the incremental predictive utility of genetic information in apparently healthy individuals. Furthermore, comprehensively phenotyped community-dwelling samples have contributed to GWAS of numerous traits that reflect normal organ function (e.g., cardiac structure and systolic and diastolic function) and for many traits along the CVD continuum (e.g., risk factors, circulating biomarkers, and subclinical disease traits). These GWAS have heretofore identified many genetic loci implicated in normal organ function and different stages of the CVD continuum. Finally, population-based cohort studies have made important contributions to Mendelian Randomization analyses, a statistical approach that uses genetic information to assess observed associations between cardiovascular traits and clinical CVD outcomes for potential causality.

Pharmacogenomics of the Natriuretic Peptide System in Heart Failure

PURPOSE OF REVIEW

Heart failure (HF) continues to be a public health burden despite advances in therapy, and the natriuretic peptide (NP) system is clearly of critical importance in this setting, spawning valuable diagnostic and prognostic testing, such as B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP), as well as current and future therapeutics, including recombinant natriuretic peptides (e.g., carperitide, nesiritide) and recently sacubitril, which inhibits the key clearance mechanism for NPs. This article intends to summarize the existing evidence for the role of NP system genetic variation on cardiovascular phenotypes relevant to HF with particular focus on the potential impact on pharmacologic therapies.

RECENT FINDINGS

Several genes in NP system have been interrogated, in many cases genetic variation impacting protein quantity and function or related disease states. Recent data supports genetic variants potentially impacting pharmacokinetics or dynamics of medications targeting the pathway. Growing evidence indicates the importance of genetic variation to the functioning of the NP system and its pharmacologic manipulation.

Genome-Wide Association Study Implicates Atrial Natriuretic Peptide Rather Than B-Type Natriuretic Peptide in the Regulation of Blood Pressure in the General Population

BACKGROUND

Cardiomyocytes secrete atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) in response to mechanical stretching, making them useful clinical biomarkers of cardiac stress. Both human and animal studies indicate a role for ANP as a regulator of blood pressure with conflicting results for BNP.

METHODS AND RESULTS

We used genome-wide association analysis (n=6296) to study the effects of genetic variants on circulating natriuretic peptide concentrations and compared the impact of natriuretic peptide-associated genetic variants on blood pressure (n=27 059). Eight independent genetic variants in 2 known (NPPA-NPPB and POC1B-GALNT4) and 1 novel locus (PPP3CC) associated with midregional proANP (MR-proANP), BNP, aminoterminal proBNP (NT-proBNP), or BNP:NT-proBNP ratio. The NPPA-NPPB locus containing the adjacent genes encoding ANP and BNP harbored 4 independent cis variants with effects specific to either midregional proANP or BNP and a rare missense single nucleotide polymorphism in NT-proBNP seriously altering its measurement. Variants near the calcineurin catalytic subunit gamma gene PPP3CC and the polypeptide N-acetylgalactosaminyltransferase 4 gene GALNT4 associated with BNP:NT-proBNP ratio but not with BNP or midregional proANP, suggesting effects on the post-translational regulation of proBNP. Out of the 8 individual variants, only those correlated with midregional proANP had a statistically significant albeit weak impact on blood pressure. The combined effect of these 3 single nucleotide polymorphisms also associated with hypertension risk (P=8.2×10-4).

CONCLUSIONS

Common genetic differences affecting the circulating concentration of ANP associated with blood pressure, whereas those affecting BNP did not, highlighting the blood pressure-lowering effect of ANP in the general population.

Whole exome sequence-based association analyses of plasma amyloid-β in African and European Americans; the Atherosclerosis Risk in Communities-Neurocognitive Study

Objective

We performed single-variant and gene-based association analyses of plasma amyloid-β (aβ) concentrations using whole exome sequence from 1,414 African and European Americans. Our goal was to identify genes that influence plasma aβ₄₂ concentrations and aβ₄₂:aβ₄₀ ratios in late middle age (mean = 59 years), old age (mean = 77 years), or change over time (mean = 18 years).

Methods

Plasma aβ measures were linearly regressed onto age, gender, APOE ε4 carrier status, and time elapsed between visits (fold-changes only) separately by race. Following inverse normal transformation of the residuals, seqMeta was used to conduct race-specific single-variant and gene-based association tests while adjusting for population structure. Linear regression models were fit on autosomal variants with minor allele frequencies (MAF)≥1%. T5 burden and Sequence Kernel Association (SKAT) gene-based tests assessed functional variants with MAF≤5%. Cross-race fixed effects meta-analyses were Bonferroni-corrected for the number of variants or genes tested.

Results

Seven genes were associated with aβ in late middle age or change over time; no associations were identified in old age. Single variants in KLKB1 (rs3733402; p = 4.33x10^-10) and F12 (rs1801020; p = 3.89x10^-8) were significantly associated with midlife aβ₄₂ levels through cross-race meta-analysis; the KLKB1 variant replicated internally using 1,014 additional participants with exome chip. ITPRIP, PLIN2, and TSPAN18 were associated with the midlife aβ₄₂:aβ₄₀ ratio via the T5 test; TSPAN18 was significant via the cross-race meta-analysis, whereas ITPRIP and PLIN2 were European American-specific. NCOA1 and NT5C3B were associated with the midlife aβ₄₂:aβ₄₀ ratio and the fold-change in aβ₄₂, respectively, via SKAT in African Americans. No associations replicated externally (N = 725).

Conclusion

We discovered age-dependent genetic effects, established associations between vascular-related genes (KLKB1, F12, PLIN2) and midlife plasma aβ levels, and identified a plausible Alzheimer’s Disease candidate gene (ITPRIP) influencing cell death. Plasma aβ concentrations may have dynamic biological determinants across the lifespan; plasma aβ study designs or analyses must consider age.

An NPPB Promoter Polymorphism Associated With Elevated N-Terminal pro-B-Type Natriuretic Peptide and Lower Blood Pressure, Hypertension, and Mortality

Background

Elevated B‐type natriuretic peptide (BNP) levels are associated with heart failure and increased mortality in the general population. We investigated rs198389, a functional variant in the promoter region of the BNP gene (NPPB), in patients from the Atherosclerosis Risk in Communities Study to investigate associations with N‐terminal pro‐BNP (NT‐proBNP) levels and outcomes.

Methods and Results

A total of 11 361 black and white patients with rs198389 genotyping attended visit 1 (aged 45–64 years; 1987–1989), with follow‐up visits occurring every 3 years (visit 2–visit 4, 1990–1999), followed by visit 5 (2011–2013). NT‐proBNP levels were measured at visits 2, 4, and 5. At visit 2, the GG genotype (frequency 18%) was associated with a 41% higher mean plasma level of NT‐proBNP compared with the AA genotype (frequency 34%), with intermediate values observed in AGs (P=4.2×10⁻⁵²). The GG genotype was associated with reduced systolic blood pressure (−1.6 mm Hg, P=0.006), diastolic blood pressure (−1 mm Hg, P=0.003), antihypertension medication use (odds ratio, 0.85; 95% CI, 0.74–0.97 [P=0.02]), and hypertension (odds ratio, 0.81; 95% CI, 0.72–0.92 [P=0.002]) compared with the AA genotype with intermediate values in AGs. These relationships persisted throughout subsequent visits. After a median follow‐up of 23 years, there were 4031 deaths. With and without covariate adjustment, the GG genotype was associated with modestly lower mortality (hazard ratio, 0.86; 95% CI, 0.78–0.95), primarily reflective of cardiovascular death (hazard ratio, 0.75; 95% CI, 0.61–0.92), and increased residual lifespan of 8 months from 50 years of age (P=0.02) versus AAs.

Conclusions

The rs198389 G allele in the NPPB promoter is associated with elevated levels of NT‐proBNP throughout adult life, reduced blood pressure, hypertension and cardiovascular mortality, and increased lifespan.

Plasma Kallikrein Inhibitors in Cardiovascular Disease: An Innovative Therapeutic Approach

Plasma prekallikrein is the liver-derived precursor of the trypsin-like serine protease plasma kallikrein, and circulates in plasma bound to high molecular weight kininogen. Plasma prekallikrein is activated to plasma kallikrein by activated factor XII or prolylcarboxypeptidase. Plasma kallikrein regulates the activity of multiple proteolytic cascades in the cardiovascular system such as the intrinsic pathway of coagulation, the kallikrein-kinin system, the fibrinolytic system, the renin-angiotensin system, and the complement pathways. As such, plasma kallikrein plays a central role in the pathogenesis of thrombosis, inflammation, and blood pressure regulation. Under physiological conditions, plasma kallikrein serves as a cardioprotective enzyme. However, its increased plasma concentration or hyperactivity perpetuates cardiovascular disease (CVD). In this article, we review the biochemistry and cell biology of plasma kallikrein and summarize data from preclinical and clinical studies that have established important functions of this serine protease in CVD states. Finally, we propose plasma kallikrein inhibitors as a novel class of drugs with potential therapeutic applications in the treatment of CVDs.

Genome-wide association reveals that common genetic variation in the kallikrein-kinin system is associated with serum L-arginine levels

L-arginine is the essential precursor of nitric oxide, and is involved in multiple key physiological processes, including vascular and immune function. The genetic regulation of blood L-arginine levels is largely unknown. We performed a genome-wide association study (GWAS) to identify genetic factors determining serum L-arginine levels, amongst 901 Europeans and 1,394 Indian Asians. We show that common genetic variations at the KLKB1 and F12 loci are strongly associated with serum L-arginine levels. The G allele of single nucleotide polymorphism (SNP) rs71640036 (T/G) in KLKB1 is associated with lower serum L-arginine concentrations (10 µmol/l per allele copy, p=1×10-24), while allele T of rs2545801 (T/C) near the F12 gene is associated with lower serum L-arginine levels (7 µmol/l per allele copy, p=7×10-12). Together these two loci explain 7 % of the total variance in serum L-arginine concentrations. The associations at both loci were replicated in independent cohorts with plasma L-arginine measurements (p<0.004). The two sentinel SNPs are in nearly complete LD with the nonsynonymous SNP rs3733402 at KLKB1 and the 5'-UTR SNP rs1801020 at F12, respectively. SNPs at both loci are associated with blood pressure. Our findings provide new insight into the genetic regulation of L-arginine and its potential relationship with cardiovascular risk.

A genome-wide association meta-analysis on apolipoprotein A-IV concentrations

Apolipoprotein A-IV (apoA-IV) is a major component of HDL and chylomicron particles and is involved in reverse cholesterol transport. It is an early marker of impaired renal function. We aimed to identify genetic loci associated with apoA-IV concentrations and to investigate relationships with known susceptibility loci for kidney function and lipids. A genome-wide association meta-analysis on apoA-IV concentrations was conducted in five population-based cohorts (n = 13,813) followed by two additional replication studies (n = 2,267) including approximately 10 M SNPs. Three independent SNPs from two genomic regions were significantly associated with apoA-IV concentrations: rs1729407 near APOA4 (P = 6.77 × 10 ^{-  44}), rs5104 in APOA4 (P = 1.79 × 10^-24) and rs4241819 in KLKB1 (P = 5.6 × 10^-14). Additionally, a look-up of the replicated SNPs in downloadable GWAS meta-analysis results was performed on kidney function (defined by eGFR), HDL-cholesterol and triglycerides. From these three SNPs mentioned above, only rs1729407 showed an association with HDL-cholesterol (P = 7.1 × 10 ^{-  07}). Moreover, weighted SNP-scores were built involving known susceptibility loci for the aforementioned traits (53, 70 and 38 SNPs, respectively) and were associated with apoA-IV concentrations. This analysis revealed a significant and an inverse association for kidney function with apoA-IV concentrations (P = 5.5 × 10^-05). Furthermore, an increase of triglyceride-increasing alleles was found to decrease apoA-IV concentrations (P = 0.0078). In summary, we identified two independent SNPs located in or next the APOA4 gene and one SNP in KLKB1 The association of KLKB1 with apoA-IV suggests an involvement of apoA-IV in renal metabolism and/or an interaction within HDL particles. Analyses of SNP-scores indicate potential causal effects of kidney function and by lesser extent triglycerides on apoA-IV concentrations.

Associations Between Common and Rare Exonic Genetic Variants and Serum Levels of 20 Cardiovascular-Related Proteins: The Tromsø Study

Supplemental Digital Content is available in the text.

Background—

Genetic variation can be used to study causal relationships between biomarkers and diseases. Here, we identify new common and rare genetic variants associated with cardiovascular-related protein levels (protein quantitative trait loci [pQTLs]). We functionally annotate these pQTLs, predict and experimentally confirm a novel molecular interaction, and determine which pQTLs are associated with diseases and physiological phenotypes.

Methods and Results—

As part of a larger case–control study of venous thromboembolism, serum levels of 51 proteins implicated in cardiovascular diseases were measured in 330 individuals from the Tromsø Study. Exonic genetic variation near each protein’s respective gene (cis) was identified using sequencing and arrays. Using single site and gene-based tests, we identified 27 genetic associations between pQTLs and the serum levels of 20 proteins: 14 associated with common variation in cis, of which 6 are novel (ie, not previously reported); 7 associations with rare variants in cis, of which 4 are novel; and 6 associations in trans. Of the 20 proteins, 15 were associated with single sites and 7 with rare variants. cis-pQTLs for kallikrein and F12 also show trans associations for proteins (uPAR, kininogen) known to be cleaved by kallikrein and with NTproBNP. We experimentally demonstrate that kallikrein can cleave proBNP (NTproBNP precursor) in vitro. Nine of the pQTLs have previously identified associations with 17 disease and physiological phenotypes.

Conclusions—

We have identified cis and trans genetic variation associated with the serum levels of 20 proteins and utilized these pQTLs to study molecular mechanisms underlying disease and physiological phenotypes.

A Cross-sectional Study of KLKB1 and PRCP Polymorphisms in Patient Samples with Cardiovascular Disease

Plasma kallikrein formed from prekallikrein (PK) produces bradykinin from kininogens and activates factor XII. Plasma PK is activated by factors αXIIa, βXIIa, or prolylcarboxypeptidase (PRCP). A cross-sectional investigation determined if there is an association of PRCP and KLKB1 polymorphisms with cardiovascular disease (CVD). DNA was obtained from 2243 individuals from the Prevention of Events with Angiotensin Converting Enzyme trial. Two PRCP SNPs, rs7104980 and rs2298668, and two KLKB1 SNPs, rs3733402 and rs3087505, were genotyped. Logistic regression models were performed for history of diabetes, myocardial infarction, stroke, angina, angiographic coronary disease, CABG, intermittent claudication, percutaneous transluminal coronary angioplasty (PTCA), and transient ischemic attack. The PRCP SNP rs7104980 increased the odds of having a history of PTCA by 21% [odds ratio (OR) = 1.211; 95% confidence intervals (CI) = (1.008, 1.454)]; P = 0.041, but was non-significant after Bonferroni correction. Alternatively, having the G allele for rs3733402 (KLKB1 gene) decreased the odds of having a history of angiographic coronary disease by 24% [OR = 0.759; 95% CI = (0.622, 0.927)]; P = 0.007 that was statistically significant (P < 0.01) after Bonferroni correction for multiple hypothesis testing. When the best-fit model based on the Akaike information criterion controlled for age, weight, gender, hypertension, and history of angina, the G allele of KLKB1 rs3733402 that is associated with less plasma kallikrein activity correlated with reduced history of CVD.