From the Cover: Whole-genome association study identifies STK39 as a hypertension susceptibility gene.

Hypertension places a major burden on individual and public health, but the genetic basis of this complex disorder is poorly understood. We conducted a genome-wide association study of systolic and diastolic blood pressure (SBP and DBP) in Amish subjects and found strong association signals with common variants in a serine/threonine kinase gene, STK39. We confirmed this association in an independent Amish and 4 non-Amish Caucasian samples including the Diabetes Genetics Initiative, Framingham Heart Study, GenNet, and Hutterites (meta-analysis combining all studies: n = 7,125, P < 10(-6)). The higher BP-associated alleles have frequencies > 0.09 and were associated with increases of 3.3/1.3 mm Hg in SBP/DBP, respectively, in the Amish subjects and with smaller but consistent effects across the non-Amish studies. Cell-based functional studies showed that STK39 interacts with WNK kinases and cation-chloride cotransporters, mutations in which cause monogenic forms of BP dysregulation. We demonstrate that in vivo, STK39 is expressed in the distal nephron, where it may interact with these proteins. Although none of the associated SNPs alter protein structure, we identified and experimentally confirmed a highly conserved intronic element with allele-specific in vitro transcription activity as a functional candidate for this association. Thus, variants in STK39 may influence BP by increasing STK39 expression and consequently altering renal Na(+) excretion, thus unifying rare and common BP-regulating alleles in the same physiological pathway.

Positional identification of variants of Adamts16 linked to inherited hypertension.

A previously reported blood pressure (BP) quantitative trait locus on rat Chromosome 1 was isolated in a short congenic segment spanning 804.6 kb. The 804.6 kb region contained only two genes, LOC306664 and LOC306665. LOC306664 is predicted to translate into A Disintegrin-like and Metalloproteinase with Thrombospondin Motifs-16 (Adamts16). LOC306665 is a novel gene. All predicted exons of both LOC306664 and LOC306665 were sequenced. Non-synonymous variants were identified in only one of these genes, LOC306664. These variants were naturally existing polymorphisms among inbred, outbred and wild rats. The full-length rat transcript of Adamts16 was detected in multiple tissues. Similar to ADAMTS16 in humans, expression of Adamts16 was prominent in the kidney. Renal transcriptome analysis suggested that a network of genes related to BP was differential between congenic and S rats. These genes were also differentially expressed between kidney cell lines with or without knock-down of Adamts16. Adamts16 is conserved between rats and humans. It is a candidate gene within the homologous region on human Chromosome 5, which is linked to systolic and diastolic BP in the Quebec Family Study. Multiple variants, including an Ala to Pro variant in codon 90 (rs2086310) of human ADAMTS16, were associated with human resting systolic BP (SBP). Replication study in GenNet confirmed the association of two variants of ADAMTS16 with SBP, including rs2086310. Overall, our report represents a high resolution positional cloning and translational study for Adamts16 as a candidate gene controlling BP.

Genome-wide association scan shows genetic variants in the FTO gene are associated with obesity-related traits.

The obesity epidemic is responsible for a substantial economic burden in developed countries and is a major risk factor for type 2 diabetes and cardiovascular disease. The disease is the result not only of several environmental risk factors, but also of genetic predisposition. To take advantage of recent advances in gene-mapping technology, we executed a genome-wide association scan to identify genetic variants associated with obesity-related quantitative traits in the genetically isolated population of Sardinia. Initial analysis suggested that several SNPs in the FTO and PFKP genes were associated with increased BMI, hip circumference, and weight. Within the FTO gene, rs9930506 showed the strongest association with BMI (p = 8.6 x10(-7)), hip circumference (p = 3.4 x 10(-8)), and weight (p = 9.1 x 10(-7)). In Sardinia, homozygotes for the rare "G" allele of this SNP (minor allele frequency = 0.46) were 1.3 BMI units heavier than homozygotes for the common "A" allele. Within the PFKP gene, rs6602024 showed very strong association with BMI (p = 4.9 x 10(-6)). Homozygotes for the rare "A" allele of this SNP (minor allele frequency = 0.12) were 1.8 BMI units heavier than homozygotes for the common "G" allele. To replicate our findings, we genotyped these two SNPs in the GenNet study. In European Americans (N = 1,496) and in Hispanic Americans (N = 839), we replicated significant association between rs9930506 in the FTO gene and BMI (p-value for meta-analysis of European American and Hispanic American follow-up samples, p = 0.001), weight (p = 0.001), and hip circumference (p = 0.0005). We did not replicate association between rs6602024 and obesity-related traits in the GenNet sample, although we found that in European Americans, Hispanic Americans, and African Americans, homozygotes for the rare "A" allele were, on average, 1.0-3.0 BMI units heavier than homozygotes for the more common "G" allele. In summary, we have completed a whole genome-association scan for three obesity-related quantitative traits and report that common genetic variants in the FTO gene are associated with substantial changes in BMI, hip circumference, and body weight. These changes could have a significant impact on the risk of obesity-related morbidity in the general population.

A whole-genome scan for stroke or myocardial infarction in family blood pressure program families.

BACKGROUND AND PURPOSE: Atherothrombotic diseases, including stroke and myocardial infarction, share a common pathogenesis. Chromosomal regions have been linked to atherothrombotic diseases in family studies, and association studies have identified candidate gene polymorphisms that affect the risk of stroke and/or myocardial infarction. Using data from the Family Blood Pressure Program, we tested for chromosomal regions linked to the composite phenotype of stroke or myocardial infarction in a large set of hypertensive families. METHODS: Nonparametric linkage analysis was implemented in MERLIN, which tests for excess allele-sharing among affected siblings. Empirical distributions based on gene dropping simulations were constructed for each test statistic, and the -log(10) of the associated probability values were compared. RESULTS: Analyses were based on 9607 individuals in 226 black, 395 Hispanic, and 207 white families; 106 families had multiple affected individuals. Several regions showed linkage to stroke or myocardial infarction, most significantly in Hispanics on chromosomes 2p21 (-log(10) P=3.0) and 7q21.1 (-log(10) P=2.8), 9q32 in blacks and Hispanics (-log(10) P=3.0), 11p13 in blacks (-log(10) P=2.1), and 12q24.33 in whites (-log(10) P=3.0). CONCLUSIONS: There is statistically significant evidence for loci affecting stroke or myocardial infarction on chromosomes 2, 9, and 12.

Anger types: heritability and relation to blood pressure, body mass index, and left ventricular mass.

The relationship between anger and cardiovascular morbidity has not been investigated among Mexican Americans. This exploratory study examined the heritability of anger types and their relationship to cardiovascular variables in samples of unrelated and related Mexican Americans residing near Chicago, Illinois. All of the anger variables of the Spielberger Anger Expression Scale (in, out, control, total expression) had significant heritabilities. Using the total sample of related individuals, higher female anger-out scores were associated with greater left ventricular mass after correction for height to the 2.7 power (LVM/HT2.7), systolic blood pressure, and diastolic blood pressure. Females had positive, significant associations for body mass index with LVM/HT2.7, systolic blood pressure, and diastolic blood pressure; among males, these variables were similarly but less strongly related. Anger (coraje in Spanish) is discussed in the context of folk medicine as a risk factor for cardiovascular morbidity.

Genetics and hypertension.

Although it has long been appreciated that there is a genetic component to hypertension, it is only recently that specific genes are being identified. This progress is part of a general advancement of our understanding of common, genetically complex human diseases. This understanding will eventually affect clinical practice.

The impact of data quality on the identification of complex disease genes: experience from the Family Blood Pressure Program.

The application of genome-wide linkage scans to uncover susceptibility loci for complex diseases offers great promise for the risk assessment, treatment, and understanding of these diseases. However, for most published studies, linkage signals are typically modest and vary considerably from one study to another. The multicenter Family Blood Pressure Program has analyzed genome-wide linkage scans of over 12 000 individuals. Based on this experience, we developed a protocol for large linkage studies that reduces two sources of data error: pedigree structure and marker genotyping errors. We then used the linkage signals, before and after data cleaning, to illustrate the impact of missing and erroneous data. A comprehensive error-checking protocol is an important part of complex disease linkage studies and enhances gene mapping. The lack of significant and reproducible linkage findings across studies is, in part, due to data quality.

Genome-wide linkage scans for fasting glucose, insulin, and insulin resistance in the National Heart, Lung, and Blood Institute Family Blood Pressure Program: evidence of linkages to chromosome 7q36 and 19q13 from meta-analysis.

Genome-wide linkage analyses were performed using a multipoint variance components method in eight study groups from four multicenter networks (whites and blacks in GenNet; whites, blacks, and Mexican Americans in GENOA; whites and blacks in HyperGEN; and Asians in SAPPHIRe) that comprise the National Heart, Lung, and Blood Institute Family Blood Pressure Program (FBPP), in order to identify quantitative trait loci (QTLs) influencing fasting glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR). These study populations were enriched with subjects who had elevated blood pressure. Participants fasting <8 h, those with a history of type 2 diabetes, or those on antidiabetic medications were excluded from the current investigation. These three phenotypes were suitably transformed to approximate normal distributions. Each phenotype was adjusted for the effects of age, BMI, and field center separately by sex within each of the eight network ethnicity groups before genetic analysis. A total of 8,664 subjects comprising 5,923 sibpairs from 4,043 families with 365 markers were available for conducting a meta-analysis using a modified Fisher's method of combining the P values from each of the eight scans. Evidence of linkages was found on chromosome 7q36 at 163 cM, with a logarithm of odds (LOD) score of 3.21 for HOMA-IR, and on chromosome 19q13 at 88 cM, with a LOD score of 3.33 for fasting glucose. We also found suggestive linkages (LOD score >/=2.2) on chromosome 7q36 at 163 cM, with LOD scores of 2.31 for fasting glucose and 2.26 for fasting insulin (versus the LOD score of 3.21 for HOMA-IR at this locus). In conclusion, QTLs were identified on chromosomes 7q36 and 19q13 for fasting glucose, insulin, and insulin resistance in large and multiple-ethnicity populations in the FBPP with good replications across several other independent studies for relevant traits. Follow-up dense mapping and association studies are warranted.

Association between a dopamine-4 receptor polymorphism and blood pressure.

BACKGROUND: Dopamine receptor genes are candidates for hypertension susceptibility. Locally released dopamine increases renal sodium excretion, and defective renal dopamine receptor signaling has been shown to play a role in hypertension. Dopamine-4 receptors are expressed in juxtaglomerular and cortical collecting cells, where dopamine activation could alter sodium and water metabolism and affect blood pressure (BP). The dopamine-4 receptor (DRD4) gene has a 16 amino acid (48 base pairs [bp]) repeat polymorphism located in exon 3 where a G-protein binding area is encoded. The long allele (defined as at least one 7 to 10 repeat) has been associated with the personality trait Novelty Seeking and with substance abuse, but associations between dopamine-4 receptor polymorphisms and BP have not been reported. METHODS: We genotyped 479 female and 385 male subjects of white ethnicity at the DRD4 repeat polymorphism site and classified each subject as having either the long or short genotype. RESULTS: We found associations between the DRD4 long allele and increased systolic BP (P = .031), diastolic BP (P = .034), and a history of regular alcohol use (P = .008). Furthermore, for systolic BP (P = .009) and pulse pressure (P = .002), we found evidence for an interaction between dopamine-4 receptor alleles and age, indicating that the effects of dopamine-4 receptor variants on BP increase with age. CONCLUSION: In this white population, the long variant of the DRD4 gene is associated with a 3-mm Hg higher systolic and 2-mm Hg higher diastolic BP.

Left ventricular hypertrophy after hypertensive pregnancy disorders.

OBJECTIVE: Cardiac changes of hypertensive pregnancy include left ventricular hypertrophy (LVH) and diastolic dysfunction. These are thought to regress postpartum. We hypothesised that women with a history of hypertensive pregnancy would have altered LV geometry and function when compared with women with only normotensive pregnancies. METHODS: In this cohort study, we analysed echocardiograms of 2637 women who participated in the Family Blood Pressure Program. We compared LV mass and function in women with hypertensive pregnancies with those with normotensive pregnancies. RESULTS: Women were evaluated at a mean age of 56 years: 427 (16%) had at least one hypertensive pregnancy; 2210 (84%) had normotensive pregnancies. Compared with women with normotensive pregnancies, women with hypertensive pregnancy had a greater risk of LVH (OR: 1.42; 95% CI 1.01 to 1.99, p=0.05), after adjusting for age, race, research network of the Family Blood Pressure Program, education, parity, BMI, hypertension and diabetes. When duration of hypertension was taken into account, this relationship was no longer significant (OR: 1.19; CI 0.08 to 1.78, p=0.38). Women with hypertensive pregnancies also had greater left atrial size and lower mitral E/A ratio after adjusting for demographic variables. The prevalence of systolic dysfunction was similar between the groups. CONCLUSIONS: A history of hypertensive pregnancy is associated with LVH after adjusting for risk factors; this might be explained by longer duration of hypertension. This finding supports current guidelines recommending surveillance of women following a hypertensive pregnancy, and sets the stage for longitudinal echocardiographic studies to further elucidate progression of LV geometry and function after pregnancy. CLINICAL TRIAL REGISTRATIONS: GENOA- NCT00005269; HyperGEN- NCT00005267; Sapphire- NCT00005270; GenNet- NCT00005268.

A genome-wide linkage analysis investigating the determinants of blood pressure in whites and African Americans.

Evidence for genomic regions influencing systolic and diastolic blood pressure (BP) were assessed in a whole genome linkage analysis in 211 African American and 160 white families as part of the GenNet network of the National Heart, Lung and Blood Institute-sponsored Family Blood Pressure Program. Multipoint regression and variance components linkage methods were used to analyze 372 polymorphic markers. Statistically compelling evidence for linkage (P values .0057 and .00023, respectively) was found on chromosome 1. Our results support the idea that BP regulation is most likely governed by multiple genetic loci, each with a relatively weak effect on BP in the population at large.

A meta-analysis of genome-wide linkage scans for hypertension: the National Heart, Lung and Blood Institute Family Blood Pressure Program.

BACKGROUND: Four multicenter Networks (GenNet, GENOA, HyperGEN, SAPPHIRe) form the National Heart, Lung and Blood Institute Family Blood Pressure Program (FBPP), to search for hypertension/blood pressure (BP) genes. The networks used different family designs and targeted multiple ethnic groups, using standardized protocols and definitions. Linkage genome scans were done on samples within each network (N = 6245 relatives). METHODS: The evidence was synthesized using meta-analysis. RESULTS: Combining ethnic groups, no region reached LOD >2, but several small peaks were identified, including chromosome 2p where two other recent reports find hypertension linkage. CONCLUSIONS: No regions show uniformly large effects on BP/hypertension in all populations.

Management of intermittent claudication.

Medical management of PAD is a considerable challenge. Although patients typically present with IC, there is a substantial pool of subclinical PAD patients. PAD, whether symptomatic or not, confers a marked cardiovascular risk; with affected patients dying of heart attack or stroke, identification of index patients and aggressive medical treatment can offer health benefits far in excess of improvement in IC or related symptoms. Management of risk factors, lifestyle interventions, and pharmacologic treatment with agents to provide symptomatic relief have a central role in improving function and quality of life and slowing the progression to advanced endpoints, such as the rest pain, nonhealing ulcers, gangrene, and cardiac death. Surgical or percutaneous revascularization for aorto-iliac disease provides durable treatment for individuals with disabling symptoms. Newer treatments, such as angiogenic growth factor treatments, are being tested in clinical trials and seem promising. There are limited treatment choices for individuals with predominant infra-popliteal disease. In the future, the availability of newer stents and therapies to prevent re-stenosis may extend the applicability of endovascular treatment to difficult-to-treat infra-inguinal lesions.

A review of blood pressure measurement protocols among hypertension trials: implications for "evidence-based" clinical practice.

Hypertension guidelines recommend following published standardized protocols to obtain accurate blood pressure (BP) readings in clinical practice. However, the various measurement techniques among clinical trials that provide the basis for evidence-based management have not been evaluated or compared with guideline recommendations. We reviewed published information regarding BP measurement in clinical trials (n = 64) from 1990-2014 by searching PubMed and Google Scholar databases. Every trial failed to provide published information regarding at least one of the 10 methodological aspects we evaluated. Details regarding the health-care provider(s) performing measurement(s), temporal-relation to last medication dosage, number of readings, resting time before (and between recordings), and the device(s) used varied among the trials and often differed from clinical recommendations. Most studies did evaluate ≥2 BP readings in a seated position, presumably from the upper arm (although explicit acknowledgment of this latter detail was rare). When indicated, "trough" BP levels were most commonly obtained (15 of 16 trials), whereas the usage of automated devices increased over time. Numerous aspects of BP measurement varied considerably across trials and often from most recent guideline recommendations. The lack of uniform methodologies in outcome studies that form the foundation of evidence-based guidelines may have significant clinical implications.

A polymorphic 3'UTR element in ATP1B1 regulates alternative polyadenylation and is associated with blood pressure.

Although variants in many genes have previously been shown to be associated with blood pressure (BP) levels, the molecular mechanism underlying these associations are mostly unknown. We identified a multi-allelic T-rich sequence (TRS) in the 3'UTR of ATP1B1 that varies in length and sequence composition (T22-27 and T12GT 3GT6). The 3'UTR of ATP1B1 contains 2 functional polyadenylation signals and the TRS is downstream of the proximal polyadenylation site (A2). Therefore, we hypothesized that alleles of this TRS might influence ATP1B1 expression by regulating alternative polyadenylation. In vitro, the T12GT 3GT6 allele increases polyadenylation at the A2 polyadenylation site as compared to the T23 allele. Consistent with our hypothesis, the relative abundance of the A2-polyadenylated ATP1B1 mRNA was higher in human kidneys with at least one copy of the T12GT 3GT6 allele than in those lacking this allele. The T12GT 3GT6 allele is also associated with higher systolic BP (beta = 3.3 mmHg, p = 0.014) and diastolic BP (beta = 2.4 mmHg, p = 0.003) in a European-American population. Therefore, we have identified a novel multi-allelic TRS in the 3'UTR of ATP1B1 that is associated with higher BP and may mediate its effect by regulating the polyadenylation of the ATP1B1 mRNA.

Low-sodium DASH diet improves diastolic function and ventricular-arterial coupling in hypertensive heart failure with preserved ejection fraction.

BACKGROUND: Heart failure with preserved ejection fraction (HFPEF) involves failure of cardiovascular reserve in multiple domains. In HFPEF animal models, dietary sodium restriction improves ventricular and vascular stiffness and function. We hypothesized that the sodium-restricted dietary approaches to stop hypertension diet (DASH/SRD) would improve left ventricular diastolic function, arterial elastance, and ventricular-arterial coupling in hypertensive HFPEF. METHODS AND RESULTS: Thirteen patients with treated hypertension and compensated HFPEF consumed the DASH/SRD (target sodium, 50 mmol/2100 kcal) for 21 days. We measured baseline and post-DASH/SRD brachial and central blood pressure (via radial arterial tonometry) and cardiovascular function with echocardiographic measures (all previously invasively validated). Diastolic function was quantified via the parametrized diastolic filling formalism that yields relaxation/viscoelastic (c) and passive/stiffness (k) constants through the analysis of Doppler mitral inflow velocity (E-wave) contours. Effective arterial elastance (Ea) end-systolic elastance (Ees) and ventricular-arterial coupling (defined as the ratio Ees:Ea) were determined using previously published techniques. Wilcoxon matched-pairs signed-rank tests were used for pre-post comparisons. The DASH/SRD reduced clinic and 24-hour brachial systolic pressure (155 ± 35 to 138 ± 30 and 130 ± 16 to 123 ± 18 mm Hg; both P=0.02), and central end-systolic pressure trended lower (116 ± 18 to 111 ± 16 mm Hg; P=0.12). In conjunction, diastolic function improved (c=24.3 ± 5.3 to 22.7 ± 8.1 g/s; P=0.03; k=252 ± 115 to 170 ± 37 g/s(2); P=0.03), Ea decreased (2.0 ± 0.4 to 1.7 ± 0.4 mm Hg/mL; P=0.007), and ventricular-arterial coupling improved (Ees:Ea=1.5 ± 0.3 to 1.7 ± 0.4; P=0.04). CONCLUSIONS: In patients with hypertensive HFPEF, the sodium-restricted DASH diet was associated with favorable changes in ventricular diastolic function, arterial elastance, and ventricular-arterial coupling. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00939640.

Orthostatic hypotension: a common, serious and underrecognized problem in hospitalized patients.

Orthostatic hypotension (OH) is strongly age-dependent, with a prevalence ranging from 5% to 11% in middle age to 30% or higher in the elderly. It is also closely associated with other common chronic diseases, including hypertension, congestive heart failure, diabetes mellitus, and Parkinson's disease. Most studies of OH have been performed in population cohorts or elderly residents of extended care facilities, but in this review, we draw attention to a problem little studied to date: OH in hospitalized patients. The prevalence of OH in all hospitalized patients is not known because most studies have included only older individuals with multiple comorbid diseases, but in some settings as many as 60% of hospitalized adults have postural hypotension. Hospitalized patients are particularly vulnerable to the consequences of OH, particularly falls, because postural blood pressure (BP) regulation may be disturbed by many common acute illnesses as well as by bed rest and drug treatment. The temporal course of OH in hospitalized patients is uncertain, both because the reproducibility of OH is poor and because conditions affecting postural BP regulation may vary during hospitalization. Finally, OH during hospitalization often persists after discharge, where, in addition to creating an ongoing risk of falls and syncope, it is strongly associated with risk of incident cardiovascular complications, including myocardial infarction, heart failure, stroke, and all-cause mortality. Because OH is a common, easily diagnosable, remediable condition with important clinical implications, we encourage caregivers to monitor postural BP change in patients throughout hospitalization.