The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal Mendelian Long QT Syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals we identified 35 common variant QT interval loci, that collectively explain ∼8-10% of QT variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 novel QT loci in 298 unrelated LQTS probands identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode for proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies novel candidate genes for ventricular arrhythmias, LQTS,and SCD.
genome-wide association study; QT interval; Long QT Syndrome; sudden cardiac death; myocardial repolarization; arrhythmias
This article describes and illustrates a novel method of microarray data analysis that couples model-based clustering and binary classification to form clusters of `response-relevant' genes; that is, genes that are informative when discriminating between the different values of the response. Predictions are subsequently made using an appropriate statistical summary of each gene cluster, which we call the `meta-covariate' representation of the cluster, in a probit regression model. We first illustrate this method by analysing a leukaemia expression dataset, before focusing closely on the meta-covariate analysis of a renal gene expression dataset in a rat model of salt-sensitive hypertension. We explore the biological insights provided by our analysis of these data. In particular, we identify a highly influential cluster of 13 genes—including three transcription factors (Arntl, Bhlhe41 and Npas2)—that is implicated as being protective against hypertension in response to increased dietary sodium. Functional and canonical pathway analysis of this cluster using Ingenuity Pathway Analysis implicated transcriptional activation and circadian rhythm signalling, respectively. Although we illustrate our method using only expression data, the method is applicable to any high-dimensional datasets. Expression data are available at ArrayExpress (accession number E-MEXP-2514) and code is available at http://www.dcs.gla.ac.uk/inference/metacovariateanalysis/.
Despite its significant genetic component, the study of hypertension by genome-wide
association presents more challenges than other common complex diseases. Its high
prevalence, heterogeneity, and somewhat unclear definition are the challenges that need
to be overcome on one hand. On the other hand, there are issues of small effect sizes and
pleiotropism that are not specific to hypertension alone but nonetheless magnify the
problems of genetic dissection when coupled with phenotypic misclassification. We
discuss issues of study design and summarise published genome-wide association studies
(GWASs) of hypertension and blood pressure. With careful study design and analysis
success is possible, as demonstrated by the recent large-scale studies. Following these, there
is still further scope to advance the field through high fidelity phenotyping and deep
Preeclampsia is a major cause of maternal morbidity and mortality worldwide. Despite decades of research into the condition, the ability of clinicians to predict preeclampsia prior to the onset of symptoms has not improved significantly. In this review, we will examine the pathophysiology underlying preeclampsia and will look at potential biomarkers for early prediction and diagnosis. In addition, we will explore potential future areas of research into the condition.
To identify novel genes influencing blood pressure response to thiazide diuretic therapy for hypertension, we conducted genome-wide association meta-analyses of ≈1.1 million single nucleotide polymorphisms in a combined sample of 424 European Americans with primary hypertension treated with hydrochlorothiazide from the Pharmacogenomic Evaluation of Antihypertensive Responses Study (N=228) and the Genetic Epidemiology of Responses to Antihypertensive Study (N=196). Polymorphisms associated with blood pressure response at p<10-5 were tested for replication of the associations in independent samples of hydrochlorothiazide-treated European hypertensives. The rs16960228 polymorphism in protein kinase C, alpha replicated for same-direction association with diastolic blood pressure response in the Nordic Diltiazem Study (N=420) and the Genetics of Drug Responsiveness in Essential Hypertension Study (N=206), and the combined four-study meta-analysis p-value achieved genome-wide significance (p=3.3 × 10-8). Systolic/diastolic blood pressure responses were consistently greater in carriers of the rs16960228 A allele than in GG homozygotes (4/4 mmHg greater) across study samples. The rs2273359 polymorphism in the GNAS-EDN3 region also replicated for same-direction association with systolic blood pressure response in the Nordic Diltiazem Study, and the combined three-study meta-analysis p-value approached genome-wide significance (p=5.5 × 10-8). The findings document clinically-important effects of genetic variation at novel loci on blood pressure response to a thiazide diuretic, which may be a basis for individualization of antihypertensive drug therapy and identification of new drug targets.
Hypertension; high blood pressure; antihypertensive therapy/diuretics; hydrochlorothiazide; genomics; pharmacogenomics; protein kinase C
We sought to identify novel pharmacogenetic markers associated with cardiovascular outcomes in patients with hypertension on antihypertensive therapy. We genotyped a 1:4 case:control cohort (n=1345) on the Illumina HumanCVD Beadchip from the International Verapamil SR-Trandolapril Study, where participants were randomized to a β blocker strategy or a calcium channel blocker strategy. Genome-spanning SNP × treatment interaction analyses of non-synonymous SNPs were conducted in white and Hispanic race/ethnic groups. Top hits from whites were tested in Hispanics for consistency. A genetic risk score was constructed from the top three signals and tested in the Nordic Diltiazem study. SIGLEC12 rs16982743 and A1BG rs893184 had a significant interaction with treatment strategy for adverse cardiovascular outcomes (International Verapamil SR-Trandolapril Study whites and Hispanics combined interaction P=0.0038, and 0.0036, respectively). A genetic risk score including rs16982743, rs893184 and rs4525 in F5, was significantly associated with treatment-related adverse cardiovascular outcomes in whites and Hispanics from the International Verapamil SR-Trandolapril Study and in the Nordic Diltiazem study (meta-analysis interaction P=2.39×10−5). In patients with a genetic risk score of zero or 1, calcium channel blocker treatment was associated with lower risk (OR (95% CI) = 0.60 (0.42-0.86)), and in those with a genetic risk score of 2-3, calcium channel blocker treatment was associated with higher risk, OR (95% CI) = 1.31 (1.08-1.59)). These results suggest cardiovascular outcomes may differ based on SIGLEC12, A1BG, F5 genotypes and antihypertensive treatment strategy. These specific genetic associations and our risk score provide insight into a potential approach to personalized antihypertensive treatment selection.
Pharmacogenomics; Hypertension; antihypertensive agents; cardiovascular outcomes; genetic variation; beta-blockers, calcium channel blockers
Familial hypercholesterolaemia (FH) is a common Mendelian condition which, untreated, results in premature coronary heart disease. An estimated 88% of FH cases are undiagnosed in the UK. We previously validated a method for FH mutation detection in a lipid clinic population using next generation sequencing (NGS), but this did not address the challenge of identifying index cases in primary care where most undiagnosed patients receive healthcare. Here, we evaluate the targeted use of NGS as a potential route to diagnosis of FH in a primary care population subset selected for hypercholesterolaemia.
We used microfluidics-based PCR amplification coupled with NGS and multiplex ligation-dependent probe amplification (MLPA) to detect mutations in LDLR, APOB and PCSK9 in three phenotypic groups within the Generation Scotland: Scottish Family Health Study including 193 individuals with high total cholesterol, 232 with moderately high total cholesterol despite cholesterol-lowering therapy, and 192 normocholesterolaemic controls.
Pathogenic mutations were found in 2.1% of hypercholesterolaemic individuals, in 2.2% of subjects on cholesterol-lowering therapy and in 42% of their available first-degree relatives. In addition, variants of uncertain clinical significance (VUCS) were detected in 1.4% of the hypercholesterolaemic and cholesterol-lowering therapy groups. No pathogenic variants or VUCS were detected in controls.
We demonstrated that population-based genetic testing using these protocols is able to deliver definitive molecular diagnoses of FH in individuals with high cholesterol or on cholesterol-lowering therapy. The lower cost and labour associated with NGS-based testing may increase the attractiveness of a population-based approach to FH detection compared to genetic testing with conventional sequencing. This could provide one route to increasing the present low percentage of FH cases with a genetic diagnosis.
Familial hypercholesterolaemia; Total cholesterol; LDLR; Molecular diagnostic testing; Next-generation sequencing; Primary care; Generation Scotland
Hypertension is associated with cerebral small vessel disease (SVD) and with diffuse white matter hyperintensities (WMH) on T2-weighted magnetic resonance imaging (MRI). We tested whether stroke-prone spontaneously hypertensive rats (SHRSP), a model of chronic hypertension, exhibit WMH. Male SHRSP (age 10 months) without stroke symptoms were compared with age-matched male WKY rats. Stroke-prone spontaneously hypertensive rats exhibited no WMH on MRI scans (T2, T2*, diffusion tensor imaging) and no neuropathological lesions. While leptomeningeal arteries exhibited fibrohyaline wall thickening, with decreased smooth muscle actin relative to WKY, deep penetrating arterioles within the caudate nuclei had no vasculopathy. We conclude that WMH are not an obligate feature of stroke-free SHRSP aged up to 10 months.
experimental; hypertension; immunohistochemistry; magnetic resonance; neuropathology; white matter disease
Genetic mapping on fully sequenced individuals is transforming our understanding of the relationship between molecular variation and variation in complex traits. Here we report a combined sequence and genetic mapping analysis in outbred rats that maps 355 quantitative trait loci for 122 phenotypes. We identify 35 causal genes involved in 31 phenotypes, implicating novel genes in models of anxiety, heart disease and multiple sclerosis. The relation between sequence and genetic variation is unexpectedly complex: at approximately 40% of quantitative trait loci a single sequence variant cannot account for the phenotypic effect. Using comparable sequence and mapping data from mice, we show the extent and spatial pattern of variation in inbred rats differ significantly from those of inbred mice, and that the genetic variants in orthologous genes rarely contribute to the same phenotype in both species.
Age-related macular degeneration (AMD) is a leading cause of visual loss in Western populations. Susceptibility is influenced by age, environmental and genetic factors. Known genetic risk loci do not account for all the heritability. We therefore carried out a genome-wide association study of AMD in the UK population with 893 cases of advanced AMD and 2199 controls. This showed an association with the well-established AMD risk loci ARMS2 (age-related maculopathy susceptibility 2)–HTRA1 (HtrA serine peptidase 1) (P =2.7 × 10−72), CFH (complement factor H) (P =2.3 × 10−47), C2 (complement component 2)–CFB (complement factor B) (P =5.2 × 10−9), C3 (complement component 3) (P =2.2 × 10−3) and CFI (P =3.6 × 10−3) and with more recently reported risk loci at VEGFA (P =1.2 × 10−3) and LIPC (hepatic lipase) (P =0.04). Using a replication sample of 1411 advanced AMD cases and 1431 examined controls, we confirmed a novel association between AMD and single-nucleotide polymorphisms on chromosome 6p21.3 at TNXB (tenascin XB)–FKBPL (FK506 binding protein like) [rs12153855/rs9391734; discovery P =4.3 × 10−7, replication P =3.0 × 10−4, combined P =1.3 × 10−9, odds ratio (OR) = 1.4, 95% confidence interval (CI) = 1.3–1.6] and the neighbouring gene NOTCH4 (Notch 4) (rs2071277; discovery P =3.2 × 10−8, replication P =3.8 × 10−5, combined P =2.0 × 10−11, OR = 1.3, 95% CI = 1.2–1.4). These associations remained significant in conditional analyses which included the adjacent C2–CFB locus. TNXB, FKBPL and NOTCH4 are all plausible AMD susceptibility genes, but further research will be needed to identify the causal variants and determine whether any of these genes are involved in the pathogenesis of AMD.
Chronic kidney disease (CKD) and coronary artery disease (CAD) are independently associated with increased vascular stiffness. We examined whether renal function contributes to vascular stiffness independently of CAD status.
We studied 160 patients with CAD and 169 subjects without CAD. The 4-variable MDRD formula was used to estimate glomerular filtration rate (eGFR); impaired renal function was defined as eGFR <60 mL/min. Carotid-femoral pulse wave velocity (PWV) was measured with the SphygmoCor® device. Circulating biomarkers were assessed in plasma using xMAP® multiplexing technology.
Patients with CAD and impaired renal function had greater PWV compared to those with CAD and normal renal function (10.2 [9.1;11.2] vs 7.3 [6.9;7.7] m/s; P < 0.001). In all patients, PWV was a function of eGFR (β = −0.293; P < 0.001) even after adjustment for age, sex, systolic blood pressure, body mass index and presence or absence of CAD. Patients with CAD and impaired renal function had higher levels of adhesion and inflammatory molecules including E-selectin and osteopontin (all P < 0.05) compared to those with CAD alone, but had similar levels of markers of oxidative stress.
Renal function is a determinant of vascular stiffness even in patients with severe atherosclerotic disease. This was paralleled by differences in markers of cell adhesion and inflammation. Increased vascular stiffness may therefore be linked to inflammatory remodeling of the vasculature in people with impaired renal function, irrespective of concomitant atherosclerotic disease.
Coronary artery disease; Chronic kidney disease; Vascular stiffness
Anaemia is a chief determinant of globalill health, contributing to cognitive impairment, growth retardation and impaired physical capacity. To understand further the genetic factors influencing red blood cells, we carried out a genome-wide association study of haemoglobin concentration and related parameters in up to 135,367 individuals. Here we identify 75 independent genetic loci associated with one or more red blood cell phenotypes at P <10−8, which together explain 4–9% of the phenotypic variance per trait. Using expression quantitative trait loci and bioinformatic strategies, we identify 121 candidate genes enriched in functions relevant to red blood cell biology. The candidate genes are expressed preferentially in red blood cell precursors, and 43 have haematopoietic phenotypes in Mus musculus or Drosophila melanogaster. Through open-chromatin and coding-variant analyses we identify potential causal genetic variants at 41 loci. Our findings provide extensive new insights into genetic mechanisms and biological pathways controlling red blood cell formation and function.
The aim of the present study was to determine whether the endothelial dysfunction associated with CAD (coronary artery disease) and T2D (Type 2 diabetes mellitus) is concomitant with elevated mtROS (mitochondrial reactive oxygen species) production in the endothelium and establish if this, in turn, regulates the activity of endothelial AMPK (AMP-activated protein kinase). We investigated endothelial function, mtROS production and AMPK activation in saphenous veins from patients with advanced CAD. Endothelium-dependent vasodilation was impaired in patients with CAD and T2D relative to those with CAD alone. Levels of mitochondrial H2O2 and activity of AMPK were significantly elevated in primary HSVECs (human saphenous vein endothelial cells) from patients with CAD and T2D compared with those from patients with CAD alone. Incubation with the mitochondria-targeted antioxidant, MitoQ10 significantly reduced AMPK activity in HSVECs from patients with CAD and T2D but not in cells from patients with CAD alone. Elevated mtROS production in the endothelium of patients with CAD and T2D increases AMPK activation, supporting a role for the kinase in defence against oxidative stress. Further investigation is required to determine whether pharmacological activators of AMPK will prove beneficial in the attenuation of endothelial dysfunction in patients with CAD and T2D.
AMP-activated protein kinase (AMPK); coronary artery disease (CAD); diabetes; endothelium; mitochondrion; oxidative stress; AICAR, 5-amino-4-imidazolecarboxamide riboside; AMPK, AMP-activated protein kinase; BMI, body mass index; CABG, coronary artery bypass graft; CAD, coronary artery disease; CaMKK, Ca2+/calmodulin-dependent kinase kinase; CVD, cardiovascular disease; 2DG, 2-deoxy-D-glucose; DTPP, decyl triphenylphosphonium bromide; eNOS, endothelial nitric oxide synthase; GAPDH, encoding glyceraldehyde-3-phosphate dehydrogenase; HbA1c, glycated haemoglobin; HDL, high-density lipoprotein; HSVEC, human saphenous vein endothelial cell; HUVEC, human umbilical vein endothelial cell; LDL, low-density lipoprotein; ROS, reactive oxygen species; mtROS, mitochondrial ROS; PRKAA1, encoding the AMPK-α1 catalytic subunit; SOD, superoxide dismutase; T2D, Type 2 diabetes; vWF, von Willebrand factor
Establishing biochemical markers of pre-hypertension and early hypertension could help earlier diagnostics and therapeutic intervention. We assess dynamics of junctional adhesion molecule-A (JAM-A) expression in rat models of hypertension and test whether JAM-A expression could be driven by angiotensin (ANG) II and whether JAM-A contributes to the progression of hypertension. We also compare JAM-A expression in normo- and hypertensive humans.
Methods and results
In pre-hypertensive and spontaneously hypertensive rats (SHRs), JAM-A protein was overexpressed in the brainstem microvasculature, lung, liver, kidney, spleen, and heart. JAM-A upregulation at early and late stages was even greater in the stroke-prone SHR. However, JAM-A was not upregulated in leucocytes and platelets of SHRs. In Goldblatt 2K-1C hypertensive rats, JAM-A expression was augmented before any increase in blood pressure, and similarly JAM-A upregulation preceded hypertension caused by peripheral and central ANG II infusions. In SHRs, ANG II type 1 (AT1) receptor antagonism reduced JAM-A expression, but the vasodilator hydralazine did not. Body-wide downregulation of JAM-A with Vivo-morpholinos in juvenile SHRs delayed the progression of hypertension. In the human saphenous vein, JAM-A mRNA was elevated in hypertensive patients with untreated hypertension compared with normotensive patients but reduced in patients treated with renin–angiotensin system antagonists.
Body-wide upregulation of JAM-A in genetic and induced models of hypertension in the rat precedes the stable elevation of arterial pressure. JAM-A upregulation may be triggered by AT1 receptor-mediated signalling. An association of JAM-A with hypertension and sensitivity to blockers of ANG II signalling were also evident in humans. We suggest a prognostic and possibly a pathogenic role of JAM-A in arterial hypertension.
Adhesion molecules; JAM-A; Hypertension; Angiotensin; Vasculature
Essential hypertension is a multi-factorial disorder and is the main risk factor for renal and cardiovascular complications. The research on the genetics of hypertension has been frustrated by the small predictive value of the discovered genetic variants. The HYPERGENES Project investigated associations between genetic variants and essential hypertension pursuing a two-stage study by recruiting cases and controls from extensively characterized cohorts recruited over many years in different European regions.
The discovery phase consisted of 1,865 cases and 1,750 controls genotyped with 1M Illumina array. Best hits were followed up in a validation panel of 1,385 cases and 1,246 controls that were genotyped with a custom array of 14,055 markers. We identified a new hypertension susceptibility locus (rs3918226) in the promoter region of the endothelial nitric oxide synthase (eNOS) gene (odds ratio 1.54; 95% CI 1.37-1.73; combined p=2.58·10−13). A meta-analysis, using other in-silico/de novo genotyping data for a total of 21714 subjects, resulted in an overall odds ratio of 1.34 (95% CI 1.25-1.44, p=1.032·10−14). The quantitative analysis on a population-based sample revealed an effect size of 1.91 (95% CI 0.16-3.66) for systolic and 1.40 (95% CI 0.25-2.55) for diastolic blood pressure. We identified in-silico a potential binding site for ETS transcription-factors directly next to rs3918226, suggesting a potential modulation of eNOS expression. Biological evidence links eNOS with hypertension, as it is a critical mediator of cardiovascular homeostasis and blood pressure control via vascular tone regulation. This finding supports the hypothesis that there may be a causal genetic variation at this locus.
genetic epidemiology; risk factors; genetics-association studies; nitric oxide; Essential Hypertension
QRS interval on the electrocardiogram reflects ventricular depolarization and conduction time, and is a risk factor for mortality, sudden death, and heart failure. We performed a genome-wide association meta-analysis in 40,407 European-descent individuals from 14 studies, with further genotyping in 7170 additional Europeans, and identified 22 loci associated with QRS duration (P < 5 × 10−8). These loci map in or near genes in pathways with established roles in ventricular conduction such as sodium channels, transcription factors, and calcium-handling proteins, but also point to novel biologic processes, such as kinase inhibitors and genes related to tumorigenesis. We demonstrate that SCN10A, a gene at our most significant locus, is expressed in the mouse ventricular conduction system, and treatment with a selective SCN10A blocker prolongs QRS duration. These findings extend our current knowledge of ventricular depolarization and conduction.
QRS interval; ECG; quantitative trait; genome-wide association study
Rationale: Genomic loci are associated with FEV1 or the ratio of FEV1 to FVC in population samples, but their association with chronic obstructive pulmonary disease (COPD) has not yet been proven, nor have their combined effects on lung function and COPD been studied.
Objectives: To test association with COPD of variants at five loci (TNS1, GSTCD, HTR4, AGER, and THSD4) and to evaluate joint effects on lung function and COPD of these single-nucleotide polymorphisms (SNPs), and variants at the previously reported locus near HHIP.
Methods: By sampling from 12 population-based studies (n = 31,422), we obtained genotype data on 3,284 COPD case subjects and 17,538 control subjects for sentinel SNPs in TNS1, GSTCD, HTR4, AGER, and THSD4. In 24,648 individuals (including 2,890 COPD case subjects and 13,862 control subjects), we additionally obtained genotypes for rs12504628 near HHIP. Each allele associated with lung function decline at these six SNPs contributed to a risk score. We studied the association of the risk score to lung function and COPD.
Measurements and Main Results: Association with COPD was significant for three loci (TNS1, GSTCD, and HTR4) and the previously reported HHIP locus, and suggestive and directionally consistent for AGER and TSHD4. Compared with the baseline group (7 risk alleles), carrying 10–12 risk alleles was associated with a reduction in FEV1 (β = –72.21 ml, P = 3.90 × 10−4) and FEV1/FVC (β = –1.53%, P = 6.35 × 10−6), and with COPD (odds ratio = 1.63, P = 1.46 × 10−5).
Conclusions: Variants in TNS1, GSTCD, and HTR4 are associated with COPD. Our highest risk score category was associated with a 1.6-fold higher COPD risk than the population average score.
FEV1; FVC; genome-wide association study; modeling risk
A sexual dimorphism exists in the incidence and prevalence of coronary artery disease—men are more commonly affected than are age-matched women. We explored the role of the Y chromosome in coronary artery disease in the context of this sexual inequity.
We genotyped 11 markers of the male-specific region of the Y chromosome in 3233 biologically unrelated British men from three cohorts: the British Heart Foundation Family Heart Study (BHF-FHS), West of Scotland Coronary Prevention Study (WOSCOPS), and Cardiogenics Study. On the basis of this information, each Y chromosome was tracked back into one of 13 ancient lineages defined as haplogroups. We then examined associations between common Y chromosome haplogroups and the risk of coronary artery disease in cross-sectional BHF-FHS and prospective WOSCOPS. Finally, we undertook functional analysis of Y chromosome effects on monocyte and macrophage transcriptome in British men from the Cardiogenics Study.
Of nine haplogroups identified, two (R1b1b2 and I) accounted for roughly 90% of the Y chromosome variants among British men. Carriers of haplogroup I had about a 50% higher age-adjusted risk of coronary artery disease than did men with other Y chromosome lineages in BHF-FHS (odds ratio 1·75, 95% CI 1·20–2·54, p=0·004), WOSCOPS (1·45, 1·08–1·95, p=0·012), and joint analysis of both populations (1·56, 1·24–1·97, p=0·0002). The association between haplogroup I and increased risk of coronary artery disease was independent of traditional cardiovascular and socioeconomic risk factors. Analysis of macrophage transcriptome in the Cardiogenics Study revealed that 19 molecular pathways showing strong differential expression between men with haplogroup I and other lineages of the Y chromosome were interconnected by common genes related to inflammation and immunity, and that some of them have a strong relevance to atherosclerosis.
The human Y chromosome is associated with risk of coronary artery disease in men of European ancestry, possibly through interactions of immunity and inflammation.
British Heart Foundation; UK National Institute for Health Research; LEW Carty Charitable Fund; National Health and Medical Research Council of Australia; European Union 6th Framework Programme; Wellcome Trust.
Background and Purpose
Stroke-prone spontaneously hypertensive rats (SHRSP) are a highly pertinent stroke model with increased sensitivity to focal ischemia compared with the normotensive reference strain (Wistar-Kyoto rats; WKY). Study aims were to investigate temporal changes in the ischemic penumbra in SHRSP compared with WKY.
Permanent middle cerebral artery occlusion was induced with an intraluminal filament. Diffusion- (DWI) and perfusion- (PWI) weighted magnetic resonance imaging was performed from 1 to 6 hours after stroke, with the PWI-DWI mismatch used to define the penumbra and thresholded apparent diffusion coefficient (ADC) maps used to define ischemic damage.
There was significantly more ischemic damage in SHRSP than in WKY from 1 to 6 hours after stroke. The perfusion deficit remained unchanged in WKY (39.9±6 mm2 at 1 hour, 39.6±5.3 mm2 at 6 hours) but surprisingly increased in SHRSP (43.9±9.2 mm2 at 1 hour, 48.5±7.4 mm2 at 6 hours; P=0.01). One hour after stroke, SHRSP had a significantly smaller penumbra (3.4±5.8 mm2) than did WKY (9.7±3.8, P=0.03). In WKY, 56% of the 1-hour penumbra area was incorporated into the ADC lesion by 6 hours, whereas in SHRSP, the small penumbra remained static owing to the temporal increase in both ADC lesion size and perfusion deficit.
First, SHRSP have significantly more ischemic damage and a smaller penumbra than do WKY within 1 hour of stroke; second, the penumbra is recruited into the ADC abnormality over time in both strains; and third, the expanding perfusion deficit in SHRSP predicts more tissue at risk of infarction. These results have important implications for management of stroke patients with preexisting hypertension and suggest ischemic damage could progress at a faster rate and over a longer time frame in the presence of hypertension.
ischemic penumbra; stroke; hypertension; magnetic resonance imaging
The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10−8) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10−8). The top IBC association for SBP was rs2012318 (P= 6.4 × 10−6) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10−6) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexity.
Serum concentrations of total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) are among the most important risk factors for coronary artery disease (CAD) and are targets for therapeutic intervention. We screened the genome for common variants associated with serum lipids in >100,000 individuals of European ancestry. Here we report 95 significantly associated loci (P < 5 × 10-8), with 59 showing genome-wide significant association with lipid traits for the first time. The newly reported associations include single nucleotide polymorphisms (SNPs) near known lipid regulators (e.g., CYP7A1, NPC1L1, and SCARB1) as well as in scores of loci not previously implicated in lipoprotein metabolism. The 95 loci contribute not only to normal variation in lipid traits but also to extreme lipid phenotypes and impact lipid traits in three non-European populations (East Asians, South Asians, and African Americans). Our results identify several novel loci associated with serum lipids that are also associated with CAD. Finally, we validated three of the novel genes—GALNT2, PPP1R3B, and TTC39B—with experiments in mouse models. Taken together, our findings provide the foundation to develop a broader biological understanding of lipoprotein metabolism and to identify new therapeutic opportunities for the prevention of CAD.
Essential hypertension affects 20 to 30% of the population worldwide and contributes significantly to cardiovascular mortality and morbidity. Heridability of blood pressure is around 15 to 40% but there are also substantial environmental factors affecting blood pressure variability. It is assumed that blood pressure is under the control of a large number of genes each of which has only relatively mild effects. It has therefore been difficult to discover the genes that contribute to blood pressure variation using traditional approaches including candidate gene studies and linkage studies. Animal models of hypertension, particularly in the rat, have led to the discovery of quantitative trait loci harbouring one or several hypertension related genes, but translation of these findings into human essential hypertension remains challenging. Recent development of genotyping technology made large scale genome-wide association studies possible. This approach and the study of monogenic forms of hypertension has led to the discovery of novel and robust candidate genes for human essential hypertension, many of which require functional analysis in experimental models.
GWAS, Genome-wide association study; QTL, Quantitative trait locus; SHR, Spontaneously hypertensive rat; SHRSP, Stroke-prone spontaneously hypertensive rat; SNP, Single nucleotide polymorphism; WTCCC, Wellcome Trust Case Control Consortium; Hypertension; Genetics; Rodents; Human
Hypertension is a heritable and major contributor to the global burden of disease. The sum of rare and common genetic variants robustly identified so far explain only 1%–2% of the population variation in BP and hypertension. This suggests the existence of more undiscovered common variants. We conducted a genome-wide association study in 1,621 hypertensive cases and 1,699 controls and follow-up validation analyses in 19,845 cases and 16,541 controls using an extreme case-control design. We identified a locus on chromosome 16 in the 5′ region of Uromodulin (UMOD; rs13333226, combined P value of 3.6×10−11). The minor G allele is associated with a lower risk of hypertension (OR [95%CI]: 0.87 [0.84–0.91]), reduced urinary uromodulin excretion, better renal function; and each copy of the G allele is associated with a 7.7% reduction in risk of CVD events after adjusting for age, sex, BMI, and smoking status (H.R. = 0.923, 95% CI 0.860–0.991; p = 0.027). In a subset of 13,446 individuals with estimated glomerular filtration rate (eGFR) measurements, we show that rs13333226 is independently associated with hypertension (unadjusted for eGFR: 0.89 [0.83–0.96], p = 0.004; after eGFR adjustment: 0.89 [0.83–0.96], p = 0.003). In clinical functional studies, we also consistently show the minor G allele is associated with lower urinary uromodulin excretion. The exclusive expression of uromodulin in the thick portion of the ascending limb of Henle suggests a putative role of this variant in hypertension through an effect on sodium homeostasis. The newly discovered UMOD locus for hypertension has the potential to give new insights into the role of uromodulin in BP regulation and to identify novel drugable targets for reducing cardiovascular risk.
Hypertension is the leading contributor to global mortality with a global prevalence of 26.4% in 2000, projected to increase to 29.2% by 2025. While 50%–60% of population variation in blood pressure can be attributable to additive genetic factors, all the genetic variants robustly identified so far explain only 1%–2% of the population variance indicating the presence of additional undiscovered risk variants. Using an extreme case-control strategy, we have discovered a SNP in the promoter region of the uromodulin gene (UMOD) to be associated with hypertension (minor allele protective against hypertension). We then validated this association using large-scale population and case-control studies, where similar extreme criteria for selection of cases and controls have been used (21,466 cases and 18,240 controls). As the locus was related to uromodulin, a protein exclusively expressed in the kidneys, we show that the association is independent of renal dysfunction. We also show preliminary evidence that the SNP allele which is protective against hypertension is also protective against cardiovascular events in 26,654 Swedish subjects followed-up for 12 years. The newly discovered UMOD locus for hypertension has the potential to give unique insights into the role of uromodulin in BP regulation and to identify novel drugable targets.
The pathogenesis of diabetes mellitus (DM) is variable, comprising different inflammatory and immune responses. Proteome analysis holds the promise of delivering insight into the pathophysiological changes associated with diabetes. Recently, we identified and validated urinary proteomics biomarkers for diabetes. Based on these initial findings, we aimed to further validate urinary proteomics biomarkers specific for diabetes in general, and particularity associated with either type 1 (T1D) or type 2 diabetes (T2D).
Therefore, the low-molecular-weight urinary proteome of 902 subjects from 10 different centers, 315 controls and 587 patients with T1D (n = 299) or T2D (n = 288), was analyzed using capillary-electrophoresis mass-spectrometry. The 261 urinary biomarkers (100 were sequenced) previously discovered in 205 subjects were validated in an additional 697 subjects to distinguish DM subjects (n = 382) from control subjects (n = 315) with 94% (95% CI: 92–95) accuracy in this study. To identify biomarkers that differentiate T1D from T2D, a subset of normoalbuminuric patients with T1D (n = 68) and T2D (n = 42) was employed, enabling identification of 131 biomarker candidates (40 were sequenced) differentially regulated between T1D and T2D. These biomarkers distinguished T1D from T2D in an independent validation set of normoalbuminuric patients (n = 108) with 88% (95% CI: 81–94%) accuracy, and in patients with impaired renal function (n = 369) with 85% (95% CI: 81–88%) accuracy. Specific collagen fragments were associated with diabetes and type of diabetes indicating changes in collagen turnover and extracellular matrix as one hallmark of the molecular pathophysiology of diabetes. Additional biomarkers including inflammatory processes and pro-thrombotic alterations were observed.
These findings, based on the largest proteomic study performed to date on subjects with DM, validate the previously described biomarkers for DM, and pinpoint differences in the urinary proteome of T1D and T2D, indicating significant differences in extracellular matrix remodeling.