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Background: Elevated sympathetic activity is associated with kidney dysfunction. Here we used twin pairs to probe heritability of GFR and its genetic covariance with other traits. Methods: We evaluated renal and adrenergic phenotypes in twins. GFR was estimated by CKD-EPI algorithm. Heritability and genetic covariance of eGFR and associated risk traits were estimated by variance-components. Meta-analysis probed reproducibility of DBH genetic effects. Effect of DBH genetic variation on renal disease was tested in the NIDDK-AASK cohort. Results: Norepinephrine secretion rose across eGFR tertiles while eGFR fell (p<0.0001). eGFR was heritable, at h2 = 67.3±4.7% (p = 3.0E-18), as were secretion of norepinephrine (h2 = 66.5±5.0%, p = 3.2E-16) and dopamine (h2 = 56.5±5.6%, p = 1.8E-13), and eGFR displayed genetic co-determination (covariance) with norepinephrine (ρG = −0.557±0.088, p = 1.11E-08) as well as dopamine (ρG = −0.223±0.101, p = 2.3E-02). Since dopamine β-hydroxylase (DBH) catalyzes conversion of dopamine to norepinephrine, we studied functional variation at DBH; DBH promoter haplotypes predicted transcriptional activity (p<0.001), plasma DBH (p<0.0001) and norepinephrine (p = 0.0297) secretion; transcriptional activity was inversely (p<0.0001) associated with basal eGFR. Meta-analysis validated DBH haplotype effects on eGFR across 3 samples. In NIDDK-AASK, we established a role for DBH promoter variation in long-term renal decline rate (GFR slope, p = 0.003). Conclusions: The heritable GFR trait shares genetic determination with catecholamines, suggesting new pathophysiologic, diagnostic and therapeutic approaches towards disorders of GFR as well as CKD. Adrenergic activity may play a role in progressive renal decline, and genetic variation at DBH may assist in profiling subjects for rational preventive treatment. [ABSTRACT FROM AUTHOR]

Background: Kallikrein-1 (KLK1) is a highly conserved serine protease that is expressed in the kidney and involved in blood pressure regulation. The activity of this enzyme is diminished in acute kidney injury (AKI). Methods: We first evaluated the potential role of functional multiallelic KLK1 promoter gene polymorphisms in a case-control study of 481 subjects (214 hospitalized patients with AKI of mixed causes and 267 healthy subjects). The complex, multiallelic G/C-rich repeat region of the proximal KLK1 promoter was determined by direct Sanger/capillary resequencing. Results: 16 alleles were identified in a complex, polymorphic G/C-rich region of the KLK1 proximal promoter; 5 of these alleles (F, G, H, I, and K) were associated with development of AKI. Alleles I and G were classified as risk-alleles (unadjusted OR 1.86; 95% CI 1.23, 2.81; p = 0.003), whereas alleles F, H, and K were classified as protective-alleles (unadjusted OR 0.32; 95% CI 0.22, 0.46; p < 0.001) according to their directional association with development of AKI. After adjustment for sex, race, preexisting chronic kidney disease and APACHE II score, the KLK1 risk-allele (I or G) carrier state was associated with the composite of ≥2-fold increase in serum creatinine, oliguria, or dialysis requirement (adjusted OR 2.71; 95% CI 1.14, 6.44; p = 0.02). The KLK1 risk-allele carrier state was also marginally associated with the composite of ≥2-fold increase in serum creatinine, oliguria, dialysis requirement, or in-hospital death (adjusted OR 2.33; 95% CI 0.98, 5.52; p = 0.06). Conclusions:KLK1 promoter polymorphisms are associated with development of AKI and adverse outcomes. Further studies are needed to validate these findings. Copyright © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background. Hyperhomocysteinemia is associated with increased venous thrombosis and cardiovascular disease (CVD). Mutations in the human methylenetetrahydrofolate reductase (MTHFR) gene have been associated with increased homocysteine levels and risks of CVD in various populations including those with kidney disease. Here, we evaluated the influence of MTHFR variants on progressive loss of kidney function. Methods. We analyzed 821 subjects with hypertensive nephrosclerosis from the longitudinal National Institute of Diabetes and Digestive and Kidney Diseases African-American Study of Kidney Disease and Hypertension (AASK) Trial to determine whether decline in glomerular filtration rate (GFR) over ∼4.2 years was predicted by common genetic variation within MTHFR at non-synonymous positions C677T (Ala222Val) and A1298C (Glu429Ala) or by MTHFR haplotypes. The effect on GFR decline was then supported by a study of 1333 subjects from the San Diego Veterans Affairs Hypertension Cohort (VAHC), followed over ∼4.5 years. Linear effect models were utilized to determine both genotype [single-nucleotide polymorphism (SNP)] and genotype (SNP)-by-time interactions. Results. In AASK, the polymorphism at A1298C predicted the rate of GFR decline: A1298/A1298 major allele homozygosity resulted in a less pronounced decline of GFR, with a significant SNP-by-time interaction. An independent follow-up study in the San Diego VAHC subjects supports that A1298/A1298 homozygotes have the greatest estimated GFR throughout the study. Haplotype analysis with C677T yielded concurring results. Conclusion. We conclude that the MTHFR-coding polymorphism at A1298C is associated with renal decline in African-Americans with hypertensive nephrosclerosis and is supported by a veteran cohort with a primary care diagnosis of hypertension. Further investigation is needed to confirm such findings and to determine what molecular mechanism may contribute to this association. [ABSTRACT FROM PUBLISHER]

Genetic strategies such as linkage analysis and quantitative trait locus (QTL) mapping have identified a multitude of loci implicated in the pathogenesis of hypertension in the spontaneously hypertensive rat (SHR). While several candidate genetic regions have been identified in the SHR and its control, the Wistar--Kyoto rat (WKY), systematic follow-up of candidate identification with polymorphism discovery has not been widespread. In the current report, we develop a data-mining strategy to identify candidate genes for hypertension in the SHR, and then sequence each gene in the SHR and WKY strains. We integrate blood pressure QTL data, microarray data and data-mining methods. First, we determined the set of genes differentially expressed in SHR and WKY adrenal glands. Next, the chromosomal position of all differentially expressed genes was compared with peak marker position of all reported SHR blood pressure QTLs. We also identified the set of differentially expressed genes with the most extreme fold-change. Finally, the QTL positional candidates and the genes with extreme differential expression were proposed as candidate genes if they had biologically plausible roles in hypertensive pathology. We identified seven candidate genes that merit resequencing (catechol- O-methyltransferase [Comt], chromogranin A [Chga], dopamine beta-hydroxylase [Dbh], electron transferring flavoprotein dehydrogenase [Etfdh], endothelin receptor type B [Ednrb], neuropeptide Y [Npy] and phenylethanolamine- N-methyltransferase [Pnmt]), and then discovered polymorphism in four of these seven candidate genes. Chga is proposed as the strongest candidate for additional functional investigation. Our method for candidate gene identification is portable and can be applied to microarray data from any tissue, in any disease model with a QTL database. [ABSTRACT FROM AUTHOR]

Background/Aims: The catecholaminergic pathway is important in the physical stress response; however, its role is not well understood in acute kidney injury (AKI). We studied single nucleotide polymorphisms (SNPs) of phenylethanolamine N-methyltransferase (PNMT), the terminal enzyme of the catecholaminergic pathway, and their association with adverse outcomes in AKI. Methods: We performed a case-control study of 961 Caucasian subjects (194 with AKI and 767 controls). The PNMT promoter G–161A (rs876493) and coding A+1543G (rs5638) SNPs were genotyped and haplotypes generated. The outcomes of interest were the development of AKI, in-hospital mortality, dialysis requirement, oliguria, and hemodynamic shock. Urine catecholamines were measured in cases to explore genotype-phenotype correlations. Results: The PNMT +1543 G allele was associated with AKI [odds ratio (OR) 2.19, 95% confidence interval (CI): 1.04–4.60]. For AKI cases, each PNMT –161 A allele was associated with lower mortality (OR 0.58, 95% CI: 0.35–0.99) and hemodynamic shock (OR 0.63, 95% CI: 0.40–1.00). The PNMT +1543 G allele was associated with oliguria (OR 3.35, 95% CI: 1.13–9.95). Urine adrenaline was associated with increased hemodynamic shock and mortality, but was lowest in PNMT –161 A/A carriers. Conclusion: In Caucasians, PNMT SNPs are associated with the development of AKI, disease severity, and in-hospital mortality. The adrenergic pathway provides another area of focus in the study of AKI. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

BackgroundAfrican Americans have a disproportionate burden of hypertension and comorbid disease. Pharmacogenetic markers of blood pressure response have yet to be defined clearly. This study explores the association between G-protein-coupled receptor kinase type 4 (GRK4) variants and blood pressure response to metoprolol among African Americans with early hypertensive nephrosclerosis.MethodsParticipants from the African American Study of Kidney Disease and Hypertension (AASK) trial were genotyped at three GRK4 polymorphisms: R65L, A142V, and A486V. A Cox proportional hazards model, stratified by gender, was used to determine the relationship between GRK4 variants and time to reach a mean arterial pressure (MAP) of 107 mm Hg, adjusted for other predictors of blood pressure response. Potential interactions between the three polymorphisms were explored by analyzing the effects of gene haplotypes and by stratifying the analysis by neighboring sites.ResultsThe hazard ratio with 95% confidence interval by A142V among men randomized to a usual MAP (102–107 mm Hg) was 1.54 (1.11–2.44; P = 0.0009). The hazard ratio by A142V with R65/L65 or L65/L65 was 2.14 (1.35–3.39; P = 0.001). Haplotype analyses were consistent but inconclusive. There was no association between A142V and blood pressure response among women.ConclusionsResults suggest a sex-specific relationship between GRK4 A142V and blood pressure response among African-American men with early hypertensive nephrosclerosis. Men with a GRK4 A142 were less responsive to metoprolol if they had a GRK4 L65 variant. The effect of GRK4 variants and blood pressure response to metoprolol should be studied in larger clinical trials.American Journal of Hypertension 2009; doi:10.1038/ajh.2008.341American Journal of Hypertension (2009); 22, 3, 332–338. doi:10.1038/ajh.2008.341 [ABSTRACT FROM AUTHOR]

Tyrosine hydroxylase (TH) is the rate-limiting enzyme in catecholamine biosynthesis. Does common genetic variation at human TH alter autonomic activity and predispose to cardiovascular disease? We undertook systematic polymorphism discovery at the TH locus, and then tested variants for contributions to sympathetic function and blood pressure. We resequenced 80 ethnically diverse individuals across the TH locus. One hundred seventy-two twin pairs were evaluated for sympathetic traits, including catecholamine production and environmental (cold) stress responses. To evaluate hypertension, we genotyped subjects selected from the most extreme diastolic blood pressure percentiles in the population. Human TH promoter haplotype/reporter plasmids were transfected into chromaffin cells. Forty-nine single nucleotide polymorphisms (SNPs) and one tetranucleotide repeat were discovered, but coding region polymorphism did not account for common phenotypic variation. A block of linkage disequilibrium spanned four common variants in the proximal promoter. Catecholamine secretory traits were significantly heritable, as were stress-induced blood pressure changes. In the TH promoter, significant associations were found for urinary catecholamine excretion, as well as blood pressure response to stress. TH promoter haplotype #2 (TGGG) showed pleiotropy, increasing both norepinephrine excretion and blood pressure during stress. In hypertension, a case–control study (1266 subjects, 53% women) established the effect of C-824T in determination of blood pressure. We conclude that human catecholamine secretory traits are heritable, displaying joint genetic determination (pleiotropy) with autonomic activity and finally with blood pressure in the population. Catecholamine secretion is influenced by genetic variation in the adrenergic pathway encoding catecholamine synthesis, especially at the classically rate-limiting step, TH. The results suggest novel pathophysiological links between a key adrenergic locus, catecholamine metabolism, and blood pressure, and suggest new strategies to approach the mechanism, diagnosis, and treatment of systemic hypertension. [ABSTRACT FROM AUTHOR]

The pore-forming α-subunit, Kv1.5, forms functional voltage-gated K+ (Kv) channels in human pulmonary artery smooth muscle cells (PASMC) and plays an important role in regulating membrane potential, vascular tone, and PASMC proliferation and apoptosis. Inhibited Kv channel expression and function have been implicated in PASMC from patients with idiopathic pulmonary arterial hypertension (IPAH). Here, we report that overexpression of the Kv1.5 channel gene (KCNA5) in human PASMC and other cell lines produced a 15-pS single channel current and a large whole cell current that was sensitive to 4-aminopyridine. Extracellular application of nicotine, bepridil, correolide, and endothelin-1 (ET-1) all significantly and reversibly reduced the Kv1.5 currents, while nicotine and bepridil also accelerated the inactivation kinetics of the currents. Furthermore, we sequenced KCNA5 from IPAH patients and identified 17 single-nucleotide polymorphisms (SNPs); 7 are novel SNPs. There are 12 SNPs in the upstream 5′ region, 2 of which may alter transcription factor binding sites in the promoter, 2 nonsynonymous SNPs in the coding region, 2 SNPs in the 3′-untranslated region, and 1 SNP in the 3′-flanking region. Two SNPs may correlate with the nitric oxide-mediated decrease in pulmonary arterial pressure. Allele frequency of two other SNPs in patients with a history of fenfluramine and phentermine use was significantly different from patients who have never taken the anorexigens. These results suggest that 1) Kv1.5 channels are modulated by various agonists (e.g., nicotine and ET-1); 2) novel SNPs in KCNA5 are present in IPAH patients; and 3) SNPs in the promoter and translated regions of KCNA5 may underlie the altered expression and/or function of Kv1.5 channels in PASMC from IPAH patients. [ABSTRACT FROM AUTHOR]

Background and Objectives: Activation of α2-adrenergic receptors regulates a broad spectrum of physiologic responses, including blood pressure (centrally and peripherally), sedation, analgesia, insulin release, renal function, cognition, and behavior. The purpose of this study was to explore systematically the local vascular responses in humans triggered by a highly selective α2-adrenergic agonist (azepexole [B-HT 933]) and whether such responses are dose-dependent or influenced by age, gender, or allelic variation at the drug's receptor. Methods: We evaluated dorsal hand vein vascular responses to the infusion of a wide spectrum of doses of azepexole, assessing any venodilation, as well as the maximal extent of venoconstriction (Bmax) and the dose that produced a half-maximal effect (Kd), in 50 healthy normotensive adults of both genders and 4 ethnicities. Genomic deoxyribonucleic acid from the study subjects was evaluated at polymorphisms of the α2B-adrenergic receptor gene (ADRA2B). Results: We found previously unreported initial venodilation to low doses (10-100 ng/min) of azepexole, followed by progressive, intense venoconstriction to higher doses (200-100,000 ng/min) of the drug. Younger individuals (aged <30 years) had less venodilation than older individuals (aged >30 years) with low doses of azepexole but had a greater extent of venoconstriction at higher doses of azepexole (ANOVA, P = .001). Men had less venodilation than women with low doses of azepexole but greater venoconstriction with higher doses (ANOVA, P = .036). Several common polymorphisms (>10% minor allele frequency) at ADRA2B (insertion/deletion polymorphism [Glu322-325],G-98C, C1182A, and C1776A) did not show an association with either Bmax or Kd for the drug response. The A36G (Thr12Thr) synonymous single nucleotide polymorphism displayed a nonsignificant trend (P = .073) toward higher Kd in A/G heterozygotes compared with A/A homozygotes. Conclusions: Local infusion into the human dorsal hand vein of a highly selective α2-adrenergic agonist, azepexole, produces biphasic responses, with venodilation at a low dose and intense venoconstriction at a higher concentration. These responses to azepexole show prominent differences as a function of age and gender but appear not to depend on common allelic variations at the ADRA2B receptor. [ABSTRACT FROM AUTHOR]

In this article the authors discuss the article "Tyrosine Hydroxylase Polymorphism (C-824T) and Hypertension: A Population-based Study," by S. J. Nielsen and colleagues. They maintain that the study showed the effects of tyrosine hydroxylase (TH) promoter variant C-824T on both office and 24-hour ambulatory blood pressure (BP), as well as the prevalence of hypertension. They suggest that the first to replicate is the finding that TH promoter variant C-824T has an effect on BP and hypertension.

Background & Aims: Plasma levels of γ-glutamyl transpeptidase (GGT) are associated with risk factors for nonalcoholic fatty liver disease (NAFLD), such as dyslipidemia, insulin resistance (IR), and hypertension. Limited data exist on whether there is genetic covariance between plasma levels of GGT and NAFLD risk factors. Variants of β2-adrenergic receptor gene (ADRB2) have been associated with dyslipidemia, IR, and hypertension, but its effect on GGT secretion is not known. We estimated the heritability of GGT using a twin-study design and examined the genetic covariance between GGT levels, IR, hypertension, levels of low-density lipoproteins and triglycerides, and ADRB2 variants. Methods: We studied phenotypes of 362 twins; the heritabilities of increased GGT activity and genetic covariance with NAFLD risk factors were estimated by variance-component methodology. ADRB2 genotype associations with plasma GGT activity were examined using generalized estimating equations to account for intra-twinship correlations. Results: GGT activity was heritable at 49% ± 8% of the twin cohort and had significant covariance with IR; insulin, triglyceride, and uric acid levels; and diastolic blood pressure. In generalized estimating equation models, the most common haplotype of ADRB2 was significantly associated with plasma GGT activity. Five single nucleotide polymorphisms in ADRB2 were associated with levels of GGT; ADRB2 haplotypes displayed pleiotropic effects on GGT and triglyceride levels. Conclusions: In a twin study, GGT shared genetic codetermination with traits of metabolic syndrome. The ADRB2 gene had pleiotropic effects on plasma levels of GGT and triglycerides, indicating linked pathways (eg, adrenergic) between genetic susceptibility to NAFLD and metabolic syndrome. [Copyright &y& Elsevier]

Three α1-adrenergic receptor (α1AR) subtypes have been identified based on results from pharmacological and molecular cloning studies: α1aAR (chr. 8), α1bAR (chr. 5) and α1dAR (chr. 20). Several naturally-occurring polymorphisms of these α1AR have been identified but their involvement in human disease states such as hypertension is not well-defined. We used MALDI-TOF mass spectrometry to analyze the coding region of all three α1AR subtype genes in a population of 807 Caucasian and African American (AA) subjects and identified only two frequent polymorphisms (SNPs): 347Arg/Cys in the α1aAR and 183Gly/Gly in the α1bAR coding sequences. The 347Arg allele was significantly more frequent in AA (347Arg=0.42, 347Cys=0.58 [Caucasians] vs. Arg=0.72, Gly=0.28 [AA], p<0.05) but we found no such ethnic differences for the α1bAR SNP. Age and gender were similar but AA had a significantly higher BMI (p=0.0003) and showed association of higher mean arterial pressure with the presence of the SNPs in either α1AR: α1aAR 347Arg/Cys: 85.1±2.2mmHg [Caucasians] vs. 95.2 ±5.2mmHg [AA], p<0.0001; α1AR 183Gly/Gly: 91.2±1.6mmHg [Caucasians] vs. 96.9±1.7mmHg [AA], p=0.0003. We conclude that α1aAR and α1bAR SNPs may help identify patients at risk for arterial hypertension, in particular in African Americans. [ABSTRACT FROM AUTHOR]

Myeloperoxidase (MPO) is a lysosomal enzyme that may be involved in oxidative stress-mediated kidney injury. Using a two-step approach, we measured the association of four polymorphisms across the length of the MPO gene with systemic markers of oxidative stress: plasma MPO and urinary 15-F2t-isoprostane levels. Adverse outcomes were measured in a primary cohort of 262 adults hospitalized with acute kidney injury, and a secondary cohort of 277 adults undergoing cardiac surgery with cardiopulmonary bypass and at risk for postoperative acute kidney injury. Dominant and haplotype multivariable logistic regression analyses found a genotype-phenotype association in the primary cohort between rs2243828, rs7208693, rs2071409, and rs2759 MPO polymorphisms and both markers of oxidative stress. In adjusted analyses, all four polymorphic allele groups had 2-3-fold higher odds for composite outcomes of dialysis or in-hospital death or a composite of dialysis, assisted mechanical ventilation, or in-hospital death. The MPO T-G-A-T haplotype copy-number was associated with lower plasma MPO levels and lower adjusted odds for the composite outcomes. Significant but less consistent associations were found in the secondary cohort. In summary, our two-step genetic association study identified several polymorphisms spanning the entire MPO gene locus and a common haplotype marker for patients at risk for acute kidney injury. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study is to understand whether isoprostane, a biomarker of oxidative stress, is subject to heritable control; whether it shares heritability with other cardiometabolic risk traits; and finally whether genetic variation at a specific candidate locus contributes to isoprostane variability. Background: Isoprostane marks oxidative stress, and elevated isoprostane excretion might be involved in cardiovascular target organ damage. Here we used the classical twin pair method to probe the role of heredity in generating the isoprostane trait. Methods: Trait heritability (h2) and shared genetic determination among traits (pleiotropy, genetic covariance, ρG) were estimated by variance components in twin pairs. Because the isoprostane and Chromogranin B (CHGB) traits shared ρG, we examined the CHGB locus for effects on the traits. Results: Urinary isoprostane excretion was substantially heritable (h2 = 65.8 ± 4.3%), and the isoprostane trait aggregated with multiple traits (CHGB, catecholamines, autonomic/baroreceptor, and renal function), including several features of the metabolic syndrome (body mass index, insulin resistance, dyslipidemia). Isoprostane excretion also aggregated with systemic hypertension. Twin studies demonstrated genetic covariance (pleiotropy) for the isoprostane and CHGB traits (ρG = 0.27), and therefore we investigated the CHGB locus for trait effects. A common variant in the 3′-UTR of CHGB (C+84A) associated with plasma CHGB as well as isoprostane excretion. The C+84A disrupted an A/U-rich messenger ribonucleic acid stability element, and in transfected luciferase/3′-UTR plasmids, the C+84 and +84A alleles differed markedly in reporter expression in chromaffin and neuroblastoma cells, whereas site-directed mutagenesis confirmed the importance of this variant within the context of the A/U-rich motif. Conclusions: Isoprostane excretion is substantially heritable and shares joint genetic determination with CHGB as well as multiple features of the metabolic syndrome. A common polymorphism in the 3′-UTR (C+84A) of CHGB, which disrupts an A/U-rich messenger ribonucleic acid stability element, associates with not only CHGB secretion but also excretion of isoprostane. We propose a chain of events whereby CHGB genetic variation results in oxidative stress, with isoprostane formation. The results suggest novel links among the catecholaminergic system, oxidative pathways, and systemic hypertension. [Copyright &y& Elsevier]

Abstract: In 1997, we identified a novel peptide, catestatin (CST: bovine chromogranin A [CHGA]344–364: RSMRLSFRARGYGFRGPGLQL; human CHGA352–372: SSMKLSFRARGYGFRGPGPQL), which is a potent inhibitor of nicotinic-cholinergic-stimulated catecholamine secretion. CST shows characteristic inhibitory effects on nicotinic cationic (Na+, Ca2+) signal transduction, which are specific to the neuronal nicotinic receptor. Utilizing systematic polymorphism discovery at the human CHGA locus we discovered three human variants of CST: G364S, P370L, and R374Q that showed differential potencies towards the inhibition of catecholamine secretion. In humans, CHGA is elevated and its processing to CST is diminished in hypertension. Diminished CST is observed not only in hypertensive individuals but also in the early-normotensive offspring of patients with hypertension, suggesting that an early deficiency of CST might play a pathogenic role in the subsequent development of the disease. Consistent with human findings, prevention of endogenous CST expression by targeted ablation (knockout) of the mouse Chga locus (Chga-KO) resulted in severe hypertension that can be “rescued” specifically by replacement of the CST peptide. CST acts directly on the heart to inhibit the inotropic and lusitropic properties of the rodent heart and also acts as a potent vasodilator in rats and humans. While the G364S CST variant caused profound changes in human autonomic activity and seemed to reduce the risk of developing hypertension, CST replacement rescued Chga-KO mice from dampened baroreflex sensitivity. In addition, CST has been shown to induce chemotaxis and acts as an antimicrobial as well as an antimalarial peptide. The present review summarizes these multiple actions of CST. [Copyright &y& Elsevier]

Objectives: The purpose of this study is to understand whether naturally occurring genetic variation in the promoter of chromogranin B (CHGB), a major constituent of catecholamine storage vesicles, is functional and confers risk for cardiovascular disease. Background: CHGB plays a necessary (catalytic) role in catecholamine storage vesicle biogenesis. Previously, we found that genetic variation at CHGB influenced autonomic function, with association maximal toward the 5′ region. Methods: Here we explored transcriptional mechanisms of such effects, characterizing 2 common variants in the proximal promoter, A-296C and A-261T, using transfection/cotransfection, electrophoretic mobility shift assay (EMSA), and chromatin immunoprecipitation (ChIP). We then tested the effects of promoter variation on cardiovascular traits. Results: The A-296C disrupted a c-FOS motif, exhibiting differential mobility shifting to chromaffin cell nuclear proteins during EMSA, binding of endogenous c-FOS on ChIP, and differential response to exogenous c-FOS. The A-261T disrupted motifs for SRY and YY1, with similar consequences for EMSA, endogenous factor binding, and responses to exogenous factors. The 2-SNP CHGB promoter haplotypes had a profound (p = 3.16E-20) effect on blood pressure (BP) in the European ancestry population, with a rank order of CT

Because dopamine D1 receptors (DRD1) influence renal sodium transport and vascular hemodynamics, we examined whether genetic polymorphisms play a role in renal function. We conducted polymorphism discovery across the DRD1 open reading frame and its 5′-UTR and then performed association studies with estimated glomerular filtration rate (eGFR), plasma creatinine (pCr), and fractional excretion of uric acid (FeUA). We used a twin/family group of 428 subjects from 195 families and a replication cohort of 677 patients from the Kaiser health-care organization sampled from the lower percentiles of diastolic blood pressures. Although the coding region lacked common non-synonymous variants, we identified two polymorphisms in the DRD1 5′-UTR (G-94A, A-48G) that occurred with frequencies of 15 and 30%, respectively. In the twin/family study, renal traits were highly heritable, such that DRD1 G-94A significantly associated with eGFR, pCr, and FeUA. Homozygotes for the G-94A minor allele (A/A) exhibited lower eGFR, higher pCr, and lower FeUA. No effects were noted for DRD1 A-48G. Patients in the Kaiser group had similar effects of G-94A on eGFR and pCr. Kidney cells transfected with the -94A variant but not the wild type vectors had increased receptor density. Because the -94A allele is common and may reduce glomerular capillary hydrostatic pressure, G-94A profiling may aid in predicting survival of renal function in patients with progressive renal disease. [ABSTRACT FROM AUTHOR]

Objectives: We asked whether naturally occurring genetic variation at the human NPY1R locus alters autonomic traits that might predispose individuals to cardiovascular disease. Background: Neuropeptide Y (NPY) interacts with the Y1 receptor, NPY1R, to control adrenergic activity and blood pressure (BP). Methods: We searched for polymorphism at NPY1R by systematic resequencing in ethnically diverse people. There were 376 twins/siblings who were evaluated for heritable autonomic traits: baroreflex function and pressor response to environmental stress. Results: The common NPY1R variant A+1050G in the 3′-untranslated region (3′-UTR) predicted baroreceptor slope (p = 0.014–0.047) and BP change to cold stress (p = 0.0091–0.016), with minor allele homozygotes displaying blunted slope and exaggerated pressor response. In 936 individuals with the most extreme BPs in the population, not only 3′-UTR A+1050G (p = 1.2 × 10−4) but also promoter A-585T (p = 0.001) affected both systolic BP and diastolic BP, in interactive fashion (p = 0.007), with combined homozygotes showing the highest diastolic BP (>20 mm Hg). The 3′-UTR variant +1050G decreased expression of a transfected luciferase reporter/NPY1R 3′-UTR plasmid; promoter variant A-585 also decreased expression of an NPY1R promoter/luciferase reporter. Thus, alleles that increased BP in vivo (3′-UTR +1050G, promoter A-585) also decreased NPY1R expression in cella. Computational alignment showed that A+1050G disrupted a microRNA motif. Conclusions: Our results indicate that naturally occurring genetic variation at the NPY1R locus has implications for heritable autonomic control of the circulation, and ultimately, for systemic hypertension. The findings suggest novel pathophysiological links between the NPY1R locus, autonomic activity, and blood pressure, and suggest new strategies to approach the mechanism, diagnosis, and treatment of systemic hypertension. [Copyright &y& Elsevier]

Objectives: We aimed to determine whether the common variation at the chromogranin A (CHGA) locus increases susceptibility to hypertension. Background: CHGA regulates catecholamine storage and release. Previously we systematically identified genetic variants across CHGA. Methods: We carried out dense genotyping across the CHGA locus in >1,000 individuals with the most extreme blood pressures (BPs) in the population, as well as twin pairs with autonomic phenotypes. We also characterized the function of a trait-associated 3′-untranslated region (3′-UTR) variant with transfected CHGA 3′-UTR/luciferase reporter plasmids. Results: CHGA was overexpressed in patients with hypertension, especially hypertensive men, and CHGA predicted catecholamines. In individuals with extreme BPs, CHGA genetic variants predicted BP, especially in men, with a peak association occurring in the 3′-UTR at C+87T, accounting for up to ∼12/∼9 mm Hg. The C+87T genotype predicted CHGA secretion in vivo, with the +87T allele (associated with lower BP) also diminishing plasma CHGA by ∼10%. The C+87T 3′-UTR variant also predicted the BP response to environmental (cold) stress; the same allele (+87T) that diminished basal BP in the population also decreased the systolic BP response to stress by ∼12 mm Hg, and the response was smaller in women (by ∼6 mm Hg). In a chromaffin cell-transfected CHGA 3′-UTR/luciferase reporter plasmid, the +87T allele associated with lower BP also decreased reporter expression by ∼30%. In cultured chromaffin cells, reducing endogenous CHGA expression by small interfering ribonucleic acid caused approximately two-thirds depletion of catecholamine storage vesicles. Conclusions: Common variant C+87T in the CHGA 3′-UTR is a functional polymorphism causally associated with hypertension especially in men of the population, and we propose steps (“intermediate phenotypes”) whereby in a sex-dependent fashion this genetic variant influences the ultimate disease trait. These observations suggest new molecular strategies to probe the pathophysiology, risk, and rational treatment of hypertension. [Copyright &y& Elsevier]

GTP cyclohydrolase 1 (GCH1) is rate limiting in the provision of the cofactor tetrahydrobiopterin for biosynthesis of catecholamines and NO. We asked whether common genetic variation at GCH1 alters transmitter synthesis and predisposes to disease. Here we undertook a systematic search for polymorphisms in GCH1, then tested variants' contributions to NO and catecholamine release as well as autonomic function in twin pairs. Renal NO and neopterin excretions were significantly heritable, as were baroreceptor coupling (heart rate response to BP fluctuation) and pulse interval (1/heart rate). Common GCH1 variant C+243T in the 3'-untranslated region (3'-UTRs) predicted NO excretion, as well as autonomic traits: baroreceptor coupling, maximum pulse interval, and pulse interval variability, though not catecholamine secretion. In individuals with the most extreme BP values in the population, C+243T affected both diastolic and systolic BP, principally in females. In functional studies, C+243T decreased reporter expression in transfected 3'-UTRs plasmids. We conclude that human NO secretion traits are heritable, displaying joint genetic determination with autonomic activity by functional polymorphism at GCH1. Our results document novel pathophysiological links between a key biosynthetic locus and NO metabolism and suggest new strategies for approaching the mechanism, diagnosis, and treatment of risk predictors for cardiovascular diseases such as hypertension. [ABSTRACT FROM AUTHOR]