clopidogrel; genetics; genotype; platelet function; ticagrelor; editorials
Thiazides and β-blockers cause adverse metabolic effects (AMEs), but whether these effects share predictors with blood pressure (BP) response is unknown. We aimed to determine whether AMEs are correlated with BP response in uncomplicated hypertensives.
In a multicenter, open-label, parallel-group trial, we enrolled 569 persons, aged 17–65, with random assignment to 9 weeks of daily hydrochlorothiazide (HCTZ) or atenolol monotherapy, followed by 9 weeks of add-on therapy with the alternate agent. Measurements included home BP, averaged over 1 week, weight and fasting levels of serum glucose, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, and uric acid (UA) before and after monotherapy and after add-on therapy.
Increases in UA correlated with reductions in systolic BP (SBP) (r = −0.18; P = 0.003) and diastolic BP (DBP) (r = −0.20; P = 0.001) following HCTZ monotherapy and add-on therapy (r = −0.27 and r = −0.21, respectively; both P < 0.001). After adjustment for age, race, gender, and baseline body mass index (BMI), only the correlation between UA and DBP response became nonsignificant. Reductions in HDL correlated with systolic response following atenolol monotherapy (r = 0.18; P = 0.002) and with systolic and diastolic response following add-on therapy (r = 0.30 and r = 0.24, respectively; both P < 0.0001). These correlations remained significant after covariate adjustment. BP responses were not correlated with changes in glucose, LDL, triglycerides, or weight following either therapy.
BP response correlated with changes in UA following HCTZ therapy and HDL following atenolol therapy. No other significant correlations were observed between BP response and AMEs, suggesting that these effects generally do not share predictors. Patients should be monitored for AMEs, regardless of BP response.
thiazide diuretics; atenolol; β-blockers; blood pressure; hydrochlorothiazide; hypertension; metabolic effects
pharmacogenomics; stakeholders; healthcare system
Leukocyte count has been associated with blood pressure, hypertension, and hypertensive complications. We hypothesized that polymorphisms in the CXCL5 gene, which encodes the neutrophilic chemokine ENA-78, are associated with blood pressure in cardiovascular disease (CVD)-free adults and that these polymorphisms are functional.
Methods and results
A total of 192 community-dwelling participants without CVD or risk equivalents were enrolled. Two CXCL5 polymorphisms (−156 G > C (rs352046) and 398 G > A (rs425535)) were tested for associations with blood pressure. Allele-specific mRNA expression in leukocytes was also measured to determine whether heterozygosity was associated with allelic expression imbalance. In −156 C variant carriers, systolic blood pressure (SBP) was 7 mmHg higher than in −156 G/G wild-type homozygotes (131 ± 17 vs. 124 ± 14 mmHg; P = 0.008). Similarly, diastolic blood pressure (DBP) was 4 mmHg higher in −156 C variant carriers (78 ± 11 vs. 74 ± 11 mmHg; P = 0.013). In multivariate analysis of SBP, age, sex, body mass index, and the −156 G > C polymorphism were identified as significant variables. Age, sex, and the −156 G > C SNP were further associated with DBP, along with white blood cells. Allelic expression imbalance and significantly higher circulating ENA-78 concentrations were noted for variant carriers.
CXCL5 gene polymorphisms are functional and associated with variable blood pressure in CVD-free individuals. The role of CXCL5 as a hypertension- and CVD-susceptibility gene should be further explored.
CXCL5; ENA-78; Blood pressure; Hypertension; Leukocytes
While numerous SNPs in Chromosome 9p21 have been associated with coronary artery disease (CAD) and incident MI in Caucasians, there are limited and conflicting reports on the association of this locus with prognosis in Caucasians with existing CAD and no reports in blacks or Hispanics. We investigated the hypothesis that 9p21 polymorphisms are associated with increased risk for adverse cardiovascular outcomes in patients with documented CAD.
Methods and Results
We studied the association of 155 chromosome 9p21 SNPs with adverse outcomes among hypertensive CAD patients of multiple races/ethnicities in INVEST GENES (the INternational VErapamil SR Trandolapril STudy GENetic Substudy, n= 1,460, n = 5,979 for 2 SNPs) and with replication testing of 4 SNPs in the INFORM (INvestigation oF Outcomes from acute coronary syndRoMe; n=714) study of acute coronary syndrome (ACS) patients. In INVEST, the haplotype comprised of the risk allele for the widely reported 9p21 SNPs was associated with better prognosis in Caucasians (OR, 95% CI: 0.72, 0.57–0.92, p = 0.0085) but not blacks (1.21, 0.68–1.24, p = 0.52) or Hispanics (0.96, 0.65–1.44, p=0.86). A less commonly reported LD block was associated with worse prognosis in INVEST among both Caucasians (OR=1.52 (1.20–1.93), p = 0.0006) and African Americans (OR = 4.11 (1.55–10.88), p = 0.004).
Our findings suggest previously reported chromosome 9p21 SNPs, which predict incident CAD, are not associated with higher risk for adverse outcomes in patients with established CAD. The less commonly reported LD block warrants further investigation.
chromosome 9p21; cardiovascular outcomes; genetic polymorphisms; INVEST; INFORM
To determine whether office, home, ambulatory daytime and nighttime blood pressure (BP) responses to antihypertensive drug therapy measure the same signal and which method provides greatest power to identify genetic predictors of BP response.
We analyzed office, home, ambulatory daytime and nighttime BP responses in hypertensive adults randomized to atenolol (N = 242) or hydrochlorothiazide (N = 257) in the Pharmacogenomic Evaluation of Antihypertensive Responses Study. Since different measured BP responses may have different predictors, we tested the "same signal" model by using linear regression methods to determine whether known predictors of BP response depend on the method of BP measurement. We estimated signal-to-noise ratios and compared power to identify a genetic polymorphism predicting BP response measured by each method separately and by weighted averages of multiple methods.
After adjustment for pretreatment BP level, known predictors of BP response including plasma renin activity, race, and sex were independent of the method of BP measurement. Signal-to-noise ratios were more than 2-fold greater for home and ambulatory daytime BP responses than for office and ambulatory nighttime BP responses and up to 11-fold greater for weighted averages of all four methods. Power to identify a genetic polymorphism predicting BP response was directly related to the signal-to-noise ratio and, therefore, greatest with the weighted averages.
Since different methods of measuring BP response to antihypertensive drug therapy measure the same signal, weighted averages of the BP responses measured by multiple methods minimize measurement error and optimize power to identify genetic predictors of BP response.
hypertension; blood pressure monitoring; antihypertensive drug therapy; beta-blocker; thiazide diuretic; plasma renin activity
The G-protein coupled receptor kinases GRK2 and GRK5 are important regulators of beta-adrenergic signaling. This study characterized single nucleotide polymorphisms in the GRK2 gene (ADRBK1)and determined if these and a GRK5 Gln41Leu polymorphism affect the blood pressure (BP)response to atenolol or hydrochlorothiazide or adverse cardiovascular outcomes in hypertensives.
ADRBK1 regions were sequenced for 48 individuals. Putative functional SNPs were tested for mRNA expression differences in 96 lymphoblastoid cell line samples and 12 leukocyte samples from hypertensives. BP response to atenolol and hydrochlorothiazide by ADRBK1 SNPs and GRK5 Gln41Leuwas tested in 418patients from the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) using linear regression. The influence of ADRBK1 SNPs and GRK5 Gln41Leuon death, myocardial infarction or stroke in treated hypertensive patients was evaluated in a case-control cohort (1:3) of the International Verapamil SR/Trandolapril Study GENEtic Substudy (INVEST GENES) using logistic regression models.
A novel ADRBK1 promoter SNP was not associated with differential GRK2 expression. GRK5 Leu41 decreased the risk for adverse cardiovascular outcomes independent of treatment strategy(adjusted odds ratio 0.535, 95% confidence interval 0.313 – 0.951, P = 0.0222)but was not associated with BP response to antihypertensive medication. An ADRBK1 SNP (rs1894111G>A) showed a signal for association with systolic and diastolic BP(SBP, DBP) response to hydrochlorothiazide in whites(DBP: −11.29±3.74 mmHg (G/A) vs. −4.26±4.79 mmHg (G/G), P = 0.0034 and SBP: −18.37±14.90 mmHg (G/A), −8.11±7.55 mmHg (G/G), P = 0.0191).
The GRK5 Leu41 allele protects from adverse cardiovascular outcomes in treated hypertensives.
GRK5; GRK2; ADRBK1; polymorphism; hypertension; beta-blocker; atenolol; diuretic; hydrochlorothiazide
Polymorphisms (SNPs) within the regulatory β2 subunit of the voltage-gated calcium channel (CACNB2) may contribute to variable treatment response to antihypertensive drugs and adverse cardiovascular outcomes.
Methods and Results
SNPs in CACNB2 from 60 ethnically diverse individuals were identified and characterized. Three common SNPs (rs2357928, rs7069292 and rs61839258) and a GWAS identified intronic SNP (rs11014166) were genotyped for a clinical association study in 5,598 hypertensive patients with coronary artery disease randomized to a beta-blocker (BB) or a calcium channel blocker (CCB) treatment strategy in INVEST-GENES. Reporter gene assays were conducted on the promoter SNP showing association with clinical outcomes. Twenty-one novel SNPs were identified. A promoter A>G SNP (rs2357928) was found to have significant interaction with treatment strategy for adverse cardiovascular outcomes (p for interaction = 0.002). In Caucasians, rs2357928 GG patients randomized to CCB were more likely to experience adverse outcome than those randomized to BB treatment strategy, with adjusted hazard ratio (CCB vs. BB) of 2.35 (1.19-4.66), p = 0.014. There was no evidence for such treatment difference in AG (1.16, 0.75-1.79, p = 0.69) and AA individuals (0.63, 0.36-1.11, p = 0.11). This finding was consistent in Hispanics and African Americans. CACNB2 rs11014166 showed similar pharmacogenetic effect in Hispanics, but not in Caucasians or African Americans. Reporter assay analysis of rs2357928 showed a significant increase in promoter activity for the G allele compared to the A allele.
These data suggest genetic variation within CACNB2 may influence treatment related outcomes in high risk hypertensive patients.
Clinical Trial Registration Information
Clinical trial identifier: NCT00133692, URL: http://clinicaltrials.gov/ct/gui/show/NCT00133692).
Genetic variations; CACNB2; hypertension; cardiovascular outcomes; INVEST-GENES
UCP2 −866G > A (rs659366) has been implicated in cardiometabolic disease and represents a novel candidate gene for β-blocker response, particularly among patients with diabetes. We assessed the function of −866G > A and its role as a modifier of β-blocker treatment outcomes by diabetes status in an acute coronary syndrome (ACS) cohort.
ACS patients with genetic samples and 12 months of follow-up for cardiac rehospitalizations or death (n = 468) were assessed. The influence of −866G > A on β-blocker treatment outcomes was evaluated in those with diabetes and without. To assess functional correlates of −866G > A, we compared uncoupling protein 2 (UCP2) expression in the skeletal muscle of obese participants by genotype and compared the activity of UCP2 luciferase promoters with −866G and −866A alleles.
An interaction between −866G > A and β-blocker treatment was found in individuals with diabetes (P = 0.002) but not those without (P = 0.79). Among G/G individuals with diabetes, discharge β-blocker use was associated with an 80% reduction in cardiac rehospitalization (adjusted hazard ratio: 0.20; 95% confidence interval: 0.04–1.02). In contrast, among A-carrier patients with diabetes, there was an 11-fold increase in cardiac rehospitalizations with discharge β-blocker therapy (adjusted hazard ratio: 11.75; 95% confidence interval: 1.28-108.2). Promoter activity assays showed that −866G had greater cyclic AMP response element binding protein-responsiveness compared with −866A, and compared with −866A carriers G/G individuals exhibited increased UCP2 expression in the skeletal muscle.
We identified a significant interaction between −866G > A and β-blocker response among ACS patients with diabetes. Furthermore, −866G conferred greater gene transcriptional activity than −866A in cell lines and in obese patients. These findings may help us gain insight into the mechanisms underlying the beneficial and detrimental effects of β-blockers in those with diabetes.
acute coronary syndromes; gene-environment interaction; pharmacogenetics; type 2 diabetes
We assessed adverse metabolic effects (AMEs) of atenolol and hydrochlorothiazide (HCTZ) among hypertensive patients with and without abdominal obesity using data from a randomized, open-label study of hypertensive patients without evidence of cardiovascular disease or diabetes. Intervention included randomization to HCTZ 25mg or atenolol 100mg monotherapy followed by their combination. Fasting glucose, insulin, triglycerides, HDL cholesterol and uric acid were measured at baseline and after mono-and combination therapy. Outcomes included new occurrence of and predictors for new cases of glucose ≥ 100mg/dl (impaired fasting glucose [IFG]), triglyceride ≥ 150 mg/dl, HDL ≤ 40mg/dl for men or ≤ 50mg/dl for women, or new onset diabetes according to presence or absence of abdominal obesity. Abdominal obesity was present in 167/395 (58%). Regardless of strategy, in those with abdominal obesity, 20% had IFG at baseline compared with 40% at end of study (p<0.0001). Proportion with triglycerides ≥ 150 mg/dl increased from 33% at baseline to 46% at end of study (p<0.01). New onset diabetes occurred in 13 (6%) with and in 4 (2%) without abdominal obesity. Baseline levels of glucose, triglyceride and HDL predicted adverse outcomes and predictors for new onset diabetes after monotherapy in those with abdominal obesity included HCTZ strategy (OR 47, 95% CI 2.55-862), female sex (OR 31.3, 95% CI 2.10-500) and uric acid (OR 3.2, 95% CI 2.35-7.50). Development of AME, including new onset diabetes associated with short term exposure to HCTZ and atenolol was more common in those with abdominal obesity.
atenolol; hydrochlorothiazide; abdominal obesity; metabolic syndrome; new onset diabetes; hypertension
CYP19A1 encodes aromatase, the enzyme responsible for the conversion of androgens to estrogens, and may play a role in variation in outcomes among men and women with cardiovascular disease. We sought to examine genetic variation in CYP19A1 for its potential role in sex differences in cardiovascular disease outcomes.
Caucasian individuals from two independent populations were assessed: 1) a prospective cohort of patients with acute coronary syndromes with 3-year mortality follow-up (n = 568) and 2) a nested case-control study from a randomized, controlled trial of hypertension patients with stable coronary disease in which the primary outcome was death, nonfatal myocardial infarction (MI) or nonfatal stroke (n = 619). Six CYP19A1 SNPs were genotyped (-81371 C>T, -45965 G>C, M201T, R264C, 80 A>G, and +32226 G>A). The sex*genotype interaction term was assessed for the primary outcome and compared by genotype in men and women when a significant interaction term was identified.
We identified a significant interaction between -81371 C>T and sex (p = 0.025) in the ACS population. The variant allele was associated with a 78% increase in mortality in men (HR 1.78, 95% confidence interval [CI] 1.08-2.94) and a nonsignificant 42% decrease in mortality among women (HR 0.58, 95% CI 0.22-1.54). We identified a similar association in the hypertensive CAD group, the -81371 C>T*sex interaction term was p<0.0001, with an associated 65% increase in death, MI, or stroke (HR 1.65, 95% CI 1.00-2.73) in men and a 69% decrease (HR 0.31, 95% CI 0.16-0.6) in women.
Using two independent populations, this study is the first to document a significant interaction between CYP19A1 genotype and sex on cardiovascular outcomes. These findings could illuminate potential mechanisms of sex differences in cardiovascular disease outcomes.
Age and race categories or renin profiling have been recommended to predict blood pressure responses to monotherapy with a β-blocker or thiazide diuretic. Whether these or other characteristics predict blood pressure responses when the drugs are administered as add-on therapy is uncertain.
We evaluated predictors of blood pressure response in 363 men and women ≤65 years of age with primary hypertension (152 blacks, 211 whites), 86 of whom (24%) were untreated and 277 of whom (76%) were withdrawn from previous antihypertensive drugs before randomization to either atenolol followed by addition of hydrochlorothiazide (N = 180) or hydrochlorothiazide followed by addition of atenolol (N = 183). Responses were determined by home blood pressure averages before and after each drug administration. Race, age, plasma renin activity, and other characteristics including pretreatment blood pressure levels were incorporated into linear regression models to quantify their contributions to prediction of blood pressure responses.
Plasma renin activity and pretreatment blood pressure level consistently contributed to prediction of systolic and diastolic responses to each drug administered as mono- and as add-on therapy. Higher plasma renin activity was consistently associated with greater blood pressure responses to atenolol and lesser responses to hydrochlorothiazide. The predictive effects of plasma renin activity were statistically independent of race, age, and other characteristics.
Plasma renin activity and pretreatment blood pressure level predict blood pressure responses to atenolol and hydrochlorothiazide administered as mono- and as add-on therapy in men and women ≤65 years of age.
antihypertensive drug therapy; blood pressure; hypertension; plasma renin activity; thiazide diuretic; β-blocker
Activation of peroxisome proliferator-activated receptor alpha (PPARα) occurs in animal models of diabetes (DM) and is implicated in pathological responses to myocardial ischemia. Using bioinformatics, we identified a single nucleotide polymorphism (SNP) in the PPARα gene promoter (PPARA −54,642 G>A; rs135561) that altered the consensus sequence for a nuclear receptor binding site. Electrophoretic mobility shift assays showed that the domain bound two known PPARA transcriptional activators, estrogen-related receptor (ERR)-α and -γ and that PPARA G bound with greater affinity than PPARA A (>2-fold; P<0.05). Likewise, promoter-reporter analyses showed enhanced transcriptional activity for PPARA G vs. PPARA A for both ERR-α and -γ (3.1 vs.1.9-fold; P<0.05). Since PPARα activation impairs post-ischemic cardiac function in experimental models of DM, we tested whether decreased PPARA transcription in PPARA A carriers favorably impacted outcome after acute coronary ischemia in 705 patients hospitalized with acute coronary syndromes (ACS; 552 Caucasian, 106 African American). PPARA A allele frequencies were similar to non-diseased subjects. However, PPARA genotype correlated with 5-year mortality in diabetic (22.2% AA vs. 18.8% AG vs. 39.5% GG; P = 0.008), but not non-diabetic (P = 0.96) subjects (genotype by diabetes interaction P = 0.008). In the diabetic ACS subjects, PPARA A carriers had strikingly reduced all-cause mortality compared to PPARA G homozygotes, (unadjusted HR 0.44, 95% CI 0.26–0.75; P = 0.003; adjusted HR 0.48, 95% CI 0.27–0.83; P = 0.009). Consistent with previous descriptions of PPARα in experimental models and human disease, we describe a novel PPARA promoter SNP that decreases transcriptional activation of PPARA and protects against mortality in diabetic patients after ACS.
The gene encoding the target of calcium channel blockers, the α1c-subunit of the L-type calcium channel (CACNA1C) has not been well characterized and only small pharmacogenetic studies testing this gene have been published to date.
Methods and Results
Resequencing of CACNA1C was performed followed by a nested case-control study of the INternational VErapamil SR/trandolapril STudy (INVEST) GENEtic Substudy (INVEST-GENES). Of 46 polymorphisms identified, eight were assessed in the INVEST-GENES. Rs1051375 was found to have a significant interaction with treatment strategy (p=0.0001). Rs1051375 A/A genotype was associated with a 46% reduction in the primary outcome among those randomized to verapamil SR treatment compared to atenolol treatment (OR 0.54 95% CI 0.32-0.92). In heterozygous A/G individuals, there was no difference in the occurrence of the primary outcome when randomized to verapamil SR versus atenolol treatment (OR 1.47 95% CI 0.86-2.53), while homozygous G/G individuals had a greater than 4-fold increased risk of the primary outcome with verapamil treatment compared to those randomized to atenolol treatment (OR 4.59 95% CI 1.67-12.67). We did not identify allelic expression imbalance or differences in mRNA expression in heart tissue by rs1051375 genotype.
Variation in CACNA1C is associated with treatment response among hypertensive patients with stable coronary artery disease. Our data suggest a genetically-defined group of patients that benefit most from calcium channel blocker therapy, a group that benefits most from β-blocker therapy, and a third group in which calcium channel blocker and β-blocker therapy are equivalent.
genetics; pharmacology; ion channels; calcium; pharmacogenetics
Office, home, and ambulatory blood pressure (BP) demonstrate variable associations with outcomes. The authors sought to compare office BP (OBP), home BP (HBP), and ambulatory BP (ABP) for measuring responses to hydrochlorothiazide (HCTZ), atenolol, and their combination. After completing washout, eligible patients were randomized to atenolol 50 mg or HCTZ 12.5 mg daily. Doses were doubled after 3 weeks and the alternate drug was added after 6 weeks if BP was >120/70 mm Hg (chosen to allow maximum opportunity to assess genetic associations with dual BP therapy in the parent study). OBP (in triplicate), HBP (twice daily for 5 days), and 24-hour ABP were measured at baseline, after monotherapy, and after combination therapy. BP responses were compared between OBP, HBP, and ABP for each monotherapy and combination therapy. In 418 patients, OBP overestimated BP response compared with HBP, with an average 4.6 mm Hg greater reduction in systolic BP (P<.0001) and 2.1 mm Hg greater reduction in diastolic BP (P<.0001) across all therapies. Results were similar for atenolol and HCTZ monotherapy. ABP response was more highly correlated with HBP response (r=0.58) than with OBP response (r=0.47; P=.04). In the context of a randomized clinical trial, the authors have identified significant differences in HBP, OBP, and ABP methods of measuring BP response to atenolol and HCTZ monotherapy.
The relationship between circulating markers of inflammation and arterial stiffness in children with type 1 diabetes is not well studied. We tested whether inflammatory monocyte chemoattractant protein (MCP)-1 concentrations correlate with arterial stiffness or type 1 diabetes status.
RESEARCH DESIGN AND METHODS
MCP-1 concentrations and radial tonometry data were available for 98 children with type 1 diabetes and 55 healthy control subjects. Arterial stiffness was calculated as augmentation index corrected for a heart rate of 75 (AI75). Correlation between MCP-1 and AI75 and differences in MCP-1 concentrations between case and control subjects were tested.
MCP-1 was significantly higher in children with type 1 diabetes than in control subjects (P < 0.001). However, there were no correlations between MCP-1 and AI75 in the overall sample or upon stratification by type 1 diabetes status (range P = 0.28–0.66).
Circulating MCP-1 was not associated with arterial stiffness but was significantly elevated in children with type 1 diabetes, indicating a proinflammatory state in children as young as 10 years. The clinical significance of MCP-1 elevation in type 1 diabetes needs further investigation.
The α-adducin (ADD1) Gly460Trp polymorphism has been associated with hypertension and response to diuretic therapy, but controversy exists.
The present study was conducted to prospectively investigate the relationship between the ADD1 Gly460Trp polymorphism, diuretic use, and adverse cardiovascular outcomes among 5,979 hypertensive coronary artery disease patients, who participated in the INternational VErapamil SR-trandolapril STudy (INVEST) and provided genomic DNA. The primary outcome was defined as first occurrence of nonfatal stroke, nonfatal myocardial infarction, or all-cause death. Secondary outcomes were the components of the primary outcome. Ancestry informative markers were used to control for population stratification.
In Blacks, ADD1 variant carriers were at higher risk for a primary outcome event than wild-type homozygotes (adjusted hazard ratio (HR) 2.62; 95% confidence interval (CI) 1.23–5.58; p = .012), with a similar trend in Whites and Hispanics, albeit a smaller magnitude of effect (adjusted HR 1.43, 0.86–2.39 in Hispanics; 1.24, 0.90–1.71 in Whites). Secondary outcome analysis showed that the all-cause death was driving the differences in primary outcomes by genotype. There was no interaction between the ADD1 polymorphism and diuretic use for either primary outcome or secondary outcomes.
In hypertensive patients with coronary artery disease, black ADD1 variant carriers showed a 2.6-fold excess risk for a primary outcome event and an 8-fold increase risk of death. White and Hispanic ADD1 variant carriers showed an increased but nonsignificant excess risk. However, the effect of diuretic use on risk of cardiovascular outcomes did not vary by ADD1 carrier status.
pharmacogenetics; ADD1; diuretics; cardiovascular outcomes
The large-conductance, Ca2+-dependent K+ channel plays a key role in the control of vascular tone. Variation in the gene encoding the β-1 subunit of the Ca2+-dependent K+ channel (KCNMB1) has been reported to be associated with hypertension, however, variants in KCNMB1 have not been systematically characterized to date. In this study, we have performed the most comprehensive evaluation to date of single nucleotide polymorphisms in KCNMB1 using genomic DNA from 60 individuals of European, African and native American ancestry. We identified and characterized single nucleotide polymorphisms in the exons, intron/exon junctions, upstream region and 3′ untranslated regions of KCNMB1 using denaturing high-performance liquid chromatography combined with direct DNA sequencing. A total of 25 single nucleotide polymorphisms in KCNMB1 were identified. Seven of the polymorphisms (28%) are novel single nucleotide polymorphisms not reported previously. Allele frequencies range from less than 1.7 to 50% and 19 single nucleotide polymorphisms had a minor allele frequency greater than 5%. A lack of strong linkage disequilibrium among the 25 single nucleotide polymorphisms was observed in all three race/ethnicity groups; therefore the identification of haplotype ‘tag’ single nucleotide polymorphisms for genetic association studies is not likely to be appropriate for KCNMB1. Multiple species comparative analysis and in-silico functional analysis were performed to identify potential functionally important single nucleotide polymorphisms within the gene. These data highlight that a tag single nucleotide polymorphism approach will not be appropriate for the study of genes such as KCNMB1, although potentially important functionally significant single nucleotide polymorphisms are suggested for future studies investigating the influence of this gene’s variability on disease and drug response.
Ca2+-dependent K+ channel; haplotype; KCNMB1; single nucleotide polymorphisms
We sought to determine whether polymorphisms in the large-conductance calcium and voltage-dependent potassium (BK) channel β1 subunit gene, KCNMB1, are associated with blood pressure response to verapamil SR or adverse outcomes in the GENEtic substudy of the INternational VErapamil SR/trandolapril STudy (INVEST-GENES).
KCNMB1 is involved in calcium sensitivity and hypertension. The association between variability in KCNMB1 and calcium antagonist response, however, has not been assessed.
Genetic samples were collected from 5979 patients in INVEST. Blood pressure response to verapamil SR and time to achieve blood pressure control was assessed in relation to Glu65Lys and Val110Leu genotypes. The primary outcome (all cause mortality, nonfatal myocardial infarction or nonfatal stroke) was compared between genotype groups, and interaction with verapamil SR therapy was assessed.
Systolic blood pressure response to verapamil SR did not differ by KCNMB1 genotype. Lys65 variant carriers, however, achieved blood pressure control earlier than Glu65Glu individuals [1.47 (interquartile ratio 2.77) versus 2.83 (interquartile ratio 4.17) months, P = 0.01] and were less likely to require multiple drugs at the time of blood pressure control (adjusted odds ratio 0.43, 95% confidence interval 0.19–0.95). Leu110 variant carriers had a reduced risk of primary outcome (hazard ratio 0.68, 95% confidence interval 0.47–0.998). Subgroup analysis revealed this finding to be more pronounced in verapamil SR-assigned patients (hazard ratio 0.587, 95% confidence interval 0.33–1.04) compared with atenolol-assigned patients (hazard ratio 0.946, 95% confidence interval 0.56–1.59). No difference was seen in the occurrence of the primary outcome compared by codon 65 genotype.
Our findings suggest that KCNMB1 genotype influences responsiveness to verapamil SR and risk of adverse cardiovascular outcomes.
KCNMB1; polymorphism; verapamil SR
Endothelial inflammation with chemokine involvement contributes to acute coronary syndromes (ACS). We tested the hypothesis that variation in the chemokine gene CXCL5, which encodes epithelial neutrophil-activating peptide (ENA-78), is associated with ACS prognosis. We also investigated whether statin use, a potent modulator of inflammation, modifies CXCL5's association with outcomes and characterized the in vitro effect of atorvastatin on endothelial ENA-78 production. Using a prospective cohort of ACS patients (n = 704) the association of the CXCL5 −156 G>C polymorphism (rs352046) with 3-year all-cause mortality was estimated with hazard ratios (HR). Models were stratified by genotype and race. To characterize the influence of statins on this association, a statin*genotype interaction was tested. To validate ENA-78 as a statin target in inflammation typical of ACS, endothelial cells (HUVECs) were treated with IL-1β and atorvastatin with subsequent quantification of CXCL5 expression and ENA-78 protein concentrations. C/C genotype was associated with a 2.7-fold increase in 3-year all-cause mortality compared to G/G+G/C (95%CI 1.19–5.87; p = 0.017). Statins significantly reduced mortality in G/G individuals only (58% relative risk reduction; p = 0.0009). In HUVECs, atorvastatin dose-dependently decreased IL-1β-stimulated ENA-78 concentrations (p<0.0001). Drug effects persisted over 48 hours (p<0.01). CXCL5 genotype is associated with outcomes after ACS with potential statin modification of this effect. Atorvastatin lowered endothelial ENA-78 production during inflammation typical of ACS. These findings implicate CXCL5/ENA-78 in ACS and the statin response.
Nearly one-third of the United States adult population suffers from hypertension. Hydrochlorothiazide (HCTZ), one of the most commonly used medications to treat hypertension, has variable efficacy. The renal epithelial sodium channel (ENaC) provides a mechanism for fine-tuning sodium excretion, and is a major regulator of blood pressure homeostasis. DOT1L, MLLT3, SIRT1, and SGK1 encode genes in a pathway that controls methylation of the histone H3 globular domain at lysine 79 (H3K79), thereby modulating expression of the ENaCα subunit. This study aimed to determine the role of variation in these regulatory genes on blood pressure response to HCTZ, and secondarily, untreated blood pressure.
We investigated associations between genetic variations in this candidate pathway and HCTZ blood pressure response in two separate hypertensive cohorts (clinicaltrials.gov NCT00246519 and NCT00005520). In a secondary, exploratory analysis, we measured associations between these same genetic variations and untreated blood pressure. Associations were measured by linear regression, with only associations with P ≤ 0.01 in one cohort and replication by P ≤ 0.05 in the other cohort considered significant.
In one cohort, a polymorphism in DOT1L (rs2269879) was strongly associated with greater systolic (P = 0.0002) and diastolic (P = 0.0016) blood pressure response to hydrochlorothiazide in Caucasians. However, this association was not replicated in the other cohort. When untreated blood pressure levels were analyzed, we found directionally similar associations between a polymorphism in MLLT3 (rs12350051) and greater untreated systolic (P < 0.01 in both cohorts) and diastolic (P < 0.05 in both cohorts) blood pressure levels in both cohorts. However, when further replication was attempted in a third hypertensive cohort and in smaller, normotensive samples, significant associations were not observed.
Our data suggest polymorphisms in DOT1L, MLLT3, SIRT1, and SGK1 are not likely associated with blood pressure response to HCTZ. However, a possibility exists that rs2269879 in DOT1L could be associated with HCTZ response in Caucasians. Additionally, exploratory analyses suggest rs12350051 in MLLT3 may be associated with untreated blood pressure in African-Americans. Replication efforts are needed to verify roles for these polymorphisms in human blood pressure regulation.
Pharmacogenomics; Pharmacogenetics; hydrochlorothiazide; hypertension; blood pressure; DOT1L; SIRT1; MLLT3; SGK1; histone methylation
Selection of antihypertensive therapy is often empiric and use of genetic information to guide drug therapy selection holds future promise.
The objective of this trial is to identify the genetic determinants of the antihypertensive and adverse metabolic responses to a thiazide diuretic (hydrochlorothiazide, HCTZ), a β-blocker (atenolol) and their combination. This will be accomplished through candidate gene and genome wide association approaches. Individuals with uncomplicated hypertension (n=800), ages 17 and 65 years, are being enrolled. Current antihypertensive therapy is discontinued and hypertension is confirmed, along with collection of other baseline data. Subjects are then randomized to either HCTZ or atenolol, with one dose titration step, followed by assessment of response to therapy after at least 6 weeks on the target dose. Those with blood pressure > 120/70 mmHg have the second drug added, with similar dose titration and response assessment procedures. Data collected include home, office and 24 hour ambulatory blood pressure. Biological samples collected in the fasting state include plasma, serum, DNA (buffy coat), and urine. Epstein Barr virus transformed lymphocyte cell lines are also being created.
Pharmacogenetic-guided therapy holds clinical potential for hypertension, but the literature in the field is limited. This trial will add substantially to our understanding of the genetic determinants of antihypertensive and adverse metabolic responses to two commonly used antihypertensive drug classes.