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JACC: HEART FAILURE VOL. 2, NO. 6, 2014 ª 2014 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION ISSN 2213-1779/$36.00 PUBLISHED BY ELSEVIER INC. http://dx.doi.org/10.1016/j.jchf.2014.04.016 MINI-FOCUS ISSUE: PHARMACOGENETICS AND PERSONALIZED MEDICINE CLINICAL RESEARCH G-Protein Beta-3 Subunit Genotype Predicts Enhanced Benefit of Fixed-Dose Isosorbide Dinitrate and Hydralazine Results of A-HeFT Dennis M. McNamara, MD, MS,* Anne L. Taylor, MD,y S. William Tam, PHD,z Manuel Worcel, MD,x Clyde W. Yancy, MD, MSC,k Karen Hanley-Yanez, BS,* Jay N. Cohn, MD,{ Arthur M. Feldman, MD, PHD# ABSTRACT OBJECTIVES The purpose of this study was to evaluate the influence of the guanine nucleotide-binding proteins (G-proteins), beta-3 subunit (GNB3) genotype on the effectiveness of a fixed-dose combination of isosorbide dinitrate and hydralazine (FDC I/H) in A-HeFT (African American Heart Failure Trial). BACKGROUND GNB3 plays a role in alpha2-adrenergic signaling. A polymorphism (C825T) exists, and the T allele is linked to enhanced alpha-adrenergic tone and is more prevalent in African Americans. METHODS A total of 350 subjects enrolled in the genetic substudy (GRAHF [Genetic Risk Assessment of Heart Failure in African Americans]) were genotyped for the C825T polymorphism. The impact of FDC I/H on a composite score (CS) that incorporated death, hospital stay for heart failure, and change in quality of life (QoL) and on event-free survival were assessed in GNB3 genotype subsets. RESULTS The GRAHF cohort was 60% male, 25% ischemic, 97% New York Heart Association functional class III, age 57 13 years, with a mean qualifying left ventricular ejection fraction of 0.24 0.06. For GNB3 genotype, 184 subjects were TT (53%), 137 (39%) CT, and 29 (8%) were CC. In GNB3 TT subjects, FDC I/H improved the CS (FDC I/H ¼ 0.50 1.6; placebo ¼ 0.11 1.8, p ¼ 0.02), QoL (FDC I/H ¼ 0.69 1.4; placebo ¼ 0.24 1.5, p ¼ 0.04), and event-free survival (hazard ratio: 0.51, p ¼ 0.047), but not in subjects with the C allele (for CS, FDC I/H ¼ 0.05 1.7; placebo ¼ 0.09 1.7, p ¼ 0.87; for QoL, FDC I/H ¼ 0.28 1.5; placebo ¼ 0.14 1.5, p ¼ 0.56; and for event-free survival, p ¼ 0.35). CONCLUSIONS The GNB3 TT genotype was associated with greater therapeutic effect of FDC I/H in A-HeFT. The role of the GNB3 genotype for targeting therapy with FDC I/H deserves further study. (J Am Coll Cardiol HF 2014;2:551–7) © 2014 by the American College of Cardiology Foundation. A s first (Vet- with heart failure (1). After the development of erans Affairs Vasodilator-Heart Failure Trial) demonstrated angiotensin-converting enzyme (ACE) inhibitors and treatment and the demonstration in V-HeFT II of greater survival hydralazine (I/H) improves survival in subjects benefit with enalapril compared with I/H (2), I/H was with in isosorbide V-HeFT dinitrate From the *Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; yColumbia University College of Physicians and Surgeons, New York, New York; zIndependent consultant, Dover, Massachusetts; xConsultant, Paris, France; kDivision of Cardiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; {University of Minnesota, Minneapolis, Minnesota; and the #Temple University School of Medicine, Philadelphia, Pennsylvania. This study was funded in part by a research grant from NitroMed, Inc., of Lexington, Massachusetts, which funded the A-HeFT investigation. It was also supported in part by grants from the National Heart, Lung, and Blood Institute (contracts K24 HL69912 and RO1 HL75038). Drs. Tam and Worcel are former employees of NitroMed. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Manuscript received November 11, 2013; revised manuscript received April 10, 2014, accepted April 18, 2014. 552 McNamara et al. JACC: HEART FAILURE VOL. 2, NO. 6, 2014 DECEMBER 2014:551–7 GNB3 Polymorphism and ISDN-HYD in Heart Failure ABBREVIATIONS relegated to less common use in heart failure. institutions. Inclusion criteria for A-HeFT included AND ACRONYMS Interestingly, the survival benefit for I/H self-designation as African Americans, heart failure differed markedly in the V-HeFT studies be- resulting from systolic dysfunction, and standard tween black and white cohorts. Post hoc anal- background therapy for heart failure with neuro- ysis demonstrated a dramatic benefit of I/H hormonal blockade including ACE inhibitors or an- ACE = angiotensin-converting enzyme CS = composite score for black subjects in V-HeFT I, with a lesser giotensin receptor antagonists and beta blockers (4). combination of isosorbide impact evident in the larger white cohort Subjects were randomized to FDC I/H or placebo in FDC I/H = fixed-dose dinitrates and hydralazine (3). A similar analysis by race for V-HeFT II addition to standard therapy. Subjects were enrolled GNB3 = guanine nucleotide- found that the superiority of ACE inhibitors in the GRAHF genetic substudy at the A-HeFT binding proteins (G-proteins), was driven by the white subset, whereas in 6-month visits after providing informed consent. For black subjects, the survival with enalapril comparisons of allele frequencies by race, the cohort and I/H appeared more equivalent. The from GRACE (Genetic Risk Assessment of Cardiac observed enhanced impact of I/H in black Events), a single-center investigation based at the subjects with heart failure in these landmark heart failure clinic at the University of Pittsburgh, studies led to A-HeFT (African American Pennsylvania (11,12), was used (n ¼ 469). beta-3 subunit I/H = isosorbide dinitrate and hydralazine LVEF = left ventricular ejection fraction LVEDD = left ventricular end-diastolic diameter Heart Failure Trial) (4), in which a fixed- QoL = quality of life dose combination (FDC) of I/H added to back- SNP = single nucleotide ground therapy was demonstrated to improve polymorphism survival in a cohort of self-designated African Americans with a reduced ejection fraction (5). Hypertension is far more prevalent among blacks, and investigations of the genomic basis for this disorder have demonstrated significant differences between black and white cohorts in the prevalence of genetic variants that affect vascular tone. One example extensively studied is the G-protein beta-3 subunit (GNB3). A common GNB3 polymorphism in the coding region of exon-10, C825T, is associated with enhanced alpha2-adrenergic receptor intracellular signaling (6). The GNB3 T allele is linked to the risk of hypertension (7,8) and low plasma renin (9), and it has a much higher prevalence in black cohorts than among whites (10). Whether the T allele linked to low plasma renin is also associated with a diminished impact of ACE inhibitors remains unknown. GNB3 GENOTYPING. DNA was isolated from periph- eral blood by leukocyte centrifugation and cell lysis using the PureGene DNA purification kit (Gentra Systems, Minneapolis, Minnesota). The guanine nucleotide binding protein (G-protein) beta polypeptide-3 (GNB3) position 825 C/T polymorphism was assessed using a TaqMan SNP Genotyping Assay (Applied Biosystems, Inc., Foster City, California) with tagged primers (reporter 1 tagged dye ¼ VIC; reporter 2 tagged dye ¼ FAM). Context sequence for the GNB3 825 C/T polymorphism was as follows: AGAGCATCATCTGC GGCATCACGTC[C/T] GTGGCCTTCTCCCTCAGTGGCCG CC. Products were read using the Applied Biosystems 7000 (ABI). FOLLOW-UP AND CLINICAL OUTCOMES. Subjects in A-HeFT were followed for 18 months with assessment of deaths, hospital stays for heart failure, and quality of life (QoL) as endpoints (4). QoL assessment was performed by the Minnesota Living with Heart Failure Questionnaire at baseline and at the 6-month SEE PAGE 558 We hypothesized that genomic differences in GNB3-mediated alpha 2-adrenergic receptor activation may underlie the racial differences in the therapeutic efficacy of FDC I/H, and that the GNB3 T allele more prevalent among African Americans would be associated with a greater impact of I/H. We investigated the interaction of drug therapy and GNB3 genotype in the genetic substudy of A-HeFT, GRAHF (Genetic Risk of Heart Failure in African Americans). visit. All subjects enrolled in A-HeFT had a clinical assessment of left ventricular ejection fraction (LVEF) before enrollment (qualifying LVEF). In addition, in a subset of subjects in a remodeling substudy, LVEF and left ventricular end-diastolic diameter (LVEDD) were quantified by echocardiography at a central core laboratory at baseline (n ¼ 267) and at the 6-month follow-up visit (n ¼ 259). The primary endpoint for A-HeFT was a composite weighted score with 3 components: mortality, hospital stay for heart failure, and change in QoL at 6 months (4,5). The change in METHODS STUDY POPULATION. A total of 350 subjects in QoL score was reported as a component of the composite score (CS) ranging from most worsening to most improvement scores of 2 to 2 (4,5). A-HeFT were enrolled in GRAHF, a substudy of ge- STATISTICAL netic risk assessment of heart failure in African compared by genotype class by Kaplan-Meier log rank ANALYSIS. Event-free Americans. This investigation was approved by the analysis. Continuous variables such as CS were institutional review boards at the participating compared by genotype class by analysis of variance survival was McNamara et al. JACC: HEART FAILURE VOL. 2, NO. 6, 2014 DECEMBER 2014:551–7 (ANOVA). Statistical analysis was performed using SPSS version 20.0 (SPSS Inc., Chicago, Illinois). T A B L E 1 Baseline Clinical Characteristics of Patients in the GRAHF by GNB3 Genotype Results are presented as mean SD. Categorical variables were compared using a nonparametric chi-square Fisher-exact test. RESULTS 553 GNB3 Polymorphism and ISDN-HYD in Heart Failure All (N ¼ 350) TT (N ¼ 184) TCþCC (N ¼ 166) p Value 57 13 57 12 58 13 0.699 40 40 40 0.930 97/3 97/3 97/3 0.894 25 24 26 0.755 Age (yrs) Female (%) NYHA functional class (%/III/IV) Ischemic (%) 0.24 0.06 0.24 0.06 0.23 0.07 0.155 jects from GRAHF were genotyped for the GNB3 LVDD (cm) qualifying 6.4 0.9 6.4 0.8 6.4 1.1 0.680 BP systolic (mm Hg) 127 17 128 16 126 17 0.290 C825T polymorphism. Of the GRAHF cohort, 184 BP diastolic (mm Hg) 77 10 77 10 76 11 0.520 subjects (53%) were homozygous for the T allele, and Heart rate (beats/min) 73 11 73 12 74 11 0.445 166 (47%) had a least 1 copy of the C allele: 137 (39%) ACE inhibitor (%) 76 76 76 0.743 were heterozygous and 29 (8%) were homozygous for Aldosterone receptor antagonist (%) 36 35 37 0.782 the C allele. Comparison with the GRACE study Beta blocker (%) 84 85 83 0.569 GNB3 GENOTYPE FREQUENCIES. A total of 350 sub- demonstrated that the prevalence of the GNB3 T allele in GRAHF was similar to that seen in the black cohort from GRACE, but it was significantly greater than in the white cohort (% TT/CT/CC GRAHF ¼ 53/ LVEF qualifying Values are mean SD or %. ACE ¼ angiotensin-converting enzyme; BP ¼ blood pressure; GRAHF ¼ Genetic Risk Assessment of Heart Failure in African Americans; LVDD ¼ left ventricular diastolic diameter; LVEF ¼ left ventricular ejection fraction; NYHA ¼ New York Heart Association. 39/8; GRACE (black cohort) ¼ 54/27/19; GRACE (white cohort) ¼ 14/41/45, p < 0.001) (Figure 1). therapy, blood pressure, and NYHA class were all PATIENT CHARACTERISTICS. The GRAHF popula- similar in subjects homozygous with the T allele tion was 60% male, 25% ischemic, and 97% New York compared with subjects with 1 or 2 copies of the C Heart Association (NYHA) class III, with a mean age of allele. 57 13 years (Table 1). Most subjects were taking beta COMPOSITE SCORE, GNB3 GENOTYPE, AND IMPACT blockers (85%) and ACE inhibitors (75%) at time of OF THERAPY. Although in A-HeFT, treatment with study entry, and more than one third (36%) were FDC I/H significantly improved both CS and QoL (5), taking aldosterone receptor antagonists. Compari- in the smaller GRAHF subset, treatment with FDC I/H sons of baseline characteristics by GNB3 genotype was associated with a trend toward improved CS and class revealed no significant differences. Medical QoL that failed to reach significance (CS: placebo ¼ 0.10 1.8; FDC I/H ¼ 0.23 1.6, p ¼ 0.07; and for QoL: placebo ¼ 0.19 1.5; FDC I/H ¼ 0.49 1.4, p ¼ 0.07). When analyzed by GNB3 genotype, FDC I/H improved the CS among TT homozygotes (placebo ¼ 0.11 1.8; FDC I/H ¼ 0.50 1.6, p ¼ 0.02) (Figure 2), but it had no impact among subjects with the C allele (placebo ¼ 0.09 1.7; FDC I/H¼ 0.05 1.7, p ¼ 0.87). Improvement for QoL score with FDC I/H was also evident for GNB3 TT subjects (QoL component for GNB3 TT subset: placebo ¼ 0.24 1.5; FDC I/H ¼ 0.69 1.4, p ¼ 0.04) (Figure 3) but not among those with the C allele (placebo ¼ 0.14 1.5; FDC I/H ¼ 0.28 1.5, p ¼ 0.56). EVENT-FREE SURVIVAL. Over the course of follow- up, there were 61 (17.3%) hospital stays for heart F I G U R E 1 GNB3 Genotype Frequencies in GRAHF (A-HeFT) and the Black and White Subsets From GRACE failure and 12 deaths (3.4%). When evaluating the combined endpoint of death or hospital stays for heart failure, the percentages of event-free survival at Frequency of the GNB3 T haplotype is significantly greater in GRAHF (p < 0.001) compared with the white subset from GRACE. A-HeFT ¼ African American Heart Failure Trial; GNB3 ¼ guanine nucleotide-binding proteins (G-proteins) beta-3 subunit; GRACE ¼ Genetic Risk Assessment of Cardiac Events; GRAHF ¼ Genetic Risk Assessment of Heart Failure in African Americans. 6, 12, and 18 months were 91%, 81%, and 73%, respectively. Overall in GRAHF, treatment with FDC I/H did not improve event-free survival (FDC I/H event-free survival at 6, 12 and 18 months ¼ 91%, 83%, 76%; placebo ¼ 90%, 78%, 69%, p ¼ 0.41) (Figure 4A). However, when evaluated in the GNB3 TT 554 McNamara et al. JACC: HEART FAILURE VOL. 2, NO. 6, 2014 DECEMBER 2014:551–7 GNB3 Polymorphism and ISDN-HYD in Heart Failure poorer event-free survival was evident with the GNB3 TT genotype for subjects receiving placebo (p ¼ 0.048) (Figure 5A); this impact was not apparent in subjects treated with FDC I/H (p ¼ 0.35) (Figure 5B). F I G U R E 2 Composite Score in GRAHF by Treatment With FDC I/H Versus Placebo overall and in GNB3 Genotype Subsets GNB3 C (CTþCC) and GNB3 TT Treatment is associated with a significantly higher composite score in GNB3 TT subjects (p ¼ 0.02). FDC I/H ¼ fixed-dose combination of isosorbide dinitrate and hydralazine; other abbreviations as in Figure 1. subset (n ¼ 184), a significant impact of treatment was evident (FDC I/H event-free survival at 6, 12, and 18 months ¼ 92%, 86%, 79%; placebo ¼ 89%, 74%, 61%, p ¼ 0.047) (Figure 4B) that was not apparent for subjects with the C allele (FDC I/H event-free survival at 6, 12 and 18 months ¼ 90%, 80%, 73%; placebo ¼ 92%, 82%, 78%, p ¼ 0.35) (Figure 4C). When evaluating the impact of genotype by treatment subset, F I G U R E 3 Improvement in QoL in GRAHF at 6 Months by F I G U R E 4 Event-Free Survival by Treatment Treatment With FDC I/H Versus Placebo Overall and in With FDC I/H Versus Placebo GNB3 Genotype Subsets GNB3 C (CTþCC) and GNB3 TT (A) Overall GRAHF cohort (n ¼ 350, p ¼ 0.41). (B) GNB3 Treatment is associated with a significantly greater improvement TT subjects (n ¼ 184, p ¼ 0.047); (C) GNB3 CTþCC subjects in quality of life (QoL) score in GNB3 TT subjects (p ¼ 0.04). FDC (N ¼ 166, p ¼ 0.35) Impact of therapy is evident only in the GNB3 I/H ¼ fixed-dose combination of isosorbide dinitrate and TT subset. FDC I/H ¼ fixed-dose combination of isosorbide hydralazine; other abbreviations as in Figure 1. dinitrate and hydralazine; other abbreviations as in Figure 1. McNamara et al. JACC: HEART FAILURE VOL. 2, NO. 6, 2014 DECEMBER 2014:551–7 GNB3 Polymorphism and ISDN-HYD in Heart Failure genotype and the impact of treatment with FDC I/H on remodeling was apparent (Table 2). DISCUSSION In GRAHF, subjects with the GNB3 TT genotype received therapeutic benefit from FDC I/H, as demonstrated by an improved event-free survival and QoL and a higher CS. In contrast, no therapeutic impact was evident in subjects with 1 or 2 copies of the C allele. The prevalence of the T allele differs markedly by race; more than 50% of black cohorts have the homozygous GNB3 TT genotype associated with enhanced benefit of FDC I/H, compared with less than 15% of whites. These findings suggest that racial differences in the prevalence of the GNB3 T allele may underlie the apparent racial differences in the impact of therapy. The GNB3 C825T polymorphism is a functionally silent single nucleotide polymorphism (SNP) in exon 10 that does not change the amino acid sequence (14). Common SNPs are also evident in the GNB3 promoter region (G-350A), intron 9 (A3882C and G5249A), the 3 0 untranslated region (C1429T), in addition to an insertion/deletion polymorphism of 4 base pairs (6496 CACA) in intron 10. These polymorphisms are in near complete linkage disequilibrium with the 350A, 3882C, 5249A, 1429T and 6496 CACA insertion alleles co-inherited with the 825T allele as the “T haplotype” F I G U R E 5 Event-Free Survival by GNB3 Genotype GNB3 (guanine nucleotide-binding proteins [G proteins], beta (15). This haplotype is strongly associated with a splicing variant of GNB3, GNB3s, which is evident only 3 subunit) TT subset versus subjects with GNB3 C (CTþCC). (A) in cell lines with the 825T allele (7). When compared Subjects receiving placebo (n ¼ 186, p ¼ 0.047). (B) Subjects with the wild-type protein, GNB3s is missing 41 amino receiving a fixed-dose combination of isosorbide dinitrate and acids, a complete repeated loop domain, but it re- hydralazine (FDC I/H) (n ¼ 164, p ¼ 0.38). mains functionally active. Enhanced activation of G LEFT VENTRICULAR REMODELING, TREATMENT AND GNB3 GENOTYPE. Overall in A-HeFT, treatment T A B L E 2 Core Lab Assessment LVEF and LVDD at Baseline and 6 Months by GNB3 Genotype Overall and by Treatment (FDC I/H or Placebo) with FDC I/H was associated with significant reverse All TT TCþCC p Value LVEF baseline all (%) 35 8 36 8 34 9 0.052 LVEF baseline placebo 35 9 36 8 34 9 0.165 LVEF baseline FDC I/H 36 8 34 9 0.180 not significantly different by treatment group (LVEF 35 8 LVDD baseline all (cm) 6.4 1.2 6.3 1.3 6.5 1.2 0.134 at 6 months: placebo ¼ 0.36 0.10; FDC I/H ¼ 0.38 LVDD baseline placebo 6.4 1.2 6.4 1.2 6.5 1.2 0.523 0.09, p ¼ 0.16; change from baseline at 6 months: LVDD baseline FDC I/H 6.4 1.3 6.2 1.3 6.6 1.2 0.141 placebo ¼ 0.02 0.09; FDC I/H ¼ 0.03 0.08, LVEF 6 months all (%) 37 9 37 10 37 9 0.644 p ¼ 0.18). No clear interaction of GNB3 genotype LVEF 6 months placebo 36 10 37 11 35 9 0.160 LVEF 6 months FDC I/H 38 9 37 9 39 10 0.337 LVDD 6 months all (cm) 6.2 1.3 6.0 1.4 6.3 1.3 0.105 LVDD 6 months placebo 6.2 1.3 6.0 1.3 6.4 1.2 0.072 LVDD 6 months FDC I/H 6.2 1.4 6.1 1.4 6.2 1.4 0.608 remodeling, as assessed by the change in LVEF by echocardiography at 6 months (13). In the GRAHF substudy, improvements in LVEF at 6 months were with remodeling was evident. For subjects with the GNB3 TT genotype the mean LVEF was slightly higher at baseline (LVEF GNB3 TT: 0.36 0.08 versus C allele: 0.34 0.09, p ¼ 0.052); however, this difference at baseline was not evident at Values are mean SD. 6 months (GNB3 TT: LVEF ¼ 0.37 0.10; C allele: ¼ FDC I/H ¼ fixed-dose combination of isosorbide dinitrate and hydralazine; LVDD ¼ left ventricular diastolic diameter; LVEF ¼ left ventricular ejection fraction. 0.37 0.09, p ¼ 0.64). No clear interaction of GNB3 555 556 McNamara et al. JACC: HEART FAILURE VOL. 2, NO. 6, 2014 DECEMBER 2014:551–7 GNB3 Polymorphism and ISDN-HYD in Heart Failure proteins is evident in immortalized cell lines from Subjects with the GNB3 TT genotype had a signifi- hypertensive compared with normotensive subjects cantly higher risk of cerebral vascular events (HR: (16), and in these same cell lines it is tightly linked to 2.22, 95% CI: 1.31 to 3.79) which remained significant the presence of the 825T allele and GNB3s (7). when adjusting for blood pressure and other cardio- The role of the GNB3 polymorphism in the risk of vascular risk factors (32). hypertension has been studied extensively (17–19), In a small Brazilian cohort with systolic heart fail- and pharmacogenetic investigations have suggested ure, the GNB3 825T and the Arg389 b1 alleles were increased alpha2-adrenergic activation with the T associated with increased cardioverter-defibrillator allele as a potential mechanism. In subjects with hy- therapies (33). In these previous studies, the GNB3 pertension, the GNB3 T allele has been associated with TT genotype subset represented only 10% to 20% of an increased response to clonidine, a centrally acting the entire cohort, whereas in the GRAHF study in alpha2-adrenergic receptor antagonist (20). In inves- African Americans, this high-risk genotype was pre- tigation of coronary vasomotor response, subjects sent in more than 50% of subjects. Consistent with with the T allele also demonstrate enhanced vaso- these previous reports, GRAHF subjects with the GNB3 constriction (8,21), and this enhanced impact can be TT genotype who received standard heart failure eliminated by selective blockade of the alpha 2 , but not therapy plus placebo demonstrated the lowest CS and the alpha1 , adrenergic receptor (22). Although in- poorest event-free survival. Importantly, treatment vestigations of the role of GNB3 in cardiovascular dis- with FDC I/H appeared to eliminate this genetic risk. ease have focused on vascular reactivity, duplication STUDY LIMITATIONS. The current study is limited by of the GNB3 locus has been implicated as a cause of study number, which diminishes the power to obesity both in murine models and in human syn- address pharmacogenetic interactions. In particular, dromes of chromosomal translocation (23). In contrast, the small number of subjects homozygous for the C genome-wide association studies (GWAS) evaluating allele limits the ability to evaluate the impact of gene the genomic basis of obesity (24) and hypertension (25) dose on the outcomes observed. In addition, although have not identified GNB3 as a disease-associated locus. the T allele has been previously linked to low plasma Pharmacogenetic investigations suggest that the renin, renin and neurohormones were not measured GNB3 C825T polymorphism influences therapeutics as part of the GRAHF analysis. Finally, whereas the directed at the nitric oxide (NO) pathway. The en- current analysis is focused on GNB3, the influence of hanced vasoconstriction in subjects with the GNB3 T genomics on the effectiveness of heart failure therapy allele can be eliminated by pretreatment with the NO is almost certainly polygenic. Previous analysis in synthase (NOS) inhibitor L-NMMA (26). Carriers of the GRAHF suggests that genetic heterogeneity of NOS3 T allele also have an enhanced vasodilator response to (34) influences the benefit of FDC I/H, and variation of nitroglycerin (27), as well as an enhanced therapeutic the aldosterone synthase promoter affects event-free response to the phosphodiesterase type 5 inhibitor survival (35); however, the limited study number in (PDE5) sildenafil in subjects with erectile dysfunction GRAHF prevents analysis of gene-gene interactions. (28) and in those with pulmonary arterial hypertension An individual’s response to pharmacological inter- (29). Insulin-induced venodilation, a response medi- vention almost certainly involves multiple genomic ated by the NO pathway, is diminished in healthy car- loci, and as a result many previous attempts to riers of the GNB3 T allele (30). Together with GRAHF, replicate other pharmacogenetic reports of single SNP these studies suggest that the GNB3 TT genotype may interactions have not succeeded. identify subjects who would obtain maximal benefit from therapeutic strategies that enhance NO. CONCLUSIONS Recent reports from 2 separate longitudinal population studies suggest a higher risk of cardiovascular A-HeFT demonstrated that treatment with FDC I/H or cerebrovascular events in subjects with the GNB3 improved survival for a cohort of self-designated Af- TT genotype. In the Fungata study of a rural Japanese rican Americans with heart failure, and it remains a cohort of 1,524 subjects, those with the GNB3 TT pivotal study that for the first time resulted in the genotype had a higher incidence of cardiovascular approval by the Food and Drug Administration of a disease (hazard ratio [HR]: 1.82, 95% confidence in- heart failure therapy in a specific racial or ethnic terval [CI]: 1.14 to 2.89) and stroke (HR: 1.76, 95% CI: group (36,37). The ability of race to predict the ther- 1.01 to 3.07) despite no differences in blood pressure apeutic impact of I/H likely reflects its role as a or hypertension (31). In the Italian LEOGRA study, marker of functional genomic differences. Pharma- Last Evidence of Genetic Risk in the Aged, a cohort of cogenomic analysis should be more effective than subjects from 2 small towns was followed for 10 years. race in predicting efficacy and targeting heart failure McNamara et al. JACC: HEART FAILURE VOL. 2, NO. 6, 2014 DECEMBER 2014:551–7 GNB3 Polymorphism and ISDN-HYD in Heart Failure therapeutics. Although the current investigation suggests that the GNB3 genotype predicts the thera- REPRINT REQUESTS AND CORRESPONDENCE: Dr. peutic impact of FDC I/H for an individual, these Dennis M. McNamara, Center for Heart Failure Research, findings should be considered hypothesis generating Heart, Lung, Blood and Vascular Medicine Institute, and will require prospective validation. Further University of Pittsburgh Medical Center, 566 Scaife Hall, investigation is warranted to explore its potential 200 Lothrop Street, Pittsburgh, Pennsylvania 15213. utility for targeting heart failure therapeutics. E-mail: [email protected]. REFERENCES 1. Cohn JN, Archibald DG, Ziesche S, et al. 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Enhanced vasoconstriction to endothelin-1, angiotensin II and noradrenaline in carriers of the GNB3 825T KEY WORDS heart failure, outcomes, pharmacogenetics, race 557