Human GWAS of obesity have been successful in identifying loci associated with adiposity, but for the most part, these are non-coding SNPs whose function, or even whose gene of action, is unknown. To ...help identify the genes on which these human BMI loci may be operating, we conducted a high throughput screen in Drosophila melanogaster. Starting with 78 BMI loci from two recently published GWAS meta-analyses, we identified fly orthologs of all nearby genes (± 250KB). We crossed RNAi knockdown lines of each gene with flies containing tissue-specific drivers to knock down (KD) the expression of the genes only in the brain and the fat body. We then raised the flies on a control diet and compared the amount of fat/triglyceride in the tissue-specific KD group compared to the driver-only control flies. 16 of the 78 BMI GWAS loci could not be screened with this approach, as no gene in the 500-kb region had a fly ortholog. Of the remaining 62 GWAS loci testable in the fly, we found a significant fat phenotype in the KD flies for at least one gene for 26 loci (42%) even after correcting for multiple comparisons. By contrast, the rate of significant fat phenotypes in RNAi KD found in a recent genome-wide Drosophila screen (Pospisilik et al. (2010) is ~5%. More interestingly, for 10 of the 26 positive regions, we found that the nearest gene was not the one that showed a significant phenotype in the fly. Specifically, our screen suggests that for the 10 human BMI SNPs rs11057405, rs205262, rs9925964, rs9914578, rs2287019, rs11688816, rs13107325, rs7164727, rs17724992, and rs299412, the functional genes may NOT be the nearest ones (CLIP1, C6orf106, KAT8, SMG6, QPCTL, EHBP1, SLC39A8, ADPGK /ADPGK-AS1, PGPEP1, KCTD15, respectively), but instead, the specific nearby cis genes are the functional target (namely: ZCCHC8, VPS33A, RSRC2; SPDEF, NUDT3; PAGR1; SETD1, VKORC1; SGSM2, SRR; VASP, SIX5; OTX1; BANK1; ARIH1; ELL; CHST8, respectively). The study also suggests further functional experiments to elucidate mechanism of action for genes evolutionarily conserved for fat storage.
The
CHRNA5
gene encodes a neurotransmitter receptor subunit involved in multiple processes, including cholinergic autonomic nerve activity and inflammation. Common variants in
CHRNA5
have been linked ...with atherosclerotic cardiovascular disease. Association of variation in
CHRNA5
and specific haplotypes with cardiovascular outcomes has not been described. The aim of this study was to examine the association of
CHRNA5
haplotypes with gene expression and mortality among patients with acute myocardial infarction (AMI) and explore potential mechanisms of this association. Patients (
N
= 2054) hospitalized with AMI were genotyped for two common variants in
CHRNA5
. Proportional hazard models were used to estimate independent association of
CHRNA5
haplotype with 1-year mortality. Both individual variants were associated with mortality (
p
= 0.0096 and 0.0004, respectively) and were in tight LD (
D
′ = 0.99). One haplotype, HAP3, was associated with decreased mortality one year after AMI (adjusted HR = 0.42, 95% CI 0.26, 0.68;
p
= 0.0004). This association was validated in an independent cohort (
N
= 637) of post-MI patients (adjusted HR = 0.23, 95% CI 0.07, 0.79;
p
= 0.019). Differences in
CHRNA5
expression by haplotype were investigated in human heart samples (
n
= 28). Compared with non-carriers, HAP3 carriers had threefold lower cardiac
CHRNA5
mRNA expression (
p
= 0.023). Circulating levels of the inflammatory marker hsCRP were significantly lower in HAP3 carriers versus non-carriers (3.43 ± 4.2 versus 3.91 ± 5.1;
p
= 0.0379). Activation of the inflammasome, an important inflammatory complex involved in cardiovascular disease that is necessary for release of the pro-inflammatory cytokine IL-1 β, was assessed in bone marrow-derived macrophages (BMDM) from
CHRNA5
knockout mice and wild-type controls. In BMDM from
CHRNA5
knockout mice, IL-1β secretion was reduced by 50% compared to wild-type controls (
p
= 0.004). Therefore, a common haplotype of
CHRNA5
that results in reduced cardiac expression of
CHRNA5
and attenuated macrophage inflammasome activation is associated with lower mortality after AMI. These results implicate
CHRNA5
and the cholinergic anti-inflammatory pathway in survival following AMI.
Genetic factors have been postulated to be involved in the etiology of diabetic peripheral neuropathy (DPN), but their identity remains mostly unknown. The aim of this study was to conduct a ...systematic search for genetic variants influencing DPN risk using two well-characterized cohorts. A genome-wide association study (GWAS) testing 6.8 million single nucleotide polymorphisms was conducted among participants of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) clinical trial. Included were 4,384 white case patients with type 2 diabetes (T2D) and prevalent or incident DPN (defined as a Michigan Neuropathy Screening Instrument clinical examination score >2.0) and 784 white control subjects with T2D and no evidence of DPN at baseline or during follow-up. Replication of significant loci was sought among white subjects with T2D (791 DPN-positive case subjects and 158 DPN-negative control subjects) from the Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes (BARI 2D) trial. Association between significant variants and gene expression in peripheral nerves was evaluated in the Genotype-Tissue Expression (GTEx) database. A cluster of 28 SNPs on chromosome 2q24 reached GWAS significance (
< 5 × 10
) in ACCORD. The minor allele of the lead SNP (rs13417783, minor allele frequency = 0.14) decreased DPN odds by 36% (odds ratio OR 0.64, 95% CI 0.55-0.74,
= 1.9 × 10
). This effect was not influenced by ACCORD treatment assignments (
for interaction = 0.6) or mediated by an association with known DPN risk factors. This locus was successfully validated in BARI 2D (OR 0.57, 95% CI 0.42-0.80,
= 9 × 10
; summary
= 7.9 × 10
). In GTEx, the minor, protective allele at this locus was associated with higher tibial nerve expression of an adjacent gene (
) coding for human voltage-gated sodium channel NaV1.2 (
= 9 × 10
). To conclude, we have identified and successfully validated a previously unknown locus with a powerful protective effect on the development of DPN in T2D. These results may provide novel insights into DPN pathogenesis and point to a potential target for novel interventions.
High variability in drug response and a narrow therapeutic index complicate warfarin therapy initiation. No existing algorithm provides recommendations on refining the initial warfarin dose based on ...genetic variables, clinical data, and international normalized ratio (INR) values. Our goal was to develop such an algorithm. We studied 92 patients undergoing primary or revision total hip or knee replacement. From each patient we collected a blood sample, clinical variables, current medications, and preoperative and postoperative laboratory values. We genotyped for polymorphisms in the cytochrome P450 (CYP) 2C9 and vitamin K epoxide reductase (VKORC1) genes. Using stepwise regression, we developed a model for refining the warfarin dose after the third warfarin dose. The algorithm explained four fifths of the variability in therapeutic dose (R2adj of 79%). Significant (P > .05) predictors were INR value after 3 doses (47% reduction per 0.25-unit rise), first warfarin dose (+7% per 1 mg), CYP2C9*3 and CYP2C9*2 genotype (−38% and −17% per allele), estimated blood loss (interacting with INR3), smoking status (+20% in current smokers), and VKORC1 (−11% per copy of haplotype A). If validated, this model should provide a safer, more effective process for initiating warfarin therapy.
The cardiovascular benefits of fibrates have been shown to be heterogeneous and to depend on the presence of atherogenic dyslipidemia. We investigated whether genetic variability in the
gene, coding ...for the pharmacological target of fibrates (PPAR-α), could be used to improve the selection of patients with type 2 diabetes who may derive cardiovascular benefit from addition of this treatment to statins. We identified a common variant at the
locus (rs6008845, C/T) displaying a study-wide significant influence on the effect of fenofibrate on major cardiovascular events (MACE) among 3,065 self-reported white subjects treated with simvastatin and randomized to fenofibrate or placebo in the ACCORD-Lipid trial. T/T homozygotes (36% of participants) experienced a 51% MACE reduction in response to fenofibrate (hazard ratio 0.49; 95% CI 0.34-0.72), whereas no benefit was observed for other genotypes (
= 3.7 × 10
). The rs6008845-by-fenofibrate interaction on MACE was replicated in African Americans from ACCORD (
= 585,
= 0.02) and in external cohorts (ACCORD-BP, ORIGIN, and TRIUMPH, total
= 3059,
= 0.005). Remarkably, rs6008845 T/T homozygotes experienced a cardiovascular benefit from fibrate even in the absence of atherogenic dyslipidemia. Among these individuals, but not among carriers of other genotypes, fenofibrate treatment was associated with lower circulating levels of CCL11-a proinflammatory and atherogenic chemokine also known as eotaxin (
for rs6008845-by-fenofibrate interaction = 0.003). The GTEx data set revealed regulatory functions of rs6008845 on
expression in many tissues. In summary, we have found a common
regulatory variant that influences the cardiovascular effects of fenofibrate and that could be used to identify patients with type 2 diabetes who would derive benefit from fenofibrate treatment, in addition to those with atherogenic dyslipidemia.
Objectives Overcoming racial differences in acute coronary syndrome (ACS) outcomes is a strategic goal for U.S. health care. Genetic polymorphisms in the adrenergic pathway seem to explain some ...outcome differences by race in other cardiovascular diseases treated with β-adrenergic receptor blockade (BB). Whether these genetic variants are associated with survival among ACS patients treated with BB, and if this differs by race, is unknown. Background β-adrenergic receptor blockade after ACS is a measure of quality care, but the effectiveness across racial groups is less clear. Methods A prospective cohort of 2,673 ACS patients (2,072 Caucasian; 601 African-American) discharged on BB from 22 U.S. hospitals were followed for 2 years. Subjects were genotyped for polymorphisms in ADRB1, ADRB2, ADRA2C, and GRK5 . We used proportional hazards regression to model the effect of genotype on mortality, stratified by race and adjusted for baseline factors. Results The overall 2-year mortality rate was 7.5% for Caucasians and 16.7% for African Americans. The prognosis associated with different genotypes in these BB-treated patients differed by race. In Caucasians, ADRA2C 322-325 deletion carriers had significantly lower mortality as compared with homozygous individuals lacking the deletion (hazard ratio: 0.46; confidence interval CI: 0.21 to 0.99; p = 0.047; race × genotype interaction p = 0.053). In African Americans, the ADRB2 16R allele was associated with significantly increased mortality (hazard ratio for RG vs. GG: 2.10; CI: 1.14 to 3.86; RR vs. GG: 2.65; CI: 1.38 to 5.08; p = 0.013; race × genotype interaction p = 0.096). Conclusions Adrenergic pathway polymorphisms are associated with mortality in ACS patients receiving BB in a race-specific manner. Understanding the mechanism by which different genes impact post-ACS mortality differently in Caucasians and African Americans might illuminate opportunities to improve BB therapy in these groups.
Abstract Background Limited evidence exists regarding the utility of genetic risk scores (GRS) in predicting recurrent cardiovascular events after acute coronary syndrome (ACS). We sought to ...determine whether a GRS would predict early recurrent cardiovascular events within 1 year of ACS. Methods & Results Participants admitted with acute coronary syndromes from the RISCA, PRAXY, and TRIUMPH cohorts, were genotyped for 30 single nucleotide polymorphisms (SNPs) associated with coronary artery disease (CAD) or myocardial infarction (MI) in prior genome wide association studies. A 30 SNP CAD/MI GRS was constructed. The primary endpoint was defined as all-cause mortality, recurrent ACS or cardiac re-hospitalization within 1 year of ACS admission. Results across all cohorts for the 30 SNP CAD/MI GRS were pooled using a random-effects model. There were 1040 patients from the RISCA cohort, 691 patients from the PRAXY cohort, and 1772 patients from the TRIUMPH cohort included in the analysis and 389 occurrences of the primary endpoint of recurrent events at 1-year post-ACS. In unadjusted and fully adjusted analyses, a 30 SNP GRS was not significantly associated with recurrent events (HR per allele 0.97 (95%CI 0.91–1.03) for RISCA, HR 0.99 (95%CI 0.93–1.05) for PRAXY, 0.98 (95%CI 0.94–1.02) for TRIUMPH, and 0.98 (95%CI 0.95–1.01) for the pooled analysis). Addition of this GRS to the GRACE risk model did not significantly improve risk prediction. Conclusion The 30 MI SNP GRS was not associated with recurrent events 1-year post ACS in pooled analyses across cohorts and did not improve risk discrimination or reclassification indices. Our results suggest that the genetic etiology of early events post-ACS may differ from later events.
Clopidogrel is recommended after acute myocardial infarction but has variable efficacy and safety, in part related to the effect of cytochrome P450 (CYP) polymorphisms on its metabolism. The effect ...of CYP polymorphisms on cardiovascular events among clopidogrel-treated patients after acute myocardial infarction remains controversial, and no studies to date have investigated the association of CYP variants with outcomes in black patients.
Subjects (2732: 2062 whites; 670 blacks) hospitalized with acute myocardial infarction enrolled in the prospective, multicenter TRIUMPH study were genotyped for CYP polymorphisms. The majority of whites (79%) and blacks (64.4%) were discharged on clopidogrel. Among whites, carriers of the loss-of-function CYP2C19*2 allele had significantly increased 1-year mortality (adjusted hazards ratio HR: 1.70; confidence interval CI: 1.01-2.86; P=0.046) and a trend toward increased rate of recurrent MI (adjusted HR: 2.10; CI: 0.95-4.63; P=0.066). Among blacks, increased 1-year mortality was associated with the gain-of-function CYP2C19*17 allele (adjusted HR for *1/*17 versus *1/*1: 2.02; CI: 0.92-4.44; *17/*17 versus *1/*1: 8.97; CI: 3.34-24.10; P<0.0001) and the CYP1A2*1C allele (adjusted HR for *1/*1C versus *1/*1: 1.89; CI: 0.85-4.22; *1C/*1C versus *1/*1: 4.96; CI: 1.69-14.56; P=0.014). Bleeding events were significantly more common among black carriers of CYP2C19*17 or CYP1A2*1C.
Both loss-of-function and gain-of-function CYP polymorphisms affecting clopidogrel metabolism are associated with increased mortality among clopidogrel-treated patients after acute myocardial infarction; the specific polymorphism and the putative mechanism vary according to race.
While smoking is a major modifiable risk factor for secondary prevention of myocardial infarction (MI), active smoking is common among patients hospitalized with acute MI. Recent studies suggest that ...nicotinic receptor variants, and specifically the high-risk CHRNA5 rs16969968 A allele, are associated with cessation failure among noncardiac patients. This study investigates the association between CHRNA5 rs16969968 and smoking cessation in patients hospitalized with acute MI.
Using data from the TRIUMPH study, we ascertained smoking status at the time of index hospitalization for acute MI and 1 year after hospitalization. After adjusting for age and sex, we used logistic regression to model the association between smoking cessation and CHRNA5 rs16969968.
At index admission, 752 Caucasian subjects were active smokers and 699 were former smokers. Among these ever-smokers, the A allele was associated with significantly decreased abstinence (45.0% abstinence for A allele carriers vs. 51.7% for GG homozygotes; odds ratio OR = 0.70, 95% confidence interval CI = 0.56-0.88, p = .0027). The A allele was also significantly associated with decreased abstinence at 1 year (69.1% abstinence for A allele carriers vs. 76.0% for GG homozygotes; OR = 0.70, 95% CI = 0.53-0.94, p = .0185).
Among patients who have smoked and who are hospitalized with acute MI, the high-risk CHRNA5 allele was associated with lower likelihood of quitting before hospitalization and significantly less abstinence 1 year after hospitalization with MI. The CHRNA5 rs16969968 genotype may therefore identify patients who would benefit from aggressive, personalized smoking cessation intervention.
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