A genetic locus on chromosome 2q24 predicting peripheral neuropathy risk in type 2 diabetes: Results from the ACCORD and BARI 2D studies

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 wellcharacterized 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 DPNnegative 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 (P < 5×10-8) 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, P = 1.9×10-9). This effect was not influenced by ACCORD treatment assignments (P 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,P=9×10-4; summary P=7.9×10-12). In GTEx, the minor, protective allele at this locus was associated with higher tibial nerve expression of an adjacent gene (SCN2A) coding for human voltage-gated sodium channel NaV1.2 (P = 9×10-4). 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

PPARA polymorphism influences the cardiovascular benefit of fenofibrate in type 2 diabetes: Findings from accord-lipid

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 PPARA gene, coding for the pharmacological target of fibrates (PPAR-a), 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 PPARA 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 (Pinteraction 5 3.7 3 1024). The rs6008845-by-fenofibrate interaction on MACE was replicated in African Americans from ACCORD (N 5 585, P 5 0.02) and in external cohorts (ACCORD-BP, ORIGIN, and TRIUMPH, total N 5 3059, P 5 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 (P for rs6008845-by-fenofibrate interaction 5 0.003). The GTEx data set revealed regulatory functions of rs6008845 on PPARA expression in many tissues. In summary, we have found a common PPARA 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

Whole-exome sequence analysis of anthropometric traits illustrates challenges in identifying effects of rare genetic variants

Anthropometric traits, measuring body size and shape, are highly heritable and significant clinical risk factors for cardiometabolic disorders. These traits have been extensively studied in genome-wide association studies (GWASs), with hundreds of genome-wide significant loci identified. We performed a whole-exome sequence analysis of the genetics of height, body mass index (BMI) and waist/hip ratio (WHR). We meta-analyzed single-variant and gene-based associations of whole-exome sequence variation with height, BMI, and WHR in up to 22,004 individuals, and we assessed replication of our findings in up to 16,418 individuals from 10 independent cohorts from Trans-Omics for Precision Medicine (TOPMed). We identified four trait associations with single-nucleotide variants (SNVs; two for height and two for BMI) and replicated the LECT2 gene association with height. Our expression quantitative trait locus (eQTL) analysis within previously reported GWAS loci implicated CEP63 and RFT1 as potential functional genes for known height loci. We further assessed enrichment of SNVs, which were monogenic or syndromic variants within loci associated with our three traits. This led to the significant enrichment results for height, whereas we observed no Bonferroni-corrected significance for all SNVs. With a sample size of ∼20,000 whole-exome sequences in our discovery dataset, our findings demonstrate the importance of genomic sequencing in genetic association studies, yet they also illustrate the challenges in identifying effects of rare genetic variants

CHRNA5 variant predicts smoking cessation in patients with acute myocardial infarction

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.Li-Shiun Chen, Richard G. Bach, Petra A. Lenzini, John A. Spertus, Laura Jean Bierut, Sharon Cresci ... at al

Clinical outcomes associated with proton pump inhibitor use among clopidogrel-treated patients within CYP2C19 genotype groups following acute myocardial infarction

We examined clinical outcomes with proton pump inhibitors (PPI) use within CYP2C19 genotype groups during clopidogrel treatment following acute myocardial infarction (AMI). 2062 patients were genotyped for CYP2C19*2 and *17 variants in TRIUMPH. 12 month clinical outcomes were analyzed among patients discharged on clopidogrel within CYP2C19*2 carrier, CYP2C19*17 carrier, and CYP2C19*1 homozygote genotype groups. PPI use was not associated with a difference in mortality. Among clopidogrel-treated Caucasians following AMI, PPI use was associated with a significantly higher rate of cardiac rehospitalization (HR 1.62, 95% CI 1.19-2.19; P=0.002) compared with no PPI use. PPI users who were carriers of the CYP2C19*17 variant experienced significantly higher rates of cardiac rehospitalization (HR 2.05, 95% CI 1.26-3.33; P=0.003), carriers of the CYP2C19*2 variant had a trend toward increased 1-year cardiac rehospitalization (HR 1.69, 95% CI 0.95-2.99; P=0.07), while no significant differences were observed among CYP2C19*1 homozygotes. These results indicate that the risks associated with PPI use among clopidogrel-treated Caucasian post-MI patients are impacted by CYP2C19 genotype, and suggest knowledge of genotype may be useful for personalizing PPI use among patients following AMI to reduce rehospitalization.J P Depta, P A Lenzini, D E Lanfear, T Y Wang, J A Spertus, R G Bach and S Cresc

Adrenergic-pathway gene variants influence beta-blockerrelated outcomes after acute coronary syndrome in a race-specific manner

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.β-adrenergic receptor blockade after ACS is a measure of quality care, but the effectiveness across racial groups is less clear.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.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).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.Sharon Cresci, Gerald W. Dorn, Philip G. Jones, Amber L. Beitelshees, Allie Y. Li ... John Spertus ... et al

A novel genetic marker of decreased inflammation and improved survival after acute myocardial infarction

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.Edward D. Coverstone, Richard G. Bach, LiShiun Chen, Laura J. Bierut, Allie Y. Li, Petra A. Lenzini ... et al