Genome-wide meta-analysis of variant-by-diuretic interactions as modulators of lipid traits in persons of European and African ancestry

Hypertension (HTN) is a significant risk factor for cardiovascular morbidity and mortality. Metabolic abnormalities, including adverse cholesterol and triglycerides (TG) profiles, are frequent comorbid findings with HTN and contribute to cardiovascular disease. Diuretics, which are used to treat HTN and heart failure, have been associated with worsening of fasting lipid concentrations. Genome-wide meta-analyses with 39,710 European-ancestry (EA) individuals and 9,925 African-ancestry (AA) individuals were performed to identify genetic variants that modify the effect of loop or thiazide diuretic use on blood lipid concentrations. Both longitudinal and cross-sectional data were used to compute cohort-specific interaction results, which were then combined through meta-analysis in each ancestry. These ancestry-specific results were further combined through trans-ancestry meta-analysis. Analysis of EA data identified two genome-wide significant (p < 5×10⁻⁸) loci with single nucleotide variant (SNV)-loop diuretic interaction on TG concentrations (including COL11A1). Analysis of AA data identified one genome-wide significant locus adjacent to BMP2 with SNV-loop diuretic interaction on TG concentrations. Trans-ancestry analysis strengthened evidence of association for SNV-loop diuretic interaction at two loci (KIAA1217 and BAALC). There were few significant SNV-thiazide diuretic interaction associations on TG concentrations and for either diuretic on cholesterol concentrations. Several promising loci were identified that may implicate biologic pathways that contribute to adverse metabolic side effects from diuretic therapy.

Pharmacogenomics study of thiazide diuretics and QT interval in multi-ethnic populations: the cohorts for heart and aging research in genomic epidemiology

Thiazide diuretics, commonly used antihypertensives, may cause QT interval (QT) prolongation, a risk factor for highly fatal and difficult to predict ventricular arrhythmias. We examined whether common single-nucleotide polymorphisms (SNPs) modified the association between thiazide use and QT or its component parts (QRS interval, JT interval) by performing ancestry-specific, trans-ethnic and cross-phenotype genome-wide analyses of European (66%), African American (15%) and Hispanic (19%) populations (N=78 199), leveraging longitudinal data, incorporating corrected standard errors to account for underestimation of interaction estimate variances and evaluating evidence for pathway enrichment. Although no loci achieved genome-wide significance (P<5 × 10-8), we found suggestive evidence (P<5 × 10-6) for SNPs modifying the thiazide-QT association at 22 loci, including ion transport loci (for example, NELL1, KCNQ3). The biologic plausibility of our suggestive results and simulations demonstrating modest power to detect interaction effects at genome-wide significant levels indicate that larger studies and innovative statistical methods are warranted in future efforts evaluating thiazide-SNP interactions.

The association of statin therapy with the risk of recurrent venous thrombosis

Essentials A lowered risk of recurrent venous thrombosis (VT) with statin treatment is controversial. Among observational inception cohort of 2,798 adults with incident VT, 457 had recurrent VT. Time-to-event models with time-varying statin use and adjustment for potential confounders was used for analysis. Compared to nonuse, current statin use was associated with 26% lower risk of recurrent VT. Click to hear Prof. Büller's perspective on Anticoagulant Therapy in the Treatment of Venous Thromboembolism

SUMMARY

Background Meta-analyses of randomized controlled trials suggest that treatment with hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) lowers the risk of incident venous thrombosis (VT), particularly among those without prevalent clinical cardiovascular disease (CVD). Whether this is true for the prevention of recurrent VT is debated. We used an observational inception cohort to estimate the association of current statin use with the risk of recurrent VT. Methods and Results The study setting was a large healthcare organization with detailed medical record and pharmacy information at cohort entry and throughout follow-up. We followed 2798 subjects 18-89 years of age who experienced a validated incident VT between January 1, 2002, and December 31, 2010, for a first recurrent VT, validated by medical record review. During follow-up, 457 (16%) developed a first recurrent VT. In time-to-event models incorporating time-varying statin use and adjusting for potential confounders, current statin use was associated with a 26% lower risk of recurrent VT: hazard ratio 0.74, 95% confidence interval 0.59-0.94. Among cohort members free of CVD (n = 2134), current statin use was also associated with a lower risk (38%) of recurrent VT: hazard ratio 0.62, 95% confidence interval 0.45-0.85. We found similar results when restricting to new users of statins and in subgroups of different statin types and doses. Conclusions In a population-based cohort of subjects who had experienced an incident VT, statin use, compared with nonuse, was associated with a clinically relevant lower risk of recurrent VT. These findings suggest a potential secondary benefit of statins among patients who have experienced an incident VT.

Case-control study of second-line therapies for type 2 diabetes in combination with metformin and the comparative risks of myocardial infarction and stroke

We conducted a population-based case-control study to assess the myocardial infarction (MI) and stroke risks associated with sulphonylureas and insulin when used in combination with metformin. Cases had type 2 diabetes and used metformin + insulin or metformin + sulphonylureas at the time of a first MI or first stroke between 1995 and 2010; controls used the same treatment combinations and were randomly sampled from the same population. MI and stroke diagnoses and potential confounders were validated by medical record reviews. Compared with metformin + sulphonylurea, metformin + insulin was associated with similar risks of MI or stroke [odds ratio 0.98 (95% confidence interval 0.63-1.52)]. Meta-analysis with another observational study improved the precision of the risk estimate [relative risk 0.92 (95% confidence interval 0.69-1.24)]. Current evidence suggests that there may not be large differences in cardiovascular risk associated with the use of insulin or sulphonylureas when used in combination with metformin.

Differential associations of oral estradiol and conjugated equine estrogen with hemostatic biomarkers

BACKGROUND

The risk of venous thrombosis (VT) associated with oral hormone therapy (HT) may differ by type of estrogen compound.

OBJECTIVE

To compare the thrombotic profile of women using oral conjugated equine estrogens (CEE) with that of women using oral estradiol (E2).

METHODS

In postmenopausal, female, health maintenance organization (HMO) members with no history of VT, we measured thrombin generation, levels of factor VII activity, antithrombin activity and total protein S antigen. Mean levels of hemostasis biomarkers were cross-sectionally compared by use and type of estrogen using multiple linear regressions. The type of estrogen used was determined primarily by the HMO formulary, which changed its preferred estrogen from CEE to E2 during the study period.

RESULTS

The sample included 92 E2 users and 48 CEE users, with a mean age of 64.1 years and mean BMI of 29.1 kg m(-2) . Twenty-seven per cent of HT contained medroxyprogesterone acetate. Compared with E2 users, CEE users had greater thrombin generation peak values and endogenous thrombin potential, and lower total protein S (multivariate adjusted differences of 49.8 nm (95% CI, 21.0, 78.6), 175.0 nm × Min (95% CI, 54.4, 295.7) and -13.4% (95% CI, -19.8, -6.9), respectively). Factor VII and antithrombin levels were not different between E2 and CEE users. Results were similar in subgroups of users of unopposed HT, opposed HT, low-dose estrogen and standard dose estrogen.

CONCLUSION

The hemostatic profile of women using CEE is more prothrombotic than that of women using E2. These findings provide further evidence for a different thrombotic risk for oral CEE and oral E2.

The association of smoking with venous thrombosis in women. A population-based, case-control study

The evidence for an association between smoking and venous thrombosis (VT) is inconsistent, and its mediation pathways remain to be fully elucidated. A population-based, case-control study was conducted in a large, integrated healthcare system in Washington State, USA. Cases were women aged 18-90 years who experienced a validated incident deep-vein thrombosis or pulmonary embolism between January 1, 1995, and December 31, 2009. Controls were randomly selected from members of the healthcare system. Smoking status (current, former, never) was assessed from medical records review and, for a subset, also by telephone interview. Multivariable logistic regression was used to estimate odds ratios (OR) associated with smoking status. We identified 2,278 cases and 5,927 controls. Subjects comprised mostly postmenopausal white women with a mean age of 66 years and a current smoking prevalence of 10%. Compared to never-smokers, current and former smokers were at higher risk of VT (adjusted OR 1.21, 95% confidence interval [CI] 1.02-1.44 and OR 1.15, 95%CI 1.03-1.29, respectively). These associations were attenuated with further adjustment for potential mediators (cardiovascular disease, congestive heart failure, cancer, recent hospitalisations and physical activity): OR 1.02 (95%CI 0.83-1.25) and 0.95 (95%CI 0.83-1.08), respectively. In conclusion, the modestly increased risk of VT in women who are current or former smokers might be explained by the occurrence of smoking-related diseases and decreased physical activity. Our results do not support a direct biological effect of smoking on the risk of VT that is clinically relevant.

A screening study of drug-drug interactions in cerivastatin users: an adverse effect of clopidogrel

An analysis of a case-control study of rhabdomyolysis was conducted to screen for previously unrecognized cytochrome P450 enzyme (CYP) 2C8 inhibitors that may cause other clinically important drug-drug interactions. Medication use in cases of rhabdomyolysis using cerivastatin (n = 72) was compared with that in controls using atorvastatin (n = 287) for the period 1998-2001. The use of clopidogrel was strongly associated with rhabdomyolysis (odds ratio (OR) 29.6; 95% confidence interval (CI), 6.1-143). In a replication effort that used the US Food and Drug Administration (FDA) Adverse Event Reporting System (AERS), it was found that clopidogrel was used more commonly in patients with rhabdomyolysis receiving cerivastatin (17%) than in those receiving atorvastatin (0%, OR infinity; 95% CI = 5.2-infinity). Several medications were tested in vitro for their potential to cause drug-drug interactions. Clopidogrel, rosiglitazone, and montelukast were the most potent inhibitors of cerivastatin metabolism. Clopidogrel and its metabolites also inhibited cerivastatin metabolism in human hepatocytes. These epidemiological and in vitro findings suggest that clopidogrel may cause clinically important, dose-dependent drug-drug interactions with other medications metabolized by CYP2C8.

Antihypertensive treatment with ACE inhibitors or beta-blockers and risk of incident atrial fibrillation in a general hypertensive population

BACKGROUND

Secondary analyses of clinical trial data suggest that, compared with other agents, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) are associated with lower risk of incident atrial fibrillation (AF) in patients with heart failure, but data from the hypertension trials have been inconsistent. Information is scant about the association of beta-blocker use with AF risk in hypertensive patients without heart failure.

METHODS

We conducted a population-based case-control study to determine whether antihypertensive treatment with ACE inhibitors/ARBs or beta-blockers, compared with diuretics, was associated with the risk of incident AF in a community practice setting. All patients (810 AF cases, 1,512 control subjects) were members of Group Health (GH), an integrated health-care delivery system, were pharmacologically treated for hypertension, and did not have heart failure. Medical records were reviewed to confirm the diagnosis of incident AF and to collect information on medical conditions and health behaviors. Information on antihypertensive medications was obtained from a pharmacy database.

RESULTS

Single-drug users of an ACE inhibitor/ARB had a lower risk of incident AF compared with single-drug users of a diuretic (adjusted odds ratio 0.63, 95% confidence interval 0.44-0.91). Single-drug use of beta-blockers was not significantly associated with lower AF risk (odds ratio 1.05, 95% confidence interval 0.73-1.52), and also none of the most commonly used two-drug regimens was significantly associated with AF risk, in comparison with single-drug use of diuretic.

CONCLUSIONS

In a general hypertensive population without heart failure, single-drug use of ACE inhibitors/ARBs was associated with lower AF risk.

ABO genotype and risk of thrombotic events and hemorrhagic stroke

BACKGROUND

The non-O alleles of the ABO genotype have been associated with an increased risk of thrombosis. Risk associated with the specific A(1), A(2) or B alleles is not well defined.

OBJECTIVES

To examine the association of the ABO genotype with myocardial infarction (MI), ischemic stroke, hemorrhagic stroke, and venous thrombosis (VT).

PATIENTS AND METHODS

We used data from two ongoing population-based case-control studies of MI, stroke, and VT. Cases included hypertensive adults and postmenopausal women with incident non-fatal MI (n = 1063), ischemic stroke (n = 469), and hemorrhagic stroke (n = 91), and postmenopausal women with incident non-fatal VT (n = 504). Controls were frequency matched to cases on age, sex, hypertension status, and year of identification. ABO genotypes were determined using single-nucleotide polymorphisms, and subjects were grouped by diplotype according to the presence of O(1), O(2), A(11), A(2) and B alleles. Logistic regression was used to test the association of diplotypes with risk of each outcome.

RESULTS

As compared with the O(1)O(1) group, the A(11) allele was associated with an increased risk of VT [odds ratio (OR) 1.79; 95% confidence interval (CI) 1.41-2.26] and MI (OR 1.23; 95% CI 1.05-1.44). The B allele was associated with an increased risk of VT (OR 1.82; 95% CI 1.29-2.57) and ischemic stroke (OR 1.59; 95% CI 1.17-2.17). The AB diplotype category was associated with a 2.7-fold risk of VT (OR 2.70; 95% CI 1.73-4.21). No other associations reached significance.

CONCLUSIONS

The VT and MI findings are confirmatory, and the ischemic stroke finding with the B allele is a novel finding and needs replication.

Variation in 24 hemostatic genes and associations with non-fatal myocardial infarction and ischemic stroke

BACKGROUND

Arterial thrombosis involves platelet aggregation and clot formation, yet little is known about the contribution of genetic variation in fibrin-based hemostatic factors to arterial clotting risk. We hypothesized that common variation in 24 coagulation-fibrinolysis genes would contribute to risk of incident myocardial infarction (MI) or ischemic stroke (IS).

METHODS

We conducted a population-based, case-control study. Subjects were hypertensive adults and postmenopausal women 30-79 years of age, who sustained a first MI (n = 856) or IS (n = 368) between 1995 and 2002, and controls matched on age, hypertension status, and calendar year (n = 2,689). We investigated the risk of MI and IS associated with (i) global variation within each gene as measured by common haplotypes and (ii) individual haplotypes and single nucleotide polymorphisms (SNPs). Significance was assessed using a 0.2 threshold of the false discovery rate q-value, which accounts for multiple testing.

RESULTS

After accounting for multiple testing, global genetic variation in factor (F) VIII was associated with IS risk. Two haplotypes in FVIII and one in FXIIIa1 were significantly associated with increased IS risk (all q-values < 0.2). A plasminogen gene SNP was associated with MI risk. All are new discoveries not previously reported. Another 24 tests had P-values < 0.05 and q-values > 0.2 in MI and IS analyses, 23 of which are new and hypothesis generating.

CONCLUSIONS

Apart from the association of FVIII variation with IS, we found little evidence that common variation in the 24 candidate fibrin-based hemostasis genes strongly influences arterial thrombotic risk, but our results cannot rule out small effects.

Orthogonal Machining of Bone

An investigation is described of the mechanics of orthogonal machining of bone. Experimental results are presented for the machining forces and specific energies for various cutting orientations, rake angles, and depths of cut. From microscopic observations on sections taken through the cutting zone, the chip formation process is seen to occur by a series of discrete fractures. A simple model is proposed to qualitatively describe the mechanics of chip formation. The energy expended by the cutting process under a wide variety of conditions is found to increase linearly with the surface area generated on the chip fragments, which is a further indication that chip formation during cutting of bone occurs by fracture.