Björn Wahlstrand

Genome-wide association study of blood pressure extremes identifies variant near UMOD associated with hypertension

Hypertension is a heritable and major contributor to the global burden of disease. The sum of rare and common genetic variants robustly identified so far explain only 1%–2% of the population variation in BP and hypertension. This suggests the existence of more undiscovered common variants. We conducted a genome-wide association study in 1,621 hypertensive cases and 1,699 controls and follow-up validation analyses in 19,845 cases and 16,541 controls using an extreme case-control design. We identified a locus on chromosome 16 in the 5′ region of Uromodulin (UMOD; rs13333226, combined P value of 3.6×10−11). The minor G allele is associated with a lower risk of hypertension (OR [95%CI]: 0.87 [0.84–0.91]), reduced urinary uromodulin excretion, better renal function; and each copy of the G allele is associated with a 7.7% reduction in risk of CVD events after adjusting for age, sex, BMI, and smoking status (H.R. = 0.923, 95% CI 0.860–0.991; p = 0.027). In a subset of 13,446 individuals with estimated glomerular filtration rate (eGFR) measurements, we show that rs13333226 is independently associated with hypertension (unadjusted for eGFR: 0.89 [0.83–0.96], p = 0.004; after eGFR adjustment: 0.89 [0.83–0.96], p = 0.003). In clinical functional studies, we also consistently show the minor G allele is associated with lower urinary uromodulin excretion. The exclusive expression of uromodulin in the thick portion of the ascending limb of Henle suggests a putative role of this variant in hypertension through an effect on sodium homeostasis. The newly discovered UMOD locus for hypertension has the potential to give new insights into the role of uromodulin in BP regulation and to identify novel drugable targets for reducing cardiovascular risk.

Common Missense Variant in the Glucokinase Regulatory Protein Gene Is Associated With Increased Plasma Triglyceride and C-Reactive Protein but Lower Fasting Glucose Concentrations

OBJECTIVE—Using the genome-wide association approach, we recently identified the glucokinase regulatory protein gene (GCKR, rs780094) region as a novel quantitative trait locus for plasma triglyceride concentration in Europeans. Here, we sought to study the association of GCKR variants with metabolic phenotypes, including measures of glucose homeostasis, to evaluate the GCKR locus in samples of non-European ancestry and to fine- map across the associated genomic interval. RESEARCH DESIGN AND METHODS—We performed association studies in 12 independent cohorts comprising >45,000 individuals representing several ancestral groups (whites from Northern and Southern Europe, whites from the U.S., African Americans from the U.S., Hispanics of Caribbean origin, and Chinese, Malays, and Asian Indians from Singapore). We conducted genetic fine-mapping across the ∼417-kb region of linkage disequilibrium spanning GCKR and 16 other genes on chromosome 2p23 by imputing untyped HapMap single nucleotide polymorphisms (SNPs) and genotyping 104 SNPs across the associated genomic interval. RESULTS—We provide comprehensive evidence that GCKR rs780094 is associated with opposite effects on fasting plasma triglyceride (Pmeta = 3 × 10−56) and glucose (Pmeta = 1 × 10−13) concentrations. In addition, we confirmed recent reports that the same SNP is associated with C-reactive protein (CRP) level (P = 5 × 10−5). Both fine-mapping approaches revealed a common missense GCKR variant (rs1260326, Pro446Leu, 34% frequency, r2 = 0.93 with rs780094) as the strongest association signal in the region. CONCLUSIONS—These findings point to a molecular mechanism in humans by which higher triglycerides and CRP can be coupled with lower plasma glucose concentrations and position GCKR in central pathways regulating both hepatic triglyceride and glucose metabolism.

Interaction Between Renal Function and Microalbuminuria for Cardiovascular Risk in Hypertension The Nordic Diltiazem Study

We investigated whether renal function and microalbuminuria are independent predictors and whether any interaction exists between them, regarding future cardiovascular disease in hypertensive patients (n=10 881) followed for 4.5 years. The primary end points (PEs) were fatal and nonfatal myocardial infarction and stroke and other cardiovascular deaths. Creatinine and glomerular filtration rate (GFR), estimated using the formulas of the Modification of Diet in Renal Disease study group and Cockroft and Gault and in a subsample (n=4929) of microalbuminuria and interaction terms of microalbuminuria and renal function, were related to the risk of the PE using Cox proportional hazards model after full adjustment. Increased creatinine (P<0.001), decreased GFR from Cockroft and Gault (P=0.001), and decreased GFR from the Modification of Diet in Renal Disease study group (P=0.001) were all independent risk factors for the PE. Stepwise exclusion of patients with the poorest renal function excluded the possibility that the relationship between decreasing renal function and the PE was driven only by patients with severely impaired renal function. Microalbuminuria and all 3 of the indices of renal function predicted the PE independent of each other. There was a significant interaction between microalbuminuria and GFR from Cockroft and Gault (P=0.040) in prediction of the PE. Both renal function and microalbuminuria add independent prognostic information regarding cardiovascular risk in hypertensive patients. The cardiovascular risk associated with microalbuminuria increases with a decline in GFR, as demonstrated by a significant interaction between microalbuminuria and GFR from Cockroft and Gault. Because estimation of the total cardiovascular risk is essential for the aggressiveness of risk factor interventions, simultaneous inclusion of GFR and microalbuminuria in global cardiovascular risk assessment is essential.

A functional variant of the NEDD4L gene is associated with beneficial treatment response with β-blockers and diuretics in hypertensive patients.

Objective The capability of the protein NEDD4L to reduce renal tubular expression of epithelial Na+ channel (ENaC) is influenced by a functional rs4149601 G→A NEDD4L polymorphism. As diuretics and β-blockers inhibit renal sodium reabsorption and renin release, respectively, we hypothesized that the β-blocker or diuretic-induced blood pressure reduction and prevention of cardiovascular disease would be greater in patients with the highest ENaC expression (rs4149601 G-allele), whereas there would be no such genetically mediated differences in treatment efficacy among patients treated with the vasodilator diltiazem. Methods We related rs4149601 status to 6-month blood pressure reduction and risk of cardiovascular events in 5152 hypertensive patients (DBP ≥ 100 mmHg) from the Nordic Diltiazem Study (NORDIL) randomized to either β-blocker and/or diuretic-based treatment or diltiazem-based treatment. Results In patients on β-blocker or diuretic monotherapy, carriers of the G-allele had greater SBP reduction (19.5 ± 16.8 vs. 15.0 ± 19.3 mmHg, P < 0.001) and DBP reduction (15.4 ± 8.3vs. 14.1 ± 8.4 mmHg, P = 0.02) and during 4.5 years of follow-up among patients randomized to β-blockers and/or diuretics, carriers of the G-allele had greater protection from cardiovascular events [relative risk (RR) = 0.52, 95% confidence interval (CI) = 0.36–0.74, P < 0.001] as compared to AA homozygotes. Within the diltiazem group, there was no difference in blood pressure reduction or risk of cardiovascular events according to genotype. Conclusion The functional NEDD4L rs4149601 polymorphism influences the efficacy of β-blocker and/or diuretic-based antihypertensive treatment both in terms of blood pressure reduction and cardiovascular disease protection, whereas diltiazem-based antihypertensive treatment efficacy is not influenced by this NEDD4L polymorphism.

Plasma Lipid Composition and Risk of Developing Cardiovascular Disease

Aims We tested whether characteristic changes of the plasma lipidome in individuals with comparable total lipids level associate with future cardiovascular disease (CVD) outcome and whether 23 validated gene variants associated with coronary artery disease (CAD) affect CVD associated lipid species. Methods and Results Screening of the fasted plasma lipidome was performed by top-down shotgun analysis and lipidome compositions compared between incident CVD cases (n = 211) and controls (n = 216) from the prospective population-based MDC study using logistic regression adjusting for Framingham risk factors. Associations with incident CVD were seen for eight lipid species (0.21≤q≤0.23). Each standard deviation unit higher baseline levels of two lysophosphatidylcholine species (LPC), LPC16∶0 and LPC20∶4, was associated with a decreased risk for CVD (P = 0.024–0.028). Sphingomyelin (SM) 38∶2 was associated with increased odds of CVD (P = 0.057). Five triglyceride (TAG) species were associated with protection (P = 0.031–0.049). LPC16∶0 was negatively correlated with the carotid intima-media thickness (P = 0.010) and with HbA1c (P = 0.012) whereas SM38∶2 was positively correlated with LDL-cholesterol (P = 0.0*10−6) and the q-values were good (q≤0.03). The risk allele of 8 CAD-associated gene variants showed significant association with the plasma level of several lipid species. However, the q-values were high for many of the associations (0.015≤q≤0.75). Risk allele carriers of 3 CAD-loci had reduced level of LPC16∶0 and/or LPC 20∶4 (P≤0.056). Conclusion Our study suggests that CVD development is preceded by reduced levels of LPC16∶0, LPC20∶4 and some specific TAG species and by increased levels of SM38∶2. It also indicates that certain lipid species are intermediate phenotypes between genetic susceptibility and overt CVD. But it is a preliminary study that awaits replication in a larger population because statistical significance was lost for the associations between lipid species and future cardiovascular events when correcting for multiple testing.

The myocardial infarction associated CDKN2A/CDKN2B locus on chromosome 9p21 is associated with stroke independently of coronary events in patients with hypertension.

Objective We tested whether two single-nucleotide polymorphisms (SNPs) (rs2383207 and rs10757278), previously strongly associated with myocardial infarction, are independently associated with stroke and coronary events in patients with hypertension. Methods The Nordic Diltiazem study compared the effects of calcium antagonist and β-blocker or diuretic-based antihypertensive treatment on cardiovascular events in 10 881 patients with hypertension, of whom 5262 patients provided DNA for the present study. We related SNPs rs2383207 and rs10757278 to stroke and to myocardial infarction and coronary revascularizations (coronary events) using crude and multivariate adjusted Cox proportional hazards models. Results The G-allele of both SNPs predicted coronary events in crude recessive models [hazard ratios = 1.36, 95% confidence interval (CI) = 1.04–1.79, P = 0.02 for rs10757278 and hazard ratios = 1.40, 95% CI = 1.08–1.81, P = 0.01 for rs2383207] as well as after adjustment for classical cardiovascular risk factors. The G-allele of both SNPs predicted incident stroke in crude additive models [rs2383207 hazard ratios = 1.25 (95% CI = 1.02–1.53), P = 0.04 and rs10757278 hazard ratios = 1.34 (95% CI = 1.09–1.65), P = 0.006], as well as after adjustment for classical cardiovascular risk factors and after additional adjustment for prevalent and incident coronary events, atrial fibrillation, ischemic heart disease and congestive heart failure. As was the case for coronary events, the excess genetic risk of stroke was driven by subjects homozygous for the risk allele. Conclusion Genetic variation at the CDKN2A/CDKN2B locus predicts stroke in hypertensive patients. The genetic association with stroke is independent of classical cardiovascular risk factors and of all prevalent and incident coronary events, suggesting that gene variation at this locus promotes either atherosclerosis or another disease mechanism that is common to both coronary and cerebrovascular disease.

Feasibility of bariatric surgery as a strategy for secondary prevention in cardiovascular disease: a report from the Swedish Obese Subjects trial.

Aims. Evaluation of bariatric surgery as secondary prevention in obese patients with ischemic heart disease (IHD). Methods. Analysis of data from 4047 subjects in the Swedish Obese Subjects (SOSs) study. Thirty-five patients with IHD are treated with bariatric surgery (n = 21) or conventional treatment (n = 14). Mean follow-up is 10.8 years. Results. Bariatric surgery resulted in sustained weight loss during the study period. After 2 years, the surgery group displayed significant reductions in cardiovascular risk factors, relief from cardiorespiratory symptoms, increments in physical activity, and improved quality of life. After 10 years, recovery from hypertension, diabetes, physical inactivity, and depression was still more common in the surgery group. There were no signs of increased cardiovascular morbidity or mortality in the surgery group. Conclusion. Bariatric surgery appears to be a safe and feasible treatment to achieve long-term weight loss and improvement in cardiovascular risk factors, symptoms, and quality of life in obese subjects with IHD.

Common polymorphisms in the CYP11B1 and CYP11B2 genes: Evidence for a digenic influence on hypertension

The locus encompassing the corticosteroidogenic genes CYP11B2 and CYP11B1 is of potential importance in essential hypertension. We analyzed the association of polymorphisms at this locus with risk of essential hypertension, using 2 white case–control collections for discovery (n=3340) and confirmation (n=2929). Single-marker and haplotype analyses were performed, with the CYP11B2 Intron 2 Conversion polymorphism showing strongest association with hypertension in both cohorts and in combined analysis (odds ratio=1.16, P=8.54×10−5). The CYP11B1 ACA haplotype associated with increased risk of hypertension relative to the alternative, GTC (odds ratio=1.11; P=7.4×10−3), whereas the CYP11B2 TWtC haplotype seemed protective relative to the contrasting CConvT (odds ratio=0.88, P=2.2×10−3). Analysis spanning the whole CYP11B1/CYP11B2 locus showed that haplotypes associated with raised risk of hypertension tend to coexist. Functional analysis of heterozygous human adrenal tissue demonstrated decreased CYP11B2 expression and increased CYP11B1 expression for those alleles associating with reduced risk of hypertension. These results confirm the hypertensive influence of this locus, with data suggesting a complex digenic mechanism whereby altered relative CYP11B1 and CYP11B2 gene expression could have a chronic effect on enzyme activity and corticosteroid synthesis.

Smoking and obesity associated BDNF gene variance predicts total and cardiovascular mortality in smokers

Objective The brain derived neurotrophic factor (BDNF) locus has been implicated in psychiatric and substance related disorders. Recent genome-wide association studies (GWAS) have shown strong associations between single nucleotide polymorphisms in BDNF, smoking behaviour and high body mass index (BMI). Our aim was to test whether genetic BDNF variation alters the risk of smoking related morbidity and mortality. Design Cox proportional hazards models were used to relate the BDNF rs4923461(A/G) polymorphisms to all-cause, cancer and cardiovascular mortality and cardiovascular disease (CVD) incidence adjusted for age, sex, BMI, and smoking quantity. Setting The Malmö Diet and Cancer Study (MDCS), a population based prospective cohort study (n=30 447). Patients We obtained complete data on 25 071 subjects, of whom 6507 were current smokers and 18 564 were non-smokers who underwent a baseline examination from 1991–1996. Main outcome measures During a mean follow-up time of 12 years, 1049 deaths (346 cardiovascular deaths and 492 cancer deaths) and 802 incident CVD events occurred among current smokers. Results The major allele (A) of rs4923461 was significantly associated with ever having smoked (p=0.03) and high BMI (p=0.001). The A-allele was associated with risk of all-cause (HR=1.12, 95% CI 1.00 to 1.25; p<0.05) and CVD (HR=1.23, 95% CI 1.01 to 1.49; p=0.04) mortality. There was no significant association between the rs4923461 and cancer mortality or CVD incidence. Conclusions Our data suggest that smoking- and obesity-associated variation of the BDNF gene affects the risk of death, especially due to cardiovascular causes, in smokers. Determination of the BDNF genotype in smokers may guide the need for smoking cessation interventions.

Systolic and diastolic component of orthostatic hypotension and cardiovascular events in hypertensive patients: the Captopril Prevention Project.

Objective: Impact of SBP vs. DBP decrement during orthostasis on cardiovascular events in hypertension is not clear. Methods: We assessed prospective association of orthostatic hypotension with mortality and major cardiovascular events [myocardial infarction (MI) and stroke] among 8788 treated hypertensive patients (52.2% men; mean age 52 years, mean BP 161/99 mmHg) without history of MI or stroke at baseline. Orthostatic hypotension was defined according to combined international consensus criteria, and as either systolic (decrease ≥20 mmHg) or diastolic orthostatic hypotension (decrease ≥10 mmHg). Final Cox regression model was adjusted for age, sex, supine SBP and DBP, diabetes, smoking, and total cholesterol. Results: A total of 1060 (12.1%) study participants fulfilled combined orthostatic hypotension criteria, of these 886 (10.1%) met systolic and 290 (3.3%) diastolic criterion. In the crude analysis, combined orthostatic hypotension criteria were predictive of the composite endpoint, major cardiovascular event, total mortality, and stroke but not MI. After full adjustment, combined orthostatic hypotension criteria and systolic orthostatic hypotension were independently associated with stroke only (hazard ratio: 1.48, 1.07–2.05, P = 0.019, and 1.53, 1.08–2.15, P = 0.015, respectively), whereas the composite endpoint tended in the same direction (hazard ratio: 1.21, 0.98–1.51, P = 0.075, and 1.24, 0.99–1.55, P = 0.066, respectively). In contrast, diastolic orthostatic hypotension was associated with increased risk of MI (hazard ratio: 2.04, 1.20–3.46, P = 0.008). Conclusion: Orthostatic hypotension has a dual role in cardiovascular events among hypertensive patients: SBP fall indicates higher risk of stroke, whereas DBP fall confers higher risk of MI.