Cristiano Fava

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.

Effect of CPAP on Blood Pressure in Patients With OSA/Hypopnea: A Systematic Review and Meta-analysis

BACKGROUND CPAP is considered the therapy of choice for OSA, but the extent to which it can reduce BP is still under debate. We undertook a systematic review and meta-analysis of randomized controlled trials (RCTs) to quantify the effect size of the reduction of BP by CPAP therapy compared with other passive (sham CPAP, tablets of placebo drug, conservative measures) or active (oral appliance, antihypertensive drugs) treatments. METHODS We searched four different databases (MEDLINE, EMBASE, Web of Science, and the Cochrane Library) with specific search terms and selection criteria. RESULTS From 1,599 articles, we included 31 RCTs that compared CPAP with either passive or active treatment. In a random-effects meta-analysis vs passive treatment (29 RCTs, 1,820 subjects), we observed a mean±SEM net difference in systolic BP of 2.6±0.6 mm Hg and in diastolic BP of 2.0±0.4 mm Hg, favoring treatment with CPAP (P<.001). Among studies using 24-h ambulatory BP monitoring that presented data on daytime and nighttime periods, the mean difference in systolic and diastolic BP was, respectively, 2.2±0.7 and 1.9±0.6 mm Hg during daytime and 3.8±0.8 and 1.8±0.6 mm Hg during nighttime. In meta-regression analysis, a higher baseline apnea/hypopnea index was associated with a greater mean net decrease in systolic BP (beta±SE, 0.08±0.04). There was no evidence of publication bias, and heterogeneity was mild ( I2, 34%-36%). CONCLUSIONS Therapy with CPAP significantly reduces BP in patients with OSA but with a low effect size. Patients with frequent apneic episodes may benefit the most from CPAP.

The V433M Variant of the CYP4F2 Is Associated With Ischemic Stroke in Male Swedes Beyond Its Effect on Blood Pressure

Cytochrome (CYP) 4A11 and CYP4F2 are responsible for renal production of 20-hydroxyeicosatetraenoic acid, a vasoconstrictor and natriuretic substance. The CYP4A11 F434S and CYP4F2 V433M polymorphisms reduce 20-hydroxyeicosatetraenoic acid production in vitro. The aim of the present study was to evaluate the effect of these polymorphisms on blood pressure (BP) levels, hypertension prevalence, and risk of incident cardiovascular events in middle-aged Swedes. The polymorphisms were genotyped in the cardiovascular cohort of the Malmö Diet and Cancer Study. The incidence of cardiovascular events (coronary events, n=276; ischemic stroke, n=199) was monitored over 10 years of follow-up. The analysis of BP levels was performed twice: either excluding or including subjects under antihypertensive treatment. In the whole population, CYP4A11 S434S homozygotes had higher systolic BP, both crude and adjusted for the number of antihypertensive drugs, and higher prevalence of hypertension with respect to F434 carriers. Male, but not female, CYP4F2 M433 carriers had significantly higher crude and adjusted systolic and diastolic BPs and a trend toward higher hypertension prevalence (P=0.06) with respect to V433V homozygotes. After adjustment for major cardiovascular risk factors, the hazard ratio for incident ischemic stroke in male CYP4F2 M433 carriers was significantly higher with respect to V433V homozygotes (hazard ratio: 1.69; 95% CI: 1.10 to 2.60) even when baseline BP levels and hypertension prevalence were included in the Cox proportional hazard model. A common CYP4F2 V433M polymorphism might increase the risk of incident ischemic stroke in male subjects only partially through its elevating effect on BP. Additional studies are needed to confirm these data.

Obstructive sleep apnea syndrome and cardiovascular diseases.

Obstructive sleep apnea syndrome (OSAS) is a chronic disease characterized by recurrent episodes of partial or complete upper airway collapse and obstruction during sleep, associated with intermittent oxygen desaturation, sleep fragmentation, and symptoms of disruptive snoring and daytime sleepiness. Increasing focus is being placed on the relationship between OSAS and all-cause and cardiovascular disease-related mortality, but it still largely unclear whether this association is causative or simply speculative and epidemiological. Basically, reliable clinical evidence supports the hypothesis that OSAS might be associated with essential and resistant hypertension, as well as with an incremental risk of developing stroke, cardiac rhythm perturbations (e.g., atrial fibrillation, bradyarrhythmias, supraventricular and ventricular arrhythmias), coronary artery disease, acute myocardial infarction, and heart failure. Although it is still unclear whether OSAS might represent an independent risk factor for several acute or chronic conditions, or rather might trigger cardiovascular disease in the presence of traditional cardiovascular risk factors (e.g., obesity, diabetes, and dyslipidemia), there is a plausible biological background underlying this association, in that most of the mechanisms implicated in the pathogenesis of OSAS (i.e., hypoxia, hypercapnia, negative intrathoracic pressure, micro-arousal, sympathetic hyperactivity, metabolic and hormonal changes, oxidative stress, phlogosis, endothelial dysfunction, hypercoagulability, and genetic predisposition) might also be involved in the pathogenesis of cardiovascular disorders. In this article we discuss the different aspects of the relationship between OSAS and pathogenically different conditions such as systemic hypertension, coronary artery disease, stroke, metabolic abnormalities, arrhythmias, and heart failure, and we also discuss the kaleidoscope of phenomena implicated in the pathogenesis of this challenging disease.

Heritability of ambulatory and office blood pressure phenotypes in Swedish families.

Objective The aim of this study was to estimate the heritability of 24-h ambulatory blood pressure and office blood pressure phenotypes in Swedish families. Methods We measured ambulatory and office blood pressure in 260 siblings without antihypertensive treatment from 118 families. Blood pressure heritability was estimated using standard quantitative genetic variance component analysis implemented in the ‘SOLAR’ software package after adjustment for significant covariates. Results Heritability values were significant for night-time systolic (37%), diastolic (32%) and mean (32%) ambulatory blood pressure (P < 0.05 for all). During daytime, systolic ambulatory blood pressure was significantly heritable (33%, P < 0.05). Twenty-four-hour systolic (30%) and diastolic (29%) ambulatory blood pressure also had significant values of heritability (P < 0.05). Pulse pressure ambulatory blood pressure was significantly heritable over 24 h (63%, P < 0.01), during daytime (53%, P < 0.01) and at night (34%, P < 0.05). None of the office blood pressure phenotypes had a significant heritability. Conclusions We conclude that ambulatory blood pressure, in particular at night, seems better than office blood pressure to capture the heritable part of blood pressure, suggesting that ambulatory blood pressure may be a more exact estimate of an individuals true blood pressure. Genetic studies using ambulatory blood pressure as the phenotype are likely to be more powerful than those using office blood pressure. The high heritability of pulse pressure ambulatory blood pressure indicates that variation in arterial stiffness in subjects free from antihypertensive medication is strongly affected by genetic factors.

Altered Release of Cytochrome P450 Metabolites of Arachidonic Acid in Renovascular Disease

The aim of the present cross-sectional study was to investigate whether activation of the renin-angiotensin system in renovascular disease affects the cytochrome P450 &ohgr;/&ohgr;-1 hydroxylase (20-hydroxyeicosatetraenoic acid [20-HETE]) and epoxygenase (epoxyeicosatrienoic acids [EETs]) pathways of arachidonic acid metabolism in vivo, each of which interacts with angiotensin II. Plasma concentration and urinary excretion of 20-HETE and EETs and their metabolites, dihydroxyeicosatrienoic acids, were measured in urine and plasma by mass spectrometry in 10 subjects with renovascular disease, 10 with essential hypertension, and 10 healthy normotensive subjects (control subjects), pair-matched for gender and age. Vascular and renal function were evaluated in all of the subjects. Plasma 20-HETE was highest in subjects with renovascular disease (median: 1.20 ng/mL; range: 0.42 to 1.92 ng/mL) compared with subjects with essential hypertension (median: 0.90 ng/mL; range: 0.40 to 2.17 ng/mL) and control subjects (median: 0.45 ng/mL; range: 0.14 to 1.70 ng/mL; P<0.05). Plasma 20-HETE significantly correlated with plasma renin activity in renovascular disease (rs=0.67; n=10; P<0.05). The urinary excretion of 20-HETE was significantly lower in subjects with renovascular disease (median: 12.9 &mgr;g/g of creatinine; range: 4.4 to 24.9 &mgr;g/g of creatinine) than in control subjects (median: 31.0 &mgr;g/g of creatinine; range: 11.9 to 102.8 &mgr;g/g of creatinine; P<0.01) and essential hypertensive subjects (median: 35.9 &mgr;g/g of creatinine; range: 14.0 to 72.5 &mgr;g/g of creatinine; P<0.05). Total plasma EETs were lowest, as was the ratio of plasma EETs to plasma dihydroxyeicosatrienoic acids, an index of epoxide hydrolase activity, in renovascular disease (ratio: 2.4; range: 1.2 to 6.1) compared with essential hypertension (ratio: 3.4; range: 1.5 to 5.6) and control subjects (ratio: 6.8; range: 1.4 to 18.8; P<0.01). In conclusion, circulating levels of 20-HETE are increased and those of EETs are decreased in renovascular disease, whereas the urinary excretion of 20-HETE is reduced. Altered cytochrome P450 arachidonic acid metabolism may contribute to the vascular and tubular abnormalities of renovascular disease.

Sex-Specific Effects of Adiponectin on Carotid Intima-Media Thickness and Incident Cardiovascular Disease

Background Plasma adiponectin levels have previously been inversely associated with carotid intima-media thickness (IMT), a marker of subclinical atherosclerosis. In this study, we used a sex-stratified Mendelian randomization approach to investigate whether adiponectin has a causal protective influence on IMT. Methods and Results Baseline plasma adiponectin concentration was tested for association with baseline IMT, IMT progression over 30 months, and occurrence of cardiovascular events within 3 years in 3430 participants (women, n =1777; men, n =1653) with high cardiovascular risk but no prevalent disease. Plasma adiponectin levels were inversely associated with baseline mean bifurcation IMT after adjustment for established risk factors (β =−0.018, P<0.001) in men but not in women (β =−0.006, P =0.185; P for interaction =0.061). Adiponectin levels were inversely associated with progression of mean common carotid IMT in men (β =−0.0022, P =0.047), whereas no association was seen in women (0.0007, P =0.475; P for interaction =0.018). Moreover, we observed that adiponectin levels were inversely associated with coronary events in women (hazard ratio 0.57, 95% CI 0.37 to 0.87) but not in men (hazard ratio 0.82, 95% CI 0.54 to 1.25). A gene score of adiponectin-raising alleles in 6 loci, reported recently in a large multi-ethnic meta-analysis, was inversely associated with baseline mean bifurcation IMT in men (β =−0.0008, P =0.004) but not in women (β =−0.0003, P =0.522; P for interaction =0.007). Conclusions This report provides some evidence for adiponectin protecting against atherosclerosis, with effects being confined to men; however, compared with established cardiovascular risk factors, the effect of plasma adiponectin was modest. Further investigation involving mechanistic studies is warranted.

Glucose and collagen regulate human platelet activity through aldose reductase induction of thromboxane

Diabetes mellitus is associated with platelet hyperactivity, which leads to increased morbidity and mortality from cardiovascular disease. This is coupled with enhanced levels of thromboxane (TX), an eicosanoid that facilitates platelet aggregation. Although intensely studied, the mechanism underlying the relationship among hyperglycemia, TX generation, and platelet hyperactivity remains unclear. We sought to identify key signaling components that connect high levels of glucose to TX generation and to examine their clinical relevance. In human platelets, aldose reductase synergistically modulated platelet response to both hyperglycemia and collagen exposure through a pathway involving ROS/PLCγ2/PKC/p38α MAPK. In clinical patients with platelet activation (deep vein thrombosis; saphenous vein graft occlusion after coronary bypass surgery), and particularly those with diabetes, urinary levels of a major enzymatic metabolite of TX (11-dehydro-TXB2 [TX-M]) were substantially increased. Elevated TX-M persisted in diabetic patients taking low-dose aspirin (acetylsalicylic acid, ASA), suggesting that such patients may have underlying endothelial damage, collagen exposure, and thrombovascular disease. Thus, our study has identified multiple potential signaling targets for designing combination chemotherapies that could inhibit the synergistic activation of platelets by hyperglycemia and collagen exposure.

Prediction of Blood Pressure Changes Over Time and Incidence of Hypertension by a Genetic Risk Score in Swedes

Recent Genome-Wide Association Studies (GWAS) have pinpointed different single nucleotide polymorphisms consistently associated with blood pressure (BP) and hypertension prevalence. However, little data exist regarding single nucleotide polymorphisms predicting BP variation over time and hypertension incidence. The aim of this study was to confirm the association of a genetic risk score (GRS), based on 29 independent single nucleotide polymorphisms, with cross-sectional BP and hypertension prevalence and to challenge its prediction of BP change over time and hypertension incidence in >17 000 middle-aged Swedes participating in a prospective study, the Malmö Preventive Project, investigated at baseline and over a 23-year average period of follow-up. The GRS was associated with higher systolic and diastolic BP values both at baseline (&bgr;±SEM, 0.968±0.102 mm Hg and 0.585±0.064 mm Hg; P<1E-19 for both) and at reinvestigation (&bgr;±SEM, 1.333±0.161 mm Hg and 0.724±0.086 mm Hg; P<1E-15 for both) and with increased hypertension prevalence (odds ratio [95% CI], 1.192 [1.140–1.245] and 1.144 [1.107–1.183]; P<1E-15 for both). The GRS was positively associated with change (&Dgr;) in BP (&bgr;±SEM, 0.033±0.008 mm Hg/y and 0.023±0.004 mm Hg/y; P<1E-04 for both) and hypertension incidence (odds ratio [95% CI], 1.110 [1.065–1.156]; P=6.7 E-07), independently from traditional risk factors. The relative weight of the GRS was lower in magnitude than obesity or prehypertension, but comparable with diabetes mellitus or a positive family history of hypertension. A C-statistics analysis does not show any improvement in the prediction of incident hypertension on top of traditional risk factors. Our data from a large cohort study show that a GRS is independently associated with BP increase and incidence of hypertension.

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.