L. Thijs

Genetic Variation in CYP11B2 and AT1R Influences Heart Rate Variability Conditional on Sodium Excretion

Sympathetic tone increases with stimulation of the renin-angiotensin system and is under the influence of salt intake. In the European Project On Genes in Hypertension (EPOGH), we investigated whether polymorphisms in the genes encoding aldosterone synthase (CYP11B2 C–344T) and the type-1 angiotensin II receptor (AT1R A1166C) affect the autonomic modulation of heart rate at varying levels of salt intake. We measured the low frequency (LF) and high frequency (HF) components of heart rate variability and their ratio (LF:HF) in the supine and standing positions in 1797 participants (401 families and 320 unrelated subjects) randomly selected from 6 European populations, whose average urinary sodium excretion ranged from 163 to 245 mmol/d. In multivariate analyses with sodium excretion analyzed as a continuous variable, we explored the phenotype–genotype associations using generalized estimating equations and quantitative transmission disequilibrium tests. Across populations, there was no heterogeneity in the phenotype–genotype relations. The genotypic effects differed according to sodium excretion. In subjects with sodium excretion <190 mmol/d (median), supine heart rate, LF, and LF:HF increased and HF decreased with the number of CYP11B2–344T alleles, and the orthostatic changes in LF, HF, and LF:HF were blunted in carriers of the AT1R 1166C allele. In subjects with sodium excretion >190 mmol/d, these associations with the CYP11B2 and AT1R polymorphisms were nonsignificant or in the opposite direction, respectively. Thus, CYP11B2 C–344T and AT1R A1166C polymorphisms affect the autonomic modulation of heart rate, but these genetic effects depend on sodium excretion.

Twenty-four hour blood pressure monitoring in the Syst-Eur trial

This article describes the objectives and protocol of a study on ambulatory blood pressure in elderly patients with isolated systolic hypertension. This study constitutes an optional side-project to the Syst-Eur trial.The multicentre Syst-Eur trial investigates whether antihypertensive treatment of elderly patients with isolated systolic hypertension will influence the incidence of stroke. Secondary endpoints include cardiovascular events, such as myocardial infarction.The main objective of the side-project is to investigate whether ambulatory blood pressure monitoring will improve the prediction of cardiovascular complications based on blood pressure measurement in the clinic. The side-project also provides the opportunity to evaluate the diurnal profile of blood pressure in elderly patients with isolated systolic hypertension randomized to placebo or active antihypertensive treatment.

The Predictive Role Of The Nighttime Blood Pressure: 4a.02

Objective: [1] To derive precise estimates for the association between outcome and ABPM during sleep as reflected by the nocturnal SBP level, the night-to-day SBP ratio (sNDR), or dipping status. [2] To evaluate the influence of accounting for BP level on the strength of these associations. Design and methods: We did a meta-analysis of summary statistics extracted from prospective studies in hypertensive patients (16 studies; 23856 patients; 1816 cases of total mortality [TM]; 1259 CV events [CVE]). We also computed pooled estimates, using individual subject data from 11 population studies (9641 patients; 1320 cases of TM; 1128 CVE). We pooled hazard ratios using the PROC MIXED procedure (SAS, 9.1.3). Results: Figure 1. No caption available. All hazard ratios (95% CI) were adjusted. Fully adjusted (FA) refers to models in which risk estimates based on daytime SBP were additionally adjusted for nighttime SBP (and vice versa), or in which risk estimates based on the sNDR or dipping status were also adjusted for the 24-h SBP. * P≤0.05; †P≤0.01; ‡P≤0.001. Conclusions: [1] Nighttime SBP is a stronger predictor than daytime SBP. [2] sNDR predicts outcome over and beyond 24-h SBP. These findings strongly support the recommendations to record BP over the whole day for risk stratification in clinical practice.

BLOOD PRESSURE, CARDIOVASCULAR OUTCOMES AND SODIUM INTAKE, A CRITICAL REVIEW OF THE EVIDENCE

Abstract Consideration of the role of NaCl (salt) in the pathogenesis and treatment of essential hypertension is one of the overriding research themes both in experimental and clinical medicine. The evidence relating blood pressure to salt intake in humans originates from population studies and randomized clinical trials of interventions on dietary salt intake. Estimates from meta-analyses of trials in normotensive subjects generally are similar to estimates derived from prospective population studies (+ 1.7-mmHg increase in systolic blood pressure per 100 mmol increment in 24-hour urinary sodium). This estimate, however, does not translate into an increased risk of incident hypertension in subjects consuming a high-salt diet. Prospective studies relating health outcomes to 24-h urinary sodium excretion produced inconsistent results. Taken together, available evidence does not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level. The public should be properly educated about the pros and cons of a decrease in sodium intake, in particular if they are healthy.

The -665 C>T polymorphism in the eNOS gene predicts cardiovascular mortality and morbidity in white Europeans.

We recently identified rs3918226 as a hypertension susceptibility locus (−665 C>T), TT homozygosity being associated with higher hypertension risk. T compared with C allele transfected cells had lower endothelial nitric oxide synthase (eNOS) expression. In the family-based Flemish Study on Environment, Genes and Health Outcomes (50.9% women; mean age 40.3 years), we investigated whether 32 TT homozygotes had worse outcomes than 2787 C allele carriers. Over 15 years (median), total and cardiovascular mortality and cardiovascular and coronary events amounted to 269 (9.5%), 98 (3.5%), 247 (8.8%) and 120 (4.3%), respectively. While accounting for family clusters, the hazard ratios associated with TT homozygosity were 4.11 (P=0.0052) for cardiovascular mortality (4 deaths), 2.75 (P=0.0067) for cardiovascular events (7 endpoints) and 3.10 (P=0.022) for coronary events (4 endpoints). With adjustment for cardiovascular risk factors, these hazard ratios were 6.01 (P=0.0003), 2.64 (P=0.0091) and 2.89 (P=0.010), respectively. Analyses unadjusted for blood pressure and antihypertensive treatment produced consistent results. For all fatal plus nonfatal cardiovascular events, the positive predictive value, attributable risk and population-attributable risk associated with TT homozygosity were 21.9, 61.5 and 2.0%, respectively. In conclusion, TT homozygosity at the position −665 in the eNOS promoter predicts adverse outcomes, independent of blood pressure and other risk factors.

1A.04: CORRELATES OF PERIPHERAL BLOOD MITOCHONDRIAL DNA COPY NUMBER IN A GENERAL POPULATION.

Objective: Mitochondrial DNA (mtDNA) molecules are highly susceptible to oxidative stress. Accumulation of mtDNA mutations leads to alterations of mitochondrial biogenesis and function that might result in decrease of mtDNA content within cells. This implies a possible role of mtDNA content as a potential biomarker in processes associated with oxidative stress and inflammation. However, data on correlates of the mtDNA content in a general population are sparse. Therefore, the objectives of the present study were to describe in a randomly recruited population sample the distribution and determinants of the peripheral blood mtDNA content. Design and method: We examined 689 individuals (50.4% women, mean age, 54.4 years), randomly selected from a Flemish population. Relative mtDNA copy number compared to nuclear DNA was measured by quantitative real-time PCR in peripheral blood. Results: There was a curvilinear relationship between the relative mtDNA copy number and age. Indeed, mtDNA content increased until the fifth decade of life and declined in older subjects (P age2 = 0.0005). Moreover, the mtDNA content significantly and independently increased with female sex (P = 0.0078) and platelet count (P < 0.0001), whereas it decreased with white blood cell count (WBC) (P < 0.0001). We also observed a slightly decrease in mtDNA content in women using oestroprogestogens (P = 0.044). Conclusions: In conclusion, we demonstrated in a general population that peripheral blood mtDNA content is significantly associated with sex and age. In addition, blood mtDNA content is influenced by platelet and WBC counts and intake of oestroprogestogens. Further studies are required to clarify the impact of inflammation and hormone therapy on mitochondrial function.

Heritability and other determinants of left ventricular diastolic function in the family-based population study.

Background: Understanding to what extent genetic factors influence diastolic Doppler indexes is an important issue in view of the relation of left ventricular diastolic dysfunction with outcome. We, therefore, investigated the heritability of left ventricular diastolic traits and the composite diastolic score in nuclear families recruited from the general population. Methods: In a random sample of 316 nuclear families (452 parents and 600 offspring, mean age, 58.5 and 33.3 years), we measured transmitral early and late diastolic velocities (E and A) by pulsed wave Doppler, and mitral annular velocities (e’ and a’) by tissue Doppler. Using principal component analysis, we summarized seven Doppler indexes – namely, E, A, e’ and a’ velocities, and their ratios – into a single diastolic score. To calculate the heritability of diastolic indexes, we used variance decomposition in nuclear families and offspring as implemented in SOLAR and SAS, and the regression slope of offspring on mid-parent residual values. Results: In variance decomposition analyses in nuclear families, the abovementioned traits with adjustment for covariables had moderate heritability ranging from 0.27 to 0.43 (P < 0.0001 for all). The parent–offspring concordances of all diastolic indexes were significant and ranged from 0.17 for A (P = 0.009) to 0.42 for e’ (P < 0.0001). In nuclear families and offspring, the heritability estimates of the composite diastolic score were 0.42 and 0.64, respectively (P < 0.0001). Conclusion: Our study demonstrated moderate heritability of various indexes reflecting left ventricular diastolic function in nuclear families. The observation highlights the necessity of further research into the genes that affect left ventricular diastolic function.

FATAL AND NONFATAL OUTCOMES, INCIDENCE OF HYPERTENSION, AND BLOOD PRESSURE CHANGES IN RELATION TO URINARY SODIUM EXCRETION IN WHITE EUROPEANS: 2C.01

Stolarz-Skrzypek K, Kuznetsova T, Thijs L, et al; European Project on Genes in Hypertension (EPOGH) Investigators: Fatal and Nonfatal Outcomes, Incidence of Hypertension, and Blood Pressure Changes in Relation to Urinary Sodium Excretion. JAMA. 2011;305(17):1777-1785. eTable 1. Characteristics of Women in the Outcome Cohort by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline eTable 2. Characteristics of Men in the Outcome Cohort by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline eTable 3. Characteristics of Women in the Hypertension Cohort by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline eTable 4. Characteristics of Men in the Hypertension Cohort by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline eTable 5. Characteristics of the Participants in the Blood Pressure Cohort at Baseline and at Follow-up by Country eTable 6. Causes of Cardiovascular Mortality and Morbidity in the Outcome Cohort eTable 7. Multivariable-Adjusted Hazard Ratios for Mortality and Cardiovascular Events by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline in 3194 Participants Younger Than 60 Years eTable 8. Multivariable-Adjusted Hazard Ratios for Mortality and Cardiovascular Events by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline in 487 Participants 60 Years or Older eTable 9. Multivariable-Adjusted Hazard Ratios for Mortality and Cardiovascular Events by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline Excluding Any Adjustment for Blood Pressure eTable 10. Multivariable-Adjusted Hazard Ratios for Mortality and Cardiovascular Events by Tertiles of the 24-Hour Urinary Sodium-to-Potassium Ratio at Baseline eTable 11. Multivariable-Adjusted Hazard Ratios for Cardiovascular Mortality by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline after Censoring of Follow-up at 6, 9, 12, 15, 18 and 21 Years eTable 12. Multivariable-Adjusted Hazard Ratios for Incidence of Hypertension by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline eTable 13. Multivariable-Adjusted Cross-Sectional Associations Between Blood Pressure and 24-Hour Urinary Sodium by Study Population and Study Phase eFigure 1. Incidence of Mortality and Cardiovascular Events eFigure 2. Kaplan-Meier Estimates for the Incidence of Hypertension by Tertiles of the 24-Hour Urinary Sodium Excretion at Baseline eFigure 3. Distribution of the Absolute (A, C, E) and Relative (B, D, F) Changes in Systolic Blood Pressure (A, B), Diastolic Blood Pressure (C, D), and 24-Hour Urinary Sodium Excretion (E, F) in 1499 Participants of the Blood Pressure Cohort Followed Up for a Median of 6.1 Years eFigure 4. Change in Systolic Blood Pressure During Follow-Up By Deciles of the Change in the 24-Hour Urinary Sodium Excretion in the Blood Pressure Cohort (n=1499) eFigure 5. Change in Diastolic Blood Pressure During Follow-Up by Deciles of the Change in 24-Hour Urinary Sodium Excretion in the Blood Pressure Cohort (n=1499)

[OP.7C.07] DIASTOLIC LEFT VENTRICULAR FUNCTION IN RELATION TO COLLAGEN-SPECIFIC URINARY AND SERUM COLLAGEN BIOMARKERS IN A GENERAL POPULATION.

Objective: Moving from multidimensional urinary proteomic markers to single urinary collagen fragments and linking these fragments to serum biomarkers of myocardial collagen turnover may generate new insights in the pathophysiology of diastolic LV function. Design and method: In 782 randomly recruited Flemish (51.3% women; 50.5 years), we assessed diastolic LV function by echocardiography, sequenced urinary collagen I (uCI) and III (uCIII) fragments, and determined serum markers of collagen I synthesis (PICP, carboxyterminal propeptide of procollagen) and breakdown (CITP, carboxyterminal telopeptide) and the tissue inhibitor of matrix metalloproteinase type 1 (TIMP 1). Results: The correlation between uCI and uCIII markers was inverse. In multivariable-adjusted analyses with Bonferroni correction, among 70 urinary peptides, six uCI and two uCIII fragments remained associated with diastolic LV function. Peak e’ and e’/a’ decreased with two uCI markers (P< = 0.0075). E/e’ increased with three uCI markers (P< = 0.0078), but decreased with one uCIII peptide (P = 0.0091). Peak A declined with two uCIII markers (P< = 0.0025). Based on age-specific echocardiographic criteria, 182 participants (23.3%) had diastolic LV dysfunction. Partial least squares discriminant analysis, confirmed association of abnormal and normal diastolic LV function with uCI and uCIII fragments. PICP, CITP and TIMP-1 increased in relation to uCI (P< = 0.0016), whereas these serum markers decreased in relation to uCIII (P< = 0.0006). Conclusions: By sequencing uCI and uCIII fragments and by linking diastolic LV function with urinary and serum collagen biomarkers and their interaction, our current findings generalize previous observations in selected patients to the population at large, thereby closing the gap between low-level diastolic LV dysfunction and overt diastolic heart failure.

Intra-erythrocyte cation concentrations in relation to the C1797T |[beta]|-adducin polymorphism in a general population

Genetic variability in the ADD1 (Gly460Trp) and ADD2 (C1797T) subunits of the cytoskeleton protein adducin plays a role in the pathogenesis of hypertension, possibly via changes in intracellular cation concentrations. ADD2 1797CC homozygous men have decreased erythrocyte count and hematocrit. We investigated possible association between intra-erythrocyte cations and the adducin polymorphisms. In 259 subjects (mean age 47.7 years), we measured intra-erythrocyte Na+ [iNa], K+ [iK] and Mg2+ [iMg], serum cations and adducin genotypes. Genotype frequencies (ADD1: GlyGly 61.5%, Trp 38.5%; ADD2: CC 80.4%, T 19.6%) complied with Hardy–Weinberg proportions. In men, ADD2 CC homozygotes (n=100) compared to T-carriers (n=23) had slightly lower iK (85.8 versus 87.5 mmol/l cells; P=0.107), higher iMg (1.92 versus 1.80 mmol/l cells; P=0.012), but similar iNa (6.86 versus 6.88 mmol/l cells; P=0.93). In men, iK, iMg and iNa did not differ according to ADD1 genotypes. In men, iK (R2=0.128) increased with age and serum Na+, but decreased with serum total calcium and the daily intake of alcohol. iMg (R2=0.087) decreased with age, but increased with serum total calcium. After adjustment for these covariates (P⩽0.04 for all), findings in men for iK (CC versus T: 85.8 versus 87.3 mmol/l; P=0.14) and iMg (1.91 versus 1.82 mmol/l; P=0.03) remained consistent. In 136 women, none of the phenotype–genotype relations reached significance. Changes in intra-erythrocyte cations in ADD2 1797CC homozygous men might lead to osmotic fragility of erythrocytes, but to what extent they reflect systemic changes or are possibly involved in blood pressure regulation remains unknown.