Urine sodium excretion is related to extracellular water volume but not to blood pressure in 510 normotensive and never-treated hypertensive subjects

PURPOSE

High sodium intake is an accepted risk factor for hypertension, while low Na⁺ intake has also been associated with increased risk of cardiovascular events. In this cross-sectional study, we examined the association of 24-h urinary Na⁺ excretion with haemodynamics and volume status.

MATERIALS AND METHODS

Haemodynamics were recorded in 510 normotensive and never-treated hypertensive subjects using whole-body impedance cardiography and tonometric radial artery pulse wave analysis. The results were examined in sex-specific tertiles of 24-h Na⁺ excretion, and comparisons between normotensive and hypertensive participants were also performed. Regression analysis was used to investigate factors associated with volume status. The findings were additionally compared to 28 patients with primary aldosteronism.

RESULTS

The mean values of 24-h urinary Na⁺ excretion in tertiles of the 510 participants were 94, 148 and 218 mmol, respectively. Average tertile age (43.4-44.7 years), office blood pressure and pulse wave velocity were corresponding in the tertiles. Plasma electrolytes, lipids, vitamin D metabolites, parathyroid hormone, renin activity, aldosterone, creatinine and insulin sensitivity did not differ in the tertiles. In supine laboratory recordings, there were no differences in aortic systolic and diastolic blood pressure, heart rate, cardiac output and systemic vascular resistance. Extracellular water volume was higher in the highest versus lowest tertile of Na⁺ excretion. In regression analysis, body surface area and 24-h Na⁺ excretion were independent explanatory variables for extracellular water volume. No differences in urine Na⁺ excretion and extracellular water volume were found between normotensive and hypertensive participants. When compared with the 510 participants, patients with primary aldosteronism had 6.0% excess in extracellular water (p = .003), and 24-h Na⁺ excretion was not related with extracellular water volume.

CONCLUSION

In the absence of mineralocorticoid excess, Na⁺ intake, as evaluated from 24-h Na⁺ excretion, predominantly influences extracellular water volume without a clear effect on blood pressure.

OP0007 MUC5B PROMOTER VARIANT AND LONG-TERM INCIDENCE OF INTERSTITIAL LUNG DISEASE IN PATIENTS WITH RHEUMATOID ARTHRITIS: A POPULATION BIOBANK STUDY OF 250,000 INDIVIDUALS

Background:

The promoter variant rs35705950 in MUC5B is the strongest known genetic risk factor for rheumatoid arthritis-associated interstitial lung disease (RA-ILD) [1]. There is, however, no large-scale data on the impact of MUC5B on the long-term incidence of RA-ILD.

Objectives:

To describe long term risk of RA-ILD in RA patients carrying MUC5B variant compared to non-carriers with RA.

Methods:

FinnGen is a collection of epidemiological cohorts and hospital biobank samples, linking genotypes with up to 46 years of follow-up within nationwide registries. Diagnoses of RA and ILD were identified from the Finnish national hospital discharge, medication reimbursement and cause-of-death registries. We estimated lifetime risks of ILD by age 80. MUC5B is a common variant and has an allele frequency of 0.1 in the Finnish population.

Results:

Out of the 248,400 individuals, 5534 patients have been diagnosed with RA, out of whom 178 (3.2%) developed ILD. MUC5B was a strong predictor of ILD in RA patients (HR 2.14, 95%CI 1.56-2.92). In patients with RA, MUC5B conferred a lifetime risk of 14.5% (95%CI 10.7-18.1%), compared to 5.2% (4.1-6.2%) in MUC5B non-carriers with RA (Figure). In the population, MUC5B carriers and MUC5B non-carriers had lifetime risks of 3.9% and 1.3%, respectively. The risk difference started to emerge at age 65. The risk was highest in men with RA who are MUC5B carriers: 18.5% (11.1-25.2%) developed ILD, compared to 8.5% (6.1-10.9%) of MUC5B non-carriers with RA.

Conclusion:

We report findings from a large longitudinal study, showing that MUC5B confers a considerable lifetime risk of RA-ILD, and contributes to increased morbidity. These findings have clinical implications for improving identification of RA patients at high risk of developing ILD.

References:

[1]Juge P-A, Lee JS, Ebstein E, et al. MUC5B Promoter Variant and Rheumatoid Arthritis with Interstitial Lung Disease. N Engl J Med 2018;379:2209–19

Disclosure of Interests:

Antti Palomäki Speakers bureau: MSD, Pfizer, Sanofi, Consultant of: Pfizer, Abbvie, Tarja Laitinen: None declared, Jukka Koskela Speakers bureau: Pfizer, Aarno Palotie: None declared, Nina Mars: None declared

Parathyroid hormone may play a role in the pathophysiology of primary hypertension

Parathyroid hormone has been related with the risk of hypertension, but the matter remains controversial. We examined the association of parathyroid hormone with central blood pressure and its determinants in 622 normotensive or never-treated hypertensive subjects aged 19-72 years without diabetes, cardiovascular or renal disease, or cardiovascular medications. The methods were whole-body impedance cardiography and analyses of pulse wave and heart rate variability. Cardiovascular function was examined in sex-specific tertiles of plasma parathyroid hormone (mean concentrations 3.0, 4.3 and 6.5 pmol/L, respectively) during head-up tilt. Explanatory factors for haemodynamics were further investigated using linear regression analyses. Mean age was 45.0 (s.d. 11.7) years, BMI 26.8 (4.4) kg/m2, seated office blood pressure 141/90 (21/12) mmHg, and 309 subjects (49.7%) were male. Only five participants had elevated plasma parathyroid hormone and calcium concentrations. Highest tertile of parathyroid hormone presented with higher supine and upright aortic diastolic blood pressure (P < 0.01) and augmentation index (P < 0.01), and higher upright systemic vascular resistance (P < 0.05) than the lowest tertile. The tertiles did not present with differences in pulse wave velocity, cardiac output, or measures of heart rate variability. In linear regression analyses, parathyroid hormone was an independent explanatory factor for aortic systolic (P = 0.005) and diastolic (P = 0.002) blood pressure, augmentation index (P = 0.002), and systemic vascular resistance (P = 0.031). To conclude, parathyroid hormone was directly related to central blood pressure, wave reflection, and systemic vascular resistance in subjects without cardiovascular comorbidities and medications. Thus, parathyroid hormone may play a role in the pathophysiology of primary hypertension.

Primary aldosteronism: Higher volume load, cardiac output and arterial stiffness than in essential hypertension

BACKGROUND

The diagnostics of primary aldosteronism (PA) are usually carried out in patients taking antihypertensive medications. We compared haemodynamics between medicated PA, medicated essential hypertension (EH), never-medicated EH and normotensive controls (n = 130 in all groups).

METHODS

The hypertensive groups were matched for age (53 years), sex (84 male/46 female) and body mass index (BMI) (30 kg m^-2 ); normotensive controls had similar sex distribution (age 48 years, BMI 27 kg m^-2 ). Haemodynamics were recorded using whole-body impedance cardiography and radial pulse wave analysis, and the results were adjusted as appropriate. Radial blood pressure recordings were calibrated by brachial blood pressure measurements from the contralateral arm.

RESULTS

Radial and aortic systolic and diastolic blood pressure was similar in PA and never-medicated EH, and higher than in medicated EH and normotensive controls (P ≤ 0.001 for all comparisons). Extracellular water balance was ~ 4% higher in PA than in all other groups (P < 0.05 for all), whilst cardiac output was ~ 8% higher in PA than in medicated EH (P = 0.012). Systemic vascular resistance and augmentation index were similarly increased in PA and both EH groups when compared with controls. Pulse wave velocity was higher in PA and never-medicated EH than in medicated EH and normotensive controls (P ≤ 0.033 for all comparisons).

CONCLUSIONS

Medicated PA patients presented with corresponding systemic vascular resistance and wave reflection, but higher extracellular water volume, cardiac output and arterial stiffness than medicated EH patients. Whether the systematic evaluation of these features would benefit the clinical diagnostics of PA remains to be studied in future.

Aldosterone-to-renin ratio is related to arterial stiffness when the screening criteria of primary aldosteronism are not met

Aldosterone-to-renin ratio (ARR) is a screening tool for primary aldosteronism (PA), but the significance of ARR when the PA criteria are not met remains largely unknown. In this cross-sectional study we investigated the association of ARR with haemodynamic variables in 545 normotensive and never-medicated hypertensive subjects (267 men, 278 women, age range 19-72 years) without suspicion of PA. Supine haemodynamic data was recorded using whole-body impedance cardiography and radial tonometric pulse wave analysis. In sex-adjusted quartiles of ARR, determined as serum aldosterone to plasma renin activity ratio, the mean values were 282, 504, 744 and 1467 pmol/µg of angiotensin I/h, respectively. The only difference in haemodynamic variables between the ARR quartiles was higher pulse wave velocity (PWV) in the highest quartile versus other quartiles (p = 0.004), while no differences in blood pressure (BP), heart rate, wave reflections, cardiac output or systemic vascular resistance were observed between the quartiles. In linear regression analysis with stepwise elimination, ARR was an independent explanatory factor for PWV (β = 0.146, p < 0.001, R2 of the model 0.634). In conclusion, ARR was directly and independently associated with large arterial stiffness in individuals without clinical suspicion of PA. Therefore, ARR could serve as a clinical marker of cardiovascular risk.Trial registration: ClinicalTrails.gov: NCT01742702.

Leukocyte telomere length is inversely associated with arterial wave reflection in 566 normotensive and never-treated hypertensive subjects

Telomeres are short segments in chromosome ends, the length of which is reduced during cell lifecycles. We examined the association of mean leukocyte telomere length (LTL) and short telomere proportion (STP) with hemodynamic variables in normotensive and never-treated hypertensive volunteers (n=566, 19-72 years). STP and mean LTL were determined using Southern blotting, and supine hemodynamics recorded using continuous tonometric pulse wave analysis and whole-body impedance cardiography. The analyses were adjusted for age, body mass index (BMI), alcohol use, smoking, plasma chemistry, and estimated glomerular filtration rate (eGFR). In univariate analyses, mean LTL and STP both correlated with age, BMI, eGFR, aortic blood pressure, augmentation index, and pulse wave velocity (p<0.05 for all). Mean LTL also correlated with systemic vascular resistance (p<0.05). In linear regression analyses of all hemodynamic variables, mean LTL was only an independent explanatory factor for augmentation index (Beta -0.006, p=0.032), while STP was not an explanatory factor for any of the hemodynamic variables, in contrast to age, BMI and several cardiovascular risk factors. To conclude, augmentation index was predominantly related with chronological aging, but also with mean LTL, suggesting that this variable of central wave reflection is a modest marker of vascular biological aging.

Plasma total calcium concentration is associated with blood pressure and systemic vascular resistance in normotensive and never-treated hypertensive subjects

Purpose: The underlying causes of primary hypertension are not fully understood. Evidence on the relation of plasma calcium concentration with blood pressure (BP) is inconsistent and relies largely on studies utilizing office BP measurements in populations using cardiovascular drugs. In many studies adjustment for confounders was not optimal. In this cross-sectional study we examined the association of plasma total calcium concentration with the haemodynamic determinants of blood pressure.Subjects and methods: Supine haemodynamics were recorded using pulse wave analysis, whole-body impedance cardiography, and heart rate variability analysis in 618 normotensive or never-treated hypertensive subjects (aged 19-72 years) without diabetes, cardiovascular or renal disease, or cardiovascular medications. Linear regression analysis was used to investigate factors associated with haemodynamic variables.Results: Mean age was 45.0 years, body mass index 26.8 kg/m², seated office BP 141/89 mmHg, and 307 subjects (49.7%) were male. Mean values of routine blood and plasma chemistry analyses were within the reference limits of the tests except for low-density lipoprotein cholesterol (3.05 mmol/l). In the laboratory, mean supine radial BP was 131/75 mmHg, and both systolic and diastolic BP correlated directly with plasma total calcium concentration (r = 0.25 and r = 0.22, respectively, p < 0.001 for both). In regression analysis plasma total calcium concentration was an independent explanatory variable for radial and aortic systolic and diastolic BP, and systemic vascular resistance, but not for cardiac output, pulse wave velocity, or any of the heart rate variability parameters.Conclusion: Plasma total calcium concentration was directly associated with systolic and diastolic BP and systemic vascular resistance in normotensive or never-treated hypertensive subjects without comorbidities and cardiovascular medications. Higher plasma calcium concentration potentially plays a role in primary hypertension via an effect on vascular resistance.

Atherogenic index of plasma is related to arterial stiffness but not to blood pressure in normotensive and never-treated hypertensive subjects

BACKGROUND AND AIMS

Atherogenic index of plasma (AIP), defined as the logarithm of triglycerides to high-density lipoprotein cholesterol (HDL-C) ratio, is a strong predictor of future cardiovascular disease. Our aim was to examine the association of AIP with haemodynamic variables in normotensive and never-treated hypertensive subjects in a cross-sectional study.

METHODS

Supine haemodynamics in 615 subjects without antihypertensive and lipid-lowering medications were examined using whole-body impedance cardiography and radial pulse wave analysis. Linear regression analysis was applied to investigate the association of AIP with haemodynamic variables and age, sex, body mass index (BMI), smoking status, alcohol consumption, plasma C-reactive protein, electrolytes, uric acid, low density lipoprotein cholesterol (LDL-C), estimated glomerular filtration rate, and quantitative insulin sensitivity check index.

RESULTS

The demographics and laboratory values of the study population were (mean ± 95% confidence interval): age 44.9 ± 1.0 years, BMI 26.8 ± 0.4 kg/m², office blood pressure 140.6 ± 1.6/89.4 ± 1.0 mmHg, total cholesterol 5.2 ± 0.08, LDL-C 3.1 ± 0.08, triglycerides 1.2 ± 0.08, HDL-C 1.6 ± 0.04 mmol/l, and AIP -0.15 ± 0.02. Age (standardized coefficient Beta 0.508, p < .001) and aortic systolic blood pressure (Beta 0.239, p < .001) presented with the strongest associations with pulse wave velocity. However, AIP was also associated with pulse wave velocity (Beta 0.145, p < .001). AIP was not related with aortic or radial blood pressure, cardiac output, systemic vascular resistance, or augmentation index.

CONCLUSIONS

AIP is directly and independently associated with arterial stiffness, a variable strongly related to cardiovascular risk. This supports more widespread use of AIP in standard clinical cardiovascular disease risk evaluation.

LDL cholesterol is associated with systemic vascular resistance and wave reflection in subjects naive to cardiovascular drugs

BACKGROUND AND AIM

Low density lipoprotein cholesterol (LDL-C) is a primary risk factor for atherosclerosis, but it is also associated with elevated blood pressure (BP) and future development of hypertension. We examined the relationship between LDL-C and haemodynamic variables in normotensive and never-treated hypertensive subjects.

METHODS

We recruited 615 volunteers (19-72 years) without lipid-lowering and BP-lowering medication. Supine haemodynamics were recorded using continuous radial pulse wave analysis, whole-body impedance cardiography, and single channel electrocardiogram. The haemodynamic relations of LDL-C were examined using linear regression analyses with age, sex, body mass index (BMI) (or height and weight as appropriate), smoking status, alcohol use, and plasma C-reactive protein, sodium, uric acid, high density lipoprotein cholesterol (HDL-C), triglycerides, estimated glomerular filtration rate, and quantitative insulin sensitivity check index as the other included variables.

RESULTS

The mean (SD) characteristics of the subjects were: age 45 (12) years, BMI 27 (4) kg/m², office BP 141/89 (21/13) mmHg, creatinine 74 (14) µmol/l, total cholesterol 5.2 (1.0), LDL-C 3.1 (0.6), triglycerides 1.2 (0.8), and HDL-C 1.6 (0.4) mmol/l. LDL-C was an independent explanatory factor for aortic systolic and diastolic BP, augmentation index, pulse wave velocity (PWV), and systemic vascular resistance index (p < 0.05 for all). When central BP was included in the model for PWV, LDL-C was no longer an explanatory factor for PWV.

CONCLUSIONS

LDL-C is independently associated with BP via systemic vascular resistance and wave reflection. These results suggest that LDL-C may play a role in the pathogenesis of primary hypertension.

Increased Cardiac Workload in the Upright Posture in Men: Noninvasive Hemodynamics in Men Versus Women

Background

Men and women differ in the risk of cardiovascular disease, but the underlying mechanisms are not completely understood. We examined possible sex‐related differences in supine and upright cardiovascular regulation.

Methods and Results

Hemodynamics were recorded from 167 men and 167 women of matching age (≈45 years) and body mass index (≈26.5) during passive head‐up tilt. None had diabetes mellitus or cardiovascular disease other than hypertension or used antihypertensive medication. Whole‐body impedance cardiography, tonometric radial blood pressure, and heart rate variability were analyzed. Results were adjusted for height, smoking, alcohol intake, mean arterial pressure, plasma lipids, and glucose. Supine hemodynamic differences were minor: Men had lower heart rate (−4%) and higher stroke index (+7.5%) than women (P<0.05 for both). Upright systemic vascular resistance was lower (−10%), but stroke index (+15%), cardiac index (+16%), and left cardiac work were clearly higher (+20%) in men than in women (P<0.001 for all). Corresponding results were observed in a subgroup of men and postmenopausal women (n=76, aged >55 years). Heart rate variability analyses showed higher low:high frequency ratios in supine (P<0.001) and upright (P=0.003) positions in men.

Conclusions

The foremost difference in cardiovascular regulation between sexes was higher upright hemodynamic workload for the heart in men, a finding not explained by known cardiovascular risk factors or hormonal differences before menopause. Heart rate variability analyses indicated higher sympathovagal balance in men regardless of body position. The deviations in upright hemodynamics could play a role in the differences in cardiovascular risk between men and women.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01742702.

Central wave reflection is associated with peripheral arterial resistance in addition to arterial stiffness in subjects without antihypertensive medication

Background

Augmentation index, a marker of central wave reflection, is influenced by age, sex, height, blood pressure, heart rate, and arterial stiffness. However, the detailed haemodynamic determinants of augmentation index, and their relations, remain uncertain. We examined the association of augmentation index with vascular resistance and other haemodynamic and non-haemodynamic factors.

Methods

Background information, laboratory values, and haemodynamics of 488 subjects (239 men, 249 women) without antihypertensive medication were obtained. Indices of central wave reflection, systemic vascular resistance, cardiac function, and pulse wave velocity were measured using continuous radial pulse wave analysis and whole-body impedance cardiography.

Results

In a regression model including only haemodynamic variables, augmentation index in males and female subjects, respectively, was associated with systemic vascular resistance (β = 0.425, β = 0.336), pulse wave velocity (β = 0.409, β = 0.400) (P < 0.001 for all), stroke volume (β = 0.256, β = 0.278) (P = 0.001 for both) and heart rate (β = −0.150, β = −0.156) (P = 0.049 and P = 0.036). When age, height, weight, smoking habits, and laboratory values were included in the regression model, the most significant explanatory variables for augmentation index in males and females, respectively, were age (β = 0.577, β = 0.557) and systemic vascular resistance (β = 0.437, β = 0.295) (P < 0.001 for all). In the final regression model, pulse wave velocity was not a significant explanatory variable for augmentation index, probably due to the high correlation of this variable with age (Spearman’s correlation ≥0.617).

Conclusion

Augmentation index is strongly associated with systemic vascular resistance in addition to arterial stiffness.

Trial registration

ClinicalTrials.gov, NCT01742702.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0303-6) contains supplementary material, which is available to authorized users.

Lower glomerular filtration rate is associated with higher systemic vascular resistance in patients without prevalent kidney disease

The authors examined the association between estimated glomerular filtration rate (eGFR), calculated using the Chronic Kidney Disease Epidemiology Collaboration creatinine-cystatin C equation, and hemodynamics in 556 normotensive or never-treated hypertensive patients without kidney disease (mean age, 46 years). Hemodynamic variables were recorded using pulse wave analysis and whole-body impedance cardiography. The mean eGFR was 98 mL/min/1.73 m(2) (range, 64-145 mL/min/1.73 m(2) and one third of the patients had values below 92, while none had proteinuria. In linear regression analyses adjusted for differences in age, weight:height ratio, low-density lipoprotein cholesterol, and sex, significant associations were found between lower eGFR and higher systolic (P=.001) and diastolic blood pressure (P<.001) and higher systemic vascular resistance (P=.001). There was no association between eGFR and cardiac output or extracellular volume. In the absence of clinical kidney disease, lower eGFR was associated with higher blood pressure and systemic vascular resistance. Therefore, early impairment in kidney function may be involved in the pathogenesis of essential hypertension.

Response initiation in young adults at risk for psychosis in the Northern Finland 1986 Birth Cohort

INTRODUCTION

This is one of the very few studies to investigate the specific executive function/processing speed component of response initiation in subjects at familial risk (FR) for psychosis, and the first such study in subjects at clinical risk (CR) for psychosis.

METHODS

Participants (N = 177) were members of the general population-based Northern Finland 1986 Birth Cohort in the following four groups: FR for psychosis (n = 62), CR for psychosis (n = 21), psychosis (n = 25) and control subjects (n = 69). The response initiation of these groups was compared in three different tests: Semantic fluency, Stockings of Cambridge and Spatial working memory.

RESULTS

The two risk groups did not differ significantly from control group, but differed from, and outperformed the psychosis group in semantic fluency response initiation.

CONCLUSIONS

Response initiation deficits were not evident in a non-help seeking psychosis high-risk sample.

Longitudinal HRQoL shows divergent trends and identifies constant decliners in asthma and COPD

BACKGROUND/AIM

Monitoring of lung function alone does not adequately identify the high-risk patients among elderly asthma and COPD cohorts. The additional value of Health-Related Quality of Life (HRQoL) development in the detection of patients with a disabling disease in clinical practice is unclear. The aim of this study was to statistically examine the individual development of HRQoL measured using respiratory-specific AQ20 and generic 15D questionnaires.

MATERIALS AND METHODS

The HRQoL of COPD (N = 739) and asthma (N = 1329) patients was evaluated at 0, 1, 2, and 4 years after recruitment. To determine a five-year HRQoL change for each patient we used mixed-effects modelling for linear trend.

RESULTS

In COPD, the majority (60-80%) of the individuals showed declining trend, whereas in asthma, the majority (46-71%) showed no attenuation in HRQoL. The proportion of constant decliners was estimated higher with the 15D both in asthma (6.3%) and COPD (6.3%) than with AQ20 (3.5 and 4.5%, respectively). The first measurement of HRQoL was found to predict future development of HRQoL. In asthma, obesity-related diseases such as hypertension, diabetes and gastro-esophageal reflux disease best explained the decline, whereas in COPD, age and the level of bronchial obstruction were the main determinants.

CONCLUSION

Based on the five-year follow-up, the HRQoL trends significantly diverging from each other could be identified both among the asthma and COPD patients. Compared to cross-sectional HRQoL, the HRQoL trend over a clinically relevant period of time allows us to ignore, to a great extent, the random error of self-assessed HRQoL and thus, it may offer a more accurate measure to describe the disease process.

Dietary phosphate binding and loading alter kidney angiotensin-converting enzyme mRNA and protein content in 5/6 nephrectomized rats

BACKGROUND

Vitamin D receptor activation with paricalcitol can modulate the transcription of renin-angiotensin system components in the surgical 5/6 nephrectomy rat model (5/6 NX) of chronic renal insufficiency. We tested the hypothesis whether dietary modification of phosphate influences kidney renin-angiotensin system gene expression at the mRNA level in 5/6 NX rats.

METHODS

Fifteen weeks after surgery, rats were given control diet (0.3% calcium, 0.5% phosphate), phosphate-lowering diet (3% calcium as carbonate) or high-phosphate diet (1.5%) for 12 weeks. Sham-operated rats were on control diet.

RESULTS

Blood pressure, plasma phosphate, parathyroid hormone, glomerulosclerosis, tubulointerstitial damage, and FGF-23 were increased in remnant kidney rats, whereas creatinine clearance was decreased. Phosphate, parathyroid hormone, glomerulosclerosis, tubulointerstitial damage, and FGF-23 were further elevated by the high-phosphate diet, but were reduced by the phosphate-lowering diet. Plasma calcium was increased with the phosphate-lowering diet and decreased with the high-phosphate diet. Remnant kidney rats on control diet showed upregulated kidney angiotensin-converting enzyme (ACE) and angiotensin (Ang) IV receptor (AT(4)) transcription, while ACE2, Ang II type 2 receptor and renin receptor transcription were downregulated in comparison with sham rats. Phosphate-lowering diet reduced whereas high-phosphate diet increased kidney ACE, and these effects were observed at both mRNA and protein levels. Dietary phosphate loading also resulted in lower AT(1a) gene transcription.

CONCLUSION

Dietary phosphate loading was associated with elevated kidney ACE expression, increased tissue damage and lower AT(1a) transcription in 5/6 NX rats. Phosphate binding with 3% calcium carbonate had opposite effects on ACE and kidney damage.

Allelic variant of NOS1AP effects on cardiac alternans of repolarization during exercise testing

INTRODUCTION

A repolarization abnormality manifested as T-wave alternans (TWA) in electrocardiogram (ECG) predicts cardiovascular mortality. A common variant in the NOS1AP gene is associated with mortality and QT interval duration, possibly in a gender-specific manner, but data is lacking on potential association with TWA. This study tested association between rs10494366 in NOS1AP and both TWA and 4-year mortality.

MATERIAL AND METHODS

A total of 1963 Finnish Cardiovascular Study participants (36.6% female, 57.1 ± 13.0 years) were genotyped and their maximal TWA values were measured from continuous ECG recordings during clinical exercise test at rest, exercise and recovery.

RESULTS

We observed a significant gender-specific effect of NOS1AP genotype on TWA. In all subjects, there was no statistically significant difference between the three genotypes (TT, TG, GG) in the responses of TWA over the entire exercise test (time-by-genotype interaction p = 0.057). In women, after adjustment for age, coronary heart disease and β-blocker medication status, changes of TWA over different phases of exercise test were significantly associated with NOS1AP genotype (time-by-genotype interaction p = 0.001). In men, NOS1AP rs10494366 was not associated with TWA. During follow-up (mean 47 months), 113 patients died. NOS1AP rs10494366 was not a statistically significant predictor of mortality.

CONCLUSION

The NOSIAP variant rs10494366 influences TWA and TWA response during clinical exercise test in females. Gender-specific effects have also been previously reported for the influence of the variant on QT interval. If replicated, these findings should prompt studies to further elucidate the mechanisms underlying the gender differences in NOS1AP effects on repolarization.

Reduced systemic vascular resistance in healthy volunteers with presyncopal symptoms during a nitrate-stimulated tilt-table test

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Nitrates may facilitate syncope through various pathways, but the precise mechanism of nitrate-induced syncope is still under debate. The purpose of the present study was to compare the underlying haemodynamic mechanisms in subjects without and with presyncopal symptoms during a nitroglycerin-stimulated tilt-table test.

WHAT THIS STUDY ADDS

A major decrease in systemic vascular resistance was documented in subjects with presyncope during 0.25 mg nitroglycerin-stimulated tilt-table test, in the absence of changes in cardiac output. These findings indicated that even a small dose of nitroglycerin significantly decreased arterial resistance and cardiac afterload. AIMS The mechanism of nitrate-induced syncope remains controversial. We examined the haemodynamic changes in healthy volunteers during nitroglycerin-stimulated tilt-table test.

METHODS

Continuous radial pulse wave analysis, whole-body impedance cardiography and plethysmographic finger blood pressure were recorded in a supine position and during head-up tilt in 21 subjects with presyncopal symptoms (6 male/15 female, age 43 ± 3 years) after 0.25 mg sublingual nitroglycerin and 21 control subjects (6 male/15 female, age 43 ± 2 years). The drug was administered in the supine position and a passive head-up tilt followed 5 min later. Additionally, nitroglycerin was only administered during head-up tilt in 19 subjects and the haemodynamics were recorded.

RESULTS

Supine and upright haemodynamics were similar before nitroglycerin administration in the two groups. During the nitroglycerin-stimulated tilt test, aortic and radial mean blood pressure decreased significantly more in the presyncope group when compared with the controls (P= 0.0006 and P= 0.0004, respectively). The decreases in systemic vascular resistance (P= 0.0008) and heart rate (P= 0.002), and increase in aortic reflection time (P= 0.0002) were greater in the presyncope group, while the change in cardiac index was not different between the groups (P= 0.14). If nitroglycerin was administered during the upright tilt and not in supine position, the haemodynamic changes were quite corresponding.

CONCLUSIONS

Presyncopal symptoms during nitrate-stimulated tilt test were explained by decreased systemic vascular resistance and increased aortic reflection time, while cardiac output remained unchanged. These findings indicated reduced arterial resistance in nitroglycerin-induced presyncope.

Non-invasive measurement of the haemodynamic effects of inhaled salbutamol, intravenous L-arginine and sublingual nitroglycerin

AIMS

To examine the effects of salbutamol and L-arginine, two compounds acting largely on the endothelium, and the endothelium-independent agent nitroglycerin on blood pressure, arterial compliance, cardiac function and vascular resistance.

METHODS

Continuous radial pulse wave analysis, whole-body impedance cardiography, and plethysmographic blood pressure from fingers in the supine position and during head-up tilt were recorded in nine healthy subjects. Data were captured before and after L-arginine (10 mg mg(-1) min(-1)) or saline infusion, salbutamol (400 microg) or placebo inhalation, and sublingual nitroglycerin (0.25 mg) or placebo resoriblet.

RESULTS

The results of all measurements were comparable before drug administration. The effects of inhaled salbutamol were apparent in the supine position: systemic vascular resistance (-9.2 +/- 2.6%) and augmentation index (-4.0 +/- 1.5%) decreased, and heart rate (8.6 +/- 2.5%) and cardiac output (8.8 +/- 3.1%) increased. L-arginine had no clear effects on supine haemodynamics, but during head-up tilt blood pressure was moderately decreased and reduction in aortic reflection time prevented, indicating improved large arterial compliance. Nitroglycerin reduced supine vascular resistance (-6.7 +/- 1.8%) and augmentation index (-7.4 +/- 1.6%), and increased cardiac output (+9.2 +/- 2.7%). During head-up tilt, nitroglycerin increased cardiac output (+10.6 +/- 5.6%) and heart rate (+40 +/- 7.5%), decreased vascular resistance (-7.8 +/- 5.8%) and augmentation index (-18.7 +/- 3.2%), and prevented the decrease in aortic reflection time.

CONCLUSIONS

Inhaled salbutamol predominantly changed supine haemodynamics, whereas the moderate effects of L-arginine were observed during the head-up tilt. In contrast, small doses of nitroglycerin induced major changes in haemodynamics both supine and during the head-up tilt. Altogether, these results emphasize the importance of haemodynamic measurements in both the supine and upright positions.

Effect of common KCNE1 and SCN5A ion channel gene variants on T-wave alternans, a marker of cardiac repolarization, during clinical exercise stress test: the Finnish Cardiovascular Study

T-wave alternans (TWA) in electrocardiography (ECG) is a marker of cardiac repolarization, the molecular regulation of which is incompletely understood. High TWA and prolonged QT intervals are both associated with ventricular arrhythmias and sudden death. Therefore, we tested the hypothesis of whether the same mutations that influence the QT interval also affect TWA variation. We examined the effect of 3 ion channel gene single nucleotide polymorphisms (SNPs), rs1805127, rs727957 KCNE1, and rs1805124 SCN5A, on TWA during a clinical exercise test. A total of 2008 subjects from the Finnish Cardiovascular Study underwent an exercise test with online ECG recording. TWA was measured by using the time-domain, modified moving average method. Maximum values at rest, during maximal exercise, and during recovery were used as outcome measures in statistical analysis. Moreover, 4-year survival data were collected and ion channel SNPs were determined. TWA was lowest in subjects with the TT genotype of rs1805127 during all phases of the exercise test (RANOVA main effect for genotype, P = 0.018). The result remained significant after adjustment for age, existing coronary heart disease, and beta-blocker medication status (RANCOVA, P = 0.035). Of the polymorphisms studied, only rs1805127 had a significant association with mortality (P = 0.047). The most common G-C haplotype, formed by rs727957 and rs1805127, was associated with TWA (RANOVA, P = 0.007) but not with mortality. The rs1805124 polymorphism was not associated with TWA. The common KCNE1 gene variant rs1805127 is associated with TWA during an exercise test in a Finnish population, which provides additional evidence that KCNE1 genetics may influence cardiac repolarization and cardiovascular mortality.

Potassium channel KCNH2 K897T polymorphism and cardiac repolarization during exercise test: The Finnish Cardiovascular Study

OBJECTIVE

Cardiac repolarization is regulated, in part, by the KCNH2 gene, which encodes a rapidly activating component of the delayed rectifier potassium channel. The gene expresses a functional single nucleotide polymorphism, K897T, which changes the biophysical properties of the channel. The objective of this study was to evaluate whether this polymorphism influences two indices of repolarization--the QT interval and T-wave alternans (TWA)--during different phases of a physical exercise test.

MATERIAL AND METHODS

The cohort consisted of 1,975 patients undergoing an exercise test during which on-line electrocardiographic data were registered. Information on coronary risk factors and medication was recorded. The 2690A>C nucleotide variation in the KCNH2 gene corresponding to the K897T amino acid change was analysed after polymerase chain reaction with allele-specific TaqMan probes.

RESULTS

Among all subjects, the QTc intervals did not differ between the three genotype groups (p> or =0.31, RANOVA). Women with the CC genotype tended to have longer QT intervals during the exercise test, but the difference was statistically significant only at rest (p = 0.011, ANOVA). This difference was also detected when the analysis was adjusted for several factors influencing the QT interval. No statistically significant effects of the K897T polymorphism on TWA were observed among all subjects (p = 0.16, RANOVA), nor in men and women separately.

CONCLUSIONS

The K897T polymorphism of the KCNH2 gene may not be a major genetic determinant for the TWA, but the influence of the CC genotype on QT interval deserves further research among women.

Genetic relationships of body composition and feed utilization traits in European whitefish (Coregonus lavaretus L.) and implications for selective breeding in fishmeal- and soybean meal-based diet environments

Body composition traits have potential use in fish breeding programs as indicator traits for selective improvement of feed efficiency. Moreover, feed companies are increasingly replacing traditional fish meal (FM) based ingredients in feeds for carnivorous farmed fish with plant protein ingredients. Therefore, genetic relationships of composition and feed utilization traits need to be quantified for both current FM-based and future plant-based aquaculture feeds. Individual whole-body lipid% and protein%, daily gain (DG), ADFI, and G:F (daily gain/daily feed intake) were measured on 1,505 European whitefish (Coregonus lavaretus) from 70 half/full-sib families reared in a split-family design with either a typical FM or a novel soybean meal (SBM) based diet. Diet-specific genetic parameters were estimated with multiple-trait animal models. Lipid% was significantly greater in the FM diet group than in the SBM group, even independent of final BW or total feed intake. In both diets, lipid% showed moderate heritability (0.12 to 0.22) and had positive phenotypic and genetic correlations with DG (0.37 to 0.82) and ADFI (0.36 to 0.88). Therefore, selection against lipid% can be used to indirectly select for lower feed intake. Protein% showed low heritability (0.05 to 0.07), and generally very weak or zero correlations with DG and ADFI. In contrast to many previous studies on terrestrial livestock, lipid% showed zero or very weak phenotypic and genetic correlations with G:F. However, selection index calculations demonstrated that simultaneous selection for high DG and reduced lipid% could be used to indirectly increase G:F; this strategy increased absolute genetic response in G:F by a factor of 1.5 to 1.6 compared with selection on DG alone. Lipid% and protein% were not greatly affected by genotype-diet environment interactions, and therefore, selection strategies for improving body composition within current FM diets should also improve populations for future SBM diets.

The effect of dietary phosphorus deficiency on the immune responses of European whitefish (Coregonus lavaretus L.)

Low phosphorous (P) feeds in aquaculture are recommended to reduce eutrophication of water systems. However, the feed should be adequate for normal growth and intact immune defence. Influence of low dietary P supply on non-specific and specific immune defence of European whitefish (Coregonus lavaretus) was studied in two trials. For Trial 1, a semi-purified, low-P diet was formulated and supplied with 0, 2.5, 5.0, 7.5, or 10.0 g P kg(-1)to obtain a P gradient of 4.4-14.9 g kg(-1)diet. Diets were fed to four replicate groups of fingerling whitefish for 42 days in a flow-through, freshwater system maintained at 15 degrees C. Fish fed with the P-unsupplemented diet had significantly lower plasma immunoglobulin M (IgM) levels than fish fed with the P-fortified diets (means 2.53 vs. 3.19 mg ml(-1); P=0.047). Plasma lysozyme activity did not differ between fish fed with the P-unsupplemented diet and fish fed with the P-fortified diets (means 21.8 vs. 25.5 U ml(-1); P=0.107). For Trial 2, fish were acclimated for 49 days by feeding the lowest or highest dietary P contents, and thereafter immunised with a single intraperitoneal injection of a novel antigen, bovine gamma globulin (BGG). A clear antibody response against BGG was elicited but the antibody levels did not differ between fish fed low-P or high-P contents. Similar to Trial 1, plasma IgM was lower in fish fed low-P diets, and low-P diet did not influence plasma lysozyme activity. In both trials the growth of fish, having received low-P diet, was significantly lowered. It is concluded that P deficiency has only minor effects on the immune parameters in whitefish, and the practical aquafeed with P contents sufficient for normal growth does not compromise immune functions of this species.

Programme sensitivity and effectiveness of mammography service screening in Helsinki, Finland

OBJECTIVES

To evaluate the effectiveness of mammography service screening.

SETTING

Helsinki (population 0.5 million), the capital of Finland, the breast cancer service screening programme was started gradually in 1986.

MATERIALS AND METHODS

The study was based on the data from the breast cancer screening programme in Helsinki. All incident cases of breast cancer and rates in the female population in Helsinki during the period 1970-97, and information on the subsequent breast cancer mortality were derived from the files of the Finnish Cancer Registry. To estimate the sensitivity of the programme, the number of screen detected cancers were compared with the overall number of breast cancers at the targeted age groups. Effects of screening were estimated for cumulative incidence and for the refined mortalities among the birth cohorts screened.

RESULTS

Altogether 144 400 invitations had been sent during 1986-97 among the 50-9 year old women as targeted in Helsinki. The average attendance rate was 82%; and 545 breast cancers were detected by screening, with a detection rate of 0.46%. In the birth cohort of women born between the start of 1935 and the end of 1939-namely, those subjected to most complete screening and long follow up time since the onset of the programme-there was an increase in the cumulative incidence of breast cancer (relative risk (RR) 1.18, 95% confidence interval (95% CI) 1.09 to 1.27). The estimated sensitivity of the screening programme was 58%; and 53% if corrected for overdiagnosis. There was also a decrease of 19% (RR 0.81, 95% CI 0.62 to 1.05) in the refined mortality within this screened birth cohort, compared with the death rate of women of comparable ages in the non-screened reference cohort.

CONCLUSION

The study provides further support to the hypothesis that service screening with mammography reduces the risk of breast cancer mortality.

Acoustic loss mechanisms in leaky SAW resonators on lithium tantalate

We discuss acoustic losses in synchronous leaky surface acoustic wave (LSAW) resonators on rotated Y-cut lithium tantalate (LiTaO3) substrates. Laser probe measurements and theoretical models are employed to identify and characterize the radiation of leaky waves into the busbars of the resonator and the excitation of bulk acoustic waves. Escaping LSAWs lead to a significant increase in the conductance, typically occurring in the vicinity of the resonance and in the stopband, but they do not explain the experimentally observed deterioration of the electrical response at the antiresonance. At frequencies above the stop-band, the generation of fast shear bulk acoustic waves is the dominant loss mechanism.

Surface acoustic wave impedance element ISM duplexer: modeling and optical analysis

Surface acoustic wave (SAW) impedance element antenna duplexers provide compact, high performance, front-end components apt for industrial fabrication. We describe investigations on the design and modeling of a compact ISM antenna duplexer fabricated on a 36 degrees YX-cut LiTaO3 substrate based on SAW impedance elements. In particular, we have performed 3-D modeling of the inductive and capacitive electromagnetic couplings caused by the package parasitics for the duplexer. The use of a 1:3 IDT structure for the reduction of the passband width is discussed. The frequency response of the duplexer is predicted with the help of circuit simulation; the modeling is refined by optimization of the model parameters to improve the fit between the measured and simulated responses. We also report scanning optical imaging of the acoustic field within the resonator structures with the help of laser interferometry; this provides insight into the loss mechanisms beyond that attainable in mere electric measurements.

Theory for shear horizontal surface acoustic waves in finite synchronous resonators

An analytic approach is developed for simulating synchronous resonators employing shear horizontally polarized surface acoustic waves, such as surface transverse waves, and leaky surface acoustic waves on LiTaO/sub 3/ and LiNbO/sub 3/ substrates. The approach, based on a simplified parametrized Green's function theory, allows the description of the localization of the wave and the interaction with bulk acoustic waves. An analytic expression is found for the harmonic admittance of an infinite periodic electrode array, and approximate corrections for finite structures are presented. The model enables fast computation of the admittance of synchronous resonators, and it compares favorably with experiments and numerical simulations.

SAW/LSAW COM parameter extraction from computer experiments with harmonic admittance of a periodic array of electrodes

A novel numerical method for determining the surface acoustic wave and the leaky surface acoustic wave characteristics is proposed. The Green's function method is used to simulate an infinite periodic transducer driven by a periodic voltage. We show that the coupling of modes parameters and the dispersion relation can be extracted from the change in the admittance as the periodicity of the driving voltage is slightly shifted. The method first introduced here leads to significant savings in computing time.

Suppression of the leaky SAW attenuation with heavy mechanical loading

We discuss effects on the propagation of surface acoustic waves (SAW) due to heavy mass loading on Y-cut lithium niobate and lithium tantalate substrates. An abrupt reduction in the leaky-SAW (LSAW) attenuation is observed in the measured admittance of a long resonator test structure on 64 degrees -YX-cut lithium niobate for aluminum electrodes of thickness h/lambda(0) beyond 9-10%. This experimental fact is explained theoretically as the slowing down of the leaky wave below the velocity of the slow shear surface-skimming bulk wave (SSBW), such that energy dissipation into bulk-wave emission becomes inhibited. An infinite transducer structure is modeled using the periodic Green's function and the boundary-element method (BEM); the computed theoretical properties well explain for the experimental findings. The model is further employed to quantify the leaky surface-wave attenuation characteristics as functions of the crystal-cut angle and the thickness of the electrodes. The resonance and antiresonance frequencies and the corresponding Q values are investigated to facilitate the selection of crystal cuts and electrode thicknesses. The transformation of the leaky SAW into a SAW-type nonleaky wave is also predicted to occur for gold electrodes, with considerably thinner finger structures.

Hb Helsinki: a variant with a high oxygen affinity and a substitution at a 2,3-DPG binding site (beta82[EF6] Lys replaced by Met)

A new haemoglobin, Hb Helsinki, in which beta 82-Lys (EF6) is replaced by Met, was found in a Finnish family. It was associated with familial erythrocytosis, and the oxygen affinity of the blood was higher than normal. The oxygen equilibrium curves of purified Hb Helsinki and HbA from the same haemolysate have been determined under vaious conditions. "Stripped' Hb Helsinki was found to show normal cooperativity, slightly low oxygen affinity and a reduced Bohr effect at physiological pH. However, the organic phosphates, 2,3-diphosphoglycerate (2,3-DPG) and inositol hexaphosphate (IHP) had a very small effect on Hb Helsinki, and the 2,3-DPG binding constant of deoxygenated Hb Helsinki is close to that of oxyhaemoglobin A. Thus, the replacement of Lys by Met at position 82 dramatically changes the nature of the central cavity of the tetramer and the effect of 2,3-DPG on the respiratory function of the molecule.