Normotensive Control Subjects Research Articles

Increase in Carotid Intima-Media Thickness in Grade I Hypertensive Subjects

We studied 74 never-treated grade I hypertensive subjects aged 18 to 45 years and 20 normotensive control subjects to define the rate of increase in carotid intima-media thickness (IMT) and the potential role played by the various risk factors. IMT was assessed as mean IMT and as maximum IMT in the right and left common carotid artery, carotid bulb, and internal carotid artery at baseline and at the 5-year follow-up. In grade I hypertensive subjects, both mean IMT and mean of maximum IMT were significantly higher compared with baseline values. Compared with normotensive subjects, both mean IMT and maximum IMT increased significantly (at least P<0.01) in each carotid artery segment. The increase in cumulative IMT was 3.4-fold for mean IMT and 3.2-fold for mean of maximum IMT. Levels of mean arterial pressure at 24-hour monitoring and total serum cholesterol were factors potentially linked to the increment in mean IMT and mean of maximum IMT. Age was also relevant for the increment in mean of maximum IMT, whereas body mass index played some role in the increment of mean IMT. During the follow-up, mean IMT and mean of maximum IMT increased to a greater degree in white-coat hypertensive subjects (n=35) and sustained hypertensive subjects (n=39) than in normotensive control subjects. No differences were found between white-coat hypertensive subjects and sustained hypertensive subjects for both mean IMT and maximum IMT. Levels of mean arterial pressure at 24-hour monitoring affected the increment in IMT in both white-coat hypertensive subjects and sustained hypertensive subjects. In conclusion, our findings indicate that carotid IMT is greater and grows faster in white-coat hypertensive subjects than in normotensive subjects without significant differences with sustained hypertensive patients.

EXAMINATION OF CHROMOSOME 7p22 CANDIDATE GENES RBaK, PMS2 AND GNA12 IN FAMILIAL HYPERALDOSTERONISM TYPE II

1. There are two types of familial hyperaldosteronism (FH): FH-I and FH-II. FH-I is caused by a hybrid CYP11B1/CYP11B2 gene mutation. The genetic cause of FH-II, which is more common, is unknown. Adrenal hyperplasia and adenomas are features. We previously reported linkage of FH-II to a approximately 5 Mb region on chromosome 7p22. We subsequently reported finding no causative mutations in the retinoblastoma-associated Kruppel-associated box gene (RBaK), a candidate at 7p22 involved in tumorigenesis and cell cycle control. 2. In the current study we investigated RBaK regulatory regions and two other candidate genes: postmeiotic segregation increased 2 (PMS2, involved in DNA mismatch repair and tumour predisposition) and guanine nucleotide-binding protein alpha-12 (GNA12, a transforming oncogene). 3. The GNA12 and PMS2 genes were examined in two affected (A1, A2) and two unaffected (U1, U2) subjects from a large 7p22-linked FH-II family (family 1). No mutations were found. 4. The RBaK and PMS2 distal promoters were sequenced to -2150 bp from the transcription start site for RBaK and-2800 bp for PMS2. Five unreported single nucleotide polymorphisms (SNPs) were found in subjects A1, A2 but not in U1 or U2; A(-2031 bp)T, T(-2030 bp)G, G(-834 bp)C, C(-821 bp)G in RBaK and A(-876 bp)G in PMS2. Additional affected and unaffected subjects from family 1 and from two other 7p22-linked FH-II families and 58 unrelated normotensive control subjects were genotyped for these SNPs. 5. The five novel SNPs were found to be present in a significant proportion of normotensive controls. The four RBaK promoter SNPs were found to be in linkage disequilibrium in the normal population. The RBaK promoter (-)2031T/2030G/834C/821T allele was found to be in linkage disequilibrium with the causative mutation in FH-II family 1, but not in families 2 and 3. The PMS2 promoter (-)876G allele was also found to be linked to affected phenotypes in family 1. 6. The RBaK and PMS2 promoter SNPs alter the binding sites for several transcription factors. Although present in the normal population, it is possible that the RBaK (-)2031T/2030G/834C/821T and PMS2 (-)876G alleles may have functional roles contributing to the FH-II phenotype in family 1.

Lack of Association Between the Type 2 Deiodinase A/G Polymorphism and Hypertensive Traits: The Framingham Heart Study

To the Editor: Thyroxine (T4) activation to T3 via the iodothyronine deiodinase type 2 allows for changes in intracellular thyroid status in a tissue-specific manner independent of serum T3. A single nucleotide polymorphism in type 2 deodinase (DIO2) gene (A/G) in humans, in which a threonine changes to alanine at codon 92, has been associated with decreased enzyme activity and higher insulin resistance in type 2 diabetes patients.1 Nevertheless, these findings were not replicated in larger studies.2 Recently, Gumieniak et al3 reported that the alanine allele doubles the risk for development of hypertension in euthyroid subjects. Pituitary and hypothalamic type 2 deiodinase play a critical role in feedback regulation of thyroid-stimulating hormone (TSH) secretion, and higher serum TSH concentrations have been demonstrated in euthyroid hypertensive compared with normotensive control subjects.4 In this context, we thought it would be of interest to evaluate whether the previous reported association of Thr92Ala polymorphism and hypertension is also present in a large unselected, community-based population. The present sample size consists of 1557 individuals who had complete phenotype and genotype information available drawn from a subset of unrelated individuals from the Framingham Heart Study offspring cohort, …

Association of Interleukin-6, Interleukin-12, and Interleukin-10 Gene Polymorphisms with Essential Hypertension in Tatars from Russia

Essential hypertension is a common disease with fatal clinical complications. Epidemiological and family studies have confirmed the role of genetic predisposition in its development. Hypertensive patients have been shown to have an altered profile of pro- and anti-inflammatory cytokines. The aim of our investigation was to reveal the association of interleukin-6, interleukin-12, and interleukin-10 gene polymorphisms with essential hypertension and its clinical complications in a Tatar ethnic group from Bashkortostan, Russia. The study involved 362 hypertensive patients and 244 healthy subjects from this Tatar ethnic group (Bashkortostan, Russia). DNA was isolated from whole venous blood using phenol-chloroform extraction by the standard method. IL6 -572 G/C, IL12B 1159 C/A, and IL10 -627 C/A genotypes were typed using polymerase chain reaction followed by restriction enzyme digestion. We found that the IL10 -627 *C/*C genotype was associated with decreased risk of hypertension (OR = 0.64, P = 0.035). IL6 genotypes and allele distribution did not differ significantly between subjects with and without hypertension, but the IL6 -572 *G/*G genotype frequency was found to be significantly higher among those patients who had stroke, compared with normotensive control subjects (P = 0.036). Carriers of the IL12B 1159 *A/*A genotype had a lower risk of stroke (OR = 0.38, P = 0.028). Our study has shown the association between IL10 -627 C/A polymorphism and essential hypertension in the Tatar ethnic group from Bashkortostan, Russia. The IL10 -627*C/*C genotype was found to be protective against hypertension. We also demonstrated that hypertensive patients with the IL12B *A/*A and IL6 *G/*G genotypes had increased risk of stroke. Our results suggest a role for cytokines in cardiovascular disease development in the Tatar ethnic group, but further investigation is needed.

Association of transient receptor potential canonical type 3 (TRPC3) channel transcripts with proinflammatory cytokines

We investigated whether expression of non-selective cation channels of the transient receptor potential canonical (TRPC) channel family are associated with proinflammatory cytokines in monocytes. Using quantitative RT-PCR we studied the expression of TRPC3, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) in monocytes from 15 patients with essential hypertension and 16 age- and sex-matched normotensive control subjects. We observed an approximately 8-fold increase of TRPC3 transcripts in monocytes from patients with essential hypertension compared to normotensive control subjects ( p < 0.05). We found an approximately 3-fold increase of IL-1β, and an approximately 9-fold increase of TNF-α in patients with essential hypertension compared to normotensive control subjects (each p < 0.05). We observed a significant correlation between TRPC3 transcripts with systolic blood pressure, expression of IL-1β, and TNF-α. Using quantitative RT-PCR we observed an association of TRPC3 transcripts and proinflammatory cytokines in monocytes.

Effect of Endothelin 1 Genotype on Blood Pressure Is Dependent on Physical Activity or Fitness Levels

Contributions of the DNA sequence variation at the endothelin 1 locus to the risk of hypertension and to endurance training-induced changes in blood pressure were investigated in the Aerobics Center Longitudinal Study and the Health, Risk Factors, Exercise Training and Genetics Family Study cohorts. We identified 586 normotensive control subjects and 607 incident hypertensive case subjects from the Aerobics Center Longitudinal Study cohort (all whites) who were normotensive and healthy at their first clinic visit. The case subjects were diagnosed with hypertension during an average follow-up of 9.5 years, whereas the control subjects remained normotensive. The allele and genotype frequencies of 5 endothelin 1 haplotype tagging single nucleotide polymorphisms did not differ significantly between the case and control subjects. However, we observed a significant (P=0.0025) interaction between the endothelin 1 rs5370 (G/T; Lys198Asn) genotype and cardiorespiratory fitness level on the risk of hypertension: among low-fit subjects, the rs5370 minor allele (T; 198Asn) was associated with higher risk of hypertension (odds ratio: 1.95; 95% CI: 1.36 to 2.81; P=0.0003), whereas the risk did not differ among genotypes in high-fit subjects. In the white Health, Risk Factors, Exercise Training and Genetics subjects (N=480), the rs5370 T allele was associated with blunted systolic blood pressure (P=0.0046) and pulse pressure (P=0.0016) responses to a 20-week endurance training program. The Lys198Asn variant of the endothelin 1 locus is associated with blood pressure phenotypes in whites. However, the expression of the genotype effect is modulated by physical activity or cardiorespiratory fitness level. Our study provides an illustrative example of how physical activity and fitness level modifies the associations between a candidate gene and outcome phenotype.

Urinary Podocyte Excretion as a Marker for Preeclampsia

The proteinuria of preeclampsia is associated with glomerular endotheliosis, and a role for damaged and lost podocytes (glomerular epithelial cells) in the development of proteinuria has received support from studies of patients with glomerular diseases. This study asked whether urinary excretion of viable podocytes, quantified by the expression of podocin and other podocyte-specific proteins, is observed in pregnant women with clinically confirmed preeclampsia. In addition, levels of angiogenic factors implicated in the pathogenesis of preeclampsia were estimated. They included soluble receptor for vascular endothelial growth factor, also called fms-like tyrosine kinase receptor-1 (sFlt-1); placental growth factor (PIGF); and serum soluble endoglin. The cross-sectional study recruited 33 pregnant women with preeclampsia, 11 with HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome, and 23 normotensive pregnant women. All of the 15 preeclamptic women evaluated and also those with HELLP syndrome, but not normotensive control subjects, had podocin-positive cells in their urine. Podocyturia was 100% sensitive and 100% specific for the diagnosis of preeclampsia, and the degree of proteinuria correlated positively with podocyturia. The positive predictive value of urinary podocyte excretion for the presence of preeclampsia was greater than that of sFlt-1, PIGF, or endoglin. Nevertheless, serum levels of sFlt-1 were significantly higher in women with preeclampsia or HELLP syndrome than in normotensive control women, and the same was the case for serum levels of soluble endoglin. Women with preeclampsia or HELLP syndrome had lower serum levels of free PlGF than did normotensive pregnant women. Urine levels of PlGF did not differ from those in normal women. Podocyturia is a very sensitive and specific marker for preeclampsia, and it may contribute to the development of proteinuria in affected women. Further studies may clarify the effects of dysregulated vascular endothelial growth factor on mechanisms regulating podocyte attachment.

Mineral Factors Controlling Essential Hypertension—a Study in the Chandigarh, India Population

Essential hypertension (EH) is a major public health problem world over and in India. Recent data on EH in the population of Chandigarh (Union Territory and capital of Punjab and Haryana States of India) revealed that the prevalence of EH has become double in the last 30 years in the residents of Chandigarh (26.9 to 45.80% in the year 1968 and 2002). Zinc (Zn), copper (Cu), magnesium (Mg), and manganese (Mn) in the serum are considered important in maintaining the human hypertension. The high Zn intake was considered to increase the blood pressure (BP) and to affect the other mineral status in the body. Recent survey on the trace metal status of different vegetables in the State of Punjab around Chandigarh (India) revealed that Zn level is significantly higher (40 mg/kg or more in above ground vegetables and 120 mg/kg or above in underground vegetables) in underground water-irrigated vegetables, but the levels of Cu and Mg are within prescribed limit. The present study was conducted on Chandigarh population to evaluate the levels of Zn, Cu, Mg, and Mn in the blood and urine of normotensive (NT) control and hypertensive (HT) subjects matched with number, age and sex. Atomic absorption spectrophotometer studies reevaluated that the levels of serum Zn, Mg, and Mn were significantly higher (p < 0.001), but the level of Cu was low in the HT subjects (BP = 160/93) compared to NT control (BP = 140/83). Higher levels of urinary Zn, Cu, Mg, and Mn were observed in the HT subject vs NT control (p < 0.001). Positive correlations were evaluated between the levels of serum Zn, Mg, and Mn vs systolic and diastolic pressures (DP and SP), respectively (r = 0.928, 0.863, 0.876, 0.808, 0.404, 0.326, p < 0.01), but negative and positive nonsignificant correlations between the serum Cu with SP and DP were recorded (r = -0.032, r = 0.024). Positive correlations were also evaluated between urinary levels of Zn, Cu, Mg, and Mn vs SP and DP (r = 0.718, 0.657, 0.750, 0.681, 0.630, 0.578, 0.516, 0.461, p < 0.01). Prevalence of essential hypertension may be due to higher Zn level in the food chain that makes the individuals vulnerable to other diseases over the time related to essential hypertension.

Baroreflex sensitivity correlates with left ventricular morphology and diastolic function in essential hypertension

Arterial hypertension is a common cause of cardiac organ damage, inducing morphological and functional modifications. Spontaneous baroreflex sensitivity (BRS) control of the heart rate is a key mechanism of blood pressure homeostasis, and is impaired in patients with hypertension. This study sought to assess the association between BRS and left ventricular morphology and function. We studied 224 hypertensive patients (125 men; aged 47.8 +/- 10.8 years, mean +/- SD) compared with 51 normotensive control subjects (25 men, aged 45.7 +/- 12.5 years). Left ventricular morphology, systolic and diastolic function were evaluated by echocardiography. Spontaneous BRS was measured using the sequence method. BRS was inversely associated with relative wall thickness (R = 0.17; P < 0.0001) and left ventricular mass index (R = 0.03; P = 0.01); in particular, BRS was significantly impaired in patients with concentric left ventricular remodelling (median [interquartile difference] 9.4 [4.1]) and hypertrophy (9.05 [3.9]) compared with the normal left ventricle (12.3 [5]; P < 0.001). BRS showed a significant association with systolic function evaluated by midwall fractional shortening (r = 0.28; P < 0.001), stroke volume (r = 0.27; P < 0.001), stroke work (r = 0.17; P < 0.05), and fractional shortening (r = 0.17; P < 0.05). BRS was significantly decreased in patients with diastolic dysfunction; it was lower in patients with diastolic dysfunction compared with both the control group and hypertensive patients with normal diastolic function. BRS is associated with left ventricular morphology, systolic and diastolic function in hypertensive patients. In particular BRS is impaired in patients with diastolic dysfunction. These findings suggest a role for BRS as a target in arterial hypertension.

Left Ventricular Hypertrophy in Hypertensive Adolescents

The National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents recently recommended staging hypertension (HTN) in children and adolescents based on blood pressure severity. The use of blood pressure staging and its corresponding therapeutic approach was examined in this pooled analysis assessing the risk for end-organ damage, specifically left ventricular hypertrophy among hypertensive adolescents stratified by working group criteria. Newly diagnosed hypertensive adolescents and normotensive control subjects similar in age, race/ethnicity, gender, and body mass index completed casual and 24-hour ambulatory blood pressure measurements, M-mode echocardiography, and fasting serum laboratories. Hypertensive subjects had higher insulin and cholesterol but similar glucose levels as compared with control subjects. Among subjects with stage 1 HTN by casual blood pressure, 34% had white-coat HTN as opposed to 15% of stage 2 hypertensive subjects. Of the subjects with normal casual measurements, 20% had HTN by ambulatory monitoring. Subjects with stage 2 HTN by casual measurement alone (odds ratio: 4.13; 95% CI: 1.04 to 16.48) and after 24-hour ambulatory confirmation (odds ratio: 7.23; 95% CI: 1.28 to 40.68) had increased odds for left ventricular hypertrophy. In addition, the risk for left ventricular hypertrophy was similar for subjects with masked and confirmed stage 1 HTN, whereas subjects with white-coat HTN had a risk comparable to normotensive subjects. Thus, recommendations that adolescents with stage 2 HTN by casual measurements alone receive medication initially along with therapeutic lifestyle counseling are reasonable, though ambulatory blood pressure monitoring remains a valuable tool for evaluating children with stage 2 HTN, because >10% have white-coat HTN.

Insulin Resistance and Hyperinsulinemia Are Related to Plasma Aldosterone Levels in Hypertensive Patients

An association between aldosterone and insulin resistance has been demonstrated in obesity and primary aldosteronism and in blacks with the metabolic syndrome. The aim of this study was to evaluate the relationship of plasma aldosterone with insulin sensitivity in white subjects. In 356 patients with essential hypertension and 102 normotensive control subjects of comparable age and BMI, we measured, after discontinuation of treatment, plasma active renin, aldosterone, cortisol, glucose, insulin, and C-peptide levels and calculated markers of insulin sensitivity. Direct assessment of insulin sensitivity was obtained in a subset of 64 hypertensive patients by a hyperinsulinemic clamp. Hypertensive patients had significantly greater fasting plasma insulin and C-peptide concentrations and homeostasis model assessment (HOMA) indexes than normotensive control subjects. A positive association with increasing plasma aldosterone concentrations was demonstrated for plasma glucose, insulin, C-peptides, and HOMA. Assessment of insulin sensitivity by clamp showed a significant decrease of the metabolic clearance rate of glucose with increasing aldosterone levels. Significant correlations were found between plasma aldosterone, plasma insulin, and C-peptide levels, HOMA, and glucose metabolic clearance rate. Blood pressure and plasma potassium, plasma cortisol, and renin levels, but not BMI, were also directly correlated with plasma aldosterone. Multiple regression analysis showed that HOMA, together with plasma potassium, cortisol, and renin levels, was independently correlated with plasma aldosterone. This study demonstrates a direct relationship between aldosterone, insulin resistance, and hyperinsulinemia in white subjects. In patients with hypertension, this relationship might contribute to maintenance of high blood pressure and increased cardiovascular risk.

Epicardial Coronary Artery Size in Hypertensive and Physiologic Left Ventricular Hypertrophy

In the hypertensive heart, epicardial arteries are not enlarged, despite increased total coronary flow related to augmented cardiac workload, wall stress, and left ventricular (LV) mass. The aims of this study were to assess the impact of different hemodynamic factors and LV mass on baseline left main coronary artery (LMA) size in hypertensive LV hypertrophy (LVH) and physiologic LVH, used as a pressure-independent model of hypertrophy. In 104 subjects without coronary disease (26 normotensive subjects without LVH, 15 athletes with physiologic LVH, and 63 untreated hypertensive subjects [28 without and 35 with LVH]), LMA size and coronary flow reserve (CFR) were measured by transesophageal echocardiography, and LV mass, volumes, stroke work, and wall stress were measured by transthoracic echocardiography. The LMA area in normotensive control subjects, athletes, and hypertensive subjects without and with LVH was 13.2 +/- 4.2, 17.5 +/- 2.9, 10.1 +/- 3.2 and 13.1 +/- 3.9 mm(2). In normotensive control subjects, LMA size increased with body surface area, rate-pressure product, stroke work, and LV mass or wall thickness (r = 0.39, 0.39, 0.47 and 0.67 or 0.62, P < .05-0.01). In athletes with physiologic LVH, LMA area increased with CFR (0.65, P < .01). In the whole hypertensive population, LMA lumen increased with LV mass (r = 0.40, P < .01), and decreased with office systolic blood pressure (r = -0.48, P < .01). In the hypertensive LVH, baseline LMA area is not increased and is inversely related to office systolic blood pressure. In the physiologic LVH, increase in baseline LMA size seems to reflect effect of high-flow stimuli.

Cerebral blood flow in essential hypotension during emotional activation

Variations of blood flow velocity in the left and right middle cerebral arteries (MCA) were measured in 20 hypotensive women and 20 normotensive control subjects during emotional stimulation using functional transcranial Doppler sonography (fTDS). The emotional stimuli were composed of three series (neutral, pleasant, and unpleasant) of 20 pictures from the International Affective Picture System (IAPS). Both groups exhibited greater increases in right than left MCA blood flow during emotional stimulation. However hypotensive subjects showed smaller increases in blood flow than did normotensive controls. Furthermore hypotensives exhibited lower MCA blood flow velocity in both hemispheres at rest than did normotensives. Nevertheless the hypotensive group rated the emotional pictures as more arousing than did the control group. Results suggest a decreased blood flow, in addition to peripheral, in the central nervous system (CNS) of hypotensives, which was associated with normal emotional responses for both valence and hemispherical asymmetry, but also with a general increase of arousal levels. This dissociation might be related to an increase in anterior cerebral arteries (ACA) blood flow and/or to hypotension-mediated baroreceptors' up-regulation to the reticular system.

High-Resolution Mapping for Essential Hypertension Using Microsatellite Markers

During the past decade, considerable efforts and resources have been devoted to elucidating the multiple genetic and environmental determinants responsible for hypertension and its associated cardiovascular diseases. The success of positional cloning, fine mapping, and linkage analysis based on whole-genome screening, however, has been limited in identifying multiple genetic determinants affecting diseases, suggesting that new research strategies for genome-wide typing may be helpful. Disease association (case-control) studies using microsatellite markers, distributed every 150 kb across the human genome, may have some advantages over linkage, candidate, and single nucleotide polymorphism typing methods in terms of statistical power and linkage disequilibrium for finding genomic regions harboring candidate disease genes, although it is not proven. We have carried out genome-wide mapping using 18,977 microsatellite markers in a Japanese population composed of 385 hypertensive patients and 385 normotensive control subjects. Pooled sample analysis was conducted in a 3-stage genomic screen of 3 independent case-control populations, and 54 markers were extracted from the original 18,977 microsatellite markers. As a final step, each single positive marker was confirmed by individual typing, and only 19 markers passed this test. We identified 19 allelic loci that were significantly different between the cases of essential hypertension and the controls.

Cardiovascular Features of Heart Failure With Preserved Ejection Fraction Versus Nonfailing Hypertensive Left Ventricular Hypertrophy in the Urban Baltimore Community: The Role of Atrial Remodeling/Dysfunction

The purpose of this study was to identify cardiovascular features of patients with heart failure with preserved ejection fraction (HFpEF) that differ from those in individuals with hypertensive left ventricular hypertrophy (HLVH) of similar age, gender, and racial background but without failure. Heart failure with preserved ejection fraction often develops in HLVH patients and involves multiple abnormalities. Clarification of changes most specific to HFpEF may help elucidate underlying pathophysiology. A cross-sectional study comparing HFpEF patients (n = 37), HLVH subjects without HF (n = 40), and normotensive control subjects without LVH (n = 56). All subjects had an EF of >50%, sinus rhythm, and insignificant valvular or active ischemic disease, and groups were matched for age, gender, and ethnicity. Comprehensive echo-Doppler and pressure analysis was performed. The HFpEF patients were predominantly African-American women with hypertension, LVH, and obesity. They had vascular and systolic-ventricular stiffening and abnormal diastolic function compared with the control subjects. However, most of these parameters either individually or combined were similarly abnormal in the HLVH group and poorly distinguished between these groups. The HFpEF group had quantitatively greater concentric LVH and estimated mean pulmonary artery wedge pressure (20 mm Hg vs. 16 mm Hg) and shorter isovolumic relaxation time than the HLVH group. They also had left atrial dilation/dysfunction unlike in HLVH and greater total epicardial volume. The product of LV mass index and maximal left atrial (LA) volume best identified HFpEF patients (84% sensitivity, 82% specificity). In an urban, principally African American, cohort, HFpEF patients share many abnormalities of systolic, diastolic, and vascular function with nonfailing HLVH subjects but display accentuated LVH and LA dilation/failure. These latter factors may help clarify pathophysiology and define an important HFpEF population for clinical trials.

Raised C-Reactive Protein and Impaired Flow-Mediated Vasodilation Precede the Development of Preeclampsia

The aim of this study was to investigate whether impaired flow mediated vasodilation precedes the clinical manifestations of preeclampsia and whether is associated with inflammation. We conducted a nested case-control study in a prospective cohort of 506 normotensive women recruited before the 30th week of gestation (mean gestational age of 21.8 weeks). At enrollment, flow-mediated dilation was measured in the brachial artery using a 7.5-MHz transducer. C-reactive protein plasma concentrations and leukocyte count were also determined at study entry. Patients were followed until delivery, and medical records were reviewed for each patient to confirm the presence or absence of preeclampsia or gestational hypertension. Of the women studied, 14 developed preeclampsia, 18 developed gestational hypertension, and 474 remained normotensive. Two normotensive pregnant control subjects were randomly selected for each case, matched by maternal age, gestational age, and body mass index at enrollment. Women who subsequently developed preeclampsia had lower flow-mediated dilation (13.4% +/- 4.3% v 18.2% +/- 7.2, P = .026), higher C-reactive protein plasma concentrations (8.7 +/- 5.5 mg/dL v 5.3 +/- 4.3 mg/dL, P = .022) and leukocyte count (10.3 +/- 2.0 x 10(9)/L v 9.1 +/- 2.0 x 10(9)/L, P = .036) at study entry. Decreased flow-mediated vasodilation and higher levels of CRP are present in early stages of gestation in women who subsequently develop preeclampsia. These alterations occur before the onset of clinical symptoms of PE. Further studies are needed to confirm that flow-mediated dilation and C-reactive protein could be useful methods to screen women at risk of developing preeclampsia.

Comparison of Interleukin-6 and C-Reactive Protein for the Risk of Developing Hypertension in Women

Although markers of systemic inflammation may have a role in the development of hypertension, supportive clinical data remain limited. We, therefore, examined interleukin (IL)-6 and C-reactive protein (CRP) in a nested case-control study of 400 women developing hypertension and an equal number of age-matched normotensive control subjects during 10 years of follow-up as part of the Women's Health Study. All of the women initially had nonhypertensive blood pressure values and no history of diagnosis or treatment. Subjects provided self-reported risk factors, and IL-6 and CRP were measured from baseline bloods. Case subjects reported elevated systolic (>or=140 mm Hg) or diastolic (>or=90 mm Hg) blood pressure, newly diagnosed hypertension, or initiating antihypertensive treatment during follow-up. In crude-matched models, IL-6 and CRP quartiles were each strongly associated with hypertension risk (both Ps for trend <0.0001). In multivariate models, the linear trends became nonsignificant, and the relative risks (95% CIs) of hypertension for IL-6 reduced to 1.00 (ref), 1.29 (0.76 to 2.19), 2.14 (1.23 to 3.73), and 1.70 (0.92 to 3.13) and for CRP were 1.00 (ref), 2.09 (1.16 to 3.76), 2.51 (1.42 to 4.44), and 2.44 (1.29 to 4.64), primarily because of confounding by body mass index. Simultaneous adjustment for IL-6 and CRP modestly attenuated both sets of relative risks, although more for IL-6. Finally, there was no effect modification by baseline blood pressure or other risk factors (all Ps for interaction >0.05). Therefore, after multivariate adjustment and strong confounding by body mass index, IL-6 was weakly associated and CRP strongly associated with hypertension risk. In models simultaneously examining IL-6 and CRP, only CRP remained strongly associated with an increased risk of hypertension.

Contribution of Endothelial Nitric Oxide to Blood Pressure in Humans

Impaired endothelial-derived NO (eNO) is invoked in the development of many pathological conditions. Systemic inhibition of NO synthesis, used to assess the importance of NO to blood pressure (BP) regulation, increases BP by approximately 15 mm Hg. This approach underestimates the importance of eNO, because BP is restrained by baroreflex mechanisms and does not account for a role of neurally derived NO. To overcome these limitations, we induced complete autonomic blockade with trimethaphan in 17 normotensive healthy control subjects to eliminate baroreflex mechanisms and contribution of neurally derived NO. Under these conditions, the increase in BP reflects mostly blockade of tonic eNO. N(G)-Monomethyl-l-arginine (250 microg/kg per minute IV) increased mean BP by 6+/-3.7 mm Hg (from 77 to 82 mm Hg) in intact subjects and by 21+/-8.4 mm Hg (from 75 to 96 mm Hg) during autonomic blockade. We did not find a significant contribution of neurally derived NO to BP regulation after accounting for baroreflex buffering. To further validate this approach, we compared the effect of NOS inhibition during autonomic blockade in 10 normotensive individuals with that of 6 normotensive smokers known to have endothelial dysfunction but who were otherwise normal. As expected, normotensive smokers showed a significantly lower increase in systolic BP during selective eNO blockade (11+/-4.5 versus 30+/-2.3 mm Hg in normotensive individuals; P<0.005). Thus, we report a novel approach to preferentially evaluate the role of eNO on BP control in normal and disease states. Our results suggest that eNO is one of the most potent metabolic determinants of BP in humans, tonically restraining it by approximately 30 mm Hg.

Increased arterial vascular tone during the night in patients with essential hypertension

The time-dependent incidence of cardiovascular events points to an important role of chronobiology for arterial properties. To evaluate arterial properties in patients with essential hypertension, we assessed arterial vascular tone during sleep at night in patients with essential hypertension and normotensive control subjects. Vascular tone was continuously quantified by the reflective index obtained by non-invasive digital photoplethysmography and an algorithm for continuous, investigator-independent, automatic analysis of digital volume pulse. During the first half of the night, the reflective index was significantly higher in 31 patients with essential hypertension compared to 30 normotensive control subjects (30.0+/-0.2 vs 28.8+/-0.2; P=0.001). In patients with essential hypertension, the reflective index significantly increased from 30.0+/-0.2 in the first half (from 2301 to 0230) to 30.7+/-0.2 in the second half (from 0231 to 0600) of the night (n=31; P=0.027). In normotensive control subjects the reflective index also significantly increased from 28.8+/-0.2 in the first half of the night to 30.2+/-0.2 in the second half of the night (n=30; P=0.001). An increase of the reflective index tone indicated systemic vasoconstriction as confirmed by cold pressure tests and a significant correlation between arterial vascular tone and sympathetic nerve activity measured by microneurography from the peroneal nerve. Photoplethysmographic determination of arterial vascular tone demonstrated a significant increase of systemic arterial vascular tone in patients with essential hypertension during the first half of the night compared to normotensive control subjects.

Association analysis of endothelial nitric oxide synthase gene polymorphism with primary hypertension in a Singapore population

Vascular endothelial cells produce nitric oxide (NO), which contributes to the regulation of blood pressure and regional blood flow. Endothelial nitric oxide synthase (eNOS) gene polymorphisms are associated with coronary artery disease, but their linkage with primary hypertension is controversial. A total of 103 individuals with primary hypertension and 104 normotensive control subjects were studied in Singapore. The specific genotypes for G894T missense variant in exon 7, variable number tandem repeats (VNTR) in intron 4 (eNOS 4A/B/C) and T-786C in the promoter were isolated using allele-specific gene amplification and restriction fragment length polymorphism to examine the association of genotype and allelic frequency in both groups. Logistic regression analysis was also used to detect the association between genotypes and hypertension. Five genotypes of intron 4 VNTR (AA, AB, BB, AC and BC) were observed. Intron 4 B/B genotype was significantly associated with the hypertension group (P = 0.035), but disequilibrium of G894T and T-786C was absent between the two groups (P = 0.419 and P = 0.227), respectively. The overall distribution of allelic frequency differed significantly between the two groups, with four-repeat allele (4A) of intron 4 more frequent in the normotensive group than the hypertensive group (P = 0.019). Logistic regression analysis showed that intron 4 B/B genotype was significantly associated with systolic blood pressure of individuals with body mass index greater than 25 kg/m2 (P = 0.04). In conclusion, the eNOS 4 B/B genotype is a genetic susceptibility factor for primary hypertension in a Singapore population.