Hypertension
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Comparative Study
Chronic antioxidant supplementation impairs coronary endothelial function and myocardial perfusion in normal pigs.
Experimental studies have shown the beneficial effects of antioxidant supplementation on endothelial function in the presence of increased endogenous oxidative stress, whereas limited data are available under normal conditions. The present study tested the hypothesis that in normal pigs long-term antioxidants would have deleterious effects on the cardiovascular system. Normal domestic pigs (V, n=6) were studied 12 weeks after dietary supplementation with vitamin E (100 IU/kg per day) and vitamin C (1 g/day) and compared with normal controls (C, n=7). ⋯ Moreover, in V, coronary nitrotyrosine and superoxide content was significantly higher than in C. The groups had similar total monomer expression of endothelial nitric oxide synthase, whereas the dimerized form, reflecting coupled enzyme, was lower in V. These findings suggest that long-term experimental antioxidant vitamin supplementation in normal pigs impairs myocardial perfusion and coronary endothelial function via an increased level of oxidative stress in the arterial wall, which may be partly related to the uncoupling of endothelial nitric oxide synthase and/or the direct prooxidant effect of vitamin radicals.
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We wanted to investigate the relationship of N-terminal pro brain natriuretic peptide (Nt-proBNP) to metabolic and hemodynamic cardiovascular (CV) risk factors in the general population. From a population-based sample of 2656 people 41, 51, 61, or 71 years of age, we selected 2070 patients without previous stroke or myocardial infarction who did not receive any CV, antidiabetic, or lipid-lowering treatment in 1993 to 1994. Traditional CV risk factors, 24-hour blood pressures, left ventricular (LV) mass, and ejection fraction by echocardiography, pulse wave velocity, urine albumin/creatinine ratio (UACR), and serum Nt-proBNP were measured in 1993 to 1994. ⋯ Higher log(Nt-proBNP) was in multiple regression analysis related to female gender (beta=-0.37), older age (beta=0.32), higher clinic pulse pressure (beta=0.20), lower serum total cholesterol (beta=-0.15), lower LVEF (beta=-0.08, all P<0.001), lower log(serum insulin) (beta=-0.07), lower log(plasma glucose) (beta=-0.06, both P<0.01, lower log(serum triglyceride) (beta=-0.06), lower body mass index (beta=-0.05); lower heart rate (beta=-0.05), higher logUACR (beta=0.04, all P<0.05) and higher log(LV mass index) (beta=0.04, P=0.07), adjusted R2=0.35, P<0.001). The metabolic syndrome was associated with lower Nt-proBNP (35 pg/mL versus 48 pg/mL; P<0.001) and shifted the positive relationship between pulse pressure and Nt-proBNP to the right (ie, higher blood pressure for a given level of Nt-proBNP). The metabolic syndrome was associated with lower Nt-proBNP levels and shifted the positive relationship between Nt-proBNP and pulse pressure to the right, creating a possible link between the metabolic syndrome and hypertension.
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Age is the dominant risk factor for cardiovascular diseases. However, until recently, convincing mechanistic or molecular explanations for the increased cardiovascular risks conferred by aging have been elusive. Aging is associated with alterations in a number of structural and functional properties of large arteries, including diameter, wall thickness, wall stiffness, and endothelial function. ⋯ These vascular alterations are thus putative candidates that could be targeted by interventions aimed at attenuating arterial aging, similar to the lifestyle and pharmacological interventions that have already been proven effective. Therefore, the notion that aging is a chronological process and that its risky components cannot be modulated is no longer tenable. It is our hope that a greater appreciation of the links between arterial aging and cardiovascular diseases will stimulate further investigation into strategies aimed at preventing or retarding arterial aging.
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Few studies have examined to what extent genetic variants of the beta2-adrenoceptor (ADRB2) are involved in the development of hypertension with age, although beta2-adrenergic receptor responsiveness declines in older subjects. To investigate this, 10 common single-nucleotide polymorphisms (SNPs) in the promoter and coding regions of the ADRB2 gene were genotyped in an unrelated population consisting of 2 ethnic groups: European American (EA; n=610) and African American (AA; n=420). ADRB2 haplotypes were estimated by expectation maximization (EM) algorithm-based methods. ⋯ This age-specific effect was further supported by the observations that young subjects carrying > or =1 copy of haplotype 1 had significantly lower diastolic blood pressure and nearly 2-fold higher ADRB2 binding density than the noncarriers (P<0.05). With aging, their ADRB2 numbers decreased to the level of the noncarriers, along with increased body mass index (7%; P<0.05) and decreased heart rate (7%; P<0.001). Our study suggests that age is an important modifier for the effects of ADRB2 polymorphisms on ADRB2 function and the development of hypertension.