Abstract: Background/Objectives: Atrial fibrillation (AF) is the most common type of cardiac arrhythmia with patients dying frequently of stroke. In view of the unclear etiologies of AF and a potential role of oxidative stress, the present study examined cardiac reactive oxygen species production and NADPH oxidase (NOX) expression in AF patients. Methods and Results: Patients with AF were older than those without (58.8 ± 11.7 vs. 47.8 ± 19.2, p = 0.047). Whereas total [Formula: see text] production (determined by electron spin resonance) was similar in patients with and without AF, H(2)O(2) production was more than doubled in AF patients (149.8 ± 26.28 vs. 66.9 ± 7.14 pmol/mg/min, p = 0.0055), which correlated well with a doubling in NOX isoform 4 (NOX4) expression. AF patients with co-existing hypertension had three-fold higher H(2)O(2) production compared to those without (239.0 ± 125.1 vs. 83.6 ± 51.3 pmol/mg/min, p = 0.003). Treatment of HL-1 atrial cells with angiotensin II, a known modulator of atrial structural remodeling, resulted in upregulation of NOX4 and H(2)O(2) production, further implicating a potential role of NOX4 in atrial remodeling. Conclusion: Our data represent the first implication that NOX4-derived H(2)O(2) may play an important role in the etiologies of AF.
Abstract: Aortic valve stenosis (AS) is the most common form of valvular heart disease in the Western world, affecting ~40% of the population over the age of 80; to date the only established treatment is valve replacement. However, AS progression occurs over many years, and is associated from its earliest stages with increased risk of coronary events. Recent insight into the pathophysiology of AS has included central roles for angiotensin II, for diminished nitric oxide effect at the level of valve endothelium and matrix, and for inflammatory activation/redox stress culminating in activation of pro-calcific stimuli. Despite the presence of atheroma within the stenotic valve, hyperlipidemia per se does not play a critic role in the development of obstructive disease. We review emerging options for pharmacotherapy of AS, including in particular retardation of disease progression. The various clinical evaluations of lipid-reducing therapy have been uniformly unsuccessful in slowing AS progression. However, recent studies in animal models and retrospective evaluations in humans suggest that ACE inhibitors and/or angiotensin receptor blockers may be effective in this regard. Furthermore, agents normally utilized to treat osteoporosis also offer promise in retarding AS. Given the considerable morbidity, mortality and health care costs associated with AS, such therapeutic developments should be expedited.
Abstract: AimsAortic valve stenosis (AS) and its precursor, aortic valve sclerosis (ASc), occur frequently in Western populations. Investigations to retard the progression of AS using statins have been unsuccessful. Development of ASc in humans is associated with increased aortic valve backscatter (AVBS) and poor tissue nitric oxide (NO) responsiveness. In an animal model, ramipril retarded AS/ASc development. We have now set out to identify factors associated with the progression of ASc in humans.Methods and resultsAt baseline and after 4 years, 204 randomly selected subjects (age 63 ± 6 years at study entry) underwent echocardiography with the determination of AVBS values, measurements of platelet NO responsiveness, plasma asymmetric dimethylarginine concentrations, lipid profile, high-sensitivity-C-reactive protein, routine biochemistry, and 25-hydroxy-vitamin D levels. During the study period, 68% of subjects had detectable AVBS progression. On multivariate analysis, higher calcium concentrations (β = 0.22; P = 0.004), poor platelet NO responsiveness (β = 0.18; P = 0.018), and increased arterial stiffness (β = 0.15; P = 0.044) were independent predictors of disease progression. The use of angiotensin-converting enzyme-inhibitors/angiotensin II receptor blockers (ACE-I/ARB) predicted the lack of disease progression (assessed categorically) in the overall cohort and in those without ASc at baseline (n = 159) (β = 0.8; P = 0.025 and β = 1.3; P = 0.001, respectively). No conventional coronary risk factors were associated with disease progression.ConclusionThis study of early aortic valve disease (i) demonstrates that disease progression occurs in the majority of the normal ageing population over a 4-year period; (ii) provides evidence of the importance of the NO signalling cascade in disease development and progression; and (iii) provides additional data linking ACE-I/ARB use with the retardation of ASc.
Abstract: Aortic sclerosis (ASc) represents the earliest stage of development of aortic valve thickening, and may eventually progress to aortic valve stenosis (AS). ASc is associated with intra-valvular inflammatory activation, and potentially with attenuation of the anti-inflammatory effect of nitric oxide (NO). We have shown that ASc occurs less frequently in obese individuals, in whom systemic inflammatory activity is generally increased. We explored these relationships further by stratifying a population of 253 ageing individuals according to BMI. Increasing BMI was associated with increased hs-CRP concentrations (r=0.43; p<0.001). However, presence/absence of ASc did not significantly modify this relationship. Furthermore, increasing BMI was independent of tissue responsiveness to NO, as measured via inhibition of platelet aggregation by the NO donor sodium nitroprusside. Therefore the association of low BMI with increased risk of ASc appears to interact neither with systemic inflammatory activation in such individuals, nor with any "paradoxical" occurrence of NO resistance.
Abstract: Aortic valve stenosis (AVS) is associated with significant cardiovascular morbidity and mortality. To date, no therapeutic modality has been shown to be effective in retarding AVS progression. We evaluated the effect of angiotensin-converting enzyme inhibition with ramipril on disease progression in a recently developed rabbit model of AVS.
Abstract: The presence of aortic sclerosis has been associated with increased LV mass, particularly in hypertensive subjects. However, aortic sclerosis has also been associated with endothelial dysfunction, which may provide stimuli for development of left ventricular hypertrophy independent of afterload. Thus, we have sought to determine whether aortic sclerosis is a determinant of increased left ventricular mass in a non-hypertensive cohort of aging subjects.
Abstract: Two hundred patients at steady-state on long-term perhexiline were identified retrospectively. The ratio of maintenance dose to steady-state plasma concentration (dose:[Px]) was correlated with the following putative determinants via simple and multiple linear regression analyses: age, weight, left ventricular ejection fraction (LVEF), and creatinine clearance (CrCl, Cockroft-Gault formula). A Mann-Whitney U test was performed to determine if severe left ventricular systolic impairment affected maintenance dose.
Abstract: Nitric oxide (NO) is a modulator of left ventricular hypertrophy (LVH) and myocardial relaxation. The impact of NO availability on development of LVH has never been demonstrated in humans. We tested the hypotheses that elevation of asymmetric dimethylarginine (ADMA) concentrations (biochemical marker of decreased NO generation), and impairment of vascular responsiveness to NO donor GTN, would each predict the presence of LVH and associated LV diastolic dysfunction in a normal aging population.
Abstract: Polycystic ovary syndrome (PCOS) is associated with incremental risk of atherosclerosis and possibly of cardiovascular events. Insulin resistance (IR) occurs frequently in PCOS subjects, which might be one of the mechanisms involved in engendering such risk. We sought to evaluate whether the impact of other factors potentially associated both with PCOS and with IR might differentially modulate degree of IR in women with and without PCOS.
Abstract: Aortic valve stenosis (AS) is the commonest form of valvular heart disease in the Western world. Its prevalence increases exponentially with age and it is present in 2-7% of all patients over 65 years of age. In view of the considerable cardiovascular morbidity and mortality associated not only with AS, but even its earlier stage, aortic sclerosis, many investigations have been directed towards better understanding of its pathogenesis, with the ultimate objective of developing strategies to retard its progression. Although risk factors and downstream mediators appear similar for AS and atherosclerosis (older age, male sex, hypertension, smoking, hypercholesterolemia, and diabetes, as many as 50% of patients with AS do not have clinically significant atherosclerosis. On the basis both of recent experimental evidence and clinical trials, it appears that atherogenesis is not pivotal to the pathogenesis of AS. On the other hand, there is increasing evidence of active involvement of aortic valve fibroblasts with resultant increased production of reactive oxygen species, active pro-inflammatory and pro-fibrotic processes culminating in calcification. We also discuss the evidence of involvement of the nitric oxide system in the pathogenesis of AS. The renin-angiotensin system has also emerged as a major player in the pathogenesis of AS. Histologically, there is increased ACE expression and elevated angiotensin II levels in stenotic valves, while we have just demonstrated amelioration of AS with the use of ACE inhibitors in an animal model. We further discuss intervention studies aimed at retarding AS progression, including recent failures of statins to retard progression of AS in large randomized clinical studies. Finally, we discuss the special case of bicuspid aortic valve, including its genetics and unique associated features.
Abstract: Vitamin D deficiency is associated with significant increases in the incidence of cardiovascular risk factors and mortality. However, the mechanisms underlying this association remain unclear. The current study evaluated the possible relationships among vitamin D status, endothelial dysfunction, and inflammation.
Abstract: A number of previous investigators have demonstrated that arterial augmentation index (AIx), a measure of apparent arterial stiffness, reflects in part vascular endothelial function, and that AIx is modulated by nitric oxide (NO) responses. We evaluated AIx in a population of 253 ageing subjects (mean age 63.4+/-6 (standard deviation, SD) years) and its relationship to (i) plasma levels of asymmetric dimethylarginine (ADMA), a marker and mediator of vascular endothelial dysfunction and (ii) the ratio of ADMA to its non-metabolised enantiomer symmetric dimethylarginine (SDMA), an inverse index of ADMA metabolic clearance. Evaluation was performed by univariate followed by multivariate analyses. On multivariate analyses, both ADMA (beta=0.16, p=0.01) and ADMA:SDMA (beta=0.21, p<0.001) ratio were significant direct correlates of AIx. Other significant correlates of AIx on multivariate analysis were: use of angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers (ACEi/ARB) (beta=-0.24, p=0.004), smoking history (beta=0.15, p=0.007), male gender (beta=-0.38, p<0.001), creatinine clearance (CrCL) (beta=-0.25, p<0.001), and history of hypertension (beta=0.17, p=0.04). We conclude that (1) endothelial dysfunction engendered by impairment of NO synthesis may represent the basis for increased arterial stiffness in ageing individuals and (2) the fundamental biochemical anomaly may be impairment of ADMA clearance. These pathophysiological factors are likely to be relevant to optimize therapy to ameliorate disorders of arterial compliance in the ageing population.
Abstract: We sought to identify clinical, physiological, and biochemical correlates, including markers of endothelial dysfunction and of tissue nitric oxide (NO) responsiveness, of the presence of aortic sclerosis (ASc) in an aging population.
Abstract: Understanding of the pathophysiology of aortic valve stenosis (AVS) and finding potentially effective treatments are impeded by the lack of suitable AVS animal models. A previous study demonstrated the development of AVS in rabbits with vitamin D(2) and cholesterol supplementation without any hemodynamic changes in the cholesterol supplemented group alone. The current study aimed to determine whether AVS develops in an animal model with vitamin D(2) supplementation alone, and to explore pathophysiological mechanisms underlying this process. The effects of 8 weeks' treatment with vitamin D(2) alone (n=8) at 25,000 IU/4 days weekly on aortic valve structure and function were examined in male New Zealand white rabbits. Echocardiographic aortic valve backscatter (AV(BS)), transvalvular velocity, and transvalvular pressure gradient were utilized to quantitate changes in valve structure and function. Valvular histology/immunochemistry and function were examined after 8 weeks. Changes in valves were compared with those in endothelial function and in valvular measurement of thioredoxin-interacting protein (TXNIP), a marker/mediator of reactive oxygen species-induced oxidative stress. Vitamin D(2) treated rabbits developed AVS with increased AV(BS) (17.6+/-1.4 dB vs 6.7+/-0.8 dB, P<0.0001), increased transvalvular velocity and transvalvular pressure gradient (both P<0.01 via 2-way ANOVA) compared to the control group. There was associated valve calcification, lipid deposition and macrophage infiltration. Endothelial function was markedly impaired, and intravalvular TXNIP concentration increased. In this model, vitamin D(2) induces the development of AVS with histological features similar to those of early AVS in humans and associated endothelial dysfunction/redox stress. AVS development may result from the loss of nitric oxide suppression of TXNIP expression.
Abstract: We tested the hypothesis that the presence of aortic stenosis (AS) is associated with elevation of plasma levels of asymmetric dimethylarginine (ADMA), a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk.
Abstract: The development of therapeutic interventions to prevent progressive valve damage is more likely to limit the progression of structural damage to the aortic valve with normal function (aortic sclerosis [ASC]) than clinically apparent aortic stenosis. Currently, the ability to appreciate the progression of ASC is compromised by the subjective and qualitative evaluation of sclerosis severity.
