Xanthine oxidase does not contribute to impaired peripheral conduit artery endothelium-dependent dilatation with ageing

Vascular Aging: Assessment and Intervention

Vascular aging represents a collection of structural and functional changes in a blood vessel with advancing age, including increased stiffness, vascular wall remodeling, loss of angiogenic ability, and endothelium-dependent vasodilation dysfunction. These age-related alterations may occur earlier in those who are at risk for or have cardiovascular diseases, therefore, are defined as early or premature vascular aging. Vascular aging contributes independently to cardio-cerebral vascular diseases (CCVDs). Thus, early diagnosis and interventions targeting vascular aging are of paramount importance in the delay or prevention of CCVDs. Here, we review the direct assessment of vascular aging by examining parameters that reflect changes in structure, function, or their compliance with age including arterial wall thickness and lumen diameter, endothelium-dependent vasodilation, arterial stiffness as well as indirect assessment through pathological studies of biomarkers including endothelial progenitor cell, lymphocytic telomeres, advanced glycation end-products, and C-reactive protein. Further, we evaluate how different types of interventions including lifestyle mediation, such as caloric restriction and salt intake, and treatments for hypertension, diabetes, and hyperlipidemia affect age-related vascular changes. As a single parameter or intervention targets only a certain vascular physiological change, it is recommended to use multiple parameters to evaluate and design intervention approaches accordingly to prevent systemic vascular aging in clinical practices or population-based studies.

Chronic mitochondria antioxidant treatment in older adults alters the circulating milieu to improve endothelial cell function and mitochondrial oxidative stress

Excessive reactive oxygen species production by mitochondria (mtROS) is a key contributor to age-related vascular endothelial dysfunction. We recently showed in a crossover design, placebo-controlled clinical trial in older adults that 6 wk of treatment with the mitochondria-targeted antioxidant (MitoQ) improved endothelial function, as measured by nitric oxide (NO)-mediated endothelium-dependent dilation (EDD), by lowering mtROS and was associated with reduced circulating levels of oxidized low-density lipoprotein (oxLDL). Here, we conducted an ancillary analysis using plasma samples from our clinical trial to determine if MitoQ treatment-mediated changes in the "circulating milieu" (plasma) contribute to improvements in endothelial function and the mechanisms involved. With the use of an ex vivo model of endothelial function, acetylcholine-stimulated NO production was quantified in human aortic endothelial cells (HAECs) exposed to plasma collected after chronic MitoQ and placebo supplementation in 19 older adults (67 ± 1 yr; 11 females). We also assessed the influence of plasma on endothelial cell (EC) mtROS bioactivity and the role of lower circulating oxLDL in plasma-mediated changes. NO production was ∼25% higher (P = 0.0002) and mtROS bioactivity was ∼25% lower (P = 0.003) in HAECs exposed to plasma collected from subjects after MitoQ treatment versus placebo. Improvements in NO production ex vivo and NO-mediated EDD in vivo with MitoQ were correlated (r = 0.4683; P = 0.0431). Increasing oxLDL in plasma collected after MitoQ to placebo levels abolished MitoQ treatment effects on NO production and mtROS bioactivity, whereas inhibition of endogenous oxLDL binding to its lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) prevented these effects. These findings provide novel insight into the mechanisms by which MitoQ treatment improves endothelial function in older adults.NEW & NOTEWORTHY Chronic supplementation with a mitochondria-targeted antioxidant (MitoQ) improves vascular endothelial function in older adults, but the mechanisms of action are incompletely understood. Here, we show that MitoQ supplementation leads to changes in the circulating milieu (plasma), including reductions in oxidized low-density lipoprotein that enhance nitric oxide production and reduce mitochondrial oxidative stress in endothelial cells. These findings provide new information regarding the mechanisms by which MitoQ improves age-related endothelial dysfunction.

Daily blueberry consumption for 12 weeks improves endothelial function in postmenopausal women with above-normal blood pressure through reductions in oxidative stress: a randomized controlled trial

Estrogen-deficient postmenopausal women have oxidative stress-mediated suppression of endothelial function that is exacerbated by high blood pressure. Previous research suggests blueberries may improve endothelial function through reductions in oxidative stress, while also exerting other cardiovascular benefits. The objective of this study was to examine the efficacy of blueberries to improve endothelial function and blood pressure in postmenopausal women with above-normal blood pressure, and to identify potential mechanisms for improvements in endothelial function. A randomized, double-blind, placebo-controlled, parallel-arm clinical trial was performed, where postmenopausal women aged 45-65 years with elevated blood pressure or stage 1-hypertension (total n = 43, endothelial function n = 32) consumed 22 g day^-1 of freeze-dried highbush blueberry powder or placebo powder for 12 weeks. Endothelial function was assessed at baseline and 12 weeks through ultrasound measurement of brachial artery flow-mediated dilation (FMD) normalized to shear rate area under the curve (FMD/SR_AUC) before and after intravenous infusion of a supraphysiologic dose of ascorbic acid to evaluate whether FMD improvements were mediated by reduced oxidative stress. Hemodynamics, arterial stiffness, cardiometabolic blood biomarkers, and plasma (poly)phenol metabolites were assessed at baseline and 4, 8, and 12 weeks, and venous endothelial cell protein expression was assessed at baseline and 12 weeks. Absolute FMD/SR_AUC was 96% higher following blueberry consumption compared to baseline (p < 0.05) but unchanged in the placebo group (p > 0.05), and changes from baseline to 12 weeks were greater in the blueberry group than placebo (+1.09 × 10^-4 ± 4.12 × 10^-5vs. +3.82 × 10^-6 ± 1.59 × 10^-5, p < 0.03, respectively). The FMD/SR_AUC response to ascorbic acid infusion was lower (p < 0.05) at 12 weeks compared to baseline in the blueberry group with no change in the placebo group (p > 0.05). The sum of plasma (poly)phenol metabolites increased at 4, 8, and 12 weeks in the blueberry group compared to baseline, and were higher than the placebo group (all p < 0.05). Increases in several plasma flavonoid and microbial metabolites were also noted. No major differences were found for blood pressure, arterial stiffness, blood biomarkers, or endothelial cell protein expression following blueberry consumption. These findings suggest daily consumption of freeze-dried blueberry powder for 12 weeks improves endothelial function through reduced oxidative stress in postmenopausal women with above-normal blood pressure. The clinical trial registry number is NCT03370991 (https://clinicaltrials.gov).

Aging, aerobic exercise, and cardiovascular health: Barriers, alternative strategies and future directions

Age-associated cardiovascular (CV) dysfunction, namely arterial dysfunction, is a key antecedent to the development of CV disease (CVD). Arterial dysfunction with aging is characterized by impaired vascular endothelial function and stiffening of the large elastic arteries, each of which is an independent predictor of CVD. These processes are largely mediated by an excess production of reactive oxygen species (ROS) and an increase in chronic, low-grade inflammation that ultimately leads to a reduction in bioavailability of the vasodilatory molecule nitric oxide. Additionally, there are other fundamental aging mechanisms that may contribute to excessive ROS and inflammation termed the "hallmarks of aging"; these additional mechanisms of arterial dysfunction may represent therapeutic targets for improving CV health with aging. Aerobic exercise is the most well-known and effective intervention to prevent and treat the effects of aging on CV dysfunction. However, the majority of mid-life and older (ML/O) adults do not meet recommended exercise guidelines due to traditional barriers to aerobic exercise, such as reduced leisure time, motivation, or access to fitness facilities. Therefore, it is a biomedical research priority to develop and implement time- and resource-efficient alternative strategies to aerobic exercise to reduce the burden of CVD in ML/O adults. Alternative strategies that mimic or are inspired by aerobic exercise, that target pathways specific to the fundamental mechanisms of aging, represent a promising approach to accomplish this goal.

Population pharmacokinetic modelling of febuxostat in healthy subjects and people with gout

AIMS

To investigate and characterise the pharmacokinetics of febuxostat and the effect of the covariates of renal function and body size descriptors on the pharmacokinetics of the drug.

METHODS

Blood samples (n = 239) were collected using sparse and rich sampling strategies from healthy (n = 9) and gouty (n = 29) subjects. Febuxostat plasma concentrations were measured by a validated high-performance liquid chromatography method. Population pharmacokinetic analysis was performed using NONMEM. A common variability on bioavailability (FVAR) approach was used to test the effect of fed status on absorption parameters. Covariates were modelled using a power model.

RESULTS

The time course of the plasma concentrations of febuxostat is best described by a two-compartment model. In the final model, the population mean for apparent clearance (CL/F), apparent central volume of distribution (Vc/F), apparent peripheral volume of distribution (Vp/F), absorption rate constant (ka) and apparent intercompartmental clearance (Q/F) were 6.91 l h^-1 , 32.8 l, 19.4 l, 3.6 h^-1 and 1.25 l h^-1 , respectively. The population parmater variability (coefficient of variation) for CL/F, Vc/F and Vp/F were 13.6, 22 and 19.5%, respectively. Food reduced the relative biovailability and ka by 67% and 87%, respectively. Renal function, as assessed by creatinine clearance, was a significant covariate for CL/F while body mass index was a significant covariate for Vc/F.

CONCLUSIONS

Renal function and body mass index were significant covariates. Further work is warranted to investigate the clinical relevance of these results, notably as renal impairment and obesity are common occurrences in people with gout.

Is It Good to Have a Stiff Aorta with Aging? Causes and Consequences

Aortic stiffness increases with advancing age, more than doubling during the human life span, and is a robust predictor of cardiovascular disease (CVD) clinical events independent of traditional risk factors. The aorta increases in diameter and length to accommodate growing body size and cardiac output in youth, but in middle and older age the aorta continues to remodel to a larger diameter, thinning the pool of permanent elastin fibers, increasing intramural wall stress and resulting in the transfer of load bearing onto stiffer collagen fibers. Whereas aortic stiffening in early middle age may be a compensatory mechanism to normalize intramural wall stress and therefore theoretically "good" early in the life span, the negative clinical consequences of accelerated aortic stiffening beyond middle age far outweigh any earlier physiological benefit. Indeed, aortic stiffness and the loss of the "windkessel effect" with advancing age result in elevated pulsatile pressure and flow in downstream microvasculature that is associated with subclinical damage to high-flow, low-resistance organs such as brain, kidney, retina, and heart. The mechanisms of aortic stiffness include alterations in extracellular matrix proteins (collagen deposition, elastin fragmentation), increased arterial tone (oxidative stress and inflammation-related reduced vasodilators and augmented vasoconstrictors; enhanced sympathetic activity), arterial calcification, vascular smooth muscle cell stiffness, and extracellular matrix glycosaminoglycans. Given the rapidly aging population of the United States, aortic stiffening will likely contribute to substantial CVD burden over the next 2-3 decades unless new therapeutic targets and interventions are identified to prevent the potential avalanche of clinical sequelae related to age-related aortic stiffness.

Oxidative Stress and Inflammation Are Associated With Age-Related Endothelial Dysfunction in Men With Low Testosterone

CONTEXT

Vascular aging, including endothelial dysfunction secondary to oxidative stress and inflammation, increases the risk for age-associated cardiovascular disease (CVD). Low testosterone in middle-aged/older men is associated with increased CVD risk.

OBJECTIVE

We hypothesized that low testosterone contributes to age-associated endothelial dysfunction, related in part to greater oxidative stress and inflammation.

METHODS

This cross-sectional study included 58 healthy, nonsmoking men categorized as young (N = 20; age 29 ± 4 years; testosterone 500 ± 58 ng/dL), middle-aged/older with higher testosterone (N = 20; age 60 ± 6 years; testosterone 512 ± 115 ng/dL), and middle-aged/older lower testosterone (N = 18; age 59 ± 8 years; testosterone 269 ± 48 ng/dL). Brachial artery flow-mediated dilation (FMDBA) was measured during acute infusion of saline (control) and vitamin C (antioxidant). Markers of oxidative stress (total antioxidant status and oxidized low-density lipoprotein cholesterol), inflammation (interleukin [IL]-6 and C-reactive protein [CRP]), and androgen deficiency symptoms were also examined.

RESULTS

During saline, FMDBA was reduced in middle-aged/older compared with young, regardless of testosterone status (P < 0.001). FMDBA was reduced in middle-aged/older lower testosterone (3.7% ± 2.0%) compared with middle-aged/older higher testosterone (5.7% ± 2.2%; P = 0.021), independent of symptoms. Vitamin C increased FMDBA (to 5.3% ± 1.6%; P = 0.022) in middle-aged/older lower testosterone but had no effect in young (P = 0.992) or middle-aged/older higher testosterone (P = 0.250). FMDBA correlated with serum testosterone (r = 0.45; P < 0.001), IL-6 (r = -0.41; P = 0.002), and CRP (r = -0.28; P = 0.041).

CONCLUSION

Healthy middle-aged/older men with low testosterone appear to have greater age-associated endothelial dysfunction, related in part to greater oxidative stress and inflammation. These data suggest that low testosterone concentrations may contribute to accelerated vascular aging in men.

Aging-Induced Impairment of Vascular Function: Mitochondrial Redox Contributions and Physiological/Clinical Implications

Significance: The vasculature responds to the respiratory needs of tissue by modulating luminal diameter through smooth muscle constriction or relaxation. Coronary perfusion, diastolic function, and coronary flow reserve are drastically reduced with aging. This loss of blood flow contributes to and exacerbates pathological processes such as angina pectoris, atherosclerosis, and coronary artery and microvascular disease. Recent Advances: Increased attention has recently been given to defining mechanisms behind aging-mediated loss of vascular function and development of therapeutic strategies to restore youthful vascular responsiveness. The ultimate goal aims at providing new avenues for symptom management, reversal of tissue damage, and preventing or delaying of aging-induced vascular damage and dysfunction in the first place. Critical Issues: Our major objective is to describe how aging-associated mitochondrial dysfunction contributes to endothelial and smooth muscle dysfunction via dysregulated reactive oxygen species production, the clinical impact of this phenomenon, and to discuss emerging therapeutic strategies. Pathological changes in regulation of mitochondrial oxidative and nitrosative balance (Section 1) and mitochondrial dynamics of fission/fusion (Section 2) have widespread effects on the mechanisms underlying the ability of the vasculature to relax, leading to hyperconstriction with aging. We will focus on flow-mediated dilation, endothelial hyperpolarizing factors (Sections 3 and 4), and adrenergic receptors (Section 5), as outlined in Figure 1. The clinical implications of these changes on major adverse cardiac events and mortality are described (Section 6). Future Directions: We discuss antioxidative therapeutic strategies currently in development to restore mitochondrial redox homeostasis and subsequently vascular function and evaluate their potential clinical impact (Section 7). Antioxid. Redox Signal. 35, 974-1015.

Effects of intensive urate lowering therapy with febuxostat in comparison with allopurinol on pulse wave velocity in patients with gout and increased cardiovascular risk: the FORWARD study

AIMS

Hyperuricaemia and gout are strongly related with traditional cardiovascular risk factors and vascular damage. This study aimed to assess whether febuxostat and allopurinol could differently influence carotid-femoral pulse wave velocity (cfPWV) in patients with gout and elevated serum uric acid (SUA) levels.

METHODS AND RESULTS

A multi-centre, multinational, phase IV, randomized, parallel-group, active-controlled, open label trial with blind end-points evaluation. One hundred and ninetyseven adults with gout and SUA levels ≥8 mg/dL were randomised to febuxostat or allopurinol in a 1:1 ratio for 36 weeks. The primary outcome was the comparison of the effects of febuxostat and allopurinol on changes in cfPWV. The mean cfPWV values at randomisation and week 36 were respectively 8.69 m/s and 9.00 m/s for subjects randomised to febuxostat and 9.02 m/s and 9.05 m/s for subjects randomised to allopurinol. No statistically significant changes in cfPWV by treatment assignment were observed at any time point for any of the assessed parameters. More subjects who received febuxostat had serum urate concentrations ≤6 mg/dL following treatment (78.3% vs 61.1% at week 36, p = 0.0137). Treatment-emergent adverse events were reported by 51 (52.0%) patients randomised to febuxostat and 63 (62.5%) patients randomised to allopurinol. The majority of events were mild in both treatment groups and included gout flares and arthralgia.

CONCLUSIONS

In patients with gout and elevated SUA levels the arterial stiffness remained stable both with febuxostat and allopurinol. Febuxostat was more effective and faster than allopurinol in achieving the SUA target. Both treatments were safe and well tolerated.

Pro-Aging Effects of Xanthine Oxidoreductase Products

The senescence process is the result of a series of factors that start from the genetic constitution interacting with epigenetic modifications induced by endogenous and environmental causes and that lead to a progressive deterioration at the cellular and functional levels. One of the main causes of aging is oxidative stress deriving from the imbalance between the production of reactive oxygen (ROS) and nitrogen (RNS) species and their scavenging through antioxidants. Xanthine oxidoreductase (XOR) activities produce uric acid, as well as reactive oxygen and nitrogen species, which all may be relevant to such equilibrium. This review analyzes XOR activity through in vitro experiments, animal studies and clinical reports, which highlight the pro-aging effects of XOR products. However, XOR activity contributes to a regular level of ROS and RNS, which appears essential for the proper functioning of many physiological pathways. This discourages the use of therapies with XOR inhibitors, unless symptomatic hyperuricemia is present.

Vascular Endothelial Function in Midlife/Older Adults Classified According to 2017 American College of Cardiology/American Heart Association Blood Pressure Guidelines

Background

Impaired endothelial function is thought to contribute to the increased cardiovascular risk associated with above‐normal blood pressure (BP). However, the association between endothelial function and BP classified by 2017 American College of Cardiology/American Heart Association guidelines is unknown. Our objective was to determine if endothelial function decreases in midlife/older adults across the 2017 American College of Cardiology/American Heart Association guidelines BP classifications and identify associated mechanisms of action.

Methods and Results

A retrospective analysis of endothelial function (brachial artery flow‐mediated dilation) from 988 midlife/older adults (aged 50+ years) stratified by BP status (normal BP; elevated BP; stage 1 hypertension; stage 2 hypertension) was performed. Endothelium‐independent dilation (sublingual nitroglycerin), reactive oxygen species–mediated suppression of endothelial function (∆brachial artery flow‐mediated dilation with vitamin C infusion), and endothelial cell and plasma markers of oxidative stress and inflammation were assessed in subgroups. Compared with normal BP (n=411), brachial artery flow‐mediated dilation was 12% (P=0.04), 15% (P<0.01) and 20% (P<0.01) lower with elevated BP (n=173), stage 1 hypertension (n=248) and stage 2 hypertension (n=156), respectively, whereas endothelium‐independent dilation did not differ (P=0.14). Vitamin C infusion increased brachial artery flow‐mediated dilation in those with above‐normal BP (P≤0.02) but not normal BP (P=0.11). Endothelial cell p47^phox (P<0.01), a marker of superoxide/reactive oxygen species–generating nicotinamide adenine dinucleotide phosphate oxidase, and circulating interleukin‐6 concentrations (P=0.01) were higher in individuals with above‐normal BP.

Conclusions

Vascular endothelial function is progressively impaired with increasing BP in otherwise healthy adults classified by 2017 American College of Cardiology/American Heart Association guidelines. Impaired endothelial function with above‐normal BP is mediated by excessive reactive oxygen species signaling associated with increased endothelial expression of nicotinamide adenine dinucleotide phosphate oxidase and circulating interleukin‐6.

Trimethylamine-N-Oxide Promotes Age-Related Vascular Oxidative Stress and Endothelial Dysfunction in Mice and Healthy Humans

Age-related vascular endothelial dysfunction is a major antecedent to cardiovascular diseases. We investigated whether increased circulating levels of the gut microbiome-generated metabolite trimethylamine-N-oxide induces endothelial dysfunction with aging. In healthy humans, plasma trimethylamine-N-oxide was higher in middle-aged/older (64±7 years) versus young (22±2 years) adults (6.5±0.7 versus 1.6±0.2 µmol/L) and inversely related to brachial artery flow-mediated dilation (r2=0.29, P<0.00001). In young mice, 6 months of dietary supplementation with trimethylamine-N-oxide induced an aging-like impairment in carotid artery endothelium-dependent dilation to acetylcholine versus control feeding (peak dilation: 79±3% versus 95±3%, P<0.01). This impairment was accompanied by increased vascular nitrotyrosine, a marker of oxidative stress, and reversed by the superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl. Trimethylamine-N-oxide supplementation also reduced activation of endothelial nitric oxide synthase and impaired nitric oxide-mediated dilation, as assessed with the nitric oxide synthase inhibitor L-NAME (NG-nitro-L-arginine methyl ester). Acute incubation of carotid arteries with trimethylamine-N-oxide recapitulated these events. Next, treatment with 3,3-dimethyl-1-butanol for 8 to 10 weeks to suppress trimethylamine-N-oxide selectively improved endothelium-dependent dilation in old mice to young levels (peak: 90±2%) by normalizing vascular superoxide production, restoring nitric oxide-mediated dilation, and ameliorating superoxide-related suppression of endothelium-dependent dilation. Lastly, among healthy middle-aged/older adults, higher plasma trimethylamine-N-oxide was associated with greater nitrotyrosine abundance in biopsied endothelial cells, and infusion of the antioxidant ascorbic acid restored flow-mediated dilation to young levels, indicating tonic oxidative stress-related suppression of endothelial function with higher circulating trimethylamine-N-oxide. Using multiple experimental approaches in mice and humans, we demonstrate a clear role of trimethylamine-N-oxide in promoting age-related endothelial dysfunction via oxidative stress, which may have implications for prevention of cardiovascular diseases.

Mechanisms of Dysfunction in the Aging Vasculature and Role in Age-Related Disease

Advancing age promotes cardiovascular disease (CVD), the leading cause of death in the United States and many developed nations. Two major age-related arterial phenotypes, large elastic artery stiffening and endothelial dysfunction, are independent predictors of future CVD diagnosis and likely are responsible for the development of CVD in older adults. Not limited to traditional CVD, these age-related changes in the vasculature also contribute to other age-related diseases that influence mammalian health span and potential life span. This review explores mechanisms that influence age-related large elastic artery stiffening and endothelial dysfunction at the tissue level via inflammation and oxidative stress and at the cellular level via Klotho and energy-sensing pathways (AMPK [AMP-activated protein kinase], SIRT [sirtuins], and mTOR [mammalian target of rapamycin]). We also discuss how long-term calorie restriction-a health span- and life span-extending intervention-can prevent many of these age-related vascular phenotypes through the prevention of deleterious alterations in these mechanisms. Lastly, we discuss emerging novel mechanisms of vascular aging, including senescence and genomic instability within cells of the vasculature. As the population of older adults steadily expands, elucidating the cellular and molecular mechanisms of vascular dysfunction with age is critical to better direct appropriate and measured strategies that use pharmacological and lifestyle interventions to reduce risk of CVD within this population.

20-MHz Ultrasound for Measurements of Flow-Mediated Dilation and Shear Rate in the Radial Artery

A high-frequency scanning system consisting of a 20-MHz linear array transducer combined with a 20-MHz pulsed Doppler probe was introduced to evaluate the degree of radial artery flow-mediated dilation (FMD [%]) in two groups of patients after 5 min of controlled forearm ischemia followed by reactive hyperemia. In group I, comprising 27 healthy volunteers, FMD (mean ± standard deviation) was 15.26 ± 4.90% (95% confidence interval [CI]: 13.32%-17.20%); in group II, comprising 17 patients with chronic coronary artery disease, FMD was significantly less at 4.53 ± 4.11% (95% CI: 2.42%-6.64%). Specifically, the ratio FMD/SR (mean ± standard deviation), was equal to 5.36 × 10^-4 ± 4.64 × 10^-4 (95% CI: 3.54 × 10^-4 to 7.18 × 10^-4) in group I and 1.38 × 10^-4 ± 0.89 × 10^-4 (95% CI: 0.70 × 10^-4 to 2.06 × 10^-4) in group II. Statistically significant differences between the two groups were confirmed by a Wilcoxon-Mann-Whitney test for both FMD and FMD/SR (p <0.01). Areas under receiver operating characteristic curves for FMD and FMD/SR were greater than 0.9. The results confirm the usefulness of the proposed measurements of radial artery FMD and SR in differentiation of normal patients from those with chronic coronary artery disease.

The influence of febuxostat on coronary artery endothelial dysfunction in patients with coronary artery disease: A phase 4 randomized, placebo-controlled, double-blind, crossover trial

BACKGROUND

The xanthine oxidase (XO) system is a significant source of vascular oxidative stress, which is believed to impair endothelial function, an important contributor to atherosclerotic disease. We tested whether febuxostat, a potent XO inhibitor, improves coronary endothelial function (CEF) in patients with stable coronary artery disease (CAD) in a single-center, randomized, placebo-controlled, double-blind crossover trial.

METHODS

CEF was measured using noninvasive magnetic resonance imaging (MRI) assessment of changes in 30 patients with stable CAD and baseline impaired CEF. Patients received either febuxostat or placebo for 6 weeks and then were crossed over to the alternative for an additional 6 weeks. MRI-detected changes in coronary flow and in coronary cross-sectional area from rest to isometric handgrip exercise, a known endothelial-dependent stressor, were measured at the end of each 6 week period.

RESULTS

Mean serum urate levels were lower at the end of the 6-week febuxostat period (2.9±0.8mg/dL) than at the end of the 6-week placebo period (5.9±0.04, P<.001). However, there were no significant differences in any of the CEF parameters measured at the end of the febuxostat and placebo periods.

CONCLUSIONS

In summary, although XO inhibition with febuxostat was well tolerated and lowered serum urate, it did not improve the primary end point of the study, CEF measured using MRI after 6 weeks of treatment. In conclusion, these findings suggest that short-term inhibition of XO does not significantly improve impaired CEF in patients with stable CAD.

Uric acid and endothelial function in elderly community-dwelling subjects

The role of serum uric acid (SUA), an inflammatory agent and potential mediator of cardiovascular diseases, in endothelial function (EF) has been tested only in middle-aged subjects affected by specific diseases. Our aim was to assess the relationship between SUA and measures of EF in a cohort of elderly community-dwellers. This study involved 424 males and 426 females aged 70years from the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS), having complete data on SUA and EF assessed by flow-mediated vasodilation (FMD) and by intra-arterial infusion of acetylcholine (endothelium-dependent vasodilation, EDV) and sodium nitroprusside (endothelium-independent vasodilation, EIDV). Univariate and multivariate regression models obtained by backward selection from initial fully-adjusted models were built to assess the relationship between SUA and measures of EF in both genders. Cardiovascular risk factors, serum hormonal and metabolic mediators, and body composition were considered as potential confounders. In the univariate model, SUA was inversely associated in both genders with log(EDV) (β±SE males -0.39±0.17, p=0.03; females -0.57±0.19, p=0.003) and log(EIDV) (males -0.23±0.12, p=0.05; females -0.49±0.15, p=0.002), but not with log(FMD). After adjustment for BMI, only the association between SUA and log(EIDV) in females persisted, though attenuated (-0.32±0.16, p=0.049), and was no longer significant in the fully-adjusted multivariate model including waist/hip ratio. In conclusion, in older subjects, especially women, SUA is associated with EF not independently of a list of confounders including BMI and trunk fat mass, suggesting a role as surrogate metabolic marker rather than an active player in EF.

Habitual aerobic exercise does not protect against micro- or macrovascular endothelial dysfunction in healthy estrogen-deficient postmenopausal women

Aging causes micro- and macrovascular endothelial dysfunction, as assessed by endothelium-dependent dilation (EDD), which can be prevented and reversed by habitual aerobic exercise (AE) in men. However, in estrogen-deficient postmenopausal women, whole forearm microvascular EDD has not been studied, and a beneficial effect of AE on macrovascular EDD has not been consistently shown. We assessed forearm blood flow in response to brachial artery infusions of acetylcholine (FBFACh), a measure of whole forearm microvascular EDD, and brachial artery flow-mediated dilation (FMD), a measure of macrovascular EDD, in 12 premenopausal sedentary women (Pre-S; 24 ± 1 yr; V̇o2max = 37.5 ± 1.6 ml·kg-1·min-1), 25 estrogen-deficient postmenopausal sedentary women (Post-S; 62 ± 1 yr; V̇o2max = 24.7 ± 0.9 ml·kg-1·min-1), and 16 estrogen-deficient postmenopausal AE-trained women (Post-AE; 59 ± 1 yr; V̇o2max = 40.4 ± 1.4 ml·kg-1·min-1). FBFACh was lower in Post-S and Post-AE compared with Pre-S women (135 ± 9 and 116 ± 17 vs. 193 ± 21 AUC, respectively, both P < 0.008), whereas Post-S and Post-AE women were not different (P = 0.3). Brachial artery FMD was 34% (5.73 ± 0.67%) and 45% (4.79 ± 0.57%) lower in Post-S and Post-AE, respectively, vs. Pre-S women (8.69 ± 0.95%, both P ≤ 0.01), but not different between Post-S and Post-AE women (P = 0.3). Post-AE women had lower circulating C-reactive protein and oxidized low-density lipoprotein compared with Post-S women (0.5 ± 0.1 vs. 1.1 ± 0.2 mg/l and 40 ± 4 vs. 55 ± 3 U/l, respectively, both P = 0.01), but these markers were not correlated to FBFACh (P = 0.3) or brachial artery FMD (P = 0.8). These findings are consistent with the idea that habitual AE does not protect against age/menopause-related whole forearm micro- and macrovascular endothelial dysfunction in healthy nonobese estrogen-deficient postmenopausal women, despite being associated with lower systemic markers of inflammation and oxidative stress.

NEW & NOTEWORTHY

This is the first study to demonstrate that habitual aerobic exercise may not protect against age/menopause-related whole forearm microvascular endothelial dysfunction in healthy nonobese estrogen-deficient postmenopausal women, consistent with recent findings regarding macrovascular endothelial function. This is in contrast to what is observed in healthy middle-aged and older aerobic exercise-trained men.

The impact of age on vascular smooth muscle function in humans

AIM

Advanced age is associated with vascular endothelial dysfunction, characterized by reductions in the endothelium-dependent vasodilation of the conduit and resistance arteries, in part, from decreased nitric oxide bioavailability. Although vascular smooth muscle function (SMF), assessed by responsiveness to an exogenous nitric oxide donor, is typically reported to be intact, many of these studies are limited by a small sample size. Therefore, the purpose of this meta-analysis is to systematically review and determine whether vascular SMF is different between older versus young healthy individuals.

DESIGN

We conducted a systematic search of MEDLINE, Cochrane and Scopus, since their inceptions until January 2014, for articles evaluating SMF in the brachial artery and/or resistance arteries (BASMF and RASMF, respectively), as assessed by the endothelium-independent vasodilator response to exogenous nitric oxide donors in older (≥60 years) and young (<30 years) groups of healthy individuals. Meta-analyses were performed to compare the mean difference in BASMF and the standardized mean difference in RASMF between older and young groups. Subgroup analyses were performed to identify sources of heterogeneity.

RESULTS

Fifteen studies assessing BASMF and 20 studies assessing RASMF were included, comprising 550 older and 516 young healthy individuals. After data pooling, BASMF and RASMF were lower in older compared with the young groups (mean difference = -1.89%, P = 0.04; standardized mean difference = -0.46, P = 0.0008, respectively). Significant heterogeneity was observed in the BASMF (I2 = 74%, P < 0.00001) and the RASMF (I2 = 57%, P = 0.0008) meta-analyses. Subgroup analyses revealed that studies with (predominantly) men showed similar SMF responses between the older and the young groups.

CONCLUSION

On the basis of the current published studies, vascular SMF is reduced in conduit and resistance arteries of otherwise healthy older individuals, particularly in women.

Cellular and molecular biology of aging endothelial cells

Cardiovascular disease (CVD) is the leading cause of death in the United States and aging is a major risk factor for CVD development. One of the major age-related arterial phenotypes thought to be responsible for the development of CVD in older adults is endothelial dysfunction. Endothelial function is modulated by traditional CVD risk factors in young adults, but advancing age is independently associated with the development of vascular endothelial dysfunction. This endothelial dysfunction results from a reduction in nitric oxide bioavailability downstream of endothelial oxidative stress and inflammation that can be further modulated by traditional CVD risk factors in older adults. Greater endothelial oxidative stress with aging is a result of augmented production from the intracellular enzymes NADPH oxidase and uncoupled eNOS, as well as from mitochondrial respiration in the absence of appropriate increases in antioxidant defenses as regulated by relevant transcription factors, such as FOXO. Interestingly, it appears that NFkB, a critical inflammatory transcription factor, is sensitive to this age-related endothelial redox change and its activation induces transcription of pro-inflammatory cytokines that can further suppress endothelial function, thus creating a vicious feed-forward cycle. This review will discuss the two macro-mechanistic processes, oxidative stress and inflammation, that contribute to endothelial dysfunction with advancing age as well as the cellular and molecular events that lead to the vicious cycle of inflammation and oxidative stress in the aged endothelium. Other potential mediators of this pro-inflammatory endothelial phenotype are increases in immune or senescent cells in the vasculature. Of note, genomic instability, telomere dysfunction or DNA damage has been shown to trigger cell senescence via the p53/p21 pathway and result in increased inflammatory signaling in arteries from older adults. This review will discuss the current state of knowledge regarding the emerging concepts of senescence and genomic instability as mechanisms underlying oxidative stress and inflammation in the aged endothelium. Lastly, energy sensitive/stress resistance pathways (SIRT-1, AMPK, mTOR) are altered in endothelial cells and/or arteries with aging and these pathways may modulate endothelial function via key oxidative stress and inflammation-related transcription factors. This review will also discuss what is known about the role of "energy sensing" longevity pathways in modulating endothelial function with advancing age. With the growing population of older adults, elucidating the cellular and molecular mechanisms of endothelial dysfunction with age is critical to establishing appropriate and measured strategies to utilize pharmacological and lifestyle interventions aimed at alleviating CVD risk. This article is part of a Special Issue entitled "SI: CV Aging".

Vascular Ageing and Exercise: Focus on Cellular Reparative Processes

Ageing is associated with an increased risk of developing noncommunicable diseases (NCDs), such as diabetes and cardiovascular disease (CVD). The increased risk can be attributable to increased prolonged exposure to oxidative stress. Often, CVD is preceded by endothelial dysfunction, which carries with it a proatherothrombotic phenotype. Endothelial senescence and reduced production and release of nitric oxide (NO) are associated with “vascular ageing” and are often accompanied by a reduced ability for the body to repair vascular damage, termed “reendothelialization.” Exercise has been repeatedly shown to confer protection against CVD and diabetes risk and incidence. Regular exercise promotes endothelial function and can prevent endothelial senescence, often through a reduction in oxidative stress. Recently, endothelial precursors, endothelial progenitor cells (EPC), have been shown to repair damaged endothelium, and reduced circulating number and/or function of these cells is associated with ageing. Exercise can modulate both number and function of these cells to promote endothelial homeostasis. In this review we look at the effects of advancing age on the endothelium and these endothelial precursors and how exercise appears to offset this “vascular ageing” process.

Endothelial cell high-enrichment from endovascular biopsy sample by laser capture microdissection and fluorescence activated cell sorting

BACKGROUND AND PURPOSE

Endovascular sampling and characterization from patients can provide very useful information about the pathogenesis of different vascular diseases, but it has been limited by the lack of an effective method of endothelial cell (EC) enrichment. We optimized the EC yield and enrichment from conventional guide wires by laser capture microdissection (LCM) and fluorescence activated cell sorting (FACS) technique, and addressed the feasibility of using these enriched ECs for downstream gene expression detection.

METHODS

Iliac artery endovascular samples from 10 patients undergoing routine catheter angiography were collected using conventional 0.038 in. J-shape guide wires. Each of these samples was equally divided into two parts, which were respectively used for EC enrichment by immunocytochemistry-coupled LCM or multiple color FACS. After RNA extraction and reverse transcription, the amplified cDNA was used for quantitative polymerase chain reaction (qPCR).

RESULTS

Fixed ECs, with positive CD31 or vWF fluorescent signal and endothelial like nucleus, were successfully separated by LCM and live single ECs were sorted on FACS by a seven color staining panel. EC yields by LCM and FACS were 51 ± 22 and 149 ± 56 respectively (P < 0.001). The minimum number of fixed ECs from ICC-coupled LCM for acceptable qPCR results of endothelial marker genes was 30, while acceptable qPCR results as enriched by FACS were attainable from a single live EC.

CONCLUSION

Both LCM and FACS can be used to enrich ECs from conventional guide wires and the enriched ECs can be used for downstream gene expression detection. FACS generated a higher EC yield and the sorted live ECs may be used for single cell gene expression detection.

Endovascular biopsy: Strategy for analyzing gene expression profiles of individual endothelial cells obtained from human vessels✩

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The combination of guide wire sampling, FACS and high throughput microfluidic single-cell quantitative RT-PCR, is an effective strategy for analyzing molecular changes of ECs in vascular lesions.

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Although heterogeneous, the ECs in normal iliac artery fall into two classes.

Purpose

To develop a strategy of achieving targeted collection of endothelial cells (ECs) by endovascular methods and analyzing the gene expression profiles of collected single ECs.

Methods and results

134 ECs and 37 leukocytes were collected from four patients' intra-iliac artery endovascular guide wires by fluorescence activated cell sorting (FACS) and analyzed by single-cell quantitative RT-PCR for expression profile of 48 genes. Compared to CD45⁺ leukocytes, the ECs expressed higher levels (p < 0.05) of EC surface markers used on FACS and other EC related genes. The gene expression profile showed that these isolated ECs fell into two clusters, A and B, that differentially expressed 19 genes related to angiogenesis, inflammation and extracellular matrix remodeling, with cluster B ECs have demonstrating similarities to senescent or aging ECs.

Conclusion

Combination of endovascular device sampling, FACS and single-cell quantitative RT-PCR is a feasible method for analyzing EC gene expression profile in vascular lesions.

Vascular biology of ageing-Implications in hypertension

Ageing is associated with functional, structural and mechanical changes in arteries that closely resemble the vascular alterations in hypertension. Characteristic features of large and small arteries that occur with ageing and during the development of hypertension include endothelial dysfunction, vascular remodelling, inflammation, calcification and increased stiffness. Arterial changes in young hypertensive patients mimic those in old normotensive individuals. Hypertension accelerates and augments age-related vascular remodelling and dysfunction, and ageing may impact on the severity of vascular damage in hypertension, indicating close interactions between biological ageing and blood pressure elevation. Molecular and cellular mechanisms underlying vascular alterations in ageing and hypertension are common and include aberrant signal transduction, oxidative stress and activation of pro-inflammatory and pro-fibrotic transcription factors. Strategies to suppress age-associated vascular changes could ameliorate vascular damage associated with hypertension. An overview on the vascular biology of ageing and hypertension is presented and novel molecular mechanisms contributing to these processes are discussed. The complex interaction between biological ageing and blood pressure elevation on the vasculature is highlighted. This article is part of a Special Issue entitled: CV Ageing.

Sattar MAA. The possible antianginal effect of allopurinol in vasopressin-induced ischemic model in rats

The anti-anginal effects of allopurinol were assessed in experimental model rats of angina and their effects were evaluated with amlodipine. In the vasopressin-induced angina model, oral administration of allopurinol in dose of 10 mg/kg revealed remarkably analogous effects in comparison with amlodipine such as dose-dependent suppression of vasopressin-triggered time, duration and severity of ST depression. In addition, allopurinol produced dose dependent suppression of plasma Malondialdehyde (MDA) level, systolic blood pressure, cardiac contractility and cardiac oxygen consumption; while in contrast, amlodipine minimally suppressed the elevation of plasma MDA level. Endothelial NO synthase (eNOS) expression, serum nitrate were strikingly increased, however lipid profile was significantly reduced. Seemingly, allopurinol was found to be more potent than amlodipine – a calcium channel antagonist. To conclude, it was explicitly observed and verified that on the ischemic electrocardiography (ECG) changes in angina pectoris model in rats, allopurinol exerts a significant protective effects, reminiscent of enhancement of vascular oxidative stress, function of endothelial cells, improved coronary blood flow in addition to the potential enhancement in myocardial stress. Moreover, our findings were in conformity with several human studies.

NADPH oxidase-derived reactive oxygen species contribute to impaired cutaneous microvascular function in chronic kidney disease

Oxidative stress promotes vascular dysfunction in chronic kidney disease (CKD). We utilized the cutaneous circulation to test the hypothesis that reactive oxygen species derived from NADPH oxidase and xanthine oxidase impair nitric oxide (NO)-dependent cutaneous vasodilation in CKD. Twenty subjects, 10 stage 3 and 4 patients with CKD (61 ± 4 yr; 5 men/5 women; eGFR: 39 ± 4 ml·min(-1)·1.73 m(-2)) and 10 healthy controls (55 ± 2 yr; 4 men/6 women; eGFR: >60 ml·min(-1)·1.73 m(-2)) were instrumented with 4 intradermal microdialysis fibers for the delivery of 1) Ringer solution (Control), 2) 10 μM tempol (scavenge superoxide), 3) 100 μM apocynin (NAD(P)H oxidase inhibition), and 4) 10 μM allopurinol (xanthine oxidase inhibition). Skin blood flow was measured via laser-Doppler flowmetry during standardized local heating (42°C). N(g)-nitro-l-arginine methyl ester (L-NAME; 10 mM) was infused to quantify the NO-dependent portion of the response. Cutaneous vascular conductance (CVC) was calculated as a percentage of the maximum CVC achieved during sodium nitroprusside infusion at 43°C. Cutaneous vasodilation was attenuated in patients with CKD (77 ± 3 vs. 88 ± 3%, P = 0.01), but augmented with tempol and apocynin (tempol: 88 ± 2 (P = 0.03), apocynin: 91 ± 2% (P = 0.001). The NO-dependent portion of the response was reduced in patients with CKD (41 ± 4 vs. 58 ± 2%, P = 0.04), but improved with tempol and apocynin (tempol: 58 ± 3 (P = 0.03), apocynin: 58 ± 4% (P = 0.03). Inhibition of xanthine oxidase did not alter cutaneous vasodilation in either group (P > 0.05). These data suggest that NAD(P)H oxidase is a source of reactive oxygen species and contributes to microvascular dysfunction in patients with CKD.

Oxidative stress and anti-oxidant enzyme activities in the trophocytes and fat cells of queen honeybees (Apis mellifera)

Trophocytes and fat cells of queen honeybees have been used for delayed cellular senescence studies, but their oxidative stress and anti-oxidant enzyme activities with advancing age are unknown. In this study, we assayed reactive oxygen species (ROS) and anti-oxidant enzymes in the trophocytes and fat cells of young and old queens. Young queens had lower ROS levels, lower superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, and higher thioredoxin reductase (TR) activity compared to old queens. These results show that oxidative stress and anti-oxidant enzyme activities in trophocytes and fat cells increase with advancing age in queens and suggest that an increase in oxidative stress and a consequent increase in stress defense mechanisms are associated with the longevity of queen honeybees.

Vascular endothelial function and oxidative stress are related to dietary niacin intake among healthy middle-aged and older adults

We tested the hypothesis that vascular endothelial function and oxidative stress are related to dietary niacin intake among healthy middle-aged and older adults. In 127 men and women aged 48-77 yr, brachial artery flow-mediated dilation (FMD) was positively related to dietary niacin intake [%change (Δ): r = 0.20, P < 0.05; mmΔ: r = 0.25, P < 0.01]. In subjects with above-average dietary niacin intake (≥ 22 mg/day, NHANES III), FMD was 25% greater than in subjects with below-average intake (P < 0.05). Stepwise linear regression revealed that dietary niacin intake (above vs. below average) was an independent predictor of FMD (%Δ: β = 1.8; mmΔ: β = 0.05, both P < 0.05). Plasma oxidized low-density lipoprotein, a marker of systemic oxidative stress, was inversely related to niacin intake (r = -0.23, P < 0.05) and was lower in subjects with above- vs. below-average niacin intake (48 ± 2 vs. 57 ± 2 mg/dl, P < 0.01). Intravenous infusion of the antioxidant vitamin C improved brachial FMD in subjects with below-average niacin intake (P < 0.001, n = 33), but not above-average (P > 0.05, n = 20). In endothelial cells sampled from the brachial artery of a subgroup, dietary niacin intake was inversely related to nitrotyrosine, a marker of peroxynitrite-mediated oxidative damage (r = -0.30, P < 0.05, n = 55), and expression of the prooxidant enzyme, NADPH oxidase (r = -0.44, P < 0.01, n = 37), and these markers were lower in subjects with above- vs. below-average niacin intake [nitrotyrosine: 0.39 ± 0.05 vs. 0.56 ± 0.07; NADPH oxidase: 0.38 ± 0.05 vs. 0.53 ± 0.05 (ratio to human umbilical vein endothelial cell control), both P < 0.05]. Our findings support the hypothesis that higher dietary niacin intake is associated with greater vascular endothelial function related to lower systemic and vascular oxidative stress among healthy middle-aged and older adults.

Oxidative stress and vascular inflammation in aging

Vascular aging, a determinant factor for cardiovascular disease and health status in the elderly, is now viewed as a modifiable risk factor. Impaired endothelial vasodilation is a early hallmark of arterial aging that precedes the clinical manifestations of vascular dysfunction, the first step to cardiovascular disease and influencing vascular outcomes in the elderly. Accordingly, the preservation of endothelial function is thought to be an essential determinant of healthy aging. With special attention on the effects of aging on the endothelial function, this review is focused on the two main mechanisms of aging-related endothelial dysfunction: oxidative stress and inflammation. Aging vasculature generates an excess of the reactive oxygen species (ROS), superoxide and hydrogen peroxide, that compromise the vasodilatory activity of nitric oxide (NO) and facilitate the formation of the deleterious radical, peroxynitrite. Main sources of ROS are mitochondrial respiratory chain and NADPH oxidases, although NOS uncoupling could also account for ROS generation. In addition, reduced antioxidant response mediated by erythroid-2-related factor-2 (Nrf2) and downregulation of mitochondrial manganese superoxide dismutase (SOD2) contributes to the establishment of chronic oxidative stress in aged vessels. This is accompanied by a chronic low-grade inflammatory phenotype that participates in defective endothelial vasodilation. The redox-sensitive transcription factor, nuclear factor-κB (NF-κB), is upregulated in vascular cells from old subjects and drives a proinflammatory shift that feedbacks oxidative stress. This chronic NF-κB activation is contributed by increased angiotensin-II signaling and downregulated sirtuins and precludes adequate cellular response to acute ROS generation. Interventions targeted to recover endogenous antioxidant capacity and cellular stress response rather than exogenous antioxidants could reverse oxidative stress-inflammation vicious cycle in vascular aging. Lifestyle attitudes such as caloric restriction and exercise training appear as effective ways to overcome defective antioxidant response and inflammation, favoring successful vascular aging and decreasing the risk for cardiovascular disease.

Activation of the unfolded protein response in vascular endothelial cells of nondiabetic obese adults

CONTEXT

Activation of the unfolded protein response (UPR) is emerging as an important molecular signature of cardiometabolic diseases associated with obesity. However, despite the well-established role of the vascular endothelium in obesity-related cardiometabolic dysfunction, it is unclear whether the UPR is activated in endothelial cells of obese adults.

OBJECTIVE

The objective of the study was to determine whether markers of UPR activation are increased in endothelial cells (ECs) of nondiabetic obese adults with impaired endothelial function.

DESIGN, SETTING, AND PARTICIPANTS

Endothelial cells were obtained from antecubital veins of the nondiabetic obese adults [body mass index (BMI) ≥ 30 kg/m(2), n = 12] with impaired endothelial function and from their nonobese peers (BMI < 30 kg/m(2), n = 14).

MAIN OUTCOME VARIABLES

UPR activation via expression (quantitative immunofluorescence) of the proximal UPR sensors, inositol-requiring endoplasmic reticulum (ER)-to-nucleus signaling protein 1 (IRE1), RNA-dependent protein kinase-like ER eukaryotic initiation factor-2α kinase (PERK), and activating transcription factor 6 (ATF6), were the main outcome variables.

RESULTS

IRE1 expression was greater in obese vs nonobese individuals (0.84 ± 0.09 vs 0.47 ± 0.02 IRE1 intensity/human umbilical vein EC (HUVEC) intensity (n = 10/8, P < .01). Obese individuals also had greater EC activation of UPR stress sensors PERK and ATF6, indicated by increased expression of phosphorylated PERK [p-PERK; 0.49 ± 0.05 vs 0.36 ± 0.03, p-PERK (threonine 981) intensity/HUVEC intensity, n = 10 men, 13 women, P < .05] and nuclear localization of ATF6 (0.38 ± 0.05 vs 0.23 ± 0.02, nuclear ATF6 intensity/HUVEC intensity, n = 5 men, 9 women, P < .01), respectively. Stepwise linear regression analysis revealed that indices of body fat (BMI and waist circumference) were the strongest independent predictors of all 3 UPR mediators, explaining between 18% and 59% of the variance in endothelial cell expression of IRE1, p-PERK, and nuclear ATF6 localization.

CONCLUSION

These results provide novel evidence for UPR activation in the endothelial cells of nondiabetic obese adults with vascular endothelial dysfunction.

Clinical factors associated with carotid plaque and intima-medial thickness in HIV-infected patients

PURPOSE

HIV-infected patients are at increased risk for cardiovascular disease, which may be mediated in part by inflammation. This study aimed to evaluate the risk factors of carotid plaque, and clinical factors associated with carotid atherosclerosis measured by carotid intima-medial thickness (cIMT) in HIV patients.

MATERIALS AND METHODS

Clinical and cardiometabolic factors as well as cIMT were prospectively measured in 145 HIV-infected participants who had received combined antiretroviral therapy for ≥6 months. The mean value of the bilateral average cIMT level was used as Mean-IMT in the analysis, and the greatest value among the measured cIMT levels was used as Max-IMT.

RESULTS

Among 145 patients, 34 (23.4%) had carotid plaque. Multivariate logistic regression analysis revealed three independent risk factors of carotid plaque: old age [odds ratio (OR) 6.16, 95% confidence interval (CI) 1.09-34.88; p=0.040], hypertension (OR 12.62, 95% CI 1.72-92.49; p=0.013) and higher low-density lipoprotein cholesterol (LDL-C) (OR 1.08, 95% CI 1.01-1.16; p=0.039). Levels of estimated glomerular filtration rate were inversely associated with Mean-IMT (r=-0.379, p<0.001) and Max-IMT (r=-0.389, p<0.001). Stepwise multivariate regression analyses revealed that age, total cholesterol and fasting glucose were positively correlated with cIMT, independent of other risk factors.

CONCLUSION

The presence of hypertension, old age and a higher level of LDL-C were independent risk factors of carotid plaque among HIV-infected subjects.

Contribution of nitric oxide in the contraction-induced rapid vasodilation in young and older adults

We tested the hypothesis that reduced nitric oxide (NO) bioavailability contributes to the attenuated peak and total vasodilation following single-muscle contractions in older adults. Young (n = 10; 24 ± 2 yr) and older (n = 10; 67 ± 2 yr) adults performed single forearm contractions at 10, 20, and 40% of maximum during saline infusion (control) and NO synthase (NOS) inhibition via N(G)-monomethyl-l-arginine. Brachial artery diameters and velocities were measured using Doppler ultrasound and forearm vascular conductance (FVC; in ml·min(-1)·100 mmHg(-1)) was calculated from blood flow (ml/min) and blood pressure (mmHg). Peak and total vasodilator responses [change (Δ) in FVC from baseline] were attenuated in older adults at all intensities (P < 0.05). NOS inhibition reduced the peak ΔFVC at 10% (88 ± 12 vs. 52 ± 9 ml·min(-1)·100 mmHg(-1)), 20% (125 ± 13 vs. 83 ± 13 ml·min(-1)·100 mmHg(-1)), and 40% (207 ± 26 vs. 133 ± 20 ml·min(-1)·100 mmHg(-1)) in young subjects, (P < 0.05 for all) and in older adults at 10% (59 ± 5 vs. 47 ± 7 ml·min(-1)·100 mmHg(-1), P < 0.05) and 20% (88 ± 9 vs. 68 ± 9 ml·min(-1)·100 mmHg(-1), P < 0.05), but not 40% (128 ± 12 vs. 105 ± 11 ml·min(-1)·100 mmHg(-1), P = 0.11). The relative (%) reduction in peak ΔFVC due to NOS inhibition was greater in young vs. older adults at 20% (-36 ± 5 vs. -23 ± 5%, P < 0.05) and 40% (-35 ± 6 vs. -16 ± 7%, P < 0.05). The reduction in the total vasodilator response (area under the curve) with NOS inhibition was also greater in young vs. older adults at all intensities. Our data suggest that contraction-induced rapid vasodilation is mediated in part by NO, and that the contribution of NO is greater in young adults.

Mechanisms involved in the aging-induced vascular dysfunction

Vascular aging is a key process determining health status of aged population. Aging is an independent cardiovascular risk factor associated to an impairment of endothelial function, which is a very early and important event leading to cardiovascular disease. Vascular aging, formerly being considered an immutable and inexorable risk factor, is now viewed as a target process for intervention in order to achieve a healthier old age. A further knowledge of the mechanisms underlying the age-related vascular dysfunction is required to design an adequate therapeutic strategy to prevent or restore this impairment of vascular functionality. Among the proposed mechanisms that contribute to age-dependent endothelial dysfunction, this review is focused on the following aspects occurring into the vascular wall: (1) the reduction of nitric oxide (NO) bioavailability, caused by diminished NO synthesis and/or by augmented NO scavenging due to oxidative stress, leading to peroxynitrite formation (ONOO(-)); (2) the possible sources involved in the enhancement of oxidative stress; (3) the increased activity of vasoconstrictor factors; and (4) the development of a low-grade pro-inflammatory environment. Synergisms and interactions between all these pathways are also analyzed. Finally, a brief summary of some cellular mechanisms related to endothelial cell senescence (including telomere and telomerase, stress-induced senescence, as well as sirtuins) are implemented, as they are likely involved in the age-dependent endothelial dysfunction, as well as in the lower vascular repairing capacity observed in the elderly. Prevention or reversion of those mechanisms leading to endothelial dysfunction through life style modifications or pharmacological interventions could markedly improve cardiovascular health in older people.

Translational evidence that impaired autophagy contributes to arterial ageing

Ageing causes arterial endothelial dysfunction that increases the risk of cardiovascular diseases (CVD), but the underlying mechanisms are incompletely understood. The aim of the present study was to determine the role of autophagy, the cellular process of recycling damaged biomolecules, in endothelial dysfunction with ageing. In older humans, expression of autophagy markers in arterial endothelial cells was impaired by ∼50% (P <0.05) and was associated with an ∼30% (P <0.05) reduction in arterial endothelium-dependent dilatation (EDD). Similarly, in C57BL/6 control mice ageing was associated with an ∼40% decrease (P <0.05) in arterial markers of autophagy and an ∼25% reduction (P <0.05) in EDD. In both humans and mice, impaired EDD was mediated by reduced nitric oxide (NO) bioavailability and was associated with increased oxidative stress and inflammation (P <0.05). In old mice, treatment with the autophagy-enhancing agent trehalose restored expression of autophagy markers, rescued NO-mediated EDD by reducing oxidative stress, and normalized inflammatory cytokine expression. In cultured endothelial cells, inhibition of autophagy increased oxidative stress and reduced NO production, whereas trehalose enhanced NO production via an autophagy-dependent mechanism. These results provide the first evidence that autophagy is impaired with ageing in vascular tissues. Our findings also suggest that autophagy preserves arterial endothelial function by reducing oxidative stress and inflammation and increasing NO bioavailability. Autophagy-enhancing strategies may therefore have therapeutic efficacy for ameliorating age-associated arterial dysfunction and preventing CVD.

Vascular endothelial function is not related to serum uric acid in healthy adults

Background

Some experimental evidence suggests that uric acid impairs endothelial function. It is controversial if high uric acid levels and impaired endothelial function are related in healthy adults. In addition, the effect of uric acid on endothelial cells (ECs) of humans is unexplored.

Methods

Data of 107 healthy adult volunteers were analyzed. The association between serum uric acid and endothelial-dependant dilation (EDD) and endothelial-independent dilation (EID) was evaluated by linear regression models. We also examined the relations between uric acid and systemic and cellular markers of inflammation and oxidative stress in all or subsets of participants.

Results

Uric acid levels and EDD were not related in unadjusted or adjusted models. There was a significant negative correlation between uric acid and EID in the pooled sample (r = −0.34, P = 0.005). This correlation remained significant after adjusting for demographics (P = 0.04) and was attenuated after adjusting for other cardiac risk factors (P = 0.12). Higher serum uric acid levels were found to correlate significantly with C-reactive protein (CRP) (r = 0.31, P = 0.002). Serum uric acid levels were not associated with brachial artery EC nuclear factor-κB (NF-κB) p65 or NADPH oxidase p47^phox expression or with nitrotyrosine staining, but were inversely associated with EC manganese superoxide dismutase (MnSOD) expression (r = −0.5, P = 0.01, n = 25).

Conclusion

Elevated serum uric acid is not associated with endothelial dysfunction among healthy adults, but is inversely related to EID and EC MnSOD, and positively related to systemic inflammation. These findings may have implications for cardiovascular risk in healthy adults.

Habitually exercising older men do not demonstrate age-associated vascular endothelial oxidative stress

We tested the hypothesis that older men who perform habitual aerobic exercise do not demonstrate age-associated vascular endothelial oxidative stress compared with their sedentary peers. Older exercising men (n=13, 62±2 years) had higher (P<0.05) physical activity (79±7 vs. 30±6 MET hours per week) and maximal exercise oxygen consumption (42±1 vs. 29±1 mL kg(-1) per minute) vs. sedentary men (n=28, 63±1 years). Brachial artery flow-mediated dilation (FMD), a measure of vascular endothelial function, was greater (P<0.05) in the exercising vs. sedentary older men (6.3±0.5 vs. 4.9±0.4%Δ) and not different than young controls (n=20, 25±1 years, 7.1±0.5%Δ). In vascular endothelial cells sampled from the brachial artery, nitrotyrosine, a marker of oxidative stress, was 51% lower in the exercising vs. sedentary older men (0.38±0.06 vs. 0.77±0.10 AU). This was associated with lower endothelial expression of the oxidant enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (p47(phox) subunit, 0.33±0.05 vs. 0.61±0.09 AU) and the redox-sensitive transcription factor nuclear factor kappa B (NFκB) (p65 subunit, 0.36±0.05 vs. 0.72±0.09 AU). Expression of the antioxidant enzyme manganese superoxide dismutase (SOD) (0.57±0.13 vs. 0.30±0.04 AU) and activity of endothelium-bound extracellular SOD were greater (6.4±0.5 vs. 5.0±0.6 U mL(-1) per minute) in the exercising men (both P<0.05), but differences no longer were significant after correcting for adiposity and circulating metabolic factors. Overall, values for the young controls differed with those for the sedentary, but not the exercising older men. Older men who exercise regularly do not demonstrate vascular endothelial oxidative stress, and this may be a key molecular mechanism underlying their reduced risk of cardiovascular diseases.

SIRT-1 and vascular endothelial dysfunction with ageing in mice and humans

We tested the hypothesis that reductions in the cellular deacetylase, sirtuin-1 (SIRT-1), contribute to vascular endothelial dysfunction with ageing via modulation of endothelial nitric oxide synthase (eNOS) acetylation/activation-associated nitric oxide (NO) production. In older (30 months, n = 14) vs. young (5-7 months, n = 16) B6D2F1 mice, aortic protein expression of SIRT-1 and eNOS phosphorylated at serine 1177 were lower (both P < 0.05), and acetylated eNOS was 6-fold higher (P < 0.05), whereas total eNOS did not differ (P = 0.65). Acetylcholine (ACh)-induced peak endothelium-dependent dilatation (EDD) was lower in isolated femoral arteries with ageing (P < 0.001). Incubation with sirtinol, a SIRT-1 inhibitor, reduced EDD in both young and older mice, abolishing age-related differences, whereas co-administration with l-NAME, an eNOS inhibitor, further reduced EDD similarly in both groups. Endothelium-independent dilatation to sodium nitroprusside (EID), was not altered by age or sirtinol treatment. In older (64 ± 1 years, n = 22) vs. young (25 ± 1 years, n = 16) healthy humans, ACh-induced forearm EDD was impaired (P = 0.01) and SIRT-1 protein expression was 37% lower in endothelial cells obtained from the brachial artery (P < 0.05), whereas EID did not differ. In the overall group, EDD was positively related to endothelial cell SIRT-1 protein expression (r = 0.44, P < 0.01). Reductions in SIRT-1 may play an important role in vascular endothelial dysfunction with ageing. SIRT-1 may be a key therapeutic target to treat arterial ageing.

Inhibition of xanthine oxidase reduces oxidative stress and improves skeletal muscle function in response to electrically stimulated isometric contractions in aged mice

Oxidative stress is a putative factor responsible for reducing function and increasing apoptotic signaling in skeletal muscle with aging. This study examined the contribution and functional significance of the xanthine oxidase enzyme as a potential source of oxidant production in aged skeletal muscle during repetitive in situ electrically stimulated isometric contractions. Xanthine oxidase activity was inhibited in young adult and aged mice via a subcutaneously placed time-release (2.5mg/day) allopurinol pellet, 7 days before the start of in situ electrically stimulated isometric contractions. Gastrocnemius muscles were electrically activated with 20 maximal contractions for 3 consecutive days. Xanthine oxidase activity was 65% greater in the gastrocnemius muscle of aged mice compared to young mice. Xanthine oxidase activity also increased after in situ electrically stimulated isometric contractions in muscles from both young (33%) and aged (28%) mice, relative to contralateral noncontracted muscles. Allopurinol attenuated the exercise-induced increase in oxidative stress, but it did not affect the elevated basal level of oxidative stress that was associated with aging. In addition, inhibition of xanthine oxidase activity decreased caspase-3 activity, but it had no effect on other markers of mitochondrial-associated apoptosis. Our results show that compared to control conditions, suppression of xanthine oxidase activity by allopurinol reduced xanthine oxidase activity, H₂O₂ levels, lipid peroxidation, and caspase-3 activity; prevented the in situ electrically stimulated isometric contraction-induced loss of glutathione; prevented the increase in catalase and copper-zinc superoxide dismutase activities; and increased maximal isometric force in the plantar flexor muscles of aged mice after repetitive electrically evoked contractions.

Increased proinflammatory and oxidant gene expression in circulating mononuclear cells in older adults: amelioration by habitual exercise

We tested the hypothesis that peripheral blood mononuclear cells (PBMC) of older adults demonstrate a proinflammatory/-oxidative gene expression profile that can be improved by regular aerobic exercise. PBMC were isolated from young (n = 25, 18-33 yr) and middle-aged/older (n = 40, 50-76 yr) healthy adults. The older adults had greater mRNA expression (real-time RT-PCR) of the proinflammatory/-oxidant transcription factor nuclear factor-κB (1.58-fold, P < 0.05) and receptor for advanced glycation end products (1.12-fold, P < 0.05), the proinflammatory cytokines tumor necrosis factor-α (1.90-fold, P < 0.05) and monocyte chemoattractant protein-1 (1.47-fold, P < 0.05), and the oxidant-producing enzymes nicotinamide adenine dinucleotide phosphate-oxidase (0.91-fold, P < 0.05) and inducible nitric oxide synthase (2.60-fold, P < 0.05). In 11 subjects (58-70 yr), maximal oxygen consumption (+11%) and exercise time (+19%) were increased (both P < 0.001), and expression of the above proinflammatory/-oxidative genes was or tended to be decreased in PBMC after vs. before 2 mo of aerobic exercise (brisk walking ∼6 days/wk, 50 min/day, 70% of maximal heart rate). Expression of interleukin-6 was not different with age or exercise intervention. Age group- and exercise intervention-related differences in gene expression were independent of other factors. PBMC of healthy older adults demonstrate increased expression of several genes associated with inflammation and oxidative stress, which is largely ameliorated by habitual aerobic exercise. This proinflammatory/-oxidative gene signature may represent a therapeutic target for lifestyle and pharmacological prevention and treatment strategies.

Vascular oxidative stress in aging: a homeostatic failure due to dysregulation of NRF2-mediated antioxidant response

There is strong evidence showing that aging is associated with vascular oxidative stress, which has been causally linked to the development of cardiovascular diseases. NF-E2-related factor-2 (Nrf2) is a transcription factor, which is activated by reactive oxygen species in the vasculature of young animals leading to the upregulation of various antioxidant genes. The present study was designed to elucidate age-related changes in the homeostatic role of Nrf2-driven free radical detoxification mechanisms in the vasculature. We found that in the aorta of Fischer 344 × Brown Norway rats, aging results in a progressive increase in O(2)(·-) production, and downregulates protein and mRNA expression of Nrf2, which is associated with a decreased nuclear Nrf2 activity and a decrease in the Nrf2 target genes NAD(P)H:quinone oxidoreductase 1, γ-glutamylcysteine synthetase, and heme oxygenase-1. There was an inverse relationship between vascular expression of Nrf2 target genes and age-related increases in the expression of the NF-κB target genes ICAM-1 and IL-6, which was significant by regression analysis. In cultured aorta segments of young (3 mo old) rats treatment with H(2)O(2) and high glucose significantly increases nuclear translocation of Nrf2 and upregulates the expression of Nrf2 target genes. In contrast, in cultured aorta segments of aged (24 mo old) rats, the induction of Nrf2-dependent responses by H(2)O(2) and high glucose are blunted. High glucose-induced vascular oxidative stress was more severe in aortas of aged rats, as shown by the significantly increased H(2)O(2) production in these vessels, compared with responses obtained in aortas from young rats. Moreover, we found that aging progressively increases vascular sensitivity to the proapoptotic effects of H(2)O(2) and high glucose treatments. Taken together, aging is associated with Nrf2 dysfunction in the vasculature, which likely exacerbates age-related cellular oxidative stress and increases sensitivity of aged vessels to oxidative stress-induced cellular damage.

Aging and vascular endothelial function in humans

Advancing age is the major risk factor for the development of CVD (cardiovascular diseases). This is attributable, in part, to the development of vascular endothelial dysfunction, as indicated by reduced peripheral artery EDD (endothelium-dependent dilation) in response to chemical [typically ACh (acetylcholine)] or mechanical (intravascular shear) stimuli. Reduced bioavailability of the endothelium-synthesized dilating molecule NO (nitric oxide) as a result of oxidative stress is the key mechanism mediating reduced EDD with aging. Vascular oxidative stress increases with age as a consequence of greater production of reactive oxygen species (e.g. superoxide) without a compensatory increase in antioxidant defences. Sources of increased superoxide production include up-regulation of the oxidant enzyme NADPH oxidase, uncoupling of the normally NO-producing enzyme, eNOS (endothelial NO synthase) (due to reduced availability of the cofactor tetrahydrobiopterin) and increased mitochondrial synthesis during oxidative phosphorylation. Increased bioactivity of the potent endothelial-derived constricting factor ET-1 (endothelin-1), reduced endothelial production of/responsiveness to dilatory prostaglandins, the development of vascular inflammation, formation of AGEs (advanced glycation end-products), an increased rate of endothelial apoptosis and reduced expression of oestrogen receptor α (in postmenopausal females) also probably contribute to impaired EDD with aging. Several lifestyle and biological factors modulate vascular endothelial function with aging, including regular aerobic exercise, dietary factors (e.g. processed compared with non-processed foods), body weight/fatness, vitamin D status, menopause/oestrogen deficiency and a number of conventional and non-conventional risk factors for CVD. Given the number of older adults now and in the future, more information is needed on effective strategies for the prevention and treatment of vascular endothelial aging.

Determinants of vascular function in patients with chronic gout

Epidemiologic studies have proposed a relationship between hyperuricemia and cardiovascular (CV) risk. However, it is unclear whether uric acid (UA) is an independent risk factor for CV disease (CVD) after controlling for other predisposing conditions. Gout patients might have persistent systemic inflammation, which, in addition to hyperuricemia, may potentiate CVD. This study examined vascular function and markers of CV damage in gout patients when compared with healthy controls. Brachial artery flow-mediated dilatation, arterial compliance, and microvascular function were measured. Circulating apoptotic endothelial cells and endothelial progenitor cells were quantified by FACS and circulating biomarkers of CVD by enzyme-linked immunosorbent assay. Gout patients displayed significant increases in body mass index, C-reactive protein, UA, and triglycerides and decreases in high-density lipoprotein. There were no significant differences in other CV traditional risk factors, adhesion molecules, or chemokines. Gout patients did not differ from controls in vascular function. In univariate and multivariate analysis, UA was not associated with the quantified CV risk parameters. Despite an increase in several CV risk factors, inflammation, and UA, gout patients display normal endothelial function and no increases in biomarkers of CVD. These results do not support the notion that gout is an independent risk factor for premature CVD.

Sex-specific effects of habitual aerobic exercise on brachial artery flow-mediated dilation in middle-aged and older adults

Brachial artery FMD (flow-mediated dilation) is impaired with aging and is associated with an increased risk of CVD (cardiovascular disease). In the present study, we determined whether regular aerobic exercise improves brachial artery FMD in MA/O (middle-aged/older) men and post-menopausal women. In sedentary MA/O adults (age, 55-79 years) without CVD, 8 weeks of brisk walking (6 days/week for approx. 50 min/day; randomized controlled design) increased treadmill time approx. 20% in both MA/O men (n=11) and post-menopausal women (n=15) (P<0.01), without altering body composition or circulating CVD risk factors. Brachial artery FMD increased >50% in the MA/O men (from 4.6±0.6 to 7.1±0.6%; P<0.01), but did not change in the post-menopausal women (5.1±0.8 compared with 5.4±0.7%; P=0.50). No changes occurred in the non-exercising controls. In a separate cross-sectional study (n=167), brachial artery FMD was approx. 50% greater in endurance-exercise-trained (6.4±0.4%; n=45) compared with sedentary (4.3±0.3%; n=60) MA/O men (P<0.001), whereas there were no differences between endurance-trained (5.3±0.7%, n=20) and sedentary (5.6±0.5%, n=42) post-menopausal women (P=0.70). Brachial artery lumen diameter, peak hyperaemic shear rate and endothelium-independent dilation did not differ with exercise intervention or in the endurance exercise compared with sedentary groups. In conclusion, regular aerobic exercise is consistently associated with enhanced brachial artery FMD in MA/O men, but not in post-menopausal women. Some post-menopausal women without CVD may be less responsive to habitual aerobic exercise than MA/O men.

Assessment of flow-mediated dilation in humans: a methodological and physiological guideline

Endothelial dysfunction is now considered an important early event in the development of atherosclerosis, which precedes gross morphological signs and clinical symptoms. The assessment of flow-mediated dilation (FMD) was introduced almost 20 years ago as a noninvasive approach to examine vasodilator function in vivo. FMD is widely believed to reflect endothelium-dependent and largely nitric oxide-mediated arterial function and has been used as a surrogate marker of vascular health. This noninvasive technique has been used to compare groups of subjects and to evaluate the impact of interventions within individuals. Despite its widespread adoption, there is considerable variability between studies with respect to the protocols applied, methods of analysis, and interpretation of results. Moreover, differences in methodological approaches have important impacts on the response magnitude, can result in spurious data interpretation, and limit the comparability of outcomes between studies. This review results from a collegial discussion between physiologists with the purpose of developing considered guidelines. The contributors represent several distinct research groups that have independently worked to advance the evidence base for improvement of the technical approaches to FMD measurement and analysis. The outcome is a series of recommendations on the basis of review and critical appraisal of recent physiological studies, pertaining to the most appropriate methods to assess FMD in humans.