Aging-associated endothelial dysfunction in humans is reversed by L-arginine

The l-Arginine pathway may act as a mediator in the association between impaired one-carbon metabolism and hypertension

Elevated fasting plasma total homocysteine (tHcy) and the methylenetetrahydrofolate reductase C677T polymorphism (rs1801133) have been associated with hypertension. Whether the l-Arginine pathway is involved, is unclear. We aimed to investigate whether the association between tHcy, the rs1801133 polymorphism and hypertension involves the l-Arginine pathway. THcy, plasma folate and cobalamin, erythrocyte glutathionine reductase activation coefficient, rs1801133 genotype, plasma l-Arginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) were determined in a cross-sectional study of 788 adults (aged 18 to 75), randomly selected from 2 town population registers. Participants participated in a medical checkup and provided a fasting blood sample. Associations between tHcy, rs1801133 genotype and l-Arginine pathway metabolites were assessed by multiple linear regression analysis and whether the tHcy and rs1801133 genotype are associated with hypertension via the l-Arginine pathway was investigated using mediation analysis. tHcy was positively associated with ADMA (B = 0.003; SE = 0.001; P < 0.001) and SDMA (B = 0.007; SE = 0.002; P < 0.001) and negatively associated with the l-Arginine/ADMA (B = -1.140; SE = 0.451; P < 0.05) and ADMA/SDMA (B = -0.006; SE = 0.003; P < 0.05) ratios. The MTHFR 677 CT vs CC genotype was negatively associated with ADMA (B = -0.013; SE = 0.007; P < 0.05) and with SDMA (B = -0.029; SE = 0.013; P < 0.05) in participants under 50 years. Each standard deviation increase (37.6) in the l-Arginine/ADMA ratio was associated with reduced hypertension risk (OR [95%CI], 0.6 [0.5, 0.8]). Mediation analysis showed that tHcy and ADMA were mediators in the association between the rs1801133 TT vs CC genotypes and hypertension. Our results support the l-Arginine pathway as a mediator in the association of impaired One-Carbon metabolism and hypertension.

Asymmetric and symmetric dimethylarginine as markers of endothelial dysfunction in cerebrovascular disease: A prospective study

BACKGROUND AND AIM

Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) have been proposed as mediators of endothelial dysfunction. In this study, we aimed to investigate the diagnostic and prognostic role of ADMA and SDMA in acute cerebrovascular disease.

METHODS AND RESULTS

A prospective case-control study was performed, enrolling 48 patients affected by ischemic stroke with no cardioembolic origin, 20 patients affected by TIA, 40 subjects at high cardiovascular risk and 68 healthy subjects. ADMA levels were significantly lower in high-risk subjects (18.85 [11.78-22.83] μmol/L) than in patients with brain ischemic event, both transient (25.70 [13.15-40.20] μmol/L; p = 0.032) and permanent (24.50 [18.0-41.33] μmol/L; p = 0.001). SDMA levels were different not only between high-risk subjects and ischemic patients, but also between TIA and stroke patients, reaching higher levels in TIA group and lower levels in stroke group (1.15 [0.90-2.0] vs 0.68 [0.30-1.07] μmol/L; p < 0.001). SDMA was also correlated with short-term prognosis, with lower levels in case of adverse clinical course, evaluated by type of discharge (p = 0.009) and need of prolonged rehabilitation (p = 0.042).

CONCLUSIONS

The present study highlights the relationship between l-arginine, ADMA, SDMA and acute cerebrovascular events. Therefore, our results suggested a potential role of SDMA as a specific marker of transient ischemic damage and as a short-term positive prognostic marker.

Increased Plasma L-Arginine Levels and L-Arginine/ADMA Ratios after Twelve Weeks of Omega-3 Fatty Acid Supplementation in Amateur Male Endurance Runners

It is not fully understood how supplementation with omega-3 fatty acids affects the metabolism of amino acids required for the bioavailability/synthesis of NO, i.e., L-arginine (L-arg), asymmetric dimethylarginine (ADMA), their metabolites, and the L-arg/ADMA ratio and their impact on running economy (RE) in runners. Thus, 26 male amateur endurance runners completed a twelve-week study in which they were divided into two supplemented groups: the OMEGA group (n = 14; 2234 mg and 916 mg of eicosapentaenoic and docosahexaenoic acid daily) or the MCT group (n = 12; 4000 mg of medium-chain triglycerides daily). At the same time, all participants followed an endurance training program. Before and after the 12-week intervention, blood was collected from participants at two time points (at rest and immediately post-exercise) to determine EPA and DHA in red blood cells (RBCs) and plasma levels of L-arg, ADMA, and their metabolites. RBC EPA and DHA significantly increased in the OMEGA group (p < 0.001), which was related to the resting increase in L-arg (p = 0.001) and in the L-arg/ADMA ratio (p = 0.005) with no changes in the MCT group. No differences were found in post-exercise amino acid levels. A total of 12 weeks of omega-3 fatty acid supplementation at a dose of 2234 mg of EPA and 916 mg of DHA daily increased levels of L-arg and the L-arg/ADMA ratio, which indirectly indicates increased bioavailability/NO synthesis. However, these changes were not associated with improved RE in male amateur endurance runners.

Bioenergetic Impairment in the Neuro-Glia-Vascular Unit: An Emerging Physiopathology during Aging

An emerging concept termed the "neuro-glia-vascular unit" (NGVU) has been established in recent years to understand the complicated mechanism of multicellular interactions among vascular cells, glial cells, and neurons. It has been proverbially reported that the NGVU is significantly associated with neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). Physiological aging is an inevitable progression associated with oxidative damage, bioenergetic alterations, mitochondrial dysfunction, and neuroinflammation, which is partially similar to the pathology of AD. Thus, senescence is regarded as the background for the development of neurodegenerative diseases. With the exacerbation of global aging, senescence is an increasingly serious problem in the medical field. In this review, the coupling of each component, including neurons, glial cells, and vascular cells, in the NGVU is described in detail. Then, various mechanisms of age-dependent impairment in each part of the NGVU are discussed. Moreover, the potential bioenergetic alterations between different cell types in the NGVU are highlighted, which seems to be an emerging physiopathology associated with the aged brain. Bioenergetic intervention in the NGVU may be a new direction for studies on delaying or diminishing aging in the future.

Role of the eNOS Uncoupling and the Nitric Oxide Metabolic Pathway in the Pathogenesis of Autoimmune Rheumatic Diseases

Atherosclerosis and its clinical complications constitute the major healthcare problems of the world population. Due to the central role of endothelium throughout the atherosclerotic disease process, endothelial dysfunction is regarded as a common mechanism for various cardiovascular (CV) disorders. It is well established that patients with rheumatic autoimmune diseases are characterized by significantly increased prevalence of cardiovascular morbidity and mortality compared with the general population. The current European guidelines on cardiovascular disease (CVD) prevention in clinical practice recommend to use a 1,5-factor multiplier for CV risk in rheumatoid arthritis as well as in other autoimmune inflammatory diseases. However, mechanisms of accelerated atherosclerosis in these diseases, especially in the absence of traditional risk factors, still remain unclear. Oxidative stress plays the major role in the endothelial dysfunction and recently is strongly attributed to endothelial NO synthase dysfunction (eNOS uncoupling). Converted to a superoxide-producing enzyme, uncoupled eNOS not only leads to reduction of the nitric oxide (NO) generation but also potentiates the preexisting oxidative stress, which contributes significantly to atherogenesis. However, to date, there are no systemic analyses on the role of eNOS uncoupling in the excess CV mortality linked with autoimmune rheumatic diseases. The current review paper addresses this issue.

Where Metabolism Meets Senescence: Focus on Endothelial Cells

Despite the decline in their proliferative potential, senescent cells display a high metabolic activity. Senescent cells have been shown to acquire a more glycolytic state even in presence of high oxygen levels, in a way similar to cancer cells. The diversion of pyruvate, the final product of glycolysis, away from oxidative phosphorylation results in an altered bioenergetic state and may occur as a response to the enhanced oxidative stress caused by the accumulation of dysfunctional mitochondria. This metabolic shift leads to increased AMP/ATP and ADP/ATP ratios, to the subsequent AMPK activation, and ultimately to p53-mediated growth arrest. Mounting evidences suggest that metabolic reprogramming is critical to direct considerable amounts of energy toward specific activities related to the senescent state, including the senescence-associated secretory phenotype (SASP) and the modulation of immune responses within senescent cell tissue microenvironment. Interestingly, despite the relative abundance of oxygen in the vascular compartment, healthy endothelial cells (ECs) produce most of their ATP content from the anaerobic conversion of glucose to lactate. Their high glycolytic rate further increases during senescence. Alterations in EC metabolism have been identified in age-related diseases (ARDs) associated with a dysfunctional vasculature, including atherosclerosis, type 2 diabetes and cardiovascular diseases. In particular, higher production of reactive oxygen species deriving from a variety of enzymatic sources, including uncoupled endothelial nitric oxide synthase and the electron transport chain, causes DNA damage and activates the NAD+-consuming enzymes polyADP-ribose polymerase 1 (PARP1). These non-physiological mechanisms drive the impairment of the glycolytic flux and the diversion of glycolytic intermediates into many pathological pathways. Of note, accumulation of senescent ECs has been reported in the context of ARDs. Through their pro-oxidant, pro-inflammatory, vasoconstrictor, and prothrombotic activities, they negatively impact on vascular physiology, promoting both the onset and development of ARDs. Here, we review the current knowledge on the cellular senescence-related metabolic changes and their contribution to the mechanisms underlying the pathogenesis of ARDs, with a particular focus on ECs. Moreover, current and potential interventions aimed at modulating EC metabolism, in order to prevent or delay ARD onset, will be discussed.

Age- and sex-dependent alteration of functions and epigenetic modifications of vessel and endothelium related biomarkers

Aging is a main risk factor for development of cardiovascular diseases associated with the impairment of endothelial function in both sexes. In the present study, age-related changes in vascular responsiveness, epigenetic modifications of vessel wall, and blood biomarkers related to endothelial functions were examined in an age- and sex-dependent manner. Acetylcholine (ACh)-induced relaxations of the aorta were decreased in 3-, 6-, and 12-month-old rats compared to those in 1-month-old female rats. In males, maximum relaxations related to ACh were higher in 1- and 6-month-old rats than in 3- and 12-month-old rats. Plasma levels of nitric oxide (NO) and asymmetric dimethylarginine (ADMA) decreased with age in female rats, and total antioxidant capacity (TAC) and hydrogen sulfide (H 2S) levels displayed biphasic alterations. In male rats, plasma levels of NO, TAC, and ADMA decreased with age, and H2S levels increased. Aging also caused a sex-dependent alteration in epigenetic modification of vessels. Expressions of H3K27me2, H3K27me3, H3K36me2, and H3K36me3 were much higher in vessels of 12-month-old female rats compared to those in younger age groups. These results indicate that vascular functions, epigenetic modifications of vessels, and plasma levels of endothelium-related biomarkers are affected by age and sex. These findings could be important for the assessment of vascular status over the course of the life span.

Oral L-arginine improves endothelial function in healthy individuals older than 70 years

Ageing is associated with progressive endothelial dysfunction in normal humans. Flow-mediated dilation (FMD) of the brachial artery is impaired in elderly individuals with cardiovascular disease and vascular nitric oxide (NO) bioavailability is reduced. We investigated whether oral L-arginine, the substrate for NO synthesis, can improve impaired FMD in healthy very old people. In a prospective, double-blind, randomized crossover trial, 12 healthy old subjects (age 73.8 6 2.7 years) took L-arginine (8 g p.o. two times daily) or placebo for 14 days each, separated by a wash-out period of 14 days. FMD was determined by high-resolution ultrasound in the brachial artery during reactive hyperaemia. Baseline artery diameter was 3.88 6 0.18 mm. l-Arginine signifi cantly improved FMD (to 5.7 6 1.2%, p, 0.0001), whereas placebo had no effect (-0.25 6 0.7%; n.s.). After L-arginine, plasma levels of L-arginine increased signifi cantly (114.9 6 11.6 versus 57.4 6 5.0 mmol/l), but placebo had no effect. As NO synthesis can be antagonized by its endogenous inhibitor asymmetric dimethyl L-arginine (ADMA), we determined ADMA plasma concentrations, which were elevated at baseline in comparison to healthy middle-aged individuals (3.9 6 0.2 versus 1.0 6 0.1 mmol/l; p, 0.0001). ADMA remained unchanged during treatment, but L-arginine supplementation normalized the L-arginine/ADMA ratio (p, 0.05). We conclude that in healthy very old age endothelial function is impaired and may be improved by oral L-arginine supplementation, probably due to normalization of the L-arginine/ADMA ratio.

Arterial structure and function in vascular ageing: are you as old as your arteries?

Advancing age may be the most potent independent predictor of future cardiovascular events, a relationship that is not fully explained by time-related changes in traditional cardiovascular risk factors. Since some arteries exhibit differential susceptibility to atherosclerosis, generalisations regarding the impact of ageing in humans may be overly simplistic, whereas in vivo assessment of arterial function and health provide direct insight. Coronary and peripheral (conduit, resistance and skin) arteries demonstrate a gradual, age-related impairment in vascular function that is likely to be related to a reduction in endothelium-derived nitric oxide bioavailability and/or increased production of vasoconstrictors (e.g. endothelin-1). Increased exposure and impaired ability for defence mechanisms to resist oxidative stress and inflammation, but also cellular senescence processes, may contribute to age-related changes in vascular function and health. Arteries also undergo structural changes as they age. Gradual thickening of the arterial wall, changes in wall content (i.e. less elastin, advanced glycation end-products) and increase in conduit artery diameter are observed with older age and occur similarly in central and peripheral arteries. These changes in structure have important interactive effects on artery function, with increases in small and large arterial stiffness representing a characteristic change with older age. Importantly, direct measures of arterial function and structure predict future cardiovascular events, independent of age or other cardiovascular risk factors. Taken together, and given the differential susceptibility of arteries to atherosclerosis in humans, direct measurement of arterial function and health may help to distinguish between biological and chronological age-related change in arterial health in humans.

The S6K protein family in health and disease

The S6K proteins are mTOR pathway effectors and accumulative evidence suggest that mTOR/S6K signaling contributes to several pathological conditions, such as diabetes, cancer and obesity. The activation of the mTOR/S6K axis stimulates protein synthesis and cell growth. S6K1 has two well-known isoforms, p70-S6K1 and p85-S6K1, generated by alternative translation initiation sites. A third isoform, named p31-S6K1, has been characterized as a truncated type of the protein due to alternative splicing, and reports have shown its important role in cancer. Studies involving S6K2 are scarce. This article aims to review what is new in the literature about these kinases and establish differences regarding their interacting proteins, activation and function, connecting their roles in the homeostasis of the cell and in pathological conditions.

Ageing and microvasculature

A decline in the function of the microvasculature occurs with ageing. An impairment of endothelial properties represents a main aspect of age-related microvascular alterations. Endothelial dysfunction manifests itself through a reduced angiogenic capacity, an aberrant expression of adhesion molecules and an impaired vasodilatory function. Increased expression of adhesion molecules amplifies the interaction with circulating factors and inflammatory cells. The latter occurs in both conduit arteries and resistance arterioles. Age-related impaired function also associates with phenotypic alterations of microvascular cells, such as endothelial cells, smooth muscle cells and pericytes. Age-related morphological changes are in most of cases organ-specific and include microvascular wall thickening and collagen deposition that affect the basement membrane, with the consequent perivascular fibrosis. Data from experimental models indicate that decreased nitric oxide (NO) bioavailability, caused by impaired eNOS activity and NO inactivation, is one of the causes responsible for age-related microvascular endothelial dysfunction. Consequently, vasodilatory responses decline with age in coronary, skeletal, cerebral and vascular beds. Several therapeutic attempts have been suggested to improve microvascular function in age-related end-organ failure, and include the classic anti-atherosclerotic and anti-ischemic treatments, and also new innovative strategies. Change of life style, antioxidant regimens and anti-inflammatory treatments gave the most promising results. Research efforts should persist to fully elucidate the biomolecular basis of age-related microvascular dysfunction in order to better support new therapeutic strategies aimed to improve quality of life and to reduce morbidity and mortality among the elderly patients.

Functional changes of the coronary microvasculature with aging regarding glucose tolerance, energy metabolism, and oxidative stress

This study was aimed at characterizing the functional progression of the endothelial (ECs) and smooth muscle cells (SMCs) of the coronary microvasculature between youth and old age, as well as at determining the mechanisms of the observed changes on the basis of the glucose tolerance, mitochondrial energy metabolism, and oxidative stress. Male rats were divided into four age groups (3, 6, 11, and 17 months for the young (Y), young adult (YA), middle-aged (MA), and old (O) animals). The cardiac mechanical function, endothelial-dependent dilatation (EDD) and endothelial-independent dilatation (EID) of the coronary microvasculature were determined in a Langendorff preparation. The mitochondrial respiration and H2O2 production were evaluated and completed by ex vivo measurements of oxidative stress. EDD progressively decreased from youth to old age. The relaxation properties of the SMCs, although high in the Y rats, decreased drastically between youth and young adulthood and stabilized thereafter, paralleling the reduction of mitochondrial oxidative phosphorylation. The ECs dilatation activity, low at youth, was stimulated in YA animals and returned to their initial level at middle age. That parameter followed faithfully the progression of the amount of active cardiac endothelial nitric oxide synthase and whole body glucose intolerance. In conclusion, the progressive decrease in EDD occurring with aging is due to different functional behaviors of the ECs and SMCs, which appear to be associated with the systemic glucose intolerance and cardiac energy metabolism.

Voluntary wheel running augments aortic l-arginine transport and endothelial function in rats with chronic kidney disease

Reduced nitric oxide (NO) synthesis contributes to risk for cardiovascular disease in chronic kidney disease (CKD). Vascular uptake of the NO precursor l-arginine (ARG) is attenuated in rodents with CKD, resulting in reduced substrate availability for NO synthesis and impaired vascular function. We tested the effect of 4 wk of voluntary wheel running (RUN) and/or ARG supplementation on endothelium-dependent relaxation (EDR) in rats with CKD. Twelve-week-old male Sprague-Dawley rats underwent ⅚ ablation infarction surgery to induce CKD, or SHAM surgery as a control. Beginning 4 wk following surgery, CKD animals either remained sedentary (SED) or received one of the following interventions: supplemental ARG, RUN, or combined RUN+ARG. Animals were euthanized 8 wk after surgery, and EDR was assessed. EDR was significantly impaired in SED vs. SHAM animals after 8 wk, in response to ACh (10(-9)-10(-5) M) as indicated by a reduced area under the curve (AUC; 44.56 ± 9.01 vs 100 ± 4.58, P < 0.05) and reduced maximal response (Emax; 59.9 ± 9.67 vs. 94.31 ± 1.27%, P < 0.05). AUC was not improved by ARG treatment but was significantly improved above SED animals in both RUN and RUN+ARG-treated animals. Maximal relaxation was elevated above SED in RUN+ARG animals only. l-[(3)H]arginine uptake was impaired in both SED and ARG animals and was improved in RUN and RUN+ARG animals. The results suggest that voluntary wheel running is an effective therapy to improve vascular function in CKD and may be more beneficial when combined with l-arginine.

Antagonist molecules in the treatment of angina

INTRODUCTION

Management of chronic angina has evolved dramatically in the last few decades with several options for pharmacotherapy outlined in various evidence-based guidelines.

AREAS COVERED

There is a growing list of drugs that are currently being investigated for treatment of chronic angina. These also include several herbal medications, which are now being scientifically evaluated as potential alternative or even adjunctive therapy for angina. Gene- and cell-based therapies have opened yet another avenue for management of chronic refractory angina in 'no-option' patients who are not candidates for either percutaneous or surgical revascularization and are on optimal medical therapy. An extensive review of literature using PUBMED, Cochrane database, clinical trial databases of the USA and European Union was done and summarized in this review. This review will attempt to discuss the traditional as well as novel therapeutic agents for angina.

EXPERT OPINION

Several pharmacological and non-pharmacological therapeutic options are now available for treatment and management of chronic refractory angina. Renewed interest in traditional therapies and cell- and gene-based modalities with targeted drug delivery systems will open the doors for personalized therapy for patients with chronic refractory angina.

Endothelial nitric oxide synthase, vascular integrity and human exceptional longevity

Aging is the sum of the deleterious changes that occur as time goes by. It is the main risk factor for the development of cardiovascular disease, and aging of the vasculature is the event that most often impacts on the health of elderly people. The “free-radical theory of aging” was proposed to explain aging as a consequence of the accumulation of reactive oxygen species (ROS). However, recent findings contradict this theory, and it now seems that mechanisms mediating longevity act through induction of oxidative stress. In fact, calorie restriction − a powerful way of delaying aging − increases ROS accumulation due to stimulation of the basal metabolic rate; moreover, reports show that antioxidant therapy is detrimental to healthy aging. We also now know that genetic manipulation of the insulin-like-growth-factor-1/insulin signal (IIS) has a profound impact on the rate of aging and that the IIS is modulated by calorie restriction and physical exercise. The IIS regulates activation of nitric oxide synthase (eNOS), the activity of which is essential to improving lifespan through calorie restriction, as demonstrated by experiments on eNOS knockout mice. Indeed, eNOS has a key role in maintaining vascular integrity during aging by activating vasorelaxation and allowing migration and angiogenesis. In this review, we will overview current literature on these topics and we will try to convince the reader of the importance of vascular integrity and nitric oxide production in determining healthy aging.

Increased plasma availability of L-arginine in the postprandial period decreases the postprandial lipemia in older adults

OBJECTIVE

Older adults have exaggerated postprandial lipemia, which increases their risk for cardiovascular disease. We sought to determine the effects of increased plasma L-arginine (L-ARG) availability on the oxidation of ingested fat (enriched with [1,1,1-(13)C]-triolein) and plasma triacylglycerol (TG) concentrations during the postprandial period in older subjects.

METHODS

On one day, eight healthy subjects (67.8 ± 1.3 y old) received an intravenous infusion of L-ARG during the first hour of the postprandial period (L-ARG trial), while on a separate day, and in a randomized order, they received saline (control trial).

RESULTS

The 8-h area under the plasma concentration-time curve describing the postprandial plasma TG concentrations was considerably lower in the L-ARG trial than in the control trial (-4 ± 21 versus 104 ± 21 mg ∙ dL(-1) ∙ h(-1), P < 0.01). The rate of the postprandial oxidation of the ingested lipid was not different between the trials, but the average contribution of the ingested oleate to the oleate of the TG of the plasma small TG-rich lipoproteins (Svedberg flotation index 20-400) was lower in the L-ARG trial (11 ± 1 versus 18 ± 2%, P < 0.01). L-ARG infusion also decreased the 8-h area under the plasma concentration-time curve of the plasma free fatty acid concentrations derived from the ingested fat compared with the saline infusion (0.77 ± 0.09 versus 1.11 ± 0.08; mmol ∙ L(-1) ∙ h(-1), P < 0.01).

CONCLUSION

Increasing the plasma L-ARG availability during the postprandial period decreases the postprandial lipemia in older adults, in association with a decrease in the postprandial contribution of ingested lipids into TGs of the plasma small TG-rich lipoproteins.

Acute reversal of endothelial dysfunction in the elderly after antioxidant consumption

Aging is associated with a pro-oxidant state and a decline in endothelial function. Whether acute, enteral antioxidant treatment can reverse this decrement in vascular function is not well known. Flow-mediated vasodilation and reactive hyperemia were evaluated after consumption of either placebo or an oral antioxidant cocktail (vitamin C, 1000 mg; vitamin E, 600 IU; α-lipoic acid, 600 mg) in 87 healthy volunteers (42 young: 25±1 years; 45 older: 71±1 years) using a double-blind, crossover design. Blood velocity and brachial artery diameter (ultrasound Doppler) were assessed before and after 5-minute forearm circulatory arrest. Serum markers of lipid peroxidation, total antioxidant capacity, endogenous antioxidant activity, and vitamin C were assayed, and plasma nitrate, nitrite, and 3-nitrotyrosine were determined. In the placebo trial, an age-related reduction in brachial artery vasodilation was evident (young: 7.4±0.6%; older: 5.2±0.4%). After antioxidant consumption, flow-mediated vasodilation improved in older subjects (placebo: 5.2±0.4%; antioxidant: 8.2±0.6%) but declined in the young (placebo: 7.4±0.6%; antioxidant: 5.8±0.6%). Reactive hyperemia was reduced with age, but antioxidant administration did not alter the response in either group. Together, these data demonstrate that antioxidant consumption acutely restores endothelial function in the elderly while disrupting normal endothelium-dependent vasodilation in the young and suggest that this age-related impairment is attributed, at least in part, to free radicals.

Microvascular coronary dysfunction in women: pathophysiology, diagnosis, and management

Women exhibit a greater symptom burden, more functional disability, and a higher prevalence of no obstructive coronary artery disease compared to men when evaluated for signs and symptoms of myocardial ischemia. Microvascular coronary dysfunction (MCD), defined as limited coronary flow reserve and/or coronary endothelial dysfunction, is the predominant etiologic mechanism of ischemia in women with the triad of persistent chest pain, no obstructive coronary artery disease, and ischemia evidenced by stress testing. Evidence shows that approximately 50% of these patients have physiological evidence of MCD. MCD is associated with a 2.5% annual major adverse event rate that includes death, nonfatal myocardial infarction, nonfatal stroke, and congestive heart failure. Although tests such as adenosine stress cardiac magnetic resonance imaging may be a useful noninvasive method to predict subendocardial ischemia, the gold standard test to diagnose MCD is an invasive coronary reactivity testing. Early identification of MCD by coronary reactivity testing may be beneficial in prognostication and stratifying these patients for optimal medical therapy. Currently, understanding of MCD pathophysiology can be used to guide diagnosis and therapy. Continued research in MCD is needed to further advance our understanding.

Longitudinal Evaluation of Fatty Acid Metabolism in Normal and Spontaneously Hypertensive Rat Hearts with Dynamic MicroSPECT Imaging

The goal of this project is to develop radionuclide molecular imaging technologies using a clinical pinhole SPECT/CT scanner to quantify changes in cardiac metabolism using the spontaneously hypertensive rat (SHR) as a model of hypertensive-related pathophysiology. This paper quantitatively compares fatty acid metabolism in hearts of SHR and Wistar-Kyoto normal rats as a function of age and thereby tracks physiological changes associated with the onset and progression of heart failure in the SHR model. The fatty acid analog, ¹²³I-labeled BMIPP, was used in longitudinal metabolic pinhole SPECT imaging studies performed every seven months for 21 months. The uniqueness of this project is the development of techniques for estimating the blood input function from projection data acquired by a slowly rotating camera that is imaging fast circulation and the quantification of the kinetics of ¹²³I-BMIPP by fitting compartmental models to the blood and tissue time-activity curves.

Central Arterial Aging and Angiotensin II Signaling

Arterial remodeling over time is a cornerstone of normal systemic aging. The age-associated arterial structural and functional changes in the intima, the media, and the adventitia are closely linked to angiotensin II (Ang II) signaling. A growing line of evidence indicates that essential elements of Ang II signaling, which encompasses milk fat globule epidermal growth factor-8, calpain-1, transforming growth factor-β1, matrix metalloproteinase-2/9, monocyte chemoattractant protein-1, nicotinamide adenine dinucleotide phosphate-oxidase, and reactive oxygen species, are upregulated within the central arterial wall in rats, nonhuman primates, and humans during aging. In vitro studies show that the elevation of Ang II signaling induces the accumulation of collagen and advanced glycated end-products, the degradation of elastin, and the increased cell cycle disorder, invasion, and hypertrophy of endothelial and vascular smooth muscle cells. Further, in vivo studies demonstrate that increased Ang II signaling accelerates arterial aging. Conversely, attenuating Ang II signaling via an inhibition of angiotensin conversing enzyme or a blockade of AT1 activation retards age-associated arterial remodeling. This review attempts to integrate complex facts of Ang II signaling within the aged central arterial wall and may shed light on new therapeutic targets for arterial aging.

Arginine and antioxidant supplement on performance in elderly male cyclists: a randomized controlled trial

BACKGROUND

Human exercise capacity declines with advancing age. These changes often result in loss of physical fitness and more rapid senescence. Nitric oxide (NO) has been implicated in improvement of exercise capacity through vascular smooth muscle relaxation in both coronary and skeletal muscle arteries, as well as via independent mechanisms. Antioxidants may prevent nitric oxide inactivation by oxygen free radicals. The purpose of this study was to investigate the effects of an L-arginine and antioxidant supplement on exercise performance in elderly male cyclists.

METHODS

This was a two-arm prospectively randomized double-blinded and placebo-controlled trial. Sixteen male cyclists were randomized to receive either a proprietary supplement (Niteworks(R), Herbalife International Inc., Century City, CA) or a placebo powder. Exercise parameters were assessed by maximal incremental exercise testing performed on a stationary cycle ergometer using breath-by-breath analysis at baseline, week one and week three.

RESULTS

There was no difference between baseline exercise parameters. In the supplemented group, anaerobic threshold increased by 16.7% (2.38 +/- 0.18 L/min, p < 0.01) at week 1, and the effect was sustained by week 3 with a 14.2% (2.33 +/- 0.44 L/min, p < 0.01). In the control group, there was no change in anaerobic threshold at weeks 1 and 3 compared to baseline (1.88 +/- 0.20 L/min at week 1, and 1.86 +/- 0.21 L/min at week 3). The anaerobic threshold for the supplement groups was significantly higher than that of placebo group at week 1 and week 3. There were no significant changes noted in VO2 max between control and intervention groups at either week 1 or week 3 by comparison to baseline.

CONCLUSION

An arginine and antioxidant-containing supplement increased the anaerobic threshold at both week one and week three in elderly cyclists. No effect on VO2 max was observed. This study indicated a potential role of L-arginine and antioxidant supplementation in improving exercise performance in elderly.

Umbilical cord blood stem cells for myocardial repair and regeneration

Cardiovascular disease remains a major cause of morbidity and mortality with substantial economic cost. There remains a need for therapeutic improvement for patients refractory to revascularization and those who redevelop occlusions following revascularization. Early evidence linked age-associated reductions in the levels of circulating marrow-derived hematopoietic stem cells (HSC), characterized by expression of early HSC markers CD133 and CD34, with the occurrence of cardiovascular events and associated death. Heart tissue has the endogenous ability to regenerate through the activation of resident cardiac stem cells or through recruitment of a stem cell population from other tissues, such as bone marrow. A number of clinical trials have utilized patient-derived autologous bone marrow-derived cells or whole BM uncultured mononuclear cells (MNC) infused or injected locally to augment angiogenesis. In most cases of treating animal models with human cells, the frequency of stem cell engraftment, the subsequent number of newly generated cardiomyocytes and vascular cells, and the augmentation of endogenous microvascular collateralization, either by deposition, transdifferentiation, and/or by cell fusion, appear to be too low to explain the significant cardiac improvement. Initially, it was hypothesized that cell therapy may work by cell replacement mechanisms, but recent evidence suggests alternatively that cell therapy works by providing trophic support to the injured tissues. An alternative hypothesis is that the transplanted stem cells release soluble cytokines and growth factors (i.e., paracrine factors) that function in a paracrine fashion, contributing to cardiac repair and regeneration by inducing cytoprotection and neovascularization. Another hypothesis which may also be operative is that cell therapy may mediate endogenous regeneration by the activation of resident cardiac stem cell. Well-established clinical trials have used cord blood for the treatment of hematological malignances (e.g., leukemia, lymphoma, myeloma) and nonmalignancies (e.g., in born errors of metabolism, sickle cells anemia, autoimmune diseases), but further advances in other areas of regenerative medicine (e.g., cardiac repair) will directly benefit with the use of cord blood. These clinical outcomes demonstrate that effector cells may be delivered by an allogeneic approach, where strict tissue matching may not be necessary and treatment may be achieved by making use of the trophic support capability of cell therapy and not by a cell replacement mechanism.

Acute ingestion of a novel whey-derived peptide improves vascular endothelial responses in healthy individuals: a randomized, placebo controlled trial

Background

Whey protein is a potential source of bioactive peptides. Based on findings from in vitro experiments indicating a novel whey derived peptide (NOP-47) increased endothelial nitric oxide synthesis, we tested its effects on vascular function in humans.

Methods

A randomized, placebo-controlled, crossover study design was used. Healthy men (n = 10) and women (n = 10) (25 ± 5 y, BMI = 24.3 ± 2.3 kg/m²) participated in two vascular testing days each preceded by 2 wk of supplementation with a single dose of 5 g/day of a novel whey-derived peptide (NOP-47) or placebo. There was a 2 wk washout period between trials. After 2 wk of supplementation, vascular function in the forearm and circulating oxidative stress and inflammatory related biomarkers were measured serially for 2 h after ingestion of 5 g of NOP-47 or placebo. Macrovascular and microvascular function were assessed using brachial artery flow mediated dilation (FMD) and venous occlusion strain gauge plethysmography.

Results

Baseline peak FMD was not different for Placebo (7.7%) and NOP-47 (7.8%). Placebo had no effect on FMD at 30, 60, and 90 min post-ingestion (7.5%, 7.2%, and 7.6%, respectively) whereas NOP-47 significantly improved FMD responses at these respective postprandial time points compared to baseline (8.9%, 9.9%, and 9.0%; P < 0.0001 for time × trial interaction). Baseline reactive hyperemia forearm blood flow was not different for placebo (27.2 ± 7.2%/min) and NOP-47 (27.3 ± 7.6%/min). Hyperemia blood flow measured 120 min post-ingestion (27.2 ± 7.8%/min) was unaffected by placebo whereas NOP-47 significantly increased hyperemia compared to baseline (29.9 ± 7.8%/min; P = 0.008 for time × trial interaction). Plasma myeloperoxidase was increased transiently by both NOP-47 and placebo, but there were no changes in markers inflammation. Plasma total nitrites/nitrates significantly decreased over the 2 hr post-ingestion period and were lower at 120 min after placebo (-25%) compared to NOP-47 (-18%).

Conclusion

These findings indicate that supplementation with a novel whey-derived peptide in healthy individuals improves vascular function.

Effect ofl-arginine on blood pressure in pregnancy-induced hypertension: A randomized placebo-controlled trial

OBJECTIVE

To evaluate the antihypertensive efficacy of L-arginine (L-Arg) repeated infusions in women affected by gestational hypertension.

METHODS

The women were referred to obstetric units in order to assess their clinical conditions and to exclude the presence of severe fetal and/or maternal complications. Inclusion criteria were: maternal age range 16-45 years, diagnosis of gestational hypertension without proteinuria (patients normotensive until the 20th week), and gestational age ranging between 24 and 36 weeks. Each woman was allocated to receive either L-arginine (20 g/500 mL) or placebo treatment through an i.v. line. The infusion was carried out in the morning from 8 a.m. to 10 a.m. and it was repeated for the next four consecutive days. Systolic and diastolic blood pressure values as well as heart rate were recorded with the patient in an upright, seated position at 08:00, 12:00, 16:00 and 20:00 h.

RESULTS

Maternal clinical features such as age, height, weight, and gestational age at inclusion were similar between groups. Both systolic and diastolic blood pressures were reduced by treatment, the effect of L-arginine being significantly higher than that of the placebo (systolic values F = 8.59, p < 0.005; diastolic values F = 3.36; p < 0.001). Twenty women assigned to the L-Arg group (32.2%) and 23 to the placebo group (37.7%) were concomitantly treated with antihypertensives before starting the study. Analyzing the subgroup of patients not receiving antihypertensive drugs we found that L-arginine was superior to placebo in lowering systolic (F = 5.42, p < 0.005) and diastolic (F = 2.20, p < 0.005) blood pressure values.

CONCLUSIONS

In conclusion, these data support the use of L-Arg as an antihypertensive agent for gestational hypertension especially in view of the other beneficial effects nitric oxide donors display in pregnancy. Further, L-Arg seems well tolerated since in this sample none of the patients reported adverse effects requiring study interruption.

Endothelial dysfunction and vascular disease

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO). The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDHF-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive G(i) (e.g. responses to serotonin and thrombin) and pertussis toxin-insensitive G(q) (e.g. adenosine diphosphate and bradykinin) coupling proteins. The release of NO by the endothelial cell can be up-regulated (e.g. by oestrogens, exercise and dietary factors) and down-regulated (e.g. oxidative stress, smoking and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively loose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and causing endothelium-dependent hyperpolarizations), endothelial cells also can evoke contraction (constriction) of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factor (EDCF). Most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells. EDCF-mediated responses are exacerbated when the production of NO is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients.

The impact of oral L-arginine supplementation on acute smoking-induced endothelial injury and arterial performance

BACKGROUND

Smoking is associated with endothelial dysfunction and increased inflammatory status. The amino acid L-arginine, improves endothelial function in patients with cardiovascular risk factors. We investigated the effect of L-arginine on vascular function and inflammatory process in healthy smokers at rest and after acute smoking.

METHODS

We studied the effect of L-arginine and/or placebo in 12 healthy young smokers on three occasions (day 0, day 1, and day 3). The study was carried out on two separate arms, one with L-arginine (3 x 7 g/day) and one with placebo, according to a randomized, placebo-controlled, double-blind, cross-over design. Measurements were carried out before, immediately after, and 20 min after cigarette smoking. Endothelial function was evaluated by flow-mediated dilation (FMD). Carotid-femoral pulse wave velocity (PWV) was measured as an index of aortic stiffness and augmentation index (AIx) and as a measure of arterial wave reflections. Serum soluble intercellular adhesion molecule-1 (sICAM-1) was measured.

RESULTS

Compared to placebo, L-arginine improved FMD (P < 0.01 at day 1 and P < 0.05 at day 3). L-Arginine reduced PWV and AIx at both days 1 and 3 (P < 0.05 vs. baseline). L-Arginine blunted the acute smoking-induced increase of AIx at both day 1 (P < 0.05) and day 3 (P < 0.01), and prevented the smoking-induced elevation of PWV at day 3 (P < 0.05). Importantly, L-arginine reduced sICAM-1 at days 1 and 3 (P < 0.05 for both vs. baseline).

CONCLUSIONS

Oral L-arginine improves endothelial function and vascular elastic properties of the arterial tree during the acute phase of smoking, an effect accompanied by reduced sICAM-1 levels in these subjects.

Exercise training reverses age-related decrements in endothelium-dependent dilation in skeletal muscle feed arteries

We tested two hypotheses, first that exercise training reverses age-related decrements in endothelium-dependent dilation in soleus muscle feed arteries and second that this improved endothelium-dependent dilation is the result of increased nitric oxide (NO) bioavailability due to increased content and phosphorylation of endothelial NO synthase (eNOS) and/or increased antioxidant enzyme content. Young (2 mo) and old (22 mo) male Fischer 344 rats were exercise trained (Ex) or remained sedentary (Sed) for 10-12 wk, yielding four groups of rats: 1) young Sed (4-5 mo), 2) young Ex (4-5 mo), 3) old Sed (24-25 mo), and 4) old Ex (24-25 mo). Soleus muscle feed arteries (SFA) were isolated and cannulated with two glass micropipettes for examination of endothelium-dependent (ACh) and endothelium-independent [sodium nitroprusside (SNP)] vasodilator function. To determine the mechanism(s) by which exercise affected dilator responses, ACh-induced dilation was assessed in the presence of N(omega)-nitro-l-arginine (l-NNA; to inhibit NO synthase), indomethacin (Indo; to inhibit cyclooxygenase), and l-NNA + Indo. Results indicated that ACh-induced dilation was blunted in old Sed SFA relative to young Sed SFA. Exercise training improved ACh-induced dilation in old SFA such that vasodilator responses in old Ex SFA were similar to young Sed and young Ex SFA. Addition of l-NNA, or l-NNA + Indo, abolished the exercise effect. Immunoblot analysis revealed that extracellular superoxide dismutase (SOD) protein content was increased by training in old SFA, whereas eNOS and SOD-1 protein content were not altered. Addition of exogenous SOD, or SOD + catalase, improved ACh-induced dilation in old Sed SFA such that vasodilator responses were similar to young Sed SFA. Addition of l-NNA abolished the effect of exogenous SOD in old Sed arteries. Collectively, these results indicate that exercise training reverses age-induced endothelial dysfunction in SFA by increasing NO bioavailability and that increases in vascular antioxidant capacity may play an integral role in the improvement in endothelial function.

Nitric oxide synthesis leads to vascular endothelial growth factor synthesis via the NO/cyclic guanosine 3',5'-monophosphate (cGMP) pathway in human corpus cavernosal smooth muscle cells

INTRODUCTION

Vascular smooth muscle cells express endothelial nitric oxide synthase (eNOS) and produce nitric oxide (NO). Recently, increased NO production has been reported to induce the synthesis and secretion of vascular endothelial growth factor (VEGF) via the NO/cyclic guanosine 3',5'-monophosphate (cGMP) pathway. L-arginine (L-arg), the precursor of NO, and selective phosphodiesterase type 5 (PDE-5) inhibitors that increase levels of intracellular cGMP may complementarily enhance VEGF synthesis in corpus cavernosal smooth muscle cells (CCSMCs), and may consequently restore impaired endothelial function. Expression of eNOS in corpus cavernosal smooth muscle has also been reported. However, it is unclear whether CCSMCs can generate NO.

AIM

To elucidate whether CCSMCs can synthesize NO and whether NO synthesis enhances VEGF synthesis via the NO/cGMP pathway.

METHODS

Corpus cavernosal cells were cultured and characterized by immunocytochemistry and immunoblotting. CCSMCs were treated with L-arg. CCSMCs were also incubated with L-arg and with vardenafil, an inhibitor of PDE-5.

MAIN OUTCOME MEASURES

Release of NO from cells was confirmed by assay of NO metabolites (NOx). Intracellular cGMP concentration and VEGF concentration in the medium were measured.

RESULTS

Isolated cells were determined to be CCSMCs. The expression of eNOS by CCSMCs was also identified. NOx and cGMP levels in the L-arg-treated group were significantly greater than those in the control group. VEGF and cGMP levels in the L-arg-treated group were also significantly greater than those in the control group. VEGF and cGMP levels in the L-arg + vardenafil-treated group were significantly greater than those in the L-arg-treated group and the control group.

CONCLUSIONS

CCSMCs express eNOS and synthesize NO. NO synthesis leads to enhancement of VEGF synthesis via the NO/cGMP pathway. Combined L-arg and vardenafil treatment, which can enhance VEGF production, may provide a novel therapeutic strategy for the treatment of erectile dysfunction as well as endothelial dysfunction in general.

Manganese superoxide dismutase and aldehyde dehydrogenase deficiency increase mitochondrial oxidative stress and aggravate age-dependent vascular dysfunction

AIMS

Imbalance between pro- and antioxidant species (e.g. during aging) plays a crucial role for vascular function and is associated with oxidative gene regulation and modification. Vascular aging is associated with progressive deterioration of vascular homeostasis leading to reduced relaxation, hypertrophy, and a higher risk of thrombotic events. These effects can be explained by a reduction in free bioavailable nitric oxide that is inactivated by an age-dependent increase in superoxide formation. In the present study, mitochondria as a source of reactive oxygen species (ROS) and the contribution of manganese superoxide dismutase (MnSOD, SOD-2) and aldehyde dehydrogenase (ALDH-2) were investigated.

METHODS AND RESULTS

Age-dependent effects on vascular function were determined in aortas of C57/Bl6 wild-type (WT), ALDH-2(-/-), MnSOD(+/+), and MnSOD(+/-) mice by isometric tension measurements in organ chambers. Mitochondrial ROS formation was measured by luminol (L-012)-enhanced chemiluminescence and 2-hydroxyethidium formation with an HPLC-based assay in isolated heart mitochondria. ROS-mediated mitochondrial DNA (mtDNA) damage was detected by a novel and modified version of the fluorescent-detection alkaline DNA unwinding (FADU) assay. Endothelial dysfunction was observed in aged C57/Bl6 WT mice in parallel to increased mitochondrial ROS formation and oxidative mtDNA damage. In contrast, middle-aged ALDH-2(-/-) mice showed a marked vascular dysfunction that was similar in old ALDH-2(-/-) mice suggesting that ALDH-2 exerts age-dependent vasoprotective effects. Aged MnSOD(+/-) mice showed the most pronounced phenotype such as severely impaired vasorelaxation, highest levels of mitochondrial ROS formation and mtDNA damage.

CONCLUSION

The correlation between mtROS formation and acetylcholine-dependent relaxation revealed that mitochondrial radical formation significantly contributes to age-dependent endothelial dysfunction.

Supplements of l-arginine attenuate the effects of high-fat meal on endothelial function and oxidative stress

BACKGROUND

Postprandial hypertriglyceridemia is known to cause endothelial dysfunction and increased oxidative stress. Oral supplements of l-arginine have been found to improve endothelial function. However, the effects of supplements of l-arginine on the influences of postprandial hypertriglyceridemia were not studied before.

METHODS

Forty young healthy men without any risk factors were equally divided into two groups. l-arginine group (age 22+/-1 years, body mass index 23.5+/-1.2 kg/m(2)) received a standard high-fat meal with 15 g oral l-arginine. Control group (age 22+/-1 years, body mass index 23.8+/-0.9 kg/m(2)) received a standard high-fat meal with placebo. A standard high-fat meal consisted of 900 kcal and 50 g of fat. Flow-mediated vasodilation (FMD), von Willebrand factor (vWF), p-Selectin, and glutathione peroxidase (GSH-Px) were measured before and 2 h after the high-fat meal.

RESULTS

Serum triglyceride levels were significantly increased 2 h after the high-fat meal in both groups. In the control group, FMD (10.5+/-1.2% vs. 6.8+/-1.4%, p<0.001) and GSH-Px (23.5+/-6.2 vs. 21.9+/-5.0 mug/ml, p=0.029) were significantly decreased after the high-fat meal. P-Selectin (20.0+/-7.7 vs. 25.9+/-10.5 mg/l, p=0.025) and vWF (731.2+/-131.5 vs. 934.9+/-133.8 mU/ml, p<0.001) were significantly increased after the high-fat meal. In the l-arginine group, FMD (10.3+/-1.3 vs. 9.3+/-0.9%, p<0.001) was slightly but significantly decreased after the high-fat meal but not GSH-Px (23.6+/-3.6 vs. 23.0+/-4.8%, p=0.468). P-Selectin (20.1+/-5.9 vs. 25.7+/-10.2 mg/l, p=0.001) and vWF (793.2+/-146.0 vs. 944.4+/-136.8 mU/ml, p<0.001) were significantly increased after the high-fat meal. Degree of FMD attenuation following the high-fat meal was significantly less in the l-arginine group (1.0+/-0.9 vs. 3.8+/-1.5%, p<0.001).

CONCLUSIONS

Concomitant supplements of l-arginine improved endothelial dysfunction and oxidative stress induced by postprandial hypertriglyceridemia. However, changes of p-Selectin and vWF were not affected by supplements of l-arginine with the high-fat meal.

Short-term treatment with L-arginine prevents the smoking-induced impairment of endothelial function and vascular elastic properties in young individuals

BACKGROUND

L-arginine, the substrate for endothelial nitric oxide synthase, is essential for normal endothelial function. Aim of the present study was to investigate in healthy smokers the effect of a short-term daily L-arginine administration on vascular function.

METHODS

We studied the effect of a 3-day oral administration of L-arginine in 10 healthy smokers (24.3+/-0.73 years old) on 3 occasions (day , day 1 and day 3). The study was carried out on two separate arms, one with L-arginine (7 gr/d) and one with placebo according to a randomized, placebo-controlled, double-blind, cross-over design. Measurements were carried out before, immediately after (Sm0) and 20 min after (Sm20) cigarette smoking. Endothelial function was evaluated by flow-mediated dilatation (FMD) of the brachial artery. Carotid-femoral pulse wave velocity (PWV) was measured as an index of aortic stiffness and augmentation index (AIx) as a measure of arterial wave reflections.

RESULTS

Compared to placebo, L-arginine led to an increase of FMD (p<0.05 at day 2), indicating a favorable effect on endothelial function, which however lost significance at day 3. l-arginine induced a progressive decrease of PWV and AIx at both day 2 and day 3 (p<0.01 vs baseline for all). L-arginine blunted the acute smoking-induced increase of AIx at both day 1 (p<0.05) and day 3 (p<0.01), and there was a trend to protect the smoking-induced change of PWV at day 3 (p<0.1).

CONCLUSIONS

Short-term daily administration of L-arginine improves arterial performance in healthy smokers and abrogates the smoking-induced increase in arterial stiffness and wave reflections in these individuals.

Short-term increases in intraluminal pressure reverse age-related decrements in endothelium-dependent dilation in soleus muscle feed arteries

We tested the hypothesis that short-term increases in intraluminal pressure improve endothelium-dependent dilation and increase endothelial nitric oxide (NO) synthase (eNOS) expression in senescent soleus muscle feed arteries (SFA). SFA isolated from young (4 mo) and old (24 mo) Fischer 344 rats were cannulated and pressurized at 90 (p90) or 130 (p130) cmH(2)O for 4 h. At the end of the 4-h protocol, pressure in p130 SFA was lowered to 90 cmH(2)O for examination of endothelium-dependent (flow- or ACh-induced) vasodilation. Flow- and ACh-induced dilations were blunted in old p90 SFA relative to young p90 SFA. Pretreatment with increased pressure (p130) improved flow- and ACh-induced dilations in old SFA, such that vasodilator responses were similar to those in young SFA. In the presence of N(omega)-nitro-l-arginine (l-NNA) or l-NNA + indomethacin (Indo), flow-induced dilation was inhibited in old p130 SFA, such that the response was not greater than the response in old p90 SFA. In old p130 SFA, ACh-induced dilation was inhibited by l-NNA + Indo (not l-NNA alone). In a separate experiment, SFA were pressurized at 70, 90, 110, or 130 cmH(2)O for 4 h, and eNOS mRNA and protein content were assessed. Increased pressure induced eNOS mRNA expression in young (not old) SFA. eNOS protein content was not altered in young or old SFA. These results indicate that short-term increases in intraluminal pressure improve endothelium-dependent dilation in senescent SFA, in part by enhancing NO bioavailability; however, the beneficial effect was not associated with increased eNOS expression.

Age-Related Vascular Stiffness and Left Ventricular Size After Myocardial Infarction

Aortic stiffness increases with age and may contribute to adverse remodeling after myocardial infarction (MI). The authors examined whether vascular stiffness affects left ventricular (LV) size after MI using contrast-enhanced cardiac magnetic resonance imaging. Despite similar infarct sizes, patients aged 60 years or older (n=30) had a lower ejection fraction (42+/-15 vs 53+/-11%, P<.01) and greater end-systolic volume index (75+/-47 vs 44+/-18 mL/m(2), P<.01) than younger patients (n=19). As infarct size increased, LV end-systolic volumes (P<.0001) and ejection fraction (P<.0001) in the older participants were progressively greater. Participants with greater aortic stiffness had greater end-systolic volume indices (P<.0001) and lower ejection fraction (P<.0001) with increasing infarct size. Using multivariate analysis, MI size (P<.001) and aortic distensibility (P=.02) were significant predictors of end-systolic volume index. Older patients have increased LV size after MI compared with younger patients, possibly related to age-related decreases in aortic distensibility affecting LV remodeling.

Vascular endothelium summary statement II: Cardiovascular disease prevention and control

The prevention and control of cardiovascular disease (CVD), principally ischemic heart disease and stroke, are a major clinical and public health challenge. Worldwide, CVD accounts for substantial morbidity and mortality. The major modifiable CVD risk factors are known and all of them cause endothelial activation and dysfunction. Preventing and controlling the established risk factors are associated with preserved endothelial function and reduced risk of CVD. Research advances that improve our understanding of strategies to preserve endothelial function or make the endothelial cells resilient to environmental insults may help improve our preventive interventions. This summary statement addresses the current state of the science with respect to endothelial dysfunction and CVD pathogenesis, diagnostic evaluation, and suggested strategies for public health practice and research.

Umbilical cord blood stem cells: Implications for cardiovascular regenerative medicine

The treatment of cardiovascular disease has benefited from advances in pharmacologic and intravascular intervention reducing the morbidity and mortality associated with this disease. To address the need in managing clinically complex vascular disease with limited therapeutic options studies have focused on cellular therapy as a means to augment compensatory mechanisms and to potentially prevent escalation and advancement of disease. Umbilical cord blood (UCB) is a rich source of hematopoietic stem cells (HSC) and thus may be a potential source of cells for this type of therapy. UCB can be collected at no risk to the donor, is immediately available, has a wider availability of HLA phenotypes with a possible lower immune reactivity and does not provoke ethically charged debates. Moreover, stem cells isolated from patients with chronic disease have impairment of their reparative abilities thus limiting their therapeutic impact. The potential of UCB HSC in augmenting this process has been studied extensively both in vitro and in vivo and has shown a benefit in acute and chronic vascular ischemia. Although studies suggest efficacy with no obvious safety concerns the mechanism for this therapeutic effect is unknown.

UC blood hematopoietic stem cells and therapeutic angiogenesis

Studies suggest that mobilized hematopoietic stem cells (HSC) are recruited to ischemic tissue and stimulate angiogenesis. Critical observations in pre-clinical studies have identified an augmentation of endogenous microvascular collateralization that is beyond that directly attributable to anatomic incorporation and differentiation of infused human cells into the vascular endothelium. Evidence links age-associated reductions in the levels of circulating marrow-derived HSC characterized by expression of early HSC markers CD133 and CD34, with the occurrence of cardiovascular events and associated death. Utilizing the patient's own HSC to augment angiogenesis has several disadvantages, including reduced function of these cells and logistical issues related to cell collection from individual patients. Thus an available source of allogeneic HSC such as UC blood for cellular therapy may be optimal.

Impaired flow-mediated dilation with age is not explained by l-arginine bioavailability or endothelial asymmetric dimethylarginine protein expression

Aging is associated with a decline in vascular endothelial function, manifesting in part as impaired flow-mediated arterial dilation (FMD), but the underlying mechanisms are uncertain. Impaired FMD may be mediated in part by a decrease in synthesis of nitric oxide by endothelial nitric oxide synthase, and in clinical populations this has been attributed to competitive inhibition of l-arginine binding sites by asymmetric dimethylarginine (ADMA). If this mechanism is involved in the age-associated decline in FMD, increasing l-arginine concentration may swing the competitive balance in favor of l-arginine binding, restoring nitric oxide synthesis, and enhancing FMD in older humans. To test this hypothesis, we measured FMD (brachial ultrasound) in 10 younger (21 ± 1 yr) and 12 older healthy men and women (60 ± 2 yr) following infusion of vehicle or vehicle + l-arginine. Baseline FMD in the older subjects was only ∼60% of that in the younger subjects ( P = 0.002). l-Arginine did not significantly increase FMD in either group despite 23-fold (older) and 19-fold (younger) increases in plasma l-arginine concentrations ( P < 0.0001 vs. control). Protein expression (immunofluorescence) in vascular endothelial cells showed that ADMA and the enzyme isoform that controls its degradation, dimethylarginine dimethylaminohydrolase II, were not different in the younger and older subjects. Endothelium-independent vasodilation (sublingual nitroglycerine) was not different between age groups or conditions. We conclude that acutely increasing plasma concentrations of l-arginine do not significantly improve brachial artery FMD in healthy older subjects and thus does not restore the age-associated loss of FMD. Together with the finding that endothelial cell ADMA protein expression was not increased in older adults, these findings suggest that competitive inhibition of l-arginine binding sites on endothelial nitric oxide synthase by ADMA is not an important mechanism contributing to impaired conduit artery endothelium-dependent dilation with aging in healthy humans.

Nitric oxide and the endothelium: history and impact on cardiovascular disease

There are few discoveries with the magnitude of the impact that NO has had on biology during the 25 years since its discovery. There is hardly a disease today not associated with altered NO homeostasis. In fact, despite numerous other endothelial functions, endothelial dysfunction has become synonymous with reduced biological activity of NO. Translating the preclinical discoveries in NO biology to new modalities for disease management has not been as impressive. Beyond the success of drugs for erectile dysfunction, clinical trials of nitric oxide synthase inhibitor have been proven either ineffective or wrought with side effects. NO donors (e.g., nitroglycerine) remain frequently used cardiovascular agents, but were discovered before 1980. Gene therapy studies have yet to become clinically useful. There is no doubt that endothelial- and NO-dysfunction is a hallmark of cardiovascular disease, including diseases which are considered as major current public health concerns: hypertension, obesity, diabetes, malnutrition. In many cases, cardiovascular disease (CVD) can be prevented by identifying and controlling modifiable risk factors. One conceivable approach to the management of multiple risk factors in CVD could be to treat endothelial dysfunction (e.g., by enhancing eNOS expression), since many CVD risk factors are related to endothelial dysfunction. In this regard one goal may include optimizing eNOS function. This can be realized by supplementing co-factors, e.g., BH4, or substrate, L-arginine, by increasing cGMP availability via phosphodiesterase inhibitors or sGC activators or by increasing NO bioavailability via antioxidants. The association of other proteins with the nitric oxide synthase (NOS) isoforms and sGC could also serve as experimental and potentially therapeutic targets to modulate NO bioactivity. There is tremendous promise behind NO itself as well as the numerous other molecules and processes associated with the L-arginine-NO-cGMP pathway. Collaborative efforts among bench scientists, clinical investigators and epidemiologists are the key in realizing this promise.

Aging and vascular responses to flavanol-rich cocoa

OBJECTIVES

Strong evidence has secured aging as a powerful predictor of both cardiovascular risk and endothelial dysfunction, yet specific treatment is not available. We tested the hypothesis that vascular responsiveness to flavanol-rich cocoa increases with advancing age. We have previously shown that flavanol-rich cocoa induced peripheral vasodilation, improving endothelial function via a nitric oxide (NO)-dependent mechanism.

METHODS

We studied blood pressure and peripheral arterial responses to several days of cocoa in 15 young (< 50 years) and 19 older (> 50) healthy subjects.

RESULTS

The nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine-methyl-ester (L-NAME) induced significant pressor responses following cocoa administration only among the older subjects: systolic blood pressure (SBP) rose 13 +/- 4 mmHg, diastolic blood pressure (DBP) 6 +/- 2 mmHg (P = 0.008 and 0.047, respectively); SBP was significantly higher in the older subjects (P < 0.05). Flow-mediated vasodilation, measured by tonometry in the finger, was enhanced with flavanol-rich cocoa in both groups, but significantly more so among the old (P = 0.01). Finally, basal pulse wave amplitude (PWA) followed a similar pattern. Four to six days of flavanol-rich cocoa caused a rise in PWA in both groups. At peak vasodilation following acute cocoa intake on the final day, both groups showed a further, significant rise in PWA. The response in the older subjects was more robust; P < 0.05. L-NAME significantly reversed dilation in both groups.

CONCLUSIONS

Flavanol-rich cocoa enhanced several measures of endothelial function to a greater degree among older than younger healthy subjects. Our data suggest that the NO-dependent vascular effects of flavanol-rich cocoa may be greater among older people, in whom endothelial function is more disturbed.

Expression of nitric oxide related enzymes in coronary heart disease

Enzymes involved in the metabolism nitric oxide (NO) and reactive oxygen species (ROS) may play a role for the decreased availability of NO in atherosclerosis. We, therefore, hypothesized that the pattern of gene expression of these enzymes is altered in atherosclerosis. Myocardial tissue from patients with coronary heart disease (CHD) or without CHD (control group) was investigated. The level of enzymes related to NO/ROS metabolism was determined both at mRNA level and protein level by rt-PCR, real-time PCR, and western blot. The expression of NOS1-3 (synthesis of NO), arginase1 (reduction of L-arginine), p22phox (active subunit of NADPH oxidase), GTPCH (rate limiting enzyme for tetrahydrobiopterin), SOD1-3 (scavengers of superoxide anions), PRTMT1-3, and DDAH2 (involved in the metabolism of ADMA) was determined. All enzymes were found to be expressed in human myocardium. NOS isoforms were decreased in CHD in protein level, but only the downregulation of NOS3 expression reached statistical significance. The expression of PRMT1 and PRMT3 was increased. In addition, the expression of DDAH2 was reduced, both theoretically leading to an increase of ADMA concentration. SOD3 was downregulated in tissue from patients with CHD. Taken together, in myocardial tissue from patients with atherosclerosis, the expression of genes increasing ADMA levels is enhanced in contrast to a reduced expression of genes promoting NO synthesis. These results may contribute to the explanation of increased oxidative stress in atherosclerosis on the level of gene expression.

L-Arginine supplementation or arginase inhibition augments reflex cutaneous vasodilatation in aged human skin

Full expression of reflex cutaneous vasodilatation is dependent on nitric oxide (NO) and vasodilatation is attenuated in healthy older humans. NO bioavailability in aged skin may be decreased by an age-related upregulation of arginase, which reciprocally regulates the NO-synthase (NOS) substrate L-arginine (L-Arg). We hypothesized that increased arginase activity contributes to attenuated vasodilatation in aged skin by limiting L-Arg for NOS-mediated NO synthesis. Five microdialysis fibres were placed in forearm skin of 10 young (Y, 23 +/- 1 years) and 9 older (O, 68 +/- 1 years) human subjects, serving as control (C, Ringer solution), NOS-inhibited (10.0 mM NG-nitro-L-arginine), arginase-inhibited (5.0 mM (S)-(2-boronoethyl)-L-cysteine + 5.0 mM Nomega-hydroxy-nor-L-arginine), L-arg supplemented (L-Arg; 10.0 mM L-arginine) and combined arginase-inhibited + L-Arg sites. After 20 min thermoneutral baseline, cutaneous vasodilatation was induced by passive whole-body heating to increase oral temperature (Tor) by 1.0 degrees C. Red blood cell flux was measured by laser-Doppler flowmetry over each microdialysis site. Cutaneous vascular conductance was calculated (CVC = flux/mean arterial pressure) and normalized to maximal CVC (CVCmax, 28.0 mM sodium nitroprusside + local heating to 43 degrees C). Cutaneous vasodilatation during heating was attenuated in O (Y, 42 +/- 1, versus O, 30 +/- 1%CVCmax, P < 0.001) at control sites. NOS inhibition decreased vasodilatation in both age groups compared to C (Y, 22 +/- 2; O, 18 +/- 2%CVCmax; P < 0.001). Arginase inhibition, L-Arg supplementation, and arginase inhibition + L-Arg supplementation augmented vasodilatation in O (arginase-inhibited, 46 +/- 4; L-Arg, 44 +/- 4; arginase-inhibited + L-arg, 46 +/- 5%CVCmax; P < 0.001 versus C) but not in Y (arginase-inhibited, 46 +/- 4; L-Arg, 38 +/- 4; arginase-inhibited + L-Arg, 44 +/- 4%CVCmax; P > 0.05 versus C). Increasing L-Arg for NO synthesis by either arginase inhibition or direct L-Arg supplementation restores the age-related deficit in reflex cutaneous vasodilatation.

Effect of diet and omega-3 fatty acid intervention on asymmetric dimethylarginine

BACKGROUND AND AIM

Impaired vasodilatation has been suggested to be caused by inhibition of nitric oxide generation by the recently described asymmetric dimethylarginine (ADMA). In the present study we wanted to explore whether n-3 polyunsaturated fatty acid (PUFA) supplementation and/or diet intervention have beneficial influence on endothelial function assessed as plasma levels of ADMA and L-arginine.

METHODS

A male population (n = 563, age 70 +/- 6 yrs) with long-standing hyperlipidemia, characterized as high risk individuals in 1970-72, was included, randomly allocated to receive placebo n-3 PUFA capsules (corn oil) and no dietary advice (control group), dietary advice (Mediterranean type), n-3 PUFA capsules, or dietary advice and n-3 PUFA combined and followed for 3 years. Fasting blood samples were drawn at baseline and the end of the study.

RESULTS

Compliance with both intervention regimens were demonstrated by changes in serum fatty acids and by recordings from a food frequency questionnaire. No influence of either regimens on ADMA levels were obtained. However, n-3 PUFA supplementation was accompanied by a significant increase in L-arginine levels, different from the decrease observed in the placebo group (p < 0.05). In individuals with low body mass index (<26 kg/m2), the decrease in L-arginine on placebo was strengthened (p = 0.01), and the L-arginine/ADMA ratio was also significantly reduced (p = 0.04).

CONCLUSION

In this rather large randomized intervention study, ADMA levels were not influenced by n-3 PUFA supplementation or dietary counselling. n-3 PUFA did, however, counteract the age-related reduction in L-arginine seen on placebo, especially in lean individuals, which might be discussed as an improvement of endothelial function.

Knockdown of arginase I restores NO signaling in the vasculature of old rats

Arginase, expressed in endothelial cells and upregulated in aging blood vessels, competes with NO synthase (NOS) for l-arginine, thus modulating vasoreactivity and attenuating NO signaling. Moreover, arginase inhibition restores endothelial NOS signaling and l-arginine responsiveness in old rat aorta. The arginase isoform responsible for modulating NOS, however, remains unknown. Because isoform-specific arginase inhibitors are unavailable, we used an antisense (AS) oligonucleotide approach to knockdown arginase I (Arg I). Western blot and quantitative PCR confirmed that Arg I is the predominant isoform expressed in endothelialized aortic rings and is upregulated in old rats compared with young. Aortic rings from 22-month-old rats were incubated for 24 hours with sense (S), AS oligonucleotides, or medium alone (C). Immunohistochemistry, immunoblotting, and enzyme assay confirmed a significant knockdown of Arg I protein and arginase activity in AS but not S or C rings. Conversely, calcium-dependent NOS activity and vascular metabolites of NO was increased in AS versus S or C rings. Acetylcholine (endothelial-dependent) vasorelaxant responses were enhanced in AS versus S or C treated rings. In addition, 1H-oxadiazolo quinoxalin-1-one (10 micromol/L), a soluble guanylyl cyclase inhibitor, increased the phenylephrine response in AS compared with S and C rings suggesting increased NO bioavailability. Finally, l-arginine (0.1 mmol/L)-induced relaxation was increased in AS versus C rings. These data support our hypothesis that Arg I plays a critical role in the pathobiology of age-related endothelial dysfunction. AS oligonucleotides may, therefore, represent a novel therapeutic strategy against age-related vascular endothelial dysfunction.