Nitrite supplementation reverses vascular endothelial dysfunction and large elastic artery stiffness with aging

Dietary Beetroot Juice - Effects in Patients with COPD: A Review

Chronic Obstructive Pulmonary Disease (COPD) exerts a severe toll on human health and the economy, with high prevalence and mortality rates. The search for bioactive components effective in the treatment of COPD has become a focal point of research. Beetroot juice, readily accessible and cost-effective, is noted for its ability to enhance athletic performance and for its preventive and therapeutic impact on hypertension. Beetroot juice is a rich source of dietary nitrates and modulates physiological processes via the nitrate-nitrite- nitric oxide pathway, exerting multiple beneficial effects such as antihypertensive, bronchodilatory, anti-inflammatory, antioxidant, hypoglycemic, and lipid-lowering actions. This paper provides a review of the existing research on the effects of beetroot juice on COPD, summarizing its potential in enhancing exercise capacity, lowering blood pressure, improving vascular function, and ameliorating sleep quality among patients with COPD. The review serves as a reference for the prospective use of beetroot juice in the symptomatic improvement of COPD, as well as in the prevention of exacerbations and associated comorbidities.

Effects of increased nitrate intake from beetroot juice on blood markers of oxidative stress and inflammation in older adults with hypertension

BACKGROUND

Vascular oxidative stress and low-grade inflammation are important in the pathology of cardiovascular disorders, including hypertension. Cell culture and animal studies suggest that inorganic dietary nitrate may attenuate oxidative stress and inflammation through nitric oxide (NO), and there is a need to investigate whether this translates to humans.

AIM

In this randomised, placebo-controlled crossover study, by measuring a combination of multiple blood biomarkers, we evaluated whether previously reported benefits of dietary nitrate translate to a reduced oxidative stress and an improved inflammation status in 15 men and women (age range: 56-71 years) with treated hypertension.

METHODS

We investigated the effects of a single ∼400 mg-dose of nitrate at 3 h post-ingestion (3H POST) and the daily consumption of 2 × ∼400 mg of nitrate over 4 weeks (4WK POST), through nitrate-rich versus nitrate-depleted (placebo) beetroot juice. Measurements included plasma nitrate and nitrite (NOx), oxidised low-density lipoprotein (oxLDL), F2-isoprostanes, protein carbonyls, oxidised (GSSG) and reduced glutathione (GSH); and serum high-sensitive C-reactive protein (hsCRP), chemokines, cytokines, and adhesion molecules. Flow cytometry was used to assess the relative proportion of blood monocyte subsets.

RESULTS

At 4WK POST nitrate intervention, the oxLDL/NOx ratio decreased (mainly due to increases in plasma nitrate and nitrite) and the GSH/GSSG ratio (a sensitive biomarker for alterations in the redox status) increased, compared with placebo (for both ratios P < 0.01). The relative proportion of classical (CD14+CD16-) monocytes decreased at 4WK POST for placebo compared to nitrate intervention (P < 0.05). Other oxidative stress and inflammatory markers were not altered by increased nitrate intake relative to placebo.

CONCLUSIONS

The data from this study point toward a subtle alteration in the redox balance toward a less pro-oxidative profile by a regular intake of inorganic nitrate from plant foods.

CLINICAL TRIAL REGISTRY NUMBER

NCT04584372 (ClinicialTrials.gov).

The plasma metabolome is associated with preservation of physiological function following lifelong aerobic exercise in mice

Declines in physiological function with aging are strongly linked to age-related diseases. Lifelong voluntary aerobic exercise (LVAE) preserves physiological function with aging, possibly by increasing cellular quality control processes, but the circulating molecular transducers mediating these processes are incompletely understood. The plasma metabolome may predict biological aging and is impacted by a single bout of aerobic exercise. Here, we conducted an ancillary analysis using plasma samples, and physiological function data, from previously reported studies of LVAE in male C57BL/6N mice randomized to LVAE (wheel running) or sedentary (SED) (n = 8-9/group) to determine if LVAE alters the plasma metabolome and whether these changes correlated with preservation of physiological function with LVAE. Physical function (grip strength, coordination, and endurance) was assessed at 3 and 18 months of age; vascular endothelial function and the plasma metabolome were assessed at 19 months. Physical function was preserved (%decline; mean ± SEM) with LVAE vs SED (all p < 0.05)-grip strength, 0.4 ± 1.7% vs 12 ± 4.0%; coordination, 10 ± 4% vs 73 ± 10%; endurance, 1 ± 15% vs 61 ± 5%. Vascular endothelial function with LVAE (88.2 ± 2.0%) was higher than SED (79.1 ± 2.5%; p = 0.03) and similar to the young controls (91.4 ± 2.9%). Fifteen metabolites were different with LVAE compared to SED (FDR < 0.05) and correlated with the preservation of physiological function. Plasma spermidine, a polyamine that increases cellular quality control (e.g., autophagy), correlated with all assessed physiological indices. Autophagy (LC3A/B abundance) was higher in LVAE skeletal muscle compared to SED (p < 0.01) and inversely correlated with plasma spermidine (r =  - 0.5297; p = 0.054). These findings provide novel insight into the circulating molecular transducers by which LVAE may preserve physiological function with aging.

Peripheral vascular dysfunction and the aging brain

Aging is the greatest non-modifiable risk factor for most diseases, including cardiovascular diseases (CVD), which remain the leading cause of mortality worldwide. Robust evidence indicates that CVD are a strong determinant for reduced brain health and all-cause dementia with advancing age. CVD are also closely linked with peripheral and cerebral vascular dysfunction, common contributors to the development and progression of all types of dementia, that are largely driven by excessive levels of oxidative stress (e.g., reactive oxygen species [ROS]). Emerging evidence suggests that several fundamental aging mechanisms (e.g., "hallmarks" of aging), including chronic low-grade inflammation, mitochondrial dysfunction, cellular senescence and deregulated nutrient sensing contribute to excessive ROS production and are common to both peripheral and cerebral vascular dysfunction. Therefore, targeting these mechanisms to reduce ROS-related oxidative stress and improve peripheral and/or cerebral vascular function may be a promising strategy to reduce dementia risk with aging. Investigating how certain lifestyle strategies (e.g., aerobic exercise and diet modulation) and/or select pharmacological agents (natural and synthetic) intersect with aging "hallmarks" to promote peripheral and/or cerebral vascular health represent a viable option for reducing dementia risk with aging. Therefore, the primary purpose of this review is to explore mechanistic links among peripheral vascular dysfunction, cerebral vascular dysfunction, and reduced brain health with aging. Such insight and assessments of non-invasive measures of peripheral and cerebral vascular health with aging might provide a new approach for assessing dementia risk in older adults.

The Nitrate-Nitrite-Nitric Oxide Pathway: Potential Role in Mitigating Oxidative Stress in Hypertensive Disorders of Pregnancy

Hypertensive diseases of pregnancy (HDPs) represent a global clinical challenge, affecting 5-10% of women and leading to complications for both maternal well-being and fetal development. At the heart of these complications is endothelial dysfunction, with oxidative stress emerging as a pivotal causative factor. The reduction in nitric oxide (NO) bioavailability is a vital indicator of this dysfunction, culminating in blood pressure dysregulation. In the therapeutic context, although antihypertensive medications are commonly used, they come with inherent concerns related to maternal-fetal safety, and a percentage of women do not respond to these therapies. Therefore, alternative strategies that directly address the pathophysiology of HDPs are required. This article focuses on the potential of the nitrate-nitrite-NO pathway, abundantly present in dark leafy greens and beetroot, as an alternative approach to treating HDPs. The objective of this review is to discuss the prospective antioxidant role of nitrate. We hope our discussion paves the way for using nitrate to improve endothelial dysfunction and control oxidative stress, offering a potential therapy for managing HDPs.

Effect of long-term inorganic nitrate administration on myocardial ischemia-reperfusion injury in ovariectomized rats

Introduction: Menopause is associated with reduced nitric oxide (NO) bioavailability and lower tolerance against myocardial ischemia-reperfusion (IR) injury. This study investigated whether long-term nitrate administration provides resistance against myocardial IR injury in ovariectomized (OVX) rats. Method: After ovariectomy, female rats were assigned to the OVX and the OVX + nitrate groups (n = 14/group); the latter group consumed nitrate (100 mg/L) for 9 months. At month 9, each group was divided into two subgroups (n = 7/subgroup), of which one subgroup was exposed to myocardial IR (IR+ hearts) and the other was not exposed (IR- hearts). The hearts of rats were isolated, and NO metabolite (NOx), oxidative stress indices, and mRNA expressions of endothelial (eNOS), inducible (iNOS), and neuronal (nNOS) NO synthases, as well as markers of apoptosis, were measured in the IR- and IR+ hearts. In the IR+ hearts, cardiac function indices (CFI) and the infarct size were also measured. Results: Nitrate increased catalase activity (97%) and eNOS expression (2.94-fold) in the IR- hearts. In the IR+ hearts, nitrate reduced left ventricular (LV) end-diastolic pressure (11.6%) and infarct size (26.2%) and increased recovery of LV developed pressure (44.0%) and peak rate of positive (28.9%) and negative (15.4%) changes in LV pressure. In addition, in the IR+ hearts, nitrate increased eNOS and B-cell lymphoma-2 (Bcl-2) as well as decreased iNOS, Bcl-2 associated X protein (Bax), caspase-3, caspase-8, caspase-9, and tumor necrosis factor-α (TNF-α) expression. Nitrate increased total antioxidant capacity (TAC) and catalase (CAT) activity and decreased malondialdehyde (MDA) levels at month nine in serum and IR+ hearts. Conclusion: The favorable effects of nitrate against IR injury were associated with higher eNOS and Bcl-2 expression, CAT activity, TAC, and lower iNOS, Bax, caspase-3, caspase-8, caspase-9 and TNF-α expression, and MDA in the heart tissue. Nitrate preconditioning alleviated IR-induced myocardial injury in OVX rats; this effect was associated with eNOS upregulation before IR and the blunting of OVX-induced eNOS downregulation, iNOS upregulation, apoptosis, and oxidative stress in heart tissue after IR.

The Cardioprotective Role of Nitrate-Rich Vegetables

Nitric oxide (NO) is an inorganic radical produced by both the non-enzymatic nitrate (NO3-)-nitrite (NO2-)-NO pathway and enzymatic reactions catalyzed by nitric oxide synthase (NOS). Also, as nitrate and nitrite from dietary and other endogenous sources can be reduced back to nitric oxide in vivo, the endogenous NO level can be increased through the consumption of nitrate-rich vegetables. Ingestion of dietary NO3- has beneficial effects which have been attributed to a subsequent increase in NO: a signaling molecule that may regulate various systems, including the cardiovascular system. A diet rich in NO3- from green leafy and root vegetables has cardioprotective effects, with beetroot products being particularly good sources of NO3-. For example, various studies have demonstrated a significant increase in nitrite levels (regarded as markers of NO) in plasma after the intake of beetroot juice. The present review describes the current literature concerning the role of nitrate-rich vegetables (especially beetroot products) in the prophylaxis and treatment of cardiovascular diseases (CVDs). This review is based on studies identified in electronic databases, including PubMed, ScienceDirect, Web of Knowledge, Sci Finder, Web of Science, and SCOPUS.

From nitrate to NO: potential effects of nitrate-reducing bacteria on systemic health and disease

Current research has described improving multisystem disease and organ function through dietary nitrate (DN) supplementation. They have provided some evidence that these floras with nitrate (NO3-) reductase are mediators of the underlying mechanism. Symbiotic bacteria with nitrate reductase activity (NRA) are found in the human digestive tract, including the mouth, esophagus and gastrointestinal tract (GT). Nitrate in food can be converted to nitrite under the tongue or in the stomach by these symbiotic bacteria. Then, nitrite is transformed to nitric oxide (NO) by non-enzymatic synthesis. NO is currently recognized as a potent bioactive agent with biological activities, such as vasodilation, regulation of cardiomyocyte function, neurotransmission, suppression of platelet agglutination, and prevention of vascular smooth muscle cell proliferation. NO also can be produced through the conventional L-arginine-NO synthase (L-NOS) pathway, whereas endogenous NO production by L-arginine is inhibited under hypoxia-ischemia or disease conditions. In contrast, exogenous NO3-/NO2-/NO activity is enhanced and becomes a practical supplemental pathway for NO in the body, playing an essential role in various physiological activities. Moreover, many diseases (such as metabolic or geriatric diseases) are primarily associated with disorders of endogenous NO synthesis, and NO generation from the exogenous NO3-/NO2-/NO route can partially alleviate the disease progression. The imbalance of NO in the body may be one of the potential mechanisms of disease development. Therefore, the impact of these floras with nitrate reductase on host systemic health through exogenous NO3-/NO2-/NO pathway production of NO or direct regulation of floras ecological balance is essential (e.g., regulation of body homeostasis, amelioration of diseases, etc.). This review summarizes the bacteria with nitrate reductase in humans, emphasizing the relationship between the metabolic processes of this microflora and host systemic health and disease. The potential effects of nitrate reduction bacteria on human health and disease were also highlighted in disease models from different human systems, including digestive, cardiovascular, endocrine, nervous, respiratory, and urinary systems, providing innovative ideas for future disease diagnosis and treatment based on nitrate reduction bacteria.

Bringing Nitric Oxide to the Molybdenum World-A Personal Perspective

Molybdenum-containing enzymes of the xanthine oxidase (XO) family are well known to catalyse oxygen atom transfer reactions, with the great majority of the characterised enzymes catalysing the insertion of an oxygen atom into the substrate. Although some family members are known to catalyse the "reverse" reaction, the capability to abstract an oxygen atom from the substrate molecule is not generally recognised for these enzymes. Hence, it was with surprise and scepticism that the "molybdenum community" noticed the reports on the mammalian XO capability to catalyse the oxygen atom abstraction of nitrite to form nitric oxide (NO). The lack of precedent for a molybdenum- (or tungsten) containing nitrite reductase on the nitrogen biogeochemical cycle contributed also to the scepticism. It took several kinetic, spectroscopic and mechanistic studies on enzymes of the XO family and also of sulfite oxidase and DMSO reductase families to finally have wide recognition of the molybdoenzymes' ability to form NO from nitrite. Herein, integrated in a collection of "personal views" edited by Professor Ralf Mendel, is an overview of my personal journey on the XO and aldehyde oxidase-catalysed nitrite reduction to NO. The main research findings and the path followed to establish XO and AO as competent nitrite reductases are reviewed. The evidence suggesting that these enzymes are probable players of the mammalian NO metabolism is also discussed.

Effects of Nitric Oxide Supplementation on the Levels of Interleukin-6 in Saliva after Dental Implant Placement - A Prospective Study

Introduction

The purpose of the study was to evaluate and compare the levels of salivary Interleukin-6 (IL-6) before and after the placement of dental implants in patients who are supplemented with nitric oxide (NO).

Materials and Methods

The study comprised 34 patients, divided into control and study groups (17 in each group). The control group was given a placebo and in the study group, nitric oxide supplement was prescribed, whereas the control group received a placebo. Saliva samples were taken before placement of dental implants, first and third day after the implant placement. The levels of salivary IL-6 were assessed using an enzyme-linked immunosorbent assay test.

Results

Statistical analysis showed a significant P value (<0.05) with respect to IL-6 levels on first and third days after placement of dental implants. Salivary IL-6 levels in the study group declined significantly. On day three, the IL-6 values for the control and study groups were 0.0639 and 0.0443, respectively. Within the groups, it was observed that there was a significant decrease in IL-6 values from day one to day three.

Discussion

The levels of salivary IL-6 reduced from day one to day three more significantly and consistently in patients prescribed with NO supplements post-dental implant placement, suggesting better resolution of inflammation.

Restoration of the gut barrier integrity and restructuring of the gut microbiome in aging by angiotensin-(1-7)

Compromised barrier function of colon epithelium with aging is largely due to gut microbial dysbiosis. Recent studies implicate an important role for angiotensin converting enzymes, ACE and ACE2, angiotensins, and the receptors, AT1 receptor (AT1R) and Mas receptor (MasR), in the regulation of colon functions. The present study tested the hypothesis that leaky gut in aging is associated with an imbalance in ACE2/ACE and that the treatment with angiotenisn-(1-7) (Ang-(1-7)) will restore gut barrier integrity and microbiome. Studies were carried out in Young (3-4 months) and old (20-24 months) male mice. Ang-(1-7) was administered by using osmotic pumps. Outcome measures included expressions of ACE, ACE2, AT1R, and MasR, intestinal permeability by using FITC-dextran, and immunohistochemistry of claudin 1 and occludin, and intestinal stem cells (ISCs). ACE2 protein and activity were decreased in Old group while that of ACE were unchanged. Increased intestinal permeability and plasma levels of zonulin-1 in the Old group were normalized by Ang-(1-7). Epithelial disintegrity, reduced number of goblet cells and ISCs in the old group were restored by Ang-(1-7). Expression of claudin 1 and occludin in the aging colon was increased by Ang-(1-7). Infiltration of CD11b+ or F4/80+ inflammatory cells in the old colons were decreased by Ang-(1-7). Gut microbial dysbiosis in aging was evident by decreased richness and altered beta diversity that were reversed by Ang-(1-7) with increased abundance of Lactobacillus or Lachnospiraceae. The present study shows that Ang-(1-7) restores gut barrier integrity and reduces inflammation in the aging colon by restoring the layer of ISCs and by restructuring the gut microbiome.

Nutraceuticals in the Prevention and Therapeutic Treatment of Cardiovascular and Cerebrovascular Disease

PURPOSE

This review overviews and highlights arterial stiffening as a key physiological process and target for the prevention and/or lowering of cardio- and cerebrovascular disease (collectively CVD) risk.

METHODS

We identified nutraceutical approaches from randomized controlled trials and discussed the associated mechanisms by which these compounds lower age-related arterial stiffness. Age-related CVD are the leading cause of mortality in modernized societies. Arterial dysfunction, specifically stiffening of the large elastic arteries during midlife, is a key physiological process resulting in increased CVD risk. Current pharmaceutical approaches for lowering age-related arterial stiffness have limited efficacy, thus highlighting the need to identify novel approaches for lowering arterial stiffness and thereby CVD risk. Lifestyle interventions are a historical first-line approach to prevent and/or lower the adverse arterial stiffening effects observed with aging. Nutraceutical interventions, defined as a food or part of a food providing health benefits, are a nonpharmacological, novel lifestyle approach to lower age-associated arterial stiffness. Therefore, identifying nutraceutical approaches to lower CVD risk is clinically significant.

SUMMARY

This review provides a basic, yet essential, understanding for emerging nutraceutical strategies for the prevention and therapeutic treatment of CVD.

Anti-oxidant effect of nitrite in the pancreatic islets of type 2 diabetic male rats

Objectives

Nitrite, a nitric oxide (NO) donor, increases insulin secretion from pancreatic islets and has positive metabolic effects in type 2 diabetes (T2D). Here, we test the hypothesis of whether nitrite-induced insulin secretion is due to blunting of diabetes-induced oxidative stress in the islets.

Materials and Methods

T2D was created in male rats using a combination of streptozotocin at 25 mg/kg and a high-fat diet. Wistar rats were assigned to 3 groups (n=6 in each group), including control, T2D, and T2D+nitrite; the latter group consumed drinking water containing sodium nitrite (50 mg/l) for eight weeks. At the end of the study, mRNA levels of NADPH oxidase (Nox1, 2, 3, and 4), superoxide dismutase (SOD1, 2, and 3), glutathione peroxides (GPX1 and 7), glutathione reductase (GR), catalase, thioredoxin (TXN1 and 2), and thioredoxin reductase (TXNRD1) were measured in the isolated pancreatic islets.

Results

In the islets of diabetic rats, mRNA expressions of Nox1, 2, and 4 were higher, whereas expressions of SOD1, 2, catalase, GPX1, 7, GR, and TXN1 were lower than controls. Nitrite significantly (all P-values<0.05) decreased gene expression of Nox1 (0.39-fold) and Nox4 (0.23-fold) and increased gene expression of SOD1 (2.2-fold), SOD2 (2.8-fold), catalase (2.7-fold), GPX1 (2.2-fold), GPX7 (6.0-fold), GR (3.0-fold), TXN1 (2.1-fold), and TXNRD1 (2.3-fold) in diabetic rats.

Conclusion

Nitrite decreased oxidative stress in isolated pancreatic islets of rats with T2D by suppressing oxidants and augmenting anti-oxidants. These findings favor the notion that nitrite-induced insulin secretion is partially due to decreased oxidative stress.

Combination Sodium Nitrite and Hydralazine Therapy Attenuates Heart Failure With Preserved Ejection Fraction Severity in a "2-Hit" Murine Model

Background Recent studies have suggested that cardiac nitrosative stress mediated by pathological overproduction of nitric oxide (NO) via inducible NO synthase (iNOS) contributes to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). Other studies have suggested that endothelial NO synthase (eNOS) dysfunction and attenuated NO bioavailability contribute to HFpEF morbidity and mortality. We sought to further investigate dysregulated NO signaling and to examine the effects of a NO-based dual therapy (sodium nitrite+hydralazine) following the onset of HFpEF using a "2-hit" murine model. Methods and Results Nine-week-old male C57BL/6 N mice (n=15 per group) were treated concurrently with high-fat diet and N(ω)-nitro-L-arginine methyl ester (L-NAME) (0.5 g/L per day) via drinking water for 10 weeks. At week 5, mice were randomized into either vehicle (normal saline) or combination treatment with sodium nitrite (75 mg/L in the drinking water) and hydralazine (2.0 mg/kg IP, BID). Cardiac structure and function were monitored with echocardiography and invasive hemodynamic measurements. Cardiac mitochondrial respiration, aortic vascular function, and exercise performance were also evaluated. Circulating and myocardial nitrite were measured to determine the bioavailability of NO. Circulating markers of oxidative or nitrosative stress as well as systemic inflammation were also determined. Severe HFpEF was evident by significantly elevated E/E', LVEDP, and Tau in mice treated with L-NAME and HFD, which was associated with impaired NO bioavailability, mitochondrial respiration, aortic vascular function, and exercise capacity. Treatment with sodium nitrite and hydralazine restored NO bioavailability, reduced oxidative and nitrosative stress, preserved endothelial function and mitochondrial respiration, limited the fibrotic response, and improved exercise capacity, ultimately attenuating the severity of "two-hit" HFpEF. Conclusions Our data demonstrate that nitrite, a well-established biomarker of NO bioavailability and a physiological source of NO, is significantly reduced in the heart and circulation in the "2-hit" mouse HFpEF model. Furthermore, sodium nitrite+hydralazine combined therapy significantly attenuated the severity of HFpEF in the "2-hit" cardiometabolic HFpEF. These data suggest that supplementing NO-based therapeutics with a potent antioxidant and vasodilator agent may result in synergistic benefits for the treatment of HFpEF.

Ageing and endothelium-mediated vascular dysfunction: the role of the NADPH oxidases

The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Endothelium-dependent [intraluminal flow- and acetylcholine (ACh)-induced] vasodilatation in human skeletal muscle feed arteries (SMFAs) of young (24 ± 1 years, n = 16), middle aged (45 ± 1 years, n = 18) and old (76 ± 2 years, n = 21) subjects was assessed in vitro with and without the inhibition of NOX1 (ML090), NOX2 (gp91) and NOX4 (plumbagin). To identify the role of nitric oxide (NO) bioavailability in these responses, NO synthase blockade (l-NG -monomethyl arginine citrate) was utilized. SMFA NOX1, NOX2 and NOX4 protein expression was determined by western blotting. Age related endothelium-dependent vasodilatory dysfunction was evident in response to flow (young: 69 ± 3; middle aged: 51 ± 3; old: 27 ± 3%, P < 0.05) and ACh (young: 89 ± 2; middle aged: 72 ± 3; old: 45 ± 4%, P < 0.05). NOX1 inhibition had no effect on SMFA vasodilatation, whereas NOX2 inhibition restored flow- and ACh-induced vasodilatation in the middle aged and the old SMFAs (middle aged + gp91: 69 ± 3; 86 ± 3, old + gp91: 65 ± 5; 83 ± 2%, P < 0.05) and NOX4 inhibition tended to restore these vasodilatory responses in these two groups, but neither achieved statistical significance (P ≈ 0.06). l-NG -monomethyl arginine citrate negated the restorative effects of NOX2 and NOX4 blockade. Only NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function (r = 0.48 to 0.93, P < 0.05). NOX2 and, to a lesser extent, NOX4 appear to play an important, probably NO-mediated, role in age-related endothelial dysfunction. KEY POINTS: The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Age related endothelium-dependent vasodilatory dysfunction was evident in skeletal muscle feed arteries in response to both flow and acetylcholine. NOX2 inhibition (gp91) restored endothelium-dependent vasodilatation in the middle aged and the old skeletal muscle feed arteries, and NOX4 inhibition (plumbagin) tended to restore these vasodilatory responses in these two groups. Nitric oxide synthase inhibition negated the restorative effects of NOX2 and NOX4 blockade. NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function. NOX2 and, to a lesser extent, NOX4 appear to play an important, probably nitric oxide-mediated, role in age-related endothelial dysfunction and could be important therapeutic targets to maintain vascular health with ageing.

Effects of Fermented Garlic Extract Containing Nitric Oxide Metabolites on Blood Flow in Healthy Participants: A Randomized Controlled Trial

Aged or fermented garlic extract (FGE) is a natural remedy that improves vascular function through increasing vascular nitric oxide (NO) bioavailability. This is because nitrite (NO2-), a NO metabolite, can be produced through bioconversion with macrobacteria during the fermentation of foods like garlic. We aimed to evaluate the effects of NO2- in FGE on blood flow (BF), blood pressure (BP), velocity of the common carotid artery (CCA) and internal carotid artery (ICA), regional cerebral BF (rCBF), and peripheral BF (PBF). The study was divided into two parts: (1) Thirty healthy adults were divided into FGE and placebo groups to compare BP and velocity of the CCA and ICA; and (2) Twenty-eight healthy adults were divided into FGE and placebo groups to compare rCBF and PBF and determine changes before/after ingestion. Significant changes were noted in BP and the velocity of both CCA 30-60 min after FGE ingestion. FGE ingestion resulted in significant increases in rCBF and increases in body surface temperature through alterations in PBF. No detectable clinical side effects were noted. Overall, oral administration of NO2- containing FGE demonstrated acute positive effects in upregulating BF, including the CCA, BP, rCBF, and PBF. Follow-up studies with larger sample sizes and long-term ingestion may be needed.

The Generation of Nitric Oxide from Aldehyde Dehydrogenase-2: The Role of Dietary Nitrates and Their Implication in Cardiovascular Disease Management

Reduced bioavailability of the nitric oxide (NO) signaling molecule has been associated with the onset of cardiovascular disease. One of the better-known and effective therapies for cardiovascular disorders is the use of organic nitrates, such as glyceryl trinitrate (GTN), which increases the concentration of NO. Unfortunately, chronic use of this therapy can induce a phenomenon known as "nitrate tolerance", which is defined as the loss of hemodynamic effects and a reduction in therapeutic effects. As such, a higher dosage of GTN is required in order to achieve the same vasodilatory and antiplatelet effects. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is a cardioprotective enzyme that catalyzes the bio-activation of GTN to NO. Nitrate tolerance is accompanied by an increase in oxidative stress, endothelial dysfunction, and sympathetic activation, as well as a loss of the catalytic activity of ALDH2 itself. On the basis of current knowledge, nitrate intake in the diet would guarantee a concentration of NO such as to avoid (or at least reduce) treatment with GTN and the consequent onset of nitrate tolerance in the course of cardiovascular diseases, so as not to make necessary the increase in GTN concentrations and the possible inhibition/alteration of ALDH2, which aggravates the problem of a positive feedback mechanism. Therefore, the purpose of this review is to summarize data relating to the introduction into the diet of some natural products that could assist pharmacological therapy in order to provide the NO necessary to reduce the intake of GTN and the phenomenon of nitrate tolerance and to ensure the correct catalytic activity of ALDH2.

Long-term inorganic nitrate administration protects against ovariectomy-induced osteoporosis in rats

The risk of osteoporotic fractures increases in women after menopause. This study aims at determining the effects of long-term inorganic nitrate administration against ovariectomy-induced osteoporosis in rats. Rats were divided into 4 groups (n=6/group): Control, control+nitrate, ovariectomized (OVX), and OVX+nitrate. Sodium nitrate (100 mg/L in drinking water) was administered for 9 months. Trabecular bone quality in the proximal tibia was measured using a Micro-Computed Tomography (micro-CT) scanner at months 0, 1, 3, and 9. Levels of nitric oxide (NO) metabolites (NOx) and oxidative stress indices, and mRNA expression of endothelial NO synthase (eNOS) were measured at month 9 in the proximal tibia. Compared to controls, OVX rats had lower NOx levels by 47 %, eNOS mRNA expression by 55 %, catalase activity (CAT) by 45 %, total antioxidant capacity (TAC) by 70 %, and higher malondialdehyde (MDA) levels by 327 % in the bone tissue at month 9. OVX rats, compared to controls, had lower bone volume/tissue volume (BV/TV), trabecular number (Tb.N.), and trabecular thickness (Tb.Th.) by 32 %, 58 %, and 17 %, respectively, and higher trabecular separation (Tb.Sp.) by 123 %, at month 9. Nitrate administration to control rats increased TAC by 46 % in the bone tissue at month 9 but did not significantly affect other parameters in serum and bone tissue. Nitrate in OVX rats significantly increased NOx levels by 86 %, eNOS expression by 2.14-fold, CAT activity by 75 %, TAC by 170 %, and decreased MDA levels by 36 % at month 9 in the bone tissue. Nitrate-treated OVX rats at month 9 had higher BV/TV (42 %) and Tb.N. (61 %) and lower Tb.Sp. (15 %). Long-term inorganic nitrate administration at a low dose has protective effects against OVX-induced osteoporosis in rats; this effect is associated with increasing eNOS-derived NO and decreasing oxidative stress in the bone tissue.

Promoting healthy cardiovascular aging: emerging topics

The development of age-related cardiovascular (CV) dysfunction increases the risk of CV disease as well as other chronic age-associated disorders, including chronic kidney disease, and Alzheimer's disease and related dementias. Major manifestations of age-associated CV dysfunction that increase disease risk are vascular dysfunction, primarily vascular endothelial dysfunction and arterial stiffening, and elevated systolic blood pressure. Declines in nitric oxide bioavailability secondary to increased oxidative stress and inflammation are established mechanisms of CV dysfunction with aging. Moreover, fundamental mechanisms of aging, termed the "hallmarks of aging" extend to the CV system and, as such, may be considered "hallmarks of CV aging". These mechanisms represent viable therapeutic targets for treating CV dysfunction with aging. Healthy lifestyle behaviors, such as regular aerobic exercise and certain dietary patterns, are considered "first-line" strategies to prevent and/or treat age-associated CV dysfunction. Despite the well-established benefits of these strategies, many older adults do not meet the recommended guidelines for exercise or consume a healthy diet. Therefore, it is important to establish alternative and/or complementary evidence-based approaches to prevent or reverse age-related CV dysfunction. Targeting fundamental mechanisms of CV aging with interventions such as time-efficient exercise training, food-derived molecules, termed nutraceuticals, or select synthetic pharmacological agents represents a promising approach. In the present review, we will highlight emerging topics in the field of healthy CV aging with a specific focus on how exercise, nutrition/dietary patterns, nutraceuticals and select synthetic pharmacological compounds may promote healthy CV aging, in part, by targeting the hallmarks of CV aging.

Sex Differences in Vascular Aging and Impact of GPER Deletion

Aging is a nonmodifiable risk factor for cardiovascular disease associated with arterial stiffening and endothelial dysfunction. We hypothesized that sex differences exist in vascular aging processes and would be attenuated by global deletion of the G protein-coupled estrogen receptor. Blood pressure was measured by tail cuff plethysmography, pulse wave velocity (PWV) and echocardiography were assessed with high resolution ultrasound, and small vessel reactivity was measured using wire myography in adult (25 weeks) and middle-aged (57 weeks) male and female mice. Adult female mice displayed lower blood pressure and PWV, but this sex difference was absent in middle-aged mice. Aging significantly increased PWV but not blood pressure in both sexes. Adult female carotids were more distensible than males, but this sex difference was lost during aging. Acetylcholine-induced relaxation was greater in female than male mice at both ages, and only males showed aging-induced changes in cardiac hypertrophy and function. GPER deletion removed the sex difference in PWV as well as ex vivo stiffness in adult mice. The sex difference in blood pressure was absent in KO mice and was associated with endothelial dysfunction in females. These findings indicate that the impact of aging on arterial stiffening and endothelial function is not the same in male and female mice. Moreover, nongenomic estrogen signaling through GPER impacted vascular phenotype differently in male and female mice. Delineating sex differences in vascular changes during healthy aging is an important first step in improving early detection and sex-specific treatments in our aging population.

Aortic Stiffness in L-NAME Treated C57Bl/6 Mice Displays a Shift From Early Endothelial Dysfunction to Late-Term Vascular Smooth Muscle Cell Dysfunction

Introduction and Aims: Endothelial dysfunction is recognized as a cardiovascular aging hallmark. Administration of nitric oxide synthase blocker N-Ω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) constitutes a well-known small animal model of cardiovascular aging. Despite extensive phenotypic characterization, the exact aortic function changes in L-NAME treated mice are largely unknown. Therefore, this study presents a longitudinal characterization of the aortic reactivity and biomechanical alterations in L-NAME treated C57Bl/6 mice.

Methods and Results: Male C57Bl/6 mice were treated with L-NAME (0.5 mg/ml drinking water) for 1, 2, 4, 8, or 16 weeks. Peripheral blood pressure measurement (tail-cuff) and transthoracic echocardiograms were recorded, showing progressive hypertension after 4 weeks of treatment and progressive cardiac hypertrophy after 8–16 weeks of treatment. Aortic stiffness was measured in vivo as aortic pulse wave velocity (aPWV, ultrasound) and ex vivo as Peterson modulus (E_p). Aortic reactivity and biomechanics were investigated ex vivo in thoracic aortic rings, mounted isometrically or dynamically-stretched in organ bath set-ups. Aortic stiffening was heightened in L-NAME treated mice after all treatment durations, thereby preceding the development of hypertension and cardiac aging. L-NAME treatment doubled the rate of arterial stiffening compared to control mice, and displayed an attenuation of the elevated aortic stiffness at high distending pressure, possibly due to late-term reduction of medial collagen types I, III, and IV content. Remarkably, endothelial dysfunction, measured by acetylcholine concentration-response stimulation in precontracted aortic rings, was only observed after short-term (1–4 weeks) treatment, followed by restoration of endothelial function which coincided with increased phosphorylation of endothelial nitric oxide synthase (S¹¹⁷⁷). In the late-disease phase (8–16 weeks), vascular smooth muscle cell (VSMC) dysfunction developed, including increased contribution of voltage-dependent calcium channels (assessed by inhibition with diltiazem), basal VSMC cytoplasmic calcium loading (assessed by removal of extracellular calcium), and heightened intracellular contractile calcium handling (assessed by measurement of sarcoplasmic reticulum-mediated transient contractions).

Conclusion: Arterial stiffness precedes peripheral hypertension and cardiac hypertrophy in chronic L-NAME treated male C57Bl/6 mice. The underlying aortic disease mechanisms underwent a distinct shift from early endothelial dysfunction to late-term VSMC dysfunction, with continued disease progression.

Heart Failure With Preserved Ejection Fraction: Heterogeneous Syndrome, Diverse Preclinical Models

Heart failure with preserved ejection fraction (HFpEF) represents one of the greatest challenges facing cardiovascular medicine today. Despite being the most common form of heart failure worldwide, there has been limited success in developing therapeutics for this syndrome. This is largely due to our incomplete understanding of the biology driving its systemic pathophysiology and the heterogeneity of clinical phenotypes, which are increasingly being recognized as distinct HFpEF phenogroups. Development of efficacious therapeutics fundamentally relies on robust preclinical models that not only faithfully recapitulate key features of the clinical syndrome but also enable rigorous investigation of putative mechanisms of disease in the context of clinically relevant phenotypes. In this review, we propose a preclinical research strategy that is conceptually grounded in model diversification and aims to better align with our evolving understanding of the heterogeneity of clinical HFpEF. Although heterogeneity is often viewed as a major obstacle in preclinical HFpEF research, we challenge this notion and argue that embracing it may be the key to demystifying its pathobiology. Here, we first provide an overarching guideline for developing HFpEF models through a stepwise approach of comprehensive cardiac and extra-cardiac phenotyping. We then present an overview of currently available models, focused on the 3 leading phenogroups, which are primarily based on aging, cardiometabolic stress, and chronic hypertension. We discuss how well these models reflect their clinically relevant phenogroup and highlight some of the more recent mechanistic insights they are providing into the complex pathophysiology underlying HFpEF.

Nitric Oxide in the Management of Respiratory Consequences in COVID-19: A Scoping Review of a Different Treatment Approach

The severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) virus causing COVID-19 significantly affects the respiratory functions of infected individuals by massively disrupting the pulmonary oxygenation and activating the synthesis of proinflammatory cytokines, inducing severe oxidative stress, enhanced vascular permeability, and endothelial dysfunction which have rendered researchers and clinicians to depend on prophylactic treatment due to the unavailability of proper disease management approaches. Previous studies have indicated that nitric oxide (NO) application appears to be significant concerning the antiviral activities, antioxidant, and anti-inflammatory properties in relieving disease-related symptoms. To identify, explore, and map the literature on the role of nitric oxide in the management of respiratory consequences in COVID-19 through this scoping review, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed during the search to answer the focal question: "What are the potential uses of nitric oxide in the management of respiratory failure in COVID-19?" Administering exogenous NO in the form of inhaled gas or stimulating the system to produce NO appears to be a suitable option to manage COVID-19-induced pneumonia and respiratory illness. This treatment modality seems to attenuate respiratory distress among patients suffering from severe infections or patients with comorbidities. Exogenous NO at different doses effectively reduces systemic hyperinflammation and oxidative stress, improves arterial oxygenation, and restores pulmonary alveolar cellular integrity to prevent the lungs and other organs from further damage. This therapy could pave the way for better management of COVID-19 before the onset of disease-related complications.

Apolipoprotein (a)/Lipoprotein(a)-Induced Oxidative-Inflammatory α7-nAChR/p38 MAPK/IL-6/RhoA-GTP Signaling Axis and M1 Macrophage Polarization Modulate Inflammation-Associated Development of Coronary Artery Spasm

Objective. Apolipoprotein (a)/lipoprotein(a) (Lp(a)), a major carrier of oxidized phospholipids, and α7-nicotinic acetylcholine receptor (α7-nAChR) may play an important role in the development of coronary artery spasm (CAS). In CAS, the association between Lp(a) and the α7-nAChR-modulated inflammatory macrophage polarization and activation and smooth muscle cell dysfunction remains unknown. Methods. We investigated the relevance of Lp(a)/α7-nAChR signaling in patient monocyte-derived macrophages and human coronary artery smooth muscle cells (HCASMCs) using expression profile correlation analyses, fluorescence-assisted cell sorting flow cytometry, immunoblotting, quantitative real-time polymerase chain reaction, and clinicopathological analyses. Results. There are increased serum Lp(a) levels (3.98-fold, $p=0.011$ ) and macrophage population (3.30-fold, $p=0.013$ ) in patients with CAS compared with patients without CAS. Serum Lp(a) level was positively correlated with high-sensitivity C-reactive protein ( $r^2=0.48$ , $p<0.01$ ), IL-6 ( $r^2=0.38$ , $p=0.03$ ), and α7-nAChR ( $r^2=0.45$ , $p<0.01$ ) in patients with CAS, but not in patients without CAS. Compared with untreated or low-density lipoprotein- (LDL-) treated macrophages, Lp(a)-treated macrophages exhibited markedly enhanced α7-nAChR mRNA expression ( $p<0.01$ ) and activity ( $p<0.01$ ), in vitro and ex vivo. Lp(a) but not LDL preferentially induced CD80+ macrophage (M1) polarization and reduced the inducible nitric oxide synthase expression and the subsequent NO production. While shRNA-mediated loss of α7-nAChR function reduced the Lp(a)-induced CD80+ macrophage pool, both shRNA and anti-IL-6 receptor tocilizumab suppressed Lp(a)-upregulated α7-nAChR, p-p38 MAPK, IL-6, and RhoA-GTP protein expression levels in cultures of patient monocyte-derived macrophages and HCASMCs. Conclusions. Elevated Lp(a) levels upregulate α7-nAChR/IL-6/p38 MAPK signaling in macrophages of CAS patients and HCASMC, suggesting that Lp(a)-triggered inflammation mediates CAS through α7-nAChR/p38 MAPK/IL-6/RhoA-GTP signaling induction, macrophage M1 polarization, and HCASMC activation.

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.

Bioinspired NO release coating enhances endothelial cells and inhibits smooth muscle cells

Thrombus and restenosis after stent implantation are the major complications because traditional drugs such as rapamycin delay the process of endothelialization. Nitric oxide (NO) is mainly produced by endothelial nitric oxide synthase (eNOS) on the membrane of endothelial cells (ECs) in the cardiovascular system and plays an important role in vasomotor function. It strongly inhibits the proliferation of smooth muscle cells (SMCs) and ameliorates endothelial function when ECs get hurt. Inspired by this, introducing NO to traditional stent coating may alleviate endothelial insufficiency caused by rapamycin. Here, we introduced SNAP as the NO donor, mimicking how NO affects in vivo, into rapamycin coating to alleviate endothelial damage while inhibiting SMC proliferation. Through wicking effects, SNAP was absorbed into a hierarchical coating that had an upper porous layer and a dense polymer layer with rapamycin at the bottom. Cells were cultured on the coatings, and it was observed that the injured ECs were restored while the growth of SMCs further diminished. Genome analysis was conducted to further clarify possible signaling pathways: the effect of cell growth attenuated by NO may cause by affecting cell cycle and enhancing inflammation. These findings supported the idea that introducing NO to traditional drug-eluting stents alleviates incomplete endothelialization and further inhibits the stenosis caused by the proliferation of SMCs.

MMP-2 knockdown blunts age-dependent carotid stiffness by decreasing elastin degradation and augmenting eNOS activation

AIMS

Arterial stiffness is a hallmark of vascular aging that precedes and strongly predicts the development of cardiovascular diseases. Age-dependent stiffening of large elastic arteries is primarily attributed to increased levels of matrix metalloproteinase-2 (MMP-2). However, the mechanistic link between age-dependent arterial stiffness and MMP-2 remains unclear. Thus, we aimed to investigate the efficacy of MMP-2 knockdown using small interfering RNA (siRNA) on age-dependent arterial stiffness.

METHODS AND RESULTS

Pulse wave velocity (PWV) was assessed in right carotid artery of wild type (WT) mice from different age groups. MMP-2 levels in the carotid artery and plasma of young (3 months) and old (20-25 months) WT mice were determined. Carotid PWV as well as vascular and circulating MMP-2 were elevated with increasing age in mice. Old WT mice (18-21-month-old) were treated for 4 weeks with either MMP-2 or scrambled (Scr) siRNA via tail vein injection. Carotid PWV was assessed at baseline, 2 and 4 weeks after start of the treatment. MMP-2 knockdown reduced vascular MMP-2 levels and attenuated age-dependent carotid stiffness. siMMP-2 treated mice showed increased elastin to collagen ratio, lower plasma desmosine (DES), enhanced phosphorylation of endothelial nitric oxide synthase (eNOS) and higher levels of vascular cyclic guanosine monophosphate (cGMP). An age-dependent increase in direct protein-protein interaction between MMP-2 and eNOS was also observed. Lastly, DES, an elastin breakdown product, was measured in a patient cohort (n = 64, 23-86 years old), where carotid-femoral PWV was also assessed; here, plasma levels of DES directly correlated with age and arterial stiffness.

CONCLUSION

MMP-2 knockdown attenuates age-dependent carotid stiffness by blunting elastin degradation and augmenting eNOS bioavailability. Given the increasing clinical use of siRNA technology, MMP2 knockdown should be investigated further as a possible strategy to mitigate age-dependent arterial stiffness and related CV diseases.

TRANSLATIONAL PERSPECTIVE

Arterial stiffness is a hallmark of vascular aging that precedes and strongly predicts the development of cardiovascular diseases. This study provides translational evidence to support a key role for MMP-2 on the development of age-associated arterial stiffness. Silencing of MMP-2 using siRNA technology shows an effect on aged mice where it attenuates age-dependent carotid stiffness by reducing elastin degradation and increasing eNOS bioavailability. Additionally, in humans we show that elastin breakdown increases with age and increased PWV. These findings indicate MMP-2 knockdown as a promising novel strategy to attenuate age-dependent arterial stiffness and cardiovascular diseases.

Effects of inorganic nitrate on ischaemia-reperfusion injury after coronary artery bypass surgery

Background

Nitric oxide (NO) is an important signalling molecule in the cardiovascular system with protective properties in ischaemia–reperfusion injury. Inorganic nitrate, an oxidation product of endogenous NO production and a constituent in our diet, can be recycled back to bioactive NO. We investigated if preoperative administration of inorganic nitrate could reduce troponin T release and other plasma markers of injury to the heart, liver, kidney, and brain in patients undergoing cardiac surgery.

Methods

This single-centre, randomised, double-blind, placebo-controlled trial included 82 patients undergoing coronary artery bypass surgery with cardiopulmonary bypass. Oral sodium nitrate (700 mg×2) or placebo (NaCl) were administered before surgery. Biomarkers of ischaemia–reperfusion injury and plasma nitrate and nitrite were collected before and up to 72 h after surgery. Troponin T release was our predefined primary endpoint and biomarkers of renal, liver, and brain injury were secondary endpoints.

Results

Plasma concentrations of nitrate and nitrite were elevated in nitrate-treated patients compared with placebo. The 72-h release of troponin T did not differ between groups. Other plasma biomarkers of organ injury were also similar between groups. Blood loss was not a predefined outcome parameter, but perioperative bleeding was 18% less in nitrate-treated patients compared with controls.

Conclusion

Preoperative administration of inorganic nitrate did not influence troponin T release or other plasma biomarkers of organ injury in cardiac surgery.

Clinical trial registration

NCT01348971.

Sex and the G Protein-Coupled Estrogen Receptor Impact Vascular Stiffness

[Figure: see text].

Boosting nitric oxide in stress and respiratory infection: Potential relevance for asthma and COVID-19

Nitric oxide (NO) is a ubiquitous signaling molecule that is critical for supporting a plethora of processes in biological organisms. Among these, its role in the innate immune system as a first line of defense against pathogens has received less attention. In asthma, levels of exhaled NO have been utilized as a window into airway inflammation caused by allergic processes. However, respiratory infections count among the most important triggers of disease exacerbations. Among the multitude of factors that affect NO levels are psychological processes. In particular, longer lasting states of psychological stress and depression have been shown to attenuate NO production. The novel SARS-CoV-2 virus, which has caused a pandemic, and with that, sustained levels of psychological stress globally, also adversely affects NO signaling. We review evidence on the role of NO in respiratory infection, including COVID-19, and stress, and argue that boosting NO bioavailability may be beneficial in protection from infections, thus benefitting individuals who suffer from stress in asthma or SARS-CoV-2 infection.

Apigenin restores endothelial function by ameliorating oxidative stress, reverses aortic stiffening, and mitigates vascular inflammation with aging

We assessed the efficacy of oral supplementation with the flavanoid apigenin on arterial function during aging and identified critical mechanisms of action. Young (6 mo) and old (27 mo) C57BL/6N mice (model of arterial aging) consumed drinking water containing vehicle (0.2% carboxymethylcellulose; 10 young and 7 old) or apigenin (0.5 mg/mL in vehicle; 10 young and 9 old) for 6 wk. In vehicle-treated animals, isolated carotid artery endothelium-dependent dilation (EDD), bioassay of endothelial function, was impaired in old versus young (70% ± 9% vs. 92% ± 1%, P < 0.0001) due to reduced nitric oxide (NO) bioavailability. Old mice had greater arterial reactive oxygen species (ROS) production and oxidative stress (higher nitrotyrosine) associated with greater nicotinamide adenine dinucleotide phosphate oxidase (oxidant enzyme) and lower superoxide dismutase 1 and 2 (antioxidant enzymes); ex vivo administration of Tempol (antioxidant) restored EDD to young levels, indicating ROS-mediated suppression of EDD. Old animals also had greater aortic stiffness as indicated by higher aortic pulse wave velocity (PWV, 434 ± 9 vs. 346 ± 5 cm/s, P < 0.0001) due to greater intrinsic aortic wall stiffness associated with lower elastin levels and higher collagen, advanced glycation end products (AGEs), and proinflammatory cytokine abundance. In old mice, apigenin restored EDD (96% ± 2%) by increasing NO bioavailability, normalized arterial ROS, oxidative stress, and antioxidant expression, and abolished ROS inhibition of EDD. Moreover, apigenin prevented foam cell formation in vitro (initiating step in atherosclerosis) and mitigated age-associated aortic stiffening (PWV 373 ± 5 cm/s) by normalizing aortic intrinsic wall stiffness, collagen, elastin, AGEs, and inflammation. Thus, apigenin is a promising therapeutic for arterial aging.NEW & NOTEWORTHY Our study provides novel evidence that oral apigenin supplementation can reverse two clinically important indicators of arterial dysfunction with age, namely, vascular endothelial dysfunction and large elastic artery stiffening, and prevents foam cell formation in an established cell culture model of early atherosclerosis. Importantly, our results provide extensive insight into the biological mechanisms of apigenin action, including increased nitric oxide bioavailability, normalization of age-related increases in arterial ROS production and oxidative stress, reversal of age-associated aortic intrinsic mechanical wall stiffening and adverse remodeling of the extracellular matrix, and suppression of vascular inflammation. Given that apigenin is commercially available as a dietary supplement in humans, these preclinical findings provide the experimental basis for future translational studies assessing the potential of apigenin to treat arterial dysfunction and reduce cardiovascular disease risk with aging.

Blunted hyperemic response to mental stress in young, non-Hispanic black men is not impacted by acute dietary nitrate supplementation

Non-Hispanic black individuals suffer from an elevated prevalence of hypertension and cardiovascular disease (CVD) relative to other populations. This elevated disease risk is, in large part, related to impaired vascular function, secondary to reduced nitric oxide (NO) bioavailability. Emerging evidence suggests that dietary nitrate supplementation improves several cardiovascular parameters, including vascular function, in part by increased NO bioavailability. However, whether these findings extend to a population of black individuals is unknown. This study tested the hypothesis that forearm blood flow responses in young, non-Hispanic, black (BL) men during a mental stress challenge would be blunted relative to young, non-Hispanic, white (WH) men. We further hypothesized that acute dietary nitrate supplementation would improve this response in BL men. This study comprised two parts (phase 1 and phase 2). Phase 1 investigated the difference in blood flow responses between young, BL, and WH men. In contrast, phase 2 investigated the effect of acute nitrate supplementation on the responses in a subset of the BL men from phase 1. Eleven (nine for phase 2) BL and eight WH men (23 ± 3 vs. 24 ± 4 yr, respectively) participated in this double-blind, placebo-controlled, randomized, crossover study. During each visit, hemodynamic responses during 3 min of mental stress were assessed in the brachial artery using duplex Doppler ultrasound. Phase 1 was completed in one visit, whereas phase 2 was completed over two visits separated by ∼1 wk. During phase 2, data were collected before and 2-h postconsumption of a beverage either high in nitrate content or nitrate depleted. In phase 1, peak forearm blood flow (FBF; P < 0.001), total FBF (P < 0.01), and forearm vascular conductance (FVC; P < 0.001) were blunted in the BL. During phase 2, prebeverage responses were similar to phase 1 and were unaffected following beverage consumption (P > 0.05 vs. prebeverage for all variables). These data indicate that young, BL men have blunted microvascular vasodilatory responses to acute mental stress, which may not be altered following acute nitrate supplementation.NEW & NOTEWORTHY This study tested the hypothesis that non-Hispanic black (BL) men have a blunted forearm hyperemic response to mental stress, which would be augmented following acute nitrate supplementation. The increase in forearm blood flow during mental stress was attenuated in BL men and was not impacted by nitrate supplementation. This supports findings of altered vascular function in this population. This is especially important as BL experience a higher prevalence of stress, which contributes to CVD risk.

Mitochondrial contributions to vascular endothelial dysfunction, arterial stiffness, and cardiovascular diseases

Cardiovascular disease (CVD) affects one in three adults and remains the leading cause of death in America. Advancing age is a major risk factor for CVD. Recent plateaus in CVD-related mortality rates in high-income countries after decades of decline highlight a critical need to identify novel therapeutic targets and strategies to mitigate and manage the risk of CVD development and progression. Vascular dysfunction, characterized by endothelial dysfunction and large elastic artery stiffening, is independently associated with an increased CVD risk and incidence and is therefore an attractive target for CVD prevention and management. Vascular mitochondria have emerged as an important player in maintaining vascular homeostasis. As such, age- and disease-related impairments in mitochondrial function contribute to vascular dysfunction and consequent increases in CVD risk. This review outlines the role of mitochondria in vascular function and discusses the ramifications of mitochondrial dysfunction on vascular health in the setting of age and disease. The adverse vascular consequences of increased mitochondrial-derived reactive oxygen species, impaired mitochondrial quality control, and defective mitochondrial calcium cycling are emphasized, in particular. Current evidence for both lifestyle and pharmaceutical mitochondrial-targeted strategies to improve vascular function is also presented.

Role of increased central arterial stiffness in macro and microvascular damage in patients with coronary artery disease

BACKGROUND

Patients with heart disease frequently have renal dysfunction manifested by a decrease in glomerular filtration rate (GFR) and / or increase of albuminuria.

OBJECTIVES

The objective was to study the possible role of increased aortic stiffness in the presence and extent of coronary artery disease (CAD) and kidney dysfunction in a group of patients with suspected CAD.

PATIENTS AND METHODS

We studied forty-eight patients undergoing coronariography for suspected coronary disease (CAD). Using applanation tonometry on the radial artery and applying a transfer function, central blood pressure values were calculated. The study of aortic stiffness was done by determining the carotid-femoral pulse velocity (Pv_c-f).

RESULTS

Of the 48 patients, 11 had no significant coronary lesions, 24 showed significant lesions in 1 or 2 coronary arteries and 13 in ≥ 3 arteries. The group with a higher degree of CD had significantly higher cPP values than the group without CD. The Pv_c-f increased progressively and significantly with the degree of CD. The logistic regression showed that Pv_c-f independently predicted the presence of CD. The relative risk of CD increased 2.5 times for each meter of increase in Pv_c-f. The GFR was negatively and significantly correlated with age and Pv_c-f was associated with albuminuria.

CONCLUSIONS

In patients with stable CD, Pv_c-f, expression of aortic stiffness, is independently associated with the existence of CD and its degree of extension. The increase in arterial stiffness also participates in the decrease in GFR and in the increase in albuminuria.

Inflammation, Nitro-Oxidative Stress, Impaired Autophagy, and Insulin Resistance as a Mechanistic Convergence Between Arterial Stiffness and Alzheimer's Disease

The average age of the world's elderly population is steadily increasing. This unprecedented rise in the aged world population will increase the prevalence of age-related disorders such as cardiovascular disease (CVD) and neurodegeneration. In recent years, there has been an increased interest in the potential interplay between CVDs and neurodegenerative syndromes, as several vascular risk factors have been associated with Alzheimer's disease (AD). Along these lines, arterial stiffness is an independent risk factor for both CVD and AD. In this review, we discuss several inflammaging-related disease mechanisms including acute tissue-specific inflammation, nitro-oxidative stress, impaired autophagy, and insulin resistance which may contribute to the proposed synergism between arterial stiffness and AD.

Tumor Necrosis Factor Alpha-Mediated Inflammation and Remodeling of the Extracellular Matrix Underlies Aortic Stiffening Induced by the Common Chemotherapeutic Agent Doxorubicin

[Figure: see text].

Network analysis of nitrate-sensitive oral microbiome reveals interactions with cognitive function and cardiovascular health across dietary interventions

Many oral bacteria reduce inorganic nitrate, a natural part of a vegetable-rich diet, into nitrite that acts as a precursor to nitric oxide, a regulator of vascular tone and neurotransmission. Aging is hallmarked by reduced nitric oxide production with associated detriments to cardiovascular and cognitive function. This study applied a systems-level bacterial co-occurrence network analysis across 10-day dietary nitrate and placebo interventions to test the stability of relationships between physiological and cognitive traits and clusters of co-occurring oral bacteria in older people. Relative abundances of Proteobacteria increased, while Bacteroidetes, Firmicutes and Fusobacteria decreased after nitrate supplementation. Two distinct microbiome modules of co-occurring bacteria, that were sensitive to nitrate supplementation, showed stable relationships with cardiovascular (Rothia-Streptococcus) and cognitive (Neisseria-Haemophilus) indices of health across both dietary conditions. A microbiome module (Prevotella-Veillonella) that has been associated with pro-inflammatory metabolism was diminished after nitrate supplementation, including a decrease in relative abundance of pathogenic Clostridium difficile. These nitrate-sensitive oral microbiome modules are proposed as potential pre- and probiotic targets to ameliorate age-induced impairments in cardiovascular and cognitive health.

Inorganic Nitrite Supplementation Improves Endothelial Function With Aging: Translational Evidence for Suppression of Mitochondria-Derived Oxidative Stress

[Figure: see text].

Dietary Nitrate and Nitric Oxide Metabolism: Mouth, Circulation, Skeletal Muscle, and Exercise Performance

Nitric oxide (NO) is a gaseous signaling molecule that plays an important role in myriad physiological processes, including the regulation of vascular tone, neurotransmission, mitochondrial respiration, and skeletal muscle contractile function. NO may be produced via the canonical NO synthase-catalyzed oxidation of l-arginine and also by the sequential reduction of nitrate to nitrite and then NO. The body's nitrate stores can be augmented by the ingestion of nitrate-rich foods (primarily green leafy vegetables). NO bioavailability is greatly enhanced by the activity of bacteria residing in the mouth, which reduce nitrate to nitrite, thereby increasing the concentration of circulating nitrite, which can be reduced further to NO in regions of low oxygen availability. Recent investigations have focused on promoting this nitrate-nitrite-NO pathway to positively affect indices of cardiovascular health and exercise tolerance. It has been reported that dietary nitrate supplementation with beetroot juice lowers blood pressure in hypertensive patients, and sodium nitrite supplementation improves vascular endothelial function and reduces the stiffening of large elastic arteries in older humans. Nitrate supplementation has also been shown to enhance skeletal muscle function and to improve exercise performance in some circumstances. Recently, it has been established that nitrate concentration in skeletal muscle is much higher than that in blood and that muscle nitrate stores are exquisitely sensitive to dietary nitrate supplementation and deprivation. In this review, we consider the possibility that nitrate represents an essential storage form of NO and discuss the integrated function of the oral microbiome, circulation, and skeletal muscle in nitrate-nitrite-NO metabolism, as well as the practical relevance for health and performance.

Pharmacokinetics of Nitrate and Nitrite Following Beetroot Juice Drink Consumption

BACKGROUND

Nitrate (NO₃ ^-)-rich beetroot (BR) juice supplementation has been shown to improve cardiovascular function via reduction to nitrite (NO₂ ^-) and then to the bioactive molecule nitric oxide (NO). However, limited research exists for the role of inorganic NO₂ ^- that is contained naturally within BR.

OBJECTIVE

As BR juice can naturally contain both NO₃ ^- and NO₂ ^- the objective of this study was to evaluate the individual effects of NO₃ ^- and NO₂ ^- consumed from BR on plasma [NO₃ ^-]/[NO₂ ^-] and their subsequent effects on various cardiovascular measures.

DESIGN

In four separate treatments, 11 healthy adults consumed 250 mL of BR containing one of the following: (i) high NO₃ ^-, low NO₂ ^- (HL; 572 mg NO₃ ^-, 32 mg NO₂ ^-); (ii) medium NO₃ ^-, medium NO₂ ^- (MM; 280 mg NO₃ ^-, 237 mg NO₂ ^-); (iii) low NO₃ ^-, medium NO₂ ^- (LM; 43 mg NO₃ ^-, 262 mg NO₂ ^-); (iv) placebo (PL; low NO₃ ^-, low NO₂ ^-: 8 mg NO₃ ^-, 5.8 mg NO₂ ^-). Plasma [NO₃ ^-]/[NO₂ ^-], blood pressure, heart rate, mean arterial pressure (MAP), cardiac output and stroke volume were measured at baseline and every hour or second hour for 6 h post-BR consumption.

OUTCOMES

Ingestion of the HL and MM BR increased plasma [NO₂ ^-] and [NO₃ ^-] after 2 h, with both remaining elevated after 6 h (p < 0.05). LM increased plasma [NO₃ ^-] (p < 0.05) but did not increase plasma [NO₂ ^-] compared to PL (p = 0.177). MAP was lower following the consumption of HL at 4 h and LM at 6 h (p < 0.05).

CONCLUSION

Inorganic NO₃ ^- consumption is the critical factor in elevating plasma [NO₃ ^-] and [NO₂ ^-]; however, both NO₂ ^- and NO₃ ^- show potential to reduce MAP. The known reduction of systolic blood pressure (SBP)/diastolic blood pressure (DBP) following NO₃ ^- supplementation was not observed, making it unclear if NO₂ ^- contributes to a reduction in SBP/DBP alongside NO₃ ^-.

Lifelong voluntary aerobic exercise prevents age- and Western diet- induced vascular dysfunction, mitochondrial oxidative stress and inflammation in mice

KEY POINTS

The results of the present study establish the temporal pattern of age-related vascular dysfunction across the adult lifespan in sedentary mice consuming a non-Western diet, and the underlying mechanisms The results demonstrate that consuming a Western diet accelerates and exacerbates vascular ageing across the lifespan in sedentary mice They also show that lifelong voluntary aerobic exercise has remarkable protective effects on vascular function throughout the lifespan, in the setting of ageing alone, as well as ageing compounded by Western diet consumption Overall, the results indicate that amelioration of mitochondrial oxidative stress and inflammation are key mechanisms underlying the voluntary aerobic exercise-associated preservation of vascular function across the lifespan in both the presence and absence of a Western dietary pattern ABSTRACT: Advancing age is the major risk factor for cardiovascular diseases, driven largely by vascular endothelial dysfunction (impaired endothelium-dependent dilatation, EDD) and aortic stiffening (increased aortic pulse wave velocity, aPWV). In humans, vascular ageing occurs in the presence of differences in diet and physical activity, but the interactive effects of these factors are unknown. We assessed carotid artery EDD and aPWV across the lifespan in mice consuming standard (normal) low-fat chow (NC) or a high-fat/high-sucrose Western diet (WD) in the absence (sedentary, SED) or presence (voluntary wheel running, VWR) of aerobic exercise. Ageing impaired nitric oxide-mediated EDD (peak EDD 88 ± 12% 6 months P = 0.003 vs. 59 ± 9% 27 months NC-SED), which was accelerated by WD (60 ± 18% 6 months WD-SED). In NC mice, aPWV increased 32% with age (423 ± 13 cm/s at 24 months P < 0.001 vs. 321 ± 12 cm/s at 6 months) and absolute values were an additional ∼10% higher at any age in WD mice (P = 0.042 vs. NC-SED). Increases in aPWV with age in NC and WD mice were associated with 30-65% increases in aortic intrinsic wall stiffness (6 vs. 19-27 months, P = 0.007). Lifelong aerobic exercise prevented age- and WD-related vascular dysfunction across the lifespan, and this protection appeared to be mediated by mitigation of vascular mitochondrial oxidative stress and inflammation. Our results depict the temporal impairment of vascular function over the lifespan in mice, acceleration and exacerbation of that dysfunction with WD consumption, the remarkable protective effects of voluntary aerobic exercise, and the underlying mechanisms.

The gut microbiome-derived metabolite trimethylamine N-oxide modulates neuroinflammation and cognitive function with aging

Aging is associated with declines in cognitive performance, which are mediated in part by neuroinflammation, characterized by astrocyte activation and higher levels of pro-inflammatory cytokines; however, the upstream drivers are unknown. We investigated the potential role of the gut microbiome-derived metabolite trimethylamine N-oxide (TMAO) in modulating neuroinflammation and cognitive function with aging. Study 1: In middle-aged and older humans (65 ± 7 years), plasma TMAO levels were inversely related to performance on NIH Toolbox Cognition Battery tests of memory and fluid cognition (both r² = 0.07, p < 0.05). Study 2: In mice, TMAO concentrations in plasma and the brain increased in parallel with aging (r² = 0.60), suggesting TMAO crosses the blood-brain barrier. The greater TMAO concentrations in old mice (27 months) were associated with higher brain pro-inflammatory cytokines and markers of astrocyte activation vs. young adult mice (6 months). Study 3: To determine if TMAO independently induces an "aging-like" decline in cognitive function, young mice (6 months) were supplemented with TMAO in chow for 6 months. Compared with controls, TMAO-supplemented mice performed worse on the novel object recognition test, indicating impaired memory and learning, and had increased neuroinflammation and markers of astrocyte activation. Study 4: Human astrocytes cultured with TMAO vs. control media exhibited changes in cellular morphology and protein markers consistent with astrocyte activation, indicating TMAO directly acts on these cells. Our results provide translational insight into a novel pathway that modulates neuroinflammation and cognitive function with aging, and suggest that TMAO might be a promising target for prevention of neuroinflammation and cognitive decline with aging.

A Paradoxical Vasodilatory Nutraceutical Intervention for Prevention and Attenuation of Migraine-A Hypothetical Review

Studies suggest that migraine pain has a vascular component. The prevailing dogma is that peripheral vasoconstriction activates baroreceptors in central, large arteries. Dilatation of central vessels stimulates nociceptors and induces cortical spreading depression. Studies investigating nitric oxide (NO) donors support the indicated hypothesis that pain is amplified when acutely administered. In this review, we provide an alternate hypothesis which, if substantiated, may provide therapeutic opportunities for attenuating migraine frequency and severity. We suggest that in migraines, heightened sympathetic tone results in progressive central microvascular constriction. Suboptimal parenchymal blood flow, we suggest, activates nociceptors and triggers headache pain onset. Administration of NO donors could paradoxically promote constriction of the microvasculature as a consequence of larger upstream central artery vasodilatation. Inhibitors of NO production are reported to alleviate migraine pain. We describe how constriction of larger upstream arteries, induced by NO synthesis inhibitors, may result in a compensatory dilatory response of the microvasculature. The restoration of central capillary blood flow may be the primary mechanism for pain relief. Attenuating the propensity for central capillary constriction and promoting a more dilatory phenotype may reduce frequency and severity of migraines. Here, we propose consideration of two dietary nutraceuticals for reducing migraine risk: L-arginine and aged garlic extracts.

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.

Targeting mitochondrial fitness as a strategy for healthy vascular aging

Cardiovascular diseases (CVD) are the leading cause of death worldwide and aging is the primary risk factor for CVD. The development of vascular dysfunction, including endothelial dysfunction and stiffening of the large elastic arteries (i.e., the aorta and carotid arteries), contribute importantly to the age-related increase in CVD risk. Vascular aging is driven in large part by oxidative stress, which reduces bioavailability of nitric oxide and promotes alterations in the extracellular matrix. A key upstream driver of vascular oxidative stress is age-associated mitochondrial dysfunction. This review will focus on vascular mitochondria, mitochondrial dysregulation and mitochondrial reactive oxygen species (ROS) production and discuss current evidence for prevention and treatment of vascular aging via lifestyle and pharmacological strategies that improve mitochondrial health. We will also identify promising areas and important considerations ('research gaps') for future investigation.

Late-life voluntary wheel running reverses age-related aortic stiffness in mice: a translational model for studying mechanisms of exercise-mediated arterial de-stiffening

Aortic stiffening, assessed as pulse-wave velocity (PWV), increases with age and is an important antecedent to, and independent predictor of, cardiovascular diseases (CVD) and other clinical disorders of aging. Aerobic exercise promotes lower levels of aortic stiffness in older adults, but the underlying mechanisms are incompletely understood, largely due to inherent challenges of mechanistic studies of large elastic arteries in humans. Voluntary wheel running (VWR) is distinct among experimental animal exercise paradigms in that it allows investigation of the physiologic effects of aerobic training without potential confounding influences of aversive molecular signaling related to forced exercise. In this study, we investigated whether VWR in mice may be a suitable model for mechanistic studies (i.e., "reverse translation") of the beneficial effects of exercise on arterial stiffness in humans. We found that 10 weeks of VWR in old mice (~ 28 months) reversed age-related elevations in aortic PWV assessed in vivo (Old VWR: 369 ± 19 vs. old sedentary: 439 ± 20 cm/s, P < 0.05). The de-stiffening effects of VWR were accompanied by normalization of age-related increases in ex vivo mechanical stiffness of aortic segments and aortic accumulation of collagen-I and advanced glycation end products, as well as lower levels of aortic superoxide and nitrotyrosine. Our results suggest that late-life VWR in mice recapitulates the aortic de-stiffening effects of exercise in humans and indicates important mechanistic roles for decreased oxidative stress and extracellular matrix remodeling. Therefore, VWR is a suitable model for further study of the mechanisms underlying beneficial effects of exercise on arterial stiffness.

Modulation of mitochondria and NADPH oxidase function by the nitrate-nitrite-NO pathway in metabolic disease with focus on type 2 diabetes

Mitochondria play fundamental role in maintaining cellular metabolic homeostasis, and metabolic disorders including type 2 diabetes (T2D) have been associated with mitochondrial dysfunction. Pathophysiological mechanisms are coupled to increased production of reactive oxygen species and oxidative stress, together with reduced bioactivity/signaling of nitric oxide (NO). Novel strategies restoring these abnormalities may have therapeutic potential in order to prevent or even treat T2D and associated cardiovascular and renal co-morbidities. A diet rich in green leafy vegetables, which contains high concentrations of inorganic nitrate, has been shown to reduce the risk of T2D. To this regard research has shown that in addition to the classical NO synthase (NOS) dependent pathway, nitrate from our diet can work as an alternative precursor for NO and other bioactive nitrogen oxide species via serial reductions of nitrate (i.e. nitrate-nitrite-NO pathway). This non-conventional pathway may act as an efficient back-up system during various pathological conditions when the endogenous NOS system is compromised (e.g. acidemia, hypoxia, ischemia, aging, oxidative stress). A number of experimental studies have demonstrated protective effects of nitrate supplementation in models of obesity, metabolic syndrome and T2D. Recently, attention has been directed towards the effects of nitrate/nitrite on mitochondrial functions including beiging/browning of white adipose tissue, PGC-1α and SIRT3 dependent AMPK activation, GLUT4 translocation and mitochondrial fusion-dependent improvements in glucose homeostasis, as well as dampening of NADPH oxidase activity. In this review, we examine recent research related to the effects of bioactive nitrogen oxide species on mitochondrial function with emphasis on T2D.