Dietary nitrate provides sustained blood pressure lowering in hypertensive patients: a randomized, phase 2, double-blind, placebo-controlled study

Recent advances in managing primary hypertension

Hypertension remains a leading risk factor for cardiovascular mortality and morbidity globally despite the availability of effective and well-tolerated antihypertensive medications. Accumulating evidence suggests a more aggressive blood pressure regulation aimed at lower targets, particularly for selected patient groups. Our concepts of the optimal method for blood pressure measurement have radically changed, maintaining appropriate standard office measurements for initial assessment but relying on out-of-office measurement to better guide our decisions. Thorough risk stratification provides guidance in decision making; however, an individualized approach is highly recommended to prevent overtreatment. Undertreatment, on the other hand, remains a major concern and is mainly attributed to poor adherence and resistant or difficult-to-control forms of the disease. This review aims to present modern perspectives, novel treatment options, including innovative technological applications and developing interventional and pharmaceutical therapies, and the major concerns emerging from several years of research and epidemiological observations related to hypertension management.

Covid-19 Quarantine: Impact of Lifestyle Behaviors Changes on Endothelial Function and Possible Protective Effect of Beetroot Juice

The current recommendation for reducing person-to-person Coronavirus 2019 (COVID-19) transmission is social distancing, including remote work and school, and home confinement. However, confinement may cause negative feelings, such as frustration, anger, boredom, and stress, in quarantined people. Furthermore, unhealthy diet and physical inactivity behaviors are commonly linked to home confinement, leading to weight gain, metabolic disorders, smoking, and exacerbated alcohol consumption. As a result, these unhealthy behaviors are typically linked to vascular endothelium damage (endothelial dysfunction), which is a first step for the development of cardiovascular disease (CVD). Given that CVD is the main cause of morbidity and mortality worldwide, attenuating the progression of endothelial dysfunction is very important for the control of CVD. Consuming vegetable rich in nitrate, such as beetroots, may be an effective way to prevent endothelial dysfunction. Several emerging studies have recommended beetroot juice in order to improve endothelial function in hypertensive, hypercholesterolemic individuals, as well as in those with CVD risk factors. Therefore, nitrate-rich vegetable consumption, such as beetroot, should be encouraged to be included in the diet during confinement from COVID-19 outbreaks in order to alleviate the potential negative effect of home confinement on cardiovascular health.

Red Beetroot Betalains: Perspectives on Extraction, Processing, and Potential Health Benefits

In recent years, red beetroot has received a growing interest due to its abundant source of bioactive compounds, particularly betalains. Red beetroot betalains have great potential as a functional food ingredient employed in the food and medical industry due to their diverse health-promoting effects. Betalains from red beetroot are natural pigments, which mainly include either yellow-orange betaxanthins or red-violet betacyanins. However, betalains are quite sensitive toward heat, pH, light, and oxygen, which leads to the poor stability during processing and storage. Therefore, it is necessary to comprehend the impacts of the processing approaches on betalains. In this review, the effective extraction and processing methods of betalains from red beetroot were emphatically reviewed. Furthermore, a variety of recently reported bioactivities of beetroot betalains were also summarized. The present work can provide a comprehensive review on both conventional and innovative extraction techniques, processing methods, and the stability of betalains.

The effect of dietary nitrate and vitamin C on endothelial function, oxidative stress and blood lipids in untreated hypercholesterolemic subjects: A randomized double-blind crossover study

BACKGROUND

Vitamin C may enhance nitric oxide (NO) production through stepwise reduction of dietary nitrate (NO₃) to nitrite (NO₂) to NO. The combined effect of vitamin C and NO₃ supplementation is relatively unexplored in untreated hypercholesterolemia.

AIMS

We aimed to examine whether co-administration of vitamin C and nitrate for 4-weeks would improve endothelial function (primary outcome), plasma NO metabolites, oxidative stress, and blood lipids (secondary outcomes).

METHODS

Subjects 50-70 years of age with low density lipoprotein (LDL) > 130 mg/dL and RHI ≤2 were enrolled in this randomized double-blind crossover study. Subjects were assigned to two 4-week supplementation treatments starting with 70 ml of concentrated beetroot juice (CBJ) with 1000 mg of vitamin C (NC) or CBJ with matched placebo (N), then switched to alternate treatment following 2-week washout. The change in reactive hyperemia index (RHI), sum of plasma NO metabolites (NO₂ + NO₃ (NOx)), oxidized LDL (oxLDL), and serum lipids were assessed at baseline and at 4-weeks of each treatment period.

RESULTS

Eighteen subjects (11M:7F) completed all study visits. No significant treatment differences were observed in RHI change (N: 0.21 ± 0.12; NC: 0.20 ± 0.17; p = 0.99). Secondary analysis revealed that a subgroup of NC subjects who started with a baseline RHI of <1.67 (threshold value for ED) had greater improvements in RHI compared to subjects with RHI >1.67 (1.23 ± 0.15 to 1.96 ± 0.19; n = 8 vs. 1.75 ± 0.11 to 1.43 ± 0.10; n = 8; p = 0.02). Compared to N, NC experienced a significant increase in plasma NOx (N: 94.2 ± 15.5 μmol/L; NC: 128.7 ± 29.1 μmol/L; p = 0.01). Although there was no significant difference in oxLDL change between treatments (N: -1.08 ± 9.8 U/L; NC: -6.07 ± 9.14 U/L; p = 0.19), NC elicited significant reductions in LDL (N: 2.2 ± 2; NC: -10.7 ± 23; p = 0.049), triglycerides (N: 14.6 ± 43; NC: -43.7 ± 45; p = 0.03), and no change in serum high density lipoprotein. Within treatment group comparisons showed that only NC reduced oxLDL significantly from baseline to 4 weeks (p = 0.01).

CONCLUSIONS

No between intervention differences were observed in RHI. RHI only improved in NC subjects with ED at intervention baseline. Four weeks of NC enriched the NO pool and promoted reduction of blood lipids and oxidative stress in subjects with hypercholesterolemia. These preliminary findings highlight a supplementation strategy that may reduce the progression of atherosclerotic disease and deserves further attention in studies using flow mediated dilation methods.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov (NCT04283630).

How Periodontal Disease and Presence of Nitric Oxide Reducing Oral Bacteria Can Affect Blood Pressure

Nitric oxide (NO), a small gaseous and multifunctional signaling molecule, is involved in the maintenance of metabolic and cardiovascular homeostasis. It is endogenously produced in the vascular endothelium by specific enzymes known as NO synthases (NOSs). Subsequently, NO is readily oxidized to nitrite and nitrate. Nitrite is also derived from exogenous inorganic nitrate (NO₃) contained in meat, vegetables, and drinking water, resulting in greater plasma NO₂ concentration and major reduction in systemic blood pressure (BP). The recycling process of nitrate and nitrite to NO (nitrate-nitrite-NO pathway), known as the enterosalivary cycle of nitrate, is dependent upon oral commensal nitrate-reducing bacteria of the dorsal tongue. Veillonella, Actinomyces, Haemophilus, and Neisseria are the most copious among the nitrate-reducing bacteria. The use of chlorhexidine mouthwashes and tongue cleaning can mitigate the bacterial nitrate-related BP lowering effects. Imbalances in the oral reducing microbiota have been associated with a decrease of NO, promoting endothelial dysfunction, and increased cardiovascular risk. Although there is a relationship between periodontitis and hypertension (HT), the correlation between nitrate-reducing bacteria and HT has been poorly studied. Restoring the oral flora and NO activity by probiotics may be considered a potential therapeutic strategy to treat HT.

Beetroot, a Remarkable Vegetable: Its Nitrate and Phytochemical Contents Can be Adjusted in Novel Formulations to Benefit Health and Support Cardiovascular Disease Therapies

The cardioprotective effects of dietary nitrate from beetroot in healthy and hypertensive individuals are undeniable and irrefutable. Nitrate and nitrate-derived nitrite are precursors for nitric oxide synthesis exhibiting an effect on cardiomyocytes and myocardial ischemia/reperfusion, improving endothelial function, reducing arterial stiffness and stimulating smooth muscle relaxation, decreasing systolic and diastolic blood pressures. Beetroot phytochemicals like betanin, saponins, polyphenols, and organic acids can resist simulated gastrointestinal digestion, raising the hypothesis that the cardioprotective effects of beetroots result from the combination of nitrate/nitrite and bioactive compounds that limit the generation of reactive oxygen species and modulate gene expression. Nitrate and phytochemical concentrations can be adjusted in beet formulations to fulfill requirements for acute or long-term supplementations, enhancing patient adherence to beet intervention. Based on in vitro, in vivo, and clinical trials, beet nitrate and its bioactive phytochemicals are promising as a novel supportive therapy to ameliorate cardiovascular diseases.

Microbial Peer Pressure: The Role of the Gut Microbiota in Hypertension and Its Complications

There is increasing evidence of the influence of the gut microbiota on hypertension and its complications, such as chronic kidney disease, stroke, heart failure, and myocardial infarction. This is not surprising considering that the most common risk factors for hypertension, such as age, sex, medication, and diet, can also impact the gut microbiota. For example, sodium and fermentable fiber have been studied in relation to both hypertension and the gut microbiota. By combining second- and, now, third-generation sequencing with metabolomics approaches, metabolites, such as short-chain fatty acids and trimethylamine N-oxide, and their producers, have been identified and are now known to affect host physiology and the cardiovascular system. The receptors that bind these metabolites have also been explored with positive findings-examples include known short-chain fatty acid receptors, such as G-protein coupled receptors GPR41, GPR43, GPR109a, and OLF78 in mice. GPR41 and OLF78 have been shown to have inverse roles in blood pressure regulation, whereas GPR43 and GPR109A have to date been demonstrated to impact cardiac function. New treatment options in the form of prebiotics (eg, dietary fiber), probiotics (eg, Lactobacillus spp.), and postbiotics (eg, the short-chain fatty acids acetate, propionate, and butyrate) have all been demonstrated to be beneficial in lowering blood pressure in animal models, but the underlying mechanisms remain poorly understood and translation to hypertensive patients is still lacking. Here, we review the evidence for the role of the gut microbiota in hypertension, its risk factors, and cardiorenal complications and identify future directions for this exciting and fast-evolving field.

Nitrite Production from Nitrate and Its Link with Lactate Metabolism in Oral Veillonella spp

Veillonella species are among the major anaerobes in the oral cavity and are frequently detected in both caries lesions and healthy oral microbiomes. They possess the ability to utilize lactate and convert nitrate (NO₃ ^-) into nitrite (NO₂ ^-). Recently, interest in NO₂ ^- has increased rapidly because of its beneficial effects on oral and general health; i.e., it inhibits the growth and metabolism of oral pathogenic bacteria, such as Streptococcus mutans, and lowers systemic blood pressure. However, there is only limited information about the biochemical characteristics of NO₂ ^- production by Veillonella species. We found that NO₃ ^- did not inhibit the growth of Veillonella atypica or Veillonella parvula, and it inhibited the growth of Streptococcus mutans only at a high concentration (100 mM). However, NO₂ ^- inhibited the growth of Streptococcus mutans at a low concentration (0.5 mM), while a higher concentration of NO₂ ^- (20 mM) was needed to inhibit the growth of Veillonella species. NO₂ ^- production by Veillonella species was increased by environmental factors (lactate, acidic pH, and anaerobic conditions) and growth conditions (the presence of NO₃ ^- or NO₂ ^-) and was linked to anaerobic lactate metabolism. A stoichiometric evaluation revealed that NO₃ ^- is reduced to NO₂ ^- by accepting reducing power derived from the oxidization of lactate. These findings suggest that the biochemical characteristics of NO₂ ^- production from NO₃ ^- and its linkage with lactate metabolism in oral Veillonella species may play a key role in maintaining good oral and general health.IMPORTANCE The prevalence of dental caries is still high around the world. Dental caries is initiated when the teeth are exposed to acid, such as lactic acid, produced via carbohydrate metabolism by acidogenic microorganisms. Veillonella species, which are among the major oral microorganisms, are considered to be beneficial bacteria due to their ability to convert lactic acid to weaker acids and to produce NO₂ ^- from NO₃ ^-, which is thought to be good for both oral and general health. Therefore, it is clear that there is a need to elucidate the biochemical characteristics of NO₂ ^- production in Veillonella species. The significance of our research is that we have found that lactate metabolism is linked to NO₂ ^- production by Veillonella species in the environment found in the oral cavity. This study suggests that Veillonella species are potential candidates for maintaining oral and general health.

Signalling, Metabolic Pathways and Iron Homeostasis in Endothelial Cells in Health, Atherosclerosis and Alzheimer's Disease

Endothelial cells drive the formation of new blood vessels in physiological and pathological contexts such as embryonic development, wound healing, cancer and ocular diseases. Once formed, all vessels of the vasculature system present an endothelial monolayer (the endothelium), lining the luminal wall of the vessels, that regulates gas and nutrient exchange between the circulating blood and tissues, contributing to maintaining tissue and vascular homeostasis. To perform their functions, endothelial cells integrate signalling pathways promoted by growth factors, cytokines, extracellular matrix components and signals from mechanosensory complexes sensing the blood flow. New evidence shows that endothelial cells rely on specific metabolic pathways for distinct cellular functions and that the integration of signalling and metabolic pathways regulates endothelial-dependent processes such as angiogenesis and vascular homeostasis. In this review, we provide an overview of endothelial functions and the recent advances in understanding the role of endothelial signalling and metabolism in physiological processes such as angiogenesis and vascular homeostasis and vascular diseases. Also, we focus on the signalling pathways promoted by the transmembrane protein Neuropilin-1 (NRP1) in endothelial cells, its recently discovered role in regulating mitochondrial function and iron homeostasis and the role of mitochondrial dysfunction and iron in atherosclerosis and neurodegenerative diseases.

Dietary nitrate reduces blood pressure and cerebral artery velocity fluctuations and improves cerebral autoregulation in transient ischemic attack patients

We found dietary nitrate supplementation reduced blood pressure and brain blood flow fluctuations and improved the relationship between blood pressure and brain blood flow in transient ischemic attack patients. Meanwhile, dietary nitrate had no effects on the brain blood vessels’ response to CO2. We attribute the improved brain blood flow stability to the improved myogenic control of blood pressure with dietary nitrate. Our findings indicate that dietary nitrate could be an effective strategy for stabilizing blood pressure and brain blood flow following transient ischemic attack.

Nitrate and nitrite-based therapy to attenuate cardiovascular remodelling in arterial hypertension

Hypertension is a highly prevalent disease marked by vascular and cardiac maladaptive remodelling induced mainly by renin-angiotensin system activation followed by oxidative stress. Here, we briefly describe these damages and review the current evidence supporting a potential role for nitrate and nitrite as antihypertensive molecules that act via nitric oxide (NO) formation-dependent and NO formation-independent mechanisms and how nitrate/nitrite inhibits cardiovascular remodelling in hypertension. The renin-angiotensin system activation and oxidative stress converge to activate proteases involved in cardiovascular remodelling in hypertension. Besides these proteases, several investigations have demonstrated that reduced endogenous NO bioavailability is a central pathological event in hypertension. In this regard, nitrate/nitrite, long considered inert products of NO, is now known as physiological molecules able to reduce blood pressure in hypertensive patients and in different experimental models of hypertension. These effects are associated with the formation of NO and other NO-related molecules, which could induce S-nitrosylation of target proteins. However, it remains unclear whether S-nitrosylation is an essential mechanism for the anti-remodelling effects of nitrate/nitrite in hypertension. Moreover, nitrate/nitrite produces antioxidant effects associated with the inhibition of signalling pathways involved in cardiovascular remodelling. Together, these findings may help to establish nitrate and nitrite as effective therapies in hypertension-induced cardiovascular remodelling.

Dietary nitrate supplementation does not influence thermoregulatory or cardiovascular strain in older individuals during severe ambient heat stress

NEW FINDINGS

What is the central question of this study? Does dietary nitrate supplementation with beetroot juice attenuate thermoregulatory and cardiovascular strain in older adults during severe heat stress? What is the main finding and its importance? A 7-day nitrate supplementation regimen lowered resting mean arterial pressure in thermoneutral conditions. During heat stress, core and mean skin temperatures, vasodilatory responses, sweat loss, heart rate and left ventricular function were unchanged, and mean arterial pressure was only transiently reduced, post-supplementation. These data suggest nitrate supplementation with beetroot juice does not mitigate thermoregulatory or cardiovascular strain in heat-stressed older individuals.

ABSTRACT

This study tested the hypothesis that dietary nitrate supplementation with concentrated beetroot juice attenuates thermoregulatory and cardiovascular strain in older individuals during environmental heat stress. Nine healthy older individuals (six females, three males; aged 67 ± 5 years) were exposed to 42.5 ± 0.1°C and 34.0 ± 0.5% relative humidity conditions for 120 min before (CON) and after 7 days of dietary nitrate supplementation with concentrated beetroot juice (BRJ; 280 ml, ∼16.8 mmol of nitrate daily). Core and skin temperatures, body mass changes (indicative of whole-body sweat loss), skin blood flow and cutaneous vascular conductance, forearm blood flow and vascular conductance, heart rate, arterial blood pressures and indices of cardiac function were measured. The 7-day beetroot juice regimen increased plasma nitrate/nitrite levels from 27.4 ± 15.2 to 477.0 ± 102.5 μmol l^-1 (P < 0.01) and lowered resting mean arterial pressure from 90 ± 7 to 83 ± 10 mmHg at baseline under thermoneutral conditions (P = 0.02). However, during subsequent heat stress, no differences in core and skin temperatures, skin blood flow and vascular conductance, forearm blood flow and vascular conductance, whole-body sweat loss, heart rate, and echocardiographic indices of systolic function and diastolic filling were evident following nitrate supplementation (all P > 0.05). Mean arterial pressure was lower in BRJ vs. CON during heat stress (treatment-by-time interaction: P = 0.02). Overall, these findings suggest that dietary nitrate supplementation with concentrated beetroot juice does not attenuate thermoregulatory or cardiovascular strain in older individuals exposed to severe ambient heat stress.

Inorganic nitrite bioactivation and role in physiological signaling and therapeutics

The bioactivation of inorganic nitrite refers to the conversion of otherwise 'inert' nitrite to the diatomic signaling molecule nitric oxide (NO), which plays important roles in human physiology and disease, notably in the regulation of vascular tone and blood flow. While the most well-known sources of NO are the nitric oxide synthase (NOS) enzymes, another source of NO is the nitrate-nitrite-NO pathway, whereby nitrite (obtained from reduction of dietary nitrate) is further reduced to form NO. The past few decades have seen extensive study of the mechanisms of NO generation through nitrate and nitrite bioactivation, as well as growing appreciation of the contribution of this pathway to NO signaling in vivo. This review, prepared for the volume 400 celebration issue of Biological Chemistry, summarizes some of the key reactions of the nitrate-nitrite-NO pathway such as reduction, disproportionation, dehydration, and oxidative denitrosylation, as well as current evidence for the contribution of the pathway to human cardiovascular physiology. Finally, ongoing efforts to develop novel medical therapies for multifarious conditions, especially those related to pathologic vasoconstriction and ischemia/reperfusion injury, are also explored.

Association between vegetable consumption and calf venous compliance in healthy young adults

BACKGROUND

Venous compliance decreases with aging and/or physical inactivity, which is thought to be involved partly in the pathogenesis of cardiovascular disease such as hypertension. This suggests that it is important to maintain high venous compliance from a young age in order to prevent cardiovascular disease. Both nutrient and exercise could play an important role in the improvement and maintenance of vascular health. Indeed, habitual endurance exercise is known to improve the venous compliance, although little is known about the effect of diet on venous compliance. Considering that higher consumption of vegetables could contribute to the arterial vascular health and the decreased blood pressure, it is hypothesized that venous compliance may be greater as vegetable intake is higher. Thus, the purpose of this study was to clarify the association between vegetable intake and venous compliance in healthy young adults.

METHODS

Dietary intake was assessed in 94 subjects (male: n = 44, female: n = 50) using a self-administered diet history questionnaire (DHQ). Intakes of nutrients and food groups that were obtained from the DHQ were adjusted according to total energy intake using the residual method. Based on the adjusted intake of food groups, total vegetable intake was calculated as the sum of green/yellow and white vegetables consumed. Calf volume was measured using venous occlusion plethysmography with a cuff deflation protocol. Calf venous compliance was calculated as the numerical derivative of the cuff pressure-calf volume curve. In addition, circulatory responses (heart rate and systolic and diastolic blood pressure) at resting and maximal oxygen uptake were assessed in all subjects.

RESULTS

Mean value of total vegetables intake was 162.2 ± 98.2 g/day. Simple linear regression analysis showed that greater venous compliance was significantly associated with higher total vegetable consumption (r = 0.260, P = 0.011) and green/yellow vegetable intake (r = 0.351, P = 0.001) but not white vegetable intake (r = 0.013, P = 0.902). These significant associations did not change in the multivariate linear regression models which were adjusted by sex and maximal oxygen uptake.

CONCLUSION

These findings suggest that higher consumption of vegetables, especially of the green/yellow vegetables, may be associated with greater venous compliance in young healthy adults.

Potential health effects of dietary nitrate supplementation in aging and chronic degenerative disease

In the United States, latest projections indicate the number of adults 65 years of age and older is expected to double by 2050. Given that increased oxidative stress is a hallmark of aging, it is understandable that waning nitric oxide and chronic degenerative disease arise in tandem. To this end, translational evidence-based strategies are needed to mitigate the impending toll on personal and public health. Dietary nitrate supplementation, particularly in the form of beetroot juice, is an active area of inquiry that has gained considerable attention in recent years. Compelling evidence has revealed beetroot juice can elicit potent physiological responses that may offer associated health benefits for multiple clinical disorders including hypertension, dementia, and sarcopenia. Even in the absence of overt disease, age-related impairments in cardiovascular and skeletal muscle function may uniquely benefit from beetroot juice supplementation as evidence has shown blood pressure lowering effects and improved muscle function/contractility - presumably from increased nitric oxide bioavailability. This, in turn, presents a practical opportunity for susceptible populations to support ease of movement and exercise tolerance, both of which may promote free-living physical activity. A theoretical rationale details the potential health effects of dietary nitrate supplementation, wherein a working framework hypothesizes beetroot juice consumption prior to structured exercise training may offer synergistic benefits to aid healthy aging and independent-living among older adults.

Does the Oral Microbiome Play a Role in Hypertensive Pregnancies?

Chronic hypertension during gestation is associated with an increased risk of adverse pregnancy outcomes including pre-eclampsia, fetal growth restriction and preterm birth. Research into new chemotherapeutic regimes for the treatment of hypertension in pregnancy is limited due to concerns about fetal toxicity and teratogenicity, and new therapeutic avenues are being sought in alternative physiological pathways. Historically, generation of the vasodilator nitric oxide was believed to be solely from L-arginine by means of nitric oxide synthase enzymes. Recently, a novel pathway for the reduction of dietary inorganic nitrate to nitrite by the bacteria in the oral cavity and subsequently to vasodilatory nitric oxide within the body has been uncovered. Dietary nitrate is abundant in green leafy vegetables, including beetroot and spinach, and reduction of exogenous nitrate to nitrite by oral bacteria can increase nitric oxide in the vasculature, lessening hypertension. Supplements rich in nitrate may be an attractive choice for treatment due to fewer side effects than drugs that are currently used to treat hypertensive pregnancy disorders. Additionally, manipulation of the composition of the oral microbiota using pro- and prebiotics in tandem with additional dietary interventions to promote cardiovascular health during gestation may offer a safe and effective means of treating hypertensive pregnancy disorders including gestational hypertension and pre-eclampsia. The use of dietary inorganic nitrate as a supplement during pregnancy requires further exploration and large scale studies before it may be considered as part of a treatment regime. The aim of this article is to review the current evidence that oral microbiota plays a role in hypertensive pregnancies and whether it could be manipulated to improve patient outcomes.

Nitrate-Rich Beetroot Juice Reduces Blood Pressure in Tanzanian Adults with Elevated Blood Pressure: A Double-Blind Randomized Controlled Feasibility Trial

BACKGROUND

In Sub-Saharan Africa, current strategies are struggling to control the burgeoning hypertension epidemic. Dietary interventions such as inorganic nitrate or folic acid supplementation could represent promising strategies for reducing blood pressure (BP) in this setting.

OBJECTIVES

This feasibility study explores the effects of dietary inorganic nitrate supplementation, alone or in combination with folic acid, on BP in Tanzanian adults with elevated BP in Tanzania.

METHODS

A placebo-controlled, double-blind, randomized controlled feasibility trial was conducted. Forty-seven middle-aged and older participants (age: 50-70 y, BMI: 26.3-29.1 kg/m2) were randomly assigned to 3 conditions for a period of 60 d: 1) high-nitrate beetroot juice (∼400 mg nitrate) and folic acid (∼5 mg folic acid) (N + F), 2) high-nitrate beetroot juice and placebo (N + P), or 3) nitrate-depleted beetroot juice and placebo (P + P). Clinic and 24-h ambulatory BP and measurements of compliance in plasma (nitrate and folate concentrations) and saliva (nitrate and nitrite) were obtained at baseline, 30 d, and 60 d.

RESULTS

Baseline resting systolic and diastolic BP (mean ± SD) was 151.0 ± 19.4 mm Hg and 91.8 ± 11.7 mm Hg, respectively. Compliance to the interventions was high (>90%) in all groups which was confirmed by the significant increase in nitrate and folic acid concentrations in plasma and saliva samples in the treatment arms. After 60 d, 24-h systolic BP dropped by -10.8 ± 9.8 mm Hg (P < 0.001), -6.1 ± 13.2 mm Hg (P = 0.03), and -0.3 ± 9.7 mm Hg (P = 0.83) in the N + P, N + F, and P + P groups, respectively. There was a significant decrease in 24-h diastolic BP in the N + P group (-5.4 ± 5.0 mm Hg, P = 0.004), whereas changes were not significant in the N + F (-1.8 ± 8.1 mm Hg, P = 0.32) and P + P (1.6 ± 8.3 mm Hg, P = 0.43) groups.

CONCLUSIONS

Dietary inorganic nitrate represents a potential nutritional strategy to lessen the hypertension epidemic in Sub-Saharan Africa. These findings support the rationale for future long-term investigations exploring the efficacy of dietary nitrate for lowering BP and attenuating cardiovascular disease risk in this setting.This trial was registered at isrctn.com as ISRCTN67978523.

The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway

In contrast to nitric oxide, which has well established and important roles in the regulation of blood flow and thrombosis, neurotransmission, the normal functioning of the genitourinary system, and the inflammation response and host defense, its oxidized metabolites nitrite and nitrate have, until recently, been considered to be relatively inactive. However, this view has been radically revised over the past decade and more. Much evidence has now accumulated demonstrating that nitrite serves as a storage form of nitric oxide, releasing nitric oxide preferentially under acidic and/or hypoxic conditions but also occurring under physiologic conditions: a phenomenon that is catalyzed by a number of distinct mammalian nitrite reductases. Importantly, preclinical studies demonstrate that reduction of nitrite to nitric oxide results in a number of beneficial effects, including vasodilatation of blood vessels and lowering of blood pressure, as well as cytoprotective effects that limit the extent of damage caused by an ischemia/reperfusion insult, with this latter issue having been translated more recently to the clinical setting. In addition, research has demonstrated that the other main metabolite of the oxidation of nitric oxide (i.e., nitrate) can also be sequentially reduced through processing in vivo to nitrite and then nitrite to nitric oxide to exert a range of beneficial effects-most notably lowering of blood pressure, a phenomenon that has also been confirmed recently to be an effective method for blood pressure lowering in patients with hypertension. This review will provide a detailed description of the pathways involved in the bioactivation of both nitrate and nitrite in vivo, their functional effects in preclinical models, and their mechanisms of action, as well as a discussion of translational exploration of this pathway in diverse disease states characterized by deficiencies in bioavailable nitric oxide. SIGNIFICANCE STATEMENT: The past 15 years has seen a major revision in our understanding of the pathways for nitric oxide synthesis in the body with the discovery of the noncanonical pathway for nitric oxide generation known as the nitrate-nitrite-nitric oxide pathway. This review describes the molecular components of this pathway, its role in physiology, potential therapeutics of targeting this pathway, and their impact in experimental models, as well as the clinical translation (past and future) and potential side effects.

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.

Effectiveness of dietary inorganic nitrate for lowering blood pressure in hypertensive adults: a systematic review

OBJECTIVE

The objective of this review was to evaluate the effectiveness of inorganic nitrate on blood pressure in hypertensive adults.

INTRODUCTION

Hypertension is associated with increased risk of morbidity and mortality in adults. Inorganic nitrate could be beneficial for lowering blood pressure and reducing cardiovascular disease risks. Evidence related to the treatment of hypertension through sources of inorganic nitrate has been presented.

INCLUSION CRITERIA

The review considered studies on adults aged 18 years and over, with blood pressure greater than 120/80 mmHg, undergoing interventions focusing on the effects of inorganic nitrate on blood pressure. Studies that included inorganic nitrate intake via dietary modification, in the form of a dietary supplement, and/or by the consumption of beetroot juice were considered. The comparator was no intervention of inorganic nitrate; different dosage, frequency, duration of inorganic nitrate; and other interventions that are administered to reduce and manage blood pressure. The primary outcomes were systolic and diastolic blood pressure effects. Experimental, quasi-experimental, analytical observational and pilot study designs were considered for inclusion.

METHODS

Databases were searched for published and unpublished studies, available in English, from January 2013 to January 2018. Critical appraisal was conducted using standardized instruments from the Joanna Briggs Institute (JBI) and the methodological quality of included studies was considered to be moderate. Data were extracted using the JBI data extraction instrument. Data were presented in a narrative form due to the heterogeneity of included studies.

RESULTS

Twelve papers were included in the systematic review with a total of 321 participants. Ten were randomized controlled trials and two were quasi-experimental studies. All participants had baseline blood pressures greater than 120/80 mmHg. Some studies included participants with comorbidities such as diabetes or heart failure with preserved ejection fraction. Inorganic nitrate was administered multiple ways throughout the studies including the following: beetroot juice, beetroot gel, nitric oxide lozenge, high nitrate diet, and raw and cooked beet juice. Doses and treatment intervals varied. Some studies included exercise as part of the intervention protocol.Meta-analysis was not conducted due to heterogeneity that existed within the studies. Blood pressure was measured in multiple settings by manual, digital or ambulatory means. The noted outcome patterns were as follows: no change in systolic blood pressure and diastolic blood pressure, decrease in systolic blood pressure and diastolic blood pressure, or decrease in systolic blood pressure with no change in diastolic blood pressure. Possible reasons for the diverse findings include the following: age, comorbidities, use of antihypertensives by participants; source and dose of nitrate; and intervention and follow-up time frames.

CONCLUSIONS

There is insufficient evidence to support or refute the use of inorganic nitrate for any effect on blood pressure at this time. Therefore, there is no concrete base for the development of practice guidelines until stronger evidence becomes available. The gaps in the literature along with the study limitations identified necessitate the need for more research on inorganic nitrate and how it relates to blood pressure.

Feasibility and acceptability of a nutritional intervention testing the effects of nitrate-rich beetroot juice and folic acid on blood pressure in Tanzanian adults with elevated blood pressure

Sub-Saharan African countries are experiencing an alarming increase in hypertension prevalence. This study evaluated the feasibility and acceptability of nitrate-rich beetroot and folate supplementation, alone or combined, for the reduction of blood pressure (BP) in Tanzanian adults with elevated BP. This was a three-arm double-blind, placebo-controlled, parallel randomised clinical trial. Forty-eight participants were randomised to one of three groups to follow a specific 60-day intervention which included a: (1) combined intervention (beetroot juice + folate), (2) single intervention (beetroot juice + placebo), and (3) control group (nitrate-depleted beetroot juice + placebo). Forty-seven participants (age: 50-70 years) completed the study. The acceptability of the interventions was high. Self-reported compliance to the interventions was more than 90% which was confirmed by the significant increase in nitrate and folate concentrations in plasma and saliva samples in the treatment arms. This study provides important information for the design of high-nitrate interventions to reduce BP in Sub-Saharan African countries.

Beetroot juice lowers blood pressure and improves endothelial function in pregnant eNOS-/- mice: importance of nitrate-independent effects

KEY POINTS

Maternal hypertension is associated with increased rates of pregnancy pathologies, including fetal growth restriction, due at least in part to reductions in nitric oxide (NO) bioavailability and associated vascular dysfunction. Dietary nitrate supplementation, from beetroot juice (BRJ), has been shown to increase NO bioavailability and improve cardiovascular function in both preclinical and clinical studies. This study is the first to investigate effects of dietary nitrate supplementation in a pregnant animal model. Importantly, the effects of nitrate-containing BRJ were compared with both 'placebo' (nitrate-depleted) BRJ as well as water to control for potential nitrate-independent effects. Our data show novel, nitrate-independent effects of BRJ to lower blood pressure and improve vascular function in endothelial nitric oxide synthase knockout (eNOS^-/- ) mice. These findings suggest potential beneficial effects of BRJ supplementation in pregnancy, and emphasize the importance of accounting for nitrate-independent effects of BRJ in study design and interpretation.

ABSTRACT

Maternal hypertension is associated with adverse pregnancy outcomes, including fetal growth restriction (FGR), due in part to reductions in nitric oxide (NO) bioavailability. We hypothesized that maternal dietary nitrate administration would increase NO bioavailability to reduce systolic blood pressure (SBP), improve vascular function and increase fetal growth in pregnant endothelial NO synthase knockout (eNOS^-/- ) mice, which exhibit hypertension, endothelial dysfunction and FGR. Pregnant wildtype (WT) and eNOS^-/- mice were supplemented with nitrate-containing beetroot juice (BRJ+) from gestational day (GD) 12.5. Control mice received an equivalent dose of nitrate-depleted BRJ (BRJ-) or normal drinking water. At GD17.5, maternal SBP was measured; at GD18.5, maternal nitrate/nitrite concentrations, uterine artery (UtA) blood flow and endothelial function were assessed, and pregnancy outcomes were determined. Plasma nitrate concentrations were increased in both WT and eNOS^-/- mice supplemented with BRJ+ (P < 0.001), whereas nitrite concentrations were increased only in eNOS^-/- mice (P < 0.001). BRJ- did not alter nitrate/nitrite concentrations. SBP was lowered and UtA endothelial function was enhanced in eNOS^-/- mice supplemented with either BRJ+ or BRJ-, indicating nitrate-independent effects of BRJ. Improvements in endothelial function in eNOS^-/- mice were abrogated in the presence of 25 mm KCl, implicating enhanced EDH signalling in BRJ- treated animals. At GD18.5, eNOS^-/- fetuses were significantly smaller than WT animals (P < 0.001), but BRJ supplementation did not affect fetal weight. BRJ may be a beneficial intervention in pregnancies associated with hypertension, endothelial dysfunction and reduced NO bioavailability. Our data showing biological effects of non-nitrate components of BRJ have implications for both interpretation of previous findings and in the design of future clinical trials.

Effect of inorganic nitrate on exercise capacity, mitochondria respiration, and vascular function in heart failure with reduced ejection fraction

This is the largest study to date to examine the effects of inorganic nitrate supplementation in patients with heart failure with reduced ejection fraction (HFrEF) and the first to include measures of vascular function and mitochondrial respiration. Although daily supplementation increased plasma nitrite, our data indicate that supplementation with inorganic nitrate as a standalone treatment is ineffective at improving exercise capacity, vascular function, or mitochondrial respiration in patients with HFrEF.

A randomised, factorial trial to reduce arterial stiffness independently of blood pressure: Proof of concept? The VaSera trial testing dietary nitrate and spironolactone

AIMS

To test if spironolactone or dietary nitrate from beetroot juice could reduce arterial stiffness as aortic pulse wave velocity (PWVart), a potential treatment target, independently of blood pressure.

METHODS

Daily spironolactone (≤50 mg) vs doxazosin (control ≤16 mg) and 70 mL beetroot juice (Beet-It ≤11 mmol nitrate) vs nitrate-depleted juice (placebo; 0 mmol nitrate) were tested in people at risk or with type-2 diabetes using a double-blind, 6-month factorial trial. Vascular indices (baseline, 12, 24 weeks) were cardiac-ankle vascular index (CAVI), a nominally pressure-independent stiffness measure (primary outcome), PWVart secondary, central systolic pressure and augmentation. Analysis was intention-to-treat, adjusted for systolic pressure differences between trial arms.

RESULTS

Spironolactone did not reduce stiffness, with evidence for reduced CAVI on doxazosin rather than spironolactone (mean difference [95% confidence interval]; 0.25 [-0.3, 0.5] units, P = .080), firmer for PWVart (0.37 [0.01, 0.7] m/s, P = .045). There was no difference in systolic pressure reduction between spironolactone and doxazosin (0.7 [-4.8, 3.3] mmHg, P = .7). Circulating nitrate and nitrite increased on active vs placebo juice, with central systolic pressure lowered -2.6 [-4.5, - 0.8] mmHg, P = .007 more on the active juice, but did not reduce CAVI, PWVart or peripheral pressure. Change in nitrate and nitrite concentrations were 1.5-fold [1.1-2.2] and 2.2-fold [1.3, 3.6] higher on spironolactone than on doxazosin respectively; both P < .05.

CONCLUSION

Contrary to our hypothesis, in at-risk/type 2 diabetes patients, spironolactone did not reduce arterial stiffness, rather PWVart was lower on doxazosin. Dietary nitrate elevated plasma nitrite, selectively lowering central systolic pressure, observed previously for nitrite.

Acute Ingestion of A Novel Nitrate-Rich Dietary Supplement Significantly Increases Plasma Nitrate/Nitrite in Physically Active Men and Women

Background: Dietary supplements purported to increase circulating nitric oxide are very popular among consumers. We determined the acute impact of two novel dietary supplements on plasma nitrate/nitrite (NOx) and nitrite alone. Methods: 20 men and women (age: 24 ± 5 years) ingested two different nitrate-rich supplements (Resync Recovery Blend at 7.5 g and 15 g; Resync Collagen Blend at 21 g), or placebo, on four different days. Fasting blood samples were obtained before and 75 min following ingestion and analyzed for NOx and nitrite. Results: Nitrite was not differently impacted by treatment (p > 0.05). The NOx response for men and women was very similar, with no sex interactions noted (p > 0.05). Condition (p < 0.0001), time (p < 0.0001), and condition x time (p < 0.0001) effects were noted for NOx. Values increased from baseline to post-ingestion for the Resync Recovery Blend at 7.5 g (11 ± 9 to 101 ± 48 µM) and at 15 g (9 ± 5 to 176 ± 91 µM), as well as for the Resync Collagen Blend (9 ± 9 to 46 ± 21 µM), while values for placebo remained stable (9 ± 7 to 8 ± 5 µM). Conclusion: While nitrite alone was not impacted by treatment, both Resync products result in an increase in plasma NOx, with the increase proportionate to the quantity of “nitric oxide blend” ingredients contained within each product. Future studies are needed to determine the physiological implications of the increased NOx, as pertaining to exercise performance and recovery, in addition to other aspects of human health.

A randomized clinical trial of the effects of leafy green vegetables and inorganic nitrate on blood pressure

BACKGROUND

A diet rich in fruits and vegetables is associated with lowering of blood pressure (BP), but the nutrient(s) responsible for these effects remain unclear. Research suggests that inorganic nitrate present in leafy green vegetables is converted into NO in vivo to improve cardiovascular function.

OBJECTIVE

In this study, we evaluated the effect of leafy green vegetables on BP in subjects with elevated BP, with the aim of elucidating if any such effect is related to their high nitrate content.

DESIGN

We enrolled 243 subjects, 50-70 y old, with a clinic systolic BP (SBP) of 130-159 mm Hg. After a 2-wk run-in period on a nitrate-restricted diet the subjects were randomly assigned to receive 1 of the following 3 interventions daily for 5 wk: low-nitrate vegetables + placebo pills, low-nitrate vegetables + nitrate pills (300 mg nitrate), or leafy green vegetables containing 300 mg nitrate + placebo pills. The primary end point measure was the difference in change in 24 h ambulatory SBP between the groups.

RESULTS

A total of 231 subjects (95%) completed the study. The insignificant change in ambulatory SBP (mean ± standard deviation) was -0.6 ± 6.2 mm Hg in the placebo group, -1.2 ± 6.8 mm Hg in the potassium nitrate group, and -0.5 ± 6.6 mm Hg in the leafy green vegetable group. There was no significant difference in change between the 3 groups.

CONCLUSIONS

A 5-wk dietary supplementation with leafy green vegetables or pills containing the same amount of inorganic nitrate does not decrease ambulatory SBP in subjects with elevated BP. This trial was registered at clinicaltrials.gov as NCT02916615.

Nitrates/Nitrites in Food-Risk for Nitrosative Stress and Benefits

In the context of impact on human health, nitrite/nitrate and related nitrogen species such as nitric oxide (NO) are a matter of increasing scientific controversy. An increase in the content of reactive nitrogen species may result in nitrosative stress-a deleterious process, which can be an important mediator of damage to cell structures, including lipids, membranes, proteins and DNA. Nitrates and nitrites are widespread in the environment and occur naturally in foods of plant origin as a part of the nitrogen cycle. Additionally, these compounds are used as additives to improve food quality and protect against microbial contamination and chemical changes. Some vegetables such as raw spinach, beets, celery and lettuce are considered to contain high concentrations of nitrates. Due to the high consumption of vegetables, they have been identified as the primary source of nitrates in the human diet. Processed meats are another source of nitrites in our diet because the meat industry uses nitrates/nitrites as additives in the meat curing process. Although the vast majority of consumed nitrates and nitrites come from natural vegetables and fruits rather than food additives, there is currently a great deal of consumer pressure for the production of meat products free of or with reduced quantities of these compounds. This is because, for years, the cancer risks of nitrates/nitrites have been considered, since they potentially convert into the nitrosamines that have carcinogenic effects. This has resulted in the development and rapid expansion of meat products processed with plant-derived nitrates as nitrite alternatives in meat products. On the other hand, recently, these two ions have been discussed as essential nutrients which allow nitric oxide production and thus help cardiovascular health. Thus, this manuscript reviews the main sources of dietary exposure to nitrates and nitrites, metabolism of nitrites/nitrates, and health concerns related to dietary nitrites/nitrates, with particular emphasis on the effect on nitrosative stress, the role of nitrites/nitrates in meat products and alternatives to these additives used in meat products.

Impact of rapid urbanization on the surface water's quality: a long-term environmental and physicochemical investigation of Tajan river, Iran (2007-2017)

Sustainable development of our society requires protection and monitoring of aquatic environments, as they are the pivotal water resources and niche for wildlife animals. In this research, physicochemical parameters of Tajan river's water were determined and compared with standards to assess the rural and human activity impact on water quality. First, monitoring and analyzing the water quality of the river were performed for 11 years (from 2007 to 2017). Based on calculated water quality index (WQI) values, Tajan river's water quality falls into four categories: good water with WQI less than 30 at upstream and middle of the river, poor water, and very poor to even unsuitable water (WQI ranges from 86 to 134) at the more urbanized locations. The high values of WQI are due to an elevated concentration of sulfate, nitrate, total dissolved solids (TDS), and chloride substances. The source of contaminations, according to the geochemistry of the area and having more than 90% growth rate in the population near to the most polluted location, is probably anthropogenic activities. Then, the long-term experimental data set has been utilized for developing a statistical model to be used for prediction of water quality with a few chemical analyses, generating a rapid and low-cost water quality evaluation for this river. The model was developed based on the stepwise multiple linear regression (MLR) approach and confirmed the experimental observation data of the most defective elements on WQI were respectively SO₄, NO₃, TDS, Cl, pH, and EC. This study presents a long-term evaluation of changes in surface water quality at a region with a recent rapid urban and civil development providing a suitable case to understand better human-water relations.

Head-to-head comparison of inorganic nitrate and metformin in a mouse model of cardiometabolic disease

BACKGROUND/PURPOSE

Unhealthy dietary habits contribute to the increasing incidence of metabolic syndrome and type 2 diabetes (T2D), which is accompanied by oxidative stress, compromised nitric oxide (NO) bioavailability and increased cardiovascular risk. Apart from lifestyle changes, biguanides such as metformin are the first-line pharmacological treatment for T2D. Favourable cardiometabolic effects have been demonstrated following dietary nitrate supplementation to boost the nitrate-nitrite-NO pathway. Here we aim to compare the therapeutic value of inorganic nitrate and metformin alone and their combination in a model of cardiometabolic disease.

EXPERIMENTAL APPROACH

Mice were fed control or high fat diet (HFD) for 7 weeks in combination with the NO synthase (NOS) inhibitor l-NAME to induce metabolic syndrome. Simultaneously, the mice were treated with vehicle, inorganic nitrate, metformin or a combination of nitrate and metformin in (drinking water). Cardiometabolic functions were assessed in vivo and tissues were collected/processed for analyses.

KEY RESULTS

HFD + L-NAME was associated with cardiometabolic dysfunction, compared with controls, as evident from elevated blood pressure, endothelial dysfunction, impaired insulin sensitivity and compromised glucose clearance as well as liver steatosis. Both nitrate and metformin improved insulin/glucose homeostasis, whereas only nitrate had favourable effects on cardiovascular function and steatosis. Mechanistically, metformin and nitrate improved AMPK signalling, whereas only nitrate attenuated oxidative stress. Combination of nitrate and metformin reduced HbA1c and trended to further increase AMPK activation.

CONCLUSION/IMPLICATIONS

Nitrate and metformin had equipotent metabolic effects, while nitrate was superior regarding protection against cardiovascular dysfunction and liver steatosis. If reproduced in future clinical trials, these findings may have implications for novel nutrition-based strategies against metabolic syndrome, T2D and associated complications.

Randomised, double-blind, placebo-controlled clinical trial investigating the effects of inorganic nitrate in hypertension-induced target organ damage: protocol of the NITRATE-TOD study in the UK

INTRODUCTION

Arterial stiffness and left ventricular (LV) hypertrophy are the key markers of hypertensive target organ damage (TOD) associated with increased cardiovascular morbidity and mortality. We have previously shown that dietary inorganic nitrate supplementation lowers blood pressure (BP) in hypertension, however, whether this approach might also improve markers of hypertensive TOD is unknown. In this study, we will investigate whether daily dietary inorganic nitrate administration reduces LV mass and improves measures of arterial stiffness.

METHODS AND DESIGN

NITRATE-TOD is a double-blind, randomised, single-centre, placebo-controlled phase II trial aiming to enrol 160 patients with suboptimal BP control on one or more antihypertensives. Patients will be randomised to receive 4 months once daily dose of either nitrate-rich beetroot juice or nitrate-deplete beetroot juice (placebo). The primary outcomes are reduction in LV mass and reduction in pulse wave velocity (PWV) and central BP.The study has a power of 95% for detecting a 9 g LV mass change by cardiovascular MRI (~6% change for a mildly hypertrophied heart of 150 g). For PWV, we have a power of >95% for detecting a 0.6 m/s absolute change. For central systolic BP, we have a>90% power to detect a 5.8 mm Hg difference in central systolic BP.Secondary end points include change in ultrasound flow-mediated dilation, change in plasma nitrate and nitrite concentration and change in BP.

ETHICS AND DISSEMINATION

The study was approved by the London-City and East Research Ethics Committee (10/H0703/98). Trial results will be published according to the Consolidated Standards of Reporting Trials statement and will be presented at conferences and reported in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03088514.

Mechanisms of the protective effects of nitrate and nitrite in cardiovascular and metabolic diseases

Within the body, NO is produced by nitric oxide synthases via converting _l-arginine to citrulline. Additionally, NO is also produced via the NOS-independent nitrate-nitrite-NO pathway. Unlike the classical pathway, the nitrate-nitrite-NO pathway is oxygen independent and viewed as a back-up function to ensure NO generation during ischaemia/hypoxia. Dietary nitrate and nitrite have emerged as substrates for endogenous NO generation and other bioactive nitrogen oxides with promising protective effects on cardiovascular and metabolic function. In brief, inorganic nitrate and nitrite can decrease blood pressure, protect against ischaemia-reperfusion injury, enhance endothelial function, inhibit platelet aggregation, modulate mitochondrial function and improve features of the metabolic syndrome. However, many questions regarding the specific mechanisms of these protective effects on cardiovascular and metabolic diseases remain unclear. In this review, we focus on nitrate/nitrite bioactivation, as well as the potential mechanisms for nitrate/nitrite-mediated effects on cardiovascular and metabolic diseases. Understanding how dietary nitrate and nitrite induce beneficial effect on cardiovascular and metabolic diseases could open up novel therapeutic opportunities in clinical practice.

Functional properties of beetroot (Beta vulgaris) in management of cardio-metabolic diseases

Red beetroot (Beta vulgaris), as a naturally occurring root vegetable and a rich source of phytochemicals and bioactive compounds, is known for its beneficial roles in the improvement of several clinical and pathologic outcome. Chronic and acute beetroot juice supplementation, as a cost-effective strategy, is proposed to hold promises in controlling diabetes and insulin hemostasis, blood pressure and vascular function, renal health and the possible effect on microbiome abundance. The secondary outcome and physiological response of microbiome abundance modulation included the non- significant fluctuation of systolic and diastolic blood pressures. Also, some studies have suggested a reno-protective property of beetroot juice that is associated with the reduction of mortality rate and favorable changes in kidney’s functional parameters among patients with renal disorders. Similarly, it is shown that the persistent consumption of beetroot juice effectively postpones the postprandial glycemic response and decreases the blood glucose peak. The significant blood pressure lowering effect has been seen among normotensive subjects, which tend to be more considerable among hypertensive individuals and progressive among overweight adults.

Within this context, this review aims to provide a comprehensive overview on the therapeutic applications of beetroot juice in metabolic disorders and theirs underlying mechanisms. Despite the inconsistencies in the set of results from the reviewed studies, there is no doubt that further contributing factors must be investigated more deeply in future studies.

Effects of dietary nitrate and folate supplementation on blood pressure in hypertensive Tanzanians: Design and baseline characteristics of a feasibility trial

The burden of hypertension in Sub-Saharan African countries is rising. Low-cost and effective interventions are needed to mitigate these alarming trends. No evidence is available on the use of dietary nitrate for treating hypertension in African populations. The objectives of this study are to assess the feasibility and efficacy of using beetroot and folate as a combined dietary intervention to treat Tanzanian adults with pre- and mild to moderate hypertension. This was a three-arm double-blind, placebo-controlled, parallel randomised clinical trial conducted within the Hai Demographic Surveillance Site in the Kilimanjaro region in Tanzania. 48 participants were randomised to one of three groups for a 60-day intervention period. Group 1: Combined dietary intervention (beetroot juice and folate), Group 2: Single dietary intervention (beetroot juice and placebo capsule), and Group 3: Control group (placebo beetroot juice and placebo capsule). The primary outcome of the trial was to evaluate the feasibility of the study in a low-income setting. Trial assessments included resting clinic and ambulatory 24-hr blood pressure measurements, lifestyle and dietary questionnaires and collection of biological samples. Our cohort included 8 (16.7%) males and 40 (83.3%) females with mean age 60.7 years (SD 6.5). The mean (SD) BMI, clinic systolic blood pressure and ambulatory systolic blood pressure at baseline were 27.6 kg/m2 (5.4), 151.0 (19.4), and 140.4 (15.0) mmHg, respectively. Eight (16.7%) participants were classified as pre-hypertensive, 20 (41.7%) as stage-1 hypertensive, and 20 (41.7%) as stage-2 hypertensive. Overall, the results support the feasibility of a study of this nature within a hypertensive African population.

TRIAL REGISTRATION NUMBER

ISRCTN67978523.

Impact of Red Beetroot Juice on Vascular Endothelial Function and Cardiometabolic Responses to a High-Fat Meal in Middle-Aged/Older Adults with Overweight and Obesity: A Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

BACKGROUND

High-fat meal (HFM) consumption may induce transient postprandial atherogenic responses, including impairment of vascular endothelial function, in individuals with overweight/obesity. Red beetroot juice (RBJ) may modulate endothelial function and other measures of cardiometabolic health.

OBJECTIVE

This study investigated the impact of acute and chronic RBJ consumption, including nitrate-dependent and -independent effects, on postprandial endothelial function and other cardiometabolic responses to a HFM.

METHODS

Fifteen men and postmenopausal women with overweight/obesity were enrolled in this randomized, double-blind, placebo-controlled, 4-period, crossover clinical trial. Following an overnight fast, participants underwent baseline assessment of endothelial function (reactive hyperemia index; RHI) and hemodynamics, and biological sample collection. In random order, participants consumed 70 mL (acute visit) of: 1) RBJ, 2) nitrate-free RBJ (NF-RBJ), 3) placebo + nitrate (PBO + NIT), or 4) placebo (PBO), followed by a HFM. RHI was remeasured 4 h post-HFM, and hemodynamic assessment and biological sample collection were performed 1, 2, and 4 h post-HFM consumption. Participants consumed treatments daily for 4 wk (chronic visit), and assessments were repeated before/after the HFM (without consuming treatments).

RESULTS

HFM consumption did not induce significant impairment of postprandial RHI. No significant differences in RHI were detected across treatment groups following acute or chronic exposure, despite increases in circulating nitrate/nitrite (NOx) concentrations in the RBJ and PBO + NIT groups compared with PBO and NF-RBJ (P < 0.0001 for all time points at the acute visit; P < 0.05 for all time points at the chronic visit). Although the HFM led to significant alterations in several secondary outcomes, there were no consistent treatment effects on postprandial cardiometabolic responses.

CONCLUSIONS

HFM consumption did not impair postprandial endothelial function in this population, and RBJ exposure did not alter postprandial endothelial function or other outcomes despite increasing NOx concentrations. This trial is registered at clinicaltrials.gov as NCT02949115.

Therapeutic Implications of Nitrite in Hypertension

Nitrite, an anion produced from the oxidative breakdown of nitric oxide (NO), has traditionally been viewed as an inert molecule. However, this dogma has been challenged with the findings that nitrite can be readily reduced to NO under pathological conditions, hence representing a physiologically relevant storage reservoir of NO either in the blood or tissues. Nitrite administration has been demonstrated to improve myocardial function in subjects with heart failure and to lower the blood pressure in hypertensive subjects. Thus, extensive amount of work has since been carried out to investigate the therapeutic potential of nitrite in treating cardiovascular diseases, especially hypertension. Studies done on several animal models of hypertension have demonstrated the efficacy of nitrite in preventing and ameliorating the pathological changes associated with the disease. This brief review of the current findings aims to re-evaluate the use of nitrite for the treatment of hypertension and in particular to highlight its role in improving endothelial function.

The role of inorganic nitrate and nitrite in cardiovascular disease risk factors: a systematic review and meta-analysis of human evidence

Context

Depleted nitric oxide levels in the human body play a major role in cardiovascular disease pathogenesis. Inorganic nitrate/nitrite (rich dietary sources include beetroot and spinach) can act as a nitric oxide donor because nitrate/nitrite can be metabolized to produce nitric oxide.

Objective

This review and meta-analysis sought to investigate the role of inorganic nitrate/nitrite in preventing or treating cardiovascular disease risk factors in humans.

Data Sources

Electronic databases, including Medline, Embase, Cumulative Index to Nursing and Allied Health Literature, Cochrane, and Scopus, were searched.

Data Extraction

Experimental trials examining the effect of oral inorganic nitrate/nitrite intake on cardiovascular disease risk factors were included for systematic analysis.

Results

Thirty-four studies were included for qualitative synthesis, 23 of which were eligible for meta-analysis. Included studies measured the following outcomes: blood pressure, endothelial function, arterial stiffness, platelet aggregation, and/or blood lipids. Inorganic nitrate intake was found to significantly reduce resting blood pressure (systolic blood pressure: -4.80 mmHg, P < 0.0001; diastolic blood pressure: -1.74 mmHg, P = 0.001), improve endothelial function (flow-mediated dilatation: 0.59%, P < 0.0001), reduce arterial stiffness (pulse wave velocity: -0.23 m/s, P < 0.0001; augmentation index: -2.1%, P = 0.05), and reduce platelet aggregation by 18.9% (P < 0.0001).

Conclusions

Inorganic nitrate consumption represents a simple strategy for targeting cardiovascular disease risk factors. Future studies investigating the long-term effects of inorganic nitrate on cardiovascular disease outcomes are warranted.

Short-Term Betanin Intake Reduces Oxidative Stress in Wistar Rats

Oxidative stress is a common condition described in risk factors for cardiovascular disease. Betanin, a bioactive pigment from red beetroot demonstrates anti-inflammatory and antioxidant properties. The main aim of this study was to evaluate the short-term intake of betanin against oxidative stress in a rodent model, a common condition described in several risk factors for cardiovascular disease. Oxidative stress was induced in Wistar rats by a hyperlipidemic diet for 60 days, followed by betanin administration (20 mg·kg-1) through oral gavage for 20 days. Plasma biochemical parameters and antioxidant enzyme activities were evaluated. Lipid peroxidation and histopathological changes were determined in the liver. The hyperlipidemic diet caused hyperglycemia, hyperinsulinemia, insulin resistance, and increases in alanine transaminase and aspartate transaminase levels. Oxidative stress status was confirmed by reduction of antioxidant enzyme activities, increased lipid peroxidation, and liver damage. Purified betanin regulated glucose levels, insulin, and insulin resistance. Hepatic damage was reversed as evidenced by the reduction in alanine transaminase and aspartate transaminase levels and confirmed by histological analyses. Betanin reduced hepatic malondialdehyde and increased superoxide dismutase, catalase, and glutathione peroxidase activities. Short-term betanin intake modulated biochemical parameters, reversed hepatic tissue damage, and attenuated oxidative stress in Wistar rats.

Influence of dietary inorganic nitrate on blood pressure and vascular function in hypertension: prospective implications for adjunctive treatment

Dietary inorganic nitrate (nitrate) is a promising adjunctive treatment to reduce blood pressure and improve vascular function in hypertension. However, it remains unknown if the efficacy of nitrate is dependent upon an elevated blood pressure or altered by medication in patients with hypertension. Therefore, blood pressure and vascular function, measured by passive leg movement (PLM) and flow-mediated dilation (FMD), were assessed following 3 days of placebo (nitrate-free beetroot juice) and nitrate (nitrate-rich beetroot juice) administration in 13 patients (age: 53 ± 12 yr) with hypertension taking antihypertensive medications (study 1) and in 14 patients (49 ± 13 yr) with hypertension not taking antihypertensive medications (study 2). In study 1, plasma nitrite concentration was greater for nitrate than placebo (341 ± 118 vs. 308 ± 123 nmol/L, P < 0.05), yet blood pressure and vascular function were unaltered. In study 2, plasma nitrite concentration was greater for nitrate than placebo (340 ± 102 vs. 295 ± 93 nmol/L, P < 0.01). Systolic (136 ± 16 vs. 141 ± 19 mmHg), diastolic (84 ± 13 vs. 88 ± 12 mmHg), and mean (101 ± 12 vs. 106 ± 13 mmHg) blood pressures were lower (P < 0.05), whereas the PLM change in leg vascular conductance (6.0 ± 3.0 vs. 5.1 ± 2.6 mL·min^-1·mmHg^-1) and FMD (6.1 ± 2.4% vs. 4.1 ± 2.7%) were greater (P < 0.05) for nitrate than placebo. The changes in systolic blood pressure (r = -0.60) and FMD (r = -0.48) induced by nitrate were inversely correlated (P < 0.05) to the respective baseline values obtained in the placebo condition. Thus, the efficacy of nitrate to improve blood pressure and vascular function in hypertension appears to be dependent on the degree of blood pressure elevation and vascular dysfunction and not antihypertensive medication status, per se.NEW & NOTEWORTHY Dietary nitrate (nitrate) is a promising intervention to improve blood pressure and vascular function in hypertension. We demonstrate that these beneficial effects of nitrate are inversely related to the baseline value in a continuous manner with no distinction between antihypertensive medication status. Thus, the efficacy of nitrate to improve blood pressure and vascular function in hypertension appears to be dependent on the degree of blood pressure elevation and vascular dysfunction and not antihypertensive mediation status.

The Effects of Beetroot Juice on Blood Pressure, Microvascular Function and Large-Vessel Endothelial Function: A Randomized, Double-Blind, Placebo-Controlled Pilot Study in Healthy Older Adults

Dietary nitrate (NO₃⁻) has been reported to improve endothelial function (EF) and blood pressure (BP). However, most studies only assess large-vessel EF with little research on the microvasculature. Thus, the aim of the present pilot study is to examine NO₃⁻ supplementation on microvascular and large-vessel EF and BP. Twenty older adults (63 ± 6 years) were randomized to a beetroot juice (BRJ) or placebo (PLA) group for 28 (±7) days and attended three laboratory visitations. Across visitations, blood pressure, microvascular function and large-vessel EF were assessed by laser Doppler imaging (LDI) with iontophoresis of vasoactive substances and flow-mediated dilatation (FMD), respectively. Plasma NO₃⁻concentrations, BP and the presence of NO₃⁻ reducing bacteria were also assessed. Plasma NO₃⁻ increased following two weeks of BRJ supplementation (p = 0.04) along with a concomitant decrease in systolic and diastolic BP of approximately −6 mmHg and −4 mmHg, respectively (p = 0.04; p = 0.01, respectively). BP remained unchanged in the PLA group. There were no significant differences in endothelium-dependent or endothelium-independent microvascular responses between groups. FMD increased by 1.5% following two weeks of BRJ (p = 0.04), with only a minimal (0.1%) change for the PLA group. In conclusion, this pilot study demonstrated that medium-term BRJ ingestion potentially improves SBP, DBP and large-vessel EF in healthy older adults. The improvements observed in the present study are likely to be greater in populations presenting with endothelial dysfunction. Thus, further prospective studies are warranted in individuals at greater risk for cardiovascular disease.

Oral microbial biofilms: an update

Human oral cavity (mouth) hosts a complex microbiome consisting of bacteria, archaea, protozoa, fungi and viruses. These bacteria are responsible for two common diseases of the human mouth including periodontal (gum) and dental caries (tooth decay). Dental caries is caused by plaques, which are a community of microorganisms in biofilm format. Genetic and peripheral factors lead to variations in the oral microbiome. It has known that, in commensalism and coexistence between microorganisms and the host, homeostasis in the oral microbiome is preserved. Nonetheless, under some conditions, a parasitic relationship dominates the existing situation and the rise of cariogenic microorganisms results in dental caries. Utilizing advanced molecular biology techniques, new cariogenic microorganisms species have been discovered. The oral microbiome of each person is quite distinct. Consequently, commonly taken measures for disease prevention cannot be exactly the same for other individuals. The chance for developing tooth decay in individuals is dependent on factors such as immune system and oral microbiome which itself is affected by the environmental and genetic determinants. Early detection of dental caries, assessment of risk factors and designing personalized measure let dentists control the disease and obtain desired results. It is necessary for a dentist to consider dental caries as a result of a biological process to be targeted than treating the consequences of decay cavities. In this research, we critically review the literature and discuss the role of microbial biofilms in dental caries.

Effects of dietary nitrate on inflammation and immune function, and implications for cardiovascular health

Inorganic dietary nitrate, found abundantly in green leafy and some root vegetables, elicits several beneficial physiological effects, including a reduction in blood pressure and improvements in blood flow through nitrate-nitrite-nitric oxide signaling. Recent animal and human studies have shown that dietary nitrate and nitrite also modulate inflammatory processes and immune cell function and phenotypes. Chronic low-grade inflammation and immune dysfunction play a critical role in cardiovascular disease. This review outlines the current evidence on the efficacy of nitrate-rich plant foods and other sources of dietary nitrate and nitrite to counteract inflammation and promote homeostasis of the immune and vascular systems. The data from these studies suggest that immune cells and immune-vasculature interactions are important targets for dietary interventions aimed at improving, preserving, or restoring cardiovascular health.

"Beet" the cold: beetroot juice supplementation improves peripheral blood flow, endothelial function, and anti-inflammatory status in individuals with Raynaud's phenomenon

Raynaud's phenomenon (RP) is characterized by recurrent transient peripheral vasospasm and lower nitric oxide (NO) bioavailability in the cold. We investigated the effect of nitrate-rich beetroot juice (BJ) supplementation on 1) NO-mediated vasodilation, 2) cutaneous vascular conductance (CVC) and skin temperature (T_sk) following local cooling, and 3) systemic anti-inflammatory status. Following baseline testing, 23 individuals with RP attended four times, in a double-blind, randomized crossover design, following acute and chronic (14 days) BJ and nitrate-depleted beetroot juice (NDBJ) supplementation. Peripheral T_sk and CVC were measured during and after mild hand and foot cooling, and during transdermal delivery of acetylcholine and sodium nitroprusside. Markers of anti-inflammatory status were also measured. Plasma nitrite concentration ([nitrite]) was increased in the BJ conditions (P < 0.001). Compared with the baseline visit, thumb CVC was greater following chronic-BJ (Δ2.0 flux/mmHg, P = 0.02) and chronic-NDBJ (Δ1.45 flux/mmHg, P = 0.01) supplementation; however, no changes in T_sk were observed (P > 0.05). Plasma [interleukin-10] was greater, pan endothelin and systolic and diastolic blood pressure (BP) were reduced, and forearm endothelial function was improved, by both BJ and NDBJ supplementation (P < 0.05). Acute and chronic BJ and NDBJ supplementation improved anti-inflammatory status, endothelial function and blood pressure (BP). CVC following cooling increased post chronic-BJ and chronic-NDBJ supplementation, but no effect on T_sk was observed. The key findings are that beetroot supplementation improves thumb blood flow, improves endothelial function and anti-inflammatory status, and reduces BP in people with Raynaud's.NEW & NOTEWORTHY This is the first study to examine the effect of dietary nitrate supplementation in individuals with Raynaud's phenomenon. The principal novel findings from this study were that both beetroot juice and nitrate-depleted beetroot juice 1) increased blood flow in the thumb following a cold challenge; 2) enhanced endothelium-dependent and -independent vasodilation in the forearm; 3) reduced systolic and diastolic blood pressure, and pan-endothelin concentration; and 4) improved inflammatory status in comparison to baseline.