Dietary nitrate improves vascular function in patients with hypercholesterolemia: a randomized, double-blind, placebo-controlled study

Positive feedback loop between dietary nitrate intake and oral health

Nitrate was once thought to be an inert end-product of endothelial-derived nitric oxide (NO) heme oxidation; however, this view has been radically revised over the past few decades. Following the clarification of the nitrate-nitrite-NO pathway, accumulated evidence has shown that nitrate derived from the diet is a supplementary source of endogenous NO generation, playing important roles in a variety of pathological and physiological conditions. However, the beneficial effects of nitrate are closely related with oral health, and oral dysfunction has an adverse effect on nitrate metabolism and further impacts overall systemic health. Moreover, an interesting positive feedback loop has been identified between dietary nitrate intake and oral health. Dietary nitrate's beneficial effect on oral health may further improve its bioavailability and promote overall systemic well-being. This review aims to provide a detailed description of the functions of dietary nitrate, with an emphasis on the key role oral health plays in nitrate bioavailability. This review also provides recommendations for a new paradigm that includes nitrate therapy in the treatment of oral diseases.

A worldwide systematic review, meta-analysis and meta-regression of nitrate and nitrite in vegetables and fruits

This study aimed to conduct on the concentration of nitrate/nitrite (mg kg^-1) in vegetables and fruits with a special emphasize on the effect of climate condition. The highest concentration (mean and 95%CI) of nitrate/nitrite was determined in Rocket (4825.15; 3044.14-6606.16), Mizuna (3500; 2702.48-4297.52), and Bok choy (3407.40; 2841.39-3973.42) in vegetable group and in wolfberry (2395.83; 1611.89-3179.77), Jack fruit (237.8; 202.88-272.71) and Cantaloupe (220.32; -224.53 to 665.19) in fruits group. Brazil (2816.77), Estonia (2133.76), Republic of China, Taiwan (2118.28) were the nations with the highest average concentration of nitrate/nitrite in all samples taken from these nations across the globe. Furthermore, Chinese fruits contain the highest concentrations of nitrates/nitrites of other countries (500.57; 416.74-584.41). Nitrate is present in greater quantities in fruits (44.02; 42.12-45.93) and vegetables (438.31; 422.51-454.11) than nitrite; however, the quantity of nitrite has a relatively similar content in both. Our findings revealed that increase in humidity (> 60%), annual rainfall (> 1500 mm), average temperature (> 10 °C) and application of fertilizers lead to significant increase in accumulation of nitrate/nitrite composition of vegetables and fruits (p < 0.05). According to the results of rating countries using the Food Security Index (GFSI), countries with high scores-like Poland and Portugal, which have GFSI scores of 75.5 and 78.7 and average contamination levels of 8.26 and 11.08, respectively-have a trend of average nitrate/nitrite levels of fruit and vegetable products that is significantly decreasing (p = 0.00). Although GFSI levels and other environmental variables can influence nitrate/nitrite levels, fertilizer usage (kg ha^-1) is one of the most significant controllable and impactful factors in contaminants residue, which should be manage. The result of our study, will serve as a basis to estimate the dietary exposure to nitrates and nitrites from fruits and vegetables among populations around the world based on climatology and monitor the related health outcomes.

Moderate dose of dietary nitrate improves skeletal muscle microvascular function in patients with peripheral artery disease

Peripheral artery disease (PAD) is an atherosclerotic disease characterized by compromised lower-extremity blood flow that impairs walking ability. We showed that a moderate dose of dietary nitrate in the form of beetroot juice (BRJ, 0.11 mmol/kg) can improve macrovascular function and maximal walking distance in patients with PAD. However, its impacts on the microcirculation and autonomic nervous system have not been examined. Therefore, we investigated the impacts of this dose of dietary nitrate on skeletal muscle microvascular function and autonomic nervous system function and further related these measurements to 6-min walking distance, pain-free walking distance, and exercise recovery in patients with PAD. Patients with PAD (n = 10) ingested either BRJ or placebo in a randomized crossover design. Heart rate variability, skeletal muscle microvascular function, and 6-min walking distance were performed pre- and post-BRJ and placebo. There were significant group × time interactions (P < 0.05) for skeletal muscle microvascular function, 6-min walking distance, and exercise recovery, but no changes (P > 0.05) in heart rate variability or pain-free walking distance were noted. The BRJ group demonstrated improved skeletal muscle microvascular function (∆ 22.1 ± 7.5 %·min-1), longer 6-min walking distance (Δ 37.5 ± 9.1 m), and faster recovery post-exercise (Δ -15.3 ± 4.2 s). Furthermore, changes in skeletal muscle microvascular function were positively associated with changes in 6-min walking distance (r = 0.5) and pain-free walking distance (r = 0.6). These results suggest that a moderate dose of dietary nitrate may support microvascular function, which is related to improvements in walking distance and claudication in patients with PAD.

Is vitamin C a booster of the effects of dietary nitrate on endothelial function? Physiologic rationale and implications for research

Endothelial dysfunction (ED) is an early marker of vascular damage linked to the loss of integrity of the endothelial lining and represents a key step in the pathogenesis of atherosclerosis and cardiovascular diseases (CVDs). ED may be reversible, hence the development and testing of effective early interventions could be beneficial for the prevention and treatment of CVDs. Recent studies have demonstrated that the consumption of dietary nitrate (NO₃^-), an inorganic anion that serves as a substrate for the gas transmitter nitric oxide (NO), can lower blood pressure, improve endothelial function and, in observational studies, reduce the risk for CVD. We hypothesize that the co-consumption of NO₃^- with vitamin C, which is a potent antioxidant, could enhance the "yield" of NO produced from a given NO₃^- dose byThis could translate into greater NO-dependent effects on endothelial function (EF) and overall vascular health (than may be experienced with NO₃^- supplementation alone). This review presents evidence to suggest that the combination of vitamin C and dietary nitrate could represent a promising and effective approach to improve EF and reduce CVD risk, and discuss opportunities for future research.

Local delivery of nitric oxide prevents endothelial dysfunction in periodontitis

AIMS

Increased cardiovascular disease risk underlies elevated rates of mortality in individuals with periodontitis. A key characteristic of those with increased cardiovascular risk is endothelial dysfunction, a phenomenon synonymous with deficiencies of bioavailable nitric oxide (NO), and prominently expressed in patients with periodontitis. Also, inorganic nitrate can be reduced to NO in vivo to restore NO levels, leading us to hypothesise that its use may be beneficial in reducing periodontitis-associated endothelial dysfunction. Herein we sought to determine whether inorganic nitrate improves endothelial function in the setting of periodontitis and if so to determine the mechanisms underpinning any responses seen.

METHODS AND RESULTS

Periodontitis was induced in mice by placement of a ligature for 14 days around the second molar. Treatment in vivo with potassium nitrate, either prior to or following establishment of experimental periodontitis, attenuated endothelial dysfunction, as determined by assessment of acetylcholine-induced relaxation of aortic rings, compared to control (potassium chloride treatment). These beneficial effects were associated with a suppression of vascular wall inflammatory pathways (assessed by quantitative-PCR), increases in the anti-inflammatory cytokine interleukin (IL)-10 and reduced tissue oxidative stress due to attenuation of xanthine oxidoreductase-dependent superoxide generation. In patients with periodontitis, plasma nitrite levels were not associated with endothelial function indicating dysfunction.

CONCLUSION

Our results suggest that inorganic nitrate protects against, and can partially reverse pre-existing, periodontitis-induced endothelial dysfunction through restoration of nitrite and thus NO levels. This research highlights the potential of dietary nitrate as adjunct therapy to target the associated negative cardiovascular outcomes in patients with periodontitis.

Bioactive compounds and functional foods as coadjuvant therapy for thrombosis

Cardiovascular diseases (CVDs) are the leading cause of death. The most common cardiovascular pathologies are thromboembolic diseases. Antithrombotic therapy prevents thrombus formation or dissolves that previously constituted. However, it presents a high rate of accidents such as gastric bleeding and cerebrovascular embolism. Plant foods and their secondary metabolites have been reported to regulate blood hemostasis. This review article aims to propose plant foods and their metabolites as adjuvant therapy for the management of thromboembolic diseases. Various databases were consulted, using antiplatelet, anticoagulant, and fibrinolytic as key terms. In total, 35 foods and 24 secondary metabolites, via in vitro, in vivo, and clinical studies, have been reported to regulate platelet aggregation, blood coagulation, and fibrinolysis. According to the studies presented in this review, plant foods with effects at concentrations less than 50 μg mL^-1 and secondary metabolites with IC₅₀ less than 100 μM can be considered agents with high antithrombotic potential. This review suggests that plant foods and their secondary metabolites should be used to develop foods, ingredients and nutraceuticals with functional properties. The evidence presented in this review shows that plant foods and their bioactive compounds could be used as adjuvants for the treatment and prevention of thrombotic complications. However, further in vivo and clinical trials are required to establish effective and safe doses.

The oral microbiome in the pathophysiology of cardiovascular disease

Despite advances in our understanding of the pathophysiology of many cardiovascular diseases (CVDs) and expansion of available therapies, the global burden of CVD-associated morbidity and mortality remains unacceptably high. Important gaps remain in our understanding of the mechanisms of CVD and determinants of disease progression. In the past decade, much research has been conducted on the human microbiome and its potential role in modulating CVD. With the advent of high-throughput technologies and multiomics analyses, the complex and dynamic relationship between the microbiota, their 'theatre of activity' and the host is gradually being elucidated. The relationship between the gut microbiome and CVD is well established. Much less is known about the role of disruption (dysbiosis) of the oral microbiome; however, interest in the field is growing, as is the body of literature from basic science and animal and human investigations. In this Review, we examine the link between the oral microbiome and CVD, specifically coronary artery disease, stroke, peripheral artery disease, heart failure, infective endocarditis and rheumatic heart disease. We discuss the various mechanisms by which oral dysbiosis contributes to CVD pathogenesis and potential strategies for prevention and treatment.

Acute Effects of Dietary Nitrate on Central Pressure and Endothelial Function in Hypertensive Patients: A Randomized, Placebo-Controlled Crossover Study

BACKGROUND

The diet's inorganic nitrate (NO3-) may provide a physiological substrate for reducing nitrate (NO2-) to NO independent of the endothelium. Studies suggest that inorganic NO3- has beneficial effects on cardiovascular health.

OBJECTIVE

This study evaluated the acute effects of 500 mL nitrate-rich beetroot juice (BRJ; containing 11.5mmol NO3-) on blood pressure and endothelial function in treated hypertensive patients.

METHODS

A randomized, placebo-controlled, crossover study was conducted in treated hypertensive patients (n=37; women=62%) who underwent clinical and nutritional evaluation and assessment of central hemodynamic parameters and microvascular reactivity. The significance level was p<0.05.

RESULTS

The mean age was 59±7 years, and mean systolic and diastolic blood pressures were 142±10/83±9mmHg. There was a significant increase in the subendocardial viability ratio (SEVR; 149±25 vs. 165±30%, p<0.001) and reduction in ejection duration (ED; 37±4 vs. 34±4%, p<0.001) in the beetroot phase but no significant SEVR difference in the control phase. The % increase in perfusion (155 vs. 159 %, p=0.042) was significantly increased in the beetroot phase, which was not observed in the control phase. In the beetroot phase, the change in SEVR showed a significant correlation with the change in the area under the curve of post-occlusive reactive hyperemia (AUC-PORH) (r=0.45, p=0.012). The change in ED showed a significant correlation with the post-intervention perfusion peak (r=-0.37, p=0.031) and AUC-PORH (r=-0.36, p=0.046).

CONCLUSIONS

The acute ingestion of BRJ by hypertensive patients resulted in an improvement of endothelial function, which was associated with higher subendocardial viability and performance in myocardial contraction.

Potential role of dietary nitrate in relation to cardiovascular and cerebrovascular health, cognition, cognitive decline and dementia: a review

There is currently no effective treatment for dementia, of which Alzheimer's disease (AD) is the most common form. It is, therefore, imperative to focus on evidence-based preventive strategies to combat this extremely debilitating chronic disease. Nitric oxide (NO) is a key signalling molecule in the cardiovascular, cerebrovascular, and central nervous systems. Vegetables rich in nitrate, such as spinach and beetroot, are an important source of NO, with beneficial effects on validated markers of cardiovascular health and an association with a lower risk of cardiovascular disease. Given the link between cardiovascular disease risk factors and dementia, together with the important role of NO in vascular health and cognition, it is important to determine whether dietary nitrate could also improve cognitive function, markers of brain health, and lower risk of dementia. This review presents an overview of NO's role in the cardiovascular, cerebrovascular, and central nervous systems; an overview of the available evidence that nitrate, through effects on NO, improves cardiovascular health; and evaluates the current evidence regarding dietary nitrate's potential role in cerebrovascular health, cognitive function, and brain health assessed via biomarkers.

Increased nitrate intake from beetroot juice does not alter soluble cellular adhesion molecules and circulating inflammatory cytokines in individuals with treated hypertension: a randomised, controlled trial

Dietary nitrate, found predominantly in green leafy vegetables and other vegetables such as radish, celery, and beetroot, has been shown to beneficially modulate inflammatory processes and immune cell function in animals and healthy individuals. The impact of increased nitrate intake on soluble inflammatory mediators in individuals with hypertension is unclear. We assessed whether the daily consumption of dietary nitrate via beetroot juice for 1-week lowered levels of circulating inflammatory markers in men and women with treated hypertension. Twenty-seven male and female participants were recruited to a randomized, placebo-controlled, double-blind crossover trial. The effects of 1-week intake of nitrate-rich beetroot juice versus 1-week intake of nitrate-depleted beetroot juice (placebo) were investigated. Plasma concentrations of circulating soluble adhesion molecules (ICAM-1, VCAM-1, CD62E, CD62P), inflammatory cytokines (IL-1β, IL-6, IL-10, IL-12p70, TNF-α) and chemokines (IL-8, MCP-1) were measured by multiplex flow cytometric bead array in samples collected on day 7 of each intervention period. Other outcomes included alterations in nitrate metabolism assessed by measuring nitrate and nitrite concentrations in plasma, saliva, and urine. One week of beetroot juice did not alter levels of the soluble adhesion markers or cytokines assessed. A 7-fold increase in salivary nitrite, an 8-fold increase in salivary nitrate, a 3-fold increase in plasma nitrate and nitrite, and a 4-fold increase in urinary nitrate and nitrite compared to the placebo was observed (p < 0.001 for all comparisons). Increasing dietary nitrate consumption over 7 days is not effective in reducing soluble inflammatory mediators in individuals with treated hypertension. This trial was registered at anzctr.org.au as ACTRN 12613000116729.

Nitrate in groundwater and agricultural products: intake and risk assessment in northeastern Iran

The suitability of groundwater and agricultural products for human consumption requires determining levels and assessing the health risks associated with potential pollutants. Here, particularly pollution with nitrate still remains a challenge, especially for those urban areas suffering from insufficient sewage collection systems, resulting in contaminating soil, endangering food safety, and deteriorating drinking water quality. In the present study, nitrate concentrations in the commonly consumed fruit and vegetable species were determined, and the results, together with the groundwater nitrate levels, were used to assess the associated health risks for Mashhad city residents. For this assessment, 261 water samples and 16 produce types were used to compute the daily intake of nitrate. Nitrate in groundwater was analyzed using a spectrophotometer, and produce species were examined using High-Performance Liquid Chromatography. Ward's hierarchical cluster analysis was applied for categorizing produce samples with regard to their nitrate content. Additionally, to account for the sanitation hazards associated with groundwater quality for drinking purposes, total coliform and turbidity were also assessed using the membrane filter (MF) technique and a nephelometer, respectively. Nitrate concentrations exceeded the prescribed permissible limits in 42% of the groundwater wells. The outcomes also exhibit significantly higher nitrate accumulation levels in root-tuber vegetables and leafy vegetables compared to fruit vegetables and fruits. Using cluster analysis, the accumulation of nitrate in vegetables and fruits was categorized into four clusters, specifying that radish contributes to 65.8% of the total content of nitrate in all samples. The Estimated Daily Intake (EDI) of nitrate and Health Risk Index (HRI) associated with consumption of groundwater exceeded the prescribed limit for the children's target group in Mashhad's south and central parts. Likewise, EDI and HRI values for produce consumption, in most samples, were found to be in the tolerable range, except for radish, lettuce, and cabbage, potentially posing risks for both children and adult consumers. The total coliforms in groundwater were found to violate the prescribed limit at 78.93% of the sampling locations and were generally much higher over the city's central and southern areas. A relatively strong correlation (R2 = 0.6307) between total coliform and nitrate concentrations suggests the release of anthropogenic pollution (i.e., sewage and manure) in the central and southern Mashhad.

Efficacy and Variability in Plasma Nitrite Levels during Long-Term Supplementation with Nitrate Containing Beetroot Juice

Long-term consumption of beetroot juice on efficacy of converting dietary nitrate to plasma nitrate and nitrite was investigated. Adults were randomized to consume either beetroot juice with 380 mg of nitrate (BR) or a beetroot juice placebo (PL) for 12-weeks. Plasma nitrate and nitrite were measured before and 90-minutes after consuming their intervention beverage. Percent change in nitrite across the 90 min was greater in BR (273.2 ± 39.9%) vs. PL (4.9 ± 36.9%). Long-term consumption of nitrate containing beetroot juice increased fasting nitrate and nitrite plasma levels compared to baseline.

Bionic Enzyme-Assisted Ion-Selective Amperometric Biosensor Based on 3D Porous Conductive Matrix for Point-of-Care Nitrite Testing

Nitrite plays a critical role in a variety of physiological processes and maintaining the nitrite level in an appropriate range is vital to keep healthy. Current nitrite analysis methods lack sensitivity and require tedious operations, which could not meet the need of point-of-care (POC) nitrite detection in precision medicine. Here we present a cyanocobalamin (VB₁₂) bionic enzyme-assisted ion-selective amperometric biosensor based on 3D porous conductive matrix (PCM), which can facilitate rapid and accurate POC nitrite monitoring in complex biofluids. The experimental findings quantitatively demonstrate that the biosensor has a sensitivity of 64.08 μA/(mM·cm²), a wide linear range of 0.025-45 mM, and low limit of detection of 1 nM. Moreover, the developed VB₁₂/BSA-PCM biosensor shows outstanding stability after 21 days with 2% decline in current signal, and high repeatability between batches with RSD of only 1.29%. Real salivary nitrite detection has been evaluated, and the results match well with the commercial nitrite analyzer. Thus, the bionic enzyme-assisted ion-selective amperometric biosensor proposed herein has potential utility as an affordable tool for POC detection and home-based healthcare.

The effect of dietary nitrate on macro- and microvascular function: A systematic review

Previous studies have investigated the impact of dietary nitrate on vascular function due to the association between dietary nitrate ingestion and improvement in nitric oxide (NO) bioavailability. Considering that NO can present different effects through vascular beds (macro- vs. microvasculature) due to the specific characteristic (function and morphology) that each vessel exhibits, it is crucial to investigate the effect of dietary nitrate ingestion on the macro- and microvascular function to understand the effect of nitrate on vascular function. For this reason, this review aimed to evaluate the impact of dietary nitrate on macro- and microvascular function in humans. A total of 29 studies were included in the systematic review, of which 19 studies evaluated the effect of nitrate supplementation on macrovascular function, eight studies evaluated the effect on microvascular function, and two studies evaluated the impact on both macro- and microvascular function. The literature suggests that dietary nitrate ingestion seems to improve the vascular function in macrovasculature, whereas microvascular function appears to be modest. Future studies investigating the effect of nitrate ingestion on vascular function should focus on measuring macro- and microvascular function whenever possible so that the impact of nitrate-rich foods on vascular segments could be better understood.

Oral Microbiota, Its Equilibrium and Implications in the Pathophysiology of Human Diseases: A Systematic Review

Imbalances of the oral microbiota and dysbiosis have traditionally been linked to the occurrence of teeth and oral diseases. However, recent findings indicate that this microbiota exerts relevant influence in systemic health. Dysbiosis of the oral microbiota is implicated in the apparition and progression of cardiovascular, neurodegenerative and other major human diseases. In fact, the oral microbiota are the second most diverse and largely populated microbiota of the human body and its relationships with systemic health, although widely explored, they still lack of proper integration. The purpose of this systematic review is thus to widely examine the implications of oral microbiota in oral, cardiovascular and neurodegenerative diseases to offer integrative and up-to-date interpretations. To achieve that aim, we identified a total of 121 studies curated in PUBMED from the time interval January 2003–April 2022, which after careful screening resulted in 79 studies included. The reviewed scientific literature provides plausible vias of implication of dysbiotic oral microbiota in systemic human diseases, and encourages further research to continue elucidating the highly relevant and still poorly understood implications of this niche microbiota in systemic health. PROSPERO Registration Number: CRD42022299692. This systematic review follows relevant PRISMA guidelines.

Effects of concentrated beetroot juice consumption on glycemic control, blood pressure, and lipid profile in type 2 diabetes patients: randomized clinical trial study

Background

While the prevalence of type 2 diabetes (T2D) is growing worldwide, dietary intake plays a remarkable role in the management of disease complications. Evidence suggests that beetroot has health-promoting potentials, including anti-inflammatory, antioxidant, and antidiabetic properties. Therefore, the present clinical trial aimed to investigate the effects of concentrated beetroot juice (BJ) supplementation on anthropometric measures, glycemic control, blood pressure (BP), and lipid profile in T2D patients.

Methods

In the simply randomized, parallel-group, controlled, and open-label trial, forty-six patients with T2D were randomly allocated to either the intervention group (BJ group), who consumed 24 ml concentrated BJ daily for 12 weeks, or the control group without any intervention. Anthropometric measurements, physical activity, dietary intakes, glycemic measures, lipid profile, and blood pressure were assessed at the baseline and the end of the study.

Results

Plasma nitric oxide (NO) in the intervention group had a higher nonsignificant increase after 12 weeks compared with the control group (8.57 ± 23.93 vs. 2.31 ± 15.98, P = 0.128). Compared with the baseline, significant reductions in plasma insulin (14.55 ± 7.85 vs. 10.62 ± 6.96, P = 0.014) and homeostasis model assessment of β-cell function (HOMA-B) (3.96 ± 0.83 vs. 3.63 ± 0.75, P = 0.038), as well as a marginally significant reduction in high-density lipoprotein cholesterol (HDL-C) (70.81 ± 11.24 vs. 65.44 ± 6.46, P = 0.058) were observed in the control group after 12 weeks. Diastolic blood pressure (DBP) was significantly reduced in the BJ group compared with the baseline (74.73 ± 16.78 vs. 72.36 ± 16.09, P = 0.046). After adjusting for baseline values, no significant effect on the levels of fasting plasma glucose (FPG), insulin, hemoglobin A1c (HgA1c), HOMA-β, homeostatic model assessment for insulin resistance (HOMA-IR), total cholesterol (TC), low-density lipoprotein (LDL), HDL, triglycerides (TG), and blood pressure (BP) was observed.

Conclusions

Our study showed that daily consumption of 24 ml concentrated BJ did not affect the levels of glycemic measures, blood pressure, and lipid profile. More studies are necessary to confirm these findings.

Trial Registration

This present clinical trial has been registered in the Iranian Registry of Clinical Trials with registration number IRCT20150815023617N5.

The Effect of Herbal Supplements on Blood Pressure: Systematic Review and Meta-Analysis

Herbal supplements rich in phenolic compounds are evidenced to have a protective effect against cardiovascular diseases. Therefore, they are suggested to be included in diets for people with hypertension (HT). HT is a global health problem and is estimated to affect billions of people until the end of 2025. For this reason, every possible and effective solution preventing HT should be considered. The aim was to perform an updated meta-analysis and review of recently published studies to evaluate the effect of selected herbal supplements on blood pressure reduction. We searched the PubMed database with specified selection criteria, analysing the RCT studies from 2011 to 2021. A total of 31 studies were included in the analysis, and the meta-analysis was conducted on the data from 16 of them. The general effect size of all the supplements via placebo was d = 1.45, p < 0.05 for systolic blood pressure (SBP) and d = 0.31, p < 0.05 for diastolic blood pressure (DBP). The meta-analysis and review of the literature demonstrated that herbal supplements, such as resveratrol, cherry juice, beetroot juice, bergamot extracts, barberry, and pycnogenol, can be effective in blood pressure reduction and cardiovascular prevention, but attention should be paid to their appropriate dosage due to the possibility of side effects from the digestive system.

Acute dietary nitrate supplementation does not change venous volume and compliance in healthy young adults

In this randomized single-blind, placebo-controlled, crossover study, we investigated the influence of inorganic nitrate (NO₃^-) supplementation on venous volume and compliance in the resting forearm and calf. Twenty healthy young adults were assigned to receive an NO₃^--rich beverage (beetroot juice [BRJ]: 140 mL; ~8 mmol NO₃^-) or an NO₃^¯-depleted control beverage (prune juice [CON]: 166 mL; < 0.01 mmol NO₃^-). Two hours after consuming the allocated beverage, each participant rested in the supine position for 20 min. Cuffs were then placed around the right upper arm and right thigh, inflated to 60 mmHg for 8 min, and then decreased to 0 mmHg at a rate of 1 mmHg/s. During inflation and deflation of cuff pressure, changes in venous volume in the forearm and calf were measured by venous occlusion plethysmography. Venous compliance was calculated as the numerical derivative of the cuff pressure‒venous volume curve in the limbs. The plasma NO₃^- concentration was elevated by intake of BRJ (before, 15.5 ± 5.8 µM; after, 572.0 ± 116.1 µM, P < 0.05) but not by CON (before, 14.8 ± 7.2 µM; after, 15.3 ± 7.4 µM, P > 0.05). On the other hand, there was no significant difference in venous volume or compliance in the forearm or calf between BRJ and CON. These findings suggest that although acute inorganic NO₃^- supplementation may enhance the activity of nitric oxide (NO) via NO₃^- → nitrite → NO pathway, it does not influence venous volume or compliance in the limbs in healthy young adults.

Strategies to Combat Caries by Maintaining the Integrity of Biofilm and Homeostasis during the Rapid Phase of Supragingival Plaque Formation

Bacteria in the oral cavity, including commensals and opportunistic pathogens, are organized into highly specialized sessile communities, coexisting in homeostasis with the host under healthy conditions. A dysbiotic environment during biofilm evolution, however, allows opportunistic pathogens to become the dominant species at caries-affected sites at the expense of health-associated taxa. Combining tooth brushing with dentifrices or rinses combat the onset of caries by partially removes plaque, but resulting in the biofilm remaining in an immature state with undesirables’ consequences on homeostasis and oral ecosystem. This leads to the need for therapeutic pathways that focus on preserving balance in the oral microbiota and applying strategies to combat caries by maintaining biofilm integrity and homeostasis during the rapid phase of supragingival plaque formation. Adhesion, nutrition, and communication are fundamental in this phase in which the bacteria that have survived these adverse conditions rebuild and reorganize the biofilm, and are considered targets for designing preventive strategies to guide the biofilm towards a composition compatible with health. The present review summarizes the most important advances and future prospects for therapies based on the maintenance of biofilm integrity and homeostasis as a preventive measure of dysbiosis focused on these three key factors during the rapid phase of plaque formation.

Plant-Based Foods and Vascular Function: A Systematic Review of Dietary Intervention Trials in Older Subjects and Hypothesized Mechanisms of Action

Cardiovascular diseases, still the leading cause of mortality in the world, are closely related to vascular function. Older subjects are more susceptible to endothelial dysfunction and therefore it is important to define possible preventive or support strategies, such as consumption of foods with health-promoting effects. This systematic review aims to summarize the currently available evidence on acute or chronic trials testing the effect of selected plant-based foods on vascular function parameters in older subjects, and consider plausible mechanisms that may support the main findings. A total of 15 trials were included and analyzed, testing the effects of beetroot, plum, blueberry, and vegetable oils. We found some interesting results regarding markers of vascular reactivity, in particular for beetroot, while no effects were found for markers of arterial stiffness. The amelioration of vascular function seems to be more related to the restoration of a condition of nitric oxide impairment, exacerbated by diseases or hypoxic condition, rather than the enhancement of a physiological situation, as indicated by the limited effects on healthy older subjects or in control groups with young subjects. However, the overall set of selected studies is, in any case, rather limited and heterogeneous in terms of characteristics of the studies, indicating the need for additional high-quality intervention trials to better clarify the role of vegetable foods in restoring and/or improving vascular function in order to better elucidate the mechanisms through which these foods may exert their vascular health benefits in older subjects.

Effect of beetroot or beetroot plus vitamin C supplementation on cardiovascular function in patients with coronary artery disease: protocol for a double-blind, placebo-controlled, randomised trial

INTRODUCTION

Coronary artery disease (CAD), classified into the atherosclerosis category, is a prevalent cardiovascular disease worldwide that is associated with serious comorbidities and death. The purpose of this study was to evaluate the effect of beetroot/beetroot plus vitamin C on cardiovascular health status and function in patients with CAD.

METHOD AND ANALYSIS

A randomised, placebo-controlled, double-blind clinical trial to recruit 90 patients with CAD at the cardiac outpatient clinic and Imam Reza Hospital, Mashhad, Iran. Participants will be divided into three groups: (1) Those who receive 500 mg three times a day of beetroot capsules, (2) Those who receive 500 mg three times a day of beetroot plus vitamin C capsules, and (3) Those who receive placebo capsules three times a day for 4 weeks. Pulse wave velocity, Augmentation Index, heart rate, volume of oxygen (VO₂) max/VO₂ peak, peak heart rate, blood pressure, interleukin 6 (IL-6), high sensitivity C reactive protein, intercellular adhesion molecule, vascular cell adhesion molecule, lipid profile and anthropometry will be measured at the beginning and end of the intervention.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee of Mashhad University of Medical Sciences (IR.MUMS.MEDICAL.REC.1399.717). All participants will be asked to complete the consent form at the beginning of the study. The results will be actively disseminated through peer-reviewed journals and conference presentations.

TRIAL REGISTRATION NUMBER

Iranian Registry of Clinical Trials, IRCT20210217050393N1 (registered 16 May 2021).

Plasma Nitrate and Nitrite Kinetics after Single Intake of Beetroot Juice in Adult Patients on Chronic Hemodialysis and in Healthy Volunteers: A Randomized, Single-Blind, Placebo-Controlled, Crossover Study

Nitric oxide (NO) contributes to maintaining normal cardiovascular and renal function. This bioactive signalling molecule is generally formed enzymatically by NO synthase in the vascular endothelium. NO bioactivity can also be attributed to dietary intake of inorganic nitrate, which is abundant in our diet, especially in green leafy vegetables and beets. Ingested nitrate is reduced to nitrite by oral commensal bacteria and further to NO systemically. Previous studies have shown that dialysis, by means of removing nitrate and nitrite from the body, can reduce NO bioactivity. Hence, dietary intervention approaches aimed to boost the nitrate-nitrite-NO pathway may be of benefit in dialysis patients. The purpose of this study was to examine the kinetics of plasma nitrate and nitrite after a single intake of nitrate-rich concentrated beetroot juice (BJ) in adult hemodialysis (HD) patients and in age-matched healthy volunteers (HV). Eight HD patients and seven HV participated in this single center, randomized, single-blind, placebo-controlled, crossover study. Each participant received a sequential single administration of active BJ (70 mL, 400 mg nitrate) and placebo BJ (70 mL, 0 mg nitrate) in a random order separated by a washout period of seven days. For the kinetic analysis, blood samples were collected at different time-points before and up to 44 h after BJ intake. Compared with placebo, active BJ significantly increased plasma nitrate and nitrite levels both in HD patients and HV. The area under the curve and the maximal concentration of plasma nitrate, but not of nitrite, were significantly higher in HD patients as compared with HV. In both groups, active BJ ingestion did not affect blood pressure or plasma potassium levels. Both BJs were well tolerated in all participants with no adverse events reported. Our data provide useful information in planning dietary nitrate supplementation efficacy studies in patients with reduced NO bioactivity.

Prior beetroot juice ingestion offsets endothelial dysfunction following prolonged sitting

Nutritional strategies to prevent endothelial dysfunction following prolonged sitting remain largely unknown. Given that beetroot juice (BRJ) ingestion enhances nitric oxide (NO) bioavailability, we aimed to evaluate whether prior BRJ ingestion would prevent sitting-induced endothelial dysfunction in the leg. Eleven healthy young males (n = 7) and females (n = 4) underwent two experimental trials of prolonged sitting with prior: 1) placebo ingestion (PL trial) and 2) BRJ ingestion (BRJ trial). All subjects ingested 140 ml of PL or BRJ (~0.0055 or ~12.8 mmol of nitrate, respectively) immediately before 3 h of sitting. Pre and post-sitting measurement of popliteal artery flow-mediated dilation (FMD) and blood pressure, and blood collection were undertaken. During the sitting period, an hourly assessment of popliteal artery diameter and blood velocity, blood pressure, and blood collection was performed. Popliteal artery blood flow and shear rate were significantly and similarly reduced during the sitting period in both trials (p < 0.001). Plasma nitrate and NOx (total nitrite and nitrate) concentrations were significantly increased relative to baseline in the only BRJ trial, and the overall concentrations were significantly higher in the BRJ trial (p < 0.001). Popliteal artery FMD was significantly reduced after the sitting period in the PL trial (p < 0.05), whereas no reduction was observed in the BRJ trial. Therefore, prior BRJ ingestion would prevent sitting-induced leg endothelial dysfunction via enhancing NO bioavailability.

The oral microbiome, nitric oxide and exercise performance

The human microbiome comprises ∼10¹³-10¹⁴ microbial cells which form a symbiotic relationship with the host and play a critical role in the regulation of human metabolism. In the oral cavity, several species of bacteria are capable of reducing nitrate to nitrite; a key precursor of the signaling molecule nitric oxide. Nitric oxide has myriad physiological functions, which include the maintenance of cardiovascular homeostasis and the regulation of acute and chronic responses to exercise. This article provides a brief narrative review of the research that has explored how diversity and plasticity of the oral microbiome influences nitric oxide bioavailability and related physiological outcomes. There is unequivocal evidence that dysbiosis (e.g. through disease) or disruption (e.g. by use of antiseptic mouthwash or antibiotics) of the oral microbiota will suppress nitric oxide production via the nitrate-nitrite-nitric oxide pathway and negatively impact blood pressure. Conversely, there is preliminary evidence to suggest that proliferation of nitrate-reducing bacteria via the diet or targeted probiotics can augment nitric oxide production and improve markers of oral health. Despite this, it is yet to be established whether purposefully altering the oral microbiome can have a meaningful impact on exercise performance. Future research should determine whether alterations to the composition and metabolic activity of bacteria in the mouth influence the acute responses to exercise and the physiological adaptations to exercise training.

Effect of Vitamin C and Protein Supplementation on Plasma Nitrate and Nitrite Response following Consumption of Beetroot Juice

Beetroot juice is a food high in nitrate and is associated with cardiometabolic health benefits and enhanced exercise performance through the production of nitric oxide in the nitrate−nitrite−nitric oxide pathway. Since various food components influence this pathway, the aim of this trial was to study the effect of beetroot juice alone and in conjunction with vitamin C or protein on the acute response to plasma nitrate and nitrite levels in healthy middle- to older-aged adults. In this cross-over trial, each participant received, in a randomized order, a single dose of Beet It Sport® alone; Beet It Sport®, plus a 200 mg vitamin C supplement; and Beet It Sport® plus 15 g of whey protein. Plasma levels of nitrate and nitrite were determined prior to and at 1 and 3 h after intervention. Log plasma nitrate and nitrite was calculated to obtain data that were normally distributed, and these data were analyzed using two-way within-factors ANOVA, with time and treatment as the independent factors. There were no statistically significant differences for log plasma nitrate (p = 0.308) or log plasma nitrite (p = 0.391) values across treatments. Log plasma nitrate increased significantly from pre-consumption levels after 1 h (p < 0.001) and 3 h (p < 0.001), but plasma nitrate was lower at 3 h than 1 h (p < 0.001). Log plasma nitrite increased from pre to 1 h (p < 0.001) and 3 h (p < 0.001) with log values at 3 h higher than at 1 h (p = 0.003). In this cohort, we observed no differences in log plasma nitrate and nitrite at 1 h and 3 h after co-ingesting beetroot juice with vitamin C or a whey protein supplement compared to beetroot juice alone. Further research needs to be undertaken to expand the blood-sampling time-frame and to examine factors that may influence the kinetics of the plasma nitrate to nitrite efficacy, such as differences in fluid volume and osmolarity between treatments employed.

Effect of red beetroot juice on oxidative status and islet insulin release in adult male rats

INTRODUCTION

Beetroot is rich in inorganic nitrate and it has been shown that inorganic nitrate has beneficial effects on metabolic syndrome. This study aims to investigate the effect of red beetroot juice (RBJ) on carbohydrate metabolism in adult insulin-resistant rats.

MATERIALS AND METHODS

Sixteen male Wistar rats (32 weeks old) were divided into two equal groups: control and RBJ. Treatment with drinking water (control) and 100% RBJ (RBJ) was lasted for 5 weeks. At the end of the 4th week the intraperitoneal glucose tolerance test was performed and at the end of the study period animals were sacrificed and blood and tissue (aorta, heart, and liver) samples were collected. Furthermore, pancreatic islets were isolated and their insulin secretion activity was investigated in different glycemic conditions.

RESULTS

Compared to the control group, RBJ-treated rats showed lower blood glucose and insulin levels in the glucose tolerance test. Serum and tissue levels of nitric oxide in the RBJ group were significantly higher than those in the control group. The liver peroxidation and serum aspartate transaminase levels were significantly increased in the RBJ-treated animals compared to the control group. The islets of RBJ group exhibited lower insulin secretion, especially in 16.7 mM glucose concentration (supraphysiologic condition) than control group.

CONCLUSIONS

RBJ consumption improves glucose metabolism in rats via increasing nitric oxide metabolites in an insulin-independent manner. However, future studies are needed to minimize the potential hepatic adverse consequences.

Nitrate Metabolism and Ischemic Cerebrovascular Disease: A Narrative Review

Inorganic and organic nitrates are present in vivo and in vitro. Inorganic nitrate is considered a pool of nitric oxide (NO), but it can be converted into nitrite and NO through various mechanisms. It plays an important role in the regulation of complex physiological and biochemical reactions, such as anti-inflammatory processes and the inhibition of platelet aggregation, which are closely related to the pathology and treatment of cerebrovascular disease. Ischemic cerebrovascular disease is characterized by high incidence, recurrence, and disability rates. Nitrate, nitrite, and NO were recently found to be involved in cerebrovascular disease. In this review, we describe the relationship between cerebrovascular disease and nitrate metabolism to provide a basis for further advances in laboratory and clinical medicine.

The Importance of Nitrate Reduction for Oral Health

Salivary glands concentrate plasma nitrate into saliva, leading to high nitrate concentrations that can reach the millimolar range after a nitrate-rich vegetable meal. Whereas human cells cannot reduce nitrate to nitrite effectively, certain oral bacteria can. This leads to an increase in systemic nitrite that can improve conditions such as hypertension and diabetes through nitric oxide availability. Apart from systemic benefits, it has been proposed that microbial nitrate reduction can also promote oral health. In this review, we discuss evidence associating dietary nitrate with oral health. Oral bacteria can reduce nitrite to nitric oxide, a free radical with antimicrobial properties capable of inhibiting sensitive species such as anaerobes involved in periodontal diseases. Nitrate has also been shown to increase resilience against salivary acidification in vivo and in vitro, thus preventing caries development. One potential mechanism is proton consumption during denitrification and/or bacterial reduction of nitrite to ammonium. Additionally, lactic acid (organic acid involved in oral acidification) and hydrogen sulfide (volatile compound involved in halitosis) can act as electron donors for these processes. The nitrate-reducing bacteria Rothia and Neisseria are consistently found at higher levels in individuals free of oral disease (vs. individuals with caries, periodontitis, and/or halitosis) and increase when nitrate is consumed in clinical studies. Preliminary in vitro and clinical evidence show that bacteria normally associated with disease, such as Veillonella (caries) and Prevotella (periodontal diseases and halitosis), decrease in the presence of nitrate. We propose nitrate as an ecologic factor stimulating eubiosis (i.e., an increase in health-associated species and functions). Finally, we discuss the preventive and therapeutic potential, as well as safety issues, related to the use of nitrate. In vivo evidence is limited; therefore, robust clinical studies are required to confirm the potential benefits of nitrate reduction on oral health.

Pathways Linking Oral Bacteria, Nitric Oxide Metabolism, and Health

Nitrate-reducing oral bacteria have gained a lot of interest due to their involvement in nitric oxide (NO) synthesis and its important cardiometabolic outcomes. Consortia of nitrate-metabolizing oral bacteria associated with cardiometabolic health and cognitive function have been recently identified. Longitudinal studies and clinical trials have shown that chronic mouthwash use is associated with increased blood pressure and increased risk for prediabetes/diabetes and hypertension. Concurrently, recent studies are beginning to shed some light on the complexity of nitrate reduction pathways of oral bacteria, such as dissimilatory nitrate reduction to ammonium (DNRA), which converts nitrite into ammonium, and denitrification, which converts nitrite to NO, nitrous oxide, and dinitrogen. These pathways can affect the composition and metabolism of the oral microbiome; consequently, salivary nitrate and nitrite metabolism have been proposed as targets for probiotics and oral health. These pathways could also affect systemic NO levels because NO generated through denitrification can be oxidized back to nitrite in the saliva, thus facilitating flux along the NO₃^--NO₂^--NO pathway, while DNRA converts nitrite to ammonium, leading to reduced NO. It is, therefore, important to understand which pathway predominates under different oral environmental conditions, since the clinical consequences could be different for oral and systemic health. Recent studies show that oral hygiene measures such as tongue cleaning and dietary nitrate are likely to favor denitrifying bacteria such as Neisseria, which are linked with better cardiometabolic health. A vast body of literature demonstrates that redox potential, carbon-to-nitrate ratio, and nitrate-to-nitrite ratio are key environmental drivers of the competing denitrification and DNRA pathways in various natural and artificial ecosystems. Based on this information, a novel behavioral and microbial model for nitric oxide metabolism and health is proposed, which links lifestyle factors with oral and systemic health through NO metabolism.

Interplay Among the Oral Microbiome, Oral Cavity Conditions, the Host Immune Response, Diabetes Mellitus, and Its Associated-Risk Factors-An Overview

This comprehensive review of the literature aimed to investigate the interplay between the oral microbiome, oral cavity conditions, and host immune response in Diabetes mellitus (DM). Moreover, this review also aimed to investigate how DM related risk factors, such as advanced age, hyperglycemia, hyperlipidemia, obesity, hypertension and polycystic ovary syndrome (PCOS), act in promoting or modifying specific mechanisms that could potentially perpetuate both altered systemic and oral conditions. We found that poorly controlled glycemic index may exert a negative effect on the immune system of affected individuals, leading to a deficient immune response or to an exacerbation of the inflammatory response exacerbating DM-related complications. Hyperglycemia induces alterations in the oral microbiome since poor glycemic control is associated with increased levels and frequencies of periodontal pathogens in the subgingival biofilm of individuals with DM. A bidirectional relationship between periodontal diseases and DM has been suggested: DM patients may have an exaggerated inflammatory response, poor repair and bone resorption that aggravates periodontal disease whereas the increased levels of systemic pro-inflammatory mediators found in individuals affected with periodontal disease exacerbates insulin resistance. SARS-CoV-2 infection may represent an aggravating factor for individuals with DM. Individuals with DM tend to have low salivary flow and a high prevalence of xerostomia, but the association between prevalence/experience of dental caries and DM is still unclear. DM has also been associated to the development of lesions in the oral mucosa, especially potentially malignant ones and those associated with fungal infections. Obesity plays an important role in the induction and progression of DM. Co-affected obese and DM individuals tend to present worse oral health conditions. A decrease in HDL and, an increase in triglycerides bloodstream levels seem to be associated with an increase on the load of periodontopathogens on oral cavity. Moreover, DM may increase the likelihood of halitosis. Prevalence of impaired taste perception and impaired smell recognition tend to be greater in DM patients. An important interplay among oral cavity microbiome, DM, obesity and hypertension has been proposed as the reduction of nitrate into nitrite, in addition to contribute to lowering of blood pressure, reduces oxidative stress and increases insulin secretion, being these effects desirable for the control of obesity and DM. Women with PCOS tend to present a distinct oral microbial composition and an elevated systemic response to selective members of this microbial community, but the association between oral microbiome, PCOS are DM is still unknown. The results of the studies presented in this review suggest the interplay among the oral microbiome, oral cavity conditions, host immune response and DM and some of the DM associated risk factors exist. DM individuals need to be encouraged and motivated for an adequate oral health care. In addition, these results show the importance of adopting multidisciplinary management of DM and of strengthening physicians-dentists relationship focusing on both systemic and on oral cavity conditions of DM patients.

Reactive Oxygen Species (ROS) and Antioxidants as Immunomodulators in Exercise: Implications for Heme Oxygenase and Bilirubin

Exercise is commonly prescribed as a lifestyle treatment for chronic metabolic diseases as it functions as an insulin sensitizer, cardio-protectant, and essential lifestyle tool for effective weight maintenance. Exercise boosts the production of reactive oxygen species (ROS) and subsequent transient oxidative damage, which also upregulates counterbalancing endogenous antioxidants to protect from ROS-induced damage and inflammation. Exercise elevates heme oxygenase-1 (HO-1) and biliverdin reductase A (BVRA) expression as built-in protective mechanisms, which produce the most potent antioxidant, bilirubin. Together, these mitigate inflammation and adiposity. Moderately raising plasma bilirubin protects in two ways: (1) via its antioxidant capacity to reduce ROS and inflammation, and (2) its newly defined function as a hormone that activates the nuclear receptor transcription factor PPARα. It is now understood that increasing plasma bilirubin can also drive metabolic adaptions, which improve deleterious outcomes of weight gain and obesity, such as inflammation, type II diabetes, and cardiovascular diseases. The main objective of this review is to describe the function of bilirubin as an antioxidant and metabolic hormone and how the HO-1-BVRA-bilirubin-PPARα axis influences inflammation, metabolic function and interacts with exercise to improve outcomes of weight management.

Dietary nitrate and nitrite and human health: a narrative review by intake source

Nitrate and nitrite are plant nutrients that, although ubiquitous in plant foods, are highly controversial substances in human nutrition because they are also used as additives in processed foods and may be found as contaminants in drinking water. The aim for this narrative review is to provide a thorough insight into the current literature on the relationship between dietary nitrate and nitrite and the health risks and benefits by source of intake. The results highlight beneficial effects of nitrate and nitrite consumption from plant origin on cardiovascular disease and, to date, no positive correlation has been reported with cancer. On the contrary, high intake of these compounds from processed animal-based foods is related to an increased risk of gastro-intestinal cancer. Nitrate in drinking water also raises some concern, because it appears to be related to adverse health effects. The up-to-date debate on the role of nitrate and nitrite in human nutrition seems to be justified and more research is required to verify safe consumption.

The Nitrate-Nitrite-Nitric Oxide Pathway on Healthy Ageing: A Review of Pre-clinical and Clinical Data on the Impact of Dietary Nitrate in the Elderly

We are living longer. Are we living healthier? As we age, cellular and molecular damage reshape our physiological responses towards environmental and endogenous stimuli. The free radical theory of ageing has been proposed long before ageing has been considered a “scientific discipline” and, since then, has been discussed and upgraded as a major contributor to aberrant ageing. Assuming that ageing results merely from the accumulation of oxidative modifications of biomolecules is not only a simplistic and reductive view of such a complex and dynamic process, but also free radicals and related oxidants are now considered pivotal signalling molecules. The fine modulation of critical signalling pathways by redox compounds demands a novel approach to tackle the role of free radicals in ageing. Nitric oxide (^⋅NO) is a paradigmatic example given its biological functions in cardiovascular, neurologic and immune systems. In addition to the canonical ^⋅NO synthesis by a family of enzymes, nitrate from green leafy vegetables, is reduced to nitrite in the oral cavity which is further reduced to ^⋅NO in the stomach. Boosting this nitrate-nitrite-NO pathway has been shown to improve gastrointestinal, cardiovascular, metabolic and cognitive performance both in humans and in animal models of disease. In the elderly, nitrate-derived ^⋅NO has been shown improve several physiological functions that typically decline during ageing. In this paper, the role of nitrate and derived nitrogen oxides will be discussed while reviewing pre-clinical and clinical data on the cardiovascular, neuronal, musculoskeletal and metabolic effects of nitrate during healthy ageing.

Beetroot as a functional food with huge health benefits: Antioxidant, antitumor, physical function, and chronic metabolomics activity

Previously, beetroot is mainly consumed as a food additive. In recent years, the beetroot, especially the betalains (betanin) and nitrates it contains, now has received increasing attention for their effective biological activity. Betalains have been proven to eliminate oxidative and nitrative stress by scavenging DPPH, preventing DNA damage, and reducing LDL. It also has been found to exert antitumor activity by inhibiting cell proliferation, angiogenesis, inducing cell apoptosis, and autophagy. In some chronic diseases, nitrate is the main component for lowing blood lipids, glucose, and pressure, while its role in treating hypertension and hyperglycemia has not been clearly stated. Moreover, the intake of nitrate-rich beetroot could enhance athletic performance and attenuate muscle soreness in certain types of exercise. The objective of this review is to provide sufficient evidence for the clarification of health benefits of beetroot, especially in the aspect of biooxidation, neoplastic diseases, some chronic diseases, and energy supplementation.

Inorganic nitrate: A potential prebiotic for oral microbiota dysbiosis associated with type 2 diabetes

Oral microbiota dysbiosis, concomitant with decreased abundance of nitrate (NO₃^-)-reducing bacteria, oral net nitrite (NO₂^-) production, and reduced nitric oxide (·NO) bioactivity, is associated with the development of cardiometabolic disorders. Therefore, restoring the oral microbiome to a health-associated state is suggested as a therapeutic approach to potentiate the NO₃^--NO₂^--·NO pathway and provide a backup resource for insufficient NO production in conditions including cardiovascular disease and type 2 diabetes mellitus (T2DM). The current review discusses how inorganic NO₃^- can improve the oral microbial community in patients with T2DM and act as a prebiotic. Both animal and human experiments indicated that inorganic NO₃^- modulates the oral microbiome by increasing the abundance of health-associated NO₃^--reducing bacteria (e.g., Neisseria and Rothia) and decreasing the plenty of species Prevotella and Veillonella, leading to oral NO₂^- accumulation and improved systemic ·NO availability. Supplementation with NO₃^- reduces caries- and periodontitis-associated bacteria and the pathogenic genus related to insulin resistance and glucose intolerance. In addition, inorganic NO₃^- may provide a more optimal environment for NO₃^- reductase activity in the oral cavity, as it increases salivary flow rate and prevents decreased pH by inhibiting acid-producing bacteria.

Pink pressure: beetroot (Beta vulgaris rubra) as a possible novel medical therapy for chronic kidney disease

Chronic kidney disease (CKD) manifests with systemic inflammation, oxidative stress, and gut dysbiosis, resulting in metabolic disorders and elevated rates of cardiovascular disease-associated death. These all correlate with a high economic cost to healthcare systems. Growing evidence indicates that diet is an indispensable ally in the prevention and management of CKD and its complications. In this context, the root vegetable beetroot (Beta vulgaris rubra) deserves special attention because it is a source of several bioactive compounds, such as nitrate, betaine, and betalain, and has shown beneficial effects in CKD, including reduction of blood pressure, anti-inflammatory effects, and antioxidant actions by scavenging radical oxidative species, as observed in preclinical studies. Beetroot consumption as a possible therapeutic strategy to improve the clinical treatment of patients with CKD and future directions for clinical studies are addressed in this narrative review.

Increasing Nitrate-Rich Vegetable Intake Lowers Ambulatory Blood Pressure in (pre)Hypertensive Middle-Aged and Older Adults: A 12-Wk Randomized Controlled Trial

BACKGROUND

Emerging evidence suggests that increasing dietary nitrate intake may be an effective approach to improve cardiovascular health. However, the effects of a prolonged elevation of nitrate intake through an increase in vegetable consumption are understudied.

OBJECTIVE

Our primary aim was to determine the impact of 12 wk of increased daily consumption of nitrate-rich vegetables or nitrate supplementation on blood pressure (BP) in (pre)hypertensive middle-aged and older adults.

METHODS

In a 12-wk randomized, controlled study (Nijmegen, The Netherlands), 77 (pre)hypertensive participants (BP: 144 ± 13/87 ± 7 mmHg, age: 65 ± 10 y) either received an intervention with personalized monitoring and feedback aiming to consume ∼250-300 g nitrate-rich vegetables/d (∼350-400 mg nitrate/d; n = 25), beetroot juice supplementation (400 mg nitrate/d; n = 26), or no intervention (control; n = 26). Before and after intervention, 24-h ambulatory BP was measured. Data were analyzed using repeated measures ANOVA (time × treatment), followed by within-group (paired t-test) and between-group analyses (1-factor ANOVA) where appropriate.

RESULTS

The 24-h systolic BP (SBP) (primary outcome) changed significantly (P-interaction time × treatment = 0.017) with an increase in the control group (131 ± 8 compared with 135 ± 10 mmHg; P = 0.036); a strong tendency for a decline in the nitrate-rich vegetable group (129 ± 10 compared with 126 ± 9 mmHg; P = 0.051) which was different from control (P = 0.020); but no change in the beetroot juice group (133 ± 11 compared with 132 ± 12 mmHg; P = 0.56). A significant time × treatment interaction was also found for daytime SBP (secondary outcome, P = 0.011), with a significant decline in the nitrate-rich vegetable group (134 ± 10 compared with 129 ± 9 mmHg; P = 0.006) which was different from control (P = 0.010); but no changes in the beetroot juice (138 ± 12 compared with 137 ± 14 mmHg; P = 0.41) and control group (136 ± 10 compared with 137 ± 11 mmHg; P = 0.08). Diastolic BP (secondary outcome) did not change in any of the groups.

CONCLUSIONS

A prolonged dietary intervention focusing on high-nitrate vegetable intake is an effective strategy to lower SBP in (pre)hypertensive middle-aged and older adults. This trial was registered at www.trialregister.nl as NL7814.

Nitric oxide for the prevention and treatment of viral, bacterial, protozoal and fungal infections

Although the antimicrobial potential of nitric oxide (NO) is widely published, it is little used clinically. NO is a key signalling molecule modulating vascular, neuronal, inflammatory and immune responses. Endogenous antimicrobial activity is largely mediated by high local NO concentrations produced by cellular inducible nitric oxide synthase, and by derivative reactive nitrogen oxide species including peroxynitrite and S-nitrosothiols. NO may be taken as dietary substrate (inorganic nitrate, L-arginine), and therapeutically as gaseous NO, and transdermal, sublingual, oral, intranasal and intravenous nitrite or nitrate. Numerous preclinical studies have demonstrated that NO has generic static and cidal activities against viruses (including β-coronaviruses such as SARS-CoV-2), bacteria, protozoa and fungi/yeasts  in vitro. Therapeutic effects have been seen in animal models  in vivo, and phase II trials have demonstrated that NO donors can reduce microbial infection. Nevertheless, excess NO, as occurs in septic shock, is associated with increased morbidity and mortality. In view of the dose-dependent positive and negative effects of NO, safety and efficacy trials of NO and its donors are needed for assessing their role in the prevention and treatment of infections. Trials should test dietary inorganic nitrate for pre- or post-exposure prophylaxis and gaseous NO or oral, topical or intravenous nitrite and nitrate for treatment of mild-to-severe infections, including due to SARS-CoV-2 (COVID-19). This review summarises the evidence base from  in vitro, in vivo and early phase clinical studies of NO activity in viral, bacterial, protozoal and fungal infections.

Nitric oxide for the prevention and treatment of viral, bacterial, protozoal and fungal infections

Although the antimicrobial potential of nitric oxide (NO) is widely published, it is little used clinically. NO is a key signalling molecule modulating vascular, neuronal, inflammatory and immune responses. Endogenous antimicrobial activity is largely mediated by high local NO concentrations produced by cellular inducible nitric oxide synthase, and by derivative reactive nitrogen oxide species including peroxynitrite and S-nitrosothiols. NO may be taken as dietary substrate (inorganic nitrate, L-arginine), and therapeutically as gaseous NO, and transdermal, sublingual, oral, intranasal and intravenous nitrite or nitrate. Numerous preclinical studies have demonstrated that NO has generic static and cidal activities against viruses (including β-coronaviruses such as SARS-CoV-2), bacteria, protozoa and fungi/yeasts  in vitro. Therapeutic effects have been seen in animal models  in vivo, and phase II trials have demonstrated that NO donors can reduce microbial infection. Nevertheless, excess NO, as occurs in septic shock, is associated with increased morbidity and mortality. In view of the dose-dependent positive and negative effects of NO, safety and efficacy trials of NO and its donors are needed for assessing their role in the prevention and treatment of infections. Trials should test dietary inorganic nitrate for pre- or post-exposure prophylaxis and gaseous NO or oral, topical or intravenous nitrite and nitrate for treatment of mild-to-severe infections, including due to SARS-CoV-2 (COVID-19). This review summarises the evidence base from  in vitro, in vivo and early phase clinical studies of NO activity in viral, bacterial, protozoal and fungal infections.

Body mass-normalized moderate dose of dietary nitrate intake improves endothelial function and walking capacity in patients with peripheral artery disease

Peripheral artery disease (PAD) is characterized by the accumulation of atherosclerotic plaques in the lower extremity conduit arteries, which impairs blood flow and walking capacity. Dietary nitrate has been used to reduce blood pressure (BP) and improve walking capacity in PAD. However, a standardized dose for PAD has not been determined. Therefore, we sought to determine the effects of a body mass-normalized moderate dose of nitrate (0.11 mmol nitrate/kg) as beetroot juice on serum nitrate/nitrite, vascular function, walking capacity, and tissue oxygen utilization capacity in patients with PAD. A total of 11 patients with PAD received either nitrate supplement or placebo in a randomized crossover design. Total serum nitrate/nitrite, resting BP, brachial and popliteal artery endothelial function (flow-mediated dilation, FMD), arterial stiffness (pulse-wave velocity, PWV), augmentation index (AIx), maximal walking distance and time, claudication onset time, and skeletal muscle oxygen utilization were measured pre- and postnitrate and placebo intake. There were significant group × time interactions (P < 0.05) for serum nitrate/nitrite, FMD, BP, walking distance and time, and skeletal muscle oxygen utilization. The nitrate group showed significantly increased serum nitrate/nitrite (Δ1.32 μM), increased brachial and popliteal FMD (Δ1.3% and Δ1.7%, respectively), reduced peripheral and central systolic BP (Δ-4.7 mmHg and Δ-8.2 mmHg, respectively), increased maximal walking distance (Δ92.7 m) and time (Δ56.3 s), and reduced deoxygenated hemoglobin during walking. There were no changes in PWV, AIx, or claudication (P > 0.05). These results indicate that a body-mass normalized moderate dose of nitrate may be effective and safe for reducing BP, improving endothelial function, and improving walking capacity in patients with PAD.

Repeated administration of inorganic nitrate on blood pressure and arterial stiffness: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

We aim to synthesize effects of repeated administration (≥3 days) of inorganic nitrate on blood pressure and arterial stiffness measures.

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials with at least 3 days treatment of inorganic nitrate on blood pressure and arterial stiffness in individuals with or without elevated cardiovascular disease risk. MEDLINE, EMBASE and the Cochrane Library were searched through 2 July 2019. Two independent reviewers extracted relevant study data. Data were pooled using the generic inverse variance method with random-effects model, and expressed as mean differences with 95% confidence intervals. Certainty in the evidence was assessed using GRADE.

RESULTS

Forty-seven trials were included (n = 1101). Administration of inorganic nitrate significantly lowered SBP [mean difference: -2.91 mmHg, 95% confidence interval (95% CI): -3.92 to -1.89, I = 76%], DBP (mean difference: -1.45 mmHg, 95% CI: -2.22 to -0.68, I = 78%], central SBP (mean difference: -1.56 mmHg, 95% CI: -2.62 to -0.50, I = 30%) and central DBP (mean difference: -1.99 mmHg, 95% CI: -2.37 to -1.60, I = 0%). There was no effect on 24-h blood pressure, augmentation index or pulse wave velocity. Certainty in the evidence was graded moderate for central blood pressure, pulse wave velocity and low for peripheral blood pressure, 24-h blood pressure and augmentation index.

CONCLUSION

Repeated administration (≥3 days) of inorganic nitrate lower peripheral and central blood pressure. Results appear to be driven by beneficial effects in healthy and hypertensive individuals. More studies are required to increase certainty in the evidence.

The effect of beetroot inorganic nitrate supplementation on cardiovascular risk factors: A systematic review and meta-regression of randomized controlled trials

OBJECTIVES

Inorganic nitrate is one of the most effective compounds in beetroot for improving cardiovascular function due to its conversion to nitric oxide in the body. This review and meta-analysis aimed to investigate the role of beetroot inorganic nitrate supplementation on adults' cardiovascular risk factors.

METHODS

We conducted a systematic literature review of articles published without time limitation until November 2020 in PubMed, Embase, ISI Web of Science, Scopus, Cochrane Library, and gray literature databases. We included the original randomized clinical trials (RCTs) in which the effect of beetroot inorganic nitrate supplementation on endothelial function, arterial stiffness, and blood pressure was studied.

RESULTS

43 studies were included for qualitative synthesis, out of which 27 were eligible for meta-analysis. Beetroot inorganic nitrate supplementation significantly decreased Arterial Stiffness (Pulse Wave Velocity (-0.27 m/s, p = 0.04)) and increased Endothelial function (Flow Mediated Dilation: 0.62%, p = 0.002) but did not change other parameters (p > 0.05).

CONCLUSION

Beetroot inorganic nitrate supplementation might have a beneficial effect on cardiovascular risk factors. Further high-quality investigations will be needed to provide sufficient evidence.

Dietary nitrate and population health: a narrative review of the translational potential of existing laboratory studies

BACKGROUND

Dietary inorganic nitrate (NO3-) is a polyatomic ion, which is present in large quantities in green leafy vegetables and beetroot, and has attracted considerable attention in recent years as a potential health-promoting dietary compound. Numerous small, well-controlled laboratory studies have reported beneficial health effects of inorganic NO3- consumption on blood pressure, endothelial function, cerebrovascular blood flow, cognitive function, and exercise performance. Translating the findings from small laboratory studies into 'real-world' applications requires careful consideration.

MAIN BODY

This article provides a brief overview of the existing empirical evidence basis for the purported health-promoting effects of dietary NO3- consumption. Key areas for future research are then proposed to evaluate whether promising findings observed in small animal and human laboratory studies can effectively translate into clinically relevant improvements in population health. These proposals include: 1) conducting large-scale, longer duration trials with hard clinical endpoints (e.g. cardiovascular disease incidence); 2) exploring the feasibility and acceptability of different strategies to facilitate a prolonged increase in dietary NO3- intake; 3) exploitation of existing cohort studies to explore associations between NO3- intake and health outcomes, a research approach allowing larger samples sizes and longer duration follow up than is feasible in randomised controlled trials; 4) identifying factors which might account for individual differences in the response to inorganic NO3- (e.g. sex, genetics, habitual diet) and could assist with targeted/personalised nutritional interventions; 5) exploring the influence of oral health and medication on the therapeutic potential of NO3- supplementation; and 6) examining potential risk of adverse events with long term high- NO3- diets.

CONCLUSION

The salutary effects of dietary NO3- are well established in small, well-controlled laboratory studies. Much less is known about the feasibility and efficacy of long-term dietary NO3- enrichment for promoting health, and the factors which might explain the variable responsiveness to dietary NO3- supplementation between individuals. Future research focussing on the translation of laboratory data will provide valuable insight into the potential applications of dietary NO3- supplementation to improve population health.

A Single Dose of Nitrate Increases Resilience Against Acidification Derived From Sugar Fermentation by the Oral Microbiome

Tooth decay starts with enamel demineralization due to an acidic pH, which arises from sugar fermentation by acidogenic oral bacteria. Previous in vitro work has demonstrated that nitrate limits acidification when incubating complex oral communities with sugar for short periods (e.g., 1-5 h), driven by changes in the microbiota metabolism and/or composition. To test whether a single dose of nitrate can reduce acidification derived from sugar fermentation in vivo, 12 individuals received a nitrate-rich beetroot supplement, which was compared to a placebo in a blinded crossover setting. Sucrose-rinses were performed at baseline and 2 h after supplement or placebo intake, and the salivary pH, nitrate, nitrite, ammonium and lactate were measured. After nitrate supplement intake, the sucrose-induced salivary pH drop was attenuated when compared with the placebo (p < 0.05). Salivary nitrate negatively correlated with lactate production and positively with ΔpH after sucrose exposure (r= -0.508 and 0.436, respectively, both p < 0.05). Two additional pilot studies were performed to test the effect of sucrose rinses 1 h (n = 6) and 4 h (n = 6) after nitrate supplement intake. In the 4 h study, nitrate intake was compared with water intake and bacterial profiles were analysed using 16S rRNA gene Illumina sequencing and qPCR detection of Rothia. Sucrose rinses caused a significant pH drop (p < 0.05), except 1 h and 4 h after nitrate supplement intake. After 4 h of nitrate intake, there was less lactate produced compared to water intake (p < 0.05) and one genus; Rothia, increased in abundance. This small but significant increase was confirmed by qPCR (p < 0.05). The relative abundance of Rothia and Neisseria negatively correlated with lactate production (r = -0.601 and -0.669, respectively) and Neisseria positively correlated with pH following sucrose intake (r = 0.669, all p < 0.05). Together, these results show that nitrate can acutely limit acidification when sugars are fermented, which appears to result from lactate usage by nitrate-reducing bacteria. Future studies should assess the longitudinal impact of daily nitrate-rich vegetable or supplement intake on dental health.

Effects of raw red beetroot consumption on metabolic markers and cognitive function in type 2 diabetes patients

OBJECTIVES

This study aimed to investigate the effects of raw red beetroot consumption on metabolic markers and cognitive function in type 2 diabetes patients.

METHODS

In a quasi-experimental study, 44 type 2 diabetes patients (57 ± 4.5 years) consumed raw red beetroot (100 g, daily), for 8 weeks. Metabolic markers including body weight, glucose and lipid profile parameters, inflammatory and oxidative stress markers, paraoxonase-1 activity, hepatic enzymes, blood pressure and cognitive function were measured at the beginning and end of 8 weeks.

RESULTS

Raw red beetroot consumption resulted in a significant decrease in fasting blood sugar (FBS) levels (-13.53 mg/dL), glycosylated hemoglobin (HbA1c)(-0.34%), apolipoproteinB100 (ApoB100) (-8.25 mg/dl), aspartate aminotransferase (AST) (-1.75 U/L), alanine aminotransferase (ALT) (-3.7 U/L), homocysteine (-7.88 μmol/l), systolic (-0.73 mmHg) and diastolic blood pressure (-0.34 mmHg), anda significant increase in total antioxidant capacity (TAC) (105 μmol/L) and cognitive function tests (all P values <0.05). Other variables did not change significantly after the intervention.

CONCLUSIONS

Raw red beetroot consumption for 8 weeks in T2DM patients has beneficial impacts on cognitive function, glucose metabolism and other metabolic markers.

Dietary nitrate prevents progression of carotid subclinical atherosclerosis through blood pressure-independent mechanisms in patients with or at risk of type 2 diabetes mellitus

AIMS

To test if 6 months' intervention with dietary nitrate and spironolactone could affect carotid subclinical atherosclerosis and stiffness, respectively, vs. placebo/doxazosin, to control for blood pressure (BP).

METHODS

A subgroup of participants in our double-blind, randomized-controlled, factorial VaSera trial had carotid imaging. Patients with hypertension and with/at risk of type 2 diabetes were randomized to active nitrate-containing beetroot juice or placebo nitrate-depleted juice, and spironolactone or doxazosin. Vascular ultrasound for carotid diameter (CD, mm) and intima-media thickness (CIMT, mm) was performed at baseline, 3- and 6-months. Carotid local stiffness (CS, m/s) was estimated from aortic pulse pressure (Arteriograph) and carotid lumen area. Data were analysed by modified intention to treat and using mixed-model effect, adjusted for confounders.

RESULTS

In total, 93 subjects had a baseline evaluation and 86% had follow-up data. No statistical interactions occurred between the juice and drug arms and BP was similar between the juices and between the drugs. Nitrate-containing vs. placebo juice significantly lowered CIMT (-0.06 [95% confidence interval -0.12, -0.01], P = .034), an overall difference of ~8% relative to baseline; but had no effect on CD or CS. Doxazosin appeared to reduce CS from baseline (-0.34 [-0.62, -0.06]) however, no difference was detected vs. spironolactone (-0.15 [-0.46, 0.16]). No differences were detected between spironolactone or doxazosin on CIMT and CD.

CONCLUSIONS

Our results show that 6 months' intervention with dietary nitrate influences vascular remodelling, but not carotid stiffness or diameter. Neither spironolactone nor doxazosin had a BP-independent effect on carotid structure and function.