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

Influence of orthodontic appliances and nitrate on the oral microbiota

In this pilot study, we investigated the bacterial changes introduced on the subgingival, tongue, and saliva microbiota during fixed orthodontic treatment, with or without daily administration of nitrate-containing beet juice for 2 weeks in 22 individuals with good general health. We followed clinical parameters in combination with microbiota changes before, after 2 weeks, and after 6 months of treatment with fixed orthodontic appliances. In accordance with variations in community composition at the sampling sites, effects to orthodontic treatment differed. Subgingival communities responded promptly to orthodontic treatment with no additional structural changes over time, whereas saliva and tongue communities were affected only after extended treatment. Periodontal pathogens such as Selenomonas sputigena were enriched in subgingival communities, whereas Streptococcus mutans was enriched in saliva. Specifically, Rothia mucilaginosa increased tremendously in relative abundance in both tongue and saliva communities. The effect of beet juice on microbial composition was significant in subgingival samples even though the differences were not mirrored in single differentially distributed genera or species. This indicates changes in the complete subgingival microbial net of interacting species. However, the prevention of Corynebacterium matruchotii enrichment by beet juice may be important for prevention of biofilm formation. Enrichment of Neisseria flavescens group bacteria and Abiotrophia and depletion of different Actinomyces and Stomatobaculum were observed on tongue communities. We conclude that subgingival microbiota are rapidly affected by fixed orthodontic appliances and can be positively influenced by regular administration of nitrate-containing juice. KEY POINTS: • The subgingival site, tongue, and saliva contain different microbiota • The microbiota react differently to orthodontic treatment and beet juice • Key genera and species affected by treatments were identified.

Nitrate supplementation affects taste by changing the oral metabolome and microbiome

Nitrate, an inorganic anion found in various foods is also present in saliva and has emerged as a potential prebiotic for the oral microbiome. Salivary glands concentrate nitrate from the bloodstream and release it into the oral cavity via the anion transporter sialin SLC17A5. In previous studies dietary nitrate supplementation altered oral bacteria composition, favouring genera like Rothia and Neisseria while reducing Streptococcus, Veillonella, Prevotella, and Actinomyces. The present study hypothesized that taste intensity might adapt to changes in the oral microbiome caused by nitrate supplementation. Participants underwent taste tests before, during, and after supplementation. All subjects showed greater levels of salivary nitrate during supplementation and had higher levels of Neisseria compared to before. Subjects were then grouped according to taste tests (before vs. during) as responders (ANOVA p < 0.05, n = 7), and non-responders (ANOVA p > 0.05, n = 6) and their salivary metabolome and oral microbiome further analysed. Responders had significantly less 5-amino pentanoate, formate, propionate and butyrate in saliva while non-responders showed no metabolite changes between before and during supplementation. In contrast, non-responders had increased Capnocytophaga gingivalis and altered lysosomal degradation pathways. Overall, nitrate supplementation shifted the oral microbiome composition in all subjects and when taste intensity was altered this correlated to bacteria-derived short-chain fatty acid production. This suggests taste perception is affected by the oral microbiome.

Accelerating inflammatory resolution in humans to improve endothelial function and vascular health: Targeting the non-canonical pathway for NO

BACKGROUND

Chronic cardiovascular diseases (CVD) are characterised by low-grade systemic inflammation in part due to reduced nitric oxide (NO) bioavailability associated with endothelial dysfunction. Bioavailability of NO can be enhanced by activation of the non-canonical pathway, through increased dietary inorganic nitrate consumption with the potential to attenuate inflammation.

METHODS

We sought to determine whether dietary inorganic nitrate influences the inflammatory response in models of localised (cantharidin-induced blisters) and systemic inflammation (typhoid vaccine), in healthy male volunteers and conducted two clinical trials; Blister-NITRATE and Typhoid-NITRATE respectively.

RESULTS

We show that dietary nitrate attenuates endothelial dysfunction following typhoid vaccine administration and accelerates resolution of cantharidin-induced blisters. Both phenomena were associated with an increased level of pro-resolving mediators consequent to a reduction in the expression and activity of pro-inflammatory monocytes. Moreover, we show that leukocytes of the monocyte lineage express the nitrite reductase XOR, that may drive localised nitrite reduction to elevate NO (and cGMP) to drive the protective phenotype.

CONCLUSIONS

Inorganic nitrate improves endothelial function in the setting of systemic inflammation. Whilst the immediate inflammatory response appeared unaffected by inorganic nitrate treatment, during the resolution phase of the acute inflammatory response lower levels of pro-inflammatory classical inflammatory and intermediate monocytes and attenuated levels of inflammatory cytokines and chemokines were evident. We propose that this reflects a pro-resolution phenotype that may be of potential therapeutic benefit in patients with established CVD.

CLINICAL TRIAL REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; unique identifiers NCT02715635, NCT03183830.

Nitrate reduction by salivary bacteria, glucose metabolism, and lifestyle

Background

Nitrate reductases (NR) expressed in oral bacteria reduce nitrate to nitrite. Depending on the environmental conditions and types of bacteria present nitrite can be further reduced to ammonium via Dissimilatory Nitrate Reduction to Ammonium (DNRA), or alternatively to nitric oxide (NO), which impacts cardiometabolic health.

Objective

To evaluate the associations between nitrate reduction by salivary bacteria, clinical markers of glucose metabolism, and lifestyle factors that can modulate the oral environment, potentially impacting DNRA and NR expression.

Methods

A cross-sectional study was conducted using a convenience sample of 144 participants from the San Juan Overweight Adult Longitudinal Study (SOALS), which includes data on glucose metabolism and lifestyle. DNRA and NR activities were measured in saliva under aerobic or CO2-enriched conditions.

Results

DNRA activity was inversely associated with insulin resistance (HOMA-IR) [aerobic3rd vs.1st tertile: β=-0.48 (-0.81, -0.15); CO2-enriched3rd vs.1st tertile β=-0.42 (-0.68, -0.17)], fasting blood glucose [aerobic3rd vs.1st tertile β=-0.144 (-0.268, -0.019); CO2-enriched3rd vs.1st tertile: β=-0.070 (-0.130, -0.011)], and 2-h glucose [CO2-enriched3rd vs.1st tertileβ=-0.21 (-0.37, -0.04)]. Current smokers had lower DNRA activity than non-smokers under aerobic conditions [β=-1.55 (-2.96, -0.14)], but higher under CO2-enriched conditions [β = 0.93 (0.15, 1.71)]. Toothbrushing frequency (twice/day vs. once/day) was positively associated with DNRA activity under CO2-enriched conditions [β = 4.11 (1.90, 6.32)] and with aerobic NR activity [β = 1.20, (0.14, 2.27)]. Physical activity was inversely associated with aerobic NR [β=-0.01, (-0.022, -0.003)]. Under CO2-enriched conditions NR was inversely associated with the BMI (β=-0.11, p = 0.007). Aerobic NR was higher when sucrose was added to the assays (NADP vs. sucrose β=-0.74, p = 0.02) and positively associated with salivary nitrate levels (β = 0.002, p = 0.002).

Conclusions

Nitrate reduction by salivary bacteria is inversely associated with insulin resistance and can be modulated by lifestyle factors. This knowledge could lead to the development of novel, non-invasive approaches for monitoring and preventing diabetes progression.

Plasma nitrate, dietary nitrate, blood pressure, and vascular health biomarkers: a GRADE-Assessed systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND

Hypertension and vascular dysfunction are major health concerns, and studies have suggested different interventions, including dietary nitrate (NO3), to improve it. We sought to elucidate the effects of dietary NO3 on plasma NO3 and nitrite (NO2) levels and to determine the shape of the effect of dietary NO3 on blood pressure (BP) and vascular health biomarkers.

METHODS

PubMed, Scopus, and Web of Science were searched up to February 2024 for eligible randomized controlled trials (RCTs). The pooled results were reported as weighted mean differences (WMD) and 95% confidence intervals (CIs).

RESULTS

Our analysis of 75 RCTs involving 1823 participants revealed that per each millimole (mmol) increase in the administered NO3 dose, both acute (WMD: 32.7µmol/L; 95%CI: 26.1, 39.4) and chronic-term (WMD: 19.6µmol/L; 95%CI: 9.95, 29.3) plasma NO3 levels increased. Per each mmol increase in NO3 intake, a reduction in systolic BP levels was observed in the acute (WMD: -0.28mmHg; 95%CI: -0.40, -0.17), short-term (WMD: -0.24mmHg; 95%CI: -0.40, -0.07), and medium-term (WMD: -0.48mmHg; 95%CI: -0.71, -0.25) periods. Furthermore, a decrease in diastolic BP for each mmol increase in NO3 intake (WMD: -0.12 mmHg; 95% CI: -0.21, -0.03) was shown. Moreover, a linear dose-response relationship was indicated between each mmol of NO3 intake and medium-term pulse wave velocity (WMD: -0.07 m/s; 95%CI: -0.11, -0.03), medium-term flow-mediated dilation (WMD: 0.30%; 95%CI: 0.15, 0.46), and medium-term augmentation index (WMD: -0.57%; 95%CI: -0.98, -0.15).

CONCLUSION

We observed dose-dependent increases in plasma NO3 and NO2 levels, along with consequent reductions in BP and enhancements in vascular health following dietary NO3 supplementation. Future high-quality, population-specific studies with optimized dietary NO3 dosages are needed to strengthen the certainty of the evidence.

REGISTRATION

The protocol for this systematic review was registered in PROSPERO under the registration number CRD42024535335.

Inter-individual differences in the blood pressure lowering effects of dietary nitrate: a randomised double-blind placebo-controlled replicate crossover trial

PURPOSE

Dietary nitrate supplementation increases nitric oxide (NO) bioavailability and reduces blood pressure (BP). Inter-individual differences in these responses are suspected but have not been investigated using robust designs, e.g., replicate crossover, and appropriate statistical models. We examined the within-individual consistency of the effects of dietary nitrate supplementation on NO biomarkers and BP, and quantified inter-individual response differences.

METHODS

Fifteen healthy males visited the laboratory four times. On two visits, participants consumed 140 ml nitrate-rich beetroot juice (~ 14.0mmol nitrate) and, on the other two visits, they consumed 140 ml nitrate-depleted beetroot juice (~ 0.03mmol nitrate). Plasma nitrate and nitrite concentrations were measured 2.5 h post-supplementation. BP was measured pre- and 2.5 h post-supplementation. Between-replicate correlations were quantified for the placebo-adjusted post-supplementation plasma nitrate and nitrite concentrations and pre-to-post changes in BP. Within-participant linear mixed models and a meta-analytic approach estimated participant-by-condition treatment response variability.

RESULTS

Nitrate-rich beetroot juice supplementation elevated plasma nitrate and nitrite concentrations and reduced systolic (mean:-7mmHg, 95%CI: -3 to -11mmHg) and diastolic (mean:-6mmHg, 95%CI: -2 to -9mmHg) BP versus placebo. The participant-by-condition interaction response variability from the mixed model was ± 7mmHg (95%CI: 3 to 9mmHg) for systolic BP and consistent with the treatment effect heterogeneity t = ± 7mmHg (95%CI: 5 to 12mmHg) derived from the meta-analytic approach. The between-replicate correlations were moderate-to-large for plasma nitrate, nitrite and systolic BP (r = 0.55 to 0.91).

CONCLUSIONS

The effects of dietary nitrate supplementation on NO biomarkers and systolic BP varied significantly from participant to participant. The causes of this inter-individual variation deserve further investigation.

TRIAL REGISTRATION

https://clinicaltrials.gov/study/NCT05514821 .

Developing multifaceted drug synergistic therapeutic strategy against neurological disorders

Drug synergism can alter the ultimate biological effects and bioavailability of phytoconstituents. Acetylcholinesterase (AChE) inhibitors as symptomatic drugs are potent therapeutic regimen for neurodegenerative diseases. In this context, this study characterized the synergistic antioxidant, anti-inflammatory and anti-AChE effects of the selected phytochemicals including standard drugs followed by enzyme kinetics, structure-based ligands screening and molecular dynamics simulation study. The synergistic interactions were evaluated through Isoradiation and Synergy finder 3.0 methods. The combinations of Quercetin (QCT), Folic acid (FA), and Swertiamarin (SWT) with specific reference drugs were studied. The combinations of SWT + GA (Gallic acid) and FA + GA at 1:1 (γ:0.10 & 0.08, respectively) showed the significant synergistic antioxidant effect via ABTS assay. Further, in combination, QCT + SWT showed the maximum synergistic effect (γ: 0.02-0.13) in anti-inflammatory assay. Moreover, the combinations QCT, FA, and SWT with reference drug, Donepezil (DP), illustrated potent synergistic activity as anti-AChE in 1:1 proportion (γ: 0.18). The interaction pattern of phytochemicals significantly exhibited synergism (γ < 1) depicting their optimum activity in combinations compared to individual components. Enzyme kinetics evaluation showed the competitive binding of SWT with AChE as of donepezil. All the parameters of ADMET study proposed the QCT and SWT as acceptable oral drug molecules. Computational docking study revealed that QCT and SWT with lowest RMSD (1.096, 2.104) and lowest docking score (-9.831, -7.435 kcal/mol) showed maximum binding efficacy. Furthermore, molecular simulation study depicted the stability of protein-ligand complexes. These findings provide novel insight in the development of dietary treatment based on their synergistic effects for neurological disorders as optimum alternative therapeutic agents.

Association of over-the-counter mouthwash use with markers of nitric oxide metabolism, inflammation, and endothelial function-a cross-sectional study

Introduction

Regular use of mouthwash can disrupt nitrate reduction by oral bacteria and may affect systemic nitric oxide (NO) levels, which are important for inflammation and endothelial function. We aim to assess the association between over-the-counter (OTC) mouthwash use and nitrate/nitrite, markers of inflammation (IL-6, TNF-α, CRP) and endothelial function (sICAM-1, sVCAM-1) in serum and saliva, and to assess the relationship between nitrate/nitrite levels and these biomarkers, as well as how OTC mouthwash modulated this relationship. We hypothesize that nitrates/nitrites are associated with these biomarkers, and that their associations would vary with the frequency of mouthwash use.

Method

Our cross-sectional study used data and specimen from the baseline of the San Juan Overweight Adult Longitudinal Study (SOALS). Robust Gamma regression with log-link function, Spearman correlations and partial correlations adjusted for covariates were used for the analysis.

Results

Using OTC mouthwash twice a day or more was significantly associated with lower serum nitrite levels compared to less frequent use (β = -0.357, 95% CI: -0.650, -0.064), but not with other markers of inflammation and endothelial function. Mouthwash use differentially impacted the relationship between nitrate/nitrite and TNF-α, sICAM-1 and sVCAM-1. Specifically, in the participants who used mouthwash less than twice a day or no use, TNF-α (β = -0.35, 95% CI: -0.52, -0.18), and sICAM-1 (β = -0.21, 95% CI: -0.32, -0.09) were negatively associated with serum nitrite. In the participants who used mouthwash twice a day or more use, TNF-α was positively associated with serum nitrate (β = 3.36, 95% CI: 2.07, 4.65), salivary nitrite (β = 1.04, 95% CI: 0.39, 1.69) and salivary nitrate (β = 0.48, 95% CI: 0.25, 0.71); sICAM-1 was positively associated with serum nitrate (β = 1.58, 95% CI: 0.86, 2.29). In both subgroups of mouthwash users, sVCAM-1 was positively correlated with serum nitrate and salivary nitrate. In addition, sVCAM-1 was positively correlated with serum nitrite in participants who used mouthwash frequently (ρ_S = 0.18, p = 0.045).

Discussion

Regular use of OTC mouthwash was associated with systemic nitric oxide. This raises concerns about its potential effects on the levels of inflammatory and endothelial biomarkers associated with cardiometabolic diseases.

Nitrite Production from Nitrate in the Oral Microbiome and Its Contribution to Oral and Systemic Health

The metabolism of nitrate to nitrite by the oral microbiome has recently attracted considerable attention. Nitrate is abundant in the green and yellow vegetables comprising our daily diet. Nitrate is reduced to nitrite by the oral microbiome in the oral cavity, absorbed through the gastrointestinal tract after ingestion, and transferred to the bloodstream, where it is gradually reoxidized to nitrate, some of which is secreted back into the oral cavity as saliva (enterosalivary circulation). Consequently, the oral environment is constantly supplied with nitrate from food and saliva. Nitrite has antibacterial and vasodilatory effects, which may contribute to the suppression of oral or intestinal bacteria and decrease blood pressure through systemic vasodilation in the enterosalivary circulation. Thus, the nitrate metabolism of oral bacteria may play an important role in maintaining and improving both oral and systemic health. On the other hand, there has been concerns that nitrate may contribute to the production of carcinogenic substances such as nitrosamines. However, there is currently a mainstream view that this idea should be reconsidered. Given the growing number of reports showing the relationship between the oral microbiome and systemic health from the perspective of nitrate metabolism; accordingly, this review summarizes the latest findings on the mechanisms of nitrite production by the oral microbiome and its relationship with oral and systemic health.

Chronic inorganic nitrate supplementation does not improve metabolic health and worsens disease progression in mice with diet-induced obesity

Inorganic nitrate (NO3-) has been proposed to be of therapeutic use as a dietary supplement in obesity and related conditions including the metabolic syndrome (MetS), type II diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). Administration of NO3- to endothelial nitric oxide synthase-deficient mice reversed aspects of MetS; however, the impact of NO3- supplementation in diet-induced obesity is not well understood. Here we investigated the whole body metabolic phenotype and cardiac and hepatic metabolism in mice fed a high-fat, high-sucrose (HFHS) diet for up to 12 mo of age, supplemented with 1 mM NaNO3 (or NaCl) in their drinking water. HFHS feeding was associated with a progressive obesogenic and diabetogenic phenotype, which was not ameliorated by NO3-. Furthermore, HFHS-fed mice supplemented with NO3- showed elevated levels of cardiac fibrosis and accelerated progression of MASLD including development of hepatocellular carcinoma in comparison with NaCl-supplemented mice. NO3- did not enhance mitochondrial β-oxidation capacity in any tissue assayed and did not suppress hepatic lipid accumulation, suggesting it does not prevent lipotoxicity. We conclude that NO3- is ineffective in preventing the metabolic consequences of an obesogenic diet and may instead be detrimental to metabolic health against the background of HFHS feeding. This is the first report of an unfavorable effect of long-term nitrate supplementation in the context of the metabolic challenges of overfeeding, warranting urgent further investigation into the mechanism of this interaction.NEW & NOTEWORTHY Inorganic nitrate has been suggested to be of therapeutic benefit in obesity-related conditions, as it increases nitric oxide bioavailability, enhances mitochondrial β-oxidation, and reverses metabolic syndrome in eNOS-/- mice. However, we here show that over 12 months nitrate was ineffective in preventing metabolic consequences in high fat, high sucrose-fed mice and worsened aspects of metabolic health, impairing cholesterol handling, increasing cardiac fibrosis, and exacerbating steatotic liver disease progression, with acceleration to hepatocellular carcinoma.

Beetroot juice intake positively influenced gut microbiota and inflammation but failed to improve functional outcomes in adults with long COVID: A pilot randomized controlled trial

BACKGROUND & AIMS

Long-term effects of coronavirus disease 2019 (long COVID) develop in a substantial number of people following an acute COVID-19 episode. Red beetroot juice may have positive effects on multiple pathways involved in long COVID. The aim of this pilot study was to explore the impact of beetroot juice supplementation on physical function, gut microbiota, and systemic inflammation in adults with long COVID.

METHODS

A single-center, double-blind, placebo-controlled randomized trial was conducted to test the effects of 14 days of beetroot juice supplementation, rich in nitrates and betalains, on functional and biological outcomes in adults aged between 20 and 60 years with long COVID. Participants were randomized 1:1 to receive either daily oral supplementation with 200 mL beetroot juice (∼600 mg nitrate) or placebo (∼60 mg nitrate) for 14 days. The primary endpoint was the change from baseline to day 14 in a fatigue resistance test. Secondary outcomes included the distance walked on the 6-min walk test, handgrip strength, and flow-mediated dilation. Secondary endpoints also included changes from baseline in circulating inflammatory mediators and metagenomic and fecal water metabolomic profiles. Partial least squares discriminant analysis (PLS-DA) models were built to evaluate the differences in biological variables associated with the interventions.

RESULTS

Thirty-one participants were randomized in the study. Twenty-five of them (median (interquartile range) age 40 (10), 14 [56 %] women), received either beetroot juice (15) or placebo (10) and completed the study. At 14 days, fatigue resistance significantly improved from baseline (mean difference [standard error]: +21.8 [3.7] s; p < 0.001) with no significant differences between intervention groups. A significant increase from baseline in the distance walked on the 6-min walk test was observed (mean difference [standard error]: +30.0 [9.4] m; p = 0.03), which was not different between groups. Flow-mediated dilation did not differ between participants who received beetroot juice and those on placebo. PLS-DA models allowed correct classification of participants with 92.2 ± 4.4 % accuracy. Those who ingested red beetroot juice had a greater abundance of bacteria with well-known beneficial effects, including Akkermansia, Oscillospira, Prevotella, Roseburia, Ruminococcaceae, and Turicibacter, compared with placebo. Participants allocated to beetroot juice supplementation were also characterized by significantly higher levels of fecal nicotinate, trimethylamine, and markers of beetroot juice intake (e.g., 5,6-dihydroxyindole). Finally, higher levels of interferon gamma and macrophage inflammatory protein-1β were found in participants who consumed beetroot juice.

CONCLUSION

Beetroot juice supplementation for two weeks did not to induce significant improvements in functional outcomes in adults with long COVID compared with placebo. Beneficial effects were observed in both gut microbiota composition (i.e., increase in probiotic species) and inflammatory mediators.

TRIAL REGISTRATION

Trial was registered under ClinicalTrials.gov. Identifier no. NCT06535165.

Periodontal treatment causes a longitudinal increase in nitrite-producing bacteria

BACKGROUND

The oral microbiome-dependent nitrate (NO3 -)-nitrite (NO2 -)-nitric oxide (NO) pathway may help regulate blood pressure. NO2 --producing bacteria in subgingival plaque are reduced in relative abundance in patients with untreated periodontitis compared with periodontally healthy patients. In periodontitis patients, the NO2 --producing bacteria increase several months after periodontal treatment. The early effects of periodontal treatment on NO2 --producing bacteria and the NO3 --NO2 --NO pathway remain unknown. The aim of this study was to determine how periodontal treatment affects the oral NO2 --producing microbiome and salivary NO3 - and NO2 - levels over time.

METHODS

The subgingival microbiota of 38 periodontitis patients was analysed before (baseline [BL]) and 1, 7 and 90 days after periodontal treatment. Changes in NO2 --producing bacteria and periodontitis-associated bacteria were determined by 16s rRNA Illumina sequencing. Saliva samples were collected at all-time points to determine NO3 - and NO2 - levels using gas-phase chemiluminescence.

RESULTS

A significant increase was observed in the relative abundance of NO2 --producing species between BL and all subsequent timepoints (all p < 0.001). Periodontitis-associated species decreased at all timepoints, relative to BL (all p < 0.02). NO2 --producing species negatively correlated with periodontitis-associated species at all timepoints, with this relationship strongest 90 days post-treatment (ρ = -0.792, p < 0.001). Despite these findings, no significant changes were found in salivary NO3 - and NO2 - over time (all p > 0.05).

CONCLUSIONS

Periodontal treatment induced an immediate increase in the relative abundance of health-associated NO2 --producing bacteria. This increase persisted throughout periodontal healing. Future studies should test the effect of periodontal treatment combined with NO3 - intake on periodontal and cardiovascular health.

Diabetes Mellitus and Cardiovascular Disease: Exploring Epidemiology, Pathophysiology, and Treatment Strategies

Diabetes mellitus (DM) affects 537 million people as of 2021, and is projected to rise to 783 million by 2045. This positions DM as the ninth leading cause of death globally. Among DM patients, cardiovascular disease (CVD) is the primary cause of morbidity and mortality. Notably, the prevalence rates of CVD is alarmingly high among diabetic individuals, particularly in North America and the Caribbean (46.0%), and Southeast Asia (42.5%). The predominant form of CVD among diabetic patients is coronary artery disease (CAD), accounting for 29.4% of cases. The pathophysiology of DM is complex, involving insulin resistance, β-cell dysfunction, and associated cardiovascular complications including diabetic cardiomyopathy (DCM) and cardiovascular autonomic neuropathy (CAN). These conditions exacerbate CVD risks underscoring the importance of managing key risk factors including hypertension, dyslipidemia, obesity, and genetic predisposition. Understanding the genetic networks and molecular processes that link diabetes and cardiovascular disease can lead to new diagnostics and therapeutic interventions. Imeglimin, a novel mitochondrial bioenergetic enhancer, represents a promising medication for diabetes with the potential to address both insulin resistance and secretion difficulties. Effective diabetes management through oral hypoglycemic agents (OHAs) can protect the cardiovascular system. Additionally, certain antihypertensive medications can significantly reduce the risk of diabetes-related CVD. Additionally, lifestyle changes, including diet and exercise are vital in managing diabesity and reducing CVD risks. These interventions, along with emerging therapeutic agents and ongoing clinical trials, offer hope for improved patient outcomes and long-term DM remission. This study highlights the urgent need for management strategies to address the overlapping epidemics of DM and CVD. By elucidating the underlying mechanisms and risk factors, this study aims to guide future perspectives and enhance understanding of the pathogenesis of CVD complications in patients with DM, thereby guiding more effective treatment strategies.

Effects of low and high dietary nitrate intake on human saliva, plasma and skeletal muscle nitrate and nitrite concentrations and their functional consequences

Dietary nitrate (NO3-) supplementation has been shown to reduce blood pressure (BP), improve exercise performance, and alter the oral microbiome. Following a "control" diet (CON), we manipulated dietary NO3- intake to examine the effect of a short-term (7-day) low NO3- diet (LOW) followed by a 3-day high NO3- diet (HIGH), compared to a 7-day standard (STD) NO3- diet followed by HIGH, on saliva, plasma, and muscle [NO3-] and nitrite ([NO2-]), BP, and cycling exercise performance in healthy young adults. We also examined the effect of LOW on the oral microbiome. Saliva [NO3-] and [NO2-], and plasma [NO3-] were significantly lower than CON following LOW (all P < 0.05) but there was no change in plasma [NO2-] or muscle [NO3-] and [NO2-] (all P > 0.05). Following HIGH, saliva and plasma [NO3-] and [NO2-], and muscle [NO3-], were significantly elevated above CON, LOW and STD (all P < 0.05), but there was no difference between CON-LOW-HIGH and CON-STD-HIGH (P < 0.05). BP and exercise performance were not altered following LOW (P > 0.05). HIGH significantly reduced systolic and diastolic BP compared to CON when preceded by STD (both P < 0.05) but not when preceded by LOW (P > 0.05). Peak (+4 %) and mean (+3 %) power output during sprint cycling was significantly improved following HIGH (both P < 0.05), with no differences between CON-LOW-HIGH and CON-STD-HIGH (both P > 0.05). LOW altered the oral microbiome composition, including decreases in relative abundances of phylum Proteobacteria and genus Neisseria. The findings indicate that a short-term low NO3- diet lowers plasma but not skeletal muscle [NO3-]. The maintenance of plasma [NO2-] and muscle [NO3-] and [NO2-] following LOW may be indicative of their importance to biological functions, including BP regulation and exercise performance.

The NITRATE-OCT study-inorganic nitrate reduces in-stent restenosis in patients with stable coronary artery disease: a double-blind, randomised controlled trial

Background

Coronary angioplasty and stent insertion is a first line treatment for patients with coronary artery disease, however it is complicated in the long-term by in-stent restenosis (ISR) in a proportion of patients with an associated morbidity. Despite this, currently there are no effective treatments available for the prevention of ISR. Repeat percutaneous revascularisation carries increased risks of major adverse cardiovascular events and a higher incidence of stent failure. In this study we report the efficacy of dietary inorganic nitrate in the prevention of ISR in a prospective, double-blind, randomised controlled trial.

Methods

NITRATE-OCT is a double-blind, randomised, single-centre, placebo-controlled phase II trial. 300 patients who were planned to undergo percutaneous coronary intervention (PCI) and drug eluting stent (DES) implantation for stable angina were randomised on a 1:1 basis to receive a daily dose of either dietary inorganic nitrate or placebo for 6 months. Block randomisation was used and patients stratified according to diabetes status. The patients then underwent quantitative coronary angiography (QCA) at baseline and at 6 months and optical coherence tomography at 6 months to quantify ISR. The primary endpoint was the QCA quantified decrease of in-stent/in-segment diameter from the baseline measure at 6 months i.e., in-stent and in-segment late-lumen loss (LLL). The study is registered with ClinicalTrials.gov, number NCT02529189.

Findings

From November 1st 2015 and March 31st 2020, NITRATE-OCT enrolled 300 patients with angina, with 150 each randomised to receive 70 mL of nitrate-containing beetroot juice or placebo (nitrate-deplete) juice for 6 months. Procedural characteristics were similar between the groups. The primary endpoint was available in 208 patients: 107 and 101 in the nitrate and placebo groups, respectively. There was a statistically significant effect of inorganic nitrate on both primary endpoints: in-stent LLL decreased by 0.16 mm (95% CI:0.06-0.25; P = 0.001) with mean = 0.09 ± 0.38 mm in the inorganic nitrate group versus 0.24 ± 0.33 mm in the placebo group; (P = 0.0052); and in-segment LLL decreased by 0.24 mm (95% CI:0.12-0.36; P < 0.001) with mean = 0.02 ± 0.52 mm in the inorganic nitrate group and 0.26 ± 0.37 mm in the placebo group (P = 0.0002). Inorganic nitrate treatment was associated with a rise in the plasma nitrate concentration of ∼6.1-fold and plasma nitrite (NO2 -) of ∼2.0-fold at 6 months. These rises were associated with sustained decreases in systolic blood pressure (SBP) at 6 months compared to baseline with a change SBP of -12.06 ± 15.88 mmHg compared to the placebo group of 2.52 ± 14.60 mmHg (P < 0.0001).

Interpretation

In patients who underwent PCI for stable coronary artery disease, a once-a-day oral inorganic nitrate treatment was associated with a significant decrease in both in-stent and in-segment LLL.

Funding

This trial and KSR was funded by the National Institute for Health and Care Research (NIHR) (DRF-2014-07-008) and NIHR ACL, HW and this study were supported by The NIHR Barts Biomedical Research Centre, IC was funded by The North and East London Clinical Research Network, CL, GM were funded by The Barts Charity Cardiovascular Programme MRG00913 and MO was funded by The British Heart Foundation Project Grant PG/19/4/33995.

Nitric Oxide Signaling and Regulation in the Cardiovascular System: Recent Advances

Nitric oxide (NO) from endothelial NO synthase importantly contributes to vascular homeostasis. Reduced NO production or increased scavenging during disease conditions with oxidative stress contribute to endothelial dysfunction and NO deficiency. In addition to the classical enzymatic NO synthases (NOS) system, NO can also be generated via the nitrate-nitrite-NO pathway. Dietary and pharmacological approaches aimed at increasing NO bioactivity, especially in the cardiovascular system, have been the focus of much research since the discovery of this small gaseous signaling molecule. Despite wide appreciation of the biological role of NOS/NO signaling, questions still remain about the chemical nature of NOS-derived bioactivity. Recent studies show that NO-like bioactivity can be efficiently transduced by mobile NO-ferroheme species, which can transfer between proteins, partition into a hydrophobic phase, and directly activate the soluble guanylyl cyclase-cGMP-protein kinase G pathway without intermediacy of free NO. Moreover, interaction between red blood cells and the endothelium in the regulation of vascular NO homeostasis have gained much attention, especially in conditions with cardiometabolic disease. In this review we discuss both classical and nonclassical pathways for NO generation in the cardiovascular system and how these can be modulated for therapeutic purposes. SIGNIFICANCE STATEMENT: After four decades of intensive research, questions persist about the transduction and control of nitric oxide (NO) synthase bioactivity. Here we discuss NO signaling in cardiovascular health and disease, highlighting new findings, such as the important role of red blood cells in cardiovascular NO homeostasis. Nonclassical signaling modes, like the nitrate-nitrite-NO pathway, and therapeutic opportunities related to the NO system are discussed. Existing and potential pharmacological treatments/strategies, as well as dietary components influencing NO generation and signaling are covered.

No Difference between the Efficacy of High-Nitrate and Low-Nitrate Vegetable Supplementation on Blood Pressure after 16 Weeks in Individuals with Early-Stage Hypertension: An Exploratory, Double-Blinded, Randomized, Controlled Trial

Dietary inorganic nitrate lowers blood pressure (BP) in healthy individuals through improved nitric oxide (NO) bioavailability. However, there is limited evidence examining the long-term effects of dietary nitrate for managing hypertension. We aimed to determine whether the sustained intake of dietary nitrate improved BP and cardiovascular disease (CVD) risk factors in individuals with early-stage hypertension. The Dietary Nitrate (NO3) on BP and CVD Risk Factors (DINO3) Trial was a multi-center, double-blinded, parallel, randomized, controlled trial in participants with elevated BP. Participants were supplemented with high-nitrate (HN) (~400 mg nitrate) or low-nitrate (LN) vegetable powder (~50 mg nitrate) on top of their usual diets for 16 weeks. The primary outcome was office systolic BP at 16 weeks. The secondary outcomes were 24 h ambulatory BP, central BP, heart-rate-corrected augmentation index (AIx75), carotid-femoral pulse wave velocity (cf-PWV), lipids, and high-sensitivity C-reactive protein (hs-CRP). Sixty-six participants were randomized at baseline (39M:27F, age: 51.5 ± 10.8 years, BMI:27.9 ± 3.2 kg/m2). In an intention-to-treat analysis, no differences were observed between HN and LN groups in terms of office systolic BP at 16 weeks (3.91 ± 3.52 mmHg, p = 0.27) or secondary outcomes. In this exploratory study, sustained HN vegetable supplementation did not exhibit more favorable vascular effects than LN vegetable supplementation in individuals with elevated BP.

Anti-obesity effects of Beta vulgaris and Eruca sativa-based extracts

Obesity is a major source of morbidity worldwide with more than 2 billion adults being overweight or obese. The incidence of obesity has tripled in the last 50 years, leading to an increased risk for a variety of noncommunicable diseases. Previous studies have demonstrated the positive effects of green leafy vegetables on weight gain and obesity and have attributed these beneficial properties, at least in part, to nitrates and isothiocyanates. Nitrates are converted to nitric oxide (NO) and isothiocyanates are known to release hydrogen sulfide (H2S). Herein, we investigated the effect of extracts and fractions produced from Beta vulgaris and Eruca sativa for their ability to limit lipid accumulation, regulate glucose homeostasis, and reduce body weight. Extracts from the different vegetables were screened for their ability to limit lipid accumulation in adipocytes and hepatocytes and for their ability to promote glucose uptake in skeletal muscle cultures; the most effective extracts were next tested in vivo. Wild type mice were placed on high-fat diet for 8 weeks to promote weight gain; animals receiving the selected B. vulgaris and E. sativa extracts exhibited attenuated body weight. Treatment with extracts also led to reduced white adipose tissue depot mass, attenuated adipocyte size, reduced expression of Dgat2 and PPARγ expression, and improved liver steatosis. In contrast, the extracts failed to improve glucose tolerance in obese animals and did not affect blood pressure. Taken together, our data indicate that extracts produced from B. vulgaris and E. sativa exhibit anti-obesity effects, suggesting that dietary supplements containing nitrates and sulfide-releasing compounds might be useful in limiting weight gain.

The Effect of Dietary Nitrate on the Oral Microbiome and Salivary Biomarkers in Individuals with High Blood Pressure

BACKGROUND

Green leafy vegetables (GLV) contain inorganic nitrate, an anion with potential prebiotic effects on the oral microbiome. However, it remains unclear whether GLV and pharmacological supplementation [potassium nitrate (PN)] with a nitrate salt induce similar effects on the oral microbiome.

OBJECTIVES

This study aimed to compare the effect of GLV with PN supplementation on the oral microbiome composition and salivary biomarkers in individuals with high blood pressure.

METHODS

Seventy individuals were randomly allocated to 3 different groups to follow a 5-wk dietary intervention. Group 1 consumed 300 mg/d of nitrate in form of GLV. Group 2 consumed pills with 300 mg/d of PN and low-nitrate vegetables. Group 3 consumed pills with potassium chloride (placebo: PLAC) and low-nitrate vegetables. The oral microbiome composition and salivary biomarkers of oral health were analyzed before and after the dietary intervention.

RESULTS

The GLV and PN groups showed similar microbial changes, probably nitrate-dependent, including an increase in the abundance of Neisseria, Capnocytophaga, Campylobacter species, and a decrease in Veillonella, Megasphaera, Actinomyces, and Eubacterium species after the treatment. Increased abundance of Rothia species, and reduced abundance of Streptococcus, Prevotella, Actinomyces, and Mogibacterium species were observed in the GLV group, which could be nitrate-independent. GLV and PN treatments increased salivary pH, but only GLV treatment showed an increase in the salivary buffering capacity and a reduction of lactate.

CONCLUSION

The combination of nitrate-dependent and nitrate-independent microbial changes in the GLV group has a stronger effect to potentially improve oral health biomarkers compared with PN.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL TRIAL REGISTRY NUMBER

NCT04584372 (ClinicialTrials.gov).

Nitrate: "the source makes the poison"

Interest in the role of dietary nitrate in human health and disease has grown exponentially in recent years. However, consensus is yet to be reached as to whether consuming nitrate from various food sources is beneficial or harmful to health. Global authorities continue to recommend an acceptable daily intake (ADI) of nitrate of 3.7 mg/kg-bw/day due to concerns over its carcinogenicity. This is despite evidence showing that nitrate consumption from vegetable sources, exceeding the ADI, is associated with decreased cancer prevalence and improvements in cardiovascular, oral, metabolic and neurocognitive health. This review examines the paradox between dietary nitrate and health and disease and highlights the key role of the dietary source and food matrix in moderating this interaction. We present mechanistic and epidemiological evidence to support the notion that consuming vegetable-derived nitrate promotes a beneficial increase in nitric oxide generation and limits toxic N-nitroso compound formation seen with high intakes of nitrate added during food processing or present in contaminated water. We demonstrate the need for a more pragmatic approach to nitrate-related nutritional research and guidelines. Ultimately, we provide an overview of our knowledge in this field to facilitate the various therapeutic applications of dietary nitrate, whilst maintaining population safety.

Health effects of 100% fruit and vegetable juices: evidence from human subject intervention studies

The health effects of 100% fruit and vegetable juices (FVJ) represent a controversial topic. FVJ contain notable amounts of free sugars, but also vitamins, minerals, and secondary compounds with proven biological activities like (poly)phenols and carotenoids. The review aimed to shed light on the potential impact of 100% FVJ on human subject health, comprehensively assessing the role each type of juice may have in specific health outcomes for a particular target population, as reported in dietary interventions. The effects of a wide range of FVJ (orange, grapefruit, mandarin, lemon, apple, white, red, and Concord grapes, pomegranate, cranberry, chokeberry, blueberry, other minor berries, sweet and tart cherry, plum, tomato, carrot, beetroot, and watermelon, among others) were evaluated on a series of outcomes (anthropometric parameters, body composition, blood pressure and vascular function, lipid profile, glucose homeostasis, biomarkers of inflammation and oxidative stress, cognitive function, exercise performance, gut microbiota composition and bacterial infections), providing a thorough picture of the contribution of each FVJ to a health outcome. Some juices demonstrated their ability to exert potential preventive effects on some outcomes while others on other health outcomes, emphasising how the differential composition in bioactive compounds defines juice effects. Research gaps and future prospects were discussed. Although 100% FVJ appear to have beneficial effects on some cardiometabolic health outcomes, cognition and exercise performance, or neutral effects on anthropometric parameters and body composition, further efforts are needed to better understand the impact of 100% FVJ on human subject health.

Effect of Acute Dietary Nitrate Supplementation on the Changes in Calf Venous Volume during Postural Change and Skeletal Muscle Pump Activity in Healthy Young Adults

Dietary nitrate (NO3-) supplementation is known to enhance nitric oxide (NO) activity and acts as a vasodilator. In this randomized crossover study, we investigated the effect of inorganic NO3- supplementation on the changes in calf venous volume during postural change and subsequent skeletal muscle pump activity. Fifteen healthy young adults were assigned to receive beetroot juice (BRJ) or a NO3--depleted control beverage (prune juice: CON). Two hours after beverage consumption, the changes in the right calf volume during postural change from supine to upright and a subsequent right tiptoe maneuver were measured using venous occlusion plethysmography. The increase in calf volume from the supine to upright position (total venous volume [VV]) and the decrease in calf volume during the right tiptoe maneuver (venous ejection volume [Ve]) were calculated. Plasma NO3- concentration was higher in the BRJ group than in the CON group 2 h after beverage intake (p < 0.05). However, VV and Ve did not differ between CON and BRJ. These results suggest that acute intake of BRJ may enhance NO activity via the NO3- → nitrite → NO pathway but does not change calf venous pooling due to a postural change or the calf venous return due to skeletal muscle pump activity in healthy young adults.

Effects of dietary nitrate supplementation on oral health and associated markers of systemic health: a systematic review

Poor oral health can impact an individual's ability to eat and has been associated with an increased risk of non-communicable diseases. While the benefits of nitrate consumption on oral health were first proposed more than 20 years ago, no systematic review has been published examining effects of dietary nitrate on oral health. This systematic review investigated the effects of dietary nitrate on markers of oral health in vivo in randomized controlled trials (RCTs). Five databases (PubMed, The Cochrane Library, CINAHL, MEDLINE, and SPORTDiscus) were searched from inception until March 2023. Nine articles reporting data on 284 participants were included. Dietary nitrate was provided via beetroot juice in most studies. The duration of the interventions ranged from one day to six weeks. Dietary nitrate supplementation increased the relative abundance of several individual bacterial genera including Neisseria and Rothia. Dietary nitrate supplementation increased salivary pH and decreased salivary acidification following consumption of a sugar-sweetened beverage. Furthermore, dietary nitrate supplementation resulted in a decrease in the gingival inflammation index. The results of this systematic review suggest that dietary nitrate could represent a potential nutritional strategy to positively modify oral health by impacting the oral microbiome, altering salivary pH, and minimizing gingival inflammation.

Oral health as a modifiable risk factor for cardiovascular diseases

Cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality worldwide with a high socioeconomic burden. Increasing evidence supports a convincing connection with increased cardiovascular risk of periodontal diseases (PD), a group of widespread, debilitating, and costly dysbiotic relapsing-remitting inflammatory diseases of the tissues supporting the teeth. Herein, we ensembled the best available evidence on the connection between CVDs and PD to review the recently emerging concept of the latter as a non-traditional risk factor for CVDs. We focused on oral dysbiosis, inflammation-associated molecular and cellular mechanisms, and epigenetic changes as potential causative links between PD and CVDs. The available evidence on the effects of periodontal treatment on cardiovascular risk factors and diseases was also described.

Evaluation of Knowledge and Awareness of Dietary Nitrate Among Clinical Dietitians in Jeddah, Saudi Arabia: A Cross-Sectional Study

Background and objectives Dietary nitrate (NO3) plays an important role in human physiological processes. In the past, inorganic NO3 was viewed negatively due to its link with carcinogenic effects, notably nitrosamine formation in the stomach; yet, current perspectives acknowledge NO3 as a potentially beneficial dietary element. Nutrition professionals (NPs) are crucial in promoting NO3 awareness in health and academic settings. The study aimed to evaluate the knowledge of NPs in Jeddah, Saudi Arabia, regarding the biological roles of dietary NO3, taking into consideration their qualifications and years of experience. Methods A cross-sectional study was conducted among NPs who had graduated from clinical nutrition programs or were employed in clinical or academic settings. A validated 12-item online questionnaire was used to assess dietary NO3 knowledge across five areas: health effects, dietary sources, recommendations, biomarkers of intake, and metabolism. The nitrate knowledge index (NKI) score was used to evaluate responses. Results Eighty-nine female NPs out of 144 completed the questionnaire. Most were ≤30 years old (75.4%) and had an undergraduate degree in clinical nutrition (70.8%), but 37 of them had ≤3 years of experience (62.7%). Overall, poor knowledge scores were observed among NPs, with a median (25th and 75th percentile) score of 10 (6, 13) out of 23. The majority (64%) perceived NO3 to be beneficial. However, most of the participants did not know its benefits in lowering blood pressure (BP) (68.5%) and were unsure about the effects of nitrate on cognitive function (60.7%) or kidney function (57.3%). Almost half of the NPs were unaware of NO3 sources and unsure about the mechanisms of the conversion of NO3 into nitrogen dioxide (NO2) in the mouth (48.3%). Overall, knowledge of factors that affect NO3 content in food was good. No significant differences were observed in the median NKI scores among the participants based on their level of education or years of experience. Conclusion This study suggests NPs lack knowledge about dietary NO3. To address this, educational programs should be developed and implemented in clinical and academic settings.

Increased nitrate intake from beetroot juice over 4 weeks affects nitrate metabolism, but not vascular function or blood pressure in older adults with hypertension

The decline in vascular function and increase in blood pressure with aging contribute to an increased cardiovascular disease risk. In this randomized placebo-controlled crossover study, we evaluated whether previously reported cardiovascular benefits of plant-derived inorganic nitrate via nitric oxide (NO) translate into improved vascular function and blood pressure-lowering in 15 men and women (age range: 56-71 years) with treated hypertension. We investigated the effects of a single ∼400 mg-dose at 3 hours post-ingestion (3H POST) and the daily consumption of 2 × ∼400 mg of nitrate through nitrate-rich compared with nitrate-depleted (placebo) beetroot juice over 4 weeks (4WK POST). Measurements included nitrate and nitrite in plasma and saliva; endothelial-dependent and -independent forearm blood flow (FBF) responses to acetylcholine (FBFACh) and glyceryltrinitrate (FBFGTN); and clinic-, home- and 24-hour ambulatory blood pressure. Compared to placebo, plasma and salivary nitrate and nitrite increased at 3H and 4WK POST following nitrate treatment (P < 0.01), suggesting a functioning nitrate-nitrite-NO pathway in the participants of this study. There were no differences between treatments in FBFACh and FBFGTN-area under the curve (AUC) ratios [AUC ratios after (3H POST, 4WK POST) compared with before (PRE) the intervention], or 24-hour ambulatory blood pressure or home blood pressure measures (P > 0.05). These findings do not support the hypothesis that an increased intake of dietary nitrate exerts sustained beneficial effects on FBF or blood pressure in hypertensive older adults, providing important information on the efficacy of nitrate-based interventions for healthy vascular aging. This study was registered under ClinicialTrials.gov (NCT04584372).

Investigating the association between nitrate dosing and nitrite generation by the human oral microbiota in continuous culture

The generation of nitrite by the oral microbiota is believed to contribute to healthy cardiovascular function, with oral nitrate reduction to nitrite associated with systemic blood pressure regulation. There is the potential to manipulate the composition or activities of the oral microbiota to a higher nitrate-reducing state through nitrate supplementation. The current study examined microbial community composition and enzymatic responses to nitrate supplementation in sessile oral microbiota grown in continuous culture. Nitrate reductase (NaR) activity and nitrite concentrations were not significantly different to tongue-derived inocula in model biofilms. These were generally dominated by Streptococcus spp., initially, and a single nitrate supplementation resulted in the increased relative abundance of the nitrate-reducing genera Veillonella, Neisseria, and Proteus spp. Nitrite concentrations increased concomitantly and continued to increase throughout oral microbiota development. Continuous nitrate supplementation, over a 7-day period, was similarly associated with an elevated abundance of nitrate-reducing taxa and increased nitrite concentration in the perfusate. In experiments in which the models were established in continuous low or high nitrate environments, there was an initial elevation in nitrate reductase, and nitrite concentrations reached a relatively constant concentration over time similar to the acute nitrate challenge with a similar expansion of Veillonella and Neisseria. In summary, we have investigated nitrate metabolism in continuous culture oral biofilms, showing that nitrate addition increases nitrate reductase activity and nitrite concentrations in oral microbiota with the expansion of putatively NaR-producing taxa.IMPORTANCEClinical evidence suggests that blood pressure regulation can be promoted by nitrite generated through the reduction of supplemental dietary nitrate by the oral microbiota. We have utilized oral microbiota models to investigate the mechanisms responsible, demonstrating that nitrate addition increases nitrate reductase activity and nitrite concentrations in oral microbiota with the expansion of nitrate-reducing taxa.

Dietary nitrate intake and net nitrite-generating capacity of the oral microbiome interact to enhance cardiometabolic health: Results from the Oral Infections Glucose Intolerance and Insulin Resistance Study (ORIGINS)

Background

We investigated the association between dietary nitrate intake and early clinical cardiometabolic risk biomarkers, and explored whether the oral microbiome modifies the association between dietary nitrate intake and cardiometabolic biomarkers.

Methods

Cross-sectional data from 668 (mean [SD] age 31 [9] years, 73% women) participants was analyzed. Dietary nitrate intakes and alternative healthy eating index (AHEI) scores were calculated from food frequency questionnaire responses and a validated US food database. Subgingival 16S rRNA microbial genes (Illumina, MiSeq) were sequenced, and PICRUSt2 estimated metagenomic content. The Microbiome Induced Nitric oxide Enrichment Score (MINES) was calculated as a microbial gene abundance ratio representing enhanced net capacity for NO generation. Cardiometabolic risk biomarkers included systolic and diastolic blood pressure, HbA1c, glucose, insulin, and insulin resistance (HOMA-IR), and were regressed on nitrate intake tertiles in adjusted multivariable linear models.

Results

Mean nitrate intake was 190[171] mg/day. Higher nitrate intake was associated with lower insulin, and HOMA-IR but particularly among participants with low abundance of oral nitrite enriching bacteria. For example, among participants with a low MINES, mean insulin[95%CI] levels in high vs. low dietary nitrate consumers were 5.8[5.3,6.5] vs. 6.8[6.2,7.5] (p=0.004) while respective insulin levels were 6.0[5.4,6.6] vs. 5.9[5.3,6.5] (p=0.76) among partcipants with high MINES (interaction p=0.02).

Conclusion

Higher dietary nitrate intake was only associated with lower insulin and insulin resistance among individuals with reduced capacity for oral microbe-induced nitrite enrichment. These findings have implications for future precision medicine-oriented approaches that might consider assessing the oral microbiome prior to enrollment into dietary interventions or making dietary recommendations.

The Role of Nutrition in the Development and Management of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a prevalent lung condition associated with significant morbidity and mortality. The management of COPD classically involves pulmonary rehabilitation, bronchodilators, and corticosteroids. An aspect of COPD management that is currently lacking in the literature is nutritional management, despite the prevalence of inadequate nutritional status in patients with COPD. In addition, certain nutritional imbalances have been reported to increase the risk of COPD development. This review summarizes the current literature on the role diet and nutrients may play in the risk and management of COPD development.

The coming future: The role of the oral-microbiota-brain axis in aroma release and perception

The field of aroma release and perception during the oral process has been well studied. However, the traditional approaches have not fully explored the integration of oral biology, microbiology, and neurology to further understand aroma release and perception mechanisms. Herein, to address the existing challenges in this field, we introduce the oral-microbiota-brain axis (OMBA), an innovative framework that encapsulates the interactive relationships among saliva and the oral mucosa, the oral microbiota, and the brain in aroma release and perception. This review introduces the OMBA and highlights its role as a key interface facilitating the sensory experience of aroma. Based on a comprehensive literature survey, the specific roles of the oral mucosa, oral microbiota, saliva, and brain in the OMBA are discussed. This integrated approach reveals the importance of each component and the interconnected relationships within this axis in the overall process of aroma release and perception. Saliva and the oral mucosa play fundamental roles in aroma release and perception; the oral microbiota regulates aroma release and impacts olfactory perception; and the brain's intricate neural circuitry is central to the decoding and interpretation of aroma signals. The components of this axis are interdependent, and imbalances can disrupt aroma perception. The OMBA framework not only enhances our comprehension of aroma release and perception but also paves the way for innovative applications that could heighten sensory experiences.

The effects of nitrate on the oral microbiome: a systematic review investigating prebiotic potential

Background

Nitrate (NO3-) has been suggested as a prebiotic for oral health. Evidence indicates dietary nitrate and nitrate supplements can increase the proportion of bacterial genera associated with positive oral health whilst reducing bacteria implicated in oral disease(s). In contrast, chlorhexidine-containing mouthwashes, which are commonly used to treat oral infections, promote dysbiosis of the natural microflora and may induce antimicrobial resistance.

Methods

A systematic review of the literature was undertaken, surrounding the effects of nitrate on the oral microbiota.

Results

Overall, n = 12 in vivo and in vitro studies found acute and chronic nitrate exposure increased (representatives of) health-associated Neisseria and Rothia (67% and 58% of studies, respectively) whilst reducing periodontal disease-associated Prevotella (33%). Additionally, caries-associated Veillonella and Streptococcus decreased (25% for both genera). Nitrate also altered oral microbiome metabolism, causing an increase in pH levels (n = 5), which is beneficial to limit caries development. Secondary findings highlighted the benefits of nitrate for systemic health (n = 5).

Conclusions

More clinical trials are required to confirm the impact of nitrate on oral communities. However, these findings support the hypothesis that nitrate could be used as an oral health prebiotic. Future studies should investigate whether chlorhexidine-containing mouthwashes could be replaced or complemented by a nitrate-rich diet or nitrate supplementation.

How probiotics, prebiotics, synbiotics, and postbiotics prevent dental caries: an oral microbiota perspective

Dental caries, a highly prevalent oral disease, impacts a significant portion of the global population. Conventional approaches that indiscriminately eradicate microbes disrupt the natural equilibrium of the oral microbiota. In contrast, biointervention strategies aim to restore this balance by introducing beneficial microorganisms or inhibiting cariogenic ones. Over the past three decades, microbial preparations have garnered considerable attention in dental research for the prevention and treatment of dental caries. However, unlike related pathologies in the gastrointestinal, vaginal, and respiratory tracts, dental caries occurs on hard tissues such as tooth enamel and is closely associated with localized acid overproduction facilitated by cariogenic biofilms. Therefore, it is insufficient to rely solely on previous mechanisms to delineate the role of microbial preparations in the oral cavity. A more comprehensive perspective should involve considering the concepts of cariogenic biofilms. This review elucidates the latest research progress, mechanisms of action, challenges, and future research directions regarding probiotics, prebiotics, synbiotics, and postbiotics for the prevention and treatment of dental caries, taking into account the unique pathogenic mechanisms of dental caries. With an enhanced understanding of oral microbiota, personalized microbial therapy will emerge as a critical future research trend.

The association of dietary nitrates/nitrites intake and the gut microbial metabolite trimethylamine N-oxide and kynurenine in adults: a population-based study

Background

Dietary nitrate and nitrite may affect the gut microbiota and its metabolites, such as trimethylamine N-oxide (TMAO) and kynurenine (KYN). However, this association and the exact mechanism are still unclear. Therefore, this study aimed to assess the association between dietary consumption of nitrite and nitrate on TMAO and KYN levels in adults.

Methods

This cross-sectional study was employed on a subsample baseline phase of the Tehran University of Medical Sciences (TUMS) Employee's Cohort Study (TEC). A total of 250 adults aged 18 years or older were included in the current analysis. Data on the dietary intakes were collected using a validated dish-based food frequency questionnaire (FFQ), and dietary intakes of nitrite and nitrate were estimated using the FFQ with 144 items. Serum profiles and TMAO and KYN were measured using a standard protocol.

Results

The findings of this study demonstrate a significant association between the intake of animal sources of nitrate and nitrite and the likelihood of having elevated levels of TMAO and KYN. Specifically, after adjustment, individuals with the highest intake adherence to nitrates from animal sources exhibited increased odds of having the highest level of TMAO (≥51.02 pg/ml) (OR = 1.51, 95% CI = 0.59-3.88, P = 0.03) and KYN (≥417.41 pg/ml) (OR = 1.75, 95% CI = 0.73-4.17, P = 0.02). Additionally, subjects with the highest animal intake from nitrite sources have 1.73 and 1.45 times higher odds of having the highest levels of TMAO and KYN. These results emphasize the potential implications of animal-derived nitrate and nitrite consumption on the levels of TMAO and KYN.

Conclusion

The present evidence indicates that a high level of nitrate and nitrite intake from animal sources can increase the odds of high levels of TMAO and KYN. Further studies suggest that we should better evaluate and understand this association.

Oral nitrate supplementation improves cardiovascular risk markers in COPD: ON-BC, a randomised controlled trial

BACKGROUND

Short-term studies suggest that dietary nitrate (NO3 -) supplementation may improve the cardiovascular risk profile, lowering blood pressure (BP) and enhancing endothelial function. It is not clear if these beneficial effects are sustained and whether they apply in people with COPD, who have a worse cardiovascular profile than those without COPD. Nitrate-rich beetroot juice (NR-BRJ) is a convenient dietary source of nitrate.

METHODS

The ON-BC trial was a randomised, double-blind, placebo-controlled parallel group study in stable COPD patients with home systolic BP (SBP) measurement ≥130 mmHg. Participants were randomly allocated (1:1) using computer-generated, block randomisation to either 70 mL NR-BRJ (400 mg NO3 -) (n=40) or an otherwise identical nitrate-depleted placebo juice (0 mg NO3 -) (n=41), once daily for 12 weeks. The primary end-point was between-group change in home SBP measurement. Secondary outcomes included change in 6-min walk distance (6MWD) and measures of endothelial function (reactive hyperaemia index (RHI) and augmentation index normalised to a heart rate of 75 beats·min-1 (AIx75)) using an EndoPAT device. Plasma nitrate and platelet function were also measured.

RESULTS

Compared with placebo, active treatment lowered SBP (Hodges-Lehmann treatment effect -4.5 (95% CI -5.9- -3.0) mmHg), and improved 6MWD (30.0 (95% CI 15.7-44.2) m; p<0.001), RHI (0.34 (95% CI 0.03-0.63); p=0.03) and AIx75 (-7.61% (95% CI -14.3- -0.95%); p=0.026).

CONCLUSIONS

In people with COPD, prolonged dietary nitrate supplementation in the form of beetroot juice produces a sustained reduction in BP, associated with an improvement in endothelial function and exercise capacity.

Association between dietary intakes of Nitrate and Nitrite with Angina and atherogenic index in adults: A cross-sectional study from Tehran University of Medical Sciences employees` cohort (TEC) study

BACKGROUND

Previous studies have shown that the intake of nitrate and nitrite may be associated with cardiovascular disease. Therefore, this study sought to investigate the association between dietary intakes of nitrate and nitrite with the odds of angina and atherogenic index in adults.

METHODS

The study analyzed 1182 adults aged 20+ in the Tehran University of Medical Sciences (TUMS) Employee's Cohort study (TEC), focusing on dietary intakes, angina, and atherogenic indexes, using a validated food frequency questionnaire (FFQ) and the Rose Angina Questionnaire (RAQ).

RESULT

The study found a significant inverse relationship between nitrate intake and odds of grade 2 angina. The highest dietary nitrate was associated with 29 % lower odds of grade 1 angina and also, 46 % lower odds of angina possible (P<0.05). Adults with the highest nitrate intake had 29 % lower odds of grade 1 angina and 46 % lower odds of angina possible. Adherence to nitrate reduced CRI, Atherogenic index of plasma, and TyG in participants, but no significant association was found with other factors.

CONCLUSION

The study suggests that high nitrate and nitrite intake can alter angina risk, and a reverse association was found between dietary nitrate intake and various atherogenic indices.

Dietary Nitrate from Plant Foods: A Conditionally Essential Nutrient for Cardiovascular Health

Under specific conditions, such as catabolic stress or systemic inflammation, endogenous nutrient production becomes insufficient and exogenous supplementation (for example, through dietary intake) is required. Herein, we propose consideration of a dietary nitrate from plant foods as a conditionally essential nutrient for cardiovascular health based on its role in nitric oxide homeostasis. Nitrate derived from plant foods may function as a conditionally essential nutrient, whereas nitrate obtained from other dietary sources, such as drinking water and cured/processed meats, warrants separate consideration because of the associated health risks. We have surveyed the literature and summarized epidemiological evidence regarding the effect of dietary nitrate on cardiovascular disease and risk factors. Meta-analyses and population-based observational studies have consistently demonstrated an inverse association of dietary nitrate with blood pressure and cardiovascular disease outcomes. Considering the available evidence, we suggest 2 different approaches to providing dietary guidance on nitrate from plant-based dietary sources as a nutrient: the Dietary Reference Intakes developed by the National Academies of Sciences, Engineering, and Medicine, and the dietary guidelines evaluated by the Academy of Nutrition and Dietetics. Ultimately, this proposal underscores the need for food-based dietary guidelines to capture the complex and context-dependent relationships between nutrients, particularly dietary nitrate, and health.

Localisation of nitrate-reducing and highly abundant microbial communities in the oral cavity

The nitrate (NO3-) reducing bacteria resident in the oral cavity have been implicated as key mediators of nitric oxide (NO) homeostasis and human health. NO3--reducing oral bacteria reduce inorganic dietary NO3- to nitrite (NO2-) via the NO3--NO2--NO pathway. Studies of oral NO3--reducing bacteria have typically sampled from either the tongue surface or saliva. The aim of this study was to assess whether other areas in the mouth could contain a physiologically relevant abundance of NO3- reducing bacteria, which may be important for sampling in clinical studies. The bacterial composition of seven oral sample types from 300 individuals were compared using a meta-analysis of the Human Microbiome Project data. This analysis revealed significant differences in the proportions of 20 well-established oral bacteria and highly abundant NO3--reducing bacteria across each oral site. The genera included Actinomyces, Brevibacillus, Campylobacter, Capnocytophaga, Corynebacterium, Eikenella, Fusobacterium, Granulicatella, Haemophilus, Leptotrichia, Microbacterium, Neisseria, Porphyromonas, Prevotella, Propionibacterium, Rothia, Selenomonas, Staphylococcus, Streptococcus and Veillonella. The highest proportion of NO3--reducing bacteria was observed in saliva, where eight of the bacterial genera were found in higher proportion than on the tongue dorsum, whilst the lowest proportions were found in the hard oral surfaces. Saliva also demonstrated higher intra-individual variability and bacterial diversity. This study provides new information on where samples should be taken in the oral cavity to assess the abundance of NO3--reducing bacteria. Taking saliva samples may benefit physiological studies, as saliva contained the highest abundance of NO3- reducing bacteria and is less invasive than other sampling methods. These results inform future studies coupling oral NO3--reducing bacteria research with physiological outcomes affecting human health.

Should the non-canonical pathway of nitric oxide generation be targeted in hypertensive pregnancies?

Hypertension in pregnancy is prevalent, affecting around 10% of pregnancies worldwide, and significantly increases the risk of adverse outcomes for both mothers and their babies. Current treatment strategies for pregnant women with hypertension are limited, and new approaches for the management of hypertension in pregnancy are urgently needed. Substantial evidence from non-pregnant subjects has demonstrated the potential for dietary nitrate supplementation to increase nitric oxide (NO) bioavailability and lower blood pressure, following bioactivation via the non-canonical NO pathway. Emerging data suggest this approach may also be of benefit in pregnant women, although studies are limited. This review aims to summarise the current evidence from preclinical and clinical studies of nitrate supplementation in pregnancy, drawing on data from non-pregnant populations where appropriate and highlighting key gaps in knowledge that remain to be addressed in future trials.

Natural mutations of human XDH promote the nitrite (NO2-)-reductase capacity of xanthine oxidoreductase: A novel mechanism to promote redox health?

Several rare genetic variations of human XDH have been shown to alter xanthine oxidoreductase (XOR) activity leading to impaired purine catabolism. However, XOR is a multi-functional enzyme that depending upon the environmental conditions also expresses oxidase activity leading to both O2·- and H2O2 and nitrite (NO2-) reductase activity leading to nitric oxide (·NO). Since these products express important, and often diametrically opposite, biological activity, consideration of the impact of XOR mutations in the context of each aspect of the biochemical activity of the enzyme is needed to determine the potential full impact of these variants. Herein, we show that known naturally occurring hXDH mutations do not have a uniform impact upon the biochemical activity of the enzyme in terms of uric acid (UA), reactive oxygen species (ROS) and nitric oxide ·NO formation. We show that the His1221Arg mutant, in the presence of xanthine, increases UA, O2·- and NO generation compared to the WT, whilst the Ile703Val increases UA and ·NO formation, but not O2·-. We speculate that this change in the balance of activity of the enzyme is likely to endow those carrying these mutations with a harmful or protective influence over health that may explain the current equipoise underlying the perceived importance of XDH mutations. We also show that, in presence of inorganic NO2-, XOR-driven O2·- production is substantially reduced. We suggest that targeting enzyme activity to enhance the NO2--reductase profile in those carrying such mutations may provide novel therapeutic options, particularly in cardiovascular disease.

Altered Oral Nitrate Reduction and Bacterial Profiles in Hypertensive Women Predict Blood Pressure Lowering Following Acute Dietary Nitrate Supplementation

BACKGROUND

The efficacy of dietary nitrate supplementation to lower blood pressure (BP) in pregnant women is highly variable. We aimed to investigate whether differences in oral microbiota profiles and oral nitrate-reducing capacity may explain interindividual differences in BP lowering following nitrate supplementation.

METHODS

Participants recruited for this study were both pregnant and nonpregnant women, with or without hypertension (n=55). Following an overnight fast, plasma, saliva, and tongue scraping samples were collected for measurement of nitrate/nitrite concentrations, oral NaR (nitrate reductase) activity, and microbiota profiling using 16S rRNA gene sequencing. Baseline BP was measured, followed by the administration of a single dose of dietary nitrate (400 mg nitrate in 70 mL beetroot juice). Post-nitrate intervention, plasma and salivary nitrate/nitrite concentrations and BP were determined 2.5 hours later.

RESULTS

Women with hypertension had significantly lower salivary nitrite concentrations (P=0.006) and reduced abundance of the nitrate-reducing taxa Veillonella(P=0.007) compared with normotensive women. Oral NaR activity was not significantly different in pregnant versus nonpregnant women (P=0.991) but tended to be lower in hypertensive compared with normotensive women (P=0.099). Oral NaR activity was associated with both baseline diastolic BP (P=0.050) and change in diastolic BP following acute nitrate intake (P=0.01, adjusted for baseline BP).

CONCLUSIONS

The abundance and activity of oral nitrate-reducing bacteria impact both baseline BP as well as the ability of dietary nitrate supplementation to lower BP. Strategies to increase oral nitrate-reducing capacity could lower BP and enhance the efficacy of dietary nitrate supplementation, in pregnancy as well as in nonpregnant adults.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT03930693.

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

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

Smoking, tooth loss and oral hygiene practices have significant and site-specific impacts on the microbiome of oral mucosal surfaces: a cross-sectional study

We investigated bacterial colonisation patterns of healthy mucosa (buccal, tongue, palate and floor of mouth) in a cohort of adults in order to determine how smoking, tooth loss, plaque levels and oral hygiene practices impacted on mucosal colonisation. A total of 322 swabs were recovered from 256 participants, of whom 46% were current smokers. We analysed colonization by sequencing the V1-V3 regions of the 16S rRNA gene. Palate and tongue microbiomes generally exhibited greater biodiversity than buccal and floor of mouth. Although Neisseria, Lautropia and Haemophilus spp. showed reduced abundance in smokers, buccal mucosa specifically showed a significant increase in Prevotella spp., whereas tongue and floor of mouth tended towards increased abundance of Streptococcus spp. Unexpectedly, tooth brushing frequency had a greater impact on mucosal community structure than plaque levels. Tooth loss was associated with significant reductions in mucosal biodiversity and had site-specific impacts, with buccal communities showing increased abundance of periodontitis-associated species and Rothia mucilaginosa, whereas tongue communities exhibited increased abundance of several streptococcal OTUs and reduced abundance of Haemophilus spp. This study highlights the complex relationship between mucosal colonisation and host factors, highlighting the need for careful consideration of these factors in mucosal microbiome studies.

Iron Deficiency Modulates Metabolic Landscape of Bacteroidetes Promoting Its Resilience during Inflammation

Bacteria have to persist under low iron conditions in order to adapt to the nutritional immunity of a host. Since the knowledge of iron stimulon of Bacteroidetes is sparse, we examined oral (Porphyromonas gingivalis and Prevotella intermedia) and gut (Bacteroides thataiotaomicron) representatives for their ability to adapt to iron deplete and iron replete conditions. Our transcriptomics and comparative genomics analysis show that many iron-regulated mechanisms are conserved within the phylum. They include genes upregulated in low iron, as follows: fldA (flavodoxin), hmu (hemin uptake operon), and loci encoding ABC transporters. Downregulated genes were frd (ferredoxin), rbr (rubrerythrin), sdh (succinate dehydrogenase/fumarate reductase), vor (oxoglutarate oxidoreductase/dehydrogenase), and pfor (pyruvate:ferredoxin/flavodoxin oxidoreductase). Some genus-specific mechanisms, such as the sus of B. thetaiotaomicron coding for carbohydrate metabolism and the xusABC coding for xenosiderophore utilization were also identified. While all bacteria tested in our study had the nrfAH operon coding for nitrite reduction and were able to reduce nitrite levels present in culture media, the expression of the operon was iron dependent only in B. thetaiotaomicron. It is noteworthy that we identified a significant overlap between regulated genes found in our study and the B. thetaiotaomicron colitis study (W. Zhu, M. G. Winter, L. Spiga, E. R. Hughes et al., Cell Host Microbe 27:376-388, 2020, http://dx.doi.org/10.1016/j.chom.2020.01.010). Many of those commonly regulated genes were also iron regulated in the oral bacterial genera. Overall, this work points to iron being the master regulator enabling bacterial persistence in the host and paves the way for a more generalized investigation of the molecular mechanisms of iron homeostasis in Bacteroidetes. IMPORTANCE Bacteroidetes are an important group of anaerobic bacteria abundant both in the oral and gut microbiomes. Although iron is a required nutrient for most living organisms, the molecular mechanisms of adaptation to the changing levels of iron are not well known in this group of bacteria. We defined the iron stimulon of Bacteroidetes by examination of the transcriptomic response of Porphyromonas gingivalis and Prevotella intermedia (both belong to the oral microbiome) and Bacteroidetes thetaiotaomicron (belongs to the gut microbiome). Our results indicate that many of the iron-regulated operons are shared among the three genera. Furthermore, using bioinformatics analysis, we identified a significant overlap between our in vitro studies and transcriptomic data derived from a colitis study, thus underscoring the biological significance of our work. Defining the iron-dependent stimulon of Bacteroidetes can help to identify the molecular mechanisms of iron-dependent regulation as well as better understand the persistence of the anaerobes in the human host.

Efficacy of beetroot juice on reducing blood pressure in hypertensive adults with autosomal dominant polycystic kidney disease (BEET-PKD): study protocol for a double-blind, randomised, placebo-controlled trial

BACKGROUND

In autosomal dominant polycystic kidney disease (ADPKD) impaired nitric oxide (NO) synthesis, in part, contributes to early-onset hypertension. Beetroot juice (BRJ) reduces blood pressure (BP) by increasing NO-mediated vasodilation. The aim of this double-blind, randomised, placebo-controlled study is to test the hypothesis that BRJ reduces systolic and diastolic clinic BP in hypertensive adults with ADPKD.

METHODS

Participants with ADPKD and treated hypertension (n = 60) will be randomly allocated (1:1) to receive a daily dose of either nitrate-replete (400 mg nitrate/day) or nitrate-deplete BRJ for 4 weeks. The co-primary outcomes are change in mean systolic and diastolic clinic BP before and after 4 weeks of treatment with daily BRJ. Secondary outcomes are changes in daily home BP, urinary albumin to creatinine ratio, serum and salivary nitrate/nitrite levels and serum asymmetric dimethylarginine levels before and after 4 weeks of BRJ.

DISCUSSION

The effect of BRJ in ADPKD has not been previously tested. BRJ is an accessible, natural dietary supplement that, if effective, will provide a novel adjunctive approach for treating hypertension in ADPKD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05401409. Retrospectively registered on 27th May 2022.

Plant-Based Nutrition: Exploring Health Benefits for Atherosclerosis, Chronic Diseases, and Metabolic Syndrome-A Comprehensive Review

Atherosclerosis, chronic non-communicable diseases, and metabolic syndrome are highly interconnected and collectively contribute to global health concerns that reduce life expectancy and quality of life. These conditions arise from multiple risk factors, including inflammation, insulin resistance, impaired blood lipid profile, endothelial dysfunction, and increased cardiovascular risk. Adopting a plant-based diet has gained popularity as a viable alternative to promote health and mitigate the incidence of, and risk factors associated with, these three health conditions. Understanding the potential benefits of a plant-based diet for human health is crucial, particularly in the face of the rising prevalence of chronic diseases like diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer. Thus, this review focused on the plausible advantages of consuming a type of food pattern for the prevention and/or treatment of chronic diseases, emphasizing the dietary aspects that contribute to these conditions and the evidence supporting the benefits of a plant-based diet for human health. To facilitate a more in-depth analysis, we present separate evidence for each of these three concepts, acknowledging their intrinsic connection while providing a specific focus on each one. This review underscores the potential of a plant-based diet to target the underlying causes of these chronic diseases and enhance health outcomes for individuals and populations.

A Critical Review on Vasoactive Nutrients for the Management of Endothelial Dysfunction and Arterial Stiffness in Individuals under Cardiovascular Risk

Pathophysiological conditions such as endothelial dysfunction and arterial stiffness, characterized by low nitric oxide bioavailability, deficient endothelium-dependent vasodilation and heart effort, predispose individuals to atherosclerotic lesions and cardiac events. Nitrate (NO₃^-), L-arginine, L-citrulline and potassium (K⁺) can mitigate arterial dysfunction and stiffness by intensifying NO bioavailability. Dietary compounds such as L-arginine, L-citrulline, NO₃^- and K⁺ exert vasoactive effects as demonstrated in clinical interventions by noninvasive flow-mediated vasodilation (FMD) and pulse-wave velocity (PWV) prognostic techniques. Daily L-arginine intakes ranging from 4.5 to 21 g lead to increased FMD and reduced PWV responses. Isolated L-citrulline intake of at least 5.6 g has a better effect compared to watermelon extract, which is only effective on endothelial function when supplemented for longer than 6 weeks and contains at least 6 g of L-citrulline. NO₃^- supplementation employing beetroot at doses greater than 370 mg promotes hemodynamic effects through the NO₃^--NO2-/NO pathway, a well-documented effect. A potassium intake of 1.5 g/day can restore endothelial function and arterial mobility, where decreased vascular tone takes place via ATPase pump/hyperpolarization and natriuresis, leading to muscle relaxation and NO release. These dietary interventions, alone or synergically, can ameliorate endothelial dysfunction and should be considered as adjuvant therapies in cardiovascular diseases.