Nitrate Consumption Research Articles

Factors Affecting to Nitrate Accumulation in Lettuces of Hydroponically Farms Grown under Close and Open Greenhouses

Leaf vegetables can accumulate nitrate. Too much nitrate consumption is harmful to human. The objective of this research is to study nitrate accumulation in three salad vegetable varieties; green oak, red oak and cos, in hydroponic farms under close and open systems during winter and summer. Solution fertilizer factors; electrical conductivity (EC), pH and nitrate concentration in fertilizer were examined and weather condition factors; temperature, humidity and light intensity were recorded. The result shows that 36-day cos had a highest nitrate accumulation of 2,342.6 mg/kg FW under close system in summer and red oak and green oak in open system in summer (1,985.6 and 1,879.0 mg/kg FW, respectively). Factors affecting nitrate accumulation in vegetables were analyzed by using stepwise regression analysis. In winter, the factors affecting nitrate accumulation in green oak, red oak and cos were sample collecting date, age, pH, greenhouse system, fresh weight and EC value. The stepwise equations were able to predict nitrate accumulation in green oak, red oak, and cos correctly 80, 89 and 77%, respectively. In summer, the factors affecting nitrate accumulation in green oak are humidity and pH value. The equations can predict as correctly as 70%. In conclusion, adjustment of pH (5.5-7.0), humidity (63-74%), and decrease of adding fertilizer on a-week pre-harvesting period could reduce nitrate accumulation in vegetables.

Factors Affecting to Nitrate Accumulation in Lettuces of Hydroponically Farms Grown under Close and Open Greenhouses

Leaf vegetables can accumulate nitrate. Too much nitrate consumption is harmful to human. The objective of this research is to study nitrate accumulation in three salad vegetable varieties; green oak, red oak and cos, in hydroponic farms under close and open systems during winter and summer. Solution fertilizer factors; electrical conductivity (EC), pH and nitrate concentration in fertilizer were examined and weather condition factors; temperature, humidity and light intensity were recorded. The result shows that 36-day cos had a highest nitrate accumulation of 2,342.6 mg/kg FW under close system in summer and red oak and green oak in open system in summer (1,985.6 and 1,879.0 mg/kg FW, respectively). Factors affecting nitrate accumulation in vegetables were analyzed by using stepwise regression analysis. In winter, the factors affecting nitrate accumulation in green oak, red oak and cos were sample collecting date, age, pH, greenhouse system, fresh weight and EC value. The stepwise equations were able to predict nitrate accumulation in green oak, red oak, and cos correctly 80, 89 and 77%, respectively. In summer, the factors affecting nitrate accumulation in green oak are humidity and pH value. The equations can predict as correctly as 70%. In conclusion, adjustment of pH (5.5-7.0), humidity (63-74%), and decrease of adding fertilizer on a-week pre-harvesting period could reduce nitrate accumulation in vegetables.

Alterations in nitrogen metabolism caused by heavy metals in the acid-tolerant microalga Coccomyxa onubensis

The microalga Coccomyxa onubensis is an extremophile microorganism with a unique ecosystem (Río Tinto, Huelva, Spain) that contains high amounts of contaminants, including heavy metals, sulphates, and nitrates, in acidic environments (pH 2.5). The current work presents an evaluation of the capacity of Coccomyxa onubensis to assimilate different nitrogen sources under Cu2+, Cd2+, AsO33−, AsO43− and Hg2+ stress, and the metabolic implications of these stressors. The results showed that ammonium consumption was less affected than nitrate consumption when microalgae were cultivated with heavy metals (except cadmium). The activities of enzymes involved in nitrogen metabolism, such as nitrite reductase (NiR; EC:1.7.7.1), glutamine synthetase (GS; EC:6.3.2.1) and glutamate dehydrogenase (GDH; EC:1.4.1.2) were characterised to determine the Michaelis-Menten constant (Km) and optimal temperature and pH values, being 45, 40 and 60 °C and pH values of 7.5, 6.0 and 9.0 for NiR, GS, and GDH, respectively. The effects of different heavy metals on these enzymes were assessed at multiple levels, and the results showed that the enzymatic activity of NiR was downregulated, specially under copper stress, maintaining 23 % of control NiR activity at 2 mM Cu2+. The enzymatic activity of GS was upregulated at low concentrations under cadmium and mercury stress (115–120 % of control cultures GS activity at 25 μM Cd2+ and 50 nM Hg2+, respectively) and downregulated at high concentrations of these elements. GDH activity was upregulated in the presence of Cu2+, Cd2+, and Hg2+, with increases up to 192, 155 and 154 % at 1 mM Cu2+, 300 μM Cd2+, and 250 nM Hg2+, respectively. These results provide a better explanation of the effects of heavy metal stress on N metabolism in Coccomyxa onubensis, which may be used as a model eukaryotic organism of the Tinto River acidophilic ecosystem.

Assessment of Nitrate Reduction by Microbes in Artificial Groundwater Medium

There are significant reasons for nitrate contamination in groundwater (Delhi, India): sewage, runoff from landfill sites, nitrogenous chemical fertilisers, and pesticides from agricultural lands. The highest recorded concentration of nitrate in Delhi’s groundwater is reported to be 1500 mg/l. Consumption of high nitrate through water may pose serious health problems in humans, especially children (below five years). The study’s primary objective was to isolate and identify nitrate-remediating microbes from the nitrate-contaminated site Okhla Barrage, located on the Yamuna River in Delhi, India. A total of 11 different strains were isolated from this site. Among these four strains exhibited 40%–50% remediation efficiency at a nitrate concentration of 1000 mg/l. Molecular characterisation revealed that these four strains, Enterobacter aerogenes, E. coli K12, <i>Klebsiella oxytoca</i> and <i>Lelliottia amnigena</i>, belong to the Enterobacteriaceae family. This study assessed the nitrate remediation potential of isolated microbes in groundwater with 1000 and 1500 mg/l nitrate concentrations. By using a 2% inoculum, the microbes were incubated anaerobically at room temperature for ten days. Nitrate concentrations were monitored every 48 hours. <i>Lelliottia</i>, <i>E. coli</i>, and <i>Enterobacter</i> reduced nitrate (1500 mg/l) by approximately 42%, 24%, and 29%, respectively, while <i>K. oxytoca</i> showed minimal reduction. <i>L. amnigena</i> exhibited superior nitrate removal efficiency compared to other strains. According to the reported data, these strains are known to reduce nitrate concentrations of 620 mg/l. However, our findings demonstrate a remarkable nitrate remediation capacity of 1500 mg/l, showcasing a novel contribution to this study. Further detailed analysis for condition optimisation and association of microbe-microbe could be more helpful.

Optimization of Ultrasonication for Chlorella sp. Growth: Impacts on Biomass Productivity and Nutrient Utilization

Aims: This study aimed to investigate the effect of ultrasonic treatment of different durations on Chlorella sp. culture to analyze biomass concentration, biomass productivity and chlorophyll and macronutrients, such as nitrate and phosphate, which were added to the Chlorella sp. culture. Study Design: This investigation sought to optimize the duration of exposure of live microalgal culture to ultrasonic treatment to estimate economically significant biomass and pigments. Microalgal biomass has potential applications in biofuels, pharmaceuticals, and nutraceuticals, and is highly sought after by industry. Consequently, it is imperative to optimize this process for large-scale production. Chlorophyll pigment is not only crucial in the photosynthesis process but also serves as a high-value component in the food, cosmetic, and health industries. Furthermore, utilizing the optimized duration of ultrasonication treatment, residual nitrate and phosphate in the medium were analyzed, providing key insights into the nutrient consumption of Chlorella sp. under ultrasonication stress. Place and Duration of Study: The present investigation was conducted over 36 days to estimate the effect of ultrasonication on biomass, chlorophyll, nitrate and phosphorus concentration in Chlorella culture at the laboratory of Synthetic Ecology and Environment Biotechnology, Department of Environmental Science, School of Earth Sciences, Central University of Rajasthan, Bandarsindri, Ajmer. Methodology: In this study, the effects of ultrasonication on biomass and chlorophyll content were evaluated by treating Chlorella sp. cultures for 5, 10, and 15 min in addition to an untreated control group. Based on these results, an optimized ultrasonication duration of 5 min was selected for further analysis. During this phase, the nitrate and phosphorus contents in the culture medium were measured to investigate the influence of ultrasonication on these nutrient levels. All treatments were conducted in triplicate to ensure reproducibility of the results, with the mean and standard deviation calculated as measures of statistical reliability. The use of mean and standard deviation in triplicate tests ensure that the results are consistent and reproducible, hence providing a measure of statistical dependability. Results: The biomass concentration and biomass productivity concentration increased from 29.9 ± 0.00240 mg/L (control) to 66.8 ± 0.01485 mg/L, 1.275 ± 0.5033 (control) to 3.71 ± 0.4163 mg/L/day respectively. The highest total chlorophyll concentration was observed in the exponential phase (9 days of culture) which was 3.7772 ± 0.0500. There was a decrease in the concentrations of nitrate and phosphate throughout the culture period, with a total nitrate consumption of 38.5% and total phosphate consumption of 24%. Conclusion: Chlorophyll and biomass concentrations were maximized after 5 min of ultrasonic treatment, but declined with longer exposure. Nutrient analysis revealed a significant decrease in nitrate and phosphate concentrations over time, consistent with nutrient uptake by the growing cells and the subsequent accumulation of metabolites.

Suppression of certain intestinal microbiota metabolites may lead to gestational diabetes in mice fed a high-fat diet.

We aim to establish a gestational diabetes mellitus (GDM) mouse model with mice fed with a high-fat diet (HFD) in comparison with pregnant mice with normal blood glucose levels to investigate the role of intestinal microbiota in the development of HFD-induced GDM. We divided healthy 6-week-old female C57BL mice into an HFD-induced GDM group and a normal diet group. Their bacterial flora and metabolites in intestinal fecal exosomes were co-analyzed using 16 s multi-region sequencing and compared. Alpha (α) diversity was lower within the model group compared to the control group. Beta (β) diversity was significantly different between the two groups. The relative abundances of Lactobacillus, Actinomyces, Rothia, and Bacteroidetes were significantly different between the two groups. Fermentation and nitrate consumption were significantly higher in the GDM group. Multiple bacteria were associated with glycerophosphocholine, S-methyl-5'-thioadenosine, quinolinate, galactinol, deoxyadenosine, DL-arginine, and 2-oxoadenic acid. Imbalances in the production of Lactobacillus, Bacteroidetes, Actinomyces, and Rothia and their related metabolites may lead to metabolic disturbances in GDM. These indicators may be used to assess changes affecting the intestinal microbiota during pregnancy and thus help modulate diet and alter blood glucose.

A randomised crossover trial of nitrate and breakfast on prefrontal cognitive and haemodynamic response functions

It remains unknown whether dietary nitrate and breakfast may enhance working memory (WM) performance by augmenting physiological mechanisms and subjective psychological well-being. We performed a 3-arm randomised within-subject crossover study, with pretest-posttest comparisons, to test whether nitrate consumption via breakfast with a beetroot juice shot or regular breakfast compared to no breakfast improved WM (measured with n-back tests) and cognitive task-related changes in prefrontal cortical haemodynamic response (oxygenated- and deoxygenated-haemoglobin derived from functional near-infrared spectroscopy). In addition, effects on peripheral vascular function and self-reported psychological factors were assessed. In 60 adolescents (13–15 years old; 66% girls), WM improved in all conditions, with no intervention effects. Intervention effects were seen for oxygenated-haemoglobin changes, such that it increased after the breakfast with a nitrate shot during the WM tests and decreased after the regular breakfast. Thus, different neurophysiological mechanisms may be at play to preserve WM in adolescents depending on their breakfast composition. The trial was registered in the ISRCTN registry (ISRCTN16596056) on 21/02/2022.

Randomised Placebo-Controlled Pilot Trial Evaluating the Anti-Anginal Efficacy of Ticagrelor in Patients with Angina with Nonobstructive Coronary Arteries and Coronary Slow Flow Phenomenon.

Background: The coronary slow flow phenomenon (CSFP) is an angiographic finding characterised by the delayed passage of contrast through the coronary arteries, despite the absence of obstructive coronary artery disease (defined as less than 50% narrowing of the vessel lumen). Patients with the CSFP experience recurrent angina, for which there are limited evidence-based therapies. Ticagrelor may serve as an effective anti-anginal therapy for these patients by increasing adenosine levels, which could alleviate coronary microvascular dysfunction and its associated angina due to its vasodilatory properties. This study aimed to determine the anti-anginal efficacy of ticagrelor 90 mg taken twice daily on spontaneous angina episodes in patients with refractory angina (i.e., episodes ≥3/week despite two anti-anginals) and documented CSFP. Methods: In a randomised, double-blind, placebo-controlled, cross-over trial, the anti-anginal efficacy of a 4-week ticagrelor therapy regimen was evaluated in 20 patients with refractory angina (mean age 61.5 ± 10.5 years; 40% women) who had documented slow coronary flow. The primary endpoint was the frequency of angina episodes, recorded using an angina diary. Secondary endpoints included the duration and severity of angina episodes, consumption of short-acting nitrates, and health status evaluations using the Seattle Angina Questionnaire (SAQ) and the Short Form-36 (SF-36) indices. Results: During the four weeks of therapy, ticagrelor did not significantly improve angina symptoms compared to the placebo (placebo 25.7 (16.7)) vs. ticagrelor 19.8 (18.1), p > 0.05). Furthermore, it did not impact other patient-related outcome measures, including angina severity, duration, frequency of prolonged angina episodes, nitrate consumption, or the SAQ/SF-36 health outcome indices. No serious adverse events related to the study drug were observed. Conclusions: In patients with documented CSFP who were unresponsive to standard anti-anginal therapy, ticagrelor did not reduce the frequency of spontaneous angina episodes or the consumption of nitrates. Further confirmation of the potential benefits of this therapy may be obtained through a larger clinical trial.

Promotion of heterotrophic nitrification-aerobic denitrification by nitrite and efficient removal of total nitrogen of strain EN-F2

The inhibition of heterotrophic nitrification-aerobic denitrification (HN-AD) process and low efficiency of total nitrogen conversion under nitrite stress were overcome by strain EN-F2. Results demonstrated that nitrite addition increased total nitrogen conversion to 91.36% and 87.02% for ammonium and nitrate systems, respectively, representing improvements of 5.61% and 15.41%. This enhancement is likely due to the simultaneous acceleration of cell growth, and consumption of ammonium and nitrate. Furthermore, 10 mg/L of hydroxylamine could be almost completely oxidized in a wide range of environmental conditions in the presence of 50 mg/L nitrite, and 100% and 89.82% of nitrite and total nitrogen could be degraded under the conditions of 25 °C, sodium succinate, 7.40 mg/L of dissolved oxygen, C/N ratio 20, initial pH 7.40–7.80 and inoculation quantity of 0.5 × 108 CFU/mL. Altogether, the HN-AD performance of strain EN-F2 can be promoted by nitrite, and no nitrate and hydroxylamine accumulation were found.

The Effects of Acute Beetroot Juice Intake on Glycemic and Blood Pressure Responses When Controlling for Medication in Individuals with Type 2 Diabetes: A Pilot Study.

Physical inactivity and poor dietary choices contribute to the rise in cardiometabolic diseases in the United States. It remains critical to identify strategies that may mitigate the negative impact of these behaviors. Several studies have shown that the consumption of dietary inorganic nitrate may improve vascular health and glucose regulation in animal models and some human studies. However, the improvements in glucose regulation have yet to be corroborated in humans with type 2 diabetes (T2D). Therefore, the purpose of this study was to assess the acute effects of beetroot juice (BRJ) on glycemic and hemodynamic responses in individuals with T2D while controlling for medication. Seven participants with a clinical diagnosis of T2D were recruited into this study and were temporarily removed from blood pressure- and glucose-lowering medications. Hemodynamic measurements (pulsewave velocity) and an oral glucose tolerance test (glycemic response) were measured following consumption of either BRJ or a denitrolized placebo. Saliva and blood samples were collected at baseline and two and four hours post supplementation to measure changes in nitrate and nitrite concentrations. We detected significant improvements in total plasma glucose exposure (p = 0.022) and the SVR change score (p = 0.009) in the BRJ condition. This study demonstrated that BRJ consumption can improve oral glucose tolerance in individuals with T2D while controlling for medication; however, future larger-cohort randomized controlled trials are needed to confirm if BRJ is a viable treatment for glucose control in individuals with T2D.

Effect of Nitrates supplementation on Muscle Hypertrophy and Athletic Performance: A Narrative Review

Background and Study Aim. The consumption of nitrate has been linked to various advantages, including aiding recovery by lessening fatigue, enhancing oxygen supply to muscles, and increasing the elimination of metabolic by-products during intense physical activity. Given the rising trend of utilizing dietary supplements for peak athletic performance, this literature review aims to explore the role and promise of nitrate supplementation in influencing muscle function and boosting physical prowess, while also shedding light on its potential perks and drawbacks. Material and Methods. Electronic databases including Web of Science (all databases), PubMed, Scopus, Google Scholar, Science Direct, were explored on June 11, 2022. The search terms were drawn from prior systematic reviews on nitrate supplementation and exercise and informed by a recent narrative review on Nitrates impact on athletic performance and muscle hypertrophy. Results. The findings of this review indicate that nitrate intake, owing to its ability to widen blood vessels, could potentially enhance blood flow and oxygen delivery to muscles during exercise. Consequently, this improved circulation might facilitate better nutrient and oxygen transportation to muscle tissue, thereby fostering muscle development through enhanced nutrient absorption and waste removal during physical exertion. However, it's crucial to note that excessive nitrate consumption might trigger adverse effects related to the formation of nitrosamines. Conclusion. In summary, investigations into the potential advantages of nitrate supplementation, whether through dietary sources or supplements, in augmenting athletic performance are promising. This is evident from the observed effects of increased muscle protein synthesis, reduced muscle soreness, and enhanced cognitive function under stressful conditions. Nonetheless, it's imperative to exercise caution against over-supplementation due to the potential risks of toxicity and associated side effects.

Estimates of the Isotope Effect for Nitrate Assimilation in the Indian Sector of the Southern Ocean

AbstractThe Southern Ocean is a high‐nutrient, low‐chlorophyll (HNLC) region characterized by incomplete nitrate (NO3−) consumption by phytoplankton in surface waters. During this incomplete consumption, phytoplankton preferentially assimilate the 14N‐ versus the 15N‐bearing form of NO3−, quantified as the NO3− assimilation isotope effect (15ε). Previous summertime estimates of the 15ε from HNLC regions range from 4 to 11‰. While culture work has shown that the 15ε varies among phytoplankton species, as well as with light and iron stress, we lack a systematic understanding of how and why the 15ε varies in the field. Here we estimate the 15ε from water‐column profile and surface‐water samples collected in the Indian sector of the Southern Ocean—the first leg of the Antarctic Circumnavigation Expedition (December 2016–January 2017) and the Crossroads transect (April 2016). Consistent with prior work in the mid‐to‐late summer Southern Ocean, we estimate a higher 15ε (8.9 ± 0.6‰) for the northern Subantarctic Zone and a lower 15ε (5.4 ± 0.9‰) at and south of the Subantarctic Front. We interpret our data in the context of coincident measurements of phytoplankton community composition and estimates of iron and light stress. Similar to prior work, we find a significant, negative relationship between the 15ε and the average mixed‐layer photosynthetically active radiation flux of 30–100 μmol m−2 s−1, while above 100 μmol m−2 s−1, 15ε increases again. In addition, while we observe no robust relationship of the 15ε to iron availability or phytoplankton community, mixed‐layer nitrification over the Kerguelen Plateau appears to strongly influence its magnitude.

Effects of dietary nitrate supplementation on markers of oral health: A systematic review

The oral cavity is a vital part of the digestive system. Poor oral health can impact an individual’s ability to eat and has been associated with increased risk of non-communicable diseases and reduced longevity. Conversely, positive oral health has been associated with improved cardiometabolic, cognitive and systemic health and greater longevity. Consumption of dietary nitrate, which is processed in the mouth into nitrite, and is subsequently converted into nitric oxide (NO) in the body (1), has been demonstrated to reduce blood pressure, improve endothelial function, and enhance exercise performance. Interestingly, recent studies suggest that nitrate consumption could also positively modulate markers of oral health (2). To our knowledge, no systematic review has been published examining the effect of inorganic dietary nitrate on oral health. However, this could be valuable to summarise current state of the knowledge, identify effect modifiers and highlight gaps for future research. Therefore, this systematic review aims to investigate the effects of dietary nitrate supplements on markers of oral health in vivo in randomised controlled trials (RCTs).This study was pre-registered with PROSPERO (CRD42023411159). Five databases (PubMed, The Cochrane Library, CINAHL, MEDLINE, and SPORTDiscus) were searched from inception until March 2023 to identify studies that met the following criteria: adult participants (≥ 18 years) and RCTs investigating the effects of oral dietary nitrate versus placebo on markers of oral health. A narrative synthesis of data was conducted. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool.Nine articles reporting data on 284 participants were included. Nitrate was provided via beetroot juice (six studies), a beetroot-derived supplement dissolved in mineral water (one study), and lettuce juice (two studies). The duration of the interventions ranged from one day to a maximum of six weeks. Dietary nitrate supplementation increased the relative abundance of several individual bacterial genera including Neisseria (increased in three studies) and Rothia (increased in three studies). Dietary nitrate supplementation increased salivary pH (increased in two studies) and decreased salivary acidification resulting from the consumption of a sugar-sweetened beverage (decreased in two studies). Furthermore, dietary nitrate supplementation resulted in a decrease in the gingival inflammation index in one study. Overall, the risk of bias in studies was mixed. One study had a low risk of bias, while the rest were rated as having some concerns. No study was considered to have a high risk of bias.The results show that dietary nitrate is a potential nutritional strategy that can potentially benefit oral health by modifying the oral microbiome, altering salivary pH, and minimising gingival inflammation.

Primary Production and Respiration in the Norwegian Sea Estimated From Biogeochemical Argo Floats

AbstractBiogeochemical (BGC) Argo floats were used in this study to investigate phytoplankton blooms. We assessed the seasonal and annual rates of net primary and community production, along with respiration in the Norwegian Sea. The years 2020 and 2021 were contrasted to illuminate similarities and differences. In both years the onset of the bloom occurred at the beginning of February, coinciding with a deep winter mixed layer. However, during spring and summer the biological production appeared to develop differently. In 2020 the mixed layer depth shoaled quickly in April due to surface heating, triggering a strong spring bloom event. In contrast, a significant surface cooling in April 2021 triggered a substantial vertical mixing, that delayed the mixed layer's shoaling. This delay initiated cascading effects impacting nitrate consumption and bloom development that resulted in increased respiration in 2021 compared to 2020. In both years, vertical nitrate mixing from deeper layers to the surface emerged as a pivotal factor determining primary production. Using a mixed layer model in combination with Argo observations, we found that the upward nutrient fluxes due to mixing doubled net community production. These findings underscore the capability of BGC‐Argo floats, operating at a 5‐day resolution, to unveil the intricate interplay between hydrography, physical drivers, and biogeochemical processes in shaping phytoplankton dynamics and overall ecosystem productivity in the Norwegian Sea.

Synergies of chemodenitrification and denitrification in a saline inland lake

The interconnection between biotic and abiotic pathways involving the nitrogen and iron biogeochemical cycles has recently gained interest. While lacustrine ecosystems are considered prone to the biotic nitrate reduction (denitrification), their potential for promoting the abiotic nitrite reduction (chemodenitrification) remains unclear. In the present study, batch incubations were performed to assess the potential for chemodenitrification and denitrification in the saline inland lake Gallocanta. Sulfidic conditions are found in top sediments of the system while below (5–9 cm), it presents low organic carbon and high sulfate and ferrous iron availability. Anoxic incubations of sediment (5–9 cm) and water from the lake with nitrite revealed potential for chemodenitrification, especially when external ferrous iron was added. The obtained isotopic fractionation values for nitrite (ɛ15NNO2) were −6.8 and −12.3 ‰ and therefore, fell in the range of those previously reported for the nitrite reduction. The more pronounced ɛ15NNO2 (−12.3 ‰) measured in the experiment containing additional ferrous iron was attributed to a higher contribution of the chemodenitrification over biotic denitrification. Incubations containing nitrate also confirmed the potential for denitrification under autotrophic conditions (low organic carbon, high ferrous iron). Higher reaction rate constants were found in the experiment containing 100 μM compared to 400 μM nitrate. The obtained ɛ15NNO3 values (−8.5 and −15.1 ‰) during nitrate consumption fell in the range of those expected for the denitrification. A more pronounced ɛ15NNO3 (−15.1 ‰) was determined in the experiment presenting a lower reaction rate constant (400 μM nitrate). Therefore, in Gallocanta lake, nitrite generated during nitrate reduction can be further reduced by both the abiotic and biotic pathways. These findings establish the significance of chemodenitrification in lacustrine systems and support further exploration in aquatic environments with different levels of C, N, S, and Fe. This might be especially useful in predicting nitrous oxide emissions in natural ecosystems.

Central and peripheral cardiovascular responses after acute dietary nitrate supplementation in post-menopausal women

The transition to menopause is accompanied by augmented cardiovascular disease risk, partially attributed to reduced nitric oxide (NO) bioavailability. Despite a lower arterial stiffness than men, postmenopausal women are susceptible to increased aortic pulsatile hemodynamic load because of greater pressure wave reflection and vascular dysfunction. Increasing bioavailable NO with dietary nitrate has shown promise to reduce aortic (aSBP) and brachial (bSBP) systolic pressure healthy postmenopausal women. However, there are limited reports comparing hypertensive (HTN) and normotensive (NTN) postmenopausal women regarding wave separation analysis and vascular function following dietary nitrate supplementation. This study investigated if acute dietary nitrate supplementation would improve aortic hemodynamics, wave reflection characteristics, vascular stiffness, and vasodilatory function. We hypothesized that dietary nitrate would lower pulse wave velocity in hypertensives, lower aortic and brachial blood pressures and forward and backward wave magnitude and increase microvascular, but not macrovascular function in both groups. Fourteen postmenopausal women (n=7 HTN; n=7 NTN) participated in a two-day randomized crossover study design with dietary nitrate (nitrate rich, NR) or a placebo control (NP). Central and peripheral hemodynamics and carotid-femoral pulse wave velocity (cfPWV) were performed with a SphygmoCOR Excel, simultaneous resting macro- and- microvascular function was assessed using flow-mediated vasodilation (FMD) and post occlusive reactive hyperemia (PORH) using near-infrared spectroscopy. aSBP was reduced significantly following NR supplement within groups (HTN: NP 126±2 NR 120±1mmHg) and NTN group (NP 110± 1 NR 104±3mmHg p<0.05). Forward pulse height HTN (NP 29±1.4 NR 26.3±1.4mmHg) NTN (NP 25.6±0.9 NR 24±2.7mmHg) and reflected pulse height HTN (NP 18.2±0.08 NR 17.2±0.4mmHg) NTN (NP 17.7±0.2 NR 15.7±1.07mmHg) were not different. cfPWV was faster in the HTN group and slowed with a NR supplement (HTN: NP 8.2±0.29 NR 7.4±0.31m/s; NTN NP 7.1±0.23 NR 6.6±0.62m/s p<0.05). A significant interaction for %FMD was found (HTN: NP 7.3±0.8 NR 6.2±0.8%; NTN NP 6.6±0.7 NR 9.4±0.7%). Further, we found no difference in the NIRS derived microvascular function measurements (HTN: NP 1.9±0.2 NR 1.7±0.3%/s; NTN NP 1.6±0.1 NR 1.4±0.2%/s p>0.05). These data indicate that dietary nitrate consumption led to a substantial reduction in aortic hemodynamics and reduced pulse wave velocity regardless of hypertension status. Interestingly, macrovascular, but not microvascular vasodilatory function was improved in the NTN women only. Dietary nitrate supplementation appears to have differential effects when considering HTN and NTN postmenopausal women. Supported with funds from The University of Wisconsin-La Crosse RSEL graduate grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of Ivabradine on Myocardial Perfusion in Chronic Angina: A Prospective, Preliminary, Open-Label, Single-Arm Study.

Ivabradine reduces heart rate (HR), episodes of angina, and nitrate consumption, and increases exercise capacity in patients with chronic angina (CA). In this exploratory study, myocardial perfusion scintigraphy (MPS) was used to evaluate changes in the percentage of myocardial ischemia after ivabradine therapy in patients with CA. This prospective, open-label, single-arm study included patients with CA receiving maximum tolerated doses of beta blockers, who had a resting HR ≥ 70bpm and had experienced ischemia according to MPS during an exercise test at baseline. Participants received ivabradine 5mg twice daily (titrated according to HR) concomitant with beta blockers. A second MPS was performed after 3months, without interruption of treatment with beta blockers or ivabradine. The primary outcome was change in the percentage of myocardial ischemia from baseline to 3months. Time to ischemia during the exercise test, the proportion of patients presenting angina during the exercise test, and health status, assessed using the seven-item Seattle Angina Questionnaire-7 (SAQ-7), were also evaluated. Twenty patients (3 females) with a mean (± standard deviation [SD]) age of 62.2 ± 6.5years were included in the study, of whom 55% had diabetes, 70% had previous myocardial revascularization, and 45% had previous myocardial infarction. The percentage of patients with myocardial ischemia significantly decreased from baseline to 3months after initiation of treatment with ivabradine (- 2.9%; 95% confidence interval [CI] - 0.3 to - 5.5; p = 0.031). Mean time to appearance of ischemia increased from 403 ± 176s at baseline to 466 ± 136s at 3 months after initiation of ivabradine (Δ62 s; 95% CI 18-106 s; p = 0.008), and the proportion of patients experiencing angina during the exercise test decreased from 40% at baseline to 5% also at 3 months (p = 0.016). Mean resting HR decreased from 76 ± 7bpm at baseline to 55 ± 8bpm at 3 months (p < 0.001). The mean SAQ-7 summary score improved from 69 ± 21 at baseline to 83 ± 12 at 3months (p = 0.001). No serious adverse effects were reported. Ivabradine added to beta blockers was associated with a reduction in detectable myocardial ischemia by MPS in patients with CA. Infographic available for this article. The trial has been retrospectively registered with the Brazilian Registry of Clinical Trials (REBEC) under the following number RBR-5fysqrh (date of registration: 30 November 2023).

Abstract P199: Oral Microbiome Potentially Modifies the Cardiometabolic Benefits of Nitrate Consumption: Results From the Oral Infections Glucose Intolerance and Insulin Resistance Study (ORIGINS)

Background: Dietary nitrate consumption is associated with cardiometabolic health in many but not all studies. The enterosalivary nitrate-nitrite-nitric oxide (NO 3 - NO 2 - NO) pathway requires the oral microbiome for NO production (a signaling molecule beneficial to cardiometabolic health) following nitrate intake. We hypothesize that the oral microbiome modifies the cardiometabolic benefits of nitrate intake. Methods: We analyzed cross-sectional data from 657 ORGINS participants. Dietary nitrate intakes and alternative healthy eating index (AHEI) scores were calculated from food frequency questionnaire responses and a 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 biomarker (systolic and diastolic blood pressure, HbA1C, glucose, insulin, and HOMA-IR) Z-scores were averaged to form a cardiometabolic Z-score (CMZ). Adjusted multivariable linear models regressed CMZ and individual Z-scores on nitrate intake tertiles. Results: Participants were mean age 31±9, 72% female, 31% White, 14% Black, and 28% Hispanic. Mean nitrate intake was 189±171 mg/day. Higher nitrate intake was significantly associated with lower CMZ, glucose, insulin, and HOMA-IR. Mean CMZ(SE) across dietary nitrate tertiles were 0.53(0.30), 0.35(0.31), and -0.11(0.30), p for trend=0.04; findings were attenuated after adjustment for AHEI (p for trend=0.12). In subgroup analysis by MINES level, higher nitrate intake was only associated with lower cardiometabolic biomarker levels among participants with a &lt;median MINES even after AHEI adjustment (Table). Conclusion: Higher dietary nitrate intake was associated with lower cardiometabolic risk biomarker levels only among those with reduced potential for oral microbiome-dependent NO generation.

Anti-Anginal Efficacy of Zibotentan in the Coronary Slow-Flow Phenomenon.

Patients with coronary microvascular disorders often experience recurrent angina for which there are limited evidence-based therapies. These patients have been found to exhibit increased plasma levels of endothelin; thus, selective endothelin-A (Et-A) receptor blockers such as zibotentan may be an effective anti-anginal therapy in these patients. The study evaluated the impact of a 10 mg daily dose of zibotentan on spontaneous angina episodes in patients with the coronary slow-flow phenomenon who had refractory angina (i.e., experiencing angina at least three times/week despite current anti-anginal therapy). Using a randomized, double-blind, placebo-controlled, crossover trial design with 4-week treatment periods, 18 patients (63.2 ± 9.9 years, 33% females) were recruited. The primary endpoint was angina frequency as measured by an angina diary, with secondary endpoints including nitrate consumption, angina duration/severity and the Seattle Angina Questionnaire (SAQ) domains. During the 4 weeks of therapy, angina frequency significantly improved with zibotentan therapy (placebo 41.4 (58.5) vs. zibotentan 29.2 (31.6), p < 0.05), and sublingual nitrate consumption significantly reduced (placebo 11.8 (15.2) vs. zibotentan 8.8 (12.9), p < 0.05. Zibotentan improved the frequency of spontaneous angina episodes and reduced sublingual nitrate consumption in patients unresponsive to standard anti-anginal therapy.

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

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. 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. 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. 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.