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

The emerging role of nitric oxide in the synaptic dysfunction of vascular dementia

With an increase in global aging, the number of people affected by cerebrovascular diseases is also increasing, and the incidence of vascular dementia-closely related to cerebrovascular risk-is increasing at an epidemic rate. However, few therapeutic options exist that can markedly improve the cognitive impairment and prognosis of vascular dementia patients. Similarly in Alzheimer's disease and other neurological disorders, synaptic dysfunction is recognized as the main reason for cognitive decline. Nitric oxide is one of the ubiquitous gaseous cellular messengers involved in multiple physiological and pathological processes of the central nervous system. Recently, nitric oxide has been implicated in regulating synaptic plasticity and plays an important role in the pathogenesis of vascular dementia. This review introduces in detail the emerging role of nitric oxide in physiological and pathological states of vascular dementia and summarizes the diverse effects of nitric oxide on different aspects of synaptic dysfunction, neuroinflammation, oxidative stress, and blood-brain barrier dysfunction that underlie the progress of vascular dementia. Additionally, we propose that targeting the nitric oxide-sGC-cGMP pathway using certain specific approaches may provide a novel therapeutic strategy for vascular dementia.

Regulation of nitric oxide generation and consumption

Nitric oxide (NO), originally discovered for its role in cardiovascular function, is a key molecule in physiological processes including metabolism, neurotransmission (including memory, learning, neuroprotection and synaptic plasticity), immunity, reproduction, and much more. NO can be synthesized by the catalytic activity of the enzyme nitric oxide synthase (NOS), which is found biologically in three isoforms, or nonenzymatically based on simple reduction of nitrate and nitrite or by the NO-donor S-nitrosothiol (R-SNO). Importantly, the deficiency of NO has been noted in a wide range of pathologies including cardiovascular disease, cancer, erectile dysfunction, male and female infertility, and mitochondrial disease. While there are several pathways that can lead to a reduction in the bioavailability of NO (i.e., consumption, inhibition, and substrate competition) it is the conclusion of the authors that multiple pathways co-exist in pathological states. This article outlines for the first time the major pathways of NO generation, the importance of NO in health, NO scavenging and enzyme inhibition, and the potential benefits of supplementation.

Causal Associations with Arterial Stiffness and Sarcopenia: A Mendelian Randomization Analysis

Observational studies and clinical trials indicate a link between arterial stiffness (AS) and sarcopenia (SAR), yet the causal relationship between these remains unclear. The study aims to investigate the causal connection from AS to SAR by Mendelian randomization (MR). We analyzed Genome-Wide Association Studies data for AS indicators: pulse wave arterial stiffness index (PWASI) and pulse wave peak-to-peak time (PPT), and SAR indicators: low hand grip strength (LHGS), usual walking pace (UWP), moderate-to-vigorous physical activity levels (MVPA), and walk or cycle unassisted for 10 minutes. The inverse variance-weighted, MR-Egger, weighted mode, and weighted median were applied to MR. There is a bidirectional causal relationship between the AS and SAR. The PWASI has a causation with UWP (odds ratio [OR] = 0.97, 95% confidence interval [CI] = 0.94-0.99). The PPT has a causal association with MVPA (OR = 1.08, 95% CI = 1.002-1.144) and UWP (OR = 1.05, 95% CI = 1.017-1.096). The LHGS is causally associated with PPT (OR = 0.95, 95% CI = 0.91-0.98) and UWP has a causal association with PWASI (OR = 0.77, 95% CI = 0.65-0.90) and PPT (OR = 1.37, 95% CI = 1.17-1.60). The increased AS could reduce the motor ability slightly and the lower upper and lower limb strength could lead to the higher AS. This bidirectional causal relationship of the two may offer novel perspectives for advancing the understanding of the underlying mechanisms related to AS and muscle pathophysiology.

Preworkout dietary nitrate magnifies training-induced benefits to physical function in late postmenopausal women: a randomized pilot study

To inform end points for future work, we explored the utility of preworkout (i.e., an acute dose before training) beetroot juice (BRJ) combined with exercise (BRJ + EX) to augment indices of physical function in postmenopausal women compared with exercise only (EX). A two-arm pilot study was used to compare 24 postmenopausal women following an 8-wk, circuit-based exercise intervention. Participants were randomized to BRJ + EX (n = 12) or EX (n = 12). BRJ + EX participants consumed 140 mL of BRJ 120-180 min (only) before training for 7 wk, then discontinued during the final week to mitigate carryover effects. Physical function indices were 6-min walk test (6MWT), estimated V̇o2peak, heart rate recovery (HRR), and maximal knee extensor power (Pmax). A treadmill task was used to measure V̇o2 on-kinetics wherein mean response time (MRT) coincided with the duration to reach 63% of steady-state V̇o2. Results showed greater changes (Δ) among BRJ + EX participants for 6MWT distance (40 ± 23 m vs. 8 ± 25 m; P = 0.003, d = 1.35), ΔV̇o2peak (1.5 ± 0.9 mL·kg-1·min-1 vs. 0.3 ± 1.0 mL·kg-1·min-1; P = 0.008, d = 1.20), and ΔHRR (-10 ± 6 beats/min vs. -1 ± 9 beats/min; P = 0.017, d = 1.05). Large and medium effect sizes favoring BRJ + EX were detected for ΔPmax (P = 0.07, d = 0.83) and ΔMRT (P = 0.257, d = 0.50), respectively. In postmenopausal women, BRJ + EX appears to magnify some adaptive benefits to physical function including aerobic capacity and recovery beyond that of training without BRJ. Investigation into contributing mechanisms is needed.NEW & NOTEWORTHY Though exercise training represents the principal strategy to combat age-related decline, the attendant effects of menopause weaken aspects of exercise adaptation compared with premenopausal women and age-matched men. Here we provide important initial evidence that preworkout (i.e., an acute dose before training) beetroot juice coupled with an 8-wk, circuit-based exercise training intervention may uniquely benefit late postmenopausal women by enhancing indices of physical function including aerobic capacity and recovery.

Dietary NO3- does not enhance endothelial dependent cutaneous vascular conductance in older women

Prior work has yet to determine whether the reduction of dietary nitrate (NO3-) to NO, via the enterosalivary pathway, may modify cutaneous vascular conductance (CVC) responses to local heating in older women. Changes occurring with the transition to menopause related to hormonal flux, increased adiposity, and/or decreased physical activity may further compound the negative influence of aging on nitric oxide (NO)-dependent CVC. Herein, we characterized changes in NO-dependent CVC following acute ingestion of 140 mL of NO3--rich beetroot juice in 24 older women (age: 65 ± 5 y, BMI: 31.2 ± 3.7 kg/m2). Red blood cell (RBC) flux was measured continuously via laser-Doppler flowmetry on the dorsal aspect of the forearm during local skin heating to 39 °C/44 °C before and 3 h after NO3- ingestion. NO-dependent changes in CVC were calculated as RBC flux/mean arterial blood pressure at 39 °C and normalized as a proportion of maximal CVC at 44 °C (%CVCmax). Changes (Δ) in fractional exhaled NO (FeNO) following NO3- ingestion were used an index of NO bioavailability. Despite increased FeNO (+81 ± 70 %, P < 0.001), %CVCmax at 39 °C was reduced (-16 ± 10 %, P < 0.001) following NO3- ingestion. A greater reduction in %CVCmax was weakly to moderately associated with higher body fat% (r = 0.45 [0.05-0.72], P = 0.029), central adiposity% (r = 0.50 [0.13-0.75], P = 0.012), neutrophil% (r = 0.42 [0.02-0.70], P = 0.041), and higher neutrophil to lymphocyte ratio (r = 0.49 [0.11-0.75], P = 0.016). These findings demonstrate a single dose of dietary NO3- does not promote CVC responses to local heating in sedentary older women with overweight and obesity. Correlation with multiple biomarkers suggest systemic inflammation may be involved.

Evaluation of 12-Week Standardized Beetroot Extract Supplementation in Older Participants: A Preliminary Study of Human Health Safety

In recent years, there has been a notable surge in the popularity of beetroot-based dietary supplements, driven by their rich nitrate composition. Several types of beetroot-based dietary supplements can be found in markets worldwide; however, ensuring the safety of dietary supplements is a crucial consideration, as there is limited evidence on their safety, especially for older populations. Therefore, the purpose of the current study was to evaluate the safety and tolerability of a nitrate-rich beetroot extract in older participants taking supplements over 12 weeks. The participants were randomly assigned to receive 20 g daily of beetroot extract or a matching placebo. The safety and tolerability of the supplementation were evaluated as the occurrence of adverse events and anthropometric, biochemical, and hemodynamic parameters were measured. No serious adverse events were reported in any group. Anthropometric, biochemical, and hemodynamic parameter changes between the baseline and the end of the study were not statistically significant in either group. However, interestingly, the group receiving beetroot extract supplementation exhibited a notable increase in plasma nitrate levels (p = 0.076, f = 0.50) and showed a decrease in insulin levels (p = 0.026, f = 0.59). In conclusion, we found that 20 g of beetroot extract supplementation for 12 weeks was safe and well tolerated in older participants.

Does dietary nitrate boost the effects of caloric restriction on brain health? Potential physiological mechanisms and implications for future research

Dementia is a highly prevalent and costly disease characterised by deterioration of cognitive and physical capacity due to changes in brain function and structure. Given the absence of effective treatment options for dementia, dietary and other lifestyle approaches have been advocated as potential strategies to reduce the burden of this condition. Maintaining an optimal nutritional status is vital for the preservation of brain function and structure. Several studies have recognised the significant role of nutritional factors to protect and enhance metabolic, cerebrovascular, and neurocognitive functions. Caloric restriction (CR) positively impacts on brain function via a modulation of mitochondrial efficiency, endothelial function, neuro-inflammatory, antioxidant and autophagy responses. Dietary nitrate, which serves as a substrate for the ubiquitous gasotransmitter nitric oxide (NO), has been identified as a promising nutritional intervention that could have an important role in improving vascular and metabolic brain regulation by affecting oxidative metabolism, ROS production, and endothelial and neuronal integrity. Only one study has recently tested the combined effects of both interventions and showed preliminary, positive outcomes cognitive function. This paper explores the potential synergistic effects of a nutritional strategy based on the co-administration of CR and a high-nitrate diet as a potential and more effective (than either intervention alone) strategy to protect brain health and reduce dementia risk.

The role of nutraceuticals in heart failure muscle wasting as a result of inflammatory activity. The International Lipid Expert Panel (ILEP) Position Paper

Muscle wasting is one of the main causes for exercise intolerance and ventilatory inefficiency in patients with heart failure and a strong predictor of frailty and reduced survival. The prevalence of sarcopenia is at least 20% in patients with heart failure. Patients with heart failure often have subclinical systemic inflammation, which may exert sustained effects on skeletal muscle. Besides exercise, nutrition should also be carefully evaluated as an appropriate diet with selected nutraceuticals may be able to stimulate muscle anabolism and inhibit muscle catabolism. This review summarizes the epidemiological and clinical trial evidence supporting the recommendations for the use of nutraceuticals with anti-inflammatory properties in heart failure and provides an overview of the state of the evidence for nutraceutical supplementation to prevent and/or mitigate heart failure muscle wasting.

Relative leg press strength relates to activity energy expenditure in older women: Implications for exercise prescription

Limited work has evaluated how leg press strength (LPS), relative to body mass (i.e., rLPS), affects heart rate (HR) responses during activities of daily living. Such information would prove useful by informing a specific level of rLPS needed to promote independent mobility and physical activity. Secondary analyses were performed on baseline measures of 76 untrained older (65 ± 4 y) women. After familiarization, one-repetition maximum leg press was converted to rLPS by dividing the external load lifted (kg) by body mass (BM). Participants were stratified according to percentile of age-group norms of rLPS: ≤50 % (low, ≤0.99 kg/BM, n = 15), 51-89 % (middle, 1.0-1.31 kg/BM, n = 31), and ≥90 % (high, ≥1.32 kg/BM, n = 30). HR was measured at rest and during laboratory-based tasks including fixed-speed (0.89 m·s^-1) non-graded treadmill walking, graded (2.5 %) treadmill walking, and stair stepping. Maximal oxygen uptake (V̇O_2max) was measured via indirect calorimetry. Doubly labeled water was used to quantify activity energy expenditure (AEE) over a 14-d period. Relative LPS per group were: 0.85 ± 0.12 (low), 1.16 ± 0.09 (middle), and 1.55 ± 0.25 (high) (p < 0.001). Significant between-group differences in HR emerged during both walking tasks and stair stepping - with the high rLPS group having the lowest HR. AEE between-group comparisons did not yield statistical significance (p = 0.084), however, rLPS correlated with AEE (r = 0.234, p = 0.042) and V̇O_2max (r = 0.430, p < 0.001). Such findings suggest a higher rLPS attenuates HR for weight-bearing activities while also demonstrating a significant, albeit modest, positive link to AEE among older women. This information may be especially relevant for informing thresholds of rLPS linked to mobility and functional independence in older women.

l-Arginine and Beetroot Extract Supplementation in the Prevention of Sarcopenia

Aging is associated with a significant decline in neuromuscular function, leading to a reduction in muscle mass and strength. The aim of the present report was to evaluate the effect of supplementation with nitric oxide precursors (l-arginine and beetroot extract) in muscular function during a training period of 6 weeks in elderly men and women. The study (double-blind, placebo-controlled) involved 66 subjects randomly divided into three groups: placebo, arginine-supplemented and beetroot extract-supplemented. At the end of this period, no changes in anthropometric parameters were observed. Regarding other circulating parameters, urea levels were significantly (p < 0.05) lower in women of the beetroot-supplemented group (31.6 ± 5.9 mg/dL) compared to placebo (41.3 ± 8.5 mg/dL) after 6 weeks of training. In addition, the circulating creatine kinase activity, as an index of muscle functionality, was significantly (p < 0.05) higher in women of the arginine- (214.1 ± 162.2 mIU/L) compared to the beetroot-supplemented group (84.4 ± 36.8 mIU/L) at the end of intervention. No significant effects were noticed with l-arginine or beetroot extract supplementation regarding strength, endurance and SPPB index. Only beetroot extract supplementation improved physical fitness significantly (p < 0.05) in the sprint exercise in men after 6 weeks (2.33 ± 0.59 s) compared to the baseline (2.72 ± 0.41 s). In conclusion, beetroot seems to be more efficient during short-term training while supplementing, preserving muscle functionality in women (decreased levels of circulating creatine kinase) and with modest effects in men.

Moving beyond inclusion: Methodological considerations for the menstrual cycle and menopause in research evaluating effects of dietary nitrate on vascular function

Recent reports have acknowledged the underrepresentation of women in the field of dietary nitrate (NO₃^-) research. Undoubtedly, greater participation from women is warranted to clarify potential sex differences in the responses to dietary NO₃^- interventions. However, careful consideration for the effects of sex hormones - principally 17β-estradiol - on endogenous nitric oxide (NO) synthesis and dietary NO₃^- reductase capacity is necessary for improved interpretation and reproducibility of such investigations. From available literature, we present a narrative review describing how hormonal variations across the menstrual cycle, as well as with menopause, may impact NO biosynthesis catalyzed by NO synthase enzymes and NO₃^- reduction via the enterosalivary pathway. In doing so, we address methodological considerations related to the menstrual cycle and hormonal contraceptive use relevant for the inclusion of premenopausal women along with factors to consider when testing postmenopausal women. Adherence to such methodological practices may explicate the utility of dietary NO₃^- supplementation as a means to improve vascular function among women across the lifespan.

Simultaneous Pharmacokinetic Analysis of Nitrate and its Reduced Metabolite, Nitrite, Following Ingestion of Inorganic Nitrate in a Mixed Patient Population

PURPOSE

The pharmacokinetic properties of plasma NO₃^- and its reduced metabolite, NO₂^-, have been separately described, but there has been no reported attempt to simultaneously model their pharmacokinetics following NO₃^- ingestion. This report describes development of such a model from retrospective analyses of concentrations largely obtained from primary endpoint efficacy trials.

METHODS

Linear and non-linear mixed effects analyses were used to statistically define concentration dependency on time, dose, as well as patient and study variables, and to integrate NO₃^- and NO₂^- concentrations from studies conducted at different times, locations, patient groups, and several studies in which sample range was limited to a few hours. Published pharmacokinetic studies for both substances were used to supplement model development.

RESULTS

A population pharmacokinetic model relating NO₃^- and NO₂^- concentrations was developed. The model incorporated endogenous levels of the two entities, and determined these were not influenced by exogenous NO₃^- delivery. Covariate analysis revealed intersubject variability in NO₃^- exposure was partially described by body weight differences influencing volume of distribution. The model was applied to visualize exposure versus response (muscle contraction performance) in individual patients.

CONCLUSIONS

Extension of the present first-generation model, to ultimately optimize NO₃^- dose versus pharmacological effects, is warranted.