Dietary nitrate supplementation improves reaction time in type 2 diabetes: Development and application of a novel nitrate-depleted beetroot juice placebo

Effect of processing on vitamin C content, total phenols and antioxidative activity of organically grown red beetroot ('Beta vulgaris' ssp. 'Rubra')

The demand for organic food is rising since consumers want food from reliable, highest quality sources originating from the environment, undisturbed by cultivation and processing. It is necessary to determine to what extent there is a scientific basis for the claims that organic food is of high quality. In this study, beetroot from an organic production system originating from 6 certified organic food producers from different geographic locations was examined. The organic beetroot samples were processed by pasteurization at 70 ºC and 90 ºC into beet juice or by drying at 55 ºC. The following samples were tested and compared: fresh beetroot, pasteurized beet juice and dried beetroot slices. The concentration of vitamin C, level of total phenol compounds (TPC) and antioxidative activity (TAA) in beetroot were influenced by the geographic origin and the applied processing method. The highest degradation for all analysed parameters was found in the samples treated by drying or pasteurisation at 90 ºC. The lowest losses of studied phytochemical components were observed during juice pasteurisation at 70 ºC. The correlation coefficient between TPC and TAA was high and significant (r2 = 0.966).

Effect of Dietary Nitrate Supplementation on Sleep in Chronic Obstructive Pulmonary Disease Patients

PURPOSE

Poor sleep quality in chronic obstructive pulmonary disease (COPD) is a result of oxygen desaturation secondary to compromised lung function. Nitrate supplementation with dietary beetroot juice is known to elevate plasma nitrate and to increase the efficiency of oxygen utilization in non-COPD individuals; whether it is of therapeutic benefit for sleep quality in COPD has not been reported.

PATIENTS AND METHODS

In a counterbalanced within-subjects design involving 15 COPD patients as subjects, the subjects consumed either beetroot juice containing nitrate (BJ; ∼6.2 mmol NO₃ ^-) or placebo (NO₃ ^- -depleted juice) immediately before a night of polysomnographic monitoring. Nitrate was measured in plasma collected immediately after waking.

RESULTS

While BJ consumption had no effect on the amount of time spent in any sleep stages, wake-to-N2 transitions and direct wake-to-rapid eye movement sleep (REMS) transitions, hallmarks of disordered sleep, were less frequent on the BJ night than on the placebo night. In the last two hours of the BJ night, percent time in REMS increased and delta power during deep (N3) non-REMS decreased, relative to the placebo night. Collectively, the reduced frequency of atypical transitions and the normalization of non-REMS/REMS dynamics after BJ are indicative of an improvement of sleep quality. BJ also resulted in sustained elevation of peripheral oxygen saturation (SpO₂), during episodes of wake after sleep onset. Plasma nitrate was elevated nearly tenfold on the morning after BJ relative to placebo.

CONCLUSION

BJ has a normalizing effect on disordered sleep in COPD, which may be related to improved oxygen delivery.

CLINICAL TRIAL REGISTRATION

The activities of the Regional Committees for Medical and Health Research Ethics (REC) are founded on the Norwegian law on research ethics and medical research. This study was approved by NTNU/REK midt, Det medisinske fakultet, Postboks 8905, 7491 Trondheim (REK midt 2016/1360).

Nitrate and nitrite exposure leads to mild anxiogenic-like behavior and alters brain metabolomic profile in zebrafish

Dietary nitrate lowers blood pressure and improves athletic performance in humans, yet data supporting observations that it may increase cerebral blood flow and improve cognitive performance are mixed. We tested the hypothesis that nitrate and nitrite treatment would improve indicators of learning and cognitive performance in a zebrafish (Danio rerio) model. We utilized targeted and untargeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis to examine the extent to which treatment resulted in changes in nitrate or nitrite concentrations in the brain and altered the brain metabolome. Fish were exposed to sodium nitrate (606.9 mg/L), sodium nitrite (19.5 mg/L), or control water for 2–4 weeks and free swim, startle response, and shuttle box assays were performed. Nitrate and nitrite treatment did not change fish weight, length, predator avoidance, or distance and velocity traveled in an unstressed environment. Nitrate- and nitrite-treated fish initially experienced more negative reinforcement and increased time to decision in the shuttle box assay, which is consistent with a decrease in associative learning or executive function however, over multiple trials, all treatment groups demonstrated behaviors associated with learning. Nitrate and nitrite treatment was associated with mild anxiogenic-like behavior but did not alter epinephrine, norepinephrine or dopamine levels. Targeted metabolomics analysis revealed no significant increase in brain nitrate or nitrite concentrations with treatment. Untargeted metabolomics analysis found 47 metabolites whose abundance was significantly altered in the brain with nitrate and nitrite treatment. Overall, the depletion in brain metabolites is plausibly associated with the regulation of neuronal activity including statistically significant reductions in the inhibitory neurotransmitter γ-aminobutyric acid (GABA; 18–19%), and its precursor, glutamine (17–22%). Nitrate treatment caused significant depletion in the brain concentration of fatty acids including linoleic acid (LA) by 50% and arachidonic acid (ARA) by 80%; nitrite treatment caused depletion of LA by ~90% and ARA by 60%, change which could alter the function of dopaminergic neurons and affect behavior. Nitrate and nitrite treatment did not adversely affect multiple parameters of zebrafish health. It is plausible that indirect NO-mediated mechanisms may be responsible for the nitrate and nitrite-mediated effects on the brain metabolome and behavior in zebrafish.

Effect of inorganic nitrate on metabolic parameters in patients with type 2 diabetes: A 24-week randomized double-blind placebo-controlled clinical trial

AIM

In this randomized placebo-controlled clinical trial, effect of oral inorganic nitrate (NO₃^-) on metabolic parameters was assessed in patients with type 2 diabetes mellitus (T2DM).

METHODS

Seventy-four eligible patients with T2DM were randomly assigned to NO₃^--rich beetroot powder (5 g/d contains ~250 mg NO₃^-) and placebo groups to complete intervention over a 24-week period. Blood HbA1c, fasting serum glucose, insulin, C-peptide, as well as lipid profile were assessed at baseline and again at weeks 4, 12, and 24; indices of insulin resistance were also calculated. To assess safety of long-term oral NO₃^-, liver and renal function tests were measured. An intention-to-treat approach was used for data analysis. To compare effect of intervention over time between the groups (time×group), repeated measures generalized estimating equation (GEE) linear regression models were used.

RESULTS

Mean age of the participants was 54.0 ± 8.5 (47.9% were male) and mean duration of diabetes was 8.5 ± 6.1 years. A total of 64 patients (n = 35 in beetroot group and n = 29 in placebo group) completed at least two visits and were included in the analyses. No significant difference was observed between the groups for glycemic and lipid parameters over time. Liver and renal function tests, as safety outcome measures, showed no undesirable changes during the study follow-up.

CONCLUSION

Supplementation with inorganic NO₃^- had no effect on metabolic parameters in patients with T2DM.

Long-term Change in Physiological Markers and Cognitive Performance in Type 2 Diabetes: The Look AHEAD Study

CONTEXT

The effects of physiological improvements on cognitive function among persons with type 2 diabetes mellitus (T2DM) are not fully understood.

OBJECTIVE

To determine whether improvements in physiological markers (body weight, blood sugar control, and physical activity) during intensive lifestyle intervention (ILI) are associated with enhancements in cognitive function in older adults with T2DM.

DESIGN

Multisite randomized controlled trial.

SETTING

Academic research centers.

PATIENTS OR OTHER PARTICIPANTS

Participants were aged 45-76 years, with T2DM.

INTERVENTION

The Action for Health in Diabetes (Look AHEAD) study, a randomized, controlled clinical trial of ILI.

MAIN OUTCOME MEASURE

Two to 3 cognitive assessments were collected from 1089 participants, the first and last occurring a mean (standard deviation) of 8.6 (1.0) and 11.5 (0.7) years after enrollment.

RESULTS

Greater improvement in blood sugar control was associated with better cognitive scores (fasting glucose and Rey Auditory Verbal Learning Test [AVLT]: P = 0.0148; fasting glucose and Digit Symbol Coding (DSC): P = 0.0360; HbA1C and DSC: P = 0.0477); but weight loss had mixed associations with cognitive scores (greater body mass index [BMI] reduction and worse AVLT overall: P = 0.0053; and greater BMI reduction and better DSC scores among those overweight but not obese at baseline: P = 0.010). Associations were strongest among those who were overweight (not obese) at baseline, and among those with a history of cardiovascular disease (CVD) at baseline.

CONCLUSIONS

Improvements in glycemic control, but not necessarily weight status, during ILI may be associated with better subsequent cognitive performance. These associations may differ by adiposity and CVD history.

Exercise-Induced Elevated BDNF Level Does Not Prevent Cognitive Impairment Due to Acute Exposure to Moderate Hypoxia in Well-Trained Athletes

Exposure to acute hypoxia causes a detrimental effect on the brain which is also manifested by a decrease in the ability to perform psychomotor tasks. Conversely, brain-derived neurotrophic factor (BDNF), whose levels are elevated in response to exercise, is a well-known factor in improving cognitive function. Therefore, the aim of our study was to investigate whether the exercise under hypoxic conditions affects psychomotor performance. For this purpose, 11 healthy young athletes performed a graded cycloergometer exercise test to volitional exhaustion under normoxia and acute mild hypoxia (FiO₂ = 14.7%). Before, immediately after exercise and after a period of recovery, choice reaction time (CRT) and number of correct reactions (NCR) in relation to changes in serum BDNF were examined. Additionally, other selected factors which may modify BDNF production, i.e., cortisol (C), nitrite, catecholamines (adrenalin-A, noradrenaline-NA, dopamine-DA, serotonin-5-HT) and endothelin-1 (ET-1), were also measured. Exercise in hypoxic conditions extended CRT by 13.8% (p < 0.01) and decreased NCR (by 11.5%) compared to rest (p < 0.05). During maximal workload, NCR was lower by 9% in hypoxia compared to normoxia (p < 0.05). BDNF increased immediately after exercise in normoxia (by 29.3%; p < 0.01), as well as in hypoxia (by 50.0%; p < 0.001). There were no differences in BDNF between normoxia and hypoxia. Considering the fact that similar levels of BDNF were seen in both conditions but cognitive performance was suppressed in hypoxia, acute elevation of BDNF did not compensate for hypoxia-induced cognition impairment. Moreover, neither potentially negative effects of C nor positive effects of A, DA and NO on the brain were observed in our study.

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

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

Rebalancing glucolipid metabolism and gut microbiome dysbiosis by nitrate-dependent alleviation of high-fat diet-induced obesity

INTRODUCTION

High-fat diet (HFD)-induced obesity is accompanied by compromised nitric oxide (NO) signaling and gut microbiome dysregulation. Inorganic dietary nitrate, which acts as a NO donor, exerts beneficial effects on metabolic disorders. Here, we evaluated the effects of dietary nitrate on HFD-induced obesity and provided insights into the underlying mechanism.

RESEARCH DESIGN AND METHODS

To investigate the preventive effect of dietary nitrate on HFD-induced obesity, C57BL/6 mice were randomly assigned into four groups (n=10/group), including normal control diet group (normal water and chow diet), HFD group (normal water and HFD), HFD+NaNO₃ group (water containing 2 mM NaNO₃ and HFD), and HFD+NaCl group (water containing 2 mM NaCl and HFD). During the experiment, body weight was monitored and glucolipid metabolism was evaluated. The mechanism underlying the effects of nitrate on HFD-induced obesity was investigated by the following: the NO₃^--NO₂^--NO pathway; endothelial NO synthase (eNOS) and cyclic guanosine monophosphate (cGMP) levels; gut microbiota via 16SRNA analysis.

RESULTS

Dietary nitrate reduced the body weight gain and lipid accumulation in adipose and liver tissues in HFD-fed mice. Hyperlipidemia and insulin resistance caused by HFD were improved in mice supplemented with nitrate. The level of eNOS was upregulated by nitrate in the serum, liver, and inguinal adipose tissue. Nitrate, nitrite, and cGMP levels were decreased in mice fed on HFD but reversed in the HFD+NaNO₃ group. Nitrate also rebalanced the colon microbiota and promoted a normal gut microbiome profile by partially attenuating the impacts of HFD. Bacteroidales S24-7, Alistipes, Lactobacillus, and Ruminococcaceae abundances were altered, and Bacteroidales S24-7 and Alistipes abundances were higher in the HFD+NaNO₃ group than that in the HFD group.

CONCLUSIONS

Inorganic dietary nitrate alleviated HFD-induced obesity and ameliorated disrupted glucolipid metabolism via NO₃^--NO₂^--NO pathway activation and gut microbiome modulation.

Nutraceuticals in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe disease characterized by the loss and obstructive remodeling of the pulmonary arterial wall, causing a rise in pulmonary arterial pressure and pulmonary vascular resistance, which is responsible for right heart failure, functional decline, and death. Although many drugs are available for the treatment of this condition, it continues to be life-threatening, and its long-term treatment is expensive. On the other hand, many natural compounds present in food have beneficial effects on several cardiovascular conditions. Several studies have explored many of the potential beneficial effects of natural plant products on PAH. However, the mechanisms by which natural products, such as nutraceuticals, exert protective and therapeutic effects on PAH are not fully understood. In this review, we analyze the current knowledge on nutraceuticals and their potential use in the protection and treatment of PAH, as well as whether nutraceuticals could enhance the effects of drugs used in PAH through similar mechanisms.

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

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

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

INTRODUCTION

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

METHODS AND DESIGN

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

ETHICS AND DISSEMINATION

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

TRIAL REGISTRATION NUMBER

NCT03088514.

Protective and curative effects of Beta vulgaris on pesticide dimethyl 2,2-dichlorovinyl phosphate-exposed albino rats

Background: This study evaluated the effect of Beta vulgaris (beetroot) smoothie on some biochemical parameters on dimethyl 2,2-dichlorovinyl phosphate (DDVP, known as dichlorvos)-exposed albino Wistar rats. Methods: A total of 30 rats of both sexes were grouped into five groups of six animals each. Group I served as the negative control and were not exposed to dichlorvos. Group II served as the positive control and were exposed to dichlorvos but received no smoothie. Group III received 500 mg/kg body weight beetroot smoothie and was not exposed to dichlorvos. Groups IV and V were exposed to dichlorvos but received beetroot before and after exposure, respectively. At the end of the 6-week experiment, the animals were euthanized, the blood samples collected for some biochemical assays while the organs (kidney and liver) were harvested and subjected to histopathological examination. Results: From the biochemical assay, it was observed that the beetroot smoothies regulated and significantly reduced the elevated levels of AST, ALT, urea and creatinine observed in the animals that were exposed to dichlorvos. Additionally, the beetroot was able to regenerate the liver and kidney organs that were damaged on exposure to dichlorvos. Conclusion: This study concluded that beetroot smoothie possesses hepato-protective, hepato-curative as well as nephro-curative properties.

Knowledge and beliefs about dietary inorganic nitrate among UK-based nutrition professionals: Development and application of the KINDS online questionnaire

OBJECTIVES

To examine knowledge and beliefs about the biological roles of dietary inorganic nitrate in UK-based nutrition professionals, and to explore potential differences by participants' education level.

SETTING

An online questionnaire was administered to UK-based nutrition professionals, exploring knowledge and/or beliefs across five areas: (1) health and performance effects of nitrate; (2) current and recommended intake values for nitrate; (3) dietary sources of nitrate; (4) methods of evaluating nitrate intake and (5) nitrate metabolism.

PARTICIPANTS

One hundred and twenty-five nutrition professionals.

PRIMARY OUTCOME

Knowledge and beliefs about inorganic nitrate.

RESULTS

Most nutrition professionals taking part in the survey had previously heard of inorganic nitrate (71%) and perceived it to be primarily beneficial (51%). The majority believed that nitrate consumption can improve sports performance (59%) and reduce blood pressure (54%), but were unsure about effects on cognitive function (71%), kidney function (80%) and cancer risk (70%). Knowledge of dietary sources of nitrate and factors affecting its content in food were generally good (41%-79% of participants providing correct answers). However, most participants were unsure of the average population intake (65%) and the acceptable daily intake (64%) of nitrate. Most participants (65%) recognised at least one compound (ie, nitric oxide or nitrosamines) that is derived from dietary nitrate in the body. Knowledge of nitrate, quantified by a 23-point index created by summing correct responses, was greater in individuals with a PhD (p=0.01; median (IQR)=13 (9-17)) and tended to be better in respondents with a masters degree (p=0.054; 13 (8-15)) compared with undergraduate-level qualifications (10 (2-14)).

CONCLUSIONS

UK-based nutrition professionals demonstrated mixed knowledge about the physiology of dietary nitrate, which was better in participants with higher education. More efficient dissemination of current knowledge about inorganic nitrate and its effects on health to nutrition professionals will support them to make more informed recommendations about consumption of this compound.

The effects of dietary nitrate on plasma glucose and insulin sensitivity in sheep

Nitrate (NO₃ ^¯ ) is an effective non-protein nitrogen source for gut microbes and reduces enteric methane (CH₄ ) production in ruminants. Nitrate is reduced to ammonia by rumen bacteria with nitrite (NO₂ ^¯ ) produced as an intermediate. The absorption of NO₂ ^¯ can cause methaemoglobinaemia in ruminants. Metabolism of NO₃ ^¯ and NO₂ ^¯ in blood and animal tissues forms nitric oxide (NO) which has profound physiological effects in ruminants and has been shown to increase glucose uptake and insulin secretion in rodents and humans. We hypothesized that absorption of small quantities of NO₂ ^¯ resulting from a low-risk dose of dietary NO₃ ^¯ will increase insulin sensitivity (S_I ) and glucose uptake in sheep. We evaluated the effect of feeding sheep with a diet supplemented with 18 g NO₃ ^¯ /kg DM or urea (Ur) isonitrogenously to NO₃ ^¯ , on insulin and glucose dynamics. A glucose tolerance test using an intravenous bolus of 1 ml/kg LW of 24% (w/v) glucose was conducted in twenty sheep, with 10 sheep receiving 1.8% supplementary NO₃ ^¯ and 10 receiving supplementary urea isonitrogenously to NO₃ ^¯ . The MINMOD model used plasma glucose and insulin concentrations to estimate basal plasma insulin (I_b ) and basal glucose concentration (G_b ), insulin sensitivity (S_I ), glucose effectiveness (S_G ), acute insulin response (AIRg) and disposition index (DI). Nitrate supplementation had no effect on I_b (p > .05). The decrease in blood glucose occurred at the same rate in both dietary treatments (S_G ; p = .60), and there was no effect of NO₃ ^¯ on either G_b , S_I , AIRg or DI. This experiment found that the insulin dynamics assessed using the MINMOD model were not affected by NO₃ ^¯ administered to fasted sheep at a low dose of 1.8% NO₃ ^¯ in the diet.

Protective and curative effects of Beta vulgaris on dimethyl 2,2-dichlorovinyl phosphate-exposed albino rats

Background: This study evaluated the effect of Beta vulgaris (beetroot) smoothie on some biochemical parameters on dimethyl 2,2-dichlorovinyl phosphate (DDVP, known as dichlorvos)-exposed albino Wistar rats. Methods: A total of 30 rats of both sexes were grouped into five groups of six animals each. Group I served as the negative control and were not exposed to dichlorvos. Group II served as the positive control and were exposed to dichlorvos but received no smoothie. Group III received 500 mg/kg body weight beetroot smoothie and was not exposed to dichlorvos. Groups IV and V were exposed to dichlorvos but received beetroot before and after exposure, respectively. At the end of the 6-week experiment, the animals were euthanized, the blood samples collected for some biochemical assays while the organs (kidney and liver) were harvested and subjected to histopathological examination. Results: From the biochemical assay, it was observed that the beetroot smoothies regulated and significantly reduced the elevated levels of AST, ALT, urea and creatinine observed in the animals that were exposed to dichlorvos. Additionally, the beetroot was able to regenerate the liver and kidney organs that were damaged on exposure to dichlorvos. Conclusion: This study concluded that beetroot smoothie possesses hepato-protective, hepato-curative as well as nephro-curative properties.

Acute Supplementation with Nitrate-Rich Beetroot Juice Causes a Greater Increase in Plasma Nitrite and Reduction in Blood Pressure of Older Compared to Younger Adults

Nitrate-rich beetroot juice supplementation has been shown to improve cardiovascular and cognitive function in younger and older adults via increased nitric oxide production. However, it is unclear whether the level of effects differs between the two groups. We hypothesized that acute supplementation with nitrate-rich beetroot juice would improve cardiovascular and cognitive function in older and younger adults, with the potential for greater improvements in older adults. Thirteen younger (18–30 years) and 11 older (50–70 years) adults consumed either 150 mL of nitrate-rich beetroot juice (BR; 10.5 mmol nitrate) or placebo (PL; 1 mmol nitrate) in a double-blind, crossover design, 2.25 h prior to a 30-min treadmill walk. Plasma nitrate and nitrite concentrations, blood pressure (BP), heart rate (HR), cognitive function, mood and perceptual tests were performed throughout the trial. BR consumption significantly increased plasma nitrate (p < 0.001) and nitrite (p = 0.003) concentrations and reduced systolic BP (p < 0.001) in both age groups and reduced diastolic BP (p = 0.013) in older adults. Older adults showed a greater elevation in plasma nitrite (p = 0.038) and a greater reduction in diastolic BP (p = 0.005) following BR consumption than younger adults. Reaction time was improved in the Stroop test following BR supplementation for both groups (p = 0.045). Acute BR supplementation increased plasma nitrite concentrations and reduced diastolic BP to a greater degree in older adults; whilst systolic BP was reduced in both older and younger adults, suggesting nitrate-rich BR may improve cardiovascular health, particularly in older adults due to the greater benefits from reductions in diastolic BP.

Acute Supplementation with Nitrate-Rich Beetroot Juice Causes a Greater Increase in Plasma Nitrite and Reduction in Blood Pressure of Older Compared to Younger Adults

Nitrate-rich beetroot juice supplementation has been shown to improve cardiovascular and cognitive function in younger and older adults via increased nitric oxide production. However, it is unclear whether the level of effects differs between the two groups. We hypothesized that acute supplementation with nitrate-rich beetroot juice would improve cardiovascular and cognitive function in older and younger adults, with the potential for greater improvements in older adults. Thirteen younger (18-30 years) and 11 older (50-70 years) adults consumed either 150 mL of nitrate-rich beetroot juice (BR; 10.5 mmol nitrate) or placebo (PL; 1 mmol nitrate) in a double-blind, crossover design, 2.25 h prior to a 30-min treadmill walk. Plasma nitrate and nitrite concentrations, blood pressure (BP), heart rate (HR), cognitive function, mood and perceptual tests were performed throughout the trial. BR consumption significantly increased plasma nitrate (p < 0.001) and nitrite (p = 0.003) concentrations and reduced systolic BP (p < 0.001) in both age groups and reduced diastolic BP (p = 0.013) in older adults. Older adults showed a greater elevation in plasma nitrite (p = 0.038) and a greater reduction in diastolic BP (p = 0.005) following BR consumption than younger adults. Reaction time was improved in the Stroop test following BR supplementation for both groups (p = 0.045). Acute BR supplementation increased plasma nitrite concentrations and reduced diastolic BP to a greater degree in older adults; whilst systolic BP was reduced in both older and younger adults, suggesting nitrate-rich BR may improve cardiovascular health, particularly in older adults due to the greater benefits from reductions in diastolic BP.

Dietary Nitrate and Physical Performance

Nitric oxide (NO) plays a plethora of important roles in the human body. Insufficient production of NO (for example, during older age and in various disease conditions) can adversely impact health and physical performance. In addition to its endogenous production through the oxidation of l-arginine, NO can be formed nonenzymatically via the reduction of nitrate and nitrite, and the storage of these anions can be augmented by the consumption of nitrate-rich foodstuffs such as green leafy vegetables. Recent studies indicate that dietary nitrate supplementation, administered most commonly in the form of beetroot juice, can ( a) improve muscle efficiency by reducing the O₂ cost of submaximal exercise and thereby improve endurance exercise performance and ( b) enhance skeletal muscle contractile function and thereby improve muscle power and sprint exercise performance. This review describes the physiological mechanisms potentially responsible for these effects, outlines the circumstances in which ergogenic effects are most likely to be evident, and discusses the effects of dietary nitrate supplementation on physical performance in a range of human populations.

Dietary Nitrate from Beetroot Juice for Hypertension: A Systematic Review

According to current therapeutic approaches, a nitrate-dietary supplementation with beetroot juice (BRJ) is postulated as a nutritional strategy that might help to control arterial blood pressure in healthy subjects, pre-hypertensive population, and even patients diagnosed and treated with drugs. In this sense, a systematic review of random clinical trials (RCTs) published from 2008 to 2018 from PubMed/MEDLINE, ScienceDirect, and manual searches was conducted to identify studies examining the relationship between BRJ and blood pressure. The specific inclusion criteria were: (1) RCTs; (2) trials that assessed only the BRJ intake with control group; and (3) trials that reported the effects of this intervention on blood pressure. The search identified 11 studies that met the inclusion criteria. This review was able to demonstrate that BRJ supplementation is a cost-effective strategy that might reduce blood pressure in different populations, probably through the nitrate/nitrite/nitric oxide (NO₃⁻/NO₂⁻/NO) pathway and secondary metabolites found in Beta vulgaris. This easily found and cheap dietary intervention could significantly decrease the risk of suffering cardiovascular events and, in doing so, would help to diminish the mortality rate associated to this pathology. Hence, BRJ supplementation should be promoted as a key component of a healthy lifestyle to control blood pressure in healthy and hypertensive individuals. However, several factors related to BRJ intake (e.g., gender, secondary metabolites present in B. vulgaris, etc.) should be studied more deeply.

Laboratory evidence for the hematopoietic potential of Beta vulgaris leaf and stalk extract in a phenylhydrazine model of anemia

This study was designed to provide laboratory evidence supporting the hematopoietic effect of Beta vulgaris (beet) leaf aqueous extract in phenylhydrazine-induced anemia model in albino rats. Extraction of the leaves/stalks was done by maceration in 30% hydro-ethanol for 48 h. An intraperitoneal injection of 20 mg/kg phenylhydrazine was applied for two consecutive days to develop hemolytic anemia on the 4th day after the 1st injection in 24 of 30 male albino rats. The animals were divided into 5 groups and received the following treatments: standard (ferrous ascorbate + folic acid; 13.5 + 0.135 mg/kg), B. vulgaris extract (100 and 200 mg/kg), or left untreated (normal and diseased controls). Blood samples were taken at 0, 4, 8, and 12 days of the experiment for hematological and clinico-chemical analysis. Beet leaf extract significantly restored the levels of red blood cells, white blood cells, hemoglobin, and hematocrit in dose- and time-dependent manners. Blood indices have been significantly corrected. Erythropoietin level was maintained at higher levels. Erythrocytic membrane oxidation biomarker (malondialdehyde) level was significantly reduced compared to the anemic untreated group. The extract exhibited potent, concentration (4–512 μg/mL)-dependent antioxidant activity indicated by the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay, with IC50 value of 37.91 μg/mL. Beet leaf extract resulted in detection of flavonoid and phenolic compounds that may underlie its hematinic properties. These findings may indicate B. vulgaris as a good natural source for pharmaceutical preparations with hematopoietic effects and treatment of anemia and/or associated conditions.

Pharmacological potentials of betalains

Betalains are water soluble plant pigments in plants of the order Caryophyllales, which are widely used as colorants. Several preclinical studies reported that betanin reveals antioxidants, anti-inflammatory, hepatoprotective, anticancer, anti-diabetes, anti-lipid emic, antimicrobial activity, radio protective and anti-proliferative activity. They are isolated from sources such as red beetroot, amaranth, prickly pear, red pitahaya, etc. Betalains are divided into two groups based on the colour and confer either the betacyanins (purple reddish) or betaxanthins (yellowish orange). Betalain is one of the promising nutraceuticals which can provide beneficial effects for prevention and cure of various diseases. The purpose of this review is to focus on nutraceutical facts of betalains by focusing on the ongoing treatment using betalains and to address its future nutraceuticals implications.

Inorganic nitrate supplementation enhances functional capacity and lower-limb microvascular reactivity in patients with peripheral artery disease

Peripheral artery disease (PAD) is characterized by functional and vascular impairments as well as elevated levels of inflammation which are associated with reduced nitric oxide (NO) bioavailability. Inorganic nitrate supplementation boosts NO bioavailability potentially improving functional and vasodilatory capacities and may reduce inflammation. Twenty-one patients with PAD were randomly assigned to sodium nitrate (NaNO₃) or placebo supplementation groups for eight-weeks. Outcome measures included a 6-min walk test (6 MWT), blood flow and vasodilator function in the forearm and calf, as well as plasma inflammatory and adhesion biomarker concentrations. NaNO₃ elevated plasma nitrate (32.3 ± 20.0 to 379.8 ± 204.6 μM) and nitrite (192.2 ± 51.8 to 353.1 ± 134.2 nM), improved 6 MWT performance (387 ± 90 to 425 ± 82 m), peak calf blood flow (BF_Peak; 11.6 ± 4.9 to 14.1 ± 5.1 mL/dL tissue/min), and peak calf vascular conductance (VC_Peak; 11.1 ± 4.3 to 14.2 ± 4.9 mL/dL tissue/min/mmHg) (p < 0.05 for all). Improvements in calf BF_Peak (r = 0.70, p < 0.05) and VC_Peak (r = 0.61, p < 0.05) correlated with changes in 6 MWT distance. Placebo supplementation did not change plasma nitrate or nitrite, 6 MWT, calf BF_Peak, or calf VC_Peak. Forearm vascular function nor inflammatory and adhesion biomarker concentrations changed in either group. Eight-weeks of NaNO₃ supplementation improves vasodilatory capacity in the lower-limbs of patients with PAD, which correlated with improvement in functional capacity.

Effects of dietary nitrate supplementation, from beetroot juice, on blood pressure in hypertensive pregnant women: A randomised, double-blind, placebo-controlled feasibility trial

Chronic hypertension in pregnancy is associated with significant adverse pregnancy outcomes, increasing the risk of pre-eclampsia, fetal growth restriction and preterm birth. Dietary nitrate, abundant in green leafy vegetables and beetroot, is reduced in vivo to nitrite and subsequently nitric oxide, and has been demonstrated to lower blood pressure, improve vascular compliance and enhance blood flow in non-pregnant humans and animals. The primary aims of this study were to determine the acceptability and efficacy of dietary nitrate supplementation, in the form of beetroot juice, to lower blood pressure in hypertensive pregnant women. In this double-blind, placebo-controlled feasibility trial, 40 pregnant women received either daily nitrate supplementation (70 mL beetroot juice, n = 20) or placebo (70 mL nitrate-depleted beetroot juice, n = 20) for 8 days. Blood pressure, cardiovascular function and uteroplacental blood flow was assessed at baseline and following acute (3 h) and prolonged (8 days) supplementation. Plasma and salivary samples were collected for analysis of nitrate and nitrite concentrations and acceptability of this dietary intervention was assessed based on questionnaire feedback. Dietary nitrate significantly increased plasma and salivary nitrate/nitrite concentrations compared with placebo juice (p < 0.001), with marked variation between women. Compared with placebo, there was no overall reduction in blood pressure in the nitrate-treated group; however there was a highly significant correlation between changes in plasma nitrite concentrations and changes in diastolic blood pressure in the nitrate-treated arm only (r = -0.6481; p = 0.0042). Beetroot juice supplementation was an acceptable dietary intervention to 97% of women. This trial confirms acceptability and potential efficacy of dietary nitrate supplementation in pregnant women. Conversion of nitrate to nitrite critically involves oral bacterial nitrate reductase activities. We speculate that differences in efficacy of nitrate supplementation relate to differences in the oral microbiome, which will be investigated in future studies.

Effects of inorganic nitrate and nitrite consumption on cognitive function and cerebral blood flow: A systematic review and meta-analysis of randomized clinical trials

We conducted a systematic review and meta-analysis of randomized clinical trials examining the effect of inorganic nitrate or nitrite supplementation on cognitive function (CF) and cerebral blood flow (CBF). Two databases (PubMed, Embase) were searched for articles from inception until May 2017. Inclusion criteria were: randomized clinical trials; participants >18 years old; trials comparing a nitrate/nitrite intervention with a control. Thirteen and nine trials were included in the meta-analysis to assess CF and CBF, respectively. Random-effects models were used and the effect size described as standardized mean differences (SMDs). A total of 297 participants (median of 23 per trial) were included for CF; 163 participants (median of 16 per trial) were included for CBF. Nitrate/nitrite supplementation did not influence CF (SMD +0.06, 95% CI: -0.06, 0.18, P = 0.32) or CBF under resting (SMD +0.14, 95% CI: -0.13, 0.41, P = 0.31), or stimulated conditions (SMD + 0.23, 95% CI: -0.11, 0.56, P = 0.19). The meta-regression showed an inverse association between duration of the intervention and CBF (P = 0.02) but no influence of age, BMI or dose (P < 0.05). Nitrate and nitrite supplementation did not modify CBF or CF. Further trials employing larger samples sizes and interventions with longer duration are warranted.

Beet Stalks and Leaves (Beta vulgaris L.) Protect Against High-Fat Diet-Induced Oxidative Damage in the Liver in Mice

Some flavonoids identified in beet stalks can help the antioxidant endogenous defenses during a chronic inflammation process. The current study investigates the effect of polyphenols present in beet stalks and leaves on liver oxidative damage in mice fed a high-fat diet (HF). The control (CT) or HF diet groups were supplemented with dehydrated beet stalks and leaves (SL) or beet stalk and leaf ethanolic extract (EX). In terms of Vitexin-rhaminoside equivalents (VRE), EX groups received ~5.91 mg of VRE·100 g⁻¹ diet, while the SL groups received ~3.07 mg VRE·100 g⁻¹ diet. After 8 weeks, we evaluated fasting blood glucose; cholesterol, hepatic Malondialdehyde (MDA) levels and hepatic Glutathione (GSH), Glutathione peroxidase (GPx), Glutathione reductase (GR) and Superoxide dismutase (SOD) activity. Dehydrated beet stalks and leaves (HFSL) attenuated the deleterious effects of a HF diet on lipid metabolism, reduced fasting blood glucose levels, ameliorated cholesterol levels and reduced GPx and GR activities (p < 0.05) compared to the HF group. However; the addition of ethanolic extract from beet stalks and leaves was unable (p > 0.05) to prevent the liver damage caused by HF diet in mice. The presence of flavonoids, such as Vitexin derivatives in beet stalks and leaves can help the liver damage induced by HF diet.

Stroke, cerebrovascular diseases and vascular cognitive impairment in Africa

With increased numbers of older people a higher burden of neurological disorders worldwide is predicted. Stroke and other cerebrovascular diseases do not necessarily present with different phenotypes in Africa but their incidence is rising in tandem with the demographic change in the population. Age remains the strongest irreversible risk factor for stroke and cognitive impairment. Modifiable factors relating to vascular disease risk, diet, lifestyle, physical activity and psychosocial status play a key role in shaping the current spate of stroke related diseases in Africa. Hypertension is the strongest modifiable risk factor for stroke but is also likely associated with co-inheritance of genetic traits among Africans. Somewhat different from high-income countries, strokes attributed to cerebral small vessel disease (SVD) are higher >30% among sub-Saharan Africans. Raised blood pressure may explain most of the incidence of SVD-related strokes but there are likely other contributing factors including dyslipidaemia and diabetes in some sectors of Africa. However, atherosclerotic and cardioembolic diseases combined also appear to be common subtypes as causes of strokes. Significant proportions of cerebrovascular diseases are ascribed to various forms of infectious disease including complications of human immunodeficiency virus. Cerebral SVD leads to several clinical manifestations including gait disturbance, autonomic dysfunction and depression. Pathological processes are characterized by arteriolosclerosis, lacunar infarcts, perivascular spaces, microinfarcts and diffuse white matter changes, which can now all be detected on neuroimaging. Except for isolated cases of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy or CADASIL, hereditary arteriopathies have so far not been reported in Africa. Prevalence estimates of vascular dementia (2-3%), delayed dementia after stroke (10-20%) and vascular cognitive impairment (30-40%) do not appear to be vastly different from those in other parts of the world. However, given the current demographic transition in both urban and rural settings these figures will likely rise. Wider application of neuroimaging modalities and implementation of stroke care in Africa will enable better estimates of SVD and other subtypes of stroke. Stroke survivors with SVD type pathology are likely to have low mortality and therefore portend increased incidence of dementia.

Dietary nitrate lowers ambulatory blood pressure in treated, uncontrolled hypertension: a 7-d, double-blind, randomised, placebo-controlled, cross-over trial

Dietary nitrate has been shown to increase nitrate/nitrite levels and decrease blood pressure (BP) in multiple populations. There are few reports among hypertensives and these reports have provided conflicting evidence. We aimed to assess the effect of daily nitrate compared with placebo in subjects with uncontrolled hypertension (HTN). On day 0, hypertensives wore an ambulatory BP monitor (ABPM) for 24 h and blood was taken. Subjects were then randomised to 7-d nitrate-rich beetroot juice (NO3−) (12·9 mmol nitrate) followed by 7-d nitrate-depleted beetroot juice (0·5 mmol nitrate) or vice versa. ABPM and blood were assessed before and after both conditions. In all, twenty subjects with treated yet uncontrolled HTN entered and completed the trial (mean age=62·5 years, mean BMI=30·7 kg/m2). Baseline BP was 137/80 (sd7/7) mmHg. Dietary nitrate was well tolerated and resulted in significantly increased plasma nitrite (P=0·0004) and decreased 24-h systolic BP and diastolic BP compared with placebo (−8 mmHg;P=0·012 and −4 mmHg;P=0·018, respectively). Our results support the existing data suggesting an anti-hypertensive effect of dietary nitrate in treated yet uncontrolled hypertensives. Targeted dietary strategies appear promising contributors to BP control.

Potential benefits of dietary nitrate ingestion in healthy and clinical populations: A brief review

This article provides an overview of the current literature relating to the efficacy of dietary nitrate (NO₃^-) ingestion in altering aspects of cardiovascular and metabolic health and exercise capacity in healthy and diseased individuals. The consumption of NO₃^--rich vegetables, such as spinach and beetroot, have been variously shown to promote nitric oxide bioavailability, reduce systemic blood pressure, enhance tissue blood flow, modulate muscle O₂ utilisation and improve exercise tolerance both in normoxia and in hypoxia, as is commonly observed in a number of disease states. NO₃^- ingestion may, therefore, act as a natural means for augmenting performance and attenuating complications associated with limited O₂ availability or transport, hypertension and the metabolic syndrome. Recent studies indicate that dietary NO₃^- might also augment intrinsic skeletal muscle contractility and improve the speed and power of muscle contraction. Moreover, several investigations suggest that NO₃^- supplementation may improve aspects of cognitive performance both at rest and during exercise. Collectively, these observations position NO₃^- as more than a putative ergogenic aid and suggest that increasing natural dietary NO₃^- intake may act as a prophylactic in countering the predations of senescence and certain cardiovascular-metabolic diseases.

Effects of long-term nitrate supplementation on carbohydrate metabolism, lipid profiles, oxidative stress, and inflammation in male obese type 2 diabetic rats

PURPOSE

Supplementation with inorganic nitrate to boost the nitrate-nitrite-nitric oxide (NO) pathway, may act as a potential therapeutic agent in diabetes. The aim of this study was to determine the effects of nitrate on carbohydrate metabolism, lipid profiles, oxidative stress, and inflammation in obese type 2 diabetic rats.

METHODS

Male Wistar rats were divided into 4 groups: Control, control + nitrate, diabetes, and diabetes + nitrate. Diabetes was induced using a high-fat diet and low-dose of streptozotocin. Sodium nitrate (100 mg/L in drinking water) was administered simultaneously for two months. Serum levels of fasting glucose, insulin, and lipid profiles were measured every 2-weeks. Glycated hemoglobin (HbA1c) was measured monthly. Serum thiobarbituric reactive substances (TBARS) level and catalase activity were measured before and after treatment. At the end of the study, glucose, pyruvate, and insulin tolerance tests were done. Glucose-stimulated insulin secretion (GSIS) and insulin content from isolated pancreatic islets were also assessed; mRNA expression of iNOS as well as mRNA expression and protein levels of GLUT4 in insulin-sensitive tissues, and serum IL-1β were determined.

RESULTS

Nitrate supplementation in diabetic rats significantly improved glucose tolerance, lipid profiles, and catalase activity as well as decreased gluconeogenesis, fasting glucose, insulin, and IL-1β; although it had no significant effect on GSIS, islet insulin content, HbA1c, and serum TBARS. Compared to the controls, in diabetic rats, mRNA expression and protein levels of GLUT4 were significantly lower in the soleus muscle (54% and 34%, respectively) and epididymal adipose tissue (67% and 41%, respectively). In diabetic rats, nitrate administration increased GLUT4 mRNA expression and protein levels in both soleus muscle (215% and 17%, respectively) and epididymal adipose tissue (344% and 22%, respectively). In diabetic rats, nitrate significantly decreased elevated iNOS mRNA expression in both the soleus muscle and epididymal adipose tissue.

CONCLUSION

Chronic nitrate supplementation in obese type 2 diabetic rats improved glucose tolerance, insulin resistance, and dyslipidemia; these favorable effects were associated with increased mRNA and protein expression of GLUT4 and decreased mRNA expression of iNOS in insulin-sensitive tissues, and with decreased gluconeogenesis, inflammation, and oxidative stress.

Effects of dietary nitrate supplementation on the response to extremity cooling and endothelial function in individuals with cold sensitivity. A double blind, placebo controlled, crossover, randomised control trial

Individuals with cold sensitivity have low peripheral skin blood flow and skin temperature possibly due to reduced nitric oxide (NO•) bioavailability. Beetroot has a high concentration of inorganic nitrate and may increase NO-mediated vasodilation. Using a placebo-controlled, double blind, randomised, crossover design, this study tested the hypotheses that acute beetroot supplementation would increase the rate of cutaneous rewarming following a local cold challenge and augment endothelium-dependent vasodilation in cold sensitive individuals. Thirteen cold sensitive participants completed foot and hand cooling (separately, in 15 °C water for 2 min) with spontaneous rewarming in 30 °C air whilst skin temperature and cutaneous vascular conductance (CVC) were measured (Baseline). On two further separate visits, participants consumed 140 ml of either concentrated beetroot juice (nitrate supplementation) or nitrate-depleted beetroot juice (Placebo) 90 min before resting seated blood pressure was measured. Endothelial function was assessed by measuring CVC at the forearm, finger and foot during iontophoresis of 1% w/v acetylcholine followed by foot and hand cooling as for Baseline. Plasma nitrite concentrations significantly increased in nitrate supplementation compared to Placebo and Baseline (502 ± 246 nmol L^-1; 73 ± 45 nmol L^-1; 74 ± 49 nmol L^-1 respectively; n = 11; P < 0.001). Resting blood pressure and the response to foot and hand cooling did not differ between conditions (all P > 0.05). Nitrate supplementation did not alter endothelial function in the forearm, finger or foot (all P > 0.05) compared to Placebo. Despite a physiologically meaningful rise in plasma nitrite concentrations, acute nitrate supplementation does not alter extremity rewarming, endothelial function or blood pressure in individuals with cold sensitivity.

Performance and Health Benefits of Dietary Nitrate Supplementation in Older Adults: A Systematic Review

Supplementation with nitrate (NO₃⁻)-rich beetroot juice has been shown to improve exercise performance and cardiovascular (CV) responses, due to an increased nitric oxide (NO) availability. However, it is unclear whether these benefits are greater in older adults who have an age-related decrease in NO and higher risk of disease. This systematic review examines 12 randomised, crossover, control trials, investigating food-based NO₃⁻ supplementation in older adults and its potential benefits on physiological and cognitive performances, and CV, cerebrovascular and metabolic health. Four studies found improvements in physiological performance (time to exhaustion) following dietary NO₃⁻ supplementation in older adults. Benefits on cognitive performance were unclear. Six studies reported improvements in CV health (blood pressure and blood flow), while six found no improvement. One study showed improvements in cerebrovascular health and two found no improvement in metabolic health. The current literature indicates positive effects of dietary NO₃⁻ supplementation in older adults on physiological performance, with some evidence indicating benefits on cardiovascular and cerebrovascular health. Effects on cognitive performance were mixed and studies on metabolic health indicated no benefit. However, there has been limited research conducted on the effects of dietary NO₃⁻ supplementation in older adults, thus, further study, utilising a randomised, double-blind, control trial design, is warranted.

Relationship Between Urinary Nitrate Excretion and Blood Pressure in the InChianti Cohort

BACKGROUND

Inorganic nitrate from the oxidation of endogenously synthesized nitric oxide (NO) or consumed in the diet can be reduced to NO via a complex enterosalivary circulation pathway. The relationship between total nitrate exposure by measured urinary nitrate excretion and blood pressure in a large population sample has not been assessed previously.

METHODS

For this cross-sectional study, 24-hour urinary nitrate excretion was measured by spectrophotometry in the 919 participants from the InChianti cohort at baseline and blood pressure measured with a mercury sphygmomanometer.

RESULTS

After adjusting for age and sex only, diastolic blood pressure was 1.9 mm Hg lower in subjects with ≥2 mmol urinary nitrate excretion compared with those excreting <1 mmol nitrate in 24 hours: systolic blood pressure was 3.4 mm Hg (95% confidence interval (CI): -3.5 to -0.4) lower in subjects for the same comparison. Effect sizes in fully adjusted models (for age, sex, potassium intake, use of antihypertensive medications, diabetes, HS-CRP, or current smoking status) were marginally larger: systolic blood pressure in the ≥2 mmol urinary nitrate excretion group was 3.9 (CI: -7.1 to -0.7) mm Hg lower than in the comparison <1 mmol excretion group.

CONCLUSIONS

Modest differences in total nitrate exposure are associated with lower blood pressure. These differences are at least equivalent to those seen from substantial (100 mmol) reductions in sodium intake.

Effect of the treatment of Type 2 diabetes mellitus on the development of cognitive impairment and dementia

BACKGROUND

Prevention of cognitive impairment and dementia is an important public health goal. Epidemiological evidence shows a relationship between cognitive impairment and Type 2 diabetes mellitus. The risk of dementia increases with duration of disease. This updated systematic review investigated the effect on cognitive function of the type of treatment and level of metabolic control in people with Type 2 diabetes.

OBJECTIVES

To assess the effects of different strategies for managing Type 2 diabetes mellitus on cognitive function and the incidence of dementia.

SEARCH METHODS

We searched ALOIS (the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group (CDCIG)), the Cochrane Library, MEDLINE, Embase, PsycINFO, CINAHL and LILACS on 15 October 2016. ALOIS contains records from all major health care databases, (CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, LILACS), as well as from many trials' registers and grey literature sources.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) which compared two or more different treatments for Type 2 diabetes mellitus and in which cognitive function was measured at baseline and after treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the quality of the included RCTs. We pooled data for comparable trials and estimated the effects of treatment by using risk ratios (RRs) and mean differences (MDs), according to the nature of the outcome. We assessed the quality of the evidence using GRADE methods.

MAIN RESULTS

We identified seven eligible studies but only four provided data we could include in efficacy analyses. Two of these studies compared intensive versus standard glycaemic control and two compared different pharmacological treatments. All studies were at unclear risk of bias in at least two domains and one large study was at high risk of performance and detection bias.(a) Two studies with 13,934 participants at high cardiovascular risk provided efficacy data on intensive versus standard glycaemic control. A third study with 1791 participants provided additional data on hypoglycaemic episodes and mortality. There is probably no difference between treatment groups in the number of participants who decline by at least 3 points on the Mini-Mental State Examination (MMSE) over five years (RR 0.98, 95% CI 0.88 to 1.08; 1 study; n = 11,140; moderate-quality evidence); and there may also be little or no difference in the incidence of dementia (RR 1.27, 95% CI 0.87 to 1.85; 1 study; n = 11,140; low-quality evidence). From another study, there was probably little or no difference in MMSE score after 40 months (MD -0.01, 95% CI -0.18 to 0.16; 1 study; n = 2794; moderate quality evidence). Participants exposed to the intensive glycaemic control strategy probably experience more episodes of severe hypoglycaemia than those who have standard treatment (RR 2.18, 95% CI 1.52 to 3.14; 2 studies; n = 12,827; moderate-quality evidence). The evidence from these trials suggests that the intensity of glycaemic control may have little or no effect on all-cause mortality (RR 0.99, 95% CI 0.87 to 1.13; 3 studies; n = 15,888; low-quality evidence).(b) One study with 156 participants compared glibenclamide (glyburide) with repaglinide. There may be a small advantage of glibenclamide on global cognitive function measured with the MMSE after 12 months (MD -0.90, 95% CI -1.68 to -0.12; low-quality evidence). No data were reported on the incidence of dementia, hypoglycaemic events or all-cause mortality.(c) One study with 145 participants compared rosiglitazone plus metformin to glibenclamide (glyburide) plus metformin over 24 weeks. It reported only on cognitive subdomains and not on global cognitive function, incidence of MCI or dementia, hypoglycaemic events or all causes of mortality.

AUTHORS' CONCLUSIONS

We found no good evidence that any specific treatment or treatment strategy for Type 2 diabetes can prevent or delay cognitive impairment. The best available evidence related to the comparison of intensive with standard glycaemic control strategies. Here there was moderate-quality evidence that the strategies do not differ in their effect on global cognitive functioning over 40 to 60 months.

Effects of Dietary Nitrate Supplementation on Physiological Responses, Cognitive Function, and Exercise Performance at Moderate and Very-High Simulated Altitude

Purpose: Nitric oxide (NO) bioavailability is reduced during acute altitude exposure, contributing toward the decline in physiological and cognitive function in this environment. This study evaluated the effects of nitrate (NO3−) supplementation on NO bioavailability, physiological and cognitive function, and exercise performance at moderate and very-high simulated altitude.

Methods:Ten males (mean (SD): V˙O2max: 60.9 (10.1) ml·kg⁻¹·min⁻¹) rested and performed exercise twice at moderate (~14.0% O₂; ~3,000 m) and twice at very-high (~11.7% O₂; ~4,300 m) simulated altitude. Participants ingested either 140 ml concentrated NO3−-rich (BRJ; ~12.5 mmol NO3−) or NO3−-deplete (PLA; 0.01 mmol NO3−) beetroot juice 2 h before each trial. Participants rested for 45 min in normobaric hypoxia prior to completing an exercise task. Exercise comprised a 45 min walk at 30% V˙O2max and a 3 km time-trial (TT), both conducted on a treadmill at a 10% gradient whilst carrying a 10 kg backpack to simulate altitude hiking. Plasma nitrite concentration ([NO2−]), peripheral oxygen saturation (SpO₂), pulmonary oxygen uptake (V˙O2), muscle and cerebral oxygenation, and cognitive function were measured throughout.

Results: Pre-exercise plasma [NO2−] was significantly elevated in BRJ compared with PLA (p = 0.001). Pulmonary V˙O2 was reduced (p = 0.020), and SpO₂ was elevated (p = 0.005) during steady-state exercise in BRJ compared with PLA, with similar effects at both altitudes. BRJ supplementation enhanced 3 km TT performance relative to PLA by 3.8% [1,653.9 (261.3) vs. 1718.7 (213.0) s] and 4.2% [1,809.8 (262.0) vs. 1,889.1 (203.9) s] at 3,000 and 4,300 m, respectively (p = 0.019). Oxygenation of the gastrocnemius was elevated during the TT consequent to BRJ (p = 0.011). The number of false alarms during the Rapid Visual Information Processing Task tended to be lower with BRJ compared with PLA prior to altitude exposure (p = 0.056). Performance in all other cognitive tasks did not differ significantly between BRJ and PLA at any measurement point (p ≥ 0.141).

Conclusion: This study suggests that BRJ improves physiological function and exercise performance, but not cognitive function, at simulated moderate and very-high altitude.

Randomised, double-blind, placebo-controlled study investigating the effects of inorganic nitrate on vascular function, platelet reactivity and restenosis in stable angina: protocol of the NITRATE-OCT study

INTRODUCTION

The mainstay treatment for reducing the symptoms of angina and long-term risk of heart attacks in patients with heart disease is stent implantation in the diseased coronary artery. While this procedure has revolutionised treatment, the incidence of secondary events remains a concern. These repeat events are thought to be due, in part, to continued enhanced platelet reactivity, endothelial dysfunction and ultimately restenosis of the stented artery. In this study, we will investigate whether a once a day inorganic nitrate administration might favourably modulate platelet reactivity and endothelial function leading to a decrease in restenosis.

METHODS AND DESIGN

NITRATE-OCT is a double-blind, randomised, single-centre, placebo-controlled phase II trial that will enrol 246 patients with stable angina due to have elective percutaneous coronary intervention procedure with stent implantation. Patients will be randomised to receive 6 months of a once a day dose of either nitrate-rich beetroot juice or nitrate-deplete beetroot juice (placebo) starting up to 1 week before their procedure. The primary outcome is reduction of in-stent late loss assessed by quantitative coronary angiography and optical coherence tomography at 6 months. The study is powered to detect a 0.22±0.55 mm reduction in late loss in the treatment group compared with the placebo group. Secondary end points include change from baseline assessment of endothelial function measured using flow-mediated dilation at 6 months, target vessel revascularisation (TVR), restenosis rate (diameter>50%) and in-segment late loss at 6 months, markers of inflammation and platelet reactivity and major adverse cardiac events (ie, myocardial infarction, death, cerebrovascular accident, TVR) at 12 and 24 months.

ETHICS AND DISSEMINATION

The study was approved by the Local Ethics Committee (15/LO/0555). Trial results will be published according to the CONSORT statement and will be presented at conferences and reported in peer-reviewed journals.

TRIAL REGISTRATION NUMBERS

NCT02529189 and ISRCTN17373946, Pre-results.

Montmorency Tart cherries (Prunus cerasus L.) modulate vascular function acutely, in the absence of improvement in cognitive performance

Cerebral blood volume and metabolism of oxygen decline as part of human ageing, and this has been previously shown to be related to cognitive decline. There is some evidence to suggest that polyphenol-rich foods can play an important role in delaying the onset or halting the progression of age-related health disorders such as CVD and Alzheimer's disease and to improve cognitive function. In the present study, an acute, placebo-controlled, double-blinded, cross-over, randomised Latin-square design study with a washout period of at least 14 d was conducted on twenty-seven, middle-aged (defined as 45-60 years) volunteers. Participants received either a 60 ml dose of Montmorency tart cherry concentrate (MC), which contained 68·0 (sd 0·26) mg cyanidin-3-glucoside/l, 160·75 (sd 0·55) mean gallic acid equivalent/l and 0·59 (sd 0·02) mean Trolox equivalent/l, respectively, or a placebo. Cerebrovascular responses, cognitive performance and blood pressure were assessed at baseline and 1, 2, 3 and 5 h following consumption. There were significant differences in concentrations of total Hb and oxygenated Hb during the task period 1 h after MC consumption (P≤0·05). Furthermore, MC consumption significantly lowered systolic blood pressure (P≤0·05) over a period of 3 h, with peak reductions of 6±2 mmHg at 1 h after MC consumption relative to the placebo. Cognitive function and mood were not affected. These results show that a single dose of MC concentrate can modulate certain variables of vascular function; however, this does not translate to improvements in cognition or mood.

Vitamin C intake modify the impact of dietary nitrite on the incidence of type 2 diabetes: A 6-year follow-up in Tehran Lipid and Glucose Study

BACKGROUND

There is no epidemiological study on the association between dietary nitrate (NO₃) and nitrite (NO₂) and intakes and the risk of type 2 diabetes (T2D).

OBJECTIVE

The aim of this study was therefore to examine the potential effect of dietary NO₃ and NO₂ on the occurrence of T2D.

DESIGN

This longitudinal study was conducted within the framework of the Tehran Lipid and Glucose Study (TLGS) on 2139 T2D-free adults, aged 20-70 years, followed for a median of 5.8 y. Dietary intakes of NO₃ and NO₂ were estimated using a 168-food items validate semi-quantitative food frequency questionnaire, at baseline. Multivariate Hazard Ratios (HR) and 95% confidence intervals (CI), adjusted for diabetes risk score (DRS), and dietary intakes of fat, fiber and vitamin C, were calculated for residual energy-adjusted NO₃ and NO₂ intakes. Since significant interaction (P = 0.024) was found between NO₂ and vitamin C intakes in the multivariable model, stratified analyses were done for < and ≥ median vitamin C intakes.

RESULTS

Median (inter quartile range; IQR) daily intake of NO₃ and NO₂ were 410 mg/d (343-499) and 8.77 mg/d (7.53-10.2). An increased risk of T2D was observed among participants who had higher intake of total and animal-based NO₂ in participants who had low vitamin C intake (HR = 2.43, 95% CI = 1.45-4.05, HR = 1.88, 95% CI = 1.12-3.15, respectively). We found no significant association between NO₃ in overall, and plant- and animal sources as well, with the risk of T2D. Plant-derived NO₂ was also unrelated to incidence of T2D.

CONCLUSION

Our findings indicated that higher intakes of total and animal-based NO₂ may be an independent dietary risk factor for development of T2D in subjects with lower vitamin C intakes.

Dietary nitrate does not affect physical activity or outcomes in healthy older adults in a randomized, cross-over trial

Although dietary nitrate (NO₃^-) ingestion appears to enhance exercise capacity and performance in young individuals, inconclusive findings have been reported in older people. Therefore, we conducted a double-blind, crossover randomized clinical trial using beetroot juice in older healthy participants, who were classified as normal weight and overweight. We tested whether consumption of beetroot juice (a rich source of NO₃^-) for 1 week would increase nitric oxide bioavailability via the nonenzymatic pathway and enhance (1) exercise capacity during an incremental exercise test, (2) physical capability, and (3) free-living physical activity. Twenty nonsmoking, healthy participants between 60 and 75 years of age and with a body mass index of 20.0 to 29.9 kg/m² were included. Presupplementation and postsupplementation resting, submaximal, maximal, and recovery gas exchanges were measured. Physical capability was measured by hand-grip strength, time-up-and-go, repeated chair rising test, and 10-m walking speed. Free-living physical activity was assessed by triaxal accelerometry. Changes in urinary and plasmaNO₃^-concentrations were measured by gas chromatography-mass spectrometry. Nineteen participants (male-to-female ratio, 9:10) completed the study.Beetroot juice increased significantly both plasma and urinary NO₃^-concentrations (P<.001) when compared with placebo. Beetroot juice did not influence resting or submaximal and maximal oxygen consumption during the incremental exercise test. In addition, measures of physical capability and physical activity levels measured in free-living conditions were not modified by beetroot juice ingestion. The positive effects of beetroot juice ingestion on exercise performance seen in young individuals were not replicated in healthy, older adults. Whether aging represents a modifier of the effects of dietary NO₃^-on muscular performance is not known, and mechanistic studies and larger trials are needed to test this hypothesis.

Improved motor and cognitive performance with sodium nitrite supplementation is related to small metabolite signatures: a pilot trial in middle-aged and older adults

Advancing age is associated with reductions in nitric oxide bioavailability and changes in metabolic activity, which are implicated in declines in motor and cognitive function. In preclinical models, sodium nitrite supplementation (SN) increases plasma nitrite and improves motor function, whereas other nitric oxide-boosting agents improve cognitive function. This pilot study was designed to translate these findings to middle-aged and older (MA/O) humans to provide proof-of-concept support for larger trials. SN (10 weeks, 80 or 160 mg/day capsules, TheraVasc, Inc.) acutely and chronically increased plasma nitrite and improved performance on measures of motor and cognitive outcomes (all p<0.05 or better) in healthy MA/O adults (62 ± 7 years). Untargeted metabolomics analysis revealed that SN significantly altered 33 (160 mg/day) to 45 (80 mg/day) different metabolites, 13 of which were related to changes in functional outcomes; baseline concentrations of 99 different metabolites predicted functional improvements with SN. This pilot study provides the first evidence that SN improves aspects of motor and cognitive function in healthy MA/O adults, and that these improvements are associated with, and predicted by, the plasma metabolome. Our findings provide the necessary support for larger clinical trials on this promising pharmacological strategy for preserving physiological function with aging.