Performance benchmarking microplate-immunoassays for quantifying target-specific cysteine oxidation reveals their potential for understanding redox-regulation and oxidative stress.

The antibody-linked oxi-state assay (ALISA) for quantifying target-specific cysteine oxidation can benefit specialist and non-specialist users. Specialists can benefit from time-efficient analysis and high-throughput target and/or sample n-plex capacities. The simple and accessible "off-the-shelf" nature of ALISA brings the benefits of oxidative damage assays to non-specialists studying redox-regulation. Until performance benchmarking establishes confidence in the "unseen" microplate results, ALISA is unlikely to be widely adopted. Here, we implemented pre-set pass/fail criteria to benchmark ALISA by robustly evaluating immunoassay performance in diverse biological contexts. ELISA-mode ALISA assays were accurate, reliable, and sensitive. For example, the average inter-assay CV for detecting 20%- and 40%-oxidised PRDX2 or GAPDH standards was 4.6% (range: 3.6-7.4%). ALISA displayed target-specificity. Immunodepleting the target decreased the signal by ∼75%. Single-antibody formatted ALISA failed to quantify the matrix-facing alpha subunit of the mitochondrial ATP synthase. However, RedoxiFluor quantified the alpha subunit displaying exceptional performance in the single-antibody format. ALISA discovered that (1) monocyte-to-macrophage differentiation amplified PRDX2-specific cysteine oxidation in THP-1 cells and (2) exercise increased GAPDH-specific cysteine oxidation in human erythrocytes. The "unseen" microplate data were "seen-to-be-believed" via orthogonal visually displayed immunoassays like the dimer method. Finally, we established target (n = 3) and sample (n = 100) n-plex capacities in ∼4 h with 50-70 min hands-on time. Our work showcases the potential of ALISA to advance our understanding of redox-regulation and oxidative stress.

LC/MS-based discrimination between plasma and urine metabolomic changes following exposure to ultraviolet radiation by using data modelling.

INTRODUCTION: This study sought to compare between metabolomic changes of human urine and plasma to investigate which one can be used as best tool to identify metabolomic profiling and novel biomarkers associated to the potential effects of ultraviolet (UV) radiation. METHOD: A pilot study of metabolomic patterns of human plasma and urine samples from four adult healthy individuals at before (S1) and after (S2) exposure (UV) and non-exposure (UC) were carried out by using liquid chromatography-mass spectrometry (LC-MS). RESULTS: The best results which were obtained by normalizing the metabolites to their mean output underwent to principal components analysis (PCA) and Orthogonal Partial least squares-discriminant analysis (OPLS-DA) to separate pre-from post-of exposure and non-exposure of UV. This separation by data modeling was clear in urine samples unlike plasma samples. In addition to overview of the scores plots, the variance predicted-Q2 (Cum), variance explained-R2X (Cum) and p-value of the cross-validated ANOVA score of PCA and OPLS-DA models indicated to this clear separation. Q2 (Cum) and R2X (Cum) values of PCA model for urine samples were 0.908 and 0.982, respectively, and OPLS-DA model values were 1.0 and 0.914, respectively. While these values in plasma samples were Q2 = 0.429 and R2X = 0.660 for PCA model and Q2 = 0.983 and R2X = 0.944 for OPLS-DA model. LC-MS metabolomic analysis showed the changes in numerous metabolic pathways including: amino acid, lipids, peptides, xenobiotics biodegradation, carbohydrates, nucleotides, Co-factors and vitamins which may contribute to the evaluation of the effects associated with UV sunlight exposure. CONCLUSIONS: The results of pilot study indicate that pre and post-exposure UV metabolomics screening of urine samples may be the best tool than plasma samples and a potential approach to predict the metabolomic changes due to UV exposure. Additional future work may shed light on the application of available metabolomic approaches to explore potential predictive markers to determine the impacts of UV sunlight.

Reduced nitric oxide synthesis in winter: A potential contributing factor to increased cardiovascular risk.

BACKGROUND: Nitric oxide is a key signalling molecule that elicits a range of biological functions to maintain vascular homeostasis. A reduced availability of nitric oxide is implicated in the progression of cardiovascular diseases and increases the risk of pathogenic events. AIMS: To compare the concentration of nitric oxide metabolites in healthy adults between winter and summer months. DESIGN: An observational study of healthy adults (age 32 ± 9 years) living in central Scotland. METHODS: Thirty-four healthy adults (13 females) were monitored for 7 days in summer and winter to record sunlight exposure (ultraviolet-A (UV-A) radiation), diet, and physical activity. At the end of each phase, blood pressure was measured, and samples of blood and saliva collected. The samples were analysed to determine the concentrations of plasma and salivary nitrate and nitrite and serum 25-hydroxyvitamin D (25(OH)D). RESULTS: The participants maintained similar diets in each measurement phase but were exposed to more UV-A radiation (550%) and undertook more moderate-vigorous physical activity (23%) in the summer than in winter. Plasma nitrite (46%) and serum 25(OH)D (59%) were higher and blood pressure was lower in the summer compared to winter months. Plasma nitrite concentration was negatively associated with systolic, diastolic, and mean arterial blood pressure. CONCLUSIONS: Plasma nitrite, an established marker of nitric oxide synthesis, is higher in healthy adults during the summer than in winter. This may be mediated by a greater exposure to UV-A which stimulates the release of nitric oxide metabolites from skin stores. While it is possible that seasonal variation in nitric oxide availability may contribute to an increased blood pressure in the winter months, the overall impact on cardiovascular health remains to be determined.

Exercise decreases PP2A-specific reversible thiol oxidation in human erythrocytes: Implications for redox biomarkers.

New readily accessible systemic redox biomarkers are needed to understand the biological roles reactive oxygen species (ROS) play in humans because overtly flawed, technically fraught, and unspecific assays severely hamper translational progress. The antibody-linked oxi-state assay (ALISA) makes it possible to develop valid ROS-sensitive target-specific protein thiol redox state biomarkers in a readily accessible microplate format. Here, we used a maximal exercise bout to disrupt redox homeostasis in a physiologically meaningful way to determine whether the catalytic core of the serine/threonine protein phosphatase PP2A is a candidate systemic redox biomarker in human erythrocytes. We reasoned that: constitutive oxidative stress (e.g., haemoglobin autoxidation) would sensitise erythrocytes to disrupted ion homeostasis as manifested by increased oxidation of the ion regulatory phosphatase PP2A. Unexpectedly, an acute bout of maximal exercise lasting ~16 min decreased PP2A-specific reversible thiol oxidation (redox ratio, rest: 0.46; exercise: 0.33) without changing PP2A content (rest: 193 pg/ml; exercise: 191 pg/ml). The need for only 3-4 µl of sample to perform ALISA means PP2A-specific reversible thiol oxidation is a capillary-fingertip blood-compatible candidate redox biomarker. Consistent with biologically meaningful redox regulation, thiol reductant-inducible PP2A activity was significantly greater (+10%) at rest compared to exercise. We establish a route to developing new readily measurable protein thiol redox biomarkers for understanding the biological roles ROS play in humans.

Does Connected Health Technology Improve Health-Related Outcomes in Rural Cardiac Populations? Systematic Review Narrative Synthesis.

Individuals living in rural areas are more likely to experience cardiovascular diseases (CVD) and have increased barriers to regular physical activity in comparison to those in urban areas. This systematic review aimed to understand the types and effects of home-based connected health technologies, used by individuals living in rural areas with CVD. The inclusion criteria included technology deployed at the participant's home and could be an mHealth (smart device, fitness tracker or app) or telehealth intervention. Nine electronic databases were searched across the date range January 1990-June 2021. A total of 207 full texts were screened, of which five studies were included, consisting of 603 participants. Of the five studies, four used a telehealth intervention and one used a form of wearable technology. All interventions which used a form of telehealth found a reduction in overall healthcare utilisation, and one study found improvements in CVD risk factors. Acceptability of the technologies was mixed, in some studies barriers and challenges were cited. Based on the findings, there is great potential for implementing connected health technologies, but due to the low number of studies which met the inclusion criteria, further research is required within rural areas for those living with cardiovascular disease.

Accuracy of Wrist-Worn Photoplethysmography Devices at Measuring Heart Rate in the Laboratory and During Free-Living Activities.

This study compared heart rate (HR) measurements taken from two wrist-worn devices; the Empatica E4 and the Apple Watch Series 5, to that taken from a Polar H10 chest strap. Ten healthy adult volunteers took part in a laboratory validation study and performed a treadmill exercise protocol. A single-subject validity study was also conducted to evaluate the accuracy of continuous HR measurements obtained during free-living activities. The participant wore both wrist devices, as well as the Polar H10 for 12-hours, as she continued her habitual daily activities. The key findings of the laboratory study were that the Apple Watch was accurate at assessing HR compared to the Polar H10 with Mean Absolute Percentage Error (MAPE) values < 5% during treadmill exercise. The accuracy of the E4 however was generally poor with MAPE values > 15%. Findings from the single-subject validity study indicate that the Apple Watch produces accurate measurements of HR, whereas the E4 device overestimated HR, except for during the more strenuous activities undertaken where HR was underestimated.Clinical Relevance- The Apple Watch has acceptable accuracy in measuring HR during treadmill exercise and during free-living activities in healthy adult volunteers.

Venous occlusion during blood collection decreases plasma nitrite but not nitrate concentration in humans.

BACKGROUND: To maintain vascular tone and blood flow when tissue oxygenation is reduced, nitrite anions are reduced to nitric oxide (NO). From a practical perspective, it is unclear how the application of a tourniquet during blood collection might influence measurement of NO metabolites. Accordingly, this study evaluated the effect of venous occlusion on plasma nitrite and nitrate during venous blood collection. METHODS: Fifteen healthy participants completed two trials that were preceded by the ingestion of nitrate-rich beetroot juice (BRJ; total of ~8.4 mmol nitrate) or no supplementation (control). In both trials, blood was collected using a venepuncture needle while a tourniquet was applied to the upper arm and using an indwelling intravenous cannula, from the opposing arm. The venepuncture samples were collected at 35 s post occlusion. Changes in the oxygenation of forearm flexor muscles were assessed using near-infrared spectroscopy. Plasma nitrite and nitrate were analysed using gas-phase chemiluminescence. RESULTS: In the control trial, plasma nitrite was significantly elevated when collected via the cannula (179 ± 67 nM) compared to venepuncture (112 ± 51 nM, P = 0.03). The ingestion of BRJ increased plasma nitrite and values remained higher when sampled from the cannula (473 ± 164 nM) compared to venepuncture (387 ± 136 nM, P < 0.001). Plasma nitrate did not differ between collection methods in either trial (all P > 0.05). The delta changes in total-, deoxy-, and oxy-haemoglobin were all significantly greater during venepuncture sample compared to the cannula sample at the point of blood collection (all P < 0.05). CONCLUSIONS: Venous occlusion during venepuncture blood collection lowers plasma nitrite concentration, potentially due to localised changes in haemoglobin concentration and/or a suppression of endogenous NO synthesis. Accordingly, the method of blood collection to enable measurements of NO metabolites should be carefully considered and consistently reported by researchers.

Co-ingestion of Antioxidant Drinks With an Unhealthy Challenge Meal Fails to Prevent Post-prandial Endothelial Dysfunction: An Open-Label, Crossover Study in Older Overweight Volunteers.

Eating a high calorie meal is known to induce endothelial dysfunction and it is reported that consuming drinks rich in antioxidants may be protective against this. In this study we assessed the effects of three antioxidant drinks with considerable disparity in their antioxidant content on endothelial function. Seven apparently healthy overweight and older adults (BMI 25-35; mean age 57 ± 3 years; one male, six females) completed four trials in a randomized counterbalanced design. Water (control), orange juice, green tea, or red wine were consumed with a high calorie meal (>900 kcal). Endothelial function was measured by flow-mediated dilatation immediately before (fasted, baseline) and 2 h after the meal. Blood samples were also obtained for lipid and glucose analysis, plasma nitrite ( NO 2 - ) and oxidized low-density lipoprotein (ox-LDL). Participants returned after a minimum 3 days washout to complete the remaining arms of the study. The results found that the high calorie meal induced a substantial increase in triglycerides, but not cholesterol or glucose, at 2 h after meal ingestion. FMD was significantly reduced by ∼35% at this timepoint, but the effect was not attenuated by co-ingestion of any of the antioxidant drinks. Reduced FMD was mirrored by a reduction in NO 2 - , but ox-LDL was not increased at 2 h after the meal. None of the undertaken measures were influenced by the antioxidant drinks. We conclude that co-ingestion of none of our test antioxidant drinks protected against the substantial post-prandial endothelial dysfunction induced by an unhealthy meal challenge in our sample population at a 2 h timepoint.

Dietary nitrate supplementation alters the oral microbiome but does not improve the vascular responses to an acute nitrate dose.

Nitrate (NO3-) contained in food and beverages can transiently increase nitric oxide (NO) availability following a stepwise reduction to nitrite (NO2-) by commensal bacteria in the oral cavity. We tested the hypothesis that regular ingestion of dietary NO3- would influence the oral microbiome, the capacity to reduce NO3- to NO2- in saliva, and the vascular responses to an acute dose of NO3-. The abundance of bacterial species on the tongue, the availability of NO markers, and vascular function were assessed in 11 healthy males before and after 7 days of supplementation with NO3--rich beetroot juice and a NO3--depleted placebo. As expected, saliva and plasma NO2- and NO3- were significantly elevated after NO3- supplementation (all P < 0.05) but not placebo. We found that NO3- supplementation increased salivary pH (7.13 ±â€¯0.54 to 7.39 ±â€¯0.68, P = 0.043) and altered the abundance of some bacteria previously implicated in NO3- reduction: Neisseria (from 2% ±â€¯3%-9% ±â€¯5%, P < 0.001), Prevotella (from 34% ±â€¯17%-23% ±â€¯11%, P = 0.001) and Actinomyces (from 1% ±â€¯1%-0.5% ±â€¯0.4%). Despite these alterations to the oral microbiota, an acute dose of NO3- increased salivary and plasma NO2-, reduced systolic blood pressure and increased the response to flow mediated dilation to a similar extent before and after 7 days of supplementation (P > 0.05). Our study establishes that supplementing the diet with NO3- for a sustained period can alter the oral environment in favour of health but does not impact the response to an acute NO3- dose. Acute ingestion of NO3- results in transient improvements in vascular function but the dietary induced adaptations to the oral bacteria did not enhance these effects.

Lower limb ischemic preconditioning combined with dietary nitrate supplementation does not influence time-trial performance in well-trained cyclists.

OBJECTIVES: Dietary nitrate (NO3-) supplementation and ischaemic preconditioning (IPC) can independently improve exercise performance. The purpose of this study was to explore whether NO3- supplementation, ingested prior to an IPC protocol, could synergistically enhance parameters of exercise. DESIGN: Double-blind randomized crossover trial. METHODS: Ten competitive male cyclists (age 34±6years, body mass 78.9±4.9kg, V⋅O2peak 55±4 mLkgmin-1) completed an incremental exercise test followed by three cycling trials comprising a square-wave submaximal component and a 16.1km time-trial. Oxygen uptake (V⋅O2) and muscle oxygenation kinetics were measured throughout. The baseline (BASE) trial was conducted without any dietary intervention or IPC. In the remaining two trials, participants received 3×5min bouts of lower limb bilateral IPC prior to exercise. Participants ingested NO3--rich gel (NIT+IPC) 90min prior to testing in one trial and a low NO3- placebo in the other (PLA+IPC). Plasma NO3- and nitrite (NO2-) were measured immediately before and after application of IPC. RESULTS: Plasma [NO3-] and [NO2-] were higher before and after IPC in NIT+IPC compared to BASE (P<0.001) but did not differ between BASE and PLA+IPC. There were no differences in V⋅O2 kinetics or muscle oxygenation parameters between trials (all P>0.4). Performance in the time-trial was similar between trials (BASE 1343±72s, PLA+IPC 1350±75s, NIT+IPC 1346±83s, P=0.98). CONCLUSIONS: Pre-exercise IPC did not improve sub-maximal exercise or performance measures, either alone or in combination with dietary NO3- supplementation.

An acute dose of inorganic dietary nitrate does not improve high-intensity, intermittent exercise performance in temperate or hot and humid conditions.

PURPOSE: Dietary nitrate (NO3-) has repeatedly been shown to improve endurance and intermittent, high-intensity events in temperate conditions. However, the ergogenic effects of dietary NO3- on intermittent exercise performance in hot conditions have yet to be investigated. METHODS: In a randomised, counterbalanced, double-blind crossover study, 12 recreationally trained males ingested a nitrate-rich beetroot juice shot (BRJ) (6.2 mmol NO3-) or a nitrate-depleted placebo (PLA) (< 0.004 mmol NO3-) 3 h prior to an intermittent sprint test (IST) in temperate (22 °C, 35% RH) and hot conditions (30 °C, 70% RH). The cycle ergometer IST consisted of twenty maximal 6 s sprints interspersed by 114 s of active recovery. Work done, power output, heart rate and RPE were measured throughout; tympanic temperature was measured prior to and upon completion. RESULTS: There were no significant effects of supplement on sprint performance in either temperate or hot, humid conditions (p > 0.05). There was a reduced peak (BRJ: 659 ± 100W vs. PLA: 693 ± 139W; p = 0.056) and mean power (BRJ: 543 ± 29W vs. PLA: 575 ± 38W; p = 0.081) following BRJ compared to PLA in the hot and humid condition, but this was not statistically significant. There was no effect of supplement on total work done irrespective of environmental condition. However, ~ 75% of participants experienced performance decreases following BRJ in the hot and humid environment. No differences were observed between trials for tympanic temperature measured at the conclusion of the exercise trial. CONCLUSION: In conclusion, an acute dose of inorganic dietary NO3- does not improve repeated-sprint performance in either temperate, or hot and humid conditions.

Variability in nitrate-reducing oral bacteria and nitric oxide metabolites in biological fluids following dietary nitrate administration: An assessment of the critical difference.

There is conflicting evidence on whether dietary nitrate supplementation can improve exercise performance. This may arise from the complex nature of nitric oxide (NO) metabolism which causes substantial inter-individual variability, within-person biological variation (CVB), and analytical imprecision (CVA) in experimental endpoints. However, no study has quantified the CVA and CVB of NO metabolites or the factors that influence their production. These data are important to calculate the critical difference (CD), defined as the smallest difference between sequential measurements required to signify a true change. The main aim of the study was to evaluate the CVB, CVA, and CD for markers of NO availability (nitrate and nitrite) in plasma and saliva before and after the ingestion of nitrate-rich beetroot juice (BR). We also assessed the CVB of nitrate-reducing bacteria from the dorsal surface of the tongue. It was hypothesised that there would be substantial CVB in markers of NO availability and the abundance of nitrate-reducing bacteria. Ten healthy male participants (age 25 ±â€¯5 years) completed three identical trials at least 6 days apart. Blood and saliva were collected before and after (2, 2.5 and 3 h) ingestion of 140 ml of BR (∼12.4 mmol nitrate) and analysed for [nitrate] and [nitrite]. The tongue was scraped and the abundance of nitrate-reducing bacterial species were analysed using 16S rRNA next generation sequencing. There was substantial CVB for baseline concentrations of plasma (nitrate 11.9%, nitrite 9.0%) and salivary (nitrate 15.3%, nitrite 32.5%) NO markers. Following BR ingestion, the CVB for nitrate (plasma 3.8%, saliva 12.0%) and salivary nitrite (24.5%) were lower than baseline, but higher for plasma nitrite (18.6%). The CD thresholds that need to be exceeded to ensure a meaningful change from baseline are 25, 19, 37, and 87% for plasma nitrate, plasma nitrite, salivary nitrate, and salivary nitrite, respectively. The CVB for selected nitrate-reducing bacteria detected were: Prevotella melaninogenica (37%), Veillonella dispar (35%), Haemophilus parainfluenzae (79%), Neisseria subflava (70%), Veillonella parvula (43%), Rothia mucilaginosa (60%), and Rothia dentocariosa (132%). There is profound CVB in the abundance of nitrate-reducing bacteria on the tongue and the concentration of NO markers in human saliva and plasma. Where these parameters are of interest following experimental intervention, the CD values presented in this study will allow researchers to interpret the meaningfulness of the magnitude of the change from baseline.

Salivary nitrite production is elevated in individuals with a higher abundance of oral nitrate-reducing bacteria.

Nitric oxide (NO) can be generated endogenously via NO synthases or via the diet following the action of symbiotic nitrate-reducing bacteria in the oral cavity. Given the important role of NO in smooth muscle control there is an intriguing suggestion that cardiovascular homeostasis may be intertwined with the presence of these bacteria. Here, we measured the abundance of nitrate-reducing bacteria in the oral cavity of 25 healthy humans using 16S rRNA sequencing and observed, for 3.5 h, the physiological responses to dietary nitrate ingestion via measurement of blood pressure, and salivary and plasma NO metabolites. We identified 7 species of bacteria previously known to contribute to nitrate-reduction, the most prevalent of which were Prevotella melaninogenica and Veillonella dispar. Following dietary nitrate supplementation, blood pressure was reduced and salivary and plasma nitrate and nitrite increased substantially. We found that the abundance of nitrate-reducing bacteria was associated with the generation of salivary nitrite but not with any other measured variable. To examine the impact of bacterial abundance on pharmacokinetics we also categorised our participants into two groups; those with a higher abundance of nitrate reducing bacteria (> 50%), and those with a lower abundance (< 50%). Salivary nitrite production was lower in participants with lower abundance of bacteria and these individuals also exhibited slower salivary nitrite pharmacokinetics. We therefore show that the rate of nitrate to nitrite reduction in the oral cavity is associated with the abundance of nitrate-reducing bacteria. Nevertheless, higher abundance of these bacteria did not result in an exaggerated plasma nitrite response, the best known marker of NO bioavailability. These data from healthy young adults suggest that the abundance of oral nitrate-reducing bacteria does not influence the generation of NO through the diet, at least when the host has a functional minimum threshold of these microorganisms.

The effects of two different doses of ultraviolet-A light exposure on nitric oxide metabolites and cardiorespiratory outcomes.

PURPOSE: The present study investigated different doses of ultraviolet-A (UV-A) light on plasma nitric oxide metabolites and cardiorespiratory variables. METHODS: Ten healthy male participants completed three experimental conditions, 7 days apart. Participants were exposed to no light (CON); 10 J cm2 (15 min) of UV-A light (UVA10) and 20 J cm2 (30 min) of UV-A light (UVA20) in a randomized order. Plasma nitrite [NO2-] and nitrate [NO3-] concentrations, blood pressure (BP), and heart rate (HR) were recorded before, immediately after exposure and 30 min post-exposure. Whole body oxygen utilization ([Formula: see text]), resting metabolic rate (RMR) and skin temperature were recorded continuously. RESULTS: None of the measured parameters changed significantly during CON (all P > 0.05). [Formula: see text] and RMR were significantly reduced immediately after UVA10 (P < 0.05) despite no change in plasma [NO2-] (P > 0.05). Immediately after exposure to UVA20, plasma [NO2-] was higher (P = 0.014) and [Formula: see text] and RMR tended to be lower compared to baseline (P = 0.06). There were no differences in [NO2-] or [Formula: see text] at the 30 min time point in any condition. UV-A exposure did not alter systolic BP, diastolic BP or MAP (all P > 0.05). UV-A light did not alter plasma [NO3-] at any time point (all P > 0.05). CONCLUSIONS: This study demonstrates that a UV-A dose of 20 J cm2 is necessary to increase plasma [NO2-] although a smaller dose is capable of reducing [Formula: see text] and RMR at rest. Exposure to UV-A did not significantly reduce BP in this cohort of healthy adults. These data suggest that exposure to sunlight has a meaningful acute impact on metabolic function.

Changes in body posture alter plasma nitrite but not nitrate concentration in humans.

PURPOSE: This study evaluated the change (Δ) in plasma volume (PV), nitrate [NO3-], and nitrite [NO2-] concentration following changes in posture in the presence and absence of elevated plasma [NO3-] and [NO2-] METHODS: Fourteen healthy participants completed two trials that were preceded by either supplementation with NO3--rich beetroot juice (BR; total of ∼31 mmol NO3-) or no supplementation (CON). Both trials comprised 30 min of lying supine followed by 2 min of standing, 2 min of sitting and 5 min of sub-maximal cycling. Measurements of plasma [NO3-] and [NO2-] were made by gas-phase chemiluminescence and ΔPV was estimated using the Dill and Costill method. RESULTS: Plasma [NO2-] decreased from baseline (CON: 120 ± 49 nM, BR: 357 ± 129 nM) after lying supine for 30 min (CON 77 ± 30 nM; BR 231 ± 92 nM, both P < 0.01) before increasing during standing (CON 109 ± 42 nM; BR 297 ± 105 nM, both P < 0.01) and sitting (CON 131 ± 43 nM; BR 385 ± 125 nM, both P < 0.01). Plasma [NO2-] remained elevated following exercise only in CON (125 ± 61 nM P = 0.02). Plasma [NO3-] was not different between measurement points in either condition (P > 0.05). PV increased from baseline during the supine phase before decreasing upon standing, sitting, and exercise in both trials (all P<0.05). CONCLUSIONS: Changing body posture causes rapid and consistent alterations in plasma [NO2-]. Researchers should therefore carefully consider the effect of posture when measuring this variable.

An examination of objectively-measured sedentary behavior and mental well-being in adults across week days and weekends.

BACKGROUND: Limited research has explored the links between sedentary behaviour, mental health and quality of life. This study examines objectively measured sedentary behaviour and perceived mental health and quality of life across week days and weekends. METHODS: 42 adults (19M, 23F; mean age 38yrs (range 18-67) & BMI 24.8kg/m2 (range 18.7-33.8) wore an activPAL monitor 24h/day for one week and completed the Hospital Anxiety and Depression Scale (HADS) and SF12 Health Survey. Average weekday and weekend day sitting time was computed. Differences between sitting (Group 1 = <8hrs/day, Group 2 = 8-10 hrs/day, Group 3 = >10hrs/day) and components of the HADS and SF12 health survey were examined using an ANCOVA with a measure of physical activity (step count) included as a covariate. RESULTS: Average sitting time on a weekday was 9hrs 29mins (range 5hrs 52mins to 12hrs 55mins) and 8hrs 59mins (range 4hrs, 07mins to 14hrs, 40mins) on a weekend day. There was a main effect (p<0.05) for weekday sitting time on total anxiety and depression (HADS) and mental health and vitality (SF12). Planned contrasts identified individuals in group 1 had lower anxiety and depression and higher mental health and vitality scores than individuals in groups 2 or 3 (p<0.05). No difference was found between individuals in group 2 and group 3 (p>0.05). No main effects were found for weekend sitting (p>0.05). CONCLUSIONS: Weekday sitting time below 8 hours/day is associated with better perceived mental health and quality of life.

Beetroot juice versus chard gel: A pharmacokinetic and pharmacodynamic comparison of nitrate bioavailability.

Dietary supplementation with inorganic nitrate (NO3-) has been shown to induce a multitude of advantageous cardiovascular and metabolic responses during rest and exercise. While there is some suggestion that pharmacokinetics may differ depending on the NO3- source ingested, to the best of our knowledge this has yet to be determined experimentally. Here, we compare the plasma pharmacokinetics of NO3-, nitrite (NO2-), and total nitroso species (RXNO) following oral ingestion of either NO3- rich beetroot juice (BR) or chard gels (GEL) with the associated changes in blood pressure (BP). Repeated samples of venous blood and measurements of BP were collected from nine healthy human volunteers before and after ingestion of the supplements using a cross-over design. Plasma concentrations of RXNO and NO2- were quantified using reductive gas-phase chemiluminescence and NO3- using high pressure liquid ion chromatography. We report that, [NO3-] and [NO2-] were increased and systolic BP reduced to a similar extent in each experimental arm, with considerable inter-individual variation. Intriguingly, there was a greater increase in [RXNO] following ingestion of BR in comparison to GEL, which may be a consequence of its higher polyphenol content. In conclusion, our data suggests that while differences in circulating NO2- and NO3- concentrations after oral administration of distinct NO3--rich supplementation sources are moderate, concentrations of metabolic by-products may show greater-than-expected variability; the significance of the latter observation for the biological effects under study remains to be investigated.

The effects of dietary nitrate supplementation on the adaptations to sprint interval training in previously untrained males.

OBJECTIVES: Dietary nitrate can improve repeated high-intensity and supramaximal exercise performance, although the effect on adaptations to training has received limited attention. The purpose of this study was to investigate the effects of dietary nitrate on the response to 3-weeks of sprint interval training (SIT). DESIGN: Randomized control trial. METHODS: Twenty-seven untrained males (Age: 28±7 y, V⋅O2Max: 42±7mlkg-1min-1) completed an incremental exercise test at the beginning and end of the study. Participants were matched for V⋅O2Max and randomly assigned to a control group (CON; n=8), SIT+placebo group (PLA; n=10), or SIT+nitrate group (NIT; n=9). The SIT comprised 4-6 repeated 15 s all out sprints on a cycle ergometer, interspersed with 4min active recovery, 3-times per week. Approximately 2.5h prior to exercise, participants consumed gels containing ∼0.1mmol (PLA) or ∼8mmol nitrate (NIT). RESULTS: Following SIT, V⋅O2Max (PLA: 5%, p=0.057, d=0.34; NIT: 6.3%, p=0.041, d=0.34) and ventilatory threshold (VT) increased to a similar extent in both SIT groups. Maximum work rate tended to increase to a greater extent in NIT (8.7%, d=0.55) compared to PLA (4.7%, d=0.31, p=0.073). Fatigue index, calculated by the change in mean power from the first to the last sprint, tended to be reduced following SIT in NIT compared to PLA (PLA: 7.3±7.4%, NIT: 0.5±7.1%, p=0.058). CONCLUSIONS: While dietary nitrate supplementation does not augment improvements to V⋅O2Max and VT following SIT, it may improve WRmax and indices of repeated high-intensity exercise.

Objectively Measured Sedentary Time in Children and Their Parents.

BACKGROUND: No studies have examined associations in objectively measured sedentary time between parents and young people using activPAL posture sensors, which provide a more accurate estimate of sedentary time compared to accelerometer-based devices. This study examines patterns and associations of activPAL measured sedentary time and number of sedentary breaks on weekdays and weekend days in preschool (2-4 yrs), primary (5-11 yrs) and secondary school aged children (12-17 yrs) and their parents. METHODS: 51 parents (16 M, 35 F; mean age 39 (+/-8) yrs) and 51 children (28 M, 23 F; mean age 9 (+/-5) yrs) wore an activPAL monitor for 7 days to measure time spent sedentary and number of breaks in sedentary time. Data was assessed by Pearson's correlations and t-tests. RESULTS: Secondary school children spent a greater percentage of their day sedentary (64.5 (+/-8.5) %) than preschool (57.4 (+/-7.3) %) and primary school children (57.2 (+/-5) %). For the secondary school parent dyad, there were no significant positive associations for time sedentary (r = -0.167, p = 0.494) and percentage of day sedentary (r = -0.247, p = 0.308). For the primary school parent dyad, there were medium, but non-significant positive correlations for time sedentary (r = 0.38, p = 0.146) and percentage of day sedentary (r = 0.363, p = 0.167). For the preschool parent dyad, there were medium-large positive correlations for percentage of waking day sedentary at weekends (r = 0.479, p = 0.083) and number of sedentary breaks (r = 0.648, p = 0.012) at weekends. CONCLUSIONS: There were positive associations in sedentary time between primary school children and their parents, and between preschool children and their parents at the weekend. Thus, interventions aimed at reducing sedentary time of parents and children together, particularly at the weekend for young children, may be effective in these age groups. Secondary school children were more sedentary and had fewer sedentary breaks than younger children, thus interventions should promote breaks in sedentary time as well as reducing total sedentary time in this age group.