Interest in inorganic nitrate and nitrite has grown substantially over the past decade as research has revealed the role of these anions in enhancing nitric oxide (NO) availability through an oral ...pathway. Nitrite synthesis in the mouth seems to be an important mechanism to feed the circulatory system with this anion. This is interesting since greater plasma nitrite concentration has been associated with better fitness levels in humans, but this question has not been investigated in relation to salivary nitrite concentration. Additionally, no previous study has investigated the oral nitrate-reducing capacity in regards to peak oxygen uptake (VO2peak) or peak power output (Wpeak) in humans. Thus, the main goal of this study was to investigate whether salivary nitrite and nitrate concentration and the oral nitrate-reducing capacity were associated with VO2peak and Wpeak in healthy humans.
Fifty individuals (22 females and 28 males; 38.8 ± 14.3 years/old; BMI = 22.8 ± 3.9) performed a graded exercise test on a cycle ergometer to assess their VO2peak and Wpeak. Unstimulated salivary samples were taken before and 20 min after exercise to measure nitrate/nitrite, pH and lactate. The oral nitrate-reducing capacity was also assessed in 25 subjects before and after exercise.
Oral nitrate-reducing capacity was positively associated with Wpeak (rs = 0.64; P = 0.001) and the VO2peak (rs = 0.54; P = 0.005). Similar correlations were found when these variables were analysed after exercise. In addition, a significant decrease in salivary pH (pre: 7.28 ± 0.361; post-exercise: 7.16 ± 0.33; P = 0.003) accompanied by an increase of salivary lactate (pre: 0.17 ± 0.14 mmol/L; post-exercise: 0.48 ± 0.38; P < 0.001) was found after exercise. However, these changes did not have any impact on salivary nitrate/nitrite concentration and the oral nitrate-reducing capacity after exercise.
In conclusion, this is the first evidence showing a link between the oral nitrate-reducing capacity and markers of aerobic fitness levels in healthy humans.
Aim
The aim of this study was to investigate the effects of 4 consecutive simulated night shifts on glucose homeostasis, mitochondrial function and central and peripheral rhythmicities compared with ...a simulated day shift schedule.
Methods
Seventeen healthy adults (8M:9F) matched for sleep, physical activity and dietary/fat intake participated in this study (night shift work n = 9; day shift work n = 8). Glucose tolerance and insulin sensitivity before and after 4 nights of shift work were measured by an intravenous glucose tolerance test and a hyperinsulinaemic euglycaemic clamp respectively. Muscles biopsies were obtained to determine insulin signalling and mitochondrial function. Central and peripheral rhythmicities were assessed by measuring salivary melatonin and expression of circadian genes from hair samples respectively.
Results
Fasting plasma glucose increased (4.4 ± 0.1 vs. 4.6 ± 0.1 mmol L−1; P = .001) and insulin sensitivity decreased (25 ± 7%, P < .05) following the night shift, with no changes following the day shift. Night shift work had no effect on skeletal muscle protein expression (PGC1α, UCP3, TFAM and mitochondria Complex II‐V) or insulin‐stimulated pAkt Ser473, pTBC1D4Ser318 and pTBC1D4Thr642. Importantly, the metabolic changes after simulated night shifts occurred despite no changes in the timing of melatonin rhythmicity or hair follicle cell clock gene expression across the wake period (Per3, Per1, Nr1d1 and Nr1d2).
Conclusion
Only 4 days of simulated night shift work in healthy adults is sufficient to reduce insulin sensitivity which would be expected to increase the risk of T2D.
Post-exercise hypotension (PEH) is a common physiological phenomenon leading to lower blood pressure after acute exercise, but it is not fully understood how this intriguing response occurs. This ...study investigated whether the nitrate-reducing activity of oral bacteria is a key mechanism to trigger PEH. Following a randomized, double blind and crossover design, twenty-three healthy individuals (15 males/8 females) completed two treadmill trials at moderate intensity. After exercise, participants rinsed their mouth with antibacterial mouthwash to inhibit the activity of oral bacteria or a placebo mouthwash. Blood pressure was measured before, 1h and 2 h after exercise. The microvascular response to a reactive hyperaemia test, as well as blood and salivary samples were taken before and 2 h after exercise to analyse nitrate and nitrite concentrations and the oral microbiome. As expected, systolic blood pressure (SBP) was lower (1 h: -5.2 ± 1.0 mmHg; P < 0.001); 2 h: -3.8 ± 1.1 mmHg, P = 0.005) after exercise compared to baseline in the placebo condition. This was accompanied by an increase of circulatory nitrite 2 h after exercise (2h: 100 ± 13 nM) compared to baseline (59 ± 9 nM; P = 0.013). Additionally, an increase in the peak of the tissue oxygenation index (TOI) during the reactive hyperaemia response was observed after exercise (86.1 ± 0.6%) compared to baseline levels (84.8 ± 0.5%; P = 0.010) in the placebo condition. On the other hand, the SBP-lowering effect of exercise was attenuated by 61% at 1 h in the recovery period, and it was fully attenuated 2 h after exercise with antibacterial mouthwash. This was associated with a lack of changes in circulatory nitrite (P > 0.05), and impaired microvascular response (peak TOI baseline: 85.1 ± 3.1%; peak TOI post-exercise: 84.6 ± 3.2%; P > 0.05). Diversity of oral bacteria did not change after exercise in any treatment. These findings show that nitrite synthesis by oral commensal bacteria is a key mechanism to induce the vascular response to exercise over the first period of recovery thereby promoting lower blood pressure and greater muscle oxygenation.
Display omitted
Nitric oxide (NO) has led a revolution in physiology and pharmacology research during the last two decades. This labile molecule plays an important role in many functions in the body regulating ...vasodilatation, blood flow, mitochondrial respiration and platelet function. Currently, it is known that NO synthesis occurs via at least two physiological pathways: NO synthase (NOS) dependent and NOS independent. In the former, L-arginine is the main precursor. It is widely recognized that this amino acid is oxidized to NO by the action of the NOS enzymes. Additionally, L-citrulline has been indicated to be a secondary NO donor in the NOS-dependent pathway, since it can be converted to L-arginine. Nitrate and nitrite are the main substrates to produce NO via the NOS-independent pathway. These anions can be reduced in vivo to NO and other bioactive nitrogen oxides. Other molecules, such as the dietary supplement glycine propionyl-L-carnitine (GPLC), have also been suggested to increase levels of NO, although the physiological mechanisms remain to be elucidated. The interest in all these molecules has increased in many fields of research. In relation with exercise physiology, it has been suggested that an increase in NO production may enhance oxygen and nutrient delivery to active muscles, thus improving tolerance to physical exercise and recovery mechanisms. Several studies using NO donors have assessed this hypothesis in a healthy, trained population. However, the conclusions from these studies showed several discrepancies. While some reported that dietary supplementation with NO donors induced benefits in exercise performance, others did not find any positive effect. In this regard, training status of the subjects seems to be an important factor linked to the ergogenic effect of NO supplementation. Studies involving untrained or moderately trained healthy subjects showed that NO donors could improve tolerance to aerobic and anaerobic exercise. However, when highly trained subjects were supplemented, no positive effect on performance was indicated. In addition, all this evidence is mainly based on a young male population. Further research in elderly and female subjects is needed to determine whether NO supplements can induce benefit in exercise capacity when the NO metabolism is impaired by age and/or estrogen status.
To assess the level of agreement between the anthropometrical method and several bioimpedance (BIA) devices to estimate the fat mass in a group of physically active young people.
55 students of ...Physical Activity Sciences and Sports of the INEFC of Barcelona; 29 men (age: 24.7 +/- 4.7 years; BMI: 23.4 +/- 1.8) and 26 women (age: 22.9 +/- 3.5; BMI: 21.5 +/- 1.9). All of them voluntarily gave their informed consent.
Anthropometrical assessment was done according to the International Society for the Advancement Kinanthropometry (ISAK) protocol, the fat % was calculated by the Siri's equation and was compared with that obtained by 4 different BIA devices: Biospace Inbody 720, Tanita BC400, Tanita TBF-521, and Omron BF-300. To assess the level of agreement of the results, the interclass correlation coefficient and the Bland Aldman method were used.
The estimated fat mass, in men, by the anthropometrical method was 7 +/- 2.2 kg. The results by the BIA systems were: 7.4 +/- 3 kg; 5.6 +/- 2.2 kg; 5.7 +/- 2.5 kg, and 7.4 +/- 3 kg for Biospace Inbody 720, Tanita BC400, Tanita TBF521, and Omron BF300, respectively. In women, the results were 10.4 +/- 2.7 kg of fat mass by means of the anthropometrical method and 10.3 +/- 2.9 kg, 11 +/- 3.3 kg, 11.5 +/- 3.0 kg, and 10 +/- 2.9 kg for Biospace Inbody 720, Tanita BC400, Tanita TBF521, and Omron BF300, respectively.
In the male group, the level of agreement between anthropometrics and BIA devices was moderate-poor, whereas in women there was a good correlation between both techniques for estimating the body fat when the Biospace Inbody 720 and Tanita BC400 devices were used.
Associations of the second-to-fourth digit ratio (2D:4D), a putative marker for prenatal androgen action, and of absolute finger length, a putative marker for pubertal-adolescent androgen action, ...with sport performance were examined in a multinational sample of 87 world-class women épée fencers. Lower (masculinized) digit ratios correlated, although not significantly so, with better current and highest past world rankings. These correlations were significant for right-hand 2D:4D with controls for the most salient factors for 2D:4D (ethnicity) and world rankings (years of international experience, height, and weight). Longer (masculinized) fingers correlated strongly with better current and highest past world rankings; these correlations became insignificant with the same controls. Replicating previous evidence for fencers, left-handedness was much more prevalent in this sample (21%) than in the female general population, and left-handers had somewhat, but not significantly so, lower 2D:4D as well as better world rankings than right-handers. These findings extend related evidence suggestive of prenatal programming of aptitude across a variety of sports, especially running and soccer. Some known extragenital effects of prenatal testosterone that contribute to the development of efficient cardiovascular systems, good visuospatial abilities, physical endurance and speed, and to the propensity for rough-and-tumble play, apparently promote sporting success in adult life.
This paper presents a new family of indices for the frequency domain analysis of heart rate variability time series that do not need any frequency band definition. After proper detrending of the time ...series, a cumulated power spectrum is obtained and frequencies that contain a certain percentage of the power below them are identified, so median frequency, bandwidth and a measure of the power spectrum asymmetry are proposed to complement or improve the classical spectral indices as the ratio of the powers of LF and HF bands (LF/HF). In normal conditions the median frequency provides similar information as the classical indices, while the bandwidth and asymmetry can be complementary measures of the physiological state of the tested subject. The proposed indices seem to be a good choice for tracking changes in the power spectrum in exercise stress, and they can guide in the determination of frequency band limits in other animal species.
PDF
