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Redox Biology Apr 2021In this paper, we describe an assay to analyze simultaneously the oxygen consumption rate (OCR) and superoxide production in a biological system. The analytical set-up...
In this paper, we describe an assay to analyze simultaneously the oxygen consumption rate (OCR) and superoxide production in a biological system. The analytical set-up uses electron paramagnetic resonance (EPR) spectroscopy with two different isotopically-labelled sensors: N-PDT (4-oxo-2,2,6,6-tetramethylpiperidine-d-N-1-oxyl) as oxygen-sensing probe and N-CMH (1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine, a cyclic hydroxylamine, as sensor of reactive oxygen species (ROS). The superoxide contribution to CMH oxidation is assessed using SOD or PEGSOD as controls. Because the EPR spectra are not superimposable, the variation of EPR linewidth of N-PDT (linked to OCR) and the formation of the nitroxide from N-CMH (linked to superoxide production) can be recorded simultaneously over time on a single preparation. The EPR toolbox was qualified in biological systems of increasing complexity. First, we used an enzymatic assay based on the hypoxanthine (HX)/xanthine oxidase (XO) which is a well described model of oxygen consumption and superoxide production. Second, we used a cellular model of superoxide production using macrophages exposed to phorbol 12-myristate 13-acetate (PMA) which stimulates the NADPH oxidase (NOX) to consume oxygen and produce superoxide. Finally, we exposed isolated mitochondria to established inhibitors of the electron transport chain (rotenone and metformin) in order to assess their impact on OCR and superoxide production. This EPR toolbox has the potential to screen the effect of intoxicants or drugs targeting the mitochondrial function.
Topics: Electron Spin Resonance Spectroscopy; Oxidation-Reduction; Oxygen Consumption; Reactive Oxygen Species; Superoxides
PubMed: 33418140
DOI: 10.1016/j.redox.2020.101852 -
Arquivos Brasileiros de Cardiologia Feb 2023Post-COVID-19 exercise intolerance is poorly understood. Cardiopulmonary exercise testing (CPET) can identify the underlying exercise limitations.
BACKGROUND
Post-COVID-19 exercise intolerance is poorly understood. Cardiopulmonary exercise testing (CPET) can identify the underlying exercise limitations.
OBJECTIVES
To evaluate the source and magnitude of exercise intolerance in post-COVID-19 subjects.
METHODS
Cohort study assessing subjects with different COVID-19 illness severities and a control group selected by propensity score matching. In a selected sample with CPET prior to viral infection, before and after comparisons were performed. Level of significance was 5% in the entire analysis.
RESULTS
One hundred forty-four subjects with COVID-19 were assessed (median age: 43.0 years, 57% male), with different illness severities (60% mild, 21% moderate, 19% severe). CPET was performed 11.5 (7.0, 21.2) weeks after disease onset, with exercise limitations being attributed to the peripheral muscle (92%), and the pulmonary (6%), and cardiovascular (2%) systems. Lower median percent-predicted peak oxygen uptake was observed in the severe subgroup (72.2%) as compared to the controls (91.6%). Oxygen uptake differed among illness severities and controls at peak and ventilatory thresholds. Conversely, ventilatory equivalents, oxygen uptake efficiency slope, and peak oxygen pulse were similar. Subgroup analysis of 42 subjects with prior CPET revealed significant reduction in only peak treadmill speed in the mild subgroup and in oxygen uptake at peak and ventilatory thresholds in the moderate/severe subgroup. By contrast, ventilatory equivalents, oxygen uptake efficiency slope, and peak oxygen pulse did not change significantly.
CONCLUSIONS
Peripheral muscle fatigue was the most common exercise limitation etiology in post-COVID-19 patients regardless of the illness severity. Data suggest that treatment should emphasize comprehensive rehabilitation programs, including aerobic and muscle strengthening components.
Topics: Humans; Male; Adult; Female; Exercise Test; Cohort Studies; COVID-19; Oxygen Consumption; Oxygen; Exercise Tolerance
PubMed: 36888777
DOI: 10.36660/abc.20220150 -
International Journal of Environmental... Nov 2022A decrease in physical activity levels among university students during the COVID-19 pandemic is well-documented in the literature. However, the effect of lockdown...
BACKGROUND
A decrease in physical activity levels among university students during the COVID-19 pandemic is well-documented in the literature. However, the effect of lockdown restrictions on cardiovascular fitness has not been thoroughly investigated.
METHODS
The aim of the study was to assess the possible changes in cardiovascular fitness among university students during a 14-week period of the COVID-19 pandemic. Thirteen female and seven male tourism and recreation students participated in the study. Examinations were conducted in November 2020 and in February/March 2021. Students performed the PWC170 test on a cycling ergometer. Maximal oxygen consumption was calculated based on the PWC170 test results. Blood pressure and heart rate were measured at rest, as well as in the 1st and 5th minute of post-exercise recovery.
RESULTS
No substantial changes were observed in maximal oxygen consumption level when comparing autumn and winter indices. Male students presented elevated blood pressure whereas female students presented normal blood pressure. Heart-rate and blood-pressure indices did not show substantial alternations in examined students during analyzed period.
CONCLUSIONS
Fourteen weeks of lockdown had little effect on the cardiovascular health of tourism and recreation students.
Topics: Humans; Male; Female; Pandemics; COVID-19; Communicable Disease Control; Oxygen Consumption; Exercise
PubMed: 36497556
DOI: 10.3390/ijerph192315483 -
Journal of Neurochemistry Jul 2016Aerobic glycolysis occurs during brain activation and is characterized by preferential up-regulation of glucose utilization compared with oxygen consumption even though... (Review)
Review
Aerobic glycolysis occurs during brain activation and is characterized by preferential up-regulation of glucose utilization compared with oxygen consumption even though oxygen level and delivery are adequate. Aerobic glycolysis is a widespread phenomenon that underlies energetics of diverse brain activities, such as alerting, sensory processing, cognition, memory, and pathophysiological conditions, but specific cellular functions fulfilled by aerobic glycolysis are poorly understood. Evaluation of evidence derived from different disciplines reveals that aerobic glycolysis is a complex, regulated phenomenon that is prevented by propranolol, a non-specific β-adrenoceptor antagonist. The metabolic pathways that contribute to excess utilization of glucose compared with oxygen include glycolysis, the pentose phosphate shunt pathway, the malate-aspartate shuttle, and astrocytic glycogen turnover. Increased lactate production by unidentified cells, and lactate dispersal from activated cells and lactate release from the brain, both facilitated by astrocytes, are major factors underlying aerobic glycolysis in subjects with low blood lactate levels. Astrocyte-neuron lactate shuttling with local oxidation is minor. Blockade of aerobic glycolysis by propranolol implicates adrenergic regulatory processes including adrenal release of epinephrine, signaling to brain via the vagus nerve, and increased norepinephrine release from the locus coeruleus. Norepinephrine has a powerful influence on astrocytic metabolism and glycogen turnover that can stimulate carbohydrate utilization more than oxygen consumption, whereas β-receptor blockade 're-balances' the stoichiometry of oxygen-glucose or -carbohydrate metabolism by suppressing glucose and glycogen utilization more than oxygen consumption. This conceptual framework may be helpful for design of future studies to elucidate functional roles of preferential non-oxidative glucose utilization and glycogen turnover during brain activation. Aerobic glycolysis, the preferential up-regulation of glucose utilization (CMRglc ) compared with oxygen consumption (CMRO2 ) during brain activation, is blocked by propranolol. Epinephrine release from the adrenal gland stimulates vagus nerve signaling to the locus coeruleus, enhancing norepinephrine release in the brain, and regulation of astrocytic and neuronal metabolism to stimulate CMRglc more than CMRO2 . Propranolol suppresses CMRglc more than CMRO2 .
Topics: Animals; Astrocytes; Energy Metabolism; Glycogen; Glycolysis; Humans; Norepinephrine; Oxygen Consumption
PubMed: 27166428
DOI: 10.1111/jnc.13630 -
Molecular Metabolism Oct 2022Alterations in mitochondrial function play an important role in the development of various diseases, such as obesity, insulin resistance, steatohepatitis,...
OBJECTIVE
Alterations in mitochondrial function play an important role in the development of various diseases, such as obesity, insulin resistance, steatohepatitis, atherosclerosis and cancer. However, accurate assessment of mitochondrial respiration ex vivo is limited and remains highly challenging. Using our novel method, we measured mitochondrial oxygen consumption (OCR) and extracellular acidification rate (ECAR) of metabolically relevant tissues ex vivo to investigate the impact of different metabolic stressors on mitochondrial function.
METHODS
Comparative analyses of OCR and ECAR were performed in tissue biopsies of young mice fed 12 weeks standard-control (STD), high-fat (HFD), high-sucrose (HSD), or western diet (WD), matured mice with HFD, and 2year-old mice aged on STD with and without fasting.
RESULTS
While diets had only marginal effects on mitochondrial respiration, respiratory chain complexes II and IV were reduced in adipose tissue (AT). Moreover, matured HFD-fed mice showed a decreased hepatic metabolic flexibility and prolonged aging increased OCR in brown AT. Interestingly, fasting boosted pancreatic and hepatic OCR while decreasing weight of those organs. Furthermore, ECAR measurements in AT could indicate its lipolytic capacity.
CONCLUSION
Using ex vivo tissue measurements, we could extensively analyze mitochondrial function of liver, AT, pancreas and heart revealing effects of metabolic stress, especially aging.
Topics: Animals; Mice; Adipose Tissue, Brown; Aging; Diet, High-Fat; Fasting; Oxygen Consumption; Stress, Physiological
PubMed: 35944898
DOI: 10.1016/j.molmet.2022.101563 -
PloS One 2022The proposed mechanisms for the development of nephropathy are many, complex and often overlapping. Although recent literature strongly supports a role of kidney hypoxia...
The proposed mechanisms for the development of nephropathy are many, complex and often overlapping. Although recent literature strongly supports a role of kidney hypoxia as an independent pathway to nephropathy, the evidence remains inconclusive since the role of hypoxia is difficult to differentiate from confounding factors such as hyperglycemia, hypertension and oxidative stress. By increasing kidney oxygen consumption using triiodothyronine (T3) and, thus, avoiding these confounding factors, the aim of the present study was to investigate renal hypoxia per se as a causal pathway for the development of nephropathy. Healthy Sprague-Dawley rats were treated with T3 (10 μg/kg/day) and the angiotensin II AT1-receptor antagonist candesartan (1 mg/kg in drinking water) to eliminate effects of T3-induced renin release; and compared to a candesartan treated control group. After 7 weeks of treatment in vivo kidney function, oxygen metabolism and mitochondrial function were evaluated. T3 did not affect glomerular filtration rate or renal blood flow, but increased total kidney oxygen consumption resulting in cortical hypoxia. Nephropathy, demonstrated as albuminuria and tubulointerstitial fibrosis, developed in T3-treated animals. Mitochondria uncoupling mediated by uncoupling protein 2 and the adenosine nucleotide transporter was demonstrated as a mechanism causing the increased kidney oxygen consumption. Importantly, blood glucose levels, mean arterial blood pressure and oxidative stress levels were not affected by T3. In conclusion, the present study provides further evidence for increased kidney oxygen consumption causing intrarenal tissue hypoxia, as a causal pathway for development of nephropathy.
Topics: Animals; Female; Humans; Hypoxia; Kidney; Kidney Diseases; Male; Oxygen; Oxygen Consumption; Rats; Rats, Sprague-Dawley; Thyroid Hormones
PubMed: 35239685
DOI: 10.1371/journal.pone.0264524 -
Training Periodization, Intensity Distribution, and Volume in Trained Cyclists: A Systematic Review.International Journal of Sports... Feb 2023A well-planned periodized approach endeavors to allow road cyclists to achieve peak performance when their most important competitions are held.
UNLABELLED
A well-planned periodized approach endeavors to allow road cyclists to achieve peak performance when their most important competitions are held.
PURPOSE
To identify the main characteristics of periodization models and physiological parameters of trained road cyclists as described by discernable training intensity distribution (TID), volume, and periodization models.
METHODS
The electronic databases Scopus, PubMed, and Web of Science were searched using a comprehensive list of relevant terms. Studies that investigated the effect of the periodization of training in cyclists and described training load (volume, TID) and periodization details were included in the systematic review.
RESULTS
Seven studies met the inclusion criteria. Block periodization (characterized by employment of highly concentrated training workload phases) ranged between 1- and 8-week blocks of high-, medium-, or low-intensity training. Training volume ranged from 8.75 to 11.68 h·wk-1 and both pyramidal and polarized TID were used. Traditional periodization (characterized by a first period of high-volume/low-intensity training, before reducing volume and increasing the proportion of high-intensity training) was characterized by a cyclic progressive increase in training load, the training volume ranged from 7.5 to 10.76 h·wk-1, and pyramidal TID was used. Block periodization improved maximum oxygen uptake (VO2max), peak aerobic power, lactate, and ventilatory thresholds, while traditional periodization improved VO2max, peak aerobic power, and lactate thresholds. In addition, a day-by-day programming approach improved VO2max and ventilatory thresholds.
CONCLUSIONS
No evidence is currently available favoring a specific periodization model during 8 to 12 weeks in trained road cyclists. However, few studies have examined seasonal impact of different periodization models in a systematic way.
Topics: Humans; Athletic Performance; Oxygen Consumption; Oxygen; Lactic Acid; Bibliometrics
PubMed: 36640771
DOI: 10.1123/ijspp.2022-0302 -
American Journal of Physiology. Cell... Nov 2022Brief, intense interval training describes a style of exercise characterized by short bouts of strenuous effort interspersed with recovery periods. The method increases... (Review)
Review
Brief, intense interval training describes a style of exercise characterized by short bouts of strenuous effort interspersed with recovery periods. The method increases whole body maximal oxygen uptake (V̇o), but the underlying physiological basis is unclear. V̇o represents the functional limit of the integrative oxygen cascade, which refers to the physiological steps involved in oxygen transport and utilization from atmospheric air to mitochondrial metabolism. There is insufficient evidence to definitively state which steps in the oxygen cascade are responsible for the improvement in V̇o after brief, intense interval training. Studies typically focus on specific physiological variables that are often characterized as "central" or "peripheral" based in part on their location in the body. Recent work suggests that training for ≥6 wk improves V̇o in part by increasing maximal cardiac output and expanding blood volume, responses that are expected to augment central oxygen delivery. Other responses to brief, intense interval training, including increased capillary and mitochondrial density, may contribute to increases in V̇o via enhanced skeletal muscle oxygen extraction and/or increased muscle diffusing capacity. This is especially evident after relatively short-term training and despite no change in central oxygen delivery factors. Mechanistic investigations, particularly employing contemporary technologies, are needed to advance our understanding of the early time course of the V̇o response to brief, intense interval training and the extent to which changes in specific oxygen cascade processes compare with traditional endurance training.
Topics: Oxygen Consumption; Exercise; Muscle, Skeletal; Oxygen; Capillaries; Adaptation, Physiological
PubMed: 36121130
DOI: 10.1152/ajpcell.00143.2022 -
Journal of Optometry 2022The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the...
The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the last 20 years to model the physiology of the human cornea during contact lens wear. Unfortunately, some of these models, based on a constant corneal oxygen consumption rate, produce areas on the cornea where the oxygen tension is negative, which has no physical sense. In order to avoid such inconsistency, different researchers have developed alternative models of oxygen consumption, which predict the likely oxygen metrics available at the interface cornea/post lens tear film by determination of oxygen flux, oxygen consumption, and oxygen tension through the different layers (endothelium, stroma, and epithelium). Although oxygen deficiency produces corneal edema, corneal swelling, hypoxia, acidosis, and other abnormalities, the estimation of the oxygen distribution below the impact of a contact lens wear is interesting to know which lens transmissibility was adequate to maintain the cornea and avoid epithelial and stromal anoxia. The estimation of minimum transmissibility for a lens for extended wear applications will be very useful for both clinicians and manufacturers. The aim of this work is to present a complete discussion based on Monod kinetics model that permits give an estimation of oxygen partial pressure distribution, the profile distribution of corneal flux and oxygen consumption rate, and finally the estimation of the relaxation mechanism of the cornea depending on the oxygen tension at the interface cornea/post lens tear film. Relaxation time in this context can quantify the capability of the corneal tissue to adapt to increasing concentrations of oxygen. It is proposed this parameter as a biological meaningful indicator of the interaction between contact lens polymers and living tissues such as the corneal cellular layer.
Topics: Contact Lenses, Hydrophilic; Cornea; Humans; Oxygen; Oxygen Consumption; Tears
PubMed: 33589396
DOI: 10.1016/j.optom.2020.12.002 -
Neural Plasticity 2016When people focus attention or carry out a demanding task, their breathing changes. But which parameters of respiration vary exactly and can respiration reliably be used... (Review)
Review
When people focus attention or carry out a demanding task, their breathing changes. But which parameters of respiration vary exactly and can respiration reliably be used as an index of cognitive load? These questions are addressed in the present systematic review of empirical studies investigating respiratory behavior in response to cognitive load. Most reviewed studies were restricted to time and volume parameters while less established, yet meaningful parameters such as respiratory variability have rarely been investigated. The available results show that respiratory behavior generally reflects cognitive processing and that distinct parameters differ in sensitivity: While mentally demanding episodes are clearly marked by faster breathing and higher minute ventilation, respiratory amplitude appears to remain rather stable. The present findings further indicate that total variability in respiratory rate is not systematically affected by cognitive load whereas the correlated fraction decreases. In addition, we found that cognitive load may lead to overbreathing as indicated by decreased end-tidal CO2 but is also accompanied by elevated oxygen consumption and CO2 release. However, additional research is needed to validate the findings on respiratory variability and gas exchange measures. We conclude by outlining recommendations for future research to increase the current understanding of respiration under cognitive load.
Topics: Animals; Attention; Cognition; Humans; Oxygen Consumption; Psychomotor Performance; Respiratory Mechanics; Tidal Volume
PubMed: 27403347
DOI: 10.1155/2016/8146809