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Nature Metabolism Aug 2022Measurement of oxygen consumption is a powerful and uniquely informative experimental technique. It can help identify mitochondrial mechanisms of action following... (Review)
Review
Measurement of oxygen consumption is a powerful and uniquely informative experimental technique. It can help identify mitochondrial mechanisms of action following pharmacologic and genetic interventions, and characterize energy metabolism in physiology and disease. The conceptual and practical benefits of respirometry have made it a frontline technique to understand how mitochondrial function can interface with-and in some cases control-cell physiology. Nonetheless, an appreciation of the complexity and challenges involved with such measurements is required to avoid common experimental and analytical pitfalls. Here we provide a practical guide to oxygen consumption measurements covering the selection of experimental models and instrumentation, as well as recommendations for the collection, interpretation and normalization of data. These guidelines are provided with the intention of aiding experimental design and enhancing the overall reputability, transparency and reliability of oxygen consumption measurements.
Topics: Energy Metabolism; Mitochondria; Oxygen Consumption; Reference Standards; Reproducibility of Results
PubMed: 35971004
DOI: 10.1038/s42255-022-00619-4 -
Acta Physiologica (Oxford, England) Jun 2017In this review, we argue that several key features of maximal oxygen uptake (VO max) should underpin discussions about the biological and reductionist determinants of... (Review)
Review
In this review, we argue that several key features of maximal oxygen uptake (VO max) should underpin discussions about the biological and reductionist determinants of its interindividual variability: (i) training-induced increases in VO max are largely facilitated by expansion of red blood cell volume and an associated improvement in stroke volume, which also adapts independent of changes in red blood cell volume. These general concepts are also informed by cross-sectional studies in athletes that have very high values for VO max. Therefore, (ii) variations in VO max improvements with exercise training are also likely related to variations in these physiological determinants. (iii) All previously untrained individuals will respond to endurance exercise training in terms of improvements in VO max provided the stimulus exceeds a certain volume and/or intensity. Thus, genetic analysis and/or reductionist studies performed to understand or predict such variations might focus specifically on DNA variants or other molecular phenomena of relevance to these physiological pathways.
Topics: Animals; Cardiovascular Physiological Phenomena; Humans; Oxygen Consumption; Physical Endurance; Respiratory Physiological Phenomena
PubMed: 27888580
DOI: 10.1111/apha.12827 -
Methods in Molecular Biology (Clifton,... 2022The propensity of cancer cells to preferentially undergo anaerobic metabolism despite oxygen being abundant is referred to as the Warburg effect. Measuring cellular...
The propensity of cancer cells to preferentially undergo anaerobic metabolism despite oxygen being abundant is referred to as the Warburg effect. Measuring cellular metabolism is therefore central to understanding the cellular physiology of cancer cells. The Seahorse XFe Analyzer series allows real-time measurement of cellular metabolism. In the basic assay, two parameters, the oxygen consumption rate (OCR) and the extracellular acidification rate (ECAR), are used to determine real-time changes in the energy needs of live cells: OCR provides a measure of aerobic mitochondrial respiration; ECAR gives a measure of anaerobic glycolysis. Through the use of various respiration inhibitors, the Seahorse assay allows baseline respiration rate and total aerobic and anaerobic ATP production to be determined under a variety of experimental conditions. Here we describe the protocol for completing the Seahorse Real-Time ATP Rate Assay for adherent and suspension cancer cell lines. Depending on individual experimental results, more refined subsequent assays can then be performed to specifically determine, for example, the ability to utilize different substrates by the cell lines in the presence and absence of pharmacological and/or genetic interventions.
Topics: Adenosine Triphosphate; Animals; Cell Line; Energy Metabolism; Glycolysis; Neoplasms; Oxygen Consumption; Smegmamorpha
PubMed: 35737244
DOI: 10.1007/978-1-0716-2376-3_17 -
Sports Medicine (Auckland, N.Z.) May 2018Taurine is central to many physiological processes, some of which are augmented by exogenous supply and have the potential to facilitate endurance performance; however,... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Taurine is central to many physiological processes, some of which are augmented by exogenous supply and have the potential to facilitate endurance performance; however, its independent effects on performance have not been systematically analysed.
OBJECTIVE
To evaluate the effects of isolated oral taurine ingestion on endurance performance and to assess the contribution of (1) the dose and (2) the supplementation period to the ergogenic effect.
METHODS
A search was performed using various databases in September 2017. The studies were screened using search criteria for eligibility. Ten peer-reviewed articles were identified for inclusion. A sub-analysis of time-to-exhaustion (TTE) trials (n = 7) was also performed. The effects of (1) dose and (2) the acute (single dose) or chronic (> 1 day) supplementation periods were assessed using meta-regression. The doses of taurine ranged from 1 to 6 g/day and were provided in single doses and for up to 2 weeks among a range of subjects.
RESULTS
Taurine ingestion improved overall endurance performance (Hedges' g = 0.40, 95% CI 0.12-0.67, P = 0.004), which was similar in TTE trials (Hedges' g = 0.43, 95% CI 0.12-0.75, P = 0.007). There were no differences between acute or chronic supplementation for the full sample (P = 0.897) or the TTE group (P = 0.896). The dose of taurine did not moderate its effect on endurance performance (P > 0.05).
CONCLUSION
Human endurance performance can be improved by orally ingesting a single dose of taurine in varying amounts (1-6 g).
Topics: Athletic Performance; Dietary Supplements; Energy Metabolism; Exercise; Female; Humans; Male; Oxygen Consumption; Physical Endurance; Taurine
PubMed: 29546641
DOI: 10.1007/s40279-018-0896-2 -
Pflugers Archiv : European Journal of... Aug 2022Our kidneys receive about one-fifth of the cardiac output at rest and have a low oxygen extraction ratio, but may sustain, under some conditions, hypoxic injuries that... (Review)
Review
Our kidneys receive about one-fifth of the cardiac output at rest and have a low oxygen extraction ratio, but may sustain, under some conditions, hypoxic injuries that might lead to chronic kidney disease. This is due to large regional variations in renal blood flow and oxygenation, which are the prerequisite for some and the consequence of other kidney functions. The concurrent operation of these functions is reliant on a multitude of neuro-hormonal signaling cascades and feedback loops that also include the regulation of renal blood flow and tissue oxygenation. Starting with open questions on regulatory processes and disease mechanisms, we review herein the literature on renal blood flow and oxygenation. We assess the current understanding of renal blood flow regulation, reasons for disparities in oxygen delivery and consumption, and the consequences of disbalance between O delivery, consumption, and removal. We further consider methods for measuring and computing blood velocity, flow rate, oxygen partial pressure, and related parameters and point out how limitations of these methods constitute important hurdles in this area of research. We conclude that to obtain an integrated understanding of the relation between renal function and renal blood flow and oxygenation, combined experimental and computational modeling studies will be needed.
Topics: Humans; Hypoxia; Kidney; Oxygen; Oxygen Consumption; Renal Circulation
PubMed: 35438336
DOI: 10.1007/s00424-022-02690-y -
Sports Medicine (Auckland, N.Z.) Mar 2023The physiological determinants of high-intensity exercise tolerance are important for both elite human performance and morbidity, mortality and disease in clinical... (Review)
Review
The physiological determinants of high-intensity exercise tolerance are important for both elite human performance and morbidity, mortality and disease in clinical settings. The asymptote of the hyperbolic relation between external power and time to task failure, critical power, represents the threshold intensity above which systemic and intramuscular metabolic homeostasis can no longer be maintained. After ~ 60 years of research into the phenomenon of critical power, a clear understanding of its physiological determinants has emerged. The purpose of the present review is to critically examine this contemporary evidence in order to explain the physiological underpinnings of critical power. Evidence demonstrating that alterations in convective and diffusive oxygen delivery can impact upon critical power is first addressed. Subsequently, evidence is considered that shows that rates of muscle oxygen utilisation, inferred via the kinetics of pulmonary oxygen consumption, can influence critical power. The data reveal a clear picture that alterations in the rates of flux along every step of the oxygen transport and utilisation pathways influence critical power. It is also clear that critical power is influenced by motor unit recruitment patterns. On this basis, it is proposed that convective and diffusive oxygen delivery act in concert with muscle oxygen utilisation rates to determine the intracellular metabolic milieu and state of fatigue within the myocytes. This interacts with exercising muscle mass and motor unit recruitment patterns to ultimately determine critical power.
Topics: Humans; Exercise; Oxygen Consumption; Exercise Tolerance; Lung; Oxygen; Muscle, Skeletal
PubMed: 36622556
DOI: 10.1007/s40279-022-01805-w -
European Journal of Preventive... Oct 2023Cardiopulmonary exercise test (CPET) is a valuable diagnostic tool with a specific application in heart failure (HF) thanks to the strong prognostic value of its...
Cardiopulmonary exercise test (CPET) is a valuable diagnostic tool with a specific application in heart failure (HF) thanks to the strong prognostic value of its parameters. The most important value provided by CPET is the peak oxygen uptake (peak VO2), the maximum rate of oxygen consumption attainable during physical exertion. According to the Fick principle, VO2 equals cardiac output (Qc) times the arteriovenous content difference [C(a-v)O2], where Ca is the arterial oxygen and Cv is the mixed venous oxygen content, respectively; therefore, VO2 can be reduced both by impaired O2 delivery (reduced Qc) or extraction (reduced arteriovenous O2 content). However, standard CPET is not capable of discriminating between these different impairments, leading to the need for 'complex' CPET technologies. Among non-invasive methods for Qc measurement during CPET, inert gas rebreathing and thoracic impedance cardiography are the most used techniques, both validated in healthy subjects and patients with HF, at rest and during exercise. On the other hand, the non-invasive assessment of peripheral muscle perfusion is possible with the application of near-infrared spectroscopy, capable of measuring tissue oxygenation. Measuring Qc allows, by having haemoglobin values available, to discriminate how much any VO2 deficit depends on the muscle, anaemia or heart.
Topics: Humans; Exercise Test; Cardiac Output; Oxygen Consumption; Prognosis; Heart Failure; Oxygen
PubMed: 37819225
DOI: 10.1093/eurjpc/zwad154 -
The British Journal of Radiology Jan 2019The concept of tumour hypoxia as a cause of radiation resistance has been prevalent for over 100 years. During this time, our understanding of tumour hypoxia has matured... (Review)
Review
The concept of tumour hypoxia as a cause of radiation resistance has been prevalent for over 100 years. During this time, our understanding of tumour hypoxia has matured with the recognition that oxygen tension within a tumour is influenced by both diffusion and perfusion mechanisms. In parallel, clinical strategies to modify tumour hypoxia with the expectation that this will improve response to radiation have been developed and tested in clinical trials. Despite many disappointments, meta-analysis of the data on hypoxia modification confirms a significant impact on both tumour control and survival. Early trials evaluated hyperbaric oxygen followed by a generation of studies testing oxygen mimetics such as misonidazole, pimonidazole and etanidazole. One highly significant result stands out from the use of nimorazole in advanced laryngeal cancer with a significant advantage seen for locoregional control using this radiosensitiser. More recent studies have evaluated carbogen and nicotinamide targeting both diffusion related and perfusion related hypoxia. A significant survival advantage is seen in muscle invasive bladder cancer and also for locoregional control in hypopharygeal cancer associated with a low haemoglobin. New developments include the recognition that mitochondrial complex inhibitors reducing tumour oxygen consumption are potential radiosensitising agents and atovaquone is currently in clinical trials. One shortcoming of past hypoxia modifying trials is the failure to identify oxygenation status and select those patient with significant hypoxia. A range of biomarkers are now available including histological necrosis, immunohistochemical intrinsic markers such as CAIX and Glut 1 and hypoxia gene signatures which have been shown to predict outcome and will inform the next generation of hypoxia modifying clinical trials.
Topics: Animals; Cell Hypoxia; Female; Humans; Male; Misonidazole; Neoplasms; Niacinamide; Oxygen Consumption; Radiation-Sensitizing Agents; Randomized Controlled Trials as Topic; Risk Assessment; Survival Analysis; Treatment Outcome; Tumor Hypoxia
PubMed: 29979089
DOI: 10.1259/bjr.20170966 -
Trends in Endocrinology and Metabolism:... Jun 2023Distance running requires a high absolute oxygen consumption, while for a breath-hold diver the opposite is preferable. We compared physiological exercise parameters and...
Distance running requires a high absolute oxygen consumption, while for a breath-hold diver the opposite is preferable. We compared physiological exercise parameters and mitochondrial function in a competitive triathlete with those seen in an accomplished breath-hold diver and notice some remarkable differences, possibly explaining why both have become successful.
Topics: Animals; Humans; Diving; Turtles; Hares; Breath Holding; Oxygen Consumption
PubMed: 37062666
DOI: 10.1016/j.tem.2023.03.003 -
International Journal of Yoga Therapy Jan 2023Yoga is widely practiced for its numerous health benefits, and it can also increase energy expenditure. Vinyasa yoga, a system of hatha yoga, meets criteria for...
Yoga is widely practiced for its numerous health benefits, and it can also increase energy expenditure. Vinyasa yoga, a system of hatha yoga, meets criteria for moderate-intensity physical activity. It is unclear whether the individual sequences produce different oxygen consumption (VO2) and heart rate responses. The purpose of the present study was therefore to evaluate potential differences in VO2 and heart rate responses across sequences of a 60-minute vinyasa session. Participants included 40 healthy male (n = 20) and female (n = 20) adults (age 30.9 ± 8.8 y) with self-reported yoga experience. The sequence implemented was based on Baron Baptiste's Journey into Power sequence. This vinyasa yoga practice included several sequences: integration, sun salutation, crescent lunges, balancing, standing, back bending, and restorative. VO2 (mL/kg/min) was measured by portable indirect calorimetry and expressed as metabolic equivalents (MET). Heart rate was measured using a Polar HR monitor and presented as a percentage of age-predicted maximal heart rate (APMHR). METs and APMHR differed significantly across sequences (each p < 0.001). METs for the integration, sun-salutation, crescent-lunges, balancing, standing, back-bending, and restorative sequences were significantly different from one another (p < 0.001); balancing and back-bending sequences, however, were similar. During the integration and restorative sequences, APMHR was similar (p = 1.00) and significantly lower compared to sun-salutation, crescent-lunge, balancing, standing, and back-bending sequences (each p < 0.001). METs and APMHR differed significantly across sequences of a vinyasa yoga practice. These data could inform an individualized yoga series based on current fitness levels to maintain or improve cardiorespiratory fitness.
Topics: Adult; Humans; Male; Female; Young Adult; Yoga; Heart Rate; Exercise; Oxygen Consumption; Cardiorespiratory Fitness
PubMed: 37169721
DOI: 10.17761/2023-D-22-00058