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Internal and Emergency Medicine Aug 2022Patients with COPD exhibit limited exercise endurance time compared to healthy age-matched individuals. Oxygen supplementation is often applied to improve endurance time... (Review)
Review
Patients with COPD exhibit limited exercise endurance time compared to healthy age-matched individuals. Oxygen supplementation is often applied to improve endurance time during pulmonary rehabilitation in patients with COPD and thus a comprehensive understanding of the mechanisms leading to improved endurance is desirable. This review analyses data from two studies by our research group investigating the effect of oxygen supplementation on cerebrovascular, systemic, respiratory and locomotor muscle oxygen availability on the same cohort of individuals with advanced COPD, and the mechanisms associated with improved endurance time in hyperoxia, which was essentially doubled (at the same power output). In hyperoxia at isotime (the time at which patients became exhausted in normoxia) exercise was associated with greater respiratory and locomotor muscle (but not frontal cortex) oxygen delivery (despite lower cardiac output), lower lactate concentration and less tachypnoea. Frontal cortex oxygen saturation was higher, and respiratory drive lower. Hence, improved endurance in hyperoxia appears to be facilitated by several factors: increased oxygen availability to the respiratory and locomotor muscles, less metabolic acidosis, and lower respiratory drive. At exhaustion in both normoxia and hyperoxia, only cardiac output and breathing pattern were not different between conditions. However, minute ventilation in hyperoxia exceeded the critical level of ventilatory constraints (V/MVV > 75-80%). Lactate remained lower and respiratory and locomotor muscle oxygen delivery greater in hyperoxia, suggesting greater muscle oxygen availability improving muscle function. Taken together, these findings suggest that central haemodynamic and ventilatory limitations and not contracting muscle conditions dictate endurance time in COPD during exercise in hyperoxia.
Topics: Exercise Tolerance; Humans; Hyperoxia; Lactates; Oxygen; Oxygen Consumption; Oxygen Inhalation Therapy; Pulmonary Disease, Chronic Obstructive
PubMed: 35819698
DOI: 10.1007/s11739-022-03037-2 -
Mayo Clinic Proceedings Apr 2021The oxygen transport cascade describes the physiological steps that bring atmospheric oxygen into the body where it is delivered and consumed by metabolically active... (Comparative Study)
Comparative Study Review
The oxygen transport cascade describes the physiological steps that bring atmospheric oxygen into the body where it is delivered and consumed by metabolically active tissue. As such, the oxygen cascade is fundamental to our understanding of exercise in health and disease. Our narrative review will highlight each step of the oxygen transport cascade from inspiration of atmospheric oxygen down to mitochondrial consumption in both healthy active males and females along with clinical conditions. We will focus on how different steps interact along with principles of homeostasis, physiological redundancies, and adaptation. In particular, we highlight some of the parallels between elite athletes and clinical conditions in terms of the oxygen cascade.
Topics: Adult; Aged; Aged, 80 and over; Athletes; Exercise; Female; Healthy Volunteers; Humans; Male; Middle Aged; Oxygen Consumption; Physical Endurance
PubMed: 33714599
DOI: 10.1016/j.mayocp.2020.06.063 -
Advances in Physiology Education Dec 2022The interchange among the energy-providing phosphagen, glycolytic, and aerobic systems during exercise is often poorly understood by beginning students in exercise...
The interchange among the energy-providing phosphagen, glycolytic, and aerobic systems during exercise is often poorly understood by beginning students in exercise physiology. Exercise is oftentimes thought of as being aerobic or anaerobic, with the body progressing sequentially from one system to the next, although the energy systems work synergistically to produce energy from the onset of exercise, and all ultimately use oxygen. Traditional methods of teaching these concepts using only indirect calorimetry and a metabolic cart can be misleading. Relatively inexpensive noninvasive monitors of muscle oxygenation levels ([Formula: see text]) provide a useful tool to help students better understand the contribution and timing of these three systems of ATP generation and convey the concept that ultimately all energy production in the human body is oxygen dependent. In this laboratory, students use near-infrared spectroscopy (NIRS) to visualize oxygen utilization by skeletal muscle during exercise by devising three exercise unique protocols, with each designed to stress a different energy system. Students then perform their protocols while using NIRS to measure and analyze [Formula: see text]. Students generate graphs with collected data, allowing them to visualize and appreciate oxygen consumption during all three protocols as well as elevated oxygen consumption after exercise. The students learn that any exercise is really all about oxygen. Traditional methods of teaching bioenergetics using indirect calorimetry and a metabolic cart may be misleading. Recent advances in technology have made near-infrared spectroscopy (NIRS) a relatively inexpensive, noninvasive means of monitoring muscle oxygen levels during exercise. In this laboratory activity, NIRS devices are used for hands-on exploration of the synergistic nature of the energy systems, allowing students to appreciate the synergistic nature of the energy systems and how all exercise is really all about oxygen.
Topics: Humans; Spectroscopy, Near-Infrared; Oxygen; Oxygen Consumption; Energy Metabolism; Muscle, Skeletal
PubMed: 36201307
DOI: 10.1152/advan.00106.2022 -
Physiological Research Dec 2022Mitochondria are considered central regulator of the aging process; however, majority of studies dealing with the impact of age on mitochondrial oxygen consumption...
Mitochondria are considered central regulator of the aging process; however, majority of studies dealing with the impact of age on mitochondrial oxygen consumption focused on skeletal muscle concluding (although not uniformly) a general declining trend with advancing age. In addition, gender related differences in mitochondrial respiration have not been satisfactorily described yet. The aim of the present study was to evaluate mitochondrial oxygen consumption in various organs of aging male and female Fischer 344 rats at the ages of 6, 12 and 24 months. Mitochondrial respiration of homogenized (skeletal muscle, left and right heart ventricle, hippocampus, cerebellum, kidney cortex), gently mechanically permeabilized (liver) tissue or intact cells (platelets) was determined using high-resolution respirometry (oxygraphs O2k, Oroboros, Austria). The pattern of age-related changes differed in each tissue: in the skeletal muscle and kidney cortex of both sexes and in female heart, parameters of mitochondrial respiration significantly declined with age. Resting respiration of intact platelets displayed an increasing trend and it did not correlate with skeletal muscle respiratory states. In the heart of male rats and brain tissues of both sexes, respiratory states remained relatively stable over analyzed age categories with few exceptions of lower mitochondrial oxygen consumption at the age of 24 months. In the liver, OXPHOS capacity was higher in females than in males with either no difference between the ages of 6 and 24 months or even significant increase at the age of 24 months in the male rats. In conclusion, the results of our study indicate that the concept of general pattern of age-dependent decline in mitochondrial oxygen consumption across different organs and tissues could be misleading. Also, the statement of higher mitochondrial respiration in females seems to be conflicting, since the gender-related differences may vary with the tissue studied, combination of substrates used and might be better detectable at younger ages than in old animals.
Topics: Animals; Female; Male; Rats; Aging; Cell Respiration; Mitochondria; Mitochondria, Muscle; Muscle, Skeletal; Oxygen Consumption; Respiration; Anesthesia
PubMed: 36647911
DOI: 10.33549/physiolres.934995 -
Seminars in Immunology May 2015Inflammatory diseases in mucosal organs as diverse as the lung, liver and intestine inevitably require the intimate interactions between neutrophils and epithelia. The... (Review)
Review
Inflammatory diseases in mucosal organs as diverse as the lung, liver and intestine inevitably require the intimate interactions between neutrophils and epithelia. The physiologic consequences of such interactions often determine endpoint organ function, and for this reason, much recent interest has developed in identifying mechanisms and novel targets to promote the resolution of mucosal inflammation. Physiologically-relevant in vitro and in vivo model systems have aided in discovery of novel pathways to define basic inflammatory mechanisms and approaches to defining the concepts of inflammatory resolution. Here, we will review the recent literature regarding the contribution of neutrophils to inflammatory resolution, with an emphasis on the role of the tissue microenvironment, endogenous pathways for promoting resolution and the molecular determinants of neutrophil-epithelial cell interactions during ongoing inflammation. These recent studies highlight the dynamic nature of pro-resolving pathways and lend insight into the complexity of treating mucosal inflammation.
Topics: Cell Communication; Cell Hypoxia; Cell Movement; Cellular Microenvironment; Epithelial Cells; Homeostasis; Humans; Inflammation; Mucous Membrane; Neutrophils; Oxygen Consumption; Purine Nucleosides
PubMed: 25818531
DOI: 10.1016/j.smim.2015.03.007 -
Pflugers Archiv : European Journal of... Jan 2023Oxygen is critical for neural metabolism, but under most physiological conditions, oxygen levels in the brain are far more than are required. Oxygen levels can be... (Review)
Review
Oxygen is critical for neural metabolism, but under most physiological conditions, oxygen levels in the brain are far more than are required. Oxygen levels can be dynamically increased by increases in respiration rate that are tied to the arousal state of the brain and cognition, and not necessarily linked to exertion by the body. Why these changes in respiration occur when oxygen is already adequate has been a long-standing puzzle. In humans, performance on cognitive tasks can be affected by very high or very low oxygen levels, but whether the physiological changes in blood oxygenation produced by respiration have an appreciable effect is an open question. Oxygen has direct effects on potassium channels, increases the degradation rate of nitric oxide, and is rate limiting for the synthesis of some neuromodulators. We discuss whether oxygenation changes due to respiration contribute to neural dynamics associated with attention and arousal.
Topics: Humans; Oxygen; Respiration; Oxygen Consumption; Brain; Nitric Oxide
PubMed: 35761104
DOI: 10.1007/s00424-022-02721-8 -
Frontiers in Bioscience (Landmark... Jul 2022This report aims to detail the use of the phosphorescence oxygen analyzer for investigation of thymic responses to pharmaceutical agents, in particular...
BACKGROUND
This report aims to detail the use of the phosphorescence oxygen analyzer for investigation of thymic responses to pharmaceutical agents, in particular immunosuppressants and immunomodulators. Sirolimus (a highly specific inhibitor of the 'molecular target of rapamycin', mTOR) and ozanimod (an agonist of the sphingosine 1-phosphate receptor, recently approved for treatment of multiple sclerosis and ulcerative colitis) are used for this purpose.
METHODS
Thymic fragments from mice were placed in glass vials containing phosphate-buffered saline, bovine albumin, and Pd(II) meso-tetra (sulfophenyl) tetrabenzoporphyrin. The vials were sealed from air, and the cellular oxygen consumption was monitored as function of time.
RESULTS
The decline of dissolved oxygen concentration with time (d[O2]/d) was linear; thus, its rate (thymocyte respiration) was expressed as μM O2 min-1. Cyanide inhibited respiration, confirming the oxygen consumption was in cytochrome oxidase. In age-matched mice, the rate of thymocyte respiration (mean ± SD, in μM O2 min-1 mg-1) was 0.046 ± 0.011 (median = 0.043, range = 0.028 to 0.062, n = 10). In thymic fragments from littermates, this rate was inhibited in the presence of sirolimus (16% lower) or ozanimod (29% lower).
CONCLUSIONS
Thymocyte respiration can serve as a surrogate biomarker for studying the mode-of-action and the cytotoxicity of immunotoxins and immunosuppressants.
Topics: Animals; Cattle; Cell Respiration; Immunosuppressive Agents; Mice; Oxygen; Oxygen Consumption; Sirolimus
PubMed: 36042174
DOI: 10.31083/j.fbl2708230 -
International Journal of Environmental... Apr 2022It was not until 1984 that women were permitted to compete in the Olympic marathon. Today, more women than men participate in road racing in all distances except the... (Review)
Review
It was not until 1984 that women were permitted to compete in the Olympic marathon. Today, more women than men participate in road racing in all distances except the marathon where participation is near equal. From the period of 1985 to 2004, the women's marathon record improved at a rate three times greater than men's. This has led many to question whether women are capable of surpassing men despite the fact that there remains a 10-12% performance gap in all distance events. The progressive developments in sports performance research and training, beginning with A.V. Hill's establishment of the concept of VO, have allowed endurance athletes to continue performance feats previously thought to be impossible. However, even today women are significantly underrepresented in sports performance research. By focusing more research on the female physiology and sex differences between men and women, we can better define how women differ from men in adapting to training and potentially use this information to improve endurance-exercise performance in women. The male advantage in endurance-exercise performance has commonly been attributed to their higher VO, even when expressed as mL/kg/min. It is widely known that oxygen delivery is the primary limiting factor in elite athletes when it comes to improving VO, but little research has explored the sex differences in oxygen delivery. Thus, the purpose of this review is to highlight what is known about the sex differences in the physiological factors contributing to VO, more specifically oxygen delivery, and the impacts on performance.
Topics: Athletic Performance; Female; Humans; Male; Oxygen; Oxygen Consumption; Physical Endurance; Sex Characteristics
PubMed: 35564339
DOI: 10.3390/ijerph19094946 -
British Journal of Anaesthesia Feb 2023Epidemiological evidence has highlighted a strong relationship between cardiorespiratory fitness and surgical outcomes; specifically, fitter patients possess heightened... (Review)
Review
Epidemiological evidence has highlighted a strong relationship between cardiorespiratory fitness and surgical outcomes; specifically, fitter patients possess heightened resilience to withstand the surgical stress response. This narrative review draws on exercise and surgical physiology research to discuss and hypothesise the potential mechanisms by which higher fitness affords perioperative benefit. A higher fitness, as indicated by higher peak rate of oxygen consumption and ability to sustain metabolic homeostasis (i.e. higher anaerobic threshold) is beneficial postoperatively when metabolic demands are increased. However, the associated adaptations with higher fitness, and the related participation in regular exercise or physical activity, might also underpin the observed perioperative benefit through a process of hormesis, a protective adaptive response to the moderate and intermittent stress of exercise. Potential mediators discussed include greater antioxidant capacity, metabolic flexibility, glycaemic control, lean body mass, and improved mood.
Topics: Humans; Cardiorespiratory Fitness; Exercise; Exercise Therapy; Anaerobic Threshold; Oxygen Consumption; Physical Fitness; Exercise Test
PubMed: 36529576
DOI: 10.1016/j.bja.2022.10.039 -
Acta Physiologica (Oxford, England) Jan 2020Obesity is a complex disorder of excessive adiposity, and is associated with adverse health effects such as cardiometabolic complications, which are to a large extent... (Review)
Review
Obesity is a complex disorder of excessive adiposity, and is associated with adverse health effects such as cardiometabolic complications, which are to a large extent attributable to dysfunctional white adipose tissue. Adipose tissue dysfunction is characterized by adipocyte hypertrophy, impaired adipokine secretion, a chronic low-grade inflammatory status, hormonal resistance and altered metabolic responses, together contributing to insulin resistance and related chronic diseases. Adipose tissue hypoxia, defined as a relative oxygen deficit, in obesity has been proposed as a potential contributor to adipose tissue dysfunction, but studies in humans have yielded conflicting results. Here, we will review the role of adipose tissue oxygenation in the pathophysiology of obesity-related complications, with a specific focus on human studies. We will provide an overview of the determinants of adipose tissue oxygenation, as well as the role of adipose tissue oxygenation in glucose homeostasis, lipid metabolism and inflammation. Finally, we will discuss the putative effects of physiological and experimental hypoxia on adipose tissue biology and whole-body metabolism in humans. We conclude that several lines of evidence suggest that alteration of adipose tissue oxygenation may impact metabolic homeostasis, thereby providing a novel strategy to combat chronic metabolic diseases in obese humans.
Topics: Adipose Tissue; Glucose; Humans; Lipid Metabolism; Obesity; Oxygen; Oxygen Consumption
PubMed: 31077538
DOI: 10.1111/apha.13298