Physiology of the respiratory system
Louis-Philippe Boulet in Applied Respiratory Pathophysiology, 2017
The arterial blood is distributed into the body at a given oxygen concentration. Oxygen uptake varies between organs and the degree of extraction is variable. For example, heart muscle extracts more oxygen than skin by a coefficient of 10. Organs that consume less oxygen usually use the blood flow for duties other than oxygenation such as thermic regulation for the skin or the filtration for the kidney glomeruli. In the mitochondria, oxygen is mostly used to oxidize the pyruvic acid into the Krebs cycle and to produce adenosine triphosphate (ATP) molecules that hold high energy links, necessary to the global operation of the body. In the absence of oxygen, the body must rely more on anaerobic metabolism. This mechanism is ineffective and generates few ATP molecules that result in acidemia. Hypoxia occurs when oxygen is not sufficient to satisfy the metabolic needs of the tissues. We consider that this occurs when PaO2 inside the mitochondria is lower than 7 mmHg.
High-intensity aerobic endurance sports
Nick Draper, Helen Marshall in Exercise Physiology, 2014
Traditionally, the metabolic processes are described by starting with short-term high-intensity exercise and then moving on to consider endurance activities. In this way textbooks move from anaerobic to aerobic metabolism. For some activities this matches the transition in energy production from the onset of exercise. However, for the high- intensity aerobic endurance activities that are the focus of this chapter there are times when the reverse pattern of energy system contribution occurs. Sports such as 1,500 m running, 400 m swimming and rowing are predominantly aerobic sports but draw upon anaerobic metabolism for short in-race bursts or for the finishing ‘kick’. An understanding of this conceptual difference is important when considering the transition from aerobic to anaerobic metabolism.
Carbohydrates
Geoffrey P. Webb in Nutrition, 2019
Lactic acid is the end product of anaerobic metabolism in mammalian cells and anaerobic energy production is only possible from carbohydrate substrate. Red blood cells do not have mitochondria and thus they metabolise glucose only as far as pyruvic acid and lactic acid. During heavy exercise, the oxygen supply to a muscle limits aerobic metabolism and so the muscles will generate some ATP anaerobically and produce lactic acid as a by-product. Accumulation of lactic acid is one factor responsible for the fatigue of exercising muscles. Note also that in thiamin deficiency (beriberi) there is effectively a partial block in the metabolism of carbohydrate beyond pyruvic acid because the conversion of pyruvic acid to acetyl coenzyme A requires a coenzyme, thiamin pyrophosphate, which is derived from thiamin. Lactic acid and pyruvic acid therefore also accumulate in victims of beriberi because of this metabolic block.
Effects of psychosocial and physical stress on lactate and anxiety levels
Published in Stress, 2019
Robin Hermann, Daniel Lay, Patrick Wahl, Walton T. Roth, Katja Petrowski
The rise in lactate to the psychosocial stressor must depend more on cognitive than muscular activity, while the opposite is the case for the physical stressor. Since lactate is the brain’s preferred energy substrate (Pellerin & Magistretti, 2003; Smith et al., 2003), the brain seems to turn to lactate for cognitive activity by shifting to metabolizing lactate itself, rather than glucose and oxygen or lipids. There is evidence that negative emotions such as anxiety raise lactate in the cingulate cortex, at least in bipolar depression, because of a shift towards anaerobic metabolism (Machado-Vieira et al., 2017). Hereby Machado-Vieira and colleagues (2017) hypothesized a metabolism shift toward the anaerobic metabolism which would be in line with our results. In addition, a lactate-associated pH decrease in the frontal lobes was seen in patients with bipolar disorder (Quiroz, Gray, Kato, & Manji, 2008).
α-Hederin inhibits the growth of lung cancer A549 cells in vitro and in vivo by decreasing SIRT6 dependent glycolysis
Published in Pharmaceutical Biology, 2021
Cong Fang, Yahui Liu, Lanying Chen, Yingying Luo, Yaru Cui, Ni Zhang, Peng Liu, Mengjing Zhou, Yongyan Xie
Reprogramming energy metabolism is a hallmark of cancer. Energy metabolism is the process in which energy is generated from nutrients, released, stored, and consumed by organisms or living cells. Energy metabolism is divided into glucose metabolism, protein metabolism, and fat metabolism. Under normal conditions, cells generate energy primarily via aerobic respiration. When the oxygen content is insufficient, cells perform glycolysis to generate energy. This process is called anaerobic respiration. Unlike normal cells, tumour cells generate energy primarily via glycolysis, even under aerobic conditions, a phenomenon known as the Warburg effect. Glycolytic capacity is characterized by rapid productivity and low efficiency. The rapid proliferation of tumour cells requires rapid energy consumption. Meanwhile, the lactic acid generated by glycolysis creates an acidic environment for tumour cells, which is conducive to their growth and leads to their rapid proliferation (Zhao et al. 2014; Potter et al. 2016). Sirtuin 6 (SIRT6) protein is a chromatin binding factor that was initially described as an inhibitor of gene instability (Mostoslavsky et al. 2006). During energy metabolism, SIRT6 regulates the fat and glucose metabolism, which is a key regulator of energy stress and is closely related to the process of tumour growth (Sebastián and Mostoslavsky 2015). With the metabolic profile used for energy production is elucidated, regulating tumour metabolism is a new therapeutic strategy to inhibit tumour growth (Zhang and Yang 2013).
Isocapnic buffering phase: a useful indicator of exercise endurance in patients with coronary artery disease
Published in The Physician and Sportsmedicine, 2018
Yun-Shan Yen, Daniel Chiung Jui Su, Kuo-Shu Yuan, Po-Wei Chen, Julie Chi Chow, Willy Chou
The IB phase duration is influenced by many factors including lactate production from anaerobic metabolism, buffering ability, and chemoreceptor sensitivity [3]. After the 1st VT, anaerobic metabolism is initiated in addition to ongoing aerobic metabolism. If the rate of aerobic metabolism is higher than that of anaerobic metabolism, the IB phase duration is extended because of a slow increase in lactic acidosis. Efficient oxygen transportation from the capillary to the mitochondria in skeletal muscle suggests high efficiency of aerobic metabolism [10,12] and consequently prolongs the IB phase duration. Moreover, higher peripheral oxygen uptake results in higher endurance performance and higher peak VO2 [10], which can indicate both central and peripheral components of cardiopulmonary function [10]. Among all CPET parameters, peak VO2 most remarkably represents aerobic capacity and endurance performance in CAD patients [9,13]. Therefore, as peak VO2 significantly correlated with the IB phase duration in our study, the IB phase could be another indicator of aerobic capacity and endurance performance in patients with CAD.
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