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Exercise Physiology
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The lactate then enters the blood and is carried to the liver, where it is converted to pyruvate and then to glucose (i.e., gluconeogenesis). This hepatic glucose enters the blood and reaches the muscle to be used for muscle contraction. This is called the Cori cycle, whereby liver converts the anaerobic metabolic product (lactate) to a fuel (glucose) that can be used anaerobically.
Muscle Fiber Types
Published in Charles Paul Lambert, Physiology and Nutrition for Amateur Wrestling, 2020
About 75% of the lactic acid produced during exercise is combusted or oxidized for energy. Two concepts underlie this phenomenon. The intracellular lactate shuttle and the cell–cell lactate shuttle. In the intracellular lactate shuttle concept, lactate from muscle fibers is produced and oxidized in those same muscle fiber. In the cell–cell lactate shuttle lactate is produced in fast twitch glycolytic fibers and goes to slow twitch oxidative fibers for oxidation either by going to adjacent muscle fibers or circulating through the blood (Brooks, Fahey, and Baldwin 2005). Another fate of lactate is called the Cori Cycle, where lactate produced from muscle fibers goes to the liver through the blood stream and is converted to glucose. The glucose either gets converted to glycogen in the liver or goes back to the muscle and is used for fuel (Brooks, Fahey, and Baldwin 2005). These three mechanisms would appear to be important during wrestling as it is extremely intermittent with periods of intense lactic acid building time and periods of less intense exercise where lactate could be oxidized in the cell it was produced in, oxidized in an adjacent muscle fiber, or released into the circulation for conversion to glucose by the liver (Cori Cycle) (Table 8.2).
Features of Lipid Metabolism in Diabetes Mellitus and Ischemic Heart Disease
Published in E.I. Sokolov, Obesity and Diabetes Mellitus, 2020
Intermediate metabolism of glucose, whose main substrate is lactate, occurs in a human organism in most tissues, where the produced lactate is oxidized in the Krebs cycle and does not enter the blood channel. The main sources of lactate are erythrocytes, the medullary substance of the kidneys, and, possibly, the brain. Under a physical load, the growth in the lactate content in the blood is due to the sharp increase in anaerobic glycolysis in the muscles. In the restoration period after a physical load, after hypoxia 10% of the lactate formed in a person’s muscles gets into the blood channel, 15% is oxidized to CO2, and 75% of the muscular lactate transforms into glycogen directly in the muscle tissues. The main pool of lactate undergoes metabolism in the Cori cycle. The lactate formed in the tissues is transferred to the kidneys and livers where it transforms into glucose. The latter again enters the tissues and is oxidized to lactate. In the long run, all the circulating lactate is utilized by the organism — 50% in the skeletal muscles and the heart, 30% in the liver, and 20% in the brain and cortical substance of the kidneys.
Pharmacotherapeutic options for cancer cachexia: emerging drugs and recent approvals
Published in Expert Opinion on Pharmacotherapy, 2023
Lorena Garcia-Castillo, Giacomo Rubini, Paola Costelli
Implying the dissipation of energy via thermogenesis, UCP up-regulation in the skeletal muscle and in the adipose tissue is one of the main causes of REE elevation in cachexia. This phenomenon is closely related to inflammation, as the UCPs are induced by pro-inflammatory cytokines, such as TNF-α and IL-6 [7,8]. Furthermore, the sarcoplasmic reticulum Ca2+-ATPase and other ATPases can be involved in energetic inefficiency, producing heat through the uncoupling of ATP hydrolysis. Additionally, in the context of ATP mismanagement, mitochondrial ATP synthesis in the skeletal muscle can be impaired, for example, due to proton leakage from the inner mitochondrial membrane. Finally, abnormalities in carbohydrate, protein, and lipid metabolism can lead to REE elevation through the activation of futile cycles. These latter consist in the cycling of metabolic intermediates using ATP without metabolic gain and generating heat, thus representing a source of energetic inefficiency. Such inefficient metabolic cycles can also be established as a consequence of tumor metabolisms, such as lactate recycling (Cori cycle) between the tumor and the host [7].
Glutathione reductase and catalase as potential biomarkers for synergistic intoxication of pesticides in fish
Published in Biomarkers, 2019
Ankur Khare, Naina Chhawani, Kanchan Kumari
LDH is a marker enzyme for cardiac function and indicates the aerobic capacity of the tissues and is inducible by oxygen stress. In this study, LDH activity has been studied in the muscle, serum to make a comparative evaluation of muscle metabolism following the treatment of the two pesticides individually and in combination. The concomitant increase in LDH levels were observed in the fish till 96 h of the study in synergistic group. This shift in anaerobic respiration was a defense mechanism to cope up with the pollutant stress. To overcome the stress and oxygen debts, muscle glycogen breaks down to glucose and favors anaerobic catabolism of glucose to lactate in muscles through Cori cycle (Abhijit et al.2016, Das et al.2004, Khan et al.2008). Next to this, lactate in mitochondria coverts to pyruvate that enters the tricarboxylic acid (TCA) cycle and supply energy in the form of adenosine triphosphate (ATP) to fish body to cope in conditions of stress. Therefore, in this study, LDH activity elevates favoring anaerobic metabolism over the aerobic one. Similar findings have been reported by Kumari and Sinha (2010) and Abhijit et al. (2016) in toad, Bufo melanostictus and Catla Catla, respectively as a function of methyl parathion.
The role of the clinical laboratory in diagnosing acid–base disorders
Published in Critical Reviews in Clinical Laboratory Sciences, 2019
In lactic acidosis, a hydrogen ion is consumed, and bicarbonate is generated, resulting in resolution of the metabolic acidosis. Lactic acidosis with high lactate levels, therefore, requires increased production and/or decreased clearance [180]. About 60% of lactate clearance occurs in the liver and 30% is cleared through the kidneys. Utilization occurs via the Cori cycle in which lactate is converted back to pyruvate and eventually to glucose through gluconeogenesis, as a major route to l-lactate clearance (about 20%) [181–183]. Lactic acid is primarily oxidized to carbon dioxide and water (70–80%). Thus, in a patient who has accumulated lactic acid, utilization of the lactate will (after conversion to pyruvate) restore the bicarbonate concentration: 184].