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Metabolism
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 combustion of fatty acids, the major energy component of fats, commences with their activation to CoA derivatives such as palmitoyl CoA. Palmitoyl CoA must be first converted to palmitoylcarnitine by carnitine-palmitoyltransferase in the outer mitochondrial membrane before it can enter the mitochondrion. At the inner mitochondrial membrane, palmitoyl carnitine is reconverted to palmitoyl CoA and then oxidized by β-oxidation, which releases two carbon compounds as acetyl CoA until the entire fatty acid molecule is broken down. β-Oxidation of free fatty acids provides a major source of acetyl CoA, an important substrate for the citric acid cycle. Free fatty acids in blood, derived from the diet or by the action of lipoprotein lipase on lipoproteins at the endothelial cell layer of tissue, are oxidized in the mitochondria. Growth hormone and glucocorticoid increase the mobilization of fat stores by increasing the amount of triglyceride lipase. Initially, free fatty acid is converted to acyl CoA utilizing one ATP. Acyl CoA is oxidized to acetyl CoA, and the residual carbon atoms re-enter the cycle to produce more acetyl CoA (Figure 65.6). This partial oxidation of free fatty acids produces hydrogen ions that are removed as NADH and reduced flavoproteins.
Carnitine palmitoyl transferase II deficiency, lethal neonatal
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
Long-chain fatty acids require a carnitine transport system in order to gain entrance to the mitochondrial matrix where β-oxidation takes place. CPT II is located on the inner side of the inner mitochondrial membrane. It catalyzes the conversion of long-chain acylcarnitine esters, like palmitoylcarnitine, to free carnitine and the corresponding CoA ester, such as palmitoyl CoA.
Metabolic Cardiology
Published in Stephen T. Sinatra, Mark C. Houston, Nutritional and Integrative Strategies in Cardiovascular Medicine, 2015
More recently, free l-carnitine levels and levels of its derivative palmitoyl-carnitine were increased in CHF patients and correlated with NT-Pro-BNP and NYHA functional class status. In this study of 183 heart failure patients and 111 healthy controls, higher levels of palmitoyl-carnitine were also associated with more adverse outcomes. The authors believed these findings suggested prognostic value and recommended additional investigational analysis of l-carnitine administration in heart failure candidates.70
Logistic role of carnitine shuttle system on radiation-induced L-carnitine and acylcarnitines alteration
Published in International Journal of Radiation Biology, 2022
Acylcarnitines represent a ‘dormant’ pool of acyl groups that may be used in biochemical pathways upon their conversion back into acyl-CoA esters by carnitine acyltransferases (Adeva Andany et al. 2017). Acyl groups pool provides activated substrates for many critical metabolic pathways such as tricarboxylic acid cycle (TCA), lipid, and cholesterol synthesis for proteins posttranslational modification and detoxication mechanisms (Niu et al. 2019). In this context, acetylcarnitine (C2) donates acetyl group for histone acetylation to modulate epigenetic properties. Acetyl-L-carnitine can be converted into malonyl-CoA in the cytosol to inhibit the activity of CPT1 and reduce the oxidation of fatty acids, which results in eliminating the adverse reactions caused by the accumulation of acyl-CoA metabolic intermediates in the mitochondria (Casals et al. 2016). The long-chain acylcarnitines, notably palmitoylcarnitine, are related to palmitoylation levels of specific proteins (Chen et al. 2017; Niu et al. 2019; Yao et al. 2019). Palmitoylation of proteins is a pervasive posttranslational modification that regulates the transport, compartmentalization and stability of protein, involved in many biological processes such as apoptosis and proliferation.
How could we forget immunometabolism in SARS-CoV2 infection or COVID-19?
Published in International Reviews of Immunology, 2021
Several acylcarnitines, including palmitoylcarnitine, stearoylcarnitine, and oleoylcarnitine decrease in COVID-19 patients. Reduced circulating levels of acylcarnitines may indicate the attenuated entry of fatty acids in the mitochondria for β-oxidation or fatty acid oxidation (FAO) [110]. TCA cycle metabolites (citrate, succinate, etc.) generally decrease in COVID-19 patients, which decrease further with the severity of the infection. Hence, decreased TCA cycle metabolites in the circulation in severe COVID-19 patients may indicate a declined metabolic response to the decreased lung functions and blood oxygen to lower reliance on oxygen for cellular energy production [110]. Lactate dehydrogenase (LDH) increases in immune cells with increasing COVID-19 severity (indicating the increased glycolysis and conversion of pyruvate into lactate), but plasma lactate level does not significantly alter in COVID-19 patients in comparison to controls [110].
Liver metabolomic characterization of Sophora flavescens alcohol extract-induced hepatotoxicity in rats through UPLC/LTQ-Orbitrap mass spectrometry
Published in Xenobiotica, 2020
Peng Jiang, Yancai Sun, Nengneng Cheng
The liver metabolomic results of the rats after they were orally exposed to SFAE showed a disturbance of fatty acid metabolism. Increased acetylcarnitine, l-carnitine, stearoylcarnitine and palmitoylcarnitine levels and decreased 3-hydroxybutyric acid levels indicated the inhibition of ketone body generation, which is the primary cause of steatosis. Betaine also plays a role in the manufacture of carnitine and protects kidneys from damage. Betaine insufficiency is associated with lipid disorders, metabolic syndrome and diabetes (Pekkinen et al., 2013). Betaine is also widely regarded as an anti-oxidant and used to treat liver disorders. Palmitoylcarnitine significantly increases from normal levels in steatosis samples. Alterations in carnitine levels are a result of abnormal lipid metabolism and high lipid loads (Schooneman et al., 2013).