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Bioenergetics
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
In adipocytes, there are two enzymes that are involved in degrading triglycerides: hormone-sensitive lipase and adipose triglyceride lipase. Adipose triglyceride lipase has a greater affinity for triglycerides compared to hormone sensitive lipase, and acts as the primary enzyme for triglyceride hydrolysis in adipocytes. Hormone sensitive lipase is found in small concentrations in muscle and can provide an intramuscular source of FFA and glycerol. In the sarcoplasm of muscle fibers, FFA are bound to CoA. Using a carnitine carrier, the FFA -acyl CoA molecule enters the mitochondria (35, 51, 129, 143). The triglyceride “backbone” glycerol can be converted to glycerol 3 phosphate and enter glycolysis for energy production.
Impairment of Lipid Metabolism in Ischemic and Reperfused Myocardial Tissue
Published in Samuel Sideman, Rafael Beyar, Analysis and Simulation of the Cardiac System — Ischemia, 2020
Ger J. van der Vusse, Marc van Bilsen, Robert S. Reneman
Theoretically, both extracellular and intracellular sources of fatty acids can contribute to the accumulation of lipid intermediates in the acute phase of ischemia. Experimental findings of Neely and coworkers19 and Moore and colleagues14,16 strongly suggest that the acyl moieties of the accumulated lipid intermediates are mainly derived from extracellular fatty acids. With respect to the intracellular fatty acid pool, no signs of depletion of phosphoglycerides have been found in tissue subjected to relatively short periods of ischemia.3,6,25 A second intracellular pool of fatty acids is triacylglycerol. Three fatty acids are covalently bound to the hydroxyl groups of a glycerol molecule. It has been suggested that the turnover of the triacylglycerol pool is accelerated during ischemia.13,28 Due to mass action of glycerol 3-phosphate, an intermediate of the glycolytic pathway which accumulates in ischemic tissue, (re)synthesis of triacylglycerol is thought to be enhanced (Figure 3). Concomitant activation of intracellular neutral or acid lipase activity, as observed by Heathers and Brunt,8 will result in a virtually unchanged triacylglycerol content,39 increased production of glycerol (and release from the heart during low-flow ischemia and/or reperfusion), and consumption of ATP by "futile cycling" of the triacylglycerol pool.
The Bioenergetics of Mammalian Sperm Motility
Published in Claude Gagnon, Controls of Sperm Motility, 2020
Spermatozoa are capable of metabolizing a wide range of extracellular substrates. Glucose, fructose, and mannose can be metabolized via the glycolytic pathway and the products oxidized in the mitochondrion. The ability of glycolysis to support motility under anaerobic conditions varies from species to species, e.g., it can do so effectively in bull, ram, and human spermatozoa, but not in boar or guinea pig sperm. Pyruvate, lactate, acetate, fatty acids, citric acid cycle intermediates, and amino acids can all be oxidized although not all stimulate oxygen uptake and, in many cases, their metabolism by intact cells is limited by permeability barriers. These data have been extensively reviewed.3-5,19 Glycerol 3-phosphate will stimulate a greater rate of oxygen uptake than any other substrate in rat, ram, and boar spermatozoa, but it is not oxidized at all by human or rabbit spermatozoa and only slowly by rhesus monkey spermatozoa.20 It is possible that glycerol 3-phosphate may arise in the female reproductive tract through the hydrolysis of seminal glyceryl phosphoryl choline.21 Intriguingly, the capacity for glycerol 3-phosphate oxidation parallels the susceptibility of these species to the male contraceptive α-chlorohydrin. Glycerol is metabolized after phosphorylation by glycerol kinase, and it is oxidized much more slowly than glycerol 3-phosphate.3,22
Hypolipidemic and anti-inflammatory properties of phenolic rich Butia odorata fruit extract: potential involvement of paraoxonase activity
Published in Biomarkers, 2020
Vanessa Plasse Ramos, Pamela Gonçalves da Silva, Pathise Souto Oliveira, Natália Pontes Bona, Mayara Sandrielly Pereira Soares, Juliane de Souza Cardoso, Jessica Fernanda Hoffmann, Fábio Clasen Chaves, Augusto Schneider, Roselia Maria Spanevello, Claiton Leoneti Lencina, Francieli Moro Stefanello, Rejane Giacomelli Tavares
Other present compounds, such as chlorogenic acid, has been investigated for its positive effect on glucose regulation, strong antioxidant, anti-inflammatory, and anticancer activities (Kong et al. 2018). Rutin is related to prevents hyperlipidaemia induced by high CHOL diet and promotes the excretion of faecal sterols, decreases the absorption of dietary cholesterol and lowers the plasma and hepatic cholesterol concentration (Monika and Geetha 2015). This compound can also reduce blood insulin, as well as inhibit glycerol-3-phosphate dehydrogenase, an enzyme linked to glycerol and triacylglycerol conversion in adipose tissue and liver (Hossain et al. 2016). In previous studies of our group, Oliveira et al. (2017) demonstrated that the extract of Eugenia uniflora, rich in phenolic compounds, prevented the increase of TG, glucose, CHOL, and LDL-C after a metabolic syndrome induced with a highly palatable diet lasting 150 days. Additionally, Cardoso et al. (2018) showed that the extract of E. uniflora and P. cattleianum prevented the increase in glucose and TG levels in an animal model of insulin resistance induced by dexamethasone.
Research on the hepatotoxicity mechanism of citrate-modified silver nanoparticles based on metabolomics and proteomics
Published in Nanotoxicology, 2018
Jiabin Xie, Wenying Dong, Rui Liu, Yuming Wang, Yubo Li
Choline is a constituent of lecithin and the precursor of acetylcholine, and two choline metabolic pathways may exist. On the one hand, choline can phosphorylate phosphorylcholine and participate in the biosynthesis of phosphatidylcholine. On the other hand, choline can be converted to glycine by dimethylglycine dehydrogenase and sarcosine dehydrogenase. Furthermore, phosphatidate phosphohydrolase can reportedly promote the synthesis of phosphatidylcholine, phosphatidylethanolamine and triacylglycerol (Simpson et al. 1989). Glycerol-3-phosphate is a key metabolite in the translocation of reducing power through mitochondrial glycerol-3-phosphate dehydrogenase. At the same time, glycerol-3-phosphate dehydrogenase, as a major link between carbohydrate metabolism and lipid metabolism, catalyzes the formation of ethanolamine lysophospholipids (Taleux et al. 2009). Glycerol phospholipids are highly biologically active molecules that are involved in inflammatory responses. When the liver is damaged, the expression of cytokine receptors in immune cells, including monocytes, macrophages and dendritic cells is inhibited. With increasing degrees of liver damage, the amounts of cytokines decreases, resulting in decreased liver synthesis, metabolism, and transformation functions. This study showed that the levels of tyrosine, tryptophan, and glycerophospholipid metabolites were reduced and tyrosine aminotransferase, and glycerol-3-phosphate dehydrogenase also showed a downward trend. These affects blocked the biosynthesis of phenylalanine, tyrosine and tryptophan and gave rise to abnormal glycerol phospholipid metabolism, which led to inflammatory reactions and liver damage.
Current and emerging gluconeogenesis inhibitors for the treatment of Type 2 diabetes
Published in Expert Opinion on Pharmacotherapy, 2021
Lipids enter gluconeogenesis through the reduction of dihydroxyacetone phosphate into glycerol 3-phosphate. Glycerol-3-phosphate dehydrogenase is a key step in allowing dephosphorylation of glycerol 3-phosphate into glycerol. This enzyme plays a role in maintaining the mitochondrial membrane redox potential. Metformin is a primary treatment of Type 2 diabetes and inhibits this enzyme [65].