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The Metabolic Cart
Published in Michael M. Rothkopf, Jennifer C. Johnson, Optimizing Metabolic Status for the Hospitalized Patient, 2023
Michael M. Rothkopf, Jennifer C. Johnson
For example, when we eat carbohydrates, the gastrointestinal (GI) tract digests them into glucose, which is absorbed and delivered to the bloodstream. The cells then transport the glucose into the cytoplasm, where the Embden–Meyerhoff (cytosolic) pathway converts glucose into pyruvate. The pyruvate dehydrogenase complex then makes pyruvate into acetyl CoA. This pathway produces energy, but the net gain from the cytosolic process is only two molecules of ATP.
Mitochondrial Dysfunction in Chronic Disease
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Christopher Newell, Heather Leduc-Pessah, Aneal Khan, Jane Shearer
Acting as a tight barrier to all ions and molecules from the matrix and intermembrane space, the IMM utilizes a proton gradient to drive ATP synthesis. Embedded in the IMM are a series of large enzyme complexes, which generate this proton gradient, collectively termed the electron transport system (ETS) (Figure 26.1). Once liberated from metabolic substrates, electrons are shuttled through the ETS via NADH dehydrogenase (Complex I) or succinate dehydrogenase (SDH; Complex II). Electrons are then carried by the mobile electron carrier ubiquinone (coenzyme Q or CoQ) to cytochrome c reductase (Complex III) before being transferred to cytochrome c, with cytochrome c oxidase (COX; Complex IV) eventually receiving the electrons. Complex IV enables O2 to accumulate four electrons, which generates one molecule of H2O. The drop in free energy that occurs drives proton pumping at Complexes I, III, and IV from the matrix into the mitochondrial intermembrane space. Complex II only transfers electrons to coenzyme Q and does not help generate the proton gradient. The proton redistribution established by mitochondrial respiration maintains and modulates the IMM proton gradient, which drives the formation of ATP via mitochondrial ATP synthase (Complex V). Interestingly, the organization of mitochondrial cristae is tightly linked to the location of ETS enzyme complexes embedded in the IMM (64).
Ultratrace Minerals
Published in Luke R. Bucci, Nutrition Applied to Injury Rehabilitation and Sports Medicine, 2020
Borates and other organoboron compounds inhibit two major classes of enzymes — oxidoreductases and serine proteases.1001,1006 In oxidoreductases, boron competes with pyridine or flavin nucleotide cofactors (NADH, NADPH, and FAD).1001 Examples include alcohol dehydrogenase, xanthine oxidase, glyceraldehyde-3-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and cytochrome b5 reductase.1002 Thrombin, chymotrypsin, and subtilisin are known to be inhibited by borate.1001 Other serine proteases are important mediators of inflammation and resulting tissue damage.150 Thus, boron may possess potential antiinflammatory actions by inhibition of enzymes used to promote inflammation, tissue degradation, and leukocyte respiratory burst (free radical formation). However, before any conclusions about the antiinflammatory nature of boron can be made, concentrations for in vitro effects must be matched to localized in vivo levels. The possible antiinflammatory effects of boron compounds deserve further attention.
Hyperglycaemia and the risk of post-surgical adhesion
Published in Archives of Physiology and Biochemistry, 2022
Gordon A. Ferns, Seyed Mahdi Hassanian, Mohammad-Hassan Arjmand
Hyperglycaemia increases superoxide production (Nishikawa et al.2000). Under hyperglycaemic conditions, there is increased glucose entering the glycolytic pathway (important biochemical pathway in the cells for glucose metabolism) that produced two molecules of pyruvate. In aerobic conditions, pyruvates are converted to acetyl-CoA by pyruvate dehydrogenase. Acetyl-CoA produced by pyruvate entered to the Krebs cycle in mitochondria. Three molecules of NADH are produced by each Krebs cycle (Sabri 1984). NADH is an electron carrier to transport electron in complex 1 of the electron transport chain in mitochondria for ATP synthesis. An excessive amount of NADH causes reductive stress by intracellular production of superoxide O2– (Liu et al.2002) (Figure 3). Superoxide is one of the most important ROS factors and can damage biomolecules and increase of inflammation (McCord 1980). Increase of ROS such as superoxide causes excessive production of proinflammatory cytokines and growth factors by immune cells which are associated with adhesion formation post-surgical (Fortin et al.2015).
Metformin mitigates impaired testicular lactate transport/utilisation and improves sexual behaviour in streptozotocin-induced diabetic rats
Published in Archives of Physiology and Biochemistry, 2021
Victor Udo Nna, Ainul Bahiyah Abu Bakar, Azlina Ahmad, Mahaneem Mohamed
Lactate dehydrogenase catalyses the interconversion of pyruvate (formed as a result of glycolysis) to lactate. When formed, pyruvate can either be: (i) interconverted to alanine by alanine transaminase, (ii) interconverted to lactate by LDH, or (iii) transferred into tricarboxylic acid cycle (Yang et al.2002, Alves et al.2013b). Increased intra-testicular LDH activity and lactate level in DC group in the present study suggests that the interconversion of pyruvate to lactate was prioritised among the three possible endpoints of pyruvate mentioned above, in a bid to up-regulate lactate production. Also, increased LDH activity in DC group may be a negative feedback targeted at producing more lactate since lactate transporters (MCTs) and LDHc were down-regulated. Interestingly, treatment with metformin decreased intra-testicular glucose and lactate levels, leading us to suggest that testicular GCs utilisation of lactate may be responsible for the decreased intra-testicular lactate levels. This is so because regardless of the up-regulation of GLUT3 mRNA transcript level, glucose level decreased, and LDH activity also decreased following treatment with metformin.
Fisetin Improved Rotenone-Induced Behavioral Deficits, Oxidative Changes, and Mitochondrial Dysfunctions in Rat Model of Parkinson’s Disease
Published in Journal of Dietary Supplements, 2021
Kanakalatha Alikatte, Suresh Palle, Jadi Rajendra Kumar, Naveen Pathakala
Succinate dehydrogenase was assayed according to the previously described method (King et al. 1976). This assay is based on the oxidation of succinate to fumarate by an artificial electron acceptor, potassium ferricyanide, catalyzed by enzyme succinate dehydrogenase. In this procedure, the reaction was initiated by the addition of a requisite amount of mitochondrial sample to the reaction mixture containing 0.2M sodium phosphate buffer (PB) (pH 7.8), 1% (w/v) bovine serum albumin, 0.6M sodium succinate, and 0.03M potassium ferricyanide. The change in absorbance was measured at 420nm for 3min. The concentration of succinate dehydrogenase was expressed as nano moles of succinate oxidized/min/mg protein using molar extinction coefficient (1000M−1cm−1).