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1.
Influence of caffeine intake on intravenous adenosine-induced fractional flow reserve.
Kasumi, I, Fujii, K, Satoru, O, Shin, T, Katsuyuki, H, Hiroto, T, Rui, I, Shingo, Y, Sho, N, Wataru, Y, et al
Journal of cardiology. 2020;(5):472-478
Abstract
BACKGROUND This study evaluated whether caffeine abstention is required before fractional flow reserve (FFR) measurement by intravenous adenosine triphosphate (ATP) administration in Japanese patients. METHODS This study was a subanalysis of a previously published study and a total of 208 intermediate lesions that underwent FFR measurements were enrolled for this analysis. Hyperemia was induced by continuous intravenous ATP infusion at 150 μg/kg/min (IVATP150) and 210 μg/kg/min (IVATP210), and by intracoronary administration of nicorandil 2 mg (ICNIC2mg) as a reference standard. RESULTS The degree of change in the FFR value after ICNIC2mg and IVATP210 was similar between the caffeine and non-caffeine groups (0.00 ± 0.02 vs. 0.01 ± 0.02). In patients who consumed caffeine before the FFR measurement, the degree of FFR change was independent of the time interval (<12 h, 12-24 h, and 24-48 h) between caffeine intake and catheterization both after IVATP150 and ICNIC2mg and after IVATP210 and ICNIC2mg. CONCLUSION When compared with the FFR value after ICNIC2mg, the degree of change in the FFR value after IVATP210 were similar regardless of caffeine intake. Strict caffeine abstention before intravenous ATP-induced FFR measurement may not be required in clinical practice.
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Quantitative analysis of amino acid metabolism in liver cancer links glutamate excretion to nucleotide synthesis.
Nilsson, A, Haanstra, JR, Engqvist, M, Gerding, A, Bakker, BM, Klingmüller, U, Teusink, B, Nielsen, J
Proceedings of the National Academy of Sciences of the United States of America. 2020;(19):10294-10304
Abstract
Many cancer cells consume glutamine at high rates; counterintuitively, they simultaneously excrete glutamate, the first intermediate in glutamine metabolism. Glutamine consumption has been linked to replenishment of tricarboxylic acid cycle (TCA) intermediates and synthesis of adenosine triphosphate (ATP), but the reason for glutamate excretion is unclear. Here, we dynamically profile the uptake and excretion fluxes of a liver cancer cell line (HepG2) and use genome-scale metabolic modeling for in-depth analysis. We find that up to 30% of the glutamine is metabolized in the cytosol, primarily for nucleotide synthesis, producing cytosolic glutamate. We hypothesize that excreting glutamate helps the cell to increase the nucleotide synthesis rate to sustain growth. Indeed, we show experimentally that partial inhibition of glutamate excretion reduces cell growth. Our integrative approach thus links glutamine addiction to glutamate excretion in cancer and points toward potential drug targets.
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Functions of Cytochrome c oxidase Assembly Factors.
Watson, SA, McStay, GP
International journal of molecular sciences. 2020;(19)
Abstract
Cytochrome c oxidase is the terminal complex of eukaryotic oxidative phosphorylation in mitochondria. This process couples the reduction of electron carriers during metabolism to the reduction of molecular oxygen to water and translocation of protons from the internal mitochondrial matrix to the inter-membrane space. The electrochemical gradient formed is used to generate chemical energy in the form of adenosine triphosphate to power vital cellular processes. Cytochrome c oxidase and most oxidative phosphorylation complexes are the product of the nuclear and mitochondrial genomes. This poses a series of topological and temporal steps that must be completed to ensure efficient assembly of the functional enzyme. Many assembly factors have evolved to perform these steps for insertion of protein into the inner mitochondrial membrane, maturation of the polypeptide, incorporation of co-factors and prosthetic groups and to regulate this process. Much of the information about each of these assembly factors has been gleaned from use of the single cell eukaryote Saccharomyces cerevisiae and also mutations responsible for human disease. This review will focus on the assembly factors of cytochrome c oxidase to highlight some of the outstanding questions in the assembly of this vital enzyme complex.
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4.
Peroxisomal Cofactor Transport.
Plett, A, Charton, L, Linka, N
Biomolecules. 2020;(8)
Abstract
Peroxisomes are eukaryotic organelles that are essential for growth and development. They are highly metabolically active and house many biochemical reactions, including lipid metabolism and synthesis of signaling molecules. Most of these metabolic pathways are shared with other compartments, such as Endoplasmic reticulum (ER), mitochondria, and plastids. Peroxisomes, in common with all other cellular organelles are dependent on a wide range of cofactors, such as adenosine 5'-triphosphate (ATP), Coenzyme A (CoA), and nicotinamide adenine dinucleotide (NAD). The availability of the peroxisomal cofactor pool controls peroxisome function. The levels of these cofactors available for peroxisomal metabolism is determined by the balance between synthesis, import, export, binding, and degradation. Since the final steps of cofactor synthesis are thought to be located in the cytosol, cofactors must be imported into peroxisomes. This review gives an overview about our current knowledge of the permeability of the peroxisomal membrane with the focus on ATP, CoA, and NAD. Several members of the mitochondrial carrier family are located in peroxisomes, catalyzing the transfer of these organic cofactors across the peroxisomal membrane. Most of the functions of these peroxisomal cofactor transporters are known from studies in yeast, humans, and plants. Parallels and differences between the transporters in the different organisms are discussed here.
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5.
Antiplatelet Effect of Carbon Monoxide Is Mediated by NAD+ and ATP Depletion.
Kaczara, P, Sitek, B, Przyborowski, K, Kurpinska, A, Kus, K, Stojak, M, Chlopicki, S
Arteriosclerosis, thrombosis, and vascular biology. 2020;(10):2376-2390
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Abstract
OBJECTIVES Carbon monoxide (CO) produced by haem oxygenases or released by CO-releasing molecules (CORM) affords antiplatelet effects, but the mechanism involved has not been defined. Here, we tested the hypothesis that CO-induced inhibition of human platelet aggregation is mediated by modulation of platelet bioenergetics. Approach and Results: To analyze the effects of CORM-A1 on human platelet aggregation and bioenergetics, a light transmission aggregometry, Seahorse XFe technique and liquid chromatography tandem-mass spectrometry-based metabolomics were used. CORM-A1-induced inhibition of platelet aggregation was accompanied by the inhibition of mitochondrial respiration and glycolysis. Interestingly, specific inhibitors of these processes applied individually, in contrast to combined treatment, did not inhibit platelet aggregation considerably. A CORM-A1-induced delay of tricarboxylic acid cycle was associated with oxidized nicotinamide adenine dinucleotide (NAD+) depletion, compatible with the inhibition of oxidative phosphorylation. CORM-A1 provoked an increase in concentrations of proximal (before GAPDH [glyceraldehyde 3-phosphate dehydrogenase]), but not distal glycolysis metabolites, suggesting that CO delayed glycolysis at the level of NAD+-dependent GAPDH; however, GAPDH activity was directly not inhibited. In the presence of exogenous pyruvate, CORM-A1-induced inhibition of platelet aggregation and glycolysis were lost, but were restored by the inhibition of lactate dehydrogenase, involved in cytosolic NAD+ regeneration, pointing out to the key role of NAD+ depletion in the inhibition of platelet bioenergetics by CORM-A1. CONCLUSIONS The antiplatelet effect of CO is mediated by inhibition of mitochondrial respiration-attributed to the inhibition of cytochrome c oxidase, and inhibition of glycolysis-ascribed to cytosolic NAD+ depletion.
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Modern theory of energy coupling and ATP synthesis. Violation of Gauss's law by the chemiosmotic theory and validation of the two-ion theory.
Nath, S
Biophysical chemistry. 2019;:106271
Abstract
Adenosine triphosphate (ATP) is the universal biological energy fuel, or nature's gasoline. The vast quantities of ATP required for sustenance of living processes in cells are synthesized by oxidative phosphorylation and photosynthesis. The chemiosmotic theory of energy coupling was proposed by Mitchell more than 50 years ago but has a contentious history. Part of the accumulated body of experimental evidence supports Mitchell's theory, and part of the evidence conflicts with the theory. Although Mitchell's theory was strongly criticized by several prominent scientists, the controversy was never resolved. Certain theoretical arguments and electrostatic calculations were originally made to justify the central tenet of the chemiosmotic theory of electrogenic proton transfer and violation of electrical neutrality in bulk aqueous phases by creation of a delocalized field. However, these calculations have not been scientifically scrutinized previously. Here it is proved from first principles that the original physical arguments and calculations made in support of steady state electrogenic ion transfer and chemiosmosis violate Gauss's law. Nath's two-ion theory of energy coupling in which the field is local, and ion translocation is dynamically electrogenic but overall electroneutral is shown to satisfactorily resolve the difficulties. Characterization of length scales in mitochondrial systems is shown to impose strong constraints on possible mechanisms of energy transduction. Some biological implications for energy coupling, transduction and ATP synthesis arising as a result of the above analysis are discussed. Examples of several other biological processes where the new theory is useful such as apoptosis, muscle contraction, the joint multisite regulation of oxidative phosphorylation and the Krebs cycle, and hindered protein aggregation arising from ATP's hydrotropic properties are outlined.
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ATP in the tumour microenvironment drives expression of nfP2X7, a key mediator of cancer cell survival.
Gilbert, SM, Oliphant, CJ, Hassan, S, Peille, AL, Bronsert, P, Falzoni, S, Di Virgilio, F, McNulty, S, Lara, R
Oncogene. 2019;(2):194-208
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Abstract
The ATP-gated receptor P2X7 is expressed in multiple malignant tumours including neuroblastoma, melanoma, prostate, lung and breast. P2X7 has a significant role in mediating diverse cell responses, which upon dysregulation are associated with tumour initiation and development. The rapid, ATP-mediated activation of P2X7 induces a fast-inward cation current in cells. However, prolonged ATP-mediated activation of P2X7 leads to formation of a pore that increases membrane permeability and eventually causes cell death. This presents a potential paradox, as the tumour microenvironment contains extracellular ATP at levels sufficient to activate the P2X7 pore and trigger cell death. However, P2X7 expression is associated with enhanced cancer cell survival, proliferation and metastatic potential. At least one distinct conformational form of P2X7, termed non-pore functional P2X7 (nfP2X7), has been described, which is not able to form a functional pore. We demonstrate for the first time in this study that exposure to a high ATP concentration, equivalent to those measured in the tumour microenvironment, drives nfP2X7 expression and also that nfP2X7 is essential for tumour cell survival. We show that monoclonal antibodies raised against a P2X7 amino acid sequence (200-216), whose conformation is distinct from that of wild-type (WT) P2X7, bind specifically to nfP2X7 expressed on the surface of tumour cells. We also show that nfP2X7 is broadly expressed in patient-derived tumour sections from a wide range of cancers. Therefore, antibodies raised against E200 provide tools that can differentiate between forms of the P2X7 receptor that have a key role in cancer.
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Effect of gummy candy containing ubiquinol on secretion of saliva: A randomized, double-blind, placebo-controlled parallel-group comparative study and an in vitro study.
Ushikoshi-Nakayama, R, Ryo, K, Yamazaki, T, Kaneko, M, Sugano, T, Ito, Y, Matsumoto, N, Saito, I
PloS one. 2019;(4):e0214495
Abstract
A randomized, double-blind, placebo-controlled, parallel-group comparative clinical study was conducted to examine the effects of ubiquinol (the reduced form of Coenzyme Q10) on secretion of saliva. This interventional study enrolled 40 subjects aged 65 years or younger who were healthy, but noted slight dryness of the mouth. Subjects were randomized with stratification according to gender and age to ingestion of gummy candy containing 50 mg of ubiquinol or placebo twice daily for 8 weeks. At the end of study, along with a significant increase of the CoQ10 level in saliva (p = 0.025*, d = 0.65), there was a significant increase of the saliva flow rate (p = 0.048*, d = 0.66) in the ubiquinol candy group (n = 18; 47.4±6.2 years; 6 men and 12 women) compared to the placebo group (n = 20; 52.2±7.7 years; 4 men and 16 women). The strength of the stomatognathic muscles was not significantly enhanced by ingestion of ubiquinol candy. Compared with baseline, significant improvement of the following four questionnaire items was observed in the ubiquinol group at the end of the study: feeling tired (p = 0.00506, d = -0.726), dryness of the mouth (p = 0.04799, d = -0.648), prone to catching a cold (p = 0.00577, d = -0.963), and diarrhea (p = 0.0166, d = -0.855). There were no serious adverse events. An in vitro study revealed that ubiquinol stimulated a significant and concentration-dependent increase of ATP production by a cell line derived from human salivary gland epithelial cells (p<0.05), while 1 nM ubiquinol significantly suppressed (p = 0.028) generation of malondialdehyde by cells exposed to FeSO4-induced oxidative stress. These findings suggest that ubiquinol increases secretion of saliva by suppressing oxidative stress in the salivary glands and by promoting ATP production. Trial Registration: UMIN-CTR UMIN000024406.
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A Single Dose of Oral ATP Supplementation Improves Performance and Physiological Response During Lower Body Resistance Exercise in Recreational Resistance-Trained Males.
Freitas, MC, Cholewa, JM, Gerosa-Neto, J, Gonçalves, DC, Caperuto, EC, Lira, FS, Rossi, FE
Journal of strength and conditioning research. 2019;(12):3345-3352
Abstract
Freitas, MC, Cholewa, JM, Gerosa-Neto, J, Gonçalves, DC, Caperuto, EC, Lira, FS, and Rossi, FE. A single dose of oral ATP supplementation improves performance and physiological response during lower body resistance exercise in recreational resistance-trained males. J Strength Cond Res 33(12): 3345-3352, 2019-The aim of this study was to investigate the acute effect of adenosine-5'-triphosphate (ATP) supplementation on performance and physiological responses during resistance exercise in recreationally resistance-trained males. Eleven men (age = 27.5 ± 5.5 years, mass = 83.4 ± 9.8 kg, height = 182 ± 0.04 cm) completed 2 randomized, double-blind trials: ATP supplement condition (ATP = 400 mg) or a placebo condition. Thirty minutes after supplement consumption, subjects performed 4 sets of half-squats until momentary muscular failure at 80% of the 1 repetition maximum with 2 minutes of recovery between sets. The total number of repetitions, blood pressure, heart rate, blood lactate, and oxygen consumption were evaluated. The total weight lifted were higher for the ATP condition compared with placebo (Placebo = 3,995.7 ± 1,137.8, ATP = 4,967.4 ± 1,497.9 kg; p = 0.005). Heart rate was higher at set-4 for ATP compared with placebo (p < 0.001) and oxygen consumption during exercise was greater for ATP (p = 0.021). There were no differences between conditions for lactate and blood pressure. In summary, a single oral dose of ATP supplementation improved lower-body resistance training performance and energy expenditure in recreational resistance-trained males.
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ATP, Mg2+, Nuclear Phase Separation, and Genome Accessibility.
Wright, RHG, Le Dily, F, Beato, M
Trends in biochemical sciences. 2019;(7):565-574
Abstract
Misregulation of the processes controlling eukaryotic gene expression can result in disease. Gene expression is influenced by the surrounding chromatin; hence the nuclear environment is also of vital importance. Recently, understanding of chromatin hierarchical folding has increased together with the discovery of membrane-less organelles which are distinct, dynamic liquid droplets that merge and expand within the nucleus. These 'sieve'-like regions may compartmentalize and separate functionally distinct regions of chromatin. This article aims to discuss recent studies on nuclear phase within the context of poly(ADP-ribose), ATP, and Mg2+ levels, and we propose a combinatorial complex role for these molecules in phase separation and genome regulation. We also discuss the implications of this process for gene regulation and discuss possible strategies to test this.