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Dumouchel JL, Kramlinger VM. Case Study 10: A Case to Investigate Acetyl Transferase Kinetics. Methods Mol Biol 2021; 2342:781-808. [PMID: 34272717 DOI: 10.1007/978-1-0716-1554-6_29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Major routes of metabolism for marketed drugs are predominately driven by enzyme families such as cytochromes P450 and UDP-glucuronosyltransferases. Less studied conjugative enzymes, like N-acetyltransferases (NATs), are commonly associated with detoxification pathways. However, in the clinic, the high occurrence of NAT polymorphism that leads to slow and fast acetylator phenotypes in patient populations has been linked to toxicity for a multitude of drugs. A key example of this is the observed clinical toxicity in patients who exhibit the slow acetylator phenotype and were treated with isoniazid. Toxicity in patients has led to detailed characterization of the two NAT isoforms and their polymorphic genotypes. Investigation in recombinant enzymes, genotyped hepatocytes, and in vivo transgenic models coupled with acetylator status-driven clinical studies have helped understand the role of NATs in drug development, clinical study design and outcomes, and potential roles in human disease models. The selected case studies herein document NAT enzyme kinetics to explore substrate overlap from two human isoforms, preclinical species considerations, and clinical genotype population concerns.
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Affiliation(s)
- Jennifer L Dumouchel
- Molecular Pharmacology and Physiology Graduate Training Program, Brown University, Providence, RI, USA.
| | - Valerie M Kramlinger
- Translational Medicine, Novartis Institutes for BioMedical Research, Inc., Cambridge, MA, USA
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Chemical activation of SAT1 corrects diet-induced metabolic syndrome. Cell Death Differ 2020; 27:2904-2920. [PMID: 32376874 DOI: 10.1038/s41418-020-0550-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 04/21/2020] [Accepted: 04/22/2020] [Indexed: 12/13/2022] Open
Abstract
The pharmacological targeting of polyamine metabolism is currently under the spotlight for its potential in the prevention and treatment of several age-associated disorders. Here, we report the finding that triethylenetetramine dihydrochloride (TETA), a copper-chelator agent that can be safely administered to patients for the long-term treatment of Wilson disease, exerts therapeutic benefits in animals challenged with hypercaloric dietary regimens. TETA reduced obesity induced by high-fat diet, excessive sucrose intake, or leptin deficiency, as it reduced glucose intolerance and hepatosteatosis, but induced autophagy. Mechanistically, these effects did not involve the depletion of copper from plasma or internal organs. Rather, the TETA effects relied on the activation of an energy-consuming polyamine catabolism, secondary to the stabilization of spermidine/spermine N1-acetyltransferase-1 (SAT1) by TETA, resulting in enhanced enzymatic activity of SAT. All the positive effects of TETA on high-fat diet-induced metabolic syndrome were lost in SAT1-deficient mice. Altogether, these results suggest novel health-promoting effects of TETA that might be taken advantage of for the prevention or treatment of obesity.
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Zhang S, Liu H, Amarsingh GV, Cheung CCH, Wu D, Narayanan U, Zhang L, Cooper GJS. Restoration of myocellular copper-trafficking proteins and mitochondrial copper enzymes repairs cardiac function in rats with diabetes-evoked heart failure. Metallomics 2019; 12:259-272. [PMID: 31821401 DOI: 10.1039/c9mt00223e] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Diabetes impairs systemic copper regulation, and acts as a major independent risk factor for heart failure (HF) wherein mitochondrial dysfunction is a key pathogenic process. Here we asked whether diabetes might alter mitochondrial structure/function and thus impair cardiac performance by damaging myocellular pathways that mediate cell-copper homeostasis. We measured activity of major mitochondria-resident copper-enzymes cytochrome c oxidase (mt-Cco) and superoxide dismutase 1 (mt-Sod1); expression of three main mitochondrial copper-chaperones [Cco copper chaperone 17 (Cox17), Cox11, and mitochondria-resident copper chaperone for Sod1 (mt-Ccs)]; of copper-dependent Cco-assembly protein Sco1; and regulation of mitochondrial biogenesis, in left-ventricular (LV) tissue from groups of non-diabetic-control, untreated-diabetic, and divalent-copper-selective chelator-treated diabetic rats. Diabetes impaired LV pump function; ∼halved LV-copper levels; substantively decreased myocellular expression of copper chaperones, and enzymatic activity of mt-Cco and mt-Sod1. Divalent-copper chelation with triethylenetetramine improved cardiac pump function, restored levels of myocardial copper, the copper chaperones, and Sco1; and enzymatic activity of mt-Cco and mt-Sod1. Copper chelation also restored expression of the key mitochondrial biogenesis regulator, peroxisome-proliferator-activated receptor gamma co-activator-1α (Pgc-1α). This study shows for the first time that altered myocardial copper-trafficking is a key pathogenic process in diabetes-evoked HF. We also describe a novel therapeutic effect of divalent-copper-selective chelation, namely restoration of myocellular copper trafficking, which is thus revealed as a potentially tractable target for novel pharmacological intervention to improve cardiac function.
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Affiliation(s)
- Shaoping Zhang
- School of Biological Sciences, University of Auckland, Private Bag 92 019, Auckland 1010, New Zealand.
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Zhang S, Liu H, Amarsingh GV, Cheung CCH, Hogl S, Narayanan U, Zhang L, McHarg S, Xu J, Gong D, Kennedy J, Barry B, Choong YS, Phillips ARJ, Cooper GJS. Diabetic cardiomyopathy is associated with defective myocellular copper regulation and both defects are rectified by divalent copper chelation. Cardiovasc Diabetol 2014; 13:100. [PMID: 24927960 PMCID: PMC4070334 DOI: 10.1186/1475-2840-13-100] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 05/27/2014] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Heart disease is the leading cause of death in diabetic patients, and defective copper metabolism may play important roles in the pathogenesis of diabetic cardiomyopathy (DCM). The present study sought to determine how myocardial copper status and key copper-proteins might become impaired by diabetes, and how they respond to treatment with the Cu (II)-selective chelator triethylenetetramine (TETA) in DCM. METHODS Experiments were performed in Wistar rats with streptozotocin (STZ)-induced diabetes with or without TETA treatment. Cardiac function was analyzed in isolated-perfused working hearts, and myocardial total copper content measured by particle-induced x-ray emission spectroscopy (PIXE) coupled with Rutherford backscattering spectrometry (RBS). Quantitative expression (mRNA and protein) and/or activity of key proteins that mediate LV-tissue-copper binding and transport, were analyzed by combined RT-qPCR, western blotting, immunofluorescence microscopy, and enzyme activity assays. Statistical analysis was performed using Student's t-tests or ANOVA and p-values of < 0.05 have been considered significant. RESULTS Left-ventricular (LV) copper levels and function were severely depressed in rats following 16-weeks' diabetes, but both were unexpectedly normalized 8-weeks after treatment with TETA was instituted. Localized myocardial copper deficiency was accompanied by decreased expression and increased polymerization of the copper-responsive transition-metal-binding metallothionein proteins (MT1/MT2), consistent with impaired anti-oxidant defences and elevated susceptibility to pro-oxidant stress. Levels of the high-affinity copper transporter-1 (CTR1) were depressed in diabetes, consistent with impaired membrane copper uptake, and were not modified by TETA which, contrastingly, renormalized myocardial copper and increased levels and cell-membrane localization of the low-affinity copper transporter-2 (CTR2). Diabetes also lowered indexes of intracellular (IC) copper delivery via the copper chaperone for superoxide dismutase (CCS) to its target cuproenzyme, superoxide dismutase-1 (SOD1): this pathway was rectified by TETA treatment, which normalized SOD1 activity with consequent bolstering of anti-oxidant defenses. Furthermore, diabetes depressed levels of additional intracellular copper-transporting proteins, including antioxidant-protein-1 (ATOX1) and copper-transporting-ATPase-2 (ATP7B), whereas TETA elevated copper-transporting-ATPase-1 (ATP7A). CONCLUSIONS Myocardial copper deficiency and defective cellular copper transport/trafficking are revealed as key molecular defects underlying LV impairment in diabetes, and TETA-mediated restoration of copper regulation provides a potential new class of therapeutic molecules for DCM.
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Affiliation(s)
- Shaoping Zhang
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
- The Maurice Wilkins Centre for Molecular Biodiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Hong Liu
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Greeshma V Amarsingh
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Carlos C H Cheung
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Sebastian Hogl
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Umayal Narayanan
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Lin Zhang
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Selina McHarg
- Centre for Advanced Discovery and Experimental Therapeutics, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, and the Centre for Diabetes and Endocrinology, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9WL, UK
| | - Jingshu Xu
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
- The Maurice Wilkins Centre for Molecular Biodiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Deming Gong
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - John Kennedy
- National Isotope Centre, GNS Science, Gracefield, Wellington, New Zealand
| | - Bernard Barry
- National Isotope Centre, GNS Science, Gracefield, Wellington, New Zealand
| | - Yee Soon Choong
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Anthony R J Phillips
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
- The Maurice Wilkins Centre for Molecular Biodiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand
| | - Garth J S Cooper
- The School of Biological Sciences, Faculty of Science, University of Auckland, Auckland, New Zealand
- The Maurice Wilkins Centre for Molecular Biodiscovery, Faculty of Science, University of Auckland, Auckland, New Zealand
- Centre for Advanced Discovery and Experimental Therapeutics, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, and the Centre for Diabetes and Endocrinology, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester M13 9WL, UK
- Department of Pharmacology, Medical Sciences Division, University of Oxford, Oxford, UK
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