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Heier C, Xie H, Zimmermann R. Nonoxidative ethanol metabolism in humans-from biomarkers to bioactive lipids. IUBMB Life 2016; 68:916-923. [PMID: 27714979 PMCID: PMC5324703 DOI: 10.1002/iub.1569] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 09/19/2016] [Indexed: 12/21/2022]
Abstract
Ethanol is a widely used psychoactive drug whose chronic abuse is associated with organ dysfunction and disease. Although the prevalent metabolic fate of ethanol in the human body is oxidation a smaller fraction undergoes nonoxidative metabolism yielding ethyl glucuronide, ethyl sulfate, phosphatidylethanol and fatty acid ethyl esters. Nonoxidative ethanol metabolites persist in tissues and body fluids for much longer than ethanol itself and represent biomarkers for the assessment of ethanol intake in clinical and forensic settings. Of note, the nonoxidative reaction of ethanol with phospholipids and fatty acids yields bioactive compounds that affect cellular signaling pathways and organelle function and may contribute to ethanol toxicity. Thus, despite low quantitative contributions of nonoxidative pathways to overall ethanol metabolism the resultant ethanol metabolites have important biological implications. In this review we summarize the current knowledge about the enzymatic formation of nonoxidative ethanol metabolites in humans and discuss the implications of nonoxidative ethanol metabolites as biomarkers of ethanol intake and mediators of ethanol toxicity. © 2016 IUBMB Life, 68(12):916-923, 2016.
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Affiliation(s)
- Christoph Heier
- Institute of Molecular Biosciences, University of GrazAustria
| | - Hao Xie
- Institute of Molecular Biosciences, University of GrazAustria
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Foti RS, Dalvie DK. Cytochrome P450 and Non-Cytochrome P450 Oxidative Metabolism: Contributions to the Pharmacokinetics, Safety, and Efficacy of Xenobiotics. ACTA ACUST UNITED AC 2016; 44:1229-45. [PMID: 27298339 DOI: 10.1124/dmd.116.071753] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/10/2016] [Indexed: 12/16/2022]
Abstract
The drug-metabolizing enzymes that contribute to the metabolism or bioactivation of a drug play a crucial role in defining the absorption, distribution, metabolism, and excretion properties of that drug. Although the overall effect of the cytochrome P450 (P450) family of drug-metabolizing enzymes in this capacity cannot be understated, advancements in the field of non-P450-mediated metabolism have garnered increasing attention in recent years. This is perhaps a direct result of our ability to systematically avoid P450 liabilities by introducing chemical moieties that are not susceptible to P450 metabolism but, as a result, may introduce key pharmacophores for other drug-metabolizing enzymes. Furthermore, the effects of both P450 and non-P450 metabolism at a drug's site of therapeutic action have also been subject to increased scrutiny. To this end, this Special Section on Emerging Novel Enzyme Pathways in Drug Metabolism will highlight a number of advancements that have recently been reported. The included articles support the important role of non-P450 enzymes in the clearance pathways of U.S. Food and Drug Administration-approved drugs over the past 10 years. Specific examples will detail recent reports of aldehyde oxidase, flavin-containing monooxygenase, and other non-P450 pathways that contribute to the metabolic, pharmacokinetic, or pharmacodynamic properties of xenobiotic compounds. Collectively, this series of articles provides additional support for the role of non-P450-mediated metabolic pathways that contribute to the absorption, distribution, metabolism, and excretion properties of current xenobiotics.
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Affiliation(s)
- Robert S Foti
- Pharmacokinetics and Drug Metabolism, Amgen, Cambridge, Massachusetts (R.S.F.); and Pharmacokinetics, Dynamics, and Metabolism, Pfizer, La Jolla, California (D.K.D.)
| | - Deepak K Dalvie
- Pharmacokinetics and Drug Metabolism, Amgen, Cambridge, Massachusetts (R.S.F.); and Pharmacokinetics, Dynamics, and Metabolism, Pfizer, La Jolla, California (D.K.D.)
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Patel K, Durgampudi C, Noel P, Trivedi RN, de Oliveira C, Singh VP. Fatty Acid Ethyl Esters Are Less Toxic Than Their Parent Fatty Acids Generated during Acute Pancreatitis. THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:874-84. [PMID: 26878214 DOI: 10.1016/j.ajpath.2015.11.022] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 10/19/2015] [Accepted: 11/19/2015] [Indexed: 12/18/2022]
Abstract
Although ethanol causes acute pancreatitis (AP) and lipolytic fatty acid (FA) generation worsens AP, the contribution of ethanol metabolites of FAs, ie, FA ethyl esters (FAEEs), to AP outcomes is unclear. Previously, pancreata of dying alcoholics and pancreatic necrosis in severe AP, respectively, showed high FAEEs and FAs, with oleic acid (OA) and its ethyl esters being the most abundant. We thus compared the toxicities of FAEEs and their parent FAs in severe AP. Pancreatic acini and peripheral blood mononuclear cells were exposed to FAs or FAEEs in vitro. The triglyceride of OA (i.e., glyceryl tri-oleate) or OAEE was injected into the pancreatic ducts of rats, and local and systemic severities were studied. Unsaturated FAs at equimolar concentrations to FAEEs induced a larger increase in cytosolic calcium, mitochondrial depolarization, and necro-apoptotic cell death. Glyceryl tri-oleate but not OAEE resulted in 70% mortality with increased serum OA, a severe inflammatory response, worse pancreatic necrosis, and multisystem organ failure. Our data show that FAs are more likely to worsen AP than FAEEs. Our observations correlate well with the high pancreatic FAEE concentrations in alcoholics without pancreatitis and high FA concentrations in pancreatic necrosis. Thus, conversion of FAs to FAEE may ameliorate AP in alcoholics.
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Affiliation(s)
- Krutika Patel
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Scottsdale, Arizona
| | - Chandra Durgampudi
- Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Pawan Noel
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Scottsdale, Arizona
| | - Ram N Trivedi
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Scottsdale, Arizona
| | - Cristiane de Oliveira
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Scottsdale, Arizona
| | - Vijay P Singh
- Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Scottsdale, Arizona.
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Zelner I, Matlow JN, Natekar A, Koren G. Synthesis of fatty acid ethyl esters in mammalian tissues after ethanol exposure: a systematic review of the literature. Drug Metab Rev 2013; 45:277-99. [PMID: 23713893 DOI: 10.3109/03602532.2013.795584] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ability to undergo non-oxidative metabolism from ethanol to fatty acid ethyl esters (FAEEs) varies greatly among tissues and organs. To gain a greater understanding of non-oxidative ethanol metabolism to FAEE, we aimed to collect all published data on FAEE synthesis in mammalian organs and tissues to identify all tissues, organs, and enzymes that are known to, or likely possess FAEE-synthetic activity. A systematic search for relevant papers was performed and two independent reviewers examined potentially relevant abstracts (articles on FAEEs that pertain to ethanol exposure) to determine whether they met the inclusion criteria. Information on FAEE synthesis was retrieved from papers meeting the inclusion/exclusion criteria and summarized by organ/tissue/matrix examined. The systematic search through four databases yielded 78 articles that investigated FAEE synthesis by tissues, tissue fractions and cell lines, and 29 articles that attempted to purify and/or characterize the enzymes involved in FAEE synthesis. Two enzyme activities have been studied: FAEE synthase (FAEES, which conjugates ethanol and free fatty acid) and acyl-CoA: ethanol O-acyltransferase (AEAT, which conjugates ethanol and fatty acyl-CoA). Both activities are expressed by a variety of different enzymes. FAEES activity is the most widely studied and has been purified from several tissues and shown to be associated with several well-known enzymes, while the identity of enzymes possessing AEAT activity remains unknown. The organs and tissues that have been shown to synthesize FAEEs are discussed, with special emphasis on the studies that attempted to elucidate the enzymology of FAEE synthesis in those tissues.
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Affiliation(s)
- Irene Zelner
- Division of Clinical Pharmacology and Toxicology, Hospital for Sick Children, Toronto, Ontario, Canada
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Bencharit S, Edwards CC, Morton CL, Howard-Williams EL, Kuhn P, Potter PM, Redinbo MR. Multisite promiscuity in the processing of endogenous substrates by human carboxylesterase 1. J Mol Biol 2006; 363:201-14. [PMID: 16962139 PMCID: PMC1762004 DOI: 10.1016/j.jmb.2006.08.025] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Revised: 08/04/2006] [Accepted: 08/10/2006] [Indexed: 11/26/2022]
Abstract
Human carboxylesterase 1 (hCE1) is a drug and endobiotic-processing serine hydrolase that exhibits relatively broad substrate specificity. It has been implicated in a variety of endogenous cholesterol metabolism pathways including the following apparently disparate reactions: cholesterol ester hydrolysis (CEH), fatty acyl Coenzyme A hydrolysis (FACoAH), acyl-Coenzyme A:cholesterol acyltransfer (ACAT), and fatty acyl ethyl ester synthesis (FAEES). The structural basis for the ability of hCE1 to perform these catalytic actions involving large substrates and products has remained unclear. Here we present four crystal structures of the hCE1 glycoprotein in complexes with the following endogenous substrates or substrate analogues: Coenzyme A, the fatty acid palmitate, and the bile acids cholate and taurocholate. While the active site of hCE1 was known to be promiscuous and capable of interacting with a variety of chemically distinct ligands, these structures reveal that the enzyme contains two additional ligand-binding sites and that each site also exhibits relatively non-specific ligand-binding properties. Using this multisite promiscuity, hCE1 appears structurally capable of assembling several catalytic events depending, apparently, on the physiological state of the cellular environment. These results expand our understanding of enzyme promiscuity and indicate that, in the case of hCE1, multiple non-specific sites are employed to perform distinct catalytic actions.
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Affiliation(s)
- Sompop Bencharit
- Department of Chemistry
- Department of Biochemistry and Biophysics and the Lineberger Comprehensive Cancer Center, School of Medicine
- Department of Prosthodontics, School of Dentistry
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Carol C. Edwards
- Department of Molecular Pharmacology, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Christopher L. Morton
- Department of Molecular Pharmacology, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | | | - Peter Kuhn
- Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd, MS 69, Menlo Park, CA 94025, USA
| | - Philip M. Potter
- Department of Molecular Pharmacology, St. Jude Children’s Research Hospital, Memphis, TN, 38105, USA, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Matthew R. Redinbo
- Department of Chemistry
- Department of Biochemistry and Biophysics and the Lineberger Comprehensive Cancer Center, School of Medicine
- *To Whom Correspondence Should be Addressed: Matthew R. Redinbo, Department of Chemistry, Campus Box #3290, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA, (919) 843-8910, (919) 966-3675 fax,
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