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Zhu L, Ge G, Liu Y, He G, Liang S, Fang Z, Dong P, Cao Y, Yang L. Potent and selective inhibition of magnolol on catalytic activities of UGT1A7 and 1A9. Xenobiotica 2012; 42:1001-8. [DOI: 10.3109/00498254.2012.681814] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Mielke H, Gundert-Remy U. Physiologically based toxicokinetic modelling as a tool to support risk assessment: three case studies. J Toxicol 2012; 2012:359471. [PMID: 22649449 PMCID: PMC3357559 DOI: 10.1155/2012/359471] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 01/28/2012] [Accepted: 02/16/2012] [Indexed: 11/17/2022] Open
Abstract
In this contribution we present three case studies of physiologically based toxicokinetic (PBTK) modelling in regulatory risk assessment. (1) Age-dependent lower enzyme expression in the newborn leads to bisphenol A (BPA) blood levels which are near the levels of the tolerated daily intake (TDI) at the oral exposure as calculated by EFSA. (2) Dermal exposure of BPA by receipts, car park tickets, and so forth, contribute to the exposure towards BPA. However, at the present levels of dermal exposure there is no risk for the adult. (3) Dermal exposure towards coumarin via cosmetic products leads to external exposures of two-fold the TDI. PBTK modeling helped to identify liver peak concentration as the metric for liver toxicity. After dermal exposure of twice the TDI, the liver peak concentration was lower than that present after oral exposure with the TDI dose. In the presented cases, PBTK modeling was useful to reach scientifically sound regulatory decisions.
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Affiliation(s)
- Hans Mielke
- Federal Institute for Risk Assessment, Max Dohrn Strasse 8-10, 10589 Berlin, Germany
| | - Ursula Gundert-Remy
- Federal Institute for Risk Assessment, Max Dohrn Strasse 8-10, 10589 Berlin, Germany
- Institute for Clinical Pharmacology and Toxicology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
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Miyagi SJ, Milne AM, Coughtrie MWH, Collier AC. Neonatal development of hepatic UGT1A9: implications of pediatric pharmacokinetics. Drug Metab Dispos 2012; 40:1321-7. [PMID: 22492655 DOI: 10.1124/dmd.111.043752] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This article reports on the development of UDP-glucuronosyltransferase 1A9 (UGT1A9) in neonatal and pediatric liver. The substrate 4-methylumbelliferone (4MU) with specific inhibition by niflumic acid was used to define specific UGT1A9 activity. Subsequently, in silico pharmacokinetic (PK) and physiology-based pharmacokinetic (PBPK) modeling was used to determine UGT1A9 maturation and hepatic clearance. Modeled maximal enzyme activity was 27.9 nmol · min(-1) · mg protein(-1) at 4 months of age, which had high concordance with the average V(max) in 45 individual adult (>20 years) livers of 29.0 nmol · min(-1) · mg protein(-1). The activity of UGT1A9 ranged 7.5-fold in the adult population (4.1-54.5 nmol · min(-1) · mg protein(-1)). Expression of UGT1A9 correlated with age only in children younger than 1 year (Spearman r = 0.70). Activity correlated with expression up to 18 years of age (Spearman r = 0.76). Furthermore, scaling intrinsic hepatic clearance of 4MU with an allometric PK model yielded a high clearance at birth and then fell to adult levels (1.3 l · h(-1) · kg(-1) at 18.1 years for well stirred or 1.4 l · h(-1) · kg(-1) at 18.7 years for parallel tube). The Simcyp PBPK models did not converge but showed an increase in clearance at under 1 year of age and then decreased to adult levels at approximately 20 years of age. Allometric scaling may be more accurate in cases of high-extraction drugs. Enzyme activities or hepatic clearances did not differ with gender or ethnicity. The UGT1A9 isoform has higher normalized clearance for 4MU at young ages, which may explain how other UGT1A9 substrates, such as propofol, have higher clearances in children than in adults.
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Affiliation(s)
- Shogo J Miyagi
- Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Mānoa, 651 Ilalo St., BSB 320, Honolulu, HI 96813, USA
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Cytostatic drugs in infants: A review on pharmacokinetic data in infants. Cancer Treat Rev 2012; 38:3-26. [DOI: 10.1016/j.ctrv.2011.03.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 03/21/2011] [Accepted: 03/24/2011] [Indexed: 01/11/2023]
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Croom E. Metabolism of xenobiotics of human environments. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 112:31-88. [PMID: 22974737 DOI: 10.1016/b978-0-12-415813-9.00003-9] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Xenobiotics have been defined as chemicals to which an organism is exposed that are extrinsic to the normal metabolism of that organism. Without metabolism, many xenobiotics would reach toxic concentrations. Most metabolic activity inside the cell requires energy, cofactors, and enzymes in order to occur. Xenobiotic-metabolizing enzymes can be divided into phase I, phase II, and transporter enzymes. Lipophilic xenobiotics are often first metabolized by phase I enzymes, which function to make xenobiotics more polar and provide sites for conjugation reactions. Phase II enzymes are conjugating enzymes and can directly interact with xenobiotics but more commonly interact with metabolites produced by phase I enzymes. Through both passive and active transport, these more polar metabolites are eliminated. Most xenobiotics are cleared through multiple enzymes and pathways. The relationship between chemical concentrations, enzyme affinity and quantity, and cofactor availability often determine which metabolic reactions dominate in a given individual.
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Zhu L, Ge G, Zhang H, Liu H, He G, Liang S, Zhang Y, Fang Z, Dong P, Finel M, Yang L. Characterization of hepatic and intestinal glucuronidation of magnolol: application of the relative activity factor approach to decipher the contributions of multiple UDP-glucuronosyltransferase isoforms. Drug Metab Dispos 2011; 40:529-38. [PMID: 22180045 DOI: 10.1124/dmd.111.042192] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Magnolol is a food additive that is often found in mints and gums. Human exposure to this compound can reach a high dose; thus, characterization of magnolol disposition in humans is very important. Previous studies indicated that magnolol can undergo extensive glucuronidation in humans in vivo. In this study, in vitro assays were used to characterize the glucuronidation pathway in human liver and intestine. Assays with recombinant human UDP-glucuronosyltransferase enzymes (UGTs) revealed that multiple UGT isoforms were involved in magnolol glucuronidation, including UGT1A1, -1A3, -1A7, -1A8, -1A9, -1A10, and -2B7. Magnolol glucuronidation by human liver microsomes (HLM), human intestine microsomes (HIM), and most recombinant UGTs exhibited strong substrate inhibition kinetics. The degree of substrate inhibition was relatively low in the case of UGT1A10, whereas the reaction catalyzed by UGT1A9 followed biphasic kinetics. Chemical inhibition studies and the relative activity factor (RAF) approach were used to identify the individual UGTs that played important roles in magnolol glucuronidation in HLM and HIM. The results indicate that UGT2B7 is mainly responsible for the reaction in HLM, whereas UGT2B7 and UGT1A10 are significant contributors in HIM. In summary, the current study clarifies the glucuronidation pathway of magnolol and demonstrates that the RAF approach can be used as an efficient method for deciphering the roles of individual UGTs in a given glucuronidation pathway in the native tissue that is catalyzed by multiple isoforms with variable and atypical kinetics.
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Affiliation(s)
- Liangliang Zhu
- Laboratory of Pharmaceutical Resource Discovery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Rd., Dalian, 116023 China
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Collier AC, Milam KA, Rougée LRA, Sugawara A, Yamauchi Y, Ward MA. Upregulation of Ugt1a genes in placentas and fetal livers in a murine model of assisted reproduction. Placenta 2011; 33:77-80. [PMID: 22115498 DOI: 10.1016/j.placenta.2011.11.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 10/10/2011] [Accepted: 11/01/2011] [Indexed: 11/16/2022]
Abstract
Genes from Ugt1a family in placenta and fetal liver are responsible for hormone, nutrient and chemical balance during pregnancy. Assisted reproduction technologies (ART) i.e. intracytoplasmic sperm injection (ICSI) and in vitro fertilization (IVF) alter steroid homeostasis in pregnancy through increased glucuronidation. Here we show that ART (particularly ICSI) upregulates Ugt1a1, 1a2, 1a6 and 1a9 expression in murine placentas and fetal livers with higher mRNA related to lower progesterone (1a1) and cholesterol (1a2, 1a6) in placentas. Greater steroid clearance in ART through transcriptional upregulation of Ugt1a in the placental-fetal unit may decrease the availability of essential molecules, mediating negative reproductive outcomes.
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Affiliation(s)
- A C Collier
- Dept. Tropical Medicine, Medical Microbiology and Pharmacology, University of Hawaii at Mānoa, Honolulu, HI 96813, United States.
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Maudens KE, Stove CP, Lambert WE. Quantitative liquid chromatographic analysis of anthracyclines in biological fluids. J Chromatogr B Analyt Technol Biomed Life Sci 2011; 879:2471-86. [PMID: 21840776 DOI: 10.1016/j.jchromb.2011.07.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 07/01/2011] [Accepted: 07/07/2011] [Indexed: 10/18/2022]
Abstract
Anthracyclines are amongst the most widely used drugs in oncology, being part of the treatment regimen in most patients receiving systemic chemotherapy. This review provides a comprehensive summary of the sample preparation techniques and chromatographic methods that have been developed during the last two decades for the analysis of the 4 most administered anthracyclines, doxorubicin, epirubicin, daunorubicin and idarubicin in plasma, serum, saliva or urine, within the context of clinical and pharmacokinetic studies or for assessing occupational exposure. Following deproteinization, liquid-liquid extraction, solid phase extraction or a combination of these techniques, the vast majority of methods utilizes reversed-phase C18 stationary phases for liquid chromatographic separation, followed by fluorescence detection, or, more recently, tandem mass spectrometric detection. Some pros and cons of the different techniques are addressed, in addition to potential pitfalls that may be encountered in the analysis of this class of compounds.
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Affiliation(s)
- Kristof E Maudens
- Toxicological Centre, Department of Pharmaceutical Sciences, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk-Antwerp, Belgium
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Pretheeban M, Hammond G, Bandiera S, Riggs W, Rurak D. Ontogenesis of UDP-glucuronosyltransferase enzymes in sheep. Comp Biochem Physiol A Mol Integr Physiol 2011; 159:159-66. [DOI: 10.1016/j.cbpa.2011.02.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2010] [Revised: 02/15/2011] [Accepted: 02/15/2011] [Indexed: 01/21/2023]
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de Wildt SN. Profound changes in drug metabolism enzymes and possible effects on drug therapy in neonates and children. Expert Opin Drug Metab Toxicol 2011; 7:935-48. [PMID: 21548840 DOI: 10.1517/17425255.2011.577739] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION There are profound changes that take place in drug metabolism enzymes during fetal and postnatal development. These changes may significantly impact drug therapy in children. AREAS COVERED A combination of focused and comprehensive literature searches using PubMed and reference lists (from inception to 7 November 2009) is undertaken to identify reports on in vitro and in vivo development of drug metabolism enzymes as well disposition of selected drugs and their effect in children. The article provides an update on development of drug metabolism enzymes and their impact on drug substrate disposition and disease, which may aid to improve clinical practice and optimally design clinical trials in children. EXPERT OPINION Drug metabolism enzyme activity changes profoundly throughout the continuum of postnatal development and often results in different disposition pathways than in adults. Genetics and co-morbidity interact significantly with these developmental changes. Translation of existing knowledge into age-adjusted dosing guidelines and clinical trial design is highly needed for there to be an improvement in drug therapy in children.
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Affiliation(s)
- Saskia N de Wildt
- Erasmus MC Sophia Children's Hospital, Pediatric Surgery & Intensive Care, GJ Rotterdam, The Netherlands.
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Hengstler JG, Foth H, Gebel T, Kramer PJ, Lilienblum W, Schweinfurth H, Völkel W, Wollin KM, Gundert-Remy U. Critical evaluation of key evidence on the human health hazards of exposure to bisphenol A. Crit Rev Toxicol 2011; 41:263-91. [PMID: 21438738 PMCID: PMC3135059 DOI: 10.3109/10408444.2011.558487] [Citation(s) in RCA: 225] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 01/19/2011] [Accepted: 01/25/2011] [Indexed: 01/08/2023]
Abstract
Despite the fact that more than 5000 safety-related studies have been published on bisphenol A (BPA), there seems to be no resolution of the apparently deadlocked controversy as to whether exposure of the general population to BPA causes adverse effects due to its estrogenicity. Therefore, the Advisory Committee of the German Society of Toxicology reviewed the background and cutting-edge topics of this BPA controversy. The current tolerable daily intake value (TDI) of 0.05 mg/kg body weight [bw]/day, derived by the European Food Safety Authority (EFSA), is mainly based on body weight changes in two- and three-generation studies in mice and rats. Recently, these studies and the derivation of the TDI have been criticized. After having carefully considered all arguments, the Committee had to conclude that the criticism was scientifically not justified; moreover, recently published additional data further support the reliability of the two- and three-generation studies demonstrating a lack of estrogen-dependent effects at and below doses on which the current TDI is based. A frequently discussed topic is whether doses below 5 mg/kg bw/day may cause adverse health effects in laboratory animals. Meanwhile, it has become clear that positive results from some explorative studies have not been confirmed in subsequent studies with higher numbers of animals or a priori defined hypotheses. Particularly relevant are some recent studies with negative outcomes that addressed effects of BPA on the brain, behavior, and the prostate in rodents for extrapolation to the human situation. The Committee came to the conclusion that rodent data can well be used as a basis for human risk evaluation. Currently published conjectures that rats are insensitive to estrogens compared to humans can be refuted. Data from toxicokinetics studies show that the half-life of BPA in adult human subjects is less than 2 hours and BPA is completely recovered in urine as BPA-conjugates. Tissue deconjugation of BPA-glucuronide and -sulfate may occur. Because of the extremely low quantities, it is only of minor relevance for BPA toxicity. Biomonitoring studies have been used to estimate human BPA exposure and show that the daily intake of BPA is far below the TDI for the general population. Further topics addressed in this article include reasons why some studies on BPA are not reproducible; the relevance of oral versus non-oral exposure routes; the degree to which newborns are at higher systemic BPA exposure; increased BPA exposure by infusions in intensive care units; mechanisms of action other than estrogen receptor activation; and the current regulatory status in Europe, as well as in the USA, Canada, Japan, New Zealand, and Australia. Overall, the Committee concluded that the current TDI for BPA is adequately justified and that the available evidence indicates that BPA exposure represents no noteworthy risk to the health of the human population, including newborns and babies.
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Affiliation(s)
- J G Hengstler
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), University of Dortmund, Dortmund, Germany.
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Johnson TN, Rostami-Hodjegan A. Resurgence in the use of physiologically based pharmacokinetic models in pediatric clinical pharmacology: parallel shift in incorporating the knowledge of biological elements and increased applicability to drug development and clinical practice. Paediatr Anaesth 2011; 21:291-301. [PMID: 20497354 DOI: 10.1111/j.1460-9592.2010.03323.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS AND OBJECTIVES (i) To describe an example of the development work required for building a 'pediatric physiologically based pharmacokinetic' (P-PBPK) model (Simcyp Pediatric ADME Simulator), (ii) to replicate pediatric clinical studies and undertake theoretical studies to show the potential applications of mechanistic PBPK in pediatric drug clinical investigation and practice, with emphasis on pediatric anesthesia. BACKGROUND PBPK models draw together the physiological and biochemical information that determine drug absorption, distribution, metabolism, and excretion and then link them in a physiologically realistic 'systems' model. Incorporating the emerging additional information on developmental physiology and biochemistry has resulted in the creation of P-PBPK. There has been a renewed interest in the application of such modeling by the pharmaceutical industry to improve the efficiency of drug development, especially in populations where designing and conducting clinical studies is more challenging, such as pediatric patients. METHODS P-PBPK was used to simulate a number of published clinical studies and clinical case scenarios with the aim of highlighting the potential applications. RESULTS Changing the P-PBPK model parameters in a number of 'what if' simulations were used to explore the likely underlying reasons for observed pharmacokinetic (PK) behavior of drugs in critically ill children. In addition, the use of P-PBPK models to predict complex drug-drug interactions (DDI) highlighted disparities with adult populations. DISCUSSION The examples highlight the use of prior knowledge of in vitro drug attributes and biology of the system (human body) to simulate PK and multiple DDI scenarios not infrequently encountered in critically ill pediatric patients.
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Miyagi SJ, Collier AC. The development of UDP-glucuronosyltransferases 1A1 and 1A6 in the pediatric liver. Drug Metab Dispos 2011; 39:912-9. [PMID: 21266593 DOI: 10.1124/dmd.110.037192] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
UDP-glucuronosyltransferases (UGTs) are critical for the metabolism and clearance of drugs, chemicals, and hormones. The development of UGT1A1 and 1A6 was studied in 50 pediatric liver samples using bilirubin, serotonin activity assays, and Western blot as well as pharmacokinetic scaling. UGT activity developed age dependently in pediatric liver. Maximal activity of 0.7690 nmol · min · (-1) mg protein(-1) was observed for UGT1A1 at 3.8 months. For UGT1A6, activity matured at 14 months (4.737 nmol · min · (-1)mg protein(-1)). Protein expression was not age-dependent, and activities did not correlate to protein levels for either enzyme. The in vitro activities were used to calculate normalized hepatic clearances using both allometric scaling and a physiologically based pharmacokinetic model. For UGT1A1, allometry predicted normalized adult clearances of 0.0070 l · h(-1) · kg(-1) at 3.0 (well stirred) and 2.8 years (parallel tube), whereas the Simcyp model showed normalized clearances of 0.0079 l · h(-1) · kg(-1) at 2.6 (well stirred) and 2.5 years (parallel tube). For UGT1A6, only the Simcyp well stirred model converged at 0.3524 l · h(-1) · kg(-1) at 12.6 months. These data imply independent regulation of UGT1A1 and 1A6 where activity has matured after 6 months to 1 year. Total hepatic clearance of substances mediated by these enzymes may mature concurrently or take longer because of other physiological factors. Late development of UGT enzymes may contribute to chemical, drug, and environmental toxicity.
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Affiliation(s)
- Shogo J Miyagi
- Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Mānoa, 651 Ilalo St., BSB 320, Honolulu, HI 96813, USA
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Court MH. Interindividual variability in hepatic drug glucuronidation: studies into the role of age, sex, enzyme inducers, and genetic polymorphism using the human liver bank as a model system. Drug Metab Rev 2010; 42:209-24. [PMID: 19821798 DOI: 10.3109/03602530903209288] [Citation(s) in RCA: 158] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The human liver bank has provided an invaluable model system for the study of interindividual variability in expression and activity of the major hepatic UGTs, including UGT1A1, 1A4, 1A6, 1A9, 2B7, and 2B15. Based on studies using UGT-isoform-selective probes, the rank order of activity variability is UGT 1A1>1A6>2B15>1A4 = 1A9>2B7, with coefficient of variation values ranging from 92 to 45%. Liver donor age, sex, enzyme inducers, and genetic polymorphism are factors that have been implicated as sources of this variability in UGT activity. The expression of UGTs prior to, and immediately following, birth is quite limited, explaining the susceptibility of neonates to certain drug toxicities. Old age appears to have minimal effect on UGT function. Sex differences in UGT activity are relatively small and are confined to several UGTs, including UGT2B15, which shows higher activity in males, compared with females. Enzyme inducers, including coadministered drugs, smoking, and alcohol, may increase hepatic UGT levels. Human liver bank phenotype-genotype studies, using UGT-isoform-selective probes have identified common genetic polymorphisms that are predictive of glucuronidation activity in vitro and that were subsequently verified as predictors of probe-drug clearance by glucuronidation in vivo.
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Affiliation(s)
- Michael H Court
- Laboratory of Comparative and Molecular Pharmacogenomics, Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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Ramírez J, Ratain MJ, Innocenti F. Uridine 5'-diphospho-glucuronosyltransferase genetic polymorphisms and response to cancer chemotherapy. Future Oncol 2010; 6:563-85. [PMID: 20373870 PMCID: PMC3102300 DOI: 10.2217/fon.10.17] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Pharmacogenetics aims to elucidate how genetic variation affects the efficacy and side effects of drugs, with the ultimate goal of personalizing medicine. Clinical studies of the genetic variation in the uridine 5'-diphosphoglucuronosyltransferase gene have demonstrated how reduced-function allele variants can predict the risk of severe toxicity and help identify cancer patients who could benefit from reduced-dose schedules or alternative chemotherapy. Candidate polymorphisms have also been identified in vitro, although the functional consequences of these variants still need to be tested in the clinical setting. Future approaches in uridine 5'-diphosphoglucuronosyltransferase pharmacogenetics include genetic testing prior to drug treatment, genotype-directed dose-escalation studies, study of genetic variation at the haplotype level and genome-wide studies.
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Affiliation(s)
- Jacqueline Ramírez
- Department of Medicine, The University of Chicago, 5841 S. Maryland Avenue, MC2115, Chicago, IL, USA 60637, Tel.: +1 773 834 2451, Fax: +1 773 702 9268,
| | - Mark J Ratain
- Department of Medicine, Committee on Clinical Pharmacology & Pharmacogenomics, Cancer Research Center, The University of Chicago, 5841 S. Maryland Avenue, MC2115, Chicago, IL, USA 60637, Tel.: +1 773 702 4400, Fax: +1 773 702 3969,
| | - Federico Innocenti
- Department of Medicine, Committee on Clinical Pharmacology & Pharmacogenomics, Cancer Research Center, The University of Chicago, 5841 S. Maryland Avenue, MC2115, Chicago, IL, USA 60637, Tel.: +1 773 834 2452, Fax: +1 773 702 9268,
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In vivo glucuronidation activity of drugs in neonates: extensive interindividual variability despite their young age. Ther Drug Monit 2010; 31:411-5. [PMID: 19494793 DOI: 10.1097/ftd.0b013e3181a8cc0a] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Compared with phase I isoenzymes, data on isoenzyme-specific phenotypic activity of uridine diphosphate glucuronosyltransferase (UGT) and its covariates in neonates are limited. In vivo observations on morphine, paracetamol (acetaminophen), and propofol disposition throughout childhood confirm the overall low-glucuronidation activity in neonates observed in in vitro studies. In addition to the phenotypic low-glucuronidation activity, in vivo observations of bilirubin (UGT1A1), morphine (UGT2B7), paracetamol (UGT1A6), and propofol (UGT1A9) glucuronidation in neonates display extensive interindividual variability, only in part explained by postmenstrual and postnatal age. Covariates like disease state characteristics (decreased morphine metabolism during therapeutic head cooling), genetic polymorphisms (UGT1A1 genetic variants and differences in bilirubin metabolism), or environmental factors (increased urinary excretion of paracetamol-glucuronide by repeated administration of paracetamol) further contribute to this variability. A focused approach to unveil covariates of the interindividual range is needed to improve our knowledge on drug disposition in early life.
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de Wildt SN, Kearns GL, Murry DJ, Koren G, van den Anker JN. Ontogeny of midazolam glucuronidation in preterm infants. Eur J Clin Pharmacol 2009; 66:165-70. [PMID: 19838691 PMCID: PMC2805794 DOI: 10.1007/s00228-009-0741-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Accepted: 09/17/2009] [Indexed: 11/25/2022]
Abstract
Purpose In preterm infants, the biotransformation of midazolam (M) to 1-OH-midazolam (OHM) by cytochrome P450 3A4 (CYP3A4) is developmentally immature, but it is currently unknown whether the glucuronidation of OHM to 1-OH-midazolam glucuronide (OHMG) is also decreased. The aim of our study was to investigate the urinary excretion of midazolam and its metabolites OHM and OHMG in preterm neonates following the intravenous (IV) or oral (PO) administration of a single M dose. Methods Preterm infants (post-natal age 3–13 days, gestational age 26–34 4/7 weeks) scheduled to undergo a stressful procedure received a 30-min IV infusion (n = 15) or a PO bolus dose (n= 7) of 0.1 mg/kg midazolam. The percentage of midazolam dose excreted in the urine as M, OHM and OHMG up to 6 h post-dose was determined. Results The median percentage of the midazolam dose excreted as M, OHM and OHMG in the urine during the 6-h interval after the IV infusion was 0.44% (range 0.02–1.39%), 0.04% (0.01–0.13%) and 1.57% (0.36–7.7%), respectively. After administration of the PO bolus dose, the median percentage of M, OHM and OHMG excreted in the urine was 0.11% (0.02–0.59%), 0.02% (0.00–0.10%) and 1.69% (0.58–7.31%), respectively. The proportion of the IV midazolam dose excreted as OHMG increased significantly with postconceptional age (r = 0.73, p < 0.05). Conclusion The glucuronidation of OHM appears immature in preterm infants less than 2 weeks of age. The observed increase in urinary excretion of OHMG with postconceptional age likely reflects the combined maturation of glucuronidation and renal function.
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Affiliation(s)
- Saskia N de Wildt
- Department of Paediatrics and Paediatric Surgery, Erasmus MC Sophia Children's Hospital, Rotterdam, The Netherlands.
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Hines RN, Sargent D, Autrup H, Birnbaum LS, Brent RL, Doerrer NG, Cohen Hubal EA, Juberg DR, Laurent C, Luebke R, Olejniczak K, Portier CJ, Slikker W. Approaches for assessing risks to sensitive populations: lessons learned from evaluating risks in the pediatric population. Toxicol Sci 2009; 113:4-26. [PMID: 19770482 DOI: 10.1093/toxsci/kfp217] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Assessing the risk profiles of potentially sensitive populations requires a "tool chest" of methodological approaches to adequately characterize and evaluate these populations. At present, there is an extensive body of literature on methodologies that apply to the evaluation of the pediatric population. The Health and Environmental Sciences Institute Subcommittee on Risk Assessment of Sensitive Populations evaluated key references in the area of pediatric risk to identify a spectrum of methodological approaches. These approaches are considered in this article for their potential to be extrapolated for the identification and assessment of other sensitive populations. Recommendations as to future research needs and/or alternate methodological considerations are also made.
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Affiliation(s)
- Ronald N Hines
- Medical College of Wisconsin, Department of Pediatrics, Children's Research Institute, Children's Hospital and Health Systems, Milwaukee, Wisconsin 53226-4801, USA
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Mielke H, Gundert-Remy U. Bisphenol A levels in blood depend on age and exposure. Toxicol Lett 2009; 190:32-40. [PMID: 19560527 DOI: 10.1016/j.toxlet.2009.06.861] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 06/17/2009] [Accepted: 06/19/2009] [Indexed: 11/15/2022]
Abstract
We present two approaches to estimate blood concentrations of Bisphenol A (BPA). Simple kinetic principles were applied to calculate steady state plasma concentrations. A physiologically based model was used to simulate the blood concentration time profile in several age groups exploring the influence of not yet fully developed metabolic capacity on the blood concentrations in the newborn. Both approaches gave concordant results and are in excellent agreement with experimental results [Völkel, W., Colnot, T., Csanady, G.A., Filser, J.G., Dekant, W., 2002. Metabolism and kinetics of bisphenol A in humans at low doses following oral administration. Chem. Res. Toxicol. 15, 1281-1287]. The predictions also agree with published results obtained with a different physiologically based model. According to model simulations, BPA is present in the blood of the normal population at concentrations several orders of magnitude lower than most measurements reported in the literature. At the same external exposure level, the newborn is predicted to have 3 times greater blood concentration than the adult. This is due to the not yet fully developed glucuronidation activity in the newborn, not fully compensated by the unimpaired sulfation pathway. For the highest measured external BPA exposure, the predicted blood concentrations of 2.6 pg/ml (steady state concentration) and 8.2 pg/ml (peak concentration) in the adult are lower than the in vitro concentrations at which inhibiting adiponectin release from human adipocytes and stimulation of beta-cell production and secretion were observed.
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Affiliation(s)
- Hans Mielke
- Federal Institute for Risk Assessment/Bundesinstitut für Risikobewertung (BfR), Thielallee 88-92, D-14195 Berlin, Germany.
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Madadi P, Koren G. Pharmacogenetic insights into codeine analgesia: implications to pediatric codeine use. Pharmacogenomics 2008; 9:1267-84. [DOI: 10.2217/14622416.9.9.1267] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Codeine has been used medicinally since the 1800s as an analgesic and antitussive agent. Although very few studies have methodically examined the safety of codeine use in the pediatric age group, it is nonetheless commonly prescribed to children and breastfeeding mothers. Empirical evidence over the last century has suggested variability in the efficacy of codeine, and recent genomic advancements have shed important light on the mechanisms leading to such variability. Aside from evaluating the role of genetic variability in drug-metabolizing enzymes, receptors and transporters, the development of the blood–brain-barrier and the ontogeny of drug-metabolizing enzymes must also be considered in newborns and young children.
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Affiliation(s)
- Parvaz Madadi
- Department of Physiology & Pharmacology and The Ivey Chair in Molecular Toxicology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Canada
| | - Gideon Koren
- Department of Physiology & Pharmacology and The Ivey Chair in Molecular Toxicology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Canada
- Motherisk Program, The Hospital for Sick Children, Toronto, Canada
- The University of Toronto, Toronto, Canada
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Hines RN. The ontogeny of drug metabolism enzymes and implications for adverse drug events. Pharmacol Ther 2008; 118:250-67. [PMID: 18406467 DOI: 10.1016/j.pharmthera.2008.02.005] [Citation(s) in RCA: 250] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Accepted: 02/27/2008] [Indexed: 10/22/2022]
Abstract
Profound changes in drug metabolizing enzyme (DME) expression occurs during development that impacts the risk of adverse drug events in the fetus and child. A review of our current knowledge suggests individual hepatic DME ontogeny can be categorized into one of three groups. Some enzymes, e.g., CYP3A7, are expressed at their highest level during the first trimester and either remain at high concentrations or decrease during gestation, but are silenced or expressed at low levels within one to two years after birth. SULT1A1 is an example of the second group of DME. These enzymes are expressed at relatively constant levels throughout gestation and minimal changes are observed postnatally. ADH1C is typical of the third DME group that are not expressed or are expressed at low levels in the fetus, usually during the second or third trimester. Substantial increases in enzyme levels are observed within the first one to two years after birth. Combined with our knowledge of other physiological factors during early life stages, knowledge regarding DME ontogeny has permitted the development of robust physiological based pharmacokinetic models and an improved capability to predict drug disposition in pediatric patients. This review will provide an overview of DME developmental expression patterns and discuss some implications of the data with regards to drug therapy. Common themes emerging from our current knowledge also will be discussed. Finally, the review will highlight gaps in knowledge that will be important to advance this field.
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Affiliation(s)
- Ronald N Hines
- Department of Pediatrics, Medical College of Wisconsin, and Children's Research Institute, Children's Hospital and Health Systems, Milwaukee, WI 53226-4801, USA.
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