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Krueger ES, Lloyd TS, Tessem JS. The Accumulation and Molecular Effects of Trimethylamine N-Oxide on Metabolic Tissues: It's Not All Bad. Nutrients 2021; 13:nu13082873. [PMID: 34445033 PMCID: PMC8400152 DOI: 10.3390/nu13082873] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/15/2021] [Accepted: 08/19/2021] [Indexed: 02/07/2023] Open
Abstract
Since elevated serum levels of trimethylamine N-oxide (TMAO) were first associated with increased risk of cardiovascular disease (CVD), TMAO research among chronic diseases has grown exponentially. We now know that serum TMAO accumulation begins with dietary choline metabolism across the microbiome-liver-kidney axis, which is typically dysregulated during pathogenesis. While CVD research links TMAO to atherosclerotic mechanisms in vascular tissue, its molecular effects on metabolic tissues are unclear. Here we report the current standing of TMAO research in metabolic disease contexts across relevant tissues including the liver, kidney, brain, adipose, and muscle. Since poor blood glucose management is a hallmark of metabolic diseases, we also explore the variable TMAO effects on insulin resistance and insulin production. Among metabolic tissues, hepatic TMAO research is the most common, whereas its effects on other tissues including the insulin producing pancreatic β-cells are largely unexplored. Studies on diseases including obesity, diabetes, liver diseases, chronic kidney disease, and cognitive diseases reveal that TMAO effects are unique under pathologic conditions compared to healthy controls. We conclude that molecular TMAO effects are highly context-dependent and call for further research to clarify the deleterious and beneficial molecular effects observed in metabolic disease research.
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Affiliation(s)
- Emily S. Krueger
- Department of Nutrition, Dietetics and Food Science, Brigham Young University, Provo, UT 84602, USA; (E.S.K.); (T.S.L.)
| | - Trevor S. Lloyd
- Department of Nutrition, Dietetics and Food Science, Brigham Young University, Provo, UT 84602, USA; (E.S.K.); (T.S.L.)
- Medical Education Program, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Jeffery S. Tessem
- Department of Nutrition, Dietetics and Food Science, Brigham Young University, Provo, UT 84602, USA; (E.S.K.); (T.S.L.)
- Correspondence: ; Tel.: +1-801-422-9082
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Simultaneous Measurement of Urinary Trimethylamine (TMA) and Trimethylamine N-Oxide (TMAO) by Liquid Chromatography-Mass Spectrometry. Molecules 2020; 25:molecules25081862. [PMID: 32316639 PMCID: PMC7222018 DOI: 10.3390/molecules25081862] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 04/15/2020] [Accepted: 04/16/2020] [Indexed: 12/14/2022] Open
Abstract
Trimethylamine (TMA) is a gut microbial metabolite—rendered by the enzymatic cleavage of nutrients containing a TMA moiety in their chemical structure. TMA can be oxidized as trimethylamine N-oxide (TMAO) catalyzed by hepatic flavin monooxygenases. Circulating TMAO has been demonstrated to portend a pro-inflammatory state, contributing to chronic diseases such as cardiovascular disease and chronic kidney disease. Consequently, TMAO serves as an excellent candidate biomarker for a variety of chronic inflammatory disorders. The highly positive correlation between plasma TMAO and urine TMAO suggests that urine TMAO has the potential to serve as a less invasive biomarker for chronic disease compared to plasma TMAO. In this study, we validated a method to simultaneously measure urine TMA and TMAO concentrations by liquid chromatography–mass spectrometry (LC/MS). Urine TMA and TMAO can be extracted by hexane/butanol under alkaline pH and transferred to the aqueous phase following acidification for LC/MS quantitation. Importantly, during sample processing, none of the nutrients with a chemical structure containing a TMA moiety were spontaneously cleaved to yield TMA. Moreover, we demonstrated that the acidification of urine prevents an increase of TMA after prolonged storage as was observed in non-acidified urine. Finally, here we demonstrated that TMAO can spontaneously degrade to TMA at a very slow rate.
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A multiplexed targeted assay for high-throughput quantitative analysis of serum methylamines by ultra performance liquid chromatography coupled to high resolution mass spectrometry. Arch Biochem Biophys 2016; 597:12-20. [PMID: 27036856 DOI: 10.1016/j.abb.2016.03.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 03/27/2016] [Accepted: 03/28/2016] [Indexed: 12/28/2022]
Abstract
Methylamines are biologically-active metabolites present in serum and urine samples, which play complex roles in metabolic diseases. Methylamines can be detected by proton nuclear magnetic resonance (NMR), but specific methods remain to be developed for their routine assay in human serum in clinical settings. Here we developed and validated a novel reliable "methylamine panel" method for simultaneous quantitative analysis of trimethylamine (TMA), its major detoxification metabolite trimethylamine-N-oxide (TMAO), and precursors choline, betaine and l-carnitine in human serum using Ultra Performance Liquid Chromatography (UPLC) coupled to High Resolution Mass Spectrometry (HRMS). Metabolite separation was carried out on a HILIC stationary phase. For all metabolites, the assay was linear in the range of 0.25-12.5 μmol/L and enabled to reach limit of detection of about 0.10 μmol/L. Relative standard deviations were below 16% for the three levels of concentrations. We demonstrated the strong reliability and robustness of the method, which was applied to serum samples from healthy individuals to establish the range of concentrations of the metabolites and their correlation relationships and detect gender differences. Our data provide original information for implementing in a clinical environment a MS-based diagnostic method with potential for targeted metabolic screening of patients at risk of cardiometabolic diseases.
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Abstract
The molecular genetics of nicotine metabolism involves multiple polymorphic catalytic enzymes. Variation in metabolic pathways results in nicotine disposition kinetics that differ between individuals and ethnic groups. Twin studies indicate that a large part of this variance is genetic in origin, although environmental influences also contribute. The primary aim of this chapter is to review the current knowledge regarding the genetic variability in the enzymes that metabolize nicotine in humans. The focus is on describing the genetic polymorphisms that exist in cytochromes P450 (CYPs), aldehyde oxidase 1 (AOX1), UDP-glucuronosyltransferases (UGTs), and flavin-containing monooxygenase 3 (FMO3). Genetic studies have demonstrated that polymorphisms in CYP2A6, the primary enzyme responsible for nicotine breakdown, make a sizable contribution to the wide range of nicotine metabolic capacity observed in humans. Thus, special attention will be given to CYP2A6, because slower nicotine metabolism requires less frequent self-administration, and accordingly influences smoking behaviors. In addition, the molecular genetics of nicotine metabolism in nonhuman primates, mice, and rats will be reviewed briefly.
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Affiliation(s)
- Jill C Mwenifumbo
- Centre for Addiction & Mental Health and Department of Pharmacology, University of Toronto, Toronto, ON, Canada
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Chalmers RA, Bain MD, Michelakakis H, Zschocke J, Iles RA. Diagnosis and management of trimethylaminuria (FMO3 deficiency) in children. J Inherit Metab Dis 2006; 29:162-72. [PMID: 16601883 DOI: 10.1007/s10545-006-0158-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 07/07/2005] [Indexed: 10/24/2022]
Abstract
Persistent trimethylaminuria in children is caused by autosomal recessively inherited impairment of hepatic trimethylamine (TMA) oxidation due to deficiency of flavin monooxygenase 3 (FMO3) secondary to mutations in the FMO3 gene. Trimethylaminuria or 'fish odour syndrome' is due to excessive excretion into body fluids and breath of TMA derived from the enterobacterial metabolism of dietary precursors. The disorder is present from birth but becomes apparent as foods containing high amounts of choline or of trimethylamine N-oxide (TMAO) from marine (sea or saltwater) fish are introduced into the diet. In our experience, trimethylaminuria (FMO3 deficiency) in children is rare. We have compared the dynamics and diagnostic efficacy of choline loading with marine fish meals in six children with trimethylaminuria. Loading with a marine fish meal provides a simple and acceptable method for confirmation of diagnosis of suspected trimethylaminuria in children, with the effects being cleared more quickly than with a choline load test. However, oral loading with choline bitartrate allows estimation of residual oxidative capacity in vivo and is a useful adjunct to molecular studies. Patients homozygous for the 'common' P153L mutation in the FMO3 gene showed virtual complete lack of residual TMA N-oxidative capacity, consistent with a nonfunctional or absent FMO3 enzyme, whereas a patient with the M82T mutation showed some residual oxidative capacity. A patient compound heterozygous for two novel mutations, G193E and R483T, showed considerable residual N-oxidative capacity. A further patient, heterozygous for two novel sequence variations in the FMO3 gene, consistently showed malodour and elevated urinary TMA/TMAO ratios under basal conditions but a negative response to both choline and marine fish meal loading. Comparison of the effects of administration of antibiotics (metronidazole, amoxicillin, neomycin) on gut bacterial production of trimethylamine from choline showed they all reduced TMA production to a limited extent, with neomycin being most effective. 'Best-practice' diagnostic and treatment guidelines are summarized.
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Affiliation(s)
- R A Chalmers
- Paediatric Metabolism Unit, St George's Hospital Medical School, London, UK.
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Busby MG, Fischer L, da Costa KA, Thompson D, Mar MH, Zeisel SH. Choline- and betaine-defined diets for use in clinical research and for the management of trimethylaminuria. ACTA ACUST UNITED AC 2005; 104:1836-45. [PMID: 15565078 DOI: 10.1016/j.jada.2004.09.027] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This article describes the development of a series of choline- and betaine-controlled diets that were served to research subjects as part of an ongoing study of diet requirements in humans. These diets were developed based on the analysis of choline and betaine in individual foods. The calculated diets were compared with analyses of all foods combined into a single sample for each day. The laboratory analyses of choline and betaine in the whole-diet aliquots matched the estimated amounts in the diets that were calculated from the analyses of individual foods. These diets were adjusted for several levels of choline and betaine and were well accepted by research subjects who consumed them for a time period of up to 2 months. This article describes applications of this diet for use in clinical research on methyl-group requirements in humans and for use in clinical practice for counseling the client who requires a choline-controlled diet.
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Affiliation(s)
- Marjorie G Busby
- Health, Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill, School of Medicine, 101 Manning Drive, Chapel Hill, NC 27599, USA.
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Podadera P, Sipahi AM, Arêas JAG, Lanfer-Marquez UM. Diagnosis of suspected trimethylaminuria by NMR spectroscopy. Clin Chim Acta 2005; 351:149-54. [PMID: 15563884 DOI: 10.1016/j.cccn.2004.09.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Revised: 08/31/2004] [Accepted: 09/01/2004] [Indexed: 11/21/2022]
Abstract
BACKGROUND Trimethylamine (TMA) is a volatile substance produced in the gut, absorbed into the blood and further metabolized by healthy individuals into trimethylamine-N-oxide (TMAO) by TMA-oxidase and then excreted in urine. Patients suffering from trimethylaminuria (TMAU) show an impaired enzymatic oxidation of TMA, excreting this amine in breath, urine and other body secretions which confers an unpleasant body odor. METHODS We diagnosed a Brazilian adult male patient suspected of trimethylaminuria with a burden of choline bitartarate by monitoring the urinary excretion of TMA and TMAO by proton nuclear magnetic resonance spectroscopy ((1)H-NMR). RESULTS The patient's urinalyses showed an augmented TMA (12.64+/-0.95 mg/l) and TMAO (88.42+/-0.82 mg/l) excretion 6 h after the overload test representing an oxidation capacity of 84.6%, consistent with a heterozygosis condition. Diets containing tuna fish or eggs resulted in an excretion of TMA and TMAO similar to that of the control diet. Only the diet based on dogfish, rich in TMAO, enhanced the excretion of TMA and TMAO reaching 24.65 and 1055.55 mg/l, respectively, in the 0-24 h urine sample. CONCLUSIONS It was concluded first, that the patient was not able to metabolize the dietary overload of TMA and second, that more studies are needed to substantiate foods that should be avoided, especially regarding fish, due to their high TMA precursor contents.
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Affiliation(s)
- Priscilla Podadera
- Departamento de Alimentos e Nutrição Experimental, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Av. Prof. Lineu Prestes, 580, CEP 05508-900-São Paulo, Brazil
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Zeisel SH, Mar MH, Howe JC, Holden JM. Concentrations of choline-containing compounds and betaine in common foods. J Nutr 2003; 133:1302-7. [PMID: 12730414 DOI: 10.1093/jn/133.5.1302] [Citation(s) in RCA: 517] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Choline is important for normal membrane function, acetylcholine synthesis and methyl group metabolism; the choline requirement for humans is 550 mg/d for men (Adequate Intake). Betaine, a choline derivative, is important because of its role in the donation of methyl groups to homocysteine to form methionine. In tissues and foods, there are multiple choline compounds that contribute to total choline concentration (choline, glycerophosphocholine, phosphocholine, phosphatidylcholine and sphingomyelin). In this study, we collected representative food samples and analyzed the choline concentration of 145 common foods using liquid chromatography-mass spectrometry. Foods with the highest total choline concentration (mg/100 g) were: beef liver (418), chicken liver (290), eggs (251), wheat germ (152), bacon (125), dried soybeans (116) and pork (103). The foods with the highest betaine concentration (mg/100 g) were: wheat bran (1339), wheat germ (1241), spinach (645), pretzels (237), shrimp (218) and wheat bread (201). A number of epidemiologic studies have examined the relationship between dietary folic acid and cancer or heart disease. It may be helpful to also consider choline intake as a confounding factor because folate and choline methyl donation can be interchangeable.
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Affiliation(s)
- Steven H Zeisel
- Department of Nutrition, School of Public Health and School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA.
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Pardini RS, Sapien RE. Trimethylaminuria (fish odor syndrome) related to the choline concentration of infant formula. Pediatr Emerg Care 2003; 19:101-3. [PMID: 12698036 DOI: 10.1097/00006565-200304000-00010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Ricci S Pardini
- Department of Emergency Medicine, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, USA
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10
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Cashman JR. Human flavin-containing monooxygenase (form 3): polymorphisms and variations in chemical metabolism. Pharmacogenomics 2002; 3:325-39. [PMID: 12052141 DOI: 10.1517/14622416.3.3.325] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The human flavin-containing monooxygenases catalyze the oxygenation of nucleophilic heteroatom-containing drugs, xenobiotics and endogenous materials. Evidence for six forms of the FMO gene exist but it is FMO form 3 (FMO3) that is the prominent form in adult human liver that is likely to be associated with the bulk of FMO-mediated metabolism. An understanding of the substrate specificity of human FMO3 is beginning to emerge and several examples of drugs and chemicals extensively metabolized by FMO3 have been reported. Expression of FMO3 is species- and tissue-specific, but unlike human cytochrome P450 (CYP450), mammalian FMO3 does not appear to be inducible. Interindividual variation in FMO3-dependent metabolism of drugs, chemicals and endogenous materials is therefore more likely to be due to genetic and not environmental effects. Certain mutations of the human FMO3 gene have been associated with abnormal N-oxygenation of trimethylamine. Deficient N-oxygenation of trimethylamine results in a condition called trimethylaminuria. Some treatment strategies for this inborn error of metabolism are discussed. Other common variants of the FMO3 gene including E158K, V257M and E308G have been observed. It is possible that allelic variation of human FMO3 causes abnormal metabolism of chemicals and has clinical implications for human drug metabolism, but this is an understudied area. Human FMO3 allelic variation may eventually be shown to contribute to interindividual and interethnic variability in FMO3-mediated metabolism. Human FMO3 may be another example of an environmental gene that participates in a protective mechanism to help shield humans from potentially toxic exposure to chemicals. Heterogeneity in the relative frequencies of single and multiple site alleles, haplotypes and genotypes of the human FMO3 amongst various ethnic groups suggests population differences.
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Affiliation(s)
- John R Cashman
- Human BioMolecular Research Institute, 5310 Eastgate Mall, San Diego, CA 92121, USA.
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Kubota M, Nakamoto Y, Nakayama K, Ujjin P, Satarug S, Mushiroda T, Yokoi T, Funayama M, Kamataki T. A Mutation in the Flavin-containing Monooxygenase 3 Gene and its Effects on Catalytic Activity for N-oxidation of Trimethylamine In Vitro. Drug Metab Pharmacokinet 2002; 17:207-13. [PMID: 15618671 DOI: 10.2133/dmpk.17.207] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To clarify the mutation of the flavin-containing monooxygenase (FMO) 3 gene causing fish-odor syndrome, we analyzed the FMO3 gene of a Thai subject who possibly suffered from fish-odor syndrome. A novel mutation, a single-base substitution from G to A at the position of 265 (G265A), was identified in exon 3. The mutation caused an amino acid substitution from valine to isoleucine at residue 58 (V58I). The mutated FMO3 protein with V58I exhibited the reduced trimethylamine N-oxidase activity when it was expressed in E. coli. The V(max)/K(m) value for the activity of the mutant-type FMO3 was about 5 times lower than that for the wild-type FMO3.
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Affiliation(s)
- Megumi Kubota
- Laboratory of Drug Metabolism, Division of Pharmacobio-dynamics, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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Janmohamed A, Dolphin CT, Phillips IR, Shephard EA. Quantification and cellular localization of expression in human skin of genes encoding flavin-containing monooxygenases and cytochromes P450. Biochem Pharmacol 2001; 62:777-86. [PMID: 11551524 DOI: 10.1016/s0006-2952(01)00718-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The expression, in adult human skin, of genes encoding flavin-containing monooxygenases (FMOs) 1, 3, 4, and 5 and cytochromes P450 (CYPs) 2A6, 2B6, and 3A4 was determined by RNase protection. Each FMO and CYP exhibits inter-individual variation in expression in this organ. Of the individuals analysed, all contained CYP2B6 mRNA in their skin, 90% contained FMO5 mRNA and about half contained mRNAs encoding FMOs 1, 3, and 4, and CYPs 2A6 and 3A4. The amount of each of the FMO and CYP mRNAs in skin is much lower than in the organ in which it is most highly expressed, namely the kidney (for FMO1) and the liver (for the others). In contrast to the latter organs, in the skin FMO mRNAs are present in amounts similar to, or greater than, CYP mRNAs. Only the mRNA encoding CYP2B6 decreased in abundance in skin with increasing age of the individual. All of the mRNAs were substantially less abundant in cultures of keratinocytes than in samples of skin from which the cells were derived. In contrast, an immortalized human keratinocyte cell line, HaCaT, expressed FMO3, FMO5, and CYP2B6 mRNAs in amounts that fall within the range detected in the whole skin samples analysed. FMO1, CYP2A6, and CYP3A4 mRNAs were not detected in HaCaT cells, whereas FMO4 expression was markedly increased in this cell line compared to whole skin. In situ hybridization showed that the expression of each of the FMOs and CYPs analysed was localized to the epidermis, sebaceous glands and hair follicles.
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Affiliation(s)
- A Janmohamed
- Department of Biochemistry and Molecular Biology, University College London, London, UK
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Murphy HC, Dolphin CT, Janmohamed A, Holmes HC, Michelakakis H, Shephard EA, Chalmers RA, Phillips IR, Iles RA. A novel mutation in the flavin-containing monooxygenase 3 gene, FM03, that causes fish-odour syndrome: activity of the mutant enzyme assessed by proton NMR spectroscopy. PHARMACOGENETICS 2000; 10:439-51. [PMID: 10898113 DOI: 10.1097/00008571-200007000-00007] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We have previously shown that primary trimethylaminuria, or fish-odour syndrome, is caused by an inherited defect in the flavin-containing monooxygenase 3 (FMO3) catalysed N-oxidation of the dietary-derived malodorous amine, trimethylamine (TMA). We now report a novel causative mutation for the disorder identified in a young girl diagnosed by proton nuclear magnetic resonance (NMR) spectroscopy of her urine. Sequence analysis of genomic DNA amplified from the patient revealed that she was homozygous for a T to C missense mutation in exon 3 of the FMO3 gene. The mutation changes an ATG triplet, encoding methionine, at codon 82 to an ACG triplet, encoding threonine. A polymerase chain reaction/restriction enzyme-based assay was devised to genotype individuals for the FMO3Thr82 allele. Wild-type and mutant FMO3, heterologously expressed in a baculovirus-insect cell system, were assayed by ultraviolet spectrophotometry and NMR spectroscopy for their ability to catalyse the N-oxidation of TMA. The latter technique has the advantage of enabling the simultaneous, direct and semi-continuous measurement of both of the products, TMA N-oxide and NADP, and of one of the reactants, NADPH. Results obtained from both techniques demonstrate that the Met82Thr mutation abolishes the catalytic activity of the enzyme and thus represents the genetic basis of the disorder in this individual. The combination of NMR spectroscopy with gene sequence and expression technology provides a powerful means of determining genotype-phenotype relationships in trimethylaminuria.
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Affiliation(s)
- H C Murphy
- Cellular and Molecular Mechanisms Research Group, St Bartholomew's and The Royal London School of Medicine and Dentistry, Queen Mary and Westfield College, Whitechapel, London, UK
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Mushiroda T, Yokoi T, Takahara E, Nagata O, Kato H, Kamataki T. The suncus (Suncus murinus) shows poor metabolic phenotype for trimethylamine N-oxygenation. Toxicol Appl Pharmacol 2000; 162:44-8. [PMID: 10631126 DOI: 10.1006/taap.1999.8820] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In vitro and in vivo N-oxygenation of trimethylamine (TMA) in the suncus (Suncus murinus) was investigated. The N-oxygenation of TMA has been thought to be catalyzed by flavin-containing monooxygenase (FMO). In a previous study, we found that the levels of mRNAs for FMOs were extremely low in the suncus. Thus, we intended to evaluate the capacity of the suncus to N-oxygenate TMA compared to the rat. Eadie-Hofstee plots of the TMA N-oxygenation by suncus liver microsomes showed a biphasic pattern, suggesting that more than two enzymes were involved in this reaction. The low K(m) component in the suncus showed a twofold higher K(m) (55 vs. 31 microM) and a fourfold lower V(max) (0.61 vs 2.5 nmol/min/mg protein) values than those obtained using rat liver microsomes, resulting in a sevenfold lower V(max)/K(m) (11 vs 82 microl/min/mg protein) value. After an intraperitoneal administration of TMA (10 mg/kg body wt), the suncus excreted 39.6% of the dose in 24-h urine as TMA, whereas the rats excreted 6.3%. Metabolic ratio in the TMA N-oxygenation was 1.42 and 0.11 in the suncus and the rat, respectively. These results indicate that the suncus can be an animal model for a poor metabolizer phenotype in TMA metabolism.
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Affiliation(s)
- T Mushiroda
- Laboratory of Drug Metabolism, Hokkaido University, Sapporo, Hokkaido, 060-0812, Japan
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Mamer OA, Choinière L, Treacy EP. Measurement of trimethylamine and trimethylamine N-oxide independently in urine by fast atom bombardment mass spectrometry. Anal Biochem 1999; 276:144-9. [PMID: 10603236 DOI: 10.1006/abio.1999.4351] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We report a method based upon fast atom bombardment mass spectrometry (FAB-MS) and stable isotope dilution techniques for the measurement of urinary trimethylamine (TMA) and trimethylamine N-oxide (TMAOx). TMA is extracted from urine that was spiked with (15)N-labeled TMA. The extracted TMA isotopomers are quaternized with trideuteromethyl iodide and analyzed in FAB-MS with hexaethylene glycol as matrix. TMAOx is measured by evaporation of another sample of the urine spiked with (15)N-labeled TMAOx on the FAB probe and analyzed as for the TMA. The method allows the ready and simple distinguishing of controls and patients with TMAuria, and is useful in monitoring patients with the disorder. We give examples of its use in determining normal control ranges for these metabolites and in evaluating patients.
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Affiliation(s)
- O A Mamer
- The Mass Spectrometry Unit, McGill University, 1130 Pine Avenue West, Montreal, Canada H3A 1A3
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Basarab T, Ashton GH, Menagé HP, McGrath JA. Sequence variations in the flavin-containing mono-oxygenase 3 gene (FMO3) in fish odour syndrome. Br J Dermatol 1999; 140:164-7. [PMID: 10215790 DOI: 10.1046/j.1365-2133.1999.02693.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Trimethylaminuria is inherited recessively as a defect in hepatic N-oxidation of dietary derived trimethylamine (TMA) which causes excess excretion of TMA so that affected individuals have a body odour resembling rotten fish. Flavin-containing mono-oxygenase 3 (FMO3) catalyses TMA oxidation and mutations in the FMO3 gene have recently been shown to underlie trimethylaminuria/fish odour syndrome. We searched for FMO3 mutations in a previously unreported individual with this disorder using polymerase chain reaction of genomic DNA, heteroduplex analysis and direct sequencing of heteroduplex band shifts. We identified a heterozygous missense Pro153-->Leu153 mutation in exon 4. Leu153 has been reported previously as a homozygous mutation in two unrelated siblings with trimethylaminuria and has been shown to result in total loss of FMO3 enzyme activity. In our patient, two further missense mutations were identified on the other FMO3 allele, Val143-->Glu143 and Glu158-->Lys158. Lys158 is known to be a common polymorphism, but has functional significance in reducing enzyme activity by 10%. Glu143 has not been documented previously, but was shown to be a rare polymorphism and may be of further relevance in reducing FMO3 activity. Mutagenesis studies and enzyme assays will be necessary to confirm or refute the potential pathogenic significance of Glu143 in this patient, but the mutation Pro153-->Leu153 appears to be a recurrent cause of this distressing metabolic disorder.
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Affiliation(s)
- T Basarab
- St. John's Institute of Dermatology, The Guy's, King's College and St Thomas' Hospitals' Medical School, St.Thomas' Hospital, Lambeth Palace Road, London SE1 7EH
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Dolphin CT, Janmohamed A, Smith RL, Shephard EA, Phillips IR. Missense mutation in flavin-containing mono-oxygenase 3 gene, FMO3, underlies fish-odour syndrome. Nat Genet 1997; 17:491-4. [PMID: 9398858 DOI: 10.1038/ng1297-491] [Citation(s) in RCA: 180] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Individuals with primary trimethylaminuria exhibit a body odour reminiscent of rotting fish, due to excessive excretion of trimethylamine (TMA; refs 1-3). The disorder, colloquially known as fish-odour syndrome, is inherited recessively as a defect in hepatic N-oxidation of dietary-derived TMA and cannot be considered benign, as sufferers may display a variety of psychosocial reactions, ranging from social isolation of clinical depression and attempted suicide. TMA oxidation is catalyzed by flavin-containing mono-oxygenase (FMO; refs 7,8), and tissue localization and functional studies have established FMO3 as the form most likely to be defective in fish-odour syndrome. Direct sequencing of the coding exons of FMO3 amplified from a patient with fish-odour syndrome identified two missense mutations. Although one of these represented a common polymorphism, the other, a C-->T transition in exon 4, was found only in an affected pedigree, in which it segregated with the disorder. The latter mutation predicts a proline-->leucine substitution at residue 153 and abolishes FMO3 catalytic activity. Our results indicate that defects in FMO3 underlie fish-odour syndrome and that the Pro 153-->Leu 153 mutation described here is a cause of this distressing condition.
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Affiliation(s)
- C T Dolphin
- Department of Biochemistry, Queen Mary & Westfield College, University of London, UK
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18
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Damani LA, Nnane IP. The assessment of flavin-containing monooxygenase activity in intact animals. DRUG METABOLISM AND DRUG INTERACTIONS 1996; 13:1-28. [PMID: 8902428 DOI: 10.1515/dmdi.1996.13.1.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A large number of drug metabolising enzymes with different substrate specificities and induction and inhibition characteristics have been described, suggesting that specific test drugs, i.e. probes, should be used for assessing the activity of distinct metabolising enzymes. The flavin-containing monooxygenase (FMO) and cytochrome P-450 (P-450) are the two main microsomal enzyme systems involved in the oxidation of xenobiotics. FMO is present in liver and other tissues of most vertebrates. It catalyses the oxidation of a wide range of xenobiotics, especially soft nucleophiles bearing nitrogen and sulphur centres. There is substantial information on both in vitro and in vivo probes for cytochrome P-450. For example antipyrine has been widely used for assessing the activity of P-450 in vivo by utilising pharmacokinetic parameters as indices of enzyme activity. In more recent years, isozyme specific probes have also been developed for some of the P-450s. Whereas a number of substrates are available for measuring FMO activity in vitro (e.g. N,N-dimethylaniline), probes for assessing FMO activity in vivo are limited. In this review a background to the use of in vitro and in vivo probes for assessing the activity of FMO is presented, and approaches and criteria for development of potential pharmacokinetic probes for FMO are described. Preliminary data on the development of ethyl methyl sulphide (EMS) and trimethylamine (TMA) as potential pharmacokinetic probes for assessing FMO activity in rats are discussed in detail. Clinical implications of modulation of FMO activity are discussed, and arguments presented as to why the development of FMO probes for use in man will be useful additions to the range of other compounds available for assessment of liver metabolic function.
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Affiliation(s)
- L A Damani
- Department of Pharmacy, Faculty of Medicine, Chinese University of Hong Kong, Shatin, N.T., Hong Kong
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19
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Lundh T, Akesson B, Skerfving S. Effect of dietary intake of trimethylamine on human metabolism of the industrial catalyst dimethylethylamine. Occup Environ Med 1995; 52:478-83. [PMID: 7670623 PMCID: PMC1128267 DOI: 10.1136/oem.52.7.478] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVES The aim was to study the effect of trimethylamine (TMA) on the metabolism of the industrial catalyst dimethylethylamine (DMEA) to ascertain whether biological monitoring of industrial exposure to DMEA is compromised and excretion of the malodorous DMEA in sweat and urine is increased by dietary intake of TMA. METHODS DMEA (0/25 mg) and TMA (0/300/600 mg) were given simultaneously once weekly for six weeks to five healthy volunteers. Plasma was collected before and one hour after the doses, and urine 0-2, 2-4, 4-6, 6-8, and 8-24 hours after the doses. Specimens were analysed by gas chromatography with a nitrogen sensitive detector. RESULTS Both amines were readily absorbed from the gastrointestinal tract and excreted in urine within 24 hours (DMEA 80%; TMA 86%). Oral intake of TMA increased the DMEA content of plasma and urine dose dependently, although there were large individual differences. Plasma and urinary TMA concentrations also increased, but not dose dependently. Moreover, the findings suggested the formation of endogenous TMA, little dealkylation of DMEA and TMA, and considerable first-pass metabolism. CONCLUSIONS Although intake of TMA reduced N-oxygenation of DMEA and TMA, total urinary DMEA values (aggregate of DMEA and its oxide DMEAO excretion) were unaffected. Thus, monitoring occupational exposure to DMEA by analysis of biological specimens is not confounded by dietary intake of TMA, provided that total urinary DMEA is monitored. Although the increased urinary and hidrotic excretion of DMEA may contribute to body odour problems, they were primarily due to TMA excretion, which is much the greater.
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Affiliation(s)
- T Lundh
- Department of Occupational and Environmental Medicine, University Hospital, Lund, Sweden
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20
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Hadidi HF, Cholerton S, Atkinson S, Irshaid YM, Rawashdeh NM, Idle JR. The N-oxidation of trimethylamine in a Jordanian population. Br J Clin Pharmacol 1995; 39:179-81. [PMID: 7742158 PMCID: PMC1364957 DOI: 10.1111/j.1365-2125.1995.tb04427.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The ability to oxidise trimethylamine (TMA) to trimethylamine N-oxide (TMAO) is distributed polymorphically within a British white population with the majority of individuals excreting greater than 90% of total urinary TMA as TMAO. The opposite extreme is characterised by a rare inborn error of TMA N-oxidation known as the fish-odour syndrome. However there is a lack of information regarding inter-individual variability in the N-oxidation of TMA in other ethnic groups. In this study the urinary excretion of TMA and TMAO was determined over a period of 24 h in 82 Jordanian subjects. A frequency distribution histogram of % of total urinary TMA excreted as TMAO revealed that the majority of subjects excreted greater than 80% of the total urinary TMA as TMAO, however eight subjects (9.7%) excreted less than 80% of the total TMA as TMAO. In a previous study of 169 white British subjects only one (0.6%) excreted less than 80% of the total TMA as TMAO. The results suggest that the prevalence of compromised ability to N-oxidise TMA may be higher in a Jordanian population than in a British population.
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Affiliation(s)
- H F Hadidi
- Department of Pharmacology, Faculty of Medicine, Jordan University of Science and Technology, Irbid
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21
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Abstract
An oral trimethylamine challenge test has been used to confirm the heterozygous status of patients with 'fish-odour syndrome'. By measuring the percentage of total urinary trimethylamine-related material excreted as the N-oxide, no discrimination could be made between obligate heterozygotes (parents of 'fish-odour syndrome' patients) (n = 15; 96 +/- 2%, range 92-98%) and control individuals (parents of unaffected children) (n = 16; 96 +/- 2%, range 93-99%) on a normal diet. However, after ingesting a trimethylamine load (600 mg base) the obligate heterozygotes were clearly distinguishable (76 +/- 3%, range 71-79%) from controls (95 +/- 2%, range 91-99%) (t-test; p <0.001). One of a hundred apparently normal volunteers who were subsequently challenged with trimethylamine had a N-oxidation capacity which fell within the range found among the obligate heterozygotes.
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Affiliation(s)
- A Q Zhang
- Department of Pharmacology and Toxicology, Imperial College of Science, Technology and Medicine, St Mary's Hospital Medical School, London, UK
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22
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Treacy E, Johnson D, Pitt JJ, Danks DM. Trimethylaminuria, fish odour syndrome: a new method of detection and response to treatment with metronidazole. J Inherit Metab Dis 1995; 18:306-12. [PMID: 7474897 DOI: 10.1007/bf00710420] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Trimethylaminuria is an autosomal recessive disorder involving deficient N-oxidation of the dietary-derived amine trimethylamine (TMA). TMA, a volatile tertiary amine, accumulates and is excreted in urine of patients with deficient TMA oxidase activity. Treatment strategies for this condition are limited. We report a new stable-isotope dilution method for rapid sequential analysis of TMA concentrations and the clinical and biochemical response to treatment with metronidazole.
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Affiliation(s)
- E Treacy
- Biochemical Genetics, Montreal Children's Hospital, Quebec, Canada
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Affiliation(s)
- S. Van Toller
- Reader in psychology, Warwick Human Chemoreception Research Group, Department of Psychology. University of Warwick, Coventry
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Ayesh R, Mitchell SC, Zhang A, Smith RL. The fish odour syndrome: biochemical, familial, and clinical aspects. BMJ (CLINICAL RESEARCH ED.) 1993; 307:655-7. [PMID: 8401051 PMCID: PMC1678986 DOI: 10.1136/bmj.307.6905.655] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
OBJECTIVES To study the biochemical, familial, and clinical features of the fish odour syndrome among subjects with suspected body malodour. DESIGN Subjects who responded to a newspaper article were screened for the fish odour syndrome by interview and biochemical tests. Families of subjects with the syndrome were tested if possible. SETTING St Mary's Hospital, London, and some interviews at subjects' homes. SUBJECTS 187 subjects (28 males) with suspected body malodour, of whom 156 (19 males) underwent biochemical tests. Five families of six of the subjects with the fish odour syndrome agreed to further tests. MAIN OUTCOME MEASURES Amounts of trimethylamine and trimethylamine N-oxide in urine collected over 24 hours under normal dietary conditions and for eight hours after oral challenge with 600 mg trimethylamine. RESULTS The fish odour syndrome was diagnosed in 11 subjects: the percentage of total trimethylamine excreted in their urine samples that was oxidised to trimethylamine N-oxide was < 55% under normal dietary conditions and < 25% after oral challenge with trimethylamine (in normal subjects > 80% of trimethylamine was N-oxidised). Parents of six of the subjects with the syndrome were tested: all showed impaired N-oxidation of excreted trimethylamine (< 80%) after oral challenge, indicating that they were heterozygous carriers of the allele for the syndrome. The syndrome was associated with various psychosocial reactions including clinical depression. CONCLUSIONS The fish odour syndrome can be inherited in an autosomal recessive fashion. It should be considered as a possible causative factor in patients complaining of body malodour.
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Affiliation(s)
- R Ayesh
- Department of Pharmacology and Toxicology, St Mary's Hospital Medical School, (Imperial College), London
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25
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Abstract
Polymorphisms have been detected in a variety of xenobiotic-metabolizing enzymes at both the phenotypic and genotypic level. In the case of four enzymes, the cytochrome P450 CYP2D6, glutathione S-transferase mu, N-acetyltransferase 2 and serum cholinesterase, the majority of mutations which give rise to a defective phenotype have now been identified. Another group of enzymes show definite polymorphism at the phenotypic level but the exact genetic mechanisms responsible are not yet clear. These enzymes include the cytochromes P450 CYP1A1, CYP1A2 and a CYP2C form which metabolizes mephenytoin, a flavin-linked monooxygenase (fish-odour syndrome), paraoxonase, UDP-glucuronosyltransferase (Gilbert's syndrome) and thiopurine S-methyltransferase. In the case of a further group of enzymes, there is some evidence for polymorphism at either the phenotypic or genotypic level but this has not been unambiguously demonstrated. Examples of this class include the cytochrome P450 enzymes CYP2A6, CYP2E1, CYP2C9 and CYP3A4, xanthine oxidase, an S-oxidase which metabolizes carbocysteine, epoxide hydrolase, two forms of sulphotransferase and several methyltransferases. The nature of all these polymorphisms and possible polymorphisms is discussed in detail, with particular reference to the effects of this variation on drug metabolism and susceptibility to chemically-induced diseases.
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Affiliation(s)
- A K Daly
- Department of Pharmacological Sciences, University of Newcastle upon Tyne, Medical School, U.K
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26
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Chen H, Aiello F. Trimethylaminuria in a girl with Prader-Willi syndrome and del(15)(q11q13). AMERICAN JOURNAL OF MEDICAL GENETICS 1993; 45:335-9. [PMID: 8434620 DOI: 10.1002/ajmg.1320450310] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We report on an individual with trimethylaminuria, Prader-Willi syndrome, and del(15) (q11q13). To our knowledge, such an association has never been reported. Skin sores secondary to choline-rich foods and amenable to dietary control have not been described in trimethylaminuria, although they are seen in some patients with Prader-Willi syndrome. Pathogenesis, clinical diagnosis, and management of reported cases with trimethylaminuria are reviewed. Serious social and behavioral problems may result from strong body odor. Amelioration of the "fish odor" by dietary choline restriction makes trimethylaminuria detection important. Association of trimethylaminuria with Prader-Willi syndrome and del(15) (q11q13) in this patient is of particular interest. It may represent a contiguous gene syndrome, or deletion of the normal allele leading to expression of a single recessive trimethylaminuria gene, or an unrelated association, such as in Noonan syndrome. However, recent development of mapping of flavin-containing monooxygenase 2 (FMO2), the likely enzyme that is defective in fish odor syndrome, to chromosome 1q probably excludes pathogenetic association of fish odor syndrome with the Prader-Willi syndrome.
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Affiliation(s)
- H Chen
- Department of Medical Genetics, University of South Alabama, Mobile 36688
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27
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Ayesh R, Kroemer H, Eichelbaum M, Smith RL. Metabolism of verapamil in a family pedigree with deficient N-oxidation of trimethylamine. Br J Clin Pharmacol 1991; 31:693-6. [PMID: 1867964 PMCID: PMC1368582 DOI: 10.1111/j.1365-2125.1991.tb05595.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The oxidative N-dealkylation of verapamil has been studied in a family of five members with two propositi with an inherited deficiency of trimethylamine N-oxidation (fish-odour syndrome). The results were assessed for possible co-segregation of the trimethylamine N-oxidation phenotype and any observed deficiency in oxidative N-dealkylation. The general pattern of metabolism of verapamil in the five subjects studied was similar to that reported in earlier investigations. Moreover, there were no differences between the two affected subjects and other family members with respect to the metabolic pattern. It is concluded that there is no functional segregation with respect to the mechanisms controlling trimethylamine N-oxidation and verapamil N-dealkylation.
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Affiliation(s)
- R Ayesh
- Department of Pharmacology and Toxicology, St Mary's Hospital Medical School, London
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28
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Anthoni U, Christophersen C, Gram L, Nielsen NH, Nielsen P. Poisonings from flesh of the Greenland shark Somniosus microcephalus may be due to trimethylamine. Toxicon 1991; 29:1205-12. [PMID: 1801314 DOI: 10.1016/0041-0101(91)90193-u] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The flesh of the Greenland shark, Somniosus microcephalus, especially in fresh condition, is toxic to both dog and man. Analysis of the toxic fractions indicates the presence of large amounts of trimethylamine oxide (TMAO) but no other substances that could be directly responsible for the poisoning. The symptoms appear to be due to an acute trimethylamine (TMA) poisoning arising from intestinal reduction of TMAO to TMA. TMA stimulates contraction of the guinea-pig ileum (antagonized by atropine but not hexamethonium). Low concentrations of TMA increase contraction of the rat phrenic nerve-diaphragm preparation, whereas higher concentrations cause blockade.
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Affiliation(s)
- U Anthoni
- Marine Chemistry Section, H. C. Orsted Institute, University of Copenhagen, Denmark
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29
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Affiliation(s)
- R Ayesh
- Department of Pharmacology & Toxicology, St. Mary's Hospital Medical School, London, U.K
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30
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Ayesh R, Al-Waiz M, McBurney A, Mitchell SC, Idle JR, Ward JW, Smith RL. Variable metabolism of pinacidil: lack of correlation with the debrisoquine and trimethylamine C- and N-oxidative polymorphisms. Br J Clin Pharmacol 1989; 27:423-8. [PMID: 2719898 PMCID: PMC1379720 DOI: 10.1111/j.1365-2125.1989.tb05389.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
1. The urinary excretion of pinacidil and its N-oxide in man was found to vary over a five-fold range. 2. Studies in individuals with inherited deficiencies for C-hydroxylation (debrisoquine type) and trimethylamine N-oxidation showed that the N-oxidation of pinacidil did not co-segregate with these oxidative polymorphisms. 3. It is concluded that the variable N-oxidation of pinacidil is most likely to be due to variations in the activity of the P-450 isozymes rather than in the microsomal flavoprotein containing mixed-function amine oxidase of Ziegler which is considered to be responsible for the N-oxidation of trimethylamine.
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Affiliation(s)
- R Ayesh
- Department of Pharmacology, St Mary's Hospital Medical School, London
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31
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al-Waiz M, Ayesh R, Mitchell SC, Idle JR, Smith RL. Trimethylaminuria: the detection of carriers using a trimethylamine load test. J Inherit Metab Dis 1989; 12:80-5. [PMID: 2501587 DOI: 10.1007/bf01805534] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A method potentially of value for investigating putative heterozygotes or carriers of trimethylaminuria by using a single oral dose of trimethylamine (TMA) is described. For healthy volunteers under normal dietary condition and following oral challenge with 300 mg and 600 mg TMA-base, over 90% of the urinary TMA was excreted in the form of TMA (93.6 +/- 1.6%). However, at a dose level of 900 mg TMA-base, there was clear evidence of saturation of the N-oxidation reaction as urinary TMA excretion declined to 77.2% (range 74.8-78.9) of the total dose of TMA. By contrast, in pedigree studies based upon propositi with trimethylaminuria, several parents were identified who showed clear evidence of saturation of the N-oxidation of TMA at the 600 mg TMA-base dose level, but not at 300 mg TMA-base or under normal dietary condition. In these individuals, the proportion of urinary TMA as trimethylamine N-oxide (TMAO) declined to (77.3 +/- 1.7%). Accordingly we propose that the oral administration of 600 mg TMA-base and the analysis of the following 0-8-h urine collection may be useful for the investigation of possible carriers of trimethylaminuria.
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Affiliation(s)
- M al-Waiz
- Department of Pharmacology, St. Mary's Hospital, Medical School, London
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