Trimethylaminuria: fishy odors in children

FMO3 deficiency of duck leads to decreased lipid deposition and increased antibacterial activity

Background

Most duck eggs possess a fishy odor, indicating that ducks generally exhibit impaired trimethylamine (TMA) metabolism. TMA accumulation is responsible for this unpleasant odor, and TMA metabolism plays an essential role in trimethylaminuria (TMAU), also known as fish odor syndrome. In this study, we focused on the unusual TMA metabolism mechanism in ducks, and further explored the unclear reasons leading to the debilitating TMA metabolism.

Methods

To achieve this, transcriptome, proteome, and metagenome analyses were first integrated based on the constructed duck populations with high and low TMA metabolism abilities. Additionally, further experiments were conducted to validate the hypothesis regarding the limited flavin-containing monooxygenase 3 (FMO3) metabolism ability of ducks.

Results

The study demonstrated that liver FMO3 and cecal microbes, including Akkermansia and Mucispirillum, participated in TMA metabolism in ducks. The limited oxidation ability of FMO3 explains the weakening of TMA metabolism in ducks. Nevertheless, it decreases lipid deposition and increases antibacterial activity, contributing to its survival and reproduction during the evolutionary adaptation process.

Conclusions

This study demonstrated the function of FMO3 and intestinal microbes in regulating TMA metabolism and illustrated the biological significance of FMO3 impairment in ducks.

Balancing the Equation: A Natural History of Trimethylamine and Trimethylamine-N-oxide

Trimethylamine (TMA) and its N-oxide (TMAO) are ubiquitous in prokaryote and eukaryote organisms as well as in the environment, reflecting their fundamental importance in evolutionary biology, and their diverse biochemical functions. Both metabolites have multiple biological roles including cell-signaling. Much attention has focused on the significance of serum and urinary TMAO in cardiovascular disease risk, yet this is only one of the many facets of a deeper TMA-TMAO partnership that reflects the significance of these metabolites in multiple biological processes spanning animals, plants, bacteria, and fungi. We report on analytical methods for measuring TMA and TMAO and attempt to critically synthesize and map the global functions of TMA and TMAO in a systems biology framework.

Olfaction scaffolds the developing human from neonate to adolescent and beyond

The impact of the olfactory sense is regularly apparent across development. The fetus is bathed in amniotic fluid (AF) that conveys the mother's chemical ecology. Transnatal olfactory continuity between the odours of AF and milk assists in the transition to nursing. At the same time, odours emanating from the mammary areas provoke appetitive responses in newborns. Odours experienced from the mother's diet during breastfeeding, and from practices such as pre-mastication, may assist in the dietary transition at weaning. In parallel, infants are attracted to and recognize their mother's odours; later, children are able to recognize other kin and peers based on their odours. Familiar odours, such as those of the mother, regulate the child's emotions, and scaffold perception and learning through non-olfactory senses. During juvenility and adolescence, individuals become more sensitive to some bodily odours, while the timing of adolescence itself has been speculated to draw from the chemical ecology of the family unit. Odours learnt early in life and within the family niche continue to influence preferences as mate choice becomes relevant. Olfaction thus appears significant in turning on, sustaining and, in cases when mother odour is altered, disturbing adaptive reciprocity between offspring and carer during the multiple transitions of development between birth and adolescence. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

Riboflavin-responsive trimethylaminuria in a patient with homocystinuria on betaine therapy

A 17-year-old female patient with pyridoxine non-responsive homocystinuria, treated with 20 g of betaine per day, developed a strong body odour, which was described as fish-like. Urinary trimethylamine (TMA) was measured and found to be markedly increased. DNA mutation analysis revealed homozygosity for a common allelic variant in the gene coding for the TMA oxidising enzyme FMO3. Without changing diet or betaine therapy, riboflavin was given at a dose of 200 mg per day. An immediate improvement in her odour was noticed by her friends and family and urinary TMA was noted to be greatly reduced, although still above the normal range.Gradual further reductions in TMA (and odour) have followed whilst receiving riboflavin. Throughout this period, betaine compliance has been demonstrated by the measurement of dimethylglycine (DMG) excretion, which has been consistently increased. Marked excretions of DMG when the odour had subsided also demonstrate that DMG was not the source of the odour.This patient study raises the possibility that betaine may be converted to TMA by intestinal flora to some degree, resulting in a significant fish odour when oxidation of TMA is compromised by FMO3 variants. The possibility exists that the body odour occasionally associated with betaine therapy for homocystinuria may not be related to increased circulating betaine or DMG, but due to a common FMO3 mutation resulting in TMAU. Benefits of riboflavin therapy for TMAU for such patients would allow the maintenance of betaine therapy without problematic body odour.

Diagnosis and management of trimethylaminuria (FMO3 deficiency) in children

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.

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

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.

Early flavor experiences: research update

Anyone who has observed infants for any period of time can testify to the intense activity occurring in and around their mouths--the primary site for learning in the first few months of life. Before they are even able to crawl, infants have learned much about their new sensory world. Though recent research we have begun to explore the impact of these early experiences on infants' acceptance of solid foods and how they explore objects in their environment. We have also begun to focus on the sensory experiences of the formula-fed infant, in particular, how their responses to particular formulas, which are extremely unpalatable to older children and adults, change during infancy. This is a relatively new and exciting area of study, with much research yet to be done. It is clear, however, that infants are not passive receptacles for flavored foods. Parents who offer a variety of foods will provide both a nutritious, well-balanced diet, as well as an opportunity for their children's own personal preferences to develop.

Trimethylaminuria in a girl with Prader-Willi syndrome and del(15)(q11q13)

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.

The identification of trimethylamine excess in man: quantitative analysis and biochemical origins

The underlying biochemical causes of chronic odor problems in humans have attracted only a few investigators. This may be due, in part, to intermittent odor complaints, to the psychological problems often associated with these patients, or to the low incidence of a true metabolic disorder. One cause of intense odor is an excessive excretion of trimethylamine (TMA) in sweat, breath, and urine and was reported to be due to a defect in the liver enzyme that converts this volatile amine to its N-oxide. Other investigators have reported TMA excess as a result of liver, kidney, and/or gastrointestinal dysfunction. We report on the development of an analytical technique for urine that can be used to identify those individuals whose chronic odor is caused by a defect in their TMA pathway. A simple extension of the basic TMA analysis can be used to measure the concentration of TMA N-oxide in the affected patients. These data can, in turn, be used to demonstrate the level of activity of the N-oxide-forming enzyme in these subjects. The results obtained from using this test on more than 50 subjects indicate, in addition to a normal population, at least two types of patients with TMA excess. One group has excess TMA excretion with low activity of the N-oxide and another group shows excess TMA excretion with normal N-oxide activity.

Effects of dietary alteration on trimethylaminuria as measured by mass spectrometry

The urine of a 9-year-old boy suffering from extreme body odour was assayed for trimethylamine (TMA) by gas chromatography-mass spectrometry. A trapping column bed, specifically designed for volatile compounds, was used in the mass spectrometry. The diagnosis of rare trimethylaminuria was confirmed by the presence of appreciable urinary TMA. Urinary TMA concentrations were reduced to virtually nil after the elimination of the major choline sources (fish and eggs) from the diet.

An unusual case of trimethylaminuria

A case is reported of trimethylaminuria that first developed in adulthood without any apparent cause. The patient developed a characteristic fish odour of his sweat, urine and to his breath after the consumption of choline-rich foods. Elevated levels of trimethylamine were present in the urine after dietary tests and identified by means of gas chromatography.

Formation of aliphatic amine precursors of N-nitrosodimethylamine after oral administration of choline and choline analogues in the rat

Trimethylamine and dimethylamine are important precursors of N-nitrosodimethylamine, which is a potent carcinogen in a wide variety of animal species. Choline, a component of the normal human diet, is metabolized by bacteria within the intestine to form trimethylamine and dimethylamine. However, animals on a choline-free diet continue to excrete some trimethylamine and dimethylamine, suggesting that other dietary precursors of these methylamines might exist. To determine whether C-N bond cleavage by the intestinal bacteria is specific to the choline molecule, we measured monomethylamine, dimethylamine, trimethylamine and trimethylamine oxide excretion in rat urine after the administration of compounds that shared structural features with choline. Water, choline, dimethylaminoethanol, diethylaminoethanol, phosphocholine, betaine, carnitine, beta-methylcholine or dimethylaminoethyl chloride were administered by orogastric intubation, and the urine was collected for 24 hr. Administration of choline (15 mmol/kg body weight) resulted in increased urinary excretion of dimethylamine, trimethylamine and trimethylamine oxide (increases of approximately twofold, 500-fold and 50-fold, respectively). Of the administered choline, 12% was converted to trimethylamine or trimethylamine oxide and excreted in the urine within 24 hr. Phosphocholine administration resulted in similar increases in dimethylamine, trimethylamine and trimethylamine oxide excretion by rats. Modification of the ethyl-backbone or quaternary amine end of the choline molecule resulted in marked suppression of methylamine formation. Though administration of some analogues of choline (methylcholine, betaine and carnitine) resulted in the formation of small amounts of trimethylamine or trimethylamine oxide, and the administration of others (dimethylaminoethanol and dimethylaminoethyl chloride) resulted in the formation of some dimethylamine, the amounts formed were minimal compared with the amounts of trimethylamine and trimethylamine oxide formed after choline administration. Thus, of the many components of foods, only choline and its esters are likely to be significant substrates for trimethylamine and dimethylamine formation. How then can we explain the persistence of trimethylamine and dimethylamine excretion observed in choline-deficient rats? We suggest that endogenous (non-bacterial) synthesis of trimethylamine and dimethylamine occurs within some tissue of the rat.

Fish odor syndrome: trimethylaminuria with milk as chief dietary factor

A 10-year-old boy had a two-year history of a rotten fish odor, noted particularly in the summer after exercise. The odor was partially controlled by frequent bathing. Dietary history was unremarkable except for large daily milk intake. Milk elimination resulted in a prompt disappearance of the odor. Studies of the patient's urine after choline loading established the diagnosis of trimethylaminuria. Restriction of dietary milk as well as foods containing choline and trimethylamine oxide eliminated the offensive odor.

The analysis of trimethylamine in body fluids by a direct medium resolution mass spectrometric method

A simple, high throughput method of analysis of trimethylamine in body fluids has been developed to assist with the management of patients with the inherited metabolic disorder, trimethylaminuria. The headspace in sealed vials was analysed using perdeuterated (2H10)trimethylamine hydrochloride as an internal standard. The gas chromatograph inlet system of the mass spectrometer was adapted to suit this method of analysis. Medium resolving power was used to measure the ion ratio of the [M-H]+ ion of trimethylamine and the [M-2H]+ ion of the internal standard. The method is faster and more accurate than gas chromatographic methods. The concentrations of trimethylamine found in normal urine are similar to those reported previously.

Olfactory diagnosis in medicine

Like the reporter who relies on a nose for news, the physician needs a nose for diseases and intoxications. Characteristic patient odors accompany many diseases and intoxications, and their recognition can provide diagnostic clues, guide the laboratory evaluation, and affect the choice of immediate therapy.

Fracture of the femur, fish odour, and copper deficiency in a preterm infant

A preterm baby boy with blood and bone changes of copper deficiency is described. Copper deficiency was suspected after fracture of the left femur during examination of the hip joint. A low serum copper concentration (2.7 mumol/l; 17.2 micrograms/100 ml) and caeruloplasmin (0.04 g/l; 0.004 g/100 ml) confirmed the diagnosis. Despite the introduction of solids at 18 weeks the copper concentration remained low, and treatment with copper sulphate (2.5 mg daily) was started at 6 months. Treatment was stopped at 9 months, when he was both physically and developmentally normal. When given a choline-containing vitamin preparation (Ketovite) he developed a fish odour because of the accumulation of trimethylamine. Withdrawal of this preparation at 6 weeks and substitution with a choline-free preparation (Abidec) was soon followed by disappearance of the odour. It is speculated that prematurity rather than copper deficiency was responsible for the poor activity of liver enzyme, trimethylamine oxidase.

Trimethylaminuria

We describe the case of an otherwise healthy 7-year-old girl whose mother noticed that she intermittently smelt of fish. This was due to the intermittent excretion of trimethylamine which could be precipitated by choline ingestion and by eating fish. Excluding eggs, liver and salt-water fish from the diet relieved the symptom. After a standard 15 g choline load, the child's father, but not her mother, excreted amounts of trimethylamine which were intermediate between those excreted by the patient and normal control subjects.

Lecithin consumption increases acetylcholine concentrations in rat brain and adrenal gland

Consumption of a single meal containing lecithin, the major source of choline occurring naturally in the diet, increased the concentrations of choline and acetylcholine in rat brain and adrenal gland. Hence, the concentration of acetylcholine in the tissues may normally be under direct, short-term nutritional control.

Oral choline administration to patients with tardive dyskinesia

We gave pharmacologic doses of choline to patients with tardive dyskinesia in an attempt to suppress involuntary facial movements. Choline is the physiologic precursor of acetylcholine, and its administration elevates brain acetylcholine levels in laboratory animals and, possibly, in human beings. Hence, we thought that its use could benefit patients with diseases like tardive dyskinesia, which is believed to result from deficient central cholinergic tone. Twenty patients with stable baccal-lingual-masticatory movements took oral doses of choline for two weeks according to a double-blind crossover protocol. Plasma choline levels rose from 12.4 +/- 1.0 to 33.5 +/- 2.5 nmol per milliliter (mean +/- S.E.M.; P less than 0.001) during this period. Choreic movements decreased in nine patients, worsened in one and were unchanged in 10. Thus, oral doses of choline can be useful in neurologic diseases in which an increase in acetylcholine release is desired.

Concentration of headspace, airborne and aqueous volatiles on Chromosorb 105 for examination by gas chromatography and gas chromatography-mass spectrometry

Techniques are described for the collection of volatile material from headspace vapours and the atmosphere and for the direct extraction of volatiles from aqueous solution by traps containing the porous polymer Chromosorb 105. The traps are inserted through a valve into a gas chromatograph which facilitates the desorption and transfer of the volatiles to high-resolution capillary columns. Selected applications of the technique are described.