Trimethylaminuria (fish-odour syndrome) and oral malodour

Living with trimethylaminuria and body and breath malodour: personal perspectives

BACKGROUND

Many people suffer from body and breath malodour syndromes. One of these is trimethylaminuria, a condition characterized by excretion in breath and bodily fluids of trimethylamine, a volatile and odorous chemical that has the smell of rotting fish. Trimethylaminuria can be primary, due to mutations in the gene encoding flavin-containing monooxygenase 3, or secondary, due to various causes. To gain a better understanding of problems faced by United Kingdom residents affected by body and breath malodour conditions, we conducted a survey.

METHODS

Two anonymous online surveys, one for adults and one for parents/guardians of affected children, were conducted using the Opinio platform. Participants were invited via a trimethylaminuria advisory website. Questions were a mix of dropdown, checkbox and open-ended responses. Forty-four adults and three parents/guardians participated. The dropdown and checkbox responses were analysed using the Opinio platform.

RESULTS

All participants reported symptoms of body/breath odour. However, not all answered every question. Twenty-three respondents experienced difficulties in being offered a diagnostic test for trimethylaminuria. Problems encountered included lack of awareness of the disorder by medical professionals and reluctance to recognise symptoms. Of those tested, 52% were diagnosed with trimethylaminuria. The main problems associated with living with body/breath malodours were bullying, harassment and ostracism in either the workplace (90%) or in social settings (88%). All respondents thought their condition had disadvantaged them in their daily lives. Open-ended responses included loss of confidence, stress, exclusion, isolation, loneliness, depression and suicidal thoughts. Respondents thought their lives could be improved by greater awareness and understanding of malodour conditions by medical professionals, employers and the general public, and appreciation that the malodour was due to a medical condition and not their fault.

CONCLUSIONS

Breath and body malodour conditions can cause immense hardship and distress, both mentally and socially, having devastating effects on quality of life. It would be advantageous to establish a standardised pathway from primary care to a specialist unit with access to a robust and reliable test and diagnostic criteria. There is a need to recognise malodour disorders as a disability, giving affected individuals the same rights as those with currently recognised disabilities.

Updates and Original Case Studies Focused on the NMR-Linked Metabolomics Analysis of Human Oral Fluids Part I: Emerging Platforms and Perspectives

1H NMR-based metabolomics analysis of human saliva, other oral fluids, and/or tissue biopsies serves as a valuable technique for the exploration of metabolic processes, and when associated with ’state-of-the-art’ multivariate (MV) statistical analysis strategies, provides a powerful means of examining the identification of characteristic metabolite patterns, which may serve to differentiate between patients with oral health conditions (e.g., periodontitis, dental caries, and oral cancers) and age-matched heathy controls. This approach may also be employed to explore such discriminatory signatures in the salivary 1H NMR profiles of patients with systemic diseases, and to date, these have included diabetes, Sjörgen’s syndrome, cancers, neurological conditions such as Alzheimer’s disease, and viral infections. However, such investigations are complicated in view of quite a large number of serious inconsistencies between the different studies performed by independent research groups globally; these include differing protocols and routes for saliva sample collection (e.g., stimulated versus unstimulated samples), their timings (particularly the oral activity abstention period involved, which may range from one to 12 h or more), and methods for sample transport, storage, and preparation for NMR analysis, not to mention a very wide variety of demographic variables that may influence salivary metabolite concentrations, notably the age, gender, ethnic origin, salivary flow-rate, lifestyles, diets, and smoking status of participant donors, together with their exposure to any other possible convoluting environmental factors. In view of the explosive increase in reported salivary metabolomics investigations, in this update, we critically review a wide range of critical considerations for the successful performance of such experiments. These include the nature, composite sources, and biomolecular status of human saliva samples; the merits of these samples as media for the screening of disease biomarkers, notably their facile, unsupervised collection; and the different classes of such metabolomics investigations possible. Also encompassed is an account of the history of NMR-based salivary metabolomics; our recommended regimens for the collection, transport, and storage of saliva samples, along with their preparation for NMR analysis; frequently employed pulse sequences for the NMR analysis of these samples; the supreme resonance assignment benefits offered by homo- and heteronuclear two-dimensional NMR techniques; deliberations regarding salivary biomolecule quantification approaches employed for such studies, including the preprocessing and bucketing of multianalyte salivary NMR spectra, and the normalization, transformation, and scaling of datasets therefrom; salivary phenotype analysis, featuring the segregation of a range of different metabolites into ‘pools’ grouped according to their potential physiological sources; and lastly, future prospects afforded by the applications of LF benchtop NMR spectrometers for direct evaluations of the oral or systemic health status of patients at clinical ‘point-of-contact’ sites, e.g., dental surgeries. This commentary is then concluded with appropriate recommendations for the conduct of future salivary metabolomics studies. Also included are two original case studies featuring investigations of (1) the 1H NMR resonance line-widths of selected biomolecules and their possible dependence on biomacromolecular binding equilibria, and (2) the combined univariate (UV) and MV analysis of saliva specimens collected from a large group of healthy control participants in order to potentially delineate the possible origins of biomolecules therein, particularly host- versus oral microbiome-derived sources. In a follow-up publication, Part II of this series, we conduct censorious reviews of reported observations acquired from a diversity of salivary metabolomics investigations performed to evaluate both localized oral and non-oral diseases. Perplexing problems encountered with these again include those arising from sample collection and preparation protocols, along with 1H NMR spectral misassignments.

Novel variants in outer protein surface of flavin-containing monooxygenase 3 found in an Argentinian case with impaired capacity for trimethylamine N-oxygenation

Flavin-containing monooxygenase 3 (FMO3) is a polymorphic drug metabolizing enzyme associated with the genetic disorder trimethylaminuria. We phenotyped a white Argentinian 11-year-old girl by medical sensory evaluation. After pedigree analysis with her brother and parents, this proband showed to harbor a new allele p.(P73L; E158K; E308G) FMO3 in trans configuration with the second new one p.(F140S) FMO3. Recombinant FMO3 proteins of the wild-type and the novel two variants underwent kinetic analyses of their trimethylamine N-oxygenation activities. P73L; E158K; E308G and F140S FMO3 proteins exhibited moderately and severely decreased trimethylamine N-oxygenation capacities (~50% and ~10% of wild-type FMO3, respectively). Amino acids P73 and F140 were located on the outer surface region in a crystallographic structure recently reported of a FMO3 analog. Changes in these positions would indirectly impact on key FAD-binding residues. This is the first report and characterization of a patient of fish odor syndrome caused by genetic aberrations leading to impaired FMO3-dependent N-oxygenation of trimethylamine found in the Argentinian population. We found novel structural determinants of FAD-binding domains, expanding the list of known disease-causing mutations of FMO3. Our results suggest that individuals homozygous for any of these new variants would develop a severe form of this disorder.

Microbiota and Malodor-Etiology and Management

Accumulating evidence indicates that microbiota plays a critical role in physiological processes in humans. However, it might also contribute to body malodor by producing numerous odorous molecules such as ammonia, volatile sulfur compounds or trimethylamine. Although malodor is commonly overlooked by physicians, it constitutes a major problem for many otherwise healthy people. Thus, this review aims to investigate most common causes of malodor and describe potential therapeutic options. We searched PUBMED and Google Scholar databases to identify the clinical and pre-clinical studies on bad body smell, malodor, halitosis and microbiota. Unpleasant smell might originate from the mouth, skin, urine or reproductive fluids and is usually caused by odorants that are produced by resident bacterial flora. The accumulation of odorous compounds might result from diet, specific composition of microbiota, as well as compromised function of the liver, intestines and kidneys. Evidence-based guidelines for management of body malodor are lacking and no universal treatment exists. However, the alleviation of the symptoms may be achieved by controlling the diet and physical elimination of bacteria and/or accumulated odorants.

Engineered Polymersomes for the Treatment of Fish Odor Syndrome: A First Randomized Double Blind Olfactory Study

Trimethylamine (TMA) is a metabolite overtly present in patients suffering from trimethylaminuria (TMAU), a rare genetic disorder characterized by a strong "fishy" body odor. To date, no approved pharmacological treatment to sequester excess TMA on the skin of patients exists. Here, transmembrane pH gradient poly(isoprene)-block-poly(ethylene glycol) (PI-b-PEG) polymersomes are investigated for the topical removal of TMA. PI-b-PEG amphiphiles of varying chain length are synthesized and evaluated for their ability to form vesicular structures in aqueous media. The optimization of the PI/PEG ratio of transmembrane pH gradient polymersomes allows for the rapid and efficient capture of TMA both in solution and after incorporation into a topical hydrogel matrix at the pH of the skin. A subsequent double blind olfactory study reveals a significant decrease in perceived odor intensity after application of the polymersome-based formulation on artificial skin substrates that has been incubated in TMA-containing medium. This simple and novel approach has the potential to ease the burden of people suffering from TMAU.

Endogenous Roles of Mammalian Flavin-Containing Monooxygenases

Flavin-containing monooxygenases (FMOs) catalyze the oxygenation of numerous foreign chemicals. This review considers the roles of FMOs in the metabolism of endogenous substrates and in physiological processes, and focuses on FMOs of human and mouse. Tyramine, phenethylamine, trimethylamine, cysteamine, methionine, lipoic acid and lipoamide have been identified as endogenous or dietary-derived substrates of FMOs in vitro. However, with the exception of trimethylamine, the role of FMOs in the metabolism of these compounds in vivo is unclear. The use, as experimental models, of knockout-mouse lines deficient in various Fmo genes has revealed previously unsuspected roles for FMOs in endogenous metabolic processes. FMO1 has been identified as a novel regulator of energy balance that acts to promote metabolic efficiency, and also as being involved in the biosynthesis of taurine, by catalyzing the S-oxygenation of hypotaurine. FMO5 has been identified as a regulator of metabolic ageing and glucose homeostasis that apparently acts by sensing or responding to gut bacteria. Thus, FMOs do not function only as xenobiotic-metabolizing enzymes and there is a risk that exposure to drugs and environmental chemicals that are substrates or inducers of FMOs would perturb the endogenous functions of these enzymes.

Trimethylamine and Trimethylamine N-Oxide, a Flavin-Containing Monooxygenase 3 (FMO3)-Mediated Host-Microbiome Metabolic Axis Implicated in Health and Disease

Flavin-containing monooxygenase 3 (FMO3) is known primarily as an enzyme involved in the metabolism of therapeutic drugs. On a daily basis, however, we are exposed to one of the most abundant substrates of the enzyme trimethylamine (TMA), which is released from various dietary components by the action of gut bacteria. FMO3 converts the odorous TMA to nonodorous TMA N-oxide (TMAO), which is excreted in urine. Impaired FMO3 activity gives rise to the inherited disorder primary trimethylaminuria (TMAU). Affected individuals cannot produce TMAO and, consequently, excrete large amounts of TMA. A dysbiosis in gut bacteria can give rise to secondary TMAU. Recently, there has been much interest in FMO3 and its catalytic product, TMAO, because TMAO has been implicated in various conditions affecting health, including cardiovascular disease, reverse cholesterol transport, and glucose and lipid homeostasis. In this review, we consider the dietary components that can give rise to TMA, the gut bacteria involved in the production of TMA from dietary precursors, the metabolic reactions by which bacteria produce and use TMA, and the enzymes that catalyze the reactions. Also included is information on bacteria that produce TMA in the oral cavity and vagina, two key microbiome niches that can influence health. Finally, we discuss the importance of the TMA/TMAO microbiome-host axis in health and disease, considering factors that affect bacterial production and host metabolism of TMA, the involvement of TMAO and FMO3 in disease, and the implications of the host-microbiome axis for management of TMAU.

Trimethylaminuria

We report the case of a 9-year-old boy referred to secondary care with an unusual presentation of a fishy odour to his hands, feet, saliva and urine. Laboratory investigations including urine analysis and genetic testing confirmed the diagnosis of trimethylaminuria. The patient was referred to a geneticist and dietician, and consequently treated with dietary modification. He now has an arguably much improved quality of life.

Relationships between flavin-containing mono-oxygenase 3 (FMO3) genotype and trimethylaminuria phenotype in a Japanese population

AIM

The aim of this study was to investigate relationships between flavin-containing mono-oxygenase 3 (FMO3) genotype and phenotype (conversion of odorous trimethylamine into non-odorous trimethylamine N-oxide) in a large Japanese cohort suffering from trimethylaminuria.

METHODS

Urinary excretion of trimethylamine and trimethylamine N-oxide was determined for 102 volunteers with self-reporting symptoms of trimethylaminuria. For each we determined the sequence of the entire coding region, plus 1.3 kb of flanking intronic and 2.5 kb of the upstream region of the FMO3 gene. The affect of upstream variants on transcription was determined with a reporter gene assay.

RESULTS

Seventy-eight subjects were diagnosed as suffering from trimethylaminuria, based on urinary excretion of <90% of total TMA as TMA N-oxide. Of these, 13 were classified as severe, 56 as moderate and nine as mild cases, excreting <43%, 48-70% and 73-83% of trimethylamine as trimethylamine N-oxide, respectively. Twenty-seven mutations were identified in FMO3, 15 in the coding region, of which eight abolish or severely impair FMO3 activity (Pro70Leu, Cys197fsX, Thr201Lys, Arg205Cys, Met260Val, Trp388Ter, Gln470Ter and Arg500Ter), and 12 in the upstream region. The mutations segregate into 19 haplotypes, including four different combinations of upstream mutations, each of which reduces transcriptional activity in comparison with the ancestral upstream sequence of FMO3.

CONCLUSIONS

Comparisons of genotype and phenotype reveal that severe trimethylaminuria is caused by loss of function mutations in FMO3. For moderate and mild cases the situation is more complex, with most resulting from factors other than FMO3 genotype. Our results have implications for the diagnosis and management of the disorder.

Trimethylaminuria (fish odor syndrome): genotype characterization among Portuguese patients

Trimethylaminuria (TMAu) or "fish odor syndrome" is a metabolic disorder characterized by the inability to convert malodorous dietarily-derived trimethylamine (TMA) to odorless TMA N-oxide by the flavin-containing monooxygenase 3 (FMO3). Affected individuals unable to complete this reaction exude a "fishy" body odor due to the secretion of TMA in their corporal fluids leading to a variety of psychosocial problems. Interindividual variability in the expression of FMO3 gene may affect drug and foreign chemical metabolism in the liver and other tissues. Therefore, it is important to screen for common TMAu mutations but also extend the search to other genetic variants in order to correlate genotype and disease-associated phenotypes. In this study, 25 Portuguese patients with phenotype suggestive of TMAu were evaluated for molecular screening of the FMO3 gene. Herein, we found 16 variants in the FMO3 coding region, some of which had not been previously documented (Gly38Trp, Asp232Val, Thr307Pro, Ser310Leu). Whenever common variants (Glu158Lys, Glu308Gly) were considered in combination a distinct pattern between the control population and patients was observed, mainly in what concerns the presence of Lys158 and Gly308 in homozygous state. Further studies are necessary to clarify the pathogenicity of novel variants identified in this study, as well as the effect of the common single nucleotide polymorphisms, which may play an important role in disease presentation and/or protective mechanism to xenobiotics drugs or environment.

High-resolution 1H NMR investigations of the oxidative consumption of salivary biomolecules by oral rinse peroxides

BACKGROUND

A multicomponent evaluation of the oxidative consumption of salivary biomolecules by a tooth-whitening oral rinse preparation has been performed using high-resolution proton ((1)H) nuclear magnetic resonance spectroscopy (NMR).

METHODS

Unstimulated human saliva samples (n = 12) were treated with aliquots of the oral rinse tested and 600 MHz (1)H NMR spectra acquired on these samples demonstrated that hydrogen peroxide (H(2)O(2)) and/or peroxodisulphate (S(2)O(8) (2-)) present in this product gave rise to the oxidative decarboxylation of the salivary electron-donor pyruvate (to acetate and CO(2)), and also oxidized methionine (a precursor to volatile sulphur compounds responsible for oral malodour), and malodourous trimethylamine to methionine sulphoxide and trimethylamine-N-oxide, respectively (reductions observed in the salivary concentrations of each biomolecular peroxide-scavenging agent were all extremely statistically significant, p < 0.005).

RESULTS

Experiments conducted on chemical model systems confirmed the consumption of pyruvate by this product, and also revealed that the amino acids cysteine and methionine were oxidatively transformed to cystine and methionine sulphoxide, respectively.

CONCLUSIONS

High-field (1)H NMR analysis provides much valuable molecular information regarding the fate of tooth-whitening oxidants in human saliva and permits an assessment of the mechanisms of action of oral healthcare products containing these agents. The biochemical and potential therapeutic significance of the results obtained are discussed.

Microbial volatile compounds in health and disease conditions

Microbial cultures and/or microbial associated diseases often have a characteristic smell. Volatile organic compounds (VOCs) are produced by all microorganisms as part of their normal metabolism. The types and classes of VOC produced is wide, including fatty acids and their derivatives (e.g. hydrocarbons, aliphatic alcohols and ketones), aromatic compounds, nitrogen containing compounds, and volatile sulfur compounds. A diversity of ecological niches exist in the human body which can support a polymicrobial community, with the exact VOC profile of a given anatomical site being dependent on that produced by both the host component and the microbial species present. The detection of VOCs is of interest to various disciplines, hence numerous analytical approaches have been developed to accurately characterize and measure VOCs in the laboratory, often from patient derived samples. Using these technological advancements it is evident that VOCs are indicative of both health and disease states. Many of these techniques are still largely confined to the research laboratory, but it is envisaged that in future bedside 'VOC profiling' will enable rapid characterization of microbial associated disease, providing vital information to healthcare practitioners.

Halitosis: could it be more than mere bad breath?

Halitosis is a generic term used to describe unpleasant odor emanating from the mouth air and breath, independent of the source where the odor substances originate. It affects between 50 and 65% of the population, but despite its frequency, this problem is often unaccepted and declared as taboo. Ninety percent of patients suffering from halitosis have oral causes: a small, but important percentage, of oral malodor cases have an extra-oral etiology, very often falling into the category of "blood-borne halitosis". Several systemic diseases have been found to provoke malodor or to be a cofactor; bad breath may be an early sign of a serious local or systemic condition. A psychogenic halitosis also exists including the variant "pseudo-halitosis", when the oral malodor does not exist, but the patient believes he or she is suffering severely from it, and the halitophobia, when, instead, there is an exaggerated fear of having halitosis. The aims of this paper are to review both oral and extra-oral causes of halitosis, especially those related to underlying systemic diseases, and to provide the primary care clinician a helpful means for its diagnosis and management. In fact, it is important to determine quickly whether the odor comes from an oral cause or not: if so, it requires referral to a dentist; if not (extra-oral origin alone or combined), its management requires the treatment of the underlying causes. Extra-oral disorders can be the cause in up to 15% of cases.

Relationship between volatile sulfur compounds in mouth air and systemic disease

This study examined the relationship between volatile sulfur compounds (VSCs), including hydrogen sulphide (H(2)S), methyl mercaptan (CH(3)SH) and dimethyl sulphide [(CH(3))(2)S], in mouth air of patients and a history of systemic disease. The subjects were 387 residents (174 males and 213 females) of Fukuoka Prefecture, Japan, who participated in an oral and systemic health survey for elderly persons (mean age: 61.8, s.d. 2.8 years). The VSCs were measured using a portable gas chromatograph (OralChroma). The H(2)S concentrations were significantly greater in the 132 subjects with a history of hypertension and the 41 subjects with a history of respiratory disease, including pneumonia, pulmonary emphysema and bronchitis, than in those without such a history. The CH(3)SH concentrations were significantly greater in those with a history of hypertension. The 16 subjects with a history of cerebrovascular disease, including intracerebral haemorrhage, cerebral infarction, and subarachnoid haemorrhage, and the 58 subjects with a history of liver disease, including hepatitis, alcoholic liver disease, drug-induced liver injury, fatty liver and liver cirrhosis, showed significantly greater (CH(3))(2)S concentrations (p < 0.05). These results suggest an association between the production of VSCs in mouth air and systemic diseases such as hypertension as well as respiratory, cerebrovascular and liver diseases.