Rapid screening assay of trimethylaminuria in urine with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

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.

Quality consideration for the validation of urine TMA and TMAO measurement by nuclear magnetic resonance spectroscopy in Fish Odor Syndrome

OBJECTIVES

Trimethylaminuria, also known as Fish Odor Syndrome (FOS), is a condition characterized by the presence of high concentrations of trimethylamine (TMA) in urine, sweat and expired air of affected patients. Diagnosis of this benign but unpleasant disease is mainly based on clinical presentation and assessment of TMA and its metabolite, TMAO (trimethylamine-N-oxide), concentrations in urine of patients.

MATERIAL AND METHODS

We here described the validation of an analytical method for measurement of TMA and TMAO in urine using nuclear magnetic resonance (NMR) according to the specifications of the ISO 15189 norm. We used a fast validation protocol, based exactitude profile method, enabling to determine accuracy, intra and inter-day precision from a limited number of samples.

RESULTS

The linearity was established from 2.5 to 100 mg/L for TMA measurement and from 10 to 1000 mg/L for TMAO measurement, with good analytical performances i.e. accuracy, intra and inter-day precision. We also report a case diagnose for FOS from this method.

CONCLUSIONS

This method validation ensures the robustness of NMR in routine use for diagnosis of trimethylaminuria, as part of the reference center for inherited metabolic diseases at the Tours hospital.

Diagnosis and phenotypic assessment of trimethylaminuria, and its treatment with riboflavin: 1H NMR spectroscopy and genetic testing

Background

Trimethylaminuria (TMAU) is a metabolic disorder characterized by the excessive excretion of the malodorous compound trimethylamine (TMA). The diagnosis of TMAU is challenging because this disorder is situated at the boundary between biochemistry and psychiatry. Here, we used nuclear magnetic resonance spectroscopy to assess TMAU in 13 patients. We also sequenced the FMO3 gene in 11 of these patients. Treatment with vitamin B2 was prescribed.

Results

Two patients (aged 3 and 9 years at the initial consultation) had a particularly unpleasant body odor, as assessed by their parents and the attending physicians. The presence of high urine TMA levels confirmed the presence of a metabolic disorder. The two (unrelated) children carried compound heterozygous variants in the FMO3 gene. In both cases, vitamin B2 administration decreased TMA excretion and reduced body odor. The 11 adults complained of an unpleasant body odor, but the physicians did not confirm this. In all adult patients, the urine TMA level was within the normal range reported for control (non-affected) subjects, although two of the patients displayed an abnormally high proportion of oxidized TMA. Seven of the 9 tested adult patients had a hypomorphic variant of the FMO3 gene; the variant was found in the homozygous state, in the heterozygous state or combined with another hypomorphic variant. All 11 adults presented a particular psychological or psychiatric phenotype, with a subjective perception of unpleasant odor.

Conclusions

The results present the clinical and biochemical data of patients complaining of unpleasant body odor. Contrary to adult patients, the two children exhibited all criteria of recessively inherited trimethylaminuria, suspected by parents in infancy. B2 vitamin treatment dramatically improved the unpleasant body odor and the ratio of TMA/Cr vs TMAO/Cr in the urine in the children. Other patients presented a particular psychological or psychiatric phenotype.

Fast LC-ESI-MS/MS analysis and influence of sampling conditions for gut metabolites in plasma and serum

In the past few years, the gut microbiome has been shown to play an important role in various disorders including in particular cardiovascular diseases. Especially the metabolite trimethylamine-N-oxide (TMAO), which is produced by gut microbial metabolism, has repeatedly been associated with an increased risk for cardiovascular events. Here we report a fast liquid chromatography tandem mass spectrometry (LC-MS/MS) method that can analyze the five most important gut metabolites with regards to TMAO in three minutes. Fast liquid chromatography is unconventionally used in this method as an on-line cleanup step to remove the most important ion suppressors leaving the gut metabolites in a cleaned flow through fraction, also known as negative chromatography. We compared different blood matrix types to recommend best sampling practices and found citrated plasma samples demonstrated lower concentrations for all analytes and choline concentrations were significantly higher in serum samples. We demonstrated the applicability of our method by investigating the effect of a standardized liquid meal (SLM) after overnight fasting of 25 healthy individuals on the gut metabolite levels. The SLM did not significantly change the levels of gut metabolites in serum.

Effect of Grape Pomace Polyphenols With or Without Pectin on TMAO Serum Levels Assessed by LC/MS-Based Assay: A Preliminary Clinical Study on Overweight/Obese Subjects

Growing evidence suggests that trimethylamine N-oxide (TMAO) is recognized as a biomarker of increased cardiovascular risk. So far, the evaluation of TMAO serum levels in the clinical practice is limited due to the lack of developing new facile methods with reduced limitations. However, few approaches were achieved to determine TMAO in serum by using mass spectrometry-based technique, some limitations were reported including the use of internal standards. Therefore, in this work, a liquid chromatography-mass spectrometry (LC/MS) based-assay was developed to evaluate the effect of grape pomace extract (Taurisolo^®, group A) or Taurisolo^®+pectin (group B) on TMAO serum levels in a cohort of overweight/obese subjects. The serum levels of TMAO have been assessed before and after treatment, through LC/MS analysis. After 8-week treatment, in both intervention groups TMAO serum levels significantly decreased (-78.58% p = 0.006 and -76.76% p = 0.001, group A and group B, respectively). Moreover, we performed several analyses aimed to validate the LC/MS method we used. The method has high precision (% C.V = from 12.12 to 3.92% and from 8.25 to 1.07% for intraday and interday, respectively) and accuracy (% bias = from -5.52 to 0.5% and from -1.42 to 3.08% for intraday and interday, respectively). TMAO recoveries from serum ranged from 99 to 97%; LOD: 2 ng/ml and LOQ: 6 ng/ml. In conclusion, we demonstrated the efficacy of a novel nutraceutical formulation in reducing TMAO serum levels in high cardiovascular risk-subjects, and proposed a useful, versatile and rapid LC/MS method for identification and quantization of TMAO, without the use of marked/isotopic internal standards. It, thus, may represent a novel and practical method with applications in clinical practice and nutraceutical research. Clinical Trial Registration: This study is listed on the ISRCTN registry with ID ISRCTN10794277 (doi: 10.1186/ISRCTN10794277).

High-pressure photon ionization time-of-flight mass spectrometry combined with dynamic purge-injection for rapid analysis of volatile metabolites in urine

Small molecule metabolites are widely used as biomarkers in the research field of metabolomics for disease diagnosis and exposure assessment. As a readily available biofluid containing plenty of volatile organic metabolites (VOMs), urine is ideal for non-invasive metabolomic analysis; however, there is still lack of rapid analysis method for VOMs in urine. Here we report a kind of rapid method for urine analysis by employing high-pressure photon ionization time-of-flight mass spectrometry (HPPI-TOFMS) combined with dynamic purge-injection. Various types of metabolites, such as ketones, alcohols, acids, sulfides, pyrroles and amines were detected directly by simple acidification or alkalization of urines. It is noteworthy that nitrogen-containing compounds, especially polar amines, could be ultrasensitively measured without any derivatization. The analytical capability of the direct HPPI-MS technique was demonstrated by analyzing five valuable metabolites, i.e., toluene, 2,5-dimethylpyrrole, trimethlyamine, styrene, and p-xylene, which exhibited relatively low limits of detection, wide linear range and satisfactory repeatability. Being highly sensitive and humidity-friendly, the whole analytical procedure is easily operated in less than 6 min. Interestingly, a new biomarker 2,5-dimethylpyrrole was exclusively found in the smoker's urine sample besides toluene. The work presents a novel tool for rapid nontarget disease biomarkers screening or target monitoring of specific compounds through the investigation of volatile metabolites in urine.

A highly sensitive liquid chromatography electrospray ionization mass spectrometry method for quantification of TMA, TMAO and creatinine in mouse urine

Our method describes the quantification in mouse urine of trimethylamine (TMA), trimethylamine N-oxide (TMAO) and creatinine. The method combines derivatization of TMA, with ethyl bromoacetate, and LC chromatographic separation on an ACE C₁₈ column. The effluent was continuously electrosprayed into the linear ion trap mass spectrometer (LTQ), which operated in selective ion monitoring (SIM) modes set for targeted analytes and their internal standards (IS). All validation parameters were within acceptable ranges of analytical method validation guidelines. Intra- and inter-day assay precision and accuracy coefficients of variation were <3.1%, and recoveries for TMA and TMAO were 97–104%. The method developed uses a two-step procedure. Firstly, TMA and TMAO are analyzed without a purification step using a 5-min gradient cap-LC- SIMs analysis, then creatinine is analyzed using the same experimental conditions. The method is robust, highly sensitive, reproducible and has the high-throughput capability of detecting TMA, TMAO and creatinine at on-column concentrations as low as 28 pg/mL, 115 pg/mL and 1 ng/mL, respectively. The method is suitable for analysis of TMA, TMAO and creatinine in both male and female mouse urine.

The key benefits of the method are:

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The small sample volume of urine required, which overcomes the difficulties of collecting sufficient volumes of urine at defined times.

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No sample pre-treatment is necessary.

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The quantification of TMA, TMAO and creatinine using the same cap-LC-MS method.

Trimethylamine N-Oxide, the Microbiome, and Heart and Kidney Disease

Trimethylamine N-oxide (TMAO) is a biologically active molecule and is a putative promoter of chronic diseases including atherosclerosis in humans. Host intestinal bacteria produce its precursor trimethylamine (TMA) from carnitine, choline, or choline-containing compounds. Most of the TMA produced is passively absorbed into portal circulation, and hepatic flavin-dependent monooxygenases (FMOs) efficiently oxidize TMA to TMAO. Both observational and experimental studies suggest a strong positive correlation between increased plasma TMAO concentrations and adverse cardiovascular events, such as myocardial infarction, stroke, and death. However, a clear mechanistic link between TMAO and such diseases is not yet validated. Therefore, it is debated whether increased TMAO concentrations are the cause or result of these diseases. Here, we have tried to review the current understanding of the properties and physiological functions of TMAO, its dietary sources, and its effects on human metabolism. Studies that describe the potential role of TMAO in the etiology of cardiovascular and other diseases are also discussed.

The complex metabolism of trimethylamine in humans: endogenous and exogenous sources

Trimethylamine (TMA) is a tertiary amine with a characteristic fishy odour. It is synthesised from dietary constituents, including choline, L-carnitine, betaine and lecithin by the action of microbial enzymes during both healthy and diseased conditions in humans. Trimethylaminuria (TMAU) is a disease typified by its association with the characteristic fishy odour because of decreased TMA metabolism and excessive TMA excretion. Besides TMAU, a number of other diseases are associated with abnormal levels of TMA, including renal disorders, cancer, obesity, diabetes, cardiovascular diseases and neuropsychiatric disorders. Aside from its role in pathobiology, TMA is a precursor of trimethylamine-N-oxide that has been associated with an increased risk of athero-thrombogenesis. Additionally, TMA is a major air pollutant originating from vehicular exhaust, food waste and animal husbandry industry. The adverse effects of TMA need to be monitored given its ubiquitous presence in air and easy absorption through human skin. In this review, we highlight multifaceted attributes of TMA with an emphasis on its physiological, pathological and environmental impacts. We propose a clinical surveillance of human TMA levels that can fully assess its role as a potential marker of microbial dysbiosis-based diseases.

A multiplexed targeted assay for high-throughput quantitative analysis of serum methylamines by ultra performance liquid chromatography coupled to high resolution mass spectrometry

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.

Detection of volatile malodorous compounds in breath: current analytical techniques and implications in human disease

For the last few decades intense scientific research has been placed on the relationship between trace substances found in exhaled breath such as volatile organic compounds (VOC) and a wide range of local or systemic diseases. Although currently there is no general consensus, results imply that VOC have a different profile depending on the organ or disease that generates them. The association between a specific pathology and exhaled breath odor is particularly evident in patients with medical conditions such as liver, renal or oral diseases. In other cases the unpleasant odors can be associated with the whole body and have a genetic underlying cause. The present review describes the current advances in identifying and quantifying VOC used as biomarkers for a number of systemic diseases. A special focus will be placed on volatiles that characterize unpleasant breath 'fingerprints' such as fetor hepaticus; uremic fetor; fetor ex ore or trimethylaminuria.

A flow injection electrospray ionization tandem mass spectrometric method for the simultaneous measurement of trimethylamine and trimethylamine N-oxide in urine

Key metabolites for the diagnosis of the genetic disorder trimethylaminuria are trimethylamine (TMA) and trimethylamine N-oxide (TMAO). A rapid, automatable flow injection ESI-MS/MS method for their measurement in urine has been developed. The TMA was derivatized with ethyl bromoacetate to form ethyl betaine bromide. The 2 min ESI-MS/MS analysis employed four multiple reaction monitoring (MRM) ion pairs for derivatized TMA (146.1, 118.1), derivatized (2)H(9)-TMA (155.1, 127.1), TMAO (76.1, 58.1) and (2)H(9)-TMAO (85.1, 66.1). In control urine samples (n = 27) referred for suspected metabolic problems TMA was 0.11-1.19 mmol/mol creatinine, TMAO was 13.5-181 mmol/mol creatinine and the TMA/TMAO ratio was 0.0025-0.055. In five patients with diagnosed trimethylaminuria, TMA was 5.3-230 mmol/mol creatinine, TMAO was 0.36-607 mmol/mol creatinine and the TMA/TMAO ratio was 0.20-134.

Rapid analysis of alpha-dicarbonyl compounds by laser desorption/ionization mass spectrometry using 9-(3,4-diaminophenyl)acridine (DAA) as a reactive matrix

A rapid, sensitive and selective method has been developed for the analysis of alpha-dicarbonyls using a readily ionizable compound, 9-(3,4-diaminophenyl)acridine (DAA), as a reactive matrix (derivatizing agent and ionization efficiency enhancer), by reactive matrix laser desorption/ionization time-of-flight mass spectrometry (RM-LDI-TOF MS). The reaction between the DAA and alpha-dicarbonyls resulted exclusively in formation of vacuum-stable dicarbonyl-quinoxaline acridine derivatives that were found to possess excellent ionization efficiency in positive ion mode, without the need to use an additional matrix. The alpha-dicarbonyls used as test compounds included methylglyoxal, dimethylglyoxal, and diphenylglyoxal. Both one-pot and rapid on-plate chemical modification approaches were employed with no extraction or purification necessary. The approach is particularly suitable for high-throughput analysis. The method was found to be selective and specific, with alpha-dicarbonyls unequivocally identified, even in complex matrices, e.g. beer. The figures of merit: relative standard deviation (RSD) 6.9-17%, (n = 4); limit of detection (LOD) < or =0.3 ng mL(-1) for the three standards tested using the one-pot derivatization method; and a good linear calibration curve using an internal standard derivatized in situ (R(2) > or = 0.979), demonstrate the applicability of the technique and its utility in improving the sensitivity and precision of the LDI analysis of small molecules.