Diagnosis of suspected trimethylaminuria by NMR spectroscopy

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 ( 1H-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.