Trimethylaminuria: The detection of carriers using a trimethylamine load test

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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 theN-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 theN-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 trimethylamineN-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.