First Report from Saudi Arabia of Trimethylaminuria Caused by a Premature Stop Codon Mutation in the Gene.

Background: Trimethylaminuria (TMAU) is a rare recessive genetic disorder with limited global prevalence. To date, there have been no official reports of TMAU cases documented in Saudi Arabia.

Purpose: In this study, we developed a liquid chromatography-mass spectrometry (LC-MS) method for the analysis of trimethylamine (TMA) and Trimethylamine N-Oxide (TMAO) in urine and plasma samples for the first reported case of TMAU in Saudi Arabia.

Patients And Methods: A 41-year-old Saudi man was diagnosed with TMAU in National Guard Hospital. Blood and urine samples were collected to confirm the diagnosis of TMAU. In this study, we have studied LC-MS, cell culture, flow cytometry, adhesion assay and Sanger sequencing analysis. Additionally, in this study, we have selected 5 healthy controls.

Results: The results have revealed elevated TMA levels were present in both urine and plasma samples, while TMAO levels were significantly lower compared to control group. Further, we utilized plasma sample from the TMAU patient as novel model to investigate the potential effect of low TMAO on monocyte and endothelial cell function in vitro. DNA sequencing analysis identified a c.622G >T (p.Glu208*) which creates a premature stop codon in FMO3 gene.

Conclusion: Our findings revealed differential responses in monocytes and endothelial cells stimulated with plasma from the TMAU patient compared to plasma from non-TMAU patients. These distinct responses may be key modulators of endothelial function and contributes to vascular damage.