Plasma trimethylamine-N-oxide quantification in patients with Hashimoto's thyroiditis by using LC-MS/MS

Introduction: Trimethylamine-N-oxide (TMAO) is an organic compound formed when flavin monooxygenases react with trimethylamine (TMA), which can be obtained from food or produced by the intestinal microbiota. Blood levels of TMAO are positively correlated with low-grade inflammation and various health conditions, including impaired renal function, colorectal cancer, and cardiovascular disease. Aim: This study presents the development and validation of an LC-MS/MS method for determining TMAO in human plasma. In the second stage, a group of 62 adults with newly diagnosed Hashimoto’s thyroiditis (HT) was tested for TMAO, thyroid hormones, autoantibodies, and markers of lipid and glucose metabolism. Results: A modified sample preparation procedure ensures that the sample is cleaned of interfering substances and proteins. Linearity was confirmed over a range of 50 µg/L–3000 µg/L, with an R² greater than 0.995. The normalized matrix values ranged from 87.1% to 111.9%, the accuracy was between 84.0% and 112.7%, and the within-run and between-run precision were both less than 9%. The patient group had a higher average TMAO level than the controls (172.5 µg/L vs. 158.5 µg/L). TMAO levels were positively correlated with BMI (r=0.380, p=0.002) and anti-TPO antibodies (r=0.264, p=0.04). Conclusion: The determined TMAO levels in p atients with Hashimoto’s thyroiditis were higher than in the control group, but the differences were not significant. They only indicated a trend, which may be associated with the presence of anti-TPO antibodies, the activity of the autoimmune process, and the presence of systemic inflammation.