Category: catabolism
Dietary choline + carnitine + phosphatidylcholine reach the colon partially intact, where gut microbiota produce trimethylamine (TMA) via cleavage. Portal venous TMA reaches the liver and is oxidized by FMO3 (flavin monooxygenase 3) to TMAO (trimethylamine-N-oxide). Plasma TMAO is associated with cardiovascular events in observational studies — proposed mechanism: TMAO impairs reverse cholesterol transport + promotes macrophage foam cell formation + enhances platelet hyperreactivity. The "gut microbiome → CVD" causal link is being actively investigated (Hazen lab series, mostly). FMO3 LOF variants cause trimethylaminuria ("fish odor syndrome") — exhaled + sweat-derived TMA produces a fish-like body odor.