Fig. 3
From: Uremic toxins mediate kidney diseases: the role of aryl hydrocarbon receptor
Pathways of trimethylamine-N-oxide (TMAO) production. Foods are enriched in TMAO precursors (choline, carnitine and betaine) or TMAO itself. Choline can be metabolized to trimethylamine (TMA) by the choline-utilizing TMA lyase (CutC/D). L-carnitine can be metabolized to TMA by the carnitine Rieske-type oxygenase/reductase (CntA/B). YeaW and YeaX, the homologs of CntA/B, can also metabolize choline, carnitine and betaine to generate TMA. The above processes occur in the microbiota. TMA produced in the gut is absorbed into the blood and transported to the liver, where flavin monooxygenase 3 (FMO3) catalyzes TMA into TMAO. Dietary TMAO can bypass processing by the gut microbiota before intestinal absorption