Elevated trimethylamine- N -oxide (TMAO) is associated with poor prognosis in primary sclerosing cholangitis patients with normal liver function.

BACKGROUND: Trimethylamine- N -oxide (TMAO) is produced in the liver from trimethylamine, which is exclusively generated by gut bacteria.

OBJECTIVE: The objective of this article is to investigate the relationship between TMAO and primary sclerosing cholangitis (PSC) and its clinical characteristics.

METHODS: Serum TMAO was measured in 305 PSC patients, 90 ulcerative colitis patients and 99 healthy controls.

RESULTS: In PSC patients with normal liver function ( n  = 197), TMAO was higher in patients reaching liver transplantation or death during follow-up than those who did not, with an optimal TMAO cut-off of 4.1 µM (AUC = 0.64, p  < 0.001). PSC patients with high TMAO (>4.1 µM, n  = 77) exhibited shorter transplantation-free survival than patients with low TMAO ( n  = 120, log-rank test: p  < 0.0001). High TMAO (>4.1 µM) was associated with reduced transplantation-free survival (HR 1.87, p  = 0.011), independently of the Mayo risk score (HR 1.74, p  < 0.001). Overall, PSC patients demonstrated reduced TMAO values compared with ulcerative colitis and healthy controls, mainly caused by PSC patients with reduced liver function (INR > 1.2), suggesting impaired oxidation of trimethylamine to TMAO. PSC patients with and without inflammatory bowel disease had similar TMAO levels.

CONCLUSION: In PSC patients with normal liver function, elevated TMAO was associated with shorter transplantation-free survival, potentially reflecting clinically relevant metabolic changes resulting from dietary interactions with the gut microbiota.