Prognostic significance of serum tyrosine concentration in patients with primary biliary cholangitis under ursodeoxycholic acid therapy.

AIM: Chronic liver insufficiency is often associated with alteration in amino acid metabolism. We evaluated the prognostic value of changes in serum amino acid concentrations in patients with primary biliary cholangitis. METHODS: A total of 75 primary biliary cholangitis patients who started urusodeoxycholic acid therapy were retrospectively enrolled. Baseline serum concentrations of branched-chain amino acids and tyrosine, and branched-chain amino acid-to-tyrosine ratio were determined. The hazard ratios of factors associated with liver-related events were analyzed by Cox proportional hazard analysis. RESULTS: Of the 75 patients enrolled, 12 showed a decrease in serum branched-chain amino acid levels, and 15 showed an increase in serum tyrosine levels. The branched-chain amino acid-to-tyrosine ratio decreased in 16 patients. During a median 5.6-year follow up, liver-related events occurred in 11 patients. Multivariate analysis showed that high serum tyrosine levels at baseline and high alkaline phosphatase levels 48 weeks after starting urusodeoxycholic acid therapy were independent risk factors for event occurrence. From the receiver operator characteristics curve analysis, serum tyrosine concentration >110 µmol/L was identified as a cut-off value with an adjusted hazard ratio of 20.9 (95% confidence interval 4.3-101.5, P < 0.001). Kaplan-Meier analysis showed that the 5-year cumulative incidences of event occurrence in patients with high and low serum tyrosine concentration were 56.5% and 5.5%, respectively (P < 0.001). The 10-year survival probabilities also showed significant differences between patients with high and low serum tyrosine concentration (44.9% vs. 92.0%, P < 0.001). CONCLUSION: Elevation of serum tyrosine concentration indicates a high risk of liver-related events in primary biliary cholangitis patients receiving urusodeoxycholic acid therapy.