Targeted Profiling of Serum Taurine-Conjugated Bile Acids in Bile Duct-Ligated Rat, a Hepatic Encephalopathy Model, by LC/MS/MS

It has been suggested that bile acids (BAs) are involved in the pathogenesis and worsening of hepatic encephalopathy (HE). In this study, the serum taurine-conjugated BA (T-BA) profile in the bile duct-ligated (BDL) rat, an HE model, was determined by liquid chromatography (LC)/electrospray ionization-tandem mass spectrometry. Under the optimized LC conditions using an Ascentis Express 90 Å C18 column, a satisfactory separation was achieved for the isomeric T-BAs. The deuterium-labeled T-BAs were synthesized and used as the internal standards. The serum analysis revealed that in the BDL rats, the levels of primary T-BAs, i.e., tauro-α-muricholic acid, tauro-β-muricholic acid, taurocholic acid and taurochenodeoxycholic acid, increased 55–590-fold as high as those in the normal rats. These very high concentrations of the serum T-BAs might lead to the breakdown of the blood-brain barrier integrity, which is thought to be one of the possible mechanisms of the pathogenesis and worsening of HE.