Abstract

Bile acids (BAs) have important roles in physiological functions including the homeostasis of cholesterol, lipid, and as ligands for G protein-coupled receptors (GPCRs). Aging is highly correlated with the incidence of various diseases related to liver and gastrointestinal tract, thus it simply can be guessed that the changes in the level of bile acids are closely related to aging. However, due to the diverse range and a variety of BAs that have different activation potency, a simple, effective and sensitive method is required to screen BAs for accurate quantification and identification. In this study, the quantification method for the 19 targeted BAs in rat bile was developed and validated using ultrahighperformance liquid chromatography-Orbitrap mass spectrometry (UHPLC-LTQ-Orbitrap MS). 22 unknown bile acids were also characterized with their fragmentation patterns at the same time in this method. With the developed method, the change of bile acids level in rat bile according to aging was evaluated. Through statistical analysis, we have found that as the rats get older, unconjugated BAs and glycine-conjugated BAs were decreasing or not changing while taurine-conjugated BAs were increasing in general. Among the unknown BAs, five of the taurine conjugated BAs increased while a glycine conjugated BA decreased that is in corroboration with the trends of the targeted BAs.