Characterization and quantification of representative bile acids in ileal contents and feces of diet-induced obese mice by UPLC-MS/MS

Abstract

• A novel quantification method for bile acids in feces was established. • This method was green and time-saving with high extraction efficiency. • CA, TCA, TCDCA and T-α-MCA were the dominant bile acids in ileal contents. • CA, DCA, α-MCA and β-MCA were the dominant bile acids in feces. • The hydrophobicity index of bile acids was increased in the obese mice. With more requirements for noninvasive diagnosis methods, metabolites in fecal samples are attracting increasing attention to be potential biomarkers of metabolic diseases. Different structured bile acids reveal variable signaling activities related to obesity. A green extraction method coupled with ultra-high performance liquid chromatography-mass spectrometry was developed to simultaneously determine bile acids (BAs) in ileal contents and fecal samples. The separations of all analytes were efficiently performed using ammonium acetate-methanol as the mobile phases with a low limit of detection (LOD at a range of 0.02-0.25 ng/mL). The precision and repeatability of the established method were well-validated. Intra/inter-day precision (relative standard deviation) were lower than 5% and 10%, respectively. And recoveries in spiked samples ranged from 80.80% to 117.83%. In the application among ileal contents and feces of high-fat and high-cholesterol diet-induced obese mice, the results showed that cholic acid was the dominant BA in both samples. Higher concentrations of hydrophobic BAs were observed in obese mice, indicating that hydrophobic BAs were closely connected with the occurrence of metabolic disorders. In summary, the proposed method evaluated the BAs profiling in ileal contents and feces of obese mice and could be used for similar samples of bile acids analysis in patients with obesity.