TDK conference 2024

Bile acids (BAs) are steroid compounds that play a crucial role, particularly in maintaining lipid metabolism and cholesterol homeostasis. They effectively emulsify fats, facilitate the absorption of their breakdown products, and are essential for the utilization of fat-soluble vitamins. In addition, BAs influence glucose and lipid metabolism as well as the condition of the gut microbiome. Changes in bile acid content and composition can serve as biomarkers for diagnosing various diseases, such as liver disorders and inflammatory processes.

In our study, in addition to determining the physiological serum BA profile of healthy dogs, we were the first to examine how feeding affects the quantity and composition of serum bile acids. By refining the LC-MS/MS method and using appropriate sample preparation, we were able to cost-effectively separate bile acid structural isomers with identical molecular weights. Blood samples were collected from six healthy dogs following a 12-hour fasting and during the first six hours after feeding at hourly intervals, followed by three additional samples taken every two hours (0, 1, 2, 3, 4, 5, 6, 8, 10, 12 hours). From these samples, we determined both the total bile acid content and the bile acid profile composition. Based on the results of these measurements, it can already be established that determining the concentrations of bile acid compounds individually (including those available at extremely low concentrations) and then summing these values using the LC-MS/MS method yields a result that is significantly higher than the reference range for total bile acids used in current clinical routines. Postprandial BA levels showed high concentrations during hours 1-2 and 3-5. An important finding is that while hemolysis has a significant impact on results using the spectrophotometric method for routine total bile acid measurement, it does not affect the results made using the LC-MS/MS method. This difference has substantial clinical relevance.

Among healthy dogs, we observed significant individual variability in BA profiles; however, in most dogs, TCA levels dominated, while glycine-conjugated BAs were barely detectable. Additionally, we have moved closer to the final determination of optimal sample collection times.