A straightforward LC-MS/MS analysis to study serum profile of short and medium chain fatty acids

Short and medium fatty acids derived from either dietary sources, gut microbiota, and liver production might play a role in the modulation of metabolism and inflammation. The outcome of different autoimmune or inflammatory diseases could be related to microbiota composition and consequently fatty acids production. Their analytical detection, historically completed by GC, was herein investigated using a sensitive approach of LC-MS/MS with straightforward chemical derivatization, using 3-NPH, to the respective acylhydrazines. An isopropanol protein precipitation coupled to LC-MS/MS analysis allowed to separate and quantify butyric, valeric, hexanoic acid and their branched forms. The serum physiological ranges of short and medium chain fatty acids were determined in a heterogeneous healthy population (n = 54) from 18 to 85 years finding a concentration of 935.6 +/- 246.5 (butyric), 698.8 +/- 204.7 (isobutyric), 62.9 +/- 15.3 (valeric), 1155.0 +/- 490.4 (isovaleric) and 468.7 +/- 377.5 (hexanoic) ng/mL respectively (mean +/- SD). As expected, the biological levels in human serum are reasonably wide-ranging depending on several factors such as body-weight, gut microbiome dysbiosis, gut permeability, cardiometabolic dysregulation, and diet.