Quantification of short chain fatty acids in serum and plasma

Sammanfattning: Type 2 diabetes (T2D) has become a major problem around the world. Current research has linked a high dietary fibre (DF)- intake with a number of health benefits and possible prevention of T2D. One proposed mechanism is via short chain fatty acids (SCFA), which are produced from fermentation of DF in the colon by the microflora. A high DF intake will cause higher concentration of SCFA in the blood. In order to investigate the role of T2D it is of importance to have an easy, robust fast and accurate method for determine the concentration of SCFA in a small volume serum and plasma from fasted individuals. In the protocol used the sample preparation relies on the ability for proteins to form a precipitate with phosphoric acid and extraction of supernatant in organic solvent. The concentration is measured by gas chromatography-mass spectrometry (GC-MS). The aim of the present study was brief to further develop and validate an existing rapid GC-MS based method to determine the concentration of SCFA in serum from human subjects, including an extension of an existing protocol for SCFA analysis in 400 µl to the reduced volume of 200 µl was evaluated, the agreement of method, using plasma or serum for determination of SCFA in a small population if individuals (n=30) was evaluated. The measured SCFAs were acetate, butyrate, iso-butyrate, propionate, valerate, iso-valerate and caproate. The method developed could analyse 200 µl serum and plasma with acceptable precision. The accuracy was tested with spiking acetate at 106.6, 53.3 and 26.7 µM and the other SCFA at 10.7, 5.3 and 2.7 µM. The recovery were between 80.1-107.7 %. The fasting concentration of acetate was 86.0-313.3 µM, 19.4-28.5 µM for propionate, 2.6-4.7 µM for iso-butyrate, 9.2-29.1 µM for butyrate, 11.2-44.4 µM for iso-valerate, 0.2-0.4 µM for valerate and 1.4-9.7 µM for caproate, of the 30 subjects. It was a good agreement between serum and plasma concentration for butyrate. For propionate, valerate, acetate, iso-butyrate, iso-valerate and caproate there were a significant difference.