ANNALS EXPRESS: Determination of Total, Free, and Esterified Short-Chain Fatty Acid in Human Serum by LC-MS/MS.

BACKGROUND: Short-chain fatty acid (SCFA) are primarily absorbed through the portal vein during lipid digestion, which is utilized as the energy source, as well as prevents type 2 diabetes and some cancers. However, reports on the determination of these SCFA in human serum are limited.

METHODS: Blood samples from human subjects (n = 547, male/female = 246/301, age 58.85 ± 12.57) were collected. Saponification was applied to obtain total FA. After derivatization by 2-nitrophenylhydrazine, FA 4:0 and FA 6:0 were measured by liquid chromatography-mass spectrometry (LC-MS/MS).

RESULTS: The developed method exhibited satisfied linearity (R2 = 0.9996 for both). All the coefficient of variation of reproducibility and accuracy for FA 4:0 and FA 6:0 ranged in 3.0%-6.1%, with the average recoveries of 87.8%-102.4% and 92.2%-98.2%, respectively. In all the samples, the concentration of FA 4:0 (162.4 ± 76.4 µmol/L) showed significantly higher than FA 6:0 (2.0 ± 2.5 µmol/L, P < 0.001). Furthermore, the esterified form showed predominant in both FA 4:0 and FA 6:0 (98.2% and 82.4% of total FA, respectively). Besides, SCFA showed no significant differences in concentration with sex or age differences.

CONCLUSION: This developed LC-MS/MS method is convenient and reliable, which might be useful for monitoring SCFA variation in blood.