Determination of total, free and esterified short

Short-chain fatty acids are primarily absorbed through the portal vein during lipid digestion, which is utilized as the energy source, as well as prevent type 2 diabetes and some cancers. However, reports on the determination of these short-chain fatty acids in human serum are limited. Blood samples from human subjects (n？=？547, male/female？=？246/301, age 58.85？±？12.57) were collected. Saponification was applied to obtain total fatty acid. After derivatization by 2-nitrophenylhydrazine, fatty acid 4:0 and fatty acid 6:0 were measured by liquid chromatography-mass spectrometry. The developed method exhibited good linearity (R2？=？0.9996 for both). All the coefficients of variation of reproducibility and accuracy for fatty acid 4:0 and fatty acid 6:0 ranged 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 fatty acid 4:0 (162.4？±？76.4 μmol/L) was significantly higher than fatty acid 6:0 (2.0？±？2.5 μmol/L, P？<？0.001). Furthermore, the esterified form was predominant in both fatty acid 4:0 and fatty acid 6:0 (98.2% and 82.4% of total fatty acids, respectively). Besides, short-chain fatty acids showed no significant differences with regard to sex or age differences. This developed liquid chromatography-mass spectrometry method is convenient and reliable, which might be useful for monitoring the variations of short-chain fatty acids in blood