Tracing the fate of plasma fatty acids
Short chain fatty acids are produced as a result of microbial digestion of fibre and resistant starch. Recent research suggests that these may be very important in the metabolism of the liver and other organs. To gain insight into their production and metabolic fate in vivo, an ideal method is to use radioactive tracers. Scientists at the Human Nutrition Research Centre in Nantes, under the umbrella of the 13C-STARCH project, have developed a refined method of gas chromatography/mass spectrometry (GC/MS) to detect SCFAs. This has the advantage of reducing the need to use a high level of 13C tracer in studies. Gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) was refined using solid phase micro-extraction (SPME). Plasma proteins were removed and the SPME fibre was held in the liquid when the acetate was desorbed. When tested against an internal standard, good linearity was obtained for the fatty acids. For example, acetate gave repeatable linear results from concentrations between zero and 400 micromoles. Accuracy was also confirmed. When tested on healthy and overweight subjects during lactulose fermentation, concentrations of acetate were consistent whether using low or high concentrations of radioactive tracer. This refined method of tracking carbon-based metabolites has increased sensitivity. Furthermore, it holds potential for the elucidation of metabolic pathways important in the prevention of chronic diseases such as type II diabetes and atherosclerosis.
