In VivoDetermination of Very-Low-Density Lipoprotein–Apolipoprotein B100 Secretion Rates in Humans with a Low Dose ofl-[1-13C]Valine and Isotope Ratio Mass Spectrometry

Abstract

The aim of the present study was to determine the rate of very-low-density lipoprotein (VLDL)–apolipoprotein (apo) B100 secretion in humans with a minimized amount ofl-[1-13C]valine infusion in combination with the use of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analysis. To compare this method with the conventional gas chromatography/mass spectrometry (GC/MS) technique, two different dosages ofl-[1-13C]valine and both analytical techniques were compared in a single study. A priming dose ofl-[1-13C]valine (2 μmol/kg) followed by a constant infusion (2 μmol/kg/h) was given for 3 h, directly followed by a second priming dose (15 μmol/kg) and a constant infusion (15 μmol/kg/h) for 4 h. The fractional secretion rate obtained by GC/C/IRMS measurements from the first 3 h of infusion (mean ± SD: 0.22 ± 0.09 pools/h) was similar to that obtained by GC/MS during the last 4 h of infusion (0.23 ± 0.07 pools/h;P= 0.56). In conclusion, superior analytical accuracy and sensitivity of GC/C/IRMS enable measurements of VLDL–apo B100 secretion with much lower doses ofl-[1-13C]valine and allow for reduction of experimental costs.