Prior to NMR analysis, plasma aliquots are thawed and homogenized using a vortex mixer. After centrifugation at 13000 g for 4 minutes at 4°C (fixed rotor Eppendorf centrifuge 5415 R, Hamburg, Germany), plasma aliquots are diluted in deuterium oxide (D2O, 99.9%, Cambridge Isotope Laboratories Inc, Andover, USA) containing 180 µg/µl trimethylsilyl-2,2,3,3-tetradeuteropropionic acid (TSP, 98%, Cambridge Isotope Laboratories Inc, Andover, USA) as a chemical shift reference. Finally, the prepared plasma samples are transferred into a 5 mm NMR tube and analyzed.