1H-NMR analyses and assignment of present resonances The 1H-NMR spectra are recorded on a 400 Megahertz (MHz) NMR spectrometer (Varian/Agilent, Nuclear Magnetic Resonance Instruments, Palo Alto, California, USA) with a magnetic field strength of 9.4 Tesla at 294 K. Slightly T2- weighted spectra are acquired using a Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence to attenuate signals of macromolecules, such as proteins and polysaccharides. Additionally, water suppression is performed in order to allow optimal detection and quantification of low-molecular weight metabolites. The 1H-NMR spectra are phased manually, baseline corrected and referenced to the TSP resonance at 0.015 parts per million (ppm). The assignment of the present 1H-NMR resonances occurs by means of spiking experiments. A reference plasma sample is alternately spiked with 34 known metabolites with a concentration of 1 mg compound per 100 µl plasma. The obtained chemical shifts are double checked with Chenomx NMR suite software (Version 7.5, Chenomx Inc., Edmonton, Alberta, Canada). Finally, 1H-NMR spectra are divided in 112 spectral regions, which are integrated and normalized relative to the total integrated area of all spectral regions, irrespective of the remaining water, TSP, fructose and glucose resonances. The end result corresponds to 110 normalized integration regions (all integration regions except those of water and TSP).