HPLC-gradient-grade ACN, water, and MeOH were obtained from J.T.Baker (Amsterdam, Netherlands); betaine aldehyde, CHCA, trifluoric acid (TFA), NEDC and glucose, galactose, mannose, fructose and 13 C6 isotopically labelled D-glucose ("glucose isotope 221") were obtained from Sigma-Aldrich/Merck; Animal treatment and Wssue preparaWon All experiments on animals were performed according to the approval of the Polish and European CommuniWes Council DirecWves (86/609/EEC) and were permi]ed by the local ethics commi]ee (approval number: 137/2018). For our analysis, the Wssues obtained from control animals used during other analyses, according to the so-called 3R (replacement/reducWon/refinement) principle. The Wssue from liver, spinal cord and cerebellum was taken to these experiments. Cerebellum was especially important due to its characterisWc pa]ern of white and grey ma]er.