Pyruvate

All metabolic assays were carried out with the supernatant of tissue preparation (see Western blot analysis). Total glucose levels in brain tissue and serum were determined spectrophotometrically at 530 nm by a glucose assay kit (Sigma‐Aldrich) following the manufacturer's instructions. Lactate and pyruvate levels were also detected colorimetrically at 530 or 570 nm, respectively, by using a lactate (Labor + Technik, Eberhard Lehmann GmbH) or pyruvate (BioAssay Systems) assay kit.
Albumin levels were determined colorimetrically at 630 nm by the bromocresol green reaction (Labor + Technik, Eberhard Lehmann GmbH). Total protein content of the cytosolic and membrane fraction was measured using the DC Protein Assay from Bio Rad.

Samples from cohort 2 were used to validate the semi-targeted metabolomic analysis. The quantification of selected metabolites was assessed by specific fluorometric assays in serum filtrates (10,000 kD). EnzyChrom™ Succinate, Pyruvate and L-Lactate assay kits were purchased from BioAssay Systems (Hayward, CA, USA). An assay kit for α-ketoglutarate was purchased from BioVision (Milpitas, CA, USA).