Figure 2

(a,b) Hierarchical clustering analysis with heatmap representation of the metabolites and the clinical parameters of (a) the first amyotrophic lateral sclerosis (ALS) group and (b) the second ALS group. Rows indicate (a) 13 metabolites with statistical significance between the control and first ALS group and (b) a subset of the 13 metabolites detected in the second ALS group. The N-acetylgalactosamine(*) row includes N-acetylmannosamine and N-acetylglucosamine. 3-Methoxytyrosine, 7-methylguanine, N-acetylputrescine, and N6-acetyllysine were excluded from the dataset because the four metabolites had a distribution along a vertical line, and thus no correlation coefficient was available. Columns indicate the 12 clinical parameters assessed in the study. (a,b) The heatmap shows a gradient color scale ranging from cyan to black to yellow, indicating the normalized score (Z-score) calculated from Spearman’s rank correlation coefficient for each combination. (c,d) Correlation analysis between taurine and nerve excitability properties (SDTC) in both groups of ALS patients. Scatterplots show the correlation between taurine and SDTC in the (c) first ALS group (n = 7) and (d) second ALS group (n = 22). Pearson’s correlation coefficient (R) and the p-value (p) are shown. a.u. arbitrary unit, BMI body mass index, FA fatty acid, %FVC percent forced vital capacity, SDTC strength duration time constant; sex (M male, F female), T2DM type 2 diabetes mellitus, Ted depolarizing threshold electrotonus; treatment with Riluzole and/or Edaravone (− negative/non-administration, +  positive/ administration); type = site of symptom onset (U upper limbs, B bulbar, L lower limbs, R respiratory failure), ΔFRS progression rate (ratio of Functional Rating Scale score to time).