2.1. Participants from the WAS Trial
weight loss
Characteristics of the patient cohort at the start of the study have been described in detail previously [At 1-year follow-up patients of the RYGB-surgery group achieved a significant weight loss of −34.3% (BMI 49.1 [46–51] kg/mA total of 188 metabolites were measured in 46 serum samples at randomization and one year after randomization. Forty-nine metabolites were not considered due to exclusion criteria. Thus, 139 metabolites (9 Cs, 21 amino acids, 9 biogenic amines, 13 lysoPCs, 72 PCs, a hexose and 14 SMs) were valid and retained for the main analysis and the derivation of metabolomic profiles. Fifty-seven metabolites were found to be significantly different between groups (1 acylcarnitine, 13 amino acids, 1 biogenic amine, 5 lysoPCs, 31 PCs, 5 SMs and a hexose) as shown in The performed principal component analysis (PCA) resulted in twelve discriminating components with an eigenvalue > 1. The first two components explained 49% of the variance. Hence, further investigation was performed based on a two-component model. The first principal component (PC1) was characterized predominantly by phosphatidylcholines and sphingolipids, whereas the second principal component (PC2) was characterized by BCAA, aromatic acids and acylcarnitines (see We performed hierarchical clustering of the 57 metabolites with significant differences between the LS and OP group (see 