3.4 Metabolome summary
A total of 9433 metabolic ion peaks were extracted from P. vachelli muscles in the control group (M0a, M0b, M0c, M0d, M0e, M0f, M0g, M0h, M0i, M0j) and those in the experimental group (M4a, M4b, M4c, M4d, M4e, M4f, M4g, M4h, M4i, M4j), including 5152 positive and 4281 negative ion peaks (Table S2 ). In addition we found that 33 unique differentially expressed metabolites (DEM with MS2; 14 up-regulated and 19 down-regulated) were among the 18 positive and 24 negative DEM (VIP > 1 andP < 0.05; Table S2 ).
The PCA model showed that the positive and negative ion modes were closely clustered. The PLS-DA model of the example set was also established. The model evaluation parameters with positive ion mode (R2 = 0.99 cum, Q2 = 0.78 cum) and negative ion mode (R2 = 0.99 cum, Q2 = 0.87 cum). Above PCA and PLS-DA results indicated that the model was reliable and stable (Table S3 ). Similar to the KEGG analysis of DEG, 14 significant pathways for the biological process of catabolism, anabolism, and muscle dysfunction were enriched by 33 DEM (P< 0.05). Significant decreases in intermediate metabolites were found in catabolism, however, the upregulated intermediate metabolites were a big part among anabolic pathways (Fig. 2C ).