In MBRole, pathway enrichment analysis indicated that differentially expressed metabolites were involved in multiple metabolic pathways, including the metabolism of glycine, taurine, arginine and alanine (Table 3). Using MetScape, metabolic network illustration shows the connection of these metabolites (Fig 4), where hexagons represente metabolites, red frames indicate the decreased metabolites, green frames indicate increased metabolites, squares indicate KEGG ID, rounded rectangles represent enzymes, and blue represents regulative genes.