2.5 Differentially expressed metabolites (DEM) analysis
Metabolome method was the same as description in a previous study, including 20 metabolite extraction (No. M0a, M0b, M0c, M0d, M0e, M0f, M0g, M0h, M0i, M0j, M4a, M4b, M4c, M4d, M4e, M4f, M4g, M4h, M4i, M4j), LC-MS analysis conditions, metabolomics data processing (Cao et al. 2020). Data analysis methods include PLS-DA and PCA. Quantitative identification of metabolites screening and supervised PLS-DA were evaluated by MetaX software (Cao et al. 2020). The VIP was calculated, and metabolites with VIP > 1 for both multidimensional statistical analysis and P < 0.05 (Student’s t-test) were selected as metabolites with significant differences (Wen et al. 2019).