Peakview workstation

For CE–MS-based metabolites, the qualitative analysis of metabolites was performed using the pre-analyzed metabolite standard library (HMT), and internal standards were used to adjust the migration time and standardize the metabolite intensity. Peak extraction and identification were carried out with Quantitative Analysis Software (Agilent). Acyl-carnitines identification was based on the mass-to-charge ratio (m/z), retention time and MS/MS pattern. Lipid identification was based on exact mass and MS/MS pattern. The applied database search engines were HMDB, Metlin (https://metlin.scripps.edu), and LIPID MAPS. Peakview workstation (AB SCIEX) was used to check MS/MS information of metabolites and Multiquant (AB SCIEX) was used to obtain the peak areas of identified metabolites. The raw data from CE–MS and LC–MS were normalized by corresponding internal standards and tissue weight to minimize errors arising from the sample pretreatment and analysis procedures as much as possible.

Lipidview software (version 1.2, AB SCIEX, USA) was utilized to select candidate lipids. Lipid identification was based on exact mass, retention time, and MS/MS pattern. Peakview workstation (AB SCIEX, USA) was used to check MS/MS information of lipids. Multiquant (version 2.1, AB SCIEX, USA) was employed to calculate the area of lipid peaks. Internal standards, Ceramide (Cer) 17 : 0, Lysophosphatidylcholine (LPC) 19 : 0, phosphatidylcholine (PC) 38 : 0, phosphatidylethanolamine (PE) 30 : 0, SM 12 : 0, and Triglyceride (TG) 45 : 0 were used to correct lipid species in the positive mode, and LPC 19 : 0, PE 30 : 0, and free fatty acid (FFA) C16:0-d4 were used to correct lipid species in the negative mode.
Data were analyzed by Graphpad Software (San Diego, CA) and were expressed as the mean ± standard deviation (SD). Repeated measures were compared by the nne-way ANOVA test followed by a Bonferroni post hoc performance test for comparisons among four groups, and a P value < 0.05 was considered significant.