4.4. Serum Metabolomic Assay
WEST
Serum samples were sent to the West Coast Metabolomics Center (Davis, CA, USA) for the analyses of primary metabolites and complex lipids by combining three analytical platforms, including gas chromatography–time-of-flight mass spectrometry (Ann Arbor, MI, USA), hydrophilic interaction chromatography–quadrupole time-of-flight tandem mass spectrometry (Davis, CA, USA), and charged-surface hybrid–quadrupole time-of-flight tandem mass spectrometry (Davis, CA, USA). Internal standards were employed for the identification of metabolites by matching the retention times as previously described [