Metabolic profile of fish muscle tissue changes with sampling method, storage strategy and time

Unstable tissue components (metabolites) are not easily captured and evaluated by traditional metabolomics methods. In this study, a comprehensive investigation of various sampling methods and storage conditions on the metabolomic profile of fish muscle was performed based on in vivo and ex vivo sampling. The GlobalStd algorithm and structure/reaction directed analysis under a linear mixed model were used to investigate the distinctive influences of these factors on the metabolomic profiles of fish tissue obtained via untargeted LC-MS analysis. Immediate analysis of samples yielded different metabolomic profiles compared to that of stored samples. Storage time was found to affect the metabolomic profile in a complex way, whereas storage temperature was shown to not substantially change this pattern. At the reaction level, metabolites involved in homologous series with butylation were shown stable during storage. Overall, our findings demonstrate that immediate instrumental analysis after in vivo solid phase microextraction (SPME) sampling and a reverse time series experimental design should be the preferred approaches for metabolomic profiling if unstable compounds are of interest.