Comparison of serum versus plasma collection in gas chromatography--mass spectrometry-based metabolomics

Bovine serum, EDTA-plasma and EDTA-plasma fortified with acetylsalicylic acid (ASA) as antioxidant were compared with regard to their suitability for metabolomic studies. Metabolic fingerprints were generated from GC-TOF-MS data using the Leco ChromaTOF software in combination with the in-house retention time correction and data alignment tool INCA. A total of 6, 9 and 21 significant features with a false discovery rate of <0.05 were identified by INCA upon comparing EDTA- versus EDTA-ASA-plasma, EDTA-plasma versus serum and EDTA-ASA-plasma versus serum, respectively. To confirm that the observed signal intensities in the GC-TOF-MS fingerprints reflected true metabolite abundances, 19 amino acids, glucose and 6 organic acids were quantified by means of GC-MS using stable-isotope-labeled internal standards. As observed with the fingerprints, only the concentrations of lactate and citrate were found to be significantly lower in EDTA-plasma and serum, respectively, whereas the concentrations of the other metabolites were similar among the three sample types investigated

Nuclear magnetic resonance and mass spectrometry-based milk metabolomics in dairy cows during early and late lactation

Milk production in dairy cows has dramatically increased over the past few decades. The selection for higher milk yield affects the partitioning of available nutrients, with more energy being allocated to milk synthesis and less to physiological processes essential to fertility and fitness. In this study, the abundance of numerous milk metabolites in early and late lactation was systematically investigated, with an emphasis on metabolites related to energy metabolism. The aim of the study was the identification and correlation of milk constituents to the metabolic status of the cows. To investigate the influence of lactation stage on physiological and metabolic variables, 2 breeds of different productivity were selected for investigation by high-resolution nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry. We could reliably quantify 44 different milk metabolites. The results show that biomarkers such as acetone and beta-hydroxybutyrate are clearly correlated to the metabolic status of the individual cows during early lactation. Based on these data, the selection of cows that cope well with the metabolic stress of early lactation should become an option