title: Targeted metabolomics identifies reliable and stable metabolites in human serum and plasma samples.
abstract: BACKGROUND
  Information regarding the variability of metabolite levels over time in an individual is required to estimate the reproducibility of metabolite measurements. In intervention studies, it is critical to appropriately judge changes that are elicited by any kind of intervention. The pre-analytic phase (collection, transport and sample processing) is a particularly important component of data quality in multi-center studies.
  
  
  METHODS
  Reliability of metabolites (within-and between-person variance, intraclass correlation coefficient) and stability (shipment simulation at different temperatures, use of gel-barrier collection tubes, freeze-thaw cycles) were analyzed in fasting serum and plasma samples of 22 healthy human subjects using a targeted LC-MS approach.
  
  
  RESULTS
  Reliability of metabolite measurements was higher in serum compared to plasma samples and was good in most saturated short-and medium-chain acylcarnitines, amino acids, biogenic amines, glycerophospholipids, sphingolipids and hexose. The majority of metabolites were stable for 24 h on cool packs and at room temperature in non-centrifuged tubes. Plasma and serum metabolite stability showed good coherence. Serum metabolite concentrations were mostly unaffected by tube type and one or two freeze-thaw cycles.
  
  
  CONCLUSIONS
  A single time point measurement is assumed to be sufficient for a targeted metabolomics analysis of most metabolites. For shipment, samples should ideally be separated and frozen immediately after collection, as some amino acids and biogenic amines become unstable within 3 h on cool packs. Serum gel-barrier tubes can be used safely for this process as they have no effect on concentration in most metabolites. Shipment of non-centrifuged samples on cool packs is a cost-efficient alternative for most metabolites.
authors.affiliation: Research Unit of Molecular Epidemiology, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany ; Institute of Epidemiology II, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany ; German Center for Diabetes Research, Neuherberg, Germany ; Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Breier
authors.affiliation: Research Unit of Molecular Epidemiology, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany ; Institute of Epidemiology II, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany ; German Center for Diabetes Research, Neuherberg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Wahl
authors.affiliation: Institute of Experimental Genetics, Genome Analysis Center, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Prehn
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany ; Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany ; Medizinische Klinik und Poliklinik IV, Diabetes Research Group Klinikum der Universität München, Munich, Germany.
authors.forename: Marina
authors.initials: M
authors.lastname: Fugmann
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany ; Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany ; Medizinische Klinik und Poliklinik IV, Diabetes Research Group Klinikum der Universität München, Munich, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Ferrari
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany ; Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany ; Medizinische Klinik und Poliklinik IV, Diabetes Research Group Klinikum der Universität München, Munich, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Weise
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany ; Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany ; Medizinische Klinik und Poliklinik IV, Diabetes Research Group Klinikum der Universität München, Munich, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Banning
authors.affiliation: Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany ; Medizinische Klinik und Poliklinik IV, Diabetes Research Group Klinikum der Universität München, Munich, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Seissler
authors.affiliation: Research Unit of Molecular Epidemiology, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany ; Institute of Epidemiology II, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany ; German Center for Diabetes Research, Neuherberg, Germany ; Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Grallert
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany ; Institute of Experimental Genetics, Genome Analysis Center, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany ; Chair for Experimental Genetics, Technical University of Munich, Freising-Weihenstephan, Germany.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Adamski
authors.affiliation: German Center for Diabetes Research, Neuherberg, Germany ; Clinical Cooperation Group Subclassification of Type 2 Diabetes, Ludwig-Maximilians-Universität Muenchen and Helmholtz Zentrum Muenchen, Munich, Germany ; Medizinische Klinik und Poliklinik IV, Diabetes Research Group Klinikum der Universität München, Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Lechner
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000097:blood; D002853:Chromatography, Liquid; D004355:Drug Stability; D005260:Female; D005615:Freezing; D006601:Hexoses / Q000097:blood; D006801:Humans; D008297:Male; D055442:Metabolome / Q000502:physiology*; D055432:Metabolomics; D008875:Middle Aged; D010743:Phospholipids / Q000097:blood; D010949:Plasma / Q000737:chemistry*; D015203:Reproducibility of Results; D044967:Serum / Q000737:chemistry*; D013048:Specimen Handling; D053719:Tandem Mass Spectrometry; D013696:Temperature
chemical_list: D000596:Amino Acids; D006601:Hexoses; D010743:Phospholipids