title: NMR metabolomics profiling of blood plasma mimics shows that medium- and long-chain fatty acids differently release metabolites from human serum albumin.
abstract: Metabolite profiling by NMR of body fluids is increasingly used to successfully differentiate patients from healthy individuals. Metabolites and their concentrations are direct reporters of body biochemistry. However, in blood plasma the NMR-detected free-metabolite concentrations are also strongly affected by interactions with the abundant plasma proteins, which have as of yet not been considered much in metabolic profiling. We previously reported that many of the common NMR-detected metabolites in blood plasma bind to human serum albumin (HSA) and many are released by fatty acids present in fatted HSA. HSA is the most abundant plasma protein and main transporter of endogenous and exogenous metabolites. Here, we show by NMR how the two most common fatty acids (FAs) in blood plasma - the long-chain FA, stearate (C18:0) and medium-chain FA, myristate (C14:0) - affect metabolite-HSA interaction. Of the set of 18 common NMR-detected metabolites, many are released by stearate and/or myristate, lactate appearing the most strongly affected. Myristate, but not stearate, reduces HSA-binding of phenylalanine and pyruvate. Citrate signals were NMR invisible in the presence of HSA. Only at high myristate-HSA mole ratios 11:1, is citrate sufficiently released to be detected. Finally, we find that limited dilution of blood-plasma mimics releases HSA-bound metabolites, a finding confirmed in real blood plasma samples. Based on these findings, we provide recommendations for NMR experiments for quantitative metabolite profiling.
authors.affiliation: Biophysical Chemistry, Institute for Materials and Molecules, Radboud University, Heyendaalseweg 135, 6524AJ Nijmegen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Jupin
authors.affiliation: Spinnovation Analytical, Toernooiveld 1, Mercator III, 6525 ED Nijmegen, The Netherlands.
authors.forename: P J
authors.initials: PJ
authors.lastname: Michiels
authors.affiliation: Spinnovation Analytical, Toernooiveld 1, Mercator III, 6525 ED Nijmegen, The Netherlands.
authors.forename: F C
authors.initials: FC
authors.lastname: Girard
authors.affiliation: Bruker-Biospin GmbH, Rheinstetten, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Spraul
authors.affiliation: Biophysical Chemistry, Institute for Materials and Molecules, Radboud University, Heyendaalseweg 135, 6524AJ Nijmegen, The Netherlands. Electronic address: S.Wijmenga@science.ru.nl.
authors.forename: S S
authors.initials: SS
authors.lastname: Wijmenga
mesh_terms: D000596:Amino Acids / Q000097:blood; D002951:Citrates / Q000097:blood; D005227:Fatty Acids / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D007773:Lactates / Q000097:blood; D055432:Metabolomics / Q000379:methods*; D008958:Models, Molecular; D019814:Myristic Acid / Q000097:blood; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010649:Phenylalanine / Q000097:blood; D010949:Plasma / Q000737:chemistry*; D019289:Pyruvic Acid / Q000097:blood; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D013228:Stearates / Q000097:blood
chemical_list: D000596:Amino Acids; D002951:Citrates; D005227:Fatty Acids; D007773:Lactates; D012709:Serum Albumin; D013228:Stearates; D019814:Myristic Acid; D010649:Phenylalanine; D019289:Pyruvic Acid
keywords: Albumin; Blood plasma; Fatty acids; Interactions; Metabolomics; Myristate; NMR; Stearate