title: Metabolite quantification by NMR and LC-MS/MS reveals differences between unstimulated, stimulated, and pure parotid saliva.
abstract: Saliva is a readily available biofluid that is sensitive to metabolic changes and can be collected through rapid and non-invasive collection procedures, and it shows great promise for clinical metabolomic studies. This work studied the metabolite composition of, and the differences between, saliva samples collected by unstimulated spitting/drooling, paraffin chewing-stimulated spitting, and parotid gland suction using targeted nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for metabolite quantification. As applied here, these two analytical techniques provide complementary metabolite information and together extend the metabolome coverage with robust NMR quantification of soluble metabolites and sensitive targeted LC-MS/MS analysis of bioactive lipids in specific metabolic pathways. The NMR analysis was performed on ultrafiltrated (3kDa cutoff) saliva samples and resulted in a total of 45 quantified metabolites. The LC-MS/MS analysis was performed on both filtered and unfiltered samples and resulted in the quantification of two endocannabinoids (AEA and PEA) and 22 oxylipins, which at present is the most comprehensive targeted analysis of bioactive lipids in human saliva. Important differences in the metabolite composition were observed between the three saliva sample collection methods, which should be taken into consideration when designing metabolomic studies of saliva. Furthermore, the combined use of the two metabolomics platforms (NMR and LC-MS/MS) proved to be viable for research and clinical studies of the salivary metabolome.
authors.affiliation: Department of Pharmacology and Clinical Neuroscience, Umeå University, SE - 901 85 Umeå, Sweden.
authors.forename: João
authors.initials: J
authors.lastname: Figueira
authors.affiliation: Department of Chemistry, Umeå University, SE - 901 87 Umeå, Sweden.
authors.forename: Sandra
authors.initials: S
authors.lastname: Gouveia-Figueira
authors.affiliation: Department of Pedodontics/Odontology, Umeå University, SE - 901 87 Umeå, Sweden.
authors.forename: Carina
authors.initials: C
authors.lastname: Öhman
authors.affiliation: Department of Pedodontics/Odontology, Umeå University, SE - 901 87 Umeå, Sweden.
authors.forename: Pernilla
authors.initials: P
authors.lastname: Lif Holgerson
authors.affiliation: Department of Chemistry, Umeå University, SE - 901 87 Umeå, Sweden; Department of Entomology and Nematology, University of California, Davis, CA 95616, USA. Electronic address: malin.nording@umu.se.
authors.forename: Malin L
authors.initials: ML
authors.lastname: Nording
authors.affiliation: Department of Pharmacology and Clinical Neuroscience, Umeå University, SE - 901 85 Umeå, Sweden. Electronic address: anders.ohman01@umu.se.
authors.forename: Anders
authors.initials: A
authors.lastname: Öhman
mesh_terms: D002853:Chromatography, Liquid; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D055442:Metabolome; D055432:Metabolomics; D012463:Saliva; D053719:Tandem Mass Spectrometry
keywords: Eicosanoids; Endocannabinoids; LC-MS/MS; NMR; Oxylipins; Saliva