title: Analysis of ECs and related compounds in plasma: artifactual isomerization and ex vivo enzymatic generation of 2-MGs.
abstract: The analysis of peripheral endocannabinoids (ECs) is a good biomarker of the EC system. Their concentrations, from clinical studies, strongly depend on sample collection and time processing conditions taking place in clinical and laboratory settings. The analysis of 2-monoacylglycerols (MGs) (i.e., 2-arachidonoylglycerol or 2-oleoylglycerol) is a particularly challenging issue because of their ex vivo formation and chemical isomerization that occur after blood sample collection. We provide evidence that their ex vivo formation can be minimized by adding Orlistat, an enzymatic lipase inhibitor, to plasma. Taking into consideration the low cost of Orlistat, we recommend its addition to plasma collecting tubes while maintaining sample cold chain until storage. We have validated a method for the determination of the EC profile of a range of MGs and N-acylethanolamides in plasma that preserves the original isomer ratio of MGs. Nevertheless, the chemical isomerization of 2-MGs can only be avoided by an immediate processing and analysis of samples due to their instability during conservation. We believe that this new methodology can aid in the harmonization of the measurement of ECs and related compounds in clinical samples.
authors.affiliation: Human Pharmacology and Clinical Neurosciences Research Group, Neuroscience Research Program, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Pastor
authors.forename: Magí
authors.initials: M
authors.lastname: Farré
authors.forename: Montserrat
authors.initials: M
authors.lastname: Fitó
authors.forename: Fernando
authors.initials: F
authors.lastname: Fernandez-Aranda
authors.forename: Rafael
authors.initials: R
authors.lastname: de la Torre
mesh_terms: D001095:Arachidonic Acids / Q000097:blood* / Q000737:chemistry* / Q000378:metabolism; D016477:Artifacts; D001774:Blood Chemical Analysis / Q000379:methods*; D004355:Drug Stability; D063388:Endocannabinoids / Q000097:blood* / Q000737:chemistry* / Q000378:metabolism; D005260:Female; D005989:Glycerides / Q000097:blood* / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007536:Isomerism; D007783:Lactones / Q000737:chemistry / Q000494:pharmacology; D008049:Lipase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D000077403:Orlistat; D015203:Reproducibility of Results
chemical_list: D001095:Arachidonic Acids; D063388:Endocannabinoids; D005989:Glycerides; D007783:Lactones; C094503:glyceryl 2-arachidonate; D000077403:Orlistat; C505247:2-oleoylglycerol; D008049:Lipase
keywords: 2-arachidonoylglycerol; 2-monoacylglycerol; 2-oleoylglycerol; Orlistat; endocannabinoids; human; validation