The analysis of peripheral endocannabinoids is a good biomarker of the endocannabinoid 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 (i.e. 2- arachidonoyl glycerol or 2-oleoyl glycerol) 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 endocannabinoid profile of a range of monoacylglycerols and N-acylethanolamides in plasma that preserves the original isomer ratio of monoacylglycerols. Nevertheless, the chemical isomerization of 2-monoacylglycerols can only be avoided by an immediate processing and analysis of samples due to the instability during conservation. We believe that this new methodology can aid in the harmonization of the measurement ofendocannabinoids and related compounds in clinical samples.

PMID:

 24610889
[PubMed – as supplied by publisher]