Part of the validation needed for future implementation of solanidine as a biomarker for CYP2D6 activity in routine practice.

Abstract

Background: Solanidine, found in potatoes, has proven to be a promising dietary biomarker for phenotyping CYP2D6 activity. Center for Psychopharmacology at Diakonhjemmet Hospital has developed a method for analyzing solanidine in serum. Although there is published evidence for solanidine as a dietary biomarker, further validation is needed before measurements of solanidine, and its metabolite can be implemented in routine analysis. Aim: The project aimed to establish limits of peak area variability for solanidine and OH- solanidine and examine if pre-analytical factors influenced the levels and detection of solanidine and OH-solanidine. The project also aimed to implement hemolyzed blood in the method for phenotyping CYP2D6 enzyme activity. Method: Samples were collected to establish limits of peak area variability for solanidine and OH-solanidine and examine the influence of preanalytical factors on levels and detection of the analytes in serum and haemolyzed blood. All samples were prepared by protein precipitation before analysis on UHPLC-HRMS. When relevant, samples from subjects that had previously been CYP-genotyped at Center for Psychopharmacology were used. OH-solanidine-to-solanidine ratio based on peak areas was used as a semi-quantitative measure for CYP2D6 phenotype. Results: TheresultsestablishedthelimitofpeakareaforsolanidineandOH- solanidine at 43,700 and 59,600, respectively. The detection of solanidine and OH- solanidine was not aVected by the collection of samples in diVerent sample tubes, but it was aVected by the storage on gel separator tubes for two days or more. The stability of the analytes in the final extract from serum was not aVected when stored for seven days. There were some deviations in the detection of solanidine and OH-solanidine when analyzed in the presence of a collection of diVerent drugs. Lastly, it is possible to phenotype CYP2D6 enzyme activity in hemolyzed blood, as it showed similar characteristics as when phenotyping with serum. Conclusion: The project established the limit of peak area variability for solanidine and OH-solanidine. Among the pre-analytical factors examined, the use of gel separator tubes and the presence of other drugs aVected the levels and/or detection of solanidine and OH-solanidine. The project demonstrated that it was possible to phenotype CYP2D6 PMs in hemolyzed blood.