Simultaneous determination of 18 d-amino acids in rat plasma by an ultrahigh-performance liquid chromatography-tandem mass spectrometry method: application to explore the potential relationship between Alzheimer’s disease and d-amino acid level alterations

Abstract

D-Amino acids are increasingly being recognized as important signaling molecules, and abnormal levels of D-amino acids have been implicated in the pathogenesis of Alzheimer's disease. To evaluate the potential relationship between Alzheimer's disease and D-amino acids, a simple, sensitive, and reliable UPLC-MS/MS method with pre-column derivatization was developed and validated for simultaneous determination of 18 D-amino acids in rat plasma. The analytes were extracted from plasma samples by a protein precipitation procedure, and then derivatized with (S)-N-(4-nitrophenoxycarbonyl) phenylalanine methoxyethyl ester [(S)-NIFE]. Chromatographic separation was achieved using an ACQUITY UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) with a mobile phase composed of acetonitrile containing 8 mM ammonium hydrogen carbonate at a flow rate of 0.6 mL min(-1). The analytes were detected by electrospray ionization in positive ion multiple reaction monitoring modes. Under the optimum experimental conditions, all the linear regressions were acquired with r > 0.9932. The limits of quantitation of all derivatized D-amino acids were within 0.05-40.0 ng mL(-1) in rat plasma. The intra- and inter-day precisions, expressed as percentage relative standard deviations (%RSD), were within the range of 12.3 and 10.1%, respectively. The recoveries for all the analytes were observed over the range of 82.8-100.5% with RSD values less than 12.5%. Finally, the proposed method was successfully applied to simultaneous determination of the 18 D-amino acids in plasma from Alzheimer's disease rats and age-matched normal controls. Results showed that the concentrations of D-serine, D-aspartate, D-alanine, D-leucine, and D-proline in Alzheimer's disease rat plasma were significantly decreased compared with those in normal controls, while D-phenylalanine levels increased. It was revealed that some of these D-amino acids would be potential diagnostic biomarkers for Alzheimer's disease.

Development of a cognitive function marker based on D-amino acid proportions using new chiral tandem LC-MS/MS systems

“…Although D-Ser is suggested to become a promising diagnostic biomarker for AD because of the low amount of D-Ser in the brain and plasma of AD model mice in comparison with that of the healthy control model 27,28 , a clear correlation between D-Ser levels in human serum and cognitive function has not been reported 29 . Conversely, in the present study, we found that the amount of D-Ser gradually increased along with cognitive decline.…”

Amino acid racemization and its relation to geochronology and archaeometry

“…In general, amino acid enantioseparation methods can include CE [44,45], GC [46][47][48][49][50][51][52], MEKC [53,54], HPLC [55,56], and UHPLC [57,58] as well as others (references provided here are for example purposes only, as many others exist). However, HPLC separation methods appear to prevail in the literature for AAR archaeological or paleontological dating purposes.…”

Enantiomeric Ratio of Amino Acids as a Tool for Determination of Aging and Disease Diagnostics by Chromatographic Measurement

“…The determination of chiral metabolites in different sample groups is currently in progress in the authors' laboratory. Xing et al developed and validated the UPLC/MS/MS method with pre-column derivatization with (S)-NIFE for the rapid and simultaneous determination of 18 D-AAs in complex rat plasma [86]. Derivatization in combination with MS/MS detection provided excellent sensitivity.…”