Development and clinical application of a LC-MS/MS method for simultaneous determination of one-carbon related amino acid metabolites in NTD tissues

Background: Neural tube defects are a group of severe neurological birth defects with one-carbon metabolism disturbance. The lack of information available on the distribution of one-carbon metabolites in lesion tissues precludes further elucidation of the pathogenesis of NTDs. Our aims were to develop and validate a simple and robust method for one-carbon related amino acid measurements in both intracellular and extracellular bio-samples and apply this method to NTD tissues for risk metabolite screening. Method: A simultaneous test for nine amino acids (homocysteine, S-adenosylhomocysteine, serine, histidine, methionine, cystathionine, cysteine, glycine, and tryptophan) in both intracellular and extracellular matrices was developed using liquid chromatography tandem mass spectrometry in a multiple reaction monitoring mode. Three kinds of tissues from folate deficient and NTD-affected embryos and controls in a NTD high-risk area were analyzed using this method. Results: Method recoveries ranged from 87.10% to 118.85% and accuracy (relative error, RE%) ranged from -14.96% to 13.96%. Calibration curves were linear (R-2 > 0.99). The within-run and between-run precision were both lower than 15%. Reproducibility CV% ranged from 0.29% to 13.37% in low, medium and high concentration standard spiked plasma, HEK-293 cells, and brain, lung, heart tissues. NTD brain tissue showed significantly high concentration of homocysteine and cystathionine, and low concentration of histidine, glycine, methionine and tryptophan. Conclusion: This high-throughput method is reliable and accurate for simultaneous determination of one-carbon amino acid metabolites in both intracellular and extracellular bio-samples.