High-throughput and simultaneous quantitative analysis of homocysteine–methionine cycle metabolites and co-factors in blood plasma and cerebrospinal fluid by isotope dilution LC–MS/MS

Abstract

The methionine cycle is a key pathway contributing to the regulation of human health, with well-established involvement in cardiovascular diseases and cognitive function. Changes in one-carbon cycle metabolites have also been associated with mild cognitive decline, vascular dementia, and Alzheimer’s disease. Today, there is no single analytical method to monitor both metabolites and co-factors of the methionine cycle. To address this limitation, we here report for the first time a new method for the simultaneous quantitation of 17 metabolites in the methionine cycle, which are homocysteic acid, taurine, serine, cysteine, glycine, homocysteine, riboflavin, methionine, pyridoxine, cystathionine, pyridoxamine, S-adenosylhomocysteine, S-adenosylmethionine, betaine, choline, dimethylglycine, and 5-methyltetrahydrofolic acid. This multianalyte method, developed using ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS), provides a highly accurate and precise quantitation of these 17 metabolites for both plasma and cerebrospinal fluid metabolite monitoring. The method requires a simple sample preparation, which, combined with a short chromatographic run time, ensures a high sample throughput. This analytical strategy will thus provide a novel metabolomics approach to be employed in large-scale observational and intervention studies. We expect such a robust method to be particularly relevant for broad and deep molecular phenotyping of individuals in relation to their nutritional requirements, health monitoring, and disease risk management.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-016-0003-1) contains supplementary material, which is available to authorized users.

Application of Metabolomics in Alzheimer’s Disease

“…In another study, Guiraud et al utilized UPLC-MS/MS to quantitate 17 metabolites of the methionine cycle in the CSF of patients diagnosed with AD ( 61 ). They applied a new multianalyte strategy to monitor both metabolites and cofactors of methionine metabolism simultaneously.…”

Possible Involvement of Hydrosulfide in B12-Dependent Methyl Group Transfer

“…Cystathionine γ-lyase has been reported to be undetectable in brain tissue and to be completely absent in the embryo (summarized in [ 52 ]). Cystathionine β-synthase has been shown to be expressed in brain but it is unlikely to be significant source of S°/H 2 S in brain because its Km for cysteine (36 mM) is much greater than the Km for the conventional substrate serine (~3 mM) [ 53 ] and far beyond the physiological level of cyst(e)ine in cerebrospinal fluid (1.1 ± 0.4 μM) [ 54 ]. Furthermore, S°/H 2 S generated elsewhere in the body cannot enter nerve tissue because it is bonded to carrier proteins that cannot cross the blood-brain barrier.…”

Folate Protects Hepatocytes of Hyperhomocysteinemia Mice From Apoptosis via Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)-Activated Endoplasmic Reticulum Stress

“…Elevated Hcy in serum can aggravate and potentially cause serious pathologies including cardiovascular diseases [Li et al, 2016a], Alzheimer's disease [Hara et al, 2016], various liver diseases [Tung et al, 2017], and certain forms of cancer [Qu et al, 2016]. The methionine cycle successively involves the synthesis of S-adenosylmethionine (SAM) from methionine and the trans-methylation reactions of a large number of substrates that use SAM as a co-substrate, and production of S-adenosylhomocysteine (SAH) [Guiraud et al, 2017]. Additionally, Hcy remethylation can also be catalyzed in the liver by enzymes, suggesting a key role of liver in Hcy metabolism.…”