Methylcitric Acid Determination in Amniotic Fluid by Electron-Impact Mass Fragmentography

Abstract

Summary:Methylcitric acid, a metabolite of abnormal propionyl-CoA metabolism, is elevated in amniotic fluid when the fetus is affected with propionic acidaemia or methylmalonic aciduria. We developed a method for quantifying methylcitric acid in amniotic fluid by solid-phase extraction, derivatisation to the /-butyldimethylsilylester, and gas chromatography-mass spectrometry with electron-impact ionisation, using the deuterated analogue of methylcitric acid as an internal standard. The main advantages are a good sensitivity, simple sample preparation, and feasibility on instruments equipped with mass specific detectors.

Assessment of an electron‐impact GC‐MS method for organic acids and glycine conjugates in amniotic fluid

“…Published methods for organic acids and acylglycines in AF are either in scan mode (Coude et al 1990;Hagenfeldt and Hagenfeldt 1972;Ho¡mann et al 1989;Ng et al 1982;Nicholls et al 1978;Williams et al 1979) or SIM mode (Baric et al 1999;Gibson et al 1990Gibson et al , 1993Hine et al 1986;Inoue and Kuhara 2002;Jakobs et al 1984b^e, 1988Jakobs et al 1984b^e, , 1991Kelley and Stamas 1993;Kretschmer and Bachmann 1988;Naylor et al 1980;Rinaldo et al 1988;Schor et al 2002;Trefz et al 1981;Zinn et al 1982). The scan methods, which are only intended for pro¢ling purposes, are not sensitive enough to quantify or even detect metabolites considered as most important for prenatal diagnosis (e.g.…”

“…methylcitrate, glutarate, succinylacetone and glycine derivatives) are poorly quanti¢ed or even remain undetected. While sensitive and reliable methods have been described for the quantitative analysis of numbers of organic acids and glycine conjugates (Baric et al 1999;Gibson et al 1990Gibson et al , 1993Hine et al 1986;Inoue and Kuhara 2002;Jakobs et al 1984b^e, 1988Jakobs et al 1984b^e, , 1991Kelley and Stamas 1993;Kretschmer and Bachmann 1988;Naylor et al 1980;Rinaldo et al 1988;Schor et al 2002;Trefz et al 1981;Zinn et al 1982), these are usually devoted to one analyte only. Moreover, these methods involve fragmentation devices (chemical ionization or electron-capture negative-ionization modes) that have not yet been generalized and/or the use of isotopic internal standards.…”

In Salmonella enterica , 2-Methylcitrate Blocks Gluconeogenesis

“…Mutations affecting the carboxylase function of the methylmalonylCoA pathway lead to propionic acidemia, an often-fatal metabolic disorder. Interestingly, reports in the literature show that patients with a deficiency in propionyl-CoA carboxylase accumulate 2-MC in their urine and cerebrospinal and amniotic fluids (3,16,35,42). Conclusions drawn from our work suggest that in patients deficient in propionyl-CoA carboxylase, 2-MC is synthesized by the citrate synthase enzyme, leading to broad negative effects and eventually cell death.…”

Metabolomics

“…Methylcitrate is increased in cell-free amniotic fluid when a fetus is affected and is a key indicator for the prenatal diagnosis of PCCD. Since the direct chemical analysis of methylcitrate in cell-free amniotic fluid using stable isotope dilution GC/MS was introduced by Naylor et al and Sweetman et al, direct methods have been developed rapidly not only for PCCD but also for the other organic acidemias [59][60][61][62][63][64][65]. Methods involving cell culture are time-consuming and potentially unreliable due to the possible contamination of amniotic fluid with maternal cells [66].…”