Measurement of urinary CDH and CTH by tandem mass spectrometry in patients hemizygous and heterozygous for Fabry disease

Abstract

Fabry disease is an X-linked disorder of glycosphingolipid metabolism resulting from a deficiency of the lysosomal enzyme alpha-galactosidase A. This deficiency leads to the progressive accumulation, in lysosomes of visceral tissues and in body fluids of hemizygotes, of the glycosphingolipids globotriaosylceramide (CTH, Gb(3) or GL-3) and galabiosylceramide (CDH) and to a lesser extent the blood group AB and B related glycolipids. Elevated levels of the glycosphingolipids are found in the urine of hemizygous males with the classic phenotype, but it is not known whether all symptomatic or asymptomatic heterozygotes have elevated levels. We have therefore measured CTH and CDH quantitatively in a multiplex assay using tandem mass spectrometry in urine from a large cohort (44) of genetically proven or obligate heterozygotes including four with the N215S mutation, from classic hemizygotes (28), from cardiac variant hemizygotes with the N215S mutation (6) and from normal controls. The levels of CTH and CDH were related to both creatinine and sphingomyelin. Urinary CTH was elevated in all 28 classic hemizygotes but only in 4/6 of the cardiac variants. The level was within or just above the normal reference range in the four individuals heterozygous for the N215S mutation but was elevated in 38/40 of the other heterozygotes. Similar results were obtained for CDH, except that only 34/40 heterozygotes had an elevated level. The level of CDH was not elevated in the four heterozygotes and 4/6 of the hemizygotes for the N215S mutation. Combining the levels of CTH and CDH did not improve the discrimination of heterozygotes from controls. The ratio of CDH to CTH was higher in heterozygotes than in hemizygotes. Measurement of urinary CTH gave the best discrimination of heterozygotes from controls.

Metabolomic Discovery of Novel Urinary Galabiosylceramide Analogs as Fabry Disease Biomarkers

“…It is a component of cellular membranes and is found in large concentration in biological fluids of Fabry patients [21][22][23]. Mills et al noted that CDHs, Ga 2 , and lactosylceramide ( Figure 1c and d), have the same empirical formula and, therefore, cannot be differentiated by mass spectrometry analysis [21].…”

UniProt Genomic Mapping for Deciphering Functional Effects of Missense Variants

“…The text BED files are in an extended BED format that These missense variants all modify the required asparagine (Asn, N) to another amino acid. The P06280:p.Asn215Ser variant has been described in the literature multiple times over the years and, in ClinVar, multiple submitters have annotated this variant as pathogenic, citing at least 10 publications describing this variant and others seen in patients and family pedigrees with Fabry disease (Davies et al 1993;Eng et al 1993;Eng and Desnick 1994;Topaloglu et al 1999;Mills et al 2005;Ishii et al 2007;Wu et al 2011;Ebrahim et al 2012;Bean et al 2013;Tian et al 2013). …”

Dosage du globotriaosylcéramide dans l’urine

“…L'étude d'autres paramètres tels que le digalactosylcéramide [5], également accumulé dans la maladie de Fabry, ou de certaines isoformes du Gb3 [6,7] n'ont pas apporté, à ce jour, de meilleures informations. Mais l'intérêt du dosage du Gb3 chez les hémizygotes concerne surtout le suivi thérapeutique.…”