HPLC for Simultaneous Quantification of Total Ceramide, Glucosylceramide, and Ceramide Trihexoside Concentrations in Plasma

Background: Simple, reproducible assays are needed for the quantification of sphingolipids, ceramide (Cer), and sphingoid bases. We developed an HPLC method for simultaneous quantification of total plasma concentrations of Cer, glucosylceramide (GlcCer), and ceramide trihexoside (CTH). Methods: After addition of sphinganine as internal calibrator, we extracted lipids from 50 μL plasma. We deacylated Cer and glycosphingolipids by use of microwave-assisted hydrolysis in methanolic NaOH, followed by derivatization of the liberated amino-group with o-phthaldialdehyde. We separated the derivatized sphingoid bases and lysoglycosphingolipids by HPLC on a C18 reversed-phase column with a methanol/water mobile phase (88:12, vol/vol) and quantified them by use of a fluorescence detector at λex 340 nm and λem 435 nm. Results: Optimal conditions in the Solids/Moisture System SAM-155 microwave oven (CEM Corp.) for the complete deacylation of Cer and neutral glycosphingolipids without decomposition were 60 min at 85% power, fan setting 7. Intra- and interassay CVs were <4% and <14%, respectively, and recovery rates were 87%–113%. The limit of quantification was 2 pmol (0.1 pmol on column), and the method was linear over the interval of 2–200 μL plasma. In samples from 40 healthy individuals, mean (SD) concentrations were 9.0 (2.3) μmol/L for Cer, 6.3 (1.9) μmol/L for GlcCer, and 1.7 (0.5) μmol/L for CTH. Plasma concentrations of GlcCer were higher in Gaucher disease patient samples and of CTH in Fabry disease patient samples. Conclusions: HPLC enables quantification of total Cer, GlcCer, and CTH in plasma and is useful for the follow-up of patients on therapy for Gaucher or Fabry disease.

Urinary Lipid Profiling for the Identification of Fabry Hemizygotes and Heterozygotes

Background: Fabry disease is an X-linked lysosomal storage disorder resulting from a deficiency of the lysosomal hydrolase, α-galactosidase, for which enzyme replacement therapy is now available. In this study, we aimed to identify Fabry heterozygotes not only for genetic counseling of families but because it is becoming increasingly obvious that many heterozygous (carrier) females are symptomatic and should be considered for treatment. Methods: We measured 29 individual lipid species, including ceramide, glucosylceramide, lactosylceramide, and ceramide trihexoside, in urine samples from Fabry hemizygotes and heterozygotes and from control individuals by electrospray ionization tandem mass spectrometry. Individual analyte species and analyte ratios were analyzed for their ability to differentiate the control and patient groups. Results: The Fabry hemizygotes had increased concentrations of the substrate for the deficient enzyme, ceramide trihexoside, as well as lactosylceramide and ceramide, along with decreased concentrations of both glucosylceramide and sphingomyelin. Ratios of these analytes improved differentiation between the control and Fabry groups, with the Fabry heterozygotes generally falling between the Fabry hemizygotes and the control group. Conclusions: These lipid profiles hold particular promise for the identification of Fabry individuals, may aid in the prediction of phenotype, and are potentially useful for the monitoring of therapy in patients receiving enzyme replacement.