sphingosine-phosphorylcholine and Niemann-Pick-Disease--Type-C

Niemann-Pick disease type C (NP-C) is a neurovisceral lysosomal cholesterol trafficking and lipid storage disorder caused by mutations in one of the two genes, NPC1 or NPC2. Diagnosis has often been a difficult task, due to the wide range in age of onset of NP-C and clinical presentation of the disease, combined with the complexity of the cell biology (filipin) laboratory testing, even in combination with genetic testing. This has led to substantial delays in diagnosis, largely depending on the access to specialist centres and the level of knowledge about NP-C of the physician in the area. In recent years, advances in mass spectrometry has allowed identification of several sensitive plasma biomarkers elevated in NP-C (e.g. cholestane-3β,5α,6β-triol, lysosphingomyelin isoforms and bile acid metabolites), which, together with the concomitant progress in molecular genetic technology, have greatly impacted the strategy of laboratory testing. Specificity of the biomarkers is currently under investigation and other pathologies are being found to also result in elevations. Molecular genetic testing also has its limitations, notably with unidentified mutations and the classification of new variants. This review is intended to increase awareness on the currently available approaches to laboratory diagnosis of NP-C, to provide an up to date, comprehensive and critical evaluation of the various techniques (cell biology, biochemical biomarkers and molecular genetics), and to briefly discuss ongoing/future developments. The use of current tests in proper combination enables a rapid and correct diagnosis in a large majority of cases. However, even with recent progress, definitive diagnosis remains challenging in some patients, for whom combined genetic/biochemical/cytochemical markers do not provide a clear answer. Expertise and reference laboratories thus remain essential, and further work is still required to fulfill unmet needs.

Topics: Age of Onset; Bile Acids and Salts; Biomarkers; Carrier Proteins; Cholestanes; Genetic Testing; Glycoproteins; Humans; Intracellular Signaling Peptides and Proteins; Membrane Glycoproteins; Niemann-Pick C1 Protein; Niemann-Pick Disease, Type C; Phosphorylcholine; Sphingosine; Vesicular Transport Proteins

Niemann-Pick disease type C (NPC) is an autosomal recessive disorder caused by mutations of NPC1 or NPC2, which encode the proteins that are responsible for intracellular cholesterol trafficking. Loss of this function results in the accumulation of cholesterol-related products, such as oxysterols, sphingolipids, and NPC-related bile acids, which were recently used as biochemical biomarkers for the diagnosis of NPC. Bile acid-408 is a new significant compound we found in Japanese NPC patients, and it likely belongs to the category of bile acids. However, the diagnosis of NPC using a single biomarker is not satisfactory for clinical application because of the high instance of false negatives or positives. Therefore, we proposed an application of NPC diagnosis using a combination of 7-ketocholesterol (7-KC), lysosphingomyelin (lysoSM), bile acid-408 and/or glucosylsphingosine (lysoGL-1).. 7-KC, lysoSM and lysoGL-1 in sera and bile acid-408 in dried blood spots (DBS) were quantified within 17 minutes using tandem mass spectrometry and high-resolution mass spectrometry, respectively. We measured these biomarkers in NPC patients (n = 19), X-linked adrenoleukodystrophy (X-ALD) patients (n = 5), patients with other lysosomal diseases (n = 300), newborns (n = 124) and healthy people (n = 74). Our results showed a promising accuracy (97%) for NPC diagnosis using the combination of 7-KC, lysoSM and bile acid-408. However, contrary to our expectations, lysoGL-1 levels did not present at a significantly greater amount in NPC patients than other patients and negative controls.. The combination of 7-KC, lysoSM and bile acid-408 improves the accuracy of NPC diagnosis and is feasible for mass screening due to its simple sample preparation and measurement. Future research should investigate the chemical structure of bile acid-408 to further facilitate its advantage in diagnosis.

Topics: Bile Acids and Salts; Biomarkers; Chromatography, Liquid; Humans; Infant, Newborn; Ketocholesterols; Niemann-Pick Disease, Type C; Phosphorylcholine; Sphingosine; Tandem Mass Spectrometry

Acid sphingomyelinase deficiency (ASMd, Niemann-Pick disease A/B) and Niemann-Pick type C disease (NPC) share core clinical symptoms. Initial diagnostic discrimination of these two rare lysosomal storage diseases is thus difficult. As sphingomyelin accumulates in ASMd as well as NPC, lysosphingomyelin (sphingosylphosphorylcholine) and its m/z 509 analog were suggested as biomarkers for both diseases. Herein we present results of simultaneous LC-ESI-MS/MS measurements of lysosphingomyelin and lysosphingomyelin 509 in plasma and dried blood spots (DBS) collected from ASMd and NPC patients and suggest that the plasma but not DBS levels of the two analytes allow differential biochemical screening of ASMd and NPC.

Topics: Biomarkers; Case-Control Studies; Chromatography, Liquid; Dried Blood Spot Testing; Humans; Niemann-Pick Disease, Type A; Niemann-Pick Disease, Type B; Niemann-Pick Disease, Type C; Phosphorylcholine; Spectrometry, Mass, Electrospray Ionization; Sphingosine; Tandem Mass Spectrometry

Niemann-Pick disease type C (NP-C) is a devastating, neurovisceral lysosomal storage disorder which is characterised by variable manifestation of visceral signs, progressive neuropsychiatric deterioration and premature death, caused by mutations in the NPC1 and NPC2 genes. Due to the complexity of diagnosis and the availability of an approved therapy in the EU, improved detection of NP-C may have a huge impact on future disease management. At the cellular level dysfunction or deficiency of either the NPC1 or NPC2 protein leads to a complex intracellular endosomal/lysosomal trafficking defect, and organ specific patterns of sphingolipid accumulation. Lysosphingolipids have been shown to be excellent biomarkers of sphingolipidosis in several enzyme deficient lysosomal storage disorders. Additionally, in a recent study the lysosphingolipids, lysosphingomyelin (SPC) and glucosylsphingosine (GlcSph), appeared to be elevated in the plasma of three adult NP-C patients. In order to investigate the clinical utility of SPC and GlcSph as diagnostic markers, an in-depth fit for purpose biomarker assay validation for measurement of these biomarkers in plasma by liquid chromatography-tandem mass spectrometry was performed. Plasma SPC and GlcSph are stable and can be measured accurately, precisely and reproducibly. In a retrospective analysis of 57 NP-C patients and 70 control subjects, median plasma SPC and GlcSph were significantly elevated in NP-C by 2.8-fold and 1.4-fold respectively. For miglustat-naïve NP-C patients, aged 2-50 years, the area under the ROC curve was 0.999 for SPC and 0.776 for GlcSph. Plasma GlcSph did not correlate with SPC levels in NP-C patients. The data indicate excellent potential for the use of lysosphingomyelin in NP-C diagnosis, where it could be used to identify NP-C patients for confirmatory genetic testing.

Topics: Adolescent; Adult; Aged; Biomarkers; Blood Specimen Collection; Case-Control Studies; Edetic Acid; Female; Heparin; Humans; Male; Niemann-Pick Disease, Type C; Phosphorylcholine; Psychosine; Reproducibility of Results; Retrospective Studies; Sphingosine; Tandem Mass Spectrometry; Young Adult