Thursday, May 5, 2016

Newborn and rapid diagnosis of Niemann-Pick type C

Xuntian Jiang, Rohini Sidhu, Laurel Mydock-McGrane, Fong-Fu Hsu, Douglas F. Covey, David E. Scherrer, Brian Earley, Sarah E. Gale, Nicole Y. Farhat, Forbes D. Porter, Dennis J. Dietzen, Joseph J. Orsini, Elizabeth Berry-Kravis, Xiaokui Zhang, Janice Reunert, Thorsten Marquardt, Heiko Runz, Roberto Giugliani, Jean E. Schaffer,  Daniel S. Ory.  Development of a bile acid–based newborn screen for Niemann-Pick disease type C.  Science Translational Medicine  04 May 2016:Vol. 8, Issue 337, pp. 337ra63 DOI: 10.1126/scitranslmed.aaf2326

Expanding the newborn screen
Niemann-Pick disease type C (NPC) is a fatal neurologic disorder caused by the deficiency of an enzyme involved in cholesterol storage. Although this disease was untreatable in the past, new therapeutics are now in clinical trials, but they are most likely to be effective if treatment is started as early as possible, before neurodegeneration has occurred. Jiang et al. identified three bile acids that are greatly increased in the blood of patients with NPC compared to healthy controls. The authors also demonstrated that one of these bile acids can be reliably measured in dried blood spots using mass spectrometry, suggesting that this bile acid test should be evaluated for potential addition to neonatal screening programs.

Niemann-Pick disease type C (NPC) is a fatal, neurodegenerative, cholesterol storage disorder. With new therapeutics in clinical trials, it is imperative to improve diagnostics and facilitate early intervention. We used metabolomic profiling to identify potential markers and discovered three unknown bile acids that were increased in plasma from NPC but not control subjects. The bile acids most elevated in the NPC subjects were identified as 3β,5α,6β-trihydroxycholanic acid and its glycine conjugate, which were shown to be metabolites of cholestane-3β,5α,6β-triol, an oxysterol elevated in NPC. A high-throughput mass spectrometry–based method was developed and validated to measure the glycine-conjugated bile acid in dried blood spots. Analysis of dried blood spots from 4992 controls, 134 NPC carriers, and 44 NPC subjects provided 100% sensitivity and specificity in the study samples. Quantification of the bile acid in dried blood spots, therefore, provides the basis for a newborn screen for NPC that is ready for piloting in newborn screening programs.
Courtesy of a colleague

Reunert J, Fobker M, Kannenberg F, Du Chesne I, Plate M, Wellhausen J, Rust S, Marquardt T. Rapid Diagnosis of 83 Patients with Niemann Pick Type C Disease and Related Cholesterol Transport Disorders by Cholestantriol Screening.  EBioMedicine. 2015 Dec 22;4:170-5.


Niemann Pick type C (NP-C) is a rare neurodegenerative disorder caused by an impairment of intracellular lipid transport. Due to the heterogeneous clinical phenotype and the lack of a reliable blood test, diagnosis and therapy are often delayed for years. In the cell, accumulating cholesterol leads to increased formation of oxysterols that can be used as a powerful screening parameter for NP-C. In a large scale study, we evaluated the oxysterol cholestane-3β,5α,6β-triol (c-triol) as potential biomarker for a rapid diagnosis of NP-C. Using GC/MS, c-triol has been analyzed in 1902 plasma samples of patients with the suspicion for NP-C. Diagnosis in patients with elevated oxysterols was confirmed by genetic analysis. 71 new NP-C patients (69 NP-C1 and two NP-C2) and 12 Niemann Pick type A/B patients were identified. 24 new mutations in NPC1, one new mutation in NPC2 and three new mutations in the SMPD1 gene were found. Cholestane-3β,5α,6β-triol was elevated in Niemann Pick type C1, type C2, type A/B and in CESD disease. No other study has ever identified so many NP-C patients, proving that c-triol is a rapid and reliable biomarker to detect patients with NP-C disease and related cholesterol transport disorders. It should replace the filipin test as the first-line diagnostic assay.

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