Molecular and biochemical biomarkers for diagnosis and therapy monitorization of Niemann-Pick type C patients

Abstract

Niemann-Pick type C (NP-C), one of 50 inherited lysosomal storage disorders caused by NPC protein impairment that leads to unesterified cholesterol accumulation in late endosomal/lysosomal compartments. The clinical manifestations of NP-C includes hepatosplenomegaly, neurological and psychiatric symptoms. Current diagnosis for NP-C is based on observation of the accumulated cholesterol in fibroblasts of affected individuals, using an invasive and time expensive test, called Filipin staining. Lately, two metabolites that are markedly increased in NP-C patients are arising as biomarkers for this disease screening: 7-ketocholesterol and cholestane-3β,5α,6β-triol, both oxidized cholesterol products. In this work, we evaluated cholestane-3β,5α,6β-triol and chitotriosidase levels, Filipin staining and molecular analysis for NPC mutation in 76 individuals with NP-C suspicion. Also, we analyzed cholestane-3β,5α,6β-triol levels in 7 patients with previous NP-C diagnosis under treatment with miglustat, in order to verify its value as a tool for therapy monitoring. For cholestane-3β,5α,6β-triol analysis using molecular assay as golden standard we found 88 % of sensibility, 96.08 % of specificity, a positive and negative predictive value calculated in 91.67 % and 94.23 %, respectively. Chitotriosidase levels were increased in patients with positive molecular analysis for NP-C. For Filipin staining, it was found 1 false positive, 7 false negative and 24 inconclusive cases, showing that this assay has important limitations in NP-C diagnosis. Besides, we found a significant decrease in cholestane-3β,5α,6β-triol concentrations in NP-C patients under therapy with miglustat when compared to non-treated patients. These data show that cholestane-3β,5α,6β-triol analysis has a high potential to be an important NP-C screening assay, and also can be used for therapy monitorization with miglustat in NP-C patients.