Niemann-Pick type C1 (NPC1) disease is a rare progressive neurodegenerative disorder characterized by endolysosomal cholesterol accumulation. Previous studies implicating oxidative stress in NPC1 disease pathogenesis raised the possibility that non-enzymatic formation of cholesterol oxidation products could serve as disease biomarkers. We measured these metabolites in the plasma and tissues of the Npc1−/− mouse model and found several cholesterol oxidation products that were elevated in Npc1−/− mice, were detectable prior to the onset of symptoms, and were associated with disease progression. Non-enzymatically formed cholesterol oxidation products were similarly increased in the plasma of all human NPC1 subjects studied and delineated an oxysterol profile specific for NPC1 disease. This oxysterol profile also correlated with age of disease onset and disease severity. We further show that the plasma oxysterol markers decreased in response to an established therapeutic intervention in the NPC1 feline model. These cholesterol oxidation products are robust blood-based biochemical markers for NPC1 disease that may prove transformative for diagnosis and treatment of this disorder, and as outcome measures to monitor response to therapy.

Niemann-Pick Disease, type C is a neurodegenerative, lysosomal storage disorder with a broad clinical spectrum and a variable age of onset. The absence of a universally accepted clinical outcome measure is an impediment to the design of a therapeutic trial for NPC. Thus, we developed a clinical severity scale to characterize and quantify disease progression. Clinical signs and symptoms in nine major (ambulation, cognition, eye movement, fine motor, hearing, memory, seizures, speech, swallowing,) and eight minor (auditory brainstem response, behavior, gelastic cataplexy, hyperreflexia, incontinence, narcolepsy, psychiatric, respiratory problems) domains were scored. Data were collected from 18 current NPC patients and were extracted from records of 19 patients. Both patient cohorts showed a linear increase in severity scores over time. Cross-sectional evaluation of current patients showed a linear increase in the severity score. Longitudinal chart review of historical data demonstrated that although age of onset varied significantly, the rate of progression appeared linear, independent of age of onset, and similar in all patients. Combining the data from both cohorts, disease progression could be modeled by the following equation: Ŝ t0+x = Ŝ t0 + 1.87x; where Ŝ t0 is the initial score and Ŝ t0+x is the predicted future score after x years. Our observation that disease progression is similar across patients and independent of age of onset is consistent with a biphasic pathological model for NPC. This scale may prove useful in the characterization of potential biomarkers, and as an outcome measure to monitor disease progression in NPC patients.

Supplementary key words cholesterol • diagnostic tools • liquid chromatography/tandem mass spectrometry • Niemann-Pick disease • oxysterols • neurodegenerationNiemann-Pick type C (NPC) disease is a rare, primarily pediatric disorder characterized by accumulation of cholesterol and other lipids in the viscera and central nervous system. Approximately 95% of NPC cases are caused by mutations of the NPC1 gene, whereas the remaining 5% are caused by mutations in the NPC2 gene ( 1, 2 ). Affected individuals typically present in early childhood with ataxia and progressive impairment of motor and intellectual function and usually die in adolescence. There are currently no FDA-approved therapies for this progressively fatal neurodegenerative disorder. However, a recent controlled study and a series of case reports suggests effi cacy for miglustat ( 3 ), an inhibitor of glycosphingolipid biosynthesis that is now licensed for use as a disease modifying therapy in multiple countries, including the European Union, Russia, Brazil, Australia, Canada, and Taiwan.Abstract Niemann-Pick type C1 (NPC1) disease is a rare, progressively fatal neurodegenerative disease for which there are no FDA-approved therapies. A major barrier to developing new therapies for this disorder has been the lack of a sensitive and noninvasive diagnostic test. Recently, we demonstrated that two cholesterol oxidation products, specifi cally cholestane-3 ␤ ,5 ␣ ,6 ␤ -triol (3 ␤ ,5 ␣ ,6 ␤ -triol) and 7-ketocholesterol (7-KC), were markedly increased in the plasma of human NPC1 subjects, suggesting a role for these oxysterols in diagnosis of NPC1 disease and evaluation of therapeutics in clinical trials. In the present study, we describe the development of a sensitive and specifi c LC-MS/ MS method for quantifying 3 ␤ ,5 ␣ ,6 ␤ -triol and 7-KC human plasma after derivatization with N,N-dimethylglycine. We show that dimethylglycine derivatization successfully enhanced the ionization and fragmentation of 3 ␤ ,5 ␣ ,6 ␤ -triol and 7-KC for mass spectrometric detection of the oxysterol species in human plasma. The oxysterol dimethylglycinates were resolved with high sensitivity and selectivity, and enabled accurate quantifi cation of 3 ␤ ,5 ␣ ,6 ␤ -triol and 7-KC concentrations in human plasma. The LC-MS/MS assay was able to discriminate with high sensitivity and specifi city between control and NPC1 subjects, and offers for the fi rst time a noninvasive, rapid, and highly sensitive method for diagnosis of NPC1