Imaging of tau deposits in adults with Niemann-Pick type C disease: a case-control study

Plasma phosphorylated-tau217 is increased in Niemann-Pick disease type C

Niemann-Pick disease type C and Alzheimer's disease are distinct neurodegenerative disorders that share the presence of neurofibrillary tangle pathology. In this multicentre study, we measured plasma phosphorylated-tau217 in controls (n = 60), Niemann-Pick disease type C (n = 71) and Alzheimer's disease (n = 30 positive for amyloid and negative for tau in CSF [A+T-] and n = 30 positive for both [A+T+]). Annual Severity Increment Score and Lysotracker measurements were evaluated in the Niemann-Pick disease type C group to estimate the rate of progression and lysosomal enlargement, respectively. In the cross-sectional analysis, plasma phosphorylated-tau217 was increased in Niemann-Pick disease type C compared with controls (2.52 ± 1.93 versus 1.02 ± 0.34 pg/mL, respectively, P < 0.001) and inversely correlated with age at disease onset (R = -0.54, P < 0.001). In the longitudinal analysis, plasma phosphorylated-tau217 was associated with disease progression determined by Annual Severity Increment Score (R = 0.48, P < 0.001) and lysosomal enlargement (R = 0.26, P = 0.004). We found no differences between A+T- Alzheimer's disease and Niemann-Pick disease type C (2.67 ± 1.18 versus 2.52 ± 1. 93 pg/mL, P = 0.31); however, A+T+ Alzheimer's disease had significantly higher levels than Niemann-Pick disease type C (3.26 ± 1.36 versus 2.52 ± 1.93 pg/mL, P = 0.001). Our findings suggest that plasma p-tau217 can increase in brain disorders with isolated tau pathology. Plasma p-tau217 associations with disease progression and severity make it a potential marker in Niemann-Pick disease type C.

Evaluation of the landscape of pharmacodynamic biomarkers in Niemann-Pick Disease Type C (NPC)

Niemann-Pick disease type C (NPC) is an autosomal recessive, progressive disorder resulting from variants in NPC1 or NPC2 that leads to the accumulation of cholesterol and other lipids in late endosomes and lysosomes. The clinical manifestations of the disease vary by age of onset, and severity is often characterized by neurological involvement. To date, no disease-modifying therapy has been approved by the United States Food and Drug Administration (FDA) and treatment is typically supportive. The lack of robust biomarkers contributes to challenges associated with disease monitoring and quantifying treatment response. In recent years, advancements in detection methods have facilitated the identification of biomarkers in plasma and cerebral spinal fluid from patients with NPC, namely calbindin D, neurofilament light chain, 24(S)hydroxycholesterol, cholestane-triol, trihydroxycholanic acid glycinate, amyloid-β, total and phosphorylated tau, and N-palmitoyl-O-phosphocholine-serine. These biomarkers have been used to support several clinical trials as pharmacodynamic endpoints. Despite the significant advancements in laboratory techniques, translation of those advancements has lagged, and it remains unclear which biomarkers correlate with disease severity and progression, or which biomarkers could inform treatment response. In this review, we assess the landscape of biomarkers currently proposed to guide disease monitoring or indicate treatment response in patients with NPC.

Case report: Clinical, imaging, and genetic characteristics of type B niemann pick disease combined with segawa syndrome diagnosed via dual gene sequencing

Niemann Pick disease B (NPB) often presents with hepatosplenomegaly and lung pathological changes, but it usually does not present with central nervous system symptoms. This report presents the unique case of a 21-year-old woman with a 10-year history of hard skin and hepatosplenomegaly. Genetic sequencing revealed NPB and also suggested Segawa syndrome. Although symptomatic supportive treatments were administered in an attempt to improve muscle tone and treat the skin sclerosis, their efficacy was not satisfactory, and the patient refused further treatment. This case provides several noteworthy findings. First, although NPB and Segawa syndrome are rare, both are autosomal recessive inherited diseases that share common clinical symptoms and imaging manifestations. Second, when NPB and Segawa syndrome are highly suspected, screening for tyrosine hydroxylase (TH) and sphingomyelin phosphodiesterase-1 (SMPD1) gene mutations is critical to determine an accurate diagnosis. Finally, early diagnosis and comprehensive therapies are crucial for improving the prognosis of patients with NPB and Segawa syndrome.

Upstream lipid and metabolic systems are potential causes of Alzheimer's disease, Parkinson's disease and dementias

Brain health requires circuits, cells and molecular pathways to adapt when challenged and to promptly reset once the challenge has resolved. Neurodegeneration occurs when adaptability becomes confined, causing challenges to overwhelm neural circuitry. Studies of rare and common neurodegenerative diseases suggest that the accumulation of lipids can compromise circuit adaptability. Using microglia as an example, we review data that suggest increased lipid concentrations cause dysfunctional inflammatory responses to immune challenges, leading to Alzheimer's disease, Parkinson's disease and dementia. We highlight current approaches to treat lipid metabolic and clearance pathways and identify knowledge gaps towards restoring adaptive homeostasis in individuals who are at-risk of losing cognition.

Investigation of Brain Iron in Niemann-Pick Type C: A 7T Quantitative Susceptibility Mapping Study

BACKGROUND AND PURPOSE

While brain iron dysregulation has been observed in several neurodegenerative disorders, its association with the progressive neurodegeneration in Niemann-Pick type C is unknown. Systemic iron abnormalities have been reported in patients with Niemann-Pick type C and in animal models of Niemann-Pick type C. In this study, we examined brain iron using quantitative susceptibility mapping MR imaging in individuals with Niemann-Pick type C compared with healthy controls.

MATERIALS AND METHODS

A cohort of 10 patients with adolescent- and adult-onset Niemann-Pick type C and 14 age- and sex-matched healthy controls underwent 7T brain MR imaging with T1 and quantitative susceptibility mapping acquisitions. A probing whole-brain voxelwise comparison of quantitative susceptibility mapping between groups was conducted. Mean quantitative susceptibility mapping in the ROIs (thalamus, hippocampus, putamen, caudate nucleus, and globus pallidus) was further compared. The correlations between regional volume, quantitative susceptibility mapping values, and clinical features, which included disease severity on the Iturriaga scale, cognitive function, and the Social and Occupational Functioning Assessment Scale, were explored as secondary analyses.

RESULTS

We observed lower volume in the thalamus and voxel clusters of higher quantitative susceptibility mapping in the pulvinar nuclei bilaterally in patients with Niemann-Pick type C compared with the control group. In patients with Niemann-Pick type C, higher quantitative susceptibility mapping in the pulvinar nucleus clusters correlated with lower volume of the thalamus on both sides. Moreover, higher quantitative susceptibility mapping in the right pulvinar cluster was associated with greater disease severity.

CONCLUSIONS

Our findings suggest iron deposition in the pulvinar nucleus in Niemann-Pick type C disease, which is associated with thalamic atrophy and disease severity. This preliminary evidence supports the link between iron and neurodegeneration in Niemann-Pick type C, in line with existing literature on other neurodegenerative disorders.

The experience of living with Niemann-Pick type C: a patient and caregiver perspective

BACKGROUND

Niemann-Pick disease type C (NPC) is a rare inherited lysosomal storage disease typified by accumulation of cholesterol and other lipids in late endosomes/lysosomes, thereby resulting in a spectrum of neurological, psychiatric, and systemic symptoms (notably liver disease). Though it is well-known that NPC exacts a physical and emotional toll on both patients and caregivers, the burden of NPC can vary between patients, while the challenges of living with NPC can evolve over time (i.e., from time of diagnosis to the present day). To further grasp patient and caregiver perceptions and experiences with NPC, we carried out focus group discussions with pediatric and adult individuals with NPC (N = 19), with partial or full representation of the patient by their caregiver. Furthermore, we utilized our NPC focus group discussion to provide guidance on study design parameters and feasibility of prospective investigations aiming to characterize the central manifestations of NPC using neuroimaging, specifically, magnetic resonance imaging (MRI) methodology.

RESULTS

Focus group discussions revealed that neurological signs, including declining cognition, memory loss, and psychiatric symptoms, as well as increasingly impaired mobility and motor function, are among the most pressing past and current concerns for patients and caregivers. Moreover, several participants also expressed concern over a loss of independence, social exclusion, and uncertainty for what the future holds. Caregivers described the challenges that participation in research poses, which included logistical difficulties mainly due to traveling with medical equipment and the need for sedation in a minority of patients when undergoing MRI.

CONCLUSIONS

The findings derived from focus group discussions highlight the outstanding challenges that NPC patients and their caregivers face daily, while also providing direction on the potential scope and feasibility of future studies focusing on the central phenotypes of NPC.

The Cerebellum in Niemann-Pick C1 Disease: Mouse Versus Man

Selective neuronal vulnerability is common to most degenerative disorders, including Niemann-Pick C (NPC), a rare genetic disease with altered intracellular trafficking of cholesterol. Purkinje cell dysfunction and loss are responsible for cerebellar ataxia, which is among the prevailing neurological signs of the NPC disease. In this review, we focus on some questions that are still unresolved. First, we frame the cerebellar vulnerability in the context of the extended postnatal time length by which the development of this structure is completed in mammals. In line with this thought, the much later development of cerebellar symptoms in humans is due to the later development and/or maturation of the cerebellum. Hence, the occurrence of developmental events under a protracted condition of defective intracellular cholesterol mobilization hits the functional maturation of the various cell types generating the ground of increased vulnerability. This is particularly consistent with the high cholesterol demand required for cell proliferation, migration, differentiation, and synapse formation/remodeling. Other major questions we address are why the progression of Purkinje cells loss is always from the anterior to the posterior lobes and why cerebellar defects persist in the mouse model even when genetic manipulations can lead to nearly normal survival.

Regulation of cholesterol homeostasis in health and diseases: from mechanisms to targeted therapeutics

Disturbed cholesterol homeostasis plays critical roles in the development of multiple diseases, such as cardiovascular diseases (CVD), neurodegenerative diseases and cancers, particularly the CVD in which the accumulation of lipids (mainly the cholesteryl esters) within macrophage/foam cells underneath the endothelial layer drives the formation of atherosclerotic lesions eventually. More and more studies have shown that lowering cholesterol level, especially low-density lipoprotein cholesterol level, protects cardiovascular system and prevents cardiovascular events effectively. Maintaining cholesterol homeostasis is determined by cholesterol biosynthesis, uptake, efflux, transport, storage, utilization, and/or excretion. All the processes should be precisely controlled by the multiple regulatory pathways. Based on the regulation of cholesterol homeostasis, many interventions have been developed to lower cholesterol by inhibiting cholesterol biosynthesis and uptake or enhancing cholesterol utilization and excretion. Herein, we summarize the historical review and research events, the current understandings of the molecular pathways playing key roles in regulating cholesterol homeostasis, and the cholesterol-lowering interventions in clinics or in preclinical studies as well as new cholesterol-lowering targets and their clinical advances. More importantly, we review and discuss the benefits of those interventions for the treatment of multiple diseases including atherosclerotic cardiovascular diseases, obesity, diabetes, nonalcoholic fatty liver disease, cancer, neurodegenerative diseases, osteoporosis and virus infection.

Differential involvement of hippocampal subfields in Niemann-Pick type C disease: a case-control study

Hippocampal brain regions are strongly implicated in Niemann Pick type C disease (NPC), but little is known regarding distinct subregions of the hippocampal complex and whether these are equally or differentially affected. To address this gap, we compared volumes of five hippocampal subfields between NPC and healthy individuals using MRI. To this end, 9 adult-onset NPC cases and 9 age- and gender-matched controls underwent a 3 T T1-weighted MRI scan. Gray matter volumes of the cornu ammonis (CA1, CA2 and CA3), dentate gyrus (DG), subiculum, entorhinal cortex and hippocampal-amygdalar transition area were calculated by integrating MRI-based image intensities with microscopically defined cytoarchitectonic probabilities. Compared to healthy controls, NPC patients showed smaller volumes of the CA1-3 and DG regions bilaterally, with the greatest difference localized to the left DG (Cohen's d = 1.993, p = 0.008). No significant associations were shown between hippocampal subfield volumes and key clinical features of NPC, including disease duration, symptom severity and psychosis. The pattern of hippocampal subregional atrophy in NPC differs from those seen in other dementias, which may indicate unique cytoarchitectural vulnerabilities in this earlier-onset disorder. Future MRI studies of hippocampal subfields may clarify its potential as a biomarker of neurodegeneration in NPC.

Neuropsychological assessment in Niemann-Pick disease type C: a systematic review

BACKGROUND

The neuropsychological profile of Niemann-Pick type C (NP-C) patients is characterized by an early deterioration in executive functions and attention. There are few studies on cognitive impairment and on neuropsychological assessment of NP-C disease. The purpose of this review is to analyze the studies on a psychological assessment for NP-C patients.

METHOD

This review aims to identify a neuropsychological assessment to evaluate cognitive domains and neuropsychological changes in these patients. There were a total of 73 articles. The search terms were identified as titles and abstracts. All articles were evaluated by title, abstract, and text.

RESULTS

Only four of the 73 articles were included because they met the criteria of our review. Furthermore, in these studies, possible diagnostic protocols are proposed on NP-C subjects.

DISCUSSION AND CONCLUSION

The cognitive impairment in NP-C has a negative impact on daily functioning and quality of life. Early diagnosis could identify cognitive deficits and promote cognitive interventions to improve the neuropsychological profile. The management of NP-C disease should be based on a multidisciplinary approach, to treating symptoms, preserving neurological functions, and guaranteeing the best possible quality of life. Early identification of neurological and psychological symptoms of the disease is necessary in order to decrease the progression of neurological disease and improve patient care and treatment outcomes. Furthermore, research should focus more on cognitive aspects, not only in the diagnostic process but also in the rehabilitation process.

Brain hypometabolic changes in 14 adolescent-adult patients with Niemann-Pick disease type C assessed by 18F-fluorodeoxyglucose positron emission tomography

OBJECTIVE

Niemann Pick disease type C (NPC) is a rare progressive neurovisceral lysosomal disorder caused by autosomal recessive mutations in the NPC1 or NPC2 genes. 18F-fluorodeoxyglucose (FDG) is a positron-emitting glucose analogue for non-invasive imaging of brain metabolism. FDG PET is commonly used for dementia imaging but its specific application to NPC is rarely described.

METHODS

This is a retrospective study of all baseline brain FDG PET performed for NPC patients. Images were assessed using a normal database statistical comparison of metabolic changes expressed in standard deviations and three-dimensional Stereotactic Surface Projection maps. Typical hypometabolic patterns in NPC were identified. We further investigated any correlation between the degree of regional brain hypometabolism and the Iturriaga clinical severity scale.

RESULTS

Brain FDG PET images of 14 adolescent-adult NPC patients were analysed, with mean age of 35 years. We found significant frontal lobe hypometabolism in 12 patients (86%), thalamic hypometabolism in eight patients (57%) and variable parietal lobe hypometabolism in 13 patients (93%). Hypometabolic changes were usually bilateral and symmetric. Ten out of 13 ataxic patients showed cerebellar or thalamic hypometabolism (sensitivity 77%, specificity 100%). Linear regression analysis showed frontal lobe hypometabolism to have the best correlation with the Iturriaga clinical scale (R² = 0.439; p = 0.01).

CONCLUSIONS

We found bilateral symmetric hypometabolism of the frontal lobes, thalami and parietal lobes (especially posterior cingulate gyrus) to be typical of adolescent-adult NPC. Ataxia was commonly associated with cerebellar or thalamic hypometabolism. Frontal lobe hypometabolism showed the best inverse correlation with clinical severity.

Role of the endolysosomal pathway and exosome release in tau propagation

The progressive deposition of misfolded and aggregated forms of Tau protein in the brain is a pathological hallmark of tauopathies, such as Alzheimer's disease (AD) and frontotemporal degeneration (FTD). The misfolded Tau can be released into the extracellular space and internalized by neighboring cells, acting as seeds to trigger the robust conversion of soluble Tau into insoluble filamentous aggregates in a prion-like manner, ultimately contributing to the progression of the disease. However, molecular mechanisms accountable for the propagation of Tau pathology are poorly defined. We reviewed the Tau processing imbalance in endosomal, lysosomal, and exosomal pathways in AD. Increased exosome release counteracts the endosomal-lysosomal dysfunction of Tau processing but increases the number of aggregates and the propagation of Tau. This review summarizes our current understanding of the underlying tauopathy mechanisms with an emphasis on the emerging role of the endosomal-lysosomal-exosome pathways in this process. The components CHMP6, TSG101, and other components of the ESCRT complex, as well as Rab GTPase such as Rab35 and Rab7A, regulate vesicle cargoes routing from endosome to lysosome and affect Tau traffic, degradation, or secretion. Thus, the significant molecular pathways that should be potential therapeutic targets for treating tauopathies are determined.

Tauopathy and Movement Disorders-Unveiling the Chameleons and Mimics

The spectrum of tauopathy encompasses heterogenous group of neurodegenerative disorders characterized by neural or glial deposition of pathological protein tau. Clinically they can present as cognitive syndromes, movement disorders, motor neuron disease, or mixed. The heterogeneity in clinical presentation, genetic background, and underlying pathology make it difficult to classify and clinically approach tauopathy. In the literature, tauopathies are thus mostly highlighted from pathological perspective. From clinical standpoint, cognitive syndromes are often been focussed while reviewing tauopathies. However, the spectrum of tauopathy has also evolved significantly in the domain of movement disorders and has transgressed beyond the domain of primary tauopathies. Secondary tauopathies from neuroinflammation or autoimmune insults and some other "novel" tauopathies are increasingly being reported in the current literature, while some of them are geographically isolated. Because of the overlapping clinical phenotypes, it often becomes difficult for the clinician to diagnose them clinically and have to wait for the pathological confirmation by autopsy. However, each of these tauopathies has some clinical and radiological signatures those can help in clinical diagnosis and targeted genetic testing. In this review, we have exposed the heterogeneity of tauopathy from a movement disorder perspective and have provided a clinical approach to diagnose them ante mortem before confirmatory autopsy. Additionally, phenotypic variability of these disorders (chameleons) and the look-alikes (mimics) have been discussed with potential clinical pointers for each of them. The review provides a framework within which new and as yet undiscovered entities can be classified in the future.

Haploinsufficiency of tau decreases survival of the mouse model of Niemann-Pick disease type C1 but does not alter tau phosphorylation

Niemann-Pick C1 (NPC1) mouse models show neurofibrillary tangles as do human patients. A previous study in NPC1/tau double-null mutant mice showed that tau knockout nulls and heterozygotes unexpectedly had decreased survival when compared with NPC1 single mutants (Pacheco et al., Hum Molec Genetics 18:956-965, 2009). This was done in a null model of NPC1 (Npc1^-/-). We have extended these results to a hypomorphic model (Npc1^nmf164) and additionally studied tau phosphorylation, which has not been previously done in a tau heterozygote. As before, NPC1/tau double-mutant mice had shortened survival when compared with the NPC1 single mutant. Tau dosage was not affected by the Npc1 mutation. The increased phosphorylation of tau-ser396 previously noted in NPC1 mouse models was also present, but unaffected by the tau knockout, indicating that changes in tau phosphorylation are not the cause of decreased survival in NPC1/tau double mutants. Thus, the reason for shortened survival of NPC1 mouse models with concomitant tau haploinsufficiency is uncertain.

Single Cell Transcriptome Analysis of Niemann-Pick Disease, Type C1 Cerebella

Niemann-Pick disease, type C1 (NPC1) is a lysosomal disease characterized by endolysosomal storage of unesterified cholesterol and decreased cellular cholesterol bioavailability. A cardinal symptom of NPC1 is cerebellar ataxia due to Purkinje neuron loss. To gain an understanding of the cerebellar neuropathology we obtained single cell transcriptome data from control (Npc1^+/+) and both three-week-old presymptomatic and seven-week-old symptomatic mutant (Npc1^-/-) mice. In seven-week-old Npc1^-/- mice, differential expression data was obtained for neuronal, glial, vascular, and myeloid cells. As anticipated, we observed microglial activation and increased expression of innate immunity genes. We also observed increased expression of innate immunity genes by other cerebellar cell types, including Purkinje neurons. Whereas neuroinflammation mediated by microglia may have both neuroprotective and neurotoxic components, the contribution of increased expression of these genes by non-immune cells to NPC1 pathology is not known. It is possible that dysregulated expression of innate immunity genes by non-immune cells is neurotoxic. We did not anticipate a general lack of transcriptomic changes in cells other than microglia from presymptomatic three-week-old Npc1^-/- mice. This observation suggests that microglia activation precedes neuronal dysfunction. The data presented in this paper will be useful for generating testable hypotheses related to disease progression and Purkinje neurons loss as well as providing insight into potential novel therapeutic interventions.

Characterization of Dysphagia and Longitudinal Changes in Swallowing Function in Adults with Niemann-Pick Disease Type C Treated with Miglustat

Niemann-Pick disease type C (NPC) is a rare, autosomal recessive neurodegenerative disease, characterized by progressive psychiatric and neurological deficits. Neurological symptoms include cognitive decline and dysphagia. Aspiration pneumonia secondary to dysphagia is a leading cause of death in NPC. Miglustat is currently the only approved disease-specific treatment shown to be effective in stabilizing neurological symptoms. Miglustat has previously been reported to halt or improve early dysphagia and cognitive symptoms. Here we examine the characteristics of dysphagia, the relationship between dysphagia and the presence of cognitive impairment, and longitudinal changes in swallowing function during miglustat treatment in adult-and-adolescent-onset NPC. Retrospective analysis of videofluoroscopic swallow studies (VFSS) was completed for ten adults with NPC (mean age 28.44 years ± 9.34 years). Participants were recruited through the Royal Melbourne Hospital in Australia between 2008 and 2015. The Bethlehem Swallowing Scale and the Penetration-Aspiration Scale were used to quantify VFSS data. Dysphagia was present in 90% of participants at baseline with reduced lingual function and a delayed swallowing reflex as the most common symptoms. Swallow impairment appeared to stabilize during miglustat therapy for periods up to 66 months, with no significant changes in scores (p > 0.05). Data were in accordance with the literature and support the use of miglustat as an efficacious treatment for reducing swallowing impairment and stabilizing cognitive function. Findings provide detailed information on the impairments experienced by patients, give context to events leading to aspiration in NPC and, importantly, inform how management of dysphagia can complement pharmaceutical treatment.

In vivo evidence of cortical amyloid deposition in the adult form of Niemann Pick type C

Background

Niemann Pick disease type C (NPC) is a lysosomal lipid storage disorder presenting visceral and neurological impairment with cognitive decline. Neurodegeneration in NPC is associated to deposition of amyloid-β and abnormal tau aggregations likewise Alzheimer disease (AD). Dementia is also related to intracortical circuiting abnormalities that can be detected by neurophysiological procedures both in NPC and in AD. Aim of this study is to find the in vivo evidence of amyloid deposition in NPC patients with cognitive impairment and to investigate the pathophysiology of dementia according to similarities with AD.

Methods

Two sisters affected by NPC and cognitive decline underwent neuropsychological tests, PET scans with ¹⁸F- Florbetaben and neurophysiological protocols to assess cortex excitability by means of transcranial magnetic stimulation (TMS), such as short-latency afferent inhibition (SAI), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF).

Results

Both patients presented a multidomain cognitive impairment. ¹⁸F- Florbetaben uptake was detected in brain frontal areas, while SAI and SICI were abnormal in both patients.

Discussion

Cognitive impairment in NPC is associated to cortical amyloid deposition as revealed by ¹⁸F- Florbetaben PET scan. Amyloid imaging data, together with specific abnormalities found at TMS studies, suggest similar mechanisms underlying NPC and AD dementia.