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

Hypometabolism and atrophy patterns associated with Niemann-Pick type C

BACKGROUND

Niemann-Pick disease type C (NP-C) is a rare genetic lysosomal lipid storage disorder characterized by progressive neurological impairment. Early diagnosis is critical for initiating treatment with miglustat, which can decelerate disease progression. In this study, we evaluated a cohort of 22 NP-C patients who underwent MRI, [18F]FDG PET, and clinical assessment at baseline. We performed a cross-sectional and longitudinal imaging study evaluating the role of [18F]FDG PET as an adjunct diagnostic tool for NP-C alongside MRI, the current neuroimaging standard.

RESULTS

Group-level MRI analysis identified significant cerebellar and thalamic atrophy (d = 1.56, p < 0.0001 and d = 1.09, p < 0.001, respectively), with less pronounced involvement of the frontal lobe and hippocampus, which aligned with existing neuropathological understanding and guidelines. Conversely, [18F]FDG PET imaging revealed extensive hypometabolism in the cerebellum, thalamus, and cingulate cortex (d = 1.42, p < 0.0001), and moderate hypometabolism in broad frontotemporal areas. [18F]FDG PET provided higher effect sizes across all brain regions, including regions without apparent atrophy, which suggests that it may be more sensitive than MRI for detecting NP-C neurodegenerative changes. Single-subject visual assessment of individual PET images further validated the clinical utility of [18F]FDG PET, with significant hypometabolism observed in the cerebellum, thalamus and anterior and posterior cingulate reported by physicians in 17/22 patients. Both hypometabolism and atrophy in the cerebellum were associated with ataxia, (more strongly indicated by [18F]FDG PET, p < 0.0001 vs. MRI, p = 0.07). Medial temporal lobe atrophy was associated with cognitive impairment (p < 0.05), and frontal hypometabolism was slightly related to behavioural impairment (p < 0.07). Longitudinal [18F]FDG PET analysis revealed progressive subcortical, cortical and cerebellar hypometabolism, which was most pronounced in the cerebellum (-12% per year, p < 0.001). Patients treated with miglustat showed a trend towards attenuated cerebellar hypometabolism progression compared to untreated patients (p = 0.10).

CONCLUSIONS

Our findings delineate a discernible hypometabolism pattern specific to NP-C that distinguishes it from other neurodegenerative conditions, thus suggesting that [18F]FDG PET might be a promising tool for NP-C diagnosis and to study disease progression.

TRIAL REGISTRATION

XUNTA 2015/140. Registered 21 April 2015.

Instationary metabolic flux analysis reveals that NPC1 inhibition increases glycolysis and decreases mitochondrial metabolism in brain microvascular endothelial cells

Niemann Pick Disease Type C (NP-C), a rare neurogenetic disease with no known cure, is caused by mutations in the cholesterol trafficking protein NPC1. Brain microvascular endothelial cells (BMEC) are thought to play a critical role in the pathogenesis of several neurodegenerative diseases; however, little is known about how these cells are altered in NP-C. In this study, we investigated how NPC1 inhibition perturbs BMEC metabolism in human induced pluripotent stem cell-derived BMEC (hiBMEC). We incorporated extracellular metabolite and isotope labeling data into an instationary metabolic flux analysis (INST-MFA) model to estimate intracellular metabolic fluxes. We found that NPC1 inhibition significantly increased glycolysis and pentose phosphate pathway flux while decreasing mitochondrial metabolism. These changes may have been driven by gene expression changes due to increased cholesterol biosynthesis, in addition to mitochondrial cholesterol accumulation. We corroborated these findings in primary BMEC, an alternative in vitro human brain endothelial model. Finally, we found that co-treatment with hydroxypropyl-β cyclodextrin (HPβCD) partially restored metabolic phenotype in U18666A-treated BMECs, suggesting that this drug may have therapeutic effects on the brain endothelium in NP-C. Together, our data highlight the importance of NPC1 in BMEC metabolism and implicate brain endothelial dysfunction in NP-C pathogenesis.

The Genetic Basis, Lung Involvement, and Therapeutic Options in Niemann-Pick Disease: A Comprehensive Review

Niemann-Pick Disease (NPD) is a rare autosomal recessive disease belonging to lysosomal storage disorders. Three types of NPD have been described: NPD type A, B, and C. NPD type A and B are caused by mutations in the gene SMPD1 coding for sphingomyelin phosphodiesterase 1, with a consequent lack of acid sphingomyelinase activity. These diseases have been thus classified as acid sphingomyelinase deficiencies (ASMDs). NPD type C is a neurologic disorder due to mutations in the genes NPC1 or NPC2, causing a defect of cholesterol trafficking and esterification. Although all three types of NPD can manifest with pulmonary involvement, lung disease occurs more frequently in NPD type B, typically with interstitial lung disease, recurrent pulmonary infections, and respiratory failure. In this sense, bronchoscopy with broncho-alveolar lavage or biopsy together with high-resolution computed tomography are fundamental diagnostic tools. Although several efforts have been made to find an effective therapy for NPD, to date, only limited therapeutic options are available. Enzyme replacement therapy with Olipudase α is the first and only approved disease-modifying therapy for patients with ASMD. A lung transplant and hematopoietic stem cell transplantation are also described for ASMD in the literature. The only approved disease-modifying therapy in NPD type C is miglustat, a substrate-reduction treatment. The aim of this review was to delineate a state of the art on the genetic basis and lung involvement in NPD, focusing on clinical manifestations, radiologic and histopathologic characteristics of the disease, and available therapeutic options, with a gaze on future therapeutic strategies.

[18F]FDG PET in conditions associated with hyperkinetic movement disorders and ataxia: a systematic review

PURPOSE

To give a comprehensive literature overview of alterations in regional cerebral glucose metabolism, measured using [18F]FDG PET, in conditions associated with hyperkinetic movement disorders and ataxia. In addition, correlations between glucose metabolism and clinical variables as well as the effect of treatment on glucose metabolism are discussed.

METHODS

A systematic literature search was performed according to PRISMA guidelines. Studies concerning tremors, tics, dystonia, ataxia, chorea, myoclonus, functional movement disorders, or mixed movement disorders due to autoimmune or metabolic aetiologies were eligible for inclusion. A PubMed search was performed up to November 2021.

RESULTS

Of 1240 studies retrieved in the original search, 104 articles were included. Most articles concerned patients with chorea (n = 27), followed by ataxia (n = 25), dystonia (n = 20), tremor (n = 8), metabolic disease (n = 7), myoclonus (n = 6), tics (n = 6), and autoimmune disorders (n = 5). No papers on functional movement disorders were included. Altered glucose metabolism was detected in various brain regions in all movement disorders, with dystonia-related hypermetabolism of the lentiform nuclei and both hyper- and hypometabolism of the cerebellum; pronounced cerebellar hypometabolism in ataxia; and striatal hypometabolism in chorea (dominated by Huntington disease). Correlations between clinical characteristics and glucose metabolism were often described. [18F]FDG PET-showed normalization of metabolic alterations after treatment in tremors, ataxia, and chorea.

CONCLUSION

In all conditions with hyperkinetic movement disorders, hypo- or hypermetabolism was found in multiple, partly overlapping brain regions, and clinical characteristics often correlated with glucose metabolism. For some movement disorders, [18F]FDG PET metabolic changes reflected the effect of treatment.

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.

Current advancements in therapy for Niemann-Pick disease: progress and pitfalls

INTRODUCTION

Niemann-Pick disease type C (NPC) is a rare, autosomal recessive, lysosomal storage disorder. To combat the progressive neurodegeneration in NPC, disease-modifying treatment needs to be introduced early in the course of the disease. The only approved, disease-modifying treatment is a substrate-reduction treatment, miglustat. Given miglustat's limited efficacy, new compounds are under development, including gene therapy; however, many are still far from clinical use. Moreover, the phenotypic heterogeneity and variable course of the disease can impede the development and approval of new agents.

AREAS COVERED

Here, we offer an expert review of these therapeutic candidates, with a broad scope not only on the main pharmacotherapies, but also on experimental approaches, gene therapies, and symptomatic strategies. The National Institute of Health (NIH) database PubMed has been searched for the combination of the words 'Niemann-Pick type C'+ 'treatment' or 'therapy' or 'trial.' The website clinicaltrials.gov has also been consulted.

EXPERT OPINION

We conclude a combination of treatment strategies should be sought, with a holistic approach, to improve the quality of life of affected individuals and their families.