23 research outputs found
Neuraminidases as potential therapeutic targets for Parkinson’s disease
No full textNeuraminidases are a family of enzymes that remove terminal sialic acid residues from glycoconjugates, including glycoproteins and glycosphingolipids (GSLs). They play critical roles in the metabolism of complex gangliosides, the most abundant GSLs in the mammalian brain, which are involved in cellular homeostasis and signalling. Parkinson’s disease (PD) is characterised by progressive motor and cognitive decline, with its aetiology linked to multiple mechanisms, including lysosomal dysfunction and impaired cellular homeostasis. Notably, over 50 genes encoding lysosomal proteins impaired in rare lysosomal storage disorders (LSDs) have now been identified as PD risk factors. Altered GSL metabolism, linked to lysosomal dysfunction, is a hallmark of both LSDs and PD. One neuroprotective GSL, GM1a, shows a significant age-related decrease in the human brain, with a more pronounced reduction in individuals with PD. In contrast, mice exhibit an age-related increase in GM1a levels and elevated activity of neuraminidases that catabolise gangliosides like GM1a, which are abundant in the mammalian brain. Mice also have an inherently higher basal neuraminidase activity than humans, which may contribute to mice being resistant to developing PD-like pathology.
Based on these findings, we hypothesised that neuraminidases are potential therapeutic targets for PD. We have therefore characterised Neu3 and/or Neu4 knockout mice, as these isoenzymes are critical in converting complex gangliosides into GM1a. These neuraminidase-deficient mice exhibited brain GSL profiles similar to those of aged humans and PD patients. These mice accumulated α-Syn and developed progressive motor deficits as they aged, suggesting their potential use as a model for PD. Finally, we have explored a novel therapeutic strategy targeting Neu3 and Neu4, evaluating the potential efficacy of enzyme enhancement in vitro and in vivo
Glycosphingolipid storage leads to the enhanced degradation of the B cell receptor in Sandhoff disease mice.
No full textGlycosphingolipid storage diseases are a group of inherited metabolic diseases in which glycosphingolipids accumulate due to their impaired lysosomal breakdown. Splenic B cells isolated from NPC1, Sandhoff, GM1-gangliosidosis and Fabry disease mouse models showed large (20- to 30-fold) increases in disease specific glycosphingolipids and up to a 4-fold increase in cholesterol. The magnitude of glycosphingolipid storage was in the order NPC1 > Sandhoff approximately GM1 gangliosidosis > Fabry. Except for Fabry disease, glycosphingolipid storage led to an increase in the lysosomal compartment and altered glycosphingolipid trafficking. In order to investigate the consequences of storage on B cell function, the levels of surface expression of B cell IgM receptor and its associated components were quantitated in Sandhoff B cells, since they are all raft-associated on activation. Both the B cell receptor, CD21 and CD19 had decreased cell surface expression. In contrast, CD40 and MHC II, surface receptors that do not associate with lipid rafts, were unchanged. Using a pulse chase biotinylation procedure, surface B cell receptors on a Sandhoff lymphoblast cell line were found to have a significantly decreased half-life. Increased co-localization of fluorescently conjugated cholera toxin and lysosomes was also observed in Sandhoff B cells. Glycosphingolipid storage leads to the enhanced formation of lysosomal lipid rafts, altered endocytic trafficking and increased degradation of the B cell receptor
Glycosphingolipid metabolism and its role in ageing and Parkinson’s disease
No full textIt is well established that lysosomal glucocerebrosidase gene (GBA) variants are a risk factor for Parkinson’s disease (PD), with increasing evidence suggesting a loss of function mechanism. One question raised by this genetic association is whether variants of genes involved in other aspects of sphingolipid metabolism are also associated with PD. Recent studies in sporadic PD have identified variants in multiple genes linked to diseases of glycosphingolipid (GSL) metabolism to be associated with PD. GSL biosynthesis is a complex pathway involving the coordinated action of multiple enzymes in the Golgi apparatus. GSL catabolism takes place in the lysosome and is dependent on the action of multiple acid hydrolases specific for certain substrates and glycan linkages. The finding that variants in multiple GSL catabolic genes are over-represented in PD in a heterozygous state highlights the importance of GSLs in the healthy brain and how lipid imbalances and lysosomal dysfunction are associated with normal ageing and neurodegenerative diseases. In this article we will explore the link between lysosomal storage disorders and PD, the GSL changes seen in both normal ageing, lysosomal storage disorders (LSDs) and PD and the mechanisms by which these changes can affect neurodegeneration
Glycosphingolipid changes in plasma in Parkinson’s disease independent of glucosylceramide levels
No full textBackground: Alteration of glycosphingolipids (GSLs) in Parkinson's disease (PD) still needs to be clarified.
Objectives: We evaluated if PD subjects show abnormal GSLs levels compared to healthy controls (HC) and if GSLs correlate with clinical features.
Methods: We analyzed GSLs and glucosylceramide (GlcCer) in plasma using two normal-phase HPLC assays; clinico-demographic data were extracted.
Results: Eighty PD subjects and twenty-five HC were analyzed. Levels of GlcCer, GD1b, Gb4, GalNAcGA1, and b-series were higher in PD vs. HC; total GSLs, GT1b, GM1a, GM3, GM2, a-series were lower in PD vs. HC. Changes in GSLs were present in PD subjects with levels of GlcCer similar to HC. Results were similar after excluding certain GBA1 mutation carriers. MDS-UPDRS part III correlated with Gb4 and MoCA with GD1b levels.
Conclusions: Multiple GSLs abnormalities in plasma were detected, both in patients with and without GlcCer changes indicating a broader shift in lipid homeostasis
NMR analysis reveals significant differences in the plasma metabolic profiles of Niemann Pick C1 patients, heterozygous carriers, and healthy controls
No full textAbstractNiemann-Pick type C1 (NPC1) disease is a rare autosomal recessive, neurodegenerative lysosomal storage disorder, which presents with a range of clinical phenotypes and hence diagnosis remains a challenge. In view of these difficulties, the search for a novel, NPC1-specific biomarker (or set of biomarkers) is a topic of much interest. Here we employed high-resolution 1H nuclear magnetic resonance spectroscopy coupled with advanced multivariate analysis techniques in order to explore and seek differences between blood plasma samples acquired from NPC1 (untreated and miglustat treated), heterozygote, and healthy control subjects. Using this approach, we were able to identify NPC1 disease with 91% accuracy confirming that there are significant differences in the NMR plasma metabolic profiles of NPC1 patients when compared to healthy controls. The discrimination between NPC1 (both miglustat treated and untreated) and healthy controls was dominated by lipoprotein triacylglycerol 1H NMR resonances and isoleucine. Heterozygote plasma samples displayed also increases in the intensities of selected lipoprotein triacylglycerol 1H NMR signals over those of healthy controls. The metabolites identified could represent useful biomarkers in the future and provide valuable insight in to the underlying pathology of NPC1 disease.</jats:p
Urinary excretion and metabolism of miglustat and valproate in patients with Niemann-Pick Type C1 disease: one- and two-dimensional solution-state 1H NMR studies
No full textNiemann-Pick type C1 (NP-C1) disease is a neurodegenerative lysosomal storage disease for which the only approved therapy is miglustat (MGS). In this study we explored the applications and value of both one- and two-dimensional high-resolution NMR analysis strategies to the detection and quantification of MGS and its potential metabolites in urine samples collected from NP-C1 disease patients (n = 47), and also applied these techniques to the analysis of the anticonvulsant drug valproate and one of its major metabolites in ca. 30% of these samples (i.e., from those who were also receiving this agent for the control of epileptic seizures). A combination of high-resolution 1D and 2D TOCSY/NOESY techniques confirmed the identity of MGS in the urinary 1H NMR profiles of NP-C1 patients treated with this agent (n = 25), and its quantification was readily achievable via electronic integration of selected 1D resonance intensities. However, this analysis provided little or no evidence for its metabolism in vivo, observations consistent with those acquired in corresponding experiments performed involving an in vitro microsomal system. Contrastingly, the major valproate metabolite 1-O-valproyl-β-glucuronide was readily detectable and quantifiable in 14/47 of the urine samples investigated, despite some resonance overlap problems (identification of this agent was confirmed by experiments involving equilibration of these samples with β-glucuronidase, a process liberating free valproate). In order to facilitate and validate the detection of MGS in urine specimens, full assignments of the 1H NMR spectra of MGS in both buffered aqueous (pH 7.10) and deuterated methanol solvent systems were also made. The pharmacological and bioanalytical significance of data acquired are discussed, with special reference to the advantages offered by high-resolution NMR analysis
Plasma phosphorylated-tau217 is increased in Niemann–Pick disease type C
No full textNiemann–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
A novel, highly sensitive and specific biomarker for Niemann-Pick type C1 disease
No full textBackground Lysosomal storage disorders (LSDs), are a heterogeneous group of
rare disorders caused by defects in genes encoding for proteins involved in
the lysosomal degradation of macromolecules. They occur at a frequency of
about 1 in 5,000 live births, though recent neonatal screening suggests a
higher incidence. New treatment options for LSDs demand a rapid, early
diagnosis of LSDs if maximal clinical benefit is to be achieved. Methods Here,
we describe a novel, highly specific and sensitive biomarker for Niemann-Pick
Type C disease type 1 (NPC1), lyso-sphingomyelin-509. We cross-validate this
biomarker with cholestane-3β,5α,6β-triol and relative lysosomal volume. The
primary cohort for establishment of the biomarker contained 135 NPC1 patients,
66 NPC1 carriers, 241 patients with other LSDs and 46 healthy controls.
Results With a sensitivity of 100.0% and specificity of 91.0% a cut-off of 1.4
ng/ml was established. Comparison with cholestane-3β,5α,6β-triol and relative
acidic compartment volume measurements were carried out with a subset of 125
subjects. Both cholestane-3β,5α,6β-triol and lyso-Sphingomyelin-509 were
sufficient in establishing the diagnosis of NPC1 and correlated with disease
severity. Conclusion In summary, we have established a new biomarker for the
diagnosis of NPC1, and further studies will be conducted to assess correlation
to disease progress and monitoring treatment
Treatment with miglustat reverses the lipid-trafficking defect in Niemann-Pick disease type C.
No full textNiemann-Pick disease type C (NP-C) is a hereditary neurovisceral lipid storage disorder. Although traditionally considered a primary cholesterol storage disorder, a variety of glycolipids accumulate in NP-C cells, which resemble those from glycosphingolipidosis patients. Substrate reduction therapy (SRT) with miglustat, an inhibitor of glycosphingolipid biosynthesis, is a novel therapy for the glycosphingolipidoses. We report the use of SRT in a patient with NP-C. We show that depletion of glycosphingolipids by miglustat treatment reduces pathological lipid storage, improves endosomal uptake and normalises lipid trafficking in peripheral blood B lymphocytes. The demonstration that treatment with miglustat, which has no direct effect on cholesterol metabolism, corrects the abnormal lipid trafficking seen in B lymphocytes in NP-C indicates that glycosphingolipid accumulation is the primary pathogenetic event in NP-C. These observations support the use of SRT in patients with this devastating neurodegenerative disease
