Glycosphingolipid Storage Disease Research Articles

Phase 1 Healthy Volunteer Study of AL01211, an Oral, Non-brain Penetrant Glucosylceramide Synthase Inhibitor, to Treat Fabry Disease and Type 1 Gaucher Disease.

Glycosphingolipid (GSL) storage diseases are caused by deficiencies in the enzymes that metabolize different GSLs in the lysosome. Glucosylceramide synthase (GCS) inhibitors reduce GSL production and have potential to treat multiple GSL storage diseases. AL01211 is a potent, oral GCS inhibitor being developed for the treatment of Type 1 Gaucher disease and Fabry disease. AL01211 has minimal central nervous system penetration, allowing for treatment of peripheral organs without risking CNS-associated adverse effects. AL01211 was evaluated in a Phase 1 healthy volunteer study with single ascending dose (SAD) and multiple ascending dose (MAD) arms, to determine safety, pharmacokinetics including food effect, and pharmacodynamic effects on associated GSLs. In the SAD arm, AL01211 showed a Tmaxof approximately 3.5 hours, mean clearance (CL/F) of 130.1 L/h, and t1/2 of 39.3 hours. Consuming a high-fat meal prior to dose administration reduced exposures 3.5-5.5-fold, indicating a food effect. In the MAD arm, AL01211 had an approximately 2-fold accumulation, reaching steady-state levels by 10 days. Increasing exposure inversely correlated with a decrease in GSL with plasma glucosylceramide and globotriacylceramide reduction from baseline levels, reaching 78% and 52% by day 14, respectively. AL01211 was generally well-tolerated with no AL01211 associated serious adverse events, thus supporting its further clinical development.

Pathophysiology of Sandhoff Disease and Novel Thrapeutic Targets

Sandhoff disease (SD) is a glycosphingolipid storage disease resulting from a genetic mutation in HEXB and associated deficiency in β-hexosaminidase activity. This defect causes abnormal accumulation of ganglioside GM2 and related glycolipids in lysosomes, resulting in progressive deterioration of the central nervous system. Hexb-knockout (Hexb-/-) mice, an established animal model, show abnormalities similar to the severe phenotype seen in human infants. We used iPS cells derived from this mouse model (SD-iPSCs) to examine abnormal neuronal lineage differentiation and development in vitro during the asymptomatic phase of SD. Differentiation ability along the time axis appears to be altered in SD-iPSCs in which the differentiation ability of neural stem cells is promoted and differentiation into neurons is completed earlier, while the timing of differentiation into astrocytes is accelerated. This abnormal differentiation was suppressed by introducing the Hexb gene. These results indicate that the abnormal differentiation of SD-iPSCs into the nervous system reflects the pathogenesis of SD. Analysis using Hexb-/- mice revealed that activated microglia causes astrogliosis at the early stage of development that can be ameliorated via immunosuppression. Furthermore, reactive astrocytes in the cortex of Hexb-/- mice express adenosine A2A receptors in the late inflammatory phase. Inhibition of this receptor resulted in a decrease in activated microglial cells and inflammatory cytokines/chemokines. These results suggest that the astrocyte A2A receptor is important as a sensor that regulates microglial activation in the late inflammatory phase. Thus, our results provide new insights into the complex pathogenesis of SD.

1029 FABRY DISEASE: A RARE CAUSE TO REMEMBER WHEN FACING ACUTE KIDNEY INJURY IN YOUNG

Abstract Introduction Anderson-Fabry disease (FD) is a rare X-linked hereditary disease caused by mutations in the alpha-galactosidase A (GLA) gene, a lysosomal hydrolase that catabolizes lipids. GLA deficency leads to a progressive accumulation of undegraded glycosphingolipids, mainly Globotriaosylceramide (GB3), within lysosomes of cells (epithelial and endothelial cells, neurons, cardiomyocytes and renal cells), leading to cellular dysfunction. The incidence of FD is 1:117.000 but in patients with end stage renal disease (ESRD), incidence is higher, ranging from 0.04% up to 1.16% in male dialysis patients. Classical form of the disease shows renal, cardiac and cerebrovascular involvements usually. Cardiac involvement includes hypertrophic cardiomyopathy, arrhythmias such as complete heart block, valve dysfunction and myocardial infarction. Renal manifestations include proteinuria, progressive loss of renal function with chronic kidney disease (CKD) that leads to ESRD. The diagnosis of FD can be very difficult and often is delayed due to subtle clinical manifestations, but an early diagnosis is crucial to start enzyme replacement therapy (ERT), based on recombinant human GLA, as soon as possible. Clinical Case we describe the case of a 36-years-old male admitted to the Emergency Room of our hospital due to asthenia, nausea, dysphagia, anuria and loss of weight. At physical examination, apical systolic murmur and a bilateral ankle edema. Blood pressure was 195/100 mmHg, heart rate 125 beats per minute, peripheral oxygen saturation 100%. Blood test showed Hemoglobin 8 g/dL, Blood Urea 422 mg/dL, Creatinine 20 mg/dL, Na+ 135 mEq/L, K+ 4 mEq/L, Phosphorus 9 mg/dL. Arterial blood gas analysis showed metabolic and lactic acidosis. The diagnosis of acute kidney injury (AKI) was made, and a dialytic treatment was scheduled. During dialytic session, the patient had a syncope. EKG showed a complete left bundle branch block (LBBB) with advanced atrio-ventricular block (2:1, complete). An echocardiogram highlighted a severe myocardial hypertrophy (septal wall 25 mm) involving also the right ventricle with “ground glass” aspect of the posterolateral, posterior and inferior septum, with minimal pericardial effusion. Heart MRI scan confirmed LV myocardial hypertrophy with circumferential aspect (interventricular septum 26.6 mm), mild decrease in left ventricular ejection fraction (47%) and myocardial hypointensity area in the FSE sequences. Renal ultrasound showed bilateral cortical hyperecogenity, small cortico-medullary border, initial reduction of kidney volume and diffuse perirenal edema. In consideration of the high probability of a storage disease, we performed genetic testing for FD and Gaucher disease, peri-umbilical fat biopsy for Amyloid Disease and a renal biopsy. The genetic test resulted positive for typical mutation of FD and renal biopsy documented ESRD secondary to glycosphingolipid storage disease ceramid type from FD. Conclusion Differential diagnosis of AKI in a young male should include FD, as suggested by the clinical case reported, and nephrologist should screen young patients for α-GLA enzyme deficiency (diagnostic for FD) possibly coupled with renal biopsy in uncertain cases.

Comprehensive clinical, biochemical, radiological and genetic analysis of 28 Turkish cases with suspected metachromatic leukodystrophy and their relatives

Metachromatic leukodystrophy (MLD) is a glycosphingolipid storage disease caused by deficiency of the lysosomal enzyme arylsulfatase A (ASA) or its activator protein saposin B. MLD can affect all age groups in severity varying from a severe fatal form to milder adult onset forms. Diagnosis is usually made by measuring leukocyte ASA activity. However, this test can give false negative or false positive laboratory results due to pseudodeficiency of ASA and saposin B deficiency, respectively. Therefore, we aimed to evaluate patients with suspected MLD in a Turkish population by comprehensive clinical, biochemical, radiological, and genetic analyses for molecular and phenotypic characterization. We analyzed 28 suspected MLD patients and 41 relatives from 24 families. ASA activity was found to be decreased in 21 of 28 patients. Sixteen patients were diagnosed as MLD (11 late infantile, 2 juvenile and 3 adult types), 2 MSD, 2 pseudodeficiency (PD) and the remaining 8 patients were diagnosed as having other leukodystrophies. Enzyme analysis showed that the age of onset of MLD did not correlate with residual ASA activity. Sequence analysis showed 11 mutations in ARSA, of which 4 were novel (p.Trp195GlyfsTer5, p.Gly298Asp, p.Arg301Leu, and p.Gly311Asp), and 2 mutations in SUMF1 causing multiple sulfatase deficiency, and confirmed the diagnosis of MLD in 2 presymptomatic relatives. All individuals with confirmed mutations had low ASA activity and urinary sulfatide excretion. Intra- and inter-familial variability was high for the same ARSA missense genotypes, indicating the contribution of other factors to disease expression. Imaging findings were evaluated through a modified brain MRI scoring system which indicated patients with protein-truncating mutations had more severe MRI findings and late-infantile disease onset. MRI findings were not specific for the diagnosis. Anti-sulfatide IgM was similar to control subjects, and IgG, elevated in multiple sulfatase deficiency. In conclusion, the knowledge on the biochemical, clinical and genetic basis of MLD was expanded, a modified diagnostic laboratory algorithm for MLD based on integrated evaluation of ASA activity, urinary sulfatide excretion and genetic tests was devised.

Positron Emission Tomography and Magnetic Resonance Imaging of the Brain in Fabry Disease: A Nationwide, Long-Time, Prospective Follow-Up.

BackgroundFabry disease is a rare metabolic glycosphingolipid storage disease caused by deficiency of the lysosomal enzyme α-galactosidase A—leading to cellular accumulation of globotriasylceramide in different organs, vessels, tissues, and nerves. The disease is associated with an increased risk of cerebrovascular disease at a young age in addition to heart and kidney failure.ObjectiveThe objective of this study was to assess brain function and structure in the Danish cohort of patients with Fabry disease in a prospective way using 18-fluoro-deoxyglucose (F-18 FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI).PatientsForty patients with Fabry disease (14 males, 26 females, age at inclusion: 10–66 years, median: 39 years) underwent a brain F-18-FDG-PET-scan at inclusion, and 31 patients were followed with FDG-PET biannually for up to seven years. All patients (except one) had a brain MRI-scan at inclusion, and 34 patients were followed with MRI biannually for up to nine years.Image AnalysisThe FDG-PET-images were inspected visually and analysed using a quantitative 3-dimensional stereotactic surface projection analysis (Neurostat). MRI images were also inspected visually and severity of white matter lesions (WMLs) was graded using a visual rating scale.ResultsIn 28 patients brain-FDG-PET was normal; in 23 of these 28 patients brain MRI was normal—of the remaining five patients in this group, four patients had WMLs and one patient never had an MRI-scan. In 10 patients hypometabolic areas were observed on brain-FDG-PET; all of these patients had cerebral infarcts/hemorrhages visualized on MRI corresponding to the main hypometabolic areas. In two patients brain-FDG-PET was ambiguous, while MRI was normal in one and abnormal in the other.ConclusionOur data indicated that, in patients with Fabry disease, MRI is the preferable clinical modality—if applicable—when monitoring cerebral status, as no additional major brain-pathology was detected with FDG-PET.

A male Fabry disease patient treated with intravenous thrombolysis for acute ischemic stroke

The use of intravenous thrombolytic therapy for acute ischemic stroke is associated with improved outcomes. Fabry disease is an X-linked glycosphingolipid storage disease with vascular endothelial deposits. Affected males with the classic phenotype develop renal, cardiac, and cerebrovascular disease and die prematurely. However, Fabry disease is rare in young men with first ischemic stroke of undetermined cause. We report a 38-year-old man with acute aphasia and a left M2 segment of the middle cerebral artery thrombus with no recanalization who was finally diagnosed with Fabry disease after left ventricular hypertrophy of undetermined cause had been identified. A gene test revealed a R227X mutation typical of Fabry disease with the classical phenotype. To our knowledge our patient is the first reported male Fabry patient who was given intravenous thrombolytic therapy and the first reported Fabry patient who received intravenous thrombolytic therapy between 3 and 4.5hours of the symptom onset. Despite favorable prognostic indicators on admission imaging, our patient suffered a significant stroke and had an unfavorable clinical outcome. Fortunately, the episode was not complicated by intracranial hemorrhage. Further studies are needed to evaluate the efficacy and safety of intravenous thrombolytic therapy in treating patients with Fabry disease and acute ischemic stroke.

The development and use of small molecule inhibitors of glycosphingolipid metabolism for lysosomal storage diseases

Glycosphingolipid (GSL) storage diseases have been the focus of efforts to develop small molecule therapeutics from design, experimental proof of concept studies, and clinical trials. Two primary alternative strategies that have been pursued include pharmacological chaperones and GSL synthase inhibitors. There are theoretical advantages and disadvantages to each of these approaches. Pharmacological chaperones are specific for an individual glycoside hydrolase and for the specific mutation present, but no candidate chaperone has been demonstrated to be effective for all mutations leading to a given disorder. Synthase inhibitors target single enzymes such as glucosylceramide synthase and inhibit the formation of multiple GSLs. A glycolipid synthase inhibitor could potentially be used to treat multiple diseases, but at the risk of lowering nontargeted cellular GSLs that are important for normal health. The basis for these strategies and specific examples of compounds that have led to clinical trials is the focus of this review.

Multifocal White Matter Lesions Associated with the D313Y Mutation of the α-Galactosidase A Gene

White matter lesions (WML) are clinically relevant since they are associated with strokes, cognitive decline, depression, or epilepsy, but the underlying etiology in young adults without classical risk factors still remains elusive. Our aim was to elucidate the possible clinical diagnosis and mechanisms leading to WML in patients carrying the D313Y mutation in the α-galactosidase A (GLA) gene, a mutation that was formerly described as nonpathogenic. Pathogenic GLA mutations cause Fabry disease, a vascular endothelial glycosphingolipid storage disease typically presenting with a symptom complex of renal, cardiac, and cerebrovascular manifestations. We performed in-depths clinical, biochemical and genetic examinations as well as advanced magnetic resonance imaging analyses in a pedigree with the genetically determined GLA mutation D313Y. We detected exclusive neurologic manifestations of the central nervous system of the “pseudo”-deficient D313Y mutation leading to manifest WML in 7 affected adult family members. Furthermore, two family members that do not carry the mutation showed no WML. The D313Y mutation resulted in a normal GLA enzyme activity in leukocytes and severely decreased activities in plasma. In conclusion, our results provide evidence that GLA D313Y is potentially involved in neural damage with significant WML, demonstrating the necessity of evaluating patients carrying D313Y more thoroughly. D313Y might broaden the spectrum of hereditary small artery diseases of the brain, which preferably occur in young adults without classical risk factors. In view of the existing causal therapy regime, D313Y should be more specifically taken into account in these patients.

Impaired Neural Differentiation of Induced Pluripotent Stem Cells Generated from a Mouse Model of Sandhoff Disease

Sandhoff disease (SD) is a glycosphingolipid storage disease that arises from mutations in the Hexb gene and the resultant deficiency in β-hexosaminidase activity. This deficiency results in aberrant lysosomal accumulation of the ganglioside GM2 and related glycolipids, and progressive deterioration of the central nervous system. Dysfunctional glycolipid storage causes severe neurodegeneration through a poorly understood pathogenic mechanism. Induced pluripotent stem cell (iPSC) technology offers new opportunities for both elucidation of the pathogenesis of diseases and the development of stem cell-based therapies. Here, we report the generation of disease-specific iPSCs from a mouse model of SD. These mouse model-derived iPSCs (SD-iPSCs) exhibited pluripotent stem cell properties and significant accumulation of GM2 ganglioside. In lineage-directed differentiation studies using the stromal cell-derived inducing activity method, SD-iPSCs showed an impaired ability to differentiate into early stage neural precursors. Moreover, fewer neurons differentiated from neural precursors in SD-iPSCs than in the case of the wild type. Recovery of the Hexb gene in SD-iPSCs improved this impairment of neuronal differentiation. These results provide new insights as to understanding the complex pathogenic mechanisms of SD.

Property-based design of a glucosylceramide synthase inhibitor that reduces glucosylceramide in the brain

Synthesis inhibition is the basis for the treatment of type 1 Gaucher disease by the glucosylceramide synthase (GCS) inhibitor eliglustat tartrate. However, the extended use of eliglustat and related compounds for the treatment of glycosphingolipid storage diseases with CNS manifestations is limited by the lack of brain penetration of this drug. Property modeling around the D-threo-1-phenyl-2-decanoylamino-3-morpholino-propanol (PDMP) pharmacophore was employed in a search for compounds of comparable activity against the GCS but lacking P-glycoprotein (MDR1) recognition. Modifications of the carboxamide N-acyl group were made to lower total polar surface area and rotatable bond number. Compounds were screened for inhibition of GCS in crude enzyme and whole cell assays and for MDR1 substrate recognition. One analog, 2-(2,3-dihydro-1H-inden-2-yl)-N-((1R,2R)-1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1-hydroxy-3-(pyrrolidin-1-yl)propan-2-yl)acetamide (CCG-203586), was identified that inhibited GCS at low nanomolar concentrations with little to no apparent recognition by MDR1. Intraperitoneal administration of this compound to mice for 3 days resulted in a significant dose dependent decrease in brain glucosylceramide content, an effect not seen in mice dosed in parallel with eliglustat tartrate.

Imaging of complex sulfatides SM3 and SB1a in mouse kidney using MALDI-TOF/TOF mass spectrometry

Sulfatides, a class of acidic glycosphingolipids, are highly expressed in mammalian myelin and in kidney, where they are thought to stabilize neuronal structures and signaling and to influence osmotic stability of renal cells, respectively. Recently, 9-aminoacridine (9-AA) has been introduced as a negative ion matrix that displays high selectivity for low complexity galactosylceramid-I(3)-sulfate sulfatides and that is suitable for quantitative analysis by matrix-assisted desorption/ionization (MALDI) mass spectrometry (MS). Analyzing acidic fractions of lipid extracts and cryosections from kidneys of wild type and arylsulfatase A-deficient (ASA -/-) mice, we demonstrate that 9-AA also enables sensitive on-target analysis as well as imaging of complex lactosylceramide-II(3)-sulfate and gangliotetraosylceramide-II(3), IV(3) bis-sulfate sulfatides by MALDI-TOF/TOF MS. Utilizing the MALDI imaging MS technique, we show differential localization in mouse kidney of (1) sulfatides with identical ceramide anchors, but different glycan-sulfate head groups but also of (2) sulfatides with identical head groups but with different acyl- or sphingoid base moieties. A comparison of MALDI images of renal sulfatides from control and sulfatide storing arylsulfatase A-deficient (ASA -/-) mice revealed relative expression differences, very likely reflecting differences in sulfatide turnover of the various renal cell types. These results establish MALDI imaging MS with 9-AA matrix as a label-free method for spatially resolved ex vivo investigation of the relative turnover of sulfatides in animal models of human glycosphingolipid storage disease.

Molecular mechanisms of pathogenesis in a glycosphingolipid and a glycoprotein storage disease

The lysosomal system comprises a specialized network of organelles crucial for the sorting, digestion, recycling and secretion of cellular components. With their content of hydrolytic enzymes, lysosomes regulate the degradation of a multitude of substrates that reach these organelles via the biosynthetic or the endocytic route. Gene defects that affect one or more of these hydrolases lead to LSDs (lysosomal storage diseases). This underscores the apparent lack of redundancy of these enzymes and the importance of the lysosomal system in cell and tissue homoeostasis. Some of the lysosomal enzymes may form multiprotein complexes, which usually work synergistically on substrates and, in this configuration, may respond more efficiently to changes in substrate load and composition. A well-characterized lysosomal multienzyme complex is the one comprising the glycosidases β-gal (β-galactosidase) and NEU1 (neuramidase-1), and of the serine carboxypeptidase PPCA (protective protein/cathepsin A). Three neurodegenerative LSDs are caused by either single or combined deficiency of these lysosomal enzymes. Sialidosis (NEU1 deficiency) and galactosialidosis (combined NEU1 and β-gal deficiency, secondary to a primary defect of PPCA) belong to the glycoprotein storage diseases, whereas GM1-gangliosidosis (β-gal deficiency) is a glycosphingolipid storage disease. Identification of novel molecular pathways that are deregulated because of loss of enzyme activity and/or accumulation of specific metabolites in various cell types has shed light on mechanisms of disease pathogenesis and may pave the way for future development of new therapies for these LSDs.

Macroautophagy Is Not Directly Involved in the Metabolism of Amyloid Precursor Protein

Alterations in the metabolism of amyloid precursor protein (APP) are believed to play a central role in Alzheimer disease pathogenesis. Burgeoning data indicate that APP is proteolytically processed in endosomal-autophagic-lysosomal compartments. In this study, we used both in vivo and in vitro paradigms to determine whether alterations in macroautophagy affect APP metabolism. Three mouse models of glycosphingolipid storage diseases, namely Niemann-Pick type C1, GM1 gangliosidosis, and Sandhoff disease, had mTOR-independent increases in the autophagic vacuole (AV)-associated protein, LC3-II, indicative of impaired lysosomal flux. APP C-terminal fragments (APP-CTFs) were also increased in brains of the three mouse models; however, discrepancies between LC3-II and APP-CTFs were seen between primary (GM1 gangliosidosis and Sandhoff disease) and secondary (Niemann-Pick type C1) lysosomal storage models. APP-CTFs were proportionately higher than LC3-II in cerebellar regions of GM1 gangliosidosis and Sandhoff disease, although LC3-II increased before APP-CTFs in brains of NPC1 mice. Endogenous murine Aβ40 from RIPA-soluble extracts was increased in brains of all three mice. The in vivo relationship between AV and APP-CTF accumulation was also seen in cultured neurons treated with agents that impair primary (chloroquine and leupeptin + pepstatin) and secondary (U18666A and vinblastine) lysosomal flux. However, Aβ secretion was unaffected by agents that induced autophagy (rapamycin) or impaired AV clearance, and LC3-II-positive AVs predominantly co-localized with degradative LAMP-1-positive lysosomes. These data suggest that neuronal macroautophagy does not directly regulate APP metabolism but highlights the important anti-amyloidogenic role of lysosomal proteolysis in post-secretase APP-CTF catabolism.

Glycosphingolipid storage leads to the enhanced degradation of the B cell receptor in Sandhoff disease mice

Glycosphingolipid 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.

Frequency of Unrecognized Fabry Disease Among Young European-American and African-American Men With First Ischemic Stroke

The cause of initial ischemic stroke in up to 30% of young patients remains unclear. Fabry disease, due to deficient alpha-galactosidase A (alpha-Gal A) activity, is a vascular endothelial glycosphingolipid storage disease typically presenting in childhood. With advancing age, patients develop renal, cardiac, and cerebrovascular disease and die prematurely. A European study suggested an increased prevalence of unrecognized Fabry disease in patients with cryptogenic stroke. We hypothesized that alpha-Gal A deficiency is a rare cause of initial early-onset ischemic stroke in men. The Stroke Prevention in Young Men Study enrolled >550 men (15 to 49 years) with first ischemic stroke in the Baltimore-Washington area in 2004 to 2007. Frozen plasma samples were assayed for alpha-Gal A activity, and DNA from patients with consistently low plasma alpha-Gal A activities were sequenced. The study sample consisted of 558 men (42% African-American; median age 44 years). Stroke was cryptogenic in 154 men (40% African-American). In 10 patients with low plasma alpha-Gal A activities, DNA sequencing identified alterations in the alpha-Gal A gene in 2 patients. The polymorphism, D313Y, which results in low plasma enzyme activity, but near normal levels of cellular activity was seen in one European-American male. The Fabry disease-causing A143T mutation was seen in an African-American male with cryptogenic stroke (0.18% of all strokes: upper 95% CI=0.53%; 0.65% of cryptogenic strokes: upper 95% CI=1.92%). In this biracial population, unrecognized Fabry disease is a rare but treatable cause of initial ischemic stroke in young men.

A new surrogate marker for CNS pathology in Niemann–Pick disease type C?

Over the past 20 years there has been unprecedented progressin the development of treatments for lysosomal storage diseases(LSDs) [1]. Enzyme replacement therapy (ERT) continues to expandwith clinical programmes in Niemann–Pick type B, MPS IV andmetachromatic leucodystrophy. One small molecule drug (miglu-stat) is approved for type 1 Gaucher disease and other substratereduction therapy (SRT) and chaperone approaches are in the pipe-line [2]. Indeed, it is possible that in the future physicians treatingGaucher disease may be able to choose from three different en-zyme preparations, two inhibitors of glucosyl ceramide synthesisand a chaperone.However, these treatments are not all equally efficacious. Onemajor obstacle is that there is no means of delivering significantamounts of enzyme across the blood–brain barrier. This meansthat whilst ERT canbe highlyeffective against the visceralmanifes-tations of LSDs, patients in whom CNS involvement is the majorfeature do not benefit. For the majority of LSDs, which involve stor-age and pathology in the brain, ERT is not currently a realisticoption.Considerable research activity is therefore currently focused ondeveloping strategies to target brain disease in these disorders,either using small molecules, gene therapy or methods to deliverenzymes across the blood–brain barrier.One major obstacle in designingclinical trialsis the definitionofsuitable clinical endpoints. Regulatory authorities demand con-trolled trials, which demonstrate statistically significant changesin quantifiable variables. Pharmaceutical companies want trialsto be completed in months rather than years. Unfortunately, theseare rare, neurodegenerative diseases, which show variable andunpredictable progression over long periods. We do not knowwhich aspects of CNS pathology may be stabilised or improvedby treatment and it is very difficult to decide which clinical mani-festations should be measured or to know how long it may take tosee a significant change.The situation would be greatly improved if there were validatedsurrogate markers of brain disease that could be monitored as sec-ondaryclinical endpoints. These wouldpotentiallyprovidean earlyindicator of efficacy, prior to significant changes in clinicalsymptoms.The utility of surrogate markers in the storage disease field isbest exemplified by type 1 Gaucher disease [3]. This is a visceralstorage disorder with the Gaucher macrophage being the centralcell type in the pathogenic cascade [4]. These cells secrete a num-ber of factors that can be measured in peripheral blood and used assurrogate markers to estimate the total storage cell burden in un-treated patients and measure the degree of improvement followingthe initiation of ERT or SRT [5].However, currentlythere are no equivalent markersfor measur-ing storage in the brain. The Holy Grail in this field would be toidentify a non-invasive method that could be performed in mosthospitals where the parameter being measured was closely linkedto the primary pathological events occurring in the brain. It wouldneed to correlate with disease severity and be altered by diseasemodifying therapies.Miglustat, a small molecule inhibitor of glucosylceramide syn-thesis, does cross the blood–brain barrier and has shown benefitwhen used for SRT in a number of mouse models of CNS glyco-sphingolipid storage diseases [6], including Niemann–Pick type C

Comparative Analysis of Brain Lipids in Mice, Cats, and Humans with Sandhoff Disease

Sandhoff disease (SD) is a glycosphingolipid (GSL) storage disease that arises from an autosomal recessive mutation in the gene for the beta-subunit of beta-Hexosaminidase A (Hexb gene), which catabolizes ganglioside GM2 within lysosomes. Accumulation of GM2 and asialo-GM2 (GA2) occurs primarily in the CNS, leading to neurodegeneration and brain dysfunction. We analyzed the total lipids in the brains of SD mice, cats, and humans. GM2 and GA2 were mostly undetectable in the normal mouse, cat, and human brain. The lipid abnormalities in the SD cat brain were generally intermediate to those observed in the SD mouse and the SD human brains. GM2 comprised 38, 67, and 87% of the total brain ganglioside distribution in the SD mice, cats, and humans, respectively. The ratio of GA2-GM2 was 0.93, 0.13, and 0.27 in the SD mice, cats, and humans, respectively, suggesting that the relative storage of GA2 is greater in the SD mouse than in the SD cat or human. Finally, the myelin-enriched lipids, cerebrosides and sulfatides, were significantly lower in the SD brains than in the control brains. This study is the first comparative analysis of brain lipids in mice, cats, and humans with SD and will be important for designing therapies for Sandhoff disease patients.

Temporal gene expression profiling reveals CEBPD as a candidate regulator of brain disease in prosaposin deficient mice

BackgroundProsaposin encodes, in tandem, four small acidic activator proteins (saposins) with specificities for glycosphingolipid (GSL) hydrolases in lysosomes. Extensive GSL storage occurs in various central nervous system regions in mammalian prosaposin deficiencies.ResultsOur hypomorphic prosaposin deficient mouse, PS-NA, exhibited 45% WT levels of brain saposins and showed neuropathology that included neuronal GSL storage and Purkinje cell loss. Impairment of neuronal function was observed as early as 6 wks as demonstrated by the narrow bridges tests. Temporal transcriptome microarray analyses of brain tissues were conducted with mRNA from three prosaposin deficient mouse models: PS-NA, prosaposin null (PS-/-) and a V394L/V394L glucocerebrosidase mutation combined with PS-NA (4L/PS-NA). Gene expression alterations in cerebrum and cerebellum were detectable at birth preceding the neuronal deficits. Differentially expressed genes encompassed a broad spectrum of cellular functions. The number of down-regulated genes was constant, but up-regulated gene numbers increased with age. CCAAT/enhancer-binding protein delta (CEBPD) was the only up-regulated transcription factor in these two brain regions of all three models. Network analyses revealed that CEBPD has functional relationships with genes in transcription, pro-inflammation, cell death, binding, myelin and transport.ConclusionThese results show that: 1) Regionally specific gene expression abnormalities precede the brain histological and neuronal function changes, 2) Temporal gene expression profiles provide insights into the molecular mechanism during the GSL storage disease course, and 3) CEBPD is a candidate regulator of brain disease in prosaposin deficiency to participate in modulating disease acceleration or progression.

Complete Correction of Enzymatic Deficiency and Neurochemistry in the GM1-gangliosidosis Mouse Brain by Neonatal Adeno-associated Virus–mediated Gene Delivery

GM1-gangliosidosis is a glycosphingolipid (GSL) lysosomal storage disease caused by autosomal recessive deficiency of lysosomal acid beta-galactosidase (betagal), and characterized by accumulation of GM1-ganglioside and GA1 in the brain. Here we examined the effect of neonatal intracerebroventricular (i.c.v.) injection of an adeno-associated virus (AAV) vector encoding mouse betagal on enzyme activity and brain GSL content in GM1-gangliosidosis (betagal(-/-)) mice. Histological analysis of betagal distribution in 3-month-old AAV-treated betagal(-/-) mice showed that enzyme was present at high levels throughout the brain. Biochemical quantification showed that betagal activity in AAV-treated brains was 7- to 65-fold higher than in wild-type controls and that brain GSL levels were normalized. Cerebrosides and sulfatides, which were reduced in untreated betagal(-/-) mice, were restored to normal levels by AAV treatment. In untreated betagal(-/-) brains, cholesterol was present at normal levels but showed abnormal cellular distribution consistent with endosomal/lysosomal localization. This feature was also corrected in AAV-treated mice. The biochemical and histological parameters analyzed in this study showed that normal brain neurochemistry was achieved in AAV-treated betagal(-/-) mice. Therefore we show for the first time that neonatal AAV-mediated gene delivery of lysosomal betagal to the brain may be an effective approach for treatment of GM1-gangliosidosis.

An Anesthetic Experience in a Patient with Tay-Sachs Disease - A case report -

Tay-Sachs Disease (TSD), the most common form of GM2 gangliosidosis, is an autosomal recessive inborn lysosomal glycosphingolipid storage disease which is resulted from the mutations that affect the α-subunit locus on chromosome 15 and cause a severe deficiency of hexosaminidase A. It is characterized by normal motor development in the first few months of life, followed by progressive weakness and loss of motor skills beginning around 6 months of life. Neurodegeneration is relentless and manifested as relentless motor and mental deterioration, beginning with motor incoordination, mental obtundation leading to muscular flaccidity, blindness, and increasing dementia, with death occurring by the age of 4 or 5 years. We report a successful anesthetic management in a patient with Tay-Sachs Diseases for tracheostomy and feeding gastrostomy.