Gaucher disease protects against tuberculosis.

Biallelic mutations in the glucocerebrosidase (GBA1) gene cause Gaucher disease, characterized by lysosomal accumulation of glucosylceramide and glucosylsphingosine in macrophages. Gaucher and other lysosomal diseases occur with high frequency in Ashkenazi Jews. It has been proposed that the underlying mutations confer a selective advantage, in particular conferring protection against tuberculosis. Here, using a zebrafish Gaucher disease model, we find that the mutation GBA1 N370S, predominant among Ashkenazi Jews, increases resistance to tuberculosis through the microbicidal activity of glucosylsphingosine in macrophage lysosomes. Consistent with lysosomal accumulation occurring only in homozygotes, heterozygotes remain susceptible to tuberculosis. Thus, our findings reveal a mechanistic basis for protection against tuberculosis by GBA1 N370S and provide biological plausibility for its selection if the relatively mild deleterious effects in homozygotes were offset by significant protection against tuberculosis, a rampant killer of the young in Europe through the Middle Ages into the 19th century.

Neuronopathic GBA1L444P Mutation Accelerates Glucosylsphingosine Levels and Formation of Hippocampal Alpha-Synuclein Inclusions.

The most common genetic risk factor for Parkinson's disease (PD) is heterozygous mutations GBA1, which encodes for the lysosomal enzyme, glucocerebrosidase. Reduced glucocerebrosidase activity associates with an accumulation of abnormal α-synuclein (α-syn) called Lewy pathology, which characterizes PD. PD patients heterozygous for the neuronotypic GBA1L444P mutation (GBA1+/L444P) have a 5.6-fold increased risk of cognitive impairments. In this study, we used GBA1+/L444P mice of either sex to determine its effects on lipid metabolism, expression of synaptic proteins, behavior, and α-syn inclusion formation. At 3 months of age, GBA1+/L444P mice demonstrated impaired contextual fear conditioning, and increased motor activity. Hippocampal levels of vGLUT1 were selectively reduced in GBA1+/L444P mice. We show, using mass spectrometry, that GBA1L444P expression increased levels of glucosylsphingosine, but not glucosylceramide, in the brains and serum of GBA1+/L444P mice. Templated induction of α-syn pathology in mice showed an increase in α-syn inclusion formation in the hippocampus of GBA1+/L444P mice compared with GBA1+/+ mice, but not in the cortex, or substantia nigra pars compacta. Pathologic α-syn reduced SNc dopamine neurons by 50% in both GBA1+/+ and GBA1+/L444P mice. Treatment with a GlcCer synthase inhibitor did not affect abundance of α-syn inclusions in the hippocampus or rescue dopamine neuron loss. Overall, these data suggest the importance of evaluating the contribution of elevated glucosylsphingosine to PD phenotypes. Further, our data suggest that expression of neuronotypic GBA1L444P may cause defects in the hippocampus, which may be a mechanism by which cognitive decline is more prevalent in individuals with GBA1-PD.SIGNIFICANCE STATEMENT Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are both pathologically characterized by abnormal α-synuclein (α-syn). Mutant GBA1 is a risk factor for both PD and DLB. Our data show the expression of neuronotypic GBA1L444P impairs behaviors related to hippocampal function, reduces expression of a hippocampal excitatory synaptic protein, and that the hippocampus is more susceptible to α-syn inclusion formation. Further, our data strengthen support for the importance of evaluating the contribution of glucosylsphingosine to PD phenotypes. These outcomes suggest potential mechanisms by which GBA1L444P contributes to the cognitive symptoms clinically observed in PD and DLB. Our findings also highlight the importance of glucosylsphingosine as a relevant biomarker for future therapeutics.

Treatment-naive and post-treatment glucosylsphingosine (lyso-GL1) levels in a cohort of pediatric patients with Gaucher disease.

Glucosylsphingosine (lyso-GL1) is a biomarker used to monitor disease and treatment response in Gaucher disease. Data from adults show that higher values of lyso-GL1 are associated with increased disease progression, however similar data in the pediatric population is lacking. In a cohort of pediatric patients, we present a relationship between lyso-GL1 value and Gaucher type, age, and treatment response. Data from this study may serve as a reference for providers monitoring children with Gaucher disease.

A Comparative Biochemical and Pathological Evaluation of Brain Samples from Knock-In Murine Models of Gaucher Disease.

Gaucher disease (GD) is a lysosomal storage disorder stemming from biallelic mutations in GBA1, characterized by glucocerebrosidase dysfunction and glucocerebroside and glucosylsphingosine accumulation. Since phenotypes of murine models of GD often differ from those in patients, the careful characterization of Gba1 mutant mice is necessary to establish their ability to model GD. We performed side-by-side comparative biochemical and pathologic analyses of four murine Gba1 models with genotypes L444P/L444P (p.L483P/p.L483P), L444P/null, D409H/D409H (p.D448H/p.D448H) and D409H/null, along with matched wildtype mice, all with the same genetic background and cage conditions. All mutant mice exhibited significantly lower glucocerebrosidase activity (p < 0.0001) and higher glucosylsphingosine levels than wildtype, with the lowest glucocerebrosidase and the highest glucosylsphingosine levels in mice carrying a null allele. Although glucocerebrosidase activity in L444P and D409H mice was similar, D409H mice showed more lipid accumulation. No Gaucher or storage-like cells were detected in any of the Gba1 mutant mice. Quantification of neuroinflammation, dopaminergic neuronal loss, alpha-synuclein levels and motor behavior revealed no significant findings, even in aged animals. Thus, while the models may have utility for testing the effect of different therapies on enzymatic activity, they did not recapitulate the pathological phenotype of patients with GD, and better models are needed.

Plasma glucosylsphingosine correlations with baseline disease burden and response to eliglustat in two clinical trials of previously untreated adults with Gaucher disease type 1.

In Gaucher disease type 1 (GD1), accumulation of the lipid substrates glucosylceramide and glucosylsphingosine (lyso-GL-1 or lyso-Gb1), primarily in the spleen, liver, and bone marrow, leads to progressive hepatosplenomegaly, anemia, thrombocytopenia, and skeletal disease. Plasma glucosylceramide elevations are modest, variable, and normalize within weeks of starting treatment before clinical changes are evident, and therefore, have limited value for monitoring treatment responses. Serum chitotriosidase activity, a widely used GD biomarker, is also elevated in many other conditions but is not measurable in 5-10% of individuals due to a common CHIT1 null variant. Plasma glucosylsphingosine is increasingly recognized as a useful biomarker for GD1: elevations are highly specific to the disease and show no overlap with normal controls, it is in the causal pathway of disease, and levels are reliably measured by liquid chromatography-tandem mass spectrometry. We report correlations of plasma glucosylsphingosine with baseline disease burden and eliglustat treatment response in previously untreated adults with GD1 in the Phase 2 (NCT00358150), open-label, single-arm trial of 26 patients with up to 8 years of follow-up and the placebo-controlled Phase 3 ENGAGE trial (NCT00891202) of 40 patients with up to 4.5 years of follow-up. At baseline, untreated patients showed moderate to strong correlations between plasma glucosylsphingosine and spleen volume, liver volume, and hemoglobin level. Organ volumes and hematologic parameters improved in parallel with reductions in plasma glucosylsphingosine during eliglustat treatment in both trials. Moderate correlations were seen between plasma glucosylsphingosine reduction and spleen and liver volume reductions during eliglustat treatment. These clinical trial data add to the growing body of evidence supporting plasma glucosylsphingosine as both a diagnostic and pharmacodynamic/response biomarker for GD1.

A Biomarker Study in Patients with GBA1-Parkinson's Disease and Healthy Controls.

BACKGROUND: Molecules related to glucocerebrosidase (GCase) are potential biomarkers for development of compounds targeting GBA1-associated Parkinson's disease (GBA-PD). OBJECTIVES: Assessing variability of various glycosphingolipids (GSLs) in plasma, peripheral blood mononuclear cells (PBMCs), and cerebrospinal fluid (CSF) across GBA-PD, idiopathic PD (iPD), and healthy volunteers (HVs). METHODS: Data from five studies were combined. Variability was assessed of glucosylceramide (various isoforms), lactosylceramide (various isoforms), glucosylsphingosine, galactosylsphingosine, GCase activity (using fluorescent 4-methylumbeliferryl-ß-glucoside), and GCase protein (using enzyme-linked immunosorbent assay) in plasma, PBMCs, and CSF if available, in GBA-PD, iPD, and HVs. GSLs in leukocyte subtypes were compared in HVs. Principal component analysis was used to explore global patterns in GSLs, clinical characteristics (Movement Disorder Society - Unified Parkinson's Disease Rating Scale Part 3 [MDS-UPDRS-3], Mini-Mental State Examination [MMSE], GBA1 mutation type), and participant status (GBA-PD, iPD, HVs). RESULTS: Within-subject between-day variability ranged from 5.8% to 44.5% and was generally lower in plasma than in PBMCs. Extracellular glucosylceramide levels (plasma) were slightly higher in GBA-PD compared with both iPD and HVs, while intracellular levels were comparable. GSLs in the different matrices (plasma, PBMCs, CSF) did not correlate. Both lactosylceramide and glucosylsphingosine were more abundant in granulocytes compared with monocytes and lymphocytes. Absolute levels of GSL isoforms differed greatly. GBA1 mutation types could not be differentiated based on GSL data. CONCLUSIONS: Glucosylceramide can stably be measured over days in both plasma and PBMCs and may be used as a biomarker in clinical trials targeting GBA-PD. Glucosylsphingosine and lactosylceramide are stable in plasma but are strongly affected by leukocyte subtypes in PBMCs. GBA-PD could be differentiated from iPD and HVs, primarily based on glucosylceramide levels in plasma. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Long-Term Evaluation of Biomarkers in the Czech Cohort of Gaucher Patients.

A personalized treatment decision for Gaucher disease (GD) patients should be based on relevant markers that are specific to GD, play a direct role in GD pathophysiology, exhibit low genetic variation, reflect the therapy, and can be used for all patients. Thirty-four GD patients treated with enzyme replacement therapy (ERT) or substrate reduction therapy (SRT) were analyzed for platelet count, chitotriosidase, and tartrate-resistant acid phosphatase activity in plasma samples, and quantitative measurement of Lyso-Gb1 was performed in dried blood spots. In our ERT and SRT study cohorts, plasma lyso-GL1 correlated significantly with chito-triosidase (ERT: r = 0.55, p < 0.001; SRT: r = 0.83, p < 0.001) and TRAP (ERT: r = 0.34, p < 0.001; SRT: r = 0.88, p < 0.001), irrespective of treatment method. A platelet count increase was associated with a Lyso-Gb1 decrease in both treatment groups (ERT: p = 0.021; SRT: p = 0.028). The association of Lyso-Gb1 with evaluated markers was stronger in the SRT cohort. Our results indicate that ERT and SRT in combination or in a switch manner could offer the potential of individual drug effectiveness for particular GD symptoms. Combination of the key biomarker of GD, Lyso-Gb1, with other biomarkers can offer improved response assessment to long-term therapy.

Contribution of Glucosylsphingosine (Lyso-Gb1) to Treatment Decisions in Patients with Gaucher Disease.

Glucosylsphingosine (lyso-Gb1), the deacylated form of glucocerebroside, was shown to be the most specific and sensitive biomarker for diagnosing Gaucher disease (GD). The aim of this study is to assess the contribution of lyso-Gb1 at the time of diagnosis for treatment decisions in naïve patients with GD. Newly diagnosed patients from July 2014 to November 2022 were included in this retrospective cohort study. The diagnosis was done by sending a dry blood spot (DBS) sample for GBA1 molecular sequencing and lyso-Gb1 quantification. Treatment decisions were based on symptoms, signs, and routine laboratory tests. We diagnosed 97 patients (41 males), both type 1 (n = 87), and neuronopathic (n = 10). The median (range) age at diagnosis was 22 (1-78), with 36 children. In 65 patients, GD-specific therapy was started with a median (range) lyso-Gb1, 337 (60-1340) ng/mL, significantly higher than in patients who did not go on to treatment, 153.5 (9-442) ng/mL. Using a receiver operating characteristic (ROC) analysis, a cutoff of lyso-Gb1 > 250 ng/mL was associated with treatment with a sensitivity of 71% and specificity of 87.5%. Predictors of treatment were thrombocytopenia, anemia, and elevated lyso-Gb1 (>250 ng/mL). In conclusion, lyso-Gb1 levels contribute to the medical decision related to the initiation of treatment, mainly among mildly affected newly diagnosed patients. For patients with a severe phenotype, as for all patients, the main value of lyso-Gb1 would be to monitor response to therapy. The variable methodology and differences in the units of lyso-Gb1 measurements between laboratories prevent the adaptation of the exact cut-off we found in general practice. However, the concept is that a significant elevation, i.e., a several-fold increase from the diagnostic lyso-Gb1 cutoff, is related to a more severe phenotype and, accordingly, to the decision regarding the initiation of GD-specific therapy.

Metabolomic Study Using Time-of-Flight Mass Spectrometry Reveals Novel Urinary Biomarkers for Gaucher Disease Type 1.

Gaucher disease (GD) is a lysosomal storage disorder resulting from a biallelic mutation in the gene GBA1, leading to deficiencies in the enzyme ß-glucocerebrosidase (Gcase). Inabilities of the Gcase to catabolize its substrate result in the accumulation of sphingolipids in macrophages, which impairs the cell functions and ultimately leads to multisystemic clinical manifestations. Important variability in symptoms and manifestations may lead to challenging diagnosis and patient care. Plasma glucosylsphingosine (lyso-Gb1) is a biomarker frequently used for prognosis, monitoring, and patient follow-up. While lyso-Gb1 appears to be a valid biomarker, few studies have investigated other matrices for potential GD biomarkers. The main objective of this study was to investigate the urine matrix as a potential source of new GD biomarkers by performing a metabolomic study using time-of-flight mass spectrometry. Our study highlighted a significant increase of eight urinary lyso-Gb1 analogues. Moreover, a novel class of biomarkers, named polycyclic lyso-Gb1 analogues, was identified. These four new molecules were more elevated than lyso-Gb1 and related analogues in urine specimens of GD patients. Further investigations are warranted to validate the efficiency of these newly found biomarkers on a larger cohort of Gaucher patients and to compare them with plasma biomarkers currently quantified in clinical laboratories.

HEPES-buffering of bicarbonate-containing culture medium perturbs lysosomal glucocerebrosidase activity.

Glucocerebrosidase (GCase), encoded by the GBA gene, degrades the ubiquitous glycosphingolipid glucosylceramide. Inherited GCase deficiency causes Gaucher disease (GD). In addition, carriers of an abnormal GBA allele are at increased risk for Parkinson's disease. GCase undergoes extensive modification of its four N-glycans en route to and inside the lysosome that is reflected in changes in molecular weight as detected with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fluorescent activity-based probes (ABPs) that covalently label GCase in reaction-based manner in vivo and in vitro allow sensitive visualization of GCase molecules. Using these ABPs, we studied the life cycle of GCase in cultured fibroblasts and macrophage-like RAW264.7 cells. Specific attention was paid to the impact of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) supplementation to bicarbonate-buffered medium. Here, we report how HEPES-buffered medium markedly influences processing of GCase, its lysosomal degradation, and the total cellular enzyme level. HEPES-containing medium was also found to reduce maturation of other lysosomal enzymes (α-glucosidase and ß-glucuronidase) in cells. The presence of HEPES in bicarbonate containing medium increases GCase activity in GD-patient derived fibroblasts, illustrating how the supplementation of HEPES complicates the use of cultured cells for diagnosing GD.

Abdominal lymphadenopathy in children with Gaucher disease: Relation to disease severity and glucosylsphingosine.

Few case reports and series reported abdominal lymphadenopathy (ALN) in people with Gaucher disease (GD). However, it's prevalence among Gaucher population, clinical implications and potential biomarkers are unknown. Hence this study aims to assess the prevalence of ALN among children with GD & to correlate it to neutrophil-lymphocytic-ratio (NLR), platelet-lymphocytic-ratio (PLR) and glucosylsphingosine (Lyso-GL1). Fifty children with GD (14 type-1 and 36 type-3) on enzyme-replacement therapy (ERT) were compared to 50 matched healthy controls, focusing on history of pressure manifestations by ALN (diarrhea, constipation, abdominal pain, intestinal obstruction), and history of splenectomy, with calculation of severity scoring index (SSI). NLR, PLR and Lyso-GL1 were measured. Abdominal-ultrasound was done with assessment of liver and spleen volumes and ALN. CT-scan was done for those having significant lymphadenopathy. Twenty-six children with GD had ALN (52%). The most common presentations were abdominal-pain (22%) & constipation (18%), with intestinal-obstruction in 3 children (6%). Children with GD had significantly higher NLR (p < .001) and decreased PLR (p = .024) compared to controls. Interestingly, children with GD having ALN had significantly higher SSI (.012), Lyso-GL1 (p = .002) and NLR (p = .001) than those without ALN. Multivariate-logistic regression showed that ALN was independently related to Lyso-GL1 (p = .027), NLR (p = .023) and SSI (p = .032). Thus, ALN is a prevalent GD morbidity with wide clinical-spectrum ranging from asymptomatic cases to intestinal obstruction. ALN is related to SSI, NLR and Lyso-GL1 in children with GD.HighlightsChildren with GD had significantly higher NLR and lower PLR compared to controls.Children with GD having ALN had significantly higher SSI, Lyso-GL1 and NLR than those without ALN.ALN was independently related to Lyso-GL1, NLR and SSI in children with GD.

Glucosylsphingosine (Lyso-Gb1): An Informative Biomarker in the Clinical Monitoring of Patients with Gaucher Disease.

Historically, disease burden and treatment responses in patients with Gaucher disease (GD) was assessed by monitoring clinical data, laboratory, imaging, chitotriosidase (CHITO), and other biomarkers; however, these biomarkers lack specificity and CHITO is uninformative in patients heterozygous or homozygous for the CHIT1 c.1049_1072dup24 variant. Recently, glucosylsphingosine (lyso-Gb1), a sensitive and specific GD biomarker, has been recommended for patient monitoring. Furthermore, studies measuring lyso-Gb1 and CHITO in patients on long-term treatment with enzyme replacement therapy (ERT) and/or substrate reduction therapy (SRT) reported as group data show a reduction in both analytes, yet individualized patient data are generally unavailable. We describe seven patients on long-term treatment with longitudinal clinical data with monitoring based on current treatment guidelines. We present four patients who exhibit stable disease with normalized CHITO despite elevated lyso-Gb1. We present one patient who transitioned from ERT to SRT due to lack of a clinical response with life-threatening thrombocytopenia who responded with marked improvement in platelets, and normalized levels of both CHITO and lyso-Gb1. Finally, we present two ERT to SRT switch patients with stable disease on ERT who exhibited non-compliance on SRT, one with mirrored marked elevations of CHITO and lyso-Gb1; and another with normal CHITO and platelets, but increasing lyso-Gb1 levels and enlarged spleen. These clinical vignettes highlight the role of lyso-Gb1 as a sensitive biomarker in management of patients with GD, and its further value when CHITO is normal and thus uninformative. We highlight the personalized medicine approach needed to optimize treatment outcomes and recommendations for these patients.

Gaucher Disease Diagnosis Using Lyso-Gb1 on Dry Blood Spot Samples: Time to Change the Paradigm?

For years, the gold standard for diagnosing Gaucher disease (GD) has been detecting reduced ß-glucocerebrosidase (GCase) activity in peripheral blood cells combined with GBA1 mutation analysis. The use of dried blood spot (DBS) specimens offers many advantages, including easy collection, the need for a small amount of blood, and simpler transportation. However, DBS has limitations for measuring GCase activity. In this paper, we recount our cross-sectional study and publish seven years of experience using DBS samples and levels of the deacylated form of glucocerebroside, glucosylsphingosine (lyso-Gb1), for GD diagnosis. Of 444 screened subjects, 99 (22.3%) were diagnosed with GD at a median (range) age of 21 (1-78) years. Lyso-Gb levels for genetically confirmed GD patients vs. subjects negative to GD diagnosis were 252 (9-1340) ng/mL and 5.4 (1.5-16) ng/mL, respectively. Patients diagnosed with GD1 and mild GBA1 variants had lower median (range) lyso-Gb1, 194 (9-1050), compared to GD1 and severe GBA1 variants, 447 (38-1340) ng/mL, and neuronopathic GD, 325 (116-1270) ng/mL (p = 0.001). Subjects with heterozygous GBA1 variants (carrier) had higher lyso-Gb1 levels, 5.8 (2.5-15.3) ng/mL, compared to wild-type GBA1, 4.9 (1.5-16), ng/mL (p = 0.001). Lyso-Gb1 levels, median (range), were 5 (2.7-10.7) in heterozygous GBA1 carriers with Parkinson's disease (PD), similar to lyso-Gb1 levels in subjects without PD. We call for a paradigm change for the diagnosis of GD based on lyso-Gb1 measurements and confirmatory GBA1 mutation analyses in DBS. Lyso-Gb1 levels could not be used to differentiate between heterozygous GBA1 carriers and wild type.

A new brain-penetrant glucosylceramide synthase inhibitor as potential Therapeutics for Gaucher disease.

Gaucher disease (GD), the most common lysosomal storage disorders, is caused by GBA gene mutations resulting in glycosphingolipids accumulations in various tissues, such as the brain. While suppressing glycosphingolipid accumulation is the central strategy for treating peripheral symptoms of GD, there is no effective treatment for the central nervous system symptoms. As glycosphingolipid biosynthesis starts from ceramide glycosylation by glucosylceramide synthase (GCS), inhibiting GCS in the brain is a promising strategy for neurological GD. Herein, we discovered T-036, a potent and brain-penetrant GCS inhibitor with a unique chemical structure and binding property. T-036 does not harbor an aliphatic amine moiety and has a noncompetitive inhibition mode to the substrates, unlike other known inhibitors. T-036 exhibited sufficient exposure and a significant reduction of glucosylsphingolipids in the plasma and brain of the GD mouse model. Therefore, T-036 could be a promising lead molecule for treating central nervous system symptoms of GD.

Impact of Long-Term Enzyme Replacement Therapy on Glucosylsphingosine (Lyso-Gb1) Values in Patients with Type 1 Gaucher Disease: Statistical Models for Comparing Three Enzymatic Formulations.

For three decades, enzyme replacement therapy (ERT), and more recently, substrate reduction therapy, have been the standard-of-care for type I Gaucher disease (GD1). Since 2012, three different ERTs have been available. No clinical trial or academic study has ever compared these ERTs beyond one year. Herein we compare the impact of the ERTs on repeated measurements of glucosylsphingosine (lyso-Gb1; the most sensitive and GD-specific biomarker). A total of 135 adult patients (77 (57%) female) with GD1, followed from July 2014 to March 2020 and treated with a single ERT (imiglucerase (n = 41, 30.4%), taliglucerase alfa (n = 21, 15.6%) and velaglucerase alfa (n = 73, 54.1%)), were included. Disease severity was defined by genotypes (mild: N370S (c.1226A>G) homozygous and N370S/R496H (c.1604G) compound heterozygous; severe: all other genotypes) and by the severity score index (SSI; mild: <7; severe: ≥7). Lyso-Gb1 testing was performed at Centogene™ on dry blood spot samples collected during routine visits. Patients treated with imiglucerase had higher lyso-Gb1 levels at different time points. A huge variation in lyso-Gb1 levels was noticeable both inter-individually and intra-individually for all three ERTs. A steeper and faster decrease of lyso-Gb1 levels was shown in velaglucerase alfa. Nevertheless, the differences between medications were not very large, and bigger numbers and more pretreatment data are required for more powerful conclusions.

Glucosylsphingosine but not Saposin C, is the target antigen in Gaucher disease-associated gammopathy.

In Gaucher disease type 1 (GD1), genetic deficiency of lysosomal glucocerebrosidase results in the accumulation of glucosylceramide and glucosylsphingosine (GlcSph), that underlie chronic lipid-mediated metabolic inflammation. An important age-related phenotype is high risk of monoclonal gammopathy (MG), including multiple myeloma. We identified GlcSph, a pathological lyso-sphingolipid exclusively elevated in GD, as a mediator of B cell activation and as an antigenic target for GD1-associated MG. Saposin C (SapC), is a lipid-binding protein and activator of lysosomal glucocerebrosidase, which when mutated, cause a rare variant of GD. Sera of GD1 patients with MG of diverse immunoglobulin types were compared to GD patients without gammopathy for reactivity against GlcSph and SapC. We show reactivity of clonal immunoglobulin in GD1 to GlcSph but not to SapC. In two patients with GD1 and gammopathy, GlcSph-reduction therapy with eliglustat resulted in reduction in clonal Ig. Together, our data show that GlcSph but not SapC is the antigenic target in GD1-associated MG and that therapy aimed at reducing the levels of immunogenic lipid resulted in reduction of clonal immunoglobulin in vivo.

Ganglion Cell Complex Thinning in Young Gaucher Patients: Relation to Prodromal Parkinsonian Markers.

BACKGROUND: Patients with Gaucher disease (GD) have an increased risk for parkinsonism. Retinal thinning has been described in parkinsonism as an early nonmotor feature. Scarce reports have addressed retinal thickness changes in GD. OBJECTIVES: The objectives of this study were to compare ganglion cell complex (GCC) thickness in adolescents and young adults (AYAs) with GD with healthy control subjects, and to correlate it with the presence of parkinsonian features (PFs), clinical prodromal markers of parkinsonism, severity score index (SSI), and glucosylsphingosine (Lyso-GL-1). METHODS: This study included 48 AYAs with GD (11-29 years), 11 with manifest PFs (Group 1) and 37 with no PFs (Group 2), and 48 matched healthy control subjects (Group 3). Age of GD onset, disease duration, medication history, history of constipation, SSI, and hematological assessment were done. Neurocognitive evaluation included Parts I, II, and III of the Unified Parkinson's Disease Rating Scale (UPDRS), Wechsler Adult and Intelligence Scale and Wechsler Intelligence Scale for Children, Beck Depression Inventory (BDI), rapid eye movement sleep behavior disorder (RBD) scale, Munich Parasomnia Screening scale, and the olfactory dysfunction scale. Molecular analyses of the acid GBA gene and Lyso-GL-1 were done. Participants underwent full ophthalmological examination and optical coherence tomography with GCC thickness measurement. RESULTS: GCC was significantly thinner in Group 1 than in Groups 2 and 3 (P < 0.001), whereas no significant difference was found between Groups 2 and 3 (P = 0.977). In addition, a significant interocular GCC thickness difference was found among the studied AYAs with GD (P = 0.007). GCC correlated positively with total intelligence quotient (P < 0.001) and negatively with Lyso-GL-1 (P = 0.019), UPDRS (P = 0.004), and BDI (P = 0.029), but not with SSI (P = 0.874), GD type (P = 0.85), or genotype (P = 0.842). A significant negative relationship was found between GCC thickness and PFs (P = 0.001), parasomnia (P = 0.003), constipation (P = 0.031), RBD (P = 0.044), and hyposmia (P = 0.033). CONCLUSIONS: GCC thinning may be a promising biomarker for central nervous system neurodegeneration that has the potential to monitor early PFs among people with GD. © 2020 International Parkinson and Movement Disorder Society.

Expanding the clinical utility of glucosylsphingosine for Gaucher disease.

Gaucher disease (GD) is an inherited metabolic disorder characterised by impaired catabolism of the glycosphingolipid, glucosylceramide. The deacetylated derivative, glucosylsphingosine (GluSph, lyso-Gb1) has materialised as a biomarker for GD. Further appraisal of the clinical utility of GluSph is required in terms of its prognostic power to inform disease course and pre-symptomatic testing. In this study, we show that plasma GluSph concentrations are significantly higher in GD patients with neuronopathic disease compared with non-neuronopathic disease, even in the neonatal period. A neonate diagnosed at 1 day of age (homozygous for N370S) due to an affected older sibling, returned GluSph of 70 nmol/L compared with 1070-2620 nmol/L for four neuronopathic patients diagnosed <20 days of age. Given this result shows promise for newborn screening, we developed a rapid, simple, and robust assay for GluSph in dried filter paper blood spots (DBS) and were able to detect 23 GD patients from 220 unaffected individuals. Neuronopathic GD patients also had significantly higher DBS concentrations of GluSph than their non-neuronopathic counterparts. We went on to measure GluSph in tissue extracts prepared from chorionic villus sampling and confirmed concentrations were undetectable in unaffected tissue but elevated in GD tissue demonstrating utility in the prenatal setting. Additionally, GluSph is a pharmacodynamic biomarker, revealing a precipitous drop following initiation of enzyme replacement therapy. In conclusion, GluSph is a reliable and specific biomarker for GD and shows promise for prenatal diagnosis and DBS screening programmes.

LC-MS/MS analysis of plasma glucosylsphingosine as a biomarker for diagnosis and follow-up monitoring in Gaucher disease in the Spanish population.

Background Gaucher disease (GD), caused by a deficiency in acid ß-glucosidase, leads to the accumulation of glucosylsphingosine (GluSph), which has been used as a powerful biomarker for the diagnosis and follow-up of GD. Our aim was to perform the first retrospective study of GluSph in Spanish patients, analyzing its relationship with classical biomarkers and other parameters of disease and its utility regarding treatment monitoring. Methods Classical biomarkers were evaluated retrospectively by standard methods in a total of 145 subjects, including 47 GD patients, carriers, healthy controls and patients suffering from other lysosomal lipidoses. GluSph was also measured using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method developed as part of the present study. Results The optimized method presented intra- and inter-assay variations of 3.1 and 11.5%, respectively, overall recovery higher than 96% and linearity up to plasma concentrations of 1000 ng/mL with 100% specificity and sensitivity. Only GD patients displayed GluSph levels above 5.4 ng/mL at diagnosis and this was significantly correlated with the classical biomarkers chitotriosidase (r = 0.560) and the chemokine CCL18/PARC (CCL18/PARC) (ρ = 0.515), as well as with the Spanish magnetic resonance imaging index (S-MRI, r = 0.364), whereas chitotriosidase correlated with liver volume (r = 0.372) and CCL18/PARC increased in patients with bone manifestations (p = 0.005). GluSph levels decreased with treatment in naïve patients. Conclusions Plasma GluSph is the most disease-specific biomarker for GD with demonstrated diagnostic value and responsiveness to therapy. GluSph in the present series of patients failed to demonstrate better correlations with clinical characteristics at onset than classical biomarkers.

Value of Glucosylsphingosine (Lyso-Gb1) as a Biomarker in Gaucher Disease: A Systematic Literature Review.

The challenges in the diagnosis, prognosis, and monitoring of Gaucher disease (GD), an autosomal recessive inborn error of glycosphingolipid metabolism, can negatively impact clinical outcomes. This systematic literature review evaluated the value of glucosylsphingosine (lyso-Gb1), as the most reliable biomarker currently available for the diagnosis, prognosis, and disease/treatment monitoring of patients with GD. Literature searches were conducted using MEDLINE, Embase, PubMed, ScienceOpen, Science.gov, Biological Abstracts, and Sci-Hub to identify original research articles relevant to lyso-Gb1 and GD published before March 2019. Seventy-four articles met the inclusion criteria, encompassing 56 related to pathology and 21 related to clinical biomarkers. Evidence for lyso-Gb1 as a pathogenic mediator of GD was unequivocal, although its precise role requires further elucidation. Lyso-Gb1 was deemed a statistically reliable diagnostic and pharmacodynamic biomarker in GD. Evidence supports lyso-Gb1 as a disease-monitoring biomarker for GD, and some evidence supports lyso-Gb1 as a prognostic biomarker, but further study is required. Lyso-Gb1 meets the criteria for a biomarker as it is easily accessible and reliably quantifiable in plasma and dried blood spots, enables the elucidation of GD molecular pathogenesis, is diagnostically valuable, and reflects therapeutic responses. Evidentiary standards appropriate for verifying inter-laboratory lyso-Gb1 concentrations in plasma and in other anatomical sites are needed.