Long- and Short-Term Glucosphingosine (lyso-Gb1) Dynamics in Gaucher Patients Undergoing Enzyme Replacement Therapy.

Background: Gaucher disease (GD) is a lysosomal storage disorder caused by mutations in the GBA1 gene, leading to ß-glucocerebrosidase deficiency and glucosylceramide accumulation. Methods: We analyzed short- and long-term dynamics of lyso-glucosylceramide (lyso-Gb1) in a large cohort of GD patients undergoing enzyme replacement therapy (ERT). Results: Eight-years analysis of lyso-Gb1 revealed statistically insignificant variability in the biomarker across the years and relatively high individual variability in patients' results. GD type 1 (GD1) patients exhibited higher variability compared to GD type 3 (GD3) patients (coefficients of variation: 34% and 23%, respectively; p-value = 0.0003). We also investigated the short-term response of the biomarker to enzyme replacement therapy (ERT), measuring lyso-Gb1 right before and 30 min after treatment administration. We tested 20 GD patients (16 GD1, 4 GD3) and observed a rapid and significant reduction in lyso-Gb1 levels (average decrease of 17%; p-value < 0.0001). This immediate response reaffirms the efficacy of ERT in reducing substrate accumulation in GD patients but, on the other hand, suggests the biomarker's instability between the infusions. Conclusions: These findings underscore lyso-Gb1's potential as a reliable biomarker for monitoring efficacy of treatment. However, individual variability and dry blood spot (DBS) testing limitations urge a further refinement in clinical application. Our study contributes valuable insights into GD patient management, emphasizing the evolving role of biomarkers in personalized medicine.

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.

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.

Real life data: follow-up assessment on Spanish Gaucher disease patients treated with eliglustat. TRAZELGA project.

BACKGROUND: The availability of multiple treatments for type 1 Gaucher disease increases the need for real-life studies to evaluate treatment efficacy and safety and provide clinicians with more information to choose the best personalized therapy for their patients. AIMS: To determine whether treatment with eliglustat produces, in adult GD1 patients, ans optimal response in daily clinical practice. METHODS: We designed a real-life study with 2 years of follow-up (TRAZELGA [GEE-ELI-2017-01]) to uniformly evaluate the response and adverse events to eliglustat treatment. This study, conducted in 30 patients across Spain and previously treated with other therapies, included the evaluation of safety and efficacy by assessing visceral enlargement, bone disease (DEXA and T and Z scores), concomitant treatments and adverse events, as well as a quality of life evaluation (SF-36). In addition, the quantification of classical biomarkers (chitotriosidase activity, CCL18/PARC and glucosylsphingosine (GluSph)) and new candidates for GD biomarkers (YKL-40, cathepsin S, hepcidin and lipocalin-2 determined by immunoassay) were also assessed. Non-parametric statistical analysis was performed and p < 0.05 was considered statistically significant. MAIN RESULTS: Thirty patients were enrolled in the study. The median age was 41.5 years and the male-female ratio was 1.1:1. 84% of the patients had received ERT and 16% SRT as previous treatment. The most common symptoms at baseline were fatigue (42%) and bone pain (38%), no patient had a bone crisis during the study, and two years after switching, 37% had reduced their use of analgesics. Patient-reported outcomes showed a significant increase in physical function scores (p = 0.027) and physical pain scores (p = 0.010). None of the enrolled patients discontinued treatment due to adverse events, which were mild and transient in nature, mainly gastrointestinal and skin dryness. None of the biomarkers show a significant increase or decompensation after switching. CCL18/PARC (p = 0.0012), YKL-40 (p = 0.00004) and lipocalin-2 (p = 0.0155) improved after two years and GluSph after one year (p = 0.0008) and two years (p = 0.0245) of oral therapy. CONCLUSION: In summary, this real-life study, showed that eliglustat maintains stability and can improve quality of life with few side effects. Significant reductions in classic and other novel biomarkers were observed after two years of therapy.

Quantitation and characterization of glucosylsphingosine in cerebrospinal fluid (CSF), plasma, and brain of monkey model with Gaucher disease.

Treatment with conduritol-ß-epoxide (CBE) in preclinical species is expected to be a powerful approach to generate animal models of Gaucher disease (GD) and Parkinson's disease associated with heterozygous mutations in Glucocerebrosidase (GBA-PD). However, it is not fully elucidated how quantitatively the change in glucosylsphingosine (GlcSph) levels in cerebrospinal fluid (CSF) correlates with that in the brain, which is expected to be clinically informative. Herein, we aimed to investigate the correlation with successfully quantified GlcSph in monkey CSF by developing highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. The GlcSph in normal monkey CSF was 0.635 ± 0.177 pg/mL at baseline and increased by CBE treatment at 3 mg/kg daily for five days up to a moderate level, comparable to that in GD patients. The balance between GlcSph and galactosylsphingosine (GalSph) in the CSF matched that in the brain rather than plasma. In addition, GlcSph in the CSF was increased, accompanied by that in the brain at a dose of 3 mg/kg daily. These results indicate that GlcSph in the CSF is worth evaluating for concentration changes in the brain. Thus, this model can be useful for evaluating GBA-related diseases such as GD and GBA-PD.

Determination of the target of monoclonal immunoglobulins: a novel diagnostic tool for individualized MGUS therapy, and prevention and therapy of smoldering and multiple myeloma.

Subsets of patients diagnosed with a monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM) or multiple myeloma (MM), present with a monoclonal immunoglobulin (Ig) specific for an infectious pathogen, including hepatitis C and B viruses (HCV, HBV), Helicobacter pylori and several Herpesviruses. Such cases are likely initiated by infection, since in the context of HCV- or HBV-infected patients, antiviral therapy can lead to the disappearance of antigenic stimulation, control of clonal plasma cells, and reduced or suppressed monoclonal Ig production. Complete remission has been obtained with anti-HCV therapy in refractory MM with a HCV-specific monoclonal Ig, and antiviral treatments significantly improved the probability of survival of MM patients infected with HCV or HBV prior to the diagnosis of MM. Monoclonal Igs may also target glucolipids, particularly glucosylsphingosine (GlcSph), and GlcSph-reducing therapy can lead to complete remission in SMM and MM patients presenting with a GlcSph-specific monoclonal Ig. The present review describes the importance of determining the target of the monoclonal Ig of MGUS, SMM and MM patients, and discusses the efficacy of target-reducing treatments in the management of MGUS, SMM and MM cases who present with a monoclonal Ig reactive against a treatable infectious pathogen or GlcSph.

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.

Insights into the Value of Lyso-Gb1 as a Predictive Biomarker in Treatment-Naïve Patients with Gaucher Disease Type 1 in the LYSO-PROOF Study.

Gaucher disease (GD) is a rare autosomal recessive disorder arising from bi-allelic variants in the GBA1 gene, encoding glucocerebrosidase. Deficiency of this enzyme leads to progressive accumulation of the sphingolipid glucosylsphingosine (lyso-Gb1). The international, multicenter, observational "Lyso-Gb1 as a Long-term Prognostic Biomarker in Gaucher Disease"-LYSO-PROOF study succeeded in enrolling a cohort of 160 treatment-naïve GD patients from diverse geographic regions and evaluated the potential of lyso-Gb1 as a specific biomarker for GD. Using genotypes based on established classifications for clinical presentation, patients were stratified into type 1 GD (n = 114) and further subdivided into mild (n = 66) and severe type 1 GD (n = 48). Due to having previously unreported genotypes, 46 patients could not be classified. Though lyso-Gb1 values at enrollment were widely distributed, they displayed a moderate and statistically highly significant correlation with disease severity measured by the GD-DS3 scoring system in all GD patients (r = 0.602, p < 0.0001). These findings support the utility of lyso-Gb1 as a sensitive biomarker for GD and indicate that it could help to predict the clinical course of patients with undescribed genotypes to improve personalized care in the future.

Effectiveness and Safety of Eliglustat Treatment in Gaucher Disease: Real-life Unicentric Experience.

PURPOSE: The therapy and management of Gaucher disease (GD) have radically changed with the use of substrate reduction therapy, of which eliglustat is the most widely known drug, allowing it to overcome the limits of enzyme replacement therapy (ERT). The rarity of GD and the limited use of eliglustat outside clinical trials require further study of its strengths and weaknesses. METHODS: In this study, we evaluated the effectiveness and safety of eliglustat in a cohort of 12 patients with GD followed up in our center, reporting a reduction in both chitotriosidase (394.3 vs 181.1 nmol/h/mL, P = 0.027) and glucosylsphingosine values (45.1 vs 18.9 ng/mL, P <0.001) after at least 12 months of therapy compared with baseline, regardless of patient demographic characteristics and GD characteristics. FINDINGS: There were no drug-related serious adverse effects and no drug-related cardiac events. Most adverse events were mild and transient, mainly dyspepsia and abdominal pain. Of interest, we reported an absence of statistical difference in terms of response regarding glucosylsphingosine reduction in relation to naive or prior exposure to ERT (P = 0.296), which was confirmed also when patients were placed in naive and treated groups for <5 vs >5 years (P = 0.667). IMPLICATIONS: The use of eliglustat immediately after diagnosis may guarantee the best treatment for patients with milder phenotypes or with aggressive disease after an initial stabilization with ERT compared with ERT, which cannot adequately remove the disease burden despite the apparent response, thus potentially reducing future complications caused by substrate deposits.

A new multiplex analysis of glucosylsphingosine and globotriaosylsphingosine in dried blood spots by tandem mass spectrometry.

Background: Gaucher's and Fabry's disease are two of the most common treatable lysosomal storage diseases, and have a wide spectrum of clinical symptoms. Early detection is important, because timely initiation of treatments can improve the disease status and prevent complications. However disease manifestations develop in childhood, diagnosis is delayed until adulthood partly due to the limitations of the currently used diagnostic pathway. The aim of this research is to develop and validate a multiplex assay and defining reference ranges, which do not exist at this moment, to improve and facilitate the entire diagnostic work up and enable treatment in an earlier stage of disease. Methods and findings: Biomarkers glucosylsphingosine (GlcSph) and globotriaosylsphingosine (Lyso-Gb3) were detected and quantified using LC-MS/MS on dried blood spots. We developed an improved and new extraction method that allowed to measure GlcSph and Lyso-Gb3 in a multiplex analytical platform. After validation of the method, samples of 1480 individuals with normal enzymatic activity were collected to determine age and gender-related reference ranges.Our combination method showed a good linearity, precision, accuracy and limit of quantification with lack of carry-over following the specific international CLSI guidelines. The suggested protocol is robust, efficient, sensitive, specific, comprehensive and relatively cheap in order to accelerate the diagnostic process for both lysosomal storage diseases. The samples, with normal enzymatic activity, defined statistical relevant and clinical correct reference ranges for each specific age group by gender. Conclusion: We report a multiplex LC-MS/MS method and relevant reference ranges that are appropriate for the targeted screening, diagnosis and follow-up of Fabry and Gaucher disease.

Alpha-Synuclein mRNA Level Found Dependent on L444P Variant in Carriers and Gaucher Disease Patients on Enzyme Replacement Therapy.

Gaucher disease (GD) is the most frequent sphingolipidosis, caused by biallelic pathogenic variants in the GBA1 gene encoding for ß-glucocerebrosidase (GCase, E.C. 3.2.1.45). The condition is characterized by hepatosplenomegaly, hematological abnormalities, and bone disease in both non-neuronopathic type 1 (GD1) and neuronopathic type 3 (GD3). Interestingly, GBA1 variants were found to be one of the most important risk factors for the development of Parkinson's disease (PD) in GD1 patients. We performed a comprehensive study regarding the two most disease-specific biomarkers, glucosylsphingosine (Lyso-Gb1) and α-synuclein for GD and PD, respectively. A total of 65 patients with GD treated with ERT (47 GD1 patients and 18 GD3 patients), 19 GBA1 pathogenic variant carriers (including 10 L444P carriers), and 16 healthy subjects were involved in the study. Lyso-Gb1 was assessed by dried blood spot testing. The level of α-synuclein as an mRNA transcript, total, and oligomer protein concentration were measured with real-time PCR and ELISA, respectively. α-synuclein mRNA level was found significantly elevated in GD3 patients and L444P carriers. GD1 patients, along with GBA1 carriers of an unknown or unconfirmed variant, as well as healthy controls, have the same low level of α-synuclein mRNA. There was no correlation found between the level of α-synuclein mRNA and age in GD patients treated with ERT, whereas there was a positive correlation in L444P carriers.

Osteonecrosis in Gaucher disease in the era of multiple therapies: Biomarker set for risk stratification from a tertiary referral center.

Background: A salutary effect of treatments for Gaucher disease (GD) has been a reduction in the incidence of avascular osteonecrosis (AVN). However, there are reports of AVN in patients receiving enzyme replacement therapy (ERT) , and it is not known whether it is related to individual treatments, GBA genotypes, phenotypes, biomarkers of residual disease activity, or anti-drug antibodies. Prompted by development of AVN in several patients receiving ERT, we aimed to delineate the determinants of AVN in patients receiving ERT or eliglustat substrate reduction therapy (SRT) during 20 years in a tertiary referral center. Methods: Longitudinal follow-ups of 155 GD patients between 2001 and 2021 were analyzed for episodes of AVN on therapy, type of therapy, GBA1 genotype, spleen status, biomarkers, and other disease indicators. We applied mixed-effects logistic model to delineate the independent correlates of AVN while receiving treatment. Results: The patients received cumulative 1382 years of treatment. There were 16 episodes of AVN in 14 patients, with two episodes, each occurring in two patients. Heteroallelic p.Asn409Ser GD1 patients were 10 times (95% CI, 1.5-67.2) more likely than p.Asn409Ser homozygous patients to develop osteonecrosis during treatment. History of AVN prior to treatment initiation was associated with 4.8-fold increased risk of AVN on treatment (95% CI, 1.5-15.2). The risk of AVN among patients receiving velaglucerase ERT was 4.68 times higher compared to patients receiving imiglucerase ERT (95% CI, 1.67-13). No patient receiving eliglustat SRT suffered AVN. There was a significant correlation between GlcSph levels and AVN. Together, these biomarkers reliably predicted risk of AVN during therapy (ROC AUC 0.894, p<0.001). Conclusions: There is a low, but significant risk of AVN in GD in the era of ERT/SRT. We found that increased risk of AVN was related to GBA genotype, history of AVN prior to treatment initiation, residual serum GlcSph level, and the type of ERT. No patient receiving SRT developed AVN. These findings exemplify a new approach to biomarker applications in a rare inborn error of metabolism to evaluate clinical outcomes in comprehensively followed patients and will aid identification of GD patients at higher risk of AVN who will benefit from closer monitoring and treatment optimization. Funding: LSD Training Fellowship from Sanofi to MB.

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.

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.

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.

Glucosylsphingosine (Lyso-Gb1) as a reliable biomarker in Gaucher disease: a narrative review.

BACKGROUND: Gaucher disease (GD) is a rare, inherited, autosomal recessive disorder caused by a deficiency of the lysosomal enzyme, acid ß-glucosidase. Its diagnosis is achieved via measurements of acid ß-glucosidase activity in either fresh peripheral blood leukocytes or dried blood spots, and confirmed by identifying characteristic mutations in the GBA1 gene. Currently, several biomarkers are available for disease monitoring. Chitotriosidase has been used over the last 20 years to assess the severity of GD, but lacks specificity in GD patients. Conversely, the deacylated form of glucosylceramide, glucosylsphingosine (also known as lyso-Gb1), represents a more reliable biomarker characterized by its high sensitivity and specificity in GD. MAIN TEXT: Herein, we review the current literature on lyso-Gb1 and describe evidence supporting its usefulness as a biomarker for diagnosing and evaluating disease severity in GD and monitoring treatment efficacy. CONCLUSION: Lyso-Gb1 is the most promising biomarker of GD, as demonstrated by its reliability in reflecting disease burden and monitoring treatment response. Furthermore, lyso-Gb1 may play an important role in the onset of monoclonal gammopathy of uncertain significance, multiple myeloma, and Parkinson's disease in GD patients.

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.

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.

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.

An observational study to investigate the relationship between plasma glucosylsphingosine (lyso-Gb1) concentration and treatment outcomes of patients with Gaucher disease in Japan.

BACKGROUND: Gaucher disease (GD) is an autosomal recessive disease caused by GBA1 mutations resulting in glucosylceramide accumulation in macrophages. GD is characterized by hepatosplenomegaly, anemia, thrombocytopenia, bone complications, and neurological complications. Glucosylsphingosine (lyso-Gb1), a deacylated form of glucosylceramide, has been identified as a promising biomarker for the diagnosis and treatment response in GD. The aim of this study was to examine the relationship between plasma lyso-Gb1 and therapeutic goals for GD (improvements in hepatomegaly, splenomegaly, anemia, thrombocytopenia, bone pain, and bone crisis), as well as disease type and GBA1 mutation type, in Japanese patients with GD receiving velaglucerase alfa, an enzyme replacement therapy (ERT). Furthermore, this study compared the plasma lyso-Gb1 concentration observed in Japanese patients included in this study with that observed in a previous non-Japanese clinical study. RESULTS: This non-interventional, open-label, multicenter observational cohort study (October 2020 to March 2021) included a total of 20 patients (of any age) with GD (type 1: n = 8; type 2: n = 9; type 3: n = 3) treated with velaglucerase alfa for ≥ 3 months. Median (minimum-maximum) duration of velaglucerase alfa treatment was 49.5 (3-107) months. A total of 14 (70.0%) patients achieved all therapeutic goals (i.e., 100% achievement; improvements in hepatomegaly, splenomegaly, anemia, thrombocytopenia, bone pain, and bone crisis). Overall, median (minimum-maximum) lyso-Gb1 concentration was 24.3 (2.1-150) ng/mL. Although not statistically significant, numerically lower plasma lyso-Gb1 concentrations were observed in patients with 100% achievement compared with those without; no statistically significant difference in plasma lyso-Gb1 concentration was observed between patients with different disease type or mutation type. Furthermore, lyso-Gb1 concentrations observed in Japanese patients were numerically lower than that observed in a previous study of non-Japanese patients with GD receiving ERT. CONCLUSIONS: In this study, high achievement rates of therapeutic goals with low lyso-Gb1 concentration were observed, demonstrating a correlation between therapeutic goals and lower plasma lyso-Gb1 concentration in Japanese patients with GD treated with velaglucerase alfa. This study further suggests that plasma lyso-Gb1 concentration may be a useful biomarker for treatment response in patients with GD.