Analysis of Globotriaosylceramide (Gb3) in Liquid Urine: A Straightforward Assay Using Tandem Mass Spectrometry.

Fabry disease (FD) is a lysosomal storage disorder caused by variants in the GLA gene encoding α-galactosidase A, an enzyme required for catabolism of globotriaosylceramide (Gb3). Accumulation of Gb3 in patients' cells, tissues, and biological fluids causes clinical manifestations including ventricular hypertrophy, renal insufficiency, and strokes. This protocol describes a methodology to analyze urinary Gb3 and creatinine. Samples are diluted with an internal standard solution containing Gb3(C17:0) and creatinine-D3, centrifuged, and directly analyzed by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) using an 8.7-min method. Eight Gb3 isoforms [C16:0, C18:0, C20:0, C22:1, C22:0, C24:1, C24:0, and (C24:0)OH] are analyzed and the total is normalized to creatinine. Confirmation ions are monitored to detect potential interferences. The Gb3 limit of quantification is 0.023 µg/ml. Its interday coefficients of variation (3 concentrations measured) are ≤15.4%. This method minimizes matrix effects (≤6.5%) and prevents adsorption or precipitation of Gb3. Urine samples are stable (bias <15%) for 2 days at 21°C, 7 days at 4°C, and 4 freeze/thaw cycles, whereas prepared samples are stable for 5 days at 21°C, and 14 days at 4°C. The Gb3/creatinine age-related upper reference limits (mean + 2 standard deviations) are 29 mg/mol creatinine (<7 years) and 14 mg/mol creatinine (≥7 years). This simple, robust protocol has been fully validated (ISO 15189) and provides a valuable tool for diagnosis and monitoring of FD patients. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Analysis of urinary globotriaosylceramide (Gb3) and creatinine by UHPLC-MS/MS Support Protocol 1: Preparation of the urinary quality controls Support Protocol 2: Preparation of the urine matrix used for the Gb3 calibration curve Support Protocol 3: Preparation of the Gb3 calibrators Support Protocol 4: Preparation of the working solution containing the internal standards Support Protocol 5: Preparation of the creatinine calibrators Support Protocol 6: Preparation of the UHPLC solutions and mobile phases.

Effects of switching from agalsidase-α to agalsidase-ß on biomarkers, renal and cardiac parameters, and disease severity in fabry disease forming neutralizing antidrug antibodies: a case report.

Fabry disease is an X-linked hereditary disorder caused by deficient α-galactosidase A (GLA) activity. Patients with Fabry disease are often treated with enzyme replacement therapy (ERT). However, ERT often induces the formation of neutralizing antidrug antibodies (ADAs), which may impair the therapeutic efficacy. Here, we report the case of a 32-year-old man with Fabry disease and resultant neutralizing ADAs who was treated by switching from agalsidase-α to agalsidase-ß. We monitored biomarkers, such as plasma globotriaosylsphingosine (lyso-Gb3), urinary globotriaosylceramide (Gb3), urinary mulberry bodies, renal and cardiac parameters, and disease severity during the treatment period. Although plasma lyso-Gb3 and urinary Gb3 levels quickly decreased within two months after the initiation of ERT with agalsidase-α, they gradually increased thereafter. The urinary mulberry bodies continued to appear. Both the ADA titer and serum mediated GLA inhibition rates started to increase after two months. Moreover, 3.5 years after ERT, the vacuolated podocyte area in the renal biopsy decreased slightly from 23.1 to 18.9%. However, plasma lyso-Gb3 levels increased, and urinary Gb3, mulberry body levels, and ADA titers remained high. Therefore, we switched to agalsidase-ß which reduced, but did not normalize, plasma lyso-Gb3 levels and stabilized renal and cardiac parameters. Disease severity was attenuated. However, urinary Gb3 and mulberry body levels did not decrease noticeably in the presence of high ADA titers. The kidneys take up a small amount of the administered recombinant enzyme, and the clearance of Gb3 that has accumulated in the kidney may be limited despite the switching from agalsidase-α to agalsidase-ß.

An antibody binding-based fluorescent assay for the rapid quantification of globotriaosylceramide levels in human Fabry cells.

Fabry disease is caused by reduced α-GAL A activity and accumulation of globotriaosylceramide (Gb3). Here, we describe a microplate Gb3 assay using fluorophore-tagged antibody and crude cellular lipid extracts. The assay is able to detect higher Gb3 concentrations in human Fabry cells compared to non-diseased cells. This result was verified by immunofluorescence staining that revealed large amounts of Gb3 deposits in Fabry cell lines, demonstrating the accuracy of this method. This assay may provide the basis for detecting Fabry disease by quantifying Gb3 deposits from human biological samples, for example, from urine and blood.

Lentivirus-mediated gene therapy for Fabry disease.

Enzyme and chaperone therapies are used to treat Fabry disease. Such treatments are expensive and require intrusive biweekly infusions; they are also not particularly efficacious. In this pilot, single-arm study (NCT02800070), five adult males with Type 1 (classical) phenotype Fabry disease were infused with autologous lentivirus-transduced, CD34+-selected, hematopoietic stem/progenitor cells engineered to express alpha-galactosidase A (α-gal A). Safety and toxicity are the primary endpoints. The non-myeloablative preparative regimen consisted of intravenous melphalan. No serious adverse events (AEs) are attributable to the investigational product. All patients produced α-gal A to near normal levels within one week. Vector is detected in peripheral blood and bone marrow cells, plasma and leukocytes demonstrate α-gal A activity within or above the reference range, and reductions in plasma and urine globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) are seen. While the study and evaluations are still ongoing, the first patient is nearly three years post-infusion. Three patients have elected to discontinue enzyme therapy.

Diurnal Variation of Urinary Fabry Disease Biomarkers during Enzyme Replacement Therapy Cycles.

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene encoding the α-galactosidase A enzyme. This enzyme cleaves the last sugar unit of glycosphingolipids, including globotriaosylceramide (Gb3), globotriaosylsphingosine (lyso-Gb3), and galabiosylceramide (Ga2). Enzyme impairment leads to substrate accumulation in different organs, vascular endothelia, and biological fluids. Enzyme replacement therapy (ERT) is a commonly used treatment. Urinary analysis of Gb3 isoforms (different fatty acid moieties), as well as lyso-Gb3 and its analogues, is a reliable way to monitor treatment. These analogues correspond to lyso-Gb3 with chemical modifications on the sphingosine moiety (-C2H4, -C2H4+O, -H2, -H2+O, +O, +H2O2, and +H2O3). The effects of sample collection time on urinary biomarker levels between ERT cycles were not previously documented. The main objective of this project was to analyze the aforementioned biomarkers in urine samples from seven Fabry disease patients (three treated males, three treated females, and one ERT-naïve male) collected twice a day (morning and evening) for 42 days (three ERT cycles). Except for one participant, our results show that the biomarker levels were generally more elevated in the evening. However, there was less variability in samples collected in the morning. No cyclic variations in biomarker levels were observed between ERT infusions.

High-risk screening for Fabry disease in a Canadian cohort of chronic kidney disease patients.

BACKGROUND: Fabry disease is an X-linked lysosomal storage disorder with a highly heterogeneous clinical presentation. This complex disease is caused by a deficient activity of the enzyme α-galactosidase A, which is involved in the catabolism of glycosphingolipids. The prevalence of Fabry disease is underestimated, due to the presence of atypical variants. High-risk screening protocols are particularly relevant for this disease due to the availability of treatments, such as enzyme replacement and chaperone therapies. As kidney manifestations are present in the majority of male and many female patients with Fabry disease, a high-risk screening protocol was performed for patients with chronic kidney disease of unknown etiology. METHODS: Recruitment of 397 participants took place in four centers across Canada from 2011 to 2017. Globotriaosylceramide (Gb3) was analyzed in dried urine spots by liquid chromatography/tandem mass spectrometry followed by globotriaosylsphingosine (lyso-Gb3) on the repeat analysis. RESULTS: The collection and shipment of urine specimens on filter paper resulted in easier handling/shipment and significant cost-saving. No Fabry patients were detected in this study. CONCLUSIONS: Increased concentrations of urinary Gb3 were observed in 13.6% of patients with chronic kidney disease suggesting that chronic kidney disease or other comorbidities might be associated with increased urinary Gb3 concentrations.

Early Biomarkers of Fabry Nephropathy: A Review of the Literature.

Progressive nephropathy is one of the main features of Fabry disease. Although some clinical signs of Fabry nephropathy are already present in childhood, patients are often diagnosed relatively late in the course of the disease due to the absence of specific clinical markers, while a timely diagnosis and the prompt start of enzyme replacement therapy may be beneficial in stabilizing renal function or slowing its decline. Proteinuria/albuminuria has been accepted as the most important marker for Fabry nephropathy; however, a large proportion of renal impairment occurs in nonalbuminuric state. Therefore, early biomarkers may be useful for early identification of kidney involvement. The aim of this article is to review the current available literature on all biomarkers of Fabry nephropathy, with a comprehensive and critical description of their utilization in early recognition of renal damage.

The effect of enzyme replacement therapy on clinical outcomes in female patients with Fabry disease - A systematic literature review by a European panel of experts.

BACKGROUND: Heterozygous females with Fabry disease have a wide range of clinical phenotypes depending on the nature of their mutation and their X-chromosome inactivation pattern; it is therefore important to examine outcomes of enzyme replacement therapy (ERT) in the female patient population specifically. This paper presents the findings of a systematic literature review of treatment outcomes with ERT in adult female patients. METHODS: A comprehensive systematic literature review was conducted through January 2017 to retrieve published papers with original data on ERT in the treatment of Fabry disease. The review included all original articles that presented ERT outcomes data on patients with Fabry disease, irrespective of the study type. RESULTS: Clinical evidence for the efficacy of ERT in female patients was available from 67 publications including six clinical trial publications, and indicates significant reductions in plasma and urine globotriaosylceramide (GL-3) accumulation (in female patients with elevated pre-treatment levels) and improvements in cardiac parameters and quality of life (QoL). To date, data are insufficient to conclude on the effects of ERT on the nervous system, gastrointestinal manifestations, and pain in female patients with Fabry disease. CONCLUSIONS: This review of available literature data demonstrates that ERT in adult female patients with Fabry disease has a beneficial effect on GL-3 levels and cardiac outcomes. The current evidence also suggests that ERT may improve QoL in this patient population, though further studies are needed to examine these results.

Investigation of correlation of urinary globotriaosylceramide (Gb3) levels with markers of renal function in patients with Fabry disease.

Fabry disease (FD) is a disorder that results from mutations of hydrolase α-galactosidase A. The enzymatic defect leads to accumulation of globotriaosylceramide (Gb3) in the kidney. Substrate deposition is related to tissue damage in FD, but the relation of urinary Gb3 levels in patients and the renal function markers remain not completely understood. Once nephropathy is one of the main features of FD and is marked by an insidious development, we investigated a possible correlation of Gb3 with biochemical markers of nephropathy including albuminuria, estimated glomerular filtration rate (eGFR), serum creatinine and urea, and proteinuria in male and female patients under or not enzyme replacement therapy (ERT).Gb3, proteinuria and albuminuria were increased in male and female FD patients. We found no correlation between urinary Gb3 levels and all renal function parameters evaluated in Fabry patients (in both sexes and using or not ERT). On the other hand, albuminuria showed negative correlation with eGFR only in male under or not ERT, demonstrating that albuminuria seems to be an early marker of renal function alteration. In conclusion, the results suggest that urinary Gb3 level does not reflect the renal function and that albuminuria is an important biomarker in male FD patients.

Separation and Analysis of Lactosylceramide, Galabiosylceramide, and Globotriaosylceramide by LC-MS/MS in Urine of Fabry Disease Patients.

Fabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase A (α-GAL A) deficiency. This enzyme contributes to the cellular recycling of glycosphingolipids such as galabiosylceramide (Ga2), globotriaosylceramide (Gb3), and globotriaosylsphingosine (lyso-Gb3) by hydrolyzing the terminal α-galactosyl moiety. Urine and plasma α-GAL A substrates are currently analyzed as biomarkers for the detection, monitoring, and follow-up of Fabry disease patients. The sensitivity of the analysis of Ga2 is decreased by the co-analysis of its structural isomer, lactosylceramide (LacCer), which is not an α-GAL A substrate. A normal-phase ultraperformance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) methodology, allowing the baseline separation of 12 Ga2 isoforms/analogues from their lactosylceramide counterparts, was developed and validated in urine. The method was multiplexed with the analysis of 12 Gb3 isoforms/analogues having the same fatty acid moieties as those of Ga2 for comparison, and with creatinine for sample normalization. Urine samples were studied from 34 untreated and 33 Fabry males treated by enzyme replacement therapy (ERT) and 54 untreated and 19 ERT-treated Fabry females, along with 34 male and 25 female healthy controls. The chromatographic separation of Ga2 from LacCer increased the sensitivity of analysis, especially in women. One untreated Fabry female and two treated Fabry females presented abnormal levels of Ga2 but normal levels of Gb3, supporting the importance of analyzing Ga2, in addition to Gb3. Our results show that urine LacCer levels from females were significantly higher than those from males. Moreover, LacCer levels were not affected by Fabry disease for both males and females.

High-Risk Screening for Fabry Disease: Analysis by Tandem Mass Spectrometry of Globotriaosylceramide (Gb3 ) in Urine Collected on Filter Paper.

Fabry disease is a complex, panethnic lysosomal storage disorder. It is characterized by the accumulation of glycosphingolipids in tissues, organs, the vascular endothelium, and biological fluids. The reported incidence in different populations is quite variable, ranging from 1:1400 to 1:117,000. Its complexity lies in the marked genotypic and phenotypic heterogeneity. Despite the fact that it is an X-linked disease, more than 600 mutations affect both males and females. In fact, some females may be affected as severely as males. The purpose of this protocol is to focus on the high-risk screening of patients who might have Fabry disease using a simple, rapid, non-invasive high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for urinary globotriaosylceramide (Gb3 ) analysis. Urine filter paper samples are easily collected at home by patients and sent by regular mail. This method has been successfully used for high-risk screening of patients with ophthalmologic manifestations and in an on-going study for high-risk screening of Fabry disease in patients with chronic kidney diseases. © 2017 by John Wiley & Sons, Inc.

High-Risk Screening of Fabry Disease: Analysis of Fifteen Urinary Methylated and Non-Methylated Gb3 Isoforms Using Tandem Mass Spectrometry.

Fabry disease is a multisystemic, X-linked lysosomal storage disorder caused by mutations in the GLA gene, leading to α-galactosidase A deficiency and resulting in the accumulation of glycosphingolipids in different tissues and biological fluids. Glycosphingolipid biomarkers, such as globotriaosylceramide (Gb3 ) isoforms, globotriaosylsphingosine (lyso-Gb3 ) and related analogs, and galabiosylceramide (Ga2 ) isoforms and analogs, are found to be abnormally increased in urine and in plasma of Fabry patients and have the potential to be used as specific biomarkers of the disease. This unit presents a protocol for the relative quantification of fifteen urinary isoforms of Gb3 analyzed simultaneously with creatinine by ultra-performance liquid chromatography (UPLC) coupled to tandem mass spectrometry (MS/MS). In order to purify urine samples, a liquid-liquid extraction is performed and samples are analyzed by MS/MS in positive electrospray ionization mode. These biomarkers are useful for screening, diagnosis, and long-term monitoring of Fabry disease patients. We have shown that the methylated Gb3 isoforms are particularly useful for screening Fabry patients who present with late-onset cardiac variant mutations. © 2016 by John Wiley & Sons, Inc.

Treatment of Fabry's Disease with the Pharmacologic Chaperone Migalastat.

BACKGROUND: Fabry's disease, an X-linked disorder of lysosomal α-galactosidase deficiency, leads to substrate accumulation in multiple organs. Migalastat, an oral pharmacologic chaperone, stabilizes specific mutant forms of α-galactosidase, increasing enzyme trafficking to lysosomes. METHODS: The initial assay of mutant α-galactosidase forms that we used to categorize 67 patients with Fabry's disease for randomization to 6 months of double-blind migalastat or placebo (stage 1), followed by open-label migalastat from 6 to 12 months (stage 2) plus an additional year, had certain limitations. Before unblinding, a new, validated assay showed that 50 of the 67 participants had mutant α-galactosidase forms suitable for targeting by migalastat. The primary end point was the percentage of patients who had a response (≥50% reduction in the number of globotriaosylceramide inclusions per kidney interstitial capillary) at 6 months. We assessed safety along with disease substrates and renal, cardiovascular, and patient-reported outcomes. RESULTS: The primary end-point analysis, involving patients with mutant α-galactosidase forms that were suitable or not suitable for migalastat therapy, did not show a significant treatment effect: 13 of 32 patients (41%) who received migalastat and 9 of 32 patients (28%) who received placebo had a response at 6 months (P=0.30). Among patients with suitable mutant α-galactosidase who received migalastat for up to 24 months, the annualized changes from baseline in the estimated glomerular filtration rate (GFR) and measured GFR were -0.30±0.66 and -1.51±1.33 ml per minute per 1.73 m(2) of body-surface area, respectively. The left-ventricular-mass index decreased significantly from baseline (-7.7 g per square meter; 95% confidence interval [CI], -15.4 to -0.01), particularly when left ventricular hypertrophy was present (-18.6 g per square meter; 95% CI, -38.2 to 1.0). The severity of diarrhea, reflux, and indigestion decreased. CONCLUSIONS: Among all randomly assigned patients (with mutant α-galactosidase forms that were suitable or not suitable for migalastat therapy), the percentage of patients who had a response at 6 months did not differ significantly between the migalastat group and the placebo group. (Funded by Amicus Therapeutics; ClinicalTrials.gov numbers, NCT00925301 [study AT1001-011] and NCT01458119 [study AT1001-041].).

Screening for Fabry Disease by Urinary Globotriaosylceramide Isoforms Measurement in Patients with Left Ventricular Hypertrophy.

BACKGROUND: Left ventricular hypertrophy (LVH) is a frequent echocardiographic feature in Fabry disease (FD) and in severe cases may be confused with hypertrophic cardiomyopathy (HCM) of other origin. The prevalence of FD in patients primarily diagnosed with HCM varies considerably in screening and case finding studies, respectively. In a significant proportion of patients, presenting with only mild or moderate LVH and unspecific clinical signs FD may remain undiagnosed. Urinary Gb3 isoforms have been shown to detect FD in both, women and men. We examined whether this non-invasive method would help to identify new FD cases in a non-selected cohort of patients with various degree of LVH. METHODS AND RESULTS: Consecutive patients older than 18 years with a diastolic interventricular septal wall thickness of ≥12mm determined by echocardiography were included. Referral diagnosis was documented and spot urine was collected. Gb3 was measured by mass spectroscopy. Subjects with an elevated Gb3-24:18 ratio were clinically examined for signs of FD, α-galactosidase-A activity in leukocytes was determined and GLA-mutation-analysis was performed. We examined 2596 patients. In 99 subjects urinary Gb3 isoforms excretion were elevated. In these patients no new cases of FD were identified by extended FD assessment. In two of three patients formerly diagnosed with FD Gb3-24:18 ratio was elevated and would have led to further diagnostic evaluation. CONCLUSION: Measurement of urinary Gb3 isoforms in a non-selected cohort with LVH was unable to identify new cases of FD. False positive results may be prevented by more restricted inclusion criteria and may improve diagnostic accuracy of this method.

A Novel Rapid MALDI-TOF-MS-Based Method for Measuring Urinary Globotriaosylceramide in Fabry Patients.

Fabry disease is an X-linked lysosomal storage disorder caused by deficiency of α-galactosidase A, resulting in the accumulation of glycosphingolipids in various organs. Globotriaosylceramide (Gb3) and its isoforms and analogues have been identified and quantified as biomarkers of disease severity and treatment efficacy. The current study aimed to establish rapid methods for urinary Gb3 extraction and quantitation. Urine samples from 15 Fabry patients and 21 healthy control subjects were processed to extract Gb3 by mixing equal volumes of urine, methanol containing an internal standard, and chloroform followed by sonication and centrifugation. Thereafter, the lower phase was analyzed by MALDI-TOF MS and the relative peak areas of the internal standard and four major species of Gb3 determined. The results showed high reproducibility with intra- and inter-assay coefficients variation of 9.9% and 13.7%, respectively. The limit of detection was 0.15 ng/µL and the limit of quantitation was 0.30 ng/µL. Total urinary Gb3 levels in both genders of classic Fabry patients were significantly higher than in healthy controls (p < 0.0001). Gb3 levels in Fabry males were higher than in Fabry females (p = 0.08). We have established a novel assay for urinary total Gb3 that takes less than 15 min from start to finish. Graphical Abstract ᅟ.

Tandem mass spectrometry multiplex analysis of methylated and non-methylated urinary Gb3 isoforms in Fabry disease patients.

BACKGROUND: Fabry disease is a lysosomal storage disorder leading to the accumulation of glycosphingolipids in biological fluids and tissues. Globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) are currently used for Fabry screening and diagnosis. However, these biomarkers are not always increased in Fabry patients with residual enzyme activity. We recently identified 7 urinary methylated Gb3-related isoforms. The aims of this study were (1) to develop and validate a novel LC-MS/MS method for the relative quantification of methylated and non-methylated Gb3 isoforms normalized to creatinine, (2) to evaluate these biomarkers in Fabry patients and healthy controls, and (3) to assess correlations between biomarker urinary excretion with age, gender, treatment and genotype of patients. METHODS: Urine samples from 150 Fabry patients and 95 healthy controls were analyzed. Samples were purified and injected in the tandem mass spectrometer working in positive electrospray ionization. Relative quantification was performed for 15 methylated and non-methylated Gb3 isoforms. RESULTS: Significant correlations (p<0.001) were established between Gb3 isoform concentrations, gender and treatment. Five patients with the late-onset cardiac mutation p.N215S showed abnormal concentrations of methylated Gb3 isoforms compared to their non-methylated homologues. CONCLUSIONS: Methylated Gb3 isoforms might be helpful urinary biomarkers for Fabry patients with late-onset cardiac variant mutations.

Variations in the GLA gene correlate with globotriaosylceramide and globotriaosylsphingosine analog levels in urine and plasma.

Recent data have shown that lyso-Gb3, the deacylated derivative of globotriaosylceramide (Gb3), is possibly involved in the pathogenesis of Fabry disease (FD) and might be a clinically useful biomarker of its metabolic load. To test this hypothesis, we assayed Gb3 and lyso-Gb3 and related analogs in plasma and/or urine samples of 12 clinically well-characterized subjects carrying several different GLA variant alleles associated with a wide range of residual α-galactosidase A activities. Urinary Gb3 was measured by HPLC-MS/MS; plasma and urinary lyso-Gb3 and related analogs were measured by UPLC-MS/MS. Individual profiles of Gb3 and lyso-Gb3 and related analogs closely correlated with the phenotypic data for each subject, discerning the classical FD patient from the two patients carrying cardiac variants as well as those from all the others without FD. The lyso-Gb3 analog at m/z 836 was found at increased levels only in patients manifesting clinically severe heart disease, irrespective of the pathogenicity of the GLA variant they carried. This finding suggests that this lyso-Gb3 analog might be an earlier biomarker of progressive heart disease, non-specific of the FD cardiomyopathy. The possibility that urinary Gb3 is a specific marker of kidney involvement in FD deserves further study.

Characterization of early disease status in treatment-naive male paediatric patients with Fabry disease enrolled in a randomized clinical trial.

TRIAL DESIGN: This analysis characterizes the degree of early organ involvement in a cohort of oligo-symptomatic untreated young patients with Fabry disease enrolled in an ongoing randomized, open-label, parallel-group, phase 3B clinical trial. METHODS: Males aged 5-18 years with complete α-galactosidase A deficiency, without symptoms of major organ damage, were enrolled in a phase 3B trial evaluating two doses of agalsidase beta. Baseline disease characteristics of 31 eligible patients (median age 12 years) were studied, including cellular globotriaosylceramide (GL-3) accumulation in skin (n = 31) and kidney biopsy (n = 6; median age 15 years; range 13-17 years), renal function, and glycolipid levels (plasma, urine). RESULTS: Plasma and urinary GL-3 levels were abnormal in 25 of 30 and 31 of 31 patients, respectively. Plasma lyso-GL-3 was elevated in all patients. GL-3 accumulation was documented in superficial skin capillary endothelial cells (23/31 patients) and deep vessel endothelial cells (23/29 patients). The mean glomerular filtration rate (GFR), measured by plasma disappearance of iohexol, was 118.1 mL/min/1.73 m(2) (range 90.4-161.0 mL/min/1.73 m(2)) and the median urinary albumin/creatinine ratio was 10 mg/g (range 4.0-27.0 mg/g). On electron microscopy, renal biopsy revealed GL-3 accumulation in all glomerular cell types (podocytes and parietal, endothelial, and mesangial cells), as well as in peritubular capillary and non-capillary endothelial, interstitial, vascular smooth muscle, and distal tubules/collecting duct cells. Lesions indicative of early Fabry arteriopathy and segmental effacement of podocyte foot processes were found in all 6 patients. CONCLUSIONS: These data reveal that in this small cohort of children with Fabry disease, histological evidence of GL-3 accumulation, and cellular and vascular injury are present in renal tissues at very early stages of the disease, and are noted before onset of microalbuminuria and development of clinically significant renal events (e.g. reduced GFR). These data give additional support to the consideration of early initiation of enzyme replacement therapy, potentially improving long-term outcome. TRIAL REGISTRATION: ClinicalTrials.gov NCT00701415.

A prospective 10-year study of individualized, intensified enzyme replacement therapy in advanced Fabry disease.

OBJECTIVES: To test the hypothesis that more frequent enzyme replacement therapy (ERT) slows the decline in kidney function in adult patients with Fabry disease. METHODS: A single center open label 10-year prospective clinical trial of 12 patients with advanced Fabry disease who, after having experienced an ongoing decline in renal function after 2-4 years of receiving ERT at the approved dose of 0.2 mg/kg agalsidase alfa every other week (EOW), were switched to weekly (EW) ERT at the same dose. We used linear regression to fit each individual patient's longitudinal estimated glomerular filtration rate (eGFR) record in order to compare the deterioration rates between EOW and EW ERT. RESULTS: For the entire group, mean slope on agalsidase alfa every 2 weeks was -7.92 ± 2.88 ml/min/1.73 m(2)/year and 3.84 ± 4.08 ml/min/1.73 m(2)/year on weekly enzyme infusions (p = 0.01, two-tailed paired t test). Three patients (25 %) completed the entire study with relatively preserved renal function while 50 % of patients reached end-stage renal disease (ESRD) during the 10 years of this study. The estimated average delay to ESRD was 13.8 years [n = 11; 95 % CI 0.66, 27]. One patient had a positive eGFR slope on weekly infusions while the patient with the highest antibody titer had a steeper slope after switching. Mean globotriaosylceramide concentrations in urine and plasma as well as urine protein excretion remained unchanged. CONCLUSIONS: Weekly enzyme infusions slow the decline of renal function in a subgroup of more severe patients thus showing that existing ERT can be further optimized.

Interfering parameters in the determination of urinary globotriaosylceramide (Gb3) in patients with chronic kidney disease.

INTRODUCTION: Globotriaosylceramide (Gb3, CD77) represents a pivotal part of the cell membrane. Measuring the urinary Gb3 content can be used to screen patients with chronic kidney disease (CKD) for Fabry disease, a disorder caused by hampered Gb3 degradation. However, little is known about factors influencing urinary Gb3 excretion other than Fabry disease. The aim of the present study was to identify routine diagnostic parameters as predictors of urinary Gb3 excretion in patients with CKD. METHODS: Our study included 609 subjects with CKD stage I-V. We analyzed the influence of age, gender, renal function, urinary cell content and chemical characteristics on urinary Gb3 concentrations (total Gb3, Gb3-24 isoform, and Gb3-24:18 isoform ratio), determined by direct electrospray ionization mass spectrometry. RESULTS: In 609 subjects the median total urinary Gb3 was 233 ng/mg and the Gb3-24:18 isoform ratio was 1.2. Twenty-one patients, none of whom had Fabry disease, had a Gb3-24:18 isoform ratio ≥2.3. Females excreted a higher total amount of Gb3, but the Gb3-24:18 isoform ratio was comparable to males. Renal function and age had no influence on total Gb3, Gb3 isoforms or the ratio. Only a distinct load of bacteria and leukocytes was associated with an increased Gb3 excretion. Urinary leukocytes, erythrocytes, bacteria, or protein content did not affect the Gb3-24:18 isoform ratio. CONCLUSION: The Gb3-24:18 isoform ratio is unaffected by several potential influencing variables and may thus be applied for screening for Fabry disease in unselected cohorts of patients presenting with CKD.