Profiles of Globotriaosylsphingosine Analogs and Globotriaosylceramide Isoforms Accumulated in Body Fluids from Various Phenotypic Fabry Patients

Objectives Fabry disease is characterized by the systemic accumulation of globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3), which are widely used as biomarkers of the disease. However, few reports have described the relationship of Lyso-Gb3 analogs and Gb3 isoforms with the disease. The present study determined the profiles of Lyso-Gb3 analogs and Gb3 isoforms accumulated in body fluids from various phenotypic Fabry patients to elucidate the basis of the disease. Methods Plasma Lyso-Gb3 and related analogs were measured in 15 classic Fabry men, 6 later-onset Fabry men, 11 Fabry women, and 36 controls, while urinary Gb3 isoforms were measured in 5 classic Fabry men, 5 later-onset Fabry men, 17 Fabry women, and 11 controls, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Furthermore, these values were monitored for a classic Fabry man, in whom neutralizing anti-drug antibodies had developed following enzyme replacement therapy (ERT). Results The levels of plasma Lyso-Gb3 analogs/urinary Gb3 isoforms were higher in Fabry patients than in controls, especially in classic Fabry men. However, minor differences in the ratio of each Lyso-Gb3 analog and Gb3 isoform with respect to the total Lyso-Gb3 analogs and Gb3 isoforms, respectively, were observed among individual classic Fabry men. Their time courses were well associated with the development and attenuation of anti-drug antibodies in a patient with classic Fabry disease during ERT. Conclusion Quantification of Lyso-Gb3 analogs and Gb3 isoforms provides us with more detailed information about the substrates that accumulated in the body fluids of Fabry patients than does quantification of Lyso-Gb3 and Gb3 alone, so this approach may be useful for elucidating the basis of Fabry disease.

Fabry Disease in Women: Genetic Basis, Available Biomarkers, and Clinical Manifestations

Fabry Disease (FD) is a rare lysosomal storage disorder caused by mutations in the GLA gene on the X chromosome, leading to a deficiency in α-galactosidase A (AGAL) enzyme activity. This leads to the accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3), in vital organs such as the kidneys, heart, and nervous system. While FD was initially considered predominantly affecting males, recent studies have uncovered that heterozygous Fabry women, carrying a single mutated GLA gene, can manifest a wide array of clinical symptoms, challenging the notion of asymptomatic carriers. The mechanisms underlying the diverse clinical manifestations in females remain not fully understood due to X-chromosome inactivation (XCI). XCI also known as "lyonization", involves the random inactivation of one of the two X chromosomes. This process is considered a potential factor influencing phenotypic variation. This review delves into the complex landscape of FD in women, discussing its genetic basis, the available biomarkers, clinical manifestations, and the potential impact of XCI on disease severity. Additionally, it highlights the challenges faced by heterozygous Fabry women, both in terms of their disease burden and interactions with healthcare professionals. Current treatment options, including enzyme replacement therapy, are discussed, along with the need for healthcare providers to be well-informed about FD in women, ultimately contributing to improved patient care and quality of life.

Effects of switching from agalsidase-α to agalsidase-β 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-β. 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-β 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-β.

An expert consensus on the recommendations for the use of biomarkers in Fabry disease

Fabry disease is an X-linked lysosomal storage disorder caused by the accumulation of glycosphingolipids in various tissues and body fluids, leading to progressive organ damage and life-threatening complications. Phenotypic classification is based on disease progression and severity and can be used to predict outcomes. Patients with a classic Fabry phenotype have little to no residual α-Gal A activity and have widespread organ involvement, whereas patients with a later-onset phenotype have residual α-Gal A activity and disease progression can be limited to a single organ, often the heart. Diagnosis and monitoring of patients with Fabry disease should therefore be individualized, and biomarkers are available to support with this. Disease-specific biomarkers are useful in the diagnosis of Fabry disease; non-disease-specific biomarkers may be useful to assess organ damage. For most biomarkers it can be challenging to prove they translate to differences in the risk of clinical events associated with Fabry disease. Therefore, careful monitoring of treatment outcomes and collection of prospective data in patients are needed. As we deepen our understanding of Fabry disease, it is important to regularly re-evaluate and appraise published evidence relating to biomarkers. In this article, we present the results of a literature review of evidence published between February 2017 and July 2020 on the impact of disease-specific treatment on biomarkers and provide an expert consensus on clinical recommendations for the use of those biomarkers.

Clinical relevance of globotriaosylceramide accumulation in Fabry disease and the effect of agalsidase beta in affected tissues

Fabry disease (FD) is a rare lysosomal storage disorder, characterized by a reduction in α-galactosidase A enzyme activity and the progressive accumulation of globotriaosylceramide (GL3) and its metabolites in the cells of various organs. Agalsidase beta, an enzyme replacement therapy (ERT), is approved for use in patients with FD in Europe, Canada, Australia, South America, and Asia, and is the only ERT approved for use in the United States. In this review, we discuss the clinical relevance of GL3 accumulation, the effect of agalsidase beta on GL3 in target tissues, and the association between treatment-related tissue GL3 clearance and long-term structure, function, or clinical outcomes. Accumulation of GL3 in the kidney, heart, vasculature, neurons, skin, gastrointestinal tract and auditory system correlates to cellular damage and irreversible organ damage, as a result of sclerosis, fibrosis, apoptosis, inflammation, and endothelial dysfunction. Damage leads to renal dysfunction and end-stage renal disease; myocardial hypertrophy with heart failure and arrhythmias; ischemic stroke; neuropathic pain; skin lesions; intestinal ischemia and dysmotility; and hearing loss. Treatment with agalsidase beta is effective in substantially clearing GL3 in a range of cells from the tissues affected by FD. Agalsidase beta has also been shown to slow renal decline and lower the overall risk of clinical progression, demonstrating an indirect link between treatment-related GL3 clearance and stabilization of FD.

Metabolic Fingerprinting of Fabry Disease: Diagnostic and Prognostic Aspects

Fabry disease (FD) is an X-linked lysosomal disease due to a deficiency in the activity of the lysosomal-galactosidase A (GalA), a key enzyme in the glycosphingolipid degradation pathway. FD is a complex disease with a poor genotype–phenotype correlation. In the early stages, FD could involve the peripheral nervous system (acroparesthesias and dysautonomia) and the ski (angiokeratoma), but later kidney, heart or central nervous system impairment may significantly decrease life expectancy. The advent of omics technologies offers the possibility of a global, integrated and systemic approach well-suited for the exploration of this complex disease. In this narrative review, we will focus on the main metabolomic studies, which have underscored the importance of detecting biomarkers for a diagnostic and prognostic purpose in FD. These investigations are potentially useful to explain the wide clinical, biochemical and molecular heterogeneity found in FD patients. Moreover, the quantitative mass spectrometry methods developed to evaluate concentrations of these biomarkers in urine and plasma will be described. Finally, the complex metabolic biomarker profile depicted in FD patients will be reported, which varies according to gender, types of mutations, and therapeutic treatment.

Pulvinar Sign, Stroke and Their Relationship with Fabry Disease: A Systematic Review and Metanalysis

Background: Fabry disease (FD) is the second most common lysosomal storage disorder. This disorder affects multiple systems that include the cardiac, renal, and nervous system. The pulvinar sign (PS) is a relatively common sign seen in patients with FD. The PS is a bilateral, symmetrical pulvinar high signal relative to the signal intensity seen on unenhanced T1-weighted brain MR imaging. Methods: We conducted a systematic review with metanalysis to analyze the pool prevalence of the disorder. We used the Moose Guidelines and PRISMA Protocol for this systematic review and Robins 1 to access the BIAS of the study. To analyze the pool prevalence, we used “Open Meta-Analysis” software for analyzing the study. We used “Review Manager 5.4” to analyze the odds ratio between patients with and without the PS and patients with and without stroke among patients with FD. Results: We gather 12 studies from 2003 to 2021 for the analysis of this study. The pool prevalence of the study was 0.146 (0.076−0.217) (62/385 cases) with a 95% CI (0.0945−0.415) (p < 0.01). The prevalence was much higher in men (59 cases) than in women (3 cases). There was no relationship between the pulvinar sign and patients with stroke among patients with Fabry disease. Odds ratio 1.97 95% CI (0.35−11.21), p = 0.44; Tau2 = 0.77. There seems to be a correlation with renal failure (RF), but there were very few studies to conduct a metanalysis with RF. Conclusions: The prevalence of the PS among all studies was 23.9%; the prevalence of this sign is higher among males. We found that FD patients who had strokes did not have higher odds of presenting with the Pulvinar Sign than the FD patients who did not suffer a stroke. Patients with renal failure and FD seem to have a higher tendency to have the PS, but there were not enough studies to analyze that theory. Overall, we think the pulvinar sign has a poor prognostic value in patients with Fabry’s disease.

Comparative urinary globotriaosylceramide analysis by thin-layer chromatography-immunostaining and liquid chromatography-tandem mass spectrometry in patients with Fabry disease

In Fabry disease, accumulation of glycolipids, predominantly globotriaosylceramide (Gb3), affects the kidneys, and nephropathy is one of the important disorders that influence the disease severity and prognosis of patients. Urinary Gb3 has been analyzed for diagnosis and monitoring of Fabry disease. In this study, we analyzed urinary Gb3 by thin-layer chromatography (TLC)-immunostaining and liquid chromatography (LC)-tandem mass spectrometry (MS/MS). An improved qualitative method, TLC-immunostaining, revealed excessive urinary Gb3 excretion in 100 (8/8), 88 (14/16), and 74% (45/61) of the classic Fabry males, later-onset Fabry males, and Fabry females examined, respectively. This authentic method is robust, easy, economic, and hardly affected by abundant urinary sediment, and this is useful for diagnosing individual Fabry patients. LC-MS/MS can determine the level of Gb3 in urine with high sensitivity, and it revealed that the Gb3 excretion level was higher in the order of classic Fabry males, later-onset Fabry males, Fabry females, and controls, respectively, and this is expected to be a useful quantitative method not only for diagnosis but also for predicting the progression of Fabry nephropathy. As to the relation of the urinary Gb3 level and renal events, our study revealed that the urinary Gb3 level in Fabry patients experiencing renal events tended to be higher than that in ones who did not have any renal events in each phenotypic group of the disease.

Biomarkers in Fabry Disease. Implications for Clinical Diagnosis and Follow-up

Fabry disease (FD) is a lysosomal storage disorder caused by deficient alpha-galactosidase A activity in the lysosome due to mutations in the GLA gene, resulting in gradual accumulation of globotriaosylceramide and other derivatives in different tissues. Substrate accumulation promotes different pathogenic mechanisms in which several mediators could be implicated, inducing multiorgan lesions, mainly in the kidney, heart and nervous system, resulting in clinical manifestations of the disease. Enzyme replacement therapy was shown to delay disease progression, mainly if initiated early. However, a diagnosis in the early stages represents a clinical challenge, especially in patients with a non-classic phenotype, which prompts the search for biomarkers that help detect and predict the evolution of the disease. We have reviewed the mediators involved in different pathogenic mechanisms that were studied as potential biomarkers and can be easily incorporated into clinical practice. Some accumulation biomarkers seem to be useful to detect non-classic forms of the disease and could even improve diagnosis of female patients. The combination of such biomarkers with some response biomarkers, may be useful for early detection of organ injury. The incorporation of some biomarkers into clinical practice may increase the capacity of detection compared to that currently obtained with the established diagnostic markers and provide more information on the progression and prognosis of the disease.

Fabry disease-what cardiologists can learn from the nephrologist: a narrative review

Fabry disease (FD) is a rare, X-linked lysosomal storage disorder resulting in decreased or absent activity of the lysosomal enzyme alpha-galactosidase A. Subsequent accumulation of storage material can occur in virtually all cells of the body. Organs and structures affected by storage material deposition include the heart, the kidney, the central and peripheral nervous system and the cornea of the eyes. Progressive cardiac hypertrophy, arrhythmias, cardiac fibrosis, heart failure and cardiac death are common characteristics of cardiac involvement. Renal depositions of glycosphingolipids are already detectable in childhood. An early clinical sign of Fabry renal involvement is albuminuria, often preceding a detectable loss of kidney function. Later in life Fabry patients may exhibit a progressive decline of their kidney function leading to end-stage renal disease (ESRD). The clinical presentation of Fabry patients regarding renal involvement depends on the underlying mutation in the GLA gene. Classically affected males typically show a gradual decrease in kidney function, patients with mild or late onset mutations as well as a subgroup of females may exhibit only little or no renal abnormalities. This review summarizes the characteristics of renal involvement in FD, the diagnostics necessary to evaluate the degree of renal impairment and possible treatment options.

Stratification of Fabry mutations in clinical practice: a closer look at α-galactosidase A-3D structure

BACKGROUND

Fabry disease (FD) is an X-linked lysosomal storage and multi-system disorder due to mutations in the α-galactosidase A (α-GalA) gene. We investigated the impact of individual amino acid exchanges in the α-GalA 3D-structure on the clinical phenotype of FD patients.

PATIENTS AND METHODS

We enrolled 80 adult FD patients with α-GalA missense mutations and stratified them into three groups based on the amino acid exchange location in the α-GalA 3D-structure: patients with active site mutations, buried mutations and other mutations. Patient subgroups were deep phenotyped for clinical and laboratory parameters and FD-specific treatment.

RESULTS

Patients with active site or buried mutations showed a severe phenotype with multi-organ involvement and early disease manifestation. Patients with other mutations had a milder phenotype with less organ impairment and later disease onset. α-GalA activity was lower in patients with active site or buried mutations than in those with other mutations (P < 0.01 in men; P < 0.05 in women) whilst lyso-Gb3 levels were higher (P < 0.01 in men; <0.05 in women).

CONCLUSIONS

The type of amino acid exchange location in the α-GalA 3D-structure determines disease severity and temporal course of symptom onset. Patient stratification using this parameter may become a useful tool in the management of FD patients.

Biomarkers in Anderson-Fabry Disease

Fabry disease is a rare lysosomal storage disorder caused by a deficiency of α-galactosidase A, resulting in multisystemic involvement. Lyso-Gb3 (globotriaosylsphingosine), the deacylated form of Gb3, is currently measured in plasma as a biomarker of classic Fabry disease. Intensive research of biomarkers has been conducted over the years, in order to detect novel markers that may potentially be used in clinical practice as a screening tool, in the context of the diagnostic process and as an indicator of response to treatment. An interesting field of application of such biomarkers is the management of female heterozygotes who present difficulty in predictable clinical progression. This review aims to summarise the current evidence and knowledge about general and specific markers that are actually measured in subjects with confirmed or suspected Fabry disease; moreover, we report potential novel markers such as microRNAs. Recent proteomic or metabolomic studies are in progress bringing out plasma proteome profiles in Fabry patients: this assessment may be useful to characterize molecular pathology of the disease, to improve diagnostic process, and to monitor response to treatment. The management of Fabry disease may be improved by the identification of biomarkers that reflect clinical course, severity, and the progression of the disease.

Assessment of plasma lyso-Gb3 for clinical monitoring of treatment response in migalastat-treated patients with Fabry disease

PURPOSE

To assess the utility of globotriaosylsphingosine (lyso-Gb₃) for clinical monitoring of treatment response in patients with Fabry disease receiving migalastat.

METHODS

A post hoc analysis evaluated data from 97 treatment-naive and enzyme replacement therapy (ERT)-experienced patients with migalastat-amenable GLA variants from FACETS (NCT00925301) and ATTRACT (NCT01218659) and subsequent open-label extension studies. The relationship between plasma lyso-Gb₃ and measures of Fabry disease progression (left ventricular mass index [LVMi], estimated glomerular filtration rate [eGFR], and pain) and the relationship between lyso-Gb₃ and incidence of Fabry-associated clinical events (FACEs) were assessed in both groups. The relationship between changes in lyso-Gb₃ and kidney interstitial capillary (KIC) globotriaosylceramide (Gb₃) inclusions was assessed in treatment-naive patients.

RESULTS

No significant correlations were identified between changes in lyso-Gb₃ and changes in LVMi, eGFR, or pain. Neither baseline lyso-Gb₃ levels nor the rate of change in lyso-Gb₃ levels during treatment predicted FACE occurrences in all patients or those receiving migalastat for ≥24 months. Changes in lyso-Gb₃ correlated with changes in KIC Gb₃ inclusions in treatment-naive patients.

CONCLUSIONS

Although used as a pharmacodynamic biomarker in research and clinical studies, plasma lyso-Gb₃ may not be a suitable biomarker for monitoring treatment response in migalastat-treated patients.

Globotriaosylsphingosine (lyso-Gb3) and analogues in plasma and urine of patients with Fabry disease and correlations with long-term treatment and genotypes in a nationwide female Danish cohort

INTRODUCTION

Recent studies showed the usefulness of globotriaosylsphingosine (lyso-Gb₃) and related analogues, deacylated forms of globotriaosylceramide (Gb₃), for high-risk screening, treatment monitoring and follow-up for patients with Fabry disease.

METHODS

We evaluated Gb₃, lyso-Gb₃ and analogues using tandem mass spectrometry in 57 women with Fabry disease followed during a period of 15.4 years. Twenty-one women were never treated and 36 received treatment (agalsidase-beta, n=30; agalsidase-alfa, n=5; or migalastat, n=1). Lyso-Gb₃ and analogues at m/z (-28), (-2), (+16), (+34) and (+50) were analysed in plasma and urine. Total Gb₃ and lyso-Gb₃ analogues at m/z (-12) and (+14) were evaluated in urine while the analogue at m/z (+18) was evaluated in plasma.

RESULTS

A strong correlation between plasma and urine lyso-Gb₃ and analogue levels was revealed. Plasma and urine lyso-Gb₃ and analogue levels were not statistically different between patients carrying missense (n=49), nonsense (n=6) or deletion mutations (n=2). Never treated patients had lower plasma lyso-Gb₃ and analogues at m/z (-28), (-2), (+16), (+34) and the seven urinary lyso-Gb₃ analogues compared with pretreatment levels of the treated patients. A significant reduction of plasma lyso-Gb₃ and five analogues, as well as urine Gb₃ and six lyso-Gb₃ analogues, but not lyso-Gb₃ and lyso-Gb₃ at m/z (+50), was observed post-treatment with agalsidase-beta. The same tendency was observed with agalsidase-alfa.

CONCLUSION

Women with Fabry disease who started treatment based on clinical manifestations had higher lyso-Gb₃ and analogue biomarker levels than never treated women. This indicates that a biomarker cut-off could potentially be a decision tool for treatment initiation in women with Fabry disease.

Biomarkers of Fabry Nephropathy: Review and Future Perspective

Progressive nephropathy is one of the main features of Fabry disease, which largely contributes to the overall morbidity and mortality burden of the disease. Due to the lack of specific biomarkers, the heterogeneity of the disease, and unspecific symptoms, diagnosis is often delayed. Clinical presentation in individual patients varies widely, even in patients from the same family carrying the same pathogenic GLA variant. Therefore, it is reasonable to anticipate that additional genomic, transcriptomic, proteomic, and metabolomics factors influence the manifestation and progression of the disease. The aim of this article is to provide an overview of nephropathy in Fabry patients and the biomarkers currently used in the diagnosis and follow-up. Current biomarkers are associated with late signs of kidney damage. Therefore, there is a need to identify biomarkers associated with early stages of kidney damage that would enable early diagnosis, which is crucial for effective treatment and prevention of severe irreversible complications. Recent advances in sequencing and -omics technologies have led to several studies investigating new biomarkers. We will provide an overview of the novel biomarkers, critically evaluate their clinical utility, and propose future perspectives, which we believe might be in their integration.

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.

An expert consensus document on the management of cardiovascular manifestations of Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by pathogenic variants in the α-galactosidase A (GLA) gene that leads to reduced or undetectable α-galactosidase A enzyme activity and progressive accumulation of globotriaosylceramide and its deacylated form globotriaosylsphingosine in cells throughout the body. FD can be multisystemic with neurological, renal, cutaneous and cardiac involvement or be limited to the heart. Cardiac involvement is characterized by progressive cardiac hypertrophy, fibrosis, arrhythmias, heart failure and sudden cardiac death. The cardiac management of FD requires specific measures including enzyme replacement therapy or small pharmacological chaperones in patients carrying amenable pathogenic GLA gene variants and more general management of cardiac symptoms and complications. In this paper, we summarize current knowledge of FD-related heart disease and expert consensus recommendations for its management.

A comprehensive testing algorithm for the diagnosis of Fabry disease in males and females

PURPOSE

Successful diagnosis of Fabry disease is often delayed or missed in patients, especially females, due to clinical heterogeneity and a lack of disease awareness. We present our experience testing for Fabry disease in high risk populations and discuss the relative sensitivities of α-galactosidase A (α-Gal A) enzyme activity in blood, plasma lyso-globotriaosylceramide (lyso-Gb₃) biomarker, and GLA gene sequencing as diagnostic tests for Fabry disease in both males and females.

METHODS

Patients with a clinical suspicion of Fabry disease were evaluated with enzyme analysis, biomarker analysis, and GLA sequencing. All three assays were performed from a single tube of EDTA blood. α-Gal A activity was determined in dried blood spots using a fluorometric assay, plasma lyso-Gb₃ by UPLC-MS/MS, and GLA analysis by Sanger sequencing.

RESULTS

Peripheral blood samples were received from 94 males and 200 females, of which 29% of males and 22% of females had a positive family history of Fabry disease. A likely pathogenic or pathogenic variant was identified in 87 (30%) patients (50 males, 37 females), confirming a diagnosis of Fabry disease. Of the remaining patients, 178 (61%) were determined to be unaffected based on normal enzyme activity (males) or normal lyso-Gb₃ and negative sequencing results (females). A VUS was identified in 29 (10%) patients. The positive and negative predictive value of plasma lyso-Gb₃ was 100% and 97% in males and 100% and 99% in females, respectively. This compares with 84% and 100% in males, and 58% and 50% in females for α-Gal A activity testing, respectively.

CONCLUSIONS

Plasma lyso-Gb₃ has high sensitivity and specificity for Fabry disease in males and females, and provides supportive diagnostic information when gene sequencing results are negative or inconclusive. α-Gal A activity in dried blood spots (DBS) has high sensitivity, but lower specificity for Fabry disease in males, as not all males with low α-Gal A activities were confirmed to have Fabry disease. Therefore, reflexing to gene sequencing and plasma lyso-Gb₃ is useful for disease confirmation in males. For females, we found that first tier testing consisting of GLA sequencing and plasma lyso-Gb₃ analysis provided the greatest sensitivity and specificity. Enzyme testing has lower sensitivity in females and is therefore less useful as a first-tier test. Enzyme analysis in females may still be helpful as a second-tier test in cases where molecular testing and plasma lyso-Gb₃ analysis are uninformative and in vitro enzyme activity is low.

SUMMARY

Sex-specific testing algorithms that prioritize tests with high specificity and sensitivity offer an effective means of identifying individuals with Fabry disease.

Diagnosis and Screening of Patients with Fabry Disease

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by absence or deficient activity of α-galactosidase A (α-Gal A) due to mutations in the α-galactosidase A gene (GLA), leading to progressive accumulation of globotriaosylceramide (Gb3) in tissues and organs including heart, kidney, the eyes, vascular endothelium, the nervous system and the skin. Cardiac involvement is leading to fatal complications and reduced life expectancy. FD is treatable with disease-specific treatment (enzyme replacement therapy (ERT) or with chaperone therapy). Therefore, the early diagnosis of FD is crucial for reducing the morbidity and mortality. Screening of high-risk populations (eg, patients with unexplained left ventricular hypertrophy (LVH), young patients with unexplained stroke, and patients with unexplained renal failure proteinuria or microalbuminuria) yields good results. The diagnostic algorithm is gender-specific. Initially, the measurement of α-Gal A activity is recommended in males, and optionally in females. In males with non-diagnostic residual activity (5–10%) activity, genetic testing is afterwards done for confirming the diagnosis. In fact, diagnosis of FD is not possible without genetic testing for both males and females. Globotriaosysphingosine (lyso-Gb3) for identification of atypical FD variants and high- sensitive troponin T (hsTNT) for identification of cardiac involvement are also important diagnostic biomarkers. The aim of this review was to provide an update on diagnosis and screening of patients with FD.

Fabry nephropathy. Role of nephrologist and clinical variables associated with the diagnosis

BACKGROUND

The early detection of Fabry nephropathy is of interest to us. Its treatment is more effective in early stages. It has been studied by analysing molecular and tissue biomarkers. These have certain disadvantages that hinder its routine use. The aim of this study is to describe the role of the nephrologist in the diagnosis of the disease, and to describe the clinical variables associated with nephropathy in affected patients.

MATERIAL AND METHODS

Cross-sectional study. Patients were included from three reference centres in Argentina.

RESULTS

Seventy two patients were studied (26.26±16.48years): 30 of which (41.6%) were men and 42 of which (58.4%) were women; 27 paediatric patients and 45 adults. Fourteen "index cases" were detected, 50% of which were diagnosed by nephrologists. Nephropathy was found in 44 patients (61%): 6 paediatric patients and 38 adults. Two types of clinical variables were associated with nephropathy: (i)peripheral nervous system compromise (P≤.001), angiokeratomas (P≤.001) and auditory compromise (P=.01-.001), with these being early clinical manifestations of the most severe disease phenotype, and (ii)structural heart disease (P=.01-.001) and central nervous system compromise (P=.05-.01), which are major and late complications, responsible for increased morbidity and mortality and lower life expectancy.

CONCLUSION

The nephrologist plays an important role in the diagnosis of Fabry nephropathy, although the detection thereof owing to its renal involvement would represent a late diagnosis, because nephropathy is associated with late complications of the most severe disease phenotype.

Low frequency of Fabry disease in patients with common heart disease

PURPOSE

To test the hypothesis that undiagnosed patients with Fabry disease exist among patients affected by common heart disease.

METHODS

Globotriaosylceramide in random whole urine using tandem mass spectroscopy, α-galactosidase A activity in dried blood spots, and next-generation sequencing of pooled or individual genomic DNA samples supplemented by Sanger sequencing.

RESULTS

We tested 2,256 consecutive patients: 852 women (median age 65 years (19-95)) and 1,404 men (median age 65 years (21-92)). The primary diagnoses were coronary artery disease (n = 994), arrhythmia (n = 607), cardiomyopathy (n = 138), and valvular disease (n = 568). Urinary globotriaosylceramide was elevated in 15% of patients and 15 males had low α-galactosidase A activity. GLA variants found included R118C (n = 2), D83N, and D313Y (n = 7); IVS6-22 C>T, IVS4-16 A>G, IVS2+990C>A, 5'UTR-10 C>T (n = 4), IVS1-581 C>T, IVS1-1238 G>A, 5'UTR-30 G>A, IVS2+590C>T, IVS0-12 G>A, IVS4+68A>G, IVS0-10 C>T, IVS2-81-77delCAGCC, IVS2-77delC. Although the pathogenicity of several of these missense mutations and complex intronic haplotypes has been controversial, none of the patients screened in this study were diagnosed definitively with Fabry disease.

CONCLUSION

This population of patients with common heart disease did not contain a substantial number of patients with undiagnosed Fabry disease. GLA gene sequencing is superior to urinary globotriaosylceramide or α-galactosidase A activity in the screening for Fabry disease.

Biomarkers and Imaging Findings of Anderson-Fabry Disease-What We Know Now

Anderson–Fabry disease (AFD) is an X-linked lysosomal storage disorder, caused by deficiency or absence of the alpha-galactosidase A activity, with a consequent glycosphingolipid accumulation. Biomarkers and imaging findings may be useful for diagnosis, identification of an organ involvement, therapy monitoring and prognosis. The aim of this article is to review the current available literature on biomarkers and imaging findings of AFD patients. An extensive bibliographic review from PubMed, Medline and Clinical Key databases was performed by a group of experts from nephrology, neurology, genetics, cardiology and internal medicine, aiming for consensus. Lyso-GB3 is a valuable biomarker to establish the diagnosis. Proteinuria and creatinine are the most valuable to detect renal damage. Troponin I and high-sensitivity assays for cardiac troponin T can identify patients with cardiac lesions, but new techniques of cardiac imaging are essential to detect incipient damage. Specific cerebrovascular imaging findings are present in AFD patients. Techniques as metabolomics and proteomics have been developed in order to find an AFD fingerprint. Lyso-GB3 is important for evaluating the pathogenic mutations and monitoring the response to treatment. Many biomarkers can detect renal, cardiac and cerebrovascular involvement, but none of these have proved to be important to monitoring the response to treatment. Imaging features are preferred in order to find cardiac and cerebrovascular compromise in AFD patients.

New biomarkers defining a novel early stage of Fabry nephropathy: A diagnostic test study

BACKGROUND

Renal involvement in Fabry disease is a major determinant of overall disease prognosis and early enzyme replacement therapy seems effective in preventing progression of kidney injury. Gb3 storage, glomerular sclerosis and tubulo-interstitial fibrosis may occur with minimal or no changes on standard renal tests, hence alternative markers of renal dysfunction are crucial. In this study we compared several biomarkers with albuminuria in the identification of incipient Fabry nephropathy and their diagnostic accuracy to identify chronic kidney disease (CKD) stage≥2.

METHODS

In this multicentre, prospective, cross-sectional and diagnostic test study, a cohort of 78 Fabry patients and 25 healthy controls was consecutively recruited. Patients were grouped by severity of nephropathy: 1) albuminuria<30mg/g; 2) albuminuria 30-299mg/g; 3) albuminuria>300mg/g; 4) glomerular filtration rate (GFR)<60mL/min/1.73m². Several index tests, namely biomarkers of glomerular (transferrin and type IV collagen) and tubular (α1-microglobulin, N-acetyl-β-glucosaminidase and alanine aminopeptidase) dysfunction were compared with the reference standard (albuminuria).

RESULTS

Significant increase of all tested biomarkers in Fabry patients, even in the subgroup of patients without evidence of nephropathy. We also found inverse significant correlations between estimated GFR and collagen type IV (ρ=-0.289; p=0.003) or N-acetyl-β-glucosaminidase (ρ=-0.448; p<0.001), which were stronger than with albumin (ρ=-0.274; p=0.019). There was also better diagnostic accuracy of N-acetyl-β-glucosaminidase to predict CKD stage≥2.

CONCLUSIONS

These results suggest that studied biomarkers may overcome the limitations of albuminuria as sensitive marker of early renal dysfunction and as marker for CKD progression risk. These biomarkers may also define novel early stages of nephropathy characterized by mesangial expansion and/or tubular damage.

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.

Characterization and phosphoproteomic analysis of a human immortalized podocyte model of Fabry disease generated using CRISPR/Cas9 technology

Fabry nephropathy is a major cause of morbidity and premature death in patients with Fabry disease (FD), a rare X-linked lysosomal storage disorder. Gb3, the main substrate of α-galactosidase A (α-Gal A), progressively accumulates within cells in a variety of tissues. Establishment of cell models has been useful as a tool for testing hypotheses of disease pathogenesis. We applied CRISPR/Cas9 genome editing technology to the GLA gene to develop human kidney cell models of FD in human immortalized podocytes, which are the main affected renal cell type. Our podocytes lack detectable α-Gal A activity and have increased levels of Gb3. To explore different pathways that could have distinct patterns of activation under conditions of α-gal A deficiency, we used a high-throughput antibody array to perform phosphorylation profiling of CRISPR/Cas9-edited and control podocytes. Changes in both total protein levels and in phosphorylation status per site were observed. Analysis of our candidate proteins suggests that multiple signaling pathways are impaired in FD.

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.

Broad spectrum of Fabry disease manifestation in an extended Spanish family with a new deletion in the GLA gene

Background

Fabry disease (FD) is an X-linked inherited disease based on the absence or reduction of lysosomal-galactosidase (Gla) activity. The enzymatic defect results in progressive impairment of cerebrovascular, renal and cardiac function. Normally, female heterozygote mutation carriers are less strongly affected than male hemizygotes aggravating disease diagnosis.

Method

Close examination of the patients by renal biopsy, echo- and electrocardiography and MRI. Blood work and subsequent DNA analysis were carried out utilizing approved protocols for PCR and Sequencing. MLPA analysis was done to unveil deletions within the GLA gene locus. Quantitative detection of Glycolipids in patient plasma and urine were carried out using HPLC/MS-MS and ESI-MS.

Results

In the presented case, a female index patient led to the examination of three generations of a Spanish family. She presented with severe oto-cochlear symptoms and covert renal and cardiac involvement. While conventional sequencing failed to detect a causative mutation, MLPA analysis revealed a deletion within the GLA gene locus, which we were able to map to a region spanning exon 2 and adjacent intronic parts. The analysis of different biomarkers revealed elevated lyso-Gb3 levels in all affected family members.

Conclusion

Our findings highlight the broad intrafamilial spectrum of symptoms of FD and emphasise the need to use MLPA screening in symptomatic females without conclusive sequencing result. Finally, plasma lyso-Gb3 proved to be a reliable biomarker for the diagnosis of FD.

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.

Fabry disease and the heart

Fabry disease is induced by a mutation in the alpha-galactosidase A gene, causing a deficiency of the enzyme alpha-galactosidase A. (1) The enzyme defect leads to progressive intracellular accumulation of globotriaosylceramide in lysosomes of various tissues and organs, including heart, kidney and nerve system. Cardiac involvement is common and is presenting as concentric left ventricular hypertrophy. Myocardial replacement fibrosis is a typical feature of more advanced stages of Fabry cardiomyopathy, first limited to the mid-myocardial layers of the basal postero-lateral wall, then spreading to transmural fibrosis. Since 2001, enzyme replacement therapy is available. If therapy is started early, before myocardial fibrosis has developed, a long-term improvement of myocardial morphology, function and exercise capacity can be achieved. In end-stage cardiomyopathy enzyme replacement therapy might prevent further progression of the disease. This review provides an overview of Fabry disease, with a focus on cardiac involvement with its characteristic features, clinical presentation and possible treatment.

Innate and Adaptive Immune Response in Fabry Disease

Fabry disease is an X-linked lysosomal storage disease in which mutations of the gene (GLA) cause a deficiency of the lysosomal hydrolase α-galactosidase A (α-Gal). This defect results in an accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3) which causes a multisystemic vasculopathy. Available since 2001 in Europe, enzyme replacement therapy consists in the administration of agalsidase, a recombinant form of α-galactosidase A. Enzyme replacement therapy was shown to improve the global prognosis but allowed partial success in preventing critical events such as strokes and cardiac arrests. As in most lysosomal storage diseases, frequent immune reactions have been described in naive Fabry disease patients. Humoral immune responses following enzyme replacement therapy have also been described, with unclear consequences on the progression of the disease. While cost-effectiveness of enzyme replacement therapy in Fabry disease begins to be questioned and new therapeutic strategies arise such as chaperone or gene therapy, it appears necessary to better understand the immune responses observed in the treatment of naive patients and during enzyme replacement therapy with agalsidase. We propose a comprehensive review of the available literature concerning both innate and adaptive responses observed in Fabry disease. We particularly highlight the probable role of the toll-like receptor 4 (TLR4) and CD1d pathways triggered by Gb3 accumulation in the development of local and systemic inflammation that could lead to irreversible organ damages. We propose an immunological point of view of Fabry disease pathogenesis involving immune cells notably the invariant natural killer T cells. We finally review anti-agalsidase antibodies, their development and impact on outcomes.

Gender-specific plasma proteomic biomarkers in patients with Anderson-Fabry disease

AIMS

Anderson-Fabry disease (AFD) is an important X-linked metabolic disease resulting in progressive end-organ involvement, with cardiac disease being the dominant determinant of survival in a gender-dependent manner. Recent epidemiological screening for AFD suggests the prevalence is much higher than previously recognized, with estimates of 1:3000. Our aim was to discover novel plasma biomarker signatures in adult patients with AFD.

METHODS AND RESULTS

We used an unbiased proteomic screening approach to discover novel plasma biomarker signatures. In the discovery cohort of 46 subjects, 14 healthy controls and 32 patients with AFD, we used a mass spectrometry iTRAQ proteomic approach followed by multiple reaction monitoring (MRM) assays to identify biomarkers. Of the 38 protein groups discovered by iTRAQ, 18 already had existing MRM assays. Based on MRM, we identified an eight-protein biomarker panel (22 kDa protein, afamin, α1 antichymotrypsin, apolipoprotein E, β-Ala His dipeptidase, haemoglobin α-2, isoform 1 of sex hormone-binding globulin, and peroxiredoxin 2) that was very specific and sensitive for male AFD patients. In female AFD patients, we identified a nine-marker panel of proteins with only three proteins, apolipoprotein E, haemoglobin α-2, and peroxiredoxin 2, common to both genders, suggesting a gender-specific alteration in plasma biomarkers in patients with AFD. The biomarkers were validated in plasma samples from 48 subjects using MRM, and they performed inferiorly in patients with heart failure.

CONCLUSIONS

We have identified gender-specific plasma protein biomarker panels that are specific and sensitive for the AFD phenotype. The gender-specific panels offer important insight into potential differences in pathophysiology and prognosis between males and females with AFD.

A metabolomic study to identify new globotriaosylceramide-related biomarkers in the plasma of Fabry disease patients

Fabry disease is an X-linked lysosomal storage disorder caused by a deficiency of the enzyme α-galactosidase A, which results in the progressive accumulation of glycosphingolipids. In addition to the two biomarkers, globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3), which are routinely used for detection and high-risk screening of Fabry disease patients, novel urinary Gb3-related isoforms/analogues as well as newly defined lyso-Gb3 analogues in plasma and urine from Fabry patients have recently been described by our group. The aim of this study was to extend our recent analyses to identify and evaluate new potential Gb3-related biomarkers in the plasma of untreated male Fabry disease patients using a mass spectrometry metabolomic approach. A multivariate statistical analysis revealed five Gb3-related novel biomarkers in the plasma of male Fabry patients. Three of these new biomarkers correspond to Gb3, which has an extra double bond on the sphingosine with C16:0, C18:0, and C22:1 fatty acid chains. The fourth biomarker corresponds to a mixture of two structural isomers, the first with a d16:1 sphingosine and a C16:0 fatty acid and the second with a d18:1 sphingosine and a C14:0 fatty acid. To our knowledge, it is the first time that a Gb3 analogue with a d16:1 sphingosine moiety has been reported. In addition, this Gb3 analogue was also present in its methylated form. These biomarkers are part of a metabolic profile that may provide insight into the pathophysiology of Fabry disease.

Urine bikunin as a marker of renal impairment in Fabry's disease

Fabry's disease is a rare lysosomal storage disorder caused by the deficiency of α-galactosidase A that leads to the accumulation of neutral glycosphingolipids in many organs including kidney, heart, and brain. Since end-stage renal disease represents a major complication of this pathology, the aim of the present work was to evaluate if urinary proteoglycan/glycosaminoglycan excretion could represent a useful marker for monitoring kidney function in these patients at high risk. Quali-quantitative and structural analyses were conducted on plasma and urine from 24 Fabry's patients and 43 control subjects. Patients were sorted for presence and degree of renal impairment (proteinuria/renal damage). Results showed that levels of urine bikunin, also known as urinary trypsin inhibitor (UTI), are significantly higher in patients with renal impairment than in controls. In this respect, no differences were evidenced in plasma chondroitin sulfate isomers level/structure indicating a likely direct kidney involvement. Noteworthy, urine bikunin levels are higher in patients since early symptoms of renal impairment occur (proteinuria). Overall, our findings suggest that urine bikunin level, as well as proteinuria, could represent a useful parameter for monitoring renal function in those patients that do not present any symptoms of renal insufficiency.

Initially Nondiagnosed Fabry's Disease when Electron Microscopy Is Lacking: The Continuing Story of Focal and Segmental Glomerulosclerosis

Focal and segmental glomerulosclerosis is classified as either primary or secondary. We present a patient with a past history of biopsy-proven focal and segmental glomerulosclerosis. Despite initial response to dual blockade and steroids, proteinuria raised when steroids were decreased. After the patient was restarted on steroids, proteinuria did not improve. Another biopsy confirmed the previous diagnosis but suggested Fabry's disease, later confirmed by electron microscopy, α-galactosidase A serum and leukocyte deficiency as well as genetic studies. Proteinuria decreased when agalsidase β was prescribed in parallel with steroid tapering, increased with steroid discontinuation and improved with meprednisone administration. This report highlights the relevance of electron microscopy in kidney biopsy. In glomerulosclerosis, despite specific treatment, secondary hemodynamic and immunologic pathways may contribute to the development of proteinuria and accelerate the renal disease progression due to the primary disease. We discuss possible pathophysiologic pathways involved in proteinuria in Fabry's disease according to the biopsy and the therapeutic response.

Renal complications of Fabry disease in children

Fabry disease is an X-linked α-galactosidase A deficiency, resulting in accumulation of glycosphingolipids, especially globotriaosylceramide, in cells in different organs in the body. Renal failure is a serious complication of this disease. Fabry nephropathy lesions are present and progress in childhood while the disease commonly remains silent by routine clinical measures. Early and timely diagnosis of Fabry nephropathy is crucial since late initiation of enzyme replacement therapy may not halt progressive renal dysfunction. This may be challenging due to difficulties in diagnosis of Fabry disease in children and absence of a sensitive non-invasive biomarker of early Fabry nephropathy. Accurate measurement of glomerular filtration rate and regular assessment for proteinuria and microalbuminuria are useful, though not sensitive enough to detect early lesions in the kidney. Recent studies support the value of renal biopsy in providing histological information relevant to kidney function and prognosis, and renal biopsy could potentially be used to guide treatment decisions in young Fabry patients. This review aims to provide an update of the current understanding, challenges, and needs to better approach renal complications of Fabry disease in children.

Safety and pharmacodynamic effects of a pharmacological chaperone on α-galactosidase A activity and globotriaosylceramide clearance in Fabry disease: report from two phase 2 clinical studies

Background

Fabry disease (FD) is a genetic disorder resulting from deficiency of the lysosomal enzyme α-galactosidase A (α-Gal A), which leads to globotriaosylceramide (GL-3) accumulation in multiple tissues. We report on the safety and pharmacodynamics of migalastat hydrochloride, an investigational pharmacological chaperone given orally at 150 mg every-other-day.

Methods

Two open-label uncontrolled phase 2 studies of 12 and 24 weeks (NCT00283959 and NCT00283933) in 9 males with FD were combined. At multiple time points, α-Gal A activity and GL-3 levels were quantified in blood cells, kidney and skin. GL-3 levels were also evaluated through skin and renal histology.

Results

Compared to baseline, increased α-Gal A activity of at least 50% was demonstrated in blood, skin and kidney in 6 of 9 patients. Patients’ increased α-Gal A activities paralleled the α-Gal A increases observed in vitro in HEK-293 cells transfected with the corresponding mutant form of the enzyme. The same 6 patients who demonstrated increases of α-Gal A activity also had GL-3 reduction in skin, urine and/or kidney, and had α-Gal A mutations that responded in transfected cells incubated with the drug. The 3 patients who did not show a consistent response in vivo had α-Gal A mutations that did not respond to migalastat HCl in transfected cells. Migalastat HCl was well tolerated.

Conclusions

Migalastat HCl is a candidate pharmacological chaperone that provides a novel genotype-specific treatment for FD. It enhanced α-Gal A activity and resulted in GL-3 substrate decrease in patients with responsive GLA mutations. Phase 3 studies are ongoing.

Trial registration

Clinicaltrial.gov: NCT00283959 and NCT00283933

Towards automatic metabolomic profiling of high-resolution one-dimensional proton NMR spectra

Nuclear magnetic resonance (NMR) and Mass Spectroscopy (MS) are the two most common spectroscopic analytical techniques employed in metabolomics. The large spectral datasets generated by NMR and MS are often analyzed using data reduction techniques like Principal Component Analysis (PCA). Although rapid, these methods are susceptible to solvent and matrix effects, high rates of false positives, lack of reproducibility and limited data transferability from one platform to the next. Given these limitations, a growing trend in both NMR and MS-based metabolomics is towards targeted profiling or "quantitative" metabolomics, wherein compounds are identified and quantified via spectral fitting prior to any statistical analysis. Despite the obvious advantages of this method, targeted profiling is hindered by the time required to perform manual or computer-assisted spectral fitting. In an effort to increase data analysis throughput for NMR-based metabolomics, we have developed an automatic method for identifying and quantifying metabolites in one-dimensional (1D) proton NMR spectra. This new algorithm is capable of using carefully constructed reference spectra and optimizing thousands of variables to reconstruct experimental NMR spectra of biofluids using rules and concepts derived from physical chemistry and NMR theory. The automated profiling program has been tested against spectra of synthetic mixtures as well as biological spectra of urine, serum and cerebral spinal fluid (CSF). Our results indicate that the algorithm can correctly identify compounds with high fidelity in each biofluid sample (except for urine). Furthermore, the metabolite concentrations exhibit a very high correlation with both simulated and manually-detected values.

Study of urinary proteomes in Anderson-Fabry disease

BACKGROUND

Anderson-Fabry disease (AFD) is an X-linked genetic disorder with deficient α-galactosidase A activity. The main aim of this work was to investigate possible differences in urine proteins between healthy controls and AFD patients and to identify abnormal proteins as potential biomarkers of disease.

MATERIAL AND METHODS

We studied 2D electrophoresis images of urine samples collected from AFD patients and healthy subjects. The proteins were separated using isoelectric focusing method followed by SDS-PAGE. The proteins were then visualized by silver staining and characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

RESULTS

We found out that the urinary spectra of all the Fabry disease samples included identical proteins with molecular weight around 20-40 kDa. The concentration of some proteins was more than three times higher in the AFD samples, compared to the controls. The abundant proteins were identified by MALDI-TOF MS and included the following: alpha-1-antitrypsin, alpha-1-microglobulin, prostaglandin H2 d-isomerase, complement-c1q tumor necrosis factor-related protein, and Ig kappa chain V-III. Possible glycosylation at Asn51 and Asn78 sites of the prostaglandin H2 d-isomerase was detected.

CONCLUSIONS

AFD urinary proteomics revealed increased secretion of several proteins. We postulate that the observed difference in the amount of prostaglandin H2 d-isomerase and its position on two-dimensional gels might be related to different glycosylation in AFD subjects.

Elevation of urinary globotriaosylceramide (GL3) in infants with Fabry disease

BACKGROUND

Fabry disease is caused by a deficiency of α-galactosidase A (α-Gal A), which results in the accumulation of globotriaosylceramide (GL3) and related glycosphingolipids in different organs. Urinary GL3 levels increase in symptomatic Fabry disease patients, but it is not clear whether urinary GL3 excretion also increases in young or pre-symptomatic patients.

SUBJECTS AND METHODS

Eighty-nine newborns with leukocyte α-Gal A activities of less than 30% of the normal mean were discovered by newborn screening. Urine samples were collected on filter paper, and GL3 levels were measured using liquid chromatography-tandem mass spectrometry.

RESULTS

Five newborns with classic Fabry disease mutations all had elevated urinary GL3 levels (mean=5.2 mg/mmol creatinine (creat.), range=0.80-14.39, normal <0.6). Among the 84 newborns with later-onset mutations, 45 (54%) had a mild elevation of urinary GL3 levels (mean=1.1 mg/mmol creat., range=0.60-3.07, normal <0.6). The urinary GL3 levels decreased in all newborns over the course of a three-year follow-up period. However, four children with classic mutations and seven with IVS4+919G>A mutations still had elevated GL3 levels at the end of the study.

CONCLUSION

Elevated urinary GL3 levels can be present at birth in Fabry disease patients, suggesting an early involvement of the kidneys in this disease. The increased urinary GL3 excretion in those with later-onset mutations supports a pathogenic role for these mutations.

How well does urinary lyso-Gb3 function as a biomarker in Fabry disease?

BACKGROUND

Fabry disease is characterized by accumulation of glycosphingolipids, such as globotriaosylceramide (Gb(3)), in many tissues and body fluids. A novel plasma biomarker, globotriaosylsphingosine (lyso-Gb(3)), is increased in patients with the disease. Until now, lyso-Gb(3) was not detectable in urine, possibly because of the presence of interfering compounds.

METHODS

We undertook to: 1) characterize lyso-Gb(3) in urine; 2) develop a method to quantitate urinary lyso-Gb(3) by mass spectrometry; 3) evaluate urinary lyso-Gb(3) as a potential biomarker for Fabry disease; and 4) determine whether lyso-Gb(3) is an inhibitor of α-galactosidase A activity. We analyzed urinary lyso-Gb(3) from 83 Fabry patients and 77 healthy age-matched controls.

RESULTS

The intraday and interday bias and precision of the method were <15%. Increases in lyso-Gb(3)/creatinine correlated with the concentrations of Gb(3) (r(2)=0.43), type of mutations (p=0.0006), gender (p<0.0001) and enzyme replacement therapy status (p=0.0012). Urine from healthy controls contained no detectable lyso-Gb(3). Lyso-Gb(3) did not inhibit GLA activity in dried blood spots. Increased urinary excretion of lyso-Gb(3) of Fabry patients correlated well with a number of indicators of disease severity.

CONCLUSION

Lyso-Gb(3) is a reliable independent biomarker for clinically important characteristics of Fabry disease.

Enzyme replacement therapy and Fabry nephropathy

Involvement of the kidneys in Fabry disease ("nephropathy") occurs in male and female individuals. The majority of patients with progressive nephropathy will have significant proteinuria and develop progressive loss of kidney function, leading to ESRD. All too often, treating physicians may ignore "normal" serum creatinine levels or "minimal" proteinuria and fail to assess properly the severity of kidney involvement and institute appropriate management. Fabry nephropathy is treatable, even in patients with fairly advanced disease. Although the cornerstone of therapy remains enzyme replacement therapy with agalsidase, this treatment alone does not reduce urine protein excretion. Treatment with angiotensin receptor blockers or angiotensin-converting enzyme inhibitors must be added to enzyme replacement therapy to reduce urine protein excretion with the hope that this will stabilize kidney function. Kidney function, with at least estimated GFR based on serum creatinine and measurements of urinary protein, should be measured at every clinic visit, and the rate of change of the estimated GFR should be followed over time. Antiproteinuric therapy can be dosed to a prespecified urine protein target rather than a specific BP goal, with the proviso that successful therapy will usually lower the BP below the goal of 130/80 mmHg that is used for other forms of kidney disease. The overall goal for treating Fabry nephropathy is to reduce the rate of loss of GFR to -1 ml/min per 1.73 m(2)/yr, which is that seen in the normal adult population. A systematic approach is presented for reaching this goal in the individual patient.