Cardiac and Vascular Hypertrophy in Fabry Disease

Inflammation, Oxidative Stress, and Endothelial Dysfunction in the Pathogenesis of Vascular Damage: Unraveling Novel Cardiovascular Risk Factors in Fabry Disease

Anderson-Fabry disease (AFD), a genetic disorder caused by mutations in the α-galactosidase-A (GLA) gene, disrupts lysosomal function, leading to vascular complications. The accumulation of globotriaosylceramide (Gb3) in arterial walls triggers upregulation of adhesion molecules, decreases endothelial nitric oxide synthesis, and induces reactive oxygen species production. This cascade results in fibrotic thickening, endothelial dysfunction, hypercontractility, vasospasm, and a pro-thrombotic phenotype. AFD patients display increased intima-media thickness (IMT) and reduced flow-mediated dilation (FMD), indicating heightened cardiovascular risk. Nailfold capillaroscopy (NFC) shows promise in diagnosing and monitoring microcirculatory disorders in AFD, though it remains underexplored. Morphological evidence of AFD as a storage disorder can be demonstrated through electron microscopy and immunodetection of Gb3. Secondary pathophysiological disturbances at cellular, tissue, and organ levels contribute to the clinical manifestations, with prominent lysosomal inclusions observed in vascular, cardiac, renal, and neuronal cells. Chronic accumulation of Gb3 represents a state of ongoing toxicity, leading to increased cell turnover, particularly in vascular endothelial cells. AFD-related vascular pathology includes increased renin-angiotensin system activation, endothelial dysfunction, and smooth muscle cell proliferation, resulting in IMT increase. Furthermore, microvascular alterations, such as atypical capillaries observed through NFC, suggest early microvascular involvement. This review aims to unravel the complex interplay between inflammation, oxidative stress, and endothelial dysfunction in AFD, highlighting the potential connections between metabolic disturbances, oxidative stress, inflammation, and fibrosis in vascular and cardiac complications. By exploring novel cardiovascular risk factors and potential diagnostic tools, we can advance our understanding of these mechanisms, which extend beyond sphingolipid accumulation to include other significant contributors to disease pathogenesis. This comprehensive approach can pave the way for innovative therapeutic strategies and improved patient outcomes.

Arrhythmogenesis in Fabry Disease

PURPOSE OF REVIEW

Fabry Disease (FD) is a rare lysosomal storage disorder characterised by multiorgan accumulation of glycosphingolipid due to deficiency in the enzyme α-galactosidase A. Cardiac sphingolipid accumulation triggers various types of arrhythmias, predominantly ventricular arrhythmia, bradyarrhythmia, and atrial fibrillation. Arrhythmia is likely the primary contributor to FD mortality with sudden cardiac death, the most frequent cardiac mode of death. Traditionally FD was seen as a storage cardiomyopathy triggering left ventricular hypertrophy, diastolic dysfunction, and ultimately, systolic dysfunction in advanced disease. The purpose of this review is to outline the current evidence exploring novel mechanisms underlying the arrhythmia substrate.

RECENT FINDINGS

There is growing evidence that FD cardiomyopathy is a primary arrhythmic disease with each stage of cardiomyopathy (accumulation, hypertrophy, inflammation, and fibrosis) contributing to the arrhythmia substrate via various intracellular, extracellular, and environmental mechanisms. It is therefore important to understand how these mechanisms contribute to an individual's risk of arrhythmia in FD. In this review, we outline the epidemiology of arrhythmia, pathophysiology of arrhythmogenesis, risk stratification, and cardiac therapy in FD. We explore how advances in conventional cardiac investigations performed in FD patients including 12-lead electrocardiography, transthoracic echocardiography, and cardiac magnetic resonance imaging have enabled early detection of pro-arrhythmic substrate. This has allowed for appropriate risk stratification of FD patients. This paves the way for future work exploring the development of therapeutic initiatives and risk prediction models to reduce the burden of arrhythmia.

Cerebrovascular Phenotype in Fabry Disease Patients Assessed by Ultrasound

OBJECTIVES

Fabry disease (FD) is a rare X-linked lysosomal storage disorder with variable phenotypes, including neurological symptoms. These can be influenced by vascular impairment. Extracranial and transcranial vascular sonography is an effective and noninvasive method for measuring arterial structures and blood flow. The study aims to investigate cerebrovascular phenotype characteristics in FD patients compared to controls using neurosonology.

METHODS

This is a single-center, cross-sectional study of 130 subjects-65 patients (38 females), with genetically confirmed FD, and 65 sex- and age-matched controls. Using ultrasonography, we measured structural and hemodynamic parameters, including distal common carotid artery intima-media thickness, inner vertebral artery diameter, resting blood flow velocity, pulsatility index, and cerebral vasoreactivity (CVR) in the middle cerebral artery. To assess differences between FD and controls and to identify factors influencing investigated outcomes, unadjusted and adjusted regression analyses were performed.

RESULTS

In comparison to sex- and age-matched controls, FD patients displayed significantly increased carotid artery intima-media thickness (observed FD 0.69 ± 0.13 mm versus controls 0.63 ± 0.12 mm; Padj  = .0014), vertebral artery diameter (observed FD 3.59 ± 0.35 mm versus controls 3.38 ± 0.33 mm; Padj  = .0002), middle cerebral artery pulsatility index (observed FD 0.98 ± 0.19 versus controls 0.87 ± 0.11; Padj  < .0001), and significantly decreased CVR (observed FD 1.21 ± 0.49 versus controls 1.35 ± 0.38; Padj  = .0409), when adjusted by age, BMI, and sex. Additionally, FD patients had significantly more variable CVR (0.48 ± 0.25 versus 0.21 ± 0.14; Padj  < .0001).

CONCLUSIONS

Our results suggest the presence of multiple vascular abnormalities and changes in hemodynamic parameters of cerebral arteries in patients with FD.

Electrocardiogram analysis in Anderson-Fabry disease: a valuable tool for progressive phenotypic expression tracking

Background

Electrocardiogram (ECG) has proven to be useful for early detection of cardiac involvement in Anderson-Fabry disease (AFD); however, little evidence is available on the association between ECG alterations and the progression of the disease.

Aim and Methods

To perform a cross sectional comparison of ECG abnormalities throughout different left ventricular hypertrophy (LVH) severity subgroups, providing ECG patterns specific of the progressive AFD stages. 189 AFD patients from a multicenter cohort underwent comprehensive ECG analysis, echocardiography, and clinical evaluation.

Results

The study cohort (39% males, median age 47 years, 68% classical AFD) was divided into 4 groups according to different degree of left ventricular (LV) thickness: group A ≤ 9 mm (n = 52, 28%); group B 10-14 mm (n = 76, 40%); group C 15-19 mm (n = 46, 24%); group D ≥ 20 mm (n = 15, 8%). The most frequent conduction delay was right bundle branch block (RBBB), incomplete in groups B and C (20%,22%) and complete RBBB in group D (54%, p < 0.001); none of the patients had left bundle branch block (LBBB). Left anterior fascicular block, LVH criteria, negative T waves, ST depression were more common in the advanced stages of the disease (p < 0.001). Summarizing our results, we suggested ECG patterns representative of the different AFD stages as assessed by the increases in LV thickness over time (Central Figure). Patients from group A showed mostly a normal ECG (77%) or minor anomalies like LVH criteria (8%) and delta wave/slurred QR onset + borderline PR (8%). Differently, patients from groups B and C exhibited more heterogeneous ECG patterns: LVH (17%; 7% respectively); LVH + LV strain (9%; 17%); incomplete RBBB + repolarization abnormalities (8%; 9%), more frequently associated with LVH criteria in group C than B (8%; 15%). Finally, patients from group D showed very peculiar ECG patterns, represented by complete RBBB + LVH and repolarization abnormalities (40%), sometimes associated with QRS fragmentation (13%).

Conclusions

ECG is a sensitive tool for early identification and long-term monitoring of cardiac involvement in patients with AFD, providing "instantaneous pictures" along the natural history of AFD. Whether ECG changes may be associated with clinical events remains to be determined.

Anderson-Fabry disease cardiomyopathy: an update on epidemiology, diagnostic approach, management and monitoring strategies

Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder caused by deficient activity of the enzyme alpha-galactosidase. While AFD is recognized as a progressive multi-system disorder, infiltrative cardiomyopathy causing a number of cardiovascular manifestations is recognized as an important complication of this disease. AFD affects both men and women, although the clinical presentation typically varies by sex, with men presenting at a younger age with more neurologic and renal phenotype and women developing a later onset variant with more cardiovascular manifestations. AFD is an important cause of increased myocardial wall thickness, and advances in imaging, in particular cardiac magnetic resonance imaging and T1 mapping techniques, have improved the ability to identify this disease non-invasively. Diagnosis is confirmed by the presence of low alpha-galactosidase activity and identification of a mutation in the GLA gene. Enzyme replacement therapy remains the mainstay of disease modifying therapy, with two formulations currently approved. In addition, newer treatments such as oral chaperone therapy are now available for select patients, with a number of other investigational therapies in development. The availability of these therapies has significantly improved outcomes for AFD patients. Improved survival and the availability of multiple agents has presented new clinical dilemmas regarding disease monitoring and surveillance using clinical, imaging and laboratory biomarkers, in addition to improved approaches to managing cardiovascular risk factors and AFD complications. This review will provide an update on clinical recognition and diagnostic approaches including differentiation from other causes of increased ventricular wall thickness, in addition to modern strategies for management and follow-up.

Management of Hypertension in Fabry Disease

Fabry disease (FD), a rare X-linked lysosomal storage disorder that depletes alpha-galactosidase A (α-GalA), is caused by mutations in the GLA gene. Diminished α-GalA enzyme activity results in the accumulation of Gb3 and lyso-Gb3. The pathophysiology of hypertension in FD is complex and unclear. The storage of Gb3 in arterial endothelial cells and smooth muscle cells is known to produce vascular injury by increasing oxidative stress and inflammatory cytokines as a primary pathophysiological mechanism. In addition, Fabry nephropathy developed, resulting in a decrease in kidney function and contributing to hypertension. The prevalence of hypertension in patients with FD was between 28.4% and 56%, whereas hypertension in patients with chronic kidney disease ranged between 33% and 79%. A study using 24-hour ambulatory blood pressure monitoring (ABPM) to measure blood pressure (BP) indicated a high prevalence of uncontrolled hypertension in FD. Thus, 24-hour ABPM ought to be considered for FD hypertension assessments. Appropriate treatment of hypertension is believed to reduce mortality in patients with FD caused by kidney disease, cardiovascular disease, and cerebrovascular disease because hypertension significantly impacts organ damage. Up to 70% of FD patients have been reported to have kidney involvement, and angiotensin-converting enzyme inhibitors and angiotensin receptor blockers prescribed for proteinuria are recommended as first-line therapy with antihypertensive drugs. In conclusion, hypertension should be controlled appropriately, given the different morbidity and mortality caused by significant organ involvement in FD patients.

Arteriolar neuropathology in cerebral microvascular disease

Cerebral microvascular disease (MVD) is an important cause of vascular cognitive impairment. MVD is heterogeneous in aetiology, ranging from universal ageing to the sporadic (hypertension, sporadic cerebral amyloid angiopathy [CAA] and chronic kidney disease) and the genetic (e.g., familial CAA, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy [CADASIL] and cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy [CARASIL]). The brain parenchymal consequences of MVD predominantly consist of lacunar infarcts (lacunes), microinfarcts, white matter disease of ageing and microhaemorrhages. MVD is characterised by substantial arteriolar neuropathology involving ubiquitous vascular smooth muscle cell (SMC) abnormalities. Cerebral MVD is characterised by a wide variety of arteriolar injuries but only a limited number of parenchymal manifestations. We reason that the cerebral arteriole plays a dominant role in the pathogenesis of each type of MVD. Perturbations in signalling and function (i.e., changes in proliferation, apoptosis, phenotypic switch and migration of SMC) are prominent in the pathogenesis of cerebral MVD, making 'cerebral angiomyopathy' an appropriate term to describe the spectrum of pathologic abnormalities. The evidence suggests that the cerebral arteriole acts as both source and mediator of parenchymal injury in MVD.

Role of cardiovascular magnetic resonance in the clinical evaluation of left ventricular hypertrophy: a 360° panorama

Left ventricular hypertrophy (LVH) is a frequent imaging finding in the general population. In order to identify the precise etiology, a comprehensive diagnostic approach should be adopted, including the prevalence of each entity that may cause LVH, family history, clinical, electrocardiographic and imaging findings. By providing a detailed evaluation of the myocardium, cardiovascular magnetic resonance (CMR) has assumed a central role in the differential diagnosis of left ventricular hypertrophy, with the technique of parametric imaging allowing more refined tissue characterization. This article aims to establish a parallel between pathophysiological features and imaging findings through the broad spectrum of LVH entities, emphasizing the role of CMR in the differential diagnosis.

Early start of enzyme replacement therapy in pediatric male patients with classical Fabry disease is associated with attenuated disease progression

BACKGROUND

Enzyme replacement therapy (ERT) slows disease progression of Fabry disease (FD), especially when initiated before the onset of irreversible organ damage. However, with the clinically asymptomatic progression of renal, cardiac and cerebral disease manifestations spanning decades, optimal timing of ERT initiation remains unclear.

METHODS

In this cross-sectional retrospective study, seven male FD patients with a classical disease phenotype (cFD) who started treatment with agalsidase-beta in childhood were evaluated after 10 years of treatment (median age at evaluation 24 years, range 14-26). Cardiac imaging (echocardiography and MRI), electrophysiological and biochemical data of these patients were compared to those of untreated male cFD patients (n = 23, median age 22 years, range 13-27).

RESULTS

Albuminuria was less common and less severe in treated patients (albumin to creatinine ratio, ACR 0-8.8 mg/mmol, median 0.4) compared to untreated patients (ACR 0-248 mg/mmol, median 3.7, p = 0.02). The treated group had a lower left ventricular mass, measured using echocardiography (median 80 g/m² versus 94 g/m², p = 0.02) and MRI (median 53 g/m² versus 68 g/m², p = 0.02). Myocardial fibrosis was absent in all included patients. eGFR was normal in all treated patients whereas 7/23 (30%) of untreated patients had abnormal eGFR. Cerebral manifestations did not differ.

CONCLUSIONS

Start of treatment with ERT before age 16, in male cFD patients is associated with reduced occurrence of renal and cardiac manifestations of FD, as assessed by intermediate endpoints. Confirmation that this approach delays or even prevents renal failure and cardiac events requires another decade of follow-up.

Neuropsychiatric Symptoms and Their Association With Sex, Age, and Enzyme Replacement Therapy in Fabry Disease: A Systematic Review

Patients suffering from Fabry disease (FD) have an increased risk of developing neuropsychiatric symptoms (NPS), mostly impairment in cognitive performance and depression. Single cases of psychosis have been reported, however, their association with FD can be coincidental. Furthermore, deficits in social functioning and adaptation as well as specific coping styles in FD patients were observed. Recent studies focused on a longitudinal course of the disease and identified risk factors associated with specific NPS. Since 2001, enzyme replacement therapy (ERT) has been available and in preliminary studies seems to improve cognitive impairment and adaptive skills. In this systematic review, we analyze the available literature on the NPS in FD and investigate if there are any differences in their distribution between males and females, children/adolescents and adults, and individuals treated with ERT and untreated. We discuss the role of the psychological, environmental, and molecular alterations and their correlation to psychiatric manifestations in FD. Finally, we would like to increase awareness of the spectrum of NPS in FD.

Pathogenesis and Molecular Mechanisms of Anderson-Fabry Disease and Possible New Molecular Addressed Therapeutic Strategies

Anderson-Fabry disease (AFD) is a rare disease with an incidenceof approximately 1:117,000 male births. Lysosomal accumulation of globotriaosylceramide (Gb3) is the element characterizing Fabry disease due to a hereditary deficiency α-galactosidase A (GLA) enzyme. The accumulation of Gb3 causes lysosomal dysfunction that compromises cell signaling pathways. Deposition of sphingolipids occurs in the autonomic nervous system, dorsal root ganglia, kidney epithelial cells, vascular system cells, and myocardial cells, resulting in organ failure. This manuscript will review the molecular pathogenetic pathways involved in Anderson-Fabry disease and in its organ damage. Some studies reported that inhibition of mitochondrial function and energy metabolism plays a significant role in AFD cardiomyopathy and in kidney disease of AFD patients. Furthermore, mitochondrial dysfunction has been reported as linked to the dysregulation of the autophagy-lysosomal pathway which inhibits the mechanistic target of rapamycin kinase (mTOR) mediated control of mitochondrial metabolism in AFD cells. Cerebrovascular complications due to AFD are caused by cerebral micro vessel stenosis. These are caused by wall thickening resulting from the intramural accumulation of glycolipids, luminal occlusion or thrombosis. Other pathogenetic mechanisms involved in organ damage linked to Gb3 accumulation are endocytosis and lysosomal degradation of endothelial calcium-activated intermediate-conductance potassium ion channel 3.1 (KCa3.1) via a clathrin-dependent process. This process represents a crucial event in endothelial dysfunction. Several studies have identified the deacylated form of Gb3, globotriaosylsphingosine (Lyso-Gb3), as the main catabolite that increases in plasma and urine in patients with AFD. The mean concentrations of Gb3 in all organs and plasma of Galactosidase A knockout mice were significantly higher than those of wild-type mice. The distributions of Gb3 isoforms vary from organ to organ. Various Gb3 isoforms were observed mainly in the kidneys, and kidney-specific Gb3 isoforms were hydroxylated. Furthermore, the action of Gb3 on the KCa3.1 channel suggests a possible contribution of this interaction to the Fabry disease process, as this channel is expressed in various cells, including endothelial cells, fibroblasts, smooth muscle cells in proliferation, microglia, and lymphocytes. These molecular pathways could be considered a potential therapeutic target to correct the enzyme in addition to the traditional enzyme replacement therapies (ERT) or drug chaperone therapy.

Fabry Cardiomyopathy: Current Treatment and Future Options

Fabry disease is a multisystem X-linked lysosomal storage disorder caused by a mutation in the alpha-galactosidase A gene. Deficiency or reduced activity of alpha-galactosidase A (GLA) is leading to progressive intracellular accumulation of globotriaosylceramide (GL3) in various organs, including the heart, kidney and nerve system. Cardiac involvement is frequent and is evident as concentric left ventricular hypertrophy. Currently, the standard treatment is enzyme replacement therapy or chaperone therapy. However, early starting of therapy, before myocardial fibrosis has developed, is essential for long-term improvement of myocardial function. For future treatment options, various therapeutic approaches including gene therapy are under development. This review describes the current and potential future therapy options for Fabry cardiomyopathy.

Fabry Disease on Peritoneal Dialysis with Cardiac Involvement

Fabry disease (FD) is an X-linked lysosomal storage disorder resulting from a lack of alpha-galactosidase A (AGALA) activity in lysosomes. We herein report a patient with FD revealed by a renal biopsy who survived seven years after the introduction of peritoneal dialysis despite having severe heart failure due to left ventricular hypertrophy (LVH). FD was diagnosed based on a renal biopsy and biochemical analysis showing a low enzymatic activity of AGALA. A microscopic examination at the autopsy revealed marked hypertrophy and vacuolation of cardiac muscle cells. In our case, cardiac involvement determined the prognosis. Peritoneal dialysis is the modality of choice in the long-term management of dialysis patients with FD.

Hypertrophy of unaffected cardiomyocytes correlates with severity of cardiomyopathy in female patients with Fabry disease

Aim

To investigate the contribution of unaffected cardiomyocytes in Fabry disease cardiomyopathy.

Findings

Left ventricular (LV) endomyocardial biopsies from twenty-four females (mean age 53 ± 11 ys) with Fabry disease cardiomyopathy were studied. Diagnosis of FD was based on the presence of pathogenic GLA mutation, Patients were divided in four groups according with LV maximal wall thickness (MWT): group 1 MWT ≤ 10.5 mm, group 2 MWT 10.5–15 mm, group 3 MWT 16–20 mm, group 4 MWT > 20 mm. At histology mosaic of affected and unaffected cardiomyocytes was documented. Unaffected myocytes’ size ranged from normal to severe hypertrophy. Hypertrophy of unaffected cardiomyocytes correlated with severity of MWT (p < 0.0001, Sperman r 0,95). Hypertrophy of unaffected myocytes appear to concur to progression and severity of FDCM. It is likely a paracrine role from neighboring affected myocytes.

Pathology and pathogenic pathways in fabry nephropathy

BACKGROUND

The pathophysiology of renal damage in Fabry nephropathy involves a complex biological mechanism. The intracellular deposition globotriaosylceramide (Gb3) is just the first step of the mechanism. The glycolipid deposition occurs in all renal cells (endothelial, epithelial and mesangial cells). It stimulates many biological processes, including cytokine release, epithelial-mesenchymal transdifferentiation, oxidative stress and the remodelling of vascular walls, resulting in subtle initial inflammation and eventually tissue fibrosis. It has been hypothesized that the processes activated by Gb3 deposition can subsequently progress independently of cellular deposition and that even Gb3 clearance by specific therapy cannot retard or stop these pathways.

AIM

This review aims to gather the reported evidence of these cellular alterations and the resulting histological changes. Our approach is similar to a routine study of kidney biopsy.

RESULTS

In the first part of the review, "histology" section, we describe the structures involved (glomeruli, vessels, tubules and interstitium) from a histological point of view. While in the second part, "pathogenesis" section, we present some interpretations about the implicated pathways based on the up-to-date available evidence.

RIPK3 Contributes to Lyso-Gb3-Induced Podocyte Death

Fabry disease is a lysosomal storage disease with an X-linked heritage caused by absent or decreased activity of lysosomal enzymes named alpha-galactosidase A (α-gal A). Among the various manifestations of Fabry disease, Fabry nephropathy significantly affects patients' morbidity and mortality. The cellular mechanisms of kidney damage have not been elusively described. Necroptosis is one of the programmed necrotic cell death pathways and is known to play many important roles in kidney injury. We investigated whether RIPK3, a protein phosphokinase with an important role in necroptosis, played a crucial role in the pathogenesis of Fabry nephropathy both in vitro and in vivo. The cell viability of podocytes decreased after lyso-Gb3 treatment in a dose-dependent manner, with increasing RIPK3 expression. Increased reactive oxygen species (ROS) generation after lyso-Gb3 treatment, which was alleviated by GSK'872 (a RIPK3 inhibitor), suggested a role of oxidative stress via a RIPK3-dependent pathway. Cytoskeleton rearrangement induced by lyso-Gb3 was normalized by the RIPK3 inhibitor. When mice were injected with lyso-Gb3, increased urine albuminuria, decreased podocyte counts in the glomeruli, and effaced foot processes were observed. Our results showed that lyso-Gb3 initiated albuminuria, a clinical manifestation of Fabry nephropathy, by podocyte loss and subsequent foot process effacement. These findings suggest a novel pathway in Fabry nephropathy.

Trabecular complexity as an early marker of cardiac involvement in Fabry disease

AIMS

Fabry cardiomyopathy is characterized by glycosphingolipid storage and increased myocardial trabeculation has also been demonstrated. This study aimed to explore by cardiac magnetic resonance whether myocardial trabecular complexity, quantified by endocardial border fractal analysis, tracks phenotype evolution in Fabry cardiomyopathy.

METHODS AND RESULTS

Study population included 20 healthy controls (12 males, age 32±9) and 45 Fabry patients divided into three groups: 15 left ventricular hypertrophy (LVH)-negative patients with normal T1 (5 males, age 28±13; Group 1); 15 LVH-negative patients with low T1 (9 males, age 33±9.6; Group 2); 15 LVH-positive patients (11 males, age 53.5±9.6; Group 3). Trabecular fractal dimensions (Dfs) (total, basal, mid-ventricular, and apical) were evaluated on cine images. Total Df was higher in all Fabry groups compared to controls, gradually increasing from controls to Group 3 (1.27±0.02 controls vs. 1.29±0.02 Group 1 vs. 1.30±0.02 Group 2 vs. 1.34±0.02 Group 3; P<0.001). Group 3 showed significantly higher values of all Dfs compared to the other Groups. Both basal and total Dfs were significantly higher in Group 1 compared with controls (basal: 1.30±0.03 vs. 1.26±0.04, P =0.010; total: 1.29±0.02 vs. 1.27±0.02, P=0.044). Total Df showed significant correlations with: (i) T1 value (r=-0.569; P<0.001); (ii) LV mass (r=0.664, P<0.001); (iii) trabecular mass (r=0.676; P <0.001); (iv) Mainz Severity Score Index (r=0.638; P<0.001).

CONCLUSION

Fabry cardiomyopathy is characterized by a progressive increase in Df of endocardial trabeculae together with shortening of T1 values. Myocardial trabeculation is increased before the presence of detectable sphingolipid storage, thus representing an early sign of cardiac involvement.

Characteristics of Vascular Phenotype in Fabry Patients

Fabry disease is a rare X-linked lysosomal disorder. Alpha-galactosidase A deficiency caused by mutation leads to accumulation of glycosphingolipids predominantly in endothelial cells, leading to impairment of vascular wall morphology and function. We assessed vascular wall hypertrophy (carotid artery intima-media thickness, cIMT), endothelial function (brachial artery flow-mediated dilation, FMD), presence of atherosclerotic plaques in the carotid and femoral arteries, and levels of endothelial adhesion and inflammatory biomarkers in 33 Fabry patients compared with 66 healthy matched controls. Fabry patients had thicker cIMT (0.07 ± 0.02 vs 0.06 ± 0.02 cm; P = .021), as well as dilated common carotid arteries (0.80 ± 0.12 vs 0.70 ± 0.06 cm; P < .001), and aortic annulus than controls (3.07 ± 0.48 vs 2.7 ± 0.48 cm; P = .001). Flow-mediated dilation was reduced (4.48 ± 8.80 vs 10.67 ± 8.72%; P = .001) and atherosclerotic plaques were less present in Fabry patients (9.10% vs 43.94%; P < .001). Vascular cell adhesion molecule-1, interleukin-6, tumor necrosis factor α, and high-sensitivity CRP were significantly higher and E-selectin lower in Fabry patients. Our results suggest that a complex vascular phenotype is present in Fabry patients. This represents a challenge for further research that could have important clinical applications.

Stroke and Fabry Disease: A Review of Literature

Fabry disease is an X-linked lysosomal storage disorder caused by a mutation in the alpha-galactosidase A (GLA) gene, leading to the deficiency of alpha-galactosidase A enzyme. The natural history of the affected patients (both males and females) includes neurovascular complications, such as cerebrovascular disease at a relatively young age. The pathophysiology behind the vascular involvement is primarily attributed to the accumulation of globotriaosylceramide and its derivatives in the vascular endothelium and vascular smooth muscle cells. MRI is the gold standard radiological investigation to detect the white matter lesions characteristic of Fabry disease's neurological involvement. More studies should focus on the utility of universally screening patients with young stroke for Fabry disease and the effectiveness of enzyme replacement therapy to prevent stroke. This review offers a synopsis of the current knowledge of the pathophysiology, neuroradiology, treatment, and prognosis of cerebrovascular disease in Fabry patients.

The role of Immunity in Fabry Disease and Hypertension: A Review of a Novel Common Pathway

Fabry disease is a progressive, X-linked inherited lysosomal storage disorder where accumulation of glycosphingolipids increases the risk for early cardiovascular complications, including heart failure, stroke, and end stage renal disease. Besides disease-specific therapy, blood pressure (BP) control is of central importance in Fabry disease to reduce disease progression and improve prognosis. Both Fabry disease and hypertension are characterized by the activation of the innate component of the immune system, with Toll-like receptor 4 (TLR4) as a common trigger to the inflammatory cascade. The renin-angiotensin system (RAS) participates in the establishment of low-grade chronic inflammation and redox unbalance that contribute to organ damage in the long term. Besides exploiting the anti-inflammatory effects of RAS blockade and enzyme replacement therapy, targeted therapies acting on the immune system represent an appealing field of research in these conditions. The aim of this narrative review is to examine the issue of hypertension in the setting of Fabry disease, focusing on the possible determinants of their reciprocal relationship, as well as on the related clinical and therapeutic implications.

Lyso-glycosphingolipids: presence and consequences

Lyso-glycosphingolipids are generated in excess in glycosphingolipid storage disorders. In the course of these pathologies glycosylated sphingolipid species accumulate within lysosomes due to flaws in the respective lipid degrading machinery. Deacylation of accumulating glycosphingolipids drives the formation of lyso-glycosphingolipids. In lysosomal storage diseases such as Gaucher Disease, Fabry Disease, Krabbe disease, GM1 -and GM2 gangliosidosis, Niemann Pick type C and Metachromatic leukodystrophy massive intra-lysosomal glycosphingolipid accumulation occurs. The lysosomal enzyme acid ceramidase generates the deacylated lyso-glycosphingolipid species. This review discusses how the various lyso-glycosphingolipids are synthesized, how they may contribute to abnormal immunity in glycosphingolipid storing lysosomal diseases and what therapeutic opportunities exist.

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.

Left ventricular radial strain impairment precedes hypertrophy in Anderson-Fabry disease

In Anderson-Fabry disease (AFD), left ventricular (LV) radial function has been scarcely investigated. We hypothesized that LV function may be affected by disease specific mechanisms and sought to comprehensively evaluate LV radial, circumferential and longitudinal function in a large population of AFD patients looking at the influence of LV geometry and fibrosis. We prospectively studied 94 consecutive AFD patients (41.5 ± 14.5 years; 41 men) with preserved LV ejection fraction (EF) utilizing speckle-tracking echocardiography. A subset of patients underwent gadolinium-enhanced cardiac magnetic resonance. Cases were compared to 48 healthy subjects matched for age and sex. LV concentric hypertrophy was found in 33 AFD patients while LV concentric remodeling (relative wall thickness ≥ 0.43) in 16 out 61 patients with normal LV mass. AFD patients had lower radial, longitudinal and circumferential strains than controls, independently by LV geometry pattern. Patients with LV hypertrophy showed reduced global longitudinal strain (p < 0.001) and early diastolic untwisting rate (p = 0.002) as compared to patients with normal geometry. In the whole AFD population, neither radial strain nor circumferential strain correlated with LV mass, while global longitudinal strain and early diastolic untwisting rate did (both p < 0.001). Late gadolinium enhancement was significantly associated with longitudinal strain, twisting rate and early diastolic untwisting rate, with twisting rate being the most powerful independent predictor (β = - 0.461; p = 0.002). Findings demonstrate impairment of LV radial strain in AFD patients with preserved EF, even in a pre-hypertrophic stage. Development of LV hypertrophy and fibrosis make worse mostly longitudinal dysfunction.

Identification of lysosomal and extralysosomal globotriaosylceramide (Gb3) accumulations before the occurrence of typical pathological changes in the endomyocardial biopsies of Fabry disease patients

PURPOSE

Evaluation standards and treatment initiation timing have been debated for a long time, particularly for late-onset Fabry disease (FD), because of its slow progression. However, early initiation of enzyme replacement therapy (ERT) for FD could be effective in stabilizing the disease progression and potentially preventing irreversible organ damage. We aimed to examine globotriaosylceramide (Gb3) deposits in patients' endomyocardial biopsies to understand the early pathogenesis of FD cardiomyopathy.

METHODS

Immunofluorescent (IF) staining of Gb3 and lysosomal-associated membrane protein 1 (LAMP-1) was performed on endomyocardial biopsies of patients suspected of Fabry cardiomyopathy who had negative or only slight Gb3 accumulation determined by toluidine blue staining and electron microscopic examination.

RESULTS

The IF staining results revealed that all patients examined had abundant Gb3 accumulation in their cardiomyocytes, including the ones who are negative for inclusion bodies. Furthermore, we found that early Gb3 deposits were mostly confined within lysosomes, while they appeared extralysosomally at a later stage.

CONCLUSION

A significant amount of lysosomal Gb3 deposits could be detected by IF staining in cardiac tissue before the formation of inclusion bodies, suggesting the cardiomyocytes might have been experiencing cellular stress and damage early on, before the appearance of typical pathological changes of FD during the disease progression.

α-Galactosidase A-deficient rats accumulate glycosphingolipids and develop cardiorenal phenotypes of Fabry disease

Fabry disease is an X-linked lysosomal storage disease caused by α-galactosidase A (α-Gal A) deficiency. Kidney and heart failure are frequent complications in adulthood and greatly contribute to patient morbidity and mortality. Because α-Gal A-deficient mouse models do not recapitulate cardiorenal findings observed in patients, a nonmouse model may be beneficial to our understanding of disease pathogenesis. In this study, we evaluated disease processes in a recently generated Fabry rat model. We found that male Fabry rats weighed significantly less than wild-type (WT) males, whereas female Fabry rats weighed significantly more than WT females. Whereas no difference in female survival was detected, we observed that male Fabry rats had a decreased lifespan. Skin histology revealed that inflammation and lipoatrophy may be chief disease mediators in patients. With respect to the kidney and heart, we found that both organs accumulate α-Gal A substrates, including the established biomarkers, globotriaosylceramide and globotriaosylsphingosine. Longitudinal serum and urine chemistry panels demonstrated pronounced renal tubule dysfunction, which was confirmed histologically. Mitral valve thickening was observed in Fabry rats using echocardiography. We conclude that Fabry rats recapitulate important kidney and heart phenotypes experienced by patients and can be further used to study disease mechanisms and test therapies.-Miller, J. J., Aoki, K., Mascari, C. A., Beltrame, A. K., Sokumbi, O., North, P. E., Tiemeyer, M., Kriegel, A. J., Dahms, N. M., α-Galactosidase A-deficient rats accumulate glycosphingolipids and develop cardiorenal phenotypes of Fabry disease.

Anderson-Fabry disease in heart failure

Anderson-Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene that result in deficiency of the enzyme alpha-galactosidase A. The worldwide incidence of Fabry's disease is reported to be in the range of 1 in 40,000-117,000, although this value may be a significant underestimate given under recognition of symptoms and delayed or missed diagnosis. Deficiency in alpha-galactosidase A causes an accumulation of neutral glycosphingolipids such as globotriaosylceramide (Gb3) in lysosomes within various tissues including the vascular endothelium, kidneys, heart, eyes, skin and nervous system. Gb3 accumulation induces pathology via the release of pro-inflammatory cytokines, growth-promoting factors and by oxidative stress, resulting in myocardial extracellular matrix remodelling, left ventricular hypertrophy (LVH), vascular dysfunction and interstitial fibrosis. Cardiac involvement manifesting as ventricular hypertrophy, systolic and diastolic dysfunction, valvular abnormalities and conduction tissue disease is common in AFD and is associated with considerable cardiovascular morbidity and mortality from heart failure, sudden cardiac death and stroke-related death.

High-Sensitivity Troponin: A Clinical Blood Biomarker for Staging Cardiomyopathy in Fabry Disease

BACKGROUND

High-sensitivity troponin (hs-TNT), a biomarker of myocardial damage, might be useful for assessing fibrosis in Fabry cardiomyopathy. We performed a prospective analysis of hs-TNT as a biomarker for myocardial changes in Fabry patients and a retrospective longitudinal follow-up study to assess longitudinal hs-TNT changes relative to fibrosis and cardiomyopathy progression.

METHODS AND RESULTS

For the prospective analysis, hs-TNT from 75 consecutive patients with genetically confirmed Fabry disease was analyzed relative to typical Fabry-associated echocardiographic findings and total myocardial fibrosis as measured by late gadolinium enhancement (LE) on magnetic resonance imaging. Longitudinal data (3.9±2.0 years), including hs-TNT, LE, and echocardiographic findings from 58 Fabry patients, were retrospectively collected. Hs-TNT level positively correlated with LE (linear correlation coefficient, 0.72; odds ratio, 32.81 [95% CI, 3.56-302.59]; P=0.002); patients with elevated baseline hs-TNT (>14 ng/L) showed significantly increased LE (median: baseline, 1.9 [1.1-3.3] %; follow-up, 3.2 [2.3-4.9] %; P<0.001) and slightly elevated hs-TNT (baseline, 44.7 [30.1-65.3] ng/L; follow-up, 49.1 [27.6-69.5] ng/L; P=0.116) during follow-up. Left ventricular wall thickness and EF of patients with elevated hs-TNT were decreased during follow-up, indicating potential cardiomyopathy progression.

CONCLUSIONS

hs-TNT is an accurate, easily accessible clinical blood biomarker for detecting replacement fibrosis in patients with Fabry disease and a qualified predictor of cardiomyopathy progression. Thus, hs-TNT could be helpful for staging and follow-up of Fabry patients.

Anderson-Fabry cardiomyopathy: prevalence, pathophysiology, diagnosis and treatment

Anderson-Fabry disease (AFD) is a lysosomal storage disease caused by the inappropriate accumulation of globotriaosylceramide in tissues due to a deficiency in the enzyme α-galactosidase A (α-Gal A). Anderson-Fabry cardiomyopathy is characterized by structural, valvular, vascular and conduction abnormalities, and is now the most common cause of mortality in patients with AFD. Large-scale metabolic and genetic screening studies have revealed AFD to be prevalent in populations of diverse ethnic origins, and the variant form of AFD represents an unrecognized health burden. Anderson-Fabry disease is an X-linked disorder, and genetic testing is critical for the diagnosis of AFD in women. Echocardiography with strain imaging and cardiac magnetic resonance imaging using late enhancement and T1 mapping are important imaging tools. The current therapy for AFD is enzyme replacement therapy (ERT), which can reverse or prevent AFD progression, while gene therapy and the use of molecular chaperones represent promising novel therapies for AFD. Anderson-Fabry cardiomyopathy is an important and potentially reversible cause of heart failure that involves LVH, increased susceptibility to arrhythmias and valvular regurgitation. Genetic testing and cardiac MRI are important diagnostic tools, and AFD cardiomyopathy is treatable if ERT is introduced early.

Enzyme replacement therapy stabilized white matter lesion progression in Fabry disease

BACKGROUND

The central nervous system manifestations in Fabry disease (FD) include progressive white matter lesions (WMLs) and stroke. Due to progressive microvascular involvement, men and women with FD over 35 years of age develop WMLs. Moreover, the prevalence of stroke has been estimated to be 12 times higher in FD compared with the general population. Enzyme replacement therapy (ERT) is available and has shown beneficial effects on renal, cardiac, and peripheral nerve function in FD, but the ERT effect on the progression of WMLs, or the reduction in cerebrovascular events, remains unknown.

METHODS

The WML burden and the effect of agalsidase beta 1 mg/kg biweekly on WML progression were assessed longitudinally in a Phase 4 agalsidase-beta placebo-controlled analysis of untreated and treated FD patients with mild-to-moderate renal involvement (serum creatinine measurements of ≥1.2 mg/dl and <3.0 mg/dl). The primary end point was the difference in the number of patients with increased WML burden between the agalsidase beta and placebo groups at the end of treatment. The diameters of the WMLs were determined manually using axial flow-attenuated-inversion-recovery-weighted magnetic resonance imaging (MRI) scans taken at baseline and follow-up.

RESULTS

MRI scans from 41 FD patients (mean age 43.9, age range 20-68, 3 females; n=25 on ERT, n=16 on placebo) were analyzed. WML burden was present in 63% of patients at baseline, increased over a mean of 27 months (range 12-33 months) follow-up, and correlated with left ventricular hypertrophy (LVPW). Patients with previous or recent strokes (n=11, 39-68 years) showed an increase in the number of WMLs (p=0.005). A greater proportion of younger patients (≤50 years) on ERT (n=18) had stable WML burden compared with younger patients in the placebo group (n=13): 44% (8 of 18) versus 31% (4 of 13), p=0.014. The number needed to treat was 8.

CONCLUSIONS

This FD patient cohort, with mild-to-moderate renal involvement, had a significant WML burden and high inter-individual variability associated with the degree of LVPW but not the degree of kidney dysfunction. These advanced patients with increased LVPW and stroke evidence may have had a higher cerebrovascular risk. The WML burden in patients on ERT was more likely to remain stable, compared with patients on placebo. Thus, ERT may reduce the progression of vascular disease, even in advanced FD patients, suggesting that early treatment may stabilize WML progression and stroke risk.

Reduction of Plasma Globotriaosylsphingosine Levels After Switching from Agalsidase Alfa to Agalsidase Beta as Enzyme Replacement Therapy for Fabry Disease

INTRODUCTION

Agalsidase alfa and agalsidase beta, recombinant enzyme preparations for treatment of Fabry disease (FD), have different approved dosing schedules: 0.2 mg/kg and 1.0 mg/kg every other week (EOW), respectively.

METHODS

This open-label, multicenter, exploratory phase 4 study evaluated plasma globotriaosylsphingosine (lyso-GL-3) and plasma and urine globotriaosylceramide (GL-3) levels at baseline and 2, 4, and 6 months after the switch from agalsidase alfa (0.2 mg/kg EOW for ≥12 months) to agalsidase beta (1.0 mg/kg EOW) in 15 male patients with FD. Immunoglobulin (Ig)G antidrug antibody titers were assessed, and safety was monitored throughout the study.

RESULTS

Plasma lyso-GL-3 concentrations decreased significantly within 2 months after switch and reductions continued through month 6 (mean absolute changes, -12.8, -16.1, and -16.7 ng/mL at 2, 4, and 6 months, respectively; all P < 0.001). The mean percentage reduction from baseline was 39.5% (P < 0.001) at month 6. For plasma GL-3, the mean absolute change from baseline (-0.9 μg/mL) and percentage reduction (17.9%) at month 6 were both significant (P < 0.05). Urine GL-3 measurements showed intra-patient variability and changes from baseline were not significant. No clinical outcomes were assessed in this 6-month study, and, therefore, no conclusions can be drawn regarding the correlation of observed reductions in glycosphingolipid concentrations with clinically relevant outcomes. There were no differences in IgG antidrug antibody titers between the two enzymes. The switch from agalsidase alfa to agalsidase beta was well tolerated.

CONCLUSION

Plasma lyso-GL-3 and GL-3 levels reduced after switching from agalsidase alfa to agalsidase beta, indicating that agalsidase beta has a greater pharmacodynamic effect on these markers at the recommended dose. These data further support the use of agalsidase beta 1.0 mg/kg EOW as enzyme replacement therapy in FD.

Epithelial-Mesenchymal Transition in Kidney Tubular Epithelial Cells Induced by Globotriaosylsphingosine and Globotriaosylceramide

Fabry disease is a lysosomal storage disorder caused by deficiency of alpha-galactosidase A (α-gal A), which results in the deposition of globotriaosylceramide (Gb3) in the vascular endothelium. Globotriaosylsphingosine (lyso-Gb3), a deacylated Gb3, is also increased in the plasma of patients with Fabry disease. Renal fibrosis is a key feature of advanced Fabry disease patients. Therefore, we evaluated the association of Gb3 and lyso-Gb3 accumulation and the epithelial–mesenchymal transition (EMT) on tubular epithelial cells of the kidney. In HK2 cells, exogenous treatments of Gb3 and lyso-Gb3 increased the expression of TGF-β, EMT markers (N-cadherin and α-SMA), and phosphorylation of PI3K/AKT, and decreased the expression of E-cadherin. Lyso-Gb3, rather than Gb3, strongly induced EMT in HK2 cells. In the mouse renal mesangial cell line, SV40 MES 13 cells, Gb3 strongly induced phenotype changes. The EMT induced by Gb3 was inhibited by enzyme α-gal A treatment, but EMT induced by lyso-Gb3 was not abrogated by enzyme treatment. However, TGF-β receptor inhibitor (TRI, SB525334) inhibited the activation of TGF-β and EMT markers in HK2 cells with Gb3 and lyso-Gb3 treatments. This study suggested that increased plasma lyso-Gb3 has a crucial role in the development of renal fibrosis through the cell-specific induction of the EMT in Fabry disease, and that TRI treatment, alongside enzyme replacement therapy, could be a potential therapeutic option for patients with Fabry disease.

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.

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.

Increased arterial diameters in the posterior cerebral circulation in men with Fabry disease

A high load of white matter lesions and enlarged basilar arteries have been shown in selected patients with Fabry disease, a disorder associated with an increased stroke risk. We studied a large cohort of patients with Fabry disease to differentially investigate white matter lesion load and cerebral artery diameters. We retrospectively analyzed cranial magnetic resonance imaging scans of 87 consecutive Fabry patients, 20 patients with ischemic stroke, and 36 controls. We determined the white matter lesion load applying the Fazekas score on fluid-attenuated inversion recovery sequences and measured the diameters of cerebral arteries on 3D-reconstructions of the time-of-flight-MR-angiography scans. Data of different Fabry patient subgroups (males-females; normal-impaired renal function) were compared with data of patients with stroke and controls. A history of stroke or transient ischemic attacks was present in 4/30 males (13%) and 5/57 (9%) females with Fabry disease, all in the anterior circulation. Only one man with Fabry disease showed confluent cerebral white matter lesions in the Fazekas score assessment (1%). Male Fabry patients had a larger basilar artery (p<0.01) and posterior cerebral artery diameter (p<0.05) compared to male controls. This was independent of disease severity as measured by renal function and did not lead to changes in arterial blood flow properties. A basilar artery diameter of >3.2 mm distinguished between men with Fabry disease and controls (sensitivity: 87%, specificity: 86%, p<0.001), but not from stroke patients. Enlarged arterial diameters of the posterior circulation are present only in men with Fabry disease independent of disease severity.

Early cardiovascular remodelling in Fabry disease

AIMS

Fabry disease (FD) is a rare X-linked genetic disorder caused by the deficiency or absent activity of lysosomal α-galactosidase A. Cardiovascular remodelling is a hallmark of FD. The present study aimed to comprehensively evaluate the cardiac, vascular and microvascular status in a population of patients with genetic mutations for FD without left ventricular hypertrophy (LVH).

METHODS AND RESULTS

This study includes subjects carrying genetic mutations for FD (Fabry disease mutation-carrier, FDMC) without LVH (n = 19). A group of control subjects (n = 19) matched for age, sex, body mass index and cardiovascular risk factors were also included. All subjects underwent echocardiography, carotid ultrasound scan, endothelial flow-mediated dilatation (FMD) and nailfold capillaroscopy (NFC) assessment. When compared to the subjects in the control group, FDMC patients showed significantly lower mean values of systolic myocardial velocity (7.33 ± 1.28 vs. 10.08 ± 1.63 cm/s, p < 0.0001), longitudinal systolic strain (-18.07 ± 1.72 vs. -21.15 ± 2.22%, p < 0.0001), significantly higher E/E' mean values (7.15 ± 1.54 vs. 5.98 ± 1.27, p = 0.016) and intima-media thickness mean values (0.80 ± 0.20 vs. 0.61 ± 0.19 mm, p = 0.005), significantly lower FMD (8.3 ± 4.6 vs. 12.2 ± 5.0%, p = 0.02), more atypical capillaries and irregular NFC architecture in FDMC than control subjects (52.6 vs. 0%, p < 0.0001; 78.9 vs. 36.8%, p = 0.02 respectively).

CONCLUSIONS

FD progressively involves cardiac, macrovascular and microvascular systems in an early stage. These features are present even in asymptomatic mutation carriers without LVH.

Pulmonary involvement in Fabry disease: overview and perspectives

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by deficiency of alpha-galactosidase A, which leads to storage of sphingolipids in virtually all human cells and consequently to organ dysfunction. Pulmonary involvement is still debated. But, obstructive lung disease is up to ten times more prevalent in patients with FD compared to general public. Also, an accelerated decline in forced expiratory volume in one second (FEV1) over time was observed in these patients. Lysosomal storage of glycosphingolipids is considered leading to small airway disease via hyperplasia of the bronchiolar smooth muscle cells. Larger airways may become involved with ongoing disease process. There is no evidence for involvement of the lung interstitium in FD. The effect of enzyme replacement therapy on respiratory involvement remains to be determined in large, prospective controlled trials.

Left atrial enlargement and reduced atrial compliance occurs early in Fabry cardiomyopathy

BACKGROUND

Fabry disease is associated with left ventricular hypertrophy (LVH) and myocardial fibrosis. The aim of this study was to evaluate left atrial (LA) size and function using tissue Doppler-derived strain in patients with Fabry disease.

METHODS

Echocardiography was performed in 33 Fabry patients (14 without LVH, 19 with LVH) before commencement of enzyme replacement therapy, and results were compared with those from age-matched and gender-matched controls (n=28 and n=38, respectively). Atrial strain and strain rate were measured from four segments in the apical four-chamber and two-chamber views of the LA, and global values were calculated. Systolic strain, systolic strain rate, early diastolic strain rate, and late diastolic strain rate were measured. Phasic LA volumes and fractions were calculated. Mitral inflow and tissue Doppler E' velocities were used to estimate left ventricular (LV) diastolic function.

RESULTS

LA volume was increased in Fabry patients, even in the absence of LVH. Importantly, diastolic function was normal in this subgroup without LVH, with E' velocities similar to those in controls. LA systolic strain and early diastolic strain rate were selectively reduced in Fabry patients with LVH and reflect reductions in LA and LV relaxation, respectively, consequent to increased LV mass. However, independent of LVH, both Fabry groups had significant reductions in systolic strain rate and increased LA stiffness index.

CONCLUSIONS

Fabry disease is associated with LA enlargement and reduced atrial compliance that occurs before the development of LVH. This suggests that Fabry cardiomyopathy may not only cause ventricular hypertrophy and fibrosis but also alters atrial myocardial properties early in the disease process. Consequently, measurements of LA size and function may be useful in the early diagnosis of Fabry disease, before the development of LVH.

Fibrosis: a key feature of Fabry disease with potential therapeutic implications

Fabry disease is a rare X-linked hereditary disease caused by mutations in the AGAL gene encoding the lysosomal enzyme alpha-galactosidase A. Enzyme replacement therapy (ERT) is the current cornerstone of Fabry disease management. Involvement of kidney, heart and the central nervous system shortens life span, and fibrosis of these organs is a hallmark of the disease. Fibrosis was initially thought to result from tissue ischemia secondary to endothelial accumulation of glycosphingolipids in the microvasculature. However, despite ready clearance of endothelial deposits, ERT is less effective in patients who have already developed fibrosis. Several potential explanations of this clinical observation may impact on the future management of Fabry disease. Alternative molecular pathways linking glycosphingolipids and fibrosis may be operative; tissue injury may recruit secondary molecular mediators of fibrosis that are unresponsive to ERT, or fibrosis may represent irreversible tissue injury that limits the therapeutic response to ERT. We provide an overview of Fabry disease, with a focus on the assessment of fibrosis, the clinical consequences of fibrosis, and recent advances in understanding the cellular and molecular mechanisms of fibrosis that may suggest novel therapeutic approaches to Fabry disease.

Lysosomal delivery of therapeutic enzymes in cell models of Fabry disease

The success of enzymatic replacement in Gaucher disease has stimulated development of targeted protein replacement for other lysosomal disorders, including Anderson-Fabry disease, which causes fatal cardiac, cerebrovascular and renal injury: deficiency of lysosomal α-Galactosidase A induces accumulation of glycosphingolipids. Endothelial cell storage was the primary endpoint in a clinical trial that led to market authorization. Two α-Galactosidase A preparations are licensed worldwide, but fatal outcomes persist, with storage remaining in many tissues. We compare mechanisms of uptake of α -Galactosidase A into cells relevant to Fabry disease, in order to investigate if the enzyme is targeted to the lysosomes in a mannose-6-phosphate receptor dependent fashion, as generally believed. α -Galactosidase A uptake was examined in fibroblasts, four different endothelial cell models, and hepatic cells in vitro. Uptake of europium-labeled human α -Galactosidase A was measured by time-resolved fluorescence. Ligand-specific uptake was quantified in inhibitor studies. Targeting to the lysosome was determined by precipitation and by confocal microscopy. The quantity and location of cation-independent mannose-6-phosphate receptors in the different cell models were investigated using confocal microscopy. Uptake and delivery of α -Galactosidase A to lysosomes in fibroblasts is mediated by the canonical mannose-6-phosphate receptor pathway, but in endothelial cells in vitro this mechanism does not operate. Moreover, this observation is supported by a striking paucity of expression of cation independent mannose-6-phosphate receptors on the plasma membrane of the four endothelial cell models and by little delivery of enzyme to lysosomes, when compared with fibroblasts. If these observations are confirmed in vivo, alternative mechanisms will be needed to explain the ready clearance of storage from endothelial cells in patients undergoing enzyme replacement therapy.

Enzyme replacement therapy improves cardiac features and severity of Fabry disease

BACKGROUND

Although left ventricular hypertrophy (LVH) in Fabry disease (FD) can improve with enzyme-replacement therapy (ERT), the response is difficult to predict. Furthermore, the response of other cardiac features such as aortic dilatation and ECG changes are poorly understood.

METHODS

A local registry of 66 patients with FD was studied. ECG, echocardiogram and Fabry Outcome Survey-Mainz Severity Score Index (FOS-MSSI) data were compared between baseline and after long-term ERT (median 36 months).

RESULTS

In patients with LVH (n=42), left ventricular mass index (LVMI), maximal wall thickness (MWT), left ventricular end-diastolic diameter (LVEDD) and ejection fraction (EF) were all seen to improve after ERT (LVMI: 135±13 vs. 133±13 g/m(2), MWT: 17±6 vs. 16±5 mm, LVEDD: 55±6 vs. 54±6 mm; EF: 62±5 vs. 64±3%; p<0.05). In the entire patient group, PQ interval and P wave duration significantly increased with ERT (PQ: 131±13 vs. 144±13 ms, P: 76±5 vs. 90±6 ms; p values<0.001); QT(c) interval significantly decreased (418±18 vs. 410±15 ms; p<0.001); and median FOS-MSSI score fell from 16 to 14 (p<0.001). On logistic-regression analysis, none of the recorded baseline features (age, gender, LVMI, MWT, LVEDD, aortic diameter, EF, PQ interval, P wave duration, QRS duration, QT interval, Romhilt-Estes score or FOS-MSSI) predicted improvements in LVH or FOS-MSSI with ERT (p>0.05).

CONCLUSIONS

ERT improved LV morphology and function in patients with LVH - but there was no relationship between age, gender, FOS-MSSI or baseline ECG/TTE features and the response. ERT also normalised long QTc intervals, short PQ intervals and short P waves; and reduced disease burden (FOS-MSSI).