Endothelial markers and homocysteine in patients with classic Fabry disease

AIM: Fabry disease is an X-linked inborn error of glycosphingolipid metabolism due to the deficient activity of alpha-galactosidase A, a lysosomal enzyme. It is a multisystem disorder characterized by progressive renal insufficiency, with added morbidity from cardio- and cerebrovascular involvement. The recent availability of genetically engineered enzyme offers an effective targeted treatment approach, but also emphasizes the need for surrogate markers to delineate organ damage and monitor the efficacy of enzyme replacement therapy (ERT). METHODS: Multiple endothelial factors and plasma homocysteine concentrations were investigated in 12 consecutive hemizygous males with classic Fabry disease and 15 controls as part of an exhaustive baseline evaluation prior to ERT. RESULTS: Compared with the controls, plasma concentrations of homocysteine were significantly (p < 0.01) higher in patients with Fabry disease in the absence of chronic renal failure or vitamin deficiency. Plasma concentrations of vascular cell adhesion molecule-1 were also significantly (p < 0.05) higher in the patients, and there was a trend for decreased endothelin-1 levels. No difference was found in serum intercellular adhesion molecule-1, plasma P-selectin, serum E-selectin and plasma thrombomodulin between the patients and controls. CONCLUSIONS: The results do not reveal measurable evidence for endothelial and leukocyte activation that could reliably serve as surrogate markers for routine monitoring of the efficacy of ERT in patients with Fabry disease. While the exact origin and clinical significance of hyperhomocysteinaemia in Fabry disease remains to be studied in a larger cohort of patients carefully monitored for their concurrent medications, especially carbamazepine, we suggest that patients may benefit from folic acid or multivitamin therapy to treat this additional vascular risk factor, when present.     

Vascular complications of Fabry disease: enzyme replacement and other therapies

Fabry disease is an X-linked glycosphingolipid storage disorder resulting from deficiency of α-galactosidase A. Storage of globotriaosylceramide ultimately results in multiorgan pathology, including cerebrovascular, cardiovascular and renal disease. Vascular involvement is evident throughout the body but the mechanisms by which storage on a cellular level leads to end-organ pathology are unknown. Here the evidence for abnormal blood flow, vessel architecture and endothelial function will be reviewed and possible models of vascular pathology discussed. The effects of reversal of storage within vessels by enzyme replacement therapy (ERT) and the possibilities for intervention with additional agents will be considered.
Conclusion: The pathology of Fabry disease has an important vascular component, although the underlying pathophysiology is unclear. Preliminary evidence suggests that ERT may have beneficial effects on the vascular component of this multisystem disease.     

Vascular complications of Fabry disease: enzyme replacement and other therapies

Fabry disease is an X-linked glycosphingolipid storage disorder resulting from deficiency of alpha-galactosidase A. Storage of globotriaosylceramide ultimately results in multiorgan pathology, including cerebrovascular, cardiovascular and renal disease. Vascular involvement is evident throughout the body but the mechanisms by which storage on a cellular level leads to end-organ pathology are unknown. Here the evidence for abnormal blood flow, vessel architecture and endothelial function will be reviewed and possible models of vascular pathology discussed. The effects of reversal of storage within vessels by enzyme replacement therapy (ERT) and the possibilities for intervention with additional agents will be considered. Conclusion: The pathology of Fabry disease has an important vascular component, although the underlying pathophysiology is unclear. Preliminary evidence suggests that ERT may have beneficial effects on the vascular component of this multisystem disease.     

Is globotriaosylceramide a useful biomarker in Fabry disease?

AIM: The aim of this study was to determine whether globotriaosylceramide (Gb3) is a useful biomarker in Fabry disease. METHODS: The levels of Gb3 were measured in plasma and urine by tandem mass spectrometry in untreated hemizygotes and heterozygotes with Fabry disease and in healthy controls, and the levels were monitored in patients on treatment with enzyme replacement therapy (ERT). RESULTS: Hemizygotes with classic Fabry disease showed elevated levels of Gb3 in both plasma and urine and could readily be distinguished from normal controls. Male patients with the N215S mutation had normal levels in their plasma but 50% had marginally elevated levels in their urine. Thirty-three percent of proven heterozygotes had elevated Gb3 concentrations in plasma but 97% of those without the N215S mutation (36/37) had an elevated level in urine. The four heterozygotes with the N215S mutation had normal Gb3 levels in urine. The level of Gb3 in plasma initially fell following the start of ERT in all patients who had an elevated level before treatment. However, in a few patients the level subsequently rose. Similar results were found for the levels of Gb3 in urine. CONCLUSION: Gb3 is not an ideal marker of Fabry disease or the response to treatment in all patients. Plasma and urine levels of Gb3 cannot be used as a marker of Fabry disease in patients with the N215S mutation and many heterozygotes do not have elevated Gb3 levels in plasma. The urine concentration is more informative in heterozygotes and can be used as a measure of the response to therapy. The fall in Gb3 levels in patients receiving ERT was not sustained in some patients, despite a clinical improvement. Additionally, Gb3 cannot be used to monitor the response to treatment in patients who initially have normal plasma and urine concentrations of this glycolipid.     

Measurement of renal function in patients with Fabry disease

Appropriate measurement of the glomerular filtration rate (GFR) is important for the assessment of renal function. This paper reviews the methods used to assess GFR in clinical trials of enzyme replacement therapy (ERT) in patients with Fabry disease, which include inulin clearance, 24-hour creatinine clearance, chromium ethylene diamine tetraacetate (51Cr-EDTA) clearance and cystatin C concentrations. GFR has also been estimated using calculations based on creatinine clearance (the Cockcroft-Gault formula) and the Modification of Diet in Renal Disease (MDRD) equation. Analysis of the results of these studies shows that there are striking discrepancies between estimated and measured GFR. For example, the MDRD equation overestimates GFR in patients with Fabry disease who have normal renal function. In addition, cystatin C has been shown to be of limited use for measuring renal function during ERT, because it is influenced by other factors such as age, gender and weight. Conclusion: The use of exact methods, such as inulin clearance, 124I-iothalamate, 99mTc-DTPA, 51Cr-EDTA and iohexol, appears to be mandatory for a robust evaluation of the effects of ERT on GFR in patients with Fabry disease.     

Measurement of renal function in patients with Fabry disease

Appropriate measurement of the glomerular filtration rate (GFR) is important for the assessment of renal function. This paper reviews the methods used to assess GFR in clinical trials of enzyme replacement therapy (ERT) in patients with Fabry disease, which include inulin clearance, 24-hour creatinine clearance, chromium ethylene diamine tetraacetate (⁵¹Cr-EDTA) clearance and cystatin C concentrations. GFR has also been estimated using calculations based on creatinine clearance (the Cockcroft–Gault formula) and the Modification of Diet in Renal Disease (MDRD) equation. Analysis of the results of these studies shows that there are striking discrepancies between estimated and measured GFR. For example, the MDRD equation overestimates GFR in patients with Fabry disease who have normal renal function. In addition, cystatin C has been shown to be of limited use for measuring renal function during ERT, because it is influenced by other factors such as age, gender and weight.
Conclusion: The use of exact methods, such as inulin clearance, ¹²⁴I-iothalamate, ⁹⁹mTc-DTPA, ⁵¹Cr-EDTA and iohexol, appears to be mandatory for a robust evaluation of the effects of ERT on GFR in patients with Fabry disease.     

Fabry disease and the heart: an overview of the natural history and the effect of enzyme replacement therapy

Fabry disease is a genetic disorder caused by the deficiency of α-galactosidase A, resulting in the lysosomal accumulation of glycosphingolipids. Fabry disease may result in cardiac, cerebral and renal complications. Cardiac abnormalities in patients with Fabry disease were first described in the 1960s. In the 1990s a form of Fabry disease confined to the heart was reported; however, this variant is extremely rare and a more appropriate concept is of cardiac predominance of the disease in some patients. Up to 60% of males with classic Fabry disease have cardiac abnormalities, including left ventricular hypertrophy, valvular dysfunction and conduction abnormalities. Recent data suggest that left ventricular mass and systolic function in patients with Fabry disease improve after 12 months of enzyme replacement therapy (ERT); however, many of the patients studied are relatively young and have mild cardiac abnormalities, suggesting that more research into the efficacy of ERT in older patients is necessary.
Conclusion: Cardiac manifestations are common in patients with Fabry disease and are not confined to a 'cardiac variant' of the disease.     

Fabry disease and the heart: an overview of the natural history and the effect of enzyme replacement therapy

Fabry disease is a genetic disorder caused by the deficiency of alpha-galactosidase A, resulting in the lysosomal accumulation of glycosphingolipids. Fabry disease may result in cardiac, cerebral and renal complications. Cardiac abnormalities in patients with Fabry disease were first described in the 1960s. In the 1990s a form of Fabry disease confined to the heart was reported; however, this variant is extremely rare and a more appropriate concept is of cardiac predominance of the disease in some patients. Up to 60% of males with classic Fabry disease have cardiac abnormalities, including left ventricular hypertrophy, valvular dysfunction and conduction abnormalities. Recent data suggest that left ventricular mass and systolic function in patients with Fabry disease improve after 12 months of enzyme replacement therapy (ERT); however, many of the patients studied are relatively young and have mild cardiac abnormalities, suggesting that more research into the efficacy of ERT in older patients is necessary. Conclusion: Cardiac manifestations are common in patients with Fabry disease and are not confined to a 'cardiac variant' of the disease.     

Apoptotic abnormalities in differential gene expression in peripheral blood mononuclear cells from children with Fabry disease

AIM: This study was designed to examine the effect of enzyme replacement therapy (ERT) on differential gene expression in peripheral blood mononuclear cells (PBMCs) of children with Fabry disease who had not previously been exposed to ERT. METHODS: Thirteen children with Fabry disease (age range, 6.5-17.0 years) were studied as part of a 6-month, open-label study of ERT with agalsidase alfa. Paired blood samples were taken at the start of the study and after 6 months of ERT. Further blood samples were also taken from 16 age-matched control subjects. PBMCs were isolated and, following RNA extraction, differential gene expression analysis was performed using the Human Genome U133 Plus 2.0 microarray. RESULTS: Twenty-one genes were determined to be differentially expressed in PBMCs of ERT-na?ve children with Fabry disease compared with healthy controls; neuronal apoptosis inhibitory protein ranked as the most significantly differentially expressed gene. Comparison of gene expression in children with Fabry disease prior to and after ERT showed that two genes were significantly differentially expressed (p < or = 0.05) following treatment; the expressed sequence tag (probe set ID, 243259_at) was downregulated, while expression of apoptosis-inducing factor was increased, possibly as an antioxidant counter-regulatory response. CONCLUSION: This study identifies a number of genes that are differentially expressed in a small cohort of children with Fabry disease relative to healthy controls. These genes may relate to the underlying biological abnormalities in Fabry disease.     

A pilot pharmacokinetic and antiangiogenic biomarker study of celecoxib and low-dose metronomic vinblastine or cyclophosphamide in pediatric recurrent solid tumors

Tumor vasculature is a reasonable target for cancer therapy and lower more frequent doses of traditional chemotherapeutics [low-dose metronomic (LDM) chemotherapy] has been shown to have antiangiogenic efficacy. This study evaluated the safety and pharmacokinetics of celecoxib and LDM vinblastine or cyclophosphamide in children with recurrent, refractory solid tumors. We also investigated whether a subset of circulating plasma proteins are surrogate markers of angiogenic activity. Thirty-three children were enrolled in this pilot study and received celecoxib (250 mg/m(2) PO b.i.d.) and either vinblastine (1 mg/m(2) IV 3 x /wk) or cyclophosphamide (30 mg/m(2) PO daily) continually. Celecoxib alone and with LDM chemotherapy was well tolerated and plasma concentrations were consistent with those shown to have antiangiogenic activity. Four patients (13%) had durable stable disease (28 to 78 wk) although no complete or partial responses were observed. The surrogate markers measured (vascular endothelial growth factor, basic fibroblast growth factor, soluble vascular cell adhesion molecule, soluble intercellular cell adhesion molecule, endostatin, and thrombospondin-1) were highly variable and no statistically significant relationship between them and disease progression or maintenance of stable disease was observed. We concluded that this regimen is well tolerated hence supporting the use of this form of therapy in pediatric patients. However, future studies should include more homogenous patient populations and focus on validating surrogate markers to monitor treatment activity.     

Inner ear function in children with Fabry disease

Aim : The prevalence of hearing loss in patients with Fabry disease is still uncertain. This paper examines hearing loss in a group of young patients with Fabry disease. Methods : A clinical ear nose and throat examination, pure-tone air and bone conduction audiometry, speech audiometry and middle ear testing (tympanometry and acoustic reflex testing) were carried out in four girls and two boys with Fabry disease (age, 7–17 years), receiving enzyme replacement therapy (ERT). Results : None of the patients complained of a hearing disorder or suffered from hearing loss. Three female patients reported tinnitus; however, this was not reported as being a problem. One boy reported tinnitus for the first time during 6 months of ERT.
Conclusion : Based on this small sample of patients, it appears that the hearing disorders associated with Fabry disease develop mainly in adulthood. Tinnitus may be an earlier symptom than previously thought in Fabry disease.     

Fabry disease--a provocation for pediatrics

Fabry disease is an inherited metabolic disease caused by the deficiency of the lysosomal enzyme alpha-Galactosidase A. In consequence, globotriaosylceramide (Gb3) accumulates in nearly all tissues and body fluids. Typically, the disease manifestation is in childhood with acroparaesthesia of burning character in hands and feet. Angioceratoma, cornea verticillata and proteinuria may be found as well at an early stage of the disease. With ongoing age vital organs are increasingly affected. Major causes for death are cerebrovascular events, myocardial infarction, and progressive renal insufficiency. Enzyme replacement therapy (ERT) offers an efficient treatment of Fabry disease. On the basis of newly diagnosed patients we describe the clinical picture, diagnosis and principles of ERT.     

Head-impulse testing in Fabry disease--vestibular function in male and female patients

AIM: To study the prevalence of peripheral vestibular deficit in male and female patients with Fabry disease and to assess the effect of enzyme replacement therapy (ERT) on peripheral vestibular function using quantitative head-impulse testing. METHODS: Using dual search-coils the vestibulo-ocular reflex during rapid rotational head thrusts to both sides was recorded in 21 patients (13 male, 8 female) with Fabry disease prior to ERT initiation. ERT consisted of infusions of gene-activated human alpha-galactosidase A (agalsidase alfa; Replagal) every 2 weeks at doses of 0.2 mg/kg. Eight patients were tested again approximately 6 and 12 months after the initiation of ERT. RESULTS: At baseline examination, 15 of the patients with Fabry disease (71%; 11 males, 4 females) showed reduced peripheral vestibular function. The deficit was unilateral in nine patients (3 females) and bilateral in six patients (1 female). The severity of the vestibular deficit was not significantly different between male and female patients. After 12 months of ERT, the average vestibular deficit on the weaker side tended to improve; however, the change was not significant (p = 0.10). CONCLUSION: Fabry disease affects peripheral vestibular function in both male and female patients. Females seem to be affected less frequently than males, but, on average, vestibular deficits are not different between the two groups. To confirm or reject the tendency for vestibular improvement during ERT, more patients need to be tested and longer follow-up periods are required.     

Fabry disease in children and the effects of enzyme replacement treatment

Fabry disease is a rare, X-linked inborn error of glycosphingolipid catabolism caused by a deficiency in the activity of the lysosomal enzyme, α-galactosidase A. In affected patients, the enzyme substrate, globotriaosylceramide (Gb3), accumulates in cells of various tissues and organs. Lysosomal accumulation of Gb3 begins in utero, and signs and symptoms of Fabry disease emerge in childhood and adolescence. The earliest presenting symptoms are typically neuropathic pain and gastrointestinal problems, which can have a substantial impact on health-related quality of life. Life-threatening major organ involvement is rare in young patients, but signs of kidney dysfunction (e.g., proteinuria), left ventricular hypertrophy, and stroke have been reported in children. There are two enzyme preparations for therapy: agalsidase alfa and beta. In two clinical trials of enzyme replacement therapy (ERT) with agalsidase alfa, including 37 children, boys demonstrated reductions in plasma Gb3 levels, and both boys and girls reported reductions in neuropathic pain and in the use of neuropathic pain medications. Heart rate variability, which is reduced in boys with Fabry disease, was statistically significantly improved with 6 months of agalsidase alfa treatment. In a single clinical study of agalsidase beta in children (n =16), skin Gb3 deposits and plasma Gb3 levels were reduced in boys. Differences exist in the administration and the safety profile of these two enzyme formulations. Follow-up of these cohorts and additional studies will be necessary to fully evaluate long-term efficacy of ERT in children with Fabry disease.     

Head-impulse testing in Fabry disease - vestibular function in male and female patients

Aim : To study the prevalence of peripheral vestibular deficit in male and female patients with Fabry disease and to assess the effect of enzyme replacement therapy (ERT) on peripheral vestibular function using quantitative head-impulse testing. Methods : Using dual search-coils the vestibulo-ocular reflex during rapid rotational head thrusts to both sides was recorded in 21 patients (13 male, 8 female) with Fabry disease prior to ERT initiation. ERT consisted of infusions of gene-activated human α-galactosidase A (agalsidase alfa; Replagal™) every 2 weeks at doses of 0.2mg/kg. Eight patients were tested again approximately 6 and 12 months after the initiation of ERT. Results : At baseline examination, 15 of the patients with Fabry disease (71%; 11 males, 4 females) showed reduced peripheral vestibular function. The deficit was unilateral in nine patients (3 females) and bilateral in six patients (1 female). The severity of the vestibular deficit was not significantly different between male and female patients. After 12 months of ERT, the average vestibular deficit on the weaker side tended to improve; however, the change was not significant ( p = 0.10).
Conclusion : Fabry disease affects peripheral vestibular function in both male and female patients. Females seem to be affected less frequently than males, but, on average, vestibular deficits are not different between the two groups. To confirm or reject the tendency for vestibular improvement during ERT, more patients need to be tested and longer follow-up periods are required.     

Plasma homocysteine concentrations in adolescents with subclinical hypothyroidism

OBJECTIVE: Hyperhomocysteinemia is a risk factor for premature atherosclerotic vascular disease and venous thrombosis. The aim of the present study was to assess plasma total homocysteine (tHCys) concentrations in adolescent patients with subclinical hypothyroidism. PATIENTS AND METHODS: Nineteen patients with subclinical hypothyroidism and 19 healthy children were studied. Fasting plasma concentrations of tHCys and its putative determinants (plasma concentrations of free thyroxine [FT4], folate, vitamin B12 and renal function) were measured. RESULTS: tHCys concentrations showed no statistical difference between patients and controls (p > 0.05). Moreover, the difference in tHCys and total cholesterol concentrations was not significant between patients with mild TSH elevations (< or = 10 mIU/l) and patients with prominent TSH elevations (> 10 mIU/l). No correlation was found between tHCys concentrations and its putative determinants. CONCLUSIONS: We concluded that plasma tHCys concentrations were not increased in adolescent patients with subclinical hypothyroidism.     

Plasma thrombomodulin levels in children with atopic dermatitis

Plasma thrombomodulin (TM) levels were measured in 68 patients with atopic dermatitis (AD) and 35 controls. Plasma TM levels in patients with AD were significantly higher than those of controls (p < 0.01). A significant correlation was observed between plasma TM levels and skin scores of AD or peripheral eosinophil counts (p < 0.01). There was also a positive correlation between plasma TM and vascular cell adhesion molecule-1 levels (p < 0.05). Conclusion: These results suggest that plasma TM levels may reflect a severity of AD and/or endothelial cell activation induced by an allergic inflammation.     

Serum soluble endothelial-cell specific adhesion molecules in children with insulin-dependent diabetes mellitus

Endothelial-cell specific adhesion molecules are reported to be elevated in patients with diabetes mellitus and related to diabetic vascular complications. We studied serum concentrations of soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), endothelial-leukocyte adhesion molecule (sE-selectin) in 30 healthy children and 35 children with type 1 diabetes without symptomatic vascular complications. sE-selectin levels were higher in diabetics than in controls (p < 0.001). sVCAM-1 and sICAM-1 levels were not different between the groups (p > 0.05). In seven newly diagnosed diabetics with ketoacidosis, concentrations of these molecules were not different before and after one month of insulin therapy (p > 0.05). In the combined group, only sE-selectin was correlated positively with serum glucose, HbA1c (r = 0.3, p < 0.05 for both) and negatively with C-peptide levels (r = -0.4, p < 0.05). In diabetic children without symptomatic vascular complications, sE-selectin but not sICAM and sVCAM levels was elevated; this finding might reflect ongoing endothelial-cell activation rather than endothelial damage.     

Hearing improvement in patients with Fabry disease treated with agalsidase alfa

Aim : To describe the nature and prevalence of hearing loss in Fabry disease, and its response to enzyme replacement therapy (ERT) with agalsidase alfa. Methods : Fifteen male patients with Fabry disease were enrolled in a randomized, double-blind study and received placebo ( n = 8) or ERT ( n = 7) with agalsidase alfa for 6 months. This was followed by an open-label extension of 36 months thus far. Alongside this trial, an additional eight men and two women have so far received open-label ERT for between 6 and 30 months. Pure-tone audiometry, impedance audio-metry and otoacoustic emission testing were performed at 0 (baseline), 6, 18, 30 and 42 months. Results : Nine patients (36%) had bilateral and ten (40%) had unilateral high-frequency sensorineural hearing loss (SNHL). Three (12%) had unilateral middle ear effusions with conductive losses persisting beyond 6 months. Only five patients (20%) had normal hearing. The high-frequency SNHL deteriorated over the first 6 months in both placebo and active treatment groups by a median 6.3 dB ( p < 0.0001, Wilcoxon matched-pairs). This hearing loss subsequently improved above baseline by 1.5 dB at 18 months (p = 0.07), by 5.0 dB at 30 months ( p = 0.006) and by 4.0 dB at 42 months ( p = 0.01).
Conclusion : Significant hearing loss, usually high-frequency SNHL, is a common manifestation of Fabry disease in adults. α-Galactosidase A replacement therapy with agalsidase alfa appears to reverse the hearing deterioration in these patients. This improvement, however, is gradual, suggesting the need for long-term ERT.     

Hearing improvement in patients with Fabry disease treated with agalsidase alfa

AIM: To describe the nature and prevalence of hearing loss in Fabry disease, and its response to enzyme replacement therapy (ERT) with agalsidase alfa. METHODS: Fifteen male patients with Fabry disease were enrolled in a randomized, double-blind study and received placebo (n = 8) or ERT (n = 7) with agalsidase alfa for 6 months. This was followed by an open-label extension of 36 months thus far. Alongside this trial, an additional eight men and two women have so far received open-label ERT for between 6 and 30 months. Pure-tone audiometry, impedance audiometry and otoacoustic emission testing were performed at 0 (baseline), 6, 18, 30 and 42 months. RESULTS: Nine patients (36%) had bilateral and ten (40%) had unilateral high-frequency sensorineural hearing loss (SNHL). Three (12%) had unilateral middle ear effusions with conductive losses persisting beyond 6 months. Only five patients (20%) had normal hearing. The high-frequency SNHL deteriorated over the first 6 months in both placebo and active treatment groups by a median 6.3 dB (p < 0.0001, Wilcoxon matched-pairs). This hearing loss subsequently improved above baseline by 1.5 dB at 18 months (p = 0.07), by 5.0 dB at 30 months (p = 0.006) and by 4.0 dB at 42 months (p = 0.01). CONCLUSION: Significant hearing loss, usually high-frequency SNHL, is a common manifestation of Fabry disease in adults. Alpha-galactosidase A replacement therapy with agalsidase alfa appears to reverse the hearing deterioration in these patients. This improvement, however, is gradual, suggesting the need for long-term ERT.