Peripheral hemodynamics in patients with Fabry's disease

Establishing 3-nitrotyrosine as a biomarker for the vasculopathy of Fabry disease

The endothelial dysfunction of Fabry disease results from α-galactosidase A deficiency leading to the accumulation of globotriaosylceramide. Vasculopathy in the α-galactosidase A null mouse is manifested as oxidant-induced thrombosis, accelerated atherogenesis, and impaired arterial reactivity. To better understand the pathogenesis of Fabry disease in humans, we generated a human cell model by using RNA interference. Hybrid endothelial cells were transiently transfected with small interfering RNA (siRNA) specifically directed against α-galactosidase A. Knockdown of α-galactosidase A was confirmed using immunoblotting and globotriaosylceramide accumulation. Endothelial nitric oxide synthase (eNOS) activity was correspondingly decreased by >60%. Levels of 3-nitrotyrosine (3NT), a specific marker for reactive nitrogen species and quantified using mass spectrometry, increased by 40- to 120-fold without corresponding changes in other oxidized amino acids, consistent with eNOS-derived reactive nitrogen species as the source of the reactive oxygen species. eNOS uncoupling was confirmed by the observed increase in free plasma and protein-bound aortic 3NT levels in the α-galactosidase A knockout mice. Finally, 3NT levels, assayed in biobanked plasma samples from patients with classical Fabry disease, were over sixfold elevated compared with age- and gender-matched controls. Thus, 3NT may serve as a biomarker for the vascular involvement in Fabry disease.

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.

Small fiber neuropathy in Fabry disease

Previous studies have explicitly shown that small nerve fibers are affected in Fabry disease which is assumed to cause the severe neuropathic pain that patients may have from childhood on. Neuropathic pain and small fiber neuropathy characteristics have therefore been considered as appropriate study endpoints in studies on the efficacy of enzyme replacement therapy. However, the relationship between small fiber neuropathy characteristics and pain, as well as the course of small fiber neuropathy in Fabry disease is still uncertain. In this article a comprehensive overview of the existing literature on small nerve fiber function and structure and the relationship with pain, age and disease severity is presented supplemented with data from the Dutch Fabry cohort, with the aim to identify consensus as well as controversies and to propose a hypothesis on the evolution of neuropathy in Fabry disease.

Vasculopathy in patients with Fabry disease: current controversies and research directions

Fabry disease is an X-linked lysosomal storage disorder due to deficiency of the enzyme alpha-galactosidase A. The principal clinical manifestations of Fabry disease consist of cardiovascular complications including cerebrovascular, renal and cardiac disease but the pathophysiology of this specific vasculopathy is unclear. With the development of targeted treatment for Fabry disease, i.e. enzyme replacement therapy, it has become apparent that the removal of stored glycosphingolipid from the endothelial cells does not prevent progression of vascular disease in many patients. The aim of this study is to review the current available literature on vascular function tests, imaging and pathology studies and propose a hypothesis on the evolution of arterial complications in Fabry disease. Clearly, although premature atherosclerosis is suggested to occur, most studies describe absence of characteristic plaque formation. Smooth muscle cell hypertrophy, is probably the earliest feature of a complex vasculopathy, as in females and atypical cardiac variants, who have residual enzyme activity, no endothelial storage of significance is found. Subsequently, processes occur as observed in neo intima formation however with formation of more fibrotic structures. In the presence of a hyperdynamic circulation in combination with a less compliant vascular wall, it is hypothesized that upregulation of local renin angiotensine systems may occur. Angiotensin II is known to increase adhesion molecules, cytokines and chemokines and exerts a pro-inflammatory effect on leucocytes, endothelial cells and vascular smooth muscle cells. This enhances release of pro-thrombotic factors and opposes actions mediated through angiotensin 2 (AT2) receptor, including the release of nitric oxide (NO). A combination of reduced vascular compliance and activation of pro-thrombotic factors can lead to vascular complications in Fabry disease.

Autonomic skin responses in females with Fabry disease

Fabry disease is a genetic lysosomal disorder with dysfunction of the lysosomal enzyme alpha-galactosidase A causing accumulation of glycolipids in multiple organs including the nervous system and with neuropathy as a prominent manifestation. Neurological symptoms include pain and autonomic dysfunction. This study examined peripheral autonomic nerve function in 19 female patients with Fabry disease and 19 sex and age-matched controls by measuring (1) sweat production following acetylcholine challenge; (2) the sympathetically mediated vasoconstrictor responses to inspiratory gasp, stress, and the cold pressor test; and (3) cutaneous blood flow following capsaicin. The vasoconstrictor response to inspiratory gasp was increased in Fabry patients compared to controls (p = 0.03), while the response to cold and mental stress did not change. Female patients with Fabry disease had a reduced sweat response to iontophoresis of acetylcholine (p = 0.04) and a smaller capsaicin-induced flare compared to controls. These findings suggest that female patients both have an impaired C-fiber function and local abnormalities in blood vessels and sweat glands.

Fabry disease in a heterozygote presenting as hand ischaemia and painful acroparaesthesia

A 48-year-old woman presented with acute unilateral ischaemia of the left hand. She had a background of chronic peripheral neuropathic pain, palpitations, anaemia and an episode of superficial thrombophlebitis. Physical examination revealed non-blanching purple discoloration of her left fingers and her left thumb, index finger and thenar eminance appeared ischaemic. Digital subtraction angiography of the left hand demonstrated reduced flow. Skin punch biopsy histology was unremarkable. The diagnosis of Fabry disease was made on urine lipid profile analysis and confirmed by reduced peripheral blood leukocyte alpha-galactosidase A activity.

Neurological manifestations in Fabry's disease

Fabry's disease is an X-linked lysosomal storage disorder caused by a defect in the gene that encodes the lysosomal enzyme alpha-galactosidase A. Symptoms arise because of accumulation of globotriaosylceramide in multiple organs, resulting in severely reduced quality of life and premature death. Neurological symptoms, such as burning sensations (occasionally accompanied by acroparesthesia) and stroke, are among the first to appear, and occur in both male and female patients. A delay in establishing the diagnosis of Fabry's disease can cause unnecessary problems, especially now that enzyme replacement treatment is available to prevent irreversible organ damage. Females with Fabry's disease who present with pain have often been ignored and misdiagnosed because of the disorder's X-linked inheritance. This Review will stress the importance of recognizing neurological symptoms for the diagnosis of Fabry's disease. The possible pathophysiological background will also be discussed.

Structural and functional changes in peripheral vasculature of Fabry patients

OBJECTIVE

Fabry disease is a lysosomal storage disorder due to deficient alpha-galactosidase A activity, which leads to glycosphingolipid accumulation especially in vascular smooth-muscle and endothelial cells. Little is known about the effects of Fabry disease on peripheral artery function and structure. Therefore, we aimed to further characterize the peripheral vascular structural and functional changes in Fabry disease.

METHODS AND RESULTS

We measured structural and functional vascular parameters, including intima-media thickness (IMT) of brachial and carotid arteries and abdominal aorta, carotid and aortic compliance, and brachial artery flow-mediated dilatation (FMD) in 17 Fabry patients and 34 healthy controls matched for age, sex and smoking. Carotid IMT (0.64 +/- 0.15 vs 0.57 +/- 0.12 mm), brachial IMT (1.02 +/- 0.25 vs 0.74 +/- 0.18 mm), and aortic IMT (0.31 +/- 0.09 vs 0.26 +/- 0.04 mm) were significantly increased, and brachial FMD was significantly impaired (6.3 +/- 5.0 vs 9.7 +/- 3.9%) in Fabry patients compared to healthy controls (p < 0.05 in all comparisons after adjustments for age, LDL-cholesterol, and systolic blood pressure). No differences were observed in arterial compliance between the groups.

CONCLUSIONS

These data suggest that Fabry disease affects arterial function and structure by disturbing peripheral endothelial function and promoting intima-media thickening.

Cardiovascular Manifestations of Fabry Disease and the Novel Therapeutic Strategies

Fabry disease is an inherited lysosomal storage disorder characterized by a pathological intracellular glycosphingolipid deposition. The disease is caused by a deficit in the lysosomal enzyme alpha-galatosidase A, the gene for which is located in the X chrosomal region Xq 22. Globotriaosylceramide (Gb3) accumulate progressively in multi-organ vulnerable cells throughout the body, including cardiovascular, renal, and cerebrovascular systems. The present manuscript is to review cardiovascular and renal manifestations of Fabry disease and the new diagnostic procedures for earlier detection and the therapeutic assessments of this disease. We are applying noninvasive cardiovascular and microcirculation analysis methods and novel cardiac biomarkers. Novel therapeutic strategies for this disease have been developing in recent years, which include the clinically introduced enzyme infusion replacement therapy and experimentally developing gene-transfer therapy. We have reported that AAV-mediated muscule-directed gene transfer is very effective for long-term systemic delivery of alpha-gal A (25% of normal mice enzyme activity), resulting in complete clearance of multi-organs Gb3 accumulation. Echocardiographic and immunohistochemical examination demonstrated structural improvement of cardiac hypertrophy. When and to whom the novel therapeutic strategies should be applied to obtain the maximum efficacy and safety remain to be established.

Monitoring the 3-year efficacy of enzyme replacement therapy in fabry disease by repeated skin biopsies

The earliest clinical signs of Fabry disease often manifest as dermatologic disturbances such as angiokeratomata, hypohidrosis, acroparesthesias, and impaired thermal and vibration detection. These disturbances are caused by cellular globotriaosylceramide accumulation in the skin due to deficient lysosomal alpha-galactosidase A activity. In this histologic study, we analyzed pre- and post-treatment dermatologic biopsies from 58 Fabry patients enrolled in a 5 mo, Phase 3 double-blind, randomized, placebo-controlled trial followed by a 30 mo open label extension study of recombinant human alpha-galactosidase A (r-halphaGalA), administered i.v. at 1 mg per kg every 2 wk. Baseline evaluations revealed globotriaosylceramide in multiple dermal cell types (vascular endothelial cells, vascular smooth muscle cells, perineurium). Five months of r-halphaGalA treatment in the Phase 3 trial resulted in complete clearance of globotriaosylceramide from the superficial capillary endothelium in all treatment patients and in only 1 (3%) placebo patient (p<0.001). The placebo group achieved similar results after 6 mo of r-halphaGalA in the open label trial. The capillary endothelium remained free of globotriaosylceramide for up to 30 mo into the extension study among 39 of 40 (98%) patients who underwent biopsies. Globotriaosylceramide clearance from deep vascular endothelial cells was similarly robust. Vascular smooth muscle cells and perineurium demonstrated moderate clearance. These findings suggest that long-term treatment with r-halphaGalA may halt the progression of pathology and prevent the dermatologic disturbances in Fabry patients, and that periodic dermal biopsies can serve as a reliable monitor of sustained efficacy.

Relative hypoxia of the extremities in Fabry disease

A purine degradation study, thermography and near infrared spectroscopy of the extremities were performed on 2 young males with Fabry disease and 2 healthy controls. Two-minute semi-ischemic forearm exercise caused a distinct increase in lactate in all subjects, but venous hypoxanthine and ammonia were greatly increased only in the Fabry patients, suggesting a relatively hypoxic state of the extremities. Limb thermograms of the patients revealed glove and stocking type disturbance at rest. Poor recovery of the skin temperature of the hands and forearms after exercise was observed in the patients, but the sharp increase in oxygenated hemoglobin after total ischemia was found to be normal or near infrared spectroscopy. Neurotropin showed an analgesic effect, i.e. a strong and selective heat-productive action on the painful lesions, and suppressed the hypoxanthine level after exercise in 1 patient. Although the pathophysiology of the pain in Fabry disease has not been clearly elucidated, a relatively hypoxic state with peripheral hypothermia might play an important role in triggering of a painful attack or chronic burning paresthesia.

Regional differences in peripheral circulation between upper and lower extremity in patients with cirrhosis

In 42 patients with compensated cirrhosis and 31 control subjects, blood flow (BF) and vascular resistance (VR) were measured at the forearm and calf, using a pneumoplethysmograph. In some of the subjects deep-body temperature (DBT) was also measured by the zero heat flow method. In cirrhosis, BF and DBT were significantly higher and VR was significantly lower in the forearm than in the calf. Corresponding differences were not observed in control subjects. When these indices of the forearm were compared between cirrhosis and controls, BF and DBT were significantly higher and VR was significantly lower in cirrhosis than in controls. In cirrhotics in whom the gradient between forearm BF and calf BF was 1 ml.dl-1.min-1 or more (forearm greater than calf), the vascular response of the forearm to cold stimulation was reduced, whereas in the remaining patients and in controls the forearm BF and VR responded significantly. These results suggest that there is a regional difference in peripheral circulation in cirrhotics, partly with participation of impaired sympathetic nervous activity, which may account for the selective distribution observed in the clinical manifestations of vascular spider, palmar erythema, and warm hand, inclined toward the upper extremities or the upper part of the body.