Overexpression of VEGFα as a biomarker of endothelial dysfunction in aortic tissue of α-GAL-Tg/KO mice and its upregulation in the serum of patients with Fabry's disease

Introduction

Fabry's disease is an X-linked lysosomal storage disorder caused by reduced activity of α-galactosidase A (GAL), leading to premature death on account of renal, cardiac, and vascular organ failure. Accumulation of the GAL substrate globotriaosylceramide (Gb3) in endothelial and smooth muscle cells is associated with early vascular cell damage, suggesting endothelial dysfunction as a driver of cardiorenal organ failure. Here, we studied the vascular expression of the key angiogenic factors, VEGFα and its antagonist angiostatin, in Fabry α-GAL-Tg/KO mice and determined circulating VEGFα and angiostatin serum levels in patients with Fabry's disease and healthy controls.

Methods

Cryopreserved aortic vessels from six α-GAL-Tg/KO and six wild-type (WT) mice were obtained and VEGFα and angiostatin levels were determined by performing Western blot analysis. VEGFα expression was visualized by an immunohistochemical staining of paraffin aortic rings. In addition, VEGFα and angiostatin serum levels were measured by using an enzyme-linked immunosorbent assay in 48 patients with genetically verified Fabry's disease (50% male) and 22 healthy controls and correlated with disease severity markers such as lyso-Gb3, albuminuria, NTproBNP, high-sensitive troponin T (hsTNT), and myocardial wall thickness.

Results

It was found that there was a significant increase in VEGFα protein expression (1.66 ± 0.35 vs. 0.62 ± 0.16, p = 0.0009) and a decrease in angiostatin expression (0.024 ± 0.007 vs. 0.053 ± 0.02, p = 0.038) in aortic lysates from α-GAL-Tg/KO compared with that from WT mice. Immunohistochemical staining revealed an adventitial VEGFα signal in α-GAL-Tg/KO mice, whereas no VEGFα signal could be detected in WT mice aortas. No differences in aortic angiostatin expression between α-GAL-Tg/KO- and WT mice could be visualized. The serum levels of VEGFα were significantly upregulated in patients with Fabry's disease compared with that in healthy controls (708.5 ± 426.3 vs. 458.5 ± 181.5 pg/ml, p = 0.048) and positively associated with albuminuria (r = 0.82, p < 0.0001) and elevated NTproBNP (r = 0.87, p < 0.0001) and hsTNT values (r = 0.41, p = 0.048) in male patients with Fabry's disease. For angiostatin, no significant difference was found between patients with Fabry's disease and healthy controls (747.6 ± 390.3 vs. 858.8 ± 599.3 pg/ml).

Discussion

In conclusion, an overexpression of VEGFα and downregulation of its counter player angiostatin in aortic tissue of α-GAL-Tg/KO mice support the hypothesis of an underlying vasculopathy in Fabry's disease. Elevated VEGFα serum levels were also observed in patients with Fabry's disease and were positively associated with elevated markers of organ manifestation in males. These findings suggest that angiogenetic markers, such as VEGFα, may be potentially useful biomarkers for the detection of endothelial dysfunction in classical Fabry's disease.

The mutation p.D313Y is associated with organ manifestation in Fabry disease

Fabry disease (FD) is a multisystem lysosomal storage disorder caused by mutations in the GLA gene. The clinical significance of the mutation p.D313Y is still under debate. Retrospective chart analysis of clinical (neurological, cardiac, renal, and ophthalmological), genetic, and biochemical (lyso-globotriaosylsphingosine, lyso-Gb3; enzyme activity) data was performed in all our patients carrying the p.D313Y mutation. Fourteen patients from 5 families (10 female, 4 male; age range 10-51) were included. Symptoms and organ manifestations compatible with FD could be identified in 10 patients. Cerebrovascular events occurred in 4 females. Seven patients reported pain or acroparaesthesia. Cornea verticillata was found in 1 patient, mild retinal vascular tortuosity in 5 patients. Lyso-Gb3 was elevated in 2 females with cerebrovascular involvement. Classical cardiac, renal or skin manifestations could not be identified. The mutation p.D313Y in the GLA gene may lead to organ manifestations and elevation of the Fabry-specific biomarker lyso-Gb3. Neurological symptoms (stroke and pain) and ocular manifestations seem to be the leading findings. Annual routine visits are recommended for patients carrying the p.D313Y mutation. Enzyme replacement therapy might be considered in symptomatic patients.

Effects of cholesterol and simvastatin treatment in patients with Smith-Lemli-Opitz syndrome (SLOS)

Smith-Lemli-Opitz syndrome (SLOS) is a malformation syndrome caused by deficiency of 7-dehydrocholesterol reductase catalysing the last step of cholesterol biosynthesis. This results in an accumulation of 7- and 8-dehydrocholesterol (7 + 8-DHC) and, in most patients, a deficiency of cholesterol. Current therapy consists of dietary cholesterol supplementation, which raises plasma cholesterol levels, but clinical effects have been reported in only a few patients. Hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors were shown to reduce 7 + 8-DHC levels and increase cholesterol concentrations in two small trials with divergent clinical outcome. This retrolective study evaluates the effects of cholesterol only and of cholesterol plus the HMG-CoA reductase inhibitor simvastatin on plasma sterols in 39 SLOS patients and on anthropometric measures in 20 SLOS patients. Cholesterol as well as additional simvastatin decreased the plasma (7 + 8-DHC)/cholesterol ratio. However, the mechanism leading to the decreasing ratio was different. Whereas it was due to an increasing cholesterol concentration in the cholesterol-only cohort, a decreasing 7 + 8-DHC concentration was demonstrated in the cohort receiving additional simvastatin. We could not confirm a positive effect of simvastatin treatment on anthropometric measures or behaviour, as previously reported.

Decreased plasma concentration of von Willebrand factor antigen (VWF:Ag) in patients with glycogen storage disease type Ia

Despite highly increased blood lipids, patients with glycogen storage disease type Ia (GSD Ia) do not develop premature vascular complications. Since this could be due to changes of coagulation factors, coagulation tests (including von Willebrand factor (VWF) antigen (VWF:Ag) ELISA, VWF:collagen binding activity (VWF:CB) and VWF multimer analysis) were performed in 10 GSD Ia patients, single cases of other GSD types, and in both healthy and hyperlipidaemic controls. In 60% of GSD Ia patients we found abnormal results, with a decrease of VWF:Ag and multimer analysis showing reduced intensity of individual oligomers in the presence of all multimers with a normal triplet structure. We interpret these findings as an acquired 'von Willebrand syndrome type I' in GSD Ia. The underlying metabolic mechanism and a potential role in the protection from vascular complication still needs to be evaluated.

Severe phenotype despite high residual glutaryl-CoA dehydrogenase activity: a novel mutation in a Turkish patient with glutaric aciduria type I

We report the first patient with the homozygous GCDH mutation M263V, displaying a high residual activity in fibroblasts of 30%, but presenting with a severe clinical phenotype.