Elevated globotriaosylsphingosine is a hallmark of Fabry disease

Abstract

Fabry disease is an X-linked lysosomal storage disease caused by deficiency of alpha-galactosidase A that affects males and shows disease expression in heterozygotes. The characteristic progressive renal insufficiency, cardiac involvement, and neuropathology usually are ascribed to globotriaosylceramide accumulation in the endothelium. However, no direct correlation exists between lipid storage and clinical manifestations, and treatment of patients with recombinant enzymes does not reverse several key signs despite clearance of lipid from the endothelium. We therefore investigated the possibility that globotriaosylceramide metabolites are a missing link in the pathogenesis. We report that deacylated globotriaosylceramide, globotriaosylsphingosine, and a minor additional metabolite are dramatically increased in plasma of classically affected male Fabry patients and plasma and tissues of Fabry mice. Plasma globotriaosylceramide levels are reduced by therapy. We show that globotriaosylsphingosine is an inhibitor of alpha-galactosidase A activity. Furthermore, exposure of smooth muscle cells, but not fibroblasts, to globotriaosylsphingosine at concentrations observed in plasma of patients promotes proliferation. The increased intima-media thickness in Fabry patients therefore may be related to the presence of this metabolite. Our findings suggest that measurement of circulating globotriaosylsphingosine will be useful to monitor Fabry disease and may contribute to a better understanding of the disorder.

Fig. 1.

Detection of lyso-Gb3 in plasma of Fabry patient. (Top) Structure of lyso-Gb3. (Middle and Bottom) Chromatograms obtained for pure lyso-Gb3 (Middle Left), normal plasma (Bottom Left), normal plasma spiked with lyso-Gb3 (Middle Right), and Fabry hemizygote plasma (Bottom Right).

Fig. 2.

Increased proliferation of smooth muscle cells by exposure to lyso-Gb3. The proliferation rate of smooth muscle cells was determined as described in Materials and Methods. Cells were exposed for 24 h to indicated concentrations of lyso-Gb3 (♦), lactosylsphingosine (□), or Gb3 (△). The incorporation of radioactive thymidine per well is depicted.

Fig. 3.

Effect of ERT on plasma lyso-Gb3. Illustrative examples of responses in plasma lyso-Gb3 in Fabry patients receiving ERT. (A) Responses in plasma lyso-Gb3 to agalsidase alfa treatment (0.2 mg/kg body weight, 2 weeks) (Left) or agalsidase beta treatment (0.2 mg/kg body weight, 2 weeks) (Right) in patients developing no antibodies. All patients were hemizygotes, except two indicated by the dotted line. (B) Response in plasma lyso-Gb3 (▲) and Gb3 (◇) to agalsidase alfa treatment (0.2 mg/kg body weight, 2 weeks) (Left) or agalsidase beta treatment (0.2 mg/kg body weight, 2 weeks) (Right) in patients developing antibodies. The dose of agalsidase beta was adjusted to (1.0 mg/kg body weight, 2 weeks) at 36 months of treatment.