Enzyme replacement therapy in patients with Fabry disease: state of the art and review of the literature.

Anderson-Fabry disease is an X-linked lysosomal storage disorder resulting from the deficiency of the hydrolytic enzyme alpha galactosidase A, with consequent accumulation of globotrioasoyl ceramide in cells and tissues of the body, resulting in a multi-system pathology including end organ failure. In the classical phenotype, cardiac failure, renal failure and stroke result in a reduced median life expectancy. The current causal treatment for Fabry disease is the enzyme replacement therapy (ERT): two different products, Replagal (agalsidase alfa) and Fabrazyme (agalsidase beta), have been commercially available in Europe for almost 10 years and they are both indicated for long-term treatment. In fact, clinical trials, observational studies and registry data have provided many evidences for safety and efficacy of ERT in improving symptoms of pain, gastrointestinal disturbances, hypohidrosis, left ventricular mass index, glomerular filtration rate and quality of life. Few data are available on comparison of the two treatments and on the clinical course of the disease. This article reviews the published evidence for clinical efficacy of the two available enzyme preparations.

Prolonged survival and remyelination after hematopoietic cell transplantation in the twitcher mouse.

The twitcher mouse is an animal model of galactosylceramidase deficiency (Krabbe's disease), a human sphingolipidosis. The effects of hematopoietic cell transplantation as potential enzyme replacement therapy were examined in the twitcher mouse. Survival in twitcher mice with transplants was significantly prolonged and was associated with gradual repair of demyelination in peripheral nerves. In contrast, there was no improvement in the neurodegenerative process in the central nervous system after transplantation. These observations indicate that cellular transplantation may effectively provide in vivo enzyme replacement for the peripheral manifestations of genetic storage diseases. Strategies to perturb the blood-brain barrier may be necessary for enzyme replacement to be therapeutic in diseases with central nervous system manifestations.

Neuronal-visceral GM1 gangliosidosis in a dog with beta-galactosidase deficiency.

A 9-month-old dog with a history of progressive motor dysfunction was shown to have a deficiency in brain beta-galactosidase activity. The canine disease, like that of children with GM1 gangliosidosis, is characterized by accumulation of GM1 ganglioside in the brain, liver, and spleen, and membranous cytoplasmic bodies in neurons. The dog's pedigree suggests an autosomal recessive pattern of inheritance.

Donor-derived cells in the central nervous system of twitcher mice after bone marrow transplantation.

The twitcher mouse is an animal model of galactosylceramidase deficiency, comparable to Krabbe's disease, a lysosomal storage disease in humans. As in most lysosomal storage diseases, neurological deterioration is a prominent feature of the disease in these mice. Transplantation of enzymatically normal congenic bone marrow was earlier found to result in prolonged survival and increased levels of galactosylceramidase in the visceral organs of twitcher mice. It is now reported that bone marrow transplantation results in increased galactosylceramidase levels in the central nervous system (CNS). Concomitantly, the levels of psychosine, a highly toxic lipid that progressively accumulates in the CNS of untreated twitcher mice, stabilized at much lower levels in the CNS of treated twitcher mice. Histologically, a gradual disappearance of globoid cells, the histological hallmark of Krabbe's disease, and the appearance of foamy macrophages capable of metabolizing the storage product were seen in the CNS. By immunohistochemical labeling it was demonstrated that these foamy macrophages were of donor origin. The infiltration of enzymatically competent, donor-derived macrophages was accompanied by extensive remyelination in the CNS. It is concluded that after bone marrow transplantation, donor-derived macrophages infiltrate the affected brain tissue and are capable of inducing a partial reversal of the enzyme deficiency.

Effect of bone marrow transplantation on enzyme levels and clinical course in the neurologically affected twitcher mouse.

The effect of allogeneic bone marrow transplantation (BMT) was investigated in the neurologically affected twitcher mouse, a model for human Krabbe's disease. Twitcher mice have a hereditary deficiency of the lysosomal enzyme galactosylceramidase, which causes growth delay, tremor, and paralysis of the hind legs. Death occurs at 30-40 d of age. After BMT galactosylceramidase activity increased to donor levels in hemopoietic organs. In lung, heart, and liver, galactosylceramidase activity rose to levels intermediate between those of twitcher and normal mice. Increased galactosylceramidase activity in liver parenchymal cells indicated uptake of the donor enzyme by recipient cells of nonhemopoietic origin. Enzyme activity also increased in kidney tissue. BMT resulted in a gradual increase in galactosylceramidase activity in the central nervous system to 15% of normal donor levels. A 5-6-fold increase in galactosylceramidase activity was found in the peripheral nervous system. This increase in enzyme activity was accompanied by a partial alleviation of neurological symptoms. In particular, paralysis of the hind legs was prevented by BMT. BMT led to a modest restoration of growth and prolonged survival. In several cases, the mice survived for more than 100 d, but eventually all animals died with severe neurological disease.

Incorporation and degradation of GM1 ganglioside and asialoGM1 ganglioside in cultured fibroblasts from normal individuals and patients with beta-galactosidase deficiency.

The uptake and degradation of GM1 ganglioside (GM1) and asialoGM1 ganglioside (GA1) were studied in cultured fibroblasts from normal individuals and patients with beta-galactosidase deficiency, using the lipid-loading test. The glycolipids were incorporated from the media into the fibroblasts and the terminal galactose was hydrolyzed in normal cells. The hydrolysis rates of GA1 were 80-86% of normal on the 3rd day after loading, while GM1 was hydrolyzed slowly; 35-54% on the 14th day. In infantile GM1 gangliosidosis and I-cell disease, little GM1 and GA1 was hydrolyzed on any day of culture, while fibroblasts from patients with adult GM1 gangliosidosis, Morquio disease type B and galactosialidosis hydrolyzed the lipids at nearly normal rates. The intracellular accumulation of the glycolipids, on the basis of protein content, was abnormally high in the case of infantile GM1 gangliosidosis and I-cell disease, but normal in the other disorders examined. These observations indicate that the in situ metabolism of GM1 and GA1 is probably normal in fibroblasts from patients with adult GM1 gangliosidosis, Morquio disease type B and galactosialidosis, although in vitro beta-galactosidase activities in these disorders are very low. The results are compatible with findings that GM1 and GA1 do not accumulate in the somatic organs of patients with adult GM1 gangliosidosis and galactosialidosis. In I-cell disease, however, the results of the loading test did not agree with the finding that there is little accumulation of glycolipids in postmortem tissues.

Multiple carbohydrate-cleaving specificities in human acidic and neutral glycosidases.

The common identity of human acidic beta-D-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) and beta-D-xylosidase (1,4-beta-D-xylan xylohydrolase, EC 3.2.1.37) as one enzyme and that of acidic beta-D-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23), beta-D-fucosidase (no allotted EC number) and alpha-L-arabinosidase (alpha-L-arabinofuranoside arabinohydrolase, EC 3.2.1.55) as another enzyme is indicated by similar binding patterns of glycosidase activities of each enzyme to various lectins. by similar ratios between their intra- and extracellular levels in normal and I-cell fibroblasts and by their deficiencies in liver tissues from patients with Gaucher disease and GM1 gangliosidosis, respectively. A third enzyme, neutral beta-D-galactosidase, purified to homogeneity from human liver has been shown to possess all these five glycosidase activities at neutral pH. These neutral enzymic activities were not bound by any of the lectins examined and found to be reduced in liver and spleen of a patient with neutral beta-D-galactosidase deficiency. An additional form of beta-D-xylosidase with optimal activity at pH 7.4 was bound by the fucose-binding lectin from Ulex eurpaeus while no binding was observed for the acidic (pH 4.8) and neutral (pH 7.0) beta-D-xylosidase activities of the multiple glycosidase enzymes.

Optimal assay conditions for enzymatic characterization of homozygous and heterozygous twitcher mouse.

The neurological mouse mutant twitcher is characterized by a genetic deficiency of galactosylceramide beta-galactosidase (galcerase) (EC 3.2.1.46) which also represents lactosylceramide beta-galactosidase I (lactosidase I) activity. The assay conditions for both these activities in several mouse tissues have been optimized to facilitate the enzymatic characterization of homozygous and heterozygous twitcher mice. Galcerase in mouse tissues is optimally activated by 7.0 mg/ml of sodium taurocholate (pure) and 1.5-2.0 mg/ml of oleic acid in this system. When lactosylceramide is used as the substrate, no more than 1 mg/ml of taurocholate is appropriate in the assay, since higher concentrations of this pure bile salt stimulate another enzyme, lactosylceramide beta-galactosidase II (lactosidase II), which is unaffected in twitcher mice. At the optimized condition, lactosidase I in the twitcher mouse amounts to 3-4% of control activity in agreement with the residual galcerase (2%) in this mouse mutant. These assay conditions provide better sensitivity to discriminate heterozygotes from controls until 40 days of age from measurement of this activity in clipped tail samples.

Immunoelectron microscopical localization of lysosomal beta-galactosidase and its precursor forms in normal and mutant human fibroblasts.

Immunoelectron microscopy was performed to study the biosynthesis of lysosomal beta-galactosidase (beta-gal) in normal and mutant human fibroblasts. Using polyclonal and monoclonal antibodies we show in normal cells precursor forms of beta-gal in the rough endoplasmic reticulum (RER) and in the Golgi apparatus throughout the stack of cisternae. In the lysosomes virtually all beta-gal exists as a high molecular weight multimer of mature enzyme. In the autosomal recessive disease GM1-gangliosidosis caused by a beta-gal deficiency and in galactosialidosis, associated with a combined deficiency of lysosomal neuraminidase and beta-gal, precursor forms of the latter enzyme are found in RER, Golgi and some labeling is present at the cell surface. The lysosomes remain unlabeled, indicative for the absence of enzyme molecules in this organelle. In galactosialidosis fibroblasts also no mature beta-gal is found in the lysosomes but in these cells the presence of the monomeric form can be increased by leupeptin (inhibition of proteolysis) whereas addition of a partly purified 32 kDa "protective protein" results in the restoration of high molecular weight beta-gal multimers in the lysosomes.

Calcium absorption from milk in lactase-deficient subjects.

Intestinal calcium absorption from milk containing lactose (+) and from another containing glucose (-) was studied in eight patients with normal lactase (NL) and seven lactase-deficient (LD) subjects to determine if lactase deficiency is implicated in Ca absorption. The results were compared with data obtained from Ca ingestion in a water solution. Ca absorption was measured by a double-isotope technique and the kinetic indices were obtained by a deconvolution method. With (-), Ca absorption was identical in NL and LD subjects and slightly higher than with water solution (15%, NS). With (+), Ca absorption in NL subjects was identical with that from water solution; in LD subjects it increased (23%, p less than 0.02). These data indicate that: Ca is absorbed equally well from milk as from water solution; (+) favors Ca absorption in LD subjects, which suggests that milk ingestion might be encouraged in LD subjects to avoid Ca deficiency; and (-) should be a valuable alternative for lactose-intolerant patients.

Severe orthostatic hypotension in a female carrier of Fabry's disease.

A 21-year-old woman in a family with a history of Fabry's disease showed orthostatic hypotension and whorl-like corneal opacity typical for Fabry's disease. Biochemical studies revealed that she was a heterozygote of the Fabry gene. A variety of autonomic function tests demonstrated both sympathetic and parasympathetic dysfunction. To our knowledge, the present case is the first report of a heterozygous female carrier of Fabry's disease presenting dysfunction of the autonomic nervous system.

Dysmyelination revisited.

Dysmyelination describes an inborn error of metabolism affecting myelinogenesis that causes it to be abnormal, arrested, or delayed. Abiotrophy or myelin as defined by Gowers, due to metabolic failure of the myelin maintenance system, is yet another feature of dysmyelination. In addition to the leukodystrophies, genetically determined conditions such as infantile amaurotic idiocy, hematosidosis, Niemann-Pick's disease and several of the aminoacidopathies are examples of dysmyelinating diseases. In order to reconcile morphological and neurochemical data in these conditions, it is necessary to reexamine a number of pathogenetic hypotheses based on known enzymatic deficiencies, and the interpretation of fragmentary biochemical analyses. The obligatory role of the neuron and axon in myelin formation and maintenance is reviewed. The hypothesis is advanced that gangliosides and their degradative products constitue precursors for the synthesis of the characteristic myelin sphingolipids cerebrosides, sulfatides, and sphingomyelin. Alterations in axoplasmic flow and of ganglioside metabolism must be condidered as important factors in the pathogenesis of dysmyelination.

Macular cherry-red spots and beta-galactosidase deficiency in an adult. An autopsy case with progressive cerebellar ataxia, myoclonus, thrombocytopathy, and accumulation of polysaccharide in liver.

An adult patient with macular cherry-red spots, a gargoyle-like physical appearance, cerebellar ataxia, myoclonus, convulsive seizures, and pyramidal tract signs showed a profound deficiency of beta-galactosidase in liver and brain. Thrombocytopathy of undetermined etiology was evident since childhood, and the patient died of intracranial bleeding at age 22. Cerebral ganglioside pattern was normal. Hepatic mucopolysaccharides were not increased. GM1-gangliosidosis and mucopolysaccharidosis were ruled out by those analytical data. However, a large amount of amylopectin-like polysaccharide was found to be accumulated in liver. Hepatocyte contained numerous inclusion bodies with granulofibrillary structure similar to Lafora bodies, corpora amylacea, and inclusion bodies in glycogenosis type IV. This case seems to represent a new inborn metabolic disease closely related to GM1-gangliosidosis and mucopolysaccharidosis. The primary metabolic defect is not known at present.

A family with beta-galactosidase deficiency: three adults with atypical clinical patterns.

Three adult patients in a single family showed severe myoclonus, ataxia, and pyramidal signs. Enzymatic analysis of lymphocytes, plasma, and cultured skin fibroblasts showed marked deficiency of beta-galactosidase activity, more profound with GM1 ganglioside than with another natural substrate, asialofetuin. Other lysosomal hydrolases were normal. Although the physical signs were similar to those of types 1 and 2 GM1 gangliosidosis, none had bony abnormalities.

Juvenile galactosialidosis in a white male: a new variant.

We describe a 19-year-old white male with juvenile galactosialidosis. He presented with hip arthralgia and was found to have facial "coarseness," corneal clouding, mitral and aortic insufficiency, and hepatosplenomegaly. Ultrastructural studies of skin biopsy and peripheral blood lymphocytes showed membrane-bound inclusions containing sparse fibrillogranular material. Biochemical analysis showed elevated urinary sialyloligosaccharides and no free sialic acid. Fibroblast enzyme analysis showed low activities of both alpha-neuraminidase and beta-galactosidase. To date, most patients with juvenile galactosialidosis have been Japanese. However, unlike those patients, our patient did not have macular cherry-red spots, neurologic abnormalities, or mental retardation. We speculate that this young man represents a new subtype of juvenile galactosialidosis with a potentially different molecular defect from that of the Japanese variant.

Inherited lysosomal storage disease associated with deficiencies of beta-galactosidase and alpha-neuraminidase in sheep.

Histopathologic, ultrastructural and Golgi impregnation studies disclosed lesions characteristic of a neuronal lysosomal storage disease in related sheep with onset of neurologic signs at 4-6 months. Biochemical and enzymatic evaluation disclosed storage of GM1 ganglioside, asialo-GM1, and neutral long chain oligosaccharides in brain, urinary excretion of neutral long chain oligosaccharides, and deficiencies of lysosomal beta-galactosidase and alpha-neuraminidase. Retrospective and limited prospective genetic studies suggested autosomal recessive inheritance. A gene-dosage effect on beta-galactosidase levels was documented in fibroblasts from putative heterozygous sheep. Fibroblasts from affected sheep did not have increased beta-galactosidase activity after incubation with the protease inhibitor, leupeptin. In some aspects this disease is similar to GM1 gangliosidosis, but is unique in that a genetic defect in lysosomal beta-galactosidase may cause the deficiency of lysosomal alpha-neuraminidase.

Advances in the management of Anderson-Fabry disease: enzyme replacement therapy.

Anderson-Fabry disease (AFD) is a lysosomal storage disorder (LSD) due to alpha-galactosidase A (alpha-Gal A) deficiency and the resultant accumulation of incompletely metabolised glycosphingolipids (GSLs), primarily globotriosylceramide (Gb(3)), within various tissues. It is an X-linked multisystem disorder characterised by progressive renal insufficiency, with added morbidity from cardio- and cerebrovascular involvement, and associated with significant impact on quality of life and diminished lifespan. The disease manifests primarily in hemizygous males; however, there is increasing recognition that heterozygous (carrier) females may also develop disease-related complications, although onset among affected women may be delayed. Until recently, treatment has been limited to symptomatic management of pain and other measures to alleviate the problems associated with end-stage complications from renal, cardiac and nervous system involvement. The availability of the recombinant enzyme offers the potential of a safe and effective targeted treatment approach. At the moment, two distinct enzyme formulations are approved in Europe (and in other countries) and both continue to undergo FDA evaluation in the US. Increasing knowledge of the natural history of AFD and greater experience with enzyme therapy should enable optimal patient care. The relative rarity and complexity of AFD necessitates a multi-disciplinary team approach that may be facilitated by a centralised registry.

Two positional isomers of sialylheptasaccharides isolated from the urine of a patient with sialidosis.

We describe the structures of two positional isomers of sialylheptasaccharide isolated from the urine of a patient with sialidosis with partial deficiency of beta-galactosidase. Based on structural studies including compositional sugar analysis, exoglycosidase digestion, chemical ionization mass spectrometry, proton nuclear magnetic resonance spectrometry, and methylation analysis, their structures were deduced to be as follows: AcNeu alpha 2----6Gal beta 1----4GlcNac beta 1----2Man alpha 1----3(Man alpha 1----6)Man beta 1----4GlcNac; AcNeu alpha 2----6Gal beta 1----4GlcNac beta 1----2Man alpha 1----6(Man alpha 1----3)Man beta 1----4GlcNac. Sialyloligosaccharide 1 has previously been found in the urine and liver of patients with mucolipidosis I and II and sialidosis, but sialyloligosaccharide 2 has not been found yet in human urine. These two sialyloligosaccharides could not be completely separated by any chromatographic procedures tested. The analytical techniques, including methylation study and NMR spectroscopy, could not clearly detect the differences between them. However, alpha-mannosidase treatment gave important information for the structural analyses of these sialyloligosaccharides.

The twitcher mouse: normal pattern of early myelination in the spinal cord.

The pattern of early myelination was investigated in the dorsal columns of the cervical spinal cord in the twitcher, an authentic murine model of human globoid cell leukodystrophy, and their littermates. There were no differences in the number of myelinated fibers until the day 20 postnatal. However, myelin sheath in the homozygous affected twitchers at the day 20 were thinner than those of heterozygous and normal littermates, while at the day 10 no significant differences were detected. These observations indicated that in the twitcher mouse, despite the genetic deficiency of galactosylceramidase, myelination progresses normally in early stages and then hypomyelination becomes apparent before myelin breakdown.

Fine structure of meganeurites and secondary growth processes in feline GM1-gangliosidosis.

Electron microscope studies were carried out on neurons of the hippocampal formation in a feline mutant with beta-galactosidase deficiency and GMI-gangliosidosis. Fusiform processes with characteristics similar to meganeurites of Golgi studies were identified between cell bodies and axons of pyramidal and granule cells. The presence of dense material subjacent to the plasma membrane at the meganeurite-axon junction provides evidence that meganeurites form at the axon-hillock region and displace the initial axonal segment distally. Meganeurites of hippocampal neurons exhibited pleomorphic secondary processes with fine structural features of growth cones. Spines and spine-synapses were abundant on perikarya and meganeurites. Numerous membranous cytoplasmic bodies (MCBs) were encountered amongst otherwise normally appearing organelles of the cell body. MCBs were densely packed in meganeurites except near their peripheral area. They were less common in dendrites and rare in synapses of the neuropil. The observations provide further support for the view that meganeurites of mature cortical neurons in ganglioside storage diseases have embryonic growth characteristics.