alpha-Glucosidase isoenzymes in normal and acid maltase-deficient human skeletal muscles

Morphologic findings in biopsied skeletal muscle and cultured fibroblasts from a female patient with Danon's disease (lysosomal glycogen storage disease without acid maltase deficiency)

A family is reported in which three members were affected by cardiomyopathy. Two members died unexpectedly in their second decade. Only a 23-year-old male suffered from the triad of clinical manifestations (cardiomyopathy, mental retardation and vacuolar myopathy). Morphologic findings and biochemical studies of his biopsied skeletal muscle and cultured fibroblasts confirmed lysosomal glycogen storage disease with normal acid maltase that was first described by Danon et al. In this study we demonstrated early morphologic changes, storage of glycogen and abnormal membranous structures in disorganized myofibers in biopsied skeletal muscle from the elder sister, who only showed cardiomyopathy clinically. The aggregation of autophagosomes was prominent in cultured fibroblasts, with an increased glycogen content. The activity of acid alpha-glucosidase was higher than normal. This is a systemic storage disease with different expression in males and females.

Cardiomyopathy, mental retardation, and autophagic vacuolar myopathy. Abnormal MRI findings in the head

A 21-year-old man with childhood-onset mental retardation, non-obstructive hypertrophic cardiomyopathy, and vacuolar myopathy is presented. A histopathological study of biopsied skeletal muscle showed lysosomal glycogen storage mimicking acid maltase deficiency, but biochemical analysis showed normal acid alpha-glucosidase activity. Glycogenosomes were also recognized in endothelial cells on electronmicroscopic examination of biopsied skeletal muscle. Magnetic resonance imaging (MRI) findings in the head revealed the involvement of the central nervous system. This is a new type of lysosomal glycogen storage disease with multisystemic involvement. The specific biochemical defect in this disorder remains to be elucidated.

Human acid maltase-deficient myogenic cell transformation with origin-defective SV40: characterization of a cloned line

A clonal human skeletal muscle cell line showing acid maltase deficiency (AMD) was established through the transfection of origin-defective SV40 DNA. The low acid alpha-glucosidase activity and glycogenosomes in this clone corresponded to AMD. This clone, in spite of loading glycogenososmes, was competent not only as to proliferation without contact inhibition but also as to myogenic differentiation to some extent. Dexamethasone promoted the formation by the transformant of multinucleated myotubes, which expressed acetylcholine receptors. The existence of glycogenosomes did not seem to affect the proliferation or differentiation of myoblasts. The aberrant acid alpha-glucosidase expressed in the transformed myogenic clone was shown to be biochemically identical to that in AMD fibroblasts. This transformant should be of great value for investigating the pathogenesis of AMD because of the possibility of supplying semi-permanently a uniform myogenic cell line expressing AMD.

Aneurysms and vacuolar degeneration of cerebral arteries in late-onset acid maltase deficiency

We present a case of late-onset acid maltase deficiency (AMD) with pronounced involvement of the liver and skeletal muscles. In addition, and in contrast to other adult cases of AMD, the case presented here shows CNS pathology with hypodense and hyperintense white matter areas on CT and MRI scans, and myelin changes ranging from focal areas of demyelination to necrosis. Neuropathologic changes seem to be related to unusual vascular pathology consisting of vacuolar degeneration of small and large arterial blood vessels. Vacuoles of varying size, partly filled with granular PAS-positive material, were found in pericytes and smooth muscle cells of arterial vessel walls. Electron microscopy revealed lysosomal and cytoplasmic free glycogen in smooth muscle cells in the intima of large cerebral arteries as well as in pericytes of arterioles and capillaries. Accumulation of glycogen locally was associated with severe cellular damage and necrosis. The formation of a great number of small aneurysms of intracerebral arteries is thought to be the result of cell damage in the vessel walls.

An investigation of the possible influence of neutral alpha-glucosidases on the clinical heterogeneity of glycogenosis type II

The lysosomal storage disorder glycogenosis type II, caused by a deficiency of lysosomal alpha-glucosidase, is very heterogeneous in its clinical presentation. It has been suggested that this heterogeneity may be due to differential expression of neutral alpha-glucosidases. We have therefore analysed the activity of the major neutral alpha-glucosidases in cultured fibroblasts or muscle cells from 26 patients with glycogenosis type II. The results indicate that there is no correlation between the expression of neutral alpha-glucosidase isoenzymes and the clinical phenotype of this disease.

Reappearance of embryonic neutral alpha-glucosidase isoenzyme in acid maltase-deficient muscle of Japanese quail

Two neutral alpha-glucosidase isoenzymes were isolated from the muscle of Japanese quails with late-onset acid maltase deficiency. One isoenzyme is predominantly expressed in embryonic muscle and the other in adult muscle. The time of switching from one to the other of these two neutral alpha-glucosidases was the same as in normal birds. The glycogen content in acid maltase-deficient muscle was not inversely proportional to the amount of embryonic neutral alpha-glucosidase. From the results, we conclude that (i) the transition of neutral alpha-glucosidase from the embryonic to the adult type is not influenced by the disease, and (ii) the embryonic neutral alpha-glucosidase seems not to be directly correlated with glycogen storage in skeletal muscle. In acid maltase-deficient muscle, the activity of the embryonic type began to increase again from 14 days after hatching, and attained a level corresponding to 18% of the total neutral alpha-glucosidase activity at 3 months (P less than 0.025). Its biochemical characteristics were the same as those of the normal embryonic neutral alpha-glucosidase. It should be clarified why the reappearance of the normal embryonic type occurs in acid maltase-deficient adult muscle and whether or not the reappearance of the embryonic neutral alpha-glucosidase represents regenerating muscle.