Muscle glycogen storage

A number of other enzymopathic substances (e.g., pyruvate kinase. Chapter 13 and pyrimidine-5 -nucleotidase. Chapter 27), abnormal hemoglobins (Chapter 28), and abnormalities of the erythrocyte cytoskeleton (Chapter 10) may cause hemolytic anemia. Because many enzymes in the red cell are identical to those in other tissues, defects in these enzymes may have pleiotropic effects. Thus, in addition to hemolytic anemia, triose phosphate isomerase deficiency causes severe neuromuscular disease, and phospho-fructokinase deficiency causes a muscle glycogen storage disease (Chapter 13). Mutations that result in decreased enzyme stability are usually most strongly expressed in erythrocytes because of their inability to synthesize proteins. 

Cori and Cori have drawn attention to the fact that abnormal storage of glycogen in skeletal muscle or heart muscle cannot be explained by a lack of G-6-Pase since this enzyme is normally absent from these tissues. Their suggestion that the activity of amylo-l,6-glucosidase be measured in these tissues has been followed up, and a deficiency of this enzymatic activity in muscle glycogen storage disease has been established (Illingworth et al., 1956). 

Zawadzki, K.M., Yaspelkis, B.B., 111, and Ivy, J.L., Carbohydrate-protein complex increases the rate of muscle glycogen storage after exercise, J Appl Physiol, 12, 1854, 1992. 

Burke, L.M., Collier, G.R., Davis, P.G., Fricker, P.A., Sanigorski, A.J., and Hargreaves, M., Muscle glycogen storage after prolonged exercise effect of the frequency of carbohydrate feedings. Am J Clin Nutr, 64, 115, 1996. 

Figure 6. Glycogen storage in acid maltase (AM) deficiency in this late-onset case not all muscle fibers are affected.

In childhood and adult-onset forms of AM, more moderate glycogen storage and vacuolation of muscle are seen and not all fibers are affected. Although cardiomegaly is not apparent in childhood AMD, glycogen storage is detectable histologically in heart muscle. 

Inherited deficiencies in specific enzymes of glycogen metabolism in both liver and muscle are the causes of glycogen storage diseases. 

Muscle biopsy shows severe vacuolar myopathy with glycogen storage. On electron microscopy, the vacuoles correspond to pools of glycogen free in the cytoplasm. 

However, in some glycogen storage diseases (see p. 128), the amount of glycogen in the liver and/or muscle can be significantly higher. 

One is found in muscle and the other in brain and other tissues.844 A hereditary lack of the muscle type enzyme is one of the known types of glycogen storage diseases (Box 20-D). 

Amalfitano, A., Yie-Wylie, A. J., Hu, H., Dawson, T. L., Raben, N., Plotz, P. and Chen, Y. T. (1999). Systemic correction of the muscle disorder glycogen storage disease type II after hepatic targeting of a modified adenovirus vector encoding human acid-alpha-glucosidase. Proc. Natl. Acad. Sci. USA 96, 8861-8866. 

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