Disorders of Glycogen Metabolism of Muscle

Perioperative care of patients with neuromuscular disease and dysfunction

A variety of different pathologies result in disease phenotypes that are summarized as neuromuscular diseases because they share commonalty in their clinical consequences for the patient: a progressive weakening of the skeletal muscles. Distinct caution and appropriate changes to the anesthetic plan are advised when care is provided during the perioperative period. The choice of anesthetic technique, anesthetic drugs, and neuromuscular blockade always depends on the type of neuromuscular disease and the surgical procedure planned. A clear diagnosis of the underlying disease and sufficient knowledge and understanding of the pathophysiology are of paramount importance to the practitioner and guide optimal perioperative management of affected patients.

Equine metabolic myopathies with emphasis on the diagnostic approach comparison with human myopathies A review

This review gives an overview of the presently known human and equine metabolic myopathies with emphasis on the diagnostic approach. Metabolic myopathies are muscle disorders caused by a biochemical defect of the skeletal muscle energy system, which results in inefficient muscle performance. Myopathies can arise in different levels of the metabolic system. In this review the metabolic myopathies are categorized in disorders of the carbohydrate metabolism, lipid metabolism, mitochondrial myopathies (other than those described in lipid metabolism), disorders of purine metabolism, primary disorders involving ion channels and electrolyte flux and secondary or acquired metabolic myopathies.

Fatal infantile neuromuscular presentation of glycogen storage disease type IV

Glycogen storage disease type IV or Andersen disease is an autosomal recessive disorder due to deficiency of glycogen branching enzyme. Typically, glycogen storage disease type IV presents with rapidly progressive liver cirrhosis and death in childhood. Variants include a cardiopathic form of childhood, a relatively benign myopathic form of young adults, and a late-onset neurodegenerative disorder (adult polyglucosan body disease). A severe neuromuscular variant resembling Werdnig-Hoffmann disease has also been described in two patients. The objective was to describe two additional infants with the neuromuscular variant and novel mutations in the GBE1 gene. Branching enzyme assay, Western blot, RT-PCR and sequencing were performed in muscle biopsies from both patients. The cDNA of patient 1 was subcloned and sequenced to define the mutations. Muscle biopsies showed accumulation of periodic acid Schiff-positive, diastase-resistant storage material in both patients and increased lysosomal enzyme activity in patient 1. Branching enzyme activity in muscle was negligible in both patients, and Western blot showed decreased branching enzyme protein. Patient 1 had two single base pair deletions, one in exon 10 (1238delT) and the other in exon 12 (1467delC), and each parent was heterozygous for one of the deletions. Patient 2 had a large homozygous deletion that spanned 627 bp and included exons 8-12. Patient 1, who died at 41 days, had neurophysiological and neuropathological features of Spinal Muscular Atrophy. Patient 2, who died at 5(1/2) weeks, had a predominantly myopathic process. The infantile neuromuscular form of glycogen storage disease type IV is considered extremely rare, but our encountering two patients in close succession suggests that the disease may be underdiagnosed.

Temperature sensitivity of glycolysis during sepsis

OBJECTIVE

To investigate the temperature sensitivity of glycolysis during sepsis.

DESIGN

A prospective, randomized, controlled animal study.

SETTING

The Physiological Department of a University Hospital.

SUBJECTS

Ten male Sprague-Dawley rats, weighing 400-500 g.

INTERVENTIONS

The rats were assigned to either a septic (n = 5) or a sham-control group (n = 5). After anesthesia (H0), experimental sepsis was induced by a cecal ligation and perforation, and the left lateral gastrocnemius was sampled. Four hours later (H4), a second anesthesia was performed to sample the contralateral muscle. The sham-control group underwent the same procedures, but the cecum was neither ligated nor incised.

MEASUREMENTS AND MAIN RESULTS

Glycolytic flux (J(B), the rate at which glycogen can be used in muscle) and the transition time (t99 : the time required for the transition from aerobic to anaerobic metabolism) were measured by using spectrophotometry. The measurements were performed at seven different temperature levels, ranging from 32 to 42 degrees C. For each measured variable, the temperature sensitivity of glycolysis was assessed by computing the Q10 values, which is the variation ratio of the measured variable, attributed to a 10 degrees C temperature increase. In control rats, anesthesia and surgical procedures induced a J(B) increase (7.9 +/- 1.6 at H0 vs. 11.9 +/- 2.1 micromol x min-1 x g(tissue) at H4, p<.05) without any t99 variation. Whatever the group (control or septic), the same temperature variation induced an effect that was approximately three times higher in the hypothermia (<37 degrees C) than in the hyperthermia range (>37 degrees C; p<.05). However, a loss in thermal sensitivity was observed in septic rats in the hyperthermia range (Q10 = 1.2 +/- 0.1 for septic animals vs. 2.3 +/- 0.4 for control animals; p<.05).

CONCLUSIONS

This study demonstrates that glycolysis is more sensitive to temperature in the hypothermia range than in the hyperthermia range. The loss in thermal sensitivity at >37 degrees C in septic rats suggests that sepsis may induce a dysregulation of glycolysis. From an energetic point of view, this signifies that hyperthermia may by itself impair energy metabolism without improving energy production and thus must be treated during sepsis.

Glycolysis in the human muscle: a new approach

The flow response time theory allows the global assessment of a metabolic pathway. This study describes the first application of this concept to explore glycolysis on human skeletal muscle extracts. The muscle extract is used to convert glucose or glucose-6-phosphate into glycerol-phosphate through the first part of glycolysis. The functioning of the experimental model is assayed by a continuous recording of the reduced nicotinamide adenine dinucleotide decay in a spectrophotometer. This measurement method was applied to normal and pathologic human skeletal muscles. The aerobic (J(A)) and anaerobic (J(B)) fluxes and the time (t99) needed for the transition from J(A) to J(B) were measured under a wide clinical temperature range (30 degrees C to 40 degrees C). The two studied muscle types (gluteus maximus and tibialis anterior) have similar glycolytic flux values, with an identical functional modality. The thermal response of glycolysis is not linear, with a high thermal sensitivity in the hypothermic range (30 degrees C to 38 degrees C) and a thermal insensitivity in the hyperthermic range (37 degrees C to 40 degrees C). On the same type of muscle (tibialis anterior), a pathologic process can induce different variations in the glycolysis patterns, but further data are needed to clear this point. The flow response time concept allows an accurate assessment of glycolysis in the human skeletal muscle, whether normal or pathologic. This approach is interesting for evaluating the global influence of different stimulations on a metabolic pathway, such as temperature variation.

Chronic fatigue syndrome: a matter of enzyme deficiencies?

The etiology of chronic fatigue syndrome (CFS) remains an enigma. But literature concerning chronic fatigue which does not focus on CFS points to all sorts of enzyme deficiencies as possible causes. The deficiencies are probably dismissed as causes of CFS because other characteristic symptoms are lacking in CFS patients. But these symptoms are often also lacking in patients with a deficiency. Symptom patterns in enzyme deficiencies are extremely variable. Therefore, patients with CFS should be screened systematically for enzyme deficiencies.

Metabolic myopathies: a clinical approach; part II

Major recent advances in the field of metabolic myopathies have helped delineate the genetic and biochemical basis of these disorders. This progress has also resulted in the development of new diagnostic and therapeutic methodologies. In this second part, we present an updated review of the main nonlysosomal and lysosomal glycogenoses and lipid metabolism defects that manifest with signs of transient or permanent muscle dysfunction. Our intent is to increase the pediatric neurologist's familiarity with these conditions and thus improve decision making in the areas of diagnosis and treatment.

Metabolic myopathies

Disorders of glycogen, lipid or mitochondrial metabolism may cause two main clinical syndromes, namely (1) progressive weakness (eg, acid maltase, debrancher enzyme, and brancher enzyme deficiencies among the glycogenoses; long- and very-long-chain acyl-CoA dehydrogenase (LCAD, VLCAD), and trifunctional enzyme deficiencies among the fatty acid oxidation (FAO) defects; and mitochondrial enzyme deficiencies) or (2) acute, recurrent, reversible muscle dysfunction with exercise intolerance and acute muscle breakdown or myoglobinuria (with or without cramps) (eg, phosphorylase (PPL), phosphorylase b kinase (PBK), phosphofructokinase (PFK), phosphoglycerate kinase (PGK), phosphoglycerate mutase (PGAM), and lactate dehydrogenase (LDH) among the glycogenoses and carnitine palmitoyltransferase II (CPT II) deficiency among the disorders of FAO or (3) both (eg, PPL, PBK, PFK among the glycogenoses; LCAD, VLCAD, short-chain L-3-hydroxyacyl-CoA dehydrogenase (SCHAD), and trifunctional enzyme deficiencies among the FAO defects; and multiple mitochondrial DNA (mtDNA) deletions). Myoadenylate deaminase deficiency, a purine nucleotide cycle defect, is somewhat controversial and is characterized by exercise-related cramps leading rarely to myoglobinuria.

Satoyoshi syndrome: an unusual postnatal multisystemic disorder

Satoyoshi syndrome is a rare disorder of unknown cause characterized by progressive, painful intermittent muscle spasms, malabsorption, alopecia, amenorrhea, and skeletal abnormalities mimicking a skeletal dysplasia. We describe a 19-year-old Caucasian woman with characteristic manifestations starting at age 9. The report of this patient confirms that this condition is not limited to the Asian population.

Manifesting heterozygotes in McArdle's disease: clinical, morphological and biochemical studies in a family

We report a family with McArdle's disease with several affected individuals in two generations. This unusual pedigree for an autosomal recessive disease is explained by the existence of manifesting heterozygotes in the maternal line. The presence of symptoms in heterozygotes seems to be due to a decrease in myophosphorylase activity below a critical threshold, ranging between 30% and 45% of normal mean value. The occurrence of several manifesting heterozygotes in the maternal line only can be explained by compound heterozygosity of a defective allele and a pseudodeficient allele for myophosphorylase, or by a genetic factor which regulates the phenotypic expression of the gene.

A case of myopathy associated with a dystrophin gene deletion and abnormal glycogen storage

A 30-year-old man with no family history of muscle disease presented with a progressive proximal myopathy and calf hypertrophy characteristic of Becker muscular dystrophy. A deletion of exons 45 to 48 in the dystrophin gene was confirmed by Southern blotting and multiplex polymerase chain reaction. However, muscle biopsy showed massive accumulation of glycogen, although no significant abnormality of glycolytic pathway enzymes could be demonstrated. This patient therefore has a previously undescribed myopathy associated with both Becker muscular dystrophy and a glycogen storage disorder of unknown aetiology.

Glycogen branching enzyme deficiency in adult polyglucosan body disease

Branching enzyme activity was assayed in muscle, peripheral nerve, and leukocytes from 2 Ashkenazi-Jewish patients with adult polyglucosan body disease and 1 African-American and 3 Caucasian patients with the same clinical and pathological features. Branching enzyme activity was normal in the muscle specimens from both Jewish and non-Jewish patients. However, the activity was markedly decreased not only in the leukocytes from the 2 Jewish patients (confirming previous findings), but also in peripheral nerve specimens, whereas it was normal in nerve tissue and leukocytes from all non-Jewish patients. These data confirm a branching enzyme deficiency in a subgroup of patients with adult polyglucosan body disease, and show that the defect is tissue-specific, suggesting that adult polyglucosan body disease has more than one biochemical basis.

Cardiomyopathy in glycogen-storage disease type III: clinical and echographic study of 18 patients

Cardiac examinations were performed on 18 patients with glycogen-storage disease (GSD) type III. Clinical examination was always normal and the electrocardiograms revealed nonspecific data. Similarly, serum muscular enzyme activities were not useful in indicating the presence of cardiomyopathy. Echocardiographic evidence of myocardiopathy was found in five of the 16 children studied (mean age, 9.5 years). Echocardiographic parameters remained stable during the follow-up period (at least 3 years). The other 11 children had no echocardiographic evidence of cardiomyopathy. No relationship was found between peripheral myopathy and cardiomyopathy. All patients with GSD type III should be regularly investigated by echocardiography in respect of their cardiac muscle status.

An adult-onset myopathy characterized by a double ring appearance of muscle fibers

We report a 33-yr-old man with an unusual neuromuscular disorder characterized by progressive generalized weakness of 3 yr duration whose muscle biopsy showed a double ring appearance in most muscle fibers. This double ring appearance was due to a peripheral outer sarcoplasmic mass and an inner ring of annular myofibrils surrounding a core of normal longitudinally oriented myofibrils. Nerve conduction studies were normal. Electromyography showed fibrillations, positive waves, and increased brief duration, low amplitude, polyphasic potentials.