A functional mini-GDE transgene corrects impairment in models of glycogen storage disease type III

Glycogen storage disease type III (GSDIII) is a rare inborn error of metabolism affecting liver, skeletal muscle, and heart due to mutations of the AGL gene encoding for the glycogen debranching enzyme (GDE). No curative treatment exists for GSDIII. The 4.6 kb GDE cDNA represents the major technical challenge toward the development of a single recombinant adeno-associated virus-derived (rAAV-derived) vector gene therapy strategy. Using information on GDE structure and molecular modeling, we generated multiple truncated GDEs. Among them, an N-terminal-truncated mutant, ΔNter2-GDE, had a similar efficacy in vivo compared with the full-size enzyme. A rAAV vector expressing ΔNter2-GDE allowed significant glycogen reduction in heart and muscle of Agl-/- mice 3 months after i.v. injection, as well as normalization of histology features and restoration of muscle strength. Similarly, glycogen accumulation and histological features were corrected in a recently generated Agl-/- rat model. Finally, transduction with rAAV vectors encoding ΔNter2-GDE corrected glycogen accumulation in an in vitro human skeletal muscle cellular model of GSDIII. In conclusion, our results demonstrated the ability of a single rAAV vector expressing a functional mini-GDE transgene to correct the muscle and heart phenotype in multiple models of GSDIII, supporting its clinical translation to patients with GSDIII.

Narrative review of glycogen storage disorder type III with a focus on neuromuscular, cardiac and therapeutic aspects

Glycogen storage disorder type III (GSDIII) is a rare inborn error of metabolism due to loss of glycogen debranching enzyme activity, causing inability to fully mobilize glycogen stores and its consequent accumulation in various tissues, notably liver, cardiac and skeletal muscle. In the pediatric population, it classically presents as hepatomegaly with or without ketotic hypoglycemia and failure to thrive. In the adult population, it should also be considered in the differential diagnosis of left ventricular hypertrophy or hypertrophic cardiomyopathy, myopathy, exercise intolerance, as well as liver cirrhosis or fibrosis with subsequent liver failure. In this review article, we first present an overview of the biochemical and clinical aspects of GSDIII. We then focus on the recent findings regarding cardiac and neuromuscular impairment associated with the disease. We review new insights into the pathophysiology and clinical picture of this disorder, including symptomatology, imaging and electrophysiology. Finally, we discuss current and upcoming treatment strategies such as gene therapy aimed at the replacement of the malfunctioning enzyme to provide a stable and long-term therapeutic option for this debilitating disease.

Pregnancy and its management in women with GSD type III - a single centre experience

We present a review of our experience and pregnancy outcome in patients with GSD III managed by our centre. Between 1997 and 2010 there were 15 pregnancies in seven women with GSD III. Four women had GSD IIIb (nine pregnancies) and three GSD IIIa (six pregnancies). There was a successful outcome in all 15 pregnancies with delivery of 15 liveborn infants. Four infants were of low birthweight (<2nd centile) but all have developed normally apart from one with behavioural/psychiatric problems. Three women had pre-existing cardiomyopathy prior to pregnancy. One of these women had deterioration of her cardiomyopathy during pregnancy and again in the post-partum period. Women with GSD III do not seem to have any issues with fertility. Overall the outcome of pregnancy for both mother and child is good. Care needs to be taken to avoid maternal hypoglycemia which may be associated with intrauterine growth restriction and low birth weight. Cardiac function should be monitored carefully particularly in those with pre-existing cardiomyopathy.

Multidisciplinary management of an obstetric patient with glycogen storage disease type 3

A 22-year-old primiparous woman with known glycogen storage disease type 3a presented to our hospital during her 12th week of pregnancy. Glycogen storage disease type 3 is a rare inherited disorder resulting from a deficiency of the glycogen debranching enzyme, causing the accumulation of abnormal short-chain glycogen in liver, blood cells, myocardium and striated muscle. Symptoms improve after puberty but the increased metabolism of pregnancy predisposes to hypoglycaemia, ketosis and lactic acidosis. Cardiomyopathy, distal weakness and peripheral neuropathy may present after the third decade. The patient was managed antenatally with regular cornflour feeds and was scheduled for elective caesarean delivery. She presented in early labour at 38 weeks and delivered a healthy neonate by urgent caesarean delivery under spinal anaesthesia. Intravenous dextrose infusion and regular blood glucose monitoring were used during the perinatal period to prevent hypoglycaemia. An arterial line was inserted in the operating room for frequent blood sampling and to avoid muscle cramps which could be induced by the intermittent inflation of the automated blood pressure cuff. Obstetric, anaesthetic and neonatal outcomes were uneventful.

Glycogen storage disease type III in the Irish population

Glycogen storage disease type III (GSD III) results from mutations of the AGL gene encoding the glycogen debrancher enzyme. The disease has clinical and biochemical heterogeneity reflecting the severity of the AGL mutations. We sought to characterise the molecular defects in our cohort of Irish patients with GSD III. Fifteen patients from eight unrelated Irish families were identified: six males and nine females. The age ranged from 2-39 years old, and all presented in the first 3 years of life. Four patients (of three families) had mild disease with hepatomegaly, mild hypoglycaemia and normal creatine kinase (CK) levels. Five families had more severe disease, with liver and skeletal muscle involvement and elevated CK. Eleven different mutations were identified amongst the eight families. Of the 11, six were novel: p.T512fs, p.S736fs, p.A1400fs, p.K1407fs, p.Y519X and p.D627Y. The family homozygous for p.A1400fs had the most severe phenotype (early-onset hypoglycaemia, massive hepatomegaly, myopathy and hypertrophic cardiomyopathy before age 2 years), which was not halted by aggressive carbohydrate and protein supplementation. Conversely, the only missense mutation identified in the cohort, p.D627Y, was associated with a mild phenotype. The phenotypic diversity in our GSD III cohort is mirrored by the allelic heterogeneity. We describe two novel null mutations in exon 32 in two families with severe GSD III resistant to current treatment modalities. Knowledge of the specific mutations segregating in this cohort may allow for the development of new therapeutic interventions.

Hyperlipidemia in glycogen storage disease type III: effect of age and metabolic control

While the presence of hyperlipidaemia in glycogen storage disease (GSD) type Ia and Ib is generally accepted, few investigators have adequately assessed lipid profiles of GSD III in children, in whom the presence of hyperlipidaemia may be most prominent. We analysed the lipid profiles in 44 GSD III patients from 6 months to 30 years of age. Hypertriglyceridaemia and hypercholesterolaemia were common in children younger than 3 years of age. Hypertriglyceridaemia correlated negatively with age, and may reflect increased severity of hypoglycaemia in this younger population. The presence of hyperlipidaemia during childhood in these patients identifies another GSD population that could be at risk for early cardiovascular disease (CVD). Consequently, the outcome of clinical trials investigating the vascular effect of hyperlipidaemia in GSD applies to types other than GSD I.

Portacaval shunt for glycogen storage disease and hyperlipidaemia

Complete portacaval shunt was used to treat 10 patients with glycogen storage disease. A favourable effect was noted on body growth and a number of metabolic abnormalities. More recently, continous night feedings with an intermittently placed gastric tube or through a gastrostomy has been shown to be helpful either before or after portacaval shunts. Such alimentation techniques may eliminate the need for shunts in some patients and be of adjuvant benefit in others. Portacaval shunt was also used for three children who had homozygous Type II hyperlipidaemia. Substantial reductions in serum cholesterol concentration were observed, as well as resorption of xanthomas. Reversal of some cardiovascular lesions has been documented. The benefits of portacaval shunt in these disorders is probably due to the change in the hormone climate of the liver and the whole organism brought about by diversion of the hormone-rich splanchnic venous blood around the liver.

Clinical, biochemical and genetic features of glycogen debranching enzyme deficiency

Deficiency of debrancher enzyme causes Glycogen Storage Disease (GSD) type III, an autosomal recessive disorder, characterized by tissue accumulation of abnormally structured glycogen. This report reviews current clinical and molecular knowledge about this disorder and describes the variability at phenotype and genotype levels of a large group of Italian GSDIII patients.

Glycogen storage diseases in Thai patients: Phramongkutklao Hospital experience

There are 3 cases of liver type glycogen storage diseases. All of them presented with protruding abdomen, failure to thrive, doll face and mark hepatomegaly. Laboratory findings were hypoglycemia, metabolic acidosis, abnormal liver function test, hyperlipidemia and prolonged bleeding time in GSD Ia. GSD III has no hypoglycemia and borderline hyperuricemia. Glucagon stimulation test helps to differentiate typing. The aim of treatment is to prevent hypoglycemia, suppress lactic acid production, decrease blood lipid and uric acid levels and enhances statural growth by uncooked cornstarch. Complications such as epistaxis and suspected liver adenoma have to be closely followed up. Genetic counseling for both types GSD are autosomal recessive with recurrence risk of 25%. Prenatal diagnosis by enzymes assay or molecular diagnosi are not available in this hospital.

[Mutation analysis of glycogen debrancher enzyme gene in five Chinese patients with glycogen storage disease type III]

OBJECTIVE

Type III glycogen storage disease (GSD-III, McKusick 232400), is a rare autosomal recessive disorder, also known as Cori's or Forbe's disease. The affected enzyme is amylo-1,6-glucosidase, 4-alpha-glucanotransferase (glycogen debrancher enzyme, GDE or amylogluco-sidase, AGL), which is responsible for the debranching of the glycogen molecule during catabolism. The AGL gene is located on chromosome 1p21 and contains 35 exons translated in a monomeric protein product. The clinical manifestations of GSD-III are represented by hepatomegaly, recurrent hypoglycemia, seizures, growth failure, dysmorphism, hyperlipidemia, raised transaminases and creatine kinase concentrations and, in a number of subjects, myopathy and cardiomyopathy. The hepatocellular adenoma, hepatocellular carcinoma, diabetes mellitus and liver fibrosis remain rare events. The diagnosis of debrancher deficiency was established by laboratory tests, electromyography (EMG), and muscle and liver biopsy.

METHODS

We studied six GSD-III families after patients or parental consent and the clinical characteristics were documented. Analysis of 33 exons and part exon-intron boundaries of the AGL gene in patients and their parents were carried out by PCR and direct DNA sequencing.

RESULTS

The clinical features included hepatomegaly, splenomegaly, recurrent hypoglycemia, hyperlipidemia, growth failure, raised transaminases and acidosis. Administration of epinephrine 2 hours after a carbohydrate meal could provoke normal rise of blood glucose in the affected individuals, but could not evoke any response after overnight fasting. Administration of raw-corn-starch could maintain normoglycemia and improve the disease condition. Mutation analysis for patient 1 was normal. Patient 2 had a compound heterozygote: a C-to-T transition at nucleotide 1294 (come from father, 1294C > T, L 298 L) in exon 8 and a G-to-T transition at nucleotide 4747 (from mother, 4747G > T, E1450X) in exon 34. Patient 3 had a compound heterozygote: a C-to-T transition at nucleotide 1294 (from father, 1294C > T, L 298 L) in exon 8 and a G-to-A transition at nucleotide -10 (from mother, -10G > A) in exon 3. Patient 4 was a homozygote: an insertion of a nucleotide CT into position +65 in exon 35 (4664 ins CT). Patient 5 had a compound heterozygote: a 8 bp deletion at nucleotide 2341 (from father, 2341delGCCATAGA, frameshift mutation) in exon 16 and a G-to-A transition at nucleotide 1559 (from mother, 1559G > A, R 387 Q) in exon 10. Patient 6 had a compound heterozygote: a T-to-G transition at nucleotide 1686 (from mother, 1686T > G, Y429 X) in exon 12 and a G-to-A transition at nucleotide 3742 (from father, 3742G > A, G 1115 R) in exon 26.

CONCLUSION

GSD-III patients have variable phenotypic characteristics. Administration of raw-corn-starch can effectively improve the disease outcome. We identified 8 new mutations on AGL gene through nucleotide sequence analysis.

Hepatocellular failure in glycogen storage disorder type 3

A case of a 21 years male patient with type 3 glycogen storage disorder diagnosed at necropsy, who died suddenly with hypovolemic shock following a massive upper gastrointestinal bleeding due to hepatocellular failure is reported. Salient features of GSD type 3 are briefly discussed.

Reversible severe myopathy of respiratory muscles due to adult-onset type III glycogenosis

Subacute severe myopathy of the respiratory muscles developed in a 47-year-old woman after a 3-week period of strict fasting. Histological and biochemical work-up of muscle biopsy specimens permitted the diagnosis of debrancher deficiency. The course of the disease was characterized by subacute respiratory failure and prolonged mechanical ventilation. After initiation of a high-protein diet the patient was successfully weaned from the respirator and recovered well. To our knowledge this is the first reported case of adult-onset debrancher deficiency myopathy presenting with subacute respiratory failure and responding to high-protein diet.

[Continuous nocturnal intragastric feeding in glycogenosis type I and III]

Three patients with type I glycogen storage disease (GT I) and four patients with type III glycogen storage disease (GT III) have been treated with nocturnal intragastric feeding and frequent daytime meals for 2 to 8.5 years. In all of them, hypoglycemia was well controlled. Patients with GT. I showed a normal growth rate and an improvement of serum lactate, triglycerides, cholesterol and urate. Patients with GT. III showed no consistent changes in serum triglycerides cholesterol and transaminases and no improvement of myocardiopathy.

Myopathy and growth failure in debrancher enzyme deficiency: improvement with high-protein nocturnal enteral therapy

Seven patients with debrancher enzyme deficiency and childhood or adolescent onset myopathy, four of whom also had growth failure, received long-term treatment consisting of high-protein enteral infusion overnight and high-protein feeds during the day for periods varying from 8 to 42 months. All patients demonstrated improvement in physical activity and endurance. Improvement in muscle strength was documented in five patients, with reversal of myopathic EMG patterns to normal in two patients and reversal of abnormal ECG findings to normal in one patient. All four patients with growth failure showed dramatic improvement in growth rates. This positive response to high-protein enteral therapy supports the concept that myopathy in debrancher enzyme deficiency is at least partly the result of reversible muscle amino acid depletion.

Diet and growth of children with glycogen storage disease Types I and III

Patients with glycogen storage disease (GSD) Types I and III were placed on a dietary treatment plan of frequent daytime feedings and continuous drip nocturnal enteral feedings of defined nutrient composition. Specific anthropometric measurements were collected to document and evaluate growth. There were a significant increase in arm muscle area and a relative decrease in triceps skinfold thickness not previously documented in the literature. Study results confirmed previous reports of accelerated growth and improvement of biochemical abnormalities. The dietitian's role in nutrition assessment and dietary management of GSD patients is emphasized.

[Treatment of glycogenosis type III with total parenteral nutrition, continuous intragastric infusion and D-thyroxine]

A 4-year-old patient with glycogenosis type III suffered from hypoglycemic attacks during the night and from an enormous hepatomegaly. The latter was the cause of a life-threatening respiratory insufficiency. Shrinkage of the liver size was an urgent necessity. The beneficial influences of total parenteral nutrition, continuous intragastric infusion during the night, and of D-tyhroxin are described.