Continuous glucose monitoring in children with glycogen storage disease type I

Glycogen storage disease type I (GSD I) is characterized by impaired production of glucose from glycogenolysis and gluconeogenesis resulting in severe fasting hypoglycaemia. The aim of the present study was to examine the efficacy of a continuous subcutaneous glucose monitoring system (CGMS MiniMed), to determine the magnitude and significance of hypoglycaemia in GSD I and to evaluate the efficacy of its dietary treatment. Four children with GSD I were studied over a 72-h period. Results indicated that the values recorded with continuous subcutaneous glucose monitoring were highly correlated with paired blood glucose values measured by glucometer. Significant periods of asymptomatic hypoglycaemia were noted, especially during night-time. The study suggests that repeated continuous subcutaneous glucose monitoring may serve as a useful tool for the assessment of the long-term management of GSD I patients.     

Endogenous glucose production in type I glycogen storage disease

The adaptive mechanisms that protect some patients with Type I glycogen storage disease from fasting hypoglycemia were examined in two young adults. Both maintained low normal fasting plasma glucose concentrations even during 3 day fasts; blood lactate concentrations increased during the first 12 hr and then decreased to normal during the second and third days. Acute hyperglycemic responses to glucagon nearly doubled after three days of starvation when compared with responses following 12 hr fasts. Enhanced glucagon-induced hyperglycemic changes also were observed following the administration of alcohol or glucocorticoids. However, fructose infusions failed to demonstrate hyperglycemic responses after a 3 day fast, alcohol or glucocorticoids. The present studies demonstrate endogenous glucose production in our patients despite an absence of the enzyme glucose-6-phosphatase. These findings could explain why some patients with Type I glycogen storage disease are protected from fasting hypoglycemia.     

Postnatal regression of glucose transport in a patient with glycogen storage disease type 1b

Summary Decreased 2-deoxyglucose (2-DOG) uptake is well described in the neutrophils of patients with glycogen storage disease type 1b (GSD 1b). We report a patient with GSD 1b who presented with a normal antenatal and perinatal 2-deoxyglucose uptake that showed a slow regression during the first months of life. These indicate limitations of 2-deoxyglucose uptake in the diagnosis of GSD 1b. While it appears that low uptake rate below 0.25 nmol/min in 10⁶ cells is of significance, normal uptake does not rule out the presence of the disease. It seems that antenatal diagnosis of GSD 1b cannot be made by measurement of 2-deoxyglucose uptake in the fetal neutrophils.     

Glucose production rates in type 1 glycogen storage disease

Summary Glucose production rates were measured in six patients with glycogen storage disease type 1 (five type 1A, one type 1B) using a primed continuous infusion of either [3-³H]glucose or [6,6-²H₂]glucose. In four patients exogenous glucose was needed to maintain normoglycaemia. At blood glucose concentrations of 2.3–4.7 mmol/L, the endogenous glucose production rates were between 34 and 100% of that predicted for healthy subjects. No relationship was found between the blood glucose concentration and glucose production rates but there was a positive correlation between that of blood lactate and glucose production rate.The initial steady state was perturbed either by reducing the exogenous glucose infusion rate or by giving intravenous glucagon (20µg/kg) or alanine (0.1–0.2 g/kg). Reducing the exogenous glucose infusion rate had little short term effect on glucose production rate. Intravenous glucagon increased the glucose production rate as well as blood glucose and lactate concentrations. A bolus of alanine (0.2 g/kg) given intravenously increased the glucose production rate and blood glucose concentrations but blood lactate concentrations fell.In four of the patients the studies were repeated under similar conditions and the glucose production rate was higher in all patients. We conclude that the glucose production rate is not fixed but varies with the prevailing metabolic status, a finding that has implications for the treatment of type 1 glycogen storage disease.     

Chronic inflammatory bowel disease in glycogen storage disease type 1B

Summary Two children with glycogen storage disease type 1B developed chronic inflammatory bowel disease. The first, a 7-year-old boy, had ileitis and later developed perianal disease. The second developed colitis by the age of 9 years; in both the features were consistent with Crohn disease. The children had neutropenia and neutrophil mobility defects characteristic of GSD-1B. It is suggested that these neutrophil abnormalities are important in the pathogenesis of the bowel inflammation.     

The regulation of growth in glycogen storage disease type 1

OBJECTIVE: To study endocrine and metabolic variables that affect growth in patients with glycogen storage disease type 1 (GSD-1) receiving standard dietary therapy. DESIGN: Observational study. PATIENTS AND MEASUREMENTS: Thirty-eight patients with GSD-1, age range 0.6-32.9 years, were investigated on their usual dietary regimens. Data on height, height velocity in prepubertal children, endocrine and metabolic responses to oral glucose load, 24-h serum cortisol and GH concentration profiles and serum IGF-1 concentrations were collected. RESULTS: The population studied was shorter than average, with a median height standard deviation score (SDS) of -1.60, but significantly taller than a historical population studied at the same institution that had not received dietary therapy at the time of study. A wide range of height SDS was encountered (-5.28 to 1.21) and a subset still exhibit marked growth failure. Median body mass index (BMI) SDS was 0.72 (range -1.34 to 3.96). Those patients with the greatest BMI SDS had the lowest serum GH concentrations but serum IGF-1 concentrations were within the normal range. Patients with the poorest growth exhibit low serum insulin concentration responses to glucose load, GH insensitivity and higher mean 24-h plasma cortisol levels when compared to those patients who were better grown. CONCLUSION: This study shows that overall the growth of this group of patients with glycogen storage disease type 1 has improved compared to that of a historical control group. There remains a subset of this population with poor growth despite therapy. The measured endocrine responses in this subset are similar to those reported for untreated patients. To improve the growth further in these individuals it will be necessary to understand whether this is failure of prescribed therapy or failure to comply with therapy.     

In search of proof-of-concept: gene therapy for glycogen storage disease type Ia

The emergence of life threatening long-term complications in glycogen storage disease type Ia (GSD-Ia) has emphasized the need for new therapies, such as gene therapy, which could achieve biochemical correction of glucose-6-phosphatase deficiency and reverse clinical involvement. We have developed gene therapy with a novel adeno-associated virus (AAV) vector that: 1) prevented mortality and corrected glycogen storage in the liver, 2) corrected hypoglycemia during fasting, and 3) achieved efficacy with a low number of vector particles in G6Pase-deficient mice and dogs. However, the gradual loss of transgene expression from episomal AAV vector genomes eventually necessitated the administration of a different pseudotype of the AAV vector to sustain dogs with GSD-Ia. Further preclinical development of AAV vector-mediated gene therapy is therefore warranted in GSD-Ia.     

Efficacy of ACE-inhibitor therapy on renal disease in glycogen storage disease type 1: a multicentre retrospective study

BACKGROUND: The efficacy of ACE-inhibitors in decreasing microalbuminuria and proteinuria has been reported in a few patients with glycogen storage disease type 1 (GSD1); however, no case-control study has ever been published. AIM: The aim of the current study was to evaluate the efficacy of ACE-inhibitors in reducing glomerular hyperfiltration, microalbuminuria and proteinuria, and in delaying the progression of renal damage. PATIENTS AND METHODS: Ninety-five patients (median age at the time of the study: 14.5 years) were enrolled from nine Italian referral centres for metabolic diseases. A retrospective study of a 10-year follow-up was conducted in order to compare the evolution of these parameters in treated patients with those who were not treated with ACE-inhibitors. RESULTS: A significant and progressive decrease of glomerular filtration rate was observed in treated patients vs. those who were not treated with ACE-inhibitors (P < 0.05). No difference was observed for microalbuminuria and proteinuria between the two groups of patients. Moreover, the ACE-inhibitors significantly delayed the progression from glomerular hyperfiltration to microalbuminuria, but not that from microalbuminuria to proteinuria. CONCLUSIONS: The results of the present study underline the importance of a strict follow-up of renal function in GSD1 patients. The detection of glomerular hyperfiltration suggests precocious initiation of ACE-inhibitor treatment to delay the progression of renal damage. A randomized prospective study is needed to establish for certain the real effectiveness of this treatment in GSD1 patients.     

Inflammatory bowel disease-like colitis in glycogen storage disease type 1b

Chronic inflammatory bowel disease (IBD)-like colitis is occasionally associated with glycogen storage disease-type 1b (GSD-1b). We describe a 17-year old boy with GSD-1b who developed an IBD-like colitis. Roentgenography and colonoscopy showed the lead-pipe appearance of the colon and circumferential ulcers. Histopathologic examination revealed nonspecific inflammation without granulomatous lesions. High-dose granulocyte-colony stimulating factor (G-CSF) and sulfasalazine led to the resolution of the colitis, although neutropenia continued. Besides this case, 10 published cases of GSD-1b and IBD-like colitis were reviewed. All cases had severe neutropenia and/or neutrophil dysfunction. The mean onset of bowel disease was 12.3 years of age. Seven cases required surgical treatment. All five patients with G-CSF/GM-CSF therapy showed clinical remission. These findings suggest that IBD-like colitis is a grave complication of GSD-1b and that recurrent enteric infections due to neutrophil deficiency may contribute to the development of this bowel disease.     

Hepatocyte transplantation as a treatment for glycogen storage disease type 1a

Treatment of many inherited disorders of hepatic metabolism is still challenging. Hepatocyte transplantation was done in a 47-year-old woman who had glycogen storage disease type 1a and severe fasting hypoglycaemia. 2 billion viable hepatocytes were infused via an indwelling portal-vein catheter, followed by a triple immunosuppression regimen with mycophenolate mofetil, tacrolimus, and steroids. 9 months after transplantation, on only tacrolimus, she eats a normal diet and can fast for 7 h without experiencing hypoglycaemia. Our results show that hepatocyte transplantation might be an alternative to liver transplantation in glycogen storage disease type 1a.     

Cardiomyopathy of glycogen storage disease type III

Summary To identify the severity of cardiac involvement in glycogen storage disease type III (GSDIII), and its relation to skeletal muscle involvement and age, 23 patients were studied. The median age was 10 years. Echocardiography, electrocardiography, and creatine phosphokinase (CK) levels were used to assess cardiac and skeletal muscle involvement. Septal and left ventricular posterior wall measurements were compared with normal data. Shortening fraction was derived from left ventricular cavity dimensions. In some patients the echocardiogram resembled that of hypertrophic cardiomyopathy. Thirteen of 20 electrocardiograms (ECG) were abnormal. Eleven patients had septal and/or posterior wall thickness >95% confidence limits (CL). Despite this, cardiac symptoms were uncommon. The CK levels were not directly associated with cardiac abnormalities. Older patients (>20 years) had more abnormal measurements of posterior wall thickness than did younger ones (<20 years). This finding, albeit in a cross-sectional series, suggests progressive myocardial involvement with age despite the absence of symptoms.     

Hepatocellular carcinoma in type I glycogen storage disease

Patients suffering from Type I glycogen storage disease frequently develop hepatic tumors. Some of these were classified as carcinoma, with the majority of tumors representing benign adenomata. However, no evidence exists of malignant transformation of adenomata in these patients. Here, we describe the occurrence of a hepatocellular carcinoma in the adenomata-bearing liver of the elder of two sisters suffering from Type I glycogen storage disease at the age of 20 years, 6 years after the diagnosis had been made. Surprisingly, alpha-fetoprotein levels were normal throughout the entire course of this patient, whereas the younger sister had elevated levels despite the absence of malignant lesions. Thus, the clinical significance of alpha-fetoprotein remains unclear in both cases. Nocturnal feeding, although performed continuously over the 6 years after the diagnosis, had obviously failed to prevent the development of hepatic tumors in both patients.