Type I glycogen storage disease: nine years of management with cornstarch

Savory Cracker Development for Blood Glucose Control and Management: Glycogen Storage Diseases

The blood glucose response of savory slow energy-release crackers (GLY-HYP) were evaluated in volunteers carrying glycogen storage diseases (GSDs), Types I (Ia) and IV. The crackers have been shown previously to provide a "flat" slow glucose response in healthy volunteers, for up to 4 h. On average for the mixed-sex volunteer group aged 53 to 70 for Type I, the blood glucose concentration increased from baseline to a maximum of 9.5 mmol/L at 60 min and remained above baseline for up to 210 min; overall, above 5 mmol/L for 4 h. In common with healthy individuals, a relatively flat blood glucose response was recorded. For Type IV, mixed-sex patients aged between 55 and 72, the blood glucose concentration reached maximum of 10.2 mmol/L at 45 min and then stayed above baseline for 150 min. Again, overall, above 5 mmol/L for 4 h. Altogether, these data indicate that these crackers would provide a valuable contribution to the nutritional needs of people of different age groups with GSDs (Clinical Registration Number: HRC10032021).

Glycogen storage disease type 1a in the Ohio Amish

Glycogen storage disease type 1a (GSD1a) is an inborn error of glucose metabolism characterized by fasting hypoglycemia, hepatomegaly, and growth failure. Late complications include nephropathy and hepatic adenomas. We conducted a retrospective observational study on a cohort of Amish patients with GSD1a. A total of 15 patients cared for at a single center, with a median age of 9.9 years (range 0.25–24 years) were included. All patients shared the same founder variant in GCPC c.1039 C > T. The phenotype of this cohort demonstrated good metabolic control with median cohort triglyceride level slightly above normal, no need for continuous overnight feeds, and a higher quality of life compared to a previous GSD cohort. The most frequent complications were oral aversion, gross motor delay, and renal hyperfiltration. We discuss our unique care delivery at a single center that cares for Amish patients with inherited disorders.

Prevalence and Complications of Glycogen Storage Disease in South Korea: A Nationwide Population-Based Study, 2007-2018

Glycogen storage disease (GSD) is a rare disease that can cause life-threatening problems owing to metabolic errors in storing or using glycogen. The disease course of GSD remains unknown, despite medical technology advances. We determined the prevalence and complications of GSD using data from the National Health Insurance Service database. Data were collected and analyzed for the entire South Korean population with GSD during 2007–2018. GSD was defined as a combination of disease code E74.0 and rare incurable disease insurance code V117, a unique disease code combination for GSD in South Korea. Overall, 23,055 patients had the E74 disease code; 404 had an additional V117 insurance code. Most GSD patients were aged <10 years. Many complications were identified, the most common being hepatomegaly, hyperuricemia, and elevated liver enzyme levels. The most prescribed drug was α-glucosidase, followed by allopurinol. Seventy-two percent of patients were treated in pediatrics. Twenty-five patients underwent liver transplantation, and 14 died after GSD diagnosis. In South Korea, more patients than expected had GSD diagnosis and were managed accordingly. GSD causes many complications and hospitalizations, resulting in high medical expenses. Serious complications can result in liver transplantation and, eventually, death in some cases. Although the patients' condition was identified only by the disease code, this is the first study to present the current situation of GSD patients in South Korea. Because GSD patients can have dangerous medical conditions, they should be managed consistently while minimizing various complications that may occur with optimal metabolic control.

Impaired Very-Low-Density Lipoprotein catabolism links hypoglycemia to hypertriglyceridemia in Glycogen Storage Disease type Ia

Prevention of hypertriglyceridemia is one of the biomedical targets in Glycogen Storage Disease type Ia (GSD Ia) patients, yet it is unclear how hypoglycemia links to plasma triglyceride (TG) levels. We analyzed whole-body TG metabolism in normoglycemic (fed) and hypoglycemic (fasted) hepatocyte-specific glucose-6-phosphatase deficient (L-G6pc^-/- ) mice. De novo fatty acid synthesis contributed substantially to hepatic TG accumulation in normoglycemic L-G6pc^-/- mice. In hypoglycemic conditions, enhanced adipose tissue lipolysis was the main driver of liver steatosis, supported by elevated free fatty acid concentrations in GSD Ia mice and GSD Ia patients. Plasma very-low-density lipoprotein (VLDL) levels were increased in GSD Ia patients and in normoglycemic L-G6pc^-/- mice, and further elevated in hypoglycemic L-G6pc^-/- mice. VLDL-TG secretion rates were doubled in normo- and hypoglycemic L-G6pc^-/- mice, while VLDL-TG catabolism was selectively inhibited in hypoglycemic L-G6pc^-/- mice. In conclusion, fasting-induced hypoglycemia in L-G6pc^-/- mice promotes adipose tissue lipolysis and arrests VLDL catabolism. This mechanism likely contributes to aggravated liver steatosis and dyslipidemia in GSD Ia patients with poor glycemic control and may explain clinical heterogeneity in hypertriglyceridemia between GSD Ia patients.

Bezafibrate Enhances AAV Vector-Mediated Genome Editing in Glycogen Storage Disease Type Ia

Glycogen storage disease type Ia (GSD Ia) is a rare inherited disease caused by mutations in the glucose-6-phosphatase (G6Pase) catalytic subunit gene (G6PC). Absence of G6Pase causes life-threatening hypoglycemia and long-term complications because of the accumulations of metabolic intermediates. Bezafibrate, a pan-peroxisome proliferator-activated receptor (PPAR) agonist, was administered in the context of genome editing with a zinc-finger nuclease-containing vector (AAV-ZFN) and a G6Pase donor vector (AAV-RoG6P). Bezafibrate treatment increased survival and decreased liver size (liver/body mass, p < 0.05) in combination with genome editing. Blood glucose has higher (p < 0.05) after 4 h of fasting, and liver glycogen accumulation (p < 0.05) was lower in association with higher G6Pase activity (p < 0.05). Furthermore, bezafibrate-treated mice had increased numbers of G6PC transgenes (p < 0.05) and higher ZFN activity (p < 0.01) in the liver compared with controls. PPAR-α expression was increased and PPAR-γ expression was decreased in bezafibrate-treated mice. Therefore, bezafibrate improved hepatocellular abnormalities and increased the transduction efficiency of AAV vector-mediated genome editing in liver, whereas higher expression of G6Pase corrected molecular signaling in GSD Ia. Taken together, bezafibrate shows promise as a drug for increasing AAV vector-mediated genome editing.

Investigation and management of the hepatic glycogen storage diseases

The glycogen storage diseases (GSD) comprise a group of disorders that involve the disruption of metabolism of glycogen. Glycogen is stored in various organs including skeletal muscle, the kidneys and liver. The liver stores glycogen to supply the rest of the body with glucose when required. Therefore, disruption of this process can lead to hypoglycaemia. If glycogen is not broken down effectively, this can lead to hepatomegaly. Glycogen synthase deficiency leads to impaired glycogen synthesis and consequently the liver is small. Glycogen brancher deficiency can lead to abnormal glycogen being stored in the liver leading to a quite different disorder of progressive liver dysfunction. Understanding the physiology of GSD I, III, VI and IX guides dietary treatments and the provision of appropriate amounts and types of carbohydrates. There has been recent re-emergence in the literature of the use of ketones in therapy, either in the form of the salt D,L-3-hydroxybutyrate or medium chain triglyceride (MCT). High protein diets have also been advocated. Alternative waxy maize based starches seem to show promising early data of efficacy. There are many complications of each of these disorders and they need to be prospectively surveyed and managed. Liver and kidney transplantation is still indicated in severe refractory disease.

A pilot longitudinal study of the use of waxy maize heat modified starch in the treatment of adults with glycogen storage disease type I: a randomized double-blind cross-over study

Background

Uncooked corn-starch (UCCS) has been the mainstay of therapy for the hepatic glycogen storage diseases (GSD) but is not always effective. A new starch (WMHMS) has demonstrated a more favourable short-term metabolic profile.

Objective

To determine efficacy and safety of a new uncooked starch (WMHMS) compared to UCCS over 16 weeks treatment with each.

Method

A double-blind cross-over study of 10 adults (aged 16 – 38 years, six male) with GSD Ia and Ib. After an individualised fast, subjects were randomised to take a 50 g starch-load of either WMHMS or UCCS. Starch-loads terminated when blood glucose was < 3.0 mmol/L or the subject felt subjectively hypoglycaemic. Anonymous biochemical profiles were assessed by 2 investigators and a starch administration schedule recommended. Each starch was delivered in coded sachets and intake was monitored for the following 16 weeks. After a washout period, the protocol was repeated with the alternative product.

Results

4 subjects failed to establish therapy on the cross-over limb. Data from 7 paired starch load showed: longer median fasting duration with WMHMS (7.5 versus 5 hours; p = 0.023), slower decrease in the glucose curve (0.357 versus 0.632 mmol/hr p = 0.028) and less area under insulin curves for the first 4 hours (p = 0.03). Two of six subjects took 50% or less WMHMS compared to UCCS and one took more. Plasma triglycerides, cholesterol and uric acid were unchanged after each study phase.

Conclusion

WMHMS leads to significant reduction in insulin release and reduced starch use in some GSD patients.

Long-term efficacy following readministration of an adeno-associated virus vector in dogs with glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD-Ia) is the inherited deficiency of glucose-6-phosphatase (G6Pase), primarily found in liver and kidney, which causes life-threatening hypoglycemia. Dogs with GSD-Ia were treated with double-stranded adeno-associated virus (AAV) vectors encoding human G6Pase. Administration of an AAV9 pseudotyped (AAV2/9) vector to seven consecutive GSD-Ia neonates prevented hypoglycemia during fasting for up to 8 hr; however, efficacy eventually waned between 2 and 30 months of age, and readministration of a new pseudotype was eventually required to maintain control of hypoglycemia. Three of these dogs succumbed to acute hypoglycemia between 7 and 9 weeks of age; however, this demise could have been prevented by earlier readministration an AAV vector, as demonstrated by successful prevention of mortality of three dogs treated earlier in life. Over the course of this study, six out of nine dogs survived after readministration of an AAV vector. Of these, each dog required readministration on average every 9 months. However, two were not retreated until >34 months of age, while one with preexisting antibodies was re-treated three times in 10 months. Glycogen content was normalized in the liver following vector administration, and G6Pase activity was increased in the liver of vector-treated dogs in comparison with GSD-Ia dogs that received only with dietary treatment. G6Pase activity reached approximately 40% of normal in two female dogs following AAV2/9 vector administration. Elevated aspartate transaminase in absence of inflammation indicated that hepatocellular turnover in the liver might drive the loss of vector genomes. Survival was prolonged for up to 60 months in dogs treated by readministration, and all dogs treated by readministration continue to thrive despite the demonstrated risk for recurrent hypoglycemia and mortality from waning efficacy of the AAV2/9 vector. These preclinical data support the further translation of AAV vector-mediated gene therapy in GSD-Ia.

Perioperative management of hemostasis for surgery of benign hepatic adenomas in patients with glycogen storage disease type ia

The development of hepatocellular adenomas in the liver of patients with glycogen storage disease type I is a well-known complication of the disease. Surgical procedures and perioperative managements described so far have reported persistent and important morbidity. We report here a series of six patients (three males and three females) who underwent hepatic resection, and we propose a new hemostatic management protocol comprising glucose infusion, corticosteroids, desmopressin, and antifibrinolytic drugs, used to prevent efficaciously hepatic hemorrhage due to glycogen storage disease (GSD) platelet dysfunction.

Dietary dilemmas in the management of glycogen storage disease type I

Over the last 50 years, understanding the biochemical bases of glycogen storage disease type I has led to vastly improved survival and health outcomes but the management still centres around an extremely intensive dietary regimen. Patients' metabolic profiles are really determined by the whole of the diet and it can be very difficult to adjust therapy accordingly. In an iso-energetic diet with reference total energy intake, high carbohydrate intake could compromise other macro- and micro-nutrients; if carbohydrates are not restricted then total energy intake is excessive. The quality of the macronutrient such as the glycemic index of carbohydrate, the type of sugar and the proportion of medium-chain triglyceride and essential fatty acids also has a bearing on an individual's long-term metabolic control with potential clinical correlates. These factors as well as the different requirements between individuals and within individuals as they get older mean that the management of glycogen storage disease type I is particularly fraught. Regular clinical and dietary review is imperative as patients grow, ensuring adequate but not excessive low glycaemic index carbohydrate intake, appropriate dynamic biochemical profiles and suitable age appropriate eating patterns. Without diligent management, and education that empowers the patient, these individuals can struggle in adult life.

Cell death and stress signaling in glycogen storage disease type I

Cell death has been traditionally classified in apoptosis and necrosis. Apoptosis, known as programmed cell death, is an active form of cell death mechanism that is tightly regulated by multiple cellular signaling pathways and requires ATP for its appropriate process. Apoptotic death plays essential roles for successful development and maintenance of normal cellular homeostasis in mammalian. In contrast to apoptosis, necrosis is classically considered as a passive cell death process that occurs rather by accident in disastrous conditions, is not required for energy and eventually induces inflammation. Regardless of different characteristics between apoptosis and necrosis, it has been well defined that both are responsible for a wide range of human diseases. Glycogen storage disease type I (GSD-I) is a kind of human genetic disorders and is caused by the deficiency of a microsomal protein, glucose-6-phosphatase-α (G6Pase-α) or glucose-6-phosphate transporter (G6PT) responsible for glucose homeostasis, leading to GSD-Ia or GSD-Ib, respectively. This review summarizes cell deaths in GSD-I and mostly focuses on current knowledge of the neutrophil apoptosis in GSD-Ib based upon ER stress and redox signaling.

Emerging therapies for glycogen storage disease type I

Glycogen storage disease type I (GSD I) is caused by deficiency of the glucose-6-phosphatase catalytic subunit in type Ia or of glucose-6-phosphate transporter in type Ib. The cellular bases for disruptions of homeostasis have been increasingly understood in GSD I, including those for anemia, renal failure and neutropenia. Advances in the understanding of cellular abnormalities in GSD I have provided rationales for new therapy, and recent developments in gene therapy have led to potential curative treatments for GSD I. These advances will benefit patients with GSD I in the future, improving both quality of life and survival, as well as illuminating the molecular effects of altered metabolism upon multiple organ systems.

Adalimumab for the treatment of Crohn-like colitis and enteritis in glycogen storage disease type Ib

Glycogen storage disease (GSD) type Ib is a congenital disorder of glycogen metabolism that is associated with neutropenia, neutrophil dysfunction, and an inflammatory bowel disease that mimics a Crohn phenotype. Gastrointestinal inflammation in GSD Ib has been successfully treated with 5-aminosalicylic acid and granulocyte colony-stimulating factor (G-CSF). However, therapeutic options for patients not responding to traditional therapies have been limited owing to untoward effects of glucocorticoids and immunomodulators in this metabolic disorder. Adalimumab is a monoclonal antibody targeting tumour necrosis factor-α that has shown promise for the treatment of patients with Crohn disease. Due to the limited options for treating GSD-associated inflammatory bowel disease, use of adalimumab was attempted in a case unresponsive to aminosalicylate, G-CSF, and antibiotic therapy. Significant clinical and histological improvement was observed in our patient, and the medication was well tolerated.

Preemptive living donor liver transplantation in glycogen storage disease Ia: case report

Even with substantial progress in the management of patients with glycogen storage disease type Ia (GSD-Ia), hepatic and renal complications may still develop during long-term follow-up. Herein, we report a case of preemptive living donor liver transplantation in a patient with GSD-Ia.

PATIENT

The patient was a 5-year-old boy in whom GSD-Ia was diagnosed at age 10 months. Clinical symptoms included frequent hypoglycemic episodes, hyperlipidemia, hyperuricemia, and growth retardation, which were poorly controlled using conventional treatments. At age 5 years, frequent massive nasal bleeds developed, which led to severe anemia. The patient was brought to our institute for living donor liver transplantation (LDLT). Because GSD-Ia usually responds to dietary and medical treatments, we had a long discussion to determine whether preemptive LDLT was indicated. Transplantation was performed using the left lateral liver segment from the patients mother. The weight of his native liver was almost 2 kg. After reperfusion of the graft, the blood glucose concentration rapidly increased, and regular glucose was administered throughout the operation. The posttransplantation course was uneventful. The patient had no episodes of hypoglycemia with a regular diet. Total cholesterol, triglyceride, and uric acid concentrations also reverted to normal without medication. The patient had a few episodes of nasal bleeding after transplantation, which stopped spontaneously. He was discharged from our hospital with normal liver function.

CONCLUSION

Patients with GSD-Ia should be considered for preemptive LDLT to improve their quality of life when clinical symptoms do not respond to appropriate treatment.

Increased de novo lipogenesis and delayed conversion of large VLDL into intermediate density lipoprotein particles contribute to hyperlipidemia in glycogen storage disease type 1a

Glycogen storage disease type 1a (GSD-1a) is a metabolic disorder characterized by fasting-induced hypoglycemia, hepatic steatosis, and hyperlipidemia. The mechanisms underlying the lipid abnormalities are largely unknown. To investigate these mechanisms seven GSD-1a patients and four healthy control subjects received an infusion of [1-(13)C]acetate to quantify cholesterogenesis and lipogenesis. In a subset of patients, [1-(13)C]valine was given to assess lipoprotein metabolism and [2-(13)C]glycerol to determine whole body lipolysis. Cholesterogenesis was 274 +/- 112 mg/d in controls and 641 +/- 201 mg/d in GSD-1a patients (p < 0.01). Plasma triglyceride-palmitate derived from de novo lipogenesis was 7.1 +/- 9.4 and 86.3 +/- 42.5 micromol/h in controls and patients, respectively (p < 0.01). Production of VLDL did not show a consistent difference between the groups, but conversion of VLDL into intermediate density lipoproteins was relatively retarded in all patients (0.6 +/- 0.5 pools/d) compared with controls (4.3 +/- 1.8 pools/d). Fractional catabolic rate of intermediate density lipoproteins was lower in patients (0.8 +/- 0.6 pools/d) compared with controls (3.1 +/- 1.5 pools/d). Whole body lipolysis was similar, i.e., 4.5 +/- 1.9 micromol/kg/min in patients and 3.8 +/- 1.9 micromol/kg/min in controls. Hyperlipidemia in GSD-1a is associated with strongly increased lipid production and a slower relative conversion of VLDL to LDL.

A novel starch for the treatment of glycogen storage diseases

OBJECTIVE

To determine whether a new starch offers better short-term metabolic control than uncooked cornstarch in patients with glycogen storage diseases (GSDs).

STUDY DESIGN

A short-term double-blind cross-over pilot study comparing uncooked physically modified cornstarch (WMHM20) with uncooked cornstarch in patients with GSD types Ia, Ib and III. Twenty-one patients (ages 3-47, 9 female) were given 2 g/kg cornstarch or WMHM20 mixed in water. Blood glucose, lactate and insulin, and breath hydrogen and (13)CO2 enrichment were measured, at baseline and after each load. The hourly biochemical evaluations terminated when blood glucose was < or = 3.0 mmol/L, when the study period had lasted 10 h or when the patient wished to end the test. The alternative starch was administered under similar trial conditions a median of 10 days later.

RESULTS

The median starch load duration was 9 h for WMHM20 versus 7 h for cornstarch. Glucose decreased more slowly (p = 0.05) and lactate was suppressed faster (p = 0.17) for WMHM20 compared with cornstarch. Peak hydrogen excretion was increased (p = 0.05) when cornstarch was taken.

CONCLUSION

These data indicate longer duration of euglycaemia and better short-term metabolic control in the majority of GSD patients with WMHM20 compared to cornstarch.

Successful long-term treatment of hepatic carnitine palmitoyltransferase I deficiency and a novel mutation

Individuals with carnitine palmitoyltransferase I (CPT-I) deficiency cannot metabolize long-chain fatty acids and can develop life-threatening hypoglycaemia. We present a boy with CPT-I deficiency maintained on a very low-fat diet with nighttime uncooked cornstarch feedings for 5(1/2) years with good success. He has had normal growth and no episodes of hypoglycaemia or adverse side-effects. We found that he was homozygous for a previously undescribed mutation, T314I, in the CPT1A protein.

Utilization of cornstarch in glycogen storage disease type Ia

OBJECTIVE

Uncooked cornstarch (UCCS) is used widely for the treatment of patients with glycogen storage disease type I (GSD-I). Previous studies suggested that glucose absorption may be impaired in GSD-I. In order to measure utilization of UCCS in young adults with GSD-Ia and healthy controls, we used a C-breath test based on the natural enrichment of C in UCCS.

DESIGN

Open, not randomized, prospective interventional study.

METHODS

Following 1 g/kg UCCS, we studied eight subjects with GSD-Ia (7 males, 1 female; mean age 28.3 years, range 16-42 years) and 15 healthy controls (10 males, 5 females; mean age 23.5 years, range 19-36 years). Breath samples for analysis of CO enrichment were collected at baseline and at 30-min intervals for 6 h or until hypoglycaemia occurred. Indirect calorimetry was used to measure respiratory gas exchange. Intermediate metabolites, lipids and glucose were measured in plasma. Breath H concentrations were measured as an indicator of malabsorption.

RESULTS

Cumulative utilization over 6 h was significantly higher in controls (18.35 +/- 6.2% of total carbohydrate intake) than in subjects with GSD-Ia (11.5 +/- 4.7%) (P < 0.02). However, utilization of UCCS was virtually identical up to 2.5 h. Two subjects with GSD-Ia fulfilled the criteria for malabsorption.

CONCLUSIONS

Starch digestion and absorption are not impaired in GSD-Ia. However, overall utilization of UCCS appears to be lower in GSD-Ia, which is most likely secondary to perturbed intermediary metabolism. There are important implications for treatment of this disorder. Ways to improve the efficacy of UCCS in GSD-I are needed.

Low bone mass in glycogen storage disease type 1 is associated with reduced muscle force and poor metabolic control

OBJECTIVE

To study the relation between muscle force, bone mass, and metabolic control in patients with glycogen storage disease type (GSD 1).

STUDY DESIGN

Distal radius bone mass and density were evaluated in 19 patients with GSD 1 (15 GSD 1a, 4 GSD 1b) by means of peripheral quantitative computed tomography. Grip force was quantified with a dynamometer.

RESULTS

Height, weight, bone mass, and grip force were significantly decreased in the patients with GSD 1a, mainly as the result of low values in the poorly controlled subgroup. Boys had lower bone mass than girls. Patients with GSD 1b had higher values for bone mineral density in the trabecular compartment. In most of the study participants bone mass appeared to be adequately adapted to the mechanical requirements imposed by muscle contraction. However, 3 patients with GSD 1a had evidence for a low bone mass.

CONCLUSIONS

In GSD 1, both reduced muscle strength and a direct disease effect can contribute to low bone mass. The quality of treatment is crucial to prevent disturbances in musculoskeletal development.

Guidelines for management of glycogen storage disease type I - European Study on Glycogen Storage Disease Type I (ESGSD I)

Life-expectancy in glycogen storage disease type I (GSD I) has improved considerably. Its relative rarity implies that no metabolic centre has experience of large series of patients and experience with long-term management and follow-up at each centre is limited. There is wide variation in methods of dietary and pharmacological treatment. Based on the data of the European Study on Glycogen Storage Disease Type I, discussions within this study group, discussions with the participants of the international SHS-symposium 'Glycogen Storage Disease Type I and II: Recent Developments, Management and Outcome' (Fulda, Germany; 22-25th November 2000) and on data from the literature, guidelines are presented concerning: (1). diagnosis, prenatal diagnosis and carrier detection; (2). (biomedical) targets; (3). recommendations for dietary treatment; (4). recommendations for pharmacological treatment; (5). metabolic derangement/intercurrent infections/emergency treatment/preparation elective surgery; and (6). management of complications (directly) related to metabolic disturbances and complications which may develop with ageing and their follow-up.

CONCLUSION

In this paper guidelines for the management of GSD I are presented.

Glycogen storage disease type I: diagnosis, management, clinical course and outcome. Results of the European Study on Glycogen Storage Disease Type I (ESGSD I)

Glycogen storage disease type I (GSD I) is a relatively rare metabolic disease and therefore, no metabolic centre has experience of large numbers of patients. To document outcome, to develop guidelines about (long-term) management and follow-up, and to develop therapeutic strategies, the collaborative European Study on GSD I (ESGSD I) was initiated. This paper is a descriptive analysis of data obtained from the retrospective part of the ESGSD I. Included were 231 GSD Ia and 57 GSD Ib patients. Median age of data collection was 10.4 years (range 0.4-45.4 years) for Ia and 7.1 years (0.4-30.6 years) for Ib patients. Data on dietary treatment, pharmacological treatment, and outcome including mental development, hyperlipidaemia and its complications, hyperuricaemia and its complications, bleeding tendency, anaemia, osteopenia, hepatomegaly, liver adenomas and carcinomas, progressive renal disease, height and adult height, pubertal development and bone maturation, school type, employment, and pregnancies are presented. Data on neutropenia, neutrophil dysfunction, infections, inflammatory bowel disease, and the use of granulocyte colony-stimulating factor are presented elsewhere (Visser et al. 2000, J Pediatr 137:187-191; Visser et al. 2002, Eur J Pediatr DOI 10.1007/s00431-002-1010-0).

CONCLUSION

there is still wide variation in methods of dietary and pharmacological treatment of glycogen storage disease type I. Intensive dietary treatment will improve, but not correct completely, clinical and biochemical status and fewer patients will die as a direct consequence of acute metabolic derangement. With ageing, more and more complications will develop of which progressive renal disease and the complications related to liver adenomas are likely to be two major causes of morbidity and mortality.

Delivery of glucose-6-phosphatase in a canine model for glycogen storage disease, type Ia, with adeno-associated virus (AAV) vectors

Therapy in glycogen storage disease type Ia (GSD Ia), an inherited disorder of carbohydrate metabolism, relies on nutritional support that postpones but fails to prevent long-term complications of GSD Ia. In the canine model for GSD Ia, we evaluated the potential of intravenously delivered adeno-associated virus (AAV) vectors for gene therapy. In three affected canines, liver glycogen was reduced following hepatic expression of canine glucose-6-phosphatase (G6Pase). Two months after AAV vector administration, one affected dog had normalization of fasting glucose, cholesterol, triglycerides, and lactic acid. Concatamerized AAV vector DNA was confirmed by Southern blot analysis of liver DNA isolated from treated dogs, as head-to-tail, head-to-head, and tail-to-tail concatamers. Six weeks after vector administration, the level of vector DNA signal in each dog varied from one to five copies per cell, consistent with variation in the efficiency of transduction within the liver. AAV vector administration in the canine model for GSD Ia resulted in sustained G6Pase expression and improvement in liver histology and in biochemical parameters.

Dietary management of inborn errors of metabolism

Inborn errors of metabolism are individually rare but are an important cause of mortality and morbidity in infants and children. Dietary therapy is the mainstay of treatment in phenylketonuria, maple syrup urine disease, homocystinuria, galactosemia and glycogen storage disease (Type I/III). Some disorders like urea cycle disorders and organic acidurias require dietary modification in addition to other modalities. Certain basic principles of dietary management should be clearly understood for proper management of these disorders. Commercially available diets are very expensive and modification in routine Indian diet may be tried based on content of different nutrients but the desirable fine control is not achieved.

Canine model and genomic structural organization of glycogen storage disease type Ia (GSD Ia)

A canine model of glycogen storage disease Ia (GSD Ia), similar clinically, biochemically, and pathologically to the human disease, was established by crossbreeding Maltese and Beagle dogs carrying a mutated, defective glucose-6-phosphatase (G-6-Pase) gene. Ten puppies were born in three litters from these crossbreedings. Six were homozygous for the previously described M121I GSD Ia mutation. Of these six affecteds, two were stillborn, and one died at 2, 32, and 60 days of life, respectively (puppies A, B, C, D, E), while one is alive at age 15 months (puppy F). Affected puppies exhibited tremors, weakness, and neurologic signs when hypoglycemic. They had postnatal growth retardation and progressive hepatomegaly. Biochemical abnormalities included fasting hypoglycemia, hyperlactacidemia, hypercholesterolemia, hypertriglyceridemia, and hyperuricemia. Microscopic examination of tissues from affected puppies showed diffuse, marked hepatocellular vacuolation, with distended clear hepatocytes and central to marginally located rounded nuclei. In the kidneys of puppies D and E, there was segmental glomerular sclerosis and vacuolation of proximal convoluted tubular epithelium. Biochemical analysis revealed increased liver glycogen content and isolated markedly reduced G-6-Pase enzyme activity in liver and kidney. The canine G-6-Pase gene was characterized by screening a canine genomic library. It spans approximately 11.8 kb and consists of five exons with >90% amino acid sequence homology to the derived human sequence. The first 1.5 kb of the 5' region was sequenced and contains several putative response element motifs homologous to the human 5' region. Establishment of this canine colony of GSD Ia that closely resembles human disease and isolation of the canine genomic gene provides an excellent model for studying pathophysiology and long-term complications and an opportunity to develop novel therapeutic approaches such as drug and gene therapy.

Glycogen storage disease type Ia: frequency and clinical course in Turkish children

The aim of this study was to determine the relative frequency of type Ia in glycogen storage disease (GSD) with prominent liver involvement and to determine its clinical and laboratory findings and prognosis in Turkish children. From 1980 to 1998, 45 out of 100 GSD patients (27 male) with liver involvement had been diagnosed for type Ia. The files were retrospectively evaluated and clinical and laboratory features were documented. In addition to routine laboratory evaluations, urine albumin, calcium excretions, and plasma biotinidase activity were measured. Breast-feeding was continued in all infants. After 6 months of age, uncooked cornstarch was administered to the patients. The relative frequency of type Ia in GSD with liver involvement was 45%. The diagnosis was made in 71% of patients before 2 years of age (median 1 year). Main complaint was abdominal protruding (57.8%), and main physical finding was hepatomegaly (100%). Forty percent of the patients had growth retardation at diagnosis. Among laboratory parameters, hypertriglyceridemia (97.8%) and hypertransaminasemia (95.6%) were the most frequent findings following plasma biotinidase activity, which was elevated in all patients. Microalbuminuria was determined in 52.8% of the patients and hypercalciuria in 23.8%. Histopathological findings of the liver included fibrosis (75.6%), steatosis (37.8%), mosaicism (24.4%) and nuclear hyperglycogenation (15.6%). During follow-up period, the ratio of patients with growth retardation did not change. Transaminases were decreased in 48.7% of the patients. Although triglyceride and cholesterol levels decreased in the majority of the patients, they did not normalise. The prevalence of type Ia in GSD with prominent liver involvement was found higher than the other reports. Microalbuminuria was also higher than the previous reports.

Liver transplantation for glycogen storage disease types I, III, and IV

Glycogen storage disease (GSD) types I, III, and IV can be associated with severe liver disease. The possible development of hepatocellular carcinoma and/or hepatic failure make these GSDs potential candidates for liver transplantation. Early diagnosis and initiation of effective dietary therapy have dramatically improved the outcome of GSD type I by reducing the incidence of liver adenoma and renal insufficiency. Nine type I and 3 type III patients have received liver transplants because of poor metabolic control, multiple liver adenomas, or progressive liver failure. Metabolic abnormalities were corrected in all GSD type I and type III patients, while catch-up growth was reported only in two patients. Whether liver transplantation results in reversal and/or prevention of renal disease remains unclear. Neutropenia persisted in both GSDIb patients post liver transplantation necessitating continuous granulocyte colony stimulating factor treatment. Thirteen GSD type IV patients were liver transplanted because of progressive liver cirrhosis and failure. All but one patient have not had neuromuscular or cardiac complications during follow-up periods for as long as 13 years. Four have died within a week and 5 years after transplantation. Caution should be taken in selecting GSD type IV candidates for liver transplantation because of the variable phenotype, which may include life-limiting extrahepatic manifestations. It remains to be evaluated, whether a genotype-phenotype correlation exists for GSD type IV, which may aid in the decision making.

CONCLUSION

Liver transplantation should be considered for patients with glycogen storage disease who have developed liver malignancy or hepatic failure, and for type IV patients with the classical and progressive hepatic form.

Nutritional deficiencies in a patient with glycogen storage disease type Ib

The current mainstay of treatment in glycogen storage disease type I (GSD I) is dietary management that includes providing a frequent source of glucose to prevent hypoglycaemia. To ensure compliance, routine follow-up by a health care team, including a dietitian, experienced in the treatment of GSD is necessary. We describe an adolescent patient with GSD Ib in good metabolic control who was admitted with a 3-month history of weakness, depression, vomiting, decreased appetite and a 11.4-kg weight loss. He had a recent onset of unsteady gait, inability to write, and sore mouth. After an extensive work-up, the patient was found to have vitamin B12, folate, iron and other nutritional deficiencies, which explained his symptoms. The patient improved within 72 h of initiation of total parenteral nutrition and therapeutic doses of deficient micronutrients, with a complete recovery in 2 months. Dietary restrictions, dependence on non-food products (e.g. cornstarch in GSD I), and social and developmental issues place individuals with metabolic disorders at a high risk for developing an array of nutritional deficiencies. This case highlights the importance of both close follow-up of the metabolic control and close monitoring of growth and nutritional intake in individuals with inborn errors of metabolism. This case also illustrates the importance of daily supplementation with appropriate multivitamins, calcium and other minerals needed to meet the Recommended Dietary Allowances (RDAs) in these patients.

Effect of continuous glucose therapy begun in infancy on the long-term clinical course of patients with type I glycogen storage disease

BACKGROUND

To evaluate the effects of continuous glucose therapy on metabolic control, occurrence of severe hypoglycemia, physical growth and development, and complications of glycogen storage disease type I (GSD-I).

METHODS

Seventeen patients (11 males) with GSD-I were studied, mean age 14.6+/-5.0 (SD) years, in whom continuous glucose therapy was begun at 0.8+/-0.4 years. At the time of this study, subjects had received continuous glucose therapy for a total duration of 13.9+/-5.0 years. Uncooked cornstarch was used as the method of providing glucose continuously for 10.2+/-3.2 years. Subjects were admitted to the Clinical Research Center and followed their usual home dietary regimens, which included cornstarch supplements at 2- to 4-hour intervals during the day and at 4- to 8-hour intervals during the night. Plasma glucose, blood lactate, and glucoregulatory hormones were measured hourly for 24 hours.

RESULTS

During a 24-hour period of biochemical monitoring, mean hourly plasma glucose concentrations for the group of 17 subjects ranged from 76+/-17 (SD) mg/dl (4.2+/-0.9 mmol/l) to 108+/-16 mg/dl (6.0+/-0.9 mmol/l), and blood lactate concentrations ranged from 2.1+/-1.2 mmol/l to 3.8+/-2.8 mmol/l. Four subjects had transient plasma glucose levels of 50 mg/dl (2.8 mmol/l) or less in the interval between midnight and 8:00 AM. Mean blood lactate levels were highest (> or =3 mmol/l) between 2:00 and 09:00 AM. Mean height standard deviation score for chronological age (SDS(CA)) was -0.8+/-1.1, significantly (p < 0.01) less than the mean target height SDS of -0.1+/-1.1; mean weight SDS was 0.3+/-1.3. Six (35%) subjects (12.2-21.4 years of age) had anemia with hemoglobin concentrations of 10.6 to 11.6 g/dl. Ultrasound examination showed one or more focal hepatic lesions, consistent with an adenoma in 5 (29%) subjects (10.4 to 21.4 y); 16 subjects had glomerular hyperfiltration; and urinary albumin excretion was increased in 2 subjects, ages 15.9 and 21.1 years.

CONCLUSIONS

Long-term continuous glucose therapy with cornstarch, begun in infancy, resulted in mean height 0.7 SDS less than target height. Optimal biochemical control of GSD-I requires meticulous adherence to an individualized dietary regimen that is based on the results of periodic metabolic evaluation and home blood glucose monitoring. Renal glomerular dysfunction and formation of hepatic adenomata remain serious long-term complications.

Glycogen storage disease and von Willebrand's disease implications for dental treatment: dental management of a pediatric patient

Glycogen storage diseases (GSD) are metabolic disorders which impair the body's ability to store glucose and utilize it later, requiring patients to take multiple daily dietary supplementation with a high carbohydrate content. Patients undergoing this treatment modality are placed at increased risk for gross dental caries and other oral abnormalities. Additionally, GSD may prolong the patient's bleeding time, which may necessitate consultation with the treating physician. In the following case, our patient required a multidisciplinary approach to address not only her dental needs, but also to coordinate the management of both her GSD and an additional complication, von Willebrand's disease. This was best achieved in a hospital setting.

Treatment with low-dose diazoxide in two growth-retarded prepubertal girls with glycogen storage disease type Ia resulted in catch-up growth

Two originally prepubertal girls suffering from glycogen storage disease type Ia and short stature were treated with low-dose diazoxide (3-4.8 mg/kg per day) for 7 and 4 years, respectively. Both showed an impressive catch-up growth following this treatment. This appeared to be due to prolongation of normoglycaemia after meals and reduction of fasting lactic acidosis by diazoxide.

Isolation and nucleotide sequence of canine glucose-6-phosphatase mRNA: identification of mutation in puppies with glycogen storage disease type Ia

Two Maltese puppies with massive hepatomegaly and failure to thrive had isolated deficient glucose-6-phosphatase (G-6-Pase) activity in liver and kidney and pathological findings compatible with GSD-Ia. To identify the mutation, we cloned G-6-Pase canine cDNA by RT-PCR with primers from the murine G-6-Pase gene sequence. The canine G-6-Pase cDNA is 2346 bp, with a 5' untranslated region of 87 bp, a coding region of 1071 bp, and a 3' untranslated region of 1185 bp. The difference between the canine and human sequences is in the 3' untranslated region. A greater than 90% amino acid sequence homology was seen with canine, human, murine, and rat G-6-Pase. G-6-Pase cDNA from affected and control puppies revealed complete homology except at nt position 450, which showed a guanine to cytosine (G to C) transversion resulting in substitution of a methionine by isoleucine at codon 121 (M121I) in all five clones studied. The loss of an NcoI restriction site on genomic DNA amplified with primers flanking the mutation allowed us to prove that affected puppies were homozygous for the mutation and parents were heterozygous carriers. The mutant G-6-Pase cDNA had 15 times less enzyme activity than wild-type cDNA following transient transfection. Northern blot analysis of puppies with GSD-Ia revealed increased G-6-Pase mRNA, compared to normal controls. Increased G-6-Pase mRNA was also seen in normal fasted puppies compared to littermates in the fed state, suggesting that the increased G-6-Pase mRNA is a physiologic response to fasting. This is the first report of a molecularly confirmed naturally occurring animal model of GSD-Ia. The establishment of a breeding colony of this dog strain will facilitate studies on the role of G-6-Pase gene in glucose homeostasis, in pathophysiology of disease, and development of novel therapeutic approaches such as gene therapy.

Glycogen storage disease type Ia in two littermate Maltese puppies

Glycogen storage disease type Ia (GSD-Ia) (von Gierke's disease) was identified in two 47-day-old littermate Maltese puppies. The puppies were presented for necropsy with a history of failure to thrive, mental depression, and poor body condition. Gross findings included small body size and emaciation (212 and 246 g versus 595 g for normal littermate), severely enlarged pale livers (48 and 61 g), and pale kidneys. Histologically, there was marked diffuse vacuolation of hepatocytes with large amounts of glycogen and small amounts of lipid. Renal tubular epithelium was mildly to moderately vacuolated. Soft tissue mineralization was present in renal tubules and pulmonary alveolar septa. Biochemical analysis showed that levels of glucose-6-phosphatase were markedly reduced in liver (0.3 and 0.4 microM/minute/g tissue versus 4.7 +/- 1.5 microM/minute/g tissue for controls) and kidney (0.45 and 0.4 microM/minute/g tissue versus 4.1 microM/minute/g tissue for controls) and that glycogen content was increased in liver (9.4% and 9.4% versus 1.3% +/- 1.4% for controls). This is the first confirmed report of animals with glycogen storage disease type Ia.

Oral cornstarch therapy: is persorption harmless?

Sediments prepared from freshly voided urine of four patients with glycogenosis Ia, or leucine-sensitive hypoglycaemia, on oral cornstarch therapy contained starch granules, evidence for persorption i.e. the incorporation of undissolved starch particles. In these patients, amyluria was more marked than in untreated controls. While cornstarch therapy is successful and causes few side-effects, the possibility of late adverse reactions to persorbed starch should not be disregarded.