Lester Baker

Glycogen Storage Disease in Adults

Table 1 The glycogen storage diseases (GSD) include more than ten separate genetic defects that impair glycogen breakdown, primarily in liver or muscle or both. Even the types most frequently encountered (GSD-Ia and GSD-III) are uncommon, each with an incidence of approximately 1 in 100 000 births. Thus, no single institution has followed and reported on a large series of patients. The importance of several major complications was recognized only recently because only single cases were initially reported. Our study represents the largest number of adults with GSD-Ia and GSD-Ib to be included in one investigation and is the first to focus on clinical and social outcomes. Although two groups of investigators recently described the clinical course of patients with GSD in Europe and Israel, most of the patients studied were children [1, 2]. Relatively little information is available about adults with these diseases. We collected information on adults with GSD-Ia, GSD-Ib, and GSD-III in the United States and Canada in order to identify long-term complications that may be amenable to prevention and to determine the effect of the disease on education, employment, and family life. Table 1. SI Units Glycogen Storage Disease Types Ia, Ib, and III Glycogen storage disease type Ia results from deficient glucose-6-phosphatase activity in liver, kidney, and intestine [3]. Glucose-6-phosphatase is a single 35-kd protein [4]. When glucose-6-phosphatase activity is deficient, the liver is unable to hydrolyze glucose from glucose-6-phosphate that has been derived either from the metabolism of stored glycogen or from gluconeogenesis. Patients must depend on dietary carbohydrate to maintain euglycemia; during a fast of more than a few hours, the serum glucose concentration may decrease profoundly, and seizures are common in children. Mental retardation is uncommon, however, because the brain is protected by its ability to metabolize lactate that is present at high concentrations in the serum. Chronic hypoglycemia causes a sustained increase of counter-regulatory hormones, such as cortisol. In childhood, GSD-Ia typically results in poor growth and delayed puberty. Hyperuricemia occurs probably because ATP synthesis from ADP is driven by deamination of the AMP product to inosine that is subsequently metabolized to uric acid. Renal excretion of uric acid may also be decreased because lactate competes for the renal anion transporter. Fatty liver and hyperlipidemia result from the large influx of adipose-derived fatty acids into the liver in response to low insulin and high glucagon and cortisol concentrations. Anemia that is refractory to iron supplementation is believed to occur because of chronic disease. In untreated adults with GSD-Ia, the blood glucose decreases only to about 2.8 mmol/L (50 mg/dL) after an overnight fast. Symptomatic hypoglycemia is uncommon in untreated adults, but increases of counter-regulatory hormones probably persist. Adults with GSD-Ia have a high incidence of hepatic adenomas and focal segmental glomerulosclerosis [3, 5, 6]. The continuing abnormalities in counter-regulatory hormones, together with the hyperuricemia and hyperlipidemia, may be responsible for many of the complications observed in adult patients. Glycogen storage disease type Ib results from a deficiency of the glucose-6-phosphate translocase that transports glucose-6-phosphate into the lumen of the endoplasmic reticulum where it is hydrolyzed by glucose-6-phosphatase [3]. The translocase has not been purified. Without the translocase, glucose-6-phosphate cannot reach the hydrolytic enzyme; thus, patients with GSD-Ib are also unable to maintain euglycemia. The resulting metabolic consequences are identical in both forms of GSD-I. Because patients with GSD-Ib also have neutropenia and recurrent bacterial infections [3, 7], it seems likely that the glucose-6-phosphate translocase plays a role in normal neutrophil function. In GSD-III, glycogen debranching enzyme is deficient [3]. This enzyme is a 165-kd protein that contains two catalytic sites that are required for activity. The enzyme has been cloned and sequenced [8]. Normally, successive glucose residues are released from glycogen by glycogen phosphorylase until the glycogen chains are within four glucose residues of a branch point. The first catalytic activity of the debranching enzyme (oligo-1,4,-1,4-glucantransferase) transfers three of the remaining glucose residues to the terminus of another glucose chain. The second catalytic activity (amylo-1,6-glucosidase) then hydrolyzes the branch-point glucose residue. Three molecular subgroups of GSD-III have been well defined [9]; each is associated with enzyme deficiency in the liver and with childhood hypoglycemia. In adults with GSD-III, hypoglycemia is uncommon. As in GSD-I, poor growth may be prominent, but the growth rate increases before puberty, and adult height is normal [10]. Additionally, increases in transaminase levels provide evidence of hepatocellular damage, and liver biopsies show periportal fibrosis [10], perhaps related to the abnormal short-branched glycogen structure. In patients with subtype GSD-IIIb, enzyme activity and immunoreactive material are absent in liver but are present in muscle; these patients do not have a myopathy. Patients with GSD-IIIa (78% of cases) lack enzyme activity and lack immunoreactive material in liver and muscle. Patients with GSD-IIId (7% of cases) lack only the transferase activity but have normal immunoreactive material in liver and muscle. In patients with GSD-IIIa and IIId, muscle weakness may occur either in childhood or after the third decade. Cardiomyopathy is apparent only after age 30 years [9]. Treatment of Glycogen Storage Disease For only the past 10 to 15 years, children with GSD-Ia and GSD-Ib were treated with either intermittent uncooked cornstarch or a nocturnal glucose infusion given by intragastric tube. When euglycemia is maintained in this manner, growth and pubertal development are normal, and it is hoped that the late complications of GSD-I will be prevented. A high-protein diet was recommended for patients with GSD-III. Diet supplementation can increase the growth rate in children with GSD-III [11], but beneficial results on the myopathy have been less well documented. In this retrospective study of adults with GSD types Ia, Ib, and III, we found, in addition to complications frequently recognized, a high incidence of osteopenia and fractures and of nephrocalcinosis, kidney stones, and pyelonephritis. We describe the long-term outlook for adult patients with GSD who have not had optimal lifelong dietary glucose therapy. Methods Information on patients 18 years of age or older was obtained by contacting specialists in pediatric metabolism, endocrinology, gastroenterology, and genetics throughout the United States and Canada and by advertising through the Association for Glycogen Storage Diseases and The New England Journal of Medicine. No registries of patients with GSD are available. Information was included on living adult patients with GSD and patients who had died since 1967. Diagnosis of GSD had been confirmed by enzyme assay of each patient or of an affected sibling. Fifty-six physicians were individually contacted. Nineteen stated that they were not treating any adult patients with GSD. Thirteen physicians in private practice or at 1 of 12 medical centers filled out a detailed questionnaire or sent copies of clinic and hospital records that were reviewed by two of us. To obtain an estimate of how many patients might be missed by this survey, we reviewed records from a reference laboratory (Washington University) of 21 patients with GSD-Ia and of 21 patients with GSD-III who were diagnosed between 1955 and 1972. If still alive, these patients would now range in age from 18 to 64 years. Our study includes only 5 of these patients with GSD-I and 1 with GSD-III. Thus, this report incompletely represents North American patients with GSD who are currently older than 18 years of age. Clinical, radiographic, and laboratory findings at the latest visit were obtained, but data were not universally available for every item on the questionnaire. In analyzing each response, information was considered to be available only if specifically recorded; omission of information was not recorded as either a negative or a positive response. The presence of liver adenomas, nephrocalcinosis, or kidney stones was based on data from ultrasound or radiographic studies. The diagnosis of osteopenia was based on data from radiographic studies. The normal values for height were taken from the National Center for Health Statistics [12]. Normal values for serum chemistry tests [13] were used. Results Glycogen Storage Disease Type Ia Case Report Patient 1, a 43-year-old divorced father of one child, is a poultry farmer. A liver biopsy and enzymatic assay were obtained at 4 years of age because of poor growth, hypoglycemia without seizures, hepatomegaly, and frequent nosebleeds. Despite frequent meals, growth continued to be poor, puberty was delayed, and the final adult height of 168 cm was achieved after 20 years of age. Allopurinol was taken inconsistently after one of many gouty attacks beginning from 18 years of age. The patient did not complete high school. As an adult, he has smoked 2 to 4 packs of cigarettes per day. After divorcing in his 20s, he frequently skipped breakfast and failed to follow a recommended diet. Instead, his diet was high in fat and consisted primarily of foods that required little preparation, such as candy and sandwiches. He has always denied symptomatic hypoglycemia, although his serum glucose concentration after an overnight fast is about 2.8 mmol/L (50 mg/dL). Beginning in his mid-20s, he had recurrent episodes of flank pain and hematuria that were treated with antibiotics, and he passed kidney stones. At age 24, an intravenous pyelogram showed punctate calcificati

Medium-chain acyl-CoA dehydrogenase deficiency in children with non-ketotic hypoglycemia and low carnitine levels.

Summary: Three children in two families presented in early childhood with episodes of illness associated with fasting which resembled Reyes syndrome: coma, hypoglycemia, hyperammonemia, and fatty liver. One child died with cerebral edema during an episode. Clinical studies revealed an absence of ketosis on fasting (plasma beta-hydroxybutyrate < 0.4 mmole/liter) despite elevated levels of free fatty acids (2.6–4.2 mmole/liter) which suggested that hepatic fatty acid oxidation was impaired. Urinary dicarboxylic acids were elevated during illness or fasting. Total carnitine levels were low in plasma (18–25 μmole/liter), liver (200–500 nmole/g), and muscle (500–800 nmole/g); however, treatment with L-carnitine failed to correct the defect in ketogenesis. Studies on ketone production from fatty acid substrates by liver tissue in vitro showed normal rates from short-chain fatty acids, but very low rates from all medium and long-chain fatty acid substrates. These results suggested that the defect was in the mid-portion of the intramitochondrial beta-oxidation pathway at the medium- chain acyl-CoA dehydrogenase step. A new assay for the electron transfer flavoprotein-linked acyl-CoA dehydrogenases was used to test this hypothesis. This assay follows the decrease in electron transfer flavoprotein fluorescence as it is reduced by acyl-CoA-acyl-CoA dehydrogenase complex. Results with octanoyl-CoA as substrate indicated that patients had less than 2.5% normal activity of medium-chain acyl-CoA dehydrogenase. The activities of short-chain and isovaleryl acyl-CoA dehydrogenases were normal; the activity of long-chain acyl-CoA dehydrogenase was one-third normal.These results define a previously unrecognized inherited metabolic disorder of fatty acid oxidation due to deficiency of medium-chain acyl-CoA dehydrogenase. The carnitine deficiency in these patients appears to be a secondary consequence of their defect in fatty acid oxidation. It is possible that other patients with “systemic carnitine deficiency,” who fail to respond to carnitine therapy, may also have defects in fatty acid oxidation similar to medium-chain acyl-CoA dehydrogenase deficiency.

Fasting hypoglycaemia and metabolic acidosis associated with deficiency of hepatic fructose-1, 6-diphosphatase activity.

Abstract A striking deficiency of hepatic fructose-1,6-diphosphatase activity has been demonstrated in a child who has hypoglycaemia and metabolic acidosis on fasting. Liver glycogen was normal, and normal activities of all of the hepatic enzymes concerned with glycogen synthesis and degradation were noted; severe ballooning of hepatic cells by large lipid-containing vacuoles was the only histological abnormality. Oral glucose and galactose tolerance tests were normal, but oral fructose and glycerol provoked hypoglycaemia. The presence of normal levels of hepatic fructose-1-phosphate aldolase activity clearly distinguishes this disease from hereditary fructose intolerance. A sibling who died with many similar features suggests that this is an inherited defect. This new syndrome of fasting hypoglycaemia and metabolic acidosis seems to represent the clinical expression of impaired gluconeogenesis due to an inherited deficiency of hepatic fructose-1,6-diphosphatase.

Glycemic response to glucagon during fasting hypoglycemia: An aid in the diagnosis of hyperinsulinism

ORGANIC HYPERINSULINISM, once felt to be rare in the pediatric age range, is now recognized more frequently in infants and children with recurrent hypoglycemia. At the Childrens Hospital of Philadelphia, hyperinsulinism is the most common cause of recurrent hypoglycemia in infants under one year of age? The diagnosis of hyperinsulinism must be made rapidly so that specific therapy may be instituted, particularly in young infants, to minimize the risk of brain damage from hypoglycemia. Inappropriate elevation of circulating plasma insulin concentration during an episode of hypoglycemia is diagnostic. However, measurement of single or multiple circulating insulin levels may fail to define the disorder since insulin levels at times of spontaneous hypoglycemia in patients with hyperinsulinism are not always diagnostically elevated. For this reason, other physiologic manifestations of excessive insuliri secretion have been utilized to help verify this diagnosis. The demonstration of low serum levels of beta-hydroxybutyrate at the time of fasting hypoglycemia is valuable in establishing the diagnosis of hyperinsulinism? Another predictable effect of hyperinsulinism is an inappropriate conservation of liver glycogen during fasting. The present study examined whether the glycemic response to glucagon at the time of fasting

Beta cell nesidioblastosis in idiopathic hypoglycemia of infancy

A histochemical technique (pinacyanole metachromasia), specific for insulin in vitro and in beta cells of pancreatic tissue sections, was used to study surgically resected pancreases of 12 patients with documented idiopathic hypoglycemia of infancy. Hematoxylin and eosin—stained sections from 3 patients revealed overt hypertrophy and hyperplasia of all insular units. In the pancreases of the other 9 patients, hematoxylin and eosin sections showed histologically unremarkable islets, whereas the histochemically stained sections revealed the presence of many additional beta cells scattered either singly or in small packets of 2 to 6 cells. These were separate from the islets and most often seen about the walls of small ducts or in the glandular acini proper. The term beta cell nesidioblastosis most appropriately describes this cellular variant. These results, including electron microscopic findings of membrane-bound insulin inclusions in many cells, provide histomorphologic correlation with other evidence in support of the concept that excess production of insulin is an important feature of idiopathic hypoglycemia of infancy.

Myo-inositol and prostaglandins reverse the glucose inhibition of neural tube fusion in cultured mouse embryos

SummaryNeural tube defects in infants of diabetic mothers constitute an important and frequent cause of neonatal mortality/morbidity and long-term chronic handicaps. The mechanism by which normal neural tube fusion occurs is not known. The failure of rostral neural tube fusion seen in mouse embryos incubated in the presence of excess-D-glucose can be significantly prevented by the supplementation of myo-inositol to the culture medium. This protective effect of myo-inositol is reversed by indomethacin, an inhibitor of arachidonic acid metabolism leading to prostaglandin synthesis. Prostaglandin E2 added to the culture medium completely protects against the glucose-induced neural tube defect. These data suggest that the failure of neural tube fusion seen in diabetic embryopathy is mediated through a mechanism involving abnormalities in both the myo-inositol and arachidonic acid pathways, resulting in a functional deficiency of prostaglandins at a critical time of neural tube fusion.

Gene dosage and susceptibility to insulin‐dependent diabetes

1. All members of 33 families in which two or more sibs have insulin‐dependent diabetes mellitus (IDDM) were HLA‐typed. The results strongly support the hypothesis that, closely linked to the HLA region, there is a locus (S) for susceptibility to IDDM. We use Sd for alleles at this locus which confer susceptibility to disease, and Sa for all other alleles.

Congenital hyperinsulinism and the surgeon: Lessons learned over 35 years

BACKGROUND/PURPOSE Congenital hyperinsulinism induces severe and unremitting hypoglycemia in newborns and infants. If poorly controlled, seizures and irreversible brain damage may result. Subtotal (<95%) or near-total (95% to 98%) pancreatectomy have been performed for glycemic control in babies who do not respond to aggressive medical therapy. Because hypoglycemia often persists after subtotal resection, 95% pancreatectomy has emerged as the procedure of choice. To define the effect of more or less extensive pancreatectomy on the management and outcome of refractory congenital hyperinsulinism, the authors examined our single institutional experience. METHODS The records of children treated between 1963 and 1998 for congenital hyperinsulinism, and who required pancreatectomy, were reviewed. Outcome parameters included glycemic response to surgery, need for reresection, surgical morbidity, surgical and long-term mortality, and development of diabetes mellitus (DM). A complete response was defined as discharge to home on no glycemic medications, no continuous feedings, and without DM. Histological reports were reviewed and categorized as either diffuse or focal disease. RESULTS Of 101 children treated for congenital hyperinsulinism during this period, 53 (50%) required pancreatectomy for glucose control. Mean follow-up for the study population was 9.8 +/- 1.1 years. Overall, 23 children (43%) showed a complete response, occurring in 50% of patients having > or = 95% pancreatectomy (n = 34), but in only 19% having less than 95% resection (n = 16). The remaining three babies had local excision of a solitary focal lesion, and each showed a complete response. Histopathology showed diffuse islet abnormalities in 42 specimens (79%) and solitary focal lesions in 11 (21%). A complete response was observed for 82% of focal but only 33% of diffuse lesions. Eight patients (15%) required reresection for persistent hypoglycemia, seven having diffuse lesions and one focal. Surgical morbidity occurred in 13 cases (26%), and the 30-day surgical mortality rate was 6%, each death (n = 3) occurring before 1975. DM developed in seven children (14%), each having diffuse lesions, and was independent of resection type. CONCLUSION Because euglycemia is more readily restored, and because the risks for surgical complications and DM do not appear increased, the authors recommend 95% pancreatectomy as the initial procedure of choice for newborns and infants with congenital hyperinsulinism.

Progressive familial cholestatic cirrhosis and bile acid metabolism

A family is described in which each of the three children, two girls and one boy, is affected by a progressive fatal cholestatic cirrhotic disorder. The disease started at 3 to 6 months of age with severe pruritus followed by an obstructive type of jaundice at 3 to 6 years of age; death occurred at 5 to 14 years of age. The histologic features consisted of centrilobular cholestasis followed by portal fibrosis, inflammatory cell infiltrate, and finally cirrhosis. Abnormal bile acid metabolism may play an etiologic role. Lithocholic acid and its conjugates were present in abnormal concentrations in all body fluids tested; the synthesis rate of its precursor, chenodeoxycholic acid, was increased as shown by isotope dilution techniques.

Progressive Retinopathy with Improved Control in Diabetic Dwarfism (Mauriac's Syndrome)

We report four children aged 11–18½ yr first seen 7–14 yr after the diagnosis of insulin-dependent diabetes. At presentation, all had marked short stature, two had hepatomegaly, and the older three had delayed adolescence. They had been severely underinsulinized. Initial funduscopy demonstrated only occasion microaneurysms in two children and a single intraretinal hemorrhage in another. The youngest was normal. Improved control required large increases in insulin dosage. Growth rate improved significantly and hepatomegaly regressed. Puberty progressed rapidly in two older patients with poor final height. Paradoxically, with improved control, retinopathy progressed rapidly with appearance of multiple microaneurysms, nerve fiber layer infarctions, intraretinal microangiopathic changes, hemorrhages, exudates, and macular edema in all the patients and severe proliferation changes in three. One child with proliferative retinopathy in both eyes developed vitreous hemorrhage and blindness in one eye. Two required panretinal photocoagulation with no further progression of their retinopathy. These rapidly progressive retinal changes remain unexplained. We advise caution when correcting metabolic derangements of diabetic patients who have been poorly controlled for a prolonged period.