Phosphoglucomutase-1 deficiency: Early presentation, metabolic management and detection in neonatal blood spots

Phosphoglucomutase 1 deficiency is a congenital disorder of glycosylation (CDG) with multiorgan involvement affecting carbohydrate metabolism, N-glycosylation and energy production. The metabolic management consists of dietary D-galactose supplementation that ameliorates hypoglycemia, hepatic dysfunction, endocrine anomalies and growth delay. Previous studies suggest that D-galactose administration in juvenile patients leads to more significant and long-lasting effects, stressing the urge of neonatal diagnosis (0-6 months of age). Here, we detail the early clinical presentation of PGM1-CDG in eleven infantile patients, and applied the modified Beutler test for screening of PGM1-CDG in neonatal dried blood spots (DBSs). All eleven infants presented episodic hypoglycemia and elevated transaminases, along with cleft palate and growth delay (10/11), muscle involvement (8/11), neurologic involvement (5/11), cardiac defects (2/11). Standard dietary measures for suspected lactose intolerance in four patients prior to diagnosis led to worsening of hypoglycemia, hepatic failure and recurrent diarrhea, which resolved upon D-galactose supplementation. To investigate possible differences in early vs. late clinical presentation, we performed the first systematic literature review for PGM1-CDG, which highlighted respiratory and gastrointestinal symptoms as significantly more diagnosed in neonatal age. The modified Butler-test successfully identified PGM1-CDG in DBSs from seven patients, including for the first time Guthrie cards from newborn screening, confirming the possibility of future inclusion of PGM1-CDG in neonatal screening programs. In conclusion, severe infantile morbidity of PGM1-CDG due to delayed diagnosis could be prevented by raising awareness on its early presentation and by inclusion in newborn screening programs, enabling early treatments and galactose-based metabolic management.

Role of continuous glucose monitoring in the management of glycogen storage disorders

Management of liver glycogen storage diseases (GSDs) primarily involves maintaining normoglycemia through dietary modifications and regular glucose monitoring. Self-monitoring of blood glucose is typically done 3-6 times per day, and may not sufficiently capture periods of asymptomatic hypoglycemia, particularly during sleep. Continuous glucose monitoring systems (CGMS) provide 24-h continuous glucose data and have been used effectively in diabetes mellitus to monitor metabolic control and optimize treatment. This is a relatively new approach in GSDs with only a handful of studies exploring this modality. In this study we used Dexcom CGMS to study the glycemic profile of 14 pediatric and six adult patients with GSD I, III, and IX. A total of 176 days of CGMS data were available. The CGMS was found to be a reliable tool in monitoring glucose levels and trends at all times of the day with good concordance with finger-stick glucose values. This study revealed that in addition to overnight hypoglycemia, CGMS can uncover previously undetected, subclinical, low glucose levels during daytime hours. Additionally, the CGMS detected daytime and overnight hyperglycemia, an often overlooked concern in liver GSDs. The CGMS with concurrent dietary adjustments made by a metabolic dietitian improved metabolic parameters and stabilized blood glucose levels. The CGMS was found to be a safe, effective, and reliable method for optimizing treatment in patients with GSD I, III, and IX.

Sleep and quality of life of patients with glycogen storage disease on standard and modified uncooked cornstarch

BACKGROUND

Glycemic control in hepatic glycogen storage diseases (GSDs) relies on specific nutritional recommendations, including strict avoidance of a fasting period. Uncooked cornstarch (UCCS) is an important therapeutic component. A new modified UCCS, Glycosade™, was created with the objective of prolonging euglycemia. We aimed to determine the length of euglycemia on Glycosade™ using a continuous glucose monitor (CGM) and to evaluate whether longer euglycemia and thus less nighttime interruptions would improve sleep and quality of life (QoL) after the introduction of the modified cornstarch.

METHODS

We conducted a prospective cohort study to assess quality and quantity of sleep and quality of life (QoL) in patients with GSDs on standard UCCS and after the introduction of Glycosade™. Sleep and QoL evaluation was done for patients using validated questionnaires, a standardized sleep diary and actigraphy. Length of fast and glucose variability were determined with CGM.

RESULTS

Nine adults with GSD Ia took part in the study. Glycosade™ introduction was done under close supervision during a hospital admission. Comparison of sleep in 9 patients showed sleep disturbances on standard UCCS that were improved with Glycosade™. QoL was normal both pre and post Glycosade™. The CGM confirmed maintenance of a longer fasting period with Glycosade™ at home.

CONCLUSION

Glycosade™ represents an alternative option for GSD patients. We showed possible benefits in terms of sleep quality. We also confirmed the longer length of fast on Glycosade™.

SYNOPSIS

A new modified form of uncooked starch for patients with glycogen storage disease represents an alternative option as it showed a longer length of fast and improvements in sleep quality.

Patients with glycogen storage diseases undergoing anesthesia: a case series

BACKGROUND

Glycogen storage diseases are rare genetic disorders of glycogen synthesis, degradation, or metabolism regulation. When these patients are subjected to anesthesia, perioperative complications can develop, including hypoglycemia, rhabdomyolysis, myoglobinuria, acute renal failure, and postoperative fatigue. The objective of this study was to describe the perioperative course of a cohort of patients with glycogen storage diseases.

METHODS

This is a retrospective review of patients with glycogen storage diseases undergoing anesthetic care at our institution from January 1, 1990, through June 30, 2015 to assess perioperative management and outcomes.

RESULTS

We identified 30 patients with a glycogen storage disease who underwent 41 procedures under anesthesia management. Intraoperative lactic acidosis developed during 4 major surgeries (3 liver transplants, 1 myectomy), and in all cases resolved within 24 postoperative hours. Lactated Ringer solution was used frequently. Preoperative and intraoperative hypoglycemia was noted in some patients with glycogen storage disease type I, all of which responded to administration of dextrose-containing solutions. No serious postoperative complications occurred.

CONCLUSIONS

Patients with glycogen storage disease, despite substantial comorbid conditions, tolerates the anesthetic management without major complications. Several patients who experienced self-limited metabolic acidosis were undergoing major surgical procedures, during which acidosis could be anticipated. Close monitoring and management of blood glucose levels of patients with glycogen storage disease type I is prudent.

Is Type 2 Diabetes a Glycogen Storage Disease of Pancreatic β Cells?

Elevated plasma glucose leads to pancreatic β cell dysfunction and death in type 2 diabetes. Glycogen accumulation, due to impaired metabolism, contributes to this "glucotoxicity" via dysregulated biochemical pathways promoting β cell dysfunction. Here, we review emerging data, and re-examine published findings, on the role of glycogen in β cells in normoglycemia and in diabetes.

Fat and carbohydrate metabolism during exercise in phosphoglucomutase type 1 deficiency

CONTEXT

Phosphoglucomutase type 1 (PGM1) deficiency is a rare metabolic myopathy in which symptoms are provoked by exercise.

OBJECTIVE

Because the metabolic block is proximal to the entry of glucose into the glycolytic pathway, we hypothesized that iv glucose could improve the exercise intolerance experienced by the patient.

DESIGN

This was an experimental intervention study.

SETTING

The study was conducted in an exercise laboratory.

SUBJECTS

Subjects were a 37-year-old man with genetically and biochemically verified PGM1 deficiency and 6 healthy subjects.

INTERVENTIONS

Cycle ergometer, peak and submaximal exercise (70% of peak oxygen consumption), and exercise with an iv glucose infusion tests were performed.

MAIN OUTCOME MEASURES

Peak work capacity and substrate metabolism during submaximal exercise with and without an iv glucose infusion were measured.

RESULTS

Peak work capacity in the patient was normal, as were increases in plasma lactate during peak and submaximal exercise. However, the heart rate decreased 11 beats minute⁻¹, the peak work rate increased 12.5%, and exercise was rated as being easier with glucose infusion in the patient. These results were in contrast to those in the control group, in whom no improvements occurred. In addition, the patient tended to become hypoglycemic during submaximal exercise.

CONCLUSIONS

This report characterizes PGM1 deficiency as a mild metabolic myopathy that has dynamic exercise-related symptoms in common with McArdle disease but no second wind phenomenon, thus suggesting that the condition clinically resembles other partial enzymatic defects of glycolysis. However, with glucose infusion, the heart rate decreased 11 beats min⁻¹, the peak work rate increased 12.5%, and exercise was considered easier by the patient.

Urine analysis of glucose tetrasaccharide by HPLC; a useful marker for the investigation of patients with Pompe and other glycogen storage diseases

A high performance liquid chromatography method, adapted from an established urinary sugars method, has been developed for the analysis of a tetraglucose oligomer (Glc(4)) in urine. Pompe disease results from defects in the activity of lysosomal acid α-glucosidase (GAA) with patients typically excreting increased amounts of Glc(4). Rapid determination of GAA in dried blood spots is now possible. However, enzymatic analysis is unable to discriminate between patients with Pompe disease and those individuals harbouring pseudo deficiency mutations. This method was able to quantify Glc(4) levels in all patients analysed with an established diagnosis of Pompe disease, and all controls analysed had Glc(4) levels below the limit of detection for this method. Importantly the method was able to discriminate between an individual known to harbour a pseudo Pompe mutation and patients with Pompe disease, providing a useful supporting test to enzymatic analysis. Sequential measurement of urinary Glc(4) has been proposed to monitor the effects of enzyme replacement therapy (ERT). We observed a clear decrease in Glc(4) levels following commencement of treatment in three patients studied. Additionally, raised levels of Glc(4) were observed in patients with glycogen storage disease (GSD) type Ia and type III suggesting that this method may have applications in other GSDs.

Liver glycogen storage diseases due to phosphorylase system deficiencies: diagnosis thanks to non invasive blood enzymatic and molecular studies

Glycogen storage disease (GSD) due to a deficient hepatic phosphorylase system defines a genetically heterogeneous group of disorders that mainly manifests in children. We investigated 45 unrelated children in whom a liver GSD VI or IX was suspected on the basis of clinical symptoms including hepatomegaly, increased serum transaminases, postprandial lactatemia and/or mild fasting hypoglycemia. Liver phosphorylase and phosphorylase b kinase activities studied in peripheral blood cells allowed to suspect diagnosis in 37 cases but was uninformative in 5. Sequencing of liver phosphorylase genes was useful to establish an accurate diagnosis. Causative mutations were found either in the PYGL (11 patients), PHKA2 (26 patients), PHKG2 (three patients) or in the PHKB (three patients) genes. Eleven novel disease causative mutations, five missense (p.N188K, p.D228Y, p.P382L, p.R491H, p.L500R) and six truncating mutations (c.501_502ins361pb, c.528+2T>C, c.856-29_c.1518+614del, c.1620+1G>C, p.E703del and c.2313-1G>T) were identified in the PYGL gene. Seventeen novel disease causative mutations, ten missense (p.A42P, p.Q95R, p.G131D, p.G131V, p.Q134R, p.G187R, p.G300V, p.G300A, p.C326Y, p.W820G) and seven truncating (c.537+5G>A, p.G396DfsX28, p.Q404X, p.N653X, p.L855PfsX87, and two large deletions) were identified in the PHKA2 gene. Four novel truncating mutations (p.R168X, p.Q287X, p.I268PfsX12 and c.272-1G>C) were identified in the PHKG2 gene and three (c.573_577del, p.R364X, c.2427+3A>G) in the PHKB gene. Patients with PHKG2 mutations evolved towards cirrhosis. Molecular analysis of GSD VI or IX genes allows to confirm diagnosis suspected on the basis of enzymatic analysis and to establish diagnosis and avoid liver biopsy when enzymatic studies are not informative in blood cells.

The use of continuous glucose monitoring in the practical management of glycogen storage disorders

Continuous glucose monitoring systems (CGMS) are now in widespread use in diabetes management with an increasing evidence base. There are few reports of their use in GSD. Liver glycogen storage disorders (GSDs) are most often managed by intensive dietary regimens. Risks of over and under-treatment remain. We describe our use of CGMS in a cohort of GSD patients, the results obtained and the frequency of complications. Our experience is that CGM is a reliable, well accepted and valid tool in the monitoring of GSD patients and allows for assessment of blood sugar control in the 'real-life' setting, unlike hospital admissions. Combining CGM with urine ketone and / or blood lactate measurements, again at home, improves the investigation yet further. It is possible to perform CGM for periods including both schooldays and weekends, and also to change the dietary regimen during the period of monitoring to reduce the frequency of assessments. Risks of decreased reliability in the low range of blood sugars may be outweighed by the increased validity of the patient being in the home environment, with a normal diet and activity schedule.

Evaluation of the biotinidase activity in hepatic glycogen storage disease patients. Undescribed genetic finding associated with atypical enzymatic behavior: an outlook

Repeated evaluation of biotinidase (BTD) activity was carried out for a long-term follow-up in patients with hepatic glycogen storage diseases (GSDs). The results indicated inter-intra variability among the GSD-Ia, GSD-III and GSD-IX patients. In addition, a c.1330G>C transversion in the BTD gene, resulting in a p.Asp444His substitution was detected in one allele of a GSD-Ia patient with sustained normal enzyme activity. Thus far, it is necessary to be cautious in the interpretation of the results of BTD activity as a presumptive GSD diagnostic element. It is not known why plasma BTD activity increases in GSDs patients, or the clinical importance of the increment. When viewed from a global perspective, there are some lines of biotin biology that could indicate a relationship between BTD´s behavior and GSDs.

Serum lipid and lipoprotein profile of patients with glycogen storage disease types I, III and IX

With current dietary therapy, life expectancy in glycogen storage disease (GSD) has improved considerably and more children reach adulthood. Notwithstanding intensive dietary therapy, moderate to severe hyperlipidaemia is still observed frequently. There is limited information about the type and extent of hyperlipidaemia. We studied the lipid profile in 20 patients, aged 8-54 years, of the three (types I, III and IX) most common forms of adult GSD. Hyperlipidaemia was shown to be type-specific, affecting predominantly patients with GSD type Ia, who showed marked combined hypercholesterolaemia and hypertriglyceridaemia. By contrast, a heterogeneous distribution of HDL was found in patients with GSD I and III. There was no significant difference in Apo Al and Apo B concentrations between groups. In addition, mass measurements of the fractions of VLDL1, VLDL2 and IDL were raised in all patients with GSD Ia by comparison with all other patients with GSD. Patients with GSD type Ia have lipid concentrations and individual mass measurements that are consistent with ranges found in patients who have a significant risk of atherosclerosis. Accumulated evidence, however, suggest GSD type Ia patients do not have an increased risk of atherosclerotic cardiovascular disease (CVD) but the reason remains unknown. Intervention to reduce their lipid levels could therefore be on the basis of seeking to prevent the risk of pancreatitis rather than that of CVD.

Is There Any Difference in Anesthetic Management of Biliary Atresia and Glycogen Storage Disease Patients Undergoing Liver Transplantation?

BACKGROUND

The purpose of the study was to compare the intraoperative blood glucose changes and the dosage of glucose infused between biliary atresia and glycogen storage disease (GSD) patients undergoing living donor liver transplantation (LDLT).

PATIENTS AND METHODS

The anesthesia records of biliary atresia and GSD patients undergoing LDLT were reviewed retrospectively. The levels of intraoperative blood glucose before operation, after induction of anesthesia, in the dissection, anhepatic, 10 min after reperfusion, and at the end of operation, as well as the dosage glucose infused, were compared between groups. The Mann-Whitney U test was used for statistical analysis; P < 0.05 was regarded as significant.

RESULTS

Seventy-two biliary atresia patients were grouped into group I (GI) and 8 GSD patients into group II (GII). The blood glucose levels of both groups increased after operation and remained hyperglycemic, around 100-300 mg/dl, until the end of the operation. The mean glucose amounts infused were 2.7 +/- 1.9 and 2.5 +/- 1.15 mg/kg/min for GI and GII, respectively.

CONCLUSION

No significant difference was found in the anesthetic management between groups. The only difference was that the GSD patients required continuous glucose supply the night before the operation, while biliary atresia patients did not.

Continuous glucose monitoring in conditions other than diabetes

BACKGROUND

The development of new systems for continuous glucose monitoring has recently increased the interest for their potential applications among physicians involved in diabetes care. One of the most common applications of such devices is the identification of hypoglycaemic events in insulin-treated diabetic patients (particularly during the night) and the evaluation of the full daily glucose excursions.

METHODS

Among commercially available glucose sensors, the Glucoday system has been utilized for practical clinical application in the last two years. One of the most important features of this device is the accuracy in monitoring interstitial glucose values, specifically in the hypoglycaemic range. This feature is clinically relevant when applied in the clinical setting of patients with type 1 diabetes mellitus. The ability to monitor glucose continuously could be indeed a useful tool for the study of hypoglycaemic conditions other than diabetes.

RESULTS

In patients with hyperinsulinaemic hypoglycaemia, recurrent episodes of asymptomatic hypoglycaemia are common, and in patients with glycogen storage diseases, avoidance of recurrent and prolonged hypoglycaemic episodes usually require frequent determinations by mean of home blood glucose monitoring.

CONCLUSIONS

Experimental preliminary evidences suggest that this new technology could be applied in the clinical setting to help the physician to identify mainly nocturnal hypoglycaemic events, otherwise not revealed by traditional self blood-glucose monitoring, even in those patients who are not treated by conventional insulin therapy.

Severe pulmonary arterial hypertension in type 1 glycogen storage disease

Pulmonary arterial hypertension is characterised by the presence of pulmonary hypertension (mean pulmonary artery pressure >25 mmHg at rest or >30 mmHg during exercise ) and normal pulmonary wedge pressure (<12 mmHg). Several risk factors for pulmonary arterial hypertension have been described. In the absence of any factor or condition suspected to play a causal or facilitating role in the process, pulmonary hypertension is "unexplained" (primary pulmonary hypertension, PPH). PPH is a rare condition, with an estimated incidence of 2 per million people. Recent genetic studies have identified mutations in the bone morphogenetic protein receptor-II (BMPR-II) gene, a receptor member of the transforming growth factor-beta family, in a majority of familial cases of PPH. Interestingly, 25% of patients displaying sporadic PPH may also have mutations in the BMPR-II gene, emphasising the relevance of genetic susceptibility for this severe condition. Other molecular and biochemical processes behind the complex vascular changes associated with pulmonary arterial hypertension are currently investigated. Type 1a glycogen storage disease caused by a deficiency of glucose-6-phosphatase has an estimated incidence of 1 per 100000 with a few reported cases of unexplained severe pulmonary hypertension. The occurrence of pulmonary arterial hypertension in type 1a glycogen storage disease could be due to vasoconstrictive amines such as serotonin, a pulmonary vasoconstrictor and growth factor for vascular smooth muscle cells stored in platelets.

The ischaemic lactate-ammonia test

The ischaemic lactate-ammonia test is widely used for investigating patients with muscle pain and fatigue. It involves measuring plasma lactate and ammonia produced as a result of forearm exercise under ischaemic conditions in a fasted subject. Its clinical use is to screen patients with muscle complaints for disorders of carbohydrate metabolism, in particular to identify those in whom further investigation may provide useful diagnostic information. There is a wide variety of methods described, reflecting attempts to optimize the response and hence the diagnostic value of the test. Although it is often considered a general screening test for metabolic muscle disease, the situations in which it is useful are specific. Here we review the use of the test and present the results of an audit of its use in our departments.

Clinical, biochemical and molecular findings in a patient with X-linked liver glycogenosis followed for 40 years

Phosphorylase kinase (PHK) is a regulatory enzyme in glycogen metabolism. Mutations in the gene encoding the alpha subunit of PHK (PHKA2) have been shown to be responsible for X-linked liver glycogenosis (XLG). XLG, a frequent type of glycogen storage disease, is characterised by hepatomegaly and growth retardation. Two subtypes of XLG have been described: XLG type I patients have a clear-cut PHK deficiency in liver and blood cells, whereas XLG type II patients have a normal or residual activity. Here, we present clinical, biochemical and molecular findings on a liver glycogenosis patient in whom the diagnosis XLG II only became clear after enzyme assays in the liver and identification of the disease-causing mutation. A missense mutation replacing arginine at amino acid position 186 by histidine (R186H) was identified in the PHKA2 gene. Mutations of the same arginine residue have been previously found in at least four other unrelated XLG II patients.

CONCLUSION

Arginine at position 186 of the alpha subunit seems to play an important role in the structure or the regulation of PHK. In patients with XLG having normal or residual PHK activity where XLG II is suspected, the identification of mutations in PHKA2 leads to the final classification.

Mutation hotspots in the PHKA2 gene in X-linked liver glycogenosis due to phosphorylase kinase deficiency with atypical activity in blood cells (XLG2)

In five cases of X-linked liver glycogenosis subtype 2 (XLG2), we have identified mutations in the gene encoding the liver isoform of the phosphorylase kinase alpha subunit (PHKA2). XLG2 is a rare variant of X-linked phosphorylase kinase (Phk) deficiency of the liver. Whereas in the more common form of X-linked hepatic Phk deficiency, XLG1, the enzyme's activity is decreased both in liver and in blood cells, Phk activity in XLG2 is low in liver but normal or even enhanced in blood cells. Although missense, nonsense and splicesite mutations in the PHKA2 gene were recently identified in several cases of XLG1, no mutations have yet been described for XLG2 and a molecular explanation for the peculiar biochemical phenotype of XLG2 has been lacking. All mutations found in the present study result in non-conservative amino acid replacements of residues that are absolutely conserved between the alpha L, alpha M and beta subunits of Phk [H132P, H132Y, R186H (twice) and D299G]. Strikingly, in two pairs of cases the mutations affect the same codon. These results demonstrate that: (i) XLG2 is caused by mutations in PHKA2 and is therefore allelic with XLG1; and (ii) XLG2 mutations appear to cluster in limited sequence regions or even individual codons.

Decreased erythrocyte deformability in glycogen storage disease

Liver glycogen storage diseases (GSD) are disorders associated with severe dyslipidaemia which can induce cell membrane alterations and possibly reduced cell deformability. Since decreased erythrocyte deformability is known to disturb blood flow in capillaries and may promote ischaemic diseases, this study was designed to investigate erythrocyte deformability using a new filtration system, the Cell Transit Analyser (CTA), and to examine lipid compounds in the blood of 23 patients affected with GSD, aged from 1 to 20 years and 18 controls aged from 1 to 17 years. The patients showed a mixed hyperlipidaemia with predominant hypertriglyceridaemia and an increase in erythrocytes mean transit times (TT) due to the presence of more rigid erythrocytes subpopulations when compared to controls. Thus the erythrocyte rigidity, in addition to the lipid abnormalities must be taken into account for long-term evolution of GSD patients. Moreover this cellular alteration may contribute to shortened erythrocyte survival.

Blood lipids and rheological modifications in glycogen storage disease

OBJECTIVES

Hyperlipidemia is a feature of liver glycogen storage disease (GSD). Recent studies have suggested that rheological mechanisms such as elevated erythrocyte aggregation may be involved in the pathogenesis of ischemic syndromes associated with hyperlipidemia.

DESIGN AND METHODS

We investigated erythrocyte aggregation, lipids, and circulatory proteins in the blood of 24 patients affected with GSD, aged from 1 to 23 years (mean = 8) and 26 controls aged from 1 to 28 years (mean = 9).

RESULTS

The aggregation results were much higher in patients than controls. The lipid data showed a mixed hyperlipidemia with predominant hypertriglyceridemia, low HDL-C, apoA-I and LpA-I/A-II, and high apoB as compared with controls. However, the LpA-I was not significantly different from controls.

CONCLUSIONS

In conclusion, patients with GSD presented hyperlipidemia and elevated erythrocyte aggregation such that they are at long-term risk of ischemic complications.

Glomerular and tubular function in glycogen storage disease

Urinary protein and calcium excretion were assessed in 77 patients with the hepatic glycogen storage diseases (GSD): 30 with GSD-I (median age 12.4 years, range 3.2-32.9 years), 25 with GSD-III (median age 10.5 years, range 4.2-31.3 years) and 22 with GSD-IX (median age 11.8 years, range 1.2-35.4 years). Inulin (Cinulin) and para-aminohippuric acid (CPAH) clearances were also measured in 33 of these patients. Those with GSD-I had significantly greater albumin (F = 15.07, P < 0.001), retinol-binding protein (RBP) (F = 14.66, P < 0.001), N-acetyl-beta-D-glucosaminidase (NAG) (F = 9.41, P < 0.001) and calcium (F = 7.41, P = 0.001) excretion than those with GSD-III and GSD-IX. GSD-I patients (n = 18) also had significantly higher Cinulin (F = 5.57, P = 0.009), but CPAH did not differ (F = 0.77, NS). Renal function was normal in GSD-III and GSD-IX patients. In GSD-I, Cinulin (r = -0.51, P = 0.03) and NAG excretion (r = -0.40, P = 0.03) were inversely correlated with age, whereas albumin excretion was positively correlated with age (r = +0.41, P = 0.03). RBP and calcium excretion were generally high throughout all age groups. Hyperfiltration in GSD-I is associated with renal tubular proteinuria that occurs before the onset of significant albuminuria. Deficiency of glucose-6-phosphatase within the proximal renal tubule may primarily cause tubular dysfunction, glomerular hyperfiltration being a secondary phenomenon.

[A case of glycogen storage disease with normal acid maltase accompanied with the abnormal platelet function]

Glycogen storage disease with normal acid maltase first reported by Danon et al. was characterized clinically by mental retardation, cardiomyopathy, and proximal myopathy. Since the first report, 17 patients have been reported including 5 patients from Japan. In this paper we described a 26-year-old man who had dilatated cardiomyopathy with a pacemaker implanted at age 22 years. He was admitted to our hospital complaining of easy fatigability in February 1992. Neurological findings showed that he had mental retardation. Serum CK, GOT, GPT and aldolase levels were elevated. Histopathological study of biopsied skeletal muscle showed intracytoplasmic vacuoles with increased acid phosphatase and slightly increased PAS positive material. Electron microscopic study revealed numerous glycogenosomes (autophagic vacuoles containing glycogen). These pathological findings were similar to acid maltase deficiency, but activities of carbohydrate metabolic enzyme including acid maltase activity were normal in the biopsied muscle. From these results, he was diagnosed as having glycogen storage disease with normal acid maltase. We also found abnormal platelet function and glycogen accumulation in the platelets, which have not been previously described. The disease is probably a systemic disorder affecting not only skeletal and cardiac muscles, but platelets.

Serum concentrations of albumin, C-reactive protein, alpha 2-macroglobulin, prealbumin, fibronectin, fibrinogen, transferrin, and retinol binding protein in 55 patients with hepatic glycogen storage diseases

Hepatic glycogen storage diseases are hereditary metabolic disorders involving the metabolism of glycogen. This study was designed to investigate the serum protein status in such diseases. Fifty-five patients with glycogen storage disease types I, III, VI, and IX, whose ages ranged from 1 month to 27 years, were included in this work. C-reactive protein, fibrinogen, alpha 2-macroglobulin, albumin, transferrin, fibronectin, retinol binding protein, and prealbumin serum concentrations were measured in each patient. In patients affected with type I glycogen storage disease, serum concentrations of alpha 2-macroglobulin, fibrinogen, C-reactive protein, and transferrin were significantly increased. In patients with types III, VI, and IX glycogen storage diseases, the concentration of alpha 2-macroglobulin was the only one that was significantly increased. Thus, even though this study raises more questions than it answers, it seems likely that the hepatic synthesis of some proteins may be increased in patients affected by hepatic glycogen storage diseases. This may indicate some degree of mild hepatic dysfunction in such metabolic disorders. However, further investigations are required to elucidate the discrepancies observed among the different types of diseases.

Impairment of the activity of the hepatic microsomal glucose-6-phosphatase system in three preterm infants

Three preterm infants born at 26-30 weeks' gestation who died between 103 and 266 days after birth were found to have elevated hepatic glycogen levels. Kinetic analysis of the hepatic microsomal glucose-6-phosphatase system demonstrated that one infant had abnormally low levels of activity of the glucose-6-phosphatase enzyme (partial type 1a glycogen storage disease) and two had deficiencies of T2, a microsomal phosphate/pyrophosphate transport protein (type 1c glycogen storage disease). In all three cases glycogen storage disease was not suspected prior to death even though both hypo- and hyperglycaemic episodes were recorded in the first 15 days after birth indicating that they had somewhat disordered blood glucose regulation. In the infant with low glucose-6-phosphatase enzyme activity, abnormal development of the glucose-6-phosphatase enzyme cannot be ruled out. This is the first description of abnormalities in the glucose-6-phosphatase system in preterm infants.

In vivo 13C-NMR evaluation of glycogen content in a patient with glycogen storage disease

Glycogen storage disease was suspected in a 10-month-old boy. Initial technical problems did not permit the determination of the precise enzyme, deficiency, and type VI glycogen storage disease was only diagnosed at the age of 2 years. In the mean time, natural abundance 13C nuclear magnetic resonance evaluation of muscular and hepatic glycogen content indicated normal muscular glycogen and increased hepatic glycogen in our patient, a finding which strongly argued for the diagnosis of type VI glycogen storage disease. Even though the use of nuclear magnetic resonance might seem, in this situation, a somewhat circuitous means of reaching the diagnosis, it appears that nuclear magnetic resonance could provide a useful tool for a non-invasive diagnosis of glycogen storage diseases.

Serum concentrations of extracellular matrix components: novel markers of metabolic control and hepatic pathology in glycogen storage disease?

Laminin, hyaluronic acid (HA), procollagen III amino-terminal propeptide (PIIINP), and procollagen I carboxy-terminal propeptide (PICP) concentrations were measured by radioimmunoassay or radiometric assay in sera from 21 patients with glycogen storage disease (GSD). Laminin was increased in 16 of 29 samples from the six children with GSD I, 25/43 from the seven with GSD III, and 3/19 from the eight with GSD IX; laminin correlated with serum aspartate aminotransferase and gamma-glutamyltransferase but not with serum triglycerides, cholesterol, lactate, or urate. HA was increased in 20% of samples from GSD I, 58% from GSD III, and in none from GSD IX; HA correlated with serum lactate and urate but not with liver function tests, serum cholesterol, or triglycerides. Serum PIIINP was increased in only eight samples and PICP in only one; children with poor linear growth had low PIIINP and PICP. Immunostaining studies of nine liver biopsies taken at diagnosis showed increased laminin and PIIINP staining in portal tracts, fibrous septa, and around sinusoids in periportal regions; children with a greater degree of immunostaining did not always show significantly higher values of serum laminin or PIIINP. We speculate that raised serum laminin may reflect fibrogenesis (but not necessarily established fibrosis) in response to tissue damage in GSD, raised HA may reflect disturbed sinusoidal endothelial cell function, and low PIIINP and PICP impaired somatic growth rather than intrahepatic pathology.

Biochemical diagnosis of hepatic glycogen storage diseases: 20 years French experience

French experience of 242 cases of liver glycogenoses is reported. Screening tests based on serum biochemical data and glucagon tolerance tests are briefly reviewed. The diagnosis of types I glycogen storage disease (GSD) was ascertained in 73 patients' liver biopsies by measurement of glycogen content and by studying the glucose-6-phosphatase system. Liver biopsies were also required at the beginning for the diagnosis of other hepatic GSDs; later on, the possibilities of diagnosis using peripheral blood cells were investigated. Eighty-four cases of type III GSD were confirmed by measurement of debranching enzyme activity and glycogen content using either liver biopsies (78 cases) and/or erythrocytes (37 cases); enzyme determination was also performed in leukocytes and/or fibroblasts for 18 patients. Twenty-four cases of type VI GSD underwent liver biopsies, and the diagnosis could be confirmed using mononuclear or polymorphonuclear cells for 11 of these patients. Sixty-one patients were identified as type IX GSD; phosphorylase kinase deficiency was demonstrated in erythrocytes for all patients, and a liver biopsy was analyzed for 26 of these cases. From this experience, the possibilities of diagnosis of liver GSD using peripheral blood cells are emphasized.

Complex carbohydrates in the dietary management of patients with glycogenosis caused by glucose-6-phosphatase deficiency

Carbohydrates with digestion characteristics between those of lente uncooked starches and rapidly digestible oligosaccharides were administered in a dose of 1.5 g/kg body weight to five patients with glycogenosis from glucose-6-phosphatase deficiency. Postprandial duration of normoglycemia and concentrations of blood insulin and lactate were determined. Uncooked barley groats in water, or incorporated in a meal turned out to behave as lente carbohydrates. Uncooked couscous in water, couscous incorporated in a meal, and partially cooked macaroni given as a meal behaved as semilente carbohydrates as compared with uncooked cornstarch and glucose. The in vitro determination of the digestibility index along with the in vivo tolerance test enables us to choose and incorporate semilente carbohydrates in the day-time treatment of patients.

Erythrocyte glycolysis and its marked alterations by muscular exercise in type VII glycogenosis

Levels of erythrocyte glycolytic intermediates after the phosphofructokinase (PFK) step, including 2,3-bisphosphoglycerate (2,3-DPG), were decreased at rest in patients from separate families with type VII glycogenosis. The concentration of 2,3-DPG was about half of the normal control value during a period of unrestricted daily activity but was further decreased to one third of normal after a one-day bed rest. Mild ergometric exercise rapidly increased the levels of fructose-1,6-bisphosphate, dihydroxyacetone phosphate plus glyceraldehyde-3-phosphate, and 2,3-DPG in patients' circulating erythrocytes but did not in those of normal subjects. This indicated that a crossover point at the PFK step in glycolysis disappeared after physical exercise and, consequently, the 2,3-DPG concentration, which had decreased because of blockage of the PFK step, was restored considerably. This apparently exercise-related alteration in intermediary metabolism at the beginning of glycolysis was reproduced in vitro by incubating normal erythrocytes in the presence of inosine or ammonia, both of which have increased levels in circulating blood during and after exercise in this disorder. We conclude that physical activity in addition to a genetic deficiency in erythrocyte PFK affects glycolysis in erythrocytes in type VII glycogenosis and that myogenic factors released from exercising muscles may be responsible for this change.

Myogenic hyperuricemia. A common pathophysiologic feature of glycogenosis types III, V, and VII

To identify the mechanism of hyperuricemia in glycogen storage diseases (glycogenoses) that affect muscle, we studied the effects of exercise and prolonged rest on purine metabolism in two patients with glycogenosis type III (debrancher deficiency), one patient with type V (muscle phosphorylase deficiency), and one patient with type VII (muscle phosphofructokinase deficiency). All had hyperuricemia except for one patient with glycogenosis type III. Plasma concentrations of ammonia, inosine, and hypoxanthine increased markedly in all the patients after mild leg exercise on a bicycle ergometer. The plasma urate concentrations also increased, but with a delayed response. Urinary excretion of inosine, hypoxanthine, and urate increased greatly after exercise, consistently with the increases in plasma levels. Hypoxanthine and urate concentrations were extremely high in the plasma and urine of the patient with glycogenosis type VII. With bed rest, the plasma hypoxanthine level returned to normal within a few hours, and the plasma urate concentration decreased from 18.6 to 10.6 mg per deciliter (1106 to 630 mumol per liter) within 48 hours. Similarly, the urinary excretion of these purine metabolites was reduced by bed rest. These findings indicate that muscular exertion in patients with glycogenosis types III, V, and VII causes excessive increases in blood ammonia, inosine, and hypoxanthine due to accelerated degradation of muscle purine nucleotides. These purine metabolites subsequently serve as substrates for the synthesis of uric acid, leading to hyperuricemia.

Impaired glucose transport in polymorphonuclear leukocytes in glycogen storage disease Ib

A study of 2-deoxyglucose transport into polymorphonuclear leukocytes (PMN) was performed in three patients with glycogen storage disease (GSD) type Ib. The rate of 2-deoxyglucose transport into GSD Ib PMN was 30% of that of cells of normal controls. In GSD Ib lymphocytes, transport was normal. Km for 2-deoxyglucose in the PMN of one patient was within the normal range. The reduced transport was not due to the elevation in Km for 2-deoxyglucose nor to the decreased rate of phosphorylation of 2-deoxyglucose. The striking limitation of glucose transport across the cell membrane may account for the impairment of leukocyte function which is characteristic of GSD Ib.

Age-related augmentation of phosphorylase b kinase in hepatic tissue from the glycogen-storage-disease (gsd/gsd) rat

The effects of food deprivation on body weight, liver weight, hepatic glycogen content, glycogenolytic enzymes and blood metabolites were compared in young and old phosphorylase b kinase-deficient (gsd/gsd) rats. Although the concentration of glycogen in liver from 9-week-old female gsd/gsd rats (730 mumol of glucose equivalents/g wet wt.) was increased by 7-8% during starvation, total hepatic glycogen was decreased by 12% after 24 h without food. In 12-month-old male gsd/gsd rats the concentration of liver glycogen (585 mumol of glucose equiv./g wet wt.) was decreased by 16% and total hepatic glycogen by nearly 40% after food deprivation for 24 h. Phosphorylase b kinase and phosphorylase a were present at approx. 10% of the control activities in 9-week-old gsd/gsd rats, but both enzyme activities were increased more than 3-fold in 12-month-old affected rodents. It is concluded that the age-related ability to mobilize hepatic glycogen appears to result from the augmentation of phosphorylase b kinase during maturation of the gsd/gsd rat.

[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.

Ischaemic exercise test in myoadenylate deaminase deficiency and McArdle's disease: measurement of plasma adenosine, inosine and hypoxanthine

Plasma adenosine, inosine and hypoxanthine concentrations were assayed in seven control subjects, five myoadenylate deaminase deficient (MADD) patients and six McArdle patients before and after ischaemic forearm exercise. The plasma adenosine increase was very low in all test groups and there were no significant differences. The MADD patients showed a significantly lower increase of plasma inosine and hypoxanthine after exercise as compared with the controls. In the McArdle patients the increase in plasma inosine and hypoxanthine after exercise did not differ significantly from the values measured in the controls. The ischaemic exercise test with measurement of plasma inosine and hypoxanthine might be of diagnostic value in MADD, but not in McArdle's disease.

[Type I glycogenosis: extending therapy with uncooked cornstarch]

Normal or slightly elevated blood lactate levels and normal to slightly elevated lactate-/creatinine-ratios in 24-h-urine were found in 12 patients (0.9 to 16 years) with glycogenosis type I under conventional treatment with nocturnal gastric drip feeding with maltodextrine combined with frequent daytime feedings. Replacing the nocturnal gastric drip feeding by two doses of uncooked cornstarch suspended in water (single dose 1.4-2.0 g/kg body weight) 4 patients at the ages of 10 to 16 years obtained similar metabolic control. A 7-year old patient with glycogenosis type Ib showing an extremely low fasting tolerance attained stable blood glucose levels by eating two doses of uncooked cornstarch in the morning, so that she was able to attend school. A 2-year old patient received 2-3 g cornstarch/kg body weight every 6 h resulting in constant blood glucose levels, so that she was able to emigrate to Turkey. The therapy with uncooked cornstarch is suitable to augment the therapy of some patients with glycogenosis type I.

Effects in vivo of food deprivation and 3-mercaptopicolinate in the glycogen-storage-disease (gsd/gsd) rat

Intraperitoneal injection of 3-mercaptopicolinate into 24 h-food-deprived 27-week-old female control (GSD/GSD) rats lowered the concentration of circulating glucose by 66%, but glycerol and lactate concentrations were increased up to 3- and 4-fold respectively. In phosphorylase b kinase-deficient (gsd/gsd) rats the corresponding changes for blood glucose, lactate and glycerol were half those observed in the controls. Although the concentration of liver glycogen (approx. 12%, w/w) in the gsd/gsd rats was not altered during food deprivation, total hepatic glycogen was decreased by 17%. It is suggested that the gradual breakdown of the extensive hepatic glycogen stores during starvation assists in the maintenance of normoglycaemia in the gsd/gsd rat.

Reversal of debrancher deficiency myopathy by the use of high-protein nutrition

A child with debrancher deficiency presented with myopathy, recurrent hypoglycemia, and growth failure. Evidence for enhanced gluconeogenesis was demonstrated by low postabsorptive gluconeogenic plasma amino acids, a marked fall in alanine during fasting, and a substantial rise in plasma glucose following protein ingestion. The patient was treated with high-protein nocturnal intragastric therapy, which resulted in marked improvement in exercise tolerance, muscle strength and mass, electromyographic findings, and growth.

Glycogen metabolism in the liver of the neonatal gsd/gsd and control (GSD/GSD) rat

1. The metabolism of hepatic glycogen, labelled with [6-3H]glucose at day 19.5 of gestation and with 14C from [U-14C]galactose at delivery, was followed for 10 h in food-deprived gsd/gsd and control (GSD/GSD) neonatal rats. 2. In the affected pups glycogen was maintained at 12% (w/w) and there was no loss of incorporated radioactivity. 3. The 3H and 14C in glycogen from the controls were both decreased by 80%, but 14C was removed at 0--5 h and [6-3H]glucose at 5--10 h. 4. Blood glucose concentrations in the unaffected neonatal rats fell from 5.3 mM at 20 min to 1.7 mM after 10 h. In the gsd/gsd pups blood glucose concentration was decreased from 2 mM at birth to 0.3 mM at 2.5 h: it was maintained at 0.8 mM between 5 and 10 h. 5. In neonatal rats that had been dead for 10 h, hepatic glycogen was decreased by 34% in the controls and by 22% in the gsd/gsd pups. These results demonstrate that liver from the affected rats contains glycogenolytic activity, but that it is not expressed in living tissue.

Glycogen storage disease: long-term follow-up of nocturnal intragastric feeding

Nocturnal intragastric feeding of patients with certain hepatic forms of glycogen storage disease has been advocated as an effective treatment, resulting in improved blood chemical values and linear growth. We are reporting the long-term follow-up of five patients with glycogen storage diseases; three with type Ia, one with type Ib, and one with type III disease. All had improvement in one or more of the following: linear growth, serum glutamic oxaloacetate transaminase, total lipids, cholesterol, phospholipids, or triglycerides. None had significant improvement in venous CO2, serum lactate or urate. One of the patients in this study died after 1.1 years of treatment, and another patient developed hepatocellular carcinoma after 4.4 years of treatment. Nocturnal intragastric feeding, in conjunction with appropriate daytime feeding, is helpful in the management of patients with glycogen storage disease but response to treatment is variable, and it remains to be determined whether the ultimate prognosis of the diseases can be improved.

Blood glucose of mother and fetus late pregnancy of rats with glycogen storage disorder

The gsd/gsd rat is unable to mobilize liver glycogen due to an absence of phosphorylase b kinase activity. Unlike the normal rat, the maternal gsd/gsd rat cannot maintain its blood glucose concentration in late pregnancy, and values of 3.25 +/- 0.22 mM were found just before birth. The blood glucose of the gsd/gsd fetus falls to 1.76 +/- 0.09 mM at day 19 of gestation and does not rise appreciably again before birth. In contrast, normal fetal rats show a steady rise in blood glucose from hypoglycemic levels at day 19 to a value of 5.70 +/- 0.12 mM on the day of birth. These results indicate that the normal fetal rat contributes towards the regulation of its own glucose in late gestation by utilizing its liver glycogen stores.