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Background: Glycogen storage disease type Ib (GSD Ib) is an autosomal recessively inherited deficiency of the glucose-6-phosphate translocase (G6PT). Clinical features include a combination of a metabolic phenotype (fasting hypoglycemia, lactic acidosis, hepatomegaly) and a hematologic phenotype with neutropenia and neutrophil dysfunction. Dietary treatment involves provision of starches such as uncooked cornstarch (UCCS) and Glycosade® to provide prolonged enteral supply of glucose. Granulocyte colony-stimulating factor (G-CSF) is the treatment of choice for neutropenia. Because long-term stimulation of hematopoiesis with G-CSF causes serious complications such as splenomegaly, hypersplenism, and osteopenia; hematopoietic stem cell transplantation (HSCT) has been considered in some patients with GSD Ib to correct neutropenia and avoid G-CSF related adverse effects. Whether HSCT also has an effect on the metabolic phenotype and utilization of carbohydrate sources has not been determined. Objective: Our objective was to measure the utilization of starch in a patient with GSD Ib before and after HSCT using the minimally invasive 13C-glucose breath test (13C-GBT). Design: A case of GSD Ib (18y; female) underwent 13C-GBT four times: UCCS (pre-HSCT), UCCS (3, 5 months post-HSCT) and Glycosade® (6 months post-HSCT) with a dose of 80 g administered via nasogastric tube after a 4 h fast according to our patient's fasting tolerance. Breath samples were collected at baseline and every 30 min for 240 min. Rate of CO2 production was measured at 120 min using indirect calorimetry. Finger-prick blood glucose was measured using a glucometer hourly to test hypoglycemia (glucose

Hypoglycemia is a pathological condition characterized by a low plasma glucose concentration associated with typical autonomic and/or neuroglycopenic symptoms, and resolution of these symptoms with carbohydrate consumption. Hypoglycemia is quite common in clinical practice, particularly in insulin-treated patients with diabetes and in other inherited or acquired conditions involving the regulation of glucose metabolism. Beyond symptoms that might strongly affect the quality of life, hypoglycemia can lead to short- and long-term detrimental consequences for health. Hypoglycemia can be prevented by appropriate changes in dietary habits or by relevant modifications of the drug treatment. Several dietary approaches based on the intake of various carbohydrate foods have been tested for hypoglycemia prevention; among them uncooked cornstarch (UCS) has demonstrated a great efficacy. In this narrative review, we have summarized the current evidence on the UCS usefulness in some conditions characterized by high hypoglycemic risk, focusing on some inherited diseases −i.e. glycogen storage diseases and other rare disorders − and acquired conditions such as type 1 diabetes, postprandial hypoglycemia consequent to esophageal-gastric or bariatric surgery, and insulin autoimmune syndrome. We also considered the possible role of UCS during endurance exercise performance. Lastly, we have discussed the dose requirement, the side effects, the limitations of UCS use, and the plausible mechanisms by which UCS could prevent hypoglycemia. [ABSTRACT FROM AUTHOR]

Background: Glycogen storage disease type Ia (GSD Ia) is an autosomal recessive disorder caused by deficiency of glucose-6-phosphatase (G6Pase), resulting in fasting hypoglycemia. Dietary treatment with provision of uncooked cornstarch (UCCS) or a novel modified cornstarch (Glycosade®) is available to treat hypoglycemia, yet choice of carbohydrate to achieve a desirable glycemic control is debated.13C-glucose breath test (13C-GBT) can be used to examine glucose metabolism from different carbohydrate sources via 13CO2 in breath. Objectives: Our objectives were: 1) establishing the use of a minimally invasive 13C-GBT to examine in vivo glucose metabolism in healthy adults, and 2) using 13C-GBT to measure utilization of the standard UCCS vs. Glycosade® in GSD Ia and healthy controls. Design: Experiment 1- Ten healthy adults (6F: 4 M, 22-33y) underwent 13C-GBT protocol twice as a proof-of-principle, once with oral isotope dose (glucose 75 g + [U-13C6] d-glucose 75 mg) and once without isotope (only glucose 75 g) to test sensitivity of natural 13C-enrichment. Breath samples were collected at baseline and every 20 min for 240 min. Rate of CO2 production was measured at 120 min using indirect calorimetry. Finger-prick blood glucose was measured using a glucometer hourly to test hypoglycemia (glucose

Aim: The aim of this study was to investigate the clinical utility of panel-based next-generation sequencing (NGS) in the diagnostic approach of glycogen storage disease (GSD).Methods: We performed a retrospective review of the 32 cases with suspected GSDs between April 2013 and November 2019 through panel-based NGS, clinical and biochemical data and long-term complications.Results: Of the 32 clinical cases, we identified 41 different variants, including 24 missense (58.5%), one synonymous (2.4%), three nonsense (8%), one splice (2.4%), four frameshift (9.8%), one deletion (2.4%), four insertions (9.8%), two deletion-insertion (4.9%) and one duplication(2.4%), of which 13(31.7%) were previously unreported in the literature. In addition, patients with different types of GSDs showed important differences in biochemical parameters (i.e., CK, rGGT, TG, and UA).Conclusions: The panel-based NGS played an important diagnostic role in the suspicious GSDs patients, especially in the mild phenotype and ruled out detectable pathologic conditions. Besides, differences between our GSDs patients reflect biochemical heterogeneity.

Abstract Background In fructose 1,6 bisphosphatase (FBPase) deficiency, management aims to prevent hypoglycaemia and lactic acidosis by avoiding prolonged fasting, particularly during febrile illness. Although the need for an emergency regimen to avoid metabolic decompensation is well established at times of illness, there is uncertainty about the need for other dietary management strategies such as sucrose or fructose restriction. We assessed international differences in the dietary management of FBPase deficiency. Methods A cross-sectional questionnaire (13 questions) was emailed to all members of the Society for the Study of Inborn Errors of Metabolism (SSIEM) and a wide database of inherited metabolic disorder dietitians. Results Thirty-six centres reported the dietary prescriptions of 126 patients with FBPase deficiency. Patients’ age at questionnaire completion was: 1-10y, 46% (n = 58), 11-16y, 21% (n = 27), and >16y, 33% (n = 41). Diagnostic age was: 16y, 2% (n = 2). Seventy-five per cent of centres advocated dietary restrictions. This included restriction of: high sucrose foods only (n = 7 centres, 19%); fruit and sugary foods (n = 4, 11%); fruit, vegetables and sugary foods (n = 13, 36%). Twenty-five per cent of centres (n = 9), advised no dietary restrictions when patients were well. A higher percentage of patients aged >16y rather than ≤16y were prescribed dietary restrictions: patients aged 1-10y, 67% (n = 39/58), 11-16y, 63% (n = 17/27) and >16y, 85% (n = 35/41). Patients classified as having a normal fasting tolerance increased with age from 30% in 1-10y, to 36% in 11-16y, and 58% in >16y, but it was unclear if fasting tolerance was biochemically proven. Twenty centres (56%) routinely prescribed uncooked cornstarch (UCCS) to limit overnight fasting in 47 patients regardless of their actual fasting tolerance (37%). All centres advocated an emergency regimen mainly based on glucose polymer for illness management. Conclusions Although all patients were prescribed an emergency regimen for illness, use of sucrose and fructose restricted diets with UCCS supplementation varied widely. Restrictions did not relax with age. International guidelines are necessary to help direct future dietary management of FBPase deficiency.

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. [ABSTRACT FROM AUTHOR]

Background: In fructose 1,6 bisphosphatase (FBPase) deficiency, management aims to prevent hypoglycaemia and lactic acidosis by avoiding prolonged fasting, particularly during febrile illness. Although the need for an emergency regimen to avoid metabolic decompensation is well established at times of illness, there is uncertainty about the need for other dietary management strategies such as sucrose or fructose restriction. We assessed international differences in the dietary management of FBPase deficiency.Methods: A cross-sectional questionnaire (13 questions) was emailed to all members of the Society for the Study of Inborn Errors of Metabolism (SSIEM) and a wide database of inherited metabolic disorder dietitians.Results: Thirty-six centres reported the dietary prescriptions of 126 patients with FBPase deficiency. Patients' age at questionnaire completion was: 1-10y, 46% (n = 58), 11-16y, 21% (n = 27), and >16y, 33% (n = 41). Diagnostic age was: <1y, 36% (n = 46); 1-10y, 59% (n = 74); 11-16y, 3% (n = 4); and >16y, 2% (n = 2). Seventy-five per cent of centres advocated dietary restrictions. This included restriction of: high sucrose foods only (n = 7 centres, 19%); fruit and sugary foods (n = 4, 11%); fruit, vegetables and sugary foods (n = 13, 36%). Twenty-five per cent of centres (n = 9), advised no dietary restrictions when patients were well. A higher percentage of patients aged >16y rather than ≤16y were prescribed dietary restrictions: patients aged 1-10y, 67% (n = 39/58), 11-16y, 63% (n = 17/27) and >16y, 85% (n = 35/41). Patients classified as having a normal fasting tolerance increased with age from 30% in 1-10y, to 36% in 11-16y, and 58% in >16y, but it was unclear if fasting tolerance was biochemically proven. Twenty centres (56%) routinely prescribed uncooked cornstarch (UCCS) to limit overnight fasting in 47 patients regardless of their actual fasting tolerance (37%). All centres advocated an emergency regimen mainly based on glucose polymer for illness management.Conclusions: Although all patients were prescribed an emergency regimen for illness, use of sucrose and fructose restricted diets with UCCS supplementation varied widely. Restrictions did not relax with age. International guidelines are necessary to help direct future dietary management of FBPase deficiency. [ABSTRACT FROM AUTHOR]

Background: Glycogen storage disease type Ib (GSD Ib) is an autosomal recessively inherited deficiency of the glucose-6-phosphate translocase (G6PT). Clinical features include a combination of a metabolic phenotype (fasting hypoglycemia, lactic acidosis, hepatomegaly) and a hematologic phenotype with neutropenia and neutrophil dysfunction. Dietary treatment involves provision of starches such as uncooked cornstarch (UCCS) and Glycosade® to provide prolonged enteral supply of glucose. Granulocyte colony-stimulating factor (G-CSF) is the treatment of choice for neutropenia. Because long-term stimulation of hematopoiesis with G-CSF causes serious complications such as splenomegaly, hypersplenism, and osteopenia; hematopoietic stem cell transplantation (HSCT) has been considered in some patients with GSD Ib to correct neutropenia and avoid G-CSF related adverse effects. Whether HSCT also has an effect on the metabolic phenotype and utilization of carbohydrate sources has not been determined., Objective: Our objective was to measure the utilization of starch in a patient with GSD Ib before and after HSCT using the minimally invasive 13 C-glucose breath test ( 13 C-GBT)., Design: A case of GSD Ib (18y; female) underwent 13 C-GBT four times: UCCS (pre-HSCT), UCCS (3, 5 months post-HSCT) and Glycosade® (6 months post-HSCT) with a dose of 80 g administered via nasogastric tube after a 4 h fast according to our patient's fasting tolerance. Breath samples were collected at baseline and every 30 min for 240 min. Rate of CO 2 production was measured at 120 min using indirect calorimetry. Finger-prick blood glucose was measured using a glucometer hourly to test hypoglycemia (glucose <4 mmol/L). Biochemical and clinical data were obtained from the medical records as a post-hoc chart review., Results: UCCS utilization was significantly higher in GSD Ib pre-HSCT, which reduced and stabilized 5 months post-HSCT. UCCS and Glycosade® utilizations were low and not different at 5 and 6 months post-HSCT. Blood glucose concentrations were not significantly different at any time point., Conclusions: Findings show that HSCT stabilized UCCS utilization, as reflected by lower and stable glucose oxidation. The results also illustrate the application of 13 C-GBT to examine glucose metabolism in response to various carbohydrate sources after other treatment modalities like HSCT in GSD Ib., Competing Interests: None., (© 2023 The Author(s).)

Objectives Glycogen storage disease (GSD) types VI and IX are caused by phosphorylase system deficiencies. To evaluate the natural history and long-term treatment outcome of the patients with GSD-VI and -IX, we performed an observational retrospective case study of 21 patients with confirmed diagnosis of GSD-VI or -IX. Methods All patients with GSD-VI or -IX, diagnosed at The Hospital for Sick Children, were included. Electronic and paper charts were reviewed for clinical features, biochemical investigations, molecular genetic testing, diagnostic imaging, long-term outcome and treatment by two independent research team members. All information was entered into an Excel database. Results We report on the natural history and treatment outcomes of the 21 patients with GSD-VI and -IX and 16 novel pathogenic mutations in the PHKA2 , PHKB , PHKG2 and PYGL genes. We report for the first time likely liver adenoma on liver ultrasound and liver fibrosis on liver biopsy specimens in patients with GSD-VI and mild cardiomyopathy on echocardiography in patients with GSD-VI and -IXb. Conclusion We recommend close monitoring in all patients with GSD-VI and -IX for the long-term liver and cardiac complications. There is a need for future studies if uncooked cornstarch and high protein diet would be able to prevent long-term complications of GSD-VI and -IX. [ABSTRACT FROM AUTHOR]

Objectives: The present study aimed to evaluate the body composition of hepatic glycogen storage disorders (GSDs) through dual energy x-ray absorptiometry., Methods: This was an exploratory, observational, cross-sectional study. Twenty-four patients with GSD (type Ia: n = 13, Ib: n = 5, III: n = 2, and IX-α/β/γ: n = 4; female sex: n = 13; age &lt;8 y: n = 3, 8-19 y: n = 14, and &gt;19 y: n = 7) were included. Three-day dietary records were collected in the week preceding dual energy x-ray absorptiometry. Body composition findings were correlated with clinical parameters, uncooked cornstarch (UCCS) regimen, dietary intake, and markers of treatment adherence., Results: An elevated fat mass (FM) index was found in 16 of 21 patients (age 8-19 y: n = 10 and &gt;19 y: n = 6; GSD type Ia: n = 12, Ib: n = 2, III: n = 1, and IX-γ: n = 1). A lean mass (LM) index evaluation showed no LM deficits in relation to corresponding reference populations. Relative skeletal muscle index values were decreased in 2 of 7 adult patients (type Ib: n = 1 and IX-α: n = 1). UCCS (g/d) correlated positively with the FM index (rs = 0.7; P ≤ 0.01). In contrast, relative UCCS intake (g/kg body weight) was negatively associated with LM/kg (rs = -0.8; P ≤ 0.01)., Conclusions: These findings suggest a high frequency of elevated FM in patients with hepatic GSDs. We also suggest that treatment with UCCS is associated with excess weight in these patients. Additionally, the treatment strategy can impair protein intake, and lead to a decrease in LM., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Avoidance of fasting and regular ingestion of uncooked-cornstarch have long been the mainstay dietary treatment of Glycogen Storage Disease type Ia (GSD-Ia). However, GSD-Ia patients who despite optimal dietary treatment show poor glycemic control and are intolerant to cornstarch, present a complex clinical challenge. We pursued Whole Exome Sequencing (WES) in three such unrelated patients, to both confirm a molecular diagnosis of GSD-Ia, and seek additional variants in other genes (e.g. genes associated with amylase production) which may explain their persistent symptoms. WES confirmed the GSD-Ia diagnosis, with all three probands harboring the homozygous p.R83C variant in G6PC. While no other significant variants were identified for patients A and B, a homozygous p.G276V variant in the SI gene was detected in patient C, establishing the dual-diagnosis of GSD-Ia and Sucrase-Isomaltase Deficiency. To conclude, we suggest that WES should be considered in GSD-Ia patients who show persistent symptoms despite optimal dietary management. [ABSTRACT FROM AUTHOR]

Background: Glycogen storage disease type Ia (GSD Ia) is an autosomal recessive disorder caused by deficiency of glucose-6-phosphatase (G6Pase), resulting in fasting hypoglycemia. Dietary treatment with provision of uncooked cornstarch (UCCS) or a novel modified cornstarch ( Glycosade® ) is available to treat hypoglycemia, yet choice of carbohydrate to achieve a desirable glycemic control is debated. 13 C-glucose breath test ( 13 C-GBT) can be used to examine glucose metabolism from different carbohydrate sources via 13 CO 2 in breath., Objectives: Our objectives were: 1) establishing the use of a minimally invasive 13 C-GBT to examine in vivo glucose metabolism in healthy adults, and 2) using 13 C-GBT to measure utilization of the standard UCCS vs. Glycosade® in GSD Ia and healthy controls., Design: Experiment 1- Ten healthy adults (6F: 4 M, 22-33y) underwent 13 C-GBT protocol twice as a proof-of-principle, once with oral isotope dose (glucose 75 g + [U- 13 C 6 ] d-glucose 75 mg) and once without isotope (only glucose 75 g) to test sensitivity of natural 13 C-enrichment. Breath samples were collected at baseline and every 20 min for 240 min. Rate of CO 2 production was measured at 120 min using indirect calorimetry. Finger-prick blood glucose was measured using a glucometer hourly to test hypoglycemia (glucose <4 mmol/L). Experiment 2- Three GSD Ia (12y, 13y, and 28y) and six healthy controls (2F: 4 M, 10-32y) underwent 13 C-GBT protocol twice: with UCCS or Glycosade® (based on their current prescribed dose 42-100 g) after ~4 h fast based on our GSD Ia patients with fasting tolerance., Results: Findings 1- Maximum 13 C-enrichments occurred at 200 min without and with [U- 13 C 6 ] d-glucose in all healthy adults, suggesting natural enrichment is sensitive for the 13 C-GBT. Findings 2- Glycosade® utilization was lower than UCCS utilization in 12y and 13y GSD Ia, but was similar in the 28y GSD Ia., Conclusions: 13 C-GBT is a novel minimally invasive functional test to examine glucose metabolism in GSD Ia, and test new products like Glycosade® , which has the potential to improve nutritional management and individualized carbohydrate supply in GSD., Competing Interests: None., (© 2022 The Authors.)

Glycogen storage disease type Ia (GSDIa) is caused by defective glucose-6-phosphatase, a key enzyme in carbohydrate metabolism. Affected individuals cannot release glucose during fasting and accumulate excess glycogen and fat in the liver and kidney, putting them at risk of severe hypoglycaemia and secondary metabolic perturbations. Good glycaemic/metabolic control through strict dietary treatment and regular doses of uncooked cornstarch (UCCS) is essential for preventing hypoglycaemia and long-term complications. Dietary treatment has improved the prognosis for patients with GSDIa; however, the disease itself, its management and monitoring have significant physical, psychological and psychosocial burden on individuals and parents/caregivers. Hypoglycaemia risk persists if a single dose of UCCS is delayed/missed or in cases of gastrointestinal intolerance. UCCS therapy is imprecise, does not treat the cause of disease, may trigger secondary metabolic manifestations and may not prevent long-term complications. We review the importance of and challenges associated with achieving good glycaemic/metabolic control in individuals with GSDIa and how this should be balanced with age-specific psychosocial development towards independence, management of anxiety and preservation of quality of life (QoL). The unmet need for treatment strategies that address the cause of disease, restore glucose homeostasis, reduce the risk of hypoglycaemia/secondary metabolic perturbations and improve QoL is also discussed. [ABSTRACT FROM AUTHOR]

To determine the optimal daytime dietary regimen for type 1 glycogen storage disease (GSD), we used uncooked cornstarch (UCS) at a basal glucose production rate (GPR) in single and divided doses, with mixed meals at 0700 and I 700 h. This regimen was compared with a 1 .5 times larger single dose of UCS at 0700 h, and with dextrose at GPR at 1200 h. Two-hour UCS loads (amount equal to GPR in 2 h) given with a mixed meal at 0700 h and I 80 mm later maintained mean blood glucose (BG) concentrations at ≥4.2 mmol/L for 300 mm. BG was significantly greater from 240 to 300 mm compared with a single 4-h UCS load, and at 300 mm compared with a single 6-h UCS load. Similar effects were noted when the divided UCS regimen was given with a mixed meal at 1700 h, but not when isoenergetic amounts of dextrose were given on the same schedules with a mixed meal at 1200 h. A daytime schedule of six UCS feedings (with the three main meals and 180 mm later) at GPR maintains BG at concentrations that should minimize biochemical abnormalities and optimize clinical outcome in patients with GSD. [ABSTRACT FROM AUTHOR]

Long-term effects of cornstarch (CS) therapy on biochemical values and physical growth in children with type I glycogen storage disease (GSD I) were compared to those of children receiving continuous nocturnal nasogastric glucose feedings (CNG). Only patients who had received more than 5 years of dietary therapy (either CS or CNG) were evaluated. Six patients (five female, age 13.5 years±1.3, range 11.7-16.5 years) received CS (1.75-2.5 g/kg, four times daily) and seven patients (five female, age 9.6±2.5 years, range 7.3-14.8 years) received CNG. Blood glucose, lactate, cholesterol and triglyceride levels were not significantly different between the two methods of treatment. All patients maintained linear growth rates normal for their age. The standard deviation score of height after 6.7±1.6 years (range 5-9 years) of CS treatment was −1.29±0.59 and after 8.8±2.4 years (range 7-14 years) of CNG was −1.24±0.63. These values did not differ significantly from each other or from the target height, an estimate of genetic potential for height as determined from parental heights. With the exceptions of diarrhea, increased flatulence and excess weight gain, there were no adverse effects of CS after 9 years of treatment. Our data suggests that cornstarch is a simple, effective and safe therapy for GSD I. [ABSTRACT FROM AUTHOR]

Three children aged 1-2 years with glycogenosis type I were treated with 2 g/kg bodyweight oral cornstarch per meal (4-5 times a day) for a period up to 16 months. In comparison to the previous dietary regimen (day and nocturnal feedings every 3 h) the cornstarch diet stabilised serum glucose profiles and dramatically improved secondary hyperlipoproteinaemia. Mean total triglycerides decreased up to one half, consistent with a fall of very low density lipoprotein-triglycerides up to two thirds. Metabolic acidosis and hyperuricaemia did not occur and normal growth rates (0.7-1 cm/month) were achieved. We conclude that the cornstarch regimen even in the age group up to 2 years can be considered as an efficient alternative in the treatment of glycogenosis type I patients with less frequent feedings and without nocturnal infusion. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to investigate the clinical utility of panel-based next-generation sequencing (NGS) in the diagnostic approach of glycogen storage disease (GSD). Methods: We performed a retrospective review of the 32 cases with suspected GSDs between April 2013 and November 2019 through panel-based NGS, clinical and biochemical data and long-term complications. Results: Of the 32 clinical cases, we identified 41 different variants, including 24 missense (58.5%), one synonymous (2.4%), three nonsense (8%), one splice (2.4%), four frameshift (9.8%), one deletion (2.4%), four insertions (9.8%), two deletion-insertion (4.9%) and one duplication(2.4%), of which 13(31.7%) were previously unreported in the literature. In addition, patients with different types of GSDs showed important differences in biochemical parameters (i.e., CK, rGGT, TG, and UA). Conclusions: The panel-based NGS played an important diagnostic role in the suspicious GSDs patients, especially in the mild phenotype and ruled out detectable pathologic conditions. Besides, differences between our GSDs patients reflect biochemical heterogeneity., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Ying, Zhihua, Yucan, Yu, Qian, Bixia, Weixia and Zhifeng.)

Aim: The urinary glucose tetrasaccharide, Glcα1-6Glcα1-4Glcα1-4Glc (Glc 4 ), is a glycogen limit dextrin that is elevated in patients with glycogen storage disease (GSD) type III. We evaluated the potential of uncooked cornstarch therapy to interfere with Glc 4 monitoring, by measuring the diurnal variability of Glc 4 excretion in patients with GSD III., Methods: Voids were collected at home over 24 hours, stored at 4°C and frozen within 48 hours. Glc 4 was analyzed using liquid chromatography-tandem mass spectrometry and normalized to creatinine., Results: Subjects with GSD III (median age: 13.5 years, range: 3.7-62; n = 18) completed one or more 24-hour urine collection, and 28/36 collections were accepted for analysis. Glc 4 was elevated in 16/18 subjects (median: 13 mmol/mol creatinine, range: 2-75, reference range: <3). In collections with elevated Glc 4 (23/28), two-thirds (15/23) had low diurnal variability in Glc 4 excretion (coefficient of variation [CV%] <25). The diurnal variability was significantly correlated with the Glc 4 concentration (Pearson R = .644, P < .05), but not with the dose of uncooked cornstarch. High intraday variability (>25%) was not consistently observed in repeat collections by the same subject., Conclusions: The extent and variability of Glc 4 excretion relative to creatinine was not correlated with cornstarch dose. A majority of collections showed low variability over 24 hours. These findings support the use of single time-point collections to evaluate Glc 4 in patients with GSD III treated with cornstarch. However, repeat sampling over short time-periods will provide the most accurate assessment of Glc 4 excretion, as intraday variability may be increased in patients with high Glc 4 excretion., Competing Interests: S. P. Y. works for a laboratory that offers Glc4 testing, has received grant support from Sanofi Genzyme, Amicus Therapeutics, Biomarin Pharmaceutical, PTC Therapeutics, and Valerion Therapeutics, and has consulted for Amicus Therapeutics, Sanofi Genzyme, and PTC Therapeutics. P. S. K. has received research/grant support from Sanofi Genzyme, Valerion Therapeutics, Shire Pharmaceuticals, Amicus Therapeutics, Pfizer, Alexion Pharmaceuticals and Ultragenyx and consulting fees and honoraria from Sanofi Genzyme, Shire Pharmaceuticals, Alexion Pharmaceuticals, Amicus Therapeutics, Vertex Pharmaceuticals, Ultragenyx, and Asklepios Biopharmaceutical, Inc. (AskBio). P. S. K. is listed as an inventor on a licensed Duke University patent for the use of rhGAA in the treatment of GSDIII and other GSDs excluding GSDII. To date, neither Duke University nor the inventor has received any money from the commercialization of rights associated with this patent. S. A. has received consulting fees from Ultragenyx. The other authors declare no conflicts of interest., (© 2020 The Authors. JIMD Reports published by John Wiley & Sons Ltd on behalf of SSIEM.)

The hepatic glycogen storage diseases (GSDs) are a group of disorders where abnormal storage or release of glycogen leads to potentially life-threatening hypoglycemia and metabolic disturbances. Dietary interventions have markedly improved the outcome for these disorders, from a previously fatal condition to one where people can do well with proper care. This article chronicles the evolution of dietary management and treatment of the hepatic GSDs (types 0, I, III, VI, IX, and XI). We examine historic and current approaches for preventing hypoglycemia associated with GSDs. There is a lack of consensus on the optimal dietary management of GSDs despite decades of research, and the ongoing controversies are discussed., (Copyright © American Society for Nutrition 2019.)

Uncooked cornstarch (UCCS) loads in 14 patients with type 1 glycogenosis revealed that satisfactory glycaemia was achieved for a median of 4.25 hours (range 2.5 to 6). Length of glycaemia was related weakly to UCCS dose, but not to patient age or measures of metabolic control. Careful monitoring is required during UCCS treatment. [ABSTRACT FROM AUTHOR]