Uncooked cornstarch treatment for hepatic phosphorylase kinase deficiency

Endocrine involvement in hepatic glycogen storage diseases: pathophysiology and implications for care

Hepatic glycogen storage diseases constitute a group of disorders due to defects in the enzymes and transporters involved in glycogen breakdown and synthesis in the liver. Although hypoglycemia and hepatomegaly are the primary manifestations of (most of) hepatic GSDs, involvement of the endocrine system has been reported at multiple levels in individuals with hepatic GSDs. While some endocrine abnormalities (e.g., hypothalamic‑pituitary axis dysfunction in GSD I) can be direct consequence of the genetic defect itself, others (e.g., osteopenia in GSD Ib, insulin-resistance in GSD I and GSD III) may be triggered by the (dietary/medical) treatment. Being aware of the endocrine abnormalities occurring in hepatic GSDs is essential (1) to provide optimized medical care to this group of individuals and (2) to drive research aiming at understanding the disease pathophysiology. In this review, a thorough description of the endocrine manifestations in individuals with hepatic GSDs is presented, including pathophysiological and clinical implications.

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

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

Features of chinese patients with sitosterolemia

Background

Sitosterolemia is a lipid disorder characterized by the accumulation of phytosterols in plasma and organs, caused by mutations in the ABCG5 and/or ABCG8 genes. The disease is frequently misdiagnosed and mistreated as familial hypercholesterolemia (FH). To gain a better understanding of the disease, the current status of diagnosis and treatment of Chinese patients with sitosterolemia was reviewed and summarized.

Method

Literature search was performed. The clinical features and molecular characteristics of Chinese patients with sitosterolemia were analysed. Four children with sitosterolemia and the treatment experience were described.

Results

Fifty-five patients with sitosterolemia have been reported in China. These patients were aged from 3 months to 67 years at diagnosis, and the median was 8 years of age. Several complications, such as xanthomas in 47 patients (85%), thrombocytopenia in 17 patients (31%), anemia in 14 patients (25%), and cardiovascular damage in 12 patients (22%), were observed. Thirty-nine patients (71%) exhibited mutations in the ABCG5 gene, 15 patients (27%) showed mutations in ABCG8, and variations in both genes occurred in one patient (2%). A patient with two clinically rare diseases, namely, sitosterolemia and glycogen storage disease type VI (GSD VI)), is reported here for the first time. The four reported patients were treated with low cholesterol and phytosterol-limited diet alone or combined with cholestyramine. Even though decreases were observed for total plasma cholesterol (TC) and low-density-lipoprotein cholesterol (LDL-C), and these levels were as low as normal in some patients, the levels of plant sterols remained above the normal range. However, TC, LDL-C and plant sterol levels remained at high levels in patients treated with a control diet control only.

Conclusions

The analysis reveals that different from Caucasians carrying mainly variations in ABCG8, most Chinese patients have mutations in the ABCG5 gene, and Arg446Ter, Gln251Ter, anArg389His might be hot-spot mutations in Chinese patients. The current survey provides clinical data to enable the development of a standardized protocol for the diagnosis and treatment of sitosterolemia in China.

Hepatic glycogen storage diseases: pathogenesis, clinical symptoms and therapeutic management

Glycogen storage diseases (GSDs) are genetically determined metabolic diseases that cause disorders of glycogen metabolism in the body. Due to the enzymatic defect at some stage of glycogenolysis/glycogenesis, excess glycogen or its pathologic forms are stored in the body tissues. The first symptoms of the disease usually appear during the first months of life and are thus the domain of pediatricians. Due to the fairly wide access of the authors to unpublished materials and research, as well as direct contact with the GSD patients, the article addresses the problem of actual diagnostic procedures for patients with the suspected diseases. Knowledge and awareness of the problem among physicians seem insufficient, and research on the diagnosis and treatment of GSD is still ongoing, resulting in a heterogeneous GSD typology and a changing way of its diagnosis and treatment.

Preclinical Research in Glycogen Storage Diseases: A Comprehensive Review of Current Animal Models

GSD are a group of disorders characterized by a defect in gene expression of specific enzymes involved in glycogen breakdown or synthesis, commonly resulting in the accumulation of glycogen in various tissues (primarily the liver and skeletal muscle). Several different GSD animal models have been found to naturally present spontaneous mutations and others have been developed and characterized in order to further understand the physiopathology of these diseases and as a useful tool to evaluate potential therapeutic strategies. In the present work we have reviewed a total of 42 different animal models of GSD, including 26 genetically modified mouse models, 15 naturally occurring models (encompassing quails, cats, dogs, sheep, cattle and horses), and one genetically modified zebrafish model. To our knowledge, this is the most complete list of GSD animal models ever reviewed. Importantly, when all these animal models are analyzed together, we can observe some common traits, as well as model specific differences, that would be overlooked if each model was only studied in the context of a given GSD.

Glycogen storage disease type VI: clinical course and molecular background

Glycogen storage disease type VI (GSD-VI; also known as Hers disease, liver phosphorylase deficiency) is caused by mutations in the gene coding for glycogen phosphorylase (PYGL) leading to a defect in the degradation of glycogen. Since there are only about 40 patients described in literature, our knowledge about the course of the disease is limited. In order to evaluate the long-term outcome of patients with GSD-VI, an observational retrospective case study of six patients was performed at the University Children's Hospital Zurich. The introduction of small, frequent meals as well as cornstarch has led to normal growth in all patients and to normalization of liver transaminases in most patients. After starting the dietary regimen, there were no signs of hypoglycemia. However, three of six patients showed persistent elevation of triglycerides. Further, we identified four novel pathogenic PYGL mutations and describe here their highly variable impact on phosphorylase function.Conclusions: After establishing the diagnosis, dietary treatment led to metabolic stability and to prevention of hypoglycemia. Molecular genetics added important information for the understanding of the clinical variability in this disease. While outcome was overall excellent in all patients, half of the patients showed persistent hypertriglyceridemia even after initiating treatment.What is Known:• Glycogen storage disease type VI (GSD-VI) is a metabolic disorder causing a defect in glycogen degradation. Dietary treatment normally leads to metabolic stability and prevention of hypoglycemia.• However, our knowledge about the natural course of patients with GSD-VI is limited.What is New:• While outcome was overall excellent in all patients, half of the patients showed persistent hypertriglyceridemia even after initiating treatment.• Molecular genetics added important information for the understanding of the clinical variability in this disease.

Variability of disease spectrum in children with liver phosphorylase kinase deficiency caused by mutations in the PHKG2 gene

Liver phosphorylase b kinase (PhK) deficiency (glycogen storage disease type IX), one of the most common causes of glycogen storage disease, is caused by mutations in the PHKA2, PHKB, and PHKG2 genes. Presenting symptoms include hepatomegaly, ketotic hypoglycemia, and growth delay. Clinical severity varies widely. Autosomal recessive mutations in the PHKG2 gene, which cause about 10-15% of cases, have been associated with severe symptoms including increased risk of liver cirrhosis in childhood. We have summarized the molecular, biochemical, and clinical findings in five patients, age 5-16 years, diagnosed with liver PhK deficiency caused by PHKG2 gene mutations. We have identified five novel and two previously reported mutations in the PHKG2 gene in these five patients. Clinical severity was variable among these patients. Histopathological studies were performed for four of the patients on liver biopsy samples, all of which showed signs of fibrosis but not cirrhosis. One of the patients (aged 9 years) developed a liver adenoma which later resolved. All patients are currently doing well. Their clinical symptoms have improved with age and treatment. These cases add to the current knowledge of clinical variability in patients with PHKG2 mutations. Long term studies, involving follow-up of these patients into adulthood, are needed.

Multiple voxel 1H MR spectroscopy of phosphorylase-b kinase deficient patients (GSD IXa) showing an accumulation of fat in the liver that resolves with aging

BACKGROUND/AIMS

Phosphorylase-b deficient patients suffer from glycogen storage disease (GSD IXa) leading to liver enlargement which usually resolves during puberty and adolescence. This pathology has not yet been documented by (1)H MR spectroscopy (MRS) investigation.

METHODS

MRS of eight GSD IXa patients was performed in this study to assess whether or not liver fat content is elevated in GSD IXa and decreases with aging. An improvement in our MRS method compared with previous liver fat MRS studies is that we measured a plane of liver voxels at once rather than a single MRS voxel, yielding a reliable determination of liver fat content.

RESULTS

Fat contents of 3.4-10% were observed in young GSD IXa patients, as compared with 0.5-0.9% in controls, these dropped to control levels in patients past age 40 (r = -0.82; P < 0.01).

CONCLUSIONS

Liver fat content is increased in glycogen storage disease (GSD IXa) and normalizes with ageing. Assessing liver fat levels in this population is a novel and interesting concept. This could potentially enhance the understanding of liver function in that 20% of the population who has increased liver fat.

Characteristic growth pattern in male X-linked phosphorylase-b kinase deficiency (GSD IX)

Growth retardation is one of the clinical characteristics of glycogen storage disease (GSD) type IX. Initial growth retardation has been described in a few case reports, followed by a complete catch-up in growth. This study aimed to determine the growth pattern of patients with GSD IX. Growth charts of 51 male Dutch patients with GSD IX (age 0-33 years, median follow-up time 8.3 years (range 0-30.5 years)) were studied retrospectively and compared with Dutch standard growth charts. Patients had a normal height at birth, significant growth retardation between the ages of 2 and 10 years (mean z-score -1.96), delayed growth spurt in puberty and catch-up towards quite normal final height (mean z-score -0.55). We conclude that GSD IX patients have a specific growth pattern characterized by initial growth retardation, a late growth spurt and complete catch-up in final height. Intervention for growth retardation is therefore in general not warranted. It is speculated that mild hypoglycaemia related to the disorder may cause endocrine changes. Because the glucose need per kg bodyweight decreases with age, the enzyme defect becomes less important with ageing and the effect on growth diminishes.

Glycogen storage diseases. Phenotypic, genetic, and biochemical characteristics, and therapy

The glycogen storage diseases are caused by inherited deficiencies of enzymes that regulate the synthesis or degradation of glycogen. In the past decade, considerable progress has been made in identifying the precise genetic abnormalities that cause the specific impairments of enzyme function. Likewise, improved understanding of the pathophysiologic derangements resulting from individual enzyme defects has led to the development of effective nutritional therapies for each of these disorders. Meticulous adherence to dietary therapy prevents hypoglycemia, ameliorates the biochemical abnormalities, decreases the size of the liver, and results in normal or nearly normal physical growth and development. Nevertheless, serious long-term complications, including nephropathy that can cause renal failure and hepatic adenomata that can become malignant, are a major concern in GSD-I. In GSD-III, the risk for hypoglycemia diminishes with age, and the liver decreases in size during puberty. Cirrhosis develops in some adult patients, and progressive myopathy and cardiomyopathy occur in patients with absent GDE activity in muscle. It remains unclear whether these complications of glycogen storage disease can be prevented by dietary therapy. Glycogen storage diseases caused by lack of phosphorylase activity are milder disorders with a good prognosis. The liver decreases in size, and biochemical abnormalities disappear by puberty.