The metabolic defect in glycogen storage disease type I (GSDI) results in fasting hypoglycemia and typical secondary metabolic abnormalities (eg, hypertriglyceridemia, hyperlactatemia, hyperuricemia). The aim of this study was to assess further perturbations of the metabolic network in GSDI patients under ongoing treatment.

Glycogen storage disease type I (GSD I) is a rare autosomal recessive disorder of carbohydate metabolism characterized by recurrent hypoglycaemia and hepatomegaly. Management of GSD I is demanding and comprises a diet with defined carbohydrate intake and the use of complex carbohydrates, nocturnal tube feeding or night-time uncooked cornstarch intake, regular blood glucose monitoring and the handling of emergency situations. With improved treatment, most patients nowadays survive into adulthood. Little research has been performed on the impact of GSD I on daily life, especially in adult patients.

Glycogen Storage Disease Type I (GSDI) is an inherited disease caused by glucose-6 phosphatase (G6Pase) deficiency, leading to a loss of endogenous glucose production and severe hypoglycemia. Moreover, most GSDI patients develop a chronic kidney disease (CKD) due to lipid accumulation in the kidney. Similar to diabetic CKD, activation of renin-angiotensin system (RAS) promotes renal fibrosis in GSDI. Here, we investigated the physiological and molecular effects of RAS blockers in GSDI patients and mice. A retrospective analysis of renal function was performed in 21 GSDI patients treated with RAS blockers. Cellular and metabolic impacts of RAS blockade were analyzed in K.G6pc-/- mice characterized by G6pc1 deletion in kidneys. GSDI patients started RAS blocker treatment at a median age of 21 years and long-term treatment reduced the progression of CKD in about 50% of patients. However, CKD progressed to kidney failure in 20% of treated patients, requiring renal transplantation. In K.G6pc-/- mice, CKD was associated with an impairment of autophagy and ER stress. RAS blockade resulted in a rescue of autophagy and decreased ER stress, concomitantly with decreased fibrosis and improved renal function, but without impact on glycogen and lipid contents. In conclusion, these data confirm the partial beneficial effect of RAS blockers in the prevention of CKD in GSDI. Mechanistically, we show that these effects are linked to a reduction of cell stress, without affecting metabolism.

Glycogen storage disease type I (GSD-I) is an autosomal recessive disorder of carbohydrate metabolism, resulting in limited production of glucose and excessive glycogen storage in the liver and kidneys. These patients are characterized by life-threatening hypoglycemia, metabolic derangements, hepatomegaly, chronic kidney disease, and failure to thrive. Liver transplantation (LT) has been performed for poor metabolic control and delayed growth. However, renal outcome was diverse in pediatric GSD patients after LT. The aim of this study was to investigate the long-term outcome of renal function in pediatric GSD-I patients after living donor LT (LDLT), and to identify modifiable variables that potentially permits LT to confer native renal preservation.

The aim of the study was to investigate the relationship between SLC37A4 gene mutation and clinical phenotype in a patient with glycogen storage disease-type I.

Glycogen storage diseases (GSD) encompass a group of rare inherited diseases due dysfunction of glycogen metabolism. Hypoglycemia is the most common primary manifestation of GSD, and disturbances in glucose metabolism can cause neurological damage. The aims of this study were to first investigate the metabolic, genetic, and neurological profiles of children with GSD, and to test the hypothesis whether GSD type I would have greater neurological impact than GSD type IX. A cross-sectional study was conducted with 12 children diagnosed with GSD [Types: Ia (n=5); 1, Ib (n=1); 4, IXa (n=5); and 1, IXb (n=1)]. Genetic testing was conducted for the following genes using multigene panel analysis. The biochemical data and magnetic resonance imaging of the brain presented by the patients were evaluated. The criteria of adequate metabolic control were adopted based on the European Study on Glycogen Storage Disease type I consensus. Pathogenic mutations were identified using multigene panel analyses. The mutations and clinical chronology were related to the disease course and neuroimaging findings. Adequate metabolic control was achieved in 67% of patients (GSD I, 43%; GSD IX, 100%). Fourteen different mutations were detected, and only two co-occurring mutations were observed across families (G6PC c.247C>T and c.1039C>T). Six previously unreported variants were identified (5 PHKA2; 1 PHKB). The proportion of GSD IX was higher in our cohort compared to other studies. Brain imaging abnormalities were more frequent among patients with GSD I, early-symptom onset, longer hospitalization, and inadequate metabolic control. The frequency of mutations was similar to that observed among the North American and European populations. None of the mutations observed in PHKA2 have been described previously. Therefore, current study reports six GSD variants previously unknown, and neurological consequences of GSD I. The principal neurological impact of GSD appeared to be related to inadequate metabolic control, especially hypoglycemia.

Glycogen storage disease type III (GSDIII) is a rare inborn error of metabolism affecting liver, skeletal muscle, and heart due to mutations of the AGL gene encoding for the glycogen debranching enzyme (GDE). No curative treatment exists for GSDIII. The 4.6 kb GDE cDNA represents the major technical challenge toward the development of a single recombinant adeno-associated virus-derived (rAAV-derived) vector gene therapy strategy. Using information on GDE structure and molecular modeling, we generated multiple truncated GDEs. Among them, an N-terminal-truncated mutant, ΔNter2-GDE, had a similar efficacy in vivo compared with the full-size enzyme. A rAAV vector expressing ΔNter2-GDE allowed significant glycogen reduction in heart and muscle of Agl-/- mice 3 months after i.v. injection, as well as normalization of histology features and restoration of muscle strength. Similarly, glycogen accumulation and histological features were corrected in a recently generated Agl-/- rat model. Finally, transduction with rAAV vectors encoding ΔNter2-GDE corrected glycogen accumulation in an in vitro human skeletal muscle cellular model of GSDIII. In conclusion, our results demonstrated the ability of a single rAAV vector expressing a functional mini-GDE transgene to correct the muscle and heart phenotype in multiple models of GSDIII, supporting its clinical translation to patients with GSDIII.

Glycogen storage disease type III (GSDIII) is an autosomal recessive disorder characterized by a deficiency of glycogen debranching enzyme (GDE) leading to cytosolic glycogen accumulation and inducing liver and muscle pathology. Skin fibroblasts from three GSDIII patients were reprogrammed into induced pluripotent stem cells (iPSCs) using non-integrated Sendai virus. All of the three lines exhibited normal morphology, expression of pluripotent markers, stable karyotype, potential of trilineage differentiation and absence of GDE expression, making them valuable tools for modeling GSDIII disease in vitro, studying pathological mechanisms and investigating potential treatments.

Glycogen storage disease type IX (GSD-IX) constitutes nearly a quarter of all GSDs. This ketotic form of GSD is caused by mutations in phosphorylase kinase (PhK), which is composed of four subunits (α, β, γ, δ). PhK is required for the activation of the liver isoform of glycogen phosphorylase (PYGL), which generates free glucose-1-phosphate monomers to be used as energy via cleavage of the α -(1,4) glycosidic linkages in glycogen chains. Mutations in any of the PhK subunits can negatively affect the regulatory and catalytic activity of PhK during glycogenolysis. To understand the pathogenesis of GSD-IX-beta, we characterized a newly created PHKB knockout (Phkb−/−) mouse model. In this study, we assessed fasting blood glucose and ketone levels, serum metabolite concentrations, glycogen phosphorylase activity, and gene expression of gluconeogenic genes and fibrotic genes. Phkb−/− mice displayed hepatomegaly with lower fasting blood glucose concentrations. Phkb−/− mice showed partial liver glycogen phosphorylase activity and increased sensitivity to pyruvate, indicative of partial glycogenolytic activity and upregulation of gluconeogenesis. Additionally, gene expression analysis demonstrated increased lipid metabolism in Phkb−/− mice. Gene expression analysis and liver histology in the livers of old Phkb−/− mice (>40 weeks) showed minimal profibrogenic features when analyzed with age-matched wild-type (WT) mice. Collectively, the Phkb−/− mouse recapitulates mild clinical features in patients with GSD-IX-beta. Metabolic and molecular analysis confirmed that Phkb−/− mice were capable of sustaining energy homeostasis during prolonged fasting by using partial glycogenolysis, increased gluconeogenesis, and potentially fatty acid oxidation in the liver.

Glycogen storage disease type 1a (GSD1a) is caused by a congenital deficiency of glucose-6-phosphatase-α (G6Pase-α, encoded by G6PC), which is primarily associated with life-threatening hypoglycemia. Although strict dietary management substantially improves life expectancy, patients still experience intermittent hypoglycemia and develop hepatic complications. Emerging therapies utilizing new modalities such as adeno-associated virus and mRNA with lipid nanoparticles are under development for GSD1a but potentially require complicated glycemic management throughout life. Here, we present an oligonucleotide-based therapy to produce intact G6Pase-α from a pathogenic human variant, G6PC c.648G>T, the most prevalent variant in East Asia causing aberrant splicing of G6PC. DS-4108b, a splice-switching oligonucleotide, was designed to correct this aberrant splicing, especially in liver. We generated a mouse strain with homozygous knockin of this variant that well reflected the pathophysiology of patients with GSD1a. DS-4108b recovered hepatic G6Pase activity through splicing correction and prevented hypoglycemia and various hepatic abnormalities in the mice. Moreover, DS-4108b had long-lasting efficacy of more than 12 weeks in mice that received a single dose and had favorable pharmacokinetics and tolerability in mice and monkeys. These findings together indicate that this oligonucleotide-based therapy could provide a sustainable and curative therapeutic option under easy disease management for GSD1a patients with G6PC c.648G>T.

A life-long dietary intervention can affect the substrates' availability for gut fermentation in metabolic diseases such as the glycogen-storage diseases (GSD). Besides drug consumption, the main treatment of types GSD-Ia and Ib to prevent metabolic complications is a specific diet with definite nutrient intakes. In order to evaluate how deeply this dietary treatment affects gut bacteria, we compared the gut microbiota of nine GSD-I subjects and 12 healthy controls (HC) through 16S rRNA gene sequencing; we assessed their dietary intake and nutrients, their microbial short chain fatty acids (SCFAs) via gas chromatography and their hematic values. Both alpha-diversity and phylogenetic analysis revealed a significant biodiversity reduction in the GSD group compared to the HC group, and highlighted profound differences of their gut microbiota. GSD subjects were characterized by an increase in the relative abundance of Enterobacteriaceae and Veillonellaceae families, while the beneficial genera Faecalibacterium and Oscillospira were significantly reduced. SCFA quantification revealed a significant increase of fecal acetate and propionate in GSD subjects, but with a beneficial role probably reduced due to unbalanced bacterial interactions; nutritional values correlated to bacterial genera were significantly different between experimental groups, with nearly opposite cohort trends.

Carbohydrate Response Element Binding Protein (ChREBP) is a glucose 6-phosphate (G6P)-sensitive transcription factor that acts as a metabolic switch to maintain intracellular glucose and phosphate homeostasis. Hepatic ChREBP is well-known for its regulatory role in glycolysis, the pentose phosphate pathway, and de novo lipogenesis. The physiological role of ChREBP in hepatic glycogen metabolism and blood glucose regulation has not been assessed in detail, and ChREBP's contribution to carbohydrate flux adaptations in hepatic Glycogen Storage Disease type 1 (GSD I) requires further investigation.

Glycogen storage disease type-1a is an inherited, autosomal recessive disorder caused by mutations in G6PC1 gene leading to deficiency of glucose-6-phosphatase-α specifically in the liver/kidney/intestine.

To study heterogeneity between patients with glycogen storage disease type Ia (GSD Ia), a rare inherited disorder of carbohydrate metabolism caused by the deficiency of glucose-6-phosphatase (G6Pase).

Glycogen storage disease type Ia (GSD-Ia), deficient in glucose-6-phosphatase-α (G6PC), is characterized by impaired glucose homeostasis and a hallmark of fasting hypoglycemia. We have developed a recombinant adeno-associated virus (rAAV) vector-mediated gene therapy for GSD-Ia that is currently in a phase I/II clinical trial. While therapeutic expression of the episomal rAAV-G6PC clinical vector is stable in mice, the long-term durability of expression in humans is currently being established. Here we evaluated CRISPR/Cas9-based in vivo genome editing technology to correct a prevalent pathogenic human variant, G6PC-p.R83C. We have generated a homozygous G6pc-R83C mouse strain and shown that the G6pc-R83C mice manifest impaired glucose homeostasis and frequent hypoglycemic seizures, mimicking the pathophysiology of GSD-Ia patients. We then used a CRISPR/Cas9-based gene editing system to treat newborn G6pc-R83C mice and showed that the treated mice grew normally to age 16 weeks without hypoglycemia seizures. The treated G6pc-R83C mice, expressing ≥ 3% of normal hepatic G6Pase-α activity, maintained glucose homeostasis, displayed normalized blood metabolites, and could sustain 24 h of fasting. Taken together, we have developed a second-generation therapy in which in vivo correction of a pathogenic G6PC-p.R83C variant in its native genetic locus could lead to potentially permanent, durable, long-term correction of the GSD-Ia phenotype.

Glycogen storage disease type 1a (GSD1a) is an autosomal recessive disorder caused by mutations of the glucose-6-phosphatase (G6PC) gene. Mutations of the G6PC gene lead to excessive accumulation of glycogen in the liver, kidney, and intestinal mucosa due to the deficiency of microsomal glucose-6-phosphatase. Human induced pluripotent stem cells (iPSCs) enable the production of patient-derived hepatocytes in culture and are therefore a promising tool for modeling GSD1a. Here, we report the establishment of human iPSCs from a GSD1a patient carrying a G6PC mutation (c.648G > T; p.Leu216 = ).

Most patients affected by glycogen storage disease type 1a (GSD1a), an inherited metabolic disorder caused by mutations in the enzyme glucose-6-phosphatase-α (G6Pase-α), develop renal and liver complications, including the development of hepatocellular adenoma/carcinoma. The purpose of this study was to identify potential biomarkers of the pathophysiology of the GSD1a-affected liver. To this end, we used the plasma exosomes of a murine model of GSD1a, the LS-G6pc-/- mouse, to uncover the modulation in microRNA expression associated with the disease. The microRNAs differentially expressed between LS-G6pc-/- and wild-type mice, LS-G6pc-/- mice with hepatocellular adenoma and LS-G6pc-/- mice without adenoma, and LS-G6pc-/- mice with amyloidosis and LS-G6pc-/- mice without amyloidosis were identified. Pathway analysis demonstrated that the target genes of the differentially expressed microRNA were significantly enriched for the insulin signaling pathway, glucose and lipid metabolism, Wnt/β-catenin, telomere maintenance and hepatocellular carcinoma, and chemokine and immune regulation signaling pathways. Although some microRNAs were common to the different pathologic conditions, others were unique to the cancerous or inflammatory status of the animals. Therefore, the altered expression of several microRNAs is correlated with various pathologic liver states and might help to distinguish them during the progression of the disease and the development of late GSD1a-associated complications.

Glycogen-storage diseases type I (GSD type I) are due to a deficiency in glucose-6-phosphatase, an enzymatic system present in the endoplasmic reticulum that plays a crucial role in blood glucose homeostasis. Unlike GSD type Ia, types Ib and Ic are not due to mutations in the phosphohydrolase gene and are clinically characterized by the presence of associated neutropenia and neutrophil dysfunction. Biochemical evidence indicates the presence of a defect in glucose-6-phosphate (GSD type Ib) or inorganic phosphate (Pi) (GSD type Ic) transport in the microsomes. We have recently cloned a cDNA encoding a putative glucose-6-phosphate translocase. We have now localized the corresponding gene on chromosome 11q23, the region where GSD types Ib and Ic have been mapped. Using SSCP analysis and sequencing, we have screened this gene, for mutations in genomic DNA, from patients from 22 different families who have GSD types Ib and Ic. Of 20 mutations found, 11 result in truncated proteins that are probably nonfunctional. Most other mutations result in substitutions of conserved or semiconserved residues. The two most common mutations (Gly339Cys and 1211-1212 delCT) together constitute approximately 40% of the disease alleles. The fact that the same mutations are found in GSD types Ib and Ic could indicate either that Pi and glucose-6-phosphate are transported in microsomes by the same transporter or that the biochemical assays used to differentiate Pi and glucose-6-phosphate transport defects are not reliable.

Pompe disease (type II glycogen storage disease) is an autosomal recessive disorder caused by a deficiency of lysosomal acid alpha-glucosidase (GAA) leading to the accumulation of glycogen in the lysosomes primarily in cardiac and skeletal muscle. The recombinant human GAA (rhGAA) is currently in clinical trials for enzyme replacement therapy of Pompe disease. Both clinical data and the results of preclinical studies in our knockout model of this disease show that rhGAA is much more effective in resolving the cardiomyopathy than the skeletal muscle myopathy. By contrast, another form of human GAA--transgenic enzyme constitutively produced in liver and secreted into the bloodstream of knockout mice (Gaa-/-)--completely prevented both cardiac and skeletal muscle glycogen accumulation. In the experiments reported here, the transgenic enzyme was much less efficient when delivered to skeletal muscle after significant amounts of glycogen had already accumulated. Furthermore, the transgenic enzyme and the rhGAA have similar therapeutic effects, and both efficiently clear glycogen from cardiac muscle and type I muscle fibers, but not type II fibers. Low abundance of proteins involved in endocytosis and trafficking of lysosomal enzymes combined with increased autophagy in type II fibers may explain the resistance to therapy.

Niemann-Pick type C (NPC) disease is an autosomal recessive lysosomal storage disease that is caused by a mutation of the NPC1 or NPC2 gene, in which un-esterified cholesterol and sphingolipids accumulate mainly in the liver, spleen, and brain. Abnormal lysosomal storage leads to cell damage, neurological problems, and premature death. The time of onset and severity of symptoms of NPC disease are highly variable. The molecular mechanisms that are responsible for NPC disease pathology are far from being understood. The present study generated and characterized a zebrafish mutant that lacks Npc2 protein that may be useful for studies at the organismal, cellular, and molecular levels and both small-scale and high-throughput screens. Using CRISPR/Cas9 technology, we knocked out the zebrafish homolog of NPC2. Five-day-old npc2 mutants were morphologically indistinguishable from wildtype larvae. We found that live npc2-/- larvae exhibited stronger Nile blue staining. The npc2-/- larvae exhibited low mobility and a high anxiety-related response. These behavioral changes correlated with downregulation of the mcu (mitochondrial calcium uniporter) gene, ppp3ca (calcineurin) gene, and genes that are involved in myelination (mbp and mpz). Histological analysis of adult npc2-/- zebrafish revealed that pathological changes in the nervous system, kidney, liver, and pancreas correlated with inflammatory responses (i.e., the upregulation of il1, nfκβ, and mpeg; i.e., hallmarks of NPC disease). These findings suggest that the npc2 mutant zebrafish may be a model of NPC disease.