RARE DISEASE
Glycogen storage disease due to glucose-6-phosphatase deficiency
Glycogen storage disease due to glucose-6-phosphatase deficiency
Glycogen storage disease due to glucose-6-phosphatase deficiency
Synonyms: G6P deficiency, GSD due to G6P deficiency, GSD type 1, GSD type I, Glycogen storage disease due to G6P deficiency, Glycogen storage disease type 1, Glycogen storage disease type I, Glycogenosis type 1, Glycogenosis type I, Hepatorenal glycogenosis, Von Gierke disease
Synonyms: G6P deficiency, GSD due to G6P deficiency, GSD type 1, GSD type I, Glycogen storage disease due to G6P deficiency, Glycogen storage disease type 1, Glycogen storage disease type I, Glycogenosis type 1, Glycogenosis type I, Hepatorenal glycogenosis, Von Gierke disease
Synonyms: G6P deficiency, GSD due to G6P deficiency, GSD type 1, GSD type I, Glycogen storage disease due to G6P deficiency, Glycogen storage disease type 1, Glycogen storage disease type I, Glycogenosis type 1, Glycogenosis type I, Hepatorenal glycogenosis, Von Gierke disease
Drug discovery
3
drugs
With orphan designations
Overview
Glycogen storage disease due to glucose-6-phosphatase deficiency (GSDI) is an autosomal recessive disorder caused by defects in the glucose-6-phosphatase system, impairing glucose homeostasis. It includes subtypes Ia (G6PC gene mutations, 80% of cases) and Ib (SLC37A4 gene mutations, 20%) [1][6][12]. Clinical features include fasting hypoglycemia, hepatomegaly, hyperlipidemia, hyperuricemia, and growth retardation [1][12]. Long-term complications involve hepatic adenomas, renal disease, and metabolic sequelae [4][20].
Burden
Chronic risks: Hepatic adenomas (15–75% of patients), progressive renal insufficiency, and osteoporosis [4][20].
Psychosocial impact: Lifelong dietary vigilance, invasive monitoring, and anxiety related to hypoglycemia [4][9].
Economic burden: High healthcare utilization for metabolic crises, organ surveillance, and transplant management [9].
Therapies
Dietary management: Frequent feedings, uncooked cornstarch, and nocturnal enteral feeding to maintain normoglycemia [3][4][13].
Pharmacotherapy: Allopurinol (hyperuricemia), lipid-lowering agents, ACE inhibitors (renal protection), and G-CSF (for GSDIb neutropenia) [6][13][20].
Transplantation: Liver and/or kidney transplantation for severe metabolic complications or malignancies [4][6].
Categories: rare genetic diseases, rare hepatic diseases, rare inborn errors of metabolism, rare renal diseases, rare transplant-related disorders
Research Papers
418 drug discovery papers about Glycogen storage disease due to glucose-6-phosphatase deficiency, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
418 drug discovery papers about Glycogen storage disease due to glucose-6-phosphatase deficiency, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
cell therapies
2023-03-14 | Outcome of liver transplantation in hepatic glycogen storage disease: A systematic review and meta-analysis.
Liver transplantation (LT) is the choice of therapeutic option for end-stage hepatic GSD patients; however, reports about the long-term outcome of LT in these patients have remained controversial. We performed a systematic review and meta-analysis of observational studies published until Dec 31, 2021, that investigated the long-term outcome of LT in hepatic GSD patients. A literature search in the MEDLINE/PubMed, EMBASE,Cochrane Library, Scopus and Web of Science Core Collection databases was performed. 14 studies with 210 patients were included in our analysis. As the results showed, the pooled proportion of GSD patients with complications after liver transplant (e.g., hemorrhagic shock, biliary complications, tacrolimus encephalopathy, chronic hepatitis, hepatic artery thrombosis, hepatic adenoma, sepsis, liver dysfunction, chronic rejection, acute cellular rejection, and CMV infection) was 27.7% (95% CI: 20.42-35.67) without heterogeneity (I2 = 24.04%), as calculated by the random-effect model. The pooled proportion of GSD patients with complications related to GSD after LT, including HCC (Hepatocellular carcinoma), renal complication, muscle problems, delayed menarche, persistent neutropenia, pneumonitis, renal failure, and hepatic adenoma was 22.2% (95% CI: 7.97-40.01) with high heterogeneity (I2 = 82.47%). Subgroup analysis including the age of patients (adult/pediatric), duration of follow-up, and type of donor was conducted to investigate the resources of heterogeneity. According to our investigation and review analysis, most GSD patients showed significant outcome improvement after liver transplantation. Overall, our findings showed an excellent outcome of liver transplantation in GSD patients; however, it needs further investigations to be confirmed.
2014-11-04 | Biodistribution of adult derived human liver stem cells following intraportal infusion in a 17-year-old patient with glycogenosis type 1A.
Current treatment of inherited liver inborn errors of metabolism in children consists in appropriate diet and drugs and, for unstable patients, final orthotopic liver transplantation. Unfortunately, liver transplantation remains not easily available because of organ shortage and imposes inherent risks and lifelong immunosuppressive therapy. Therefore alternative treatments are required. Hepatocytes transplantation and its limitations led to consider innovative alternative such as transplantation of adult derived human liver stem cells (ADLHSC). These cells present high proliferative capacity, good resistance to cryopreservation and ability to differentiate into hepatocyte-like cells displaying mature hepatocyte functions. Biodistribution of ADHLSC had never been assessed after infusion through the portal vein in patients. This information is required to determine the safety of the method. ADHLSC were efficiently labelled with 111-Indium DTPA radiotracer and SPECT imaging was used for the acquisition of whole body imaging to document short term biodistribution of ADHLSC. Following infusion through the portal vein, ADHLSC diffused homogenously throughout the liver and remained strictly within the targeted organ. Images were acquired until 5 days after infusion. At that time, no signal was observed in any other organs except the liver. Urinary excretion of 111-Indium DTPA was also monitored. For the first time, we documented the short term biodistribution of ADHLSC within the liver after infusion through the portal vein.
2014-04-09 | Liver transplantation in glycogen storage disease type I
Glycogen storage disease type I (GSDI), an inborn error of carbohydrate metabolism, is caused by defects in the glucose-6-transporter/glucose-6-phosphatase complex, which is essential in glucose homeostasis. Two types exist, GSDIa and GSDIb, each caused by different defects in the complex. GSDIa is characterized by fasting intolerance and subsequent metabolic derangements. In addition to these clinical manifestations, patients with GSDIb suffer from neutropenia with neutrophil dysfunction and inflammatory bowel disease. With the feasibility of novel cell-based therapies, including hepatocyte transplantations and liver stem cell transplantations, it is essential to consider long term outcomes of liver replacement therapy. We reviewed all GSDI patients with liver transplantation identified in literature and through personal communication with treating physicians. Our review shows that all 80 GSDI patients showed improved metabolic control and normal fasting tolerance after liver transplantation. Although some complications might be caused by disease progression, most complications seemed related to the liver transplantation procedure and subsequent immune suppression. These results highlight the potential of other therapeutic strategies, like cell-based therapies for liver replacement, which are expected to normalize liver function with a lower risk of complications of the procedure and immune suppression.
2014-03-25 | Treating inborn errors of liver metabolism with stem cells: current clinical development
Abstract Advanced therapies including stem cells are currently a major biotechnological development. Adult liver stem cells can differentiate into hepatocyte like cells and be infused in the recipient's liver to bring a missing metabolic function. These cells can be produced in large quantities in vitro. Allogeneic stem cells are required to treat genetic diseases, and this approach allows to use one single source of tissue to treat different diseases and many recipients. Mesenchymal stem cells can in addition play an immunomodulatory and anti‐inflammatory role and possibly prevent the accumulation of fibrous tissue in the liver. From a regulatory point of view, stem cells are considered as medicinal products, and must undergo a pharmaceutical development that goes beyond the research and proof‐of‐concept phases. Here, we review the track followed from the first hepatocyte transplantation in 2000 to the next generation product issued from stem cell technology, and the start of EMA approved clinical trials to evaluate the safety and potency of liver stem cells for the treatment of inborn errors of the liver metabolism.
2013-09-06 | Clinical outcome of hepatocyte transplantation in four pediatric patients with inherited metabolic diseases.
Hepatocyte transplantation (HT) has become an effective therapy for patients with metabolic inborn errors. We report the clinical outcome of four children with metabolic inborn errors that underwent HT, describing the cell infusion protocol and the metabolic outcome of transplanted patients. Cryopreserved hepatocytes were used as this allows scheduling of treatments. Functional competence (viability, cell attachment, major cytochrome P450 and UDP-glucuronosyltransferase 1A1 activities, and urea synthesis) and microbiological safety of cell batches were assessed prior to clinical use. Four pediatric patients with liver metabolic diseases [ornithine transcarbamylase (OTC) deficiency, Crigler-Najjar (CNI) syndrome, glycogen storage disease Ia (GSD-Ia), and tyrosinemia type I (TYR-I)] underwent HT. Indication for HT was based on severity of disease, deterioration of quality of life, and benefits for the patients, with the ultimate goal to improve their clinical status whenever liver transplantation (LT) was not indicated or to bridge LT. Cells were infused into the portal vein while monitoring portal flow. The protocol included antibiotic prophylaxis and immunosuppressant therapy. After HT, analytical data on the disease were obtained. The OTC-deficient patient showed a sustained decrease in plasma ammonia levels and increased urea production after HT. Further cell infusions could not be administered given a fatal nosocomial fungus sepsis 2 weeks after the last HT. The CNI and GSD-Ia patients improved their clinical status after HT. They displayed reduced serum bilirubin levels (by ca. 50%) and absence of hypoglycaemic episodes, respectively. In both cases, the HT contributed to stabilize their clinical status as LT was not indicated. In the infant with TYR-I, HT stabilized temporarily the biochemical parameters, resulting in the amelioration of his clinical status while diagnosis of the disease was unequivocally confirmed by full gene sequencing. In this patient, HT served as a bridge therapy to LT.
proteins
2026-07-28 | Sequence determinants of pathogenicity in glucose-6-phosphatase linked to glycogen storage disease type 1a
Glycogen storage disease type 1a (GSD1a) is an autosomal recessive Mendelian disorder that can be caused by missense variants in glucose-6-phosphatase catalytic subunit 1 (G6PC1). Although hundreds of missense variants have been identified, the vast majority are of unknown clinical significance, and the molecular mechanism(s) of bona fide pathogenic variants are ill-defined. We combine bioinformatic data and clinical associations with the protein language model AlphaMissense to guide mechanistic exploration of 78 missense variants at 55 residue positions using robust biochemical and biophysical assays to distill general principles of enzyme dysfunction. Correlation analysis established a strong linear relationship between folded G6PC1 abundance and catalytic capacity for most variants. Pathogenic variants within this paradigm were linked to compromised stability and activation of the unfolded protein response. However, outliers characterized by relatively high abundance, yet low activity clustered to a network of sidechains adjacent to the active site that allosterically modulate catalysis. Contextualized by recent high-resolution structures and AlphaFold modeling, our holistic analysis of G6PC1 in vitro metrics facilitates clinical (re)classification of variants according to explicit molecular phenotypes and identifies therapeutic design directions. Moreover, our approach illustrates a blueprint for variant characterization that integrates computational prediction with experimental validation to discover disease etiology.
2026-07-28 | Structural basis for substrate recognition and inhibition of human glucose-6-phosphate transporter SLC37A4.
Glucose 6 phosphate (G6P) homeostasis is essential for maintaining blood glucose levels and coordinating anabolic and catabolic pathways. A key step in this process is the delivery of G6P into the endoplasmic reticulum (ER), where it is hydrolyzed by glucose 6 phosphatase to glucose and inorganic phosphate (Pi). This transport step is carried out by the ER carrier SLC37A4 (also known as the G6P transporter, G6PT), which imports G6P into the ER lumen while exporting Pi to the cytosol, and loss-of-function mutations in SLC37A4 cause glycogen storage disease type Ib. Despite its central role in G6P homeostasis, how SLC37A4 recognizes G6P and couples its transport to Pi antiport has remained unclear. Here we report cryo-electron microscopy structures of human SLC37A4 in three states: the apo form at 2.8 Å resolution, a G6P-bound state at 3.2 Å resolution and a chlorogenic acid (CHA) bound state at 3.3 Å resolution. SLC37A4 adopts the canonical Major Facilitator Superfamily fold and harbors a central, positively charged cavity that accommodates anionic substrates. In the G6P-bound structure, SLC37A4 adopts an outward-open conformation facing the ER lumen, in which G6P binds to the electropositive pocket. In the CHA-bound structure, SLC37A4 adopts an inward-facing conformation, with CHA bound at a cytosolic site that locks the transporter in an arrested state and prevents the conformational transitions required for G6P/Pi exchange. Combined with thermostability and transport-based analyses of G6P binding and disease variants, these structures support a rocker switch mechanism in which electrostatic neutralization of the central positively charged cavity by anionic substrate drives the conformational changes underlying G6P/Pi exchange. Together, these findings define the structural basis of G6P/Pi exchange by SLC37A4, provide a molecular rationale for pathogenic mutations in glycogen storage disease type Ib, and provide a framework for targeting SLC37A4 to modulate G6P homeostasis.
2025-11-13 | Structural basis of G6P/Pi transport and inhibition in SLC37A4.
Glycogen storage disease type Ib (GSD-Ib), caused by loss-of-function mutations in the endoplasmic reticulum transporter SLC37A4, disrupts glucose homeostasis through impaired glucose-6-phosphate (G6P)/phosphate (Pi) antiport. Despite its central role in glycogen metabolism and immune regulation, the structural mechanisms governing SLC37A4's transport cycle and pathological dysfunction remain elusive. Here we report cryo-electron microscopy structures of human SLC37A4 in four functional states, capturing conformational transitions between lumen-facing and cytoplasm-facing states. Combined with mutational analysis, molecular dynamics simulations and functional assays, we identify a conserved substrate-binding pocket that alternately accommodates G6P and Pi through electrostatic complementarity and domain-dependent interactions. We further demonstrate that the high-affinity inhibitor S-4048 sterically occludes the cytoplasmic entry pathway by trapping the transporter in a cytoplasm-facing conformation. Our work elucidates the molecular pathology of GSD-Ib-linked mutations and provides a structural framework for developing therapies targeting this transporter in metabolic diseases.
2025-07-17 | Human glycogenins maintain glucose homeostasis by regulating glycogen metabolism.
Proper regulation of glycogen metabolism is fundamental to cellular energy homeostasis, and its disruption is associated with various metabolic disorders, including glycogen storage diseases (GSDs) and potentially diabetes. Despite glycogen's role as an essential energy reservoir, the mechanisms governing its synthesis and structural diversity across tissues remain unclear. Here, we uncover the distinct physiological roles of the human glycogenins GYG1 and GYG2 in glycogen synthesis. Through cellular models, structural biology, and biochemical analyses, we demonstrate that, unlike GYG1, GYG2 exhibits minimal autoglycosylation activity and acts as a suppressor of glycogen formation. Together, these two glycogenins coordinate glycogen synthase activity and influence glycogen assembly in a cell-type-dependent manner. Importantly, these glycogenins modulate glucose metabolic pathways, thereby ensuring cellular glucose homeostasis. These findings address longstanding questions in glycogen metabolism and establish both GYG1 and GYG2 as critical regulators of glycogen synthesis and breakdown in human, providing insights with potential therapeutic implications for treating GSDs and metabolic diseases.
2023-05-26 | Glycogen Storage Disease Type I: Prognostic Factors and Treatment
Glycogen storage disease type I (GSD I) is an inherited disorder that hinders theability of the liver to effectively break down stored glycogen, leading to difficulties inmaintaining appropriate blood sugar levels. The main treatment for this aspect ofGSD I involves the use of filgrastim, although patients often require additionaltreatment for recurrent infections, and an enlarged spleen is a common side effect.Acute lactic acidosis, which can cause respiratory distress and ketoacidosis innewborns, can be triggered by minor illnesses and accompanied by severehypoglycemia. Early diagnosis and prompt initiation of appropriate metabolictreatment are crucial in preventing the devastating effects of this condition. Theoverall prognosis and long-term efficacy of treatment are influenced by variousfactors, including the timing of diagnosis, adherence to dietary protocols, andavailability of appropriate medical interventions.
small molecules
2026-08-14 | Empagliflozin in GSD-Ib: Long-term safety and sustained recovery of neutrophil function including NET formation.
Glycogen storage disease type Ib (GSD-Ib) engenders neutropenia and severe neutrophil dysfunction, leading to recurrent infections and inflammatory complications. Recent studies have identified intracellular accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P) as a key mechanism underlying neutrophil impairment and have suggested therapeutic benefits of sodium-glucose cotransporter 2 (SGLT2) inhibitors, which lower plasma levels of its precursor 1,5-AG. In this study, we performed a four-year longitudinal evaluation of empagliflozin therapy in a genetically confirmed GSD-Ib infant, contributing to the growing body of long-term data on empagliflozin treatment in GSD-Ib. Routine laboratory parameters and key neutrophil effector functions were assessed before and during treatment, as well as in two additional GSD-Ib patients with and without therapy. Empagliflozin therapy resulted in complete restoration of neutrophil function, including reactive oxygen species (ROS) production and bactericidal activity. Notably, neutrophil extracellular trap (NET) formation and neutrophil survival recovered to levels comparable to healthy donors. These functional improvements occurred in conjunction with reduced plasma 1,5-AG levels, supporting the concept that GSD-Ib neutrophils are sensitive to physiological 1,5-AG concentrations. Functional recovery and normalization of neutrophil survival observed in vitro, was paralleled by improvement of absolute neutrophil counts to low-normal levels in vivo. Clinically, treatment was associated with a substantial reduction of severe infections. Collectively, these findings further support that empagliflozin corrects neutrophil dysfunction in GSD-Ib and demonstrate its potential to improve long-term clinical outcome across the lifespan, from infancy through adulthood.
2026-06-07 | Continuous glucose monitoring shows limited impact of daytime cornstarch on glycemia in glycogen storage disease type I.
Glycogen storage disease type I (GSD I) is characterized by impaired endogenous glucose production, leading to fasting hypoglycemia and multiple metabolic complications. Cornstarch supplementation is a cornerstone of dietary management, primarily to prevent fasting hypoglycemia. However, its role in modulating daytime postprandial glycemia in adults remains unclear. This study aimed to evaluate the impact of mealtime cornstarch supplementation on postprandial glucose dynamics in adults with GSD I under real-life conditions. In this cross-sectional observational study, 10 consecutive adults with genetically confirmed GSD I underwent a 7-day dietary assessment and continuous glucose monitoring (CGM). Meals were classified according to the presence or absence of cornstarch supplementation (Starch and noStarch meals). Postprandial glucose responses were analyzed over a 240-min observation window using dynamic CGM-derived metrics, including peak, nadir, time to peak, time to nadir, and incremental area under the curve (iAUC). A total of 102 meals (60 noStarch, 42 Starch) allowed for the 4-h analysis. No significant differences were observed between Starch and noStarch meals in overall 4-h glucose profiles (p = 0.209), iAUC (p = 0.234), peak and nadir glucose levels, or dynamic indices (p always >0.05). Postprandial hypoglycemia was infrequent, with only 14 events <70 mg/dL and a single event <54 mg/dL. Results remained consistent after adjustment for daily starch intake and subject-level effects. In adults with GSD I and stable metabolic control, mealtime cornstarch supplementation does not significantly modify postprandial glucose dynamics over 4 h. These findings support individualized, CGM-guided strategies to optimize cornstarch use.
2026-05-04 | Shifting Towards Empagliflozin First-Line Therapy in Glycogen Storage Disease Type Ib: A Nationwide Real-World Study.
Neutrophil dysfunction and neutropenia are burdensome findings in glycogen storage disease type Ib (GSDIb). Treatment with granulocyte-colony stimulating factor (G-CSF) often corrects neutropenia but fails to improve clinical symptoms like inflammatory bowel disease (IBD). Recently, empagliflozin (EMPA) was shown to correct the neutrophil dysfunction and its clinical consequences. It is increasingly used as first-line monotherapy, but long-term, real-world data are lacking. This nation-wide retrospective study investigated 42 GSD1b patients (36 children) treated with EMPA as first-line monotherapy and compared them with those receiving combination therapy with G-CSF and treatment-naïve patients (I:EMPA first-line monotherapy [n = 9]; II:G-CSF monotherapy [n = 7]; III:EMPA plus G-CSF [n = 16]; and IV: neither EMPA nor GCSF [n = 10]). Pediatric (P) patients were evaluated separately. In pediatric patients receiving EMPA as first-line monotherapy (P-I) and those with EMPA plus G-CSF (P-III), the frequency of infections, hospital admissions, and IBD was significantly lower than in patients receiving GCSF-monotherapy (P-II) or no treatment (P-IV). Additionally, significantly improved weight gain was observed in P-I. While clinical improvement related to correction of neutrophil dysfunction was seen with EMPA first-line monotherapy (P-I), significant improvement in absolute neutrophil count (ANC) and hemoglobin levels was only seen in P-III with additional G-CSF treatment. In three cases, EMPA was safely paused and subsequently resumed, for example, during pregnancy or liver transplantation. First-line EMPA monotherapy effectively corrects clinical symptoms of neutrophil dysfunction in GSD Ib patients, even in the absence of a statistically significant increase in ANC.
2026-04-14 | Effects of Extended-Release Cornstarch Supplementation on Glycemic Stability and Metabolic Parameters in Korean Patients with Glycogen Storage Disease.
Background/Objectives: Patients with hepatic glycogen storage disease (GSD) require frequent nighttime intake of uncooked corn starch (UCCS) to prevent fasting hypoglycemia, which imposes a substantial burden. Glycosade, an extended-release cornstarch, was developed to prolong overnight glucose availability. However, data regarding South Korean patients are limited. Therefore, we aimed to evaluate the efficacy and safety of Glycosade in South Korean patients with hepatic GSD. Methods: In this single-center prospective observational study, patients with hepatic GSD underwent laboratory evaluations before and 1 month after Glycosade administration. Continuous glucose monitoring (CGM) was performed during UCCS and Glycosade administration periods. The nocturnal mean glucose, coefficient of variation, time in range (70-180 mg/dL), and time below the range (<70 and <54 mg/dL) were compared between the periods using paired analyses. Results: No significant differences were observed in the nocturnal CGM metrics between the treatment periods. However, time-aligned CGM profiles revealed distinct temporal patterns, with a decline in glucose levels approximately 3-4 h after UCCS intake, whereas Glycosade showed a more sustained glucose profile over an extended period. Liver enzyme and lipid levels improved significantly after 1 month of Glycosade supplementation. Conclusions: In a cohort of South Korean patients with hepatic GSD, Glycosade maintained nocturnal glycemic stability comparable to that of conventional cornstarch without increasing the risk of hypoglycemia. Glycosade was also associated with improved biochemical parameters, supporting its role in nighttime dietary management.
2026-03-20 | Infantile extreme hypertriglyceridemia diagnosed as glycogen storage disease type Ia: A case report.
Glycogen storage disease type Ia (GSD Ia) typically presents with fasting hypoglycemia and hyperlipidemia. Atypical infantile presentations can delay diagnosis. We report an infant with extreme hypertriglyceridemia ultimately diagnosed as GSD Ia. A 5-month-old girl presented with poor appetite, growth retardation, hepatomegaly, and extreme hypertriglyceridemia (72 mmol/L), hypercholesterolemia, elevated transaminases, hyperuricemia, and hyperlactatemia, but initial normal blood glucose. Initial differentials included familial hypertriglyceridemia, but metabolic screening was normal. Whole-exome sequencing confirmed GSD Ia with compound heterozygous G6PC mutations (c.648G>T and c.814G>T). Initial lipid-lowering (low-fat diet, fenofibrate, omega-3, plasma exchange) reduced triglyceride. Post-diagnosis, she received lactose-free formula with frequent feeds and nocturnal nutrition; uncooked cornstarch was introduced at 6 months, though adherence was initially poor. Metabolic control was unstable until age 2 due to poor adherence. After 24 months of structured cornstarch therapy, fasting glucose normalized (4.2-6.6 mmol/L), triglycerides decreased (1.8-6.7 mmol/L), and catch-up growth occurred (height Z-score from -3.9 to -2.2 by 36 months). GSD Ia should be considered in infantile extreme hypertriglyceridemia with growth retardation, even without classic hypoglycemia. Sustained metabolic control requires multidisciplinary strategies addressing both biochemical and adherence barriers.
gene therapies
2026-07-23 | Base editing for precision therapeutics.
Base editing (BE), the precise installation of single-nucleotide changes in DNA or RNA without inducing double-strand breaks, holds substantial therapeutic promise for correcting single-nucleotide variants, which constitute more than half of the known pathogenic genetic variants. Recent advances have improved base editor specificity, efficiency, and delivery, enabling clinically oriented procedures. Clinically, BE has shown early success or strong translational promise in sickle cell disease, β-thalassemia, leukemia (via CAR T and epitope engineering), hypercholesterolemia (PCSK9 and ANGPTL3), alpha-1-antitrypsin deficiency, and glycogen storage disease type Ia. Key remaining challenges include bystander editing within the activity window, residual off-target DNA and RNA editing, delivery constraints (payload size, tissue targeting, and redosing limits), immunogenicity, and the need for durable long-term safety evidence across relevant cell types and disease contexts. Continued technological refinements, careful preclinical validation, and rigorous clinical assessment will be essential to fully realize BE's transformative potential in precision medicine.
2026-06-11 | Hepatocyte-specific Cas9-mediated editing of G6pc and Slc37a4 elicits comparable biochemical and regulatory responses between glycogen storage disease (GSD) type Ia and Ib mice.
Glycogen storage disease type I (GSD I) is an autosomal recessive inborn error of carbohydrate metabolism. Patients with GSD type Ia and Ib exhibit overlapping and distinct symptoms and complications. Notably, GSD Ia patients show more severe hypertriglyceridemia and higher risk of hepatic tumors than GSD Ib patients. Given the liver's pivotal role in these processes, this study utilized hepatocyte-specific CRISPR/Cas9-mediated somatic gene editing to explore the pathophysiological and biochemical adaptations in hepatic GSD Ia and Ib side-by-side. Additionally, hepatic histology, transcriptomics, and proteomics analysis was performed. Compared to controls, hepatic GSD Ia and Ib mice showed hepatomegaly, fasting hypoglycemia, hyperlactatemia, and increased uric acid in plasma, which was somewhat more pronounced in GSD Ia than Ib. Both GSD I subtypes showed similar reductions in hepatic acetyl-CoA precursor pool enrichment and increases in de novo biosynthesis of hepatic stearate and oleate. Interestingly, only GSD Ia mice showed mildly elevated plasma triglyceride and hepatic phosphate sugars. Metabolic changes were reflected at the transcriptomic and proteomic levels, with largely similar responses between GSD Ia and Ib livers. Moreover, altered mRNAs and protein levels related to nucleotide-binding oligomerization domain (NOD) signaling pathways, infection and inflammation, liver disease, and chemical carcinogenesis were somewhat more pronounced in hepatic GSD Ia than in GSD Ib mice. Overall, the metabolic disturbance was more severe in hepatocyte-specific GSD Ia than in GSD Ib mice, consistent with the clinical phenotype in patients. The metabolic disorders and specific metabolites, genes, and proteins identified in this study provided new insights into the pathophysiological and biochemical phenotypes of GSD I subtypes in the liver.
2025-08-05 | Efficacious genome editing in infant mice with glycogen storage disease type Ia.
Glycogen storage disease type Ia (GSD Ia) is caused by a deficiency of glucose-6-phosphatase (G6Pase) in the liver leading to lethal hypoglycemia. Gene therapy with adeno-associated virus (AAV) vectors encoding G6Pase fails to stably treat GSD Ia early in life. We evaluated genome editing in 12-day-old infant mice with GSD Ia using 2 AAV vectors, one containing Cas9 from Streptococcus pyogenes and a second Donor vector that expresses a guide RNA and a G6PC transgene. Gene therapy with the Donor vector only was compared with genome editing using both Donor and CRISPR vectors. Treatment with genome editing (total vector dose 0.2 × 1013 to 2 × 1013 vector genomes/kg) and bezafibrate (to stimulate autophagy) was efficacious, as assessed by hypoglycemia prevention and the frequency of transgene integration, which correlated with improved survival. This therapy achieved 5.9% chromosomal transgene integration through homology-directed repair, which surpassed a threshold to prevent long-term hepatic complications. No integration was detected in the absence of the CRISPR vector. Importantly for safety, CRISPR vector genomes were depleted, and no intact, integrated CRISPR genomes were detected by long-read sequencing. Thus, genome editing warrants further development as a potentially stable treatment for human infants with GSD Ia.
2024-04-17 | Base-editing corrects metabolic abnormalities in a humanized mouse model for glycogen storage disease type-Ia
Abstract Glycogen storage disease type-Ia (GSD-Ia) patients, deficient in glucose-6-phosphatase-α (G6Pase-α or G6PC), manifest impaired glucose homeostasis with hallmark fasting hypoglycemia. We generated a humanized knock-in mouse model, huR83C, that is homozygous for the pathogenic G6PC -R83C variant and manifests a GSD-Ia phenotype. We evaluated the efficacy of BEAM-301, lipid nanoparticles containing guide RNA and mRNA encoding a newly-engineered adenine base editor, to correct the G6PC -R83C variant in huR83C mice and monitored phenotypic correction through one year. BEAM-301-treated mice exhibited a maximum base-editing efficiency of ~60% in the liver and achieved physiologicallevels of hepatic G6Pase-α activity with just ~10% base-editing rate. The edited mice displayed an improved metabolic phenotype, sustained 24-hour fasting, and survived long-term. In contrast, untreated mice exhibited fasting hypoglycemia and died prematurely. The durable pharmacological efficacy of base editing in huR83C mice supports the development of BEAM-301 as a potential therapeutic for patients with GSD-Ia carrying the G6PC -R83C variant.
2023-11-22 | Hepatic ChREBP orchestrates intrahepatic carbohydrate metabolism to limit hepatic glucose 6-phosphate and glycogen accumulation in a mouse model for acute Glycogen Storage Disease type Ib
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. The current study aimed to investigate the role of ChREBP as a regulator of glycogen metabolism in response to hepatic G6P accumulation, using a model for acute hepatic GSD type Ib. The immediate biochemical and regulatory responses to hepatic G6P accumulation were evaluated upon G6P transporter inhibition by the chlorogenic acid S4048 in mice that were either treated with a short hairpin RNA (shRNA) directed against ChREBP (shChREBP) or a scrambled shRNA (shSCR). Complementary stable isotope experiments were performed to quantify hepatic carbohydrate fluxes in vivo. ShChREBP treatment normalized the S4048-mediated induction of hepatic ChREBP target genes to levels observed in vehicle- and shSCR-treated controls. In parallel, hepatic shChREBP treatment in S4048-infused mice resulted in a more pronounced accumulation of hepatic glycogen and further reduction of blood glucose levels compared to shSCR treatment. Hepatic ChREBP knockdown modestly increased glucokinase (GCK) flux in S4048-treated mice while it enhanced UDP-glucose turnover as well as glycogen synthase and phosphorylase fluxes. Hepatic GCK mRNA and protein levels were induced by shChREBP treatment in both vehicle- and S4048-treated mice, while glycogen synthase 2 (GYS2) and glycogen phosphorylase (PYGL) mRNA and protein levels were reduced. Finally, knockdown of hepatic ChREBP expression reduced starch domain binding protein 1 (STBD1) mRNA and protein levels while it inhibited acid alpha-glucosidase (GAA) activity, suggesting reduced capacity for lysosomal glycogen breakdown. Our data show that ChREBP activation controls hepatic glycogen and blood glucose levels in acute hepatic GSD Ib through concomitant regulation of glucose phosphorylation, glycogenesis, and glycogenolysis. ChREBP-mediated control of GCK enzyme levels aligns with corresponding adaptations in GCK flux. In contrast, ChREBP activation in response to acute hepatic GSD Ib exerts opposite effects on GYS2/PYGL enzyme levels and their corresponding fluxes, indicating that GYS2/PYGL expression levels are not limiting to their respective fluxes under these conditions.
other
2026-08-08 | ApoC-III Antisense Oligonucleotide Therapy Used in Glycogen Storage Disease Type 1a.
Glycogen storage disease type 1a (GSD1a) is an autosomal recessive disorder characterized by impaired glycogenolysis and gluconeogenesis. Individuals with GSD1a manifest significant hypertriglyceridemia refractory to dietary and lipid-lowering medication therapies. Apolipoprotein C-III antisense oligonucleotide (apoCIII-ASO) therapy is approved to reduce severe hypertriglyceridemia in familial chylomicronemia syndrome but is also effective in moderate hypertriglyceridemia of varied genetic backgrounds. We describe a 22-year-old with GSD1a and hypertriglyceridemia with past pancreatitis despite fibric acid derivative, niacin, and bempedoic acid therapy in whom apoCIII-ASO was associated with triglyceride reduction from 4,951 to 1,643 mg/dL. As GSD1a-associated hypertriglyceridemia is often refractory to standard therapies, apoCIII-ASO therapy may offer promise as a treatment. This case describes the first use of apoCIII-ASO in GSD1a-related hypertriglyceridemia. GSD1a-driven hypertriglyceridemia may be treatable using apoCIII-ASO.
2023-12-04 | A splice-switching oligonucleotide treatment ameliorates glycogen storage disease type 1a in mice with G6PC c.648G>T.
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.
2023-06-09 | Amnio acid substitution at position 298 of human glucose-6 phosphatase-α significantly impacts its stability in mammalian cells.
Glucose-6-phosphatase-α (G6Pase-α) catalyzes the hydrolysis of glucose-6-phosphate to glucose and functions as a key regulator in maintaining blood glucose homeostasis. Deficiency in G6Pase-α causes glycogen storage disease 1a (GSD1a), an inherited disorder characterized by life-threatening hypoglycemia and other long-term complications. We have developed a potential mRNA-based therapy for GSD1a and demonstrated that a human G6Pase-α (hG6Pase-α) variant harboring a single serine (S) to cysteine (C) substitution at the amino acid site 298 (S298C) had > twofold increase in protein expression, resulting in improved in vivo efficacy. Here, we sought to investigate the mechanisms contributing to the increased expression of the S298C variant. Mutagenesis of hG6Pase-α identified distinct protein variants at the 298 amino acid position with substantial reduction in protein expression in cultured cells. Kinetic analysis of expression and subcellular localization in mammalian cells, combined with cell-free in vitro translation assays, revealed that altered protein expression stemmed from differences in cellular protein stability rather than biosynthetic rates. Site-specific mutagenesis studies targeting other cysteines of the hG6Pase-α S298C variant suggest the observed improvements in stability are not due to additional disulfide bond formation. The glycosylation at Asparagine (N)-96 is critical in maintaining enzymatic activity and mutations at position 298 mainly affected glycosylated forms of hG6Pase-α. Finally, proteasome inhibition by lactacystin improved expression levels of unstable hG6Pase-α variants. Taken together, these data uncover a critical role for a single amino acid substitution impacting the stability of G6Pase-α and provide insights into the molecular genetics of GSD1a and protein engineering for therapeutic development.
2020-09-30 | Analyzing the Distribution of Mutations for Glycogen Storage Disease Type 1a in Turkey and Suggested Gene Therapy Methods for Its Treatment
One of the rare diseases throughout the world is Glycogen Storage Disease, which appears due to problems in glycogen metabolism. Among various subtypes of GSD, GSD Type 1a is the most abundant one of GSD Type 1, seen in approximately 80% and caused by different kinds of mutations in the Glucose-6-Phosphatase Catalytic Subunit (G6PC) gene in human chromosome 17q21. G6PC gene encodes for glucose-6-phosphatase (G6Pase) protein, which cleaves glucose-6-phosphate into glucose and inorganic phosphate (Pi), and GSD Type 1a patients fail to breakdown glucose-6-phosphate due to several mutations in the G6PC gene. In our study, we aim to create new therapeutic approaches for GSD 1a. We collected mutation data of 57 GSD Type 1a patients from Turkey. According to the data, 16 types of mutations were observed in the G6PC gene. Allele frequencies of these mutations are calculated as 59% for R83C/H, 11% for W160*, 7% for G270V, and 28% for others which have less frequency. Up to now, the tertiary protein structure of G6Pase has not been structured yet. To understand the possible impacts of these mutations, we statistically obtained possible tertiary structure predictions of G6Pase by running 5 different tools. At the end of the study, we suggest two effective and promising gene therapy methods for GSD Type 1a, Prime Editing for R83C/H mutations, and mRNA delivery for other mutations, in addition to a promising, commercially available drug suggestion for patients with W160*, W86*, and S15* mutations, although the drug belongs to another disease.
2019-06-26 | Inhibition of Glycogen Synthase II with RNAi Prevents Liver Injury in Mouse Models of Glycogen Storage Diseases.
Glycogen storage diseases (GSDs) of the liver are devastating disorders presenting with fasting hypoglycemia as well as hepatic glycogen and lipid accumulation, which could lead to long-term liver damage. Diet control is frequently utilized to manage the potentially dangerous hypoglycemia, but there is currently no effective pharmacological treatment for preventing hepatomegaly and concurrent liver metabolic abnormalities, which could lead to fibrosis, cirrhosis, and hepatocellular adenoma or carcinoma. In this study, we demonstrate that inhibition of glycogen synthesis using an RNAi approach to silence hepatic Gys2 expression effectively prevents glycogen synthesis, glycogen accumulation, hepatomegaly, fibrosis, and nodule development in a mouse model of GSD III. Mechanistically, reduction of accumulated abnormally structured glycogen prevents proliferation of hepatocytes and activation of myofibroblasts as well as infiltration of mononuclear cells. Additionally, we show that silencing Gys2 expression reduces hepatic steatosis in a mouse model of GSD type Ia, where we hypothesize that the reduction of glycogen also reduces the production of excess glucose-6-phosphate and its subsequent diversion to lipid synthesis. Our results support therapeutic silencing of GYS2 expression to prevent glycogen and lipid accumulation, which mediate initial signals that subsequently trigger cascades of long-term liver injury in GSDs.
cell therapies
2023-03-14 | Outcome of liver transplantation in hepatic glycogen storage disease: A systematic review and meta-analysis.
Liver transplantation (LT) is the choice of therapeutic option for end-stage hepatic GSD patients; however, reports about the long-term outcome of LT in these patients have remained controversial. We performed a systematic review and meta-analysis of observational studies published until Dec 31, 2021, that investigated the long-term outcome of LT in hepatic GSD patients. A literature search in the MEDLINE/PubMed, EMBASE,Cochrane Library, Scopus and Web of Science Core Collection databases was performed. 14 studies with 210 patients were included in our analysis. As the results showed, the pooled proportion of GSD patients with complications after liver transplant (e.g., hemorrhagic shock, biliary complications, tacrolimus encephalopathy, chronic hepatitis, hepatic artery thrombosis, hepatic adenoma, sepsis, liver dysfunction, chronic rejection, acute cellular rejection, and CMV infection) was 27.7% (95% CI: 20.42-35.67) without heterogeneity (I2 = 24.04%), as calculated by the random-effect model. The pooled proportion of GSD patients with complications related to GSD after LT, including HCC (Hepatocellular carcinoma), renal complication, muscle problems, delayed menarche, persistent neutropenia, pneumonitis, renal failure, and hepatic adenoma was 22.2% (95% CI: 7.97-40.01) with high heterogeneity (I2 = 82.47%). Subgroup analysis including the age of patients (adult/pediatric), duration of follow-up, and type of donor was conducted to investigate the resources of heterogeneity. According to our investigation and review analysis, most GSD patients showed significant outcome improvement after liver transplantation. Overall, our findings showed an excellent outcome of liver transplantation in GSD patients; however, it needs further investigations to be confirmed.
2014-11-04 | Biodistribution of adult derived human liver stem cells following intraportal infusion in a 17-year-old patient with glycogenosis type 1A.
Current treatment of inherited liver inborn errors of metabolism in children consists in appropriate diet and drugs and, for unstable patients, final orthotopic liver transplantation. Unfortunately, liver transplantation remains not easily available because of organ shortage and imposes inherent risks and lifelong immunosuppressive therapy. Therefore alternative treatments are required. Hepatocytes transplantation and its limitations led to consider innovative alternative such as transplantation of adult derived human liver stem cells (ADLHSC). These cells present high proliferative capacity, good resistance to cryopreservation and ability to differentiate into hepatocyte-like cells displaying mature hepatocyte functions. Biodistribution of ADHLSC had never been assessed after infusion through the portal vein in patients. This information is required to determine the safety of the method. ADHLSC were efficiently labelled with 111-Indium DTPA radiotracer and SPECT imaging was used for the acquisition of whole body imaging to document short term biodistribution of ADHLSC. Following infusion through the portal vein, ADHLSC diffused homogenously throughout the liver and remained strictly within the targeted organ. Images were acquired until 5 days after infusion. At that time, no signal was observed in any other organs except the liver. Urinary excretion of 111-Indium DTPA was also monitored. For the first time, we documented the short term biodistribution of ADHLSC within the liver after infusion through the portal vein.
2014-04-09 | Liver transplantation in glycogen storage disease type I
Glycogen storage disease type I (GSDI), an inborn error of carbohydrate metabolism, is caused by defects in the glucose-6-transporter/glucose-6-phosphatase complex, which is essential in glucose homeostasis. Two types exist, GSDIa and GSDIb, each caused by different defects in the complex. GSDIa is characterized by fasting intolerance and subsequent metabolic derangements. In addition to these clinical manifestations, patients with GSDIb suffer from neutropenia with neutrophil dysfunction and inflammatory bowel disease. With the feasibility of novel cell-based therapies, including hepatocyte transplantations and liver stem cell transplantations, it is essential to consider long term outcomes of liver replacement therapy. We reviewed all GSDI patients with liver transplantation identified in literature and through personal communication with treating physicians. Our review shows that all 80 GSDI patients showed improved metabolic control and normal fasting tolerance after liver transplantation. Although some complications might be caused by disease progression, most complications seemed related to the liver transplantation procedure and subsequent immune suppression. These results highlight the potential of other therapeutic strategies, like cell-based therapies for liver replacement, which are expected to normalize liver function with a lower risk of complications of the procedure and immune suppression.
2014-03-25 | Treating inborn errors of liver metabolism with stem cells: current clinical development
Abstract Advanced therapies including stem cells are currently a major biotechnological development. Adult liver stem cells can differentiate into hepatocyte like cells and be infused in the recipient's liver to bring a missing metabolic function. These cells can be produced in large quantities in vitro. Allogeneic stem cells are required to treat genetic diseases, and this approach allows to use one single source of tissue to treat different diseases and many recipients. Mesenchymal stem cells can in addition play an immunomodulatory and anti‐inflammatory role and possibly prevent the accumulation of fibrous tissue in the liver. From a regulatory point of view, stem cells are considered as medicinal products, and must undergo a pharmaceutical development that goes beyond the research and proof‐of‐concept phases. Here, we review the track followed from the first hepatocyte transplantation in 2000 to the next generation product issued from stem cell technology, and the start of EMA approved clinical trials to evaluate the safety and potency of liver stem cells for the treatment of inborn errors of the liver metabolism.
2013-09-06 | Clinical outcome of hepatocyte transplantation in four pediatric patients with inherited metabolic diseases.
Hepatocyte transplantation (HT) has become an effective therapy for patients with metabolic inborn errors. We report the clinical outcome of four children with metabolic inborn errors that underwent HT, describing the cell infusion protocol and the metabolic outcome of transplanted patients. Cryopreserved hepatocytes were used as this allows scheduling of treatments. Functional competence (viability, cell attachment, major cytochrome P450 and UDP-glucuronosyltransferase 1A1 activities, and urea synthesis) and microbiological safety of cell batches were assessed prior to clinical use. Four pediatric patients with liver metabolic diseases [ornithine transcarbamylase (OTC) deficiency, Crigler-Najjar (CNI) syndrome, glycogen storage disease Ia (GSD-Ia), and tyrosinemia type I (TYR-I)] underwent HT. Indication for HT was based on severity of disease, deterioration of quality of life, and benefits for the patients, with the ultimate goal to improve their clinical status whenever liver transplantation (LT) was not indicated or to bridge LT. Cells were infused into the portal vein while monitoring portal flow. The protocol included antibiotic prophylaxis and immunosuppressant therapy. After HT, analytical data on the disease were obtained. The OTC-deficient patient showed a sustained decrease in plasma ammonia levels and increased urea production after HT. Further cell infusions could not be administered given a fatal nosocomial fungus sepsis 2 weeks after the last HT. The CNI and GSD-Ia patients improved their clinical status after HT. They displayed reduced serum bilirubin levels (by ca. 50%) and absence of hypoglycaemic episodes, respectively. In both cases, the HT contributed to stabilize their clinical status as LT was not indicated. In the infant with TYR-I, HT stabilized temporarily the biochemical parameters, resulting in the amelioration of his clinical status while diagnosis of the disease was unequivocally confirmed by full gene sequencing. In this patient, HT served as a bridge therapy to LT.
proteins
2026-07-28 | Sequence determinants of pathogenicity in glucose-6-phosphatase linked to glycogen storage disease type 1a
Glycogen storage disease type 1a (GSD1a) is an autosomal recessive Mendelian disorder that can be caused by missense variants in glucose-6-phosphatase catalytic subunit 1 (G6PC1). Although hundreds of missense variants have been identified, the vast majority are of unknown clinical significance, and the molecular mechanism(s) of bona fide pathogenic variants are ill-defined. We combine bioinformatic data and clinical associations with the protein language model AlphaMissense to guide mechanistic exploration of 78 missense variants at 55 residue positions using robust biochemical and biophysical assays to distill general principles of enzyme dysfunction. Correlation analysis established a strong linear relationship between folded G6PC1 abundance and catalytic capacity for most variants. Pathogenic variants within this paradigm were linked to compromised stability and activation of the unfolded protein response. However, outliers characterized by relatively high abundance, yet low activity clustered to a network of sidechains adjacent to the active site that allosterically modulate catalysis. Contextualized by recent high-resolution structures and AlphaFold modeling, our holistic analysis of G6PC1 in vitro metrics facilitates clinical (re)classification of variants according to explicit molecular phenotypes and identifies therapeutic design directions. Moreover, our approach illustrates a blueprint for variant characterization that integrates computational prediction with experimental validation to discover disease etiology.
2026-07-28 | Structural basis for substrate recognition and inhibition of human glucose-6-phosphate transporter SLC37A4.
Glucose 6 phosphate (G6P) homeostasis is essential for maintaining blood glucose levels and coordinating anabolic and catabolic pathways. A key step in this process is the delivery of G6P into the endoplasmic reticulum (ER), where it is hydrolyzed by glucose 6 phosphatase to glucose and inorganic phosphate (Pi). This transport step is carried out by the ER carrier SLC37A4 (also known as the G6P transporter, G6PT), which imports G6P into the ER lumen while exporting Pi to the cytosol, and loss-of-function mutations in SLC37A4 cause glycogen storage disease type Ib. Despite its central role in G6P homeostasis, how SLC37A4 recognizes G6P and couples its transport to Pi antiport has remained unclear. Here we report cryo-electron microscopy structures of human SLC37A4 in three states: the apo form at 2.8 Å resolution, a G6P-bound state at 3.2 Å resolution and a chlorogenic acid (CHA) bound state at 3.3 Å resolution. SLC37A4 adopts the canonical Major Facilitator Superfamily fold and harbors a central, positively charged cavity that accommodates anionic substrates. In the G6P-bound structure, SLC37A4 adopts an outward-open conformation facing the ER lumen, in which G6P binds to the electropositive pocket. In the CHA-bound structure, SLC37A4 adopts an inward-facing conformation, with CHA bound at a cytosolic site that locks the transporter in an arrested state and prevents the conformational transitions required for G6P/Pi exchange. Combined with thermostability and transport-based analyses of G6P binding and disease variants, these structures support a rocker switch mechanism in which electrostatic neutralization of the central positively charged cavity by anionic substrate drives the conformational changes underlying G6P/Pi exchange. Together, these findings define the structural basis of G6P/Pi exchange by SLC37A4, provide a molecular rationale for pathogenic mutations in glycogen storage disease type Ib, and provide a framework for targeting SLC37A4 to modulate G6P homeostasis.
2025-11-13 | Structural basis of G6P/Pi transport and inhibition in SLC37A4.
Glycogen storage disease type Ib (GSD-Ib), caused by loss-of-function mutations in the endoplasmic reticulum transporter SLC37A4, disrupts glucose homeostasis through impaired glucose-6-phosphate (G6P)/phosphate (Pi) antiport. Despite its central role in glycogen metabolism and immune regulation, the structural mechanisms governing SLC37A4's transport cycle and pathological dysfunction remain elusive. Here we report cryo-electron microscopy structures of human SLC37A4 in four functional states, capturing conformational transitions between lumen-facing and cytoplasm-facing states. Combined with mutational analysis, molecular dynamics simulations and functional assays, we identify a conserved substrate-binding pocket that alternately accommodates G6P and Pi through electrostatic complementarity and domain-dependent interactions. We further demonstrate that the high-affinity inhibitor S-4048 sterically occludes the cytoplasmic entry pathway by trapping the transporter in a cytoplasm-facing conformation. Our work elucidates the molecular pathology of GSD-Ib-linked mutations and provides a structural framework for developing therapies targeting this transporter in metabolic diseases.
2025-07-17 | Human glycogenins maintain glucose homeostasis by regulating glycogen metabolism.
Proper regulation of glycogen metabolism is fundamental to cellular energy homeostasis, and its disruption is associated with various metabolic disorders, including glycogen storage diseases (GSDs) and potentially diabetes. Despite glycogen's role as an essential energy reservoir, the mechanisms governing its synthesis and structural diversity across tissues remain unclear. Here, we uncover the distinct physiological roles of the human glycogenins GYG1 and GYG2 in glycogen synthesis. Through cellular models, structural biology, and biochemical analyses, we demonstrate that, unlike GYG1, GYG2 exhibits minimal autoglycosylation activity and acts as a suppressor of glycogen formation. Together, these two glycogenins coordinate glycogen synthase activity and influence glycogen assembly in a cell-type-dependent manner. Importantly, these glycogenins modulate glucose metabolic pathways, thereby ensuring cellular glucose homeostasis. These findings address longstanding questions in glycogen metabolism and establish both GYG1 and GYG2 as critical regulators of glycogen synthesis and breakdown in human, providing insights with potential therapeutic implications for treating GSDs and metabolic diseases.
2023-05-26 | Glycogen Storage Disease Type I: Prognostic Factors and Treatment
Glycogen storage disease type I (GSD I) is an inherited disorder that hinders theability of the liver to effectively break down stored glycogen, leading to difficulties inmaintaining appropriate blood sugar levels. The main treatment for this aspect ofGSD I involves the use of filgrastim, although patients often require additionaltreatment for recurrent infections, and an enlarged spleen is a common side effect.Acute lactic acidosis, which can cause respiratory distress and ketoacidosis innewborns, can be triggered by minor illnesses and accompanied by severehypoglycemia. Early diagnosis and prompt initiation of appropriate metabolictreatment are crucial in preventing the devastating effects of this condition. Theoverall prognosis and long-term efficacy of treatment are influenced by variousfactors, including the timing of diagnosis, adherence to dietary protocols, andavailability of appropriate medical interventions.
small molecules
2026-08-14 | Empagliflozin in GSD-Ib: Long-term safety and sustained recovery of neutrophil function including NET formation.
Glycogen storage disease type Ib (GSD-Ib) engenders neutropenia and severe neutrophil dysfunction, leading to recurrent infections and inflammatory complications. Recent studies have identified intracellular accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P) as a key mechanism underlying neutrophil impairment and have suggested therapeutic benefits of sodium-glucose cotransporter 2 (SGLT2) inhibitors, which lower plasma levels of its precursor 1,5-AG. In this study, we performed a four-year longitudinal evaluation of empagliflozin therapy in a genetically confirmed GSD-Ib infant, contributing to the growing body of long-term data on empagliflozin treatment in GSD-Ib. Routine laboratory parameters and key neutrophil effector functions were assessed before and during treatment, as well as in two additional GSD-Ib patients with and without therapy. Empagliflozin therapy resulted in complete restoration of neutrophil function, including reactive oxygen species (ROS) production and bactericidal activity. Notably, neutrophil extracellular trap (NET) formation and neutrophil survival recovered to levels comparable to healthy donors. These functional improvements occurred in conjunction with reduced plasma 1,5-AG levels, supporting the concept that GSD-Ib neutrophils are sensitive to physiological 1,5-AG concentrations. Functional recovery and normalization of neutrophil survival observed in vitro, was paralleled by improvement of absolute neutrophil counts to low-normal levels in vivo. Clinically, treatment was associated with a substantial reduction of severe infections. Collectively, these findings further support that empagliflozin corrects neutrophil dysfunction in GSD-Ib and demonstrate its potential to improve long-term clinical outcome across the lifespan, from infancy through adulthood.
2026-06-07 | Continuous glucose monitoring shows limited impact of daytime cornstarch on glycemia in glycogen storage disease type I.
Glycogen storage disease type I (GSD I) is characterized by impaired endogenous glucose production, leading to fasting hypoglycemia and multiple metabolic complications. Cornstarch supplementation is a cornerstone of dietary management, primarily to prevent fasting hypoglycemia. However, its role in modulating daytime postprandial glycemia in adults remains unclear. This study aimed to evaluate the impact of mealtime cornstarch supplementation on postprandial glucose dynamics in adults with GSD I under real-life conditions. In this cross-sectional observational study, 10 consecutive adults with genetically confirmed GSD I underwent a 7-day dietary assessment and continuous glucose monitoring (CGM). Meals were classified according to the presence or absence of cornstarch supplementation (Starch and noStarch meals). Postprandial glucose responses were analyzed over a 240-min observation window using dynamic CGM-derived metrics, including peak, nadir, time to peak, time to nadir, and incremental area under the curve (iAUC). A total of 102 meals (60 noStarch, 42 Starch) allowed for the 4-h analysis. No significant differences were observed between Starch and noStarch meals in overall 4-h glucose profiles (p = 0.209), iAUC (p = 0.234), peak and nadir glucose levels, or dynamic indices (p always >0.05). Postprandial hypoglycemia was infrequent, with only 14 events <70 mg/dL and a single event <54 mg/dL. Results remained consistent after adjustment for daily starch intake and subject-level effects. In adults with GSD I and stable metabolic control, mealtime cornstarch supplementation does not significantly modify postprandial glucose dynamics over 4 h. These findings support individualized, CGM-guided strategies to optimize cornstarch use.
2026-05-04 | Shifting Towards Empagliflozin First-Line Therapy in Glycogen Storage Disease Type Ib: A Nationwide Real-World Study.
Neutrophil dysfunction and neutropenia are burdensome findings in glycogen storage disease type Ib (GSDIb). Treatment with granulocyte-colony stimulating factor (G-CSF) often corrects neutropenia but fails to improve clinical symptoms like inflammatory bowel disease (IBD). Recently, empagliflozin (EMPA) was shown to correct the neutrophil dysfunction and its clinical consequences. It is increasingly used as first-line monotherapy, but long-term, real-world data are lacking. This nation-wide retrospective study investigated 42 GSD1b patients (36 children) treated with EMPA as first-line monotherapy and compared them with those receiving combination therapy with G-CSF and treatment-naïve patients (I:EMPA first-line monotherapy [n = 9]; II:G-CSF monotherapy [n = 7]; III:EMPA plus G-CSF [n = 16]; and IV: neither EMPA nor GCSF [n = 10]). Pediatric (P) patients were evaluated separately. In pediatric patients receiving EMPA as first-line monotherapy (P-I) and those with EMPA plus G-CSF (P-III), the frequency of infections, hospital admissions, and IBD was significantly lower than in patients receiving GCSF-monotherapy (P-II) or no treatment (P-IV). Additionally, significantly improved weight gain was observed in P-I. While clinical improvement related to correction of neutrophil dysfunction was seen with EMPA first-line monotherapy (P-I), significant improvement in absolute neutrophil count (ANC) and hemoglobin levels was only seen in P-III with additional G-CSF treatment. In three cases, EMPA was safely paused and subsequently resumed, for example, during pregnancy or liver transplantation. First-line EMPA monotherapy effectively corrects clinical symptoms of neutrophil dysfunction in GSD Ib patients, even in the absence of a statistically significant increase in ANC.
2026-04-14 | Effects of Extended-Release Cornstarch Supplementation on Glycemic Stability and Metabolic Parameters in Korean Patients with Glycogen Storage Disease.
Background/Objectives: Patients with hepatic glycogen storage disease (GSD) require frequent nighttime intake of uncooked corn starch (UCCS) to prevent fasting hypoglycemia, which imposes a substantial burden. Glycosade, an extended-release cornstarch, was developed to prolong overnight glucose availability. However, data regarding South Korean patients are limited. Therefore, we aimed to evaluate the efficacy and safety of Glycosade in South Korean patients with hepatic GSD. Methods: In this single-center prospective observational study, patients with hepatic GSD underwent laboratory evaluations before and 1 month after Glycosade administration. Continuous glucose monitoring (CGM) was performed during UCCS and Glycosade administration periods. The nocturnal mean glucose, coefficient of variation, time in range (70-180 mg/dL), and time below the range (<70 and <54 mg/dL) were compared between the periods using paired analyses. Results: No significant differences were observed in the nocturnal CGM metrics between the treatment periods. However, time-aligned CGM profiles revealed distinct temporal patterns, with a decline in glucose levels approximately 3-4 h after UCCS intake, whereas Glycosade showed a more sustained glucose profile over an extended period. Liver enzyme and lipid levels improved significantly after 1 month of Glycosade supplementation. Conclusions: In a cohort of South Korean patients with hepatic GSD, Glycosade maintained nocturnal glycemic stability comparable to that of conventional cornstarch without increasing the risk of hypoglycemia. Glycosade was also associated with improved biochemical parameters, supporting its role in nighttime dietary management.
2026-03-20 | Infantile extreme hypertriglyceridemia diagnosed as glycogen storage disease type Ia: A case report.
Glycogen storage disease type Ia (GSD Ia) typically presents with fasting hypoglycemia and hyperlipidemia. Atypical infantile presentations can delay diagnosis. We report an infant with extreme hypertriglyceridemia ultimately diagnosed as GSD Ia. A 5-month-old girl presented with poor appetite, growth retardation, hepatomegaly, and extreme hypertriglyceridemia (72 mmol/L), hypercholesterolemia, elevated transaminases, hyperuricemia, and hyperlactatemia, but initial normal blood glucose. Initial differentials included familial hypertriglyceridemia, but metabolic screening was normal. Whole-exome sequencing confirmed GSD Ia with compound heterozygous G6PC mutations (c.648G>T and c.814G>T). Initial lipid-lowering (low-fat diet, fenofibrate, omega-3, plasma exchange) reduced triglyceride. Post-diagnosis, she received lactose-free formula with frequent feeds and nocturnal nutrition; uncooked cornstarch was introduced at 6 months, though adherence was initially poor. Metabolic control was unstable until age 2 due to poor adherence. After 24 months of structured cornstarch therapy, fasting glucose normalized (4.2-6.6 mmol/L), triglycerides decreased (1.8-6.7 mmol/L), and catch-up growth occurred (height Z-score from -3.9 to -2.2 by 36 months). GSD Ia should be considered in infantile extreme hypertriglyceridemia with growth retardation, even without classic hypoglycemia. Sustained metabolic control requires multidisciplinary strategies addressing both biochemical and adherence barriers.
gene therapies
2026-07-23 | Base editing for precision therapeutics.
Base editing (BE), the precise installation of single-nucleotide changes in DNA or RNA without inducing double-strand breaks, holds substantial therapeutic promise for correcting single-nucleotide variants, which constitute more than half of the known pathogenic genetic variants. Recent advances have improved base editor specificity, efficiency, and delivery, enabling clinically oriented procedures. Clinically, BE has shown early success or strong translational promise in sickle cell disease, β-thalassemia, leukemia (via CAR T and epitope engineering), hypercholesterolemia (PCSK9 and ANGPTL3), alpha-1-antitrypsin deficiency, and glycogen storage disease type Ia. Key remaining challenges include bystander editing within the activity window, residual off-target DNA and RNA editing, delivery constraints (payload size, tissue targeting, and redosing limits), immunogenicity, and the need for durable long-term safety evidence across relevant cell types and disease contexts. Continued technological refinements, careful preclinical validation, and rigorous clinical assessment will be essential to fully realize BE's transformative potential in precision medicine.
2026-06-11 | Hepatocyte-specific Cas9-mediated editing of G6pc and Slc37a4 elicits comparable biochemical and regulatory responses between glycogen storage disease (GSD) type Ia and Ib mice.
Glycogen storage disease type I (GSD I) is an autosomal recessive inborn error of carbohydrate metabolism. Patients with GSD type Ia and Ib exhibit overlapping and distinct symptoms and complications. Notably, GSD Ia patients show more severe hypertriglyceridemia and higher risk of hepatic tumors than GSD Ib patients. Given the liver's pivotal role in these processes, this study utilized hepatocyte-specific CRISPR/Cas9-mediated somatic gene editing to explore the pathophysiological and biochemical adaptations in hepatic GSD Ia and Ib side-by-side. Additionally, hepatic histology, transcriptomics, and proteomics analysis was performed. Compared to controls, hepatic GSD Ia and Ib mice showed hepatomegaly, fasting hypoglycemia, hyperlactatemia, and increased uric acid in plasma, which was somewhat more pronounced in GSD Ia than Ib. Both GSD I subtypes showed similar reductions in hepatic acetyl-CoA precursor pool enrichment and increases in de novo biosynthesis of hepatic stearate and oleate. Interestingly, only GSD Ia mice showed mildly elevated plasma triglyceride and hepatic phosphate sugars. Metabolic changes were reflected at the transcriptomic and proteomic levels, with largely similar responses between GSD Ia and Ib livers. Moreover, altered mRNAs and protein levels related to nucleotide-binding oligomerization domain (NOD) signaling pathways, infection and inflammation, liver disease, and chemical carcinogenesis were somewhat more pronounced in hepatic GSD Ia than in GSD Ib mice. Overall, the metabolic disturbance was more severe in hepatocyte-specific GSD Ia than in GSD Ib mice, consistent with the clinical phenotype in patients. The metabolic disorders and specific metabolites, genes, and proteins identified in this study provided new insights into the pathophysiological and biochemical phenotypes of GSD I subtypes in the liver.
2025-08-05 | Efficacious genome editing in infant mice with glycogen storage disease type Ia.
Glycogen storage disease type Ia (GSD Ia) is caused by a deficiency of glucose-6-phosphatase (G6Pase) in the liver leading to lethal hypoglycemia. Gene therapy with adeno-associated virus (AAV) vectors encoding G6Pase fails to stably treat GSD Ia early in life. We evaluated genome editing in 12-day-old infant mice with GSD Ia using 2 AAV vectors, one containing Cas9 from Streptococcus pyogenes and a second Donor vector that expresses a guide RNA and a G6PC transgene. Gene therapy with the Donor vector only was compared with genome editing using both Donor and CRISPR vectors. Treatment with genome editing (total vector dose 0.2 × 1013 to 2 × 1013 vector genomes/kg) and bezafibrate (to stimulate autophagy) was efficacious, as assessed by hypoglycemia prevention and the frequency of transgene integration, which correlated with improved survival. This therapy achieved 5.9% chromosomal transgene integration through homology-directed repair, which surpassed a threshold to prevent long-term hepatic complications. No integration was detected in the absence of the CRISPR vector. Importantly for safety, CRISPR vector genomes were depleted, and no intact, integrated CRISPR genomes were detected by long-read sequencing. Thus, genome editing warrants further development as a potentially stable treatment for human infants with GSD Ia.
2024-04-17 | Base-editing corrects metabolic abnormalities in a humanized mouse model for glycogen storage disease type-Ia
Abstract Glycogen storage disease type-Ia (GSD-Ia) patients, deficient in glucose-6-phosphatase-α (G6Pase-α or G6PC), manifest impaired glucose homeostasis with hallmark fasting hypoglycemia. We generated a humanized knock-in mouse model, huR83C, that is homozygous for the pathogenic G6PC -R83C variant and manifests a GSD-Ia phenotype. We evaluated the efficacy of BEAM-301, lipid nanoparticles containing guide RNA and mRNA encoding a newly-engineered adenine base editor, to correct the G6PC -R83C variant in huR83C mice and monitored phenotypic correction through one year. BEAM-301-treated mice exhibited a maximum base-editing efficiency of ~60% in the liver and achieved physiologicallevels of hepatic G6Pase-α activity with just ~10% base-editing rate. The edited mice displayed an improved metabolic phenotype, sustained 24-hour fasting, and survived long-term. In contrast, untreated mice exhibited fasting hypoglycemia and died prematurely. The durable pharmacological efficacy of base editing in huR83C mice supports the development of BEAM-301 as a potential therapeutic for patients with GSD-Ia carrying the G6PC -R83C variant.
2023-11-22 | Hepatic ChREBP orchestrates intrahepatic carbohydrate metabolism to limit hepatic glucose 6-phosphate and glycogen accumulation in a mouse model for acute Glycogen Storage Disease type Ib
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. The current study aimed to investigate the role of ChREBP as a regulator of glycogen metabolism in response to hepatic G6P accumulation, using a model for acute hepatic GSD type Ib. The immediate biochemical and regulatory responses to hepatic G6P accumulation were evaluated upon G6P transporter inhibition by the chlorogenic acid S4048 in mice that were either treated with a short hairpin RNA (shRNA) directed against ChREBP (shChREBP) or a scrambled shRNA (shSCR). Complementary stable isotope experiments were performed to quantify hepatic carbohydrate fluxes in vivo. ShChREBP treatment normalized the S4048-mediated induction of hepatic ChREBP target genes to levels observed in vehicle- and shSCR-treated controls. In parallel, hepatic shChREBP treatment in S4048-infused mice resulted in a more pronounced accumulation of hepatic glycogen and further reduction of blood glucose levels compared to shSCR treatment. Hepatic ChREBP knockdown modestly increased glucokinase (GCK) flux in S4048-treated mice while it enhanced UDP-glucose turnover as well as glycogen synthase and phosphorylase fluxes. Hepatic GCK mRNA and protein levels were induced by shChREBP treatment in both vehicle- and S4048-treated mice, while glycogen synthase 2 (GYS2) and glycogen phosphorylase (PYGL) mRNA and protein levels were reduced. Finally, knockdown of hepatic ChREBP expression reduced starch domain binding protein 1 (STBD1) mRNA and protein levels while it inhibited acid alpha-glucosidase (GAA) activity, suggesting reduced capacity for lysosomal glycogen breakdown. Our data show that ChREBP activation controls hepatic glycogen and blood glucose levels in acute hepatic GSD Ib through concomitant regulation of glucose phosphorylation, glycogenesis, and glycogenolysis. ChREBP-mediated control of GCK enzyme levels aligns with corresponding adaptations in GCK flux. In contrast, ChREBP activation in response to acute hepatic GSD Ib exerts opposite effects on GYS2/PYGL enzyme levels and their corresponding fluxes, indicating that GYS2/PYGL expression levels are not limiting to their respective fluxes under these conditions.
other
2026-08-08 | ApoC-III Antisense Oligonucleotide Therapy Used in Glycogen Storage Disease Type 1a.
Glycogen storage disease type 1a (GSD1a) is an autosomal recessive disorder characterized by impaired glycogenolysis and gluconeogenesis. Individuals with GSD1a manifest significant hypertriglyceridemia refractory to dietary and lipid-lowering medication therapies. Apolipoprotein C-III antisense oligonucleotide (apoCIII-ASO) therapy is approved to reduce severe hypertriglyceridemia in familial chylomicronemia syndrome but is also effective in moderate hypertriglyceridemia of varied genetic backgrounds. We describe a 22-year-old with GSD1a and hypertriglyceridemia with past pancreatitis despite fibric acid derivative, niacin, and bempedoic acid therapy in whom apoCIII-ASO was associated with triglyceride reduction from 4,951 to 1,643 mg/dL. As GSD1a-associated hypertriglyceridemia is often refractory to standard therapies, apoCIII-ASO therapy may offer promise as a treatment. This case describes the first use of apoCIII-ASO in GSD1a-related hypertriglyceridemia. GSD1a-driven hypertriglyceridemia may be treatable using apoCIII-ASO.
2023-12-04 | A splice-switching oligonucleotide treatment ameliorates glycogen storage disease type 1a in mice with G6PC c.648G>T.
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.
2023-06-09 | Amnio acid substitution at position 298 of human glucose-6 phosphatase-α significantly impacts its stability in mammalian cells.
Glucose-6-phosphatase-α (G6Pase-α) catalyzes the hydrolysis of glucose-6-phosphate to glucose and functions as a key regulator in maintaining blood glucose homeostasis. Deficiency in G6Pase-α causes glycogen storage disease 1a (GSD1a), an inherited disorder characterized by life-threatening hypoglycemia and other long-term complications. We have developed a potential mRNA-based therapy for GSD1a and demonstrated that a human G6Pase-α (hG6Pase-α) variant harboring a single serine (S) to cysteine (C) substitution at the amino acid site 298 (S298C) had > twofold increase in protein expression, resulting in improved in vivo efficacy. Here, we sought to investigate the mechanisms contributing to the increased expression of the S298C variant. Mutagenesis of hG6Pase-α identified distinct protein variants at the 298 amino acid position with substantial reduction in protein expression in cultured cells. Kinetic analysis of expression and subcellular localization in mammalian cells, combined with cell-free in vitro translation assays, revealed that altered protein expression stemmed from differences in cellular protein stability rather than biosynthetic rates. Site-specific mutagenesis studies targeting other cysteines of the hG6Pase-α S298C variant suggest the observed improvements in stability are not due to additional disulfide bond formation. The glycosylation at Asparagine (N)-96 is critical in maintaining enzymatic activity and mutations at position 298 mainly affected glycosylated forms of hG6Pase-α. Finally, proteasome inhibition by lactacystin improved expression levels of unstable hG6Pase-α variants. Taken together, these data uncover a critical role for a single amino acid substitution impacting the stability of G6Pase-α and provide insights into the molecular genetics of GSD1a and protein engineering for therapeutic development.
2020-09-30 | Analyzing the Distribution of Mutations for Glycogen Storage Disease Type 1a in Turkey and Suggested Gene Therapy Methods for Its Treatment
One of the rare diseases throughout the world is Glycogen Storage Disease, which appears due to problems in glycogen metabolism. Among various subtypes of GSD, GSD Type 1a is the most abundant one of GSD Type 1, seen in approximately 80% and caused by different kinds of mutations in the Glucose-6-Phosphatase Catalytic Subunit (G6PC) gene in human chromosome 17q21. G6PC gene encodes for glucose-6-phosphatase (G6Pase) protein, which cleaves glucose-6-phosphate into glucose and inorganic phosphate (Pi), and GSD Type 1a patients fail to breakdown glucose-6-phosphate due to several mutations in the G6PC gene. In our study, we aim to create new therapeutic approaches for GSD 1a. We collected mutation data of 57 GSD Type 1a patients from Turkey. According to the data, 16 types of mutations were observed in the G6PC gene. Allele frequencies of these mutations are calculated as 59% for R83C/H, 11% for W160*, 7% for G270V, and 28% for others which have less frequency. Up to now, the tertiary protein structure of G6Pase has not been structured yet. To understand the possible impacts of these mutations, we statistically obtained possible tertiary structure predictions of G6Pase by running 5 different tools. At the end of the study, we suggest two effective and promising gene therapy methods for GSD Type 1a, Prime Editing for R83C/H mutations, and mRNA delivery for other mutations, in addition to a promising, commercially available drug suggestion for patients with W160*, W86*, and S15* mutations, although the drug belongs to another disease.
2019-06-26 | Inhibition of Glycogen Synthase II with RNAi Prevents Liver Injury in Mouse Models of Glycogen Storage Diseases.
Glycogen storage diseases (GSDs) of the liver are devastating disorders presenting with fasting hypoglycemia as well as hepatic glycogen and lipid accumulation, which could lead to long-term liver damage. Diet control is frequently utilized to manage the potentially dangerous hypoglycemia, but there is currently no effective pharmacological treatment for preventing hepatomegaly and concurrent liver metabolic abnormalities, which could lead to fibrosis, cirrhosis, and hepatocellular adenoma or carcinoma. In this study, we demonstrate that inhibition of glycogen synthesis using an RNAi approach to silence hepatic Gys2 expression effectively prevents glycogen synthesis, glycogen accumulation, hepatomegaly, fibrosis, and nodule development in a mouse model of GSD III. Mechanistically, reduction of accumulated abnormally structured glycogen prevents proliferation of hepatocytes and activation of myofibroblasts as well as infiltration of mononuclear cells. Additionally, we show that silencing Gys2 expression reduces hepatic steatosis in a mouse model of GSD type Ia, where we hypothesize that the reduction of glycogen also reduces the production of excess glucose-6-phosphate and its subsequent diversion to lipid synthesis. Our results support therapeutic silencing of GYS2 expression to prevent glycogen and lipid accumulation, which mediate initial signals that subsequently trigger cascades of long-term liver injury in GSDs.
Access all drug discovery papers and probability of success in trials forecasts:
Access all drug discovery papers and probability of success in trials forecasts:
Drug Discovery Landscape
3 orphan drug designations for Glycogen storage disease due to glucose-6-phosphatase deficiency.
3 orphan drug designations for Glycogen storage disease due to glucose-6-phosphatase deficiency.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
Diazoxide choline | small molecules | EMA | 2024-12-13 | — | Soleno Therapeutics Europe Limited |
Diazoxide Choline | small molecules | FDA | 2021-05-26 | — | Soleno Therapeutics, Inc. |
recombinant adeno-associated virus serotype 8 vector encoding human glucose-6-phosphatase-alpha (G6Pase or G6PC) | gene therapies | FDA | 2016-09-28 | — | Ultragenyx Pharmaceutical, Inc. |
Let's accelerate rare disease drug discovery
Let's accelerate drug discovery
Get access to Explority AI’s forecasts to outperform average preclinical success rates. Whether you’re expanding your R&D pipeline, evaluating a partnership, or simply have a question — we’d love to hear from you.