Neutropenia, neutrophil dysfunction, and inflammatory bowel disease in glycogen storage disease type Ib: results of the European Study on Glycogen Storage Disease type I

Causality of genetically determined blood metabolites on inflammatory bowel disease: a two-sample Mendelian randomization study

Inflammatory bowel disease (IBD) is a chronic and recurrent inflammatory disease of the gastrointestinal tract, including two subtypes: Crohn's disease (CD) and ulcerative colitis (UC). Metabolic disorders are important factors in the development of IBD. However, the evidence for the causal relationship between blood metabolites and IBD remains limited. A two-sample MR analysis was applied to evaluate relationships between 486 blood metabolites and IBD. The inverse variance weighted method was chosen as the primary MR analysis method. False discovery rate correction was used to control for false positives in multiple testing. Following complementary and sensitivity analyses were conducted using methods such as weight median, MR-egger, weighted mode, simple mode, Cochran Q test, and MR-PRESSO. Moreover, we performed replication, meta-analysis, Steiger test, and linkage disequilibrium score regression to enhance the robustness of the results. Additionally, we performed metabolic pathway analysis to identify potential metabolic pathways. As a result, we identified four significant causal associations between four blood metabolites and two IBD subtypes. Specifically, one metabolite was identified as being associated with the development of CD (mannose: odds ratio (OR) = 0.19, 95% confidence interval (CI) 0.08-0.43, P = 8.54 × 10-5). Three metabolites were identified as being associated with the development of UC (arachidonate (20:4n6): OR = 0.18, 95% CI 0.11-0.30, P = 2.09 × 10-11; 1, 5-anhydroglucitol: OR = 2.21, 95% CI 1.47-3.34, P = 1.50 × 10-4; 2-stearoylglycerophosphocholine: OR = 2.66, 95% CI 1.53-4.63, P = 5.30 × 10-4). The findings of our study suggested that the identified metabolites and metabolic pathways can be considered as useful circulating metabolic biomarkers for the screening and prevention of IBD in clinical practice, as well as candidate molecules for future mechanism exploration and drug target selection.

Neutrophil functions in patients with neutropenia due to glycogen storage disease type 1b treated with empagliflozin

ABSTRACT

Neutropenia and neutrophil dysfunction in glycogen storage disease type 1b (GSD1b) are caused by the accumulation of 1,5-anhydroglucitol-6-phosphate in granulocytes. The antidiabetic drug empagliflozin reduces the concentration of 1,5-anhydroglucitol (1,5-AG), thus restoring neutrophil counts and functions, leading to promising results in previous case reports. Here, we present a comprehensive analysis of neutrophil function in 7 patients with GSD1b and 11 healthy donors, aiming to evaluate the immediate (after 3 months) and long-term (after 12 months) efficacy of empagliflozin compared with the reference treatment with granulocyte-colony stimulating factor (G-CSF). We found that most patients receiving G-CSF remained neutropenic with dysfunctional granulocytes, whereas treatment with empagliflozin increased neutrophil counts and improved functionality by inhibiting apoptosis, restoring phagocytosis and the chemotactic response, normalizing the oxidative burst, and stabilizing cellular and plasma levels of defensins and lactotransferrin. These improvements correlated with the decrease in serum 1,5-AG levels. However, neither G-CSF nor empagliflozin overcame deficiencies in the production of cathelicidin/LL-37 and neutrophil extracellular traps. Given the general improvement promoted by empagliflozin treatment, patients were less susceptible to severe infections. G-CSF injections were therefore discontinued in 6 patients (and the dose was reduced in the seventh) without adverse effects. Our systematic analysis, the most extensive reported thus far, has demonstrated the superior efficacy of empagliflozin compared with G-CSF, restoring the neutrophil population and normal immune functions. This trial was registered as EudraCT 2021-000580-78.

Case report: The success of empagliflozin therapy for glycogen storage disease type 1b

Introduction

Glycogen storage disease type 1b (GSD-1b) is characterized by neutropenia and neutrophil dysfunction generated by the accumulation of 1,5-anhydroglucitol-6-phosphate in neutrophils. Sodium-glucose co-transporter 2 inhibitors, such as empagliflozin, facilitate the removal of this toxic metabolite and ameliorate neutropenia-related symptoms, including severe infections and inflammatory bowel disease (IBD). Our case series presents the treatment of three pediatric GSD-1b patients with empagliflozin over a follow-up of three years; the most extended reported follow-up period to date.

Cases description

A retrospective analysis of empagliflozin treatment of three pediatric GSD-1b patients (two male and one female; ages at treatment initiation: 4.5, 2.5 and 6 years) was performed. Clinical and laboratory data from a symmetrical period of up to three years before and after the therapy introduction was reported. Data on the clinical course of the treatment, IBD activity, the need for antibiotic treatment and hospitalizations, neutrophil count and function, and markers of inflammation were assessed. Prior the introduction of empagliflozin, patients had recurrent oral mucosa lesions and infections, abdominal pain, and anemia. During empagliflozin treatment, the resolution of aphthous stomatitis, termination of abdominal pain, reduced frequency and severity of infections, anemia resolution, increased appetite, and improved wound healing was observed in all patients, as well as an increased body mass index in two of them. In a patient with IBD, long-term deep remission was confirmed. An increased and stabilized neutrophil count and an improved neutrophil function enabled the discontinuation of G-CSF treatment in all patients. A trend of decreasing inflammation markers was detected.

Conclusions

During the three-year follow-up period, empagliflozin treatment significantly improved clinical symptoms and increased the neutrophil count and function, suggesting that targeted metabolic treatment could improve the immune function in GSD-1b patients.

Empagliflozin in children with glycogen storage disease-associated inflammatory bowel disease: a prospective, single-arm, open-label clinical trial

Glycogen storage disease type Ib (GSD-Ib) is a rare inborn error of glycogen metabolism caused by mutations in SLC37A4. Patients with GSD-Ib are at high risk of developing inflammatory bowel disease (IBD). We evaluated the efficacy of empagliflozin, a renal sodium‒glucose cotransporter protein 2 (SGLT2) inhibitor, on colonic mucosal healing in patients with GSD-associated IBD. A prospective, single-arm, open-label clinical trial enrolled eight patients with GSD-associated IBD from Guangdong Provincial People's Hospital in China from July 1, 2022 through December 31, 2023. Eight patients were enrolled with a mean age of 10.34 ± 2.61 years. Four male and four female. The endoscopic features included deep and large circular ulcers, inflammatory hyperplasia, obstruction and stenosis. The SES-CD score significantly decreased at week 48 compared with before empagliflozin. Six patients completed 48 weeks of empagliflozin therapy and endoscopy showed significant improvement or healing of mucosal ulcers, inflammatory hyperplasia, stenosis, and obstruction. One patient had severe sweating that required rehydration and developed a urinary tract infection. No serious or life-threatening adverse events. This study suggested that empagliflozin may promote colonic mucosal healing and reduce hyperplasia, stenosis, and obstruction in children with GSD-associated IBD.

Clinical spectrum, over 12-year follow-up and experience of SGLT2 inhibitors treatment on patients with glycogen storage disease type Ib: a single-center retrospective study

BACKGROUND

Glycogen storage disease type Ib (GSD Ib) is a rare disorder characterized by impaired glucose homeostasis caused by mutations in the SLC37A4 gene. It is a severe inherited metabolic disease associated with hypoglycemia, hyperlipidemia, lactic acidosis, hepatomegaly, and neutropenia. Traditional treatment consists of feeding raw cornstarch which can help to adjust energy metabolism but has no positive effect on neutropenia, which is fatal for these patients. Recently, the pathophysiologic mechanism of the neutrophil dysfunction and neutropenia in GSD Ib has been found, and the treatment with the SGLT2 inhibitor empaglifozin is now well established. In 2020, SGLT2 inhibitor empagliflozin started to be used as a promising efficient remover of 1,5AG6P in neutrophil of GSD Ib patients worldwide. However, it is necessary to consider long-term utility and safety of a novel treatment.

RESULTS

In this study, we retrospectively examined the clinical manifestations, biochemical examination results, genotypes, long-term outcomes and follow-up of thirty-five GSD Ib children who visited our department since 2009. Fourteen patients among them underwent empagliflozin treatment since 2020. This study is the largest cohort of pediatric GSD Ib patients in China as well as the largest cohort of pediatric GSD Ib patients treated with empagliflozin in a single center to date. The study also discussed the experience of long-term management on pediatric GSD Ib patients.

CONCLUSION

Empagliflozin treatment for pediatric GSD Ib patients is efficient and safe. Increase of urine glucose is a signal for pharmaceutical effect, however attention to urinary infection and hypoglycemia is suggested.

Repurposing empagliflozin in individuals with glycogen storage disease Ib: A value-based healthcare approach and systematic benefit-risk assessment

Off-label repurposing of empagliflozin allows pathomechanism-based treatment of neutropenia/neutrophil-dysfunction in glycogen storage disease type Ib (GSDIb). From a value-based healthcare (VBHC) perspective, we here retrospectively studied patient-reported, clinical and pharmacoeconomic outcomes in 11 GSDIb individuals before and under empagliflozin at two centers (the Netherlands [NL], Austria [AT]), including a budget impact analysis, sensitivity-analysis, and systematic benefit-risk assessment. Under empagliflozin, all GSDIb individuals reported improved quality-of-life-scores. Neutrophil dysfunction related symptoms allowed either granulocyte colony-stimulating factor cessation or tapering. Calculated cost savings per patient per year ranged between € 6482-14 190 (NL) and € 1281-41 231 (AT). The budget impact analysis estimated annual total cost savings ranging between € 75 062-225 716 (NL) and € 37 697-231 790 (AT), based on conservative assumptions. The systematic benefit-risk assessment was favorable. From a VBHC perspective, empagliflozin treatment in GSDIb improved personal and clinical outcomes while saving costs, thereby creating value at multiple pillars. We emphasize the importance to reimburse empagliflozin for GSDIb individuals, further supported by the favorable systematic benefit-risk assessment. These observations in similar directions in two countries/health care systems strongly suggest that our findings can be extrapolated to other geographical areas and health care systems.

Treatment recommendations for glycogen storage disease type IB- associated neutropenia and neutrophil dysfunction with empagliflozin: Consensus from an international workshop

Glycogen storage disease type Ib (GSD Ib, biallelic variants in SLC37A4) is a rare disorder of glycogen metabolism complicated by neutropenia/neutrophil dysfunction. Since 2019, the SGLT2-inhibitor empagliflozin has provided a mechanism-based treatment option for the symptoms caused by neutropenia/neutrophil dysfunction (e.g. mucosal lesions, inflammatory bowel disease). Because of the rarity of GSD Ib, the published evidence on safety and efficacy of empagliflozin is still limited and does not allow to develop evidence-based guidelines. Here, an international group of experts provides 14 best practice consensus treatment recommendations based on expert practice and review of the published evidence. We recommend to start empagliflozin in all GSD Ib individuals with clinical or laboratory signs related to neutropenia/neutrophil dysfunction with a dose of 0.3-0.4 mg/kg/d given as a single dose in the morning. Treatment can be started in an outpatient setting. The dose should be adapted to the weight and in case of inadequate clinical treatment response or side effects. We strongly recommend to pause empagliflozin immediately in case of threatening dehydration and before planned longer surgeries. Discontinuation of G-CSF therapy should be attempted in all individuals. If available, 1,5-AG should be monitored. Individuals who have previously not tolerated starches should be encouraged to make a new attempt to introduce starch in their diet after initiation of empagliflozin treatment. We advise to monitor certain safety and efficacy parameters and recommend continuous, alternatively frequent glucose measurements during the introduction of empagliflozin. We provide specific recommendations for special circumstances like pregnancy and liver transplantation.

Understanding very early onset inflammatory bowel disease (VEOIBD) in relation to inborn errors of immunity

Inflammatory bowel diseases (IBD) are multifactorial diseases which are caused by the combination of genetic predisposition, exposure factors (environmental and dietary), immune status, and dysbiosis. IBD is a disease which presents at any age, ranging from newborns to the elderly. The youngest of the pediatric IBD population have a more unique presentation and clinical course and may have a different etiology. Very early onset IBD (VEOIBD) patients, designated as those diagnosed prior the age of 6, have distinct features which are more frequent in this patient population including increased incidence of monogenetic causes for IBD (0%-33% depending on the study). This proportion is increased in the youngest subsets, which is diagnosed prior to the age of 2. To date, there are approximately 80 monogenic causes of VEOIBD that have been identified and published. Many of these monogenic causes are inborn errors of immunity yet the majority of VEOIBD patients do not have an identifiable genetic cause for their disease. In this review, we will focus on the clinical presentation, evaluation, and monogenic categories which have been associated with VEOIBD including (1) Epithelial cell defects (2) Adaptive immune defects, (3) Innate Immune/Bacterial Clearance and Recognition defects, and (4) Hyperinflammatory and autoinflammatory disorders. We will highlight differential diagnosis of VEOIBD presentations, as well as evaluation and treatment, which will be helpful for those who study and care for VEOIBD patients outside of the pediatric gastroenterology field. This is a fast-moving field of research which has grown significantly based on knowledge that we gain from our patients. These scientific findings have identified novel mucosal biology pathways and will continue to inform our understanding of gastrointestinal biology.

Neutrophils: from IBD to the gut microbiota

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract that results from dysfunction in innate and/or adaptive immune responses. Impaired innate immunity, which leads to lack of control of an altered intestinal microbiota and to activation of the adaptive immune system, promotes a secondary inflammatory response that is responsible for tissue damage. Neutrophils are key players in innate immunity in IBD, but their roles have been neglected compared with those of other immune cells. The latest studies on neutrophils in IBD have revealed unexpected complexities, with heterogeneous populations and dual functions, both deleterious and protective, for the host. In parallel, interconnections between disease development, intestinal microbiota and neutrophils have been highlighted. Numerous IBD susceptibility genes (such as NOD2, NCF4, LRRK2, CARD9) are involved in neutrophil functions related to defence against microorganisms. Moreover, severe monogenic diseases involving dysfunctional neutrophils, including chronic granulomatous disease, are characterized by intestinal inflammation that mimics IBD and by alterations in the intestinal microbiota. This observation demonstrates the dialogue between neutrophils, gut inflammation and the microbiota. Neutrophils affect microbiota composition and function in several ways. In return, microbial factors, including metabolites, regulate neutrophil production and function directly and indirectly. It is crucial to further investigate the diverse roles played by neutrophils in host-microbiota interactions, both at steady state and in inflammatory conditions, to develop new IBD therapies. In this Review, we discuss the roles of neutrophils in IBD, in light of emerging evidence proving strong interconnections between neutrophils and the gut microbiota, especially in an inflammatory context.

Congenital neutropenia: From lab bench to clinic bedside and back

Neutropenia is a hematological condition characterized by a decrease in absolute neutrophil count (ANC) in peripheral blood, typically classified in adults as mild (1-1.5 × 109/L), moderate (0.5-1 × 109/L), or severe (< 0.5 × 109/L). It can be categorized into two types: congenital and acquired. Congenital severe chronic neutropenia (SCN) arises from mutations in various genes, with different inheritance patterns, including autosomal recessive, autosomal dominant, and X-linked forms, often linked to mitochondrial diseases. The most common genetic cause is alterations in the ELANE gene. Some cases exist as non-syndromic neutropenia within the SCN spectrum, where genetic origins remain unidentified. The clinical consequences of congenital neutropenia depend on granulocyte levels and dysfunction. Infants with this condition often experience recurrent bacterial infections, with approximately half facing severe infections within their first six months of life. These infections commonly affect the respiratory system, digestive tract, and skin, resulting in symptoms like fever, abscesses, and even sepsis. The severity of these symptoms varies, and the specific organs and systems affected depend on the genetic defect. Congenital neutropenia elevates the risk of developing acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS), particularly with certain genetic variants. SCN patients may acquire CSF3R and RUNX1 mutations, which can predict the development of leukemia. It is important to note that high-dose granulocyte colony-stimulating factor (G-CSF) treatment may have the potential to promote leukemogenesis. Treatment for neutropenia involves antibiotics, drugs that boost neutrophil production, or bone marrow transplants. Immediate treatment is essential due to the heightened risk of severe infections. In severe congenital or cyclic neutropenia (CyN), the primary therapy is G-CSF, often combined with antibiotics. The G-CSF dosage is gradually increased to normalize neutrophil counts. Hematopoietic stem cell transplants are considered for non-responders or those at risk of AML/MDS. In cases of WHIM syndrome, CXCR4 inhibitors can be effective. Future treatments may involve gene editing and the use of the diabetes drug empagliflozin to alleviate neutropenia symptoms.

Three novel SLC37A4 variants in glycogen storage disease type 1b and a literature review

Glycogen storage disease type 1b (GSD1b) is a rare genetic disorder, resulting from mutations in the SLC37A4 gene located on chromosome 11q23.3. Although the SLC37A4 gene has been identified as the pathogenic gene for GSD1b, the complete variant spectrum of this gene remains to be fully elucidated. In this study, we present three patients diagnosed with GSD1b through genetic testing. We detected five variants of the SLC37A4 gene in these three patients, with three of these mutations (p. L382Pfs*15, p. G117fs*28, and p. T312Sfs*13) being novel variants not previously reported in the literature. We also present a literature review and general overview of the currently reported SLC37A4 gene variants. Our study expands the mutation spectrum of SLC37A4, which may help enable genetic testing to facilitate prompt diagnosis, appropriate intervention, and genetic counseling for affected families.

Serum cytokines MCP-1 and GCS-F as potential biomarkers in pediatric inflammatory bowel disease

BACKGROUND

Inflammatory bowel diseases (IBDs) with the subtypes ulcerative colitis (UC) and Crohn disease (CD), are chronic autoimmune inflammatory disorders of the gastrointestinal tract. Cytokines are associated with the development and progression in pediatric IBD. We measured cytokine levels in pediatric IBD patients to assess their potential function as biomarkers in disease assessment.

METHOD

In this prospective cohort study, we enrolled 33 children with IBD. All patients were in stable remission for 3 months on enrollment. Patients who developed a relapse within six months after enrollment were classified as relapsers. Blood sampling was performed at enrolment and for relapsers in relapse and post-relapse. Serum concentrations of 14 cytokines, chemokines and growth factors (IL-1α, IL-1β, IL-6, IL-12p40, IP-10, TNF-α, IFN-γ, IL-10, IL-8, MIP-1α, MCP-1, MCP-3, G-CSF, GM-CSF) were measured simultaneously using multiplex bead-based sandwich immunoassay on Luminex 100 system.

RESULTS

MCP-1 was significantly higher in CD patients compared to UC patients at each disease stage: stable remission (P<0.048), unstable remission (P<0.013), relapse (P<0.026) and post-relapse (P<0.024). G-CSF was significantly increased in UC patients developing a relapse and in post-relapse stage compared to UC patients in remission (P<0.02 and p<0.03, respectively).

CONCLUSION

MCP-1 showed potential as a diagnostic biomarker in CD patients independent of disease activity as it was able to discriminate between subtypes of pediatric IBD. In UC patients, G-CSF was significantly elevated in relapsers indicating its use and role as a potential prognostic biomarker.

DBS are suitable for 1,5-anhydroglucitol monitoring in GSD1b and G6PC3-deficient patients taking SGLT2 inhibitors to treat neutropenia

Glycogen storage disease type Ib (GSD1b) and G6PC3-deficiency are rare autosomal recessive diseases caused by inactivating mutations in SLC37A4 (coding for G6PT) and G6PC3, respectively. Both diseases are characterized by neutropenia and neutrophil dysfunction due to the intracellular accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P), a potent inhibitor of hexokinases. We recently showed that the use of SGLT2 inhibitor therapy to reduce tubular reabsorption of its precursor, 1,5-anhydroglucitol (1,5-AG), a glucose analog present in blood, successfully restored the neutropenia and neutrophil function in G6PC3-deficient and GSD1b patients. The intra-individual variability of response to the treatment and the need to adjust the dose during treatment, especially in pediatric populations, can only be efficiently optimized if the concentration of 1,5-AG in blood is monitored during treatment, together with the patients' clinical signs and symptoms. Monitoring the 1,5-AG levels would be greatly simplified if it could be performed on dry blood spots (DBS) which are easy to collect, store and transport. The challenge is to know if a suitable method can be developed to perform accurate and reproducible assays for 1,5-AG using DBS. Here, we describe and validate an assay that quantifies 1,5-AG in DBS using isotopic dilution quantitation by LC-MS/MS that should greatly facilitate patients' follow-up. 1,5-AG levels measured in plasma and DBS give comparable values. This assay was used to monitor the levels of 1,5-AG in DBS from 3 G6PC3-deficient and 6 GSD1b patients during treatment with SGLT2 inhibitors. We recommend this approach to verify the adequate therapeutical response and compliance to the treatment in G6PC3-deficient and GSD1b patients treated with SGLT2 inhibitors.

Aberrant glucose metabolism underlies impaired macrophage differentiation in glycogen storage disease type Ib

Glycogen storage disease type Ib (GSD-Ib) is an autosomal recessive disorder caused by a deficiency in the glucose-6-phosphate (G6P) transporter (G6PT) that is responsible for transporting G6P into the endoplasmic reticulum. GSD-Ib is characterized by disturbances in glucose homeostasis, neutropenia, and neutrophil dysfunction. Although some studies have explored neutrophils abnormalities in GSD-Ib, investigations regarding monocytes/macrophages remain limited so far. In this study, we examined the impact of G6PT deficiency on monocyte-to-macrophage differentiation using bone marrow-derived monocytes from G6pt-/- mice as well as G6PT-deficient human THP-1 monocytes. Our findings revealed that G6PT-deficient monocytes exhibited immature differentiation into macrophages. Notably, the impaired differentiation observed in G6PT-deficient monocytes seemed to be associated with abnormal glucose metabolism, characterized by enhanced glucose consumption through glycolysis, even under quiescent conditions with oxidative phosphorylation. Furthermore, we observed a reduced secretion of inflammatory cytokines in G6PT-deficient THP-1 monocytes during the inflammatory response, despite their elevated glucose consumption. In conclusion, this study sheds light on the significance of G6PT in monocyte-to-macrophage differentiation and underscores its importance in maintaining glucose homeostasis and supporting immune response in GSD-Ib. These findings may contribute to a better understanding of the pathogenesis of GSD-Ib and potentially pave the way for the development of targeted therapeutic interventions.

Crohn-like disease long remission in a pediatric patient with glycogen storage disease type Ib treated with empagliflozin: a case report

Glycogen storage disease type Ib (GSD Ib) is a rare hereditary glycogen disorder that results in inadequate maintenance of glucose homeostasis, accumulation of glycogen in different organs, loss and dysfunction of neutrophils. Crohn's-like disease is observed in up to 24-77% of GDS Ib cases. Recently, empagliflozin has been recommended as a treatment for neutrophil dysfunction in GDS Ib patients with or without Crohn's-like disease. There are no guidelines for the treatment of inflammatory bowel disease (IBD) manifestation in GSD Ib patients, although some cases have been treated with granulocyte colony-stimulating factor and others with IBD conventional therapy, resulting in partial IBD remission. Herein, we describe a child with GDS Ib and Crohn's-like disease who was treated with empagliflozin and achieved complete remission after 2 years of treatment. This case is the first one with such a long follow-up evaluation including endoscopic and magnetic resonance enterography assessment. Our clinical evidence of remission of IBD manifestation in our GSD Ib patient and the role of neutrophils in GDS Ib described in the literature suggest a strong association with IBD pathophysiology and neutrophil function. The use of empagliflozin resulted in significant improvements in gastrointestinal symptoms, reduced drug usage, and enhanced quality of life in the patient, with a favorable safety profile, offering a promising new therapeutic option for this population.

Glycogen storage diseases

Glycogen storage diseases (GSDs) are a group of rare, monogenic disorders that share a defect in the synthesis or breakdown of glycogen. This Primer describes the multi-organ clinical features of hepatic GSDs and muscle GSDs, in addition to their epidemiology, biochemistry and mechanisms of disease, diagnosis, management, quality of life and future research directions. Some GSDs have available guidelines for diagnosis and management. Diagnostic considerations include phenotypic characterization, biomarkers, imaging, genetic testing, enzyme activity analysis and histology. Management includes surveillance for development of characteristic disease sequelae, avoidance of fasting in several hepatic GSDs, medically prescribed diets, appropriate exercise regimens and emergency letters. Specific therapeutic interventions are available for some diseases, such as enzyme replacement therapy to correct enzyme deficiency in Pompe disease and SGLT2 inhibitors for neutropenia and neutrophil dysfunction in GSD Ib. Progress in diagnosis, management and definitive therapies affects the natural course and hence morbidity and mortality. The natural history of GSDs is still being described. The quality of life of patients with these conditions varies, and standard sets of patient-centred outcomes have not yet been developed. The landscape of novel therapeutics and GSD clinical trials is vast, and emerging research is discussed herein.

Glycogen storage diseases: An update

Glycogen storage diseases (GSDs), also referred to as glycogenoses, are inherited metabolic disorders of glycogen metabolism caused by deficiency of enzymes or transporters involved in the synthesis or degradation of glycogen leading to aberrant storage and/or utilization. The overall estimated GSD incidence is 1 case per 20000-43000 live births. There are over 20 types of GSD including the subtypes. This heterogeneous group of rare diseases represents inborn errors of carbohydrate metabolism and are classified based on the deficient enzyme and affected tissues. GSDs primarily affect liver or muscle or both as glycogen is particularly abundant in these tissues. However, besides liver and skeletal muscle, depending on the affected enzyme and its expression in various tissues, multiorgan involvement including heart, kidney and/or brain may be seen. Although GSDs share similar clinical features to some extent, there is a wide spectrum of clinical phenotypes. Currently, the goal of treatment is to maintain glucose homeostasis by dietary management and the use of uncooked cornstarch. In addition to nutritional interventions, pharmacological treatment, physical and supportive therapies, enzyme replacement therapy (ERT) and organ transplantation are other treatment approaches for both disease manifestations and long-term complications. The lack of a specific therapy for GSDs has prompted efforts to develop new treatment strategies like gene therapy. Since early diagnosis and aggressive treatment are related to better prognosis, physicians should be aware of these conditions and include GSDs in the differential diagnosis of patients with relevant manifestations including fasting hypoglycemia, hepatomegaly, hypertransaminasemia, hyperlipidemia, exercise intolerance, muscle cramps/pain, rhabdomyolysis, and muscle weakness. Here, we aim to provide a comprehensive review of GSDs. This review provides general characteristics of all types of GSDs with a focus on those with liver involvement.

Gene therapy and genome editing for type I glycogen storage diseases

Type I glycogen storage diseases (GSD-I) consist of two major autosomal recessive disorders, GSD-Ia, caused by a reduction of glucose-6-phosphatase-α (G6Pase-α or G6PC) activity and GSD-Ib, caused by a reduction in the glucose-6-phosphate transporter (G6PT or SLC37A4) activity. The G6Pase-α and G6PT are functionally co-dependent. Together, the G6Pase-α/G6PT complex catalyzes the translocation of G6P from the cytoplasm into the endoplasmic reticulum lumen and its subsequent hydrolysis to glucose that is released into the blood to maintain euglycemia. Consequently, all GSD-I patients share a metabolic phenotype that includes a loss of glucose homeostasis and long-term risks of hepatocellular adenoma/carcinoma and renal disease. A rigorous dietary therapy has enabled GSD-I patients to maintain a normalized metabolic phenotype, but adherence is challenging. Moreover, dietary therapies do not address the underlying pathological processes, and long-term complications still occur in metabolically compensated patients. Animal models of GSD-Ia and GSD-Ib have delineated the disease biology and pathophysiology, and guided development of effective gene therapy strategies for both disorders. Preclinical studies of GSD-I have established that recombinant adeno-associated virus vector-mediated gene therapy for GSD-Ia and GSD-Ib are safe, and efficacious. A phase III clinical trial of rAAV-mediated gene augmentation therapy for GSD-Ia (NCT05139316) is in progress as of 2023. A phase I clinical trial of mRNA augmentation for GSD-Ia was initiated in 2022 (NCT05095727). Alternative genetic technologies for GSD-I therapies, such as gene editing, are also being examined for their potential to improve further long-term outcomes.

Vaccination strategies for people living with inborn errors of metabolism in Brazil

OBJECTIVE

Through a literature review, make recommendations regarding immunizations in people living with Inborn Error of Metabolism (IEM) in Brazil, assess the possible impact on metabolic decompensations after immunization, and if this specific population may have an impaired immune response to vaccines.

SOURCE OF DATA

The MeSH Terms vaccination OR vaccine OR immunization associated with the term inborn error of metabolism AND recommendation were used in combination with search databases. Only articles published after 1990, in the languages English, Spanish, French or Portuguese, human-related were included.

SYNTHESIS OF DATA

A total of 44 articles were included to make the following recommendations. Individuals with IEMs need to be up to date with their immunizations. Regarding which vaccines should be offered, children and adults should follow the routine immunization schedules locally available, including the COVID-19 vaccines. The only exception is the rotavirus vaccine for hereditary fructose intolerance. The benefit of immunization outweighs the very low risk of metabolic decompensation. Since not all patients will have an adequate immune response, measuring antibody conversion and titers is recommended CONCLUSIONS: All patients should receive age-appropriate immunizations in their respective schedules without delays. The only situation when vaccination may be contraindicated is with oral rotavirus vaccine in hereditary fructose intolerance. Monitoring the levels of antibodies should be done to detect any immune dysfunction or the necessity for boosters. A personalized immunization schedule is ideal for patients with IEMs. The reference organizations could improve their recommendations to address all IEMs, not only some of them.

Novel mutation of SLC37A4 in a glycogen storage disease type Ib patient with neutropenia, horseshoe kidney, and arteriovenous malformation: a case report

Glycogen storage disease type Ib (GSDIb) is an autosomal recessive disorder caused by mutations of SLC37A4 gene, which encodes glucose 6-phosphate translocase (G6PT). Malfunction of G6PT leads to excessive fat and glycogen in liver, kidney, and intestinal mucosa. The clinical manifestations of GSD1b include hepatomegaly, renomegaly, neutropenia, hypoglycemia, and lactic acidosis. Furthermore, the disorder may result in severe complications in long-term including inflammatory bowel disease (IBD), hepatocellular adenomas (HCA), short stature, and autoimmune disorders, which stem from neutropenia and neutrophil dysfunction. Here, we represent a novel mutation of SLC37A4 in a 5-month girl who has a history of hospitalizations several times due to recurrent infection and her early presentations were failure to thrive and tachypnea. Further investigations revealed mild atrial septal defect, mild arteriovenous malformation from left lung, esophageal reflux, Horseshoe kidney, and urinary reflux in this patient. Moreover, the lab tests showed neutropenia, immunoglobulin (Ig) G and IgA deficiency, as well as thrombocytosis. Whole exome sequencing revealed c.1245G > A P.W415 homozygous mutation in SLC37A4 gene and c.580G > A p.V1941 heterozygous mutation in PIK3CD gene. This study shows that manifestations of GSD1b may not be limited to what was previously known and it should be considered in a wider range of patients.

Cytokine profiling in patients with hepatic glycogen storage disease: Are there clues for unsolved aspects?

INTRODUCTION

Hepatic Glycogen Storage Diseases (GSD) are rare genetic disorders in which the gluconeogenesis pathway is impaired. Cytokines control virtually every aspect of physiology and may help to elucidate some unsolved questions about phenotypes presented by GSD patients.

METHODS

This was an exploratory study in which 27 GSD patients on treatment (Ia = 16, Ib = 06, III = 02, IXα = 03) and 24 healthy age- and sex-matched subjects had plasma samples tested for a panel of 20 cytokines (G-CSF,GM-CSF, IL-1α,IL-1β, IL-4, IL-6, IL-8, IL-10, IL-13, IL-17A, GRO, IP-10/CXCL10, MCP-1/CCL2, MIP-1α/CCL3, MIP-1β/CCL4, MDC/CCL22, IFN-γ, TNF-α, TNF-β, VEGF) through a multiplex kit and analyzed in comparison to controls and among patients, regarding to clinical features as anemia, hepatic adenocarcinoma and triglyceride levels.

RESULTS

Patients (GSD-Ia/III/IX) presented reduced levels of IL-4 (p = 0.040), MIP-1α/CCL3 (p = 0.003), MDC/CCL22 (p < 0.001), TNF-β (p = 0.045) and VEGF (p = 0.043) compared to controls. When different types of GSD were compared, G-CSF was higher in GSD-Ib than -Ia (p < 0.001) and than -III/IX (p = 0.033) patients; IL-10 was higher in GSD-Ib than in GSD-Ia patients (p = 0.019); and GSD-III/IX patients had increased levels of IP-10/CXCL10 than GSD-Ib patients (p = 0.019). When GSD-I patients were gathered into the same group and compared with GSD-III/IX patients, IP10/CXCL10 and MCP-1 were higher in the latter group (p = 0.005 and p = 0.013, respectively). GSD-I patients with anemia presented higher levels of IL-4 and MIP-1α in comparison with patients who had not. Triglyceride level was correlated with neutrophil count and MDC levels on GSD-Ia patients without HCA.

CONCLUSION

Altogether, altered levels of cytokines in GSD-I patients reflect an imbalance in immunoregulation process. This study also indicates that neutrophils and some cytokines are affected by triglyceride levels, and future studies on the theme should consider this variable.

Current understanding on pathogenesis and effective treatment of glycogen storage disease type Ib with empagliflozin: new insights coming from diabetes for its potential implications in other metabolic disorders

Glycogen storage type Ib (GSDIb) is a rare inborn error of metabolism caused by glucose-6-phosphate transporter (G6PT, SLC37A4) deficiency. G6PT defect results in excessive accumulation of glycogen and fat in the liver, kidney, and intestinal mucosa and into both glycogenolysis and gluconeogenesis impairment. Clinical features include hepatomegaly, hypoglycemia, lactic acidemia, hyperuricemia, hyperlipidemia, and growth retardation. Long-term complications are liver adenoma, hepatocarcinoma, nephropathy and osteoporosis. The hallmark of GSDIb is neutropenia, with impaired neutrophil function, recurrent infections and inflammatory bowel disease. Alongside classical nutritional therapy with carbohydrates supplementation and immunological therapy with granulocyte colony-stimulating factor, the emerging role of 1,5-anhydroglucitol in the pathogenesis of neutrophil dysfunction led to repurpose empagliflozin, an inhibitor of the renal glucose transporter SGLT2: the current literature of its off-label use in GSDIb patients reports beneficial effects on neutrophil dysfunction and its clinical consequences. Surprisingly, this glucose-lowering drug ameliorated the glycemic and metabolic control in GSDIb patients. Furthermore, numerous studies from big cohorts of type 2 diabetes patients showed the efficacy of empagliflozin in reducing the cardiovascular risk, the progression of kidney disease, the NAFLD and the metabolic syndrome. Beneficial effects have also been described on peripheral neuropathy in a prediabetic rat model. Increasing evidences highlight the role of empagliflozin in regulating the cellular energy sensors SIRT1/AMPK and Akt/mTOR, which leads to improvement of mitochondrial structure and function, stimulation of autophagy, decrease of oxidative stress and suppression of inflammation. Modulation of these pathways shift the oxidative metabolism from carbohydrates to lipids oxidation and results crucial in reducing insulin levels, insulin resistance, glucotoxicity and lipotoxicity. For its pleiotropic effects, empagliflozin appears to be a good candidate for drug repurposing also in other metabolic diseases presenting with hypoglycemia, organ damage, mitochondrial dysfunction and defective autophagy.

Dapagliflozin Prevents Kidney Glycogen Accumulation and Improves Renal Proximal Tubule Cell Functions in a Mouse Model of Glycogen Storage Disease Type 1b

BACKGROUND

Mutations in SLC37A4, which encodes the intracellular glucose transporter G6PT, cause the rare glycogen storage disease type 1b (GSD1b). A long-term consequence of GSD1b is kidney failure, which requires KRT. The main protein markers of proximal tubule function, including NaPi2A, NHE3, SGLT2, GLUT2, and AQP1, are downregulated as part of the disease phenotype.

METHODS

We utilized an inducible mouse model of GSD1b, TM-G6PT-/-, to show that glycogen accumulation plays a crucial role in altering proximal tubule morphology and function. To limit glucose entry into proximal tubule cells and thus to prevent glycogen accumulation, we administered an SGLT2-inhibitor, dapagliflozin, to TM-G6PT-/- mice.

RESULTS

In proximal tubule cells, G6PT suppression stimulates the upregulation and activity of hexokinase-I, which increases availability of the reabsorbed glucose for intracellular metabolism. Dapagliflozin prevented glycogen accumulation and improved kidney morphology by promoting a metabolic switch from glycogen synthesis toward lysis and by restoring expression levels of the main proximal tubule functional markers.

CONCLUSION

We provide proof of concept for the efficacy of dapagliflozin in preserving kidney function in GSD1b mice. Our findings could represent the basis for repurposing this drug to treat patients with GSD1b.

Are the Bacteria and Their Metabolites Contributing for Gut Inflammation on GSD-Ia Patients?

Recently, patients with glycogen storage disease (GSD) have been described as having gut dysbiosis, lower fecal pH, and an imbalance in SCFAs due to an increase in acetate and propionate levels. Here, we report the fecal measurement of bacterial-related metabolites formic, acetic, lactic, propionic, and succinic acid, a key metabolite of both host and microbiota, on a previously described cohort of 24 patients (GSD Ia = 15, GSD Ib = 5, 1 GSD III = 1 and GSD IX = 3) and 16 healthy controls, with similar sex and age, using the high-performance liquid chromatography technique. The succinic acid levels were higher in the GSD patients than in the controls (patients = 38.02; controls = 27.53; p = 0.045), without differences between the groups for other metabolites. Fecal pH present inverse correlation with lactic acid (R = −0.54; p = 0.0085), while OTUs were inversely correlated with both lactic (R = −0.46; p = 0.026) and formic (R = −0.54; p = 0.026) acids. Using two distinct metrics of diversity, borderline significance was obtained for propionic acid, affecting the microbial structure on Euclidean basis in 8% (r² = 0.081; p = 0.079), and for lactic acid, affecting 6% of microbial structure using Bray–Curtis distance (r² = 0.065; p = 0.060). No correlation was found between SCFAs and total carbohydrate consumption among the participants or uncooked cornstarch consumption among the patients.

Prevalence and Complications of Glycogen Storage Disease in South Korea: A Nationwide Population-Based Study, 2007-2018

Glycogen storage disease (GSD) is a rare disease that can cause life-threatening problems owing to metabolic errors in storing or using glycogen. The disease course of GSD remains unknown, despite medical technology advances. We determined the prevalence and complications of GSD using data from the National Health Insurance Service database. Data were collected and analyzed for the entire South Korean population with GSD during 2007–2018. GSD was defined as a combination of disease code E74.0 and rare incurable disease insurance code V117, a unique disease code combination for GSD in South Korea. Overall, 23,055 patients had the E74 disease code; 404 had an additional V117 insurance code. Most GSD patients were aged <10 years. Many complications were identified, the most common being hepatomegaly, hyperuricemia, and elevated liver enzyme levels. The most prescribed drug was α-glucosidase, followed by allopurinol. Seventy-two percent of patients were treated in pediatrics. Twenty-five patients underwent liver transplantation, and 14 died after GSD diagnosis. In South Korea, more patients than expected had GSD diagnosis and were managed accordingly. GSD causes many complications and hospitalizations, resulting in high medical expenses. Serious complications can result in liver transplantation and, eventually, death in some cases. Although the patients' condition was identified only by the disease code, this is the first study to present the current situation of GSD patients in South Korea. Because GSD patients can have dangerous medical conditions, they should be managed consistently while minimizing various complications that may occur with optimal metabolic control.

Very early-onset inflammatory bowel disease: Novel description in glycogen storage disease type Ia

Although inflammatory bowel disease is a well-described feature of glycogen storage disease type Ib, it has been reported in only a small number of individuals with glycogen storage disease type Ia (GSDIa). We describe, to our knowledge, the first patient with GSDIa and very early-onset inflammatory bowel disease (VEO-IBD). Larger studies are needed to better understand this possible association, elucidate the mechanism of VEO-IBD in GSDIa, and inform management.

Untargeted metabolomic profiling in a patient with glycogen storage disease Ib receiving empagliflozin treatment

Glycogen storage disease type Ib (GSD‐Ib) is a rare inborn error of glycogen metabolism uniquely associated with neutropenia and neutrophil dysfunction, causing severe infections, inflammatory bowel disease (IBD), and impaired wound healing. Recently, kidney sodium‐glucose co‐transporter‐2 (SGLT2) inhibitors such as empagliflozin known to reduce plasma levels of 1,5‐anhydroglucitol (1,5‐AG) and its toxic derivatives in neutrophils, have been described as a new treatment option in case reports of patients with GSD‐Ib from Europe and Asia. We report our experience with an 11‐year‐old girl with GSD‐Ib presenting with short fasting hypoglycemia, neutropenia with neutrophil dysfunction, recurrent infections, suboptimal growth, iron‐deficiency anemia, and IBD. Treatment with daily empagliflozin improved neutrophil counts and function with a significant reduction in G‐CSF needs. Significant improvement in IBD has led to weight gain with improved nutritional markers and improved fasting tolerance. Reduction of maximum empagliflozin dose was needed due to arthralgia. No other significant side effects of empagliflozin were observed. This report uniquely highlights the novel use of untargeted metabolomics profiling for monitoring plasma levels of 1,5‐AG to assess empagliflozin dose responsiveness and guide dietary management and G‐CSF therapy. Clinical improvement correlated to rapid normalization of 1,5‐AG levels in plasma sustained after dose reduction. In conclusion, empagliflozin appeared to be a safe treatment option for GSD‐Ib‐associated neutropenia and neutrophil dysfunction. Global untargeted metabolomics is an efficient method to assess biochemical responsiveness to treatment.

Understanding the role of SGLT2 inhibitors in glycogen storage disease type Ib: the experience of one UK centre

BACKGROUND

Glycogen storage disease type Ib (GSD Ib) is a severe disorder of carbohydrate metabolism due to bi-allelic variants in SLC37A4. It is associated with neutropaenia and neutrophil dysfunction, which has recently been attributed to the accumulation of 1,5-anhydroglucitol-6-phosphate (1,5AG6P) within neutrophils. Treatment with sodium-glucose co-transporter-2 (SGLT2) inhibitors, such as empagliflozin, is a novel therapy that reduces 1,5-anhydroglucitol (1,5AG) in plasma.

RESULTS

We report our experience in treating 8 paediatric GSD Ib patients with empagliflozin with a cumulative treatment time greater than 12 years. Treatment with a median dose of 5 mg (0.22 mg/kg height weight) of empagliflozin resulted in improvement in bowel health, growth, and laboratory parameters. Plasma 1,5AG levels reduced by a median of 78%. Baseline 1,5AG levels in our cohort were higher than in adult patients with GSD Ib. Hypoglycaemia on empagliflozin treatment occurred in 50% of our cohort.

CONCLUSION

We report the largest single centre cohort of GSD Ib patients treated with empagliflozin to date. Treatment with SGLT2 inhibitors is a novel and favourable treatment option for neutropaenia and neutrophil dysfunction in GSD Ib. We suggest a low starting dose of empagliflozin with careful titration due to the risk of hypoglycaemia. The interpretation of 1,5AG levels and their role in treatment monitoring is yet to be established, and requires ongoing research.

Efficacy and safety of empagliflozin in glycogen storage disease type Ib: Data from an international questionnaire

PURPOSE

This paper aims to report collective information on safety and efficacy of empagliflozin drug repurposing in individuals with glycogen storage disease type Ib (GSD Ib).

METHODS

This is an international retrospective questionnaire study on the safety and efficacy of empagliflozin use for management of neutropenia/neutrophil dysfunction in patients with GSD Ib, conducted among the respective health care providers from 24 countries across the globe.

RESULTS

Clinical data from 112 individuals with GSD Ib were evaluated, representing a total of 94 treatment years. The median age at start of empagliflozin treatment was 10.5 years (range = 0-38 years). Empagliflozin showed positive effects on all neutrophil dysfunction-related symptoms, including oral and urogenital mucosal lesions, recurrent infections, skin abscesses, inflammatory bowel disease, and anemia. Before initiating empagliflozin, most patients with GSD Ib were on G-CSF (94/112; 84%). At the time of the survey, 49 of 89 (55%) patients previously treated with G-CSF had completely stopped G-CSF, and another 15 (17%) were able to reduce the dose. The most common adverse event during empagliflozin treatment was hypoglycemia, occurring in 18% of individuals.

CONCLUSION

Empagliflozin has a favorable effect on neutropenia/neutrophil dysfunction-related symptoms and safety profile in individuals with GSD Ib.

Molecular mechanisms of aberrant neutrophil differentiation in glycogen storage disease type Ib

Glycogen storage disease type Ib (GSD-Ib), characterized by impaired glucose homeostasis, neutropenia, and neutrophil dysfunction, is caused by a deficiency in glucose-6-phosphate transporter (G6PT). Neutropenia in GSD-Ib has been known to result from enhanced apoptosis of neutrophils. However, it has also been raised that neutrophil maturation arrest in the bone marrow would contribute to neutropenia. We now show that G6pt-/- mice exhibit severe neutropenia and impaired neutrophil differentiation in the bone marrow. To investigate the role of G6PT in myeloid progenitor cells, the G6PT gene was mutated using CRISPR/Cas9 system, and single cell-derived G6PT-/- human promyelocyte HL-60 cell lines were established. The G6PT-/- HL-60s exhibited impaired neutrophil differentiation, which is associated with two mechanisms: (i) abnormal lipid metabolism causing a delayed metabolic reprogramming and (ii) reduced nuclear transcriptional activity of peroxisome proliferator-activated receptor-γ (PPARγ) in G6PT-/- HL-60s. In this study, we demonstrated that G6PT is essential for neutrophil differentiation of myeloid progenitor cells and regulates PPARγ activity.

Clinical, pathological and molecular spectrum of patients with glycogen storage diseases in Pakistan

OBJECTIVES

Evaluation of clinical, biochemical and molecular analysis of Pakistani patients with hepatic GSDs.

METHODS

Medical charts, biochemical, histopathological and molecular results of patients with hepatic GSD were reviewed.

RESULTS

Out of 55 GSD patients, 41 (74.5%) were males and 14 (25.5%) were females with consanguinity in 50 (91%) patients. The median age of initial symptoms, clinic diagnosis and molecular diagnosis were 450 (IQR: 270-960), 1,095 (IQR: 510-1,825) and 1717 (IQR: 796-3,011) days, respectively. Molecular analysis and enzyme activity was available for 33 (60%) and two patients, respectively. GSD III (n=9) was most prevalent followed by GSD Ib (n=7), GSD IXc (n=6), GSD VI (n=4), GSD Ia (n=3), GSD XI (n=3), GSD IXb (n=2) and GSD IXa (n=1). In patients (n=33) who underwent molecular analysis; 19 different variants in eight genes associated with GSD were identified. We also report five novel variants, two in SLC37A4, one in AGL and two in PYGL contributing to the diagnosis of GSD Ib, GSD III and GSD VI, respectively.

CONCLUSIONS

Fifty-five patients of GSDs in 26 families from a single care provider indicate a relatively high frequency of GSD in Pakistan, with multiple unrelated families harboring identical disease-causing variants, on molecular analysis, including two known pathogenic variants in SLC37A4 and PHKG2, and a novel variant in AGL.

Histopathology of intestinal villi in neonatal and paediatric age: main features with clinical correlation - Part I

The neonatal and paediatric spectrum of small bowel disorders encompass a wide variety of conditions, ranging from food allergies to life-threatening surgical emergencies or life-long medical conditions and, as such, it comes with a whole set of diagnostic challenges for the non-paediatric pathologist. Histologic examination is a cornerstone of diagnosis in a large number of diseases and may still provide important diagnostic clues in the appropriate clinical context. In this review, divided in two sections, we aim to provide a comprehensive histopathological summary of paediatric small bowel alteration and their differential diagnoses with a reference to the main clinical aspects required for appropriate interpretation. Specifically, in this first part, we describe congenital and metabolic disorders, intestinal lymphangiectasia, immunodeficiencies, GVHD, and necrotising enterocolitis.

Favorable outcome of empagliflozin treatment in two pediatric glycogen storage disease type 1b patients

BACKGROUND

Glycogen storage disease type 1b (GSD1b) is an ultra-rare autosomal recessive disorder, caused by mutations in SLC37A4 gene. Affected patients present with episodes of fasting hypoglycemia and lactic acidosis, hepatomegaly, growth retardation, hyperlipidemia and renal impairment. In addition, patients present neutropenia, neutrophil dysfunction and oral, and skin infections as well as a significant predisposition to develop inflammatory bowel disease (IBD). Low neutrophil counts and function is related to the toxic accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P). Recently, several reports have shown that off-label treatment with empagliflozin (EMPA), an inhibitor of the renal glucose transporter SGLT2, decreased blood 1,5-anhydroglucitol (1,5-AG), and neutrophil 1,5-AG6P, thus resulting in a new therapeutic option for neutropenia and neutrophil dysfunction in patients.

METHODS

Off-label treatment with EMPA was established in two GSD1b patients after signed informed consent. The patients were followed clinically. We monitored neutrophil counts and function, 1,5-AG levels in plasma and its renal clearance before and during EMPA treatment.

RESULTS

A 17 year-old girl who had long standing oral ulcers and developed IBD, requiring systemic steroid and regular granulocyte colony-stimulating factor (GCSF) therapy and an 8 year-old boy who had steady non healing oral lesions were treated with empagliflozin during 18-24 months. Treatment led to increase of neutrophil counts and function with substantial clinical improvement. This included remission of IBD in the first patient which allowed to discontinue both GCSF and steroid therapy and resolution of oral lesions in both patients. The concentration of 1,5-AG in blood was greatly decreased within two weeks of treatment and remained stable thereafter.

CONCLUSIONS

Repurposing of empagliflozin to treat neutropenia in two GSD1b patients was safe and resulted in the urinary excretion of 1,5-AG, the normalization of neutrophil function, and a remarkable improvement of neutropenia-related clinical traits. We showed for the first time that empagliflozin increases concomitantly the renal clearance of both 1,5-anhydroglucitol and glucose in GSD1b patients.

The SGLT2-inhibitor dapagliflozin improves neutropenia and neutrophil dysfunction in a mouse model of the inherited metabolic disorder GSDIb

Glycogen Storage Disease type 1b (GSDIb) is a genetic disorder with long term severe complications. Accumulation of the glucose analog 1,5-anhydroglucitol-6-phosphate (1,5AG6P) in neutrophils inhibits the phosphorylation of glucose in these cells, causing neutropenia and neutrophil dysfunctions. This condition leads to serious infections and inflammatory bowel disease (IBD) in GSDIb patients. We show here that dapagliflozin, an inhibitor of the renal sodium-glucose co-transporter-2 (SGLT2), improves neutrophil function in an inducible mouse model of GSDIb by reducing 1,5AG6P accumulation in myeloid cells.

Infliximab treatment of glycogenosis Ib with Crohn's-like enterocolitis: A case report

BACKGROUND

Glycogen storage disease type Ib (GSD-Ib) is a glycogen metabolism disorder that leads to the manifestations of inflammatory bowel disease (IBD), especially Crohn’s disease (CD)-like colitis. Although biological agents are effective for treating CD, their application in the treatment of GSD-Ib with CD-like colitis has been rarely reported.

CASE SUMMARY

A 13-year-old Han male was diagnosed with GSD-Ib with CD. The patient was treated with granulocyte colony-stimulating factor. When he had symptoms of CD-like colitis, he was continuously pumped with enteral nutrition and administered oral mesalazine for 2 wk; however, the symptoms did not improve significantly. Hence, infliximab (IFX) was administered. Hitherto, the patient has been followed up for 1 year, and no clinical manifestations have been observed. After 6 mo of treatment (fifth IFX treatment), the disease activity index and all inflammatory indexes decreased, and a review of the colonoscopy data showed that the ulcers appeared smooth.

CONCLUSION

In this study, the patient was successfully treated with IFX. In cases of GSD-Ib, IBD should be highly considered.

Crohn disease-like enterocolitis remission after empagliflozin treatment in a child with glycogen storage disease type Ib: a case report

BACKGROUND

Besides major clinical/biochemical features, neutropenia and inflammatory bowel disease (IBD) constitute common complications of Glycogen storage disease type Ib (GSD Ib). However, their management is still challenging. Although previous reports have shown benefit of empagliflozin administration on neutropenia, no follow-up data on bowel (macro/microscopic) morphology are available. We herein present for the first time longitudinal assessment of bowel morphology in a GSD Ib child suffering from Crohn disease-like enterocolitis treated with empagliflozin.

CASE PRESENTATION

A 14-year-old boy with GSD Ib and severe IBD was (off-label) treated with empagliflozin (20 mg/day) after informed oral and written consent was obtained from the patient's parents. No adverse events were noted. Clinical symptoms and stool frequency improved within the first week of treatment. Pediatric Crohn disease activity index (PCDAI) normalised within the first month of treatment. Abdomen magnetic resonance imaging (MRI) performed 3 months after treatment initiation showed dramatic decrease in disease activity and length. Similar findings were reported on histology at 5.5 months. At 7.5 months hemoglobin levels normalised and fecal calprotectin almost normalised. Improved neutrophil count, metabolic control and quality of life were also noted. G-CSF dose was decreased by 33% and the patient was partly weaned from tube feeding.

CONCLUSIONS

This is the first report presenting extensive gastrointestinal morphology follow-up in a GSD Ib patient receiving empagliflozin. The present case suggests that empagliflozin can be safe and effective in inducing IBD remission in GSD Ib patients and can even postpone surgery. Future studies are required to confirm its effect over time and assess its benefit in various disease stages. The development of an international collaborating networks for systematic data collection is worthy.

Rare complication of inflammatory bowel disease-like colitis from glycogen storage disease type 1b and its surgical management: A case report

BACKGROUND

Glycogen storage disease (GSD) is an autosomal recessive inborn metabolic disorder. Patients with GSD are prone to hypoglycaemia, hyperlactacidemia and bleeding. GSD type 1b (GSD-1b) patients specifically can develop neutropenia, recurrent bacterial infection and inflammatory bowel disease (IBD). Documentation of the long-term outcomes of surgical management of GSD-1b has been scarce, especially for Asian patients. We herein describe a case of GSD-1b complicated by IBD-like colitis and coloduodenal fistula. The patient was managed successfully with surgical intervention.

CASE SUMMARY

A 20-year-old Chinese lady confirmed by genetic testing to have GSD-1b was initially managed with uncooked cornstarch and granulocyte-colony stimulating factor. With recurrent abdominal symptoms, her condition was treated as clinical “Crohn’s disease” with mesalazine, prednisolone and azathioprine conservatively. Colonoscopy showed a tight stricture at the hepatic flexure. Subsequent computerized tomographic colonography revealed a phlegmon at the ileocaecal region with a suspected coloduodenal fistula. Eventually an exploratory laparotomy was performed and severe colitis at the ascending colon with coloduodenal fistula was confirmed. Right hemicolectomy with primary anastomosis and repair of the duodenum were performed. Surgical management of complications from GSD-1b associated IBD-like colitis has rarely been described. First-line treatment would usually be conservative. Surgical intervention like hemicolectomy is mainly reserved for refractory cases.

CONCLUSION

Surgical management of coloduodenal fistula in GSD-1b patients is a feasible and safe option when failed conservative management.

LONG TERM MANAGEMENT OF GLYCOGEN STORAGE DISEASE TYPE 1B: A BRAZILIAN TERTIARY CENTER EXPERIENCE

BACKGROUND

Glycogen storage disease (GSD) type 1b is a multisystemic disease in which immune and infectious complications are present, in addition to the well-known metabolic manifestations of GSD. Treatment with granulocyte-colony stimulating factor (G-CSF) is often indicated in the management of neutropenia and inflammatory bowel disease.

OBJECTIVE

To report on the demographics, genotype, clinical presentation, management, and complications of pediatric patients with glycogen storage disease type 1b (GSD 1b), with special attention to immune-related complications.

METHODS

Retrospective case series of seven patients with GSD 1b diagnosed and followed at a tertiary university hospital in Brazil, from July/2000 until July/2016.

RESULTS

Mean age at referral was fourteen months. Diagnosis of GSD 1b was based on clinical and laboratory findings and supported by genetic studies in five cases. All patients presented suffered from neutropenia, managed with G-CSF - specifically Filgrastim. Hospitalizations for infections were frequent. Two patients developed inflammatory bowel disease. Six patients remained alive, one died at age 14 years and 9 months. The mean age at the end of the follow-up was 11.5 years. Compliance to treatment was suboptimal: poor compliance to medications, starch and dietetic management of GSD were documented, and outpatient appointments were frequently missed.

CONCLUSION

Managing GSD 1b is challenging not only for the chronic and multisystemic nature of this disease, but also for the additional demands related dietary restrictions, use of multiple medications and the need for frequent follow-up visits; furthermore in Brazil, the difficulties are increased in a scenario where we frequently care for patients with unfavorable socioeconomic status and with irregular supply of medications in the public health system.

Inborn errors of immunity and metabolic disorders: current understanding, diagnosis, and treatment approaches

Inborn errors of metabolism consist of a heterogeneous group of disorders with various organ systems manifestations, and some metabolic diseases also cause immunological disorders or dysregulation. In this review, metabolic diseases that affect the immunological system and particularly lead to primary immune deficiency will be reviewed. In a patient with frequent infections and immunodeficiency, the presence of symptoms such as growth retardation, abnormal facial appearance, heart, skeletal, lung deformities, skin findings, arthritis, motor developmental retardation, seizure, deafness, hepatomegaly, splenomegaly, impairment of liver function tests, the presence of anemia, thrombocytopenia and eosinophilia in hematological examinations should suggest metabolic diseases for the underlying cause. In some patients, these phenotypic findings may appear before the immunodeficiency picture. Metabolic diseases leading to immunological disorders are likely to be rare but probably underdiagnosed. Therefore, the presence of recurrent infections or autoimmune findings in a patient with a suspected metabolic disease should suggest that immune deficiency may also accompany the picture, and diagnostic examinations in this regard should be deepened.

Treating neutropenia and neutrophil dysfunction in glycogen storage disease type Ib with an SGLT2 inhibitor

Neutropenia and neutrophil dysfunction cause serious infections and inflammatory bowel disease in glycogen storage disease type Ib (GSD-Ib). Our discovery that accumulating 1,5-anhydroglucitol-6-phosphate (1,5AG6P) caused neutropenia in a glucose-6-phosphatase 3 (G6PC3)-deficient mouse model and in 2 rare diseases (GSD-Ib and G6PC3 deficiency) led us to repurpose the widely used antidiabetic drug empagliflozin, an inhibitor of the renal glucose cotransporter sodium glucose cotransporter 2 (SGLT2). Off-label use of empagliflozin in 4 GSD-Ib patients with incomplete response to granulocyte colony-stimulating factor (GCSF) treatment decreased serum 1,5AG and neutrophil 1,5AG6P levels within 1 month. Clinically, symptoms of frequent infections, mucosal lesions, and inflammatory bowel disease resolved, and no symptomatic hypoglycemia was observed. GCSF could be discontinued in 2 patients and tapered by 57% and 81%, respectively, in the other 2. The fluctuating neutrophil numbers in all patients were increased and stabilized. We further demonstrated improved neutrophil function: normal oxidative burst (in 3 of 3 patients tested), corrected protein glycosylation (2 of 2), and normal neutrophil chemotaxis (1 of 1), and bactericidal activity (1 of 1) under treatment. In summary, the glucose-lowering SGLT2 inhibitor empagliflozin, used for type 2 diabetes, was successfully repurposed for treating neutropenia and neutrophil dysfunction in the rare inherited metabolic disorder GSD-Ib without causing symptomatic hypoglycemia. We ascribe this to an improvement in neutrophil function resulting from the reduction of the intracellular concentration of 1,5AG6P.

Periodontal Manifestation of Type Ib Glycogen Storage Disease: A Rare Case Report

INTRODUCTION

Glycogen storage diseases (GSD) are genetic metabolic disorders of glycogen metabolism. There are >15 types based on the enzyme deficiency and the affected organ. Glycogen storage disease Type Ib is the only type associated with neutropenia and periodontitis. This type is caused by a deficiency of glucose-6-phosphate (G6P) translocase which prevents the transport of G6P across the endoplasmic reticulum. As a result, glycogen cannot be metabolized into glucose with its subsequent accumulation in tissues. The affected organs involved in Type Ib are the liver, kidney, and intestine.

CASE PRESENTATION

A 5-year-old Jordanian boy from a consanguineous family referred to the periodontal clinic in February 2014 with an established diagnosis of GSD-Ib. The systemic manifestations include hepatomegaly, hypoglycemia, hyperprolactenemia, inflammatory bowel disease, osteoporosis, and neutropenia. Oral manifestations include severe gingival inflammation and recurrent oral ulceration disease.

CONCLUSIONS

The clinical signs and symptoms of periodontal disease in GSD Type Ib are similar to those found in patients diagnosed with neutropenia. Future studies are needed to clarify whether severe generalized inflammation of the gingiva in children is part of the GSD Type Ib or is a separate entity caused by neutrophil dysfunction.

Combined liver-kidney transplantation for rare diseases

Combined liver and kidney transplantation (CLKT) is indicated in patients with failure of both organs, or for the treatment of end-stage chronic kidney disease (ESKD) caused by a genetic defect in the liver. The aim of the present review is to provide the most up-to-date overview of the rare conditions as indications for CLKT. They are major indications for CLKT in children. However, in some of them (e.g., atypical hemolytic uremic syndrome or primary hyperoxaluria), CLKT may be required in adults as well. Primary hyperoxaluria is divided into three types, of which type 1 and 2 lead to ESKD. CLKT has been proven effective in renal function replacement, at the same time preventing recurrence of the disease. Nephronophthisis is associated with liver fibrosis in 5% of cases and these patients are candidates for CLKT. In alpha 1-antitrypsin deficiency, hereditary C3 deficiency, lecithin cholesterol acyltransferase deficiency and glycogen storage diseases, glomerular or tubulointerstitial disease can lead to chronic kidney disease. Liver transplantation as a part of CLKT corrects underlying genetic and consequent metabolic abnormality. In atypical hemolytic uremic syndrome caused by mutations in the genes for factor H, successful CLKT has been reported in a small number of patients. However, for this indication, CLKT has been largely replaced by eculizumab, an anti-C5 antibody. CLKT has been well established to provide immune protection of the transplanted kidney against donor-specific antibodies against class I HLA, facilitating transplantation in a highly sensitized recipient.

Lumenal Galectin-9-Lamp2 interaction regulates lysosome and autophagy to prevent pathogenesis in the intestine and pancreas

Intracellular galectins are carbohydrate-binding proteins capable of sensing and repairing damaged lysosomes. As in the physiological conditions glycosylated moieties are mostly in the lysosomal lumen but not cytosol, it is unclear whether galectins reside in lysosomes, bind to glycosylated proteins, and regulate lysosome functions. Here, we show in gut epithelial cells, galectin-9 is enriched in lysosomes and predominantly binds to lysosome-associated membrane protein 2 (Lamp2) in a Asn(N)-glycan dependent manner. At the steady state, galectin-9 binding to glycosylated Asn175 of Lamp2 is essential for functionality of lysosomes and autophagy. Loss of N-glycan-binding capability of galectin-9 causes its complete depletion from lysosomes and defective autophagy, leading to increased endoplasmic reticulum (ER) stress preferentially in autophagy-active Paneth cells and acinar cells. Unresolved ER stress consequently causes cell degeneration or apoptosis that associates with colitis and pancreatic disorders in mice. Therefore, lysosomal galectins maintain homeostatic function of lysosomes to prevent organ pathogenesis.

Improved inflammatory bowel disease, wound healing and normal oxidative burst under treatment with empagliflozin in glycogen storage disease type Ib

Background

Glycogen storage disease type Ib (GSD Ib) is a rare inborn error of glycogen metabolism due to mutations in SLC37A4. Besides a severe form of fasting intolerance, the disorder is usually associated with neutropenia and neutrophil dysfunction causing serious infections, inflammatory bowel disease, oral, urogenital and perianal lesions as well as impaired wound healing. Recently, SGLT2 inhibitors such as empagliflozin that reduce the plasma levels of 1,5-anhydroglucitol have been described as a new treatment option for the neutropenia and neutrophil dysfunction in patients with GSD Ib.

Results

We report on a 35-year-old female patient with GSD Ib who had been treated with G-CSF for neutropenia since the age of 9. She had a large chronic abdominal wound as a consequence of recurrent operations due to complications of her inflammatory bowel disease. Treatment with 20 mg empagliflozin per day resulted in normalisation of the neutrophil count and neutrophil function even after termination of G-CSF. The chronic abdominal wound that had been unchanged for 2 years before the start of empagliflozin nearly closed within 12 weeks. No side effects of empagliflozin were observed.

Conclusion

SGLT2 inhibitors are a new and probably safe treatment option for GSD Ib-associated neutropenia and neutrophil dysfunction. We hypothesize that restoration of neutrophil function and normalisation of neutrophil apoptosis leads to improvement of wound healing and ameliorates symptoms of inflammatory bowel disease.

Infectious and digestive complications in glycogen storage disease type Ib: Study of a French cohort

Glycogenosis type Ib (GSD1B) causes not only hypoglycemia but also infections and “Crohn's disease like” inflammatory bowel disease (IBD) that can significantly impair patient's quality of life. We retrospectively evaluated infectious and digestive complications in 9 French patients (3 girls, 6 boys) diagnosed at 0.8 years on average, with a mean follow-up of 19.1 years. Infections occurred earlier than IBD, at mean ages of 1.7 and 3.8 years, respectively. The number of acute hospitalizations was 0.7/year due to infectious (0.4/year) or digestive symptoms (0.4/year). Clinical presentations allowed separating patients into mild (n = 5) and severe (n = 4) intestinal involvement. Patients in the severe group had more serious digestive symptoms but also earlier neutropenia (median 0.3 vs. 1.5 years, p =0 .046) with a tendency to a lower neutrophil count (NC) during follow-up, and a higher number of acute hospitalizations (median 1.3/year vs. 0.2/year, p =0 .014) due to digestive symptoms (median 0.6/year vs. 0.05/year, p = 0,012) and infections (median 0.8/year vs. 0.2/year, p =0 .014). Treatments included G-CSF and cotrimoxazole (n = 7), 5-aminosalicylic acid (n = 2), and a polymeric solution enriched in the anti-inflammatory cytokine TGF-β (n = 4, “severe” group), and immunomodulatory treatment (n = 1). In conclusion, infections and IBD are rare but severe complications in GSD1B. Neutropenia tended to be more prevalent in the severe IBD group than in the mild IBD group. Dietetic treatment with specific anti-inflammatory solutions seems particularly appropriate in these patients.

Genotype-phenotype correlation and description of two novel mutations in Iranian patients with glycogen storage disease 1b (GSD1b)

Background

Glycogen storage disease (GSD) is a rare inborn error of the synthesis or degradation of glycogen metabolism. GSD1, the most common type of GSD, is categorized into GSD1a and GSD1b which caused by the deficiency of glucose-6-phosphatase (G6PC) and glucose-6-phosphate transporter (SLC37A4), respectively. The high rates of consanguineous marriages in Iran provide a desirable context to facilitate finding the homozygous pathogenic mutations. This study designates to evaluate the clinical and genetic characteristics of patients with GSD1b to assess the possible genotype-phenotype correlation.

Results

Autozygosity mapping was performed on nineteen GSD suspected families to suggest the causative loci. The mapping was done using two panels of short tandem repeat (STR) markers linked to the corresponding genes. The patients with autozygous haplotype block for the markers flanking the genes were selected for direct sequencing. Six patients showed autozygosity in the candidate markers for SLC37A4. Three causative variants were detected. The recurrent mutation of c.1042_1043delCT (p.Leu348Valfs*53) and a novel missense mutation of c.365G > A (p.G122E) in the homozygous state were identified in the SLC37A4. In silico analysis was performed to predict the pathogenicity of the variants. A novel whole SLC37A4 gene deletion using long-range PCR and sequencing was confirmed as well. Severe and moderate neutropenia was observed in patients with frameshift and missense variants, respectively. The sibling with the whole gene deletion has shown both severe neutropenia and leukopenia.

Conclusions

The results showed that the hematological findings may have an appropriate correlation with the genotype findings. However, for a definite genotype-phenotype correlation, specifically for the clinical and biochemical phenotype, further studies with larger sample sizes are needed.

CDG and immune response: From bedside to bench and back

Glycosylation is an essential biological process that adds structural and functional diversity to cells and molecules, participating in physiological processes such as immunity. The immune response is driven and modulated by protein-attached glycans that mediate cell-cell interactions, pathogen recognition and cell activation. Therefore, abnormal glycosylation can be associated with deranged immune responses. Within human diseases presenting immunological defects are congenital disorders of glycosylation (CDG), a family of around 130 rare and complex genetic diseases. In this review, we have identified 23 CDG with immunological involvement, characterized by an increased propensity to-often life-threatening-infection. Inflammatory and autoimmune complications were found in 7 CDG types. CDG natural history(ies) and the mechanisms behind the immunological anomalies are still poorly understood. However, in some cases, alterations in pathogen recognition and intracellular signaling (eg, TGF-β1, NFAT, and NF-κB) have been suggested. Targeted therapies to restore immune defects are only available for PGM3-CDG and SLC35C1-CDG. Fostering research on glycoimmunology may elucidate the involved pathophysiological mechanisms and open new therapeutic avenues, thus improving CDG patients' quality of life.