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.

Immunological features and complications in patients with glycogen storage disease 1b after living donor liver transplantation.

BACKGROUND: LT is an elective treatment choice for children diagnosed with GSD1b that can improve their quality of life and stabilize their glucose intolerance. However, careful attention should be paid to immunosuppression after LT due to the susceptibility to infection because of neutropenia and neutrophil dysfunction in GSD1b patients. This study revealed the immunological features and complications in the early post-LT period. METHODS: We compared findings between 11 (1.9%) children with GSD1b and 273 children with BA. Analyses using the PSM were performed to overcome selection bias. RESULTS: Despite persistent low tacrolimus trough levels in GSD1b patients, none of these children developed TCMR within 1 month after LDLT (GSD1b: 0/11 [0%] vs. BA: 86/273 [31.5%], p = .038). This result was also confirmed in PSM. The incidence of bloodstream infections was higher in GSD1b patients than in BA patients in the early phase of the post-transplant period (GSD1b: 4/11 [36.4%] vs. BA: 33/273 [12.1%], p = .041), but not reach statistical significance in PSM. In a phenotypic analysis, the ratio of CD8+ T cells in GSD1b recipients' peripheral blood mononuclear cell samples was lower than in recipients with BA through the first month after LDLT. CONCLUSIONS: We found that GSD1b recipients were more likely to develop postoperative bloodstream infection than recipients with BA but did not experience TCMR despite low tacrolimus levels in the early post-LDLT period. A tailored immunosuppression protocol should be prepared for GSD1b recipients after LDLT.

Cutting Edge: Increased Autoimmunity Risk in Glycogen Storage Disease Type 1b Is Associated with a Reduced Engagement of Glycolysis in T Cells and an Impaired Regulatory T Cell Function.

Glycogen storage disease type 1b (GSD-1b) is an autosomal-recessive disease caused by mutation of glucose-6-phosphate transporter and characterized by altered glycogen/glucose homeostasis. A higher frequency of autoimmune diseases has been observed in GSD-1b patients, but the molecular determinants leading to this phenomenon remain unknown. To address this question, we investigated the effect of glucose-6-phosphate transporter mutation on immune cell homeostasis and CD4+ T cell functions. In GSD-1b subjects, we found lymphopenia and a reduced capacity of T cells to engage glycolysis upon TCR stimulation. These phenomena associated with reduced expression of the FOXP3 transcription factor, lower suppressive function in peripheral CD4+CD25+FOXP3+ regulatory T cells, and an impaired capacity of CD4+CD25- conventional T cells to induce expression of FOXP3 after suboptimal TCR stimulation. These data unveil the metabolic determinant leading to an increased autoimmunity risk in GSD-1b patients.

G6PC3 Deficiency: Primary Immune Deficiency Beyond Just Neutropenia.

Glucose-6-phosphatase catalytic subunit 3 (G6PC3) deficiency was recently defined as a new severe congenital neutropenia subgroup remarkable with congenital heart defects, urogenital malformations, endocrine abnormalities, and prominent superficial veins. Here, we report 3 patients with G6PC3 deficiency presenting with recurrent diarrhea, failure to thrive, and sinopulmonary infections leading to bronchiectasis. In patient I and II, a combined immune deficiency was suspected due to early-onset disease with lymphopenia, neutropenia, and thrombocytopenia, along with variable reductions in lymphocyte subpopulations and favorable response to intravenous γ-globulin therapy. Apart from neutropenia, all 3 patients had intermittent thrombocytopenia, anemia, and lymphopenia. All patients had failure to thrive and some of the classic syndromic features of G6PC3 deficiency, including cardiac abnormalities and visibility of superficial veins in all, endocrinologic problems in PI and PIII, and urogenital abnormalities in PII. Our experience suggests that a diagnosis of congenital neutropenia due to G6PC3 may not be as straightforward in such patients with combined lymphopenia and thrombocytopenia. A high index of suspicion and the other syndromic features of G6PC3 were clues to diagnosis. Screening of all combined immune deficiencies with neutropenia may help to uncover the whole spectra of G6PC3 deficiency.

[Cochlear implantation in immunocompromised patients].

This paper reports a clinical case that gives evidence of the possibility of cochlear implantation after liver transplantation. Patient K. aged 3 years 10 months was admitted to the Russian Research and Practical Centre of Audiology and Hearing Rehabilitation with the diagnosis of type IB glycogenosis after maternal liver transplantation associated with chronic neutropenia, chronic cutaneous and mucosal infection, partial symptomatic partial epilepsy, retarded psycho-motor development, and complaints of the absence of auditory response. The audiological examination provided materials for the diagnosis of grade IV bilateral sensorineural hearing loss tending toward deafness. Cochlear implantation recommended to the patient was performed on February 20, 2013 using the HiRes 90 K implant with the HiFocus Helix electrode (Advanced Bionics, USA). The surgical intervention and the postoperative period passed without complications. The speech processor was activated one month after surgery. The results of surdopedagogical testing gave evidence of successful rehabilitation promising the further improvement. It is concluded that immunosuppressive therapy is not an absolute contraindication for cochlear implantation, but this procedure requires detailed examination and thorough preparation for the forthcoming surgery.

Antibodies to CBir1 are associated with glycogen storage disease type Ib.

OBJECTIVES: : Glycogen storage disease (GSD) type Ib is a congenital disorder of glycogen metabolism that is associated with neutropenia, neutrophil and monocyte dysfunction, and an inflammatory bowel disease (IBD) that mimics a Crohn disease phenotype. The enteric microflora is implicated in the pathogenesis of IBD; however, its role in the development of GSD-associated IBD is unknown. Antibody reactivity to Saccharomyces cerevisiae antibodies (ASCA), Escherichia coli outer membrane porin C (anti-OmpC), and bacterial flagellin (anti-CBir1) have been associated with Crohn disease in the general population, but they have an undetermined association in children and adults with GSD-Ib. Our goal was to examine the association of ASCA, anti-OmpC, and anti-CBir1 with the clinical features of GSD-Ib enterocolitis. PATIENTS AND METHODS: : A retrospective review identified 19 patients with GSD-Ib with or without a known diagnosis of enterocolitis. Radiographic, endoscopic, and serologic data were collected and assays for ASCA, anti-OmpC, and anti-CBir1 obtained. RESULTS: : Seven patients had combined radiographic, endoscopic, and histologic evidence of intestinal inflammation; the majority had ileocolonic involvement. Seventeen of 19 (89%) patients had elevated anti-CBir1 levels (6/7 in the IBD group and 11/12 in the no clinical evidence of IBD group). Thirteen of 19 (68%) had elevated anti-OmpC levels (5/7 in the IBD group and 8/12 in the no clinical evidence of IBD group). Eleven of 19 (58%) patients had elevated ASCA IgA levels (4/7 in the IBD group and 7/12 in the no clinical evidence of IBD group). CONCLUSIONS: : Nearly all of the patients with GSD-Ib had elevated anti-CBir1 levels. The antibody did not differentiate those with and without a diagnosis of GSD-Ib-associated IBD. Seroreactivity to flagellin may represent immune dysfunction rather than active enterocolitis in this patient population. Long-term follow-up of the group without known IBD is required to determine whether these antibodies can predict intestinal inflammation.

[Cutaneous ulcers and glycogen storage disease type 1b]. / Ulcères cutanés au cours d'une glycogénose de type 1b.

BACKGROUND: Glycogen storage disease type 1b is a rare disorder caused by 6-glucose-phosphatase transport deficiency. It is characterised primarily by metabolic disorders combined with hypoglycaemia and hyperlactacidaemia and a predisposition to staphylococcal infections associated with polynuclear neutrophil abnormality. Herein, we report the case of a patient with glycogen storage disease type 1b who developed ulcers of the lower limbs and we discuss the possible significance of this association which, to our knowledge, has not yet been described in the medical literature. PATIENTS AND METHODS: A 38-year-old man, presenting glycogen storage disease type 1b diagnosed when he was 13 months old, was hospitalised for ulcers of the lower limbs occurring over the preceding five years. The patient had a quantitative polynuclear neutrophil deficit that was treated with filgrastim. The various ulcers all developed according to the same pattern, namely pustules progressing towards necrosis followed by painful ulceration. No fever or collection of pus was observed. A number of samples of pustules proved sterile while others contained Staphylococcus aureus, sensitive to numerous antibiotics. Histopathological examination proved relatively inconclusive and laboratory tests showed no vascular cause of the ulcers. DISCUSSION: Hypothetical diagnoses of staphylococcal ecthyma suggested by the neutrophil deficiency and of pyoderma gangrenosum were proposed but could not be confirmed with certainty. Involvement of other predisposing factors independent of the patient's glycogen storage disease cannot be ruled out. This combination, not previously reported, nevertheless deserves to be singled out, despite its as yet unclear significance.

Glycogen storage disease type Ib: role of glucose-6-phosphate transporter in cell metabolism and function.

Cellular metabolism generally refers to biochemical processes that produce or consume energy within the cell. Recent studies have established that aberrant metabolic states caused by internal or external stresses and genetic mutations are intertwined with several human pathologies. Gaining insight into these metabolic alterations is, therefore, essential for understanding the pathophysiology of various diseases. Glycogen storage disease type Ib (GSD-Ib) is an autosomal recessive disorder characterized by hypoglycemia, excessive glycogen accumulation in the liver and kidney, neutropenia, neutrophil dysfunction, and inflammatory bowel disease. GSD-Ib is caused by a deficiency of glucose-6-phosphate transporter (G6PT). Recently, it was reported that deficiency of G6PT also leads to the aberrant proliferation and differentiation of mesenchymal stem cells and impaired regulatory T-cell function. This review describes the broad impact of altered cellular metabolism resulting from a lack of G6PT activity on cellular function and considers the prospects of developing novel approaches for GSD-Ib treatment.

Myasthenia gravis in a patient affected by glycogen storage disease type Ib: a further manifestation of an increased risk for autoimmune disorders?

Glycogen storage disease type Ib (GSD Ib, OMIM 232220) is an inborn disorder of glucose metabolism, caused by mutations in the G6PT gene, encoding a glucose 6-phosphate transporter (G6PT). GSD Ib is mainly associated with fasting hypoglycaemia and hepatomegaly. Most GSD Ib patients also show neutropenia and neutrophil dysfunction and therefore are at risk of developing severe infections and inflammatory bowel disease (IBD). An increased risk for autoimmune disorders, such as thyroid autoimmunity and Crohn-like disease, has also been demonstrated, but no systematic study on the prevalence of autoimmune disorders in GSD Ib patients has ever been performed. We describe a 25-year-old patient affected by GSD Ib who developed 'seronegative' myasthenia gravis (MG), presenting with bilateral eyelid ptosis, diplopia, dysarthria, severe dysphagia, dyspnoea and fatigue. The repetitive stimulation of peripheral nerves test showed signs of exhaustion of neuromuscular transmission, particularly evident in the cranial area. Even in the absence of identifiable anti-acetylcholine receptor antibodies, seronegative MG is considered an autoimmune disorder and may be related to the disturbed immune function observed in GSD Ib patients.

Hemolysis and hyperbilirubinemia in an African American neonate heterozygous for glucose-6-phosphate dehydrogenase deficiency.

Despite recent case reports of bilirubin encephalopathy in African American glucose-6-phosphate dehydrogenase (G6PD)-deficient neonates, there is a misconception that, in African Americans, G6PD deficiency need not be considered in the differential diagnosis of hyperbilirubinemia. We present a case of a hyperbilirubinemic African American female neonate in whom coexisting G6PD deficiency in the heterozygous state, and Gilbert's syndrome, were confirmed by DNA analysis. Hemolysis, predictive of the subsequent icterus, was documented by end-tidal carbon monoxide determinations at two time periods within the first 25 hours of life. A diagnosis of G6PD deficiency should be considered in African American neonates, females as well as males, with unexplained hemolysis or hyperbilirubinemia.

Involvement of endocrine system in a patient affected by glycogen storage disease 1b: speculation on the role of autoimmunity.

Glycogen storage disease type 1b (GSD1b) is an inherited metabolic defect of glycogenolysis and gluconeogenesis due to mutations of the SLC37A4 gene and to defective transport of glucose-6-phosphate. The clinical presentation of GSD1b is characterized by hepatomegaly, failure to thrive, fasting hypoglycemia, and dyslipidemia. Patients affected by GSD1b also show neutropenia and/or neutrophil dysfunction that cause increased susceptibility to recurrent bacterial infections. GSD1b patients are also at risk for inflammatory bowel disease. Occasional reports suggesting an increased risk of autoimmune disorders in GSD1b patients, have been published. These complications affect the clinical outcome of the patients. Here we describe the occurrence of autoimmune endocrine disorders including thyroiditis and growth hormone deficiency, in a patient affected by GSD1b. This case further supports the association between GSD1b and autoimmune diseases.

Early, sustained efficacy of adeno-associated virus vector-mediated gene therapy in glycogen storage disease type Ia.

The deficiency of glucose-6-phosphatase (G6Pase) underlies life-threatening hypoglycemia and growth retardation in glycogen storage disease type Ia (GSD-Ia). An adeno-associated virus (AAV) vector encoding G6Pase was pseudotyped as AAV8 and administered to 2-week-old GSD-Ia mice (n = 9). Median survival was prolonged to 7 months following vector administration, in contrast to untreated GSD-Ia mice that survived for only 2 weeks. Although GSD-Ia mice were initially growth-retarded, treated mice increased fourfold in weight to normal size. Blood glucose was partially corrected by 2 weeks following treatment, whereas blood cholesterol normalized. Glucose-6-phosphatase activity was partially corrected to 25% of the normal level at 7 months of age in treated mice, and blood glucose during fasting remained lower in treated, affected mice than in normal mice. Glycogen storage was partially corrected in the liver by 2 weeks following treatment, but reaccumulated to pre-treatment levels by 7 months old (m.o.). Vector genome DNA decreased between 3 days and 3 weeks in the liver following vector administration, mainly through the loss of single-stranded genomes; however, double-stranded vector genomes were more stable. Although CD8+ lymphocytic infiltrates were present in the liver, partial biochemical correction was sustained at 7 m.o. The development of efficacious AAV vector-mediated gene therapy could significantly reduce the impact of long-term complications in GSD-Ia, including hypoglycemia, hyperlipidemia and growth failure.

Short communication. Glycogenosis Ib: neutrophil microbicidal defects due to impaired hexose monophosphate shunt.

We studied neutrophil microbicidal function and oxidative metabolic activity in a patient with glycogenosis Ib. The intracellular killing defect and the respiratory burst abnormality in gycogenosis Ib neutrophils were confirmed. The impaired oxygen-dependent microbicidal activity was shown to result from impaired hexose monophosphate shunt activity (impaired endogenous NADPH synthesis) and could be corrected by homogenization of the cells, followed by the addition of exogenous NADPH. Our data are thus consistent with a possible role for glucose-6-phosphate transport in neutrophil microbicidal function. We recommend a continuous prophylaxis with co-trimoxazole in patients with glycogen storage disease Ib.

Purification of human microsomal liver glucose-6-phosphatase system by affinity chromatography and immunodetection.

A multiple purification of phosphohydrolase (PH) and phosphotranslocase (PT) of the human liver microsomal glucose-6-phosphatase system has been obtained by a rapid two-step procedure using affinity chromatography. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the final products showed one major band each at 63 and 37 kDa for PH and PT respectively. The immunoblot analysis of SDS-PAGE of various purification steps for human liver using rabbit antibodies raised against the enzyme preparations also showed major bands at 63 and 37 kDa for PH and PT respectively. A major band at 260 kDa was observed by the Western blot of native PAGE of the enzyme preparation for PH. Cross-reacting materials at the positions of 63 and 37 kDa were detected only in liver, kidney and intestine. From five liver samples of patients suffering from type Ia glycogenosis there were diminished amounts of crossreacting materials at 63 kDa only in two samples. The uptake of glucose-6-phosphate has taken place in liposomes of Sepharose affinity purified products suggesting that this preparation may be a complex of PH and glucose-6-phosphate translocase.

Immune deficiency in glycogen storage disease type 1B.

Patients with glycogen storage disease type 1B present the clinical features of glycogen storage disease type 1A. In addition, they are susceptible to recurrent bacterial infection and have recurrent oral ulcers and occasionally Crohn's-like disease. There features are due to immune dysfunction caused by a combination of neutropenia and impaired phagocytic functions.

[Present-day status of glycogenosis Ib. Report of a new case]. / Estado actual de la glucogenosis Ib. Aportación de un nuevo caso.

A four-month-old boy affected by glycogen storage disease type I is presented. The child suffered from hepatomegaly, lactic acidosis, fasting hypoglycemia and failure to thrive. He had repeated infectious and cyclic neutropenia. Immunoglobulin and chemotactic neutrophil motility was impaired. Liver biopsy showed increased amounts of glycogen in hepatic cells as assessed by morphological and biochemical grounds. The activity of glucose-6-phosphatase as well as other glycogenolytic enzymes was normal in the frozen liver. The aforementioned characteristics suggested the diagnosis of glycogen storage disease type Ib. The child was first treated by enteral continuous feeding and later on by frequent meals during the daytime and enteral continuous feeding during the night time, improving the hypoglycemia as well as the other biochemical and metabolic abnormalities.

Inflammatory bowel disease in glycogen storage disease type Ib.

We have observed the development of chronic inflammatory bowel disease, indistinguishable from Crohn disease, in two boys with glycogen storage disease type Ib (GSD-Ib). A chance association of these diseases in two patients is unlikely. Studies of their neutrophils showed severe chronic neutropenia (mean absolute granulocyte counts of less than 500 cells/microliter) and markedly deficient chemotactic response (less than 5% of reference values) in the patients with GSD-Ib and normal neutrophil values in four patients with glycogen storage disease type Ia (GSD-Ia). Monocyte counts and responses to chemotactic stimulation were normal in both GSD-Ia and GSD-Ib. Chronic inflammatory bowel disease appears to be associated with GSD-Ib, and neutrophil abnormalities may be involved in the pathogenesis of the bowel inflammation.

Neutropenia and impaired neutrophil function in glycogenosis type Ib.

The impairment of different neutrophil functions has recently been reported in some patients with glycogenosis Ib and neutropenia. However, no satisfactory explanation for these findings has so far been supplied. In order to investigate this problem, we have studied neutrophil functions (random locomotion and chemotaxis, O-2 release, [1-14C]glucose oxidation and cellular cytotoxicity) in two further patients with glycogenosis Ib and neutropenia. The results show that neutrophil dysfunctions related to the involvement of both hexose monophosphate shunt and anaerobic glycolysis were variable. The heterogeneity of neutrophil functional impairment in glycogenosis Ib and their possible relationship with the basic metabolic defect of the disease are discussed.

In vitro and in vivo effects of granulocyte colony-stimulating factor on neutrophils in glycogen storage disease type 1B: granulocyte colony-stimulating factor therapy corrects the neutropenia and the defects in respiratory burst activity and Ca2+ mobilization.

Children with glycogen storage disease (GSD) type 1b are susceptible to recurrent bacterial infections and have chronic neutropenia accompanied by phagocytic cell dysfunction including decreased superoxide anion (O2-) generation, calcium (Ca2+) mobilization, and chemotactic activity. Granulocyte colony-stimulating factor (G-CSF), a cytokine that corrects neutropenia in other diseases, in vitro enhances f-Met-Leu-Phe-triggered neutrophil O2- generation. Short-term pretreatment (15 min) of GSD 1b neutrophils with G-CSF increased the rate of O2- production (p < 0.01); however, this rate was still significantly below the rate of O2- production in control neutrophils. Recombinant human G-CSF (5 micrograms/kg/d) was administered s.c. to a GSD 1b patient. Before treatment, absolute neutrophil counts were < 500/mm3. Two d after G-CSF administration, the absolute neutrophil counts increased to 1333 and remained in the normal range during a 12-mo follow-up period. In vivo, G-CSF therapy increased f-Met-Leu-Phe-stimulated O2- production to 52% of control after 1 mo, and by mo 4, O2- production reached control levels. Our previous studies (J Clin Invest 56:196-202, 1990) demonstrated that decreased O2- production in neutrophils was associated with impaired Ca2+ mobilization. In vivo administration of G-CSF increased f-Met-Leu-Phe-triggered Ca2+ mobilization by neutrophils to 43% of control by mo 1 of G-CSF therapy and to 93% of control by mo 4, thus paralleling the improvements in O2- generation. In contrast, G-CSF therapy had no effect on the defective neutrophil chemotaxis. In summary, G-CSF therapy produced a rapid increase in circulating neutrophils and a gradual correction of O2- production.(ABSTRACT TRUNCATED AT 250 WORDS)