The overall benefits of empagliflozin treatment in adult siblings with glycogen storage disease type Ib: one year experience

IntroductionRecently published case reports suggest the benefit of empagliflozin use in subjects with glycogen storage disease Ib (GSD Ib).MethodsWe present the clinical and laboratory data of 2 adult brothers with GSD Ib treated with empagliflozin for 12 months.ResultsThere was no severe infection during administration of empagliflozin. The improvement of clinical symptoms of inflammatory bowel disease and arthritis along with reduction in serum CRP levels and urinary albumin excretion was noted. Neutrophil count increased, allowing for reduction or temporary withdrawal of G-CSF treatment.ConclusionsEmpagliflozin may be a new safe treatment in GSD Ib patients with an advanced stage of the disease.     

Noncompaction myocardium in association with type Ib glycogen storage disease

Noncompaction myocardium is a rare disorder assumed to occur as an arrest of the compaction process during the normal development of the heart. Left ventricular noncompaction has been reported to be associated with a variety of cardiac and extracardiac, especially neuromuscular abnormalities. Moreover, it has been suggested that metabolic alterations could be responsible for the noncompaction. However, no association of noncompaction myocardium with type Ib glycogen storage disease (GSD) has been reported so far. Type Ib GSD is due to a defect of a transmembrane protein which results, similar to type Ia GSD, in hypoglycemia, a markedly enlarged liver and, additionally, in neutropenia, recurrent infections, and inflammatory bowel disease. Until now, no muscular or cardiac involvement has been described in type Ib GSD patients. The present case represents the first report of a noncompaction myocardium in a child with type Ib GSD who died of sudden clinical deterioration at the age of four.     

Functional analysis of mutations in the glucose-6-phosphate transporter that cause glycogen storage disease type Ib

The glucose-6-phosphate transporter (G6PT) deficient in glycogen storage disease type Ib is a phosphate (P_i)-linked antiporter capable of G6P: P_i and P_i:P_i exchanges. We previously characterized G6PT mutations by measuring G6P uptake activities in microsomes co-expressing G6PT and glucose-6-phosphatase-α. Here we report a new assay, based on reconstituted proteoliposomes carrying only G6PT, and characterize G6P and P_i uptake activities of 23 G6PT mutations. We show that co-expression and G6PT-only assays are equivalent in measuring G6PT activity. However, the p.Q133P mutation exhibits differential G6P and P_i transport activities, suggesting that characterizing G6P and P_i transport activities of G6PT mutations may yield insights to this genetic disorder.     

Hepatocellular adenoma and metabolic balance in patients with type Ia glycogen storage disease

Glycogen storage disease type I (GSD I) is a metabolic disorder resulting from defects in the glucose-6-phosphatase system. Approximately 75% of adolescent and adult patients develop hepatocellular adenomas, which can lead to considerable morbidity and mortality. The pathogenesis of adenomas is unclear and the risk of developing adenomas in treated patients is uncertain. The objective of this study was to determine whether metabolic imbalance was related to the occurrence of adenomas in patients with GSD I, and to determine what specific biochemical pathways were involved. We performed a 1:1 case–control retrospective study; cases were GSD I patients with adenomas and controls were GSD I patients without adenomas. Controls and cases were matched according to age at diagnosis, age at adenoma detection, and gender. We investigated biochemical abnormalities indicative of metabolic balance and exogenous factors potentially related to the onset of adenomas in the two groups. We detected no significant differences in dietetic treatment, compliance to treatment, or biochemical parameters related to metabolic balance between the two groups. In conclusion, we were unable to identify any significant differences in metabolic balance between GSD I patients who developed adenomas and those who did not.     

Genetic testing of glycogen storage disease type Ib in Japan: five novel G6PT1 mutations and a rapid detection method for a prevalent mutation W118R

We devised a simple method using a TaqMan fluorogenic probe for detection of a prevalent G6PT1 mutation W118R among Japanese patients with glycogen storage disease type Ib. The W118R mutation was detected in three of six newly diagnosed Japanese patients. The W118R-negative alleles were screened for causative mutations by sequencing analysis, revealing five novel mutations. The genetic tests using the simple TaqMan method coupled with sequencing analysis would facilitate the early diagnosis of this disorder.     

Glycemic control and complications in glycogen storage disease type I: Results from the Swiss registry

BackgroundRegular carbohydrate intake to avoid hypoglycemia is the mainstay of dietary treatment in glycogen storage disease type I (GSDI). The aim of this study was to evaluate the quality of dietary treatment and glycemic control in a cohort of GSDI patients, in relation to the presence of typical long-term complications.MethodsData of 25 patients (22 GSD subtype Ia and 3 GSDIb, median age 20y) from the Swiss hepatic glycogen storage disease registry was analyzed cross-sectionally. Frequency and type of hypoglycemia symptoms were assessed prospectively using a structured questionnaire. Diagnostic continuous glucose monitoring (CGM) was performed as part of usual clinical care to assess glycemic control in 14 patients, usually once per year with a mean duration of 6.2 ± 1.1 consecutive days per patient per measurement.ResultsAlthough maintenance of euglycemia is the primary goal of dietary treatment, few patients (n = 3, 13%) performed capillary blood glucose measurements regularly. Symptoms possibly associated with hypoglycemia were present in 13 patients (57%), but CGM revealed periods of low glucose (<4 mmol/l) in all patients, irrespective of the presence of symptoms. GSDIa patients with liver adenomas (n = 9, 41%) showed a higher frequency and area under the curve (AUC) of low blood glucose than patients without adenomas (frequency 2.7 ± 0.8 vs. 1.5 ± 0.7 per day, AUC 0.11 ± 0.08 vs. 0.03 ± 0.02 mmol/l/d; p < 0.05). Similarly, the presence of microalbuminuria was also associated with the frequency of low blood glucose. Z-Scores of bone density correlated negatively with lactate levels.ConclusionThe quality of glucose control is related to the presence of typical long-term complications in GSDI. Many patients experience episodes of asymptomatic low blood glucose. Regular assessment of glucose control is an essential element to evaluate the quality of treatment, and increasing the frequency of glucose self-monitoring remains an important goal of patient education and motivation. CGM devices may support patients to optimize dietary therapy in everyday life.     

Glucose-6-phosphatase gene mutations in Taiwan Chinese patients with glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD Ia) is caused by a deficiency of glucose-6-phosphatase (G6Pase) activity. Eighteen GSD Ia families were studied for G6Pase gene mutations. Thirty-two mutations were found in 36 GSD Ia chromosomes: 16 were 727 G→T (44.44%); 13 were R83H (327 G→T; 36.11%); 1 was 341delG; 1 was 933insAA; and 1 was 793 G→T. The 727 G→T and R83H mutations together accounted for 80.56% (29/36) of the GSD Ia chromosomes. These two mutations were easily examined by polymerase chain reaction-based methods, and the prenatal diagnosis of a non-affected fetus was successfully made. The 727 G→T mutation is the predominant mutation in Japanese GSD Ia patients, but is rarely seen in Western counties. The 727 G→T mutation is also the most prevalent mutation in Taiwan Chinese, although the incidence is not as high as in Japan. Received: January 4, 2000 / Accepted: February 28, 2000     

Molecular characterization of Egyptian patients with glycogen storage disease type IIIa

Glycogen storage disease type IIIa (GSD IIIa) is an autosomal recessive disorder characterized by excessive accumulation of abnormal glycogen in the liver and muscles and caused by a deficiency in the glycogen debranching enzyme. The spectrum of AGL mutations in GSD IIIa patients depends on ethnic group—prevalent mutations have been reported in the North African Jewish population and in an isolate such as the Faroe islands, because of the founder effect, whereas heterogeneous mutations are responsible for the pathogenesis in Japanese patients. To shed light on molecular characteristics in Egypt, where high rate of consanguinity and large family size increase the frequency of recessive genetic diseases, we have examined three unrelated patients from the same area in Egypt. We identified three different individual AGL mutations; of these, two are novel deletions [4-bp deletion (750–753delAGAC) and 1-bp deletion (2673delT)] and one the nonsense mutation (W1327X) previously reported. All are predicted to lead to premature termination, which completely abolishes enzyme activity. Three consanguineous patients are homozygotes for their individual mutations. Haplotype analysis of mutant AGL alleles showed that each mutation was located on a different haplotype. Our results indicate the allelic heterogeneity of the AGL mutation in Egypt. This is the first report of AGL mutations in the Egyptian population.     

Diffuse reticuloendothelial system involvement in type IV glycogen storage disease with a novel GBE1 mutation: a case report and review

Glycogen storage disease type IV is a rare autosomal recessive disorder of glycogen metabolism caused by mutations in the GBE1 gene that encodes the 1,4-alpha-glucan-branching enzyme 1. Its clinical presentation is variable, with the most common form presenting in early childhood with primary hepatic involvement. Histologic manifestations in glycogen storage disease type IV typically consist of intracytoplasmic non-membrane-bound inclusions containing abnormally branched glycogen (polyglucosan bodies) within hepatocytes and myocytes. We report a female infant with classic hepatic form of glycogen storage disease type IV who demonstrated diffuse reticuloendothelial system involvement with the spleen, bone marrow, and lymph nodes infiltrated by foamy histiocytes with intracytoplasmic polyglucosan deposits. Sequence analysis of the GBE1 gene revealed compound heterozygosity for a previously described frameshift mutation (c.1239delT) and a novel missense mutation (c.1279G>A) that is predicted to alter a conserved glycine residue. GBE enzyme analysis revealed no detectable activity. A review of the literature for glycogen storage disease type IV patients with characterized molecular defects and deficient enzyme activity reveals most GBE1 mutations to be missense mutations clustering in the catalytic enzyme domain. Individuals with the classic hepatic form of glycogen storage disease type IV tend to be compound heterozygotes for null and missense mutations. Although the extensive reticuloendothelial system involvement that was observed in our patient is not typical of glycogen storage disease type IV, it may be associated with severe enzymatic deficiency and a poor outcome.     

A novel mutation (A148V) in the glucose 6-phosphate translocase (SLC37A4) gene in a Korean patient with glycogen storage disease type 1b

We report a Korean patient with glycogen storage disease type 1b (GSD-1b) whose diagnosis was confirmed by liver biopsy and laboratory results. The patient presented with delay of puberty and short stature on admission and had typical clinical symptoms of GSD as well as chronic neutropenia and inflammatory bowel disease. Mutation analysis of the glucose 6-phosphate translocase 6-phosphate translocase (SLC37A4) gene revealed that the patient was a compound heterozygote of two different mutations including a deletion mutation (c.1042_1043delCT; L348fs) and a missense mutation (A148V). The L348fs mutation was inherited from the patient's father and has been reported in an Italian family with GSD-1b, while the A148V mutation was transmitted from the patient's mother and was a novel mutation. To the best of our knowledge, this is the first report of genetically confirmed case of GSD-1b in Korean.     

Activation of glycolysis and apoptosis in glycogen storage disease type Ia

The deficiency of glucose-6-phosphatase (G6Pase) underlies glycogen storage disease type Ia (GSD-Ia, von Gierke disease; MIM 232200), an autosomal recessive disorder of metabolism associated with life-threatening hypoglycemia, growth retardation, renal failure, hepatic adenomas, and hepatocellular carcinoma. Liver involvement includes the massive accumulation of glycogen and lipids due to accumulated glucose-6-phosphate and glycolytic intermediates. Proteomic analysis revealed elevations in glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and other enzymes involved in glycolysis. GAPDH was markedly increased in murine G6Pase-deficient hepatocytes. The moonlighting role of GAPDH includes increasing apoptosis, which was demonstrated by increased TUNEL assay positivity and caspase 3 activation in the murine GSD-Ia liver. These analyses of hepatic involvement in GSD-Ia mice have implicated the induction of apoptosis in the pathobiology of GSD-Ia.     

Glycogen storage disease type Ia: molecular study in Brazilian patients

Mutations in the glucose-6-phosphatase (G6Pase) gene are responsible for glycogen storage disease type Ia (GSDIa). This disease is characterized by growth retardation, hepatomegaly, hypoglycemia, hyperlipidemia, and lactic acidosis. In this study, we report mutations in the G6Pase gene in 8 of 25 Brazilian patients with clinical symptoms of GSDIa. Five previously described mutations (R83C, Q347X, V338F, D38V, and G68R) were detected. The two most common mutations identified were R83C and Q347X, accounting for 8 of 14 (57.14%) mutant alleles. A 1176 single-nucleotide polymorphism and two intronic mutations (IVS3-58T>A and IVS4+10G>A) were also analyzed. We used the minigene strategy in order to verify the effect of these intronic mutations on the splicing mechanism. This study emphasizes that molecular genetic analysis is a reliable and convenient alternative to the assay of enzyme activity in a fresh liver biopsy specimen for diagnosing GSDIa. Received: November 13, 2000 / Accepted: December 25, 2000     

Metabolic characterisation of plasma in juveniles with glycogen storage disease type 1a (GSD1a) by high-resolution (1)H NMR spectroscopy

This paper reports the first application of high-resolution (1)H NMR spectroscopy to the plasma of five juveniles with glycogen storage disease type 1a (GSD1a), permitting the characterisation of the plasma metabolic profile and the identification of alterations relative to a set of control samples. The relaxation-weighted spectra allowed changes in low molecular weight compounds to be detected more clearly, whereas diffusion-edited spectra were used to characterise the plasma lipoprotein profile. Low molecular weight metabolites with altered levels in most patients were lactate, ketone bodies, acetate, creatine/creatinine and glucose. One of the patients showed distinctively lower glucose levels and higher lactate and ketone body contents, suggesting poorer metabolic control of the disease compared with other patients. In addition, a metabolite tentatively identified as alpha-hydroxyisobutyrate was only detected in the spectra of GSD1a plasmas, representing, therefore, a possible novel GSD1a biomarker. Total lipoprotein contents were higher in the plasma from GSD1a patients. Furthermore, lower HDL and higher VLDL + LDL levels also characterised the plasma of these patients. Preliminary results on principal component analysis of (1)H NMR spectra allowed a clear separation between GSD1a and control plasmas. The specificity of the changes observed to GSD1a is discussed, together with the recognised potential of NMR and pattern recognition methods for aiding the diagnosis of GSD1a.     

Mutations in the glucose-6-phosphatase-alpha (G6PC) gene that cause type Ia glycogen storage disease

Glucose-6-phosphatase-alpha (G6PC) is a key enzyme in glucose homeostasis that catalyzes the hydrolysis of glucose-6-phosphate to glucose and phosphate in the terminal step of gluconeogenesis and glycogenolysis. Mutations in the G6PC gene, located on chromosome 17q21, result in glycogen storage disease type Ia (GSD-Ia), an autosomal recessive metabolic disorder. GSD-Ia patients manifest a disturbed glucose homeostasis, characterized by fasting hypoglycemia, hepatomegaly, nephromegaly, hyperlipidemia, hyperuricemia, lactic acidemia, and growth retardation. G6PC is a highly hydrophobic glycoprotein, anchored in the membrane of the endoplasmic reticulum with the active center facing into the lumen. To date, 54 missense, 10 nonsense, 17 insertion/deletion, and three splicing mutations in the G6PC gene have been identified in more than 550 patients. Of these, 50 missense, two nonsense, and two insertion/deletion mutations have been functionally characterized for their effects on enzymatic activity and stability. While GSD-Ia is not more prevalent in any ethnic group, mutations unique to Caucasian, Oriental, and Jewish populations have been described. Despite this, GSD-Ia patients exhibit phenotypic heterogeneity and a stringent genotype-phenotype relationship does not exist.     

Mutational and haplotype analysis of <Emphasis Type="Italic">AGL</Emphasis> in patients with glycogen storage disease type III

Glycogen storage disease type III (GSD III) is a rare autosomal recessive inherited disorder caused by a deficiency of the glycogen-debranching enzyme (AGL). We investigated two GSD III patients and identified four different mutations. Nucleotide sequence analysis revealed patient 1 of Chinese descent to be a compound heterozygote for a novel nonsense mutation, R34X, and the splicing mutation (IVS32−12A > G) reported in a Japanese patient. Patient 2 of Japanese origin was found to be compound heterozygous for a novel nonsense mutation, Y1148X, and the splicing mutation (IVS14+1G > T) that we had described previously. To determine whether splicing mutations occurred independently, we performed intense AGL haplotype analysis using 21 intragenic polymorphic markers plus a novel polymorphism IVS32−97 A/G in the vicinity of the IVS32 splicing mutation. Patient 1 of Chinese origin and the Japanese patient homozygous for the IVS32−12A > G were found to have different haplotypes, indicating the IVS32−12A > G mutation to be a recurrent mutation. This is the first recurrent mutation established by intense haplotyping in the AGL gene. Received: October 3, 2001 / Accepted: November 12, 2001     

Sleep and quality of life of patients with glycogen storage disease on standard and modified uncooked cornstarch

Background

Glycemic control in hepatic glycogen storage diseases (GSDs) relies on specific nutritional recommendations, including strict avoidance of a fasting period. Uncooked cornstarch (UCCS) is an important therapeutic component. A new modified UCCS, Glycosade?, was created with the objective of prolonging euglycemia. We aimed to determine the length of euglycemia on Glycosade? using a continuous glucose monitor (CGM) and to evaluate whether longer euglycemia and thus less nighttime interruptions would improve sleep and quality of life (QoL) after the introduction of the modified cornstarch.

Identification of three novel mutations (Q54P,W70X and T108I) in the glucose‐6‐phosphatase gene of patients with glycogen storage disease type Ia

Three novel mutations, Q54P, W70X and T108I, were identified in the gene encoding glucose‐6‐phosphatase in three patients with glycogen storage disease type Ia. Two sibs of Portuguese origin were homozygous for the Q54P mutation whereas the third patient, originating from both France and Lebanon, was a compound heterozygote for the W70X and T108I mutations. Glycogen storage disease type Ia is a heterogeneous autosomal recessive condition. Hum Mutat 14:91, 1999. © 1999 Wiley‐Liss, Inc.     

Direct or indirect association in a complex disease: the role of SLC22A4 and SLC22A5 functional variants in Crohn disease

A common haplotype spanning 250 kb on chromosome 5q31 is strongly associated with Crohn disease (CD). Recently, two functional variants within the SLC22A4 and SLC22A5 genes at this locus (IBD5), L503F (c.1507C > T) and G-207C (c.-207G > C), have been proposed to contribute directly to susceptibility to CD. However, extensive linkage disequilibrium at the IBD5 locus has complicated efforts to distinguish causal variants from association of the general risk haplotype. We genotyped the SLC22A4 and SLC22A5 variants and other polymorphisms across the risk haplotype in four populations of European origin, and applied regression-based haplotype analysis to over 1,200 fully genotyped case-control pairs, modeling case/control status on the presence of one or more SNPs to test for conditional association and to identify risk haplotypes. We found highly significant association of SNPs at the IBD5 locus with Crohn disease in all populations tested. However, the frequencies of L503F and G-207C in individuals who did not carry the general IBD5 risk haplotype were not significantly different in cases and controls, with associated disease odds ratios (ORs) of 0.90 (95% CI, 0.57-1.40) and 0.90 (95% CI, 0.65-1.23), respectively. Haplotype analysis showed that addition of the SLC22A4 and SLC22A5 variants to a null model that included the background risk haplotype did not significantly improve the model fit. In addition to the common risk haplotype, several rare haplotypes had an increased frequency in cases compared to controls. This study suggests that the molecular basis for Crohn disease susceptibility at the IBD5 locus remains to be defined, and highlights the challenge of the identification of causal variants in a complex disease in regions of extensive linkage disequilibrium.     

一个糖原累积病Ⅱ型家系的酸性-α-葡萄糖苷酶及其产前基因诊断

目的 为1个糖原累积病Ⅱ型(glycogen storage disease typeⅡ,GSDⅡ)家系进行酶学和产前基因诊断.方法 用酸性-α-葡萄糖苷酶(acid-alpha-glucosidase,GAA)特异性水解荧光底物4-甲基伞型酮-α-D-吡喃葡萄糖苷(4-methylumbelliferyl-α-D-glucopyranoside,4-MUG)和阿卡波糖抑制其同工酶的方法检测外周血白细胞和羊水细胞GAA酶活性,聚合酶链反应扩增GAA基因外显子编码区序列,直接测序分析GAA基因突变情况.结果 先证者外周血白细胞与胎儿羊水细胞GAA酶活性均明显低于正常参考值范围,分别为正常对照平均值的12.3% 和1.1%.先证者和胎儿均携带新无义突变 p.W738X 和已报道的无义突变p.E888X;先证者、母亲和胎儿均携带假性缺陷等位基因[c.1726G>A; c.2065G>A].结论 通过GAA酶活性检测结合GAA基因分析对1个GSDⅡ家系进行了产前诊断.由于假性缺陷等位基因可引起GAA酶活性降低,故GAA基因分析应作为亚洲人群GSDⅡ产前诊断的常规手段.

Abstract：

Objective To carry out prenatal diagnosis for a glycogen storage disease typeⅡ(GSDⅡ) affected family. Methods The acid-α-glucosidase (GAA) activity was measured in whole leukocytes and cultured amniocytes with 4-methylumbelliferyl-α-D-glucopyranoside as substrate and with acarbose as inhibitor. The coding regions of GAA gene were amplified by polymerase chain reaction and analyzed by direct DNA sequencing. Results The proband and the fetus had low GAA activity (12.3% and 1.1% of the average normal range, respectively). Mutation analysis of the GAA gene revealed a novel nonsense mutation p.W738X and a reported nonsense mutation p.E888X in both the proband and the fetus; the reported pseudodeficiency allele c.[1726G>A;2065G>A] was found in the proband, the mother and the fetus. Conclusion The proband and the fetus were both GSDⅡaffected. A combination of GAA activity analysis and mutation analysis is efficient for the prenatal diagnosis of GSDⅡ. Mutation analysis should be a routine method in the prenatal diagnosis of GSDⅡ in Asian population, where pseudodeficiency allele can cause low GAA activity in normal individuals which is relatively common in Asian.     

Genetic analysis of the glucose-6-phosphatase mutation of type la glycogen storage disease in a Chinese family

Type la glycogen storage disease (GSD) is an autosomal recessive metabolic disorder caused by a deficiency in glucose-6-phosphatase (GóPase). Polymerase chain reaction (PCR) and nucleotide sequence analysis were used to identify the location and nature of mutations at the GóPase locus in two siblings affected with type la GSD. Both patients are compound heterozygotes with two different single nucleotide substitutions in the two GóPase alleles. A guanine to adenine transition was identified at base position 327 in the exon 2, converting an arginine to a histidine at codon 83. The second substitution was a thymine to adenine transversion at base position 1101 in the exon 5, converting an isoleucine to an asparagine at codon 341. Family study reveals that both parents are heterozygous carriers: the father with a mutant GóPase allele at exon 2, the mother with another mutant GóPase allele at exon 5. This is the first family study in Taiwan on type la GSD identified by molecular analysis. The mutations identified herein are novel substitutions in the GóPase gene. In addition, an adenine to guanine substitution was observed at base position 653 in the exon 5 of GóPase gene in both sibling patients and their parents, as well as in 15 normal Chinese subjects and three normal Caucasian subjects.