Glycogen storage disease type I: diagnosis, management, clinical course and outcome. Results of the European Study on Glycogen Storage Disease Type I (ESGSD I)

Disturbed sphingolipid metabolism with elevated 1-deoxysphingolipids in glycogen storage disease type I - A link to metabolic control

BACKGROUND

1-Deoxysphingolipids (1-deoxySLs) are atypical sphingolipids. They are formed during sphingolipid de novo synthesis by the enzyme serine palmitoyltransferase, due to the alternate use of alanine over its canonical substrate serine. Pathologically elevated 1-deoxySL are involved in several neurological and metabolic disorders. The objective of this study was to investigate the role of 1-deoxySL in glycogen storage disease type I (GSDI).

METHODS

In this prospective, longitudinal observational study (median follow-up 1.8y), the plasma 1-deoxySL profile was analyzed in 15 adult GSDI patients (12 GSDIa, 3 GSDIb), and 31 healthy controls, along with standard parameters for monitoring GSDI.

RESULTS

1-Deoxysphinganine (1-deoxySA) concentrations were elevated in GSDI compared to controls (191 ± 129 vs 35 ± 14 nmol/l, p < 0.0001). Concordant with the mechanism of 1-deoxySL synthesis, plasma alanine was higher (625 ± 182 vs 398 ± 90 μmol/l, p < 0.0001), while serine was lower in GSDI than in controls (88 ± 22 vs 110 ± 18 μmol/l. p < 0.001). Accordingly, serine, alanine and triglycerides were determinants of 1-deoxySA in the longitudinal analysis of GSDIa. 1-deoxySA concentrations correlated with the occurrence of low blood glucose (area under the curve below 4 mmol/l) in continuous glucose monitoring. The 1-deoxySL profile in GSDIb was distinct from GSDIa, with a different ratio of saturated to unsaturated 1-deoxySL.

CONCLUSION

In addition to the known abnormalities of lipoproteins, GSDI patients also have a disturbed sphingolipid metabolism with elevated plasma 1-deoxySL concentrations. 1-DeoxySA relates to the occurrence of low blood glucose, and may constitute a potential new biomarker for assessing metabolic control. GSDIa and Ib have distinct 1-deoxySL profiles indicating that both GSD subtypes have diverse phenotypes regarding lipid metabolism.

Intracellular lipids are an independent cause of liver injury and chronic kidney disease in non alcoholic fatty liver disease-like context

Objective

Ectopic lipid accumulation in the liver and kidneys is a hallmark of metabolic diseases leading to non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD). Moreover, recent data have highlighted a strong correlation between NAFLD and CKD incidences. In this study, we use two mouse models of hepatic steatosis or CKD, each initiated independently of the other upon the suppression of glucose production specifically in the liver or kidneys, to elucidate the mechanisms underlying the development of CKD in the context of NAFLD-like pathology.

Methods

Mice with a deletion of G6pc, encoding glucose-6 phosphatase catalytic subunit, specifically in the liver (L.G6pc^−/− mice) or the kidneys (K.G6pc^−/− mice), were fed with either a standard diet or a high fat/high sucrose (HF/HS) diet during 9 months. These mice represent two original models of a rare metabolic disease named Glycogen Storage Disease Type Ia (GSDIa) that is characterized by both NAFLD-like pathology and CKD. Two other groups of L.G6pc^−/− and K.G6pc^−/− mice were fed a standard diet for 6 months and then treated with fenofibrate for 3 months. Lipid and glucose metabolisms were characterized, and NAFLD-like and CKD damages were evaluated.

Results

Lipid depot exacerbation upon high-calorie diet strongly accelerated hepatic and renal pathologies induced by the G6pc-deficiency. In L.G6pc^−/− mice, HF/HS diet increased liver injuries, characterized by higher levels of plasmatic transaminases and increased hepatic tumor incidence. In K.G6pc^−/− mice, HF/HS diet increased urinary albumin and lipocalin 2 excretion and aggravated renal fibrosis. In both cases, the worsening of NAFLD-like injuries and CKD was independent of glycogen content. Furthermore, fenofibrate, via the activation of lipid oxidation significantly decreased the hepatic or renal lipid accumulations and prevented liver or kidney damages in L.G6pc^−/− and K.G6pc^−/− mice, respectively. Finally, we show that L.G6pc^−/− mice and K.G6pc^−/− mice developed NAFLD-like pathology and CKD independently.

Conclusions

This study highlights the crucial role that lipids play in the independent development of both NAFLD and CKD and demonstrates the importance of lipid-lowering treatments in various metabolic diseases featured by lipid load, from the “rare” GSDIa to the “epidemic” morbid obesity or type 2 diabetes.

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Exacerbating lipid accumulation aggravates liver/kidney injury in GSDI.

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Fenofibrate-mediated PPARα activation induces hepatic and renal lipid turnover.

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Increased lipid turnover prevents glycogen synthesis and accumulation.

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PPARα–mediated metabolic reprograming prevents hepatic and renal GSDI complications.

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NAFLD and CKD develop independently.

The Physiopathological Role of the Exchangers Belonging to the SLC37 Family

The human SLC37 gene family includes four proteins SLC37A1-4, localized in the endoplasmic reticulum (ER) membrane. They have been grouped into the SLC37 family due to their sequence homology to the bacterial organophosphate/phosphate (Pi) antiporter. SLC37A1-3 are the less characterized isoforms. SLC37A1 and SLC37A2 are Pi-linked glucose-6-phosphate (G6P) antiporters, catalyzing both homologous (Pi/Pi) and heterologous (G6P/Pi) exchanges, whereas SLC37A3 transport properties remain to be clarified. Furthermore, SLC37A1 is highly homologous to the bacterial glycerol 3-phosphate permeases, so it is supposed to transport also glycerol-3-phosphate. The physiological role of SLC37A1-3 is yet to be further investigated. SLC37A1 seems to be required for lipid biosynthesis in cancer cell lines, SLC37A2 has been proposed as a vitamin D and a phospho-progesterone receptor target gene, while mutations in the SLC37A3 gene appear to be associated with congenital hyperinsulinism of infancy. SLC37A4, also known as glucose-6-phosphate translocase (G6PT), transports G6P from the cytoplasm into the ER lumen, working in complex with either glucose-6-phosphatase-α (G6Pase-α) or G6Pase-β to hydrolyze intraluminal G6P to Pi and glucose. G6PT and G6Pase-β are ubiquitously expressed, whereas G6Pase-α is specifically expressed in the liver, kidney and intestine. G6PT/G6Pase-α complex activity regulates fasting blood glucose levels, whereas G6PT/G6Pase-β is required for neutrophil functions. G6PT deficiency is responsible for glycogen storage disease type Ib (GSD-Ib), an autosomal recessive disorder associated with both defective metabolic and myeloid phenotypes. Several kinds of mutations have been identified in the SLC37A4 gene, affecting G6PT function. An increased autoimmunity risk for GSD-Ib patients has also been reported, moreover, SLC37A4 seems to be involved in autophagy.

Inborn Errors of Metabolism with Hypoglycemia: Glycogen Storage Diseases and Inherited Disorders of Gluconeogenesis

Although hyperinsulinism is the predominant inherited cause of hypoglycemia in the newborn period, inborn errors of metabolism are the primary etiologies after 1 month of age. Disorders of carbohydrate metabolism often present with hypoglycemia when fasting occurs. The presentation, diagnosis, and management of the hepatic glycogen storage diseases and disorders of gluconeogenesis are reviewed.

Late presentation of glycogen storage disease types Ia and III in children with short stature and hepatomegaly

BACKGROUND

Glycogen storage diseases (GSDs) are a collection of disorders related to glycogen synthesis or degradation that classically present in infancy with hypoglycemia, failure to thrive and hepatomegaly; however, their phenotype can vary significantly.

CASE PRESENTATION

We present the cases of two children, 5 years old and 3.5 years old, who were referred to endocrinology for short stature. They were ultimately found to have hepatomegaly, fasting hypoglycemia, mild elevation of transaminases and ketosis. Laboratory and genetic studies were consistent with double heterozygosity for GSDs Ia and III, with one novel mutation discovered in each patient. Nightly, both children were treated with cornstarch, which resulted in resolution of laboratory abnormalities and improvement in their growth velocity. These cases are unusual in that GSD was diagnosed relatively late in life in patients with no previous history of severe hypoglycemia.

CONCLUSIONS

They highlight the importance of considering glycogen storage disease in a child presenting with short stature, as it is a treatable disease that can be diagnosed non-invasively with genetic testing.

Liver-directed gene therapy for murine glycogen storage disease type Ib

Glycogen storage disease type-Ib (GSD-Ib), deficient in the glucose-6-phosphate transporter (G6PT), is characterized by impaired glucose homeostasis, myeloid dysfunction, and long-term risk of hepatocellular adenoma (HCA). We examined the efficacy of G6PT gene therapy in G6pt-/- mice using recombinant adeno-associated virus (rAAV) vectors, directed by either the G6PC or the G6PT promoter/enhancer. Both vectors corrected hepatic G6PT deficiency in murine GSD-Ib but the G6PC promoter/enhancer was more efficacious. Over a 78-week study, using dose titration of the rAAV vectors, we showed that G6pt-/- mice expressing 3-62% of normal hepatic G6PT activity exhibited a normalized liver phenotype. Two of the 12 mice expressing < 6% of normal hepatic G6PT activity developed HCA. All treated mice were leaner and more sensitive to insulin than wild-type mice. Mice expressing 3-22% of normal hepatic G6PT activity exhibited higher insulin sensitivity than mice expressing 44-62%. The levels of insulin sensitivity correlated with the magnitudes of hepatic carbohydrate response element binding protein signaling activation. In summary, we established the threshold of hepatic G6PT activity required to prevent tumor formation and showed that mice expressing 3-62% of normal hepatic G6PT activity maintained glucose homeostasis and were protected against age-related obesity and insulin resistance.

Hepatocytes contribute to residual glucose production in a mouse model for glycogen storage disease type Ia

It is a long-standing enigma how glycogen storage disease (GSD) type I patients retain a limited capacity for endogenous glucose production despite the loss of glucose-6-phosphatase activity. Insight into the source of residual endogenous glucose production is of clinical importance given the risk of sudden death in these patients, but so far contradictory mechanisms have been proposed. We investigated glucose-6-phosphatase-independent endogenous glucose production in hepatocytes isolated from a liver-specific GSD Ia mouse model (L-G6pc^-/- mice) and performed real-time analysis of hepatic glucose fluxes and glycogen metabolism in L-G6pc^-/- mice using state-of-the-art stable isotope methodologies. Here we show that G6pc-deficient hepatocytes are capable of producing glucose. In vivo analysis of hepatic glucose metabolism revealed that the hepatic glucokinase flux was decreased by 95% in L-G6pc^-/- mice. It also showed increased glycogen phosphorylase flux in L-G6pc^-/- mice, which is coupled to the release of free glucose through glycogen debranching. Although the ex vivo activities of debranching enzyme and lysosomal acid maltase, two major hepatic α-glucosidases, were unaltered in L-G6pc^-/- mice, pharmacological inhibition of α-glucosidase activity almost completely abolished residual glucose production by G6pc-deficient hepatocytes.

CONCLUSION

Our data indicate that hepatocytes contribute to residual glucose production in GSD Ia. We show that α-glucosidase activity, i.e. glycogen debranching and/or lysosomal glycogen breakdown, contributes to residual glucose production by GSD Ia hepatocytes. A strong reduction in hepatic GCK flux in L-G6pc-/- mice furthermore limits the phosphorylation of free glucose synthesized by G6pc-deficient hepatocytes, allowing the release of glucose into the circulation. The almost complete abrogation of GCK flux in G6pc-deficient liver also explains the contradictory reports on residual glucose production in GSD Ia patients. (Hepatology 2017;66:2042-2054).

[Characteristics of lipid metabolism and the cardiovascular system in glycogenosis types I and III]

Glycogen storage disease (GSD) is an inherited metabolic disorder characterized by early childhood lipid metabolic disturbances with potentially proatherogenic effects. The review outlines the characteristics of impaired lipid composition and other changes in the cardiovascular system in GSD types I and III. It analyzes the factors enabling and inhibiting the development of atherosclerosis in patients with GSD. The review describes the paradox of vascular resistance to the development of early atherosclerosis despite the proatherogenic composition of lipids in the patients of this group.

Tight metabolic control plus ACE inhibitor therapy improves GSD I nephropathy

The onset of microalbuminuria (MA) heralds the onset of glomerulopathy in patients with glycogen storage disease (GSD) type I. Unlike tubulopathy, which responds to improved metabolic control, glomerulopathy in GSD I is considered refractory to medical intervention, and it is thought to inexorably progress to overt proteinuria and renal failure. Recent reports of reduced microalbuminuria following strict adherence to therapy counter this view. In contrast to type Ia, little is known regarding the prevalence of kidney disease in GSD Ib, 0, III, VI, and IX. Subjects were evaluated with 24-h urine collections between 2005 and 2014 as part of a longitudinal study of the natural history of GSD. ACE inhibitor therapy (AIT) was commenced after documentation of microalbuminuria. Elevated urine albumin excretion was detected in 23 of 195 GSD Ia patients (11.7%) and six of 45 GSD Ib (13.3%). The median age of onset of microalbuminuria in GSD Ia was 24 years (range 9-56); in GSD Ib it was 25 years (range 20-38). Of 14 with GSD Ia who complied with dietary and AIT during the study period, microalbuminuria decreased in 11, in whom metabolic control improved. All 135 patients with the ketotic forms of GSD (0, III, VI and IX) consistently had normal microalbumin excretion. Strict adherence to dietary therapy and maintenance of optimal metabolic control is necessary to halt the progression of GSD Ia glomerulopathy in patients treated with AIT. With optimal care, protein excretion can be reduced and even normalize.

Clinical and biochemical heterogeneity between patients with glycogen storage disease type IA: the added value of CUSUM for metabolic control

OBJECTIVE

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

STUDY DESIGN

Descriptive retrospective study of longitudinal clinical and biochemical data and long-term complications in 20 GSD Ia patients. We included 11 patients with homozygous G6PC mutations and siblings from four families carrying identical G6PC genotypes. To display subtle variations for repeated triglyceride measurements with respect to time for individual patients, CUSUM-analysis graphs were constructed.

RESULTS

Patients with different homozygous G6PC mutations showed important differences in height, BMI, and biochemical parameters (i.e., lactate, uric acid, triglyceride, and cholesterol concentrations). Furthermore, CUSUM-analysis predicts and displays subtle changes in longitudinal blood triglyceride concentrations. Siblings in families also displayed important differences in biochemical parameters (i.e., lactate, uric acid, triglycerides, and cholesterol concentrations) and long-term complications (i.e., liver adenomas, nephropathy, and osteopenia/osteoporosis).

CONCLUSIONS

Differences between GSD Ia patients reflect large clinical and biochemical heterogeneity. Heterogeneity between GSD Ia patients with homozygous G6PC mutations indicate an important role of the G6PC genotype/mutations. Differences between affected siblings suggest an additional role (genetic and/or environmental) of modifying factors defining the GSD Ia phenotype. CUSUM-analysis can facilitate single-patient monitoring of metabolic control and future application of this method may improve precision medicine for patients both with GSD and remaining inherited metabolic diseases.

Recent development and gene therapy for glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD-Ia) is an autosomal recessive metabolic disorder caused by a deficiency in glucose-6-phosphatase-α (G6Pase-α or G6PC) that is expressed primarily in the liver, kidney, and intestine. G6Pase-α catalyzes the hydrolysis of glucose-6-phosphate (G6P) to glucose and phosphate in the terminal step of gluconeogenesis and glycogenolysis, and is a key enzyme for endogenous glucose production. The active site of G6Pase-α is inside the endoplasmic reticulum (ER) lumen. For catalysis, the substrate G6P must be translocated from the cytoplasm into the ER lumen by a G6P transporter (G6PT). The functional coupling of G6Pase-α and G6PT maintains interprandial glucose homeostasis. Dietary therapies for GSD-Ia are available, but cannot prevent the long-term complication of hepatocellular adenoma that may undergo malignant transformation to hepatocellular carcinoma. Animal models of GSD-Ia are now available and are being exploited to both delineate the disease more precisely and develop new treatment approaches, including gene therapy.

Glycogen storage disease type Ia mice with less than 2% of normal hepatic glucose-6-phosphatase-α activity restored are at risk of developing hepatic tumors

Glycogen storage disease type Ia (GSD-Ia), characterized by impaired glucose homeostasis and chronic risk of hepatocellular adenoma (HCA) and carcinoma (HCC), is caused by a deficiency in glucose-6-phosphatase-α (G6Pase-α or G6PC). We have previously shown that G6pc-/- mice receiving gene transfer mediated by rAAV-G6PC, a recombinant adeno-associated virus (rAAV) vector expressing G6Pase-α, and expressing 3-63% of normal hepatic G6Pase-α activity maintain glucose homeostasis and do not develop HCA/HCC. However, the threshold of hepatic G6Pase-α activity required to prevent tumor formation remained unknown. In this study, we constructed rAAV-co-G6PC, a rAAV vector expressing a codon-optimized (co) G6Pase-α and showed that rAAV-co-G6PC was more efficacious than rAAV-G6PC in directing hepatic G6Pase-α expression. Over an 88-week study, we showed that both rAAV-G6PC- and rAAV-co-G6PC-treated G6pc-/- mice expressing 3-33% of normal hepatic G6Pase-α activity (AAV mice) maintained glucose homeostasis, lacked HCA/HCC, and were protected against age-related obesity and insulin resistance. Of the eleven rAAV-G6PC/rAAV-co-G6PC-treated G6pc-/- mice harboring 0.9-2.4% of normal hepatic G6Pase-α activity (AAV-low mice), 3 expressing 0.9-1.3% of normal hepatic G6Pase-α activity developed HCA/HCC, while 8 did not (AAV-low-NT). Finally, we showed that the AAV-low-NT mice exhibited a phenotype indistinguishable from that of AAV mice expressing ≥3% of normal hepatic G6Pase-α activity. The results establish the threshold of hepatic G6Pase-α activity required to prevent HCA/HCC and show that GSD-Ia mice harboring <2% of normal hepatic G6Pase-α activity are at risk of tumor development.

Partial correction of neutrophil dysfunction by oral galactose therapy in glycogen storage disease type Ib

Glycogen storage disease type Ib (GSD-Ib) is characterized by impaired glucose homeostasis, neutropenia and neutrophil dysfunction. Mass spectrometric glycomic profiling of GSD-Ib neutrophils showed severely truncated N-glycans, lacking galactose. Experiments indicated the hypoglycosylation of the electron transporting subunit of NADPH oxidase, which is crucial for the defense against bacterial infections. In phosphoglucomutase 1 (PGM1) deficiency, an inherited disorder with an enzymatic defect just one metabolic step ahead, hypogalactosylation can be successfully treated by dietary galactose. We hypothesized the same pathomechanism in GSD-Ib and started a therapeutic trial with oral galactose and uridine. The aim was to improve neutrophil dysfunction through the correction of hypoglycosylation in neutrophils. The GSD-Ib patient was treated for 29weeks. Monitoring included glycomics analysis of the patient's neutrophils and neutrophil function tests including respiratory burst activity, phagocytosis and migration. Although no substantial restoration of neutrophil glycosylation was found, there was partial improvement of respiratory burst activity.

Recoverable, Record-High Lactic Acidosis in a Patient with Glycogen Storage Disease Type 1: A Mixed Type A and Type B Lactate Disorder

A 17-year-old patient with GSD type 1a (von Gierke disease) was hospitalized with an extremely elevated serum lactate following an intercurrent infection and interruption of his frequent intake of carbohydrates. The patient developed shock, oliguric renal failure, and cardiorespiratory failure requiring mechanical ventilation and inotropes. At the peak of metabolic decompensation and clinical instability, serum lactate reached a level of 47.6 mmol/L which was accompanied by a severe anion gap metabolic acidosis with a pH of 6.8 and bicarbonate of 4 meq/L. The patient was stabilized with massive infusions of sodium bicarbonate (45 meq/h) and glucose and recovered without the need for dialysis. This patient illustrates pathophysiologic mechanisms involved in the development of extreme mixed type A and type B lactic acidemia, reflecting altered metabolic pathways in GSD type 1, combined with tissue hypoperfusion. The rationale for the specific interventions in this case is outlined.

Glycogen storage disease type III: diagnosis, genotype, management, clinical course and outcome

Glycogen storage disease type III (GSDIII) is a rare disorder of glycogenolysis due to AGL gene mutations, causing glycogen debranching enzyme deficiency and storage of limited dextrin. Patients with GSDIIIa show involvement of liver and cardiac/skeletal muscle, whereas GSDIIIb patients display only liver symptoms and signs. The International Study on Glycogen Storage Disease (ISGSDIII) is a descriptive retrospective, international, multi-centre cohort study of diagnosis, genotype, management, clinical course and outcome of 175 patients from 147 families (86 % GSDIIIa; 14 % GSDIIIb), with follow-up into adulthood in 91 patients. In total 58 AGL mutations (non-missense mutations were overrepresented and 21 novel mutations were observed) were identified in 76 families. GSDIII patients first presented before the age of 1.5 years, hepatomegaly was the most common presenting clinical sign. Dietary management was very diverse and included frequent meals, uncooked cornstarch and continuous gastric drip feeding. Chronic complications involved the liver (hepatic cirrhosis, adenoma(s), and/or hepatocellular carcinoma in 11 %), heart (cardiac involvement and cardiomyopathy, in 58 % and 15 %, respectively, generally presenting in early childhood), and muscle (pain in 34 %). Type 2 diabetes mellitus was diagnosed in eight out of 91 adult patients (9 %). In adult patients no significant correlation was detected between (non-) missense AGL genotypes and hepatic, cardiac or muscular complications. This study demonstrates heterogeneity in a large cohort of ageing GSDIII patients. An international GSD patient registry is warranted to prospectively define the clinical course, heterogeneity and the effect of different dietary interventions in patients with GSDIII.

Liver transplantation for pediatric inherited metabolic disorders: Considerations for indications, complications, and perioperative management

LT is an effective therapeutic option for a variety of IEM. This approach can significantly improve the quality of life of patients who suffer from severe disease manifestations and/or life-threatening metabolic decompensations despite medical/dietary management. Due to the significant risks for systemic complications from surgical stressors, careful perioperative management is vital. Even after LT, some disorders require long-term dietary restriction, medical management, and monitoring of metabolites. Successful liver transplant for these complex disorders can be achieved with disease- and patient-specific strategies using a multidisciplinary approach. In this article, we review indications, complications, perioperative management, and long-term follow-up recommendations for IEM that are treatable with LT.

Progressive development of renal cysts in glycogen storage disease type I

Glycogen storage disease type I (GSDI) is a rare metabolic disease due to glucose-6 phosphatase deficiency, characterized by fasting hypoglycemia. Patients also develop chronic kidney disease whose mechanisms are poorly understood. To decipher the process, we generated mice with a kidney-specific knockout of glucose-6 phosphatase (K.G6pc^-/- mice) that exhibited the first signs of GSDI nephropathy after 6 months of G6pc deletion. We studied the natural course of renal deterioration in K.G6pc^-/- mice for 18 months and observed the progressive deterioration of renal functions characterized by early tubular dysfunction and a later destruction of the glomerular filtration barrier. After 15 months, K.G6pc^-/- mice developed tubular-glomerular fibrosis and podocyte injury, leading to the development of cysts and renal failure. On the basis of these findings, we were able to detect the development of cysts in 7 out of 32 GSDI patients, who developed advanced renal impairment. Of these 7 patients, 3 developed renal failure. In addition, no renal cysts were detected in six patients who showed early renal impairment. In conclusion, renal pathology in GSDI is characterized by progressive tubular dysfunction and the development of polycystic kidneys that probably leads to the development of irreversible renal failure in the late stages. Systematic observations of cyst development by kidney imaging should improve the evaluation of the disease's progression, independently of biochemical markers.

Esophageal Stricture Secondary to Candidiasis in a Child with Glycogen Storage Disease 1b

Esophageal candidiasis is commonly seen in immunocompromised patients; however, candida esophagitis induced stricture is a very rare complication. We report the first case of esophageal stricture secondary to candidiasis in a glycogen storage disease (GSD) 1b child. The patient was diagnosed with GSD type 1b by liver biopsy. No mutation was found in the G6PC gene, but SLC37A4 gene sequencing revealed a compound heterozygous mutation (p.R28H and p.W107X, which was a novel mutation). The patient's absolute neutrophil count was continuously under 1,000/µL when he was over 6 years of age. He was admitted frequently for recurrent fever and infection, and frequently received intravenous antibiotics, antifungal agents. He complained of persistent dysphagia beginning at age 7 years. Esophageal stricture and multiple whitish patches were observed by endoscopy and endoscopic biopsy revealed numerous fungal hyphae consistent with candida esophagitis. He received esophageal balloon dilatation four times, and his symptoms improved.

Current Proceedings in the Molecular Dissection of Hepatocellular Adenomas: Review and Hands-on Guide for Diagnosis

Molecular dissection of hepatocellular adenomas has brought forward a diversity of well-defined entities. Their distinction is important for routine practice, since prognosis is tightly related to the individual subgroup. Very recent activity has generated new details on the molecular background of hepatocellular adenoma, which this article aims to integrate into the current concepts of taxonomy.

Glycogen storage disease type Ia (GSDIa) but not Glycogen storage disease type Ib (GSDIb) is associated to an increased risk of metabolic syndrome: possible role of microsomal glucose 6-phosphate accumulation

BACKGROUND

In GSDIa, glucose 6-phosphate (G6P) accumulates in the endoplasmic reticulum (ER); in GSDIb, G6P levels are reduced in ER. G6P availability directly modulates the activity of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), an ER-bound enzyme playing a key role in the development of the metabolic syndrome (MS).

OBJECTIVE

To evaluate the prevalence of MS and Insulin Resistance (IR) in GSDIa and GSDIb patients.

PATIENTS AND METHODS

This was a prospective study. All the enrolled patients were followed at the Department of Pediatrics "Federico II" University of Naples for 10 years. Clinical and biochemical parameters of MS and the presence of IR were recorded. The results were correlated with the biochemical parameters of GSDI-related metabolic control. 10 GSDIa patient (median age 12.10 ± 1.50), 7 GSDIb patients (median age 14.90 ± 2.20 were enrolled in the study. They were compared to 20 and 14 age and sex matched controls, respectively. 10 GSDIa patients (median age 24.60 ± 1.50) and 6 GSDIb patients (median age 25.10 ± 2.00) completed the 10-year-follow-up. At the end of the study the patients' data were compared to 10 and 6 age and sex matched controls, respectively.

RESULTS

At study entry, 20 % GSDIa patients had MS and 80 % showed 2 criteria for MS. GSDIa patients showed higher HOMA-IR than controls and GSDIb patients (p < 0.001, p < 0.05), respectively. Baseline ISI was lower in GSDIa than controls (p < 0.001). QUICKI was significantly lower in GSDIa than in controls (p < 0.001). At the end of the study 70 % of GSDIa patients had MS and 30 % showed 2 criteria for MS. HOMA-IR was higher in GSDIa than controls (p < 0.01). Baseline ISI was higher in GSDIb than controls (p < 0.005) and GSD1a (p < 0.05). QUICKI was lower in GSD1a patients than in controls (p < 0.03). VAI was higher in GSDIa patients than controls (p < 0.001) and GSDIb patients (p = 0.002).

CONCLUSIONS

Our data showed high prevalence of IR and MS in GSDIa patients. We speculate a possible role of 11βHSD1 modulation by G6P availability. We suggest a routine metabolic assessment in GSDIa patients.

Hepatic glycogen storage disorders: what have we learned in recent years?

PURPOSE OF REVIEW

Glycogen storage disorders (GSDs) are inborn errors of metabolism with abnormal storage or utilization of glycogen. The present review focuses on recent advances in hepatic GSD types I, III and VI/IX, with emphasis on clinical aspects and treatment.

RECENT FINDINGS

Evidence accumulates that poor metabolic control is a risk factor for the development of long-term complications, such as liver adenomas, low bone density/osteoporosis, and kidney disease in GSD I. However, mechanisms leading to these complications remain poorly understood and are being investigated. Molecular causes underlying neutropenia and neutrophil dysfunction in GSD I have been elucidated. Case series provide new insights into the natural course and outcome of GSD types VI and IX. For GSD III, a high protein/fat diet has been reported to improve (cardio)myopathy, but the beneficial effect of this dietary concept on muscle and liver disease manifestations needs to be further established in prospective studies.

SUMMARY

Although further knowledge has been gained regarding pathophysiology, disease course, treatment, and complications of hepatic GSDs, more controlled prospective studies are needed to assess effects of different dietary and medical treatment options on long-term outcome and quality of life.

High Incidence of Serologic Markers of Inflammatory Bowel Disease in Asymptomatic Patients with Glycogen Storage Disease Type Ia

Most patients with glycogen storage disease (GSD) type Ib show features related to inflammatory bowel disease (IBD). The development of IBD seems to be associated with the defect of neutrophil function in GSD Ib. Patients with GSD Ia were not recognized to have similar gastrointestinal complaints until recently and are not associated with a neutrophil defect. Fifty consecutive GSD Ia inpatients over the age of 2 years without a diagnosis of IBD were screened using serologic and genetic markers via the Prometheus IBD sgi Diagnostic test. Eleven patients were tested positive for IBD (22%), with five fitting the pattern for Crohn's disease, five for ulcerative colitis, and one with nonspecific IBD. Only 2 out of the 11 patients had any gastrointestinal complaints. No pattern could be distinguished from individual inflammatory markers, genetics, inflammation antibodies, age, complications, or metabolic control. Of note, 9 out of 11 patients testing positive were female. Patients with GSD Ia were found to have a higher rate of serologically indicated IBD when compared with the general population. While these subjects will need to be followed to determine if these serologic markers correlate with clinical disease, this study supports that IBD may be more common in the GSD Ia population. Further studies are warranted to explain the relationship between IBD and GSD I since it may provide clues regarding the pathogenesis of IBD development in the general population.

[Renal involvement in glycogen storage disease type 1: Practical issues]

AIM

To investigate risk factors of renal complications in glycogen storage disease type I, in order to identify practical implications for renal preservation.

METHODS

A retrospective study of 38 patients with glycogen storage disease type I.

RESULTS

The patients studied were 8.6 years old in average (1.5 to 22 years) and were followed during 7.4 ± 4.5 years. Hypercalciuria was detected in 23 patients and was related to acidosis (P=0.028), higher lactate levels (5.9 ± 3.5 versus 3.7 ± 1.7 mmol/L; P=0.013) and smaller height (-2.1 ± 1.5 SD versus -0.8 ± 1.5 SD; P=0.026). Urolithiasis was diagnosed in 7 cases. Glomerular disease (19/38) was more frequent in cases with severe hypertriglyceridemia (P=0.042) and occurred at an older age (P=0.007). Microalbuminuria occurred in 15/31 cases; ACE inhibitors were prescribed in only 8 cases. The frequency of renal complications did not differ according to the diet group (continuous enteral feeding or uncooked starch). Logistic regression concluded as risk factors: lactic acidosis for tubular disease and age>10 years for glomerular disease.

CONCLUSIONS

Renal involvement is common in glycogen storage disease type I patients. Tubular abnormalities are precocious, related to lactic acidosis and may be detected by monitoring of urinary calcium. Glomerular hyperfiltration is the first stage of a progressive glomerular disease and is related to age. Practical implications for renal preservation are discussed based on our results and literature.

Type I glycogen storage diseases: disorders of the glucose-6-phosphatase/glucose-6-phosphate transporter complexes

Disorders of the glucose-6-phosphatase (G6Pase)/glucose-6-phosphate transporter (G6PT) complexes consist of three subtypes: glycogen storage disease type Ia (GSD-Ia), deficient in the liver/kidney/intestine-restricted G6Pase-α (or G6PC); GSD-Ib, deficient in a ubiquitously expressed G6PT (or SLC37A4); and G6Pase-β deficiency or severe congenital neutropenia syndrome type 4 (SCN4), deficient in the ubiquitously expressed G6Pase-β (or G6PC3). G6Pase-α and G6Pase-β are glucose-6-phosphate (G6P) hydrolases with active sites lying inside the endoplasmic reticulum (ER) lumen and as such are dependent upon the G6PT to translocate G6P from the cytoplasm into the lumen. The tissue expression profiles of the G6Pase enzymes dictate the disease's phenotype. A functional G6Pase-α/G6PT complex maintains interprandial glucose homeostasis, while a functional G6Pase-β/G6PT complex maintains neutrophil/macrophage energy homeostasis and functionality. G6Pase-β deficiency is not a glycogen storage disease but biochemically it is a GSD-I related syndrome (GSD-Irs). GSD-Ia and GSD-Ib patients manifest a common metabolic phenotype of impaired blood glucose homeostasis not shared by GSD-Irs. GSD-Ib and GSD-Irs patients manifest a common myeloid phenotype of neutropenia and neutrophil/macrophage dysfunction not shared by GSD-Ia. While a disruption of the activity of the G6Pase-α/G6PT complex readily explains why GSD-Ia and GSD-Ib patients exhibit impaired glucose homeostasis, the basis for neutropenia and myeloid dysfunction in GSD-Ib and GSD-Irs are only now starting to be understood. Animal models of all three disorders are now available and are being exploited to both delineate the disease more precisely and develop new treatment approaches, including gene therapy.

In vitro digestion of starches in a dynamic gastrointestinal model: an innovative study to optimize dietary management of patients with hepatic glycogen storage diseases

Uncooked cornstarch (UCCS) is a widely used treatment strategy for patients with hepatic glycogen storage disease (GSD). It has been observed that GSD-patients display different metabolic responses to different cornstarches. The objective was to characterize starch fractions and analyze the digestion of different starches in a dynamic gastrointestinal in vitro model. The following brands of UCCS were studied: Argo and Great Value from the United States of America; Brazilian Maizena Duryea and Yoki from Brazil; Dutch Maizena Duryea from the Netherlands. Glycosade, a modified starch, and sweet polvilho, a Brazilian starch extracted from cassava, were also studied. The starch fractions were analyzed by glycemic TNO index method and digestion analyses were determined by the TIM-1 system, a dynamic, computer-controlled, in vitro gastrointestinal model, which simulates the stomach and small intestine. The final digested amounts were between 84 and 86% for the UCCS and Glycosade, but was 75.5% for sweet povilho. At 180 min of the experiment, an important time-point for GSD patients, the digested amount of the starches corresponded to 67.9-71.5 for the UCCS and Glycosade, while it was 55.5% for sweet povilho. In an experiment with a mixture of sweet polvilho and Brazilian Maizena Duryea, a final digested amount of 78.4% was found, while the value at 180 min was 61.7%. Sweet polvilho seems to have a slower and extended release of glucose and looks like an interesting product to be further studied as it might lead to extended normoglycemia in GSD-patients.

Lipids in hepatic glycogen storage diseases: pathophysiology, monitoring of dietary management and future directions

Hepatic glycogen storage diseases (GSD) underscore the intimate relationship between carbohydrate and lipid metabolism. The hyperlipidemias in hepatic GSD reflect perturbed intracellular metabolism, providing biomarkers in blood to monitor dietary management. In different types of GSD, hyperlipidemias are of a different origin. Hypertriglyceridemia is most prominent in GSD type Ia and associated with long-term outcome morbidity, like pancreatitis and hepatic adenomas. In the ketotic subtypes of GSD, hypertriglyceridemia reflects the age-dependent fasting intolerance, secondary lipolysis and increased mitochondrial fatty acid oxidation. The role of high protein diets is established for ketotic types of GSD, but non-traditional dietary interventions (like medium-chain triglycerides and the ketogenic diet) in hepatic GSD are still controversial and necessitate further studies. Patients with these rare inherited disorders of carbohydrate metabolism meet several criteria of the metabolic syndrome, therefore close monitoring for cardiovascular diseases in ageing GSD patients may be justified.

Lessons from new mouse models of glycogen storage disease type 1a in relation to the time course and organ specificity of the disease

Patients with glycogen storage diseases type 1 (GSD1) suffer from life-threatening hypoglycaemia, when left untreated. Despite an intensive dietary treatment, patients develop severe complications, such as liver tumors and renal failure, with aging. Until now, the animal models available for studying the GSD1 did not survive after weaning. To gain further insights into the molecular mechanisms of the disease and to evaluate potential treatment strategies, we have recently developed novel mouse models in which the catalytic subunit of glucose-6 phosphatase (G6pc) is deleted in each glucose-producing organ specifically. For that, B6.G6pc(ex3lox/ex3lox) mice were crossed with transgenic mice expressing a recombinase under the control of the serum albumin, the kidney androgen protein or the villin promoter, in order to obtain liver, kidney or intestine G6pc(-/-) mice, respectively. As opposed to total G6pc knockout mice, tissue-specific G6pc deficiency allows mice to maintain their blood glucose by inducing glucose production in the other gluconeogenic organs. Even though it is considered that glucose is produced mainly by the liver, liver G6pc(-/-) mice are perfectly viable and exhibit the same hepatic pathological features as GSD1 patients, including the late development of hepatocellular adenomas and carcinomas. Interestingly, renal G6pc(-/-) mice developed renal symptoms similar to the early human GSD1 nephropathy. This includes glycogen overload that leads to nephromegaly and morphological and functional alterations in the kidneys. Thus, our data suggest that renal G6Pase deficiency per se is sufficient to induce the renal pathology of GSD1. Therefore, these new mouse models should allow us to improve the strategies of treatment on both nutritional and pharmacological points of view.

Case of cholangiocellular carcinoma in a patient with glycogen storage disease type Ia

Glycogen storage disease (GSD) type Ia is caused by a deficiency in glucose-6-phosphatase. Long-term complications, including renal disease, gout, osteoporosis and pulmonary hypertension, develop in patients with GSD type Ia. In the second or third decade, 22-75% of GSD type Ia patients develop hepatocellular adenoma (HCA). In some of these patients, the HCA evolves into hepatocellular carcinoma. However, little is known about GSD type Ia patients with HCA who develop cholangiocellular carcinoma (CCC). Here, we report for the first time, a patient with GSD type Ia with HCA, in whom intrahepatic CCC was developed.

Minimal hepatic glucose-6-phosphatase-α activity required to sustain survival and prevent hepatocellular adenoma formation in murine glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD-Ia), characterized by impaired glucose homeostasis and chronic risk of hepatocellular adenoma (HCA), is caused by a deficiency in glucose-6-phosphatase-α (G6Pase-α or G6PC) activity. In a previous 70–90 week-study, we showed that a recombinant adeno-associated virus (rAAV) vector-mediated gene transfer that restores more than 3% of wild-type hepatic G6Pase-α activity in G6pc^−/− mice corrects hepatic G6Pase-α deficiency with no evidence of HCA. We now examine the minimal hepatic G6Pase-α activity required to confer therapeutic efficacy. We show that rAAV-treated G6pc^−/− mice expressing 0.2% of wild-type hepatic G6Pase-α activity suffered from frequent hypoglycemic seizures at age 63–65 weeks but mice expressing 0.5–1.3% of wild-type hepatic G6Pase-α activity (AAV-LL mice) sustain 4–6 h of fast and grow normally to age 75–90 weeks. Despite marked increases in hepatic glycogen accumulation, the AAV-LL mice display no evidence of hepatic abnormalities, hepatic steatosis, or HCA. Interprandial glucose homeostasis is maintained by the G6Pase-α/glucose-6-phosphate transporter (G6PT) complex, and G6PT-mediated microsomal G6P uptake is the rate-limiting step in endogenous glucose production. We show that hepatic G6PT activity is increased in AAV-LL mice. These findings are encouraging for clinical studies of G6Pase-α gene-based therapy for GSD-Ia.

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Establish the minimal hepatic G6Pase-α activity restoration required to provide a blood glucose level that enables GSD-Ia mice grow to old age (75–90 weeks).

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Establish the minimal hepatic G6Pase-α activity restoration required that enables GSD-Ia mice grow to old age (75-90 weeks).

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Define the lowest dose for G6Pase-α gene therapy that provides efficacy in mice, which informs a phase I/II clinical trial design in human GSD-Ia.

A pilot longitudinal study of the use of waxy maize heat modified starch in the treatment of adults with glycogen storage disease type I: a randomized double-blind cross-over study

Background

Uncooked corn-starch (UCCS) has been the mainstay of therapy for the hepatic glycogen storage diseases (GSD) but is not always effective. A new starch (WMHMS) has demonstrated a more favourable short-term metabolic profile.

Objective

To determine efficacy and safety of a new uncooked starch (WMHMS) compared to UCCS over 16 weeks treatment with each.

Method

A double-blind cross-over study of 10 adults (aged 16 – 38 years, six male) with GSD Ia and Ib. After an individualised fast, subjects were randomised to take a 50 g starch-load of either WMHMS or UCCS. Starch-loads terminated when blood glucose was < 3.0 mmol/L or the subject felt subjectively hypoglycaemic. Anonymous biochemical profiles were assessed by 2 investigators and a starch administration schedule recommended. Each starch was delivered in coded sachets and intake was monitored for the following 16 weeks. After a washout period, the protocol was repeated with the alternative product.

Results

4 subjects failed to establish therapy on the cross-over limb. Data from 7 paired starch load showed: longer median fasting duration with WMHMS (7.5 versus 5 hours; p = 0.023), slower decrease in the glucose curve (0.357 versus 0.632 mmol/hr p = 0.028) and less area under insulin curves for the first 4 hours (p = 0.03). Two of six subjects took 50% or less WMHMS compared to UCCS and one took more. Plasma triglycerides, cholesterol and uric acid were unchanged after each study phase.

Conclusion

WMHMS leads to significant reduction in insulin release and reduced starch use in some GSD patients.

Does type I truly dominate hepatic glycogen storage diseases in Korea?: a single center study

PURPOSE

There are no studies of hepatic glycogen storage diseases (GSDs) other than type I and III in Korea. We aimed on investigating the characteristics of hepatic GSDs in Korea diagnosed and followed at a single center.

METHODS

We retrospectively analyzed patients who were diagnosed as GSD and followed at Samsung Medical Center from January, 1997 to December, 2013. Clinical manifestations, laboratory results, treatment, and prognosis were investigated.

RESULTS

Twenty-one patients were included in the study. The types of 17 patients were confirmed by enzyme activity tests and/or gene analysis. GSD Ia was diagnosed in 7 patients (33.3%), Ib in 1 patient (4.8%), III in 2 patients (9.5%), IV in 1 patient (4.8%), and IX in 6 patients (28.6%). Types other than GSD I constituted 52.9% (9/17) of the patients diagnosed with a specific type of hepatic GSD. The median age at presentation was 2 years. Hepatomegaly was observed in 95.2%, elevated liver transaminases in 90.5%, and hyperlactacidemia in 81.0% of the patients. The duration for follow-up was 77±62.0 months. Uncooked corn starch was initiated in all the patients. No mortality was observed during the follow-up period, and liver transplantation was performed in 14.3%.

CONCLUSION

Types other than GSD I comprised more than half of the patients diagnosed with a specific type of hepatic GSD. Clinical suspicion and thorough evaluation of hepatic GSDs in Korea should be focused not only on GSD I, but also on other types.

Gastric cancer following a liver transplantation for glycogen storage disease type Ia (von Gierke disease): A case report

Glycogen storage disease type Ia (GSD-Ia; also termed von Gierke disease) is an inherited metabolic disorder resulting from a glucose-6-phosphatase deficiency. Liver transplantation is considered to be the most effective treatment for GSD-Ia patients. In the present study, the case of a patient with GSD-Ia who received a liver transplantation at 17 years of age is presented. During the 12 years following transplantation, the patient’s quality of life markedly improved. However, recently, the patient was diagnosed with de novo gastric cancer following a biopsy. Thus, a total gastrectomy with lymph node dissection was performed and the tumor was histologically determined to be a poorly differentiated adenocarcinoma (histopathological stage, pT4N1M0). The patient recovered well and was discharged on postoperative day 10 without any complications. To the best of our knowledge, this is the first case of de novo gastric cancer in a patient with GSD-Ia to be reported.

Identification of differentially expressed microRNAs in human hepatocellular adenoma associated with type I glycogen storage disease: a potential utility as biomarkers

BACKGROUND

It is known that malignant transformation to hepatocellular carcinoma (HCC) occurs at a higher frequency in hepatocellular adenoma (HCA) from type I glycogen storage disease (GSD I) compared to HCA from other etiologies. In this study, we aimed to identify differentially expressed miRNAs in GSD Ia HCA as candidates that could serve as putative biomarkers for detection of GSD Ia HCA and/or risk assessment of malignant transformation.

METHODS

Utilizing massively parallel sequencing, the miRNA profiling was performed for paired adenomas and normal liver tissues from seven GSD Ia patients. Differentially expressed miRNAs were validated in liver tumor tissues, HCC cell lines and serum using quantitative RT-PCR.

RESULTS

miR-34a, miR-34a, miR-224, miR-224, miR-424, miR-452 and miR-455-5p were found to be commonly deregulated in GSD Ia HCA, general population HCA, and HCC cell lines at compatible levels. In comparison with GSD Ia HCA, the upregulation of miR-130b and downregulation of miR-199a-5p, miR-199b-5p, and miR-214 were more significant in HCC cell lines. Furthermore, serum level of miR-130b in GSD Ia patients with HCA was moderately higher than that in either GSD Ia patients without HCA or healthy individuals.

CONCLUSION

We make the first observation of distinct miRNA deregulation in HCA associated with GSD Ia. We also provide evidence that miR-130b could serve as a circulating biomarker for detection of GSD Ia HCA. This work provides prominent candidate miRNAs worth evaluating as biomarkers for monitoring the development and progress of liver tumors in GSD Ia patients in the future.

Liver transplantation in glycogen storage disease type I

Glycogen storage disease type I (GSDI), an inborn error of carbohydrate metabolism, is caused by defects in the glucose-6-transporter/glucose-6-phosphatase complex, which is essential in glucose homeostasis. Two types exist, GSDIa and GSDIb, each caused by different defects in the complex. GSDIa is characterized by fasting intolerance and subsequent metabolic derangements. In addition to these clinical manifestations, patients with GSDIb suffer from neutropenia with neutrophil dysfunction and inflammatory bowel disease.

With the feasibility of novel cell-based therapies, including hepatocyte transplantations and liver stem cell transplantations, it is essential to consider long term outcomes of liver replacement therapy. We reviewed all GSDI patients with liver transplantation identified in literature and through personal communication with treating physicians. Our review shows that all 80 GSDI patients showed improved metabolic control and normal fasting tolerance after liver transplantation. Although some complications might be caused by disease progression, most complications seemed related to the liver transplantation procedure and subsequent immune suppression. These results highlight the potential of other therapeutic strategies, like cell-based therapies for liver replacement, which are expected to normalize liver function with a lower risk of complications of the procedure and immune suppression.

A novel homozygous no-stop mutation in G6PC gene from a Chinese patient with glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD-Ia) is an autosomal recessive genetic disorder resulting in hypoglycemia, hepatomegaly and growth retardation. It is caused by mutations in the G6PC gene encoding Glucose-6-phosphatase. To date, over 80 mutations have been identified in the G6PC gene. Here we reported a novel mutation found in a Chinese patient with abnormal transaminases, hypoglycemia, hepatomegaly and short stature. Direct sequencing of the coding region and splicing-sites in the G6PC gene revealed a novel no-stop mutation, p.*358Yext*43, leading to a 43 amino-acid extension of G6Pase. The expression level of mutant G6Pase transcripts was only 7.8% relative to wild-type transcripts. This mutation was not found in 120 chromosomes from 60 unrelated healthy control subjects using direct sequencing, and was further confirmed by digestion with Rsa I restriction endonuclease. In conclusion, we revealed a novel no-stop mutation in this study which expands the spectrum of mutations in the G6PC gene. The molecular genetic analysis was indispensable to the diagnosis of GSD-Ia for the patient.

Living donor liver transplantation for pediatric patients with metabolic disorders: the Japanese multicenter registry

LDLT is indicated for a variety of metabolic disorders, primarily in Asian countries due to the absolute scarcity of deceased donor LT. We analyzed data for all pediatric LDLTs performed between November 1989 and December 2010, during which 2224 pediatric patients underwent LDLT in Japan. Of these patients, 194 (8.7%) underwent LDLT for metabolic disorders. Wilson's disease (n = 59; 30.4%) was the most common indication in the patients with metabolic disorders, followed by OTCD (n = 40; 20.6%), MMA (n = 20; 10.3%), and GSD (n = 15; 7.7%). The one-, five-, 10-, and 15-yr patient and graft survival rates were 91.2%, 87.9%, 87.0%, and 79.3%, and 91.2%, 87.9%, 86.1%, and 74.4%, respectively. Wilson's disease and urea cycle deficiency were associated with better patient survival. The use of heterozygous donors demonstrated no negative impact on either the donors or recipients. With regard to X-linked OTCD, symptomatic heterozygote maternal donors should not be considered potential donor candidates. Improving the understanding of the long-term suitability of this treatment modality will require the registration and ongoing evaluation of all patients with inherited metabolic disease considered for LT.

Quality of life in adult patients with glycogen storage disease type I: results of a multicenter italian study

BACKGROUND

Glycogen storage disease type I (GSD I) is a chronic metabolic disease that requires a lifelong strict dietetic treatment to avoid hypoglycemia and can lead to severe complications during adult age. Impaired quality of life (QoL) has been reported in affected children, but this aspect has not been previously investigated in adults.

OBJECTIVE

To assess QoL in adult patients with GSD I.

PATIENTS AND METHODS

Italian patients with GSD type Ia and Ib, who were 16 years or older, were asked to complete the SF-36 questionnaire, assessing their QoL. Data on demographic characteristics and clinical history were collected from clinical records and interviews.

RESULTS

Thirty-eight patients (22 females, 16 males; 27 with GSD Ia, 11 with GSD Ib, median age 26.5 years) completed the SF-36 questionnaire. Overall, when compared to normal values, patients with GSD I had lower median scores in general health perception and social functioning, but better median scores for bodily pain and mental health. Patients with GSD Ib had a lower Z-score than GSD Ia patients for emotional health problems. Male patients showed better Z-scores in physical functioning, general health perception, and social functioning when compared to females. Emotional health problems Z-score was lower in nephropathic patients.

CONCLUSION

QoL can be impaired in adult patients with GSD I. The results of this study show that patients with GSD type Ib, women, and those with renal complications are more likely to experience a poorer QoL.

The upstream enhancer elements of the G6PC promoter are critical for optimal G6PC expression in murine glycogen storage disease type Ia

Glycogen storage disease type-Ia (GSD-Ia) patients deficient in glucose-6-phosphatase-α (G6Pase-α or G6PC) manifest impaired glucose homeostasis characterized by fasting hypoglycemia, growth retardation, hepatomegaly, nephromegaly, hyperlipidemia, hyperuricemia, and lactic acidemia. Two efficacious recombinant adeno-associated virus pseudotype 2/8 (rAAV8) vectors expressing human G6Pase-α have been independently developed. One is a single-stranded vector containing a 2864-bp of the G6PC promoter/enhancer (rAAV8-GPE) and the other is a double-stranded vector containing a shorter 382-bp minimal G6PC promoter/enhancer (rAAV8-miGPE). To identify the best construct, a direct comparison of the rAAV8-GPE and the rAAV8-miGPE vectors was initiated to determine the best vector to take forward into clinical trials. We show that the rAAV8-GPE vector directed significantly higher levels of hepatic G6Pase-α expression, achieved greater reduction in hepatic glycogen accumulation, and led to a better toleration of fasting in GSD-Ia mice than the rAAV8-miGPE vector. Our results indicated that additional control elements in the rAAV8-GPE vector outweigh the gains from the double-stranded rAAV8-miGPE transduction efficiency, and that the rAAV8-GPE vector is the current choice for clinical translation in human GSD-Ia.

Suppression of gluconeogenic gene expression by LSD1-mediated histone demethylation

Aberrant gluconeogenic gene expression is associated with diabetes, glycogen storage disease, and liver cancer. However, little is known how these genes are regulated at the chromatin level. In this study, we investigated in HepG2 cells whether histone demethylation is a potential mechanism. We found that knockdown or pharmacological inhibition of histone demethylase LSD1 causes remarkable transcription activation of two gluconeogenic genes, FBP1 and G6Pase, and consequently leads to increased de novo glucose synthesis and decreased intracellular glycogen content. Mechanistically, LSD1 occupies the promoters of FBP1 and G6Pase, and modulates their H3K4 dimethylation levels. Thus, our work identifies an epigenetic pathway directly governing gluconeogenic gene expression, which might have important implications in metabolic physiology and diseases.

Pathogenesis of growth failure and partial reversal with gene therapy in murine and canine Glycogen Storage Disease type Ia

Glycogen Storage Disease type Ia (GSD-Ia) in humans frequently causes delayed bone maturation, decrease in final adult height, and decreased growth velocity. This study evaluates the pathogenesis of growth failure and the effect of gene therapy on growth in GSD-Ia affected dogs and mice. Here we found that homozygous G6pase (-/-) mice with GSD-Ia have normal growth hormone (GH) levels in response to hypoglycemia, decreased insulin-like growth factor (IGF) 1 levels, and attenuated weight gain following administration of GH. Expression of hepatic GH receptor and IGF 1 mRNAs and hepatic STAT5 (phospho Y694) protein levels are reduced prior to and after GH administration, indicating GH resistance. However, restoration of G6Pase expression in the liver by treatment with adeno-associated virus 8 pseudotyped vector expressing G6Pase (AAV2/8-G6Pase) corrected body weight, but failed to normalize plasma IGF 1 in G6pase (-/-) mice. Untreated G6pase (-/-) mice also demonstrated severe delay of growth plate ossification at 12 days of age; those treated with AAV2/8-G6Pase at 14 days of age demonstrated skeletal dysplasia and limb shortening when analyzed radiographically at 6 months of age, in spite of apparent metabolic correction. Moreover, gene therapy with AAV2/9-G6Pase only partially corrected growth in GSD-Ia affected dogs as detected by weight and bone measurements and serum IGF 1 concentrations were persistently low in treated dogs. We also found that heterozygous GSD-Ia carrier dogs had decreased serum IGF 1, adult body weights and bone dimensions compared to wild-type littermates. In sum, these findings suggest that growth failure in GSD-Ia results, at least in part, from hepatic GH resistance. In addition, gene therapy improved growth in addition to promoting long-term survival in dogs and mice with GSD-Ia.

In vivo hepatic lipid quantification using MRS at 7 Tesla in a mouse model of glycogen storage disease type 1a

The assessment of liver lipid content and composition is needed in preclinical research to investigate steatosis and steatosis-related disorders. The purpose of this study was to quantify in vivo hepatic fatty acid content and composition using a method based on short echo time proton magnetic resonance spectroscopy (MRS) at 7 Tesla. A mouse model of glycogen storage disease type 1a with inducible liver-specific deletion of the glucose-6-phosphatase gene (L-G6pc(-/-)) mice and control mice were fed a standard diet or a high-fat/high-sucrose (HF/HS) diet for 9 months. In control mice, hepatic lipid content was found significantly higher with the HF/HS diet than with the standard diet. As expected, hepatic lipid content was already elevated in L-G6pc(-/-) mice fed a standard diet compared with control mice. L-G6pc(-/-) mice rapidly developed steatosis which was not modified by the HF/HS diet. On the standard diet, estimated amplitudes from olefinic protons were found significantly higher in L-G6pc(-/-) mice compared with that in control mice. L-G6pc(-/-) mice showed no noticeable polyunsaturation from diallylic protons. Total unsaturated fatty acid indexes measured by gas chromatography were in agreement with MRS measurements. These results showed the great potential of high magnetic field MRS to follow the diet impact and lipid alterations in mouse liver.