Short-term effect of captopril on microalbuminuria in children with glycogen storage disease type Ia

Glycogen storage diseases: An update

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

[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.

Glycogen Storage Disease type 1a - a secondary cause for hyperlipidemia: report of five cases

BACKGROUND AND AIMS

Glycogen storage disease type Ia (GSD Ia) is a rare metabolic disorder, caused by deficient activity of glucose-6-phosphatase-α. It produces fasting induced hypoglycemia and hepatomegaly, usually manifested in the first semester of life. Besides, it is also associated with growth delay, anemia, platelet dysfunction, osteopenia and sometimes osteoporosis. Hyperlipidemia and hyperuricemia are almost always present and hepatocellular adenomas and renal dysfunction frequent late complications.

METHODS

The authors present a report of five adult patients with GSD Ia followed in internal medicine appointments and subspecialties.

RESULTS

Four out of five patients were diagnosed in the first 6 months of life, while the other one was diagnosed in adult life after the discovery of hepatocellular adenomas. In two cases genetic tests were performed, being identified the missense mutation R83C in one, and the mutation IVS4-3C > G in the intron 4 of glucose-6-phosphatase gene, not previously described, in the other. Growth retardation was present in 3 patients, and all of them had anemia, increased bleeding tendency and hepatocellular adenomas; osteopenia/osteoporosis was present in three cases. All but one patient had marked hyperlipidemia and hyperuricemia, with evidence of endothelial dysfunction in one case and of brain damage with refractory epilepsy in another case. Proteinuria was present in two cases and end-stage renal disease in another case. There was a great variability in the dietary measures; in one case, liver transplantation was performed, with correction of the metabolic derangements.

CONCLUSIONS

Hyperlipidemia is almost always present and only partially responds to dietary and drug therapy; liver transplantation is the only definitive solution. Although its association with premature atherosclerosis is rare, there have been reports of endothelial dysfunction, raising the possibility for increased cardiovascular risk in this group of patients. Being a rare disease, no single metabolic center has experience with large numbers of patients and the recommendations are based on clinical experience more than large scale studies.

Hepatorenal correction in murine glycogen storage disease type I with a double-stranded adeno-associated virus vector

Glycogen storage disease type Ia (GSD-Ia) is caused by the deficiency of glucose-6-phosphatase (G6Pase). Long-term complications of GSD-Ia include life-threatening hypoglycemia and proteinuria progressing to renal failure. A double-stranded (ds) adeno-associated virus serotype 2 (AAV2) vector encoding human G6Pase was pseudotyped with four serotypes, AAV2, AAV7, AAV8, and AAV9, and we evaluated efficacy in 12-day-old G6pase (-/-) mice. Hypoglycemia during fasting (plasma glucose <100 mg/dl) was prevented for >6 months by the dsAAV2/7, dsAAV2/8, and dsAAV2/9 vectors. Prolonged fasting for 8 hours revealed normalization of blood glucose following dsAAV2/9 vector administration at the higher dose. The glycogen content of kidney was reduced by >65% with both the dsAAV2/7 and dsAAV2/9 vectors, and renal glycogen content was stably reduced between 7 and 12 months of age for the dsAAV2/9 vector-treated mice. Every vector-treated group had significantly reduced glycogen content in the liver, in comparison with untreated G6pase (-/-) mice. G6Pase was expressed in many renal epithelial cells of with the dsAAV2/9 vector for up to 12 months. Albuminuria and renal fibrosis were reduced by the dsAAV2/9 vector. Hepatorenal correction in G6pase (-/-) mice demonstrates the potential of AAV vectors for the correction of inherited diseases of metabolism.

Glycogen storage diseases: New perspectives

Glycogen storage diseases (GSD) are inherited metabolic disorders of glycogen metabolism. Different hormones, including insulin, glucagon, and cortisol regulate the relationship of glycolysis, gluconeogenesis and glycogen synthesis. The overall GSD incidence is estimated 1 case per 20000-43000 live births. There are over 12 types and they are classified based on the enzyme deficiency and the affected tissue. Disorders of glycogen degradation may affect primarily the liver, the muscle, or both. Type Ia involves the liver, kidney and intestine (and Ib also leukocytes), and the clinical manifestations are hepatomegaly, failure to thrive, hypoglycemia, hyperlactatemia, hyperuricemia and hyperlipidemia. Type IIIa involves both the liver and muscle, and IIIb solely the liver. The liver symptoms generally improve with age. Type IV usually presents in the first year of life, with hepatomegaly and growth retardation. The disease in general is progressive to cirrhosis. Type VI and IX are a heterogeneous group of diseases caused by a deficiency of the liver phosphorylase and phosphorylase kinase system. There is no hyperuricemia or hyperlactatemia. Type XI is characterized by hepatic glycogenosis and renal Fanconi syndrome. Type II is a prototype of inborn lysosomal storage diseases and involves many organs but primarily the muscle. Types V and VII involve only the muscle.

Efficacy of ACE-inhibitor therapy on renal disease in glycogen storage disease type 1: a multicentre retrospective study

BACKGROUND

The efficacy of ACE-inhibitors in decreasing microalbuminuria and proteinuria has been reported in a few patients with glycogen storage disease type 1 (GSD1); however, no case-control study has ever been published.

AIM

The aim of the current study was to evaluate the efficacy of ACE-inhibitors in reducing glomerular hyperfiltration, microalbuminuria and proteinuria, and in delaying the progression of renal damage.

PATIENTS AND METHODS

Ninety-five patients (median age at the time of the study: 14.5 years) were enrolled from nine Italian referral centres for metabolic diseases. A retrospective study of a 10-year follow-up was conducted in order to compare the evolution of these parameters in treated patients with those who were not treated with ACE-inhibitors.

RESULTS

A significant and progressive decrease of glomerular filtration rate was observed in treated patients vs. those who were not treated with ACE-inhibitors (P < 0.05). No difference was observed for microalbuminuria and proteinuria between the two groups of patients. Moreover, the ACE-inhibitors significantly delayed the progression from glomerular hyperfiltration to microalbuminuria, but not that from microalbuminuria to proteinuria.

CONCLUSIONS

The results of the present study underline the importance of a strict follow-up of renal function in GSD1 patients. The detection of glomerular hyperfiltration suggests precocious initiation of ACE-inhibitor treatment to delay the progression of renal damage. A randomized prospective study is needed to establish for certain the real effectiveness of this treatment in GSD1 patients.

Ramipril treatment in a patient with glycogen storage disease I non-A

We studied the effect of ramipril on proteinuria and mild hypertension in a 21-year-old patient affected by glycogen storage disease type I non-A. After few months of therapy we obtained a decrease in total urine protein excretion that later re-increased in spite of the high dose of ACE inhibitor. Even if ACE inhibitors are the only effective therapy for GSD I nephropathy, further studies are requested.

Effect of ramipril in a patient with glycogen storage disease type I and nephrotic-range proteinuria

We studied the effect of ramipril on urinary protein excretion and arterial pressure in a 27-year-old patient with GSD Ia and heavy proteinuria (2-3 g /24 h). Ramipril therapy resulted in an important reduction of proteinuria (0.3-0.5 g/24 h): no changes were observed in arterial pressure and renal function during the 12-month follow-up. We conclude that treatment with ramipril can be employed effectively and safely in GSD Ia patients with nephrotic-range proteinuria.