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BACKGROUND: Urinary excretion of the tetrasaccharide 6-α-D-glucopyranosyl-maltotriose (Glc4) is increased in various clinical conditions associated with increased turnover or storage of glycogen, making Glc4 a potential biomarker for glycogen storage diseases (GSD). We developed an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay to detect Glc4 in urine without interference of the Glc4 isomer maltotetraose (M4). METHODS: Urine samples, diluted in 0.1% ammonium hydroxide containing the internal standard acarbose, were filtered, and the filtrate was analyzed by UPLC-MS/MS. RESULTS: We separated and quantified acarbose, M4, and Glc4 using the ion pairs m/z 644/161, 665/161, and 665/179, respectively. Response of Glc4 was linear up to 1500 µmol/L and the limit of quantification was 2.8 µmol/L. Intra- and interassay CVs were 18.0% and 18.4% (10 µmol/L Glc4), and 10.5% and 16.2% (200 µmol/L Glc4). Glc4 in control individuals (n = 116) decreased with increasing age from a mean value of 8.9 mmol/mol to 1.0 mmol/mol creatinine. M4 was present in 5% of urine samples. Mean Glc4 concentrations per age group in untreated patients with Pompe disease (GSD type II) (n = 66) were significantly higher, ranging from 39.4 to 10.3 mmol/mol creatinine (P < 0.001-0.005). The diagnostic sensitivity of Glc4 for GSD-II was 98.5% and the diagnostic specificity 92%. Urine Glc4 was also increased in GSD-III (8 of 9), GSD-IV (2 of 3) and GSD-IX (6 of 10) patients. CONCLUSIONS: The UPLC-MS/MS assay of Glc4 in urine was discriminative between Glc4 and M4 and confirmed the diagnosis in >98% of GSD-II cases.

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A high performance liquid chromatography method, adapted from an established urinary sugars method, has been developed for the analysis of a tetraglucose oligomer (Glc(4)) in urine. Pompe disease results from defects in the activity of lysosomal acid α-glucosidase (GAA) with patients typically excreting increased amounts of Glc(4). Rapid determination of GAA in dried blood spots is now possible. However, enzymatic analysis is unable to discriminate between patients with Pompe disease and those individuals harbouring pseudo deficiency mutations. This method was able to quantify Glc(4) levels in all patients analysed with an established diagnosis of Pompe disease, and all controls analysed had Glc(4) levels below the limit of detection for this method. Importantly the method was able to discriminate between an individual known to harbour a pseudo Pompe mutation and patients with Pompe disease, providing a useful supporting test to enzymatic analysis. Sequential measurement of urinary Glc(4) has been proposed to monitor the effects of enzyme replacement therapy (ERT). We observed a clear decrease in Glc(4) levels following commencement of treatment in three patients studied. Additionally, raised levels of Glc(4) were observed in patients with glycogen storage disease (GSD) type Ia and type III suggesting that this method may have applications in other GSDs.

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Patients with glycogen storage disease (GSD) types I, III and IX show reduced bone mineral content, but there is scarce data on new serum and urine markers of bone turnover or their relationship to bone densitometry. Six GSD I, four GSD III and four GSD IX patients underwent bone mineral density (BMD) measurement by dual-energy X-ray absorptiometry. Free pyridinoline (fPYD):creatinine and free deoxypyridinoline (fDPD):creatinine ratios were analysed on random urines. Procollagen type I C-terminal propeptide, procollagen type I N-terminal propeptide (PINP), carboxyterminal telopeptide of type I collagen and bone-specific alkaline phosphatase were analysed in serum. Some GSD I and GSD III patients had low or very low BMD. There was no difference in total body BMD z-score between the GSD types after adjusting for height (p=0.110). Bone marker analysis showed no consistent pattern. Urine fPYD:creatinine ratio was raised in four GSD I and two GSD III patients, while serum PINP was inappropriately low in some of these patients. There was no clear correlation between any markers of bone destruction and total body z-score, but the patient with the lowest total body z-score showed the highest concentrations of both urinary fPYD:creatinine and fDPD:creatinine ratios. We conclude that some GSD I and GSD III patients have very low bone mineral density. There is no correlation between mineral density and bone markers in GSD patients. The inappropriately low concentration of PINP in association with the raised urinary fPYD:creatinine and fDPD:creatinine ratios seen in two GSD I patients reflect uncoupling of bone turnover. All these findings taken together suggest that some GSD I and GSD III patients may be at an increased risk of osteoporosis.

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An infant with glycogen storage disease and prolonged malnourishment showed a urinary organic acid profile during an episode of fasting hypoglycaemia with inappropriate hypoketotic dicarboxylic aciduria that was indistinguishable from that reported in long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency. Although there was a striking elevation of urinary 3-hydroxydecanedioic acid, the ratios between hydroxydicarboxylic acids were consistent with values reported to be indicate of medium-chain acyl-CoA dehydrogenase deficiency. We suspect that the fasting 3-hydroxydicarboxylic aciduria was attributable to secondarily impaired enzyme activities, the consequence of malnutrition, early infancy, and/or glycogen storage disease. Caution is advised in the interpretation of urinary organic acid patterns that indicate a 3-hydroxydicarboxylic aciduria, as well as an inappropriate hypoketotic dicarboxylic aciduria, as they may represent non-specific findings.

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A 46-year-old Japanese woman had disseminated angiokeratoma, confirmed by electron microscopy which showed numerous cytoplasmic vacuoles in cells of the kidney and skin. Enzyme activities against synthetic and natural substrates in leucocytes and fibroblasts were normal. Her urine contained a large amount of sialylglycoaminoacids, with predominant excretion of an O-glycoside-linked glycoaminoacid.

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Neutral oligosaccharides were isolated from urine of an adult patient with glycogen storage disease type II, a deficiency of lysosomal acid alpha-glucosidase, by chromatography on columns of activated charcoal, Dowex 50 X 2 and Dowex 1 X 2. Total neutral oligosaccharides in the urine of the patient were increased about 5-fold as compared with those in normal controls. The most accumulated oligosaccharide was separated by Bio-Gel P-2 column chromatography, and finally purified by paper chromatography. Based on various studies, including carbohydrate analysis, chemical ionization mass spectrometry, fast atom bombardment mass spectrometry, degradation by glucoamylase and isopullulanase, and methylation analysis, the structure of this oligosaccharide was deduced to be Glc alpha 1----6Glc alpha 1----4Glc alpha 1----4Glc. This oligosaccharide appears to be accumulated in urine of the patient with acid alpha-glucosidase deficiency as an end product of the hydrolysis of glycogen.

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In recent years great interest has centered around metabolic disorders in which excessive oligosacchariduria is a prominent feature. This review describes the methods of both structural and diagnostic investigations of oligosaccharides in a number of these diseases. Special emphasis has been laid upon simple screening methods which would avail themselves to the clinical chemistry laboratory

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A modified thin-layer chromatographic screening method is presented for the rapid diagnosis of glycoprotein storage disorders based upon excess oligosaccharide excretion. The system has been used successfully in the diagnosis of mannosidosis, GM1 gangliosidosis, mucolipidoses types I and III, aspartyl-glycosaminuria and fucosidosis.

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Patients with glycogen storage disease type II and type III were recently found to excrete increased amounts of a glucose-containing tetrasaccharide DGlcp(alpha1 leads to 6)DGlcp(alpha1 leads to 4)DGlcp(alpha1 leads to 4)DGlc [Lennartson, G., Lundblad, A., Sjöblad, S., Svensson, S. and Ockerman, P.A. (1976) Biomed. Mass Spectrom. 3, 51--54]. In addition to this tetrasaccharide, urine from these patients also contains larger oligosaccharides containing only glucose. From urine of patients with glycogen storage disease type II and type III, three and four oligosaccharides respectively have been isolated. Structural studies including sugar analyses, methylation analyses, partial acid hydrolysis and optical rotation revealed that three compounds were present in the urine of both patients. Their proposed structures or partial structures are as follows: DGlcp(alpha1--6)DGlcp(alpha1--6)DGlcp(alpha1--4)DGlcp(alpha1--4)DGlcp(alpha1--4)DGlc, DGlcp(alpha1--4)DGlcp(alpha1--6)DGlcp(alpha1--6)DGlcp(alpha1--4)DGlcp(alpha1--4)DGlc, and DGlcp(alpha1--6)DGlcp(alpha1--4)DGlcp(alpha1--4)DGlcp(alpha1--4)DGlcp(alpha1--6)DGlcp(alpha1--4)DGlcp(alpha1--4)DGlc. A fourth compound has been partially characterized as a branched heptasaccharide with four (1 leads to 4) linkages and two (1 lead to 6) linkages. Glycogen is possibly the origin of these compounds. However, the number of (1 leads to 6) linkages is higher than expected and may indicate a shorter distance between branches in glycogen than has been generally assumed.

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A gas chromatographic mass spectrometric method has been developed for the rapid determination of a urinary tetrasaccharide (alpha-D-Glc-(1 leads to 6)-alpha-D-Glc-(1 leads to 4)-alpha-D-Glc-(1 leads to 4)-D-Glc). The urine sample is first fractionated by gel chromatography. An appropriate internal standard is added to the pooled tri-pentasaccharide fraction, which is then reduced, methylated and fractionated by g.c. The identification of the tetrasaccharide derivative is based on the g.c. relative retention time and the mass spectrum of the reduced permethylated tetrasaccharide. The normal excretion rate was in the range of 0.1-2.5 mg per 24 hours. Greatly increased amounts (9.4-89.6 mg 24 h-1) were found in the urine of patients with glycogen storage disease type II and type III and in one patient with unclassified muscular disease. A moderate increase (3.6m6 mg 24 h-1) was observed in one patient with glycogen storage disease type VI, in two patients with Duchenne muscular dystrophy and in two other patients with unclassified muscular disease.

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