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Abstract Aim The urinary glucose tetrasaccharide, Glcα1‐6Glcα1‐4Glcα1‐4Glc (Glc4), is a glycogen limit dextrin that is elevated in patients with glycogen storage disease (GSD) type III. We evaluated the potential of uncooked cornstarch therapy to interfere with Glc4 monitoring, by measuring the diurnal variability of Glc4 excretion in patients with GSD III. Methods Voids were collected at home over 24 hours, stored at 4°C and frozen within 48 hours. Glc4 was analyzed using liquid chromatography‐tandem mass spectrometry and normalized to creatinine. Results Subjects with GSD III (median age: 13.5 years, range: 3.7‐62; n = 18) completed one or more 24‐hour urine collection, and 28/36 collections were accepted for analysis. Glc4 was elevated in 16/18 subjects (median: 13 mmol/mol creatinine, range: 2‐75, reference range: 25%) was not consistently observed in repeat collections by the same subject. Conclusions The extent and variability of Glc4 excretion relative to creatinine was not correlated with cornstarch dose. A majority of collections showed low variability over 24 hours. These findings support the use of single time‐point collections to evaluate Glc4 in patients with GSD III treated with cornstarch. However, repeat sampling over short time‐periods will provide the most accurate assessment of Glc4 excretion, as intraday variability may be increased in patients with high Glc4 excretion.

Whole‐body magnetic resonance imaging (WBMRI) has clinical utility in measuring the amount of fatty infiltration in late‐onset Pompe disease (LOPD). Muscle strength and function testing also provide valuable insight to the progression of myopathy seen in these patients. The main purpose of this study was to determine how closely muscle strength and functional testing correlate to the amount of fatty infiltration seen on WBMRI. LOPD patients were followed longitudinally and WBMRI, muscle strength testing using the modified Medical Research Council (mMRC) scale, muscle function testing using the Gait, Stairs, Gowers, Chair (GSGC) score, and labs including urinary glucose tetrasaccharide (Glc4) were performed at each visit. The amount of fat seen on WBMRI was quantified using proton density fat fraction (PDFF) and correlated to appropriate muscle strength and functional tests. Nineteen patients with LOPD aged 10 to 67 years were followed for a 1 to 2 year duration. There was a small increase of 1.26% (±2.57%) in overall PDFF per year in patients on ERT. Muscle strength (mMRC) and functional testing (GSGC) correlated highly with PDFF (r = −.7596, P <.0001 and r =.8267, P <.0001, respectively). Time to carry out individual tasks of the GSGC also correlated highly with PDFF of the muscles involved. Glc4 levels were normal on most visits (27/39) despite varying severity of muscle weakness in patients. Muscle strength and GSGC scores correlate highly with PDFF values from WBMRI. They may be used in assessing severity of muscle disease and to follow LOPD patients over time. [ABSTRACT FROM AUTHOR]

Abstract: A tetraglucose oligomer, Glcα1-6Glcα1-4Glcα1-4Glc, designated Glc4, has been shown to be a putative biomarker for the diagnosis of Pompe disease. The purpose of this study was to assess whether Glc4 could be used to monitor the therapeutic response to recombinant human acid α glucosidase (rhGAA) enzyme replacement therapy (ERT) in patients with Pompe disease. Urinary Glc4 levels in 11 patients receiving rhGAA therapy was determined by both HPLC-UV and stable isotope dilution ESI-MS/MS. Combined Glc4 and maltotetraose, Glcα1-4Glcα1-4Glcα1-4Glc, (M4) concentrations, designated Hex4, in plasma from these patients were measured by HPLC-UV only. Baseline urinary Glc4 and plasma Hex4 in these patients (mean±SD: 34.2±11.3mmol/mol creatinine and 1.7±0.8μM, respectively) were higher than age-matched control values (mean±SD, 6.1±5.1mmol/mol creatinine and 0.22±0.15μM, respectively). Both urinary Glc4 and plasma Hex4 levels decreased after initiation of ERT for all patients. In the four patients with the best overall clinical response in both skeletal and cardiac muscle, levels decreased to within, or near, normal levels during the first year of treatment. In contrast, levels fluctuated and were persistently elevated above the control ranges in those patients with a less favorable clinical response (good cardiac response but limited motor improvement). These results suggest that urinary Glc4 and plasma Hex4 could serve as a valuable adjunct to clinical endpoints for monitoring the efficacy of therapeutic interventions such as rhGAA ERT in Pompe disease. [Copyright &y& Elsevier]

Aim: The urinary glucose tetrasaccharide, Glcα1-6Glcα1-4Glcα1-4Glc (Glc 4 ), is a glycogen limit dextrin that is elevated in patients with glycogen storage disease (GSD) type III. We evaluated the potential of uncooked cornstarch therapy to interfere with Glc 4 monitoring, by measuring the diurnal variability of Glc 4 excretion in patients with GSD III., Methods: Voids were collected at home over 24 hours, stored at 4°C and frozen within 48 hours. Glc 4 was analyzed using liquid chromatography-tandem mass spectrometry and normalized to creatinine., Results: Subjects with GSD III (median age: 13.5 years, range: 3.7-62; n = 18) completed one or more 24-hour urine collection, and 28/36 collections were accepted for analysis. Glc 4 was elevated in 16/18 subjects (median: 13 mmol/mol creatinine, range: 2-75, reference range: <3). In collections with elevated Glc 4 (23/28), two-thirds (15/23) had low diurnal variability in Glc 4 excretion (coefficient of variation [CV%] <25). The diurnal variability was significantly correlated with the Glc 4 concentration (Pearson R = .644, P < .05), but not with the dose of uncooked cornstarch. High intraday variability (>25%) was not consistently observed in repeat collections by the same subject., Conclusions: The extent and variability of Glc 4 excretion relative to creatinine was not correlated with cornstarch dose. A majority of collections showed low variability over 24 hours. These findings support the use of single time-point collections to evaluate Glc 4 in patients with GSD III treated with cornstarch. However, repeat sampling over short time-periods will provide the most accurate assessment of Glc 4 excretion, as intraday variability may be increased in patients with high Glc 4 excretion., Competing Interests: S. P. Y. works for a laboratory that offers Glc4 testing, has received grant support from Sanofi Genzyme, Amicus Therapeutics, Biomarin Pharmaceutical, PTC Therapeutics, and Valerion Therapeutics, and has consulted for Amicus Therapeutics, Sanofi Genzyme, and PTC Therapeutics. P. S. K. has received research/grant support from Sanofi Genzyme, Valerion Therapeutics, Shire Pharmaceuticals, Amicus Therapeutics, Pfizer, Alexion Pharmaceuticals and Ultragenyx and consulting fees and honoraria from Sanofi Genzyme, Shire Pharmaceuticals, Alexion Pharmaceuticals, Amicus Therapeutics, Vertex Pharmaceuticals, Ultragenyx, and Asklepios Biopharmaceutical, Inc. (AskBio). P. S. K. is listed as an inventor on a licensed Duke University patent for the use of rhGAA in the treatment of GSDIII and other GSDs excluding GSDII. To date, neither Duke University nor the inventor has received any money from the commercialization of rights associated with this patent. S. A. has received consulting fees from Ultragenyx. The other authors declare no conflicts of interest., (© 2020 The Authors. JIMD Reports published by John Wiley & Sons Ltd on behalf of SSIEM.)

Background: β-N-acetylhexosaminidases, which are involved in a variety of biological processes including energy metabolism, cell proliferation, signal transduction and in pathogen-related inflammation and autoimmune diseases, are widely distributed in Bacteria and Eukaryotes, but only few examples have been found in Archaea so far. However, N-acetylgluco- and galactosamine are commonly found in the extracellular storage polymers and in the glycans decorating abundantly expressed glycoproteins from different Crenarchaeota Sulfolobus sp., suggesting that β-N-acetylglucosaminidase activities could be involved in the modification/recycling of these cellular components., Methods: A thermophilic β-N-acetylglucosaminidase was purified from cellular extracts of S. solfataricus, strain P2, identified by mass spectrometry, and cloned and expressed in E. coli. Glycosidase assays on different strains of S. solfataricus, steady state kinetic constants, substrate specificity analysis, and the sensitivity to two inhibitors of the recombinant enzyme were also reported., Results: A new β-N-acetylglucosaminidase from S. solfataricus was unequivocally identified as the product of gene sso3039. The detailed enzymatic characterization demonstrates that this enzyme is a bifunctional β-glucosidase/β-N-acetylglucosaminidase belonging to family GH116 of the carbohydrate active enzyme (CAZy) classification., Conclusions: This study allowed us to propose that family GH116 is composed of three subfamilies, which show distinct substrate specificities and inhibitor sensitivities., General Significance: The characterization of SSO3039 allows, for the first time in Archaea, the identification of an enzyme involved in the metabolism β-N-acetylhexosaminide, an essential component of glycoproteins in this domain of life, and substantially increases our knowledge on the functional role and phylogenetic relationships amongst the GH116 CAZy family members., (© 2013.)