Urinary Glycosaminoglycans: Characterization and Quantification

The growing body of evidence supports the potential of using urinary glycosaminoglycans (uGAGs) levels as biomarkers to guide diagnosis and as predictive biomarkers of treatment efficacy. Recently, studies have shown that, in addition to MPS, the prognosis and treatment of cancers and viral infections, including COVID-19, are enabled by characterization and/or traits by GAGs. Reliable and accessible detection and assay protocols of urinary GAGs are therefore of great support for laboratory workers and clinicians. Here we describe a semiquantitative and quantitative urinary glycosaminoglycans determination using 1,9-dimethylmethylene blue (DMB) and the characterization of uGAGs using thin layer chromatography (TLC).

Update of a colorimetric method for quantitative determination of galactose in blood samples: A simple and rapid method for the early detection of inherited metabolic diseases

BACKGROUND

A colorimetric microassay for the quantitative determination of galactose in the blood was taken and updated. This method helps in diagnosis and follow-up of several inherited metabolic diseases connected to galactose metabolism deficiency such as galactosemia, glycogenosis, glycosylation, tyrosinemia and citrin deficiency. Galactose assay in the blood presents difficulties due to interference with glucose. In this study, we update a method to get around these difficulties.

METHOD

This procedure was based on the incubation of whole blood with orcinol in a strongly acidic solution to form a galactose and glucose complexes able to absorb at two different wavelengths.

RESULTS

The standard curve analysis for the individual solutions of these two sugars showed a wide range of linearity from 0 to 200 mg / l. Under optimal experimental conditions, the stirring time of the orcinol is 3 minutes, the heating time of the reaction is 20 minutes at 56 ° C, and the duration of the incubation in the dark is 40 minutes. The analysis is carried out on fresh blood. The maximum absorbance of galactose and glucose is respectively 569 nm and 421 nm. An adapted diagnosis algorithm was developed based on our results.

CONCLUSION

this method could help in screening and identifying patients with hypergalactosemia that need further investigations. It could represent a promising method for neonatal screening in countries with limited resources.

Usefulness of urinary glycosaminoglycans assay for a mucopolysaccharidosis-specific screening

BACKGROUND

Mucopolysaccharidoses (MPS), a group of inherited metabolic disorders characterized by the accumulation of glycosaminoglycans, can be diagnosed early through newborn screening programs. Establishing newborn screening in Morocco is a challenging task for multiple economic and social reasons. Screening in a Moroccan population using 1,9-dimethylmethylene blue urinary glycosaminoglycan (GAG) assays may allow for an earlier diagnosis of MPS. We studied the feasibility of implementing screening in Moroccan children as an alternative to national newborn screening. We determined the reference ranges for GAGs in the Moroccan population, their stability during transport, the effectiveness of this test as a screening procedure for MPS in patients, and its use as a screening test for MPS in the Imssouane region, where the rate of consanguineous marriage is 38%.

METHODS

Using dimethylmethylene blue assays, urine samples of 47 MPS patients were analyzed, together with urine samples from healthy controls (n = 368, age ranging from 1 month to 25 years), and from Imssouane region children (n = 350, age ranging from 6 months to 24 month). Precision, linearity, recovery, limits, and stability were tested.

RESULTS

Urinary GAGs reference values are age and ethnicity dependent. The validation parameters established displayed great precision and accuracy leading to recoveries according to internationally accepted values for bioanalytical methods. Urinary GAGs were stable for a maximum of 7 weeks at 40 °C. Screening of Imssouane children resulted in the detection of a 6-month-old child, diagnosed with MPS I.

CONCLUSIONS

Our results demonstrate the usefulness of quantifying glycosaminoglycans for early screening of MPS.