High-throughput determination of urinary hexosamines for diagnosis of mucopolysaccharidoses by capillary electrophoresis and high-performance liquid chromatography

Importance of the combined urinary procedure for the diagnosis of Mucopolysaccharidoses

BACKGROUND

Mucopolysaccharidoses are characterized by the accumulation of undegraded glycosaminoglycans in lysosomes in multiple organs and by their excretion in high amounts in urine. The aim of this study is to determine if this simple, reliable and reproducible method is useful for the diagnosis of Mucopolysaccharidoses.

METHODS

The study included 2154 normal urine samples and 210 samples from 73 patients affected by different types of Mucopolysaccharidoses. The glycosaminoglycans were quantified by a dimethylmethylene blue method and size-fractionated by a modified one-dimensional electrophoresis method.

RESULTS

The combination of the two methods allowed to identify all the patients affected by the different types of Mucopolysaccharidosis with 100% sensitivity and specificity.

CONCLUSION

This combined approach gives fast diagnostic orientation about the different types of Mucopolysaccharidoses, offering an important tool for a better understanding of diagnosis and patient management.

Total and single species of uronic acid-bearing glycosaminoglycans in urine of newborns of 2-3days of age for early diagnosis application

BACKGROUND

Urine are easily accessible and relatively simple to process and uronic acid-bearing glycosaminoglycans (UA-GAGs) may serve as biomarkers for several diseases, like for mucopolysaccharidosis.

METHODS

We report a study from a large cohort of healthy newborns of 2-3days to have a basic profile of total content of urinary UA-GAGs, their composition and structural signatures utilizing a rapid extractive method and sensitive separation of enzymatic released disaccharides by capillary electrophoresis-light induced fluorescence. Results were also compared with those obtained from normal adult subjects.

RESULTS

A total of UA-GAGs content of ~35μg/mg creatinine was observed in 331 newborns versus 1.5μg/mg creatinine of adult urine composed of ~90% chondroitin sulfate (CS), ~7% heparan sulfate (HS) and ~3% hyaluronic acid (HA). No significant differences were observed with adults. Specific ratios between the main CS disaccharides were informative of a significant greater 4-sulfation and charge density for newborn compared to adults. The HS from newborn urine was mainly composed by the non-sulfated (~64%) and mono-sulfated (~28%) disaccharides. No significant differences were observed versus adult urine.

CONCLUSIONS

The present method is able to measure changes in UA-GAG composition and their structure independently of the age of subjects and rapidly applicable to the newborn diagnosis without necessity to have creatinine levels. Moreover, modifications in charge density values as well as the presence of sulfate groups in specific positions may be indicative of altered conditions.

Mental retardation in mucopolysaccharidoses correlates with high molecular weight urinary heparan sulphate derived glucosamine

Mucopolysaccharidoses (MPS) are characterized by mental retardation constantly present in the severe forms of Hurler (MPS I), Hunter (MPS II) and Sanfilippo (MPS III) diseases. On the contrary, mental retardation is absent in Morquio (MPS IV) and Maroteaux-Lamy (MPS VI) diseases and absent or only minimal in the attenuated forms of MPS I, II and III. Considering that MPS patients affected by mental disease accumulate heparan sulfate (HS) due to specific enzymatic defects, we hypothesized a possible correlation between urinary HS-derived glucosamine (GlcN) accumulated in tissues and excreted in biological fluids and mental retardation. 83 healthy subjects were found to excrete HS in the form of fragments due to the activity of catabolic enzymes that are absent or impaired in MPS patients. On the contrary, urinary HS in 44 patients was observed to be composed of high molecular weight polymer and fragments of various lengths depending on MPS types. On this basis we correlated mental retardation with GlcN belonging to high and low molecular weight HS. We demonstrate a positive relationship between the accumulation of high molecular weight HS and mental retardation in MPS severe compared to attenuated forms. This is also supported by the consideration that accumulation of other GAGs different from HS, as in MPS IV and MPS VI, and low molecular weight HS fragments do not impact on central nervous system disease.

Plasmatic dermatan sulfate and chondroitin sulfate determination in mucopolysaccharidoses

The evaluation of plasmatic galactosaminoglycans, dermatan sulfate (DS) and chondroitin sulfate (CS) can be helpful in the early identification of MPS patients, also considering that primary storage of one type of GAG can lead to secondary accumulation of other lysosomal substrates. We explore the possibility to determine plasmatic DS and CS in numerous healthy pediatric (and sometimes adult) subjects depending on age and in patients affected by various forms of MPS. A highly sensitive HPLC separation and fluorescence detection was applied for plasma/serum DS and CS determination after a specific enzymatic treatment able to release their constituent disaccharides. DS and CS content decrease significantly with age in controls having high values in the first year (~8 μg/mL). A highly significant decrease was observed for 1-5-year-old (∼-33%) and 5-10-year-old (∼-65%) healthy subgroups. No further decrease was determined showing a stabilization after 5 years of age. MPS I Scheie and Hurler patients showed rather similar DS and CS content significantly higher than controls matched for age. Similarly, MPS II, III and IV subjects all presented significantly higher plasmatic DS and CS content compared to healthy subjects matched for age. The same trend was determined for the only patient affected by MPS VI. Plasmatic DS and CS analyzed by the present procedure may be a useful diagnostic and screening marker for various forms of MPS.

Mild mental retardation and low levels of urinary heparan sulfate in a patient with the attenuated phenotype of mucopolysaccharidosis type IIIA

OBJECTIVES

We report the case of a 28-year-old female subject affected by the attenuated phenotype of mucopolysaccharidosis type IIIA characterized by moderate slowly evolving mental retardation in which the urinary content of heparan sulfate was demonstrated as being substantially low compared to that found in patients with the severe phenotype.

DESIGN AND METHODS

The specific evaluation of macromolecular heparan sulfate by electrophoresis and the determination of related glucosamine in the urine were performed.

RESULTS

In our patient, the urinary macromolecular heparan sulfate content (4.2μg/mg creatinine) was ~7.5-times higher than in healthy subjects (0.56μg/mg creatinine±0.9 SD) while it was ~28-times lower compared to the severe mucopolysaccharidosis IIIA group (117μg/mg creatinine±44.8 SD). Furthermore, the urinary glucosamine (86.4μg/mg creatinine) was ~2.4-times greater than in healthy subjects (36.0μg/mg creatinine±18.2 SD) but ~2.4-times lower than in severe subjects (208.1μg/mg creatinine±55.0 SD).

CONCLUSIONS

The above data could reflect the reduced heparan sulfate storage in her tissues and organs, and in particular in the brain, consequently explaining her moderate mental retardation. Furthermore, the clinical presentation of patients with an attenuated form of MPS III confirms the need for a specific evaluation of urinary GAGs in all young and adult subjects showing a not well-defined or not particularly severe mental retardation, along with an early MPS diagnosis. Such investigation should also be associated with a more specific characterization of heparan sulfate.

Diagnosis of the mucopolysaccharidoses

The mucopolysaccharidoses (MPSs) often present a diagnostic challenge, particularly for patients who have more slowly progressive disease phenotypes, as early disease manifestations can be subtle or non-specific. However, certain types of bone and joint involvement should always prompt consideration of an MPS diagnosis, such as early joint involvement without classic inflammatory features or erosive bone lesions, claw hand, spinal deformities or dysostosis multiplex. All such patients should be referred to a geneticist or metabolic specialist for diagnostic evaluation. The earlier the diagnosis is made, the better the potential outcome of treatment. Each type of MPS is associated both with deficient activity of a specific lysosomal enzyme that degrades specific glycosaminoglycans (GAGs) and with abnormalities in urinary GAG excretion. MPS patients usually excrete excess GAG in urine and/or have different relative proportions of types of GAG in urine as compared with age-matched normal subjects. Although urinary GAG analyses (both quantitative and qualitative) can suggest the most likely type of MPS, diagnosis must be confirmed by enzyme assay. Multiple assays may be necessary to identify the disease subtype. Correct identification of the MPS type is essential to guide treatment and management decisions.