Biomarkers currently available for the diagnosis, prognosis, and therapeutic monitoring of GM1 gangliosidosis type 2 (GM1T2) disease are mainly limited to those discovered in targeted proteomic-based studies. In order to identify and establish new, predominantly low-molecular-mass biomarkers for this disorder, we employed an untargeted, multi-analyte approach involving high-resolution 1H NMR analysis coupled to a range of multivariate analysis and computational intelligence technique (CIT) strategies to explore biomolecular distinctions between blood plasma samples collected from GM1T2 and healthy control (HC) participants (n = 10 and 28, respectively). The relationship of these differences to metabolic mechanisms underlying the pathogenesis of GM1T2 disorder was also investigated. 1H NMR-linked metabolomics analyses revealed significant GM1T2-mediated dysregulations in ≥13 blood plasma metabolites (corrected p < 0.04), and these included significant upregulations in 7 amino acids, and downregulations in lipoprotein-associated triacylglycerols and alanine. Indeed, results acquired demonstrated a profound distinctiveness between the GM1T2 and HC profiles. Additionally, employment of a genome-scale network model of human metabolism provided evidence that perturbations to propanoate, ethanol, amino-sugar, aspartate, seleno-amino acid, glutathione and alanine metabolism, fatty acid biosynthesis, and most especially branched-chain amino acid degradation (p = 10-12-10-5) were the most important topologically-highlighted dysregulated pathways contributing towards GM1T2 disease pathology. Quantitative metabolite set enrichment analysis revealed that pathological locations associated with these dysfunctions were in the order fibroblasts > Golgi apparatus > mitochondria > spleen ≈ skeletal muscle ≈ muscle in general. In conclusion, results acquired demonstrated marked metabolic imbalances and alterations to energy demand, which are consistent with GM1T2 disease pathogenesis mechanisms.

In GM1 gangliosidosis the lack of function of β-galactosidase results in an accumulation of GM1 ganglioside and related glycoconjugates in visceral organs, and particularly in the central nervous system, leading to severe disability and premature death. In the type 2 form of the disease, early intervention would be important to avoid precocious complications. To date, there are no effective therapeutic options in preventing progressive neurological deterioration. Substrate reduction therapy with Miglustat, a N-alkylated sugar that inhibits the enzyme glucosylceramide synthase, has been proposed for the treatment of several lysosomal storage disorders such as Gaucher type 1 and Niemann Pick Type C diseases. However, data on Miglustat therapy in patients with GM1 gangliosidosis are still scarce. We report here the results of Miglustat administration in four Italian children (average age: 55 months, range 20-125) affected by GM1 gangliosidosis type 2 treated in three different Italian pediatric hospitals specialized in metabolic diseases. This treatment was safe and relatively well tolerated by all patients, with stabilization and/or slowing down of the neurological progression in three subjects.

GM1 gangliosidosis is a lysosomal storage disorder caused by mutations in GLB1 encoding a lysosomal β-galactosidase. This disease is a continuum from the severe infantile form with rapid neurological decline to the chronic adult form, which is not life-limiting. The intermediate or type 2 form can be further classified into late infantile and juvenile forms. The frequency and severity of skeletal outcomes in late infantile and juvenile patients have not been characterized. Our goals are to describe the radiological skeletal abnormalities, bone mineral density (BMD), and frequency of fractures in patients with intermediate GM1 gangliosidosis. We evaluated 13 late infantile and 21 juvenile patients as part of an ongoing natural history study. Average time from onset of symptoms to diagnosis was 1.9 and 6.3 years for late infantile and juvenile patients, respectively. All late infantile patients had odontoid hypoplasia and pear-shaped vertebral bodies, the frequency of which was significantly different than in patients with juvenile disease (none and 14%, respectively). Juvenile patients had irregular endplates of the vertebral bodies (15/21), central indentation of endplates (10/21), and squared and flat vertebral bodies (10/21); all allowed radiographic differentiation from late infantile patients. Lumbar spine, femoral neck, and total hip BMD were significantly decreased (-2.1, -2.2, and -1.8 Z-scores respectively). Lumbar spine BMD peaked at 19 years, while distal forearm BMD peaked at 30 years. Despite low BMD, no patients exhibited fractures. We have demonstrated that all late infantile patients have some degree of odontoid hypoplasia suggesting the need for cervical spine evaluation particularly prior to anesthesia, whereas juvenile patients had variable skeletal involvement often affecting activities of daily living. Type 2 GM1 gangliosidosis patients have skeletal abnormalities that are both an early indication of their diagnosis, and require monitoring and management to ensure the highest possible quality of life.