A new liquid chromatography/tandem mass spectrometry method for quantification of gangliosides in human plasma

A multiplexed targeted method for profiling of serum gangliosides and glycosphingolipids: application to GM2-gangliosidosis

The analysis of gangliosides and glycosphingolipids is crucial for understanding cellular membrane structure and function as well as to accurately diagnose certain inborn errors of metabolism. GM2-gangliosidosis represents a rare and fatal group of lysosomal storage disorders characterized by accumulation of GM2 gangliosides in various tissues and organs. These disorders arise due to deficiency or functional impairment of the β-hexosaminidase A or B enzymes, which are responsible for degradation of GM2 ganglioside. Deficient enzyme activity primarily leads to the accumulation of GM2 gangliosides within the lysosomes of cells. Accurate and rapid diagnostic methods that detect increased levels of GM2 gangliosides in patients with GM2-gangliosidosis can play a significant role in early diagnosis and appropriate treatment of this condition. To address this need, we developed a multiplexed liquid chromatography-tandem mass spectrometry method targeting 84 species of gangliosides and other glycosphingolipids involved in ganglioside metabolism. Reproducibility, linearity, extraction efficiency, and sample stability were evaluated and proof-of-concept data obtained from analysis of serum samples from confirmed cases of GM2-gangliosidosis. This method has the potential to simultaneously monitor the biosynthesis of gangliosides and the lysosomal catabolic pathway serving as a valuable tool for screening and diagnosing an important group of lysosomal storage disorders.

An Optimized Liquid Chromatography-Mass Spectrometry Method for Ganglioside Analysis in Cell Lines

Gangliosides are glycosphingolipids composed of a sialylated glycan head group and a ceramide backbone. These anionic lipids form lipid rafts and play crucial roles in regulating various proteins involved in signal transduction, adhesion, and cell-cell recognition. Neuroblastoma, a pediatric cancer of the sympathetic nervous system, is treated with intensive chemotherapy, radiation, and an antibody targeting the GD2 ganglioside. Gangliosides are critical in neuroblastoma development and serve as therapeutic targets, making it essential to establish a reliable, rapid, and cost-effective method for profiling gangliosides, particularly one capable of isomeric separation of intact species. In this study, liquid chromatography-mass spectrometry (LC-MS) was optimized using standard gangliosides, followed by the optimization of sphingolipid extraction methods from cell lines by comparing Folch and absolute methanol extraction techniques. Percent recovery and the number of identified sphingolipids were used to evaluate the analytical merits of these methods. A standard gangliosides calibration curve demonstrated excellent linearity (R2 = 0.9961-0.9975). The ZIC-HILIC column provided the best separation of ganglioside GD1 isomers with a 25 min runtime. GD1a elutes before GD1b on the ZIC-HILIC column. Absolute methanol yielded better percent recovery (96 ± 7) and identified 121 different sphingolipids, the highest number between the two extraction methods. The optimized method was applied to profile gangliosides in neuroblastoma (COG-N-683), pancreatic cancer (PSN1), breast cancer (MDA-MB-231BR), and brain tumor (CRL-1620) cell lines. The ganglioside profile of the neuroblastoma cell line COG-N-683 showed an inverse relationship between GD1 and GD2. Ceramide, Hex1Cer, GM1, and GM3 were highly abundant in CRL-1620, PSN1, and MDA-MB-231BR, respectively. These results suggest that our method provides a sensitive, reliable, and high-throughput workflow for ganglioside profiling across different cell types.

Robust quantitation of gangliosides and sulfatides in human brain using UHPLC-MRM-MS: Method development and application in Alzheimer's disease

Gangliosides (GAs) and sulfatides (STs) are acidic glycosphingolipids that are particularly abundant in the nervous system and are closely related to aging and neurodegenerative disorders. To explore their roles in brain diseases, in-depth molecular profiling, including structural variations of sphingoid backbone, fatty acyl group, and sugar chain of GAs and STs was performed. A total of 210 GAs and 38 STs were characterized in the inferior frontal gyrus (IFG) of human brain, with 90 GAs discovered in brain tissues for the first time. Influential MS parameters for detecting GAs and STs in multiple reaction monitoring (MRM) mode were systematically examined and optimized to minimize in-source fragmentation, resulting in remarkable signal intensity enhancement for GAs and STs, especially for polysialylated species. To eliminate analytical variations, isotopic interference-free internal standards were prepared by simple and fast reduction reaction. The final established method facilitated the simultaneous quantitation of 184 GAs and 30 STs from 25 subtypes, which represents the highest number of GAs quantitated among all quantitation methods recorded in literature so far. The method was further validated and applied to reveal the aberrant change of GAs and STs in the IFG of 12 Alzheimer's disease (AD) patients. Four GAs exhibited high classification capacity for AD (AUC ≥0.80) and were thereby considered the most promising signatures for AD. These findings suggested the close correlation between GAs and the pathogenesis of AD, highlighting the achievements of our robust method for investigating the roles of GAs and STs in various physiological states and diseases.

High-throughput quantitation of serological dimethylarginines by LC/MS/MS: Potential cardiovascular biomarkers for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by systemic inflammation of the joints and extra-articular tissues. The incidence of cardiovascular disease (CVD) remains the main cause of morbidity and mortality in patients with RA. Despite the development of new therapeutics targeting the articular manifestations, the relief of the cardiovascular burden is still an unmet medical need during the management of RA. So, the early prognosis of RA-associated CVD plays a crucial role in improving the clinical outcomes of RA patients. Recently, circulating dimethylarginines have gained attention as potential biomarkers for CVDs. Here, we present the development and validation of a high-throughput liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for simultaneous quantification of creatinine, arginine, and dimethylarginines in human serum within 2 mins by isotope dilution mass spectrometry. This method employed a protein precipitation method for rapid sample preparation, trichloroacetic acid (TCA)-based ion pairing chromatography for fast analyte separation, and multiple reaction monitoring (MRM) with stable isotope-labeled internal standards (ISs) for simultaneous quantitation. To assure the quality, our method was validated against the FDA guidelines for lower limit of quantitation (0.2 µM), linearity (square of coefficient correlation>0.99), precision (intra-&inter-assay imprecision < 10 %), accuracy (intra-&inter-assay inaccuracy < 10 %), sample preparation recovery (recovery ≥ 90 %), stability (instability < 10 %), matrix effect (signal suppression < 55 %), and carryover ( < 0.01 %). Afterward, we applied the validated method to a retrospective cross-sectional study. We aimed to evaluate the utility of serological dimethylarginines as potential cardiovascular biomarkers in the development of RA-associated CVD. Our results revealed that the serological ratio of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), an indicator of physiological arginine methylation status, was significantly elevated in patients with RA. This finding might provide value in detecting CVD to improve clinical outcomes in RA management.

Plasma GM2 ganglioside potential biomarker for diagnosis, prognosis and disease monitoring of GM2-Gangliosidosis

GM2-Gangliosidosis are a group of inherited lysosomal storage pathologies characterized by a large accumulation of G_M2 ganglioside in the lysosome. They are caused by mutation in HEXA or HEXB causing reduced or absent activity of a lysosomal β-hexosaminidase A, or mutation in GM2A causing defect in GM2 activator protein (GM2AP), an essential protein for the activity of the enzyme. Biochemical diagnosis relies on the measurement of β-hexosaminidases A and B activities, which is able to detect lysosomal enzyme deficiency but fails to identify defects in GM2AP. We developed a rapid, specific and sensitive liquid chromatography-mass spectrometry-based method to measure simultaneously G_M1, G_M2, G_M3 and G_D3 molecular species. Gangliosides were analysed in plasma from 19 patients with GM2-Gangliosidosis: Tay-Sachs (n = 9), Sandhoff (n = 9) and AB variant of GM2-Gangliosidosis (n = 1) and compared to 20 age-matched controls. Among patients, 12 have a late adult-juvenile-onset and 7 have an infantile early-onset of the disease. Plasma G_M2 molecular species were increased in all GM2-Gangliosidosis patients (19/19), including the patient with GM2A mutation, compared to control individuals and compared to patients with different other lysosomal storage diseases. G_M234:1 and G_M234:1/G_M334:1 ratio discriminated patients from controls with 100% sensitivity and specificity. G_M234:1 and G_M234:1/G_M334:1 were higher in patients with early-onset compared to those with late-onset of the disease, suggesting a relationship with severity. Longitudinal analysis in one adult with Tay-Sachs disease over 9 years showed a positive correlation of G_M234:1 and G_M234:1/G_M334:1 ratio with age at sampling. We propose that plasma G_M2 34:1 and its ratio to G_M3 34:1 could be sensitive and specific biochemical diagnostic biomarkers for GM2-Gangliosidosis including AB variant and could be useful as a first line diagnostic test and potential biomarkers for monitoring upcoming therapeutic efficacy.

Development and validation of capillary electrophoresis method for quantification of gangliosides in brain synaptosomes

Gangliosides are sialic acid containing glycosphingolipids of the plasma membrane with diverse biological functions. They are most abundant in neural tissues where their dysregulation has been suggested to be involved in various pathological conditions. Due to their importance, efficient analytical methods are needed to determine individual gangliosides in biological samples. Here we report a capillary electrophoresis method, optimized and validated for the simultaneous quantification of major neural gangliosides GM1, GD1a, GD1b, GT1b and GQ1b in their underivatized form. The most abundant extraneural monosialogangloside, GM3 can also be separated by this method. Micelles of the highly amphiphilic gangliosides were disrupted with cyclodextrins (CyDs) in the aqueous separation buffer. Among the tested CyDs, the best resolution was observed using 20 mM randomly methylated alpha-CyD in alkaline sodium borate buffer enabling the separation of all studied gangliosides. The method was applied for the quantification of gangliosides in rat cerebral and cerebellar synaptosomes.

Serum Cytokine Profile, Beta-Hexosaminidase A Enzymatic Activity and GM2 Ganglioside Levels in the Plasma of a Tay-Sachs Disease Patient after Cord Blood Cell Transplantation and Curcumin Administration: A Case Report

Tay-Sachs disease (TSD) is a progressive neurodegenerative disorder that occurs due to a deficiency of a β hexosaminidase A (HexA) enzyme, resulting in the accumulation of GM₂ gangliosides. In this work, we analyzed the effect of umbilical cord blood cell transplantation (UCBCT) and curcumin administration on the course of the disease in a patient with adult TSD. The patient’s serum cytokine profile was determined using multiplex analysis. The level of GM₂ gangliosides in plasma was determined using mass spectrometry. The enzymatic activity of HexA in the plasma of the patient was assessed using a fluorescent substrate assay. The HexA α-subunit (HexA) concentration was determined using ELISA. It was shown that both UCBCT and curcumin administration led to a change in the patient’s cytokine profile. The UCBCT resulted in an increase in the concentration of HexA in the patient’s serum and in an improvement in the patient’s neurological status. However, neither UCBCT nor curcumin were able to alter HexA activity and the level of GM₂ in patient’s plasma. The data obtained indicate that UCBCT and curcumin administration can alter the immunity of a patient with TSD, reduce the level of inflammatory cytokines and thereby improve the patient’s condition.

Advances in the separation of gangliosides by counter-current chromatography (CCC)

Gangliosides play critical roles in the development of many progressive diseases. Due to their structural diversity, efficient methods are needed to separate individual gangliosides for studies of their functions, and for use as standards in the analysis of ganglioside mixtures. This proof-of-concept study reports a useful analytical-semi-preparative scale counter-current chromatography (CCC) enrichment of multiple ganglioside homologues of various species and classes at the milligram level. Since few individual ganglioside standards were available, this research aimed to achieve analytical-semi-preparative scale separation of gangliosides by differences in saccharide monomer compositions (classes), their arrangements (species), or ceramide compositions (homologues), using CCC. The solvent system composition, addition of solvent modifiers, and elution modes were all adjusted to separate porcine gangliosides, mainly GM1 (d36:1), GD1a (d36:1), GD1b (d36:1) and their (d38:1) homologues as a demonstration. The eluted compounds were analyzed by flow-injection analysis (FIA)-MS and LC-MS/MS. A two-phase solvent system, consisting of butanol/methyl t-butyl ether/acetonitrile/water at a ratio of 2:4:3:8 (v/v/v/v) with 0.5% (v/v) acetic acid added to the lower phase, was used to separate mg-levels of porcine gangliosides under dual-mode elution. The relative abundances of the above 6 gangliosides increased from 10 to 21% in the ganglioside extract to 55-73% in the collected fractions through the purification.

Isomer separation and analysis of amphiphilic polysialogangliosides using reversed-phase liquid chromatography-mass spectrometry

Gangliosides are amphiphilic, acidic glycosphingolipids possessing one or more sialic acid residues and several isobaric structural isomers with different abundances and bioactivities. Therefore, the distinction between these isomers is crucial for their proper profiling. Although liquid chromatography-mass spectrometry has been successfully employed for this purpose, the distinction process can still be improved, particularly regarding liquid chromatography. Recently, a reversed-phase liquid chromatography method that could separate disialoganglioside isomers was reported; however, the distinction of trisialoganglioside isomers using reversed-phase liquid chromatography has not been demonstrated. Here, we investigated the practicality of a reversed-phase liquid chromatography with an octadecylsilane column for separating polysialoganglioside isomers and successfully achieved the isomer separation of disialogangliosides and trisialogangliosides for the first time. We also confirmed several crucial factors in the mobile-phase composition, which affect the differential retention and mass spectral response of the isomers. First, an organic modifier, acetonitrile, exhibited superior selectivity against polysialogangliosides over methanol. Second, ammonium bicarbonate was the best ammonium salt additive among those tested, in terms of the separation efficiency and mass spectral response. Third, as the ammonium salt concentration increased, the negative electrospray ionization response was extensively suppressed, and the retention of gangliosides increased.

High-throughput quantitation of serological ceramides/dihydroceramides by LC/MS/MS: Pregnancy baseline biomarkers and potential metabolic messengers

Ceramides and dihydroceramides are sphingolipids that present in abundance at the cellular membrane of eukaryotes. Although their metabolic dysregulation has been implicated in many diseases, our knowledge about circulating ceramide changes during the pregnancy remains limited. In this study, we present the development and validation of a high-throughput liquid chromatography-tandem mass spectrometric method for simultaneous quantification of 16 ceramides and 10 dihydroceramides in human serum within 5 min. by using stable isotope-labeled ceramides as internal standards. This method employs a protein precipitation method for high throughput sample preparation, reverse phase isocratic elusion for chromatographic separation, and Multiple Reaction Monitoring for mass spectrometric detection. To qualify for clinical applications, our assay has been validated against the FDA guidelines for Lower Limit of Quantitation (1 nM), linearity (R²>0.99), precision (imprecision<15 %), accuracy (inaccuracy<15 %), extraction recovery (>90 %), stability (>85 %), and carryover (<0.01 %). With enhanced sensitivity and specificity from this method, we have, for the first time, determined the serological levels of ceramides and dihydroceramides to reveal unique temporal gestational patterns. Our approach could have value in providing insights into disorders of pregnancy.

Metabolism of Glycosphingolipids and Their Role in the Pathophysiology of Lysosomal Storage Disorders

Glycosphingolipids (GSLs) are a specialized class of membrane lipids composed of a ceramide backbone and a carbohydrate-rich head group. GSLs populate lipid rafts of the cell membrane of eukaryotic cells, and serve important cellular functions including control of cell-cell signaling, signal transduction and cell recognition. Of the hundreds of unique GSL structures, anionic gangliosides are the most heavily implicated in the pathogenesis of lysosomal storage diseases (LSDs) such as Tay-Sachs and Sandhoff disease. Each LSD is characterized by the accumulation of GSLs in the lysosomes of neurons, which negatively interact with other intracellular molecules to culminate in cell death. In this review, we summarize the biosynthesis and degradation pathways of GSLs, discuss how aberrant GSL metabolism contributes to key features of LSD pathophysiology, draw parallels between LSDs and neurodegenerative proteinopathies such as Alzheimer's and Parkinson's disease and lastly, discuss possible therapies for patients.

Combinatory Data-Independent Acquisition and Parallel Reaction Monitoring Method for Deep Profiling of Gangliosides

Ganglioside is an important class of lipid species involved in intercellular signaling and various diseases, especially for neurodegenerative diseases. Systematic ganglioside profiling is challenging because of their naturally low abundance and highly diverse species. Herein, a new data-independent acquisition and parallel reaction monitoring (DIA/PRM) method with superior sensitivity was developed. The untargeted DIA acquisition consecutively records all the precursor ion and fragment ions at the same time, while the targeted PRM analysis with versatile higher collisional dissociation generates full MS/MS spectra for structure elucidation and verification. As compared with traditional data-dependent acquisition (DDA), the DIA/PRM method unbiasedly detected the majority of abundant ganglioside species and as low as 50 pg of ganglioside in an untargeted manner. Gangliosides in four kinds of biological samples including the mouse brain, mouse plasma, HeLa cell, and human colon cancer tissue were systematically identified, and low-abundance ganglioside species were further extended on the basis of linear chromatography retention rules of the most frequently detected ganglioside species. A total of 383 ganglioside features were defined with 329 of them derived from 32 ganglioside species. Taking advantage of the high-resolution MS analysis, rare ganglioside species were further elucidated according to their characteristic fragment ions and neutral losses. In total, 18 gangliosides with a ceramide carbon number from 20 to 25 and modified gangliosides, including 18 acetylated, 8 diacetylated, 1 phosphorylated, 36 N-glycolyneuraminic acid (NeuGc)-containing, and 7 di-NeuGc-containing gangliosides, were newly identified. The developed DIA/PRM method therefore generated a rich ganglioside resource for further functional exploration and is a unique alternative for DDA analysis for global ganglioside profiling in various biological systems.

Enhanced Susceptibility to Chemoconvulsant-Induced Seizures in Ganglioside GM3 Synthase Knockout Mice

Ganglioside GM3 synthase (α-2,3-sialyltransferase, ST3GAL5, GM3S) is a key enzyme involved in the biosynthesis of gangliosides. ST3GAL5 deficiency causes an absence of GM3 and all downstream biosynthetic derivatives. The affected individuals manifest deafness, severe irritability, intractable seizures, and profound intellectual disability. To investigate whether deficiency of GM3 is involved in seizure susceptibility, we induced seizures with different chemoconvulsants in ST3GAL5 knockout mice. We report here that ST3GAL5 knockout mice are hyperactive and more susceptible to seizures induced by chemoconvulsants, including kainate and pilocarpine, compared with normal controls. In the hippocampal dentate gyrus, loss of GM3 aggravates seizure-induced aberrant neurogenesis. These data indicate that GM3 and gangliosides derived from GM3 may serve as important regulators of epilepsy and may play an important role in aberrant neurogenesis associated with seizures.

Brain endothelial specific gene therapy improves experimental Sandhoff disease

In Tay-Sachs and Sandhoff disease, a deficiency of the lysosomal enzyme β-hexosaminidase causes GM2 and other gangliosides to accumulate in neurons and triggers neurodegeneration. Although the pathology centers on neurons, β-hexosaminidase is mainly expressed outside of neurons, suggesting that gene therapy of these diseases should target non-neuronal cells to reconstitute physiological conditions. Here, we tested in Hexb^-/- mice, a model of Sandhoff disease, to determine whether endothelial expression of the genes for human β-hexosaminidase subunit A and B (HEXA, HEXB) is able to reduce disease symptoms and prolong survival of the affected mice. The brain endothelial selective vectors AAV-BR1-CAG-HEXA and AAV-BR1-CAG-HEXB transduced brain endothelial cells, which subsequently released β-hexosaminidase enzyme. In vivo intravenous administration of the gene vectors to adult and neonatal mice prolonged survival. They improved neurological function and reduced accumulation of the ganglioside GM2 and the glycolipid GA2 as well as astrocytic activation. Overall, the data demonstrate that endothelial cells are a suitable target for intravenous gene therapy of GM2 gangliosidoses and possibly other lysosomal storage disorders.

Exploring In Vivo Dynamics of Bovine Milk Derived Gangliosides

Gangliosides are glycosphingolipids present in mammalian cell membranes, playing important structural and functional roles. Human studies on the health benefits of gangliosides are increasing, but knowledge gaps regarding ganglioside analysis exist. The study aimed to investigate blood sample type (serum/plasma), storage conditions, diurnal, day-to-day variation and acute effects of consuming bovine-derived gangliosides on circulating monosialylated gangliosides. Seventy-one women (18–40 yrs, 20–≤30.0 kg/m²) were enrolled and 61 completed the intervention. They visited the clinic three times following overnight fasting. Serum/plasma gangliosides were analyzed over 2 h (visit-1), 8 h (visit-2) and 8 h following either zero or high ganglioside meals (visit-3). Samples stored at −20 °C and −70 °C were analyzed at 3-, 6-, 12- and 18-months. Plasma and serum GM3-gangliosides did not differ, plasma GM3 did not change diurnally, from day-to-day, in response to a high vs. low ganglioside meal or after 7-days low ganglioside vs. habitual diet (P > 0.05). GM3 concentrations were lower in samples stored at −70 °C vs. −20 °C from 6-months onwards and decreased over time with lowest levels at 12- and 18-months stored at −70 °C. In conclusion, either serum/plasma stored at −20- or −70 °C for up to 6 months, are acceptable for GM3-ganglioside analysis. Blood samples can be collected at any time of the day and participants do not have to be in the fasted state.

Comprehensive Identification of Amadori Compound-Modified Phosphatidylethanolamines in Human Plasma

Amadori compound modified lipids are the result of nonenzymatic glycation and play an important role in several physiological and pathological processes. However, glycation of phosphatidylethanolamine (PE), the most abundant amine-containing lipid in blood plasma, is underexplored and so far only a few glycated PEs have been reported. Herein, we report comprehensive profiling of Amadori-PE and -LysoPE species in human plasma. Using synthetic standards, we first optimized the enrichment procedure for extracting Amadori-PE/LysoPE from plasma. On the basis of the characteristic neutral losses of 303 Da in positive and 162 Da in negative ionization mode, we then applied neural loss scanning-liquid chromatography tandem mass spectrometry (LC-NLS-MS) to identify potentially glycated PE and LysoPE, which was followed by targeted product ion scanning (LC-PIS-MS) to confidently confirm the fatty acyl substitutions of the modified lipids. A total of 20 Amadori-LysoPE and 62 Amadori-PE species, including diacyl, plasmanyl, and plasmenyl, were identified. Among them, the concentrations of 12 Amarodi-LysoPE and 54 Amadori-PE were also quantified in native human plasma, using stable isotope labeled Amadori lipids as internal standards.

Gangliosidome of human anencephaly: A high resolution multistage mass spectrometry study

Widely dispersed throughout the entire body tissues, gangliosides (GGs) are essential components of neuronal cell membranes, where exhibit a vital role in neuronal function and brain development, directly influencing the neural tube formation, neurogenesis, neurotransmission, etc. Due to several factors, partial or complete closing faults of the fetal neural tube may occur in the first trimester of pregnancy, generating a series of neural tube defects (NTD), among which anencephaly. The absence in anencephaly of the forebrain and skull bones determines the exposure to the amniotic fluid of the remaining brain tissue and the spinal cord, causing the degeneration of the nervous system tissue. Based on the previously achieved information related to the direct alteration of neural development with deficient concentration of several GGs, a systematic and comparative mass spectrometry (MS) mapping assay on GGs originating from fetuses in different intrauterine developmental stages, i.e. the 29th (denoted An29), 35th (An35) and the 37th (An37) gestational weeks was here conducted. Our approach, based on Orbitrap MS under high sensitivity, resolution and mass accuracy conditions, enabled for the first time the nanoelectrospray ionization, detection and identification of over 150 glycoforms, mainly novel, polysialylated species. Such a pattern, specific for incipient developmental stages reliably documents the brain development stagnation, characteristic for anencephaly. Further, the fragmentation MS²-MS³ experiments by collision induced dissociation (CID) confirmed the incidence in all three samples of GT2(d18:1/16:2) as a potential biomarker. Therefore, this fingerprinting of the anencephalic gangliosidome may serve in development of approaches for routine screening and early diagnosis.

Oral Ganglioside Supplement Improves Growth and Development in Patients with Ganglioside GM3 Synthase Deficiency

Ganglioside GM3 synthase is a key enzyme involved in the biosynthesis of gangliosides. GM3 synthase deficiency (GM3D) causes an absence of GM3 and all downstream biosynthetic derivatives. The affected individuals manifest with severe irritability, intractable seizures, and profound intellectual disability. The current study is to assess the effects of an oral ganglioside supplement to patients with GM3D, particularly on their growth and development during early childhood. A total of 13 young children, 11 of them under 40 months old, received oral ganglioside supplement through a dairy product enriched in gangliosides, for an average of 34 months. Clinical improvements were observed in most children soon after the supplement was initiated. Significantly improved growth and development were documented in these subjects as average percentiles for weight, height, and occipitofrontal circumference increased in 1-2 months. Three children with initial microcephaly demonstrated significant catch-up head growth and became normocephalic. We also illustrated brief improvements in developmental and cognitive scores, particularly in communication and socialization domains through Vineland-II. However, all improvements seemed transient and gradually phased out after 12 months of supplementation. Gangliosides GM1 and GM3, although measureable in plasma during the study, were not significantly changed with ganglioside supplementation for up to 30 months. We speculate that the downstream metabolism of ganglioside biosynthesis is fairly active and the potential need for gangliosides in the human body is likely substantial. As we search for new effective therapies for GM3D, approaches to reestablish endogenous ganglioside supplies in the affected individuals should be considered.

Contribution of tandem mass spectrometry to the diagnosis of lysosomal storage disorders

Tandem mass spectrometry (MS/MS) is a highly sensitive and specific technique. Thanks to the development of triple quadrupole analyzers, it is becoming more widely used in laboratories working in the field of inborn errors of metabolism. We review here the state of the art of this technique applied to the diagnosis of lysosomal storage disorders (LSDs) and how MS/MS has changed the diagnostic rationale in recent years. This fine technology brings more sensitive, specific, and reliable methods than the previous biochemical ones for the analysis of urinary glycosaminoglycans, oligosaccharides, and sialic acid. In sphingolipidoses, the quantification of urinary sphingolipids (globotriaosylceramide, sulfatides) is possible. The measurement of new plasmatic biomarkers such as oxysterols, bile acids, and lysosphingolipids allows the screening of many sphingolipidoses and related disorders (Niemann-Pick type C), replacing tedious biochemical techniques. Applied to amniotic fluid, a more reliable prenatal diagnosis or screening of LSDs is now available for fetuses presenting with antenatal manifestations. Applied to enzyme measurements, it allows high throughput assays for the screening of large populations, even newborn screening. The advent of this new method can modify the diagnostic rationale behind LSDs.

Isobaric Labeling of Intact Gangliosides toward Multiplexed LC-MS/MS-Based Quantitative Analysis

Gangliosides are sialic acid-containing glycosphingolipids recognized to play essential role in biological processes. Both the glycan and lipid structures influence their biological function and thus necessitate their determination as intact molecular species. To our knowledge, no multiplexed method for intact gangliosides currently exists. In this paper, we aimed to demonstrate an approach for isobaric labeling of intact gangliosides. Specifically, we carried out the rapid, chemoselective oxidation of sialic acid side chain in common ganglioside core structures using NaIO₄ followed by ligation with a carbonyl-reactive isobaric tandem mass tag (TMT) reagent and subsequent RPLC-MS/MS analysis. Attachment of the isobaric label was observed to improve the ionization efficiency of complex gangliosides using electrospray ionization. Fragmentation of the resulting [M + 2H]²⁺ ions of TMT-labeled gangliosides provided information-rich spectra containing fragments from the glycan, lipid, and TMT reporter ions. This facile approach enabled simultaneous quantification of up to six samples as well as identification of glycan and lipid compositions in a single injection. As a proof-of-concept, using porcine brain total ganglioside extracts pooled at known ratios, we obtained overall sample-to-sample precision of <12% RSD and mean error of <10%. This showcased the great promise and feasibility of this strategy for high-throughput analysis of intact gangliosides in biological extracts.

Gangliosides: Structures, Biosynthesis, Analysis, and Roles in Cancer

Gangliosides are acidic glycosphingolipids containing one or more sialic acid residues. They are essential compounds at the outer leaflet of the plasma membrane, where they interact with phospholipids, cholesterol, and transmembrane proteins, forming lipid rafts. They are involved in cell adhesion, proliferation, and recognition processes, as well as in the modulation of signal transduction pathways. These functions are mainly governed by the glycan moiety, and changes in the structures of gangliosides occur under pathological conditions, particularly in neuro-ectoderm-derived cancers. With the progress in mass spectrometry analysis of gangliosides, their role in cancer progression can be now investigated in more detail. In this review we summarize the current knowledge on the biosynthesis of gangliosides and their role in cancers, together with the recent development of cancer immunotherapy targeting gangliosides.

Tandem Mass Spectrometry of Sphingolipids: Applications for Diagnosis of Sphingolipidoses

In recent years, mass spectrometry (MS) has become the dominant technology in lipidomic analysis. It is widely used in diagnosis and research of lipid metabolism disorders including those characterized by impairment of lysosomal functions and storage of nondegraded-degraded substrates. These rare diseases, which include sphingolipidoses, have severe and often fatal clinical consequences. Modern MS methods have contributed significantly to achieve a definitive diagnosis, which is essential in clinical practice to begin properly targeted patient care. Here we summarize MS and tandem MS methods used for qualitative and quantitative analysis of sphingolipids (SL) relative to the diagnostic process for sphingolipidoses and studies focusing on alterations in cell functions due to these disorders. This review covers the following topics: Tandem MS is sensitive and robust in determining the composition of sphingolipid classes in various biological materials. Its ability to establish SL metabolomic profiles using MS bench-top analyzers, significantly benefits the first stages of a diagnosis as well as metabolic studies of these disorders. It can thus contribute to a better understanding of the biological significance of SL.

Ganglioside Composition in Beef, Chicken, Pork, and Fish Determined Using Liquid Chromatography-High-Resolution Mass Spectrometry

Gangliosides (GA) are found in animal tissues and fluids, such as blood and milk. These sialo-glycosphingolipids have bioactivities in neural development, the gastrointestinal tract, and the immune system. In this study, a high-performance liquid chromatography-mass spectrometry (HPLC-MS) method was validated to characterize and quantitate the GA in beef, chicken, pork, and fish species (turbot, snapper, king salmon, and island mackerel). For the first time, we report the concentration of GM3, the dominant GA in these foods, as ranging from 0.35 to 1.1 mg/100 g and 0.70 to 5.86 mg/100 g of meat and fish, respectively. The minor GAs measured were GD3, GD1a, GD1b, and GT1b. Molecular species distribution revealed that the GA contained long- to very-long-chain acyl fatty acids attached to the ceramide moiety. Fish GA contained only N-acetylneuraminic acid (NeuAc) sialic acid, while beef, chicken, and pork contained GD1a/b species that incorporated both NeuAc and N-glycolylneuraminic acid (NeuGc) and hydroxylated fatty acids.

GM3 synthase deficiency due to ST3GAL5 variants in two Korean female siblings: Masquerading as Rett syndrome-like phenotype

There have been a few reports of GM3 synthase deficiency since the disease of the ganglioside biosynthetic pathway was first reported in 2004. It is characterized by infantile-onset epilepsy with severe intellectual disability, blindness, cutaneous dyspigmentation, and choreoathetosis. Here we report the cases of two Korean female siblings with ST3GAL5 variants, who presented with a Rett-like phenotype. They had delayed speech, hand stereotypies with a loss of purposeful hand movements, and choreoathetosis, but no clinical seizures. One of them had microcephaly, while the other had small head circumference less than 10th centile. There were no abnormal laboratory findings with the exception of a high lactate level. MECP2/CDKL5/FOXG1 genetic tests with an array comparative genomic hybridization revealed no molecular defects. Through whole-exome sequencing of the proband, we found compound heterozygous ST3GAL5 variants (p.Gly201Arg and p.Cys195Ser), both of which were novel. The siblings were the same compound heterozygotes and their unaffected parents were heterozygous carriers of each variant. Liquid chromatography-mass spectrometry analysis confirmed a low level of GM3 and its downstream metabolites, indicating GM3 synthase deficiency. These cases expanded the clinical and genetic spectrum of the ultra-rare disease, GM3 synthase deficiency with ST3GAL5 variants. © 2016 Wiley Periodicals, Inc.

Comprehensive Profiling of Glycosphingolipid Glycans Using a Novel Broad Specificity Endoglycoceramidase in a High-Throughput Workflow

The biological function of glycosphingolipids (GSLs) is largely determined by their glycan headgroup moiety. This has placed a renewed emphasis on detailed GSL headgroup structural analysis. Comprehensive profiling of GSL headgroups in biological samples requires the use of endoglycoceramidases with broad substrate specificity and a robust workflow that enables their high-throughput analysis. We present here the first high-throughput glyco-analytical platform for GSL headgroup profiling. The workflow features enzymatic release of GSL glycans with a novel broad-specificity endoglycoceramidase I (EGCase I) from Rhodococcus triatomea, selective glycan capture on hydrazide beads on a robotics platform, 2AB-fluorescent glycan labeling, and analysis by UPLC-HILIC-FLD. R. triatomea EGCase I displayed a wider specificity than known EGCases and was able to efficiently hydrolyze gangliosides, globosides, (n)Lc-type GSLs, and cerebrosides. Our workflow was validated on purified GSL standard lipids and was applied to the characterization of GSLs extracted from several mammalian cell lines and human serum. This study should facilitate the analytical workflow in functional glycomics studies and biomarker discovery.

In situ detection of GM1 and GM2 gangliosides using immunohistochemical and immunofluorescent techniques for auxiliary diagnosis of canine and feline gangliosidoses

Background

GM1 and GM2 gangliosidoses are progressive neurodegenerative lysosomal storage diseases resulting from the excessive accumulation of GM1 and GM2 gangliosides in the lysosomes, respectively. The diagnosis of gangliosidosis is carried out based on comprehensive findings using various types of specimens for histological, ultrastructural, biochemical and genetic analyses. Therefore, the partial absence or lack of specimens might have resulted in many undiagnosed cases. The aim of the present study was to establish immunohistochemical and immunofluorescent techniques for the auxiliary diagnosis of canine and feline gangliosidoses, using paraffin-embedded brain specimens stored for a long period.

Results

Using hematoxylin and eosin staining, cytoplasmic accumulation of pale to eosinophilic granular materials in swollen neurons was observed in animals previously diagnosed with GM1 or GM2 gangliosidosis. The immunohistochemical and immunofluorescent techniques developed in this study clearly demonstrated the accumulated material to be either GM1 or GM2 ganglioside.

Conclusions

Immunohistochemical and immunofluorescent techniques using stored paraffin-embedded brain specimens are useful for the retrospective diagnosis of GM1 and GM2 gangliosidoses in dogs and cats.

Quantitative GSL-glycome analysis of human whole serum based on an EGCase digestion and glycoblotting method

Glycosphingolipids (GSLs) are lipid molecules linked to carbohydrate units that form the plasma membrane lipid raft, which is clustered with sphingolipids, sterols, and specific proteins, and thereby contributes to membrane physical properties and specific recognition sites for various biological events. These bioactive GSL molecules consequently affect the pathophysiology and pathogenesis of various diseases. Thus, altered expression of GSLs in various diseases may be of importance for disease-related biomarker discovery. However, analysis of GSLs in blood is particularly challenging because GSLs are present at extremely low concentrations in serum/plasma. In this study, we established absolute GSL-glycan analysis of human serum based on endoglycoceramidase digestion and glycoblotting purification. We established two sample preparation protocols, one with and the other without GSL extraction using chloroform/methanol. Similar amounts of GSL-glycans were recovered with the two protocols. Both protocols permitted absolute quantitation of GSL-glycans using as little as 20 μl of serum. Using 10 healthy human serum samples, up to 42 signals corresponding to GSL-glycan compositions could be quantitatively detected, and the total serum GSL-glycan concentration was calculated to be 12.1-21.4 μM. We further applied this method to TLC-prefractionated serum samples. These findings will assist the discovery of disease-related biomarkers by serum GSL-glycomics.

Liquid chromatography mass spectrometry-based O-glycomics to evaluate glycosylation alterations in gastric cancer

PURPOSE

Gastric cancer is the fourth most common malignant cancer worldwide. Important for tumorigenesis and progression, aberrant glycosylation occurs frequently in cancers. We investigated the differences in O-glycosylation in the serum of 157 gastric cancer patients (GC) and 144 healthy donors.

EXPERIMENTAL DESIGN

We used the method of labeling O-glycans (released from proteins) with 1-phenyl-3-methyl-5-pyrazolone followed by LC-MS analysis. Analyzing the LC-MS data by partial least squares discriminant and unpaired Student t test, combined with the structural information of O-glycans from LC-MS/MS in positive mode.

RESULTS

The expression level of core1, core2, ST antigen, and core2 complex O-glycans (m/z 733.33, m/z 809.42) were increased significantly (p < 0.0001), whereas m/z 529.75 and diST-antigen were decreased in the serum of GC compared with controls (p < 0.001). In addition, there were significant correlations between the abundance of the O-glycans and glycoproteins (MUC1, CEA) in the serum of GC.

CONCLUSION AND CLINICAL RELEVANCE

Glycomics approaches identified multiple candidate antigens for patients with GC. The O-glycan structures are increased in the serum of GC, they may be candidates for carbohydrate tumor markers.

Apprehending ganglioside diversity: a comprehensive methodological approach

Gangliosides (GGs) make a wide family of glycosphingolipids ubiquitously expressed in mammalian tissues and particularly abundant in the brain and nervous system. They exhibit a huge diversity due to structural variations in both their oligosaccharidic chain and ceramide moiety, which represent a real analytical challenge. Since their discovery in the 1940s, methods have persistently improved until the emergence of LC/MS, which offers a high level of specificity and sensitivity and is suitable with high-throughput profiling studies. We describe here a comprehensive approach relying on various techniques and aiming at fully characterizing GGs in biological samples. First, total GG content was determined by a biochemical assay. Second, GG class composition was assessed by high-performance thin-layer chromatography followed by colorimetric revelation. Then, ceramide types of GG classes were identified, and their relative quantification was performed thanks to the development of a powerful and reliable LC/MS method. Finally, ceramides were structurally characterized, and minor and less common GG classes were identified using high-resolution MS. These methods were applied to the rat retina to provide an exhaustive description of its GG composition, giving the base for a better understanding of the precise roles of GGs in this tissue.

Disialoganglioside GD2 as a therapeutic target for human diseases

INTRODUCTION

Ganglioside GD2 is found in vertebrates and invertebrates, overexpressed among pediatric and adult solid tumors, including neuroblastoma, glioma, retinoblastoma, Ewing's family of tumors, rhabdomyosarcoma, osteosarcoma, leiomyosarcoma, liposarcoma, fibrosarcoma, small cell lung cancer and melanoma. It is also found on stem cells, neurons, some nerve fibers and basal layer of the skin.

AREAS COVERED

GD2 provides a promising clinical target for radiolabeled antibodies, bispecific antibodies, chimeric antigen receptor (CAR)-modified T cells, drug conjugates, nanoparticles and vaccines. Here, we review its biochemistry, normal physiology, role in tumorigenesis, important characteristics as a target, as well as anti-GD2-targeted strategies.

EXPERT OPINION

Bridging the knowledge gaps in understanding the interactions of GD2 with signaling molecules within the glycosynapses, and the regulation of its cellular expression should improve therapeutic strategies targeting this ganglioside. In addition to anti-GD2 IgG mAbs, their drug conjugates, radiolabeled forms especially when genetically engineered to improve therapeutic index and novel bispecific forms or CARs to retarget T-cells are promising candidates for treating metastatic cancers.