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Mass spectrometric approach for screening modifications of total serum N-glycome in human diseases: application to cirrhosis.

Congenital and acquired modifications of glycosylation in diseases are a rapidly growing field that demonstrates the importance of glycosylation in human biology. Unfortunately, in clinical biochemistry, very few tests are available to explore oligosaccharide metabolism on a large scale. Such an assay needs to be of high throughput, rapid, and preferentially noninvasive. In the present study, we describe a method to analyze qualitative variations of N-glycosylation of human serum proteins. The method is based on direct release of N-linked oligosaccharides from patient serum samples, a single-step purification, and a matrix-assisted laser desorption ionization time of flight mass spectrometric analysis. A complementary structural study of the released oligosaccharides was achieved by enzymatic digestions, linkage analysis, and electrospray ionization ion trap mass spectrometry (ESI-IT-MS) of the permethylated N-glycome. A total of 26 oligosaccharide structures were individualized, their presence in human serum being the result of the combination of the biosynthesis and catabolic pathways. Application of the protocol to the serum of patients with cirrhosis demonstrates the ability of this assay to identify acquired modifications of glycosylation. Furthermore, we have analyzed the N-glycans and showed the increase in bisecting N-acetylglucosamine residue, core fucosylation, and the presence of an important population of neutral oligosaccharides. The study of total serum N-glycome modifications is a preliminary for the discovery of new noninvasive diagnostic or prognostic biomarkers resulting from the variations of the N-glycan metabolism during diseases.

Biomarkers↗

Serum N-glycomics for non-invasive detection of significant liver pathology across clinical phases of treatment-naïve chronic hepatitis B.

BACKGROUND: Early identification of significant liver pathology is crucial for timely antiviral intervention in individuals with chronic hepatitis B (CHB) infection. Current non-invasive methods show limited accuracy in detecting occult liver damage, particularly in those with normal ALT. This study evaluated serum N-glycan profiles for diagnosing significant liver pathology in treatment-na&#xef;ve CHB patients across clinical phases. METHODS: This cross-sectional study analyzed 626 treatment-na&#xef;ve CHB patients confirmed by liver biopsy, classified according to 2025 EASL guidelines. Serum N-glycan profiles were determined using DNA sequencer-assisted fluorophore-assisted carbohydrate electrophoresis. Significant liver pathology was defined as inflammation grade&#x2009;&#x2265;&#x2009;G2 and/or fibrosis stage&#x2009;&#x2265;&#x2009;S2 (per Scheuer scoring system). Multivariate logistic regression models were developed and compared with traditional non-invasive markers. RESULTS: Among 626 CHB patients, 66.0% had significant inflammation and 58.9% had significant fibrosis. Patients with significant pathology showed characteristic alterations, with elevated P1, P3, P6, P7, P11 peaks and decreased P0, P5, P8, P10 peaks (all p&#x2009;<&#x2009;0.0001). Compared to respective infection phases, hepatitis phases showed P1 increases of 19.6% and 36% in HBeAg(+) and HBeAg(-) patients, with P11 increases of 82.4% and 73.4%, while P0 decreased by 20.3% and 27.6%, and P10 by 21.6% and 20.3%. Relative to mild pathology (G and S&#x2009;<&#x2009;2), P1 increased by 27% in significant pathology (G and/or S&#x2009;&#x2265;&#x2009;2), reaching 58.7%/48.7% in G4/S4 stages (vs. G0/S0). In ALT-normal HBeAg(+) infection phase, P1 increased by 80.2%/65.8% in G4/S4 stages (vs. G0/S0), with P2 also increasing by 54.1%/45.2%. Multivariate analysis identified P11 as strongest risk factor (OR&#x2009;=&#x2009;3.84, 95%CI: 1.74-8.45, p&#x2009;=&#x2009;0.0008), followed by P1 (OR&#x2009;=&#x2009;2.04, 95%CI: 1.57-2.64, p&#x2009;<&#x2009;0.0001) and P7 (OR&#x2009;=&#x2009;1.75, 95%CI: 1.31-2.34, p&#x2009;=&#x2009;0.0002), while P2 (OR&#x2009;=&#x2009;0.07, 95%CI: 0.02-0.26, p&#x2009;<&#x2009;0.0001) and P0 (OR&#x2009;=&#x2009;0.30, 95%CI: 0.12-0.79, p&#x2009;=&#x2009;0.0140) served as protective factors. The glycomics combined model (AUC&#x2009;=&#x2009;0.876 (0.844-0.908)) achieved superior performance and outperformed the clinical model (AUC&#x2009;=&#x2009;0.818 (0.779-0.857)), LSM (AUC&#x2009;=&#x2009;0.817 (0.775-0.858)), APRI (AUC&#x2009;=&#x2009;0.830 (0.792-0.867)), and FIB-4 (AUC&#x2009;=&#x2009;0.672 (0.621-0.723)) (all p&#x2009;<&#x2009;0.001), with 78.7% sensitivity and 83.2% specificity. The optimized model reached AUC&#x2009;=&#x2009;0.917 (0.891-0.942) with accuracy 84.2%, with 78.7% sensitivity and 94.6% specificity. Both glycomics-based models maintained diagnostic capability in ALT-normal patients particularly in HBeAg(+) infection. CONCLUSIONS: Serum N-glycomics demonstrates promising potential for non-invasive identification of significant liver pathology in treatment-na&#xef;ve CHB patients, providing an alternative approach for early treatment decisions, especially in ALT-normal patients with occult liver damage.

Humans↗

Total serum protein N-glycome profiling on a capillary electrophoresis-microfluidics platform.

We implemented 8-aminopyrene-1,3,6-trisulfonic acid (APTS)-labeled asparagine-linked glycan (N-glycan) profiling on a microfluidic electrophoresis platform. Using 11.5 cm effective length etched channels and 4% linear polyacrylamide as the separation matrix, the major N-glycans in human serum were profiled in 12 min with a resolution comparable to what is achieved for these analytes on gel-based DNA sequencers. This demonstration suggests a practical clinical application for high-speed compact analyzers which might be uniquely based on microfluidic devices.

Electrophoresis, Capillary↗

Strategy for Simultaneous Multiomic Survey of N-Glycomic and Extracellular Matrix Proteome by Mass Spectrometry Imaging.

Recent advances in spatially resolved molecular profiling have positioned matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) as a powerful platform for multiomic tissue analyses. However, conventional workflows that sequentially target distinct molecular classes are time- and resource-intensive, requiring repeated sequential sample preparation, imaging, and data integration. Here, we evaluate streamlined strategies for simultaneous or combined acquisition of N-glycan and collagen-derived peptide information using PNGase F and collagenase. In-solution studies demonstrate that simultaneous enzymatic digestion yields comparable peptide identifications and glycan profiles relative to traditional sequential workflows, with minimal impact on enzymatic specificity. On the basis of these findings, we developed and optimized MALDI-MSI protocols enabling either simultaneous enzyme application or sequential enzyme treatment with unified matrix deposition and single-pass imaging. While direct coapplication reduced image uniformity, a hybrid approach that used sequential enzyme deposition with combined imaging preserved spatial fidelity and spectral quality while significantly reducing processing and computational demands. Application to human tissues, including vertebral bone and ocular samples, highlights the utility of this workflow for fragile specimens and exploratory multiomic surveys. Collectively, these results establish a framework for integrated glycomic and proteomic imaging targeting the extracellular microenvironment, expanding multiomic MALDI-MSI analyses.

Spectrometry, Mass, Matrix-Assisted Laser Desorpti↗

Dysregulation of the serum and IgG N-glycome in decompensated cirrhosis and its association with Model for End-Stage Liver Disease-Sodium (MELD-Na).

BACKGROUND AND AIMS: N-glycans modulate glycoprotein structure and function and are altered during chronic inflammation. We sought to define the extent of serum and IgG N-glycan disruption in patients with decompensated liver cirrhosis from alcohol-related liver disease (ALD), primary sclerosing cholangitis (PSC), and ALD-related hepatocellular carcinoma (HCC). Finally, we aimed to examine whether serum and IgG glycosylation is associated with changes in Model for End-stage Liver Disease-Sodium (MELD-Na) scores, a clinical marker used to prioritise liver transplantation. METHODS: Serum samples were obtained from patients with ALD (n&#x2009;=&#x2009;17), PSC (n&#x2009;=&#x2009;7), ALD-related HCC (n&#x2009;=&#x2009;4), and healthy controls (n&#x2009;=&#x2009;10). N-glycans were released, fluorescently labelled, and profiled by hydrophilic interaction ultra performance liquid chromatography (HILIC-UPLC). Chromatograms were integrated into 46 and 23 glycan peaks for serum and IgG respectively. These peaks and their associated glycosylation traits were statistically compared with healthy controls using age- and sex-adjusted linear regression models. RESULTS: In serum, decompensated cirrhosis shows statistically significant shifts toward less complex, agalactosylated and asialylated biantennary glycans, accompanied by significant losses of highly branched, galactosylated and sialylated structures. IgG mirrored this pattern, which is characteristic of a pro-inflammatory signature, with increased agalactosylation and bisected glycan levels, along with reduced levels of digalactosylated and sialylated species. N-glycan profiles showed significant associations with MELD-Na scores, indicating that inflammatory processes in decompensated liver cirrhosis continue to reshape serum glycoproteins. CONCLUSION: Decompensated liver cirrhosis shows profound remodelling of serum and IgG N-glycans. These data establish a reference framework for terminal glycomic disruption in liver disease and highlight the potential value of incorporating glycosylation analysis into broader assessments of liver disease progression.

Humans↗

Genetic Association of the Transcriptome and Immunoglobulin G N-glycome with Cognitive Function.

OBJECTIVE: Immunoglobulin G (IgG) N-glycosylation is associated with mild cognitive impairment through the regulation of inflammatory balance; however, the underlying mechanisms remain unclear. METHODS: Our study utilized a post-genome-wide association studies (GWAS) method that integrated GWAS data for cognitive function with gene expression quantitative trait loci (eQTL), protein QTL (pQTL), and IgG N-glycan-QTL data. RESULTS: Mendelian randomization (MR) analyses suggested bidirectional causalities between glycan peaks (GPs) and cognitive function, with GP7, GP12, and GP19 showing a causal effect on cognitive function, while cognitive function conversely showed a causal effect on GP1 and GP8. Two proteins and 10 genes were implicated in the regulation of IgG N-glycosylation. Furthermore, multivariable MR results suggested complex causalities between genes/proteins and IgG N-glycans, which jointly promote or independently affect cognitive function. CONCLUSION: Our study reveals a novel mechanism by which genes, proteins, and modified IgG N-glycans converge to pathologically affect cognitive function.

Immunoglobulin G↗

Increased fucosylation and reduced branching of serum glycoprotein N-glycans in all known subtypes of congenital disorder of glycosylation I.

The N-glycans present on the total mixture of serum glycoproteins (serum N-glycome) were analyzed in 24 subjects with congenital disorder of glycosylation type I (CDG-I) and 7 healthy, age-matched individuals. No new N-glycan structures were observed in the sera of CDG-I patients as compared with normal sera. However, we observed in all subtypes a significantly increased degree of core alpha-1,6-fucosylation of the biantennary glycans as compared to normal, as well as a significant decrease in the amount of triantennary glycans. These serum N-glycome changes appear to be a milder manifestation of some of the changes observed in adult liver cirrhosis patients, which is compatible with the reported steatosis and fibrosis in CDG-I patients. In the CDG-Ia subgroup, the extent of the serum N-glycome changes correlates with the aberration of the serum transferrin isoelectric focusing pattern, which measures the severity of the lack of entire N-glycan chains (primary consequence of CDG-I) in the liver and is the standard diagnostic test for this category of inherited diseases.

Adult↗

Rapid glycomic analysis of serum EVs reveals altered N-glycosylation patterns in ASD.

Objective laboratory diagnostics for autism spectrum disorder (ASD) are lacking, necessitating rapid clinical screening tools. Because serum extracellular vesicle (EV) N-glycosylation captures critical neurodevelopmental signatures, we developed a fast, biologically interpretable diagnostic strategy. EVs from ASD patients with language impairment and neurotypical controls were isolated using a rapid extra-polyethylene glycol precipitation/filtration (EPF) workflow, benchmarked against ultracentrifugation. Following MALDI-TOF/MS profiling, machine learning was re-evaluated using repeated nested cross-validation to reduce optimistic bias and potential information leakage. Among five classifiers, Random Forest (RF) showed the best overall balance across discrimination, calibration, and classification metrics. RF-based SHAP analysis provided transparent interpretation, highlighting key discriminative glycans, including H4N3S1F1, H5N5S1F1, and H3N5F1. To elucidate molecular mechanisms, we integrated public EV transcriptomic data. This revealed significant dysregulation of N-glycosylation machinery genes (e.g., MAN1A1, NEU1, OSTC, RPN2), whose expression directionally aligned with observed glycan shifts in synaptic pathways. Collectively, this rapid serum EV N-glycomic workflow, combined with leakage-controlled RF-based interpretation, provides a promising foundation for non-invasive ASD biomarker discovery and future multicenter validation.

Humans↗

The fine structure of Caenorhabditis elegans N-glycans.

We report the fine structure of a nearly contiguous series of N-glycans from the soil nematode Caenorhabditis elegans. Five major classes are revealed including high mannose, mammalian-type complex, hybrid, fuco-pausimannosidic (five mannose residues or fewer substituted with fucose), and phosphocholine oligosaccharides. The high mannose, complex, and hybrid N-glycan series show a high degree of conservation with the mammalian biosynthetic pathways. The fuco-pausimannosidic glycans contain a novel terminal fucose substitution of mannose. The phosphocholine oligosaccharides are high mannose type and are multiply substituted with phosphocholine. Although phosphocholine oligosaccharides are known immunomodulators in human nematode and trematode infections, C. elegans is unique as a non-parasitic nematode containing phosphocholine N-glycans. Therefore, studies in C. elegans should aid in the elucidation of the biosynthetic pathway(s) of this class of biomedically relevant compounds. Results presented here show that C. elegans has a functional orthologue for nearly every known enzyme found to be deficient in congenital disorders of glycosylation types I and II. This nematode is well characterized genetically and developmentally. Therefore, elucidation of its N-glycome, as shown in this report, may place it among the useful systems used to investigate human disorders of glycoconjugate synthesis such as the congenital disorders of glycosylation syndromes.

Animals↗