The importance of IgG glycosylation-What did we learn after analyzing over 100,000 individuals

IgG N-glycosylation contributes to different severities of insulin resistance: implications for 3P medical approaches

Background

Reliable biomarkers capturing immunometabolic processes in insulin resistance (IR) remain limited. IgG N-glycosylation modulates immune responses and reflects metabolic disorders, yet its role in IR remains unclear. This study investigated its potential for early detection, risk stratification, and targeted prevention within the framework of predictive, preventive, and personalised medicine (PPPM/3PM).

Methods

A total of 313 participants were categorized into three groups based on the homeostatic model assessment for insulin resistance (HOMA-IR): insulin-sensitive (HOMA-IR < 2.69 without diabetes, n = 75), mild IR (HOMA-IR ≥ 2.69 without diabetes, n = 155), and severe IR (HOMA-IR ≥ 2.69 with type 2 diabetes, n = 83). Canonical correlation analysis was conducted to explore the overall relationship between IgG N-glycosylation and IR-related inflammation, indicated by tumour necrosis factor-α, interleukin- 6, C-reactive protein, and adiponectin. Mediation analysis was performed to evaluate the effect of IgG N-glycans on IR. Ordinal logistic regression was used to assess the association between IgG N-glycans and IR severity, with discriminative power evaluated using receiver operating characteristic curves.

Results

Pro-inflammatory IgG N-glycoforms, characterized by reduced sialylation and galactosylation, along with increased bisecting N-acetylglucosamine, were observed as IR severity increased. IgG N-glycosylation significantly correlated with inflammatory markers in the insulin-sensitive (r = 0.599, p < 0.05), mild (r = 0.461, p < 0.05), and severe (r = 0.666, p < 0.01) IR groups. IgG N-glycosylation significantly influenced IR (β = 0.406) partially via modulation of inflammation. Increased glycoforms FA2[6]G1 (OR: 0.86, 95% CI: 0.78-0.96) and A2G2S2 (OR: 0.88, 95% CI: 0.82-0.94) were associated with a lower IR risk, with respective area under the curves (AUCs) of 0.752, 0.683, and 0.764 for the insulin sensitive, mild, and severe IR groups.

Conclusions

IgG N-glycosylation contributes to IR by modulating inflammatory responses. Glycoforms FA2[6]G1 and A2G2S2 emerge as protective biomarkers, offering potential for predicting and preventing IR through primary prevention strategies within the PPPM framework.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-025-00410-x.

High-Throughput Site-Specific N-Glycosylation Profiling of Human Fibrinogen in Atrial Fibrillation

Fibrinogen is a major plasma glycoprotein involved in blood coagulation and inflammatory responses. Alterations in its glycosylation have been implicated in various pathological conditions; yet, its site-specific N-glycosylation profile remains largely unexplored in a clinical context. Here, we present a high-throughput LC-MS workflow for site-specific analysis of fibrinogen N-glycosylation using a cost-effective ethanol precipitation enrichment method. The method demonstrated good intra- and interplate repeatability (CV: 5% and 12%, respectively) and was validated through the first assessment of intraindividual temporal stability in healthy individuals, revealing consistent glycosylation patterns within individuals. Application to 181 atrial fibrillation (AF) patients and 52 healthy controls identified three gamma chain glycoforms significantly associated with AF. Most notably, increased levels of the asialylated N4H5, known to enhance fibrin bundle thickness and promote clot formation, suggest a potential mechanism linking glycosylation changes to the prothrombotic state in AF. Furthermore, fibrinogen sialylation showed strong associations with cardiovascular risk factors, including triglycerides, BMI, and glucose levels. Longitudinal analysis of 108 AF patients six months postcatheter ablation showed stability in the AF-associated glycan profile. Our findings establish fibrinogen glycosylation as a potential biomarker for cardiovascular conditions and demonstrate the utility of site-specific glycosylation analysis for clinical applications.

OS-01 Peptide Topical Formulation Improves Skin Barrier Function and Reduces Systemic Inflammation Markers: A Pilot 12-Week Clinical Trial

OBJECTIVE

As the body's largest organ, the skin plays a crucial role in defending against external stressors. Skin characteristics change with age, decreasing skin barrier integrity and compromising skin and body health. This study aimed to investigate the potential of a topical formulation containing OS-01 (a.k.a. Peptide 14), a senotherapeutic peptide, to counteract age-related skin changes and their systemic consequences.

METHODS

A randomized, double-blinded clinical trial involving 60 female volunteers aged 60-90 was conducted over 12 weeks. Participants received either an OS-01 topical formulation or a commercially available moisturizer control formulation. Skin parameters, subjective perceptions, and circulating cytokine levels were assessed. Skin instrumental analysis included transepidermal water loss (TEWL), skin hydration, and pH measurements.

RESULTS

Participants treated with the OS-01 topical formulation displayed significantly improved skin barrier function and hydration compared to the control group. Participant perceptions aligned with objective findings: after 12 weeks, 70% of participants in the OS-01 group noticed an improvement in general skin appearance versus 42% for the control group. The systemic levels of proinflammatory cytokines tended to normalize, with a significant decrease in IL-8 in the blood analysis of participants from the OS-01 group. On the other hand, the control group demonstrated an increase in a few circulating cytokines, particularly TNF-ɑ and IFN-γ. Moreover, GlycanAge analysis measuring participants' biological age suggested the slowing of systemic aging in the group treated with the OS-01 topical formulation.

CONCLUSION

The study suggests that the OS-01 formulation can impact skin health by improving the skin barrier function, potentially influencing systemic inflammation and biological age. In conclusion, the study supports that targeting skin health may contribute to better longevity outcomes, underscoring the skin's pivotal role in systemic aging and supporting an integrated approach to health management.

Quantitative N-glycoproteomic analysis reveals glycosylation signatures of plasma immunoglobulin G in systemic sclerosis

Systemic sclerosis (SSc) is a perplexing autoimmune disorder, characterized by mysterious causes, high mortality rates, and a lack of effective treatments. The role of abnormal glycosylation in the onset of autoimmune diseases has been recognized for some time. Nonetheless, the intricate details of intact glycopeptides in SSc remain elusive owing to challenges in their detection. In this study, we characterized plasma immunoglobulin G (IgG) intact N-glycopeptides from 30 SSc patients and 30 healthy controls (HCs) via our recently developed intact glycopeptide analysis method GlycoQuant. Through this approach, twelve differentially expressed intact N-glycopeptides were identified. The correlation of specific intact N-glycopeptides with the clinical features of SSc patients was analyzed. The results revealed a notable increase in the levels of 6 intact N-glycopeptides (IgG2-N3H3F1, IgG2-N3H4F1, IgG2-N4H4F1, IgG2-N4H5F1, IgG2-N5H4F1, and IgG2-N5H5F1) and a decrease in the levels of another set of 6 intact N-glycopeptides (IgG1-N4H3F1, IgG2-N3H6F1A1, IgG2-N4H4F1A1, IgG2-N5H3F1, IgG3-N4H3F1, and IgG3-N4H4F1). These changes in the levels of intact N-glycopeptides are associated with various aspects of SSc, including diffuse SSc (dSSc), interstitial lung disease (ILD), disease progression, cardiovascular involvement and C-reactive protein in the peripheral blood. In summary, this study offers a detailed overview of the intact N-glycopeptide profile in the peripheral blood of patients with SSc, providing valuable insights that could propel further research into SSc.

The Glycosylation of Serum IgG Antibodies in Post-COVID-19 and Post-Vaccination Patients

The signature of human serum IgG glycosylation is critical in the defense against pathogens. Alterations of IgG N-glycome were associated with COVID-19 (Coronavirus disease 2019) severity, although knowledge on the response to vaccination is limited. IgG N-glycome was analyzed in this study in post-COVID-19 and post-vaccination patients to reveal potential glycosylation-based alterations using hydrophilic interaction liquid chromatography (HILIC-UPLC) with fluorescence (FLR) and mass-spectrometric (MS) detection. IgG antibodies were purified from serum samples through protein G affinity chromatography followed by PNGase F digestion-based deglycosylation. The released glycans were fluorescently derivatized by procainamide labeling and purified via solid-phase extraction. Higher levels of sialylation and afucosylation were identified in post-COVID-19 patients, which was further expanded by vaccination, but only in those who were previously SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) infected.