LC-MS/MS Isomeric Profiling of N-Glycans Derived from Low-Abundant Serum Glycoproteins in Mild Cognitive Impairment Patients

Abstract

Mild cognitive impairment (MCI) is an early stage of memory loss that affects cognitive abilities, such as language or virtual/spatial comprehension. This cognitive decline is mostly observed with the aging of individuals. Recently, MCI has been considered as a prodromal phase of Alzheimer’s disease (AD), with a 10–15% conversion rate. However, the existing diagnostic methods fail to provide precise and well-timed diagnoses, and the pathophysiology of MCI is not fully understood. Alterations of serum N-glycan expression could represent essential contributors to the overall pathophysiology of neurodegenerative diseases and be used as a potential marker to assess MCI diagnosis using non-invasive procedures. Herein, we undertook an LC-MS/MS glycomics approach to determine and characterize potential N-glycan markers in depleted blood serum samples from MCI patients. For the first time, we profiled the isomeric glycome of the low abundant serum glycoproteins extracted from serum samples of control and MCI patients using an LC-MS/MS analytical strategy. Additionally, the MRM validation of the identified data showed five isomeric N-glycans with the ability to discriminate between healthy and MCI patients: the sialylated N-glycans GlcNAc5,Hex6,Neu5Ac3 and GlcNAc6,Hex7,Neu5Ac4 with single AUCs of 0.92 and 0.87, respectively, and a combined AUC of 0.96; and the sialylated-fucosylated N-glycans GlcNAc4,Hex5,Fuc,Neu5Ac, GlcNAc5,Hex6,Fuc,Neu5Ac2, and GlcNAc6,Hex7,Fuc,Neu5Ac3 with single AUCs of 0.94, 0.67, and 0.88, respectively, and a combined AUC of 0.98. According to the ingenuity pathway analysis (IPA) and in line with recent publications, the identified N-glycans may play an important role in neuroinflammation. It is a process that plays a fundamental role in neuroinflammation, an important process in the progression of neurodegenerative diseases.

N-Glycome Profile of the Spike Protein S1: Systemic and Comparative Analysis from Eleven Variants of SARS-CoV-2

“…In addition to the N -glycan profiles of the S1 protein variants, we briefly investigated the differences in the isomeric expression across variants. The N -glycan isomeric separation was achieved using our previously developed methodology [ 38 ]. Supplementary Table S3 shows the relative abundance of the identified isomeric N -glycans.…”

“…A previously developed in-house methodology [ 38 ] was used to complete the N -glycan profile of the SARS-CoV-2 spike protein S1 of the variants alpha, beta, gamma, delta, epsilon, eta, iota, kappa, lambda, mu, and omicron. Two micrograms of the permethylated N -glycan sample were introduced into the LC-MS system.…”

LC-MS/MS Quantitation of HILIC-Enriched N-glycopeptides Derived from Low-Abundance Serum Glycoproteins in Patients with Narcolepsy Type 1

“…The role of sialylated glycans was discussed by the Bhide group with regard to cancer. They observed that cancer cell lines exhibited an altered glycosylation pattern, which could aid cancer cell survival, drug resistance, and metastasis [61][62][63]. However, there is currently no research available on the presence of particular glycans and glycopeptides for NT1.…”

Metabolomic Changes in Rat Serum after Chronic Exposure to Glyphosate-Based Herbicide

“…Omics is an emerging field that holds promise to shine light on the molecular mechanisms causing diseases [ 10 ]. Most recently, proteomics, glycomics, glycoproteomics, and metabolomics changes have been implicated in several diseases [ 11 , 12 , 13 , 14 , 15 , 16 ]. To facilitate better understanding of diseases, many omics fields have advanced methods for better identification of glycans, glycopeptides, and their isomers [ 17 , 18 , 19 , 20 ], and have developed several bioinformatic tools [ 21 ] that improve interpretations of omics data.…”