Mild cognitive impairment is increasingly recognized as a complication of type 2 diabetes (T2D). Although currently no disease-modifying treatments for cognitive disorders exist, interest surged in potential neuroprotective effects of newer anti-diabetic drugs. This study investigates the impact of newer anti-diabetic drug classes, dipeptidyl peptidase-4 (DPP-4i) and sodium-glucose cotransporter-2 inhibitors (SGLT2i) - on cognitive decline in T2D patients on metformin therapy. A prospective observational cohort study was conducted, with a follow-up duration of 6 months. The study compared the cognitive performance of T2D patients on metformin monotherapy to those on a combination of metformin with DPP-4i or SGLT2i, using the Montreal Cognitive Assessment Battery. A group of healthy volunteers served as a reference. At baseline, patients receiving combination therapy had a cognitive performance comparable to that of healthy volunteers, while those on metformin monotherapy scored lower. These differences persisted for patients who completed the follow-up, though there was no change within group. Baseline differences were independent of glycemic control, blood lipids, renal function, and serum inflammatory markers. Comprehensive metabolomics and lipidomics revealed that T2D patients on metformin monotherapy exhibited enriched purine, glutathione and sphingolipid metabolism, with alterations in xanthine, L-pyroglutamic acid, and several sphingomyelins. These changes suggest increased oxidative stress in T2D, mitigated in the combination therapy group, as evidenced by total serum antioxidant capacity. As such, we conclude that the combination of DPP-4i or SGLT2i with metformin positively impacts cognitive function in T2D patients by modulating metabolic pathways rather than improving glycemic control, peripheral diabetic complications, or systemic inflammation.

The SARS-CoV-2 virus rapidly spread worldwide, threatening public health. Since it emerged, the scientific community has been engaged in the development of effective therapeutics and vaccines. The subunit S1 in the spike protein of SARS-CoV-2 mediates the viral entry into the host and is therefore one of the major research targets. The S1 protein is extensively glycosylated, and there is compelling evidence that glycans protect the virus’ active site from the human defense system. Therefore, investigation of the S1 protein glycome alterations in the different virus variants will provide a view of the glycan evolution and its relationship with the virus pathogenesis. In this study, we explored the N-glycosylation expression of the S1 protein for eleven SARS-CoV-2 variants: five variants of concern (VOC), including alpha, beta, gamma, delta, and omicron, and six variants of interest (VOI), including epsilon, eta, iota, lambda, kappa, and mu. The results showed significant differences in the N-glycome abundance of all variants. The N-glycome of the VOC showed a large increase in the abundance of sialofucosylated glycans, with the greatest abundance in the omicron variant. In contrast, the results showed a large abundance of fucosylated glycans for most of the VOI. Two glycan compositions, GlcNAc₄,Hex₅,Fuc,NeuAc (4-5-1-1) and GlcNAc₆,Hex₈,Fuc,NeuAc (6-8-1-1), were the most abundant structures across all variants. We believe that our data will contribute to understanding the S1 protein’s structural differences between SARS-CoV-2 mutations.

The highly glycosylated S protein plays a vital role in host cell invasion, making it the principal target for vaccine development. Differences in mutations observed on the spike (S) protein of SARS-CoV-2 variants may result in distinct glycosylation patterns, thus influencing immunological evasion, infectivity, and transmissibility. The glycans can mask key epitopes on the S1 protein and alter its structural conformation, allowing the virus to escape the immune system. Therefore, we comprehensively characterize O-glycosylation in eleven variants of SARS-CoV-2 S1 subunits to understand the differences observed in the biology of the variants. In-depth characterization was performed with a double digestion strategy and an efficient LC-MS/MS approach. We observed that O-glycosylation is highly conserved across all variants in the region between the NTD and RBD, whereas other domains and regions exhibit variation in O-glycosylation. Notably, omicron has the highest number of O-glycosylation sites on the S1 subunit. Also, omicron has the highest level of sialylation in the RBD and RBM functional motifs. Our findings may shed light on how differences in O-glycosylation impact viral pathogenicity in variants of SARS-CoV-2 and facilitate the development of a robust vaccine with high protective efficacy against the variants of concern.

Small extracellular vesicles (sEVs) are gaining recognition as potential biomarkers for diseases, including cancer, due to their involvement in key pathophysiological processes. However, the glycosylation of EVs and the specific roles of their glycans remain poorly understood. While several methods exist for isolating sEVs from complex biological samples, achieving sufficient purity and quantity for mass spectrometry-based glycoproteomic analysis remains a significant challenge. In this study, we compared two commonly used isolation methods, ultracentrifugation (UC) and immunoaffinity capture (MagCapture kit), across different starting volumes of human serum (200 µL and 500 µL) to evaluate their performance for downstream glycoproteomic analysis. While prior studies have examined protein content across isolation methods, our work uniquely investigates how isolation technique and sample volume affect glycoproteomic yield and quality. We show that UC, particularly at higher sample volumes, enables deeper glycoproteomic coverage, whereas MagCapture is advantageous when serum availability is limited. Notably, we report for the first time site-specific glycan microheterogeneity on sEV glycoproteins derived from human serum, including multiple glycoforms at the same glycosylation site. These findings highlight the complexity and biological relevance of glycosylation in sEV proteins and offer practical guidance for optimizing isolation protocols based on specific omics applications.