N-Glycomic changes in serum proteins in type 2 diabetes mellitus correlate with complications and with metabolic syndrome parameters

Background: Glycosylation, i.e the enzymatic addition of oligosaccharides (or glycans) to proteins and lipids, known as glycosylation, is one of the most common co-/posttranslational modifications of proteins. Many important biological roles of glycoproteins are modulated by N-linked oligosaccharides. As glucose levels can affect the pathways leading to glycosylation of proteins, we investigated whether metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM), pathological conditions characterized by altered glucose levels, are associated with specific modifications in serum N-glycome. Methods: We enrolled in the study 562 patients with Type 2 Diabetes Mellitus (T2DM) (mean age 65.6 +/- 8.2 years) and 599 healthy control subjects (CTRs) (mean age, 58.5 +/- 12.4 years). N-glycome was evaluated in serum glycoproteins. Results: We found significant changes in N-glycan composition in the sera of T2DM patients. In particular, alpha(1,6)-linked arm monogalactosylated, core-fucosylated diantennary N-glycans (NG1(6)A2F) were significantly reduced in T2DM compared with CTR subjects. Importantly, they were equally reduced in diabetic patients with and without complications (P