1669 Gangliosides as biomarkers for early diagnosis of diabetic kidney disease: detection and characterization by high-performance mass spectrometry

Abstract Background and Aims The early identification of diabetic kidney disease (DKD) is crucial as it may facilitate immediate intervention, thus impeding the progression of the condition and the risk of developing end-stage renal disease (ESRD). Enhancing our understanding of the pathophysiology of this microvascular complication as well as developing therapeutic strategies are imperative. Hence, the aim of the current study was to address the problematics of detection and characterization of gangliosides in the urine of type 2 diabetes mellitus (DM) patients with DKD. Method In this cross-sectional study, the urine ganglioside content from 24 h collected urine samples of 60 type 2 DM patients (20 with normal to mildly increased albuminuria—A1 group, 20 with moderately increased albuminuria—A2 group, 20 with severe increased albuminuria—A3 group) was compared to that of 20 healthy controls using a promising technique based on high-resolution (HR) mass spectrometry (MS). Furthermore, for structural elucidation of individual compounds, we isolated the ions GT1 (d18:1/18:0), identified at m/z 708.3379 and, GQ1 (d18:1/18:0) at m/z 812.7068, observed only in the screening analysis of A3 patients, and exposed them to Higher-energy collisional dissociation (HCD MS/MS) in the negative ion mode. Results Patients with type 2 diabetes mellitus display a considerably greater abundance of different species in their urinary gangliosidome, which varies in either glycan or ceramide structure, in comparison to the control group. Even within the A1 group, a greater variety of structures exhibiting varying degrees of sialylation were observed. A wide range of carbohydrate chains were discovered, ranging from short, monosialylated chains (GM) to complex, pentasialylated chains (GP). Additionally, some ganglioside chains were modified with and O-acetyl (O-Ac) attachments. The gangliosidome of the A3 group comprises a higher variety of structures, compared to A1 and A2, differing in their overall sialic acid content, and more complex structures, including various biologically significant modifications, such as O-fucosylation, O-GalNAc and CH3COO− attachments. Both albuminuria and glomerular filtration rate proved to be correlated with the degree of sialylation of species. Furthermore, significant alterations occur also in the ceramide part, with the most noteworthy being the presence of sphingoid base trihydroxylation, which is shown in both A1 and A3 samples. Additionally,