Alterations in the Glycan Composition of Serum Glycoproteins in Attention-Deficit Hyperactivity Disorder

Abstract

Changes in protein glycosylation are associated with most biological processes, and the importance of glycomic analysis in the research of disorders is constantly increasing, including in the neurodevelopmental field. We glycoprofiled sera in 10 children with attention-deficit hyperactivity disorder (ADHD) and 10 matching healthy controls for 3 types of samples: whole serum, sera after depletion of abundant proteins (albumin and IgG), and isolated IgG. The analytical methods used were a lectin-based glycoprotein microarray enabling high-throughput glycan analysis and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) as a standard method for the identification of glycan structures. For microarray analysis, the samples printed on microarray slides were incubated with biotinylated lectins and detected using the fluorescent conjugate of streptavidin by a microarray scanner. In the ADHD patient samples, we found increased antennary fucosylation, decreased di-/triantennary N-glycans with bisecting N-acetylglucosamine (GlcNAc), and decreased α2-3 sialylation. The results obtained by both independent methods were consistent. The study's sample size and design do not allow far-reaching conclusions to be drawn. In any case, there is a strong demand for a better and more comprehensive diagnosis of ADHD, and the obtained results emphasize that the presented approach brings new horizons to studying functional associations of glycan alterations in ADHD.

Keywords: ADHD; MALDI-TOF mass spectrometry; biomarker; glycosylation; lectin-based glycoprotein microarray.

Figure 1

Graphic representation of relative signal intensities and normalized relative signal intensities (inserted figures) of interactions for the (A) sera, (B) DS (depleted sera without albumin and IgG), and (C) IgG fraction with lectins measured by the lectin-based glycoprotein microarray. Statistically significant differences (t-test, ** p < 0.01, * p < 0.05) are shown between the ADHD and control groups.

Figure 1

Graphic representation of relative signal intensities and normalized relative signal intensities (inserted figures) of interactions for the (A) sera, (B) DS (depleted sera without albumin and IgG), and (C) IgG fraction with lectins measured by the lectin-based glycoprotein microarray. Statistically significant differences (t-test, ** p < 0.01, * p < 0.05) are shown between the ADHD and control groups.

Figure 2

Representative MS spectra of samples labeled as A6 for (A) serum, (B) DS, and (C) IgG, with marked signals of N-glycans present in all spectra of individual groups of samples. The m/z range is 1500–4000.