Grosskopf Anne, Rahn Jette, Kim Ahyoung, Szabó Gábor, Rujescu Dan, Klawonn Frank, Frolov Andrej, Simm Andreas
Clinic for Cardiac Surgery, University Medicine Halle, Martin Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany.
Biomedicines. 2024 Sep 19;12(9):2127. doi: 10.3390/biomedicines12092127.
The diagnosis of Alzheimer's disease (AD) relies on core cerebrospinal fluid (CSF) biomarkers, amyloid beta (Aβ) and tau. As the brain is then already damaged, researchers still strive to discover earlier biomarkers of disease onset and the progression of AD. Glycation, advanced glycation end products (AGEs) and oxidative modifications on proteins in CSF mirror the underlying biological mechanisms that contribute to early AD pathology. However, analyzing free AGEs in the body fluids of AD patients has led to controversial results. Thus, this pilot study aimed to test the feasibility of detecting, identifying and quantifying differentially glycated, AGE or oxidatively modified peptides in CSF proteins of AD patients ( = 5) compared to a control group ( = 5). To this end, we utilized a data-dependent (DDA) nano liquid chromatography (LC) linear ion trap-Orbitrap tandem mass spectrometry (MS/MS) ) approach and database search that included over 30 glycative and oxidative modifications in four search nodes to analyze endogenous modifications on individual peptides. Furthermore, we quantified candidate peptide abundance using LC Quan. We identified 299 sites of early and advanced glycation and 53 sites of oxidatively modified tryptophan. From those, we identified 17 promising candidates as putative biomarkers (receiver operating curve-area under the curve (ROC-AUC) > 0.8), albeit without statistical significance. The potential candidates with higher discrimination power showed correlations with established diagnostic markers, thus hinting toward the potential of those peptides as biomarkers.
阿尔茨海默病（AD）的诊断依赖于脑脊液（CSF）中的核心生物标志物，即淀粉样β蛋白（Aβ）和tau蛋白。由于此时大脑已经受损，研究人员仍在努力寻找疾病发作和AD进展的早期生物标志物。脑脊液中蛋白质的糖基化、晚期糖基化终产物（AGEs）和氧化修饰反映了导致早期AD病理的潜在生物学机制。然而，分析AD患者体液中的游离AGEs得出了有争议的结果。因此，这项初步研究旨在测试与对照组（n = 5）相比，检测、鉴定和定量AD患者脑脊液蛋白质中差异糖基化、AGE或氧化修饰肽段的可行性（n = 5）。为此，我们采用了数据依赖（DDA）纳升液相色谱（LC）线性离子阱-轨道阱串联质谱（MS/MS）方法和数据库搜索，该搜索在四个搜索节点中包含30多种糖基化和氧化修饰，以分析单个肽段上的内源性修饰。此外，我们使用液相色谱定量法（LC Quan）对候选肽段丰度进行了定量。我们鉴定出299个早期和晚期糖基化位点以及53个氧化修饰色氨酸位点。从中，我们鉴定出17个有前景的候选物作为潜在生物标志物（受试者工作特征曲线下面积（ROC-AUC）> 0.8），尽管没有统计学意义。具有更高鉴别力的潜在候选物与已确立的诊断标志物显示出相关性，因此暗示了这些肽段作为生物标志物的潜力。
