Background: Alzheimer’s (AD) and Parkinson’s diseases (PD) show deposits of improperly folded modified proteins. Protein expression mechanisms are involved since the early stages. Several studies evaluated epigenomics and proteomics profiles in these patients, with promising results. In general, they focused on early, specific, and minimally invasive biomarkers for the diagnosis and prognosis of AD and PD.

Objectives: This review aimed at summarizing results to find the most reliable evidence in the field.

Results: Among epigenomics studies, there is a focus on microRNAs (miRNAs) as candidate diagnostic biomarkers for AD or PD from blood samples like miR-342-3p, miR-107, miR-106a-5p, miR-106b- 5p, miR-195, and miR-19b. In addition, DNA methylation has been tested in a few works, obtaining significant differences in some genes (NCAPH2/LMF2 COASY, SPINT1, BDNFTREM1, TREM2, NPAS2, PDE4D), which could be useful for evaluating the disease progression as well as potential risk factors. Regarding proteomics, most of the studies were untargeted and used plasma or serum samples. In general, they highlighted the importance of coagulation, inflammation pathways, and oxidative stress. Among targeted studies, some proteins (phosphorylated tau, C reactive protein (CRP), interleukins, necrosis factors, transferrin, glial fibrillary acidic protein (GFAP), and neurofilaments) showed different plasma levels in AD and PD patients in comparison with healthy participants. Finally, a few studies have identified specific-AD and PD epigenetic and proteomic biomarkers (ApoE and oxidized DJ-1) in comparison with other similar pathologies.

Conclusion: In general, there is a common lack of clinical validation of these potential biomarkers because of which its use in clinical practice is still limited.

背景：阿尔茨海默病 (AD) 和帕金森病 (PD) 显示不正确折叠的修饰蛋白沉积。从早期阶段就涉及蛋白质表达机制。几项研究评估了这些患者的表观基因组学和蛋白质组学特征，并取得了可喜的结果。一般来说，他们专注于早期、特异性和微创的生物标志物，用于 AD 和 PD 的诊断和预后。

目的：本综述旨在总结结果，以找到该领域最可靠的证据。

结果：在表观基因组学研究中，重点关注作为 AD 或 PD 的候选诊断生物标志物的 microRNA (miRNA)，来自血液样本，如 miR-342-3p、miR-107、miR-106a-5p、miR-106b-5p、miR -195 和 miR-19b。此外，DNA甲基化已经在一些工作中进行了测试，在一些基因（NCAPH2/LMF2 COASY、SPINT1、BDNFTREM1、TREM2、NPAS2、PDE4D）中获得了显着差异，这可能有助于评估疾病进展以及潜在风险因素。关于蛋白质组学，大多数研究是非靶向的，使用血浆或血清样本。总的来说，他们强调了凝血、炎症途径和氧化应激的重要性。在靶向研究中，一些蛋白质（磷酸化 tau、C 反应蛋白 (CRP)、白细胞介素、坏死因子、转铁蛋白、胶质纤维酸性蛋白 (GFAP)、和神经丝）与健康参与者相比，在 AD 和 PD 患者中显示出不同的血浆水平。最后，与其他类似病理学相比，一些研究已经确定了特定的 AD 和 PD 表观遗传和蛋白质组学生物标志物（ApoE 和氧化 DJ-1）。

结论：总的来说，这些潜在的生物标志物普遍缺乏临床验证，因此其在临床实践中的使用仍然有限。