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.