Objective:

This study aims to investigate age-associated changes in the proteome and peptide-level modifications in matched cerebrospinal fluid (CSF) and plasma samples from cognitively normal younger and older adults, focusing on post-translational modifications (PTMs) and alternative protein processing.

Background:

Normal aging involves complex molecular changes, including structural, metabolic, and inflammatory alterations. While studies have explored plasma proteomics in aging, comprehensive peptide-level analysis in CSF remains limited. This work addresses the gap by investigating differential protein and peptide abundances, PTMs, and alternative splicing/cleavage events to uncover potential biomarkers and therapeutic targets.

Design/Methods:

CSF and plasma were collected from cognitively normal young (n=52) and older adults (n=40). Mass spectrometry-based proteomic analysis was performed to identify differentially abundant peptides and proteins. Gene-set enrichment analysis (GSEA) and weighted gene correlation network analysis (WGCNA) were employed to identify enriched biological pathways and co-expression modules. Differential phosphorylation and protein cleavage events were analyzed to explore aging-related post-translational changes.

Results:

The study identified 7730 and 1379 peptides with differential expression in CSF and plasma, respectively, and 131 proteins showing significant overlap between both biofluids. Aging was associated with an upregulation of extracellular matrix components and inflammatory pathways in CSF, and a downregulation of insulin-like growth factor-1 (IGF-1) signaling in plasma. Novel alternative splicing and cleavage events were detected in proteins, including APP and APOE, with implications for lipid metabolism and synaptic function.

Conclusions:

This study highlights the intricate molecular landscape of normal cognitive aging by providing new insights into protein-level modifications. The findings suggest potential biomarkers and therapeutic targets related to ECM remodeling, lipid metabolism, and inflammation. These insights underscore the importance of peptide-level analyses for understanding the mechanisms driving healthy aging and cognitive resilience.