# Distinct Proteomic Signatures Driving Progression of Sarcopenia: A Longitudinal Multicohort Study

## TL;DR

This study identifies specific proteins and biological pathways linked to the progression of sarcopenia, a muscle-wasting condition in older adults, using data from two independent groups.

## Contribution

The study provides the first validated plasma proteomic signatures and key biological pathways associated with sarcopenia progression across multiple longitudinal cohorts.

## Key findings

- Seventy proteins were differentially expressed in sarcopenia progression, with specific proteins like APOA1, KLKB1, and LECT2 showing significant changes.
- Seven protein signatures (e.g., LRG1, CST3, TIMP1) consistently associated with sarcopenia components were identified and validated across cohorts.
- Key pathways like LXR/RXR signaling, acute phase response, and complement cascade activation were found to be central to sarcopenia progression.

## Abstract

Sarcopenia is an age‐related condition characterized by progressive muscle mass, strength and physical performance declines, contributing to frailty and adverse health outcomes. Despite increasing interest in molecular biomarkers, longitudinal data with external validation are limited.

This study applied high‐throughput proteomic analysis to identify and validate biomarkers associated with sarcopenia progression in two independent prospective cohorts. The discovery cohort (n = 171) was classified into three groups: (1) nonsarcopenic at both baseline and the 2‐year follow‐up; (2) newly developed sarcopenia; and (3) persistently sarcopenic. The validation cohort (n = 93) was followed up for 2 years. Plasma proteomic profiling was conducted using data‐independent acquisition (DIA) mass spectrometry. For the validation cohort, targeted quantification (Hyper Reaction Monitoring‐DIA) and immunoassays were employed to verify key findings. Statistical analyses included multivariable regression and pathway enrichment analysis.

In the discovery cohort, 102 proteins were differentially expressed between groups (p < 0.05). Compared to the stable nonsarcopenic group, individuals who developed sarcopenia demonstrated significant APOA1 (fold change −1.42, p < 0.001) and KLKB1 downregulation and LECT2 upregulation. Those who remained sarcopenic exhibited persistent B2M (+1.58, p < 0.001), S100A9 and LYZ elevation. We identified seven robust protein signatures (LRG1, CST3, TIMP1, C2, ITIH1, AMBP and LYZ) that showed consistent significant associations with sarcopenia components in both cohorts. LRG1 and TIMP1, CST3 and C2 were reproducibly associated with muscle strength, physical performance and muscle mass, respectively. Pathway enrichment analyses consistently highlighted LXR/RXR signalling, acute phase response signalling and complement cascade activation as central mechanisms across these domains.

This study identified and validated plasma protein signatures and pathways associated with sarcopenia progression. Complement activation, acute inflammatory response and lipid dysregulation emerged as central mechanisms. These robustly validated biomarkers may represent targets for early detection and intervention strategies in sarcopenia.