Serum protein profiling reveals hallmark-level age-associated differences and strain-specific patterns in CB6F1J and C57BL/6J male mice

Aging involves progressive changes across interconnected biological pathways, but minimally invasive approaches for assessing these processes remain limited. We used serum protein profiling to characterize age-associated differences in 8- and 32-month-old male CB6F1J and C57BL/6J mice. Circulating proteins were mapped to established hallmarks of aging and evaluated for age- and strain-dependent patterns. Differences were identified across inflammatory, vascular, intercellular communication, metabolism, and tissue maintenance pathways. After Benjamini-Hochberg correction, 45 proteins remained significant at FDR q < 0.05 in CB6F1J mice and none in C57BL/6J mice. Hallmark-level analyses were therefore based primarily on all mapped proteins, with FDR-defined subsets considered secondary. Hallmark categories showed substantial overlap, and analyses restricted to uniquely assigned proteins showed attenuated cross-strain concordance. These findings demonstrate that serum protein profiling can capture hallmark-level age-associated differences across genetic backgrounds. As this study compared only two age groups cross-sectionally, the findings do not establish aging trajectories but provide a framework for future longitudinal serum-based assessment.