We employed an untargeted proteo-metabolomic approach to profile circulating biomarkers in plasma samples from the I-Lan Longitudinal Aging Study, aiming to identify biomarkers and pathways associated with physio-cognitive decline syndrome (PCDS). In 115 propensity score-matched PCDS case-control pairs, pathway analyses implicated dysregulation of fatty acid metabolism and inflammation in PCDS pathogenesis. Sex-specific associations were observed, with disruptions in central carbon metabolism (elevated PKM, MDH1, and GAPDH
decreased MINPP1) and tyrosine metabolism (decreased MIF, DBH
increased thyroxine) characterizing in men. In contrast, perturbations in glutathione and phenylalanine metabolism, including increased ANPEP, GSTP1, and decreased pyroglutamic acid, were identified in women. Results suggest that dysregulated energy and redox homeostasis likely contribute to PCDS development. Notably, ANPEP, PKM, and MIF emerged as potential biomarkers, elucidating the muscle-brain crosstalk framework. Our findings provide insights into potential molecular mechanisms underlying PCDS and the muscle-brain crosstalk, marking progress toward elucidating biomarkers in the journey of healthy aging.