Exercise-Induced Muscle–Fat Crosstalk: Molecular Mediators and Their Pharmacological Modulation for the Maintenance of Metabolic Flexibility in Aging

Regular physical activity induces a dynamic crosstalk between skeletal muscle and adipose tissue, modulating the key molecular pathways that underlie metabolic flexibility, mitochondrial function, and inflammation. This review highlights the role of myokines and adipokines—particularly IL-6, irisin, leptin, and adiponectin—in orchestrating muscle–adipose tissue communication during exercise. Exercise stimulates AMPK, PGC-1α, and SIRT1 signaling, promoting mitochondrial biogenesis, fatty acid oxidation, and autophagy, while also regulating muscle hypertrophy through the PI3K/Akt/mTOR and Wnt/β-catenin pathways. Simultaneously, adipose-derived factors like leptin and adiponectin modulate skeletal muscle metabolism via JAK/STAT3 and AdipoR1-mediated AMPK activation. Additionally, emerging exercise mimetics such as the mitochondrial-derived peptide MOTS-c and myostatin inhibitors are highlighted for their roles in increasing muscle mass, the browning of white adipose tissue, and improving systemic metabolic function. The review also addresses the role of anti-inflammatory compounds, including omega-3 polyunsaturated fatty acids and low-dose aspirin, in mitigating NF-κB and IL-6 signaling to protect mitochondrial health. The resulting metabolic flexibility, defined as the ability to efficiently switch between lipid and glucose oxidation, is enhanced through repeated exercise, counteracting age- and disease-related mitochondrial and functional decline. Together, these adaptations demonstrate the importance of inter-tissue signaling in maintaining energy homeostasis and preventing sarcopenia, obesity, and insulin resistance. Finally, here we propose a stratified treatment algorithm based on common age-related comorbidities, offering a framework for precision-based interventions that may offer a promising strategy to preserve metabolic plasticity and delay the age-associated decline in cardiometabolic health.