Mitokines as bioenergetic stress signals in cardiovascular disease: mitochondrial communication, endocrine adaptation, and translational implications.

Cardiovascular disease is strongly influenced by mitochondrial dysfunction, yet how mitochondrial stress is communicated beyond the affected cell to coordinate systemic responses remains incompletely understood. Mitokines are stress-responsive signaling factors that link mitochondrial perturbation to cellular and interorgan adaptation. These include nuclear-encoded proteins such as fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15), as well as mitochondrial-derived peptides including Humanin and MOTS-c. This review critically examines mitokine regulation and signaling in the context of cardiovascular stress, with emphasis on mitochondrial unfolded protein response and integrated stress response pathways, receptor and downstream signaling mechanisms, and the functional divergence among major mitokines. Transient mitokine responses during physiological or metabolic challenge may support metabolic flexibility, cytoprotection, and stress adaptation, whereas persistent elevations of FGF21 and GDF15 in cardiovascular and cardiometabolic disease frequently accompany unresolved mitochondrial stress and adverse clinical phenotypes. Importantly, such associations do not establish that sustained mitokine signaling is itself maladaptive, and major mechanistic uncertainties remain, particularly for mitochondrial-derived peptides. We integrate these observations within a proposed "mitokine code" framework in which mitokine identity, relative patterns, temporal dynamics, and disease context may collectively provide information about mitochondrial stress and systemic adaptation. We further evaluate the potential and current limitations of mitokines as cardiovascular biomarkers and therapeutic targets. This framework positions mitokine signaling at the interface between mitochondrial dysfunction, systemic stress adaptation, and cardiovascular disease while identifying mechanistic and translational questions requiring prospective validation.