Mitochondrial Distress Signals at the Heart-Liver Interface: Molecular Links Between MASLD and Heart Failure.

Metabolic dysfunction-associated steatotic liver disease (MASLD) and heart failure (HF) frequently coexist within a shared cardiometabolic environment, yet their mitochondrial abnormalities are stage- and phenotype-dependent rather than uniform. In MASLD, mitochondrial adaptation evolves from increased oxidative metabolism in early steatosis toward impaired respiratory flexibility, oxidative stress, and defective quality control with disease progression, whereas the failing myocardium develops reduced energetic reserve and altered substrate utilization. These organ-specific disturbances can modify mitochondria-linked metabolites, mitochondrial damage-associated molecular patterns, stress-responsive endocrine mediators, and extracellular vesicle-associated mitochondrial cargo. However, similar mitochondrial abnormalities or circulating signals in the liver and heart do not by themselves establish direct inter-organ communication. This review distinguishes shared systemic drivers and organ-intrinsic mitochondrial stress from source-resolved cardio-hepatic signaling, highlighting hepatic ketogenesis, fibroblast growth factor 21 (FGF21), mitochondrial DNA (mtDNA)-dependent inflammatory pathways, and extracellular vesicle-mediated cargo transfer as mechanistically distinct examples with different levels of evidence. We further discuss biomarker limitations, HF-related hemodynamic liver injury, and therapeutic strategies ranging from established cardiometabolic unloading to emerging mitochondria-centered interventions. A stage-, phenotype-, and source-resolved framework may improve interpretation of mitochondrial signals and guide future mechanistic and translational studies in the MASLD-HF overlap.