TL;DR
More research in the field may unravel the mechanistic details of the organellar crosstalk that works in concert with classical aging pathways to sustain aging progression, which may help promote healthier aging.
Because of population aging and morbidity expansion, extending healthspan has become a global challenge and it is required to elucidate molecular mechanisms underlying aging and age-related diseases. Mitochondrial dysfunction is a hallmark of aging, characterized by impaired oxidative phosphorylation, increased production of reactive oxygen species (ROS), and metabolic imbalance. Therefore, maintaining mitochondrial homeostasis is essential for healthspan. Mitochondrial respiratory chain complexes organize into higher-order assemblies known as supercomplexes (SCs), which enable to efficient energy or ATP production with repressed ROS generation. Notably, the assembly and stability of these SCs likely decline in aged mammals. In addition, factors such as COX7RP/SCAF1 and mitochondrial lipid cardiolipin have emerged as key regulators of SC assembly. In this review, we summarize the molecular assembly, physiological roles, and longevity implications of SC in healthy mammals. We further discuss emerging evidence supporting SC modulation as a potential strategy for promoting healthy aging.
Although the mitochondria are known as the cellular powerhouse, their function is beyond energy generation. These organelles regulate cellular metabolism, yet maintains a tightly regulated reactive oxygen species (ROS) generation and optimal redox state. In addition, mitochondria serve as mediators of physiological and pathological processes, such as maintenance of calcium balance, and control of apoptosis and mitophagy. All these make the mitochondria a major factor in both cellular and organismal regulation. However, mitochondria dysfunction may occur through many processes, including genetic mutations, increased production of ROS, metabolic failure from impaired electron transport chain activity, and dysregulated dynamics or mitophagy. Several self-perpetuating damages accumulate from these processes and influence clinical pathologies, such as aging, metabolic syndrome, cancer, neurodegeneration, and reproductive disorders. Recent studies demonstrate promising therapeutic targets for mitochondrial dysfunction. Examples include targeted antioxidants, such as MitoQ and SkQ1, to selectively neutralize mitochondrial ROS, pharmacological modulators to enhance mitochondrial biogenesis and to restore NAD + homeostasis via PGC-1α activation, gene-editing technologies, such as mitoTALENs and mtZFNs to selectively eliminate pathogenic mitochondrial DNA mutations, and mitochondrial transplantation as a new technique to replace damaged organelles. Together, these novel approaches highlight the need for research in mitochondrial function to change the therapeutic landscape in the management of mitochondrial dysfunction-associated diseases.
This review proposes that tailored exercise strategies targeting mitophagy may provide a scalable, non‐pharmacological approach to preserve mitochondrial quality and functional resilience during aging.
This review elucidates the core mechanisms underpinning this dysfunction, including reactive oxygen species (ROS)-induced redox imbalance, mitochondrial DNA (mtDNA) damage accumulation, impaired mitophagy, and metabolic reprogramming, and critically examines how mitochondria act as signaling hubs for inter-organ crosstalk.
Although mtISR has been characterized in primary mitochondrial myopathies, secondary mitochondrial dysfunction in neuromuscular disorders suggests that mtISR-related pathways may also be activated in these conditions, and its roles in skeletal muscle pathology are discussed.
How aging of human neurons affects dynamics of essential organelle such as mitochondria and autophagosomes remains largely unknown. MicroRNA-induced directly reprogrammed neurons (miNs) derived from adult fibroblasts retain age-associated signatures of the donor, enabling the study of age-dependent features in human neurons, including longitudinal isogenic samples. Transcriptomic analysis revealed that neurons derived from elderly individuals are characterized by gene expression changes associated with the regulation of autophagosomes, lysosomes, and mitochondria, compared to young counterparts. To clarify these changes at the cellular level, we performed live-cell imaging of cellular organelles in miNs from donors of different ages. Older donor miNs exhibit decreased mitochondrial membrane potential, which surprisingly co-occurs with a significant increase in mitochondrial fission and fusion events. We posit that the increased fission and fusion of mitochondria may reflect age-dependent compensation for impaired mitochondrial turnover, perhaps due to changes in macroautophagy/autophagy. We subsequently identified a significant decrease in autophagosome acidification in neurons derived from individuals > 65 years compared to younger donors, and a corresponding age-dependent reduction in neuritic lysosomes resulting in fewer lysosomes available to acidify autophagosomes. This age-dependent deficit in autolysosome flux was rescued by promoting autophagosome generation through TFEB, which also reversed the age-dependent increase in mitochondrial fission and fusion and improved mitochondrial health. Partial organelle recovery occurred after inducing mitophagy or inhibiting mitochondrial fission. Together, this work reveals a mechanism by which aging reduces autophagic flux secondary to a loss of neuritic lysosomes, resulting in mitochondria-intrinsic mechanisms to avoid loss of energy production.
