Humanin

Humanin is a 24-amino acid endogenous peptide encoded within the 16S ribosomal RNA region of the mitochondrial genome. It was first identified in 2001 as a neuroprotective factor capable of suppressing the neuronal cell death induced by proteins associated with familial Alzheimer's disease. Since that discovery, humanin has been recognized as a founding member of a broader class called mitochondrial-derived peptides (MDPs), small signaling molecules that communicate mitochondrial stress states to distant tissues.

Circulating humanin levels decline with advancing age and correlate inversely with multiple markers of metabolic dysfunction, cardiovascular disease, and cognitive decline. Research from USC's Leonard Davis School of Gerontology found that offspring of centenarians have significantly higher humanin levels than age-matched controls, providing human evidence linking this peptide to exceptional longevity. Long-lived species such as the naked mole rat maintain high humanin levels across decades of life, while short-lived rodent models show steep declines within the first 16 months.

Mechanistically, humanin exerts cytoprotective effects through several interconnected pathways. It activates the PI3K/Akt survival pathway in cardiomyocytes, inactivates the pro-apoptotic protein BAX, and upregulates the anti-apoptotic protein BCL-2. In neurons, it blocks amyloid-beta toxicity and prevents tau hyperphosphorylation. It also reduces reactive oxygen species (ROS) production in multiple cell types, limiting the oxidative damage that accumulates with age.

Animal studies demonstrated that treating middle-aged mice with the potent humanin analog HNG (S14G-humanin) twice weekly improved metabolic healthspan parameters and reduced systemic inflammatory markers. Chronic treatment of aged female mice over 14 months with HNG prevented age-related myocardial fibrosis. Human clinical evidence remains limited, and humanin therapy is currently an investigational research tool, not an approved medical treatment.