Humanin

Humanin is a 24-amino acid peptide encoded within the mitochondrial 16S rRNA gene. It was discovered in 2001 by Japanese researchers who identified it in an unaffected brain region of an Alzheimer's disease patient. Humanin was one of the first mitochondrial-derived peptides (MDPs) to be characterized and has since become a key molecule in understanding the role of mitochondria as signaling organelles.

The cytoprotective properties of Humanin are its most studied feature. The peptide has been shown to protect cells from apoptosis (programmed cell death) induced by a variety of stressors, including amyloid beta (the protein associated with Alzheimer's disease), oxidative stress, and serum deprivation. It exerts these effects through multiple mechanisms, including binding to the IGFBP-3 receptor, activation of the STAT3 signaling pathway, and interaction with BAX, a pro-apoptotic protein.

Research has explored Humanin's potential in neurodegenerative diseases, cardiovascular protection, and metabolic regulation. In animal models of Alzheimer's disease, Humanin and its more potent analog HNG (Humanin G, with a glycine substitution that increases potency 1000-fold) have shown improvements in cognitive function and reduction of amyloid pathology. Cardiovascular research has demonstrated that Humanin can protect cardiac tissue from ischemia-reperfusion injury and reduce atherosclerosis in animal models.

Like MOTS-c, circulating Humanin levels decline with age, suggesting it may serve as a biomarker of mitochondrial function and biological aging. Epidemiological data have shown that higher Humanin levels are associated with better health outcomes in elderly populations. The peptide represents a growing understanding that mitochondria communicate with the rest of the cell and body through peptide signaling, opening new avenues for therapeutic intervention in age-related diseases.