Humanin: The Mitochondrial Peptide Linked to Cellular Senescence and Neuroprotection

Humanin was discovered in 2001 by a Japanese research group studying Alzheimer's disease (Hashimoto et al., Proceedings of the National Academy of Sciences, 2001). They screened a cDNA library made from the occipital cortex, a relatively spared region of an Alzheimer's patient's brain, for genes that stopped neuronal cells dying, and identified a previously unknown short peptide. Its sequence lies within the 16S ribosomal RNA region of mitochondrial DNA (Cobb et al., 2016). This peptide, named humanin, protected neuronal cells against amyloid beta toxicity in vitro.

Since its discovery, humanin has been recognised as the founding member of a class called mitochondrial-derived peptides (MDPs), which also includes MOTS-c (Lee et al., 2015) and the small humanin-like peptides SHLP1 to SHLP6 (Cobb et al., 2016). These peptides are encoded by short open reading frames within mitochondrial DNA and function as systemic signalling molecules.

Mechanism of Action

Humanin exerts its effects through multiple pathways:

• IGFBP-3 interaction: Humanin binds to insulin-like growth factor binding protein-3 (IGFBP-3). In cell studies it blocked IGFBP-3-induced apoptosis in some cell types, while in neurons IGFBP-3 enhanced humanin's protective effect (Ikonen et al., 2003).
• STAT3 signalling: Humanin activates the STAT3 pathway through the CNTFR/WSX-1/gp130 receptor complex, promoting neuronal cell survival (Hashimoto et al., 2009).
• BAX inhibition: Humanin directly interacts with the pro-apoptotic protein BAX, preventing it from moving to the mitochondria and triggering cytochrome c release. This blocks the intrinsic apoptosis pathway in cell studies (Guo et al., 2003).
• AMPK activation: Humanin and its analogue HNG have been reported to increase AMPK activation in liver cells exposed to fatty acids (Kwon et al., 2020) and in mouse hearts after ischaemia-reperfusion (Muzumdar et al., 2010).

Humanin and Cellular Senescence

Circulating humanin levels appear to decline with age in mice, but human data are mixed. Muzumdar et al. (2009, PLoS ONE) reported lower circulating humanin with age in both mice and humans, and lower humanin in the hypothalamus, skeletal muscle and cortex of older rodents. A later study, however, found plasma humanin was higher in older healthy adults (Conte et al., 2021). The authors of the 2009 study proposed that an age-related decline could contribute to:

• Impaired insulin action and type 2 diabetes
• Neurodegenerative disease such as Alzheimer's disease

These links remain hypotheses. Lower humanin levels have been reported in people with Alzheimer's disease and the mitochondrial disease MELAS (Yen et al., 2020) and in people with coronary endothelial dysfunction (Widmer et al., 2013).

Interestingly, in a small study, children of centenarians had higher circulating humanin levels than age-matched controls (18 versus 19 people; Yen et al., 2020). The authors suggest this may reflect higher humanin levels from early life; the finding is an association only.

Neuroprotection

Humanin's neuroprotective effects are the most extensively studied. In Alzheimer's disease models, humanin and its analogues have been shown to:

• Protect against amyloid beta-induced neurotoxicity in cultured neuronal cells (Hashimoto et al., 2001)
• Reduce amyloid beta-induced tau hyperphosphorylation in rats (Chai et al., 2014)
• Improve cognitive performance in AD mouse models, both after amyloid beta injection (Tajima et al., 2005) and in triple-transgenic mice (Niikura et al., 2011)
• Reduce infarct size and neuronal apoptosis in a mouse stroke model (Xu et al., 2006)

These findings have not yet been replicated in human clinical trials.

Metabolic Effects

Beyond neuroprotection, humanin influences metabolic health:

• Insulin sensitivity: Humanin infused into the brain, and potent analogues given intravenously, improved insulin sensitivity in rats, and an analogue lowered blood glucose in Zucker diabetic fatty rats (Muzumdar et al., 2009)
• Visceral fat reduction: Mice given the analogue HNG from middle age had less visceral fat without changes in food intake (Yen et al., 2020; five mice per group)
• Cardiac protection: Pretreatment with a humanin analogue reduced infarct size and arrhythmias and improved cardiac mitochondrial function in a rat ischaemia-reperfusion model (Thummasorn et al., 2016)

Humanin vs MOTS-c

Both peptides represent the emerging field of "mitochondrial medicine" and are central to the thesis that mitochondrial dysfunction is a root driver of cellular senescence. For more on MOTS-c, see our research overview.

Current Research Status

As of March 2026, humanin research remains predominantly preclinical. No commercially available humanin supplements exist. The peptide's primary value currently lies as a biomarker for mitochondrial health and cellular senescence potential, and as a therapeutic target for neurodegenerative disease.

Synthetic humanin analogues with improved stability and potency (such as S14G-humanin, also called HNG, and HNGF6A) are used in research settings. S14G-humanin is about 1,000-fold more potent than native humanin in cell-based neuroprotection assays (Tajima et al., 2005).

References

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3. Conte M, et al. (2021). Disease-specific plasma levels of mitokines FGF21, GDF15, and Humanin in type II diabetes and Alzheimer's disease in comparison with healthy aging. GeroScience. PubMed 33131010
4. D'Souza RF, et al. (2020). Increased expression of the mitochondrial derived peptide, MOTS-c, in skeletal muscle of healthy aging men is associated with myofiber composition. Aging. PubMed 32182209
5. Guo B, et al. (2003). Humanin peptide suppresses apoptosis by interfering with Bax activation. Nature. PubMed 12732850
6. Hashimoto Y, et al. (2001). A rescue factor abolishing neuronal cell death by a wide spectrum of familial Alzheimer's disease genes and Abeta. Proceedings of the National Academy of Sciences. PubMed 11371646
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15. Thummasorn S, et al. (2016). Humanin exerts cardioprotection against cardiac ischemia/reperfusion injury through attenuation of mitochondrial dysfunction. Cardiovascular Therapeutics. PubMed 27434747
16. Widmer RJ, et al. (2013). Circulating humanin levels are associated with preserved coronary endothelial function. American Journal of Physiology: Heart and Circulatory Physiology. PubMed 23220334
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