Humanin

Mechanism of action

Humanin is a 24-amino-acid endogenous peptide encoded by an open reading frame within the mitochondrial 16S rRNA gene (MTRNR2). It was discovered by Yuichi Hashimoto and colleagues at Keio University in 2003 through a functional cDNA library screen for peptides protecting neuronal culture from β-amyloid (Aβ)-induced cytotoxicity — the seminal identification of mitochondrial-derived peptides (MDPs) as a bioactive protein class distinct from the more familiar nuclear-genome-encoded peptides. Humanin translation occurs on mitochondrial ribosomes; the mature peptide is either retained in the cytoplasm or exported to plasma, where it exerts endocrine effects on distant tissues. The molecular mechanism of humanin involves two principal receptor systems and one intracellular mitochondrial-membrane-level effect. The extracellular receptor mechanism engages a heterotrimeric receptor complex comprising the formyl peptide receptor-like 1 (FPRL1/FPR2) alongside the ciliary neurotrophic factor receptor (CNTFR), the shared receptor subunit gp130, and WSX-1. Ligand binding activates JAK/STAT3 signalling with downstream cytoprotective effects on neuronal, cardiac, and metabolic tissue targets. The G-protein-coupled FPRL1/FPR2 component is shared with several other bioactive peptides including LL-37 (the antimicrobial cathelicidin) and lipoxin A4, providing a molecular basis for coordinated inflammatory-and-cytoprotective signalling. At the mitochondrial level, humanin directly interacts with the pro-apoptotic Bax and Bak proteins, preventing their oligomerisation and consequent mitochondrial outer membrane permeabilisation (MOMP) — the point-of-commitment step in intrinsic apoptosis. By blocking MOMP, humanin prevents cytochrome c release, apoptosome assembly, and caspase-mediated cell death. This anti-apoptotic mechanism accounts for the cytoprotective phenotype across multiple stressor contexts: β-amyloid toxicity (original neuronal context), oxidative stress, ischaemia-reperfusion injury (cardiac and cerebral), and metabolic stress. The Bax/Bak-inhibitory mechanism operates cell-autonomously; the FPRL1/FPR2 mechanism enables paracrine and endocrine signalling to distant tissues. Downstream physiological effects reflect the coordinated cytoprotective and metabolic pharmacology. Neuroprotective effects include reduction of β-amyloid-induced neuronal death (the founding context), reduction of ischaemic neuronal loss in stroke models, and reduction of neuronal apoptosis in models of Alzheimer's disease and Parkinson's disease. Cardioprotective effects include reduction of ischaemia-reperfusion injury in cardiac models, improved cardiac function in heart failure models, and modulation of atherosclerotic plaque development. Metabolic effects include improved insulin sensitivity, reduced hepatic gluconeogenesis, and modulation of adipose tissue insulin action — a phenotype partly overlapping with MOTS-c but through distinct receptor mechanisms. A critical practical feature of humanin pharmacology is the S14G analogue (HNG) — a synthetic humanin variant with a serine-to-glycine substitution at position 14 that dramatically increases potency (approximately 1000-fold on cytoprotective endpoints in cell culture) while preserving the receptor binding and mitochondrial mechanism. The enhanced potency has been essential to much of the therapeutic-focused humanin research, since native humanin's efficacy at physiological concentrations is modest. Most research protocols and pre-clinical drug-development work using humanin have used S14G-humanin (HNG) rather than the native sequence. Circulating humanin plasma concentrations decline with age in humans and rodents, with 30-50% reductions documented in older versus younger cohorts. Reduced humanin has been documented in Alzheimer's disease, type-2 diabetes, chronic kidney disease, and other age-related conditions, supporting the hypothesis of humanin as an endogenous cytoprotective regulator whose loss contributes to the ageing phenotype.

Humanin was discovered as an endogenous peptide encoded within the mitochondrial 16S rRNA region — the founding member of the mitochondrial-derived peptide (MDP) class (Hashimoto et al., PNAS 2001) — establishing that the mitochondrial genome encodes bioactive peptides beyond the electron-transport-chain proteins, transforming understanding of mitochondrial-nuclear retrograde signalling.

— Notable finding

Research history

Humanin was discovered by Yuichi Hashimoto and colleagues at Keio University, published in PNAS in 2001 (Nishimoto lab), through a functional cDNA library screen for peptides protecting neuronal culture from familial-Alzheimer's-disease-associated V642I amyloid precursor protein (APP) mutation cytotoxicity. The screen identified an unusual cDNA encoding a 24-amino-acid peptide whose sequence corresponded not to a nuclear gene but to a putative open reading frame within the mitochondrial 16S rRNA region — an entirely unexpected discovery that established the existence of biologically active mitochondrial-genome-encoded peptides. Subsequent characterisation across the 2000s established humanin as the founding member of the mitochondrial-derived peptide (MDP) class, with mechanistic characterisation of the FPRL1/gp130/CNTFR/WSX-1 receptor complex, the Bax/Bak-inhibitory mechanism, and the neuroprotective activity across multiple neurodegenerative models. The S14G analogue (HNG) was developed by 2003 to address the modest potency of native humanin, dramatically expanding the pre-clinical research toolkit. Extension of humanin research beyond the original neuroprotective framework has produced substantial evidence for cardioprotective (Muzumdar et al., Circulation 2010) and metabolic (Muzumdar et al., 2009) effects. Age-related decline in circulating humanin plasma concentration was documented across the 2010s, supporting the broader longevity-research framework. The MOTS-c discovery in 2015 by the Cohen laboratory (also mitochondrial-derived) subsequently established that humanin was not a solitary MDP but the founding member of a broader class. Clinical development of humanin has been limited. Early-phase exploratory clinical work has been initiated at academic centres but has not progressed to formal Phase II/III commercial development. CohBar Inc. (the biotechnology company founded by Pinchas Cohen and colleagues to develop MDP-based therapeutics) advanced several MDP-related compounds through Phase I but did not progress to registration; direct commercial humanin development has been complicated by the off-patent nature of the endogenous peptide sequence and by the delivery challenges of central-nervous-system-targeted peptide pharmacology. Humanin and HNG (S14G-humanin) are available through research-chemical suppliers as pre-clinical research compounds. Neither holds marketing authorisation in any jurisdiction as of 2026.

Reported research-model dose ranges

The ranges below are taken from published pre-clinical literature. They do not constitute a dosing recommendation for human use.

Summarised studies

Safety profile

Humanin safety data derive primarily from pre-clinical work with native humanin and the more-studied HNG analogue. The pre-clinical safety record across rodent studies has been favourable: subcutaneous and intracerebroventricular doses across the research dose range have produced no overt toxicity, no significant changes in routine haematology or hepatic enzymes, and no organ-specific lesions in standard histopathology. As an endogenous peptide (native humanin) or minor variant of an endogenous peptide (HNG), immunogenicity risk is low; anti-humanin antibodies have not been a documented issue in the pre-clinical work. Theoretical safety considerations centre on the broad cytoprotective phenotype. Chronic Bax/Bak inhibition could theoretically impair beneficial physiological apoptosis (immune cell selection, tumour suppression, developmental apoptosis) with potential long-term consequences that are incompletely characterised. Specific concerns about impaired tumour suppression through inhibited apoptosis have been considered but not substantiated in pre-clinical work. The FPRL1/FPR2 receptor engagement is shared with several bioactive peptides including LL-37; this receptor engagement is generally cytoprotective but could theoretically produce unwanted inflammatory or immunomodulatory effects at chronic supraphysiological doses. The pre-clinical data have not surfaced significant signals in these domains, but the chronic-dosing pharmacology is incompletely characterised. No serious adverse events have been reported in any published humanin research. The acute safety profile in research animals is favourable; chronic-dosing and human safety records remain limited.

UK regulatory status

Humanin (native or HNG analogue) is not authorised as a medicinal product by the UK Medicines and Healthcare products Regulatory Agency (MHRA) and holds no marketing authorisation in any jurisdiction. It is not a controlled substance under the Misuse of Drugs Act 1971. Research-grade material for in-vitro and animal research is available from research-chemical suppliers; possession for bona fide laboratory research is generally unrestricted in the UK. Supply or administration of humanin to humans outside an authorised clinical-trial framework engages the Human Medicines Regulations 2012 and is generally an offence. Humanin is not currently on the WADA Prohibited List. Its cytoprotective and metabolic mechanisms do not currently fall within any WADA category, though athletes should verify the current annual Prohibited List. For animal research under ASPA, humanin work in vertebrates requires standard project and personal licences from the Home Office Drugs and Firearms Licensing Unit.

Frequently asked questions