Humanin

What is Humanin?

Humanin (HN) is a 24-amino-acid micropeptide encoded by a small open reading frame within the 16S ribosomal RNA gene (MT-RNR2) of the human mitochondrial genome. It was first identified in 2001 by Hashimoto, Niikura, and Nishimoto at Keio University School of Medicine, who isolated it from the occipital cortex of an Alzheimer's disease patient via a functional cDNA library screen for clones capable of suppressing neuronal cell death induced by familial AD mutant genes and amyloid-beta (Aβ). The full-length 24-amino acid cytosolic form carries the sequence MAPRGFSCLLLLTSEIDLPVKRRA; the 21-amino acid mitochondrially-produced form is MAPRGFSCLLLLTSEIDLPV, with four C-terminal residues cleaved during mitochondrial processing. Both forms have been demonstrated to exhibit biological activity in preclinical experimental systems.

The peptide's production depends on its site of synthesis: when produced inside mitochondria, it yields the 21-residue form; when produced in the cytosol from nuclear-integrated copies of mitochondrial DNA (NUMTs), it produces the 24-residue form. Humanin is the most phylogenetically conserved of the mitochondria-derived peptides (MDPs), with homologs identified in naked mole rats, rodents, and nematodes. Its serum levels decline with age in rodent models and human clinical studies, and it has been investigated in preclinical models for its roles in neuroprotection, anti-apoptotic signalling, Bax inhibition, insulin sensitivity modulation, and cytoprotection against ischaemia-reperfusion injury.

A well-characterised synthetic analogue, Humanin-glycine (HNG), carries a serine-to-glycine substitution at position 14 (S14G) and is up to 1000-fold more potent than native Humanin in neuroprotection assays, making it the primary analogue used in Alzheimer's disease rodent model investigations. Humanin is not approved by the Food and Drug Administration for human or veterinary use. It is not a dietary supplement and is not intended for human consumption or therapeutic self-administration. All RCDbio research compounds are supplied strictly for laboratory and research purposes only.

All preclinical studies referenced in this document were conducted under institutional oversight consistent with IRB, IACUC, and AWA guidelines. Humanin is supplied by RCDbio exclusively for use under equivalent institutional research compliance frameworks.

Chemical Properties

How Does Humanin Work?

Humanin exerts its cytoprotective and neuroprotective effects through multiple intersecting intracellular and receptor-mediated signalling pathways. The compound's activity is best characterised by its anti-apoptotic Bax inhibition, cytokine receptor complex activation, and IGFBP-3 binding, though additional mechanisms continue to be characterised in ongoing preclinical research.

Bax Inhibition and Mitochondrial Apoptosis Pathway

The most extensively characterised mechanism of Humanin is direct inhibition of Bax, a pro-apoptotic member of the Bcl-2 family. In isolated cell preparations, Humanin binds Bax and prevents its translocation to the mitochondrial outer membrane, thereby inhibiting the release of cytochrome c and downstream caspase activation [Guo et al., 2003]. Single-molecule fluorescence and FRET studies in lipid bilayer preparations confirmed that Humanin (100 nmol/L) inhibits Bax self-association, tBid-activated membrane association, and tetramer formation in artificial membrane systems. Cys8 has been identified as a critical residue for this Bax-binding activity, with substitution of Cys8 abolishing neuroprotective function in isolated cell preparations [Hashimoto et al., 2001].

CNTFR/WSX-1/gp130 Cytokine Receptor Complex Activation

Humanin has been characterised as a ligand for a heterotrimeric cytokine receptor complex comprising ciliary neurotrophic factor receptor (CNTFR), interleukin-27 receptor subunit alpha (WSX-1), and gp130. Receptor complex activation initiates JAK-STAT3 signalling, with STAT3 phosphorylation characterised as a downstream effector of Humanin-mediated neuroprotection in isolated cell preparations and rodent in vivo models [Hashimoto et al., 2001]. This receptor pathway overlaps mechanistically with the CNTF signalling system, suggesting shared cytoprotective signalling architecture.

IGFBP-3 Binding and Cell Survival Modulation

In isolated cell systems, Humanin has been shown to bind insulin-like growth factor binding protein-3 (IGFBP-3), a pro-apoptotic factor that mediates cell death independently of IGF-1. Humanin binding to IGFBP-3 inhibits IGFBP-3-induced nuclear translocation and apoptotic signalling in isolated cell preparations, with the IGFBP-3 binding domain mapped to amino acid residues 6–21 of the Humanin sequence [Hashimoto et al., 2001].

Insulin Sensitivity and Metabolic Pathway

In rodent in vivo models, intracerebroventricular and intravenous administration of HNG has been investigated for effects on peripheral insulin sensitivity. In Zucker diabetic fatty rat models, Humanin infusion was associated with increased peripheral insulin sensitivity and improved glucose homeostasis, implicating central hypothalamic CNTFR/gp130 receptor pathways in metabolic regulation. These observations are derived from rodent in vivo models and have not been replicated in human clinical studies.

Key Research Findings

In preclinical and in vitro research contexts, Humanin has been associated with the following observations:

• Bax inhibition: Humanin binds Bax and prevents its translocation to the mitochondrial outer membrane and cytochrome c release in isolated cell preparations and lipid bilayer systems; Cys8 is identified as the critical binding residue [Guo et al., 2003].
• Neuronal cell death suppression: Humanin treatment associated with suppression of neuronal cell death induced by multiple familial AD mutant genes (APP V642I, NL-APP, PS1 M146L, PS2 N141I) and Aβ1-43 in isolated neuronal cell preparations; effect was action-specific and did not extend to polyglutamine or SOD1 mutant toxicity [Hashimoto et al., 2001].
• HNG potency: S14G substitution (HNG) produces up to 1000-fold greater neuroprotective potency than native Humanin in cell death assay systems; HNG is the primary analogue used in rodent AD model studies.
• Cerebral ischaemia protection: HNG administration associated with reduced infarct volume and improved neuronal viability in focal cerebral ischaemia/reperfusion mouse models; PI3K/Akt pathway identified as a mediating mechanism.
• Age-related serum decline: Humanin serum levels decrease significantly with age in rodent models and have been associated with increased vulnerability to age-related pathologies in observational studies.

All findings listed above are derived from preclinical in vitro and in vivo rodent model data. No human clinical trial data have been established for Humanin. These observations do not constitute evidence of efficacy or safety in any human condition or organism.

What are the Potential Research Applications of Humanin?

In controlled laboratory environments, Humanin has been investigated for the following research applications. These are observed in preclinical and in vitro contexts only and do not constitute claims of efficacy or safety in any organism.

Bax Inhibition and Mitochondrial Apoptosis Research. Humanin is employed as a primary tool for investigating Bax-mediated mitochondrial apoptosis pathways in isolated cell and lipid bilayer preparations. It is used in fluorescence microscopy, FRET assay systems, and cytochrome c release assays to characterise the mechanisms by which Bax membrane association and oligomerisation can be inhibited.

Alzheimer's Disease Neuronal Death Model Studies. In isolated neuronal cell preparations transfected with familial AD mutant genes and in Aβ-treated cell cultures, Humanin is used as a neuroprotective reference compound to probe the relationship between AD pathological stimuli and neuronal survival pathways. Research examines dose-response relationships, receptor dependency, and structural requirements for activity.

CNTFR/gp130/STAT3 Signalling Research. Humanin is investigated as a ligand for the CNTFR/WSX-1/gp130 heterotrimeric receptor complex in isolated cell systems. Research employs JAK-STAT3 pathway reporter assays and co-immunoprecipitation studies to characterise receptor binding kinetics and downstream phosphorylation cascades.

Ischaemia-Reperfusion Injury Models. In rodent focal cerebral ischaemia/reperfusion models, Humanin and HNG are investigated for neuroprotective effects on infarct volume, neuronal viability, and PI3K/Akt pathway activation. Research examines the relationship between Bax inhibition, PI3K/Akt signalling, and neuronal survival under ischaemic conditions.

Metabolic Pathway and Insulin Sensitivity Research. In rodent in vivo models (Zucker diabetic fatty rats and aged rodent preparations), Humanin and HNG are investigated for effects on peripheral insulin sensitivity, hypothalamic receptor signalling, and glucose homeostasis via central CNTFR/gp130 pathway engagement. Research examines the relationship between mitochondria-derived peptide signalling and systemic metabolic regulation.

What are the Potential Side Effects of Humanin?

Researchers in preclinical and in vitro settings have noted the following observations. Long-term safety profiles in humans have not been established, and no clinical trial data exist for Humanin.

• No significant toxicity observed in rodent preclinical studies at concentrations used in neuroprotection research; acute toxicity profile characterised as low in published studies
• Free cysteine residue at position 8 (Cys8) renders the native Humanin peptide susceptible to oxidative dimerisation under aerobic storage conditions; oxidised or dimerised forms may have altered activity profiles in experimental systems
• Antibody formation against Humanin peptide is a theoretical consideration for chronic in vivo administration models; not been reported to date in published preclinical studies
• HNG analogue (S14G) shares the same safety profile as native Humanin in published rodent studies, with no adverse effects reported at cytoprotective doses
• No human safety or tolerability data have been established for Humanin. These observations are derived from in vitro and rodent experimental systems and should not be extrapolated to human or animal outcomes.

Risk & Handling

Handling Precautions

Humanin should only be handled by trained laboratory personnel familiar with synthetic neuropeptide research compounds. Appropriate personal protective equipment is required: nitrile gloves, a laboratory coat, and eye protection at a minimum. When working with lyophilized powder, use within a laminar flow cabinet or clean area to avoid inhalation of particulate matter. Avoid aerosol generation during reconstitution. The free cysteine residue at position 8 renders the native peptide susceptible to oxidation and disulfide bond formation; all handling should minimise exposure to oxidising conditions and atmospheric oxygen where possible.

Exposure Risks

Risk Tier: LOW

Humanin has demonstrated a low acute toxicity profile in published preclinical rodent studies at neuroprotective concentrations. The peptide's primary pharmacological mechanism — Bax inhibition and anti-apoptotic signalling — is active at nanomolar concentrations in isolated cell systems. No systemic toxicity findings have been reported in published preclinical studies. No human safety or tolerability data has been established for Humanin.

Storage

• Lyophilized form: Store at −20°C in original sealed, light-protected container with desiccant
• Reconstituted form: Store at 4°C; use within 48–72 hours of reconstitution
• Protect from oxidising conditions; the free Cys8 residue is susceptible to oxidative dimerisation under aerobic conditions — consider nitrogen or argon overlay for long-term reconstituted storage
• Do not subject to repeated freeze-thaw cycles; peptide integrity and Cys8 redox state may be compromised
• Protect from prolonged light exposure and elevated temperatures

Frequently Asked Questions

Q: What is Humanin, and what is it investigated for in research? A: Humanin (HN) is a synthetic mitochondria-derived 24-amino acid micropeptide investigated in preclinical and in vitro research contexts for neuroprotection against Alzheimer's disease-related neuronal death, Bax-mediated apoptosis inhibition, CNTFR/gp130 cytokine receptor signalling, and cerebral ischaemia-reperfusion injury models. It is not approved by the FDA for human use and is intended strictly for laboratory and research purposes.

Q: What is HNG, and how does it differ from native Humanin? A: HNG (Humanin-glycine) is a synthetic analogue of Humanin with a serine-to-glycine substitution at position 14 (S14G). In neuroprotection assay systems, HNG has been characterised as up to 1000-fold more potent than native Humanin, depending on the assay system. HNG is the primary analogue employed in Alzheimer's disease rodent model studies. The S14G substitution is associated with reduced helical propensity and increased conformational flexibility relative to wild-type Humanin, which is proposed to contribute to its enhanced receptor binding and Bax inhibition activity.

Q: How was Humanin discovered? A: Humanin was discovered in 2001 by Hashimoto, Niikura, and Nishimoto at Keio University, Tokyo, via a functional cDNA library screen of occipital cortex from an Alzheimer's disease patient. The screen identified clones capable of suppressing neuronal cell death induced by familial AD mutant genes. The isolated cDNA encoded a 24-amino acid peptide, which was designated Humanin and characterised in two foundational 2001 papers (BBRC PMID 11327724; PNAS PMID 11371646).

Q: Why is Cys8 important for Humanin's activity? A: Cysteine at position 8 has been identified as a critical residue for Humanin's Bax-binding and neuroprotective activity. Substitution of Cys8 with any of the 19 other amino acids results in a drastic loss of neuroprotective function in isolated cell assay systems. This makes Cys8 integrity critical for experimental consistency; oxidative dimerisation or modification of Cys8 under aerobic storage conditions will reduce or abolish the compound's activity in cell-based assays.

Q: How should Humanin be stored to maintain stability? A: Lyophilized Humanin should be stored at −20°C in a sealed, light-protected container with desiccant. Once reconstituted, solutions should be stored at 4°C and used within 48–72 hours. Repeated freeze-thaw cycles should be avoided. Due to the free Cys8 residue's susceptibility to oxidative dimerisation, reconstituted solutions should be protected from atmospheric oxygen; nitrogen or argon overlay may be used for working stocks requiring extended storage.

Q: What toxicity observations have been reported for Humanin in preclinical studies? A: Published preclinical studies in rodent models have not reported significant toxicity at neuroprotective doses of Humanin or HNG. No acute toxicity findings have been characterised in the published literature at research-relevant concentrations. No human safety or tolerability data have been established. Observations should not be extrapolated to human or animal outcomes. Visit RCD Bio to explore our full research compound catalog.