Humanin

1. Overview

Humanin is a 24-amino acid mitochondrial-derived peptide (MDP) with the sequence MAPRGFSCLLLLTSEIDLPVKRRA and an approximate molecular weight of 2,687 Da [1]. It was discovered in 2001 by Yuichi Hashimoto and colleagues at KEIO University in Tokyo through functional expression screening of a cDNA library constructed from the occipital lobe of an Alzheimer's disease (AD) patient [1]. This discovery was paradigm-shifting: humanin was the first bioactive peptide shown to be encoded by a short open reading frame (sORF) within the mitochondrial genome, specifically within the 16S ribosomal RNA gene (MT-RNR2), challenging the longstanding view that mitochondrial DNA encodes only 13 proteins, 22 tRNAs, and 2 rRNAs.

Humanin is the founding member of the mitochondrial-derived peptide (MDP) family, which now includes MOTS-c (discovered 2015) and the small humanin-like peptides SHLP1-6 (discovered 2016). Together, these peptides represent a class of retrograde mitochondrial signals that regulate nuclear gene expression, cellular stress responses, and systemic metabolism.

The peptide was originally named "humanin" because it was identified as a factor that rescues human neurons from death -- it abolished cell death caused by three distinct familial Alzheimer's disease genes (V642I-APP, M146L-PS1, N141I-PS2) and by amyloid-beta (Abeta) itself [1]. The protective effect was strictly dependent on the primary structure of the peptide, and humanin was found to be secreted extracellularly, acting in both autocrine and paracrine fashion [1].

Since its discovery, humanin has been shown to exert cytoprotective effects far beyond the nervous system, including cardioprotection, insulin sensitization, anti-inflammatory activity, and longevity promotion. Circulating humanin levels decline with age in both rodents and humans, are reduced in Alzheimer's disease and coronary artery disease, remain stable in exceptionally long-lived naked mole-rats, and are elevated in children of centenarians [7][17]. The S14G-humanin analog (HNG), in which serine at position 14 is replaced by glycine, exhibits approximately 1,000-fold greater potency than native humanin and has become the standard tool compound for in vivo research [8].

Amino Acid Sequence

MAPRGFSCLLLLTSEIDLPVKRRA (24 residues)

Molecular Weight

~2687 Da

Encoded By

Mitochondrial 16S rRNA gene (MT-RNR2)

Discovery

Hashimoto et al. 2001, functional expression screening from AD patient brain

Primary Mechanisms

CNTFR/WSX-1/gp130 trimeric receptor -> JAK2/STAT3; BAX antagonism; IGFBP-3 binding; FPRL1/FPRL2 activation

Key Target Tissues

Brain (neurons), heart, liver, skeletal muscle, vasculature

FDA Status

Not approved for any therapeutic use

Most Potent Analog

S14G-Humanin (HNG) -- ~1000x potency vs. native humanin

2. Mechanism of Action

Humanin operates through at least four distinct molecular mechanisms, an unusual feature for a 24-amino acid peptide. These mechanisms are not mutually exclusive and may function in concert depending on cell type and context.

2.1 Trimeric Receptor Complex (CNTFR/WSX-1/gp130) and JAK2/STAT3 Signaling

The best-characterized signaling pathway for humanin involves binding to a heterotrimeric cell-surface receptor complex composed of ciliary neurotrophic factor receptor alpha (CNTFR), WSX-1 (IL-27 receptor alpha), and gp130 (the common signal-transducing subunit of the IL-6 receptor family) [6]. This receptor complex resembles IL-6 family cytokine receptors and, upon humanin binding, triggers hetero-oligomerization and activation of the JAK2 (Janus kinase 2) / STAT3 (signal transducer and activator of transcription 3) signaling cascade [5][6].

Hashimoto et al. (2009) demonstrated that gp130 is essential for humanin-induced neuroprotection, and that overexpression of CNTFR and WSX-1 enhanced humanin binding to cells [6]. The importance of STAT3 activation was established by Hashimoto et al. (2005), who showed that humanin's neuroprotective effects in F11 neuronal cells are mediated by STAT3 and specific tyrosine kinases [5]. Downstream, STAT3 activation promotes transcription of survival genes and anti-apoptotic factors.

This trimeric receptor mechanism appears to be the primary pathway through which humanin provides neuroprotection. In studies using humanin analogs with selective disruption of different binding domains, the membrane receptor antagonist HN-L12A completely abolished protective effects, confirming the centrality of receptor-mediated signaling [11].

2.2 BAX Antagonism and Anti-Apoptotic Activity

A landmark 2003 study published in Nature by Guo et al. demonstrated that humanin directly interferes with Bax-mediated apoptosis [2]. Bax is a pro-apoptotic member of the Bcl-2 protein family that, upon activation, translocates from the cytosol to the outer mitochondrial membrane, oligomerizes, and forms pores that release cytochrome c to trigger the intrinsic apoptosis cascade.

Humanin blocks this pathway at multiple levels: it prevents BAX translocation from cytosol to mitochondria, inhibits BAX oligomerization at the membrane, and blocks the related pro-apoptotic factor Bid from activating BAX [2][14]. Ma and Liu (2018) further elucidated that humanin decreases mitochondrial outer membrane permeability by directly inhibiting membrane association and oligomerization of both Bax and Bid proteins [14]. Reducing endogenous humanin levels using siRNA rendered cells more vulnerable to Bax-mediated death, confirming humanin's role as an endogenous anti-apoptotic factor [2].

2.3 IGFBP-3 Interaction

In 2003, Ikonen et al. demonstrated through co-immunoprecipitation that humanin directly binds to insulin-like growth factor-binding protein 3 (IGFBP-3) through its heparin-binding domain [3]. IGFBP-3 is the most abundant circulating IGF-binding protein and possesses IGF-independent pro-apoptotic activity. The humanin-IGFBP-3 interaction is functionally complex: humanin blocks IGFBP-3-induced apoptosis in some cell types (glioblastoma), yet in primary neurons, IGFBP-3 markedly potentiated humanin's rescue ability from amyloid-beta toxicity [3].

This interaction modulates the IGF-1 signaling axis, with humanin and IGFBP-3 having opposing effects on cell survival in certain contexts. Notably, IGFBP-3 binding does not appear to be required for all of humanin's protective effects -- in testicular tissue, HNG-F6A (a humanin analog lacking IGFBP-3 binding capacity) retained full cytoprotective activity [11].

2.4 Formyl Peptide Receptor Binding (FPRL1/FPRL2)

Harada et al. (2004) discovered that humanin functions as a ligand for the formyl peptide receptor-like receptors FPRL1 and FPRL2, which are G protein-coupled receptors expressed on immune cells and neurons [4]. N-formylated humanin (fHN) was substantially more potent as a FPRL1 ligand than unmodified humanin (EC50 of 0.012 nM vs. 3.5 nM), and both variants exhibited strong chemotactic activity [4].

The formyl peptide receptor pathway is particularly relevant because the mitochondrial genome, like its bacterial ancestor, produces N-formylated proteins, making humanin a natural ligand for these pattern-recognition receptors. Zhu et al. (2022) showed that FPR2 (formerly FPRL1) mediates both amyloid-beta neurotoxicity and humanin's neuroprotective effects, revealing a competitive mechanism at the receptor level [20]. However, Hashimoto et al. (2005) found that disrupting FPR2 expression did not prevent humanin's neuroprotection in F11 neuronal cells, suggesting the trimeric receptor pathway may be dominant in neurons [5].

2.5 Central Nervous System Signaling

Muzumdar et al. (2009) demonstrated that humanin acts centrally in the brain to regulate peripheral metabolism [7]. Intracerebroventricular (ICV) infusion of humanin significantly improved whole-body insulin sensitivity through activation of hypothalamic STAT-3 signaling. Gong et al. (2015) extended this finding by showing that both ICV and intravenous HNG acutely increased hepatic triglyceride secretion, and that vagotomy blocked these effects, identifying a brain-liver axis mediated by vagal signaling [12]. This central mechanism links humanin to metabolic regulation beyond its direct cellular cytoprotective actions.

3. Researched Applications

3.1 Neuroprotection and Alzheimer's Disease

Evidence level: Preclinical (in vitro and animal studies) with human biomarker data

Humanin was discovered in the context of Alzheimer's disease and neuroprotection remains its best-characterized function. The original Hashimoto et al. (2001) study showed that humanin abolished neuronal cell death caused by three familial AD genes (V642I-APP, M146L-PS1, N141I-PS2) and by amyloid-beta itself [1]. Subsequent studies demonstrated that [Gly14]-humanin (HNG) protected against amyloid-beta peptide-induced impairment of spatial learning and memory in rats.

The neuroprotective mechanism involves multiple pathways: STAT3-mediated transcription of survival genes via the trimeric receptor [5][6], direct BAX antagonism preventing mitochondrial apoptosis [2][14], and competitive binding at FPR2 against amyloid-beta [20]. Humanin also improves hippocampal acetylcholine levels and attenuates oxidative stress in AD models.

Circulating humanin levels are reduced in AD patients compared to healthy controls [17]. The P3S variant (proline to serine at position 3), found to be enriched in centenarians who carry the APOE4 allele -- the strongest genetic risk factor for AD -- showed protective effects against APOE4-induced brain pathology in mice [21]. This provides a natural genetic example of humanin variants modifying Alzheimer's risk.

3.2 Cardiovascular Protection

Evidence level: Preclinical (rodent and porcine studies) with human biomarker data

Cardiovascular protection by humanin has been documented across multiple models and species. Muzumdar et al. (2010) first demonstrated that HNG reduced myocardial infarct size dose-dependently in mice and activated AMPK signaling [8]. Klein et al. (2013) showed that HNG reduced intracellular reactive oxygen species, preserved mitochondrial membrane potential and ATP levels in cardiac myoblasts subjected to oxidative stress, activating catalase and glutathione peroxidase within minutes [9]. Thummasorn et al. (2016) confirmed cardioprotection in rats through attenuation of mitochondrial dysfunction during ischemia-reperfusion [13].

The most clinically significant preclinical advance came from Sharp et al. (2020), who demonstrated HNG efficacy at 2 mg/kg in a porcine model of myocardial ischemia-reperfusion, providing the first large-animal validation [18].

Long-term treatment also shows benefit. Qin et al. (2018) treated mice with HNG twice weekly for 14 months (from age 18 to 32 months) and found significantly increased cardiomyocyte-to-fibroblast ratios, decreased collagen deposition, and activation of Akt/GSK-3beta signaling -- demonstrating prevention of age-related cardiac fibrosis [15].

In human observational studies, Widmer et al. (2013) found that patients with preserved coronary endothelial function had significantly higher circulating humanin levels (2.2 +/- 1.5 ng/mL vs. 1.3 +/- 1.1 ng/mL, P=0.03) [10]. Cai et al. (2022) studied 327 subjects and found that circulating humanin was progressively lower from controls to angina to myocardial infarction patients, identifying low humanin as an independent risk factor for coronary artery disease [19].

3.3 Metabolic and Insulin-Sensitizing Effects

Evidence level: Preclinical (animal studies) with human correlative data

Muzumdar et al. (2009) demonstrated that humanin is a central regulator of peripheral insulin action [7]. Central (ICV) humanin infusion significantly improved insulin sensitivity through hypothalamic STAT-3 activation, and peripheral HNG administration reproduced these effects. Critically, humanin levels declined with age in both rodent tissues and human plasma, suggesting this decline contributes to age-related metabolic deterioration [7].

Gong et al. (2015) showed that humanin regulates hepatic lipid metabolism: HNG acutely increased triglyceride secretion from the liver, reducing hepatic steatosis in obese mice through a vagus nerve-dependent brain-liver axis [12]. This mechanism links humanin to central regulation of peripheral lipid homeostasis.

The insulin-sensitizing and metabolic effects of humanin have implications for type 2 diabetes as a shared pathological process with neurodegeneration, as originally proposed by Muzumdar et al. [7].

3.4 Aging, Longevity, and Centenarian Associations

Evidence level: Preclinical (multi-species) with human genetic and biomarker data

The relationship between humanin and aging has been characterized across multiple species and human cohorts. Yen et al. (2020) conducted a landmark multi-species study showing that humanin extended lifespan in C. elegans through daf-16/Foxo pathways, that transgenic mice overexpressing humanin showed improved metabolic profiles, and that middle-aged mice treated with HNG had improved metabolic healthspan [17]. Particularly notable were two findings: humanin levels remained stable in naked mole-rats (which live approximately 30 years, far exceeding predictions for their body size), while declining in normal mice; and children of centenarians had significantly elevated circulating humanin levels compared to age-matched controls [17].

Conte et al. (2019) analyzed 693 subjects aged 21-113 years and found that plasma humanin (along with FGF21 and GDF15) increased with age, with the highest levels found in centenarians [16]. However, the authors noted an inverse correlation between these mitokine levels and survival in the oldest subjects, consistent with a hormetic model where elevated levels may reflect both the organism's compensatory stress response and the burden of mitochondrial damage in extreme old age [16].

Miller et al. (2024) identified the P3S humanin variant as enriched in centenarians carrying APOE4, demonstrating that naturally occurring humanin variants can modify disease risk and potentially contribute to exceptional longevity [21].

3.5 Anti-Inflammatory and Immune Effects

Evidence level: Early preclinical

A 2025 study by Maraux et al. discovered that human macrophages actively produce and secrete humanin during efferocytosis -- the clearance of apoptotic cells, a process critical for resolving inflammation [22]. Macrophage-derived humanin promoted the resolution of inflammation in both in vitro and in vivo models, identifying a previously unknown endogenous source of humanin and expanding its functional repertoire to include immune regulation.

4. Clinical Evidence Summary

5. Dosing in Research

The following table summarizes doses used in published preclinical research studies. These are not therapeutic recommendations. Humanin and its analogs are not approved for human use, and no human dosing studies have been published. The vast majority of in vivo studies use the S14G-humanin (HNG) analog due to its approximately 1,000-fold greater potency compared to native humanin.

6. Pharmacokinetics

Native Humanin

Native humanin (24 amino acids, ~2,687 Da) has limited pharmacokinetic data in the published literature. No formal PK studies in humans have been conducted. Based on its size and structure, native humanin is expected to have a plasma half-life in the range of minutes, consistent with other small unmodified peptides. The primary route of clearance is presumed to be enzymatic degradation by circulating and tissue peptidases, with renal filtration as a secondary pathway given its low molecular weight.

S14G-Humanin (HNG) Analog Stability

The S14G substitution (serine to glycine at position 14) was specifically engineered to enhance stability and potency. HNG exhibits approximately 1,000-fold greater biological activity than native humanin across neuroprotective, cardioprotective, and metabolic assays [8]. This dramatic potency enhancement allows effective in vivo dosing at concentrations where native humanin would be insufficient due to rapid degradation. Key observations from in vivo studies suggest adequate stability for therapeutic effects:

• Acute IV dosing: Sharp et al. (2020) administered a single 2 mg/kg IV dose of HNG in pigs and observed significant cardioprotection (reduced infarct size), indicating sufficient circulating levels to reach cardiac tissue and exert effects within the ischemia-reperfusion timeframe [18].
• Chronic IP dosing: Qin et al. (2018) administered HNG at 4 mg/kg twice weekly IP for 14 months in mice with sustained cardiac remodeling benefits, demonstrating that intermittent dosing (every 3-4 days) maintains therapeutic efficacy [15]. This suggests either sufficient tissue accumulation, sustained downstream signaling, or both.
• ICV administration: Muzumdar et al. (2009) showed that a single 2.25 nmol ICV bolus of humanin produced measurable systemic insulin-sensitizing effects, indicating central-to-peripheral signal transduction that extends the effective pharmacodynamic window beyond the expected peptide half-life [7].

Endogenous Levels and Age-Related Decline

Circulating humanin levels have been measured in several human cohorts:

• Healthy adults: Plasma humanin in the low ng/mL range. Widmer et al. (2013) measured mean levels of 1.3-2.2 ng/mL in patients undergoing coronary angiography, with higher levels in those with preserved endothelial function [10].
• Age-related decline: Humanin levels decline with age in both mice and humans [7][17]. Yen et al. (2020) documented this decline across rodent tissues and human plasma samples [17].
• Centenarian paradox: Despite the general age-related decline, Conte et al. (2019) found that centenarians (n=693 subjects, ages 21-113) had the highest plasma humanin levels, along with FGF21 and GDF15 [16]. This apparent paradox is interpreted as reflecting an elevated compensatory stress response in the oldest survivors.
• Children of centenarians: Yen et al. (2020) found significantly elevated circulating humanin in children of centenarians compared to age-matched controls, suggesting a heritable component to humanin regulation [17].
• Coronary artery disease: Cai et al. (2022) showed progressively lower humanin from controls to angina to MI patients (n=327) [19].

Distribution

Humanin is expressed in multiple tissues including brain, retina, heart, liver, skeletal muscle, testes, and vasculature [1][7]. It is both an intracellular factor (localizing to mitochondria, cytoplasm, and potentially the nucleus) and a secreted peptide that acts in autocrine, paracrine, and endocrine fashion [1]. The peptide has been detected in cerebrospinal fluid, suggesting BBB penetration or local CNS production.

Route Considerations

• Intravenous: Rapid onset; used in acute models (MI/R, insulin sensitization). Single 2 mg/kg IV dose effective in porcine MI/R [18].
• Intraperitoneal: Most common route in chronic mouse studies. 4 mg/kg twice weekly maintains effects over 14 months [15].
• Intracerebroventricular: Targets central mechanisms; 2.25 nmol bolus produces systemic insulin sensitization via hypothalamic STAT3 [7]. Effects are vagus nerve-dependent [12].
• Oral: Not studied; expected negligible bioavailability due to gastrointestinal proteolysis.

7. Dose-Response Relationships

Neuroprotection

The dose-response for humanin's neuroprotective effects has been characterized primarily in vitro:

• Native humanin: EC50 for protection against Abeta-induced neuronal death is in the low micromolar range (1-10 mcM) in cell culture [1].
• HNG (S14G-humanin): EC50 approximately 100 pM to 1 nM -- representing the approximately 1,000-fold potency enhancement conferred by the S14G substitution [1][8]. This potency gain makes in vivo neuroprotection feasible at systemically administered doses.
• Structure-activity relationship: Deletion or mutation of residues 3-19 abolishes neuroprotective activity. The C8P mutation disrupts BAX binding; the L12A mutation blocks trimeric receptor binding; the F6A mutation eliminates IGFBP-3 interaction -- each providing tools to dissect the relative contribution of each mechanism [2][11][14].

Cardioprotection

Muzumdar et al. (2010) established the cardiac dose-response for HNG in mouse MI/R [8]:

• 0.4 mg/kg IV: Partial infarct size reduction.
• 2 mg/kg IV: Near-maximal infarct size reduction with enhanced cardiac function and AMPK activation.
• 4 mg/kg IV: Maximal protection; no significant additional benefit over 2 mg/kg.
• Porcine model: Sharp et al. (2020) used 2 mg/kg IV in pigs with successful infarct size reduction, validating the rodent dose-response in a large animal model [18].

Insulin Sensitization

• Central (ICV) dosing: A single 2.25 nmol bolus of humanin improved whole-body insulin sensitivity through hypothalamic STAT3 activation [7].
• Peripheral (IV) dosing: HNG analogs at varying doses reproduced insulin-sensitizing effects, though the peripheral dose-response curve has not been as precisely defined as the cardiac dose-response [7].
• Chronic dosing: 4 mg/kg HNG twice weekly IP improved metabolic healthspan in middle-aged mice (Yen et al. 2020) [17].

Anti-Apoptotic Activity

• In vitro BAX antagonism: Humanin prevents BAX translocation to mitochondria at concentrations as low as 10 nM (HNG) [2].
• Formyl peptide receptor binding: N-formylated humanin (fHN) activates FPRL1 with EC50 of 0.012 nM; unmodified humanin has EC50 of 3.5 nM -- a 290-fold difference [4].
• Chemotherapy protection: HNG protected testicular germ cells from cyclophosphamide-induced apoptosis in vivo at standard doses, with the antagonist HN-L12A completely blocking protection [11].

Long-Term Anti-Aging Dose-Response

Qin et al. (2018) administered HNG at 4 mg/kg twice weekly for 14 months (ages 18-32 months in mice) and observed dose-sustained (not dose-escalated) benefits [15]:

• Significant increase in cardiomyocyte-to-fibroblast ratio.
• Decreased collagen deposition (quantified histologically).
• Reduced fibroblast proliferation markers.
• Activated Akt/GSK-3beta pathway.
• No evidence of tachyphylaxis or tolerance development over 14 months of chronic dosing.

8. Comparative Effectiveness

Humanin vs. MOTS-c

Both are mitochondrial-derived peptides, but they serve fundamentally different biological roles:

| Feature | Humanin | MOTS-c | |---------|---------|--------| | Gene location | 16S rRNA (MT-RNR2) | 12S rRNA (MT-RNR1) | | Size | 24 amino acids | 16 amino acids | | Primary mechanism | CNTFR/WSX-1/gp130 receptor, BAX antagonism | Folate cycle inhibition, AMPK, CK2 | | Primary function | Cytoprotection, neuroprotection | Metabolic regulation, exercise mimetic | | Target tissues | Brain, heart, vasculature | Skeletal muscle, adipose | | Signaling | JAK2/STAT3, anti-apoptotic | AMPK/PGC-1alpha, NRF2/ARE | | Potent analog | HNG (~1000x potency) | None developed | | Centenarian data | P3S variant protects APOE4 carriers; elevated in children of centenarians | K14Q variant alters diabetes/muscle phenotype | | Clinical translation | Porcine MI/R model validated | No large-animal studies |

The two MDPs appear to represent complementary arms of a mitochondrial signaling system: humanin for cellular survival and stress resistance, MOTS-c for metabolic adaptation and energy homeostasis. No studies have examined combined administration.

Humanin vs. SHLP1-6 (Small Humanin-Like Peptides)

The SHLPs were discovered in 2016, also encoded within the 16S rRNA gene, and include six peptides (SHLP1-6) with varying biological activities:

• SHLP2: Anti-apoptotic, insulin-sensitizing; shares functional similarities with humanin but acts through distinct signaling pathways. SHLP2 levels correlate with prostate cancer risk.
• SHLP6: Pro-apoptotic -- the only MDP with death-promoting activity, suggesting a role in tumor surveillance or tissue homeostasis.
• SHLP3: Promotes mitochondrial metabolism and cellular proliferation.
• Humanin remains the most extensively studied MDP with the strongest preclinical evidence base. No SHLP has reached the stage of large-animal validation.

Humanin vs. Neurotrophic Factors (BDNF, NGF, CNTF)

Humanin's neuroprotective mechanism (via the CNTFR/WSX-1/gp130 receptor complex) places it in functional comparison with other neurotrophic factors:

• BDNF (Brain-Derived Neurotrophic Factor): Acts via TrkB receptor; promotes neuronal survival, synaptic plasticity, and neurogenesis. BDNF does not specifically target amyloid-beta toxicity or BAX-mediated apoptosis.
• CNTF (Ciliary Neurotrophic Factor): Shares CNTFR and gp130 receptor components with humanin but uses a different signaling subunit (LIFRbeta instead of WSX-1). CNTF has been tested clinically for ALS and retinal degeneration with limited success.
• Humanin advantage: Unique combination of neuroprotection + cardioprotection + metabolic effects through multiple receptor systems. No other single neurotrophic factor provides this breadth of protection.

Centenarian Associations

The relationship between humanin and exceptional human longevity has been characterized through multiple lines of evidence:

• Circulating levels in centenarians: Conte et al. (2019) found the highest plasma humanin levels in centenarians among 693 subjects aged 21-113, though an inverse correlation with survival in the oldest group suggests a hormetic interpretation [16].
• Children of centenarians: Yen et al. (2020) demonstrated significantly elevated humanin levels in offspring of centenarians vs. age-matched controls, suggesting inherited high humanin production confers longevity advantage [17].
• Naked mole-rats: This exceptionally long-lived rodent (lifespan ~30 years vs. ~3 years for similar-sized mice) maintains stable humanin levels throughout life, unlike the age-related decline in normal mice [17].
• P3S variant: Miller et al. (2024) identified a humanin coding variant (P3S) enriched in centenarians who carry APOE4, the strongest AD genetic risk factor. P3S-humanin resisted APOE4-induced brain pathology in mice, providing a genetic mechanism by which some APOE4 carriers avoid dementia and achieve exceptional longevity [21].
• C. elegans lifespan: Humanin extended lifespan in C. elegans through daf-16/Foxo pathways, placing it in the insulin/IGF-1 signaling longevity network [17].

9. Safety and Side Effects

Preclinical Safety Profile

Humanin is an endogenous peptide naturally produced by human mitochondria and present in circulating plasma at measurable levels (1.3-2.2 ng/mL in healthy adults [10]), which provides a theoretical safety advantage over fully synthetic therapeutic compounds [7][10].

Quantitative Preclinical Safety Data

• Acute IV dosing (mice): HNG at 0.4-4 mg/kg IV in the MI/R model -- no adverse hemodynamic effects, no arrhythmias, no mortality attributable to treatment [8].
• Acute IV dosing (pigs): HNG at 2 mg/kg IV in Yorkshire pigs -- no adverse hemodynamic events, no arrhythmias, stable blood pressure throughout the experiment [18].
• Chronic IP dosing (14 months): HNG at 4 mg/kg twice weekly from age 18 to 32 months in mice -- the longest MDP treatment study published. No toxicity, no weight loss, no behavioral abnormalities. Only beneficial cardiac outcomes (increased cardiomyocyte-to-fibroblast ratio, decreased collagen deposition) [15].
• Multi-species lifespan study: Yen et al. (2020) administered HNG to middle-aged mice chronically with improved metabolic healthspan and no reported adverse effects [17]. Transgenic humanin-overexpressing mice showed improved metabolic profiles without reported pathology [17].
• C. elegans: Humanin extended lifespan without apparent toxicity [17].
• Testicular protection: HNG protected germ cells from cyclophosphamide toxicity in vivo without adverse reproductive effects [11].
• Body weight: Humanin treatment has not been associated with pathological weight changes in any study. Metabolic studies show improved insulin sensitivity and lipid metabolism without weight loss beyond normalization of HFD-induced obesity.
• Organ toxicity: No studies report formal histopathological organ surveys following humanin treatment, which remains a gap.

The S14G-Humanin (HNG) Analog

The S14G substitution (serine to glycine at position 14) was developed to overcome the relatively low potency of native humanin. HNG exhibits approximately 1,000-fold greater neuroprotective, cytoprotective, and metabolic activity compared to native humanin, and is the predominant form used in all in vivo research [8]. Other analogs include [Gly14]-humanin, HN-L12A (a receptor antagonist), HN-C8P (BAX-binding disrupted), and HNG-F6A (IGFBP-3-binding disrupted), which are used as pharmacological tools [11].

Unknown Risks and Considerations

Despite the favorable preclinical profile, significant safety unknowns remain:

• No human clinical trials: The safety, pharmacokinetics, and pharmacodynamics of exogenous humanin in humans have not been systematically evaluated.
• Potential tumor biology considerations: Humanin's anti-apoptotic activity theoretically could promote survival of malignant cells. Ha et al. (2024) showed that humanin activates integrin alphaV-TGFbeta signaling and promotes glioblastoma progression, raising concern about use in cancer-bearing individuals (PMID: 38942749).
• Complex dose-response in aging: Conte et al. (2019) found that while mitokine levels (including humanin) were highest in centenarians, they inversely correlated with survival in the oldest subjects [16], suggesting that supraphysiological levels may not be uniformly beneficial.
• Drug interactions: No studies have examined interactions between exogenous humanin and pharmaceutical agents.
• Long-term anti-apoptotic effects: Chronic suppression of BAX-mediated apoptosis could theoretically interfere with normal tissue homeostasis and tumor surveillance.
• Reproductive and developmental safety: No systematic data, although humanin and HNG have shown protective effects in reproductive tissue models [11].

Regulatory Status

Humanin and its analogs are not approved by the FDA or any other regulatory authority for human therapeutic use. No Investigational New Drug (IND) applications are on public record. No human clinical trials are registered on ClinicalTrials.gov as of March 2026. Humanin is available from peptide suppliers for research purposes only.

10. Related Peptides

See also: MOTS-c, SS-31 (Elamipretide), Epitalon, Semax

11. References

1. [1] Hashimoto Y, Niikura T, Tajima H, Yasukawa T, Sudo H, Ito Y, Kita Y, Kawasumi M, Kouyama K, Doyu M, Sobue G, Koide T, Tsuji S, Lang J, Kurokawa K, Nishimoto I. (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 U.S.A.. DOI PubMed
2. [2] Guo B, Zhai D, Cabezas E, Welsh K, Nouraini S, Satterthwait AC, Reed JC. (2003). Humanin peptide suppresses apoptosis by interfering with Bax activation. Nature. DOI PubMed
3. [3] Ikonen M, Liu B, Hashimoto Y, Ma L, Lee KW, Niikura T, Nishimoto I, Cohen P. (2003). Interaction between the Alzheimer's survival peptide humanin and insulin-like growth factor-binding protein 3 regulates cell survival and apoptosis. Proceedings of the National Academy of Sciences U.S.A.. DOI PubMed
4. [4] Harada M, Habata Y, Hosoya M, Nishi K, Fujii R, Kobayashi M, Hinuma S. (2004). N-Formylated humanin activates both formyl peptide receptor-like 1 and 2. Biochemical and Biophysical Research Communications. DOI PubMed
5. [5] Hashimoto Y, Suzuki H, Aiso S, Niikura T, Nishimoto I, Matsuoka M. (2005). Involvement of tyrosine kinases and STAT3 in Humanin-mediated neuroprotection. Life Sciences. DOI PubMed
6. [6] Hashimoto Y, Kurita M, Aiso S, Nishimoto I, Matsuoka M. (2009). Humanin inhibits neuronal cell death by interacting with a cytokine receptor complex or complexes involving CNTF receptor alpha/WSX-1/gp130. Molecular Biology of the Cell. DOI PubMed
7. [7] Muzumdar RH, Huffman DM, Atzmon G, Buettner C, Cobb LJ, Fishman S, Budagov T, Cui L, Einstein FH, Poduval A, Hwang D, Barzilai N, Cohen P. (2009). Humanin: a novel central regulator of peripheral insulin action. PLoS One. DOI PubMed
8. [8] Muzumdar RH, Huffman DM, Calvert JW, Jha S, Weinberg Y, Cui L, Nemkal A, Atzmon G, Klein L, Gundewar S, Ji SY, Lavu M, Predmore BL, Lefer DJ. (2010). Acute humanin therapy attenuates myocardial ischemia and reperfusion injury in mice. Arteriosclerosis, Thrombosis, and Vascular Biology. DOI PubMed
9. [9] Klein LE, Cui L, Gong Z, Su K, Muzumdar RH. (2013). A humanin analog decreases oxidative stress and preserves mitochondrial integrity in cardiac myoblasts. Biochemical and Biophysical Research Communications. DOI PubMed
10. [10] Widmer RJ, Flammer AJ, Herrmann J, Rodriguez-Porcel M, Wan J, Cohen P, Lerman LO, Lerman A. (2013). Circulating humanin levels are associated with preserved coronary endothelial function. American Journal of Physiology - Heart and Circulatory Physiology. DOI PubMed
11. [11] Jia Y, Ohanyan A, Lue YH, Swerdloff RS, Liu PY, Cohen P, Wang C. (2015). The effects of humanin and its analogues on male germ cell apoptosis induced by chemotherapeutic drugs. Apoptosis. DOI PubMed
12. [12] Gong Z, Su K, Cui L, Tas E, Zhang T, Dong HH, Yakar S, Muzumdar RH. (2015). Central effects of humanin on hepatic triglyceride secretion. American Journal of Physiology - Endocrinology and Metabolism. DOI PubMed
13. [13] Thummasorn S, Apaijai N, Kerdphoo S, Shinlapawittayatorn K, Chattipakorn SC, Chattipakorn N. (2016). Humanin exerts cardioprotection against cardiac ischemia/reperfusion injury through attenuation of mitochondrial dysfunction. Cardiovascular Therapeutics. DOI PubMed
14. [14] Ma ZW, Liu DX. (2018). Humanin decreases mitochondrial membrane permeability by inhibiting membrane association and oligomerization of Bax and Bid proteins. Acta Pharmacologica Sinica. DOI PubMed
15. [15] Qin Q, Mehta H, Yen K, Navarrete G, Brandhorst S, Wan J, Delrio S, Zhang X, Lerman LO, Cohen P, Lerman A. (2018). Chronic treatment with the mitochondrial peptide humanin prevents age-related myocardial fibrosis in mice. American Journal of Physiology - Heart and Circulatory Physiology. DOI PubMed
16. [16] Conte M, Ostan R, Fabbri C, Santoro A, Guidarelli G, Vitale G, Mari D, Sevini F, Capri M, Sandri M, Monti D, Franceschi C, Salvioli S. (2019). Human Aging and Longevity Are Characterized by High Levels of Mitokines. Journals of Gerontology Series A: Biological Sciences and Medical Sciences. DOI PubMed
17. [17] Yen K, Mehta HH, Kim SJ, Lue Y, Hoang J, Guerrero N, Port J, Bi Q, Navarrete G, Brandhorst S, Lewis KN, Wan J, Swerdloff R, Mattison JA, Buffenstein R, Breton CV, Wang C, Longo V, Atzmon G, Wallace D, Barzilai N, Cohen P. (2020). The mitochondrial derived peptide humanin is a regulator of lifespan and healthspan. Aging. DOI PubMed
18. [18] Sharp TE 3rd, Gong Z, Scarborough A, et al. (2020). Efficacy of a Novel Mitochondrial-Derived Peptide in a Porcine Model of Myocardial Ischemia/Reperfusion Injury. JACC: Basic to Translational Science. DOI PubMed
19. [19] Cai H, Cao P, Sun W, Shao W, Li R, Wang L, Zou L, Forno E, Muzumdar R, Gong Z, Zheng Y. (2022). Circulating humanin is lower in coronary artery disease and is a prognostic biomarker for major cardiac events in humans. Biochimica et Biophysica Acta - General Subjects. DOI PubMed
20. [20] Zhu Y, Lin X, et al. (2022). FPR2 mediates both amyloid-beta toxicity and humanin neuroprotection. Nature Communications. PubMed
21. [21] Miller B, Kim SJ, Cao K, Mehta HH, Thumaty N, Kumagai H, Iida T, McGill C, Pike CJ, Nurmakova K, Levine ZA, Sullivan PM, Yen K, Ertekin-Taner N, Atzmon G, Barzilai N, Cohen P. (2024). Humanin variant P3S is associated with longevity in APOE4 carriers and resists APOE4-induced brain pathology. Aging Cell. PubMed
22. [22] Maraux M, Vetter M, Zuffo LD, Bonnefoy F, Wetzel A, Varin A, Lamarthee B, Tassy O, Ducloux D, Saas P, Cherrier T. (2025). HUMANIN produced by human efferocytic macrophages promotes the resolution of inflammation. Cell Reports. PubMed