Humanin Peptide: A Research Review of the Mitochondrial-Derived Cytoprotective Peptide, Its Receptors and the HNG/HNGF6A Analogs

By Peptide Insider Research Team · 11 min read · Last updated 2026-09-08

Humanin (HN) is a 24-residue peptide encoded not in the nuclear genome but in a short open reading frame inside the mitochondrial 16S ribosomal RNA gene. Identified in 2001 as a factor that protected cultured neurons from familial Alzheimer's disease mutations, it became the first recognized mitochondrial-derived peptide (MDP) and the reference point for the later discovery of MOTS-c and the small humanin-like peptides. This review covers the biology of mitochondrial retrograde signaling, humanin's structure and its two receptor systems, the preclinical evidence by research domain, and the analogs (HNG, HNGF6A, colivelin) that dominate the literature. All content is provided strictly for research reference and is not intended for human or veterinary use.

Humanin at a glance

Attribute	Detail
Compound class	Mitochondrial-derived peptide (MDP); cytoprotective signaling peptide
Sequence	Met-Ala-Pro-Arg-Gly-Phe-Ser-Cys-Leu-Leu-Leu-Leu-Thr-Ser-Glu-Ile-Asp-Leu-Pro-Val-Lys-Arg-Arg-Ala (24 residues) [1]
Genetic origin	sORF within mitochondrial 16S rRNA (MT-RNR2); 13 nuclear MT-RNR2-like loci also predicted to encode humanin-like isoforms [1,12]
Cell-surface receptors	CNTFR-α/WSX-1/gp130 trimer (STAT3); FPR2/FPRL1 (ERK1/2) [4,5]
Intracellular partners	Bax, tBid, BimEL (apoptosis); IGFBP-3 (heparin-binding domain) [6,7]
Common research analogs	HNG (S14G), HNGF6A (S14G + F6A), colivelin (ADNF-HNG hybrid) [3,6,13]
Evidence stage	In-vitro and rodent preclinical; human data limited to endogenous-level cohort studies [10,13]

Introduction

In 2001 Hashimoto, Nishimoto and colleagues at Keio University reported an unusual experiment. Reasoning that a brain region spared by Alzheimer's disease should express protective genes, they built a cDNA library from the occipital lobe of an autopsy-confirmed Alzheimer's patient and screened it in a "death-trap" assay for clones that rescued neuronal cells from toxicity induced by familial Alzheimer's disease (FAD) genes. One clone abolished cell death caused by mutant amyloid precursor protein (V642I-APP, NL-APP), presenilin-1 (M146L) and presenilin-2 (N141I), as well as by Aβ_1–43. It encoded a 24-residue peptide, which the group named humanin [1]. Protection was selective: the peptide did not block death from glutamate, prion fragments or polyglutamine repeats [1,2].

The finding was surprising for two reasons. The rescue factor was a peptide rather than a classical neurotrophin, and its coding sequence mapped to the 16S rRNA gene of the mitochondrial genome — a region assumed to be non-coding [1]. Over the next decade the peptide was shown to bind Bax [7], to interact with IGFBP-3 [6], to signal through two distinct cell-surface receptors [4,5], and to act as a circulating factor whose levels change with age [8,10]. Its discovery prompted a systematic search of mitochondrial rRNA genes, yielding MOTS-c from the 12S rRNA and six small humanin-like peptides (SHLP1–6) from the 16S rRNA [9,10]. Humanin is therefore studied today less as a single molecule than as the prototype of a class.

Biological background: mitochondrial retrograde signaling

The mitochondrial genome is a 16.6-kb circle encoding 13 respiratory-chain proteins, 22 tRNAs and two rRNAs (12S and 16S). Its compactness led to the long-held view that it contained no other functional genes. Humanin overturned this assumption: its 75-nucleotide open reading frame lies inside MT-RNR2, the 16S rRNA gene, and the peptide can be translated either in the mitochondrion (using the mitochondrial code, which yields a 21-residue variant) or in the cytoplasm from exported transcripts (yielding the 24-residue form) [1,9]. Bodzioch and colleagues later identified 13 nuclear MT-RNR2-like loci — nuclear insertions of mitochondrial DNA — predicted to encode 15 humanin-like isoforms, at least ten of which are expressed in human tissues and respond to stressors such as staurosporine [12]. Which locus produces the humanin measured in blood remains an open question.

Conceptually, humanin belongs to the field of mitochondrial retrograde signaling: communication from the organelle back to the nucleus and to other cells. Lee, Yen and Cohen framed humanin as the "harbinger" of a broader set of mitochondrial-derived peptides that report on mitochondrial status and modulate stress resistance, apoptosis and metabolism [9]. Because it is secreted and detectable in plasma and cerebrospinal fluid, humanin is also studied as a candidate endocrine signal, with levels reported to be lower in aged rodents and humans and in mitochondrial disorders such as MELAS [8,10,13].

Compound structure and mechanism of action

Structure. Humanin is a short, largely hydrophobic peptide with a central Leu-Leu-Leu-Leu stretch flanked by charged termini. Structure–activity work in the original Keio studies mapped the neuroprotective core to residues Pro³–Pro¹⁹ and identified Cys⁸ and Ser¹⁴ as critical [2,3]. Substituting Ser¹⁴ with glycine produced S14G-humanin (HNG), reported to be roughly 1,000-fold more potent in neuronal rescue assays; this analog is now the workhorse of the field [3]. Alanine scanning showed that Phe⁶ is required for IGFBP-3 binding, giving rise to HNGF6A, an analog that retains receptor activity but no longer binds IGFBP-3 [6]. Conserved motifs at residues 5–11 (GFSCLLL) and 14–19 (SEIDLP) recur across species and nuclear isoforms; Pro¹⁹ versus Ser¹⁹ has been proposed to govern secretion [12].

Intracellular mechanism. Guo, Reed and colleagues showed in Nature that humanin binds the pro-apoptotic Bcl-2 family protein Bax, preventing its conformational activation and translocation from cytosol to the outer mitochondrial membrane, and thereby suppressing cytochrome c release; siRNA knockdown of endogenous humanin sensitized cells to Bax-induced death [7]. Subsequent work extended this to truncated Bid (tBid) and BimEL [13]. Ikonen and colleagues identified IGFBP-3 as a second partner via yeast two-hybrid screening: humanin binds the heparin-binding domain of IGFBP-3 without displacing IGF-I, and the interaction is context-dependent — antagonistic to IGFBP-3-induced apoptosis in glioblastoma cells but synergistic with humanin's rescue of primary neurons from Aβ [6].

Cell-surface mechanism. Two receptor systems have been characterized. Ying and colleagues reported that humanin is a ligand for the G protein-coupled formyl peptide receptor FPRL1 (now FPR2), a promiscuous receptor that also binds Aβ₄₂, and that humanin competes with Aβ at this site [5]. Hashimoto and colleagues then showed that neuroprotection against FAD insults requires a trimeric cytokine receptor composed of CNTF receptor-α, WSX-1 (IL-27Rα) and gp130, the shared subunit of the IL-6 family, with gp130 essential for activity [4]. Downstream, humanin activates STAT3 via JAK, ERK1/2 via MEK and AKT via PI3K; Kim and colleagues reported that these responses differ between young and old mouse hippocampus [11]. Centrally, hypothalamic STAT3 activation was shown to be required for humanin's effect on peripheral insulin action [8].

Evidence by research domain

Research domain	Typical models	Reported findings	Evidence maturity
Neuronal survival / Alzheimer's models	F11 and SH-SY5Y cells, primary cortical neurons; Aβ-injected and triple-transgenic mice	Rescue from FAD-gene and Aβ toxicity; HNG reduced Aβ accumulation and memory deficits in transgenic mice [1,2,3,15,16]	Extensive in vitro; multiple rodent studies
Apoptosis regulation	Cell lines, isolated mitochondria, siRNA knockdown	Binding to Bax blocks translocation and cytochrome c release; IGFBP-3 interaction modulates survival [6,7]	Mechanistic, well replicated
Metabolism / insulin action	Rat hyperinsulinemic-euglycemic clamps; Zucker diabetic fatty rats; aged mice	Central or IV humanin analogs increased peripheral insulin sensitivity via hypothalamic STAT3; endogenous levels fall with age [8,10,13]	Rodent preclinical
Cardiovascular	Mouse myocardial ischemia–reperfusion; ApoE-deficient mice	HNG reduced infarct size with AMPK–eNOS activation; HNGF6A preserved endothelial function and reduced aortic plaque area [14,17]	Rodent preclinical
Aging and lifespan biology	C. elegans, humanin-transgenic mice, human cohorts	Overexpression extended worm lifespan via daf-16/FOXO; levels decline with age in most species but not naked mole-rats; higher levels in centenarian offspring [13]	Model-organism and observational
Ocular / retinal cells	Human RPE cultures under oxidative and ER stress	Reduced senescence and apoptosis; preserved mitochondrial bioenergetics and glutathione [18]	In vitro

Neuroprotection and Alzheimer's disease models

The founding observation — that humanin abolishes neuronal death from FAD mutations and Aβ peptides — was extended by the same group to the Swedish mutant APP, where the peptide targeted both intracellular APP-triggered toxicity and extracellular Aβ toxicity [2]. In vivo, Tajima and colleagues reported that HNG prevented Aβ-induced memory impairment in mice [15], and Niikura and colleagues reported that a humanin derivative reduced Aβ accumulation and ameliorated memory deficits in triple-transgenic (3xTg-AD) mice [16]. These are behavioral and histological readouts in rodent models; they are not evidence of any effect in human disease.

Metabolic regulation

Muzumdar and colleagues used clamp methodology to show that intracerebroventricular humanin increased peripheral insulin sensitivity in rats, and that the effect required hypothalamic STAT3. Intravenous HNGF6A reproduced the effect, and a single exposure to HNG lowered blood glucose in Zucker diabetic fatty rats [8]. Cobb and colleagues reported parallel insulin-sensitizing activity for SHLP2 and SHLP3, together with age-dependent declines in circulating SHLP2 [10]. The metabolic literature therefore positions humanin as a centrally acting insulin sensitizer in rodents, sitting alongside MOTS-c, which acts through AMPK in skeletal muscle.

Cardiovascular models

In a mouse model of 45-minute coronary occlusion followed by reperfusion, HNG administered before ischemia or at reperfusion reduced infarct size relative to area-at-risk and preserved ejection fraction, with activation of AMPK–eNOS signaling and reduced Bax expression [14]. In ApoE-deficient mice on a high-cholesterol diet, 16 weeks of HNGF6A prevented endothelial dysfunction, reduced plaque area in the proximal aorta and restored eNOS expression without altering cholesterol [17]. Humanin has also been detected within human carotid plaque endothelium, suggesting an endogenous stress response [17].

Aging and lifespan biology

Yen and colleagues assembled evidence across species: humanin overexpression extended C. elegans lifespan in a daf-16/FOXO-dependent manner; humanin-transgenic mice resisted toxic insults; HNG treatment of middle-aged mice improved metabolic healthspan markers and lowered inflammatory markers; circulating humanin declined with age in most species examined but remained stable in the long-lived naked mole-rat; and offspring of centenarians had higher humanin levels than controls [13]. This body of work links humanin to the same FOXO axis targeted, by a different route, in FOXO4-DRI research.

Humanin vs. HNG, HNGF6A, MOTS-c and SS-31

Compound	Origin / structure	Primary mechanism	How it differs from humanin
Humanin (HN)	24 aa, MT-RNR2 sORF	Bax/IGFBP-3 binding; CNTFR/WSX-1/gp130 and FPR2 signaling	Reference compound; lowest potency of the series [1,7]
HNG (S14G-HN)	Synthetic; Ser14→Gly	Same targets as HN	~1,000-fold higher potency in neuronal assays; most-used tool analog [3]
HNGF6A	Synthetic; S14G + F6A	Receptor signaling retained; IGFBP-3 binding abolished	Separates receptor pathway from IGFBP-3 interaction [6,8]
Colivelin	Hybrid of ADNF fragment + HNG	Neuroprotective at femtomolar range in vitro	Not a natural sequence; chimeric design [13]
MOTS-c	16 aa, MT-RNR1 (12S rRNA) sORF	AMPK activation, folate–methionine cycle, nuclear translocation	Different gene, receptor-independent metabolic mechanism [9]
SS-31 (elamipretide)	Synthetic tetrapeptide	Binds cardiolipin in inner membrane	Not mitochondrially encoded; membrane-targeted rather than signaling [9]

Limitations and research considerations

• Analog dominance. Most in-vivo data derive from HNG or HNGF6A rather than wild-type humanin; findings should not be assumed to transfer between analogs [3,6,8].
• Uncertain gene of origin. With 13 nuclear MT-RNR2-like loci, the source of circulating humanin and the relative contribution of mitochondrial versus nuclear transcripts are unresolved [12].
• Assay variability. Humanin immunoassays differ in specificity, and reported plasma concentrations vary widely across studies, complicating cross-study comparison [10,13].
• Receptor promiscuity. FPR2 binds many ligands, including Aβ; attributing effects to humanin at this receptor requires careful controls [5].
• No controlled human trials. Human data are observational measurements of endogenous humanin. The literature does not support any claim about human use [13].
• Peptide handling. The hydrophobic Leu⁹–Leu¹² core and free Cys⁸ make aggregation and oxidation practical concerns in solution; storage and reconstitution practices affect assay outcomes.

Where to source for research

Humanin and its analogs are available as lyophilized research-grade material from several suppliers serving the laboratory market. For in-vitro and analytical work the relevant selection criteria are batch-specific HPLC purity, mass-spectrometry identity confirmation, documented peptide content and clear research-use-only labeling. Short Chain Aminos lists mitochondrial-derived peptides with lot-level certificates of analysis; BioPep supplies research peptides with third-party testing documentation; Catalyst Research and Apex Research Services also carry research-grade peptide catalogs. Peptide Insider's supplier evaluation guide and suppliers directory outline documentation to request before purchase. None of these sources is endorsed over another; all material is for laboratory research only.

Frequently asked research questions

What is humanin?

Humanin is a 24-amino-acid peptide (MAPRGFSCLLLLTSEIDLPVKRRA) encoded by a short open reading frame inside the mitochondrial 16S ribosomal RNA gene (MT-RNR2). It was discovered in 2001 by functional screening of a cDNA library from the surviving occipital cortex of an Alzheimer's disease brain and is the founding member of the mitochondrial-derived peptide family [1,2].

Is humanin a mitochondrial-derived peptide like MOTS-c?

Yes. Humanin, MOTS-c and the six small humanin-like peptides (SHLP1-6) are all mitochondrial-derived peptides encoded by short open reading frames in mitochondrial rRNA genes. Humanin and the SHLPs come from the 16S rRNA gene; MOTS-c comes from the 12S rRNA gene. They differ in sequence, receptors and reported biology [9,10].

What is HNG (S14G-humanin)?

HNG is a synthetic analog of humanin in which serine-14 is replaced by glycine. In the original neuronal death assays it was reported to be roughly 1,000-fold more potent than the wild-type peptide, and it has since become the most widely used tool compound in humanin research, including cardiac, metabolic and neurological rodent models [3,13].

What receptors does humanin bind?

Two cell-surface receptor systems have been reported: a trimeric cytokine receptor composed of CNTFR-alpha, WSX-1 and gp130 that signals through JAK/STAT3, and the G protein-coupled formyl peptide receptor FPR2 (formerly FPRL1) that signals through ERK1/2. Intracellularly, humanin binds the pro-apoptotic protein Bax and the carrier protein IGFBP-3 [4,5,6,7].

Does humanin decline with age?

Multiple studies report that circulating and tissue humanin levels fall with age in rodents and humans, while the naked mole-rat maintains stable levels. Offspring of centenarians were reported to have higher circulating humanin than age-matched controls. These are correlational observations from preclinical and cohort studies, not evidence of any human application [8,10,13].

What is the difference between humanin and HNGF6A?

HNGF6A carries two substitutions relative to wild-type humanin: S14G (which raises potency) and F6A (which abolishes binding to IGFBP-3). It was designed to separate receptor-mediated signaling from the IGFBP-3 interaction and has been used in insulin-clamp and atherosclerosis models in rodents [6,8,14].

Is humanin research preclinical?

Yes. The evidence base consists of in-vitro cell models, rodent studies and observational human cohort data measuring endogenous humanin. No completed controlled human efficacy trials of exogenous humanin or its analogs have been published. Humanin is supplied strictly as a research-use-only reference material [10,13].

Works Cited

1. Hashimoto Y, Niikura T, Tajima H, et al. “A rescue factor abolishing neuronal cell death by a wide spectrum of familial Alzheimer's disease genes and Aβ.” Proceedings of the National Academy of Sciences USA. 2001;98(11):6336–6341. PMID: 11371646. DOI: 10.1073/pnas.101133498.
2. Hashimoto Y, Niikura T, Ito Y, et al. “Detailed characterization of neuroprotection by a rescue factor humanin against various Alzheimer's disease-relevant insults.” Journal of Neuroscience. 2001;21(23):9235–9245. PMID: 11717357.
3. Hashimoto Y, Ito Y, Niikura T, et al. “Mechanisms of neuroprotection by a novel rescue factor humanin from Swedish mutant amyloid precursor protein.” Biochemical and Biophysical Research Communications. 2001;283(2):460–468. PMID: 11327724. DOI: 10.1006/bbrc.2001.4765.
4. Hashimoto Y, Kurita M, Aiso S, Nishimoto I, Matsuoka M. “Humanin inhibits neuronal cell death by interacting with a cytokine receptor complex or complexes involving CNTF receptor α/WSX-1/gp130.” Molecular Biology of the Cell. 2009;20(12):2864–2873. PMID: 19386761. DOI: 10.1091/mbc.e09-02-0168.
5. Ying G, Iribarren P, Zhou Y, et al. “Humanin, a newly identified neuroprotective factor, uses the G protein-coupled formylpeptide receptor-like-1 as a functional receptor.” Journal of Immunology. 2004;172(11):7078–7085. PMID: 15153530. DOI: 10.4049/jimmunol.172.11.7078.
6. Ikonen M, Liu B, Hashimoto Y, et al. “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 USA. 2003;100(22):13042–13047. PMID: 14561895. DOI: 10.1073/pnas.2135111100.
7. Guo B, Zhai D, Cabezas E, et al. “Humanin peptide suppresses apoptosis by interfering with Bax activation.” Nature. 2003;423(6938):456–461. PMID: 12732850. DOI: 10.1038/nature01627.
8. Muzumdar RH, Huffman DM, Atzmon G, et al. “Humanin: a novel central regulator of peripheral insulin action.” PLoS One. 2009;4(7):e6334. PMID: 19623253. DOI: 10.1371/journal.pone.0006334.
9. Lee C, Yen K, Cohen P. “Humanin: a harbinger of mitochondrial-derived peptides?” Trends in Endocrinology & Metabolism. 2013;24(5):222–228. PMID: 23402768. DOI: 10.1016/j.tem.2013.01.005.
10. Cobb LJ, Lee C, Xiao J, et al. “Naturally occurring mitochondrial-derived peptides are age-dependent regulators of apoptosis, insulin sensitivity, and inflammatory markers.” Aging (Albany NY). 2016;8(4):796–809. PMID: 27070352. DOI: 10.18632/aging.100943.
11. Kim SJ, Guerrero N, Wassef G, et al. “The mitochondrial-derived peptide humanin activates the ERK1/2, AKT, and STAT3 signaling pathways and has age-dependent signaling differences in the hippocampus.” Oncotarget. 2016;7(30):46899–46912. PMID: 27384491. DOI: 10.18632/oncotarget.10380.
12. Bodzioch M, Lapicka-Bodzioch K, Zapala B, Kamysz W, Kiec-Wilk B, Dembinska-Kiec A. “Evidence for potential functionality of nuclearly-encoded humanin isoforms.” Genomics. 2009;94(4):247–256. PMID: 19477263. DOI: 10.1016/j.ygeno.2009.05.006.
13. Yen K, Mehta HH, Kim SJ, et al. “The mitochondrial derived peptide humanin is a regulator of lifespan and healthspan.” Aging (Albany NY). 2020;12(12):11185–11199. PMID: 32575074. DOI: 10.18632/aging.103534.
14. Muzumdar RH, Huffman DM, Calvert JW, et al. “Acute humanin therapy attenuates myocardial ischemia and reperfusion injury in mice.” Arteriosclerosis, Thrombosis, and Vascular Biology. 2010;30(10):1940–1948. PMID: 20651283. DOI: 10.1161/ATVBAHA.110.205997.
15. Tajima H, Kawasumi M, Chiba T, et al. “A humanin derivative, S14G-HN, prevents amyloid-β-induced memory impairment in mice.” Journal of Neuroscience Research. 2005;79(5):714–723. PMID: 15678515. DOI: 10.1002/jnr.20391.
16. Niikura T, Sidahmed E, Hirata-Fukae C, Aisen PS, Matsuoka Y. “A humanin derivative reduces amyloid beta accumulation and ameliorates memory deficit in triple transgenic mice.” PLoS One. 2011;6(1):e16259. PMID: 21264226. DOI: 10.1371/journal.pone.0016259.
17. Oh YK, Bachar AR, Zacharias DG, et al. “Humanin preserves endothelial function and prevents atherosclerotic plaque progression in hypercholesterolemic ApoE deficient mice.” Atherosclerosis. 2011;219(1):65–73. PMID: 21763658. DOI: 10.1016/j.atherosclerosis.2011.06.038.
18. Sreekumar PG, Ishikawa K, Spee C, et al. “The mitochondrial-derived peptide humanin protects RPE cells from oxidative stress, senescence, and mitochondrial dysfunction.” Investigative Ophthalmology & Visual Science. 2016;57(3):1238–1253. PMID: 26990160. DOI: 10.1167/iovs.15-17053.

Research Use Only. The information above summarizes published preclinical literature and observational human data for laboratory reference. It is not medical advice and does not describe or endorse any human or veterinary use, dosing, or administration. Humanin and the analogs discussed here are intended solely for in-vitro and research applications. All content strictly for research reference; not for human or veterinary use.

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