Glossary of longevity peptide terms

62 concise definitions for terms used across this site — peptide names, mechanistic vocabulary, biology, regulatory framing and research methodology. Each entry links back from peptide pages and protocol pages.

A

AEDGAla-Glu-Asp-GlyPeptide compounds

The single-letter sequence designation for the synthetic tetrapeptide Epitalon (Ala-Glu-Asp-Gly), developed in the Khavinson cytomedine programme as a synthetic equivalent of the active fraction of the pineal polypeptide epithalamin.

AMPKAMP-activated protein kinaseMechanism

A master regulator of cellular energy homeostasis. Activated when cellular AMP:ATP ratio rises, it switches metabolism toward catabolic ATP-generating pathways (fatty-acid oxidation, glucose uptake) and away from anabolic pathways (lipogenesis, protein synthesis). Central to the mechanism of MOTS-c.

Amyloid-βBiology

A peptide fragment cleaved from amyloid precursor protein (APP) that accumulates in Alzheimer's-disease brain tissue. Aggregation into oligomers and plaques is one of the principal pathological hallmarks of Alzheimer's. Multiple peptide research compounds (Humanin) have been studied for protective effects against amyloid-β cytotoxicity.

Anabolic signallingMechanism

Cellular signalling pathways that drive protein synthesis, growth and tissue building. Includes mTORC1, IGF-1/insulin signalling and androgen-receptor pathways. Declines progressively across the adult lifespan, contributing to sarcopenia and recovery deficits.

ApoptosisBiology

Programmed cell death — the controlled, non-inflammatory form of cell death used to remove damaged, pre-malignant or surplus cells. Mediated by caspase enzyme cascade and pro-apoptotic Bcl-2 family proteins (Bax, Bid). Humanin's mechanism includes direct inhibition of Bax-mediated apoptosis.

B

BPC-157Body Protection Compound 157Peptide compounds

A 15-amino-acid synthetic peptide derived from a sequence found in gastric juice. Extensively studied in preclinical models for tendon, ligament, gastric mucosal and neural-tissue repair. Has not progressed into completed human RCT. UK regulatory status: unlicensed research compound.

C

CardiolipinBiology

A unique four-acyl phospholipid concentrated almost exclusively in the inner mitochondrial membrane. Essential for cristae structural integrity, respiratory-supercomplex assembly and the function of inner-membrane proteins. Oxidation and disorganisation of cardiolipin is a feature of aged mitochondria and is the binding target of SS-31/elamipretide.

Circadian rhythmBiology

Approximately 24-hour cycles in physiology and behaviour coordinated by the suprachiasmatic nucleus (SCN) clock gene cycling (BMAL1, CLOCK, PER, CRY). Disrupts with age, contributing to sleep-architecture decline. Pineal-axis peptides (Epitalon, Pinealon) are studied for circadian restoration in aged neural tissue.

CJC-1295Peptide compounds

A modified GHRH 1-29 analogue with amino-acid substitutions and (in the DAC variant) a drug-affinity-complex modification that binds circulating albumin. Without DAC: ~30-minute half-life producing brief enhanced pulsatile GH release. With DAC: 6–8 day half-life producing sustained GH elevation.

Connectivity MapCMapResearch methodology

A computational analysis methodology that compares a query gene-expression signature against a library of reference signatures from drug or perturbation experiments to identify mechanistic similarities. The 2014 Pickart laboratory paper used CMap analysis to classify GHK-Cu's transcriptional signature as a 'reverser' of multiple oncogenic and inflammatory states.

CytomedinesResearch methodology

Term coined in the Khavinson research programme at the St Petersburg Institute of Bioregulation and Gerontology to describe short bioregulatory peptides derived from tissue extracts. The cytomedine framework proposes that short tissue-derived peptides act as gene-regulatory signals selective for the tissue of origin.

D

Dendritic cellBiology

A major antigen-presenting cell type that bridges innate and adaptive immunity. Captures antigens, presents them to T cells in lymphoid tissue, and influences T-cell differentiation through cytokine secretion. Thymosin Alpha-1's principal mechanism involves TLR-mediated activation of dendritic-cell maturation.

DSIPDelta-Sleep-Inducing PeptidePeptide compounds

A nonapeptide identified in 1977 from cerebral venous blood of sleeping rabbits and named for its ability to increase delta-wave (slow-wave) activity in EEG recordings. The endogenous role is contested and the receptor identity is not definitively established.

E

ElamipretidePeptide compounds

The international non-proprietary name (INN) for SS-31, also known as Bendavia or MTP-131. A synthetic aromatic-cationic tetrapeptide that binds inner-mitochondrial-membrane cardiolipin. In clinical development with Stealth BioTherapeutics; not licensed.

EpitalonPeptide compounds

Synthetic tetrapeptide AEDG (Ala-Glu-Asp-Gly), developed in the Khavinson programme as a synthetic equivalent of pineal-polypeptide epithalamin active fraction. Studied for telomerase induction, pineal-axis restoration and lifespan extension in rodent models.

EpithalaminBiology

A polypeptide extract of bovine pineal gland from which Epitalon was derived as a synthetic equivalent. The original 'pineal polypeptide complex' studied by the Khavinson group in the 1970s and 1980s as a candidate ageing intervention.

F

FPRL1Formyl peptide receptor-like 1 / FPR2Mechanism

A G-protein-coupled receptor expressed on innate and adaptive immune cells. Part of the heterotrimeric receptor complex (with CNTFR and WSX-1/gp130) through which extracellular Humanin signals to produce its cytoprotective effects.

G

GHK-CuGlycyl-L-histidyl-L-lysine copperPeptide compounds

The copper(II)-bound form of the endogenous tripeptide GHK. First isolated from human plasma in 1973 by Loren Pickart. Plasma levels fall ~60% across the adult lifespan. Acts via copper trafficking to lysyl-oxidase, broad gene-expression modulation, and direct fibroblast/keratinocyte signalling.

GHRHGrowth hormone-releasing hormoneBiology

A 44-amino-acid hypothalamic peptide that signals to anterior pituitary somatotrophs to release growth hormone in pulses. The active N-terminal 29 residues constitute the GHRH 1-29 fragment that is the basis of synthetic GHRH analogues (Sermorelin, CJC-1295).

GHRPGrowth hormone-releasing peptidePeptide compounds

A class of synthetic peptide ghrelin-receptor agonists that stimulate pituitary GH release through GHS-R1a binding. Includes early-generation GHRP-2 and GHRP-6 (broader hormonal off-target effects) and selective compounds like Ipamorelin (minimal prolactin/cortisol effects).

GHS-R1aGrowth hormone secretagogue receptor 1aMechanism

The endogenous ghrelin receptor, expressed on anterior pituitary somatotrophs and hypothalamic neurons. Activation triggers phospholipase-C-mediated calcium signalling and complements GHRH-mediated cAMP signalling to drive GH release. Target of Ipamorelin and other GHRPs.

Glymphatic clearanceBiology

The brain's waste-clearance system, in which CSF-ISF exchange flushes metabolic waste (including amyloid-β) from the brain. Active predominantly during slow-wave sleep. Declines with age and is one of the mechanistic links between sleep-architecture preservation and cognitive ageing.

H

Hallmarks of ageingResearch methodology

The conceptual framework introduced by López-Otín et al. (Cell, 2013, expanded 2023) cataloguing the molecular and cellular processes contributing to biological ageing. Includes genomic instability, telomere attrition, mitochondrial dysfunction, cellular senescence, stem-cell exhaustion, altered intercellular communication, and others. Provides the mechanistic vocabulary for most longevity-peptide research.

HumaninHNPeptide compounds

A 24-amino-acid peptide encoded within the mitochondrial 16S ribosomal RNA gene. First mitochondrially-derived peptide (MDP) identified (Hashimoto 2001). Cytoprotective; plasma levels decline with age and are preserved in centenarians.

I

IGF-1Insulin-like growth factor 1Biology

A 70-amino-acid peptide produced predominantly by the liver in response to GH stimulation. Mediates most of the anabolic effects attributed to GH. Lower IGF-1 is associated with longer lifespan in multiple animal models and in some human cohorts — the 'IGF-1 longevity paradox'.

ImmunosenescenceBiology

The age-related decline of adaptive immunity, particularly naive T-cell output. Driven by progressive thymic involution beginning in early adulthood. Clinical consequences include reduced vaccine-response efficiency and increased vulnerability to novel pathogens. Target of Thymosin Alpha-1 research.

InflammagingBiology

Chronic low-grade elevation of inflammatory cytokines (IL-6, TNF-α, CRP) characteristic of aged tissues. Contributes to muscle ageing, vascular pathology, neurodegeneration and reduced effective immune-response capacity. GHK-Cu's transcriptional signature includes broad suppression of inflammaging-associated genes.

IpamorelinPeptide compounds

A selective GHS-R1a agonist developed by Novo Nordisk in the late 1990s. Distinguished from earlier-generation GHRPs by minimal off-target effects on prolactin, ACTH and cortisol release. Commonly combined with CJC-1295 in research-context GH-axis protocols.

K

Khavinson programmeResearch methodology

The continuous short-peptide research programme conducted at the St Petersburg Institute of Bioregulation and Gerontology, founded by Vladimir Khavinson. Includes Epitalon, Pinealon, Thymalin and a substantial catalogue of tissue-specific bioregulatory peptides.

M

MDPMitochondrially-derived peptideBiology

A class of peptides encoded within mitochondrial genome open reading frames (predominantly within rRNA gene sequences). Includes Humanin (16S rRNA), MOTS-c (12S rRNA) and the SHLP family. Function as endocrine mitokines.

MelatoninBiology

An indolamine produced by the pineal gland from serotonin via AANAT and HIOMT enzymatic steps. Synthesised in darkness; coordinates circadian sleep-wake rhythm. Pineal output declines progressively across the adult lifespan. Not a peptide.

MHRAMedicines and Healthcare products Regulatory AgencyRegulatory

The UK regulator responsible for medicinal product authorisation, pharmacovigilance and clinical-trial oversight. None of the peptides covered on this site holds an MHRA marketing authorisation for any therapeutic indication.

MitokineBiology

A signalling molecule released by mitochondria under stress that produces effects in distant tissues — by analogy with cytokine and adipokine biology. MOTS-c and Humanin are the canonical peptide mitokines.

MOTS-cMitochondrial Open-reading-frame of the Twelve S rRNA-cPeptide compounds

A 16-amino-acid mitochondrially-derived peptide encoded within the mitochondrial 12S rRNA gene. Identified 2015 (Lee et al.). Functions as an endogenous exercise-mimetic through AMPK activation in skeletal muscle.

N

NAD⁺Nicotinamide adenine dinucleotideBiology

A central cellular redox cofactor required for sirtuin activity, PARP-mediated DNA damage response and mitochondrial electron transport. Levels decline with age across human tissues. Targeted by small-molecule precursors NMN and NR (which are not peptides).

NMNNicotinamide mononucleotideChemistry

A small-molecule NAD⁺ precursor, not a peptide. Supplied as a nutraceutical in some jurisdictions for NAD⁺-axis support. Outside the primary scope of this peptide-focused site.

NRNicotinamide ribosideChemistry

A small-molecule NAD⁺ precursor and vitamin B3 form, not a peptide. Closely related to NMN. Outside the primary scope of this peptide-focused site.

O

Open-labelResearch methodology

A study design in which participants and investigators are aware of the treatment being administered (no blinding). Lower methodological strength than randomised double-blind designs. Most published human evidence for Epitalon and Pinealon comes from open-label observational cohorts.

P

PGC-1αPPAR-gamma coactivator-1 alphaMechanism

A transcriptional coactivator that drives mitochondrial biogenesis programmes. Upregulated by AMPK activation; downstream effector of exercise training and of MOTS-c administration. Reduced expression in aged tissues contributes to mitochondrial-dysfunction phenotypes.

Pineal glandBiology

A small endocrine gland in the brain producing melatonin and other neuroendocrine signals. Output declines progressively across the adult lifespan. Target of Khavinson short-peptide programme interventions (Epitalon, Pinealon).

PinealonPeptide compounds

Khavinson tripeptide Glu-Asp-Arg (EDR). Positioned within the cytomedine framework as a neurotropic short peptide, studied for neuroprotective effects and cognitive-function preservation in aged rodents.

PolysomnographyPSGResearch methodology

The clinical-standard sleep-study methodology, incorporating EEG, EMG, EOG and other physiological signals. Provides objective measurement of sleep architecture. Published peptide research on sleep has relied predominantly on self-report rather than PSG, limiting evidence quality.

R

Replicative senescenceBiology

The permanent cell-cycle arrest entered by somatic cells after a finite number of divisions (the Hayflick limit), driven by progressive telomere shortening. Foundation of telomere biology and a target of telomerase-activating peptide research (Epitalon).

RLSRisk Limited StatementRegulatory

Editorial framing applied to research-context peptide content where translational efficacy claims would be inappropriate. All peptide pages on this site lead with explicit research-only framing rather than therapeutic claims.

S

SarcopeniaBiology

Age-related loss of skeletal muscle mass and function. Diagnostic criteria include reduced grip strength, slow gait speed and reduced appendicular lean-mass index. UK-recognised clinical diagnosis. Target of GH-axis and mitochondrial-peptide research.

SARMSelective androgen receptor modulatorChemistry

A class of small-molecule (not peptide) androgen-receptor agonists. Often discussed alongside peptide research-protocol literature but mechanistically and structurally distinct. Outside the primary scope of this peptide-focused site.

SermorelinPeptide compounds

Synthetic GHRH 1-29 — the active N-terminal 29 residues of human GHRH. Originally licensed (FDA 1997) for paediatric GH-deficiency diagnosis as Geref. Stimulates pulsatile pituitary GH release with intact negative feedback.

SHLP familySmall Humanin-Like Peptide familyPeptide compounds

A group of six mitochondrially-derived peptides (SHLP1–SHLP6) encoded within the mitochondrial 16S rRNA gene alongside Humanin. Identified by the Cohen laboratory (USC). Function less well-characterised than Humanin and MOTS-c.

SirtuinBiology

A family of NAD⁺-dependent protein deacetylases (SIRT1–SIRT7) with central roles in metabolism, DNA-damage response and ageing biology. SIRT3, SIRT4 and SIRT5 are mitochondrially-localised. Activity declines with age in parallel with NAD⁺ availability.

Slow-wave sleepN3 / SWSBiology

The deepest stage of non-REM sleep, characterised by delta-wave EEG activity. Critical for memory consolidation and glymphatic clearance. Time spent in SWS declines steeply from middle age. Target of DSIP and pineal-axis peptide research.

SomatopauseBiology

The age-related progressive decline in GH output across the adult lifespan, driven primarily by reduced hypothalamic GHRH signalling rather than pituitary failure. Foundation of GH-axis peptide research (Sermorelin, CJC-1295/Ipamorelin).

SpecialsRegulatory

A UK pharmacy supply route for unlicensed medicines manufactured to order against a specific clinical need. Has historically been used for limited UK access to Thymosin Alpha-1 (licensed elsewhere but without UK MHRA authorisation).

SS-31Peptide compounds

A synthetic aromatic-cationic tetrapeptide developed by Szeto and Schiller at Weill Cornell. Selectively binds inner-mitochondrial-membrane cardiolipin and stabilises cristae structure. Also known as elamipretide, Bendavia, MTP-131. In clinical development.

StackResearch methodology

Informal term for a combination protocol — multiple peptides administered together for synergistic or complementary effects. Used widely in research-peptide literature. Examples include CJC-1295 + Ipamorelin, MOTS-c + SS-31.

SynergyResearch methodology

An interaction in which the combined effect of two agents exceeds the sum of their individual effects. Demonstrated for combined GHRH-receptor + GHS-R1a stimulation (CJC-1295 + Ipamorelin) on pituitary GH release.

T

T-cellBiology

A major lymphocyte type central to adaptive immunity. Matures in the thymus. Output of naive T cells declines progressively across adult life (immunosenescence), the principal target of Thymosin Alpha-1 research.

TB-500Thymosin Beta-4 fragmentPeptide compounds

A synthetic 17-amino-acid peptide corresponding to the active fragment of Thymosin Beta-4. Studied for actin-dynamics-mediated cell migration and tissue-repair effects. Distinct from Thymosin Alpha-1 covered elsewhere on this site.

TelomeraseBiology

A reverse-transcriptase enzyme complex (hTERT catalytic subunit + hTR RNA template) that extends telomeric repeats. Active in stem cells and germline, low or absent in normal somatic tissue. Reactivation is observed in most cancers. Target of Epitalon research.

TelomereBiology

Repetitive non-coding DNA sequences (TTAGGG in humans) capping the ends of linear chromosomes. Progressive shortening with each cell division underlies replicative senescence. Telomere length is one of the better-characterised molecular biomarkers of biological ageing.

Thymosin Alpha-1Tα1 / thymalfasinPeptide compounds

A synthetic 28-amino-acid N-acetylated peptide originally derived from thymic tissue. Licensed in 30+ countries (Zadaxin, Thymalfasin) for chronic hepatitis B/C and as vaccine adjuvant. Not currently licensed in the UK.

Thymosin Beta-4TB-4Peptide compounds

A 43-amino-acid actin-sequestering peptide. Regulates G-actin/F-actin dynamics and cell migration during wound healing. Distinct from Thymosin Alpha-1; the two share a name but operate through unrelated mechanisms.

TLRToll-like receptorMechanism

A family of innate-immune pattern-recognition receptors (TLR-1 through TLR-10 in humans) that recognise conserved pathogen-associated molecular patterns. Thymosin Alpha-1 signals through TLR-2 and TLR-9 on dendritic cells to produce its immune-restorative effects.