{"id":21,"slug":"21-epitalon-c-terminal-amidation-of-gly-4-free-cooh-conh2-yielding-aedg-","title":"Epitalon C-terminal amidation (AEDG-NH2) to resist carboxypeptidase degradation","status":"DISCARDED","fold_verdict":"DISCARDED","discard_reason":null,"peptide":{"name":"Epitalon","class":"LONGEVITY","sequence":"AEDG","modified_sequence":"AEDG-NH2","modification_description":"C-terminal amidation of Gly-4 (free -COOH → -CONH2), yielding AEDG-NH2"},"target":{"protein":"Telomerase reverse transcriptase","uniprot_id":"O14746","chembl_id":"CHEMBL2916","gene_symbol":"TERT"},"rationale":{"hypothesis":"We hypothesize that C-terminal amidation of Epitalon's Gly-4 carboxylate will protect the tetrapeptide from carboxypeptidase-mediated degradation in plasma while preserving — and potentially enhancing — the AEDG pharmacophore. Because Fold #6 (N-terminal D-Ala) collapsed (pLDDT 0.34), suggesting backbone chirality changes disrupt the already-marginal compact fold, we instead pursue a backbone-preserving, terminus-only modification that targets the opposite degradation pathway (exoprotease at the C-terminus rather than aminopeptidase at the N-terminus).","rationale":"Epitalon is a flexible tetrapeptide with very short plasma half-life; both aminopeptidases and carboxypeptidases contribute to its degradation. C-terminal amidation is a well-established stabilization strategy for short peptides (e.g., many GPCR-targeting tetra/pentapeptides) that removes the negatively charged carboxylate recognized by carboxypeptidase A/B-family enzymes. Importantly, amidation eliminates a terminal negative charge near Gly-4, which may also reduce electrostatic repulsion with the acidic Glu-2/Asp-3 side chains and slightly compact the peptide — potentially improving the engagement of the Glu/Asp acidic face with basic residues on the TERT/TEP1 surface implicated in telomerase regulation. Unlike D-Ala-1, this modification leaves all backbone stereochemistry intact, avoiding the structural collapse seen in Fold #6.","predicted_outcome":"We expect a modest pLDDT improvement over Fold #6 (target >0.5) because backbone L-chirality is preserved; absolute pLDDT will remain limited by the intrinsic flexibility of a 4-mer. The amidated C-terminus should appear in the predicted ensemble with reduced terminal charge-driven extension and a slightly more compact AEDG turn geometry compared to free-acid Epitalon.","mechanism_class":null,"biohacker_use":null},"confidence":{"plddt":0.34227892756462097,"ptm":0.20329158008098602,"iptm":0.20849427580833435,"chai_agreement":null,"chai1_gated_decision":"SKIPPED_LOW_CONFIDENCE","binding_probability":null,"binding_pic50":null,"predicted_binding_change":null},"profile":{"aggregation_propensity":0.0,"stability_score":0.504,"bbb_penetration_score":0.17,"half_life_estimate":"short (~15–45 minutes)"},"narrative":{"tldr":"Fold #21 tests C-terminal amidation of Epitalon (AEDG → AEDG-NH2) as a carboxypeptidase-resistant analog, following the pLDDT collapse of the D-Ala N-terminal variant in Fold #6. The structural prediction returned an identical pLDDT of 0.34 and an ipTM of 0.21, confirming that a 4-residue peptide is simply too short and too disordered for AlphaFold-class tools to resolve a confident complex geometry. The amidation modification is pharmacologically rational, but the prediction infrastructure cannot evaluate it meaningfully at this sequence length. The DISCARDED verdict reflects a tool-resolution failure rather than evidence against the modification's biological merit.","detailed_analysis":"Epitalon (Ala-Glu-Asp-Gly, AEDG) is a synthetic tetrapeptide derived from the bovine pineal peptide complex Epithalamin. Over roughly 25 years of published research, it has accumulated evidence for telomerase upregulation — specifically hTERT mRNA induction and enzymatic activation — alongside broader geroprotective, antioxidant, and cytoprotective effects across rodent, bovine, and human cell systems. The most mechanistically detailed proposal in the literature (PMID:32019204) places AEDG's action upstream of hTERT at the level of histone H1 binding, implying an epigenetic transcriptional route rather than direct enzymatic engagement of the telomerase complex. This mechanistic ambiguity is important context for evaluating any chemical modification.\n\nThe modification under investigation in this fold is C-terminal amidation: conversion of the Gly-4 free carboxylate (-COOH) to an amide (-CONH2), yielding AEDG-NH2. The chemical rationale is well-grounded. Carboxypeptidase A and B family enzymes recognize and cleave C-terminal free acids; replacing the carboxylate with a neutral amide removes the electrostatic recognition element for these exoproteases. C-terminal amidation is a validated medicinal chemistry strategy employed across many short peptide therapeutics and is isosteric with the carboxylate at the level of heavy atom count and volume, meaning steric penalties are minimal. The modification also adds a hydrogen-bond donor (the amide NH2) that could conceivably enhance interactions with carbonyl-accepting residues on target proteins such as the histone H1 basic domain.\n\nThe hypothesis was developed directly in response to lessons from Fold #6, which tested N-terminal D-Ala substitution on the same peptide and returned a pLDDT of 0.34 — a complete structural collapse. The team correctly inferred that backbone chirality changes are poorly tolerated for this marginal compact fold and pivoted to a backbone-preserving, terminus-only modification targeting the opposite exoprotease pathway. This is methodologically sound reasoning: exhausting N-terminal and C-terminal protection strategies in sequence allows the lab to map the degradation vulnerability landscape of AEDG systematically.\n\nUnfortunately, the structural prediction for AEDG-NH2 returned nearly identical metrics to Fold #6: pLDDT 0.34, pTM 0.20, ipTM 0.21. The predicted complex shows a disordered 4-mer with no convergent fold and a poorly defined interface. Critically, these scores are not meaningfully distinguishable from the D-Ala collapse — the prediction has not failed because the amidation is destabilizing, but because a 4-residue peptide falls below the effective resolution floor of structure prediction tools trained on longer, more structured proteins. The Boltz-2 affinity module returned no values, and no Chai-1 agreement metric was available. The heuristic sequence-based profile (stability score 0.504, short half-life estimate, low BBB penetration) reflects the parent peptide's intrinsic properties more than the amidation delta.\n\nThe literature context is relevant but cannot rescue the prediction. The strongest mechanistic evidence for telomerase engagement (PMID:40908429, Al-Dulaimi et al. 2025) was subject to a published correction (PMID:41240216), warranting interpretive caution. The histone H1 binding proposal (PMID:32019204) implies that the Glu-2/Asp-3 acidic face and potentially the Gly-4 carboxylate engage basic Lys/Arg residues on histone H1 — in which case removing the C-terminal negative charge via amidation could actually impair, rather than preserve, target engagement. This is a genuine pharmacological risk that wet-lab SAR studies would need to resolve and that computational tools at this length scale cannot adjudicate.\n\nFrom a cross-fold perspective, Fold #21 closes a logical pair with Fold #6: both N-terminal and C-terminal protection strategies for Epitalon have now returned pLDDT 0.34, establishing a ceiling on what current structure prediction tools can deliver for this tetrapeptide against TERT. The contrast with successful longevity peptide folds in this lab — SS-31 variants at pLDDT 0.85 (Folds #11, #17) and MOTS-c K13R at pLDDT 0.63 (Fold #19) — underscores that peptide length and intrinsic structuredness are the primary determinants of prediction confidence, not modification quality.\n\nThe DISCARDED verdict should be read as a tool limitation verdict, not a negative biological signal. The amidation modification remains pharmacologically rational. Future work should pursue orthogonal validation approaches: molecular dynamics simulation of AEDG-NH2 in explicit solvent, plasma stability assay (carboxypeptidase B incubation with HPLC quantification), and a cell-based hTERT reporter assay comparing AEDG and AEDG-NH2 at matched concentrations. These wet-lab and simulation approaches are not constrained by the 4-mer length floor that limits structure prediction tools.","executive_summary":"Epitalon AEDG-NH₂: pLDDT 0.34, ipTM 0.21 — identical to Fold #6's D-Ala collapse. Two terminus-only strategies, same prediction floor. The 4-mer is simply too short for AF2-class tools; plasma stability assay and hTERT reporter are the right next moves.","tweet_draft":"DISTILLATION №21 — discarded.\nEpitalon C-terminal amidation (AEDG-NH2).\npLDDT 0.34 | ipTM 0.21 — matches Fold #6 exactly.\nThe 4-mer hits the tool floor regardless of modification.\nChemistry is rational. Prediction can't evaluate it.\nWet lab next. In silico only. alembic.bio","research_brief_markdown":"# DISTILLATION №21 — DISCARDED\n## Epitalon C-terminal amidation (AEDG-NH2)\n**Verdict: DISCARDED** | pLDDT 0.34 | ipTM 0.21 | Peptide: AEDG-NH2 | Target: hTERT (O14746)\n\n---\n\n## Mechanism of action (background)\n\nEpitalon (AEDG) is a 4-residue synthetic tetrapeptide with ~25 years of published research spanning telomerase activation, histone binding, antioxidant defense, and geroprotection. Its best-supported mechanistic proposal positions AEDG as a histone H1 ligand at DNA-interacting basic domains (PMID:32019204), with downstream epigenetic upregulation of hTERT mRNA as the primary route to telomerase activation — rather than direct binding to the TERT catalytic domain. Functional effects include dose-dependent telomere length extension in human epithelial and fibroblast cells (PMID:40908429), improved bovine oocyte maturation linked to nuclear telomerase relocalization (PMID:39788414), and ROS reduction with spindle protection in post-ovulatory aging oocytes (PMID:35413689). The native peptide's plasma half-life has not been formally quantified in the peer-reviewed literature, but reliance on intranasal delivery and millimolar in vitro concentrations indirectly suggests significant metabolic lability.\n\n---\n\n## Modification hypothesis (what we tested)\n\nThis fold tested **C-terminal amidation** of Gly-4 — conversion of the free carboxylate (-COOH) to a primary amide (-CONH₂) — yielding **AEDG-NH₂**. The pharmacological rationale is established: carboxypeptidase A and B family enzymes recognise and cleave C-terminal free acids; amidation removes the electrostatic recognition element and is isosteric with the carboxylate, imposing minimal steric cost. The modification also introduces a hydrogen-bond donor that could enhance interactions with carbonyl-accepting residues at the putative histone H1 binding site.\n\nThis fold was designed as the logical complement to **Fold #6**, which tested N-terminal D-Ala substitution and collapsed to pLDDT 0.34 — attributed to poor tolerance of backbone chirality changes in a marginally compact 4-mer. C-terminal amidation preserves all backbone stereochemistry while targeting the opposite exoprotease degradation pathway, representing the minimal-perturbation strategy indicated by Fold #6's failure mode.\n\n---\n\n## Why the prediction was uninformative (technical analysis of the metrics)\n\n| Metric | Fold #6 (D-Ala) | Fold #21 (AEDG-NH2) | Threshold for confidence |\n|---|---|---|---|\n| pLDDT | 0.34 | **0.34** | ≥0.60 suggested |\n| pTM | — | 0.20 | ≥0.50 suggested |\n| ipTM | — | **0.21** | ≥0.60 for complex |\n| Chai-1 agreement | — | None | — |\n| Boltz-2 affinity | — | No values | — |\n\nThe scores are statistically indistinguishable from Fold #6. The critical insight is that **both failures returned identical pLDDT values (0.34) despite completely different modifications** — one a backbone chirality change, one a terminal charge-state change. This convergence strongly suggests the scores are not reflecting the quality of the modification at all: they reflect the **hard floor imposed by sequence length**. AlphaFold-class tools are trained predominantly on structured proteins and longer peptides; a 4-residue, intrinsically disordered sequence provides insufficient information for confident fold prediction regardless of terminal chemistry.\n\nAdditionally, ipTM of 0.21 means the predicted interface geometry is essentially random — no specific contact pattern with the TERT surface can be extracted. The Boltz-2 affinity module requires a sufficiently confident structural template to operate and returned no values. The heuristic sequence-based profile (stability 0.504, half-life 15–45 min, aggregation propensity 0.0) reflects properties of the amino acid composition and is not sensitive to the terminal amide change.\n\n**The prediction failed to evaluate the modification — it failed to model the peptide.**\n\n---\n\n## What this tells us (negative results are data)\n\nFold #21, combined with Fold #6, now establishes a clear empirical boundary: **current AF2-class structure prediction tools operating against TERT cannot return actionable metrics for 4-residue Epitalon analogs, regardless of modification type.** This is a meaningful negative result for the lab's computational pipeline rather than for the chemistry.\n\nWhat this does *not* tell us:\n- Whether AEDG-NH₂ retains hTERT-upregulating activity\n- Whether C-terminal amidation improves plasma stability of AEDG\n- Whether the Gly-4 carboxylate is a pharmacophore element required for histone H1 engagement\n\nWhat this *does* tell us:\n- The Epitalon scaffold sits below the resolution floor for structure prediction confidence at this target\n- N-terminal and C-terminal terminus-only protection strategies have been identified as the next logical wet-lab experiments, not further computational folds of the same 4-mer\n- The pharmacological risk of removing the C-terminal negative charge (potentially disrupting electrostatic engagement with histone H1's Lys/Arg-rich domain) cannot be evaluated computationally and must be addressed by cell-based SAR\n- Comparison with SS-31 variants (pLDDT 0.85, Folds #11 and #17) and MOTS-c K13R (pLDDT 0.63, Fold #19) confirms that peptide length and intrinsic structuredness — not modification quality — are the dominant determinants of prediction confidence in this lab\n\n---\n\n## Alternative hypotheses to test (avoid the failure mode)\n\n**Computational alternatives:**\n1. **Molecular dynamics simulation** — explicit-solvent MD (e.g., GROMACS, AMBER) of AEDG and AEDG-NH₂ in free solution or docked against a histone H1 homology model would capture the conformational ensemble of a disordered tetrapeptide without requiring a confident fold prediction as input\n2. **Coarse-grained docking** against histone H1 basic domain — the Khavinson 2020 model (PMID:32019204) provides a putative binding site that could be used for blind docking of AEDG vs. AEDG-NH₂ to assess whether carboxylate removal changes binding geometry\n3. **Longer constructs** — if the scientific question is TERT engagement, a fusion of AEDG or AEDG-NH₂ to a structured carrier peptide or scaffold might exceed the pLDDT floor and enable meaningful prediction\n\n**Wet-lab alternatives (highest priority):**\n1. **Plasma stability assay** — incubate AEDG and AEDG-NH₂ with human plasma (or purified carboxypeptidase B) and quantify intact peptide by HPLC/LC-MS at 0, 15, 30, 60, 120 min. This directly tests the amidation hypothesis and doesn't require structural prediction\n2. **hTERT reporter assay** — compare AEDG vs. AEDG-NH₂ in a cell-based hTERT-luciferase reporter at matched concentrations (0.01–1 mM range) to determine whether amidation preserves, enhances, or abolishes transcriptional activity\n3. **Histone H1 binding assay** — SPR or ITC titration of AEDG vs. AEDG-NH₂ against recombinant histone H1 to directly test whether the C-terminal carboxylate contributes to binding affinity\n4. **N+C dual protection** — if both termini are independently modulable, a head-to-head comparison of AEDG-NH₂ (Fold #21), Ac-AEDG (N-terminal acetylation, not yet tested), and Ac-AEDG-NH₂ (dual protection) in a stability assay would establish the dominant degradation pathway empirically","structural_caption":"The predicted complex shows a disordered, low-confidence 4-mer with no convergent fold and a poorly defined interface (ipTM 0.21). The C-terminal amide is modeled but its geometric placement cannot be trusted at this confidence level. No stable AEDG turn geometry is resolved, and no specific contact pattern with the target can be extracted.","key_findings_summary":"Epitalon (AEDG; Ala-Glu-Asp-Gly) is a synthetic tetrapeptide originally derived from the amino acid composition of Epithalamin, a bovine pineal gland extract. Over roughly 25 years of research, it has been studied in vitro, in vivo, and in silico for geroprotective, neuroendocrine, antioxidant, and antimutagenic effects (PMID:40141333). The compound's most mechanistically studied action relevant to the current hypothesis is its capacity to upregulate telomerase: the 2025 Al-Dulaimi et al. study (PMID:40908429) demonstrated dose-dependent telomere length extension in normal human epithelial and fibroblast cells via hTERT mRNA upregulation and telomerase enzyme activity, and separately showed ALT pathway activation in cancer cell lines. The bovine oocyte study (PMID:39788414) corroborates telomerase activation by Epitalon, showing improved maturation rates and post-thaw blastocyst development linked to nuclear relocalization of telomerase protein. Together these provide the strongest available direct evidence that the AEDG pharmacophore engages the telomerase/hTERT axis.\n\nBeyond telomerase, Epitalon's biological effects span multiple systems. The 2020 Khavinson et al. paper (PMID:32019204) reported that AEDG binds histone H1 subtypes at DNA-interacting domains, suggesting an epigenetic transcriptional mechanism that could explain broad gene expression changes including hTERT upregulation. This is consistent with the 2002 Khavinson review (PMID:12374906) documenting Epithalamin's wide-ranging effects on melatonin synthesis, immunity, antioxidant defense, and longevity in rodents. More recently, Epitalon was shown to reduce ROS, protect spindle integrity, and improve mitochondrial membrane potential in post-ovulatory aging oocytes (PMID:35413689), and to restore wound healing in a diabetic retinopathy model by suppressing hyperglycemia-induced EMT and fibrosis (PMID:40493162). These diverse effects all point to ROS reduction and transcriptional modulation as downstream consequences of AEDG activity, rather than direct enzymatic inhibition of a single target.\n\nWith respect to the specific modification proposed — C-terminal amidation (AEDG-NH2) — no published study in this corpus has characterized this analog. The literature consistently studies the free-acid tetrapeptide AEDG. However, the structural and physicochemical literature on Epitalon is described as 'quite limited' even for the parent compound (PMID:40141333), meaning the pharmacophore determinants responsible for hTERT engagement have not been rigorously mapped. The Gly-4 carboxylate is the C-terminal residue, and while glycine's flexible, small side chain is known to be important for peptide terminal conformations, there is no direct evidence on whether its free carboxylate is required for receptor/enzyme engagement or is merely a degradation liability.\n\nThe degradation rationale for C-terminal amidation is pharmacologically sound in general: carboxypeptidases are active in plasma and tissues, and amidation is a validated strategy for extending peptide half-life. Epitalon's intranasal administration in the Sibarov et al. study (PMID:12500171) and its in vitro use at 0.1 mM concentrations (PMID:35413689) suggest the native peptide has limited stability or bioavailability concerns that have been worked around by route of administration or high concentration, indirectly motivating a stability-enhancing modification. The pLDDT collapse of the D-Ala N-terminal analog (Fold #6) aligns with the general principle that short tetrapeptides have marginal intrinsic structure, and that backbone chirality changes are poorly tolerated — the literature does not directly address this computational finding but it is consistent with the fragile compact-fold inference."},"structured":{"known_activity":null,"known_binders":null,"candidate_variants":null,"domain_annotations":null,"literature_context":{"pubmed":[{"pmid":"40141333","title":"Overview of Epitalon-Highly Bioactive Pineal Tetrapeptide with Promising Properties.","abstract":"Epitalon, also known as Epithalon or Epithalone, is a tetrapeptide, Ala-Glu-Asp-Gly (AEDG), which was synthesized based on the amino acids composition of Epithalamin, a bovine pineal gland extract, prior to its discovery in pineal gland polypeptide complex solution. During the last 25 years, this compound has been extensively studied using in vitro, in vivo, and in silico methods. The results of these studies indicate significant geroprotective and neuroendocrine effects of Epitalone, resulting from its antioxidant, neuro-protective, and antimutagenic effects, originating from both specific and nonspecific mechanisms. Although it has been demonstrated that Epitalon exerts, among other effects, a direct influence on melatonin synthesis, alters the mRNA levels of interleukin-2, modulates the mitogenic activity of murine thymocytes, and enhances the activity of various enzymes, including AChE, BuChE, and telomerase, it remains uncertain whether these are the sole mechanisms of action of this compound. Moreover, despite the considerable volume of research on the biological and pharmacodynamic characteristics of Epitalon, the quantity of physico-chemical and structural investigations of this peptide remains quite limited. This review aims to conclude the most important findings from such studies, thus presenting the current state of knowledge on Epitalon.","authors":["Araj Szymon Kamil","Brzezik Jakub","Mądra-Gackowska Katarzyna","Szeleszczuk Łukasz"],"year":2025,"journal":"International journal of molecular sciences"},{"pmid":"35413689","title":"Epitalon protects against post-ovulatory aging-related damage of mouse oocytes","abstract":"The developmental potential of oocytes decreases with time after ovulation in vivo or in vitro. Epitalon is a synthetic short peptide made of four amino acids (alanine, glutamic acid, aspartic acid, and glycine), based on a natural peptide called epithalamion extracted from the pineal gland. It is a potent antioxidant, comparable to melatonin, that may confer longevity benefits. The current study aims to test the protective effects of Epitalon on the quality of post-ovulatory aging oocytes. Epitalon at 0.1mM was added to the culture medium, and the quality of oocytes was evaluated at 6h, 12h, and 24h of culture. We found that 0.1mM Epitalon reduced intracellular reactive oxygen species. Epitalon treatment significantly decreased frequency of spindle defects and abnormal distribution of cortical granules during aging for 12h and 24h, while increased mitochondrial membrane potential and DNA copy number of mitochondria, thus decreasing apoptosis of oocytes by 24h of in vitro aging. Our results suggest that Epitalon can delay the aging process of oocytes in vitro via modulating mitochondrial activity and ROS levels.","authors":["Yue Xue","Liu Sai-Li","Guo Jia-Ni","Meng Tie-Gang","Zhang Xin-Ran","Li Hong-Xia","Song Chun-Ying","Wang Zhen-Bo","Schatten Heide","Sun Qing-Yuan","Guo Xing-Ping"],"year":2022,"journal":"Aging"},{"pmid":"40908429","title":"Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity.","abstract":"Epitalon, a naturally occurring tetrapeptide, is known for its anti-aging effects on mammalian cells. This happens through the induction of telomerase enzyme activity, resulting in the extension of telomere length. A strong link exists between telomere length and aging-related diseases. Therefore, telomeres are considered to be one of the biomarkers of aging, and increasing or maintaining telomere length may contribute to healthy aging and longevity. Epitalon has been the subject of several anti-aging studies however, quantitative data on the biomolecular pathway leading to telomere length increase, hTERT mRNA expression, telomerase enzyme activity, and ALT activation have not been extensively studied in different cell types. In this article, the breast cancer cell lines 21NT, BT474, and normal epithelial and fibroblast cells were treated with epitalon then DNA, RNA, and proteins were extracted. qPCR and Immunofluorescence analysis demonstrated dose-dependent telomere length extension in normal cells through hTERT and telomerase upregulation. In cancer cells, significant telomere length extension also occurred through ALT (Alternative Lengthening of Telomeres) activation. Only a minor increase in ALT activity was observed in Normal cells, thereby showing that it was specific to cancer cells. Our data suggests that epitalon can extend telomere length in normal healthy mammalian cells through the upregulation of hTERT mRNA expression and telomerase enzyme activity.","authors":["Al-Dulaimi Sarah","Thomas Ross","Matta Sheila","Roberts Terry"],"year":2025,"journal":"Biogerontology"},{"pmid":"40493162","title":"The Antioxidant Tetrapeptide Epitalon Enhances Delayed Wound Healing in an in Vitro Model of Diabetic Retinopathy.","abstract":"Diabetic retinopathy (DR) is the most common complication of diabetes mellitus and a leading cause of vision loss. Short peptides, such as di-, tri-, and tetrapeptides, have various beneficial activities, including antioxidant, antimicrobial, and anti-inflammatory effects. This study aims to test the hypothesis that the antioxidant effect of the synthetic tetrapeptide AEDG (Ala-Glu-Asp-Gly, Epitalon) improves the delayed healing process associated with hyperglycemia in DR, using a high glucose (HG)-injured human retinal pigment epithelial cell line (ARPE-19). We found that HG exposure delayed wound healing in ARPE-19 cells and increased intracellular levels of reactive oxygen species (ROS), while decreasing antioxidant gene expression. HG also induced epithelial-mesenchymal transition (EMT) and upregulated fibrosis-related genes, suggesting that HG-induced EMT contributes to subretinal fibrosis, the end-stage of eye diseases, including proliferative DR. The antioxidant Epitalon restored impaired wound healing in HG-injured ARPE-19 cells by inhibiting hyperglycemia-induced EMT and fibrosis. These findings support using the antioxidant agent Epitalon as a promising therapeutic strategy for DR to improve retinal wound healing compromised by hyperglycemia. More mechanistic investigations are needed to confirm Epitalon's benefits and safety. Developing ophthalmic forms of Epitalon may enhance its delivery directly to the retina, potentially improving its therapeutic efficacy.","authors":["Gatta Marco","Dovizio Melania","Milillo Cristina","Ruggieri Anna Giulia","Sallese Michele","Antonucci Ivana","Trofimov Aleksandr","Khavinson Vladimir","Trofimova Svetlana","Bruno Annalisa","Ballerini Patrizia"],"year":2025,"journal":"Stem cell reviews and reports"},{"pmid":"39788414","title":"Epitalon-activated telomerase enhance bovine oocyte maturation rate and post-thawed embryo development.","abstract":"Telomerase is highly expressed in oocyte cumulus cells and plays a significant role in follicular development and oocyte maturation. In this study, we hypothesized that in vitro culture conditions may affect telomerase activity during in vitro embryo production (IVP) and that its activation may improve embryo quality. We first examined telomerase protein levels and localization in bovine cumulus-oocyte complexes via immunofluorescence assays. The results showed that healthy cumulus-oocyte complexes have the nuclear localization of the telomerase while the degraded cumulus-oocyte complex had reduced telomerase levels and that telomerase was localized in the cytoplasm. We activated telomerase via Epitalon, a tetrapeptide with the amino acid sequence Ala-Glut-Asp-Gly. We observed a significant improvement in the oocyte maturation rate compared with the control group (p < 0.05). Furthermore, telomerase activity was significantly compromised in post-thawed embryos, and Epitalon treatment significantly improved blastocyst hatching rate and implantation potential (p < 0.05). Moreover, we performed qPCR, reactive oxygen species, and JC-1 (ΔΨm) assays to evaluate the effect of Epitalon on the health of in vitro mature oocytes, cumulus cells, and post-thawed blastocysts, and the result showed that Epitalon highly enhances the quality and health of the oocyte, cumulus cell, and post-thawed blastocyst. Our results suggest that telomerase activation via Epitalon improves bovine in vitro embryo production.","authors":["Ullah Safeer","Haider Zaheer","Perera Chalani Dilshani","Lee Su Hyeon","Idrees Muhammad","Park Song","Kong Il-Keun"],"year":2025,"journal":"Life sciences"},{"pmid":"12374906","title":"Peptides and Ageing.","abstract":"A technology has been developed for manufacturing of biologically active complex peptide preparations from extracts of different tissues. In particular, the pineal preparation (Epithalamin) augments the in vitro outgrowth of explants from the pineal gland but not from other tissues, the latter being stimulated by peptide preparations from respective tissues. Epithalamin increases melatonin production by the pineal gland of rats, improves immunological parameters in rats and mice, produces anticarcinogenic effects in different experimental models, stimulates antioxidant defenses, and restores the reproductive function in old rats. These effects are combined in the ability of Epithalamin to increase the lifespan in rats, mice, and fruit flies. Many of these effects are reproduced in clinical trials, which have demonstrated the geroprotector activity of Epithalamin in humans. Among the effects of the thymic preparation Thymalin, those related to its ability to stimulate immunity are the most prominent. This ability is associated with anticarcinogenic and geroprotector activities. Clinical trials of the peptide preparations obtained from other organs including the prostate, the cerebral cortex, and the eye retina, have demonstrated beneficial effects reflected by the improvement of the conditions of respective organs. Based on the data about the amino acid compositions of the peptide preparations, novel principles of the design of biologically active short peptides possessing tissue-specific activities has been developed. Dipeptides specific for the thymus and tetrapeptides specific for the heart, liver, brain cortex, and pineal glands stimulate the in vitro outgrowth of explants of respective organs. Interestingly, for eye retina and the pineal gland, a common tetrapeptide Ala-Glu-Asp-Gly (Epitalon) has been designed, probably reflecting the common embryonal origin of these two organs. Epitalon reproduces the effects of Epithalamin including those related to its geroprotector activity. In particular, Epitalon increases the lifespan of mice and fruit flies and restores the circadian rhythms of melatonin and cortisol production in old rhesus monkeys. At the same time, Epitalon prolongs the functional integrity of the eye retina in Campbell rats with hereditary Retinitis Pigmentosa and improves the visual functions in patients with pigmental retinal degeneration. Changes in gene expression were observed to be produced by the short peptide preparations. Therefore, the effects of Epitalon are suggested to be mediated by transcriptional machinery common for the pineal gland and the retina and, probably, for regulation of melatonin production in fruit flies. Based on three decades of studies of the peptide preparations, the peptide theory of ageing has been put forward. According this theory, ageing is an evolutionary determined biological process of changes in gene expression resulting in impaired synthesis of regulatory and tissue-specific peptides in organs and tissues, which provokes their structural and functional changes and the development of diseases. Correspondingly, correction of such disorders by means of stimulation of peptide production in the organism or through their delivery can promote the normalisation of disturbed body functions.","authors":["Khavinson Vladimir Kh"],"year":2002,"journal":"Neuro endocrinology letters"},{"pmid":"12500171","title":"Epitalon influences pineal secretion in stress-exposed rats in the daytime.","abstract":"OBJECTIVES: The content of C-Fos protein was tested in rat pinealocytes in the norm and stress and in case of intranasal administration of Epitalon (Ala-Glu-Asp-Gly), which regulated pineal secretion processes, presumably, via protooncogenes.\n\nSETTING: Intact and osmotic-stress-exposed rats were used for the immunohistochemical detection of C-Fos protein. All animals were intranasally administered with Epitalon, the last infusion made in two hours before the biopsy. Simultaneously, light microscopy of the pineal parenchyma was performed in all groups of animals.\n\nRESULTS: A slight but significant C-Fos increase was observed only in stress-exposed pinealocytes of rats after intranasal Epitalon infusions. C-Fos was irregularly distributed throughout pineal cells. In stress, the clusters of 5 10 cells containing C-Fos in their cytoplasm were detected. The dilation of capillaries and pericapillary space induced by an osmotic stress was partially reduced by the intranasal infusions of Epitalon.\n\nCONCLUSIONS: Tetrapeptide Epitalon is synthesised on the basis of the amino acid composition of pineal peptide extract Epithalamin. Epitalon modulates pineal secretion only under a stress impact but never in the norm. It prevents osmotic-stress-induced pathologic changes in the pineal parenchyma structure. Besides, the physiological activity of Epitalon seems to be mediated by the activation of protooncogenes in pinealocytes.","authors":["Sibarov Dmitry A","Kovalenko Rimma I","Malinin Vladimir V","Khavinson Vladimir Kh"],"year":2002,"journal":"Neuro endocrinology letters"},{"pmid":"32019204","title":"AEDG Peptide (Epitalon) Stimulates Gene Expression and Protein Synthesis during Neurogenesis: Possible Epigenetic Mechanism.","abstract":"It was shown that AEDG peptide (Ala-Glu-Asp-Gly, Epitalon) regulates the function of the pineal gland, the retina, and the brain. AEDG peptide increases longevity in animals and decreases experimental cancerogenesis. AEDG peptide induces neuronal cell differentiation in retinal and human periodontal ligament stem cells. The aim of the study was to investigate the influence of AEDG peptide on neurogenic differentiation gene expression and protein synthesis in human gingival mesenchymal stem cells, and to suggest the basis for the epigenetic mechanism of this process. AEDG peptide increased the synthesis of neurogenic differentiation markers: Nestin, GAP43, β Tubulin III, Doublecortin in hGMSCs. AEDG peptide increased Nestin, GAP43, β Tubulin III and Doublecortin mRNA expression by 1.6-1.8 times in hGMSCs. Molecular modelling method showed, that AEDG peptide preferably binds with H1/6 and H1/3 histones in His-Pro-Ser-Tyr-Met-Ala-His-Pro-Ala-Arg-Lys and Tyr-Arg-Lys-Thr-Gln sites, which interact with DNA. These results correspond to previous experimental data. AEDG peptide and histones H1/3, H1/6 binding may be one of the mechanisms which provides an increase of Nestin, GAP43, β Tubulin III, and Doublecortin neuronal differentiation gene transcription. AEDG peptide can epigenetically regulate neuronal differentiation gene expression and protein synthesis in human stem cells.","authors":["Khavinson Vladimir","Diomede Francesca","Mironova Ekaterina","Linkova Natalia","Trofimova Svetlana","Trubiani Oriana","Caputi Sergio","Sinjari Bruna"],"year":2020,"journal":"Molecules (Basel, Switzerland)"},{"pmid":"41240216","title":"Correction: Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity.","abstract":"","authors":["Al-Dulaimi Sarah","Thomas Ross","Matta Sheila","Roberts Terry"],"year":2025,"journal":"Biogerontology"}],"biorxiv":[{"pmid":"","doi":"10.21203/rs.3.rs-7066545/v1","title":"Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity","abstract":"<title>Abstract</title>  <p>Epitalon, a naturally occurring tetrapeptide, is known for its anti-aging effects on mammalian cells. This happens through the induction of telomerase enzyme activity, resulting in the extension of telomere length. A strong link exists between telomere length and aging-related diseases. Therefore, telomeres are considered to be one of the biomarkers of aging, and increasing or maintaining telomere lengths may contribute to healthy aging and longevity. Epitalon has been the subject of several anti-aging studies however, quantitative data on the biomolecular pathway leading to telomere length increase, <italic>hTERT mRNA </italic>expression, telomerase enzyme activity, and ALT activation have not been extensively studied in different cell types. In this article, the breast cancer cell lines 21NT, BT474, and normal epithelial and fibroblast cells were treated with epitalon then DNA, RNA, and proteins were extracted. qPCR and Immunofluorescence analysis demonstrated dose-dependent telomere length extension in normal cells through <italic>hTERT</italic>and telomerase upregulation. In cancer cells, significant telomere length extension also occurred through ALT (Alternative Lengthening of Telomeres) activation. Only a minor increase in ALT activity was observed in Normal cells, thereby showing that it was specific to cancer cells. Our data suggests that Epitalon can extend telomere length in normal healthy mammalian cells through the upregulation of <italic>hTERT</italic> mRNA expression and telomerase enzyme activity.</p>","authors":["Al-dulaimi S","Thomas R","Matta S","Roberts T."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"preprints":[{"pmid":"","doi":"10.21203/rs.3.rs-7066545/v1","title":"Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity","abstract":"<title>Abstract</title>  <p>Epitalon, a naturally occurring tetrapeptide, is known for its anti-aging effects on mammalian cells. This happens through the induction of telomerase enzyme activity, resulting in the extension of telomere length. A strong link exists between telomere length and aging-related diseases. Therefore, telomeres are considered to be one of the biomarkers of aging, and increasing or maintaining telomere lengths may contribute to healthy aging and longevity. Epitalon has been the subject of several anti-aging studies however, quantitative data on the biomolecular pathway leading to telomere length increase, <italic>hTERT mRNA </italic>expression, telomerase enzyme activity, and ALT activation have not been extensively studied in different cell types. In this article, the breast cancer cell lines 21NT, BT474, and normal epithelial and fibroblast cells were treated with epitalon then DNA, RNA, and proteins were extracted. qPCR and Immunofluorescence analysis demonstrated dose-dependent telomere length extension in normal cells through <italic>hTERT</italic>and telomerase upregulation. In cancer cells, significant telomere length extension also occurred through ALT (Alternative Lengthening of Telomeres) activation. Only a minor increase in ALT activity was observed in Normal cells, thereby showing that it was specific to cancer cells. Our data suggests that Epitalon can extend telomere length in normal healthy mammalian cells through the upregulation of <italic>hTERT</italic> mRNA expression and telomerase enzyme activity.</p>","authors":["Al-dulaimi S","Thomas R","Matta S","Roberts T."],"year":2025,"journal":"PPR","source":"PPR","preprint":true}],"consensus_view":"The literature consensus is that native Epitalon (AEDG free acid) activates telomerase — specifically inducing hTERT mRNA expression and telomerase enzymatic activity — and produces a range of downstream anti-aging, antioxidant, and cytoprotective effects across multiple cell types and model organisms. The telomerase-activating effect appears robust across cell lines and species (human, bovine, murine). However, the molecular mechanism of target engagement remains incompletely resolved: histone H1 binding with epigenetic transcriptional modulation is the best-supported mechanistic proposal, but direct binding to hTERT protein or a validated receptor has not been characterized. There is no literature consensus — or indeed any published study — on the pharmacological properties of the C-terminally amidated analog AEDG-NH2. Structural studies of the parent peptide are explicitly described as 'quite limited,' meaning the contribution of specific residues or terminal functional groups to activity is not established.","knowledge_gaps":"Several critical knowledge gaps are directly relevant to the proposed modification. (1) The pharmacophore has not been rigorously mapped: no systematic SAR study has determined which residues or terminal functionalities of AEDG are required for hTERT upregulation versus dispensable for activity. (2) The plasma half-life of native AEDG has not been quantified in peer-reviewed literature, nor have the responsible degradative enzymes (carboxypeptidases vs. aminopeptidases vs. endopeptidases) been identified for this specific tetrapeptide — the degradation pathway assumption is pharmacologically reasonable but empirically unvalidated for AEDG. (3) Whether the Gly-4 free carboxylate participates in any hydrogen-bond donor/acceptor interaction at the putative binding site (histone H1, hTERT surface, or otherwise) is unknown. (4) The 3D binding mode of AEDG to its molecular target(s) has not been solved experimentally, limiting the ability to predict whether C-terminal amidation changes charge distribution in a functionally relevant way. (5) No analog series (N-methylated, D-amino acid at positions 2–4, C-terminal esters, amides) appears to have been published, leaving a complete void in comparative structure-activity data.","supporting_evidence":"C-terminal amidation is a well-established medicinal chemistry strategy for protecting peptides from carboxypeptidase activity, and the rationale is sound given AEDG's small size and susceptibility to exoproteases. The 2025 review (PMID:40141333) notes that physicochemical and structural studies of Epitalon are limited, implying the pharmacophore has not been over-constrained by prior findings — leaving room for the amide to be tolerated. The Gly-4 residue lacks a side chain, so amidation converts -CH2-COOH to -CH2-CONH2 with minimal steric change; the neutral amide is isosteric in size with the carboxylate and adds a hydrogen-bond donor that could actually enhance interactions with carbonyl-accepting residues on histone H1 (as modelled in PMID:32019204). The decision to pursue terminus-only modification after pLDDT collapse of the D-Ala backbone variant is supported by the fragile compact-fold inference: conserving the backbone while modifying only the terminal charge state is a minimal perturbation strategy consistent with preserving the marginal but functional fold. The high in vitro concentrations used (0.1 mM in PMID:35413689) and the reliance on intranasal delivery (PMID:12500171) are indirect indicators of stability limitations in the parent compound, motivating a degradation-resistant analog.","challenging_evidence":"The most important challenge is that AEDG appears to act primarily via transcriptional/epigenetic mechanisms (histone H1 binding; PMID:32019204) rather than direct enzymatic activation of hTERT — which means any modification that alters the electrostatic surface or hydrogen-bond capacity of the C-terminus could disrupt interaction with the histone H1 basic domain, which is rich in Lys/Arg residues that could engage the Gly-4 carboxylate through electrostatic attraction. Converting -COOH (pKa ~3.5, anionic at physiological pH) to -CONH2 (neutral) removes a negative charge that may be a pharmacophore element for binding positively charged histone surfaces. Additionally, the 2025 Al-Dulaimi study (PMID:40908429) — the strongest mechanistic evidence for hTERT engagement — was published as both a preprint and a peer-reviewed paper with a published correction (PMID:41240216), suggesting data quality issues that merit caution when interpreting the mechanistic claims. Furthermore, Epitalon has demonstrated biological activity via multiple routes at millimolar-range concentrations in cell culture, which may indicate that stability in plasma is not the rate-limiting factor for in vivo efficacy, potentially weakening the primary rationale for the amidation. Finally, the cancer cell ALT activation finding (PMID:40908429) raises a safety concern for any Epitalon analog intended for in vivo use: if AEDG-NH2 retains or enhances telomerase/ALT activity, use in individuals with subclinical malignancies could theoretically promote tumor progression, a concern that is not resolved by the modification strategy."},"caveats":["in silico prediction only — requires wet lab validation","single-run prediction (not ensembled)","predicted properties may not reflect real-world biological behavior","this is research, not medical advice","pLDDT 0.34 and ipTM 0.21 fall below meaningful confidence thresholds — no structural or binding conclusions can be drawn from this prediction","4-residue peptides are below the effective resolution floor for AF2-class tools; DISCARDED verdict reflects tool failure, not modification failure","heuristic peptide profile (stability, half-life, BBB) is sequence-composition-based and not sensitive to C-terminal amide vs. carboxylate distinction","Boltz-2 affinity module returned no values — no predicted binding change is available","the strongest mechanistic paper for AEDG telomerase activation (PMID:40908429) has a published correction (PMID:41240216); mechanistic claims should be interpreted with caution","C-terminal amidation removes a potentially pharmacophoric negative charge that may engage histone H1 Lys/Arg residues — biological activity of AEDG-NH₂ is empirically unknown","cancer cell ALT pathway activation by native AEDG (PMID:40908429) raises unresolved safety considerations for any telomerase-activating analog intended for in vivo use"],"works_cited":[{"pmid_or_doi":"40141333","title":"Overview of Epitalon-Highly Bioactive Pineal Tetrapeptide with Promising Properties","year":2025,"relevance":"Comprehensive review establishing the AEDG pharmacophore, summarizing 25 years of biological data including telomerase enhancement, and explicitly noting the limited physicochemical/structural literature — directly relevant to assessing how well the pharmacophore is understood before modifying it."},{"pmid_or_doi":"40908429","title":"Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity","year":2025,"relevance":"Most direct evidence that AEDG upregulates hTERT mRNA and telomerase enzyme activity in human normal cells in a dose-dependent manner, establishing the molecular target for the proposed AEDG-NH2 modification."},{"pmid_or_doi":"39788414","title":"Epitalon-activated telomerase enhance bovine oocyte maturation rate and post-thawed embryo development","year":2025,"relevance":"Corroborates telomerase activation by native AEDG in a functional in vitro model; provides mechanistic context for telomerase nuclear localization relevant to understanding how structural changes might affect target engagement."},{"pmid_or_doi":"32019204","title":"AEDG Peptide (Epitalon) Stimulates Gene Expression and Protein Synthesis during Neurogenesis: Possible Epigenetic Mechanism","year":2020,"relevance":"Proposes histone H1 binding as an epigenetic mechanism for AEDG's transcriptional effects, which could include hTERT upregulation; molecular modelling of native AEDG binding provides a baseline for evaluating whether C-terminal amidation would alter binding geometry."},{"pmid_or_doi":"35413689","title":"Epitalon protects against post-ovulatory aging-related damage of mouse oocytes","year":2022,"relevance":"Demonstrates activity of native AEDG at 0.1 mM in culture, suggesting the parent compound requires high concentrations in vitro — consistent with a stability or bioavailability limitation that C-terminal amidation could address."},{"pmid_or_doi":"40493162","title":"The Antioxidant Tetrapeptide Epitalon Enhances Delayed Wound Healing in an in Vitro Model of Diabetic Retinopathy","year":2025,"relevance":"Demonstrates therapeutic utility of native AEDG and explicitly calls for development of optimized delivery forms, providing translational context for the stability-enhancing amidation strategy."},{"pmid_or_doi":"12374906","title":"Peptides and Ageing","year":2002,"relevance":"Foundational review of Epithalamin and short peptide geroprotective activity; establishes the historical and mechanistic basis from which Epitalon was derived and contextualizes its telomerase and longevity effects."},{"pmid_or_doi":"12500171","title":"Epitalon influences pineal secretion in stress-exposed rats in the daytime","year":2002,"relevance":"Demonstrates in vivo biological activity via intranasal administration route, indirectly suggesting that native AEDG has plasma stability or permeability challenges that informed the choice of alternative delivery routes."},{"pmid_or_doi":"10.21203/rs.3.rs-7066545/v1","title":"Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity (preprint)","year":2025,"relevance":"Preprint version of Al-Dulaimi et al. confirming the hTERT/telomerase upregulation findings; noted as the underlying preprint for PMID:40908429, with broadly consistent data supporting telomerase as the primary target."}]},"onchain":{"hash":"33JfJZegt43xNoQjGjYEETCXMRA6hhJsjJ7hgDrLLF5LLrz83mpuqbmRe7XLfVExSLwFovCQZgv6feCUa2iVUpEg","signature":"33JfJZegt43xNoQjGjYEETCXMRA6hhJsjJ7hgDrLLF5LLrz83mpuqbmRe7XLfVExSLwFovCQZgv6feCUa2iVUpEg","data_hash":"e4b3d1a21bcb96c67f5ac89350897e0d37c7f0bd99a9162d91a95640b5e92e08","logged_at":"2026-05-03T04:11:20.132850+00:00","explorer_url":"https://solscan.io/tx/33JfJZegt43xNoQjGjYEETCXMRA6hhJsjJ7hgDrLLF5LLrz83mpuqbmRe7XLfVExSLwFovCQZgv6feCUa2iVUpEg"},"ipfs_hash":null,"created_at":"2026-05-03T04:03:20.144965+00:00","updated_at":"2026-05-03T04:11:20.144844+00:00"}