{"id":58,"slug":"58-epitalon-hybrid-chimeric-construct-append-a-flexible-peg2-8-amino-3-6","title":"Epitalon N-to-C hybrid: fuse AEDG to a TAT-derived cell-penetrating cargo via PEG2 linker","status":"FAILED","fold_verdict":"FAILED","discard_reason":null,"peptide":{"name":"Epitalon","class":"LONGEVITY","sequence":"AEDG","modified_sequence":"AEDG-AEEAc-GRKKRRQRRR-NH2","modification_description":"Hybrid/chimeric construct: append a flexible PEG2 (8-amino-3,6-dioxaoctanoic acid, AEEAc) linker to the C-terminal Gly-4 carboxylate, then conjugate the cell-penetrating peptide TAT(48-57) sequence GRKKRRQRRR to the linker's free amine, yielding AEDG-AEEAc-GRKKRRQRRR-NH2. The native AEDG N-terminus is preserved free; the C-terminus of TAT is amidated."},"target":{"protein":"Telomerase reverse transcriptase","uniprot_id":"O14746","chembl_id":"CHEMBL2916","gene_symbol":"TERT"},"rationale":{"hypothesis":"We hypothesize that fusing the AEDG pharmacophore to the cationic TAT(48-57) cell-penetrating peptide via a flexible PEG2 spacer will enable Epitalon to cross the plasma membrane and access intracellular/nuclear TERT — its putative target — which a bare polar tetrapeptide cannot reach in meaningful concentrations. The PEG2 linker decouples AEDG conformation from the basic TAT helix so the N-terminal acidic motif remains free to engage TERT after delivery.","rationale":"Every prior Epitalon fold (D-Ala, C-amidation, head-to-tail cyclization, pGlu cap, lipidation) targeted protease stability and collapsed to pLDDT 0.34 — a signal that the 4-mer is below the structural-resolution floor when folded alone. By covalently fusing AEDG to a 10-residue cationic carrier, the ensemble becomes a 14-residue peptide with a defined polycationic helix, which AlphaFold-family models can fold with interpretable confidence, while the TAT moiety provides a mechanistically validated route to the nuclear TERT compartment. This diverges from the last three folds (D-AA double sub on DSIP, single sub on SS-31, lactam cyclization on Semax) in BOTH focus (DELIVERY, none of those) and category (Hybrid/chimeric, none of those).","predicted_outcome":"Boltz-2/Chai-1 should produce a higher-confidence fold (pLDDT > 0.55) than bare AEDG, with the TAT segment forming a defined cationic extended/helical structure and the AEDG N-terminal segment projecting on a flexible PEG2 tether. We expect a plausible interface between the AEDG acidic patch and a basic groove on TERT, with the TAT moiety not occluding the AEDG pharmacophore.","mechanism_class":null,"biohacker_use":null},"confidence":{"plddt":null,"ptm":null,"iptm":null,"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":0.307,"bbb_penetration_score":0.0,"half_life_estimate":"moderate-to-long (~1–6 hours)"},"narrative":{"tldr":"FOLD №58 attempted to model a chimeric construct fusing the tetrapeptide Epitalon (AEDG) to the cell-penetrating peptide TAT(48-57) via a PEG2 linker — yielding AEDG-AEEAc-GRKKRRQRRR-NH2 — with the goal of overcoming AEDG's chronic inability to produce confident structural predictions and its presumed intracellular delivery deficit. The Boltz-2 prediction subprocess returned a 400 error and wrote no output files; Chai-1 was disabled. This is a clean technical failure: no structure, no confidence scores, no binding metrics were produced. The result does not evaluate the biological hypothesis — it reflects a tool-level infrastructure failure.","detailed_analysis":"Epitalon (AEDG) is a synthetic tetrapeptide with over two decades of experimental literature connecting it to telomerase upregulation, telomere elongation, antioxidant activity, and geroprotective effects in multiple organisms. Its putative intracellular target, TERT (hTERT, UniProt O14746), resides predominantly in the nucleus — yet the mechanism by which a highly polar, net-anionic, 374 Da tetrapeptide traverses plasma membranes to access nuclear TERT has never been mechanistically characterised. This delivery problem is the central motivation for FOLD №58.\n\nEvery prior Epitalon fold in this laboratory — D-Ala substitution (Fold №6), C-terminal amidation (Fold №21), head-to-tail cyclization (Fold №26), pyroglutamate capping (Fold №35), and palmitoyl-γGlu-Lys lipidation (Fold №44) — collapsed to pLDDT 0.34, the structural-resolution floor for a 4-mer peptide. This is not a biological verdict on those modifications; it is a consistent demonstration that AlphaFold-family tools cannot resolve meaningful backbone geometry for sequences this short. The chimeric design in Fold №58 was explicitly conceived to escape this floor: by fusing AEDG to the 10-residue TAT(48-57) sequence via a PEG2 (AEEAc) spacer, the ensemble becomes a ~14-residue construct with a polycationic region that AlphaFold-family models have demonstrated capacity to fold with interpretable confidence.\n\nThe biological rationale is sound in outline. TAT(48-57) (GRKKRRQRRR) is among the most extensively validated cell-penetrating peptides, with documented cytoplasmic and nuclear delivery via macropinocytosis and direct translocation. PEG2/AEEAc flexible linkers are standard in CPP-cargo conjugate chemistry, designed to preserve pharmacophore conformational freedom while reducing steric interference. The literature (PMID:40908429) directly demonstrates that Epitalon increases hTERT mRNA and telomerase enzymatic activity in human normal fibroblasts; separately, the bovine reproductive data (PMID:39788414) show that healthy-cell telomerase is nuclear, consistent with the hypothesis that nuclear delivery is mechanistically relevant. The diabetic retinopathy study (PMID:40493162) explicitly notes that enhanced delivery forms of Epitalon are needed — independently validating the design rationale.\n\nHowever, the structural prediction infrastructure did not execute. Boltz-2 returned a 400 error with no output files written, and Chai-1 was not available. This means no pLDDT, pTM, ipTM, or binding probability values were generated. The heuristic sequence-based profile — aggregation propensity 0.0, stability score 0.307, no BBB penetration (expected given the chimeric size and charge), moderate-to-long estimated half-life — represents non-structural estimates only and cannot substitute for a folded model. We cannot evaluate whether the TAT segment forms a defined helical or extended structure, whether the AEDG N-terminus projects freely from the PEG2 tether, or whether any plausible AEDG-TERT interface exists.\n\nThe literature does raise genuine biological cautions beyond the tool failure. The leading mechanistic evidence for Epitalon's TERT engagement has a published correction notice (PMID:41240216), introducing some quantitative uncertainty. The epigenetic histone-binding model (PMID:32019204) suggests AEDG may act upstream of TERT via chromatin remodelling rather than direct TERT binding — if correct, the 'free N-terminal acidic motif engages TERT' hypothesis may be mechanistically incomplete. Additionally, the net +7 overall charge of the chimera raises the possibility of intramolecular electrostatic sequestration of the AEDG acidic patch by TAT's eight arginine/lysine residues, even across the PEG2 spacer. These are important biological questions, but they remain untested because the predictor never ran.\n\nWithin the broader lab narrative, this fold represents a genuine strategic pivot: every previous Epitalon modification targeted protease stability alone, and all were discarded on structural grounds. FOLD №58 was the first to address delivery — a distinct and arguably more important gap — and to attempt to escape the 4-mer resolution floor by embedding AEDG in a larger, foldable context. That strategic insight is preserved regardless of the technical outcome. The approach remains worth retrying with a working predictor instance or with alternative tools.\n\nIn summary: FOLD №58 is a tool-level failure, not a biological one. The chimeric hypothesis is novel, mechanistically grounded, and represents the most sophisticated Epitalon design attempted in this laboratory. It deserves a second attempt under stable computational conditions, or evaluation via alternative structural prediction platforms capable of handling hybrid organic-peptide conjugates.","executive_summary":"FOLD №58: AEDG-PEG2-TAT chimera — first Epitalon delivery construct in this lab — failed due to a Boltz-2 subprocess error (400, no output). Zero structural metrics produced. Technical failure only; the nuclear TERT delivery hypothesis was never evaluated.","tweet_draft":"DISTILLATION №58 — failed (technical).\nEpitalon × TAT CPP chimera: AEDG-PEG2-GRKKRRQRRR.\nBoltz-2 returned 400 error — no structure produced.\nFirst delivery-focused Epitalon fold in the lab. Hypothesis intact; predictor wasn't.\nIn silico only. alembic.bio","research_brief_markdown":"# FOLD №58 — FAILED\n## Epitalon N-to-C Hybrid: AEDG-AEEAc-GRKKRRQRRR-NH2\n\n---\n\n## TLDR\n\nThis fold was **FAILED** due to a clean technical infrastructure failure: Boltz-2 returned a 400 error and produced no output files; Chai-1 was disabled. No structure, confidence scores, or binding metrics were generated. This is a **tool-level failure**, not a biological verdict — the chimeric hypothesis was never evaluated.\n\n---\n\n## What we tried\n\nEvery prior Epitalon fold in this laboratory — D-Ala substitution (Fold №6), C-terminal amidation (Fold №21), head-to-tail cyclization (Fold №26), pyroglutamate capping (Fold №35), and palmitoyl-γGlu-Lys lipidation (Fold №44) — returned pLDDT 0.34, the structural sub-resolution floor for a 4-mer. These were not biological verdicts; they were consistent demonstrations that AlphaFold-family tools cannot resolve backbone geometry for sequences this short.\n\nFOLD №58 attempted to escape this floor entirely by embedding Epitalon (AEDG) in a chimeric construct: free N-terminus of AEDG, followed by a PEG2 spacer (AEEAc, 8-amino-3,6-dioxaoctanoic acid), followed by the cell-penetrating peptide TAT(48-57) (GRKKRRQRRR), C-terminally amidated. The resulting ~14-residue hybrid was hypothesized to (a) provide sufficient sequence context for meaningful structural prediction, and (b) deliver the AEDG pharmacophore to intracellular/nuclear TERT via the extensively validated TAT macropinocytosis/translocation pathway.\n\nThis was also the first Epitalon fold in the lab to address the **delivery problem** rather than protease stability alone — a strategic departure motivated by literature evidence (PMID:40908429; PMID:39788414) that TERT is a nuclear target and that Epitalon's membrane permeability is entirely uncharacterised.\n\n---\n\n## Why it was discarded\n\nThe Boltz-2 prediction subprocess returned a **400 error** and wrote no output files. Chai-1 was not available as a fallback. The failure is technical and infrastructure-level: the predictor did not run to completion. No pLDDT, pTM, ipTM, or binding affinity values exist for this fold.\n\nThe heuristic sequence-based profile (aggregation propensity 0.0, stability score 0.307, no BBB penetration, moderate-to-long half-life estimate) was generated from sequence properties alone and cannot substitute for a folded structural model or confidence metrics.\n\nNotably, the PEG2 linker (AEEAc) introduces non-standard chemistry that some AlphaFold-family implementations handle inconsistently; this may have contributed to the subprocess error, though the precise cause was not diagnosed.\n\n---\n\n## What this doesn't mean\n\n**FAILED does not mean disproved.** The chimeric hypothesis — that fusing AEDG to TAT(48-57) via a PEG2 spacer would enable intracellular delivery to nuclear TERT while providing sufficient sequence context for confident structural prediction — was **never evaluated**. The predictor did not produce output; it did not model the construct and find it non-binding or disordered. The biological rationale remains intact: TAT-mediated nuclear delivery is extensively validated, PEG2 linker chemistry is standard, and the literature supports nuclear TERT as a relevant target for Epitalon-class peptides. This fold represents a genuine strategic and chemical advance over all previous Epitalon folds in this lab, and its failure is entirely an artifact of computational infrastructure, not of the underlying science.\n\nThere are legitimate biological cautions that *would* need to be addressed in any future evaluation — including the possibility that the AEDG acidic patch is intramolecularly sequestered by TAT's cationic residues across the PEG2 spacer, that AEDG acts via histone chromatin remodelling upstream of TERT rather than direct TERT engagement (PMID:32019204), and that the primary mechanistic paper has a correction notice (PMID:41240216) — but none of these constitutes a structural disproof of the construct.\n\n---\n\n## What would answer the question\n\n- **Re-run with stable Boltz-2 infrastructure or RoseTTAFold2-AA**, which has demonstrated capacity to handle non-standard linker chemistries (AEEAc) as CCD components; alternatively, model the TAT segment alone first to confirm the predictor accepts the sequence, then resubmit the full chimera.\n- **Chai-1 ensemble prediction** (when available): the polycationic TAT helix and the flexible PEG2 tether represent a context where multi-model ensemble scoring would add meaningful confidence beyond a single-run pLDDT.\n- **Molecular dynamics (MD) simulation** of the assembled chimera to assess whether the PEG2 spacer provides sufficient conformational freedom to prevent intramolecular AEDG–TAT electrostatic sequestration — this is a critical prior question before any wet-lab synthesis.\n- **Cellular NMR or fluorescence co-localisation** of a labelled AEDG-PEG2-TAT conjugate in hTERT-expressing fibroblasts (e.g., IMR-90 cells used in PMID:40908429) to directly test nuclear delivery and TERT co-localisation — the most direct experimental adjudication of the hypothesis.\n- **Surface plasmon resonance (SPR) or ITC** with recombinant hTERT catalytic domain to test whether AEDG alone, or the chimera, binds TERT directly — this would resolve the outstanding question of whether TERT engagement is direct or indirect (histone-mediated).\n\n---\n\n## Raw metrics\n\n| Metric | Value |\n|---|---|\n| pLDDT | — (no output) |\n| pTM | — (no output) |\n| ipTM | — (no output) |\n| Boltz-2 affinity module | — (no output) |\n| Chai-1 agreement | — (disabled) |\n| Heuristic aggregation propensity | 0.0 |\n| Heuristic stability score | 0.307 |\n| Heuristic BBB penetration | 0.0 |\n| Heuristic half-life estimate | Moderate-to-long (~1–6 hours) |\n\n*All heuristic values are sequence-based estimates only — not structural predictions or wet-lab measurements.*\n\n---\n\n*In silico prediction only. No wet-lab validation performed. This is research, not medical advice.*","structural_caption":"No structure was produced for the AEDG-AEEAc-GRKKRRQRRR-NH2 chimera. Boltz-2 returned a 400 error indicating the prediction subprocess wrote no output files, and Chai-1 was disabled. As a result, neither the proposed flexible PEG2-tethered AEDG presentation nor a putative TAT/TERT interface could be visualized or scored.","key_findings_summary":"Epitalon (AEDG; Ala-Glu-Asp-Gly) is a synthetic tetrapeptide originally derived from the bovine pineal gland extract Epithalamin. Over ~25 years of investigation, it has demonstrated a broad spectrum of biological activities including geroprotective, antioxidant, neuroendocrine-modulatory, and antimutagenic effects (PMID:40141333). The most mechanistically relevant finding for the present hypothesis is its capacity to upregulate telomerase: the 2025 Al-Dulaimi et al. study (PMID:40908429) directly demonstrated that Epitalon treatment of normal epithelial and fibroblast cell lines produces dose-dependent increases in hTERT mRNA expression, telomerase enzyme activity, and telomere length extension, establishing a quantitative link between AEDG and TERT at the molecular level. In cancer cell lines, telomere extension occurred predominantly through ALT activation rather than TERT upregulation, suggesting the mechanism is cell-context dependent. Complementary evidence from bovine reproductive biology (PMID:39788414) shows that Epitalon-activated telomerase resides in the nucleus of healthy cumulus-oocyte complexes, whereas in degraded complexes telomerase is cytoplasmic — implying that nuclear access of TERT (or its upstream regulators) is physiologically significant and that intracellular delivery may matter.\n\nDespite these telomerase-related findings, the mechanism by which a small, highly polar, negatively charged tetrapeptide (net charge ~−1 at physiological pH; two acidic residues versus one free amine) crosses the plasma membrane to reach intracellular or nuclear TERT remains essentially uncharacterised. Several studies apply Epitalon to cells simply by addition to culture medium (PMID:40908429; PMID:35413689; PMID:39788414) without addressing intracellular bioavailability, receptor-mediated uptake, or nuclear translocation. One proposed mechanism involves an epigenetic route: molecular modelling suggests AEDG preferentially binds histone H1/3 and H1/6 at DNA-interacting residues, potentially modulating chromatin accessibility to regulate neurogenic gene transcription (PMID:32019204). If this histone-binding model is correct, TERT upregulation may be a secondary downstream effect of chromatin remodelling rather than direct AEDG–TERT interaction — a distinction that the proposed chimeric construct must account for.\n\nThe rational basis for the TAT(48–57)-PEG2-AEDG construct is that bare Epitalon, as a polar tetrapeptide, is unlikely to passively diffuse through lipid bilayers in pharmacologically meaningful concentrations. TAT(48–57) (GRKKRRQRRR) is among the most widely validated cell-penetrating peptides (CPPs), internalised via macropinocytosis and direct translocation routes; its cationic character is well-established for cargo delivery into the cytoplasm and nucleus. PEG-based flexible linkers (including AEEAc/PEG2) are a standard approach to reduce steric interference between a CPP and its cargo, preserve cargo conformational freedom, and improve solubility. The literature on Epitalon does not include any published CPP-fusion or permeability-enhancement strategy, meaning this is a genuinely novel design space.\n\nThe broader Epitalon literature (PMID:40141333; PMID:12374906) documents effects on melatonin synthesis, immune modulation, antioxidant defences, and lifespan extension in multiple organisms, largely through in vivo and cell-culture models. Effects on wound healing in a diabetic retinopathy model (PMID:40493162) and on pineal c-Fos expression (PMID:12500171) further illustrate pleiotropic activity that may or may not converge on TERT. Importantly, the quality of the mechanistic evidence is variable: many older studies are observational or rely on bulk tissue extracts, and the most direct molecular mechanistic data (Al-Dulaimi et al.) is recent and, at the time of writing, has an associated correction notice (PMID:41240216), warranting some caution about the quantitative claims."},"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 accepts that Epitalon (AEDG) activates or upregulates telomerase (TERT) in mammalian cells, leading to telomere elongation, and that this represents a key mechanism underlying its anti-aging effects. There is also agreement that Epitalon exerts antioxidant, anti-apoptotic, and potentially epigenetic effects. However, there is no consensus on the precise molecular mechanism of TERT engagement — whether AEDG acts as a direct TERT ligand/activator, acts indirectly via chromatin/histone remodelling to de-repress hTERT transcription, or signals via a surface receptor to activate downstream TERT expression. Crucially, the literature entirely lacks any investigation of the intracellular pharmacokinetics or membrane permeability of Epitalon itself; bioactivity after extracellular addition to cells is assumed but the delivery problem is never explicitly addressed. No CPP-fusion, nanoparticle, or other intracellular delivery strategy for Epitalon has been published.","knowledge_gaps":"1) The biophysical mechanism by which bare AEDG (pKa-estimated net charge ~−1, MW ~374 Da, highly hydrophilic) enters cells at pharmacologically active intracellular concentrations is completely unstudied — no permeability, endocytosis, or transporter data exist for Epitalon. 2) Whether AEDG directly binds TERT protein or acts upstream (e.g., via histone-mediated hTERT gene de-repression) has not been resolved by direct binding assays (no co-IP, SPR, or ITC data for AEDG–TERT interaction). 3) The dose-response relationship for intracellular versus extracellular Epitalon concentrations relative to TERT activation is unknown. 4) The effect of CPP conjugation on the conformational freedom of the AEDG pharmacophore — particularly the acidic N-terminal Ala and the Glu-Asp dyad — and on its ability to engage any putative binding site has never been tested. 5) Whether the TAT CPP itself independently affects TERT expression (given its arginine-rich nature and known nuclear penetration) has not been studied as a confound. 6) No pharmacokinetic or nuclear localisation data exist for any Epitalon conjugate or modified form.","supporting_evidence":"1) Al-Dulaimi et al. (PMID:40908429) establishes that Epitalon upregulates hTERT mRNA and increases telomerase enzymatic activity in human normal fibroblasts and epithelial cells treated with peptide added to medium, confirming TERT is a bona fide downstream target. 2) Ullah et al. (PMID:39788414) show that telomerase nuclear localisation correlates with healthy cell state and that Epitalon restores nuclear telomerase function, implying that an intracellularly delivered Epitalon construct would encounter TERT in the nucleus — consistent with the hypothesis's targeting rationale. 3) The diabetic retinopathy study (PMID:40493162) explicitly states that ophthalmic/enhanced delivery forms of Epitalon are needed to improve therapeutic efficacy, validating the unmet need for intracellular delivery strategies. 4) The epigenetic histone-binding model (PMID:32019204) supports the idea that AEDG must enter the nucleus (to bind nuclear histones), lending indirect support to the rationale that nuclear delivery is mechanistically necessary. 5) TAT(48–57) has extensive independent literature demonstrating nuclear delivery of cargo molecules, and PEG2/AEEAc linkers are validated for CPP-cargo conjugates; while not in the Epitalon literature specifically, the toolbox is well-established.","challenging_evidence":"1) The Al-Dulaimi et al. paper (PMID:40908429) has a published correction (PMID:41240216), casting some uncertainty on the quantitative mechanistic claims regarding hTERT upregulation magnitude. 2) The epigenetic histone-binding mechanism (PMID:32019204) suggests AEDG may act via chromatin remodelling upstream of hTERT transcription rather than by directly binding TERT protein; if true, the CPP-AEDG chimera may upregulate TERT indirectly through nuclear histone interactions rather than via direct TERT engagement, meaning the hypothesis that the 'free N-terminal acidic motif engages TERT after delivery' may be mechanistically incorrect or oversimplified. 3) Epitalon is bioactive when simply added to cell culture medium at concentrations of 0.01–0.1 mM (PMID:35413689; PMID:40908429; PMID:39788414), raising the possibility that it acts via a cell-surface receptor, extracellular signalling cascade, or receptor-mediated endocytosis — in which case the premise that intracellular delivery is rate-limiting may be incorrect for some cell types. 4) Appending a highly cationic CPP (net +8 charge from GRKKRRQRRR) to an anionic tetrapeptide (net ~−1) creates an overall cationic conjugate; the electrostatic interaction between the AEDG acidic residues and the TAT arginines could occur intramolecularly even with a PEG2 spacer, potentially sequestering the AEDG pharmacophore. 5) The literature contains no structural biology (X-ray, NMR, cryo-EM) of an AEDG–TERT complex, so the claim that the 'N-terminal acidic motif engages TERT' lacks direct structural validation. 6) In cancer cells, Epitalon activates ALT rather than TERT (PMID:40908429), raising the concern that in proliferating assay cells commonly used for CPP-conjugate testing, the readout may reflect ALT activation rather than TERT engagement, complicating mechanistic interpretation."},"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","no structural output was produced — all metrics are absent; heuristic profile is sequence-based only and does not substitute for a folded model","PEG2 (AEEAc) non-standard linker chemistry may be incompatible with current Boltz-2 CCD handling — this may be a proximate cause of the 400 error","FAILED verdict reflects tool-level infrastructure failure, not biological invalidation of the chimeric hypothesis","intramolecular electrostatic sequestration of AEDG by TAT's cationic residues across the PEG2 spacer is an unresolved structural concern","primary mechanistic reference for Epitalon-TERT link (PMID:40908429) has a published correction notice (PMID:41240216) — quantitative claims should be treated with caution"],"works_cited":[{"pmid_or_doi":"40141333","title":"Overview of Epitalon-Highly Bioactive Pineal Tetrapeptide with Promising Properties","year":2025,"relevance":"Comprehensive review summarising 25 years of Epitalon research, explicitly noting telomerase activation among its documented effects and highlighting the paucity of physicochemical/structural studies — directly contextualising the knowledge gap around intracellular delivery."},{"pmid_or_doi":"40908429","title":"Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity","year":2025,"relevance":"The most direct molecular evidence linking Epitalon to TERT: demonstrates dose-dependent hTERT mRNA upregulation, increased telomerase enzyme activity, and telomere elongation in normal human cells, making TERT the primary mechanistic target relevant to the hypothesis."},{"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","year":2025,"relevance":"Preprint version of the Al-Dulaimi et al. study; provides the same TERT/telomerase mechanistic data and is noted here as the precursor to the peer-reviewed publication for transparency regarding publication stage."},{"pmid_or_doi":"39788414","title":"Epitalon-activated telomerase enhance bovine oocyte maturation rate and post-thawed embryo development","year":2025,"relevance":"Shows that functional telomerase is nuclear-localised in healthy cells and cytoplasmic in degraded cells, supporting the importance of nuclear access for TERT engagement and the rationale for an intracellular delivery strategy."},{"pmid_or_doi":"32019204","title":"AEDG Peptide (Epitalon) Stimulates Gene Expression and Protein Synthesis during Neurogenesis: Possible Epigenetic Mechanism","year":2020,"relevance":"Proposes that AEDG acts epigenetically via histone H1 binding rather than direct intracellular receptor engagement, which complicates the hypothesis that free N-terminal AEDG directly engages TERT after CPP-mediated delivery."},{"pmid_or_doi":"35413689","title":"Epitalon protects against post-ovulatory aging-related damage of mouse oocytes","year":2022,"relevance":"Demonstrates that exogenously applied Epitalon (0.1 mM in culture medium) reduces ROS and improves mitochondrial function, but does not address membrane permeability — illustrating the unresolved question of how the polar peptide accesses intracellular targets."},{"pmid_or_doi":"40493162","title":"The Antioxidant Tetrapeptide Epitalon Enhances Delayed Wound Healing in an in Vitro Model of Diabetic Retinopathy","year":2025,"relevance":"Provides evidence of Epitalon bioactivity in human retinal epithelial cells and explicitly calls for development of enhanced delivery formulations, supporting the translational rationale for the CPP-conjugate approach."},{"pmid_or_doi":"12374906","title":"Peptides and Ageing","year":2002,"relevance":"Foundational paper establishing the geroprotective and telomerase-stimulating properties of the Epithalamin/Epitalon lineage; provides historical context for the TERT-targeting hypothesis."},{"pmid_or_doi":"12500171","title":"Epitalon influences pineal secretion in stress-exposed rats in the daytime","year":2002,"relevance":"Demonstrates intranasal administration of Epitalon modulates c-Fos in pinealocytes via proto-oncogene pathways, indicating the peptide reaches intracellular signalling targets in vivo — albeit the delivery mechanism remains unclear."},{"pmid_or_doi":"41240216","title":"Correction: Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity","year":2025,"relevance":"Correction notice for the primary mechanistic paper (PMID:40908429); noted for transparency as it flags the need for cautious interpretation of quantitative claims in that study."}]},"onchain":{"hash":null,"signature":null,"data_hash":null,"logged_at":null,"explorer_url":null},"ipfs_hash":null,"created_at":"2026-05-04T08:51:50.175063+00:00","updated_at":"2026-05-04T08:55:29.982488+00:00"}