The peptide, known as MOTS-c, is transcribed from the mitochondrial open-reading-frame of the 12S rRNA-c region. Since its discovery, MOTS-c has attracted intense interest as one of a handful of mitochondrial-derived peptides that can act as signaling molecules, influencing metabolism, stress responses and aging far beyond the organelle where they are made. What the Nanjing-led team has done is to trace its role in the eye with unusual precision. Using retinal tissue, they showed that MOTS-c is predominantly localized in retinal endothelial cells, the thin, tightly connected cells that form the inner lining of blood vessels and constitute the blood-retinal barrier, the critical interface that keeps the light-sensitive tissue protected and properly nourished.

That localization matters because the earliest events in diabetic retinopathy are vascular. Chronically high blood sugar injures endothelial cells, weakens the junctions between them, and allows fluid and blood components to leak into the retina. It also damages mitochondria within the endothelial cells themselves, promoting the accumulation of reactive lipid peroxides that attack cellular membranes. To test whether MOTS-c is a casualty of this process, the researchers exposed human retinal endothelial cells to high glucose concentrations and studied a streptozotocin-induced diabetic mouse model, a standard experimental system in which the drug destroys insulin-producing cells and produces sustained hyperglycemia. In both settings, high glucose reduced the expression of MOTS-c in the retinal vasculature, suggesting that the loss of this mitochondrial signal is part of the injury program that diabetes unleashes on the eye.

The therapeutic logic followed directly. When the team supplied MOTS-c to human retinal endothelial cells suffering high-glucose-induced injury, the peptide protected the endothelial barrier and ameliorated mitochondrial dysfunction. The same benefit appeared in the diabetic mice: MOTS-c treatment rescued vascular endothelial damage in the retina. These genetic and pharmacological approaches, applied both in cell culture and in living animals, established that the peptide’s dysregulation is not merely a byproduct of disease but a mechanistically meaningful contributor to the vascular breakdown that drives diabetic retinopathy.

The deeper question was how a 16-amino-acid peptide could accomplish this. To find out, the researchers turned to unbiased molecular profiling. Transcriptomic analyses, which survey changes in gene expression across the whole genome, and lipidomic analyses, which map the constellation of fats and phospholipids inside the cells, converged on a surprising pathway: MOTS-c increased the activity of phospholipase A2, a family of enzymes that cleave phospholipids, the molecules that form the backbone of every cellular membrane, and thereby regulated phospholipid metabolism. In other words, the mitochondrial peptide appears to reprogram how endothelial cells maintain and remodel their own membranes under diabetic stress.

Among the differentially expressed genes associated with this upregulated phospholipase A2 activity, one stood out. Phospholipase A2 group VI, known as PLA2G6, showed the most significant upregulation following MOTS-c treatment. PLA2G6, an intracellular calcium-independent phospholipase, is best known in other contexts for its role in lipid homeostasis and, when mutated, in neurodegenerative disease. In the diabetic retina, the new work assigns it a protective job: PLA2G6-mediated degradation of lipid peroxides served as a primary mediator of the endothelial barrier protection seen during MOTS-c treatment. Lipid peroxides are the corrosive products of unsaturated fatty acid oxidation, and their accumulation is a hallmark of ferroptosis and related forms of oxidative cell death. By accelerating their breakdown, PLA2G6 effectively detoxifies the membrane environment of stressed endothelial cells.

The causal chain was then tested in the most demanding way, by removing the link. When the researchers knocked down PLA2G6, the protective effect of MOTS-c against vascular endothelial damage collapsed, both in vitro and in vivo. The peptide could no longer defend the endothelial barrier without its enzymatic partner. This loss-of-function result elevates the finding from correlation to mechanism: MOTS-c acts upstream, PLA2G6 acts downstream, and the degradation of lipid peroxides is the functional bridge between them. It also suggests that patients or experimental systems with insufficient PLA2G6 activity might respond poorly to MOTS-c-based interventions, a consideration that could shape future strategies for patient selection.

Taken together, the study identifies a novel role for MOTS-c dysregulation in mediating vascular endothelial damage in diabetic retinopathy and proposes MOTS-c supplementation as a potential therapeutic approach, one that works by regulating phospholipid homeostasis and protecting the endothelial barrier through PLA2G6. The conceptual appeal is considerable. Rather than blocking a single growth factor after the vasculature has already begun to fail, a MOTS-c-based strategy would aim to reinforce the fundamental resilience of endothelial membranes early in the disease, when intervention could still prevent the cascade of leakage, inflammation and pathological vessel growth that ultimately destroys vision. It also adds to a growing appreciation that mitochondrial-derived peptides are not metabolic footnotes but active hormones with tissue-specific protective functions.

Substantial work remains before this biology reaches the clinic. The findings, published as an open-access article in Cell Death Discovery on 10 October 2026, were obtained in cell culture and in a mouse model of diabetes, and translating a mitochondrial peptide into a safe, durable therapy for human eyes will require solving questions of delivery, dosing, stability and long-term safety that the current study did not address. Human diabetic retinas, exposed to years of metabolic fluctuation, may behave differently from acute experimental hyperglycemia. Yet the study offers something the field has lacked: a defined molecular axis, running from a mitochondrial genome-encoded peptide through phospholipase A2 activity and lipid peroxide clearance to the integrity of the blood-retinal barrier. If that axis holds up in further preclinical and clinical testing, the smallest genome in our cells may turn out to hold one of the larger answers to diabetic blindness.

Subject of Research: The role of the mitochondrial-derived peptide MOTS-c and phospholipase A2 group VI in protecting retinal endothelial cells in diabetic retinopathy

Article Title: Mitochondrial-derived peptide MOTS-c rescues vascular endothelial damage via PLA2G6 in diabetic retinopathy

Article References: Liao, Y., Xiang, J., Xia, Y., Liu, C., He, C., Tong, J., Chen, Y., Yao, G., & Xie, Z. (2026). Mitochondrial-derived peptide MOTS-c rescues vascular endothelial damage via PLA2G6 in diabetic retinopathy. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03384-5

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03384-5

Keywords: MOTS-c, mitochondrial-derived peptide, diabetic retinopathy, retinal endothelial cells, PLA2G6, phospholipase A2, lipid peroxides, endothelial barrier, mitochondrial dysfunction, phospholipid metabolism, blood-retinal barrier, diabetes complications

The story of MOTS-c began with the recognition that the mitochondrial genome, long assumed to encode only 13 proteins of the oxidative phosphorylation machinery plus tRNAs and rRNAs, harbors short open reading frames that yield functional peptides. MOTS-c, whose name derives from “mitochondrial open reading frame of the 12S rRNA type-c,” emerged as a representative member of this expanding family of mitochondrial-derived peptides, which also includes humanin and the small humanin-like peptides SHLP1 through 6. Structurally, MOTS-c is unusual: it is rich in methionine and basic residues, and it can translocate to the nucleus, where it acts directly on chromatin, a property that distinguishes it from most circulating peptide hormones and gives it a uniquely intimate connection to gene regulation.

At the mechanistic level, the review lays out a coherent signaling framework. In the cytosol, MOTS-c can activate the AMP-activated protein kinase, or AMPK, a master energy sensor, partly through accumulation of AICAR, an intermediate of the purine synthesis pathway that MOTS-c helps generate from folate cycle metabolites. AMPK activation in turn suppresses the mechanistic target of rapamycin complex 1, mTORC1, shifting cells from an anabolic, growth-oriented state toward a catabolic, stress-adaptive one. In the nucleus, MOTS-c interacts with transcription factors and chromatin-modifying machinery, including the transcription factor ATF4-dependent integrated stress response and, in some settings, the antioxidant transcription factor Nrf2, driving the expression of genes bearing antioxidant response elements. These pathways converge on redox control, promoting the activity of enzymes such as superoxide dismutase, catalase, heme oxygenase-1, and NAD(P)H quinone dehydrogenase 1, thereby buffering reactive oxygen species and stabilizing cellular homeostasis under metabolic stress.

The physiological repertoire attributed to MOTS-c is remarkably broad. The review catalogs reported roles in exercise adaptation, where MOTS-c levels rise with physical activity and the peptide appears to contribute to muscle metabolic remodeling and thermogenesis through pathways involving PGC-1α and uncoupling proteins. It details protective effects in models of diet-induced obesity and insulin resistance, where MOTS-c administration improves glucose tolerance and lipid profiles. It also covers endothelial protection, suppression of inflammatory signaling through the NF-κB and NLRP3 inflammasome axes, regulation of apoptosis via the Bcl-2 and Bax balance, and benefits in preclinical models of chronic kidney disease, osteoporosis, and cardiopulmonary bypass injury. In each of these contexts, the peptide behaves as a homeostatic buffer, helping cells and tissues adapt to metabolic and oxidative stress rather than succumbing to it.

Yet the clinical evidence is strikingly heterogeneous, and the authors devote considerable attention to why. Measurements of circulating MOTS-c abundance in human cohorts have produced inconsistent results, with some studies reporting lower levels in type 2 diabetes, obesity, or coronary artery disease, and others finding elevated or unchanged concentrations. The review identifies plausible biological and methodological culprits: assay variability between enzyme-linked immunosorbent assay kits and mass spectrometry, the short half-life and rapid clearance of the peptide, the influence of age, sex, body mass index, and circadian rhythms, and the fact that circulating MOTS-c may not reflect intracellular or intramitochondrial pools that could be the functionally decisive fraction. Without standardized detection methods and agreed-upon reference compartments, the authors argue, the true relationship between MOTS-c abundance and human disease remains an open question.

The most provocative section of the review concerns cancer, where the context-dependence of MOTS-c becomes starkest. In some tumor models, MOTS-c acts as a suppressor: it can promote apoptosis of cancer cells, sensitize them to chemotherapy, and restrain epithelial-mesenchymal transition through modulation of pathways involving YAP, STAT3, and TGF-β. The peptide has also been implicated in promoting ferroptosis, the iron-dependent form of cell death, by influencing glutathione metabolism, the cystine transporter SLC7A11, and the GPX4 axis, offering a potential route to undermine the redox resilience that tumors depend upon.

In other contexts, however, the same peptide appears to work in the tumor’s favor. The review describes evidence that MOTS-c can contribute to metabolic reprogramming that supports tumor cell survival, help cancer cells adapt to oxidative stress, remodel the tumor microenvironment through effects on cancer-associated fibroblasts and extracellular matrix deposition, and modulate immune cell populations, including regulatory T cells and dendritic cells, in ways that may blunt antitumor immunity. There are also indications that MOTS-c signaling may contribute to therapeutic resistance, potentially through mechanisms involving multidrug resistance transporters, enhanced stress granule formation, and activation of survival kinases such as AKT and ERK. The authors are careful to frame this evidence as emerging and still limited, but the conceptual implication is clear: a signal that protects normal cells from stress can, under the altered selection pressures of malignancy, protect tumor cells from the very therapies designed to kill them.

This duality is not a contradiction but a lesson in biological context. The review emphasizes that MOTS-c’s action is shaped by subcellular localization, since nuclear MOTS-c reprograms gene expression while cytosolic and mitochondrial pools may act locally; by cell type, since stromal and immune cells in the tumor microenvironment may respond differently from epithelial cancer cells; by the metabolic state of the tissue, since AMPK and mTOR signaling are interpreted differently in nutrient-replete versus nutrient-deprived conditions; and by the inflammatory milieu, since the same redox-buffering activity that quells damaging inflammation in chronic disease may also shield tumor cells from oxidative attack by immune cells. Any therapeutic strategy that delivers MOTS-c systemically, or blocks it indiscriminately, would therefore need to account for which compartment and which cell population is being targeted.

The authors close with a research agenda that reads like a checklist for the field’s maturation. Priority tasks include establishing standardized, quantitative detection methods for MOTS-c in plasma, tissues, and subcellular fractions; mapping the trafficking routes that carry the peptide from mitochondria to nucleus and into the circulation; identifying the full set of molecular targets and binding partners in a cell-specific manner; and dissecting the effects of MOTS-c separately in tumor cells and in the stromal and immune compartments of the microenvironment. Only with that granularity, they argue, can the field determine in which disease contexts boosting MOTS-c signaling would be therapeutically beneficial and in which it could be detrimental.

For a 16-amino-acid peptide discovered barely a decade ago, MOTS-c has traveled an extraordinary conceptual distance, from metabolic curiosity to a candidate mediator of exercise, aging, inflammation, and cancer biology. The review’s central message is a caution against hype in either direction: MOTS-c is neither a universal elixir of metabolic health nor a straightforward oncogene. It is a stress signal, and like all stress signals, its meaning depends entirely on who is listening, under what conditions, and to what end. As mitochondria continue to shed their reputation as mere power plants, MOTS-c stands as a vivid example of how much biology remains encoded in the small, overlooked corners of the human genome, and how carefully that biology must be read before it is exploited in the clinic.

Subject of Research: The mitochondria-derived peptide MOTS-c as a context-dependent stress signal in metabolic homeostasis and cancer

Article Title: MOTS-c: a context-dependent mitochondrial stress signal in homeostasis and tumor

Article References: Kong, W., Yin, Y., Zhao, S., Ma, B., Chen, Z., Xi, J., & Yang, H. (2026). MOTS-c: a context-dependent mitochondrial stress signal in homeostasis and tumor. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-09029-6

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09029-6

Keywords: MOTS-c, mitochondrial-derived peptide, mitochondrial signaling, AMPK, oxidative stress, inflammation, tumor microenvironment, ferroptosis, metabolic homeostasis, cancer biology, therapeutic resistance, mitochondrial genome

The logic of the field has shifted because metabolites themselves turn out to be messengers. S-adenosylmethionine, or SAM, a product of one-carbon metabolism, serves as the methyl donor for chemical marks placed on mitochondrial DNA, including 5-methylcytosine and the bacteria-like N6-methyladenine. The methyltransferase METTL4 installs 6-methyladenine on mitochondrial DNA, which disrupts binding of the transcription factor TFAM and suppresses mitochondrial transcription. Hypoxia strongly induces METTL4 in liver and breast cancer cells, throttling mitochondrial metabolism precisely when tumors want it restrained. Methylation of the mitochondrial genome appears to protect it from oxidative damage, and DNA methyltransferases DNMT3A and DNMT3B mediate this in embryonic cells — enzymes whose aberrant expression or mutation drives cancer initiation. The picture is complicated, however: the true abundance of 5-methylcytosine on mitochondrial DNA remains debated, with optimized protocols reporting levels of only 0.19 to 0.67 percent in mouse oocytes and human lung carcinoma cells, and technical artifacts such as inefficient bisulfite conversion and mis-mapping of nuclear-integrated mitochondrial sequences continuing to muddy clinical analyses.

The replication machinery itself is equally metabolically entangled. DNA polymerase gamma, POLG, together with its accessory subunit POLG2, copies the mitochondrial genome, and its overactivation has been linked to elevated risk of prostate cancer and acute myeloid leukemia. Proteomic surveys have revealed a dense landscape of post-translational modifications on POLG and POLG2 that couple cellular fuel state to genome maintenance. The acetyltransferase GCN5 acetylates POLG at lysine 1039 using acetyl-CoA as donor, while the NAD+-dependent deacetylase SIRT3 reverses the mark — a push-pull system that reads acetyl-CoA and NAD+ availability directly. In parallel, poly(ADP-ribose) polymerase 1 uses NAD+ to attach ADP-ribose groups to POLG, triggering ubiquitination and degradation. Through these routes, the cell’s energy currency and redox state literally decide how much replication enzyme survives, and cancer cells exploit these metabolite-sensing nodes to rewire mitochondrial function to their advantage.

Transcription is governed by the same logic. The mitochondrial RNA polymerase POLRMT is succinylated at lysine 622, a modification that impairs its DNA-binding activity. The metabolic enzyme SUCLG1, part of the succinyl-CoA ligase complex, restricts mitochondrial succinyl-CoA levels to keep POLRMT hypo-succinylated, sustaining mitochondrial respiration and driving leukemia progression. Succinyl-CoA thus functions as a key metabolic signal bridging mitochondrial metabolism and transcription in both leukemia and solid tumors. TFAM, the packaging factor that recruits POLRMT to promoters, is itself phosphorylated, acetylated, and — most recently — arginine-methylated at position 82 by PRMT5, a modification essential for DNA binding and mitochondrial genome integrity. Loss of PRMT5 leaves breast carcinoma cells vulnerable to mitochondrial DNA damage and oxidative stress, and several PRMT5 inhibitors are already in clinical trials, raising the prospect of attacking tumor bioenergetics through the transcription apparatus itself.

Downstream, RNA processing and ribosome assembly consume enormous metabolic resources. The 12S and 16S ribosomal RNAs of the mitoribosome are studded with SAM-dependent methylation marks: TFB1M dimethylates the 3′ end of 12S rRNA to stabilize the small subunit, NSUN4 methylates cytosine 911, METTL15 installs N4-methylcytidine at position 839, and TRMT61B places N1-methyladenosine at position 947 of 16S rRNA, a modification conserved across all vertebrates that stabilizes local ribosome structure. Strikingly, when SAM is depleted, unprocessed pre-rRNA accumulates and mitoribosome assembly grinds to a halt. The same SAM pool feeds transfer RNA modifications, including the taurine-and-GTP-dependent wobble modification 5-taurinomethyluridine installed by GTPBP3 and MTO1, which is essential for translation fidelity — and, notably, MTO1 upregulation in melanoma sustains oxidative phosphorylation and confers resistance to vemurafenib. The dioxygenase ALKBH7, which depends on alpha-ketoglutarate and oxygen to erase methylation marks that otherwise delay transfer RNA maturation, adds another metabolite-gated checkpoint to the pipeline.

At the level of protein synthesis, the review highlights an increasingly granular view of mitoribosome regulation. Human mitoribosomes contain three iron-sulfur clusters installed by GLRX5 and BOLA3, enzymes with prognostic value in bladder cancer and lung adenocarcinoma, while METTL17 carries a [4Fe-4S] cluster that confers redox-sensing activity to protein synthesis. Lipid metabolism matters too: cardiolipin, enriched in cristae membranes where mitochondrial protein synthesis is spatially confined, promotes the inner-membrane docking of ribosomes, and the remodeling enzyme tafazzin maintains the membrane curvature this requires. Perhaps the most striking recent discovery is lactylation — the attachment of lactate-derived lactyl groups to proteins — now documented on TFAM and multiple ribosomal proteins in clinical tumor tissues, and linked to chemoresistance and metastasis in breast, kidney and lung cancers. Lactate, once dismissed as waste, is actively consumed by mitochondria as fuel and now appears to write epigenetic marks on the very machinery that builds the respiratory chain.

The mitochondrial genome also hides a second layer of coding information. Beyond its thirteen canonical proteins, it produces microproteins with potent biological activity. Humanin, a 24-amino-acid peptide, suppresses apoptosis by interfering with Bax activation; it is elevated in the serum of breast cancer patients and accelerates tumor growth, lung metastasis, glioblastoma invasion and temozolomide resistance in experimental models. MOTS-c, a 16-amino-acid peptide from the 12S rRNA open reading frame, activates AMPK and shows context-dependent effects — circulating levels rise in prostatic precancerous lesions and hepatocellular carcinoma yet fall in adrenal tumors, while in liver cancer MOTS-c promotes apoptosis under hypoxia and suppresses tumor growth. Additional peptides such as the SHLP family, SHMOOSE and CYTB-187AA underscore that the mitochondrial central dogma generates unanticipated regulators whose roles in cancer are only beginning to be mapped.

The translational payoff is substantial. The allosteric POLRMT inhibitor IMT1B blocks mitochondrial transcription with minimal toxicity in normal tissues and suppresses leukemia, endometrial carcinoma and other tumors in preclinical models. The thymidine analog alovudine inhibits POLG, impairing oxidative phosphorylation in acute myeloid leukemia, while small-molecule activators such as PZL-A allosterically restore mutant polymerase activity. FDA-approved antibiotics quinupristin and dalfopristin inhibit mitochondrial translation and reduce glioblastoma stem cell clonogenicity, and linezolid suppresses T cell metabolism through the same route, with hematological toxicities limiting its use. Inhibition of dihydroorotate dehydrogenase by ML390 starves leukemia cells of pyrimidines needed for mitochondrial biogenesis, and the iron chelator deferoxamine disrupts OXPHOS super-complexes in breast cancer with encouraging selectivity. Genome-wide sequencing has also revealed that colorectal cancer mitochondrial DNA mutations carry prognostic weight, with MT-CYB mutations significantly correlating with poor patient survival.

Perhaps the most futuristic front is mitochondrial genome editing itself. DddA-derived cytosine base editors and TALE-linked deaminases now allow precise CG-to-TA and A-to-G conversions in mitochondrial DNA, and adeno-associated virus vectors have delivered these editors to post-mitotic mouse tissue, while engineered mitoARCUS nucleases have cleared mutant mitochondrial DNA systemically in animal models. Off-target nuclear editing — reported at rates up to 17.5 percent at some sites — and unintended heteroplasmy shifts remain serious concerns, spurring strategies such as nuclear export signals, strand-selective editors like CyDENT, and tumor-specific promoters to restrict editing to cancer cells. The review’s authors close with a call to integrate high-resolution structural biology, single-cell metabolomics and in vivo lineage tracing to decode the spatiotemporal choreography of mitochondrial gene expression. If they are right, the organelle’s second genome — long overshadowed by the nucleus — may prove to be one of the most exploitable weaknesses a tumor carries.

evolutionary backdrop helps explain why this control system is so intricate. Mitochondria descend from a free-living prokaryotic ancestor engulfed more than 1.45 billion years ago, and the long history of metabolic trade-offs with the host cell left the organelle semi-autonomous: most of its roughly 1,500 proteins are nuclear-encoded, yet the thirteen genes retained in the compact circular genome encode core respiratory chain subunits whose expression must be tuned to local energy demand. Because mtDNA copy number varies naturally across tissues, its dysregulation is directly tied to cancer risk, and tumor cells dynamically adjust both genome abundance and gene output to match proliferative and metastatic needs.

Structural organization adds another layer of control. The mitochondrial genome packs into nucleoids within the matrix, with most protein- and rRNA-coding regions flanked by transfer RNA genes, and regulatory marks such as 5-methylcytosine concentrate in the displacement loop, the non-coding region where replication and transcription originate. Recent structural work has also complicated the classic picture of the replicase: POLG2 can contact DNA independently of POLG without altering polymerase activity, hinting at versatile functions beyond processive elongation.

Methodological caveats deserve emphasis for readers weighing the evidence. Detecting low-frequency mitochondrial modifications demands careful technique; antibody-based capture, bisulfite conversion, isotope labelling, HPLC–mass spectrometry and next-generation sequencing each carry distinct biases, and incomplete light-strand coverage can distort tumor measurements. As optimised protocols spread and quantitative data accumulate across tumor types, the field should be better placed to separate genuine metabolic regulation from technical noise, sharpening the therapeutic opportunities this review maps out.

Subject of Research: Metabolic regulation of the mitochondrial central dogma in cancer

Article Title: Exploring mitochondrial central dogma in cancer from a metabolic perspective

Article References: Zhang, S., Han, B., Chen, L., Chen, L., Wang, T., Lin, M., Liu, J., & Wang, Y. (2026). Exploring mitochondrial central dogma in cancer from a metabolic perspective. Clinical Cancer Bulletin, 5(1), Article 19. https://doi.org/10.1007/s44272-026-00071-5

Image Credits: AI Generated

DOI: 10.1007/s44272-026-00071-5

Keywords: mitochondria, mitochondrial DNA, mtDNA replication, POLRMT, TFAM, mitoribosome, RNA modifications, lactylation, mitochondrial translation, humanin, MOTS-c, mitochondrial genome editing