MOTS-c, Humanin, and the MDP Family | Ordinary Peptides

MOTS-c, Humanin, and the MDP Family | Ordinary Peptides
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Science & Medicine Mitochondria Aging Research Cellular Biology
Investigative Science Journalism

The Mitochondrial Genome's Hidden Library: How a Forgotten Stretch of DNA Became the Hottest Frontier in Aging Research

For most of the twentieth century, biologists believed they had finished reading mitochondrial DNA. They had counted thirty-seven products and called it a complete inventory. They were wrong. The story of how that error was corrected began in a Tokyo lab in 2001, accelerated in Los Angeles in 2015, and is still being written.
2026 · By the Ordinary Peptides Research Team

The Textbook That Was Wrong

If you opened a cell biology textbook in 1999, the section on mitochondrial DNA was a closed file. The mitochondrion, the cell's energy organelle, carried its own small genome — sixteen thousand five hundred and sixty-nine base pairs of circular DNA, separate from the three billion base pairs in the cell nucleus. That genome was thought to encode exactly thirty-seven products. Thirteen proteins involved in the electron transport chain. Twenty-two transfer RNAs. Two ribosomal RNAs. End of list. The list felt complete because it had to be. The mitochondrion was, in evolutionary terms, a former bacterium that had been swallowed by an ancestral cell about a billion and a half years ago. Over time it had handed most of its genetic functions over to the host nucleus and kept a stripped-down operating manual for the things it still needed to do locally. Thirteen proteins for the energy machinery, the rest for the translation infrastructure. A clean, parsimonious accounting. Then, in 2001, a Japanese research group looking for something else entirely found a peptide where no peptide was supposed to be. They called it Humanin. Fourteen years later, a USC team working with completely different tools found a second one. They called it MOTS-c. Then a related family of six more peptides showed up in 2016. By the mid-2020s, the count of known mitochondrial-derived peptides had risen from zero to at least eight, with credible bioinformatic suggestions that several more remain to be characterized. The mitochondrial genome wasn't a finished story. It was an unread library.
A note before going further Nothing in this article is medical advice. Mitochondrial-derived peptides are research compounds. None of them are FDA-approved for human therapeutic use. Some are on WADA's prohibited list. For the chemistry, mechanism, and current research status of MOTS-c itself, see the dedicated reference page. This piece is about the broader scientific story.

The Mitochondrial Genome Paradox

To understand why the discovery of the first mitochondrial-derived peptide was such a shock, you have to understand why nobody was looking for one. The mitochondrion's evolutionary history is the reason. Once a free-living bacterium, it surrendered most of its DNA to the nucleus over hundreds of millions of years and kept only a small, dense set of genes that handled local respiratory function. The remaining genome was so compact that biologists could (and did) sequence it completely and account for every codon. The notion that there were unread regions, hidden coding sequences capable of producing functional peptides, ran counter to almost every assumption about how this genome worked. Compounding the problem: the peptides we now know about are short. Twenty-four amino acids in one case. Sixteen in another. The translation machinery in the cytoplasm normally ignores open reading frames that small. Standard gene-prediction algorithms in the late 1990s were tuned to filter them out as noise. The instruments capable of detecting tiny circulating peptides (mass spectrometry sensitive enough to flag a sixteen-residue molecule against a complex biological background) were only just becoming routine in research labs around 2000. And there was a deeper assumption baked into cell biology: that signaling went one direction. The nucleus told the mitochondrion what to do. The mitochondrion delivered ATP and shut up. The idea that the organelle was sending its own messages back to the nucleus, and farther afield to other tissues, was not on the radar. The first crack in that picture came from people who weren't even looking at mitochondria.

2001: The First Crack (Humanin)

The Hashimoto and Nishimoto laboratories at Keio University in Tokyo were studying neurodegeneration. They wanted to find genes that could rescue brain cells from the toxic effects of Alzheimer's disease mutations — a screening approach known at the time as "death-trap" cloning. They built a cDNA library from the occipital lobe of an Alzheimer's patient (a brain region that tends to remain intact in the disease) on the reasoning that whatever was protecting it should be expressed there. What they pulled out of that screen was a 24-amino-acid peptide that suppressed neuronal death from multiple Alzheimer's-related insults. They named it Humanin, on the principle that it might "bring back humanity" to patients with the disease. The 2001 paper appeared in Proceedings of the National Academy of Sciences. It was, on its face, a neuroscience finding. The mitochondrial origin took longer to establish. The Humanin gene mapped to the 16S ribosomal RNA region of the mitochondrial genome — a region that, by all prior assumptions, was supposed to encode structural RNA only, not bioactive peptides. There were complications: nuclear pseudogenes resembling Humanin existed too, and for several years researchers debated whether the peptide was authentically mitochondrial or an artifact of nuclear contamination. Two independent replications in 2003, one by a group studying IGFBP3 and another working on Bax-related apoptosis, confirmed the peptide was real and biologically active. By the late 2000s, Humanin was being detected in human plasma, cerebrospinal fluid, testes, hypothalamus, and vascular wall tissue. It had measurable effects in cell-survival, anti-apoptotic, and metabolic assays. It was not an artifact. For about a decade, Humanin sat as a single anomaly. One peptide, one mitochondrial-encoded exception to the textbook rule. The field treated it as an interesting curiosity rather than the start of a category. That changed in 2015.

2015: The Second Discovery (MOTS-c)

The Pinchas Cohen laboratory at the USC Davis School of Gerontology was, by 2015, one of the few groups taking the mitochondrial-peptide question seriously. Cohen had been working on Humanin since the mid-2000s and was convinced more peptides had to be hiding in the mitochondrial genome. The lab, led on this project by postdoctoral researcher Changhan Lee, ran a different kind of screen: not a cell-survival assay, but a systematic bioinformatic search of mitochondrial DNA for short open reading frames that might produce functional peptides. They found one in the 12S rRNA region (the MT-RNR1 gene), a different ribosomal RNA gene from the one that encoded Humanin. The predicted peptide was sixteen amino acids long. Its sequence: MRWQEMGYIFYPRKLR. They named it MOTS-c, for "mitochondrial open reading frame of the 12S rRNA-c." The 2015 Cell Metabolism paper (PMID 25738459) reported that MOTS-c was widely expressed in tissues, circulated in plasma, and acted as a powerful metabolic regulator. In high-fat-diet mice, exogenous MOTS-c improved insulin sensitivity and reduced obesity at magnitudes that researchers compared to metformin — the standard first-line drug for type 2 diabetes. The mechanism, worked out over subsequent years, ran through the folate cycle: MOTS-c modulated one-carbon metabolism in a way that drove accumulation of AICAR, an established AMPK activator, which then triggered the broader downstream metabolic effects. A peptide encoded inside the mitochondrion was reaching across the cell to nuclear gene expression and across the body to skeletal muscle. A follow-up paper from the same lab in 2021, published in Nature Communications, demonstrated that MOTS-c administration to aged mice substantially restored running performance on treadmill tests. The peptide was being framed in the literature as something more provocative than a metabolic regulator: an "exercise mimetic." Whether that framing holds up in humans is one of the live questions of the field. For the chemistry, regulatory status, and current research data on MOTS-c itself, the MOTS-c reference page is the better source. The point worth emphasizing here is structural: the second mitochondrial-derived peptide had been characterized using a completely different methodology from the first, in a different rRNA gene, with a different mechanism of action. This was no longer a one-off. It was a pattern.

The Family Expands (2016 to 2024)

Once the existence of MOTS-c was established, the obvious question became: how many more are there? The answer, as of 2026, is at least six more, all from the same general region of the mitochondrial genome. In 2016, Laura Cobb and colleagues in the Cohen lab (now collaborating with the Albert Einstein College of Medicine) published a paper in Aging describing six small humanin-like peptides (SHLP1 through SHLP6, pronounced "shlep") encoded in the 16S rRNA region of mitochondrial DNA. The bioinformatic approach was the same one used for MOTS-c. The peptides differed from each other in their biological effects: SHLP2 turned out to be a potent insulin sensitizer with neuroprotective activity; SHLP6 promoted apoptosis in some cancer cell lines; SHLP3 enhanced fat-cell differentiation. Like Humanin and MOTS-c, circulating levels of SHLP2 declined with age. The total inventory of well-characterized mitochondrial-derived peptides reached eight: Humanin, MOTS-c, and SHLP1 through SHLP6. Several less-characterized candidates have appeared in the literature since. The mechanistic story has continued to deepen. A 2024 paper in iScience by Kumagai and colleagues reported that MOTS-c binds directly to casein kinase 2 (CK2) in skeletal muscle, identifying a previously unknown molecular target for the peptide's metabolic effects. A separate 2024 paper in Theranostics by Jia and colleagues showed that MOTS-c participates in plasma-membrane repair through translocation of TRIM72 to damaged membrane regions — a function that has nothing obvious to do with metabolism and points to a much broader role in cell biology than the original framing suggested. Both papers extended the mechanism beyond what was known a decade earlier.
A useful detail The first eleven amino acid residues of MOTS-c are highly conserved across fourteen mammalian species. That degree of conservation across deep evolutionary time is one of the strongest indicators biologists have that a sequence is doing something biologically important — nature does not preserve protein sequences for hundreds of millions of years if they are functionally inert.

Why Mitochondrial-Derived Peptides Are Different

A naive reading of this story is that the field has simply added eight new peptides to the long list of bioactive peptides already known to biology. That reading misses what is actually new. The first thing that is new is the direction of signaling. Most of the regulatory peptides catalogued in twentieth-century biology (insulin, glucagon, growth hormone, the hypothalamic releasing factors) are encoded by the nuclear genome and then sent out through the cell or the bloodstream to act on receptors elsewhere. Mitochondrial-derived peptides reverse that direction. They are encoded inside the organelle, translated locally, and then sent upstream to the nucleus to alter gene expression, or sent into general circulation to act on distant tissues. This is a category of communication called retrograde signaling, and it had been suspected to exist for years; mitochondrial-derived peptides are the first concrete molecular examples of how it actually works. The second thing that is new is what these peptides report on. Humanin levels rise during cellular stress. MOTS-c production increases with exercise. SHLP2 declines as the organism ages. These are not just signaling molecules; they are biomarkers of mitochondrial state. The cell is using peptide messengers to tell the rest of the body something specific about how its energy organelles are doing. The literature has begun calling this class of molecules "mitokines" (mitochondrial cytokines or mitochondrial hormones), and the term has stuck. The third thing that is new, and perhaps most important, is what this implies about the mitochondrial genome itself. If sixteen thousand five hundred base pairs can encode at least eight bioactive peptides that mainstream biology missed for half a century, the natural question is what else the same approach might surface elsewhere. Other organelles. Non-coding regions of the nuclear genome. The dark genome. Nobody knows the answer yet, but the methodology that produced MOTS-c (bioinformatic screening of regions previously assumed to be "informationally complete") is now being applied widely.

Where the Field Is Heading

Three currents are moving the research forward in 2026. Aging and longevity. Humanin and MOTS-c both decline measurably with age, in mice and in human cohort data. The therapeutic question that follows is obvious and has been driving much of the field: does restoring those levels (pharmacologically, through analogs, or through interventions that increase endogenous production) affect health span or lifespan? The answer in laboratory mice is, in some studies, yes. The answer in humans is unknown. Genetic association studies have tried to use natural sequence variants in these peptides as a substitute for an intervention trial; the results have been inconsistent. An early study suggesting a longevity association was followed by a much larger 2021 meta-analysis on more than twenty-seven thousand participants that found a different signal entirely, this one tied to type 2 diabetes risk rather than longevity. The biology is real. The clinical translation is harder than the cellular work suggested it would be. Metabolic disease. CB4211, a synthetic MOTS-c analog developed by the biotech company CohBar, completed Phase I/II clinical trials in non-alcoholic fatty liver disease in 2021. The result was the first clinical-stage trial of any mitochondrial-derived peptide. CohBar's commercial trajectory has been uneven, but the precedent matters: the regulatory pathway from "interesting research compound" to "drug candidate evaluated in human patients" has been walked at least once. Several other groups are working on Humanin analogs for metabolic and neurodegenerative indications. Detection and pharmacology. One of the underappreciated obstacles in this field is methodological. Detecting a sixteen-amino-acid peptide circulating at picomolar concentrations against a complex plasma background is hard. Quantifying its half-life, distribution, and tissue-specific uptake is harder. Most of the published pharmacokinetic data on these peptides comes from rodent studies; human data are sparse. Until measurement improves, dose-finding for clinical applications will lag behind mechanistic understanding. There is also an open regulatory question. MOTS-c was added to the World Anti-Doping Agency's prohibited list as an example of an AMPK activator under sub-class S4.4.1 (Metabolic Modulators), effective with the 2024 list. The decision was driven, USADA explained, by the peptide being "heavily marketed by wellness and anti-aging clinics and on social media as a weight loss peptide" despite its experimental status. Both Humanin and MOTS-c have appeared on FDA Category 2 compounding restrictions. Whether the broader 2026 reclassification activity around peptides under HHS Secretary Robert F. Kennedy Jr. extends to MOTS-c is one of the open questions of this calendar year.

The Bottom Line

Twenty-five years ago, no one thought the mitochondrial genome could encode bioactive peptides. The view was that this genome had been comprehensively read and the inventory closed. That view turned out to be wrong by at least eight peptides, with strong indications that the real number is higher. The implications are still being worked out. Mitochondrial-derived peptides sit at the intersection of several active research fronts: the basic biology of how organelles communicate, the mechanism of aging at the cellular level, the search for new metabolic-disease therapies, and the broader question of what other "informationally complete" regions of the genome might still be hiding functional sequences. None of these questions has a settled answer in 2026. All of them have more credibility now than they did in 2014. The mitochondrion was supposed to be the cell's energy factory. It is turning out to also be one of the cell's most sophisticated communication systems. Biology has not finished mapping that conversation.
Editorial Disclosure Ordinary Peptides supplies research-grade MOTS-c as a laboratory compound. This article is editorial coverage of mitochondrial-derived peptides as a scientific category, not promotion of any specific product. For the chemistry, evidence base, and regulatory status of MOTS-c itself, see the linked reference page. For the broader research-peptide category most closely tied to longevity and aging, see the aging research section.
Sources & Further Reading
  1. Hashimoto Y, Niikura T, Tajima H, et al. "A rescue factor abolishing neuronal cell death by a wide spectrum of familial Alzheimer's disease genes and Aβ." Proc Natl Acad Sci USA. 2001;98(11):6336-6341. pnas.org
  2. Lee C, Zeng J, Drew BG, et al. "The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance." Cell Metab. 2015;21(3):443-454. PMID 25738459. pubmed.ncbi.nlm.nih.gov
  3. Cobb LJ, Lee C, Xiao J, et al. "Naturally occurring mitochondrial-derived peptides are age-dependent regulators of apoptosis, insulin sensitivity, and inflammatory markers." Aging. 2016;8(4):796-809. aging-us.com
  4. Reynolds JC, Lai RW, Woodhead JST, et al. "MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis." Nat Commun. 2021;12:470.
  5. Kim SJ, Mehta HH, Wan J, et al. "Mitochondria-derived peptides in aging and age-related disease: a systematic review." GeroScience. 2016. PMID 27052166.
  6. Kumagai H, et al. MOTS-c modulates skeletal muscle function via casein kinase 2 binding. iScience. 2024. pmc.ncbi.nlm.nih.gov
  7. Jia H, et al. "Mitochondria-encoded peptide MOTS-c participates in plasma membrane repair by facilitating the translocation of TRIM72 to membrane." Theranostics. 2024. pmc.ncbi.nlm.nih.gov
  8. Wan W, Zhang L, Lin Y, et al. "Mitochondria-derived peptide MOTS-c: effects and mechanisms related to stress, metabolism and aging." J Transl Med. 2023;21:36.
  9. Merry TL, Chan A, Woodhead JST, et al. "Mitochondrial-derived peptides in energy metabolism." Am J Physiol Endocrinol Metab. 2020.
  10. USADA. "Athlete Advisory: What's New on the 2025 WADA Prohibited List." usada.org
  11. WADA Prohibited List 2025, S4.4.1 Metabolic Modulators. wada-ama.org
  12. USC Today. "Newly discovered proteins may protect against age-related illnesses." 2016. today.usc.edu
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