Why were they discovered so recently?

They sit in short reading frames nested inside sequences already annotated as ribosomal RNA genes, so nobody was looking for them.

MOTS-c (Mitochondrial Peptide)

A Class, Not a Compound

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-234 cited sources

Mitochondrial-derived peptides are short peptides encoded within the mitochondrial genome, including humanin, MOTS-c and the SHLP family. Reviews by Merry and colleagues and by Wu and colleagues survey their reported roles in energy metabolism and in diabetes.

Key facts

Known members: Humanin, MOTS-c, SHLP1–6
Encoded in: Mitochondrial DNA
Energy metabolism review: Merry 2020 (PMID 32776825)
Diabetes review: Wu 2021 (PMID 35185787)
MOTS-c review: Zheng 2023 (PMID 36761202)
Human interventional data: Absent

Why they were found late

The mitochondrial genome was considered fully annotated. Short open reading frames nested inside sequences already assigned to ribosomal RNA genes were not looked for, because there was no reason to expect them. They were found by deliberately searching for reading frames that annotation had passed over, which is why the whole class emerged within a couple of decades rather than alongside the genome itself.

What the class shares

Short length, mitochondrial encoding, and reported effects on metabolism that are broader than a peptide of that size would suggest. All were identified by sequence analysis rather than by isolating a substance responsible for an observed activity — the reverse of the usual route, and a reason the biology has lagged the discovery.

Research material referenced

MOTS-C 10mg — third-party HPLC tested

View — £24.99

What the reviews cover

Merry and colleagues reviewed mitochondrial-derived peptides in energy metabolism in the American Journal of Physiology in 2020. Wu and colleagues reviewed the class in diabetes and its complications in Frontiers in Endocrinology in 2021. Zheng and colleagues reviewed MOTS-c specifically in 2023 under the framing of therapeutic exploitation — the word promising in that title conveys the stage accurately.

Why review volume is not evidence quality

Several reviews of one small literature indicates interest rather than resolution. A field with settled answers produces fewer surveys, not more. Reading three reviews of the same underlying studies gives three summaries of the same evidence, and the underlying evidence for this class remains preclinical and correlational.

The question the class shares

Where these peptides are translated, and therefore what their sequence actually is in vivo. A reading frame in mitochondrial DNA read by mitochondrial ribosomes gives one peptide; the same frame read in the cytoplasm gives another, because the codes differ. That is a foundational question and it is not settled for the class.

Regulatory position

No mitochondrial-derived peptide holds a marketing authorisation from the MHRA, EMA or FDA, and none has an established human clinical programme. Material supplied here is for laboratory research only, with no claim about metabolism or any condition in any person.

Extended research context

The MOTS-c (Mitochondrial Peptide) deep dive

Deep dive: why a peptide encoded in mitochondrial DNA is unusual

The human mitochondrial genome is 16,569 base pairs encoding 37 genes, and was considered fully characterised by the 1980s: thirteen respiratory-chain proteins, twenty-two transfer RNAs, two ribosomal RNAs. MOTS-c is encoded by a short open reading frame nested inside the 12S rRNA gene — sequence already annotated as doing something else, which is exactly why it went unnoticed. Humanin, found in 2001 inside the 16S rRNA gene, established that the genome held more than its annotation suggested; MOTS-c was found in 2015 by looking deliberately. The implication is that the mitochondrion encodes and releases signalling molecules of its own, rather than only executing instructions sent from the nucleus.

Deep dive: AMPK activation without touching AMPK

AMPK is normally activated when AMP and ADP bind its gamma subunit, making it a direct sensor of the AMP-to-ATP ratio. MOTS-c does not raise that ratio and does not bind the kinase. It inhibits the folate cycle, the one-carbon pathway feeding de novo purine biosynthesis, and the intermediate AICAR accumulates as a result. AICAR is an AMP mimetic — phosphorylated to ZMP, it binds the same regulatory site AMP occupies. So the peptide reaches a cytosolic energy sensor through one-carbon metabolism and a diffusible small molecule, which is a materially different architecture from a receptor-ligand interaction, and different again from metformin's inhibition of complex I.

Deep dive: reading a preclinical literature honestly

Roughly 250 indexed papers exist, and the overwhelming majority are cell and rodent studies. Where humans appear, the work is generally observational: measuring circulating concentrations and correlating them with age, fitness or metabolic state. The 2021 Nature Communications paper is the clearest example of the structure — the human arm measured MOTS-c before and after exercise, finding roughly a 12-fold rise in skeletal muscle against 1.6-fold in circulation, while the interventional work was done in mice. Two inferences the secondary literature routinely makes and the primary literature does not support: that a correlation between low concentrations and poor metabolic health establishes direction, and that a molecule which rises during exercise would reproduce exercise if administered.

Research applications

▸Study of mitochondrial-derived peptides and retrograde signalling
▸AMPK pathway research through non-canonical activation
▸One-carbon and folate-cycle metabolism models
▸Exercise physiology and mitochondrial bioenergetics research
▸Ageing biology and mitochondrial genome expression studies

Handling checklist

✓Store lyophilised material cold, dry and protected from light
✓Expect methionine oxidation as the primary degradation route (+16 Da per residue)
✓No reducing agent needed — the sequence contains no cysteine
✓Introduce diluent gently against the vial wall; swirl rather than shake
✓Aliquot to avoid repeated freeze-thaw cycles
✓Check mass spectrometry for +16 and +32 satellites before relying on a batch

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Reading exercise induction as proof that administration mimics exercise

Fix: The papers report that exercise raises MOTS-c. The reverse inference is not supported and is not claimed.

✗ Treating human observational data as interventional evidence

Fix: Human work measures endogenous concentrations; administration studies were conducted in mice.

✗ Assuming MOTS-c has a cell-surface receptor like humanin

Fix: No receptor is established. Its characterised activity is intracellular.

✗ Storing reconstituted material as though it were as stable as the powder

Fix: Solution-phase material is subject to hydrolysis and oxidation; the lyophilised form is far more stable.

✗ Overlooking WADA status in athlete-adjacent research

Fix: MOTS-c is on the prohibited list; this is relevant to any research context involving competitors.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

What are mitochondrial-derived peptides?: Short peptides encoded within the mitochondrial genome, including humanin, MOTS-c and the SHLP family.
Why were they discovered so recently?: They sit in short reading frames nested inside sequences already annotated as ribosomal RNA genes, so nobody was looking for them.
How strong is the evidence?: Preclinical and correlational. Several reviews of one small literature indicates interest rather than resolution.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

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