MOTS-c: the exercise signal hidden in mitochondrial DNA

A second message inside a ribosome gene

Mitochondria, the power plants of our cells, carry their own small circle of DNA. One of its genes builds part of the mitochondrial ribosome, the machine that makes mitochondrial proteins. In 2015, researchers reported that this gene hides a second message: a 51-letter open reading frame that codes for a tiny peptide ^[1].

There is a twist. Read with the mitochondria's own genetic code, the message stops almost as soon as it starts. Read in the main body of the cell with the standard code, it yields a working 16-amino-acid peptide ^[1]. So a signal written in mitochondrial DNA appears to be built outside the mitochondria.

Why do longevity researchers care? In mice, MOTS-c behaves like a chemical echo of exercise. It improved insulin sensitivity, blocked diet-induced weight gain and made old animals run farther ^[1,3]. Its levels in mouse muscle and blood also fall with age, in step with rising insulin resistance ^[1].

Origin: a hunt for hidden genes in Los Angeles

The discovery came from the lab of Pinchas Cohen at the University of Southern California's Leonard Davis School of Gerontology, with Changhan Lee as first author ^[1]. The lead was humanin, an earlier peptide known to be encoded in mitochondrial DNA. If one hidden reading frame existed, the team reasoned, there might be others ^[1].

A computer search of the 12S rRNA gene found a candidate with a strong start signal. The team named its product MOTS-c, short for "mitochondrial open reading frame of the 12S rRNA type-c" ^[1]. They then detected the peptide in mouse and rat tissues and in human plasma. Fasting lowered its levels in muscle and blood, while brain and heart levels held steady ^[1].

How a mitochondrial peptide talks to muscle

Think of AMPK as the cell's fuel gauge. When it reads "low", the cell burns more glucose and fat and builds less. MOTS-c seems to tap that gauge indirectly. In cell studies it slowed the folate cycle and the purine-building pathway attached to it, which made an intermediate called AICAR pile up more than 20-fold. AICAR is a known AMPK activator ^[1].

AMPK explains part of the effect, not all of it: blocking AMPK only partly reduced the boost in glucose use ^[1]. A 2024 study added a second route, reporting that MOTS-c binds and activates an enzyme called CK2 in muscle ^[7].

The most unusual finding concerns location. Under glucose restriction or oxidative stress, MOTS-c travels from the cytoplasm into the nucleus, a move that depends on AMPK. There it helps regulate genes with antioxidant response elements and interacts with the stress-response factor NRF2 ^[2]. In plain terms, the power plant appears to send its own field report to head office.

What the research shows

Metabolism in mice

In the 2015 study, a week of MOTS-c injections improved whole-body insulin sensitivity in mice, with a roughly 30% rise in the glucose infusion rate needed during a clamp test ^[1]. In 12-month-old mice, whose muscles had become insulin resistant, the same course restored muscle insulin sensitivity to young levels. In mice on a high-fat diet, MOTS-c prevented obesity and insulin resistance, partly by raising energy expenditure ^[1].

Exercise and ageing muscle

The 2021 follow-up in Nature Communications added human data ^[3]. Ten sedentary young men did cycling intervals while researchers sampled muscle and blood. Muscle MOTS-c rose 11.9-fold after exercise and stayed raised after a 4-hour rest. Blood levels rose 1.6-fold during exercise and 1.5-fold after, then returned to baseline ^[3].

In mice, two weeks of MOTS-c made 22-month-old animals run about twice as long and 2.16 times as far on a treadmill. Seventeen percent reached the fastest stage, against none of the untreated old mice ^[3]. When treatment started at 23.5 months, the mice later showed better grip strength, stride length and walking ability. There was a trend toward a 6.4% longer median and 7.0% longer maximum lifespan, but the overall survival curves did not differ significantly (p = 0.23) ^[3].

A Japanese gene variant with a puzzling record

A single DNA change, m.1382A>C, swaps one amino acid in MOTS-c (lysine 14 becomes glutamine, "K14Q"). It is found mainly in Northeast Asian populations and had been linked to exceptional longevity in Japan, which led researchers to ask whether MOTS-c plays a part ^[4].

Later work complicated the story. The K14Q form is less active. In a meta-analysis of three cohorts totalling 27,527 people, men carrying the variant had a higher prevalence of type 2 diabetes, while women did not. In one cohort, the excess appeared only in the least physically active men ^[5]. In 721 Japanese athletes and 873 controls, the variant was most common in sprint and power athletes (6.5%) and least common in endurance athletes (2.9%), and carriers had more fast-twitch muscle fibres ^[6].

The same one-letter change in mitochondrial DNA has been linked to living past 100, to sprinting talent and to a higher risk of diabetes in sedentary men ^[4-6].

The first drug attempt: CB4211

CohBar, a biotech company in which Cohen and Lee held shares ^[2,3], built an improved MOTS-c analogue called CB4211. The phase 1b stage of its first trial included 20 adults with obesity and fatty liver disease, 11 on CB4211 and 9 on placebo, for four weeks ^[8]. Liver fat fell by similar amounts in both groups. CB4211 lowered the liver enzymes ALT (by 21%, against a 4% rise on placebo) and AST, and lowered glucose by 6% ^[8].

The programme then stalled. The trial had already been paused in 2018 over injection-site reactions, and in 2023 CohBar said the phase 1b formulation was not suitable for further development ^[9]. After a planned merger collapsed in November 2023, the company announced it would liquidate and dissolve ^[10].

What we don't know yet

• Human efficacy. No published randomised trial has tested native MOTS-c in people. The human data show natural levels rising with exercise, in just 10 young men ^[3].
• Lifespan. The mouse lifespan gain did not reach significance, and larger cohorts were called for ^[3].
• Which mechanism matters. AMPK, nuclear signalling and CK2 have all been proposed, and their relative weight in living animals is unclear ^[1,2,7].
• The genetic paradox. A variant tied to longevity is also tied to diabetes risk in inactive men, and nobody has fully explained why ^[4,5].
• Who did the work. Most foundational studies came from one academic network, and several key authors disclosed consulting and shareholding ties to CohBar ^[2,3,5].
• Safety. Long-term safety in humans is unknown. Injection-site reactions were the main problem in the analogue's development ^[8,9]. FDA staff reviewing MOTS-c in 2026 cited limited clinical data ^[12].

Regulatory status

• Medicine status: MOTS-c is not approved as a medicine by the FDA ^[14], and we found no authorisation from the EMA or any other regulator.
• FDA compounding review (2026): On 23 July 2026, the FDA's Pharmacy Compounding Advisory Committee reviewed MOTS-c for possible addition to the 503A bulk substances list, for the nominated uses of obesity and osteoporosis ^[11]. The panel voted 7-5 in favour, with two abstentions ^[13], although FDA staff scientists had recommended against it ^[12]. The vote is advisory, and at the time of writing (October 2026) we found no final FDA decision.
• Sport: WADA prohibits MOTS-c at all times under section S4.4.1 (AMPK activators), where it is named explicitly ^[14].
• CB4211: Development ended with CohBar's wind-down in 2023 ^[9,10].

In the lab: handling and storage

MOTS-c is normally supplied as a lyophilised (freeze-dried) powder, which is far more stable than any solution. Common practice is long-term storage at −20 °C, with 2–8 °C acceptable for short periods, protected from light and moisture. The sequence contains two methionines and a tryptophan, residues prone to oxidation, so limiting air exposure and repeated opening of vials is sensible. After reconstitution, many labs split solutions into single-use aliquots to avoid freeze-thaw cycles. Our guides on storing research peptides and reading a certificate of analysis cover the details, and the MOTS-c product page lists the lot specifications.

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