MOTS-c and Aging: Why This Peptide Declines with Age

MOTS-c

21% decline

Circulating MOTS-c levels drop 21% between young (18-30) and older (70-81) men, while skeletal muscle expression paradoxically increases 1.5-fold.

D'Souza et al., Aging, 2020

D'Souza et al., Aging, 2020

View as image

MOTS-c (mitochondrial open reading frame of the 12S rRNA type-c) is a 16-amino-acid peptide encoded by the mitochondrial genome and secreted into the bloodstream. Discovered in 2015 by Changhan Lee's laboratory at the University of Southern California, it was the first mitochondrial-derived peptide shown to regulate systemic metabolism.^[1] MOTS-c activates AMPK, improves insulin sensitivity, and has been called an "exercise mimetic" because it reproduces several metabolic benefits of physical activity in animal models. The pillar article on MOTS-c covers its mechanism and the exercise connection. This article focuses on what happens to MOTS-c as we age, and why that decline may matter.

What MOTS-c is and where it comes from

MOTS-c belongs to a class of signaling molecules called mitochondrial-derived peptides (MDPs). Unlike most peptides, which are encoded by nuclear DNA, MOTS-c is encoded within the mitochondrial genome, specifically from a short open reading frame (sORF) within the 12S rRNA gene.^[1]

This mitochondrial origin has direct implications for aging. Mitochondrial DNA (mtDNA) lacks the robust repair mechanisms that nuclear DNA possesses. As cells age, mtDNA accumulates mutations, deletions, and oxidative damage at a rate 10-17 times higher than nuclear DNA. Every mitochondrion contains multiple copies of mtDNA, and as damaged copies accumulate (a process called heteroplasmy), the cell's capacity to produce mitochondrial-encoded proteins, including MOTS-c, degrades.

MOTS-c is produced in multiple tissues and secreted into the circulation, where it acts as a systemic signaling molecule. Its primary target appears to be skeletal muscle, where it activates AMPK and enhances glucose uptake.^[1] For a detailed explanation of this pathway, see how MOTS-c activates AMPK and improves insulin sensitivity.

How circulating MOTS-c changes with age

D'Souza and colleagues published the most detailed human data on MOTS-c and aging in 2020.^[2] They measured circulating MOTS-c and skeletal muscle MOTS-c expression across three age groups of healthy men: young (18-30), middle-aged (45-55), and older (70-81).

The findings were both expected and surprising:

Circulating MOTS-c declined with age. Middle-aged men had 11% lower plasma MOTS-c than young men. Older men had 21% lower levels. This decline parallels the deterioration of mitochondrial function and mtDNA integrity that characterizes aging.

Skeletal muscle MOTS-c expression increased with age. Older and middle-aged men had approximately 1.5-fold higher MOTS-c expression in skeletal muscle compared to young men. This seems contradictory until you consider the context: the increase in local muscle expression may represent a compensatory response to declining systemic MOTS-c supply, or it may reflect age-related fiber type shifts.

The increase correlated with slow-twitch fibers. Skeletal muscle MOTS-c expression was associated with markers of slow-type (Type I) muscle fibers. Aging is characterized by a progressive shift from fast-twitch (Type II) to slow-twitch (Type I) fibers. The increased MOTS-c expression in aging muscle may simply reflect this shift in fiber composition rather than an upregulation of MOTS-c production per fiber.^[2]

Plasma MOTS-c correlated with muscle quality in older men. In the older group specifically, higher circulating MOTS-c was associated with better muscle quality, defined as maximal leg-press load relative to thigh cross-sectional area. This suggests that those who maintain higher MOTS-c levels into old age may preserve muscle function better than those whose levels decline more steeply.

Why circulating levels drop

The decline in circulating MOTS-c with age has multiple converging causes.

Mitochondrial DNA damage. Each cell contains hundreds to thousands of mitochondria, each with multiple copies of mtDNA. Aging brings cumulative oxidative damage, point mutations, and large-scale deletions in mtDNA. Because MOTS-c is encoded in mtDNA, degradation of the mitochondrial genome directly reduces the template available for MOTS-c production.

Mitochondrial biogenesis slows. The creation of new mitochondria (biogenesis) is regulated by PGC-1alpha and other transcription factors whose activity declines with age. Fewer mitochondria per cell means fewer factories producing MOTS-c. Exercise upregulates PGC-1alpha and mitochondrial biogenesis, which may explain why exercise partially counteracts the age-related MOTS-c decline.

Cellular senescence accumulates. Senescent cells accumulate with age and have dysfunctional mitochondria. A 2025 study demonstrated that MOTS-c levels decrease with aging and senescence in pancreatic islet cells, and that MOTS-c treatment could prevent islet cell senescence and delay diabetes in mouse models.

Reduced physical activity. Exercise acutely increases circulating MOTS-c. Reynolds and colleagues showed that MOTS-c is exercise-induced and functions as a mitochondrial-encoded regulator of physical capacity.^[3] The sedentary lifestyles common in aging populations reduce this exercise-mediated MOTS-c stimulus, compounding the biological decline.

MOTS-c decline and metabolic aging

The original Lee 2015 discovery paper established MOTS-c's connection to metabolic health. In mouse models, MOTS-c treatment prevented both age-dependent and high-fat-diet-induced insulin resistance, and reduced obesity.^[1]

The metabolic mechanism centers on AMPK activation and the folate cycle. MOTS-c inhibits the folate cycle and its tethered de novo purine biosynthesis, which leads to AMPK activation. Under metabolic stress, MOTS-c translocates from the cytoplasm to the nucleus, where it regulates gene expression through antioxidant response element (ARE) binding. This nuclear translocation is AMPK-dependent.

In humans, the metabolic connection is supported by observational data: patients with type 2 diabetes have significantly lower circulating MOTS-c than healthy controls.^[1] Whether low MOTS-c contributes to diabetes development or whether diabetes suppresses MOTS-c production is not established. The likely answer is both, creating a cycle where metabolic dysfunction reduces MOTS-c, which further impairs metabolic function.

The Mohtashami 2022 review in the International Journal of Molecular Sciences compiled the evidence linking MOTS-c decline to age-related diseases including type 2 diabetes, cardiovascular disease, Alzheimer's disease, and osteoporosis.^[4] The review noted that MOTS-c gene polymorphisms have been found to be associated with human lifespan, most notably the m.1382A>C variant found at higher frequency in Japanese centenarians.

The Reynolds 2021 study: reversing aging in mice

The most compelling evidence for MOTS-c's role in aging came from Reynolds and colleagues, published in Nature Communications in 2021.^[3]

The study demonstrated several key findings:

MOTS-c is exercise-induced. Plasma MOTS-c levels increased after exercise in both mice and humans. In young male mice, a single bout of exercise increased circulating MOTS-c, and this response was attenuated in older mice.

Exogenous MOTS-c improved physical capacity in old mice. When old mice received MOTS-c injections, their physical performance improved, including enhanced treadmill running capacity. The effect was particularly striking because it occurred without exercise training; MOTS-c alone was sufficient to improve physical capacity in aged animals.

MOTS-c reversed age-related insulin resistance. Systemic MOTS-c injection restored insulin sensitivity in aged mice, reducing fasting glucose and improving glucose tolerance. This reversal of metabolic decline occurred in mice that were already old, suggesting MOTS-c could potentially treat, not just prevent, age-related metabolic dysfunction.

Life-long MOTS-c measurements showed progressive decline. The study tracked MOTS-c levels across the mouse lifespan, confirming that circulating MOTS-c decreases progressively with age. Exercise-induced MOTS-c release also diminished with aging.

These results positioned MOTS-c as a potential mediator of exercise's anti-aging benefits. The peptide may be one of the signals through which physical activity communicates metabolic information from working muscle to other tissues.

The longevity genetics connection

The m.1382A>C polymorphism in the MOTS-c coding sequence has been associated with exceptional longevity in Japanese populations. This variant changes one amino acid in the MOTS-c peptide, and its frequency is higher in centenarians than in the general population.

This genetic association does not prove that MOTS-c determines lifespan. Mitochondrial DNA variants are inherited maternally and exist in linkage with other mtDNA variants, making it difficult to attribute longevity effects to a single polymorphism. But the association adds to the circumstantial case that MOTS-c biology is relevant to human aging trajectories.

The Zheng 2023 review in Frontiers in Endocrinology expanded on this, noting that MOTS-c's therapeutic potential extends across metabolic, cardiovascular, and neurodegenerative diseases, all of which increase with aging.^[5]

What exogenous MOTS-c does in animal models

Mouse studies have tested MOTS-c injection across multiple aging-related conditions:

Insulin resistance. MOTS-c treatment prevented age-dependent insulin resistance in mice and reversed established insulin resistance in old mice.^[1][3]

Obesity. Diet-induced obesity was prevented by MOTS-c treatment, with effects on both fat accumulation and metabolic parameters.^[1]

Physical decline. Old mice receiving MOTS-c showed improved running capacity and muscle homeostasis.^[3]

Cellular senescence. MOTS-c treatment reduced markers of senescence in pancreatic islet cells, suggesting a direct anti-aging effect at the cellular level.

Skeletal muscle. Gudiksen and colleagues (2026) demonstrated that MOTS-c improves intrinsic muscle function in animal models, supporting the idea that this peptide acts directly on the tissue most affected by age-related decline.^[6]

These animal results are consistent and compelling. The critical caveat: no human clinical trial has tested exogenous MOTS-c administration. All human data is observational (measuring endogenous levels) or genetic (polymorphism associations). Whether injecting MOTS-c in humans would reproduce the mouse results is unknown. Whether it could be administered safely, at what dose, and for how long are all unanswered questions.

The gap between mouse data and human reality

MOTS-c research exists at an earlier translational stage than most peptides covered on this site. The evidence hierarchy currently stands at:

Strong animal evidence: Mouse studies from multiple laboratories show consistent effects on insulin sensitivity, physical capacity, and age-related metabolic decline. The mechanism (AMPK activation, nuclear translocation, ARE-mediated gene regulation) is well-characterized.

Supportive human observational data: Circulating MOTS-c declines with age in humans. Low MOTS-c is associated with type 2 diabetes. A genetic variant in the MOTS-c gene is associated with exceptional longevity.

Zero human interventional data: No published trial has administered exogenous MOTS-c to humans and measured outcomes. The safety profile in humans is entirely unknown.

This gap is not unusual for a peptide discovered less than a decade ago. But it means that claims about MOTS-c's anti-aging benefits in humans are extrapolations from mouse biology, not conclusions from clinical evidence. Given the differences in mitochondrial metabolism between mice and humans (including different mtDNA mutation rates, different tissue-specific expression patterns, and different lifespans), the mouse-to-human translation is not guaranteed.

The Bottom Line

MOTS-c, a 16-amino-acid peptide encoded by mitochondrial DNA, declines 21% in circulating levels between young and older men. This decline parallels the deterioration of mitochondrial function that characterizes aging. In mouse models, MOTS-c replacement reverses age-related insulin resistance and improves physical capacity. Human observational data links low MOTS-c to type 2 diabetes and high MOTS-c genetic variants to exceptional longevity. The evidence is compelling at the mechanistic and animal level, but no human trial of exogenous MOTS-c has been conducted. The peptide represents a promising target for understanding, and potentially treating, metabolic aging, but the clinical evidence does not yet exist.

Frequently Asked Questions

Does MOTS-c decrease with age?

Yes. In a study of healthy men across three age groups, circulating MOTS-c was 11% lower in middle-aged men (45-55) and 21% lower in older men (70-81) compared to young men (18-30). Skeletal muscle MOTS-c expression paradoxically increased with age, likely reflecting fiber type shifts from fast-twitch to slow-twitch muscle.

What is MOTS-c peptide?

MOTS-c is a 16-amino-acid peptide encoded by the mitochondrial genome, discovered in 2015. It activates AMPK, improves insulin sensitivity, and has been called an "exercise mimetic" because it reproduces metabolic benefits of exercise in animal models. It is secreted into the bloodstream and acts on skeletal muscle and other tissues.

Can MOTS-c reverse aging?

In mouse models, MOTS-c injection reversed age-related insulin resistance, improved physical capacity in old mice, and reduced cellular senescence in pancreatic cells. A genetic variant in the MOTS-c gene is associated with exceptional longevity in Japanese centenarians. No human clinical trial has tested exogenous MOTS-c, so anti-aging effects in humans are unproven.

Why do MOTS-c levels decline with age?

Multiple factors converge. Mitochondrial DNA accumulates damage 10-17 times faster than nuclear DNA, reducing the template for MOTS-c production. Mitochondrial biogenesis slows with aging. Physical activity decreases, removing the exercise-mediated stimulus for MOTS-c release. Cellular senescence accumulates, further impairing mitochondrial function.

Is MOTS-c available as a supplement?

MOTS-c is available from gray market peptide suppliers but is not approved for human use by any regulatory agency. No human safety or efficacy trial has been published. The purity, stability, and bioactivity of commercially available MOTS-c are unverified. All claims about human benefits are based on mouse studies and observational human data, not clinical trials.

Does exercise increase MOTS-c?

Yes. Reynolds and colleagues showed in a 2021 Nature Communications study that exercise acutely increases circulating MOTS-c in both mice and humans. This response is attenuated in older organisms, meaning elderly individuals get less MOTS-c boost from the same exercise stimulus. Regular physical activity may help maintain MOTS-c levels that would otherwise decline with age.