Mitochondrial-Derived Peptides: Humanin and the MDP Family

What Mitochondria Have to Do with Longevity

Mitochondria are commonly described as the "power plants" of the cell, but that framing undersells them. These organelles retain their own genome, a remnant of an ancient bacterial ancestor, and that genome encodes functional proteins. For decades, mitochondrial DNA was thought to produce only 13 proteins involved in energy production. Research from the lab of Pinchas Cohen at the USC Leonard Davis School of Gerontology has challenged that assumption substantially.

Beginning in the early 2000s, Cohen's group identified a series of small open reading frames within the mitochondrial genome that encode bioactive peptides, molecules capable of traveling outside the mitochondria and signaling within the cell and even systemically through the bloodstream. The first discovered was humanin. More followed: MOTS-c, then SHLP1 through SHLP6. Each appears to have distinct proposed biological properties, and together they constitute a new functional class of signaling molecule with potential relevance to aging, metabolic health, and neurological resilience.

Humanin: The First Mitochondrial-Derived Peptide

Humanin was identified in 2001 by Japanese researchers studying the brains of Alzheimer's disease patients. They found a small peptide encoded in a mitochondrial ribosomal RNA region that appeared to protect neurons from amyloid-beta toxicity in cell studies. The name "humanin" was chosen to reflect this apparent capacity to protect human neurons.

Subsequent research has explored humanin in several contexts:

Neuroprotection. In rodent models, humanin has been shown to mitigate the neuronal damage associated with amyloid-beta. The mechanisms under study include inhibiting apoptosis pathways and reducing oxidative stress in neural tissue. This work remains preclinical; no humanin-based therapy has been approved for neurological conditions.

Metabolic regulation. Cohen's lab described humanin as a "centrally acting insulin sensitizer," meaning it may influence glucose metabolism through brain-mediated pathways. Administration in rodent models improved insulin sensitivity markers.

Lifespan associations in animal models. In worms and mice, higher humanin levels or exogenous administration has been associated with extended lifespan in some experimental settings. Naked mole rats, which are notably long-lived, show only a slow age-related decline in circulating humanin. In contrast, mice show roughly a 40% drop in humanin over the first 18 months of life.

Human observational data. In a study published in the journal Aging, Cohen's group examined offspring of centenarians: individuals whose parents reached age 100. The offspring group showed measurably higher circulating humanin levels compared to age-matched controls without long-lived parents. This is an observational correlation and does not establish humanin as a cause of longevity or a viable therapy. The study population was small, and these findings require larger, prospective replication.

The MDP Family: A Quick-Reference Table

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MOTS-c: The Exercise Peptide (Brief Overview)

MOTS-c is encoded from the 12S ribosomal RNA region of mitochondrial DNA. It has been characterized as an exercise-mimetic in rodent models, meaning it appears to activate some of the same cellular pathways engaged during physical exercise, particularly those related to skeletal muscle metabolism and insulin signaling. Circulating MOTS-c levels rise in response to exercise in some human studies.

Because MyProtocolStack has a dedicated post covering MOTS-c in depth, this post focuses on humanin and the SHLP series. Visit [MOTS-c on MyProtocolStack](/peptides/mots-c) for that complete coverage.

The SHLP Series: Six Humanin Cousins

The six small humanin-like peptides were identified by Cohen's lab as additional open reading frames within the 16S rRNA region of the mitochondrial genome. Published in the journal Aging in 2016, this work significantly expanded the known MDP family. A 2022 review in the Journal of Clinical Investigation synthesized what is understood about all six.

SHLP2 has received the most research attention after humanin. Studies show it acts as a mitochondrial modulator and protein chaperone, reduces reactive oxygen species production in cell models, promotes mitochondrial biogenesis alongside SHLP3 in preclinical work, and shows lower circulating levels in association with higher prostate cancer risk in observational data, though causality has not been established.

SHLP3 has been studied alongside SHLP2 for effects on mitochondrial biogenesis and cell viability.

SHLP6 is the outlier. Where most SHLPs appear cytoprotective in preclinical models, SHLP6 has been shown to induce apoptosis (programmed cell death) in multiple cell lines. This finding illustrates that the MDP family is not uniformly "protective," and that individual peptides within the same family can serve different biological purposes, potentially including cellular quality control through apoptosis of damaged cells.

SHLPs 1, 4, and 5 remain in early characterization stages with limited published data.

The Pinchas Cohen Lab and Why This Research Matters

The majority of MDP discovery work originates from the Cohen Lab at USC, one of the few research groups in the world focused specifically on mitochondrial-encoded peptides as a functional class. The conceptual importance of this work extends beyond any individual peptide. If mitochondria function as signaling organs in addition to energy producers, and if the decline in circulating MDP levels with age contributes to age-related vulnerabilities, then the mitochondrial genome represents a largely unexplored source of potential longevity-relevant biology.

Critically, none of the MDPs discussed here are approved drugs. Research is ongoing. Most mechanistic evidence comes from cell culture and animal models. Human data is largely observational. Anyone considering peptides for personal use should consult a licensed healthcare provider.

MDPs and Related Peptides Already in Research

It is worth briefly noting how MDPs relate to other peptides under research. [Epithalon](/peptides/epithalon) is studied for telomere-related effects, representing a different class of peptide biology. [Tesamorelin](/peptides/tesamorelin) is an FDA-approved GRF analogue studied for visceral fat and IGF-1 effects. These peptides are distinct from MDPs mechanistically but are tracked by many of the same health-focused individuals interested in longevity biology. Browse the full [peptide library at MyProtocolStack](/peptides) for structured overviews of each.

What to Track if You Are Interested in MDP Biology

While clinical assays for circulating humanin or SHLP2 are not available through standard lab panels today, researchers consistently study MDP biology alongside metabolic and inflammatory markers that are measurable now:

Metabolic markers (relevant to humanin and MOTS-c research):

Inflammatory markers (relevant to cytoprotective MDP research):

Tracking these consistently over time through [MyProtocolStack's biomarker dashboard](/biomarkers) lets you build a longitudinal record that is actually useful when discussing your health data with a provider.

The Open Questions

MDP research is genuinely early. Several important questions remain unresolved:

1. What drives the age-related decline in circulating humanin and other MDPs in humans?

2. Do higher circulating MDPs in centenarian offspring reflect a heritable mitochondrial phenotype, lifestyle factors, or both?

3. Can SHLP2 levels serve as a reliable biomarker for cancer risk or metabolic health in large prospective studies?

4. Are the neuroprotective effects of humanin seen in rodent models translatable to human neurological disease?

5. What are the appropriate therapeutic windows and delivery mechanisms for any MDP-based intervention?

These questions are why MDP research is active and why the evidence tier for all MDPs remains preclinical or observational. Tracking the field carefully and working with providers who follow the literature is the appropriate approach for anyone interested in this space.

Frequently Asked Questions

What are mitochondrial-derived peptides (MDPs)?

MDPs are small proteins encoded directly in mitochondrial DNA. The known family includes humanin, MOTS-c, and six small humanin-like peptides (SHLP1-6). Researchers study them for potential roles in metabolic regulation, neuroprotection, and aging. None are FDA-approved therapies.

Is humanin the same thing as MOTS-c?

No. Both are MDPs encoded in mitochondrial DNA, but they come from different regions and appear to have distinct proposed roles. Humanin was the first discovered and is studied primarily for cytoprotective and neuroprotective effects. MOTS-c is studied as a potential exercise-mimetic influencing insulin sensitivity. MyProtocolStack has a dedicated post covering MOTS-c in detail at [/peptides/mots-c](/peptides/mots-c).

What did the centenarian offspring research find about humanin?

In observational research from the USC Cohen Lab, offspring of centenarians showed measurably higher circulating humanin levels compared to age-matched controls whose parents were not long-lived. This is an observational association, not proof of causation, and has not established humanin as a longevity treatment.

What is SHLP6 and why is it different from the other SHLPs?

Unlike SHLP2 and SHLP3, which are studied for potentially cytoprotective effects, SHLP6 has been shown in preclinical cell studies to induce apoptosis (programmed cell death) rather than protect against it. This illustrates that even within the same peptide family, individual members can have very different proposed biological roles.

Can I measure humanin or other MDPs through standard bloodwork?

Clinical reference ranges for circulating humanin and SHLPs are not yet established in routine lab panels. Researchers use specialized assays in study settings. Tracking the metabolic and inflammatory markers that researchers associate with MDP biology, such as fasting insulin, HbA1c, IGF-1, and hs-CRP, is a practical approach through MyProtocolStack today.

Sources

1. Hashimoto Y, et al. "A rescue factor abolishing neuronal cell death by a wide spectrum of familial Alzheimer's disease genes and Abeta." PNAS, 2001.

2. Lee C, et al. "The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance." Cell Metabolism, 2015.

3. Cobb LJ, et al. "Naturally occurring mitochondrial-derived peptides are age-dependent regulators of apoptosis, insulin sensitivity, and inflammatory markers." Aging, 2016.

4. Yen K, et al. "The mitochondrial derived peptide humanin is a regulator of lifespan and healthspan in mice." Aging, 2020.

5. Reynolds JC, et al. "MOTS-c is an exercise-induced mitochondrial-encoded regulator of age-dependent physical decline and muscle homeostasis." Nature Communications, 2021.

6. Kim KH, et al. "The mitochondrial-encoded peptide MOTS-c translocates to the nucleus to regulate nuclear gene expression in response to metabolic stress." Cell Metabolism, 2018.

7. Miller B, et al. "Mitochondria-derived peptides in aging and healthspan." Journal of Clinical Investigation, 2022.

8. Wan J, et al. "Mitochondria-derived peptides in healthy ageing and therapy of age-related diseases." Best Practice and Research: Clinical Endocrinology and Metabolism, 2023.

9. "Low circulating levels of the mitochondrial-peptide hormone SHLP2: novel biomarker for prostate cancer risk." Oncotarget, 2017.

*MyProtocolStack is a tracking and education tool, not medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any changes to your health protocol. None of the mitochondrial-derived peptides discussed here are FDA-approved for clinical use. Research in this area is ongoing and largely preclinical. Ready to start building your longitudinal health record? [Create a free MyProtocolStack account](/auth/login?mode=signup).*