The MOTS-c, Humanin & SHLP Axis: Mitochondrial Peptides Explained

Mitochondrial-derived peptides (MDPs) are among the most intriguing molecules in longevity science: short, bioactive peptides translated not from the nuclear genome but from small open reading frames inside mitochondrial DNA itself. The three headline members — MOTS-c, humanin, and the six small humanin-like peptides (SHLP1 through SHLP6) — act as retrograde signals carrying information from the mitochondria to the nucleus and the wider body.7 This monograph maps the shared biology of the axis, then separates what is proven in humans from what remains animal and cell-culture work.

This article is informational and editorial content for research and educational purposes only. It is not medical advice, not a protocol to follow, and not a sourcing guide. These peptides are not FDA-approved; humanin and the SHLPs are sold as research compounds with no completed human efficacy trials. Dosing figures are reported strictly as seen in the published literature for completeness — never as recommendations. Consult a licensed clinician before any health decision.

What are the MOTS-c, humanin and SHLP peptides?

The founding MDP, humanin, is a 24-amino-acid peptide encoded within the mitochondrial 16S rRNA (MT-RNR2) gene. An in-silico scan of that same MT-RNR2 region — performed by Cobb, Lee and Cohen in 2016 — revealed six additional peptides, named small humanin-like peptides, ranging roughly 20 to 38 amino acids.1 MOTS-c, a 16-amino-acid peptide, is encoded separately in the 12S rRNA region and functions as an AMPK activator.7 Together these form the known MDP set, and a unifying observation runs through all of them: circulating levels decline with age, in both mice and humans, which is the central rationale for longevity interest.1

The standout small humanin-like peptide is SHLP2, a 26-amino-acid peptide (molecular weight approximately 3017 Da) that circulates in plasma and is detectable in tissue and cerebrospinal fluid.32 Tissue expression differs across the family — SHLP1 in heart, kidney and spleen; SHLP2 in liver, kidney and muscle; SHLP3 in brain and spleen — underscoring that "SHLP" is not one molecule but a heterogeneous set.8

How does the mitochondrial peptide axis work?

The best-defined mechanism in the SHLP family is SHLP2's receptor biology. A high-throughput β-arrestin screen of 168 G-protein-coupled receptors identified the atypical chemokine receptor CXCR7 (ACKR3) as SHLP2's top target. SHLP2 recruited β-arrestin2 to CXCR7, reaching about 70% of the efficacy of the canonical ligand CXCL12 with an EC₅₀ near 0.97 µM, drove receptor internalization, and bound directly — while notably not engaging CXCR4.2 Downstream, the cascade runs SHLP2 → CXCR7 → β-arrestin2 → ERK1/2 (MAPK) phosphorylation; a MAPK inhibitor abolished SHLP2-induced POMC neuron depolarization in hypothalamic slices, whereas a PI3K inhibitor did not.2 SHLP2 has additionally been linked to STAT3 and Akt survival signaling and acts as a molecular chaperone that inhibits protein misfolding.4

Centrally, systemic or central SHLP2 induces c-Fos in the hypothalamic arcuate nucleus, preferentially activating anorexigenic POMC neurons over orexigenic AgRP neurons. Chemogenetic silencing of POMC neurons blunted SHLP2's appetite-suppressing and thermogenic effects, confirming POMC as the functional node.2 At the organelle level, SHLP2 binds respiratory complex I, raises oxygen consumption and ATP, increases mtDNA copy number and PGC-1α (biogenesis), and lowers reactive oxygen species and caspase-mediated apoptosis.3 Across the axis, humanin shares this insulin-sensitizing and anti-apoptotic profile, while MOTS-c acts chiefly through AMPK to mimic an exercise-like metabolic state.7 No formal human or even rodent pharmacokinetic dataset exists for SHLP, so half-life, clearance and oral bioavailability are unreported.2

What is the evidence by member and indication?

The entire axis is preclinical at the efficacy level. The most developed indication is metabolic: in hyperinsulinemic-euglycemic clamp studies, centrally infused SHLP2 increased glucose uptake and suppressed hepatic glucose production, and in high-fat-diet male mice, SHLP2 at 2 mg/kg/day for three weeks protected against weight gain, improved glucose tolerance and insulin sensitivity, raised energy expenditure, and upregulated brown-fat thermogenic genes.2 The only human signal is a dot-blot of male sera showing lower serum SHLP2 in obese and diabetic men versus healthy controls — a correlation in a tiny sample, hypothesis-generating only.2

Beyond metabolism, SHLP2 has shown cytoprotection: in human transmitochondrial ARPE-19 macular-degeneration cybrid cells, 3.2 µM SHLP2 restored OXPHOS subunits, cut caspase expression, raised mtDNA copy number and PGC-1α, and partially rescued viability after amyloid-β insult — but with no effect in normal cybrids, indicating disease-state-specific action.3 The longevity rationale rests only on age-related decline of these peptides plus their mitochondrial-fitness biology; no lifespan or healthspan intervention study in any organism has been reported for SHLP, making direct anti-aging claims Grade D.1 A critical caveat: the family is not uniform — SHLP2 and SHLP3 are pro-survival, SHLP4 is proliferative, and SHLP6 is pro-apoptotic.5

How safe are these peptides and what is their 2026 status?

For SHLP and humanin, human safety data simply do not exist — no toxicology, no adverse-event registry, no maximum tolerated dose, because no human has been studied in a trial.2 Three weeks of intraperitoneal SHLP2 in mice was reported without overt toxicity, but those studies were not designed as formal safety assessments and used males only.2 The dominant theoretical concern is mechanistic: SHLP2 signals via CXCR7/ACKR3 and ERK/MAPK plus STAT3 and Akt — pathways implicated in cell survival, proliferation and tumor biology, with CXCR7 overexpressed in several cancers, making chronic agonism a theoretical oncologic and angiogenic concern.2 Because research-use-only peptides are unregulated for human administration, purity, sterility, endotoxin and identity are not guaranteed — a real-world hazard independent of the molecule.12 By default, pregnancy, lactation, pediatrics and active malignancy are avoid populations.

Legally, no MDP is FDA-approved for any indication.7 SHLPs are not on FDA's 503A bulk-drug-substance lists and have no recognized compounding pathway; they are sold only as "research use only / not for human use" reagents, and human use violates FDA rules regardless of that label.1012 Patents describe therapeutic uses for SHLP2 and the family, but a patent is not evidence of approval or human efficacy.11 For athletes, the axis is effectively off-limits: MOTS-c was banned by WADA in 2024 as an AMPK-activating metabolic modulator, and although SHLPs are not individually enumerated on the 2026 Prohibited List, as injectable peptide signaling agents with metabolic, exercise-mimetic activity they plausibly fall under Section S2; competitive athletes should treat the family as prohibited and verify with their anti-doping organization.13

Bottom line. The mitochondrial-derived peptide axis is genuinely interesting biology — a coherent mechanism (CXCR7/ACKR3 → β-arrestin → ERK, hypothalamic POMC activation, complex-I binding and mitochondrial biogenesis) with reproducible rodent and cell-culture benefits in insulin sensitivity, anti-obesity and cytoprotection. But what is proven in humans is minimal: MOTS-c alone has reached first-in-human and a registered Phase 2a, while humanin and SHLP have no interventional human trial at all. Marketing any of these as a metabolic or longevity therapy runs ahead of the evidence (Grade D for any human-benefit claim), and the family's heterogeneity — SHLP6 is pro-apoptotic — means claims must be member-specific. Until first-in-human safety and PK studies exist for humanin and SHLP, the rung MOTS-c has already reached, those members belong in the lab, not the clinic. Regulatory and WADA facts here are current as of June 2026 and should be re-verified for any specific use.