The "exercise mimetic" label gets stuck on multiple compounds, but they are not interchangeable. SLU-PP-332 and MOTS-c both produce a transcriptional and metabolic phenotype that overlaps with what endurance training produces — but they take opposite philosophical routes to get there. SLU-PP-332 is a synthetic small molecule designed to flip a specific receptor switch. MOTS-c is a natural peptide your mitochondria already encode and release under metabolic stress.
Research-context information only. SLU-PP-332 is an investigational small-molecule pan-agonist of the estrogen-related receptors (ERRα/β/γ). MOTS-c is a research peptide encoded within mitochondrial DNA. Both have been characterized in cell and animal models; neither has entered a registered human clinical trial. This article reports what has been documented, not what should be done. Consult a licensed physician for personal medical decisions.
This is the comparison most-searched against SLU-PP-332 that has clean published data on both sides and no carcinogenicity flag complicating the conversation.
What Each Compound Is
SLU-PP-332
Synthetic small molecule, molecular formula C22H21N5O3, ~419.4 Da. Identified and characterized at Saint Louis University by the Burris lab (Billon et al., ACS Chem Biol 2023, PMID 36988910). It binds and activates all three estrogen-related receptors — ERRα, ERRβ, and ERRγ — with highest potency at ERRα.
Despite the name, ERRs do not bind estrogen. They are orphan nuclear receptors that share structural homology with classical estrogen receptors. ERRα sits downstream of PGC-1α and regulates the transcriptional program for mitochondrial biogenesis, fatty acid β-oxidation, and oxidative phosphorylation (Schreiber et al., PNAS 2004, PMID 15087503; Tripathi et al., review 2014, PMID 25222219).
Class: Synthetic ERR pan-agonist (small molecule, not a peptide).
MOTS-c
Sixteen-amino-acid peptide encoded inside the mitochondrial 12S rRNA gene — making it part of a class called mitochondrial-derived peptides (MDPs) discovered in 2015 by Lee et al. (Cell Metabolism 2015, PMID 25738459). MOTS-c targets the folate-AICAR-AMPK pathway in skeletal muscle, where it activates AMP-activated protein kinase (AMPK).
Under metabolic stress, MOTS-c translocates from cytoplasm to nucleus and regulates expression of nuclear genes in an AMPK-dependent manner (Kim et al., 2018, PMID 29983246). This is a previously unknown form of mitochondrial-to-nuclear retrograde signaling.
Class: Mitochondrial-derived peptide, AMPK activator.
Mechanism: Same Endpoint, Different Entry Points
Both compounds drive mitochondrial biogenesis. The difference is where they enter the regulatory network.
| Layer | SLU-PP-332 | MOTS-c |
|---|---|---|
| Direct target | ERRα/β/γ nuclear receptors | Folate-AICAR-AMPK pathway |
| Cellular signal | ERR-mediated transcription via PGC-1α coregulation | AMPK activation → downstream metabolic adaptation |
| Tissue with strongest signal | Skeletal muscle, heart, liver | Skeletal muscle |
| Endogenous status | Synthetic — no natural counterpart | Naturally encoded in mitochondrial DNA |
| Phenotype in mice | ↑ endurance (~70%), ↓ fat mass (~12%), ↑ type IIa fibers | ↑ exercise capacity, ↑ insulin sensitivity, ↓ DIO obesity |
Both endpoints converge on increased mitochondrial mass, increased fatty acid oxidation, and a shift toward oxidative metabolism. But ERR pan-agonism (SLU-PP-332) is a transcriptional intervention at the receptor level, while AMPK activation (MOTS-c) is a kinase-level intervention that propagates through a different network of effectors.
This is the mechanistic basis for the "additive rather than redundant" framing — the two pathways meet at the mitochondrial output but enter the regulatory web at different upstream points.
Origin: Synthetic vs Natural
The origin difference is not philosophical — it has practical implications.
SLU-PP-332 was rationally designed and synthesized to be an ERR pan-agonist. It does not exist in any organism. Receptor selectivity profiles, dose-response, and tissue distribution were engineered into the molecule.
MOTS-c is a peptide your own mitochondria release under metabolic stress. Endogenous MOTS-c levels rise during exercise in human plasma (D'Souza et al., 2020, PMID 32182209). Administering exogenous MOTS-c is more accurately framed as supplementing a peptide the body already produces than as introducing a new pharmacological entity.
That difference shows up in the safety conversation. MOTS-c has measured human exposure (endogenous + observational pharmacokinetic studies). SLU-PP-332 has zero human exposure data — no Phase 1, no IND, no formal pharmacokinetics in any human.
Effect Comparison: What Each Does Best
Endurance and aerobic capacity
SLU-PP-332: strongest signal here. Mouse treadmill data showed ~70% longer running time and ~45% farther distance versus vehicle controls before exhaustion (Billon et al., ACS Chem Biol 2023, PMID 36988910). Required ERRα — knockout mice showed no benefit, confirming the mechanism.
MOTS-c: also produces endurance-capacity benefits in mice. In mid-aged and aged mouse models, MOTS-c improved physical performance and grip strength. Endogenous MOTS-c rises during exercise in humans, suggesting it is part of the natural exercise-adaptation signaling.
Edge: SLU-PP-332 has the larger effect-size in mouse endurance work. Both produce the same direction of change.
Fat loss
SLU-PP-332: DIO mice on 25 mg/kg IP BID for 28 days lost ~12% body weight and gained ~10× less fat than vehicle controls on the same diet (Billon et al., J Biol Chem 2023, PMID 37739806). Mechanism: increased fatty acid oxidation plus increased basal metabolic rate.
MOTS-c: in DIO mice, MOTS-c improved insulin sensitivity and reduced fat accumulation. The fat-loss signal is real but modest compared with the SLU-PP-332 numbers.
Edge: SLU-PP-332 has the larger fat-loss signal in mice. MOTS-c is an insulin-sensitizer with secondary fat-loss benefit, not a primary fat-loss tool.
Insulin sensitivity and glucose handling
SLU-PP-332: improved glucose tolerance reported in DIO mice (Billon 2023, PMID 37739806). Likely mediated by increased oxidative capacity in skeletal muscle.
MOTS-c: this is where MOTS-c has the cleanest data. Direct AMPK activation drives glucose uptake in skeletal muscle, and the original 2015 paper documented improved insulin sensitivity in DIO mouse models. Subsequent work has reinforced the metabolic-syndrome reversal phenotype.
Edge: MOTS-c. Insulin sensitivity is its strongest mechanism.