Cyclic Glycine-Proline
Also known as: cGP
IGF-1 Bioavailability Regulator & Neuroprotective Peptide
Overview
Endogenous cyclic dipeptide found in plasma, breast milk, and cerebrospinal fluid. Functions as metabolite of IGF-1, regulating its bioavailability through competitive binding to IGFBP-3. Demonstrates neuroprotective, cognitive-enhancing, and cardioprotective properties supported by clinical trials.
Key benefits
- Neuroprotection and cognitive enhancement
- IGF-1 optimization
- Cardiovascular support
- Metabolic health improvement
- Blood-brain barrier penetration
- Convenient oral administration
Mechanism of action
Competes with IGF-1 for IGFBP-3 binding, normalizing bioavailable IGF-1 levels. Acts as positive allosteric modulator of AMPA and GABA-A receptors. Increases BDNF levels via Akt/MDM2-p53 pathway activation.
Molecular data
- Type
- Cyclic dipeptide (2,5-diketopiperazine)
- Half-life
- Extended stability (more stable than linear GPE precursor)
Sequence
cyclo(Gly-Pro)
Indications
What the research community uses this compound for, with self-reported effectiveness.
Neurological
Cognitive Enhancement
EffectiveHigher cGP levels correlate with improved memory retention in elderly populations
Neuroprotection
EffectiveProtects neural stem cells from oxidative stress; efficacy demonstrated in stroke models
Alzheimer's Disease
ModerateMouse studies show reduced amyloid plaque load and improved spatial memory
Parkinson's Disease
ModerateClinical study showed increased CSF cGP and reduced anxiety/depression scores
Metabolic
Type-2 Diabetes
ModerateClinical trial improved vascular complications and normalized HbA1c%
Blood Pressure Regulation
ModerateDemonstrated systolic blood pressure reduction in clinical observations
Recovery
Stroke Recovery
EffectiveHigher cGP/IGF-1 ratios associated with favorable clinical outcomes
Healthy Aging
EffectiveMaintained ratios correlate with preserved cognitive function with age
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Oral
Preferred route with excellent bioavailability and blood-brain barrier crossing.
| Protocol | Dose | Frequency | Route / duration |
|---|---|---|---|
| General cognitive support | 20-40 μg | 1x daily | Oral capsule |
| Neuroprotection/anti-aging | 40-50 μg | 1x daily | Oral capsule |
| Metabolic/cardiovascular support | 40-100 μg | 1x daily | Oral capsule |
| Via blackcurrant extract | 300 mg BCA | 2x daily | Oral capsule |
Interactions
Pairwise interactions with other compounds you might be cycling — the same data behind the cycle builder's safety check.
GH Secretagogues
MonitorBoth affect growth hormone/IGF-1 axis; monitor combined effects on levels
IGF-1
SynergisticcGP is metabolite of IGF-1; regulates bioavailability through competitive IGFBP-3 binding
BPC-157
CompatibleDifferent pathways; BPC-157 promotes tissue repair, cGP modulates IGF-1
Semax
CompatibleBoth offer neuroprotection and nootropic effects through distinct pathways
Selank
CompatibleComplementary cognitive effects; Selank addresses anxiety, cGP optimizes IGF-1
Timeline
Typical week-by-week effects reported in clinical and observational data.
- Week 1-2
Possible subtle improvements in mental clarity
- Week 2-4
Enhanced cognitive function and focus may become noticeable
- Week 4-8
Neuroprotective and metabolic benefits accumulating
- Week 8-12
Optimal IGF-1 regulation and sustained cognitive support
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Rare side effects
- Individual sensitivity reactions
Stop signs — stop and seek advice
- Allergic reactions (rash, difficulty breathing, swelling)
- Unexpected blood glucose changes
- Unusual fatigue or weakness
Contraindications
- Consult healthcare provider if taking IGF-1 or growth hormone medications
- Limited long-term human data available
- Not studied in pregnancy
Quality checks
What a legitimate product looks like, what should give pause, and what should make you stop.
Good signs
- Third-party tested for purity and potency
- Clear cGP content labeling (typically in micrograms per serving)
- Natural blackcurrant-derived sources from New Zealand
- Sealed containers protected from moisture and light
Warning signs
- Products lacking clear cGP content specification
Stop signs — don't use
- Extreme therapeutic claims unsupported by research
- Vague concentration descriptions
References
Primary literature and clinical-trial data informing this entry.
IGF-1 Homeostasis Regulation Study
Scientific Reports · 2014
cGP regulates IGF-1 bioavailability through IGFBP-3 competitive binding
Alzheimer's Mouse Model Study
PMC · 2023
Significantly improved spatial memory; reduced hippocampal plaques 42.3→14.5 per mm²
Parkinson's Disease Clinical Study
PMC · 2018
Blackcurrant supplementation increased CSF cGP 74%; reduced anxiety/depression
Stroke Recovery & Cognitive Function Review
PMC · 2023
Higher cGP/IGF-1 ratios associated with favorable stroke outcomes
Last updated . How this page was sourced is described in the methodology.