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
Metabolic
Recovery
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Delivery method
| Protocol | Dose | Frequency | Duration |
|---|---|---|---|
| — | 20-40 μg | 1x daily | — |
| — | 40-50 μg | 1x daily | — |
| — | 40-100 μg | 1x daily | — |
| — | 300 mg BCA | 2x daily | — |
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Rare side effects
- Individual sensitivity reactions
Contraindications
- Consult healthcare provider if taking IGF-1 or growth hormone medications
- Limited long-term human data available
- Not studied in pregnancy
References
Primary literature and clinical-trial data informing this entry.