About IGF-1 LR3
IGF-1 LR3 (Long R3 Insulin-like Growth Factor 1) is a synthetically modified 83-amino acid analog of human IGF-1. The modification consists of an arginine substitution for glutamic acid at position 3, combined with a 13-amino acid extension at the N-terminus. Together, these changes dramatically reduce the peptide's binding affinity for IGF-binding proteins (IGFBPs) — proteins that, in their native form, sequester roughly 95–99% of circulating IGF-1 and limit its bioavailability and half-life to just minutes.
By minimizing IGFBP binding, IGF-1 LR3 extends its biological half-life to an estimated 20–30 hours, allowing far more free, bioactive peptide to remain in circulation. Research interest centers on its activation of the IGF-1 receptor, which triggers the PI3K/Akt/mTOR signaling pathway — a cascade strongly associated with increased protein synthesis. Of particular note, IGF-1 LR3 is studied for its potential to stimulate satellite cell proliferation, a process linked to muscle fiber hyperplasia (the formation of new muscle fibers) rather than just hypertrophy of existing fibers, as well as effects on fatty-acid metabolism and body recomposition.
Research Applications
IGF-1 LR3 is used in research investigating muscle hypertrophy and hyperplasia, satellite cell activation, protein synthesis pathways (PI3K/Akt/mTOR), fatty-acid metabolism, and body recomposition. It is also studied alongside growth-hormone secretagogues to examine downstream IGF-1 receptor signaling independent of pituitary GH output.