Scientific Reference
IGF-1 LR3 (Long R3 IGF-1)
Evidence profile: Controlled human evidence
IGF-1 LR3 is an 83-residue analogue of insulin-like growth factor 1, with an N-terminal extension and arginine replacing glutamate at position 3. The extension adds 13 amino acids to the 70 of native IGF-1, and the name records both changes: L for long, R3 for the arginine. Together the modifications lower its affinity for the IGF-binding proteins that normally hold most IGF-1 in bound complexes. It is produced recombinantly and is used as a supplement in serum-free media for growing mammalian cell lines. Outside cell culture, published work consists mainly of animal studies, and human data are very limited.
Mechanism of Action
IGF-1 LR3 is reported to activate the type 1 IGF receptor, a receptor tyrosine kinase, with an affinity similar to or somewhat lower than that of native IGF-1. Its defining property is weak binding to the IGF-binding proteins, which in serum and conditioned culture media normally sequester most IGF-1. With less of it held in complexes, more is free to reach the receptor, which is the usual explanation for its higher apparent activity in cell culture. Receptor activation engages insulin receptor substrate proteins and the PI3K–Akt–mTOR and Ras–MAPK pathways, which govern protein synthesis, proliferation and survival in the cell types studied.
Molecular Information
- Type: Modified IGF-1 analog
Published Research
Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults
Teichman SL et al. · The Journal of clinical endocrinology and metabolism · 2006 · Clinical
PMID 16352683 — View on PubMedPlace of cabergoline in acromegaly: a meta-analysis
Sandret L et al. · The Journal of clinical endocrinology and metabolism · 2011 · Review
PMID 21325455 — View on PubMed