Scientific Reference
IGF-1 LR3
Evidence profile: Controlled human evidence
IGF-1 LR3 is insulin-like growth factor 1 altered in two ways, and the name is a record of both: L for the long N-terminal extension of 13 amino acids added to native IGF-1's 70, giving 83 residues in total, and R3 for arginine replacing glutamate at position 3. Together these changes reduce its affinity for the IGF-binding proteins that normally hold most IGF-1 in bound complexes. It is made by recombinant methods and is best known as a supplement in serum-free media for growing mammalian cell lines. Beyond cell culture the published work is chiefly animal studies, with very limited human data.
Mechanism of Action
IGF-1 LR3 is reported to activate the type 1 IGF receptor, a receptor tyrosine kinase, with affinity about equal to or a little below that of native IGF-1. What sets it apart is weak binding to the IGF-binding proteins that in serum and conditioned medium sequester most IGF-1. Less is locked away, so more reaches the receptor, which is the usual reason given for its higher apparent potency in culture. Receptor activation recruits insulin receptor substrate proteins and the PI3K-Akt-mTOR and Ras-MAPK pathways, which control protein synthesis, proliferation and survival in the cell types examined.
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