IGF-1 LR3 (also known as Long R3 IGF-1 or IGF-1 Long Arg3) is a synthetic analog of human insulin-like growth factor 1 (IGF-1), a naturally occurring hormone primarily produced in the liver in response to growth hormone (GH) stimulation. IGF-1 plays a key role in growth, development, cell proliferation, and anabolic processes like muscle repair and metabolism.
Structure and Modifications
Native human IGF-1 is a 70-amino-acid peptide. IGF-1 LR3 is engineered with two key changes to enhance its potency and duration:
- Replacement of glutamic acid with arginine at position 3 (hence “R3”).
- Addition of a 13-amino-acid extension at the N-terminus (sequence: MFPAMPLLSLFVN).
This results in an 83-amino-acid peptide with a molecular weight of approximately 9,117 Da. These modifications reduce binding to insulin-like growth factor-binding proteins (IGFBPs), which normally limit IGF-1’s activity, and improve metabolic stability.
