IGF1-LR3

IGF-1 LR3 (Long-Arg3-IGF-1) is a synthetic 83-amino acid analog of human insulin-like growth factor-1 (IGF-1) engineered with two key modifications: substitution of glutamic acid with arginine at position 3 and addition of a 13-amino acid N-terminal extension. Together these alterations dramatically reduce affinity for insulin-like growth factor-binding proteins (IGFBPs), which normally sequester IGF-1 in the circulation and limit its bioavailability. The result is approximately 3-fold greater potency than native IGF-1 and an extended plasma half-life of 20–30 hours versus 12–15 hours for the native hormone. Upon binding to the IGF-1 receptor — a transmembrane receptor tyrosine kinase — IGF-1 LR3 triggers autophosphorylation and initiates downstream PI3K/Akt and MAPK signaling cascades. PI3K/Akt activation drives protein synthesis, glucose uptake, and cell survival; MAPK activation promotes cellular proliferation and differentiation. In skeletal muscle research, IGF-1 LR3 stimulates satellite cell (myoblast) proliferation producing myonuclear hyperplasia, and drives myofibrillar protein synthesis causing hypertrophic fiber growth. In adipose tissue, it enhances lipolysis and triglyceride mobilization through IGF-1R-mediated pathways. Research applications include investigation of muscle wasting disorders (cachexia, sarcopenia), growth hormone deficiency, cellular senescence, and metabolic disease. The compound's superior pharmacokinetic profile versus native IGF-1 makes it the preferred research tool for isolating IGF-1R-mediated signaling from short-lived endogenous peptide effects.