IGF-1 LR3 Peptide

IGF-1 LR3 Peptide is a hormone with a molecular weight of 7.6 kDa, and its molecular structure is similar to that of insulin. Its main mechanism of action is to induce intracellular signaling through binding to its specific receptor (IGF1R). IGF-1LR3 is one of the most potent activators of the AKT signaling pathway; activation of the AKT pathway stimulates cell growth and proliferation and inhibits cell apoptosis. IGF-1LR3 is formed by adding 13 amino acids to the N-terminus of the complete IGF-1 molecule, creating an 83-amino acid chain. The third amino acid of the IGF-1 molecule, glutamate (E), is replaced with arginine (R), hence the name R3. Compared to unmodified IGF-1, IGF-1LR3 exhibits higher stability and biological activity.

IGF-1 LR3 (Insulin-Like Growth Factor-1 Long R3) is a modified analog of native IGF-1 that holds a unique position in the peptide stack: it acts directly at the IGF-1 receptor with a much longer half-life (~20–30 hours) than the natural version, which clears in under 15 minutes. That extended window means it can drive sustained muscle protein synthesis, satellite cell activation, and nutrient partitioning in a way that short-acting IGF-1 simply can't.

Shaanxi Medibridge Biotech Co., Ltd. supplies this material as bulk powder or vial-filled lyophilized powder for research projects. Batch specifications, packaging details, COA, HPLC, and LC-MS files can be provided according to the agreed order requirements.

IGF-1 LR3 works by mimicking aspects of insulin-like growth factor-1 activity, especially interaction with IGF-1 receptor signaling pathways described for IGF-1 biology. The main proposed mechanism involves receptor-mediated signal transduction that can influence cell proliferation, protein biosynthesis, glucose handling, and tissue growth in experimental contexts.

The most important limitation is that receptor activation does not automatically predict a therapeutic outcome. A signal seen in a muscle cell, animal model, or in vitro study may not produce meaningful or safe results in humans.

The primary biological effects of IGF-1 LR3 are mediated through the IGF-1 receptor, IGF-1R. IGF-1R is a transmembrane receptor tyrosine kinase that is structurally similar to the insulin receptor.

After IGF-1 LR3 binds to IGF-1R, it can induce:

• Receptor conformational changes;
• Receptor autophosphorylation;
• Recruitment of adaptor proteins such as IRS and Shc;
• Activation of downstream signaling pathways;
• Changes in gene expression related to cell proliferation, survival, metabolism, and protein synthesis.

IGF-1 LR3 belongs to the insulin-like growth factor family and is structurally similar to natural IGF-1. It usually contains several conserved cysteine residues and forms characteristic disulfide bonds. These disulfide bonds are important for maintaining correct folding and receptor-binding activity.

Its biochemical characteristics include:

• Water-soluble peptide/protein nature;
• Sensitive to proteases and storage conditions;
• Biological activity depends on correct folding;
• Capable of activating downstream signaling through IGF-1R;
• Lower binding affinity for IGFBPs than natural IGF-1;
• Commonly used in cell culture to replace or enhance natural IGF-1 signaling.

IGF-1 LR3 is a structurally modified version of natural IGF-1. Natural IGF-1 is a growth factor produced by the liver and various local tissues, and it participates in growth and development, cell proliferation, protein synthesis, glucose and lipid metabolism, and tissue repair.

Compared with natural IGF-1, IGF-1 LR3 usually has two key structural modifications:

N-terminal extension sequence

IGF-1 LR3 contains an additional peptide sequence at the N-terminus of natural IGF-1, which is why it is referred to as "Long."

Amino acid substitution at position 3 with arginine, Arginine, R3

"R3" means that the amino acid at position 3 is replaced by arginine. This modification affects its affinity for IGF-binding proteins.

PI3K-AKT-mTOR Pathway

This is one of the most important downstream pathways of IGF-1 LR3.

This pathway is closely associated with:

• Cell survival;
• Anti-apoptosis;
• Protein synthesis;
• Glucose uptake;
• Cellular metabolic regulation;
• Muscle cell hypertrophy-related signaling;
• mTOR-mediated growth responses.

In simple terms, after IGF-1 LR3 activates IGF-1R, it can enhance cell survival through PI3K-AKT signaling and influence protein synthesis and cell growth through mTOR.

RAS-RAF-MEK-ERK / MAPK Pathway

Another important pathway is the MAPK/ERK pathway.

This pathway is mainly associated with:

• Cell proliferation;
• Cell-cycle progression;
• Differentiation regulation;
• Tissue repair;
• Developmental processes;
• Tumor cell proliferation research.

In many cell models, IGF-1R activation simultaneously initiates both AKT and ERK signaling, giving IGF-1 LR3 significant research value for studying pro-proliferative and pro-survival mechanisms.

Anti-Apoptotic Effects

IGF-1 LR3 is commonly used to study cell protection and anti-apoptotic mechanisms. Through the AKT pathway, it may affect:

• BAD;
• BCL-2 family proteins;
• Caspase activity;
• FOXO transcription factors;
• Mitochondrial apoptosis pathways.

Therefore, in neuronal cells, muscle cells, chondrocytes, stem cells, epithelial cells, and other models, IGF-1 LR3 is often used to observe changes in cell survival under stress, injury, or nutrient-limited conditions.

Promotion of Protein Synthesis and Cell Growth

The IGF-1 system is closely related to protein synthesis. IGF-1 LR3 can regulate the AKT-mTOR axis, including:

• mTORC1;
• p70S6K;
• 4E-BP1;
• Translation initiation;
• Amino acid utilization;
• Cell volume growth.

This is also one of the reasons why it has attracted attention in muscle cell research, exercise physiology, metabolic research, and tissue engineering.

Cell Proliferation and Survival Research

IGF-1 LR3 is commonly used to study proliferation, migration, and anti-apoptotic responses in various cell types.

Its advantage lies in its ability to activate IGF-1R signaling relatively consistently, allowing researchers to observe changes in the cell cycle, apoptosis, metabolism, and protein synthesis.

Muscle Biology Research

IGF-1 LR3 is frequently used in muscle cell research.

However, it should be emphasized that signaling changes observed in muscle cell studies cannot be directly equated with safe and effective muscle-building effects in humans.

Tissue Repair and Regeneration Research

Because IGF-1R signaling is associated with cell survival, migration, and proliferation, IGF-1 LR3 is also used in tissue repair-related studies.

However, its strong pro-proliferative properties also mean that researchers must pay attention to abnormal proliferation and safety boundaries.

Stem Cell and Cell Culture Systems

In certain cell culture systems, IGF-1 LR3 can be used as a culture medium supplement.

For example, in biopharmaceutical manufacturing, cell therapy process development, or tissue engineering research, IGF-1 LR3 may serve as a growth factor tool molecule. However, its actual use must be carefully optimized according to the cell type and process objective.

Tumor Biology Research

The IGF-1R pathway is associated with cell proliferation, anti-apoptosis, migration, invasion, and treatment resistance in many tumors. Therefore, IGF-1 LR3 can also be used to establish or enhance IGF-1R activation models.