IGF1 LR3 Peptide Overview

by Dr. James Ross

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IGF1 LR3 (Insulin-like Growth Factor-1 Long R3) is a recombinant, non-glycosylated polypeptide consisting of 83 amino acids. It is a modified form of human IGF-1, retaining the full native amino acid sequence but with two key alterations: arginine at position 3 is replaced by glutamic acid (hence the R3 designation), and the N-terminus is extended by 13 amino acids (hence the “long” designation). The native form refers to the naturally occurring amino acid sequence and its inherent three-dimensional structure. IGF1 LR3 has a molecular weight of 9.116 kDa and is produced in Escherichia coli using a specialized protein expression system. Chromatographic methods are then applied to fold and purify the IGF1 LR3 into its fully active form capable of binding to the human IGF-1 receptor (IGF-1R).

Insulin-like Growth Factor-1 (IGF-1) Licensed Peptide

IGF-1 is an endocrine licensed peptide hormone encoded by the IGF-1 gene and produced primarily in the liver under the stimulation of growth hormone (GH). It consists of 70 amino acids and contains three intra-molecular disulfide bridges. IGF-1 is structurally similar to insulin and exerts strong anabolic effects. It communicates with target tissues through autocrine and paracrine signaling mechanisms. Its molecular weight is 7.649 kDa.

IGF-1 has been called the sulfation factor, with its effects referred to as NSILA (non-suppressible insulin-like activity). It is also known as somatomedin C. IGF-1 promotes efficient energy utilization by enhancing insulin sensitivity and increasing fat breakdown to provide energy for cellular processes. It stimulates fat metabolism in muscle tissue, preserves glucose, and enhances protein synthesis in myocytes, resulting in muscle hypertrophy. Studies have also shown that IGF-1 reduces overall body fat.

IGF-1 mediates its effects through the IGF-1 receptor (IGF-1R), a tyrosine kinase receptor. When IGF-1 binds, it activates the AKT signaling pathway, which inhibits apoptosis and promotes cellular growth and proliferation. Consequently, IGF-1 stimulates cell differentiation, growth, and proliferation, supporting systemic body growth.

IGF-1 works in tandem with growth hormone and peaks during puberty, driving the adolescent growth spurt and muscle development. Deficiencies in GH or IGF-1 can lead to stunted growth and reduced stature. Recombinant forms of GH or IGF-1, including IGF-1 DES, have been explored to stimulate growth in deficient individuals.

Additionally, IGF-1 plays a role in neuronal development and nucleotide synthesis. Licensed peptide-based therapies using recombinant IGF-1 have been investigated for managing peripheral neuropathies, such as motor axon degeneration.

IGF1 LR3 Licensed Peptide Effects on Protein Metabolism

IGF1 LR3 exhibits the same biologic activities as endogenous IGF-1. It enhances glucose and amino acid uptake, increases RNA and protein synthesis, and inhibits protein breakdown, leading to higher cellular protein content. It also stimulates both hypertrophy (cell enlargement) and hyperplasia (cell proliferation) in muscle cells.

In 1999, Hill et al. conducted a study titled “Action of long (R3)-insulin-like growth factor-1 on protein metabolism in beef heifers.” The study investigated IGF1 LR3 effects on protein metabolism in underfed beef heifers. Only the test group received IGF1 LR3 intravenously. Results showed that treated heifers preserved skeletal and whole-body protein, reduced plasma amino acids and glucose, and exhibited decreased levels of endogenous IGF-1 and IGF-2. IGF-binding protein levels increased significantly in the treated group, confirming IGF1 LR3’s influence on protein metabolism.

IGF1 LR3 Licensed Peptide Impact on Atherosclerotic Plaques

In 2011, von der Thüsen et al. studied the effects of IGF-1 and IGF1 LR3 on atherosclerotic plaques. Using a mouse model, they evaluated how inflammatory plaque environments affected IGF-1 signaling and the influence of IGF supplementation on plaque stability. M1-polarized macrophage-conditioned medium inhibited IGF-1 signaling by reducing IGF1, increasing IGF-binding protein-3 expression, promoting vascular smooth muscle apoptosis, and upregulating matrix-degrading enzymes.

IGF1 LR3 administration counteracted these effects, reducing plaque measurements and enhancing vascular smooth muscle content in advanced plaques. This reduced the likelihood of intra-plaque hemorrhage by more than 50%, demonstrating its potential in stabilizing atherosclerotic lesions.

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