IGF-1 LR3 Peptides and Tissue Growth

by | Dec 21, 2022 | Research

Scientists have created IGF-1 LR3 peptides by modifying the amino acid sequence of IGF-1. The new peptide has similar potential but possibly higher potency and improved stability. The LR3 in the name describes the two modifications to the IGF-1 molecule. Long R3 IGF-1, or IGF-1 LR3, is an analog of insulin-like growth factor 1 (IGF-1). IGF-1 is an anabolic peptide hormone naturally produced. Primarily, it is considered a mediator of the anabolic effects of growth hormone (HGH). Growth hormone appears to stimulate the production of IGF-1. The IGF-1 produced in the liver is released in the bloodstream and exerts anabolic effects, while the IGF-1 produced in all other tissues acts locally to stimulate growth. The first is R3 which describes the replacement of the 3rd amino acid in IGF-1 with arginine. Scientists ascribed an additional 13 amino acids to the N-terminus of the R3 IGF-1 molecule, turning it into Long R3 IGF-1. IGF-1 LR3 is an experimental peptide with potential anabolic and mitogenic effects.



Scientists developed IGF-1 analogs such as IGF-1 LR3 primarily for experiments to stimulate cell growth. IGF-1 and its analogs appear to be highly anabolic towards actively proliferating cells. They may speed up cell replication, ultimately shortening the time required to create a cell culture and use it to conduct laboratory studies.

IGF-1 LR3 works by activating IGF-1 receptors in most animal cells. Activating these anabolic receptors increases protein synthesis and tissue growth.  IGF-1 LR3 peptide appears to bind to a much lesser degree to IGF-1 proteins than other available analogs. Therefore, its affinity to the anabolic IGF-1 receptors may be much higher, and animal studies show that continuous exposure to IGF-1 LR3 leads to a 2-fold higher anabolic effect than IGF-1. Researchers also noted that “LR3 IGF-I remained more potent than IGF-I in several of these effects even when the peptides were given.[1]

The reduced affinity to IGF-1 binding proteins may also result in a shorter half-life of IGF-1 LR3 peptide. Animal suggest show that IGF-1 LR3 is eliminated within 4 hours.[2] At the same time, it may induce higher weight gain and organ mass increase in the tested animals compared to IGF-1.

The metabolites of IGF-1 LR3 may have a longer half-life and might remain detectable in test animals for up to 16 hours. In comparison, a high percentage of the natural IGF-1 appears to bind to IGF-1 binding proteins, which may reduce its effectiveness and prolongs half-life by up to 15 hours.[3]

According to one study in a mice model of muscular dystrophy, IGF-1 LR3peptide exposure appeared highly effective in reducing contraction-mediated injury.[4] Contraction damage is a major contributing factor to the pathophysiology of muscular dystrophy.

Another animal trial by Hill et al. also suggested that an IGF-1 LR3 exposure for 8 hours may have a protective effect against loss of muscle mass loss and muscle catabolism during periods of restricted energy intake and caloric deficit. The researchers reported that “Long(R3)-IGF-1 [exposure] tended to preserve whole-body and muscle protein in beef heifers on a low-quality diet.” The continuous exposure also led to significant suppression of the natural IGF-1 synthesis.[5]

One trial in guinea pigs also reported a significant increase in the organ weight of the animals after a 7-day exposure of IGF-1 LR3. The researchers note that the exposure most significantly enlarged the adrenals, gut, kidneys, and spleen.[6] It is important to note that IGF-1 LR3 and all other IGF-1 analogs are only hypothesized to mediate the anabolic effects of growth hormone.


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Dr. Usman

Dr. Usman (BSc, MBBS, MaRCP) completed his studies in medicine at the Royal College of Physicians, London. He is an avid researcher with more than 30 publications in internationally recognized peer-reviewed journals. Dr. Usman has worked as a researcher and a medical consultant for reputable pharmaceutical companies such as Johnson & Johnson and Sanofi.