IGF-1 LR3 (Insulin-Like Growth Factor-1 Long R3)
IGF-1 LR3 (Insulin-Like Growth Factor-1 Long R3) is a modified and enhanced form of IGF-1, designed to offer a significantly longer duration of action and expanded biological effectiveness. The peptide is derived from natural IGF-1 but incorporates 13 additional amino acids at the N-terminal end and a key substitution of glutamic acid at position 3 with arginine. These structural modifications result in a greatly reduced affinity for IGF-binding proteins (IGFBPs), the proteins that normally limit the activity of circulating IGF-1. As a consequence, IGF-1 LR3 remains active in the bloodstream up to 120 times longer than the original molecule, making it one of the most potent and studied IGF derivatives in research.
IGFs are considered essential growth factors in processes of cell division, proliferation, differentiation, and cell-to-cell communication. IGF-1 LR3 substantially enhances these functions thanks to its prolonged half-life, providing a continuous and more stable growth signal to target cells. This characteristic makes it an extremely relevant research tool in fields such as muscle regeneration, endocrine research, energy metabolism, longevity, and myostatin modulation.
Mechanism of action on cell division
One of the most notable effects of IGF-1 LR3 is its ability to stimulate mitosis and cellular proliferation. Like IGF-1, the peptide acts primarily through the IGF-1R receptor, activating intracellular pathways such as PI3K/Akt and MAPK. These pathways directly regulate cellular growth and survival. However, the particular structure of IGF-1 LR3 enables the peptide to remain active much longer, generating a continuous and more intense pro-proliferative signal.
IGF-1 LR3 shows marked effects on connective tissues, including muscle and bone, but its activity has also been observed in cells of the liver, kidneys, nerves, skin, lungs, and blood. It is often described as a “maturation hormone” because it not only increases the number of cells but also promotes their differentiation, ensuring their ability to perform specialized functions.
A key distinction between IGF-1 LR3 and other anabolic factors is the way it acts on muscle tissue. It does not directly induce hypertrophy (an increase in cell size) but instead stimulates hyperplasia, meaning an increase in the total number of muscle cells. This characteristic makes IGF-1 LR3 of interest for studies focused on muscle growth driven by cellular expansion rather than enlargement of existing cells.
In comparative terms, a dose of IGF-1 LR3 produces approximately three times the cellular activation compared to the same amount of traditional IGF-1, making it one of the most effective versions available for biological research.
Fat metabolism and insulin sensitivity
IGF-1 LR3 exerts significant effects on glucose and lipid metabolism. The molecule can bind both the IGF-1R receptor and, to some extent, the insulin receptor. This dual binding enhances glucose uptake in muscle, liver, and nerve cells, lowers blood sugar levels, and triggers a cascade of metabolic responses.
Lower blood glucose stimulates adipose tissue and the liver to initiate lipolysis and the use of triglycerides and glycogen as energy sources. The net result is increased fat oxidation and an overall reduction of adipose stores. This combined action produces a state of controlled catabolism that contributes to body-weight modulation and improved metabolic efficiency.
Studies show that IGF-1 LR3 may also contribute to a reduction in the need for exogenous insulin in experimental diabetes models, with an average decrease of about 10% in insulin requirements. This suggests that IGF-1 LR3 may be an important research tool for understanding mechanisms involved in insulin resistance and potentially developing new approaches for the prevention of type 2 diabetes.
Interaction with Myostatin
One of the most interesting aspects of IGF-1 LR3 is its interaction with myostatin (or GDF-8), a protein that limits muscle growth and prevents uncontrolled hypertrophy. In conditions such as Duchenne muscular dystrophy (DMD), inhibition of myostatin could help slow muscle degeneration and preserve functionality.
Studies on murine models of DMD show that IGF-1 LR3 is able to counteract the negative effects of myostatin, protecting muscle cells from apoptosis and promoting differentiation processes mediated by the activation of the MyoD protein. MyoD is one of the main proteins responsible for muscular adaptation following exercise or tissue damage, and it plays a key role in hypertrophy and regeneration.
Thanks to its long persistence in the bloodstream, IGF-1 LR3 can exert this effect more efficiently than the native molecule, making it a significant candidate for research on degenerative muscle conditions and severe immobilization states.
IGF-1 LR3 and longevity
IGF-1 LR3 is actively studied in the field of aging biology due to its ability to promote tissue repair and maintenance. In animal models, IGF-1 is associated with improvements in regenerative capacity, cellular function, and, in some cases, a prolongation of lifespan.
Studies in cattle and pigs indicate that IGF-1 LR3 may counteract effects associated with cellular deterioration, while mouse research suggests a potential role in preventing or slowing conditions such as dementia, muscle atrophy, and nephropathies. Increased IGF-1 levels have been associated with greater vitality and reduced disability, making this research field increasingly relevant.
Glucocorticoid signaling
Another area of research involves the interaction of IGF-1 LR3 with glucocorticoids, hormones widely used to reduce inflammation, pain, and autoimmune responses. Although effective, glucocorticoids can cause muscle atrophy, increased body fat, and reduced bone density. Studies suggest that IGF-1 LR3 may help mitigate some of these side effects, supporting the preservation of muscle mass and bone structure during prolonged treatments.
Warning
IGF-1 LR3 is intended exclusively for scientific research. It is not intended for human, veterinary, or therapeutic use.
Scientific References
PubMed 24575400
Oxford Academic – Endocrinology
Oxford Academic – Endocrine Reviews
