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Insulin-like growth factor-1 (IGF1) is also known as somatomedin C and has a similar structure to insulin. It is a hormone that has been found to play a role in growth of young mammals and has anabolic effects on adult animals.
It is synthesized in the liver as an endocrine hormone and in target organs in a paracrine or autocrine way. It is produced all through life and highest levels during puberty in animals and lowest in infant and aged populations.
Structure of Insulin-like Growth Factor
It is a small peptide consisting of 70 amino acids with a molecular weight of 7649Da. IGF-1 has an alpha and beta chain that are linked by disulphide bonds. Rat IGF-1 is synthesized as four precursor isoforms with alternate N- and C-terminal propeptides. Mature IGF-1 is identical between isoforms and is generated by the cleavage of propetide terminals. The C-peptide region has 12 amino acids.
Mechanism of Action
Research with animal subjects have demonstrated that IGF-1 is a primary mediator of Growth Hormone effects. Growth hormone is produced by the pituitary gland and circulates in the blood stream to cause IGF-1 production by the liver.
IGF-1 binds to at least two cell membrane receptor tyrosine kinases which includes IGF-1 receptor and insulin receptor. Its main action occurs due to its binding with IGF-1 receptor which is ubiquitous among tissues. This ligand-receptor complex ignites intracellular messages through AKT signaling pathway which is known for its cell growth and proliferation stimulation and its inhibition of programmed cell death.
Insulin can also bind to IGF-1 receptor but with much less affinity and IGF-1 can also bind to insulin receptor to produce actions at 10% of the potency insulin produces. Insulin Growth Factor-1 has been shown to interact with all 7 IGF-1 binding proteins especially IGFBP2, IGFBP5 and serum levels of these two is inversely proportional to circulating IGF-1.
Blood transported IGF-1 coordinates balanced growth across many tissues and organs. Stimulation of autocrine or paracrine IGF-1 can result in unbalanced growth since effects are exerted without the influence of growth hormone.
Insulin-like Growth Factor-1 Effects
The first demonstration of the effects of exogenous IGF-1 stimulates growth was with administration of purified hormone to rats that had their pituitary gland removed.
- In rats with diabetes, it was found to help in glucose control and potency depended on duration of diabetes in an inverse manner.
- Administration of IGF-1 in vivo showed anabolic effects with the subsequent rapid growth of neonatal rats but evidence suggests that nutritional sufficiency is necessary for full expression of the give dose.
- Exogenous administration of IGF-1 induced hepatoprotective and antifibrinogenic actions in experimental liver cirrhosis. These effects were associated with a diminution of the hepatic contents of several factors involved in oxidative damage like myeloperoxidase and nitric oxide
- When brain ischemia was induced by right, middle cerebral artery occlusion, IGF-1 expression in central nervous system was significantly reduced. Intramuscular IGF-1 injection increased expression in affected muscles, sciatic nerve, lumbar spinal cord and motor cortex. This was decreased neuronal apoptosis and improved motor function.
- Immunohistochemical analysis of rat testis at different ages revealed that the level of IGF-1 receptor increases from birth to 20 days postnatal life. Tests revealed that IGF- decreases the level of apoptosis in Leydig cells at all stages of development.
Side Effects of Insulin-like Growth Factor-1
These are usually mild and linked to its administration. It is however important to know what to expect during testing. Some adverse effects of IGF-1 discovered experimentally include:
- Nausea and vomiting
- Local irritation at injection site
- Pain or swelling at site of injection
- Links to certain forms of cancer development (studies are inconclusive and IGF levels are extremely high in those case)
- Fluid retention
- Orthostatic hypertension
Recombinant IGF produced by the bacteria E. coli is obtained via chromatographic techniques for research use. Insulin-like growth factor-1 can be purchased from Loti labs. It is necessary to use only USA made peptides ensure optimal quality of your research. IGF-1 LR3 and IGF DES 1,3 produced and sold by Loti labs undergoes top-notch quality control and is tested with high power liquid chromatography (HPLC) and mass spectrometry to make sure it is of the highest purity. IGF-1 is usually sold in 1mg vials.
Chang et al. 2004: Expression of liver insulin-like growth factor-1 and its serum level in rats with diabetes.
Garcia-Fernandez et al. (2005): Antioxidant effects of insulin-like growth factor-1 in rats with advanced liver cirrhosis.
Werner et al. (2008): Similarities and differences between insulin and IGF-1 structures, receptors, and signaling pathways.
Denley et al. (2005): Molecular interactions of the IGF system. Cytokine Growth Factor Rev.
Nurten et al. (2016): Efffect of insulin-like growth factor-1 on random pattern skin flap survival in rats.