Insulin-Like Growth Factor-I LR3
Long R3 IGF-1, IGF LR3 or Insulin-Like Growth Factor-I LR3, somatomedin C
83 amino chain: MFPAMPLSSL FVNGPRTLCG AELVDALQFV CGDRGFYFNK PTGYGSSSRR APQTGIVDEC CFRSCDLRRL EMYCAPLKPA KSA
IGF-1 LR3 Description
Long R3 IGF-1 (Insulin-like Growth Factor -1) is a polypeptide hormone that structurally and molecularly, shares some properties with insulin, which is where it got “Insulin-like” from in its nomenclature. IGF-1’s primary roles include long bone growth in kids, and in adults it affects the growth and repair of muscle tissue. Regular IGF has a half life of only about 20 minutes, where as the modified version called LR3 is altered some to prevent deactivation by binding proteins in the blood and extends the half life to about 20 hours making it able to be more effective.
IGF-1 LR3 contains the complete IGF-1 sequence, but with the substitution of an Arginine (Arg) for the Glutamic Acid (Glu) at position 3, as well as a 13 amino acid extension peptide is an 83 amino acid analog making the chain 83 aminos in length. This slight change in sequence allows the IGF-1 to avoid binding to proteins and have a much longer half life, around 20-30 hours. This effectively increases the biological activity of the IGF peptide. Effects seen in research are increased glucose transport, increased protein synthesis, decreased protein degradation and increased amino acid transport to cells. Active IGF behaves differently in different tissues. In muscle cells proteins and associated cell components are stimulated. Protein synthesis is increased along with amino acid absorption. IGF mobilizes fat for use as energy in adipose tissue. In lean tissue the cells have to switch to burning off fat as a source of energy, as IGF prevents insulin from transporting glucose across cell membranes. IGF-1 promotes nitrogen retention and protein synthesis. This assists the growth of muscles through both hyperplasia (increased number of muscle cells) and mitogenesis (growth of new muscle fibers).
IGF-1 LR3 Conserves Muscle in Heifers
This study indicates that IGF treated livestock retained muscle mass while in a catabolic state as a result of underfeeding indicating that IGF-1’s importance in controlling muscle growth. On a restricted, low calorie, low quality diet heifers maintained lean mass while being infused with IGF-1 LR3.
“Insulin-like growth factor-1 (IGF-1) is perhaps the most important endogenous factor controlling growth. Most studies to date in livestock have shown that IGF-1 has greatest efficacy when animals are in a catabolic state. We have determined the effects of an i.v. infusion of the IGF-1 analog Long(R3)-IGF-1 on protein metabolism in beef heifers that were slowly losing liveweight because of restricted feeding. There was a tendency for both whole-body protein and skeletal muscle protein to be conserved in Long(R3)-IGF-1-treated heifers. Long(R3)-IGF-1 administration markedly reduced the plasma concentrations of all amino acids measured and glucose. There was a significant change in the profile differences of endogenous plasma IGF-1 concentrations during the 8-hr infusion period, with plasma IGF-1 decreasing sharply in the test group. There was a significant difference in mean profiles for plasma IGF-2 between the test and control groups. Overall, plasma IGF-2 for the control group decreased only slightly over time (about 40 ng/ml), whereas the test group decreased dramatically (by about 140 ng/ml). Increased plasma concentrations of a 31-32-kDa IGF-binding protein (possibly IGF-binding protein-1) in the treated group was detected by radioligand blot. We found that Long(R3)-IGF-1 infusion tended to preserve whole-body and muscle protein in beef heifers on a low-quality diet, and suggest that further investigation of this treatment may provide an alternative approach to reducing weight loss during the dry season.” 
IGF-1 LR3 used to help a cancer drug work better
“The insulin-like growth factor receptor is overexpressed on many types of cancer cells and has been implicated in metastasis and resistance to apoptosis. We report here the development of a novel covalent conjugate that contains the antifolate drug methotrexate coupled to an engineered variant of insulin-like growth factor-1 (IGF-1), long-R3-IGF-1, which was designed to target methotrexate to tumor cells that overexpress the membrane IGF-1 receptor. The IGF-methotrexate conjugate was found to contain at least 4 methotrexate molecules per IGF-1 protein. The IGF-methotrexate conjugate bound to MCF7 breast cancer cells with greater than 3.3-fold higher affinity than unconjugated long-R3-IGF-1 in a competition binding assay against radiolabeled wild-type IGF-1. Compared with free methotrexate, the IGF-methotrexate conjugate required slightly higher concentrations to inhibit the in vitro growth of the human prostate cancer cell line LNCaP. In vivo, however, in a mouse xenograft model using LNCaP cells, the IGF-methotrexate conjugate was more effective than free methotrexate even at a 6.25-fold lower molar dosage. Similarly, MCF7 xenografts were inhibited more effectively by the IGF-methotrexate conjugate than free methotrexate, even at a 4-fold lower molar dosage. Our results suggest that the targeting of the IGF receptor on tumor cells and tumor-related tissues with IGF-chemotherapy conjugates may substantially increase the specific drug localization and therapeutic effect in the tumor. ”
Due to the amount of IGF receptors in cancer cells, physicians and scientists used this to their advantage in placing a cancer drug into cells using IGF as a type of carrier or transport. The result was a significantly higher ability to localize the drug and fight cancer cells:
Study shows IGF-1 to have plaque stabilizing effect in patients with atherosclerosis
Atherosclerosis (also known as ASVD which is arteriosclerotic vascular disease) is a condition where thickening of an arterial wall occurs from the build-up of cholesterol and fatty materials. It is commonly referred to as a hardening of the arteries, caused by the formation of multiple plaques within the arteries.
Atherosclerosis can go unnoticed for decades and not show any symptoms. Atherosclerotic lesions, or plaques can be separated into two categories: Stable and unstable.
Stable atherosclerotic plaques, which tend to be asymptomatic, are rich in extracellular matrix and smooth muscle cells, while, unstable plaques are rich in macrophages and foam cells and the extracellular matrix separating the lesion from the arterial lumen is usually weak and prone to rupture. Ruptures of the fibrous cap expose thrombogenic material, such as collagen to the circulation and eventually induce thrombus formation in the lumen. Upon formation, intraluminal thrombi can occlude arteries outright (i.e. coronary occlusion), but more often they detach, move into the circulation and eventually occlude smaller downstream branches causing thromboembolism (i.e. Stroke is often caused by thrombus formation in the carotid arteries).
These complications of advanced atherosclerosis are chronic, slowly progressive and cumulative. Most commonly, soft plaque suddenly ruptures, causing the formation of a thrombus that will rapidly slow or stop blood flow, leading to death of the tissues fed by the artery in approximately 5 minutes. This catastrophic event is called an infarction. One of the most common recognized scenarios is called coronary thrombosis of a coronary artery, causing myocardial infarction (a heart attack). The same process in an artery to the brain is commonly called stroke. Another common scenario in very advanced disease is claudication from insufficient blood supply to the legs, typically caused by a combination of both stenosis and aneurysmal segments narrowed with clots. 
By preventing instability in arterial plaque, this study suggests that IGF could help reduce strokes, infarctions and other life threatening complications due to atherosclerosis. With more study this could be a huge medical find for patients suffering with hardened arteries.
Recent study showing IGF-1 having muscle hypertrophy effects
A study completed in October 2012 shows some promise in IGF promoting muscle mass in combination with resistance training in rats.
“The purpose of this study was to test the hypothesis that skeletal muscle adaptations induced by long-term resistance training (RT) are associated with increased myogenic regulatory factors (MRF) and insulin-like growth factor-I (IGF-I) mRNA expression in rats skeletal muscle. Male Wistar rats were divided into 4 groups: 8-week control (C8), 8-week trained (T8), 12-week control (C12) and 12-week trained (T12). Trained rats were submitted to a progressive RT program (4 sets of 10-12 repetitions at 65-75% of the 1RM, 3 day/week), using a squat-training apparatus with electric stimulation. Muscle hypertrophy was determined by measurement of muscle fiber cross-sectional area (CSA) of the muscle fibers, and myogenin, MyoD and IGF-I mRNA expression were measured by RT-qPCR. A hypertrophic stabilization occurred between 8 and 12 weeks of RT (control-relative % area increase, T8: 29% vs. T12: 35%; p>0.05) and was accompanied by the stabilization of myogenin (control-relative % increase, T8: 44.8% vs. T12: 37.7%, p>0.05) and MyoD (control-relative % increase, T8: 22.9% vs. T12: 22.3%, p>0.05) mRNA expression and the return of IGF-I mRNA levels to the baseline (control-relative % increase, T8: 30.1% vs. T12: 1.5%, p<0.05). Moreover, there were significant positive correlations between the muscle fiber CSA and mRNA expression for MyoD (r=0.85, p=0.0001), myogenin (r=0.87, p=0.0001), and IGF-I (r=0.88, p=0.0001). The significant (p<0.05) increase in myogenin, MyoD and IGF-I mRNA expression after 8 weeks was not associated with changes in the fiber-type frequency. In addition, there was a type IIX/D-to-IIA fiber conversion at 12 weeks, even with the stabilization of MyoD and myogenin expression and the return of IGF-I levels to baseline. These results indicate a possible interaction between MRFs and IGF-I in the control of muscle hypertrophy during long-term RT and suggest that these factors are involved more in the regulation of muscle mass than in fiber-type conversion.” 
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 Hill RA, Hunter RA, Lindsay DB, Owens PC. (1999). “Action of long(R3)-insulin-like growth factor-1 on protein metabolism in beef heifers.” Domestic Animal Endocrinology. 16(4):219-29.
 McTavish H, Griffin RJ, Terai K, Dudek AZ. (2009). “Novel insulin-like growth factor-methotrexate covalent conjugate inhibits tumor growth in vivo at lower dosage than methotrexate alone.” Translational research: The Journal of Lab and Clinical Medicine. 153(6):275-82.
 "Atherosclerosis." Wikipedia, The Free Encyclopedia. Wikimedia Foundation, Inc. 22 July 2004. Web. 10 Aug. 2004.
 von der Thüsen JH, Borensztajn KS, Moimas S, van Heiningen S, Teeling P, van Berkel TJ, Biessen EA. (2011). “IGF-1 has plaque-stabilizing effects in atherosclerosis by altering vascular smooth muscle cell phenotype.” American Journal of Pathology.” 178(2):924-34.
 Aguiar AF, Vechetti-Júnior IJ, Alves de Souza RW, Castan EP, Milanezi-Aguiar RC, Padovani CR, Carvalho RF, Silva MD. (2012). “Myogenin, MyoD and IGF-I Regulate Muscle Mass but not Fiber-type Conversion during Resistance Training in Rats.” International Journal of Sports Medicine. October 2012 (published before print)