View Full Version : Insulin Like Growth Factor~IGF 1

12-23-2010, 08:12 PM
by Anthony Roberts - Insulin-like growth factor 1 is a growth factor which is very closely related to insulin. It carries the same amount of amino acids as insulin and responsible for the anabolic reactions to GH. IGF-1 is an important factor in childhood growth and is highly anabolic in adults. It is also known by the brand name Increlex and the generic name mecasermin.


In the 1970's, IGF-1 was known as as "Sulfation Factor" and "Nonsuppressible Insulin-like Activity" (NSILA). In the 1980's, it was known as "Somatomedin C." The most popular type of IGF-1 available on the Black Market is a longer lasting version (more amino acids in length) known as Long R3 Insulin-like Growth Factor-I or Long R3IGF-I. Lr3igf-1 is more potent than the lesser versions which are no longer available on the black market. Of that type of IGF, there are two types commonly available (Media and Receptor grades, respectively). These last two types of IGF mostly just refer to the purity of what is actually in the bottle.


IGF-1 is released in the liver and binds to the IGF receptors within the cells, which ultimately causes a stimulation of cell growth (both causing new tissue formation and existing tissue growth) and an inhibition of cell death. It is a highly anabolic and anti-catabolic compound. For the athlete or bodybuilder, this had many positive effects: increased nitrogen retention and protein synthesis because it is highly anabolic. IGF-1 (in the presence of sufficient protein) actually promotes growth of new muscle cells, which increases the overall number of cells in the muscle.

IGF protects the neurons of the brain as well as promotes growth of new motor neurons, making it more possible to rapidly learn new skills during its use. IGF-1 is also responsible in connective tissue production, improves collagen formation and aids in cartilage repair. Similarly, it affects the bones by aiding in bone production and repair.

Technical Data

In a study done on young adult mice, a compound responsible for increased secretion of IGF-1 in muscle fibers was administered. There was an average increase of 15% in muscle mass and a 14% increase in strength. When the study was then conducted on adult mice, there was a 27% increase in strength in the injected muscles as compared with non-injected muscles. It was also found to prevent aging of the muscles. Muscle mass and muscle fiber growth were similar to the levels found in young adults. These effects are most likely due to the ability of IGF-1 to activate satellite cells, therefore stimulating muscle rejuvenation (1).

In studies conducted where GH and IGF1 were used together, a greater increase of Lean Body Mass and fat reduction was found than by use with each compound alone (2). Researches also believe that use of testosterone would also increase IGF levels in muscle (3). In a 12 week study on subjects using IGF-1, IGF-1+GH, or GH alone subjects in this study, gained around 3kgs of lean mass, and lost around 2kgs of fat(4) .

The complete human IGF-1 Long R3 IGF-1 is 2-3 times more potent than IGF-1 due to less ability to be made inactive by IGF binding proteins (5) (6).

User Notes

I'm actually a very big fan of Lr3 IGF-1. For me, I've found that it's had beneficial effects on helping me recover from training injuries and has shown to be very helpful in improving my strength, speed, and performance. I also noted some pretty enhanced muscle building effects and very enhanced fat burning when I've been on IGF-1 nothing on the level of Anabolic Steroids, but still, the effect was very pronounced.
Most users opt for a dose of about 100mcg/day injected bilaterally in the muscle group just trained, immediately post workout.

I suspect that in the coming years, more and more professional athletes will be using IGF, as it is very difficult to test for, and many have switched over from GH to this compound already.

Anecdotally, IGF seems to stack best with Trenbolone and Testosterone, and there's certainly some synergy between these compounds. Lately, MGF is being added to most IGF protocols. For a fuller discussion of how has been done, check out my article "Peptides: The Next Frontier in Hypertrophy (http://www.mesomorphosis.com/articles/anthony-roberts/peptides.htm)."

IGF-1 Resources

http://www.mesomorphosis.com/images/file-extensions/iconPDF.gif IGF-1 Prescribing Information (http://www.mesomorphosis.com/downloads/uspi-increlex.pdf)


Viral mediated expression of insulin-like growth factor I blocks the aging-related loss of skeletal muscle function.Proc Natl Acad Sci U S A. 1998 Dec 22;95(26):15603-7.
Recombinant human growth hormone, insulin-like growth factor 1, and combination therapy in AIDS-associated wasting. A randomized, double-blind, placebo-controlled trial. Ann Intern Med. 1996 Dec 1;125(11):865-72.
Am J Physiol Endocrinol Metab. 2002 Mar;282(3):E601
Am J Physiol Endocrinol Metab. 2002 Mar;282(3):E601-
IGF-I variants which bind poorly to IGF-binding proteins show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys.J Endocrinol. 1997 Nov;155(2):377-86.
In vivo actions of IGF analogues with poor affinities for IGFBPs: metabolic and growth effects in pigs of different ages and GH responsiveness. Prog Growth Factor Res. 1995;6(2-4):385-95. Review.

12-23-2010, 08:13 PM
Recombinant human growth hormone, insulin-like growth factor 1, and combination therapy in AIDS-associated wasting. A randomized, double-blind, placebo-controlled trial.

Waters D (http://forums.rxmuscle.com/pubmed?term=%22Waters%20D%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Danska J (http://forums.rxmuscle.com/pubmed?term=%22Danska%20J%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Hardy K (http://forums.rxmuscle.com/pubmed?term=%22Hardy%20K%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Koster F (http://forums.rxmuscle.com/pubmed?term=%22Koster%20F%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Qualls C (http://forums.rxmuscle.com/pubmed?term=%22Qualls%20C%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Nickell D (http://forums.rxmuscle.com/pubmed?term=%22Nickell%20D%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Nightingale S (http://forums.rxmuscle.com/pubmed?term=%22Nightingale%20S%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Gesundheit N (http://forums.rxmuscle.com/pubmed?term=%22Gesundheit%20N%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Watson D (http://forums.rxmuscle.com/pubmed?term=%22Watson%20D%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Schade D (http://forums.rxmuscle.com/pubmed?term=%22Schade%20D%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract).
Department of Medicine/Endocrinology, University of New Mexico School of Medicine, Albuquerque 87131-5271, USA.

Comment in:

Ann Intern Med. 1996 Dec 1;125(11):932-4. (http://forums.rxmuscle.com/pubmed/8967675?itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ ResultsPanel.Pubmed_RVAbstract)
OBJECTIVE: To increase lean body mass and improve health status in patients with wasting associated with the acquired immunodeficiency syndrome (AIDS) by treatment with recombinant human growth hormone (rhGH), recombinant human insulin-like growth factor 1 (rhIGF-1), or both. DESIGN: Randomized, double-blind, placebo-controlled clinical trial. SETTING: University of New Mexico Clinical Research Center and University of Texas Southwestern Medical Center. PATIENTS: 60 patients with AIDS and wasting as defined by the Centers for Disease Control and Prevention. Patients were divided into four groups of 15 patients each. INTERVENTION: Group 1 received 1.4 mg of rhGH once daily plus placebo twice daily; group 2 received 5 mg of rhIGF-1 twice daily plus placebo once daily; group 3 received 5 mg of rhIGF-1 twice daily plus 1.4 mg of rhGH once daily; and group 4 received placebo three times daily. MEASUREMENTS: Body weight, body composition, muscle strength, protein catabolism, quality of life, and immune status were assessed at baseline, and changes in these variables were measured at 6 and 12 weeks. RESULTS: At 6 weeks, lean body mass had increased and total fat mass had decreased in the groups receiving rhGH, rhIGF-1, or both. Group 3 had the greatest changes in lean body mass (mean +/- SE, 3.2 +/- 0.59 kg; P < 0.001); only in this group were changes in body mass maintained at 12 weeks. Only patients in group 1 had improvement in muscular strength of the knees and upper body (P = 0.04) and quality of life (P = 0.01). Immunologic function did not improve in any group. CONCLUSIONS: Growth factor therapy had significantly increased lean body mass and decreased fat mass by 6 weeks, but these improvements persisted for 12 weeks only in group 3. Growth factor therapy at the dosages used in this study is not recommended because the magnitude of weight gain was modest and improvements in quality-of-life measures varied.

PMID: 8967666 [PubMed - indexed for MEDLINE]

12-23-2010, 08:13 PM
IGF-I variants which bind poorly to IGF-binding proteins show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys.

Tomas FM (http://forums.rxmuscle.com/pubmed?term=%22Tomas%20FM%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Walton PE (http://forums.rxmuscle.com/pubmed?term=%22Walton%20PE%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Dunshea FR (http://forums.rxmuscle.com/pubmed?term=%22Dunshea%20FR%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract), Ballard FJ (http://forums.rxmuscle.com/pubmed?term=%22Ballard%20FJ%22%5BAuthor%5D&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVAbstract).
Cooperative Research Centre for Tissue Growth and Repair, Adelaide, South Australia, Australia.

The relative acute hypoglycaemic potencies of IGF-I and several variants of IGF-I which bind poorly to the IGF-I binding proteins (IGFBPs) have been examined in marmosets (Callithrix jacchus) and the pig. In the marmoset study, IGF-I and des(1-3)IGF-I were compared in anaesthetised and conscious animals in a range of bolus doses from 42 to 270 micrograms/kg body weight. In the pig study, IGF-I was compared with four variants, des(1-3)IGF-I long-IGF-I, R3IGF-I and long-R3IGF-I (LR3IGF-I), which show reduced affinity for the IGFBPs as well as with insulin. Doses in the pig were 20 and 50 micrograms/kg body weight for the IGFs and 3 micrograms/kg for insulin. In each study serial blood samples were taken from 30 min before to 4 h after the bolus injection. Plasma glucose levels were decreased in a dose-responsive manner with the pig more sensitive than either the conscious or anaesthetised marmoset (maximum lowering 4.8, 3.7 and 2.5 mmol/l respectively). The IGF variants were consistently 2- to 3-fold more potent than IGF-I in each animal for lowering of plasma glucose to the nadir, with the potency reflecting the relative affinities for binding to the IGFBPs and the IGF-I receptors. Thus, hypoglycaemic potency was in the order IGF-I < long-IGF-I < R3IGF-I approximately LR3IGF-I < des (1-3)IGF-I. Notably the variants suppressed plasma glucose levels over a much longer period than did IGF-I, the cumulative suppression over four hours showing an approximately 4- to 8-fold increase in the extent of hypoglycaemia. The prolonged suppression was not simply proportional to the hypoglycaemic nadir; at doses equipotent for glucose lowering, the cumulative hypoglycaemic effect for the variants in either species was about 2-fold that for IGF-I. The differential effect of the variants in the marmoset could not be accounted for by correlated changes in plasma insulin, IGF-I or IGFBP levels in plasma. Indirect effects via inhibition of glucagon, or direct effects via hepatic insulin receptors are postulated to account for the results. There was a dose-related reduction in plasma amino acids in the pig but, unlike the case for plasma glucose, only one analogue, LR3IGF-I was more potent than IGF-I. The response to LR3IGF-I was accentuated at the high dosage but on the basis of the other variants tested this effect could not be ascribed to either of the incorporated molecular variations. Despite their more rapid clearance from the circulation, variants of IGF-I which show lower affinity for binding to IGFBPs show proportionately superior potency for sustained hypoglycaemic action. Since our data were obtained in animal models of accepted relevance to humans these results point to the possible superior efficacy of the variants, especially des(1-3)IGF-I, over IGF-I for use as an adjunct to insulin treatment of hyperglycaemic conditions.

PMID: 9415072 [PubMed - indexed for MEDLINE]

12-23-2010, 08:14 PM
In vivo actions of IGF analogues with poor affinities for IGFBPs: metabolic and growth effects in pigs of different ages and GH responsiveness.

Walton PE, Dunshea FR, Ballard FJ.

Cooperative Research Centre for Tissue Growth and Repair, Adelaide, Australia.

IGF-I analogues that bind poorly to IGFBPs are substantially more potent than IGF-I at stimulating growth in rats. However, rodents differ from other mammals because they contain only minimal circulating levels of IGF-II and they are poorly responsive to GH. In this report we review a series of experiments carried out in pigs, a species that is both GH responsive and has high blood concentrations of IGF-II. Intravenous bolus administration of IGFs to 55 kg pigs depressed blood glucose with the potency greatest for analogues such as des (1-3) IGF-I, R3IGF-I and Long R3IGF-I that showed the weakest binding to pig IGFBP-3, a similar efficacy pattern to that reported in the rat. Chronic subcutaneous administration of Long R3IGF-I, however, reduced growth rates, led to a depression in food intake and lowered concentrations of IGF-I, IGF-II and IGFBP-3. IGF-I itself depressed IGF-II concentrations and did not stimulate growth. Subcutaneous infusion of IGFs over a 3-day period, also in 55 kg pigs, demonstrated that analogues that bound least well to IGFBP-3 were the most effective at reducing the concentration of this binding protein, suggesting that the inhibition of growth was related to the depression of IGFBP-3. On the other hand, IGF-I and Long R3IGF-I increased growth rats in neonatal pigs, especially under conditions of reduced food intake. As these anabolic effects occur at a developmental stage where the animals are insensitive to GH in a manner analogous to the situation in rats, it is plausible that the feed-back inhibition of GH secretion explains the catabolic response to IGFs in older pigs.

PMID: 8817682 [PubMed - indexed for MEDLINE]

12-23-2010, 08:14 PM

Most of the benefits of HGH are derived from IGF-1 including fat loss and lean mass gains. In many ways HGH can be thought of as an IGF-1 precursor. In vivo IGF-1 is created by the metabolization of HGH in the liver.

The most noticeable short term result of IGF is fat loss. IGF prevents insulin from transporting glucose across cell membranes. As a result the cells have to switch to burning off fat as a source of energy. Other benefits of IGF-1 include:

increased amino acid transport to cells
increased glucose transport
increased protein synthesis
decreased protein degradation
increased RNA synthesis

The one limitation of IGF-1 is that its half-life in vivo is extremely short. This limitation is overcome with the creation of synthetic long r3 IGF-1, which has a much longer half-life than both synthetic and endogenous IGF-1. Insulin-Like Growth Factor I, Long R3 is a Synthetic Peptide that is an analog of human IGF-I with a 13 amino acid extension at the N-terminus.

Long R3 IGF-1 is in sterile lypholized kits with Acetic Acid for dilution. Long R3 IGF-1 is a research peptide and is not intended to treat or cure any conditions and should be used as a research chemical ONLY.

Steps for Dilution:

Each Long r3 IGF-1 kit contains:
1000mcg of lypholized Long R3 IGF-1
2 CC's of 0.6% Acetic Acid
10 CC's of IV grade Sodium Chloride

Step one:

Remove the tops of the IGF-1 vial and the Acetic Acid

Step two:

Dilute the IGF-1 with 2 cc's of Acetic Acid.

***Note: This creates a concentration of 500mcg/ml. So each 1/10 of a CC is 50mcg's. After dilution store the IGF-1 in the refrigerator at approximately 4 degrees Celsius.

Step three:

Draw the desired amount of IGF in to a syringe.

Step four:

Draw twice the liquid amount Sodium Chloride in to the same syringe

Step five:

Administer to your test subject

12-23-2010, 08:17 PM
Effects of insulin-like growth factor-I and platelet-rich plasma on sciatic nerve crush injury in a rat model.

Emel E (http://www.ncbi.nlm.nih.gov/pubmed?term=%22Emel%20E%22%5BAuthor%5D), Ergün SS (http://www.ncbi.nlm.nih.gov/pubmed?term=%22Erg%C3%BCn%20SS%22%5BAuthor%5D), Kotan D (http://www.ncbi.nlm.nih.gov/pubmed?term=%22Kotan%20D%22%5BAuthor%5D), Gürsoy EB (http://www.ncbi.nlm.nih.gov/pubmed?term=%22G%C3%BCrsoy%20EB%22%5BAuthor%5D), Parman Y (http://www.ncbi.nlm.nih.gov/pubmed?term=%22Parman%20Y%22%5BAuthor%5D), Zengin A (http://www.ncbi.nlm.nih.gov/pubmed?term=%22Zengin%20A%22%5BAuthor%5D), Nurten A (http://www.ncbi.nlm.nih.gov/pubmed?term=%22Nurten%20A%22%5BAuthor%5D).
Departments of Neurosurgery.

Object Local administration of insulin-like growth factor-I (IGF-I) has been shown to increase the rate of axon regeneration in crush-injured and freeze-injured rat sciatic nerves. Local administration of platelet-rich plasma (PRP) has been also shown to have a measurable effect on facial nerve regeneration after transection in a rat model. The objective of the study was to compare the effects of locally administered IGF-I and PRP on the parameters of the Sciatic Function Index (SFI), sensory function (SF), axon count, and myelin thickness/axon diameter ratio (G-ratio) in a rat model of crush-injured sciatic nerves. Methods The right sciatic nerve of Wistar albino rats (24 animals) was crushed using a Yasargil-Phynox aneurysm clip for 45 minutes. All animals were randomly divided into 3 groups: Group 1 (control group) was treated with saline, Group 2 was treated with IGF-I, and Group 3 was treated with PRP. Injections were performed using the tissue expander's injection port with a connecting tube directed at the crush-injured site. Functional recovery was assessed with improvement in the SFI. Recovery of sensory function was using the pinch test. Histopathological examination was performed 3 months after the injury. Results The SFI showed an improved functional recovery in the IGF-I-treated animals (Group 2) compared with the saline-treated animals (Group 1) 30 days after the injury. In IGF-I-treated rats, sensory function returned to the baseline level significantly faster than in saline-treated and PRP-treated rats as shown in values between SF-2 and SF-7. The G-ratios were found to be significantly higher in both experimental groups than in the control group. Conclusions This study suggests that the application of IGF-I to the crush-injured site may expedite the functional recovery of paralyzed muscle by increasing the rate of axon regeneration.

02-07-2011, 10:34 AM
Acta Physiol Scand. (http://javascript<b></b>:AL_get(this, 'jour', 'Acta Physiol Scand.');) 1999 Dec;167(4):301-5.

Contribution of satellite cells to IGF-I induced hypertrophy of skeletal muscle.

Barton-Davis ER (http://www.ironmagazineforums.com/pubmed?term=%22Barton-Davis%20ER%22%5BAuthor%5D), Shoturma DI (http://www.ironmagazineforums.com/pubmed?term=%22Shoturma%20DI%22%5BAuthor%5D), Sweeney HL (http://www.ironmagazineforums.com/pubmed?term=%22Sweeney%20HL%22%5BAuthor%5D).
Department of Physiology, A700 Richards Bldg., University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA.


Insulin-like growth factor I (IGF-I) is critical in promoting growth of skeletal muscle. When IGF-I is introduced into mouse hindlimb muscles by viral-mediated gene transfer, local overexpression of IGF-I produces significant increases in muscle mass and strength compared with untreated controls (Barton-Davis et al. 1998). We have proposed that this functional hypertrophy is primarily owing to the activation of satellite cells which leads to increased muscle regeneration. In order to test if satellite cells are essential in mediating the hypertrophic effects of IGF-I, we used gamma radiation to destroy the proliferative capacity of satellite cells. The right hindlimbs of adult C57BL/6 male mice were subjected to one of the following treatments: (1) 2,500 rad gamma radiation only, (2) viral-mediated gene transfer of IGF-I only, (3) 2,500 rad gamma radiation plus viral-mediated gene transfer of IGF-I, or (4) no intervention as a control. Approximately 4 months after treatment, the extensor digitorum longus muscles (EDL) from both hindlimbs were removed for mechanical and morphological measurements. Treatment with gamma radiation significantly prevented normal growth of the muscle. When combined with IGF-I treatment, approximately half of the IGF-I effect was prevented by gamma radiation treatment. This suggests that the remaining half of IGF-I induced hypertrophy is owing to paracrine/autocrine effects on the adult myofibres. Thus, these data are consistent with a mechanism by which IGF-I induced muscle hypertrophy via a combination of satellite cell activation and increasing protein synthesis in differentiated myofibres.

PMID: 10632630 [PubMed - indexed for MEDLINE]

06-08-2013, 07:35 PM
Exp Physiol. (http://www.ncbi.nlm.nih.gov/pubmed/23291913#) 2013 May;98(5):1038-52. doi: 10.1113/expphysiol.2012.070722. Epub 2013 Jan 4.

Overexpression of insulin-like growth factor-1 attenuates skeletal muscle damage and accelerates muscle regeneration and functional recovery after disuse.

Ye F (http://www.ncbi.nlm.nih.gov/pubmed?term=Ye%20F%5BAuthor%5D&cauthor=true&cauthor_uid=23291913), Mathur S (http://www.ncbi.nlm.nih.gov/pubmed?term=Mathur%20S%5BAuthor%5D&cauthor=true&cauthor_uid=23291913), Liu M (http://www.ncbi.nlm.nih.gov/pubmed?term=Liu%20M%5BAuthor%5D&cauthor=true&cauthor_uid=23291913), Borst SE (http://www.ncbi.nlm.nih.gov/pubmed?term=Borst%20SE%5BAuthor%5D&cauthor=true&cauthor_uid=23291913), Walter GA (http://www.ncbi.nlm.nih.gov/pubmed?term=Walter%20GA%5BAuthor%5D&cauthor=true&cauthor_uid=23291913), Sweeney HL (http://www.ncbi.nlm.nih.gov/pubmed?term=Sweeney%20HL%5BAuthor%5D&cauthor=true&cauthor_uid=23291913), Vandenborne K (http://www.ncbi.nlm.nih.gov/pubmed?term=Vandenborne%20K%5BAuthor%5D&cauthor=true&cauthor_uid=23291913).

Department of Physical Therapy, PO Box 100154, Room 1142, PHHP Building, University of Florida, Gainesville, FL 32610, USA.


Skeletal muscle is a highly dynamic tissue that responds to endogenous and external stimuli, including alterations in mechanical loading and growth factors. In particular, the antigravity soleus muscle experiences significant muscle atrophy during disuse and extensive muscle damage upon reloading. Given that insulin-like growth factor-1 (IGF-1) has been implicated as a central regulator of muscle repair and modulation of muscle size, we examined the effect of virally mediated overexpression of IGF-1 on the soleus muscle following hindlimb cast immobilization and upon reloading. Recombinant IGF-1 cDNA virus was injected into one of the posterior hindlimbs of the mice, while the contralateral limb was injected with saline (control). At 20 weeks of age, both hindlimbs were immobilized for 2 weeks to induce muscle atrophy in the soleus and ankle plantarflexor muscle group. Subsequently, the mice were allowed to reambulate, and muscle damage and recovery were monitored over a period of 2-21 days. The primary finding of this study was that IGF-1 overexpression attenuated reloading-induced muscle damage in the soleus muscle, and accelerated muscle regeneration and force recovery. Muscle T2 assessed by magnetic resonance imaging, a non-specific marker of muscle damage, was significantly lower in IGF-1-injected compared with contralateral soleus muscles at 2 and 5 days reambulation (P<0.05). The reduced prevalence of muscle damage in IGF-1-injected soleus muscles was confirmed on histology, with a lower fractional area of abnormal muscle tissue in IGF-1-injected muscles at 2 days reambulation (33.2?3.3 versus 54.1?3.6%, P<0.05). Evidence of the effect of IGF-1 on muscle regeneration included timely increases in the number of central nuclei (21% at 5 days reambulation), paired-box transcription factor 7 (36% at 5 days), embryonic myosin (37% at 10 days) and elevated MyoD mRNA (7-fold at 2 days) in IGF-1-injected limbs (P<0.05). These findings demonstrate a potential role of IGF-1 in protecting unloaded skeletal muscles from damage and accelerating muscle repair and regeneration.

PMID: 23291913 [PubMed - in process]