Let’s start with an explanation of Mechano Growth Factor (MGF) and what it does. The muscle insulin-like growth factor-I (IGF-I) mRNA splice variant (IGF-IEc) has been identified in rodents. IGF-IEc, also called mechano growth factor (MGF) has been found to be up-regulated by exercise or muscle damage. Growth hormone (GH) is the principal regulator of IGF-I expression in several tissues including the skeletal muscle.

MGF is derived from IGF-I but its sequence differs from the systemic IGF-I produced by the liver. MGF is expressed by mechanically overloaded muscle and is involved in tissue repair and adaptation. It is expressed as a pulse following muscle damage and is apparently involved in the activation of muscle satellite (stem) cells. These donate nuclei to the muscle fibres that are required for repair and for the hypertrophy processes which may have similar regulatory mechanisms (Goldspink, G., 2005, p. 22).

The C-terminal peptide MGF, an alternatively spliced variant IGF-1, was found to function independently from the rest of the molecule. At any rate, IGF-I exists in multiple isoforms (tissue-specific proteins of functional and structural similarity). One isoform, which differs from the systemic or liver type, happens to be particularly sensitive to mechanical signals such as the gamut of exercise overload. MGF is a local splice variant of IGF-I produced by damaged or loaded skeletal muscle (Dluzniewska J, et al.., 2005 p. 1).

The physiological function of MGF was studied using an in vitro cell model. Unlike mature IGF-I, the distinct E domain of MGF inhibits terminal differentiation whilst increasing myoblast proliferation. Blocking the IGF-I receptor with a specific antibody indicated that the function of MGF E domain is mediated via a different receptor. The results provide a basis for localized tissue adaptation and helps explain why loss of muscle mass occurs in the elderly and in dystrophic muscle in which MGF production is markedly affected (Yang SY, Goldspink G., 2002, p. 156-60).

Ok, enough of the science. I am sure your brain is probably hurting after reading that, I know mine was. In really simple terms, MGF is a variant of IGF-1, an isoform that is particularly sensitive to muscle trauma (weight training) and is essential for repair and growth of new cells, similar in manner to IGF-1. What you need to know is MGF triggers new cell growth or hyperplasia in rat testing, and since we as bodybuilders fancy ourselves as lab rats, it is currently the in vogue peptide by top amateurs and pro’s.

Well all of this sounds great but what is the catch? This is where we reach a cross-road, a potential problem with MGF. As great as MGF has been in clinical trials and rat studies, the fact is that injected MGF has a half life of minutes….yes minutes. So how are you going to make this work, besides injecting every hour or so of your waking day? The answer lies in a little known molecule protection agent knows as PEGylation.

So what is or PEGylation? In simple terms it is the process of attaching one or more chains of a substance called polyethylene glycol (PEG) to a protein molecule such as IGF or in this case MGF. Since the body does not react to PEG, it helps provide a protective barrier around an attached protein so it can survive in the body longer. This is highly beneficial for systemic products that must survive repeated attacks by enzymatic exposure. PEG is an inert non-toxic substance that can provide protection to amine groups since they are flexible and allow attachment by bioengineered processes to the receptor bearing cell. Finally a quick explanation of polyethylene glycol; Any of a family of high molecular weight compounds that can be liquid or wax-like in consistency and are soluble in water and in many organic solvents.

Polyethylene glycol itself does not react in the body and is very safe. PEG has been approved by the US Food and Drug Administration (FDA) as a base or vehicle for use in foods and cosmetics and in injectable, topical, rectal and nasal pharmaceutical formulations. The risk associated with current PEGylated drugs are due to the way the drug itself acts not the PEG.

PEGylation can improve dosing convenience of many small molecules by increasing bioavailability and reducing dosing frequency. PEGylation also increases the amount of time the cell sits at the target site. This can be both good and bad. It is good because it increases the drug concentration, and with a longer time at the site, there is more chance of uptake by the cell. The bad news is that while it is sitting at the cell, there is increased risk of damage by enzymes that attack the cell. This is a double-edge sword that is a necessary evil; you must protect the molecule but at the same time increase the risk factor of damage due to longer exposure times at the target cell. As a result of the increased time at the cell, the optimal drug concentration can be achieved with less frequent dosing; a significant benefit to bodybuilders who are usually using poly-pharmacy at its finest.

PEGylated MGF is systemic in nature, meaning that the method of administration is not important. Most people are using MGF in a fashion similar to IGF, meaning they inject the peptide intramuscularly in recently trained muscle groups, hoping for an increase in cell repair and proliferation of new cells. While this thinking is optimistic at best, there is no research that would support site specific injections being beneficial for localized growth. This is a myth that has purveyed aas and peptide use for years. At this time, the literature and lab studies support subcutaneous injection, using small gauge insulin syringes.

Obviously there are no human research trials at this time; the peptide is still in research phases. Bodybuilder use at this time is all by trial and error. One company that currently carries MGF has conducted their own research trials, using test participants from underground steroid boards who are providing feedback in weekly intervals. While this is hardly a controlled environment and may have to many variables to accurately assess the product, at least it is a start.

I have also been conducting my own research, on myself and my clients, who often refer to themselves as Gavin’s guinea pigs. As with most peptides, more is not better. Smaller doses with less frequent injection schedules have proven to be optimal. I personally have been using 200mcg injected sub-q, two times per week. I have had my clients try 100mcg, two times per week, three times per week, daily, etc. So far the best results have been my personal method, 200mcg, two times per week.

Elite athletes are experiencing incredible body fat loss, increased pumps, fullness, and vascularity. I was able to gain 6 pounds of lean mass and lose 4.2% body fat in 4 weeks of use. I kept using it for weeks 5 and 6 but with no further gains or body fat loss. It seems that MGF stalls out at the 4 week mark, my theory being that much like with media grade IGF-1 LR3, the cells reach super saturation and cannot process any further uptake of the peptide sequence. It is possible to bypass this saturation, but it will take some time to work out the differential nature of the timing, much like I had to do with IGF-1 LR3, where I have now found ways to take it for up to 20 weeks with little to no cell down-regulation.

At this time all use and injection schedules are by word of mouth, sometimes by erroneous information on underground boards. Proper use of MGF is merely by speculation; it will take some time to sort out the best method of administration, although with the ever changing world of science, where nothing ever stands still, it may take years to sort out optimal dosing schedules. Even with such stable peptide structures as growth hormone that have had years of research, new information is always being studied, and I speculate that it will with all peptides.

Rex