Bodybuilding with Mechano growth factor
MGF (mechano growth factor) has been used by bodybuilders and athletes for a few years already. After resistance exercise, IGF-1 is released within the muscle. Specifically, at this time, immediately following the mechanical use of a muscle, the IGF-I gene is spliced towards MGF which initiates hypertrophy and repair of local muscle damage. It does so both by activating muscle stem cells and satellite cells, but also via various other anabolic processes. (1) It differs from “regular” IGF-1 mainly due to it’s C-Terminal sequence.
MECHANO GROWTH FACTOR Background
It was first discovered in the muscle by Goldspink, et al. In human muscle, a 49-base insert changes the reading frame in mechano growth factor (MGF) as compared to IGF-1.
What does MGF do?
When mechanical overload is introduced to a muscle (as by weight training), the IGF-1 gene released and is differentially spliced during the bodies response. Initially, it it is spliced to produce predominantly IGF-1Ec (called the MGF splice variant of IGF-1). This early splicing stimulates satellite cells into activation. Which in turn allows the activation of extra undamaged nuclei to grow new muscle fiber and tissue. The appearance of MGF also initiates the upregulation of new protein synthesis. After this initial splicing of IGF-1 into MGF, production then switches towards producing a systemic release of IGF-1Ea from the liver, which also upregulates protein synthesis as well. The expression of IGF-1 splice variants, over the course of the healing and regrowth phase of muscle repair is thought to be the primary anabolic mechanism by which the body produces new muscle. MGF is available as an injectable peptide, and it has been anecdotally shown that injecting it will cause a response in the area resulting in localized muscle growth.
From Studies done on MGF
In a rodent study, a single intramuscular injection into muscle resulted in a 25% increase in mean muscle fibre cross section area within three weeks. Using a similar protocol, liver-derived IGF-1 took four months to produce a 15% increase.
It would also appear that with regards to age, the young have a better ability to respond to MGF (4), and that the elderly experience a decreased response to MGF which results in a decreased ability to stimulate the growth of new muscle tissue.