Growth factors and muscle ageing.
Goldspink G, Harridge SD.
Aximygen/UCL Biomedica, Division of Surgery, Royal Free and University College Medical School, The Archway Campus, 2-10 Highgate Hill, London N19 5LW, UK. [email protected]
Loss of muscle mass (sarcopenia) is one of the main problems associated with ageing as it has major health care as well as socioeconomic implications. The growth hormone (GH)/IGF-I axis is regarded as an important regulator of muscle mass. However, it is now appreciated that other tissues in addition to the liver express IGF-I and that there are local as well as systemic forms of IGF-I which have different functions. At least two different kinds of IGF-I that are expressed by skeletal muscle are derived from the IGF-I gene by alternative splicing, one of which is expressed in response to physical activity which has now been called 'mechano growth factor' (MGF). The other is similar to the systemic or liver type (IGF-IEa) and is important as the provider of mature IGF-I required for upregulating protein synthesis. MGF differs from systemic IGF-IEa in that it has a different peptide sequence which is responsible for replenishing the satellite (stem) cells in skeletal muscle. The ability to produce MGF declines with age, and this is commensurate with the decline in circulating GH levels. GH treatment up regulates the level of IGF-I gene expression in older people and when combined with resistance exercise more is spliced towards MGF and hence should improve the ability of muscle to respond to physical activity. The possibility of ameliorating sarcopenia using MGF is discussed.
This is an outstanding article. I had been contemplating the effects of an IGF and MGF combined cycle because of some theories that I had been creating and I finally found evidence to back it! This article shows that increased IGF-1 actually creates more MGF through splicing, so its interesting to see whether or not it is even worth taking MGF when you can take IGF-1 and get the effects of both. However, we don't know how much is spliced towards it OR if the long chain r3 version can even be spliced towards MGF.
If the latter is the case than it is interesting to see how an IGF + MGF cycle would be since the MGF replenishes the satellite cells that IGF uses to create hyperplasia!!!! MGF alone would almost be pointless because of this fact. We want hyperplasia NOT hypertrophy with this stuff guys.
:woohoo: maybe I am on to something.
Goldspink G, Harridge SD.
Aximygen/UCL Biomedica, Division of Surgery, Royal Free and University College Medical School, The Archway Campus, 2-10 Highgate Hill, London N19 5LW, UK. [email protected]
Loss of muscle mass (sarcopenia) is one of the main problems associated with ageing as it has major health care as well as socioeconomic implications. The growth hormone (GH)/IGF-I axis is regarded as an important regulator of muscle mass. However, it is now appreciated that other tissues in addition to the liver express IGF-I and that there are local as well as systemic forms of IGF-I which have different functions. At least two different kinds of IGF-I that are expressed by skeletal muscle are derived from the IGF-I gene by alternative splicing, one of which is expressed in response to physical activity which has now been called 'mechano growth factor' (MGF). The other is similar to the systemic or liver type (IGF-IEa) and is important as the provider of mature IGF-I required for upregulating protein synthesis. MGF differs from systemic IGF-IEa in that it has a different peptide sequence which is responsible for replenishing the satellite (stem) cells in skeletal muscle. The ability to produce MGF declines with age, and this is commensurate with the decline in circulating GH levels. GH treatment up regulates the level of IGF-I gene expression in older people and when combined with resistance exercise more is spliced towards MGF and hence should improve the ability of muscle to respond to physical activity. The possibility of ameliorating sarcopenia using MGF is discussed.
This is an outstanding article. I had been contemplating the effects of an IGF and MGF combined cycle because of some theories that I had been creating and I finally found evidence to back it! This article shows that increased IGF-1 actually creates more MGF through splicing, so its interesting to see whether or not it is even worth taking MGF when you can take IGF-1 and get the effects of both. However, we don't know how much is spliced towards it OR if the long chain r3 version can even be spliced towards MGF.
If the latter is the case than it is interesting to see how an IGF + MGF cycle would be since the MGF replenishes the satellite cells that IGF uses to create hyperplasia!!!! MGF alone would almost be pointless because of this fact. We want hyperplasia NOT hypertrophy with this stuff guys.
:woohoo: maybe I am on to something.