MGF IGF-1 Ec Peptide Potential For Muscle Cell Research

MGF IGF-1 Ec is a short peptide that is also referred to as the E-domain of full-length MGF (mechano-growth factor). It appears to be a peptide made of 24 amino acids that is produced when the IGF-1 gene is translated into an amino acid sequence. During this process, cells generate a longer precursor (full-length MGF), which later gives rise to the standard IGF-1 molecule and an additional short tail at its end. This tail appears to be MGF IGF-1 Ec, which corresponds to the final 24 amino acids of that precursor.

Research by scientists such as Dai et al. suggests that this 24-amino-acid MGF IGF-1 Ec may act differently from the popular IGF-1, as it does not appear to activate the classical IGF-1 receptor or insulin receptor.⁽¹⁾ Instead, it is associated with activation of ERK-type signaling pathways without triggering Akt signaling in mammalian models. Based on these observations, MGF IGF-1 Ec peptide is posited to function as an IGF-related signaling fragment with potential to promote proliferative and stress-adaptive responses in mechanically sensitive cell systems, such as muscle cell cultures and their progenitors.

 

Research

MGF IGF-1 Ec Peptide Actions On Muscle Cell Growth and Division

Research by Li et al. suggests that MGF IGF-1 Ec peptide may stimulate a hypertrophy response by pushing muscle cells toward growth in size and structural content rather than toward cell division. The scientists apparently applied the peptide repeatedly to cultured smooth muscle cells over several days, and consequently, the cells became larger and accumulated more total protein per cell. It was apparently observed that cell volume may have also increased progressively, and protein content may have risen in parallel. In contrast, markers of proliferation, such as DNA synthesis, did not indicate any apparent increase under the same conditions. This pattern appears different from the response to mature IGF-1, which promoted proliferation instead.

Therefore, the study suggests that this hypertrophy response may depend on a pathway distinct from classical IGF-1 receptor signaling. The MGF IGF-1 Ec peptide did not appear to activate the IGF-1 receptors measurably. Instead, the researchers apparently observed an increase in phosphorylation of ERK5. ERK5 is considered a member of the MAP kinase family that is activated by mechanical or biochemical stimuli and, once phosphorylated, may translocate from the cytoplasm into the nucleus.

Activated ERK5 may then be translocated from the cytoplasm into the nucleus, followed by activation of MEF2C, a transcription factor posited to regulate muscle-specific gene expression related to muscle cell hypertrophy. This apparently increases production of contractile and cytoskeletal proteins, leading to larger, more protein-dense cells. To further evaluate this hypothesis, the researchers blocked ERK5, which apparently mitigated both ERK5 nuclear translocation and hypertrophy. When the scientists attempted to reduce MEF2C expression, this apparently diminished the peptide-induced increase in cell size and blocked upregulation of muscle structural genes such as α-smooth muscle actin, γ-smooth muscle actin, smoothelin, and desmin.

MGF IGF-1 Ec Peptide and Muscle Cell Injury and Apoptosis

Research by Liu et al. suggests the potential of MGF IGF-1 Ec peptide on the inflammatory environment of injured muscle cells.⁽³⁾ Initially,y the researchers induced muscle cell injury and fibrosis reflected by increased collagen I and III expression and larger fibrotic areas within the muscle. Yet, adding MGF IGF-1 Ec peptide to the cell cultures apparently reduced fibrosis, both histologically and at the mRNA level. It is posited that, mechanistically, this may be due to reduced inflammatory signaling. Specifically, the authors commented that MGF IGF-1 Ec peptide may reduce several signals that promote inflammation. Apparently, it may have lowered the expression of pro-inflammatory cytokines such as TNF-α, IL-1β, IFN-γ, and especially TGF-β, which is considered a key driver of inflammation and remodeling.

The authors of the study also commented on apparent reductions in “chemokines (CCL2, CCL5, and CXCR4), oxidative stress factors (gp91phox) and matrix metalloproteinases (MMP-1, MMP-2, MMP-9, MMP-10, and MMP-14)”. By decreasing the expression of gp91phox, the peptide may lower the expression of a core component of oxidative stress referred to as NADPH oxidase. But apparently,  MGF IGF-1 Ec peptide did not change markers of satellite cell activation or differentiation, such as MyoD or myogenin, in the injured muscle cells. This indicates that its protective potential may not be mediated by direct stimulation of satellite cell function in this context.

Further research by Doroudian et al. in stressed cardiomyocyte cells exposed to hypoxia (1% O₂ for 8 hours) suggests that, apart from inflammation, the MGF E-domain may also work to reduce apoptosis.⁽⁴⁾ The authors posit that, based on the fewer TUNEL-positive nuclei and the 2-fold higher expression of the anti-apoptotic gene Bcl-2, which they apparently observed. Functionally, that suggests the peptide may shift cells away from programmed cell death during injury-like stress. Moreover, the authors also mention research in mesenchymal stem cells, where the peptide appeared to upregulate migration by about 1.7-fold vs controls. The researchers posited that this may be a signal that helps recruit repair-capable cells toward damaged tissue.

MGF IGF-1 Ec Peptide and Replicative Senescence of Muscle Cells

A study by Kandalla et al. suggests MGF IGF-1 Ec peptide may delay the functional onset of replicative senescence in primary myogenic precursor cultures by keeping a larger fraction of cells cycling late into their in vitro lifespan.⁽⁵⁾ The key observation by the researchers was purported to be an extension of the period of ability of the muscle cell progenitors to divide before they completely lose their mitotic activity. Quantitatively, the increase in proliferative lifespan was about a 14% increase. The authors interpret this as a short-term delay in replicative senescence in mammals, rather than a wholesale reset of replicative limits, since the net implications corresponded to only a few additional divisions on average.

The authors suggest the peptide might regulate cell-cycle control proteins in a way that resembles other common growth factor actions. They also propose that it may support a stress-associated senescence program linked to p16 accumulation, possibly dampening or delaying that checkpoint. P16 is posited to be a small regulatory protein that acts as a brake on the cell cycle. It is also posited to belong to the INK4 family of cyclin-dependent kinase inhibitors. It primarily blocks the activity of CDK4 and CDK6, enzymes that are required for cells to progress from the G1 phase into DNA synthesis. Thus, the researchers commented that the MGF IGF-1 Ec peptide may have “marked ability to [support] satellite cell activation, proliferation and fusion for muscle repair and maintenance.”

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References:

1. Dai Z, Wu F, Yeung EW, Li Y. IGF-IEc expression, regulation, and biological function in different tissues. Growth Horm IGF Res. 2010 Aug;20(4):275-81. doi: 10.1016/j.ghir.2010.03.005. Epub 2010 May 21. PMID: 20494600.
2. Li C, Vu K, Hazelgrove K, Kuemmerle JF. Increased IGF-IEc expression and mechano-growth factor production in intestinal muscle of fibrostenotic Crohn’s disease and smooth muscle hypertrophy. Am J Physiol Gastrointest Liver Physiol. 2015 Dec 1;309(11):G888-99. doi: 10.1152/ajpgi.00414.2014. Epub 2015 Oct 1. PMID: 26428636; PMCID: PMC4669353.
3. Liu X, Zeng Z, Zhao L, Chen P, Xiao W. Impaired Skeletal Muscle Regeneration Induced by Macrophage Depletion Could Be Partly Ameliorated by MGF Injection. Front Physiol. 2019 May 17;10:601. doi: 10.3389/fphys.2019.00601. PMID: 31164836; PMCID: PMC6534059.
4. Doroudian G, Pinney J, Ayala P, Los T, Desai TA, Russell B. Sustained delivery of MGF peptide from microrods attracts stem cells and reduces apoptosis of myocytes. Biomed Microdevices. 2014 Oct;16(5):705-15. doi: 10.1007/s10544-014-9875-z. PMID: 24908137; PMCID: PMC4418932.
5. Kandalla PK, Goldspink G, Butler-Browne G, Mouly V. Mechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages. Mech Ageing Dev. 2011 Apr;132(4):154-62. Epub 2011 Feb 25. PMID: 21354439.https://doi.org/10.1016/j.mad.2011.02.007