Abstract
Background: Insulin-like growth factor (IGF-I) is a growth factor that modulates the growth and development of skeletal muscles. The E-peptide is the C-terminal part of the IGF-I growth factor, and its function remains unknown. Amino acid sequencing of E-peptides suggests that they are either EA or EB peptides. Aim: To establish the time course modulation effect of E-peptide on IGF-I receptor activation in skeletal muscle cells. Method: We tested IGF-IR activation by immunoblotting for Phospho-Protein Kinase B (P-AKT) and Phospho-Extracellular signal-Regulated KinasesP-ERKI/II, the signal proteins of the AKT/PK13 and MAPK/ERK pathways. The C2C12 muscle cell line was starved overnight in serum-freemedia, then treated with either IGF-I alone or IGF-I plus either EA or EB synthetic peptides. The final group received NoTx, (negative control). Cells were treated for different periods of time (15, 30, 60, and 120 min). For quantification of the protein in each sample, equal amounts of protein were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to polyvinylidene fluoride membranes. Results: The potency of IGF-I receptor activation was increased in cells were treated with IGF-I plus EA peptide (for 30 min) compared to IGF-I alone. IGF-I plus EB managed to sustain the signal for a longer period. Conclusion: E-peptides have apotent modulating effect on IGF-I function and further studies are now needed to identify their exact function.