MGF — 2 mg

Mechano growth factor, or MGF, is associated with an alternatively spliced IGF-1 transcript, commonly termed IGF-1Ec in humans, and with synthetic material derived from its distinctive E-domain. Those meanings are related but not interchangeable: expression of a full precursor does not establish the behavior of an isolated fragment. Umbrella Labs describes its vial as a synthetic E-domain research peptide and links the concept to muscle responses after mechanical loading. The literature investigates cell proliferation, differentiation, and the relationship between the E-domain and mature IGF-I.

Yang and Goldspink reported in 2002 that an MGF E-domain preparation increased myoblast proliferation while inhibiting terminal differentiation in an in vitro model, unlike the effects they attributed to mature IGF-I. A later experimental paper, published in 2014 after online publication in 2013, reported no apparent activity of the proposed MGF peptide on myoblasts or primary muscle stem cells under its tested conditions. Both reports belong in a description of what researchers are saying. The resulting research picture is a disputed cellular mechanism, not a single established effect that can be freely transferred among MGF, full-length IGF-1 variants, and PEG-MGF.