Diarylheptanoid 1-(4-hydroxyphenyl)-7-phenyl-(6E)-6-hepten-3-one enhances C2C12 myoblast differentiation by targeting membrane estrogen receptors and activates Akt-mTOR and p38 MAPK-NF-κB signaling axes.

Diarylheptanoid, 1-(4-hydroxyphenyl)-7-phenyl(6E)-6-hepten-3-one (HPPH), has been reported to enhance myoblast differentiation via estrogen receptor (ER). However, the underlying signaling pathway promising this action remains unknown. The present study thus aimed to investigate the signaling pathway of HPPH that enhances myoblast differentiation. Confluence C2C12 myoblasts were induced to differentiate in the absence or presence of HPPH (10 nM). Differentiation markers (myosin heavy chain (MHC) and myogenin) and other signaling molecules implicated in myogenic differentiation were analyzed by immunostaining and western blotting methods. To identify the location of ER and the signaling molecules, specific inhibitors were applied targeting these molecules. Nuclear factor-κB (NF-κB) DNA binding activity was measured using the electrophoresis mobility shift assay. The results showed that HPPH enhanced myoblast differentiation by increasing MHC and myogenin levels, number, and size as well as the fusion index of myotubes. These actions occurred via membrane ER. Several MAPK proteins were activated at the early stage of differentiation. However, only Akt and p38 MAPK, but not ERK, were implicated in these effects. The underlying signaling molecules of Akt to enhance myogenic differentiation by HPPH, at least in part, were mTOR/P70S6K and GSK-3β. On the other hand, the downstream signaling molecule of p38 MAPK was NF-κB. Our results suggested that HPPH enhanced myogenic differentiation by binding with membrane ER, which in turn recruited multiple axes including Akt-mTOR-P70S6K, Akt-GSK-3β, and p38 MAPK-NF-κB.