Activation of IGF-1 pathway and suppression of atrophy related genes are involved in Epimedium extract (icariin) promoted C2C12 myotube hypertrophy

Yi-An Lin,Szu-Tah Chen,Yan-Rong Li,Yi-Ching Chang,Mei-Chich Hsu

doi:10.1038/s41598-021-89039-0

Abstract

The regenerative effect of Epimedium and its major bioactive flavonoid icariin (ICA) have been documented in traditional medicine, but their effect on sarcopenia has not been evaluated. The aim of this study was to investigate the effects of Epimedium extract (EE) on skeletal muscle as represented by differentiated C2C12 cells. Here we demonstrated that EE and ICA stimulated C2C12 myotube hypertrophy by activating several, including IGF-1 signal pathways. C2C12 myotube hypertrophy was demonstrated by enlarged myotube and increased myosin heavy chains (MyHCs). In similar to IGF-1, EE/ICA activated key components of the IGF-1 signal pathway, including IGF-1 receptor. Pre-treatment with IGF-1 signal pathway specific inhibitors such as picropodophyllin, LY294002, and rapamycin attenuated EE induced myotube hypertrophy and MyHC isoform overexpression. In a different way, EE induced MHyC-S overexpression can be blocked by AMPK, but not by mTOR inhibitor. On the level of transcription, EE suppressed myostatin and MRF4 expression, but did not suppress atrogenes MAFbx and MuRF1 like IGF-1 did. Differential regulation of MyHC isoform and atrogenes is probably due to inequivalent AKT and AMPK phosphorylation induced by EE and IGF-1. These findings suggest that EE/ICA stimulates pathways partially overlapping with IGF-1 signaling pathway to promote myotube hypertrophy.

Highlights

The regenerative effect of Epimedium and its major bioactive flavonoid icariin (ICA) have been documented in traditional medicine, but their effect on sarcopenia has not been evaluated
Atrogenes MAFbx and muscle RING finger 1 (MuRF1) are important E3 ubiquitin ligases directly regulated by the insulin-like growth factor-1 (IGF-1)/AKT/FoxO pathway, IGF-1 and Epimedium extract (EE) both activated the IGF-1/AKT/mammalian target of rapamycin (mTOR) pathway, we found that only IGF-1 could suppress the expression of MAFbx and MuRF1
The extent of myotube hypertrophy induced by IGF-1, EE, and testosterone was similar through the IGF-1 signal pathway, we found that IGF-1 synergistically suppressed MRF4, MAFbx, MuRF1, and MSTN; whereas testosterone could only suppress MSTN, and EE attenuated MRF4 and MSTN expression in differentiated C2C12 cells

Summary

Introduction

The regenerative effect of Epimedium and its major bioactive flavonoid icariin (ICA) have been documented in traditional medicine, but their effect on sarcopenia has not been evaluated. Pre-treatment with IGF-1 signal pathway specific inhibitors such as picropodophyllin, LY294002, and rapamycin attenuated EE induced myotube hypertrophy and MyHC isoform overexpression. Differential regulation of MyHC isoform and atrogenes is probably due to inequivalent AKT and AMPK phosphorylation induced by EE and IGF-1 These findings suggest that EE/ICA stimulates pathways partially overlapping with IGF-1 signaling pathway to promote myotube hypertrophy. The androgenic effect was conducted through the binding of testosterone to androgen receptor (AR)[19,20]

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