Synergistic effect of glucocorticoids and IGF-1 on myogenic differentiation through the Akt/GSK-3β pathway in C2C12 myoblasts

Abstract

Purpose: Glucocorticoids are the only therapeutics that can delay the progression of Duchenne musculardystrophy (DMD), the most prevalent type of inherited neuromuscular disorder in males. However, beyond theiranti-inflammatory effects, glucocorticoids have other underlying mechanisms that remain unclear. Moreover, muscleand circulating levels of insulin growth factor-1 (IGF-1) often decrease in response to glucocorticoids. Therefore, wehypothesized that glucocorticoids, either alone or in combination with IGF-1, can improve myogenic differentiation.

Materials and methods: Established C2C12 myoblasts were employed as an in vitro model of myogenic differentiation,and myogenic differentiation markers, as assessed by Western blot (myogenin, MyoD, and MyHC protein expression),cellular morphology analysis (fusion index) and RT-PCR (MCK mRNA expression), were measured.

Results: Myogenic differentiation markers were increased by glucocorticoid treatment. Furthermore, this effect was furtherenhanced by IGF-1, and these results suggest that glucocorticoids, either alone or together with IGF-1, can promotemyogenic differentiation. Akt and GSK-3β play important roles in myogenic differentiation. Interestingly, the levels ofboth phosphorylated Ser473-Akt and phosphorylated Ser9-GSK-3β were increased by glucocorticoid and IGF-1 cotreatment.Pharmacological manipulation with LY294002 and LiCl was employed to inhibit Akt and GSK-3β, respectively.We found that cellular differentiability was inhibited by LY294002 and enhanced by LiCl, indicating that theAkt/GSK-3β signaling pathway is activated by glucocorticoid and IGF-1 treatment to promote myogenic differentiation.

Conclusions: Glucocorticoids together with IGF-1 promote myogenic differentiation through the Akt/GSK-3βpathway. Thus, these results further our knowledge of myogenic differentiation and may offer a potential alternativestrategy for DMD treatment based on glucocorticoid and IGF-1.

Keywords:

• Duchenne muscular dystrophy
• glucocorticoid
• IGF-1
• Akt
• GSK-3β

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data are available upon request from the authors:The data that support the findings of this study are available from the corresponding author upon reasonable request.

Ethical approval

This article does not contain any studies involving human participants or animals that were performed by any of the authors.

Additional information

Funding

This study was supported by grants from the National Natural Science Foundation of China (81371260); the National Key R&D Program of China (2018YFC1311304); the Error! Hyperlink reference not valid. (2017A030313850); the Guangzhou Clinical Research and Translational Center for Major Neurological Diseases (201604020010); and the National Key Clinical Department, National Key Discipline, Guangdong Provincial Key Laboratory for Diagnosis and Treatment of Major Neurological Diseases (2014B030301035). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.