The Effects of Anabolic-Androgenic Steroids on Gene Expression in Skeletal Muscle: A Systematic Review

Anabolic-androgenic steroids (AAS) act via androgen receptor (AR) interaction to induce muscle protein synthesis. This process is achieved via altered gene expression via the Notch, Wnt, and Numb pathways and their interactions at the AR, manifesting in key skeletal muscle (SM) phenotypes such as morphology, ion conductance, and functionality. This review aims to report on the effects of AAS administration on gene expression in SM. Peer-reviewed empirical studies evaluating AAS administration on SM phenotypes and gene expression were considered for inclusion. The following databases were searched using a data range of Jan 2000-November 2020: MEDLINE Complete, Academic Search Complete, APA PsycInfo, SPORTDiscus, CINAHL Plus, Cochrane Central Register of Controlled Trials, Rehabilitation & Sports Medicine Source, GreenFILE, and APA PsycArticles. Potential risks of bias were assessed via a modified PEDro Scale. Twenty-nine peer-reviewed titles were included. All studies consisted of either human or rodent subjects and included an AAS dosing protocol, investigated SM phenotypes, and measured gene expression as an outcome variable. Studies investigated the effects of eight AAS compounds across a total of 88 different genes in SM. The most commonly identified genes increased by AAS were IGF, MYOG, and MyoD. There was a general lack of standardized dosing and AAS variety. Future studies should attempt to incorporate multiple AAS compounds and their effects on key SM gene expression.