MiR-221 Overexpression Alters Cell-Cycle Distribution and Reduces Myogenic Gene Expression in C2C12 Myoblasts

Background: Exercise improves skeletal muscle function in diabetic patients, although the underlying molecular mechanisms remain incompletely understood. Methods: Bioinformatic and molecular experiments were performed. Results: Published dataset analyses reported that miR-221 was upregulated in the skeletal muscle of diabetic patients after exercise and downregulated in an aged mouse skeletal muscle model. Target gene prediction and enrichment analysis suggested a potential association between miR-221 and myoblast proliferation. Overexpression of miR-221 in C2C12 myoblasts altered cell-cycle distribution, characterized by an increased G1 fraction and a decreased G2/M fraction, and reduced differentiation-associated gene expression. Through intersection analysis of predicted target genes with differentially expressed genes from a reported miR-221-overexpressing mouse model, Ctcf, a gene previously reported to be associated with myoblast proliferation and differentiation, was nominated as a candidate downstream target. However, Ctcf was not measured in this study; whether it is directly regulated by miR-221 and whether it mediates the observed effects remain to be experimentally validated, and a Ctcf rescue experiment would be required to establish functional mediation. Conclusions: this study suggests that miR-221 overexpression alters cell-cycle distribution and reduces differentiation-associated gene expression in C2C12 myoblasts. These findings may provide insights into the role of exercise-responsive skeletal muscle miRNAs in metabolic diseases.