Figure 2.

The potential role of miRNAs in the attenuated myogenic process in the elderly. Let-7b and let-7e may contribute to the inhibition of satellite cell activation and proliferation via downregulating cell cycle regulators CKD6, CDC25A, and CDC34. In addition miR-181a may inhibit ActRIIA (activin type IIa receptor) and as a consequence permit activation of the proliferation inhibitors SMAD2/3. The combination of miR-221 and miR-698 further inhibits proliferation by down regulating various MRFs and driving terminal differentiation of the myocytes. Anabolic stimulus is known to reduce miR-1. Failure to downregulate miR-1 in elderly skeletal muscle following anabolic stimulation may contribute to anabolic resistance in mature myotubes via inhibition of IGF-1/Akt signaling., ↑ = stimulatory pathway; or, T = inhibitory pathway; ↑, upregulated miRNA; ↓, downregulated miRNA; ?, cause-and-effect relationship not established.