Expression changes in human skeletal muscle mi RNA s following 10 days of bed rest in young healthy males

Aim Studies in humans show global changes in mRNA and protein expression occur in human skeletal muscle during bed rest. As micro RNA s are important regulators of expression, we analysed the global micro RNA expression changes in human muscle following 10 days of sustained bed rest, with the rationale that mi RNA s play key roles in atrophy of skeletal muscle. Methods We analysed expression of mi RNA and selected target proteins before and after 10 days of bed rest in biopsies obtained from the vastus lateralis muscle of 6 healthy males. Results Fifteen of 152 mi RNA s detected in human muscle tissue were differentially expressed, and all of them with exception of two were downregulated. The downregulated mi RNAs include the following: miR‐206, a myomir involved in function and maintenance of skeletal muscle; miR‐23a, involved in insulin response and atrophy defence; and several members of the let‐7 family involved in cell cycle, cell differentiation and glucose homeostasis. Predicted gene targets of these mi RNAs are members of the MAPK , TNF receptor, ALK 1, TGF ‐beta receptor and SMAD signalling pathways. All of these pathways were previously indicated to be involved in skeletal muscle response to physical inactivity. We also measured protein expression of selected mi RNA targets and observed a decrease in HDAC 4. Conclusion Our data demonstrate that mi RNA s in postural muscles are affected by sustained inactivity and unloading, as induced by prolonged bed rest, and hence are potentially involved in regulation of skeletal muscle adjustments to inactivity. We also propose new mi RNA s involved in regulation of biological processes in adult human muscle.