miRNA in the regulation of skeletal muscle adaptation to acute endurance exercise in C57Bl/6J male mice

Abstract

MicroRNAs (miRNAs) are evolutionarily conserved small non-coding RNA species involved in post-transcriptional gene regulation. In vitro studies have identified a small number of skeletal muscle-specific miRNAs which play a crucial role in myoblast proliferation and differentiation. In skeletal muscle, an acute bout of endurance exercise results in the up-regulation of transcriptional networks that regulate mitochondrial biogenesis, glucose and fatty acid metabolism, and skeletal muscle remodelling. The purpose of this study was to assess the expressional profile of targeted miRNA species following an acute bout of endurance exercise and to determine relationships with previously established endurance exercise responsive transcriptional networks. C57Bl/6J wild-type male mice (N = 7/group) were randomly assigned to either sedentary or forced-endurance exercise (treadmill run @ 15 m/min for 90 min) group. The endurance exercise group was sacrificed three hours following a single bout of exercise. The expression of miR- 181, 1, 133, 23, and 107, all of which have been predicted to regulate transcription factors and co-activators involved in the adaptive response to exercise, was measured in quadriceps femoris muscle. Endurance exercise significantly increased the expression of miR-181, miR-1, and miR-107 by 37%, 40%, and 56%, respectively, and reduced miR-23 expression by 84% (P<or=0.05 for all), with no change in miR-133. Importantly, decreased expression of miRNA-23, a putative negative regulator of PGC-1alpha was consistent with increased expression of PGC-1alpha mRNA and protein along with several downstream targets of PGC-1alpha including ALAS, CS, and cytochrome c mRNA. PDK4 protein content remains unaltered despite an increase in its putative negative regulator, miR-107, and PDK4 mRNA expression. mRNA expression of miRNA processing machinery (Drosha, Dicer, and DGCR8) remained unchanged. We conclude that miRNA-mediated post-transcriptional regulation is potentially involved in the complex regulatory networks that govern skeletal muscle adaptation to endurance exercise in C57Bl/6J male mice.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. PGC-1α content and miR-23 expression following exercise.

PGC-1α (A) mRNA expression and (B) protein content, and (C) miR-23 expression in the quadriceps of C57Bl/6J mice (N = 7/group) 3-hour following an acute bout of END exercise vs. SED group. (D) PGC-1α protein content negatively correlates (R = 0.62) with miR-23 content. PGC-1α mRNA expression, protein content and miR-23 expression are normalized to β-2 microglobulin, actin and Rnu6, respectively. Asterisks denote significant changes (P≤0.05).

Figure 2. Transcription of PGC-1α target genes following exercise.

Activation of ALAS, CS and cyt. c mRNA expression (fold-change) in the quadriceps of C57Bl/6J mice (N = 7/group) 3-hour following an acute bout of END exercise vs. SED group. ALAS, CS and cyt. c mRNA expression are normalized to β-2 microglobulin. Asterisks denote significant changes (P≤0.05).

Figure 3. PDK4 content and miR-107 expression following exercise.

(A) PDK4 mRNA expression and (B) protein content, and (C) miR-107 expression in the quadriceps of C57Bl/6J mice (N = 7/group) 3-hour following an acute bout of END exercise vs. SED group. PDK4 mRNA expression, protein content and miR-107 expression are normalized to β-2 microglobulin, actin and Rnu6, respectively. Asterisks denote significant changes (P≤0.05).

Figure 4. miR-1 and miR-181 expression following exercise.

miR-1 and miR-181 expression in the quadriceps of C57Bl/6J mice (N = 7/group) 3-hour following an acute bout of END exercise vs. SED group. miR-1 and miR-181 expression are normalized to Rnu6. Asterisks denote significant changes (P≤0.05).