Endurance exercise decreases protein synthesis and ER-mitochondria contacts in mouse skeletal muscle

Abstract

Exercise is important to maintain skeletal muscle mass through stimulation of protein synthesis, which is a major ATP-consuming process for cells. However, muscle cells have to face high energy demand during contraction. The present study aimed to investigate protein synthesis regulation during aerobic exercise in mouse hindlimb muscles. Male C57Bl/6J mice ran at 12 m/min for 45 min or at 12 m/min for the first 25 min followed by a progressive increase in velocity up to 20 m/min for the last 20 min. Animals were injected intraperitoneally with 40 nmol/g of body weight of puromycin and euthanized by cervical dislocation immediately after exercise cessation. Analysis of gastrocnemius, plantaris, quadriceps, soleus, and tibialis anterior muscles revealed a decrease in protein translation assessed by puromycin incorporation, without significant differences among muscles or running intensities. The reduction of protein synthesis was associated with a marked inhibition of mammalian target of rapamycin complex 1 (mTORC1)-dependent phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1, a mechanism consistent with reduced translation initiation. A slight activation of AMP-activated protein kinase consecutive to the running session was measured but did not correlate with mTORC1 inhibition. More importantly, exercise resulted in a strong upregulation of regulated in development and DNA damage 1 (REDD1) protein and gene expressions, whereas transcriptional regulation of other recognized exercise-induced genes ( IL-6, kruppel-like factor 15, and regulator of calcineurin 1) did not change. Consistently with the recently discovered role of REDD1 on mitochondria-associated membranes, we observed a decrease in mitochondria-endoplasmic reticulum interaction following exercise. Collectively, these data raise questions concerning the role of mitochondria-associated endoplasmic reticulum membrane disruption in the regulation of muscle proteostasis during exercise and, more generally, in cell adaptation to metabolic stress. NEW & NOTEWORTHY How muscles regulate protein synthesis to cope with the energy demand during contraction is poorly documented. Moreover, it is unknown whether protein translation is differentially affected among mouse hindlimb muscles under different physiological exercise modalities. We showed here that 45 min of running decreases puromycin incorporation similarly in 5 different mouse muscles. This decrease was associated with a strong increase in regulated in development and DNA damage 1 protein expression and a significant disruption of the mitochondria and sarcoplasmic reticulum interaction.

Is REDD1 a metabolic double agent? Lessons from physiology and pathology

“…MAM disruption and inhibition of glycogen storage by REDD1 could therefore spare ATP via reduction of macromolecule synthesis. Consistently, exercise-induced REDD1 expression is associated with MAM disruption and protein synthesis inhibition in skeletal muscle (125). Conversely, REDD1 deletion reduces maximal aerobic performance, and REDD1 silencing in myoblasts increases both MAM number and protein synthesis under basal conditions (20,152).…”

Effects of the anti-oxidant PDTC in combination with a single bout of treadmill running on murine skeletal muscle

“…Interestingly, we could not detect induction of Il6 expression in skeletal muscle tissue. This might be due to specific expression kinetics of this gene, since Merle et al [26], also failed to observe enhanced concentrations of Il6 mRNA in various murine muscle tissues immediately after a single bout of treadmill running. Furthermore, based on Il6 expression kinetics in human skeletal muscle ( [27], and references therein), it is likely that the time points we chose for our analysis, 0 and 3 h, might have missed the rise, peak and decline of Il6 mRNA.…”

Muscle Phenotype, Proteolysis, and Atrophy Signaling During Reloading in Mice: Effects of Curcumin on the Gastrocnemius

“…As such, mice were injected puromycin (intraperitoneally 0.04 µmol/g body weight) 30 min prior to sacrifice. Samples from these animals were also collected (see below) [32].…”