Abstract
Objective: The physiological characteristics and acute responses underpinning uphill running differ from those of downhill running and remain less understood. This study aimed to evaluate time-course changes of muscle-specific microRNA (miRNA) responses in striated muscle or circulation in response to uphill and downhill running.Methods: Male Sprague-Dawley rats (n = 84) were randomly assigned to a sedentary group (n = 12) and an exercise group (n = 72). The exercise group performed 90 min of uphill or downhill running. The striated muscle (quadriceps, gastrocnemius, soleus, and cardiac muscle) or circulation (plasma, exosome, exosome-free) levels of six muscle-specific miRNAs (miR-1, miR-133a, miR-133b, miR-206, miR-208a, and miR-499) were assessed at rest, immediately following exercise, and during recovery (1 h and 48 h).Results: Our results show that miR-1 and miR-133a levels are both decreased in quadriceps following downhill running (p < 0.05) while there is no change after uphill running (p > 0.05). In gastrocnemius, both uphill and downhill running decreased miR-1 level immediately after exercise and returned to baseline during recovery (p < 0.05): interestingly, only miR-499 significantly increased following uphill running (p > 0.05). Of the cell-free miRNAs in circulation, only the miR-133b levels in plasma were not affected following uphill running (p > 0.05); the other miRNA levels significantly increased immediately after exercise (p < 0.05), decreased at 1 h and significantly increased at 48 h after exercise (p < 0.05). All selected miRNA levels in exosomes were not affected following uphill running (p > 0.05), while all selected miRNA levels significantly increased during early recovery after downhill running (p > 0.05). In addition, only the miR-133a level in the exosome-free condition showed significant changes following uphill running (p < 0.05), while miR-1, miR-133a, and miR-499 levels showed significant changes after downhill running (p < 0.05).Conclusion: The results indicate that miRNA undergoes dynamic changes in tissue may play an important role in regulating different stress/adaptation following uphill and downhill running. It is likely that changed miRNA levels in plasma may act as a new biomarker for monitoring whole muscular stress during recovery.
Highlights
Exercise is a form of physiological stress that has a marked effect on the muscle system (Egan and Zierath, 2013)
A schematic scheme was conducted to summarize the whole ideal of the experiment (Figure 1)
The results showed that the time-course changes in the musclespecific miRNA profile are associated with several acute differences in physiological responses to eccentrically emphasized exercise in comparison to concentric exercise, mainly including various parts of muscle tissue, different time-course of changes in plasma, and exosome or exosome-free conditions
Summary
Exercise is a form of physiological stress that has a marked effect on the muscle system (Egan and Zierath, 2013). Many daily activities require muscles to perform concentric/eccentric contractions. Uphill or downhill running is often used as a model of concentric/eccentric exercise in rats to examine skeletal muscle function/damage processes following concentric/eccentric-induced mechanical stress (Munehiro et al, 2012). It is suggested that several grade-specific differences exist between level, uphill, and downhill running regarding biomechanics, neuromuscular adaptations and physiological responses (Vernillo et al, 2017). Because eccentric exercise offers a promising training modality to enhance performance and to prevent injuries in clinical settings, it is important to precisely determine skeletal muscle adaptation processes underpinning these different training stimuli (Assumpcao Cde et al, 2013)
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