Apoptotic response to acute and chronic exercises in rat skeletal muscle: Eccentric & sprint interval.

AIMS: Apoptosis is a type of cell death that is vital for tissue homeostasis. Exercise can lead to initial stimulation of apoptotic regulator genes. We investigated their response to an acute exercise and their adaptations to chronic exercise training with an emphasis on eccentric and sprint interval exercises. MAIN METHODS: Male Sprague Dawley rats were randomly assigned to five groups (n = 8): acute eccentric exercise (AEE), acute sprint interval exercise (ASE), chronic eccentric exercise (CEE), chronic sprint interval exercise (CSE) and control (C). The AEE group underwent downhill running (at -16° slope) at 16 m/min 18 sets. The ASE group run for 7 sets and the speed increased gradually to 70-80 m/min. The chronic groups were implemented for 9 weeks. The CEE run 1 set for 15 min at -4° slope that increased gradually to 90 min at -16°. The CSE sprinted 1 min with 2-5 min rest. The mRNA in soleus (slow-twitch muscle) and super vastus lateralis (SVL) (fast-twitch muscle) muscles was analyzed by real-time RT-PCR. KEY FINDINGS: According to the gene expression level in soleus muscle, apoptotic responses to acute and chronic sprint interval exercise as well as towards chronic eccentric exercise were clearly evident. But in SVL muscle, the only acute eccentric exercise group showed significance increase in apoptotic factors. SIGNIFICANCE: these results revealed the apoptotic response to the exercise depends on the type and intensity of exercise and also on the sensitivity and susceptibility of the muscle.

Effect of acute and chronic eccentric exercise on FOXO1 mRNA expression as fiber type transition factor in rat skeletal muscles.

Skeletal muscle is a highly elastic tissue which can respond to various functional demands by altering fiber-type composition. Exercise affects muscle fiber phenotype. One of the transcription factors that induce fiber-type transition is forkhead box O1 (FOXO1). Since eccentric contraction considered an essential part of exercise, so we are interested to see the effects of eccentric exercise (acute/chronic) on FOXO1 as an important factor of fiber-type transition in rat skeletal muscles. Twenty-four Sprague-Dawley rats (190-235g) were divided to 3 groups of 8 rats: 1) chronic eccentric exercise (CEE), 2) acute eccentric exercise (AEE), and 3) control (C). The exercise groups underwent downhill running protocol. CEE was running on treadmill in 3 days of week for 9 weeks, that slope and duration gradually managed from -4° to -16° and 15 to 90 min, respectively. AEE group was running with 16 m/min on -16° slope for 3 consecutive days that included 18 sets of 5 min with rest interval of 2 min in between. Soleus and super vastus lateralis (SVL) muscles mRNA were analyzed by real-time RT-PCR. SVL FOXO1 mRNA levels increased by 3.92-fold in the AEE and decreased 0.56-fold in the CEE group and were not significant in soleus muscle. In soleus muscle, myosin heavy chain (MHC) IIa, IIx, and IIb decreased in the AEE group and MHC IIa and IIx decreased in the CEE group. In SVL muscle, MHC I, IIa, and IIx increased in the AEE group and MHC IIa and IIX increased in the CEE group. In summary, both acute and chronic eccentric exercise could lead to change in FOXO1 mRNA only in fast SVL muscle of rat and so could induce fiber-type transition in both muscles regardless of changes in expression of FOXO1. So, oxidative stress can play important role in change of FOXO1.