@2024 Afarand., IRAN

---

ISSN: 2252-0805    The Horizon of Medical Sciences 2016;22(2):111-116

Background
… [1-10] Animal and human studies show the negative regulatory role of myostatin in skeletal muscle growth [11]. … [12, 13]
Previous Studies
Regular resistance exercise is associated with reduced expression of myostatin gene [14]. … [15, 16] Also, myostatin gene expression in cardiac muscle following physical activities [17] or in the infarcted heart can be changed [5].
Aim(s)
This study aimed to investigate the effect of eight weeks of resistance training on the cardiac muscle myostatin gene expression in healthy male Wistar rats.
Research type
This is an experimental research.
Research society, place and time
Healthy adult male Wistar rats weighing 250.0 ± 26.5 gr and aged 5 weeks were studied.
Sampling method and number
13 rats were studied.
Used devices&materials
The mice were divided into two groups including experimental (7 rats) and control (6 rats). 10- to 15-minute daily resistance training introduction was done at the first week for the mice to become familiar with climbing the ladder. In this stage, a weight equivalent to 30% of the animal`s weight was attached through a cylinder to its tail and the animal had to climb up the ladder. This exercise was carried out 8 weeks through climbing a 1-meter ladder with 26 stairs and 85 degree slope with a weight. Exercises were held in 3 sessions per week and each session included 3 sets with 5 repetitions. At the first week, the weight fastened to the rats was 30% of their body weight and then, gradually increased to 200% of body weight in the last 2 weeks [18]. 24 hours after the last training session and 12 hours of fasting, mice were dissected after their transition to the genetic laboratory, and a sample of muscle tissue was taken to estimate the levels of myostatin mRNA [19]. To investigate myostatin mRNA in the cardiac muscle, real time PCR method with the prime sequences 5’-TAA CCT TCC CAG GAC CAG GA-3’ was used. For conducting real time PCR reaction, Chromo device and SYBER-Green (TAKARA, USA) were used. Collected data were analyzed by SPSS 16 software. After ensuring the normality of theoretical distribution of data using Shapiro-Wilk test and homogeneity of variance by Levene test, independent T-test was used to assess the mean inter-group differences.
Findings by Text
After eight weeks of resistance training, there was no significant difference in the myostatin mRNA expression level in cardiac muscle in resistance group (1.56 ± 0.44) compared to control group (1.94 ± 0.55; p=0.197).
Main comparison to the similar studies
Eight weeks of resistance training did not result in a significant change in the levels of cardiac muscle myostatin mRNA levels of healthy male Wistar rats. These findings are consistent with the results of some studies [20, 21], but it is not consistent with the results of some other studies [15, 17, 22] in terms of the change in the myostatin mRNA level. No statistical change has been reported in myostatin levels after 12 weeks of strengthening and endurance exercises in active subjects [20]. Eight weeks of resistance training result in no change in the level of activin IIb mRNA of muscle [21]. Investigating the effects of 9 weeks heavy training knee extension (3 days a week with maximum 50 repetitions) on myostatin mRNA levels of Vastus lateralis of the stronger foot collected by Biopsy shows 37% reduction in the muscle myostatin mRNA level at the end of the period [15]. After 4 weeks swimming training, skeletal muscle myostatin mRNA expression decreases especially in the twitch and red muscles (gastrocnemius muscle) and it increases nearly doubled in the cardiac muscle [17]. In the study focusing on the effect of resistance training (3 sets; 8 to 12 repetitions up to the voluntary exhaustion including Scott movements, leg press and knee opening) on mRNA expression of myostatin, myostatin mRNA levels have decreased at the end of the period [22]. Lifelong inactivation of myostatin limits the variety of aerobic functions in mice [23-25]. … [26] In older mice, inactivation of myostatin in combination with physical exercise can improve endurance performance [27]. … [28-32]
Suggestions
In future studies, larger sample size should be used, and factors influencing myostatin should be investigated.
Limitations
Of the limitations of this study were mortality of some mice in some groups and the reduction of the sample size. Also, in this study, there was no possibility of expression of myostatin receptor and the amount of myostatin protein.
Conclusions
8 weeks of resistance training in healthy Wistar rats does not result in any change in the cardiac muscle myostatin mRNA expression level.
Acknowledgments
The people who helped us in conducting this research are appreciated.
Conflict of interest
Non-declared
Ethical Permissions
Non-declared
Funding Sources
This study was funded by Department of Research and Technology of Ferdowsi University of Mashhad.