Effect of Resistance Exercise and Vitamin C Intake on Expression of Telomerase Reverse Transcriptase and Telomere Repeat Binding Factor-2 Genes and the Diameter and Number of Myofibrils in Old Rats

* Corresponding Author: Maghsoud Peeri, PhD. Address: Department of Sports Physiology, Faculty of Physical Education and Sports Sciences, Central Tehran Branch, Islamic Azad University, Tehran, Iran. Tel: +98 (21) 22481622 E-mail: m.peeri@gmail.com 1. Department of Sports Physiology, Faculty of Physical Education and Sports Sciences, Central Tehran Branch, Islamic Azad University, Tehran, Iran. Yousef Shirkhani1 , *Maghsoud Peeri1* , Mohammad Ali Azarbayjani1 , Hassan Matinhomaee1


Introduction
he aging cell has certain characteristics, the most important of which are increased cell size, distinct morphology, extensive changes in gene expression, and shortened telomere length [1]. Telomerase Reverse Transcriptase (TERT) is a catalytic subunit of enzyme telomerase. TERT is a protein with catalytic and transcriptase activity [2]. Other important proteins that play an important role in telomeric structure are telomere repeat binding factors (TRFs) with isoforms 1 and 2 and bind directly to TTAGGG repeats [3]. Oxidative pressure appears to affect the length of telomerase and myofibrils.
Vitamin C is mixed with antioxidant activity. However, there are no clear results about the effect of vitamin C consumption on telomerase length as well as TERT and TRF2. Some studies have shown that long-term physical activity plays an important role in controlling aging by affecting chromosomes [4]. There are no clear results about the effect of resistance exercise as well as the effect of vitamin C intake and their combined effect on telomerase length and especially on TRF2 and TERT gene expression. In this regard, this study aims to evaluate the effect of resistance exercise along with liposomal vitamin C intake on the expression of TERT and TRF2 genes and on the diameter and number of myofibrils in old male Wistar rats.

Materials and Methods
This is an experimental study on 25 male Wistar rats aged 24 weeks and weighted 280-320 g. They were randomly divided into five groups of young control (n=5), old+resistance exercise (n=5), old+vitamin intake (n=5), old+resistance exercise+vitamin intake (n=5), and old control (n=5). In the exercise groups, 20 minutes of resistance exercise with ladders and weights were performed for 8 weeks, 3 days per week. At the end of the exercise period, rats in each group were examined for further studies. In the supplementation groups, liposomal vitamin C was administered daily by gavage per kg body weight. Shapiro-Wilk test was used to investigate the normality of data distribution. One-way ANOVA test was used to examine the differences between groups and Tukey's post hoc test was used to determine where these differences were found. All analyses were performed in SPSS V. 22 software considering a significance level of 0.05.

Results
The results of ANOVA showed a significant difference between the groups in terms of TERT expression (P=0.001). The results of Tukey's post hoc test showed that the significant differences were between the old control and young control groups (P=0.001). For TRF2 expression, ANOVA test results also showed a significant difference between the groups (P=0.001). Tukey's post hoc test showed that the significant differences were between the old control and young control groups

Young Elder
Elder+Sport+Vitamin C Elder+Vitamin C Elder+Sport (P=0.001) and between the old+resistance exercise and young control groups (P=0.001). There was also a significant difference between the groups in terms of myofibril diameter (P=0.001). The results of Tukey's post hoc test showed that the significant difference was between the young control and the old control groups, between the old+resistance exercise+vitamin intake and the old control groups (P=0.001), between the old+resistance exercise and the old+resistance exercise+vitamin intake groups (P=0.001), between the old+vitamin intake and the old+resistance exercise+vitamin intake groups, and between the old+vitamin intake and the young control groups (P=0.001). There was also a significant difference between the groups in terms of the number of myofibrils (P=0.001). The results of Tukey's post hoc test showed that the significant difference was between the young control and the old control groups, between the old+resistance exercise+vitamin intake and the old control groups (P=0.001), between the old+resistance exercise and the old+resistance exercise+vitamin intake groups (P=0.001), between the old+resistance exercise and the young control groups (P=0.001), between the old+vitamin intake and the old+resistance exercise+vitamin intake groups, and between the old+vitamin intake and the young control groups (P=0.001) (Figures 1, 2

Conclusion
The purpose of this study was to investigate the effect of resistance exercise along with vitamin C consumption on the expression of TERT, TRF2 genes and the diameter and number of skeletal muscle myofibrils in old male Wistar rats. The results showed that there was a significant difference between the old and young control groups. However, no significant difference was observed between the other groups. Regarding TRF2 level, a significant difference was observed between the old and young control group (P=0.001) and between the trained old group and the young control group. in a study, rats with Manganese superoxide dismutase deficiency in muscle or heart tissue had inhibited telomerase activity and decreased expression of TERT and TRF2. However, antioxidant supplements prevented this process [5]. Part of the adaptation of telomerase to exercise should be attributed to the MAPK pathways. Activation of MAPK leads to a change in the positional activity of a variety of transcription factors that are associated with altered expression of telomere gene components [6]. On the other hand, exercise increases the antioxidant content and reduces the oxidative pressure [7]. It seems that the interactive effect of exercise and vitamin C intake is effective in reducing the maximum oxidative pressure on telomere length.
In the present study, the expression of TERT and TRF2, and the diameter and number of myofibrils in the group of old rats that did resistance exercise and took vitamin C, was close to those of young control rats. Increased TERT and especially TRF2 levels can be considered as the reasons for the increase in diameter and number of myofibrils in old rats. Due to the limited research on TERT and TRF2 levels in the elderly, as well as the effects of vitamin C and resistance exercise on it, no other rational mechanisms can be mentioned.
Eight weeks of resistance exercise along with vitamin C supplementation can significantly increase the number and diameter of skeletal muscle myofibrils in older rats.

Compliance with ethical guidelines
This study was approved by the Ethics Committee of Sport Sciences Research Institute of Iran (Code: IR.SSRI. REC.1399.115).

Funding
This study was extracted from a PhD. dissertation of the first author, at the Department of Sports Physiology, Faculty of Physical Education and Sports Sciences, Islamic Azad University, Central Tehran Branch, Tehran.

Conflicts of interest
The authors declared no conflict of interest.