نوع مقاله : مقاله پژوهشی
نویسندگان
1 کارشناس ارشد فیزیولوژی ورزشی کاربردی، دانشگاه پیام نور، مرکز کرج، کرج، ایران.
2 دانشیار گروه فیزیولوژی ورزشی، پژوهشگاه تربیت بدنی و علوم ورزشی، تهران، ایران.
3 استادیار گروه علوم ورزشی، دانشگاه پیام نور، تهران، ایران.
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Extended Abstract
Background and Aim: Subcutaneous fat refers to the fat cells that are stored under the skin of the body. The normal subcutaneous fat is very cruciall to survive and, in particular, maintain body temperature, but excessive accumulation of subcutaneous fat can affect fitness or cause hormonal imbalances. In addition, some genes also affect the growth and proliferation of subcutaneous adipose tissue. One of these genes is peroxisome proliferator-activated receptor gamma (PPARγ), which is expressed in adipose tissue, the colon, and macrophages. One factor that affects the expression of PPAR-γ in adipose tissue is the transcriptional intermediary factor -2 (TIF2). It has been reported that in white adipose tissue, the absence of TIF2 can reduce PPARγ activity and also decrese fat accumulation.
The effect of exercise training on TIF2 gene expression in subcutaneous adipos tissue of male Wistar rats is an area of scientific uncertainty due to contradictory findings in some studies. While some research suggests that exercise training can modulate gene expression in adipose tissue, including genes related to metabolism and adipogenesis, the specific role of TIF2 is also unclear. For example, continuous moderate-intensity exercise has been shown to reduce TGF-β expression in diabetic Wistar rats, whereas other studies suggest that acute or short-term exercise may regulate specific adipogenic genes in white adipose tissue. These inconsistencies raise questions about whether similar patterns apply to TIF2 or not. Other studies of exercise-induced gene expression in adipose tissue have shown also inconsistent results between subcutaneous and other fat depots, as well as between acute and chronic exercise interventions. This diversity of efforts and results complicates generalizations to TIF2. Given these discrepancies, there is a critical need for targeted studies that identify whether different exercise training regimens can specifically affect TIF2 expression in subcutaneous adipose tissue of male Wistar rats. Such research could clarify whether the effects observed across different exercise protocols are the same or depend on other factors such as intensity, duration, or metabolic conditions.
Materials and Methods: After grouping the rats as moderate-intensity aerobic training (MIT, n=7), high-intensity aerobic training (HIT, n=7), and high-intensity interval training (HIIT, n=7), the average aerobic power of the rats in each group was evaluated according to the protocol of Hoydal et al. (2007), and therefore the training intensity of the first week of each group was determined. The training began for 8 weeks and was repeated 5 days a week according to the instructions. The training protocle was performed during morning. Further eight weeks of training 24 hours after the last training session and also 12 hours of fasting, tissue sampling was captured. All stages of maintenance and sacrifice of the rats were performed according to the laboratory animal maintenance instructions. The animals were anesthetized with Xylazine and Ketamine injections, and subcutaneous adipose tissue was gathering from the abdominal area. The tissue sample was immediately placed in a microtube and placed in a liquid nitrogen solution. The weight of the rats was also measured at the beginning and end of the study.
Due to the lack of direct instrumentation, the animals' maximal oxygen consumption was indirectly assessed by performing an incremental treadmill test according to the protocol of Høydal et al. (2007). A 10-minute warming-up was performed at an intensity of 40–50% of maximal oxygen consumption (VO2max). Then, the rats started running at a speed of 15 m/min for 2 min, when the speed was increased by 2 m/min every 2 min until exhaustion. The MIT was consisted of running at 65% of VO2max for a total of 47-min, therefore the workout consisted of a 5 min warm-up, a 5 min cool-down, and 37 min of the main body of exercise at 65% of VO2max. The HIT protocol consisted of running at a speed of 20 m/min for 40-min on treadmill with a progressively increasing incline. The treadmill incline was set at 0% during the first week and increased by 2% every two weeks, reaching 8% by the eighth week. Each session also included a 5-min warm-up, a 30-min main exercise phase, and a 5-min cool-down. The HIIT consisted of 4 high-intensity intervals with 4 min of running at an intensity of 90–100% VO2max followed by 3-min of active rest at 50–60% VO2max. In this way, the workout consisted of a 5 min warm-up, a 5 min cool-down, and 28 min of the main body of the workout. It lasted a total of 38-min.
In the descriptive statistics section, mean and standard deviation were used. For Statistical analysis, the Shapiro-Wilk test was used to determine the normality of data distribution and a one-way analysis of variance with the least significant difference (LSD) post hoc test was used to determine the significance of the difference between groups at a significance level of p<0.05.
Findings: The results showed that all 3 training models caused a significant decrease in the TIF2 gene expression in the subcutaneous adipose tissue of rats (Control vs MIT, p=0.007; Control vs HIT, p=0.001; Control vs HIIT, p=0.009) (Figure 1); The greatest reduction was observed in the HIT group. However, no significant differences were found among the HIT, HIIT, and MIT groups (HIT vs. HIIT, p=0.12; HIT vs. MIT, p=0.16).
Conclusion: Based on the result of this study, TIF2 gene expression in subcutaneous adipose tissue (MIT, HIT and HIIT) was significantly reduced compared to the control group. However, the greatest reduction was observed in the HIT group, which may be due to the high intensity and greater stimulation of metabolic and inflammatory pathways. HIT plays a more effective role in suppressing TIF2 by inducing more rapid changes in the regulation of genes related to fat metabolism. The high intensity of this type of aerobic exercise leads to greater metabolic stress. It also stimulates pathways related to inflammation and metabolism, such as lactate production and hypothalamic neuroplasticity, which may underlie its superior effect in reducing TIF2 gene expression compared to moderate-intensity exercise. This results also suggests that HIT can induce stronger cell signaling changes. Moreover, the studies showed that HIT can induce greater increases in the expression of specific receptors and signaling molecules, including estrogen receptor α, in hypothalamic pathways associated with fat loss than MIT, suggesting an intensity-dependent molecular adaptation. Also, based on the results of other studies, the reduction of TIF2 expression leads to an increase in SRC-1 activity, which is associated with improved mitochondrial function and resistance to oxidative stress in muscles; therefore, it is likely that HIT indirectly affects its expression or activity by altering metabolic pathways or transcriptional regulators. However, further research is needed to directly assess how endurance training, and specifically HIT training, affects TIF2 gene expression and pathways affecting fat metabolism. However, current evidence suggests an important role for HIT in muscle adaptation and metabolic regulation.
Ethical Considerations: This study was conducted with approval from the Research Ethics Committee of Payam Noor University with ethics code IR.PNU.REC.1400.052.
Compliance with ethical guideline: Ethical guidelines for working with laboratory animals were strictly followed, including provisions for adequate food, water, and appropriate housing conditions.
Funding: This research was conducted based on a master’s thesis of Payame Noor University, Karaj Center, without financial support.
Conflicts of interes: There are no conflicts of interest regarding this article.
کلیدواژهها [English]
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