The Effect of Different Intensities of Aerobic Exercise on the Expression of Darpp32 Markers in the Liver of Male Wistar Rat

The liver, as the largest gland in the body, can manufacture, store, change and secrete a large number of metabolic substances the body. The liver receives blood rich in nutrients from the digestive and esophageal tracts, then stores them or changes them into chemical substances that are used elsewhere in the body for metabolic needs. This tissue is especially important in regulating glucose and protein metabolism. The liver makes and secretes bile, which plays a major role in the digestion and absorption of fats in the digestive system. On the other hand, the lack of physical activity and the decrease in cardio-respiratory fitness related to it is related to the increase in diseases. Among obese individuals, sedentary individuals have an increased risk of developing fatty liver compared to physically active individuals of similar weight. These data support the hypothesis that increasing physical activity through exercise, which is defined as a planned, structured, and repetitive physical activity with specific intensity and duration, has beneficial effects on liver diseases. On the other hand, in the liver tissue, a large number of targeted proteins are connected to specific enzymes and cell structures and scaffolding proteins, which collect enzyme intermediates. Insulin increases the accumulation of glycogen by phosphorylating these enzymes and as a result, activates glycogen synthase and deactivates glycogen Desynthase. The DARPP-32 gene, which is also known as PPP1R1B regulatory subunit, is a strong inhibitor of protein phosphatase-1 (PP1). It is phosphorylated at Thr34 by cAMP. DARPP-32 shows a significant regional distribution in the brain, which is almost similar to dopamine innervation. Molecular studies of DARPP-32 have shown that its regulation and function are more complex. DARPP-32 protein is phosphorylated by stimulation of D1 and D2 dopamine receptors and is coded by the PPP1R1B gene. DARPP-32 is a small, unstructured protein of about 202 amino acids. Since the mid-1980s, DARPP-32 has been recognized as a critical mediator of dopamine's biochemical, electrophysiological, transcriptional, and behavioral effects. It has been shown that the phosphorylation state of DARPP-32 provides a mechanism to integrate information received by dopamine neurons and in different brain regions through a variety of neurotransmitters, neuromodulators, neuropeptides, and steroid hormones. Most studies have investigated the effect of endurance training on hormones and factors secreted from liver tissue. However, in none of the studies has it been determined which intensity of exercise can have a greater effect on the expression of the DARPP-32 gene. Therefore, in this study, we seek to investigate and answer the question of whether there is a significant difference between different intensities of aerobic exercise on the expression of Darpp32 markers in the liver of male Wistar rats.

The present research was experimental, for this purpose, 32 8-week-old male Wistar rats with an average weight of 237 ± 33 grams were purchased from Pasteur Institute. After being transferred to the animal laboratory environment, these animals were kept in groups of 8 mice in transparent polycarbonate cages in an environment with a temperature of 22 ± 1.4 degrees Celsius, a humidity of 45 to 55%, and a light-dark cycle of 12:12. The animals were randomly divided into 4 groups and each group had 8 heads including a control group, moderate-intensity aerobic training (MIT), high-intensity aerobic training (HIT) and high-intensity interval aerobic training (HIIT). Animal care was carried out in accordance with the guidelines of the International Institute of Health and the protocols of this study, following the principles of the Declaration of Helsinki and the rules of medical ethics. Also, this study was approved by the Ethics Committee of Payam Noor University with code IR.PNU.REC.1398.040. During the research period, the food made by Behparvor company was given to the animals in the form of pellets and according to the weekly weighing at the rate of 10 grams per 100 grams of body weight. The water needed by the animal was also freely available. In order to get acquainted with the conditions of the laboratory and the treadmill, the animals ran on the treadmill for 2 weeks, 5 days per week and for 10 to 15 minutes each day at a speed of 5 to 15 m/min. Rats were active for 8 weeks after warming up for 5 minutes (at a speed of 5 m/min). The number of sessions per week was 5 sessions. The MIT exercise protocol consisted of running at 65% of maximum oxygen consumption for a total time of 47 minutes. The exercise consisted of 5 minutes of warm-up and 5 minutes of cool-down and 37 minutes of the main body of the exercise at 65% of maximal oxygen consumption. The HIT exercise protocol included running at a speed of 20 meters per minute for 40 minutes with an increasing incline of the treadmill. The exercise consisted of 5 minutes of warm-up and 5 minutes of cooling down and 30 minutes of the main body of the exercise at 65% of maximal oxygen consumption. The incline of the treadmill was zero in the first week and 2% was added every 2 weeks until it reached 8% in the eighth week. The HIIT training protocol included 4 high-intensity intervals with 4 minutes of running at an intensity of 90 to 100% of maximum oxygen consumption and 4 low-intensity intervals with 3 minutes of running at 50 to 60% of maximum oxygen consumption, which lasted a total of 38 minutes. It consisted of 10 minutes of warm-up and 28 minutes of the main body of the exercise (16). In order to ensure the isolation of exercise in all 4 groups, the exercises were performed according to the method of Rokenmo et al. (2004). Based on this method, the net training time in each group was calculated and equalized based on the time, intensity, and repetition of the work. After finishing the training period, the mice were anesthetized, blood was taken and tissue was separated, and the data obtained by PCR-Real time device were measured and analyzed.

The results obtained from the implementation of this test showed that there is a significant difference between the research groups in the expression values of the Darpp32 protein gene. Comparison between groups showed that there is a significant difference in the expression of the Darpp32 protein gene of Wistar rats between control training groups (P ≥ 0.001). Comparison between groups was done with Tukey's test and the results showed that there is a significant difference in the expression of the DARPP32 gene in male Wistar rats between the HIIT group compared to the MIT, HIT, and control groups (P ≥ 0.001). So in the MIT group, they decreased by 0.021 units, in the HIT group by 0.011 units, and in the control group by 0.030 units compared to the HIIT group. On the other hand, a significant difference was also observed between the HIT and control groups compared to the MIT group (P ≥ 0.001), so that in the HIT group it increased by 0.010 units compared to the MIT group, and in the group, The control also decreased by 0.008 units compared to the MIT group. Also, the follow-up test in the training groups showed that there is a significant difference in the expression of the DARPP32 gene between the HIT and control exercise training groups (P ≥ 0.001), so in the HIT group it was 0.019 The unit has increased compared to the control group.

In general, it can be concluded that sports training produces favorable changes in the metabolic system of the liver - these effects were seen in aerobic exercise with high intensity. Aerobic exercise with high intensity for 8 weeks can increase the expression of the Darpp-32 protein gene. The results of the present study can be concluded that 8 weeks of aerobic exercise improves the function of genes involved in glucose metabolism. Among the limitations of the present study, we can point out the lack of control over the number of calories consumed by rats and the lack of control over physical activity outside of the animal research program. Despite this, the research background on the effect of the exercise protocols of the present research on Darpp-32 in liver tissue is very limited and needs more investigations.