Effect of aerobic training and octopamine on the gene expression of Drp-1 and Mfn-1 and MDA concentration in liver of male rats fed with repeated heated oil

Now days, frying and heating the oils are used to prepare the food in all over the world. During the heating, the oil decomposes continuously at high temperatures in the presence of air and moisture, and oxidation, isomerization, polymerization, and hydrolysis occur. Oxidized and heated oils contain oxidized monomers, dimers, polymers, free radicals, hydroperoxidases and aldehydes. These products have detrimental effects on human health and can cause harmful changes in body organs. Free radicals and oxidative stress in heated oils influence the body's energy sources such as mitochondria and genes involved in mitochondrial dynamics. Mitochondrial dynamics factors include Opa1 protein (optic atrophy 1) and mitofusin 1 and 2 (Mfn1 and 2), dynamin-related protein (Drp-1) and fusion protein 1 (Fis1). Deviation towards fusion optimizes mitochondrial function and is useful in maintaining long-term bioenergy capacity. Conversely, deviation toward division leads to the removal of the damaged part of the mitochondria. Exercise has recently been recognized as an effective way to increase mitochondrial function, and the role of exercise in improving mitochondrial damage and oxidative stress in various diseases has been reported. On the other hand, today, researchers are paying attention to sports supplements to reduce the physiological damage caused by exercise such as oxidative stress. One of these supplements is octopamine, which according to studies has antioxidant properties and stimulates fat metabolism. The aim of this study was to determine the aerobic training and octopamine on the gene expression of Drp-1 and Mfn-1 and MDA concentration in liver of male rats fed with repeated heated oil.

In an experimental study, 25 adult male Wistar rats weighing an average of 300 to 350 g and aged 8 weeks were purchased. All the rats were kept in polycarbonate cages (5 mice per cage) at 22 ± 2 ° C, 55% humidity and under the light and dark cycle for 12:12 hours without restriction on water and food. All the rats were randomly divided into five groups, healthy control group (n=5), DFO group (n=5), aerobic training + DFO group (n=5), octopamine + DFO group (n=5) and aerobic training + octopamine + DFO group (n=5). Intraperitoneal injection of octopamine and Gavage of repeated heated oil were done five times a week and every day, respectively. The aerobic training protocol consisted of 4 weeks of aerobic training and 5 sessions per week. The training session included 5 minutes of warm-up at 7 m / min and 5 minutes of cooling at 5 m / min. The intensity of training started in the first week with 50% VO2max and a speed of 16 m / min, and in the last week it reached 65% Vo2max and a speed of 26 m / min. 48 hours after the last training session and 8 hours of fasting, all the rats were anesthetized with chloroform and then sacrificed. Blood samples were taken directly from the liver by heparin-soaked syringe and the liver tissue was immediately removed from the body and stored in a nitrogen tank at -80 ° C. Gene expression of DRP-1 and Mfn1 were measured by Real time-PCR and MDA concentration was measured by ELISA test. One-way ANOVA and Tukey post hoc test were used to analysis the data. The significant level was set at p<0.05.

The results showed that consumption of repeated heated oil induced significant decrease in gene expression of DRP-1 (P =0/001) and Mfn1 (P =0/001) and non significant change in MDA (P =0/071) compared to healthy control group. Interaction effect of aerobic training and octopamine caused the significant increase in gene expression of DRP-1 (P =0/001) compared to all the groups except that healthy control group and non significant difference in Mfn1 gene expression and MDA concentration (P =0/008) in comparison with DFO group.

During the oil heating process, mitochondrial oxygen species reduce the synthesis of new mitochondria and the mitochondrial network, and since this reduction reduces antioxidant defense, it results in oxidative stress in the cell. MDA is one of the final products of lipid peroxidation, which is considered as an indicator of oxidative damage. At the end of 4 weeks of training protocol, the groups were not significantly different from each other, but physiologically, a nonsignificant increase in MDA indicates an increase in oxidative stress. And a significant decrease in Mfn1 gene expression indicates a decrease in cell strength to maintain mitochondria and the integration process, which can act as a complementary defense process in the cell. In this study, mitochondrial fusion proteins tended to increase statistically insignificantly, possibly due to the increase in oxidative stress caused by consuming oil heated several times in liver tissue. However, direct comparisons between the effects of reheated oil consumption and mitochondrial dysfunction and the effect of aerobic exercise and octopamine on the expression of variables in the present study in the liver are difficult due to the lack of access to similar studies. Studies have shown that octopamine, with properties similar to epinephrine, can selectively and strongly bind to β3 adrenoceptors and increase lipolysis and fat metabolism in general. Fat loss is associated with a decrease in oxidative stress and subsequent increase in Mfn1 gene expression. Aerobic exercise can also increase Mfn1 gene expression by stimulating epinephrine, increasing β3 adrenoceptor gene expression, increasing fat catabolism, and reducing fat-induced oxidative stress, all of which interact physiologically to increase Mfn1 gene expression. Therefore, the use of aerobic exercise and octopamine as a stimulant to reduce fat and subsequently reduce ROS and maintain mitochondrial activity and homeostasis. In addition, since the transcriptional regulation of mitochondrial dynamics correlates with exercise intensity, there is likely to happen a positive interaction between consumption of repeated heated oil and effects of exercise intensity and even exercise duration that significantly increase Drp-1 gene expression compared to the DFO group. However, it seems that more studies are needed.