Comparison the Effect of Eight-Week of Resistance and Combined Training on Pro-Opiomelanocortin Gene Expression in Brain Tissue and Insulin Resistance of Obese Wistar Rats

Background and purpose: Studies have shown that exercise improves glucose uptake by acutely increasing insulin sensitivity. Additionally, acute exercise or adaptation to exercise training activates pro-opiomelanocortin (POMC) neurons, which affect glucose metabolism. Therefore, the aim of this study was to compare the effects of eight weeks of resistance training and combined training on pro-opiomelanocortin gene expression in brain tissue and insulin resistance in obese Wistar rats. Materials and methods: In this experimental study, 30 male rats with an average weight of 175–195 grams were fed a high-fat diet for 12 weeks. After confirming obesity (weight over 300 grams), the rats were divided into three groups: control (10 rats), combined training (10 rats), and resistance training (10 rats). The rats continued the high-fat diet until the end of the training intervention. Resistance training consisted of climbing a one-meter ladder with an 85° incline and a 2 cm distance between steps. This resistance training protocol was performed for 8 weeks, 5 days a week, at an intensity of 40–60% of maximum load, with each session involving 15 ascents and a one-minute recovery between ascents. Combined training included both aerobic and resistance exercises; rats in the combined training group performed aerobic exercises on alternate days and resistance exercises on the other days. Aerobic exercises consisted of 60-minute sessions at 40–60% of maximum running speed on a treadmill with no incline. Insulin resistance was calculated using the formula: blood glucose (mg/dl) × fasting plasma insulin (IU mg/L in fasting state) / 405. To evaluate gene expression changes, 20–40 mg of brain tissue was used. After cDNA synthesis from extracted RNA, a Real-Time PCR reaction with a volume of 20 µl was performed for each sample, followed by thermocycling to complete the reaction, and the comparative ∆∆Ct method was used for quantification. Results: The results of this study demonstrated a significant decrease in the body weight of rats following eight weeks of resistance and combined training (P<0.05). Furthermore, both resistance and combined training led to a significant reduction in insulin resistance in obese rats (P<0.05). Tukey’s HSD post hoc test showed a significant increase in POMC gene expression in the combined training group (P<0.05) and an increase in the resistance training group, though this was not statistically significant (P>0.05). Conclusion: Overall, the combined training intervention led to an increase in POMC gene expression in the brain tissue of obese rats. This increase in POMC gene expression was associated with a reduction in insulin resistance following the intervention. These findings suggest that combined training may be a practical strategy for improving genetic adaptations in brain tissue and reducing insulin resistance.