Background and Objective: Exercise training and limb limb ischemia cycles have been shown to exert cardioprotective effects against myocardial injury. However, the role of the volume of muscle mass subjected to ischemia, as well as the potential additive effects of limb ischemic conditioning combined with exercise training, in mediating cardioprotection remains unclear. Therefore, this study aimed to evaluate the effects of aerobic exercise training and limb ischemia involving varying muscle mass volumes on the gene expressions of JNK and GSK3β in the heart tissue of a rat model of myocardial infarction.

Materials and Methods: In this experimental research, 35 wistar rats were randomly divided into seven groups (n=5 per group): control (C), MI, MI single-limb ischemia (SI), MI dual-limb ischemia (DI), MI aerobic training (T), MI single-limb ischemia+ training (SIT) and MI dual-limb ischemia+ training (DIT). MI was induced via injections of isoproterenol at a dose of 100 mg/kg/day on two consecutive days. Limb ischemic cycles were applied by positioning a tourniquet on the upper thigh of one hindlimb (low muscle mass) or both hindlimbs (high muscle mass), consisting of three cycles of 5-minute ischemia followed by 5-minute reperfusion. Aerobic exercise commenced 20 minutes after the final ischemia cycle. The aerobic exercise protocol was conducted for eight-week, five days per week, using a rodent-specific treadmill. During weeks 1 and 2, the rats ran for 15 minutes at a speed of 10 m/min; during weeks 3 and 4, for 20 minutes at 15 m/min; during weeks 5 and 6, for 25 minutes at 20 m/min; and during weeks 7 and 8, for 30 minutes at a speed of 25 m/min. The JNK and GSK3β gene expression was measured by RT-PCR method. Data were analyzed by one-way analysis of variance and Bonferroni post hoc tests.

Results: JNK and GSK3β expression significantly increased in MI compared to C (p=0.0001). JNK and GSK3β significantly decreased in SI (p=0.0001, p=0.0001), DI (p=0.0001, p=0.0001), T (p=0.0001, p=0.006), SIT (p=0.0001), and DIT (p=0.0001) compared to the C. Single-limb ischemia+ training and dual-limb ischemia ischemia+ training resulted in significant decrease JNK and GSK3β compared SI (P=0.0001), DI (P=0.0001) and T (P=0.0001).

Conclusion: Aerobic exercise and limb ischemia cycles appear to attenuate cardiac JNK and GSK-3β expression in a rat model of myocardial infarction, which may represent a shared cellular mechanism contributing to the cardioprotective effects of both interventions. Furthermore, single-limb and bilateral limb ischemic conditioning exerted comparable effects in reducing cardiac JNK and GSK-3β levels.