Swimming Prevents Memory Impairment by Increasing the Antioxidant Defense in an Animal Model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a genetic disease which is associated to a progressive skeletical muscle degeneration. Swimming is usually indicated for avoiding impact and facilitating adherence because of a better adaptation to a warm water invironment and also for its benefits on cognition, and modulating memory and learning processes and for increasing antioxidant defenses in oxidative stress. The objective of this study was to evaluate the effects of a swimming protocol on memory and oxidative stress in an animal model of Duchenne muscular dystrophy. Methods: male mdx and wild type mice within 28 days were used in this study. The animals were trained in an stepped swimming protocol for four consecutive weeks. Twenty four hours after the last exercise day, aversive memory and habituation memory tests were performed and removed the encephalic structures of striatus, pre frontal cortex, hippocampus, and cortex and gastrocnemius and diafragma muscles to evaluate protein carbonilation and lipid peroxidation and free thiols. Results: it was verified that swimming was able to reduce significantly the levels of lipid peroxidation and protein carbonilation in gastrocnemius and hippocampus and striatus in exercised animals. Swimming has also prevented lipid peroxidation in diafragma. Besides, this swimming protocol was able to increase free thiols in gastrocnemius, diafragma and in analysed SNC structures. These results showed that swimming prevented aversive and habituation memory in mdx mice.


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Duchenne muscular dystrophy (DMD) is one of the recessive X-linked PMS and 39 mainly affects males. DMD usually presents in early childhood, characterized by delays 40 in motor milestones. DMD leads to weakening of the skeletal muscles and is known to be 41 the most common and severe type, due to its early onset and the rapid evolving of 42 symptoms [1][2][3]. 43 Treatment of patients diagnosed with Duchenne muscular dystrophy (DMD) needs 44 to be multidisciplinary, careful, and always focused on the well-being of the patient. 45 Given this, the role of physical therapy becomes crucial to the success of treatment, as it 46 has achieved good results in the short term, such as maintenance of the autonomy of these 47 individuals [4,5]. Another method that has been used to treat DMD is physical exercise 48 [6,7]. Studies have been using physical exercise to decrease muscle deterioration, muscle 49 contractures, bone fractures, and increase the time of functional independence, in 50 individuals with DMD [8,9]. 51 Swimming is one of the aerobic exercise modalities that has become very popular. 52 Aerobic exercise in water is a viable alternative to exercise on land, because water, 3 53 through its physical properties such as thrust, hydrostatic pressure, and viscosity, among 54 others, brings increased well-being and quality of life [10]. Swimming, like walking and 55 running, has health benefits compared to a sedentary lifestyle [11]. Swimming is 56 generally indicated because with heated water it avoids impact and facilitates adherence 57 by better adaptation to the environment [11]. Swimming is further described in the 58 literature as having beneficial effects on patients: on cognition by modulating memory 59 and learning processes; and in oxidative stress, by increasing antioxidant defenses [11].  were submitted to the swimming type aerobic exercise protocol for four weeks. Twenty 78 four hours after the last day of training, aversive memory and habituation tests were 79 performed. Afterward, the animals were sedated and submitted to assisted painless death 80 procedure and the following structures were removed: gastrocnemius; quadriceps; 81 diaphragm; prefrontal cortex; cerebellum; hippocampus; striatum; and cerebral cortex, 82 for determination of lipid peroxidation, protein carbonylation, and thiol grouping.  Exercise intensity was determined in the fourth week of protocol in WT and mdx 95 animals. Blood samples were collected before the test and at the 10 th and 30 th minutes of 96 exercise for subsequent analysis of lactate concentration. The criterion for considering 97 intensity was the increase in concentration of no more than 1 mmol / L between the 10 th 98 and 30 th minute of physical exercise. Hygienization of the blood collection site was 99 performed with alcohol (70%). After this procedure, the distal portion of the tail of the 100 animal was slightly sectioned with surgical scissors and 25 μl and a drop of blood was 101 inserted in the lactate collection tape, and then, by means of a portable lactimeter, the 5 102 blood level was measured. Before each test, the equipment was calibrated according to 103 the manufacturer's instructions [14].  This time is called latency. Immediately after descending from the platform, the animal 111 received a 0.2 mA shock for 2 s. In the test session, the animal was again placed on the 112 platform and the time it took to descend (latency) the platform was measured, but no 113 shock was given. The test was also terminated if the animal did not descend within a     HCl) were added. It was allowed to react for 30 minutes and transferred to a 96-well plate.

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The samples were read in a 412 nm microplate reader.  in the diaphragm muscle of mdx animals ( Figure 6A). Figure 6B shows the result of the  Figures 8B and 8C show that the four-week swimming protocol was unable to 301 prevent increased protein carbonation in the hippocampus and striatum. Figure 8D shows 302 that in the cortex structure there was no significant change between the analyzed groups.

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It can be observed that the non-exercised mdx animals showed a significant

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DMD is characterized by an absence of dystrophin protein in skeletal muscle5.

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However, the literature also shows that dystrophin is absent in brain tissue, and this