Jansen Fernandes

SPATIAL MEMORY IS IMPROVED BY AEROBIC AND RESISTANCE EXERCISE THROUGH DIVERGENT MOLECULAR MECHANISMS

A growing body of scientific evidence indicates that exercise has a positive impact on human health, including neurological health. Aerobic exercise, which is supposed to enhance cardiovascular functions and metabolism, also induces neurotrophic factors that affect hippocampal neurons, thereby improving spatial learning and memory. Alternatively, little is known about the effect of resistance exercise on hippocampus-dependent memory, although this type of exercise is increasingly recommended to improve muscle strength and bone density and to prevent age-related disabilities. Therefore, we evaluated the effects of resistance training on spatial memory and the signaling pathways of brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF-1), comparing these effects with those of aerobic exercise. Adult male Wistar rats underwent 8 weeks of aerobic training on a treadmill (AERO group) or resistance training on a vertical ladder (RES group). Control and sham groups were also included. After the training period, both AERO and RES groups showed improved learning and spatial memory in a similar manner. However, both groups presented distinct signaling pathways. Although the AERO group showed increased level of IGF-1, BDNF, TrkB, and β-CaMKII (calcium/calmodulin-dependent kinase II) in the hippocampus, the RES group showed an induction of peripheral and hippocampal IGF-1 with concomitant activation of receptor for IGF-1 (IGF-1R) and AKT in the hippocampus. These distinct pathways culminated in an increase of synapsin 1 and synaptophysin expression in both groups. These findings demonstrated that both aerobic and resistance exercise can employ divergent molecular mechanisms but achieve similar results on learning and spatial memory.

The beneficial effects of strength exercise on hippocampal cell proliferation and apoptotic signaling is impaired by anabolic androgenic steroids

Previous studies have shown that strength exercise improves memory and increases expression of a myriad of proteins involved on neuronal survival and synaptic plasticity in the hippocampus. Conversely, chronic exposure to supraphysiological levels of anabolic androgenic steroids (AAS) can induce psychiatric abnormalities, cognitive deficits, impair neurotransmission, alter the levels of neurotrophic factors, decrease cell proliferation and neurogenesis, and enhance neuronal cell death. In the present study, we investigated the effects of the AAS nandrolone decanoate (ND) administration during a strength exercise program on cell proliferation, apoptotic status and brain-derived neurotrophic factor (BDNF) expression in the rat hippocampus. Adult male Wistar rats were subjected to 4 weeks of progressive strength exercise in a vertical ladder apparatus with or without daily doses (5.0 mg/kg, SC) of ND. Immunohistochemistry analysis revealed that strength exercise increased significantly the number of Ki-67-positive cells (a cell proliferation marker) in dentate gyrus (DG) of hippocampus. However, this effect was abrogated when strength exercise was combined with ND. Although western blot analysis of whole hippocampus showed no significant differences in Bax and Bcl-2 protein expression among groups, the immunoreactivity of the pro-apoptotic protein Bax was significantly increased in DG, CA1 and CA3 hippocampal subfields of sedentary rats treated with ND. Moreover, the increase in the immunoreactivity of anti-apoptotic protein Bcl-2 (DG and CA3) induced by strength exercise was diminished by ND. There were no significant differences in BDNF expression among experimental groups. Therefore, the present findings suggest that the beneficial effects of strength exercise on hippocampal cell proliferation and apoptotic signaling are impaired by ND.

Differential effects of exercise intensities in hippocampal BDNF, inflammatory cytokines and cell proliferation in rats during the postnatal brain development

It has been established that low intensities of exercise produce beneficial effects for the brain, while high intensities can cause some neuronal damage (e.g. exacerbated inflammatory response and cell death). Although these effects are documented in the mature brain, the influence of exercise intensities in the developing brain has been poorly explored. To investigate the impact of exercise intensity in developing rats, we evaluated the hippocampal level of brain derived neurotrophic factor (BDNF), inflammatory cytokines (TNFα, IL6 and IL10) and the occurrence of hippocampal cell degeneration and proliferation at different stages of postnatal brain development of rats submitted to two physical exercise intensities. To this point, male rats were divided into different age groups: P21, P31, P41 and P51. Each age group was submitted to two exercise intensities (low and high) on a treadmill over 10 consecutive days, except the control rats. We verified that the density of proliferating cells was significantly higher in the dentate gyrus of rats submitted to low-intensity exercise from P21 to P30 compared with high-intensity exercise and control rats. A significant increase of proliferative cell density was found in rats submitted to high-intensity exercise from P31 to P40 when compared to low-intensity exercise and control rats. Elevated hippocampal levels of IL6 were detected in rats submitted to high-intensity exercise from P21 to P30 compared to control rats. From P41 to P50 period, higher levels of BDNF, TNFα and IL10 were found in the hippocampal formation of rats submitted to high-intensity exercise in relation to their control rats. Our data show that exercise-induced neuroplastic effects on BDNF levels and cellular proliferation in the hippocampal region are dependent on exercise intensity and developmental period. Thus, exercise intensity is an inflammation-inducing factor and exercise-induced inflammatory response during the postnatal brain development is also related to developmental stage. Our findings indicate that neuroplastic changes induced by exercise in developing rats depend on both age and training intensity.

A strength exercise program in rats with epilepsy is protective against seizures

The beneficial effects of physical exercise on epilepsy, such as a decreased seizure frequency, have been observed following aerobic exercise programs in both clinical and experimental studies. However, it is not well clarified whether other types of exercise, including strength exercise, can provide similar benefits for epilepsy. Forty four animals with epilepsy were continuously monitored 24 h a day for 60 days and divided into two periods of 30 days. The first period was used to determine the number of seizures before beginning the physical exercise program, and the second period was utilized to determine the number of seizures during the strength training. The mean frequency of seizures in the control and SHAM groups increased significantly from period 1 to period 2. Although the frequency of seizures did not change significantly between the two periods of 30 days of observation in the strength exercise group, a significant reduction in the seizure frequency was observed compared with the control and SHAM groups in period 2. Our study demonstrated that a strength exercise program exerted a significant influence on the seizure frequency in animals with epilepsy and strengthens the observed beneficial effect of exercise on epilepsy that has been demonstrated in animal studies. The finding of this nonclinical study can open a new window to verify the beneficial contribution of strength exercise in epilepsy. Further experimental and clinical investigations are necessary to explore the extent to which strength exercise interferes with the epileptic condition.

Maternal Exercise during Pregnancy Increases BDNF Levels and Cell Numbers in the Hippocampal Formation but Not in the Cerebral Cortex of Adult Rat Offspring

Clinical evidence has shown that physical exercise during pregnancy may alter brain development and improve cognitive function of offspring. However, the mechanisms through which maternal exercise might promote such effects are not well understood. The present study examined levels of brain-derived neurotrophic factor (BDNF) and absolute cell numbers in the hippocampal formation and cerebral cortex of rat pups born from mothers exercised during pregnancy. Additionally, we evaluated the cognitive abilities of adult offspring in different behavioral paradigms (exploratory activity and habituation in open field tests, spatial memory in a water maze test, and aversive memory in a step-down inhibitory avoidance task). Results showed that maternal exercise during pregnancy increased BDNF levels and absolute numbers of neuronal and non-neuronal cells in the hippocampal formation of offspring. No differences in BDNF levels or cell numbers were detected in the cerebral cortex. It was also observed that offspring from exercised mothers exhibited better cognitive performance in nonassociative (habituation) and associative (spatial learning) mnemonic tasks than did offspring from sedentary mothers. Our findings indicate that maternal exercise during pregnancy enhances offspring cognitive function (habituation behavior and spatial learning) and increases BDNF levels and cell numbers in the hippocampal formation of offspring.

Aerobic exercise attenuates inhibitory avoidance memory deficit induced by paradoxical sleep deprivation in rats

The deleterious effects of paradoxical sleep deprivation (SD) on memory processes are well documented. Physical exercise improves many aspects of brain functions and induces neuroprotection. In the present study, we investigated the influence of 4 weeks of treadmill aerobic exercise on both long-term memory and the expression of synaptic proteins (GAP-43, synapsin I, synaptophysin, and PSD-95) in normal and sleep-deprived rats. Adult Wistar rats were subjected to 4 weeks of treadmill exercise training for 35 min, five times per week. Twenty-four hours after the last exercise session, the rats were sleep-deprived for 96 h using the modified multiple platform method. To assess memory after SD, all animals underwent training for the inhibitory avoidance task and were tested 24h later. The aerobic exercise attenuated the long-term memory deficit induced by 96 h of paradoxical SD. Western blot analysis of the hippocampus revealed increased levels of GAP-43 in exercised rats. However, the expression of synapsin I, synaptophysin, and PSD-95 was not modified by either exercise or SD. Our results suggest that an aerobic exercise program can attenuate the deleterious effects of SD on long-term memory and that this effect is not directly related to changes in the expression of the pre- and post-synaptic proteins analyzed in the study.

A single bout of resistance exercise improves memory consolidation and increases the expression of synaptic proteins in the hippocampus

Over the past decade, several studies have indicated that chronic resistance exercise (i.e., strength training, weight lifting, etc.) is beneficial for brain health and cognitive function. However, little is known about the effects of a single bout of resistance exercise on brain function, particularly on memory consolidation. Therefore, the purpose of the present study is to examine the effects of a single bout of resistance exercise applied immediately after the training of fear conditioning on memory consolidation and on the expression of IGF‐1 and synaptic proteins in the hippocampus. Male Wistar rats were familiarized with climbing a ladder without a load for 3 days and randomly assigned into control (CTL) and resistance exercise (RES) groups. The RES group was subjected to a single bout of resistance exercise applied immediately after fear conditioning training. Subsequently, the animals were tested for contextual (24 h) and tone (48 h) fear memory. Another group of animals were subjected to a single bout of resistance exercise and euthanized 24 h later for hippocampal analysis of IGF‐1 and synaptic proteins (synapsin I, synaptophysin, and PSD‐95). The exercised rats improved contextual but not tone fear memory. Hippocampal IGF‐1 was not altered by resistance exercise. However, the levels of synapsin I, synaptophysin, and PSD‐95 increased significantly in the RES group. The results suggested that a single bout of resistance exercise applied immediately after fear conditioning could improve contextual memory, probably through the activation of pre‐ and postsynaptic machinery required for memory consolidation.

Animal model for progressive resistance exercise: a detailed description of model and its implications for basic research in exercise

The Several animal models have been proposed for resistance training. In addition, the results of these studies have been highly variable. Some of the studies have used negative reinforcement, electric shock or food deprivation to motivate the learning of the task. Features such as conditioning through electric shock may undermine the significance of the results or even prevent the model from being successfully executed. Due to these reasons, in this study we propose to use an adaptation of the vertical ladder climbing model for progressive resistance training in rats, albeit with a unique feature to ensure the homogeneity of the study groups: a period of adaptation to the apparatus without any negative reinforcement followed by a subsequent pairing of animals based on their ability to learn. The animals were distributed in the experimental group who were subjected to 8 weeks of a progressive resistance exercise protocol and the control group. After 8wks, the gastrocnemius, soleus, flexor digitorum longus (FDL), and plantaris muscles were removed and the cross-sectional area morphometry was obtened. The animals from experimental group showed hypertrophy [F(4, 15)=17,404, P < 0.001] for gastrocnemius [60% of hipertrophy; Control (2628,64 ± 348,50) versus Experimental (4207,77 ± 1256,52); ES=1.96; Power=0,86]; FDL [35% of hipertrophy; Control (2753,80 ± 359,54) versus Experimental (3711,84 ± 279,45); ES=2.99; Power=0.99] and plantaris [38% of hipertrophy; Control (2730,44 ± 320,56) versus Experimental (3767,30 ± 625,80); ES=2.19; Power=0.92], without modifications for soleus. All animals successfully completed the 8-week progressive resistance training program without any injuries, abandonment or death. Negative reinforcements such as electric shock were not required at any time in the experiment. In conclusion, we showed an adaptation of the previus model for progressive resistance training in rats. A period of adaptation to the apparatus without any negative reinforcement followed by a subsequent pairing of animals based on their ability to learn may be a alternative strategy for the original protocol. We also observed hypertrophy (gastrocnemius, FDL, and plantaris) showed the vality of this procolos for resistance exercise issues. The results of this study may be useful in basic/ applied neuroscience research and resistance exercise.

Resistance Exercise Reduces Seizure Occurrence, Attenuates Memory Deficits and Restores BDNF Signaling in Rats with Chronic Epilepsy

Epilepsy is a disease characterized by recurrent, unprovoked seizures. Cognitive impairment is an important comorbidity of chronic epilepsy. Human and animal model studies of epilepsy have shown that aerobic exercise induces beneficial structural and functional changes and reduces the number of seizures. However, little is yet understood about the effects of resistance exercise on epilepsy. We evaluated the effects of a resistance exercise program on the number of seizures, long-term memory and expression/activation of signaling proteins in rats with epilepsy. The number of seizures was quantified by video-monitoring and long-term memory was assessed by an inhibitory avoidance test. Using western blotting, multiplex and enzyme-linked immunosorbent assays, we determined the effects of a 4-week resistance exercise program on IGF-1 and BDNF levels and ERK, CREB, mTOR activation in the hippocampus of rats with epilepsy. Rats with epilepsy submitted to resistance exercise showed a decrease in the number of seizures compared to non-exercised epileptic rats. Memory deficits were attenuated by resistance exercise. Rats with epilepsy showed an increase in IGF-1 levels which were restored to control levels by resistance exercise. BDNF levels and ERK and mTOR activation were decreased in rats with epilepsy and resistance exercise restored these to control levels. In conclusion, resistance exercise reduced seizure occurrence and mitigated memory deficits in rats with epilepsy. These resistance exercise-induced beneficial effects can be related to changes in IGF-1 and BDNF levels and its signaling protein activation. Our findings indicate that the resistance exercise might be included as complementary therapeutic strategy for epilepsy treatment.

Aerobic exercise reduces hippocampal ERK and p38 activation and improves memory of middle-aged rats

Aging is often accompanied by cognitive decline, memory impairment, and an increased susceptibility to neurodegenerative disorders. Although the physiological processes of aging are not fully understood, these age‐related changes have been interpreted by means of various cellular and molecular theories. Among these theories, alterations in the intracellular signaling pathways associated with cell growth, proliferation, and survival have been highlighted. Based on these observations and on recent evidence showing the beneficial effects of exercise on cognitive function in the elderly, we investigated the cell signaling pathways in the hippocampal formation of middle‐aged rats (18 months old) submitted to treadmill exercise over 10 days. To do this, we evaluated the hippocampal activation of intracellular signaling proteins linked to cell growth, proliferation, and survival, such as Akt, mTOR, p70S6K, ERK, CREB, and p38. We also explored the cognitive performance (inhibitory avoidance) of middle‐aged rats. It was found that physical exercise reduces ERK and p38 activation in the hippocampal formation of aged rats, when compared to the control group. The hippocampal activation and expression of Akt, mTOR, p70S6K, and CREB were not statistically different between the groups. It was also observed that aged rats from the exercise group exhibited better cognitive performance in the inhibitory avoidance task (aversive memory) than aged rats from the control group. Our results indicate that physical exercise reduces intracellular signaling pathways linked to inflammation and cell death (i.e., ERK and p38) and improves memory in middle‐aged rats.