Voluntary exercise does not enhance long-term potentiation in the adolescent female dentate gyrus

Circuit Training Improves the Levels of β-Amyloid and Brain-Derived Neurotrophic Factor Related to Cognitive Impairment Risk Factors in Obese Elderly Korean Women

Background: The purpose of this study was to investigate the effect of circuit training on β-amyloid, BDNF, and cognitive function in untrained obese elderly Korean women. Methods: The subjects for the study were aged 65-70 years and were each assigned to a circuit training group (EG, n = 12) or a control group (CG, n = 11). The 60 min combined exercise was performed 3 times per week for 16 weeks. The exercise intensity was progressively increased from a 40% heart rate reserve to a 70% heart rate reserve. The test data were analyzed using a paired t-test, an independent t-test, and a two-way repeated measures ANOVA, and an alpha level of 0.05 was set for all tests of significance. Results: Group-by-time interaction effects were observed for β-amyloid (p < 0.05), brain-derived neurotrophic factor (p < 0.01), and cognitive function (p < 0.05). Within the exercise group, significant differences were found in β-amyloid (p < 0.05), brain-derived neurotrophic factor (p < 0.001), and cognitive function (p < 0.05) when comparing across different time points. Additionally, there were statistically significant differences between groups in post-exercise β-amyloid (p < 0.05), change in β-amyloid (p < 0.05), brain-derived neurotrophic factor (p < 0.01), and cognitive function (p < 0.05). Conclusions: Therefore, it is suggested that the circuit training used in this study could be an effective exercise method for improving the risk factors of cognitive impairment in obese elderly Korean women.

Early-life exercise primes the murine neural epigenome to facilitate gene expression and hippocampal memory consolidation

Aerobic exercise is well known to promote neuroplasticity and hippocampal memory. In the developing brain, early-life exercise (ELE) can lead to persistent improvements in hippocampal function, yet molecular mechanisms underlying this phenomenon have not been fully explored. In this study, transgenic mice harboring the "NuTRAP" (Nuclear tagging and Translating Ribosome Affinity Purification) cassette in Emx1 expressing neurons ("Emx1-NuTRAP" mice) undergo ELE during adolescence. We then simultaneously isolate and sequence translating mRNA and nuclear chromatin from single hippocampal homogenates containing Emx1-expressing neurons. This approach allowed us to couple translatomic with epigenomic sequencing data to evaluate the influence of histone modifications H4K8ac and H3K27me3 on translating mRNA after ELE. A subset of ELE mice underwent a hippocampal learning task to determine the gene expression and epigenetic underpinnings of ELE's contribution to improved hippocampal memory performance. From this experiment, we discover gene expression - histone modification relationships that may play a critical role in facilitated memory after ELE. Our data reveal candidate gene-histone modification interactions and implicate gene regulatory pathways involved in ELE's impact on hippocampal memory.

Temporal endurance of exercise-induced benefits on hippocampus-dependent memory and synaptic plasticity in female mice

Exercise facilitates hippocampal neurogenesis and neuroplasticity that in turn, promotes cognitive function. Our previous studies have demonstrated that in male mice, voluntary exercise enables hippocampus-dependent learning in conditions that are normally subthreshold for long-term memory formation in sedentary animals. Such cognitive enhancement can be maintained long after exercise has ceased and can be re-engaged by a subsequent subthreshold exercise session, suggesting exercise-induced benefits are temporally dynamic. In females, the extent to which the benefits of exercise can be maintained and the mechanisms underlying this maintenance have yet to be defined. Here, we examined the exercise parameters required to initiate and maintain the benefits of exercise in female C57BL/6J mice. Using a subthreshold version of the hippocampus-dependent task called object-location memory (OLM) task, we show that 14d of voluntary exercise enables learning under subthreshold acquisition conditions in female mice. Following the initial exercise, a 7d sedentary delay results in diminished performance, which can be re-facilitated when animals receive 2d of reactivating exercise following the sedentary delay. Assessment of estrous cycle reveals enhanced wheel running activity during the estrus phase relative to the diestrus phase, whereas estrous phase on training or test had no effect on OLM performance. Utilizing the same exercise parameters, we demonstrate that 14d of exercise enhances long-term potentiation (LTP) in the CA1 region of the hippocampus, an effect that persists throughout the sedentary delay and following the reactivating exercise session. Previous studies have proposed exercise-induced BDNF upregulation as the mechanism underlying exercise-mediated benefits on synaptic plasticity and cognition. However, our assessment of hippocampal Bdnf mRNA expression following memory retrieval reveals no difference between exercise conditions and control, suggesting that persistent Bdnf upregulation may not be required for maintenance of exercise-induced benefits. Together, our data indicate that 14d of voluntary exercise can initiate long-lasting benefits on neuroplasticity and cognitive function in female mice, establishing the first evidence on the temporal endurance of exercise-induced benefits in females.

Pregnancy swimming prevents early brain mitochondrial dysfunction and causes sex-related long-term neuroprotection following neonatal hypoxia-ischemia in rats

Neonatal hypoxia-ischemia (HI) is a major cause of cognitive impairments in infants. Antenatal strategies improving the intrauterine environment can have high impact decreasing pregnancy-derived intercurrences. Physical exercise alters the mother-fetus unity and has been shown to prevent the energetic challenge imposed by HI. This study aimed to reveal neuroprotective mechanisms afforded by pregnancy swimming on early metabolic failure and late cognitive damage, considering animals' sex as a variable. Pregnant Wistar rats were submitted to daily swimming exercise (20' in a tank filled with 32 °C water) during pregnancy. Neonatal HI was performed in male and female pups at postnatal day 7. Electron chain transport, mitochondrial mass and function and ROS formation were assessed in the right brain hemisphere 24 h after HI. From PND45, reference and working spatial memory were tested in the Morris water maze. MicroPET-FDG images were acquired 24 h after injury (PND8) and at PND60, following behavioral analysis. HI induced early energetic failure, decreased enzymatic activity in electron transport chain, increased production of ROS in cortex and hippocampus as well as caused brain glucose metabolism dysfunction and late cognitive impairments. Maternal swimming was able to prevent mitochondrial dysfunction and to improve spatial memory. The intergenerational effects of swimming were sex-specific, since male rats were benefited most. In conclusion, maternal swimming was able to affect the mitochondrial response to HI in the offspring's brains, preserving its function and preventing cognitive damage in a sex-dependent manner, adding relevant information on maternal exercise neuroprotection and highlighting the importance of mitochondria as a therapeutic target for HI neuropathology.

Cognitive Impairments of Sleep-Deprived Ovariectomized (OVX) Female Rats by Voluntary Exercise

Introduction:

Previous studies demonstrated that forced and voluntary exercise had ameliorative effects on behavioral tasks followed by Sleep Deprivation (SD) in intact female rats. The main goal of this research was evaluating the impact of voluntary exercise on cognitive functions while SD and ovariectomization is induced in female wistar rats.

Methods:

The rats were anesthesized combining dosage of ketamine and xylazine. Then, both ovaries were eliminated and 3 weeks after surgery the animals entered the study. The exercise protocol took 4 weeks of voluntary exercise in a wheel which was connected to home cage. For inducing a 72 hours deprivation the multiple platforms was applied. The cognitive functions were studied by exploiting the Morris Water Maze (MWM) and Novel object recognition tests. Anxiety was evaluated by open field test and corticostrone measurement was carried out by ELISA method. One-way and two-way ANOVA and repeated measures were utilized for data analysis and P<0.05 was considered statistically significant.

Results:

We observed significant spatial and recognition learning and memory impairments in OVX sleep-deprived rats compared to the control group and voluntary exercise alleviated the SD-induced learning and memory defects.

Conclusion:

We concluded that voluntary exercise can improve cognitive impairments followed by SD in OVX female rats.

Sexual dimorphism of physical activity on cognitive aging: Role of immune functioning

OBJECTIVE

Exercise is one of the most potent strategies available to support cognitive health with age, yet substantial variability exists. Sexual dimorphism is evident for brain and immune functioning, the latter being implicated as important pathway for exercise. We examined the moderating role of sex on the relationship between physical activity and systemic inflammatory and brain health outcomes in support of more personalized approaches to behavioral interventions.

METHODS

Our discovery cohort included 45 typically aging women matched on age (±5y) and education (±2y) to 45 men (mean age = 72.5; Clinical Dementia Rating = 0) who completed self-reported current physical activity (Physical Activity Scale for Elderly), blood draw, neuropsychological evaluation, and brain MRI. An independent sample of 45 typically aging women and 36 men who completed the same measures comprised a replication cohort. Plasma was analyzed for 11 proinflammatory cytokine and chemokine markers via MesoScale Discovery.

RESULTS

Discovery cohort: Reported physical activity did not differ between sexes (150 vs. 157, p = 0.72). There was a significant interaction between sex and physical activity on chemokine markers MDC, MIP-1b, MCP-4, and eotaxin-3 (ps < 0.03), with a similar trend for MCP-1 and INFγ (ps < 0.09). Men who reported greater activity demonstrated lower inflammatory markers, an effect attenuated-to-absent in women. An interaction between sex and physical activity was also observed for parahippocampal volumes (p = 0.02) and cognition (processing speed and visual memory; ps < 0.04). Again, the beneficial effect of physical activity on outcomes was present in men, but not women. Replication cohort analyses conferred a consistent effect of sex on the relationship between physical activity and immune markers; models examining neurobehavioral outcomes did not strongly replicate. Across cohorts, post-hoc models demonstrated an interaction between sex and activity-related inflammatory markers on total gray matter volume and visual memory. Men with higher inflammatory markers demonstrated poorer brain structure and function, whereas inflammatory markers did not strongly relate to neurobehavioral outcomes in women.

CONCLUSIONS

Greater physical activity was associated with lower markers of inflammation in clinically normal older men, but not women - an effect consistently replicated across cohorts. Additionally, men appeared disproportionately vulnerable to the adverse effects of peripheral inflammatory markers on brain structure and function compared to women. Immune activation may be a male-specific pathway through which exercise confers neurobehavioral benefit.

Interplay between hormones and exercise on hippocampal plasticity across the lifespan

The hippocampus is a brain structure known to play a central role in cognitive function (namely learning and memory) as well as mood regulation and affective behaviors due in part to its ability to undergo structural and functional changes in response to intrinsic and extrinsic stimuli. While structural changes are achieved through modulation of hippocampal neurogenesis as well as alterations in dendritic morphology and spine remodeling, functional (i.e., synaptic) changes can be noted through the strengthening (i.e., long-term potentiation) or weakening (i.e., long-term depression) of the synapses. While age, hormone homeostasis, and levels of physical activity are some of the factors known to module these forms of hippocampal plasticity, the exact mechanisms through which these factors interact with each other at a given moment in time are not completely understood. It is well known that hormonal levels vary throughout the lifespan of an individual and it is also known that physical exercise can impact hormonal homeostasis. Thus, it is reasonable to speculate that hormone modulation might be one of the various mechanisms through which physical exercise differently impacts hippocampal plasticity throughout distinct periods of an individual's life. The present review summarizes the potential relationship between physical exercise and different types of hormones (namely sex, metabolic, and stress hormones) and how this relationship may mediate the effects of physical activity during three distinct life periods, adolescence, adulthood, and senescence. Overall, the vast majority of studies support a beneficial role of exercise in maintaining hippocampal hormonal levels and consequently, hippocampal plasticity, cognition, and mood regulation.

A Unique Mouse Model of Early Life Exercise Enables Hippocampal Memory and Synaptic Plasticity

Physical exercise is a powerful modulator of learning and memory. Mechanisms underlying the cognitive benefits of exercise are well documented in adult rodents. Exercise studies targeting postnatal periods of hippocampal maturation (specifically targeting periods of synaptic reorganization and plasticity) are lacking. We characterize a model of early-life exercise (ELE) in male and female mice designed with the goal of identifying critical periods by which exercise may have a lasting impact on hippocampal memory and synaptic plasticity. Mice freely accessed a running wheel during three postnatal periods: the 4^th postnatal week (juvenile ELE, P21–27), 6^th postnatal week (adolescent ELE, P35–41), or 4^th-6^th postnatal weeks (juvenile-adolescent ELE, P21–41). All exercise groups increased their running distances during ELE. When exposed to a subthreshold learning stimulus, juv ELE and juv-adol ELE formed lasting long-term memory for an object location memory task, whereas sedentary and adol ELE mice did not. Electrophysiological experiments revealed enhanced long-term potentiation in hippocampal CA1 in the juvenile-adolescent ELE group. I/O curves were also significantly modulated in all mice that underwent ELE. Our results suggest that early-life exercise, specifically during the 4^th postnatal week, can enable hippocampal memory, synaptic plasticity, and alter hippocampal excitability when occurring during postnatal periods of hippocampal maturation.

The therapeutic potential of exercise for neuropsychiatric diseases: A review

Exercise is known to have a myriad of health benefits. There is much to be learned from the effects of exercise and its potential for prevention, attenuation and treatment of multiple neuropsychiatric diseases and behavioral disorders. Furthermore, recent data and research on exercise benefits with respect to major health crises, such as, that of opioid and general substance use disorders, make it very important to better understand and review the mechanisms of exercise and how it could be utilized for effective treatments or adjunct treatments for these diseases. In addition, mechanisms, epigenetics and sex differences are examined and discussed in terms of future research implications.

Voluntary exercise modulates learning & memory and synaptic plasticity impairments in sleep deprived female rats

Previous studies have indicated that forced exercise plays a preventive role in synaptic plasticity deficits in the hippocampus and behavioral impairments in sleep-deprived male and female rats. The objective of the present study was to evaluate the effects of voluntary exercise on early long-term potentiation (E-LTP) at the Cornu Ammonis (CA1) area of the hippocampus and behavioral functions by barnes maze and novel location tests in sleep-deprived female rats. Intact female Wistar rats were used in the present study. The exercise protocol was four weeks wheel running and the multiple platform method was applied to induce 72 h Sleep deprivation (SD). We examine the effect of exercise and/or SD on synaptic plasticity using in vivo extracellular recording in the CA1 area of the hippocampus. Spatial learning and memory examined by Barnes maze and recognition memory assessed by novel location test. Field potential recording indicated that the induction and maintenance phase of E-LTP impaired in the sleep deprived animals compared to the other groups. After 72 h SD, LTP impairments were reduced by 4 weeks of voluntary exercise but do not go back to control values. SD impairs learning and memory and exercise could improve these deficits. In conclusion, the synaptic plasticity deficit in sleep-deprived female rats was improved by voluntary exercise. Further studies are suggested to evaluate the possible underlying mechanisms.

Early exercise induces long-lasting morphological changes in cortical and hippocampal neurons throughout of a sedentary period of rats

Life experiences at early ages, such as physical activity in childhood and adolescence, can result in long-lasting brain effects able to reduce future risk of brain disorders and to enhance lifelong brain functions. However, how early physical exercise promotes these effects remains unclear. A possible hypothesis is that physical exercise increases the expression of neurotrophic factors and stimulates neuronal growth, resulting in a neural reserve to be used at later ages. Basing our study on this hypothesis, we evaluated the absolute number and morphology of neuronal cells, as well as the expression of growth, proliferation and survival proteins (BDNF, Akt, mTOR, p70S6K, ERK and CREB) in the cerebral cortex and hippocampal formation throughout of a sedentary period of rats who were physically active during youth. To do this, male Wistar rats were submitted to an aerobic exercise protocol from the 21^st to the 60^th postnatal days (P21–P60), and evaluated at 0 (P60), 30 (P90) and 60 (P120) days after the last exercise session. Results showed that juvenile exercise increased, and maintained elevated, the number of cortical and hippocampal neuronal cells and dendritic arborization, when evaluated at the above post-exercise ages. Hippocampal BDNF levels and cortical mTOR expression were found to be increased at P60, but were restored to control levels at P90 and P120. Overall, these findings indicate that, despite the short-term effects on growth and survival proteins, early exercise induces long-lasting morphological changes in cortical and hippocampal neurons even during a sedentary period of rats.

Effects of Maternal Voluntary Wheel Running During Pregnancy on Adult Hippocampal Neurogenesis, Temporal Order Memory, and Depression-Like Behavior in Adult Female and Male Offspring

Research suggests that maternal exercise in pregnancy may have beneficial effects on the brain function of offspring. This study sought to determine if voluntary wheel running during pregnancy improves depression-like behavior, temporal order memory, and hippocampal neurogenesis in both female and male offspring mice. Pregnant mice were allowed to run voluntarily by introducing running wheels into the housing cages throughout the gestational period. Male and female mice offspring at the age of 8- to 9-week-old were then tested on the temporal order task and forced swim test, then euthanized for immunostaining for examining adult hippocampal cell proliferation and neuronal differentiation. Results showed that both male and female pups had reduced depression-like behavior, while only male offspring demonstrated improvement in temporal order memory. Immunostaining revealed that male offspring showed an increase in the number of immature neurons in the ventral hippocampus, whereas female offspring showed enhanced cell proliferation in the dorsal hippocampus. These findings indicate that maternal voluntary wheel running benefits both female and male offspring on reducing depression-like behavior, but with gender effect on promoting hippocampal cell proliferation, neuronal differentiation, and temporal order memory.

Effects of physical exercise and stress on hippocampal CA1 and dentate gyrus synaptic transmission and long-term potentiation in adolescent and adult Wistar rats

It is commonly recognized that physical exercise positively affects several CNS regions and improves cognitive abilities. For example, exercise is associated with an increase in neurogenesis and facilitation of long-term potentiation in the hippocampus. Conversely, animal models for depression are associated with a decrease in neurogenesis and a reduction of long-term potentiation in the hippocampus. Although exercise could be a viable option in the treatment of some forms of depression, the mechanisms responsible for such improvements have not been elucidated. In this study, we examine hippocampal function using electrophysiological field recordings in CA1 and dentate gyrus to study baseline synaptic transmission and long-term potentiation in adolescent and adult rats prenatally exposed to the glucocorticoid dexamethasone. One group of animals was allowed to run voluntarily for 10 or 21 days using an exercise wheel before the experiments, and the control group was prevented from running (i.e. the exercise wheel was locked). In adult saline-exposed animals, exercise was associated with increased long-term potentiation in the dentate gyrus. Unexpectedly, in dexamethasone-exposed animals, dentate gyrus long-term potentiation was facilitated, whereas long-term potentiation in CA1 was unaffected by prenatal dexamethasone or by 10 or 21 days of voluntary running. Irrespective of age, prenatal dexamethasone and running had limited effects on synaptic transmission and presynaptic release in CA1 and dentate gyrus. In summary, running facilitates dentate gyrus long-term potentiation in adult animals that resembles the effects of prenatal dexamethasone.

Interactive Effects of Exercise, Sex Hormones, and Transient Congenital Hypothyroidism on Long-Term Potentiation in Hippocampal Slices of Rat Offspring

Introduction:

The long-term adverse effects of transient thyroid function abnormalities at birth on intellectual development are proven. The effect of exercise increases in the presence of sex hormones. The current study aimed at investigating the possibility that a combination of sex hormones and exercise has synergistic effects on neural plasticity in Transient Congenital Hypothyroidism (TCH) rats.

Methods:

To induce hypothyroidism in the mothers, Propylthiouracil (PTU) was added to drinking water (100 mg/L) on the 6th day of gestation and continued until the 21^st Postnatal Day. From Postnatal Day (PND) 28 to 47, the female and male pups received 17β-estradiol and testosterone, respectively. The mild treadmill exercise began 30 minutes after the sex hormones or vehicle administration. On PND 48, electrophysiological experiments were performed on brain slices.

Results:

Increase of Long-Term Potentiation (LTP) was observed in sedentary-non-hormone female rats of TCH group, compared with that of the control. The exercise enhanced LTP in control rats, but the hormones showed no significant effect. The effect of exercise and sex hormone was not significant in the TCH group. The combination of exercise and testosterone enhanced LTP in TCH male rats, while the combination of exercise and estradiol or each of them individually did not produce such an effect on LTP in TCH female rats.

Conclusion:

The study findings showed an increase in excitatory transmission despite the returning of thyroid hormone levels to normal range in TCH female rats. Also a combination treatment including exercise and testosterone enhanced LTP in male rats of TCH group, which was a gender-specific event.

Aerobic Exercise: Evidence for a Direct Brain Effect to Slow Parkinson Disease Progression

No medications are proven to slow the progression of Parkinson disease (PD). Of special concern with longer-standing PD is cognitive decline, as well as motor symptoms unresponsive to dopamine replacement therapy. Not fully recognized is the substantial accumulating evidence that long-term aerobic exercise may attenuate PD progression. Randomized controlled trial proof will not be forthcoming due to many complicating methodological factors. However, extensive and diverse avenues of scientific investigation converge to argue that aerobic exercise and cardiovascular fitness directly influence cerebral mechanisms mediating PD progression. To objectively assess the evidence for a PD exercise benefit, a comprehensive PubMed literature search was conducted, with an unbiased focus on exercise influences on parkinsonism, cognition, brain structure, and brain function. This aggregate literature provides a compelling argument for regular aerobic-type exercise and cardiovascular fitness attenuating PD progression.

The Long Run: Neuroprotective Effects of Physical Exercise on Adult Neurogenesis from Youth to Old Age

BACKGROUND

The rapid lengthening of life expectancy has raised the problem of providing social programs to counteract the age-related cognitive decline in a growing number of older people. Physical activity stands among the most promising interventions aimed at brain wellbeing, because of its effective neuroprotective action and low social cost. The purpose of this review is to describe the neuroprotective role exerted by physical activity in different life stages. In particular, we focus on adult neurogenesis, a process which has proved being highly responsive to physical exercise and may represent a major factor of brain health over the lifespan.

METHODS

The most recent literature related to the subject has been reviewed. The text has been divided into three main sections, addressing the effects of physical exercise during childhood/ adolescence, adulthood and aging, respectively. For each one, the most relevant studies, carried out on both human participants and rodent models, have been described.

RESULTS

The data reviewed converge in indicating that physical activity exerts a positive effect on brain functioning throughout the lifespan. However, uncertainty remains about the magnitude of the effect and its biological underpinnings. Cellular and synaptic plasticity provided by adult neurogenesis are highly probable mediators, but the mechanism for their action has yet to be conclusively established.

CONCLUSION

Despite alternative mechanisms of action are currently debated, age-appropriate physical activity programs may constitute a large-scale, relatively inexpensive and powerful approach to dampen the individual and social impact of age-related cognitive decline.

Sex differences in aerobic exercise efficacy to improve cognition: A systematic review and meta-analysis of studies in older rodents

Research in humans indicates that women may show greater cognitive benefits from aerobic training (AT) than men. To determine whether this sex difference extends to rodents, we conducted a systematic review and meta-analysis of studies in healthy, older rodents. Results indicate that compared to controls, AT improved hippocampus-dependent and -independent learning and memory. A sex difference was found with males showing larger benefits from AT on conditioned-avoidance and non-spatial memory tasks. AT also increased brain-derived neurotrophic factor compared to controls, with larger effects in females. As an exploratory analysis, sex differences in voluntary AT were examined separately from forced AT. Voluntary AT enhanced non-spatial memory to a greater extent in males. Forced AT enhanced hippocampus-dependent learning and memory more so in females. These findings suggest that sex is an important factor to consider, and studies directly assessing sex differences in the ability of exercise to improve brain function are needed.

Sex-dependent and independent effects of long-term voluntary wheel running on Bdnf mRNA and protein expression

The beneficial effects of physical activity on brain health (synaptogenesis, neurogenesis, enhanced synaptic plasticity, improved learning and memory) appear to be mediated through changes in region-specific expression of neurotrophins, transcription factors, and postsynaptic receptors, though investigations of sex differences in response to long-term voluntary wheel running are limited.

PURPOSE

To examine the effect of five months of voluntary wheel running on hippocampal mRNA and protein expression of factors critical for exercise-induced structural and functional plasticity in male and female adult mice.

METHODS

At 8weeks of age, male and female C57BL/6 mice were individually housed with (PA; n=20; 10 male) or without (SED; n=20; 10 male) access to a computer monitored voluntary running wheel. At 28weeks, all mice were sacrificed and hippocampi removed. Total RNA was isolated from the hippocampus and expression of total Bdnf, Bdnf transcript IV, tPA, Pgc-1a, GluR1, NR2A, and NR2B were assessed with quantitative RT-PCR and total and mature Bdnf protein were assessed with ELISA.

RESULTS

We found significantly higher Bdnf IV mRNA expression in PA males (p=0.03) and females (p=0.03) compared to SED animals. Total Bdnf mRNA expression was significantly greater in PA males compared to SED males (p=0.01), but there was no difference in females. Similarly, we observed significantly higher mature Bdnf protein in PA males compared to SED males (p=0.04), but not in females.

CONCLUSION

These findings indicate that the impact of long-term voluntary wheel running on transcriptional and post-translational regulation of Bdnf may be sex-dependent, though the activity-dependent Bdnf IV transcript is sensitive to exercise independent of sex.

Control of the Cell Cycle in Adult Neurogenesis and its Relation with Physical Exercise

In the adult brain the neurogenesis is mainly restricted to two neurogenic regions: newly generated neurons arise at the subventricular zone (SVZ) of the lateral ventricle and at the subgranular zone of the hippocampal subregion named the dentate gyrus. The hippocampus is involved in learning and memory paradigms and the generation of new hippocampal neurons has been hypothesized to be a pivotal form of plasticity involved in the process. Moreover the dysregulation of hippocampal adult neurogenesis has been recognized and could anticipate several varieties of brain disease such as Alzheimer disease, epilepsy and depression. Over the last few decades numerous intrinsic, epigenetic and environmental factors have been revealed to deeply influence the process of adult neurogenesis, although the underlying mechanisms remain largely unknown. Growing evidence indicates that physical exercise represents one of the main extrinsic factor able to profoundly increase hippocampal adult neurogenesis, by altering neurochemistry and function of newly generated neurons. The present review surveys how neurogenesis can be modulated by cell cycle kinetics and highlights the putative role of the cell cycle length as a key component of the beneficial effect of running for hippocampal adult neurogenesis, both in physiological conditions and in the presence of defective neurogenesis.

Physical activity and brain development

Brain development is a complex process, and stimuli during this developmental period may modulate the brain's functional maturation and determine its lifelong integrity. Human and animal studies have shown that environmental stimuli such as physical activity habits seem to have a favorable influence on brain development. Research on humans has demonstrated improvement in cognitive performance in the children of women who exercised regularly throughout pregnancy and in individuals who were physically active during childhood and adolescence. Investigations using animal models have also reported that physical activity improves the cognitive function of developing rats. In this review, we will present the neurobiological mechanisms of such effects.

Treadmill exercise enhances synaptic plasticity, but does not alter β-amyloid deposition in hippocampi of aged APP/PS1 transgenic mice

Several studies reveal that the beneficial effects of exercise interventions are dependent on the progression of Alzheimer's disease (AD). We have previously shown that long-term treadmill exercise begun before the onset of β-amyloid (Aβ) pathology prevents the deficits of cognition and long-term potentiation (LTP) in amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice (8 months of age) paralleled by the reduction of soluble Aβ levels and Aβ deposition in the hippocampus. In the present study, treadmill exercise was initiated at a developed Aβ deposition stage in order to further investigate whether or not treadmill exercise in this phase can delay the progression of AD in aged APP/PS1 mice (17 months of age). Our results show that 5-month treadmill exercise ameliorates the impairment of spatial learning and memory with age paralleled by synaptic plasticity enhancement in aged APP/PS1 mice. In addition, exercise-induced enhancement of synaptic plasticity was accompanied by a significant reduction of soluble Aβ levels rather than Aβ plaque deposition. Therefore, the investigation demonstrates that long-term treadmill exercise has beneficial effects on cognition and synaptic plasticity even when the brain has developed Aβ deposition, and changes in soluble Aβ levels rather than Aβ plaque deposition may contribute to exercise-induced benefits.

Prior regular exercise reverses the decreased effects of sleep deprivation on brain-derived neurotrophic factor levels in the hippocampus of ovariectomized female rats

Previous studies indicated that brain-derived neurotrophic factor (BDNF) is the main candidate to mediate the beneficial effects of exercise on cognitive function in sleep deprived male rats. In addition, our previous findings demonstrate that female rats are more vulnerable to the deleterious effects of sleep deprivation on cognitive performance and synaptic plasticity. Therefore, the current study was designed to investigate the effects of treadmill exercise and/or sleep deprivation (SD) on the levels of BDNF mRNA and protein in the hippocampus of female rats. Intact and ovariectomized (OVX) female Wistar rats were used in the present experiment. The exercise protocol was four weeks treadmill running and sleep deprivation was accomplished using the multiple platform method. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblot analysis were used to evaluate the level of BDNF mRNA and protein in the rat hippocampus respectively. Our results showed that protein and mRNA expression of BDNF was significantly (p<0.05) decreased after 72 h SD in OVX rats in compared with other groups. Furthermore, sleep deprived OVX rats under exercise conditions had a significant (p<0.05) up-regulation of the BDNF protein and mRNA in the hippocampus. These findings suggest that regular exercise can exert a protective effect against hippocampus-related functions and impairments induced by sleep deprivation probably by inducing BDNF expression.

A cognitive rehabilitation paradigm effective in male rats lacks efficacy in female rats

Cognitive dysfunction, as a consequence of dementia, is a significant cause of morbidity lacking efficacious treatment. Females comprise at least half of this demographic but have been vastly underrepresented in preclinical studies. The current study addressed this gap by assessing the protective efficacy of physical exercise and cognitive activity on learning and memory outcomes in a rat model of vascular dementia. Forty ovariectomized Sprague-Dawley rats (∼6 months old) were exposed to either a diet high in saturated fats and refined sugars or standard laboratory chow and underwent either chronic bilateral carotid occlusion or Sham surgery. Learning and memory abilities were evaluated using standard cognitive outcomes over the ensuing 6 months, followed by histologic analyses of hippocampal CA1 neurons. In Experiment 1, we confirmed hypoperfusion-induced cognitive dysfunction using a 2 × 2 (Surgery × Diet) experimental design, without alterations in hippocampal architecture. In Experiment 2, hypoperfused animals were either exposed to alternating days of physical (wheel running) and cognitive activity (modified Hebb-Williams maze) or sedentary housing. In contrast to males, this combination rehabilitation paradigm did not improve cognition or histopathologic outcomes in hypoperfused animals. These findings, highlighting differences between female and male animals, show the necessity of including both sexes in preclinical experimentation.

Translating the impact of exercise on cognition: methodological issues in animal research

Physical exercise and fitness have been proposed as potential factors that promote healthy cognitive aging. Some of the support for this hypothesis has come from animal research. Animal studies are also used to propose the physiological mechanisms underlying the cognitive performance improvement associated with exercise. In the present review and meta-analysis, we discuss several methodological problems that limit the contribution of animal studies to the understanding of the putative effects of exercise on cognitive aging. We suggest that the most likely measure to equate exercise intensity in rodent and humans may be oxygen consumption (VO2) because observed values are surprisingly similar in young and older rodents and humans. For practical reasons, several animal studies use young rodents kept in social isolation. We show that social isolation is associated with an enhanced impact of exercise on cognitive performance but not on some physiological measures thought to mediate the effect of exercise. Surprisingly, two months or more of exercise intervention appeared to be ineffective to promote cognitive performance compared to shorter durations. We argue that impact of exercise in socially isolated animals is explained by an alleviation of environmental impoverishment as much as an effect of physical exercise. It is possible that the introduction of exercise in rodents is partly mediated by environmental changes. It may explain why larger effects are observed for the shorter durations of exercise while much smaller effects are found after longer periods of exercise.

Long-term exercise is needed to enhance synaptic plasticity in the hippocampus

Exercise can have many benefits for the body, but it also benefits the brain by increasing neurogenesis, synaptic plasticity, and performance on learning and memory tasks. The period of exercise needed to realize the structural and functional benefits for the brain have not been well delineated, and previous studies have used periods of exercise exposure that range from as little as 3 d to up to 6 mo. In this study, we systematically evaluated the effects of differential running periods (3, 7, 14, 28, and 56 d) on both structural (cell proliferation and maturation) and functional (in vivo LTP) changes in the dentate gyrus of adult male Sprague-Dawley rats. We found that voluntary access to a running wheel for both short- and long-term periods can increase cell proliferation in the adult DG; however, increases in neurogenesis required longer term exposure to exercise. Increases in immature neurons were not observed until animals had been running for a minimum of 14 d. Similarly, short-term periods of wheel running did not facilitate LTP in the DG of adult animals, and reliable increases in LTP were only observed with 56 d of running. These results provide us with a greater understanding of the time course of wheel running access needed to enhance DG function. Furthermore, the results indicate that the new neurons produced in response to exercise in rats do not contribute significantly to synaptic plasticity until they mature.

All about running: synaptic plasticity, growth factors and adult hippocampal neurogenesis

Accumulating evidence from animal and human research shows exercise benefits learning and memory, which may reduce the risk of neurodegenerative diseases, and could delay age-related cognitive decline. Exercise-induced improvements in learning and memory are correlated with enhanced adult hippocampal neurogenesis and increased activity-dependent synaptic plasticity. In this present chapter we will highlight the effects of physical activity on cognition in rodents, as well as on dentate gyrus (DG) neurogenesis, synaptic plasticity, spine density, neurotransmission and growth factors, in particular brain-derived nerve growth factor (BDNF).

Long-term consequences of developmental alcohol exposure on brain structure and function: therapeutic benefits of physical activity

Developmental alcohol exposure both early in life and during adolescence can have a devastating impact on normal brain structure and functioning, leading to behavioral and cognitive impairments that persist throughout the lifespan. This review discusses human work as well as animal models used to investigate the effect of alcohol exposure at various time points during development, as well as specific behavioral and neuroanatomical deficits caused by alcohol exposure. Further, cellular and molecular mediators contributing to these alcohol-induced changes are examined, such as neurotrophic factors and apoptotic markers. Next, this review seeks to support the use of aerobic exercise as a potential therapeutic intervention for alcohol-related impairments. To date, few interventions, behavioral or pharmacological, have been proven effective in mitigating some alcohol-related deficits. Exercise is a simple therapy that can be used across species and also across socioeconomic status. It has a profoundly positive influence on many measures of learning and neuroplasticity; in particular, those measures damaged by alcohol exposure. This review discusses current evidence that exercise may mitigate damage caused by developmental alcohol exposure and is a promising therapeutic target for future research and intervention strategies.

Brief environmental enrichment elicits metaplasticity of hippocampal synaptic potentiation in vivo

Long-term environmental enrichment (EE) elicits enduring effects on the adult brain, including altered synaptic plasticity. Synaptic plasticity may underlie memory formation and includes robust (>24 h) and weak (<2 h) forms of long-term potentiation (LTP) and long-term depression (LTD). Most studies of the effect of EE on synaptic efficacy have examined the consequences of very prolonged EE-exposure. It is unclear whether brief exposure to EE can alter synaptic plasticity. Clarifying this issue could help develop strategies to address cognitive deficits arising from neglect in children or adults. We assessed whether short-term EE elicits alterations in hippocampal synaptic plasticity and if social context may play a role. Adult mice were exposed to EE for 14 consecutive days. We found that robust late-LTP (>24 h) and short-term depression (<2 h) at Schaffer-collateral-CA1 synapses in freely behaving mice were unaltered, whereas early-LTP (E-LTP, <2 h) was significantly enhanced by EE. Effects were transient: E-LTP returned to control levels 1 week after cessation of EE. Six weeks later, animals were re-exposed to EE for 14 days. Under these conditions, E-LTP was facilitated into L-LTP (>24 h), suggesting that metaplasticity was induced during the first EE experience and that EE-mediated modifications are cumulative. Effects were absent in mice that underwent solitary enrichment or were group-housed without EE. These data suggest that EE in naïve animals strengthens E-LTP, and also promotes L-LTP in animals that underwent EE in the past. This indicates that brief exposure to EE, particularly under social conditions can elicit lasting positive effects on synaptic strength that may have beneficial consequences for cognition that depends on synaptic plasticity.

Physical exercise as a preventive or disease-modifying treatment of dementia and brain aging

A rapidly growing literature strongly suggests that exercise, specifically aerobic exercise, may attenuate cognitive impairment and reduce dementia risk. We used PubMed (keywords exercise and cognition) and manuscript bibliographies to examine the published evidence of a cognitive neuroprotective effect of exercise. Meta-analyses of prospective studies documented a significantly reduced risk of dementia associated with midlife exercise; similarly, midlife exercise significantly reduced later risks of mild cognitive impairment in several studies. Among patients with dementia or mild cognitive impairment, randomized controlled trials (RCTs) documented better cognitive scores after 6 to 12 months of exercise compared with sedentary controls. Meta-analyses of RCTs of aerobic exercise in healthy adults were also associated with significantly improved cognitive scores. One year of aerobic exercise in a large RCT of seniors was associated with significantly larger hippocampal volumes and better spatial memory; other RCTs in seniors documented attenuation of age-related gray matter volume loss with aerobic exercise. Cross-sectional studies similarly reported significantly larger hippocampal or gray matter volumes among physically fit seniors compared with unfit seniors. Brain cognitive networks studied with functional magnetic resonance imaging display improved connectivity after 6 to 12 months of exercise. Animal studies indicate that exercise facilitates neuroplasticity via a variety of biomechanisms, with improved learning outcomes. Induction of brain neurotrophic factors by exercise has been confirmed in multiple animal studies, with indirect evidence for this process in humans. Besides a brain neuroprotective effect, physical exercise may also attenuate cognitive decline via mitigation of cerebrovascular risk, including the contribution of small vessel disease to dementia. Exercise should not be overlooked as an important therapeutic strategy.