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

Transcriptional Expression of Histone Acetyltransferases and Deacetylases During the Recovery of Acute Exercise in Mouse Hippocampus

Protein acetylation, which is dynamically maintained by histone acetyltransferases (HATs) and deacetylases (HDACs), might play essential roles in hippocampal exercise physiology. However, whether HATs/HDACs are imbalanced during the recovery phase following acute exercise has not been determined. Groups of exercised mice with different recovery periods after acute exercise (0 h, 0.5 h, 1 h, 4 h, 7 h, and 24 h) were constructed, and a group of sham-exercised mice was used as the control. The mRNA levels of HATs and HDACs were detected via real-time quantitative polymerase chain reaction. Lysine acetylation on the total proteins and some specific locations on histones were detected via western blotting, as were various acylation modifications on the total proteins. Except for four unaffected genes (Hdac4, Ncoa1, Ncoa2, and Sirt1), the mRNA expression trajectories of 21 other HATs or HDACs affected by exercise could be categorized into three clusters. The genes in Cluster 1 increased quickly following exercise, with a peak at 0.5 h and/or 1 h, and remained at high levels until 24 h. Cluster 2 genes presented a gradual increase with a delayed peak at 4 h or 7 h postexercise before returning to baseline. The expression of Cluster 3 genes decreased at 0.5 h and/or 1 h, with some returning to overexpression (Hdac1 and Sirt3). Although most HATs were upregulated and half of the affected HDACs were downregulated at 0.5 h postexercise, the global or residue-specific histone acetylation levels were unchanged. In contrast, the levels of several metabolism-related acylation products of total proteins, including acetylation, succinylation, 2-hydroxyisobutyryllysine, β-hydroxybutyryllysine, and lactylation, decreased and mainly occurred on nonhistones immediately after exercise. During the 24-h recovery phase after acute exercise, the transcriptional trajectory of HATs or the same class of HDACs in the hippocampus exhibited heterogeneity. Although acute exercise did not affect the selected sites on histone lysine residues, it possibly incurred changes in acetylation and other acylation on nonhistone proteins.

PAW, a cost-effective and open-source alternative to commercial rodent running wheels

Voluntary wheel running is a common measure of general activity in many rodent models across neuroscience and physiology. However, current commercial wheel monitoring systems can be cost-prohibitive to many investigators, with many of these systems requiring investments of thousands of dollars. In recent years, several open-source alternatives have been developed, and while these tools are much more cost effective than commercial system, they often lack the flexibility to be applied to a wide variety of projects. Here, we have developed PAW, a 3D Printable Arduino-based Wheel logger. PAW is wireless, fully self-contained, easy to assemble, and all components necessary for its production can be obtained for only $75 CAD. Furthermore, with its compact internal electronics, the 3D printed casing can be easily modified to be used with a wide variety of running wheel designs for a wide variety of rodent species. Data recorded with the PAW system shows circadian patterns of activity which is expected from mice and is consistent with results found in the literature. Altogether, PAW is a flexible, low-cost system that can be beneficial to a broad range of researchers who study rodent models.

Antidepressant properties of voluntary exercise mediated by gut microbiota

Although regular exercise has been reported to prevent depression, it has not been clarified whether the gut microbiota is involved in the factors that prevent depression through exercise. We investigated the effects of voluntary exercise on the gut microbiota and the prevention of depression-like behaviors using mice. C57BL/6 J male mice were subjected to 10 weeks of sedentary control or wheel running, then they were subjected to social defeat stress (SDS). Exercise attenuated that sucrose drinking was decreased by SDS treatment. Exercise increased the expression of Bdnf and decreased expression of Zo-1 and Claudin5 in the brain. Fecal Turicibacter, Allobaculum, and Clostridium sensu stricto, and propionate in the cecum were decreased by the exercise. Voluntary exercise-induced antidepressant properties might be partially caused by suppression of serotonin uptake into gut microbiota and increase the permeability of the blood-brain barrier via reduced propionate production.

Voluntary wheel running during adolescence prevents the increase in ethanol intake induced by social defeat in male mice

RATIONALE

Exposure to social defeat (SD) induces a depressive phenotype, increased ethanol seeking and consumption, accompanied by activation of the neuroinflammatory response. However, a resilient response can be potentiated through physical exercise in the form of voluntary wheel running (VWR) during or after exposure to social stress. Therefore, the aim of this study was to test whether physical exercise during adolescence prior to being exposed to SD can enhance resilience to the increase in ethanol intake.

METHODS

Male mice had access to VWR during adolescence and the effects of social defeat (4 sessions every 72 h) on oral ethanol self-administration (SA) was evaluated. Based on the social interaction test, mice were classified as resilient or susceptible to depressive-like behavior. Two weeks after the last encounter, mice were subjected to the drinking in the dark and oral ethanol SA paradigms. Mice were then sacrificed to measure brain-derived neurotrophic factor (BDNF) levels in the striatum and hippocampus.

RESULTS

As expected, susceptible mice increased ethanol intake in the oral SA protocol. However, susceptible mice in the exercise condition did not increase ethanol intake, showing similar consumption and motivation for ethanol than the control and resilient groups. On the other hand, decreased BDNF levels were observed in susceptible mice in both experimental conditions compared to the control groups after ethanol SA.

CONCLUSIONS

The pre-exposure of VWR prevented the increase in consumption and motivation for ethanol induced by SD in susceptible mice. On the other hand, it appears that VWR did not exhibit any significant long-term effects on BDNF signaling, which is mainly affected in susceptible mice after ethanol intake.

Walking, Running, Swimming: An Analysis of the Effects of Land and Water Aerobic Exercises on Cognitive Functions and Neural Substrates

In the brain and cognitive reserves framework, aerobic exercise is considered as a protective lifestyle factor able to induce positive effects on both brain structure and function. However, specific aspects of such a beneficial effect still need to be completely clarified. To this aim, the present narrative review focused on the potential brain/cognitive/neural reserve-construction mechanisms triggered by different aerobic exercise types (land activities; such as walking or running; vs. water activities; such as swimming), by considering human and animal studies on healthy subjects over the entire lifespan. The literature search was conducted in PubMed database. The studies analyzed here indicated that all the considered kinds of activities exert a beneficial effect on cognitive/behavioral functions and on the underlying brain neurobiological processes. In particular, the main effects observed involve the cognitive domains of memory and executive functions. These effects appear related to structural and functional changes mainly involving the fronto-hippocampal axis. The present review supports the requirement of further studies that investigate more specifically and systematically the effects of each type of aerobic activity, as a basis to plan more effective and personalized interventions on individuals as well as prevention and healthy promotion policies for the general population.

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.

Effects of wheel-running on anxiety and depression-relevant behaviours in the MCAO mouse model of stroke: moderation of brain-derived neurotrophic factor and serotonin receptor gene expression

Stroke continues to be a major cause of mortality globally. Post-stroke treatment is complicated by the heterogenous nature of pathology and the emergence of secondary psychological symptoms are an additional challenge to the recovery process. Poststroke depression (PSD) is a common co-morbidity and is a major impediment to recovery. While selective serotonin reuptake inhibitors (SSRIs) have proven to be clinically efficacious in treating PSD, the pathogenic processes that underlie the manifestation of depressive mood post-stroke remains unclear. Furthermore, the use of SSRIs is associated with risks of intracerebral haemorrhage, so alternative treatment options need to be continuously explored. Exercise has been demonstrated to be beneficial for improving mood in humans and preclinical models of neurological conditions. Little is known of the mood-related benefits of physical exercise post-stroke. Using the middle cerebral artery occlusion (MCAO) mouse model of cerebral ischaemia, we investigated whether behavioural deficits emerge post-MCAO and could be rescued by voluntary wheel-running. We report that MCAO induced hypo-locomotion and anhedonia-related behaviours, with some improvements conferred by wheel-running. Serotonin transporter gene expression was increased in the MCAO hippocampus and frontal cortex, but this increase remained despite wheel-running. Wheel-running associated up-regulation of BDNF gene expression was unaffected in MCAO mice, reflecting conservation of key neuroplasticity molecular pathways. Taken together, our results highlight the need for further research into serotonergic modulation of the affective symptoms of stroke.

Prefrontal cortex hemodynamic response to acute high intensity intermittent exercise during executive function processing

We investigated prefrontal cortex (PFC) hemodynamic response, through functional near infrared spectroscopy (fNIRS) during executive function (EF) processing in response to acute high intensity intermittent exercise (HIIE) in young adults. We also assessed the associated sex differences in the cognitive scores and related PFC hemodynamic functions in response to HIIE. 49 young healthy adult participants (32 women, 17 men) were randomly assigned to either control or HIIE intervention groups. HIIE group participants performed 4 × 4 minutes of HIIE on cycle ergometer with 3 minutes of active recovery between the bouts; control group relaxed for the time equivalent to intervention. fNIRS data was collected during the performance of the EF tests including Color Word Stroop Test (CWST) and Trail Making Test (TMT) in pre and post sessions in both the groups. Results indicated a significant change in the hemodynamic response in the form of increased oxygenated and decreased deoxygenated hemoglobin in the PFC areas specific to the EF tasks, with improved CWST and TMT scores in response to HIIE intervention. PFC activation was different in men and women in response to HIIE, however similar scores of task performance were observed in men and women during the performance of executive functions in response to HIIE. The study concludes that an acute HIIE session improves executive function which is associated with an increase activation of PFC. Sex differences exist in the activation of PFC in response to HIIE during EF processing. Our study adds to the current evidence regarding exercise and cognition.

Sex-dependent effects of chronic exercise on cognitive flexibility but not hippocampal Bdnf in aging mice

Cognitive impairments associated with advanced age involve alterations in the hippocampus that changes with experience throughout life. The hippocampus is critical for cognitive flexibility involved with extinction and reinstatement of conditioned fear. It is widely accepted that regular exercise can be beneficial for hippocampal function. Therefore, we asked whether chronic voluntary exercise in middle-aged mice can improve extinction and/or reinstatement of conditioned fear compared with standard-housing. Eight-month-old male and female C57Bl/6J mice had access to a running wheel or remained in standard-housing until 11 months of age. Alongside control standard-housed young adult (3-month-old) mice, they received tone-footshock pairings, which were subsequently extinguished with tone-alone presentations the next day. Half of the mice then received a reminder in the form of a single footshock. Male and female 11-month-old mice housed in standard conditions exhibited impaired reinstatement compared with young adult mice. However, for males that had access to a running wheel from 8 months of age, the reminder treatment rescued reinstatement ability. This was not observed in females. Additionally, exercise during middle age in both sexes increased expression of brain-derived neurotrophic factor (Bdnf) mRNA in the hippocampus, specifically exon 4 mRNA. These results show that, at least for males, physical exercise is beneficial for reducing age-related decline in cognitive abilities. Despite not affecting reinstatement, exercise also increased Bdnf gene expression in the female hippocampus, which could potentially benefit other forms of hippocampus-dependent cognition.

Exercise mimetics: harnessing the therapeutic effects of physical activity

Exercise mimetics are a proposed class of therapeutics that specifically mimic or enhance the therapeutic effects of exercise. Increased physical activity has demonstrated positive effects in preventing and ameliorating a wide range of diseases, including brain disorders such as Alzheimer disease and dementia, cancer, diabetes and cardiovascular disease. This article discusses the molecular mechanisms and signalling pathways associated with the beneficial effects of physical activity, focusing on effects on brain function and cognitive enhancement. Emerging therapeutic targets and strategies for the development of exercise mimetics, particularly in the field of central nervous system disorders, as well as the associated opportunities and challenges, are discussed.

Effects of Prenatal Phthalate Exposure and Childhood Exercise on Maternal Behaviors in Female Rats at Postpartum: A Role of Oxtr Methylation in the Hypothalamus

Both the detrimental effect of prenatal exposure to di-(2-ethylhexyl)-phthalate (DEHP) and the beneficial effects of physical exercise on brain functions have been reported. The oxytocin pathway has been implicated in the onset of maternal behaviors. Epigenetic modification of the oxytocin receptor gene (OXTR) through DNA methylation has been associated with the pathogenesis of neuropsychiatric disorders. The purpose of this study was to investigate the effects of prenatal DEHP exposure on oxytocin-regulated maternal behaviors and to examine the protective effect of exercise. Pregnant rats (F0) were fed with vehicle or DEHP during gestation and the offspring females (F1) were assessed for their maternal behaviors by pup retrieval test at postpartum. The results showed that reduced pup retrieval activities without significant alteration of stress responses were observed in the prenatally DEHP-exposed females. Prenatal DEHP exposure decreased the expressions of oxytocin, Oxtr mRNA, and oxytocin receptor, and increased Oxtr methylation in the hypothalamus of postpartum female rats. There were no significant effects of exercise on behavioral, biochemical, and epigenetic measurements. These results suggest that prenatal DEHP exposure has a long-term adverse effect on maternal behaviors; Oxtr hyper-methylation may be a potential epigenetic mechanism for this alteration, which cannot be prevented by physical exercise during childhood.

The effect of zinc supplementation on brain derived neurotrophic factor: A meta-analysis

BACKGROUND

Zinc in one of the most abundant trace minerals in human body which is involved in numerous biological pathways and has variety of roles in the nervous system. It has been assumed that zinc exerts its role in nervous system through increasing brain derived neurotrophic factor (BDNF) concentrations.

OBJECTIVES

Present meta-analysis was aimed to review the effect of zinc supplementation on serum concentrations of BDNF.

METHODS AND MATERIALS

Four electronic databases (Pubmed, Scopus, Web of Science, Embase) were searched for identifying studies that examined BDNF levels prior and after zinc supplementation up to May 2020. According to the Cochrane guideline, a meta-analysis was performed to pool the effect size estimate (Hedges' test) of serum BDNF across studies. Risk of publication bias was assessed using a funnel plot and Egger's test.

RESULTS

Five studies were eligible and 238 participants were included. These studies enrolled subjects with premenstrual syndrome, diabetic retinopathy, major depression disorder, overweight/obese and obese with mild to moderate depressive disorders. Zinc supplementation failed to increase blood BDNF concentrations with effect size of 0.30 (95 % CI: -0.08, 0.67, P = 0.119). Funnel plot did not suggest publication bias.

CONCLUSION

Zinc supplementation may not significantly increase BDNF levels. However, the small number of included articles and significant heterogeneity between them can increase the risk of a false negative result; therefore, the results should be interpreted with caution.

When your brain looks older than expected: combined lifestyle risk and BrainAGE

Lifestyle may be one source of unexplained variance in the great interindividual variability of the brain in age-related structural differences. While physical and social activity may protect against structural decline, other lifestyle behaviors may be accelerating factors. We examined whether riskier lifestyle correlates with accelerated brain aging using the BrainAGE score in 622 older adults from the 1000BRAINS cohort. Lifestyle was measured using a combined lifestyle risk score, composed of risk (smoking, alcohol intake) and protective variables (social integration and physical activity). We estimated individual BrainAGE from T1-weighted MRI data indicating accelerated brain atrophy by higher values. Then, the effect of combined lifestyle risk and individual lifestyle variables was regressed against BrainAGE. One unit increase in combined lifestyle risk predicted 5.04 months of additional BrainAGE. This prediction was driven by smoking (0.6 additional months of BrainAGE per pack-year) and physical activity (0.55 less months in BrainAGE per metabolic equivalent). Stratification by sex revealed a stronger association between physical activity and BrainAGE in males than females. Overall, our observations may be helpful with regard to lifestyle-related tailored prevention measures that slow changes in brain structure in older adults.

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.

Disruption of synaptic expression pattern and age-related DNA oxidation in a neuronal model of lead-induced toxicity

Lead (Pb) is recognized as a potent inducer of synaptic toxicity generally associated with reduced synaptic transmission and increased neuronal fiber excitability, becoming an environmental risk for neurodegenerative processes. Despite numerous toxicological studies on Pb have been directed to the developing brain, attention concerning long-term consequences of pubertal chronic Pb exposure on neuronal activity is still lacking. Thus, we exposed 4-week-old male mice to 0.2 % lead acetate solution for one month, then, conducted behavioral tests or extracted brain homogenate from mice prefrontal cortex (PFC) and hippocampus at the age of 4, 13 and 16-month-old respectively. Our results showed that treated mice exhibited an evident increase in latency to reach platform following pubertal Pb exposure and aging. The increase of 8-OHdG revealed evident neural DNA oxidative damage across time upon pubertal Pb exposure. In the hippocampus of lead exposed mice at three age nodes, the expression of brain-derived neurotrophic factor precursor (proBDNF) increased, while that of mature BDNF (mBDNF), cAMP-response element binding protein (CREB) and phosphorylated CREB (pCREB) decreased compared with the control group. Furthermore, the expression of BACE1 protein and tau phosphorylation level in PFC and hippocampus increased, APP mRNAs in PFC and prolonged induction of BACE1 in hippocampus. Our results show that chronic Pb exposure from pubertal stage onward can either initiate divergent synaptic-related gene expression patterns in adulthood or trigger time-course of neurodegenerative profile within the PFC or hippocampus, which can contribute consistent deficits of cognition across subsequent age-nodes.

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.

Hippocampal Growth Factor and Myokine Cathepsin B Expression following Aerobic and Resistance Training in 3xTg-AD Mice

Aerobic training (AT) can support brain health in Alzheimer's disease (AD); however, the role of resistance training (RT) in AD is not well established. Aside from direct effects on the brain, exercise may also regulate brain function through secretion of muscle-derived myokines. Aims. This study examined the effects of AT and RT on hippocampal BDNF and IGF-1 signaling, β-amyloid expression, and myokine cathepsin B in the triple transgenic (3xTg-AD) model of AD. 3xTg-AD mice were assigned to one of the following groups: sedentary (Tg), aerobic trained (Tg+AT, 9 wks treadmill running), or resistance trained (Tg+RT, 9 wks weighted ladder climbing) (n = 10/group). Rotarod latency and strength were assessed pre- and posttraining. Hippocampus and skeletal muscle were collected after training and analyzed by high-resolution respirometry, ELISA, and immunoblotting. Tg+RT showed greater grip strength than Tg and Tg+AT at posttraining (p < 0.01). Only Tg+AT improved rotarod peak latency (p < 0.01). Hippocampal IGF-1 concentration was ~15% greater in Tg+AT and Tg+RT compared to Tg (p < 0.05); however, downstream signals of p-IGF-1R, p-Akt, p-MAPK, and p-GSK3β were not altered. Cathepsin B, hippocampal p-CREB and BDNF, and hippocampal mitochondrial respiration were not affected by AT or RT. β-Amyloid was ~30% lower in Tg+RT compared to Tg (p < 0.05). This data suggests that regular resistance training reduces β-amyloid in the hippocampus concurrent with increased concentrations of IGF-1. Both types of training offered distinct benefits, either by improving physical function or by modifying signals in the hippocampus. Therefore, inclusion of both training modalities may address central defects, as well as peripheral comorbidities in AD.

Role of glucocorticoid signaling in exercise-associated changes in high-fat diet preference in rats

The simultaneous introduction of wheel running (WR) and diet choice (high-carbohydrate chow vs. high-fat diet) results in sex-specific diet choice patterns in rats. WR induces a high-fat (HF) diet avoidance, and such avoidance persists in the majority of males, but not females, throughout a 2-wk period. Exercise is a physiological stressor that activates the hypothalamic-pituitary-adrenal (HPA) axis and stimulates glucocorticoid (GC) release, which can alter dietary preferences. Here, we examined the role of the HPA axis and GC signaling in mediating exercise-induced changes in diet preference and the associated neurobiological adaptations that may underlie sex differences in diet choice patterns. Experiment 1 revealed that adrenalectomy did not significantly alter the initiation and persistence of running-induced HF diet avoidance in male rats. Experiment 2 showed that acute WR resulted in greater neural activation than chronic WR in the medial prefrontal (mPFC) and insular cortices (IC) in male rats. Experiment 3 revealed sex differences in the molecular adaptation to exercise and diet preference. First, exercise increased gene expression of fkbp5 in the mPFC, IC, and hippocampus of WR females but had limited influence in males. Second, male and female WR rats that reversed or maintained HF diet avoidance showed distinct sex- and HF diet preference-dependent expression profiles of genes involved in cortical GC signaling (e.g., nr3c1, nr3c2, and src1). Taken together, our results suggest sex differences in region-specific neural adaptations may underlie sex differences in diet preference and the health benefits from exercise.

Impact of different intensities of forced exercise on deficits of spatial and aversive memory, anxiety-like behavior, and hippocampal BDNF during morphine abstinence period in male rats

Forced exercise can alleviate cognitive-behavioral deficits in an experimental model of addiction. However, the effects of different intensities of forced exercise in improving behavioral, cognitive and biochemical deficits during morphine abstinence period are not well investigated. Thus, the current work examined the effects of different loads of forced exercise on cognition functions, anxiety behavior and BDNF changes in the hippocampus, and prefrontal cortex (PFC), and also serum levels of BDNF and corticosterone during the abstinent period in male rats. Animals received morphine injections (10 mg/kg, twice a day) for 10 consecutive days. Then, the animals were exposed to a 4-week forced exercise training program under low, moderate or high intensities (30 min per session on 5 days a week), which accompanied by behavioral and biochemical tests. In Experiment 1, anxiety-like behaviors using elevated plus maze (EPM), and light/dark box (L/D box) were examined. In Experiment 2, cognitive functions using T-maze alteration and passive avoidance tasks were tested, which accompanied by BDNF measurements in the hippocampus and PFC. In Experiment 3, serum levels of BDNF and corticosterone following the termination of forced exercise regimen were measured. Morphine-abstinent animals exhibited anxiogenic -like behaviors in the EPM, but not L/D box. They also exhibited impaired T-maze alternation performance and passive avoidance memory, and a decline in hippocampal BDNF, but not PFC. Forced exercise at a moderate intensity alleviated anxiety, cognitive and BDNF defects in morphine-abstinent animals. The high load exercise enhanced serum levels of corticosterone in both saline and morphine groups. Thus, regular moderate forced exercise may be beneficial in preserving cognitive and mood functions in male addicts during the abstinent period and drug rehabilitation.

Acute forced exercise increases Bdnf IV mRNA and reduces exploratory behavior in C57BL/6J mice

Acute exercise has been shown to improve memory in humans. Potential mechanisms include increased Bdnf expression, noradrenergic activity and modification of glutamate receptors. Because mice are commonly used to study exercise and brain plasticity, it is important to explore how acute exercise impacts behavior in this model. C57BL/6J mice were assigned to three groups: control, moderate-intensity running, and high-intensity running. Control mice were placed on a stationary treadmill for 30 minutes and moderate- and high-intensity mice ran for 30 minutes at 12 and 15-17 m/min, respectively. Mice were sacrificed immediately after running and the hippocampus removed. Total Bdnf, Bdnf exon IV, and glutamate receptor subunits were quantified with quantitative polymerase chain reaction. Total and phosphorylated GluR1 (Ser845 and Ser831) protein was quantified following immunoblotting. Utilizing the same protocol for control and high-intensity running, object location memory was examined in a separate cohort of mice. Anxiety-like behavior was assessed in the open field task (OFT) in a third cohort of mice that were separated into four groups: control-saline, control-DSP-4, acute exercise-saline, and acute exercise-DSP-4. DSP-4 was used to lesion the central noradrenergic system. We observed higher Bdnf IV mRNA in high-intensity runners compared to controls, but no effects of acute exercise on memory. In the OFT, runners traveled less distance and spent more time grooming than controls. DSP-4 did not attenuate the effects of exercise. A single bout of exercise increases Bdnf IV mRNA in an intensity-dependent manner; however, high-intensity running reduces exploratory behavior in C57BL/6J mice.

Low-Intensity Running and High-Intensity Swimming Exercises Differentially Improve Energy Metabolism in Mice With Mild Spinal Muscular Atrophy

Spinal Muscular Atrophy (SMA), an autosomal recessive neurodegenerative disease characterized by the loss of spinal-cord motor-neurons, is caused by mutations on Survival-of-Motor Neuron (SMN)-1 gene. The expression of SMN2, a SMN1 gene copy, partially compensates for SMN1 disruption due to exon-7 excision in 90% of transcripts subsequently explaining the strong clinical heterogeneity. Several alterations in energy metabolism, like glucose intolerance and hyperlipidemia, have been reported in SMA at both systemic and cellular level, prompting questions about the potential role of energy homeostasis and/or production involvement in disease progression. In this context, we have recently reported the tolerance of mild SMA-like mice (Smn^Δ7/Δ7; huSMN2^+/+) to 10 months of low-intensity running or high-intensity swimming exercise programs, respectively involving aerobic and a mix aerobic/anaerobic muscular metabolic pathways. Here, we investigated whether those exercise-induced benefits were associated with an improvement in metabolic status in mild SMA-like mice. We showed that untrained SMA-like mice exhibited a dysregulation of lipid metabolism with an enhancement of lipogenesis and adipocyte deposits when compared to control mice. Moreover, they displayed a high oxygen consumption and energy expenditure through β-oxidation increase yet for the same levels of spontaneous activity. Interestingly, both exercises significantly improved lipid metabolism and glucose homeostasis in SMA-like mice, and enhanced oxygen consumption efficiency with the maintenance of a high oxygen consumption for higher levels of spontaneous activity. Surprisingly, more significant effects were obtained with the high-intensity swimming protocol with the maintenance of high lipid oxidation. Finally, when combining electron microscopy, respiratory chain complexes expression and enzymatic activity measurements in muscle mitochondria, we found that (1) a muscle-specific decreased in enzymatic activity of respiratory chain I, II, and IV complexes for equal amount of mitochondria and complexes expression and (2) a significant decline in mitochondrial maximal oxygen consumption, were reduced by both exercise programs. Most of the beneficial effects were obtained with the high-intensity swimming protocol. Taking together, our data support the hypothesis that active physical exercise, including high-intensity protocols, induces metabolic adaptations at both systemic and cellular levels, providing further evidence for its use in association with SMN-overexpressing therapies, in the long-term care of SMA patients.

Examining the contribution of histone modification to sex differences in learning and memory

The epigenome serves as a signal integration platform that encodes information from experience and environment that adds tremendous complexity to the regulation of transcription required for memory, beyond the directions encoded in the genome. To date, our understanding of how epigenetic mechanisms integrate information to regulate gene expression required for memory is primarily obtained from male derived data despite sex-specific life experiences and sex differences in consolidation and retrieval of memory, and in the molecular mechanisms that mediate these processes. In this review, we examine the contribution of chromatin modification to learning and memory in both sexes. We provide examples of how exposure to a number of internal and external factors influence the epigenome in sex-similar and sex-specific ways that may ultimately impact transcription required for memory processes. We also pose a number of key open questions and identify areas requiring further investigation as we seek to understand how histone modifying mechanisms shape memory in females.

Sex Moderates the Effect of Aerobic Exercise on Some Aspects of Cognition in Cognitively Intact Younger and Middle-Age Adults

We recently reported the results of a randomized, parallel-group, observer-masked, community-based clinical trial of 132 cognitively normal individuals aged 20–67 with below median aerobic capacity who were randomly assigned to one of two 6-month, four-times-weekly conditions: aerobic exercise and stretching/toning. We now assessed potential sex moderation on exercise-related changes in aerobic capacity, BMI and cognitive function. There was no sex moderation of the effect of aerobic exercise on aerobic capacity or BMI. We had previously reported an effect of aerobic exercise on executive function that was moderated by age. We found additional moderation by sex, such that in any age range men improved more than women. Processing speed showed significant sex moderation but not significant age moderation. In men, processing speed significantly improved by week 12 (b = 0.35, p = 0.0051), but the effect was diminished relative to week 12 at week 24 (b = 0.24, p = 0.0578). In women, there was no exercise effect at either time point (week 12: b = −0.06, p = 0.4156; week 24: b = −0.11, p = 0.1841). Men benefited cognitively more than women from aerobic exercise. This study highlights the importance of using sex-disaggregated analyses when assessing the impact of physical exercise intervention, and the need to ascertain the underlying mechanisms for differential cognitive benefit by sex.

Sex differences in Alzheimer's disease: Understanding the molecular impact

Alzheimer's disease (AD) is a common neurodegenerative disorder that presents with cognitive impairment and behavioral disturbance. Approximately 5.5 million people in the United States live with AD, most of whom are over the age of 65 with two-thirds being woman. There have been major advancements over the last decade or so in the understanding of AD neuropathological changes and genetic involvement. However, studies of sex impact in AD have not been adequately integrated into the investigation of disease development and progression. It becomes indispensable to acknowledge in both basic science and clinical research studies the importance of understanding sex-specific differences in AD pathophysiology and pathogenesis, which could guide future effort in the discovery of novel targets for AD. Here, we review the latest and most relevant literature on this topic, highlighting the importance of understanding sex dimorphism from a molecular perspective and its association to clinical trial design and development in AD research field.

Rehabilitation following spinal cord injury: how animal models can help our understanding of exercise-induced neuroplasticity

Spinal cord injury is a devastating condition that is followed by long and often unsuccessful recovery after trauma. The state of the art approach to manage paralysis and concomitant impairments is rehabilitation, which is the only strategy that has proven to be effective and beneficial for the patients over the last decades. How rehabilitation influences the remodeling of spinal axonal connections in patients is important to understand, in order to better target these changes and define the optimal timing and onset of training. While clinically the answers to these questions remain difficult to obtain, rodent models of rehabilitation like bicycling, treadmill training, swimming, enriched environments or wheel running that mimic clinical rehabilitation can be helpful to reveal the axonal changes underlying motor recovery. This review will focus on the different animal models of spinal cord injury rehabilitation and the underlying changes in neuronal networks that are improved by exercise and rehabilitation.

Changes in Circulating BDNF in relation to Sex, Diet, and Exercise: A 12-Week Randomized Controlled Study in Overweight and Obese Participants

Circulating BDNF is higher in women than in men and suggested to be affected by changes in food intake, body weight, and exercise. The purpose of this study was to compare BDNF concentrations in women and men during a 12-week weight loss intervention. Using a previously published 12-week randomized study, serum BDNF was assessed at baseline and after 12 weeks using an enzyme-linked immunosorbent assay method. Fifty overweight or obese but healthy individuals (26 women, mean age of 36.4 ± 7.9 years; 24 men, mean age of 38.0 ± 5.9 years) were included and allocated into three groups: exercise-only (EXO; 12 weeks of aerobic exercise and isocaloric diet), diet-only (DIO; 8 weeks of very low energy diet (VLED 600 kcal/day) followed by a 4-week weight maintenance diet), or diet and exercise (DEX; 12 weeks of aerobic exercise in parallel with 8 weeks of VLED (800 kcal/day) followed by a 4-week weight maintenance diet). At baseline, BDNF levels were 25% higher in women compared to men (p=0.006). Body weight was reduced in all intervention groups (p < 0.006). Exercise (EXO group) induced a 22% reduction in circulating BDNF in men (p=0.037) and women (p=0.080). In the DIO and DEX groups, a significant reduction in BDNF levels (29.9%; p=0.035 and 32.5%; p=0.003, respectively) was observed in women but not in men. In conclusion, circulating BDNF was significantly changed by diet alone or combined with exercise in women and only by exercise alone in men. This suggests that changes in circulating BDNF depend on weight loss methods (diet/exercise) as well as sex.

Hippocampal distribution of parvalbumin neurons in female and male rats submitted to the same volume and intensity of aerobic exercise

Several studies report the influence of gender on physical exercise-induced brain plasticity, including neurotrophic factor levels, neurogenesis, and navigation strategies in spatial memory task. However, it has been noted that females are physically more active than males in animal models of physical exercise. With this in mind, we conducted an experimental study to investigate the effect of sex on the brain of rats submitted to same volume and intensity of aerobic exercise. To do so, we used calcium-binding protein parvalbumin as neuroplastic marker to explore the hippocampal formation (a brain neurogenic/mnemonic region) of male and female rats submitted to 4 weeks of aerobic exercise on a treadmill at 12 m/min, 30 min per day. Our results show that, in both sexes, physical exercise increased hippocampal density of parvalbumin neurons in the cornus ammonis (CA1, CA2/3) and hilus subfields, but not in the dentate gyrus and subiculum. No difference in exercise-induced hipocampal parvalbumin density was found between male and female rats. These findings suggest that aerobic exercise promotes similar effects on hippocampal distribution of parvalbumin neurons of male and female rats, especially when they are submitted to the same volume and intensity of physical exercise.

Voluntary Exercise During Adolescence Mitigated Negative the Effects of Maternal Separation Stress on the Depressive-Like Behaviors of Adult Male Rats: Role of NMDA Receptors

Evidence indicates that experiencing early-life stress (ELS) is a risk factor for the development of mental disorders such as depression. Maternal separation stress (MS) is a valid animal model of ELS that caused to induce long-lasting effects on the brain and behaviors of animals. It hypothesized that adolescence is a critical stage in which the brain is still developing, and applying (non)pharmacological therapies in this period may attenuate the effects of ELS on the brain and behavior. Male rats were subjected to MS from postnatal day (PND) 2-14, and the stressed animals were then treated with (1) chronic fluoxetine (FLX) (5 mg/kg) and (2) voluntary running wheel exercise (RW) from PND 30, for 30 days. Then, we subjected the animals to behavioral and molecular assessments at PND 60. Our data showed that MS provoked depressive-like behaviors in rats, tested by the forced swimming test, splash test, and sucrose preference test. Additionally, we found that MS increased the gene expression of the NR2A (and not NR2B) subunit of N-methyl-D-aspartate (NMDA) receptors in the hippocampus of adult rats. Both FLX and RW treatments during adolescence were able to mitigate the negative effects of ELS on stressed animals. These results highlighted the importance of adolescence in treating stressed animals with FLX/voluntary RW exercise to alleviate the depressive effects of ELS. In addition, we found that ELS altered the transcriptional level of Grin2a (and not Grin2b) in the hippocampus. Finally, our results showed that FLX/voluntary RW exercise during adolescence could normalize altered expression of Grin2a in the hippocampus of adult rats.

Exercise as a Sex-Specific Treatment for Substance Use Disorder

PURPOSE OF REVIEW

Exercise is a promising treatment for substance use disorder that may reduce withdrawal symptoms and prevent relapse. In this review, we discuss recent evidence from clinical and preclinical studies for its efficacy, from a behavioral to a molecular level, in order to understand the exercise conditions that lead to beneficial effects. We also highlight the few recent findings of sex-specific differences.

RECENT FINDINGS

Clinical and preclinical findings show that exercise decreases withdrawal symptoms, including craving, in both males and females. Evidence from clinical studies support the efficacy of exercise to prevent relapse to smoking, although further research is needed to examine sex differences, establish long-term efficacy, and to determine if effects extend to other substance use disorders. Preclinical findings also support the potential utility of exercise to prevent relapse with evidence suggesting that its efficacy is enhanced in males, and mediated by blocking drug-induced adaptations that occur during early abstinence.

SUMMARY

Sex differences and timing of exercise availability during abstinence should be considered in future studies examining exercise as an intervention for relapse. A better understanding of the neurobiological mechanisms underlying the efficacy of exercise to reduce withdrawal symptoms and prevent relapse is needed to guide its development as a sex-specific treatment.

Sex differences in brain-derived neurotrophic factor signaling: Functions and implications

Brain-derived neurotrophic factor (BDNF) regulates diverse processes such as neuronal survival, differentiation, and plasticity. Accumulating evidence suggests that molecular events that direct sexual differentiation of the brain interact with BDNF signaling pathways. This Mini-Review first examines potential hormonal and epigenetic mechanisms through which sex influences BDNF signaling. We then examine how sex-specific regulation of BDNF signaling supports the development and function of sexually dimorphic neural circuits that underlie male-specific genital reflexes in rats and song production in birds. Finally, we discuss the implications of sex differences in BDNF signaling for gender-biased presentation of neurological and psychiatric diseases such as Alzheimer's disease. Although this Mini-Review focuses on BDNF, we try to convey the general message that sex influences brain functions in complex ways and underscore the requirement for and challenge of expanding research on sex differences in neuroscience. © 2016 Wiley Periodicals, Inc.

Temporal relationships between food acquisition and voluntary exercise in mice

Patterns of operant food acquisition in a closed economy and bouts of either voluntary wheel running (WR) or spontaneous locomotor activity in a standard condition (SC) with no wheel were examined in young adult male and female C57BL/6 mice across a range of nose poke prices (FUP) per food pellet. Both sexes showed vigorous WR or locomotor activity. At each FUP, WR groups had higher food intake than SC groups. Despite substantially higher mean body weight of males compared with females, intakes and activity did not differ by sex in the SC groups and males lost weight more rapidly as FUP increased. In contrast, WR males ran ∼33% further per day than females, increased their food intake (above that of SC counterparts) more than females, and lost less body weight than SC males. By parsing the night in four 3h epochs it was found that food intake declined progressively through the night in both WR and SC mice and that the hyperphagia of WR relative to SC groups was most evident early in the night, coincident with highest activity. No large or systematic sex differences were revealed in these temporal analyses. Analysis of data at 60s resolution showed that pellet acquisition occurred in many small or short bouts, the timing of which was either intercalated or concurrent with either locomotor activity or WR. The results show that increased eating due to WR occurs concurrently with maximum running, and with no evidence of delayed compensation.

Effects of acute exercise on fear extinction in rats and exposure therapy in humans: Null findings from five experiments

BACKGROUND

Exposure therapy is an established learning-based intervention for the treatment of anxiety disorders with an average response rate of nearly 50%, leaving room for improvement. Emerging strategies to enhance exposure therapy in humans and fear extinction retention in animal models are primarily pharmacological. These approaches are limited as many patients report preferring non-pharmacological approaches in therapy. With general cognitive enhancement effects, exercise has emerged as a plausible non-pharmacological augmentation strategy. The present study tested the hypothesis that fear extinction and exposure therapy would be enhanced by a pre-training bout of exercise.

METHODS

We conducted four experiments with rats that involved a standardized conditioning and extinction paradigm and a manipulation of exercise. In a fifth experiment, we manipulated vigorous-intensity exercise prior to a standardized virtual reality exposure therapy session among adults with fear of heights.

RESULTS

In experiments 1-4, exercise did not facilitate fear extinction, long-term memory, or fear relapse tests. In experiment 5, human participants showed an overall reduction in fear of heights but exercise did not enhance symptom improvement.

CONCLUSIONS

Although acute exercise prior to fear extinction or exposure therapy, as operationalized in the present 5 studies, did not enhance outcomes, these results must be interpreted within the context of a broader literature that includes positive findings. Taken all together, this suggests that more research is necessary to identify optimal parameters and key individual differences so that exercise can be implemented successfully to treat anxiety disorders.

Acute exercise enhances the consolidation of fear extinction memory and reduces conditioned fear relapse in a sex-dependent manner

Fear extinction-based exposure therapy is the most common behavioral therapy for anxiety and trauma-related disorders, but fear extinction memories are labile and fear tends to return even after successful extinction. The relapse of fear contributes to the poor long-term efficacy of exposure therapy. A single session of voluntary exercise can enhance the acquisition and consolidation of fear extinction in male rats, but the effects of exercise on relapse of fear after extinction are not well understood. Here, we characterized the effects of 2 h of voluntary exercise during the consolidation phase of contextual or auditory fear extinction learning on long-term fear extinction memory and renewal in adult, male and female, Long-Evans rats. Results indicate that exercise enhances consolidation of fear extinction memory and reduces fear relapse after extinction in a sex-dependent manner. These data suggest that brief bouts of exercise could be used as an augmentation strategy for exposure therapy, even in previously sedentary subjects. Fear memories of discrete cues, rather than of contextual ones, may be most susceptible to exercise-augmented extinction, especially in males. Additionally, exercise seems to have the biggest impact on fear relapse phenomena, even if fear extinction memories themselves are only minimally enhanced.

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.

A single bout of exercise increases hippocampal Bdnf: influence of chronic exercise and noradrenaline

Research in human subjects suggests that acute exercise can improve memory performance, but the qualities of the exercise necessary to promote improved memory, and the signaling pathways that mediate these effects are unknown. Brain-derived neurotrophic factor (Bdnf), noradrenergic signaling, and post-translational modifications to AMPA receptors have all been implicated in the enhancement of memory following emotional or physical arousal; however, it is not known if a single bout of exercise is sufficient to engage these pathways. Here we use a rodent model to investigate the effects of acute and chronic exercise on hippocampal transcript-specific Bdnf expression and phosphorylation of the GluR1 subunit of the AMPA-type glutamate receptor. A single bout of treadmill exercise was insufficient to mimic the increased expression of GluR1 protein and phosphorylation at Ser845 observed following 1 month of voluntary wheel running. However, acute exercise was sufficient to increase Bdnf transcript IV messenger RNA (mRNA) expression in sedentary subjects, but not subjects housed for 1 month with a running wheel. High-intensity acute exercise increased total Bdnf mRNA in sedentary mice, but not above levels observed following chronic access to the running wheel. Although depletion of central noradrenergic signaling with DSP-4 reduced Bdnf IV mRNA, the effect of acute exercise on Bdnf mRNA persisted. Our characterization of the effects of acute exercise on Bdnf expression and persistence in the absence of noradrenergic modulation may inform strategies to employ physical activity to combat cognitive aging and mental health disorders.

Cross-sectional associations of objectively measured physical activity with brain-derived neurotrophic factor in adolescents

OBJECTIVE

The purpose of this study was to examine the associations between objectively measured physical activity and serum brain-derived neurotrophic factor (BDNF) in adolescents.

METHODS

Cross-sectional analyses were performed using data from 415 adolescents who participated in the 2015 follow-up of the Childhood Health Activity and Motor Performance School Study Denmark (the CHAMPS-study DK). Physical activity was objectively measured by accelerometry monitors. Serum BDNF levels were analyzed using the Enzyme-linked immunosorbent assay (ELISA). Anthropometrics and pubertal status were measured using standardized procedures.

RESULTS

With adjustment for age, pubertal status and body mass index, mean physical activity (counts per minute) was negatively associated with serum BDNF in boys (P=0.013). Similarly, moderate-to-vigorous physical activity (MVPA) was negatively associated with serum BDNF in boys (P=0.035). In girls, mean physical activity and MVPA were not associated with serum BDNF. Without adjustment for wear time, sedentary time was not associated with serum BDNF in either sex.

CONCLUSION

These findings indicate that higher physical activity is associated with lower serum BDNF in boys, but not in girls.