Adult Hippocampal Neurogenesis: A Possible Way how Physical Exercise Counteracts Stress

Beneficial effects of physical exercise on cognitive-behavioral impairments and brain-derived neurotrophic factor alteration in the limbic system induced by neurodegeneration

Neurodegenerative diseases (NDDs) are a class of neurological disorders marked by the progressive loss of neurons that afflict millions of people worldwide. These illnesses affect brain connection, impairing memory, cognition, behavior, sensory perception, and motor function. Alzheimer's, Parkinson's, and Huntington's diseases are examples of common NDDs, which frequently include the buildup of misfolded proteins. Cognitive-behavioral impairments are early markers of neurodevelopmental disorders, emphasizing the importance of early detection and intervention. Neurotrophins such as brain-derived neurotrophic factor (BDNF) are critical for neuron survival and synaptic plasticity, which is required for learning and memory. NDDs have been associated with decreased BDNF levels. Physical exercise, a non-pharmacological intervention, benefits brain health by increasing BDNF levels, lowering cognitive deficits, and slowing brain degradation. Exercise advantages include increased well-being, reduced depression, improved cognitive skills, and neuroprotection by lowering amyloid accumulation, oxidative stress, and neuroinflammation. This study examines the effects of physical exercise on cognitive-behavioral deficits and BDNF levels in the limbic system impacted by neurodegeneration. The findings highlight the necessity of including exercise into NDD treatment to improve brain structure, function, and total BDNF levels. As research advances, exercise is becoming increasingly acknowledged as an important technique for treating cognitive decline and neurodegenerative disorders.

Can exercise benefits be harnessed with drugs? A new way to combat neurodegenerative diseases by boosting neurogenesis

Adult hippocampal neurogenesis (AHN) is affected by multiple factors, such as enriched environment, exercise, ageing, and neurodegenerative disorders. Neurodegenerative disorders can impair AHN, leading to progressive neuronal loss and cognitive decline. Compelling evidence suggests that individuals engaged in regular exercise exhibit higher production of proteins that are essential for AHN and memory. Interestingly, specific molecules that mediate the effects of exercise have shown effectiveness in promoting AHN and cognition in different transgenic animal models. Despite these advancements, the precise mechanisms by which exercise mimetics induce AHN remain partially understood. Recently, some novel exercise molecules have been tested and the underlying mechanisms have been proposed, involving intercommunications between multiple organs such as muscle-brain crosstalk, liver-brain crosstalk, and gut-brain crosstalk. In this review, we will discuss the current evidence regarding the effects and potential mechanisms of exercise mimetics on AHN and cognition in various neurological disorders. Opportunities, challenges, and future directions in this research field are also discussed.

Adult hippocampal neurogenesis (AHN) controls central nervous system and promotes peripheral nervous system regeneration via physical exercise

Physical exercise has beneficial effects on adult hippocampal neurogenesis (AHN) and cognitive processes, including learning. Although it is not known if anaerobic resistance training and high-intensity interval training, which involve alternating brief bouts of highly intense anaerobic activity with rest periods, have comparable effects on AHN. Also, while less thoroughly investigated, individual genetic diversity in the overall response to physical activity is likely to play a key role in the effects of exercise on AHN. Physical exercise has been shown to improve health on average, although the benefits may vary from person to person, perhaps due to genetic differences. Maximal aerobic capacity and metabolic health may improve significantly with aerobic exercise for some people, while the same amount of training may have little effect on others. This review discusses the AHN's capability for peripheral nervous system (PNS) regeneration and central nervous system (CNS) control via physical exercise. Exercise neurogenicity, effective genes, growth factors, and the neurotrophic factors involved in PNS regeneration and CNS control were discussed. Also, some disorders that could be affected by AHN and physical exercise are summarized.

Age-varying association between depression and cognitive function among a national sample of older U.S. immigrant adults: the potential moderating role of physical activity

OBJECTIVES

This study aimed to (1) investigate age-associated trends in depression and cognition, (2) determine whether the association between depression and cognition varies across age, and (3) test whether this association is moderated by different levels of physical activity among older U.S. immigrant adults aged 60 to 80 years.

METHODS

Using national data on elderly U.S. immigrants (N = 375) from the 2011-2014 NHANES, we employed weighted intercept-only linear time-varying effect modeling (TVEM) and weighted linear TVEM to address our research questions.

RESULTS

Weighted intercept-only linear TVEM indicated no trend in depression, but its mean peaked at age 67. Cognition consistently decreased with age, reaching its lowest point at age 78. Weighted linear TVEM revealed a significant inverse association between depression and cognition at some age ranges, with the strongest association at around age 66. Yet, we did not find the moderational relation of physical activity to this age-varying association.

CONCLUSIONS

Although we observed a significant inverse relationship between depression and cognition at a certain age point, physical activity did not moderate the age-varying association. Understanding of age-varying effects on the depression-cognition interaction will promote prevention efforts targeting aging immigrant populations at highest risk for these health outcomes. Further work is needed to test moderating effects of other health behaviors on this association across age.

Supplemental data for this article is available online at https://doi.org/10.1080/13607863.2022.2056139 .

Targeting hippocampal neurogenesis to protect astronauts' cognition and mood from decline due to space radiation effects

Neurogenesis is an essential, lifelong process during which neural stem cells generate new neurons within the hippocampus, a center for learning, memory, and mood control. Neural stem cells are vulnerable to environmental insults spanning from chronic stress to radiation. These insults reduce their numbers and diminish neurogenesis, leading to memory decline, anxiety, and depression. Preserving neural stem cells could thus help prevent these neurogenesis-associated pathologies, an outcome particularly important for long-term space missions where environmental exposure to radiation is significantly higher than on Earth. Multiple developments, from mechanistic discoveries of radiation injury on hippocampal neurogenesis to new platforms for the development of selective, specific, effective, and safe small molecules as neurogenesis-protective agents hold great promise to minimize radiation damage on neurogenesis. In this review, we summarize the effects of space-like radiation on hippocampal neurogenesis. We then focus on current advances in drug discovery and development and discuss the nuclear receptor TLX/NR2E1 (oleic acid receptor) as an example of a neurogenic target that might rescue neurogenesis following radiation.

RNA-binding protein signaling in adult neurogenesis

The process of neurogenesis in the brain, including cell proliferation, differentiation, survival, and maturation, results in the formation of new functional neurons. During embryonic development, neurogenesis is crucial to produce neurons to establish the nervous system, but the process persists in certain brain regions during adulthood. In adult neurogenesis, the production of new neurons in the hippocampus is accomplished via the division of neural stem cells. Neurogenesis is regulated by multiple factors, including gene expression at a temporal scale and post-transcriptional modifications. RNA-binding Proteins (RBPs) are known as proteins that bind to either double- or single-stranded RNA in cells and form ribonucleoprotein complexes. The involvement of RBPs in neurogenesis is crucial for modulating gene expression changes and posttranscriptional processes. Since neurogenesis affects learning and memory, RBPs are closely associated with cognitive functions and emotions. However, the pathways of each RBP in adult neurogenesis remain elusive and not clear. In this review, we specifically summarize the involvement of several RBPs in adult neurogenesis, including CPEB3, FXR2, FMRP, HuR, HuD, Lin28, Msi1, Sam68, Stau1, Smaug2, and SOX2. To understand the role of these RBPs in neurogenesis, including cell proliferation, differentiation, survival, and maturation as well as posttranscriptional gene expression, we discussed the protein family, structure, expression, functional domain, and region of action. Therefore, this narrative review aims to provide a comprehensive overview of the RBPs, their function, and their role in the process of adult neurogenesis as well as to identify possible research directions on RBPs and neurogenesis.

Noradrenaline activation of hippocampal dopamine D1 receptors promotes antidepressant effects

Dopamine D₁ receptors (D₁Rs) in the hippocampal dentate gyrus (DG) are essential for antidepressant effects. However, the midbrain dopaminergic neurons, the major source of dopamine in the brain, only sparsely project to DG, suggesting possible activation of DG D₁Rs by endogenous substances other than dopamine. We have examined this possibility using electrophysiological and biochemical techniques and found robust activation of D₁Rs in mouse DG neurons by noradrenaline. Noradrenaline at the micromolar range potentiated synaptic transmission at the DG output and increased the phosphorylation of protein kinase A substrates in DG via activation of D₁Rs and β adrenergic receptors. Neuronal excitation preferentially enhanced noradrenaline-induced synaptic potentiation mediated by D₁Rs with minor effects on β-receptor-dependent potentiation. Increased voluntary exercise by wheel running also enhanced noradrenaline-induced, D₁R-mediated synaptic potentiation, suggesting a distinct functional role of the noradrenaline-D₁R signaling. We then examined the role of this signaling in antidepressant effects using mice exposed to chronic restraint stress. In the stressed mice, an antidepressant acting on the noradrenergic system induced a mature-to-immature change in the DG neuron phenotype, a previously proposed cellular substrate for antidepressant action. This effect was evident only in mice subjected to wheel running and blocked by a D₁R antagonist. These results suggest a critical role of noradrenaline-induced activation of D₁Rs in antidepressant effects in DG. Experience-dependent regulation of noradrenaline-D₁R signaling may determine responsiveness to antidepressant drugs in depressive disorders.

Exercise to spot the differences: a framework for the effect of exercise on hippocampal pattern separation in humans

Exercise has a beneficial effect on mental health and cognitive functioning, but the exact underlying mechanisms remain largely unknown. In this review, we focus on the effect of exercise on hippocampal pattern separation, which is a key component of episodic memory. Research has associated exercise with improvements in pattern separation. We propose an integrated framework mechanistically explaining this relationship. The framework is divided into three pathways, describing the pro-neuroplastic, anti-inflammatory and hormonal effects of exercise. The pathways are heavily intertwined and may result in functional and structural changes in the hippocampus. These changes can ultimately affect pattern separation through direct and indirect connections. The proposed framework might guide future research on the effect of exercise on pattern separation in the hippocampus.

A terrifying sound stress inhibits hippocampal neurogenesis in the adult male mice

Stress impairs hippocampal neurogenesis. The traditional animal model of stress contains a mixture of physical and psychological stress factors. This leads to difficulty in the evaluation of the effect of pure psychological stress on neurogenesis. In this study, we investigated the effect of pure psychological stress on hippocampal neurogenesis. The pure psychological stress model and the mixed stress model were carried out by terrifying sound and restraint, respectively. The open field test showed that restraint treatment improved the general locomotor activity levels, while terrifying sound treatment had opposite effects. Compared with a normal condition, both terrifying sound stimulation and restraint treatment significantly decreased the number of BrdU and Ki-67 and reduced the positive rate of SOX2/GFAP in the hippocampus. These phenomena indicated that pure psychological stress could decrease the number of neural stem cells and inhibit cell proliferation in the hippocampus of a mouse. Furthermore, compared with the restraint treatment, the neurotransmitters including norepinephrine (NE), 5-hydroxytryptamine (5-HT), and gamma-aminobutyric acid (GABA) had not been affected drastically by terrifying sound stimulation. Our results suggest that the terrifying sound stimulation can be considered as a novel and effective pure psychological stress animal model for the further research on the hippocampus.

The Effect of Tai Chi Chuan on Emotional Health: Potential Mechanisms and Prefrontal Cortex Hypothesis

Deep involvement in the negative mood over long periods of time likely results in emotional disturbances/disorders and poor mental health. Tai Chi Chuan (TCC) is regarded as a typical mind-body practice combining aerobic exercise and meditation to prevent and treat negative mood. Although there are an increasing number of TCC studies examining anxiety, depression, and mental stress, the mechanisms underlying these negative emotions are not fully understood. This review study examined TCC studies related to emotional health from both clinical patients and healthy individuals. Next, several potential mechanisms from physiological, psychological, and neurological perspectives were evaluated based on direct and indirect research evidence. We reviewed recent functional magnetic resonance imaging studies, which demonstrated changes in brain anatomy and function, mainly in the prefrontal cortex, following TCC practice. Finally, the effects of TCC on emotion/mental health is depicted with a prefrontal cortex hypothesis that proposed “an immune system of the mind” indicating the role of the prefrontal cortex as a flexible hub in regulating an individual's mental health. The prefrontal cortex is likely a key biomarker among the multiple complex neural correlates to help an individual manage negative emotions/mental health. Future research is needed to examine TCC effects on mental health by examining the relationship between the executive control system (mainly prefrontal cortex) and limbic network (including amygdala, insula, and hippocampal gyrus).

L-lactate induces neurogenesis in the mouse ventricular-subventricular zone via the lactate receptor HCA1

AIM

Adult neurogenesis occurs in two major niches in the brain: the subgranular zone of the hippocampal formation and the ventricular-subventricular zone. Neurogenesis in both niches is reduced in ageing and neurological disease involving dementia. Exercise can rescue memory by enhancing hippocampal neurogenesis, but whether exercise affects adult neurogenesis in the ventricular-subventricular zone remains unresolved. Previously, we reported that exercise induces angiogenesis through activation of the lactate receptor HCA1. The aim of the present study is to investigate HCA₁ -dependent effects on neurogenesis in the two main neurogenic niches.

METHODS

Wild-type and HCA₁ knock-out mice received high intensity interval exercise, subcutaneous injections of L-lactate, or saline injections, five days per week for seven weeks. Well-established markers for proliferating cells (Ki-67) and immature neurons (doublecortin), were used to investigate neurogenesis in the subgranular zone and the ventricular-subventricular zone.

RESULTS

We demonstrated that neurogenesis in the ventricular-subventricular zone is enhanced by HCA₁ activation: Treatment with exercise or lactate resulted in increased neurogenesis in wild-type, but not in HCA₁ knock-out mice. In the subgranular zone, neurogenesis was induced by exercise in both genotypes, but unaffected by lactate treatment.

CONCLUSION

Our study demonstrates that neurogenesis in the two main neurogenic niches in the brain is regulated differently: Neurogenesis in both niches was induced by exercise, but only in the ventricular-subventricular zone was neurogenesis induced by lactate through HCA₁ activation. This opens for a role of HCA₁ in the physiological control of neurogenesis, and potentially in counteracting age-related cognitive decline.

Hippocampal volume, function, and related molecular activity in anorexia nervosa: A scoping review

INTRODUCTION

Anorexia nervosa (AN) is a serious and persistent eating disorder, characterized by severe dietary restriction and weight loss, with a third of patients developing a  severe-enduring form. The factors contributing to this progression are poorly understood, although there is evidence for impairments in neural structures such as the hippocampus, an area particularly affected by malnutrition and chronic stress.

AREAS COVERED

This study aimed to map the evidence for alterations in hippocampal volume, function, and related molecular activity in anorexia nervosa. PubMed, PsycINFO, and Web of Science were searched for studies related to hippocampal function and integrity using a range of methodologies, such as neuropsychological paradigms, structural and functional magnetic resonance imaging, and analysis of blood components.

EXPERT OPINION

Thirty-nine studies were included in this review. The majority were neuroimaging studies, which found hippocampus-specific volumetric and functional impairments. Neuropsychological studies showed evidence for a specific memory and learning impairments. There was some evidence for molecular abnormalities (e.g. cortisol), although these were few studies. Taken together, our review suggests that the hippocampus might be a particular region of interest when considering neurobiological approaches to understanding AN. These findings warrant further investigation and may lead to novel treatment approaches.

VEGF and TNF-α Responses to Acute and Chronic Aerobic Exercise in the Patients with Multiple Sclerosis

Background: Aerobic exercise has been shown to decrease the functional disorders related to multiple sclerosis (MS). Nevertheless, the effect of aerobic exercise training on the cytokines and neuroprotective mediators associated with the disease activity has remained relatively unknown. Objectives: The present research was conducted to evaluate the responses of the vascular endothelial growth factor (VEGF) and tumor necrosis factor-alpha (TNF-α) to single-bout and six-week aerobic exercise training in the patients with MS. Methods: Totally, 20 subjects ((n = 10) patients with MS and (n = 10) controls) who were matched in terms of gender, weight, body mass, and age were included in the study. Participants received aerobic exercise training at approximately 60% of VO2max in 30-min sessions 3 times a week for six weeks. Serum concentrations of the VEGF and TNF-α were analyzed pre- and post-exercise training (in the first session and after 18 sessions of the study). Results: Serum concentration of the TNF-α decreased significantly after a single bout and 6-week aerobic exercise training (P = 0.002 and P = 0.005) in the intervention group. Serum concentration of the VEGF increased significantly only after exercise in the first and 18th sessions in the intervention group (P = 0.017 and P = 0.022). Conclusions: Our results revealed that exercise may influence the VEGF regulation in patients with MS. Although, further research is needed to determine the effect of exercise on the immune variables in patients with MS.

The Role of Physical Exercise and Omega-3 Fatty Acids in Depressive Illness in the Elderly

Background:

In adulthood, depression is the most common type of mental illness and will be the second leading cause of disease by 2020. Major depression dramatically affects the function of the central nervous system and degrades the quality of life, especially in old age.

Several mechanisms underlie the pathophysiology of depressive illness, since it has a multifactorial etiology. Human and an-imal studies have demonstrated that depression is mainly associated with imbalances in neurotransmitters and neurotrophins, hypothalamic-pituitary-adrenal axis alterations, brain volume changes, neurogenesis dysfunction, and dysregulation of in-flammatory pathways. Also the gut microbiota may influence mental health outcomes.

Although depression is not a consequence of normal aging, depressive disorders are common in later life, even if often undi-agnosed or mis-diagnosed in old age. When untreated, depression reduces life expectancy, worsens medical illnesses, en-hances health care costs and is the primary cause of suicide among older people. To date, the underpinnings of depression in the elderly are still to be understood, and the pharmacological treatment is the most commonly used therapy.

Objective:

Since a sedentary lifestyle and poor eating habits have recently emerged as crucial contributors to the genesis and course of depression, in the present review, we have focused on the effects of physical activity and omega-3 fatty acids on depressive illness in the elderly.

Results:

A growing literature indicates that both exercise and dietary interventions can promote mental health throughout one’s lifespan.

Conclusion:

There thus emerges the awareness that an active lifestyle and a balanced diet may constitute valid low-cost pre-vention strategies to counteract depressive illness in the elderly.

Whole body vibration added to treatment as usual is effective in adolescents with depression: a partly randomized, three-armed clinical trial in inpatients

There is growing evidence for the effectiveness of exercise in the treatment of adult major depression. With regard to adolescents, clinical trials are scarce. Due to the inherent symptoms of depression (lack of energy, low motivation to exercise), endurance training forms could be too demanding especially in the first weeks of treatment. We hypothesized that an easy-to-perform passive muscular training on a whole body vibration (WBV) device has equal anti-depressive effects compared to a cardiovascular training, both administered as add-ons to treatment as usual (TAU). Secondly, we presumed that both exercise interventions would be superior in their response, compared to TAU. In 2 years 64 medication-naïve depressed inpatients aged 13-18, were included. Both exercise groups fulfilled a supervised vigorous training for 6 weeks. Depressive symptoms were assessed by self-report ("Depressions Inventar für Kinder und Jugendliche"-DIKJ) before intervention and after weeks 6, 14 and 26. Compared to TAU, both groups responded earlier and more strongly measured by DIKJ scores, showing a trend for the WBV group after week 6 (p = 0.082). The decrease became statistically significant for both intervention groups after week 26 (p = 0.037 for ergometer and p = 0.042 for WBV). Remission rates amounted to 39.7% after week 6 and 66% after week 26, compared to 25% after week 26 in TAU. These results provide qualified support for the effectiveness of exercise as add-on treatment for medication-naïve depressed adolescents. The present results are limited by the not randomized control group.

Executive Control Mediates the Association Between Aerobic Fitness and Emotion Regulation in Preadolescent Children

Objective

This study evaluated direct and indirect associations between aerobic fitness, executive control, and emotion regulation among a community sample of preadolescent children.

Methods

Two-hundred and seventy-eight children aged 8-12 years completed measures of aerobic fitness (Progressive Aerobic Cardiovascular Endurance Run) and executive control (Stroop Test). Parents completed questionnaires assessing child emotion regulation and executive control (Emotion Regulation Checklist; Early Adolescent Temperament Questionnaire). We evaluated associations between these constructs using structural equation modeling.

Results

Study findings supported a moderate direct association between childhood aerobic fitness and executive control, a strong direct negative association between executive control and emotion regulation, and a moderate indirect association between aerobic fitness and emotion regulation through executive control.

Conclusions

These findings provide preliminary evidence that executive control functions as a mediator between aerobic fitness and emotion regulation and may help explain the mechanism by which aerobic exercise influences emotional well-being among preadolescent children.

Nutritional Factors Affecting Adult Neurogenesis and Cognitive Function

Adult neurogenesis, a complex process by which stem cells in the hippocampal brain region differentiate and proliferate into new neurons and other resident brain cells, is known to be affected by many intrinsic and extrinsic factors, including diet. Neurogenesis plays a critical role in neural plasticity, brain homeostasis, and maintenance in the central nervous system and is a crucial factor in preserving the cognitive function and repair of damaged brain cells affected by aging and brain disorders. Intrinsic factors such as aging, neuroinflammation, oxidative stress, and brain injury, as well as lifestyle factors such as high-fat and high-sugar diets and alcohol and opioid addiction, negatively affect adult neurogenesis. Conversely, many dietary components such as curcumin, resveratrol, blueberry polyphenols, sulforaphane, salvionic acid, polyunsaturated fatty acids (PUFAs), and diets enriched with polyphenols and PUFAs, as well as caloric restriction, physical exercise, and learning, have been shown to induce neurogenesis in adult brains. Although many of the underlying mechanisms by which nutrients and dietary factors affect adult neurogenesis have yet to be determined, nutritional approaches provide promising prospects to stimulate adult neurogenesis and combat neurodegenerative diseases and cognitive decline. In this review, we summarize the evidence supporting the role of nutritional factors in modifying adult neurogenesis and their potential to preserve cognitive function during aging.

Contribution of neuroinflammation and immunity to brain aging and the mitigating effects of physical and cognitive interventions

It is widely accepted that the brain and the immune system continuously interact during normal as well as pathological functioning. Human aging is commonly accompanied by low-grade inflammation in both the immune and central nervous systems, thought to contribute to many age-related diseases. This review of the current literature focuses first on the normal neuroimmune interactions occurring in the brain, which promote learning, memory and neuroplasticity. Further, we discuss the protective and dynamic role of barriers to neuroimmune interactions, which have become clearer with the recent discovery of the meningeal lymphatic system. Next, we consider age-related changes of the immune system and possible deleterious influences of immunosenescence and low-grade inflammation (inflammaging) on neurodegenerative processes in the normally aging brain. We survey the major immunomodulators and neuroregulators in the aging brain and their highly tuned dynamic and reciprocal interactions. Finally, we consider our current understanding of how physical activity, as well as a combination of physical and cognitive interventions, may mediate anti-inflammatory effects and thus positively impact brain aging.

Walking away from depression-motor activity increases ratings of mood and incentive drive in patients with major depression

Reduced motor activity is associated with depression. Lewinsohn's cognitive behavioural model of depression assumes a lack of positive experience due to a reduced level of activity as a key aspect of depression. The acute relationship between motor activity and mood as well as between motor activity and incentive drive (the motivation to engage in activities) is unknown. An augmentation of mood and incentive drive could precede or follow motor activity. We examined (1) whether motor activity would be correlated with the course of depression and (2) the temporal relationship between motor activity and acute changes in mood and incentive drive. Motor activity was measured with actigraphy in 12 patients with depression for one week. Severity of depression was assessed before and at the end of the study with depression rating scales. The patients reported mood and incentive drive once per hour. With lag sequential analysis, the temporal relationship between motor activity and mood and incentive drive was evaluated. Higher motor activity was associated with depression improvement. Motor activity had an acute association with mood and incentive drive, especially one hour after activity. The results support the Lewinsohn's model of depression and underline the impact of behavioural activation in antidepressant treatment.

Spatial learning and neurogenesis: Effects of cessation of wheel running and survival of novel neurons by engagement in cognitive tasks

Physical exercise stimulates cell proliferation in the adult dentate gyrus and facilitates acquisition and/or retention of hippocampal-dependent tasks. It is established that regular physical exercise improves cognitive performance. However, it is unclear for how long these benefits last after its interruption. Independent groups of rats received both free access to either unlocked (EXE Treatment) or locked (No-EXE Treatment) running wheels for 7 days, and daily injections of bromodeoxyuridine (BrdU) in the last 3 days. After a time delay period of either 1, 3, or 6 weeks without training, the animals were tested in the Morris water maze (MWM) either in a working memory task dependent on hippocampal function (MWM-HD) or in a visible platform searching task, independent on hippocampal function (MWM-NH). Data confirmed that exposure of rats to 7 days of spontaneous wheel running increases cell proliferation and neurogenesis. In contrast, neurogenesis was not accompanied by significant improvements of performance in the working memory version of the MWM. Longer time delays between the end of exercise and the beginning of cognitive training in the MWM resulted in lower cell survival; that is, the number of novel surviving mature neurons was decreased when this delay was 6 weeks as compared with when it was 1 week. In addition, data showed that while exposure to the MWM-HD working memory task substantially increased survival of novel neurons, exposure to the MWM-NH task did not, thus indicating that survival of novel dentate gyrus neurons depends on the engagement of this brain region in performance of cognitive tasks. © 2015 Wiley Periodicals, Inc.

Association Between Objectively Measured Physical Activity and Cognitive Function in Older Adults-The Reasons for Geographic and Racial Differences in Stroke Study

OBJECTIVES

To examine the relationship between objectively measured physical activity (PA) and cognitive function in white and black older adults.

DESIGN

Cross-sectional.

SETTING

REasons for Geographic and Racial Differences in Stroke (REGARDS) study.

PARTICIPANTS

Older adults who provided valid data from accelerometer and cognitive function tests (N = 7,098).

MEASUREMENTS

Accelerometers provided estimates of PA variables for 4 to 7 consecutive days. PA cut-points of 50 counts per minute (cpm) and 1,065 cpm were applied to differentiate between being sedentary and light PA and between light and moderate to vigorous PA (MVPA), respectively. Prevalence of cognitive impairment was defined using the Six-Item Screener (<4/6). Letter fluency, animal fluency, word list learning, and Montreal Cognitive Assessment (orientation and recall) were used to assess memory and executive function.

RESULTS

Of 7,098 participants (aged 70.1 ± 8.5, 54.2% female, 31.5% black), 359 (5.1%) had impaired cognition within ±12 months of PA measurement. The average proportion of time spent in MVPA (MVPA%) was 1.4 ± 1.9%. Participants in the highest quartile of MVPA% (~258.3 min/wk) were less likely to be cognitively impaired than those in the lowest quartile (odds ratio = 0.65, 95% confidence interval = 0.43-0.97). MVPA% was also significantly associated with executive function and memory z-scores (P < .001). Similar analyses of proportion of time spent in light PA (LPA%) and sedentary time (ST%) showed no significant associations with cognitive function.

CONCLUSION

Higher levels of objectively measured MVPA%, rather than LPA% or ST%, were associated with lower prevalence of cognitive impairment and better performance in memory and executive function in aging people. The amount of MVPA associated with lower prevalence of cognitive impairment is consistent with meeting PA guidelines.

Involvement of Adult Hippocampal Neurogenesis in Learning and Forgetting

Adult hippocampal neurogenesis is a process involving the continuous generation of newborn neurons in the hippocampus of adult animals. Mounting evidence has suggested that hippocampal neurogenesis contributes to some forms of hippocampus-dependent learning and memory; however, the detailed mechanism concerning how this small number of newborn neurons could affect learning and memory remains unclear. In this review, we discuss the relationship between adult-born neurons and learning and memory, with a highlight on recently discovered potential roles of neurogenesis in pattern separation and forgetting.

Inducible knockout of Mef2a, -c, and -d from nestin-expressing stem/progenitor cells and their progeny unexpectedly uncouples neurogenesis and dendritogenesis in vivo

Myocyte enhancer factor (Mef)-2 transcription factors are implicated in activity-dependent neuronal processes during development, but the role of MEF2 in neural stem/progenitor cells (NSPCs) in the adult brain is unknown. We used a transgenic mouse in which Mef2a, -c, and -d were inducibly deleted in adult nestin-expressing NSPCs and their progeny. Recombined cells in the hippocampal granule cell layer were visualized and quantified by yellow fluorescent protein (YFP) expression. In control mice, postmitotic neurons expressed Mef2a, -c, and -d, whereas type 1 stem cells and proliferating progenitors did not. Based on this expression, we hypothesized that Mef2a, -c, and -d deletion in adult nestin-expressing NSPCs and their progeny would result in fewer mature neurons. Control mice revealed an increase in YFP(+) neurons and dendrite formation over time. Contrary to our hypothesis, inducible Mef2 KO mice also displayed an increase in YFP(+) neurons over time-but with significantly stunted dendrites-suggesting an uncoupling of neuron survival and dendritogenesis. We also found non-cell-autonomous effects after Mef2a, -c, and -d deletion. These in vivo findings indicate a surprising functional role for Mef2a, -c, and -d in cell- and non-cell-autonomous control of adult hippocampal neurogenesis that is distinct from its role during development.

Exercise-based treatments for substance use disorders: evidence, theory, and practicality

BACKGROUND

Epidemiological studies reveal that individuals who report risky substance use are generally less likely to meet physical activity guidelines (with the exception of certain population segments, such as adolescents and athletes). A growing body of evidence suggests that individuals with substance use disorders (SUDs) are interested in exercising and that they may derive benefits from regular exercise, in terms of both general health/fitness and SUD recovery.

OBJECTIVES

The aims of this paper were to: (i) summarize the research examining the effects of exercise-based treatments for SUDs; (ii) discuss the theoretical mechanisms and practical reasons for investigating this topic; (iii) identify the outstanding relevant research questions that warrant further inquiry; and (iv) describe potential implications for practice.

METHODS

The following databases were searched for peer-reviewed original and review papers on the topic of substance use and exercise: PubMed Central, MEDLINE, EMBASE, PsycINFO, and CINAHL Plus. Reference lists of these publications were subsequently searched for any missed but relevant manuscripts. Identified papers were reviewed and summarized by both authors.

RESULTS

The limited research conducted suggests that exercise may be an effective adjunctive treatment for SUDs. In contrast to the scarce intervention trials to date, a relative abundance of literature on the theoretical and practical reasons supporting the investigation of this topic has been published.

CONCLUSIONS

Definitive conclusions are difficult to draw due to diverse study protocols and low adherence to exercise programs, among other problems. Despite the currently limited and inconsistent evidence, numerous theoretical and practical reasons support exercise-based treatments for SUDs, including psychological, behavioral, neurobiological, nearly universal safety profile, and overall positive health effects.

Physical exercise-induced adult neurogenesis: a good strategy to prevent cognitive decline in neurodegenerative diseases?

Cumulative evidence has indicated that there is an important role for adult hippocampal neurogenesis in cognitive function. With the increasing prevalence of cognitive decline associated with neurodegenerative diseases among the ageing population, physical exercise, a potent enhancer of adult hippocampal neurogenesis, has emerged as a potential preventative strategy/treatment to reduce cognitive decline. Here we review the functional role of adult hippocampal neurogenesis in learning and memory, and how this form of structural plasticity is altered in neurodegenerative diseases known to involve cognitive impairment. We further discuss how physical exercise may contribute to cognitive improvement in the ageing brain by preserving adult neurogenesis, and review the recent approaches for measuring changes in neurogenesis in the live human brain.

Cardiovascular fitness in early adulthood and future suicidal behaviour in men followed for up to 42 years

BACKGROUND

Cardiovascular fitness influences many aspects of brain function. However, the relationship between cardiovascular fitness and suicidal behaviour is unknown. Therefore, we aimed to determine whether cardiovascular fitness at age 18 years is associated with future risk of suicide attempt/death.

METHOD

We performed a population-based Swedish longitudinal cohort study of male conscripts with no previous or ongoing mental illness (n = 1,136,527). The conscription examination, which took place during 1968-2005, included the cycle ergonometric test and tests of cognitive performance. Future risk of suicide attempt/death over a 5- to 42-year follow-up period was calculated with Cox proportional hazards models controlling for several confounders including familial factors.

RESULTS

At least one suicide attempt was recorded for 12,563 men. Death by suicide without a prior attempt was recorded in 4814 additional individuals. In fully adjusted models low cardiovascular fitness was associated with increased risk for future attempt/death by suicide [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.64-1.94]. The HR changed only marginally after exclusion of persons who received in-patient care for depression (HR 1.76, 95% CI 1.61-1.94). Poor performance on both the cardiovascular fitness and cognitive tests was associated with a fivefold increased risk of suicide attempt or suicide death (HR 5.46, 95% CI 4.78-6.24).

CONCLUSIONS

Lower cardiovascular fitness at age 18 years was, after adjustment for a number of potential confounders, associated with an increased risk of attempt/death by suicide in adulthood. It remains to be clarified whether interventions designed to improve fitness in teens can influence the risk of suicidal behaviour later in life.

Adult neurogenesis and dendritic remodeling in hippocampal plasticity: which one is more important?

Accumulating knowledge has shown that a decrease in hippocampal neurogenesis is linked to the pathophysiology of mood disorders and some hippocampal-dependent learning and memory tasks. The role of adult neurogenesis has initially been proposed based on correlations between decreases or increases in neurogenesis and impairments or improvements, respectively, in animal behaviors following interventions. Its role has been further elucidated through the ablation of neurogenesis. However, the functional roles of neurogenesis in hippocampal-dependent behaviors have been challenged by inconsistent findings between different studies. Despite the fact that factors affecting neurogenesis also induce dendritic or synaptic changes in newborn or existing neurons, these two aspects of structural changes within the hippocampus have always been examined separately. Thus, it is difficult to interpret the functional role of adult neurogenesis or dendritic remodification in hippocampal-dependent behaviors. This review discusses the relative contribution of adult neurogenesis and dendritic/synaptic remodeling of existing neurons to hippocampal plasticity.

Aerobic exercise interacts with neurotrophic factors to predict cognitive functioning in adolescents

Recent findings have suggested that aerobic exercise may have a positive effect on brain functioning, in addition to its well-recognized beneficial effects on human physiology. This study confirmed the cognitive effects of aerobic exercise on the human brain. It also examined the relationships between exercise and the serum levels of neurotrophic factors (BDNF, IGI-1, and VEGF). A total of 91 healthy teens who exercised regularly participated in this study. A between-group design was adopted to compare cognitive functioning subserved by the frontal and temporal brain regions and the serum levels of neurotrophic factors between 45 regular exercisers and 46 matched controls. The exercisers performed significantly better than the controls on the frontal and temporal functioning parameters measured. This beneficial cognitive effect was region-specific because no such positive cognitive effect on task-tapping occipital functioning was observed. With respect to the serum levels of the neurotrophic factors, a negative correlation between neurotrophic factors (BDNF and VEGF) with frontal and medial-temporal lobe function was revealed. Furthermore, the levels of BDNF and VEGF interacted with exercise status in predicting frontal and temporal lobe function. This is the first report of the interaction effects of exercise and neurotrophic factors on cognitive functioning. Herein, we report preliminary evidence of the beneficial effects of regular aerobic exercise in improving cognitive functions in teens. These beneficial effects are region-specific and are associated with the serum levels of neurotrophic factors. Our findings lay the path for future studies looking at ways to translate these beneficial effects to therapeutic strategies for adolescents.

Voluntary exercise followed by chronic stress strikingly increases mature adult-born hippocampal neurons and prevents stress-induced deficits in 'what-when-where' memory

We investigated whether voluntary exercise prevents the deleterious effects of chronic stress on episodic-like memory and adult hippocampal neurogenesis. After bromodeoxyuridine (BrdU) administration, mice were assigned to receive standard housing, chronic intermittent restraint stress, voluntary exercise or a combination of both (stress starting on the seventh day of exercise). Twenty-four days later, mice were tested in a 'what-when-where' object recognition memory task. Adult hippocampal neurogenesis (proliferation, differentiation, survival and apoptosis) and c-Fos expression in the hippocampus and extra-hippocampal areas (medial prefrontal cortex, amygdala, paraventricular hypothalamic nucleus, accumbens and perirhinal cortex) were assessed after behavior. Chronic intermittent restraint stress impaired neurogenesis and the 'when' memory, while exercise promoted neurogenesis and improved the 'where' memory. The 'when' and 'where' memories correlated with c-Fos expression in CA1 and the dentate gyrus, respectively. Furthermore, analysis suggested that each treatment induced a distinct pattern of functional connectivity among the areas analyzed for c-Fos. In the animals in which stress and exercise were combined, stress notably reduced the amount of voluntary exercise performed. Nevertheless, exercise still improved memory and counteracted the stress induced-deficits in neurogenesis and behavior. Interestingly, compared with the other three treatments, the stressed exercising animals showed a larger increase in cell survival, the maturation of new neurons and apoptosis in the dentate gyrus, with a considerable increase in the number of 24-day-old BrdU+cells that differentiated into mature neurons. The interaction between exercise and stress in enhancing the number of adult-born hippocampal neurons supports a role of exercise-induced neurogenesis in stressful conditions.

Exercise-based smoking cessation interventions among women

Although smoking rates are lower among women than men, women are less likely to quit smoking in cessation trials. This is in part due to their tendency to smoke to help prevent or mitigate negative mood/affect, depression and/or postcessation weight gain. Exercise helps to alleviate women's fear of postcessation weight gain and reduces their cessation-related mood symptoms, making it a theoretically ideal smoking cessation intervention for women. In addition, short bouts of exercise decrease cigarette cravings and withdrawal symptoms among temporarily abstinent smokers. However, results from exercise-based smoking cessation interventions to date have been mostly nonsignificant. This paper describes the theoretical mechanisms (psychological, behavioral, physiological and neurobiological) and practical reasons underlying our belief that exercise-based smoking cessation interventions should not yet be abandoned despite their current paucity of supporting evidence. It also presents ideas for modifying future exercise-based smoking cessation interventions to increase adherence and, as a result, more accurately evaluate the effect of exercise on smoking cessation.

Ghrelin, neuropeptide Y, and other feeding-regulatory peptides active in the hippocampus: role in learning and memory

The hippocampus is a brain region of primary importance for neurogenesis, which occurs during early developmental states as well as during adulthood. Increases in neuronal proliferation and in neuronal death with age have been associated with drastic changes in memory and learning. Numerous neurotransmitters are involved in these processes, and some neuropeptides that mediate neurogenesis also modulate feeding behavior. Concomitantly, feeding peptides, which act primarily in the hypothalamus, are also present in the hippocampus. This review aims to ascertain the role of several important feeding peptides in cognitive functions, either through their local synthesis in the hippocampus or through their actions via specific receptors in the hippocampus. A link between neurogenesis and the orexigenic or anorexigenic properties of feeding peptides is discussed.

Exercise in the treatment of major depression: a systematic review grading the quality of evidence

OBJECTIVE

To examine the quality of evidence for exercise in the treatment of major depression, comparing specific study types; aerobic exercise vs. antidepressants, aerobic exercise vs. any physical activity, and aerobic exercise as augmentation therapy to treatment as usual vs. treatment as usual.

METHODS

Electronic searches for randomized controlled studies, reporting on treatment outcome in adults with major depression confirmed by a clinical interview. Quality of evidence was assessed using the Grading and Recommendations Assessment, Development and Evaluation and an additional risk of bias-protocol.

RESULTS

Fourteen eligible studies were retrieved, of which nine had low risk of bias. We found moderate quality of evidence that aerobic exercise has no significant effect compared to antidepressants. We found moderate quality of evidence that aerobic exercise at a moderate to high intensity has no significant effect compared to other forms of physical activity. We found low quality of evidence that exercise as augmentation to treatment as usual has a small effect - depression scores were on average 0.44 of a standard deviation lower - compared to treatment as usual.

CONCLUSION

In general, exercise appears to be beneficial in the treatment of depression when used in combination with medication. A significant issue that is not well addressed in previous studies is the risks associated with exercise. Further, this review indicates that aerobic exercise is not more effective than other types of physical activity, pointing to a need to further investigate active components.

Exercise benefits brain function: the monoamine connection

The beneficial effects of exercise on brain function have been demonstrated in animal models and in a growing number of clinical studies on humans. There are multiple mechanisms that account for the brain-enhancing effects of exercise, including neuroinflammation, vascularization, antioxidation, energy adaptation, and regulations on neurotrophic factors and neurotransmitters. Dopamine (DA), noradrenaline (NE), and serotonin (5-HT) are the three major monoamine neurotransmitters that are known to be modulated by exercise. This review focuses on how these three neurotransmitters contribute to exercise affecting brain function and how it can work against neurological disorders.

Neuroplastic changes in depression: a role for the immune system

Accumulating evidence suggests that there is a rich cross-talk between the neuroimmune system and neuroplasticity mechanisms under both physiological conditions and pathophysiological conditions in depression. Anti-neuroplastic changes which occur in depression include a decrease in proliferation of neural stem cells (NSCs), decreased survival of neuroblasts and immature neurons, impaired neurocircuitry (cortical-striatal-limbic circuits), reduced levels of neurotrophins, reduced spine density and dendritic retraction. Since both humoral and cellular immune factors have been implicated in neuroplastic processes, in this review we present a model suggesting that neuroplastic processes in depression are mediated through various neuroimmune mechanisms. The review puts forward a model in that both humoral and cellular neuroimmune factors are involved with impairing neuroplasticity under pathophysiological conditions such as depression. Specifically, neuroimmune factors including interleukin (IL)-1, IL-6, tumour necrosis factor (TNF)-α, CD4⁺CD25⁺T regulatory cells (T reg), self-specific CD4⁺T cells, monocyte-derived macrophages, microglia and astrocytes are shown to be vital to processes of neuroplasticity such as long-term potentiation (LTP), NSC survival, synaptic branching, neurotrophin regulation and neurogenesis. In rodent models of depression, IL-1, IL-6 and TNF are associated with reduced hippocampal neurogenesis; mechanisms which are associated with this include the stress-activated protein kinase (SAPK)/Janus Kinase (JNK) pathway, hypoxia-inducible factors (HIF)-1α, JAK-Signal Transducer and Activator of Transcription (STAT) pathway, mitogen-activated protein kinase (MAPK)/cAMP responsive element binding protein (CREB) pathway, Ras-MAPK, PI-3 kinase, IKK/nuclear factor (NF)-κB and TGFβ activated kinase-1 (TAK-1). Neuroimmunological mechanisms have an active role in the neuroplastic changes associated with depression. Since therapies in depression, including antidepressants (AD), omega-3 polyunsaturated fatty acids (PUFAs) and physical activity exert neuroplasticity-enhancing effects potentially mediated by neuroimmune mechanisms, the immune system might serve as a promising target for interventions in depression.

Neuroimmunological effects of physical exercise in depression

The search for an extended understanding of the causes of depression, and for the development of additional effective treatments is highly significant. Clinical and pre-clinical studies suggest stress is a key mediator in the pathophysiology of depression. Exercise is a readily available therapeutic option, effective as a first-line treatment in mild to moderate depression. In pre-clinical models exercise attenuates stress-related depression-like behaviours. Cellular and humoral neuroimmune mechanisms beyond inflammation and oxidative stress are highly significant in understanding depression pathogenesis. The effects of exercise on such mechanisms are unclear. When clinical and pre-clinical data is taken together, exercise may reduce inflammation and oxidation stress via a multitude of cellular and humoral neuroimmune changes. Astrocytes, microglia and T cells have an antiinflammatory and neuroprotective functions via a variety of mechanisms. It is unknown whether exercise has effects on specific neuroimmune markers implicated in the pathogenesis of depression such as markers of immunosenescence, B or T cell reactivity, astrocyte populations, self-specific CD4+ T cells, T helper 17 cells or T regulatory cells.

Neurological disorders and the potential role for stem cells as a therapy

Introduction Neurological disorders are routinely characterized by loss of cells in response to an injury or a progressive insult. Stem cells could therefore be useful to treat these disorders. Sources of data Pubmed searches of recent literature. Areas of agreement Stem cells exhibit proliferative capacity making them ideally suited for replacing dying cells. However, instead of cell replacement therapy stem cell transplants frequently appear to work via neurotrophic factor release, immunomodulation and upregulation of endogenous stem cells. Areas of controversy and areas timely for developing research Many questions remain with respect to the use of stem cells as a therapy, the answers to which will vary depending on the disorder to be treated and mode of action. Whereas the potential tumorigenic capability of stem cells is a concern, most studies do not support this notion. Further determination of the optimal cell type, and whether to perform allogeneic or autologous transplants warrant investigation before the full potential of stem cells can be realized. In addition, the use of stem cells to develop disease models should not be overlooked.