Reversal of glial and neurovascular markers of unhealthy brain aging by exercise in middle-aged female mice

Vascular dysfunction in Alzheimer's disease: Exploring the potential of aerobic and resistance exercises as therapeutic strategies

Alzheimer's disease (AD) is the leading cause of morbidity and mortality worldwide, as a result of cognitive decline and neurological dysfunction. In AD, reduced cerebral blood flow and impaired vascularization result from capillary bed degeneration and decreased angiogenesis, as observed in both patients and animal models. Physical exercise is recognized as a potential intervention to delay AD progression and reduce disease risk. While most studies have focused on the benefits of aerobic exercise (AE), emerging evidence suggests that resistance exercise (RE) also exerts positive effects on overall health and cognitive function in aging and AD. However, a notable gap in knowledge remains regarding the effects of RE on cerebral blood flow and vascular structure. This review explores the processes by which AE and RE influence brain vascularization in aging and AD, including blood flow, endothelial function, angiogenesis and neurotrophic factor levels. Based on pre-clinical and clinical studies, we conclude that both AE and RE contribute to improved cerebral blood flow and vascular function, promoting vascular repair in the aging and AD-affected brain. By examining the relationship between exercise modalities and brain vascularization, this review expands knowledge regarding the processes underlying the neuroprotective effects of exercise in neurodegenerative and aging conditions.

Cognitive and sensorimotor benefits of moderate- and high-intensity exercise are associated with specific expression of neurotrophic markers in older rats

Endurance training is strongly recommended for older adults to maintain cognitive and motor function. The respective effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on improving behavioural function and cerebral plasticity remain unknown. The purpose of this study was to determine the relative effects of 4 weeks of MICT and HIIT training on endurance, sensorimotor, and cognitive performance, as well as on the expression of neurotrophic markers in the hippocampus and cerebral cortex in aged rats. Twenty-two old male Wistar rats were assigned to one of the following groups: MICT (n = 7), HIIT (n = 6), and Control (n = 9). Incremental treadmill exercise tests, the forelimb grip strength test, the adhesive removal test, and the novel object recognition test were performed. Cerebral cortex and hippocampus were then removed for ELISA and Western blot measurements. The results showed similar benefits of MICT and HIIT on sensorimotor and cognitive functions, and a greater benefit of HIIT on endurance performance. HIIT and MICT differentially promoted cortical and hippocampal neurotrophic markers, demonstrating their complementarity. However, MICT was found to be more effective in promoting a broader range of markers, suggesting its potential as an initial training strategy for older adults.

Effects of exercise on patients with vascular cognitive impairment based on ACSM recommendations: a systematic review of randomized controlled trials

BACKGROUND

Exercise is considered to be an effective method for functional recovery in patients with vascular cognitive impairment (VCI), but there is a paucity of research on exercise dosage. There has been no meta-analysis of the effects of exercise therapy for vascular cognitive impairment based on the American College of Sports Medicine (ACSM) exercise prescription for a seemingly healthy population. We therefore conducted a study to analyze the effects of various exercise therapies on cognitive functioning, physical functioning, and ability to perform activities of daily living in patients diagnosed with vascular cognitive impairment.

METHODS

Four electronic databases, namely PubMed, Embase, Web of Science, and Cochrane, were systematically searched for studies examining the effects of exercise on patients with VCI. The exercise interventions were categorized into an ACSM high adherence group versus an ACSM low or indeterminate adherence group, following the recommendations for exercise testing and prescribing for seemingly healthy populations developed by ACSM. Meta-analyses were conducted using a random effects model to compare results among subgroups.

RESULTS

The study encompassed 14 trials involving 1333 subjects. Among these, 8 studies adhered highly to ACSM recommendations, while 6 studies demonstrated low or uncertain adherence. Subgroup analyses revealed differing effects: in the high adherence group, SMDs for cognitive functioning, living ability, and physical functioning were 0.53 (95% CI 0.13-0.94), 0.53 (95% CI 0.11-0.94), and 0.66 (95% CI 0.45-0.87), respectively. Conversely, in the low or indeterminate adherence group, SMDs for cognitive functioning, living ability, and physical functioning were 0.09 (95% CI - 0.13 to 0.32), - 0.11 (95% CI - 0.57 to 0.34), and 0.65 (95% CI - 0.04 to 1.35). We performed subgroup analyses by type of vascular cognitive impairment, and meta-analyses showed positive SMDs of 0.59 (95% CI 0.22-0.97) and 0.68 (95% CI 0.47-0.90) for exercise on cognitive impairment after stroke in terms of cognitive function and physical function, respectively.

CONCLUSION

The results suggest that exercise interventions exhibiting high adherence to ACSM guidelines yield more favorable outcomes concerning cognitive functioning, physical functioning, and daily living abilities among patients with VCI compared to interventions with low or uncertain adherence to ACSM recommendations.

Differential Glial Response and Neurodegenerative Patterns in CA1, CA3, and DG Hippocampal Regions of 5XFAD Mice

In this study, the distinct patterns of glial response and neurodegeneration within the CA1, CA3, and dentate gyrus (DG) regions of the hippocampus were examined in 5XFAD mice at 6 and 12 months of age. The primary feature of this transgenic mouse model is the rapid onset of amyloid pathology. We employed quantitative assessments via immunohistochemistry, incorporating double staining techniques, followed by observation with light microscopy and subsequent digital analysis of microscopic images. We identified significantly increased Aβ deposition in these three hippocampal regions at 6 and 12 months of transgenic mice. Moreover, the CA1 and CA3 regions showed higher vulnerability, with signs of reactive astrogliosis such as increased astrocyte density and elevated GFAP expression. Additionally, we observed a significant rise in microglia density, along with elevated inflammatory markers (TNFα) in these hippocampal regions. These findings highlight a non-uniform glial and neuronal response to Aβ plaque deposition within the hippocampal regions of 5xFAD mice, potentially contributing to the neurodegenerative and memory deficit characteristics of Alzheimer's disease in this model.

Spatiotemporal transcriptomic profiling and modeling of mouse brain at single-cell resolution reveals cell proximity effects of aging and rejuvenation

Old age is associated with a decline in cognitive function and an increase in neurodegenerative disease risk1. Brain aging is complex and accompanied by many cellular changes2-20. However, the influence that aged cells have on neighboring cells and how this contributes to tissue decline is unknown. More generally, the tools to systematically address this question in aging tissues have not yet been developed. Here, we generate spatiotemporal data at single-cell resolution for the mouse brain across lifespan, and we develop the first machine learning models based on spatial transcriptomics ('spatial aging clocks') to reveal cell proximity effects during brain aging and rejuvenation. We collect a single-cell spatial transcriptomics brain atlas of 4.2 million cells from 20 distinct ages and across two rejuvenating interventions-exercise and partial reprogramming. We identify spatial and cell type-specific transcriptomic fingerprints of aging, rejuvenation, and disease, including for rare cell types. Using spatial aging clocks and deep learning models, we find that T cells, which infiltrate the brain with age, have a striking pro-aging proximity effect on neighboring cells. Surprisingly, neural stem cells have a strong pro-rejuvenating effect on neighboring cells. By developing computational tools to identify mediators of these proximity effects, we find that pro-aging T cells trigger a local inflammatory response likely via interferon-γ whereas pro-rejuvenating neural stem cells impact the metabolism of neighboring cells possibly via growth factors (e.g. vascular endothelial growth factor) and extracellular vesicles, and we experimentally validate some of these predictions. These results suggest that rare cells can have a drastic influence on their neighbors and could be targeted to counter tissue aging. We anticipate that these spatial aging clocks will not only allow scalable assessment of the efficacy of interventions for aging and disease but also represent a new tool for studying cell-cell interactions in many spatial contexts.

Exploring Successful Cognitive Aging: Insights Regarding Brain Structure, Function, and Demographics

In the realm of cognitive science, the phenomenon of "successful cognitive aging" stands as a hallmark of individuals who exhibit cognitive abilities surpassing those of their age-matched counterparts. However, it is paramount to underscore a significant gap in the current research, which is marked by a paucity of comprehensive inquiries that deploy substantial sample sizes to methodically investigate the cerebral biomarkers and contributory elements underpinning this cognitive success. It is within this context that our present study emerges, harnessing data derived from the UK Biobank. In this study, a highly selective cohort of 1060 individuals aged 65 and above was meticulously curated from a larger pool of 17,072 subjects. The selection process was guided by their striking cognitive resilience, ascertained via rigorous evaluation encompassing both generic and specific cognitive assessments, compared to their peers within the same age stratum. Notably, the cognitive abilities of the chosen participants closely aligned with the cognitive acumen commonly observed in middle-aged individuals. Our study leveraged a comprehensive array of neuroimaging-derived metrics, obtained from three Tesla MRI scans (T1-weighted images, dMRI, and resting-state fMRI). The metrics included image-derived phenotypes (IDPs) that addressed grey matter morphology, the strength of brain network connectivity, and the microstructural attributes of white matter. Statistical analyses were performed employing ANOVA, Mann-Whitney U tests, and chi-square tests to evaluate the distinctive aspects of IDPs pertinent to the domain of successful cognitive aging. Furthermore, these analyses aimed to elucidate lifestyle practices that potentially underpin the maintenance of cognitive acumen throughout the aging process. Our findings unveiled a robust and compelling association between heightened cognitive aptitude and the integrity of white matter structures within the brain. Furthermore, individuals who exhibited successful cognitive aging demonstrated markedly enhanced activity in the cerebral regions responsible for auditory perception, voluntary motor control, memory retention, and emotional regulation. These advantageous cognitive attributes were mirrored in the health-related lifestyle choices of the surveyed cohort, characterized by elevated educational attainment, a lower incidence of smoking, and a penchant for moderate alcohol consumption. Moreover, they displayed superior grip strength and enhanced walking speeds. Collectively, these findings furnish valuable insights into the multifaceted determinants of successful cognitive aging, encompassing both neurobiological constituents and lifestyle practices. Such comprehensive comprehension significantly contributes to the broader discourse on aging, thereby establishing a solid foundation for the formulation of targeted interventions aimed at fostering cognitive well-being among aging populations.

The effect of exercise on cerebral blood flow and executive function among young adults: a double-blinded randomized controlled trial

Studies have demonstrated that exercise benefits executive function. However, it remains unclear which type of exercise is optimal for preserving executive function among young adults and the cerebral blood flow (CBF) mechanisms that underlie exercise-induced cognitive benefits. Therefore, this study aims to compare the intervention effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on executive function and the CBF mechanism. This was a double-blinded, randomized, controlled trial study conducted between October 2020 and January 2021 (ClinicalTrials.gov identifier: NCT04830059). Ninety-three healthy young adults (25.23 ± 2.18 years old; 49.82% male) were randomized into the HIIT (N = 33), MICT (N = 32), and control (N = 28) groups. Participants in exercise groups were guided to perform 40 min of HIIT and MICT three times a week for 12 weeks, while the control group received health education for the same period. The primary outcomes, changes in executive function assessed by the trail-making test (TMT), and CBF measured by transcranial Doppler flow analyzer (EMS-9WA), were evaluated before and after the interventions. The time taken to complete the TMT task improved significantly in the MICT group compared to the control group [β = -10.175, 95%, confidence interval (CI) =  -20.320, -0.031]. Additionally, the MICT group showed significant improvements in the pulsatility index (PI) (β = 0.120, 95% CI = 0.018, 0.222), resistance index (RI) (β = 0.043, 95% CI = 0.005, 0.082), and peak-systolic/end-diastolic velocity (S/D) (β = 0.277, 95% CI = 0.048, 0.507) of CBF compared to the control group. The time taken to complete the TMT was associated with the velocity of peak-systolic (F = 5.414, P = 0.022), PI (F = 4.973, P = 0.012), and RI (F = 5.845, P = 0.006). Furthermore, the accuracy of TMT was associated with PI (F = 4.797, P = 0.036), RI (F = 5.394, P = 0.024), and S/D (F = 4.312, P = 0.05) of CBF. A 12-week MICT intervention improved CBF and executive function more effectively than HIIT among young adults. Furthermore, the findings suggest that CBF was one of the potential mechanisms underlying the cognitive benefits of exercise in young people. These results provide practical evidence supporting the promotion of regular exercise to maintain executive function and improve brain health.

Barrier-environment interactions along the gut-brain axis and their influence on cognition and behaviour throughout the lifespan

Environment is known to substantially alter mental state and behaviour across the lifespan. Biological barriers such as the blood-brain barrier (BBB) and gut barrier (GB) are major hubs for communication of environmental information. Alterations in the structural, social and motor environment at different stages of life can influence function of the BBB and GB and their integrity to exert behavioural consequences. Importantly, each of these environmental components is associated with a distinct immune profile, glucocorticoid response and gut microbiome composition, creating unique effects on the BBB and GB. These barrier-environment interactions are sensitive to change throughout life, and positive or negative alterations at critical stages of development can exert long-lasting cognitive and behavioural consequences. Furthermore, because loss of barrier integrity is implicated in pathogenesis of mental disorders, the pathways of environmental influence represent important areas for understanding these diseases. Positive environments can be protective against stress- and age-related damage, raising the possibility of novel pharmacological targets. This review summarizes known mechanisms of environmental influence - such as social interactions, structural complexity and physical exercise - on barrier composition, morphology and development, and considers the outcomes and implications of these interactions in the context of psychiatric disorders.

The Sedentary Lifestyle and Masticatory Dysfunction: Time to Review the Contribution to Age-Associated Cognitive Decline and Astrocyte Morphotypes in the Dentate Gyrus

As aging and cognitive decline progresses, the impact of a sedentary lifestyle on the appearance of environment-dependent cellular morphologies in the brain becomes more apparent. Sedentary living is also associated with poor oral health, which is known to correlate with the rate of cognitive decline. Here, we will review the evidence for the interplay between mastication and environmental enrichment and assess the impact of each on the structure of the brain. In previous studies, we explored the relationship between behavior and the morphological features of dentate gyrus glial fibrillary acidic protein (GFAP)-positive astrocytes during aging in contrasting environments and in the context of induced masticatory dysfunction. Hierarchical cluster and discriminant analysis of GFAP-positive astrocytes from the dentate gyrus molecular layer revealed that the proportion of AST1 (astrocyte arbors with greater complexity phenotype) and AST2 (lower complexity) are differentially affected by environment, aging and masticatory dysfunction, but the relationship is not straightforward. Here we re-evaluated our previous reconstructions by comparing dorsal and ventral astrocyte morphologies in the dentate gyrus, and we found that morphological complexity was the variable that contributed most to cluster formation across the experimental groups. In general, reducing masticatory activity increases astrocyte morphological complexity, and the effect is most marked in the ventral dentate gyrus, whereas the effect of environment was more marked in the dorsal dentate gyrus. All morphotypes retained their basic structural organization in intact tissue, suggesting that they are subtypes with a non-proliferative astrocyte profile. In summary, the increased complexity of astrocytes in situations where neuronal loss and behavioral deficits are present is counterintuitive, but highlights the need to better understand the role of the astrocyte in these conditions.

Exercise duration differentially effects age-related neuroinflammation and hippocampal neurogenesis

The physiological effects of exercise vary as a function of frequency and length. However, research on the duration-dependent effects of exercise has focused primarily on young adults and less is known about the influence of exercise duration in the aged. The current study compared the effects of short-term and long-term running wheel access on hippocampal neurogenesis and neuroimmune markers in aged (19-23 months) male C57BL/6J mice. Aged mice were given 24-hour access to a running wheel for 14 days (short-term) or 51 days (long-term). Groups of non-running aged and young (5 months) mice served as comparison groups to detect age-related differences and effects of exercise. Long-term, but not short-term, exercise increased hippocampal neurogenesis as assessed by number of doublecortin (DCX) positive cells in the granular cell layer. Assessment of cytokines, receptors, and glial-activation markers showed the expected age-related increase compared to young controls. In the aged, exercise as a function of duration regulated select aspects of the neuroimmune profile. For instance, hippocampal expression of interleukin (IL)-10 was increased only following long-term exercise. While in contrast brain levels of IL-6 were reduced by both short- and long-term exercise. Additional findings showed that exercise does not modulate all aspects of age-related neuroinflammation and/or may have differential effects in hippocampal compared to brain samples. Overall, the data indicate that increasing exercise duration produces more robust effects on immune modulation and hippocampal neurogenesis.

Directly Reprogrammed Human Neurons to Understand Age-Related Energy Metabolism Impairment and Mitochondrial Dysfunction in Healthy Aging and Neurodegeneration

Brain aging is characterized by several molecular and cellular changes grouped as the hallmarks or pillars of aging, including organelle dysfunction, metabolic and nutrition-sensor changes, stem cell attrition, and macromolecular damages. Separately and collectively, these features degrade the most critical neuronal function: transmission of information in the brain. It is widely accepted that aging is the leading risk factor contributing to the onset of the most prevalent pathological conditions that affect brain functions, such as Alzheimer's, Parkinson's, and Huntington's disease. One of the limitations in understanding the molecular mechanisms involved in those diseases is the lack of an appropriate cellular model that recapitulates the “aged” context in human neurons. The advent of the cellular reprogramming of somatic cells, i.e., dermal fibroblasts, to obtain directly induced neurons (iNs) and induced pluripotent stem cell- (iPSC-) derived neurons is technical sound advances that could open the avenues to understand better the contribution of aging toward neurodegeneration. In this review, we will summarize the commonalities and singularities of these two approaches for the study of brain aging, with an emphasis on the role of mitochondrial dysfunction and redox biology. We will address the evidence showing that iNs retain age-related features in contrast to iPSC-derived neurons that lose the aging signatures during the reprogramming to pluripotency, rendering iNs a powerful strategy to deepen our knowledge of the processes driving normal cellular function decline and neurodegeneration in a human adult model. We will finally discuss the potential utilization of these novel technologies to understand the differential contribution of genetic and epigenetic factors toward neuronal aging, to identify and develop new drugs and therapeutic strategies.

Treadmill Exercise Training Ameliorates Functional and Structural Age-Associated Kidney Changes in Male Albino Rats

Aging is a biological process that impacts multiple organs. Unfortunately, kidney aging affects the quality of life with high mortality rate. So, searching for innovative nonpharmacological modality improving age-associated kidney deterioration is important. This study aimed to throw more light on the beneficial effect of treadmill exercise on the aged kidney. Thirty male albino rats were divided into three groups: young (3-4 months old), sedentary aged (23-24 months old), and exercised aged (23-24 months old, practiced moderate-intensity treadmill exercise 5 days/week for 8 weeks). The results showed marked structural alterations in the aged kidney with concomitant impairment of kidney functions and increase in arterial blood pressure with no significant difference in kidney weight. Also, it revealed that treadmill exercise alleviated theses effects in exercised aged group with reduction of urea and cystatin C. Exercise training significantly decreased glomerulosclerosis index, tubular injury score, and % area of collagen deposition. Treadmill exercise exerted its beneficial role via a significant reduction of C-reactive protein and malondialdehyde and increase in total antioxidant capacity. In addition, exercise training significantly decreased desmin immunoreaction and increased aquaporin-3, vascular endothelial growth factor, and beclin-1 in the aged kidney. This study clarified that treadmill exercise exerted its effects via antioxidant and anti-inflammatory mechanisms, podocyte protection, improving aquaporin-3 and vascular endothelial growth factor expression, and inducing autophagy in the aged kidney. This work provided a new insight into the promising role of aerobic exercise to ameliorate age-associated kidney damage.

Microstructural Plasticity in the Hippocampus of Healthy Older Adults after Acute Exercise

INTRODUCTION

The hippocampus experiences structural and functional decline with age and is a critical region for memory and many cognitive processes. Exercise is beneficial for the aging brain and shows preferential benefits for hippocampal volume, activation, and memory-related cognitive processes. However, research thus far has primarily focused on the effects of exercise on long-term volumetric changes in the hippocampus using structural magnetic resonance imaging. Critically, microstructural alterations within the hippocampus over short time intervals are associated with neuroplasticity and cognitive changes that do not alter its volume but are still functionally relevant. However, it is not yet known if microstructural neuroplasticity occurs in the hippocampus in response to a single session of exercise.

METHODS

We used a within-subject design to determine if a 30-min bout of moderate-intensity aerobic exercise altered bilateral hippocampal diffusion tensor imaging measures in healthy older adults (n = 30) compared with a seated rest control condition.

RESULTS

Significantly lower fractional anisotropy and higher mean diffusivity were found after exercise relative to seated rest within the bilateral hippocampus, and this effect was driven by higher radial diffusivity. No significant differences in axial diffusivity were observed.

CONCLUSIONS

These findings suggest that a single exercise session can lead to microstructural alterations in the hippocampus of healthy older adults. These differences may be associated with changes in the extracellular space and glial, synaptic, and dendritic processes within the hippocampus. Repeated microstructural alterations resulting from acute bouts of exercise may accumulate and precede larger volumetric and functional improvements in the hippocampus.

Exercise, Arterial Stiffness, and Cerebral Vascular Function: Potential Impact on Brain Health

Exercise is associated with higher cognitive function and is a promising intervention to reduce the risk of dementia. With advancing age, there are changes in the vasculature that have important clinical implications for brain health and cognition. Primary aging and vascular risk factors are associated with increases in arterial stiffness and pulse pressure, and reductions in peripheral vascular function.

OBJECTIVE

The purpose is to discuss the epidemiological, observational, and mechanistic evidence regarding the link between age-related changes in vascular health and brain health.

METHODS

We performed a literature review and integrated with our published data.

RESULTS

Epidemiological evidence suggests a link between age-related increases in arterial stiffness and lower cognitive function, which may be mediated by cerebral vascular function, including cerebral vasoreactivity and cerebral pulsatility. Age-associated impairments in central arterial stiffness and peripheral vascular function have been attenuated or reversed through lifestyle behaviors such as exercise. Greater volumes of habitual exercise and higher cardiorespiratory fitness are associated with beneficial effects on both peripheral vascular health and cognition. Yet, the extent to which exercise directly influences cerebral vascular function and brain health, as well as the associated mechanisms remains unclear.

CONCLUSION

Although there is evidence that exercise positively impacts cerebral vascular function, more research is necessary in humans to optimize experimental protocols and address methodological limitations and physiological considerations. Understanding the impact of exercise on cerebral vascular function is important for understanding the association between exercise and brain health and may inform future intervention studies that seek to improve cognition.

Targeting the Cerebrovascular System: Next-Generation Biomarkers and Treatment for Mild Traumatic Brain Injury

The diagnosis, prognosis, and treatment of mild traumatic brain injuries (mTBIs), such as concussions, are significant unmet medical issues. The kinetic forces that occur in mTBI adversely affect the cerebral vasculature, making cerebrovascular injury (CVI) a pathophysiological hallmark of mTBI. Given the importance of a healthy cerebrovascular system in overall brain function, CVI is likely to contribute to neurological dysfunction after mTBI. As such, CVI and related pathomechanisms may provide objective biomarkers and therapeutic targets to improve the clinical management and outcomes of mTBI. Despite this potential, until recently, few studies have focused on the cerebral vasculature in this context. This article will begin by providing a brief overview of the cerebrovascular system followed by a review of the literature regarding how mTBI can affect the integrity and function of the cerebrovascular system, and how this may ultimately contribute to neurological dysfunction and neurodegenerative conditions. We then discuss promising avenues of research related to mTBI biomarkers and interventions that target CVI, and conclude that a clinical approach that takes CVI into account could result in substantial improvements in the care and outcomes of patients with mTBI.

Healthy aging and the blood-brain barrier

The blood-brain barrier (BBB) protects the central nervous system (CNS) from unregulated exposure to the blood and its contents. The BBB also controls the blood-to-brain and brain-to-blood permeation of many substances, resulting in nourishment of the CNS, its homeostatic regulation and communication between the CNS and peripheral tissues. The cells forming the BBB communicate with cells of the brain and in the periphery. This highly regulated interface changes with healthy aging. Here, we review those changes, starting with morphology and disruption. Transporter changes include those for amyloid beta peptide, glucose and drugs. Brain fluid dynamics, pericyte health and basement membrane and glycocalyx compositions are all altered with healthy aging. Carrying the ApoE4 allele leads to an acceleration of most of the BBB's age-related changes. We discuss how alterations in the BBB that occur with healthy aging reflect adaptation to the postreproductive phase of life and may affect vulnerability to age-associated diseases.

Tumor Necrosis Factor Alpha in Amyotrophic Lateral Sclerosis: Friend or Foe?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a massive neuroinflammatory reaction, which plays a key role in the progression of the disease. One of the major mediators of the inflammatory response is the pleiotropic cytokine tumor necrosis factor α (TNFα), mainly released within the central nervous system (CNS) by reactive astrocytes and microglia. Increased levels of TNFα and its receptors (TNFR1 and TNFR2) have been described in plasma, serum, cerebrospinal fluid and CNS tissue from both ALS patients and transgenic animal models of disease. However, the precise role exerted by TNFα in the context of ALS is still highly controversial, since both protective and detrimental functions have been reported. These opposing actions depend on multiple factors, among which includes the type of TNFα receptor activated. In fact, TNFR2 seems to mediate a harmful role being involved in motor neuron cell death, whereas TNFR1 signaling mediates neuroprotective effects, promoting the expression and secretion of trophic factors. This suggests that a better understanding of the cytokine impact on ALS progression may enable the development of effective therapies aimed at strengthening the protective roles of TNFα and at suppressing the detrimental ones.

Benefits of exercise training on cerebrovascular and cognitive function in ageing

Derangements in cerebrovascular structure and function can impair cognitive performance throughout ageing and in cardiometabolic disease states, thus increasing dementia risk. Modifiable lifestyle factors that cause a decline in cardiometabolic health, such as physical inactivity, exacerbate these changes beyond those that are associated with normal ageing. The purpose of this review was to examine cerebrovascular, cognitive and neuroanatomical adaptations to ageing and the potential benefits of exercise training on these outcomes in adults 50 years or older. We systematically searched for cross-sectional or intervention studies that included exercise (aerobic, resistance or multimodal) and its effect on cerebrovascular function, cognition and neuroanatomical adaptations in this age demographic. The included studies were tabulated and described narratively. Aerobic exercise training was the predominant focus of the studies identified; there were limited studies exploring the effects of resistance exercise training and multimodal training on cerebrovascular function and cognition. Collectively, the evidence indicated that exercise can improve cerebrovascular function, cognition and neuroplasticity through areas of the brain associated with executive function and memory in adults 50 years or older, irrespective of their health status. However, more research is required to ascertain the mechanisms of action.

Obesity-induced cognitive impairment in older adults: a microvascular perspective

Over two-thirds of individuals aged 65 and older are obese or overweight in the United States. Epidemiological data show an association between the degree of adiposity and cognitive dysfunction in the elderly. In this review, the pathophysiological roles of microvascular mechanisms, including impaired endothelial function and neurovascular coupling responses, microvascular rarefaction, and blood-brain barrier disruption in the genesis of cognitive impairment in geriatric obesity are considered. The potential contribution of adipose-derived factors and fundamental cellular and molecular mechanisms of senescence to exacerbated obesity-induced cerebromicrovascular impairment and cognitive decline in aging are discussed.

Aerobic exercise increases sprouting angiogenesis in the male rat motor cortex

Exercise is beneficial to brain health, and historically, the advantageous effects of exercise on the brain have been attributed to neuronal plasticity. However, it has also become clear that the brain vascular system also exhibits plasticity in response to exercise. This plasticity occurs in areas involved in movement, such as the motor cortex. This experiment aimed to further characterize the effects of exercise on structural vascular plasticity in the male rat motor cortex, by specifically identifying whether features of angiogenesis, the growth of new capillaries, or changes in vessel diameter were present. Male rats in the exercise group engaged in a 5-week bout of voluntary wheel running, while a second group of rats remained sedentary. After the exercise regimen, vascular corrosion casts, resin replicas of the brain vasculature, were made for all animals and imaged using a scanning electron microscope. Results indicate sprouting angiogenesis was the primary form of structural vascular plasticity detected in the motor cortex under these aerobic exercise parameters. Additionally, exercised rats displayed a slight increase in capillary diameter and expanded endothelial cell nuclei diameters in this region.

Acute Low-Intensity Aerobic Exercise Modulates Intracortical Inhibitory and Excitatory Circuits in an Exercised and a Non-exercised Muscle in the Primary Motor Cortex

Recent studies have reported that acute aerobic exercise modulates intracortical excitability in the primary motor cortex (M1). However, whether acute low-intensity aerobic exercise can also modulate M1 intracortical excitability, particularly intracortical excitatory circuits, remains unclear. In addition, no previous studies have investigated the effect of acute aerobic exercise on short-latency afferent inhibition (SAI). The aim of this study was to investigate whether acute low-intensity aerobic exercise modulates intracortical circuits in the M1 hand and leg areas. Intracortical excitability of M1 (Experiments 1, 2) and spinal excitability (Experiment 3) were measured before and after acute low-intensity aerobic exercise. In Experiment 3, skin temperature was also measured throughout the experiment. Transcranial magnetic stimulation was applied over the M1 non-exercised hand and exercised leg areas in Experiments 1, 2, respectively. Participants performed 30 min of low-intensity pedaling exercise or rested while sitting on the ergometer. Short- and long-interval intracortical inhibition (SICI and LICI), and SAI were measured to assess M1 inhibitory circuits. Intracortical facilitation (ICF) and short-interval intracortical facilitation (SICF) were measured to assess M1 excitatory circuits. We found that acute low-intensity aerobic exercise decreased SICI and SAI in the M1 hand and leg areas. After exercise, ICF in the M1 hand area was lower than in the control experiment, but was not significantly different to baseline. The single motor-evoked potential, resting motor threshold, LICI, SICF, and spinal excitability did not change following exercise. In conclusion, acute low-intensity pedaling modulates M1 intracortical circuits of both exercised and non-exercised areas, without affecting corticospinal and spinal excitability.

Astrocytes in Motor Neuron Diseases

Motor neuron disorders are highly debilitating and mostly fatal conditions for which only limited therapeutic options are available. To overcome this limitation and develop more effective therapeutic strategies, it is critical to discover the pathogenic mechanisms that trigger and sustain motor neuron degeneration with the greatest accuracy and detail. In the case of Amyotrophic Lateral Sclerosis (ALS), several genes have been associated with familial forms of the disease, whilst the vast majority of cases develop sporadically and no defined cause can be held responsible. On the contrary, the huge majority of Spinal Muscular Atrophy (SMA) occurrences are caused by loss-of-function mutations in a single gene, SMN1. Although the typical hallmark of both diseases is the loss of motor neurons, there is increasing awareness that pathological lesions are also present in the neighbouring glia, whose dysfunction clearly contributes to generating a toxic environment in the central nervous system. Here, ALS and SMA are sequentially presented, each disease section having a brief introduction, followed by a focussed discussion on the role of the astrocytes in the disease pathogenesis. Such a dissertation is substantiated by the findings that built awareness on the glial involvement and how the glial-neuronal interplay is perturbed, along with the appraisal of this new cellular site for possible therapeutic intervention.

Imaging the aged brain: pertinence and methods

The global population is ageing at an accelerating speed. The ability to perform working memory tasks together with rapid processing becomes increasingly difficult with increases in age. With increasing national average life spans and a rise in the prevalence of age-related disease, it is pertinent to discuss the unique perspectives that can be gained from imaging the aged brain. Differences in structure, function, blood flow, and neurovascular coupling are present in both healthy aged brains and in diseased brains and have not yet been explored to their full depth in contemporary imaging studies. Imaging methods ranging from optical imaging to magnetic resonance imaging (MRI) to newer technologies such as photoacoustic tomography each offer unique advantages and challenges in imaging the aged brain. This paper will summarize first the importance and challenges of imaging the aged brain and then offer analysis of potential imaging modalities and their representative applications. The potential breakthroughs in brain imaging are also envisioned.

The role of astrocytes on the effects of exercise on episodic memory function

This review discusses the potential role that glial cells may play in influencing the relationship between exercise and episodic memory function. A narrative review methodology is employed. Herein, the different types of glial cells, their implications in subserving episodic memory function, and how exercise can modulate glial cell activity, particularly astrocyte functionality, are discussed. Although additional experimental work is needed, astrocytes appear to play an important role in the exercise-memory interaction. Exercise may increase astrocytic size, attenuate astrogliodegeneration, improve astrocytic aquaporin-4 expression, and increase astrocytic transporter levels. These effects, in turn, may help to increase the number of synapses that neurons form, increase the number of synaptic structures, and increase presynaptic function and postsynaptic receptor localization. Ultimately, these effects may help influence long-term potentiation and episodic memory function.

Investigating links between habitual physical activity, cerebrovascular function, and cognitive control in healthy older adults

A growing body of evidence indicates regular physical activity benefits older adults' cognitive functioning, particularly when a high level of cognitive control is required. Recent research has pointed to improved cerebrovascular function as one mechanism through which such benefits might arise. This study built on previous research by investigating in 51 healthy older adults aged 60-72 years relationships between habitual physical activity, cerebrovascular function (indicated by resting cerebral blood flow velocity in the middle cerebral artery [n = 42], and its responsiveness to hypercapnia [n = 26] and hypocapnia [n = 25]), and cognitive control (inhibition and switching). Linear regression analyses showed moderate positive associations between physical activity and inhibitory control, but not cerebrovascular function. There were also no significant relationships between the cerebrovascular measures and cognitive control. These results indicate that regular engagement in physical activity is associated with superior inhibitory control in older adulthood, but cerebrovascular function was not found to explain those relationships. Taken together, the current findings reinforce reports of positive links between habitual physical activity and cognition in healthy older adults, but also signal that interrelationships with cerebrovascular function may be more complex than currently indicated by the literature, necessitating further research to elucidate the role cerebrovascular function might play in accounting for physical activity-cognition links in healthy older adults.

Exercise Improves Vascular Function, but does this Translate to the Brain?

The number of adults with Alzheimer’s disease (AD) or related dementia is expected to increase exponentially. Interventions aimed to reduce the risk and progression of AD and dementia are critical to the prevention and treatment of this devastating disease. Aging and cardiovascular disease risk factors are associated with reduced vascular function, which can have important clinical implications, including brain health. The age-associated increase in blood pressure and impairment in vascular function may be attenuated or even reversed through lifestyle behaviors. Greater volumes of habitual exercise and higher cardiorespiratory fitness are associated with beneficial effects on vascular health and cognition. Exercise and cardiorespiratory fitness may be most important during midlife, as physical activity and cardiorespiratory fitness during the middle-aged years are associated with future cognitive function. The extent to which exercise, and more specifically aerobic exercise, influences the cerebral circulation is not well established. In this review, we present our working hypothesis showing how cerebrovascular function may be a mediating factor underlying the association between exercise and cognition, as well as discuss recent studies evaluating the effect of exercise interventions on the cerebral circulation.

Different Patterns of Neurodegeneration and Glia Activation in CA1 and CA3 Hippocampal Regions of TgCRND8 Mice

We investigated the different patterns of neurodegeneration and glia activation in CA1 and CA3 hippocampal areas of TgCRND8 mice. The main feature of this transgenic model is the rapid development of the amyloid pathology, which starts already at 3 months of age. We performed immunohistochemical analyses to compare the different sensibility of the two hippocampal regions to neurodegeneration. We performed qualitative and quantitative evaluations by fluorescence immunohistochemistry with double or triple staining, followed by confocal microscopy and digital image analysis in stratum pyramidale (SP) and stratum radiatum (SR) of CA1 and CA3, separately. We evaluated time-dependent Aβ plaques deposition, expression of inflammatory markers, as well as quantitative and morphological alterations of neurons and glia in transgenic mice at 3 (Tg 3M) and 6 (Tg 6M) months of age, compared to WT mice. In CA1 SR of Tg 6M mice, we found significantly more Medium and Large plaques than in CA3. The pattern of neurodegeneration and astrocytes activation was different in the two areas, indicating higher sensitivity of CA1. In the CA1 SP of Tg 6M mice, we found signs of reactive astrogliosis, such as increase of astrocytes density in SP, increase of GFAP expression in SR, and elongation of astrocytes branches. We found also common patterns of glia activation and neurodegenerative processes in CA1 and CA3 of Tg 6M mice: significant increase of total and reactive microglia density in SP and SR, increased expression of TNFα, of iNOS, and IL1β in astrocytes and increased density of neurons-astrocytes-microglia triads. In CA1 SP, we found decrease of volume and number of pyramidal neurons, paralleled by increase of apoptosis, and, consequently, shrinkage of CA1 SP. These data demonstrate that in TgCRND8 mice, the responses of neurons and glia to neurodegenerative patterns induced by Aβ plaques deposition is not uniform in the two hippocampal areas, and in CA1 pyramidal neurons, the higher sensitivity may be related to the different plaque distribution in this area. All these modifications may be at the basis of memory loss, the peculiar symptom of AD, which was demonstrated in this transgenic mouse model of Aβ deposition, even at early stages.

Exploring Exercise- and Context-Induced Peptide Changes in Mice by Quantitative Mass Spectrometry

Recent research suggests that exercise may help facilitate abstinence from cocaine addiction, though the mechanisms are not well understood. In mice, wheel running accelerates the extinction of conditioned place preference (CPP) for cocaine, providing an animal model for evaluating potential neurological mechanisms. The objective of this study was to quantify dynamic changes in endogenous peptides in the amygdala and dentate gyrus of the hippocampus in mice exposed to a context paired with the effects of cocaine, and in response to exercise. Male C57BL/6J mice conditioned to cocaine were housed with or without running wheels for 30 days. Following a CPP test and final exposure to either a cocaine- or saline-associated context, peptides were measured in brain tissue extracts using label-free matrix-assisted laser desorption/ionization mass spectrometry (MS) and stable isotopic labeling with liquid chromatography and electrospray ionization MS. CPP in mice was significantly reduced with running, which correlated to decreased myelin basic protein derivatives in the dentate gyrus extracts, possibly reflecting increased unmyelinated granule neuron density. Exposure to a cocaine-paired context increased hemoglobin-derived peptides in runners and decreased an actin-derived peptide in sedentary animals. These results allowed us to characterize a novel set of biomarkers that are responsive to exercise in the hippocampus and in a cocaine-paired context in the amygdala.

White matter pathways as both a target and mediator of health behaviors

Health behaviors arise from the dynamics of highly interconnected networks in the brain and variability in these networks drives individual differences in behavior. In this review, we show how many factors that predict the physical health of the body also correlate with variability of the myelinated fascicles, called white matter, that connect brain regions together. The general pattern present in the literature is that as predictors of physical health decline, there is often a coincident reduction in the integrity of major white matter pathways. We also highlight a plausible mechanism, inflammatory pathways, whereby health-related activation of the immune system can impact the myelin sheath, a protective tissue that facilitates long range communication in the brain. The growing body of evidence supports the hypothesis that degrading health in the periphery may disrupt the communication efficiency of the macroscopic neural circuits that mediate complex behaviors, which can in turn contribute to poorer physical health.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Endothelial cell-oligodendrocyte interactions in small vessel disease and aging

Cerebral small vessel disease (SVD) is a prevalent, neurological disease that significantly increases the risk of stroke and dementia. The main pathological changes are vascular, in the form of lipohyalinosis and arteriosclerosis, and in the white matter (WM), in the form of WM lesions. Despite this, it is unclear to what extent the key cell types involved–the endothelial cells (ECs) of the vasculature and the oligodendrocytes of the WM–interact. Here, we describe the work that has so far been carried out suggesting an interaction between ECs and oligodendrocytes in SVD. As these interactions have been studied in more detail in other disease states and in development, we explore these systems and discuss the role these mechanisms may play in SVD.

Effects of long‑term post‑ischemic treadmill exercise on gliosis in the aged gerbil hippocampus induced by transient cerebral ischemia

Therapeutic exercise is an integral component of the rehabilitation of patients who have suffered a stroke. The objective of the present study was to use immunohistochemistry to investigate the effects of post-ischemic exercise on neuronal damage or death and gliosis in the aged gerbil hippocampus following transient cerebral ischemia. Aged gerbils (male; age, 22–24 months) underwent ischemia and were subjected to treadmill exercise for 1 or 4 weeks. Neuronal death was detected in the stratum pyramidale of the hippocampal CA1 region and in the polymorphic layer of the dentate gyrus using cresyl violet and Fluoro-Jade B histofluorescence staining. No significant difference in neuronal death was identified following 1 or 4 weeks of post-ischemic treadmill exercise. However, post-ischemic treadmill exercise affected gliosis (the activation of astrocytes and microglia). Glial fibrillary acidic protein-immunoreactive astrocytes and ionized calcium binding adaptor molecule 1-immunoreactive microglia were activated in the CA1 and polymorphic layer of the dentate gyrus of the group without treadmill exercise. Conversely, 4 weeks of treadmill exercise significantly alleviated ischemia-induced astrocyte and microglial activation; however, 1 week of treadmill exercise did not alleviate gliosis. These findings suggest that long-term post-ischemic treadmill exercise following transient cerebral ischemia does not influence neuronal protection; however, it may effectively alleviate transient cerebral ischemia-induced astrocyte and microglial activation in the aged hippocampus.

Aging asymmetry: systematic survey of changes in age-related biomarkers in the annual fish Nothobranchius guentheri

Aging asymmetry is the observation that different tissues age in different ways and at different rates. This has not been assessed in a single organism using multiple biomarkers of aging. Here we clearly demonstrated that the levels of protein oxidation and lipid peroxidation as well as CAT, SOD and GPX activities all showed a tissue-dependent change with advancing age; and DNA repair ability, as revealed by the expression of ercc1 and its protein levels, also exhibited a tissue-specific variation with age. We also found that protein oxidation and lipid peroxidation levels remained relatively stable in the liver, intestine, skin and testis as well as in the brain, eye and heart of young, adult and aged fishes; SOD and GPX activities displayed little variation in the intestine, eye and skin as well as in the brain and skin of young, adult and aged fishes; and low and stable expression of ercc1 was observed in the spleen, eye and heart of young, adult and aged fishes. Collectively, these results indicate that aging is tissue specific and asymmetric in N. guentheri. The observation of aging asymmetry may have practical implications for the application of non-intrusion intervention approaches to prolong lifespan.

Physical exercise induces structural alterations in the hippocampal astrocytes: exploring the role of BDNF-TrkB signaling

While it has been known that physical activity can improve cognitive function and protect against neurodegeneration, the underlying mechanisms for these protective effects are yet to be fully elucidated. There is a large body of evidence indicating that physical exercise improves neurogenesis and maintenance of neurons. Yet, its possible effects on glial cells remain poorly understood. Here, we tested whether physical exercise in mice alters the expression of trophic factor-related genes and the status of astrocytes in the dentate gyrus of the hippocampus. In addition to a significant increase in Bdnf mRNA and protein levels, we found that 4 weeks of treadmill and running wheel exercise in mice, led to (1) a significant increase in synaptic load in the dentate gyrus, (2) alterations in astrocytic morphology, and (3) orientation of astrocytic projections towards dentate granule cells. Importantly, these changes were possibly linked to increased TrkB receptor levels in astrocytes. Our study suggests that astrocytes actively respond and could indeed mediate the positive effects of physical exercise on the central nervous system and potentially counter degenerative processes during aging and neurodegenerative disorders.

Short-term environmental enrichment enhances synaptic plasticity in hippocampal slices from aged rats

Age-associated changes in cognition are mirrored by impairments in cellular models of memory and learning, such as long-term potentiation (LTP) and long-term depression (LTD). In young rodents, environmental enrichment (EE) can enhance memory, alter LTP and LTD, as well as reverse cognitive deficits induced by aging. Whether short-term EE can benefit cognition and synaptic plasticity in aged rodents is unclear. Here, we tested if short-term EE could overcome age-associated impairments in induction of LTP and LTD. LTP and LTD could not be induced in the CA1 region of hippocampal slices in control, aged rats using standard stimuli that are highly effective in young rats. However, exposure of aged littermates to EE for three weeks enabled successful induction of LTP and LTD. EE-facilitated LTP was dependent upon N-methyl-d-aspartate receptors (NMDARs). These alterations in synaptic plasticity occurred with elevated levels of phosphorylated cAMP response element-binding protein and vascular endothelial growth factor, but in the absence of changes in several other synaptic and cellular markers. Importantly, our study suggests that even a relatively short period of EE is sufficient to alter synaptic plasticity and molecular markers linked to cognitive function in aged animals.

Obesity Reduces Cognitive and Motor Functions across the Lifespan

Due to a sedentary lifestyle, more and more people are becoming obese nowadays. In addition to health-related problems, obesity can also impair cognition and motor performance. Previous results have shown that obesity mainly affects cognition and motor behaviors through altering brain functions and musculoskeletal system, respectively. Many factors, such as insulin/leptin dysregulation and inflammation, mediate the effect of obesity and cognition and motor behaviors. Substantial evidence has suggested exercise to be an effective way to improve obesity and related cognitive and motor dysfunctions. This paper aims to discuss the association of obesity with cognition and motor behaviors and its underlying mechanisms. Following this, mechanisms of exercise to improve obesity-related dysfunctions are described. Finally, implications and future research direction are raised.

Exercise-induced changes of cerebrospinal fluid vascular endothelial growth factor in adult chronic hydrocephalus patients

Vascular endothelial growth factor (VEGF) is a growth factor demonstrated to be a key factor in cerebral angiogenesis and neurogenesis. It has been considered a critical component in hippocampus neurogenesis and memory formation and has been observed to increase in the rat hippocampus after exercise. We previously found increased VEGF levels in experimental chronic hydrocephalus in several brain areas and cerebrospinal fluid (CSF), suggesting a role in the adaption to chronic hypoxia. Here we investigate the ability of moderate exercise to increase CSF-VEGF levels in adult chronic hydrocephalus patients. Lumbar CSF samples were collected from 17 normal pressure hydrocephalus patients. During CSF collection, 11 patients (exercise group) underwent a standard in-room occupational therapy session; six patients (no-exercise group) did not undergo a physical therapy session. CSF-VEGF levels were evaluated for increase related to exercise and the clinical response to CSF drainage. CSF-VEGF levels in the exercise group demonstrated significant increases 1-3 hours post-exercise compared with the levels 1-2 hours pre-exercise (p=0.04), and also showed significantly higher levels than the no-exercise groups (p=0.03). The post-exercise CSF-VEGF level in the group that did not clinically improve was significantly higher than both their own pre-exercise level (p=0.02) and that seen in the clinically improving group (p=0.05) after exercise. We conclude that CSF-VEGF levels can increase after moderate exercise even in elderly hydrocephalus patients. This suggests that a potential benefit of exercise, especially in CSF drainage non-improved patients, may exist via a central VEGF mechanism.

Glial Fibrillary Acidic Protein-Expressing Glia in the Mouse Lung

Autonomic nerves regulate important functions in visceral organs, including the lung. The postganglionic portion of these nerves is ensheathed by glial cells known as non-myelinating Schwann cells. In the brain, glia play important functional roles in neurotransmission, neuroinflammation, and maintenance of the blood brain barrier. Similarly, enteric glia are now known to have analogous roles in gastrointestinal neurotransmission, inflammatory response, and barrier formation. In contrast to this, very little is known about the function of glia in other visceral organs. Like the gut, the lung forms a barrier between airborne pathogens and the bloodstream, and autonomic lung innervation is known to affect pulmonary inflammation and lung function. Lung glia are described as non-myelinating Schwann cells but their function is not known, and indeed no transgenic tools have been validated to study them in vivo. The primary goal of this research was, therefore, to investigate the relationship between non-myelinating Schwann cells and pulmonary nerves in the airways and vasculature and to validate existing transgenic mouse tools that would be useful for studying their function. We focused on the glial fibrillary acidic protein promoter, which is a cognate marker of astrocytes that is expressed by enteric glia and non-myelinating Schwann cells. We describe the morphology of non-myelinating Schwann cells in the lung and verify that they express glial fibrillary acidic protein and S100, a classic glial marker. Furthermore, we characterize the relationship of non-myelinating Schwann cells to pulmonary nerves. Finally, we report tools for studying their function, including a commercially available transgenic mouse line.

Astrocyte physiopathology: At the crossroads of intercellular networking, inflammation and cell death

Recent breakthroughs in neuroscience have led to the awareness that we should revise our traditional mode of thinking and studying the CNS, i.e. by isolating the privileged network of "intelligent" synaptic contacts. We may instead need to contemplate all the variegate communications occurring between the different neural cell types, and centrally involving the astrocytes. Basically, it appears that a single astrocyte should be considered as a core that receives and integrates information from thousands of synapses, other glial cells and the blood vessels. In turn, it generates complex outputs that control the neural circuitry and coordinate it with the local microcirculation. Astrocytes thus emerge as the possible fulcrum of the functional homeostasis of the healthy CNS. Yet, evidence indicates that the bridging properties of the astrocytes can change in parallel with, or as a result of, the morphological, biochemical and functional alterations these cells undergo upon injury or disease. As a consequence, they have the potential to transform from supportive friends and interactive partners for neurons into noxious foes. In this review, we summarize the currently available knowledge on the contribution of astrocytes to the functioning of the CNS and what goes wrong in various pathological conditions, with a particular focus on Amyotrophic Lateral Sclerosis, Alzheimer's Disease and ischemia. The observations described convincingly demonstrate that the development and progression of several neurological disorders involve the de-regulation of a finely tuned interplay between multiple cell populations. Thus, it seems that a better understanding of the mechanisms governing the integrated communication and detrimental responses of the astrocytes as well as their impact towards the homeostasis and performance of the CNS is fundamental to open novel therapeutic perspectives.

Cardiorespiratory fitness is associated with white matter integrity in aging

Objective

Aging is associated with reduced neural integrity, yet there are remarkable individual differences in brain health among older adults (OA). One factor that may attenuate age-related neural decline is cardiorespiratory fitness (CRF). The primary aim of this study was to link CRF to neural white matter microstructure using diffusion tensor imaging in OA.

Methods

Young adults (YA; n = 32) and OA (n = 27) completed a graded maximal exercise test to evaluate CRF and diffusion tensor magnetic resonance imaging to examine neural white matter integrity.

Results

As expected, pervasive age-related declines in white matter integrity were observed when OA were compared to YA. Further, peak VO₂ was positively associated with fractional anisotropy (FA), an indicator of white matter integrity, in multiple brain regions in OA, but not YA. In multiple posterior regions such as the splenium, sagittal stratum, posterior corona radiata, and superior parietal white matter, FA values were similar in YA and OA classified as higher fit, with both groups having greater FA than lower fit OA. However, age-related differences in FA values remained in other regions, including the body and genu of the corpus callosum, precuneus, and superior frontal gyrus.

Interpretation

CRF is positively associated with neural white matter microstructure in aging. The relationship between peak VO₂ and FA appears to be tract-specific, as equivalent FA values were observed in higher fit OA and YA in some white matter tracts, but not others. Further, the association between peak VO₂ and FA appears to be age-dependent.

Obesity and diabetes cause cognitive dysfunction in the absence of accelerated β-amyloid deposition in a novel murine model of mixed or vascular dementia

Mid-life obesity and type 2 diabetes mellitus (T2DM) confer a modest, increased risk for Alzheimer's disease (AD), though the underlying mechanisms are unknown. We have created a novel mouse model that recapitulates features of T2DM and AD by crossing morbidly obese and diabetic db/db mice with APPΔNL/ΔNLx PS1P264L/P264L knock-in mice. These mice (db/AD) retain many features of the parental lines (e.g. extreme obesity, diabetes, and parenchymal deposition of β-amyloid (Aβ)). The combination of the two diseases led to additional pathologies-perhaps most striking of which was the presence of severe cerebrovascular pathology, including aneurysms and small strokes. Cortical Aβ deposition was not significantly increased in the diabetic mice, though overall expression of presenilin was elevated. Surprisingly, Aβ was not deposited in the vasculature or removed to the plasma, and there was no stimulation of activity or expression of major Aβ-clearing enzymes (neprilysin, insulin degrading enzyme, or endothelin-converting enzyme). The db/AD mice displayed marked cognitive impairment in the Morris Water Maze, compared to either db/db or APPΔNLx PS1P264L mice. We conclude that the diabetes and/or obesity in these mice leads to a destabilization of the vasculature, leading to strokes and that this, in turn, leads to a profound cognitive impairment and that this is unlikely to be directly dependent on Aβ deposition. This model of mixed or vascular dementia provides an exciting new avenue of research into the mechanisms underlying the obesity-related risk for age-related dementia, and will provide a useful tool for the future development of therapeutics.

Exercise training could improve age-related changes in cerebral blood flow and capillary vascularity through the upregulation of VEGF and eNOS

This study aimed to investigate the effect of exercise training on age-induced microvascular alterations in the brain. Additionally, the association with the protein levels of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) was also assessed. Male Wistar rats were divided into four groups: sedentary-young (SE-Young, n = 5), sedentary aged (SE-Aged, n = 8), immersed-aged (IM-Aged, n = 5), and exercise trained-aged (ET-Aged, 60 minutes/day and 5 days/week for 8 weeks, n = 8) rats. The MAPs of all aged groups, SE-Aged, IM-Aged, and ET-Aged, were significantly higher than that of the SE-Young group. The regional cerebral blood flow (rCBF) in the SE-Aged and IM-Aged was significantly decreased as compared to SE-Young groups. However, rCBF of ET-Aged group was significantly higher than that in the IM-Aged group (P < 0.05). Moreover, the percentage of capillary vascularity (%CV) and the levels of VEGF and eNOS in the ET-Aged group were significantly increased compared to the IM-Aged group (P < 0.05). These results imply that exercise training could improve age-induced microvascular changes and hypoperfusion closely associated with the upregulation of VEGF and eNOS.

Mapping NAD(+) metabolism in the brain of ageing Wistar rats: potential targets for influencing brain senescence

Over the last decade, the importance of NAD(+) has expanded beyond its role as an essential cofactor for energy metabolism. NAD(+) has emerged as a major signalling molecule that serves as the sole substrate for several enzymatic reactions including the DNA repair enzyme, poly(ADP-ribose) polymerase (PARP), NAD-dependent protein deacetylases or CD38, and transcriptional factors by a new class of histone deacetylases known as sirtuins. NAD(+) levels are regulated by the metabolic status and cellular stress caused by oxidative stress and DNA damage. Since a detailed study of NAD(+) metabolism in the healthy ageing mammalian brain is nascent, we examined the effect of ageing on intracellular NAD(+) metabolism in different brain regions in female Wistar rats in young (3 months), middle aged (12 months) and older adults (24 months). Our results are the first to show a significant decline in intracellular NAD(+) levels and NAD:NADH ratio with ageing in the CNS, occurring in parallel to an increase in lipid peroxidation and protein oxidation (o- and m-tyrosine) and a decline in total antioxidant capacity. Hyperphosphorylation of H2AX levels was also observed together with increased PARP-1 and PARP-2 expression, and CD38 activity, concomitantly with reduced NAD(+) and ATP levels and SIRT1 function in the cortex, brainstem, hippocampus and cerebellum. Reduced activity of mitochondrial complex I-IV and impaired maximum mitochondrial respiration rate were also observed in the ageing rat brain. Among the multiple physiological pathways associated with NAD(+) catabolism, our discovery of CD38 as the major regulator of cellular NAD(+) levels in rat neurons indicates that CD38 is a promising therapeutic target for the treatment of age-related neurodegenerative diseases.

The glia doctrine: addressing the role of glial cells in healthy brain ageing

Glial cells in their plurality pervade the human brain and impact on brain structure and function. A principal component of the emerging glial doctrine is the hypothesis that astrocytes, the most abundant type of glial cells, trigger major molecular processes leading to brain ageing. Astrocyte biology has been examined using molecular, biochemical and structural methods, as well as 3D brain imaging in live animals and humans. Exosomes are extracelluar membrane vesicles that facilitate communication between glia, and have significant potential for biomarker discovery and drug delivery. Polymorphisms in DNA repair genes may indirectly influence the structure and function of membrane proteins expressed in glial cells and predispose specific cell subgroups to degeneration. Physical exercise may reduce or retard age-related brain deterioration by a mechanism involving neuro-glial processes. It is most likely that additional information about the distribution, structure and function of glial cells will yield novel insight into human brain ageing. Systematic studies of glia and their functions are expected to eventually lead to earlier detection of ageing-related brain dysfunction and to interventions that could delay, reduce or prevent brain dysfunction.

Multispectral Imaging

The field of anatomic pathology has changed significantly over the last decades and, as a result of the technological developments in molecular pathology and genetics, has had increasing pressures put on it to become quantitative and to provide more information about protein expression on a cellular level in tissue sections. Multispectral imaging (MSI) has a long history as an advanced imaging modality and has been used for over a decade now in pathology to improve quantitative accuracy, enable the analysis of multicolor immunohistochemistry, and drastically reduce the impact of contrast-robbing tissue autofluorescence common in formalin-fixed, paraffin-embedded tissues. When combined with advanced software for the automated segmentation of different tissue morphologies (eg, tumor vs stroma) and cellular and subcellular segmentation, MSI can enable the per-cell quantitation of many markers simultaneously. This article covers the role that MSI has played in anatomic pathology in the analysis of formalin-fixed, paraffin-embedded tissue sections, discusses the technological aspects of why MSI has been adopted, and provides a review of the literature of the application of MSI in anatomic pathology.

Analysis of transduction efficiency, tropism and axonal transport of AAV serotypes 1, 2, 5, 6, 8 and 9 in the mouse brain

Recombinant Adeno-associated virus vectors (rAAV) are widely used for gene delivery and multiple naturally occurring serotypes have been harnessed to target cells in different tissues and organs including the brain. Here, we provide a detailed and quantitative analysis of the transduction profiles of rAAV vectors based on six of the most commonly used serotypes (AAV1, AAV2, AAV5, AAV6, AAV8, AAV9) that allows systematic comparison and selection of the optimal vector for a specific application. In our studies we observed marked differences among serotypes in the efficiency to transduce three different brain regions namely the striatum, hippocampus and neocortex of the mouse. Despite the fact that the analyzed serotypes have the general ability to transduce all major cell types in the brain (neurons, microglia, astrocytes and oligodendrocytes), the expression level of a reporter gene driven from a ubiquitous promoter varies significantly for specific cell type / serotype combinations. For example, rAAV8 is particularly efficient to drive transgene expression in astrocytes while rAAV9 appears well suited for the transduction of cortical neurons. Interestingly, we demonstrate selective retrograde transport of rAAV5 along axons projecting from the ventral part of the entorhinal cortex to the dentate gyrus. Furthermore, we show that self-complementing rAAV can be used to significantly decrease the time required for the onset of transgene expression in the mouse brain.

Bridging animal and human models of exercise-induced brain plasticity

Significant progress has been made in understanding the neurobiological mechanisms through which exercise protects and restores the brain. In this feature review, we integrate animal and human research, examining physical activity effects across multiple levels of description (neurons up to inter-regional pathways). We evaluate the influence of exercise on hippocampal structure and function, addressing common themes such as spatial memory and pattern separation, brain structure and plasticity, neurotrophic factors, and vasculature. Areas of research focused more within species, such as hippocampal neurogenesis in rodents, also provide crucial insight into the protective role of physical activity. Overall, converging evidence suggests exercise benefits brain function and cognition across the mammalian lifespan, which may translate into reduced risk for Alzheimer's disease (AD) in humans.