Improvements to Healthspan Through Environmental Enrichment and Lifestyle Interventions: Where Are We Now?

Environmental Enrichment Improves Motor Function and Muscle Transcriptome of Aged Mice

Aging results in the progressive decline of muscle strength. Interventions to maintain muscle strength may mitigate the age-related loss of physical function, thus maximizing health span. The work on environmental enrichment (EE), an experimental paradigm recapitulating aspects of an active lifestyle, has revealed EE-induced metabolic benefits mediated by a brain-fat axis across the lifespan of mice. EE initiated at 18-month of age shows a trend toward an increased mean lifespan. While previous work described EE's influences on the aging dynamics of several central-peripheral processes, its influence on muscle remained understudied. Here, the impact of EE is investigated on motor function, neuromuscular physiology, and the skeletal muscle transcriptome. EE is initiated in 20-month-old mice for a five-month period. EE mice exhibit greater relative lean mass that is associated with improved mobility and hindlimb grip strength. Transcriptomic profiling of muscle tissue reveals an EE-associated enrichment of gene expression within several metabolic pathways related to oxidative phosphorylation and the TCA cycle. Many mitochondrial-related genes-several of which participate in the electron transport chain-are upregulated. Stress-responsive signaling pathways are downregulated because of EE. The results suggest that EE improves motor function-possibly through preservation of mitochondrial function-even late in life.

Effects of combined physical and cognitive program performed in socially enriched environment on older people's cognitive abilities and quality of life (StimCoAPS): study protocol for a randomized controlled trial

The number of older people worldwide is constantly increasing. However, ageing is accompanied by a decline in cognitive ability that can affect quality of life. Cognitive, physical and social activities can all slow this decline but social factors and their contribution to the well-being remain under-researched. The aim of this study is to analyse how the practice environment can foster these social relations and thus enhance well-being and to identify the psychological dimensions that are activated by social relations. This study is a 3-year randomised controlled trial designed to assess the effects on participants' cognitive abilities and quality of life of a combined (ie, physical and cognitive) training programme in different social practice environments. A total of 159 older people (≥65 years old) will be recruited and randomly assigned to one of three practice environments: individual practice at home (n=53), group practice in a gymnasium (n=53) and group practice in an enriched environment (n=53). All participants will complete 12-week combined training sessions and will be assessed four times: before the start, in the middle, at the end and 6 months after the end of the programme. They will undergo cognitive function (episodic memory and executive functions), physical capacity (aerobic fitness, muscle strength and dynamic balance) and psychosocial assessments (indicators of psychological well-being, social support, self-esteem, anxiety, depression and achievement goal strategies), as well as semistructured interviews. Statistical analyses will be conducted to assess the effect of the practice environment on the perceived benefits of this programme in terms of cognitive abilities and quality of life, and to determine the role of psychosocial factors in this relationship. This protocol has been approved by an institutional review board (CERSTAPS: IRB00012476-2022-20-01-146). Trials registration number: NCT05721508.

Efficacy of an environmental enrichment intervention for endometriosis: a pilot study

Introduction

We have previously shown that Environmental Enrichment (EE), a multi-modal psychosocial intervention consisting of increased social interaction, novelty, and open spaces, improved disease presentation, anxiety, and immune-related disturbances in the rat model of endometriosis. However, there is a knowledge gap regarding the effects of EE interventions in patients with this painful, inflammatory chronic disease.

Aim

To adapt and test the efficacy of an EE intervention on pelvic pain, mental health, perceived stress, quality of life, and systemic inflammation in endometriosis patients through a randomized clinical trial (RCT).

Materials and methods

A multidisciplinary team with expertise in physiology, neuroscience, psychology, and women's health adapted and implemented a two-arm RCT comparing an EE intervention with a wait-list control group. Six EE modules administered on alternate weeks were provided to patients in the intervention (N = 29); controls received education only. Survey data and biospecimens were collected at baseline, end-of-study, and 3-months post-intervention to assess pain (Brief Pain Inventory, BPI), endometriosis-related quality of life-QoL (Endometriosis Health Profile-30, EHP30), anxiety (Generalized Anxiety Disorder 7, GAD7), depression (Patient Health Questionnaire for Depression 8, PHQ8), pain catastrophizing (Pain Catastrophizing Score, PCS), stress (Perceived Stress Scale-14, PSS14), and saliva cortisol levels (AM, PM).

Results

Compared to the wait-list controls, participants in the EE intervention showed significantly decreased GAD-7 scores at the end of the intervention and 3-month follow-up. Depression, perceived stress, and QoL improved at the 3-month follow-up compared to baseline. While pain levels did not improve, they significantly correlated with anxiety, depression, QoL and pain catastrophizing scores.

Conclusion

This pilot RCT demonstrated significant improvements in anxiety and depressive symptoms, QoL, and perceived stress, supporting enriched environments as an integrative psychosocial intervention to be used as adjuvant to the standard of care for endometriosis pain.

Neuroprotection in metabolic syndrome by environmental enrichment. A lifespan perspective

Metabolic syndrome (MetS) is defined by the concurrence of different metabolic conditions: obesity, hypertension, dyslipidemia, and hyperglycemia. Its incidence has been increasingly rising over the past decades and has become a global health problem. MetS has deleterious consequences on the central nervous system (CNS) and neurological development. MetS can last several years or be lifelong, affecting the CNS in different ways and treatments can help manage condition, though there is no known cure. The early childhood years are extremely important in neurodevelopment, which extends beyond, encompassing a lifetime. Neuroplastic changes take place all life through - childhood, adolescence, adulthood, and old age - are highly sensitive to environmental input. Environmental factors have an important role in the etiopathogenesis and treatment of MetS, so environmental enrichment (EE) stands as a promising non-invasive therapeutic approach. While the EE paradigm has been designed for animal housing, its principles can be and actually are applied in cognitive, sensory, social, and physical stimulation programs for humans. Here, we briefly review the central milestones in neurodevelopment at each life stage, along with the research studies carried out on how MetS affects neurodevelopment at each life stage and the contributions that EE models can provide to improve health over the lifespan.

Does Incident Cardiovascular Disease Lead to Greater Odds of Functional and Cognitive Impairment? Insights From the Health and Retirement Study

BACKGROUND

Although studies to date have broadly shown that cardiovascular disease (CVD) increases cognitive and physical impairment risk, there is still limited understanding of the magnitude of this risk among relevant CVD subtypes or age cohorts.

METHODS

We analyzed longitudinal data from 16 679 U.S. Health and Retirement Study participants who were aged ≥65 years at study entry. Primary endpoints were physical impairment (activities of daily living impairment) or cognitive impairment (Langa-Weir Classification of dementia). We compared these endpoints among participants who developed incident CVD versus those who were CVD free, both in the short term (<2-year postdiagnosis) and long term (>5 years), controlling for sociodemographic and health characteristics. We then analyzed the effects by CVD subtype (atrial fibrillation, congestive heart failure, ischemic heart disease, and stroke) and age-at-diagnosis (65-74, 75-84, and ≥85).

RESULTS

Over a median follow-up of 10 years, 8 750 participants (52%) developed incident CVD. Incident CVD was associated with significantly higher adjusted odds (aOR) of short-term and long-term physical and cognitive impairment. The oldest (≥85) age-at-diagnosis subgroup had the highest risk of short-term physical (aOR 3.01, 95% confidence interval [CI]: 2.40-3.77) and cognitive impairment (aOR 1.96, 95% CI: 1.55-2.48), as well as long-term impairment. All CVD subtypes were associated with higher odds of physical and cognitive impairment, with the highest risk for patients with incident stroke.

CONCLUSIONS

Incident CVD was associated with an increased risk of physical and cognitive impairment across CVD subtypes. Impairment risk after CVD was highest among the oldest patients (≥85 years) who should therefore remain a target for prevention efforts.

Impact of environmental enrichment on the GABAergic neurons and glucocorticoid receptors in the hippocampus and nucleus accumbens of Wistar rats: pro-resilient effects

The unpredictable chronic mild stress (UCMS) model has been used to induce depressive-like symptoms in animal models. Our work aims to evaluate the impact of environmental enrichment on male Wistar rats in an animal model for depression. For this purpose, we aim to assess changes in GR and GABAergic (PV+) density in cerebral regions related to cognitive-affective processes associated with depressive disorder, such as the dorsal- ventral hippocampus and accumbens nuclei. Three groups of rats were used: UCMs (unpredictable chronic mild stress), EE+ UCMs (enrichment + stress) and CONT (behavioral tests only). Hedonic responses elicited by sucrose solution were examined by licking behavior analysis; the anxiety level was evaluated using the elevated zero maze and the forced swimming (passive coping) tests. The environmental enrichment reduced the effects of chronic stress, promoting greater resilience. Thus, the UCMs group showed an anhedonia response, more anxiety and immobility behavior than either the control or the EE+ UCMs groups. Regarding immunochemistry results, there was a reduction in GABAergic activity coupled with increased activation of GR in UCMs in the dorsal hippocampus, but there were no differences between groups in the ventral hippocampus. These results suggest environmental enrichment could enhance greater resilience, reducing the vulnerability of the subjects to develop disorders such as depression and anxiety.

Valuing embodiment: insights from dance practice among people living with dementia

There is a growing appreciation for the ability of person-centered arts-based approaches to extend multiple domains of brain health of people living with dementia. Dance is a multi-modal artistic engagement which has positive impacts on cognition, mobility and the emotional and social aspects of brain health. Although research into multiple domains of brain health among older adults and people living with dementia is promising, several gaps remain, specifically in understanding the benefits of co-creative and improvisational dance practices. Collaborative research between dancers, researchers, people living with dementia and care partners is needed to design and evaluate future research on dance and to determine relevance and usability. Furthermore, the respective praxes and experience of researchers, dance artists and people living with dementia contribute distinctly and uniquely to the identification and the assignment of value to dance in the context of the lives of people living with dementia. In this manuscript the author, a community-based dance artist, creative aging advocate and Atlantic Fellow for Equity in Brain Health, discusses current challenges and gaps in the understanding of the value of dance for and with people living with dementia and how transdisciplinary collaboration between neuroscientists, dance artists and people living with dementia can advance collective comprehension and implementation of dance practice.

Modulating chronic outcomes after pediatric traumatic brain injury: Distinct effects of social and environmental enrichment

Impairments in social and cognitive function are a common consequence of pediatric traumatic brain injury (TBI). Rehabilitation has the potential to promote optimal behavioral recovery. Here, we evaluated whether an enhanced social and/or cognitive environment could improve long-term outcomes in a preclinical model of pediatric TBI. Male C57Bl/6 J mice received a moderately-severe TBI or sham procedure at postnatal day 21. After one week, mice were randomized to different social conditions (minimal socialization, n = 2/cage; or social grouping, n = 6/cage), and housing conditions (standard cage, or environmental enrichment (EE), incorporating sensory, motor, and cognitive stimuli). After 8 weeks, neurobehavioral outcomes were assessed, followed by post-mortem neuropathology. We found that TBI mice exhibited hyperactivity, spatial memory deficits, reduced anxiety-like behavior, and reduced sensorimotor performance compared to age-matched sham controls. Pro-social and sociosexual behaviors were also reduced in TBI mice. EE increased sensorimotor performance, and the duration of sociosexual interactions. Conversely, social housing reduced hyperactivity and altered anxiety-like behavior in TBI mice, and reduced same-sex social investigation. TBI mice showed impaired spatial memory retention, except for TBI mice exposed to both EE and group housing. In the brain, while TBI led to significant regional tissue atrophy, social housing had modest neuroprotective effects on hippocampal volumes, neurogenesis, and oligodendrocyte progenitor numbers. In conclusion, manipulation of the post-injury environment has benefit for chronic behavioral outcomes, but the benefits are specific to the type of enrichment available. This study improves understanding of modifiable factors that may be harnessed to optimize long-term outcomes for survivors of early-life TBI.

[Touch, a crucial sense in social interactions to improve homeostasis in aging and promote healthy longevity]

Aging is associated with the generalized deterioration of the organism, being of great relevance experienced by homeostatic systems such as the nervous, immune, and endocrine systems, which increases the risk of morbidity and mortality. Among the lifestyle strategies that have been researched to improve these systems and achieve greater healthy longevity, this review will focus on the social environment. In order to verify the effectiveness of these both in the improvement of homeostasis and in life expectancy, the research carried out with experimental animals that have allowed this to be done will be discussed. In addition, as it has been observed that physical contact is crucial for the positive outcomes of social interaction on homeostatic systems and longevity to occur, we will focus on that mechanism, as well as some of the possible molecular pathways underlying the effects found.

Enriched environment during adolescence modulates lipid metabolism and emotion-related behaviors in mice

Enriched environment (EE) is an important animal experimental paradigm to decipher gene-environment interaction. It is thought to be efficient in aiding recovery from certain metabolism disorders or cognitive impairments. Recently, the effects of EE during adolescence in mice gradually draw much attention. We first established an EE model in adolescent mice, dissected lipid metabolism, and further examined baseline level of anxiety and depression by multiple behavioral tests, including open field test (OFT), elevated zero maze (EZM), tail suspension test (TST), and forced swimming test (FST). EE mice exhibited lower weights, lower cholesterol than standard housing (SH) mice. Behaviorally, EE mice traveled more distance and had higher velocity than SH mice in OFT and EZM. Besides, EE mice showed reduced anxiety levels in OFT and EZM. Furthermore, EE mice also had less immobility time than SH mice in TST and FST. Thus, these results suggest that EE during adolescence has metabolic and behavioral benefits in mice.

Reorganization of Brain Networks as a Substrate of Resilience: An Analysis of Cytochrome c Oxidase Activity in Rats

The unpredictable chronic mild stress (UCMS) model has been used to induce depressive-like symptoms in animal models, showing adequate predictive validity. Our work aims to evaluate the effects of environmental enrichment (EE) on resilience in this experimental model of depression. We also aim to assess changes in brain connectivity using cytochrome c oxidase histochemistry in cerebral regions related to cognitive-affective processes associated with depressive disorder: dorsal hippocampus, prefrontal cortex, amygdala, accumbens, and habenula nuclei. Five groups of rats were used: UCMS, EE, EE + UCMS (enrichment + stress), BG (basal level of brain activity), and CONT (behavioral tests only). We assessed the hedonic responses elicited by sucrose solution using a consumption test; the anxiety level was evaluated using the elevated zero maze test, and the unconditioned fear responses were assessed by the cat odor test. The behavioral results showed that the UCMS protocol induces elevated anhedonia and anxiety. But these responses are attenuated previous exposure to EE. Regarding brain activity, the UCMS group showed greater activity in the habenula compared to the EE + UCMS group. EE induced a functional reorganization of brain activity. The EE + UCMS and UCMS groups showed different patterns of connections between brain regions. Our results showed that EE favors greater resilience and could reduce vulnerability to disorders such as depression and anxiety, modifying metabolic brain activity.

Trauma-Informed Design of Supported Housing: A Scoping Review through the Lens of Neuroscience

There is growing recognition of the importance of the design of the built environment in supporting mental health. In this context, trauma-informed design has emerged as a new field of practice targeting the design of the built environment to support wellbeing and ameliorate the physical, psychological and emotional impacts of trauma and related pathologies such as Post Traumatic Stress Disorder (PTSD). With high levels of prevalence of PTSD among people escaping homelessness and domestic violence, a priority area is the identification and application of evidence-based design solutions for trauma-informed supported housing. This study sought to examine the scope of existing evidence on the relationship between trauma, housing and design and the correlation of this evidence with trauma-informed design principles, and to identify gaps and opportunities for future research. In response to the commonly articulated limitations of the evidence-base in built environment design research, we combined a scoping review of literature on trauma, housing and design with insights from neuroscience to focus and extend understanding of the opportunities of trauma-informed design. We found that while limited in scope, there is strong alignment between existing evidence and the principles of trauma-informed design. We also identify three areas of future research related to the key domains of safety and security; control; and enriched environments.

Enriched Environment Attenuates Enhanced Trait Anxiety in Association with Normalization of Aberrant Neuro-Inflammatory Events

Neuroinflammation is discussed to play a role in specific subgroups of different psychiatric disorders, including anxiety disorders. We have previously shown that a mouse model of trait anxiety (HAB) displays enhanced microglial density and phagocytic activity in key regions of anxiety circuits compared to normal-anxiety controls (NAB). Using minocycline, we provided causal evidence that reducing microglial activation within the dentate gyrus (DG) attenuated enhanced anxiety in HABs. Besides pharmacological intervention, "positive environmental stimuli", which have the advantage of exerting no side-effects, have been shown to modulate inflammation-related markers in human beings. Therefore, we now investigated whether environmental enrichment (EE) would be sufficient to modulate upregulated neuroinflammation in high-anxiety HABs. We show for the first time that EE can indeed attenuate enhanced trait anxiety, even when presented as late as adulthood. We further found that EE-induced anxiolysis was associated with the attenuation of enhanced microglial density (using Iba-1 as the marker) in the DG and medial prefrontal cortex. Additionally, EE reduced Iba1 + CD68+ microglia density within the anterior DG. Hence, the successful attenuation of trait anxiety by EE was associated in part with the normalization of neuro-inflammatory imbalances. These results suggest that pharmacological and/or positive behavioral therapies triggering microglia-targeted anti-inflammatory effects could be promising as novel alternatives or complimentary anxiolytic therapeutic approaches in specific subgroups of individuals predisposed to trait anxiety.

Association of Pace of Aging Measured by Blood-Based DNA Methylation With Age-Related Cognitive Impairment and Dementia

BACKGROUND AND OBJECTIVES

DNA methylation algorithms are increasingly used to estimate biological aging; however, how these proposed measures of whole-organism biological aging relate to aging in the brain is not known. We used data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and the Framingham Heart Study (FHS) Offspring Cohort to test the association between blood-based DNA methylation measures of biological aging and cognitive impairment and dementia in older adults.

METHODS

We tested 3 "generations" of DNA methylation age algorithms (first generation: Horvath and Hannum clocks; second generation: PhenoAge and GrimAge; and third generation: DunedinPACE, Dunedin Pace of Aging Calculated from the Epigenome) against the following measures of cognitive impairment in ADNI: clinical diagnosis of dementia and mild cognitive impairment, scores on Alzheimer disease (AD) / Alzheimer disease and related dementias (ADRD) screening tests (Alzheimer's Disease Assessment Scale, Mini-Mental State Examination, and Montreal Cognitive Assessment), and scores on cognitive tests (Rey Auditory Verbal Learning Test, Logical Memory test, and Trail Making Test). In an independent replication in the FHS Offspring Cohort, we further tested the longitudinal association between the DNA methylation algorithms and the risk of developing dementia.

RESULTS

In ADNI (N = 649 individuals), the first-generation (Horvath and Hannum DNA methylation age clocks) and the second-generation (PhenoAge and GrimAge) DNA methylation measures of aging were not consistently associated with measures of cognitive impairment in older adults. By contrast, a third-generation measure of biological aging, DunedinPACE, was associated with clinical diagnosis of Alzheimer disease (beta [95% CI] = 0.28 [0.08-0.47]), poorer scores on Alzheimer disease/ADRD screening tests (beta [Robust SE] = -0.10 [0.04] to 0.08[0.04]), and cognitive tests (beta [Robust SE] = -0.12 [0.04] to 0.10 [0.03]). The association between faster pace of aging, as measured by DunedinPACE, and risk of developing dementia was confirmed in a longitudinal analysis of the FHS Offspring Cohort (N = 2,264 individuals, hazard ratio [95% CI] = 1.27 [1.07-1.49]).

DISCUSSION

Third-generation blood-based DNA methylation measures of aging could prove valuable for measuring differences between individuals in the rate at which they age and in their risk for cognitive decline, and for evaluating interventions to slow aging.

Scoping review on environmental enrichment: Are critical periods and sex differences adequately studied?

BACKGROUND

Decades of research have shown the robust behavioral, structural, and molecular effects of environmental enrichment (EE) which predominantly improves neuropathological conditions. However, systematic examination of age and sex influences in response to EE is limited.

OBJECTIVE

Examine the use of EE and evaluate where sex differences (or similarities) are described and whether critical developmental periods are addressed. A critical examination of review articles about EE will establish a framework for the context of the findings of EE-induced effects, improve the impact of future EE studies and improve translatability.

ELIGIBILITY CRITERIA

Narrative, systematic reviews (not original reports) and meta-analyses of any animal species published during 2011 to 2021. Clinical and farming studies were excluded.

SOURCES OF EVIDENCE

Indexed review articles in Pubmed and Psychinfo.

RESULTS

Most studies examine EE during adulthood such as following an injury or following repeated addictive drug exposure. However, in various genetic models of disease states, little attention is paid to effects of EE at different ages. Only some reviews acknowledge that sex differences exist even when the disease state under study is known to be sexually dimorphic. Identified issues include lack of systematic reporting; status of the "control group" (i.e., isolation or pair housing); the use and reporting of proper statistical analyses.

CONCLUSION

Reviews have concluded that EE is most effective when administered early in life but that EE during adulthood is certainly effective. Too few review studies have compared sexes for the effects of EE to make a statement about sex differences. Overall, articles reflect a lack of integration of information on age and sex differences in response to EE. Future studies of EE should examine both sexes and consider critical periods of the lifespan in the experimental models to facilitate the adequate translation of EE as a non-pharmaceutical intervention.

Environmental enrichment and the aging brain: is it time for standardization?

Aging entails a progressive decline of cognitive abilities. However, since the brain is endowed with considerable plasticity, adequate stimulation can delay or partially compensate for age-related structural and functional impairment. Environmental enrichment (EE) has been reported to determine a wide range of cerebral changes. Although most findings have been obtained in young and adult animals, research has recently turned to aged individuals. Notably, EE can contribute identifying key lifestyle factors whose change can help extend the "mind-span", i.e., the time an individual lives in a healthy cognitive condition. Here we discuss specific methodological issues that can affect the outcomes of EE interventions applied to aged rodents, summarize the main variables that would need standardization (e.g., timing and duration, enrichment items, control animals and setting), and offer some suggestions on how this goal may be achieved. Reaching a consensus on EE experiment design would significantly reduce differences between and within laboratories, enable constructive discussions among researchers, and improve data interpretation.

Neurogenesis in aging and age-related neurodegenerative diseases

Adult neurogenesis, the process by which neurons are generated in certain areas of the adult brain, declines in an age-dependent manner and is one potential target for extending cognitive healthspan. Aging is a major risk factor for neurodegenerative diseases and, as lifespans are increasing, these health challenges are becoming more prevalent. An age-associated loss in neural stem cell number and/or activity could cause this decline in brain function, so interventions that reverse aging in stem cells might increase the human cognitive healthspan. In this review, we describe the involvement of adult neurogenesis in neurodegenerative diseases and address the molecular mechanistic aspects of neurogenesis that involve some of the key aggregation-prone proteins in the brain (i.e., tau, Aβ, α-synuclein, …). We summarize the research pertaining to interventions that increase neurogenesis and regulate known targets in aging research, such as mTOR and sirtuins. Lastly, we share our outlook on restoring the levels of neurogenesis to physiological levels in elderly individuals and those with neurodegeneration. We suggest that modulating neurogenesis represents a potential target for interventions that could help in the fight against neurodegeneration and cognitive decline.

An Indicator of environmental enrichment to measure physical, social and cognitive activities in human daily life

BACKGROUND

The concept of environmental enrichment (EE) encompasses complex physical, social, cognitive, motor, and somatosensory stimuli to which individuals are differentially exposed. An indicator of EE comprising these elements would facilitate the study of the impact of EE in diverse clinical settings by allowing an easy and comparable measurement. This study aimed to create and test such an EE indicator based on the Florida Cognitive Activities Scale (FCAS), the Multidimensional Social Integration in Later Life Scale (SILLS), and the International Physical Activity Questionnaire (IPAQ).

METHODS

Participants with major depression and control subjects were recruited in this cross-sectional comparative study. Depressive symptom severity was assessed with the Hamilton Depression Rating Scale (HAM-D). The EE indicator was used to evaluate cognitive, social, and physical activity. We divided the sample into three levels of cognitive and social activities to construct an EE indicator and compared the obtained scores between participants with major depression and control subjects.

RESULTS

40 patients suffering from major depression and 50 control subjects were included. Higher HAM-D scores were associated with lower EE levels. Cognitive and social items exhibited adequate reliability. Control subjects reported higher scores in all three activities evaluated, except for some items of physical activities. This indicator of EE clearly differentiated between participants with major depression from control subjects.

CONCLUSIONS

FCAS, SILLS, and IPAQ used together are valid to evaluate EE. This EE indicator may be a useful tool during clinical practice. The cross-sectional design and the small sample size are limitations of the present study.

Clinical and genetic characteristics of late-onset Huntington's disease in a large European cohort

Background and purpose

Huntington's disease (HD) is an autosomal dominant condition caused by CAG‐triplet repeat expansions. CAG‐triplet repeat expansion is inversely correlated with age of onset in HD and largely determines the clinical features. The aim of this study was to examine the phenotypic and genotypic correlates of late‐onset HD (LoHD) and to determine whether LoHD is a more benign expression of HD.

Methods

This was a retrospective observational study of 5053 White European HD patients from the ENROLL‐HD database. Sociodemographic, genetic and phenotypic variables at baseline evaluation of subjects with LoHD, common‐onset HD (CoHD) and young‐onset HD (YoHD) were compared. LoHD subjects were compared with healthy subjects (HS) aged ≥60 years. Differences between the CoHD and LoHD groups were also explored in subjects with 41 CAG triplets, a repeat number in the lower pathological expansion range associated with wide variability in age at onset.

Results

Late‐onset HD presented predominantly as motor‐onset disease, with a lower prevalence of both psychiatric history and current symptomatology. Absent/unknown HD family history was significantly more common in the LoHD group (31.2%) than in the other groups. The LoHD group had more severe motor and cognitive deficits than the HS group. Subjects with LoHD and CoHD with 41 triplets in the larger allele were comparable with regard to cognitive impairment, but those with LoHD had more severe motor disorders, less problematic behaviors and more often an unknown HD family history.

Conclusions

It is likely that cognitive disorders and motor symptoms of LoHD are at least partly age‐related and not a direct expression of the disease. In addition to CAG‐triplet repeat expansion, future studies should investigate the role of other genetic and environmental factors in determining age of onset.

Assessing Moderate to Vigorous Physical Activity in Older Adults: Validity of a Commercial Activity Tracker

Purpose: Despite the potential for commercial activity devices to promote moderate to vigorous physical activity (MVPA), limited information is available in older adults, a high-priority target population with unique gait dynamics and energy expenditure. The study purpose was to investigate the content validity of the Garmin Vivosmart HR device for step counts and MVPA in adults ≥65 years of age in free-living conditions. Methods: Thirty-five participants (M age= 73.7 (6.3) years) wore Garmin and ActiGraph GT3X+ devices for a minimum of 2 days. Accuracy and intra-person reliability were tested against a hip worn ActiGraph device. Separate analyses were conducted using different accelerometer cut-off values to define MVPA, a population-based threshold (≥2,020 counts/minute) and a recommended threshold for older adults (≥1,013 counts/minute). Results: Overall, the Garmin device overestimated MVPA compared with the hip-worn ActiGraph. However, the difference was small using the lower, age-specific, MVPA cut-off value [median (IQR) daily minutes; 50(85) vs. 32(49), p = 0.35] in contrast to the normative standard (50(85) vs. 7(24), p < 0.001). Regardless of the MVPA cut-off, intraclass correlation showed poor reliability [ICC (95% CI); 0.16(-0.40, 0.55) to 0.35(-0.32, 0.7)] which was supported by Bland-Altman plots. Garmin step count was both accurate (M step difference: 178.0, p = 0.22) and reliable [ICC (95% CI; 0.94) (0.88, 0.97)]. Conclusion: Results support the accuracy of a commercial activity device to measure MVPA in older adults but further research in diverse patient populations is needed to determine clinical utility and reliability over time.

Leisure Activity Variety and Brain Volume Among Community-Dwelling Older Adults: Analysis of the Neuron to Environmental Impact Across Generations Study Data

Background: Recent findings indicate that leisure activity (LA) delays cognitive decline and reduces the risk of dementia. However, the association between LA and brain volume remains unclear. This study aimed to examine the association between LA variety and brain volume with a focus on the hippocampus and gray matter. Methods: Data were obtained from the baseline survey of the Neuron to Environmental Impact across Generations study, which had targeted community-dwelling older adults living in Niigata, Japan. We divided LAs into 10 categories, and counted the number of categories of activities in which the participants engaged. We classified them as follows: 0 (i.e., no activity), 1, 2, or ≥ 3 types. Brain volume was assessed through magnetic resonance imaging, and hippocampal and gray matter volumes were ascertained. Results: The sample size was 482. Multiple linear regression analysis showed that hippocampal and gray matter volumes were significantly greater among participants with ≥ 3 types of LAs than among their no-activity counterparts. Hippocampal volume was significantly greater among those who engaged in one type of LA than among those who engaged in no such activity. Sex-stratified analysis revealed that hippocampal volumes were significantly greater among males who engaged in ≥ 3 types of LAs and one type of LA. However, no such association was found among females. Conclusion: The present findings suggest that engaging in a wide range of LAs is related to hippocampal and gray matter volumes. Furthermore, there was a sex difference in the association between LA variety and brain volume.

Environmental Enrichment Mitigates Age-Related Metabolic Decline and Lewis Lung Carcinoma Growth in Aged Female Mice

Aging is a complex physiological process that leads to the progressive decline of metabolic and immune function, among other biological mechanisms. As global life expectancy increases, it is important to understand determinants of healthy aging-including environmental and genetic factors-and thus slow the onset or progression of age-related disease. Environmental enrichment (EE) is a housing environment wherein laboratory animals engage with complex physical and social stimulation. EE is a prime model to understand environmental influences on aging dynamics, as it confers an antiobesity and anticancer phenotype that has been implicated in healthy aging and health span extension. Although EE is frequently used to study malignancies in young mice, fewer studies characterize EE-cancer outcomes in older mice. Here, we used young (3-month-old) and aged (14-month-old) female C57BL/6 mice to determine whether EE would be able to mitigate age-related deficiencies in metabolic function and thus alter Lewis lung carcinoma (LLC) growth. Overall, EE improved metabolic function, resulting in reduced fat mass, increased lean mass, and improved glycemic processing; many of these effects were stronger in the aged cohort than in the young cohort, indicating an age-driven effect on metabolic responses. In the aged-EE cohort, subcutaneously implanted LLC tumor growth was inhibited and tumors exhibited alterations in various markers of apoptosis, proliferation, angiogenesis, inflammation, and malignancy. These results validate EE as an anticancer model in aged mice and underscore the importance of understanding environmental influences on cancer malignancy in aged populations. PREVENTION RELEVANCE: Environmental enrichment (EE) serves as a model of complex physical and social stimulation. This study validates EE as an anticancer intervention paradigm in aged mice and underscores the importance of understanding environmental influences on cancer malignancy in aged populations.

Enhancing Effects of Environmental Enrichment on the Functions of Natural Killer Cells in Mice

The environment of an organism can convey a powerful influence over its biology. Environmental enrichment (EE), as a eustress model, has been used extensively in neuroscience to study neurogenesis and brain plasticity. EE has also been used as an intervention for the treatment and prevention of neurological and psychiatric disorders with limited clinical application. By contrast, the effects of EE on the immune system are relatively less investigated. Recently, accumulating evidence has demonstrated that EE can robustly impact immune function. In this review, we summarize the major components of EE, the impact of EE on natural killer (NK) cells, EE's immunoprotective roles in cancer, and the underlying mechanisms of EE-induced NK cell regulation. Moreover, we discuss opportunities for translational application based on insights from animal research of EE-induced NK cell regulation.

Microglial Morphology Across Distantly Related Species: Phylogenetic, Environmental and Age Influences on Microglia Reactivity and Surveillance States

Microglial immunosurveillance of the brain parenchyma to detect local perturbations in homeostasis, in all species, results in the adoption of a spectrum of morphological changes that reflect functional adaptations. Here, we review the contribution of these changes in microglia morphology in distantly related species, in homeostatic and non-homeostatic conditions, with three principal goals (1): to review the phylogenetic influences on the morphological diversity of microglia during homeostasis (2); to explore the impact of homeostatic perturbations (Dengue virus challenge) in distantly related species (Mus musculus and Callithrix penicillata) as a proxy for the differential immune response in small and large brains; and (3) to examine the influences of environmental enrichment and aging on the plasticity of the microglial morphological response following an immunological challenge (neurotropic arbovirus infection). Our findings reveal that the differences in microglia morphology across distantly related species under homeostatic condition cannot be attributed to the phylogenetic origin of the species. However, large and small brains, under similar non-homeostatic conditions, display differential microglial morphological responses, and we argue that age and environment interact to affect the microglia morphology after an immunological challenge; in particular, mice living in an enriched environment exhibit a more efficient immune response to the virus resulting in earlier removal of the virus and earlier return to the homeostatic morphological phenotype of microglia than it is observed in sedentary mice.

Sedentary Life and Reduced Mastication Impair Spatial Learning and Memory and Differentially Affect Dentate Gyrus Astrocyte Subtypes in the Aged Mice

To explore the impact of reduced mastication and a sedentary lifestyle on spatial learning and memory in the aged mice, as well as on the morphology of astrocytes in the molecular layer of dentate gyrus (MolDG), different masticatory regimens were imposed. Control mice received a pellet-type hard diet, while the reduced masticatory activity group received a pellet diet followed by a powdered diet, and the masticatory rehabilitation group received a pellet diet, followed by powder diet and then a pellet again. To mimic sedentary or active lifestyles, mice were housed in an impoverished environment of standard cages or in an enriched environment. The Morris Water Maze (MWM) test showed that masticatory-deprived group, regardless of environment, was not able to learn and remember the hidden platform location, but masticatory rehabilitation combined with enriched environment recovered such disabilities. Microscopic three-dimensional reconstructions of 1,800 glial fibrillary acidic protein (GFAP)-immunolabeled astrocytes from the external third of the MolDG were generated using a stereological systematic and random sampling approach. Hierarchical cluster analysis allowed the characterization into two main groups of astrocytes with greater and lower morphological complexities, respectively, AST1 and AST2. When compared to compared to the hard diet group subjected to impoverished environment, deprived animals maintained in the same environment for 6 months showed remarkable shrinkage of astrocyte branches. However, the long-term environmental enrichment (18-month-old) applied to the deprived group reversed the shrinkage effect, with significant increase in the morphological complexity of AST1 and AST2, when in an impoverished or enriched environment. During housing under enriched environment, complexity of branches of AST1 and AST2 was reduced by the powder diet (pellet followed by powder regimes) in young but not in old mice, where it was reversed by pellet diet (pellet followed by powder and pellet regime again). The same was not true for mice housed under impoverished environment. Interestingly, we were unable to find any correlation between MWM data and astrocyte morphological changes. Our findings indicate that both young and aged mice subjected to environmental enrichment, and under normal or rehabilitated masticatory activity, preserve spatial learning and memory. Nonetheless, data suggest that an impoverished environment and reduced mastication synergize to aggravate age-related cognitive decline; however, the association with morphological diversity of AST1 and AST2 at the MolDG requires further investigation.

The environmental enrichment model revisited: A translatable paradigm to study the stress of our modern lifestyle

Mounting evidence shows that physical activity, social interaction and sensorimotor stimulation provided by environmental enrichment (EE) exert several neurobehavioural effects traditionally interpreted as enhancements relative to standard housing (SH) conditions. However, this evidence rather indicates that SH induces many deficits, which could be ameliorated by exposing animals to an environment vaguely mimicking some features of their wild habitat. Rearing rodents in social isolation (SI) can aggravate such deficits, which can be restored by SH or EE. It is not surprising, therefore, that most preclinical stress models have included severe and unnatural stressors to produce a stress response prominent enough to be distinguishable from SH or SI-frequently used as control groups. Although current stress models induce a stress-related phenotype, they may fail to represent the stress of our urban lifestyle characterized by SI, poor housing and working environments, sedentarism, obesity and limited access to recreational activities and exercise. In the following review, we discuss the stress of living in urban areas and how exposures to and performing activities in green environments are stress relievers. Based on the commonalities between human and animal EE, we discuss how models of housing conditions (e.g., SI-SH-EE) could be adapted to study the stress of our modern lifestyle. The housing conditions model might be easy to implement and replicate leading to more translational results. It may also contribute to accomplishing some ethical commitments by promoting the refinement of procedures to model stress, diminishing animal suffering, enhancing animal welfare and eventually reducing the number of experimental animals needed.

Hypothalamic gene transfer of BDNF promotes healthy aging

The aging process and age-related diseases all involve metabolic decline and impaired ability to cope with adversity. Environmental enrichment (EE)-a housing environment which recapitulates aspects of active lifestyle-exerts a wide range of health benefits in laboratory rodents. Brain-derived neurotrophic factor (BDNF) in the hypothalamus orchestrates autonomic and neuroendocrine processes, serving as one key brain mediator of EE-induced resistance to obesity, cancer, and autoimmunity. Recombinant adeno-associated virus (AAV)-mediated hypothalamic BDNF gene transfer alleviates obesity, diabetes, and metabolic syndromes in both diet-induced and genetic models. One recent study by our lab demonstrates the efficacy and safety of a built-in autoregulatory system to control transgene BDNF expression, mimicking the body's natural feedback systems in middle-age mice. Twelve-month old mice were treated with autoregulatory BDNF vector and monitored for 7months. BDNF gene transfer prevented age-associated metabolic decline by: reducing adiposity, preventing the decline of brown fat activity, increasing adiponectin while reducing leptin and insulin in circulation, improving glucose tolerance, increasing energy expenditure, alleviating hepatic steatosis, and suppressing inflammatory genes in the hypothalamus and adipose tissues. Furthermore, BDNF treatment reduced anxiety-like and depression-like behaviors. This chapter summarizes this work and discusses potential roles that hypothalamic BDNF might play in promoting healthy aging.

Adipose PTEN acts as a downstream mediator of a brain-fat axis in environmental enrichment

Background/Objectives

Environmental enrichment (EE) is a physiological model to investigate brain-fat interactions. We previously discovered that EE activates the hypothalamic-sympathoneural adipocyte (HSA) axis via induction of brain-derived neurotrophic factor (BDNF), thus leading to sympathetic stimulation of white adipose tissue (WAT) and an anti-obesity phenotype. Here, we investigate whether PTEN acts as a downstream mediator of the HSA axis in the EE.

Methods

Mice were housed in EE for 4- and 16-week periods to determine how EE regulates adipose PTEN. Hypothalamic injections of adeno-associated viral (AAV) vectors expressing BDNF and a dominant negative form of its receptor were performed to assess the role of the HSA axis in adipose PTEN upregulation. A β-blocker, propranolol, and a denervation agent, 6-hydroydopamine, were administered to assess sympathetic signaling in the observed EE-PTEN phenotype. To determine whether inducing PTEN is sufficient to reproduce certain EE adipose remodeling, we overexpressed PTEN in WAT using an AAV vector. To determine whether adipose PTEN is necessary for the EE-mediated reduction in adipocyte size, we injected a rAAV vector expressing Cre recombinase to the WAT of adult PTEN^flox mice and placed the mice in EE.

Results

EE upregulated adipose PTEN expression, which was associated with suppression of AKT and ERK phosphorylation, increased hormone-sensitive lipase (HSL) phosphorylation, and reduced adiposity. PTEN regulation was found to be controlled by the HSA axis—with the hypothalamic BDNF acting as the upstream mediator—and dependent on sympathetic innervation. AAV-mediated adipose PTEN overexpression recapitulated EE-mediated adipose changes including suppression of AKT and ERK phosphorylation, increased HSL phosphorylation, and reduced adipose mass, whereas PTEN knockdown blocked the EE-induced reduction of adipocyte size.

Conclusions

These data suggest that adipose PTEN responds to environmental stimuli and serves as downstream mediator of WAT remodeling in the EE paradigm, resulting in decreased adipose mass and decreased adipocyte size.

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Environmental enrichment (EE) induces adipose PTEN expression and is associated with (1) suppression of AKT phosphorylation, (2) increased hormone-sensitive lipase phosphorylation, and (3) decreased adiposity

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The hypothalamic-sympathoneural-adipocyte (HSA) axis mediates EE-induced adipose PTEN

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rAAV-mediated gene delivery of PTEN to adipose tissues mimics EE-related adipose remodeling

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Knockdown of adipose PTEN blocks EE-induced reductions in adipocyte size