Role of neuroendocrine pathways in cognitive decline during aging

Specific but not general declines in attention and executive function with aging: Converging cross-sectional and longitudinal evidence across the adult lifespan

Objective

Attention and executive function (EF) are vulnerable to aging. However, whether all these functions generally decline with aging is not known. Furthermore, most evidence is based on cross-sectional data and fewer follow-up data are available in the literature. Longitudinal follow-up studies are necessary to characterize individualized and precise changes in cognitive function. Additionally, relatively few aging studies have included middle-aged adults to examine age-related differences in attention and EF. Therefore, this study aims to examine whether general or specific attention and EF decline with aging from adulthood to old age by combining cross-sectional and longitudinal follow-up approaches.

Methods

This study recruited 253 participants aged 20 to 78  years. passing a prescreening procedure (see main text for detail) for the baseline session, and 123 of them were invited to return 1 ~ 2  years after their first visit to participate in the follow-up session. The participants completed a series of attention and EF tasks at both the baseline and follow-up sessions, which measured alerting, orienting, conflict control, stopping, memory updating, and switching abilities. We applied linear and nonlinear regression models to evaluate the cross-sectional age effect on attention and EF and employed a modified Brinley plot to inspect follow-up performance against baseline in attention and EF.

Results

The results of cross-sectional data showed that older adults exhibited decreased efficiency in alerting, stopping, and memory updating but paradoxically increased efficiency in conflict control and switching abilities and no changes in orienting efficiency with age. However, the results of longitudinal data showed that only alerting and memory updating continued to show decreased efficiency. Furthermore, conflict control and switching showed increased efficiency with aging, whereas the orienting network, and stopping no longer showed decreased efficiency.

Conclusion

Thus, converging the cross-sectional and longitudinal data showed that the alerting and memory updating function exhibited the most robust deficit with age (cross-sectional) and aging (longitudinal). Alerting and memory updating abilities are crucial survival skills for human beings. Therefore, developing methods to prevent and improve an individual’s alertness and working memory ability is an important practical issue in aging research.

Effect of the one-day fasting on cortisol and DHEA daily rhythm regarding sex, chronotype, and age among obese adults

Introduction

Physiological and biochemical processes in the human body occur in a specific order and show rhythmic variability. Time dependence characterizes the secretion of cortisol and dehydroepiandrosterone (DHEA). One-day fasting implies alternating fasting days and eating days. The study aimed to determine how 24-h fasting affects the daily rhythm of cortisol and DHEA levels in obese people while taking into account gender and chronotype.

Methods

Forty-nine obese patients (BMI 32.2-67.1 kg/m²; 25 women and 24 men) underwent a 3-week hospital-controlled calorie restriction diet to reduce body weight. During hospitalization, patients fasted for 1 day, during which only water could be consumed. Samples of whole mixed unstimulated saliva were collected at 2-3-h intervals over a 64-h period and analyzed for cortisol and DHEA by immunoassays. The individual chronotypes were assessed by the morning and evening questionnaire, according to Horne and Östberg. Three components of daily rhythm were evaluated: amplitude, acrophase, and the so-called MESOR.

Results

Cortisol rhythm showed differences in amplitude (p = 0.0127) and acrophase (p = 0.0005). The amplitude on the fasting day was 11% higher (p = 0.224) than the day after. The acrophase advanced on the day of fasting, 48 min earlier than the day before (p = 0.0064), and by 39 min to the day after fasting (p = 0.0005). In the rhythm of DHEA, differences were found in the MESOR (p = 0.0381). The MESOR on the fasting day increased.

Discussion

Our results obtained during 64 consecutive hours of saliva sampling suggest that one-day fasting may affect three components of cortisol and DHEA daily rhythm. Additionally, no differences were found in the daily rhythm between the morning and evening chronotypes and between females and males. Although aging did not influence daily cortisol rhythm, DHEA amplitude, MESOR, and acrophase changed with age. To the best of our knowledge, this is the first presentation of changes in DHEA rhythm during one-day fasting.

Age, adrenal steroids, and cognitive functioning in captive chimpanzees (Pan troglodytes)

Background

Dehydroepiandrosterone-sulfate is the most abundant circulating androgen in humans and other catarrhines. It is involved in several biological functions, such as testosterone production, glucocorticoid antagonist actions, neurogenesis and neuroplasticty. Although the role of dehydroepiandrosterone-sulfate (DHEAS) in cognition remains elusive, the DHEAS/cortisol ratio has been positively associated with a slower cognitive age-decline and improved mood in humans. Whether this relationship is found in nonhuman primates remains unknown.

Methods

We measured DHEAS and cortisol levels in serum of 107 adult chimpanzees to investigate the relationship between DHEAS levels and age. A subset of 21 chimpanzees was used to test the potential associations between DHEAS, cortisol, and DHEAS/cortisol ratio in cognitive function, taking into account age, sex, and their interactions. We tested for cognitive function using the primate cognitive test battery (PCTB) and principal component analyses to categorize cognition into three components: spatial relationship tasks, tool use and social communication tasks, and auditory-visual sensory perception tasks.

Results

DHEAS levels, but not the DHEAS/cortisol ratio, declined with age in chimpanzees. Our analyses for spatial relationships tasks revealed a significant, positive correlation with the DHEAS/cortisol ratio. Tool use and social communication had a negative relationship with age. Our data show that the DHEAS/cortisol ratio, but not DHEAS individually, is a promising predictor of spatial cognition in chimpanzees.

Physiological Systems in Promoting Frailty

Frailty is a complex syndrome affecting a growing sector of the global population as medical developments have advanced human mortality rates across the world. Our current understanding of frailty is derived from studies conducted in the laboratory as well as the clinic, which have generated largely phenotypic information. Far fewer studies have uncovered biological underpinnings driving the onset and progression of frailty, but the stage is set to advance the field with preclinical and clinical assessment tools, multiomics approaches together with physiological and biochemical methodologies. In this article, we provide comprehensive coverage of topics regarding frailty assessment, preclinical models, interventions, and challenges as well as clinical frameworks and prevalence. We also identify central biological mechanisms that may be at play including mitochondrial dysfunction, epigenetic alterations, and oxidative stress that in turn, affect metabolism, stress responses, and endocrine and neuromuscular systems. We review the role of metabolic syndrome, insulin resistance and visceral obesity, focusing on glucose homeostasis, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and nicotinamide adenine dinucleotide (NAD+ ) as critical players influencing the age-related loss of health. We further focus on how immunometabolic dysfunction associates with oxidative stress in promoting sarcopenia, a key contributor to slowness, weakness, and fatigue. We explore the biological mechanisms involved in stem cell exhaustion that affect regeneration and may contribute to the frailty-associated decline in resilience and adaptation to stress. Together, an overview of the interplay of aging biology with genetic, lifestyle, and environmental factors that contribute to frailty, as well as potential therapeutic targets to lower risk and slow the progression of ongoing disease is covered. © 2022 American Physiological Society. Compr Physiol 12:1-46, 2022.

A population-based prospective study on rest-activity rhythm and mild cognitive impairment among Hong Kong healthy community-dwelling older adults

Background

Relatively few studies investigated the association between rest-activity circadian rhythm and cognitive impairment in population-based study, and the evidence from Asian populations is sparse. We aimed to examine the relationship of actigraphy measured rest-activity circadian rhythm with mild cognitive impairment (MCI) or cognitive impairment in Hong Kong healthy community-dwelling older adults.

Methods

We recruited 174 Hong Kong healthy adults aged ≥65 years (36 male vs. 138 female) during April-September 2018, and followed up them for 12 months. Participants were invited to wear wrist actigraphy for 7 days in both baseline and follow-up study. We used the actigraph data to calculate their midline statistic of rhythm (MESOR), amplitude, acrophase and percent rhythm. Montreal Cognitive Assessment (MoCA) was used to assess their cognitive scores at baseline and follow-up. Multivariate logistic regression model was performed to estimate the association of rest-activity circadian rhythm parameters with MCI; whilst multinomial logistic regression model was used to examine the association between rhythm parameters and changes of cognitive scores (i.e., worsen: <-1, stable: -1 to 1, better cognition: ≥2) after 12-months follow-up respectively.

Results

There was no association between rest-activity circadian rhythm parameters and MCI or cognitive impairment at baseline. Compared to those with an averaged value of acrophase (1:24pm-3:00pm), results of multinominal logistic regression showed that participants with a delayed acrophase (after 3:00pm) were less likely to have better cognition (adjusted odds ratio (AOR) = 0.32, 95% confidence interval (CI) = 0.11-0.88). Upon one year of follow-up, participants who delayed their acrophase for 24 min than their baseline measurements were also less likely to have better cognitive functions (AOR = 0.26, 95%CI = 0.08-0.79).

Conclusions

Results from both the baseline survey and follow-up study consistently confirmed that older adults, especially in light of the majority of participants being the females, with delayed acrophase were less likely to have better cognition in the Asian population.

Stabilization of telomere by the antioxidant property of polyphenols: Anti-aging potential

Aging is a form of a gradual loss of physiological integrity that results in impaired cellular function and ultimately increased vulnerability to disease and death. This process is a significant risk factor for critical age-related disorders such as cancer, diabetes, cardiovascular disease, and neurological conditions. Several mechanisms contribute to aging, most notably progressive telomeres shortening, which can be counteracted by telomerase enzyme activity and increasing in this enzyme activity associated with partly delaying the onset of aging. Individual behaviors and environmental factors such as nutrition affect the life-span by impact the telomerase activity rate. Healthy eating habits, including antioxidant intakes, such as polyphenols, can have a positive effect on telomere length by this mechanism. In this review, after studying the underlying mechanisms of aging and understanding the relationships between telomeres, telomerase, and aging, it has been attempted to explain the effect of polyphenols on reversing the oxidative stress and aging process.

Interplay between hormones and exercise on hippocampal plasticity across the lifespan

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

Cognitive processes in aging effects on attentional alerting

Alerting, the process of achieving and maintaining a state of optimal vigilance, is crucial for detecting relevant stimuli and task performance. Age-related decline in the ability to use alerting cues is widely reported and attributed to changes in noradrenergic signaling. However, it remains to be determined whether aging affects all forms of alerting cues equally and whether older adults differently modulate their alerting sensitivity based on differences in cue predictivity relevant to the target task. We examined the performance of 135 younger adults and 103 older adults on three versions of the Attention Networks Test, using locational but spatially nonpredictive visual cues, locational spatially predictive visual cues, and spatially predictive auditory cues. Analysis of alerting effects indicated that while older adults derived less benefit from visual alerting cues than younger adults, they used auditory alerting cues equally well. Furthermore, cue spatial predictivity did not impact on aging effects on alerting. This heterogeneity in aging effects on alerting may indicate that they result primarily from cognitive rather than neuromodulatory changes.

Tinnitus, hearing loss and inflammatory processes in an older Portuguese population

Objective: Tinnitus is associated with various conditions such as presbycusis, infectious, autoimmune and many other diseases. Our study aims to identify an association between inflammatory markers and the presence of tinnitus or hearing loss (HL).Design: Exploratory study including a structured interview, complete ENT observation, audiological and inflammatory markers evaluation.Study Sample: Sixty women and 54 men (55 to 75 years) from the Portuguese population, with or without sensory presbycusis and/or tinnitus.Results: IL10 levels were significantly lower in participants with tinnitus than in those without tinnitus. Moreover, TGF-β was lower in older participants (p = 0.034), IL1α was higher in participants with tonal tinnitus (p = 0.033), and IL2 was lower in participants who reported partial or complete residual inhibition (p = 0.019). Additionally, we observed a negative correlation between tinnitus duration and IL10 levels (r= -.281), and between HSP70 levels and tinnitus loudness (r= -.377). TNF-α and HSP70 levels appears to be sensitive to the time when samples were collected (morning or afternoon).Conclusions: The results of our study showing fluctuations in inflammatory markers along the hearing loss process, reinforce the idea that inflammatory mechanisms are involved in hearing loss pathogenesis but also in tinnitus. IL10 levels appear significantly altered in tinnitus but not in hearing loss.

From Healthy Aging to Frailty: In Search of the Underlying Mechanisms

Population aging is accelerating rapidly worldwide, from 461 million people older than 65 years in 2004 to an estimated 2 billion people by 2050, leading to critical implications for the planning and delivery of health and social care. The most problematic expression of population aging is the clinical condition of frailty, which is a state of increased vulnerability that develops as a consequence of the accumulation of microscopic damages in many physiological systems that lead to a striking and disproportionate change in health state, even after an apparently small insult. Since little is known about the biology of frailty, an important perspective to understand this phenomenon is to establish how the alterations that physiologically occur during a condition of healthy aging may instead promote cumulative decline with subsequent depletion of homoeostatic reserve and increase the vulnerability also after minor stressor events. In this context, the present review aims to provide a description of the molecular mechanisms that, by having a critical impact on behavior and neuronal function in aging, might be relevant for the development of frailty. Moreover, since these biological systems are also involved in the coping strategies set in motion to respond to environmental challenges, we propose a role for lifestyle stress as an important player to drive frailty in aging.

Integrating Frailty and Cognitive Phenotypes: Why, How, Now What?

PURPOSE OF REVIEW

This review elucidates the concept of frailty in relationship to reserve and resilience, the relationships and shared pathophysiology between physical frailty and cognitive impairment, the theoretical underpinnings of three integrated phenotypes of physical and cognitive impairments, and the potential of incorporating biomarkers into phenotype refinement and validation.

RECENT FINDINGS

The fact that frailty and cognitive impairment are associated and often coexist in older adults has led to the popular view of expanding the definition of frailty to include cognitive impairment. However, there is great variability in approaches to and assumptions regarding the integrated phenotypes of physical frailty and cognitive impairment.

SUMMARY

The development of integrated frailty and cognitive phenotypes should explicate the types of frailty and cognitive impairment they intend to capture and prioritize the incorporation of biological theories that help determine shared and distinct pathways in the progression to physical and cognitive impairments.

Mental health in familial caregivers of Alzheimer's disease patients: are the effects of chronic stress on cognition inevitable?

Familial caregivers of Alzheimer's disease (AD) patients experience an emotional and physical burden which characterizes a chronic stress condition. The resulting hypothalamic-pituitary-adrenal axis dysfunction favors an imbalance of neurotoxic/neuroprotective factors and causes cognitive impairments, increasing the caregivers' risk for cognitive decline and compromising their ability to provide adequate care of the patient. Therefore, the present study aimed to investigate the reversibility of the cognitive impairments of familial caregivers of AD patients during their caregiving-related chronic stress condition. Thirty-three caregivers (61.42 + 2.68 years; 27 women) and thirty-four controls (57.91 ± 2.16 years, 20 women) were evaluated for their cognitive functioning (attention, executive function, processing speed and memory) with a neuropsychological battery (Digit-span, Trail Making, Stroop and the Logical Memory tests). Subjects' cortisol/dehydroepiandrosterone (DHEA) ratios were determined by radioimmunoassay, and their brain-derived neurotrophic factor (BDNF) levels were analyzed by ELISA. An incidental contextual memory task, with or without an associative encoding instruction, was used to investigate if caregivers have a cognitive reserve prone to rehabilitation. The contextual memory impairment of caregivers was associated with prefrontal and hippocampal cognitive dysfunctions, alterations of the cortisol/DHEA ratio and lower BDNF levels. Even so, the contextual memory impairment could be improved by the associative encoding condition. This study suggests that the cognitive impairments of caregivers are not necessarily irreversible, as indicated by the results obtained for contextual memory, which could be improved despite the ongoing chronic stress and associated hormonal and neurotrophin dysfunctions. Lay summary The support of a relative with Alzheimer's Disease submits the familial caregivers to a chronic stress condition that increases their own risk of cognitive decline. This study suggests that, irrespective to their alterations on cortisol/DHEA ratio and BDNF levels, caregivers have a cognitive reserve that could probably be engaged to limit the negative effects of chronic stress on cognition.

Central intracrine DHEA synthesis in ageing-related neuroinflammation and neurodegeneration: therapeutic potential?

It is a well-known fact that DHEA declines on ageing and that it is linked to ageing-related neurodegeneration, which is characterised by gradual cognitive decline. Although DHEA is also associated with inflammation in the periphery, the link between DHEA and neuroinflammation in this context is less clear. This review drew from different bodies of literature to provide a more comprehensive picture of peripheral vs central endocrine shifts with advanced age—specifically in terms of DHEA. From this, we have formulated the hypothesis that DHEA decline is also linked to neuroinflammation and that increased localised availability of DHEA may have both therapeutic and preventative benefit to limit neurodegeneration. We provide a comprehensive discussion of literature on the potential for extragonadal DHEA synthesis by neuroglial cells and reflect on the feasibility of therapeutic manipulation of localised, central DHEA synthesis.

Effect of Coelogyne cristata Lindley in alleviation of chronic fatigue syndrome in aged Wistar rats

BACKGROUND

Swarna Jibanti scientifically known as Coelogyne cristata Lindley (Orchidaceae), an orchid mentioned in Ayurvedic medicine is used to promote healthy life span.

OBJECTIVE(S)

The present work was planned to study the efficacy of hydro-alcoholic extract of pseudobulbs of C. cristata (CCE) to assess its role on chronic fatigue syndrome (CFS) induced behavioural and biochemical changes in aged Wistar rats compared to Panax ginseng (PG), a prototype anti-stress agent.

MATERIALS AND METHODS

CFS was induced by forced swimming for consecutive 21 days for fixed duration (15 min sessions). The criteria of CFS due to fatigue were counted using locomotor activity, depression and anxiety through automated photactometer, immobility time and plus maze activity respectively. Acute toxicity study of CCE (upto 2 g/kg, Limit test) was also performed. For CFS, animals were divided into five groups, naive control, control, CCE treated (25 mg/kg b.w., 250 mg/kg b.w.) and standard PG treated (100 mg/kg b.w.) groups. All drugs were given orally for consecutive 21 days along with CFS. After assessing behavioural parameters, all animals were sacrificed at day 21 and in vivo antioxidant potential of CCE was determined by lipid peroxides, nitrite, catalase (CAT) and superoxide dismutase (SOD) in brain tissue.

RESULTS

CCE was found to be non-toxic. CCE treated aged rats significantly improved (p < 0.001) the spontaneous locomotor movement with respect to control rats, while, decreased the mobility period or depression score. In CFS, CCE also enhanced the time spent (p < 0.001) in open arms while reducing the time spent in closed arm as compared to CFS control, indicating lowering anxiety score. Moreover, marked diminution in lipid peroxidation, nitrite and SOD level was exhibited after CCE treatment and significantly enhanced catalase level significantly (p < 0.01) with respect to CFS control. PG also showed similar actions.

CONCLUSION

The results confirmed the potential therapeutic actions of CCE against experimentally induced CFS in aged rats that might be due to its CNS mediatory antioxidant properties.

Memory Training Program Decreases the Circulating Level of Cortisol and Pro-inflammatory Cytokines in Healthy Older Adults

Aging cognitive decline has been associated to impairment of the Hypothalamus Pituitary Adrenals (HPA) axis activity and a higher level of the systemic inflammation. However, little is known about the molecules driving this process at peripheral level. In addition, the cognitive function is to some extent modifiable with Memory Training (MT) programs, even among older adults and beyond. The study aims to evaluate whether MT could contribute to ameliorate cognitive performance and modulate the HPA axis activity as well the low level inflammation in the aging phenotype. Whether the phosphatase WIP-1, a negative regulator for inflammation, is involved in this process was also investigated. We recruited 31 young adults (19-28, years of age) and 62 older adults aged over 60. Thirty-two older adults were submitted to 6-months of MT program (EG), and 28 older adults were no treated and used as Control Group (CG). Global cognitive functioning (MMSE score), verbal and visual memory, and attention were assessed at baseline (T0) and after 6-months (T1). At the same time, plasmatic level of Cortisol (C), IL-1β, IL-18, IL-6, and the expression of WIP-1 mRNA and protein in ex vivo Peripheral Blood Mononuclear Cells were analyzed in young adults at T0, as well in older adults at T0 and T1. Together, the results suggest that MT improves the global cognitive functionality, verbal and visual memory, as well as the level of attention. At the same time we observed a decrease of the plasmatic level of C, of the cytokines, and an increase of the expression of mRNA and protein of WIP-1. The analysis of correlations highlighted that the level of the mRNA of WIP-1 was positively associated to the MMSE score, and negatively to the C and cytokine levels. In conclusion, we purpose the MT as tool that could help support successful aging through the improving of memory, attention and global cognitive function performance. Furthermore, this approach could participate to maintain lower the peripheral levels of the C and pro-inflammatory cytokines. The WIP-1 as a potential new target of the pathophysiology of aging is theorized.

The effects of aging in the hippocampus and cognitive decline

Aging is a natural process that is associated with cognitive decline as well as functional and social impairments. One structure of particular interest when considering aging and cognitive decline is the hippocampus, a brain region known to play an important role in learning and memory consolidation as well as in affective behaviours and mood regulation, and where both functional and structural plasticity (e.g., neurogenesis) occur well into adulthood. Neurobiological alterations seen in the aging hippocampus including increased oxidative stress and neuroinflammation, altered intracellular signalling and gene expression, as well as reduced neurogenesis and synaptic plasticity, are thought to be associated with age-related cognitive decline. Non-invasive strategies such as caloric restriction, physical exercise, and environmental enrichment have been shown to counteract many of the age-induced alterations in hippocampal signalling, structure, and function. Thus, such approaches may have therapeutic value in counteracting the deleterious effects of aging and protecting the brain against age-associated neurodegenerative processes.

Acute central effects of corticotropin-releasing factor (CRF) on energy balance: Effects of age and gender

Previously demonstrated age-related changes in the catabolic melanocortin system that may contribute to middle-aged obesity and aging anorexia, raise the question of the potential involvement of corticotropin-releasing factor (CRF) in these phenomena, as this catabolic hypothalamic mediator acts downstream to melanocortins. Catabolic effects of CRF were shown to be mediated by both CRF1 (hypermetabolism) and CRF2 (anorexia) receptors. To test the potential role of CRF in age-related obesity and aging anorexia, we investigated acute central effects of the peptide on energy balance in male and female rats during the course of aging. Effects of an intracerebroventricular CRF injection on food intake (FI), oxygen-consumption (VO₂), core- and tail skin temperatures (Tc and Ts) were studied in male and female Wistar rats of five different age-groups (from 3- to 24-month). Anorexigenic responsiveness was tested during 180-min re-feeding (FeedScale) following 24-h fasting. Thermoregulatory analysis was performed by indirect calorimetry (Oxymax) complemented by thermocouples recording Tc and Ts (indicating heat loss). CRF suppressed FI in 3-month male and female animals. In males, CRF-induced anorexia declined with aging, whereas in females it was maintained in all groups. The peptide increased VO₂ and Tc in all male age-groups, while the weaker hypermetabolic response characterizing 3-month females declined rapidly with aging. Thus, age-related alterations in acute central anorexigenic and hypermetabolic effects of CRF show different non-parallel patterns in males and females. Our findings underline the importance of gender differences. They also call the attention to the differential age-related changes in the CRF1 and CRF2 receptor systems.

Age Effects on Cognitive and Physiological Parameters in Familial Caregivers of Alzheimer's Disease Patients

OBJECTIVES

Older familial caregivers of Alzheimer's disease patients are subjected to stress-related cognitive and psychophysiological dysfunctions that may affect their quality of life and ability to provide care. Younger caregivers have never been properly evaluated. We hypothesized that they would show qualitatively similar cognitive and psychophysiological alterations to those of older caregivers.

METHOD

The cognitive measures of 17 young (31-58 years) and 18 old (63-84 years) caregivers and of 17 young (37-57 years) and 18 old (62-84 years) non-caregiver controls were evaluated together with their salivary cortisol and dehydroepiandrosterone (DHEA) levels, as measured by radioimmunoassays and ELISA assays of brain-derived neurotrophic factor (BDNF) in serum.

RESULTS

Although younger caregivers had milder impairments in memory and executive functions than older caregivers, their performances fell to the same or lower levels as those of the healthy older controls. Decreases in DHEA and BDNF levels were correlated with the cognitive dysfunctions observed in the older and younger caregivers, respectively. Cortisol at 10PM increased in both caregiver groups.

DISCUSSION

Younger caregivers were prone to cognitive impairments similar to older caregivers, although the degree and the neuropsychological correlates of the cognitive dysfunctions were somewhat different between the two groups. This work has implications for caregiver and care-recipient health and for research on the neurobiology of stress-related cognitive dysfunctions.

Effect of age, gender and exercise on salivary dehydroepiandrosterone circadian rhythm profile in human volunteers

There has been a lot of effort by scientists to elucidate the multi functions of the naturally occurring hormone, dehydroepiandrosterone (DHEA). However, to plan research experiments optimally, it is important first to characterize the diurnal rhythm in healthy individuals. The aim of this research was to investigate the daily circadian rhythms of DHEA among the 2 genders, and the effect of age and exercise on salivary DHEA circadian rhythms. Volunteers (20-39 and 40-60 years) were recruited for 2 studies investigating the salivary DHEA circadian rhythm. The first study looked at the effect of gender and age on DHEA levels on 2 non-consecutive days, and the second study explored the effect of exercise on DHEA circadian rhythm in males. DHEA levels were estimated by a sensitive and specific ELISA method. The results showed a clear daily circadian rhythm in salivary DHEA in all participants groups, however the profile was flatter in the older female group. There was a significant difference between age and gender groups particularly at 8.00 h. In young males DHEA reduced from 541.1 ± 101.3 (mean ± sd) at 8.00 h to 198.9 ± 90.7 pg/mL at 18.00 h; p<0.0001, and young females from 401.6 ± 149.5 to 215.4 ± 95.3 pg/mL; p<0.001. In older males DHEA reduced from 267.5 ± 32.4 to 132.5 ± 46.7 pg/mL; p<0.001, and older females from 147.7 ± 78.1 to 89.5 ± 29.1 pg/mL; p=0.05. DHEA levels on 2 non-consecutive days showed some variations but this was not significant. Aerobic exercise has significantly increased DHEA levels at 2 time points of the day (p=0.05) in male subjects. In conclusion, our study showed a clear daily circadian rhythm in salivary DHEA in all participants was observed, but the profile was flatter in the older groups.

Melatonin and cortisol profiles in late midlife and their association with age-related changes in cognition

Previous studies have reported an association between circadian disturbances and age-related cognitive impairment. The aim was to study the 24-hour profiles of melatonin and cortisol in relation to cognitive function in middle-aged male subjects. Fifty healthy middle-aged males born in 1953 were recruited from a population-based cohort based on previous cognitive assessments in young adulthood and late midlife. The sample included 24 cognitively high-functioning and 26 cognitively impaired participants. Saliva samples were collected every 4 hours over a 24-hour period and analyzed for cortisol and melatonin levels by immunoassay. All participants exhibited clear circadian rhythms of salivary melatonin and cortisol. Salivary melatonin concentrations had a nocturnal peak at approximately 4 am. The median nocturnal melatonin response at 4 am was significantly lower in the cognitively impaired group than in the high-functioning group (-4.6 pg/mL, 95% CI: -7.84, -1.36, P=0.006). The 24-hour mean melatonin concentration (high-functioning group: 4.80±0.70 pg/mL, vs cognitively impaired group: 4.81±0.76 pg/mL; P>0.05) (or the area under the curve, AUC) was not significantly different between the two groups. Cortisol levels were low during the night, and peaked at approximately 8 am. Median cortisol concentrations were similar at all times, as were the 24-hour mean cortisol concentrations and AUC. To the best of our knowledge, ours is the first study to assess circadian measures (ie, melatonin and cortisol) in healthy middle-aged men with different cognitive trajectories in midlife. We found evidence of altered circadian rhythms with a reduced nocturnal melatonin response at 4 am in men with cognitive impairment. The 24-hour concentration and AUC of melatonin and cortisol were similar in the cognitively high-functioning group and in the cognitively impaired.

Genetic contributions to variation in general cognitive function: a meta-analysis of genome-wide association studies in the CHARGE consortium (N=53949)

General cognitive function is substantially heritable across the human life course from adolescence to old age. We investigated the genetic contribution to variation in this important, health- and well-being-related trait in middle-aged and older adults. We conducted a meta-analysis of genome-wide association studies of 31 cohorts (N=53,949) in which the participants had undertaken multiple, diverse cognitive tests. A general cognitive function phenotype was tested for, and created in each cohort by principal component analysis. We report 13 genome-wide significant single-nucleotide polymorphism (SNP) associations in three genomic regions, 6q16.1, 14q12 and 19q13.32 (best SNP and closest gene, respectively: rs10457441, P=3.93 × 10(-9), MIR2113; rs17522122, P=2.55 × 10(-8), AKAP6; rs10119, P=5.67 × 10(-9), APOE/TOMM40). We report one gene-based significant association with the HMGN1 gene located on chromosome 21 (P=1 × 10(-6)). These genes have previously been associated with neuropsychiatric phenotypes. Meta-analysis results are consistent with a polygenic model of inheritance. To estimate SNP-based heritability, the genome-wide complex trait analysis procedure was applied to two large cohorts, the Atherosclerosis Risk in Communities Study (N=6617) and the Health and Retirement Study (N=5976). The proportion of phenotypic variation accounted for by all genotyped common SNPs was 29% (s.e.=5%) and 28% (s.e.=7%), respectively. Using polygenic prediction analysis, ~1.2% of the variance in general cognitive function was predicted in the Generation Scotland cohort (N=5487; P=1.5 × 10(-17)). In hypothesis-driven tests, there was significant association between general cognitive function and four genes previously associated with Alzheimer's disease: TOMM40, APOE, ABCG1 and MEF2C.

Antiglucocorticoid therapy for older adults with anxiety and co-occurring cognitive dysfunction: results from a pilot study with mifepristone

OBJECTIVES

In older adults with anxiety disorders, chronically elevated cortisol may contribute to cognitive impairment and elevated anxiety. We conducted a pilot study with mifepristone, a glucocorticoid receptor antagonist, as a potential treatment for late-life anxiety disorders and co-occurring cognitive dysfunction.

METHODS

Fifteen individuals 60 years and older with an anxiety disorder plus cognitive dysfunction participated in the 12-week study. In the first week, participants were randomly assigned to mifepristone 300 mg daily or placebo. In the subsequent 3 weeks, all participants received mifepristone 300 mg. Mifepristone was then discontinued, and the participants were reassessed 8 weeks later. We examined the following: (1) cognitive changes; (2) worry symptom severity; (3) safety and tolerability; and (4) salivary cortisol before, during, and after mifepristone exposure.

RESULTS

Overall safety, tolerability, and high retention supported the feasibility of this research. Participants with higher baseline cortisol levels (peak cortisol >6.0 ng/ml, n = 5) showed improvements in memory, executive function, and worry severity after 3-4 weeks of mifepristone with persistent memory and worry improvements 8 weeks after mifepristone discontinuation. Individuals with low-to-normal baseline cortisol (n = 8) showed little to no improvement. As expected, cortisol levels rose during mifepristone exposure and returned to pretreatment levels 8 weeks after mifepristone discontinuation. In the first week of treatment, there were no differences between placebo-treated and mifepristone-treated participants.

CONCLUSION

The results of this pilot study warrant further testing of antiglucocorticoid agents in late-life anxiety disorders with co-occurring cognitive dysfunction. Mifepristone is hypothesized to have benefits in patients with evidence of glucocorticoid excess. Directions for further study are discussed.

Hospitalization and cognitive decline: Can the nature of the relationship be deciphered?

BACKGROUND

Evidence for a relationship between hospitalization and incident cognitive decline exists mainly in the literature focusing on critical care hospitalization. Recent studies, however, have also found an association between noncritical care hospitalization and the development of cognitive decline.

OBJECTIVE

This article will review the literature pertaining to hospitalization and cognitive decline, including hospitalizations for both critical and noncritical care, and in medical and surgical patients. The article will also explore the various factors that have been implicated in the development of cognitive decline and dementia.

METHODS

Review of the literature was completed using PubMed and Medline search programs.

RESULTS

Several articles supporting evidence for the association between hospitalization and cognitive decline are available. Evidence for potential mediating factors also does exist.

CONCLUSIONS

There is evidence to support an association between hospitalization and development of cognitive decline. Factors that could mediate this association include, but may not be limited to, delirium, medications, stress, and depression. There is a need for further research in this area in order to better understand the underlying pathophysiology involved in the development of cognitive decline and dementia and to determine if preventive measures might be beneficial in decreasing risk for cognitive decline for patients who are hospitalized.

Aged rats are hypo-responsive to acute restraint: implications for psychosocial stress in aging

Cognitive processes associated with prefrontal cortex and hippocampus decline with age and are vulnerable to disruption by stress. The stress/stress hormone/allostatic load hypotheses of brain aging posit that brain aging, at least in part, is the manifestation of life-long stress exposure. In addition, as humans age, there is a profound increase in the incidence of new onset stressors, many of which are psychosocial (e.g., loss of job, death of spouse, social isolation), and aged humans are well-understood to be more vulnerable to the negative consequences of such new-onset chronic psychosocial stress events. However, the mechanistic underpinnings of this age-related shift in chronic psychosocial stress response, or the initial acute phase of that chronic response, have been less well-studied. Here, we separated young (3 month) and aged (21 month) male F344 rats into control and acute restraint (an animal model of psychosocial stress) groups (n = 9–12/group). We then assessed hippocampus-associated behavioral, electrophysiological, and transcriptional outcomes, as well as blood glucocorticoid and sleep architecture changes. Aged rats showed characteristic water maze, deep sleep, transcriptome, and synaptic sensitivity changes compared to young. Young and aged rats showed similar levels of distress during the 3 h restraint, as well as highly significant increases in blood glucocorticoid levels 21 h after restraint. However, young, but not aged, animals responded to stress exposure with water maze deficits, loss of deep sleep and hyperthermia. These results demonstrate that aged subjects are hypo-responsive to new-onset acute psychosocial stress, which may have negative consequences for long-term stress adaptation and suggest that age itself may act as a stressor occluding the influence of new onset stressors.

Causes and consequences of age-related steroid hormone changes: insights gained from nonhuman primates

Similar to humans, rhesus macaques (Macaca mulatta) are large, long-lived diurnal primates, and show similar age-related changes in the secretion of many steroid hormones, including oestradiol, testosterone, cortisol and dehydroepiandrosterone (DHEA). Consequently, they represent a pragmatic animal model in which to examine the mechanisms by which these steroidal changes contribute to perturbed sleep-wake cycles and cognitive decline in the elderly. Using remote serial blood sampling, we have found the circulating levels of DHEA sulphate, as well as oestradiol and testosterone, decline markedly in old monkeys. Furthermore, using the real-time polymerase chain reaction, we have shown that the genes for the enzymes associated with the conversion of DHEA to oestradiol and testosterone (3β-hydroxysteroid dehydrogenase, 17β-hydroxysteroid dehydrogenase, and aromatase) are highly expressed in brain areas associated with cognition and behaviour, including the hippocampus, prefrontal cortex and amygdala. Taken together, these findings suggest that the administration of supplementary DHEA in the elderly may have therapeutic potential for cognitive and behavioural disorders, although with fewer negative side effects outside of the central nervous system. To test this, we have developed a novel steroid supplementation paradigm for use in old animals; this involves the oral administration of DHEA and testosterone at physiologically relevant times of the day to mimic the circadian hormone patterns observed in young adults. We are currently evaluating the efficacy of this steroid supplementation paradigm with respect to reversing age-associated disorders, including perturbed sleep-wake cycles and cognitive decline, as well as an impaired immune response.

Tryptophan-enriched cereal intake improves nocturnal sleep, melatonin, serotonin, and total antioxidant capacity levels and mood in elderly humans

Melatonin and serotonin rhythms, which exhibit a close association with the endogenous circadian component of sleep, are attenuated with increasing age. This decrease seems to be linked to sleep alterations in the elderly. Chrononutrition is a field of chronobiology that establishes the principle of consuming foodstuffs at times of the day when they are more useful for health, improving, therefore, biorhythms and physical performance. Our aim was to analyze whether the consumption of cereals enriched with tryptophan, the precursor of both serotonin and melatonin, may help in the reconsolidation of the sleep/wake cycle and counteract depression and anxiety in 35 middle-aged/elderly (aged 55-75 year) volunteers in a simple blind assay. Data were collected for 3 weeks according to the following schedule: The control week participants consumed standard cereals (22.5 mg tryptophan in 30 g cereals per dose) at breakfast and dinner; for the treatment week, cereals enriched with a higher dose of tryptophan (60 mg tryptophan in 30 g cereals per dose) were eaten at both breakfast and dinner; the posttreatment week volunteers consumed their usual diet. Each participant wore a wrist actimeter that logged activity during the whole experiment. Urine was collected to analyze melatonin and serotonin urinary metabolites and to measure total antioxidant capacity. The consumption of cereals containing the higher dose in tryptophan increased sleep efficiency, actual sleep time, immobile time, and decreased total nocturnal activity, sleep fragmentation index, and sleep latency. Urinary 6-sulfatoxymelatonin, 5-hydroxyindoleacetic acid levels, and urinary total antioxidant capacity also increased respectively after tryptophan-enriched cereal ingestion as well as improving anxiety and depression symptoms. Cereals enriched with tryptophan may be useful as a chrononutrition tool for alterations in the sleep/wake cycle due to age.

Chrononutrition against oxidative stress in aging

Free radicals and oxidative stress have been recognized as important factors in the biology of aging and in many age-associated degenerative diseases. Antioxidant systems deteriorate during aging. It is, thus, considered that one way to reduce the rate of aging and the risk of chronic disease is to avoid the formation of free radicals and reduce oxidative stress by strengthening antioxidant defences. Phytochemicals present in fruits, vegetables, grains, and other foodstuffs have been linked to reducing the risk of major oxidative stress-induced diseases. Some dietary components of foods possess biological activities which influence circadian rhythms in humans. Chrononutrition studies have shown that not only the content of food, but also the time of ingestion contributes to the natural functioning of the circadian system. Dietary interventions with antioxidant-enriched foods taking into account the principles of chrononutrition are of particular interest for the elderly since they may help amplify the already powerful benefits of phytochemicals as natural instruments with which to prevent or delay the onset of common age-related diseases.

Role of mineralocorticoid receptors on the hypothalamus-pituitary-adrenal axis in humans

This clinical review will summarize the available data regarding the role of mineralocorticoid receptors (MRs) on the hypothalamus-pituitary-adrenal (HPA) axis control in physiological and pathological conditions and in the memory processes involved in the control and appraisal of a stress event. MRs are predominantly expressed in the limbic structures, with the hippocampus being the main localization, although MRs are also found at the hypothalamic level. It is known that hyppocampal MRs control the proactive feedback involved in the maintenance of the basal HPA activity, mainly at the nadir of the circadian rhythm. In physiological conditions, the administration of pharmacological doses of both MR antagonists and agonists is able to interact with the HPA activity, modifying the quiescent phase-nadir of the circadian rhythm, although some data in the literature do not support these observations. Also, in a physiological condition such as aging, an enhanced HPA axis activity is found in the time window, when MRs are predominantly occupied by cortisol circulating levels, possibly reflecting an MR impairment in this period of life. In pathology, major depression has been correlated to MR qualitative-quantitative alterations which could reflect differences on psychological and physiological responses, possibly predicting psychopathologies. Most of the remarks reported in this review seem to indicate, in agreement with animal data, a role played by MRs in the delicate control of the HPA axis in humans and the possible predisposition to the development of pathologies in case of their alterations.

Evening cortisol is associated with intra-individual instability in daytime napping in nursing home residents with dementia: an allostatic load perspective

BACKGROUND

Circadian rhythm disruption, reflected in alterations in sleep-wake activity and daytime napping behavior, is consistently reported in nursing home (NH) residents with dementia. This disruption may be reflected in day-to-day instability. The concept of allostatic load (AL), a measure of cumulative biological burden over a lifetime, may be a helpful model for understanding cortisol diurnal rhythm and daytime napping activity in this population. The purpose of this study was to examine the association between intra-individual daytime napping episodes and basal cortisol diurnal rhythm in NH residents with dementia in the context of AL.

METHOD

U sing a within-individual longitudinal design (N = 51), the authors observed and recorded daytime napping activity every 20 min for 10 hr per day across 4 consecutive days. The authors obtained saliva samples 4 times each day (upon participants' waking and within 1 hr, 6 hr, and 12 hr of participants' wake time) for cortisol analysis.

RESULTS

The authors categorized participants as high changers (HCs; day-to-day instability in napping activity) or low changers (LCs; day-to-day stability). There were no significant differences in resident characteristics between groups. There was a significant difference between HCs and LCs in napping episodes (F = 4.86, p = .03), with an interaction effect of evening cortisol on napping episodes in the HC group (F = 10.161, p = .001).

CONCLUSIONS

NH residents with unstable day-to-day napping episodes are more responsive to alterations in evening cortisol, an index of a dysregulated hypothalamic-pituitary-adrenal (HPA) axis. They may also be more amenable to environmental intervention, an avenue for further research.

[Cellular aspects of aging in the pineal gland of the shrew, Crocidura russula]

The Greater White-toothed shrew Crocidura russula is short-lived species and the phase of senescence is greatly elongated in captivity. The loss of rhythmicity of biological functions that accompanies its aging is also well documented. C. russula is thus an excellent model to test the effects of aging on biological clocks. Melatonin is a key hormone in the synchronization of behaviors, metabolisms and physiological regulations with environmental factors. In the present work we want to know if the loss of rhythmicity and the reduced melatonin levels registered by the second year of life in this species could be associated to modified ultrastructural features of the pineal parenchyma, site of melatonin synthesis. Transmission electron microscopy (TEM) analysis of young (1-4 months) and old (25-28 months) shrew's pineals show that in older individuals, the parenchyma undergoes alterations affecting mainly nucleus, mitochondria and endoplasmic reticulum cisternae, with increased numbers of dense bodies and the formation of many concretions as well as a depletion of secretory products. These changes suggest a process of slowing pinealocytes metabolism which could explain the gradual reduction of melatonin levels registered during aging in C. russula.

To nap or not to nap: excessive daytime napping is associated with elevated evening cortisol in nursing home residents with dementia

BACKGROUND

Alterations in the sleep-wake cycle, including daytime napping, are consistently reported in persons with dementia (PWD). A dysregulation in the hypothalamic-pituitary-adrenal (HPA) axis, indexed by elevated evening cortisol, may offer one explanation for these alterations. Alternatively, excessive daytime sleeping may alter cortisol rhythm and increase intraindividual variability, potentially contributing to increased environmental reactivity and behavioral symptoms. The purpose of this substudy (N = 12) was to examine the association between daytime napping and basal cortisol diurnal rhythm in nursing home residents with dementia.

METHOD

In this within-individual longitudinal design, saliva samples were obtained daily for 5 consecutive days upon waking and 30-45 min, 6 hr, and 12 hr after waking to obtain a cortisol diurnal rhythm. Behavior and sleep-wake state (nap/no nap) were observed and recorded every 20 min for 12 hr per day for 5 days.

RESULTS

Participants were categorized as high nappers (HNs) or low nappers (LNs). There was a significant difference in evening cortisol levels (t = -2.38, p = .032) and continence (t = 3.37, p = .007) between groups, with HNs exhibiting higher evening cortisol levels. There were no other significant differences in resident characteristics between the two groups.

CONCLUSIONS

These data suggest a link between excessive daytime napping and elevated evening cortisol in PWD consistent with findings in children. Elevated evening cortisol is an indication of a dysregulation in the HPA axis. These preliminary data support a close association between the sleep-wake cycle and HPA-axis regulation in PWD.

Neurophysiological and epigenetic effects of physical exercise on the aging process

Aging is a gradual process during which molecular and cellular processes deteriorate progressively, often leading to such pathological conditions as vascular and metabolic disorders and cognitive decline. Although the mechanisms of aging are not yet fully understood, inflammation, oxidative damage, mitochondrial dysfunction, functional alterations in specific neuronal circuits and a restricted degree of apoptosis are involved. Physical exercise improves the efficiency of the capillary system and increases the oxygen supply to the brain, thus enhancing metabolic activity and oxygen intake in neurons, and increases neurotrophin levels and resistance to stress. Regular exercise and an active lifestyle during adulthood have been associated with reduced risk and protective effects for mild cognitive impairment and Alzheimer's disease. Similarly, studies in animal models show that physical activity has positive physiological and cognitive effects that correlate with changes in transcriptional profiles. According to numerous studies, epigenetic events that include changes in DNA methylation patterns, histone modification and alterations in microRNA profiles seem to be a signature of aging. Hence, insight into the epigenetic mechanisms involved in the aging process and their modulation through lifestyle interventions such as physical exercise might open new avenues for the development of preventive and therapeutic strategies to treat aging-related diseases.

Stressing zebrafish for behavioral genetics

The stress response is a normal reaction to a real or perceived threat. However, stress response systems that are overwhelmed or out of balance can increase both the incidence and severity of diseases including addiction and mood and anxiety disorders. Using an animal model with both genetic diversity and large family size can help discover the specific genetic and environmental contributions to these behavioral diseases. The stress response has been studied extensively in teleosts because of their importance in food production. The zebrafish (Danio rerio) is a major model organism with a strong record for use in developmental biology, genetic screening, and genomic studies. More recently, the stress response of larval and adult zebrafish has been documented. High-throughput automated tracking systems make possible behavioral readouts of the stress response in zebrafish. This non-invasive measure of the stress response can be combined with mutagenesis methods to dissect the genes involved in complex stress response behaviors in vertebrates. Understanding the genetic and epigenetic basis for the stress response in vertebrates will help to develop advanced screening and therapies for stress-aggravated diseases such as addiction and mood and anxiety disorders.

Perimenopausal regulation of steroidogenesis in the nonhuman primate

Human aging is characterized by a marked decrease in circulating levels of dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS), hormonal changes associated with cognitive decline. Despite beneficial effects of DHEA supplementation in rodents, studies in elderly humans have generally failed to show cognitive improvement after treatment. In the present study we evaluate the effects of age and estradiol supplementation on expression of genes involved in the de novo synthesis of DHEA and its conversion to estradiol in the rhesus macaque hippocampus. Using reverse transcription polymerase chain reaction (RT-PCR) we demonstrate the expression of genes associated with this synthesis in several areas of the rhesus brain. Furthermore, real-time PCR reveals an age-related attenuation of hippocampal expression level of the genes CYP17A1, STS, and 3BHSD1/2. Additionally, short-term administration of estradiol is associated with decreased expression of CYP17A1, STS, SULT2B1, and AROMATASE, consistent with a downregulation not only of estrogen synthesis from circulating DHEA, but also of de novo DHEA synthesis within the hippocampus. These findings suggest a decline in neurosteroidogenesis may account for the inefficacy of DHEA supplementation in elderly humans, and that central steroidogenesis may be a function of circulating hormones and menopausal status.

Diurnal variation of cortisol in people with dementia: relationship to cognition and illness burden

Cortisol patterns in nursing home residents with dementia are described and examined in relation to cognition and comorbid illnesses. Saliva was sampled 4 times in a 24-hour period (week 1) and at the same times 1 week later (week 2). In general, cortisol levels decreased from morning to evening, with 50% exhibiting a negative slope. In contrast, 38% of the participants had a relatively flat cortisol diurnal rhythm, and 7% exhibited an afternoon increase. The cortisol pattern was consistent between weeks 1 and 2 for 39% with a negative slope, 13% with a flat profile, and for 2% with an afternoon increase pattern. Cortisol rhythm was not statistically significantly related to cognition or illness burden. While this study contributes to the understanding of differences in the diurnal pattern of cortisol for older adults with dementia, more research is needed to understand the etiology of the differences and the biological mechanisms involved.

HPA axis responsiveness to stress: implications for healthy aging

The major neuroendocrine response mediating stress adaptation is activation of the hypothalamic pituitary adrenal axis, with stimulation of corticotropin releasing hormone (CRH) and vasopressin (VP) from parvocellular neurons of the hypothalamic paraventricular nucleus, leading to stimulation of pituitary ACTH secretion and increases in glucocorticoid secretion from the adrenal cortex. Basal production and transient increases during stress of glucocorticoids and its hypothalamic regulators are essential for neuronal plasticity and normal brain function. While activation of the HPA axis is essential for survival during stress, chronic exposure to stress hormones can predispose to psychological, metabolic and immune alterations. Thus, prompt termination of the stress response is essential to prevent negative effects of inappropriate levels of CRH and glucocorticoids. This review addresses the regulation of HPA axis activity with emphasis on the mechanisms of termination of CRH transcription, which is a critical step in this process. In addition, the actions by which glucocorticoids, CRH and VP can affect the aging process will be discussed.

The neurosteroid dehydroepiandrosterone (DHEA) and its metabolites alter 5-HT neuronal activity via modulation of GABAA receptors

Dehydroepiandrosterone (DHEA) and its metabolites, DHEA-sulphate (DHEA-S) and androsterone, have neurosteroid activity. In this study, we examined whether DHEA, DHEA-S and androsterone, can influence serotonin (5-HT) neuronal firing activity via modulation of γ-aminobutryic acid (GABA(A)) receptors. The firing of presumed 5-HT neurones in a slice preparation containing rat dorsal raphe nucleus was inhibited by the GABA(A) receptor agonists 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridinyl-3-ol (THIP) (25 μM) and GABA (100 μM). DHEA (100 and 300 μM) and DHEA-S (1, 10 and 100 μM) caused a rapid and reversible attenuation of the response to THIP. DHEA (100 μM) and DHEA-S (100 μM) also attenuated the effect of GABA. Androsterone (10 and 30 μM) markedly enhanced the inhibitory response to THIP (25 μM). The effect was apparent during androsterone administration but persisted and even increased in magnitude after drug wash-out. The data indicate that GABA(A) receptor-mediated regulation of 5-HT neuronal firing is sensitive to negative modulation by DHEA and its metabolite DHEA-S is sensitive to positive modulation by the metabolite androsterone. The effects of these neurosteroids on GABA(A) receptor-mediated regulation of 5-HT firing may underlie some of the reported behavioural and psychological effects of endogenous and exogenous DHEA.

Concurrent change in dehydroepiandrosterone sulfate and functional performance in the oldest old: results from the Cardiovascular Health Study All Stars study

INTRODUCTION

The correlation between dehydroepiandrosterone sulfate (DHEAS) decline and age led to the hypothesis that DHEAS might be a marker of primary aging, though conflicting data from observational studies of mortality do not support this. We evaluated concurrent DHEAS and functional decline in a very old cohort to test if DHEAS change tracks with functional change during aging.

METHODS

DHEAS and functional performance (gait speed, grip strength, Modified Mini-Mental State Examination [3MSE] score, and digit symbol substitution test [DSST] score) were measured in 1996-1997 and 2005-2006 in 989 participants in the Cardiovascular Health Study All Stars study (mean age 85.2 years in 2005-2006, 63.5% women and 16.5% African American). We used multivariable linear regression to test the association of DHEAS decline with functional decline.

RESULTS

After adjustment, each standard deviation decrease in DHEAS was associated with greater declines in gait speed (0.12 m/s, p = .01), grip strength (0.09 kg, p = .03), 3MSE score (0.13 points, p < .001), and DSST score (0.14 points, p = .001) in women only. Additional adjustment for baseline DHEAS attenuated the association with grip strength but did not alter other estimates appreciably, and baseline DHEAS was unassociated with functional decline.

CONCLUSIONS

In this cohort of very old individuals, DHEAS decline tracked with declines in gait speed, 3MSE score, and DSST score, but not grip strength, in women independent of baseline DHEAS level. DHEAS decline might be a marker for age-associated performance decline, but its relevance is specific to women.