Alzheimer's disease, dementia, mild cognitive impairment and the menopause: a 'window of opportunity'?

Hormone therapy is associated with lower Alzheimer's disease tau biomarkers in post-menopausal females -evidence from two independent cohorts

BACKGROUND

Females represent approximately 70% of the Alzheimer's disease (AD) cases and the literature has proposed a connection between the decreased estrogen levels during menopause and an increased AD risk. Previous investigations have predominantly focused on assessing how hormone therapy (HT) affects the likelihood of AD development and cognitive deterioration. However, as the research framework has shifted toward a biomarker-defined AD and alterations in specific biomarkers could take place years before cognitive decline becomes discernible, it is crucial to examine how HT influences AD biomarkers. The main goal of this study was to evaluate the impact of HT on AD biomarker-informed pathophysiology in both cognitively unimpaired (CU) and cognitively impaired (CI) post-menopausal females across the aging and AD spectrum.

METHODS

This cross-sectional study included post-menopausal females without HT history (HT-) and with HT (HT+) at the time of PET imaging assessment from two cohorts: the Translational Biomarkers in Aging and Dementia (TRIAD) cohort, and the Alzheimer's Disease Neuroimaging Initiative (ADNI). Participants underwent magnetic resonance imaging (MRI), positron emission tomography (PET) and biofluid collection. Voxel-based t-tests were performed to assess the differences in amyloid-β (Aβ) and tau neurofibrillary tangles (NFTs) loads between HT- and HT + females. Linear regression models with interaction terms were also conducted to examine the interactive effects of HT and Aβ-PET on regional tau-PET.

RESULTS

HT + females demonstrated significantly lower tau-PET standardized uptake value ratio (SUVR) in Braak I-II ROIs (P < 0.05, Hedges' g = 0.73), Braak III-IV ROIs (P < 0.0001, Hedges' g = 0.74) and Braak V-VI ROIs (P < 0.0001, Hedges' g = 0.69) compared to HT- females. HT + females also showed significantly lower CSF p-tau181 (P < 0.001) and plasma p-tau181 (P < 0.0001) concentrations. Additionally, results from multivariate linear regression models indicated that HT interacts with cortical Aβ and is associated with lower regional NFT load.

CONCLUSIONS

Overall, findings from this observational study suggest that HT is associated with lower tau neuroimaging and fluid biomarkers in postmenopausal females. Due to the close link between tau and cognition, this study highlights the need for large randomized controlled trials designed to systemically study the influences of HT on AD biomarkers and disease progression.

Associations of ambient manganese exposure with brain gray matter thickness and white matter hyperintensities

Manganese (Mn) exposure is associated with increased risks of dementia and cerebrovascular disease. However, evidence regarding the impact of ambient Mn exposure on brain imaging markers is scarce. We aimed to investigate the association between ambient Mn exposure and brain imaging markers representing neurodegeneration and cerebrovascular lesions. We recruited a total of 936 adults (442 men and 494 women) without dementia, movement disorders, or stroke from the Republic of Korea. Ambient Mn concentrations were predicted at each participant's residential address using spatial modeling. Neurodegeneration-related brain imaging markers, such as the regional cortical thickness, were estimated using 3 T brain magnetic resonance images. White matter hyperintensity volume (an indicator of cerebrovascular lesions) was also obtained from a certain number of participants (n = 397). Linear regression analyses were conducted after adjusting for potential confounders. A log-transformed ambient Mn concentration was associated with thinner parietal (β = -0.02 mm; 95% confidence interval [CI], -0.05 to -0.01) and occipital cortices (β = -0.03 mm; 95% CI, -0.04 to -0.01) after correcting for multiple comparisons. These associations remained statistically significant in men. An increase in the ambient Mn concentration was also associated with a greater volume of deep white matter hyperintensity in men (β = 772.4 mm3, 95% CI: 36.9 to 1508.0). None of the associations were significant in women. Our findings suggest that ambient Mn exposure may induce cortical atrophy in the general adult population.

Nondeclarative associative learning in Alzheimer's disease: An overview of eyeblink, fear, and other emotion-based conditioning

Alzheimer's disease is a neurodegenerative disorder that is characterized by progressive cognitive decline, particularly in declarative memory, and the presence of β-amyloid plaques, neurofibrillary tangles, and cortical atrophy (especially in the temporal lobe). Unlike the relationship between the temporal cortex and declarative memory, nondeclarative memories (e.g., motor, fear, and other emotion-based memories) involve distinct neural structures. The present review investigates nondeclarative associative learning ability in Alzheimer's disease. We discuss eyeblink conditioning, fear conditioning, and other emotion-based learning and present the functions and brain areas that are involved in each type of learning. Evidence suggests that nondeclarative learning is also affected by Alzheimer's disease, although some forms of learning may be relatively preserved. Details about each nondeclarative associative learning process and the implications of these findings are presented.

The effect of hormone replacement therapy on cognition and mood

OBJECTIVES

To summarise the available data regarding the effect of hormone replacement therapy (HRT) on cognition and mood in women.

BACKGROUND

Complaints of impaired cognition and mood are common in the peri-menopausal and menopausal period. There is debate as to whether HRT can ameliorate this phenomenon.

DESIGN

A literature search of studies using electronic databases was conducted. Both randomised control trials and observational studies were included.

PATIENTS

Perimenopausal and menopausal women.

RESULTS

Due to the heterogenicity of results it is challenging to draw firm conclusions. The preparations used in many of the studies are older regimes no longer routinely used clinically. The notion of a 'critical window' for HRT is compelling, suggesting HRT has a positive impact on cognition when administered in the peri-menopausal or early postmenopausal period but may have negative effects on cognition in the older, postmenopausal woman. The evidence would seem to suggest importance of hormonal replacement in woman undergoing a surgical menopause, especially when young. It remains unclear for how long they ought to continue HRT though until at least the natural age of the menopause seems reasonable. Evidence for a positive effect of HRT on mood is more convincing, though possibly more efficacious in the younger age group. The effect of HRT on anxiety is less clear.

CONCLUSIONS

Further study, particularly focusing on the more contemporaneous HRT preparations, is warranted before evidence-based conclusions can be drawn.

MCU knockdown in hippocampal neurons improves memory performance of an Alzheimer's disease mouse model

Alzheimer's disease (AD) is a progressive and degenerative disorder accompanied by cognitive decline, which could be promoted by mitochondrial dysfunction induced by mitochondrial Ca ²⁺ (mCa ²⁺) homeostasis Mitochondrial calcium uniporter (MCU), a key channel of mCa ²⁺ uptake, may be a target for AD treatment. In the present study, we reveal for the first time that MCU knockdown in hippocampal neurons improves the memory performance of APP/PS1/tau mice through radial arm maze task. Western blot analysis, transmission electron microscopy (TEM), Golgi staining, immunohistochemistry (IHC) and ELISA results demonstrate that MCU knockdown in hippocampal neurons upregulates the levels of postsynaptic density protein 95 (PSD95) and synaptophysin (SYP), and increases the numbers of synapses and dendritic spines. Meanwhile, MCU knockdown in hippocampal neurons decreases the neuroinflammatory response induced by astrogliosis and high levels of IL-1β and TNF-α, and improves the PINK1-Parkin mitophagy signaling pathway and increases the level of Beclin-1 but decreases the level of P62. In addition, MCU knockdown in hippocampal neurons recovers the average volume and number of mitochondria. These data confirm that MCU knockdown in hippocampal neurons improves the memory performance of APP/PS1/tau mice through ameliorating the synapse structure and function, relieving the inflammation response and recovering mitophagy, indicating that MCU inhibition has the potential to be developed as a novel therapy for AD.

The Systemic Effects of Exercise on the Systemic Effects of Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive degenerative disorder and a leading cause of dementia in the elderly. The etiology of AD is multifactorial, including an increased oxidative state, deposition of amyloid plaques, and neurofibrillary tangles of the tau protein. The formation of amyloid plaques is considered one of the first signs of the illness, but only in the central nervous system (CNS). Interestingly, results indicate that AD is not just localized in the brain but is also found in organs distant from the brain, such as the cardiovascular system, gut microbiome, liver, testes, and kidney. These observations make AD a complex systemic disorder. Still, no effective medications have been found, but regular physical activity has been considered to have a positive impact on this challenging disease. While several articles have been published on the benefits of physical activity on AD development in the CNS, its peripheral effects have not been discussed in detail. The provocative question arising is the following: is it possible that the beneficial effects of regular exercise on AD are due to the systemic impact of training, rather than just the effects of exercise on the brain? If so, does this mean that the level of fitness of these peripheral organs can directly or indirectly influence the incidence or progress of AD? Therefore, the present paper aims to summarize the systemic effects of both regular exercise and AD and point out how common exercise-induced adaptation via peripheral organs can decrease the incidence of AD or attenuate the progress of AD.

Preliminary Support for a Cognitive Remediation Intervention for Women During the Menopausal Transition: A Pilot Study

Background: Menopause is associated with physical and emotional symptoms, and subjective cognitive concerns that are generally not borne out on objective cognitive measures. This discrepancy suggests that a psychological rather than biological mechanism likely mediates the cognitive concerns of women in menopause. The current study assessed the feasibility and effectiveness of a cognitive remediation intervention with the goal of reducing subjective perceptions of cognitive difficulty during the menopause. Methods: Twenty-seven menopausal women (M age = 53.74, SD = 4.14) completed a 5-week group-based intervention (with a post-group booster) consisting of 2-h weekly sessions. Participants completed pre- and post-intervention measures capturing subjective cognitive ability, mood, anxiety, stress, personality, and objective cognitive tests. The primary variable of interest was self-reported cognitive confidence measured by the Memory and Cognitive Confidence Scale (MACCS). Results: All but one MACCS subscale significantly decreased over the course of treatment (with lower scores associated with higher confidence) and effect sizes ranged from small to large (d = -0.39 to -0.91) with gains maintained at 1-month follow-up. Interestingly, no change in objective cognitive test performance was observed, indicating increases in subjective cognitive confidence in the absence of objective cognitive improvement. There was no change in mood, anxiety, or stress scores. Two-level HLM analyses revealed that those with higher baseline neuroticism, as measured by the NEO Personality Inventory, had smaller decreases in post-group MACCS High Standards subscale relative to those with lower baseline neuroticism (p = 0.027, d = -0.45). Those with higher baseline depression scores on the Depression Anxiety Stress Scale (DASS-21) had a smaller decrease in post-intervention MACCS Total Score relative to those with lower depression ratings. Conclusion: To our knowledge, this is the first feasibility study of its kind targeting perceptions of cognitive impairment during menopause. Although generally well-tolerated, recruitment and scheduling difficulties were flagged as challenges to engagement while a small sample size and lack of control group limit conclusions about efficacy. Providing current results could be replicated with enhanced methods, these results provide support that cognitive remediation is a feasible and credible treatment, and may improve quality of life for women in menopause. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03311880.

Prevalence and risks of mild cognitive impairment of Chinese community-dwelling women aged above 60 years: A cross-sectional study

Evidence has shown that risks of cognitive impairment differ between genders. This cross-sectional study sought to determine the prevalence of mild cognitive impairment (MCI) in Chinese community-dwelling women aged above 60 years and identify risks of MCI by multivariate logistic regression analysis. Totally, 1760 Chinese community-dwelling women entered the study. Cognitive function was assessed with Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). MCI was diagnosed by Petersen's criteria. Sociodemographic information, past medical conditions, and age at menopause were screened. The primary study outcome was prevalence of MCI. MCI was diagnosed in 378 (21.5%) women. Older age was a significant risk of MCI (OR 1.621, 95%CI 1.386-1.894; P < 0.001). Low education was associated a 4-fold increase in the risk of MCI (OR 4.036, 95%CI 3.168-5.142). Furthermore, current depression was associated with 2.6-fold increase in the risk of MCI (OR 2.618, 95%CI 1.499-4.587, P = 0.001). Moreover, frequent physical exercise and more leisure and social time activities were associated with significantly reduced risks of MCI, while poor financial status was associated with a significantly increased risk of MCI. Slightly more than 20% of Chinese women aged above 60 years had MCI, and independent risks included older age, low education status, and current depression, highlighting the importance of screening for and removing or minimizing risks of MCI in this specific population.

Therapeutic Potential of Human Stem Cell Implantation in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive debilitating neurodegenerative disease and the most common form of dementia in the older population. At present, there is no definitive effective treatment for AD. Therefore, researchers are now looking at stem cell therapy as a possible treatment for AD, but whether stem cells are safe and effective in humans is still not clear. In this narrative review, we discuss both preclinical studies and clinical trials on the therapeutic potential of human stem cells in AD. Preclinical studies have successfully differentiated stem cells into neurons in vitro, indicating the potential viability of stem cell therapy in neurodegenerative diseases. Preclinical studies have also shown that stem cell therapy is safe and effective in improving cognitive performance in animal models, as demonstrated in the Morris water maze test and novel object recognition test. Although few clinical trials have been completed and many trials are still in phase I and II, the initial results confirm the outcomes of the preclinical studies. However, limitations like rejection, tumorigenicity, and ethical issues are still barriers to the advancement of stem cell therapy. In conclusion, the use of stem cells in the treatment of AD shows promise in terms of effectiveness and safety.

Tet1 Deficiency Leads to Premature Ovarian Failure

Tet enzymes participate in DNA demethylation and play critical roles in stem cell pluripotency and differentiation. DNA methylation alters with age. We find that Tet1 deficiency reduces fertility and leads to accelerated reproductive failure with age. Noticeably, Tet1-deficient mice at young age exhibit dramatically reduced follicle reserve and the follicle reserve further decreases with age, phenomenon consistent with premature ovarian failure (POF) syndrome. Consequently, Tet1-deficient mice become infertile by reproductive middle age, while age matched wild-type mice still robustly reproduce. Moreover, by single cell transcriptome analysis of oocytes, Tet1 deficiency elevates organelle fission, associated with defects in ubiquitination and declined autophagy, and also upregulates signaling pathways for Alzheimer's diseases, but down-regulates X-chromosome linked genes, such as Fmr1, which is known to be implicated in POF. Additionally, Line1 is aberrantly upregulated and endogenous retroviruses also are altered in Tet1-deficient oocytes. These molecular changes are consistent with oocyte senescence and follicle atresia and depletion found in premature ovarian failure or insufficiency. Our data suggest that Tet1 enzyme plays roles in maintaining oocyte quality as well as oocyte number and follicle reserve and its deficiency can lead to POF.

Aging and aging-associated diseases: a microRNA-based endocrine regulation hypothesis

Although there are numerous hypotheses explaining the nature of aging and associated processes, two concepts are dominant: (i) aging is a result of cell-autonomous processes, such as the accumulation of DNA mutations, aberrant methylations, protein defects, and shortening of telomeres, leading to either inhibition of cellular proliferation and death of non-dividing terminally differentiated cells or tumor development; (ii) aging is a result of a central program that is switched on at a specific stage of organismic development. The microRNA-based endocrine regulation hypothesis combines the two above concepts by proposing central regulation of cell death occurrences via hypothalamus-pituitary gland (PG)-secreted miRNA hormones, the expression and/or secretion of which are regulated by sex hormones. This hypothesis explains such well-known phenomena as inverse comorbidity of either cancer or Alzheimer’s (AD) and other neurodegenerative diseases; higher AD morbidity and lower frequency of many common types of cancer in women vs. men; higher risk of early AD and lower risk of cancer in subjects with Down syndrome; longer life expectancy in women vs. men and much lower sex-dependent differences, if any, in other mammals; increased lifespans due to hypophysectomy or PG hypofunction; and parabiotic effects of blood or plasma transfusions between young and old animals.

Menopause, cognition and dementia - A review

There is increasing evidence that menopausal changes can have an impact on women’s cognition and potentially, the future development of dementia. In particular, the role of reduced levels of estrogen in postmenopausal changes has been linked to an increased risk of developing dementia in observational studies. Not surprisingly, this has led to several clinical trials investigating whether postmenopausal hormone replacement therapy can potentially delay/avoid cognitive changes and subsequently, the onset of dementia. However, the evidence of these trials has been mixed, with some showing positive effects while others show no or even negative effects. In the current review, we investigate this controversy further by reviewing the existing studies and trials in cognition and dementia. Based on the current evidence, we conclude that previous approaches may have used a mixture of women with different genetic risk factors for dementia which might explain these contradicting findings. Therefore, it is recommended that future interventional studies take a more personalised approach towards hormone replacement therapy use in postmenopausal women, by taking into account the women’s genetic status for dementia risk.

Prevention of Alzheimer's disease, cerebrovascular disease and dementia in women: the case for menopause hormone therapy

Alzheimer's disease, cerebrovascular disease and aging-related cognitive impairment and dementia (ARCID) increase in prevalence in women with advancing age. The development of Alzheimer's disease, cerebrovascular disease and ARCID may be postponed or prevented by protective measures including the active treatment of vascular risk factors and continuing exercise and healthy lifestyle from early- and mid-life onward. Bilateral oophorectomy before the natural menopause is associated with an increased incidence of ARCID and the increased risk is significantly reduced by estrogen therapy. Recent advances in menopause hormone therapy including transdermal estrogen therapy have favorably influenced the balance of benefits and risks. A case can be made for menopause hormone therapy in healthy postmenopausal women for 5-10 years starting during the menopausal transition (the 'window of opportunity'), together with all other protective measures, to delay or prevent the development of ARCID in later life.

Middle-Aged Diabetic Females and Males Present Distinct Susceptibility to Alzheimer Disease-like Pathology

Type 2 diabetes (T2D) is a highly concerning public health problem of the twenty-first century. Currently, it is estimated that T2D affects 422 million people worldwide with a rapidly increasing prevalence. During the past two decades, T2D has been widely shown to have a major impact in the brain. This, together with the cognitive decline and increased risk for dementia upon T2D, may arise from the complex interaction between normal brain aging and central insulin signaling dysfunction. Among the several features shared between T2D and some neurodegenerative disorders (e.g., Alzheimer disease (AD)), the impairment of insulin signaling may be a key link. However, these may also involve changes in sex hormones' function and metabolism, ultimately contributing to the different susceptibilities between females and males to some pathologies. For example, female sex has been pointed as a risk factor for AD, particularly after menopause. However, less is known on the underlying molecular mechanisms or even if these changes start during middle-age (perimenopause). From the above, we hypothesized that sex differentially affects hormone-mediated intracellular signaling pathways in T2D brain, ultimately modulating the risk for neurodegenerative conditions. We aimed to evaluate sex-associated alterations in estrogen/insulin-like growth factor-1 (IGF-1)/insulin-related signaling, oxidative stress markers, and AD-like hallmarks in middle-aged control and T2D rat brain cortices. We used brain cortices homogenates obtained from middle-aged (8-month-old) control Wistar and non-obese, spontaneously T2D Goto-Kakizaki (GK) male and female rats. Peripheral characterization of the animal models was done by standard biochemical analyses of blood, plasma, or serum. Steroid sex hormones, oxidative stress markers, and AD-like hallmarks were given by specific ELISA kits and colorimetric techniques, whereas the levels of intracellular signaling proteins were determined by Western blotting. Albeit the high levels of plasma estradiol and progesterone observed in middle-aged control females suggested that they were still under their reproductive phase, some gonadal dysfunction might be already occurring in T2D ones, hence, anticipating their menopause. Moreover, the higher blood and lower brain cholesterol levels in female rats suggested that its dysfunctional uptake into the brain cortex may also hamper peripheral estrogen uptake and/or its local brain steroidogenic metabolism. Despite the massive drop in IGF-1 levels in females' brains, particularly upon T2D, they might have developed some compensatory mechanisms towards the maintenance of estrogen, IGF-1, and insulin receptors function and of the subsequent Akt- and ERK1/2-mediated signaling. These may ultimately delay the deleterious AD-like brain changes (including oxidative damage to lipids and DNA, amyloidogenic processing of amyloid precursor protein and increased tau protein phosphorylation) associated with T2D and/or age (reproductive senescence) in female rats. By demonstrating that differential sex steroid hormone profiles/action may play a pivotal role in brain over T2D progression, the present study reinforces the need to establish sex-specific preventive and/or therapeutic approaches and an appropriate time window for the efficient treatment against T2D and AD.

Can Exercise Ameliorate Aromatase Inhibitor-Induced Cognitive Decline in Breast Cancer Patients?

Aromatase inhibitors (AIs) have been commonly used as an effective adjuvant therapy in treatment of breast cancer, especially for menopausal women with estrogen receptor-positive breast cancer. Due to the nature of aromatase, the key enzyme for endogenous estrogen synthesis, inhibitory of aromatase-induced side effects, such as cognitive impairment has been reported in both human and animal studies. While extensive evidence suggested that physical exercises can improve learning and memory activity and even prevent age-related cognitive decline, basic research revealed some common pathways between exercise and estrogen signaling that affected cognitive function. This review draws on clinical and basic studies to assess the potential impact of exercise in cognitive function from women treated with AIs for breast cancer and explore the potential mechanism and effects of exercise on estrogen-related cognition.

Screening executive function and global cognition with the Nine-Card Sorting Test: healthy participant studies and ageing implications

BACKGROUND

The Nine-Card Sorting Test provides valid and reliable scores when screening executive function, intelligence, and academic achievement. It is also useful for detecting cognitive impairment and dementia in the elderly and for assessing disease evolution and treatment effectiveness. It deals with three non-verbal sorting principles, individually and in pairs. The presence of risk in the ability to discover and organize visual logical stimuli is explored.

OBJECTIVES

This study aimed to describe performance on the Nine-Card Sorting Test in a non-clinical sample, to analyze the effect of demographic variables, and to propose suitable (i.e. the simplest and most homogeneous) cut-off points for possible deficits. Combinations in pairs (double arrays) were assessed (range: 0-3).

RESULTS

Significant effects of age and education were observed, but no interactions among the demographic variables were seen. Differences between the second and third levels of education and between men and women were not significant. The simplest cut-off points were as follows: (i) the median for people younger than 45 years old was 2, independent of educational level; (ii) the median for people older than 74 years old was 1, independent of educational level; and (iii) the median for people aged 45-74 years old was 1 for the first level of education and 2 for higher levels of education.

CONCLUSION

By considering both the statistical nature of the present dependent variable (number of completed categories) and the clear-cut performance of the different samples studied, this neuropsychological test can be defined as a categorical screening for executive function and global cognition. This is advantageous for reporting risk. Of the whole sample, the 25th percentile (score = 1) represented a valid index for possible deficits. Ageing questions are highlighted. The test is also fruitful for studies on visuospatial organization and its facilitatory and inhibitory mechanisms.

Identifying brain functional alterations in postmenopausal women with cognitive impairment

INTRODUCTION

Gender differences and menopause are associated with the cognitive decline and pathogenesis of Alzheimer's disease (AD). Although deficits of subcortical-cortical loops have been implicated in AD, no study has directly examined the resting-state brain functional alterations in postmenopausal women with mild cognitive impairment (MCI).

METHODOLOGY

Forty-eight subjects were recruited, including 15 older females with MCI, 13 older females without MCI, 10 older males with MCI and 10 older males without MCI. Full-scale neuropsychological tests were used to evaluate cognitive function. Resting-state fMRI and the amplitude of low-frequency fluctuation (ALFF) approach were used to investigate changes in the brain function in these subjects. A voxel-wise analysis of variance (ANOVA: gender × disease) was performed, and gender-brain-behavior relationships were further examined.

RESULTS

First, older females with MCI showed cognitive dysfunction in multiple domains compared to normal controls. Second, the brain function of subcortical-cortical loops was disrupted in older females with MCI. Finally, regional resting-state function of the left precuneus was significantly associated with altered episodic memory in these female patients.

CONCLUSIONS

This study revealed the patterns of neural networks in older females with cognitive disorders, and may provide new ideas and evidence regarding the mechanism of cognitive impairment in postmenopausal women.

Association of dietary intake and lifestyle pattern with mild cognitive impairment in the elderly

INTRODUCTION

OBJECTIVES

Specific diets or lifestyles have an impact on cognitive function in previous studies. However, the association of the complex action of Chinese daily diets and lifestyle patterns with mild cognitive impairment (MCI) among elderly people had not been studied exactly. The aim of this study was to explore the association of dietary and lifestyle patterns with MCI among elderly people in Beijing.

DESIGN

Population-based and case-control design.

SETTING

The physical examination center in Xuanwu Hospital, Capital Medical University in Beijing.

PARTICIPANTS

A total of 404 subjects, aged 60 years old or above, with or without MCI.

MEASUREMENTS

The Montreal cognitive assessment (MoCA) was used to screen the subjects with MCI. All subjects were required to complete a questionnaire which was comprised of their demographic information, health status, lifestyles, and food frequency questionnaire (FFQ). Binary multivariable logistic regression was used to evaluate the potential association between MCI and these factors.

RESULTS

With adjustment for some factors, higher daily intake of eggs (OR, 0.975, 95% CI, 0.959-0.992, P=.003) and marine products (OR, 0.96, 95% CI, 0.943-0.979, P=.000), longer time of watching TV (OR, 0.763, 95% CI, 0.628-0.928, P=.007), reading (OR, 0.540, 95% CI, 0.379-0.769, P=.001) and physical exercise (OR, 0.382, 95% CI, 0.185-0.789) had significantly decreased odds of suffering from MCI compared with the control group.

CONCLUSIONS

Our findings suggested that daily higher intake of eggs and marine products, watching TV, reading and physical exercise were associated with preventing the development of MCI in this population-based samples.

Spatial memory impairment is associated with hippocampal insulin signals in ovariectomized rats

Estrogen influences memory formation and insulin sensitivity. Meanwhile, glucose utilization directly affects learning and memory, which are modulated by insulin signals. Therefore, this study investigated whether or not the effect of estrogen on memory is associated with the regulatory effect of this hormone on glucose metabolism. The relative expression of estrogen receptor β (ERβ) and glucose transporter type 4 (GLUT4) in the hippocampus of rats were evaluated by western blot. Insulin level was assessed by ELISA and quantitative RT-PCR, and spatial memory was tested by the Morris water maze. Glucose utilization in the hippocampus was measured by 2-NBDG uptake analysis. Results showed that ovariectomy impaired the spatial memory of rats. These impairments are similar as the female rats treated with the ERβ antagonist tamoxifen (TAM). Estrogen blockade by ovariectomy or TAM treatment obviously decreased glucose utilization. This phenomenon was accompanied by decreased insulin level and GLUT4 expression in the hippocampus. The female rats were neutralized with hippocampal insulin with insulin antibody, which also impaired memory and local glucose consumption. These results indicated that estrogen blockade impaired the spatial memory of the female rats. The mechanisms by which estrogen blockade impaired memory partially contributed to the decline in hippocampal insulin signals, which diminished glucose consumption.

Estradiol replacement extends the window of opportunity for hippocampal function

We previously reported that treating aged female rats, ovariectomized (OVX) as young adults, with acute proestrous levels of 17β estradiol (E2) increases CA1 spine density, NMDAR to AMPAR ratio, GluN2B-mediated NMDAR current, and long-term potentiation at CA3-CA1 synapses if administered by 15, but not at 19-month post-OVX, defining the critical window of opportunity. Importantly, when rats are aged with ovaries intact until OVX at 20 months, hippocampal E2 responsiveness is maintained, indicating the deficit at 19-month post-OVX is a consequence of the duration of hormone deprivation and not chronological age. Here, we find the beneficial effect of E2 on novel object recognition in OVX rats was constrained by the same critical window. Furthermore, chronic low-level E2 replacement, commenced by 11-month post-OVX using subcutaneous capsules removed 2 weeks before acute proestrous E2 treatment, prevents the loss of hippocampal responsiveness at 19-month post-OVX. These data define the dynamic nature of the critical window showing that chronic replacement with physiological E2 levels within a certain period post-OVX can lengthen the window.

Correlation between visual acuity and cognitive functions

A possible association between visual acuity (VA) and dementia was investigated in 2716 subjects who were aged between 53 and 102 at first visit and had varying degrees of dementia. Better VA was found to be significantly correlated with a lower dementia level (person coefficient range 0.146-0.261 over 10 years of follow-up, all correlations are significant, p<0.0001) as well as with a higher global cognitive score (person coefficient range -0.254 to -0.318 over 10 years of follow-up, all correlations are significant, p<0.0001), a grade encompassing 19 different cognitive tests. This correlation remained significant after adjustment for age, years of education, gender, use of ophthalmic drugs and years of follow-up.