In vivo effects by estrone sulfate on the central nervous system-senile dementia (Alzheimer's type)

Utilization of Human Induced Pluripotent Stem Cells-Derived In vitro Models for the Future Study of Sex Differences in Alzheimer's Disease

Alzheimer’s disease (AD) is an aging-dependent neurodegenerative disease that impairs cognitive function. Although the main pathologies of AD are the aggregation of amyloid-beta (Aβ) and phosphorylated Tau protein, the mechanisms that lead to these pathologies and their effects are believed to be heterogeneous among patients. Many epidemiological studies have suggested that sex is involved in disease prevalence and progression. The reduction of sex hormones contributes to the pathogenesis of AD, especially in females, suggesting that the supplementation of sex hormones could be a therapeutic intervention for AD. However, interventional studies have revealed that hormone therapy is beneficial under limited conditions in certain populations with specific administration methods. Thus, this suggests the importance of identifying crucial factors that determine hormonal effects in patients with AD. Based on these factors, it is necessary to decide which patients will receive the intervention before starting it. However, the long observational period and many uncontrollable environmental factors in clinical trials made it difficult to identify such factors, except for the APOE ε4 allele. Induced pluripotent stem cells (iPSCs) derived from patients can differentiate into neurons and recapitulate some aspects of AD pathogenesis. This in vitro model allows us to control non-cell autonomous factors, including the amount of Aβ aggregates and sex hormones. Hence, iPSCs provide opportunities to investigate sex-dependent pathogenesis and predict a suitable population for clinical trials of hormone treatment.

The endocrine dyscrasia that accompanies menopause and andropause induces aberrant cell cycle signaling that triggers re-entry of post-mitotic neurons into the cell cycle, neurodysfunction, neurodegeneration and cognitive disease

This article is part of a Special Issue "SBN 2014". Sex hormones are physiological factors that promote neurogenesis during embryonic and fetal development. During childhood and adulthood these hormones support the maintenance of brain structure and function via neurogenesis and the formation of dendritic spines, axons and synapses required for the capture, processing and retrieval of information (memories). Not surprisingly, changes in these reproductive hormones that occur with menopause and during andropause are strongly correlated with neurodegeneration and cognitive decline. In this connection, much evidence now indicates that Alzheimer's disease (AD) involves aberrant re-entry of post-mitotic neurons into the cell cycle. Cell cycle abnormalities appear very early in the disease, prior to the appearance of plaques and tangles, and explain the biochemical, neuropathological and cognitive changes observed with disease progression. Intriguingly, a recent animal study has demonstrated that induction of adult neurogenesis results in the loss of previously encoded memories while decreasing neurogenesis after memory formation during infancy mitigated forgetting. Here we review the biochemical, epidemiological and clinical evidence that alterations in sex hormone signaling associated with menopause and andropause drive the aberrant re-entry of post-mitotic neurons into an abortive cell cycle that leads to neurite retraction, neuron dysfunction and neuron death. When the reproductive axis is in balance, gonadotropins such as luteinizing hormone (LH), and its fetal homolog, human chorionic gonadotropin (hCG), promote pluripotent human and totipotent murine embryonic stem cell and neuron proliferation. However, strong evidence supports menopausal/andropausal elevations in the LH:sex steroid ratio as driving aberrant mitotic events. These include the upregulation of tumor necrosis factor; amyloid-β precursor protein processing towards the production of mitogenic Aβ; and the activation of Cdk5, a key regulator of cell cycle progression and tau phosphorylation (a cardinal feature of both neurogenesis and neurodegeneration). Cognitive and biochemical studies confirm the negative consequences of a high LH:sex steroid ratio on dendritic spine density and human cognitive performance. Prospective epidemiological and clinical evidence in humans supports the premise that rebalancing the ratio of circulating gonadotropins:sex steroids reduces the incidence of AD. Together, these data support endocrine dyscrasia and the subsequent loss of cell cycle control as an important etiological event in the development of neurodegenerative diseases including AD, stroke and Parkinson's disease.

Alzheimer's disease: review of hormone therapy trials and implications for treatment and prevention after menopause

Hormonal changes associated with the menopausal transition and postmenopause have the potential to influence processes linked to Alzheimer's disease symptoms and pathogenesis, but effects of menopause on Alzheimer risk can be addressed only indirectly. Nine randomized clinical trials of estrogen-containing hormone therapy in Alzheimer's disease patients were identified by a systematic literature search. Findings suggest that hormone therapy does not improve cognitive symptoms of women with Alzheimer's disease. No clinical trials of hormone therapy address Alzheimer prevention, but one clinical trial provides moderate evidence that continuous, combined estrogen plus progestogen initiated at age 65 years or older increases the risk of dementia. The timing, or critical window, hypothesis suggests that hormone therapy initiated at a younger age in closer temporal proximity to menopause may reduce the risk of Alzheimer's disease. This hypothesis is supported by observational research but is not addressed by clinical trial data. Unrecognized confounding is of concern in interpreting observational results, and research that helps resolve this issue will have important public health implications. Well-designed cohort studies, convergent evidence from appropriate laboratory models, and long-term clinical trials using surrogate biomarkers of brain function and neural pathology could provide relevant answers. Other estrogenic compounds are of theoretical interest with respect to Alzheimer treatment and risk. Effects of selective estrogen receptor modulators such as raloxifene may differ from those of estrogens; potential effects of phytoestrogens are not well studied. This article is part of a Special Issue entitled 'Menopause'.

Tumor necrosis factor-induced cerebral insulin resistance in Alzheimer's disease links numerous treatment rationales

The evident limitations of the amyloid theory of the pathogenesis of Alzheimer's disease are increasingly putting alternatives in the spotlight. We argue here that a number of independently developing approaches to therapy-including specific and nonspecific anti-tumor necrosis factor (TNF) agents, apolipoprotein E mimetics, leptin, intranasal insulin, the glucagon-like peptide-1 mimetics and glycogen synthase kinase-3 (GSK-3) antagonists-are all part of an interlocking chain of events. All these approaches inform us that inflammation and thence cerebral insulin resistance constitute the pathway on which to focus for a successful clinical outcome in treating this disease. The key link in this chain presently absent is a recognition by Alzheimer's research community of the long-neglected history of TNF induction of insulin resistance. When this is incorporated into the bigger picture, it becomes evident that the interventions we discuss are not competing alternatives but equally valid approaches to correcting different parts of the same pathway to Alzheimer's disease. These treatments can be expected to be at least additive, and conceivably synergistic, in effect. Thus the inflammation, insulin resistance, GSK-3, and mitochondrial dysfunction hypotheses are not opposing ideas but stages of the same fundamental, overarching, pathway of Alzheimer's disease pathogenesis. The insight this provides into progenitor cells, including those involved in adult neurogenesis, is a key part of this approach. This pathway also has therapeutic implications for other circumstances in which brain TNF is pathologically increased, such as stroke, traumatic brain injury, and the infectious disease encephalopathies.

Is TNF a link between aging-related reproductive endocrine dyscrasia and Alzheimer's disease?

This commentary addresses a novel mechanism by which aging-related changes in reproductive hormones could mediate their action in the brain. It presents the evidence that dyotic endocrine signals modulate the expression of tumor necrosis factor (TNF) and related cytokines, and that these cytokines are a functionally important downstream link mediating neurodegeneration and dysfunction. This convergence of dyotic signaling on TNF-mediated degeneration and dysfunction has important implications for understanding the pathophysiology of AD, stroke, and traumatic brain disease, and also for the treatment of these diseases.

Gonadal hormones and cognitive aging: a midlife perspective

Gonadal steroids affect a variety of brain processes. Cognitive consequences of hormonal changes associated with menopause are of scientific interest and of relevance to public health. Natural menopause is a normal physiological process that can only be directly studied through observational research. Similarly, surgical menopause in humans is rarely directly amenable to experimental research. Causality with respect to cognitive outcomes is, therefore, difficult to infer. Cross-sectional and longitudinal findings from the Melbourne Women's Midlife Health Project, the Study of Women's Health Across the Nation and other midlife cohorts suggest that cognitive consequences of the natural menopausal transition are probably small, at least during midlife and at least for episodic memory, which is a key cognitive domain. The data for episodic memory are the most robust. Midlife episodic memory performance is similar both shortly before and after natural menopause, and serum estradiol concentration in midlife is not associated with episodic memory performance. Effects of natural menopause on other cognitive domains, cognitive consequences of surgical menopause and late-life cognitive consequences of midlife hormonal exposures are less well understood and merit continued study.

Estrogen therapy and Alzheimer's dementia

Previous studies in postmenopausal women have reported that estrogen treatment (ET) modulates the risk for developing Alzheimer's disease (AD). It has recently been hypothesized that there may be a "critical period" around the time of menopause during which the prescription of ET may reduce the risk of developing AD in later life. This effect may be most significant in women under 49 years old. Furthermore, prescription of ET after this point may have a neutral or negative effect, particularly when initiated in women over 60-65 years old. In this paper, we review recent studies that use in vivo techniques to analyze the neurobiological mechanisms that might underpin estrogen's effects on the brain postmenopause. Consistent with the "critical period" hypothesis, these studies suggest that the positive effects of estrogen are most robust in young women and in older women who had initiated ET around the time of menopause.

Menopause and mitochondria: windows into estrogen effects on Alzheimer's disease risk and therapy

Metabolic derangements and oxidative stress are early events in Alzheimer's disease pathogenesis. Multi-faceted effects of estrogens include improved cerebral metabolic profile and reduced oxidative stress through actions on mitochondria, suggesting that a woman's endogenous and exogenous estrogen exposures during midlife and in the late post-menopause might favourably influence Alzheimer risk and symptoms. This prediction finds partial support in the clinical literature. As expected, early menopause induced by oophorectomy may increase cognitive vulnerability; however, there is no clear link between age at menopause and Alzheimer risk in other settings, or between natural menopause and memory loss. Further, among older post-menopausal women, initiating estrogen-containing hormone therapy increases dementia risk and probably does not improve Alzheimer's disease symptoms. As suggested by the 'critical window' or 'healthy cell' hypothesis, better outcomes might be expected from earlier estrogen exposures. Some observational results imply that effects of hormone therapy on Alzheimer risk are indeed modified by age at initiation, temporal proximity to menopause, or a woman's health. However, potential methodological biases warrant caution in interpreting observational findings. Anticipated results from large, ongoing clinical trials [Early Versus Late Intervention Trial with Estradiol (ELITE), Kronos Early Estrogen Prevention Study (KEEPS)] will help settle whether midlife estrogen therapy improves midlife cognitive skills but not whether midlife estrogen exposures modify late-life Alzheimer risk. Estrogen effects on mitochondria adumbrate the potential relevance of estrogens to Alzheimer's disease. However, laboratory models are inexact embodiments of Alzheimer pathogenesis and progression, making it difficult to surmise net effects of estrogen exposures. Research needs include better predictors of adverse cognitive outcomes, biomarkers for risks associated with hormone therapy, and tools for monitoring brain function and disease progression.

Hormone replacement therapy to maintain cognitive function in women with dementia

BACKGROUND

As estrogens have been shown to have several potentially beneficial effects on the central nervous system, it is biologically plausible that maintaining high levels of estrogens in postmenopausal women by means of estrogen replacement therapy (ERT) could be protective against cognitive decline in women with Alzheimer's disease (AD) or other dementia syndromes.

OBJECTIVES

To investigate the effects of ERT (estrogens only) or HRT (estrogens combined with a progestagen) compared with placebo in randomized controlled trials (RCTs) on cognitive function of postmenopausal women with dementia.

SEARCH STRATEGY

The Cochrane Dementia and Cognitive Improvement Group Specialized Register, which contains records from many medical databases, The Cochrane Library, EMBASE, MEDLINE, CINAHL, PsycINFO and LILACS were searched on 7 November 2007 using the terms ORT, PORT, ERT, HRT, estrogen*, oestrogen* and progesterone*.

SELECTION CRITERIA

All double-blind randomized controlled trials (RCTs) into the effect of ERT or HRT for cognitive function with a treatment period of at least two weeks in postmenopausal women with AD or other types of dementia.

DATA COLLECTION AND ANALYSIS

Abstracts of the references retrieved by the searches were read by two reviewers (EH and KY) independently in order to discard those that were clearly not eligible for inclusion. The two reviewers studied the full text of the remaining references and independently selected studies for inclusion. Any disparity in the ensuing lists was resolved by discussion with all reviewers in order to arrive at the final list of included studies. The selection criteria ensured that the blinding and randomization of the included studies was adequate. The two reviewers also assessed the quality of other aspects of the included trials. One reviewer (EH) extracted the data from the studies, but was aided and checked by JB from Cochrane.

MAIN RESULTS

A total of seven trials including 351 women with AD were analysed. Because different drugs were used at different studies it was not possible to combine more than two studies in any analysis.On a clinical global rating, clinicians scored patients taking CEE as significantly worse compared with the placebo group on the Clinical Dementia Rating scale after 12 months (overall WMD = 0.35, 95% CI = 0.01 to 0.69, z = 1.99, P < 0.05).Patients taking CEE had a worse performance on the delayed recall of the Paragraph Test (overall WMD = -0.45, 95% CI = -0.79 to -0.11, z = 2.60, P < 0.01) after one month than those taking placebo. They had a worse performance on Finger Tapping after 12 months (WMD = -3.90, 95% CI = -7.85 to 0.05, z = 1.93, P < 0.05).Limited positive effects were found for the lower dosage of CEE (0.625 mg/day) which showed a significant improvement in MMSE score only when assessed at two months, and disappeared after correction for multiple testing. No significant effects for MMSE were found at longer end points (3, 6 and 12 months of treatment). With a dosage of 1.25 mg/d CEE, short-term significant effects were found for Trial-Making test B at one month and Digit Span backward at four months. After two months of transdermal diestradiol (E2) treatment, a highly significant effect was observed for the word recall test (WMD = 6.50, 95% CI = 4.04 to 8.96, z = 5.19, P < 0.0001). No other significant effects were found for other outcomes measured.

AUTHORS' CONCLUSIONS

Currently, HRT or ERT for cognitive improvement or maintenance is not indicated for women with AD.

The contribution of luteinizing hormone to Alzheimer disease pathogenesis

Several hypotheses have been proposed that attempt to explain the pathogenesis of Alzheimer Disease (AD) including theories involving senile plaque and neurofibrillary tangle formation, increased oxidative stress, and cell cycle abnormalities, since evidence for each of these pathological phenomena have been well documented in AD. Recent epidemiological and experimental data also support a role for the gonadotropin luteinizing hormone in AD. Paralleling the female predominance for developing AD, luteinizing hormone levels are significantly higher in females as compared to males, and furthermore, luteinizing hormone levels are higher still in individuals who succumb to AD. Luteinizing hormone, which is capable of modulating cognitive behavior, is not only present in the brain, but also has the highest receptor levels in the hippocampus, a key processor of cognition that is severely deteriorated in AD. Furthermore, we recently examined cognitive performance in a well-characterized transgenic mouse that over-expresses luteinizing hormone and found that these animals show decreased cognitive performance when compared to controls. We have also found that abolishing luteinizing hormone in amyloid-beta protein precursor transgenic mice (Tg2576) using a potent gonadotropin-lowering gonadotropin-releasing hormone agonist, leuprolide acetate, resulted in improved hippocampally-related cognitive performance and decreased amyloid-beta deposition. These findings, together with data indicating that luteinizing hormone modulates amyloid-beta protein precursor processing in vivo and in vitro, suggest that luteinizing hormone may contribute to AD pathology through an amyloid-dependent mechanism. These promising findings support the importance of luteinizing hormone in AD and bring to the forefront an alternative, and much needed, therapeutic avenue for the treatment of this insidious disease.

Symptoms related to the menopause and sex steroid treatments

In the menopause transition, ovarian steroid production is gradually inhibited and around 35% of women will seek medical help for postmenopausal symptoms. The hot flush is a characteristic manifestation occurring in about 70% of women; it is associated with oestrogen withdrawal and disappears with oestrogen-based hormone replacement therapy. The exact mechanism behind it is still unclear but is probably related to heat loss mechanisms. The flush often occurs in parallel to changes in skin temperature, blood flow, pulse rate and pulses of luteinizing hormone (LH). These are probably secondary to a disturbance in the thermoregulatory centre of the CNS, which is anatomically close to neurons containing gonadotropin-releasing hormone. Depression is no more frequent in the menopausal transition than at other times in life. After surgical menopause, however, oestrogen improves low mood over placebo. In women with premenstrual syndrome, an increased feeling of well-being is associated with the pre-ovulatory oestrogen peak. Progestogens are associated with negative mood changes during the menstrual cycle, oral contraception and postmenopausal replacement therapy. Certain progesterone metabolites are anaesthetic and have anti-epileptic and anxiolytic properties, effects which are mediated via the type A gamma-aminobutyric acid (GABAA) receptor. Oestrogen is associated with increased sensory perception, locomotory activity, limb coordination and balance: this may help explain the increased frequency of bone fractures in the early postmenopausal period. Oestrogen improves memory and performance in patients with mild Alzheimer's dementia and increases epileptic activity in patients with partial epilepsy. These effects can be related to amplifying effects of oestrogen on excitatory amino acids in the CNS.

Oestrogens and the structural and functional plasticity of neurons: implications for memory, ageing and neurodegenerative processes

Oestrogens have numerous effects on the brain, beginning during gestation and continuing on into adulthood. Many of these actions involve areas of the brain that are not primarily involved in reproduction, such as the basal forebrain, hippocampus, caudate putamen, midbrain raphe and brainstem locus coeruleus. This paper describes three actions of oestrogens that are especially relevant to brain mechanisms involved in memory processes and their alterations during ageing and neurodegenerative diseases: (1) the regulation of cholinergic neurons by oestradiol in the rat basal forebrain, involving induction of choline acetyltransferase and acetylcholinesterase according to a sexually dimorphic pattern; (2) the regulation of synaptogenesis in the CA1 region of the hippocampus by oestrogens and progestins during the four- to five-day oestrus cycle of the female rat. Formation of new excitatory synapses is induced by oestradiol and involves N-methyl-D-aspartate receptors; removal of these synapses involves intracellular progestin receptors; (3) sex differences in hippocampal structure, which may help to explain differences in the strategies that male and female rats use to solve spatial navigation problems. During the period of development when testosterone is elevated in the male, aromatase and oestrogen receptors are also elevated, making it likely that this pathway is involved in the masculinization of hippocampal structure.

The complex role of estrogens in inflammation

There is still an unresolved paradox with respect to the immunomodulating role of estrogens. On one side, we recognize inhibition of bone resorption and suppression of inflammation in several animal models of chronic inflammatory diseases. On the other hand, we realize the immunosupportive role of estrogens in trauma/sepsis and the proinflammatory effects in some chronic autoimmune diseases in humans. This review examines possible causes for this paradox. This review delineates how the effects of estrogens are dependent on criteria such as: 1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses (e.g., T cell inhibited by estrogens vs. activation of B cell); 2) the cell types involved during different phases of the disease; 3) the target organ with its specific microenvironment; 4) timing of 17beta-estradiol administration in relation to the disease course (and the reproductive status of a woman); 5) the concentration of estrogens; 6) the variability in expression of estrogen receptor alpha and beta depending on the microenvironment and the cell type; and 7) intracellular metabolism of estrogens leading to important biologically active metabolites with quite different anti- and proinflammatory function. Also mentioned are systemic supersystems such as the hypothalamic-pituitary-adrenal axis, the sensory nervous system, and the sympathetic nervous system and how they are influenced by estrogens. This review reinforces the concept that estrogens have antiinflammatory but also proinflammatory roles depending on above-mentioned criteria. It also explains that a uniform concept as to the action of estrogens cannot be found for all inflammatory diseases due to the enormous variable responses of immune and repair systems.

Steroidogenic acute regulatory protein (StAR): evidence of gonadotropin-induced steroidogenesis in Alzheimer disease

BACKGROUND

Alzheimer disease (AD) is clinically characterized by progressive memory loss, impairments in behavior, language and visual-spatial skills and ultimately, death. Epidemiological data reporting the predisposition of women to AD has led to a number of lines of evidence suggesting that age-related changes in hormones of the hypothalamic-pituitary-gonadal (HPG) axis following reproductive senescence, may contribute to the etiology of AD. Recent studies from our group and others have reported not only increases in circulating gonadotropins, namely luteinizing hormone (LH) in individuals with AD compared with control individuals, but also significant elevations of LH in vulnerable neuronal populations in individuals with AD compared to control cases as well as the highest density of gonadotropin receptors in the brain are found within the hippocampus, a region devastated in AD. However, while LH is higher in AD patients, the downstream consequences of this are incompletely understood. To begin to examine this issue, here, we examined the expression levels of steroidogenic acute regulatory (StAR) protein, which regulates the first key event in steroidogenesis, namely, the transport of cholesterol into the mitochondria, and is regulated by LH through the cyclic AMP second messenger pathway, in AD and control brain tissue.

RESULTS

Our data revealed that StAR protein was markedly increased in both the cytoplasm of hippocampal pyramidal neurons as well as in the cytoplasm of other non-neuronal cell types from AD brains when compared with age-matched controls. Importantly, and suggestive of a direct mechanistic link, StAR protein expression in AD brains colocalized with LH receptor expression.

CONCLUSION

Therefore, our findings suggest that LH is not only able to bind to its receptor and induce potentially pathogenic signaling in AD, but also that steroidogenic pathways regulated by LH may play a role in AD.

Development of 17alpha-estradiol as a neuroprotective therapeutic agent: rationale and results from a phase I clinical study

17alpha-estradiol (17alpha-E2) differs from its isomer, the potent feminizing hormone 17beta-estradiol (17beta-E2), only in the stereochemistry at one carbon, but this is sufficient to render it at least 200-fold less active as a transactivating hormone. Despite its meager hormonal activity, 17alpha-E2 is as potent as 17beta-E2 in protecting a wide variety of cell types, including primary neurons, from a diverse array of lethal and etiologically relevant stressors, including amyloid toxicity, serum withdrawal, oxidative stress, excitotoxicity, and mitochondrial inhibition, among others. Moreover, both estradiol isomers have shown efficacy in animal models of stroke, Alzheimer's disease (AD), and Parkinson's disease (PD). Data from many labs have yielded a mechanistic model in which 17alpha-E2 intercalates into cell membranes, where it terminates lipid peroxidation chain reactions, thereby preserving membrane integrity, and where it in turn is redox cycled by glutathione or by NADPH through enzymatic coupling. Maintaining membrane integrity is critical to mitochondrial function, where loss of impermeability of the inner membrane initiates both necrotic and apoptotic pathways. Thus, by serving as a mitoprotectant, 17alpha-E2 forestalls cell death and could correspondingly provide therapeutic benefit in a host of degenerative diseases, including AD, PD, Friedreich's ataxia, and amyotrophic lateral sclerosis, while at the same time circumventing the common adverse effects elicited by more hormonally active analogues. Positive safety and pharmacokinetic data from a successful phase I clinical study with oral 17alpha-E2 (sodium sulfate conjugate) are presented here, and several options for its future clinical assessment are discussed.

Methodological Issues in Estrogen Treatment Trials for Alzheimer's Disease

Over the past two decades, many clinical trials have been conducted using different forms of estrogen therapy with and without progestin supplementation in an effort to treat diagnosed Alzheimer's disease. Design variations among these trials may account for the inconsistent results of these investigations and the persistent gap in knowledge about the appropriate use of estrogen in the treatment paradigm for degenerative diseases.

Clinical Pharmacology and Differential Cognitive Efficacy of Estrogen Preparations

Menopause is associated with a significant decline in levels of estrogen, which reportedly leads to several distressing symptoms and adverse health effects on various target tissues including those on bones, heart, and brain. Although effective, the long-term safety and feasibility of therapy with both unopposed and opposed oral conjugated equine estrogen has been questioned by the recent findings of both the Women's Health Initiative (WHI) and the Women's Health Initiative Memory Study (WHIMS). The findings of both these studies have raised several critical issues related to hormone therapy that need to be systematically evaluated in clinical studies. Specifically, these issues relate to the differential efficacy and adverse-effects profile of various forms of estrogen and progestins, the importance of the route of administration of estrogen, the best timing to initiate postmenopausal hormone therapy, and the efficacy of cyclic versus continuous hormone therapy. This article focuses on estrogen and discusses issues related to selecting the best form and route of administration of the hormone. It includes information on basic clinical pharmacology of various forms of estrogen, neuroendocrinology of the menopause, neurobiology of estradiol and estrone, and results of selected basic science and human intervention studies with relevance to identifying the best form and route of administration of estrogen.

Estrogen replacement therapy, Alzheimer's disease, and mild cognitive impairment

This article highlights the latest findings regarding estrogen replacement therapy in the treatment and prevention of Alzheimer's disease (AD) and mild cognitive impairment in women. Despite considerable evidence from observational studies, recent randomized clinical trials of conjugated equine estrogens, alone and in combination with progestin, have shown no benefit for either the treatment of established AD or for the short-term prevention of AD, mild cognitive impairment, or cognitive decline. Based on the evidence, there is no role at present for estrogen replacement therapy in the treatment or prevention of AD or cognitive decline, despite intriguing results from the laboratory and from observational studies. However, numerous questions remain about the biologic effects of estrogens on brain structure and function. Additional basic and clinical investigations are necessary to examine different forms and dosages of estrogens, other populations, and the relevance of timing and duration of exposure.

Estrogen modulates microglial inflammatory mediator production via interactions with estrogen receptor beta

Estrogens are well known to exert antiinflammatory effects outside the central nervous system (CNS). They have also been shown to exert neuroprotective effects in the CNS after several types of injury, including neurodegeneration. However, the molecular mechanisms by which these effects occur remain unclear. Because microglial hyperactivation and their production of neurotoxins is associated with many types of brain injury for which estrogens are beneficial, we sought to investigate the ability of estrogen to modulate microglial function. Furthermore, because little is known regarding the role of each of the two known estrogen receptors (ERs) in microglia, our studies were designed to test the hypothesis that 17beta-estradiol (E(2)) exerts antiinflammatory effects in microglia, specifically via interactions with ERbeta. We tested this hypothesis using the murine microglial cell line BV-2, which naturally expresses only ERbeta. Our results indicate that not only does E(2) decrease lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression, it also reduces the expression of cyclooxygenase-2, a target for estrogen that has not previously been reported for ERbeta. We also observed that LPS-stimulated TNFalpha mRNA was increased by estrogen. E(2) exerts these effects within 30 min compared with typical estrogen transcriptional responses. Tamoxifen and ICI 182,780 differentially blocked the inhibitory effects of E(2) on LPS-stimulated iNOS and cyclooxygenase-2. In addition, we show that E(2) alters LPS-stimulated MAPK pathway activation, supporting the idea that alterations in the MAPKs may be a potential mechanism by which ERbeta mediates decreased microglial activation.

Gender differences in the amount and deposition of amyloidbeta in APPswe and PS1 double transgenic mice

Transgenic mice carrying both the human amyloid precursor protein (APP) with the Swedish mutation and the presenilin-1 A246E mutation (APP/PS1 mice) develop Alzheimer's disease-like amyloidbeta protein (Abeta) deposits around 9 months of age. These mice show an age-dependent increase in the level of Abeta40 and Abeta42 and in the number of amyloid plaques in the brain. Abeta40 and Abeta42 levels were measured, and amyloid burden and plaque number were quantified, in the hippocampus at the age of 4, 12, and 17 months in both male and female APP/PS1 mice. In all mice, amyloid burden and plaque number increased markedly with age, with female mice bearing a heavier amyloid burden and higher plaque number compared to male mice of the same age, both at 12 and at 17 months of age. The level of both Abeta40 and Abeta42 significantly increased in female mice with age and was always significantly higher in female than in male mice of the same age. Further, there were significant correlations between amyloid burden and Abeta42 level in female mice and between amyloid burden and plaques in both female and male mice. Together these data show that female APP/PS1 mice accumulate amyloid at an earlier age and that they build up more amyloid deposits in the hippocampus than age-matched male mice. Together, these results provide new insights in the potential mechanisms of the observed gender differences in the pathogenesis of AD.

The use of estrogen in older women

The menopause is associated with a relatively abrupt decline in the ovarian production of estrogen that results in a state of estrogen deficiency. This estrogen deficiency state is associated with an accelerated expression of cardiovascular disease, osteoporosis, urogenital atrophy, dermal aging, an increased expression of colorectal cancer, an alteration in the expression of breast cancer that results in more malignant forms of the disease, and the loss of neurons from the brain that is associated with a more rapid decline in cognitive function, balance, and an earlier expression of Alzheimer's disease. Macular degeneration and cataract formation may be additional consequences of the estrogen deficiency state. Thus the estrogen deficiency state may be characterized as a state of accelerated aging. The abrupt transition from the reproductive state of multiple estrogen-dependent neural systems within the brain may affect their function as manifested by the typical menopausal symptoms of hot flashes, mood changes, sleep disturbance, and cognitive impairment. This transition may trigger a cascade of events that contributes to the acceleration of brain aging and the expression of neurodegenerative processes as Alzheimer's disease. This article discusses the use of estrogen to prevent these age-related changes.

Current Treatment for Alzheimer Disease and Future Prospects

A cascade of pathophysiological events is triggered in Alzheimer disease (AD) that ultimately involves common cellular signaling pathways and leads to cellular and network dysfunction, failure of neurotransmission, cell death, and a common clinical outcome. The process is asynchronous, meaning that viable neurons remain as targets for therapy even in the diseased state, and each stage of the cascade affords the possibility for therapeutic intervention. Cholinesterase inhibitors are the only available treatment in the United States for patients with mild to moderate AD, helping maintain cognitive and functional abilities in most patients and conferring beneficial behavioral effects in some. Memantine is an NMDA receptor antagonist that has recently been approved in Europe for treatment of moderately severe to severe AD and is under investigation in the United States. Its mechanism of action may include enhanced neurotransmission in several systems as well as antiexcitotoxic effects. There are data regarding the effectiveness of the combination of memantine with cholinesterase inhibitors that will be useful for the practicing clinician. Other agents have shown some benefit in clinical trials, including the antioxidants vitamin E, selegiline, and Ginkgo biloba extracts, although the weight of evidence regarding their effects is not sufficient to define clinical practice. Potential future therapies currently are in development that target multiple aspects of the illness cascade, including aberrant inflammation, neurotrophic function, and processing of beta amyloid and tau proteins. These newer approaches hold promise for disease modification but are as yet unproven. Whether or not disease-modifying or preventive therapies become a reality, clinicians will be faced with AD patients who require treatment at all stages of illness for the indefinite future. Cholinergic and emerging noncholinergic medications will likely prevail as the standards of treatment for years to come.

Role of the medial septum diagonal band of Broca cholinergic neurons in oestrogen-induced spine synapse formation on hippocampal CA1 pyramidal cells of female rats

Oestrogen is known to influence pyramidal cell spine synapse plasticity in the CA1 subfield of the hippocampus. Apart from direct oestrogen action on the hippocampus, oestrogen effects mediated by subcortical structures are known to be important. The purpose of this study was to investigate whether the medial septum diagonal band of Broca (MSDB) takes part in mediating oestrogen effects to the hippocampus. Special attention was given to the role of cholinergic MSDB neurons that project to the hippocampus, as a rather large population of them contains oestrogen receptors and, consequently, may be sensitive to oestrogen signals. Adult female rats were ovariectomized. Oestradiol- and cholesterol-filled cannulae (control) were implanted into the MSDB. To selectively eliminate the cholinergic population of MSDB neurons of oestrogen-treated animals, a group of rats was injected with 192 IgG-saporin (SAP) into the lateral ventricle 1 week before the cannula implant. Immunostaining with anti-choline acetyltransferase and parvalbumin (PA) showed that cholinergic but not PA-containing GABAergic neurons were substantially reduced in the MSDB of SAP rats. Comparative electron microscopic unbiased stereological analysis on the spine synapse density of CA1 area pyramidal cells was performed between all animal groups. Rats that received oestradiol-filled cannulae showed a higher (30%) spine synapse density than control animals. Oestrogen-treated rats that had received SAP treatment showed no significant difference to controls. Thus, this observation indicates that septo-hippocampal cholinergic neurons are involved in mediating oestrogen effects to the hippocampus. The relevance of this observation to mnemonic functions and Alzheimer's disease is discussed.

Estrogen and cognitive functioning in women

Research in basic neuroscience has provided biological plausibility for the hypothesis that estrogen replacement therapy (ERT) would protect against cognitive aging in healthy women. The weight of the evidence from randomized controlled trials of estrogen and cognition in women shows that this hormone preferentially protects verbal memory in postmenopausal women, whereas findings from observational studies are less consistent and show a more diffuse effect of estrogen on a range of cognitive functions. There is fairly consistent evidence from epidemiological studies that ERT significantly reduces the risk of Alzheimer's disease (AD) in women. On the other hand, findings from controlled treatment trials of women diagnosed with probable AD failed to show that physiological doses of ERT ameliorate existing deficits in cognitive functioning and/or prevent further deterioration in memory that inevitably occurs in these women over time. Finally, an accumulating body of evidence is beginning to suggest that the immediate postmenopausal period may constitute a critical window for treatment with ERT that maximizes its potential to protect against cognitive decline with aging and/or to reduce the risk of AD.

In vitro study of the functional expression of organic anion transporting polypeptide 3 at rat choroid plexus epithelial cells and its involvement in the cerebrospinal fluid-to-blood transport of estrone-3-sulfate

The cerebrospinal fluid-to-blood efflux transport of estrone-3-sulfate (E(1)S) via the blood-cerebrospinal fluid barrier (BCSFB) may play an important role in regulating E(1)S levels in the brain. Here, we investigated the efflux transport of E(1)S at the BCSFB using conditionally immortalized rat choroid plexus epithelial cells (TR-CSFB) and identified the responsible transporter. The [(3)H]E(1)S uptake by TR-CSFB cells was composed of saturable and nonsaturable components, and the K(m) and V(max) values of the saturable component were determined to be 16.8 +/- 5.1 microM and 12.3 +/- 2.3 pmol/min/mg of protein, respectively. [(3)H]E(1)S uptake was inhibited by probenecid, cholate, taurocholate, sulfobromophthalein, dehydroepiandrosterone sulfate, triiodothyronine, thyroxin, and digoxin but not by p-aminohippuric acid, gamma-aminobutyric acid, or methotrexate, suggesting the involvement of organic anion transporting polypeptide (oatp) in the uptake. Reverse transcription-polymerase chain reaction analysis revealed that oatp3 was expressed in TR-CSFB cells and isolated rat choroid plexus, although oatp1 was not detected in either. Xenopus laevis oocytes expressing oatp3 exhibited [(3)H]E(1)S uptake activity with a K(m) of 8.09 +/- 2.83 microM and V(max) of 8.02 +/- 0.87 pmol/h/oocyte. Moreover, oatp3 is localized at the brush-border membrane of choroid plexus epithelial cells. These results suggest that oatp3 is involved in the E(1)S efflux transport at the BCSFB.

Expanding the association between the APOE gene and the risk of Alzheimer's disease: possible roles for APOE promoter polymorphisms and alterations in APOE transcription

Alzheimer's disease (AD) is the most commonly diagnosed form of dementia in the elderly. Predominantly this disease is sporadic in nature with only a small percentage of patients exhibiting a familial trait. Early-onset AD may be explained by single gene defects; however, most AD cases are late onset (> 65 years) and, although there is no known definite cause for this form of the disease, there are several known risk factors. Of these, the epsilon4 allele of the apolipoprotein E (apoE) gene (APOE) is a major risk factor. The epsilon4 allele of APOE is one of three (epsilon2 epsilon3 and epsilon4) common alleles generated by cysteine/arginine substitutions at two polymorphic sites. The possession of the epsilon 4 allele is recognized as the most common identifiable genetic risk factor for late-onset AD across most populations. Unlike the pathogenic mutations in the amyloid precursor or those in the presenilins, APOE epsilon4 alleles increase the risk for AD but do not guarantee disease, even when present in homozygosity. In addition to the cysteine/arginine polymorphisms at the epsilon2/epsilon3/epsilon4 locus, polymorphisms within the proximal promoter of the APOE gene may lead to increased apoE levels by altering transcription of the APOE gene. Here we review the genetic and biochemical evidence supporting the hypothesis that regulation of apoE protein levels may contribute to the risk of AD, distinct from the well known polymorphisms at the epsilon2/epsilon3/epsilon4 locus.

Can estrogen play a significant role in the prevention of Alzheimer's disease?

In women the abrupt decline estrogen levels at menopause may be associated with cognitive deficits and increased risk for Alzheimer's disease (AD); estrogen replacement therapy may reduce this risk. Animal studies indicate that estrogen modulates neurotransmitter systems, regulates synaptogenesis, and is neuroprotective. These beneficial effects occur in brain areas critical to cognitive function and involved in AD. Reduced estrogen levels can compromise neuronal function and survival. Estrogen replacement therapy can reverse cognitive deficits associated with low estrogen levels and may reduce the risk of AD. However, clinical trials for estrogen replacement in the treatment of AD have produced ambiguous results. Initial, small, open-label and double blind clinical trials indicated improved cognitive function in women with AD. Recent large trials failed to show a beneficial effect for long-term estrogen replacement for women with AD. There are several variables that could affect these results, such as genetic factors, time between estrogen loss and replacement, extent and types of AD pathology, and other environmental and health factors. Presently large prospective studies are being conducted as the National Institutes of Health in the Women's Health Initiative and the Preventing Postmenopausal Memory Loss and Alzheimer's with Replacement Estrogens studies to provide a better assessment of the role of estrogen for age related health issues, including dementia.

Estrogen receptor-alpha distribution in the human hypothalamus in relation to sex and endocrine status

The present study reports the first systematic rostrocaudal distribution of estrogen receptor-alpha immunoreactivity (ERalpha-ir) in the human hypothalamus and its adjacent areas in young adults. Postmortem material taken from 10 subjects (five male and five female), between 20 and 39 years of age, was investigated. In addition, three age-matched subjects with abnormal levels of estrogens were studied: a castrated, estrogen-treated 50-year-old male-to-female transsexual (T1), a 31-year-old man with an estrogen-producing tumor (S2), and an ovariectomized 46-year-old woman (S8). A strong sex difference, with more nuclear ERalpha-ir in women, was observed rostrally in the diagonal band of Broca and caudally in the medial mamillary nucleus. Less robust sex differences were observed in other brain areas, with more intense nuclear ERalpha-ir in men, e.g., in the sexually dimorphic nucleus of the medial preoptic area, paraventricular nucleus, and lateral hypothalamic area, whereas women had more nuclear ERalpha-ir in the suprachiasmatic nucleus and ventromedial nucleus. No nuclear sex differences in ERalpha were found, e.g., in the central part of the bed nucleus of the stria terminalis. In addition to nuclear staining, ERalpha-ir appeared to be sex-dependently present in the cytoplasm of neurons and was observed in astrocytes, plexus choroideus, and other non-neuronal cells. ERalpha-ir in T1, S2, and S8 suggested that most of the observed sex differences in ERalpha-ir are "activational" (e.g., ventromedial nucleus/medial mamillary nucleus) rather than "organizational." Species similarities and differences in ERalpha-ir distribution and possible functional implications are discussed.

Long-term estrogen therapy worsens the behavioral and neuropathological consequences of chronic brain inflammation

Alzheimer's disease (AD) is accompanied by chronic neuroinflammation and occurs with greater incidence in postmenopausal women. The increased incidence may be delayed by estrogen replacement therapy (ERT). The authors investigated the interaction of chronic ERT and lipopolysaccharide (LPS)-induced neuroinflammation in the female rat. Ovariectomy did not impair water maze performance; however, addition of chronic ERT or neuroinflammation resulted in an impairment that became exacerbated by the simultaneous occurrence of both conditions. Chronic LPS activated microglia, which was not reduced by ERT. Intact females receiving LPS infusion were not impaired in the water maze and had significantly fewer activated microglia. Results suggest that chronic ERT in postmenopausal women may exacerbate the memory impairment induced by the chronic neuroinflammation associated with AD.

Estrogen and Alzheimer's disease: the story so far

The ovarian hormone estrogen has long been used to treat the physical symptoms of menopause and to aid in the prevention of osteoporosis in postmenopausal women. Cumulative evidence from basic science and clinical research suggests that estrogen also plays a significant neuromodulatory and neuroprotective role. The numerous estrogenic effects in the brain include the modulation of synaptogenesis, increased cerebral blood flow, mediation of important neurotransmitters and hormones, protection against apoptosis, anti-inflammatory actions, and antioxidant properties. These multiple actions in the central nervous system support estrogen as a potential treatment for the cognitive decline associated with Alzheimer's disease (AD), the most common form of dementia. Evidence from epidemiological studies supports enhanced cognitive function in women with AD taking estrogen replacement therapy (ERT) as well as a reduced risk for developing AD in healthy women receiving ERT. Additional clinical evidence suggests that estrogen may modulate specific cognitive functions such as working memory and verbal learning and memory. However, results from more recent controlled trials have not consistently shown a beneficial effect of estrogen on the cognitive function of women with AD. Future research should focus on examining the influence of multiple potential mediators of ERT including the route of estrogen administration, form of estrogen (conjugated estrogens vs estradiol), duration of treatment, opposed versus unopposed estrogen and the use of estrogen analogues. Further, sensitive neuropsychological measures may provide more detailed information concerning the specific effects of estrogen on cognitive function. These important issues must be addressed in order to establish the role of estrogen for the prevention and treatment of AD in women.

Oestrogen has neuroprotective effects and may reduce the risk of Alzheimer's disease

Evidence from both animals and humans supports a neuroprotective role of oestrogen. Epidemiological studies showing that oestrogen improves cognitive performance in postmenopausal women, clinical trials showing effects of oestrogen on cognition and data suggesting that oestrogen reduces the risk of Alzheimer's disease (AD) led to the proposal that oestrogen may be effective for improving symptoms or slowing decline in women with AD. Studies evaluating oestrogen as a treatment for AD have been performed with mixed findings. While a few studies have found modest improvements, the results have largely been disappointing. However, many of the studies suffer from substantial methodological problems that leave the findings in question. The role of oestrogen for the prevention or treatment of AD is not yet clear, but large, well-controlled, ongoing trials should provide definitive answers to many questions in the near future.

The influence of hormone replacement therapy on the aging-related change in cognitive performance. Analysis based on a Danish cohort study

OBJECTIVE

A maintenance and/or improvement of cognitive performance with postmenopausal hormone replacement therapy (HRT) is biological plausible. The objectives of this study were to analyze the impact of HRT on aging-related changes in cognitive performances, and to assess whether women who choose HRT have better cognitive performance prior to HRT.

METHODS

Data derives from a longitudinal sub-cohort of women participating in a large survey of the general adult population-The Danish MONICA (MONItoring CArdiovascular risk factors) Study. Main variables for analyses come from neuropsychological examination consisting of 28 cognitive parameters collected in 1982-1983 and again in 1993-1994, by a computer-aided test technique, the Cognitive Function Scanner((R)). The final analyses comprised 126 'never users', 40 'current users' at follow-up, and 30 'future users' of HRT (women who started HRT during the observation period subsequent to baseline registration).

RESULTS

'Current users' of HRT at follow-up showed a less pronounced decline in cognitive performance compared to 'never users' in one of six parameters for concentration ability and two of eight parameters for visuomotor function. 'Future users' of HRT had better cognitive performance at baseline compared to 'never users' in long-term visual memory, concentration, and reaction time. 'Future users' of HRT were more precise but spent more time in the tests for visuomotor function than 'never users'.

CONCLUSION

HRT-treated women show a postponed aging-related decline in cognitive functioning, partly in concentration and partly in visuomotor function. However, women who choose HRT have better cognitive performance prior to the treatment.

The effects of estrogen replacement therapy on neuropsychological functioning in postmenopausal women with and without dementia: a critical and theoretical review

We review 42 studies examining the effects of estrogen replacement therapy (ERT) on memory and cognition in nondemented postmenopausal women. Although there are an appreciable number of nonsignificant findings, the number of significant findings favoring ERT users considerably outnumbers the rare findings of better performance in controls. Experimental studies demonstrate a consistent beneficial effect on verbal memory, but these are short-term studies of the more acute effects of ERT. The observational studies suggest that there may be a long-lasting effect of continued ERT on cognitive functioning, but these studies need to be interpreted with caution because of the lack of random assignment and a possible "healthy user bias." We also summarize findings from studies on the effects of ERT on Alzheimer's disease (AD). ERT is associated with a decreased risk for dementia, but there is little evidence for a positive effect on cognition in women with AD. Definitive answers to questions about the long-term effects of ERT on cognitive aging and risk of developing AD should be provided by 3 ongoing clinical trials.

Neuroactive steroids and central nervous system disorders

Steroid hormones are vital for the cell life and affect a number of neuroendocrine and behavioral functions. In contrast to their endocrine actions, certain steroids have been shown to rapidly alter brain excitability and to produce behavioral effects within seconds to minutes. In this article we direct attention to this issue of neuroactive steroids by outlining several aspects of current interest in the field of steroid research. Recent advances in the neurobiology of neuroactive are described along with the impact of advances on drug design for central nervous system (CNS) disorders provoked by neuroactive steriods. The theme was selected in association with the clinical aspects and therapeutical potentials of the neuroactive steroids in CNS disorders. A wide range of topics relating to the neuroactive steroids are outlined, including steroid concentrations in the brain, premenstrual syndrome, estrogen and Alzheimer's disease, side effects of oral contraceptives, mental disorder in menopause, hormone replacement therapy, Catamenial epilepsy, and neuractive steroids in epilepsy treatment.

Menopause and perimenopause: the role of ovarian hormones in common neuroendocrine syndromes in primary care

The climacteric and menopause are characterized by erratic fluctuations and decline in ovarian steroid hormones that have broad impact on physical and psychological phenomena leading to a number of clinical syndromes encountered in primary care settings. This endocrine transition is abrupt in women and is not often adequately assessed using objective measures, leading to potential overuse of various medications to treat the physiological and psychological consequences of decline in ovarian hormones. This article reviews such issues and explains how primary care physicians may incorporate the endocrine changes more effectively in their evaluation and treatment of midlife women.

Estrogen replacement therapy for cognitive benefits: viable treatment or forgettable "senior moment"?

The perceived benefits of estrogen on cognitive function are one of the few remaining potential roles for estrogen replacement therapy. The justification for such a role has a strong biologic basis and is easily shown in animal models. Purported benefits for estrogen on cognitive function include neuroprotective, neurostimulating, and neurotrophic effects. The objective of this study was to review the literature and to evaluate the role of estrogen replacement therapy in improving cognition in Alzheimer disease, vascular dementia, premenopausal women, and postmenopausal women without dementia. Additionally, the authors separately looked at the neuroprotective effects of estrogen replacement therapy on the subsequent risk of dementia. The available data fail to show a therapeutic benefit of estrogen replacement therapy in Alzheimer disease. Surprisingly, limited data allow consideration of a possible role of estrogen in the management of vascular dementia. Additionally, younger females with low estrogen levels secondary to primary ovarian failure and Turner syndrome benefit from estrogen replacement therapy. Despite the limited role of estrogen replacement therapy in cognitive enhancement, neuroprotective properties are likely because several prospective studies indicate a reduced risk of Alzheimer disease. A critical window of opportunity seems to exist for this protective effect in Alzheimer disease because once established, the course of the disease is not affected by concomitant estrogen replacement therapy. The authors conclude that the use of estrogen replacement therapy is not substantiated for the treatment of patients with Alzheimer disease. Alternatively, because of the evidence for a possible neuroprotective effect, women at high risk for the development of Alzheimer disease may be appropriate candidates for estrogen replacement therapy. Such a decision should be made on a case-by-case basis, after careful consideration of the risks and benefits.

Selective estrogen receptor modulators as a new therapeutic drug group: concept to reality in a decade

This article provides an overview of the historical development, current research, clinical benefits, and potential future applications of the selective estrogen receptor modulators (SERMs), tamoxifen and raloxifene. The understanding of the mechanism of action of SERMs led not only to the development of tamoxifen, the first widely used antiestrogen for breast cancer treatment, but also to its application as a chemopreventive agent. The SERM principle of antiestrogenic actions in the breast but estrogenlike actions in bone is reviewed in clinical practice through analysis of the current applications and the potential for expanding the role of SERMs. The current view of the molecular mechanism of SERM action is summarized to identify potential target sites for future research. The clinical success of tamoxifen and raloxifene for the prevention and treatment of breast cancer and osteoporosis, respectively, has encouraged the development of a range of new agents that target breast cancer, osteoporosis, coronary heart disease, and endometrial safety.

Hormone replacement therapy to maintain cognitive function in women with dementia

BACKGROUND

As estrogens have been shown to have several potentially beneficial effects on the central nervous system, it is biologically plausible that maintaining high levels of estrogens in postmenopausal women by means of estrogen replacement therapy (ERT) could be protective against cognitive decline and the development of Alzheimer's disease (AD) or other dementia syndromes.

OBJECTIVES

To investigate the effects of ERT (estrogens only) or HRT (estrogens combined with a progestagen) compared with placebo in randomized controlled trials (RCTs) on cognitive function of postmenopausal women with dementia.

SEARCH STRATEGY

The CDCIG Specialized Register, which contains up-to-date records from many medical databases was searched using the terms ORT, PORT, ERT, HRT, estrogen*, oestrogen*, progesteron* and Alzheim* on 16th of May 2002. In addition, MEDLINE (1966-2002/01); EMBASE (1985-2002/01); and PsyINFO (1967-2002/01) were searched.

SELECTION CRITERIA

All double-blind randomized controlled trials (RCTs) into the effect of ERT or HRT for cognitive function with a treatment period of at least two weeks in postmenopausal women with AD or other types of dementia.

DATA COLLECTION AND ANALYSIS

Abstracts of the references retrieved by the searches were read by two reviewers (EH and KY) independently in order to discard those that were clearly not eligible for inclusion. The two reviewers studied the full text of the remaining references and independently selected studies for inclusion. Any disparity in the ensuing lists was resolved by discussion with all reviewers in order to arrive at the final list of included studies. The selection criteria ensured that the blinding and randomization of the included studies was adequate. The two reviewers also assessed the quality of other aspects of the included trials. One reviewer (EH) extracted the data from the studies, but was aided and checked by JB from Cochrane.

MAIN RESULTS

A total of five trials including 210 women with AD were analysed. Meta-analyses showed that there was a limited positive effect from low dosage of conjugated equine estrogens (CEE, 0.625 mg once a day) but not from higher dosage (1.25 mg of CEE once a day) on the Mini-Mental Status Examination after 2 months (WMD=1.28, 95% C.I.=0.26 to 2.30, z=2.45, p<0.01) and the effect disappeared after 3, 6 and 12 months of treatment. This effect was small and not clinically relevant as there was only a difference of 1 point on average in comparison with the placebo users (the scale range is 0-30). There were also short-term effects of 1.25 mg of CEE on tests of concentration and executive function, namely the Trail Making Test-B (WMD=-40.90, 95% C.I.-79.29 to -2.51, z=2.09, p<0.05) and Digit Span backward (WMD=0.67, 95% C.I.=-0.01 to 1.34, z=1.94, p<0.05). With regard to memory, only cued delayed recall of a word list was positively affected by 2 months of transdermal diestradiol (E2) (WMD=6.50, 95% C.I.=4.04 to 8.96, z=5.19, p<0.0001). No HRT effects were seen on other word lists, Paragraph Recall or Paired Associate Learning. In addition, no effects were seen on visual memory, language functions, most speeded tests, clinical rating scales or depression. Controls had better performance on the delayed recall of the Paragraph Test (overall WMD=-0.45, 95% C.I.=-0.79 to -0.11, z=2.60, p<0.01) after 1 month and on Finger Tapping after 12 months (WMD=-3.90, 95% C.I.=-7.85 to 0.05, z=1.93, p<0.05). Clinicians also gave controls a better score on a dementia rating scale (CDR, overall WMD=0.35, 95% C.I.=0.01 to 0.69, z=1.99, p<0.05). Positive findings in favour of treatment or placebo could have been random effects caused by multiple analyses. After correction for multiple testing, only the short-term positive treatment effect of E2 on memory remained.

REVIEWER'S CONCLUSIONS

Currently, HRT or ERT for cognitive improvement or maintenance is not indicated for women with AD. As we did not have data on women with other types of dementia (e.g. vascular dementia) this remains to be investigated. As most studies only used CEE and our earlier review in healthy women found effects only after a bolus injection of E2, it remains possible that different preparations or types of ERT or HRT could have a different effects. Several questions are raised in this review, including whether factors such as age, dementia onset (early AD), or the use of a particular preparation for a longer duration of treatment could have different effects. Perhaps the most important question is whether ERT or HRT can delay the time of onset of dementia. For answers to these questions, we have to await the results of the large RCTs currently in progress in the UK, USA, and Canada.

Estrogen replacement therapy for the potential treatment or prevention of Alzheimer's disease

Alzheimer's disease (AD) is an irreversible, progressive brain disorder that occurs gradually and results in memory loss, behavior and personality changes, and a decline in cognitive abilities. Although basic biological data suggest that estrogen may have neuroprotective and neuroenhancing functions, a number of studies have produced conflicting findings on the use of estrogen for maintaining cognitive function in older people. This review summarizes clinical studies that have examined the effects of estrogen in women with AD.

Estrogens, selective estrogen receptor modulators, and dementia: what is the evidence?

At least 10% of people aged 65 or older have some form of cognitive impairment, increasing to around 50% by age 85. Several studies have suggested that estrogen may improve cognitive function or prevent the development of dementia, but other studies have not shown a benefit, and results from large randomized trials are lacking. Fortunately, further trials are currently being conducted. With the recognition that selective estrogen receptor modulators (SERMs) have differential tissue-dependent effects on estrogen receptor function, there is recent interest in the effects of raloxifene, tamoxifen, and other SERMs on cognition. In this paper, the current state of knowledge of the role of estrogen for preventing dementia in postmenopausal women will be reviewed. In addition, the status of ongoing and recently completed trials of estrogen and SERMs on cognitive function or on Alzheimer's disease severity will be summarized.

Relationships of sex hormone levels to dependence in activities of daily living in the frail elderly

OBJECTIVES

We undertook this nursing home study in order to determine the relationships between dependency in activities of daily living (ADL) and blood levels of estrone, testosterone, androstenedione, and dehydroepiandrosterone (DHEA). Little is known about this issue.

METHODS

cross-sectional study of 370 nursing home residents. Hormone levels in blood specimens drawn in 1997 and 1998 were correlated with degree of ADL dependency recorded in medical charts.

RESULTS

Because of multiple comparisons associations were deemed significant for P-values < or =0.017 for males and < or =0.0125 for females. In males, the following were inversely related: testosterone levels with dependency in transferring and eating; estrone with eating and a summary ADL index; and androstenedione with toileting and a summary ADL index (in all cases, r=-0.4; P=0.007-0.015). Inverse trends existed between testosterone levels and dependency in mobility and a summary ADL index; and androstenedione and eating (in all cases r=-0.3; P=0.030-0.055). Among females the following were directly related: estrone levels with dependence in mobility, toileting, transferring, and a summary ADL index; and DHEA with transferring and a summary ADL index (r=0.2-0.3, P=0.0001-0.01). Trends existed between estrone and eating, and DHEA and toileting (r=0.1-0.2, P=0.04).

CONCLUSION

In male residents, higher sex hormone levels are associated with better ADL performance. Among females the opposite is true. While further studies are needed to elucidate these relationships, our results and recent findings of others suggest sex hormone actions in older women differ from those in younger populations. A possible stress-related mechanism is also presented.

Age-related changes of evoked potentials

The aim of this review is to analyse the current state of our knowledge on evoked potentials (EPs) in ageing and to report some conclusions on the relation between EPs and elder age. Evoked potentials provide a measure of the function of sensory systems that change during the different stages of life. Each sensory system has its own time of maturation. The individuation of the exact period of life when brain ageing starts is difficult to define. Normally, the amplitude of EPs decreases, and their latency increases from adult to elder life. Many authors speculate that these modifications might depend on neuronal loss, changes in cell membrane, composition or senile plaques present in older patients, but there is no evidence that these changes might modify the cerebral function in healthy aged individuals. This review emphasises some incongruities present in different studies confirmed by daily neurophysiologic practice. Different techniques as event-related desynchronization (ERD), contingent negative variation (CNV) and Bereitschaftspotential, are available to study central neuronal changes in normal and pathologic ageing.