The healthy cell bias of estrogen action: mitochondrial bioenergetics and neurological implications

Predictive factors for postoperative delirium in thoracic surgery

OBJECTIVE

We examined cases in which delirium developed after thoracic surgery under general anesthesia at our hospital to determine the predictive factors for postoperative delirium, as well as the perioperative findings in cases showing postoperative delirium.

METHODS

This retrospective study included 1674 patients who underwent surgery under general anesthesia at our hospital between 2012 and 2022, A psychiatrist diagnosed postoperative delirium using the Confusion Assessment Method.

RESULTS

There were 99 (5.9%) patients with postoperative delirium in our study, including 85 (86%) men, of whom 31 (31%) had a history of cerebrovascular disease. The incidence of postoperative delirium in patients aged > 80 years was 20% (36/182). The postoperative delirium group showed significantly longer hospital stays and more frequent postoperative complications than the group without postoperative delirium. In univariate analysis, age ≥ 80 years, male sex, history of cerebrovascular disease, hypertension, history of atrial fibrillation, and history of smoking were identified as significant factors, while multivariate analysis identified age ≥ 80 years, male sex, history of cerebrovascular disease, hypertension, and history of smoking as significant factors (odds ratios = 5.15, 2.04, 3.10, 1.67, and 2.36, respectively). In the 169 cases with none of these five factors, the postoperative delirium risk was 0% (0/169).

CONCLUSIONS

In patients undergoing thoracic surgery, predictive factors for postoperative delirium include age ≥ 80 years, male sex, history of cerebrovascular disease, hypertension, and smoking history. The findings also indicate that patients with these risk factors may require psychiatric consultation before surgery.

Reproductive life factors and estro-progestin exposure in women with early-onset Parkinson's disease compared to late-onset disease and controls: A retrospective cohort study

BACKGROUND

Parkinson's disease (PD) is more common in men than women. Although hormonal factors may partially explain this difference, there are no studies evaluating reproductive life factors and exogenous estroprogestin exposure in women with Early Onset Parkinson Disease (EOPD).

OBJECTIVE

To compare reproductive life factors and exogenous estroprogestin exposure among female patients with EOPD, late-onset Parkinson's disease (LOPD), and EOPD-matched unaffected controls.

METHODS

We identified female patients with EOPD from 1989 to 2021, defining EOPD as PD with motor-symptoms onset before age 50 and LOPD as PD with motor onset after 50. We paired EOPD patients to age-matched, unaffected controls. We reviewed medical records to determine demographic characteristics, clinical history, and reported reproductive menopausal history (reviewing medical records).

RESULTS

We included 87 EOPD patients, 84 LOPD patients, and 91 unaffected controls with information about reproductive life factors and exogenous estroprogestin exposure in their medical records. There were no significant differences in race, ethnicity, or BMI between the three groups. EOPD patients were more likely to have used hormonal contraception than LOPD patients (23/49 (47 %) vs 0/84 (0 %), p < 0.001). LOPD patients had higher numbers of pelvic surgeries (48/84 [57 %] in LOPD, 23/87 [26 %] in EOPD, p < 0.001) and higher usage of perimenopausal hormonal therapy (52/84 [62 %] in LOPD, 10/87 [11 %] in EOPD, p < 0.001) in LOPD than EOPD.

CONCLUSIONS

Our study reports no significant difference in reproductive life factors and exogenous estroprogestin exposure between controls and EOPD patients, except for higher exposure to hormonal contraception in EOPD. There was no apparent difference in reproductive life factors and exogenous estroprogestin exposure between EOPD and LOPD patients. Our findings therefore do not observe that hormonal exposure is different between earlier onset of female EOPD compared to female LOPD patients, or between female EOPD patients and unaffected female controls.

Remote Ischemia Postconditioning Mitigates Hippocampal Neuron Impairment by Modulating Cav1.2-CaMKIIα-Aromatase Signaling After Global Cerebral Ischemia in Ovariectomized Rats

Brain-derived estrogen (BDE2) is gaining attention as an endogenous neurotransmitter. Recent research has revealed that selectively removing the aromatase gene, the pivotal enzyme responsible for BDE2 synthesis, in forebrain neurons or astrocytes can lead to synaptic loss and cognitive impairment. It is worth noting that remote ischemia post-conditioning (RIP), a non-invasive technique, has been shown to activate natural protective mechanisms against severe ischemic events. The aim of our study was to investigate whether RIP triggers aromatase-BDE2 signaling, shedding light on its neuroprotective mechanisms after global cerebral ischemia (GCI) in ovariectomized rats. Our findings are as follows: (1) RIP was effective in mitigating ischemic damage in hippocampal CA1 neurons and improved cognitive function after GCI. This was partially due to increased Aro-BDE2 signaling in CA1 neurons. (2) RIP intervention efficiently enhanced pro-survival kinase pathways, such as AKT, ERK1/2, CREB, and suppressed CaMKIIα signaling in CA1 astrocytes induced by GCI. Remarkably, inhibiting CaMKIIα activity led to elevated Aro-BDE2 levels and replicated the benefits of RIP. (3) We also identified the positive mediation of Cav1.2, an LVGCC calcium channel, on CaMKIIα-Aro/BDE2 pathway response to RIP intervention. (4) Significantly, either RIP or CaMKIIα inhibition was found to alleviate reactive astrogliosis, which was accompanied by increased pro-survival A2-astrocyte protein S100A10 and decreased pro-death A1-astrocyte marker C3 levels. In summary, our study provides compelling evidence that Aro-BDE2 signaling is a critical target for the reparative effects of RIP following ischemic insult. This effect may be mediated through the CaV1.2-CaMKIIα signaling pathway, in collaboration with astrocyte-neuron interactions, thereby maintaining calcium homeostasis in the neuronal microenvironment and reducing neuronal damage after ischemia.

Neuroprotective effect of hormone replacement therapy: a review of the literature

OBJECTIVE

Menopause is a physiological period characterized by the cessation of ovarian activity. Sequential changes during this transition affect multiple systems, including the brain. Sixty percent of women experience cognitive impairment. The objective of this review is to show the neuroprotective effect of hormone replacement therapy (HRT) through the different scales and whether there is a benefit of this in women.

METHOD

A search was conducted in six databases. Eligibility criteria included women within 10 years of menopause, receiving HRT controlled with placebo, studies lasting more than 6 months and women without a history of chronic underlying pathology.

RESULTS

A total of nine randomized controlled trials met the inclusion criteria. Regarding memory, two studies reported better performance of HRT with a significant odds ratio (OR) of 0.67; regarding attention, one study reported potential improvement in women receiving HRT with a significant OR of 0.87; and neuroimaging assessment found an increase in ventricular volume compared to placebo over a 3-year period.

CONCLUSIONS

The early initiation of menopausal HRT in healthy women appears to yield a positive effect on certain cognitive aspects, such as attention and cortical volume in the central nervous system. These findings should be confirmed through future prospective studies.

The role of estrogen in Alzheimer's disease pathogenesis and therapeutic potential in women

Estrogens are pivotal regulators of brain function throughout the lifespan, exerting profound effects from early embryonic development to aging. Extensive experimental evidence underscores the multifaceted protective roles of estrogens on neurons and neurotransmitter systems, particularly in the context of Alzheimer's disease (AD) pathogenesis. Studies have consistently revealed a greater risk of AD development in women compared to men, with postmenopausal women exhibiting heightened susceptibility. This connection between sex factors and long-term estrogen deprivation highlights the significance of estrogen signaling in AD progression. Estrogen's influence extends to key processes implicated in AD, including amyloid precursor protein (APP) processing and neuronal health maintenance mediated by brain-derived neurotrophic factor (BDNF). Reduced BDNF expression, often observed in AD, underscores estrogen's role in preserving neuronal integrity. Notably, hormone replacement therapy (HRT) has emerged as a sex-specific and time-dependent strategy for primary cardiovascular disease (CVD) prevention, offering an excellent risk profile against aging-related disorders like AD. Evidence suggests that HRT may mitigate AD onset and progression in postmenopausal women, further emphasizing the importance of estrogen signaling in AD pathophysiology. This review comprehensively examines the physiological and pathological changes associated with estrogen in AD, elucidating the therapeutic potential of estrogen-based interventions such as HRT. By synthesizing current knowledge, it aims to provide insights into the intricate interplay between estrogen signaling and AD pathogenesis, thereby informing future research directions and therapeutic strategies for this debilitating neurodegenerative disorder.

The Uncoupling Effect of 17β-Estradiol Underlies the Resilience of Female-Derived Mitochondria to Damage after Experimental TBI

Current literature finds females have improved outcomes over their male counterparts after severe traumatic brain injury (TBI), while the opposite seems to be true for mild TBI. This begs the question as to what may be driving these sex differences after TBI. Estrogen is thought to be neuroprotective in certain diseases, and its actions have been shown to influence mitochondrial function. Mitochondrial impairment is a major hallmark of TBI, and interestingly, this dysfunction has been shown to be more severe in males than females after brain injury. This suggests estrogen could be playing a role in promoting "mitoprotection" following TBI. Despite the existence of estrogen receptors in mitochondria, few studies have examined the direct role of estrogen on mitochondrial function, and no studies have explored this after TBI. We hypothesized ex vivo treatment of isolated mitochondria with 17β-estradiol (E2) would improve mitochondrial function after experimental TBI in mice. Total mitochondria from the ipsilateral (injured) and contralateral (control) cortices of male and female mice were isolated 24 h post-controlled severe cortical impact (CCI) and treated with vehicle, 2 nM E2, or 20 nM E2 immediately before measuring reactive oxygen species (ROS) production, bioenergetics, electron transport chain complex (ETC) activities, and β-oxidation of palmitoyl carnitine. Protein expression of oxidative phosphorylation (OXPHOS) complexes was also measured in these mitochondrial samples to determine whether this influenced functional outcomes with respect to sex or injury. While mitochondrial ROS production was affected by CCI in both sexes, there were other sex-specific patterns of mitochondrial injury 24 h following severe CCI. For instance, mitochondria from males were more susceptible to CCI-induced injury with respect to bioenergetics and ETC complex activities, whereas mitochondria from females showed only Complex II impairment and reduced β-oxidation after injury. Neither concentration of E2 influenced ETC complex activities themselves, but 20 nM E2 appeared to uncouple mitochondria isolated from the contralateral cortex in both sexes, as well as the injured ipsilateral cortex of females. These studies highlight the significance of measuring mitochondrial dysfunction in both sexes after TBI and also shed light on another potential neuroprotective mechanism in which E2 may attenuate mitochondrial dysfunction after TBI in vivo.

From Young to Old: Mimicking Neuronal Aging in Directly Converted Neurons from Young Donors

A substantial challenge in human brain aging is to find a suitable model to mimic neuronal aging in vitro as accurately as possible. Using directly converted neurons (iNs) from human fibroblasts is considered a promising tool in human aging since it retains the aging-associated mitochondrial donor signature. Still, using iNs from aged donors can pose certain restrictions due to their lower reprogramming and conversion efficacy than those from younger individuals. To overcome these limitations, our study aimed to establish an in vitro neuronal aging model mirroring features of in vivo aging by acute exposure on young iNs to either human stress hormone cortisol or the mitochondrial stressor rotenone, considering stress as a trigger of in vivo aging. The impact of rotenone was evident in mitochondrial bioenergetic properties by showing aging-associated deficits in mitochondrial respiration, cellular ATP, and MMP and a rise in glycolysis, mitochondrial superoxide, and mitochondrial ROS; meanwhile, cortisol only partially induced an aging-associated mitochondrial dysfunction. To replicate the in vivo aging-associated mitochondrial dysfunctions, using rotenone, a mitochondrial complex I inhibitor, proved to be superior to the cortisol model. This work is the first to use stress on young iNs to recreate aging-related mitochondrial impairments.

In vivo brain estrogen receptor density by neuroendocrine aging and relationships with cognition and symptomatology

17β-estradiol, the most biologically active estrogen, exerts wide-ranging effects in brain through its action on estrogen receptors (ERs), influencing higher-order cognitive function and neurobiological aging. However, our knowledge of ER expression and regulation by neuroendocrine aging in the living human brain is limited. This in vivo brain 18F-fluoroestradiol (18F-FES) Positron Emission Tomography (PET) study of healthy midlife women reveals progressively higher ER density over the menopause transition in estrogen-regulated networks. Effects were independent of age, plasma estradiol and sex hormone binding globulin, and were highly consistent, correctly classifying all women as being postmenopausal or premenopausal. Higher ER density in target regions was associated with poorer memory performance for both postmenopausal and perimenopausal groups, and predicted presence of self-reported mood and cognitive symptoms after menopause. These findings provide novel insights on brain ER density modulation by female neuroendocrine aging, with clinical implications for women's health.

Alzheimer's disease as a women's health challenge: a call for action on integrative precision medicine approaches

Alzheimer's Disease (AD) is marked by pronounced sex differences in pathophysiology and progression. However, the field has yet to fully recognize AD as a women's health issue, delaying the development of targeted preventative strategies and treatments. This perspective explores the elements impacting AD in women, identifying sex specificity in risk factors, highlighting new diagnostic approaches with electronic health records, and reviewing key molecular studies to underscore the need for integrative precision medicine approaches. Established AD risk factors such as advancing age, the apolipoprotein E4 allele, and poorer cardiovascular health affect women differently. We also shed light on sociocultural risk factors, focusing on the gender disparities that may play a role in AD development. From a biological perspective, sex differences in AD are apparent in biomarkers and transcriptomics, further emphasizing the need for targeted diagnostics and treatments. The convergence of novel multiomics data and cutting-edge computational tools provides a unique opportunity to study the molecular underpinnings behind sex dimorphism in AD. Thus, precision medicine emerges as a promising framework for understanding AD pathogenesis through the integration of genetics, sex, environment, and lifestyle. By characterizing AD as a women's health challenge, we can catalyze a transformative shift in AD research and care, marked by improved diagnostic accuracy, targeted interventions, and ultimately, enhanced clinical outcomes.

Menopausal hormone therapy and the female brain: leveraging neuroimaging and prescription registry data from the UK Biobank cohort

Background and Objectives

Menopausal hormone therapy (MHT) is generally thought to be neuroprotective, yet results have been inconsistent. Here, we present a comprehensive study of MHT use and brain characteristics in middle- to older aged females from the UK Biobank, assessing detailed MHT data, APOE ε4 genotype, and tissue-specific gray (GM) and white matter (WM) brain age gap (BAG), as well as hippocampal and white matter hyperintensity (WMH) volumes.

Methods

A total of 19,846 females with magnetic resonance imaging data were included (current-users = 1,153, 60.1 ± 6.8 years; past-users = 6,681, 67.5 ± 6.2 years; never-users = 12,012, mean age 61.6 ± 7.1 years). For a sub-sample (n = 538), MHT prescription data was extracted from primary care records. Brain measures were derived from T1-, T2- and diffusion-weighted images. We fitted regression models to test for associations between the brain measures and MHT variables including user status, age at initiation, dosage and duration, formulation, route of administration, and type (i.e., bioidentical vs synthetic), as well as active ingredient (e.g., estradiol hemihydrate). We further tested for differences in brain measures among MHT users with and without a history of hysterectomy ± bilateral oophorectomy and examined associations by APOE ε4 status.

Results

We found significantly higher GM and WM BAG (i.e., older brain age relative to chronological age) as well as smaller left and right hippocampus volumes in current MHT users, not past users, compared to never-users. Effects were modest, with the largest effect size indicating a group difference of 0.77 years (~9 months) for GM BAG. Among MHT users, we found no significant associations between age at MHT initiation and brain measures. Longer duration of use and older age at last use post menopause was associated with higher GM and WM BAG, larger WMH volume, and smaller left and right hippocampal volumes. MHT users with a history of hysterectomy ± bilateral oophorectomy showed lower GM BAG relative to MHT users without such history. Although we found smaller hippocampus volumes in carriers of two APOE ε4 alleles compared to non-carriers, we found no interactions with MHT variables. In the sub-sample with prescription data, we found no significant associations between detailed MHT variables and brain measures after adjusting for multiple comparisons.

Discussion

Our results indicate that population-level associations between MHT use, and female brain health might vary depending on duration of use and past surgical history. Future research is crucial to establish causality, dissect interactions between menopause-related neurological changes and MHT use, and determine individual-level implications to advance precision medicine in female health care.

Systematic review and meta-analysis of the effects of menopause hormone therapy on cognition

Introduction

Despite evidence from preclinical studies suggesting estrogen's neuroprotective effects, the use of menopausal hormone therapy (MHT) to support cognitive function remains controversial.

Methods

We used random-effect meta-analysis and multi-level meta-regression to derive pooled standardized mean difference (SMD) and 95% confidence intervals (C.I.) from 34 randomized controlled trials, including 14,914 treated and 12,679 placebo participants.

Results

Associations between MHT and cognitive function in some domains and tests of interest varied by formulation and treatment timing. While MHT had no overall effects on cognitive domain scores, treatment for surgical menopause, mostly estrogen-only therapy, improved global cognition (SMD=1.575, 95% CI 0.228, 2.921; P=0.043) compared to placebo. When initiated specifically in midlife or close to menopause onset, estrogen therapy was associated with improved verbal memory (SMD=0.394, 95% CI 0.014, 0.774; P=0.046), while late-life initiation had no effects. Overall, estrogen-progestogen therapy for spontaneous menopause was associated with a decline in Mini Mental State Exam (MMSE) scores as compared to placebo, with most studies administering treatment in a late-life population (SMD=-1.853, 95% CI -2.974, -0.733; P = 0.030). In analysis of timing of initiation, estrogen-progestogen therapy had no significant effects in midlife but was associated with improved verbal memory in late-life (P = 0.049). Duration of treatment >1 year was associated with worsening in visual memory as compared to shorter duration. Analysis of individual cognitive tests yielded more variable results of positive and negative effects associated with MHT.

Discussion

These findings suggest time-dependent effects of MHT on certain aspects of cognition, with variations based on formulation and timing of initiation, underscoring the need for further research with larger samples and more homogeneous study designs.

Investigating the synergistic effects of hormone replacement therapy, apolipoprotein E and age on brain health in the UK Biobank

Global prevalence of Alzheimer's Disease has a strong sex bias, with women representing approximately two-thirds of the patients. Yet, the role of sex-specific risk factors during midlife, including hormone replacement therapy (HRT) and their interaction with other major risk factors for Alzheimer's Disease, such as apolipoprotein E (APOE)-e4 genotype and age, on brain health remains unclear. We investigated the relationship between HRT (i.e., use, age of initiation and duration of use) and brain health (i.e., cognition and regional brain volumes). We then consider the multiplicative effects of HRT and APOE status (i.e., e2/e2, e2/e3, e3/e3, e3/e4 and e4/e4) via a two-way interaction and subsequently age of participants via a three-way interaction. Women from the UK Biobank with no self-reported neurological conditions were included (N = 207,595 women, mean age = 56.25 years, standard deviation = 8.01 years). Generalised linear regression models were computed to quantify the cross-sectional association between HRT and brain health, while controlling for APOE status, age, time since attending centre for completing brain health measure, surgical menopause status, smoking history, body mass index, education, physical activity, alcohol use, ethnicity, socioeconomic status, vascular/heart problems and diabetes diagnosed by doctor. Analyses of structural brain regions further controlled for scanner site. All brain volumes were normalised for head size. Two-way interactions between HRT and APOE status were modelled, in addition to three-way interactions including age. Results showed that women with the e4/e4 genotype who have used HRT had 1.82% lower hippocampal, 2.4% lower parahippocampal and 1.24% lower thalamus volumes than those with the e3/e3 genotype who had never used HRT. However, this interaction was not detected for measures of cognition. No clinically meaningful three-way interaction between APOE, HRT and age was detected when interpreted relative to the scales of the cognitive measures used and normative models of ageing for brain volumes in this sample. Differences in hippocampal volume between women with the e4/e4 genotype who have used HRT and those with the e3/e3 genotype who had never used HRT are equivalent to approximately 1-2 years of hippocampal atrophy observed in typical health ageing trajectories in midlife (i.e., 0.98%-1.41% per year). Effect sizes were consistent within APOE e4/e4 group post hoc sensitivity analyses, suggesting observed effects were not solely driven by APOE status and may, in part, be attributed to HRT use. Although, the design of this study means we cannot exclude the possibility that women who have used HRT may have a predisposition for poorer brain health.

Cognitive-exercise dual-task promotes cognitive function recovery in chronic cerebral ischemia male rats through regulating PI3K/Akt signaling pathway via inhibition of EphrinA3/EphA4

Chronic cerebral ischemia (CCI) can lead to vascular cognitive impairment, but therapeutic options are limited. Cognitive-exercise dual-task (CEDT), as a potential rehabilitation intervention, can attenuate cognitive impairment. However, the related mechanisms remain unclear. In this study, 2-vessel occlusion (2-VO) in male SD rats was performed to establish the CCI model. The rats were treated with cognitive, exercise, or CEDT intervention for 21 days. The Morris water maze (MWM) test was used to assess cognitive ability. TUNEL staining was used to detect the neuronal apoptosis. Immunofluorescence, RT-qPCR and Western blot were used to detect the protein or mRNA levels of EphrinA3, EphA4, p-PI3K, and p-Akt. The results showed that CEDT could improve performance in the MWM test, reverse the increased expression of EphrinA3 and EphA4, and the reduced expression of p-PI3K and p-Akt in CCI rats, which was superior to exercise and cognitive interventions. In vitro, oxygenglucose deprivation (OGD) challenge of astrocytes and neuronal cells were used to mimic cerebral ischemia. Immunofluorescence assay revealed that the levels of MAP-2, p-PI3K, and p-Akt were reduced in EphrinA3 overexpressed cells after OGD stimulation. Finally, the knock-down of EphrinA3 by shRNA significantly promoted the recovery of cognitive function and activation of PI3K/Akt after CEDT treatment in CCI rats. In conclusion, our study suggests that CEDT promotes cognitive function recovery after CCI by regulating the signaling axis of EphrinA3/EphA4/PI3K/Akt.

Mitochondrial might: powering the peripartum for risk and resilience

The peripartum period, characterized by dynamic hormonal shifts and physiological adaptations, has been recognized as a potentially vulnerable period for the development of mood disorders such as postpartum depression (PPD). Stress is a well-established risk factor for developing PPD and is known to modulate mitochondrial function. While primarily known for their role in energy production, mitochondria also influence processes such as stress regulation, steroid hormone synthesis, glucocorticoid response, GABA metabolism, and immune modulation - all of which are crucial for healthy pregnancy and relevant to PPD pathology. While mitochondrial function has been implicated in other psychiatric illnesses, its role in peripartum stress and mental health remains largely unexplored, especially in relation to the brain. In this review, we first provide an overview of mitochondrial involvement in processes implicated in peripartum mood disorders, underscoring their potential role in mediating pathology. We then discuss clinical and preclinical studies of mitochondria in the context of peripartum stress and mental health, emphasizing the need for better understanding of this relationship. Finally, we propose mitochondria as biological mediators of resilience to peripartum mood disorders.

Estradiol and 3β-diol protect female cortical astrocytes by regulating connexin 43 Gap Junctions

While estrogens have been described to protect or preserve neuronal function in the face of insults such as oxidative stress, the prevailing mechanistic model would suggest that these steroids exert direct effects on the neurons. However, there is growing evidence that glial cells, such as astrocytes, are key cellular mediators of protection. Noting that connexin 43 (Cx43), a protein highly expressed in astrocytes, plays a key role in mediating inter-cellular communication, we hypothesized that Cx43 is a target of estradiol (E2), and the estrogenic metabolite of DHT, 3β-diol. Additionally, we sought to determine if either or both of these hormones attenuate oxidative stress-induced cytotoxicity by eliciting a reduction in Cx43 expression or inhibition of Cx43 channel permeability. Using primary cortical astrocytes, we found that E2 and 3β-diol were each protective against the mixed metabolic/oxidative insult, iodoacetic acid (IAA). Moreover, these effects were blocked by estrogen receptor antagonists. However, E2 and 3β-diol did not alter Cx43 mRNA levels in astrocytes but did inhibit IAA-induced Cx43 gap junction opening/permeability. Taken together, these data implicate astrocyte Cx43 gap junction as an understudied mediator of the cytoprotective effects of estrogens in the brain. Given the wide breadth of disease states associated with Cx43 function/dysfunction, further understanding the relationship between gonadal steroids and Cx43 channels may contribute to a better understanding of the biological basis for sex differences in various diseases.

The role of genetics and gender specific differences in neurodegenerative disorders: Insights from molecular and immune landscape

Neurodegenerative disorders (NDDs) are the most common neurological disorders with high prevalence and have significant socioeconomic implications. Understanding the underlying cellular and molecular mechanisms associated with the immune system can be effective in disease etiology, leading to more effective therapeutic approaches for both females and males. The central nervous system (CNS) actively participates in immune responses, both within and outside the CNS. Immune system activation is a common feature in NDDs. Gender-specific factors play a significant role in the prevalence, progression, and manifestation of NDDs. Neuroinflammation, in both inflammatory neurological and neurodegenerative conditions, is defined by the triggering of microglia and astrocyte cell activation. This results in the secretion of pro-inflammatory cytokines and chemokines. Numerous studies have documented the role of neuroinflammation in neurological diseases, highlighting the involvement of immune signaling pathways in disease development. Converging evidence support immune system involvement during neurodegeneration in NDDs. In this review, we summarize emerging evidence that reveals gender-dependent differences in immune responses related to NDDs. Also, we highlight sex differences in immune responses and discuss how these sex-specific influences can increase the risk of NDDs. Understanding the role of gender-specific factors can aid in developing targeted therapeutic strategies and improving patient outcomes. Ultimately, the better understanding of these mechanisms contributed to sex-dependent immune response in NDDs, can be critically usful in targeting of immune signaling cascades in such disorders. In this regard, sex-related immune responses in NDDs may be promising and effective targets in therapeutic strategies.

Systematic review and meta-analysis of the effects of menopause hormone therapy on risk of Alzheimer's disease and dementia

Introduction

Despite a large preclinical literature demonstrating neuroprotective effects of estrogen, use of menopausal hormone therapy (HT) for Alzheimer's disease (AD) risk reduction has been controversial. Herein, we conducted a systematic review and meta-analysis of HT effects on AD and dementia risk.

Methods

Our systematic search yielded 6 RCT reports (21,065 treated and 20,997 placebo participants) and 45 observational reports (768,866 patient cases and 5.5 million controls). We used fixed and random effect meta-analysis to derive pooled relative risk (RR) and 95% confidence intervals (C.I.) from these studies.

Results

Randomized controlled trials conducted in postmenopausal women ages 65 and older show an increased risk of dementia with HT use compared with placebo [RR = 1.38, 95% C.I. 1.16-1.64, p < 0.001], driven by estrogen-plus-progestogen therapy (EPT) [RR = 1.64, 95% C.I. 1.20-2.25, p = 0.002] and no significant effects of estrogen-only therapy (ET) [RR = 1.19, 95% C.I. 0.92-1.54, p = 0.18]. Conversely, observational studies indicate a reduced risk of AD [RR = 0.78, 95% C.I. 0.64-0.95, p = 0.013] and all-cause dementia [RR = .81, 95% C.I. 0.70-0.94, p = 0.007] with HT use, with protective effects noted with ET [RR = 0.86, 95% C.I. 0.77-0.95, p = 0.002] but not with EPT [RR = 0.910, 95% C.I. 0.775-1.069, p = 0.251]. Stratified analysis of pooled estimates indicates a 32% reduced risk of dementia with midlife ET [RR = 0.685, 95% C.I. 0.513-0.915, p = 0.010] and non-significant reductions with midlife EPT [RR = 0.775, 95% C.I. 0.474-1.266, p = 0.309]. Late-life HT use was associated with increased risk, albeit not significant [EPT: RR = 1.323, 95% C.I. 0.979-1.789, p = 0.069; ET: RR = 1.066, 95% C.I. 0.996-1.140, p = 0.066].

Discussion

These findings support renewed research interest in evaluating midlife estrogen therapy for AD risk reduction.

Gestational stress decreases postpartum mitochondrial respiration in the prefrontal cortex of female rats

Postpartum depression (PPD) is a major psychiatric complication of childbirth, affecting up to 20% of mothers, yet remains understudied. Mitochondria, dynamic organelles crucial for cell homeostasis and energy production, share links with many of the proposed mechanisms underlying PPD pathology. Brain mitochondrial function is affected by stress, a major risk factor for development of PPD, and is linked to anxiety-like and social behaviors. Considering the importance of mitochondria in regulating brain function and behavior, we hypothesized that mitochondrial dysfunction is associated with behavioral alterations in a chronic stress-induced rat model of PPD. Using a validated and translationally relevant chronic mild unpredictable stress paradigm during late gestation, we induced PPD-relevant behaviors in adult postpartum Wistar rats. In the mid-postpartum, we measured mitochondrial function in the prefrontal cortex (PFC) and nucleus accumbens (NAc) using high-resolution respirometry. We then measured protein expression of mitochondrial complex proteins and 4-hydroxynonenal (a marker of oxidative stress), and Th1/Th2 cytokine levels in PFC and plasma. We report novel findings that gestational stress decreased mitochondrial function in the PFC, but not the NAc of postpartum dams. However, in groups controlling for the effects of either stress or parity alone, no differences in mitochondrial respiration measured in either brain regions were observed compared to nulliparous controls. This decrease in PFC mitochondrial function in stressed dams was accompanied by negative behavioral consequences in the postpartum, complex-I specific deficits in protein expression, and increased Tumor Necrosis Factor alpha cytokine levels in plasma and PFC. Overall, we report an association between PFC mitochondrial respiration, PPD-relevant behaviors, and inflammation following gestational stress, highlighting a potential role for mitochondrial function in postpartum health.

Menopausal transition in multiple sclerosis: relationship with disease activity and brain volume measurements

Background

Recent evidence has shown a significant association between menopause and multiple sclerosis (MS) progression. This study investigated the possible role of menopause in influencing MS from clinical and neuroradiological perspectives. Notably, the possible association between menopause and brain atrophy has been evaluated.

Materials and methods

This study included women with MS whose ages ranged from 45 to 55 years. Demographic and clinical characteristics were collected, and the reproductive phase was defined as non-menopausal or menopausal based on the final menstrual period. Thus, MS activity over the past year was reported as the annualised relapse rate (ARR), and MRI activity (defined as new T2 lesions and/or the presence of gadolinium-enhancing lesions at the last MRI assessment in comparison with the MRI performed within the previous 12 months) were compared between non-menopausal women (non-MW) and menopausal women (MW). Volume measurements of the whole brain (WB), white matter (WM), grey matter (GM), and cortical GM were estimated using the SIENAX software, and the possible relationship with menopausal status was assessed by regression analysis.

Results

The study included 147 women with MS. Eighty-four (57.1%) were MW, with a mean age of 48.5 ± 4.3 years at menopause onset and a mean duration of menopause of 4.1 ± 1.1 years. When compared for ARR, MW reported a lower rate than the non-MW (ARR of 0.29 ± 0.4 vs. 0.52 ± 0.5; p < 0.01). MRI activity was observed in 13.1% of MW and 20.6% of non-MW (p = 0.03). Lower cortical GM volumes (578.1 ± 40.4 mL in MW vs. 596.9 ± 35.8 mL in non-MW; p < 0.01) have also been reported. Finally, multivariate analysis showed a significant association of lower ARR (p = 0.001) and cortical GM volume (p = 0.002) with menopausal status after correction for chronological age and other variables.

Discussion

Menopause may be an adverse prognostic factor of MS. Our preliminary results suggest that menopause may facilitate cortical GM atrophy, probably due to a decline in the neuroprotective effects of estrogen, with negative effects on MS evolution.

Sex-specific actions of estradiol and testosterone on human fibroblast and endothelial cell proliferation, bioenergetics, and vasculogenesis

Progress toward the development of sex-specific tissue engineered systems has been hampered by the lack of research efforts to define the effects of sex-specific hormone concentrations on relevant human cell types. Here, we investigated the effects of defined concentrations of estradiol (E2) and dihydrotestosterone (DHT) on primary human dermal and lung fibroblasts (HDF and HLF), and human umbilical vein endothelial cells (HUVEC) from female (XX) and male (XY) donors in both 2D expansion cultures and 3D stromal vascular tissues. Sex-matched E2 and DHT stimulation in 2D expansion cultures significantly increased the proliferation index, mitochondrial membrane potential, and the expression of genes associated with bioenergetics (Na+/K+ ATPase, somatic cytochrome C) and beneficial stress responses (chaperonin) in all cell types tested. Notably, cross sex hormone stimulation, i.e., DHT treatment of XX cells in the absence of E2 and E2 stimulation of XY cells in the absence of DHT, decreased bioenergetic capacity and inhibited cell proliferation. We used a microengineered 3D vasculogenesis assay to assess hormone effects on tissue scale morphogenesis. E2 increased metrics of vascular network complexity compared to vehicle in XX tissues. Conversely, and in line with results from 2D expansion cultures, E2 potently inhibited vasculogenesis compared to vehicle in XY tissues. DHT did not significantly alter vasculogenesis in XX or XY tissues but increased the number of non-participating endothelial cells in both sexes. This study establishes a scientific rationale and adaptable methods for using sex hormone stimulation to develop sex-specific culture systems.

Cardiometabolic health, menopausal estrogen therapy and the brain: How effects of estrogens diverge in healthy and unhealthy preclinical models of aging

Research in preclinical models indicates that estrogens are neuroprotective and positively impact cognitive aging. However, clinical data are equivocal as to the benefits of menopausal estrogen therapy to the brain and cognition. Pre-existing cardiometabolic disease may modulate mechanisms by which estrogens act, potentially reducing or reversing protections they provide against cognitive decline. In the current review we propose mechanisms by which cardiometabolic disease may alter estrogen effects, including both alterations in actions directly on brain memory systems and actions on cardiometabolic systems, which in turn impact brain memory systems. Consideration of mechanisms by which estrogen administration can exert differential effects dependent upon health phenotype is consistent with the move towards precision or personalized medicine, which aims to determine which treatment interventions will work for which individuals. Understanding effects of estrogens in both healthy and unhealthy models of aging is critical to optimizing the translational link between preclinical and clinical research.

Beyond sex differences: short- and long-term effects of pregnancy on the brain

Growing attention has been directed to the inclusion of females in neuroscience studies, and to the importance of studying sex as a biological variable. However, how female-specific factors such as menopause and pregnancy, affect the brain remains understudied. In this review, we use pregnancy as a case in point of a female-unique experience that can alter neuroplasticity, neuroinflammation, and cognition. We examine studies in both humans and rodents indicating that pregnancy can modify neural function in the short term, as well as alter the trajectory of brain aging. Furthermore, we discuss the influence of maternal age, fetal sex, number of pregnancies, and presence of pregnancy complications on brain health outcomes. We conclude by encouraging the scientific community to prioritize researching female health by recognizing and including factors such as pregnancy history in research.

The Role of Diet as a Modulator of the Inflammatory Process in the Neurological Diseases

Neurological diseases are recognized as major causes of disability and mortality worldwide. Due to the dynamic progress of diseases such as Alzheimer’s disease (AD), Parkinson’s Disease (PD), Schizophrenia, Depression, and Multiple Sclerosis (MD), scientists are mobilized to look for new and more effective methods of interventions. A growing body of evidence suggests that inflammatory processes and an imbalance in the composition and function of the gut microbiome, which play a critical role in the pathogenesis of various neurological diseases and dietary interventions, such as the Mediterranean diet the DASH diet, or the ketogenic diet can have beneficial effects on their course. The aim of this review was to take a closer look at the role of diet and its ingredients in modulating inflammation associated with the development and/or progression of central nervous system diseases. Presented data shows that consuming a diet abundant in fruits, vegetables, nuts, herbs, spices, and legumes that are sources of anti-inflammatory elements such as omega-3 fatty acids, polyphenols, vitamins, essential minerals, and probiotics while avoiding foods that promote inflammation, create a positive brain environment and is associated with a reduced risk of neurological diseases. Personalized nutritional interventions may constitute a non-invasive and effective strategy in combating neurological disorders.

In vivo Brain Estrogen Receptor Expression By Neuroendocrine Aging And Relationships With Gray Matter Volume, Bio-Energetics, and Clinical Symptomatology

17β-estradiol,the most biologically active estrogen, exerts wide-ranging effects in brain through its action on estrogen receptors (ERs), influencing higher-order cognitive function and neurobiological aging. However, our knowledge of ER expression and regulation by neuroendocrine aging in the living human brain is limited. This in vivo multi-modality neuroimaging study of healthy midlife women reveals progressively higher ER density over the menopause transition in estrogen-regulated networks. Effects were independent of age and plasma estradiol levels, and were highly consistent, correctly classifying all women as being post-menopausal or not. Higher ER density was generally associated with lower gray matter volume and blood flow, and with higher mitochondria ATP production, possibly reflecting compensatory mechanisms. Additionally, ER density predicted changes in thermoregulation, mood, cognition, and libido. Our data provide evidence that ER density impacts brainstructure, perfusion and energy production during female endocrine aging, with clinical implications for women's health.

Is Hormone Replacement Therapy a Risk Factor or a Therapeutic Option for Alzheimer's Disease?

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that accounts for more than half of all dementia cases in the elderly. Interestingly, the clinical manifestations of AD disproportionately affect women, comprising two thirds of all AD cases. Although the underlying mechanisms for these sex differences are not fully elucidated, evidence suggests a link between menopause and a higher risk of developing AD, highlighting the critical role of decreased estrogen levels in AD pathogenesis. The focus of this review is to evaluate clinical and observational studies in women, which have investigated the impact of estrogens on cognition or attempted to answer the prevailing question regarding the use of hormone replacement therapy (HRT) as a preventive or therapeutic option for AD. The articles were retrieved through a systematic review of the databases: OVID, SCOPUS, and PubMed (keywords "memory", "dementia," "cognition," "Alzheimer's disease", "estrogen", "estradiol", "hormone therapy" and "hormone replacement therapy" and by searching reference sections from identified studies and review articles). This review presents the relevant literature available on the topic and discusses the mechanisms, effects, and hypotheses that contribute to the conflicting findings of HRT in the prevention and treatment of age-related cognitive deficits and AD. The literature suggests that estrogens have a clear role in modulating dementia risk, with reliable evidence showing that HRT can have both a beneficial and a deleterious effect. Importantly, recommendation for the use of HRT should consider the age of initiation and baseline characteristics, such as genotype and cardiovascular health, as well as the dosage, formulation, and duration of treatment until the risk factors that modulate the effects of HRT can be more thoroughly investigated or progress in the development of alternative treatments can be made.

Role of estrogen in women's Alzheimer's disease risk as modified by APOE

Alzheimer's disease (AD) is characterized by numerous sexual dimorphisms that impact the development, progression, and probably the strategies to prevent and treat the most common form of dementia. In this review, we consider this topic from a female perspective with a specific focus on how women's vulnerability to the disease is affected by the individual and interactive effects of estrogens and apolipoprotein E (APOE) genotype. Importantly, APOE appears to modulate systemic and neural outcomes of both menopause and estrogen-based hormone therapy. In the brain, dementia risk is greater in APOE4 carriers, and the impacts of hormone therapy on cognitive decline and dementia risk vary according to both outcome measure and APOE genotype. Beyond the CNS, estrogen and APOE genotype affect vulnerability to menopause-associated bone loss, dyslipidemia and cardiovascular disease risk. An emerging concept that may link these relationships is the possibility that the effects of APOE in women interact with estrogen status by mechanisms that may include modulation of estrogen responsiveness. This review highlights the need to consider the key AD risk factors of advancing age in a sex-specific manner to optimize development of therapeutic approaches for AD, a view aligned with the principle of personalized medicine.

Sex and menopause impact 31P-Magnetic Resonance Spectroscopy brain mitochondrial function in association with 11C-PiB PET amyloid-beta load

Increasing evidence implicates sex and endocrine aging effects on brain bioenergetic aging in the greater lifetime risk of Alzheimer's disease (AD) in women. We conducted 31Phosphorus Magnetic Resonance Spectroscopy (31P-MRS) to assess the impact of sex and menopause on brain high-energy phosphates [adenosine triphosphate (ATP), phosphocreatine (PCr), inorganic phosphate (Pi)] and membrane phospholipids [phosphomonoesters/phosphodiesters (PME/PDE)] in 216 midlife cognitively normal individuals at risk for AD, 80% female. Ninety-seven participants completed amyloid-beta (Aβ) 11C-PiB PET. Women exhibited higher ATP utilization than men in AD-vulnerable frontal, posterior cingulate, fusiform, medial and lateral temporal regions (p < 0.001). This profile was evident in frontal cortex at the pre-menopausal and peri-menopausal stage and extended to the other regions at the post-menopausal stage (p = 0.001). Results were significant after multi-variable adjustment for age, APOE-4 status, midlife health indicators, history of hysterectomy/oophorectomy, use of menopause hormonal therapy, and total intracranial volume. While associations between ATP/PCr and Aβ load were not significant, individuals with the highest Aβ load were post-menopausal and peri-menopausal women with ATP/PCr ratios in the higher end of the distribution. No differences in Pi/PCr, Pi/ATP or PME/PDE were detected. Outcomes are consistent with dynamic bioenergetic brain adaptations that are associated with female sex and endocrine aging.

The association of reproductive stage with lobular cerebellar network connectivity across female adulthood

Sex-specific differences in the aging cerebellum may be related to hormone changes with menopause. We evaluated the association between reproductive stage and lobular cerebellar network connectivity using data from the Cambridge Centre for Ageing and Neuroscience repository. We used raw structural and resting state neuroimaging data and information regarding age, sex, and menopause-related variables. Crus I and II and Lobules V and VI were our cerebellar seeds of interest. We characterized reproductive stage using the Stages of Reproductive Aging Workshop criteria. Results show that postmenopausal females have lower cerebello-striatal and cerebello-cortical connectivity, particularly in frontal regions, along with lower connectivity within the cerebellum, compared to reproductive females. Postmenopausal females also exhibit greater connectivity in some brain areas as well. Differences begin to emerge across transitional stages of menopause. Further, results reveal sex-specific differences in connectivity between female reproductive groups and age-matched male control groups. This suggests that menopause may be associated with cerebellar network connectivity in aging females, and sex differences in the aging brain may be related to this biological process.

Estrogen deficiency exacerbates learning and memory deficits associated with glucose metabolism disorder in APP/PS1 double transgenic female mice

Alterations in glucose metabolism occur in the brain in the early stage of Alzheimer's disease (AD), and menopausal women have more severe metabolic dysfunction and are more prone to dementia than men. Although estrogen deficiency-induced changes in glucose metabolism have been previously studied in animal models, their molecular mechanisms in AD remain elusive. To investigate this issue, double transgenic (APP/PS1) female mice were subjected to bilateral ovariectomy at 3 months of age and were sacrificed 1 week, 1 month and 3 months after surgery to simulate early, middle and late postmenopause, respectively. Our analysis demonstrated that estrogen deficiency exacerbates learning and memory deficits in this mouse model of postmenopause. Estrogen deficiency impairs the function of mitochondria in glucose metabolism. It is possible that the occurrence of AD is associated with the aberrant mitochondrial ERβ-mediated IGF-1/IGF-1R/GSK-3β signaling pathway. In this study, we established a potential mechanism for the increased risk of AD in postmenopausal women and proposed a therapeutic target for AD due to postmenopause.

Estradiol treatment in young postmenopausal women with self-reported cognitive complaints: Effects on cholinergic-mediated cognitive performance

OBJECTIVE

Older women are at increased risk of developing Alzheimer's disease compared to men. One proposed reason is that following menopause there is a decline in estrogens. Estrogens are important for cholinergic functioning and attenuate the impact of cholinergic antagonists on cognitive performance in postmenopausal women. Self-reported or subjective cognitive complaints in middle or older age may represent a harbinger of cognitive decline and those who endorse cognitive complaints appear more likely to develop future cognitive impairment. However, the response of individuals with cognitive complaints after menopause to estrogen and the relationship to cholinergic functioning has not been investigated. This study investigated the effect of estrogen treatment using 17β-estradiol on cognitive performance following anticholinergic blockade in postmenopausal women and the relationship of this interaction with the level of self-reported (subjective) postmenopausal cognitive complaints.

METHODS

Forty postmenopausal women (aged 50-60 years) completed a 3-month treatment regimen of either 1 mg oral estradiol or placebo. Participants then completed four challenge days in which they completed cognitive and behavioral tasks after one of four cholinergic antagonist drug conditions (oral mecamylamine (MECA), intravenous scopolamine, combined MECA and scopolamine, or PLC).

RESULTS

Compared to PLC, the estradiol treated group performed worse on attention tasks under cholinergic challenge including the choice reaction time task and the critical flicker fusion task. In addition, participants who endorsed greater cognitive complaints showed reduced performance on the N-back working memory task, regardless of whether they received estradiol treatment.

CONCLUSIONS

The findings of this study indicate that estradiol treatment was unable to mitigate anticholinergic blockade in postmenopausal women with subjective cognitive complaints, and worsened performance on attention tasks. Moreover, the present study suggests that greater levels of cognitive complaints following menopause may be associated with an underlying decline in cholinergic function that may manifest as an inability to compensate during working memory tasks.

Ovarian steroid hormones: A long overlooked but critical contributor to brain aging and Alzheimer's disease

Ovarian hormones, particularly 17β-estradiol, are involved in numerous neurophysiological and neurochemical processes, including those subserving cognitive function. Estradiol plays a key role in the neurobiology of aging, in part due to extensive interconnectivity of the neural and endocrine system. This aspect of aging is fundamental for women's brains as all women experience a drop in circulating estradiol levels in midlife, after menopause. Given the importance of estradiol for brain function, it is not surprising that up to 80% of peri-menopausal and post-menopausal women report neurological symptoms including changes in thermoregulation (vasomotor symptoms), mood, sleep, and cognitive performance. Preclinical evidence for neuroprotective effects of 17β-estradiol also indicate associations between menopause, cognitive aging, and Alzheimer's disease (AD), the most common cause of dementia affecting nearly twice more women than men. Brain imaging studies demonstrated that middle-aged women exhibit increased indicators of AD endophenotype as compared to men of the same age, with onset in perimenopause. Herein, we take a translational approach to illustrate the contribution of ovarian hormones in maintaining cognition in women, with evidence implicating menopause-related declines in 17β-estradiol in cognitive aging and AD risk. We will review research focused on the role of endogenous and exogenous estrogen exposure as a key underlying mechanism to neuropathological aging in women, with a focus on whether brain structure, function and neurochemistry respond to hormone treatment. While still in development, this research area offers a new sex-based perspective on brain aging and risk of AD, while also highlighting an urgent need for better integration between neurology, psychiatry, and women's health practices.

Sex Hormones, Sleep, and Memory: Interrelationships Across the Adult Female Lifespan

As the population of older adults grows, so will the prevalence of aging-related conditions, including memory impairments and sleep disturbances, both of which are more common among women. Compared to older men, older women are up to twice as likely to experience sleep disturbances and are at a higher risk of cognitive decline and Alzheimer's disease and related dementias (ADRD). These sex differences may be attributed in part to fluctuations in levels of female sex hormones (i.e., estrogen and progesterone) that occur across the adult female lifespan. Though women tend to experience the most significant sleep and memory problems during the peri-menopausal period, changes in memory and sleep have also been observed across the menstrual cycle and during pregnancy. Here, we review current knowledge on the interrelationships among female sex hormones, sleep, and memory across the female lifespan, propose possible mediating and moderating mechanisms linking these variables and describe implications for ADRD risk in later life.

Biochanin A alleviates cognitive impairment and hippocampal mitochondrial damage in ovariectomized APP/PS1 mice

BACKGROUND

Estrogen deficiency leads to mitochondrial defects that precede Alzheimer's disease (AD)-associated pathological changes in a postmenopausal mouse model. Biochanin A (BCA) is a phytoestrogen isolated from Trifolium pratense L. used to relieve postmenopausal problems in women. In previous work, we observed that oral BCA treatment led to neuroprotection in an ovariectomized rat model. The objective of this study was to investigate whether and how BCA protects against hippocampal mitochondrial damage in a postmenopausal model of AD.

METHOD

APP/PS1 mice underwent bilateral ovariectomy and then, seven days later, received oral BCA at 20 or 40 mg/kg, or oral estradiol at 0.5 mg/kg, daily for 90 days. Sham animals were not ovariectomized and received no additional treatments. Cognitive function was examined using the passive avoidance task, novel object recognition test, and Morris water maze test. The level of circulating estrogen in vivo was assessed indirectly by measuring the wet weight of the uterus. We detected Aβ deposition and PGC-1α in brain by immunohistochemistry; p62, by immunofluorescence; and ERα, ERβ, PGC-1α, NRF1, mtTFA, Drp1, OPA1, Mfn2, Beclin1, LC3B, Pink1, and Parkin by immunoblotting.

RESULTS

BCA treatment rescued cognitive decline and reduced Aβ deposition and BACE1 expression in the hippocampus of ovariectomized APP/PS1 mice. BCA reversed the imbalance of mitochondrial dynamics caused by ovariectomy by increasing the expression of phospho-Drp1 (ser637), OPA1, and Mfn2. BCA reversed abnormal mitophagy induced by ovariectomy by increasing the expression of Beclin1, LC3B, Pink1, and Parkin, as well as by reducing the expression of p62.

CONCLUSIONS

BCA treatment enhances learning and memory abilities and alleviates AD symptoms in a postmenopausal model of AD. A possible mechanism is that BCA rescues the reduction of mitochondrial biogenesis, imbalance of mitochondrial dynamics, and abnormal mitophagy caused by ovariectomy. This study supports further research on BCA to develop treatments for postmenopausal women with AD.

Mechanisms of Mitochondrial Malfunction in Alzheimer’s Disease: New Therapeutic Hope

Mitochondria play a critical role in neuron viability or death as it regulates energy metabolism and cell death pathways. They are essential for cellular energy metabolism, reactive oxygen species production, apoptosis, Ca⁺⁺ homeostasis, aging, and regeneration. Mitophagy and mitochondrial dynamics are thus essential processes in the quality control of mitochondria. Improvements in several fundamental features of mitochondrial biology in susceptible neurons of AD brains and the putative underlying mechanisms of such changes have made significant progress. AD's etiology has been reported by mitochondrial malfunction and oxidative damage. According to several recent articles, a continual fusion and fission balance of mitochondria is vital in their normal function maintenance. As a result, the shape and function of mitochondria are inextricably linked. This study examines evidence suggesting that mitochondrial dysfunction plays a significant early impact on AD pathology. Furthermore, the dynamics and roles of mitochondria are discussed with the link between mitochondrial malfunction and autophagy in AD has also been explored. In addition, recent research on mitochondrial dynamics and mitophagy in AD is also discussed in this review. It also goes into how these flaws affect mitochondrial quality control. Furthermore, advanced therapy techniques and lifestyle adjustments that lead to improved management of the dynamics have been demonstrated, hence improving the conditions that contribute to mitochondrial dysfunction in AD.

Estrogen, Cognitive Performance, and Functional Imaging Studies: What Are We Missing About Neuroprotection?

Menopause transition can be interpreted as a vulnerable state characterized by estrogen deficiency with detrimental systemic effects as the low-grade chronic inflammation that appears with aging and partly explains age-related disorders as cancer, diabetes mellitus and increased risk of cognitive impairment. Over the course of a lifetime, estrogen produces several beneficial effects in healthy neurological tissues as well as cardioprotective effects, and anti-inflammatory effects. However, clinical evidence on the efficacy of hormone treatment in menopausal women has failed to confirm the benefit reported in observational studies. Unambiguously, enhanced verbal memory is the most robust finding from longitudinal and cross-sectional studies, what merits consideration for future studies aiming to determine estrogen neuroprotective efficacy. Estrogen related brain activity and functional connectivity remain, however, unexplored. In this context, the resting state paradigm may provide valuable information about reproductive aging and hormonal treatment effects, and their relationship with brain imaging of functional connectivity may be key to understand and anticipate estrogen cognitive protective effects. To go in-depth into the molecular and cellular mechanisms underlying rapid-to-long lasting protective effects of estrogen, we will provide a comprehensive review of cognitive tasks used in animal studies to evaluate the effect of hormone treatment on cognitive performance and discuss about the tasks best suited to the demonstration of clinically significant differences in cognitive performance to be applied in human studies. Eventually, we will focus on studies evaluating the DMN activity and responsiveness to pharmacological stimulation in humans.

Gender differences in cognitive reserve: implication for subjective cognitive decline in women

BACKGROUND

Subjective Cognitive Decline (SCD) is a self-experienced decline in cognitive capacity with normal performance on standardized cognitive tests, showing to increase risk of Alzheimer's Disease (AD). Cognitive reserve seems to influence the progression from SCD to Mild Cognitive Impairment (MCI) and to AD. The aim of our study was to investigate gender differences in cognitive reserve evaluating how sex might modulate the role of cognitive reserve on SCD.

METHODS

We included 381 SCD patients who underwent clinical evaluation, neuropsychological assessment, evaluation of premorbid intelligence by the Test di Intelligenza Breve (TIB), cognitive complaints by the Memory Assessment Clinics Questionnaire (MAC-Q), and apolipoprotein E (APOE) genotyping.

RESULTS

The proportion between women and men was significantly different (68.7% [95% CI 63.9-73.4 vs 31.4%, 95% CI 26.6-36.0]). Women were younger than men at onset of SCD and at the baseline visit (p = 0.021), had lower years of education (p = 0.007), lower TIB scores (p < 0.001), and higher MAC-Q scores (p = 0.012). TIB was directly associated with age at onset of SCD in both women and men, while years of education was inversely associated with age at onset only in women. Multivariate analysis showed that sex influences TIB independently from years of education. TIB was directly associated with MAC-Q in men.

CONCLUSIONS

Sex interacts with premorbid intelligence and education level in influencing the age at onset and the severity of SCD. As the effect of education was different between men and women, we speculated that education might act as a minor contributor of cognitive reserve in women.

Endogenous and Exogenous Estrogen Exposures: How Women's Reproductive Health Can Drive Brain Aging and Inform Alzheimer's Prevention

After advanced age, female sex is the major risk factor for late-onset Alzheimer's disease (AD), the most common cause of dementia affecting over 24 million people worldwide. The prevalence of AD is higher in women than in men, with postmenopausal women accounting for over 60% of all those affected. While most research has focused on gender-combined risk, emerging data indicate sex and gender differences in AD pathophysiology, onset, and progression, which may help account for the higher prevalence in women. Notably, AD-related brain changes develop during a 10-20 year prodromal phase originating in midlife, thus proximate with the hormonal transitions of endocrine aging characteristic of the menopause transition in women. Preclinical evidence for neuroprotective effects of gonadal sex steroid hormones, especially 17β-estradiol, strongly argue for associations between female fertility, reproductive history, and AD risk. The level of gonadal hormones to which the female brain is exposed changes considerably across the lifespan, with relevance to AD risk. However, the neurobiological consequences of hormonal fluctuations, as well as that of hormone therapies, are yet to be fully understood. Epidemiological studies have yielded contrasting results of protective, deleterious and null effects of estrogen exposure on dementia risk. In contrast, brain imaging studies provide encouraging evidence for positive associations between greater cumulative lifetime estrogen exposure and lower AD risk in women, whereas estrogen deprivation is associated with negative consequences on brain structure, function, and biochemistry. Herein, we review the existing literature and evaluate the strength of observed associations between female-specific reproductive health factors and AD risk in women, with a focus on the role of endogenous and exogenous estrogen exposures as a key underlying mechanism. Chief among these variables are reproductive lifespan, menopause status, type of menopause (spontaneous vs. induced), number of pregnancies, and exposure to hormonal therapy, including hormonal contraceptives, hormonal therapy for menopause, and anti-estrogen treatment. As aging is the greatest risk factor for AD followed by female sex, understanding sex-specific biological pathways through which reproductive history modulates brain aging is crucial to inform preventative and therapeutic strategies for AD.

Association Between Lipid Accumulation Product and Cognitive Function in Hypertensive Patients With Normal Weight: Insight From the China H-type Hypertension Registry Study

Background

Hypertension is a major cardiovascular risk factor for cognitive impairment. Lipid accumulation product (LAP), an index that represents fat overaccumulation in the body, has been shown to be associated with cardiovascular disease. Nevertheless, the relationship between LAP and cognitive function in hypertensive patients with normal weight has been infrequently studied.

Objective

This study aimed to assess the relationship between LAP and cognitive function in hypertensive patients with normal weight.

Methods

This study included 5,542 Chinese hypertensive patients with normal weight. Cognitive function was evaluated using the Mini-Mental State Examination (MMSE). The relationship between LAP and MMSE scores was evaluated using multiple linear regression.

Results

The mean age of the participants was 64.8 ± 9.3 years, and 2,700 were men (48.7%). The mean MMSE score was 24.5 ± 5.1 in men and 19.2 ± 6.5 in women. The mean LAP was 26.2 ± 25.5 in men and 42.5 ± 34 in women. Log₁₀-LAP showed a significant positive association with MMSE score (men: β = 0.69, 95% CI 0.14–1.24, p = 0.015; women: β = 1.03, 95% CI 0.16–1.90, p = 0.020). When LAP was divided into 3 groups according to tertiles, participants in the third LAP tertile had higher MMSE scores for both men (p for trend = 0.04) and women (p for trend = 0.015).

Conclusion

LAP showed an independent positive association with MMSE in Chinese hypertensive patients with normal weight.

A tale of two systems: Lessons learned from female mid-life aging with implications for Alzheimer's prevention & treatment

Neurological aging is frequently viewed as a linear process of decline, whereas in reality, it is a dynamic non-linear process. The dynamic nature of neurological aging is exemplified during midlife in the female brain. To investigate fundamental mechanisms of midlife aging that underlie risk for development of Alzheimer's disease (AD) in late life, we investigated the brain at greatest risk for the disease, the aging female brain. Outcomes of our research indicate that mid-life aging in the female is characterized by the emergence of three phases: early chronological (pre-menopause), endocrinological (peri-menopause) and late chronological (post-menopause) aging. The endocrinological aging program is sandwiched between early and late chronological aging. Throughout the three stages of midlife aging, two systems of biology, metabolic and immune, are tightly integrated through a network of signaling cascades. The network of signaling between these two systems of biology underlie an orchestrated sequence of adaptative starvation responses that shift the brain from near exclusive dependence on a single fuel, glucose, to utilization of an auxiliary fuel derived from lipids, ketone bodies. The dismantling of the estrogen control of glucose metabolism during mid-life aging is a critical contributor to the shift in fuel systems and emergence of dynamic neuroimmune phenotype. The shift in fuel reliance, puts the largest reservoir of local fatty acids, white matter, at risk for catabolism as a source of lipids to generate ketone bodies through astrocytic beta oxidation. APOE4 genotype accelerates the tipping point for emergence of the bioenergetic crisis. While outcomes derived from research conducted in the female brain are not directly translatable to the male brain, the questions addressed in a female centric program of research are directly applicable to investigation of the male brain. Like females, males with AD exhibit deficits in the bioenergetic system of the brain, activation of the immune system and hallmark Alzheimer's pathologies. The drivers and trajectory of mechanisms underlying neurodegeneration in the male brain will undoubtedly share common aspects with the female in addition to factors unique to the male. Preclinical and clinical evidence indicate that midlife endocrine aging can also be a transitional bridge to autoimmune disorders. Collectively, the data indicate that endocrinological aging is a critical period "tipping point" in midlife which can initiate emergence of the prodromal stage of late-onset-Alzheimer's disease. Interventions that target both immune and metabolic shifts that occur during midlife aging have the potential to alter the trajectory of Alzheimer's risk in late life. Further, to achieve precision medicine for AD, chromosomal sex is a critical variable to consider along with APOE genotype, other genetic risk factors and stage of disease.

Update on hormone therapy for the management of postmenopausal women

Hormone therapy (HT) has been used in postmenopausal women for decades in clinical practice. With further analysis and newer studies, the benefits and risks of HT have been repeatedly verified and discussed. HT is recommended for the treatment of vasomotor symptoms (VMS), genitourinary syndrome of menopause (GSM) and the prevention of osteoporosis. However, the precise association between HT and the risks of cardiovascular diseases, venous thromboembolism, neurodegenerative diseases, breast cancer, and endometrial cancer remains controversial. Therefore, determining how to take advantage of and control the risks of HT by adjusting the initiation time, regimen, and duration is crucial. Recent studies have indicated that HT is not related to the risk of all-cause, cardiovascular, or breast cancer mortality although it might increase the incidence of some chronic diseases. For symptomatic postmenopausal women under the age of 60 without contraindications, early initiation of HT is safe and probably has a mortality benefit over the long term. Initiating HT close to menopause at the lowest effective dose is more likely to have maximal benefits and the lowest risks. Transdermal and vaginal HT may have a lower risk, but recent evidence suggests additional clinical benefits of oral HT formulations in relieving VMS and preventing osteoporosis. The pooled cohort risk equation for atherosclerotic cardiovascular disease (ASCVD) and the free app named Menopro can be used to perform individual risk assessments. In addition, Chinese herbal medicines have benefits in alleviating hot flashes, depression, and menopausal symptoms, although further data are needed to strongly support their efficacy. Acupuncture and electroacupuncture have definite efficacy in the treatment of postmenopausal symptoms with few adverse effects, so they are a reasonable option as an alternative therapy for high-risk women. This review discusses the history of, guidelines on, and strategies for HT in order to make suggestions based on the most up-to-date evidence for the management of postmenopausal women.

Associations between reproductive history, hormone use, APOE ε4 genotype and cognition in middle- to older-aged women from the UK Biobank

Introduction

Relative to men, women are at a higher risk of developing age-related neurocognitive disorders including Alzheimer's disease. While women's health has historically been understudied, emerging evidence suggests that reproductive life events such as pregnancy and hormone use may influence women's cognition later in life.

Methods

We investigated the associations between reproductive history, exogenous hormone use, apolipoprotein (APOE) ε4 genotype and cognition in 221,124 middle- to older-aged (mean age 56.2 ± 8.0 years) women from the UK Biobank. Performance on six cognitive tasks was assessed, covering four cognitive domains: episodic visual memory, numeric working memory, processing speed, and executive function.

Results

A longer reproductive span, older age at menopause, older age at first and last birth, and use of hormonal contraceptives were positively associated with cognitive performance later in life. Number of live births, hysterectomy without oophorectomy and use of hormone therapy showed mixed findings, with task-specific positive and negative associations. Effect sizes were generally small (Cohen's d < 0.1). While APOE ε4 genotype was associated with reduced processing speed and executive functioning, in a dose-dependent manner, it did not influence the observed associations between female-specific factors and cognition.

Discussion

Our findings support previous evidence of associations between a broad range of female-specific factors and cognition. The positive association between a history of hormonal contraceptive use and cognition later in life showed the largest effect sizes (max. d = 0.1). More research targeting the long-term effects of female-specific factors on cognition and age-related neurocognitive disorders including Alzheimer's disease is crucial for a better understanding of women's brain health and to support women's health care.

Associations between abdominal adipose tissue, reproductive span, and brain characteristics in post-menopausal women

The menopause transition involves changes in oestrogens and adipose tissue distribution, which may influence female brain health post-menopause. Although increased central fat accumulation is linked to risk of cardiometabolic diseases, adipose tissue also serves as the primary biosynthesis site of oestrogens post-menopause. It is unclear whether different types of adipose tissue play diverging roles in female brain health post-menopause, and whether this depends on lifetime oestrogen exposure, which can have lasting effects on the brain and body even after menopause. Using the UK Biobank sample, we investigated associations between brain characteristics and visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (ASAT) in 10,251 post-menopausal females, and assessed whether the relationships varied depending on length of reproductive span (age at menarche to age at menopause). To parse the effects of common genetic variation, we computed polygenic scores for reproductive span. The results showed that higher VAT and ASAT were both associated with higher grey and white matter brain age, and greater white matter hyperintensity load. The associations varied positively with reproductive span, indicating more prominent associations between adipose tissue and brain measures in females with a longer reproductive span. The effects were in general small, but could not be fully explained by genetic variation or relevant confounders. Our findings indicate that associations between abdominal adipose tissue and brain health post-menopause may partly depend on individual differences in cumulative oestrogen exposure during reproductive years, emphasising the complexity of neural and endocrine ageing processes in females.

A Mitochondrial DNA Haplogroup Defines Patterns of Five-Year Cognitive Change

BACKGROUND

Mitochondrial DNA (mtDNA) may play a role in Alzheimer's disease (AD) and cognitive decline. A particular haplogroup of mtDNA, haplogroup J, has been observed more commonly in patients with AD than in cognitively normal controls.

OBJECTIVE

We used two mtDNA haplogroups, H and J, to predict change in cognitive performance over five years. We hypothesized that haplogroup J carriers would show less cognitive resilience.

METHODS

We analyzed data from 140 cognitively normal older adults who participated in the University of Kansas Alzheimer's Disease Research Center clinical cohort between 2011 and 2020. We used factor analysis to create three composite scores (verbal memory, attention, and executive function) from 11 individual cognitive tests. We performed latent growth curve modeling to describe trajectories of cognitive performance and change adjusting for age, sex, years of education, and APOE ɛ4 allele carrier status. We compared haplogroup H, the most common group, to haplogroup J, the potential risk group.

RESULTS

Haplogroup J carriers had significantly lower baseline performance and slower rates of improvement on tests of verbal memory compared to haplogroup H carriers. We did not observe differences in executive function or attention.

CONCLUSION

Our results reinforce the role of mtDNA in changes to cognitive function in a domain associated with risk for dementia, verbal memory, but not with other cognitive domains. Future research should investigate the distinct mechanisms by which mtDNA might affect performance on verbal memory as compared to other cognitive domains across haplogroups.

Postmortem mitochondrial membrane permeability transition assessment of apoptotic cell death in brain and liver of insulin resistant, ovariectomised rats

The adverse alterations in mitochondrial functions can affect neuronal function negatively, as they play a crucial role in neuronal plasticity and death. Direct measurements of mitochondrial activity, including membrane potential and ATP production, are not easily achieved in post-mortem brain and liver samples because most organ functions cease to work after death; in fact, with increasing post-mortem intervals (PMI), the brain and liver tissues deteriorate rapidly. Standard procedures of mitochondria isolation, protein determination expressed as BSA equivalent, and spectrophotometric assessment of pore opening at 540 nm were employed. Our results showed that (a) intact mitochondria may be isolated from rat brain and liver of these rats after storage in animal body (in situ) at -20 °C for 7 days (168 h, post-mortem), (b) some population of these mitochondria can still take up exogenous Ca2+ and (c) they can still resist osmotically induced large amplitude swelling in a suitable buffer. The need for mitochondrial purity, structural integrity and abundance for functional studies are common hindrances that can encumber mitochondrial research. Therefore, this study is significant to have shown that PMI up to 7 days did not extensively, diminish MMPT pore status in normal and diabetic, ovariectomised rats. This can be relevant for forensic data mining.

Cognition and mental health in menopause: A review

Cognitive and mood changes are frequently mentioned as complaints before, during and after menopausal transition. There is substantial biological evidence for such associations to occur, as there are many mechanisms through which oestrogens can affect the brain: by regulating metabolism, increasing cerebral blood flow and dendritic outgrowth, by acting on nerve growth factors through the co-localisation of receptors via neurotransmitter synthesis and turnover and many more. However, the evidence for objective and longer-term changes in cognitive function and mental health over the menopausal transition and beyond is less clear. While hormone treatment (HT) including oestrogens could potentially reverse these psychological issues, the evidence of long-term benefit is also inconclusive. However, for women with severe menopausal complaints, and particularly for those who undergo early menopause, including women with premature ovarian insufficiency, personalised HT at least up to the natural age of menopause around 50 should be considered, which is probably safe up to 10 years of treatment, unless contraindicated. This paper reviews the evidence for changes in psychological health related to menopausal transition and HTs.

Hormones and neuroplasticity: A lifetime of adaptive responses

Major life transitions often co-occur with significant fluctuations in hormones that modulate the central nervous system. These hormones enact neuroplastic mechanisms that prepare an organism to respond to novel environmental conditions and/or previously unencountered cognitive, emotional, and/or behavioral demands. In this review, we will explore several examples of how hormones mediate neuroplastic changes in order to produce adaptive responses, particularly during transitions in life stages. First, we will explore hormonal influences on social recognition in both males and females as they transition to sexual maturity. Next, we will probe the role of hormones in mediating the transitions to motherhood and fatherhood, respectively. Finally, we will survey the long-term impact of reproductive experience on neuroplasticity in females, including potential protective effects and risk factors associated with reproductive experience in mid-life and beyond. Ultimately, a more complete understanding of how hormones influence neuroplasticity throughout the lifespan, beyond development, is necessary for understanding how individuals respond to life changes in adaptive ways.

Sex Differences in the Effect of Diabetes on Cerebral Glucose Metabolism

The neuroimaging literature indicates that brain structure and function both deteriorate with diabetes, but information on sexual dimorphism in diabetes-related brain alterations is limited. This study aimed to ascertain whether brain metabolism is influenced by sex in an animal model of diabetes. Eleven rats (male, n = 5; female, n = 6) received a single intraperitoneal injection of 70 mg/kg streptozotocin (STZ) to develop diabetes. Another 11 rats (male, n = 5; female, n = 6) received the same amount of solvent through a single intraperitoneal injection. Longitudinal positron emission tomography scans were used to assess cerebral glucose metabolism before and 4 weeks after STZ or solvent administration. Before STZ or solvent injections, there was no evidence of sexual dimorphism in cerebral metabolism (p > 0.05). Compared with healthy control animals, rats with diabetes had significantly decreased brain metabolism in all brain regions (all p < 0.05). In addition, female diabetic rats exhibited further reduction in cerebral metabolism, relative to male diabetic rats (p < 0.05). The results of this study may provide some biological evidence, supporting the existence of a sexual dimorphism in diabetes-related complications.

Sex Differences in Mitochondrial Function Following a Controlled Cortical Impact Traumatic Brain Injury in Rodents

Traumatic brain injury (TBI) is a complex disease to study due to the multifactorial injury cascades occurring after the initial blow to the head. One of the most vital players in this secondary injury cascade, and therapeutic target of interest, is the mitochondrion. Mitochondria are important for the generation of cellular energy, regulation of cell death, and modulation of intracellular calcium which leaves these “powerhouses” especially susceptible to damage and dysfunction following traumatic brain injury. Most of the existing studies involving mitochondrial dysfunction after TBI have been performed in male rodent models, leaving a gap in knowledge on these same outcomes in females. This mini-review intends to highlight the available data on mitochondrial dysfunction in male and female rodents after controlled cortical impact (CCI) as a common model of TBI.

Neurodegenerative Disease: Roles for Sex, Hormones, and Oxidative Stress

Neurodegenerative diseases cause severe impairments in cognitive and motor function. With an increasing aging population and the onset of these diseases between 50 and 70 years, the consequences are bound to be devastating. While age and longevity are the main risk factors for neurodegenerative diseases, sex is also an important risk factor. The characteristic of sex is multifaceted, encompassing sex chromosome complement, sex hormones (estrogens and androgens), and sex hormone receptors. Sex hormone receptors can induce various signaling cascades, ranging from genomic transcription to intracellular signaling pathways that are dependent on the health of the cell. Oxidative stress, associated with aging, can impact the health of the cell. Sex hormones can be neuroprotective under low oxidative stress conditions but not in high oxidative stress conditions. An understudied sex hormone receptor that can induce activation of oxidative stress signaling is the membrane androgen receptor (mAR). mAR can mediate nicotinamide adenine dinucleotide-phosphate (NADPH) oxidase (NOX)-generated oxidative stress that is associated with several neurodegenerative diseases, such as Alzheimer disease. Further complicating this is that aging can alter sex hormone signaling. Prior to menopause, women experience more estrogens than androgens. During menopause, this sex hormone profile switches in women due to the dramatic ovarian loss of 17β-estradiol with maintained ovarian androgen (testosterone, androstenedione) production. Indeed, aging men have higher estrogens than aging women due to aromatization of androgens to estrogens. Therefore, higher activation of mAR-NOX signaling could occur in menopausal women compared with aged men, mediating the observed sex differences. Understanding of these signaling cascades could provide therapeutic targets for neurodegenerative diseases.

Hormone therapy in the postmenopausal years: considering benefits and risks in clinical practice

BACKGROUND

Menopausal symptoms can be very distressing and considerably affect a woman's personal and social life. It is becoming more and more evident that leaving bothersome symptoms untreated in midlife may lead to altered quality of life, reduced work productivity and, possibly, overall impaired health. Hormone therapy (HT) for the relief of menopausal symptoms has been the object of much controversy over the past two decades. At the beginning of the century, a shadow was cast on the use of HT owing to the concern for cardiovascular and cerebrovascular risks, and breast cancer, arising following publication of a large randomized placebo-controlled trial. Findings of a subanalysis of the trial data and extended follow-up studies, along with other more modern clinical trials and observational studies, have provided new evidence on the effects of HT.

OBJECTIVE AND RATIONALE

The goal of the following paper is to appraise the most significant clinical literature on the effects of hormones in postmenopausal women, and to report the benefits and risks of HT for the relief of menopausal symptoms.

SEARCH METHODS

A Pubmed search of clinical trials was performed using the following terms: estrogens, progestogens, bazedoxifene, tibolone, selective estrogen receptor modulators, tissue-selective estrogen complex, androgens, and menopause.

OUTCOMES

HT is an effective treatment for bothersome menopausal vasomotor symptoms, genitourinary syndrome, and prevention of osteoporotic fractures. Women should be made aware that there is a small increased risk of stroke that tends to persist over the years as well as breast cancer risk with long-term estrogen-progestin use. However, healthy women who begin HT soon after menopause will probably earn more benefit than harm from the treatment. HT can improve bothersome symptoms, all the while conferring offset benefits such as cardiovascular risk reduction, an increase in bone mineral density and a reduction in bone fracture risk. Moreover, a decrease in colorectal cancer risk is obtainable in women treated with estrogen-progestin therapy, and an overall but nonsignificant reduction in mortality has been observed in women treated with conjugated equine estrogens alone or combined with estrogen-progestin therapy. Where possible, transdermal routes of HT administration should be preferred as they have the least impact on coagulation. With combined treatment, natural progesterone should be favored as it is devoid of the antiapoptotic properties of other progestogens on breast cells. When beginning HT, low doses should be used and increased gradually until effective control of symptoms is achieved. Unless contraindications develop, patients may choose to continue HT as long as the benefits outweigh the risks. Regular reassessment of the woman's health status is mandatory. Women with premature menopause who begin HT before 50 years of age seem to have the most significant advantage in terms of longevity.

WIDER IMPLICATIONS

In women with bothersome menopausal symptoms, HT should be considered one of the mainstays of treatment. Clinical practitioners should tailor HT based on patient history, physical characteristics, and current health status so that benefits outweigh the risks.