An analysis of neuroscience and psychiatry papers published from 2009 and 2019 outlines opportunities for increasing discovery of sex differences

ComBatLS: A Location- and Scale-Preserving Method for Multi-Site Image Harmonization

Recent study has leveraged massive datasets and advanced harmonization methods to construct normative models of neuroanatomical features and benchmark individuals' morphology. However, current harmonization tools do not preserve the effects of biological covariates including sex and age on features' variances; this failure may induce error in normative scores, particularly when such factors are distributed unequally across sites. Here, we introduce a new extension of the popular ComBat harmonization method, ComBatLS, that preserves biological variance in features' locations and scales. We use UK Biobank data to show that ComBatLS robustly replicates individuals' normative scores better than other ComBat methods when subjects are assigned to sex-imbalanced synthetic "sites." Additionally, we demonstrate that ComBatLS significantly reduces sex biases in normative scores compared to traditional methods. Finally, we show that ComBatLS successfully harmonizes consortium data collected across over 50 studies. R implementation of ComBatLS is available at https://github.com/andy1764/ComBatFamily.

Androgens mediate sexual dimorphism in Pilarowski-Bjornsson Syndrome

Sex-specific penetrance in autosomal dominant Mendelian conditions is largely understudied. The neurodevelopmental disorder Pilarowski-Bjornsson syndrome (PILBOS) was initially described in females. Here, we describe the clinical and genetic characteristics of the largest PILBOS cohort to date, showing that both sexes can exhibit PILBOS features, although males are overrepresented. A mouse model carrying a human-derived Chd1 missense variant (Chd1 R616Q/+) displays female-restricted phenotypes, including growth deficiency, anxiety and hypotonia. Orchiectomy unmasks a growth deficiency phenotype in male Chd1 R616Q/+ mice, while testosterone rescues the phenotype in females, implicating androgens in phenotype modulation. In the gnomAD and UK Biobank databases, rare missense variants in CHD1 are overrepresented in males, supporting a male protective effect. We identify 33 additional highly constrained autosomal genes with missense variant overrepresentation in males. Our results support androgen-regulated sexual dimorphism in PILBOS and open novel avenues to understand the mechanistic basis of sexual dimorphism in other autosomal Mendelian disorders.

Menstrual cycle and perceived stress predict performance on the mnemonic similarity task

A growing body of literature demonstrates strong effects of ovarian hormones on the hippocampus and adjacent structures. However, resulting impacts on human cognition remain unclear. Addressing this gap, we examine pattern separation ability, a core hippocampal process, across the menstrual cycle using the mnemonic similarity task as a behavioral index (N = 183). We find a non-linear effect of the menstrual cycle, with pattern separation performance peaking in the high-estradiol, late follicular phase and reaching its lowest point during the mid-luteal phase, which is characterized by moderate estradiol and high progesterone levels. Additionally, we find that perceived stress may facilitate pattern separation performance. These results point to the importance of ovarian hormones for human cognition, reveal novel effects of perceived stress on mnemonic similarity task performance, and provide preliminary evidence of possible effects of menstrual cycle phase on neural pathways involved in pattern separation.

Navigating the paradigm shift of sex inclusive preclinical research and lessons learnt

As progress is made in sex-inclusive preclinical research, the author highlights areas of research practice where significant development has been achieved & where more change is needed towards community accepted standards in equitable research

Leveraging research into sex differences and steroid hormones to improve brain health

Sex differences, driven in part by steroid hormones, shape the structure and function of the brain throughout the lifespan and manifest across brain health and disease. The influence of steroid hormones on neuroplasticity, particularly in the adult hippocampus, differs between the sexes, which has important implications for disorders and diseases that compromise hippocampus integrity, such as depression and Alzheimer disease. This Review outlines the intricate relationship between steroid hormones and hippocampal neuroplasticity across the adult lifespan and explores how the unique physiology of male and female individuals can affect health and disease. Despite calls to include sex and gender in research, only 5% of neuroscience studies published in 2019 directly investigated the influence of sex. Drawing on insights from depression, Alzheimer disease and relevant hippocampal plasticity, this Review underscores the importance of considering sex and steroid hormones to achieve a comprehensive understanding of disease susceptibility and mechanisms. Such consideration will enable the discovery of personalized treatments, ultimately leading to improved health outcomes for all.

Operant ethanol self-administration behaviors do not predict sex differences in continuous access home cage drinking

Understanding sex differences in disease prevalence is critical to public health, particularly in the context of alcohol use disorder (AUD). The goal of this study was to understand sex differences in ethanol drinking behavior and define the precise conditions under which sex differences emerge. Consistent with prior work, C57BL/6J females drank more than males under continuous access two-bottle choice conditions. However, using ethanol self-administration - where an operant response results in access to an ethanol sipper for a fixed time period - we found no sex differences in operant response rates or ethanol consumption (volume per body weight consumed, as well as lick behavior). This remained true across a wide range of parameters including acquisition, when the ethanol sipper access period was manipulated, and when the concentration of the ethanol available was scaled. The only sex differences observed were in total ethanol consumption, which was explained by differences in body weight between males and females, rather than by sex differences in motivation to drink. Using dimensionality reduction approaches, we found that drinking behavior in the operant context did not cluster by sex, but rather clustered by high and low drinking phenotypes. Interestingly, these high and low drinking phenotypes in the operant context showed no correlation with those same categorizations in the home cage context within the same animals. These data underscore the complexity of sex differences in ethanol consumption, highlighting the important role that drinking conditions/context plays in the expression of these differences.

The role of the dopamine D1 receptor in anticipatory pleasure and social play

Social play is a highly rewarding activity seen across mammalian species that is vital for neurobehavioural development. Dysfunctions in social play are seen across psychiatric and neurodevelopmental disorders positing the importance of understanding the neurobiological mechanisms underlying social play. A multitude of neurotransmitter systems have been implicated in social play, with the present study focused on the role of dopamine, specifically the dopamine D1 receptor. Pharmacological manipulations of dopamine and the D1 receptor reveal mixed findings. Given the limited selectivity of pharmacological tools, we explored the role of the dopamine D1 receptor in social play using dopamine D1 mutant (DAD1-/-) rats which have a genetic reduction in functional D1 receptors. Aligning with the rewarding properties of social play, the present study also examined anticipatory behaviour for the opportunity to engage in social play. Contrary to our predictions, DAD1-/- mutants initiated and engaged in social play similarly to wildtype controls with only subtle differences in specific elements of play behaviour. Subjects did not differ in 50 kHz vocalisations emitted during play, suggesting similar levels of consummatory pleasure. Although subjects initiated and engaged in play similarly, as predicted, DAD1-/- mutants displayed deficits in anticipatory behaviour and pleasure for the opportunity to engage in social play. These findings support a prominent role of the D1 receptor in anticipatory behaviour, with further research needed to elucidate its role in social play.

28 days later: A prospective daily study on psychological well-being across the menstrual cycle and the effects of hormones and oral contraceptives

BACKGROUND

We aimed to study how hormonal status (oral contraceptive [OC] users vs naturally cycling [NC]) affects different dimensions and variability of psychological well-being, and how they relate to sex hormone levels (estradiol, progesterone, and testosterone).

METHODS

Twenty-two NC participants and 18 OC users reported daily affective and physical symptoms and collected daily salivary samples across 28 days. Groups were compared using psychological well-being averages (linear mixed models), day-to-day variability (Levene's test), and network models. Within NC participants, cycle phase effects and time-varying associations between hormones and psychological well-being were assessed using both person-centered mean and change (subtracting mean from daily score) scores.

RESULTS

Lowered variability was found for OC users' agitation, risk-taking, attractiveness, and energy levels. They showed lower overall ratings of happiness, attractiveness, risk-taking, and energy levels (range R2m = .004: .019) but also reported more relaxation, sexual desire, and better sleep quality (range R2m = .005; .01) compared to the NC group. The impact of sex hormones on psychological well-being varied significantly across cycle phases, with the largest effects for progesterone levels.

CONCLUSIONS

Our results confirm that hormonal status is associated with a range of psychological well-being domains beyond mood and sexual desire, including energy levels, feelings of attractiveness, risk taking, and agitation. Lowered variability in OC users versus NC participants fit with 'emotional blunting' as a possible mechanism behind OC's side effects. Our findings that show the menstrual cycle and sex hormones differentially influenced markers of psychological well-being emphasize the need to adequately account for the menstrual cycle.

Considering the interconnected nature of social identities in neuroimaging research

Considerable heterogeneity exists in the expression of complex human behaviors across the cognitive, personality and mental health domains. It is increasingly evident that individual variability in behavioral expression is substantially affected by sociodemographic factors that often interact with life experiences. Here, we formally address the urgent need to incorporate intersectional identities in neuroimaging studies of behavior, with a focus on research in mental health. We highlight how diverse sociodemographic factors influence the study of psychiatric conditions, focusing on how interactions between those factors might contribute to brain biology and illness expression, including prevalence, symptom burden, help seeking, treatment response and tolerance, and relapse and remission. We conclude with a discussion of the considerations and actionable items related to participant recruitment, data acquisition and data analysis to facilitate the inclusion and incorporation of diverse intersectional identities in neuroimaging.

Unveiling the burden of premenstrual dysphoric disorder: a narrative review to call for gender perspective and intersectional approaches

The present narrative review discusses the burden of Premenstrual Dysphoric Disorder (PMDD) and highlights the lack of awareness by analyzing the following key points: -Prevalence and Diagnosis: PMDD affects a significant portion of women during their reproductive years, but diagnosis is often delayed due to limited understanding and awareness. -Mental Health Burden: PMDD increases the risk of suicide attempts and negatively impacts quality of life. There are also economic costs associated with absenteeism and healthcare use. -Cultural and Gender Perspectives: Societal stigma surrounding menstruation and mental health likely contributes to underdiagnosis. -Lack of Sex and Gender Perspective in the Healthcare System: Research bias towards male subjects and historical neglect of women's health issues contribute to limited knowledge about PMDD. -Non-Intersectional Approaches: Disparities in access to healthcare and the unique experiences of women further complicate PMDD diagnosis and treatment. -Vicious Cycle: The lack of research and awareness creates a vicious cycle where PMDD remains misunderstood and inaccurately treated. Finally, it emphasizes the need for increased awareness, education, and research on PMDD, particularly with a gendered and intersectional optic. The situation in Latin America is presented as a particular concern due to a lack of recent data and potentially higher prevalence due to socioeconomic factors.

Sex in aging matters: exercise and chronic stress differentially impact females and males across the lifespan

Assessing sex as a biological variable is critical to determining the influence of environmental and lifestyle risks and protective factors mediating behavior and neuroplasticity across the lifespan. We investigated sex differences in affective behavior, memory, and hippocampal neurogenesis following short- or long-term exposure to exercise or chronic mild stress in young and aged mice. Male and female mice were assigned control, running, or chronic stress rearing conditions for 1 month (young) or for 15 months (aged), then underwent a behavioral test battery to assess activity, affective behavior, and memory. Stress exposure into late-adulthood increased hyperactivity in both sexes, and enhanced anxiety-like and depressive-like behavior in aged female, but not male, mice. One month of stress or running had no differential effects on behavior in young males and females. Running increased survival of BrdU-labelled hippocampal cells in both young and aged mice, and enhanced spatial memory in aged mice. These findings highlight the importance of considering sex when determining how aging is differently impacted by modifiable lifestyle factors across the lifespan.

Contraceptives and conditioning: Different profiles of fear and expectancy ratings during fear conditioning and extinction according to menstrual cycle phase and hormonal contraceptive use

Hormonal contraceptives (HC) such as the oral contraceptive pill (OC) and the hormonal intrauterine device (IUD) have been associated with depressed mood, but research on their role in anxiety is scarce and inconsistent. In a fear acquisition and extinction paradigm, self-report fear, expectancy, and skin conductance responses (SCR) were assessed, along with sex hormone levels. Naturally cycling (NC) participants were measured during the mid-follicular and mid-luteal phases (within subjects, n = 26) and compared with OC (n = 36) and IUD (n = 25) users. IUD users and -participants in the luteal phase showed overall reduced self-reported CS+ vs CS- differentiation compared to the follicular phase and OC use (which both reflect relatively low levels of endogenous gonadal hormones). This overall reduced differentiation in self-reported fear in the luteal phase was attributed to a generalization of fear from CS+ to CS-. NC-individuals with high premenstrual syndrome (PMS) ratings had higher overall fear ratings regardless of cycle phase. For SCR, hormonal status effects were restricted to specific experimental phases during acquisition. SCR to the CS+ was higher at the end of acquisition in the luteal phase compared to the follicular phase, and in OC users during early acquisition (compared to the follicular phase) and mid acquisition (compared to the IUD group). There were no direct associations with sex hormone levels. These findings demonstrate the impact of menstrual cycle and HC use on fear learning and highlight the need for further research that considers different outcome measures across a wide array of menstrual cycle and HC-related characteristics.

Impact of gender on the willingness to participate in clinical trials and undergo related procedures in individuals from an Alzheimer's prevention research cohort

BACKGROUND

Although there is growing evidence of the association between gender and early diagnosis of preclinical Alzheimer's disease, little attention has been given to the enrolment ratio of men and women in clinical trials and data reporting.

METHODS

This study aims to analyze gender differences in sociodemographic factors associated with the willingness to participate in clinical trials and undergo specific procedures in the context of an Alzheimer's disease prevention research cohort. 2544 cognitively unimpaired participants from the ALFA parent cohort (age 45-75 years) of the Barcelonaβeta Brain Research Center were contacted through a structured phone call to determine their willingness to participate in Alzheimer's disease clinical trials and undergo trial-related procedures (magnetic resonance imaging, lumbar puncture, positron emission tomography, and cognitive assessment). Sociodemographic data on education, occupational attainment, civil and caregiver status were gathered. Stepwise logistic regression models were performed in order to study the interaction between gender and sociodemographic factors in the willingness to participate in clinical trials and to undergo clinical trial-related procedures.

RESULTS

1,606 out of the 2,544 participants were women (63.1%). Women were significantly younger and had lower educational attainment compared with men. In addition, women were more likely to be caregivers, single and unemployed. Women showed a significantly lower willingness than men to participate in a clinical trial (p = 0.003) and to undergo a lumbar puncture (p < 0.001). Single women were less willing to participate in clinical trials than single men (p = 0.041). Regarding clinical trial-related procedures, women with higher years of education were significantly less willing to undergo a lumbar puncture (p = 0.031).

CONCLUSION

We found gender differences regarding the sociodemographic factors that predict the willingness to participate in clinical trials and to undergo clinical trial-related procedures. Our results highlight the urgent need to design recruitment strategies accounting for gender-related factors, particularly those related to marital status and education.

Influences of sex and gender on the associations between risk and protective factors, brain, and behavior

Risk and protective factors for psychiatric illnesses are linked to distinct structural and functional changes in the brain. Further, the prevalence of these factors varies across sexes and genders, yet the distinct and joint effects of sex and gender in this context have not been extensively characterized. This suggests that risk and protective factors may map onto the brain and uniquely influence individuals across sexes and genders. Here, we review how specific risk (childhood maltreatment, the COVID-19 pandemic, experiences of racism), and protective factors (social support and psychological resilience) distinctly influence the brain across sexes and genders. We also discuss the role of sex and gender in the compounding effects of risk factors and in the interdependent influences of risk and protective factors. As such, we call on researchers to consider sex and gender when researching risk and protective factors for psychiatric illnesses, and we provide concrete recommendations on how to account for them in future research. Considering protective factors alongside risk factors in research and acknowledging sex and gender differences will enable us to establish sex- and gender-specific brain-behavior relationships. This will subsequently inform the development of targeted prevention and intervention strategies for psychiatric illnesses, which have been lacking. To achieve sex and gender equality in mental health, acknowledging and researching potential differences will lead to a better understanding of men and women, males and females, and the factors that make them more vulnerable or resilient to psychopathology.

Trajectories and sex differences of brain structure, oxygenation and perfusion functions in normal aging

BACKGROUND

Brain structure, oxygenation and perfusion are important factors in aging. Coupling between regional cerebral oxygen consumption and perfusion also reflects functions of neurovascular unit (NVU). Their trajectories and sex differences during normal aging important for clinical interpretation are still not well defined. In this study, we aim to investigate the relationship between brain structure, functions and age, and exam the sex disparities.

METHOD

A total of 137 healthy subjects between 20∼69 years old were enrolled with conventional MRI, structural three-dimensional T1-weighted imaging (3D-T1WI), 3D multi-echo gradient echo sequence (3D-mGRE), and 3D pseudo-continuous arterial spin labeling (3D-pCASL). Oxygen extraction fraction (OEF) and cerebral blood flow (CBF) were respectively reconstructed from 3D-mGRE and 3D-pCASL images. Cerebral metabolic rate of oxygen (CMRO2) were calculated as follows: CMRO2=CBF·OEF·[H]a, [H]a=7.377 μmol/mL. Brains were segmented into global gray matter (GM), global white matter (WM), and 148 cortical subregions. OEF, CBF, CMRO2, and volumes of GM/WM relative to intracranial volumes (rel_GM/rel_WM) were compared between males and females. Generalized additive models were used to evaluate the aging trajectories of brain structure and functions. The coupling between OEF and CBF was analyzed by correlation analysis. P or PFDR < 0.05 was considered statistically significant.

RESULTS

Females had larger rel_GM, higher CMRO2 and CBF of GM/WM than males (P < 0.05). With control of sex, CBF of GM significantly declined between 20 and 32 years, CMRO2 of GM declined subsequently from 33 to 41 years and rel_GM decreased significantly at all ages (R2 = 0.27, P < 0.001; R2 = 0.17, P < 0.001; R2 = 0.52, P < 0.001). In subregion analysis, CBF declined dispersedly while CMRO2 declined widely across most subregions of the cortex during aging. Robust negative coupling between OEF and CBF was found in most of the subregions (r range = -0.12∼-0.48, PFDR < 0.05).

CONCLUSION

The sex disparities, age trajectories of brain structure and functions as well as the coupling of NVU in healthy individuals provide insights into normal aging which are potential targets for study of pathological conditions.

Animal Models of Human Pathology: Revision, Relevance and Refinements

Animal Models of Human Pathology [...].

Inflammatory injury induces pain sensitization that is expressed beyond the site of injury in male (and not in female) mice

Pain is a crucial protective mechanism for the body. It alerts us to potential tissue damage or injury and promotes the avoidance of harmful stimuli. Injury-induced inflammation and tissue damage lead to pain sensitization, which amplifies responses to subsequent noxious stimuli even after an initial primary injury has recovered. This phenomenon, commonly referred to as hyperalgesic priming, was investigated in male and female mice to determine whether it is specific to the site of previous injury. We used 10μl of 50 % Freund's complete adjuvant (CFA) administered to the left hind paw as a model of peripheral injury. Both male and female mice exhibited robust site-specific mechanical hypersensitivity after CFA, which resolved within one-week post-injection. After injury resolution, only male CFA-primed mice showed enhanced and prolonged mechanical sensitivity in response to a chemical challenge or a single 0.5 mA electric footshock. Among CFA-primed male mice, shock-induced mechanical hypersensitivity was expressed in both the left (previously injured) and the right (uninjured) hind paws, suggesting a pivotal role for altered centralized processes in the expression of pain sensitization. These findings indicate that pain history regulates sensory responses to subsequent mechanical and chemical pain stimuli in a sex-specific manner-foot-shock-induced hyperalgesic priming expression among male mice generalized beyond the initial injury site.

Female rodents in behavioral neuroscience: Narrative review on the methodological pitfalls

Since the NIH 'Sex as biological variable' policy, the percentage of studies including female subjects have increased largely. Nonetheless, many researchers fail to adequate their protocols to include females. In this narrative review, we aim to discuss the methodological pitfalls of the inclusion of female rodents in behavioral neuroscience. We address three points to consider in studies: the manipulations conducted only in female animals (such as estrous cycle monitoring, ovariectomy, and hormone replacement), the consideration of males as the standard, and biases related to interpretation and publication of the results. In addition, we suggest guidelines and perspectives for the inclusion of females in preclinical research.

Hemispheric asymmetries in borderline personality disorder: a systematic review

Borderline personality disorder (BPD) is characterized by increased mood reactivity and affective instability. Since core structures involved in emotion processing, such as the amygdala, demonstrate strong lateralization, BPD is an interesting target for laterality research. So far, a systematic integration of findings on lateralization in BPD is missing. Therefore, we systematically reviewed studies published until February 2024 in PubMed, Web of Science, and PsycInfo databases that measured hemispheric asymmetries and behavioral lateralization in patients with BPD. Inclusion criteria were (a) diagnosis of BPD and (b) results on hemispheric or behavioral asymmetries. Specifically for neuroimaging studies, hemispheres need to be assessed separately. Review articles and studies with disorders other than BPD were excluded. Risk of bias was assessed with the Newcastle Ottawa Scale for non-randomized, non-comparative intervention studies. A total of 21 studies met the inclusion criteria. Thirteen studies investigated structural hemispheric asymmetries, five functional hemispheric asymmetries, two examined handedness, and one studied hemispheric asymmetry in visuospatial attention. Overall, studies examining structural asymmetries in BPD report bilateral volume reduction in the amygdala and hippocampus but a right-sided reduction in the orbitofrontal cortex. For functional lateralization, asymmetrical de/activation patterns in the default mode network in BPD and reduced right-frontal asymmetry were evident. Also, studies indicate a trend towards increased non-right-handedness in BPD. Risk factors for BPD, such as childhood abuse, may play a crucial role in the development of structural and functional alterations. However, the generalization of results may be limited by small sample sizes and varying study designs.

Behavioral neuroscience's inevitable SABV growing pains

The field of rodent behavioral neuroscience is undergoing two major sea changes: an ever-growing technological revolution, and worldwide calls to consider sex as a biological variable (SABV) in experimental design. Both have enormous potential to improve the precision and rigor with which the brain can be studied, but the convergence of these shifts in scientific practice has exposed critical limitations in classic and widely used behavioral paradigms. While our tools have advanced, our behavioral metrics - mostly developed in males and often allowing for only binary outcomes - have not. This opinion article explores how this disconnect has presented challenges for the accurate depiction and interpretation of sex differences in brain function, arguing for the expansion of current behavioral constructs to better account for behavioral diversity.

Analysis of Spontaneously Reported Adverse Drug Events: Towards Developing Systems for Preventability

Background: Analysing data on adverse drug reactions (ADRs) in health facilities is an essential step to help develop effective strategies to reduce their incidence. The objective was to analyse spontaneous ADR reports sent to the Ghanaian Food and Drugs Authority (FDA) by two reporting health facilities over 5 years. Methods: Data from duplicate spontaneous ADR reports sent to the FDA (Ghana) from 2014 to 2018 were extracted. The relationship between independent variables such as age, sex, and source of drugs and ADR outcomes was assessed with either chi-square or a Cramer's V test for association where appropriate. Results: Type A reactions (65.2%) were the most prevalent of the ADRs, followed by Type B (34.1%), with the majority (80%) of patients affected recovering fully. The majority of Type A reactions (54.1%) occurred in the clinic, while the majority of Type B reactions (43.5%) occurred in the hospital. The skin and central nervous system (CNS) were the most affected (70.8%) organs. A higher incidence of CNS and skin-related ADRs was recorded in patients older than 30 (RR = 1.28 (1.07-1.53)). Also, females were more likely to experience a CNS-related ADR. The seriousness of the ADR was found to be significantly associated with the (1) type of prescriber, (2) whether the drug was prescribed, or (3) whether the drug regimen prescribed was appropriate. Even though, in 86% of cases, the offending drug was withdrawn within the first 5 days, it exceeded 20 days in about 6% of cases. The record of allergy status in a patient's folder and the source of the drug were significantly associated with the chance that the offending drug was withdrawn. However, recording ADRs did not influence whether the offending drug was stopped. Conclusion: Most of the ADRs experienced by patients could be avoided if the current systems are improved to prevent the rechallenge of offending drugs. Efforts to improve and update patient medication records and steps to ensure continuity of care are essential in preventing these adverse drug events.

Sex differences in patterns of white matter neuroplasticity after balance training in young adults

Introduction

In past work we demonstrated different patterns of white matter (WM) plasticity in females versus males associated with learning a lab-based unilateral motor skill. However, this work was completed in neurologically intact older adults. The current manuscript sought to replicate and expand upon these WM findings in two ways: (1) we investigated biological sex differences in neurologically intact young adults, and (2) participants learned a dynamic full-body balance task.

Methods

24 participants (14 female, 10 male) participated in the balance training intervention, and 28 were matched controls (16 female, 12 male). Correlational tractography was used to analyze changes in WM from pre- to post-training.

Results

Both females and males demonstrated skill acquisition, yet there were significant differences in measures of WM between females and males. These data support a growing body of evidence suggesting that females exhibit increased WM neuroplasticity changes relative to males despite comparable changes in motor behavior (e.g., balance).

Discussion

The biological sex differences reported here may represent an important factor to consider in both basic research (e.g., collapsing across females and males) as well as future clinical studies of neuroplasticity associated with motor function (e.g., tailored rehabilitation approaches).

Integration of sex/gender and utilization of ecological Momentary assessment of cognition in clinical populations: A scoping review

Objectives: We aimed to describe the methods of smartphone-based cognitive ecological momentary assessment designs in clinical populations, with an intention to evaluate how the role of sex and/or gender has been considered in the design and analyses, particularly including female-specific physiology. Methods: This scoping review was conducted based on JBI scoping review methodology. On March 2nd, 2023, we searched for literature across four databases. Screening of the results and data extraction were conducted in duplicate according to the a priori methods in the pre-registered protocol. Results: 31 articles were included in this review. Participants ranged in age from 15-85 years old with various clinical disorders. Prompts were given between 1-7 times per day for 7-84 days. Executive function was the most frequently assessed cognitive domain. Over half the studies (n = 17, 55%) did not investigate the effects of sex and/or gender, and only one study considered the impact of hormonal therapy. Many studies (n = 14, 45%) used sex and gender interchangeably or incorrectly. Conclusions: Studies varied in design, with heterogeneity in the reporting of methodological information. The lack of attention to sex/gender on neuropsychological outcomes can lead to confusion and contradiction regarding its potential impact on cognition in clinical populations. This may hinder the identification of effective interventions for those assigned female at birth who have been overlooked or considered indistinguishable from their male counterparts. Given the well-documented impact of sex/gender on cognition, it is essential that future neuropsychological research, especially EMA-based studies, prioritize investigating sex/gender to ensure better outcomes for all.

Sex-dependent differences in vulnerability to early risk factors for posttraumatic stress disorder: results from the AURORA study

BACKGROUND

Knowledge of sex differences in risk factors for posttraumatic stress disorder (PTSD) can contribute to the development of refined preventive interventions. Therefore, the aim of this study was to examine if women and men differ in their vulnerability to risk factors for PTSD.

METHODS

As part of the longitudinal AURORA study, 2924 patients seeking emergency department (ED) treatment in the acute aftermath of trauma provided self-report assessments of pre- peri- and post-traumatic risk factors, as well as 3-month PTSD severity. We systematically examined sex-dependent effects of 16 risk factors that have previously been hypothesized to show different associations with PTSD severity in women and men.

RESULTS

Women reported higher PTSD severity at 3-months post-trauma. Z-score comparisons indicated that for five of the 16 examined risk factors the association with 3-month PTSD severity was stronger in men than in women. In multivariable models, interaction effects with sex were observed for pre-traumatic anxiety symptoms, and acute dissociative symptoms; both showed stronger associations with PTSD in men than in women. Subgroup analyses suggested trauma type-conditional effects.

CONCLUSIONS

Our findings indicate mechanisms to which men might be particularly vulnerable, demonstrating that known PTSD risk factors might behave differently in women and men. Analyses did not identify any risk factors to which women were more vulnerable than men, pointing toward further mechanisms to explain women's higher PTSD risk. Our study illustrates the need for a more systematic examination of sex differences in contributors to PTSD severity after trauma, which may inform refined preventive interventions.

ComBatLS: A location- and scale-preserving method for multi-site image harmonization

Recent work has leveraged massive datasets and advanced harmonization methods to construct normative models of neuroanatomical features and benchmark individuals' morphology. However, current harmonization tools do not preserve the effects of biological covariates including sex and age on features' variances; this failure may induce error in normative scores, particularly when such factors are distributed unequally across sites. Here, we introduce a new extension of the popular ComBat harmonization method, ComBatLS, that preserves biological variance in features' locations and scales. We use UK Biobank data to show that ComBatLS robustly replicates individuals' normative scores better than other ComBat methods when subjects are assigned to sex-imbalanced synthetic "sites". Additionally, we demonstrate that ComBatLS significantly reduces sex biases in normative scores compared to traditional methods. Finally, we show that ComBatLS successfully harmonizes consortium data collected across over 50 studies. R implementation of ComBatLS is available at https://github.com/andy1764/ComBatFamily.

Cyclosorus Terminans Extract Alleviates Neuroinflammation in Insulin Resistant Rats

High-fat diet consumption for an extended period causes obesity, systemic metabolic disturbance, and brain insulin resistance, resulting in neuroinflammation. Although the beneficial effect of Cyclosorus terminans extract on obesity-related insulin resistance has been demonstrated, little is known about how it affects neuroinflammation and brain insulin resistance in obese rats. Male Wistar rats were given either a normal diet (ND, n = 6) or a high-fat diet (HFD, n = 24) for a total of 14 weeks. At the beginning of the week, 13 rats in the ND group were given vehicle orally for 2 weeks, while rats on HFD diets were randomized to one of four groups and given either vehicle, 100 mg/kg/day of Cyclosorus terminans extract, 200 mg/kg/day of Cyclosorus terminans extract, or 20 mg/kg/day of pioglitazone orally for 2 weeks. After the experimental period, blood and brain samples were taken to assess metabolic and brain parameters. HFD-fed rats had obesity, systemic and brain insulin resistance, brain inflammation, microglial and astrocyte hyperactivity, and brain necroptosis. Treatment with 200 mg/kg/day of Cyclosorus terminans extract and pioglitazone equally attenuated obesity, insulin resistance, brain insulin dysfunction, and neuroinflammation in insulin resistant rats. Our findings suggest that Cyclosorus terminans extract may hold promise as a therapeutic agent for insulin resistance and neuroinflammation in obese conditions.

Handedness in Alzheimer Disease: A Systematic Review

Handedness has been a topic of scientific interest for many years. However, false and misleading ideas have dominated this field with a still limited amount of research into the association with clinical disorders like Alzheimer disease (AD). In accordance with PRISMA guidelines, PubMed, Embase, and Cochrane Library were searched for studies regarding the association of handedness and AD. Twelve articles were included. Case-control studies show that left-handedness is not a risk factor for late-onset AD (LOAD). However, nonright handedness was found to be more prevalent in patients with early-onset AD (EOAD). Moreover, handedness does not seem to affect neuropsychological performance. We also show that collapsing versus separating mixed and left-handedness may yield different results. Future research on the relation between handedness and AD may provide new insight into disease pathogenesis, improve rehabilitation, and help identify patients who will progress, aiding the design of prevention trials.

The Promise and Practicality of Addressing Sex as a Biological Variable and the Ovarian Cycle in Preclinical Epilepsy Research

Seizures and epilepsy affect people of all sexes and genders. In the last several years, funding agency initiatives such as the U.S. National Institutes of Health policy on sex as a biological variable (SABV) have intended to encourage researchers to study both males and females from cell to tissue to organism and analyze and report the resulting data with sex as a factor. Preclinical epilepsy research, however, continues to be plagued by confusion regarding both the SABV policy and its implementation, reflecting similar beliefs in the larger neuroscience research community. This article aims to address some common misconceptions and provide practical tools and suggestions for preclinical epilepsy researchers in implementing SABV and analysis of the female ovarian cycle (estrous cycle in rodents) in their research programs, with a focus on studies using rodent models. Examples of recent publications in preclinical epilepsy research highlighting the value of incorporating SABV and information on the estrous cycle are included. The specifics of how best to address SABV and the estrous cycle can vary depending on the needs and goals of a particular research program, but an embrace of these physiological factors by the preclinical epilepsy research community promises to yield more rigorous research and improved treatment strategies for all people with epilepsy.

Female obesity: clinical and psychological assessment toward the best treatment

Obesity is a heterogeneous condition which results from complex interactions among sex/gender, sociocultural, environmental, and biological factors. Obesity is more prevalent in women in most developed countries, and several clinical and psychological obesity complications show sex-specific patterns. Females differ regarding fat distribution, with males tending to store more visceral fat, which is highly correlated to increased cardiovascular risk. Although women are more likely to be diagnosed with obesity and appear more motivated to lose weight, as confirmed by their greater representation in clinical trials, males show better outcomes in terms of body weight and intra-abdominal fat loss and improvements in the metabolic risk profile. However, only a few relatively recent studies have investigated gender differences in obesity, and sex/gender is rarely considered in the assessment and management of the disease. This review summarizes the evidence of gender differences in obesity prevalence, contributing factors, clinical complications, and psychological challenges. In addition, we explored gender differences in response to obesity treatments in the specific context of new anti-obesity drugs.

Chronic variable stress leads to sex specific gut microbiome alterations in mice

Stress has been implicated in the incidence and severity of psychiatric and gastrointestinal disorders. The immune system is capable of modulating the activity and composition of the gut following stress and vice versa. In this study we sought to examine the sequential relationship between immune signaling and microbiome composition occurring in male and female mice over time using a variable stress paradigm. Tissue was collected prior to, during, and after the stress paradigm from the same mice. Cytokines from plasma and brain were quantified using a multiplexed cytokine assay. Fecal samples were collected at the same timepoints and 16S rRNA amplicon sequencing was performed to determine the relative abundance of microbiota residing in the guts of stressed and control mice. We found sex differences in the response of the gut microbiota to stress following 28 days of chronic variable stress but not 6 days of sub-chronic variable stress. Immune activation was quantified in the nucleus accumbens immediately following Sub-chronic variable when alterations of gut composition had not yet occurred. In both sexes, 28 days of stress induced significant changes in the proportion of Erysipelotrichaceae and Lactobacillaceae, but in opposite directions for male and female mice. Alterations to the gut microbiome in both sexes were associated with changes in cytokines related to eosinophilic immune activity. Our use of an animal stress model reveals the immune mechanisms that may underly changes in gut microbiome composition during and after stress. This study reveals potential drug targets and microbiota of interest for the intervention of stress related conditions.

Disentangling sex differences in PTSD risk factors

Despite extensive research on sex/gender differences in posttraumatic stress disorder (PTSD), underlying mechanisms are still not fully understood. Here we present a systematic overview of three sex/gender-related risk pathways. We assessed 16 risk factors as well as 3-month PTSD severity in a prospective cohort study (n=2924) of acutely traumatized individuals and investigated potential mediators in the pathway between sex assigned at birth and PTSD severity using multiple mediation analysis with regularization. Six risk factors were more prevalent/severe in women, and none were more pronounced in men. Analyses showed that acute stress disorder, neuroticism, lifetime sexual assault exposure, anxiety sensitivity, and pre-trauma anxiety symptoms fully mediated and uniquely contributed to the relationship between sex assigned at birth and PTSD severity. Our results demonstrate different risk mechanisms for women and men. Such knowledge can inform targeted interventions. Our systematic approach to differential risk pathways can be transferred to other mental disorders to guide sex- and gender-sensitive mental health research.

Training in the implementation of sex and gender research policies: an evaluation of publicly available online courses

BACKGROUND

Recently implemented research policies requiring the inclusion of females and males have created an urgent need for effective training in how to account for sex, and in some cases gender, in biomedical studies.

METHODS

Here, we evaluated three sets of publicly available online training materials on this topic: (1) Integrating Sex & Gender in Health Research from the Canadian Institutes of Health Research (CIHR); (2) Sex as a Biological Variable: A Primer from the United States National Institutes of Health (NIH); and (3) The Sex and Gender Dimension in Biomedical Research, developed as part of "Leading Innovative measures to reach gender Balance in Research Activities" (LIBRA) from the European Commission. We reviewed each course with respect to their coverage of (1) What is required by the policy; (2) Rationale for the policy; (3) Handling of the concepts "sex" and "gender;" (4) Research design and analysis; and (5) Interpreting and reporting data.

RESULTS

All three courses discussed the importance of including males and females to better generalize results, discover potential sex differences, and tailor treatments to men and women. The entangled nature of sex and gender, operationalization of sex, and potential downsides of focusing on sex more than other sources of variation were minimally discussed. Notably, all three courses explicitly endorsed invalid analytical approaches that produce bias toward false positive discoveries of difference.

CONCLUSIONS

Our analysis suggests a need for revised or new training materials that incorporate four major topics: precise operationalization of sex, potential risks of over-emphasis on sex as a category, recognition of gender and sex as complex and entangled, and rigorous study design and data analysis.

Sex differences in anhedonia in bipolar depression: a resting-state fMRI study

Previous studies about anhedonia symptoms in bipolar depression (BD) ignored the unique role of gender on brain function. This study aims to explore the regional brain neuroimaging features of BD with anhedonia and the sex differences in these patients. The resting-fMRI by applying fractional amplitude of low-frequency fluctuation (fALFF) method was estimated in 263 patients with BD (174 high anhedonia [HA], 89 low anhedonia [LA]) and 213 healthy controls. The effects of two different factors in patients with BD were analyzed using a 3 (group: HA, LA, HC) × 2 (sex: male, female) ANOVA. The fALFF values were higher in the HA group than in the LA group in the right medial cingulate gyrus and supplementary motor area. For the sex-by-group interaction, the fALFF values of the right hippocampus, left medial occipital gyrus, right insula, and bilateral medial cingulate gyrus were significantly higher in HA males than in LA males but not females. These results suggested that the pattern of high activation could be a marker of anhedonia symptoms in BD males, and the sex differences should be considered in future studies of BD with anhedonia symptoms.

From means to meaning in the study of sex/gender differences and similarities

The incorporation of sex and gender (S/G) related factors is commonly acknowledged as a necessary step to advance towards more personalized diagnoses and treatments for somatic, psychiatric, and neurological diseases. Until now, most attempts to integrate S/G-related factors have been reduced to identifying average differences between females and males in behavioral/ biological variables. The present commentary questions this traditional approach by highlighting three main sets of limitations: 1) Issues stemming from the use of classic parametric methods to compare means; 2) challenges related to the ability of means to accurately represent the data within groups and differences between groups; 3) mean comparisons impose a results' binarization and a binary theoretical framework that precludes advancing towards precision medicine. Alternative methods free of these limitations are also discussed. We hope these arguments will contribute to reflecting on how research on S/G factors is conducted and could be improved.

Sex differences in multiple sclerosis relapse presentation and outcome: a retrospective, monocentric study of 134 relapse events

Background

Reporting of sex-specific analyses in multiple sclerosis (MS) is sparse. Disability accrual results from relapses (relapse-associated worsening) and independent thereof (progression independent of relapses).

Objectives

A population of MS patients during relapse treated per standard of care was analyzed for sex differences and short-term relapse outcome (3-6 months) as measured by Expanded Disability Status Scale (EDSS) change.

Design

Single-center retrospective study.

Methods

We analyzed 134 MS relapses between March 2016 and August 2020. All events required relapse treatment (steroids and/or plasma exchange). Demographic, disease, and paraclinical characteristics [cerebrospinal fluid (CSF) and magnetic resonance imaging (MRI)] were displayed separated by sex. Multivariable linear regression was run to identify factors associated with short-term EDSS change.

Results

Mean age at relapse was 38.4 years (95% confidence interval: 36.3-40.4) with a proportion of 71.6% women in our cohort. Smoking was more than twice as prevalent in men (65.8%) than women (32.3%). In- and after-relapse EDSSs were higher in men [men: 3.3 (2.8-3.9), women: 2.7 (2.4-3.0); men: 3.0 (1.3-3.6); women: 1.8 (1.5-2.1)] despite similar relapse intervention. Paraclinical parameters revealed no sex differences. Our primary model identified female sex, younger age, and higher EDSS at relapse to be associated with EDSS improvement. A higher immunoglobulin G (IgG) quotient (CSF/serum) was associated with poorer short-term outcome [mean days between first relapse treatment and last EDSS assessment 130.2 (79.3-181.0)].

Conclusion

Sex and gender differences are important in outcome analyses of MS relapses. Effective treatment regimens need to respect putative markers for a worse outcome to modify long-term prognosis such as clinical and demographic variables, complemented by intrathecal IgG synthesis. Prospective trials should be designed to address these differences and confirm our results.

Sex contextualism in laboratory research: Enhancing rigor and precision in the study of sex-related variables

Understanding sex-related variation in health and illness requires rigorous and precise approaches to revealing underlying mechanisms. A first step is to recognize that sex is not in and of itself a causal mechanism; rather, it is a classification system comprising a set of categories, usually assigned according to a range of varying traits. Moving beyond sex as a system of classification to working with concrete and measurable sex-related variables is necessary for precision. Whether and how these sex-related variables matter-and what patterns of difference they contribute to-will vary in context-specific ways. Second, when researchers incorporate these sex-related variables into research designs, rigorous analytical methods are needed to allow strongly supported conclusions. Third, the interpretation and reporting of sex-related variation require care to ensure that basic and preclinical research advance health equity for all.

Track-by-Day: A standardized approach to estrous cycle monitoring in biobehavioral research

Despite known sex differences in brain function, female subjects are underrepresented in preclinical neuroscience research. This is driven in part by concerns about variability arising from estrous cycle-related hormone fluctuations, especially in fear- and anxiety-related research where there are conflicting reports as to whether and how the cycle influences behavior. The inconsistency may arise from a lack of common standards for tracking and reporting the cycle as opposed to inherent unpredictability in the cycle itself. The rat estrous cycle is conventionally tracked by assigning vaginal cytology smears to one of four qualitatively-defined stages. Although the cytology stages are of unequal length, the stage names are often, but not always, used to refer to the four cycle days. Subjective staging criteria and inconsistent use of terminology are not necessarily a problem in research on the cycle itself, but can lead to irreproducibility in neuroscience studies that treat the stages as independent grouping factors. We propose the explicit use of cycle days as independent variables, which we term Track-by-Day to differentiate it from traditional stage-based tracking, and that days be indexed to the only cytology feature that is a direct and rapid consequence of a hormonal event: a cornified cell layer formed in response to the pre-ovulatory 17β-estradiol peak. Here we demonstrate that cycle length is robustly regular with this method, and that the method outperforms traditional staging in detecting estrous cycle effects on Pavlovian fear conditioning and on a separate proxy for hormonal changes, uterine histology.

Investigating female versus male differences in white matter neuroplasticity associated with complex visuo-motor learning

Magnetic resonance imaging (MRI) has increasingly been used to characterize structure-function relationships during white matter neuroplasticity. Biological sex differences may be an important factor that affects patterns of neuroplasticity, and therefore impacts learning and rehabilitation. The current study examined a participant cohort before and after visuo-motor training to characterize sex differences in microstructural measures. The participants (N = 27) completed a 10-session (4 week) complex visuo-motor training task with their non-dominant hand. All participants significantly improved movement speed and their movement speed variability over the training period. White matter neuroplasticity in females and males was examined using fractional anisotropy (FA) and myelin water fraction (MWF) along the cortico-spinal tract (CST) and the corpus callosum (CC). FA values showed significant differences in the middle portion of the CST tract (nodes 38-51) across the training period. MWF showed a similar cluster in the inferior portion of the tract (nodes 18-29) but did not reach significance. Additionally, at baseline, males showed significantly higher levels of MWF measures in the middle body of the CC. Combining data from females and males would have resulted in reduced sensitivity, making it harder to detect differences in neuroplasticity. These findings offer initial insights into possible female versus male differences in white matter neuroplasticity during motor learning. This warrants investigations into specific patterns of white matter neuroplasticity for females versus males across the lifespan. Understanding biological sex-specific differences in white matter neuroplasticity may have significant implications for the interpretation of change associated with learning or rehabilitation.

Recommendations for a Better Understanding of Sex and Gender in the Neuroscience of Mental Health

There are prominent sex/gender differences in the prevalence, expression, and life span course of mental health and neurodiverse conditions. However, the underlying sex- and gender-related mechanisms and their interactions are still not fully understood. This lack of knowledge has harmful consequences for those with mental health problems. Therefore, we set up a cocreation session in a 1-week workshop with a multidisciplinary team of 25 researchers, clinicians, and policy makers to identify the main barriers in sex and gender research in the neuroscience of mental health. Based on this work, here we provide recommendations for methodologies, translational research, and stakeholder involvement. These include guidelines for recording, reporting, analysis beyond binary groups, and open science. Improved understanding of sex- and gender-related mechanisms in neuroscience may benefit public health because this is an important step toward precision medicine and may function as an archetype for studying diversity.

Consideration of sex as a biological variable in diabetes research across twenty years

BACKGROUND

Sex differences exist in the risk of developing type 1 and type 2 diabetes, and in the risk of developing diabetes-associated complications. Sex differences in glucose homeostasis, islet and β cell biology, and peripheral insulin sensitivity have also been reported. Yet, we lack detailed information on the mechanisms underlying these differences, preventing the development of sex-informed therapeutic strategies for persons living with diabetes. To chart a path toward greater inclusion of biological sex as a variable in diabetes research, we first need a detailed assessment of common practices in the field.

METHODS

We developed a scoring system to evaluate the inclusion of biological sex in manuscripts published in Diabetes, a journal published by the American Diabetes Association. We chose Diabetes as this journal focuses solely on diabetes and diabetes-related research, and includes manuscripts that use both clinical and biomedical approaches. We scored papers published across 3 years within a 20-year period (1999, 2009, 2019), a timeframe that spans the introduction of funding agency and journal policies designed to improve the consideration of biological sex as a variable.

RESULTS

Our analysis showed fewer than 15% of papers used sex-based analysis in even one figure across all study years, a trend that was reproduced across journal-defined categories of diabetes research (e.g., islet studies, signal transduction). Single-sex studies accounted for approximately 40% of all manuscripts, of which > 87% used male subjects only. While we observed a modest increase in the overall inclusion of sex as a biological variable during our study period, our data highlight significant opportunities for improvement in diabetes research practices. We also present data supporting a positive role for journal policies in promoting better consideration of biological sex in diabetes research.

CONCLUSIONS

Our analysis provides significant insight into common practices in diabetes research related to the consideration of biological sex as a variable. Based on our analysis we recommend ways that diabetes researchers can improve inclusion of biological sex as a variable. In the long term, improved practices will reveal sex-specific mechanisms underlying diabetes risk and complications, generating knowledge to enable the development of sex-informed prevention and treatment strategies.

Sex and Gender Publications in Brain Health: A Mapping Review of the Asia-Pacific Region

INTRODUCTION

Reporting of sex and gender analysis in medical research has been shown to improve quality of the science and ensure findings are applicable to women and men. There is conflicting evidence on whether efforts by funding agencies and medical journals to encourage reporting of sex and gender analysis have resulted in tangible improvements. This study mapped the inclusion of sex and gender analysis in stroke and dementia research conducted in the Asia-Pacific region.

METHODS

A systematic search for Asia-Pacific stroke and dementia research was conducted in PubMed and papers included from the period 2012 to 2022. Eligible studies were reviewed for inclusion of a primary sex or gender focus and categorized by type of sex and gender analysis. Author gender was determined using an algorithm and its associations with inclusion of sex and gender analysis were examined.

RESULTS

Total Asia-Pacific publications increased from 109 in 2012 to 313 in 2022, but the rate of studies with a primary sex or gender focus did not increase significantly (R2 = 0.06, F(1, 9) = 0.59, p = 0.46). Australia, China, India, Japan, and South Korea produced the most publications over the study period and were the only countries with at least 50 publications. The impact of author gender was mixed, with female first authorship associated with inclusion of sex or gender analysis and last female authorship associated with studies having a primary sex or gender focus.

CONCLUSIONS

In the Asia-Pacific, brain health research is currently centred around high-income countries, and efforts are needed to ensure research findings are applicable throughout the region. While there was a general increase in brain health publications over the last decade, the rate of sex and gender analysis was unchanged. This demonstrates that even with efforts in some countries in place, there is currently a lack of progress in the Asia-Pacific region to produce more research focussing on sex and gender analysis.

Neuroimmune Activation and Microglia Reactivity in Female Rats Following Alcohol Dependence

The rates of alcohol use disorder among women are growing, yet little is known about how the female brain is affected by alcohol. The neuroimmune system, and specifically microglia, have been implicated in mediating alcohol neurotoxicity, but most preclinical studies have focused on males. Further, few studies have considered changes to the microglial phenotype when examining the effects of ethanol on brain structure and function. Therefore, we quantified microglial reactivity in female rats using a binge model of alcohol dependence, assessed through morphological and phenotypic marker expression, coupled with regional cytokine levels. In a time- and region-dependent manner, alcohol altered the microglial number and morphology, including the soma and process area, and the overall complexity within the corticolimbic regions examined, but no significant increases in the proinflammatory markers MHCII or CD68 were observed. The majority of cytokine and growth factor levels examined were similarly unchanged. However, the expression of the proinflammatory cytokine TNFα was increased, and the anti-inflammatory IL-10, decreased. Thus, female rats showed subtle differences in neuroimmune reactivity compared to past work in males, consistent with reports of enhanced neuroimmune responses in females across the literature. These data suggest that specific neuroimmune reactions in females may impact their susceptibility to alcohol neurotoxicity and other neurodegenerative events with microglial contributions.

Early modulation of the gut microbiome by female sex hormones alters amyloid pathology and microglial function

It is well-established that women are disproportionately affected by Alzheimer's disease. The mechanisms underlying this sex-specific disparity are not fully understood, but several factors that are often associated-including interactions of sex hormones, genetic factors, and the gut microbiome-likely contribute to the disease's etiology. Here, we have examined the role of sex hormones and the gut microbiome in mediating Aβ amyloidosis and neuroinflammation in APPPS1-21 mice. We report that postnatal gut microbiome perturbation in female APPPS1-21 mice leads to an elevation in levels of circulating estradiol. Early stage ovariectomy (OVX) leads to a reduction of plasma estradiol that is correlated with a significant alteration of gut microbiome composition and reduction in Aβ pathology. On the other hand, supplementation of OVX-treated animals with estradiol restores Aβ burden and influences gut microbiome composition. The reduction of Aβ pathology with OVX is paralleled by diminished levels of plaque-associated microglia that acquire a neurodegenerative phenotype (MGnD-type) while estradiol supplementation of OVX-treated animals leads to a restoration of activated microglia around plaques. In summary, our investigation elucidates the complex interplay between sex-specific hormonal modulations, gut microbiome dynamics, metabolic perturbations, and microglial functionality in the pathogenesis of Alzheimer's disease.

Emerging Subspecialties in Neurology: Women's Neurology

The influence of sex and gender on neurologic disease has become increasingly recognized in science and medicine. This is evident across a woman's lifespan especially during periods of hormonal transitions. Leaders in neurology have advocated for the importance of sex and gender-enriched clinical care, education, and research. The scope of women's neurology spans across a woman's life including puberty, adolescence, peripartum care, menopause, and aging. Women's neurology is a new subspecialty that aligns with a specific patient population and intersects with established neurology subspecialties and other specialties such as obstetrics, maternal fetal medicine, endocrinology, and psychiatry. Its establishment and collaboration with existing and emerging fields enables a more comprehensive approach to neurologic illness through the lens of sex and gender. Women's neurology is rapidly evolving through increased focus at academic centers, including expanded women's neurology curricula, dedicated women's neurology fellowship programs, improved understanding of sex and gender issues in neurosciences, and expansion of therapeutic options. Herein, we describe the history of the women's neurology field, emerging need for women's neurology specialists, information about training and career opportunities, and future directions.