X chromosome inactivation (XCI) is a female-specific process in which one X chromosome is silenced to balance X-linked gene expression between the sexes. XCI is initiated in early development by upregulation of the lncRNA Xist on the future inactive X (Xi). A subset of X-linked genes escape silencing and thus have higher expression in females, suggesting female-specific functions. One of these genes is the highly conserved gene Kdm6a, which encodes a histone demethylase that removes methyl groups at H3K27 to facilitate gene expression. KDM6A mutations have been implicated in congenital disorders such as Kabuki Syndrome, as well as in sex differences in development and cancer.

Apolipoprotein E4 (ApoE4) is associated with an increased risk of Alzheimer's disease (AD), depression, and anxiety, which were reported to improve after the administration of metformin. However, sex influence on the effect of ApoE4 and metformin on cognition and mental health is poorly understood.

Presentations and outcomes of acute myocardial infarction (MI) differ between women and men, with the worst outcomes being reported in younger women. Mental stress induced ischemia and sympathetic activation have been suggested to play a prominent role in the pathogenesis of MI in younger women, however, the impact of sex hormones on these parameters remains unknown.

As the earliest measure of social communication in rodents, ultrasonic vocalizations (USVs) in response to maternal separation are critical in preclinical research on neurodevelopmental disorders (NDDs). While sex differences in both USV production and behavioral outcomes are reported, many studies overlook sex as a biological variable in preclinical NDD models. We aimed to evaluate sex differences in USV call parameters and determine if USVs are differently impacted based on sex in the preclinical maternal immune activation (MIA) model. Results indicate that sex differences in USVs vary with developmental stage and are more pronounced in MIA offspring. Specifically, developmental stage is a moderator of sex differences in USV call duration, with control females emitting longer calls than males in early development (up to postnatal day [PND] 8), but this pattern reverses after PND8. MIA leads to a reduction in call numbers for females compared to same-sex controls in early development, with a reversal post-PND8. MIA decreased call duration and increased total call duration in males, but unlike females, developmental stage did not influence these differences. In males, MIA effects varied by species, with decreased call numbers in rats but increased call numbers in mice. MIA timing (gestational day ≤ 12.5 vs. > 12.5) did not significantly affect results. Our findings highlight the importance of considering sex, developmental timing, and species in USVs research. We discuss how analyzing USV call types and incorporating sex as a biological variable can enhance our understanding of neonatal ultrasonic communication and its translational value in NDD research.

The global incidence of obesity continues to rise, which increases the prevalence of metabolic diseases. We previously demonstrated the beneficial effect of adipose-specific growth hormone receptor (Ghr) knockout (KO) on metabolic parameters in male mice exposed to high fat diet. Although the effect of the growth hormone (GH) axis on lipid metabolism has been well studied, sexual dimorphism has not been considered. Furthermore, the effects of the GH axis on intergenerational adipose development are understudied. The present study aimed to evaluate whether adipose-specific Ghr knockout is associated with sex-specific differences in metabolic health of female offspring.

In humans, the X and Y chromosomes determine the biological sex, XX specifying for females and XY for males. The long noncoding RNA X-inactive specific transcript (lncRNA XIST) plays a crucial role in the process of X chromosome inactivation (XCI) in cells of the female, a process that ensures the balanced expression of X-linked genes between sexes. Initially, it was believed that XIST can be expressed only from the inactive X chromosome (Xi) and is considered a typically female-specific transcript. However, accumulating evidence suggests that XIST can be detected in male cells as well, and it participates in the development of cancers and other human diseases by regulating gene expression at epigenetic, chromatin remodeling, transcriptional, and translational levels. XIST is abnormally expressed in many sexually dimorphic diseases, including autoimmune and neurological diseases, pulmonary arterial hypertension (PAH), and some types of cancers. However, the underlying mechanisms are not fully understood. Escape from XCI and skewed XCI also contributes to sex-biased diseases and their severity. Interestingly, in humans, similar to experimental animal models of human disease, the males with the XIST gene activated display the sex-biased disease condition at a rate close to females, and significantly greater than males who had not been genetically modified. For instance, the men with supernumerary X chromosomes, such as men with Klinefelter syndrome (47, XXY), are predisposed toward autoimmunity similar to females (46, XX), and have increased risk for strongly female biased diseases, compared to 46, XY males. Interestingly, chromosome X content has been linked to a longer life span, and the presence of two chromosome X contributes to increased longevity regardless of the hormonal status. In this review, we summarize recent knowledge about XIST structure/function correlation and involvement in human disease with focus on XIST abnormal expression in males. Many human diseases show differences between males and females in penetrance, presentation, progression, and survival. In humans, the X and Y sex chromosomes determine the biological sex, XX specifying for females and XY for males. This numeric imbalance, two X chromosomes in females and only one in males, known as sex chromosome dosage inequality, is corrected in the first days of embryonic development by inactivating one of the X chromosomes in females. While this "dosage compensation" should in theory solve the difference in the number of genes between sexes, the expressed doses of X genes are incompletely compensated by X chromosome inactivation in females. In this review we try to highlight how abnormal expression and function of XIST, a gene on the X chromosome responsible for this inactivation process, may explain the sex differences in human health and disease. A better understanding of the molecular mechanisms of XIST participation in the male-female differences in disease is highly relevant since it would allow for improving the personalization of diagnosis and sex-specific treatment of patients.

The circadian clock integrates external environmental changes into the internal physiology of organisms. Perturbed circadian clocks due to misaligned light cycles increase the risk of diseases, including metabolic disorders. However, the effects of sex differences in this context remain unclear.

Women have a higher risk of developing osteoarthritis (OA) than men, including with obesity. To better understand this disparity, we investigated sex differences in metabolic and inflammatory factors associated with OA using a diet-induced mouse model of obesity. We hypothesized that 20 weeks of high-fat diet (HFD) would induce sexually dimorphic changes in both systemic and local risk factors of knee OA.

Obesity is a growing pandemic that increases the risk for cardiovascular diseases, type 2 diabetes, and particularly in women also the risk of cancer and neurodegenerative disorders such as dementia and multiple sclerosis. Preclinical studies on obesity focus on male mice as they gain bodyweight faster and show a clear pro-inflammatory phenotype. Here, using male and female mice, we induced obesity by feeding a high fat diet (HFD), and compared adipose tissue (AT) inflammation at the same adiposity stage (% AT/bodyweight) between both sexes. Doing so, we identified that female mice show an increase in the number of pro-inflammatory immune cells in the visceral AT at a lower adiposity stage than male mice, but the effect of HFD is diminished with higher adiposity. Interestingly, only female mice showed an increase in immune cells in the subcutaneous AT after HFD feeding. Nonetheless, we found that pro-inflammatory cytokines in blood plasma mirror the inflammatory stage of the visceral AT in both male and female mice. Uniquely in male mice, myeloid cells in the visceral AT showed a higher inflammasome activation upon HFD. In summary, we showed that adiposity differentially affects immune cells in fat depots based on sex.

Myocarditis is an inflammation of the heart muscle most often caused by viral infections. Sex differences in the immune response during myocarditis have been well described but upstream mechanisms in the heart that might influence sex differences in disease are not completely understood.

DNA methylation (DNAm) influences both sex differences and cancer development, yet the mechanisms connecting these factors remain unclear.

In vitro models serve as indispensable tools for advancing our understanding of biological processes, elucidating disease mechanisms, and establishing screening platforms for drug discovery. Kidneys play an instrumental role in the transport and elimination of drugs and toxins. Nevertheless, despite the well-documented inter-individual variability in kidney function and the multifaceted nature of renal diseases-spanning from their origin, trigger and which segment of the kidney is affected-to presentation, progression and prognosis, few studies take into consideration the variable of sex. Notably, the inherent disparities between female and male biology warrants a more comprehensive representation within in vitro models of the kidney. The omission of sex as a fundamental biological variable carries the substantial risk of overlooking sex-specific mechanisms implicated in health and disease, along with potential differences in drug responsiveness and toxicity profiles between sexes. This review emphasizes the importance of incorporating cellular, biological and functional sex-specific features of renal activity in health and disease in in vitro models. For that, we thoroughly document renal sex-specific features and propose a strategic experimental framework to integrate sex-based differences into human kidney in vitro models by outlining critical design criteria to elucidate sex-based features at cellular and tissue levels. The goal is to enhance the accuracy of models to unravel renal mechanisms, and improve our understanding of their impact on drug efficacy and safety profiles, paving the way for a more comprehensive understanding of patient-specific treatment modalities.

Smoking, particularly chronic smoking (CS), is a threat to global health, contributing to increased mortality and morbidity associated with cardiovascular disease (CVD). CS induces oxidative stress and endothelial dysfunction, which has a profound impact on cardiac structure and function. While the protective effects of estrogen, particularly 17β-estradiol (E2), on cardiovascular health are well-documented in premenopausal women, the interaction between estrogen and CS remains poorly understood. The aim of this study is to investigate the impact of chronic cigarette smoking on cardiac health in relation to ethinylestradiol (EE) oral contraceptive (OC) usage in premenopausal females. Female mice were exposed to chronic cigarette smoke and co-administered EE. Cardiac structural and functional parameters were assessed alongside inflammatory markers, oxidative stress indicators, and histological changes. Results revealed that the combination of EE and CS led to adverse cardiac remodeling characterized by increased left ventricular end-diastolic volume and elevated left ventricular mass. In addition, an inflammatory state was evident, marked by increased expression of IL-4, IL-1β, IL-13, IL-10, and PARP-1, as well as increased interstitial collagen deposition. These findings suggest a progression towards adverse cardiac remodeling resembling dilated cardiomyopathy. Furthermore, our observations highlight the complexity of the inflammatory response triggered by smoking, potentially exacerbated by estrogen supplementation. The main finding of this study is that the combination of CS and EE enhanced adverse cardiac remodeling, which was shown structurally, histologically, and biochemically.

Previous studies have found that the temporal duration required for males to perceive visual motion direction is significantly shorter than that for females. However, the neural correlates of such shortened duration perception remain yet unclear. Given that motion perception is primarily associated with the neural activity of the middle temporal visual complex (MT+), we here test the novel hypothesis that the neural mechanism of these behavioral sex differences is mainly related to the MT+ region.

Women comprise approximately half of the world's population, yet they are often underrepresented and inadequately considered in medical and public health research and in health care delivery in the United States and around the world. Elucidating sex and gender differences in disease and fundamental hormonal drivers of women's health is instrumental to informing our overall understanding of human health and improving women's health outcomes across the lifespan. The Society for Women's Health Research and ECH Alliance-The Global Health Connector hosted a women's health program as part of the United Nations 79th General Assembly Science Summit. Here, I briefly describe the basis for this convening to address global gender health gaps and reflect on the event's presentations and discussions to recognize and better integrate women's unique health needs in the sustainable development goals.

A-kinase anchoring protein 12 (AKAP12) is a key scaffolding protein that regulates cellular signaling by anchoring protein kinase A (PKA) and other signaling molecules. While recent studies suggest an important role for AKAP12 in the brain, including cognitive functions, its role in middle-aged mice and potential sex differences are not fully understood. Therefore, this study investigated the effects of AKAP12 on cognitive and exploratory behavior in middle-aged mice, focusing on sex differences. Cognitive function was assessed using the spontaneous Y-maze test and the novel object recognition test (NORT). No significant sex differences in cognitive function were found in middle-aged C57BL/6J mice; however, female mice showed greater exploratory behavior during the NORT. In addition, both middle-aged male and female Akap12 knockout (KO) mice performed similarly to wild-type (WT) mice in the Y-maze test, but had lower discrimination indices in the NORT, suggesting a potential role for AKAP12 in short-term memory. Notably, exploratory behavior was suppressed in female Akap12 KO mice compared to WT mice, whereas male Akap12 KO mice did not show this effect. There were no significant differences in movement distance and velocity during the Y-maze test and NORT between WT and KO mice of either sex. These results indicate that AKAP12 affects cognitive function and exploratory behavior in middle-aged mice and that these effects differ between sexes.

Hypertensive disorders of pregnancy (HDP) affect 2-8% of pregnancies and are associated postpartum with increased cardiovascular disease (CVD) risk, although mechanisms are poorly understood.

Sex and gender play important roles in contributing to disease and health outcomes and represent essential, but often overlooked, measures in biomedical research. The context-specific, multifaceted, and relational nature of gender norms, roles, and relations (i.e., gender dimensions) make their incorporation into biomedical research challenging. Gender scores-measures of gender dimensions-can help researchers incorporate gender into quantitative methodologies. These measures enable researchers to quantify the gendered dimensions of interest using data collected from survey respondents. To highlight the complexities of using gender scores within biomedical research, we used the application of the Bem Sex Role Inventory (BSRI) scale, a commonly used gender score, to explore gender differences in adverse events to the influenza vaccine among older adults (75+). Within this paper, we focus on the findings from our longitudinal gender score data collected over three influenza seasons (2019-20, 2020-21, and 2021-22), irrespective of adverse event data, to provide commentary on the reliability of gender scores, such as the BSRI, and the complexities of their application. Of the 162 total study participants included within the study, 69 were enrolled in all three consecutive seasons and 35 participants were enrolled in two consecutive seasons. The majority of participants had a different gender score in at least one of the years, demonstrating the nuances and fluidity of gender identity. Interpretations of BSRI data (or other gender score data) when measured against outcome data must, therefore, be time and context specific, as results are unlikely to be replicated across years.

Mitochondrial dysfunction and associated inflammatory signaling are pivotal in both aging and in Alzheimer's disease (AD). Studies have also shown that hypothalamic function is affected in AD. The hypothalamus may be a target for AD drugs given that mitochondrial alterations are observed in the hypothalamus. This study investigated how age and sex affect mitochondrial bioenergetics and inflammatory signaling in the hypothalamic mitochondria of 3xTg and control mice at 2, 6, and 13 months, aiming to enhance our understanding of these processes in aging and AD. Parameters included oxygen consumption rates, expression levels of subunits comprising mitochondrial complexes I-V, the enzymatic activity of cytochrome c oxidase (COX), transcription factors associated with inflammation such as NF-κB, pIκB-α, Nrf2, and other inflammatory biomarkers. Hypothalamic mitochondrial dysfunction was observed in 3xTg females as early as 2 months, but no changes were detected in 3xTg males until 6 months of age. In 3xTg mice, subunit expression levels for mitochondrial complexes I-II were significantly reduced in both sexes. Significant sex-based differences in COX activity were also observed at 13 months of age, with levels being lower in females compared to males. In addition, significant sex differences were indicated in NF-κB, pIκB-α, Nrf2, and other inflammatory biomarkers at different age groups during normal aging and AD progression. These findings highlight important sex differences in hypothalamic bioenergetics and inflammation, offering insights into potential new targets for preventing and/or treating AD.

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.

Chronic cigarette smokers report withdrawal symptomology, including affective dysfunction and cognitive deficits. While there are studies demonstrating sex specific withdrawal symptomology in nicotine-dependent individuals, literature examining the underlying biological mediators of this is scant and not in complete agreement. Therefore, in this study, we evaluated the sex specific effects of nicotine and withdrawal on contextual fear memory, a hippocampally dependent aspect of cognition that is disrupted in nicotine withdrawal.