Androgens and Their Role in Regulating Sex Differences in the Hypothalamic/Pituitary/Adrenal Axis Stress Response and Stress-Related Behaviors

Photoplethysmography-based HRV analysis and machine learning for real-time stress quantification in mental health applications

Prolonged exposure to high-stress environments can lead to mental illnesses such as anxiety disorders, depression, and posttraumatic stress disorder. Here, a wearable device utilizing photoplethysmography (PPG) technology is developed to noninvasively measure physiological signals and analyze heart rate variability (HRV) parameters. Traditional normative HRV databases typically do not account for responses induced by specific stressors such as cognitive tasks. Therefore, machine learning is used to build a more dynamic stress assessment model. Machine learning can capture complex nonlinear relationships among HRV parameters during stress-inducing tasks, adapts to individual stress response variations, and provides real-time stress level predictions. Furthermore, machine learning models can integrate temporal patterns in HRV data to achieve nuanced stress level assessment. This study examines the feasibility of PPG signals and validates the developed stress model. The RR intervals derived from PPG signals were highly positively correlated with those from electrocardiography signals (correlation coefficient = 0.9920, R-squared = 0.9837); this confirms the usability of PPG signals for HRV analysis. The stress model is constructed via the open-source Swell dataset. In the experiments, participants complete the Depression Anxiety Stress Scales-21-Chinese (DASS-21-C) questionnaire to quantify levels of depression, anxiety, and stress over a week. Baseline and stress-state PPG data are collected, converted into HRV values, and input into the model for stress quantification. The Stroop test is used to elicit stress responses. After the experiment, the DASS-21-C stress scores were compared with the model's baseline, stress state, and combined scores. The highest correlation was observed between the model's baseline score and the DASS-21-C stress score (correlation coefficient = 0.92, R-squared =  0.8457), supporting the model's psychological significance in quantifying everyday stress. HRV parameter changes across experimental phases are discussed as well as sex differences in stress responses. In the future, this device may be applied in clinical scenarios for further validation and could be integrated with additional physiological indicators for broader application in daily health management and stress warning systems.

The Long-Term Effects of Chronic Unpredictable Mild Stress Experienced During Adolescence Could Vary Depending on Biological Sex

Sex differences in the neurobiology of responses to chronic stress have been widely discussed but remain poorly understood. We found that chronic unpredictable mild stress (CUMS) experienced during adolescence induced different behavioral patterns in adult males and females. Immunohistochemical analysis of the CA1 field of the dorsal and ventral hippocampus revealed no quantitative or morphological changes in astrocytes in the long term after CUMS. Real-time PCR analysis showed no increase in the expression level of SigmaR1 after CUMS relative to individual housekeeping genes. Analysis of mouse cerebral cortex homogenates showed that IL-1β levels only decreased after CUMS in males. However, the SigmaR1 levels were significantly higher in the CUMS groups than in the control groups in both sexes. It can be concluded that biological sex and age influence the response to CUMS, although not in all cases. Further studies are needed to understand the effects of chronic stress on males and females. This is important because men and women have different risks for stress and mental disorders.

The Interaction of Vasopressin with Hormones of the Hypothalamo-Pituitary-Adrenal Axis: The Significance for Therapeutic Strategies in Cardiovascular and Metabolic Diseases

A large body of evidence indicates that vasopressin (AVP) and steroid hormones are frequently secreted together and closely cooperate in the regulation of blood pressure, metabolism, water-electrolyte balance, and behavior, thereby securing survival and the comfort of life. Vasopressin cooperates with hormones of the hypothalamo-pituitary-adrenal axis (HPA) at several levels through regulation of the release of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and multiple steroid hormones, as well as through interactions with steroids in the target organs. These interactions are facilitated by positive and negative feedback between specific components of the HPA. Altogether, AVP and the HPA cooperate closely as a coordinated functional AVP-HPA system. It has been shown that cooperation between AVP and steroid hormones may be affected by cellular stress combined with hypoxia, and by metabolic, cardiovascular, and respiratory disorders; neurogenic stress; and inflammation. Growing evidence indicates that central and peripheral interactions between AVP and steroid hormones are reprogrammed in cardiovascular and metabolic diseases and that these rearrangements exert either beneficial or harmful effects. The present review highlights specific mechanisms of the interactions between AVP and steroids at cellular and systemic levels and analyses the consequences of the inappropriate cooperation of various components of the AVP-HPA system for the pathogenesis of cardiovascular and metabolic diseases.

Is membrane androgen and estrogen receptor signaling imperative in the governing function of the adrenal cortex in the Eurasian beaver (Castor fiber L.)?

There is a need to fully know the physiology of Eurasian beaver due to its essential role in environmental homeostasis. However, a "human factor" impacts this, including stress conditions and environmental pollution. Adrenal glands protect these all. The regulation of endocrine processes by nonclassical androgen and estrogen signaling, the first and fastest control, is still a matter of research. The specific analyses performed here in mature female and male beaver adrenals contained: anatomical and histological examinations, expression and localization of membrane androgen receptor (zinc transporter, Zinc- and Iron-like protein 9; ZIP9) and membrane estrogen receptor coupled with G protein (GPER), and measurement of zinc (Zn2+) and copper (Ca2+) ion levels and corticosterone levels. We revealed normal anatomical localization, size, and tissue histology in female and male beavers, respectively. Equally, ZIP9 and GPER were localized in the membrane of all adrenal cortex cells. The protein expression of these receptors was higher (p < 0.001) in male than female adrenal cortex cells. Similarly, Zn2+ and Ca2+ ion levels were higher (p < 0.05, p < 0.01) in male than female adrenal cortex. The increased corticosterone levels (p < 0.001) were detected in the adrenal cortex of females when compared to males. The present study is the first to report the presence of nonclassical androgen and estrogen signaling and its possible regulatory function in the adrenal cortex of Eurasian beavers. We assume that this first-activated and fast-transmitted regulation can be important in the context of the effect of environmental physical and chemical stressors especially on adrenal cortex cells. The beaver adrenals may constitute an additional supplementary model for searching for universal mechanisms of adrenal cortex physiology and diseases.

Evaluating different models of maternal stress on stress-responsive systems in prepubertal mice

Introduction

Maternal adversity during pregnancy influences neurodevelopment in human and model animal offspring. Adversity can result from stressors coming from many different directions ranging from environmental to nutritional and physiological to immune (e.g., infection). Most stressors result in fetal overexposure to glucocorticoids that have been directly linked to long- and short-term negative impacts on neurological health of offspring. Neuropsychiatric diseases postulated to have fetal origins are diverse and include such things cardiovascular disease, obesity, affective disorders, and metabolic and immune disorders.

Methods

The experiments in the current study compare 3 stressors: prenatal exposure to dexamethasone (DEX), maternal high fat diet (HFD), and maternal caloric restriction (CR). Offspring of mothers with these treatments were examined prepubertally to evaluate stress responsiveness and stress-related behaviors in in male and female mice.

Results

Prenatal exposure to synthetic glucocorticoid, DEX, resulted in decreased neonatal body weights, reduced social interaction behavior, and hypoactive stress response offspring exposed to maternal DEX. Maternal CR resulted in decreased body weights and social interaction behavior in males and females and increased anxiety-like behavior and acute stress response only in males. HFD resulted in altered body weight gain in both sex offspring with decreased anxiety-like behavior in a female-biased manner.

Discussion

The idea that glucocorticoid responses to different stressors might serve as a common stimulus across stress paradigms is insufficient, given that different modes of prenatal stress produced differential effects. Opposite nutritional stressors produced similar outcomes for anxiety-like behavior in both sexes, social-like behavior in females, and a hyperactive adrenal stress response in males. One common theme among the three models of maternal stress (DEX, CR, and HFD) was consistent data showing their role in activating the maternal and fetal immune response. By tuning in on the more immediate immunological aspect on the developing fetus (e.g., hormones, cytokines), additional studies may tease out more direct outcomes of maternal stress in rodents and increase their translational value to human studies.

Maternal steroids during pregnancy and their associations with exposure to lifetime stressful life events, prenatal stress appraisal and psychological functioning

BACKGROUND

During pregnancy, steroids enable physiological adaptations in response to many factors, including maternal stress or psychological functioning. While stress and psychological dysfunction can have endocrine-disrupting effects beyond cortisol disruption, associations between prenatal maternal stress or related psychological dysfunction and the broader steroid milieu remain understudied.

AIM

To assess associations between independent and joint maternal stress and psychological functioning measures and steroid profiles in pregnancy (22-40 gestational weeks) in the Programming of Intergenerational Stress Mechanisms (PRISM) birth cohort (n = 334).

METHODS

Serum metabolomics detected 42 steroids and their metabolites, which were grouped into five classes (pregnenolone, androgens, estrogens, progestin, and corticosteroids). The Perceived Stress Scale, Life Stressor Checklist-Revised, and Edinburgh Postnatal Depression Scale indexed lifetime traumatic/non-traumatic stressors, global prenatal stress appraisal, and depressive symptoms during pregnancy, respectively. Exposures were categorized as high-low using the corresponding 3rd quartiles. We assessed associations between both individual and joint stress exposures with steroid classes using linear mixed effect models and with individual steroids using linear regressions. We also examined fetal sex-specific effects.

RESULTS

High prenatal perceived stress was independently associated with lower levels of androgens and estrogens in the overall sample [β (95%CI): androgens: -0.13 (-0.25;-0.01); estrogens: -0.16 (-0.31;-0.01)], particularly among women carrying males [androgens: -0.22 (-0.39;-0.05); estrogens: -0.28 (-0.50;-0.07)]. Results on estrogens were consistent when considering joint exposure to both greater lifetime stressors and higher prenatal perceived stress. We also found a single testosterone metabolite-5alpha-androstan-3alpha,17alpha-diol disulfate-negatively associated with both individual high perceived stress and joint exposure to high lifetime stressors and high perceived stress among women carrying males.

CONCLUSIONS

Increased maternal perceived stress experienced in pregnancy was independently associated with lower maternal androgen and estrogen levels during pregnancy in the overall sample, particularly among women carrying males. Results on estrogens were consistent when we considered the joint exposure of increased lifetime stressors and higher prenatal perceived stress.

Sex differences in androgen receptor, estrogen receptor alpha, and c-Fos co-expression with corticotropin releasing factor expressing neurons in restrained adult mice

Gonadal hormone actions through androgen receptor (AR) and estrogen receptor alpha (ERα) regulate sex differences in hypothalamic-pituitary-adrenal (HPA) axis responsivity and stress-related behaviors. Here we tested whether corticotropin releasing factor (CRF) expressing neurons, which are widely known to regulate neuroendocrine and behavioral stress responses, co-express AR and ERα as a potential mechanism for gonadal hormone regulation of these responses. Using Crh-IRES-Cre::Ai9 reporter mice we report high co-localization of AR in CRF neurons within the medial preoptic area (MPOA), bed nucleus of the stria terminalis (BST), medial amygdala (MeA), and ventromedial hypothalamus (VMH), moderate levels within the central amygdala (CeA) and low levels in the paraventricular hypothalamus (PVN). Sex differences in CRF/AR co-expression were found in the principal nucleus of the BST (BSTmpl), CeA, MeA, and VMH (males>females). CRF co-localization with ERα was generally lower relative to AR co-localization. However, high co-expression was found within the MPOA, AVPV, and VMH, with moderate co-expression in the arcuate nucleus (ARC), BST, and MeA and low levels in the PVN and CeA. Sex differences in CRF/ERα co-localization were found in the BSTmpl and PVN (males>females). Finally, we assessed neural activation of CRF neurons in restraint-stressed mice and found greater CRF/c-Fos co-expression in females in the BSTmpl and periaqueductal gray, while co-expression was higher in males within the ARC and dorsal CA1. Given the known role of CRF in regulating behavioral stress responses and the HPA axis, AR/ERα co-expression and sex-specific activation of CRF cell groups indicate potential mechanisms for modulating sex differences in these functions.

Gut Microsex/Genderome, Immunity and the Stress Response in the Sexes: An Updated Review

Sex has been universally acknowledged as a confounding factor in every type of biological study, while there are strong sex differences in morbidity along the lifespan. Humans have almost identical genomes (99.2%), yet minor variance in their DNA produces remarkable phenotypic diversity across the human population. On the other hand, metagenomic analysis of the human microbiome is more variable, depending on the sex, lifestyle, geography, and age of individuals under study. Immune responses in humans also exhibit variations, with an especially striking sexual dimorphism, which is at play in several other physiologic processes. Sex steroids have noticeable effects on the composition of the human microbiome along the lifespan, accompanied by parallel changes in immunity and the stress response. Gut microsex/genderome, a recently coined term, defines the sexually dimorphic gut microbiome. Apart from the sex steroids, the stress hormones are also at play in the proliferation of microbes. This review summarizes the concept of gut microsex/genderome under the prism of recent studies on the interrelations of the sexually dimorphic microbiome with immunity and stress.

Mitigating the impact of adolescence isolation on the development of social anxiety: A potential role for oxytocin

Exposure to isolation can lead to the development of social anxiety disorder (SAD), which affects 13% of Americans. There are sex differences in the prevalence of anxiety disorders, as women experience higher rates of SAD relative to men. Importantly, isolation experienced during adolescence increases the likelihood of developing SAD in adulthood. Unfortunately, the current treatments for SAD are only effective in 50–65% of patients. As such, it is critical to identify therapeutic targets for the treatment and prevention of SAD, particularly in women. Here, we discuss the links between childhood isolation and adulthood SAD. Next, we examine the preclinical models used to study the impact of isolation on social anxiety-like behaviors in rodents. Increasing evidence from both clinical and pre-clinical studies suggests oxytocin signaling is a potential target to modify social anxiety-like behaviors. We present the evidence that sex hormones influence the oxytocin system. Finally, we highlight future directions for both clinical and pre-clinical studies to further evaluate the efficacy of oxytocin as a treatment for isolation-induced SAD.

Androgens, brain and androgen deprivation therapy in paraphilic disorders: A narrative review

Sexual delinquency is a global problem where those with paraphilic disorders, such as paedophiles, are more likely to commit and reoffend. Androgen deprivation therapy (ADT) has been suggested as a solution. The objective of this narrative review is to present current information on its risks, benefits and limitations as a treatment for paraphilias. The importance of testosterone in sexual function, the effect of its deficiency by age or by pharmacological treatment (anti-androgens, GnRH agonists and GnRH antagonists) and the effect of testosterone replacement therapy will be reviewed. The relationship between androgens, brain, sexual behaviour and pathophysiology of paraphilic disorders will also be explored. ADT reduces sexual urges, but has adverse effects and, because its reversible nature, it does not ensure less recidivism. Likewise, the research quality of ADT drugs is limited and not enough to support their use. Child sex offenders, and not paraphilic subjects who have not committed assaults, show signs of elevated prenatal exposure to androgens and a higher methylation state of the androgen receptor gene. Sexual behaviour is regulated by subcortical (hypothalamus, brainstem and spinal cord) and cortical structures of the brain, in addition to brain circuits (dopaminergic, serotonergic). Those with paraphilic disorders show abnormalities at these levels that could relate to the risk of sexual offences. In conclusion, androgens represent a significant part of the pathophysiology of paraphilias and therefore, ADT seems promising. Nonetheless, more studies are needed to make definite conclusions about the efficacy of long-term ADT in paraphilic patients.

Sex Differences in Acute Neuroendocrine Responses to Stressors in Rodents and Humans

Sex differences in the neuroendocrine response to acute stress occur in both animals and humans. In rodents, stressors such as restraint and novelty induce a greater activation of the hypothalamic-pituitary-adrenal axis (HPA) in females compared to males. The nature of this difference arises from steroid actions during development (organizational effects) and adulthood (activational effects). Androgens decrease HPA stress responsivity to acute stress, while estradiol increases it. Androgenic down-regulation of HPA responsiveness is mediated by the binding of testosterone (T) and dihydrotestosterone (DHT) to the androgen receptor, as well as the binding of the DHT metabolite, 3β-diol, to the β form of the estrogen receptor (ERβ). Estradiol binding to the α form of the estrogen receptor (ERα) increases HPA responsivity. Studies of human sex differences are relatively few and generally employ a psychosocial paradigm to measure stress-related HPA activation. Men consistently show greater HPA reactivity than women when being evaluated for achievement. Some studies have found greater reactivity in women when being evaluated for social performance. The pattern is inconsistent with rodent studies but may involve the differential nature of the stressors employed. Psychosocial stress is nonphysical and invokes a significant degree of top-down processing that is not easily comparable to the types of stressors employed in rodents. Gender identity may also be a factor based on recent work showing that it influences the neural processing of positive and negative emotional stimuli independent of genetic sex. Comparing different types of stressors and how they interact with gender identity and genetic sex will provide a better understanding of sex steroid influences on stress-related HPA reactivity.