Sex differences in the HPA axis

Marked sexual dimorphism in neuroendocrine mechanisms for the exacerbation of paclitaxel-induced painful peripheral neuropathy by stress

Chemotherapy-induced neuropathic pain is a serious adverse effect of chemotherapeutic agents. Clinical evidence suggests that stress is a risk factor for development and/or worsening of chemotherapy-induced peripheral neuropathy (CIPN). We evaluated the impact of stress and stress axis mediators on paclitaxel CIPN in male and female rats. Paclitaxel produced mechanical hyperalgesia, over the 4-day course of administration, peaking by day 7, and still present by day 28, with no significant difference between male and female rats. Paclitaxel hyperalgesia was enhanced in male and female rats previously exposed to unpredictable sound stress, but not in rats that were exposed to sound stress after developing paclitaxel CIPN. We evaluated the role of the neuroendocrine stress axes: in adrenalectomized rats, paclitaxel did not produce hyperalgesia. Intrathecal administration of antisense oligodeoxynucleotides (ODN) reduced expression of β2-adrenergic receptors on nociceptors, and paclitaxel-induced hyperalgesia was slightly attenuated in males, but markedly attenuated in females. By contrast, after intrathecal administration of antisense ODN to decrease expression of glucocorticoid receptors, hyperalgesia was markedly attenuated in males, but unaffected in females. Both ODNs together markedly attenuated paclitaxel-induced hyperalgesia in both males and females. We evaluated paclitaxel-induced CIPN in stress-resilient (produced by neonatal handling) and stress-sensitive (produced by neonatal limited bedding). Neonatal handling significantly attenuated paclitaxel-induced CIPN in adult male, but not in adult female rats. Neonatal limited bedding did not affect the magnitude of paclitaxel-induced CIPN in either male or female. This study provides evidence that neuroendocrine stress axis activity has a marked, sexually dimorphic, effect on paclitaxel-induced painful CIPN.

Selection and verification of the combination of reference genes for RT-qPCR analysis in rat adrenal gland development

Quantitative reverse transcription polymerase chain reaction (RT-qPCR) is commonly used for gene expression analysis, and the accuracy of its results depends greatly on chosen reference genes. Adrenal gland is the core of the occurrence and development of fetal-originated adult diseases. Its dysplasia or dysfunction may increase susceptibility to adult disease, which has apparent sex differences. To explore the optimal combination of reference genes for RT-qPCR in female and male rats adrenal development, we selected seven reference genes (GAPDH, β-actin, etc.), and use RT-qPCR to detect genes expression during different stages of rats adrenal development under physiological conditions. Then we analysed data using GeNorm, NormFinder and BestKeeper to select the optimal combination of reference genes. Further, we used the intrauterine growth retardation (IUGR) model of rat caused by prenatal caffeine exposure (PCE) to verify the stability and accuracy of the selected combination of reference genes under physiological conditions. The results showed that TBP + β-actin could be the optimal combination of reference genes for fetal rat adrenals under physiological conditions, without obvious sex differences. In infancy and adolescence, the optimal combination of reference genes for adrenals had sex differences, and females were GAPDH + β-actin, while males were GAPDH + SDHA. In PCE model, the optimal combination of reference genes was consistent with physiological conditions. Using combination of reference genes to analyze target genes can improve the accuracy of the results. In summary, this study provided reliable combination of reference genes for RT-qPCR and experimental supports for researches on adrenal development.

Sex-related differences in diabetic kidney disease: A review on the mechanisms and potential therapeutic implications

Sexual dimorphism may play a key role in the pathogenesis of diabetic kidney disease (DKD) and explain differences observed in disease phenotypes, responses to interventions, and disease progression between men and women with diabetes. Therefore, omitting the consideration of sex as a biological factor may result in delayed diagnoses and suboptimal therapies. This review will summarize the effects of sexual dimorphism on putative metabolic and molecular mechanisms underlying DKD, and the potential implications of these differences on therapeutic interventions. To successfully implement precision medicine, we require a better understanding of sexual dimorphism in the pathophysiologic progression of DKD. Such insights can unveil sex-specific therapeutic targets that have the potential to maximize efficacy while minimizing adverse events.

Childhood adversity and cortisol habituation to repeated stress in adulthood

BACKGROUND

Childhood adversity is a robust predictor of poor health outcomes in adulthood and hypothalamic-pituitary-adrenocortical (HPA) axis dysfunction may be a key mechanism explaining this association. However, little is known about the influence childhood adversity may exhibit on adult HPA axis habituation (i.e., decreased cortisol output in response to a repeated stressor), where HPA axis dysfunction can be inferred if habituation deviates from normal patterns.

METHODS

The current study used data from a larger study that examined the effects of stress management interventions on cortisol habituation to repeated stress. Eighty-three adults reported childhood adversity with the Adverse Childhood Experience scale and completed the Trier Social Stress Test (TSST) twice (48 h apart) scheduled after a 6-wk intervention period. Salivary cortisol was assessed pre-stressor and +25, +35, and +60 mins post-stressor onset during both visits.

RESULTS

Results indicated that childhood adversity was associated with a marginally larger decrease in total cortisol from visit 1 to visit 2 among men (i.e., habituation), but not women (i.e. non-habituation).

CONCLUSIONS

These findings suggest that childhood adversity may alter HPA axis habituation to repeated stress later in life, with possible sex differences. Future research should investigate whether HPA axis habituation to repeated stress may be a pathway through which childhood adversity affects adult health, and how it may affect men and women differently.

Experience and activity-dependent control of glucocorticoid receptors during the stress response in large-scale brain networks

The diversity of actions of the glucocorticoid stress hormones among individuals and within organs, tissues and cells is shaped by age, gender, genetics, metabolism, and the quantity of exposure. However, such factors cannot explain the heterogeneity of responses in the brain within cells of the same lineage, or similar tissue environment, or in the same individual. Here, we argue that the stress response is continuously updated by synchronized neural activity on large-scale brain networks. This occurs at the molecular, cellular and behavioral levels by crosstalk communication between activity-dependent and glucocorticoid signaling pathways, which updates the diversity of responses based on prior experience. Such a Bayesian process determines adaptation to the demands of the body and external world. We propose a framework for understanding how the diversity of glucocorticoid actions throughout brain networks is essential for supporting optimal health, while its disruption may contribute to the pathophysiology of stress-related disorders, such as major depression, and resistance to therapeutic treatments.

The Characterization of Sex Differences in Hypoglycemia-Induced Activation of HPA Axis on the Transcriptomic Level

Activation of the hypothalamic-pituitary-adrenal (HPA) axis using an insulin tolerance test (ITT) is a medical diagnostic procedure that is frequently used in humans to assess the HPA and growth-hormone (GH) axes. Whether sex differences exist in the response to ITT stress is unknown. Thus, investigations into the analysis of transcripts during activation of the HPA axis in response to hypoglycemia have revealed the underlying influences of sex in signaling pathways that stimulate the HPA axis. We assessed four time points of ITT application in Balb/c mice. After insulin injection, expression levels of 192 microRNAs and 41 mRNAs associated with the HPA, GH and hypothalamic-pituitary-gonadal (HPG) axes were determined by real-time RT-PCR in the hypothalamus, pituitary and adrenal tissues, as well as blood samples (Raw data accession: https://drive.google.com/drive/folders/10qI00NAtjxOepcNKxSJnQbJeBFa6zgHK?usp=sharing ). Although the ITT is commonly used as a gold standard for evaluating the HPA axis, we found completely different responses between males and females with respect to activation of the HPA axis. While activation of several transcripts in the hypothalamus and pituitary was observed after performing the ITT in males within 10 min, females responded via the pituitary and adrenal immediately and durably over 40 min. Additionally, we found that microRNA alterations precede mRNA responses in the HPA axis. Furthermore, robust changes in the levels of several transcripts including Avpr1b and Avpr2 observed at all time points strongly suggest that transcriptional control of these genes occurs mostly via differential signaling in pituitary and blood between males and females. Male and female HPA axis responses to ITT involve a number of sophisticated regulatory signaling pathways of miRNAs and mRNAs. Our results highlight the first robust markers in several layers of HPA, HPG and GH axis involved in ITT/hypoglycemia stress-induced dynamics.

The Hypothalamic-Pituitary-Adrenal Axis: Development, Programming Actions of Hormones, and Maternal-Fetal Interactions

The hypothalamic-pituitary-adrenal axis is a complex system of neuroendocrine pathways and feedback loops that function to maintain physiological homeostasis. Abnormal development of the hypothalamic-pituitary-adrenal (HPA) axis can further result in long-term alterations in neuropeptide and neurotransmitter synthesis in the central nervous system, as well as glucocorticoid hormone synthesis in the periphery. Together, these changes can potentially lead to a disruption in neuroendocrine, behavioral, autonomic, and metabolic functions in adulthood. In this review, we will discuss the regulation of the HPA axis and its development. We will also examine the maternal-fetal hypothalamic-pituitary-adrenal axis and disruption of the normal fetal environment which becomes a major risk factor for many neurodevelopmental pathologies in adulthood, such as major depressive disorder, anxiety, schizophrenia, and others.

Sex differences in the association between obsessive-compulsive symptom dimensions and diurnal cortisol patterns

Previous studies in non-clinical populations suggest that obsessive-compulsive symptoms are associated with hypothalamic-pituitary-adrenal (HPA) axis measures and that there are sex differences in these associations. We aimed to replicate these findings in a sample of 57 patients with obsessive-compulsive disorder (OCD) and 98 healthy subjects. Current and lifetime OCD symptom dimensions were assessed with the Dimensional Yale-Brown Obsessive Compulsive Scale (DY-BOCS). Depressive symptoms and state and trait anxiety were also assessed. The following HPA axis measures were analysed in saliva: the diurnal cortisol slope (calculated using two formulas: [1] awakening to 11 p.m. [AWE diurnal slope] and [2] considering fixed time points [FTP diurnal slope] from 10 a.m. to 11 p.m.) and the dexamethasone suppression test ratio (DSTR) after 0.25 mg of dexamethasone. Multiple linear regression analyses were conducted to explore the contribution of OCD symptom dimensions to each HPA axis measure while adjusting for age, sex, BMI, smoking, trait anxiety and depressive symptoms. A sex-specific association between current ordering/symmetry symptoms and AWE diurnal cortisol slope (positive association [flattened slope] in men, inverse association [stepper slope] in women) was found. Two similar sex by OCD dimensions interactions were found for lifetime aggressive and ordering/symmetry symptoms and both (FTP, AWE) diurnal cortisol slopes. Current and lifetime hoarding symptoms were associated to a more flattened FTP diurnal cortisol slope in women. The DSTR was not associated with OCD symptoms. The lifetime interference in functionality was associated with a more flattened AWE diurnal cortisol slope. In conclusion, our study suggests that there are sex differences in the association between OCD subtypes and specific HPA axis measures.

P11 deficiency increases stress reactivity along with HPA axis and autonomic hyperresponsiveness

Patients suffering from mood disorders and anxiety commonly exhibit hypothalamic-pituitary-adrenocortical (HPA) axis and autonomic hyperresponsiveness. A wealth of data using preclinical animal models and human patient samples indicate that p11 deficiency is implicated in depression-like phenotypes. In the present study, we used p11-deficient (p11KO) mice to study potential roles of p11 in stress responsiveness. We measured stress response using behavioral, endocrine, and physiological readouts across early postnatal and adult life. Our data show that p11KO pups respond more strongly to maternal separation than wild-type pups, even though their mothers show no deficits in maternal behavior. Adult p11KO mice display hyperactivity of the HPA axis, which is paralleled by depression- and anxiety-like behaviors. p11 was found to be highly enriched in vasopressinergic cells of the paraventricular nucleus and regulates HPA hyperactivity in a V_1B receptor-dependent manner. Moreover, p11KO mice display sympathetic-adrenal-medullary (SAM) axis hyperactivity, with elevated adrenal norepinephrine and epinephrine levels. Using conditional p11KO mice, we demonstrate that this SAM hyperactivity is partially regulated by the loss of p11 in serotonergic neurons of the raphe nuclei. Telemetric electrocardiogram measurements show delayed heart rate recovery in p11KO mice in response to novelty exposure and during expression of fear following auditory trace fear conditioning. Furthermore, p11KO mice have elevated basal heart rate in fear conditioning tests indicating increased autonomic responsiveness. This set of experiments provide strong and versatile evidence that p11 deficiency leads to HPA and SAM axes hyperresponsiveness along with increased stress reactivity.

Sex and Age Effects on Neurobehavioral Toxicity Induced by Binge Alcohol

Historically, most alcohol neurotoxicity studies were conducted in young adult males and focused on chronic intake. There has been a shift towards studying the effects of alcohol on the adolescent brain, due to alcohol consumption during this formative period disrupting the brain's developmental trajectory. Because the most typical pattern of adolescent alcohol intake is heavy episodic (binge) drinking, there has also been a shift towards the study of binge alcohol-induced neurobehavioral toxicity. It has thus become apparent that binge alcohol damages the adolescent brain and there is increasing attention to sex-dependent effects. Significant knowledge gaps remain in our understanding of the effects of binge alcohol on the female brain, however. Moreover, it is unsettling that population-level studies indicate that the prevalence of binge drinking is increasing among American women, particularly those in older age groups. Although study of adolescents has made it apparent that binge alcohol disrupts ongoing brain maturational processes, we know almost nothing about how it impacts the aging brain, as studies of its effects on the aged brain are relatively scarce, and the study of sex-dependent effects is just beginning. Given the rapidly increasing population of older Americans, it is crucial that studies address age-dependent effects of binge alcohol, and given the increase in binge drinking in older women who are at higher risk for cognitive decline relative to men, studies must encompass both sexes. Because adolescence and older age are both characterized by age-typical brain changes, and because binge drinking is the most common pattern of alcohol intake in both age groups, the knowledge that we have amassed on binge alcohol effects on the adolescent brain can inform our study of its effects on the aging brain. In this review, we therefore cover the current state of knowledge of sex and age-dependent effects of binge alcohol, as well as statistical and methodological considerations for studies aimed at addressing them.

Impact of COVID-19 pandemic on mental health in the general population: A systematic review

BACKGROUND

As a major virus outbreak in the 21st century, the Coronavirus disease 2019 (COVID-19) pandemic has led to unprecedented hazards to mental health globally. While psychological support is being provided to patients and healthcare workers, the general public's mental health requires significant attention as well. This systematic review aims to synthesize extant literature that reports on the effects of COVID-19 on psychological outcomes of the general population and its associated risk factors.

METHODS

A systematic search was conducted on PubMed, Embase, Medline, Web of Science, and Scopus from inception to 17 May 2020 following the PRISMA guidelines. A manual search on Google Scholar was performed to identify additional relevant studies. Articles were selected based on the predetermined eligibility criteria.

RESULTS

Relatively high rates of symptoms of anxiety (6.33% to 50.9%), depression (14.6% to 48.3%), post-traumatic stress disorder (7% to 53.8%), psychological distress (34.43% to 38%), and stress (8.1% to 81.9%) are reported in the general population during the COVID-19 pandemic in China, Spain, Italy, Iran, the US, Turkey, Nepal, and Denmark. Risk factors associated with distress measures include female gender, younger age group (≤40 years), presence of chronic/psychiatric illnesses, unemployment, student status, and frequent exposure to social media/news concerning COVID-19.

LIMITATIONS

A significant degree of heterogeneity was noted across studies.

CONCLUSIONS

The COVID-19 pandemic is associated with highly significant levels of psychological distress that, in many cases, would meet the threshold for clinical relevance. Mitigating the hazardous effects of COVID-19 on mental health is an international public health priority.

Rapid Jetlag Resetting of Behavioral, Physiological, and Molecular Rhythms in Proestrous Female Mice

A gradual adaptation to a shifted light-dark (LD) cycle is a key element of the circadian clock system and believed to be controlled by the central circadian pacemaker, the suprachiasmatic nucleus (SCN). Endocrine factors have a strong influence on the regulation of the circadian clock network and alter acute photic responses of the SCN clock. In females, endocrine function depends on the stage of the ovarian cycle. So far, however, little is known about the effect of the estrous cycle on behavioral and molecular responses to shifts in the LD rhythm. Based on this, we investigated whether estrous state affects the kinetics of phase shift during jetlag in behavior, physiology, and molecular clock rhythms in the SCN and in peripheral tissues. Female mice exposed to an advanced LD phase at proestrous or metestrous showed different phase-shift kinetics, with proestrous females displaying accelerated adaptation in behavior and physiology. Constant darkness release experiments suggest that these fast phase shifts do not reflect resetting of the SCN pacemaker. Explant experiments on SCN, adrenal gland, and uterus confirmed this finding with proestrous females showing significantly faster clock phase shifts in peripheral tissues compared with the SCN. Together, these findings provide strong evidence for an accelerated adaptation of proestrous compared with metestrous females to new LD conditions that is accompanied by rapid behavioral, physiological, and molecular rhythm resetting. Not only do these findings open up a new avenue to understand the effect of estrous cycle on the clock network under changing environmental conditions but also imply a greater susceptibility in proestrous females.

Acute exposure of rats to a severe stressor alters the circadian pattern of corticosterone and sensitizes to a novel stressor: Relationship to pre-stress individual differences in resting corticosterone levels

Traumatic events have been proposed to be associated with hypo-activity of the hypothalamic-pituitary-adrenal (HPA) axis, but data in animal models exposed to severe stressors are controversial and have important methodological concerns. Individual differences in resting or stress levels of corticosterone might explain some of the inconsistencies. We then studied this issue in male rats exposed to 2 h immobilization on boards (IMO), a severe stressor. Thirty-six rats were blood sampled under resting conditions four times a day on three non-consecutive days. Then, they were assigned to control (n = 14) or IMO (n = 22) to study the HPA response to IMO, the stressor-induced alterations in the circadian pattern of corticosterone (CPCORT), and the behavioral and HPA responsiveness to an open-field. Individual differences in pre-IMO resting corticosterone were inconsistent, but averaging data markedly improved consistency. The CPCORT was markedly altered on day 1 post-IMO (higher trough and lower peak levels), less altered on day 3 and apparently normal on day 7. Importantly, when rats were classified in low and high resting corticosterone groups (LCORT and HCORT, respectively), on the basis of the area under the curve (AUC) of the averaged pre-IMO data, AUC differences between LCORT and HCORT groups were maintained in controls but disappeared in IMO rats during the post-IMO week. Open-field hypo-activity and corticosterone sensitization were similar in LCORT and HCORT groups nine days after IMO. A single IMO exposure causes long-lasting HPA alterations, some of them dependent on pre-stress resting corticosterone levels, with no evidence for post-IMO resting corticosterone hypo-activity.

Rotated nursing environment with underfeeding: A form of early-life adversity with sex- and age-dependent effects on coping behavior and hippocampal neurogenesis

We investigated how a unique form of early-life adversity (ELA), caused by rotated nursing environment to induce underfeeding, alters anxiety-like and stress-coping behaviors in male and female Sprague Dawley rats in adolescence and adulthood. Adult female rats underwent either thelectomy (thel; surgical removal of teats), sham surgery, or no surgery (control) before mating. Following parturition, litters were rotated between sham and thel rats every 12 h to generate a group of rats that experienced ELA (rotated housing, rotated mother, and 50% food restriction) from postnatal day 0 to 26. Control litters remained with their natal, nursing dams. Regardless of age and sex, ELA reduced activity in the periphery of the open field. ELA increased immobility in the forced swim test, particularly in adults. We used doublecortin immunohistochemistry to identify immature neurons in the hippocampus. ELA increased the number and density of immature neurons in the dentate gyrus of adolescent males (but not females) and reduced the density of immature neurons in adult males (but not females). This research indicates that a unique form of ELA alters stress-related passive coping and hippocampal neurogenesis in an age- and sex-dependent manner.

Sex differences in cortisol and memory following acute social stress in amnestic mild cognitive impairment

OBJECTIVE

Older adults with amnestic mild cognitive impairment (aMCI) develop Alzheimer's type dementia approximately 10 times faster annually than the normal population. Adrenal hormones are associated with aging and cognition. We investigated the relationship between acute stress, cortisol, and memory function in aMCI with an exploratory analysis of sex.

METHOD

Salivary cortisol was sampled diurnally and during two test sessions, one session with the Trier Social Stress Test (TSST), to explore differences in the relationship between cortisol and memory function in age-normal cognition (NA) and aMCI. Participants with aMCI (n = 6 women, 9 men; mean age = 75) or similarly aged NA (n = 9 women, 7 men, mean age = 75) were given tests of episodic, associative, and spatial working memory with a psychosocial stressor (TSST) in the second session.

RESULTS

The aMCI group performed worse on the memory tests than NA as expected, and males with aMCI had elevated cortisol levels on test days. Immediate episodic memory was enhanced by social stress in NA but not in the aMCI group, indicating that stress-induced alterations in memory are different in individuals with aMCI. High cortisol was associated with impaired performance on episodic memory in aMCI males only. Cortisol in Session 1 moderated the relationship with spatial working memory, whereby higher cortisol was associated with worse performance in NA, but better spatial working memory in aMCI. In addition, effects of aMCI on perceived anxiety in response to stress exposure were moderated by stress-induced cortisol in a sex-specific manner.

CONCLUSIONS

We show effects of aMCI on Test Session cortisol levels and effects on perceived anxiety, and stress-induced impairments in memory in males with aMCI in our exploratory sample. Future studies should explore sex as a biological variable as our findings suggest that effects at the confluence of aMCI and stress can be obfuscated without sex as a consideration.

Influence of cortisol awakening response on telomere length: Trends for males and females

Although telomere attrition is associated with the process of normal ageing, shorter telomere length (TL) has been associated with acute and chronic stressors. A neurobiological factor hypothesised to be responsible for this accelerated attrition is the dysregulation of the cortisol stress response, which can induce DNA damage affecting DNA telomeric caps. Marked sex differences are reported in both the cortisol stress response and telomere dynamics, yet no explicit investigation of sex specificity on the relationship between cortisol and TL exists. This study used mathematical equation modelling to describe the relationship between diurnal cortisol levels and telomere length within the context of sex, in a healthy population. Cortisol awakening responses (CAR) were measured via ELISA methodology in fifty-one healthy participants (28 males, 23 females). qPCRs determined TL from genomic DNA extracted from saliva. To assess the effect of free cortisol on relative TL ratio, a semi-log regression plot of the two variables trended for sex were fitted using spline curves. Results demonstrated significant differences between males and females in the relationship defining CAR and TL association (p = 0.03). These results suggest the relationship is not linear and can be represented as a complex arcsin function, and that the patterns are opposite in males and females. Males demonstrate a positive correlation, with higher levels of CAR being associated with longer telomere sequences. Females demonstrated a negative correlation. Future studies must carefully take into consideration moderating factors such as sex, and sex hormones across the lifespan when investigating telomere length.

Overexpression of angiotensin converting enzyme 2 reduces anxiety-like behavior in female mice

Accumulating evidence has revealed an intricate role for the renin-angiotensin system (RAS) in the progression or alleviation of stress-related disorders. Along these lines, the 'pro-stress' actions of angiotensin-II (Ang-II) are largely thought to be mediated by the angiotensin type-1a receptor (AT1aR). On the other hand, a counter regulatory limb of the RAS that depends on the conversion of Ang-II to angiotensin-(1-7) by angiotensin-converting enzyme 2 (ACE2) has been postulated to exert stress-dampening actions. We have previously found that augmenting ACE2 activity is potently anxiolytic and blunts stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis in male mice. Whether increasing ACE2 activity also relieves stress and anxiety in females has not yet been determined. Consequently, this series of experiments tests the hypothesis that augmenting ACE2 expression is anxiolytic and dampens the activity of the HPA axis in female mice. Using the Cre-LoxP system, we generated female mice that were homo-, heterozygous or wild-type for a mutated allele resulting in ubiquitous overexpression of ACE2. Next, we used qPCR to determine that levels of ACE2 mRNA isolated from central and peripheral tissues was dependent on genotype. That is, mice homo- and heterozygous for the ACE2 overexpression had significantly greater levels of ACE2 mRNA relative to littermate matched wild-type controls. Interestingly, anxiety-like behavior as determined by the elevated plus maze, light-dark box and novelty-induced hypophagia tests was also affected by genotype. Specifically, ACE2 overexpression significantly decreased anxiety-like behavior in paradigms dependent on approach-avoidance conflict and novelty; however, locomotor activity was similar amongst the genotypes. Final experiments measured plasma corticosterone to evaluate whether increasing ACE2 alters basal and/or stress-induced HPA axis activity. In contrast to what was previously found in males, increasing ACE2 expression had no effect on plasma corticosterone under basal conditions or subsequent to an acute restraint challenge. Collectively, these results suggest that increasing ACE2 expression potently elicits anxiolysis in female mice without altering HPA axis activity.

Sex-Dependent Pathology in the HPA Axis at a Sub-acute Period After Experimental Traumatic Brain Injury

Over 2.8 million traumatic brain injuries (TBIs) are reported in the United States annually, of which, over 75% are mild TBIs with diffuse axonal injury (DAI) as the primary pathology. TBI instigates a stress response that stimulates the hypothalamic-pituitary-adrenal (HPA) axis concurrently with DAI in brain regions responsible for feedback regulation. While the incidence of affective symptoms is high in both men and women, presentation is more prevalent and severe in women. Few studies have longitudinally evaluated the etiology underlying late-onset affective symptoms after mild TBI and even fewer have included females in the experimental design. In the experimental TBI model employed in this study, evidence of chronic HPA dysregulation has been reported at 2 months post-injury in male rats, with peak neuropathology in other regions of the brain at 7 days post-injury (DPI). We predicted that mechanisms leading to dysregulation of the HPA axis in male and female rats would be most evident at 7 DPI, the sub-acute time point. Young adult age-matched male and naturally cycling female Sprague Dawley rats were subjected to midline fluid percussion injury (mFPI) or sham surgery. Corticotropin releasing hormone, gliosis, and glucocorticoid receptor (GR) levels were evaluated in the hypothalamus and hippocampus, along with baseline plasma adrenocorticotropic hormone (ACTH) and adrenal gland weights. Microglial response in the paraventricular nucleus of the hypothalamus indicated mild neuroinflammation in males compared to sex-matched shams, but not females. Evidence of microglia activation in the dentate gyrus of the hippocampus was robust in both sexes compared with uninjured shams and there was evidence of a significant interaction between sex and injury regarding microglial cell count. GFAP intensity and astrocyte numbers increased as a function of injury, indicative of astrocytosis. GR protein levels were elevated 30% in the hippocampus of females in comparison to sex-matched shams. These data indicate sex-differences in sub-acute pathophysiology following DAI that precede late-onset HPA axis dysregulation. Further understanding of the etiology leading up to late-onset HPA axis dysregulation following DAI could identify targets to stabilize feedback, attenuate symptoms, and improve efficacy of rehabilitation and overall recovery.

Genetic risk-factors for anxiety in healthy individuals: polymorphisms in genes important for the HPA axis

BACKGROUND

Two important aspects for the development of anxiety disorders are genetic predisposition and alterations in the hypothalamic-pituitary-adrenal (HPA) axis. In order to identify genetic risk-factors for anxiety, the aim of this exploratory study was to investigate possible relationships between genetic polymorphisms in genes important for the regulation and activity of the HPA axis and self-assessed anxiety in healthy individuals.

METHODS

DNA from 72 healthy participants, 37 women and 35 men, were included in the analyses. Their DNA was extracted and analysed for the following Single Nucleotide Polymorphisms (SNP)s: rs41423247 in the NR3C1 gene, rs1360780 in the FKBP5 gene, rs53576 in the OXTR gene, 5-HTTLPR in SLC6A4 gene and rs6295 in the HTR1A gene. Self-assessed anxiety was measured by the State and Trait Anxiety Inventory (STAI) questionnaire.

RESULTS

Self-assessed measure of both STAI-S and STAI-T were significantly higher in female than in male participants (p = 0.030 and p = 0.036, respectively). For SNP rs41423247 in the NR3C1 gene, there was a significant difference in females in the score for STAI-S, where carriers of the G allele had higher scores compared to the females that were homozygous for the C allele (p < 0.01). For the SNP rs53576 in the OXTR gene, there was a significant difference in males, where carriers of the A allele had higher scores in STAI-T compared to the males that were homozygous for the G allele (p < 0.01).

CONCLUSION

This study shows that SNP rs41423247 in the NR3C1 gene and SNP rs53576 in the OXTR gene are associated with self-assessed anxiety in healthy individuals in a gender-specific manner. This suggests that these SNP candidates are possible genetic risk-factors for anxiety.

Masculinized Second-to-Fourth Digit Ratio (2D:4D Ratio) Is Associated With Lower Cortisol Response in Infant Female Rhesus Monkeys (Macaca mulatta)

The second-to-fourth digit ratio (2D:4D ratio) is considered a postnatal proxy measure for the degree of prenatal androgen exposure (PAE), which is the primary factor responsible for masculinizing the brain of a developing fetus. Some studies suggest that the organizational effects of PAE may extend to the hypothalamic-pituitary-adrenal (HPA) axis response to stress. This study investigates the relationship between 2D:4D ratio and HPA axis functioning using a rhesus monkey (Macaca mulatta) model. Subjects were N = 268 (180 females, 88 males) rhesus monkey infants (3–4 months of age). Plasma cortisol concentrations were assayed from two blood samples obtained during a 25-h experimental social separation stressor at 2- and 7-h post-separation. Subjects’ 2D:4D ratio was measured later in life (M_age = 6.70 years). It was hypothesized that infant rhesus monkeys that exhibited a more masculine-like 2D:4D ratio would show lower levels of circulating cortisol after a social separation and relocation stressor. The results showed that there was a sex difference in the left-hand 2D:4D ratio. The results also showed that there was an overall sex difference in cortisol concentrations and that female, but not male, monkeys that exhibited a more masculine-like right- and left-hand 2D:4D ratio exhibited lower mean stress-induced cortisol concentrations early in life. These findings suggest that higher levels of prenatal androgens in females, as measured by 2D:4D ratio, may be related to an attenuated HPA axis stress-response, as measured by plasma cortisol levels. To the extent that these findings generalize to humans, they suggest that the organizational effects of PAE extend to the infant HPA axis, modulating the HPA axis response, particularly in females.

Blue light at night acutely impairs glucose tolerance and increases sugar intake in the diurnal rodent Arvicanthis ansorgei in a sex-dependent manner

In our modern society, the exposure to light at night (LAN) has increased considerably, which may impact human health negatively. Especially exposure to light at night containing short wavelength emissions (~450–500 nm) can disrupt the normal function of the biological clock, altering sleep‐wake cycles and inducing metabolic changes. Recently, we reported that light at night acutely impairs glucose tolerance in nocturnal rats. However, light at night in nocturnal rodents coincides with their activity period, in contrast to artificial light at night exposure in humans. The aim of this study was to evaluate the acute effects of blue (λ = 490 ± 20 nm) artificial light at night (bALAN) on glucose metabolism and food intake in both male and female diurnal Sudanian grass rats (Arvicanthis ansorgei) fed either regular chow or a free choice high‐fat high sucrose diet (HFHS). In both chow and HFHS fed male Arvicanthis, 1‐hour of bALAN exposure induced a higher glucose response in the oral glucose tolerance test (OGTT) accompanied by a significant decrease in plasma insulin. Furthermore, in HFHS fed animals, bALAN induced an increase in sucrose intake during the dark phase in males but not in females. Additionally, 1‐h of bALAN increased the nonfasted glucose levels together with plasma corticosterone in female grass rats. These results provide new and further evidence for the deleterious effects of exposure to short wavelength emission‐containing artificial light at night on glucose metabolism in a diurnal rodent in a sex‐dependent manner.

Differential Regulation of the Glucocorticoid Receptor in a Rat Model of Inflammatory Pain

BACKGROUND

Anti-inflammatory corticosteroids are a common treatment for different conditions involving chronic pain and inflammation. Clinically used steroids target the glucocorticoid receptor (GR) for its anti-inflammatory effects. We previously reported that GR in sensory neurons may play central roles in some pain models and that GR immunoreactivity signal in dorsal root ganglia (DRG) decreased after local inflammation of the DRG (a model of low back pain). In the current study, we aimed to determine if similar changes in GR signal also exist in a skin inflammation model, the complete Freund's adjuvant (CFA) model (a model of peripheral inflammatory pain), in which the terminals of the sensory neurons rather than the somata are inflamed.

METHODS

A low dose of CFA was injected into the hind paw to establish the peripheral inflammation model in Sprague-Dawley rats of both sexes, as confirmed by measurements of behavior and paw swelling. Immunohistochemical and western blotting techniques were used to determine the expression pattern of the GR in the inflamed hind paw and the DRGs. Plasma corticosterone levels were measured with radioimmunoassay.

RESULTS

The immunohistochemical staining revealed that GR is widely expressed in the normal DRG and skin tissues. Paw injection with CFA caused upregulation of the GR in the skin tissue on postinjection day 1, mostly detected in the dermis area. However, paw inflammation significantly reduced the GR signal in the L5 DRG 1 day after the injection. The GR downregulation was still evident 14 days after CFA inflammation. On day 1, western blotting confirmed this downregulation and showed that it could also be observed in the contralateral L5 DRG, as well as in the L2 DRG (a level which does not innervate the paw). Plasma corticosterone levels were elevated in both sexes on day 14 after CFA compared to day 1, suggesting autologous downregulation of the GR by corticosterone may have contributed to the downregulation observed on day 14 but not day 1.

CONCLUSIONS

There are distinctive patterns of GR activation under different pain conditions, depending on the anatomical location. The observed downregulation of the GR in sensory neurons may have a significant impact on the use of steroids as treatment in these conditions and on the regulatory effects of endogenous glucocorticoids.

Sex Differences in the Inflammatory Consequences of Stress: Implications for Pharmacotherapy

Women are at significantly greater risk of developing stress-related disorders such as depression. The increased risk begins during puberty and continues throughout life until menopause, suggesting a role for ovarian hormones in this increased susceptibility. Importantly, inflammation has been gaining momentum in its role in the pathogenesis of depression. Herein, clinical and preclinical studies have been reviewed to better understand how sex differences within the immune system may contribute to exaggerated risk of depression in females. First, studies that investigate the ability of psychologic stress episodes to engage the inflammatory systems both in the brain and periphery are reviewed with a special focus on sex-specific effects. Moreover, studies are discussed that identify whether imbalanced inflammatory milieu contributes to the development of depression in males versus females and whether these effects are regulated by estradiol. Importantly, we propose a locus coeruleus-norepinephrine-cytokine circuit as a conduit through which stress could increase stress susceptibly in females. Finally, the anti-inflammatory capacity of traditional and nontraditional antidepressants is investigated, with the goal of providing a better understanding of pharmacotherapeutics to enhance strategies to personalize antidepressant treatments between the sexes. The studies reviewed herein strongly support the need for further studies to elucidate whether females are especially sensitive to anti-inflammatory compounds as adjuvants to traditional therapies. SIGNIFICANCE STATEMENT: Women have hve an increased risk of developing stress-related disorders such as depression. In this review, literature from clinical and preclinical studies are integrated to define sex differences in stress-induced inflammatory responses as a potential source for the etiology of sex differences in depressive disorders. Moreover, the anti-inflammatory capacity of traditional and nontraditional antidepressants is reviewed to inform on potential pharmacotherapeutic strategies to personalize antidepressant therapy in a sex-dependent manner.

Sex-linked neurofunctional basis of psychological resilience in late adolescence: a resting-state functional magnetic resonance imaging study

Psychological resilience refers to the ability to adapt effectively in the face of adversity, which is closely related to an individual's psychological and physical health and well-being. Although previous behavioural studies have shown sex differences in psychological resilience, little is known about the neural basis of sex differences in psychological resilience. Here, we measured amplitude of low-frequency fluctuations (ALFF) via resting-state functional magnetic resonance imaging to investigate the sex-linked neurofunctional basis of psychological resilience in 231 healthy adolescents. At the behavioural level, we replicated previous findings indicating that males are more resilient than females. At the neural level, we found sex differences in the relationship between psychological resilience and ALFF in the right orbitofrontal cortex (OFC). Specifically, males showed a positive correlation between psychological resilience and ALFF in the right OFC, while females showed a negative correlation in this region. The sex-specific association between psychological resilience and spontaneous brain activity might be dependent on differences in hormonal systems and brain development between male and female adolescents. Taken together, the results of our study might provide the first evidence of sex-specific neurofunctional substrates of psychological resilience in adolescents, emphasizing the vital role of sex effects in future psychological resilience-related studies.

A single ovarian stimulation, as performed in assisted reproductive technologies, can modulate the anxiety-like behavior and neuronal activation in stress-related brain areas in rats

Infertility affects about 8 to 12% of couples of childbearing age around the world, and is recognized as a global public health issue by the WHO. From a psychosocial perspective, infertile individuals experience intense psychological distress, related to emotional disorders, which have repercussions on marital and social relationships. The symptoms persist even after seeking specialized treatment, such as assisted reproductive technologies (ART). While the stress impact of ART outcome has been comprehensively studied, the role of supraphysiological concentrations of gonadal hormones on stress response, remains to be elucidated. This study aimed to evaluate the effect of a single ovarian stimulation on the stress response in rats. To mimic the context of ART in rodents, female rats were submitted to the superovulation (150 UI/kg of PMSG and 75 UI/kg of hCG) and then to psychogenic stress (restraint stress for 30 min/day, repeated for three days). Anxiety-like behavior was evaluated in the elevated plus-maze, and neuronal activation in the stress-related brain areas assessed by Fos protein immunoreactivity. Corticosterone, estradiol, progesterone and corpora lutea were quantified. Data were analyzed using Generalized Linear Model (GzLM). Our findings indicate anxiolytic-like and protective effects of supraphysiological concentrations of gonadal hormones induced by a single ovarian stimulation on stress response. An activation of hypothalamus-pituitary-adrenal response inhibitory pathways, with participation of the prefrontal cortex, basomedial amygdala, lateral septum, medial preoptic area, dorsomedial and paraventricular hypothalamus, was detected.

The effects of early life adversity on growth, maturation, and steroid hormones in male and female rats

Early life adversity is a risk factor for psychiatric disorders, yet the mechanisms by which adversity increases this risk are still being delineated. Here, we used a limited bedding and nesting (LBN) manipulation in rats that models a low resource environment to examine effects on growth, developmental milestones, and endocrine endpoints. In LBN, dams and pups, from pups' postnatal days 2-9, are exposed to an environment where dams lack proper materials to build a nest. This manipulation is compared to control housing conditions, where rat dams have access to ample nesting materials and enrichment throughout pups' development. We found that the LBN condition altered maternal care, increasing pup-directed behaviors while reducing self-care. This, perhaps compensatory, increase in nursing and attention to pups did not mitigate against changes in metabolism, as LBN reduced weight gain in both sexes and this effect persisted into adulthood. Although adult stress hormone levels in both sexes and vaginal opening and estrous cycle length in females were not disrupted, there was other evidence of endocrine dysregulation. Compared to controls, LBN rats of both sexes had shortened anogenital distances, indicating reduced androgen exposure. LBN males also had higher plasma estradiol levels in adulthood. This combination of results suggests that LBN causes a demasculinizing effect in males that could contribute to lasting changes in the brain and behavior. Importantly, alterations in metabolic and endocrine systems due to early life adversity could be one mechanism by which stress early in life increases risk for later disease.

Serum Neurosteroid Levels Are Associated With Cortical Thickness in Individuals Diagnosed With Posttraumatic Stress Disorder and History of Mild Traumatic Brain Injury

Posttraumatic stress disorder (PTSD) co-occurring with mild traumatic brain injury (mTBI) is common in veterans. Worse clinical outcome in those with PTSD has been associated with decreased serum neurosteroid levels. Furthermore, decreased cortical thickness has been associated with both PTSD and mTBI. However, it is not known whether decreased neurosteroids are associated with decreased cortical thickness in PTSD co-occurring with mTBI. This study included 141 individuals divided into the following groups: (a) mTBI group (n = 32 [10 female, 22 male] veterans with a history of mTBI); (b) PTSD + mTBI group (n = 41 [6 female, 35 male] veterans with current PTSD with a history of mTBI); and (c) control group (n = 68 [35 female, 33 male] control participants), which were acquired through the Injury and Traumatic Stress (INTRuST) Clinical Consortium. Subjects underwent clinical assessment, magnetic resonance imaging at 3 T, and serum neurosteroid quantifications of allopregnanolone (ALLO) and pregnenolone (PREGN). Group differences in cortical thickness and associations between serum neurosteroid levels and cortical thickness were investigated. Cortical thickness was decreased in the PTSD + mTBI group compared with the other groups. In the PTSD + mTBI group, decreased cortical thickness was also associated with lower serum ALLO (right superior frontal cortex) and lower serum PREGN (left middle temporal and right orbitofrontal cortex). Cortical thickness in the middle temporal and orbitofrontal cortex was associated with PTSD symptom severity. There were no significant associations between neurosteroids and cortical thickness in the mTBI or control groups. Decreased cortical thickness in individuals with PTSD + mTBI is associated with decreased serum neurosteroid levels and greater PTSD symptom severity. Causality is unclear. However, future studies might investigate whether treatment with neurosteroids could counteract stress-induced neural atrophy in PTSD + mTBI by potentially preserving cortical thickness.

Prolonged treatment with the synthetic glucocorticoid methylprednisolone affects adrenal steroidogenic function and response to inflammatory stress in the rat

Synthetic glucocorticoids are widely prescribed for the treatment of numerous inflammatory and autoimmune diseases and they can also affect the way the adrenal gland produces endogenous glucocorticoids. Indeed, patients undergoing synthetic glucocorticoid treatment can develop adrenal insufficiency, a condition characterised by reduced responsiveness of the adrenal to ACTH stimulation or stressors (e.g. surgical or inflammatory stress). To better elucidate the long-term effect of synthetic glucocorticoids treatment and withdrawal on adrenal function, we have investigated the long-term effects of prolonged treatment with methylprednisolone on HPA axis dynamics and on the adrenal steroidogenic pathway, both in basal conditions and in response to an inflammatory stress (lipopolysaccharide, LPS). We have found that 5-days treatment with methylprednisolone suppresses basal ACTH and corticosterone secretion, as well as corticosterone secretion in response to a high dose of ACTH, and down-regulates key genes in the adrenal steroidogenic pathway, including StAR, MRAP, CYP11a1 and CYP11b1. These effects were paralleled by changes in the adrenal expression of transcription factors regulating steroidogenic gene expression, as well as changes in the expression of adrenal clock genes. Importantly, 5 days after withdrawal of the treatment, ACTH levels are restored, yet basal levels of corticosterone, as well as most of the key steroidogenic genes and their regulators, remain down regulated. We also show that, although 5-days treatment with methylprednisolone reduces the corticosterone response to LPS, an increase in intra-adrenal pro-inflammatory cytokine gene expression was observed. Our data suggests that the steroidogenic pathway is directly affected by synthetic glucocorticoid treatment in the long-term, presumably via a mechanism involving activation of the glucocorticoid receptor. Furthermore, our data suggests a pro-inflammatory effect of synthetic glucocorticoids treatment in the adrenal gland.

Infrared Thermography Reveals Sex-Specific Responses to Stress in Mice

Psychogenic hyperthermia is a stress-related condition reported mostly in women. Neuroendocrine responses to stress in females differ from those in males, and these differences cannot be explained solely based on hypothalamic-pituitary-adrenal (HPA) axis activity. Here, we used infrared (IR) thermographic imaging to record changes in cutaneous temperature following two types of stressful experiences in female and male mice. Mice were exposed to either single-session restraint stress or vertical exploration (rearing) deprivation and were monitored for exploratory activity and IR surface thermal changes. Females displayed higher rearing activity than males during the dark phase of the light cycle. Both sexes showed similar plasma corticosterone (CORT) responses after a challenge with restraint and rearing deprivation. However, only females responded to rearing deprivation with increased cutaneous temperature in the head and back, and a reduced thermal response in the tail. Circulating CORT levels were not correlated with the thermal variations. These findings, for the first time, provide evidence for sex-specific cutaneous thermal responses to short-term stress in mice following transient vertical-activity deprivation that may mimic clinical psychogenic hyperthermia.

Androgen-dependent sexual dimorphism in pituitary tryptophan hydroxylase expression: relevance to sex differences in pituitary hormones

Serotonin is a biogenic monoamine conserved across phyla that is implicated in diverse physiological and behavioural functions. On examining the expression of the rate-limiting enzymes in serotonin synthesis, tryptophan hydroxylases (TPHs), in the teleost medaka (Oryzias latipes), we found that males have much higher levels of tph1 expression as compared with females. This robust sexual dimorphism was found to probably result from the direct stimulation of tph1 transcription by androgen/androgen receptor binding to canonical bipartite androgen-responsive elements in its proximal promoter region. Our results further revealed that tph1 expression occurs exclusively in pro-opiomelanocortin (pomc)-expressing cells and that the resulting serotonin and its derivative melatonin inhibit the expression of the pituitary hormone genes, fshb, sl and tshb. This suggests that serotonin and/or melatonin synthesized in pomc-expressing cells act in a paracrine manner to suppress pituitary hormone levels. Consistent with these findings and the male-biased expression of tph1, the expression levels of fshb, sl and tshb were all higher in females than in males. Taken together, the male bias in tph1 expression and consequent serotonin/melatonin production presumably contribute to sex differences in the expression of pituitary hormones and ultimately in the physiological functions mediated by them.

Long-Term Aberrations To Cerebellar Endocannabinoids Induced By Early-Life Stress

Emerging evidence points to the role of the endocannabinoid system in long-term stress-induced neural remodeling with studies on stress-induced endocannabinoid dysregulation focusing on cerebral changes that are temporally proximal to stressors. Little is known about temporally distal and sex-specific effects, especially in cerebellum, which is vulnerable to early developmental stress and is dense with cannabinoid receptors. Following limited bedding at postnatal days 2-9, adult (postnatal day 70) cerebellar and hippocampal endocannabinoids, related lipids, and mRNA were assessed, and behavioral performance evaluated. Regional and sex-specific effects were present at baseline and following early-life stress. Limited bedding impaired peripherally-measured basal corticosterone in adult males only. In the CNS, early-life stress (1) decreased 2-arachidonoyl glycerol and arachidonic acid in the cerebellar interpositus nucleus in males only; (2) decreased 2-arachidonoyl glycerol in females only in cerebellar Crus I; and (3) increased dorsal hippocampus prostaglandins in males only. Cerebellar interpositus transcriptomics revealed substantial sex effects, with minimal stress effects. Stress did impair novel object recognition in both sexes and social preference in females. Accordingly, the cerebellar endocannabinoid system exhibits robust sex-specific differences, malleable through early-life stress, suggesting the role of endocannabinoids and stress to sexual differentiation of the brain and cerebellar-related dysfunctions.

Wild chimpanzees exhibit humanlike aging of glucocorticoid regulation

Cortisol, a key product of the stress response, has critical influences on degenerative aging in humans. In turn, cortisol production is affected by senescence of the hypothalamic-pituitary-adrenal (HPA) axis, leading to progressive dysregulation and increased cortisol exposure. These processes have been studied extensively in industrialized settings, but few comparative data are available from humans and closely related species living in natural environments, where stressors are very different. Here, we examine age-related changes in urinary cortisol in a 20-y longitudinal study of wild chimpanzees (n = 59 adults) in the Kanyawara community of Kibale National Park, Uganda. We tested for three key features of HPA aging identified in many human studies: increased average levels, a blunted diurnal rhythm, and enhanced response to stressors. Using linear mixed models, we found that aging was associated with a blunting of the diurnal rhythm and a significant linear increase in cortisol, even after controlling for changes in dominance rank. These effects did not differ by sex. Aging did not increase sensitivity to energetic stress or social status. Female chimpanzees experienced their highest levels of cortisol during cycling (versus lactation), and this effect increased with age. Male chimpanzees experienced their highest levels when exposed to sexually attractive females, but this effect was diminished by age. Our results indicate that chimpanzees share some key features of HPA aging with humans. These findings suggest that impairments of HPA regulation are intrinsic to the aging process in hominids and are side effects neither of extended human life span nor of atypical environments.

Sexual Dimorphism of Heart Rate Variability in Adolescence: A Case-Control Study on Depression, Anxiety, Stress Levels, Body Composition, and Heart Rate Variability in Adolescents with Impaired Fasting Glucose

Prediabetes in the form of impaired fasting glucose, impaired glucose tolerance, or both is considered as a preliminary stage for the onset of diabetes and diabetic complications. Hormonal fluctuations in adolescence are accompanied by body composition modifications, which are associated with insulin resistance and subclinical inflammation. Bioimpedance (BIA) accurately evaluates body composition, and heart rate variability (HRV) assesses cardiac autonomic function, which are frequently afflicted by insulin resistance. We aimed at evaluating the effect of glycemic status on mental stress, anxiety, and depression status in adolescents with impaired fasting glucose, body composition, and HRV parameters. This is a case-control study to evaluate the effect of the hyperglycemia on depression, anxiety, and stress levels (DASS21 questionnaire), body composition (BIA-ACC—BIOTEKNA©), and HRV (PPG Stress Flow—BIOTEKNA©), between euglycemic adolescents (euglycemic group) and adolescents with impaired fasting glucose (prediabetic group), aged 12–20 years. No differences were found between the prediabetic (n = 13) and the euglycemic (n = 16) groups in the outcome measures, possibly due to the number of participants. Interestingly, females, irrespective of their glycemic status, exhibited altered sympathovagal function as revealed by impaired HRV. In the euglycemic group, HRV parameters were significantly correlated and in line with the DASS21 scores, but in the prediabetic group, similarities to those of adults were observed. Impaired fasting glucose had no impact on mental health, body composition, or HRV parameters in adolescents. HRV parameters were impaired in females, irrespective of their glycemic status. This finding implies that females seem to be more prone to stress disorders, even from a young age. Future studies are needed to confirm these findings.

Extent of cortisol suppression at baseline predicts improvement in HPA axis function during antidepressant treatment

BACKGROUND

A dysregulation in the hypothalamic-pituitary-adrenal (HPA)-axis function has been repeatedly observed in major depressive disorders (MDD). Normalization of this dysregulation, i.e. of cortisol suppression after glucocorticoid receptor (GR)-stimulation, may be mandatory for clinical remission in some patient subgroups. However, there are no biological measures applied in the clinical setting to identify patient subgroups with HPA axis alterations.

OBJECTIVE

We aimed to define a suppression index of cortisol concentrations before and after GR stimulation with dexamethasone to predict the variability in improvement of HPA axis activity during antidepressant treatment.

METHODS

A modified dexamethasone suppression test (mDST) was performed with blood withdrawal for cortisol and ACTH measurement before and 3 h after 1.5 mg dexamethasone intake at 18:00 in two cohorts of depressed patients treated in a naturalistic setting. The discovery sample consisted of 106 patients, the replication sample of 117 patients. The suppression index was defined as cCORTpreDEXcCORTpostDEX.

RESULTS

The baseline suppression index explained 27.4 % of the variance in changes of HPA axis activity before and after treatment with antidepressants. Age, cCORTpreDEXcACTHpreDEX at baseline and sex explained further variance up to 56.2 % (stepwise linear regression, p = 7.8e^-8). A threshold of the suppression index at baseline was determined by ROC analysis and revealed, that only patients with a maximum index of 2.32 achieved a normalization of the HPA axis activity after antidepressant treatment. In the replication sample, the threshold was 2.86. However, the estimated suppression index was not associated with treatment response.

CONCLUSION

For the first time, by establishing a short-term suppression index of cortisol before and after GR-stimulation a threshold could be identified to predict improvement of HPA axis activity during antidepressant therapy. After replication in further studies this index may help to identify patients who benefit from a specific treatment that targets components of the HPA axis in the future.

Selective activation of estrogen receptors α and β: Implications for depressive-like phenotypes in female mice exposed to chronic unpredictable stress

The estrogen receptor (ER) mechanisms by which 17β-estradiol influences depressive-like behaviour have primarily been investigated acutely and not within an animal model of depression. Therefore, the current study aimed to dissect the contribution of ERα and ERβ to the effects of 17β-estradiol under non-stress and chronic stress conditions. Ovariectomized (OVX) or sham-operated mice were treated chronically (47 days) with 17β-estradiol (E2), the ERβ agonist diarylpropionitrile (DPN), the ERα agonist propylpyrazole-triol (PPT), or vehicle. On day 15 of treatment, mice from each group were assigned to chronic unpredictable stress (CUS; 28 days) or non-CUS conditions. Mice were assessed for anxiety- and depressive-like behaviour and hypothalamic-pituitary-adrenal (HPA) axis function. Cytokine and chemokine levels, and postsynaptic density protein 95 were measured in the hippocampus and frontal cortex, and adult hippocampal neurogenesis was assessed. Overall, the effects of CUS were more robust that those of estrogenic treatments, as seen by increased immobility in the tail suspension test (TST), reduced PSD-95 expression, reduced neurogenesis in the ventral hippocampus, and HPA axis negative feedback dysregulation. However, we also observe CUS-dependent and -independent effects of ovarian status and estrogenic treatments. The effects of CUS on PSD-95 expression, the cytokine milieu, and in TST were largely driven by PPT and DPN, indicating that these treatments were not protective. Independent of CUS, estradiol increased neurogenesis in the dorsal hippocampus, blunted the corticosterone response to an acute stressor, and increased anxiety-like behaviour. These findings provide insights into the complexities of estrogen signaling in modulating depressive-like phenotypes under non-stress and chronic stress conditions.

Ancestral stress programs sex-specific biological aging trajectories and non-communicable disease risk

The incidence of non-communicable diseases (NCDs) is rising globally but their causes are generally not understood. Here we show that cumulative ancestral stress leads to premature aging and raises NCD risk in a rat population. This longitudinal study revealed that cumulative multigenerational prenatal stress (MPS) across four generations (F0-F3) raises age- and sex-dependent adverse health outcomes in F4 offspring. MPS accelerated biological aging processes and exacerbated sex-specific incidences of respiratory and kidney diseases, inflammatory processes and tumors. Unbiased deep sequencing of frontal cortex revealed that MPS altered expression of microRNAs and their target genes involved in synaptic plasticity, stress regulation, immune function and longevity. Multi-layer top-down deep learning metabolite enrichment analysis of urine markers revealed altered metabolic homeodynamics in MPS males. Thus, peripheral metabolic signatures may provide sensitive biomarkers of stress vulnerability and disease risk. Programming by MPS appears to be a significant determinant of lifetime mental health trajectories, physical wellbeing and vulnerability to NCDs through altered epigenetic regulation.

Selected Sex Related Differences in Pathophysiology of Cardiovascular System

The annual incidence of cardiovascular diseases is age-dependently increasing both in men and women, however, the prevalence is higher in men until midlife. The higher incidence of cardiovascular disease in men than in women of similar age, and the menopause-associated increase in cardiovascular disease in women, has led to speculation that gender-related differences in sex hormones might have a key role in the development and evolution of cardiovascular disease. There are several suggested pathways in which gender and sex hormones can affect human cardiovascular system to produce original sexually different pathophysiology between women and men. Sex steroid hormones and their receptors are critical determinants of cardiovascular gender differences. Also arterial blood pressure is typically lower in women than in men what could be explained particularly by greater synthesis of nitric oxide (NO) in women. Female cardiomyocytes have a greater survival advantage when challenged with oxidative stress, suggesting that female hormones may play an important role in antioxidative protection of myocardium. It was also demonstrated in animal models that combination of XX chromosomes versus an XY chromosomes enhances sex differences in higher HDL cholesterol. Women were found to have reduced sympathetic activity (reflected by lower total peripheral resistance) and pulmonary artery pressure and enhanced parasympathetic activity relative to men. Similarly, men were found to have higher plasma norepinephrine levels than women. Regarding differences between the sexes in electrophysiology of the heart, two principle mechanisms have been proposed to explain them: hormonal effects on the expression or function of ion channels or, conversely, differences in autonomic tone. To improve diagnosis and treatment of cardiovascular diseases, greater focus on understanding the molecular and cellular physiology of the sex steroid hormones and their receptors in the cardiovascular system will be required.

Rhythmicity matters: Circadian and ultradian patterns of HPA axis activity

Oscillations are a fundamental feature of neural and endocrine systems. The hypothalamic-pituitary-adrenal (HPA) axis dynamically controls corticosteroid secretion in basal conditions and in response to stress. Across the 24-h day, HPA axis activity oscillates with both an ultradian and circadian rhythm. These rhythms have been shown to be important for regulating metabolism, inflammation, mood, cognition and stress responsiveness. Here we will discuss the neural and endocrine mechanisms driving these rhythms, the physiological importance of these rhythms and health consequences when they are disrupted.

Evidence for Similar Prefrontal Structural and Functional Alterations in Male and Female Rats Following Chronic Stress or Glucocorticoid Exposure

Previous work of ours and others has documented regressive changes in neuronal architecture and function in the medial prefrontal cortex (mPFC) of male rats following chronic stress. As recent focus has shifted toward understanding whether chronic stress effects on mPFC are sexually dimorphic, here we undertake a comprehensive analysis to address this issue. First, we show that chronic variable stress (14-day daily exposure to different challenges) resulted in a comparable degree of adrenocortical hyperactivity, working memory impairment, and dendritic spine loss in mPFC pyramidal neurons in both sexes. Next, exposure of female rats to 21-day regimen of corticosterone resulted in a similar pattern of mPFC dendritic spine attrition and increase in spine volume. Finally, we examined the effects of another widely used regimen, chronic restraint stress (CRS, 21-day of daily 6-h restraint), on dendritic spine changes in mPFC in both sexes. CRS resulted in response decrements in adrenocortical output (habituation), and induced a pattern of consistent, but less widespread, dendritic spine loss similar to the foregoing challenges. Our data suggest that chronic stress or glucocorticoid exposure induces a relatively undifferentiated pattern of structural and functional alterations in mPFC in both males and females.

Transcendental meditation and hypothalamic-pituitary-adrenal axis functioning: a pilot, randomized controlled trial with young adults

Transcendental meditation (TM) is effective in alleviating stress and anxiety and promoting well-being. While the underlying biological mechanisms of TM are not yet fully explored, the hypothalamic-pituitary-adrenal (HPA) axis represents an index providing important clues embodying the stress system cascade. In this pilot study, young adults were randomly assigned to TM training followed by 8 weeks of meditation practice or a wait-list control condition. TM was conducted over 8 weeks. Thirty-four young adult participants were randomized; 27 participants completed the HPA outcome assessments (41% male). To assess HPA axis functioning, salivary samples to assess cortisol awakening response (CAR) that were collected in the morning, both at baseline and at week-4. Salivary cortisol in the context of a social stressor using the Trier Social Stress Test (TSST) was collected at week-8. The results indicate that participants who were randomly assigned to TM had lower awakening salivary cortisol levels and a greater drop in CAR from baseline to week-4 than the control group. There were no significant differences in HPA axis functioning in the context of the TSST. Primary limitations of this randomized controlled trial were the small sample size, the use of a wait-list as opposed to an active control, and the limited scope of HPA axis assessments. The results of this pilot study provide tentative evidence that TM may impact biological stress system functioning and suggests that this may be a worthwhile avenue to continue to examine. It will also be useful to extend these findings to a broader array of meditative and mindful practices, particularly for those who are experiencing more distress.

The role of sex and gender in anxiety disorders: Being scared "like a girl"?

Anxiety disorders are among the most prevalent mental disorders, and women are at much higher risk to develop an(y) anxiety disorder. Women seem to experience more severe and long-lasting symptoms than men. Sex differences regarding etiology can be best understood from a vulnerability-stress perspective. A different exposure to psychosocial stressors and an increased biologic and/or psychologic vulnerability toward anxiety in women may contribute to the sex differences in anxiety disorders. Evidently, these findings have implications for both the diagnosis and treatment of patients with anxiety disorders. Therapists should be aware of gender bias during the diagnostic process and be sensitive for self-reporting bias (i.e., the reluctance to report "female-like" symptoms by men). Research on sex differences with respect to treatment is lacking and gender-related knowledge has rarely been integrated into clinical interventions. Interventions aimed at transdiagnostic factors that have been shown to relate to sex differences in anxiety seem rather promising and have the potential to enhance the care for both men and women with anxiety disorders.

The promises and pitfalls of sex difference research

Funding agencies in North America and Europe are recognizing the importance of the integration of sex differences into basic and clinical research. Although these mandates are in place to improve our knowledge of health for both men and women, there have been a number of implementation issues that require vigilance on the part of funders and the research community. Here we discuss issues on simple inclusion of both sexes in studies to specialisation of sex differences with attention paid to statistics and the need for sex-specific treatments. We suggest differing mandates need to be considered regarding simple integration versus the need for studies in the specialisation of sex differences and/or the need for research that recognises the importance of male-specific or female-specific factors that influence subsequent health such as menstruation, menopause or pregnancy.

Ovarian status dictates the neuroinflammatory and behavioral consequences of sub-chronic stress exposure in middle-aged female mice

Ovarian hormones influence the outcomes of stress exposure and are implicated in stress-related disorders including depression, yet their roles are often complex and seemingly contradictory. Importantly, depression and stress exposure are associated with immune dysregulation, and ovarian hormones have immunomodulatory properties. However, how ovarian hormones can influence the inflammatory outcomes of stress exposure is poorly understood. Here, we examined the effects of long-term ovariectomy on the behavioral and neuroinflammatory outcomes of sub-chronic stress exposure in middle-aged mice. Briefly, sham-operated and ovariectomized mice were assigned to non-stress groups or exposed to 6 days of variable stress. Mice were assessed on a battery of behavioral tests, and cytokine concentrations were quantified in the frontal cortex and hippocampus. In the frontal cortex, postsynaptic density protein-95 expression was examined as an index of excitatory synapse number and/or stability, and phosphorylated mitogen-activated protein kinases (MAPKs) were measured to explore potential cell signaling pathways elicited by stress exposure and/or ovarian hormones. Long-term ovariectomy modified the central cytokine profile by robustly reducing cytokine concentrations in the frontal cortex and modestly increasing concentrations in the hippocampus. Under non-stress conditions, long-term ovariectomy also reduced extracellular signal-regulated kinase (ERK) phosphoprotein expression in the frontal cortex and increased some measures of depressive-like behavior. The effects of sub-chronic stress exposure were however more pronounced in sham-operated mice. Notably, in sham-operated mice only, sub-chronic stress exposure increased IL-1β and IL-6:IL-10 ratio in the frontal cortex and hippocampus and reduced pERK1/2 expression in the frontal cortex. Further, although sub-chronic stress exposure increased anhedonia-like behavior regardless of ovarian status, it increased passive-coping behavior in sham-operated mice only. These data indicate that long-term ovariectomy has potent effects on the central cytokine milieu and dictates the neuroinflammatory and behavioral effects of sub-chronic stress exposure in middle-aged mice. These findings therefore suggest that the immunomodulatory properties of ovarian hormones are of relevance in the context of stress and possibly depression.

Neuroendocrinology of reward in anorexia nervosa and bulimia nervosa: Beyond leptin and ghrelin

The pathophysiology of anorexia nervosa (AN) and bulimia nervosa (BN) are still poorly understood, but psychobiological models have proposed a key role for disturbances in the neuroendocrines that signal hunger and satiety and maintain energy homeostasis. Mounting evidence suggests that many neuroendocrines involved in the regulation of homeostasis and body weight also play integral roles in food reward valuation and learning via their interactions with the mesolimbic dopamine system. Neuroimaging data have associated altered brain reward responses in this system with the dietary restriction and binge eating and purging characteristic of AN and BN. Thus, neuroendocrine dysfunction may contribute to or perpetuate eating disorder symptoms via effects on reward circuitry. This narrative review focuses on reward-related neuroendocrines that are altered in eating disorder populations, including peptide YY, insulin, stress and gonadal hormones, and orexins. We provide an overview of the animal and human literature implicating these neuroendocrines in dopaminergic reward processes and discuss their potential relevance to eating disorder symptomatology and treatment.

The effects of prenatal dexamethasone exposure and fructose challenge on pituitary-adrenocortical activity and anxiety-like behavior in female offspring

Prenatal glucocorticoid overexposure could largely influence pituitary-adrenal activity and anxiety-like behavior in offspring. Our aim was to study the possible potentiating effect of moderate dose of fructose - common ingredient of today's diet - on prenatal glucocorticoid treatment-induced hypothalamo-pituitary-adrenal (HPA) axis changes. Pregnant female rats were treated with multiple dexamethasone (Dx) doses (3 x 0.5 mg/kg/b.m. Dx; 16th-18th gestational day). Half of female offspring from control and Dx treated dams were supplemented with 10% fructose solution, from weaning till adulthood. Immunohistochemistry, unbiased stereological evaluation and hormonal analysis are used to provide the morpho-functional state of pituitary and adrenal gland. Anxiety-like behavior was assessed using the light/dark box test and the elevated plus maze test. Prenatally Dx exposed females, with or without fructose consumption, had markedly reduced adrenocortical volume (p < 0.05) comparing to controls. Increased basal plasma ACTH level in these females (p < 0.05) maintained corticosterone concentration at control level produced by smaller adrenal glands. In parallel, anxiety-like behavior was shown by both tests used. In conclusion, prenatal Dx exposure cause negative psychophysiological outcome reflected in increased HPA axis activity and anxiety behavior in female offspring, while moderately increased fructose consumption failed to evoke any alteration or to potentiate effects of prenatal Dx exposure.

Sex Differences in Adrenal Bmal1 Deletion-Induced Augmentation of Glucocorticoid Responses to Stress and ACTH in Mice

The circadian glucocorticoid (GC) rhythm is dependent on a molecular clock in the suprachiasmatic nucleus (SCN) and an adrenal clock that is synchronized by the SCN. To determine whether the adrenal clock modulates GC responses to stress, experiments used female and male Cyp11A1Cre/+::Bmal1Fl/Fl knockout [side-chain cleavage (SCC)-KO] mice, in which the core clock gene, Bmal1, is deleted in all steroidogenic tissues, including the adrenal cortex. Following restraint stress, female and male SCC-KO mice demonstrate augmented plasma corticosterone but not plasma ACTH. In contrast, following submaximal scruff stress, plasma corticosterone was elevated only in female SCC-KO mice. Adrenal sensitivity to ACTH was measured in vitro using acutely dispersed adrenocortical cells. Maximal corticosterone responses to ACTH were elevated in cells from female KO mice without affecting the EC50 response. Neither the maximum nor the EC50 response to ACTH was affected in male cells, indicating that female SCC-KO mice show a stronger adrenal phenotype. Parallel experiments were conducted using female Cyp11B2 (Aldosterone Synthase)Cre/+::Bmal1Fl/Fl mice and adrenal cortex-specific Bmal1-null (Ad-KO) mice. Plasma corticosterone was increased in Ad-KO mice following restraint or scruff stress, and in vitro responses to ACTH were elevated in adrenal cells from Ad-KO mice, replicating data from female SCC-KO mice. Gene analysis showed increased expression of adrenal genes in female SCC-KO mice involved in cell cycle control, cell adhesion-extracellular matrix interaction, and ligand receptor activity that could promote steroid production. These observations underscore a role for adrenal Bmal1 as an attenuator of steroid secretion that is most prominent in female mice.

Sex-specific roles of cellular inflammation and cardiometabolism in obesity-associated depressive symptomatology

BACKGROUND

Obesity and depression are complex conditions with stronger comorbid relationships among women than men. Inflammation and cardiometabolic dysfunction are likely mechanistic candidates for increased depression risk, and their prevalence differs by sex. Whether these relationships extend to depressive symptoms is poorly understood. Therefore, we analyzed sex in associations between inflammation and metabolic syndrome (MetS) criteria on depressive symptomatology. Specifically, we examined whether sex positively moderates the relationship between depressive symptoms and inflammation among women, and whether MetS has parallel effects among men.

METHODS

Depressive symptoms, MetS, and inflammation were assessed in 129 otherwise healthy adults. Depressive symptoms were assessed using Beck Depression Inventory (BDI-Ia). Monocyte inflammation regulation (BARIC) was quantified using flow cytometry measurement of TNF-α suppression by β-agonist. Moderation effects of sex on associations between BARIC, MetS criteria, and BDI were estimated using two-way ANOVA and linear regression, adjusting for BMI, and by sex subgroup analyses.

RESULTS

Obese individuals reported more depressive symptoms. Sex did not formally moderate this relationship, though BDI scores tended to differ by BMI among women, but not men, in subgroup analysis. Poorer inflammation control and higher MetS criteria were correlated with somatic depressive symptoms. Sex moderated associations between MetS criteria and somatic symptoms; among men, MetS criteria predicted somatic symptoms, not among women. Subgroup analysis further indicated that poorer inflammation control tended to be associated with higher somatic symptoms in women.

CONCLUSIONS

These results indicate that obesity-related inflammation and MetS factors have sex-specific effects on depressive symptoms in a non-clinical population. Although pathophysiological mechanisms underlying sex differences remain to be elucidated, our findings suggest that distinct vulnerabilities to depressive symptoms exist between women and men, and highlight the need to consider sex as a key biological variable in obesity-depression relationships. Future clinical studies on comorbid obesity and depression should account for sex, which may optimize therapeutic strategies.

Neurobiological mechanisms underlying sex-related differences in stress-related disorders: Effects of neuroactive steroids on the hippocampus

Men and women differ in their vulnerability to a variety of stress-related illnesses, but the underlying neurobiological mechanisms are not well understood. This is likely due to a comparative dearth of neurobiological studies that assess male and female rodents at the same time, while human neuroimaging studies often don't model sex as a variable of interest. These sex differences are often attributed to the actions of sex hormones, i.e. estrogens, progestogens and androgens. In this review, we summarize the results on sex hormone actions in the hippocampus and seek to bridge the gap between animal models and findings in humans. However, while effects of sex hormones on the hippocampus are largely consistent in animals and humans, methodological differences challenge the comparability of animal and human studies on stress effects. We summarise our current understanding of the neurobiological mechanisms that underlie sex-related differences in behavior and discuss implications for stress-related illnesses.