Sex steroid hormones and brain function: PET imaging as a tool for research

Relating sex-bias in human cortical and hippocampal microstructure to sex hormones

Determining sex-bias in brain structure is of great societal interest to improve diagnostics and treatment of brain-related disorders. So far, studies on sex-bias in brain structure predominantly focus on macro-scale measures, and often ignore factors determining this bias. Here we study sex-bias in cortical and hippocampal microstructure in relation to sex hormones. Investigating quantitative intracortical profiling in-vivo using the T1w/T2w ratio in 1093 healthy females and males of the cross-sectional Human Connectome Project young adult sample, we find that regional cortical and hippocampal microstructure differs between males and females and that the effect size of this sex-bias varies depending on self-reported hormonal status in females. Microstructural sex-bias and expression of sex hormone genes, based on an independent post-mortem sample, are spatially coupled. Lastly, sex-bias is most pronounced in paralimbic areas, with low laminar complexity, which are predicted to be most plastic based on their cytoarchitectural properties. Albeit correlative, our study underscores the importance of incorporating sex hormone variables into the investigation of brain structure and plasticity.

Sex as a Determinant of Age-Related Changes in the Brain

The notion of notable anatomical, biochemical, and behavioral distinctions within male and female brains has been a contentious topic of interest within the scientific community over several decades. Advancements in neuroimaging and molecular biological techniques have increasingly elucidated common mechanisms characterizing brain aging while also revealing disparities between sexes in these processes. Variations in cognitive functions; susceptibility to and progression of neurodegenerative conditions, notably Alzheimer's and Parkinson's diseases; and notable disparities in life expectancy between sexes, underscore the significance of evaluating aging within the framework of gender differences. This comprehensive review surveys contemporary literature on the restructuring of brain structures and fundamental processes unfolding in the aging brain at cellular and molecular levels, with a focus on gender distinctions. Additionally, the review delves into age-related cognitive alterations, exploring factors influencing the acceleration or deceleration of aging, with particular attention to estrogen's hormonal support of the central nervous system.

Heart-brain axis: Pushing the boundaries of cardiovascular molecular imaging

Despite decades of research, the heart-brain axis continues to challenge investigators seeking to unravel its complex pathobiology. Strong epidemiologic evidence supports a link by which insult or injury to one of the organs increases the risk of pathology in the other. The putative pathways have important differences between sexes and include alterations in autonomic function, metabolism, inflammation, and neurohormonal mechanisms that participate in crosstalk between the heart and brain and contribute to vascular changes, the development of shared risk factors, and oxidative stress. Recently, given its unique ability to characterize biological processes in multiple tissues simultaneously, molecular imaging has yielded important insights into the interplay of these organ systems under conditions of stress and disease. Yet, additional research is needed to probe further into the mechanisms underlying the heart-brain axis and to evaluate the impact of targeted interventions.

The impact of 17β-estradiol on the estrogen-deficient female brain: from mechanisms to therapy with hot flushes as target symptoms

Sex steroids are essential for whole body development and functions. Among these steroids, 17β-estradiol (E2) has been known as the principal "female" hormone. However, E2's actions are not restricted to reproduction, as it plays a myriad of important roles throughout the body including the brain. In fact, this hormone also has profound effects on the female brain throughout the life span. The brain receives this gonadal hormone from the circulation, and local formation of E2 from testosterone via aromatase has been shown. Therefore, the brain appears to be not only a target but also a producer of this steroid. The beneficial broad actions of the hormone in the brain are the end result of well-orchestrated delayed genomic and rapid non-genomic responses. A drastic and steady decline in circulating E2 in a female occurs naturally over an extended period of time starting with the perimenopausal transition, as ovarian functions are gradually declining until the complete cessation of the menstrual cycle. The waning of endogenous E2 in the blood leads to an estrogen-deficient brain. This adversely impacts neural and behavioral functions and may lead to a constellation of maladies such as vasomotor symptoms with varying severity among women and, also, over time within an individual. Vasomotor symptoms triggered apparently by estrogen deficiency are related to abnormal changes in the hypothalamus particularly involving its preoptic and anterior areas. However, conventional hormone therapies to "re-estrogenize" the brain carry risks due to multiple confounding factors including unwanted hormonal exposure of the periphery. In this review, we focus on hot flushes as the archetypic manifestation of estrogen deprivation in the brain. Beyond our current mechanistic understanding of the symptoms, we highlight the arduous process and various obstacles of developing effective and safe therapies for hot flushes using E2. We discuss our preclinical efforts to constrain E2's beneficial actions to the brain by the DHED prodrug our laboratory developed to treat maladies associated with the hypoestrogenic brain.

High-amplitude network co-fluctuations linked to variation in hormone concentrations over the menstrual cycle

Many studies have shown that the human endocrine system modulates brain function, reporting associations between fluctuations in hormone concentrations and brain connectivity. However, how hormonal fluctuations impact fast changes in brain network organization over short timescales remains unknown. Here, we leverage a recently proposed framework for modeling co-fluctuations between the activity of pairs of brain regions at a framewise timescale. In previous studies we showed that time points corresponding to high-amplitude co-fluctuations disproportionately contributed to the time-averaged functional connectivity pattern and that these co-fluctuation patterns could be clustered into a low-dimensional set of recurring "states." Here, we assessed the relationship between these network states and quotidian variation in hormone concentrations. Specifically, we were interested in whether the frequency with which network states occurred was related to hormone concentration. We addressed this question using a dense-sampling dataset (N = 1 brain). In this dataset, a single individual was sampled over the course of two endocrine states: a natural menstrual cycle and while the subject underwent selective progesterone suppression via oral hormonal contraceptives. During each cycle, the subject underwent 30 daily resting-state fMRI scans and blood draws. Our analysis of the imaging data revealed two repeating network states. We found that the frequency with which state 1 occurred in scan sessions was significantly correlated with follicle-stimulating and luteinizing hormone concentrations. We also constructed representative networks for each scan session using only "event frames"-those time points when an event was determined to have occurred. We found that the weights of specific subsets of functional connections were robustly correlated with fluctuations in the concentration of not only luteinizing and follicle-stimulating hormones, but also progesterone and estradiol.

Peering into the Brain's Estrogen Receptors: PET Tracers for Visualization of Nuclear and Extranuclear Estrogen Receptors in Brain Disorders

Estrogen receptors (ERs) play a multitude of roles in brain function and are implicated in various brain disorders. The use of positron emission tomography (PET) tracers for the visualization of ERs' intricate landscape has shown promise in oncology but remains limited in the context of brain disorders. Despite recent progress in the identification and development of more selective ligands for various ERs subtypes, further optimization is necessary to enable the reliable and efficient imaging of these receptors. In this perspective, we briefly touch upon the significance of estrogen signaling in the brain and raise the setbacks associated with the development of PET tracers for identification of specific ERs subtypes in the brain. We then propose avenues for developing efficient PET tracers to non-invasively study the dynamics of ERs in the brain, as well as neuropsychiatric diseases associated with their malfunction in a longitudinal manner. This perspective puts several potential candidates on the table and highlights the unmet needs and areas requiring further research to unlock the full potential of PET tracers for ERs imaging, ultimately aiding in deepening our understanding of ERs and forging new avenues for potential therapeutic strategies.

Mitochondria are midfield players in steroid synthesis

Steroids are important membrane components and signaling metabolites and thus are required for cellular homeostasis. All mammalian cells retain the ability to uptake and synthesize steroids. Dysregulation of steroid levels leads to profound effects on cellular function and organismal health. Hence it comes as no surprise that steroid synthesis is tightly regulated. It is well established that the main site for steroid synthesis and regulation is the endoplasmic reticulum. However, mitochondria are essential for: (1) cholesterol production (the precursor of all steroids) by exporting citrate and; (2) the products of steroidogenesis (such as mineralocorticoids and glucocorticoids). In this review, we describe the midfield player role of mitochondria in steroid synthesis and bring the idea of mitochondria actively participating in steroid synthesis regulation. A better understanding of the mitochondrial regulatory roles in steroid synthesis would open new avenues to targeted approaches aiming to control steroid levels.

Reproductive endocrine disruption and gonadal intersex induction in male Japanese medaka chronically exposed to betamethasone at environmentally relevant levels

The broad utilization of betamethasone in medical treatments may pose a significant ecotoxicological risk to aquatic organisms, yet its potential reproductive toxicity remains unclear. The present study examined the impacts of environmental exposure on male reproduction using Japanese medaka (Oryzias latipes). After 110 days of betamethasone exposure at environmentally relevant concentrations (0, 20 and 200 ng/L), LH/FSH synthesis and release in the pituitary was inhibited, and the production of sex hormones and their signaling pathways in the gonads of male medaka were greatly influenced. This synthetic glucocorticoid restrained testosterone (T) synthesis and gave rise to a significant increase in E₂/T and E₂/11-KT ratios. Furthermore, chronic betamethasone exposure (20 and 200 ng/L) led to the suppression of androgen receptor (AR) signaling and enhancement of estrogen receptors (ERs) signaling. An increase in hepatic vitellogenin contents was also detected, and testicular oocytes were observed in both 20 and 200 ng/L betamethasone-treated groups. It showed that 20 and 200 ng/L betamethasone could induce male feminization and even intersex, triggering abnormal spermatogenesis in medaka males. With its adverse effects on male fertility, betamethasone could potentially influence the fishery productivity and population dynamics in aquatic ecosystems.

Association between aldehyde exposure and sex steroid hormones among adults

Exogenous and endogenous exposure to aldehydes is seen worldwide. Aldehydes are closely associated with human diseases, especially reproductive toxicity. However, the effect of aldehyde exposure on sex steroid hormones among adults remains uninvestigated. A total of 851 participants aged over 18 years were included in this cross-sectional analysis based on data from National Health and Nutrition Examination Survey (NHANES) 2013-2014. Serum aldehyde concentrations were quantified following an automated analytical method. Sex steroid hormones including total testosterone, estradiol, and sex hormone binding globulin (SHBG) were detected. Multivariate linear regression models, forest plots, generalized additive model (GAM), and smooth curve fitting analysis were used to assess the associations between quartiles of aldehydes and sex steroid hormones levels after adjusting for potential confounders. Butyraldehyde and propanaldehyde were found to be negatively associated with estradiol and SHBG in females and males, respectively. β values with 95% confidence intervals (95% CIs) were - 20.59 (- 38.30 to - 2.88) for Q2 vs. Q1 of butyraldehyde and - 8.13 (- 14.92 to - 1.33) and - 7.79 (- 14.91 to - 0.67) for Q2 vs. Q1 and Q4 vs. Q1 of propanaldehyde. No significant associations were observed between other aldehydes and sex hormones. In premenopausal women, isopentanaldehyde was inversely associated with serum total testosterone levels (Q4 vs. Q1: OR =  - 7.95, 95% CI: - 15.62 to - 0.27), whereas propanaldehyde was positively associated with serum estradiol concentration (Q3 vs. Q1: β = 28.88, 95% CI: 0.83 to 56.94). Compared with Q1, Q3 of isopentanaldehyde was associated with 3.53 pg/mL higher concentration of estradiol in postmenopausal women (β = 3.53, 95% CI: 0.08 to 6.97). Moreover, in males under 40 years, butyraldehyde and heptanaldehyde were inversely proportional to total testosterone levels and heptanaldehyde and butyraldehyde were negatively associated with estradiol and SHBG. Decreased total testosterone, elevated estradiol, and decreased SHBG levels were found in higher quartiles of benzaldehyde, hexanaldehyde and isopentanaldehyde, and propanaldehyde, respectively, in males aged over 60 years. In male participants aged 40-60 years, only hexanaldehyde was observed to be correlated with higher serum estradiol levels. In conclusion, our current research presented the association between six serum aldehydes and sex hormones. Of note, stratification analyses were conducted in participants with different menopausal statuses and age among males and females. Sex- and age-specific effect of aldehyde exposure on alterations in sex hormone levels were observed. Further studies are warranted to confirm the causal relationship and explore the underlying mechanisms.

The Effect of Menopause on Antipsychotic Response

Background: It has been hypothesized that, whenever estrogen levels decline, psychosis symptoms in women increase. At menopause, this can happen in two main ways: (a) the loss of estrogen (mainly estradiol) can directly affect central neurotransmission, leading to increase in schizophrenia-related symptoms, and (b) the loss of estrogen can decrease the synthesis of enzymes that metabolize antipsychotic drugs, thus weakening their efficacy. Aims and Methods: The aim of this narrative review was to investigate the second possibility by searching PubMed and ClinicalTrials.gov for studies over the last two decades that investigated the metabolism of antipsychotics and their efficacy before and after menopause in women or that studied systemic and local estrogen level effects on the pharmacokinetics and pharmacodynamics of individual antipsychotic drugs. Results: The evidence suggests that symptom level in women with schizophrenia rises after menopause for many reasons beyond hormones but, importantly, there is an estrogen-dependent loss of efficacy related to antipsychotic treatment. Conclusion: Effective clinical intervention is challenging; nevertheless, several promising routes forward are suggested.

The Genomic Architecture of Pregnancy-Associated Plasticity in the Maternal Mouse Hippocampus

Pregnancy is associated with extraordinary plasticity in the maternal brain. Studies in humans and other mammals suggest extensive structural and functional remodeling of the female brain during and after pregnancy. However, we understand remarkably little about the molecular underpinnings of this natural phenomenon. To gain insight into pregnancy-associated hippocampal plasticity, we performed single nucleus RNA sequencing (snRNA-seq) and snATAC-seq from the mouse hippocampus before, during, and after pregnancy. We identified cell type-specific transcriptional and epigenetic signatures associated with pregnancy and postpartum adaptation. In addition, we analyzed receptor-ligand interactions and transcription factor (TF) motifs that inform hippocampal cell type identity and provide evidence of pregnancy-associated adaption. In total, these data provide a unique resource of coupled transcriptional and epigenetic data across a dynamic time period in the mouse hippocampus and suggest opportunities for functional interrogation of hormone-mediated plasticity.

PET Imaging of Estrogen Receptors Using 18F-Based Radioligands

In vivo molecular imaging of estrogen receptor alpha (ER) can be performed via positron emission tomography (PET) using ER-specific radioligands, such as 16α-[¹⁸F]fluoro-17β-estradiol (¹⁸F-FES). ¹⁸F-FES is a radiopharmaceutical recently approved by the United States Food and Drug Administration for use with PET imaging to detect ER+ lesions in patients with recurrent or metastatic breast cancer as an adjunct to biopsy. ¹⁸F-FES PET imaging has been used in clinical studies and preclinical research to assess whole-body ER protein expression and ligand binding function across multiple metastatic sites, to demonstrate inter-tumoral and temporal heterogeneity of ER expression, to quantify the pharmacodynamic effects of ER antagonist treatment, and to predict endocrine therapy response. ¹⁸F-FES PET has also been studied for imaging ER in endometrial and ovarian cancer. This chapter details the experimental protocol for ¹⁸F-FES PET imaging of ER in preclinical tumor xenograft models. Consistent adherence to key methodologic details will facilitate obtaining meaningful and reproducible ¹⁸F-FES PET preclinical imaging results, which could yield additional insight for clinical trials regarding imaging biomarkers and oncologic therapy.

Hormones and Sex-Specific Medicine in Human Physiopathology

A prodigious increment of scientific evidence in both preclinical and clinical studies is narrowing a major gap in knowledge regarding sex-specific biological responses observed in numerous branches of clinical practices. Some paradigmatic examples include neurodegenerative and mental disorders, immune-related disorders such as pathogenic infections and autoimmune diseases, oncologic conditions, and cardiovascular morbidities. The male-to-female proportion in a population is expressed as sex ratio and varies eminently with respect to the pathophysiology, natural history, incidence, prevalence, and mortality rates. The factors that determine this scenario incorporate both sex-associated biological differences and gender-dependent sociocultural issues. A broad narrative review focused on the current knowledge about the role of hormone regulation in gender medicine and gender peculiarities across key clinical areas is provided. Sex differences in immune response, cardiovascular diseases, neurological disorders, cancer, and COVID-19 are some of the hints reported. Moreover, gender implications in occupational health and health policy are offered to support the need for more personalized clinical medicine and public health approaches to achieve an ameliorated quality of life of patients and better outcomes in population health.

Sex is a defining feature of neuroimaging phenotypes in major brain disorders

Sex is a biological variable that contributes to individual variability in brain structure and behavior. Neuroimaging studies of population-based samples have identified normative differences in brain structure between males and females, many of which are exacerbated in psychiatric and neurological conditions. Still, sex differences in MRI outcomes are understudied, particularly in clinical samples with known sex differences in disease risk, prevalence, and expression of clinical symptoms. Here we review the existing literature on sex differences in adult brain structure in normative samples and in 14 distinct psychiatric and neurological disorders. We discuss commonalities and sources of variance in study designs, analysis procedures, disease subtype effects, and the impact of these factors on MRI interpretation. Lastly, we identify key problems in the neuroimaging literature on sex differences and offer potential recommendations to address current barriers and optimize rigor and reproducibility. In particular, we emphasize the importance of large-scale neuroimaging initiatives such as the Enhancing NeuroImaging Genetics through Meta-Analyses consortium, the UK Biobank, Human Connectome Project, and others to provide unprecedented power to evaluate sex-specific phenotypes in major brain diseases.

PET imaging of brain aromatase in humans and rhesus monkeys by 11C-labeled cetrozole analogs

Aromatase is an estrogen synthetic enzyme that plays important roles in brain functions. To quantify aromatase expression in the brain by positron emission tomography (PET), we had previously developed [¹¹C]cetrozole, which showed high specificity and affinity. To develop more efficient PET tracer(s) for aromatase imaging, we synthesized three analogs of cetrozole. We synthesized meta-cetrozole, nitro-cetrozole, and iso-cetrozole, and prepared the corresponding ¹¹C-labeled tracers. The inhibitory activities of these three analogs toward aromatase were evaluated using marmoset placenta, and PET imaging of brain aromatase was performed using the ¹¹C-labeled tracers in monkeys. The most promising analog in the monkey study, iso-cetrozole, was evaluated in the human PET study. The highest to lowest inhibitory activity of the analogs toward aromatase in the microsomal fraction from marmoset placenta was in the following order: iso-cetrozole, nitro-cetrozole, cetrozole, and meta-cetrozole. This order showed good agreement with the order of the binding potential (BP) of each ¹¹C-labeled analog to aromatase in the rhesus monkey brain. A human PET study using [¹¹C]iso-analog showed a similar distribution pattern of binding as that of [¹¹C]cetrozole. The time-activity curves showed that elimination of [¹¹C]iso-cetrozole from brain tissue was faster than that of ¹¹C-cetrozole, indicating more rapid metabolism of [¹¹C]iso-cetrozole. [¹¹C]Cetrozole has preferable metabolic stability for brain aromatase imaging in humans, although [¹¹C]iso-cetrozole might also be useful to measure aromatase level in living human brain because of its high binding potential.

The Effects of Testosterone on the Brain of Transgender Men

Transgender men (TM) experience an incongruence between the female sex assigned when they were born and their self-perceived male identity. Some TM seek for a gender affirming hormone treatment (GAHT) to induce a somatic transition from female to male through continuous administration of testosterone. GAHT seems to be relatively safe. However, testosterone produces structural changes in the brain as detected by quantitative magnetic resonance imaging. Mainly, it induces an increase in cortical volume and thickness and subcortical structural volume probably due to the anabolic effects. Animal models, specifically developed to test the anabolic hypothesis, suggest that testosterone and estradiol, its aromatized metabolite, participate in the control of astrocyte water trafficking, thereby controlling brain volume.

Voxel-Based Analysis of [18F]-FDG Brain PET in Rats Using Data-Driven Normalization

Introduction: [18F]-FDG PET is a widely used imaging modality that visualizes cellular glucose uptake and provides functional information on the metabolic state of different tissues in vivo. Various quantification methods can be used to evaluate glucose metabolism in the brain, including the cerebral metabolic rate of glucose (CMR_glc) and standard uptake values (SUVs). Especially in the brain, these (semi-)quantitative measures can be affected by several physiological factors, such as blood glucose level, age, gender, and stress. Next to this inter- and intra-subject variability, the use of different PET acquisition protocols across studies has created a need for the standardization and harmonization of brain PET evaluation. In this study we present a framework for statistical voxel-based analysis of glucose uptake in the rat brain using histogram-based intensity normalization.

Methods: [18F]-FDG PET images of 28 normal rat brains were coregistered and voxel-wisely averaged. Ratio images were generated by voxel-wisely dividing each of these images with the group average. The most prevalent value in the ratio image was used as normalization factor. The normalized PET images were voxel-wisely averaged to generate a normal rat brain atlas. The variability of voxel intensities across the normalized PET images was compared to images that were either normalized by whole brain normalization, or not normalized.

To illustrate the added value of this normal rat brain atlas, 9 animals with a striatal hemorrhagic lesion and 9 control animals were intravenously injected with [18F]-FDG and the PET images of these animals were voxel-wisely compared to the normal atlas by group- and individual analyses.

Results: The average coefficient of variation of the voxel intensities in the brain across normal [18F]-FDG PET images was 6.7% for the histogram-based normalized images, 11.6% for whole brain normalized images, and 31.2% when no normalization was applied. Statistical voxel-based analysis, using the normal template, indicated regions of significantly decreased glucose uptake at the site of the ICH lesion in the ICH animals, but not in control animals.

Conclusion: In summary, histogram-based intensity normalization of [18F]-FDG uptake in the brain is a suitable data-driven approach for standardized voxel-based comparison of brain PET images.

Differential Gene Expression in Post-Finasteride Syndrome Patients

BACKGROUND

An organic etiology underpinning post-finasteride syndrome, a constellation of persistent sexual, neuropsychiatric, and somatic symptoms reported by men exposed to 5-alpha-reductase inhibitors (5ARIs), is debated. Persistent changes in neurosteroid levels or androgen receptor expression have been implicated.

AIM

To determine whether differences in gene expression, especially in relevant biologic pathways, exist between patients reporting post-finasteride syndrome symptoms and healthy controls.

METHODS

This was a single center, prospective case-control study taking place between March 2013 and September 2018. Men 18 years and older being evaluated for sexual dysfunction (study) or circumcision (control) were eligible for inclusion. Twenty-six men with a history of 5ARI use reporting symptoms consistent with post-finasteride syndrome were included in the patient group. Twenty-six men consented to inclusion in the control group.

OUTCOMES

The primary outcome measure is gene expression data for genes affecting neurosteroid levels and androgen receptor activity from penile skin cells.

RESULTS

Gene expression of cells from penile skin samples from twenty-six men of median age 38 years (IQR, 33-42) in the study group was compared with that from twenty-six men of median age 41 years (IQR, 35-62) in the control group (P = .13), with 1,446 genes significantly over-expressed and 2,318 genes significantly under-expressed in study patients. Androgen receptor expression was significantly higher in study patients compared to controls (9.961 vs 9.494, adjusted P value = .01). Serum levels of androgen receptor activity markers 5α-androstanediol (0.950 ng/mL [0.749-1.587] vs 0.949 [0.817-1.337], P = .34) or 3α-androstanedione (3.1 ng/mL [1.925-5.475] vs 6.7 [3.375-11.4], P = .31) revealed no significant differences. No significant differences were found between the number of trinucleotide repeats (21.5 [20-23.75], 22 [19-25], P = .94).

CLINICAL IMPLICATIONS

In this study we present evidence of gene expression correlating with observed biologic differences in patients with post-finasteride syndrome; providers who prescribe 5ARIs should be aware and advise their patients accordingly.

STRENGTHS & LIMITATIONS

Strengths of this study include the evaluation of multiple proposed etiologies for post-finasteride syndrome. The study is also strengthened by the fact that not all data matched the initial hypotheses, qualifying the argument for the existence of PFS. Limitations include potential selection bias arising from more severe phenotypes seeking care; lack of gene expression data prior to 5ARI exposure; lack of non-penile tissue samples supposedly involved; and a lack of mechanistic data to imply causality.

CONCLUSION

This study is the first to consider and demonstrate gene expression differences in patients with PFS as a potential etiology of sexual dysfunction. Howell S, Song W, Pastuszak A, et al. Differential Gene Expression in Post-Finasteride Syndrome Patients. J Sex Med 2021;18:1479-1490.

Dehydroepiandrosterone (DHEA) Serum Levels Indicate Cerebrospinal Fluid Levels of DHEA and Estradiol (E2) in Women at Term Pregnancy

Neuroactive steroids such as dehydroepiandrosterone (DHEA), estradiol (E2), and progesterone (P4) are associated with structural and functional changes in the central nervous system (CNS). Measurement of steroid levels in the CNS compartments is restricted in accessibility. Consequently, there is only limited human data on the distributional equilibrium for steroid levels between peripheral and central compartments. While some neuroactive steroids including DHEA and E2 have been reported to convey excitatory and proconvulsant properties, the opposite was demonstrated for P4. We aimed to elucidate the correlation between peripheral and central DHEA, E2, and P4 levels in women at term pregnancy. CSF and serum samples of 27 healthy pregnant women (22–39 years) at term pregnancy were collected simultaneously under combined spinal and epidural anesthesia and used for DHEA ELISA and E2, and P4 ECLIA. All three neuroactive steroids were detected at markedly lower levels in CSF compared to their corresponding serum concentrations (decrease, mean ± SD, 97.66 ± 0.83%). We found a strong correlation for DHEA between its serum and the corresponding CSF levels (r = 0.65, p = 0.003). Serum and CSF levels of E2 (r = 0.31, p = 0.12) appeared not to correlate in the investigated cohort. DHEA serum concentration correlated significantly with E2 (r = 0.58, p = 0.0016) in CSF. In addition, a strong correlation was found between DHEA and E2, both measured in CSF (r = 0.65, p = 0.0002). Peripheral DHEA levels might serve as an indicator for central nervous levels of the neuroactive steroids DHEA and E2 in pregnant women.

The influence of high-frequency repetitive transcranial magnetic stimulation on endogenous estrogen in patients with disorders of consciousness

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a promising therapeutic intervention for neurological disorders. However, the precise mechanisms of rTMS in neural excitability remains poorly understood. Estradiol is known to have strong influence on cortical excitability. This study aimed to determine whether high-frequency (HF) rTMS influences endogenous estradiol in male patients with disorders of consciousness (DOC).

METHODS

A randomized controlled trial was conducted with a total of 57 male patients with DOC. Eventually, 50 patients completed the study. Twenty-five patients underwent real rTMS, and 25 patients underwent sham rTMS, which were delivered over the dorsolateral prefrontal cortex. The primary outcome measure was the change in serum estradiol from baseline to after 10 sessions of HF-rTMS. The improvement in the total score of the JFK Coma Recovery Scale-Revised (CRS-R) was also assessed.

RESULTS

Changes in estradiol levels and CRS-R scores from pre-to post-treatment were significantly different between the active rTMS and sham stimulation conditions. A significant enhancement of CRS-R scores in the patients receiving rTMS stimulation was observed compared to the sham group. Serum estradiol levels in patients following HF-rTMS were significantly higher than their baseline levels, whereas no significant changes were found in the sham group from pre-to post-stimulation. The rise in estradiol levels was greater in responders than in non-responders. The changes in estradiol levels were significantly positively correlated with the improvement in CRS-R scores.

CONCLUSION

These preliminary findings indicate that serum estradiol levels are affected by HF-rTMS and positively related to clinical responses in male patients with DOC. The elevation of estradiol levels may lay a physiological foundation for successful rTMS treatment for DOC patients by increasing cortical excitability.

Identification of vascular dementia and Alzheimer's disease hub genes expressed in the frontal lobe and temporal cortex by weighted co-expression network analysis and construction of a protein-protein interaction

Background: It is difficult to distinguish cognitive decline due to AD from that sustained by cerebrovascular disease in view of the great overlap. It is uncertain in the molecular biological pathway behind AD and VaD.Objective: Our study aimed to explore the hub molecules and their associations with each other to identify potential biomarkers and therapeutic targets for the AD and VaD.Methods: We screened the differentially expressed genes of AD and VaD, used weighted gene co-expression network analysis and then constructed a VaD-AD-specific protein-protein interaction network with functional annotation to their related metabolic pathways. Finally, we performed a ROC curve analysis of hub proteins to get an idea about their diagnostic value.Results: In the frontal lobe and temporal cortex, hub genes were identified. With regard to VaD, there were only three hub genes which encoded the neuropeptides, SST, NMU and TAC1. The AUC of these genes were 0.804, 0.768 and 0.779, respectively. One signature was established for these three hub genes with AUC of 0.990. For the identification of AD and VaD, all hub genes were receptors. These genes included SH3GL2, PROK2, TAC3, HTR2A, MET, TF, PTH2R CNR1, CHRM4, PTPN3 and CRH. The AUC of these genes were 0.853, 0.859, 0.796, 0.775, 0.706, 0.677, 0.696, 0.668 and 0.652, respectively. The other signature was built for eleven hub genes with AUC of 0.990.Conclusion: In the frontal lobe and temporal cortex regions, hub genes are used as diagnostic markers, which may provide insight into personalized potential biomarkers and therapeutic targets for patients with VaD and AD.

Shaping of the Female Human Brain by Sex Hormones: A Review

Traditionally sex hormones have been associated with reproductive and developmental processes only. Since the 1950s we know that hormones can have organizational effects on the developing brain and initiate hormonal transition periods such as puberty. However, recent evidence shows that sex hormones additionally structure the brain during important hormonal transition periods across a woman's life including short-term fluctuations during the menstrual cycle. However, a comprehensive review focusing on structural changes during all hormonal transition phases of women is still missing. Therefore, in this review structural changes across hormonal transition periods (i.e., puberty, menstrual cycle, oral contraceptive intake, pregnancy and menopause) were investigated in a structured way and correlations with sex hormones evaluated. Results show an overall reduction in grey matter and region-specific decreases in prefrontal, parietal and middle temporal areas during puberty. Across the menstrual cycle grey matter plasticity in the hippocampus, the amygdala as well as temporal and parietal regions were most consistently reported. Studies reporting on pre- and post-pregnancy measurements revealed volume reductions in midline structures as well as prefrontal and temporal cortices. During perimenopause, the decline in sex hormones was paralleled with a reduction in hippocampal and parietal cortex volume. Brain volume changes were significantly correlated with estradiol, testosterone and progesterone levels in some studies, but directionality remains inconclusive between studies. These results indicate that sex hormones play an important role in shaping women's brain structure during different transition periods and are not restricted to specific developmental periods.

Male Infertility Knowledgebase: decoding the genetic and disease landscape

Male infertility is a multifactorial condition that contributes to around one-third of cases of infertility worldwide. Several chromosomal aberrations, single-gene and polygenic associations with male factor defects have been reported. These defects manifest as sperm number or sperm quality defects leading to infertility. However, in almost 40% of cases, the genetic etiology of male infertility remains unexplained. Understanding the causal genetic factors is crucial for effective patient management and counseling. Integrating the vast amount of available omics data on male infertility is a first step towards understanding, delineating and prioritizing genes associated with the different male reproductive disorders. The Male Infertility Knowledgebase (MIK) is a manually curated repository developed to boost research on the elusive genetic etiology of male infertility. It integrates information on ∼17 000 genes, their associated pathways, gene ontology, diseases and gene and sequence-based analysis tools. In addition, it also incorporates information on reported chromosomal aberrations and syndromic associations with male infertility. Disease enrichment of genes in MIK indicate a shared genetic etiology between cancer, male and female infertility disorders. While the genes involved in cancer pathways were found to be common causal factors for sperm number and sperm quality defects, the interleukin pathways were found to be shared and enriched between male factor defects and non-reproductive conditions like cardiovascular diseases, metabolic diseases, etc. Disease information in MIK can be explored further to identify high-risk conditions associated with male infertility and delineate shared genetic etiology. Utility of the knowledgebase in predicting novel genes is illustrated by identification of 149 novel candidates for cryptorchidism using gene prioritization and network analysis. MIK will serve as a platform for review of genetic information on male infertility, identification pleiotropic genes, prediction of novel candidate genes for the different male infertility diseases and for portending future high-risk diseases associated with male infertility.

Database URL: http://mik.bicnirrh.res.in/

A Narrative Review of Sex Differences in Eating Disorders: Is There a Biological Basis?

PURPOSE

Eating disorders and their core symptoms (eg, binge eating, body weight/shape concerns) disproportionately affect females, and these sex-differentiated effects become prominent during and after puberty. Although psychosocial influences such as heightened sociocultural pressures for thinness in girls and women contribute to this sex imbalance, biological factors could also play an important role.

METHODS

This narrative review summarizes evidence of biological factors underlying the sex-differentiated prevalence of eating pathology as well as within-sex variability in risk.

FINDINGS

There are sex differences in the pubertal emergence of genetic effects on eating pathology (adrenarche in males; gonadarche in females), and at least some genetic contributions to eating pathology seem to vary between the sexes. Furthermore, sex steroid hormones (eg, testosterone, estradiol, progesterone) are leading contributors to differential risk for eating pathology in males and females across the life span. Emerging data suggest that between-sex and within-sex variability in risk might occur via hormone-driven modulation (activation/deactivation) of genetic influences and neural responsiveness to food-related cues.

IMPLICATIONS

There is a biological basis to heightened risk for eating pathology in females, relative to males, as well as unique biological influences within each sex. Findings from this review highlight the importance of studying both sexes and considering sex-specific biological mechanisms that may underlie differential risk for eating pathology.

Sex hormones and human brain function

Sex hormones have organizational and activational effects on the human brain and can interact with the neurotransmitter systems. These biologic mechanisms may have a far-reaching impact, with both behavioral consequences and structural as well as functional brain modulation. The impact of cycling hormone levels throughout the menstrual cycle on cognitive and emotion processing has especially received some attention recently. Therefore, the aim of this chapter is to give an overview of findings regarding the effects of estradiol and progesterone, but also testosterone, on functional brain domains comprising cognition, emotion, and reward processing.

[Influence of malignant growth and chronic neurogenic pain on neurosteroid levels in rat brain]

The aim of the study was to determine the level of sex steroid hormones in white matter of the brain of rats with tumors combined with chronic neurogenic pain (CNP), which was modeled by bilateral sciatic nerve ligation. The study included albino male rats (n=74). In the main group, M1 sarcoma was transplanted subcutaneously (n=11) or into the subclavian vein (n=11) 45 days after CNP modeling. Two comparison groups (n=13 each) included sham operated animals (without CNP) with M1 sarcoma transplanted subcutaneously and intravenously. Control groups included animals with CNP and sham operated animals. Rats were euthanized on day 21 of the carcinogenesis. Levels of total and free testosterone (T), estrone (E1), estradiol (E2), estriol (E3) and progesterone (P4) in the brain white matter were measured using ELISA kits ("Cusabio", China). CNP caused a decrease in the total and free T by 1.5 times (p<0.05), E2 and P4 by 1.9 and 3 times, respectively, E3 by 1.6 times (p<0.05), as well as an increase in E1 by 1.4 times (p<0.05) as compared to the corresponding levels in the brain white matter of rats without CNP. CNP stimulated M1 sarcoma growth in both subcutaneous and intravenous transplantation. Regardless of the tumor site, the dynamics of total T, E2 and E3 in the brain had similar features, but the dynamics of free T, P4 and E1 differed. Thus, changes in the level of neurosteroids in the white matter of rat brain with CNP and tumor growth alone or associated with CNP are a reaction to stress.

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 role of personality, cognition, and affective state in same-sex contests in the red junglefowl

Abstract

Intra-species contests are common in the animal kingdom and can have fitness consequences. Most research on what predicts contest outcome focuses on morphology, although differences in personality and cognition may also be involved. Supporting this, more proactive individuals often have dominant status, although the causality of this relationship is rarely investigated. Contest initiators often win; thus, individuals that are more proactive in their personality (e.g., more aggressive, risk-taking) or cognition (e.g., more optimistic, impulsive) may initiate contests more often. To investigate this, we assayed the behavior and cognition of sexually mature male and female red junglefowl (Gallus gallus), a species in which both sexes contest over social status, before staging intra-sexual contests. We confirm that contest initiators were more likely to win. In males, individuals that behaved more boldly in a novel arena test were more likely to initiate and win contests. Female initiators tended to be less active in novel object test, more aggressive in a restrained opponent test, and respond less optimistically in a cognitive judgement bias test, whereas the main predictor of whether a female would win a contest was whether she initiated it. These results suggest that behaviors attributed to proactive and reactive personalities, and—at least for female red junglefowl—optimism, can affect contest initiation and outcome. Therefore, within species, and depending on sex, different aspects of behavior and cognition may independently affect contest initiation and outcome. The generality of these findings, and their fitness consequences, requires further investigation.

Significance statement

In red junglefowl, we explored how behavior previously shown to describe personality, cognition, and affective state affected initiation and outcome of intra-sexual contests, by staging contests between sexually mature individuals previously assayed in behavioral and cognitive tests. In both sexes, contest initiators usually won. Bolder males were more likely to initiate and win contests. Female contests initiators were less active, more aggressive, and less optimistic. Our results suggest that personality and cognition could affect the initiation and outcome of contests and that how this occurs may differ between sexes.

Effects of Hormonal Contraceptives on Mood: A Focus on Emotion Recognition and Reactivity, Reward Processing, and Stress Response

PURPOSE OF REVIEW

We review recent research investigating the relationship of hormonal contraceptives and mood with a focus on relevant underlying mechanisms, such as emotion recognition and reactivity, reward processing, and stress response.

RECENT FINDINGS

Adverse effects of hormonal contraceptives (HCs) on mood seem most consistent in women with a history of depressive symptoms and/or previous negative experience with HC-intake. Current evidence supports a negativity bias in emotion recognition and reactivity in HC-users, although inconsistent to some extent. Some data, however, do indicate a trend towards a blunted reward response and a potential dysregulation of the stress response in some HC-users. HC-effects on psychological and neurophysiological mechanisms underlying mood are likely context-dependent. We provide suggestions on how to address some of the contributing factors to this variability in future studies, such as HC-dose, timing, administration-mode, and individual risk. A better understanding of how and when HCs affect mood is critical to provide adequate contraceptive choices to women worldwide.

Anxiety in transition: Neuroendocrine mechanisms supporting the development of anxiety pathology in adolescence and young adulthood

Adolescence marks a key developmental window during which emotion dysregulation increases, along with risk for the onset of anxiety and other affect-related pathologies. Although emotion dysregulation and related pathologies normatively decline during the transition into adulthood, this does not occur for a sizable minority of individuals. Finally, sex differences in anxiety emerge during adolescence, with females developing a 2-fold increase in risk relative to males. Unfortunately, a neurobiological model of the mechanisms that cause these changes during adolescence has yet to be proposed. In the present work, we first provide brief reviews of relevant literature. Next, we outline a dual-mechanism model focused on (i) the influence of pubertal testosterone on key emotion-regulation circuitry (i.e., orbitofrontal cortex-amygdala coupling) and (ii) myelination of the fiber bundles connecting such circuitry (i.e., uncinate fasciculus). The proposed model offers a set of specific, testable hypotheses that will hopefully spur much needed cross-disciplinary research.

Neuropsychiatric and Behavioral Involvement in AAS Abusers. A Literature Review

Background and Objectives: Anabolic androgenic steroids (AASs) are a complex group of molecules that include both steroidal androgens and synthetic compounds, derived from testosterone. AASs are commonly used to support pharmacological therapy in cases of primary or secondary hypogonadism, major burns, and neoplastic cachexia. Their prolonged and supra-physiological consumption can provoke several adverse effects on various organs and systems. Among these, the physiopathological mechanisms that induce neuropsychiatric disorders related to AAS abuse are poorly known. For this reason, the proposed review aims to retrace the pathway of action of testosterone to focus on the effects on the central nervous system and specifically highlight the effects of AASs on neuropsychiatric and behavioral functions, as well as on lifestyle. Materials and Methods: This review was conducted using PubMed and Google Scholar databases. On these database websites, we searched for articles from 1 January 1980 to March 2019 using the key terms: "AAS," "Anabolic Androgenic Steroids," "brain," and "neurology." Results: The use of AASs through self-administration yields circulating androgens levels, inducing neuron apoptosis, which is linked to thinner cortex and, in general, less cortical volume. The same alterations affect the putamen. These differences were more evident when correlated with longer use. From a functional point of view, prolonged AAS consumption seemed to be related to lower connectivity between amygdala and frontal, striatal, limbic, hippocampal and visual cortical areas. On the other hand, AAS use seems to negatively condition the positive effects of the sport exercise, reducing its important anti-apoptotic and pro-proliferative functions on the hippocampus, implicated in anxiolytic control. Conclusion: This review clarifies the major aspects of the side effects related to AAS use/abuse highlighting the complex mechanisms on neuropsychiatric and cognitive pathological alterations and also the emotional and behavioral dysfunctions.

The Modulating Role of Sex and Anabolic-Androgenic Steroid Hormones in Cannabinoid Sensitivity

Cannabis is the most commonly used illicit drug worldwide. Although its use is associated with multiple adverse health effects, including the risk of developing addiction, recreational and medical cannabis use is being increasing legalized. In addition, use of synthetic cannabinoid drugs is gaining considerable popularity and is associated with mass poisonings and occasional deaths. Delineating factors involved in cannabis use and addiction therefore becomes increasingly important. Similarly to other drugs of abuse, the prevalence of cannabis use and addiction differs remarkably between males and females, suggesting that sex plays a role in regulating cannabinoid sensitivity. Although it remains unclear how sex may affect the initiation and maintenance of cannabis use in humans, animal studies strongly suggest that endogenous sex hormones modulate cannabinoid sensitivity. In addition, synthetic anabolic-androgenic steroids alter substance use and further support the importance of sex steroids in controlling drug sensitivity. The recent discovery that pregnenolone, the precursor of all steroid hormones, controls cannabinoid receptor activation corroborates the link between steroid hormones and the endocannabinoid system. This article reviews the literature regarding the influence of endogenous and synthetic steroid hormones on the endocannabinoid system and cannabinoid action.

Sexually Dimorphic Effects of Aromatase on Neurobehavioral Responses

Aromatase is the enzyme responsible for converting testosterone to estradiol. In mammals, aromatase is expressed in the testes, ovaries, brain, and other tissues. While estrogen is traditionally associated with reproduction and sexual behavior in females, our current understanding broadens this perspective to include such biological functions as metabolism and cognition. It is now well-recognized that aromatase plays a vital lifetime role in brain development and neurobehavioral function in both sexes. Thus, ongoing investigations seek to highlight potentially vital sex differences in the role of aromatase, particularly regarding its centrally mediated effects. To characterize the role of aromatase in mediating such functions, effects of aromatase inhibitor (AI) treatments on humans and animal models have been determined. Aromatase knockout (ArKO) mice that systemically lack the enzyme have also been employed. Humans possessing mutations in the gene encoding aromatase, CYP19, have also provided critical insight into how aromatase affects brain function in a possible sex-dependent manner. A better understanding of how AIs, used to treat breast cancer and other clinical conditions, may detrimentally affect neurobehavioral responses will likely promote development of future therapies to combat these effects. Herein, we will provide a critical review of the current knowledge of sex differences in aromatase regulation of various neurobehavioral functions. Although many species have been used to better understand the functions of aromatase, this review focuses on rodent models and humans. Critical gaps in our present understanding of this area will be considered, and important future research directions will be discussed.

Non-reproductive Functions of Aromatase in the Central Nervous System Under Physiological and Pathological Conditions

The modulation of brain function and behavior by steroid hormones was classically associated with their secretion by peripheral endocrine glands. The discovery that the brain expresses the enzyme aromatase, which produces estradiol from testosterone, expanded this traditional concept. One of the best-studied roles of brain estradiol synthesis is the control of reproductive behavior. In addition, there is increasing evidence that estradiol from neural origin is also involved in a variety of non-reproductive functions. These include the regulation of neurogenesis, neuronal development, synaptic transmission, and plasticity in brain regions not directly related with the control of reproduction. Central aromatase is also involved in the modulation of cognition, mood, and non-reproductive behaviors. Furthermore, under pathological conditions aromatase is upregulated in the central nervous system. This upregulation represents a neuroprotective and likely also a reparative response by increasing local estradiol levels in order to maintain the homeostasis of the neural tissue. In this paper, we review the non-reproductive functions of neural aromatase and neural-derived estradiol under physiological and pathological conditions. We also consider the existence of sex differences in the role of the enzyme in both contexts.

Sex steroid hormones and brain function: PET imaging as a tool for research

Sex steroid hormones are major regulators of sexual characteristic among species. These hormones, however, are also produced in the brain. Steroidal hormone-mediated signalling via the corresponding hormone receptors can influence brain function at the cellular level and thus affect behaviour and higher brain functions. Altered steroid hormone signalling has been associated with psychiatric disorders, such as anxiety and depression. Neurosteroids are also considered to have a neuroprotective effect in neurodegenerative diseases. So far, the role of steroid hormone receptors in physiological and pathological conditions has mainly been investigated post mortem on animal or human brain tissues. To study the dynamic interplay between sex steroids, their receptors, brain function and behaviour in psychiatric and neurological disorders in a longitudinal manner, however, non-invasive techniques are needed. Positron emission tomography (PET) is a non-invasive imaging tool that is used to quantitatively investigate a variety of physiological and biochemical parameters in vivo. PET uses radiotracers aimed at a specific target (eg, receptor, enzyme, transporter) to visualise the processes of interest. In this review, we discuss the current status of the use of PET imaging for studying sex steroid hormones in the brain. So far, PET has mainly been investigated as a tool to measure (changes in) sex hormone receptor expression in the brain, to measure a key enzyme in the steroid synthesis pathway (aromatase) and to evaluate the effects of hormonal treatment by imaging specific downstream processes in the brain. Although validated radiotracers for a number of targets are still warranted, PET can already be a useful technique for steroid hormone research and facilitate the translation of interesting findings in animal studies to clinical trials in patients.