Estradiol Replacement Research Articles

8603 Sex Steroids Have Opposing Impacts on Female Gonadotrope Metabolism and LH Secretion via GLUT1

Abstract Disclosure: C. Garcia: None. C. Nguyen: None. S. Wang: None. D. Trinh: None. U. Le: None. R. Kapadia: None. J. De La Torre: None. C.K. De La Cruz: None. D. Nicholas: None. Gonadotropes of the anterior pituitary regulate reproductive hormone synthesis and secretion not only through GnRH signaling from the hypothalamus, but by also determining if glucose availability, via GLUT1, meets the current requirements to support reproduction. GLUT1 facilitates glucose uptake and in gonadotropes its expression increases during the LH surge which indicates its necessity in the maximal secretion of LH through glycolysis. However, the mechanisms underlying the feedback from sex steroids that also mediate female reproduction have not been completely elucidated. By manipulating GLUT1 expression and sex steroid levels using cell lines and a conditional knockout of GLUT1 in mouse gonadotrope we show that sex steroids alter GLUT1 expression and translocation effecting gonadotrope glycolysis and subsequent gonadotropin secretion. Tamoxifen treated iGricCre +/+ GLUT1 fl/fl mice display disrupted estrous cycles and changes in serum gonadotropins. Dihydrotestosterone (DHT) or estradiol (E2) replacement in gonadectomized male and female, respectively, surprisingly result in increased (by DHT) or reduced (by E2) pituitary GLUT1 protein as measured by western blot despite both inhibiting serum LH. Using extracellular flux analysis and imaging flow cytometry, we show that LβT2 cells treated with DHT increase while E2 decreases glycolysis and translocation of GLUT1 to the cellular surface. We conclude that sex steroids regulate gonadotropin secretion and reproduction through direct impacts on gonadotrope metabolism through GLUT1. Presentation: 6/1/2024

Abstract P160: Sex Differences in Age-Dependent Hypertension and Cognitive Impairment in Sprague-Dawley Rats

Objective: We previously found that male (M), but not female (F), Sprague-Dawley (SD) rats develop age-dependent hypertension (HTN) that is associated with cognitive impairment. We hypothesized that ovariectomy (OVRX) at midlife, to model human menopause, would induce hypertension and cognitive impairment with age. Methods: In M and F SD rats at 3-, 8-, and 16-months-old (MO), blood pressure (MAP; mmHg) and sympathetic tone to the vasculature (iv hexamethonium, PeakΔMAP; mmHg) was measured via femoral artery cannulation. Recognition memory was assessed using the novel object recognition task. Blood brain barrier (BBB) integrity in the PVN was assessed as FITC extravasation following carotid artery cannulation. In a separate group of female rats at 8 MO, sham procedure, OVRX, or OVRX with estradiol replacement for 8-months (s.c. estradiol valerate, 1.5 mg extended-release pellet) was performed and rats were aged to 16MO. At 16MO, the previously described procedures were carried out. Results: M, but not F, SD rats develop age-dependent HTN and increased sympathoexcitation that is associated with recognition memory deficits and BBB disruption. Following OVRX, female rats develop age-dependent HTN that is associated with recognition memory deficits and BBB disruption. Replacement of estrogen with 17β-estradiol prevented the development of HTN, cognitive impairment, and BBB disruption. Conclusions: In males, HTN induces BBB disruption and is associated with cognitive impairment. Our studies suggest midlife loss of estrogen likely contributes to the development of age-dependent HTN and cognitive impairment in females. We speculate estrogen supplementation may mitigate HTN-related changes in memory with age.

Cardiac Left Ventricular miRNA-26a Is Downregulated in Ovariectomized Mice, Upregulated upon 17-Beta Estradiol Replacement, and Inversely Correlated with Collagen Type 1 Gene Expression.

Heart failure with preserved ejection fraction (HFpEF) is more prevalent in post- compared to pre-menopausal women. The underlying mechanisms are not fully understood. Data in humans is confounded by age and co-morbidities. We investigated the effects of ovariectomy and estrogen replacement on the left ventricular (LV) gene expression of pro-inflammatory and pro-fibrotic factors involved in HFpEF and putative regulating miRNAs. Nine-week-old C57BL/6 female mice were subjected to ovariectomy (OVX) or SHAM operation. OVX and SHAM groups were sacrificed 1-, 6-, and 12-weeks post-surgery (T1/SHAM; T1/OVX; T6/SHAM; T6/OVX, T12/SHAM). 17β-estradiol (E2) or vehicle (VEH) was then administered to the OVX groups for 6 weeks (T12/OVX/E2; T12/OVX/VEH). Another SHAM group was sacrificed 12-weeks post-surgery. RNA and miRNAs were extracted from the LV apex. An early 3-fold increase in the gene expression of IL-1α, IL-6, Mmp9, Mmp12, Col1α1, and Col3α1 was observed one-week post-surgery in T1/OVX vs. T1/SHAM, but not at later time points. miRNA-26a was lower in T1/OVX vs. T1/SHAM and was inversely correlated with Col1α1 and Col3α1 expression 1-week post-surgery (r = -0.79 p < 0.001; r = -0.6 p = 0.007). miRNAs-26a, 29b, and 133a were significantly higher, while Col1α1, Col3α1, IL-1α, IL-6, Tnfα, Mmp12, and FasL gene expression was significantly lower in E2- compared to vehicle-treated OVX mice. miRNA-26a was inversely correlated with Col3α1 in T12/OVX/ E2 (r = -0.56 p = 0.02). OVX triggered an early increase in the gene expression of pro-inflammatory and pro-fibrotic factors, highlighting the importance of the early phase post-cessation of ovarian function. E2 replacement therapy, even if it was not immediately initiated after OVX, reversed these unfavorable changes and upregulated cardiac miRNA-26a, previously unknown to be affected by menopausal status.

Estradiol mediates greater germinal center responses to influenza vaccination in female than male mice.

Adult females of reproductive age develop greater antibody responses to inactivated influenza vaccines (IIV) than males. How sex, age, and sex steroid concentrations impact B cells and durability of IIV-induced immunity and protection over 4 months post-vaccination (mpv) was analyzed. Vaccinated adult females had greater germinal center B cell and plasmablast frequencies in lymphoid tissues, higher neutralizing antibody responses 1-4 mpv, and better protection against live H1N1 challenge than adult males. Aged mice, regardless of sex, had reduced B cell frequencies, less durable antibody responses, and inferior protection after challenge than adult mice, which correlated with diminished estradiol among aged females. To confirm that greater IIV-induced immunity was caused by sex hormones, four core genotype (FCG) mice were used, in which the testes-determining gene, Sry, was deleted from chromosome Y (ChrY) and transferred to Chr3 to separate gonadal sex (i.e., ovaries or testes) from sex chromosome complement (i.e., XX or XY complement). Vaccinated, gonadal female FCG mice (XXF and XYF) had greater numbers of B cells, higher antiviral antibody titers, and reduced pulmonary virus titers following live H1N1 challenge than gonadal FCG males (XYM and XXM). To establish that lower estradiol concentrations cause diminished immunity, adult and aged females received either a placebo or estradiol replacement therapy prior to IIV. Estradiol replacement significantly increased IIV-induced antibody responses and reduced morbidity after the H1N1 challenge among aged females. These data highlight that estradiol is a targetable mechanism mediating greater humoral immunity following vaccination among adult females.IMPORTANCEFemales of reproductive ages develop greater antibody responses to influenza vaccines than males. We hypothesized that female-biased immunity and protection against influenza were mediated by estradiol signaling in B cells. Using diverse mouse models ranging from advanced-age mice to transgenic mice that separate sex steroids from sex chromosome complement, those mice with greater concentrations of estradiol consistently had greater numbers of antibody-producing B cells in lymphoid tissue, higher antiviral antibody titers, and greater protection against live influenza virus challenge. Treatment of aged female mice with estradiol enhanced vaccine-induced immunity and protection against disease, suggesting that estradiol signaling in B cells is critical for improved vaccine outcomes in females.

Passive exercise is an effective alternative to HRT for restoring OVX induced mitochondrial dysfunction in skeletal muscle.

Postmenopausal women are more prone to develop muscle weakness, which is strongly associated with impairment of mitochondrial function in skeletal muscle. This study aimed to examine the impact of a passive exercise modality, whole-body vibration training (WBVT), on muscle mitochondrial function in ovariectomized (OVX) mice, in comparison with 17β-estradiol (E2) replacement. Female C57BL/6J mice were assigned to four groups: sham operation control group (Sham), ovariectomized group (OVX), OVX with E2 supplement group (OVX+E), and OVX with WBVT group (OVX+W). The estrous cycle, body weight, body composition, and muscle strength of the mice were monitored after the operation. Serum E2 level was assessed by enzyme-linked immunosorbent assay (ELISA). The ATP levels were determined using a luciferase-catalyzed bioluminescence assay. The activity of mitochondrial respiration chain complexes was evaluated using high-resolution respirometry (O2K). Expression levels of oxidative phosphorylation (OXPHOS), peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), and mitochondrial transcription factor A (TFAM) were detected using western blotting. We observed decreased muscle strength and impaired mitochondrial function in the skeletal muscle of OVX mice. The vibration training alleviated these impairments as much as the E2 supplement. In addition, the vibration training was superior to the ovariectomy and the estradiol replacement regarding the protein expression of PGC-1α and TFAM. WBVT improves the OVX-induced decline in muscle strength and impairment of mitochondrial function in the skeletal muscle. This passive exercise strategy may be useful as an alternative to E2 replacement for preventing menopausal muscular weakness. Further studies are needed to understand the effects of WBVT on various physiological systems, and precautions should be taken when implementing it in patient treatment.

Ovarian tissue autotransplantation improves longevity in mice.

In this study, we show the improvement in life longevity in an experimental mouse model after step-by-step autologous ovarian transplantation and compare its effects with exogenic transdermal estradiol usage. This has proven to be more efficient than "traditional" hormonal replacement therapy. Despite the high speed and effectiveness of estradiol replacement deficiency in blood by its oral or transdermal use, no significant increase in the life longevity of animals and possibly in women was noted. The function of the transplanted fragment is usually limited to 6-12months. This is enough for oncofertility purposes, sometimes, but not for longevity improvement. We performed periodical tissue return (autologous transplantation), containing both the cortex and medulla in the experimental mouse model, which resulted in a statistically reliable improvement in longevity. Our experience indicates the important role of medullary ovarian factors in slowing the aging process in the body and increasing the life expectancy in the experiment. As shown, the transdermal estrogen supportive therapy for ovarian deficiency improves estrogen levels but causes much slower decreases in the follicle stimulating hormone (FSH) and luteinizing hormone (LH). Moreover, we attained the best longevity with step-by-step periodic ovarian autotransplantation, thus making "prosthetics" of ovarian function longer than it is preplanned physiologically [direct correlation between the levels of FSH and lifespan (r = 0.98)]. The experimental model we suggested could be projected to other mammals or humans as cortical transplantation provides the same results for reproduction restoration in mice and humans and even for hormone level normalization, but there is still a lack of information about anti-aging factors in the ovarian medulla and cortex. Hence, we consider that the most important factor for the anti-aging ovarian transplantation technology is to preserve and transfer both the medulla and cortex as parts of the whole ovary.

Working and episodic memory trajectories over time following bilateral oophorectomy in early midlife women

AbstractBackgroundEarly ovarian hormone deprivation due to bilateral salpingo‐oophorectomy (BSO; ovarian and fallopian tube removal) is a risk for late‐life AD, but estradiol replacement therapy (ERT) may be protective (Rocca et al., 2007). Working and episodic memory decrements have been observed without ERT soon after surgery (Sherwin et al., 1988) and on average 5 years post‐BSO in midlife compared to premenopausal controls (Gervais et al., 2020). Unknown is whether memory continues to decrease over time in early midlife, a critical period for understanding cognitive trajectories that presage AD. We investigated memory changes in early midlife over time post‐BSO, and whether those taking ERT had different trajectories than those without.MethodParticipants with BSO taking ERT (BSO+ERT: M age = 44.5y; n = 71) were compared to those not taking ERT (BSO: M age = 43.2y; n = 55), recruited from Toronto and Montreal, Canada, and Linköping, Sweden, and completed up to four yearly visits. Episodic memory was evaluated using Logical Memory Task (LM) percent forgetting and Rey Auditory Verbal Learning Test (RAVLT) total learning. Working memory was assessed using Spatial Working Memory Task (SPWM) trial 1 errors, Digit Ordering Task (DOT) errors, and Digit Span Backward Task (DSB) span length. Multilevel models were used to examine whether ERT influenced memory over time post‐BSO and disaggregate within‐ and between‐person effects. Estimated marginal means (Aiken and West, 1991) were calculated to delineate significant interactions.ResultThere were no significant changes over time post‐BSO on LM or RAVLT. The DSB showed significant within‐ and between‐person effects; the BSO group showed decreases in span length over time post‐BSO, while the BSO+ERT group showed increases and had significantly longer span lengths at seven years post‐BSO and beyond (Fig.1A&amp;B). The SPWM Task showed a significant within‐person effect; the BSO group had stable errors over time post‐BSO, while the BSO+ERT group had working memory improvements and made fewer errors (Fig.1C).ConclusionFindings suggest that immediate verbal episodic memory declines we observed previously may stabilize. They also reveal that without ERT, most women have working memory declines post‐BSO. These data support ERT administration post‐BSO for working memory preservation. If ERT is contraindicated, cognitive training or lifestyle interventions may mitigate working memory declines.

Estradiol mediates colonic epithelial protection in aged mice after stroke and is associated with shifts in the gut microbiome

ABSTRACT The gut is a major source of bacteria and antigens that contribute to neuroinflammation after brain injury. Colonic epithelial cells (ECs) are responsible for secreting major cellular components of the innate defense system, including antimicrobial proteins (AMP) and mucins. These cells serve as a critical regulator of gut barrier function and maintain host-microbe homeostasis. In this study, we determined post-stroke host defense responses at the colonic epithelial surface in mice. We then tested if the enhancement of these epithelial protective mechanisms is beneficial in young and aged mice after stroke. AMPs were significantly increased in the colonic ECs of young males, but not in young females after experimental stroke. In contrast, mucin-related genes were enhanced in young females and contributed to mucus formation that maintains the distance between the host and gut bacteria. Bacterial community profiling was done using universal amplification of 16S rRNA gene sequences. The sex-specific colonic epithelial defense responses after stroke in young females were reversed with ovariectomy and led to a shift from a predominately mucin response to the enhanced AMP expression seen in males after stroke. Estradiol (E2) replacement prior to stroke in aged females increased mucin gene expression in the colonic ECs. Interestingly, we found that E2 treatment reduced stroke-associated neuronal hyperactivity in the insular cortex, a brain region that interacts with visceral organs such as the gut, in parallel to an increase in the composition of Lactobacillus and Bifidobacterium in the gut microbiota. This is the first study demonstrating sex differences in host defense mechanisms in the gut after brain injury.

Clinical and phototrichogrammatic evaluation of estradiol replacement therapy on hair growth in postmenopausal Japanese women with female pattern hair loss: a pilot study.

Female pattern hair loss (FPHL) is known to present with characteristic pathological conditions, including reduced overall hair density. Female hormones affect hair condition; however, the detailed mechanism is unknown. Furthermore, research on the topic is complicated by the fact that senescent alopecia often occurs concurrently with FPHL. Therefore, we investigated the effect of estradiol, a female hormone, on hair growth by eliminating aging factors and objectively evaluating hair changes caused by female hormone replacement therapy (HRT). This study was conducted to elucidate the mechanism through which female hormones exert their effects on hair. The study included 11 female patients undergoing HRT who were evaluated before initiating HRT, 3 months after initiating HRT, and 6 months after initiating HRT. The thinning hair score, hair density, telogen hair rate, telogen plucking strength, hair growth rate, and hair thickness were measured and evaluated. Furthermore, hematological tests were performed to assess the general physical condition of the participants. HRT increased the telogen hair rate (P = .010, paired t test) at 3 months, improved frontal hairline thinning score (P = .008, Wilcoxon test), and increased the plucking strength (P = .013, paired t test) at 6 months. The limitation of this study included the relatively small sample size, inability to conduct further long-term tests because of participant burden, and lack of a control group. The results suggested that HRT improved the appearance of the frontal hairline. As few studies have analyzed the effects of female hormones on human hair, a novel finding of this study was the effects of estradiol on the plucking strength after excluding age as a factor. We believe that these findings will contribute to understanding FPHL and developing female hormone-related treatments.

Sex-dependent cholinergic effects on amyloid pathology: A translational study.

About two-thirds of Alzheimer's Disease (AD) patients are women, who exhibit more severe pathology and cognitive decline than men. Whether biological sex causally modulates the relationship between cholinergic signaling and amyloid pathology remains unknown. We quantified amyloid beta (Aβ) in male and female App-mutant mice with either decreased or increased cholinergic tone and examined the impact of ovariectomy and estradiol replacement in this relationship. We also investigated longitudinal changes in basal forebrain (cholinergic function) and Aβ in elderly individuals. We show a causal relationship between cholinergic tone and amyloid pathology in males and ovariectomized female mice, which is decoupled in ovary-intact and ovariectomized females receiving estradiol. In elderly humans, cholinergic loss exacerbates Aβ. Our findings emphasize the importance of reflecting human menopause in mouse models. They also support a role for therapies targeting estradiol and cholinergic signaling to reduce Aβ. Cholinergic tone regulates amyloid beta (Aβ) pathology in males and ovariectomized female mice. Estradiol uncouples the relationship between cholinergic tone and Aβ. In elderly humans, cholinergic loss correlates with increased Aβ in both sexes.

Effect of estradiol replacement on hippocampal concentrations of estrogens in aged rhesus macaques maintained on an obesogenic diet

Replacement involving estrogens has proven efficacy at treating a wide range of disorders that develop with menopause or after surgical removal of the ovaries. Here, we tested whether an estradiol (E2) replacement paradigm that recapitulates physiological E2 levels in the circulation also recapitulates physiological E2 levels within the hippocampus. E2 was delivered continuously to old ovariectomized (OVX) rhesus macaques, maintained on a high-fat, high-sugar Western-style diet (WSD) for ∼30 months, via subcutaneous implants; this resulted in physiological concentrations of both estrone (E1) and E2 in the circulation (determined by LC-MS/MS). Surprisingly, however, hippocampal concentrations of E2 were markedly (P < 0.01) higher than in ovary-intact animals maintained on a regular chow diet. The data suggest that E2 replacement paradigms that appear to recapitulate physiological E2 concentrations in the circulation may produce hyper-physiological E2 levels within some brain areas, especially when individuals are maintained on a WSD.

Clinical Manifestations, Genetic Variants and Therapeutic Evaluation in Sporadic Chinese Patients with Idiopathic Hypogonadotropic Hypogonadism.

Genetic factors account for a large proportion of idiopathic hypogonadotropic hypogonadism (IHH) etiologies, although not necessarily a complete genetic basis. This study aimed to characterize the clinical presentations, genetic variants, and therapeutic outcomes of patients with sporadic IHH, which may be helpful for genetic counseling and treatment decisions. Eleven Chinese patients with IHH were retrospectively analyzed. Rare genetic variants were evaluated using whole-exome sequencing and bioinformatics analysis and were further classified according to the ACMG-AMP guidelines. The therapeutic responses of patients were further evaluated. Six heterozygous variants of SOX10, WDR11, PROKR2, CHD7 and FGF17 were detected in five Kallmann syndrome (KS) patients, whereas two heterozygous variants of CHD7 and PROKR2 were detected in two normosmic IHH (nIHH) patients. Among these variants, a novel likely pathogenic variant in the SOX10 (c.429-1G>C) was considered to cause the KS phenotype in patient 02, and two potential variants of uncertain significance (VUS) in CHD7 (c.3344G>A and c.7391A>G) possibly contributed to the KS phenotype in patient 05 and the nIHH phenotype in patient 07, which need to be confirmed by further evidence. Additionally, long-term testosterone or estradiol replacement treatment effectively improved the development of sexual characteristics in patients with IHH. Next-generation sequencing is a powerful tool for identifying the molecular etiology and early diagnosis of IHH. Efficient therapeutic outcomes strongly indicate a need for timely treatment.

(017) Systemic Estradiol Menopause Management: Return to the Old-Fashioned Way

Abstract Introduction The mean systemic estradiol value in menopausal women is &amp;lt; 10 pg/ml, consistent with ovarian failure. Such low values are associated with multiple symptoms including hot flashes, night sweats, insomnia, mood changes and irritability, cognitive changes, weight gain and slowed metabolism. Contemporary management with systemic estradiol, maximizing safety and efficacy, emphasizes non-oral, non-injection estradiol replacement therapies including systemic daily gels, twice weekly or weekly patches or three-month vaginal rings. Most women (&amp;gt;60%) who try these systemic therapies in our sexual medicine clinic have been successful at reducing bothersome symptoms. We have identified a subset of women who cannot achieve sufficient symptom relief despite using contemporary estradiol strategies due to lack of efficacy, negative side effects, (rings cannot stay in the vagina or values are too high initially and then too low, patches cause rashes or fall off, gels are too messy) or financial concerns. For these patients, we have advised a return to the “old-fashioned way” using weekly intramuscular (IM) injection of either estradiol valerate or cypionate. Estradiol cypionate was first described as well as introduced for medical use in 1952. Objectives This study examines the experiences of this subset of women in one practice using weekly injections of estradiol valerate or cypionate for either efficacy or financial reasons. Methods This chart review identified a subset of 16 patients (mean age 59 +/− 8 years) at a single site who had been prescribed estradiol valerate or cypionate when symptoms of genitourinary syndrome of menopause (GSM) persisted despite use of estradiol replacement gels, patches or rings, or cost was prohibitive. We have advised weekly IM injection of either estradiol valerate (20 mg/ml; starting dose 0.05 ml or 1 mg) or estradiol cypionate (5 mg/ml; starting dose 0.2 ml or 1 mg). We compared relief of bothersome symptoms from earlier estradiol treatments to current IM injection and compared monthly costs of each treatment based on GoodRx prices, assuming medications were not covered by insurance. Results All patients using weekly injections of estradiol valerate or cypionate had their estradiol-based GSM symptoms ameliorated without complaint of inconvenience or discomfort using injections. The risks of IM injections of estradiol are similar to those of topical administration, requiring concomitant progesterone use in women with a uterus. Concerning finances, using a GoodRx coupon, a 5 ml bottle of estradiol valerate costs approximately $50 and should last at least one year, reducing monthly cost to approximately $5/month. A 5 ml bottle of estradiol cypionate costs approximately $150 and should last at least 6 months, thus about $25/month. In contrast, generic patches are approximately $40/month, gels $150/month and the ring $170/month. While there remains an abhorrence for injections, the motivation for systemic estradiol replacement superseded any inconvenience of using an injectable medication and the 27-gauge ½ inch needle is associated with minimal pain. No significant side effects were noted with IM injection. Conclusions For certain individuals, sometimes the “old-fashioned way” works better both in terms of efficacy and cost, providing relief of bothersome menopausal symptoms. Disclosure No.

Estradiol Protects Female ApoE KO Mice against Western-Diet-Induced Non-Alcoholic Steatohepatitis.

we evaluated if female apolipoprotein E (ApoE) KO mice were protected against Western-diet (WD)-induced NASH. Female ovariectomized (OVX) ApoE KO mice or sham-operated (SHAM) mice were fed either a WD or a regular chow (RC) for 7 weeks. Additionally, OVX mice fed a WD were treated with either estradiol (OVX + E2) or vehicle (OVX). Whole-body fat, plasma glucose, and plasma insulin were increased and associated with increased glucose intolerance in OVX mice fed a WD (OVX + WD). Plasma and hepatic triglycerides, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) hepatic enzymes were also increased in the plasma of OVX + WD group, which was associated with hepatic fibrosis and inflammation. Estradiol replacement in OVX mice reduced body weight, body fat, glycemia, and plasma insulin associated with reduced glucose intolerance. Treatment also reduced hepatic triglycerides, ALT, AST, hepatic fibrosis, and inflammation in OVX mice. These data support the hypothesis that estradiol protects OVX ApoE KO mice from NASH and glucose intolerance.

Ovariectomy in mice primes hippocampal microglia to exacerbate behavioral sickness responses

Estrogens are a group of steroid hormones that promote the development and maintenance of the female reproductive system and secondary sex characteristics. Estrogens also modulate immune responses; estrogen loss at menopause increases the risk of inflammatory disorders. Elevated inflammatory responses in the brain can lead to affective behavioral changes, which are characteristic of menopause. Thus, here we examined whether loss of estrogens sensitizes microglia, the primary innate immune cell of the brain, leading to changes in affective behaviors. To test this question, adult C57BL/6 mice underwent an ovariectomy to remove endogenous estrogens and then received estradiol hormone replacement or vehicle. After a one-month recovery, mice received an immune challenge with lipopolysaccharide (LPS) or vehicle control treatment and underwent behavioral testing. Ovariectomized, saline-treated mice exhibited reduced social investigation compared to sham-operated mice. Furthermore, ovariectomized mice that received LPS exhibited an exacerbated decrease in sucrose preference, which was ameliorated by estradiol replacement. These results indicate that ovariectomy modulates affective behaviors at baseline and in response to an inflammatory challenge. Ovariectomy-related behavioral changes were associated with downregulation of Cx3cr1, a microglial receptor that limits activation, suggesting that estrogen loss can disinhibit microglia to immune stimuli. Indeed, estradiol treatment reduced ovariectomy-induced increases in Il1b and Il6 expression after an immune challenge. Changes in microglial reactivity following ovariectomy are likely subtle, as overt changes in microglial morphology (e.g., soma size and branching) were limited. Collectively, these results suggest that a lack of estrogens may allow microglia to confer exaggerated neuroimmune responses, thereby raising vulnerability to adverse affective- and sickness-related behavioral changes.

Estradiol Enhances the Development of Addiction-Like Features in a Female Rat Model of Opioid Use Disorder

Introduction: Women are more vulnerable than men in many aspects of opioid use disorder (OUD); a major theory of sex differences in substance use disorders is that these differences are due to ovarian hormones with estradiol enhancing vulnerability in females. However, most of this evidence is for psychostimulants and alcohol; evidence with opioids is sparse. Thus, the goal of this study was to determine the impact of estradiol on vulnerability in females in a rat model of OUD. Method: Following self-administration training, ovariectomized (OVX) females with (E) or without (V) estradiol replacement were given extended (24 h/day), intermittent access (2, 5-min trials/h) to fentanyl for 10 days. Then, the development of three key features of OUD were assessed, including physical dependence, defined by the magnitude and time course of weight loss during withdrawal; an enhanced motivation for fentanyl, assessed using a progressive-ratio schedule; and relapse vulnerability, assessed using an extinction/cue-induced reinstatement procedure. These later two characteristics were examined following 14 days of withdrawal when the phenotypes are known to be highly expressed. Results: OVX+E females self-administered markedly higher levels of fentanyl under extended, intermittent-access conditions and showed a longer time course of physical dependence, a greater increase in motivation for fentanyl, and an enhanced sensitivity to the reinstating effects of fentanyl-associated cues compared to OVX+V rats. Severe health complications were also observed in OVX+E, but not OVX+V females, during withdrawal. Conclusion: These results indicate that, as with findings with psychostimulants and alcohol, estradiol enhances vulnerability in females to developing opioid addiction-like features and serious opioid-related health complications.

Estradiol regulates voltage-gated potassium currents in corticotropin-releasing hormone neurons.

Corticotropin-releasing hormone (CRH) neurons are the primary neural population controlling the hypothalamic-pituitary-adrenal (HPA) axis and the secretion of adrenal stress hormones. Previous work has demonstrated that stress hormone secretion can be regulated by circulating levels of estradiol. However, the effect of estradiol on CRH neuron excitability is less clear. Here, we show that chronic estradiol replacement following ovariectomy increases two types of potassium channel currents in CRH neurons: fast inactivating voltage-gated A-type K+ channel currents (IA) and non-inactivating M-type K+ channel currents (IM). Despite the increase in K+ currents following estradiol replacement, there was no overall change in CRH neuron spiking excitability assessed with either frequency-current curves or current ramps. Together, these data reveal a complex picture whereby ovariectomy and estradiol replacement differentially modulate distinct aspects of CRH neuron and HPA axis function.

Estrogen receptors mediate the antidepressant effects of aerobic exercise: A possible new mechanism.

This study aimed to examine whether aerobic exercise exerts mood-modulating effects through an estrogen signaling mechanism. The experiment was divided into two parts. The first part is to compare the three modeling methods to obtain the most obvious method of depression-like phenotype for further study in the second part. The first part of ovariectomized rats (age, 13 weeks) was tested when rats were 14 or 22 weeks old or in the sixth week after 3 weeks of chronic restraint stress. The second part was to treat the animals with the most obvious depression-like phenotype in different ways, placebo treatment or estradiol (E2) replacement therapy was administered, aerobic training, or estrogen receptor antagonist treatment. The cognitive (Barnes maze and 3-chamber social tests), anxiety-like (open-field and elevated plus maze tests) and depression-like (sucrose preference and forced swim tests) behaviors of rats in both parts were analyzed to study the effects of estrogen depletion and aerobic exercise. Rats did not develop depressive symptoms immediately after ovariectomy, however, the symptoms became more pronounced with a gradual decrease in ovarian hormone levels. Compared with the placebo or control groups, the exercise and E2 groups showed improved performance in all behavioral test tasks, and the antidepressant effects of aerobic exercise were comparable to those of estrogen. Moreover, the estrogen receptor antagonist has markedly inhibited the antidepressant effects of aerobic exercise. Estrogen receptors may mediate the antidepressant effects of aerobic exercise. In addition, an increasingly fragile ovarian hormonal environment may underlies chronic restraint stress-induced depression.

Estradiol Replacement as a Potential Enhancer of Working Memory and Neuroplasticity in Hypogonadal Trans Women

Introduction: The cognitive effects of cross-sex hormone therapy (CSHT) are not well understood. In cisgender individuals, sex hormone therapy can impact neurotransmitter levels and structural anatomy. Similarly, in gender-diverse persons, CSHT has been associated with neural adaptations, such as growth in brain structures resembling those observed in cisgender individuals of the same sex. Hormone-related changes in learning and memory, as seen in menopause, are associated with physiological hypogonadism or a decline in hormones, such as estradiol. The present study examined the effect of estradiol administration in humans on glutamate concentration in brain regions involved in semantic and working memory (i.e., the dorsolateral prefrontal cortex [DLPFC], the posterior hippocampus, and the pregenual anterior cingulate cortex) and its relationship with memory. Methods: Eighteen trans women (male biological sex assigned at birth) ceased CSHT for 30 days for a washout phase (t1) upon study enrollment to reach a hypogonadal state. Working and semantic memory, cognition, hormonal assays, and brain imaging were assessed. Participants resumed CSHT for 60 days for a replacement phase (t2), after which the same evaluations from t1 were repeated. Results: Estradiol increased among trans women after 60 days of resumed CSHT with significant improvements in semantic memory compared to the hypogonadal phase. Working memory recall was significantly and positively correlated to glutamate in the DLPFC during the reinstatement phase, although the relationship was not moderated by levels of estradiol. Discussion: These results may have clinical implications for the therapeutic effects of estradiol replacement, serving as a protective factor against cognitive decline and impairment for trans women post-gonadectomy.

287 Impact of pre- and Post-Natal Nutritional Extremes on Responsiveness of Ovariectomized, Sexually Mature Heifers to a Neurokinin B Agonist During Progesterone Dominance

Abstract Objectives were to test the hypothesis that nutritional extremes during prenatal development interact with postnatal nutrition during the juvenile period of heifers to impact KNDy neuron responsiveness to a neurokinin B (NKB) agonist (Senktide) during progesterone dominance. Heifers were selected from a larger population programmed nutritionally using a 3x2 factorial arrangement of pre- and post-natal diets. Bos indicus-influenced cows (n = 95) were fed to achieve body condition scores (BCS; 1-9 scale) of 3-3.5 (L; thin), 5.5-6 (M; moderate), or 7.5-8 (H; obese) by the onset of the third trimester and maintained thereafter. Heifer offspring were weaned at 3-3.5 mo of age and assigned to either a low- (L; 0.5 kg/day) or high-gain (H; 1 kg/day) diet until 8 mo of age, then fed a common diet until puberty. For the current experiment, heifers (n = 18; 6/group) representing LL, MH, and HH combinations were ovariectomized postpubertally (17.1 mo of age) and received estradiol (E2) replacement to maintain basal E2 concentrations at 2-4 pg/mL. To achieve progesterone dominance, 3 CIDR devices were placed intravaginally 6 days prior to the initiation of Senktide challenge. Heifers were sampled for a 4.5-h period and received intravenous injections of saline or Senktide (14.8 ug/kg I.V.) at 0, 90, and 180 min. Jugular blood samples were collected at 10-min intervals for radioimmunoassay of LH. Irrespective of Senktide treatment, heifers in the MH group had greater pulse amplitudes (P = 0.016) and mean concentrations (P &amp;lt; 0.0001) of LH compared with both the HH and LL groups. Senktide treatment increased (P = 0.003) concentrations of LH compared with saline in all groups; however, the response to Senktide was greatest in the MH group compared with HH and LL. Pre- and postnatal nutritional extremes appear to interact to impact KNDy neuron responsiveness to NKB receptor signaling in heifers.