Stress levels of glucocorticoids inhibit LHβ-subunit gene expression in gonadotrope cells

Longitudinal Evaluation of Reproductive Endocrine Function in Men With ACTH-Dependent Cushing Syndrome

CONTEXT

Hypogonadism may be caused by Cushing syndrome (CS) and may intensify its adverse consequences.

OBJECTIVE

This work aimed to determine the frequency of male hypogonadism before and after curative surgery for CS, and its cause.

METHODS

Post hoc analyses of prospective cohort studies were conducted at a clinical research center. Study participants were men with adrenocorticotropic hormone (ACTH)-dependent CS: cohort 1 (C1) (n = 8, age 32.5 ± 12 years; studied 1985-1989) and cohort 2 (C2) (n = 44, 42.7 ± 15.1 years; studied 1989-2021). Interventions included the following: C1: every 20-minute blood sampling for 24 hours before and 1 to 40 months after surgical cure. Three individuals underwent gonadotropin-releasing hormone (GnRH) stimulation tests pre and post surgery. C2: Hormone measurements at baseline and 6 and 12 months (M) post cure. Main outcome measures included the following: C1: LH, FSH, LH pulse frequency, and LH response to GnRH. C2: LH, FSH, testosterone (T), free T, free thyroxine, 3,5,3'-triiodothyronine, thyrotropin, and urine free cortisol (UFC) levels and frequency of hypogonadism pre and post surgery.

RESULTS

C1: mean LH and LH pulse frequency increased after surgery (P < .05) without changes in LH pulse amplitude, mean FSH, or peak gonadotropin response to GnRH. C2: 82% had baseline hypogonadism (total T 205 ± 28 ng/dL). Thyroid hormone levels varied inversely with UFC and cortisol. LH, total and free T, and sex hormone-binding globulin increased at 6 and 12 M post surgery, but hypogonadism persisted in 51% at 6 M and in 26% at 12 M.

CONCLUSION

Hypogonadism in men with CS is widely prevalent but reversible in approximately 75% of patients 1 year after surgical cure and appears to be mediated through suppression of hypothalamic GnRH secretion, and modulated by thyroid hormones.

Stress and parental behaviors

In nearly all mammalian species, newborn pups are weak and vulnerable, relying heavily on care and protection from parents for survival. Thus, developmentally hardwired neural circuits are in place to ensure the timely expression of parental behaviors. Furthermore, several neurochemical systems, including estrogen, oxytocin, and dopamine, facilitate the emergence and expression of parental behaviors. However, stress can adversely affect these systems, impairing parental behaviors. In this review, we will summarize our current knowledge regarding the impact of stress on pup-directed behavior circuits that lead to infant neglect, abuse, and, in extreme cases, killing. We will discuss various stressors that influence parental behaviors at different life stages and how stress induces changes in the neurochemical systems that support parental care, ultimately leading to its poor performance.

The cycle of stress: A systematic review of the impact of chronic psychological stress models on the rodent estrous cycle

Stress is known to impair reproduction through interactions between the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. However, while it is well accepted that stress can alter estrous cycle regularity, a key indicator of female's HPG axis function, effects of different types of psychological stress have been inconsistent. This systematic review evaluated the impact of rodent models of psychological stress on estrous cyclicity, while reporting biological parameters pertaining to HPA or HPG axis function assessed within these studies. We performed a systematic database search and included articles that implemented a psychological stress model in rodents and reported estrous cyclicity for at least two cycles after initiation of stress. Of the 32 studies included, 62.5% reported post-stress alterations to estrous cyclicity, with Chronic Mild Stress (CMS) models showing the most conclusive effects. Twenty-five studies measured HPG or HPA axis markers, with cycle disruptions being commonly observed in parallel with altered estradiol and increased corticosterone levels. Our review highlights gaps in reporting estrous cyclicity assessments and makes recommendations to improve comparability between studies.

Gonads under stress: A systematic review and meta-analysis on the effects of acute psychosocial stress on gonadal steroids secretion in humans

Animal research has shown that the hypothalamus-pituitary-gonadal (HPG) axis is inhibited by (chronic and/or severe) stress, which can lead to impaired fertility and reproductive functioning, presumably caused by the inhibition of gonadal steroid secretion and in interactions with glucocorticoids. However, what has not been clarified is how acute psychosocial stress modulates gonadal steroid secretion in humans. Here we summarize the experimental research on the acute effects of stress on the secretion of gonadal steroids in humans. A systematic literature search revealed 21 studies (with N=881 individuals) measuring testosterone, progesterone or estradiol in response to a standardized acute laboratory stressor in healthy humans. Both our literature review and quantitative meta-analysis suggest that in humans, acute stress stimulates rather than inhibits HPG axis activity, although there is a considerable heterogeneity in the reported methods and results. Increased gonadal steroids in response to acute stress contrasts with many animal studies reporting the opposite pattern, at least regarding severe and/or chronic stressors. We discuss methodological issues and challenges for future research and hope to stimulate experimental studies within this area. A better understanding of these mechanisms is needed, and may have important implications for health and disease, as well as the modulation of various behaviors by acute stressors.

Menstrual cycle-related changes in HPA axis reactivity to acute psychosocial and physiological stressors - a systematic review and meta-analysis of longitudinal studies

Sex disparities are evident in the biological response to acute stressors, with a suggested influence of ovarian hormones on hypothalamic-pituitary-adrenal (HPA) axis functioning. This systematic review and meta-analysis investigates differences in HPA axis reactivity to acute psychosocial or physiological stressors between menstrual cycle phases. A systematic literature search of six databases resulted in 12 longitudinal studies (n = 182) examining HPA axis reactivity in healthy, naturally-cycling, non-breastfeeding participants aged between 18 and 45 years in at least two cycle phases. The quality of cortisol and menstrual cycle assessment was rated and a descriptive synthesis and meta-analysis of HPA axis reactivity between two broader and five more precise cycle phases was conducted. Three studies provided sufficient data for the meta-analysis and showed a significant, small-sized effect, indicating higher cortisol reactivity in the luteal than in the follicular cycle phase. More primary studies with high-quality menstrual cycle and cortisol assessment are needed. The review did not receive funding and was pre-registered (PROSPERO; CRD42020181632).

Chronic Restraint Stress Alters Rat Behavior Depending on Sex and Duration of Stress

Chronic restraint stress (CRS) can have different behavioral effects depending on variables associated with the stressor and the organism. This study aimed to verify the effect of the interaction between sex and duration of the CRS protocol in rats. Sprague-Dawley rats were divided by sex, intervention (CRS; control), and CRS duration (11 days; 22 days). Rats exposed to CRS showed better spatial learning than controls in the Morris water maze test, regardless of sex and stress duration. Males exposed to CRS for 11 days showed a higher rate of behaviors associated with anxiety than males exposed to 22 days of CRS at the elevated plus maze test, but the same was not observed in females. The weight gain of animals exposed to stress decreased in the first 11 days, showing a recovery from day 11 to day 22 of intervention. No effects of CRS were observed on behaviors associated with depression in the sucrose preference test. The results suggest habituation to the protocol, with a progressive decrease in the harmful effects of stress on and maintenance of the beneficial effects. It is possible that females are more resistant to the harmful effects of CRS on anxiety.

Altered GnRH neuron and ovarian innervation characterize reproductive dysfunction linked to the Fragile X messenger ribonucleoprotein (Fmr1) gene mutation

Introduction

Mutations in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene cause Fragile X Syndrome, the most common monogenic cause of intellectual disability. Mutations of FMR1 are also associated with reproductive disorders, such as early cessation of reproductive function in females. While progress has been made in understanding the mechanisms of mental impairment, the causes of reproductive disorders are not clear. FMR1-associated reproductive disorders were studied exclusively from the endocrine perspective, while the FMR1 role in neurons that control reproduction was not addressed.

Results

Here, we demonstrate that similar to women with FMR1 mutations, female Fmr1 null mice stop reproducing early. However, young null females display larger litters, more corpora lutea in the ovaries, increased inhibin, progesterone, testosterone, and gonadotropin hormones in the circulation. Ovariectomy reveals both hypothalamic and ovarian contribution to elevated gonadotropins. Altered mRNA and protein levels of several synaptic molecules in the hypothalamus are identified, indicating reasons for hypothalamic dysregulation. Increased vascularization of corpora lutea, higher sympathetic innervation of growing follicles in the ovaries of Fmr1 nulls, and higher numbers of synaptic GABAA receptors in GnRH neurons, which are excitatory for GnRH neurons, contribute to increased FSH and LH, respectively. Unmodified and ovariectomized Fmr1 nulls have increased LH pulse frequency, suggesting that Fmr1 nulls exhibit hyperactive GnRH neurons, regardless of the ovarian feedback.

Conclusion

These results reveal Fmr1 function in the regulation of GnRH neuron secretion, and point to the role of GnRH neurons, in addition to the ovarian innervation, in the etiology of Fmr1-mediated reproductive disorders.

The Corticosterone–Glucocorticoid Receptor–AP1/CREB Axis Inhibits the Luteinizing Hormone Receptor Expression in Mouse Granulosa Cells

Under stress conditions, luteinizing hormone (LH)-mediated ovulation is inhibited, resulting in insufficient oocyte production and excretion during follicular development. When the body is stressed, a large amount of corticosterone (CORT) is generated, which will lead to a disorder of the body’s endocrine system and damage to the body. Our previous work showed that CORT can block follicular development in mice. Since LH acts through binding with the luteinizing hormone receptor (Lhcgr), the present study aimed to investigate whether and how corticosterone (CORT) influences Lhcgr expression in mouse ovarian granulosa cells (GCs). For this purpose, three-week-old ICR female mice were injected intraperitoneally with pregnant mare serum gonadotropin (PMSG). In addition, the treatment group was injected with CORT (1 mg/mouse) at intervals of 8 h and the control group was injected with the same volume of methyl sulfoxide (DMSO). GCs were collected at 24 h, 48 h, and 55 h after PMSG injection. For in vitro experiments, the mouse GCs obtained from healthy follicles were treated with CORT alone, or together with inhibitors against the glucocorticoid receptor (Nr3c1). The results showed that the CORT caused a downregulation of Lhcgr expression in GCs, which was accompanied by impaired cell viability. Moreover, the effect of the CORT was mediated by binding to its receptor (Nr3c1) in GCs. Further investigation revealed that Nr3c1 might regulate the transcription of Lhcgr through inhibiting the expression of Lhcgr transcription factors, including AP1 and Creb. Taken together, our findings suggested a possible mechanism of CORT-induced anovulation involving the inhibition of Lhcgr expression in GCs by the CORT–Nr3c1–AP1/Creb axis.

A Modified Ultra-Sensitive ELISA for Measurement of LH in Mice

A major obstacle to monitoring pulsatile luteinizing hormone (LH) secretion in mice has been an assay with sufficient sensitivity in small blood volumes. In 2013, Steyn and colleagues published a highly sensitive enzyme-linked immunosorbent assay (ELISA) that overcame this barrier by coupling a duo of LH antibodies effective in accurately measuring LH in 4-µL whole-blood aliquots. To address the unavailability of the original detection antibody, AFP240580Rb, we validated a replacement detection antibody, biotinylated-5303 SPRN-5, to be used within the established ELISA. This modified LH ELISA demonstrated a minimum detection limit of 0.0028 ng/mL and a limit of quantification of 0.0333 ng/mL or 0.0666 ng/mL in diluted whole-blood samples of volume 6.4 µL (1:10) or 3.2 µL (1:20), respectively. Detection antibody 5303 SPRN-5 demonstrated parallelism, high precision, and accuracy across the standard curve. LH concentrations in comparison assays, using either 5303 SPRN-5 or AFP240580Rb, were highly correlated (R2 = 0.9829) and demonstrated LH pulse profiles from gonadectomized mice that were nearly superimposable. Pulsatile LH secretion was demonstrated in gonad-intact males and diestrous females and basal LH levels measured with 5303 SPRN-5 were approximately 5-fold higher than the limit of quantification. In addition, we document utility of this new LH ELISA to accurately measure LH in whole blood or serum across multiple sampling sites, as well as in pituitary extracts, LβT2 cells, or media. In summary, the modified LH ELISA described here is highly effective in measuring LH across a range of sample types and small volumes in mice.

Regulation of the gonadotropin-releasing hormone neuron during stress

The effect of stress on reproduction and gonadal function has captivated investigators for almost 100 years. Following the identification of gonadotropin-releasing hormone (GnRH) 50 years ago, a niche research field emerged fixated on how stress impairs this central node controlling downstream pituitary and gonadal function. It is now clear that both episodic GnRH secretion in males and females and surge GnRH secretion in females are inhibited during a variety of stress types. There has been considerable advancement in our understanding of numerous stress-related signaling molecules and their ability to impair reproductive neuroendocrine activity during stress. Recently, much attention has turned to the effects of stress on two populations of kisspeptin neurons: the stimulatory afferents to GnRH neurons that regulate pulsatile and surge-type gonadotropin secretion. Indeed, future work is still required to fully construct the neuroanatomical framework underlying stress effects, directly or indirectly, on GnRH neuron function. The present review evaluates and synthesizes evidence related to stress-related signaling molecules acting directly on GnRH neurons. Here, we review the evidence for and against the action of a handful of signaling molecules as inhibitors of GnRH neuron function, including corticotropin-releasing hormone, urocortins, norepinephrine, cortisol/corticosterone, calcitonin gene-related peptide and arginine-phenylalanine-amide-related peptide-3.

Regulation of stress response on the hypothalamic-pituitary-gonadal axis via gonadotropin-inhibitory hormone

Under stressful condition, reproductive function is impaired due to the activation of various components of the hypothalamic-pituitaryadrenal (HPA) axis, which can suppress the activity of the hypothalamic-pituitary-gonadal (HPG) axis at multiple levels. A hypothalamic neuropeptide, gonadotropin-inhibitory hormone (GnIH) is a key negative regulator of reproduction that governs the HPG axis. Converging lines of evidence have suggested that different stress types and their duration, such as physical or psychological, and acute or chronic, can modulate the GnIH system. To clarify the sensitivity and reactivity of the GnIH system in response to stress, we summarize and critically review the available studies that investigated the effects of various stressors, such as restraint, nutritional/metabolic and social stress, on GnIH expression and/or its neuronal activity leading to altered HPG action. In this review, we focus on GnIH as the potential novel mediator responsible for stress-induced reproductive dysfunction.

Neuroendocrine interactions of the stress and reproductive axes

Reproduction is controlled by a sequential regulation of the hypothalamo-pituitary-gonadal (HPG) axis. The HPG axis integrates multiple inputs to maintain proper reproductive functions. It has long been demonstrated that stress alters fertility. Nonetheless, the central mechanisms of how stress interacts with the reproductive system are not fully understood. One of the major pathways that is activated during the stress response is the hypothalamo-pituitary-adrenal (HPA) axis. In this review, we discuss several aspects of the interactions between these two neuroendocrine systems to offer insights to mechanisms of how the HPA and HPG axes interact. We have also included discussions of other systems, for example GABA-producing neurons, where they are informative to the overall picture of stress effects on reproduction.

Impact of chronic variable stress on neuroendocrine hypothalamus and pituitary in male and female C57BL/6J mice

Chronic stress exerts multiple negative effects on the physiology and health of an individual. In the present study, we examined hypothalamic, pituitary and endocrine responses to 14 days of chronic variable stress (CVS) in male and female C57BL/6J mice. In both sexes, CVS induced a significant decrease in body weight and enhanced the acute corticosterone stress response, which was accompanied by a reduction in thymus weight only in females. However, single-point blood measurements of basal prolactin, thyroid-stimulating hormone, luteinising hormone, growth hormone and corticosterone levels taken at the end of the CVS were not different from those of controls. Similarly, pituitary mRNA expression of Fshb, Lhb, Prl and Gh was unchanged by CVS, although Pomc and Tsh were significantly elevated. Within the adrenal medulla, mRNA for Th, Vip and Gal were elevated following CVS. Avp transcript levels within the paraventricular nucleus of the hypothalamus were increased by CVS; however, levels of Gnrh1, Crh, Oxt, Sst, Trh, Ghrh, Th and Kiss1 remained unchanged. Oestrous cycles were lengthened slightly by CVS and ovarian histology revealed a reduction in the number of preovulatory follicles and corpora lutea. Taken together, these observations indicate that 14 days of CVS induces an up-regulation of the neuroendocrine stress axis and creates a mild disruption of female reproductive function. However, the lack of changes in other neuroendocrine axes controlling anterior and posterior pituitary secretion suggest that most neuroendocrine axes are relatively resilient to CVS.

Unexpected Role of Physiological Estrogen in Acute Stress-Induced Memory Deficits

Stress may promote emotional and cognitive disturbances, which differ by sex. Adverse outcomes, including memory disturbances, are typically observed following chronic stress, but are now being recognized also after short events, including mass shootings, assault, or natural disasters, events that consist of concurrent multiple acute stresses (MAS). Prior work has established profound and enduring effects of MAS on memory in males. Here we examined the effects of MAS on female mice and probed the role of hormonal fluctuations during the estrous cycle on MAS-induced memory problems and the underlying brain network and cellular mechanisms. Female mice were impacted by MAS in an estrous cycle-dependent manner: MAS impaired hippocampus-dependent spatial memory in early-proestrous mice, characterized by high levels of estradiol, whereas memory of mice stressed during estrus (low estradiol) was spared. As spatial memory requires an intact dorsal hippocampal CA1, we examined synaptic integrity in mice stressed at different cycle phases and found a congruence of dendritic spine density and spatial memory deficits, with reduced spine density only in mice stressed during high estradiol cycle phases. Assessing MAS-induced activation of brain networks interconnected with hippocampus, we identified differential estrous cycle-dependent activation of memory- and stress-related regions, including the amygdala. Network analyses of the cross-correlation of fos expression among these regions uncovered functional connectivity that differentiated impaired mice from those not impaired by MAS. In conclusion, the estrous cycle modulates the impact of MAS on spatial memory, and fluctuating physiological levels of sex hormones may contribute to this effect.SIGNIFICANCE STATEMENT: Effects of stress on brain functions, including memory, are profound and sex-dependent. Acute stressors occurring simultaneously result in spatial memory impairments in males, but effects on females are unknown. Here we identified estrous cycle-dependent effects of such stresses on memory in females. Surprisingly, females with higher physiological estradiol experienced stress-induced memory impairment and a loss of underlying synapses. Memory- and stress-responsive brain regions interconnected with hippocampus were differentially activated across high and low estradiol mice, and predicted memory impairment. Thus, at functional, network, and cellular levels, physiological estradiol influences the effects of stress on memory in females, providing insight into mechanisms of prominent sex differences in stress-related memory disorders, such as post-traumatic stress disorder.

Glucocorticoids affect male testicular steroidogenesis

Through their receptors at each level of hypothalamo-pituitary-gonadal axis glucocorticoid excess, either endogenous or administered or stress-induced, could affect steroid production in the testis and thus male fertility. The main ways by which glucocorticoids act are as follows: 1) Affecting gonadoliberin and LH synthesis and release through glucocorticoid receptors in hypothalamic neurons and pituitary gonadotropes. 2) By so far not clearly evidenced reduction of the number of LH receptors on the membrane of Leydig cells. 3) By affecting expression and function of steroidogenic enzymes in the testis. 4) By regulation of in situ access of glucocorticoid to its target cells in the testis. 5) By promotion Leydig cell apoptosis. The review provides a survey of physiological and molecular mechanisms staying behind these effects. It does not deal with the clinical effects of glucocorticoid treatment which would substantially exceed the scope of the pater.

Seizure burden fluctuates with the female reproductive cycle in a mouse model of chronic temporal lobe epilepsy

Women with catamenial epilepsy often experience increased seizure burden near the time of ovulation (periovulatory) or menstruation (perimenstrual). To date, a rodent model of chronic temporal lobe epilepsy (TLE) that exhibits similar endogenous fluctuations in seizures has not been identified. Here, we investigated whether seizure burden changes with the estrous cycle in the intrahippocampal kainic acid (IHKA) mouse model of TLE. Adult female IHKA mice and saline-injected controls were implanted with EEG electrodes in the ipsilateral hippocampus. At one and two months post-injection, 24/7 video-EEG recordings were collected and estrous cycle stage was assessed daily. Seizures were detected using a custom convolutional neural network machine learning process. Seizure burden was compared within each mouse between diestrus and combined proestrus and estrus days (pro/estrus) at two months post-injection. IHKA mice showed higher seizure burden on pro/estrus compared with diestrus, characterized by increased time in seizures and longer seizure duration. When all IHKA mice were included, no group differences were observed in seizure frequency or EEG power. However, increased baseline seizure burden on diestrus was correlated with larger cycle-associated differences, and when analyses were restricted to mice that showed the severe epilepsy typical of the IHKA model, increased seizure frequency on pro/estrus was also revealed. Controls showed no differences in EEG parameters with cycle stage. These results suggest that the stages of proestrus and estrus are associated with higher seizure burden in IHKA mice. The IHKA model may thus recapitulate at least some aspects of reproductive cycle-associated seizure clustering.

Neuroendocrine disruption is associated to infertility in chronically stressed female rats

Infertility is a growing worldwide public health problem, and stress is a main factor exerting detrimental effects on female reproduction. However, knowledge regarding the neuroendocrine changes caused by chronic stress in females is limited. Therefore, this study assessed the effects of stress on hormones that control female reproduction during the proestrus and diestrus stages of the estrous cycle, as well as its effects on fertility. Adult females were assigned to either a control or a stress group. Stress consisted of exposure, for 15 min, to cold-water immersion daily for 30 days. Estrous cyclicity, female sexual behavior, as well as hypothalamic kisspeptin, gonadotropin releasing hormone (GnRH) content, serum luteinizing hormone (LH), estradiol (E₂), progesterone (P₄), corticosterone (CORT) and fertility were assessed after chronic stress. The results show that chronically stressed females exhibited disrupted estrous cyclicity, decreased receptivity, low pregnancy rates and lower numbers of fetuses. The content of Kisspeptin and GnRH in the Anteroventral Periventricular/medial Preoptic Area decreased during proestrus, while Kisspeptin increased in the Arcuate nucleus in proestrus and diestrus. Serum LH decreased only during proestrus, whereas E₂ and P₄ concentrations decreased during proestrus and diestrus, with a concomitant increase in CORT levels in both stages. As a whole, these results indicate that chronic stress decreases Kisspeptin content in AVPV nucleus and GnRH in POA in females, and might induce disruption of the LH surge, consequently disrupting estrous cyclicity and fertility, leading to lower rates of pregnancy and number of fetuses.

Metabolic control of teleost reproduction by leptin and its complements: Understanding current insights from mammals

Reproduction is expensive. Hence, reproductive physiology is sensitive to an array of endogenous signals that provide information on metabolic and nutritional sufficiency. Although metabolic gating of reproductive function in mammals, as evidenced by studies demonstrating delayed puberty and perturbed fertility, has long been understood to be a function of energy sufficiency, an understanding of the endocrine regulators of this relationship have emerged only within recent decades. Peripheral signals including leptin and cortisol have long been implicated in the physiological integration of metabolism and reproduction. Recent studies have begun to explore possible roles for these two hormones in the regulation of reproduction in teleost fishes, as well as a role for leptin as a catabolic stress hormone. In this review, we briefly explore the reproductive actions of leptin and cortisol in mammals and teleost fishes and possible role of both hormones as putative modulators of the reproductive axis during stress events.

Expression of genes that regulate follicle development and maturation during ovarian stimulation in poor responders

RESEARCH QUESTION

Sex hormone-binding globulin (SHBG), androgen receptor (AR), LH beta polypeptide (LHB), progesterone receptor membrane component 1 (PGRMC1) and progesterone receptor membrane component 2 (PGRMC2) regulate follicle development and maturation. Their mRNA expression was assessed in peripheral blood mononuclear cells (PBMC) of normal and poor responders, during ovarian stimulation.

DESIGN

Fifty-two normal responders and 15 poor responders according to the Bologna criteria were enrolled for IVF and intracytoplasmic sperm injection and stimulated with 200 IU of follitrophin alpha and gonadotrophin-releasing hormone antagonist. HCG was administered for final oocyte maturation. On days 1, 6 and 10 of stimulation, blood samples were obtained, serum hormone levels were measured, RNA was extracted from PBMC and real-time polymerase chain reaction was carried out to identify the mRNA levels. Relative mRNA expression of each gene was calculated by the comparative 2^-DDCt method.

RESULTS

Differences between mRNA levels of each gene on the same time point between the two groups were not significant. PGRMC1 and PGRMC2 mRNA levels were downregulated, adjusted for ovarian response and age. Positive correlations between PGRMC1 and AR (standardized beta = 0.890, P < 0.001) from day 1 to 6 and PGRMC1 and LHB (standardized beta = 0.806, P < 0.001) from day 1 to 10 were found in poor responders. PGRMC1 and PGRMC2 were positively correlated on days 6 and 10 in normal responders.

CONCLUSIONS

PGRMC1 and PGRMC2 mRNA are significantly decreased during ovarian stimulation, with some potential differences between normal and poor responders.

Effects of new generation progestins, including as mixtures and in combination with other classes of steroid hormones, on zebrafish early life stages

Fish are exposed to progestins and steroid mixtures in contaminated waters but the ecotoxicological implications are not sufficiently known. Here we analyze effects of the new generation progestin dienogest (DNG) followed by investigating effects of mixtures of new generation progestins containing DNG, cyproterone acetate and drospirenone and the hormone progesterone. Furthermore, effects of this mixture were studied after adding 17β-estradiol (E2) and clobetasol propionate (CLO) in zebrafish embryos and larvae at concentrations between 0.01 and 10 μg/L. DNG showed only very minor transcriptional alterations among the 24 assessed genes with downregulation of the fshb transcript only. The progestin mixture caused weak induction of the lhb, cyp2k22 and sult2st3 transcripts. Addition of E2 to the mixture caused strong induction vtg1, cyp19b, esr1 and lhb, as well as downregulation of fshb from 0.01 μg/L onwards. Besides altering the same transcripts, addition of CLO altered glucocorticoid regulated genes mmp-9, mmp-13, g6pca, fkbp5 and irg1l. While each steroid class exhibited its specific activity independently in the mixture, sult2st3 and cyp2k22 were regulated by both E2 and CLO. Furthermore, CLO alone and in mixtures decreased spontaneous muscle contractions, increased heartrate and induced edema. Our study highlights the prominent effects of E2 and CLO in environmental steroid mixtures, while new generation progestins show relatively low activity.

Estradiol Enables Chronic Corticosterone to Inhibit Pulsatile Luteinizing Hormone Secretion and Suppress Kiss1 Neuronal Activation in Female Mice

INTRODUCTION

Two common responses to stress include elevated circulating glucocorticoids and impaired luteinizing hormone (LH) secretion. We have previously shown that a chronic stress level of corticosterone can impair ovarian cyclicity in intact mice by preventing follicular-phase endocrine events.

OBJECTIVE

This study is aimed at investigating if corticosterone can disrupt LH pulses and whether estradiol is necessary for this inhibition.

METHODS

Our approach was to measure LH pulses prior to and following the administration of chronic corticosterone or cholesterol in ovariectomized (OVX) mice treated with or without estradiol, as well as assess changes in arcuate kisspeptin (Kiss1) neuronal activation, as determined by co-expression with c-Fos.

RESULTS

In OVX mice, a chronic 48 h elevation in corticosterone did not alter the pulsatile pattern of LH. In contrast, corticosterone induced a robust suppression of pulsatile LH secretion in mice treated with estradiol. This suppression represented a decrease in pulse frequency without a change in amplitude. We show that the majority of arcuate Kiss1 neurons contain glucocorticoid receptor, revealing a potential site of corticosterone action. Although arcuate Kiss1 and Tac2 gene expression did not change in response to corticosterone, arcuate Kiss1 neuronal activation was significantly reduced by chronic corticosterone, but only in mice treated with estradiol.

CONCLUSIONS

Collectively, these data demonstrate that chronic corticosterone inhibits LH pulse frequency and reduces Kiss1 neuronal activation in female mice, both in an estradiol-dependent manner. Our findings support the possibility that enhanced sensitivity to glucocorticoids, due to ovarian steroid milieu, may contribute to reproductive impairment associated with stress or pathophysiologic conditions of elevated glucocorticoids.

The role of prolactin in co-ordinating fertility and metabolic adaptations during reproduction

Mammalian pregnancy and lactation is accompanied by a period of infertility that takes place in the midst of a sustained increase in food intake. Indeed, successful reproduction in females is dependent on co-ordination of the distinct systems that regulate reproduction and metabolism. Rather than arising from different mechanisms during pregnancy and lactation, we propose that elevations in lactogenic hormones (predominant among these being prolactin and the placental lactogens), are ideally placed to influence both of these systems at the appropriate time. We review the literature examining the impacts of lactogens on fertility and energy homeostasis in the virgin state, during pregnancy and lactation and potential long-term impacts of reproductive experience. Taken together, the literature indicates that duration and pattern of lactogen exposure is a vital factor in the ability of these hormones to alter reproduction and food intake. Transient increases in prolactin, as typically seen in healthy virgin females and males, are unable to exert lasting impacts. Importantly, both suppression of fertility and increased food intake are only observed following exposure to chronically-elevated levels of lactogens. Physiologically, the only time this pattern of lactogenic secretion is maintained in the healthy female is during pregnancy and lactation, when co-ordination between these regulatory systems emerges. This article is part of the special issue on 'Neuropeptides'.

Cortisol differentially affects cell viability and reproduction-related gene expression in Atlantic cod pituitary cultures dependent on stage of sexual maturation

Through the action of cortisol, stress can affect reproductive biology with behavioural and physiological alterations. Using mixed sex primary pituitary cultures from Atlantic cod (Gadus morhua), the present study aimed to investigate potential direct effects of basal and stress level cortisol on the pituitary in terms of cell viability and reproduction-related gene expression at different stages of sexual maturity. Stress level of cortisol stimulated cell viability in cells derived from sexually maturing and mature fish. In cells from spent fish, high cortisol levels did not affect cell viability in terms of metabolic activity, but did stimulate viability in terms of membrane integrity. Basal cortisol levels did not affect cell viability. Ethanol, used as solvent for cortisol, decreased cell viability at all maturity stages, but did generally not affect gene expression. Genes investigated were fshb, lhb and two Gnrh receptors expressed in cod gonadotropes (gnrhr1b and gnrhr2a). Cortisol had dual effects on fshb expression; stimulating expression in cells from mature fish at stress dose, while inhibiting expression in cells from spent fish at both doses. In contrast, cortisol had no direct effect on lhb expression. While gnrhr2a transcript levels largely increased following cortisol treatment, gnrhr1b expression decreased in cells from spent fish and was unaffected at other maturity stages. These findings demonstrate that cortisol can act directly and differentially at the pituitary level in Atlantic cod and that factors facilitating these actions are dose-dependently activated and vary with level of sexual maturity.

Estrous Cycle Monitoring in Mice with Rapid Data Visualization and Analysis

The estrous cycle provides a readout of reproductive health in female laboratory rodents, and estrous cycle stage can be an important physiological variable. Accurate assessment of estrous cycle stage is also important in producing timed pregnancies for developmental studies. Here, we provide a protocol for evaluation of estrous cycle stage through a minimally invasive procedure of acquiring cells lining the vaginal cavity and immediate microscopic visual assessment of these cells without drying or staining. When performed over several consecutive days, the pattern of progression through the four main stages of the estrous cycle, and disruptions to this pattern, can be determined. We also present software that enables more efficient cycle stage data analysis and pattern visualization. These protocols and tools will thus facilitate the incorporation of female animals in laboratory experiments and enhance the assessment of relationships between the reproductive cycle and overall physiology and behavior.

Emerging insights into hypothalamic-pituitary-gonadal axis regulation and interaction with stress signalling

Reproduction and fertility are regulated via hormones of the hypothalamic-pituitary-gonadal (HPG) axis. Control of this reproductive axis occurs at all levels, including the brain and pituitary, and allows for the promotion or inhibition of gonadal sex steroid secretion and function. In addition to guiding proper gonadal development and function, gonadal sex steroids also act in negative- and positive-feedback loops to regulate reproductive circuitry in the brain, including kisspeptin neurones, thereby modulating overall HPG axis status. Additional regulation is also provided by sex steroids made within the brain, including neuroprogestins. Furthermore, because reproduction and survival need to be coordinated and balanced, the HPG axis is able to modulate (and be modulated by) stress hormone signalling, including cortiscosterone, from the hypothalamic-pituitary-adrenal (HPA) axis. This review covers recent data related to the neural, hormonal and stress regulation of the HPG axis and emerging interactions between the HPG and HPA axes, focusing on actions at the level of the brain and pituitary.

Diet-Induced Obesity Elicits Macrophage Infiltration and Reduction in Spine Density in the Hypothalami of Male but Not Female Mice

Increasing prevalence in obesity has become a significant public concern. C57BL/6J mice are prone to diet-induced obesity (DIO) when fed high-fat diet (HFD), and develop chronic inflammation and metabolic syndrome, making them a good model to analyze mechanisms whereby obesity elicits pathologies. DIO mice demonstrated profound sex differences in response to HFD with respect to inflammation and hypothalamic function. First, we determined that males are prone to DIO, while females are resistant. Ovariectomized females, on the other hand, are susceptible to DIO, implying protection by ovarian hormones. Males, but not females, exhibit changes in hypothalamic neuropeptide expression. Surprisingly, ovariectomized females remain resistant to neuroendocrine changes, showing that ovarian hormones are not necessary for protection. Second, obese mice exhibit sex differences in DIO-induced inflammation. Microglial activation and peripheral macrophage infiltration is seen in the hypothalami of males, while females are protected from the increase in inflammatory cytokines and do not exhibit microglia morphology changes nor monocyte-derived macrophage infiltration, regardless of the presence of ovarian hormones. Strikingly, the anti-inflammatory cytokine IL-10 is increased in the hypothalami of females but not males. Third, this study posits a potential mechanism of obesity-induced impairment of hypothalamic function whereby obese males exhibit reduced levels of synaptic proteins in the hypothalamus and fewer spines in GnRH neurons, located in the areas exhibiting macrophage infiltration. Our studies suggest that inflammation-induced synaptic remodeling is potentially responsible for hypothalamic impairment that may contribute to diminished levels of gonadotropin hormones, testosterone, and sperm numbers, which we observe and corresponds to the observations in obese humans. Taken together, our data implicate neuro-immune mechanisms underlying sex-specific differences in obesity-induced impairment of the hypothalamic function with potential consequences for reproduction and fertility.

A Novel Method for Chronic Social Defeat Stress in Female Mice

Historically, preclinical stress studies have often omitted female subjects, despite evidence that women have higher rates of anxiety and depression. In rodents, many stress susceptibility and resilience studies have focused on males as one commonly used paradigm-chronic social defeat stress-has proven challenging to implement in females. We report a new version of the social defeat paradigm that works in female mice. By applying male odorants to females to increase resident male aggressive behavior, we find that female mice undergo repeated social defeat stress and develop social avoidance, decreased sucrose preference, and decreased time in the open arms of the elevated plus maze relative to control mice. Moreover, a subset of the female mice in this paradigm display resilience, maintaining control levels of social exploration and sucrose preference. This method produces comparable results to those obtained in male mice and will greatly facilitate studying female stress susceptibility.

Comparative aspects of GnRH-Stimulated signal transduction in the vertebrate pituitary - Contributions from teleost model systems

Gonadotropin-releasing hormone (GnRH) is a major regulator of reproduction through actions on pituitary gonadotropin release and synthesis. Although it is often thought that pituitary cells are exposed to only one GnRH, multiple GnRH forms are delivered to the pituitary of teleost fishes; interestingly this can include the cGnRH-II form usually thought to be non-hypophysiotropic. GnRHs can regulate other pituitary cell-types, both directly as well as indirectly, and multiple GnRH receptors (GnRHRs) may also be expressed in the pituitary, and even within a single pituitary cell-type. Literature on the differential actions of native GnRH isoforms in primary pituitary cells is largely derived from teleost fishes. This review will outline the diversity and complexity of GnRH-GnRHR signal transduction found within vertebrate gonadotropes as well as extra-gonadotropic sites with special emphasis on comparative studies from fish models. The implications that GnRHR transduction mechanisms are GnRH isoform-, function-, and cell-specific are also discussed.

Early postnatal treatment with clomipramine induces female sexual behavior and estrous cycle impairment

Administration of clomipramine (CMI), a tricyclic antidepressant, in early stages of development in rats, is considered an animal model for the study of depression. This pharmacological manipulation has induced behavioral and physiological alterations, i.e., less pleasure-seeking behaviors, despair, hyperactivity, cognitive dysfunction, alterations in neurotransmitter systems and in HPA axis. These abnormalities in adult male rats are similar to the symptoms observed in major depressive disorders. One of the main pleasure-seeking behaviors affected in male rats treated with CMI is sexual behavior. However, to date, no effects of early postnatal CMI treatment have been reported on female reproductive cyclicity and sexual behavior. Therefore, we explored CMI administration in early life (8-21 PN) on the estrous cycle and sexual behavior of adult female rats. Compared to the rats in the early postnatal saline treatment (CTRL group), the CMI rats had fewer estrous cycles, fewer days in the estrous stage, and longer cycles during a 20-day period of vaginal cytology analysis. On the behavioral test, the CMI rats displayed fewer proceptive behaviors (hopping, darting) and had lower lordosis quotients. Also, they usually failed to display lordosis and only rarely manifested marginal or normal lordosis. In contrast, the CTRL rats tended to display normal lordosis. These results suggest that early postnatal CMI treatment caused long-term disruptions of the estrous cycle and female sexual behavior, perhaps by alteration in the hypothalamic-pituitary-gonadal (HPG) axes and in neuronal circuits involved in the regulation of the performance and motivational of sexual behavior as the noradrenergic and serotonergic systems.

Acute Psychosocial Stress Inhibits LH Pulsatility and Kiss1 Neuronal Activation in Female Mice

Psychosocial stress, such as isolation and restraint, disrupts reproductive neuroendocrine activity. Here we investigate the impact of psychosocial stress on luteinizing hormone (LH) pulses and gene expression and neuronal activation within Rfrp and Kiss1 cells in female mice. Mice were ovariectomized (OVX) and handled daily to habituate to the tail-tip blood collection procedure. Blood was collected every 5 minutes for 180 minutes for measurement of LH. After 90 minutes, stress animals were placed into restraint devices and isolated to new cages. No-stress control animals remained in their home cages. LH pulses occurred at regular intervals during the entire 180-minute sampling period in controls. In contrast, stress induced a rapid and robust suppression of pulsatile LH secretion. Stress reduced the frequency of pulses by 60% and diminished basal LH levels by 40%; pulse amplitude was unaffected. In a separate cohort of OVX females, brains were collected after 45, 90, or 180 minutes of stress or in no-stress controls. At all time points, stress induced a potent decrease in arcuate Kiss1 neuronal activation, using cfos induction as a marker, with a 50% to 60% suppression vs control levels, whereas Rfrp and cfos coexpression in the dorsal-medial nucleus was elevated after 45 minutes of stress. Although arcuate Kiss1 gene expression remained stable, Rfrp expression was elevated 20% after 180 minutes of stress. These findings demonstrate rapid suppression of LH pulsatile secretion by psychosocial stress, associated with reduced cfos induction in Kiss1 neurons and time-dependent increases in Rfrp neuronal activation and messenger RNA.

Stress and the HPA Axis: Balancing Homeostasis and Fertility

An organism’s reproductive fitness is sensitive to the environment, integrating cues of resource availability, ecological factors, and hazards within its habitat. Events that challenge the environment of an organism activate the central stress response system, which is primarily mediated by the hypothalamic–pituitary–adrenal (HPA) axis. The regulatory functions of the HPA axis govern the cardiovascular and metabolic system, immune functions, behavior, and reproduction. Activation of the HPA axis by various stressors primarily inhibits reproductive function and is able to alter fetal development, imparting a biological record of stress experienced in utero. Clinical studies and experimental data indicate that stress signaling can mediate these effects through direct actions in the brain, gonads, and embryonic tissues. This review focuses on the mechanisms by which stress activation of the HPA axis impacts fertility and fetal development.

Omega-3 polyunsaturated fatty acid docosahexaenoic acid and its role in exhaustive-exercise-induced changes in female rat ovulatory cycle

Exhaustive exercises can cause delayed menarche or menstrual cycle irregularities in females. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) are incorporated into a wide range of benefits in many physiological systems. Our work aimed to assess the role of ω-3 PUFA docosahexaenoic acid (DHA) on the deleterious effects of exhaustive exercise on the female reproductive system in rats. Virgin female rats were randomly divided into 4 groups (12 rats in each): control group, omega-3 group treated with DHA, exhaustive exercise group, and exhaustive exercised rats treated with DHA. Omega-3 was given orally to the rats once daily for 4 estrous cycles. Exhaustive exercises revealed lower levels in progesterone and gonadotropins together with histopathological decrease in number of growing follicles and corpora lutea. Moreover, the exercised rats showed low levels of ovarian antioxidants with high level of caspase-3 and plasma cortisol level that lead to disruption of hypothalamic-pituitary-gonadal axis. ω-3 PUFA DHA has beneficial effects on the number of newly growing follicles in both sedentary and exercised rats with decreasing the level of caspase-3 and increasing the antioxidant activity in ovaries. Exhaustive exercises can cause ovulatory problems in female rats that can be improved by ω-3 supplementation.

Linking Stress and Infertility: A Novel Role for Ghrelin

Infertility affects a remarkable one in four couples in developing countries. Psychological stress is a ubiquitous facet of life, and although stress affects us all at some point, prolonged or unmanageable stress may become harmful for some individuals, negatively impacting on their health, including fertility. For instance, women who struggle to conceive are twice as likely to suffer from emotional distress than fertile women. Assisted reproductive technology treatments place an additional physical, emotional, and financial burden of stress, particularly on women, who are often exposed to invasive techniques associated with treatment. Stress-reduction interventions can reduce negative affect and in some cases to improve in vitro fertilization outcomes. Although it has been well-established that stress negatively affects fertility in animal models, human research remains inconsistent due to individual differences and methodological flaws. Attempts to isolate single causal links between stress and infertility have not yet been successful due to their multifaceted etiologies. In this review, we will discuss the current literature in the field of stress-induced reproductive dysfunction based on animal and human models, and introduce a recently unexplored link between stress and infertility, the gut-derived hormone, ghrelin. We also present evidence from recent seminal studies demonstrating that ghrelin has a principal role in the stress response and reward processing, as well as in regulating reproductive function, and that these roles are tightly interlinked. Collectively, these data support the hypothesis that stress may negatively impact upon fertility at least in part by stimulating a dysregulation in ghrelin signaling.

Exposure to Acute Psychosocial Stress Disrupts the Luteinizing Hormone Surge Independent of Estrous Cycle Alterations in Female Mice

The disruptive effects of severe stress on reproductive function are well documented, but surprisingly few studies exist that demonstrate milder psychosocial stressors interfere with the ovarian cycle in females. We hypothesized repeated application of psychosocial stress would disrupt estrous cycles in mice. Mice were transferred to a new cage, transported to a new room, and restrained (2 hours) for 21 consecutive days. Contrary to our hypothesis, this paradigm did not affect estrous cycles. We next tested the hypothesis that a single exposure to mild stress disrupts a specific aspect of the cycle: the proestrous luteinizing hormone (LH) surge. We developed a model of acute, layered psychosocial stress (sequential application of new cage, transport to new room, restraint and predator cues lasting 5 hours total) that consistently increased circulating corticosterone. Application of this stress paradigm on midmorning of proestrus disrupted the LH surge measured near lights out in 14 of 24 mice; there was no evidence for a 24-hour delay of the surge. Following stress, mice continued to have normal estrous cycles, even when the LH surge was disrupted. Stressed mice failing to exhibit an LH surge had uterine masses suggesting the proestrous estradiol rise occurred. To test specifically whether the layered stress paradigm blocks estradiol-dependent positive feedback mechanisms, we examined the estradiol-induced LH surge. Stress blocked the estradiol-induced LH surge in all mice. These results suggest exposure to mild, acute psychosocial stress on proestrus can severely disrupt the generation of the LH surge in mice without affecting the overall estrous cycle.

A novel non genomic glucocorticoid signaling mediated by a membrane palmitoylated glucocorticoid receptor cross talks with GnRH in gonadotrope cells

Glucocorticoid hormones (GC) are the main stress mediators associated with reproductive disorders. GC exert their effects through activation of the glucocorticoid receptor (GR) principally acting as a transcription factor. Beside well-established GR-mediated genomic actions, several lines of evidence suggest a role for rapid membrane-initiated GC signaling in gonadotrope cells triggered by a membrane-associated GR. Herein, we demonstrate the existence of a specific membrane-initiated GC signaling in LβT2 gonadotrope cells involving two related phosphoproteins: Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII) and synapsin-I. Within 5 min, LβT2 cells treated with stress range of 10⁻⁷ M Corticosterone or a membrane impermeable-GC, BSA-conjugated corticosterone, exhibited a 2-fold increase in levels of phospho-CaMKII and phospho-synapsin-I. Biochemical approaches revealed that this rapid signaling is promoted by a palmitoylated GR. Importantly, GC significantly alter GnRH-induced CaMKII phosphorylation, consistent with a novel cross-talk between the GnRH receptor and GC. This negative effect of GC on GnRH signaling was further observed on LH release by mouse pituitary explants. Altogether, our work provides new findings in GC field by bringing novel understanding on how GR integrates plasma membrane, allowing GC membrane-initiated signaling that differs in presence of GnRH to disrupt GnRH-dependent signaling and LH secretion.

Estradiol and corticosterone stimulate the proliferation of a GH cell line, MtT/S: Proliferation of growth hormone cells

OBJECTIVES

Estrogens are known as a potent growth-stimulator of the anterior pituitary cells such as prolactin cells and somatomammotroph cell lines, while glucocorticoids often inhibit cellular proliferation in the pituitary gland as well as in the extra-pituitary tissues. In this study, the involvement of these steroid hormones in the regulation of proliferation was examined in the MtT/S cells, secreting growth hormone (GH).

DESIGN

Effects of estrogens and glucocorticoids were examined in MtT/S cells grown in the medium containing dextran-coated charcoal treated serum. The relative cell density after culture was estimated by the Cell Titer-Glo Luminescent Cell Viability Assay System, and the proliferation rate was determined by the BrdU incorporation method. The mRNA levels were determined by real-time PCR.

RESULTS

Estradiol and the specific agonist for both estrogen receptor (ER) α and ERβ stimulated MtT/S growth at a dose dependent manner. The membrane impermeable estrogen, 17β-estradiol-bovine serum albumin conjugate also stimulated the MtT/S proliferation. The effects of all estrogens were inhibited by an estrogen receptor antagonist, ICI182780. Corticosterone stimulated the proliferation of MtT/S cells at doses lower than 10nM without stimulating GH gene transcription, whereas it did not change the proliferation rate at 1μM. The effects of corticosterone were inhibited by glucocorticoid receptor inhibitor, RU486, but not by the mineralocorticoid receptor antagonist, spironolactone. Both estrogens and glucocorticoids were found to stimulate the proliferation of MtT/S, increasing the mRNA expression of cyclins D1, D3, and E.

CONCLUSIONS

The results suggest that estrogens and glucocorticoids may be involved in the mechanisms responsible for the proliferation of GH cells in the course of pituitary development, to maintain the population of GH cells in the adult pituitary gland, and also in the promotion of GH cell tumors.

Multiple Endocrine Disruption by the MET/ALK Inhibitor Crizotinib in Patients With Non-small Cell Lung Cancer

OBJECTIVES

Non-small cell lung cancer (NSCLC) is a heterogenous group of disorders that can be subclassified based upon molecular characterization. Anaplastic lymphoma kinase translocation and MET aberrations occur in a subset of NSCLC. Anaplastic lymphoma kinase/MET have been shown to be inhibited by the small molecule tyrosine kinase inhibitor crizotinib. Recently, crizotinib was shown to decrease testosterone in males. Herein, we describe the effects of crizotinib on multiple hormonal axes.

MATERIALS AND METHODS

Seven consecutive patients with NSCLC who were receiving crizotinib as part of their standard care were evaluated for hormonal disruptions.

RESULTS

Primary hypogonadism was detected in 4/5 of males, whereas mildly elevated prolactin was observed in 4/7 patients. Hypocalcemia was observed in 3/7 patients. Interestingly, 5/7 patients had elevated levels of insulin-like growth factor-1 (IGF-1) levels, and the remaining 2 individuals had levels that were near the upper limits of the normal range.

CONCLUSIONS

Because of cellular cross-talk between MET and IGF-1 signaling, elevated IGF-1 levels induced by crizotinib treatment may have implications for long-term drug efficacy. Furthermore, this finding suggests a potential avenue of therapeutic synergy, namely coordinate inhibition of the MET and IGF-1 signaling pathways. Finally, as crizotinib has been recently approved, it is prudent to check hormone and calcium biomarkers and correct noted deficiencies for improved outcomes and quality of life.

Corticosterone Blocks Ovarian Cyclicity and the LH Surge via Decreased Kisspeptin Neuron Activation in Female Mice

Stress elicits activation of the hypothalamic-pituitary-adrenal axis, which leads to enhanced circulating glucocorticoids, as well as impaired gonadotropin secretion and ovarian cyclicity. Here, we tested the hypothesis that elevated, stress-levels of glucocorticoids disrupt ovarian cyclicity by interfering with the preovulatory sequence of endocrine events necessary for the LH surge. Ovarian cyclicity was monitored in female mice implanted with a cholesterol or corticosterone (Cort) pellet. Cort, but not cholesterol, arrested cyclicity in diestrus. Subsequent studies focused on the mechanism whereby Cort stalled the preovulatory sequence by assessing responsiveness to the positive feedback estradiol signal. Ovariectomized mice were treated with an LH surge-inducing estradiol implant, as well as Cort or cholesterol, and assessed several days later for LH levels on the evening of the anticipated surge. All cholesterol females showed a clear LH surge. At the time of the anticipated surge, LH levels were undetectable in Cort-treated females. In situ hybridization analyses the anteroventral periventricular nucleus revealed that Cort robustly suppressed the percentage of Kiss1 cells coexpressing cfos, as well as reduced the number of Kiss1 cells and amount of Kiss1 mRNA per cell, compared with expression in control brains. In addition, Cort blunted pituitary expression of the genes encoding the GnRH receptor and LHβ, indicating inhibition of gonadotropes during the blockage of the LH surge. Collectively, our findings support the hypothesis that physiological stress-levels of Cort disrupts ovarian cyclicity, in part, through disruption of positive feedback mechanisms at both the hypothalamic and pituitary levels which are necessary for generation of the preovulatory LH surge.

Omega-3 Fatty Acid Supplementation Lowers Serum FSH in Normal Weight But Not Obese Women

CONTEXT

Dietary omega-3 fatty acids delay ovarian aging and promote oocyte quality in mice.

OBJECTIVE

To test whether dietary supplementation with omega-3 polyunsaturated fatty acids (PUFA) modulates reproductive hormones in reproductive-age women.

DESIGN

Prospective interventional study.

SETTING

Academic center.

PARTICIPANTS

Fifteen obese and 12 normal-weight (NW) eumenorrheic women, ages 28-34 years.

INTERVENTION

Two frequent blood-sampling studies were performed before and after 1 month of omega-3 PUFA supplementation with 4 g of eicosapentaenoic acid and docosahexaenoic acid daily.

MAIN OUTCOME MEASURES

Serum LH and FSH (basal and after GnRH stimulation).

RESULTS

The ratio of omega-6 to omega-3 PUFA was significantly reduced in plasma and red blood cell components for both groups after treatment (both P < .01). Omega-3 PUFA supplementation resulted in reduction of FSH and FSH response to GnRH by 17% on average (P = .06 and P = .03, respectively) in NW but not obese women. Serum levels of IL-1β and TNF-α were reduced after omega-3 PUFA supplementation (-72% for IL-1β; -56% for TNF-α; both, P < .05) in obese but not in NW women. This reduction, however, was not associated with a hormonal change in obese women.

CONCLUSIONS

Dietary administration with omega-3 PUFA decreased serum FSH levels in NW but not in obese women with normal ovarian reserve. This effect is intriguing and is directionally consistent with murine data whereby higher dietary omega-3 PUFA extends reproductive lifespan. Our results imply that this nutritional intervention should be tested in women with diminished ovarian reserve in an attempt to delay ovarian aging.

Physical activity: benefit or weakness in metabolic adaptations in a mouse model of chronic food restriction?

In restrictive-type anorexia nervosa (AN) patients, physical activity is usually associated with food restriction, but its physiological consequences remain poorly characterized. In female mice, we evaluated the impact of voluntary physical activity with/without chronic food restriction on metabolic and endocrine parameters that might contribute to AN. In this protocol, FRW mice (i.e., food restriction with running wheel) reached a crucial point of body weight loss (especially fat mass) faster than FR mice (i.e., food restriction only). However, in contrast to FR mice, their body weight stabilized, demonstrating a protective effect of a moderate, regular physical activity. Exercise delayed meal initiation and duration. FRW mice displayed food anticipatory activity compared with FR mice, which was strongly diminished with the prolongation of the protocol. The long-term nature of the protocol enabled assessment of bone parameters similar to those observed in AN patients. Both restricted groups adapted their energy metabolism differentially in the short and long term, with less fat oxidation in FRW mice and a preferential use of glucose to compensate for the chronic energy imbalance. Finally, like restrictive AN patients, FRW mice exhibited low leptin levels, high plasma concentrations of corticosterone and ghrelin, and a disruption of the estrous cycle. In conclusion, our model suggests that physical activity has beneficial effects on the adaptation to the severe condition of food restriction despite the absence of any protective effect on lean and bone mass.

Soluble epoxide hydrolase gene deletion improves blood flow and reduces infarct size after cerebral ischemia in reproductively senescent female mice

Soluble epoxide hydrolase (sEH), a key enzyme in the metabolism of vasodilatory epoxyeicosatrienoic acids (EETs), is sexually dimorphic, suppressed by estrogen, and contributes to underlying sex differences in cerebral blood flow and injury after cerebral ischemia. We tested the hypothesis that sEH inhibition or gene deletion in reproductively senescent (RS) female mice would increase cerebral perfusion and decrease infarct size following stroke. RS (15–18 month old) and young (3–4 month old) female sEH knockout (sEHKO) mice and wild type (WT) mice were subjected to 45 min middle cerebral artery occlusion (MCAO) with laser Doppler perfusion monitoring. WT mice were treated with vehicle or a sEH inhibitor t-AUCB at the time of reperfusion and every 24 h thereafter for 3 days. Differences in regional cerebral blood flow were measured in vivo using optical microangiography (OMAG). Infarct size was measured 3 days after reperfusion. Infarct size and cerebral perfusion 24 h after MCAO were not altered by age. Both sEH gene deletion and sEH inhibition increased cortical perfusion 24 h after MCAO. Neither sEH gene deletion nor sEH inhibition reduced infarct size in young mice. However, sEH gene deletion, but not sEH inhibition of the hydrolase domain of the enzyme, decreased infarct size in RS mice. Results of these studies show that sEH gene deletion and sEH inhibition enhance cortical perfusion following MCAO and sEH gene deletion reduces damage after ischemia in RS female mice; however this neuroprotection in absent is young mice.

Glucocorticoid Regulation of Reproduction

It is well accepted that stress, measured by increased glucocorticoid secretion, leads to profound reproductive dysfunction. In times of stress, glucocorticoids activate many parts of the fight or flight response, mobilizing energy and enhancing survival, while inhibiting metabolic processes that are not necessary for survival in the moment. This includes reproduction, an energetically costly procedure that is very finely regulated. In the short term, this is meant to be beneficial, so that the organism does not waste precious energy needed for survival. However, long-term inhibition can lead to persistent reproductive dysfunction, even if no longer stressed. This response is mediated by the increased levels of circulating glucocorticoids, which orchestrate complex inhibition of the entire reproductive axis. Stress and glucocorticoids exhibits both central and peripheral inhibition of the reproductive hormonal axis. While this has long been recognized as an issue, understanding the complex signaling mechanism behind this inhibition remains somewhat of a mystery. What makes this especially difficult is attempting to differentiate the many parts of both of these hormonal axes, and new neuropeptide discoveries in the last decade in the reproductive field have added even more complexity to an already complicated system. Glucocorticoids (GCs) and other hormones within the hypothalamic-pituitary-adrenal (HPA) axis (as well as contributors in the sympathetic system) can modulate the hypothalamic-pituitary-gonadal (HPG) axis at all levels-GCs can inhibit release of GnRH from the hypothalamus, inhibit gonadotropin synthesis and release in the pituitary, and inhibit testosterone synthesis and release from the gonads, while also influencing gametogenesis and sexual behavior. This chapter is not an exhaustive review of all the known literature, however is aimed at giving a brief look at both the central and peripheral effects of glucocorticoids on the reproductive function.

Cellular distribution of Egr1 transcription in the male rat pituitary gland

The transcription factor gene Egr1 is necessary for female fertility; EGR1 protein is an established molecular regulator of adult female gonadotroph function where it mediates GNRH-stimulated transcription of the Lhb gene. Recent studies have also implicated pituitary EGR1 in the mediation of other physiological signals indicating an integrative function. However, the role of EGR1 in males is less well defined and this uncertainty is compounded by the absence of cellular expression data in the male pituitary gland. The aim of this study, therefore, was to define the distribution of Egr1 gene expression in the adult male rat pituitary. To further this aim, we have evaluated cellular populations in a transgenic rat model (Egr1-d2EGFP), in which we demonstrate regulated green fluorescent protein (GFP) expression in EGR1+ pituitary cells. Cellular filling by GFP enabled morphological and molecular differentiation of different populations of gonadotrophs; Egr1 transcription and LHB were highly co-localised in a major population of large cells but only minimally co-localised in small GFP+ cells; the latter cells were shown to be largely (80%) composed of minority populations of GH+ somatotrophs (9% of total GH+) and PRL+ lactotrophs (3% of total PRL+). Egr1 transcription was not found in TSH+, ACTH+ or SOX2+ precursor cells and was only minimally co-localised in S-100β+ folliculostellate cells. Our demonstration that the Egr1 gene is actively and selectively transcribed in a major sub-population of male LHB+ cells indicates a largely conserved role in gonadotroph function and has provided a basis for further defining this role.

Influence of stress-induced intermediates on gonadotropin gene expression in gonadotrope cells

Despite extensive investigation, a comprehensive understanding of the mechanisms whereby stress impacts fertility remains elusive. Since the 1930s, when Hans Selye popularized studying adaptations to stress (Selye, 1937), we have learned that compensatory mechanisms involve a complex interplay of neural and hormonal processes that allow various body functions to adjust to stress, in a coordinated manner. In terms of reproduction, the adjustment to a stressor interferes with integrated functioning at multiple levels of regulation--the hypothalamus, anterior pituitary gland, gonads, and neural centers coordinating behavior. Various mediators are postulated to participate in reproductive suppression. These include catecholamines, cytokines, prostaglandins, endogenous opioid peptides, and hormones of the hypothalamic-pituitary-adrenal axis. This review focuses on one class of mediators, the glucocorticoids, and provides our views on the relevance and mode of action of this inhibitory intermediate within the anterior pituitary gonadotrope, as a potential cellular site whereby glucocorticoids contribute to stress-induced reproductive suppression.