The role of the brain in female reproductive aging

Hormones and Aging: An Endocrine Society Scientific Statement

Multiple changes occur across various endocrine systems as an individual ages. The understanding of the factors that cause age-related changes and how they should be managed clinically is evolving. This statement reviews the current state of research in the growth hormone, adrenal, ovarian, testicular, and thyroid axes, as well as in osteoporosis, vitamin D deficiency, type 2 diabetes, and water metabolism, with a specific focus on older individuals. Each section describes the natural history and observational data in older individuals, available therapies, clinical trial data on efficacy and safety in older individuals, key points, and scientific gaps. The goal of this statement is to inform future research that refines prevention and treatment strategies in age-associated endocrine conditions, with the goal of improving the health of older individuals.

Preparation of pumpkin oil-based nanoemulsion as a potential estrogen replacement therapy to alleviate neural-immune interactions in an experimental postmenopausal model

As estrogen production decreases during menopause; the brain's metabolism tends to stall and become less effective. Estrogen most likely protects against neurodegeneration. Consequently, a comprehensive study of the benefits of hormone replacement therapy as a neuroprotective effect is urgently required. This study was designed to fabricate pumpkin seed oil nanoparticles (PSO) in nanoemulsion form (PSO-NE) and investigate their potential role in attenuating the neural-immune interactions in an experimental postmenopausal model.Sixty female white albino rats were divided into six groups: control, sham, ovariectomized (OVX), and three OVX groups treated with 17β-estradiol, PSO, and PSO-NE respectively. Transmission Electron Microscopy (TEM), and particle size analyzer were performed for nanoemulsion evaluation. Serum levels of estrogen, brain amyloid precursor protein (APP), serum levels of nuclear factor kappa B (NF-κβ), interleukin 6 (IL-6), transthyretin (TTR), and synaptophysin (SYP) were evaluated. The expression of estrogen receptors (ER-α, β) in the brain tissue was estimated. The findings revealed that the approached PSO-NE system was able to reduce the interfacial tension, enhance the dispersion entropy, lower the system free energy to an extremely small value, and augment the interfacial area. PSO-NE, showed a significant increase in the levels of estrogen, brain APP, SYP, and TTR accompanied with a significant increased in the expression of brain ER-α, β compared to the OVX group. In conclusion, the phytoestrogen content of PSO exhibited a significant prophylactic effect on neuro-inflammatory interactions, ameliorating both estrogen levels and the inflammatory cascades.

Development of adverse outcome pathways relevant for the identification of substances having endocrine disruption properties Uterine adenocarcinoma as adverse outcome

Development of adverse outcome pathways (AOPs) for uterine adenocarcinoma can provide a practical tool to implement the EFSA-ECHA Guidance (2018) for the identification of endocrine disruptors in the context of Regulations (EU) No 528/2012 and (EC) No 1107/2009. AOPs can give indications about the strength of the relationship between an adverse outcome (intended as a human health outcome) and chemicals (pesticides but not only) affecting the pathways. In this scientific opinion, the PPR Panel explored the development of AOPs for uterine adenocarcinoma. An evidence-based approach methodology was applied, and literature reviews were produced using a structured framework assuring transparency, objectivity, and comprehensiveness. Several AOPs were developed; these converged to a common critical node, that is increased estradiol availability in the uterus followed by estrogen receptor activation in the endometrium; therefore, a putative AOP network was considered. An uncertainty analysis and a probabilistic quantification of the weight of evidence have been carried out via expert knowledge elicitation for each set of MIEs/KEs/KERs included in individual AOPs. The collected data on the AOP network were evaluated qualitatively, whereas a quantitative uncertainty analysis for weight of the AOP network certainty has not been performed. Recommendations are provided, including exploring further the uncertainties identified in the AOPs and putative AOP network; further methodological developments for quantifying the certainty of the KERs and of the overall AOPs and AOP network; and investigating of NAMs applications in the context of some of the MIEs/KEs currently part of the putative AOP network developed.

The landscape of aging

Aging is characterized by a progressive deterioration of physiological integrity, leading to impaired functional ability and ultimately increased susceptibility to death. It is a major risk factor for chronic human diseases, including cardiovascular disease, diabetes, neurological degeneration, and cancer. Therefore, the growing emphasis on “healthy aging” raises a series of important questions in life and social sciences. In recent years, there has been unprecedented progress in aging research, particularly the discovery that the rate of aging is at least partly controlled by evolutionarily conserved genetic pathways and biological processes. In an attempt to bring full-fledged understanding to both the aging process and age-associated diseases, we review the descriptive, conceptual, and interventive aspects of the landscape of aging composed of a number of layers at the cellular, tissue, organ, organ system, and organismal levels.

Positron Emission Tomography reveals age-associated hypothalamic microglial activation in women

In rodents, hypothalamic inflammation plays a critical role in aging and age-related diseases. Hypothalamic inflammation has not previously been assessed in vivo in humans. We used Positron Emission Tomography (PET) with a radiotracer sensitive to the translocator protein (TSPO) expressed by activated microglia, to assess correlations between age and regional brain TSPO in a group of healthy subjects (n = 43, 19 female, aged 23-78), focusing on hypothalamus. We found robust age-correlated TSPO expression in thalamus but not hypothalamus in the combined group of women and men. This pattern differs from what has been described in rodents. Prominent age-correlated TSPO expression in thalamus in humans, but in hypothalamus in rodents, could reflect evolutionary changes in size and function of thalamus versus hypothalamus, and may be relevant to the appropriateness of using rodents to model human aging. When examining TSPO PET results in women and men separately, we found that only women showed age-correlated hypothalamic TSPO expression. We suggest this novel result is relevant to understanding a stark sex difference in human aging: that only women undergo loss of fertility-menopause-at mid-life. Our finding of age-correlated hypothalamic inflammation in women could have implications for understanding and perhaps altering reproductive aging in women.

Age-dependent change of RFRP-3 neuron numbers and innervation in female mice

In female mammals, reproductive senescence is a complex process involving progressive ovarian dysfunction, associated with altered central control of the hypothalamic-pituitary-gonadal axis and desynchronization of the circadian system. The objective of this study was to investigate age-dependent changes in the daily regulation of Arg-Phe amide-related peptide-3 (RFRP-3), a hypothalamic peptide involved in reproduction, in female C57BL/6 J mice of different age groups (4, 13, and 19 months old) sampled at their diestrus stage. We found an age-dependent decrease in the total number of RFRP-3 neurons and in the relative number of activated (i.e. c-Fos-positive) RFRP-3 neurons. RFRP-3 neuronal activation exhibited a daily variation in young and middle-aged mice, which was abolished in 19-month-old mice. We also found a daily variation in the number of RFRP-3 neurons receiving close vasopressin (AVP)- and vasoactive intestinal peptide (VIP)-ergic fiber appositions in mice aged 4 and 13 months, but not in 19-month-old mice. However, we found no daily or age-dependent changes in the AVP and VIP fiber density in the dorsomedial hypothalamus. Plasma LH levels were similar in mice aged 4 and 13 months, but were markedly increased in 19-month-old mice. The present findings indicate that the number of RFRP-3 positive neurons is downregulated during old age and that the daily changes in their innervation by the circadian peptides AVP and VIP are abolished. This age-associated reduced (rhythmic) activity of the inhibitory RFRP-3 system could be implicated in the elevated LH secretion observed during reproductive senescence.

Neuroendocrine Changes during Menopausal Transition

Menopause is the permanent cessation of menstrual cycles following the loss of ovarian follicular activity. Quality of life of postmenopausal woman is the result of a series of psychobiological transformations, that see in the reduction of sex hormones and steroids the etiopathogenetic determinant moment. Symptoms of menopause range from somatic side such as metabolic changes, increased cardiovascular disease, irregular vaginal bleeding, urogenital symptoms, vaginal dryness, osteoporosis and risk of bones fractures to changes of central nervous system as vasomotor symptoms, sleep disruption, mood changes, migraine, sexual dysfunctions. It is fundamental to know the mechanisms underlying changes in the central nervous system during menopause, related to hypoestrogenism, to be able to create appropriate target therapy for patients, improving their quality of life. In fact, the central nervous system is now one of the major targets of sex steroids that cannot be achieved disregard when dealing with the problem of choice of a particular type of MHT.

Effects of estradiol supplementation on the brain transcriptome of old rhesus macaques maintained on an obesogenic diet

Obesity, the cessation of ovarian steroids with menopause, and age are risk factors for mood disorders, dementia, and Alzheimer's disease (AD). However, immediate hormone therapy (HT) after menopause may have beneficial effects in different brain regions involved in memory and cognition. To more closely replicate the age, endocrine, and metabolic environment of obese postmenopausal women, either on or off HT, middle-aged female rhesus macaques were ovariectomized/hysterectomized (OvH) and maintained on a high-fat, high-sugar, obesogenic Western-style diet (WSD) for 30 months; half of the animals received HT immediately after OvH and half served as placebo controls. RNAseq of the occipital (OC) and prefrontal cortex (PFC), hippocampus (HIP), and amygdala (AMG) identified 293, 379, 505, and 4993 differentially expressed genes (DEGs), respectively. Pathway enrichment analysis identified an activation of neuroinflammation in OC and HIP, but an inhibition in the AMG with HT. Synaptogenesis, circadian rhythm, mitochondrial dysfunction, mTOR, glutamate, serotonin, GABA, dopamine, epinephrine/norepinephrine, glucocorticoid receptor signaling, neuronal NOS, and amyloid processing were exclusively enriched in AMG. As compared to the placebo control group, most of these signaling pathways are downregulated after HT, suggesting a protective effect of HT in OvH females under a WSD. Overall, our results suggest that a chronic obesogenic diet may induce a wide range of alterations in multiple signaling pathways that are linked to age-associated brain pathology and dementia. In these individuals, HT seems to have a protective effect against neuroinflammation, amyloid beta depositions, and tau tangle formation.

Menopause, hormone therapy and cognition: maximizing translation from preclinical research

Menopause-associated and hormone-associated cognitive research has a rich history built from varied disciplines and species. This review discusses landmark rodent and human work addressing cognitive outcomes associated with varied experiences of menopause and hormone therapy. Critical variables in menopause and cognitive aging research are considered, including menopause etiology, background hormone milieu and parameters of exposure to estrogens and progestogens. Recent preclinical research has identified that menopause and ovarian hormone fluctuations across many neurobiological systems affect cognitive aging, mapping novel avenues for future research. Preclinical models provide insight into complex interdisciplinary relationships in a systematic and highly controlled fashion. We highlight that acknowledging the strengths and weaknesses for both preclinical and clinical research approaches is vital to accurate interpretation, optimal translation and the direction of future research. There is great value in collaboration and communication across preclinical and clinical realms, especially regarding reciprocal feedback of findings to advance preclinical models, improve experimental designs and enrich basic science translation to the clinic. In searching for biological mechanisms underlying the cognitive consequences of menopause and hormone therapies, it is noteworthy that clinical and preclinical scientists are grounded in the same fundamental goal of optimizing health outcomes for women across the lifespan.

Hypericum perforatum L. Regulates Glutathione Redox Stress and Normalizes Ggt1/Anpep Signaling to Alleviate OVX-Induced Kidney Dysfunction

Menopause and associated renal complications are linked to systemic redox stress, and the causal factors remain unclear. As the role of Hypericum perforatum L. (HPL) in menopause-induced kidney disease therapy is still ambiguous, we aim to explore the effects of HPL on systemic redox stress under ovariectomy (OVX)-induced kidney dysfunction conditions. Here, using combined proteomic and metabolomic approaches, we constructed a multi-scaled “HPL-disease-gene-metabolite” network to generate a therapeutic “big picture” that indicated an important link between glutathione redox stress and kidney impairment. HPL exhibited the potential to maintain cellular redox homeostasis by inhibiting gamma-glutamyltransferase 1 (Ggt1) overexpression, along with promoting the efflux of accumulated toxic amino acids and their metabolites. Moreover, HPL restored alanyl-aminopeptidase (Anpep) expression and metabolite shifts, promoting antioxidative metabolite processing, and recovery. These findings provide a comprehensive description of OVX-induced glutathione redox stress at multiple levels and support HPL therapy as an effective modulator in renal tissues to locally influence the glutathione metabolism pathway and subsequent redox homeostasis.

Overaccumulation of Fat Caused Rapid Reproductive Senescence but not Loss of Ovarian Reserve in ob/ob Mice

Ovarian reserve and fertility are reduced by aging and a poor energy balance. To date, the relationships of high energy accumulation and aging with the ovarian reserve have not been elucidated. Here, the effects of obesity on the aging ovarian reserve were evaluated in a leptin-deficient (ob/ob) mouse model. Abnormal estrous cyclicity appeared as early as 6 weeks and worsened with aging. The blood level patterns of 17β-estradiol (E2), testosterone (T), and progesterone (P4) with aging were similar between lean and ob/ob mice. The blood level of E2 but not P4 or T was similar at 24 weeks. Many more atretic follicles but fewer corpora lutea were observed in ob/ob mice than in lean mice within all age groups. Anti-Müllerian hormone (Amh) mRNA levels were similar between genotypes. Dazl, Stra8, and ZP3 mRNAs were highly expressed in ob/ob mice after 12 weeks. Sohlh1 and Ybx2 mRNAs were highly expressed at 24 weeks in ob/ob compared with lean mice. In addition, SOHLH1-positive primordial follicle counts were significantly increased in ob/ob mice at 24 weeks. The proportions of AMH-positive secondary and small antral follicles were similar between genotypes. Together, these results show that the ovarian reserve lasts longer in ob/ob mice than in lean mice, suggesting that the loss of normal physiological or physical status causes decreased fertility at a young age in ob/ob mice and that an increase in adipocytes without leptin, as in ob/ob mice, can improve the ovarian reserve. Such knowledge can be applied to understanding reproductive dysfunction.

Neuroimmunomodulation by estrogen in health and disease

Systemic homeostasis is maintained by the robust bidirectional regulation of the neuroendocrine-immune network by the active involvement of neural, endocrine and immune mediators. Throughout female reproductive life, gonadal hormones undergo cyclic variations and mediate concomitant modulations of the neuroendocrine-immune network. Dysregulation of the neuroendocrine-immune network occurs during aging as a cumulative effect of declining neural, endocrine and immune functions and loss of compensatory mechanisms including antioxidant enzymes, growth factors and co-factors. This leads to disruption of homeostasis and sets the stage for the development of female-specific age-associated diseases such as autoimmunity, osteoporosis, cardiovascular diseases and hormone-dependent cancers. Ovarian hormones especially estrogen, play a key role in the maintenance of health and homeostasis by modulating the nervous, endocrine and immune functions and thereby altering neuroendocrine-immune homeostasis. Immunologically estrogen's role in the modulation of Th1/Th2 immune functions and contributing to pro-inflammatory conditions and autoimmunity has been widely studied. Centrally, hypothalamic and pituitary hormones influence gonadal hormone secretion in murine models during onset of estrous cycles and are implicated in reproductive aging-associated acyclicity. Loss of estrogen affects neuronal plasticity and the ensuing decline in cognitive functions during reproductive aging in females implicates estrogen in the incidence and progression of neurodegenerative diseases. Peripherally, sympathetic noradrenergic (NA) innervations of lymphoid organs and the presence of both adrenergic (AR) and estrogen receptors (ER) on lymphocytes poise estrogen as a potent neuroimmunomodulator during health and disease. Cyclic variations in estrogen levels throughout reproductive life, perimenopausal surge in estrogen levels followed by its precipitous decline, concomitant with decline in central hypothalamic catecholaminergic activity, peripheral sympathetic NA innervation and associated immunosuppression present an interesting study to explore female-specific age-associated diseases in a new light.

Mini-review: Aging of the neuroendocrine system: Insights from nonhuman primate models

The neuroendocrine system (NES) plays a crucial role in synchronizing the physiology and behavior of the whole organism in response to environmental constraints. The NES consists of a hypothalamic-pituitary-target organ axis that acts in coordination to regulate growth, reproduction, stress and basal metabolism. The growth (or somatotropic), hypothalamic-pituitary-gonadal (HPG), hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-thyroid (HPT) axes are therefore finely tuned by the hypothalamus through the successive release of hypothalamic and pituitary hormones to control the downstream physiological functions. These functions rely on a complex set of mechanisms requiring tight synchronization between peripheral organs and the hypothalamic-pituitary complex, whose functionality can be altered during aging. Here, we review the results of research on the effects of aging on the NES of nonhuman primate (NHP) species in wild and captive conditions. A focus on the age-related dysregulation of the master circadian pacemaker, which, in turn, alters the synchronization of the NES with the organism environment, is proposed. Finally, practical and ethical considerations of using NHP models to test the effects of nutrition-based or hormonal treatments to combat the deterioration of the NES are discussed.

Circadian Clock, Time-Restricted Feeding and Reproduction

The goal of this review was to seek a better understanding of the function and differential expression of circadian clock genes during the reproductive process. Through a discussion of how the circadian clock is involved in these steps, the identification of new clinical targets for sleep disorder-related diseases, such as reproductive failure, will be elucidated. Here, we focus on recent research findings regarding circadian clock regulation within the reproductive system, shedding new light on circadian rhythm-related problems in women. Discussions on the roles that circadian clock plays in these reproductive processes will help identify new clinical targets for such sleep disorder-related diseases.

Individual evaluation of luteinizing hormone in aged C57BL/6 J female mice

In female mammals, reproductive senescence is a complex process involving progressive ovarian dysfunction associated with an altered central control of the hypothalamic-pituitary axis. The objective of this study was to compare the longitudinal change in preovulatory luteinizing hormone (LH) secretion as well as estrous cycle in individual C57BL/6 J female mice at 3, 6, 9 and 12 months. Amplitude and timing of LH secretion at the surge were similar from 3 to 9 months but were altered in 12-month old mice with a significant decrease of more than 50% of peak LH value and a 2 h delay in the occurrence of the LH surge as compared to younger mice. The analysis of two to three successive LH surges at 3, 6, 9 and 12 months showed low and similar intra-individual variability at all ages. The estrous cycle length and intra/inter variability were stable over the age. This study shows that female mice in regular environmental conditions display stable LH surge timing and amplitude up to 9 months, but at 12 months, the LH surge is delayed with a reduced amplitude, however without overt modification in the estrous cycles. Analysis of individual preovulatory LH secretion and estrous cycle indicates that mice can be followed up to 9 months to investigate the detrimental effects of various parameters on mouse reproductive activity.

Accelerated Ovarian Failure as a Unique Model to Study Peri-Menopause Influence on Alzheimer's Disease

Despite decades of extensive research efforts, efficacious therapies for Alzheimer's disease (AD) are lacking. The multi-factorial nature of AD neuropathology and symptomatology has taught us that a single therapeutic approach will most likely not fit all. Women constitute ~70% of the affected AD population, and pathology and rate of symptoms progression are 2-3 times higher in women than men. Epidemiological data suggest that menopausal estrogen loss may be causative of the more severe symptoms observed in AD women, however, results from clinical trials employing estrogen replacement therapy are inconsistent. AD pathological hallmarks-amyloid β (Aβ), neurofibrillary tangles (NFTs), and chronic gliosis-are laid down during a 20-year prodromal period before clinical symptoms appear, which coincides with the menopause transition (peri-menopause) in women (~45-54-years-old). Peri-menopause is marked by widely fluctuating estrogen levels resulting in periods of irregular hormone-receptor interactions. Recent studies showed that peri-menopausal women have increased indicators of AD phenotype (brain Aβ deposition and hypometabolism), and peri-menopausal women who used hormone replacement therapy (HRT) had a reduced AD risk. This suggests that neuroendocrine changes during peri-menopause may be a trigger that increases risk of AD in women. Studies on sex differences have been performed in several AD rodent models over the years. However, it has been challenging to study the menopause influence on AD due to lack of optimal models that mimic the human process. Recently, the rodent model of accelerated ovarian failure (AOF) was developed, which uniquely recapitulates human menopause, including a transitional peri-AOF period with irregular estrogen fluctuations and a post-AOF stage with low estrogen levels. This model has proven useful in hypertension and cognition studies with wild type animals. This review article will highlight the molecular mechanisms by which peri-menopause may influence the female brain vulnerability to AD and AD risk factors, such as hypertension and apolipoprotein E (APOE) genotype. Studies on these biological mechanisms together with the use of the AOF model have the potential to shed light on key molecular pathways underlying AD pathogenesis for the development of precision medicine approaches that take sex and hormonal status into account.

Alterations of estradiol-induced histone H3 acetylation in the preoptic area and anteroventral periventricular nucleus of middle-aged female rats

In this study we investigated the characteristics of histone H3 acetylation in the anterior hypothalamus under E2 positive feedback to gain a better understanding of the mechanism underlying reduced GnRH neuron activation and altered gene expression in female reproductive aging. Young and middle-aged female rats were ovariectomized (OVX) and treated with estradiol (E2) or oil. C-Fos expression, the number of GnRH neurons co-localized with c-Fos in the preoptic area (POA), and the number of acetylated histone H3 cells in the POA and anteroventral periventricular nucleus (AVPV) were quantified at the time of the expected GnRH neuron activation. We used real-time PCR to evaluate the expression of Esr1 target genes including Kiss1 and VGluT2 and genes known as Esr1 coregulators in the anterior hypothalamus. Our results show that in the young females, E2 markedly increased histone H3 acetylation in the POA and AVPV, coincident with increased c-Fos and GnRH neuron activation in the POA. In middle-aged females, E2-induced histone H3 acetylation was reduced in the POA but was not significantly altered in the AVPV. This occurred in association with a reduction of c-Fos expression and the number of GnRH cells expressing c-Fos in the POA as well as a down-regulation of Kiss1 and VGluT2 mRNA expression in the anterior hypothalamus of the animals. E2 caused significant decreases in Ncoa2 and Crebbp mRNA expression in the anterior hypothalamus of young, but not middle-aged females. Taken together, these data suggest that alterations of histone H3 acetylation in the POA and AVPV and the inability of Ncoa2 and Crebbp to respond to E2 in the middle-aged anterior hypothalamus partially contribute to the decline of GnRH neuron activation and E2 target gene expression changes that occur in female along with reproductive aging.

Grey matter differences associated with age and sex hormone levels between premenopausal and perimenopausal women: A voxel-based morphometry study

The present study aimed to explore brain morphological alterations associated with age and sex hormone levels between premenopausal and perimenopausal women using magnetic resonance imaging (MRI) T₁ -weighted structural images. Thirty-two premenopausal women aged (mean ± SD) 47.75 ± 1.55 years and twenty-five recently perimenopausal women aged 51.60 ± 1.63 years were evaluated for sex hormone levels, including prolactin, follicle-stimulating hormone, luteinising hormone, oestradiol, free testosterone and progesterone. A 3.0-Tesla MRI scanner was utilised to acquire T₁ images. Voxel-based morphometry (VBM) was used to evaluate changes in grey matter volume between the two groups. The general linear model was applied with false discovery rate correction for between group voxel-wise statistics. Spearman partial correlation analyses were conducted between age, sex hormone levels and regions of grey matter volume showing significant differences between the two groups. The VBM analysis revealed that age and menopause per se lead to grey matter volume reduction in certain brain structures. These structural changes might be potential causes of sexual dysfunction, nervous system degeneration and depression, which need to be examined in future studies. Our findings might provide evidence and guide future research in understanding the menopausal transition.

Estrogen-induced neuroimmunomodulation as facilitator of and barrier to reproductive aging in brain and lymphoid organs

Reproductive aging in females is marked by alterations in gonadal hormones, estrogen and progesterone, that facilitate cessation of reproductive cycles and onset of female-specific diseases such as autoimmune and neurodegenerative diseases, hormone-dependent cancers, and osteoporosis. Bidirectional communication between the three homeostatic systems, nervous system, endocrine system, and immune system, is essential for the maintenance of health and any dysfunction in the cross-talk promotes the development of diseases and cancer. The pleiotropic effects of estrogen on neural-immune interactions may promote either neuroprotection or inflammatory conditions depending on the site of action, dose and duration of treatment, type of estrogen receptors and its influence on intracellular signaling pathways, etc. Our studies involving treatment of early middle-aged female rats with low and high doses of estrogen and examining the brain areas, thymus, spleen, and lymph nodes revealed that estrogen-induced changes in neural-immune interactions are markedly affected in thymus followed by spleen and lymph nodes while it confers neuroprotection in the brain areas. These alterations are determined by antioxidant enzyme status, growth factors, intracellular signaling pathways involved in cell survival and inflammation, and metabolic enzymes and thus, may regulate the various stages in female reproductive aging. It is imperative that detailed longitudinal studies are carried out to understand the mechanisms of neuroendocrine-immune interactions in reproductive aging to facilitate healthy aging and for the development of better treatment strategies for female-specific diseases.

Inhibiting Production of New Brain Cells during Puberty or Adulthood Blunts the Hormonally Induced Surge of Luteinizing Hormone in Female Rats

New cells are added during both puberty and adulthood to hypothalamic regions that govern reproduction, homeostasis, and social behaviors, yet the functions of these late-born cells remain elusive. Here, we pharmacologically inhibited cell proliferation in ventricular zones during puberty or in adulthood and determined subsequent effects on the hormone-induced surge of luteinizing hormone (LH) in female rats. Initial neuroanatomical analyses focused on verifying incorporation, activation, and pharmacological inhibition of pubertally or adult born cells in the anteroventral periventricular nucleus (AVPV) of the hypothalamus because of the essential role of the AVPV in triggering the preovulatory LH surge in females. We first showed that approximately half of the pubertally born AVPV cells are activated by estradiol plus progesterone (P) treatment, as demonstrated by Fos expression, and that approximately 10% of pubertally born AVPV cells express estrogen receptor alpha (ERα). Next, we found that mitotic inhibition through intracerebroventricular (ICV) administration of cytosine β-D-arabinofuranoside (AraC), whether during puberty or in adulthood, decreased the number of new cells added to the AVPV and the suprachiasmatic nucleus (SCN), and also blunted and delayed the hormone-induced LH surge. These studies do not prove, but are highly suggestive, that ongoing postnatal addition of new cells in periventricular brain regions, including the AVPV and SCN, may be important to the integrity of female reproduction.

Cognitive changes across the menopause transition: A longitudinal evaluation of the impact of age and ovarian status on spatial memory

Cognitive changes that occur during mid-life and beyond are linked to both aging and the menopause transition. Studies in women suggest that the age at menopause onset can impact cognitive status later in life; yet, little is known about memory changes that occur during the transitional period to the postmenopausal state. The 4-vinylcyclohexene diepoxide (VCD) model simulates transitional menopause in rodents by depleting the immature ovarian follicle reserve and allowing animals to retain their follicle-deplete ovarian tissue, resulting in a profile similar to the majority of perimenopausal women. Here, Vehicle or VCD treatment was administered to ovary-intact adult and middle-aged Fischer-344 rats to assess the trajectory of cognitive change across time with normal aging and aging with transitional menopause via VCD-induced follicular depletion, as well as to evaluate whether age at the onset of follicular depletion plays a role in cognitive outcomes. Animals experiencing the onset of menopause at a younger age exhibited impaired spatial memory early in the transition to a follicle-deplete state. Additionally, at the mid- and post- follicular depletion time points, VCD-induced follicular depletion amplified an age effect on memory. Overall, these findings suggest that age at the onset of menopause is a critical parameter to consider when evaluating learning and memory across the transition to reproductive senescence. From a translational perspective, this study illustrates how age at menopause onset might impact cognition in menopausal women, and provides insight into time points to explore for the window of opportunity for hormone therapy during the menopause transition period. Hormone therapy during this critical juncture might be especially efficacious at attenuating age- and menopause- related cognitive decline, producing healthy brain aging profiles in women who retain their ovaries throughout their lifespan.

Reproductive history and breast cancer prevention

The hormonal milieu of an early full-term pregnancy induces lobular development, completing the cycle of differentiation of the breast. This process induces a specific genomic signature in the mammary gland that is represented by the stem cell containing a heterochomatin condensed nucleus (HTN). Even though differentiation significantly reduces cell proliferation in the mammary gland, the mammary epithelium remains capable of responding with proliferation to given stimuli, such as a new pregnancy. The stem cell HTN is able to metabolize the carcinogen and repair the induced DNA damage more efficiently than the stem cell containing an euchromatinic structure (EUN), as it has been demonstrated in the rodent experimental system. The basic biological concept is that pregnancy shifts the stem cell EUN to the stem cell HTN that is refractory to carcinogenesis. Data generated by the use of cDNA micro array techniques have allowed to demonstrate that while lobular development regressed after pregnancy and lactation, programmed cell death genes, DNA repair genes, chromatin remodeling, transcription factors and immune-surveillance gene transcripts all of these genes are upregulated and are part of the genomic signature of pregnancy that is associated with the preventive effect of this physiological process.

Estrogen-induced neuroprotective and anti-inflammatory effects are dependent on the brain areas of middle-aged female rats

BACKGROUND

Reproductive aging in females is characterized by fluctuations and precipitous decline in estrogen levels, which may lead to reduction in cognitive function and age-associated neurodegenerative disorders. The nature of estrogen-mediated neuronal plasticity is unknown during reproductive aging. We hypothesize that estrogen treatment of early middle-aged ovariectomized rats may exert specific effects in the brain by modulating signaling pathways regulating metabolic enzymes, inflammatory markers, antioxidant status, cholinergic function and survival signals.

PURPOSE

To investigate the mechanisms of estrogen-induced effects on neuroprotection and neuroinflammation through the involvement of intracellular signaling pathways in brain areas of ovariectomized (OVX) middle-aged (MA) female rats.

METHODS

Ovariectomized early MA female Sprague-Dawley rats (n=8/group) were implanted with 17β-estradiol (E2) 30-day release pellets (0.6μg and 300μg). At the end of the treatment period, frontal cortex (FC), striatum (STR), medial basal hypothalamus (MBH), and hippocampus (HP) were isolated and examined for the expression of tyrosine hydroxylase (p-TH), nerve growth factor (NGF), p-NF-κB (p50 and p65)and p-ERK, p-CREB, p-Akt, and activities of cholinesterases and antioxidant enzymes, key regulatory enzymes of metabolic pathways, and nitric oxide production.

RESULTS

E2 enhanced p-TH expression in FC and HP, reduced NGF expression in HP, and suppressed p-NF-κB expression in FC and STR. It also increased the expression of molecular markers (p-ERK, p-CREB and p-Akt), and nitric oxide production in various brain areas, while differentially regulating the activities of metabolic enzymes and cholinesterases.

CONCLUSION

Estrogen modulates the neural and inflammatory factors, and intracellular markers depending on the brain areas that may influence differential remodeling of neuronal circuitry which can be used to develop therapeutic strategies in cognitive impairment and neurodegenerative disorders in aging.

Modeling menopause: The utility of rodents in translational behavioral endocrinology research

The human menopause transition and aging are each associated with an increase in a variety of health risk factors including, but not limited to, cardiovascular disease, osteoporosis, cancer, diabetes, stroke, sexual dysfunction, affective disorders, sleep disturbances, and cognitive decline. It is challenging to systematically evaluate the biological underpinnings associated with the menopause transition in the human population. For this reason, rodent models have been invaluable tools for studying the impact of gonadal hormone fluctuations and eventual decline on a variety of body systems. While it is essential to keep in mind that some of the mechanisms associated with aging and the transition into a reproductively senescent state can differ when translating from one species to another, animal models provide researchers with opportunities to gain a fundamental understanding of the key elements underlying reproduction and aging processes, paving the way to explore novel pathways for intervention associated with known health risks. Here, we discuss the utility of several rodent models used in the laboratory for translational menopause research, examining the benefits and drawbacks in helping us to better understand aging and the menopause transition in women. The rodent models discussed are ovary-intact, ovariectomy, and 4-vinylcylohexene diepoxide for the menopause transition. We then describe how these models may be implemented in the laboratory, particularly in the context of cognition. Ultimately, we aim to use these animal models to elucidate novel perspectives and interventions for maintaining a high quality of life in women, and to potentially prevent or postpone the onset of negative health consequences associated with these significant life changes during aging.

The Role of RFamide-Related Peptide-3 in Age-Related Reproductive Decline in Female Rats

Reproductive senescence, the point in time when females cease to show estrous cyclicity, is associated with endocrine changes in the hypothalamus, pituitary, and gonads. However, the mechanisms triggering this transition are not well understood. To gain a better understanding of the top-down control of the transition from reproductive competence to a state of reproductive senescence, we investigated middle-aged female rats exhibiting varying degrees of reproductive decline, including individuals with normal cycles, irregular cycles, and complete cessation of cycles. We identified hormonal changes in the brain that manifest before ovarian cycles exhibit any deterioration. We found that females exhibit an increase in RFamide-related peptide-3 (RFRP3) mRNA expression in the hypothalamus in middle age prior to changes in estrous cycle length. This increase is transient and followed by subsequent decreases in kisspeptin (KiSS1) and gonadotropin-releasing hormone (GnRH) mRNA expression. Expression of RFRP3 and its receptor also increased locally in the ovaries with advancing age. While it is well known that aging is associated with decreased GnRH release and downstream disruption of the hypothalamic-pituitary-gonadal (HPG) axis, herein, we provide evidence that reproductive senescence is likely triggered by alterations in a network of regulatory neuropeptides upstream of the GnRH system.

Physiologic Course of Female Reproductive Function: A Molecular Look into the Prologue of Life

The genetic, endocrine, and metabolic mechanisms underlying female reproduction are numerous and sophisticated, displaying complex functional evolution throughout a woman's lifetime. This vital course may be systematized in three subsequent stages: prenatal development of ovaries and germ cells up until in utero arrest of follicular growth and the ensuing interim suspension of gonadal function; onset of reproductive maturity through puberty, with reinitiation of both gonadal and adrenal activity; and adult functionality of the ovarian cycle which permits ovulation, a key event in female fertility, and dictates concurrent modifications in the endometrium and other ovarian hormone-sensitive tissues. Indeed, the ultimate goal of this physiologic progression is to achieve ovulation and offer an adequate environment for the installation of gestation, the consummation of female fertility. Strict regulation of these processes is important, as disruptions at any point in this evolution may equate a myriad of endocrine-metabolic disturbances for women and adverse consequences on offspring both during pregnancy and postpartum. This review offers a summary of pivotal aspects concerning the physiologic course of female reproductive function.

Trajectories and phenotypes with estrogen exposures across the lifespan: What does Goldilocks have to do with it?

This article is part of a Special Issue "Estradiol and cognition". Estrogens impact the organization and activation of the mammalian brain in both sexes, with sex-specific critical windows. Throughout the female lifespan estrogens activate brain substrates previously organized by estrogens, and estrogens can induce non-transient brain and behavior changes into adulthood. Therefore, from early life through the transition to reproductive senescence and beyond, estrogens are potent modulators of the brain and behavior. Organizational, reorganizational, and activational hormone events likely impact the trajectory of brain profiles during aging. A "brain profile," or quantitative brain measurement for research purposes, is typically a snapshot in time, but in life a brain profile is anything but static--it is in flux, variable, and dynamic. Akin to this, the only thing continuous and consistent about hormone exposures across a female's lifespan is that they are noncontinuous and inconsistent, building and rebuilding on past exposures to create a present brain and behavioral landscape. Thus, hormone variation is especially rich in females, and is likely the destiny for maximal responsiveness in the female brain. The magnitude and direction of estrogenic effects on the brain and its functions depend on a myriad of factors; a "Goldilocks" phenomenon exists for estrogens, whereby if the timing, dose, and regimen for an individual are just right, markedly efficacious effects present. Data indicate that exogenously-administered estrogens can bestow beneficial cognitive effects in some circumstances, especially when initiated in a window of opportunity such as the menopause transition. Could it be that the age-related reduction in efficacy of estrogens reflects the closure of a late-in-life critical window occurring around the menopause transition? Information from classic and contemporary works studying organizational/activational estrogen actions, in combination with acknowledging the tendency for maximal responsiveness to cyclicity, will elucidate ways to extend sensitivity and efficacy into post-menopause.

Using Histopathologic Evidence to Differentiate Reproductive Senescence from Xenobiotic Effects in Middle-aged Female Sprague-Dawley Rats

The female reproductive cycle is orchestrated by cyclical and coordinated hormonal changes under the direction of the hypothalamic–pituitary–gonadal (HPG) axis. Any disruption of the HPG axis may lead to functional and structural alterations in the female reproductive system. Test article–related disturbances in the estrous cycle can be recognized in nonclinical toxicity studies by staging the cycle based on microscopic evaluation of female reproductive organs. In chronic rat toxicity studies, an additional complication is the development of reproductive senescence, which is associated with natural alterations in the reproductive cycle leading to changes in the female reproductive system that can potentially be confused with test article effects. The current article describes the features of persistent estrus, one stage of reproductive senescence, in middle-aged Sprague-Dawley rats and discusses elements to help differentiate senescence from induced effects.

Menopause

Menopause is an inevitable component of ageing and encompasses the loss of ovarian reproductive function, either occurring spontaneously or secondary to other conditions. It is not yet possible to accurately predict the onset of menopause, especially early menopause, to give women improved control of their fertility. The decline in ovarian oestrogen production at menopause can cause physical symptoms that may be debilitating, including hot flushes and night sweats, urogenital atrophy, sexual dysfunction, mood changes, bone loss, and metabolic changes that predispose to cardiovascular disease and diabetes. The individual experience of the menopause transition varies widely. Important influential factors include the age at which menopause occurs, personal health and wellbeing, and each woman's environment and culture. Management options range from lifestyle assessment and intervention through to hormonal and non-hormonal pharmacotherapy, each of which has specific benefits and risks. Decisions about therapy for perimenopausal and postmenopausal women depend on symptomatology, health status, immediate and long-term health risks, personal life expectations, and the availability and cost of therapies. More effective and safe therapies for the management of menopausal symptoms need to be developed, particularly for women who have absolute contraindications to hormone therapy. For an illustrated summary of this Primer, visit: http://go.nature.com/BjvJVX.

The perimenopausal aging transition in the female rat brain: decline in bioenergetic systems and synaptic plasticity

The perimenopause is an aging transition unique to the female that leads to reproductive senescence which can be characterized by multiple neurological symptoms. To better understand potential underlying mechanisms of neurological symptoms of perimenopause, the present study determined genomic, biochemical, brain metabolic, and electrophysiological transformations that occur during this transition using a rat model recapitulating fundamental characteristics of the human perimenopause. Gene expression analyses indicated two distinct aging programs: chronological and endocrine. A critical period emerged during the endocrine transition from regular to irregular cycling characterized by decline in bioenergetic gene expression, confirmed by deficits in fluorodeoxyglucose-positron emission tomography (FDG-PET) brain metabolism, mitochondrial function, and long-term potentiation. Bioinformatic analysis predicted insulin/insulin-like growth factor 1 and adenosine monophosphate-activated protein kinase/peroxisome proliferator-activated receptor gamma coactivator 1 alpha (AMPK/PGC1α) signaling pathways as upstream regulators. Onset of acyclicity was accompanied by a rise in genes required for fatty acid metabolism, inflammation, and mitochondrial function. Subsequent chronological aging resulted in decline of genes required for mitochondrial function and β-amyloid degradation. Emergence of glucose hypometabolism and impaired synaptic function in brain provide plausible mechanisms of neurological symptoms of perimenopause and may be predictive of later-life vulnerability to hypometabolic conditions such as Alzheimer's.

Age-related decline in ovarian follicle stocks differ between chimpanzees (Pan troglodytes) and humans

Similarity in oldest parturitions in humans and great apes suggests that we maintain ancestral rates of ovarian aging. Consistent with that hypothesis, previous counts of primordial follicles in postmortem ovarian sections from chimpanzees (Pan troglodytes) showed follicle stock decline at the same rate that human stocks decline across the same ages. Here, we correct that finding with a chimpanzee sample more than three times larger than the previous one, which also allows comparison into older ages. Analyses show depletion rates similar until about age 35, but after 35, the human counts continue to fall with age, while the change is much less steep in chimpanzees. This difference implicates likely effects on ovarian dynamics from other physiological systems that are senescing at different rates, and, potentially, different perimenopausal experience for chimpanzees and humans.

Maintenance of homeostasis in the aging hypothalamus: the central and peripheral roles of succinate

Aging is the phenotype resulting from accumulation of genetic, cellular, and molecular damages. Many factors have been identified as either the cause or consequence of age-related decline in functions and repair mechanisms. The hypothalamus is the source and a target of many of these factors and hormones responsible for the overall homeostasis in the body. With advanced age, the sensitivity of the hypothalamus to various feedback signals begins to decline. In recent years, several aging-related genes have been identified and their signaling pathways elucidated. These gene products include mTOR, IKK-β/NF-κB complex, and HIF-1α, an important cellular survival signal. All of these activators/modulators of the aging process have also been identified in the hypothalamus and shown to play crucial roles in nutrient sensing, metabolic regulation, energy balance, reproductive function, and stress adaptation. This illustrates the central role of the hypothalamus in aging. Inside the mitochondria, succinate is one of the most prominent intermediates of the Krebs cycle. Succinate oxidation in mitochondria provides the most powerful energy output per unit time. Extra-mitochondrial succinate triggers a host of succinate receptor (SUCN1 or GPR91)-mediated signaling pathways in many peripheral tissues including the hypothalamus. One of the actions of succinate is to stabilize the hypoxia and cellular stress conditions by inducing the transcriptional regulator HIF-1α. Through these actions, it is hypothesized that succinate has the potential to restore the gradual but significant loss in functions associated with cellular senescence and systemic aging.

Disrupted reproduction, estrous cycle, and circadian rhythms in female mice deficient in vasoactive intestinal peptide

The female reproductive cycle is gated by the circadian timing system and may be vulnerable to disruptions in the circadian system. Prior work suggests that vasoactive intestinal peptide (VIP)-expressing neurons in the suprachiasmatic nucleus (SCN) are one pathway by which the circadian clock can influence the estrous cycle, but the impact of the loss of this peptide on reproduction has not been assessed. In the present study, we first examine the impact of the genetic loss of the neuropeptide VIP on the reproductive success of female mice. Significantly, mutant females produce about half the offspring of their wild-type sisters even when mated to the same males. We also find that VIP-deficient females exhibit a disrupted estrous cycle; that is, ovulation occurs less frequently and results in the release of fewer oocytes compared with controls. Circadian rhythms of wheel-running activity are disrupted in the female mutant mice, as is the spontaneous electrical activity of dorsal SCN neurons. On a molecular level, the VIP-deficient SCN tissue exhibits lower amplitude oscillations with altered phase relationships between the SCN and peripheral oscillators as measured by PER2-driven bioluminescence. The simplest explanation of our data is that the loss of VIP results in a weakened SCN oscillator, which reduces the synchronization of the female circadian system. These results clarify one of the mechanisms by which disruption of the circadian system reduces female reproductive success.

Sertoli-Leydig cell tumor with unique nail findings in a post-menopausal woman: a case report and literature review

Background

Sertoli-Leydig cell tumor (SLCT) is a rare sex-cord tumor that usually occurs unilaterally and accounts for < 0.5% of all ovarian tumors. SLCT is uncommon in post-menopausal women, with the average age of diagnosis being 25 years.

Case

We present a case of a 63-year-old post-menopausal woman presenting with progressive hirsutism, and male-pattern baldness. Unusual nail changes were also observed.

Methods

Hormonal profile of the patient revealed increased testosterone and estradiol levels, and a 3.5 cm left ovarian mass. The patient was evaluated and was not found to be anemic or iron-deficient. Intraoperative frozen section assessment during laparoscopic exploration revealed SLCT, which was confirmed subsequently by histopathological and immunohistochemical (IHC) examination. Nail bed tissues were collected from normal females and evaluated by IHC for the presence of androgen receptors (AR).

Results

The patient had an excellent postoperative course and all her testosterone-related manifestations were reversed within one year of surgery. Following surgery, the patient’s unique nail abnormalities also resolved gradually. The IHC evaluation also confirmed the presence of AR in nail bed tissues of females.

Conclusion

SLCT, albeit rare, should be considered in post-menopausal women presenting with virilization and elevated androgen levels. Unusual nail signs may develop in response to increased androgen levels in these patients.

Vasoactive intestinal peptide modulation of the steroid-induced LH surge involves kisspeptin signaling in young but not in middle-aged female rats

Age-related LH surge dysfunction in middle-aged rats is characterized, in part, by reduced responsiveness to estradiol (E2)-positive feedback and reduced hypothalamic kisspeptin neurotransmission. Vasoactive intestinal peptide (VIP) neurons in the suprachiasmatic nucleus project to hypothalamic regions that house kisspeptin neurons. Additionally, middle-age females express less VIP mRNA in the suprachiasmatic nucleus on the day of the LH surge and intracerebroventricular (icv) VIP infusion restores LH surges. We tested the hypothesis that icv infusion of VIP modulates the LH surge through effects on the kisspeptin and RFamide-related peptide-3 (RFRP-3; an estradiol-regulated inhibitor of GnRH neurons) neurotransmitter systems. Brains were collected for in situ hybridization analyses from ovariectomized and ovarian hormone-primed young and middle-aged females infused with VIP or saline. The percentage of GnRH and Kiss1 cells coexpressing cfos and total Kiss1 mRNA were reduced in saline-infused middle-aged compared with young females. In young females, VIP reduced the percentage of GnRH and Kiss1 cells coexpressing cfos, suggesting that increased VIP signaling in young females adversely affected the function of Kiss1 and GnRH neurons. In middle-aged females, VIP increased the percentage of GnRH but not Kiss1 neurons coexpressing cfos, suggesting VIP affects LH release in middle-aged females through kisspeptin-independent effects on GnRH neurons. Neither reproductive age nor VIP affected Rfrp cell number, Rfrp mRNA levels per cell, or coexpression of cfos in Rfrp cells. These data suggest that VIP differentially affects activation of GnRH and kisspeptin neurons of female rats in an age-dependent manner.

G-protein coupled estrogen receptor, estrogen receptor α, and progesterone receptor immunohistochemistry in the hypothalamus of aging female rhesus macaques given long-term estradiol treatment

Steroid hormone receptors are widely and heterogeneously expressed in the brain, and are regulated by age and gonadal hormones. Our goal was to quantify effects of aging, long-term estradiol (E2 ) treatment, and their interactions, on expression of G protein-coupled estrogen receptor (GPER), estrogen receptor α (ERα) and progesterone receptor (PR) immunoreactivity in two hypothalamic regions, the arcuate (ARC) and the periventricular area (PERI) of rhesus monkeys as a model of menopause and hormone replacement. Ovariectomized (OVX) rhesus macaques were young (∼ 11 years) or aged (∼ 25 years), given oil (vehicle) or E2 every 3 weeks for 2 years. Immunohistochemistry and stereologic analysis of ERα, PR, and GPER was performed. More effects were detected for GPER than the other two receptors. Specifically, GPER cell density in the ARC and PERI, and the percent of GPER-immunoreactive cells in the PERI, were greater in aged than in young monkeys. In addition, we mapped the qualitative distribution of GPER in the monkey hypothalamus and nearby regions. For ERα, E2 treated monkeys tended to have higher cell density than vehicle monkeys in the ARC. The percent of PR density in the PERI tended to be higher in E2 than vehicle monkeys of both ages. This study shows that the aged hypothalamus maintains expression of hormone receptors with age, and that long-term cyclic E2 treatment has few effects on their expression, although GPER was affected more than ERα or PR. This result is surprising in light of evidence for E2 regulation of the receptors studied here, and differences may be due to the selected regions, long-term nature of E2 treatment, among other possibilities.

Insulin-like growth factor-I regulates LH release by modulation of kisspeptin and NMDA-mediated neurotransmission in young and middle-aged female rats

This study investigated potential mechanisms by which age and IGF-I receptor (IGF-Ir) signaling in the neuroendocrine hypothalamus affect estradiol-positive feedback effects on GnRH neuronal activation and on kisspeptin and N-methyl-D-aspartate (NMDA)-induced LH release and on the abundance of NMDA receptor subunits Nr1 and Nr2b and Kiss1r transcript and protein in the hypothalamus of young and middle-aged female rats. We infused vehicle, IGF-I, or JB-1, a selective antagonist of IGF-Ir, into the third ventricle of ovariectomized female rats primed with estradiol or vehicle and injected with vehicle, kisspeptin (3 or 30 nmol/kg), or NMDA (15 or 30 mg/kg). Regardless of dose, NMDA and kisspeptin resulted in significantly more LH release, GnRH/c-Fos colabeling, and c-Fos immunoreative cells in young than in middle-aged females. Estradiol priming significantly increased Kiss1r, Nr1, and Nr2b receptor transcript and protein abundance in young but not middle-aged female hypothalamus. JB-1 attenuated kisspeptin and NMDA-induced LH release, numbers of GnRH/c-Fos and c-Fos cells, and Kiss1r, Nr1, and Nr2b transcript and protein abundance in young females to levels observed in middle-aged females. IGF-I significantly enhanced NMDA and kisspeptin-induced LH release in middle-aged females without increasing numbers of GnRH/c-Fos or c-Fos immunoreactive cells. IGF-I infusion in middle-aged females also increased Kiss1r, Nr1, and Nr2b protein and transcript to levels that were equivalent to young estradiol-primed females. These findings indicate that age-related changes in estradiol-regulated responsiveness to excitatory input from glutamate and kisspeptin reflect reduced IGF-Ir signaling.

Neonatal exposure to 17α-ethinyl estradiol affects kisspeptin expression and LH-surge level in female rats

Contamination of estrogenic compounds disrupts endocrinological and neurological reproductive systems in animals. Neonatal exposure to 17α-ethinyl estradiol (EE) induced an abnormal estrous cycle at postnatal day (PND) 180, but not at PND90. We found that serum level of luteinizing hormone (LH) at the latter half of proestrus in EE-treated rats was lower than in the controls at PND90 when there was no significant difference on estrous cyclicity. Additionally, kiss1 mRNA levels in the anteroventral periventricular nucleus-preoptic area (AVPV/POA) were lower in EE-treated rats than in the controls. The expression of GnRH precursor (GNRH1) mRNA in the AVPV/POA and that of LH beta subunit (LHb) mRNA in the pituitary were similar in the control- and EE-treated groups. Our results indicated that neonatal exposure to EE leads to reduced expression of kiss1 mRNA in AVPV/POA and LH-surge, which is likely related to the delayed reproductive dysfunction seen in adult female rats.

Gonadotropin-inhibitory hormone promoter-driven enhanced green fluorescent protein expression decreases during aging in female rats

Gonadotropin-inhibitory hormone (GnIH) neurons project to GnRH neurons to negatively regulate reproductive function. To fully explore the projections of the GnIH neurons, we created transgenic rats carrying an enhanced green fluorescent protein (EGFP) tagged to the GnIH promoter. With these animals, we show that EGFP-GnIH neurons are localized mainly in the dorsomedial hypothalamic nucleus (DMN) and project to the hypothalamus, telencephalon, and diencephalic thalamus, which parallels and confirms immunocytochemical and gene expression studies. We observed an age-related reduction in c-Fos-positive GnIH cell numbers in female rats. Furthermore, GnIH fiber appositions to GnRH neurons in the preoptic area were lessened in middle-aged females (70 weeks old) compared with their younger counterparts (9-12 weeks old). The fiber density in other brain areas was also reduced in middle-aged female rats. The expression of estrogen and progesterone receptors mRNA in subsets of EGFP-GnIH neurons was shown in laser-dissected single EGFP-GnIH neurons. We then examined estradiol-17β and progesterone regulation of GnIH neurons, using c-Fos presence as a marker. Estradiol-17β treatment reduced c-Fos labeling in EGFP-GnIH neurons in the DMN of young ovariectomized adult females but had no effect in middle-aged females. Progesterone had no effect on the number of GnIH cells positive for c-Fos. We conclude that there is an age-related decline in GnIH neuron number and GnIH inputs to GnRH neurons. We also conclude that the response of GnIH neurons to estrogen diminishes with reproductive aging.

(1)H NMR metabolic profiling analysis offers evaluation of Nilestriol treatment in ovariectomised rats

Nilestriol (NIL) has been applied to treat menopausal dysfunctions, yet its mechanism has remained unknown. To understand the relationship between the changes in homeostatic metabolites and ovarian oestrogen deficiency syndromes after NIL treatment, proton Nuclear Magnetic Resonance ((1)H NMR)-based metabonomic technologies were used to analyse a rat model of oestrogen deficiency. An orthogonal partial least-squares regression (OPLS) differentiation model was used on 12-week metabolic analyses of ovariectomised (OVX) rats treated or mock treated with NIL. Furthermore, data analysis using Chenomx software quantified results to identify the most significantly altered metabolite concentrations, allowing for metabolic explanations of the effects of NIL therapies. In this study, PLS results revealed that there are considerably distinct differences between treatment groups. Additionally, a total of 45 metabolites shown to have a high variation between groups were selected for target quantification. Using a one-way LSD ANOVA analysis, 32 metabolite concentrations were significantly altered in the OVX group. A total of 21 metabolites were altered significantly in the NIL-treatment group but later returned to normal. According to the OPLS VIP calculation, the metabolites most affected by NIL treatment were mostly involved in insulin resistance. In addition, abnormal concentration changes in lactate in the NIL-treatment group and 3-indoxylsulfate in the OVX group were observed. To our knowledge, this study is the first to address the molecular mechanism of NIL from a metabonomic perspective, and, more specifically, to establish a catalogue of endo-molecular changes effected by NIL in the regulation of oestrogen deficiency disorder.