Human Menopause Research Articles

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

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

Sexual Dimorphism in the Musculoskeletal System: Sex Hormones and Beyond.

Mounting evidence indicates that whereas some fundamental aspects of bone cell differentiation and function are similar in females and males, there is a clear contribution of sex/gender on the effects of signaling molecules on bone mass and strength and, consequently, on the effects of pharmacologic approaches to treat skeletal disorders. However, until recently, most studies were designed and performed using only 1 sex, resulting in a scarcity of published information on sexual dimorphism of the musculoskeletal system, including the mandible/masticatory muscles and the axial and appendicular bones and skeletal muscles. Further, it is now recognized that scientific rigor requires the study of both males and females. Therefore, there is an increasing need to understand the molecular and cellular basis for the differential outcomes of genetic manipulations and therapeutic agent administration depending on the sex of the experimental animals. Studies have shown higher muscle mass, cancellous bone mass, and long bone width in males compared with females as well as different traits in the pelvis and the skull, which are usually used for gender identification in forensic anthropology. Yet, most reports focus on the role of sex hormones, in particular, the consequences of estrogen deficiency with menopause in humans and in ovariectomized animal models. In addition, emerging data is starting to unveil the effects of gender-affirming hormonal therapy on the musculoskeletal system. We summarize here the current knowledge on the sex/gender-dependent phenotypic characteristics of the bone and skeletal muscles in humans and rodents, highlighting studies in which side by side comparisons were made.

Menopause in adult women with human papillomavirus: health-related quality of life and determinants.

Human papillomavirus (HPV) infection and menopause entail a considerable impairment in health-related quality of life (HRQoL). The objective of the present study was to analyze the impact of the menopause status on HRQoL in women with HPV infection. A cross-sectional, nationwide, multicenter sample of women with HPV infection was conducted throughout clinics of gynecology representative of the Spanish population with regard to age, geographic density, and autonomous regions. Demographic and clinical characteristics and the specific HPV-QoL questionnaire score with its domains were compared according to reproductive status: premenopausal and peri-/postmenopausal. Correlation with other validated patient-reported outcomes measurements was also tested, including General Health Questionnaire-12 (GHQ-12), Female Sexual Function Index (FSFI), and Hospital Anxiety and Depression Scale (HADS). A sample of 1,016 noninstitutionalized women, aged 18-80 y, was recorded, 191 (18.8%) peri-/postmenopausal and 825 (81.2%) premenopausal. Total HPV-QoL scoring was significantly lower in peri-/postmenopausal (38.8, 95% CI [35.2-42.4]) compared to premenopausal (46.4, 95% CI [45.0-47.8]) women, and also in every domain of the scale (P < 0.05), except in social well-being and health domains, with a small effect size of 0.39. In women with sexual dysfunction according to FSFI, adjusted total scoring and domains sexuality, general well-being, and psychological well-being scored significantly higher in premenopause women (P < 0.01), although the magnitude of differences were of small to moderate size. HRQoL was impaired during menopause in women with HPV infection according to HPV-QoL questionnaire. The sexuality domain was the most differentiating dimension between these populations.

Ostruthin, a TWIK-Related Potassium Channel Agonist, Increases the Body Temperature in Ovariectomized Rats With or Without Progesterone Administration.

The TWIK-related potassium (TREK) channel subfamily, including TREK1 and TREK2, is a novel cold receptor. Ostruthin, a TREK1 and TREK2 agonist, is a component found in the plant Paramignya trimera and is traditionally used as an anticancer medicine in Vietnam, with its stems and roots treating various ailments. The female hormone progesterone (P4) influences body temperature in women; however, the effect of P4 on thermoregulation via TREK has not been examined. This study aims to investigate the effects of P4 on thermoregulatory responses in ostruthin-administered ovariectomized rats, which are animal models of human menopause. Wistar rats were ovariectomized and implanted with silastic tubes with or without P4 (P4(+) and P4(-) groups). The TREK agonist or vehicle was injected intraperitoneally. Body temperature, locomotor activity, tail skin temperature, and thermoregulatory behavior (assessed by tail-hiding behavior) were continuously measured. Plasma concentrations of catecholamines, triiodothyronine, and thyroxine were also measured. In both the P4(+) and P4(-) groups, the change in body temperature was greater among the rats administered the TREK agonist compared to the vehicle. No significant differences were observed between the groups in locomotor activity, tail skin temperature, or tail-hiding behavior. The dopamine concentration in the P4(+) group was lower than that in the P4(-) group. Ostruthin, the TREK agonist, increases body temperature in ovariectomized rats; however, P4 may not affect these responses in ovariectomized rats.

Perimenopausal and Menopausal Mammary Glands In A 4-Vinylcyclohexene Diepoxide Mouse Model

As both perimenopausal and menopausal periods are recognized critical windows of susceptibility for breast carcinogenesis, development of a physiologically relevant model has been warranted. The traditional ovariectomy model causes instant removal of the entire hormonal repertoire produced by the ovary, which does not accurately approximate human natural menopause with gradual transition. Here, we characterized the mammary glands of 4-vinylcyclohexene diepoxide (VCD)-treated animals at different time points, revealing that the model can provide the mammary glands with both perimenopausal and menopausal states. The perimenopausal gland showed moderate regression in ductal structure with no responsiveness to external hormones, while the menopausal gland showed severe regression with hypersensitivity to hormones. Leveraging the findings on the VCD model, effects of a major endocrine disruptor (polybrominated diphenyl ethers, PBDEs) on the mammary gland were examined during and after menopausal transition, with the two exposure modes; low-dose, chronic (environmental) and high-dose, subacute (experimental). All conditions of PBDE exposure did not augment or compromise the macroscopic ductal reorganization resulting from menopausal transition and/or hormonal treatments. Single-cell RNA sequencing revealed that the experimental PBDE exposure during the post-menopausal period caused specific transcriptomic changes in the non-epithelial compartment such as Errfi1 upregulation in fibroblasts. The environmental PBDE exposure resulted in similar transcriptomic changes to a lesser extent. In summary, the VCD mouse model provides both perimenopausal and menopausal windows of susceptibility for the breast cancer research community. PBDEs, including all tested models, may affect the post-menopausal gland including impacts on the non-epithelial compartments.

Effect of menstrual cycle and menopause on human gastric electrophysiology.

Chronic gastroduodenal symptoms disproportionately affect females of childbearing age; however, the effect of menstrual cycling on gastric electrophysiology is poorly defined. To establish the effect of the menstrual cycle on gastric electrophysiology, healthy subjects underwent noninvasive Body Surface Gastric Mapping (BSGM; 8x8 array) with the validated symptom logging App (Gastric Alimetry, New Zealand). Participants included were premenopausal females in follicular (n = 26) and luteal phases (n = 18) and postmenopausal females (n = 30) and males (n = 51) were controls. Principal gastric frequency (PGF), body mass index (BMI) adjusted amplitude, Gastric Alimetry Rhythm Index (GA-RI), Fed:Fasted Amplitude Ratio (ff-AR), meal response curves, and symptom burden were analyzed. Menstrual cycle-related electrophysiological changes were then transferred to an established anatomically accurate computational gastric fluid dynamics model (meal viscosity 0.1 Pas) to predict the impact on gastric mixing and emptying. PGF was significantly higher in the luteal versus follicular phase [mean 3.21 cpm, SD (0.17) vs. 2.94 cpm, SD (0.17), P < 0.001] and versus males [3.01 cpm, SD (0.2), P < 0.001]. In the computational model, this translated to 8.1% higher gastric mixing strength and 5.3% faster gastric emptying for luteal versus follicular phases. Postmenopausal females also exhibited higher PGF than females in the follicular phase [3.10 cpm, SD (0.24) vs. 2.94 cpm, SD (0.17), P = 0.01], and higher BMI-adjusted amplitude [40.7 µV (33.02-52.58) vs. 29.6 µV (26.15-39.65), P < 0.001], GA-RI [0.60 (0.48-0.73) vs. 0.43 (0.30-0.60), P = 0.005], and ff-AR [2.51 (1.79-3.47) vs. 1.48 (1.21-2.17), P = 0.001] than males. There were no differences in symptoms. These results define variations in gastric electrophysiology with regard to human menstrual cycling and menopause.NEW & NOTEWORTHY This study evaluates gastric electrophysiology in relation to the menstrual cycle using a novel noninvasive high-resolution methodology, revealing substantial variations in gastric activity with menstrual cycling and menopause. Gastric slow-wave frequency is significantly higher in the luteal versus follicular menstrual phase. Computational modeling predicts that this difference translates to higher rates of gastric mixing and liquid emptying in the luteal phase, which is consistent with previous experimental data evaluating menstrual cycling effects on gastric emptying.

Female mice with menopause exhibit coronary microvascular disease

Menopause is a natural process as women age, and women with menopause are at higher risk of having cardiovascular diseases than men at the same age. Coronary microvascular disease (CMD) is one of the causes of angina, and the prevalence of CMD is higher in women than in men, and more postmenopausal women have CMD than premenopausal women. However, the causes of CMD in postmenopausal women are not clear. In this study, we investigate whether and how menopause leads to coronary microvascular disease in female mice. Menopausal mice were generated by administering a 20-day injection of 4-Vinylcyclohexene diepoxide (VCD, 160 mg/kg/day in sesame oil, i.p.). VCD gradually destroys primordial and primary follicles in ovaries and leads to ovary failure while keeping the ovary tissues intact; this model is close to the natural progression of human menopause. The vehicle, sesame oil, was administered in control mice. Coronary flow velocity reserve (CFVR) was measured to assess coronary microvascular function. Isometric tension was conducted in third-order coronary arteries (CAs). Capillary density was measured and compared in the left ventricle. Experiments were performed at 6 weeks (perimenopause period) and 8 weeks (post-menopause period) after the injection of VCD or vehicle in female mice. There was no significant difference in CFVR between VCD-injected mice and vehicle-injected mice 6 weeks after the injection. However, at 8 weeks after the injection, VCD-injected mice exhibited a significant decline in CFVR compared to the control mice. Coronary microvascular dysfunction can be driven by attenuated vascular relaxation in small coronary arteries and/or capillary rarefaction. We first conducted isometric tension and found that endothelium-dependent relaxation was significantly attenuated in VCD-injected mice at 8 weeks after the injection, but not at 6 weeks, compared to the controls. There was no significant difference in EC-independent relaxation between the two groups at any age. Interestingly, there was no significant difference in capillary density between VCD-injected mice and vehicle-injected mice at 6 weeks and 8 weeks after the injection. Postmenopausal mice, but not perimenopausal mice, develop CMD due to attenuated endothelium-dependent relaxation. This suggests that improving endothelium-dependent relaxation is the potential mechanism to treat CMD in postmenopausal women. Supported by NIH R01HL142214 and DOD W81XWH2110472. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The evolution of menopause in toothed whales

Understanding how and why menopause has evolved is a long-standing challenge across disciplines. Females can typically maximize their reproductive success by reproducing for the whole of their adult life. In humans, however, women cease reproduction several decades before the end of their natural lifespan1,2. Although progress has been made in understanding the adaptive value of menopause in humans3,4, the generality of these findings remains unclear. Toothed whales are the only mammal taxon in which menopause has evolved several times5, providing a unique opportunity to test the theories of how and why menopause evolves in a comparative context. Here, we assemble and analyse a comparative database to test competing evolutionary hypotheses. We find that menopause evolved in toothed whales by females extending their lifespan without increasing their reproductive lifespan, as predicted by the ‘live-long’ hypotheses. We further show that menopause results in females increasing their opportunity for intergenerational help by increasing their lifespan overlap with their grandoffspring and offspring without increasing their reproductive overlap with their daughters. Our results provide an informative comparison for the evolution of human life history and demonstrate that the same pathway that led to menopause in humans can also explain the evolution of menopause in toothed whales.

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

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

Reproduction and production in a social context: Group size, reproductive skew and increasing returns.

Evolutionary success requires both production (acquisition of food, protection and warmth) and reproduction. We suggest that both may increase disproportionately as group size grows, reflecting 'increasing returns' or 'group augmentation benefits', raising fitness in groups that cooperate in production and limit reproduction to one or a few high fertility females supported by non-reproductives, with high reproductive skew. In our optimisation theory both Allee effects (when individual fitness increases with group size or density) and reproductive skew arise when increasing returns determine optimal group size and proportion of reproductive females. Depending on which of food or maternal time is more important for reproduction, evolutionary trajectories of lineages may (1) reach a boundary constraint where only one female reproduces in a period (as with African wild dogs) or (2) reach a boundary where all females reproduce during their lifetimes but only during an early life stage (human menopause) or a late life stage (birds with non-dispersing helpers), where stage length optimises the proportion of females that is reproductive at any time or (3) reach the intersection of these boundary constraints where a single reproductive female is fully specialised in reproduction (as with eusocial insects). We end with some testable hypotheses.

Lack of accelerated ovarian aging in a follicle-stimulating hormone receptor haploinsufficiency model

Follicle-stimulation hormone (FSH) and FSH receptor (FSHR) signaling is essential for lifelong ovarian and endocrine functions in females. Previous studies have reported that Fshr haploinsufficiency in female mice led to accelerated ovarian aging, including anticipated progressive fertility decline, irregular estrus cycles, increased follicular atresia and premature ovarian failure at 7–9 months of age. Interestingly, these phenotypes resemble key characteristics of human menopause and thus Fshr haploinsufficiency was proposed as a promising research mouse model of menopause. However, the Fshr haploinsufficiency model had not been fully explored, especially at the molecular level. In this study, we characterized the ovarian and endocrine functions of a Fshr heterozygous knockout allele that was generated on the C57BL/6 genetic background as part of the Knockout Mouse Project (KOMP). Based on our analyses of these mice using a breeding assay, ovarian tissue histology and serum hormone quantifications (i.e. FSH, AMH, INHA) analyses, the KOMP Fshr heterozygous knockout female mice do not show the anticipated phenotypes of ovarian aging in terms of fertility and endocrine function. We further confirmed that the expression of Fshr is unaltered in the ovaries of the KOMP Fshr heterozygous knockout animals compared to wild-type. Together, our data suggests that the KOMP Fshr heterozygous knockout strain does not recapitulate the previously reported ovarian aging phenotypes associated to another model of Fshr haploinsufficiency.

PMON210 Ovariectomy of Middle-Aged Female Mice Leads to Decreased Fat Oxidation and Energy Expenditure Accompanied by Weight Gain and Dysregulated Blood Glucose

Abstract Introduction In humans, menopause brings upon total body weight gain with increased visceral adiposity and a resulting increase in cardiometabolic risk profile. Although well described, the specific sequence and underlying mechanisms for this remain elusive. Rodent ovariectomy (OVX) is routinely used as an animal model for the study of human menopause but is often performed in young reproducing specimen, failing to replicate the complex interaction of concomitant chronological aging with the loss of sex hormones observed in humans. In this study we used middle-aged ovariectomized mice to explore the effect of concomitant estrogen deficiency with chronological aging on key aspects of cardiometabolic health and energy expenditure. Methods 10-month-old C57BLj/6 female mice, were subjected to a SHAM or OVX procedure and followed for 6 weeks post-surgery (n=5 per group). Non-fasting blood glucose (BG) and body weight were measured weekly. Prior to sacrifice mice were observed in metabolic cages using the Promethion Metabolic Phenotyping System (Sable Systems International). Body composition including total body fat and lean mass were evaluated by EchoMRI. A Reduction in uterine weight was used to confirm successful OVX. Results Relative to baseline weight, OVX mice weighed 13% more than SHAM mice 6-weeks after surgery (p= 0.04; t-test) with no significant change in body composition. Non-fasting BG was consistently higher throughout the study period in OVX vs SHAM mice (p&amp;lt;0.01; ANOVA). OVX mice exhibited an increased respiratory quotient (0.84 vs 0.81; p&amp;lt;0.01; t-test) driven by a reduction in fat oxidation (24 vs 34 g/d/kgeff. mass p&amp;lt;0.000; t-test). OVX mice showed a 17% percent decrease in total energy expenditure in both the light and dark phases (p&amp;lt;0.01), driven by a 38% percent decrease in ambulatory activity (p=0.04) and close to a 3-fold decrease in wheel running (p&amp;lt;0.001). No significant change was observed in overall food or water intake between the groups. Discussion It is difficult to detangle the complex web of causes and effects relating to the deranged metabolic phenotype induced by menopause. Here we show that even without additional insults such as a high-fat-diet or genetic manipulation, the combination of chronological aging at middle-age with the sex hormone deficiency resulting from OVX, led to an increase in total body weight, a dysregulated glucose profile and a deranged energy expenditure pattern. Additional studies are warranted using similar animal models to tease out cause and effect as well explore novel therapeutics and biomarkers for the rapidly increasing population of post-menopausal women at risk for cardiometabolic disease. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Effect of rosuvastatin on spatial learning, memory, and anxiety-like behaviour in ovariectomized rats

The effect of rosuvastatin (Ros) on cognitive function and anxiety-like behaviour in ovariectomized rats were evaluated. Eighteen female Wistar rats (218–310 g, 6–8 months old) were allocated into sham (n = 6), ovariectomy (Ovx, n = 6) or Ovx + Ros (up to eighth week n = 6, then n = 4) groups. Ros was administered at 20 mg/kg/day by oral gavage for 12 weeks. Behavioural tests were performed at 4, 8 and 12 weeks following Ovx. At 12 weeks, Ovx group had significantly longer escape latency than the sham group at the first day of the four-day training period of the Morris Water Maze test (p < .01). In the Elevated Plus Maze test, Ovx group spent significantly more time in the closed arms than the sham group (p < .01), and this anxiety-like behavioural effect of Ovx was prevented by 12-weeks Ros treatment (p < .05). In conclusion, Ros prevents memory deficit and anxiety-like behaviour in the ovariectomized rats, a model for human surgical menopause. Impact Statement What is already known on this subject? Reduced levels of oestrogen in surgical postmenopausal period has been linked to an increased risk of cognitive dysfunction. Although statins have been shown to improve cognitive function in experimental and clinical studies, there are limited studies evaluating the effect of statins on the cognitive decline and anxiety-like behaviour associated with surgical menopause. What do the results of this study add? Rosuvastatin, a long-acting statin, prevents learning and memory deficit and anxiety-like behaviour in the ovariectomized rat model. What are the implications of these findings for future clinical practice and/or future clinical research? These findings will form the basis for further experimental and clinical research on the effects of statins on cognitive functions and anxiety-like behaviour in the surgical menopause.

Mechanisms of Estrogen Influence on Skeletal Muscle: Mass, Regeneration, and Mitochondrial Function.

Human menopause is widely associated with impaired skeletal muscle quality and significant metabolic dysfunction. These observations pose significant challenges to the quality of life and mobility of the aging population, and are of relevance when considering the significantly greater losses in muscle mass and force-generating capacity of muscle from post-menopausal females relative to age-matched males. In this regard, the influence of estrogen on skeletal muscle has become evident across human, animal, and cell-based studies. Beneficial effects of estrogen have become apparent in mitigation of muscle injury and enhanced post-damage repair via various mechanisms, including prophylactic effects on muscle satellite cell number and function, as well as membrane stability and potential antioxidant influences following injury, exercise, and/or mitochondrial stress. In addition to estrogen replacement in otherwise deficient states, exercise has been found to serve as a means of augmenting and/or mimicking the effects of estrogen on skeletal muscle function in recent literature. Detailed mechanisms behind the estrogenic effect on muscle mass, strength, as well as the injury response are beginning to be elucidated and point to estrogen-mediated molecular cross talk amongst signalling pathways, such as apoptotic signaling, contractile protein modifications, including myosin regulatory light chain phosphorylation, and the maintenance of muscle satellite cells. This review discusses current understandings and highlights new insights regarding the role of estrogen in skeletal muscle, with particular regard to muscle mass, mitochondrial function, the response to muscle damage, and the potential implications for human physiology and mobility.

Altered brain rhythms and behaviour in the accelerated ovarian failure mouse model of human menopause.

To date, potential mechanisms of menopause-related memory and cognitive deficits have not been elucidated. Therefore, we studied brain oscillations, their phase–amplitude coupling, sleep and vigilance state patterns, running wheel use and other behavioural measures in a translationally valid mouse model of menopause, the 4-vinylcyclohexene-diepoxide-induced accelerated ovarian failure. After accelerated ovarian failure, female mice show significant alterations in brain rhythms, including changes in the frequencies of θ (5–12 Hz) and γ (30–120 Hz) oscillations, a reversed phase–amplitude coupling, altered coupling of hippocampal sharp-wave ripples to medial prefrontal cortical sleep spindles and reduced δ oscillation (0.5–4 Hz) synchrony between the two regions during non-rapid eye movement sleep. In addition, we report on significant circadian variations in the frequencies of θ and γ oscillations, and massive synchronous δ oscillations during wheel running. Our results reveal novel and specific network alterations and feasible signs for diminished brain connectivity in the accelerated ovarian failure mouse model of menopause. Taken together, our results may have identified changes possibly responsible for some of the memory and cognitive deficits previously described in this model. Corresponding future studies in menopausal women could shed light on fundamental mechanisms underlying the neurological and psychiatric comorbidities present during this important transitional phase in women’s lives.

The impact of natural aging and ovariectomy on neuroplasticity in female rats: Is all estrogen loss the same?

In adult female rats, circulating sex hormone levels fluctuate significantly across the normal estrus cycle. The most abundant and neuroactive of these sex hormones is 17β‐estradiol (a form of estrogen). We previously demonstrated that 17β‐estradiol is necessary to permit development of respiratory neuroplasticity induced by acute intermittent hypoxia (AIH), called phrenic long‐term facilitation (pLTF). Female rats only develop pLTF during proestrus when circulating estrogen levels are high, and do not express plasticity during periods of low circulating 17β‐estradiol. Additionally, ovariectomy (OVX) abolishes neuroplasticity, but it can be restored with estrogen supplementation. As part of the natural aging process in female rats, estrous‐cycle related fluctuations in circulating 17β‐estradiol levels gradually cease. Rats settle into a state of persistent diestrus, with low levels of circulating estrogen, similar to human menopause. Accordingly, we hypothesized that a reduction in circulating estrogen, either through ovariectomy (OVX) or with natural aging, would eliminate the expression of pLTF. Four experimental groups of female rats were used to test this hypothesis: (1) aged (&gt;22 months old), ovary‐intact, in persistent diestrus (min of 2, 5‐day cycles), (2) young (3 months old), ovary‐intact, in proestrus, (3) young, OVX (2wk post‐surgery), and (4) time controls (both young and aged). Phrenic neurophysiology was used to assess pLTF in anesthetized, ventilated, and vagotomized rats. Circulating estrogen levels were quantified using an ELISA assay for all groups. Contrary to our hypothesis, preliminary results indicate that aged female rats in persistent diestrus produce robust AIH‐induced pLTF (&gt;250% increase in integrated phrenic amplitude 60min post‐AIH). Full results and mechanistic discussion will be presented.

Tibial nerve stimulation increases vaginal blood perfusion and bone mineral density and yield load in ovariectomized rat menopause model.

Human menopause transition and post-menopausal syndrome, driven by reduced ovarian activity and estrogen levels, are associated with an increased risk for symptoms including but not limited to sexual dysfunction, metabolic disease, and osteoporosis. Current treatments are limited in efficacy and may have adverse consequences, so investigation for additional treatment options is necessary. Previous studies have demonstrated that percutaneoustibial nerve stimulation (PTNS) and electro-acupuncture near the tibial nerve are minimally invasive treatments that increase vaginal blood perfusion or serum estrogen in the rat model. We hypothesized that PTNS would protect against harmful reproductive and systemic changes associated with menopause. We examined the effects of twice-weekly PTNS (0.2 ms pulse width, 20 Hz, 2× motor threshold) under ketamine-xylazine anesthesia in ovariectomized (OVX) female Sprague-Dawley rats on menopause-associated physiological parameters including serum estradiol, body weight, blood glucose, bone health, and vaginal blood perfusion. Rats were split into three groups (n = 10 per group): (1) intact control (no stimulation), (2) OVX control (no stimulation), and (3) OVX stimulation (treatment group). PTNS did not affect serum estradiol levels, body weight, or blood glucose. PTNS transiently increased vaginal blood perfusion during stimulation for up to 5 weeks after OVX and increased areal bone mineral density and yield load of the right femur (side of stimulation) compared to the unstimulated OVX control. PTNS may ameliorate some symptoms associated with menopause. Additional studies to elucidate the full potential of PTNS on menopause-associated symptoms under different experimental conditions are warranted.

Justice for the Menopause: A Research Agenda

&#x0D; &#x0D; &#x0D; Menopause is defined by its relationship to menstruation––it is the cessation of menstruation. Medical texts identify menopause as part of the cycle of “decay” associated with female reproductive functions; early menopause is often a dreaded result of various medical treatments and a sign of disfunction.&#x0D; It turns out that only three types of animals experience menopause: killer whales, short-finned pilot whales, and humans, while other animals can reproduce until death. Although the precise relationship between evolutionary theory and the physical development of human menopause is still uncertain, scientists and anthropologists suggest that the “grandmother hypothesis” provides a partial explanation: older women, who can no longer produce their own children, ensure their genetic legacy by playing a critical role in helping to feed, raise, and nurture their grandchildren.&#x0D; &#x0D; &#x0D; &#x0D; The average woman will spend almost as many years “post-menopause” as they will menstruating, and they may spend four years (or more) experiencing perimenopausal symptoms, the transition time between “normal” menstruation and menopause. But legal issues relating to perimenopause, menopause, and post-menopause are just beginning to surface, prompted by the movement towards menstrual justice, feminist jurisprudence, and developments in the law of aging.&#x0D; This Essay is an initial effort to catalogue various legal approaches to menopause and to set out areas for further analysis. It briefly explores cultural images of menopause and post-menopausal women, including the ubiquitous hot flashes; analyzes potential legal claims for menopausal justice; and suggests the interrelationship between such approaches and social attitudes towards menopause. It suggests that “normalizing” menopause––acknowledging its realities––is one means for removing the associated stigma and “disabilities” and might result in reinterpreting existing laws and guiding future legal reforms.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D;

Human Immunodeficiency Virus (HIV) and Menopause Are Independently Associated With Lower Bone Mineral Density: Results From the Women's Interagency HIV Study.

We previously reported lower bone mineral density (BMD) among premenopausal women with HIV (WWH) compared to women without HIV (HIV-). Rate of bone loss may be even greater for WWH during the menopausal transition. Pre-, peri- and postmenopausal women in the Women\'s Interagency HIV Study (WIHS) underwent whole body DXA and central quantitative computed tomography to measure areal BMD (aBMD) and volumetric BMD (vBMD), respectively. Multivariable regression models with covariates associated with low aBMD (T score < -1.0) in univariate analyses (P≤.05) and known risk factors for low BMD assessed contributions of HIV and menopausal stage to the prediction of aBMD. Compared to HIV- women, in unadjusted analyses, WWH had 5-9% lower aBMD at the lumbar spine (P=.001), femoral neck (P=.04), total hip (P=.003) and the ultradistal radius (P=.004), and higher osteoporosis prevalence (T score<-2.5) at the ultradistal radius only (13.5% vs 0%, P=.0003). WWH also had lower vBMD at the spine and hip. In fully adjusted models, HIV independently predicted reduced aBMD at the lumbar spine, total hip, femoral neck, and ultradistal radius; menopausal stage remained a significant predictor of lumbar spine and ultradistal radius aBMD. HIV infection and menopausal stage were independent predictors of lower BMD, and had an additive effect on lumbar spine and total hip BMD. Additional research is needed to better understand underlying mechanisms by which HIV impacts BMD as women age and transition through menopause, and develop strategies to mitigate osteoporosis and fracture risk in this growing population.

Menopause impacts human brain structure, connectivity, energy metabolism, and amyloid-beta deposition

All women undergo the menopause transition (MT), a neuro-endocrinological process that impacts aging trajectories of multiple organ systems including brain. The MT occurs over time and is characterized by clinically defined stages with specific neurological symptoms. Yet, little is known of how this process impacts the human brain. This multi-modality neuroimaging study indicates substantial differences in brain structure, connectivity, and energy metabolism across MT stages (pre-menopause, peri-menopause, and post-menopause). These effects involved brain regions subserving higher-order cognitive processes and were specific to menopausal endocrine aging rather than chronological aging, as determined by comparison to age-matched males. Brain biomarkers largely stabilized post-menopause, and gray matter volume (GMV) recovered in key brain regions for cognitive aging. Notably, GMV recovery and in vivo brain mitochondria ATP production correlated with preservation of cognitive performance post-menopause, suggesting adaptive compensatory processes. In parallel to the adaptive process, amyloid-β deposition was more pronounced in peri-menopausal and post-menopausal women carrying apolipoprotein E-4 (APOE-4) genotype, the major genetic risk factor for late-onset Alzheimer’s disease, relative to genotype-matched males. These data show that human menopause is a dynamic neurological transition that significantly impacts brain structure, connectivity, and metabolic profile during midlife endocrine aging of the female brain.