A Comprehensive Method To Quantify Adaptations by Male and Female Mice With Hot Flashes Induced by the Neurokinin B Receptor Agonist Senktide

Efficacy and Safety of Fezolinetant in Moderate to Severe Vasomotor Symptoms Associated With Menopause: A Phase 3 RCT

CONTEXT

Vasomotor symptoms (VMS) are common, bothersome, and can persist for years before and after menopause.

OBJECTIVE

We aimed to assess efficacy/safety of fezolinetant for treatment of moderate to severe VMS associated with menopause.

METHODS

In this double-blind, placebo-controlled, 12-week phase 3 trial with a 40-week active treatment extension (NCT04003142; SKYLIGHT 2), women aged 40 to 65 years with minimum average 7 moderate to severe VMS/day were randomized to 12 weeks of once-daily placebo, fezolinetant 30 mg, or fezolinetant 45 mg. Completers were rerandomized to fezolinetant 30/45 mg for 40 additional weeks. Coprimary efficacy endpoints were mean daily change from baseline to week 4 (W4) and W12 in VMS frequency and severity. Safety was also assessed.

RESULTS

Both fezolinetant doses statistically significantly reduced VMS frequency/severity at W4 and W12 vs placebo. For VMS frequency, W4 least squares mean (SE) reduction vs placebo: fezolinetant 30 mg, -1.82 (0.46; P < .001); 45 mg, -2.55 (0.46; P < .001); W12: 30 mg, -1.86 (0.55; P < .001); 45 mg, -2.53 (0.55; P < .001). For VMS severity, W4: 30 mg, -0.15 (0.06; P < .05); 45 mg, -0.29 (0.06; P < .001); W12: 30 mg, -0.16 (0.08; P < .05); 45 mg, -0.29 (0.08; P < .001). Improvement in VMS frequency and severity was observed by W1 and maintained through W52. Serious treatment-emergent adverse events were infrequent, reported by 2%, 1%, and 0% of those receiving fezolinetant 30 mg, fezolinetant 45 mg, and placebo, respectively.

CONCLUSION

Daily fezolinetant 30 and 45 mg were efficacious and well tolerated for treating moderate to severe VMS associated with menopause.

Norepinephrine modulation of heat dissipation in female rats lacking estrogen

Postmenopausal hot flushes are caused by lack of estradiol (E2) but their neuroendocrine basis is still poorly understood. Here, we investigated the interrelationship between norepinephrine and hypothalamic neurons, with emphasis on kisspeptin neurons in the arcuate nucleus (ARC), as a regulatory pathway in the vasomotor effects of E2. Ovariectomized (OVX) rats displayed increased tail skin temperature (TST), and this increase was prevented in OVX rats treated with E2 (OVX + E2). Expression of Fos in the hypothalamus and the number of ARC kisspeptin neurons coexpressing Fos were increased in OVX rats. Likewise, brainstem norepinephrine neurons of OVX rats displayed higher Fos immunoreactivity associated with the increase in TST. In the ARC, the density of dopamine-ß-hydroxylase (DBH)-immunoreactive (ir) fibers was not altered by E2 but, importantly, DBH-ir terminals were found in close apposition to kisspeptin cells, revealing norepinephrine inputs to ARC kisspeptin neurons. Intracerebroventricular injection of the α2-adrenergic agonist clonidine (CLO) was used to reduce central norepinephrine release, confirmed by the decreased 3-methoxy-4-hydroxyphenylglycol/norepinephrine ratio in the preoptic area and ARC. Accordingly, CLO treatment in OVX rats reduced ARC Kiss1 mRNA levels and TST to the values of OVX + E2 rats. Conversely, CLO stimulated Kiss1 expression in the anteroventral periventricular nucleus (AVPV) and increased luteinizing hormone secretion. These findings provide evidence that augmented heat dissipation in OVX rats involves the increase in central norepinephrine that modulates hypothalamic areas related to thermoregulation, including ARC kisspeptin neurons. This neuronal network is suppressed by E2 and its imbalance may be implicated in the vasomotor symptoms of postmenopausal hot flushes.

Metabolic actions of kisspeptin signaling: Effects on body weight, energy expenditure, and feeding

Kisspeptin (encoded by the Kiss1 gene) and its receptor, KISS1R (encoded by the Kiss1r gene), have well-established roles in stimulating reproduction via central actions on reproductive neural circuits, but recent evidence suggests that kisspeptin signaling also influences metabolism and energy balance. Indeed, both Kiss1 and Kiss1r are expressed in many metabolically-relevant peripheral tissues, including both white and brown adipose tissue, the liver, and the pancreas, suggesting possible actions on these tissues or involvement in their physiology. In addition, there may be central actions of kisspeptin signaling, or factors co-released from kisspeptin neurons, that modulate metabolic, feeding, or thermoregulatory processes. Accumulating data from animal models suggests that kisspeptin signaling regulates a wide variety of metabolic parameters, including body weight and energy expenditure, adiposity and adipose tissue function, food intake, glucose metabolism, respiratory rates, locomotor activity, and thermoregulation. Herein, the current evidence for the involvement of kisspeptin signaling in each of these physiological parameters is reviewed, gaps in knowledge identified, and future avenues of important research highlighted. Collectively, the discussed findings highlight emerging non-reproductive actions of kisspeptin signaling in metabolism and energy balance, in addition to previously documented roles in reproductive control, but also emphasize the need for more research to resolve current controversies and uncover underlying molecular and physiological mechanisms.

Inhibiting Kiss1 Neurons With Kappa Opioid Receptor Agonists to Treat Polycystic Ovary Syndrome and Vasomotor Symptoms

CONTEXT

Recent evidence suggests that vasomotor symptoms (VMS) or hot flashes in the postmenopausal reproductive state and polycystic ovary syndrome (PCOS) in the premenopausal reproductive state emanate from the hyperactivity of Kiss1 neurons in the hypothalamic infundibular/arcuate nucleus (KNDy neurons).

OBJECTIVE

We demonstrate in 2 murine models simulating menopause and PCOS that a peripherally restricted kappa receptor agonist (PRKA) inhibits hyperactive KNDy neurons (accessible from outside the blood-brain barrier) and impedes their downstream effects.

DESIGN

Case/control.

SETTING

Academic medical center.

PARTICIPANTS

Mice.

INTERVENTIONS

Administration of peripherally restricted kappa receptor agonists and frequent blood sampling to determine hormone release and body temperature.

MAIN OUTCOME MEASURES

LH pulse parameters and body temperature.

RESULTS

First, chronic administration of a PRKA to bilaterally ovariectomized mice with experimentally induced hyperactivity of KNDy neurons reduces the animals' elevated body temperature, mean plasma LH level, and mean peak LH per pulse. Second, chronic administration of a PRKA to a murine model of PCOS, having elevated plasma testosterone levels and irregular ovarian cycles, suppresses circulating levels of LH and testosterone and restores normal ovarian cyclicity.

CONCLUSION

The inhibition of kisspeptin neuronal activity by activation of kappa receptors shows promise as a novel therapeutic approach to treat both VMS and PCOS in humans.

Estrogen Regulation of the Molecular Phenotype and Active Translatome of AVPV Kisspeptin Neurons

In females, ovarian estradiol (E2) exerts both negative and positive feedback regulation on the neural circuits governing reproductive hormone secretion, but the cellular and molecular mechanisms underlying this remain poorly understood. In rodents, estrogen receptor α-expressing kisspeptin neurons in the hypothalamic anteroventral periventricular region (AVPV) are prime candidates to mediate E2 positive feedback induction of preovulatory gonadotropin-releasing hormone and luteinizing hormone (LH) surges. E2 stimulates AVPV Kiss1 expression, but the full extent of estrogen effects in these neurons is unknown; whether E2 stimulates or inhibits other genes in AVPV Kiss1 cells has not been determined. Indeed, understanding of the function(s) of AVPV kisspeptin cells is limited, in part, by minimal knowledge of their overall molecular phenotype, as only a few genes are currently known to be co-expressed in AVPV Kiss1 cells. To provide a more detailed profiling of co-expressed genes in AVPV Kiss1 cells, including receptors and other signaling factors, and test how these genes respond to E2, we selectively isolated actively translated mRNAs from AVPV Kiss1 cells of female mice and performed RNA sequencing (RNA-seq). This identified >13 000 mRNAs co-expressed in AVPV Kiss1 cells, including multiple receptor and ligand transcripts positively or negatively regulated by E2. We also performed RNAscope to validate co-expression of several transcripts identified by RNA-seq, including Pdyn (prodynorphin), Penk (proenkephalin), Vgf (VGF), and Cartpt (CART), in female AVPV Kiss1 cells. Given the important role of AVPV kisspeptin cells in positive feedback, E2 effects on identified genes may relate to the LH surge mechanism and/or other physiological processes involving these cells.

Effects of neurokinin 3 receptor antagonist fezolinetant on hot flash-like symptoms in ovariectomized rats

The majority of women experience vasomotor symptoms (VMS), such as hot flashes and night sweats, during the menopausal transition. Recent evidence strongly suggests a connection between neurokinin 3 (NK3) receptor signaling and VMS associated with menopause. The NK3 receptor antagonist fezolinetant is currently in phase 3 development for treatment of moderate to severe VMS associated with menopause. We investigated the pharmacological effects of repeated administration of fezolinetant on levels of sex hormones and gonadotropins, neuronal activity in the hypothalamus, and skin temperature as an index of hot flash-like symptoms in ovariectomized rats as a model of menopause. Ovariectomized rats exhibited several typical menopausal symptoms: hyperphagia, increased body weight, significantly decreased plasma estradiol levels, increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, and significantly increased skin temperature. Increased c-Fos expression (an indirect marker of neuronal activity) in median preoptic nucleus (MnPO) hypothalamic neurons was also observed in ovariectomized rats. Repeated oral administration of fezolinetant (1-10 mg/kg, twice daily) for 1 week dose-dependently reduced plasma LH levels without affecting estradiol or FSH levels, inhibited the activation of MnPO neurons, and attenuated hot flash-like symptoms. In addition, fezolinetant dose-dependently reduced hyperphagia and weight gain in ovariectomized rats. These preclinical findings suggest that fezolinetant attenuates hot flash-like symptoms via inhibition of neuronal activity in the MnPO of ovariectomized rats and provides further support for the ongoing clinical development of fezolinetant for the treatment of VMS associated with menopause.

Long-term oral administration of a novel estrogen receptor beta agonist enhances memory and alleviates drug-induced vasodilation in young ovariectomized mice

Development of estrogen therapies targeting the β (ERβ) but not α (ERα) estrogen receptor is critically needed for the treatment of negative menopausal symptoms, as ERα activation increases health risks like cancer. Here, we determined the effects of long-term oral treatment with EGX358, a novel highly selective ERβ agonist, on memory, vasodilation, and affect in young ovariectomized mice. Mice were orally gavaged daily for 9 weeks with vehicle, 17β-estradiol (E₂), the ERβ agonist diarylpropionitrile (DPN), or EGX358 at doses that enhance memory when delivered acutely. Tail skin temperature was recorded as a proxy for vasodilation following injection of vehicle or senktide, a tachykinin receptor 3 agonist used to model hot flashes. Anxiety-like behavior was assessed in the open field (OF) and elevated plus maze (EPM), and depression-like behavior was measured in the tail suspension (TST) and forced swim tests (FST). Finally, memory was assessed in object recognition (OR) and object placement (OP) tasks. E₂, DPN, and EGX358 reduced senktide-mediated increases in tail skin temperature compared to vehicle. All three treatments also enhanced memory in the OR and OP tasks, whereas vehicle did not. Although E₂ increased time spent in the center of the OF, no other treatment effects were observed in the OF, EPM, TST, or FST. These data suggest that long-term ERβ activation can reduce hot flash-like symptoms and enhance spatial and object recognition memories in ovariectomized mice. Thus, the highly selective ERβ agonist EGX358 may be a promising avenue for reducing menopause-related hot flashes and memory dysfunction.

Neurokinin 3 receptor-selective agonist, senktide, decreases core temperature in Japanese Black cattle

Heat stress disrupts reproductive function in cattle. In summer, high ambient temperature and humidity elevate core body temperature, which is considered to be detrimental to reproductive abilities in cattle. Neurokinin B (NKB) is a factor that generates pulsatile GnRH and subsequent LH secretion in mammals. Recent studies have reported that NKB-neurokinin 3 receptor (NK3R) signaling is associated with heat-defense responses in rodents. The present study aimed to clarify the role of NKB-NK3R signaling in thermoregulation in cattle. We examined the effects of an NK3R-selective agonist, senktide, on vaginal temperature as an indicator of core body temperature in winter and summer. In both seasons, continuous infusion of senktide for 4 h immediately decreased vaginal temperature, and the mean temperature change in the senktide-treated group was significantly lower than that of both vehicle- and GnRH-treated groups. Administration of GnRH induced LH elevation, but there was no significant difference in vaginal temperature change between GnRH- and vehicle-treated groups. Moreover, we investigated the effects of senktide on ovarian temperature. Senktide treatment seemed to suppress the increase in ovarian temperature from 2 h after the beginning of administration, although the difference between groups was not statistically significant. Taken together, these results suggest that senktide infusion caused a decline in the vaginal temperature of cattle, in both winter and summer seasons, and this effect was not due to the gonadotropin-releasing action of senktide. These findings provide new therapeutic options for senktide to support both heat-defense responses and GnRH/LH pulse generation.

Genetic predictors to acupuncture response for hot flashes: an exploratory study of breast cancer survivors

OBJECTIVE

Because hot flashes are a common symptom experienced by women with breast cancer, we sought to explore genetic predictors associated with response to acupuncture for the treatment of hot flashes.

METHODS

Using data from our completed randomized controlled trial (Clinicaltrials.gov identifier: NCT01005108) on hot flashes among breast cancer survivors who provided biomarker collection (N = 108), we extracted and assayed DNA for single nucleotide polymorphisms in genes involved in neurotransmission, thermoregulation, and inflammation (ADORA1, COMT, TCL1A, and TRPV1). For our primary outcome we classified individuals with a 50% or more reduction in their hot flash composite score at the end of treatment as responders. We used Fisher exact test to identify individual and combined single nucleotide polymorphisms associated with treatment response.

RESULTS

Among women (N = 57) who received acupuncture treatment (electro or sham), we found that women who were carriers of at least one of these six genotypes (ADORA1 rs41264025-GA or rs16851029-GG or rs12744240-GT, COMT rs6269-GA, TCL1A rs2369049-GG, and TRPV1 rs8065080-TT) were more likely to respond to acupuncture for hot flashes than noncarriers (70.3% vs 37.5%, P = 0.035). These six genotypes were not associated with response in women (N = 51) who received pharmacological hot flash treatment (gabapentin or placebo pill; 37.5% vs 37.5%, P = 1.0).

CONCLUSIONS

In this exploratory, proof of concept study, we identified six genotypes that may predict response to acupuncture for hot flashes in breast cancer survivors. If confirmed by future studies, these findings may inform the development of personalized acupuncture for managing hot flashes.

A Neural Circuit Underlying the Generation of Hot Flushes

Hot flushes are a sudden feeling of warmth commonly associated with the decline of gonadal hormones at menopause. Neurons in the arcuate nucleus of the hypothalamus that express kisspeptin and neurokinin B (Kiss1^ARH neurons) are candidates for mediating hot flushes because they are negatively regulated by sex hormones. We used a combination of genetic and viral technologies in mice to demonstrate that artificial activation of Kiss1^ARH neurons evokes a heat-dissipation response resulting in vasodilation (flushing) and a corresponding reduction of core-body temperature in both females and males. This response is sensitized by ovariectomy. Brief activation of Kiss1^ARH axon terminals in the preoptic area of the hypothalamus recapitulates this response, while pharmacological blockade of neurokinin B (NkB) receptors in the same brain region abolishes it. We conclude that transient activation of Kiss1^ARH neurons following sex-hormone withdrawal contributes to the occurrence of hot flushes via NkB release in the rostral preoptic area.

Glutamatergic Neurokinin 3 Receptor Neurons in the Median Preoptic Nucleus Modulate Heat-Defense Pathways in Female Mice

We have proposed that arcuate neurons coexpressing kisspeptin, neurokinin B, and dynorphin (KNDy neurons) contribute to hot flushes via projections to neurokinin 3 receptor (NK3R)-expressing neurons in the median preoptic nucleus (MnPO). To characterize the thermoregulatory role of MnPO NK3R neurons in female mice, we ablated these neurons using injections of saporin toxin conjugated to a selective NK3R agonist. Loss of MnPO NK3R neurons increased the core temperature (TCORE) during the light phase, with the frequency distributions indicating a regulated shift in the balance point. The increase in TCORE in the ablated mice occurred despite changes in the ambient temperature and regardless of estrogen status. We next determined whether an acute increase in ambient temperature or higher TCORE would induce Fos in preoptic enhanced green fluorescent protein (EGFP)-immunoreactive neurons in Tacr3-EGFP mice. Fos activation was increased in the MnPO but no induction of Fos was found in NK3R (EGFP-immunoreactive) neurons. Thus, MnPO NK3R neurons are not activated by warm thermosensors in the skin or viscera and are not warm-sensitive neurons. Finally, RNAscope was used to determine whether Tacr3 (NK3R) mRNA was coexpressed with vesicular glutamate transporter 2 or vesicular γ-aminobutyric acid (GABA) transporter mRNA, markers of glutamatergic and GABAergic neurotransmission, respectively. In the MnPO, 94% of NK3R neurons were glutamatergic, but in the adjacent medial preoptic area, 97% of NK3R neurons were GABAergic. Thus, NK3R neurons in the MnPO are glutamatergic and play a role in reducing TCORE but are not activated by warm thermal stimuli (internal or external). These findings suggest that KNDy neurons modulate thermosensory pathways for heat defense indirectly via a subpopulation of glutamatergic MnPO neurons that express NK3R.

Is calcitonin gene-related peptide a modulator of menopausal vasomotor symptoms?

PURPOSE

Calcitonin gene-related peptide (CGRP) is a neuropeptide widely distributed in the central and peripheral nervous systems, which is known as a potent vasodilator. Postmenopausal women who experience hot flushes have high levels of plasma CGRP, suggesting its involvement in menopausal vasomotor symptoms.

METHODS

In this review, we describe the biochemical aspects of CGRP and its effects associated with deficiencies of sexual hormones on skin temperature, vasodilatation, and sweating as well as the possible peripheral and central mechanisms involved in these events.

RESULTS

Several studies have shown that the effects of CGRP on increasing skin temperature and inducing vasodilatation are potentiated by a deficiency of sex hormones, a common condition of postmenopausal women. Additionally, the medial preoptic area of the hypothalamus, involved in thermoregulation, contains over 25-fold more CGRP-immunoreactive cells in female rodents compared with male rodents, reinforcing the role of female sex hormones on the action of CGRP. Some studies suggest that ovarian hormone deficiency decreases circulating endogenous CGRP, inducing an upregulation of CGRP receptors. Consequently, the high CGRP receptor density, especially in blood vessels, amplifies the stimulatory effects of this neuropeptide to raise skin temperature in postmenopausal women during hot flushes.

CONCLUSIONS

The duration of the perception of each hot flush in a woman is brief, while local reddening after intradermal administration of α-CGRP persists for 1 to 6 h. This contrast remains unclear.

The 3rd World Conference on Kisspeptin, "Kisspeptin 2017: Brain and Beyond":Unresolved questions, challenges and future directions for the field

The 3rd World Conference on Kisspeptin, "Kisspeptin 2017: Brain and Beyond" was held March 30-31 at the Rosen Centre Hotel in Orlando, Florida, providing an international forum for multidisciplinary scientists to meet and share cutting-edge research on kisspeptin biology and its relevance to human health and disease. The meeting built upon previous world conferences focused on the role of kisspeptin and associated peptides in the control of gonadotropin-releasing hormone (GnRH) secretion and reproduction. Based on recent discoveries, the scope of this meeting was expanded to include functions of kisspeptin and related peptides in other physiological systems including energy homeostasis, pregnancy, ovarian and uterine function, and thermoregulation. In addition, discussions addressed the translation of basic knowledge of kisspeptin biology to the treatment of disease, with the goal of seeking consensus about the best approaches to improve human health. The two-day meeting featured a non-traditional structure, with each day starting with poster sessions followed by lunch discussions and facilitated large-group sessions with short presentations to maximize the exchange of new, unpublished data. Topics were identified by a survey prior to the meeting, and focused on major unresolved questions, important controversies, and future directions in the field. Finally, career development activities provided mentoring for trainees and junior investigators, and networking opportunities for those individuals with established researchers in the field. Overall, the meeting was rated as a success by attendees and covered a wide range of lively and provocative discussion topics on the changing nature of the field of "kisspeptinology" and its future. This article is protected by copyright. All rights reserved.

Estradiol alters body temperature regulation in the female mouse

Hot flushes are due to estrogen withdrawal and characterized by the episodic activation of heat dissipation effectors. Recent studies (in humans and rats) have implicated neurokinin 3 (NK₃) receptor signaling in the genesis of hot flushes. Although transgenic mice are increasingly used for biomedical research, there is limited information on how 17β-estradiol and NK₃ receptor signaling alters thermoregulation in the mouse. In this study, a method was developed to measure tail skin temperature (T_SKIN) using a small data-logger attached to the surface of the tail, which, when combined with a telemetry probe for core temperature (T_CORE), allowed us to monitor thermoregulation in freely-moving mice over long durations. We report that estradiol treatment of ovariectomized mice reduced T_CORE during the light phase (but not the dark phase) while having no effect on T_SKIN or activity. Estradiol also lowered T_CORE in mice exposed to ambient temperatures ranging from 20 to 36°C. Unlike previous studies in the rat, estradiol treatment of ovariectomized mice did not reduce T_SKIN during the dark phase. Subcutaneous injections of an NK₃ receptor agonist (senktide) in ovariectomized mice caused an acute increase in T_SKIN and a reduction in T_CORE, consistent with the activation of heat dissipation effectors. These changes were reduced by estradiol, suggesting that estradiol lowers the sensitivity of central thermoregulatory pathways to NK₃ receptor activation. Overall, we show that estradiol treatment of ovariectomized mice decreases T_CORE during the light phase, reduces the thermoregulatory effects of senktide and modulates thermoregulation differently than previously described in the rat.