κ Agonists as a novel therapy for menopausal hot flashes

New advances in menopause symptom management

Vasomotor symptoms (VMS) are characteristic of menopause experienced by over 75% of postmenopausal women with significant health and socioeconomic implications. Although the average duration of symptoms is seven years, 10% of women experience symptoms for more than a decade. Although menopausal hormone therapy (MHT) remains an efficacious and cost-effective treatment, its use may not be suitable in all women, such as those at an increased risk of breast cancer or gynaecological malignancy. The neurokinin B (NKB) signaling pathway, together with its intricate connection to the median preoptic nucleus (MnPO), has been postulated to provide integrated reproductive and thermoregulatory responses, with a central role in mediating postmenopausal VMS. This review describes the physiological hypothalamo-pituitary-ovary (HPO) axis, and subsequently the neuroendocrine changes that occur with menopause using evidence derived from animal and human studies. Finally, data from the latest clinical trials using novel therapeutic agents that antagonise NKB signaling are reviewed.

Elinzanetant: a phase III therapy for postmenopausal patients with vasomotor symptoms

INTRODUCTION

Menopausal vasomotor symptoms (VMS) are experienced by most women and are often debilitating and can last for years. While hormone replacement therapy is effective, it carries risks that have impacted its wider use, and it can be contraindicated. There is a large unmet need for a safe, effective non-hormonal therapy.

AREAS COVERED

The importance of the neurokinin (NK) system in the hypothalamic regulation of the vasomotor center has become clear. NK antagonists, previously developed for other indications, have therefore been investigated for the treatment of VMS. Elinzanetant is a potent antagonist at both NK1 (endogenous ligand Substance P) and NK3 (neurokinin B) receptors, whereas other related drugs in development are selective NK3 antagonists. Elinzanetant has been investigated in 2 Phase II trials for menopausal VMS, demonstrating rapid onset and dose-dependant efficacy for the relief of VMS and improvement in quality of life for up to 12 weeks. Phase III trials are underway in women both with physiological menopause and after treatment for breast cancer.

EXPERT OPINION

Elinzanetant is a very promising non-hormonal approach to a highly prevalent symptom constellation, with rapid onset and high efficacy. Wider indications are being explored in current Phase III trials.

Kisspeptin Modulation of Reproductive Function

Kisspeptin is a peptide expressed mainly in the infundibular nucleus of the hypothalamus. Kisspeptin plays a crucial role in the regulation of reproductive functions. It is regarded as the most important factor responsible for the control of the hypothalamic–pituitary–gonadal axis, the onset of puberty, and the regulation of menstruation and fertility. Kisspeptin activity influences numerous processes such as steroidogenesis, follicular maturation, ovulation, and ovarian senescence. The identification of kisspeptin receptor mutations that cause hypogonadotropic hypogonadism has initiated studies on the role of kisspeptin in puberty. Pathologies affecting the neurons secreting kisspeptin play a major role in the development of PCOS, functional hypothalamic amenorrhea, and perimenopausal vasomotor symptoms. Kisspeptin analogs (both agonists and antagonists), therefore, may be beneficial as therapy in those afflicted with such pathologies. The aim of this review is to summarize the influence of kisspeptin in the physiology and pathology of the reproductive system in humans, as well as its potential use in therapy.

Resistance training reduced luteinising hormone levels in postmenopausal women in a substudy of a randomised controlled clinical trial: A clue to how resistance training reduced vasomotor symptoms

Background

Vasomotor symptoms (VMS) are common around menopause. Menopausal hormone therapy is the most effective treatment for VMS. Physical exercise has been proposed as an alternative treatment since physically active women have previously been found to experience fewer VMS than inactive women. In our randomised controlled trial on resistance training to treat VMS, sympoms were reduced by 50% in the intervention group compared with the control group.

Objectives

To propose a mechanism to explain how resistance training reduced VMS and to assess if luteinizing hormone (LH) and follicle stimulating hormone (FSH) were affected in accordance with the proposed mechanism.

Trial design and methods

A substudy of a randomized controlled trial on 65 postmenopausal women with VMS and low physical activity who were randomised to 15 weeks of resistance training three times per week (n = 33) or to a control group (n = 32). To be regarded compliant to the intervention we predecided a mean of two training sessions per week. The daily number of VMS were registered before and during the 15 weeks. Blood samples were drawn for analysis of LH and FSH at baseline and after 15 weeks.

Results

LH decreased significantly in the compliant intervention group compared with the control group (-4.0±10.6 versus 2.9±9.0, p = 0.028 with Mann-Whitney U test). FSH also decreased in the compliant intervention group compared with the control group, however not enough to reach statistical significance (-3.5±16.3 versus 3.2±18.2, p = 0.063 with Mann-Whitney U test). As previously published the number of hot flushes decreased significantly more in the intervention group than in the control group but there was no association between change in LH or FSH and in number of VMS.

Conclusions

We propose that endogenous opiods such as β-endorphin or dynorphin produced during resistance training decreased VMS by stimulating KNDγ-neurons to release neurokinin B to the hypothalamic thermoregulatory centre. Through effects on KNDγ-neurons, β-endorphin could also inhibit GnRH and thereby decrease the production of LH and FSH. The significanty decreased LH in the compliant intervention group compared with the control group was in accordance with the proposed mechanism.

The roles of kisspeptin and neurokinin B in GnRH pulse generation in humans, and their potential clinical application

The delivery of gonadotropin-releasing hormone (GnRH) in a pulsatile mode to the gonadotropes has long been known to be essential for normal reproductive function. There have been numerous studies aimed at dissecting out the mechanisms underlying GnRH pulse generation. The discovery of kisspeptin as an upstream regulator of GnRH attracted the possibility that pulsatile kisspeptin governed the pulsatile secretion of GnRH. Subsequent studies have shown the importance of the neurokinin B (NKB) system in modulating kisspeptin secretion and this GnRH. A number of studies in laboratory rodents have supported this notion. By contrast, we present data from clinical studies in men and women, in a range of contexts, showing that continuous infusion of kisspeptin 10 at receptor-saturating levels gives rise to an increase in luteinizing hormone (LH) (GnRH) pulse frequency. This has been demonstrated in normal healthy and hypogonadal men, in normal women during the mid-cycle LH surge, in men and women with mutations in the genes encoding NKB or its receptor, neurokinin 3 receptor (NK3R), in women with polycystic ovary syndrome treated with NK3R antagonist, and in women treated with NK3R antagonist during the LH surge. These finds indicate that pulsatile secretion and action of kisspeptin on GnRH neurons is not required for the generation of LH (GnRH) pulses in humans. We also report that there is an absence of desensitization in humans exposed to continuous infusion of kisspeptin-10 at receptor-saturating concentrations over 22 h and briefly review GnRH, kisspeptin and NKB analogs and their clinical application.

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.

Hypothalamic neurokinin signalling and its application in reproductive medicine

The discovery of the essential requirement for kisspeptin and subsequently neurokinin B signalling for human reproductive function has sparked renewed interest in the neuroendocrinology of reproduction. A key discovery has been a population of cells co-expressing both these neuropeptides and dynorphin in the hypothalamus, directly regulating gonadotropin hormone releasing hormone (GnRH) secretion and thus pituitary secretion of gonadotropins. These neurons also project to the vasomotor centre, and their overactivity in estrogen deficiency results in the common and debilitating hot flushes of the menopause. Several antagonists to the neurokinin 3 receptor, for which neurokinin B is the endogenous ligand, have been developed, and are entering clinical studies in human reproductive function and clinical trials. Even single doses can elicit marked declines in testosterone levels in men, and their use has elicited evidence of the regulation of ovarian follicle growth in women. The most advanced indication is the treatment of menopausal vasomotor symptoms, where these drugs show remarkable results in both the degree and speed of symptom control. A range of other reproductive indications are starting to be explored, notably in polycystic ovary syndrome, the most common endocrinopathy in women.

Genetic variants predictive of reproductive aging are associated with vasomotor symptoms in a multiracial/ethnic cohort

OBJECTIVE

Vasomotor symptoms (VMS), hot flashes, and night sweats are cardinal symptoms of the menopausal transition. Little is known about genetic influences on VMS. This study evaluated whether previously identified genetic factors predictive of VMS, age at menarche, and age at menopause were associated with VMS in a multiracial/ethnic cohort.

METHODS

For 702 White, 306 Black, 126 Chinese, and 129 Japanese women from the Study of Women's Health Across the Nation (SWAN) Genomic Substudy, we created polygenic risk scores (PRSs) from genome-wide association studies of VMS and ages at menarche and menopause. PRSs and single nucleotide polymorphisms (SNPs) from a previously identified VMS locus (tachykinin receptor 3 [TACR3]) were evaluated for associations with frequent VMS (VMS ≥6 days in the past 2 weeks at any visit) and with VMS trajectories (persistently low, early onset, final menstrual period onset, persistently high).

RESULTS

The C-allele of rs74827081 in TACR3 was associated with reduced likelihood of frequent VMS in White women (odds ratio [OR] = 0.49 [95% CI, 0.29-0.83]). With higher menarche PRS (later menarche), Black women were less likely (OR = 0.55 [95% CI, 0.38-0.78]) to report frequent VMS. With higher PRS for age at menarche, Black women were also less likely to have a persistently high VMS trajectory (OR = 0.55 [95% CI, 0.34-0.91]), whereas White women (OR = 0.75 [95% CI, 0.58-0.98]) were less likely to have a final menstrual period onset trajectory (vs persistently low). Chinese women with higher menopause PRS were more likely to have frequent VMS (OR = 2.29 [95% CI, 1.39-3.78]). Associations were substantively similar after excluding rs74827081 C-allele carriers.

CONCLUSIONS

Genetic factors predictive of reproductive aging are also associated with VMS, suggesting that VMS have a polygenic architecture. Further study in this area may help to identify new targets for novel VMS therapies.

Lights on MsFLASH: a review of contributions

OBJECTIVE

The Menopause Strategies: Finding Lasting Answers for Symptoms and Health clinical trials network was funded by the National Institutes of Health to find new ways to alleviate the most common, bothersome menopausal symptoms by designing and conducting multiple concurrent clinical intervention studies, accommodating a wide scope of populations and intervention strategies.

METHODS

Trials were conducted in Boston, Indianapolis, Minneapolis, Oakland, Philadelphia, and Seattle, with the Data Coordinating Center in Seattle, and were designed with standardized eligibility criteria and endpoints. Primary outcomes focused on vasomotor symptoms, sleep quality and insomnia symptoms, and vaginal symptoms. Secondary outcomes included quality of life, sexual function, and mood.

RESULTS

We completed five randomized clinical trials and three ancillary studies, testing nine interventions in over 1,300 women and collecting nearly 16,000 bio-specimens. Escitalopram, venlafaxine hydrochloride extended release, and low-dose estradiol diminished hot flashes by approximately 50% as compared with a 30% decrease by placebo. No benefits on vasomotor symptoms were observed with yoga or exercise compared with usual activity, nor with omega-3 supplementation compared with placebo. Cognitive behavioral therapy for insomnia reduced self-reported insomnia symptoms and improved overall sleep quality compared with menopause education control. We did not find significant benefit from a vaginal estradiol tablet or a vaginal moisturizer compared with placebo tablet and gel in diminishing the severity of vaginal symptoms.

CONCLUSIONS

The MsFLASH trials contributed substantially to our understanding of bothersome menopausal symptom treatment. It is important that clinicians counseling women about available treatment options consider all therapies-both nonhormonal and hormonal.

Effect of sulpiride on menopausal hot flashes: a randomized, double-blind, placebo-controlled clinical trial

Low doses of sulpiride have been used off-label to treat menopausal hot slashes in Southern Brazil despite limited scientific evidence. This randomized controlled trial aimed at assessing the effects of sulpiride as compared to placebo on the frequency and severity of hot flashes. Postmenopausal women, aged 47-62, were recruited from the Menopause Clinic at Hospital de Clínicas de Porto Alegre, Rio Grande do Sul, Brazil, between March 2016 and January 2017. After a baseline assessment of 4 weeks, women were included if they had at least a mean of five moderate to severe hot flashes per day and then randomized to receive for 8 weeks either placebo (n= 14) or sulpiride 50 mg/d (n= 14). The number and severity of hot flashes were evaluated after the 8-week intervention. A generalized estimating equations (GEE) model with Bonferroni correction was used to simultaneously assess the frequency and severity of hot flashes. Baseline frequency and severity of hot flashes/day were similar in both groups. Sulpiride significantly reduced the total weekly mean of hot flash frequency (GEE, p_interaction=.019) and the total weekly mean of severity scores (GEE, p_interaction=.09, p_group=.006, p_time≤.0001) after 4 and 8 weeks of treatment. Treatment with sulpiride 50 mg/d significantly reduced the frequency and severity of hot flashes. Further studies are needed to confirm its benefits and related mechanisms of action.

Urtica dioica in comparison with placebo and acupuncture: A new possibility for menopausal hot flashes: A randomized clinical trial

OBJECTIVES

The purpose of this research was to investigate the effect of Urtica dioica in comparison with placebo, acupuncture and combined therapy on hot flashes and quality of life in postmenopausal women.

METHODS

In a double-blinded randomized controlled trial, patients were treated for 7 weeks then followed up 4 weeks. Seventy-two postmenopausal women who reported at least 20 hot flashes attacks per week were randomly allocated into one of the 4 groups of Urtica dioica 450 mg/day and acupuncture 11 sessions (A), acupuncture and placebo (B), sham acupuncture and Urtica dioica (C), and sham acupuncture and placebo (D). The primary outcomes were the change in hot flashes score from baseline to the end of treatment and follow up; and the change in the quality of life (MENQOL) from baseline to the end of treatment. Secondary outcomes included changes in FSH, LH, and ESTRADIOL levels from baseline to the end of treatment. The trial was conducted from October 2017 to July 2018 in Acupuncture clinic of a teaching hospital in Iran.

RESULTS

A total of 72 women 45-60 years old were enrolled, and 68 were included in the analyses. The median (IQR) hot flashes score decreased in the A group by 20.2 (31.7) and 21.1 (25.1), B group by 19 (18) and 17.3 (27), C group by 14.6 (25.4) and 20.8 (13), and D group by 1.6 (11.6) and 1 (13.3) at the end of treatment and follow up (P < 0.0001, P < 0.0001); no significant difference between A, B and C groups. The mean (SD) of MENQOL score decreased in the A group by 42.6 (21.1), B group by 40.7 (29.8), C group by 37.8 (26.8) and D group by 9.8 (14.3) at the end of treatment (P = 0.001); no significant difference between A, B and C groups.

CONCLUSIONS

Urtica dioica can decrease menopausal hot flashes and increase the quality of life of postmenopausal women better than placebo-sham control but same as acupuncture. The combination of Urtica dioica and acupuncture did not add to the effects of those therapies.

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.

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

Vasomotor symptoms (VMS; or hot flashes) plague millions of reproductive-aged men and women who have natural or iatrogenic loss of sex steroid production. Many affected individuals are left without treatment options because of contraindications to hormone replacement therapy and the lack of equally effective nonhormonal alternatives. Moreover, development of safer, more effective therapies has been stymied by the lack of an animal model that recapitulates the hot-flash phenomenon and enables direct testing of hypotheses regarding the pathophysiology underlying hot flashes. To address these problems, we developed a murine model for hot flashes and a comprehensive method for measuring autonomic and behavioral thermoregulation in mice. We designed and constructed an instrument called a thermocline that produces a thermal gradient along which mice behaviorally adapt to a thermal challenge to their core body temperature set point while their thermal preference over time is tracked and recorded. We tested and validated this murine model for VMS by administration of a TRPV1 agonist and a neurokinin B receptor agonist, capsaicin and senktide, respectively, to unrestrained mice and observed their autonomic and behavioral responses. Following both treatments, the mice exhibited a VMS-like response characterized by a drop in core body temperature and cold-seeking behavior on the thermocline. Senktide also caused a rise in tail skin temperature and increased Fos expression in the median preoptic area, a hypothalamic temperature control center. This dynamic model may be used to fully explore the cellular and molecular bases for VMS and to develop and test new therapeutic options.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.