Alleviation of thermoregulatory dysfunction with the new serotonin and norepinephrine reuptake inhibitor desvenlafaxine succinate in ovariectomized rodent models

The impact of 17β-estradiol on the estrogen-deficient female brain: from mechanisms to therapy with hot flushes as target symptoms

Sex steroids are essential for whole body development and functions. Among these steroids, 17β-estradiol (E2) has been known as the principal "female" hormone. However, E2's actions are not restricted to reproduction, as it plays a myriad of important roles throughout the body including the brain. In fact, this hormone also has profound effects on the female brain throughout the life span. The brain receives this gonadal hormone from the circulation, and local formation of E2 from testosterone via aromatase has been shown. Therefore, the brain appears to be not only a target but also a producer of this steroid. The beneficial broad actions of the hormone in the brain are the end result of well-orchestrated delayed genomic and rapid non-genomic responses. A drastic and steady decline in circulating E2 in a female occurs naturally over an extended period of time starting with the perimenopausal transition, as ovarian functions are gradually declining until the complete cessation of the menstrual cycle. The waning of endogenous E2 in the blood leads to an estrogen-deficient brain. This adversely impacts neural and behavioral functions and may lead to a constellation of maladies such as vasomotor symptoms with varying severity among women and, also, over time within an individual. Vasomotor symptoms triggered apparently by estrogen deficiency are related to abnormal changes in the hypothalamus particularly involving its preoptic and anterior areas. However, conventional hormone therapies to "re-estrogenize" the brain carry risks due to multiple confounding factors including unwanted hormonal exposure of the periphery. In this review, we focus on hot flushes as the archetypic manifestation of estrogen deprivation in the brain. Beyond our current mechanistic understanding of the symptoms, we highlight the arduous process and various obstacles of developing effective and safe therapies for hot flushes using E2. We discuss our preclinical efforts to constrain E2's beneficial actions to the brain by the DHED prodrug our laboratory developed to treat maladies associated with the hypoestrogenic brain.

Compound of Cynanchum wilfordii and Humulus lupulus L. Ameliorates Menopausal Symptoms in Ovariectomized Mice

Cynanchum wilfordii and Humulus lupulus L. have been used for their various pharmacological properties in South Korea as a traditional medicine or health functional food, respectively, and their intake may relieve menopausal symptoms. The purpose of current study was to determine the effect of compound of Cynanchum wilfordii and Humulus lupulus L. (CWHL) in menopausal symptoms of ovariectomized (OVX) mice. OVX mice received CWHL or caudatin (an active ingredient of CWHL) once daily for 7 weeks. Values for hypothalamic serotonin (5-HT), dopamine, norepinephrine, estrogen receptor (ER)-β, 5-HT1A, and 5-HT2A were significantly enhanced, while value for hypothalamic monoamine oxidase A was reduced in CWHL and caudatin groups compared with the OVX group. CWHL and caudatin significantly reduced tail skin temperature and rectal temperature of OVX mice through partial recovering of the levels of serum estrogen, nitric oxide, follicle-stimulating hormone, luteinizing hormone, and receptor-activator of the NF-κB ligand (RANKL). Moreover, CWHL and caudatin improved bone mineral density via decreasing levels of serum RANKL, tartrate-resistant acid phosphatase, and collagen type 1 cross-linked N-telopeptide and improving levels of serum alkaline phosphatase, osteoprotegerin, and osteocalcin compared with the OVX group without adverse effects such as dyslipidemia. CWHL increased uterine ER-β levels but did not change uterus and vaginal weights. Taken together, the results indicate that CWHL may relieve menopausal symptoms by controlling depression-, hot flashes-, and osteoporosis-associated biomarkers. Therefore, we propose that CWHL might be a safe and potential candidate for management of menopause as a health functional food.

Treat more than heat-New therapeutic implications of Cimicifuga racemosa through AMPK-dependent metabolic effects

BACKGROUND

Cimicifuga racemosa extracts (CRE) have obtained a "well-established use status" in the treatment of postmenopausal (i.e., climacteric) complaints, which predominantly include vasomotor symptoms such as hot flushes and sweating, as well as nervousness, irritability, and metabolic changes. Although characteristic postmenopausal complaints are known for a very long time and the beneficial effects of CRE on climacteric symptoms are well accepted, both the pathophysiology of postmenopausal symptoms and the mechanism of action of CREs are not yet fully understood. In particular, current hypotheses suggest that changes in the α-adrenergic and serotonergic signaling pathways secondary to estrogen depletion are responsible for the development of hot flushes.

PURPOSE

Some of the symptoms associated with menopause cannot be explained by these hypotheses. Therefore, we attempted to extend our classic understanding of menopause by integrating of partly age-related metabolic impairments.

METHODS

A comprehensive literature survey was performed using the PubMed database for articles published through September 2021. The following search terms were used: (cimicifuga OR AMPK) AND (hot flush* OR hot flash* OR menopaus* OR osteoporos* OR cancer OR antioxida* OR cardiovasc*). No limits were set with respect to language, and the references cited in the articles retrieved were used to identify additional publications.

RESULTS

We found that menopause is a manifestation of the general aging process, with specific metabolic changes that aggravate menopausal symptoms, which are accelerated by estrogen depletion and associated neurotransmitter dysregulation. Cimicifuga extracts with their metabolic effects mitigate climacteric symptoms but may also modulate the aging process itself. Central to these effects are effects of CRE on the metabolic key regulator, the AMP-activated protein kinase (AMPK).

CONCLUSIONS

As an extension of this effect dimension, other off-label indications may appear attractive in the sense of repurposing of this herbal treatment.

No evidence of abnormal metabolic or inflammatory activity in the brains of patients with rheumatoid arthritis: results from a preliminary study using whole-brain magnetic resonance spectroscopic imaging (MRSI)

Introduction/objectives

Many individuals with rheumatoid arthritis (RA) report persistent fatigue even after management of peripheral disease activity. This study used whole-brain magnetic resonance spectroscopic imaging (MRSI) to investigate whether abnormal inflammatory activity in the central nervous system may be associated with such symptoms. We hypothesized that RA patients would show higher brain choline (CHO), myo-inositol (MI), and lactate (LAC), and higher brain temperature than healthy controls. We further hypothesized that the metabolite levels would be positively correlated with self-reported fatigue.

Method

Thirteen women with RA provided fatigue severity ratings and underwent whole-brain MRSI and a joint examination. Thirteen healthy controls (HC) provided comparison imaging and fatigue data. CHO, MI, LAC, and brain temperature in 47 brain regions were contrasted between groups using independent-samples t tests. Significant differences were determined using a false discovery rate (FDR)-adjusted p value threshold of ≤ 0.0023. Secondary analyses obtained correlations between imaging and clinical outcomes in the RA group.

Results

No brain metabolic differences were identified between the groups. In the RA group, fatigue severity was positively correlated with CHO in several brain regions—most strongly the right frontal lobe (r_s = 0.823, p < 0.001). MI was similarly correlated with fatigue, particularly in the right calcarine fissure (r_s = 0.829, p < 0.001). CHO in several regions was positively correlated with joint swelling and tenderness.

Conclusions

We conclude that abnormal brain metabolites are not a common feature of RA, but may been seen in patients with persistent fatigue or disease activity after conventional treatment.

Key Points • Whole-brain magnetic resonance spectroscopy revealed no metabolic abnormalities in the brain in patients with rheumatoid arthritis. • Brain choline levels were correlated with fatigue severity reported by RA patients and with peripheral joint swelling and tenderness. • Brain myo-inositol levels were similarly correlated with fatigue severity in RA patients.

Electronic supplementary material

The online version of this article (10.1007/s10067-019-04923-5) contains supplementary material, which is available to authorized users.

Treatment with an orally bioavailable prodrug of 17β-estradiol alleviates hot flushes without hormonal effects in the periphery

Estrogen deprivation has a profound effect on the female brain. One of the most obvious examples of this condition is hot flushes. Although estrogens relieve these typical climacteric symptoms, many women do not want to take them owing to unwanted side-effects impacting, for example, the uterus, breast and blood. Therefore, there is a need for developing safer estrogen therapies. We show here that treatment with 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED), a novel brain-targeting bioprecursor prodrug of the main human estrogen, 17β-estradiol, alleviates hot flushes in rat models of thermoregulatory dysfunction of the brain. Oral administration of DHED elicits a significant reduction of tail skin temperature (TST) rise representing hot flushes in the morphine-dependent ovariectomized rat model and results in the restoration of estrogen deprivation-induced loss of diurnal rhythm in TST. These beneficial effects occur without detrimental peripheral hormonal exposure; thus, the treatment avoids potentially harmful stimulation of estrogen-sensitive peripheral organs, including the uterus and the anterior pituitary, or the proliferation of MCF-7a breast cancer cell xenografts. Our promising preclinical assessments warrant further considerations of DHED for the development of a brain-selective 17β-estradiol therapy to relieve hot flushes without undesirable peripheral side-effects.

A potentially functional variant in the serotonin transporter gene is associated with premenopausal and perimenopausal hot flashes

OBJECTIVE

An increase in the use of selective serotonin reuptake inhibitors (SSRIs) and/or serotonin-norepinephrine reuptake inhibitors (SNRIs) to relieve menopausal hot flashes (HFs) has been observed recently. However, response to them has been heterogeneous. We hypothesized that this heterogeneity might be partially attributed to genetic variations in genes encoding the serotonin and/or norepinephrine transporters (SLC6A4 and SLC6A2). As a first step in testing the role of genetics in response to SSRIs/SNRIs, we examined the association between HFs and genetic variants within these two genes.

METHODS

We tested 29 haplotype-tagging single nucleotide polymorphisms within SLC6A4 and SLC6A2 for their association with HFs separately for European-American (396 cases and 392 controls) and African-American (125 cases and 81 controls) premenopausal and perimenopausal women.

RESULTS

We found that the minor allele of SLC6A4_rs11080121 was associated with protection against HFs (odds ratio, 0.75; 95% CI, 0.60-0.94) only in European-American women. Bioinformatics analyses indicated that rs11080121 is fully correlated with rs1042173 in the 3' untranslated region of SLC6A4. The minor allele of rs1042173 seems to disrupt a conserved binding site for hsa-miR-590-3p microRNA.

CONCLUSIONS

Disruption of a microRNA binding site leads to higher expression of SLC6A4, higher expression of SLC6A4 leads to depletion of serotonin in synaptic clefts, and depletion of serotonin triggers the presynaptic autoreceptor feedback mechanism to produce more serotonin, which is protective against HFs. This is the first study to test the association between HFs in both European-American and African-American premenopausal and perimenopausal women and genetic variants in two neurotransmitter transporter genes, SLC6A2 and SLC6A4. This information can be used in tailoring the pharmaceutical use of SSRIs/SNRIs for HF relief.

Gq-mER signaling has opposite effects on hypothalamic orexigenic and anorexigenic neurons

Two populations of cells within the hypothalamus exert opposite actions on food intake: proopiomelanocortin (POMC) neurons decrease it, while neuropeptide Y (NPY)/agouti-related peptide (AgRP) neurons increase it. 17β-Estradiol (E2) is a potent anorexigenic hormone that exerts both genomic and non-genomic, rapid actions on these metabolic neurons. This review focuses on the rapid membrane effects of E2 in both POMC and NPY/AgRP neurons and how these combined effects mediate the anorexigenic effects of this steroid.

Modulation of body temperature and LH secretion by hypothalamic KNDy (kisspeptin, neurokinin B and dynorphin) neurons: a novel hypothesis on the mechanism of hot flushes

Despite affecting millions of individuals, the etiology of hot flushes remains unknown. Here we review the physiology of hot flushes, CNS pathways regulating heat-dissipation effectors, and effects of estrogen on thermoregulation in animal models. Based on the marked changes in hypothalamic kisspeptin, neurokinin B and dynorphin (KNDy) neurons in postmenopausal women, we hypothesize that KNDy neurons play a role in the mechanism of flushes. In the rat, KNDy neurons project to preoptic thermoregulatory areas that express the neurokinin 3 receptor (NK3R), the primary receptor for NKB. Furthermore, activation of NK₃R in the median preoptic nucleus, part of the heat-defense pathway, reduces body temperature. Finally, ablation of KNDy neurons reduces cutaneous vasodilatation and partially blocks the effects of estrogen on thermoregulation. These data suggest that arcuate KNDy neurons relay estrogen signals to preoptic structures regulating heat-dissipation effectors, supporting the hypothesis that KNDy neurons participate in the generation of flushes.

A selective membrane estrogen receptor agonist maintains autonomic functions in hypoestrogenic states

It is well known that many of the actions of estrogens in the central nervous system are mediated via intracellular receptor/transcription factors that interact with steroid response elements on target genes. But there is also a compelling evidence for the involvement of membrane estrogen receptors in hypothalamic and other CNS functions. However, it is not well understood how estrogens signal via membrane receptors, and how these signals impact not only membrane excitability but also gene transcription in neurons. Indeed, it has been known for sometime that estrogens can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane delimited events. In addition, estrogens can affect second messenger systems including calcium mobilization and a plethora of kinases within neurons to alter cellular functions. Therefore, this brief review will summarize our current understanding of rapid membrane-initiated and intracellular signaling by estrogens in the hypothalamus, the nature of receptors involved and how these receptors contribute to maintenance of homeostatic functions, many of which go awry in menopausal states. This article is part of a Special Issue entitled Hormone Therapy.

Non-hormonal management of vasomotor symptoms

Vasomotor symptoms are the most common indication for the prescription of hormone replacement therapy since it is effective in over 80% of cases. In 1995, 37% of American women took hormone replacement therapy, principally for this purpose. However, following the publication of results from the Women's Health Initiative, as many as half of these women in the US and in the UK and New Zealand discontinued hormone therapy. Discontinuation of estrogen is often accompanied by a return of vasomotor symptoms; however, only a small number (18%) of women report restarting hormone therapy. Alternatives are available, but limited knowledge on etiology and mechanisms of hot flushing represents a major obstacle for the development of new, targeted, non-hormonal treatments, and no current alternatives are as effective as estrogen.

Maintenance of the efficacy of desvenlafaxine in menopausal vasomotor symptoms: a 1-year randomized controlled trial

OBJECTIVE

The purpose of this study was to assess the 1-year maintenance of the efficacy of desvenlafaxine 100 mg/day (administered as desvenlafaxine succinate) established on week 12 in a 1-year, double-blind, randomized, placebo-controlled trial in postmenopausal women seeking treatment of bothersome vasomotor symptoms.

METHODS

Primary efficacy endpoints were changes in hot flush (HF) frequency and severity on weeks 12, 26, and 52 in an efficacy substudy population (≥50 moderate and severe HFs per week at baseline). Secondary endpoints were Greene climacteric scale, patient global impression symptom rating, and patient global impression of change scores (weeks 12, 26, and 52) for the main study efficacy population. Safety was assessed throughout the trial.

RESULTS

The mean baseline HF frequency (efficacy substudy population, n = 365) was 12 moderate and severe HFs per day; the mean baseline severity score was 2.4. At 1 year, women treated with desvenlafaxine maintained the efficacy established on week 12. Desvenlafaxine reduced HF frequency by 7.47 moderate and severe HFs per day on week 12 (adjusted mean difference from placebo, -2.48; 95% CI, -3.47 to -1.50; P < 0.001) and by 7.70 moderate and severe HFs per day on month 12 (adjusted mean difference from placebo, -2.86; 95% CI, -4.14 to -1.57; P < 0.001). Desvenlafaxine reduced the mean severity score by 0.63 on week 12 (placebo, -0.30; P < 0.001) and by 0.75 on month 12 (placebo, -0.44; P = 0.003). Reductions in Greene Climacteric Scale total score (main study efficacy population, n = 1,950) were significantly greater for desvenlafaxine than for placebo on months 3, 6, and 12 (all P < 0.001). Treatment-emergent adverse event rates were 84% for desvenlafaxine and 79% for placebo (P = 0.006). Full safety results are reported separately.

CONCLUSIONS

The treatment efficacy of desvenlafaxine 100 mg/day achieved on week 12 in postmenopausal women with vasomotor symptoms is maintained for 1 year.

Role for kisspeptin/neurokinin B/dynorphin (KNDy) neurons in cutaneous vasodilatation and the estrogen modulation of body temperature

Estrogen withdrawal in menopausal women leads to hot flushes, a syndrome characterized by the episodic activation of heat dissipation effectors. Despite the extraordinary number of individuals affected, the etiology of flushes remains an enigma. Because menopause is accompanied by marked alterations in hypothalamic kisspeptin/neurokinin B/dynorphin (KNDy) neurons, we hypothesized that these neurons could contribute to the generation of flushes. To determine if KNDy neurons participate in the regulation of body temperature, we evaluated the thermoregulatory effects of ablating KNDy neurons by injecting a selective toxin for neurokinin-3 expressing neurons [NK(3)-saporin (SAP)] into the rat arcuate nucleus. Remarkably, KNDy neuron ablation consistently reduced tail-skin temperature (T(SKIN)), indicating that KNDy neurons facilitate cutaneous vasodilatation, an important heat dissipation effector. Moreover, KNDy ablation blocked the reduction of T(SKIN) by 17β-estradiol (E(2)), which occurred in the environmental chamber during the light phase, but did not affect the E(2) suppression of T(SKIN) during the dark phase. At the high ambient temperature of 33 °C, the average core temperature (T(CORE)) of ovariectomized (OVX) control rats was significantly elevated, and this value was reduced by E(2) replacement. In contrast, the average T(CORE) of OVX, KNDy-ablated rats was lower than OVX control rats at 33 °C, and not altered by E(2) replacement. These data provide unique evidence that KNDy neurons promote cutaneous vasodilatation and participate in the E(2) modulation of body temperature. Because cutaneous vasodilatation is a cardinal sign of a hot flush, these results support the hypothesis that KNDy neurons could play a role in the generation of flushes.

Membrane-initiated actions of estradiol that regulate reproduction, energy balance and body temperature

It is well known that many of the actions of estrogens in the central nervous system are mediated via intracellular receptor/transcription factors that interact with steroid response elements on target genes. However, there now exists compelling evidence for membrane estrogen receptors in hypothalamic and other brain neurons. But, it is not well understood how estrogens signal via membrane receptors, and how these signals impact not only membrane excitability but also gene transcription in neurons. Indeed, it has been known for sometime that estrogens can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane delimited events. In addition, estrogens can affect second messenger systems including calcium mobilization and a plethora of kinases to alter cell signaling. Therefore, this review will consider our current knowledge of rapid membrane-initiated and intracellular signaling by estrogens in the hypothalamus, the nature of receptors involved and how they contribute to homeostatic functions.

Treatment options for vasomotor symptoms in menopause: focus on desvenlafaxine

Vasomotor symptoms (VMS), including hot flashes and night sweats, occur in as many as 68.5% of women as a result of menopause. While the median duration of these symptoms is 4 years, approximately 10% of women continue to experience VMS as many as 12 years after their final menstrual period. As such, VMS have a significant impact on the quality of life and overall physical health of women experiencing VMS, leading to their pursuance of treatment to alleviate these symptoms. Management of VMS includes lifestyle modifications, some herbal and vitamin supplements, hormonal therapies including estrogen and tibolone, and nonhormonal therapies including clonidine, gabapentin, and some of the serotonin and serotonin-norepinephrine reuptake inhibitors. The latter agents, including desvenlafaxine, have been the focus of increased research as more is discovered about the roles of serotonin and norepinephrine in the thermoregulatory control system. This review will include an overview of VMS as they relate to menopause. It will discuss the risk factors for VMS as well as the proposed pathophysiology behind their occurrence. The variety of treatment options for VMS will be discussed. Focus will be given to the role of desvenlafaxine as a treatment option for VMS management.

S-equol and the fermented soy product SE5-OH containing S-equol similarly decrease ovariectomy-induced increase in rat tail skin temperature in an animal model of hot flushes

OBJECTIVE

The aim of this study was to compare the effect of SE5-OH, a fermented soy product containing S-equol, with purified S-equol on hot flushes in an ovariectomized rat model.

METHODS

Eleven-week-old female Sprague-Dawley rats were assigned to either the sham group (vehicle; n = 30) or one of four ovariectomized groups: control (vehicle; n = 30), conjugated equine estrogens (CEE; 6.0 mg kg(-1) d(-1) CEE; n = 10), SE5-OH (2,000 mg kg(-1) d(-1) SE5-OH containing 11.7 mg kg(-1) d(-1) as S-equol; n = 30), and S-equol (11.7 mg kg(-1) d(_1) S-equol; n = 30). Three days after sham operation or ovariectomy, animals were treated once daily for 38 days. Tail skin temperature (TST) was assessed on days 21, 28, and 35 after surgery. Plasma estradiol and follicle-stimulating hormone levels and uterine weight and uteri histology were evaluated at the end of treatment.

RESULTS

The rise in TST resulting from ovariectomy was inhibited by CEE, SE5-OH, and S-equol. Compared with the control, TST was decreased by 68.9% and 86.2% in SE5-OH group on days 21 and 28, respectively (P = 0.014, 0.020), and by 60.1% and 89.1% in S-equol group, respectively (P = 0.038, 0.016). Unlike in the CEE group, plasma estradiol and follicle-stimulating hormone levels, uterine weight, epithelial height, stromal expansion, and myometrial thickness were not affected in SE5-OH and S-equol groups.

CONCLUSIONS

The results of this animal model of hot flushes suggest that S-equol is one of the primary components of SE5-OH and that both SE5-OH and S-equol represent promising alternatives for the treatment of menopausal symptoms. Clinical research is needed to confirm these findings.

Physiological consequences of membrane-initiated estrogen signaling in the brain

Many of the actions of 17beta-estradiol (E2) in the central nervous system (CNS) are mediated via the classical nuclear steroid receptors, ER(alpha) and ERbeta, which interact with the estrogen response element to modulate gene expression. In addition to the nuclear-initiated estrogen signaling, E2 signaling in the brain can occur rapidly within minutes prior to any sufficient effects on transcription of relevant genes. These rapid, membrane-initiated E2 signaling mechanisms have now been characterized in many brain regions, most importantly in neurons of the hypothalamus and hippocampus. Furthermore, our understanding of the physiological effects of membrane-initiated pathways is now a major field of interest in the hypothalamic control of reproduction, energy balance, thermoregulation and other homeostatic functions as well as the effects of E2 on physiological and pathophysiological functions of the hippocampus. Membrane signaling pathways impact neuronal excitability, signal transduction, cell death, neurotransmitter release and gene expression. This review will summarize recent findings on membrane-initiated E2 signaling in the hypothalamus and hippocampus and its contribution to the control of physiological and behavioral functions.

An improved method for recording tail skin temperature in the rat reveals changes during the estrous cycle and effects of ovarian steroids

In the rat, tail skin vasomotion is a primary heat loss mechanism that can be monitored by changes in tail skin temperature (T(SKIN)). Previous studies showed that ovariectomy and estrogen replacement modify T(SKIN) in the rat. Based on these findings, the ovariectomized (OVX) rat has been used as a model to study the mechanisms and treatment of menopausal hot flushes. It is not known, however, if T(SKIN) changes across the estrous cycle in intact rats. Here, we describe an improved method for monitoring T(SKIN) in freely moving rats using a SubCue Mini datalogger mounted on the ventral surface of the tail. This method is noninvasive, cost-effective, and does not require restraints or tethering. We observed a distinct pattern of T(SKIN) across the estrous cycle characterized by low T(SKIN) on proestrous night. To determine whether this pattern was secondary to secretion of ovarian steroids, we monitored the thermoregulatory effects of 17β-estradiol (E(2)) and E(2) plus progesterone, administered via SILASTIC capsules to OVX rats. E(2) treatment of OVX rats significantly reduced T(SKIN) in the dark phase from 2 to 21 d after hormone treatment. The T(SKIN) of E(2)-treated OVX animals was not significantly different from OVX rats receiving E(2) plus progesterone. These data provide evidence that the reduction in T(SKIN) on proestrous night was secondary to elevated levels of ovarian estrogens. This study provides the first description of T(SKIN) changes with the estrous cycle and supports the role of estrogens in normal thermoregulation in the rat.

Contribution of a membrane estrogen receptor to the estrogenic regulation of body temperature and energy homeostasis

The hypothalamus is a key region of the central nervous system involved in the control of homeostasis, including energy and core body temperature (Tc). 17β-Estradiol (E2) regulates Tc, in part, via actions in the basal hypothalamus and preoptic area. E2 primarily controls hypothalamic functions via the nuclear steroid receptors, estrogen receptor α/β. However, we have previously described an E2-responsive, Gq-coupled membrane receptor that reduces the postsynaptic inhibitory γ-aminobutyric acid-ergic tone and attenuates postovariectomy body weight gain in female guinea pigs through the administration of a selective Gq-mER ligand, STX. To determine the role of Gq-mER in regulating Tc, energy and bone homeostasis, ovariectomized female guinea pigs, implanted ip with temperature probes, were treated with STX or E2 for 7-8 wk. Tc was recorded for 4 wk, whereas food intake and body weight were monitored daily. Bone density and fat accumulation were determined postmortem. Both E2 and STX significantly reduced Tc in the females compared with controls. STX, similar to E2, reduced food intake and fat accumulation and increased tibial bone density. Therefore, a Gq-mER-coupled signaling pathway appears to be involved in maintaining homeostatic functions and may constitute a novel therapeutic target for treatment of hypoestrogenic symptoms.

Hot flushes: are there effective alternatives to estrogen?

Hot flushes are the most common indication for the prescription of hormone replacement therapy (HRT) since it is effective in over 80% of cases. In 1995, 37% of American women took HRT, principally for this purpose. However, over the last five years, publications such as those from the Women's Health Initiative (WHI) have caused concern among women since they perceive that the risks outweigh the benefits. Following this publication, half of the women taking HRT in the UK, USA and New Zealand discontinued HRT. With the discontinuation of estrogen many women re-developed hot flushes; however only a small number (18%) of women report restarting hormone therapy. The majority of these (76%) for the recurrence of severe hot flushes or night sweats. Alternatives are available, but limited knowledge on aetiology and mechanisms of hot flushing represents a major obstacle for the development of new, targeted, non-hormonal treatments, and no current alternatives are as effective as estrogen.

Management of menopause-associated vasomotor symptoms: Current treatment options, challenges and future directions

Hot flashes are one of the most common and distressing symptoms associated with menopause, occurring in more than 75% of postmenopausal women. They are especially problematic in breast cancer patients since some breast cancer therapies can induce hot flashes. For mild hot flashes, it is proposed that behavioral modifications are the first step in management. Hormonal therapies, including estrogens and progestogens, are the most well known effective agents in relieving hot flashes; however, the safety of these agents is controversial. There is an increasing amount of literature on nonhormonal agents for the treatment of hot flashes. The most promising data regard newer antidepressant agents such as venlafaxine, which reduces hot flashes by about 60%. Gabapentin is another nonhormonal agent that is effective in reducing hot flashes. While many complimentary therapies, including phytoestrogens, black cohosh, and dehydroepiandrosterone, have been explored for the treatment of hot flashes; none can be recommended at this time. Furthermore, there is a lack of strong evidence to support exercise, yoga, or relaxation for the treatment of hot flashes. Paced respirations and hypnosis appear to be promising enough to warrant further investigation. Another promising nonpharmacological therapy, currently under investigation, involves a stellate ganglion block.

Discovery of WAY-260022, a Potent and Selective Inhibitor of the Norepinephrine Transporter

The potency and selectivity of a series of 1-{(1S)-2-[amino]-1-[3-(trifluoromethoxy)phenyl]ethyl}cyclohexanol analogues are described. These compounds were prepared to improve in vitro metabolic stability and achieve brain penetration. Compound 13 (WAY-260022, NRI-022) was found to be a potent inhibitor of norepinephrine reuptake and demonstrated excellent selectivity over the serotonin and dopamine transporters. Additionally, 13 exhibited oral efficacy in a rat model of thermoregulatory dysfunction.

1-(Indolin-1-yl)-1-phenyl-3-propan-2-olamines as potent and selective norepinephrine reuptake inhibitors

Efforts to identify new selective and potent norepinephrine reuptake inhibitors (NRIs) for multiple indications by structural modification of the previous 3-(arylamino)-3-phenylpropan-2-olamine scaffold led to the discovery of a novel series of 1-(indolin-1-yl)-1-phenyl-3-propan-2-olamines (9). Investigation of the structure-activity relationships revealed that small alkyl substitution at the C3 position of the indoline ring enhanced selectivity for the norepinephrine transporter (NET) over the serotonin transporter (SERT). Several compounds bearing a 3,3-dimethyl group on the indoline ring, 9k, 9o,p, and 9s,t, exhibited potent inhibition of NET (IC(50) = 2.7-6.5 nM) and excellent selectivity over both serotonin and dopamine transporters. The best example from this series, 9p, a potent and highly selective NRI, displayed oral efficacy in a telemetric rat model of ovariectomized-induced thermoregulatory dysfunction, a mouse p-phenylquinone (PPQ) model of acute visceral pain, and a rat spinal nerve ligation (SNL) model of neuropathic pain.

Desvenlafaxine succinate: a newer antidepressant for the treatment of depression and somatic symptoms

Desvenlafaxine succinate (DVS) is one of several serotonin-norepinephrine reuptake inhibitors (SNRIs). Others are venlafaxine hydrochloride, milnacipran, and duloxetine. Desvenlafaxine has been approved by the US Food and Drug Administration (FDA) for the treatment of major depressive disorder (MDD) based on a number of randomized, placebo-controlled clinical trials. Clinical studies have investigated the efficacy of DVS in doses ranging from 50 to 400 mg/day for the treatment of MDD in adult outpatients. The effects of DVS 50 mg/day have been clearly distinguished from placebo in the reduction of MDD symptoms in such clinical trials. No additional therapeutic benefits were found at doses > 50 mg/day. The recommended dose of DVS ranges from 50 to 100 mg. Desvenlafaxine is currently the third SNRI approved by the FDA for this indication. Preliminary evidence also suggests the clinical usefulness of DVS in the treatment of vasomotor symptoms of menopause, anxiety symptoms, and painful physical symptoms. The modified pharmacokinetic and pharmacodynamic profiles of DVS differentiate this drug from the original product, venlafaxine. Significant points of difference, compared with venlafaxine, are once-daily dosing and the achievement of steady-state plasma concentrations within 4 to 5 days. To summarize, current evidence indicates that DVS has proven efficacy, acceptable safety and tolerability profiles, convenient dosing, and minimal impact on the cytochrome P450 enzyme system. A reduced risk for pharmacokinetic drug interactions is a potential advantage over other selective serotonin noradrenaline reuptake inhibitors. Desvenlafaxine succinate has demonstrated its efficacy for treating MDD but its variable efficacy, as shown in individual studies, limited long-term data, and its different risk-to-benefit ratio compared with earlier antidepressants, means that further investigation of this drug is necessary.

Structure-activity relationships of norepinephrine reuptake inhibitors with benzothiadiazine dioxide or dihydrosulfostyril cores

Two related series of selective norepinephrine reuptake inhibitors were synthesized based on 3,4-dihydro-1H-2,1,3-benzothiadiazine 2,2-dioxide or 3,4-dihydrosulfostyril cores, and screened for monoamine reuptake inhibition. Structure-activity relationships were determined for the series' in vitro potency and selectivity versus serotonin or dopamine transporter inhibition, and analogs based on both cores were identified as potent and selective NRIs. The 3,4-dihydrosulfostyril series was further tested for microsome stability, and compound 16j, which was optimized for both potency and stability, showed efficacy in an in vivo model of thermoregulatory dysfunction.

1- or 3-(3-Amino-2-hydroxy-1-phenyl propyl)-1,3-dihydro-2H-benzimidazol-2-ones: potent, selective, and orally efficacious norepinephrine reuptake inhibitors

Sequential structural modifications of the aryloxypropanamine template (e.g., atomoxetine, 2) led to a novel series of 1-(3-amino-2-hydroxy-1-phenyl propyl)-1,3-dihydro-2H-benzimidazol-2-ones as selective norepinephrine reuptake inhibitors (NRIs). In general, this series of compounds potently blocked the human norepinephrine transporter (hNET) while exhibiting selectivity at hNET against both the human serotonin (hSERT) and dopamine transporters (hDAT). Numerous compounds (e.g., 19-22) had low nonamolar hNET potency with IC(50) values of 7-10 nM and excellent selectivity (>500 fold) at hNET over hSERT and hDAT. Several compounds, such as 20 and 22, were tested in a telemetric rat model of ovariectomized-induced thermoregulatory dysfunction and were efficacious at oral doses of 3 mg/kg in reducing the tail skin temperature. In addition, compound 20 was also studied in the rat hot plate and spinal nerve ligation (SNL) models of acute and neuropathic pain, respectively, and was orally efficacious at doses of 3-10 mg/kg.

Desvenlafaxine: a new antidepressant or just another one?

Desvenlafaxine (DVS) is a serotonin-norepinephrine reuptake inhibitor (SNRI) with a different pharmacokinetic and pharmacodynamic profile to venlafaxine. It was approved in February 2008 by the United States Food and Drug Administration for the treatment of major depressive disorder (MDD) based on a number of randomized, placebo-controlled clinical trials demonstrating efficacy and safety for patients with MDD. Current evidence indicates that DVS has proven efficacy, acceptable safety and tolerability profiles, convenient once-daily dosing and minimal impact on cytochrome P450 enzyme system and adverse event-prone neuroreceptors. As with all monoamine-based antidepressants, DVS has mixed efficacy results from individual studies, unestablished dosing strategies and limited long-term data, and comparative efficacy/safety with other existing antidepressants should be further investigated. Preliminary evidence also suggests the clinical usefulness of DVS in the treatment of vasomotor symptoms of menopause, anxiety symptoms and painful physical symptoms, although only MDD is the approved indication.

What causes hot flushes? The neuroendocrine origin of vasomotor symptoms in the menopause

Vasomotor symptoms (VMS) such as hot flushes and night sweats are frequently encountered during menopause and can greatly reduce the quality of life. These symptoms are causally related to decreasing estradiol concentrations, mainly in the serum and subsequently also in the hypothalamic temperature regulating centre. The lack of estrogens alters neurotransmitter activity, especially in the serotonergic and noradrenergic pathways. Because sex steroids act as potent neuromodulators, the substitution of ovarian sex steroids by hormone replacement therapy is the most effective treatment option for VMS. When contraindications exist for the use of sex steroids, steroid-free drugs are a possible alternative. A better understanding of the physiology of thermoregulation, thermoregulatory dysfunction and adaptive processes of the brain may facilitate the development of new therapeutic approaches. Such drugs could then be used to treat vasomotor disorders even when the use of steroid hormones is contraindicated. This review article summarises our knowledge on the mechanisms of temperature regulation and describes deviations from this regulation during altered sex steroid conditions. Our current knowledge on neuroendocrinology of thermoregulation may serve as a basis for the use of steroid-free pharmacological intervention.

Menopausal hot flushes revisited

Vasomotor symptoms are generally recognized as one of the most common symptoms, or signs, of the menopause, together with menstrual cycle changes. The etiology of hot flushes is unknown, although several mechanisms have been implicated. The reduction in hot flushes with estrogen replacement therapy suggests a hormonal etiology. However, the levels of estrogens do not appear to correlate with hot flushes. It seems more likely that the rate of change of plasma estrogen concentrations influences the thermoregulatory system via the hypothalamus. During the past few decades, remedies for the treatment of hot flushes have advanced from simple sedatives and purgatives to the use of ovarian extracts and, finally, to pharmacological estrogen preparations. In view of the contraindications and side-effects of estrogens and progestogens in postmenopausal women, however, there is a need to consider treatments other than hormone replacement for the relief of hot flushes.

Desvenlafaxine for the treatment of vasomotor symptoms associated with menopause: a double-blind, randomized, placebo-controlled trial of efficacy and safety

OBJECTIVE

The objective of the study was to assess the efficacy and safety of desvenlafaxine (administered as desvenlafaxine succinate) for the treatment of vasomotor symptoms.

STUDY DESIGN

This was a 26 week, double-blind, placebo-controlled trial of 567 postmenopausal women (mean age, 53.7 years; time since natural menopause, 4.8 years) experiencing 50 or more hot flushes (HFs) per week, randomly assigned to desvenlafaxine (100 or 150 mg) or placebo. Change from baseline in average daily number of moderate to severe HFs and average daily HF severity were compared with placebo at weeks 4, 12, and 26.

RESULTS

A significantly greater decrease from baseline in number of HFs occurred at weeks 4 and 12 with 100 and 150 mg desvenlafaxine compared with placebo (week 12 reductions: 60%, 66%, and 47%, respectively; all P < or = .002). Only the 150 mg dose showed significant improvement from baseline at 26 weeks compared with placebo (week 26 reductions: 61%, 69%, and 51%, respectively), although the study was not powered to demonstrate efficacy beyond the initial 12 weeks of therapy. The average daily severity decreased significantly more at weeks 4 and 12 with desvenlafaxine compared with placebo (all P < or = .002). Significantly more desvenlafaxine-treated subjects than placebo-treated subjects discontinued because of adverse events during week 1 only.

CONCLUSION

Desvenlafaxine is an effective treatment for menopausal HFs.

A double-blind, randomly assigned, placebo-controlled study of desvenlafaxine efficacy and safety for the treatment of vasomotor symptoms associated with menopause

OBJECTIVE

The objective of the study was to assess the efficacy and safety of desvenlafaxine (administered as desvenlafaxine succinate) for menopausal vasomotor symptoms.

STUDY DESIGN

Postmenopausal women (n = 458) experiencing 50 or more moderate to severe hot flushes per week received desvenlafaxine 100 or 150 mg/d, with titration at therapy initiation, or placebo. Hot flush number and severity were assessed at weeks 4 and 12. Safety data were collected throughout the trial.

RESULTS

Desvenlafaxine 100 and 150 mg/d significantly reduced the number of hot flushes compared with placebo at weeks 4 and 12 (all P < or = .012), achieving 65.4% and 66.6% reductions from baseline at week 12, respectively (placebo, 50.8%). Hot flush severity and number of nighttime awakenings were significantly reduced at both time points (all P < or = .048). Desvenlafaxine groups reported significantly more adverse events compared with placebo during week 1 only. No difference in discontinuations because of adverse events was observed.

CONCLUSION

Desvenlafaxine is an effective nonhormonal treatment for menopausal hot flushes. Dose titration improves initial tolerability.

Simultaneous telemetric monitoring of tail-skin and core body temperature in a rat model of thermoregulatory dysfunction

Temperature dysfunction, clinically described as hot flashes/flushes and night sweats, commonly occur in women transitioning through menopause. Research in this field has yet to fully elucidate the biological underpinnings explaining this dysfunction. The need to develop animal models that can be used to study hormone-dependent temperature regulation is essential to advancing this scientific area. Development of telemetric transmitters for monitoring tail-skin (TST) and core body (CBT) temperatures for animal research has increased the accuracy of data by reducing extraneous factors associated with previous methods. However, until recently, TST and CBT could not be simultaneously measured telemetrically within the same animal. In this report, new dual temperature monitoring transmitters were validated by simultaneously evaluating them with the single measurement transmitters using the ovariectomized (OVX) rat thermoregulatory dysfunction model. A major advantage of measuring TST and CBT in the same animal is the ability to relate temporal changes on these two temperature parameters. Comparative experimentation was performed by single administration of clonidine (alpha(2) adrenergic agonist), MDL-100907 (5-HT(2a) antagonist), or a 7-day treatment of 17alpha-ethinyl estradiol (EE). Clonidine caused decreases in TST and CBT, MDL-100907 caused increases in TST while decreasing CBT, and EE caused decreases in TST with minor CBT decreases only at the higher dose. Data from either probe type showed similar results on temperature parameters regardless of transmitter used. These findings support the use of the new dual temperature transmitters and should enhance the quality and interpretation of data being generated in thermoregulation studies.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 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; alcohol and drugs of abuse; 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.

ICI 182,780 penetrates brain and hypothalamic tissue and has functional effects in the brain after systemic dosing

Previous reports suggest the antiestrogen ICI 182,780 (ICI) does not cross the blood-brain barrier (BBB). However, this hypothesis has never been directly tested. In the present study, we tested whether ICI crosses the BBB, penetrates into brain and hypothalamic tissues, and affects known neuroendocrine functions in ovariectomized rats. Using HPLC with mass spectrometry, ICI (1.0 mg/kg.d, 3 d) was detected in plasma and brain and hypothalamic tissues for up to 24 h with maximum concentrations of 43.1 ng/ml, and 31.6 and 38.8 ng/g, respectively. To evaluate antiestrogenic effects of ICI in the brain after systemic dosing, we tested its ability to block the effect of 17 alpha-ethinyl estradiol (EE) (0.3 mg/kg, 8 d) on tail-skin temperature abatement in the morphine-dependent model of hot flush and on body weight change. In the morphine-dependent model, EE abated 64% of the naloxone-induced tail-skin temperature increase. ICI pretreatment (1.0, 3.0 mg/kg.d) dose dependently inhibited this effect. ICI (3.0 mg/kg.d) alone showed estrogenic-like actions, abating 30% the naloxone-induced flush. In body weight studies, EE-treated rats weighed 58.5 g less than vehicle-treated rats after 8 d dosing. This effect was partially blocked by ICI (3.0 mg/kg.d) pretreatment. Similar to EE treatment, rats receiving 1.0 or 3.0 mg/kg.d ICI alone showed little weight gain compared with vehicle-treated controls. Thus, ICI crosses the BBB, penetrates into brain and hypothalamic tissues, and has both antiestrogenic and estrogenic-like actions on neuroendocrine-related functions.

Understanding the pathophysiology of vasomotor symptoms (hot flushes and night sweats) that occur in perimenopause, menopause, and postmenopause life stages

Vasomotor symptoms (VMS), commonly called hot flashes or flushes (HFs) and night sweats, are the menopausal symptoms for which women seek treatment during menopause most often. VMS are a form of temperature dysfunction that occurs due to changes in gonadal hormones. Normally, core body temperature (CBT) remains within a specific range, oscillating with daily circadian rhythms. Physiological processes that conserve and dissipate heat are responsible for maintaining CBT, and tight regulation is important for maintenance of optimal internal organ function. Disruption of this tightly controlled temperature circuit results in exaggerated heat-loss responses and presents as VMS. The mechanistic role related to changes in gonadal hormones associated with VMS is not understood. Hormone therapy is the most effective treatment for VMS and other menopausal symptoms. Estrogens are known potent neuromodulators of numerous neuronal circuits throughout the central nervous system. Changing estrogen levels during menopause may impact multiple components involved in maintaining temperature homeostasis. Understanding the pathways and mechanisms involved in temperature regulation, probable causes of thermoregulatory dysfunction, and "brain adaptation" will guide drug discovery efforts. This review considers the processes and pathways involved in normal temperature regulation and the impact of fluctuating and declining hormones that result in VMS during the menopausal transition.

Efficacy and tolerability of desvenlafaxine succinate treatment for menopausal vasomotor symptoms: a randomized controlled trial

OBJECTIVE

To compare efficacy and safety of desvenlafaxine succinate (desvenlafaxine) with placebo for the treatment of vasomotor symptoms.

METHODS

This randomized, double-blind, placebo-controlled trial enrolled 707 healthy, postmenopausal women experiencing 50 or more moderate-to-severe hot flushes per week. Participants randomly received desvenlafaxine 50, 100, 150, or 200 mg or placebo daily. Trial duration was 52 weeks. Primary outcomes were change from baseline in average daily number of moderate-to-severe hot flushes and in daily hot flush severity score at weeks 4 and 12.

RESULTS

Six hundred twenty women with an average of 11 moderate-to-severe hot flushes per day at baseline completed at least one on-therapy evaluation for primary efficacy end points; 519 participants completed 12 weeks of treatment, and 368 completed the study. Desvenlafaxine 100 mg/d achieved a significantly greater reduction compared with placebo in average daily number of hot flushes at weeks 4 (P=.013) and 12 (P=.005), reaching a 64% decrease from baseline at week 12, and the 75% responder rate was significantly higher for desvenlafaxine 100 mg (50%) compared with placebo (29%; P=.003; number needed to treat=4.7) at week 12. Average daily severity of hot flushes was significantly lower in the desvenlafaxine 100-mg group compared with placebo at week 12 (P=.020). Desvenlafaxine-treated women reported significantly more treatment-emergent adverse events than placebo-treated women during the first week of therapy only.

CONCLUSION

Desvenlafaxine is an effective nonhormonal treatment for vasomotor symptoms in postmenopausal women. Its tolerability profile is consistent with that of other serotonin-norepinephrine reuptake inhibitors.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00421031

LEVEL OF EVIDENCE

I.

New products and regimens (since 2003)

The downturn in the use of hormone replacement therapy since the original publication of the Women's Health Initiative (2002) and Million Women studies (2003) has now stabilized. New products are now being developed which maintain benefits and minimise risks. However, some useful products have been withdrawn by Pharma companies through profitability decisions; other products will regrettably not be launched despite favorable data. New low- and ultra-low-dose oral preparations (containing 0.3 mg conjugated equine estrogens and 0.5 mg estradiol, respectively) appear to maintain benefits for symptom relief and osteoporosis whilst minimizing side-effects and risks. A 14 microg transdermal system appears to maintain bone protection without the need for endometrial protection. New progestogens can minimize progestogenic side-effects through antiandrogenic and antimineralocorticoid effects, e.g. drospirenone, bioidentical progesterone and selective progesterone receptor modulators. A new female androgen patch has been licensed in Europe for treatment of low libido causing distress (hypoactive sexual desire disorder) in surgically menopaused women on estrogen therapy. A non-hormonal option, desvenlafaxine succinate (a serotonin and noradrenaline reuptake inhibitor), for vasomotor symptoms is currently in phase-III clinical trial stage and should be launched in the next year. Additionally, a selective estrogen receptor modulator/conjugated equine estrogen preparation combination currently in phase-III clinical trials is showing encouraging data for efficacy/risks and should provide a further option for women using hormone therapy in the future.