De Novo Synthesized Estradiol: A Role in Modulating the Cerebellar Function

Pharmacokinetics and Safety of Estradiol Valerate Tablet and Its Generic: A Phase 1 Bioequivalence Study in Healthy Chinese Postmenopausal Female Subjects

Purpose

Estradiol valerate (Progynova®) is used as hormone therapy to supplement estrogen deficiency. This study aimed to assess the bioequivalence of an estradiol valerate tablet and its generic form, under fasting and fed conditions.

Methods

A randomized, open-label, single-dose, 2-period crossover study was conducted on healthy postmenopausal Chinese female volunteers under fasting and fed conditions. For each period, the subjects received either a 1 mg tablet of estradiol valerate or its generic. Blood samples were collected before dosing and up to 72 hours after administration. Plasma levels of total estrone, estradiol, and unconjugated estrone were quantified using a validated liquid chromatography-tandem mass spectrometry method.

Results

A total of 54 volunteers were enrolled in this study. The primary pharmacokinetic parameters, including Cmax, AUC0-t, and AUC0-∞, were similar for the two drugs under both fasting and fed conditions, with 90% confidence intervals for the geometric mean ratios of these parameters, all meeting the bioequivalence criterion of 80-125%. A total of 48 adverse events (AEs) were reported in the fed study compared with 24 AEs in the fasting study.

Conclusion

Estradiol valerate and its generic form were bioequivalent and well tolerated under both fasting and fed conditions.

Female sex steroids and epilepsy: Part 1. A review of reciprocal changes in reproductive systems, cycles, and seizures

Seizures, antiseizure medications, and the reproductive systems are reciprocally entwined. In Section 2 of this review, we outline how seizures may affect the hypothalamic-pituitary-gonadal axis, thereby altering sex steroids, and changes in sex steroids across the menstrual cycle and changes in pharmacokinetics during pregnancy may alter seizure susceptibility. The literature indicates that females with epilepsy experience increased rates of menstrual disturbances and reproductive endocrine disorders. The latter include polycystic ovary syndrome, especially for females on valproate. Studies of fertility have yielded mixed results. We aim to summarize and attempt to detangle the existing knowledge on these reciprocal interactions. The menstrual cycle causes changes in seizure intensity and frequency for many females. When this occurs perimenstrually, during ovulation, or in association with an inadequate luteal phase, it is termed catamenial epilepsy. There is a clear biophysiological rationale for how the key female reproductive neurosteroids interact with the brain to alter the seizure threshold, and Section 3 outlines this important relationship. Critically, what remains unknown is the specific pathophysiology of catamenial epilepsy that describes why not all females are affected. There is a need for mechanism-focused investigations in humans to uncover the complexity of the relationship between reproductive hormones, menstrual cycles, and the brain.

Locally Synthetized 17-β-Estradiol Reverses Amyloid-β-42-Induced Hippocampal Long-Term Potentiation Deficits

Amyloid beta 1-42 (Aβ42) aggregates acutely impair hippocampal long-term potentiation (LTP) of synaptic transmission, and 17β-estradiol is crucial for hippocampal LTP. We tested whether boosting the synthesis of neural-derived 17β-estradiol (nE2) saves hippocampal LTP by the neurotoxic action of Aβ42. Electrophysiological recordings were performed to measure dentate gyrus (DG) LTP in rat hippocampal slices. Using a pharmacological approach, we tested the ability of nE2 to counteract the LTP impairment caused by acute exposure to soluble Aβ42 aggregates. nE2 was found to be required for LTP in DG under physiological conditions. Blockade of steroid 5α-reductase with finasteride, by increasing nE2 synthesis from testosterone (T), completely recovered LTP in slices treated with soluble Aβ42 aggregates. Modulation of the glutamate N-methyl-D aspartate receptor (NMDAR) by memantine effectively rescued the LTP deficit observed in slices exposed to Aβ42, and memantine prevented LTP reduction observed under the blocking of nE2 synthesis. nE2 is able to counteract Aβ42-induced synaptic dysfunction. This effect depends on a rapid, non-genomic mechanism of action of nE2, which may share a common pathway with glutamate NMDAR signaling.

Regulation of uterus and placenta remodeling under high estradiol levels in gestational diabetes mellitus models†

The present study aimed to investigate the regulation of placentas and uterus remodeling and involvement of estradiol in gestational diabetes mellitus. To achieve this, we established in vitro and in vivo models for gestational diabetes mellitus placentas by culturing human placental choriocarcinoma cells (BeWo) under hyperglycemic concentration and treating pregnant rats with streptozotocin. We evaluated the expression of angiogenesis-related proteins. The expression of the anti-angiogenic factor, excess placental soluble fms-like tyrosine kinase 1 was increased in our in vitro gestational diabetes mellitus model compared with the control. Moreover, the expressions of placental soluble fms-like tyrosine kinase 1 and the von Willebrand factor were also significantly elevated in the placenta of streptozotocin-treated rats. These data indicate the disruption of angiogenesis in the gestational diabetes mellitus placentas. The expression levels of connexin 43, a component of the gap junction and collagen type I alpha 2 chain, a component of the extracellular matrix, were decreased in the gestational diabetes mellitus uterus. These results suggest that uterus decidualization and placental angiogenesis are inhibited in gestational diabetes mellitus rats. Our results also showed upregulation of the expression of genes regulating estradiol synthesis as well as estrogen receptors in vivo models. Accordingly, the concentration of estradiol measured in the culture medium under hyperglycemic conditions, as well as in the serum and placenta of the streptozotocin-treated rats, was significantly elevated compared with the control groups. These results suggest that the dysregulated remodeling of the placenta and uterus may result in the elevation of estradiol and its signaling pathway in the gestational diabetes mellitus animal model to maintain pregnancy.

The Influence of Sex Hormones in Liver Function and Disease

The liver performs a multitude of bodily functions, whilst retaining the ability to regenerate damaged tissue. In this review, we discuss sex steroid biology, regulation of mammalian liver physiology and the development of new model systems to improve our understanding of liver biology in health and disease. A major risk factor for the development of liver disease is hepatic fibrosis. Key drivers of this process are metabolic dysfunction and pathologic activation of the immune system. Although non-alcoholic fatty liver disease (NAFLD) is largely regarded as benign, it does progress to non-alcoholic steatohepatitis in a subset of patients, increasing their risk of developing cirrhosis and hepatocellular carcinoma. NAFLD susceptibility varies across the population, with obesity and insulin resistance playing a strong role in the disease development. Additionally, sex and age have been identified as important risk factors. In addition to the regulation of liver biochemistry, sex hormones also regulate the immune system, with sexual dimorphism described for both innate and adaptive immune responses. Therefore, sex differences in liver metabolism, immunity and their interplay are important factors to consider when designing, studying and developing therapeutic strategies to treat human liver disease. The purpose of this review is to provide the reader with a general overview of sex steroid biology and their regulation of mammalian liver physiology.

Oral contraceptives and stroke: Foes or friends

Incidents of strokes are increased in young women relative to young men, suggesting that oral contraceptive (OC) use is one of the causes of stroke among young women. Long-term exposures to the varying combinations of estrogen and progestogen found in OCs affect blood clotting, lipid and lipoprotein metabolism, endothelial function, and de novo synthesis of neurosteroids, especially brain-derived 17β-estradiol. The latter is essential for neuroprotection, memory, sexual differentiation, synaptic transmission, and behavior. Deleterious effects of OCs may be exacerbated due to comorbidities like polycystic ovary syndrome, sickle cell anemia, COVID-19, exposures to endocrine disrupting chemicals, and conventional or electronic cigarette smoking. The goal of the current review is to revisit the available literature regarding the impact of OC use on stroke, to explain possible underlying mechanisms, and to identify gaps in our understanding to promote future research to reduce and cure stroke in OC users.

Steroid Sulfation in Neurodegenerative Diseases

Steroid sulfation and desulfation participates in the regulation of steroid bioactivity, metabolism and transport. The authors focused on sulfation and desulfation balance in three neurodegenerative diseases: Alzheimer´s disease (AD), Parkinson´s disease (PD), and multiple sclerosis (MS). Circulating steroid conjugates dominate their unconjugated counterparts, but unconjugated steroids outweigh their conjugated counterparts in the brain. Apart from the neurosteroid synthesis in the central nervous system (CNS), most brain steroids cross the blood-brain barrier (BBB) from the periphery and then may be further metabolized. Therefore, steroid levels in the periphery partly reflect the situation in the brain. The CNS steroids subsequently influence the neuronal excitability and have neuroprotective, neuroexcitatory, antidepressant and memory enhancing effects. They also exert anti-inflammatory and immunoprotective actions. Like the unconjugated steroids, the sulfated ones modulate various ligand-gated ion channels. Conjugation by sulfotransferases increases steroid water solubility and facilitates steroid transport. Steroid sulfates, having greater half-lives than their unconjugated counterparts, also serve as a steroid stock pool. Sulfotransferases are ubiquitous enzymes providing massive steroid sulfation in adrenal zona reticularis and zona fasciculata.. Steroid sulfatase hydrolyzing the steroid conjugates is exceedingly expressed in placenta but is ubiquitous in low amounts including brain capillaries of BBB which can rapidly hydrolyze the steroid sulfates coming across the BBB from the periphery. Lower dehydroepiandrosterone sulfate (DHEAS) plasma levels and reduced sulfotransferase activity are considered as risk factors in AD patients. The shifted balance towards unconjugated steroids can participate in the pathophysiology of PD and anti-inflammatory effects of DHEAS may counteract the MS.

Xenoestrogens impact brain estrogen receptor signaling during the female lifespan: A precursor to neurological disease?

Xenoestrogens, foreign synthetic chemicals mimicking estrogens, are lurking in our surroundings. Climate change may alter their toxicity and bioavailability. Since xenoestrogens have extremely high lipid solubility and are structurally similar to natural endogenous estrogens, they can bind to estrogen receptors (ERs) -alpha (ER-α) and -beta (ER-β). Scientific evidence accumulated over the past decades have suggested that natural 17β-estradiol (E2; a potent estrogen), via activation of its receptors, plays a pivotal role in regulation of brain development, differentiation, metabolism, synaptic plasticity, neuroprotection, cognition, anxiety, body temperature, feeding and sexual behavior. In the brain, ER-β is predominantly expressed in the various regions, including cerebral cortex and hippocampus, that have been shown to play a key role in cognition. Therefore, disturbances in function of ER-β mediated E2 signaling by xenoestrogens can lead to deleterious effects that potentiate a variety of neurological diseases starting from prenatal to post-menopause in women. The goal of this review is to identify the possible neurological effects of xenoestrogens that can alter estrogen receptor-mediated signaling in the brain during different stages of the female lifespan.

Aromatase in the Human Brain

The aromatase cytochrome P450 (P450arom) enzyme, or estrogen synthase, which is coded by the CYP19A1 gene, is widely expressed in a subpopulation of excitatory and inhibitory neurons, astrocytes, and other cell types in the human brain. Experimental studies in laboratory animals indicate a prominent role of brain aromatization of androgens to estrogens in regulating different brain functions. However, the consequences of aromatase expression in the human brain remain poorly understood. Here, we summarize the current knowledge about aromatase expression in the human brain, abundant in the thalamus, amygdala, hypothalamus, cortex, and hippocampus and discuss its role in the regulation of sensory integration, body homeostasis, social behavior, cognition, language, and integrative functions. Since brain aromatase is affected by neurodegenerative conditions and may participate in sex-specific manifestations of autism spectrum disorders, major depressive disorder, multiple sclerosis, stroke, and Alzheimer's disease, we discuss future avenues for research and potential clinical and therapeutic implications of the expression of aromatase in the human brain.

Developmental expression of genes involved in progesterone synthesis, metabolism and action during the post-natal cerebellar myelination

Progesterone is involved in dendritogenesis, synaptogenesis and maturation of cerebellar Purkinge cells, major sites of steroid synthesis in the brain. To study a possible time-relationship between myelination, neurosteroidogenesis and steroid receptors during development of the postnatal mouse cerebellum, we determined at postnatal days 5 (P5),18 (P18) and 35 (P35) the expression of myelin basic protein (MBP), components of the steroidogenic pathway, levels of endogenous steroids and progesterone's classical and non-classical receptors. In parallel with myelin increased expression during development, P18 and P35 mice showed higher levels of cerebellar progesterone and its reduced derivatives, higher expression of steroidogenic acute regulatory protein (StAR) mRNA, cholesterol side chain cleavage enzyme (P450scc) and 5α-reductase mRNA vs. P5 mice. Other steroids such as corticosterone and its reduced derivatives and 3β-androstanodiol (ADIOL) showed a peak increase at P18 compared to P5. Progesterone membrane receptors and binding proteins (PGRMC1, mPRα, mPRβ, mPRγ, and Sigma1 receptors) mRNAs levels increased during development while that of classical progesterone receptors (PR) remained invariable. PRKO mice showed similar MBP levels than wild type. Thus, these data suggests that progesterone and its neuroactive metabolites may play a role in postnatal cerebellar myelination.

Sex differences in glucoprivic regulation of glycogen metabolism in hypothalamic primary astrocyte cultures: Role of estrogen receptor signaling

Hypoglycemia causes sex-reliant changes in hypothalamic astrocyte glycogen metabolism in vivo. The role of nuclear versus membrane astrocyte estrogen receptors (ER) in glucoprivic regulation of glycogen is unclear. Here, primary hypothalamic astrocyte cultures were treated with selective ER antagonists during glucoprivation to investigate the hypothesis that ER mediate sex-specific glycogen responses to glucoprivation. Results show that glucoprivic down-regulation of glycogen synthase expression is mediated by transmembrane G protein-coupled ER-1 (GPER) signaling in each sex and estrogen receptor (ER)-beta (ERβ) activity in females. Glucoprivic inhibition of glycogen phosphorylase involves GPER and ERβ in females, but ER-independent mechanisms in males. GPER, ERβ, and ER-alpha (ERα) inhibit or stimulate AMPK protein expression in male versus female astrocytes, respectively. Glucoprivic augmentation of phospho-AMPK profiles in male glia was opposed by GPER activation, whereas GPER and ERβ suppress this protein in females. Astrocyte ERα and GPER content was down-regulated in each sex during glucose deficiency, whereas ERβ levels was unaltered (males) or increased (females). Glucoprivation correspondingly elevated or diminished male versus female astrocyte glycogen content; ER antagonism reversed this response in males, but not females. Results identify distinctive ER variants involved in sex-similar versus sex-specific astrocyte protein responses to withdrawal of this substrate fuel. Notably, glucoprivation elicits a directional switch or gain-of-effect of GPER and ERβ on specific glial protein profiles. Outcomes infer that ERs are crucial for glucoprivic regulation of astrocyte glycogen accumulation in males. Alternatively, estradiol may act independently of ER signaling to disassemble this reserve in females.

Rapid Estrogenic and Androgenic Neurosteroids Effects in the Induction of Long-Term Synaptic Changes: Implication for Early Memory Formation

Mounting experimental evidence demonstrate that sex neuroactive steroids (neurosteroids) are essential for memory formation. Neurosteroids have a profound impact on the function and structure of neural circuits and their local synthesis is necessary for the induction of both long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission and for neural spine formation in different areas of the central nervous system (CNS). Several studies demonstrated that in the hippocampus, 17β-estradiol (E2) is necessary for inducing LTP, while 5α-dihydrotestosterone (DHT) is necessary for inducing LTD. This contribution has been proven by administering sex neurosteroids in rodent models and by using blocking agents of their synthesis or of their specific receptors. The general opposite role of sex neurosteroids in synaptic plasticity appears to be dependent on their different local availability in response to low or high frequency of synaptic stimulation, allowing the induction of bidirectional synaptic plasticity. The relevant contribution of these neurosteroids to synaptic plasticity has also been described in other brain regions involved in memory processes such as motor learning, as in the case of the vestibular nuclei, the cerebellum, and the basal ganglia, or as the emotional circuit of the amygdala. The rapid effects of sex neurosteroids on neural synaptic plasticity need the maintenance of a tonic or phasic local steroid synthesis determined by neural activity but might also be influenced by circulating hormones, age, and gender. To disclose the exact mechanisms how sex neurosteroids participate in finely tuning long-term synaptic changes and spine remodeling, further investigation is required.