Activation of estrogen response elements is mediated both via estrogen and muscle contractions in rat skeletal muscle myotubes

Exercise training alters skeletal muscle microvascular endothelial cell properties in recent postmenopausal females

The present study examined and compared the impact of exercise training on redox and molecular properties of human microvascular endothelial cells derived from skeletal muscle biopsies from sedentary recent (RPF, ≤ 5 years as postmenopausal) and late (LPF, ≥ 10 years as postmenopausal) postmenopausal females. Resting skeletal muscle biopsies were obtained before and after 8 weeks of intense aerobic exercise training for isolation of microvascular endothelial cells and determination of skeletal muscle angiogenic proteins and capillarisation. The microvascular endothelial cells were analysed for mitochondrial respiration and production of reactive oxygen species (ROS), glycolysis and proteins related to vascular function, redox balance and oestrogen receptors. Exercise training led to a reduced endothelial cell ROS formation (∼50%; P = 0.009 and P = 0.020 for intact and permeabilized cells (state 3), respectively) in RPF only, with no effect on endothelial mitochondrial capacity in either group. Basal endothelial cell lactate formation was higher (7%; P = 0.028), indicating increased glycolysis, after compared to before the exercise training period in RPF only. Baseline endothelial G protein-coupled oestrogen receptor (P = 0.028) and muscle capillarisation (P = 0.028) was lower in LPF than in RPF. Muscle vascular endothelial growth factor protein was higher (32%; P = 0.002) following exercise training in LPF only. Exercise training did not influence endothelial cell proliferation or skeletal muscle capillarisation in either group, but the CD31 level in the muscle tissue, indicating endothelial cell content, was higher (>50%; P < 0.05) in both groups. In conclusion, 8 weeks of intense aerobic exercise training reduces ROS formation and enhances glycolysis in microvascular endothelial cells from RPF but does not induce skeletal muscle angiogenesis. KEY POINTS: Late postmenopausal females have been reported to achieve limited vascular adaptations to exercise training. There is a paucity of data on the effect of exercise training on isolated skeletal muscle microvascular endothelial cells (MMECs). In this study the formation of reactive oxygen species in MMECs was reduced and glycolysis increased after 8 weeks of aerobic exercise training in recent but not late postmenopausal females. Late postmenopausal females had lower levels of G protein-coupled oestrogen receptor in MMECs and lower skeletal muscle capillary density at baseline. Eight weeks of intense exercise training altered MMEC properties but did not induce skeletal muscle angiogenesis in postmenopausal females.

Unveiling the potential of estrogen: Exploring its role in neuropsychiatric disorders and exercise intervention

Neuropsychiatric disorders shorten human life spans through multiple ways and become major threats to human health. Exercise can regulate the estrogen signaling, which may be involved in depression, Alzheimer's disease (AD) and Parkinson's disease (PD), and other neuropsychiatric disorders as well in their sex differences. In nervous system, estrogen is an important regulator of cell development, synaptic development, and brain connectivity. Therefore, this review aimed to investigate the potential of estrogen system in the exercise intervention of neuropsychiatric disorders to better understand the exercise in neuropsychiatric disorders and its sex specific. Exercise can exert a protective effect in neuropsychiatric disorders through regulating the expression of estrogen and estrogen receptors, which are involved in neuroprotection, neurodevelopment, and neuronal glucose homeostasis. These processes are mediated by the downstream factors of estrogen signaling, including N-myc downstream regulatory gene 2 (Ndrg2), serotonin (5-HT), delta like canonical Notch ligand 1 (DLL1), NOD-like receptor thermal protein domain associated protein 3 (NLRP3), etc. In addition, exercise can act on the estrogen response element (ERE) fragment in the genes of estrogenic downstream factors like β-amyloid precursor protein cleavase 1 (BACE1). However, there are few studies on the relationship between exercise, the estrogen signaling pathway, and neuropsychiatric disorders. Hence, we review how the estrogen signaling mediates the mechanism of exercise intervention in neuropsychiatric disorders. We aim to provide a theoretical perspective for neuropsychiatric disorders affecting female health and provide theoretical support for the design of exercise prescriptions.

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

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

Sex Steroid Receptors in Polycystic Ovary Syndrome and Endometriosis: Insights from Laboratory Studies to Clinical Trials

Polycystic ovary syndrome (PCOS) and endometriosis are reproductive disorders that may cause infertility. The pathology of both diseases has been suggested to be associated with sex steroid hormone receptors, including oestrogen receptors (ER), progesterone receptors (PRs) and androgen receptors (ARs). Therefore, with this review, we aim to provide an update on the available knowledge of these receptors and how their interactions contribute to the pathogenesis of PCOS and endometriosis. One of the main PCOS-related medical conditions is abnormal folliculogenesis, which is associated with the downregulation of ER and AR expression in the ovaries. In addition, metabolic disorders in PCOS are caused by dysregulation of sex steroid hormone receptor expression. Furthermore, endometriosis is related to the upregulation of ER and the downregulation of PR expression. These receptors may serve as therapeutic targets for the treatment of PCOS-related disorders and endometriosis, considering their pathophysiological roles. Receptor agonists may be applied to increase the expression of a specific receptor and treat endometriosis or metabolic disorders. In contrast, receptor antagonist functions to reduce receptor expression and can be used to treat endometriosis and induce ovulation. Understanding PCOS and the pathological roles of endometriosis sex steroid receptors is crucial for developing potential therapeutic strategies to treat infertility in both conditions. Therefore, research should be continued to fill the knowledge gap regarding the subject.

Estrogens and the regulation of glucose metabolism

The main estrogens: estradiol, estrone, and their acyl-esters have been studied essentially related to their classical estrogenic and pharmacologic functions. However, their main effect in the body is probably the sustained control of core energy metabolism. Estrogen nuclear and membrane receptors show an extraordinary flexibility in the modulation of metabolic responses, and largely explain gender and age differences in energy metabolism: part of these mechanisms is already sufficiently known to justify both. With regard to energy, the estrogen molecular species act essentially through four key functions: (1) Facilitation of insulin secretion and control of glucose availability; (2) Modulation of energy partition, favoring the use of lipid as the main energy substrate when more available than carbohydrates; (3) Functional protection through antioxidant mechanisms; and (4) Central effects (largely through neural modulation) on whole body energy management. Analyzing the different actions of estrone, estradiol and their acyl esters, a tentative classification based on structure/effects has been postulated. Either separately or as a group, estrogens provide a comprehensive explanation that not all their quite diverse actions are related solely to specific molecules. As a group, they constitute a powerful synergic action complex. In consequence, estrogens may be considered wardens of energy homeostasis.

Aerobic High-Intensity Exercise Training Improves Cardiovascular Health in Older Post-menopausal Women

The aim of this study was to determine the effect of a period of aerobic high intensity training on central- and peripheral cardiovascular parameters in older post-menopausal women. Eleven healthy post-menopausal (>10 years after menopause) women (mean age: 64 years; BMI: 25.3 kg m⁻²) completed an 8-week period of supervised, high intensity cycle training, with sessions conducted three times per week. Before and after the training period maximal oxygen uptake, body composition, popliteal artery flow mediated dilation, exercise hyperemia, arterial blood pressure, and plasma lipids were assessed. In addition, levels of estrogen related receptor α (ERRα) and vasodilator enzymes were determined in muscle biopsy samples. Training induced an 18% increase (P < 0.001) in maximal oxygen uptake. Plasma High-density lipoprotein (HDL) was higher (P < 0.05) after than before the training period. Fat mass was reduced (4.9%; P < 0.01), whereas lean body mass was unaltered. Mean arterial blood pressure was unchanged (91 vs. 88 mmHg; P = 0.058) with training. Training did not induce a change in popliteal flow mediated dilation. Exercise hyperemia at submaximal exercise was lower (P < 0.01; 11 and 4.6% at 10 and 16 W, respectively) after compared to before training. Muscle ERRα (~1.7-fold; P < 0.01) and eNOS (~1.4-fold; P < 0.05) were higher after the training intervention. The current study demonstrates that, in older post-menopausal women, a period of aerobic high intensity training effectively increases maximal oxygen uptake and improves the cardiovascular health profile, without a parallel improvement in conduit artery function.

Estrogens, Estrogen Receptors Effects on Cardiac and Skeletal Muscle Mitochondria

Mitochondria are unique organelles present in almost all cell types. They are involved not only in the supply of energy to the host cell, but also in multiple biochemical and biological processes like calcium homeostasis, production, and regulation of reactive oxygen species (ROS), pH control, or cell death. The importance of mitochondria in cell biology and pathology is increasingly recognized. Being maternally inherited, mitochondria exhibit a tissue-specificity, because most of the mitochondrial proteins are encoded by the nuclear genome. This renders them exquisitely well-adapted to the physiology of the host cell. It is thus not surprising that mitochondria show a sexual dimorphism and that they are also prone to the influence of sex chromosomes and sex hormones. Estrogens affect mitochondria through multiple processes involving membrane and nuclear estrogen receptors (ERs) as well as more direct effects. Moreover, estrogen receptors have been identified within mitochondria. The effects of estrogens on mitochondria comprise protein content and specific activity of mitochondrial proteins, phospholipid content of membranes, oxidant and anti-oxidant capacities, oxidative phosphorylation, and calcium retention capacities. Herein we will briefly review the life cycle and functions of mitochondria, the importance of estrogen receptors and the effects of estrogens on heart and skeletal muscle mitochondria.

Effects of genistein on pentylenetetrazole-induced behavioral and neurochemical deficits in ovariectomized rats

Estrogenic compounds have been documented in literature to exert neuroprotective effects. This study investigated the potential neuroprotective effect of genistein; a phytoestrogen at doses of 5, 10, 20, and 40 mg/kg p.o. in ovariectomized rats challenged with pentylenetetrazole (PTZ) 90 mg/kg i.p. Systemic acute administration of PTZ induced seizures, increased oxidative stress, and caused apoptosis and histological abnormalities. Pretreatment with genistein delayed seizure onset, reduced the seizure duration, improved oxidative stress profile, decreased estrogen receptor expression, reduced apoptosis, and improved the histopathological pattern. Overall, the genistein doses (10 and 20 mg/kg) showed the strongest protective effects. In conclusion, the current study suggests that genistein exhibits neuroprotective effects against PTZ-induced seizures. Such effects might be attributed to its estrogenic, antioxidant, and/or anti-apoptotic properties.

Leg vascular and skeletal muscle mitochondrial adaptations to aerobic high-intensity exercise training are enhanced in the early postmenopausal phase

KEY POINTS

Exercise training effectively improves vascular and skeletal muscle function; however, these effects of training may be blunted in postmenopausal women as a result of the loss of oestrogens. Accordingly, the capacity to deliver oxygen to the active muscles may also be impaired in postmenopausal women. In both premenopausal and recent postmenopausal women, exercise training was shown to improve leg vascular and skeletal muscle mitochondrial function. Interestingly, these effects were more pronounced in postmenopausal women. Skeletal muscle oxygen supply and utilization were similar in the two groups of women. These findings suggest that the early postmenopausal phase is associated with an enhanced capacity of the leg vasculature and skeletal muscle mitochondria to adapt to exercise training and that the ability to deliver oxygen to match the demand of the active muscles is preserved in the early phase following the menopausal transition.

ABSTRACT

Exercise training leads to favourable adaptations within skeletal muscle; however, this effect of exercise training may be blunted in postmenopausal women as a result of the loss of oestrogens. Furthermore, postmenopausal women may have an impaired vascular response to acute exercise. We examined the haemodynamic response to acute exercise in matched pre- and postmenopausal women before and after 12 weeks of aerobic high intensity exercise training. Twenty premenopausal and 16 early postmenopausal (mean ± SEM: 3.1 ± 0.5 years after final menstrual period) women only separated by 4 years of age (mean ± SEM: 50 ± 0 years vs. 54 ± 1 years) were included. Before training, leg blood flow, O₂ delivery, O₂ uptake and lactate release during knee-extensor exercise were similar in pre- and postmenopausal women. Exercise training reduced (P < 0.05) leg blood flow, O₂ delivery, O₂ uptake, lactate release, blood pressure and heart rate during the same absolute workloads in postmenopausal women. These effects were not detected in premenopausal women. Quadriceps muscle protein contents of mitochondrial complex II, III and IV; endothelial nitric oxide synthase (eNOS); cyclooxygenase (COX)-1; COX-2; and oestrogen-related receptor α (ERRα) were increased (P < 0.05) with training in postmenopausal women, whereas only the levels of mitochondrial complex V, eNOS and COX-2 were increased (P < 0.05) in premenopausal women. These findings demonstrate that vascular and skeletal muscle mitochondrial adaptations to aerobic high intensity exercise training are more pronounced in recent post- compared to premenopausal women, possibly as an effect of enhanced ERRα signalling. Also, the hyperaemic response to acute exercise appears to be preserved in the early postmenopausal phase.

Naringenin modulates skeletal muscle differentiation via estrogen receptor α and β signal pathway regulation

Several experiments sustain healthful benefits of the flavanone naringenin (Nar) against chronic diseases including its protective effects against estrogen-related cancers. These experiments encourage Nar use in replacing estrogen treatment in post-menopausal women avoiding the serious side effects ascribed to this hormone. However, at the present, scarce data are available on the impact of Nar on E2-regulated cell functions. This study was aimed at determining the impact of Nar on the estrogen receptor (ERα and β)-dependent signals important for 17β-estradiol (E2) effect in muscle cells (rat L6 myoblasts, mouse C2C12 myoblasts, and mouse skeletal muscle satellite cells). Dietary relevant concentration of Nar delays the appearance of skeletal muscle differentiation markers (i.e., GLUT4 translocation, myogenin, and both fetal and slow MHC isoforms) and impairs E2 effects specifically hampering ERα ability to activate AKT. Intriguingly, Nar effects are specific for E2-initiating signals because IGF-I-induced AKT activation, and myoblast differentiation markers were not affected by Nar treatment. Only 7 days after Nar stimulation, early myoblast differentiation markers (i.e., myogenin, and fetal MHC) start to be accumulated in myoblasts. On the other hand, Nar stimulation activates, via ERβ, the phosphorylation of p38/MAPK involved in reducing the reactive oxygen species formation in skeletal muscle cells. As a whole, data reported here strongly sustain that although Nar action mechanisms include the impairment of ERα signals which drive muscle cells to differentiation, the effects triggered by Nar in the presence of ERβ could balance this negative effect avoiding the toxic effects produced by oxidative stress .

Multiple phytoestrogens inhibit cell growth and confer cytoprotection by inducing manganese superoxide dismutase expression

Phytoestrogens are of interest because of their reported beneficial effects on many human maladies including cancer, neurodegeneration, cardiovascular disease and diabetes. As data on phytoestrogens continues to accumulate, it is clear that there is significant overlap in the cellular effects elicited by these various compounds. Here, we show that one mechanism by which a number of phytoestrogens achieve their growth inhibitory and cytoprotective effects is via induction of the mitochondrial manganese superoxide dismutase (MnSOD). Eight phytoestrogens, including resveratrol, coumestrol, kaempferol, genistein, daidzein, apigenin, isoliquirtigenin and glycitin, were tested for their ability to induce MnSOD expression in mouse C2C12 and primary myoblasts. Five of these, resveratrol, coumestrol, kaempferol, genistein and daidzein, significantly increased MnSOD expression, slowed proliferative growth and enhanced stress resistance (hydrogen peroxide LD50) . When siRNA was used to prevent the MnSOD induction by genistein, coumestrol or daidzein, none of these compounds exerted any effect on proliferative growth, and only the effect of coumestrol on stress resistance persisted. The estrogen antagonist ICI182780 prevented the increased MnSOD expression and also the changes in cell growth and stress resistance, indicating that these effects are mediated by estrogen receptors (ER). The absence of effects of resveratrol or coumestrol, but not genistein, in ERβ-null cells further indicated that this ER in particular is important in mediating these effects. Thus, an ER-mediated induction of MnSOD expression appears to underlie the growth inhibitory and cytoprotective activities of multiple phytoestrogens.

Tissue-Specific Effects of Loss of Estrogen during Menopause and Aging

The roles of estrogens have been best studied in the breast, breast cancers, and in the female reproductive tract. However, estrogens have important functions in almost every tissue in the body. Recent clinical trials such as the Women's Health Initiative have highlighted both the importance of estrogens and how little we know about the molecular mechanism of estrogens in these other tissues. In this review, we illustrate the diverse functions of estrogens in the bone, adipose tissue, skin, hair, brain, skeletal muscle and cardiovascular system, and how the loss of estrogens during aging affects these tissues. Early transcriptional targets of estrogen are reviewed in each tissue. We also describe the tissue-specific effects of selective estrogen receptor modulators (SERMs) used for the treatment of breast cancers and postmenopausal symptoms.

Histaminergic responses by hypothalamic neurons that regulate lordosis and their modulation by estradiol

How do fluctuations in the level of generalized arousal of the brain affect the performance of specific motivated behaviors, such as sexual behaviors that depend on sexual arousal? A great deal of previous work has provided us with two important starting points in answering this question: (i) that histamine (HA) serves generalized CNS arousal and (ii) that heightened electrical activity of neurons in the ventromedial nucleus of the hypothalamus (VMN) is necessary and sufficient for facilitating the primary female sex behavior in laboratory animals, lordosis behavior. Here we used patch clamp recording technology to analyze HA effects on VMN neuronal activity. The results show that HA acting through H1 receptors (H1R) depolarizes these neurons. Further, acute administration of estradiol, an estrogen necessary for lordosis behavior to occur, heightens this effect. Hyperpolarization, which tends to decrease excitability and enhance inhibition, was not affected by acute estradiol or mediated by H1R but was mediated by other HA receptor subtypes, H2 and H3. Sampling of mRNA from individual VMN neurons showed colocalization of expression of H1 receptor mRNA with estrogen receptor (ER)-alpha mRNA but also revealed ER colocalization with the other HA receptor subtypes and colocalization of different subtypes with each other. The latter finding provides the molecular basis for complex "push-pull" regulation of VMN neuronal excitability by HA. Thus, in the simplest causal route, HA, acting on VMN neurons through H1R provides a mechanism by which elevated states of generalized CNS arousal can foster a specific estrogen-dependent, aroused behavior, sexual behavior.

17β-Estradiol regulates the first steps of skeletal muscle cell differentiation via ER-α-mediated signals

17β-Estradiol (E2) mediates a wide variety of complex biological processes determining the growth and development of reproductive tract as well as nonreproductive tissues of male and female individuals. While E2 effects on the reproductive system, bone, and cardiovascular system are quite well established, less is known about how it affects the physiology of other tissues. Skeletal muscle is a tissue that is expected to be E2 responsive since both isoforms of estrogen receptor (ER-α and ER-β) are expressed. Significant sex-related differences have been described in skeletal muscle, although the role played by E2 and the mechanisms underlying it remain to be determined. Here, we demonstrate that E2 increases the glucose transporter type 4 translocation at membranes as well as the expression of well-known differentiation markers of myogenesis (i.e., myogenin and myosin heavy chain) in rat myoblast cells (L6). These E2-induced effects require rapid extranuclear signals and the presence of ER-α, whereas no contribution of IGF-I receptor has been observed. In particular, ER-α-dependent Akt activation participates in regulating the first step of myogenic differentiation. Moreover, both receptors mediate the E2-induced activation of p38, which, in turn, affects the expression of myogenin and myosin heavy chain. All together, these data indicate that E2 should be included in the list of skeletal muscle trophic factors.