Steroid hormone action during brain development exerts profound effects on reproductive physiology and behavior that last into adulthood. A variety of in vitro studies indicate that steroid receptors require nuclear receptor coactivators for efficient transcriptional activity. To determine the functional significance of the nuclear receptor coactivator SRC-1 in developing brain, we investigated the consequence of reducing SRC-1 protein during sexual differentiation of the brain. We report that reducing SRC-1 protein interferes with the defeminizing actions of estrogen in neonatal rat brain. Our data indicate that SRC-1 protein expression is critically involved in the hormone-dependent development of normal male reproductive behavior and brain morphology. Intracellular receptors for steroid hormones constitute a superfamily of transcription factors that includes receptors for estrogens, progestins, androgens, glucocorticoids, thyroid hormone, retinoic acid, and 9-cis retinoic acid along with numerous orphan receptors with as-yet unidentified ligands (1). Spontaneously occurring mutations in steroid receptors or disruptions of normal steroid hormone levels during development have profound and devastating effects on adult reproductive physiology (2-4). However, not all endocrine-related disorders can be explained by disruptions in steroid receptors or hormone levels, and a potential role for an additional class of proteins, nuclear receptor coregulators, has been implicated (5).Steroid hormones act in the brain by binding to intracellular receptors located predominantly in neurons. On ligand binding, the steroid-receptor complex binds to a hormone response element located on DNA (6, 7) where it regulates gene transcription and ultimately neuronal function (7,8). Recent studies reveal that steroid receptors interact with other proteins, nuclear receptor coactivators or corepressors, that increase or decrease their binding and action at the hormone response element, respectively. The first nuclear receptor coactivator to be characterized is steroid receptor coactivator-1 (SRC-1; refs. 9 and 10). The majority of studies to date have used transfection assays in cell culture systems in which large quantities of steroid receptors are expressed to elucidate interactions with coactivators and corepressors. Although this approach is valid, it does not allow for assessment of the in vivo role of nuclear receptor coactivators and their physiological significance, which remain largely unknown at this time. A recent study indicates that peripheral steroid target organs of mice containing a targeted disruption of the SRC-1 gene have a decreased response to steroid hormones (11); however, it is not known whether SRC-1 protein mediates steroid hormone action within the developing brain.To determine the functional significance of SRC-1, we examined the influence of SRC-1 on sexual differentiation of the rodent brain. The developing brain is an exquisitely sensitive target organ for steroid hormones, which differentiate the neural s...

ABSTRACT The microorganisms of the vaginal tract are critical for vaginal and reproductive health. However, the regulation of these microorganisms is not well understood. Therefore, we investigated whether different factors regulate the vaginal microbiota of healthy college-aged women (n = 26) with high temporal resolution by collecting daily self-administered vaginal swabs and using 16S rRNA sequencing for bacterial identification. As expected, vaginal microbiota clustered into five predefined community state types. Vaginal microbial diversity, stability, and Lactobacillus abundances were associated with the menstrual cycle and hormonal contraceptive use. Vaginal microbial diversity, as measured using the Shannon index, increased during menses (P < 0.001), while Lactobacillus abundances decreased (P = 0.01). The covariance of these microbial measures with previously established estradiol levels suggests that estrogens can regulate vaginal microbiota. Moreover, the use of hormonal contraceptives may alter the temporal dynamics of the vaginal microbiota and decrease Lactobacillus abundances, depending on hormonal content and release method. Interestingly, intrasample diversity was greater in participants on a vegetarian diet (P = 0.004) and among participants who exercised more (P = 0.04). These findings indicate that ovarian hormones, diet, and exercise can regulate vaginal microbial composition and stability and may impact vaginal and reproductive health. IMPORTANCE The vaginal microbiome is a critical component of women’s sexual and reproductive health, with variations in microbial composition, particularly the loss of Lactobacillus species, being implicated in gynecologic and obstetric diseases. Given that the vaginal microbiome is so crucial, why do vaginal microbial profiles vary strikingly from person to person and even change over time within the same person? In the present study, which tracked the daily vaginal microbiomes of young healthy women through different lifestyles, we found that use of a locally released progestin contraceptive, a vegetarian diet, and intense exercise appear to lead to vaginal microbiome alterations and loss of Lactobacillus species. The impact of these vaginal microbiome changes on immediate and long-term health remain to be investigated.

It is becoming well established that the gut microbiome has a profound impact on human health and disease. In this review, we explore how steroids can influence the gut microbiota and, in turn, how the gut microbiota can influence hormone levels.Within the context of the gut microbiome-brain axis, we discuss how perturbations in the gut microbiota can alter the stress axis and behaviour. In addition, human studies on the possible role of gut microbiota in depression and anxiety are examined. Finally, we present some of the challenges and important questions that need to be addressed by future research in this exciting new area at the intersection of steroids, stress, gutbrain axis and human health. K E Y W O R D Sandrogen, microbiota, oestrogen, steroid hormones, stress | INTRODUCTIONWithin each human gastrointestinal tract, there is an exclusive combination of different communities of organisms, including bacteria, viruses, archaea, protozoa and fungi, which are collectively referred to as the gut microbiota and outnumber the total amount of human cells in the human body.1 The collection of these microorganisms, their genomes and the factors that they produce are all part of the gut microbiome. 2 Increasing evidence suggests that these microorganisms actively participate in shaping and maintaining our physiology almost as an extra organ. ranging from obesity 7 and asthma 8 to a variety of brain disorders. 3,9-14The gut microbiota helps break down food and, in doing so, produces metabolites that can directly influence the physiology of host cells, including brain cells. Moreover, immune responses to pathogenic bacteria produce cytokines and lymphokines that can affect brain physiology. 15Because the nervous system is a master regulator of host function, this allows microbes to influence a broad range of complex physiologicalprocesses. An improved mechanistic understanding of how bacterial molecules act on the nervous system could yield improved therapeutics for treating behavioural and neurological disorders. 16The human gut microbiota is usually stable and resilient to transient perturbations. 17 However, microbial composition or activity of the gut can be modified by a variety of factors, including internal factors such as hormonal changes, or external factors such as diet, antibiotics and stress. 3,18 In this review, the influence of steroids and stress on the gut microbiome-brain axis is discussed, as well as the challenges that face future research in this area. | STEROID HORMONES INFLUENCE THE GUT MICROBIOTAThere is mounting evidence that steroid hormones can affect the gut microbiota. In support of steroids influencing the gut bacterial communities, sex differences have been noted in the composition of the gut microbiota, with specific phyla, family and genera variances occurring with clear effects of gonadectomy and hormone replacement on gut bacteria in rodents. [19][20][21] In mice, the sex differences in the gut microbiota observed between males and females are decreased after castration, indicating a...

Full transcriptional activation by steroid hormone receptors requires functional synergy between two transcriptional activation domains (AF) located in the amino (AF-1) and carboxyl (AF-2) terminal regions. One possible mechanism for achieving this functional synergy is a physical intramolecular association between amino (N-) and carboxyl (C-) domains of the receptor. Human progesterone receptor (PR) is expressed in two forms that have distinct functional activities: full-length PR-B and the amino-terminally truncated PR-A. PR-B is generally a stronger activator than PR-A, whereas under certain conditions PR-A can act as a repressor in trans of other steroid receptors. We have analyzed whether separately expressed N- (PR-A and PR-B) and C-domains [hinge plus ligand-binding domain (hLBD)] of PR can functionally interact within cells by mammalian two-hybrid assay and whether this involves direct protein contact as determined in vitro with purified expressed domains of PR. A hormone agonist-dependent interaction between N-domains and the hLBD was observed functionally by mammalian two-hybrid assay and by direct protein-protein interaction assay in vitro. With both experimental approaches, N-C domain interactions were not induced by the progestin antagonist RU486. However, in the presence of the progestin agonist R5020, the N-domain of PR-B interacted more efficiently with the hLBD than the N-domain of PR-A. Coexpression of steroid receptor coactivator-1 (SRC-1) and the CREB binding protein (CBP), enhanced functional interaction between N- and C-domains by mammalian two-hybrid assay. However, addition of SRC-1 and CBP in vitro had no influence on direct interaction between purified N- and C-domains. These results suggest that the interaction between N- and C-domains of PR is direct and requires a hormone agonist-induced conformational change in the LBD that is not allowed by antagonists. Additionally, coactivators are not required for physical association between the N- and C-domains but are capable of enhancing a functionally productive interaction. In addition, the more efficient interaction of the hLBD with the N-domain of PR-B, compared with that of PR-A, suggests that distinct interactions between N- and C-terminal regions contribute to functional differences between PR-A and PR-B.

Vaginal-cervical stimulation (VCS), provided by mating or manual probing, induces many reproductive behavioral and endocrine changes in female rats. These changes include an increase in lordosis duration, heat termination and pseudopregnancy. Electrophysiological and [14C]2-deoxy-D-glucose studies collectively show that neurons in the medial preoptic area, ventromedial hypothalamus and midbrain central gray respond to manual VCS. In the present study we immunocytochemically labeled brain sections for Fos, the protein product of the immediate early gene c-fos, to detect VCS-responsive neurons in hormone-primed animals receiving VCS by mating or manual probing. In Experiment 1, females receiving mounts and intromissions were compared to: 1) vaginally-masked females receiving mounts but no VCS, 2) females exposed to an intact anesthetized male or 3) females not exposed to males or the testing arena. Those animals receiving VCS showed a dramatic increase in the number of Fos-immunoreactive cells in the medial preoptic area, posterodorsal portion of the medial amygdala and bed nucleus of the stria terminalis, as well as the dorsomedial hypothalamus, ventromedial hypothalamus and midbrain central gray. These effects of VCS were confirmed in Experiment 2 in animals receiving manual vaginal-cervical probing. These findings extend previous electrophysiological and [14C]2-deoxy-D-glucose studies by providing evidence that additional brain areas respond to VCS by mating, as well as manual probing.

The ovarian hormones, estradiol (E) and progesterone (P) facilitate the expression of sexual behavior in female rats. E and P mediate many of these behavioral effects by binding to their respective intracellular receptors in specific brain regions. Nuclear receptor coactivators, including Steroid Receptor Coactivator-1 (SRC-1) and CREB Binding Protein (CBP), dramatically enhance ligand-dependent steroid receptor transcriptional activity in vitro. Previously, our lab has shown that SRC-1 and CBP modulate estrogen receptor (ER)-mediated induction of progestin receptor (PR) gene expression in the ventromedial nucleus of the hypothalamus (VMN) and hormone-dependent sexual receptivity in female rats. Female sexual behaviors can be activated by high doses of E alone in ovariectomized rats, and thus are believed to be ER-dependent. However, the full repertoire of female sexual behavior, in particular, proceptive behaviors such as hopping, darting and ear wiggling, are considered to be PR-dependent. In the present experiments, the function of SRC-1 and CBP in distinct ER- (Exp. 1) and PR- (Exp. 2) dependent aspects of female sexual behavior was investigated. In Exp. 1, infusion of antisense oligodeoxynucleotides to SRC-1 and CBP mRNA into the VMN decreased lordosis intensity in rats treated with E alone, suggesting that these coactivators modulate ER-mediated female sexual behavior. In Exp. 2, antisense to SRC-1 and CBP mRNA around the time of P administration reduced PR-dependent ear wiggling and hopping and darting. Taken together, these data suggest that SRC-1 and CBP modulate ER and PR action in brain and influence distinct aspects of hormone-dependent sexual behaviors. These findings support our previous studies and provide further evidence that SRC-1 and CBP function together to regulate ovarian hormone action in behaviorally-relevant brain regions.

Gonadal steroid hormones act in the brain to elicit changes in gene expression that result in profound effects on behavior and physiology. A variety of in vitro studies indicate that nuclear receptor coactivators are required for efficient transcriptional activity of steroid receptors. Two nuclear receptor coactivators, steroid receptor coactivator-1 (SRC-1) and cAMP response element binding protein-binding protein (CBP), have been shown to act in concert to enhance ER activity in vitro. In the present study, we investigated the function of these important nuclear receptor coactivators in estrogen action in rodent brain. Reduction of SRC-1 and CBP protein in brain disrupted ER-mediated activation of the behaviorally relevant progestin receptor gene. Furthermore, we found that SRC-1 and CBP function in brain to modulate the expression of hormone-dependent female sexual behavior. These findings indicate that these nuclear receptor coactivators function in brain to modulate ER transcriptional activity and the expression of hormone-dependent behavior.

estrogens protect against diet-induced obesity in women and female rodents. for example, a lack of estrogens in postmenopausal women is associated with an increased risk of weight gain, cardiovascular diseases, low-grade inflammation, and cancer. Estrogens act with leptin to regulate energy homeostasis in females. Leptin-deficient mice (ob/ob) exhibit morbid obesity and insulin resistance. the gut microbiome is also critical in regulating metabolism. the present study investigates whether estrogens and leptin modulate gut microbiota in ovariectomized ob/ob (obese) or heterozygote (lean) mice fed high-fat diet (HFD) that received either 17β-Estradiol (E2) or vehicle implants. E2 attenuated weight gain in both genotypes. Moreover, both obesity (ob/ob mice) and E2 were associated with reduced gut microbial diversity. ob/ob mice exhibited lower species richness than control mice, while E2-treated mice had reduced evenness compared with vehicle mice. Regarding taxa, E2 was associated with an increased abundance of the S24-7 family, while leptin was associated with increases in coriobacteriaceae, Clostridium and Lactobacillus. Some taxa were affected by both E2 and leptin, suggesting these hormones alter gut microbiota of HFD-fed female mice. Understanding the role of E2 and leptin in regulating gut microbiota will provide important insights into hormone-dependent metabolic disorders in women. Estrogens profoundly influence energy homeostasis 1-3 , as well as reproductive physiology and behavior 4-6. Estrogens reduce food intake, attenuate body weight gain and adiposity, and increase physical activity in humans and rodents 1,2. Postmenopausal women have lower levels of circulating estrogens and an increased tendency to gain fat weight, which increases their risk for obesity, cardiovascular disease, stroke, and type 2 diabetes 7-9. Similarly, in mice on a high-fat diet (HFD), ovariectomy increases energy intake and obesity, while estradiol (E2) treatment prevents weight gain 2,10-13 , indicating that estrogens protect against HFD-induced obesity. Leptin is a peptide hormone secreted primarily by adipocytes, which acts primarily in the brain to stimulate metabolism, promote satiety, and regulate fat storage 14-16. A mutation in the ob gene that encodes leptin results in mice lacking the hormone (ob/ob) 17. While phenotypically normal at birth, ob/ob mice quickly develop obesity and diabetes 18. Additionally, ob/ob mice exhibit increased food intake and decreased physical activity, energy metabolism, and body temperature compared to lean controls, making ob/ob mice an excellent genetic model of obesity 19-21. Administering leptin to adult ob/ob mice reverses these effects by decreasing food intake, increasing energy output and decreasing circulating levels of glucose and insulin 19,22. Leptin and estrogen signaling pathways interact to influence reproduction and energy metabolism. High levels of E2 are associated with increased leptin sensitivity in both male and female rodents 23. In contrast, decreased estrogens in ovar...