Aromatase in human bone tissue

Steroidogenic cytochrome P450 enzymes as drug target

Human cytochrome P450 (CYP) enzymes are composed of 57 individual enzymes that perform monooxygenase activities. They have diverse physiological roles in metabolizing xenobiotics and producing important endogenous compounds, such as steroid hormones and vitamins. At least seven CYP enzymes are involved in steroid biosynthesis. Steroidogenesis primarily occurs in the adrenal glands and gonads, connecting each reaction to substrates and products. Steroids are essential for maintaining life and significantly contribute to sexual differentiation and reproductive functions within the body. Disorders in steroid biosynthesis can frequently cause serious health problems and lead to the development of diseases, such as prostate cancer, breast cancer, and Cushing's syndrome. In this review, we provide current updated knowledge on the major CYP enzymes involved in the biosynthetic process of steroids, with respect to their enzymatic mechanisms and clinical implications for the development of new drug candidates.

The multi-faceted nature of age-associated osteoporosis

Age-associated osteoporosis (AAOP) poses a significant health burden, characterized by increased fracture risk due to declining bone mass and strength. Effective prevention and early treatment strategies are crucial to mitigate the disease burden and the associated healthcare costs. Current therapeutic approaches effectively target the individual contributing factors to AAOP. Nonetheless, the management of AAOP is complicated by the multitude of variables that affect its development. Main intrinsic and extrinsic factors contributing to AAOP risk are reviewed here, including mechanical unloading, nutrient deficiency, hormonal disbalance, disrupted metabolism, cognitive decline, inflammation and circadian disruption. Furthermore, it is discussed how these can be targeted for prevention and treatment. Although valuable as individual targets for intervention, the interconnectedness of these risk factors result in a unique etiology for every patient. Acknowledgement of the multifaceted nature of AAOP will enable the development of more effective and sustainable management strategies, based on a holistic, patient-centered approach.

Aromatase deficiency in transplanted bone marrow cells improves vertebral trabecular bone quantity, connectivity, and mineralization and decreases cortical porosity in murine bone marrow transplant recipients

Estradiol is an important regulator of bone accumulation and maintenance. Circulating estrogens are primarily produced by the gonads. Aromatase, the enzyme responsible for the conversion of androgens to estrogen, is expressed by bone marrow cells (BMCs) of both hematopoietic and nonhematopoietic origin. While the significance of gonad-derived estradiol to bone health has been investigated, there is limited understanding regarding the relative contribution of BMC derived estrogens to bone metabolism. To elucidate the role of BMC derived estrogens in male bone, irradiated wild-type C57BL/6J mice received bone marrow cells transplanted from either WT (WT(WT)) or aromatase-deficient (WT(ArKO)) mice. MicroCT was acquired on lumbar vertebra to assess bone quantity and quality. WT(ArKO) animals had greater trabecular bone volume (BV/TV p = 0.002), with a higher trabecular number (p = 0.008), connectivity density (p = 0.017), and bone mineral content (p = 0.004). In cortical bone, WT(ArKO) animals exhibited smaller cortical pores and lower cortical porosity (p = 0.02). Static histomorphometry revealed fewer osteoclasts per bone surface (Oc.S/BS%), osteoclasts on the erosion surface (ES(Oc+)/BS, p = 0.04) and low number of osteoclasts per bone perimeter (N.Oc/B.Pm, p = 0.01) in WT(ArKO). Osteoblast-associated parameters in WT(ArKO) were lower but not statistically different from WT(WT). Dynamic histomorphometry suggested similar bone formation indices' patterns with lower mean values in mineral apposition rate, label separation, and BFR/BS in WT(ArKO) animals. Ex vivo bone cell differentiation assays demonstrated relative decreased osteoblast differentiation and ability to form mineralized nodules. This study demonstrates a role of local 17β-estradiol production by BMCs for regulating the quantity and quality of bone in male mice. Underlying in vivo cellular and molecular mechanisms require further study.

Estradiol increases cortical and trabecular bone accrual and bone strength in an adolescent male-to-female mouse model of gender-affirming hormone therapy

The effects of gender-affirming hormone therapy on the skeletal integrity and fracture risk in transitioning adolescent trans girls are unknown. To address this knowledge gap, we developed a mouse model to simulate male-to-female transition in human adolescents in whom puberty is first arrested by using gonadotrophin-releasing hormone analogs with subsequent estradiol treatment. Puberty was suppressed by orchidectomy in male mice at 5 weeks of age. At 3 weeks post-surgery, male-to-female mice were treated with a high dose of estradiol (~0.85 mg) by intraperitoneal silastic implantation for 12 weeks. Controls included intact and orchidectomized males at 3 weeks post-surgery, vehicle-treated intact males, intact females and orchidectomized males at 12 weeks post-treatment. Compared to male controls, orchidectomized males exhibited decreased peak bone mass accrual and a decreased maximal force the bone could withstand prior to fracture. Estradiol treatment in orchidectomized male-to-female mice compared to mice in all control groups was associated with an increased cortical thickness in the mid-diaphysis, while the periosteal circumference increased to a level that was intermediate between intact male and female controls, resulting in increased maximal force and stiffness. In trabecular bone, estradiol treatment increased newly formed trabeculae arising from the growth plate as well as mineralizing surface/bone surface and bone formation rate, consistent with the anabolic action of estradiol on osteoblast proliferation. These data support the concept that skeletal integrity can be preserved and that long-term fractures may be prevented in trans girls treated with GnRHa and a sufficiently high dose of GAHT. Further study is needed to identify an optimal dose of estradiol that protects the bone without adverse side effects.

Lower serum testosterone is associated with increased likelihood of arthritis

Studies have suggested that serum testosterone levels may be strongly correlated with the pathogenesis of arthritis. Therefore, the aim of this study was to assess the relationship between serum testosterone levels and arthritis in US adults using the National Health and Nutrition Examination Survey (NHANES). We used the database from NHANES, 2013-2016 to perform a cross-sectional study. This study investigated the relationship between serum testosterone and arthritis using multivariate logistic regression models and also used smoothed curve fitting and generalized additivity models. A total of 10,439 adults were included in this analysis. A significant negative association between serum testosterone and arthritis was found in a linear regression analysis. The study showed that the arthritis group had lower testosterone levels than the non-arthritis group. The univariate multivariate analyses of Q4, using Q1 as a reference, all showed a significantly lower risk of developing arthritis. In subgroup analyses, the negative correlation between serum testosterone levels and arthritis was more significant in women and those with a body mass index (BMI) ≥ 30 kg/m2. After controlling for various variables, we found a significant association between serum testosterone and arthritis in this analysis. Further study of the relationship between testosterone and arthritis is necessary to clarify the specific mechanism of serum testosterone action on arthritis.

Sex Differences in Athletic Performance: Perspectives on Transgender Athletes

Sex hormone concentrations, particularly testosterone, are primary determinants of sex-based differences in athletic and sports performance, and this relationship may inform fair competition and participation for athletes. This article describes the sex-based dichotomy in testosterone and the implications for sex-based differences in individual sports performance, including factors that relate to athletic performance for transgender individuals, and areas of future investigation.

RANK signaling in osteoclast precursors results in a more permissive epigenetic landscape and sexually divergent patterns of gene expression

Background

Sex is an important risk factor in the development of osteoporosis and other bone loss disorders, with women often demonstrating greater susceptibility than men. While variation in sex steroids, such as estradiol, accounts for much of the risk, there are likely additional non-endocrine factors at transcriptional and epigenetic levels that result in a higher rate of bone loss in women. Identification of these factors could improve risk assessment and therapies to preserve and improve bone health.

Methods

Osteoclast precursors were isolated male and female C57Bl/6 mice and cultured with either MCSF alone or MCSF and RANKL. Following the culture period RNA was isolated for RNA sequencing and DNA was isolated for tagmentation and ATAC sequencing. RNA-Seq and ATAC-seq were evaluated via pathway analysis to identify sex- and RANKL-differential transcription and chromatin accessibility.

Results

Osteoclasts demonstrated significant alterations in gene expression compared to macrophages with both shared and differential pathways between the sexes. Transcriptional pathways differentially regulated between male and female cells were associated with immunological functions with evidence of greater sensitivity in male macrophages and female osteoclasts. ATAC-Seq revealed a large increase in chromatin accessibility following RANKL treatment with few alterations attributable to sex. Comparison of RNA-Seq and ATAC-seq data revealed few common pathways suggesting that many of the transcriptional changes of osteoclastogenesis occur independently of chromatin remodeling.

Nuclear factor erythroid 2-related factor 2 (Nrf2) deficiency causes age-dependent progression of female osteoporosis

BACKGROUND

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a crucial transcription factor for cellular redox homeostasis. The association of Nrf2 with elderly female osteoporotic has yet to be fully described. The aim was to elucidate a potential age-dependent Nrf2 contribution to female osteoporosis in mice.

METHODS

Eighteen female wild type (WT) and 16 Nrf2-knockout (KO) mice were sacrificed at different ages (12 weeks = young mature adult and 90 weeks = old) to analyze their femurs. The morphological properties (trabecular and cortical) were evaluated by micro-computed tomography (μCT) and compared to gold standard histochemistry analysis. The quasi-static compression tests were performed to calculate the mechanical properties of bones. Additionally, the population of bone resorbing cells and aromatase expression by osteocytes was immunohistochemically evaluated and empty osteocyte lacunae was counted in cortical bone.

RESULTS

Old Nrf2-KO mice revealed a significantly reduced trabecular bone mineral density (BMD), cortical thickness, cortical area, and bone fraction compared to old WT mice, regardless of no significant difference in skeletally mature young adult mice between WT and KO. Specifically, while all old WT mice showed thin metaphyseal trabeculae, trabecular bone was completely absent in 60% of old KO mice. Additionally, old KO mice showed significantly more osteoclast-like cells and fewer aromatase-positive osteocytes than WT mice, whereas the occurrence of empty osteocyte lacunae did not differ between both groups. Nrf2-KO mice further showed an age-dependently reduced fracture resilience compared to age-matched WT mice.

CONCLUSION

Our results suggest that chronic Nrf2 loss can lead to age-dependent progression of female osteoporosis.

The role of estrogens in osteosarcopenia: from biology to potential dual therapeutic effects

Osteoporosis and sarcopenia are two conditions associated with aging and characterized by a simultaneous decline in bone and muscle mass, respectively. These conditions share common risk factors (genetic, endocrine, nutritional and lifestyle factors) and biological pathways that often co-exist in a syndrome known as osteosarcopenia. Among the endocrine causes, estrogens play a critical role, especially in women. Estrogens have been demonstrated to exert a positive effect on bone and muscle development and maintenance. For this reason, menopause is characterized by a loss in bone mineral density and skeletal muscle quality and quantity. To date, studies indicate a positive effect of hormonal therapy on the prevention and management of osteoporosis, to the point that estrogen is prescribed as a first-line treatment for osteoporosis by the major international authorities. While results on sarcopenia are still disputable, such that estrogens are not recommended to prevent muscle loss in postmenopausal women, increased response to anabolic stimuli with estrogen therapy suggests similar beneficial effects on muscle as seen with bone, particularly when combined with resistance exercise.

Molecular Signaling Pathways and Essential Metabolic Elements in Bone Remodeling: An Implication of Therapeutic Targets for Bone Diseases

Bone is one of the dynamic tissues in the human body that undergoes continuous remodelling through subsequent actions of bone cells, osteoclasts, and osteoblasts. Several signal transduction pathways are involved in the transition of mesenchymal stem cells into osteoblasts. These primarily include Runx2, ATF4, Wnt signaling and sympathetic signalling. The differentiation of osteoclasts is controlled by M-CSF, RANKL, and costimulatory signalling. It is well known that bone remodelling is regulated through receptor activator of nuclear factor-kappa B ligand followed by binding to RANK, which eventually induces the differentiation of osteoclasts. The resorbing osteoclasts secrete TRAP, cathepsin K, MMP-9 and gelatinase to digest the proteinaceous matrix of type I collagen and form a saucer-shaped lacuna along with resorption tunnels in the trabecular bone. Osteoblasts secrete a soluble decoy receptor, osteoprotegerin that prevents the binding of RANK/RANKL and thus moderating osteoclastogenesis. Moreover, bone homeostasis is also regulated by several growth factors like, cytokines, calciotropic hormones, parathyroid hormone and sex steroids. The current review presents a correlation of the probable molecular targets underlying the regulation of bone mass and the role of essential metabolic elements in bone remodelling. Targeting these signaling pathways may help to design newer therapies for treating bone diseases.

Structural study of letrozole and metronidazole and formation of self-assembly with graphene and fullerene with the enhancement of physical, chemical and biological activities

Letrozole and metronidazole are two commonly used drugs for the management of breast cancer and parasitic infections, respectively. This manuscript attempts to study their structure, geometry, search for stable conformers using relaxed potential energy scan, spectral properties, quantum mechanical properties like energy and reactivity descriptors, intra molecular electron transfer properties, non-linear properties etc using various computational tools. It is found that these compounds will form a self-assembly with graphene sheets and fullerenes and exhibit a surface-enhanced Raman spectra and enhancement in non-linear optical properties when compared to the single molecule. The electronic absorption behavior of the compounds was studied using TD-DFT method. Global chemical reactivity descriptors and activity sites toward electrophilic and nucleophilic attack have been discussed. Studies of intra molecular electron transfer gave information about the relative stability of the compounds. Molecular docking studies indicate that the pure compounds and their self-assemblies with graphene have excellent biological activities.Communicated by Ramaswamy H. Sarma.

Role of hydroxysteroid (17beta) dehydrogenase type 1 in reproductive tissues and hormone-dependent diseases

Abnormal synthesis and metabolism of sex steroids is involved in the pathogenesis of various human diseases, such as endometriosis and cancers arising from the breast and uterus. Steroid biosynthesis is a multistep enzymatic process proceeding from cholesterol to highly active sex steroids via different intermediates. Human Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) enzyme shows a high capacity to produce the highly active estrogen, estradiol, from a precursor hormone, estrone. However, the enzyme may also play a role in other steps of the steroid biosynthesis pathway. In this article, we have reviewed the literature on HSD17B1, and summarize the role of the enzyme in hormone-dependent diseases in women as evidenced by preclinical studies.

Prevalence and Predictors of Osteoporosis Among the Chinese Population in Klang Valley, Malaysia

The prevalence of osteoporosis is forecasted to escalate in Malaysia with an increasing elderly population. This study aimed to analyze the prevalence and the risk factors of osteoporosis among middle-aged and elderly Chinese Malaysians. Three hundred sixty seven Malaysian Chinese aged ≥40 years in Klang Valley, Malaysia, were recruited. All subjects completed a structured questionnaire comprised of demographic details, medical history, diet, and lifestyle practices. Body anthropometry and bone mineral density measurements were also performed. The relationship between bone health status and risk factors was determined using multivariate logistic regression. Fifteen-point-three percent of the overall study population and 32.6% of those aged ≥71 years had osteoporosis. The prevalence of osteoporosis among women (18.9%) was higher than men (11.5%). The significant predictors of osteoporosis were age, body weight, and low monthly income. Lean mass, low education level, and being underweight predicted osteoporosis in women. Lean mass was the only significant predictor of osteoporosis in men. Overall, 15.3% of the Malaysian Chinese aged ≥40 years from Klang Valley, Malaysia, had osteoporosis. Osteoporosis was associated positively with increased age and low monthly income and negatively with body weight. Therefore, osteoporosis preventive strategies targeting Chinese elderly from a low socioeconomic background is necessary.

Porcine intestinal lymphoid tissues synthesize estradiol

Estradiol (17β-estradiol) is synthesized primarily in the gonads of both sexes and regulates the development and function of reproductive organs. Recently, we reported that intestinal lymphocyte homeostasis is regulated by estradiol synthesized de novo in the endothelial cells of the high endothelial venules (HEVs) of mesenteric lymph nodes and Peyer's patches in mice. This observation prompted us to hypothesize that HEVs of intestinal lymphoid tissues are sites of estradiol synthesis across species. In this study, we examined whether estradiol is synthesized in the intestinal lymphoid tissues of adolescent piglets. Comparisons of estradiol levels in blood and tissue showed that estradiol concentrations in mesenteric lymph nodes and Peyer's patches were significantly higher than the level in serum. Reverse transcription polymerase chain reaction showed that porcine intestinal lymphoid tissues express mRNAs for steroidogenic enzymes (StAR, 17β-Hsd,3β-Hsd, Cyp17a1, and Cyp19a1), and immunohistochemical results in ilial tissue showed expression of aromatase (CYP19) in Peyer's patch-localized endothelial cells of HEVs. When mesenteric lymph node and Peyer's patch tissues were cultured in vitro, they produced estradiol. Taken together, the results indicate that mesenteric lymph nodes and Peyer's patches are sites of estradiol synthesis in adolescent piglets.

Intracrine Regulation of Estrogen and Other Sex Steroid Levels in Endometrium and Non-gynecological Tissues; Pathology, Physiology, and Drug Discovery

Our understanding of the intracrine (or local) regulation of estrogen and other steroid synthesis and degradation expanded in the last decades, also thanks to recent technological advances in chromatography mass-spectrometry. Estrogen responsive tissues and organs are not passive receivers of the pool of steroids present in the blood but they can actively modify the intra-tissue steroid concentrations. This allows fine-tuning the exposure of responsive tissues and organs to estrogens and other steroids in order to best respond to the physiological needs of each specific organ. Deviations in such intracrine control can lead to unbalanced steroid hormone exposure and disturbances. Through a systematic bibliographic search on the expression of the intracrine enzymes in various tissues, this review gives an up-to-date view of the intracrine estrogen metabolisms, and to a lesser extent that of progestogens and androgens, in the lower female genital tract, including the physiological control of endometrial functions, receptivity, menopausal status and related pathological conditions. An overview of the intracrine regulation in extra gynecological tissues such as the lungs, gastrointestinal tract, brain, colon and bone is given. Current therapeutic approaches aimed at interfering with these metabolisms and future perspectives are discussed.

Leptin stimulates aromatase in the growth plate: limiting catch-up growth efficiency

Catch-up growth (CUG) in childhood is defined as periods of growth acceleration, after the resolution of growth attenuation causes, bringing the children back to their original growth trajectory. Sometimes, however, CUG is incomplete, leading to permanent growth deficit and short stature. The aim of this study was to investigate the mechanisms that limit nutritional-CUG. Specifically, we focused on the crosstalk between leptin, increased by re-feeding, and sex hormones, which increase with age. In vivo studies were performed in young male Sprague Dawley rats fed ad libitum or subjected to 10/36 days of 40% food restriction followed by 90-120 days of re-feeding. In vitro studies were performed on ATDC5 cells. Analyses of mRNA and protein levels were done using qPCR and Western blot, respectively. CUG was complete in body weight and humerus length in animals that were food-restricted for 10 days but not for those food-restricted for 36 days. In vitro studies showed that leptin significantly increased aromatase gene expression and protein level as well as the expression of estrogen and leptin receptors in a dose- and time-dependent manner. The effect of leptin on aromatase was direct and was mediated through the MAPK/Erk, STAT3 and PI3K pathways. The crosstalk between leptin and aromatase in the growth plate suggests that re-feeding during puberty may lead to increased estrogen level and activity, and consequently, irreversible premature epiphyseal growth plate closure. These results may have important implications for the development of novel treatment strategies for short stature in children.

Local estrogen axis in the human bone microenvironment regulates estrogen receptor-positive breast cancer cells

BACKGROUND

Approximately 70% of all breast cancers express the estrogen receptor, and are regulated by estrogen. While the ovaries are the primary source of estrogen in premenopausal women, most breast cancer is diagnosed following menopause, when systemic levels of this hormone decline. Estrogen production from androgen precursors is catalyzed by the aromatase enzyme. Although aromatase expression and local estrogen production in breast adipose tissue have been implicated in the development of primary breast cancer, the source of estrogen involved in the regulation of estrogen receptor-positive (ER+) metastatic breast cancer progression is less clear.

METHODS

Bone is the most common distant site of breast cancer metastasis, particularly for ER+ breast cancers. We employed a co-culture model using trabecular  bone tissues obtained from total hip replacement (THR) surgery specimens to study ER+ and estrogen receptor-negative (ER-) breast cancer cells within the human bone microenvironment. Luciferase-expressing ER+ (MCF-7, T-47D, ZR-75) and ER- (SK-BR-3, MDA-MB-231, MCF-10A) breast cancer cells were cultured directly on bone tissue fragments or in bone tissue-conditioned media, and monitored over time with bioluminescence imaging (BLI). Bone tissue-conditioned media were generated in the presence vs. absence of aromatase inhibitors, and testosterone. Bone tissue fragments were analyzed for aromatase expression by immunohistochemistry.

RESULTS

ER+ breast cancer cells were preferentially sustained in co-cultures with bone tissues and bone tissue-conditioned media relative to ER- cells. Bone fragments analyzed by immunohistochemistry revealed expression of the aromatase enzyme. Bone tissue-conditioned media generated in the presence of testosterone had increased estrogen levels and heightened capacity to stimulate ER+ breast cancer cell proliferation. Pretreatment of cultured bone tissues with aromatase inhibitors, which inhibited estrogen production, reduced the capacity of conditioned media to stimulate ER+ cell proliferation.

CONCLUSIONS

These results suggest that a local estrogen signaling axis regulates ER+ breast cancer cell viability and proliferation within the bone metastatic niche, and that aromatase inhibitors modulate this axis. Although endocrine therapies are highly effective in the treatment of ER+ breast cancer, resistance to these treatments reduces their efficacy. Characterization of estrogen signaling networks within the bone microenvironment will identify new strategies for combating metastatic progression and endocrine resistance.

Roles of Aryl Hydrocarbon Receptor in Aromatase-Dependent Cell Proliferation in Human Osteoblasts

Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor and its expression is influenced by environmental compounds, such as 3-methylcholanthrene (3-MC) and β-naphthoflavone (β-NF). AhR and its downstream genes, such as CYP1A1, are considered to play a pivotal role in xenobiotic responses. AhR signaling has also been proposed to mediate osteogenesis in experimental animals, but its details have remained unclear. Therefore, in this study, we examined the possible roles of AhR in human bone. Immunohistochemical analysis revealed that AhR was detected in both osteoblasts and osteoclasts. We then screened AhR-target genes using a microarray analysis in human osteoblastic hFOB cells. Results of microarray and subsequent PCR analysis did reveal that estrogen metabolizing and synthesizing enzymes, such as CYP1B1 and aromatase, were increased by 3-MC in hFOB and osteosarcoma cell line, MG-63. The subsequent antibody cytokine analysis also demonstrated that interleukin-1β and -6 expression was increased by 3-MC and β-NF in hFOB cells and these interleukins were well known to induce aromatase. We then examined the cell proliferation rate of hFOB and MG-63 cells co-treated with 3-MC and testosterone as an aromatase substrate. The status of cell proliferation in both hFOB and MG-63 cells was stimulated by 3-MC and testosterone treatment, which was also inhibited by an estrogen blocker, aromatase inhibitor, or AhR antagonist. These findings indicated that AhR could regulate estrogen synthesis and metabolism in bone tissues through cytokine/aromatase signaling.

Stress differentially affects the systemic and leukocyte estrogen network in common carp

Both systemic and locally released steroid hormones, such as cortisol and estrogens, show immunomodulatory actions. This research gives evidence that circulating and leukocyte-derived estrogens can be involved in the regulation of the immune response in common carp, during homeostasis and upon restraining stress. It was found that stress reduced level of blood 17β-estradiol (E2) and down-regulated the gene expression of components of the "classical" estrogen system: the nuclear estrogen receptors and the aromatase CYP19, in the hypothalamus, the pituitary and in the ovaries. In contrast, higher gene expression of the nuclear estrogen receptors and cyp19a was found in the head kidney of stressed animals. Moreover, stress induced changes in the E2 level and in the estrogen sensitivity at local/leukocyte level. For the first time in fish, we showed the presence of physiologically relevant amounts of E2 and the substrates for its conversion (estrone - E1 and testosterone - T) in head kidney monocytes/macrophages and found that its production is modulated upon stress. Moreover, stress reduced the sensitivity of leukocytes towards estrogens, by down-regulation the expression of the erb and cyp19 genes in carp phagocytes. In contrast, era expression was up-regulated in the head kidney monocytes/macrophages and in PBLs derived from stressed animals. We hypothesize that, the increased expression of ERα, that was observed during stress, can be important for the regulation of leukocyte differentiation, maturation and migration. In conclusion, these results indicate that, in fish, the estrogen network can be actively involved in the regulation of the systemic and local stress response and the immune response.

An Embryonic and Induced Pluripotent Stem Cell Model for Ovarian Granulosa Cell Development and Steroidogenesis

Embryoid bodies (EBs) can serve as a system for evaluating pluripotency, cellular differentiation, and tissue morphogenesis. In this study, we use EBs derived from mouse embryonic stem cells (mESCs) and human amniocyte-derived induced pluripotent stem cells (hAdiPSCs) as a model for ovarian granulosa cell (GC) development and steroidogenic cell commitment. We demonstrated that spontaneously differentiated murine EBs (mEBs) and human EBs (hEBs) displayed ovarian GC markers, such as aromatase (CYP19A1), FOXL2, AMHR2, FSHR, and GJA1. Comparative microarray analysis identified both shared and unique gene expression between mEBs and the maturing mouse ovary. Gene sets related to gonadogenesis, lipid metabolism, and ovarian development were significantly overrepresented in EBs. Of the 29 genes, 15 that were differentially regulated in steroidogenic mEBs displayed temporal expression changes between embryonic, postnatal, and mature ovarian tissues by polymerase chain reaction. Importantly, both mEBs and hEBs were capable of gonadotropin-responsive estradiol (E2) synthesis in vitro (217-759 pg/mL). Live fluorescence-activated cell sorting-sorted AMHR2⁺ granulosa-like cells from mEBs continued to produce E2 after purification (15.3 pg/mL) and secreted significantly more E2 than AMHR2^- cells (8.6 pg/mL, P < .05). We conclude that spontaneously differentiated EBs of both mESC and hAdiPSC origin can serve as a biologically relevant model for ovarian GC differentiation and steroidogenic cell commitment. These cells should be further investigated for therapeutic uses, such as stem cell-based hormone replacement therapy and in vitro maturation of oocytes.

Estradiol for the mitigation of adverse effects of androgen deprivation therapy

Prostate cancer (PCa) is the second most commonly diagnosed cancer in men. Conventional endocrine treatment for PCa leads to global sex steroid deprivation. The ensuing severe hypogonadism is associated with well-documented adverse effects. Recently, it has become apparent that many of the biological actions attributed to androgens in men are in fact not direct, but mediated by estradiol. Available evidence supports a primary role for estradiol in vasomotor stability, skeletal maturation and maintenance, and prevention of fat accumulation. Hence there has been interest in revisiting estradiol as a treatment for PCa. Potential roles for estradiol could be in lieu of conventional androgen deprivation therapy or as low-dose add-back treatment while continuing androgen deprivation therapy. These strategies may limit some of the side effects associated with conventional androgen deprivation therapy. However, although available data are reassuring, the potential for cardiovascular risk and pro-carcinogenic effects on PCa via estrogen receptor signalling must be considered.

Male Hypogonadism and Osteoporosis: The Effects, Clinical Consequences, and Treatment of Testosterone Deficiency in Bone Health

It is well recognized that bone loss accelerates in hypogonadal states, with female menopause being the classic example of sex hormones affecting the regulation of bone metabolism. Underrepresented is our knowledge of the clinical and metabolic consequences of overt male hypogonadism, as well as the more subtle age-related decline in testosterone on bone quality. While menopause and estrogen deficiency are well-known risk factors for osteoporosis in women, the effects of age-related testosterone decline in men on bone health are less well known. Much of our knowledge comes from observational studies and retrospective analysis on small groups of men with variable causes of primary or secondary hypogonadism and mild to overt testosterone deficiencies. This review aims to present the current knowledge of the consequences of adult male hypogonadism on bone metabolism. The direct and indirect effects of testosterone on bone cells will be explored as well as the important differences in male osteoporosis and assessment as compared to that in females. The clinical consequence of both primary and secondary hypogonadism, as well as testosterone decline in older males, on bone density and fracture risk in men will be summarized. Finally, the therapeutic options and their efficacy in male osteoporosis and hypogonadism will be discussed.

Extra-gonadal sites of estrogen biosynthesis and function

Estrogens are the key hormones regulating the development and function of reproductive organs in all vertebrates. Recent evidence indicates that estrogens play important roles in the immune system, cancer development, and other critical biological processes related to human well-being. Obviously, the gonads (ovary and testis) are the primary sites of estrogen synthesis, but estrogens synthesized in extra- gonadal sites play an equally important role in controlling biological activities. Understanding non-gonadal sites of estrogen synthesis and function is crucial and will lead to therapeutic interventions targeting estrogen signaling in disease prevention and treatment. Developing a rationale targeting strategy remains challenging because knowledge of extra-gonadal biosynthesis of estrogens, and the mechanism by which estrogen activity is exerted, is very limited. In this review, we will summarize recent discoveries of extra-gonadal sites of estrogen biosynthesis and their local functions and discuss the significance of the most recent novel discovery of intestinal estrogen biosynthesis. [BMB Reports 2016; 49(9): 488-496]

Aromatase expression in human chondrocytes: An induction due to culture

OBJECTIVES

Despite the high prevalence of osteoarthritis (OA) in postmenopausal women, a relationship between circulating estrogen levels and the development of OA has not been found. Therefore, the purpose of this study was to evaluate the expression and activity of aromatase, a key enzyme in local production of estrogens, in human OA cultured articular chondrocytes, and to determine the physiological relevance of this enzyme in cartilage.

METHODS

Human OA articular chondrocytes were isolated and cultured. Local production of estradiol was measured after incubation with 100 ng/ml testosterone for 8 and 24h. Furthermore, chondrocytes were culture for 2h, 48 h, 7 days or 15 days, or in alginate beads for 10 days. Aromatase, type II and X collagen, aggrecan, alkaline phosphatase, and Runx2 expression were evaluated in cartilage, freshly isolated chondrocytes and cultured chondrocytes.

RESULTS

Aromatase was expressed and active in cultured human chondrocytes. Human cartilage, freshly isolated chondrocytes, and chondrocytes cultured for 2h expressed an insignificant amount of aromatase; however, expression arose after 48 h of culture and remained increased thereafter. Aromatase expression was not related to estrogen deprivation and was inversely correlated with differentiation. Re-differentiation did not reduce its expression.

CONCLUSIONS

Aromatase presents an almost undetectable expression in human cartilage but is induced in cultured chondrocytes. Therefore, human cartilage might act as a mere target for estrogens rather than a producer, and researchers using cell expansion in culture for latter therapies should consider these changes in estrogen metabolism which may not be reverted after re-differentiation.

Influence of sex steroids on inflammation and bone metabolism

Sex steroids are central to sexual development and reproduction, exerting pleiotropic effects on multiple tissues and organs throughout the lifespan of humans. Sex steroids are fundamental to skeletal development, bone homeostasis and immune function. The composite effect of sex-specific genetic architecture and circulating levels of sex-steroid hormones closely parallels differences in the immune response and may account for corresponding sex-related differences in risk for chronic periodontitis, with men exhibiting greater susceptibility than women. Age-associated reductions in sex steroids also provide insight into apparent temporal increases in susceptibility to periodontitis and alveolar bone loss, particularly among women. Chronic infection and inflammatory conditions, such as periodontal disease, provide a unique platform for exploring the interface of sex steroids, immunity and bone metabolism.

Relation of adrenal-derived steroids with bone maturation, mineral density and geometry in healthy prepubertal and early pubertal boys

BACKGROUND

Little is known about the effects of adrenal steroids on skeletal maturation and bone mass acquisition in healthy prepubertal boys.

OBJECTIVE

To study whether adrenal-derived steroids within the physiological range are associated with skeletal maturation, areal and volumetric bone mineral density (aBMD and vBMD) and bone geometry in healthy prepubertal and early pubertal boys.

METHODS

98 healthy prepubertal and early pubertal boys (aged 6-14 y) were studied cross-sectionally. Androstenedione (A) and estrone (E1) were determined by liquid chromatography tandem mass spectrometry and DHEAS was determined by immunoassay. Whole body and lumbar spine aBMD and bone area were determined by dual-energy X-ray absorptiometry. Trabecular (distal site) and cortical (proximal site) vBMD and bone geometry were assessed at the non-dominant forearm and leg using peripheral QCT. Skeletal age was determined by X-ray of the left hand.

RESULTS

Adrenal-derived steroids (DHEAS, A and E1) are positively associated with bone age in prepubertal and early pubertal children, independently of age. There are no associations between the adrenal-derived steroids and the studied parameters of bone size (lumbar spine and whole body bone area, trabecular or cortical area at the radius or tibia, periosteal circumference and cortical thickness at the radius or tibia) or BMD (aBMD or vBMD).

CONCLUSION

In healthy prepubertal and early pubertal boys, serum adrenal-derived steroid levels, are associated with skeletal maturation, independently of age, but not with bone size or (v)BMD. Our data suggest that adrenal derived steroids are not implicated in the accretion of bone mass before puberty in boys.

Endocrine Resistance in Breast Cancer

Around 70% of all breast cancers are estrogen receptor alpha positive and hence their development is highly dependent on estradiol. While the invention of endocrine therapies has revolusioned the treatment of the disease, resistance to therapy eventually occurs in a large number of patients. This paper seeks to illustrate and discuss the complexity and heterogeneity of the mechanisms which underlie resistance and the approaches proposed to combat them. It will also focus on the use and development of methods for predicting which patients are likely to develop resistance.

Association of the (TTTA)n repeat polymorphism of CYP19 gene with bone mineral density in Greek peri- and postmenopausal women

Aromatase is encoded by the CYP19 gene and catalyses the conversion of androgens to oestrogens, which in turn regulate skeletal homeostasis. CYP19 gene polymorphisms have been studied for their association with bone mineral density (BMD) in the general population with mixed results.

OBJECTIVE

To explore the influence of the CYP19 (TTTA)n repeat polymorphism on BMD and serum levels of osteoprotegerin (OPG), receptor activator of nuclear factor-κΒ ligand (RANKL), and bone metabolic markers in a Greek female population.

DESIGN

Cross-sectional study.

PARTICIPANTS AND MEASUREMENTS

Two hundred and seventeen peri- and postmenopausal women aged 42-63 years were enrolled. All participants underwent spinal BMD evaluation by dual-energy X-ray absorptiometry (DXA). Genotyping of the (TTTA)n repeat polymorphism was performed by polymerase chain reaction. Levels of OPG, soluble RANKL (sRANKL) and bone metabolic markers were measured.

RESULTS

Genotype analysis revealed alleles having 7-12 TTTA repeats. Women carrying the (TTTA)11 and/or (TTTA)12 alleles had significantly higher spinal BMD than women not carrying these alleles in the total study population as well as in the subgroup of women with osteoporosis (P = 0·042 and P = 0·006, respectively). The aforementioned associations remained significant after adjustment for age, years since menopause, smoking and body mass index (P = 0·048 and P = 0·023, respectively, by multivariate analysis). Moreover, the urinary calcium to creatinine ratio was associated with the (TTTA)n polymorphism. No association of the (TTTA)n polymorphism with circulating levels of OPG, sRANKL was observed.

CONCLUSIONS

The (TTTA)n polymorphism of the CYP19 gene is associated with spinal BMD in peri- and postmenopausal Greek women.

Articular cartilage chondrocytes express aromatase and use enzymes involved in estrogen metabolism

Introduction

Sex hormones, especially estrogens, have been implicated in articular cartilage metabolism and the pathogenesis of postmenopausal osteoarthritis. The conversion by aromatase (CYP19A1) of androstenedione into estrone (E1) and of testosterone into 17β-estradiol (E2) plays a key role in the endogenous synthesis of estrogens in tissue.

Methods

We analyzed the expression of aromatase (CYP19A1) in immortalized C-28/I2 and T/C-28a2 chondrocytes, as well as in cultured primary human articular chondrocytes and human articular cartilage tissue, by means of RT-PCR, Western blotting and immunohistochemistry. By means of quantitative RT-PCR and enzyme-linked immunosorbent assay, we also determined whether the aromatase inhibitor letrozole influences estrogen metabolism of cultured chondrocytes in immortalized C-28/I2 chondrocytes.

Results

Aromatase mRNA was detected in both immortalized chondrocyte cell lines, in cultured primary human chondrocytes, and in human articular cartilage tissue. By means of Western blot analysis, aromatase was detected at the protein level in articular cartilage taken from various patients of both sexes and different ages. Cultured primary human articular chondrocytes, C-28/I2 and T/C-28a2, and human articular cartilage tissue reacted with antibodies for aromatase. Incubation of C-28/I2 chondrocytes with 10⁻¹¹ M to 10⁻⁷ M letrozole as an aromatase inhibitor revealed significantly increased amounts of the mRNAs of the enzyme cytochrome P4501A1 (CYP1A1), which is involved in the catagen estrogen metabolism, and of the estrogen receptors ER-α and ER-β. Concomitantly, synthesis of estrone (E1) was significantly downregulated after incubation with letrozole.

Conclusions

We demonstrate that human articular cartilage expresses aromatase at the mRNA and protein levels. Blocking of estrone synthesis by the aromatase inhibitor letrozole is counteracted by an increase in ER-α and ER-β. In addition, CYP1A1, an enzyme involved in catabolic estrogen metabolism, is upregulated. This suggests that articular chondrocytes use ERs functionally. The role of endogenous synthesized estrogens in articular cartilage health remains to be elucidated.

What's the matter with MAT? Marrow adipose tissue, metabolism, and skeletal health

Marrow adipose tissue (MAT) is functionally distinct from both white and brown adipose tissue and can contribute to systemic and skeletal metabolism. MAT formation is a spatially and temporally defined developmental event, suggesting that MAT is an organ that serves important functions and, like other organs, can undergo pathologic change. The well-documented inverse relationship between MAT and bone mineral density has been interpreted to mean that MAT removal is a possible therapeutic target for osteoporosis. However, the bone and metabolic phenotypes of patients with lipodystrophy argues that retention of MAT may actually be beneficial in some circumstances. Furthermore, MAT may exist in two forms, regulated and constitutive, with divergent responses to hematopoietic and nutritional demands. In this review, we discuss the role of MAT in lipodystrophy, bone loss, and metabolism, and highlight our current understanding of this unique adipose tissue depot.

Upregulation of ANK protein expression in joint tissue in calcium pyrophosphate dihydrate crystal deposition disease

OBJECTIVE

Accumulation of excess extracellular inorganic pyrophosphate leads to calcium pyrophosphate dihydrate (CPPD) crystal formation in articular cartilage. CPPD crystal formation occurs near morphologically abnormal chondrocytes resembling hypertrophic chondrocytes. The ANK protein was recently implicated as an important factor in the transport of intracellular inorganic pyrophosphate across the cell membrane. We characterized ANK in joint tissues from patients with and without CPPD deposition and correlated the presence of ANK with markers of chondrocyte hypertrophy.

METHODS

Articular tissues were obtained from 24 patients with CPPD crystal deposition disease, 11 patients with osteoarthritis (OA) without crystals, and 6 controls. We determined the number of ANK-positive cells in joint tissues using immunohistochemistry and in situ hybridization, and correlated ANK positivity with markers of chondrocyte hypertrophy including Runx2, type X collagen, osteopontin (OPN), and osteocalcin (OCN).

RESULTS

ANK was detected in synoviocytes, chondrocytes, osteoblasts, and osteocytes. ANK was seen extracellularly only in the matrix of cartilage and meniscus. The number of ANK-positive cells was significantly higher in CPPD than in OA or normal joint tissues. The amount and intensity of ANK immunoreactivity reached maximum levels in the large chondrocytes around crystal deposits. ANK was similarly distributed to and significantly correlated with Runx2, type X collagen, OPN, and OCN.

CONCLUSION

ANK levels were higher in articular tissues from patients with CPPD deposition. ANK was concentrated around crystal deposits and correlated with markers of chondrocyte hypertrophy. These findings support a role for ANK in CPPD crystal formation in cartilage.

Estrogen favors the differentiation of ovarian tissues in the ambisexual gonads of anemonefish Amphiprion clarkii

All undifferentiated gonads of anemonefish first differentiate into ovaries, and then testicular tissue appear among ovarian tissue, and finally form ambisexual gonads with both ovarian and testicular tissues. The role of estradiol-17beta (E2) in differentiation of ovarian cells is well conserved across phyla; however, its role in development of ambisexual gonads is poorly understood. Here we demonstrate that the E2 produced during the differentiation of ovarian cells does not allow testicular cells to differentiate in the prospective ambisexual gonad. We examined the immunolocalization of the steroidogenic enzyme cytochrome aromatase (P450(arom)), which is involved in E2 production. In the gonads, numbers of the P450(arom) -positive cells increased during ovarian differentiation. However, immunopositive cells with weak signal intensity were seen in the interstitial areas among oocytes and between oocytes and testicular tissue undergoing testicular differentiation. In contrast, P450(arom) -positive cells were not found in any testicular tissues of the ambisexual gonads. We also examined changes in E2 production in vitro in the gonads during testicular differentiation. E2 was high in the ovaries before the appearance all of testicular tissue, and decreased accompanying the differentiation of testicular tissue. These results suggest a balance of estrogen/androgen seems to be important during sex differentiation, and then a shift from estrogen to androgen production may induce testicular differentiation in the ovary. Further, exogenous E2 treatment suppressed naturally occurring differentiation of testicular cells forming exclusively ovarian tissues in the gonad in vivo, suggesting the increase of estrogen blocks the differentiation of testicular tissue and the formation of ambisexual gonad.

Bone mineral density and vitamin D in PCOS and hirsutism

Polycystic ovary syndrome (PCOS) is the most frequent endocrinopathy in reproductive-aged women. The majority of hirsute patients are diagnosed with PCOS. Hyperandrogenemia, central obesity and insulin resistance may protect patients with PCOS from osteoporosis, whereas increased cortisol levels, low growth hormone and amenorrhea may be associated with decreased bone mineral density (BMD). Recent studies suggested that insulin resistance in PCOS is associated with decreased vitamin D levels that could not be explained by obesity alone. Vitamin D treatment may therefore have positive effects on insulin sensitivity and perhaps also hyperandrogenemia in patients with PCOS. In the present article, we review the evidence of changed BMD, bone mineral turnover and vitamin D status in PCOS and hirsutism compared with healthy women and the effects of medical intervention on BMD in PCOS.

Intracrine oestrogen production and action in breast cancer: an epigenetic focus

Epigenome changes have been widely demonstrated to contribute to the initiation and progression of a vast array of cancers including breast cancer. The reversible process of many epigenetic modifications is thus an attractive feature for the development of novel therapeutic measures. In oestrogen receptor α (hereinafter referred to as ER) positive tumours, endocrine therapies have proven beneficial in patient care, particularly in postmenopausal women where two-thirds of tumours are oestrogen dependent. However, resistance to such therapies is a common feature amongst individuals. In the current review, we discuss the influence that epigenetics has on oestrogen dependent breast cancers, in particular (i) the production of intracrine oestrogen in postmenopausal women, (ii) the action of oestrogen on epigenetic processes, and (iii) the links between epigenetics and endocrine resistance and the current advancements in epigenetic therapy that target this process. This article is part of a Special Issue entitled 'CSR 2013'.

Low androstenedione/sex hormone binding globulin ratio increases fracture risk in postmenopausal women. The Women's Health in the Lund Area study

The Women's Health in the Lund Area (WHILA) project (n=6917) is a cohort study that started in 1995 and includes a postal questionnaire, physical examination, bone density measurement and blood laboratory analyses. Fracture data have been added, and in this report fracture risk and its association with sex hormones was analysed in postmenopausal women without current hormone therapy (HT). A total of 409 women (median age 56.8 years) with 489 fractures were identified from the postmenopausal women without HT during a median follow-up time of 8.4 years. Lower serum levels of androstenedione (p<0.001), testosterone (p=0.008), androstenedione/sex hormone binding globulin (SHBG) ratio (p<0.001), testosterone/SHBG ratio (p=0.003) and higher levels of SHBG (p=0.005) were observed in women with fractures compared to no fracture. No difference in oestradiol levels was observed. Androstenedione and androstenedione/SHBG ratio were further divided into percentiles. Increased fracture risk was found in postmenopausal women with androstenedione in 5th percentile compared to 11-89th percentile HR 1.51 (95% CI 1.02-2.24). The androstenedione/SHBG ratio (11-89th percentile as reference) showed increased fracture risk in women with low ratio 5th percentile HR 1.75 (95% CI 1.20-2.54) and decreased fracture risk with high ratio 95th percentile HR 0.52 (95% CI 0.28-0.98). An increased fracture risk during follow-up was encountered in postmenopausal women with low serum androstenedione and androstenedione/SHBG ratio at baseline and a decreased fracture risk with high androstenedione/SHBG ratio. This study suggests that postmenopausal osteoporosis is influenced by lower levels of androgens.

New insights into osteoporosis: the bone-fat connection

Osteoporosis and obesity are chronic disorders that are both increasing in prevalence. The pathophysiology of these conditions is multifactorial and includes genetic, environmental and hormonal determinants. Although it has long been considered that these are distinct disorders rarely found in the same individual, emerging evidence from basic and clinical studies support an important interaction between adipose tissue and the skeleton. It is proposed that adiposity may influence bone remodelling through three mechanisms: (i) secretion of cytokines that directly target bone, (ii) production of adipokines that influence the central nervous system thereby changing sympathetic impulses to bone and (iii) paracrine influences on adjacent skeletal cells. Here we focus on the current understanding of bone-fat interactions and the clinical implications of recent studies linking obesity to osteoporosis.

Pharmacogenomics of third-generation aromatase inhibitors

INTRODUCTION

Breast cancer is a common, life-threatening disease among women. Contemporary hormonal therapy with third-generation aromatase inhibitors for estrogen-receptor-positive breast cancers in postmenopausal women is still facing the challenge of interpatient variability in therapeutic response and intensity of adverse effects.

AREAS COVERED

This review highlights up-to-date literature regarding genomic findings in the literature pertaining to anastrozole, exemestane and letrozole metabolism, as well as the drug target aromatase. Genetic polymorphisms in phase I and II aromatase inhibitor metabolizing enzymes that contribute to altered responses among different patient genotypes are discussed. Similarly, aromatase CYP19A1 functional genetic polymorphisms are presented in correlation to altered aromatase activity, disease prognosis and severity of aromatase inhibitor adverse effects.

EXPERT OPINION

The field of pharmacogenomics has shown remarkable progress over the last few years, notably in cancer. However, large comprehensive genotyping studies, evaluated under clinical settings, are still needed to unravel the potential impact of aromatase inhibitor pharmacogenomics on breast cancer treatment, monitoring and predicting adverse effects.

Estrogen receptor dependent gene expression by osteoblasts - direct, indirect, circumspect, and speculative effects

Hormone activated estrogen receptors (ERs) have long been appreciated as potent mediators of gene expression in female reproductive tissues. These highly targeted responses likely evolved from more elemental roles in lower organisms, in agreement with their widespread effects in the cardiovascular, immunological, central nervous, and skeletal tissue systems. Still, despite intense investigation, the multiple and often perplexing roles of ERs retain significant attention. In the skeleton, this in part derives from apparently opposing effects by ER agonists on bone growth versus bone remodeling, and in younger versus older individuals. The complexity associated with ER activation can also derive from their interactions with other hormone and growth factor systems, and their direct and indirect effects on gene expression. We propose that part of this complexity results from essential interactions between ERs and other transcription factors, each with their own biochemical and molecular intricacies. Solving some of the many questions that persist may help to achieve better, or better directed, use of agents that can drive ER activation in focused and possibly tissue restricted ways.

Blockade of transforming growth factor-beta (TGFβ) signaling inhibits osteoblastic tumorigenesis by a novel human prostate cancer cell line

BACKGROUND

The skeleton is the most common site of prostate cancer metastasis, which often results in osteoblastic lesions. The role of transforming growth factor-beta (TGFβ) signaling in prostate cancer-induced osteoblastic metastasis is not clear. We investigated the role of TGFβ signaling in prostate cancer-induced bone metastasis using a novel human prostate cancer cell line, PacMetUT1.

METHODS

We injected PacMetUT1/Luc-GFP cells in male nude mice by intracardiac and intratibia injections and then investigated the effect of TGFβ signaling abrogation on osteoblastic tumor growth and incidence in vivo by using fluorescence and bioluminescence imaging analysis and quantifying bone and tumor volume by histomorphometry analysis. Osteoclasts were counted using TRAP assay.

RESULTS

Osteoblastic bone metastasis in skull, rib, and femur was detected after 10-16 weeks of intracardiac injection of the PacMetUT1 cells. Stable knockdown of TGFβ1 with an shRNA resulted in decreased tumor incidence and bone formation when the cells were directly injected into the tibiae. Systemic administration of either a small inhibitor of TGFβ type I receptor kinase or a pan TGFβ binding protein (BG(E) RII) also decreased bone tumor growth and osteoblastic bone formation in vivo after 7 weeks of treatment.

CONCLUSIONS

Our results for the first time indicate that blockade of TGFβ signaling in the PacMetUT1 model significantly inhibits osteoblastic bone formation and tumor incidence. Thus, TGFβ signaling pathway may be a viable target for the prevention and treatment of prostate cancer-induced bone metastasis.

11β-hydroxysteroid dehydrogenases and the brain: from zero to hero, a decade of progress

Glucocorticoids have profound effects on brain development and adult CNS function. Excess or insufficient glucocorticoids cause myriad abnormalities from development to ageing. The actions of glucocorticoids within cells are determined not only by blood steroid levels and target cell receptor density, but also by intracellular metabolism by 11β-hydroxysteroid dehydrogenases (11β-HSD). 11β-HSD1 regenerates active glucocorticoids from their inactive 11-keto derivatives and is widely expressed throughout the adult CNS. Elevated hippocampal and neocortical 11β-HSD1 is observed with ageing and causes cognitive decline; its deficiency prevents the emergence of cognitive defects with age. Conversely, 11β-HSD2 is a dehydrogenase, inactivating glucocorticoids. The major central effects of 11β-HSD2 occur in development, as expression of 11β-HSD2 is high in fetal brain and placenta. Deficient feto-placental 11β-HSD2 results in a life-long phenotype of anxiety and cardiometabolic disorders, consistent with early life glucocorticoid programming.

Aromatase activity and bone loss in men

Aromatase is a specific component of the cytochrome P450 enzyme system responsible for the transformation of androgen precursors into estrogens. This enzyme is encoded by the CYP19A1 gene located at chromosome 15q21.2, that is, expressed in ovary and testis, but also in many extraglandular sites such as the placenta, brain, adipose tissue, and bone. The activity of aromatase regulates the concentrations of estrogens with endocrine, paracrine, and autocrine effects on target issues including bone. Importantly, extraglandular aromatization of circulating androgen precursors is the major source of estrogen in men. Clinical and experimental evidences clearly indicate that aromatase activity and estrogen production are necessary for longitudinal bone growth, the attainment of peak bone mass, pubertal growth spurt, epiphyseal closure, and normal bone remodeling in young individuals. Moreover, with aging, individual differences in aromatase activity may significantly affect bone loss and fracture risk in men.

Potential utility of natural products as regulators of breast cancer-associated aromatase promoters

Aromatase, the key enzyme in estrogen biosynthesis, converts androstenedione to estrone and testosterone to estradiol. The enzyme is expressed in various tissues such as ovary, placenta, bone, brain, skin, and adipose tissue. Aromatase enzyme is encoded by a single gene CYP 19A1 and its expression is controlled by tissue-specific promoters. Aromatase mRNA is primarily transcribed from promoter I.4 in normal breast tissue and physiological levels of aromatase are found in breast adipose stromal fibroblasts. Under the conditions of breast cancer, as a result of the activation of a distinct set of aromatase promoters (I.3, II, and I.7) aromatase expression is enhanced leading to local overproduction of estrogen that promotes breast cancer. Aromatase is considered as a potential target for endocrine treatment of breast cancer but due to nonspecific reduction of aromatase activity in other tissues, aromatase inhibitors (AIs) are associated with undesirable side effects such as bone loss, and abnormal lipid metabolism. Inhibition of aromatase expression by inactivating breast tumor-specific aromatase promoters can selectively block estrogen production at the tumor site. Although several synthetic chemical compounds and nuclear receptor ligands are known to inhibit the activity of the tumor-specific aromatase promoters, further development of more specific and efficacious drugs without adverse effects is still warranted. Plants are rich in chemopreventive agents that have a great potential to be used in chemotherapy for hormone dependent breast cancer which could serve as a source for natural AIs. In this brief review, we summarize the studies on phytochemicals such as biochanin A, genistein, quercetin, isoliquiritigenin, resveratrol, and grape seed extracts related to their effect on the activation of breast cancer-associated aromatase promoters and discuss their aromatase inhibitory potential to be used as safer chemotherapeutic agents for specific hormone-dependent breast cancer.

Aromatase inhibitor-associated bone and musculoskeletal effects: new evidence defining etiology and strategies for management

Aromatase inhibitors are widely used as adjuvant therapy in postmenopausal women with hormone receptor-positive breast cancer. While the agents are associated with slightly improved survival outcomes when compared to tamoxifen alone, bone and musculoskeletal side effects are substantial and often lead to discontinuation of therapy. Ideally, the symptoms should be prevented or adequately treated. This review will focus on bone and musculoskeletal side effects of aromatase inhibitors, including osteoporosis, fractures, and arthralgias. Recent advances have been made in identifying potential mechanisms underlying these effects. Adequate management of symptoms may enhance patient adherence to therapy, thereby improving breast cancer-related outcomes.

Aromatase activity and bone loss

Aromatase is a specific component of the cytochrome P450 enzyme system that is responsible for the transformation of C19 androgen precursors into C18 estrogenic compounds. This enzyme is encoded by the CYP19A1 gene located at chromosome 15q21.2, that is expressed in ovary and testis not only but also in many extraglandular sites such as the placenta, brain, adipose tissue, and bone. The regulation of the level and activity of aromatase determines the levels of estrogens that have endocrine, paracrine, and autocrine effects on target issues including bone. Importantly, extraglandular aromatization of circulating androgen precursors is the major source of estrogen not only in men (since only 15% of circulating estradiol is released directly by the testis) but also in women after the menopause. Several lines of clinical and experimental evidence now clearly indicate that aromatase activity and estrogen production are necessary for longitudinal bone growth, attainment of peak bone mass, the pubertal growth spurt, epiphyseal closure, and normal bone remodeling in young individuals. Moreover, with aging, individual differences in aromatase activity and thus in estrogen levels may significantly affect bone loss and fracture risk in both genders.