Regulation of aromatase expression in estrogen-responsive breast and uterine disease: from bench to treatment

Zeranol stimulates proliferation and aromatase activation in human breast preadipocytes

Aromatase is a crucial enzyme for the biosynthesis of estrogens and is involved in the process of breast carcinogenesis. Concerns have been raised regarding the effects of environmental estrogens as potential regulators of aromatase expression in human breast cells. Zeranol is a non‑steroidal agent with potent estrogenic activity, which is widely used as a growth promoter for cattle in certain countries. The present study hypothesized that aromatase expression and activity may be elevated by low dose zeranol exposure, providing a source of estrogens that may stimulate cell proliferation. In the present study, primary cultured human breast preadipocytes were used as an in vitro model. The effects of zeranol on cell proliferation were measured using the MTS assay, aromatase expression levels were determined by immunocytochemical staining and reverse transcription‑polymerase chain reaction, and aromatase enzyme activity and estrogen production were analyzed using corresponding assay kits. The results demonstrated that low dose zeranol (2‑50 nM) was able to significantly promote cell proliferation, aromatase mRNA expression, aromatase activity and estrogen production in primary cultured human breast preadipocytes, thus suggesting that zeranol may act as an aromatase activator. The findings of the present study suggest that zeranol promotes breast cancer cell growth by stimulating aromatase activation and increasing estrogen biosynthesis in adipose tissue.

Epigenetic alterations of CYP19A1 gene in Cumulus cells and its relevance to infertility in endometriosis

PURPOSE

The purpose of the present study was to investigate the epigenetic mechanisms responsible for the aberrant aromatase expression (CYP19A1) in Cumulus Cells (CCs) of infertile endometriosis patients.

METHOD

Cumulus cells were obtained from 24 infertile patients with and without endometriosis who underwent ovarian stimulation for intracytoplasmic sperm injection. Expression of CYP19A1 gene was quantified using Reverse Transcription Q-PCR. DNA methylation, histone modifications, and binding of Estrogen Receptor, ERβ to regulatory DNA sequences of CYP19A1 gene were evaluated by Chromatin ImmunoPrecipitation (ChIP) assay.

RESULTS

CYP19A1 gene expression in CCs of endometriosis patients was significantly lower than the control group (P = 0.04). Higher incorporation of MeCP2 (as a marker of DNA methylation) on PII and PI.4 promoters, and hypoacetylation at H3K9 in PII and hypermethylation at H3K9 in PI.4 were observed in CYP19A1 gene in endometriosis patients (P < 0.05). Moreover, a decreased level of ERβ binding to PII and an increased level of its binding to PI.3 and PI.4 promoters of CYP19A1 were observed in endometriosis patients when compared to control.

CONCLUSION

Significant reduction of CYP19A1 gene expression in CCs of endometriosis patients may be the result of epigenetic alterations in its regulatory regions, either by DNA methylation or histone modifications. These epigenetic changes along with differential binding of ERβ (as a transcription factor) in CYP19A1 promoters may impair follicular steroidogenesis, leading to poor Oocyte and embryo condition in endometriosis patients.

The effects of the standardized extracts of Ginkgo biloba on steroidogenesis pathways and aromatase activity in H295R human adrenocortical carcinoma cells

OBJECTIVES

Aromatase inhibitors that block estrogen synthesis are a proven first-line hormonal therapy for postmenopausal breast cancer. Although it is known that standardized extract of Ginkgo biloba (EGb761) induces anti-carcinogenic effects like the aromatase inhibitors, the effects of EGb761 on steroidogenesis have not been studied yet. Therefore, the effects of EGb761 on steroidogenesis and aromatase activity was studied using a H295R cell model, which was a good in vitro model to predict effects on human adrenal steroidogenesis.

METHODS

Cortisol, aldosterone, testosterone, and 17β-estradiol were evaluated in the H295R cells by competitive enzyme-linked immunospecific assay after exposure to EGb761. Real-time polymerase chain reaction were performed to evaluate effects on critical genes in steroid hormone production, specifically cytochrome P450 (CYP11/ 17/19/21) and the hydroxysteroid dehydrogenases (3β-HSD2 and 17β-HSD1/4). Finally, aromatase activities were measured with a tritiated water-release assay and by western blotting analysis.

RESULTS

H295R cells exposed to EGb761 (10 and 100 μg/mL) showed a significant decrease in 17β-estradiol and testosterone, but no change in aldosterone or cortisol. Genes (CYP19 and 17β-HSD1) related to the estrogen steroidogenesis were significantly decreased by EGb761. EGb761 treatment of H295R cells resulted in a significant decrease of aromatase activity as measured by the direct and indirect assays. The coding sequence/ Exon PII of CYP19 gene transcript and protein level of CYP19 were significantly decreased by EGb761.

CONCLUSIONS

These results suggest that EGb761 could regulate steroidogenesis-related genes such as CYP19 and 17β-HSD1, and lead to a decrease in 17β-estradiol and testosterone. The present study provides good information on potential therapeutic effects of EGb761 on estrogen dependent breast cancer.

Serum steroid concentrations remain within normal postmenopausal values in women receiving daily 6.5mg intravaginal prasterone for 12 weeks

This study integrates all data obtained in women aged 40-80years enrolled with moderate to severe symptoms of vulvovaginal atrophy (VVA) who received daily intravaginal administration of 0.50% (6.5mg) dehydroepiandrosterone (DHEA; prasterone) for 12weeks (n=723; ITT-S population) as compared with placebo (n=266; ITT-S population). To this end, serum steroid levels (DHEA, DHEA-sulfate (DHEA-S), androst-5-ene-3β, 17β-diol (5-diol), testosterone, dihydrotestosterone (DHT), androstenedione (4-dione), estrone (E1), estradiol (E2), estrone sulfate (E1-S), androsterone glucuronide (ADT-G), and androstane-3α, 17β-diol 17-glucuronide (3α-diol-17G)) were measured at Day 1 and Week 12 by liquid chromatography-tandem mass spectrometry (LC-MS/MS) following validation performed according to the FDA guidelines [1-6]. In agreement with the mechanisms of intracrinology where DHEA is exclusively transformed intracellularly into active sex steroids which act and are inactivated locally before being released as glucuronided or sulfated metabolites for elimination by the kidneys and liver, all sex steroids remained well within normal postmenopausal values following administration of intravaginal DHEA. Serum estradiol, the most relevant sex steroid, was measured after 12weeks of treatment at 3.36pg/ml (cITT-S population) or 19% below the normal postmenopausal value of 4.17pg/ml. On the other hand, serum E1-S, the best recognized marker of global estrogenic activity, shows an average value of 209pg/ml at 12 weeks compared to 220pg/ml in normal postmenopausal women. Moreover, serum ADT-G, the main metabolite of androgens, also remains well within normal postmenopausal values. The present data shows that a low daily intravaginal dose (6.5mg) of DHEA (prasterone) which is efficacious on the symptoms and signs of VVA, permits to achieve the desired local efficacy without systemic exposure, in agreement with the stringent mechanisms of menopause established after 500 million years of evolution where each cell in each tissue is the master of its sex steroid exposure.

Tranylcypromine, a lysine-specific demethylase 1 (LSD1) inhibitor, suppresses lesion growth and improves generalized hyperalgesia in mouse with induced endometriosis

BACKGROUND

Growing evidence indicates that endometriosis is an epigenetic disease. Encouragingly, histone deacetylases (HDACs) and DNA methyltransferases have been shown to be promising targets by numerous in vitro studies. However, only a few studies have shown promising effects of HDAC inhibition in preclinical studies in endometriosis. While lysine-specific demethylase 1 (LSD1) is recently found to be aberrantly expressed in endometriosis, and that the treatment of endometriotic stromal cells with tranylcypromine (TC), an LSD1 inhibitor, significantly reduced cellular proliferation, cell cycle progression, and invasiveness, the in vivo effect of TC treatment is currently lacking. This study sought to evaluate the effect of TC in a mouse model of endometriosis.

METHODS

Forty-seven female C57BL/6 mice were used in this experimentation. All mice, except those randomly selected to form Sham surgery (M) and specificity control (S) groups, received an endometriosis-inducing surgery. Group S was set up mainly to ensure that the reduced generalized hyperalgesia in mice treated with TC is not due to any possible analgesic effect of TC, but rather resulting from the treatment effect specific to endometriosis. Two weeks after the surgery, mice that received surgery were further divided randomly into 3 groups: 1) untreated group (U); 2) low-dose TC group (L); 3) high-dose TC group (H). Group S received the same treatment as in group H. Two weeks after treatment, all mice were sacrificed and their ectopic endometrial tissues were harvested and analyzed by immunohistochemistry analysis. Hotplate test was administrated to all mice before the induction, treatment and sacrifice. Lesion size, hotplate latency, immunoreactivity against markers of proliferation, angiogenesis, H3K4 methylation, and of epithelial-mesenchymal transition (EMT).

RESULTS

TC treatment significantly and substantially reduced the lesion size and improved generalized hyperalgesia in a dose-dependent fashion in mice with induced endometriosis. In addition, TC treatment resulted in reduced immunoreactivity to biomarkers of proliferation, angiogenesis, and H3K4 methylation, leading to arrested EMT and lesion growth.

CONCLUSION

In light of our previously reported reduced cellular proliferation, cell cycle progression and invasiveness resulting from the LSD1 inhibition in in vitro studies, our data strongly suggest that LSD1 is a promising therapeutic target for endometriosis.

TRIAL REGISTRATION

Not applicable.

Endometrial Expression of Steroidogenic Factor 1 Promotes Cystic Glandular Morphogenesis

Epigenetic silencing of steroidogenic factor 1 (SF1) is lost in endometriosis, potentially contributing to de novo local steroidogenesis favoring inflammation and growth of ectopic endometrial tissue. In this study, we examine the impact of SF1 expression in the eutopic uterus by a novel mouse model that conditionally expresses SF1 in endometrium. In vivo SF1 expression promoted the development of enlarged endometrial glands and attenuated estrogen and progesterone responsiveness. Endometriosis induction by autotransplantation of uterine tissue to the mesenteric membrane resulted in the increase in size of ectopic lesions from SF1-expressing mice. By integrating the SF1-dependent transcriptome with the whole genome binding profile of SF1, we identified uterine-specific SF1-regulated genes involved in Wingless and Progesterone receptor-Hedgehog-Chicken ovalbumin upstream promoter transcription factor II signaling for gland development and epithelium-stroma interaction, respectively. The present results indicate that SF1 directly contributes to the abnormal uterine gland morphogenesis, an inhibition of steroid hormone signaling and activation of an immune response, in addition to previously postulated estrogen production.

Body mass index and survival after diagnosis of invasive breast cancer: a study based on the Japanese National Clinical Database-Breast Cancer Registry

Few studies have reported the association between body mass index (BMI) and outcome among Asian breast cancer patients. We analyzed data for 20,090 female invasive breast cancer patients who had been followed‐up for a median period of 6.7 years entered in the National Clinical Database–Breast Cancer Registry between 2004 and 2006. We used mainly the WHO criteria for BMI (kg/m²) categories; <18.5 (underweight), ≥18.5–<21.8 (reference), ≥21.8–<25, ≥25–<30 (overweight), and ≥30 (obese). We divided normal weight patients into two subgroups because this category includes many patients compared to others. The timing of BMI measurement was not specified. The Cox proportional hazards model and cubic spline regression were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Smoking, alcohol, and physical activity were not controlled. A total of 1418 all‐cause, 937 breast cancer–specific deaths, and 2433 recurrences were observed. Obesity was associated with an increased risk of all‐cause (HR: 1.46; 95% CI: 1.16–1.83) and breast cancer–specific death (HR: 1.47; 95% CI: 1.11–1.93) for all patients, and with all‐cause (HR: 1.47; 95% CI: 1.13–1.92) and breast cancer–specific death (HR: 1.58; 95% CI: 1.13–2.20) for postmenopausal patients. Being underweight was associated with an increased risk of all‐cause death for all (HR: 1.41; 95% CI: 1.16–1.71) and for postmenopausal patients (HR: 1.45; 95% CI: 1.15–1.84). With regard to subtype and menopausal status, obesity was associated with an increased risk of breast cancer–specific death for all cases of luminal B tumor (HR: 2.59; 95% CI: 1.51–4.43; P_{heterogeneity} of Luminal B vs. Triple negative = 0.016) and for postmenopausal patients with luminal B tumor (HR: 3.24; 95% CI: 1.71–6.17). Being obese or underweight is associated with a higher risk of death among female breast cancer patients in Japan.

Endometriosis-Derived Stromal Cells Secrete Thrombin and Thromboxane A2, Inducing Platelet Activation

Platelets have been recently revealed to play important roles in the development of endometriosis. However, it is unclear whether endometriotic lesions can secrete any platelet inducers outside the menstruation window. Hence, this study was undertaken to see whether endometriosis-derived stromal cells secrete platelet activators and cause platelet activation. We employed in vitro experimentation using primary ectopic endometrial stromal cells (EESCs) and platelets from healthy male volunteers and evaluated the extent of platelet aggregation by aggregometer and the platelet activation rate by flow cytometry using supernatants harvested from EESCs of different cell densities. We also measured the concentration of thromboxane B2 (TXB2), a metabolite of thromboxane A2 (TXA2), and thrombin activity in supernatants harvested from EESCs of different densities and evaluated the extent of platelet aggregation after treatment of EESCs with hirudin, Ozagrel, and apyrase. Finally, the concentration of TXB2, thrombin, and transforming growth factor β1 (TGF-β1) in platelets cocultured with different densities of EESCs is measured by enzyme-linked immunosorbent assay. We found that EESCs secrete thrombin and TXA2 and induce platelet activation and aggregation in a density-dependent fashion. Treatment of platelets with EESCs resulted in increased concentration of TXB2, thrombin, and TGF-β1 in a density-dependent manner. Treatment of EESCs with hirudin and Ozagrel, but not apyrase, resulted in significant suppression of platelet aggregation. Thus, given recently reported effects of activated platelets on the cell behaviors of EESCs and endometriotic lesions in general, our findings establish that endometriotic lesions and platelets engage active cross-talks in the development of endometriosis, highlighting the importance of lesion microenvironment in endometriosis.

Nipple Aspirate Fluid Hormone Concentrations and Breast Cancer Risk

Prior reports identify higher serum concentrations of estrogens and androgens as risk factors for breast cancer, but steroids in nipple aspirate fluid (NAF) may be more related to risk. Incident breast cancer cases and mammography controls were recruited. Sex steroids were measured in NAF from the unaffected breasts of cases and one breast of controls. Menopausal status and menstrual cycle phase were determined. NAF steroids were purified by HPLC and quantified by immunoassays. Conditional logistic regression models were used to examine associations between NAF hormones and case-control status. NAF samples from 160 cases and 157 controls were evaluable for hormones. Except for progesterone and dehydroepiandrosterone (DHEA), the NAF and serum concentrations were not significantly correlated. NAF estradiol and estrone were not different between cases and controls. Higher NAF (but not serum) DHEA concentrations were associated with cases, particularly among estrogen receptor (ER)-positive cases (NAF odds ratio (OR) = 1.18, 95 % confidence interval (CI) 1.02, 1.36). NAF DHEA was highly correlated with NAF estradiol and estrone but not with androstenedione or testosterone. Higher progesterone concentrations in both NAF and serum were associated with a lower risk of ER-negative cancer (NAF OR = 0.69, 95 % CI 0.51, 0.92). However, this finding may be explained by case-control imbalance in the number of luteal phase subjects (2 cases and 19 controls). The significantly higher concentration of DHEA in NAF of cases and its correlation with NAF estradiol indicates a potentially important role of this steroid in breast cancer risk; however, the negative association of progesterone with risk is tentative.

Enhancement of anticancer potential of polyphenols by covalent modifications

As evidenced by a growing number of respective clinical trials, a promising and increasingly valued approach to cancer prevention is chemoprevention which is based on using synthetic, semisynthetic, or natural compounds with the aim of preventing, delaying, arresting, or reversing carcinogenesis. Research carried out in the last two decades indicates that natural polyphenols isolated from plants (as well as their derivatives and synthetic analogs) exhibit pleiotropic actions toward cancer cells and therefore they could be used in both cancer prevention and therapy. This review discusses selected covalent modifications of polyphenols as a means for increasing their anticancer potential in relation to the parent compounds. The modifications include hydroxylation, methylation, acylation, and galloylation, among others. They were demonstrated to enhance cytotoxic, pro-oxidant, antiproliferative, proapoptotic, proautophagic, and antimigratory activities of phenolics toward various cancer cell lines in vitro. Importantly, some derivatives proved to suppress tumor growth and metastasis in animal models more strongly than the parent compounds. Some of the above-mentioned covalent modifications were also shown to increase absorption and tissue distribution of tested phenolic compounds in vivo. Anticancer clinical trials with polyphenol derivatives therefore seem warranted.

In vivo visualization of aromatase in animals and humans

Aromatase catalyzes the last and obligatory step in the biosynthesis of estrogens across species. In vivo visualization of aromatase can be performed using positron emission tomography (PET) with radiolabeled aromatase inhibitors such as [(11)C]vorozole. PET studies in rats, monkeys and healthy human subjects demonstrate widespread but heterogeneous aromatase availability in brain and body, which appears to be regulated in a species, sex and region-specific manner. Thus, aromatase availability is high in brain amygdala and in ovaries of all species examined to date, with males demonstrating higher levels than females in all comparable organs. However, the highest concentrations of aromatase in the human brain are found in specific nuclei of the thalamus while the highest levels in rats and monkeys are found in the amygdala. Regional brain aromatase availability is increased by androgens and inhibited by nicotine. Future studies may improve diagnosis and treatment in brain disorders and cancers overexpressing aromatase.

Role of the steroidogenic acute regulatory protein in health and disease

Steroid hormones are an important class of regulatory molecules that are synthesized in steroidogenic cells of the adrenal, ovary, testis, placenta, brain, and skin, and influence a spectrum of developmental and physiological processes. The steroidogenic acute regulatory protein (STAR) predominantly mediates the rate-limiting step in steroid biosynthesis, i.e., the transport of the substrate of all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane. At the inner membrane, cytochrome P450 cholesterol side chain cleavage enzyme cleaves the cholesterol side chain to form the first steroid, pregnenolone, which is converted by a series of enzymes to various steroid hormones in specific tissues. Both basic and clinical evidence have demonstrated the crucial involvement of the STAR protein in the regulation of steroid biosynthesis. Multiple levels of regulation impinge on STAR action. Recent findings demonstrate that hormone-sensitive lipase, through its action on the hydrolysis of cholesteryl esters, plays an important role in regulating STAR expression and steroidogenesis which involve the liver X receptor pathway. Activation of the latter influences macrophage cholesterol efflux that is a key process in the prevention of atherosclerotic cardiovascular disease. Appropriate regulation of steroid hormones is vital for proper functioning of many important biological activities, which are also paramount for geriatric populations to live longer and healthier. This review summarizes the current level of understanding on tissue-specific and hormone-induced regulation of STAR expression and steroidogenesis, and provides insights into a number of cholesterol and/or steroid coupled physiological and pathophysiological consequences.

Burden of symptomatic uterine fibroids in Canadian women: a cohort study

OBJECTIVE

Due to variability in size, number, and location of uterine fibroids (UFs), symptoms can range widely among women. We sought to characterize burden of illness and quality of life (QoL) among women with symptomatic UFs.

RESEARCH DESIGN AND METHODS

An online survey queried the gynecologic health and menstrual cycle of Canadian women aged 20 to 49. Respondents reporting current UFs were assigned an Overall Severity Score based on a validated health-related QoL questionnaire (the UFS-QOL) and were dichotomized as having mild or moderate/severe UF. Subjects with moderate/severe UFs were matched 1:3 to non-UF subjects on age, race, and parity.

RESULTS

Of 9413 women with complete data, 384 (4.1%) reported physician-diagnosed UFs; of these, 50.6% met criteria for moderate/severe symptoms. Compared with matched non-UF respondents, moderate/severe UF respondents reported significantly greater mean menstrual duration (6.2 vs 5.0 days), more healthcare visits (emergency department, walk-in, family doctor, and specialist; total 10.5 vs 4.9 visits/6 months), and greater use of prescription analgesics (47.7% vs 26.7%) and iron supplements (29.7% vs 12.2%) (P < 0.05 for all). They spent more on feminine hygiene products ($32.0 vs $21.6/month) and reported losing nearly a full day of work/month (mean 7.6 hours) due to UFs. Women with moderate/severe UFs also scored lower on all QoL domains, compared to those with mild UF symptoms. Survey responses consistent with moderate/severe UFs were also identified in women who made no report of physician-diagnosed UFs, some of whom may be experiencing substantial burden due to undiagnosed UFs or other gynecologic conditions with related symptoms.

LIMITATIONS

All outcomes recorded in this online survey were based on self-report. Therefore, respondents' claims of medical diagnoses, including medical history, UF status and the presence or absence of potentially confounding comorbidities, could not be confirmed clinically.

CONCLUSIONS

Women experienced significant healthcare utilization, medication use, and financial and QoL burdens as a result of moderate/severe UF symptoms. Prevalence of moderate/severe UFs may be conservatively estimated at 2%, based on this cohort of reproductive-age Canadian women. The extent of UF underdiagnosis in the general population remains to be elucidated.

Melatonin enhancement of the radiosensitivity of human breast cancer cells is associated with the modulation of proteins involved in estrogen biosynthesis

Enhancing the radiosensitivity of cancer cells is one of the most important tasks in clinical radiobiology. Endocrine therapy and radiotherapy are two cancer treatment modalities which are often given together in patients with locally-advanced breast cancer and positive hormone-receptor status. Oncostatic actions of melatonin are relevant on estrogen-dependent mammary tumors. In the present study, we wanted to evaluate the effects of the combination of ionizing radiation and melatonin on proteins involved in estrogen biosynthesis in breast cancer cells. We demonstrated a role of melatonin in mediating the sensitization of human breast cancer cells to the ionizing radiation by decreasing around 50% the activity and expression of proteins involved in the synthesis of estrogens in these cells. Thus, melatonin pretreatment before radiation reduces the amount of active estrogens at cancer cell level. Melatonin 1 nM induced a 2-fold change in p53 expression as compared to radiation alone. The regulatory action of melatonin on p53 could be a link between melatonin and its modulatory action on the sensitivity of breast cancer cells to ionizing radiation. These findings may have implications for designing clinical trials using melatonin and radiotherapy.

Effectiveness of aromatase inhibitors in the treatment of advanced endometrial adenocarcinoma

PURPOSE

Type I endometrial cancer is a common tumor of the female genital tract. Since in post-menopausal women aromatase enzyme can stimulate the endometrial tissue neoplastic growth, the use of aromatase inhibitors may have a therapeutic effect, especially in patients not eligible for surgery.

METHODS

A systematic review has been performed, with a very specific scope, i.e., the use of aromatase inhibitors in the treatment of advanced or recurrent endometrial cancer, as a single agent or in combination with others drugs.

RESULTS

On the basis of the 117 records retrieved from the bibliographic search, the rationale for the use of aromatase inhibitors in endometrial cancer therapy is discussed. Six papers fall within the scope of our systematic review and their results are thoroughly analyzed. Moreover, we report our experience on the clinical effectiveness of anastrozole in the post-chemotherapy treatment of a patient affected by advanced-stage endometrial cancer.

CONCLUSION

In general, aromatase inhibitors seem to have limited clinical benefit in the treatment of advanced and recurrent endometrial cancer, although further clinical trials are necessary to investigate more in depth their role. In our case, we experienced a positive feedback in terms of control of an advanced-stage disease.

Transcriptomic characterization of fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma (FLHCC) tumors all carry a deletion of ∼ 400 kb in chromosome 19, resulting in a fusion of the genes for the heat shock protein, DNAJ (Hsp40) homolog, subfamily B, member 1, DNAJB1, and the catalytic subunit of protein kinase A, PRKACA. The resulting chimeric transcript produces a fusion protein that retains kinase activity. No other recurrent genomic alterations have been identified. Here we characterize the molecular pathogenesis of FLHCC with transcriptome sequencing (RNA sequencing). Differential expression (tumor vs. adjacent normal tissue) was detected for more than 3,500 genes (log2 fold change ≥ 1, false discovery rate ≤ 0.01), many of which were distinct from those found in hepatocellular carcinoma. Expression of several known oncogenes, such as ErbB2 and Aurora Kinase A, was increased in tumor samples. These and other dysregulated genes may serve as potential targets for therapeutic intervention.

Oestrogen action and male fertility: experimental and clinical findings

A proper balance between androgen and oestrogen is fundamental for normal male reproductive development and function in both animals and humans. This balance is governed by the cytochrome P450 aromatase, which is expressed also under spatio-temporal control. Oestrogen receptors ERα and/or ERβ, together with the membrane-associated G-protein-coupled functional ER (GPER), mediate the effects of oestrogen in the testis. Oestrogen action in male reproduction is more complex than previously predicted. The androgen/oestrogen balance and its regulation in the masculinisation programming window (MPW) during foetal life is the most critical period for the development of the male reproductive system. If this balance is impaired during the MPW, the male reproductive system may be negatively affected. Recent data from genetically modified mice and human infertile patients have shown that oestrogens may promote the engulfment of live Leydig cells by macrophages leading to male infertility. We also discuss recent data on environmental oestrogen exposure in men and rodents, where a rodent-human distinction is crucial and analyse some aspects of male fertility potentially related to impaired oestrogen/androgen balance.

In vitro interactions between mammary fibroblasts (Hs 578Bst) and cancer epithelial cells (MCF-7) modulate aromatase, steroid sulfatase and 17β-hydroxysteroid dehydrogenases

Our objectives were to investigate the interactions between mammary cancer epithelial cells (MCF-7) and stromal cells (Hs-578Bst) at the level of the expression and inhibition of steroidogenesis enzymes by using monolayer and three dimensional co-culture models. Expressions of steroidogenesis enzymes and E2/DHT conversions in co-cultured MCF-7 and Hs-578Bst cells as well as the effects of aromatase inhibitor combined to steroid sulfatase (STS) and 17β-hydroxysteroid dehydrogenases (17βHSDs) inhibitors were evaluated. 17β-HSD type 7 was mostly modulated in MCF-7 cells whereas aromatase was mostly regulated in Hs578Bst cells thereby increasing E2 conversion and MCF-7 cell growth. A combination of inhibitors toward aromatase, STS and 17β-HSD7, was found to be the most significant treatment in decreasing E2 and elevating DHT thus inhibiting MCF-7 cell proliferation and spheroid-like cancer cell aggregation in collagen gel. The interactions between those cells modulated E2 formation in paracrine/intracrine manners by synergistically regulating aromatase, 17β-HSD7 and STS. Among tumor-associated cells, stromal fibroblasts may participate in intratumoral E2 deposition; therefore promoting breast cancer cell growth.

Cross-Talk Between FSH and Endoplasmic Reticulum Stress: A Mutually Suppressive Relationship

Suboptimal cellular conditions result in the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and trigger ER stress. In this study, we investigated the effects of follicle stimulating hormone (FSH) on ER stress in granulosa cells (GCs) obtained from 3-week-old female C57BL6 mice 24 or 48 hours after intraperitoneal injection of 5 IU pregnant mare's serum gonadotropin (PMSG), and in primary mouse GCs in culture treated with FSH (10-100 mIU/mL) for 24 or 48 hours. Moreover, mouse GCs in culture were treated with tunicamycin (Tm) or thapsigargin (Tp), which induce ER stress by inhibiting N-glycosylation of ER proteins and ER calcium adenosine triphosphatase, respectively, and their response to FSH was evaluated. We found that FSH attenuated ER stress in mouse GCs in vivo and in vitro; messenger RNA levels of ER stress-associated genes Xbp1s, Atf6, Chop, and Casp12 were decreased upon exposure to FSH/PMSG. Activating transcription factor 4 protein levels also demonstrated consistent decrease following FSH stimulation. Both Tm and Tp treatments inhibited FSH response, ER stress-induced cells did not show any change in estradiol levels in response to FSH, whereas in untreated GCs, estradiol production increased 3-fold after incubation with FSH for 60 hours. Furthermore, ER stress-induced cells failed to demonstrate aromatase (Cyp19a1) expression upon exposure to FSH. Importantly, under high-ER stress conditions FSH stimulation was unable to downregulate the expression of ER stress-associated genes. Our findings suggest that FSH decreases ER stress in GCs under physiologic conditions. However, under conditions that cause a significant increase in ER stress, FSH response is attenuated.

Role of RUNX2 in Breast Carcinogenesis

RUNX2 is a transcription factor playing the major role in osteogenesis, but it can be involved in DNA damage response, which is crucial for cancer transformation. RUNX2 can interact with cell cycle regulators: cyclin-dependent kinases, pRB and p21Cip1 proteins, as well as the master regulator of the cell cycle, the p53 tumor suppressor. RUNX2 is involved in many signaling pathways, including those important for estrogen signaling, which, in turn, are significant for breast carcinogenesis. RUNX2 can promote breast cancer development through Wnt and Tgfβ signaling pathways, especially in estrogen receptor (ER)-negative cases. ERα interacts directly with RUNX2 and regulates its activity. Moreover, the ERα gene has a RUNX2 binding site within its promoter. RUNX2 stimulates the expression of aromatase, an estrogen producing enzyme, increasing the level of estrogens, which in turn stimulate cell proliferation and replication errors, which can be turned into carcinogenic mutations. Exploring the role of RUNX2 in the pathogenesis of breast cancer can lead to revealing new therapeutic targets.

Asymmetric dimethylarginine (ADMA), nitric oxide metabolite, and estradiol levels in serum and peritoneal fluid in women with endometriosis

BACKGROUND

Increase in nitric oxide (NO) concentration accompanied by alteration in peritoneal immune defense reactions is involved in the pathogenesis of endometriosis. Asymmetric dimethylarginine is an endogenous competitive inhibitor of NO synthase. This study was designed to compare NO metabolite (nitrite), asymmetric dimethylarginine, and estradiol concentrations in serum and peritoneal fluid (PF) of patients with and without endometriosis.

MATERIALS AND METHODS

Subjects were assigned to two groups based on their laparoscopic results. The groups consisted of women with and without endometriosis (90 and 89 participants, respectively). The serum and peritoneal levels of nitrite (stable NO metabolite), asymmetric dimethylarginine, and estradiol were measured using enzyme-linked immunosorbent assay (ELISA) kits. These parameters were analyzed and compared between the groups statistically using SPSS software version 16.

RESULTS

Both nitrite and asymmetric dimethylarginine levels were significantly higher in the serum of the participants from both groups than those in the PF group (P < 0.05). However, no significant difference in the asymmetric dimethylarginine level was detected between the two groups. In addition, the PF level of nitrite increased significantly in patients with endometriosis when compared with non-endometriosis subjects (P < 0.05). The PF levels of estradiol in both groups were significantly higher than the serum levels of estradiol (P < 0.05).

CONCLUSIONS

The NO metabolite level of PF implies the possible role of NO in the pathogenesis of endometriosis.

Partial hepatectomy induces delayed hepatocyte proliferation and normal liver regeneration in ovariectomized mice

Estrogens play central roles in sexual development, reproduction, and hepatocyte proliferation. The ovaries are one of the main organs for estradiol (E2) production. Ovariectomies (OVXs) were performed on the female mice, and hepatocyte proliferation was analyzed. The ovariectomized mice exhibited delayed hepatocyte proliferation after partial hepatectomy (PH) and also exhibited delayed and reduced E2 induction. Both E2 administration and PH induced the gene expression of estrogen receptor α (ERα). The transcripts of ERα were detected specifically in periportal hepatocytes after E2 administration and PH. Moreover, the E2 concentrations and hepatocyte proliferation rates were highest in the proestrus period of the estrous cycle. Taken together, these findings indicate that E2 accelerated ERα expression in periportal hepatocytes and hepatocyte proliferation in the female mice.

Metformin Suppresses Prostaglandin E2-Induced Cytochrome P450 Aromatase Gene Expression and Activity via Stimulation of AMP-Activated Protein Kinase in Human Endometriotic Stromal Cells

BACKGROUND

Cytochrome P450 aromatase (encoded by the CYP19A1/aromatase gene) plays a critical physiologic role in endometriosis. Metformin is known to suppress prostaglandin E2 (PGE2)-induced CYP19A1 messenger RNA (mRNA) expression in human endometriotic stromal cells (ESCs). However, the possible mechanism behind this suppression remains to be determined.

METHODS

In this study, ESCs were cultured with metformin, PGE2, and adenosine monophosphate (AMP)-activated protein kinase (AMPK) inhibitors. Expression of CYP19A1 mRNA and aromatase activity were measured by quantitative polymerase chain reaction and aromatase activity assay, respectively. The binding of the cyclic AMP response element-binding (CREB) protein to CYP19A1 promoter II (PII) was assessed by chromatin immunoprecipitation assay.

RESULTS

We demonstrated that metformin downregulated the expression of aromatase mRNA (32%) and activity (25%) stimulated by PGE2 (4.18-fold and 2.14-fold) in ESCs via stimulation of AMPK. Following PGE2 treatment, there was a marked increase in CREB binding to aromatase PII, while metformin attenuated the above-mentioned stimulation by 67%.

CONCLUSION

Metformin could inhibit PGE2-induced CYP19A1 mRNA expression and aromatase activity via AMPK activation and inhibition of CREB to CYP19A1 PII in human ESCs. The results of the present study suggest that metformin may have unique therapeutic potential as an antiendometriotic drug in the future.

Estrogen Protects against Obesity-Induced Mammary Gland Inflammation in Mice

Obesity is a risk factor for the development of hormone receptor (HR)-positive breast cancer in postmenopausal women. Obesity causes subclinical inflammation in white adipose tissue (WAT), characterized by macrophages surrounding dead or dying adipocytes forming crown-like structures (CLS). Estrogen synthesis is catalyzed by aromatase. Previously, we demonstrated CLS and elevated levels of proinflammatory mediators and aromatase in the mammary glands of obese mice and breast tissue of obese women. Here, we tested the hypothesis that supplemental estrogen could prevent or reverse WAT inflammation (WATi) and related molecular changes in the mammary gland. C57BL/6J mice were ovariectomized (OVX) to simulate the postmenopausal state. Supplementation with 17β-estradiol (E2) protected against high fat diet (HFD)-induced weight gain and mammary glands WATi. Expression of proinflammatory mediators (Cox-2, TNFα, IL1β) and aromatase were also reduced in the mammary glands of mice that received supplemental E2. Next, to determine whether E2 supplementation can reverse WATi, obese OVX mice were treated with E2 or placebo and then continued on HFD. E2 supplementation induced weight loss, reversed mammary gland inflammation, and downregulated expression of proinflammatory mediators and aromatase. Finally, we determined whether the protective effects of E2 were mediated by estrogen receptor-α (ERα). Knocking out ERα in ovary intact mice fed a HFD led to weight gain, WATi and elevated levels of proinflammatory mediators and aromatase mimicking the effects of OVX. Taken together, our findings indicate that estrogen via ERα protects against weight gain, WATi and associated increases in proinflammatory mediators and aromatase in the mammary gland.

Androgens and esophageal cancer: What do we know?

Significant disparities exist between genders for the development and progression of several gastro-intestinal (GI) diseases including cancer. Differences in incidence between men vs women for colon, gastric and hepatocellular cancers suggest a role for steroid sex hormones in regulation of GI carcinogenesis. Involvement of intrinsic gender-linked mechanisms is also possible for esophageal adenocarcinoma as its incidence is disproportionally high among men. However, the cause of the observed gender differences and the potential role of androgens in esophageal carcinogenesis remains unclear, even though the cancer-promoting role of androgen receptors (AR) shown in other cancers such as prostate and bladder suggests this aspect warrants exploration. Several studies have demonstrated expression of ARs in esophageal cancer. However, only one study has suggested a potential link between AR signaling and outcome - poorer prognosis. Two groups have analyzed data from cohorts with prostate cancer and one of these found a decreased incidence of esophageal squamous and adenocarcinoma after androgen deprivation therapy. However, very limited information is available about the effects of androgen and AR-initiated signaling on esophageal cancer cell growth in vitro and in vivo. Possible mechanisms for androgens/AR involvement in the regulation of esophageal cancer growth are considered, and the potential use of AR as a prognostic factor and clinical target is highlighted, although insufficient evidence is available to support clinical trials of novel therapies. As esophageal adenocarcinoma is a gender linked cancer with a large male predominance further studies are warranted to clarify the role of androgens and ARs in shaping intracellular signaling and genomic responses in esophageal cancer.

Clinical utilities of aromatase inhibitors in breast cancer

Aromatase is an enzyme that converts testosterones to estrogens. Inhibition of this enzyme has been shown to have several clinical utilities in breast cancer. Currently, there are three aromatase inhibitors (AIs) in clinical use, namely anastrozole, letrozole, and exemestane. AIs have been used in various clinical settings for breast cancer, ranging from chemoprevention in breast cancer to treating breast cancer in both early stage in the adjuvant setting and metastatic disease. This article reviews mechanism of action, AI classification, and clinical utilities of AIs in various clinical settings in the context of breast cancer.

Antihormonal potential of selected D-homo and D-seco estratriene derivatives

Since many estrogen derivatives exhibit anti-hormone or enzyme inhibition potential, a large number of steroidal derivatives have been synthesised from appropriate precursors, in order to obtain potential therapeutics for the treatment of hormone-dependent cancers. In molecular docking studies, based on X-ray crystallographic analysis, selected D-homo and D-seco estratriene derivatives were predicted to bind strongly to estrogen receptor α (ERα), aromatase and 17,20 lyase, suggesting they could be good starting compounds for antihormonal studies. Test results in vivo suggest that these compounds do not possess estrogenic activity, while some of them showed weak anti-estrogenic properties. In vitro anti-aromatase and anti-lyase assays showed partial inhibition of these two enzymes, while some compounds activated aromatase. Aromatase activators are capable of promoting estrogen synthesis for treatment of pathological conditions caused by estrogen depletion, e.g. osteopenia or osteoporosis.

Targeting the COX-2 Pathway to Improve Therapeutic Response in the Obese Breast Cancer Patient Population

Multiple studies have demonstrated that obesity is associated with a worse outcome for all breast cancer subtypes and that obese breast cancer patients do not respond as well as normal weight patients to aromatase inhibitor treatment and chemotherapy. While a number of mechanisms have been proposed to explain this link, recent studies have provided evidence that elevated local cyclooxygenase-2 (COX-2) expression and the resulting increase in prostaglandin E2 (PGE2) production may play an important role. COX-2 upregulation in breast tumors is associated with a poor prognosis, a connection generally attributed to PGE2's direct effects on apoptosis and invasion as well as its stimulation of pre-adipocyte aromatase expression and subsequent estrogen production. Research in this area has provided a strong foundation for the hypothesis that COX-2 signaling is involved in the obesity-breast cancer link, and further study regarding the role of COX-2 in this link is warranted.

The correlation of aromatase activity and obesity in women with or without polycystic ovary syndrome

Background

This study aimed to investigate the effect of polycystic ovary syndrome (PCOS) on the association of aromatase activity assessed by estradiol-to-testosterone ratio (E₂/T) with body mass index (BMI) in women.

Methods

This was a cohort study in five centers for reproductive medicine in China. Data were collected from July 2012 to December 2013. PCOS patients (n = 785) and non PCOS, healthy, age-matched controls (n = 297) were included. Plasma sex hormones including estradiol (E₂), testosterone (T), follicle stimulating hormone (FSH), and luteinizing hormone (LH) were measured by ELISA, together with BMI and E₂/T being calculated, on the third day of the menstrual cycle. Aromatase activity in PCOS patients with different BMI, T and E₂ levels were compared.

Results

E₂/T was significantly lower (P < 0.05) while BMI was significantly increased (P < 0.05) in PCOS than non-PCOS. No significant difference was observed in E₂/T among different BMI subgroups of either PCOS or control. Ovarian aromatase activity was decreased in PCOS patients which was independent of BMI. Hyperestrogen promoted ovarian aromatase activity, while hyperandrogen inhibited such activity, both in a dose-dependent, biphasic manner.

Conclusions

Ovarian aromatase activity was lower in PCOS, which was independent of BMI. New therapeutic strategies can be developed by targeting aromatase activity for treating PCOS women, especially those with obesity.

The CYP19 RS4646 polymorphism IS related to the prognosis of stage I-II and operable stage III breast cancer

Purpose

Aromatase, encoded by the CYP19 gene, catalyzes the final step of the conversion of androgens to estrogens. Given the critical role of CYP19 in estrogen synthesis, the potential influence of CYP19 rs4646 polymorphism on breast cancer survival, deserves further study.

Methods

Genotyping for CYP19 rs4646 variants was performed on 406 Chinese women with stage I–II and operable stage III breast cancer. Associations were evaluated between CYP19 rs4646 genotypes and disease-free survival (DFS).

Results

In premenopausal patients, women who are homozygous for the minor allele (AA) have a longer DFS compared with those carrying the major allele (CC or AC) (87 months versus 48.7 months; Hazard ratio (HR) = 0.56, 95 % CI = 0.318-0.985, P = 0.041). These differences were further demonstrated by a multivariate analysis (HR = 0.456, 95 % CI = 0.249-0.836, P = 0.011). Conversely, the same variant (AA) was estimated to be associated with a poorer DFS in postmenopausal women (AA versus AC or CC: 13.7 months versus 56.3 months; HR = 2.758, 95 % CI = 1.432-5.313, P = 0.002). Furthermore, the differences were confirmed by the COX proportional hazards model (HR = 2.983, 95% CI =1.494-5.955, P = 0.002).

Conclusions

The present study indicates that CYP19 rs4646 polymorphism is related to DFS in early breast cancer and that the prognosis index of the homozygous for the minor allele (AA) may depend on menopause status. The findings are novel, if confirmed, rs4646 genotypes may provide useful information for routine management in breast cancer.

Endometriosis, leiomyoma and adenomyosis: the risk of gynecologic malignancy

The aim of this review article was to evaluate the relationship and the possible etiological mechanisms between endometriosis, leiomyoma (LM) and adenomyosis and gynecological cancers, such as ovarian and endometrial cancer and leiomyosarcoma (LMS). MEDLINE was searched for all articles written in the English literature from July 1966 to May 2013. Reports were collected systematically and all the references were also reviewed. Malignant transformation of gynecologic benign diseases such as endometriosis, adenomyosis and LM to ovarian and endometrial cancer remains unclear. Hormonal factors, inflammation, familial predisposition, genetic alterations, growth factors, diet, altered immune system, environmental factors and oxidative stress may be causative factors in carcinogenesis. Early menarche, low parity, late menopause and infertility have also been implicated in the pathogenesis of these cancers. Ovarian cancers and endometriosis have been shown to have common genetic alterations such as loss of heterozygosity (LOH), PTEN, p53, ARID1A mutations. MicroRNAs have also been implicated in malignant transformation. Inflammation releases proinflammatory cytokines, and activates tumor associated macrophages (TAMS) and nuclear factor kappa b (NF-KB) signaling pathways that promote genetic mutations and carcinogenesis. MED12 mutations in LM and smooth muscle tumors of undetermined malignant potential (STUMP) may contribute to malignant transformation to LMS. A hyperestrogenic state may be shared in common with pathogenesis of adenomyosis, LM and endometrial cancer. However, the effect of these benign gynecologic diseases on endometrial cancer should be studied in detail. This review study indicates that endometriosis, LM, adenomyosis may be associated with increased risk of gynecological cancers such as endometrial and ovarian cancers. The patients who have these gynecological benign diseases should be counseled about the future risks of developing cancer. Further studies are needed to investigate the relationship between STUMPs, LMS and LM and characteristics and outcome endometrial carcinoma in adenomyotic patients.

Effect of COX-2 inhibitors and other non-steroidal inflammatory drugs on breast cancer risk: a meta-analysis

Evidence on non-steroidal anti-inflammatory drugs (NSAID) use and breast cancer risk shows a slightly protective effect of these drugs, but previous studies lack randomized clinical trial results and present high heterogeneity in exposure measurement. This systematic review and meta-analysis widens the knowledge about NSAID use and breast cancer risk, updating the information from the last meta-analysis, focusing on evidence on specific effects of COX-2 inhibitors and differential expression patterns of hormonal receptors. A PubMed-database search was conducted to include all entries published with the keywords "BREAST CANCER NSAID ANTI-INFLAMMATORY" until 10/24/2013 providing original results from cohort studies, case-control studies, or randomized clinical trials with at least one reported relative risk (RR) or odds ratio (OR) on the association between any NSAID use and incidence of invasive breast cancer. This resulted in 49 publications, from which the information was retrieved about type of study, exposure characteristics, breast cancer characteristics, and breast cancer-NSAID association. Meta-analyses were performed separately for case-control and cohort studies and for different hormone-receptor status. NSAID use reduced invasive breast cancer risk by about 20 %. A similar effect was found for aspirin, acetaminophen, COX-2 inhibitors and, to a lesser extent, ibuprofen. The effect of aspirin was similar in preventing hormone-receptor-positive breast cancer. This meta-analysis suggests a slightly protective effect of NSAIDs-especially aspirin and COX-2 inhibitors- against breast cancer, which seems to be restricted to ER/PR+tumors.

All sex steroids are made intracellularly in peripheral tissues by the mechanisms of intracrinology after menopause

Following the arrest of estradiol secretion by the ovaries at menopause, all estrogens and all androgens in postmenopausal women are made locally in peripheral target tissues according to the physiological mechanisms of intracrinology. The locally made sex steroids exert their action and are inactivated intracellularly without biologically significant release of the active sex steroids in the circulation. The level of expression of the steroid-forming and steroid-inactivating enzymes is specific to each cell type in each tissue, thus permitting to each cell/tissue to synthesize a small amount of androgens and/or estrogens in order to meet the local physiological needs without affecting the other tissues of the organism. Achieved after 500 million years of evolution, combination of the arrest of ovarian estrogen secretion, the availability of high circulating levels of DHEA and the expression of the peripheral sex steroid-forming enzymes have permitted the appearance of menopause with a continuing access to intratissular sex steroids for the individual cells/tissues without systemic exposure to circulating estradiol. In fact, one essential condition of menopause is to maintain serum estradiol at biologically inactive (substhreshold) concentrations, thus avoiding stimulation of the endometrium and risk of endometrial cancer. Measurement of the low levels of serum estrogens and androgens in postmenopausal women absolutely requires the use of MS/MS-based technology in order to obtain reliable accurate, specific and precise assays. While the activity of the series of steroidogenic enzymes can vary, the serum levels of DHEA show large individual variations going from barely detectable to practically normal "premenopausal" values, thus explaining the absence of menopausal symptoms in about 25% of women. It should be added that the intracrine system has no feedback elements to adjust the serum levels of DHEA, thus meaning that women with low DHEA activity will not be improved without external supplementation. Exogenous DHEA, however, follows the same intracrine rules as described for endogenous DHEA, thus maintaining serum estrogen levels at substhreshold or biologically inactive concentrations. Such blood concentrations are not different from those observed in normal postmenopausal women having high serum DHEA concentrations. Androgens, on the other hand, are practically all made intracellularly from DHEA by the mechanisms of intracrinology and are always maintained at very low levels in the blood in both pre- and postmenopausal women. Proof of the importance of intracrinology is also provided, among others, by the well-recognized benefits of aromatase inhibitors and antiestrogens used successfully for the treatment of breast cancer in postmenopausal women where all estrogens are made locally. Each medical indication for the use of DHEA, however, requires clinical trials performed according to the FDA guidelines and the best rules of clinical medicine.

Transcriptional control of local estrogen formation by aromatase in the breast

Aromatase is the critical enzyme that converts androgens to estrogens. It is frequently highly expressed in the tumour bearing breast of women diagnosed with estrogen receptor positive tumours, resulting in dramatically increased local estrogen production to drive tumour progression. Expression of aromatase is regulated primarily at the transcriptional level of its encoding gene CYP19A1, located on chromosome 15 of the human genome. A characteristic feature of CYP19A1 expression is its use of alternative promoters to regulate transcription in a tissue-specific manner. In breast cancer, the increase in aromatase expression is mediated via higher expression of the distal adipose-specific promoter I.4 and a switch to the preferential use of proximal promoters I.3 and II. This results in a net increase of CYP19A1 transcripts in tumour-bearing breast up to 3-4-fold higher than normal breast. Current aromatase inhibitors - whilst efficacious - exhibit significant side effects that reduce patient compliance. Understanding the transcription factors and signalling pathways that control aromatase expression will lead to opportunities to develop breast-specific inhibitors with an improved side-effects profile. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Enzymatic intracrine regulation of white adipose tissue

Abdominal fat formation has become a permanent risk factor for metabolic syndrome and various cancers in one-third of the world's population of obese and even lean patients. Formation of abdominal fat involves additional mechanisms beyond an imbalance in energy intake and expenditure, which explains systemic obesity. In this review, we briefly summarized autonomous regulatory circuits that locally produce hormones from inactive precursors or nutrients for intra-/auto-/paracrine signaling in white adipose depots. Enzymatic pathways activating steroid and thyroid hormones in adipose depots were compared with enzymatic production of retinoic acid from vitamin A. We discussed the role of intracrine circuits in fat-depot functions and strategies to reduce abdominal adiposity through thermogenic adipocytes with interrupted generation of retinoic acid.