Comparison of mechanisms of angiostasis caused by the anti-inflammatory steroid 5α-tetrahydrocorticosterone versus conventional glucocorticoids.

5α-Tetrahydrocorticosterone (5αTHB) is an effective topical anti-inflammatory agent in mouse, with less propensity to cause skin thinning and impede new blood vessel growth compared with corticosterone. Its anti-inflammatory effects were not prevented by RU38486, a glucocorticoid receptor antagonist, suggesting alternative mechanisms. The hypothesis that 5αTHB directly inhibits angiogenesis to a lesser extent than hydrocortisone was tested, focussing on glucocorticoid receptor mediated actions. New vessel growth from aortae from C57BL/6 male mice was monitored in culture, in the presence of 5αTHB, hydrocortisone (mixed glucocorticoid/mineralocorticoid receptor agonist) or the selective glucocorticoid receptor agonist dexamethasone. Transcript profiles were studied, as was the role of the glucocorticoid receptor, using the antagonist, RU38486. Ex vivo, 5αTHB suppressed vessel growth from aortic rings, but was less potent than hydrocortisone (EC50 2512 nM 5αTHB, versus 762 nM hydrocortisone). In contrast to conventional glucocorticoids, 5αTHB did not alter expression of genes related to extracellular matrix integrity or inflammatory signalling, but caused a small increase in Per1 transcript, and decreased transcript abundance of Pecam1 gene. RU38486 did not antagonise the residual effects of 5αTHB to suppress vessel growth or regulate gene expression, but modified effects of dexamethasone. 5αTHB did not alter expression of glucocorticoid-regulated genes Fkbp51 and Hsd11b1, unlike hydrocortisone and dexamethasone. In conclusion, compared with hydrocortisone, 5αTHB exhibits limited suppression of angiogenesis, at least directly in blood vessels and probably independent of the glucocorticoid receptor. Discriminating the mechanisms employed by 5αTHB may provide the basis for the development of novel safer anti-inflammatory drugs for topical use.

Sexual dimorphism in mouse metanephroi exposed to 17 beta-estradiol in vitro.

UNLABELLED: 17beta-Estradiol, the most potent circulating estrogen, has been shown to greatly impact on the development and formation of tissues of the urogenital tract. The adult kidney has previously been shown to be highly responsive to 17beta-estradiol stimulation. However, the direct effect of 17beta-estradiol on kidney development remains unclear. AIM: To investigate the direct effect of 17beta-estradiol on male and female metanephric kidney development. METHODS: Whole embryonic-day-12.5 (E12.5) C57Bl/6 male and female mouse metanephroi were cultured in the presence of varying concentrations of 17beta-estradiol (0.1-5.0 nM) for 72 h. Metanephric development was assessed using immunofluorescence labeling techniques. The real-time polymerase chain reaction was used to investigate estrogen receptor-alpha (ERalpha), glial-cell-line-derived neurotrophic factor (GDNF) and its associated receptor cRET, transforming growth factor-beta (TGFbeta1), TGFbeta2 and TGFbeta3 mRNA expression levels. RESULTS: ERalpha was present in developing metanephroi at E12.5; however, ERbeta was absent. No significant sex difference in ERalpha mRNA expression was observed. Significant increases in the number of ureteric branch points, terminal tips and developing glomeruli were observed in female metanephroi cultured in the presence of 1.0 and 5.0 nM 17beta-estradiol. Conversely, no significant effect was observed in male metanephroi cultured with 17beta-estradiol. GDNF and cRET mRNA expression was increased in both male and female metanephroi, whilst TGFbeta1 and TGFbeta2 mRNA expression was decreased following culture in the presence of 17beta-estradiol. CONCLUSION: This study is the first to establish that the mouse metanephros displays a sexual dimorphism in response to specific concentrations of estrogens.

Characterisation of aromatase expression in the human adipocyte cell line SGBS.

Aromatase is a member of the cytochrome P450 superfamily of enzymes which catalyses the rate-limiting step in the biosynthesis of estrogens. A number of clinical studies have highlighted the importance of local estrogen production in adipose tissue. In particular, in the postmenopausal woman, the degree of her estrogenization is mainly determined by the extent of her adiposity and it is this extragonadal source of estrogen that likely contributes to breast cancer development and progression. The mechanisms regulating aromatase expression in adipose tissue however, have not been fully elucidated. In this study, we have characterised the expression of aromatase and its activity in a human preadipocyte cell strain, SGBS. Aromatase is expressed in SGBS cells and its expression and activity are strongly stimulated by forskolin (FSK) and phorbol 12-myristate-13-acetate (PMA) treatment. Consistent with this, FSK and PMA treatment also increased activation of the proximal aromatase promoter, promoter II. These findings mimic those that have previously been shown in isolated primary human preadipocytes. These data suggest that SGBS cells are a valuable model with which to further elucidate the mechanisms regulating aromatase expression, and therefore local estrogen synthesis in human adipose tissue.

Estrogen deficient male mice develop compulsive behavior.

BACKGROUND: Aromatase converts androgen to estrogen. Thus, the aromatase knockout (ArKO) mouse is estrogen deficient. We investigated the compulsive behaviors of these animals and the protein levels of catechol-O-methyltransferase (COMT) in frontal cortex, hypothalamus and liver. METHODS: Grooming was analyzed during the 20-min period immediately following a water-mist spray. Running wheel activity over two consecutive nights and barbering were analyzed. COMT protein levels were measured by Western analysis. RESULTS: Six-month old male but not female ArKO mice develop compulsive behaviors such as excessive barbering, grooming and wheel-running. Excessive activities were reversed by 3 weeks of 17beta-estradiol replacement. Interestingly, the presentation of compulsive behaviors is accompanied by concomitant decreases (p < .05) in hypothalamic COMT protein levels in male ArKO mice. These values returned to normal upon 17beta-estradiol treatment. In contrast, hepatic and frontal cortex COMT levels were not affected by the estrogen status, indicating region- and tissue-specific regulation of COMT levels by estrogen. No differences in COMT levels were detectable between female animals of both genotypes. CONCLUSIONS: This study describes the novel observation of a possible link between estrogen, COMT and development of compulsive behaviors in male animals which may have therapeutic implications in obsessive compulsive disorder (OCD) patients.

Regulation of adenosine 5',monophosphate-activated protein kinase and lipogenesis by androgens contributes to visceral obesity in an estrogen-deficient state.

Menopause is associated with an accumulation of visceral fat. An emerging concept suggests that relatively elevated levels of circulating androgens, compared with estrogens in postmenopausal women, underlie this shift in body fat distribution. In this study we administered dihydrotestosterone (DHT) to ovariectomized mice to examine the effect of relative androgen excess on adipose tissue distribution and function in estrogen-deficient mice. Compared with controls, DHT-treated mice exhibited increased body weight and visceral fat mass associated with triglyceride accumulation. Phosphorylation of AMP-activated protein kinase (AMPK) and acetyl CoA carboxylase was significantly decreased by DHT in visceral fat. In 3T3-L1 cells, DHT decreased phosphorylation of AMPK in a dose-dependent manner. In addition, DHT increased the expression of lipogenic genes (fatty acid synthase, sterol regulatory element binding protein-2, and lipoprotein lipase) in visceral fat. These data provide the first in vivo evidence that an increased androgen to estrogen ratio can promote visceral fat accumulation by inhibiting AMPK activation and stimulating lipogenesis.

Aromatase Inhibition Reduces Insulin Sensitivity in Healthy Men.

CONTEXT: Deficiency of aromatase, the enzyme that catalyzes the conversion of androgens to estrogens, is associated with insulin resistance in humans and mice. OBJECTIVE: We hypothesized that pharmacological aromatase inhibition results in peripheral insulin resistance in humans. DESIGN: This was a double-blind, randomized, controlled, crossover study. SETTING: The study was conducted at a clinical research facility. PARTICIPANTS: Seventeen healthy male volunteers (18-50 y) participated in the study. INTERVENTION: The intervention included oral anastrozole (1 mg daily) and placebo, each for 6 weeks with a 2-week washout period. MAIN OUTCOME MEASURE: Glucose disposal and rates of lipolysis were measured during a stepwise hyperinsulinemic euglycemic clamp. Data are mean (SEM). RESULTS: Anastrozole therapy resulted in significant estradiol suppression (59.9 ± 3.6 vs 102.0 ± 5.7 pmol/L, P = < .001) and a more modest elevation of total T (25.8 ± 1.2 vs 21.4 ± 0.7 nmol/L, P = .003). Glucose infusion rate, during the low-dose insulin infusion, was lower after anastrozole administration (12.16 ± 1.33 vs 14.15 ± 1.55 µmol/kg·min, P = .024). No differences in hepatic glucose production or rate of lipolysis were observed. CONCLUSION: Aromatase inhibition reduces insulin sensitivity, with respect to peripheral glucose disposal, in healthy men. Local generation and action of estradiol, at the level of skeletal muscle, is likely to be an important determinant of insulin sensitivity.

Deletion of the androgen receptor in adipose tissue in male mice elevates retinol binding protein 4 and reveals independent effects on visceral fat mass and on glucose homeostasis.

Testosterone deficiency is epidemic in obese ageing males with type 2 diabetes, but the direction of causality remains unclear. Testosterone-deficient males and global androgen receptor (AR) knockout mice are insulin resistant with increased fat, but it is unclear whether AR signaling in adipose tissue mediates body fat redistribution and alters glucose homoeostasis. To investigate this, mice with selective knockdown of AR in adipocytes (fARKO) were generated. Male fARKO mice on normal diet had reduced perigonadal fat but were hyperinsulinemic and by age 12 months, were insulin deficient in the absence of obesity. On high-fat diet, fARKO mice had impaired compensatory insulin secretion and hyperglycemia, with increased susceptibility to visceral obesity. Adipokine screening in fARKO mice revealed a selective increase in plasma and intra-adipose retinol binding protein 4 (RBP4) that preceded obesity. AR activation in murine 3T3 adipocytes downregulated RBP4 mRNA. We conclude that AR signaling in adipocytes not only protects against high-fat diet-induced visceral obesity but also regulates insulin action and glucose homeostasis, independently of adiposity. Androgen deficiency in adipocytes in mice resembles human type 2 diabetes, with early insulin resistance and evolving insulin deficiency.

Association of 11ß-hydroxysteroid dehydrogenase type I expression and activity with estrogen receptor ß in adipose tissue from postmenopausal women.

OBJECTIVE: 11ß-Hydroxysteroid dehydrogenase type I (11ßHSD1) regenerates active cortisol from inert cortisone in adipose tissue. Elevated adipose tissue 11ßHSD1 activity is observed in obese humans and rodents, where it is linked to obesity and its metabolic consequences. Menopause is also associated with increased abdominal fat accumulation, suggesting that estrogen is also important in adipose tissue metabolism. The purpose of this current study was to establish whether estrogen signaling through estrogen receptor α (ER-α) and estrogen receptor ß (ER-ß) could influence 11ßHSD1 in premenopausal and postmenopausal adipose tissues. METHODS: Nineteen premenopausal (aged 26 ± 5 y; body mass index, 23.6 ± 1.6 kg/m) and 23 postmenopausal (aged 63 ± 4 y; body mass index, 23.4 ± 1.9 kg/m) healthy women were studied. Subcutaneous adipose tissue biopsies and fasting venous blood samples were taken. Body composition was measured by bioelectrical impedance analysis. Human Simpson-Golabi-Behmel syndrome adipocyte cells were treated with ER-α- and ER-ß-specific agonists for 24 hours. Basic anthropometric data, serum 17ß-estradiol and progesterone concentrations, ER-α and ER-ß messenger RNA (mRNA) levels, and 11ßHSD1 mRNA, protein, and activity levels were assessed. RESULTS: ER-ß and 11ßHSD1, but not ER-α, mRNAs were significantly increased in adipose tissue from postmenopausal women compared with premenopausal women. ER-ß had a significant positive correlation with the mRNA level of 11ßHSD1 in adipose tissue from premenopausal and postmenopausal women. This association between ER-ß and 11ßHSD1 was greatest in adipose tissue from postmenopausal women. In human Simpson-Golabi-Behmel syndrome adipocytes, diarylpropiolnitrile, a selective ER-ß agonist, increased 11ßHSD1 mRNA, protein, and activity levels. CONCLUSIONS: We conclude that, in adipose tissue, ER-ß-mediated estrogen signaling can up-regulate 11ßHSD1 and that this may be of particular importance in postmenopausal women.

LKB1 expression is inhibited by estradiol-17ß in MCF-7 cells.

The liver kinase B1 (LKB1) is encoded by the STK11 gene and acts as a tumour suppressor and a regulator of energy homeostasis. LKB1 expression is reduced in primary breast tumours compared to normal breast epithelium. Although its expression in primary tumours does not appear to correlate with estrogen receptor (ER) status, it is differentially expressed in breast cancer cell lines where ER-negative cells have lower LKB1 expression than ER-positive cells. The present study aimed to examine the effects of estradiol on LKB1 expression and activity in the ER-positive breast cancer cell line MCF-7. Results demonstrate that estradiol causes a dose-dependent decrease in LKB1 transcript and protein expression and consistent with this, a significant decrease in the phosphorylation of the LKB1 target AMPK (P ≤ 0.05). In order to assess whether effects of estradiol were due to effects on ERα binding to the STK11 promoter, ChIP was performed. Results demonstrate that ERα binds to the STK11 promoter in a ligand-independent manner and that this interaction is decreased in the presence of estradiol. Moreover, STK11 promoter activity is significantly decreased in the presence of estradiol (P ≤ 0.05). LKB1 transcript and IHC score were assessed in primary tumours of 18 patients and demonstrated no significant correlation with ER status (n = 18). Our results thereby provide a mechanism whereby LKB1 is decreased in ER-positive breast tumours.

Prenatal dexamethasone programs expression of genes in liver and adipose tissue and increased hepatic lipid accumulation but not obesity on a high-fat diet.

The association between low birth weight and cardiovascular disease is amplified by the development of obesity. We explored the effects of postnatal high-fat (HF) feeding in dexamethasone (Dex)-programmed rats, in which prenatal glucocorticoid overexposure is associated with reduced birth weight and adult glucose intolerance. Male Wistar rats exposed to Dex or vehicle (Veh) during the last week of gestation were weaned onto HF or control diets for 6 months. Dex-exposed animals were of lower birth weight and showed catch-up growth by 7 wk. There were no differences in obesity or hyperinsulinaemia between Dex-HF and Veh-HF animals. However, Dex-HF animals had increased hepatic triglyceride content compared with Veh-HF animals. mRNA transcript profiles in adipose tissue revealed depot-specific changes in the expression of genes involved in fatty acid esterification and triglyceride synthesis and storage with prenatal Dex exposure. Thus, antenatal glucocorticoid overexposure in rats does not confer increased sensitivity to HF diet-induced obesity, but increases susceptibility to fatty liver. This may be due to depot-specific-programmed alterations in fat metabolism in adipose tissue.

Subcellular localization of cyclic AMP-responsive element binding protein-regulated transcription coactivator 2 provides a link between obesity and breast cancer in postmenopausal women.

Epidemiologic evidence supports a correlation between obesity and breast cancer in women. AMP-activated protein kinase plays an important role in energy homeostasis and inhibits the actions of cyclic AMP-responsive element binding protein-regulated transcription coactivator 2 (CRTC2). In postmenopausal women, the cyclic AMP-responsive element binding protein-dependent regulation of aromatase is a determinant of breast tumor formation through local production of estrogens. The present work aimed to examine the effect of adipokines on aromatase expression and identify additional mechanisms by which prostaglandin E(2) causes increased aromatase expression in human breast adipose stromal cells. Treatment of human adipose stromal cells with forskolin and phorbol 12-myristate 13-acetate (PMA), to mimic prostaglandin E(2), resulted in nuclear translocation of CRTC2. Aromatase promoter II (PII) activity assays showed that CRTC2 in addition to forskolin/PMA treatment significantly increased PII-induced activity. CRTC2 binding to PII was examined by chromatin immunoprecipitation, and forskolin/PMA treatment was associated with increased binding to PII. Treatment of human adipose stromal cells with leptin significantly up-regulated aromatase expression associated with nuclear translocation of CRTC2 and increased binding of CRTC2 to PII. Adiponectin treatment significantly decreased forskolin/PMA-stimulated aromatase expression, consistent with the decreased nuclear translocation of CRTC2 and the decreased binding of CRTC2 to PII. The expression and activity of the AMP-activated protein kinase LKB1 was examined and found to be significantly decreased following either forskolin/PMA or leptin treatment. In contrast, adiponectin significantly increased LKB1 expression and activity. In conclusion, the regulation of aromatase by CRTC2, in response to the altered hormonal milieu associated with menopause and obesity, provides a critical link between obesity and breast cancer.

Topical oestrogen keratinises the human foreskin and may help prevent HIV infection.

With the growing incidence of HIV, there is a desperate need to develop simple, cheap and effective new ways of preventing HIV infection. Male circumcision reduces the risk of infection by about 60%, probably because of the removal of the Langerhans cells which are abundant in the inner foreskin and are the primary route by which HIV enters the penis. Langerhans cells form a vital part of the body's natural defence against HIV and only cause infection when they are exposed to high levels of HIV virions. Rather than removing this natural defence mechanism by circumcision, it may be better to enhance it by thickening the layer of keratin overlying the Langerhans cells, thereby reducing the viral load to which they are exposed. We have investigated the ability of topically administered oestrogen to induce keratinization of the epithelium of the inner foreskin. Histochemically, the whole of the foreskin is richly supplied with oestrogen receptors. The epithelium of the inner foreskin, like the vagina, responds within 24 hours to the topical administration of oestriol by keratinization, and the response persists for at least 5 days after the cessation of the treatment. Oestriol, a cheap, readily available natural oestrogen metabolite, rapidly keratinizes the inner foreskin, the site of HIV entry into the penis. This thickening of the overlying protective layer of keratin should reduce the exposure of the underlying Langerhans cells to HIV virions. This simple treatment could become an adjunct or alternative to surgical circumcision for reducing the incidence of HIV infection in men.

Increased A-ring reduction of glucocorticoids in obese Zucker rats: effects of insulin sensitization.

OBJECTIVE: Obesity is associated with altered glucocorticoid metabolism, which may impact on hypothalamic-pituitary-adrenal axis activity. Here we characterize hepatic 5alpha- and 5beta-reductase in obese rats and their responses to insulin sensitization. RESEARCH METHODS AND PROCEDURES: Hepatic A-ring reductase protein and mRNA were assessed in lean and obese Zucker rats after insulin sensitization with metformin or rosiglitazone (n = 7 to 8/group). RESULTS: Hepatic 5alpha-reductase 1 and 5beta-reductase mRNA and protein (p < 0.01) were increased in obese rats. Insulin sensitization ameliorated increased 5alpha-reductase 1 mRNA in obese rats (p < 0.01) and partially reversed increased 5beta-reductase activity. DISCUSSION: Hepatic clearance of glucocorticoids by 5alpha- and 5beta-reductase is increased in obese Zucker rats, and this increase in clearance is attenuated by insulin sensitization. This increased hepatic clearance may underpin compensatory activation of the hypothalamic-pituitary-adrenal axis in obesity.

5alpha-reduced glucocorticoids, novel endogenous activators of the glucocorticoid receptor.

Metabolism of glucocorticoids to A-ring-reduced dihydro- and tetrahydro-derivatives by means of hepatic 5alpha- and 5beta-reductases has long been regarded as a pathway of irreversible inactivation. However, 5alpha-reduced metabolites of other steroids, e.g. testosterone and aldosterone, have significant biological activity. We investigated whether 5alpha-reduced metabolites of corticosterone are glucocorticoid receptor (GR) agonists. Corticosterone, 5alpha-tetrahydrocorticosterone (5alphaTHB), and 5alpha-dihydrocorticosterone (5alphaDHB) were similarly effective in displacing tritiated dexamethasone from binding sites in hepatocytes, whereas 5beta-reduced metabolites were less effective in binding. 5alphaTHB had glucocorticoid receptor agonist effects in vitro and in vivo. After transient co-transfection of hGR and a murine mammary tumor virus-luciferase reporter into HeLa cells, 5alphaTHB was active to a comparable extent as corticosterone (28-fold versus 37-fold induction, respectively, at 1 microm) and additive to the effect of corticosterone. 5beta-Reduced metabolites did not activate GR. In H4IIE hepatoma cells, both 5alphaTHB and corticosterone induced mRNA expression of tyrosine aminotransferase and phosphoenolpyruvate carboxykinase (6.0-versus 10.1-fold and 3.5-versus 3.9-fold at 1 microM, respectively), an effect that was inhibited by RU486. To assess in vivo glucocorticoid activity, suppression of plasma ACTH was demonstrated in adrenalectomized rats after intraperitoneal administration of vehicle (ACTH trough 80.2 pm), corticosterone (5 mg/kg; 22 pm, p < 0.001) or 5alphaTHB (5 mg/kg; 51.3 pm, p < 0.005). Similar endogenous concentrations of corticosterone and 5alphaTHB were detected in rat liver homogenates by gas chromatography mass spectrometry. We conclude that 5alpha-reduced glucocorticoids bind to and activate GR. Transcription of glucocorticoid-regulated genes in tissues that express 5alpha-reductases will thus be influenced by intracellular levels of both corticosterone and its 5alpha-reduced metabolites.