Response of the adipose tissue transcriptome to dihydrotestosterone in mice

Glucocorticoid Receptor Antagonism Improves Glucose Metabolism in a Mouse Model of Polycystic Ovary Syndrome

Context

Polycystic ovary syndrome (PCOS) is a complex metabolic disorder associated with obesity, insulin resistance, and dyslipidemia. Hyperandrogenism is a major characteristic of PCOS. Increased androgen exposure is believed to deregulate metabolic processes in various tissues as part of the PCOS pathogenesis, predominantly through the androgen receptor (AR). Notably, various metabolic features in PCOS are similar to those observed after excess glucocorticoid exposure.

Objective

We hypothesized that glucocorticoid receptor (GR) signaling is involved in the metabolic symptoms of PCOS.

Methods

In a PCOS model of chronic dihydrotestosterone (DHT) exposure in female mice, we investigated whether GR signaling machinery was (de)regulated, and if treatment with a selective GR antagonist alleviated the metabolic symptoms.

Results

We observed an upregulation of GR messenger RNA expression in the liver after DHT exposure. In white adipose tissues and liver we found that DHT upregulated Hsd11b1, which encodes for the enzyme that converts inactive into active glucocorticoids. We found that preventive but not therapeutic administration of a GR antagonist alleviated DHT-induced hyperglycemia and restored glucose tolerance. We did not observe strong effects of GR antagonism in DHT-exposed mice on other features like total fat mass and lipid accumulation in various tissues.

Conclusion

We conclude that GR activation may play a role in glucose metabolism in DHT-exposed mice.

The Postnatal Offspring of Finasteride-Treated Male Rats Shows Hyperglycaemia, Elevated Hepatic Glycogen Storage and Altered GLUT2, IR, and AR Expression in the Liver

Background: A growing body of data indicates that the physiology of the liver is sex-hormone dependent, with some types of liver failure occurring more frequently in males, and some in females. In males, in physiological conditions, testosterone acts via androgen receptors (AR) to increase insulin receptor (IR) expression and glycogen synthesis, and to decrease glucose uptake controlled by liver-specific glucose transporter 2 (GLUT-2). Our previous study indicated that this mechanism may be impaired by finasteride, a popular drug used in urology and dermatology, inhibiting 5α-reductase 2, which converts testosterone (T) into dihydrotestosterone (DHT). Our research has also shown that the offspring of rats exposed to finasteride have an altered T–DHT ratio and show changes in their testes and epididymides. Therefore, the goal of this study was to assess whether the administration of finasteride had an trans-generational effect on (i) GLUT-2 dependent accumulation of glycogen in the liver, (ii) IR and AR expression in the hepatocytes of male rat offspring, (iii) a relation between serum T and DHT levels and the expression of GLUT2, IR, and AR mRNAs, (iv) a serum glucose level and it correlation with GLUT-2 mRNA. Methods: The study was conducted on the liver (an androgen-dependent organ) from 7, 14, 21, 28, and 90-day old Wistar male rats (F1:Fin) born by females fertilized by finasteride-treated rats. The control group was the offspring (F1:Control) of untreated Wistar parents. In the histological sections of liver the Periodic Acid Schiff (PAS) staining (to visualize glycogen) and IHC (to detect GLUT-2, IR, and AR) were performed. The liver homogenates were used in qRT-PCR to assess GLUT2, IR, and AR mRNA expression. The percentage of PAS-positive glycogen areas were correlated with the immunoexpression of GLUT-2, serum levels of T and DHT were correlated with GLUT-2, IR, and AR transcript levels, and serum glucose concentration was correlated with the age of animals and with the GLUT-2 mRNA by Spearman’s rank correlation coefficients. Results: In each age group of F1:Fin rats, the accumulation of glycogen was elevated but did not correlate with changes in GLUT-2 expression. The levels of GLUT-2, IR, and AR transcripts and their immunoreactivity statistically significantly decreased in F1:Fin animals. In F1:Fin rats the serum levels of T and DHT negatively correlated with androgen receptor mRNA. The animals from F1:Fin group have statistically elevated level of glucose. Additionally, in adult F1:Fin rats, steatosis was observed in the liver (see Appendix A). Conclusions: It seems that treating male adult rats with finasteride causes changes in the carbohydrate metabolism in the liver of their offspring. This can lead to improper hepatic energy homeostasis or even hyperglycaemia, insulin resistance, as well as some symptoms of metabolic syndrome and liver steatosis.

Androgen Reduces Mitochondrial Respiration in Mouse Brown Adipocytes: A Model for Disordered Energy Balance in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common endocrinopathy that is associated with an adverse metabolic profile including reduced postprandial thermogenesis. Although abnormalities in adipose tissue function have been widely reported in women with PCOS, less is known about direct effects of androgen on white and, particularly, brown adipocytes. The purpose of this study was to investigate the effect of the nonaromatizable androgen dihydrotestosterone (DHT) on (1) lipid accumulation and expression of adipogenic markers in immortalized mouse brown adipose cell lines (IMBATs), (2) mitochondrial respiration in IMBATs, (3) mitochondrial DNA content and gene expression, (4) expression of brown adipose tissue (BAT) markers and thermogenic activation. In addition, we profiled the relative levels of 38 adipokines secreted from BAT explants and looked at androgen effects on adipokine gene expression in both IMBATs and immortalized mouse white adipose (IMWATs) cell lines. Androgen treatment inhibited IMBAT differentiation in a dose-dependent manner, reduced markers of adipogenesis, and attenuated the β-adrenoceptor-stimulated increase in uncoupling protein-1 (UCP1) expression. In explants of mouse interscapular BAT, androgen reduced expression of UCP1, peroxisome proliferator-activated receptor-γ coactivator-1 (PCG-1) and Cidea. Significantly, as well as affecting genes involved in thermogenesis in BAT, androgen treatment reduced mitochondrial respiration in IMBATs, as measured by the Seahorse XF method. The results of this study suggest a role for excess androgen in inhibiting brown adipogenesis, attenuating the activation of thermogenesis and reducing mitochondrial respiration in BAT. Together, these data provide a plausible molecular mechanism that may contribute to reduced postprandial thermogenesis and the tendency to obesity in women with PCOS.

Antioxidant enzyme expression of mRNA and protein in the epididymis of finasteride-treated male rat offspring during postnatal development

INTRODUCTION

We verify whether finasteride had a transgenerational effect on the epididymal expression of antioxidant enzymes, and the correlation between these enzymes and blood androgen concentrations in male offspring (F1:Fin) of females fertilized by finasteride-treated male rats.

MATERIAL AND METHODS

The expression of CAT, SOD1, GPX5, GR on the mRNA and protein levels was evaluated in the epididymis at postnatal day (PND) 7, 14, 21, 28 and 90. Levels of T and DHT were correlated with mRNA levels of enzymes by Spearman's rank correlation coefficient.

RESULTS

A change in the levels of transcripts was noted in F1:Fin rats: CAT decreased at PND 28 (p < 0.01) and increased at PND 90 (p < 0.01); SOD1 increased at PND 7 (p < 0.0001), 21 (p < 0.001), 90 (p < 0.0001) and decreased at 14 PND (p < 0.01); GPX5 increased at PND 14 and 21 (p < 0.0001); GR decreased at PND 21 and 28 (p < 0.0001). Altered immunolocalization of enzymes within the epididymal epithelium was observed. Negative correlations between GPX5 mRNA with androgens (T, p = 0.0002; DHT, p = 0.0009) were visible in the control rats, and positive correlation between DHT and CAT mRNA (p = 0.03), in opposite to F1:Fin group were was negative for both androgens (T, p = 0.044 and DHT, p = 0.02).

CONCLUSIONS

Finasteride treatment of adult male rats may cause changes in antioxidant defense system in the epididymis of their offspring, leading to improper ROS concentrations that can affect post-testicular sperm maturation.

Sex-Dimorphic and Sex Hormone-Dependent Role of Steroid Sulfatase in Adipose Inflammation and Energy Homeostasis

Steroid sulfatase (STS), a desulfating enzyme that converts steroid sulfates to hormonally active steroids, plays an important role in the homeostasis of sex hormones. STS is expressed in the adipose tissue of both male and female mice, but the role of STS in the development and function of adipose tissue remains largely unknown. In this report, we show that the adipose expression of Sts was induced in the high-fat diet (HFD) and ob/ob models of obesity and type 2 diabetes. Transgenic overexpression of the human STS in the adipose tissue of male mice exacerbated the HFD-induced metabolic phenotypes, including increased body weight gain and fat mass, and worsened insulin sensitivity, glucose tolerance, and energy expenditure, which were accounted for by adipocyte hypertrophy, increased adipose inflammation, and dysregulation of adipogenesis. The metabolic harm of the STS transgene appeared to have resulted from increased androgen activity in the adipose tissue, and castration abolished most of the phenotypes. Interestingly, the transgenic effects were sex specific, because the HFD-fed female STS transgenic mice exhibited improved metabolic functions, which were associated with attenuated adipose inflammation. The metabolic benefit of the STS transgene in female mice was accounted for by increased estrogenic activity in the adipose tissue, whereas such benefit was abolished upon ovariectomy. Our results revealed an essential role of the adipose STS in energy homeostasis in sex- and sex hormone-dependent manner. The adipose STS may represent a therapeutic target for the management of obesity and type 2 diabetes.

A Role for Androgens in Epithelial Proliferation and Formation of Glands in the Mouse Uterus

The endometrium consists of stromal and epithelial compartments (luminal and glandular) with distinct functions in the regulation of uterine homeostasis. Ovarian sex steroids, namely 17β-estradiol and progesterone, play essential roles in modulating uterine cell proliferation, stromal-epithelial cross-talk and differentiation in preparation for pregnancy. The effect of androgens on uterine function remains poorly understood. The current study investigated the effect of the non-aromatizable androgen dihydrotestosterone (DHT) on mouse endometrial function. Ovx female mice were given a single sc injection (short treatment) or 7 daily injections (long treatment) of vehicle alone (5% ethanol, 0.4% methylcellulose) or vehicle with the addition of 0.2 mg DHT (n=8/group) and a single injection of bromodeoxyuridine 2 hours prior to tissue recovery. Treatment with DHT increased uterine weight, the area of the endometrial compartment and immunoexpression of the androgen receptor in the luminal and glandular epithelium. Treatment-dependent proliferation of epithelial cells was identified by immunostaining for MKi67 and bromodeoxyuridine. Real-time PCR identified significant DHT-dependent changes in the concentrations of mRNAs encoded by genes implicated in the regulation of the cell cycle (Wee1, Ccnd1, Rb1) and stromal-epithelial interactions (Wnt4, Wnt5a, Wnt7a, Cdh1, Vcl, Igf1, Prl8, Prlr) as well as a striking effect on the number of endometrial glands. This study has revealed a novel role for androgens in regulating uterine function with an effect on the glandular compartment of the endometrium. This previously unrecognized role for androgens has implications for our understanding of the role of androgens in regulation of endometrial function and fertility in women.

Possible involvement of glucocorticoids in 5α-dihydrotestosterone-induced PCOS-like metabolic disturbances in the rat visceral adipose tissue

Polycystic ovary syndrome (PCOS) is a reproductive and metabolic disorder characterized by hyperandrogenism, ovulatory dysfunction, visceral obesity and insulin resistance. We hypothesized that changes in glucocorticoid metabolism and signaling in the visceral adipose tissue may contribute to disturbances of lipid metabolism in the rat model of PCOS obtained by 5α-dihydrotestosterone (DHT) treatment of prepubertal female Wistar rats. The results confirmed that DHT treatment caused anovulation, obesity and dyslipidemia. Enhanced glucocorticoid prereceptor metabolism, assessed by elevated intracellular corticosterone and increased 11 beta-hydroxysteroid dehydrogenase type 1 mRNA and protein levels, was accompanied by glucocorticoid receptor (GR) nuclear accumulation. In concert with the increased expression of GR-regulated prolipogenic genes (lipin-1, sterol regulatory element binding protein 1, fatty acid synthase, phosphoenolpyruvate carboxykinase), histological analyses revealed hypertrophic adipocytes. The results suggest that glucocorticoids influence lipid metabolism in the visceral adipose tissue in the way that may contribute to pathogenesis of metabolic disturbances associated with PCOS.

Loss of androgen receptor promotes adipogenesis but suppresses osteogenesis in bone marrow stromal cells

Gender differences have been described in osteoporosis with females having a higher risk of osteoporosis than males. The differentiation of bone marrow stromal cells (BMSCs) into bone or fat is a critical step for osteoporosis. Here we demonstrated that loss of the androgen receptor (AR) in BMSCs suppressed osteogenesis but promoted adipogenesis. The mechanism dissection studies revealed that AR deficiency suppressed osteogenesis-related genes to inhibit osteoblast differentiation from BMSCs. Knockout of AR promoted adipogenesis of BMSCs via Akt activation through IGFBP3-mediated IGF signaling, and the 5' promoter assay and chromatin immunoprecipitation assays further proved that AR could modulate IGFBP3 expression at the transcriptional level. Finally, addition of IGF inhibitors successfully masked the AR deficiency-induced Akt activation, and inhibitions of Akt, IGF1, and IGF2 pathways reversed the AR depletion effects on the adipogenesis process. These results suggested that AR-mediated changes in IGFBP3 might modulate the IGF-Akt axis to regulate adipogenesis in BMSCs.

Caveolin-1 and prostate cancer progression

Caveolin-1 was identified in the 1990s as a marker of aggressive prostate cancer. The caveolin-1 protein localizes to vesicular structures called caveolae and has been shown to bind and regulate many signaling proteins involved in oncogenesis. Caveolin-1 also has lipid binding properties and mediates aspects of cholesterol and fatty acid metabolism and can elicit biological responses in a paracrine manner when secreted. Caveolin-1 is also present in the serum of prostate cancer patients and circulating levels correlate with extent of disease. Current evidence indicates that increased expression of caveolin-1 in prostate adenocarcinoma cells and commensurate downregulation of the protein in prostate stroma, mediate progression to the castration-resistant phase of prostate cancer through diverse pathways. This chapter summarizes the current state of our understanding of the cellular and physiologic mechanisms in which caveolin-1 participates in the evolution of prostate cancer cell phenotypes.

Tissue-selective regulation of androgen-responsive genes

INTRODUCTION

Androgens regulate a wide array of physiological processes, including male sexual development, bone and muscle growth, and behavior and cognition. Because androgens play a vital role in so many tissues, changes in androgen signaling are associated with a plethora of diseases. How such varied responses are achieved by a single stimulus is not well understood. Androgens act primarily through the androgen receptor (AR), a hormone nuclear receptor that is expressed in a select variety of tissues.

METHODS

In order to gain a better understanding of how the tissue-selective effects of androgens are achieved, we performed a comparison of microarray data, using previously published datasets and several of our own microarray datasets. These datasets were derived from clinically relevant, AR-expressing tissues dissected from rodents treated with the full androgen dihydrotestosterone (DHT).

RESULTS

We found that there is a diverse response to DHT, with very little overlap of androgen regulated genes in each tissue. Gene ontology analyses also indicated that, while several tissues regulate similar biological processes in response to DHT, most androgen regulated processes are specific to one or a few tissues. Thus, it appears that the disparate physiological effects mediated by androgens begin with widely varying effects on gene expression in different androgen-sensitive tissues.

CONCLUSION

The analysis completed in this study will lead to an improved understanding of how androgens mediate diverse, tissue-specific processes and better ways to assess the tissue-selective effects of AR modulators during drug development.

A single dose of dihydrotestosterone induced a myogenic transcriptional program in female intra-abdominal adipose tissue

Sex steroids are key regulators of adipose tissue (AT) mass, determining gender-specific differences in fat distribution and accumulation. With the aim of exploring the relevance and peculiarities of androgen action in female intra-abdominal AT, we used the serial analysis of gene expression (SAGE) method to analyze the AT transcriptome in four groups of female mice: intact, ovariectomized (OVX), OVX plus dihydrotestosterone (DHT) injection at 3h or 24h before sacrifice (DHT3h, DHT24h). An average of 19555 transcript species was examined in retroperitoneal fat. We found a total of 321 transcripts differentially modulated by DHT and OVX, including 125 novel genes. Several genes involved in energy metabolism/ATP production were up-regulated by DHT, whereas important regulators of lipid metabolism were reduced. Transcripts involved in Ca(2+) uptake/release, cell signalling, cell defence and protein expression were differentially modulated by DHT. A surprising number of myogenic genes were up-regulated, including myosin light and heavy polypeptides, troponins, as well as several actin-binding proteins. These results suggest that DHT24h may have induced a myogenic-like transcriptional program in adipocytes. The present study sheds light on the distinctive female transcriptional pattern acutely induced by androgens in intra-abdominal fat, and may add new insights into the global understanding of menopausal endocrinology and its association to intra-abdominal obesity.