Dehydroepiandrosterone and related steroids alter 3T3-L1 preadipocyte proliferation and differentiation

Vertebral bone marrow fat fraction changes in postmenopausal women with breast cancer receiving combined aromatase inhibitor and bisphosphonate therapy

Background

Quantification of vertebral bone marrow (VBM) water–fat composition has been proposed as advanced imaging biomarker for osteoporosis. Estrogen deficiency is the primary reason for trabecular bone loss in postmenopausal women. By reducing estrogen levels aromatase inhibitors (AI) as part of breast cancer therapy promote bone loss. Bisphosphonates (BP) are recommended to counteract this adverse drug effect. The purpose of our study was to quantify VBM proton density fat fraction (PDFF) changes at the lumbar spine using chemical shift encoding-based water-fat MRI (CSE-MRI) and bone mineral density (BMD) changes using dual energy X-ray absorptiometry (DXA) related to AI and BP treatment over a 12-month period.

Methods

Twenty seven postmenopausal breast cancer patients receiving AI therapy were recruited for this study. 22 subjects completed the 12-month study. 14 subjects received AI and BP (AI+BP), 8 subjects received AI without BP (AI-BP).

All subjects underwent 3 T MRI. An eight-echo 3D spoiled gradient-echo sequence was used for CSE-based water-fat separation at the lumbar spine to generate PDFF maps. After manual segmentation of the vertebral bodies L1-L5 PDFF values were extracted for each vertebra and averaged for each subject.

All subjects underwent DXA of the lumbar spine measuring the average BMD of L1-L4.

Results

Baseline age, PDFF and BMD showed no significant difference between the two groups (p > 0.05). There was a relative longitudinal increase in mean PDFF (∆rel_PDFF) in both groups (AI+BP: 5.93%; AI-BP: 3.11%) which was only significant (p = 0.006) in the AI+BP group. ∆rel_PDFF showed no significant difference between the two groups (p > 0.05). There was no significant longitudinal change in BMD (p > 0.05).

Conclusions

Over a 12-month period, VBM PDFF assessed with CSE-MRI significantly increased in subjects receiving AI and BP. The present results contradict previous results regarding the effect of only BP therapy on bone marrow fat content quantified by magnetic resonance spectroscopy and bone biopsies. Future longer-term follow-up studies are needed to further characterize the effects of combined AI and BP therapy.

Prenatal Steroids and Metabolic Dysfunction: Lessons from Sheep

Prenatal exposure to excess steroids or steroid mimics can disrupt the normal developmental trajectory of organ systems, culminating in adult disease. The metabolic system is particularly susceptible to the deleterious effects of prenatal steroid excess. Studies in sheep demonstrate that prenatal exposure to excess native steroids or endocrine-disrupting chemicals with steroidogenic activity, such as bisphenol A, results in postnatal development of numerous cardiometabolic perturbations, including insulin resistance, increased adiposity, altered adipocyte size and distribution, and hypertension. The similarities in the phenotypic outcomes programmed by these different prenatal insults suggest that common mechanisms may be involved, and these may include hormonal imbalances (e.g., hyperandrogenism and hyperinsulinemia), oxidative stress, inflammation, lipotoxicity, and epigenetic alterations. Animal models, including the sheep, provide mechanistic insight into the metabolic repercussions associated with prenatal steroid exposure and represent valuable research tools in understanding human health and disease. Focusing on the sheep model, this review summarizes the cardiometabolic perturbations programmed by prenatal exposure to different native steroids and steroid mimics and discusses the potential mechanisms underlying the development of adverse outcomes.

Developmental Programming of Capuchin Monkey Adrenal Dysfunction by Gestational Chronodisruption

In the capuchin monkey (Cebus apella), a new-world nonhuman primate, maternal exposure to constant light during last third of gestation induces precocious maturation of the fetal adrenal and increased plasma cortisol in the newborn. Here, we further explored the effects of this challenge on the developmental programming of adrenal function in newborn and infant capuchin monkeys. We measured (i) plasma dehydroepiandrosterone sulphate (DHAS) and cortisol response to ACTH in infants with suppressed endogenous ACTH, (ii) plasma DHAS and cortisol response to ACTH in vitro, and (iii) adrenal weight and expression level of key factors in steroid synthesis (StAR and 3β-HSD). In one-month-old infants from mothers subjected to constant light, plasma levels of cortisol and cortisol response to ACTH were twofold higher, whereas plasma levels of DHAS and DHAS response to ACTH were markedly reduced, compared to control conditions. At 10 months of age, DHAS levels were still lower but closer to control animals, whereas cortisol response to ACTH was similar in both experimental groups. A compensatory response was detected at the adrenal level, consisting of a 30% increase in adrenal weight and about 50% reduction of both StAR and 3β-HSD mRNA and protein expression and the magnitude of DHAS and cortisol response to ACTH in vitro. Hence, at birth and at 10 months of age, there were differential effects in DHAS, cortisol production, and their response to ACTH. However, by 10 months of age, these subsided, leading to a normal cortisol response to ACTH. These compensatory mechanisms may help to overcome the adrenal alterations induced during pregnancy to restore normal cortisol concentrations in the growing infant.

Transcriptome analysis of mRNA and microRNAs in intramuscular fat tissues of castrated and intact male Chinese Qinchuan cattle

Intramuscular fat (IMF) is known to enhance beef palatability and can be markedly increased by castration. However, there is little understanding of the molecular mechanism underlying the IMF deposition after castration of beef cattle. We hypothesize that genetic regulators function differently in IMF from bulls and steers. Therefore, after detecting serum testosterone and lipid parameter, as well as the contents of IMF at 6, 12, 18 and 24 months, we have investigated differentially expressed (DE) microRNAs (miRNAs) and mRNAs in IMF of bulls and steers at 24 months of age in Qinchuan cattle using next-generation sequencing, and then explored the possible biopathways regulating IMF deposition. Serum testosterone levels were significantly decreased in steers, whereas IMF content, serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglycerides (TGs) were markedly increased in steers. Comparing the results of steers and bulls, 580 upregulated genes and 1,120 downregulated genes in IMF tissues were identified as DE genes correlated with IMF deposition. The upregulated genes were mainly associated with lipid metabolism, lipogenesis and fatty acid transportation signalling pathways, and the downregulated genes were correlated with immune response and intracellular signal transduction. Concurrently, the DE miRNAs—important players in adipose tissue accumulation induced by castration—were also examined in IMF tissues; 52 DE miRNAs were identified. The expression profiles of selected genes and miRNAs were also confirmed by quantitative real-time PCR (qRT-PCR) assays. Using integrated analysis, we constructed the microRNA-target regulatory network which was supported by target validation using the dual luciferase reporter system. Moreover, Ingenuity Pathway Analysis (IPA) software was used to construct a molecular interaction network that could be involved in regulating IMF after castration. The detected molecular network is closely associated with lipid metabolism and adipocyte differentiation, which is supported by functional identification results of bta-let-7i on bovine preadipocytes. These results provided valuable insights into the molecular mechanisms of the IMF phenotype differences between steers and bulls.

Transcriptional Regulation of Adipogenesis

Adipocytes are the defining cell type of adipose tissue. Once considered a passive participant in energy storage, adipose tissue is now recognized as a dynamic organ that contributes to several important physiological processes, such as lipid metabolism, systemic energy homeostasis, and whole-body insulin sensitivity. Therefore, understanding the mechanisms involved in its development and function is of great importance. Adipocyte differentiation is a highly orchestrated process which can vary between different fat depots as well as between the sexes. While hormones, miRNAs, cytoskeletal proteins, and many other effectors can modulate adipocyte development, the best understood regulators of adipogenesis are the transcription factors that inhibit or promote this process. Ectopic expression and knockdown approaches in cultured cells have been widely used to understand the contribution of transcription factors to adipocyte development, providing a basis for more sophisticated in vivo strategies to examine adipogenesis. To date, over two dozen transcription factors have been shown to play important roles in adipocyte development. These transcription factors belong to several families with many different DNA-binding domains. While peroxisome proliferator-activated receptor gamma (PPARγ) is undoubtedly the most important transcriptional modulator of adipocyte development in all types of adipose tissue, members of the CCAAT/enhancer-binding protein, Krüppel-like transcription factor, signal transducer and activator of transcription, GATA, early B cell factor, and interferon-regulatory factor families also regulate adipogenesis. The importance of PPARγ activity is underscored by several covalent modifications that modulate its activity and its ability to modulate adipocyte development. This review will primarily focus on the transcriptional control of adipogenesis in white fat cells and on the mechanisms involved in this fine-tuned developmental process. © 2017 American Physiological Society. Compr Physiol 7:635-674, 2017.

Region-specific effects of oestradiol on adipose-derived stem cell differentiation in post-menopausal women

The goal of this study was to determine the effect of acute transdermal 17β‐oestradiol (E₂) on the adipogenic potential of subcutaneous adipose‐derived stem cells (ASC) in post‐menopausal women. Post‐menopausal women (n = 11; mean age 57 ± 4.5 years) were treated for 2 weeks, in a randomized, cross‐over design, with transdermal E₂ (0.15 mg) or placebo patches. Biopsies of abdominal (AB) and femoral (FEM) subcutaneous adipose tissue (SAT) were obtained after each treatment and mature adipocytes were analysed for cell size and ASC for their capacity for proliferation (growth rate), differentiation (triglyceride accumulation) and susceptibility to tumour necrosis factor alpha‐induced apoptosis. Gene expression of oestrogen receptors α and β (ESR1 and ESR2), perilipin 1 and hormone‐sensitive lipase (HSL), was also assessed. In FEM SAT, but not AB SAT, 2 weeks of E₂ significantly (P = 0.03) increased ASC differentiation and whole SAT HSL mRNA expression (P = 0.03) compared to placebo. These changes were not associated with mRNA expression of oestrogen receptors α and β, but HSL expression was significantly increased in FEM SAT with transdermal E₂ treatment. Adipose‐derived stem cells proliferation and apoptosis did not change in either SAT depot after E₂ compared with placebo. Short‐term E₂ appeared to increase the adipogenic potential of FEM, but not AB, SAT in post‐menopausal women with possible implications for metabolic disease. Future studies are needed to determine longer term impact of E₂ on regional SAT accumulation in the context of positive energy imbalance.

Developmental Programming: Impact of Gestational Steroid and Metabolic Milieus on Adiposity and Insulin Sensitivity in Prenatal Testosterone-Treated Female Sheep

Prenatally testosterone (T)-treated sheep present metabolic disruptions similar to those seen in women with polycystic ovary syndrome. These females exhibit an increased ratio of small to large adipocytes, which may be the earliest event in the development of adult insulin resistance. Additionally, our longitudinal studies suggest the existence of a period of compensatory adaptation during development. This study tested whether 1) in utero cotreatment of prenatally T-treated sheep with androgen antagonist (flutamide) or insulin sensitizer (rosiglitazone) prevents juvenile insulin resistance and adult changes in adipocyte size; and 2) visceral adiposity and insulin sensitivity are both unaltered during early adulthood, confirming the predicted developmental trajectory in this animal model. Insulin sensitivity was tested during juvenile development and adipose tissue distribution, adipocyte size, and concentrations of adipokines were determined during early adulthood. Prenatal T-treated females manifested juvenile insulin resistance, which was prevented by prenatal rosiglitazone cotreatment. Neither visceral adiposity nor insulin sensitivity differed between groups during early adulthood. Prenatal T-treated sheep presented an increase in the relative proportion of small adipocytes, which was not substantially prevented by either prenatal intervention. A large effect size was observed for increased leptin concentrations in prenatal T-treated sheep compared with controls, which was prevented by prenatal rosiglitazone. In conclusion, gestational alterations in insulin-glucose homeostasis likely play a role in programming insulin resistance, but not adipocyte size distribution, in prenatal T-treated sheep. Furthermore, these results support the notion that a period of compensatory adaptation of the metabolic system to prenatal T exposure occurs between puberty and adulthood.

Global gene expression profiling of brown to white adipose tissue transformation in sheep reveals novel transcriptional components linked to adipose remodeling

BACKGROUND

Large mammals are capable of thermoregulation shortly after birth due to the presence of brown adipose tissue (BAT). The majority of BAT disappears after birth and is replaced by white adipose tissue (WAT).

RESULTS

We analyzed the postnatal transformation of adipose in sheep with a time course study of the perirenal adipose depot. We observed changes in tissue morphology, gene expression and metabolism within the first two weeks of postnatal life consistent with the expected transition from BAT to WAT. The transformation was characterized by massively decreased mitochondrial abundance and down-regulation of gene expression related to mitochondrial function and oxidative phosphorylation. Global gene expression profiling demonstrated that the time points grouped into three phases: a brown adipose phase, a transition phase and a white adipose phase. Between the brown adipose and the transition phase 170 genes were differentially expressed, and 717 genes were differentially expressed between the transition and the white adipose phase. Thirty-eight genes were shared among the two sets of differentially expressed genes. We identified a number of regulated transcription factors, including NR1H3, MYC, KLF4, ESR1, RELA and BCL6, which were linked to the overall changes in gene expression during the adipose tissue remodeling. Finally, the perirenal adipose tissue expressed both brown and brite/beige adipocyte marker genes at birth, the expression of which changed substantially over time.

CONCLUSIONS

Using global gene expression profiling of the postnatal BAT to WAT transformation in sheep, we provide novel insight into adipose tissue plasticity in a large mammal, including identification of novel transcriptional components linked to adipose tissue remodeling. Moreover, our data set provides a useful resource for further studies in adipose tissue plasticity.

The role of estrogen in the modulation of autologous fat graft outcomes

BACKGROUND

Autologous fat grafting is a widely used procedure, yet the mechanisms that regulate graft outcomes are poorly understood. Estrogen signaling is a potent regulator of lipid handling, inflammation, fibrosis, and adipocyte progenitor recruitment in adipose tissues. To date, no studies have investigated the effect of circulating estrogens on fat graft outcomes.

METHODS

Immunosuppressed (Nu/Nu) mice underwent ovariectomy or sham surgery. Forty-five days later, half the mice (donors) were killed, and adipose tissue was taken and transplanted into the remaining cohort (recipients). Forty-five days after transplantation, grafts were dissected, weighed, and assessed for expression of vascular endothelial growth factor, estrogen receptor-α, and vascular density.

RESULTS

Grafts harvested from and transplanted into sham environments are smaller but more highly vascularized compared with ovariectomy environments. The estrogenic effects on grafts are more critical at the site of the donor tissue than the recipient. Finally, expression of estrogen receptor-α in the grafted tissue correlates with the observed graft characteristics, which is altered by both the donor and recipient environments.

CONCLUSIONS

Circulating estrogens have significant effects on fat graft outcomes, primarily at the site of the donor tissue. As there are well-established depot-specific estrogenic responses, the choice of adipose depot used as a donor for fat grafting may affect outcomes. In addition, outcomes may be confounded by the patient's hormonal status. Understanding the mechanisms by which estrogen signaling regulates graft outcomes is important in refining this commonly used clinical procedure.

Updated survey of the steroid-converting enzymes in human adipose tissues

Over the past decade, adipose tissues have been increasingly known for their endocrine properties, that is, their ability to secrete a number of adipocytokines that may exert local and/or systemic effects. In addition, adipose tissues have long been recognized as significant sites for steroid hormone transformation and action. We hereby provide an updated survey of the many steroid-converting enzymes that may be detected in human adipose tissues, their activities and potential roles. In addition to the now well-established role of aromatase and 11β-hydroxysteroid dehydrogenase (HSD) type 1, many enzymes have been reported in adipocyte cell lines, isolated mature cells and/or preadipocytes. These include 11β-HSD type 2, 17β-HSDs, 3β-HSD, 5α-reductases, sulfatases and glucuronosyltransferases. Some of these enzymes are postulated to bear relevance for adipose tissue physiology and perhaps for the pathophysiology of obesity. This elaborate set of steroid-converting enzymes in the cell types of adipose tissue deserves further scientific attention. Our work on 20α-HSD (AKR1C1), 3α-HSD type 3 (AKR1C2) and 17β-HSD type 5 (AKR1C3) allowed us to clarify the relevance of these enzymes for some aspects of adipose tissue function. For example, down-regulation of AKR1C2 expression in preadipocytes seems to potentiate the inhibitory action of dihydrotestosterone on adipogenesis in this model. Many additional studies are warranted to assess the impact of intra-adipose steroid hormone conversions on adipose tissue functions and chronic conditions such as obesity, diabetes and cancer.

Oestrogen signalling in white adipose progenitor cells inhibits differentiation into brown adipose and smooth muscle cells

Oestrogen, often via oestrogen receptor alpha (ERα) signalling, regulates metabolic physiology, highlighted by post-menopausal temperature dysregulation (hot flashes), glucose intolerance, increased appetite and reduced metabolic rate. Here we show that ERα signalling has a role in adipose lineage specification in mice. ERα regulates adipose progenitor identity and potency, promoting white adipogenic lineage commitment. White adipose progenitors lacking ERα reprogramme and enter into smooth muscle and brown adipogenic fates. Mechanistic studies highlight a TGFβ programme involved in progenitor reprogramming downstream of ERα signalling. The observed reprogramming has profound metabolic outcomes; both female and male adipose-lineage ERα-mutant mice are lean, have improved glucose sensitivity and are resistant to weight gain on a high-fat diet. Further, they are hypermetabolic, hyperphagic and hyperthermic, all consistent with a brown phenotype. Together, these findings indicate that ERα cell autonomously regulates adipose lineage commitment, brown fat and smooth muscle cell formation, and systemic metabolism, in a manner relevant to prevalent metabolic diseases.

Expression and subcellular localization of estrogen receptors α and β in human fetal brown adipose tissue

CONTEXT

Brown adipose tissue (BAT) has the unique ability of generating heat due to the expression of mitochondrial uncoupling protein 1 (UCP1). A recent discovery regarding functional BAT in adult humans has increased interest in the molecular pathways of BAT development and functionality. An important role for estrogen in white adipose tissue was shown, but the possible role of estrogen in human fetal BAT (fBAT) is unclear.

OBJECTIVE

The objective of this study was to determine whether human fBAT expresses estrogen receptor α (ERα) and ERβ. In addition, we examined their localization as well as their correlation with crucial proteins involved in BAT differentiation, proliferation, mitochondriogenesis and thermogenesis including peroxisome proliferator-activated receptor γ (PPARγ), proliferating cell nuclear antigen (PCNA), PPARγ-coactivator-1α (PGC-1α), and UCP1.

DESIGN

The fBAT was obtained from 4 human male fetuses aged 15, 17, 20, and 23 weeks gestation. ERα and ERβ expression was assessed using Western blotting, immunohistochemistry, and immunocytochemistry. Possible correlations with PPARγ, PCNA, PGC-1α, and UCP1 were examined by double immunofluorescence.

RESULTS

Both ERα and ERβ were expressed in human fBAT, with ERα being dominant. Unlike ERβ, which was present only in mature brown adipocytes, we detected ERα in mature adipocytes, preadipocytes, mesenchymal and endothelial cells. In addition, double immunofluorescence supported the notion that differentiation in fBAT probably involves ERα. Immunocytochemical analysis revealed mitochondrial localization of both receptors.

CONCLUSION

The expression of both ERα and ERβ in human fBAT suggests a role for estrogen in its development, primarily via ERα. In addition, our results indicate that fBAT mitochondria could be targeted by estrogens and pointed out the possible role of both ERs in mitochondriogenesis.

Testosterone induces cell proliferation and cell cycle gene overexpression in human visceral preadipocytes

Evidence from the literature suggests that testosterone plays an important role in visceral fat accumulation since both men and women with hyperandrogenism accumulate more adipose tissue in the abdominal cavity than healthy women. However, the underlying mechanisms remain to be elucidated. To shed light on this issue, we have used an in vitro approach to examine the effect of testosterone on human visceral preadipocyte proliferation. Our results showed that testosterone treatment significantly increased proliferation of human visceral preadipocytes in proliferation assays using flow cytometric analysis. We next performed a microarray gene expression analysis of human visceral preadipocytes treated with testosterone or vehicle to identify which genes were involved in the testosterone-induced increase in preadipocyte proliferation. The results showed a total of 140 genes differentially expressed between testosterone vs. vehicle. Among the top 10 upregulated genes, 5 were involved in cellular cycle and proliferation, and 3 (APOBEC3b, CCNA2, and PRC1) were significantly overexpressed by testosterone treatment when analyzed by real-time PCR. We conclude that testosterone exerts a proliferative effect on preadipocytes that may participate in the sex differences in fat distribution and that it may explain visceral fat accumulation in women with hyperandrogenism.

Adipogenesis

Adipose tissue is an important site for lipid storage, energy homeostasis, and whole-body insulin sensitivity. It is important to understand the mechanisms involved in adipose tissue development and function, which can be regulated by the endocrine actions of various peptide and steroid hormones. Recent studies have revealed that white and brown adipocytes can be derived from distinct precursor cells. This review will focus on transcriptional control of adipogenesis and its regulation by several endocrine hormones. The general functions and cellular origins of adipose tissue and how the modulation of adipocyte development pertains to metabolic disease states will also be considered.

The estrogenic endocrine disrupting chemical bisphenol A (BPA) and obesity

There is increasing experimental and epidemiological evidence that fetal programming of genetic systems is a contributing factor in the recent increase in adult obesity and other components of metabolic syndrome. In particular, there is evidence that epigenetic changes associated with the use of manmade chemicals may interact with other factors that influence fetal and postnatal growth in contributing to the current obesity epidemic. The focus of this review is on the developmental effects of estrogenic endocrine disrupting chemicals (EDCs), and more specifically on effects of exposure to the estrogenic EDC bisphenol A (BPA), on adipocytes and their function, and the ultimate impact on adult obesity; BPA exposure also results in impaired reproductive capacity. We discuss the interaction of EDCs with other factors that impact growth during fetal and neonatal life, such as placental blood flow and nutrient transport to fetuses, and how these influence fetal growth and abnormalities in homeostatic control systems required to maintain normal body weight throughout life.

Differential estrogenic 17beta-hydroxysteroid dehydrogenase activity and type 12 17beta-hydroxysteroid dehydrogenase expression levels in preadipocytes and differentiated adipocytes

Estradiol (E2) is produced locally in adipose tissue and could play an important role in fat distribution and accumulation, especially in women. It is well recognized that aromatase is expressed in adipose tissue; however the identity of its estrogenic 17beta-hydroxysteroid dehydrogenase (17beta-HSD) partner is not identified. To gain a better knowledge about the enzyme responsible for the conversion of estrone into estradiol, we determined the activity and expression levels of known estrogenic 17beta-HSDs, namely types 1, 7 and 12 17beta-HSD in preadipocytes before and after differentiation into mature adipocytes using an adipogenic media. Estrogenic 17beta-HSD activity was assessed using [(14)C]-labelled estrone, while mRNA expression levels of types 1, 7 and 12 17beta-HSD were quantified using real-time PCR and protein expression levels of type 12 17beta-HSD was determined using immunoblot analysis. The data indicate that there is a low conversion of E1 into E2 in preadipocytes; however this activity is increased approximately 5-fold (p<0.0001) in differentiated adipocytes. The increased estrogenic 17beta-HSD activity is consistent with the increase in protein expression levels of 17beta-HSD12.

Gender-specific expression and mechanism of regulation of estrogen sulfotransferase in adipose tissues of the mouse

Although primarily regarded as a sex steroid, estrogen plays an important role in many other physiological processes including adipose development and disposition. Estrogen sulfotransferase (EST) regulates estrogen activity by catalyzing the sulfoconjugation and inactivation of estrogens. In the present study, we report the gender-specific expression of EST in adipose tissues of the mouse and describe contrasting mechanisms of EST regulation in the fat and liver. EST is expressed in the white adipose tissues of the male but not female mouse. Within the various fat depots of male mice, it is most abundantly expressed in the epididymal fat pad, with variable levels in other white fats and no expression in the brown fat. Fractionation of epididymal fat cells showed EST to be predominantly associated with stromal vascular cells (preadipocyte). EST expression in male mouse adipose tissues is dependent on testosterone as castration ablated, and administration of exogenous testosterone restored, EST expression. Furthermore, testosterone treatment induced abnormal EST expression in the parametrial fat of female mice. EST induction by testosterone in female mice is tissue specific because testosterone treatment had no effect on liver EST expression. Conversely, the liver X receptor agonist TO-901317 induced EST expression in female mouse liver but not in their adipose tissues. Finally, we demonstrate that male EST knockout mice developed increased epididymal fat accumulation with enlarged adipocyte size. We conclude that EST is expressed in adipose tissues in a sexually dimorphic manner, is regulated by testosterone, and plays a physiological role in regulating adipose tissue accumulation in male mice.

alpha2- to beta3-Adrenoceptor switch in 3T3-L1 preadipocytes and adipocytes: modulation by testosterone, 17beta-estradiol, and progesterone

Sex steroid hormones are important factors in the determination of fat distribution and accumulation. The aim of this study was to investigate the effect of testosterone (T), 17beta-estradiol (17betaE), and progesterone (P) on adrenergic receptor (AR) gene expression in 3T3-L1 preadipocytes and adipocytes and their relation to the proliferation and differentiation processes. Our data clearly show that alpha(2A)-AR was the highest AR subtype expressed in preadipocytes, whereas in mature adipocytes was by far beta(3)-AR. In the differentiation process to adipocytes, alpha(2A)-AR expression was decreased to 0.3-fold (P < 0.01), whereas beta(3)-AR was upregulated 578-fold (P < 0.001) compared with preadipocytes. In addition, the expression of alpha(2A)-AR in preadipocytes was increased upon incubation with T, 17betaE, and P, and a stimulation of proliferation was also observed in 17betaE- and P-treated cells. In mature adipocytes, 17betaE and P enhanced both alpha(2A)- and beta(3)-AR gene expression (although the effects on beta(3)-AR mRNA levels could be more relevant, since beta(3)-AR was the most highly expressed), whereas T only increased alpha(2A)-AR mRNA levels. Leptin and adipocyte fatty acid-binding protein mRNA levels were higher after 17betaE and P treatment, possibly indicating a proadipogenic effect of these hormones. In conclusion, this study indicates that AR gene expression is affected by these hormones in both preadipocytes and adipocytes, which could have potential importance when considering the role of ARs in the mechanisms underlying the sex-related differences in adipose tissue regional distribution.

Role of estrogens in adipocyte development and function

Estrogen has historically been viewed as a major regulator of adipose tissue in adult females, but recent work has indicated that estrogen's role in adipose biology may be broader than initially appreciated and has also provided important insights into the mechanism of estrogen effects on adipose tissue. Estrogen has direct effects on adipocytes to inhibit lipogenesis and may also have direct effects on other cellular constituents of adipose tissue, as well as metabolic effects on other target organs that can regulate adipose tissue. Estrogen has central effects on food consumption and energy expenditure that contribute to its overall inhibitory effects on adipose deposition. Estrogen also plays an important role in regulating adipose deposition in males and recently has been shown to be an important factor in the determination of adipocyte number, indicating that it regulates key developmental events in adipogenesis. Although critical questions still remain in our understanding of the overall role of estrogen in adipose tissue, it is clear that estrogen plays a more important role in adipose tissue than originally realized and that it is a major regulator of adipose tissue in both sexes during development and adulthood.