RESUMO
The aromatase knockout (ArKO) mouse is completely estrogen deficient. We previously detected apoptosis in the hypothalamus of 1 year-old male ArKO mice. This study shows that 12 week-old female ArKO mice display spontaneous apoptosis of pyramidal neurons in the frontal cortex while wild-type (WT) littermates show no signs of apoptosis. Concomitantly, bcl-2 related anti-apoptotic genes are down-regulated whereas the pro-apoptotic gene TRADD is up-regulated in the female ArKO frontal cortex. This phenotype can be rescued by 3-week replacement of 17beta-estradiol. Furthermore, the apoptosis phenotype is exacerbated in 12-15 month-old female ArKO mice, which have 30% less neurons in the frontal cortex and lower brain weights than WT counterparts. These data show that estrogens are essential for the survival of female cortical neurons even in the absence of pathological conditions or external assaults. Our observations also demonstrate the sexually dimorphic susceptibility of neurons to estrogen deficiency.
Assuntos
Apoptose/fisiologia , Aromatase , Estrogênios/deficiência , Lobo Frontal/metabolismo , Lobo Frontal/patologia , Animais , Aromatase/genética , Aromatase/metabolismo , Caspase 3/metabolismo , Sobrevivência Celular , Proteínas de Ligação a DNA , Estradiol/administração & dosagem , Feminino , Lobo Frontal/citologia , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas do Tecido Nervoso/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Neurônios/patologia , Proteínas Nucleares/metabolismo , Tamanho do ÓrgãoRESUMO
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.
Assuntos
Comportamento Compulsivo/fisiopatologia , Comportamento Compulsivo/psicologia , Estrogênios/deficiência , Animais , Aromatase/genética , Aromatase/fisiologia , Western Blotting , Encéfalo/enzimologia , Catecol O-Metiltransferase/genética , Catecol O-Metiltransferase/metabolismo , Comportamento Compulsivo/genética , Estradiol/farmacologia , Estrogênios/farmacologia , Feminino , Asseio Animal/fisiologia , Fígado/enzimologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora/fisiologiaRESUMO
Estrogen regulates tissue development, function, and aging by regulating expression of critical genes. Recent studies suggest that estrogen promotes cell proliferation by stimulating telomerase activity, an enzyme that plays a key role in extending cell life span. In some estrogen-responsive tissues, estrogen appears important in regulating telomerase activity in vivo. Further characterization will provide a greater understanding of the link between estrogen, telomerase, and aging.
Assuntos
Envelhecimento/metabolismo , Estrogênios/fisiologia , Telomerase/metabolismo , Envelhecimento/fisiologia , Animais , HumanosRESUMO
Aromatase deficiency is rare in humans. Affected individuals cannot synthesize endogenous estrogens. Aromatase is the enzyme that catalyzes conversion of androgens into estrogens, and if aromatase is nonfunctional because of an inactivating mutation, estrogen synthesis cannot occur. If the fetus lacks aromatase activity, dehydroepiandrosterone sulfate produced by the fetal adrenal glands cannot be converted to estrogen by the placenta, so is converted to testosterone peripherally and results in virilization of both fetus and mother. Virilization manifests as pseudohermaphroditism in female infants, with hirsutism and acne in the mother; the maternal indicators resolve following delivery. To date, only seven males and seven females with aromatase deficiency have been reported. Affected females are typically diagnosed at birth because of the pseudohermaphroditism. Cystic ovaries and delayed bone maturation can occur during childhood and adolescence in these girls, who present at puberty with primary amenorrhea, failure of breast development, virilization, and hypergonadotrophic hypogonadism. Affected males, on the other hand, do not present with obvious defects at birth, so are diagnosed much later in life, presenting with clinical symptoms, which include tall stature, delayed skeletal maturation, delayed epiphyseal closure, bone pain, eunuchoid body proportions and excess adiposity. Estrogen replacement therapy reverses the symptoms in male and female patients.
Assuntos
Aromatase/deficiência , Adiposidade/fisiologia , Adolescente , Adulto , Aromatase/genética , Osso e Ossos/metabolismo , Terapia de Reposição de Estrogênios , Estrogênios/uso terapêutico , Feminino , Hormônios/uso terapêutico , Humanos , Infertilidade Masculina/metabolismo , Resistência à Insulina/fisiologia , Masculino , Erros Inatos do Metabolismo/diagnóstico , Erros Inatos do Metabolismo/genética , Erros Inatos do Metabolismo/terapia , Mutação , Gravidez , Fatores SexuaisRESUMO
We are rapidly becoming aware of the importance of estrogen in maintaining virtually all facets of male health. In order for estrogens to be synthesized endogenously, the enzyme responsible for their synthesis from androgens, aromatase, must be functional. The seven known men in whom aromatase is nonfunctional all have a mutation in either exon V or IX of the CYP19 gene, which encodes aromatase. Collectively, these men are reported to have undetectable estrogen; normal to high levels of testosterone and gonadotropins; tall stature with delayed skeletal maturation and epiphyseal closure; osteoporosis; impaired lipid and insulin metabolism; and impaired reproductive function. The aromatase knockout mouse presents with a phenotype that is similar in many aspects and provides a valuable tool with which to examine and manipulate the actions of estrogen. By studying the naturally occurring aromatase-deficient humans, together with studies of the aromatase-knockout mouse, we are expanding our understanding of the essential role of estrogen in male physiology.
Assuntos
Aromatase/deficiência , Androgênios/fisiologia , Animais , Aromatase/fisiologia , Comportamento/fisiologia , Desenvolvimento Ósseo/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Metabolismo Energético/fisiologia , Estrogênios/deficiência , Estrogênios/fisiologia , Humanos , Sistema Imunitário/fisiologia , Síndrome Metabólica/fisiopatologia , Camundongos , FenótipoRESUMO
We investigated the effects of estrogens on glucose homeostasis using the Aromatase Knockout (ArKO) mouse, which is unable to convert androgens into estrogens. The ArKO mouse is a model of total estrogen ablation which develops symptoms of metabolic syndrome. To determine the development and progression of whole body state of insulin resistance of ArKO mice, comprehensive whole body tolerance tests were performed on WT, ArKO and estrogen administrated mice at 3 and 12 months of age. The absence of estrogens in the male ArKO mice leads to hepatic insulin resistance, glucose and pyruvate intolerance from 3 to 12 months with consistent improvement upon estrogen treatment. Estrogen absence in the female ArKO mice leads to glucose intolerance without pyruvate intolerance or insulin resistance. The replacement of estrogens in the female WT and ArKO mice exhibited both insulin sensitizing and resistance effects depending on age and dosage. In conclusion, this study presents information on the sexually dimorphic roles of estrogens on glucose homeostasis regulation.
Assuntos
Aromatase/deficiência , Aromatase/genética , Estrogênios/metabolismo , Glucose/metabolismo , Homeostase , Animais , Aromatase/metabolismo , Índice de Massa Corporal , Feminino , Teste de Tolerância a Glucose , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fenótipo , Caracteres SexuaisRESUMO
The aromatase knockout (ArKO) mouse is estrogen deficient. Using reverse-transcription and real-time PCR, we showed that transcript levels of the N-methyl-d-aspartate (NMDA) receptor subunit NR2B are significantly higher in the hippocampus of female ArKO mice compared to wild-type (WT) littermates. Expression levels of NR1, NR2A, but not NR2C, also tended to be higher in ArKO mice. In the Morris watermaze test for spatial memory, both genotypes displayed equal significant improvement in the latency in locating the invisible platform over the 5-day training period. These findings show that selective loss of estrogen synthesis is associated with changes in NMDA receptor subunit expression in the hippocampus but little change in spatial learning ability.
Assuntos
Estrogênios/deficiência , Hipocampo/fisiologia , Aprendizagem em Labirinto/fisiologia , Receptores de N-Metil-D-Aspartato/genética , Animais , Sequência de Bases , Primers do DNA , Feminino , Regulação da Expressão Gênica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Reação em Cadeia da PolimeraseRESUMO
Steroids play a critical role in gonadal differentiation in birds, reptiles, and amphibia whereas gonadal differentiation in mammals is thought to be determined by genetic mechanisms. The gonads of female mice incapable of synthesizing estrogens due to disruption of the aromatase gene (ArKO) provide a unique model to test the role of estrogen in regulating the gonadal phenotype. We have shown that in the absence of estrogen, genetically female mice develop testicular tissue within their ovaries. The ovaries develop cells that possess structural and functional characteristics of testicular interstitial cells and of seminiferous tubule-like structures lined with Sertoli cells. Moreover, the ovaries express mRNA for the testis-specific Sertoli cell transcription factor Sox 9 and espin protein, which is specific for inter-Sertoli cell junctions. The development of the testicular tissue in this model can be reverted/postponed by replacing estrogen. When ArKO female mice were fed a diet containing phytoestrogens, the appearance of Leydig and Sertoli cells was postponed and reduced. Furthermore, administration of estradiol-17beta decreased the number of Sertoli and Leydig cells in the ovaries. These findings constitute definitive evidence that estrogen plays a critical role in maintaining female somatic interstitial and granulosa cells in the eutherian ovary.
Assuntos
Estrogênios/farmacologia , Isoflavonas , Ovário/citologia , Animais , Aromatase/genética , Diferenciação Celular/efeitos dos fármacos , Estradiol/farmacologia , Estrogênios/fisiologia , Estrogênios não Esteroides/farmacologia , Feminino , Gonadotropinas/sangue , Células da Granulosa/ultraestrutura , Proteínas de Grupo de Alta Mobilidade/biossíntese , Proteínas de Grupo de Alta Mobilidade/genética , Imuno-Histoquímica , Células Intersticiais do Testículo/ultraestrutura , Masculino , Camundongos , Camundongos Knockout , Proteínas dos Microfilamentos/análise , Proteínas dos Microfilamentos/imunologia , Ovário/efeitos dos fármacos , Ovário/metabolismo , Ovário/ultraestrutura , Fenótipo , Fitoestrógenos , Preparações de Plantas , RNA Mensageiro/biossíntese , Fatores de Transcrição SOX9 , Células de Sertoli/ultraestrutura , Testículo/química , Testículo/citologia , Testículo/ultraestrutura , Fatores de Transcrição/biossíntese , Fatores de Transcrição/genéticaRESUMO
The maintenance of glucose homeostasis within the body is crucial for constant and precise performance of energy balance and is sustained by a number of peripheral organs. Estrogens are known to play a role in the maintenance of glucose homeostasis. Aromatase knockout (ArKO) mice are estrogen-deficient and display symptoms of dysregulated glucose metabolism. We aim to investigate the effects of estrogen ablation and exogenous estrogen administration on glucose homeostasis regulation. Six month-old female wildtype, ArKO, and 17ß-estradiol (E2) treated ArKO mice were subjected to whole body tolerance tests, serum examination of estrogen, glucose and insulin, ex-vivo muscle glucose uptake, and insulin signaling pathway analyses. Female ArKO mice display increased body weight, gonadal (omental) adiposity, hyperinsulinemia, and liver triglycerides, which were ameliorated upon estrogen treatment. Tolerance tests revealed that estrogen-deficient ArKO mice were pyruvate intolerant hence reflecting dysregulated hepatic gluconeogenesis. Analyses of skeletal muscle, liver, and adipose tissues supported a hepatic-based glucose dysregulation, with a down-regulation of Akt phosphorylation (a key insulin signaling pathway molecule) in the ArKO liver, which was improved with E2 treatment. Concurrently, estrogen treatment lowered ArKO serum leptin and adiponectin levels and increased inflammatory adipokines such as tumour necrosis factor alpha (TNFα) and interleukin 6 (IL6). Furthermore, estrogen deficiency resulted in the infiltration of CD45 macrophages into gonadal adipose tissues, which cannot be reversed by E2 treatment. This study describes the effects of estrogens on glucose homeostasis in female ArKO mice and highlights a primary phenotype of hepatic glucose dysregulation and a parallel estrogen modified adipokine profile.
Assuntos
Adipocinas/sangue , Aromatase/genética , Estradiol/sangue , Estrogênios/sangue , Gluconeogênese , Glucose/metabolismo , Homeostase/efeitos dos fármacos , Tecido Adiposo/metabolismo , Animais , Estradiol/farmacologia , Estrogênios/farmacologia , Feminino , Interleucina-6/sangue , Leptina/sangue , Fígado/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Músculo Esquelético/metabolismo , Triglicerídeos/metabolismo , Fator de Necrose Tumoral alfa/sangueRESUMO
The aromatase knockout (ArKO) mouse cannot synthesize endogenous estrogens due to disruption of the Cyp19 gene. We have shown previously, that ArKO mice present with age-progressive obesity and hepatic steatosis, and by 1 yr of age both male and female ArKO mice develop hypercholesterolemia. In this present study 10- to 12-wk-old ArKO mice were challenged for 90 d with high cholesterol diets. Our results show a sexually dimorphic response to estrogen deficiency in terms of cholesterol homeostasis in the liver. ArKO females presented with elevated serum cholesterol; conversely, ArKO males had elevated hepatic cholesterol levels. In response to dietary cholesterol, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase transcript levels were significantly reduced in females, whereas males showed more modest changes. Neither low density lipoprotein nor sterol regulatory element-binding protein expression levels were significantly altered by diet or genotype. The expression of Cyp7a, which encodes cholesterol 7 alpha-hydroxylase, was significantly reduced in ArKO females compared with wild-type females and was increased by cholesterol feeding. Cyp7a expression was significantly elevated in the wild-type males on the high cholesterol diet, although no difference was seen between genotypes on the control diet. The ATP-binding cassette G5 and ATP-binding cassette G8 transporters do not appear to be regulated by estrogen. The expression of acyl-coenzyme A:cholesterol acyltransferase 2 showed a sexually dimorphic response, where estrogen appeared to have a stimulatory effect in females, but not males. This study reveals a sexually dimorphic difference in mouse hepatic cholesterol homeostasis and roles for estrogen in the regulation of cholesterol uptake, biosynthesis, and catabolism in the female, but not in the male.
Assuntos
Aromatase/genética , Colesterol na Dieta/farmacocinética , Caracteres Sexuais , Membro 5 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Membro 8 da Subfamília G de Transportadores de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Animais , Aromatase/metabolismo , Colesterol/biossíntese , Colesterol 7-alfa-Hidroxilase/genética , Colesterol 7-alfa-Hidroxilase/metabolismo , Colesterol na Dieta/sangue , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Estrogênios/metabolismo , Feminino , Expressão Gênica/fisiologia , Homeostase/fisiologia , Hidroximetilglutaril-CoA Redutases/genética , Hidroximetilglutaril-CoA Redutases/metabolismo , Lipoproteínas/genética , Lipoproteínas/metabolismo , Fígado/metabolismo , Masculino , Camundongos , Camundongos Knockout , Receptores de LDL/genética , Receptores de LDL/metabolismo , Esterol O-Aciltransferase/genética , Esterol O-Aciltransferase/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 2 , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Esterol O-Aciltransferase 2RESUMO
Available data on the influence of estradiol (E(2)) on GH levels remains controversial. A factor contributing to this uncertainty is a lack of knowledge of both E(2) action on somatotropes as well as the molecular mechanisms involved. In this study we investigated gene expression implicated in GH secretion in somatotropes derived from female aromatase knockout (ArKO) mice. In these mice E(2) production is blocked due to disruption of the Cyp19 gene encoding aromatase, the enzyme responsible for estrogen biosynthesis. The effect of E(2) replacement was also studied by in vivo treatment of mice with E(2) for 3 wk. It was demonstrated that somatotropes from ArKO mice had a low expression of GH, GH secretagogue receptor, GHRH receptor (GHRH-R), and pituitary-specific transcription factor (Pit-1). On the other hand, the somatotropes exhibited elevated expression of somatostatin receptors (sst1-5). Overall, these effects resulted in a reduction in GH secretion. E(2) replacement increased GHRH-R, Pit-1, and GH mRNA levels to 185%, 193%, and 157% and reduced the levels of sst1, sst2, sst4, and sst5 mRNA expression in ArKO mice, respectively. E(2) replacement did not affect the levels of pituitary estrogen (alpha and beta) and androgen receptor mRNA expression. It is concluded that the expression of important genes involved in GH synthesis in somatotropes of the female ArKO mouse are functionally down-regulated, and such a down-regulation is reversed to normal levels by E(2) replacement. The levels of GH secretagogue receptor, GHRH-R, and Pit-1 mRNA expression were also reduced, and sst1 and sst3 mRNA expression enhanced in aging ArKO and wild-type mice, resulting in a decrease in GH mRNA expression. It is suggested that aging is another important impact factor for the pituitary expression and regulation of GH mRNA in female mice.
Assuntos
Aromatase/deficiência , Estradiol/farmacologia , Hormônio do Crescimento/genética , Hipófise/metabolismo , Envelhecimento , Animais , Aromatase/genética , Aromatase/fisiologia , Peso Corporal , Proteínas de Ligação a DNA/genética , Feminino , Expressão Gênica , Gliceraldeído-3-Fosfato Desidrogenases/genética , Hormônio do Crescimento/sangue , Camundongos , Camundongos Knockout , Tamanho do Órgão , Hipófise/química , Hipófise/efeitos dos fármacos , RNA Mensageiro/análise , Receptores Androgênicos/genética , Receptores de Estrogênio/genética , Receptores Acoplados a Proteínas G/genética , Receptores de Grelina , Receptores de Neuropeptídeos/genética , Receptores de Hormônios Reguladores de Hormônio Hipofisário/genética , Receptores de Somatostatina/genética , Fator de Transcrição Pit-1 , Fatores de Transcrição/genéticaRESUMO
The aromatase knockout (ArKO) mouse cannot synthesize endogenous estrogens due to a disruption to the Cyp19 gene. Previously we have shown both male and female ArKO mice have an age progressive obese phenotype and a sexually dimorphic disruption to hepatic cholesterol and triglyceride homeostasis. Only ArKO males have elevated hepatic triglyceride levels leading to hepatic steatosis partly due to an increase in expression of enzymes involved in de novo lipogenesis and transporters involved in fatty acid uptake. In this study ArKO males were treated with 17beta-estradiol (3 microg/ kg x d) at 18 wk old for 6 wk. Wild-type controls were not treated, and ArKO controls received vehicle oil injections. Estrogen replacement reverses the previously reported obese and fatty liver phenotypes; this was achieved by reductions in gonadal, visceral, and brown adipose tissue weights and significantly decreased hepatic triglyceride levels. Estrogen deficiency led to a significant up-regulation of hepatic fatty acid synthase expression, which was reduced with 17beta-estradiol replacement, although not quite reaching significance. Acetyl Coenzyme A carboxylase alpha mRNA expression showed no significant changes. Expression of transcripts encoding adipocyte differentiated regulatory protein, a fatty acid transporter, was significantly elevated in estrogen-deficient males, and 17beta-estradiol replacement significantly reduced these levels. Scavenger receptor class b type 1 showed no significantly changes. This study reveals that the previously reported disruption to triglyceride homeostasis in estrogen-deficient males can be reversed with 17beta-estradiol treatment, indicating an important role for estrogen in maintaining triglyceride and fatty acid homeostasis in males.
Assuntos
Aromatase/deficiência , Estradiol/farmacologia , Fígado Gorduroso/enzimologia , Fígado Gorduroso/genética , Tecido Adiposo/patologia , Animais , Aromatase/genética , Peso Corporal , Proteínas de Transporte/genética , Colesterol/metabolismo , Enzimas/genética , Enzimas/metabolismo , Ácidos Graxos/biossíntese , Ácidos Graxos/metabolismo , Fígado Gorduroso/metabolismo , Fígado Gorduroso/patologia , Expressão Gênica , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Camundongos Knockout/genética , Tamanho do Órgão , Fenótipo , RNA Mensageiro/metabolismo , Triglicerídeos/metabolismoRESUMO
Estrogen is synthesized in the testis, both in Leydig cells and seminiferous epithelium, and its importance in spermatogenesis is highlighted by the phenotype of the aromatase knockout (ArKO) mouse. These mice are unable to synthesize endogenous estrogens. The males develop postmeiotic defects by 18 wk of age. We hypothesized that maintenance of spermatogenesis in younger animals may be mediated by exogenous estrogenic substances. Dietary soy meal, contained in almost all commercial rodent diets, provides a source of estrogenic isoflavones. We thus investigated spermatogenesis in wild-type and ArKO mice raised on a diet containing soy, compared with a soy-free diet, to elucidate the biological action of phytoestrogens on the testis. In ArKO mice, dietary phytoestrogens could partially prevent disruptions to spermatogenesis, in that they prevented the decline in germ cell numbers. They also seemed to maintain Sertoli cell function, and they blocked elevations in FSH. The impairment of spermatogenesis seen in soy-free ArKOs occurred in the absence of a decreased gonadotropic stimulus, suggesting that the effects of dietary phytoestrogens are independent of changes to the pituitary-gonadal axis. Our study highlights the importance of estrogen in spermatogenesis and shows that relatively low levels of dietary phytoestrogens have a biological effect in the testis.
Assuntos
Aromatase/fisiologia , Estrogênios não Esteroides/farmacologia , Isoflavonas , Testículo/efeitos dos fármacos , Animais , Aromatase/genética , Estrogênios/fisiologia , Hormônio Foliculoestimulante/sangue , Hormônio Luteinizante/sangue , Masculino , Camundongos , Camundongos Knockout , Fenótipo , Fitoestrógenos , Preparações de Plantas , Células de Sertoli/fisiologia , Contagem de Espermatozoides , Espermatogênese/efeitos dos fármacos , Testículo/patologia , Testículo/fisiologiaRESUMO
Estrogen deficiency in the aromatase knockout (ArKO) mouse leads to the development of obesity by as early as 3 months of age, which is characterized by a marked increase in the weights of gonadal and infrarenal fat pads. Humans with natural mutations of the aromatase gene also develop a metabolic syndrome. In the present study cellular and molecular parameters were investigated in gonadal adipose tissue from 10-wk-old wild-type (WT) and ArKO female mice treated with 17beta-estradiol or placebo to identify the basis for the increase in intraabdominal obesity. Stereological examination revealed that adipocytes isolated from ArKO mice were significantly larger and more abundant than adipocytes isolated from WT mice. Upon treatment with estrogen, the volume of these adipocytes was greatly reduced, whereas the reduction in the number of adipocytes was much less pronounced. Transcriptional analysis using real-time PCR revealed concomitant changes with adipocyte volume in the levels of transcripts encoding leptin and lipoprotein lipase, whereas peroxisome proliferator-activated receptor gamma levels followed a pattern closer to that of adipocyte number. Little change was observed in levels of transcripts for factors involved in de novo fatty acid synthesis, beta-oxidation, and lipolysis, suggesting that changes in the uptake of lipids from the circulation are the main mechanisms by which estrogen regulates lipid metabolism in these mice.
Assuntos
Tecido Adiposo/citologia , Tecido Adiposo/enzimologia , Aromatase/genética , Adipócitos/citologia , Adipócitos/efeitos dos fármacos , Adipócitos/enzimologia , Animais , Aromatase/metabolismo , Proteínas Estimuladoras de Ligação a CCAAT/genética , Contagem de Células , Tamanho Celular , Proteínas de Ligação a DNA/genética , Estradiol/farmacologia , Ácido Graxo Sintases/genética , Ácidos Graxos/metabolismo , Feminino , Expressão Gênica/fisiologia , Leptina/sangue , Metabolismo dos Lipídeos , Lipólise/fisiologia , Lipase Lipoproteica/genética , Masculino , Camundongos , Camundongos Knockout , Oxirredução , Fenótipo , Reação em Cadeia da Polimerase , RNA Mensageiro/análise , Receptores Citoplasmáticos e Nucleares/genética , Proteína de Ligação a Elemento Regulador de Esterol 1 , Fatores de Transcrição/genéticaRESUMO
Estrogens are known to play a role in modulating metabolic processes within the body. The Aromatase knockout (ArKO) mice have been shown to harbor factors of Metabolic syndrome with central adiposity, hyperinsulinemia and male-specific hepatic steatosis. To determine the effects of estrogen ablation and subsequent replacement in males on whole body glucose metabolism, three- and six-month-old male ArKO mice were subjected to whole body glucose, insulin and pyruvate tolerance tests and analyzed for ensuing metabolic changes in liver, adipose tissue, and skeletal muscle. Estrogen-deficient male ArKO mice showed increased gonadal adiposity which was significantly reduced upon 17ß-estradiol (E2) treatment. Concurrently, elevated ArKO serum leptin levels were significantly reduced upon E2 treatment and lowered serum adiponectin levels were restored to wild type levels. Three-month-old male ArKO mice were hyperglycemic, and both glucose and pyruvate intolerant. These phenotypes continued through to 6 months of age, highlighting a loss of glycemic control. ArKO livers displayed changes in gluconeogenic enzyme expression, and in insulin signaling pathways upon E2 treatment. Liver triglycerides were increased in the ArKO males only after 6 months of age, which could be reversed by E2 treatment. No differences were observed in insulin-stimulated ex vivo muscle glucose uptake nor changes in ArKO adipose tissue and muscle insulin signaling pathways. Therefore, we conclude that male ArKO mice develop hepatic glucose intolerance by the age of 3 months which precedes the sex-specific development of hepatic steatosis. This can be reversed upon the administration of exogenous E2.
Assuntos
Aromatase/deficiência , Aromatase/metabolismo , Intolerância à Glucose/enzimologia , Fígado/metabolismo , Fígado/patologia , Adiponectina/sangue , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/patologia , Animais , Glicemia/metabolismo , Peso Corporal/efeitos dos fármacos , Estrogênios/farmacologia , Gluconeogênese/efeitos dos fármacos , Gluconeogênese/genética , Intolerância à Glucose/sangue , Intolerância à Glucose/patologia , Insulina/sangue , Resistência à Insulina , Leptina/sangue , Fígado/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Músculos/metabolismo , Tamanho do Órgão/efeitos dos fármacos , Fosforilação/efeitos dos fármacos , Ácido Pirúvico/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Triglicerídeos/metabolismoRESUMO
Male aromatase knockout mice (ArKO; an estrogen-deficient model) present with male-specific hepatic steatosis that is reversible upon 17ß-estradiol replacement. This study aims to elucidate which estrogen receptor (ER) subtype, ERα or ERß, is involved in the regulation of triglyceride (TG) homeostasis in the liver. Nine-month-old male ArKO mice were treated with vehicle, ERα- or ERß-specific agonists via s.c. injection, daily for 6 weeks. Male ArKO mice treated with ERα agonist had normal liver histology and TG contents compared with vehicle-treated ArKO; omental (gonadal) and infra-renal (visceral) fat pad weights were normalized to those of vehicle-treated wild-type (WT). In contrast, ERß agonist treatment did not result in the similar reversal of these ArKO phenotypes. In vehicle-treated ArKO mice, hepatic transcript expression of fatty acid synthase (Fasn) and stearoyl-coenzyme A desaturase 1 (key enzymes in de novo FA synthesis) were significantly elevated compared with vehicle-treated WT, but only Fasn expression was lowered to WT level after ERα agonist treatment. There were no significant changes in the transcript levels of carnitine palmitoyl transferase 1 (required for transfer of FA residues into the mitochondria for ß-oxidation) and sterol regulatory element-binding factor 1c (the upstream regulator of de novo FA synthesis). We also confirmed by RT-PCR that only ERα is expressed in the mouse liver. There were no changes in hepatic androgen receptor transcript level across all treatment groups. Our data suggest that estrogens act via ERα to regulate TG homeostasis in the ArKO liver. Since the liver, adipose tissue and arcuate nucleus express mainly ERα, estrogens could regulate hepatic functions via peripheral and central pathways.
Assuntos
Aromatase/deficiência , Receptor alfa de Estrogênio/agonistas , Fígado Gorduroso/tratamento farmacológico , Fígado Gorduroso/metabolismo , Moduladores Seletivos de Receptor Estrogênico/farmacologia , Animais , Aromatase/genética , Sequência de Bases , Primers do DNA/genética , Modelos Animais de Doenças , Receptor alfa de Estrogênio/genética , Receptor beta de Estrogênio/agonistas , Receptor beta de Estrogênio/genética , Ácidos Graxos/biossíntese , Fígado Gorduroso/genética , Fígado Gorduroso/patologia , Fígado/efeitos dos fármacos , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Hepatopatia Gordurosa não Alcoólica , RNA/genética , RNA/metabolismo , Transdução de Sinais , Triglicerídeos/metabolismoRESUMO
Estrogen is implicated as playing an important role in aging and tumorigenesis of estrogen responsive tissues; however the mechanisms underlying the mitogenic actions of estrogen are not fully understood. Here we report that estrogen deficiency in mice caused by targeted disruption of the aromatase gene results in a significant inhibition of telomerase maintenance of telomeres in mouse ovaries in a tissue-specific manner. The inhibition entails a significant shortening of telomeres and compromised proliferation in the follicular granulosa cell compartment of ovary. Gene expression analysis showed decreased levels of proto-oncogene c-Myc and the telomerase catalytic subunit, telomerase reverse transcriptase (TERT), in response to estrogen deficiency. Estrogen replacement therapy led to increases in TERT gene expression, telomerase activity, telomere length and ovarian tissue growth, thereby reinstating ovary development to normal in four weeks. Our data demonstrate for the first time that telomere maintenance is the primary mechanism mediating the mitogenic effect of estrogen on ovarian granulosa cell proliferation by upregulating the genes of c-Myc and TERT in vivo. Estrogen deficiency or over-activity may cause ovarian tissue aging or tumorigenesis, respectively, through estrogen regulation of telomere remodeling.
Assuntos
Transtornos 46, XX do Desenvolvimento Sexual/genética , Envelhecimento/genética , Aromatase/genética , Estrogênios , Células da Granulosa/metabolismo , Ginecomastia/genética , Infertilidade Masculina/genética , Erros Inatos do Metabolismo/genética , Telomerase/metabolismo , Telômero/química , Transtornos 46, XX do Desenvolvimento Sexual/tratamento farmacológico , Transtornos 46, XX do Desenvolvimento Sexual/metabolismo , Envelhecimento/metabolismo , Animais , Aromatase/deficiência , Aromatase/metabolismo , Proliferação de Células/efeitos dos fármacos , Terapia de Reposição de Estrogênios , Estrogênios/deficiência , Estrogênios/farmacologia , Feminino , Expressão Gênica , Genes myc/genética , Células da Granulosa/efeitos dos fármacos , Células da Granulosa/patologia , Ginecomastia/tratamento farmacológico , Ginecomastia/metabolismo , Humanos , Infertilidade Masculina/tratamento farmacológico , Infertilidade Masculina/metabolismo , Erros Inatos do Metabolismo/tratamento farmacológico , Erros Inatos do Metabolismo/metabolismo , Camundongos , Camundongos Knockout , Proto-Oncogene Mas , Telomerase/genética , Telômero/metabolismo , Telômero/patologiaRESUMO
OBJECTIVE: To explore the effects of tibolone on adiposity in the absence of aromatase and determine which of the hormonal properties of tibolone are exerting these effects. METHODS: In this study, vehicle; tibolone; estrogenic (ethinyl estradiol [EE]), progestogenic (ORG2058), or androgenic (dihydrotestosterone) compounds; or a combination of ORG2058 + EE was administered to 6-month-old ovariectomized aromatase knockout (ArKO) mice for a period of 6 weeks. RESULTS: In response to tibolone or EE-alone treatments, omental adipose tissue and infrarenal adipose tissue weights were significantly reduced (P = 0.004 and P = 0.01; P = 0.009 and P = 0.014, respectively) compared with those in ovariectomized and vehicle-treated ArKO mice. In contrast, adipose tissue weight tended to increase after ORG2058-alone treatment. Furthermore, EE in the presence of ORG2058 (ORG2058 + EE group) results in little effect on adiposity when compared with that in ovariectomized and vehicle-treated ArKO mice, showing that ORG2058 can negate the effect of EE. Dihydrotestosterone treatment did not have an impact on adipose tissue mass. Adipocyte volume and numbers followed the same treatment trends. CONCLUSIONS: In summary, our study in the ArKO mouse has confirmed the efficacy of tibolone as a hormone therapy to reduce adipose tissue accumulation after menopause and also shows that aromatization of tibolone is not required to elicit these estrogenic effects.
Assuntos
Adiposidade/efeitos dos fármacos , Anabolizantes/farmacologia , Aromatase/metabolismo , Norpregnenos/farmacologia , Ovariectomia , Adiposidade/fisiologia , Animais , Feminino , Camundongos , Camundongos KnockoutRESUMO
The mechanism of regulation of growth hormone (GH) secretion by oestrogens and androgens is still controversial. Available data on the action of oestrogens on GH expression and secretion in somatotropes is poorly understood. We previously reported that the aromatase knockout (ArKO) mouse with oestrogen deficiency and excessive androgen levels had dysfunctional somatotropes. In order to clarify the influence of androgen and oestrogen, we investigated the in vivo treatment of ovariectomised (OVX) ArKO mice with exogenous oestradiol (E2) on the mRNA expression of GH, GH-secretagogue receptor (GHS-R), GH-releasing hormone receptor (GHRH-R), pituitary-specific transcription factor (Pit-1), and somatostatin receptors (sst1-5) in pituitary glands. Circulating plasma GH levels were also evaluated. The results showed that ArKO/OVX mice have a low expression of pituitary GH, GHRH-R, GHS-R and Pit-1, and significantly reduced GH levels. Treatment of female ArKO/OVX (E2-deficient without excessive androgen) mice with E2 for 21 days enhanced expression of pituitary GHRH-R and Pit-1 to 151 and 168%, respectively, of that in mice without treatment. E2 treatment increased GH expression and plasma levels in ArKO/OVX mice to levels comparable with those in wild-type female mice. We conclude therefore that long-term E2 replacement rescues the dysfunction of somatotropes in ArKO/OVX mice through increases in expression of GH, GHRH-R, and Pit-1 in the pituitary somatotropes, whereas the level of androgen in this oestrogen-deficient female mouse does not significantly influence the function of somatotropes.
Assuntos
Aromatase/fisiologia , Estradiol/fisiologia , Hormônio do Crescimento/metabolismo , Hipófise/metabolismo , Androgênios/fisiologia , Animais , Aromatase/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Estradiol/deficiência , Terapia de Reposição de Estrogênios , Feminino , Hormônio do Crescimento/genética , Camundongos , Camundongos Knockout , Tamanho do Órgão , Ovariectomia , Hipófise/citologia , RNA Mensageiro/análise , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Receptores de Grelina , Receptores de Neuropeptídeos/genética , Receptores de Neuropeptídeos/metabolismo , Receptores de Hormônios Reguladores de Hormônio Hipofisário/genética , Receptores de Hormônios Reguladores de Hormônio Hipofisário/metabolismo , Receptores de Somatostatina/genética , Receptores de Somatostatina/metabolismo , Fator de Transcrição Pit-1 , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
BACKGROUND: Red clover (RC)-derived dietary isoflavones have been implicated as potential preventative agents for the development and prevalence of non-malignant prostate diseases. This study investigated whether dietary isoflavones inhibit prostate growth in vivo in the aromatase knock-out (ArKO) mouse that exhibits lifelong elevation of androgens leading to prostate enlargement. METHODS: Adult (11-week-old) wild-type (WT) and ArKO mice were fed on protein matched isoflavones free (IF) and RC (isoflavone rich) diets for 28 days. Individual prostate lobes and testes were weighed and collected for histological analysis and serum androgens were measured. Responses were compared to castration and estrogen administration to ArKO mice to determine the mechanism of action. RESULTS: ArKO mice fed on IF diet exhibited enlarged prostate lobes and elevated serum androgens compared to WT mice. Following 28 days of RC diet, ArKO VP, AP, and SV weights were reduced to WT weights, although testis and body weights remained unaltered. Stereological analysis of VPs revealed a reduction in all components of the tissue, particularly the lumen. The RC diet reduced ArKO serum testosterone and dihydrotestosterone to WT levels. In comparison to castration and estrogen administration, the dietary isoflavones were shown to be anti-androgenic rather than weakly estrogenic, mimicking responses observed in the castrated ArKO, rather than estrogen treated ArKOs. CONCLUSIONS: This study demonstrates that RC-derived isoflavones have a significant effect on prostatic growth, and are capable of reducing the enlarged non-malignant prostate phenotype of the adult ArKO mouse, by acting as anti-androgenic agents rather than weak estrogenic substances.