Biomedical subjects

Margaret E E Jones

Publications and source records attributed to Margaret E E Jones.

13 recordsLinked to original sources

PubMed2006

Estrogen deficient male mice develop compulsive behavior.

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

Animals↗

PubMed2006

Of mice and men: the evolving phenotype of aromatase deficiency.

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.

Androgens↗

PubMed2005

Hippocampal NMDA receptor subunit expression and watermaze learning in estrogen deficient female mice.

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.

Animals↗

PubMed2005

Oestrogen replacement in vivo rescues the dysfunction of pituitary somatotropes in ovariectomised aromatase knockout mice.

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.

Androgens↗

PubMed2004

Estrogen deficiency leads to apoptosis in dopaminergic neurons in the medial preoptic area and arcuate nucleus of male mice.

The aromatase knockout (ArKO) mouse is unable to synthesize estrogens. Immunohistochemical studies on active caspase-3 and tyrosine hydroxylase (TH) revealed apoptosis of dopaminergic neurons in the medial preoptic area (MPO) and arcuate nucleus (Arc) of the hypothalamus of 1-year-old (1yo) male ArKO mice while no active caspase-3 was detected in wild type (WT). Furthermore, the number of TH-positive cells in the MPO and caudal Arc was significantly decreased in 1yo ArKO compared to WT. RNase protection assays support the presence of apoptosis in 1yo ArKO hypothalamus, revealing an up-regulation of pro-apoptotic genes: FASL, FADD, and caspase-8. Concomitantly, the ratio of bcl-2-related anti-apoptotic genes to pro-apoptotic genes in the hypothalamus of 1yo ArKO mice was significantly down-regulated. Previously, we have reported that no such changes were observed in the hypothalamus of female ArKO mice. Thus, we have provided direct evidence that estrogen is required to maintain the survival and functional integrity of dopaminergic neurons in the MPO and Arc of male, but not female mice.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Estrogen is not directly required for oocyte developmental competence.

Oocyte maturation and ovulation require a coordinated interaction between gonadotrophs, steroid hormones, and growth factors. The extent to which estrogen is required in this process, however, remains unclear. To better understand the role of estrogen in maintaining developmental competence of mammalian oocytes, we studied the Aromatase knockout (ArKO) mouse, which has been genetically engineered to be incapable of synthesizing endogenous estrogen. Previous studies have established that ArKO female mice are anovulatory with ovaries that progressively degenerate, developing hemorrhagic cystic follicles. In young ArKO females, however, apparently healthy follicles and oocytes have been observed. We investigated if these oocytes could be induced to ovulate, then mature, fertilize, and develop in vitro. Following a standard superovulation protocol, ArKO oocytes did not ovulate. When recovered manually from the ovary, however, ArKO oocytes successfully progressed through in vitro maturation, fertilization, and development to the blastocyst stage at the same rate as wild-type and heterozygote littermates. Therefore, it appears that estrogen is not required for the production and growth of oocytes capable of maturation and complete preimplantation development but is required for continued follicle growth and feedback regulation of ovulation.

Animals↗

PubMed2003

Estrogen replacement reverses the hepatic steatosis phenotype in the male aromatase knockout mouse.

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.

Adipose Tissue↗

PubMed2003

Functional modification of pituitary somatotropes in the aromatase knockout mouse and the effect of estrogen replacement.

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.

Aging↗

PubMed2003

Anti-androgenic action by red clover-derived dietary isoflavones reduces non-malignant prostate enlargement in aromatase knockout (ArKo) mice.

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.

Animal Feed↗

PubMed2003

Cellular and molecular characterization of the adipose phenotype of the aromatase-deficient mouse.

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.

Adipocytes↗

PubMed2003

The aromatase knockout mouse presents with a sexually dimorphic disruption to cholesterol homeostasis.

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.

ATP Binding Cassette Transporter, Subfamily G, Mem↗

PubMed2002

Estrogen regulates development of the somatic cell phenotype in the eutherian ovary.

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.

Animals↗

PubMed2002

The phenotype of the aromatase knockout mouse reveals dietary phytoestrogens impact significantly on testis function.

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.

Animals↗